vizag steal plant es-f

Industrial training

INDUSTRIAL TRANING REPORT OF A STUDY ON,

ENGINEERING SHOPS AND FOUNDRY.VISAKHAPATNAM

STEEL PLANT

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Industrial training ES&F, VISAKHAPATNAM STEELPLANT

. AN OVER VIEW OF VISAKHAPATNAM STEEL PLANT

Visakha pa tna m is popul arly calle d as t he S teel Ci ty of India a nd cr edit was b e c a u s e o f t h e V i z a g S t e e l P l a n t – a v e n t u r e o f I s p a t N i g a m . V S P i s t h e f i r s t c o a s t a l b a s e d s t e e l p l a n t o f I n d i a a n d is l o c a t e d16 km s o u t h w e s t o f c i t y o f destiny. VSP has an i nsta lled ca pa city of 3million Tons per a nnum of li qui d s t e e l a n d 2 . 6 5 6 m i l l i o n t o n s o f s a l e a b le s t e e l . V S P p r o d u c t s m e e t e x a l t i n g international quality standards such as JIS, DIN, BIS, BS etc.VSP has the distinction to be the first integrated steel plant in India to becomea f u l l y I S O -9002 c e r t i f i e d c o m p a n y . T h e c e r t i f i c a t e c o v e r s q u a l i t y s y s t e m s , tr aining and marketing functions spreading over 4 regional marketing officer,20branch offices and 22 stockyards located all over the country VSP successfully installi ng a nd o per ating efficiently Rs . 460 cores worth of pollution control and enviro nme nt co ntrol equipme nt a nd co nver ting t he barre n land scape by planting more than 3 million plants has made the steel plant, steel township a greener, cleaner place, which can boas of 3 to 40C lesser temperature even in the peak summer compared to Visakhapatnam City.

E x p o r t s q u a l i t y p i g i r o n a n d s t e e l p r o j e c t s to S r i L a n k a ,M y a n m a r , N e p a l , Middle East, USA & South East Asia (Pig Iron). RINL VSP was awarded “State Trading House” status during 1997-2000.Besides these a captive power plant with a capacity of 247.5 MW, Oxygen plant, Acetylene plant, compressed iron plant, extensive repair, maintenance facilities, form part of facilities available at VSP. VSP has sufficient infrastructure to expand the plant to10 Million tons per annum of liquid steel capacity


MAJOR PLANT FACILITIES:

VSP has the following major production facilities:• 4 coke oven batteries of 67 ovens each having 41.6 M3 Volume.• 2 Sinter machines of 312 M3 area.• 3 Blast furnace of 3200 M3 useful volume.• Steel Melts Shop with three L.D. converters of 150 Tons capacity each and 6N0s.of 4 standard continuous bloom casters.• Light and Medium Merchant Mill of 710000 Tons per year capacity.• Wire rod mill of 850,000 tons per year capacity.• Medium Merchant & Structural Mill of 850,000 tons per year capacity. Besides these a capacity power plant site a capacity of 286.5 MW, OxygenPlant, Acetylene plant with Air plant, extensive repair maintenance facilities formPart of the facilities available at VSP.Number of ovens in series one after the other form a coke oven Battery. AtVSP there Coke oven Batteries, 7 Meter tall and having 67 Ovens each. Each ovenIs having a volume of 41.6 m3 & can hold up 31.6 Tons of dry coal charge.

DEPARTMENTS:Power generation and distribution.Water management.Traffic department.Engineering shops and foundry.Utilities department.Quality assurance and technology development departmentCalcining and refractory material plant.

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ENGINEER ING SHOP S & FO UN DRY:

INTRODUCTION:-

Engineering shops are set up to meet the requirements of ferrous and non-ferrous spares of different departments in VSP. The engineering shops manufacture and repair the needed spare parts of equipment and tools according to the order of the certain dept., which is called as customer dept.

Engineering shops & foundry is set up to meet the requirements of Ferrous &nonferrous spares of different departments. Engineering shops &Foundry is divided into 5 shops.

1. Central Machine Shop.2. Forge Shop.3. Steel Structural Shop.4. Foundry.5. Utility equipment repair shop.

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CENT RAL MA CHINE S HOPCMS is designed to carry the following manufacturing and repairing

activities.

1) Manufacturing and finishing of castings, forgings, fabricated and rolled sections.

2) Heat treatment and reconditioning of parts3) Tool room work including manufacturing and repair of jigs and

fixtures, regrinding and sharpening of cutting tools4) Dismantling, repair and assembling of worn out machinery and

equipment.

This shop has four longitudinal bays and one cross bay. Heavy and medium duty machines are located in the first two bays. The third bay has light machines, for material preparation and tool room. The forth bay houses the heat treatment and thermal surfacing sections. Cross bay connecting other four bays is the fitting and assembly bay and also houses some of heavy machine tools. Each bay is provided with three EOT cranes with adequate capacity.

INP U TS: Iron &Steel castings .forgings, rolled sections, repair and rectificationParts, nonferrous castings, fabrication structures.

P RODUCTS AND SE R VIC E : shafts, pinions, Gears, crane Wheels, Rollers

Machining of various fabrication jobs done in SSS. Repair &reconditioning of various assembly jobs like L&T housing, To stands, pulleys, previsioning facing and centering machines ,hacksaws, and gas cutting facilities are provided. The machining section has over 100 major machine including lathes, milling, boring, and planning, slotting, shaping, grinding and other machines. The assembly section undertakes medium repair and general overhauling of mechanical equipment. Horizontal and vertical presses, washing tanks oil berths etc. are provided. The tool room has facilities for manufacture of special tools, jigs and fixtures, re-grinding of tools and brazing of tipped tools. The heat treatment section is provided withannealing, normalizing , heat treatment furnaces, carbonizing furnaces, heat

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treatment furnace with protective gas atmospheres, high frequency hardening machine, quenching tanks with oil cooling arrangements, welding generator and transformers for normal welding, sub-merged arc welding machine etc. Facilities for surface grinding, pipe bending and threading are provided.

MAJ OR JOBS OF CMS :

Repairing and reconditioning of TK stands of continuous casting machine.

Manufacturing and repairing of different types of gears and couplings.

Reconditioning of single roll crusher rotor assembly and spiral classifier assembly.

Repair of machining of cooling plates carbon blocks

Central Machine Shop

Fitting & assemblysection

Machining Maintenance

Assembly & repair work

Reclamation

Machining Gear cutting

Heat treatment

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EQ U I PM E N T IN CM S: Plano milling machine Heavy lathes Horizontal boring machine Vertical turret boring machine Grinding machine

Slotting machine Milling machine Planning machine Drilling machine Gear hobbing machine Gear shaper Bevel gear generator Balancing machine Shot blasting machine Submerged arc welding Induction gear hardening machine

HEAVY LATHE ;

The HEC LC 100/ LC 125 type center lathes are heavy duty lathe machines using in CMS. These are fully satisfying the claims modern technology. Their rigid structure permits roughing and also precision finishing work. It uses cemented carbide tipped tools and high speed steel tools.

Working range specifications: LC100 LC125Swing over bed mm 1000 1250

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Swing over carriage mm 710 900Height of bed above carriage mm 500 630Distance between centers mm 3000 12000Max. Torque kgm 2500 3150Max. Weight kg 10000 14000Spindle speeds: in 36 steps

First range rpm 1.8-90 1.4-71second range rpm 8-400 6.3-315

Dia of taper in spindle mm 80/1:10Main motor speed rpm 1460; kW 40Longitudinal feeds in 36 steps:

First range mm/rev 0.125 to 6Second range mm/rev 1 to 48

Movement of:Cross slide mm 530 650Compound rest mm 360Tool post mm 110

Max. Cross section of tool for 4wayTool post mm 50×50

Long. Rapid transverse mm/min 3600Motor for Long. Rapid transverse rpm 1400; kW 1.1Dia of sleeve of tail stock mm 170Dia of taper in sleeve mm 80/1:10

Rate of travel tail stock mm/min 2150Offsetting of tail stock mm +-10Motor of tailstock rpm 1400; kW 0.05Pitch of lead screw inch ½Motor for lubricating oil pump kW 0.18

The main parts of a lathe are:1) Bed2) Head stock3) Tail stock4) Carriage

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BED: It forms the base of the machine. On the bed racks for carriage, tail stock, head stock, and bearings for feed rod and lead screw are fixed.The bed is provided with 3 transverse holes for lifting. It also act as reservoir forlubricating oil.

HEADSTOCK: It is on the left side of the lathe bed. It contains the lathe spindle and spindle driving mechanism. The spindle is hollow throughout its length to allow bar stock to pass through. It is located and runs in precision anti friction bearings in head stock housing. The spur gear attached to the left end of the spindle drives the trains gear to provide motion and direction to the feed rod, quick change gear box and thread cutting mechanism. This lathe is driven by constant speed motor. Change of spindle speeds are obtained by a series of gear combinations by shifting two or three levers in different positions. The main motor is housed in head stock.

CLUTCH and BRAKE: The brake serves to reduce the costing of machine to the maximum. It applies automatically as soon as the main motor is switched off and is released again when the main motor is started. The clutch id of centrifugal type which permits a soft starting and the full torque is gradually built up, starting load being less, starting current of motor is less.

CARRIAGE: It controls the movement of cutting tool either parallel or perpendicular to lathe axis. It moves on the guide ways of the bed. It again consists of:

saddle compound rest tool post

Saddle is mounted on the guide ways carriage and supports the cross slide Compound rest is mounted on the guide ways of the saddle and supports the tool post. The base of the compound rest can be swiveled to any angle between 0-360o and mainly used during taper turning operation.Tool post, its main purpose is to hold the tool during operation. There are two types of tool posts:

standard tool post four way tool post

The LC100/125 lathes use the four way tool posts.

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TAILSTOCK: or loose head stock is located on right side of the bed. It is used to support work piece during rotation and to hold drill or reamer during drilling and other operations. It is provided with set over screw at its base for taper turning alignment. It has a cast iron body with bore to accommodate tail stock spindle and top portion contains the feed screw hand wheel, a spindle lock clamp. It slides on the guide ways of the bed and positioned according to the length of the work. In case of heavy lathes a special motor is provided to move the tailstock on the bed.

Hydraulics:The head stock of the lathe houses two hydraulic clutches in the drive system

and one hydraulic brake. The clutches and brake operate at pressure of 10kg/cm2. The hydraulic system consists of an oil tank fixed to front leg of the machine, a suction strainer, the gear pump driven by main motor, a relief valve, a pressure filter and a rotary valve.

In VSP central machine shop the lathes up to 1.7m length are belt driven and lathes of bed length 3m, 5m are all geared headstocks.Headstock of NH-22 lathe is designed to give spindle 16 forward speeds or 8 forwardand 8 reverse speeds.

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HORI ZONTAL B ORI NG MACHI NE:

The table type of horizontal boring and milling machine has a wide range of machining possibilities.

The details of machine used in VSP, CMS:

Type: BH 100

Version: standard/special

Overall length: mm 6000

Overall width: mm 2650

Overall height mm 3050

Total weight kg 13550

Supply voltage 4157 A; 50 Hz; 3Ph AC

The main assemblies of machine are:

HEAD STOCK: It houses the spindles and main drive. The main and hollow spindles are mounted in the radial two row roller bearings with a tapered hole and inn the one row ball nearing. The thrust bearings take up axial loads.

The working spindle has the same revolutions as hollow spindle and is slide able. It is mounted in the bush and in taper bush. This is slit alongside. The torsion movement is transferred from hollow spindle to working spindle by wedges. The feed of work spindle is delivered from thread shaft on the axis by means of feeding nut, over the plug to extension bearing of the lib.

Die of spindle: mm 100

Taper in spindle: mm 6

Max boring dia mm 560

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Max boring depth mm 900

FACE PLATE: The face plate is solid with main spindle the tool slide, sliding nut in a prismatic guide. It is possible to take up the lateral clearance by a correct setting of the adjusting screws. When turning then the position of adjusting wedges change in relation to prismatic guide in faces plate. Thus the lateral clearance ofthe tool slide increases or decreases.

Dia of face plate: mm 600

Centering dia: mm 280

Depth of Centering dia mm 8

Max. Distance between face plate and back rest mm 2800

COLUMN: The cast iron column has a narrow guide on the right side when viewing from front. The position of column in relation to the bed is secured, by taper pins. The space inside the stand serves for the counter weight hangs on a chain leading over the pulleys on the top of the column.

BED: The sliding surfaces of beds are to be regularly lubricated, inspected and looked after the bed ways. The bed must not be used for putting away tools etc.

SLIDE and TABLE: A lever engages different automatic feeds in the group “slide and table”.

Clamping the work piece:

Work pieces are clamped on the turn table with clamping T-slots. The medium slot intersects the rotation axis. The centering dia for fixture centering is turned on the clamping surface in the rotation axis. It is possible to fix simultaneously by the holder of cooling system with feed piping to this table.

The table may be loaded with a work piece of the max weight of 4000kg on condition of uniform distribution.

Clamping surface: mm 1250×1250

Centering dia: mm 180

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Depth of Centering dia:

Long. Travel of table

Cross travel:

mm

mm

mm

6

1250 to 1750

1250

BACK REST: the back rest is provided with an independent asynchronous electric motor for the vertical adjustment of bearing. The direction sense corresponds to the position of the changeover switch. The longitudinal movement of back rest is done only by hand. For this a crank put on the shaft is rotated. The back rest is locked ata particular position by tightening of screws.

The working principle of machine consists of a coordinate travel of the individual working groups; vertical feed of head stock; longitudinal feed of the slide and cross feed of table.

VERTI CAL TURRE T BORI NG MACHI NE :

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It is a special vertical type of lathe machine. This is used for a large dia and small depth jobs.

CONSTRUCTION:Vertical turret lathe has a single turret head and a side on right hand upright.

This turret head can be moved rightward and leftward on a cross slide ways. The cross slide can be raised and lowered on uprights by lever to accommodate various depths of work, by pulleys and suitable elevating screws. In this machine work is placed on a vertically mounted face plate and held in chuck. The job must be carefully balanced and run at a slow speed, owing to vibration caused by the wear in spindle bearings, whereas with work mounted on vertical spindle, all the weight is evenly distributed downward on bearing s, so that smooth running results and heavy cutting is possible. The main drive is by the electric motor to a gear box giving 18 speeds operated by levers and then to a large ring gear fastened to the table. Feeds are available in all directions.OPERATION:

The job is rotated on table and the turret head is lowered and set to the top of the job and downward feed of turret is engaged. Depth of cut is given by rightward feed or leftward movement of tool head. If outside of the job is doing it is turning; if inside of job it is boring; if it is top of job it is facing; the maximum dia of job is 2.5m to 3m. A pilot bush is fixed in a central hole of table. It has a series of drilled holes in order to facilitate the escape of cuttings down the hollowspindle to the floor.

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PLANO MILLING MACHINE:

Plano milling machine is a milling machine, but designed to execute certain work formerly confined to the planer. It is a multipurpose machine on which milling, planning, drilling, boring etc. can be done. It has a cross rail, capable of being raised or lowered, carrying the cutters, their heads and the saddles, all supported by stout uprights. There may be multiple cutter heads on the rail, as well as two heads on the uprights. Each cutter head in the Plano-miller is separately driven. The drive of the bed is through hydraulic system.

The length of the bed is 8 m and the width of bed is 2 m. so that 16 m lengthjobs can be done easily. This machine is safe on mechanical side using German technology. The electrical power to machine is immediately cut off when over load or any other interruption like lack of lubricating oil etc. is occurred. Therefore the mechanical breakdown doesn’t occur and this machine is running

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successfully from 20 years.

HORIZONTAL MILLING MACHINE:In horizontal milling machines the cutter is mounted on horizontal arbor by

spacing collars and work is clamped on the table. Horizontal milling machine is generally used for cutting gears by using indexing and for cutting keyways.

VERTICAL MILLING MACHINE:In vertical milling machine milling cutter is fixed to the vertical spindle and

work is clamped on the table. It is generally employed for producing flat surfaces. Because of its multi-point cutter milling machine is mostly preferred than shaper in producing flat surfaces.

Coolant systems:

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Correct cooling and lubrication of cutting tool faces is important. Coolant should have following properties:

good cooling effect good lubrication effect protection against rust or other chemical influences

Depending upon the requirement of the specific milling operations coolants may be used.

Supply:The milling machine is provided with a coolant pump for the supply of

coolant. The sump for the coolant of approximately 35 liters is arranged in the base of the machine. The coolant pump runs as long as spindle runs and is automatically switched off when spindle stops. A separate switch is provided to switch off coolant independently to the spindle when not required.

SHAPER:SHAPER is used for machining flat surfaces. Machining on shaper is more

economical with better work setting and cheaper tooling. In shaper work is held stationary on the table and tool reciprocates across the work. The tool used on shaper is of single point cutting tool, thus the work on shaper is transferred to milling machine which is a multi-point cutting tool. In shaper material is removed during forward stroke and return stroke is an idle stroke. The quick return mechanism is employed in shaper to minimize the working time.

SLOTTER:

SLOTTING machine is used for cutting keyways, grooves etc., It consists of ram reciprocates vertically and tool is fed to the work piece on the rotating table. In slotting machine material is removed only during forward stroke & return is idle stroke. In slotter single point cutting tool is used for the operation. Slotter is mainlyused for internal turning.

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GEAR HOBBING MACHINE:

It is used for machining gears from gear blank. In this machine cutting is carried out by a tool called hob. The work is fixed on rotary table and the hob is rotated by means of an electric motor and work is fed across the hob.Operation:

Set the fixture and clamps in the T-slots provided on table. Clamp the work on the table and check the trueness using dial indicator. Select the type of hob on the arbor with a lock nut. Set the required helix angle on the hob. Start the machine tocut the teeth on the gear blank.

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BALANCING MACHINE:

A balancing machine is a measuring tool used for balancing rotating machine parts such as rotors for e l ec t r i c m ot o r s , f a n s , tu r b in e s , di s c b r a k e s , d i s c d r i v e s , p r o p e l l ers and p u m p s . The machine usually consists of two rigid pedestals, with suspension and b ea r i n g s on top. As the part is rotated, the vibration in the suspension is detected with sensors and that information is used to determine the amount of unbalance in the part. Along with phase information, the machine can determine how much and where to add weights to balance the part.

HARD-BEARI NG VS SOFT-BEARI NG:

There are two main types of balancing machines, hard-bearing and soft-bearing. The difference between them, however, is in the suspension and not the bearings.

Hard- and soft-bearing machines can be automated to remove weight automatically, such as by drilling or milling, but hard-bearing machines are more robust and reliable. Both machine principles can be integrated into a production line and loaded by a robot arm or gantry, requiring very little human control.

Working of machine:

With the rotating part resting on the bearings, a vibration sensor is attached to the suspension. In most soft-bearing machines, a velocity sensor is used. This sensor works by moving a magnet in relation to a fixed coil that generates voltage proportional to the velocity of the vibration. A cce l e r o m e t er s , which measure acceleration of the vibration, can also be used.

A ph ot o c e l l (sometimes called a phase), proximity sensor, or encoder is used to determine the rotational speed, as well as the relative phase of the rotating part. This phase information is then used to filter the vibration information to determine the amount of movement, or force, in one rotation of the part. Also, the time difference between the phase and the vibration peak gives the angle at which the unbalance exists. Amount of unbalance and angle of unbalance give an unbalance vector.

Calibration is performed by adding a known weight at a known angle. In a soft- bearing machine, trial weights must be added in correction planes for each part. This is because the location of the correction planes along the rotational axis is unknown, and therefore it is unknown how much a given amount of weight will affect the balance. By using trial weights, you are adding a known weight at a known angle and getting the unbalance vector caused by it. This vector is then compared to the

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original unbalance vector to find the resultant vector, which gives the weight and angles needed to bring the part into balance. In a hard-bearing machine, the location of the correction plane must be given in advance so that the machine always knows how much a given amount of weight will affect the balance.

S U BM ER G E D AR C W ELD I N G M A CH I N E :

Submerged arc welding machine

Submerged arc welding (SAW) is a common arc w e l d i n g process, originally devolved by the Linde - Union Carbide Company.

It requires a continuously fed consumable solid or tubular (f l u x cored) electrode. The molten weld and the arc zone are protected from atmospheric contamination by being “submerged” under a blanket of granular fusible f lu x consisting of li m e ,s i l i c a , manganese oxide, c a l c i u m fl u o ri d e , and other compounds. When molten, the f l u x becomes conductive, and provides a current path between the electrode andthe work. This thick layer of f l u x completely covers the molten metal thus preventing spatter and sparks as well as suppressing the intense ultraviolet radiation and fumes that are a part of the SMAW (shi e l d e d m e t al arc w e ld i n g )process.

SAW is normally operated in the automatic or mechanized mode, however, semi- automatic (hand-held) SAW guns with pressurized or gravity flux feed delivery are available. The process is normally limited to the Flat or Horizontal-Fillet welding positions (although Horizontal Groove position welds have been done with a

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special arrangement to support the flux). Deposition rates approaching 100 lb. /h (45 kg/h) have been reported — this compares to ~10 lb. /h (5 kg/h) (max) for s h i e l d ed m e t al arc w e l d i n g . Although C u r r e n t s ranging from 300 to 2000 an are commonly utilized, [1] currents of up to 5000 A have also been used (multiple arcs).

Single or multiple (2 to 5) electrode wire variations of the process exist. SAW strip-cladding utilizes a flat strip electrode (e.g. 60 mm wide x 0.5 mm thick). DC or AC power can be used, and combinations of DC and AC are common on multiple electrode systems. Constant Voltage w e ld i n g po w er s u p p l i es are most commonly used; however, Constant Current systems in combination with a voltage sensing wire-feeder are available.

Electrode

SAW filler material usually is a standard wire as well as other special forms. This wire normally has a thickness of 1/16 in. to 1/4 in. (1.6 mm to 6 mm). In certain circumstances, twisted wire can be used to give the arc an oscillating movement. This helps fuse the toe of the weld to the base metal.

SHOT BLASTI NG MACHI NE:

The major operations of a blast machine are as follows:

Cleaning of metalsSand from the primary foundry process, rust, paint and powder, epoxy or other coatings may be removed from metals through the process of blast cleaning. Normally, the metal is being prepared for another coating process, so it is important to remove all matter that would sacrifice the quality of the surface and cause a poor finish.

Descaling mill productsMill scale produced in the primary process of manufacturing metals is removed by blast machines. Plate, sheet, strip, wire, bars, billets and other products can be descaled.

Peening metalsIn the peening process, a stream of metal particles is applied at a high velocity viaa Rot oblast wheel against the surface of a metal part. The contact alters the surface

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of the part and creates a rounded depression where the edges of the depression will rise slightly above the original surface. Aircraft components, gears, springs and other critical parts undergo peening operations.

BLAST MACHI NE OPERATI ON IN 10 STEPS

Most wheel blast machine systems operate as follows:

1. Steel abrasive is conveyed into a hopper which is located in a position that is toward the middle of the system but higher than the Rot oblast Wheels.

2. An abrasive gate located above the wheel controls the abrasive through a feed spout toward the Rotoblast wheel.

3. In the Rotoblast wheel is an impeller that rotates. The feed spout directs the abrasive toward the rotating impeller and the impeller directs the abrasive to an opening in an impeller case.

4. The impeller case then directs the abrasive towards the vanes. The vanes are connected to a runner head, which is being driven by an electric motor system. Direct drive motors rotate the runner head at 1800 or 3600 RPM. For bearing and spindle drives, the speeds can vary from 2100 to 3200 RPM.

5. With the vanes rotating at a high speed by the runner head, and the abrasive being fed onto the vanes, centrifugal force hurls the abrasive at high speeds toward the work to be cleaned.

6. The steel on steel contact cleans peens, descales or performs other functions designed into the system.

7. After contacting the work, the spent abrasive falls into a recovery hopper along with other non-abrasive materials (sand, scale, etc.) which has been removed from the work. The recovery hopper is located below the work that is being cleaned.

8. The recovery hopper has a screw conveyor, or oscillating conveyor that conveys the material toward an elevator belt. The elevator belt, driven by another electric motor, is equipped with buckets that carry the material to the very top of the system.

9. At the top of the system is a scalping drum or another screw conveyor that initiates a process where good abrasive is separated from foreign matter. The scalping drum detects larger contaminants compared to the size of the abrasive. It

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directs the larger contaminants toward a scrap drum on the floor, and sends the balance of the abrasive toward a separator which detects abrasive that may be worn due to use.

10. The separator discharges the good abrasive into a storage bin and recycles to the Rotoblast® wheels. The spent and broken abrasive is discharged out of the system and into a refuse container.

HE A T T R E A T M E N T S EC T I O N : It is a post machining operation and is carried out for changing the

structure and properties of metals and alloys by controlled heating and cooling.It is performed to relieve internal stresses, refine grain size etc., the heat treatmentsection in VSP machine shop consists of:

3 heating furnaces Oil bath Water bath Induction hardening furnace Carburizing furnace Nit riding furnace

I NDUCTI ON HARDENI NG FURNAC E :

Induction hardening is a form of heat treatment in which a metal part is heated by induction heating and then quenched. The quenched metal undergoes a martensitic transformation, increasing the hardness and brittleness of the part. Induction

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hardening is used to selectively harden areas of a part or assembly without affecting the properties of the part as a whole.

Process:

Induction heating is a non-contact heating process which utilizes the principle of electromagnetic induction to produce heat inside the surface layer of a work-piece. By placing a conductive material into a strong alternating magnetic field electrical current can be made to flow in the steel thereby creating heat due to the I2R losses in the material. In magnetic materials, further heat is generated below the Curie point due to hysteresis losses. The current generated flows predominantly in the surface layer, the depth of this layer being dictated by the frequency of the alternating field, the surface power density, the permeability of the material, the heat time and the diameter of the bar or material thickness. By quenching this heated layer in water, oil or a polymer based quench the surface layer is altered to form a martensitic structure which is harder than the base metal.

P r i nc i p a l m eth o d s ;

Single shot hardening:

In single shot systems the component is held statically or rotated in the coil and the whole area to be treated is heated simultaneously for a pre-set time followed by either a flood quench or a drop quench system. Single shot is often used in cases where no other method will achieve the desired result for example for flat face hardening of hammers, edge hardening complex shaped tools or the production of small gears.

Traverse hardening:

In traverse hardening systems the work piece is passed through the induction coil progressively and a following quench spray or ring is utilized. Traverse hardening is used extensively in the production of shaft type components such as axle shafts, excavator bucket pins, steering components, power tool shafts and drive shafts. The component is fed through a ring type inductor which normally features a single turn. The width of the turn is dictated by the traverse speed, the available power and frequency of the generator. This creates a moving band of heat which when quenched creates the hardened surface layer. The quench ring can be either integral a following arrangement or a combination of both subject to therequirements of the application. By varying speed power etc. it is possible to create

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a shaft which is hardened along its whole length or just in specific areas and also to harden shafts with steps in diameter or spines. It is normal when hardening round shafts to rotate the part during the process to ensure any variations due to concentricity of the coil and the component are removed.

Equipment:

Power required:

Power supplies for induction hardening vary in power from a few kilowatts tohundreds of kilowatts dependent of the size of the component to be heated and the production method employed i.e. single shot hardening, traverse hardening or submerged hardening.

Frequency

Induction heating systems for hardening are available in a variety of different operating frequencies typically from 1 kHz to 400 kHz. Higher and lower frequencies are available but typically these will be used for specialist applications. The relationship between operating frequency and current penetration depth and therefore hardness depth is inversely proportional.

CARBURI SI NG FU RNACE:

It is used for case hardening of products are done. In this process the heating is carried out up to 600oC for 4 hours at 150oC/hr., and then holding for half an hour at 600oCtaken place, again heating takes place at the rate of 61oC/hr. to 875oC. Thus the heating cycle is completed and cooling is done by quenching them in the water bath.

The main components which are heat treated in this section are Bull head hammers of flux crushing plant in the sinter plant, gear blanks etc.

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Ho riz ontal Boring Mach ines : -

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Radial Drilling Machin es: -

Uni versal Drillin g Machi nes

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Milling Machines:-

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FO RGING SHOP :

In forging shop, the parts and objects which are needed high strength and hardness that required to VSP.

Forging is one of the oldest hot metal working processes. It is defined as the shaping of a heated metal by hammering and pressing. In this process metals are made plastic by heating them and deformed by hammering while they are hot. The components made b this are called forgings. The process is carried out at recrystallization temperature of metals.

INP U TS: Ingots from foundry, blooms from SMS, billets, rods from mills etc.

PRODUCTI ON AN D SER VICES:Raw material for shafts, coupling, gears, pinions, Flanges bull head hammers for plant hammer crusher, drill rods for blast Furnace, v-hooks for SMS, straightening of pallet frames of sinter plant. The shop is designed for production of shafts, coupling: - flanges Etc. and also of forged shapes such as crusher hammer heads, special bolts, nuts, Etc. The repair and testing of chains are also carried out. The annual production from the shop is about 2,400 tons based On 300 working days per year and two Shifts per day. These inputs consisting of ingots, billets, blooms and flats of various sizes. In heavy forging section, open die forging of long shafts, gear blanks, couplings etc.is made with the help of 2-ton bridge type pneumatic hammers. Each hammer will be provided with thin chamber heating furnaces. Floor type manipulator and jib Crane are provided for handling heavy jobs. In general forging section, 1 ton, 500 Kg, and 200 Kg hammers with separate heating furnaces are provided. A 2 ton drop stamp hammer with a heating furnace trimming press etc. is provided for stamping. For cutting them to size, a cold saw, a billet shear and gas cutting facilities are provided. For stress relieving, bogietype-annealing furnace is provided.

HEAVY FORGI NG BAY:

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In this bay, the jobs which needed a large deformation and the large jobs which required high forces to deform are done.

General heavy forge jobs;

Squares to rounds (shafts) Round to hexagon Gear blanks Stepped shafts(bottom roll shafts) Bull head hammers etc.

Raw materials:

Blooms (rectangle) → 240 * 320 mm Squares → 240*240 mm Ingots → larger dia 350mm; smaller dia 240 mm

Equipment in this bay:

Heating furnaces – 4 Bogie furnace for heat treatment 2 ton & 3 ton pneumatic hammers Manipulators – 2; 1 T & 2 T capacity

LI GHT FORGI NG BAY:

In this bay the jobs which need light deformation and smaller in size are done.

General light forging jobs:

Mud guns (4000; 3500; 2500 mm length) Tongs Squares etc.

Equipment:

Pneumatic hammers – 1.6 T

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500kg hammers – 2no’s 250kg hammers – 1 no Open hearth furnace – 1 Drop stamp hammer Trimming press

TOOL ROOM:

It is provided to cut the shafts, billets, making holes etc.

Equipment:

Circular saw Power hacksaw Band saw Drilling machine Shaping machine Grinding machine Billet shearing machine

TYPES OF FORGI NG:

There are many different kinds of forging processes available, however they can be grouped into three main classes.

Drawn out: length increases, cross-section decreases

Upset: Length decreases, cross-section increases

Squeezed in closed compression dies: produces multidirectional flow

Common forging processes include: roll forging, swaging, cogging, open-die forging, impression-die forging, press forging, automatic hot forging and upsetting

OPEN-DI E DROP-HAMMER FORGI NG

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In open-die forging a hammer comes down and deforms the work piece, which is placed on a stationary anvil. The dies (the working surfaces of the forge that contact the work piece) do not enclose the work piece, allowing it to flow except where contacted by the dies. Therefore the operator needs to orient and position the work piece to get the desired shape.

I MPR ESSION- DI E D R O P -H AMM ER F O R G I N G

Impression-die forging is also called closed-die forging. In impression-die work metal is placed in a die resembling a mold, which is attached to the anvil. The hammer die is shaped as well. The hammer is then dropped on the work piece, causing the metal to flow and fill the die cavities.

PR ESS F O R G I N G

Press forging is variation of drop-hammer forging.

Press forges work slowly by applying continuous pressure or force. The amount of time the dies are in contact with the work piece is measured in seconds (as compared to the milliseconds of drop-hammer forges). The press forging operation can be done either cold or hot.

UP SET F O R G I N G

Upset forging increases the diameter of the work piece by compressing its length. Engine valves, couplings, bolts, screws, and other fasteners.

R OLL F O R G I N G

Roll forging is a process where round or flat bar stock is reduced in thickness and increased in length.

HEATI NG FURNA CE:

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The furnace is equipment used to provide heat for a process. Inn this type of furnace, a room type fixed hearth gas fired heating furnace is used.

The pilot burner and main burner in two sets are at roof. The coke oven gas is supplied to burner and is burnt with the air provided from an air blower. Different valves are provided for air and gas controls.

Operatio n of furna ce:

A. starting procedure:

2) Informing to gas control department indicating the starting of furnace.3) Observe the ‘water over flow’ condition to ensure that ‘U’ seal is full of wateror not.4) Ensure that there are no any defects in gas line fitting.5) Remove if any ‘blanks’ in gas line6) Keep the furnace door and damper open.7) Keep the main isolation switch of electrical panel in ‘on’ position.8) Switch on the individual feeders.9) Start the blower after blower discharge valve close and then open the valve.

“U” seal dewatering process:

a. Close the water inlet valve of u seal and open the drain valve to escape water.

b. Close the over flow valve line and drain valve after escaping of water

10) Open the gas valve and check the pressure whether it is 500-600 mm of water column.11) Energize the solenoid and reset the annunciation.12) Set the required temperature in controller.

B. Lig hti ng the burner:

13) Keep the main burner air valve close while the pilot burner air valve is partially opened.14) Lit the pilot burner by opening gas valve.15) Open the gas and air valves of main burner.16) Open pilot air valve completely while pilot gas valve is closed.17) Above same procedure is followed for second set of burners.

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18) Close the furnace door and check the flame is stable or not.

When the furnace room temperature is 900 deg C the jobs are introduced. The forging temperature is up to 1200 deg C.

C.

19) Inform the gas control dept. that furnace is fired off.20) Close the main airline valve and accept the annunciation.21) Close the main burner gas line valves.

HEAVY FORGI NG HAMMER:

It is a bridge type pneumatic hammer.

Construction:

The machine supports on two columns. Two columns are joined with an arch which forms a multi prismatic guide of mono block type cylinder at center. A ram is slide inside the cylinder and the top die is fitted to the ram. The bottom die is placed on an anvil located below top die. A stuffing box which houses valve controls is placed before entrance and exhaust of the cylinder. The machine and anvil are installed with strong and deep basement i.e. 25to 35 feet to make the machine robust to absorb high shocks.

Operation:

The top die is the actual tool which performs the hammering action. The die is operated upwards and downwards in cylinder by air pressure. The inlet and exhaust valves are controlled by a lever which is connected to stuffing box. When upper inlet valve is opened, the highly pressurized air is supplied into the top of the piston from ‘Air Separation Plant, Utilities dept.’. Then the ram moves downwards and blows on the job, which is placed on the bottom die. The air below the ram is exhausted through lower exhaust valve. There is a top pressure buffer cap in cylinder which inserts the ram safely by an aid cushion at the end of its upward stroke. The cylinder and ram is lubricated with oil for free and smooth movement.

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L I GHT F O R G I N G H AMM E R : It is widely used for the manufacture of medium size forgings. The ram is

directly connected to piston working in a steam or air cylinder. The capacity of column hammer is about 500kg.

It operates with steam or compressed air. As compared to pneumatic bridgehammer, column hammer does not possess built in compressor and therefore, requires additional arrangement for supplying high pressure steam or compressed air.

Pneumatic column hammer

DROP STAMP HAMMER:

It is a closed die forging hammer. Spanners, nuts, bolts etc. are made by this method. The dies are made for these jobs, they can produce at rapid rate because as fast as the heated lumps of steel are taken out of furnace they can be put into drop stamp, pounded by it with dies to the required shape and then removed to have the surplus metal cut off.

Mecha nis m and o pera tio n o f thi s ha mmer :

This hammer is used the friction lift mechanism. This consists of two multi grooved friction drums fixed to the main shaft. A one piece cast lifting arm is fitted between these two drums and is mounted on anti-friction bearings are carried on main shaft on the outside of each drum cast steel lifting levers are tied to the lifting

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arm by the tie plate and a cam spindle is carried through arm and levers. Frodo-lined Vee brakes operated on the cam spindle by means of a control lever at one end of the lifter and engage with the friction drum, which is fixed to the revolving main shaft. Thus by a pull on the control lever, the stationary lifting arm, levers and brakes are locked with drum and the lifting mechanism is put into the operation. The hammer head is connected to the lifting arm by means of a belt, which is guided by a loosen pulley bushed on to the lifting arm. The main shaft carries a fixed winch, around which is a control rope is worked by an operator, who by a slight pull can lift the hammer and hold it at any position in guide rods. The drive is by means of an electric motor placed in a suitable position on the floor engaging by a belt to a heavy fly wheel driving the main shaft through a single train to accuracy machine cut gears.

The process includes providing a super abundance of power over the live weight which it has to control by lifting, mechanism such that the forger can obtain that sharp elastic ‘snappy’ blow when it is left over the job that immediately the instantaneously merged together.

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MANI PULATORS: -

Manipulators are used to hold the heated jobs while the forging operation isdoing on heavy forging hammer. It has two jaws which can be rotated around 360deg. When maximum flexibility in transport and handling capabilities during the forging process is important a Mobile Forging Manipulator is your first choice. The compact design and maneuverability of manipulators from DANGO & DIENENTHAL allow the transport of work pieces even when space is limited. Whether small or very large handling capacities are needed DANGO & DIENENTHAL offers both standard and customized solutions. Our machines offer high reliability as well as great flexibility. The sturdy and compact design is adapted to the special operating conditions.Ergonomically aspects and hands-on experience are the decisive factors forselecting and arranging control levers, switches and buttons.

Characteristics:-Powerful tongs unit with large gripping rangeMultistage adjustment of closing forceSpring systems acting both vertically and horizontally to absorb shock loadsHigh maneuverability due to quick and flexible travelling behaviorSemi-automatic working cycles at requestTravel, steering, and tongs motions can be carried out at the same time excellent operator's view in all directions air conditioned driver's cabin at requestpumpsdriven by electric motor or diesel engine Emergency functions

BOGI E FURNACE :

A bogie furnace is used for heat treatment of the forged jobs.

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BI LLET SHEARI NG MACHI NE :

Description:The shear is mechanically driven and provided with a fixed blade and vertically

moving top blade. The drive is by electric motor via v-belts and fly wheel. By the switch able friction clutch the continuously rotating fly wheel can be connected with the toothed gear. The blade slide with the top blade is driven by the gear via crank shaft and connecting rod. With the clutch disengaged the toothed gear is connected with shear frame by a single disc brake. The blade slide moves in the re-adjustable guides in the machine frame.

The machine frame consists of mainly two steel plates and the blade frame from cast steel which accommodates the bottom blade and the down holders. Top blade and bottom blade are mounted in special blade accommodations from cast steel which holds the contact surfaces between machine and blade no wear on frame & blade slide is ensured.

The down holder is arranged in the front of the shear over the bottom blade. The down holder stroke is made by means of a wedge shaped sliding member which driving motion is taken off by the eccentric shaft. The down holder seats on the cutting material prior to cutting and clamp during the total cutting operation. The height for adaptation to the cross section is adjusted by means of a spindle gear.The required cutting gap between top & bottom blades can be achieved by the

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Specifications: horizontal displacement of the bottom blade accommodations bymeans of a wedge.

Oper a t i o n : The billets are placed in the cradle in bundles or separately up to 10

tons. It is important that the cradle must be completely lowered to avoid damages in case of hard placing.

An orderly and quantitatively regulated transfer of billets is performed bylifting the cradle until the first billets are moved into the horizontally moved chute. If the billets are disorderly moved on to the chute, it can be lifted until the billets are arranged & ejector is adjusted.

If the cradle is lowered completely the ejector takes the bottom billet and ejects it. Then the billet in chute moves up to the required length stop regulated manually and clutch is engaged which cuts the billet into required length. Then the clutch is disengaged.

The forged jobs are dispatched to the customers after heat treatment is done.

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S TE EL STRUCT URAL S H OP

In sss, the structural work and mainly fabrication work of steel is done. The repairs of huge parts are also done. When used as industrial term, fabrication applies to the building of machine, structures and other equipment, by cutting, shaping and assembling components made from raw materials.

Fabrication (steel structural) shop concentrated on the metal preparation, welding and assembling aspects.

I N P UT S : Sheets of various sizes, plates angles, channels, beams for fabricationOf jobs.PRODUCTION & SERVICES: All types of fabrication jobs, repair of slag pots ofSMS, Mfg. And repair of punishes for SMS, Mfg. Of scrap boxes for SMS for sinterPlant, hot metal ladle for SMS, 500 meters launder for SMS, mfg. of KAMAGBody for FMD. Repairing of buckets for LMMM, WRM. The annual production of Fabricated structures are about 4,500 tones and the input consisting of sheets, Plates, channels, angles, beams, etc. are about 5,100 T.For marking, cutting to size, forming and bending, guillotineShear, circular saw plate bender, gas cutting unit etc. are provided, for weldingTransformer, automatic and semi-automatic machines and submerged arc Welding machines are provided. Painting is carried out partly with help of spray Guns and partly by hand .Wire brush, spray guns etc. are provided. A maintenanceSection equipped with lathe, shaper, drill etc. are provided for runningRepair of shop equipment.

DETA I L S O F SHO P :

Capacity: annual production is 4500 tones and material needed is 5100 tones.

Activities and work root:

Marking the material on stock Cutting to prepare material for object Assembling various parts or plates prepared for an object Welding the assembled parts to join them Inspection for the defects Dispatching to customer after ensuring no defects.

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Welding techniques used in this shop are:

Arc welding Metal in earth gas welding Thermite welding

Maintenance of stores:

A store is maintained for the new materials, spare parts and tools etc.

Raw materials for sss:

Channels Sheets Plates Beams Billets Angles

The raw materials are stored in open bay of the shop.

Major and regular jobs:

Hot metal ladle (BF) Tundishes, Slag pot (SMS) Coke bucket (Coke ovens) Cones (SP) Ducts (CRMP) Rakes (Mills) Hooks (for cranes)

Equipment in sss:

Shearing machine Bending machine Hydraulic press Combination shearing machine Radial drilling machine CNC gas cutting machine

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Tool roomThis equipment is located in material preparation bay in shop.

In material preparation bay the metal sheets and plates of required dimensions are prepared by making and cutting on the various machines.

Marking is done in required profile by developing the surfaces of finalshape of the object using micrometer, steel rule, compass etc… tools.

After marking, material will be cut and shaped. The operation of cutting may be in the form of shearing, bending, punching, pressing, punching, notching etc.

SHEARI NG MACHI NE:

She a r i n g ( m et a l w o r k i n g ):

Shearing is a metalworking process which cuts stock without the formation of chips or the use of burning or melting. If the cutting blades are straight the process is called shearing; if the cutting blades are curved then they are shearing-type operations. The most commonly sheared materials are in the form of sheet metal or plates; however rods can also be sheared. Shearing- type operations include: blanking, piercing, roll slitting, and trimming.

P r i nc i p l e a nd w o r k i n g :

A punch (or moving blade) is used to push the work piece against the die (or fixed blade), which is fixed. Usually the clearance between the two is 5 to10% of the thickness of the material, but dependent on the material.

Clearance is defined as the separation between the blades, measured at the point where the cutting action takes place and perpendicular to the direction of blade movement. It affects the finish of the cut (burr) and the machine's power consumption.

This causes the material to experience highly localized shear stresses between the punch and die.

The fracture will begin at the weakest point and progress to the next weakest point until the entire work piece has been sheared; this causes the rough edge.

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The material will then fail when the punch has moved 15 to 60% the thickness of the material, because the shear stresses are greater than the shear strength of the material and the remainder of the material is torn.

The rough edge can be reduced if the work piece is clamped from the top with a die cushion. Above a certain pressure the fracture zone can be completely eliminated. However, the sheared edge of the work piece will usually experience work hardening and cracking. Two distinct sections can be seen on a sheared work piece, the first part being plastic deformation and the second being fractured.

Straight shearin g :

Shearing machineStraight shearing is done on sheet metal, coils, and plates. The machine usedis called a squaring shear, power shear, or guillotine.

The machine may be foot powered (or less commonly hand powered), or mechanically powered. It works by first clamping the material with a ram.

A moving blade then comes down across a fixed blade to shear the material. For larger shears the moving blade may be set on an angle or "rocked" in order to shear the material progressively from one side to the other; this angle is referred to as the shear angle.

This decreases the amount of force required, but increases the stroke. A 5 degree shear angle decreases the force by about 20%. The amount of energy used is still the same.

The moving blade may also be inclined 0.5 to 2.5°, this angle is called the rake angle, to keep the material from becoming wedged between the blades, however it compromises the square ness of the edge.[3] As far as equipment

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is concerned, the machine consists of a shear table, work-holding device, upper and lower blades, and a gauging device.

The shear table is the part of the machinery that the work piece rests on while being sheared. The work-holding device is used to hold the work piece in place and keep it from moving or buckling while under stress.

The upper and lower blades are the piece of machinery that actually do the cutting, while the gauging device is used to ensure that the work piece is being cut where it is supposed to be.

The design of press tools is an engineering compromise. A sharp edge, strength and durability are ideal; however a sharp edge is not very strong or durable so blades for metal work tend to be square-edged rather than knife- edged.

Typical work piece materials include aluminum, brass, bronze, and mild steel because of their outstanding shear ability ratings, however, stainless steel is not used as much due to its tendencies to work-harden.

There are also other types of Geometrical Possibilities besides straight shearing though: These include the Squaring Shear, the Angle Shear, the Bow- Tie Shear and the Bar Shear. All of these have many different uses and are all used pretty regularly in certain manufacturing fields.

T o o l M a te r i a l s :

Low alloy steel is used in low production of materials that range up to 1/4 in. thick

High-carbon, high chromium steel is used in high production of materials that also range up to 1/4 in. in thickness

Shock-resistant steel is used in materials that are equal to 1/4 in. thick or more

COMBI NATI ON SHEARI NG MACHINE:

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It is a multi-purpose machine. It is completely mechanically operated. Five types of operations can be done simultaneously on the machine.

These operations are:

2) Punching: it is a purpose of making a desired hole by using a punch and die (Ø 35, Ø32; sq. 28, 32 ;).

3) Notching: it is a process of cutting out the edges of the strip to obtain the desired outer contour of the work piece (dimensions of blade:180×180×18).

4) Cropping: cutting the square bars and round bars (Ø63, sq55).5) Shearing: cutting stocks without formation of chips.

The machine consists of individual units for each operation having punches, dies, blades which are necessary for the above operations.

The punching unit is located in the front of the machine. Shearing and cropping units in the rear side and notching unit is in the middle of the machine. At one side of the machine a fly wheel is located and connected to motor to balance the machine and also drive all units. This machine is used crank lever mechanism to drive. A gear train is mounted to fly wheel shaft and all drives shafts. When the lever of unit is engaged to this gear train, that unit is then starting working. All the units of this machine can be operated simultaneously, thus it can be used for mass production.

BENDI NG MACHI NE :

This is used to bend the plates or sheets in order to form into cylindrical shape, conical shape and other curved shapes as well as to straighten the curved and abstracted plates or sheets and made them flat.

Principle:

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The plates are fed between top roller and bottom rollers and pressure is given from bottom to top of the plate and plate is fed to and fro so that it is gradually bent into required shape.

C o n s t r u c ti o n a n d o p e ra t i o n :

Bending and straightening machine consists of five rollers one is mounted at center of upper side of machine and four rollers are inserted in radial slots at bottom, can be lowered and raised radically. A reversible electric motor is connected to each bottom roller to drive them and the main motor is connected to top roller.

The plate is placed on the bottom rollers ensuring that the edges of the plate and rollers are parallel. When the machine is switched on the rollers start rotating and slowly raised. Then the plate starts bending about the top roller. At the same time the plate is fed to and fro by reversing the motor and bending progresses to the final shape.

For conical sections the plate is bent in different sections a parted equalspace.

Bending has to overcome both tensile and compressive stresses. When bending is done the residual stresses make it spring back towards its original position, therefore it should be over bend.

For straightening process first, two alternate rollers are raised and then the passed through remaining bottom rollers. The raised rollers are lowered against plate, and then the plate is straightened.

The capacity of the machine is 25 mm thick ness and 2 m width of theplate.

HYDRAULI C PRE SS:

It is used to pressing large castings. The ram is moved by the pressure of the fluid. Oil is mostly used fluid for this press. The pressure of oil is increased by pump and is transmitted to the cylinder in order to lift the ram of or to force the ram downwards. The capacity of machine is 200 T.

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CNC GAS CUTTING MACHI NE:

CNC:

In modern CNC systems, end-to-end component design is highly automated using C AD /CAM programs. The programs produce a computer file that is interpreted to extract the commands needed to operate a particular cutting operation.

The movement of the tool resulted in varying forces on the controls that would mean a linear output would not result in linear motion of the tool. The key development in this area was the introduction of the servo, which produced highly accurate measurement information. Attaching two servos together produced a selsyn, where a remote servo's motions was accurately matched by another. Using a variety of mechanical or electrical systems, the output of the selsyn could be read to ensure proper movement had occurred.

MIT fit gears to the various hand wheel inputs and drove them with r o l l er c h a in s connected to motors, one for each of the machine's three axes (X, Y, and Z). The associated controller consisted of five refrigerator-sized cabinets that, together, were almost as large as the mill they were connected to. Three of the cabinets contained the motor controllers, one controller for each motor, the other two the digital reading system.[7]

The MIT design used standard 7-track p u n c h t a p e for input. Three of the tracks were used to control the different axes of the machine, while the other four encoded various control information.[8] The tape was read in a cabinet that also housed six re l a y -based h ar d w a r e re g i st er s , two for each axis. With every read operation the previously read point was copied into the "starting point" register, and the newly read one into the "ending point".[8] The tape was read continually and the number in the register increased until a "stop" instruction, four holes in a line, was encountered.

The final cabinet held a clock that sent pulses through the registers, compared them, and generated output pulses that interpolated between the points. The pulses are sent into a summing register in the motor controllers, counting up by the number of pulses every time they were received. The summing registers

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were connected to a d i g i t a l t o a n a l o g c on v e r t er that output increasing power to the motors.

Once the second point was reached the pulses from the clock would stop, and the motors would eventually drive the mill to the encoded position. The speed of the cut by selecting points that was closer together for slow movements, or further apart for rapid ones.

The system was terribly complex, including 250 v a c u u m tub e s , 175 relays and numerous moving parts, reducing its reliability in a production setting. Curves are as easy to cut as straight lines, complex 3-D structures are relatively easy to produce, and the number of machining steps that required human action has been dramatically reduced.

The standard "G - c o d e " was adapted for CNC use. In turn, G-code was supplanted by S TE P - N C , a system that was deliberately designed for CNC, rather than grown from an existing plotter standard.

G-Code, or preparatory code or function, are functions in the N u m er i cal c o nt r o l p r o g ra m m in g l a ng u a g e . The G-codes are the codes that position the tool and do the actual work, as opposed to M-codes, that manages the machine; T for tool-related codes. S and F are tool-Speed and tool-Feed, and finally D-codes for tool compensation.

Partial list of M-Codes

M00=Program Stop (non-optional), M01=Optional Stop, machine will only stop if operator selects this option, M02=End of Program, M03=Spindle on (CW rotation), M04=Spindle on (CCW rotation), M05=Spindle Stop, M06=Tool Change, M07=Coolant on (flood), M08=Coolant on (mist), M09=Coolant off, M10=Pallet clamp on, M11=Pallet clamp off,

M30=End of program/rewind tape (may still be required for older CNCmachines).

Common G Codes:

G00 Rapid positioning; G01 Linear interpolation; G02 CW circular interpolation; G03 CCW circular interpolation; G12 CW Circle Cutting; G13CCW Circle Cutting; G17 X-Y plane selection; G18 X-Z plane selection; G19

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Y-Z plane selection; G20 Programming in inches; G21 Programming in mm; G90 Absolute programming; G91 Incremental programming;

CNC gas cutting machine’s main parts are:

Control panel Frame Cutting torch Nozzles Gas cylinders

Control panel is the main part of the CNC gas cutting machine which consists of various buttons to enter the data into the machine. It consists of various controls to regulate the speed of the torch to perform operation.

Frame includes the bed for placing the sheet and mild steel frame which holds cutting torch and moves according to the given program to cut the required structure.

Torch is made of brass to with stand high temperatures. It has two ends. To the one end nozzle is fixed and the other end has the provision to connect two hoses for oxygen and acetylene.

Nozzle in the part of the torch where flame comes out and the cutting takes place. Various sizes of nozzles are provided for various thicknesses.

Gas cylinders of oxygen and acetylene are used for gas cutting. Inthis machine cutting is carried out by using oxy- acetylene.

RAD I A L D R I LL I N G M AC H I N E : Radial drilling is used for drilling heavy works and especially for the

jobs where high degree of accuracy is required. Its main parts are: Base Column Radial arm Drill head Spindle

BASE is a rigid cast iron casting which is designed to support column and table. It also contains fluid reservoir for coolant &for lubrication.COLUMN is mounted vertically on the base and supports radial arm. It also houses drive mechanism for spindle.RADIAL ARM is supported by column and rotates 360o to provide easy drilling in

pg. 49


heavier works.DRILL HEAD moves on the guide ways of the radial arm and it houses spindle and speed and feed.SPINDLE is the main part which holds the drill and performs the operation. Bothparallel shank and taper shank drills are used in drilling. The standard taper of taper shank drill is called MORSE TAPER.

The prepared plates, sections in material preparation bay, they are transferred to assembly may for assembling of various parts of a structure. The plates are welded to make a required structure.

Welding is process of making a permanent joint by establishing inter atomic bonds between two or more pieces of metal using heat or heat and pressure.

In SSS, three types of welding techniques are using. They are:

i. Arc welding ii. MIG welding

iii. Thermite welding

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F O U N D R Y S HOP Foundry work deals with manufacture of products from molten metal and obtained products are called castings.

The iron and steel foundry at VSP produces metal castingsMeant for internal uses at different departments like SMS, sinter plant,continuous Casting, blast furnace, coke ovens etc. The raw materials for the foundry are blast furnace pig iron and steel scrap.

This foundry has excellent facilities to produce Quality castings economically on a large scale. The VSP foundry is mainly a captive Foundry because the castings produced by it are used only in VSP and is jobbing in Nature as variety of castings varying in chemistry and weight are being made. Recently started executing outside orders for special steel ingots.

SEQ U E NC E O P E RA T I O N S:

1. Pattern Making2. Mould and Core making3. Melting and Pouring4. Fettling5. Inspection

PA TTE R N M A K I N G :

Pattern is the replica or full size model of castings to be made. It gives its shape to the mould cavity in which the molten metal solidifies to that desired form and size.

PA TTE R N A LLOW ANC ES:

A pattern differs from the casting dimensions. The size of pattern is slightly largerthan the finished casting by an amount called ‘allowance’.

The allowances given to pattern are:

1) Shrinkage allowance:

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When molten liquid metal solidifies, the contraction or shrinkage will takes place i.e. reduces its original size. Therefore the pattern is made larger or oversized than the required casting dimensions. The correction for this is expressed as a ratio.

2) Machining allowance:After casting is made machining is done in order to get smooth and cleanfinishing. Therefore the excess dimensions are given to the pattern.

3) Draft allowance:

When a pattern is removed from a mould the tendency to tear away the edges of the mould is reduced if vertical surfaces of the pattern are tapered inwards.

4) Rapping allowance:Due to rapping of the pattern in the mould, the size of the mould cavityincreases slightly. Therefore ‘shake or rapping’ allowances shall be givento pattern making it smaller to compensate for rapping.

T y pes o f p a t t e rn s : 1) Solid pattern:

In this type one side is made flat which serves as a parting surface. Themould cavity will be entirely in the drag.

2) Split pattern:It is used for intricate and complex shaped casting. In two piece pattern one

part producing the mould in drag and the other in cope. In three piece pattern molding box is with these parts. Center one is cheek box and remaining are same.

3) Gated pattern:The pattern which includes gates and riser for producing castings are called

‘gated pattern’.

4) Sweep pattern:It is a template made of wood or metal revolving around a fixed axis in

mould, shapes the sand to desired contour.

5) Cope and Drag pattern:This pattern is made up of two halves, which are mounted on different

plates. Cope and drag parts are made separately and then assembled.

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6) Skelton pattern:It is used for making large castings in small number. This is a wooden frameout lining the shape of the casting. The frame is filled with loam sand and rammed.

7) Segmental pattern:It is form of a segment and used for molding circular objects such as rings,

wheel rims etc. This pattern revolves about center.

PA TTE R N M A TE RI A LS:

1) Wood2) Metal3) Steel4) Thermo coal5) Plaster of Paris6) Ceramics

In foundry shop the castings are made that is necessary to VSP’s needs.

The sand is used for molding as it has high thermal shock absorption.

Various types of sands used in Foundry are:

Green sand: Molding sand containing moisture is called ‘green sand’. Itconsists of silica, clay, water (5%). It can be reused by reconditioning.

Dry sand: Sand free from moisture is dry sand, which is used for large castings as it having high strength...

Parting sand: It is used to prevent the moulding sand from sticking to surfaces. It is free from clay.

Core sand: It is silicon sand mixed with organic compound like oils, resins etc. It has high refractive ness used for core making.

Silica sand: It consists of 98% to 90% silica mixed with clay. It is mixed with coal powder and used for CO2 moulding process.

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M O ULD I N G P R O CESS E S :According to method:

Bench moulding: In this moulding flasks are kept on bench used for small castings.

Flour moulding: The mould is made on flour. It does not required cope box.

Pit moulding: Mould is made in pit and dug in flour. It acts as drag box and the cope box is used separately.

According to material:

CO2 process:

In this process silica sand is mixed with a small amount of sodium silicate and is placed in moulding box and rammed. After moulding Co2 gas at certain pressure is flowed through mould by vent holes. As the result of chemical reaction between CO2 and sodium silicate, sodium carbonate is formed. Therefore the sand is made harder and ready for pouring. This sand can be used only once and not suitable for reconditioning.

Green sand moulding:

It uses moist sand in which clay will be added to with stand the forces. Drying is not necessary and molten metal is poured as soon as the mould is prepared.

M E L T I NG :Melting is a process of changing the solid state of iron or steel to liquid state. The molten metal is poured into the mould and then solidifies in order to get required casting.

The furnaces used in this shop are:

1) Direct Electric Arc Furnace2) Induction Furnace

Direct Elec t ric A r c F urn a c e : - This is used to melt steel and other metals.

Charge: Steel scrap, Limestone. Steel scrap is the metal which is used for casting and lime stone is used as flux which eliminates impurities.

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Construction: it consists of a roof which can be raised and lowered by hydraulic system; three electrodes and big cylinder which houses all these things and furnace. The cylinder is lined with refractory bricks to resist heat and melting of cylinder.

Process: In this the arc is struck between electrodes and steel scrap. At the electrode points the temperature is about 3600 degree centigrade. The steel is heated gradually and its temperature increases. When it is reached to 1570 deg. Centigrade oxygen is injected into furnace. This O2 is used to form slag by making oxides with impure elements like MN, O, SO2 etc. It forms slag and floats over the molten metal and protects it from atmospheric contaminations and acts as a cover. While melting the metal piece, sample is sent for the analysis of required additives and made the required corrections in composition. After sampling the reduction of metal is done. The additives required are added. Here lime stone acts as a reducing agent.

After temperature is raised to 1640 deg centigrade, the metal is tapped off through tap hole. The furnace is tilted and molten metal is poured into ladle which is placed underground level beside tap hole. The cooling system is arranged in furnace flows through pipes in order to cool the rotating parts of furnace. Generally water is used as coolant.

Electric arc furnace details:

Furnace capacity - 8-10tons

Transformer rating - 4000KVA

Secondary voltage - 125-250volts

Water pressure for electrode - 15kg/cm2

Control and tilting

Water pressure for cooling - 3kg/cm2

Max tilting angle at tapping - 40o

Slagging - 20o

Water for cooling - 6lit/sec

Power consumption - 492KWH/ton

Melt down period - 77min

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I NDUC T I ON F U R NAC E :-

This furnace is used to melt cast iron.

Charge: pig iron scrap, silica.

Construction and process: - The charge is placed in a crucible. It is surrounded by primary copper coils. The space between the crucible and the coil is packed with sand or any insulating material. The high frequency electric current is passed through coil, and this current produces an intense heat in metal charge. This heat is enough to melt the charge. The molten cast iron is tapped off through tap hole and poured into ladle by tilting the furnace.

The primary coil is cooled by water which flows through a separate pipe surrounding the primary coil. In this furnace the charge pig iron is refined in order to get molten cast iron.

Induction furnace details:-

Capacity: 5.3 tons

No. Of crucibles: 2 no’s

Furnace voltage: 1100 KV

Furnace power: 1190 KW

Transformer: 1350 KVA

Primary Voltage: 11KW, 3Ø, 50Hz

Secondary Voltage: 1100KW max

Cooling water flow rate: 12.75 m3 /hr.

Pressure: 4 kg/ cm2

Inlet temperature: 45 deg cg

Outlet temperature: 65 deg cg max

P O U RI N G :The molten metal from furnace is poured into ladle by tilting the furnace. The

ladle is made from steel plate and is lined with fire clay. Ladle is used to carry the molten metal from furnace to mould and pouring the metal into mould. The ladle is

pg. 56


kept as heat as in furnace so that the metal doesn’t loss heat in traveling. These ladlesare carried by overhead cranes.

The molten metal is poured into mould from ladle in two ways:

1) The ladle is tilted by two hoists of overhead crane and molten metal is poured from top of ladle into the mould using pouring cups. This type of pouring is used for small and medium castings. In this slag inclusions may occur.

2) Bottom pouring ladle is used for large castings. The molten metal is poured through bottom hole of ladle which is operated by a graphite stopper. The temperature in ladle is also controlled by the stopper. As metal is poured frombottom, slag is not included and gives better pouring than top pouring.

SAND PLAN T :Sand for moulding is brought from CHEERALA. The sand is of 98% and

also of 90% silica. The sand is stored in a pit. The sand should be prepared before its use in order to get required moulding properties.

Sand handling equipment:

1) Sand mixer2) Belt conveyor3) Bucket elevator4) Sand aerator5) Sand storage bins6) Drier7) Cooler

Sand preparation:

The sand is poured into bunker from storage pit by a grab. This sand is dropped on the belt conveyor by a disc feeder which rotates and

drops the sand down by centripetal force. It is traveled up and passed in drier by screw feeder through another bunker. A blower forces the sand into drier and sand is heated by coke oven gas to

eliminate moisture in it. Then it is passed through cooler to cool the sand to room temperature. Then the sand is passed to storage bin by a bucket elevator. There the sand is

stored when it is not required.

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When the gate of storage bin is opened the sand is dropped into mixer by a vibrating feeder.

In mixers the required additives are added and mixed thoroughly. The additives are: for one ton of sand:

Bentonite – 6%

Dextrin – 2%

Molasses – 1%

Moisture – 5%.

Mixing cycle time is 6 minutes.

The water is added for green sand only. Then the sand is ready for moulding. The prepared sand is sent to small storage bins which are at moulding places

by bucket elevators and belt conveyors. A sand aerator is placed before each bin and it is used to crush the small sand

lumps (included in sand) and make it powder. Sand can be dropped in any storage bin in its traveling path with help of a

plough which diverts the sand to sides of conveyor.

The used sand is also can be reconditioned as the similar way of sand preparation and stored in separate bins.

The sand plant is operated automatically by control panel in controlling room. 10 ton of sand can be prepared in one hour.

C O RE S : Cores are specially made sand bodies intended to form holes and cavities in castings. Cores are placed in the mould cavity before pouring to form interior surface of the casting.

C O R E M A K I N G:

Cores are made in boxes. Core boxes may be a simple solid type or split type made of wood. The two parts of core box is clamped together and kept in vertical position. Wires to provide venting and metal rods to strengthen are reinforced in core. The two halves of box are separated and the core is turned out. Then the core is backedin an oven about 230 deg C.

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C O R E P R I N TS:

The core rest in the mould in recesses specially made for this purpose. Theseare made from pattern in the form of projections known as ‘core prints’.

Horizontal; Vertical; Balanced; Cover and hanging core; etc. types of cores are there according to their position and orientation.

FET T L I N G :- When the molten metal is completely solidified, the casting is to be cleaned and finished. After they are removed from mould they have several unwanted projections as the shape of runners, risers, fed gates etc. And also sand is sticker to it. These all waste material should be removed by some means. This removal of material is called‘FETTLING’.

For iron these projections are removed by nicking them with a chisel and snapping them off. Nonferrous runners etc. are sawn off. Steel ones are removed by oxy acetylene cutting process. The core holes should be cleaned out and any fins are removed with a cold chisel. Cores are cleaned up by means of drifts. The use of wire brush on the exterior faces of a casting will remove any sands adhering to it and sand blasting is also used for this purpose. Castings that are not too delicate may be cleaned by tumbling in rattler and fragile castings are properly filled.

As per the norms of requirement for cast spares, it was foundThat 12000 Tons of castings will be required for the steel plant comprising of 5400T of cast iron spares, 6240 T of steel spares and 360 T of non-ferrous spares. Keeping the requirements in view various equipment were installed to meet the above targets.

T h e c a p a c ities of t h e s h op are:- The maximum weight of single casting in steel – 10 T.The maximum weight of single casting in iron – 10 T.The maximum weight of single casting in non-ferrous – 1T.Captive foundry was envisaged for the supply of consumables and spares for theSteel plant with an investment of 25 cores, followed with the man power of 160

pg. 59


People.The fou nd ry is divi ded i nto fi ve baysAB Bay: - Raw materials sectionBC Bay: - sand preparation, core making CD Bay: - Melting, mound making, casting DE Bay: - Fettling and cleaningEF Bay: Heat treatment and non-ferrous section

UT I L I T Y EQUIPMENT R EPAIR SHOP (UERS)

IN PU TS: Sheets, Plates, Channels, Angles, Beams, Billets, Rounds from ForgeShop for manufacturing Shafts, Steel & Iron castings.

PRODUCTS AND SERVICES:-Manufacturing of Impellers to various departments, repair ofGCP ID Fan, Repair of Steam exhausters for SMS, supply of Cones and Ducts ofVarious sizes, build up & machining of various components, reclamation jobs likeValve repairs, Conveyor Idlers, PCM Rollers etc.

pg. 60

vizag steal plant es-f

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