10.metal-ok.docx

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METAL WORKSHOP 1

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Page 1: 10.METAL-OK.docx

METAL WORKSHOP

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1. INTRODUCTION

The shop has partitioned into many section according to their working functions.

Such as:-

Fabrication work

pipe welding

Brazing

Metal cutting.

Main idea for being in the Metal workshop was to get some practical knowledge of arc welding and gas cutting.

At the same time I was able to follow some other interesting jobs also.

METAL ARC WELDING PROCESS

In this case, an electric welding machine produces a specific amount of current, which passes through the cable

to the electrode. They are also covered with flux. An arc is struck by moving the electrode close to the metal

being welding. The arc is extremely hot, enough to melt both the end of the electrode and the edges of the metal.

MIG WELDING (METAL INERT GAS WELDING)

Gas Metal Arc Welding (GMAW) is frequently referred to as MIG welding. MIG welding is a commonly used high

deposition rate welding process. Wire is continuously fed from a spool. MIG welding is therefore referred to as a

semiautomatic welding process. Brass and aluminum plates were also welded by this method.

A wire feed motor supplying wire guide rollers through a contact tube in the torch to the arc. An inert gas is

supplied to the torch to shield the arc and electrical connections are made to the contact tube and work piece .

When the Welding is done with a D.C source and electrode positive for regular metal transfer and when welding

aluminum to remove the oxide film by the action of the arc cathode.

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Fig 1.1 MIG Welding

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MIG WELDING SHIELDING GAS

The shielding gas, forms the arc plasma, stabilizes the arc on the metal being welded, shields the arc and molten

weld pool, and allows smooth transfer of metal from the weld wire to the molten weld pool.

THE PRIMARY SHIELDING GASSES USED ARE:

Argon

Argon - 1 to 5% Oxygen

Argon - 3 to 25% CO2

CO2 is also used in its pure form in some MIG welding processes. However, in some applications the presence

of CO2 in the shielding gas may adversely affect the mechanical properties of the weld.

TIG WELDING (TUNGSTAN INERT GAS ARC WELDING)

Gas Tungsten Arc Welding (GTAW) is frequently referred to as TIG welding. TIG welding is a commonly used

high quality welding process. TIG welding has become a popular choice of welding processes when high quality,

precision welding is required.

In TIG welding an arc is formed between a non-consumable tungsten electrode and the metal being

welded. Gas is fed through the torch to shield the electrode and molten weld pool. Filler wire is added to the weld

pool separately. When the gas leaves the nozzle, it completely envelops the tip of the electrode and the work

under it.

In this process either direct current or alternating current may be used. The direct current with straight

polarity is used for welding copper alloys and stainless steel, whereas the reversed polarity is used for

magnesium.

The AC current is move versatile in its application and is used for steel, Cast iron, aluminum and

magnesium. The process is capable of making good welds in aluminum without the use of corrosive fluxes. Yet it

is best suited for the welding of relatively these pieces of metal. The tungsten inert gas welding may be done

either by a manual processor by the automatic machine welding.

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Fig 1.2 TIG Welding

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TIG WELDING BENEFITS

Superior quality welds

Precise control of welding variables (heat)

Free of spatter

Low distortion

SHIELDING GASES

Argon

Argon + Hydrogen

Argon/Helium

WELDING ELECTRODES

There are many different types of welding rods for different type of purposes.

Low hydrogen rods ( 7018 )

Mild steel rods ( 6013 )

Stainless steel rods

Carbon Steel electrodes - E6013, E7018, E7024, E7018-1 & E 7048

WELDING SPECIFICATION

The coding system for steel electrodes is given below.

AWS E 6 0 1 3

A B C D

AWS (American Welding Society)

A – Prefix E marks that it is an arc-welding electrode

B - The First two or three digits give the tensile strength of

Weld in thousand pounds per square inch.

C – Digit Before the final gives the welding position

(1= all, 2= flat, horizontal 3= flat only)

D – Final digit gives the composition of flux coating

WELDING POSITION

There are six major types of welding positions.

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1. Flat 1G

2. Horizontal 2G

3. Vertical 3G

4. Overhead 4G

5. Fixed pipe 5G(welder move under it)

6. . Fixed 45’ angled pipe 6G

PUG MACHINE

This machine, also use to cut the metal plate. First we had to connect the pug machine with the

c2H2 and O2 supply. We have to choose a correct nozzle according to the metal thickness. Then we

clean the nozzle by using nozzle cleaning tool. (The nozzle angle varies -60 to +60 degrees.)

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There were two O2 lines and one C2H2 line. One O2 line give pressurize air for cutting purpose.

Then we mark the line which wants to cut on the plate. Then we lighted the nozzle and place it to

correct position where the metal should cut.

Then we pressurize the flame and when it was started to cut, we switch on a button under the machine

to run the machine automatically.

After the cutting stopped we stop the pug machine and off C2H2 then O2.

This machine can cut circles and straight lines in the plate.

When cutting the straight lines, it running through the pug cutter track as shown in figure.

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Fig 1.3 Pug Machine

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CUTTING THE PLATES BY USING THE SHEAR MACHINE

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This was a brand-new machine which was bringing to this shop for cutting operation. First we had to

switch on the machine. For it we had to put the button on (1) position and (0) for off position.

After that we had to enter the data to the machine.

So we had to enter,

Thickness of the plate

Length of the plate

When we gave the thickness and the type of the metal, automatically machine adjusted the angle of the

cutting blade.

As an example:- blade angle was 2.6 for Fe 6mm thickness plate.

After the data was entered, we pressed the green button. Then the back gauge moving out ward from

the machine.

Before cutting was started, the jacks were lowered and tight the plate and after that the cutting started

when we pressed the foot button by foot.

The distance between cutting space and barrier can vary 10mm - 1080mm.

SAFETY ON THE MACHINE

There were protective devices at the backside of the machine.

They are

Transmitter

Receiver

When someone passes this, the machine will stop.

Also there was an emergency, the machine will stop.

AUTOMATIC GAS CUTTER

First we had to create template according to the drawing.

Then we had to light the nozzle.

For it, we had to open the C2H2 simply O2 and lighted the torch. [If only open C2H2 , it create black

smoke]

Then the O2 line was opened.

After that we placed the nozzle tip near the plate.

After that we had to choose the correct flame.

Then we started to cut the plate.

Then we reached the tip of the arm to the boundary of the template.

The tip moves around this template and due to this the nozzle followed the same path as the template.

Then we could cut the real shape as the template.

Then we off the machine from the gasses lines.

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So automatic gas cutter can cut any shape according to the template.

Cutting capacity of this machine is 3 – 100mm and cutting speed 100 – 1000mm.

It cause waste plate pieces and can cut easily same shapes.

MAKE CYLINDER BY USING THE ROLLING MACHINE

First the correct plate was chosen for the purpose.

After that it was put through the roller.

After, the roller was lowered up to the plate. Then the machine was rotated.

Then the roller was lowered little by little and the machine was rotated until it formed in to the

shape.

Then the upper roller one end was dismantled at the right side of the machine. It could move

horizontally.

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Fig 1.5 Automatic Gas Cutter

Fig 1.6 Rolling Machine

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Then we were able to take the cylinder shape plate out from machine.

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