I M l I !. , ' ' ' ' ' '~ . " . , . ; ; ~ ' ~ . . . , f . . . : : _ . . c . . . 0 ' - . _ . : ' " . " . _ ~ . . - / .r> " SENIOR WELDING INSPECTION (WIS 10) ~ . . ) ,/ 'I Y TWI VOl WORLD CENfRE FOR MATERIALS JOINING TECHNOLOGY Copyright o 2002, TWI Limited Training & Examination Services Granta Park, Great Abington Cambridge, CB 1 6AL, UK SENIOR WELDING INSPECTION (WlS 10) Section Title 1) Terms & Definitions 2) Duties & Responsibilities 2a) Duties of a Senior 'Welding Inspector 2b) QA/QC 3) Welding Imperfections 4) Mechanical Testing j) 5) Welding Procedures/Welder approval 6) Materials Inspection 7) Codes and Standards 8) Welding Symbols on Drawings 9) Introduction to 'Welding Processes 0) Manual Metal Arc Welding 11) Tungsten Inert Gas Welding 12) Metal Inert/Active Gas Welding 13) Submerged Arc Welding 14) Welding Consumables 15) Non Destructive Testing ,, 16) Weld Repairs 17) Residual Stress & Distortion 18) Heat Treatment of Steels 19) Oxy-Fuel Gas Welding & Cutting 20) Arc Cutting Processes 21) Welding Safety 22) Weldability of steels 23) Fracture Assessments ( ( '2a.9 Copyright 2002 TW [ Ltd. TWIV!l!ll. _ THE WELDII\JG II\JSTITUTE Concepts relating to an audit Audit client Organization or person requesting an audit Audit program Set of one or more audits planned for a specific time frame and directed towards a specific purpose Audit criteria / Set of policy procedures or requirements used as a reference Technical expert Person who provides specific knowledge of or expertise on the subject to be audited Audit 24 volts. With steels it can be used only in down-hand butts and H/V fillet welds, but gives higher deposition rate, penetration and fusion than dip transfer because of the continuous arc heating. It is mainly used for plate steel > 3mm but may be have limited use for positional welding due to the potential large weld pool involved. 3) Pulsed Transfer: Pulse transfer uses pulses of current to fire a single globule of metal across the arc gap at a frequency between 50 -300 Pulses/second. Pulse transfer is a development of spray transfer, that gives positional welding capability for steels, combined with controlled heat input, good fusion, and high productivity. It may be used for all sheet steel thickness> 1mm, but is mainly used for positional welding of steels> 6mm. As all the parameters require extremely fine adjustment synergic equipment is normally used for pulse transfer. 4) Synergic Pulsed Transfer: Synergic MIG/MAG was developed in the 1980's and uses microprocessor control to adjust the parameters of the electric arc, in maintaining an optimum conditions for a selection of wire type & diameter, material and gas. The microprocessor control will change all other pulse parameters automatically and immediately, for any change in WFS (Wire feed speed). Equipment may also be used for standard dip, spray and globular transfer. 5) Globular Transfer: Globular transfer occurs between dip & spray, but is not normally used for solid wire MIG-MAG welding, but is sometimes used in FCAW. (Flux cored arc welding) Senior Welding Inspection- Metal Inert/Active Gas Weldingt2.6 Rev 09-09-02 Copyright 2002 TWI Ltd. TWI1l701. _ THE WELDING INSTITUTE Variable Parameters: 1) Wire Feed Speed: Increasing the wire feed speed automatically increases the current in the wire. Wires are generally produced in 0.6/0.8/1.0/1.2/1.4 & 1.6 mm diameter. 2) Voltage: The voltage setting is the most important setting in spray transfer as it controls the arc length. In dip transfer it also effects the rise of current and the overall heat input into the weld. An increase of both WFS/current and voltage will increase heat input. The welding connections need to be checked for soundness, as any slack connections will give a hot junction where voltage will be lost from the circuit and will affect the characteristic of the welding arc greatly. The voltage will affect the type of transfer achievable, but this is also highly dependant on the type of gas being used. 3) Gases: C02 gas cannot sustain spray transfer, as the Ionisation Potential of the gas is too high. Because of this high ionisation potential it gives very good penetration, but also a very unstable arc and lots of spatter. Argon has a much lower Ionisation potential and can sustain spray transfer above 24 welding volts. Argon gives a very stable arc and little spatter, but lower penetration than CO2 We mix both argon and CO2 gas in mixtures of between 5 - 20% CO2 in argon to get the benefit of both gases i.e. good penetration with a stable arc and very little spatter. CO2 gas is much cheaper than argon or its mixtures. 4) Inductance: Inductance causes a backpressure of voltage to occur in the wire and operates only when there is a changing current value. In dip transfer welding the current rises as the electrode short circuits -on the plate and it is then that the inductance resists the rapid rate of rise of current at the tip ofthe electrode. This has a main effect of reducing the level of spatter. Important Inspection Points/Checks when MIG/MAG Welding: 1) The Welding Equipment: A visual check should be made to ensure the welding equipment is in good condition. 2) The Electrode Wire The diameter, specification and the quality of the wire are the main inspection headings. The level of de-oxidation of the wire is an important factor with Single, Double & Triple de-oxidized wires being available. The quality of the wire winding is also important. The higher the level of de-oxidants in the wire, then the lower is the chance of occurrence of porosity in the weld. The quality of the copper coating, and the quality of the wire temper and winding are also important factors in minimizing wire feed problems. Quality of wire windings aud increasing costs (a) Random wound. (b) Layer wound.c) Precision layer woun Senior Welding Inspection - Metal Inert!Active Gas Welding),2.7 Rev 09-09-02 Copyright 2002 TWI Ltd. TWIVllOI. _ \) ~ THE WELDING INSTITUTE 3) The Drive Rolls and Liner. Check the drive rolls are of the correct size for the wire and that the pressure is only hand tight, or just sufficient to drive the wire. Any excess pressure will deform the wire to an ovular shape. This will make the wire very difficult to drive through the liner and result in arcing in the contact tip and excessive wear of the contact tip and liner. . Check that the liner is the correct type and size for the wire. A size of liner will generally fit 2 sizes of wire i.e. (0.6 & 0.8) (1.0 & 1.2) (1.4 & 1.6) mm diameter. Steel liners are used for steel wires and Teflon liners for aluminium wires. 4) The Contact Tip. Check that the contact tip is the correct size for the wire being driven, and check the amount of wear frequently. Any loss of contact between the wire and contact tip will reduce the efficiency of current pick. Most steel wires are copper coated to maximise the transfer of current by contact between 2 copper surfaces at the contact tip, this also inhibits corrosion. The contact tip should be replaced regularly. 5) The Connections. The length of the electric arc in MIG/MAG welding is controlled by the voltage settings. This is achieved by using a constant voltage volt/amp characteristic inside the equipment. Any poor connection in the welding circuit will affect the nature and stability of the electric are, and is thus is a major inspection point. 6) Gas & Gas Flow Rate. The type of gas used is extremely important to MIG/MAG welding, as is the flow rate from the cylinder, which must be adequate to give good coverage over the solidifying and molten metal to avoid oxidation and porosity. 7) Other Variable Welding Parameters. Checks should be made for correct WFS, Voltage, Speed of travel, and all other essential variables of the process given on the approved welding procedure. 8) Safety Checks: Checks should be made on the current carrying capacity, or duty cycle of equipment and electrical insulation. Correct extraction systems should be in use to avoid exposure to ozone and fumes. A check should always be made to ensure that the welder is qualified to weld the procedure being employed. Typical Welding Imperfections: 1) Silica inclusions, (on ferritic steels only) caused by poor inter-run cleaning. 2) Lack of sidewall fusion during dip transfer welding thick section vertically down. 3) Porosity caused from loss of gas shield and low tolerance to contaminants 4) Burn through from using the incorrect metal transfer mode on sheet metal. Senior Welding Inspection - Metal Inert! Active Gas Welding! 2. 8 Rev 09-09-02 Copyright 2002 TWI Ltd. TWIV!lOI. _ THE WELDING INSTITUTE Advantages of Flux Cored Arc Welding: In the mid 80's the development of self-shielded and dual-shielded FCAW was a major step in the successful application of on-site semi automatic welding, and has also enabled a much wider range of materials to be welded. The wire consists of a metal sheath containing a granular flux. This flux can contain elements that would normally be used in MMA electrodes and so the process has a very wide range of applications. In addition we can also add gas producing elements and compounds to the flux and so the process can become independent of a separate gas shield, which restricted the use of conventional MIG/MAG welding in many field applications. "Dual Shield" wires obtain their gas shielding from a combination of flux and separate shielding gas. Most wires are sealed mechanically and hermetically with various forms of joint. The effectiveness of the joint of the wire is an inspection point of cored wire welding, particularly with wires containing basic fluxes, as moisture can easily be.' absorbed into a damaged or poor seam. It is the accepted practise when using basic wires that the first few meters of wire from the reel is stripped off and discarded as moisture can be absorbed up the length of the wire through the core of flux if incorrectly stored. Baking of cored wires is ineffective and will do nothing to restore the condition of a contaminated flux within a wire. A major advantage of fluxed cored wires is that they produce extremely good penetration. This is caused by the amount of current density in the wire, or in other words the amount of current carried in the available CSA of the conductor. This area is very small in flux-cored wires, in comparison with other welding processes. ( . MMA Solid MIG Wire Flux Cored Wires 3.25 mm (2) @125 Amps 1.2 mm e @180 Amps 2.0mm (} @180 Amps Wire sheath . ~ carrying current ~ Flux core centre - - - - - - - - - - - ~ Increasing Current Density & Penetration Power Senior Welding Inspection - Metal Inert!Active Gas Welding}, 2.9 Rev 09-09-02 Copyright 2002 TW[ Ltd. TWIV!l!ll.' _ THE WELDII\JG II\JSTITUTE Summarv of Solid wu- NIlG/MAG GyIA"V: Equipment requirements: I) A Transformer/Rectifier. (Constant voltage type) 2) A power and power return cable. 3) An Inert, active, or mixed shielding gas. (Argon or C02) 4) Gas hose, flow meter, & gas regulator. S) MIG torch with hose, liner, diffuser, contact tip & nozzle. 6) Wire feed unit with correct drive rolls. 7) Electrode wire to correct specification and diameter. 8) Correct visor/glass, all safety clothing and good extraction. () Parameters & Inspection Points: I) WFS/Amperage. 2) OCV & Welding voltage. 3) Wire type & diameter. 4) Gas type & flow rate. 5) Contact tip size and condition. 6) Roller type, size and pressure. 7) Liner size. 8) Inductance settings. 9) Insulation/extraction. 10) Connections. (Voltage drops) l l ) Duty cycles. 12) Travel speed, direction & angles. Typical Welding Imperfections: 1) Silica inclusions. 2) Lack of fusion. (Mainly dip transfer) 3) SurfacePorosity. 4) Bum through (Using spray for sheet) Advantages & Disadvantages: \ . Advantages: Disadvantages: 1) High productivity (o/f). 1) Lack of fusion. (Dip Transfer) 2) Easily automated. 2) Small range of consumables. 3) All positional. (Dip & Pulse) 3) Protection for site working. 4) Material thickness range. 4) Complex equipment. 5) Continuous electrode. 5) High ozone levels. Senior Welding Inspection - Metal Inert! Active Gas Weldingt2.1 0 Rev 09-09-02 Copyright 2002 TWI Ltd. TWIV!701. _ Questions QU1. QU2. QU3. (, ') QU4. QU5. THE WELDING INSTITUTE MIG/MAG Welding Process State the possible problems, which may occur when using the dip transfer mode in the MAG welding process State the application areas for the spray transfer mode when using the MAG welding process What power source characteristic is considered essential for a semiautomatic welding process and state the current type and electrode polarity State the main variables for the MAG welding process State the advantages and disadvantages of the MAG welding process when compared to the MMA welding process Senior Welding Inspection - Qll Metal Active Gas Sec 12 Copyright 2003 TWI Ltd ) C \ \ . v s : J J V 1 n O n J a s TWI1ll01. _ THE WELDING INSTITUTE Submerged Arc Welding: SAW or Submerged arc welding was developed in the Soviet Union during the 2nd world war as an economical means of welding thick steel sections. Definitions: SAW: Submerged Arc \Velding. (UK & USA) Introduction: This welding process is normally mechanised and uses a constant voltage power source, as it is the voltage that controls the arc length. Amperages can range from 100 up to and over 2,000 amps, which gives very high current density in the wire and deep penetration and dilution into the base metal. The arc is struck in the same manner as MIG, which is generally aided by the linear movement of the electrode tip across the surface of the run on tab, though H/F arc striking is also possible on some equipment. As its name suggests the arc is submerged beneath a covering of flux, which is of a granular nature. ( ~ A flux delivery system must be incorporated into the equipment, which may also be accompanied by a flux recovery system. It is restricted in position and is generally used for thickness of over 10mm. Run-on and run-off tabs are normally used on welded seams, as this allows the welding arc to settle to its required conditions prior to the commencement of the actual welding seam. The run off plate allows a similar set of conditions to occur at the end of the weld. Both run-on and run-off tabs are removed after the weld seam has been completed. The arc is normally formed as the point of the wire comes into moving contact with the plate. The flux blanket protects 'the arc from atmosphere and decomposes in the heat of the arc adding alloying elements and deoxidants to the molten weld metal. The flux also provides a slag, which forms a protective barrier to the cooling weld in a similar manner to MMA. Photographs 1 and 2 show a stationary SAW head with rotated pipe, and photograph 3 shows a mobile tractor/carriage assembly, which may be used for welding deck plates. Senior Welding Inspection - Submerged Arc Welding Rev 09-09-02 13.1 Copyright 2002 TW[ Ltd ' TWIV!JI. _ THE WELDING INSTITUTE Submerged Arc Welding Basic Equipment Requirements: 'I 1) Welding carriage control panel. -'!o',",,_,i 2) Welding carriage assembly. 3) Reel of wire. 4) Granulated flux. 5) Transformer rectifier. 6) Power source control panel. 7) Power return cable. 8) Flux hopper. Senior Welding Inspection - Submerged Arc Welding Rev 09-09-02 13.2 Copyright 2002 TWI Ltd TWIV!lOI. _ THE WELDING INSTITUTE Immediately on pressing the switch, the following occurs: a) The flux is released forming a layer beneath the torch head. b) The wire begins to feed and strikes the arc. c) The contactor closes and delivers current to the contact tip. d) The tractor begins to move. (If mechanised) Because of the nature of the granular flux, the use of Submerged Arc Welding for positional welding has been restricted to the flat position. However the process has been continually developed and is now capable of certain degree of positional welding, with an addition of some simple extra equipment (i.e. flux dams). Submerged arc welding has many applications, but certain limitations exist other than the positional capability of the process, as with the restriction of full penetration welds from one side without the use of a backing bar or backing strip. One of the most popular applications for SAW is in the welding of "Spirally welded pipe" where a fixed unit is stationed inside the pipe to weld the internal seam with an additional fixed unit placed on the top of the pipe for the outer seam. Full penetration welding takes place as the pipe is spiralled through. Other factors that may need to be taken into consideration are the toughness requirements of the joint, as the arc energy input is comparatively high. Arc blow can also be a major problem as its occurrence due to magnetic field is proportional to the current used and in SAW currents of over 1,500 amps are not uncommon. Arc blow can be minimised by the use of tandem wire systems with the leading wire on DC+ and the trailing wire on AC producing opposing magnetic fields. The use of double, or multi run techniques also has effects on the properties of the weld metal and HAZ. Multi run techniques tends to normalise previous weld deposits and HAZ, giving 'superior properties, The resultant SAW weld metal is difficult to predict, as the weld is made up from 3 elements. A typical set of values is given below, but this can change dramatically with any changes in the welding parameters: 1) The Electrode. (25%) _ '::.:.;', SAW Weld Metal Analysis . 2) Elements in the flux. (15%) I :. __. 3) . Dilution. (60%) .. ;.. . ... '.3/2) 3) Sb.rinkage cavities caused by a weld depth/ratio of > 3/2 4) Lack of fusion caused by the effects of arc blow. Senior Welding Inspection - Submerged Arc Welding Rev 09-09-0213.5 Copyright 2002 TWI Ltd " TWIV!lOI. _ THE W E L D I ~ I G INSTITUTE Summary of Sub Arc \Velding: Equipment requirements: 1) A Transformer/Rectifier. (Constant voltage type) 2) A power and power return cable. 3) A torch head assembly. 4) A granulated flux of the correct type/specification and mesh size. 5) A flux delivery system. 6) A flux recovery system. 7) Electrode wire to correct specification and diameter. 8) Correct safety clothing and good extraction. Parameters & Inspection Points: IJ 1) AC/DC WFS/Amperage. 2) OCV & Welding Voltage. 3) Flux type and mesh size. 4) Flux condition. (Baking etc.) 5) Electrode wire and condition. 6) Wire specification. 7) Flux delivery/recovery system. 8) Electrode stick-out. 9) Insulation/duty cycles. 10) Connections. 11) Contact tip size/condition. 12) Speed of travel. Typical Welding Imperfections: 1) Lack of fusion. 2) Solidification, or centreline cracks. 3) Shrinkage cavities. 4) Porosity. Advantages & Disadvantages: ( Advantages: Disadvantages: 1) Low weld-metal costs. 1) Restricted in positional welding. 2) Easily mechanised. 2) High probability of arc-blow. (DC+/-) 3) Low levels of ozone production. 3) Prone to shrinkage cavities. 4) High productivity (o/t). 4) Difficult penetration control. 5) No visible arc light. 5) Variable compositions. (Arc length) Senior Welding Inspection - Submerged Arc Welding Rev 09-09-0213.6 Copyright 2002 TWI Ltd TWIV!7[JI. _ THE WELDING INSTITUTE Questions QU1. QU2. QU3. QU4. QU5. Submerged Arc Welding Process State the possible problems when using damp and contaminated fluxes in the SAW welding process. State the two flux types used in the SAW welding process. Generally what power source characteristic is required for the SAW welding process? State three main items of SAW fluxes, which require inspection State the advantages and disadvantages of the SAW welding process Senior Welding Inspection - QU Submerged Arc Welding Process Sec 13 Copyright 2003 TWI Ltd ( M V S ~ D V W / D I W D I L V W l t \ 1 . 1 0 J s o j q a u m s u o . j ~ u ! P I a M 1 7 1 u 0 ! l ; , a s TWIV!lOI. _ THE WELDING INSTITUTE Welding Consumables: Welding consumables are defined as all those things that are used up in the production 0 t' a weld. This list could include many things including electrical energy, however we normally refer to welding consumables as those things used up by a particular welding process. These are namely: Electrodes wires Fluxes Gases i't'. , :1:;-' :.; ;::: I;'1 . _ ""0':':" U',l . . S"A'U'1' .i,' .::FVStP: .. 'Fl' .. ,... , llX.' ,\,;.,.. I....... ./' When inspecting welding consumables arriving at site, it is important that they are inspected for the following: 1) Size. 2) Type or Specification. 3) Condition. Senior Welding Inspection -Welding Consumables 14.1 Rev 09-09-02 Copyright 2002 TWI Ltd TWIV!lOI. _ THE WELDING INSTITUTE Consumables for 1VIMA Welding: Welding consumable for MMA consist of a core wire typically between 350 and 450m01 length and from 2.5 - 6mm diameter. Other lengths and diameters are also available. The wire is covered with an extruded flux coating. The core wire is generally of low quality steel (Rimming Steel) as the weld can be considered as a casting, and therefore the weld can be refined by the addition of cleaning, or refining agents in the flux coating. The flux coating contains many elements and compounds that all have a variety of jobs during welding. Silicon is mainly added as a de-oxidising agent (in the form of Ferro silicate), which removes oxygen from the weld metal by forming the oxide Silica. Manganese additions of up 1.6% will improve the strength and toughness of steel. Other metallic and non-metallic compounds are added that have many functions, some of which are as follows: 1) To aid arc ignition. 2) To improve arc stabilisation. 3) To produce a shielding gas to protect the arc column. 4) To refine and clean the solidifying weld-metal. 5) To form a slag which protects the solidifying weld-metal. 6) To add alloying elements. 7) To control hydrogen content of the weld metal. 8) To form a cone at the end of the electrode, which directs the arc. Electrodes for MMAJSMAW are grouped depending on the main constituent in their flux coating, which in turn has a major effect on the weld properties and ease of use. . ; The common groups, are given below: Group Constituent Shield gas Uses AWS AS.1 Rutile Titania CO2 General purpose E 6013 Basic Calcium compounds CO2 High quality E 7018 Cellulosic Cellulose Hydrogen + CO Pipe root runs E 6010 Senior Welding Inspection -Welding Consumables 14.2 Rev 09-09-02 Copyright 2002 TWI Ltd --TWIV!lOI. _ THE WELDING INSTITUTE A Typical BS 639 Specification: E 51 33 B 160 2 0 H Reference given in box letter: A) B) C) D) E) F) G) A) Tensile strength: Symbol Min Yield Tensile Strength Strength Nzmrrr' I N/mm2 43 430-550 51 330 380 510-650 C) Covering types: B Basic BB Basic High Efficiency C Cellulosic 0 Oxidising R Rutile Medium Coated Rutile Heavy Coated S RR Other Types E) Welding position: Symbol Position 1 All positions 2 All positions except Vertical Down 3 Flat Butt & Fillets + HV Fillets. 4 Flat Butt & Fillets 5 Vertical Down + positions of symbol 3 9 Any position not I classified by the above. 'I B) Toughness: First Digit Second Digit Testing 28 J 47 J Temperature 0 0 Not specified +20 2 1 1 2 0 3 -20 4 3 4 -30 5 5 -40 [ D) Electrode Efficiency: I l % Recovery to nearest 10% (> = 110) F) Electrical characteristic: Symbol DC Polarity AC Min OCV 0 Polarity as recommended Not recommended 1 + or 500CV 2 - 500CV 3 + 500CV 4 + or 700CV 5 - 700CV 6 + 700CV 7 + or 900CV 8 - 900CV 9 + 900CV ) I G) Control: H Indicates Low Hydrogen Potential ( Senior Welding Inspection -Welding Consumables 14.3 Rev 09-09-02 Copyright 2002 TWI Ltd TWIVOI. _ THE WELDII\JG INSTITUTE A Typical Electrode Specification to BSEn 499 ". ( A Typical Electrode Specification to AWS A 5.1 \. ') Senior Welding Inspection -Welding Consumables 14.4 Rev 09-09-02 Copyright 2002 TWI Ltd TWIV!lOI. _ THE WELDING INSTITUTE A Typical BSEn 499 Specification: E 46 3 INi B 5 4 HS Reference given in box letter: A) B) C) D) E) F) G) A) Tensile strength: Symbol Min Yield Tensile Min Strength Strength E% Nzmrrr' N/rnm2 35 355 440-570 22 38 380 470-600 20 42 420 500-640 20 46 460 530-680 20 SO 500 560-720 18 C) Alloying: B) Toughness at minimum impact energy 47 Joules: Z No requirement A +20 0 0 2 -20 3 -30 4 -40 5 -50 6 -60 (Deposited weld chemical composition) Symbol Mn Mo Ni None 2.0 - -Mo 104 0.3-0.6 -MoMo >104-2.0 0.3-0.6 -INi 104 - 0.6-1.2 2Ni 104 - 1.8-2.6 3NI 104 - >2.6-3.8 Mo INi >104-2.0 - 0.6-1.2 INiMo 104 0.3-0.6 0.6-1.2 D) Covering types: A Acid C Cellulosic R Rutile RR Rutile thick covering RC Rutile/Cellulosic RA Rutile/Acid RB Rutile/Basic B Basic Z Any other agreed composition E) Electrical characteristic + recovery % Symbol Recovery % Current type 1 ac +"dc 2 < 105 < 105 dc 3 > 105 < 125 ac +dc 4 > 105 < 125 dc 5 > 125 < 160 ac+ de 6 > 125 < 160 dc 7 > 160 ac+dc 8 > 160 dc G) Hydrogen Content of deposited weld metal: Symbol Max H2Content ml/100mgm H5 5 HIO 10 HIS 15 F) Welding position: Symbol Position I All positions 2 All positions except Vertical Down 3 Flat Butt & Fillets + HV Fillets. 4 Flat Butt & Fillets 5 Vertical Down + positions of symbol 3 The strength, toughness, coating of BS 639 plus any light alloying elements of BS EN 499 (If applicable) are the mandatory elements of information that shall be shown on all electrodes. All other information is normally given on the electrode carton. Senior Welding Inspection -Welding Consumables 14.5 Rev 09-09-02 Copyright 2002 TWI Ltd TWIV!lOI. _ THE WELDING INSTITUTE Inspection Points for MlVIA Consurnables 1: Size: Wire Diameter & length. -E . , ... r,.' 2: Condition: Cracks, chips & concentricity. ) 3: Type (Specification): Correct specification/code. ", Checks should also be made to ensure that basic electrodes have been through the correct pre-use procedure. Having been baked to the correct temperature (typically 300350C) for 1 hour and then held in a holding oven at 150C before being issued to the welders in heated quivers. Most electrode flux coatings will deteriorate rapidly when damp and care should be taken to inspect storage facilities to ensure that they are adequately dry, and that all electrodes are stored in conditions of controlled humidity. Vacuum packed electrodes may be used directly from the carton, only if the vacuum has been maintained. Directions for hydrogen control are always given on the carton and should be strictly adhered to. The cost of each electrode is insignificant compared with the cost of any repair, thus basic electrodes that are left in the heated quiver after the day's shift may potentially be re baked, but would normally be discarded to avoid the risk of H, induced problems. Senior Welding Inspection -Weiding Consumables 14.6 Rev 09-09-02 Copyright 2002 TWI Ltd TWIV!lOI. _ THE WELDING INSTITUTE Consumables for TIG Welding: Consumables for TIG/GTAW consist of a wire and gas, though tungsten electrodes may also be grouped in this. Though it is considered as a non-consumable electrode process, the electrode is consumed by erosion in the arc, and by grinding and incorrect welding technique. The wire needs to be of a very high quality as normally no extra cleaning elements can be added into the weld. The wire is refined at the original casting stage to a very high quality where it is then rolled and finally drawn down to the correct size. It is then copper coated and cut into 1m lengths. A code is then stamped on the wire with a manufacturer's, or nationally recognised number for the correct identification of chemical composition. A grade of wire is selected from a table of compositions. The wires are mostly copper coated which inhibits the effects of corrosion. Gases for TIG/GTAWare generally inert. Pure argon or helium gases are generally used for TIG welding. The gases are extracted from the air by liquefaction. Argon is more common in air than helium and thus it is generally cheaper than helium. In the USA vast pockets of naturally occurring helium are found and thus helium gas is more often used in USA. Helium gas produces a deeper penetrating arc than argon. It is less dense (lighter) than air and needs 2 to 3 times the flow rate of argon gas to produce sufficient cover to the weld area when welding down-hand. Argon on the other hand is denser (heavier) than air and thus less gas needs to be used in the down-hand position. We often use mixtures of argon and helium to balance the properties of the arc and the shielding cover ability of the gas. Gases for TIG/GTAW need to be of the highest purity (99.99% pure). Careful attention and inspection should be given to the purging of, and the condition of gas hoses, as it is possible that contamination of the shielding gas can be made through a worn, or withered hose. Tungsten electrodes for TIG welding are generally produced by powder forging technology. The electrodes contain other oxides to increase their conductivity, electron emission and also have an effect on the characteristics of the arc. Sizes of tungsten electrodes are available off the shelf between 1.6 - lOmm diameter. Ceramic shields may also be considered as a consumable item, as they are easily broken. The size and shape of ceramic used depends on the type ofjoint design and the diameter of the tungsten. Senior Welding Inspection -Welding Consumables 14.7 Rev 09-09-02 Copyright 2002 TWI Ltd TWIV!lOI. _ THE WELDII\JG II\JSTITUTE Consumables for MIG/lVIAG Welding: Consumables for MIG/MAG welding consist of a wire and gas. The wire specifications used for TIG welding are also used for MIG/MAG welding, as a similar level of quality is required in the wire. The main purpose of the copper coating of steel MIG/MAG welding wire is to maximise current pick-up at the contact tip and reduce the level of coefficient of friction in the liner, with protection against the effects of corrosion being a secondary function. Wires are available that have not been copper coated as the effects of copper flaking in the liner can cause many wire feed problems. These wires may be coated in a graphite compound, which again increases current pick up and reduces friction in the liner. Some wires, including many cored wires are nickel coated. ) Wires are available in sizes from 0.6 - 1.6 mm diameter with finer wires available on a lkg reel though most wires are supplied on a 15kg drum. Common gases and mixtures used for MIG/MAG welding include: Gas Type Process Used for Characteristic Pure Argon MIG Spray or Pulse Welding of Steels and Aluminium alloys Very stable arc with poor penetration and low spatter levels. Pure CO2 MAG Dip Transfer Welding of Steels Good penetration Unstable arc and high levels of spatter. Argon + 5 - 20% CO2 MAG Dip Spray or Pulse Welding of Steels Good penetration with a stable arc and low levels of spatter. Argon + 1-2% O2 MAG Spray or Pulse Welding of Austenitic or Ferritic Stainless Steels Only Active additive gives good fluidity to the molten stainless, and improves toe blend. ( . Senior Welding Inspection -Welding Consumables 14.8 Rev 09-09-02 Copyright 2002 TW[ Ltd TWIV!lOI. _ THE WELDING INSTITUTE Consumables for Sub Arc Welding: Consumable for Submerged Arc SAW consist of an electrode wire and flux. Electrode wires are normally of high quality and for welding C/Mn steels are generally graded on their increasing Carbon and Manganese content, and the level of de-oxidation. Electrode wires for welding other alloy steels are generally graded by chemical composition in a table, in a similar way to MIG and TIG electrode wires. Fluxes for Submerged Arc Welding are graded by their manufacture and composition. There are 2 normal methods of manufacture known as fused and agglomerated. 1) Fused fluxes: Fused fluxes are mixed together and baked at a very high temperature where all the components become fused together. When cooled the resultant mass resembles a sheet of black glass, which is then pulverised into small particles. These particles again resemble small slivers of black glass. They are hard, reflective, irregular shaped, and cannot be crushed in the hand. It is impossible to incorporate certain alloying compounds into the flux such as Ferro manganese, as these would be destroyed in the high temperatures of the manufacturing process. Fused fluxes tend to be of the acidic type, which are fairly tolerant of poor surface conditions, but produce comparatively low quality weld metal in terms of the mechanical properties of tensile strength and toughness. -:'I . ';. ....;:,-:,:.I, .' . Senior Welding Inspection -Welding Consumables 14.9 Rev 09-09-02 Copyright 2002 TWI Ltd TWIVOOI. _ THE WELDING 1t\ISTITUTE Agglomerated tluxes: Agglomerated fluxes on the other hand are a mixture of compounds that are baked at a much lower temperature and are essentially bonded together by bonding agents into small particles. The recognition points of these types of fluxes is easier, as they are dull, generally round granules, that are friable (easily crushed), and can also be very brightly coloured, as colouring agents may be added in manufacture as a method of identification, unlike fused fluxes. Agglomerated fluxes tend to be of the basic type and will produce weld metal that is of much higher quality in terms of strength and toughness. This is at the expense of usability as these fluxes are much less tolerant of poor surface conditions. ) \ , '\>!:. ':". ~ :'i:.... ;:.it:": . ~ : . : It can be seen that the weld metal properties will result from using a particular wire, with a particular flux, in a particular weld sequence and therefore the grading of SAW consumables is given as a function of a wirelflux combination and welding sequence. A typical grade will give values for: 1) Tensile Strength. 2) Elongation %. 2) Toughness (Joules at temp) 3) Toughness testing temperature. The re-use or mixing of used and new flux will depend on the class of work being undertaken and is generally addressed in the application standard. All consumables for SAW (wires and fluxes) should be stored in a dry and humid free atmosphere. Basic fluxes may require baking prior to use, and the manufacturers instructions should be strictly followed. On no account should different types of fluxes be mixed together. Senior Welding Inspection -Welding Consumables 14.10 Rev 09-09-02 Copyright 2002 TWI Ltd ( TWIV!JI. _ Questions QU1. Consumables THE WELDING INSTITUTE Why are basic electrodes used mainly on high strength materials? And what controls are required when using basic electrodes. QU2. What standard is the following electrode classification taken from and briefly discuss each separate part of the electrodes coding E 80 18 M. QU3. Why are cellulose electrodes commonly used for the welding of pressure pipelines? ( QU4. Give a brief description of a fusible insert and state two alternative names give for the insert QU5. What standard is the following electrode classification taken from and discuss each separate part of the electrodes coding. E 42 3 1Ni B 4 2 H1 Senior Welding Inspection - Consumables Sec 14 Copyright 2003 TWI Ltd ( ~ n I l s a I a A I l J D J : l s a a - n o N S l u O I l J a S TWIV!lOI. -' _ THE WELDING INSTITUTE Non-Destructive Testing: NDT, or Non Destructive Testing is used to assess the quality of a component without destroying it. There are many methods ofNDT some of which require a very high level of skill both in application and analysis and therefore NDT operators for these methods require a high degree of training and experience to apply them successfully. The four basic methods ofNDT are: 1) Penetrant testing. 2) Magnetic particle testing. ( /, \ 3) Ultrasonic testing. 4) Radiographic testing. A welding inspector should have a working knowledge of all these methods, their applications, advantages and disadvantages. NDT operators are examined to establish their level of skill, which is dependant on their knowledge and experience, in the same way as welders and welding inspectors are examined and tested to establish their level of skill. Various examination schemes exist for this purpose throughout the world. In the UK the CSWIP and PCN examination schemes are those that are recognised most widely. A good NDT operator has both knowledge and experience, however some of the above (techniques are more reliant on these factors than others. Senior Welding Inspection - Non-Destructive Testing 15.1 Rev 09-09-02 Copyright 2002 TWI Ltd uouoadsuj l U U . l l ~ U ~ d (lAO SI u0!l;}\lS ( TWIV!lOI. _ THE WELDING II\JSTITUTE Penetrant Testing: Basic Procedure: 1) Surface preparation. Component must be thoroughly cleaned. 2) Penetrant application. Penetrant applied and allowed ~ o dwell for a specified time. (Contact time) 3) Removal of excess penetrant. Once the dwell or contact time has elapsed, the excess penetrant is removed by wiping with a clean lint free cloth, finally wipe with a soft paper towel moistened with liquid solvent. (solvent wipe) 1\ ) 4) Application of developer. Penetrant that has been drawn into a crack by capillary action will be drawn out of the defect by reverse capillary action. 5) Inspection. 6) Post cleaning and protection. Method: (Colour contrast, solvent removable) 1) Apply Penetrant. 2) Clean then apply Developer. 3) Result. C I Senior Welding Inspection - Non-Destructive Testing 15.2 Rev 09-09-02 Copyright 2002 T\\"I Ltd TWIV!l!ll. _ THE WELDING INSTITUTE Advantage Disadvantages 1) Low operator skill level. 1) Careful surface preparation required. 2) Applicable to non-ferromagnetic materials. 2) Surface breaking flaws only. 3) Low cost. 3) Not-applicable to porous materials. 4) 5) Simple, cheap and easy to interpret. Portability. 4) 5) No permanent record. Potentially hazardous chemicals. ( Senior Welding Inspection - Non-Destructive Testing 15.3 Rev 09-09-02 Copyright 2002 TWI Ltd TWI VOl. THE WELDING INSTITUTE Senior Welding Inspection - WIS 10 Multi - Choice Question Paper (MSR-SWI-PT-1) Narne: . Answer all questions t. What is the flash point of a solvent based product? a. The minimum temperature at which the solvent will be flammable. b. The temperature at which the vapours given off will spontaneously ignite. l) c. The minimum temperature at which the vapours given off will ignite if source of ~ ignition is introduced. d. The temperature at which the dye in a solvent based penetrant losses its capillary action. 2. What primarily governs the rate (speed) of a penetrant entering a surface breaking discontinuity? a. Viscosity. b. Capillary action. c. Wetting ability. d. How the penetrant is applied. (. 3. Aluminium alloy test specimens that have been tested with penetrant should be thoroughly cleaned after testing because: a. The remaining toxic residue from the test may react with the aluminium causing a fire hazard. b. The acid in the penetrant may cause server corrosion. c. Any remaining alkaline penetrant will leave a red permanent stain on the surface of the aluminium. d. The alkaline content of wet and most emulsifiers could lead to surface pitting, especially in high humidity environments. WIS 10 Qu paper MSR-SWI-PT- issue 3 Date: 28/05/03 1 of 8 TWI VOL THE WELDING INSTITUTE 4. Which penetrant type does not exist? a. Post-emulsifiable fluorescent. b. Post-emulsifiable visible. c. Dual sensitivity penetrant. d. Dry particulate penetrant. 5. Why is it bad practice to prepare soft alloy surfaces with a wire brush prior to testing with a penetrant test method? a. It may cause damage to the part. b. It may close any surface breaking discontinuities. ) c. It may contaminate the developer. d. It is not considered to be bad practice. e. Both a and b are correct. 6. Which of the following NDE method is most likely to detect fatigue cracking? a. Dye penetrant. b. Magnetic particle (a.c. current) c. Ultrasonics. d. It depends on many factors, none of the above can be selected due to the lack of information given. ( -7. Which of the following cleaning methods is generally considered unsuitable for pentrant testing without further processing? a. Vapour degreasing. b. Abrasive blasting. c. Solvent cleaning. d. Steam cleaning. WIS 10 Qu paper MSR-SWI-PT- issue 3 Date: 28/05/03 20f8 TWI VOL THE WELDIr'\IG INSTITUTE 8. Which of the following penetrant properties influences capillary pressure? a. Surface tension. b. Wetting ability. c. Dimension of surface breaking flaw. d. All of the above e. Both a and b. 9. Of the following, which are the most important reasons for filtering the UV-A light used for fluorescent penetrant inspection? -, ) a. To minimise the total light intensity by filtering out the visible light rays. b. To produce better viewing conditions in darkened areas. c. To reduce overall wavelength bands to allow only green fluorescence. d. To prevent personal injury from the more penetrating UV-A rays. 10. How would an ideal emulsification time be established when using post-emulsifiable penetrants? a. By calculation b. By experimentation. c. By measuring the contact angle of the penetrant. d. By determining the viscosity of the emulsifier. ( 11. Generally speaking, which of the following penetrant systems would be the most time consuming to use on the same type of component? a. Solvent based. b. Post-emulsifiable. c. \'Vater-washable. d. All of the above generally would take the same time. WIS 10 Qu paper MSR-SWI-PT- issue 3 Date: 28/05/03 3 of8 TWI VOL THE WELDING INSTITUTE 12. Which of the following may be used to apply penetrant effectively? a. Spray. b. Immersion. c. Brush. d. All of the above 13. Dry developer should be applied: a. So that a heavy coat of developer covers all surfaces to be inspected. b. So that a light dusting covers all surfaces to be inspected. c. With a dry soft brush, e.g. paint brush. d. By dipping. 14. Which of the following is not considered good practice when penetrant testing? a. Applying emulsifier by dipping. b. Applying developer by dipping. c. Removing water based penetrant by water spray. d. Applying emulsifier by brush. 15. The profile of the meniscus of a penetrant would be: a. Concave when compared to the meniscus of a penetrant with lower penetration. b. Convex when compared to the meniscus of a penetrant with lower penetration properties. c. Flat. d. All of the above. 16. Why is it advisable to have an UV-A light source installed at the wash station when using fluorescent penetrant systems? a. So that the drying stage can be eliminated to save time. b. To increase the bleed out speed of the penetrant. c. To check the effectiveness of the wash cycle. d. To check that the test components have been adequately covered with penetrant. WIS 10 Qu paper MSR-SWI-PT- issue 3 Date: 28/05/03 40f8 TWI VOl. THE WELDING INSTITUTE 17. Which factor would be used for determining the penetrants contact time required for the test method to be effective? a. Type of discontinuity sought. b. Shape of component. c. Size of component. d. All of the above. 18. Why is the wetting ability a consideration in the design of penetrants? a. Because it has an effect on capillary action. ) b. Because it has an effect on the penetrants coverage of the components surface. c. Both a and b. d. None of the above. 19. Why are contrast penetrants usually red? a. Red provides high definition. b. Red provides high contrast against a white background. c. Red penetrants are more cost effective than other penetrants of different colours. d. Both a and b. 20. Which of the following statements is false? ( a. Penetrant testing can find most types of surface breaking defects. b. Penetrant testing can under most conditions be just as reliable when testing ferritic materials as MPI. c. Penetrant testing can be used to detect fatigue cracks. d. Penetrant testing is less reliable than radiographic testing when attempting to detect minute surface breaking defects. WIS 10 Qu paper MSR-SWI-PT- issue 3 Date: 28/05/03 50f8 TWI VOL THE WELDING INSTITUTE 21. Which of the following would be the most desirable centre wavelength for the light used in the fluorescent penetrant process. a. 3200A (320nm). b. 3650A (365nm). c. 4650A (465nm). d. 5960A (596nm). 22. A good commercial penetrant should have a: a. Low flash point. b. High flash point. c. Flash point less than 55C. d. A flash point is not relevant. 23. Which of the following materials is often difficult to test with a penetrant test method, due to lack of contrast during final interpretation? a. Ferromagnetic C-Mn steels. b. Aluminium. c. Titanium alloys. d. Cast iron. \.24. If a penetrant system is halogen free it will contain no: a. Sulphur. b. Dye. c. Chlorine. d. Solvent. WIS 10 Qu paper MSR-SWI-PT- issue 3 Date: 28/05/03 601'8 TWI VOl. THE WELDING INSTITUTE 25. Which of the following statements is false regarding the use of cracked panels or comparator blocks? a. To establish a standard size of crack, which can be reproduced as, needed. b. To determine the relative sensitivities of two penetrants. c. To determine if a fluorescent penetrant has lost or reduced its fluorescence. d. To determine the degree or method of cleaning necessary to remove penetrant from the surface without removing it from the crack. 26. Which of the following pentrant test methods is the most common found on site work if used on ferromagnetic pipework or pressure vessels? ) a. Water-washable (Fluorescent). b. Post-emulsifiable (fluorescent). c. Solvent base (contrast) d. Penetrant testing is not used on ferromagnetic materials. 27. When using fluorescent water-washable penetrants, adequate rinsing time is assured by: a. Timing the rinse cycle. b. Scrubbing the part surface. c. Rinsing under UV-A light. ( .. _ d. Using a high-pressure water blast. 28. How long must a penetrant be left on a component before removal? a. As long as possible to ensure good test sensitivity. b. 20 minutes. c. It varies depending on the type of penetrant used, defects to be detected. d. Always between 6 and 20 minutes. WIS to Qu paper MSR-SWI-PT- issue 3 Date: 28/05/03 70f8 TWI. VOl. THE WELDING INSTITUTE 29. Which of the following are unique to a penetrant test report a. Penetrant used, developer used and dwell time. b. Penetrant used, development time and contrast paint. c. Penetrant used, fluorescent particles and drying time. d. Penetrant used, dwell time and drying time. 30. Which of the following surface breaking defects are best detected using DPI? a. Equiaxed defects. b. Planar defects. (c. Linear defects. ) d. All of the above. ( WIS 10 Qu paper MSR-SWI-PT- issue 3 Date: 28/05/03 80f8 u o u a a d s u ] ; } ] J H J U d J H J u t l u W 1 U O ! l J ~ S TWI VOL THE WELDII\JG INSTITUTE 5. Materials which are repelled magnetically are called: a. Paramagnetic. b. Diamagnetic. c. Ferromagnetic. d. Non-magnetic. 6. Which of the following NOT method would be best suited for the detection of surface breaking defects on a austenitic steel weld: a. Dye penetrant. b. Magnetic particle (AC current) ) c. Ultrasonic. d. All of the above. 7. Which of the following are unique to a magnetic particle inspection report: a. Dwell time, magnetic ink, contrast paint b. Couplant, magnetic ink, crack detection unit. c. Magnetic ink, contrast paint, crack detection unit. d. Development time, magnetic ink, contrast paint. 8. An ASME penetrameter may be used in MPI: a. To measure test sensitivity. b. To detect the direction of magnetic flux. (' I c. To measure black/fluorescent ink suspensions. d. Both a and b. 9. What is the curie temperature of a ferromagnetic material? a. The temperature at which it becomes radioactive. b. The temperature at which it losses magnetism. c. The temperature at which it becomes magnetic. d. None of the above. WIS 10 Qu paper MSR-SWI-MT-l issue 3 Date: 28/05//03 20f7 TWI VOL THE WELDING INSTITUTE 10. The build up of a non-relevant indication due to a sharp contour change in the test component is referred to as: a. A defect. b. Furring. c. Magnetic writing. d. None of above. 11. Which of the following are important considerations when carrying out MPI? a. Material type. b. Surface condition c. Type of defects sort after. d. All of the above 12. A 5 turn coil around a part being tested produces: a. A longitudinal field. b. A circular field. c. An intermittent field. d. Both a and b depending on current type. 13. Which of the following MPI test methods may be used for the detection of longitudinal defects on a pipes external surface? a. The threader bar method. ( . b. Rigid coil method. c. Flexible cable wrapped around the pipe making a coil. d. All of the above. 14. Which of the following is considered the most sensitive test method when using MPI. a. Fluorescent particle, wet method. b. Contrast particle, wet method. c. Dry powder method. d. All of the above are considered to be the same sensitivity. WIS 10 Qu paper MSR-SWI-MT-l issue 3 Date: 28/05//03 3 of? TWI uOI. THE WELDING INSTITUTE 15. Which of the following will produce circular magnetism: a. A.C. yokes. b. Passing current through a coil. c. Prods. d. All of the above. 16. Which of the following methods would be best suited for the detection of surface breaking defects on duplex stainless steel? a. Dye penetrant. b. Magnetic particle. ( J c. Radiography. d. The method used depends on the procedure requirements. 17. In accordance with the relevant standard, what is the specific percentage of fluorescent particles to the base: a. 1.25%. b. 0.8 to 3.5%. c. 0.1 to 0.3%. d. 0.3 to 0.8%. 18. When demagnetising a component in situ in a structure that cannot be easily removed from the parent structure, which of the following techniques is normally used? a. Stroking the component in the same direction using an AC yoke. b. Stroking the component in different directions using a DC Yoke. c. Stroking the component in the different directions using an AC. yoke. d. Stroking the component in same direction using a DC Yoke. 19. When using AC. electromagnets, the strength of the magnet shall be assessed by measuring the lifting power. The lifting power shall be equivalent to or not less than: a. 4.5 kg for poll spacing of 300 mm. b. 2.25 kg for poll spacing of 300 rnrn. c. 18 kg for poll spacing greater than 75 mm. d. The sensitivity of AC. electromagnets is assessed using penetrameters. WIS 10 Qu paper MSR-SWI"MT-l issue 3 Date: 28/05//03 40f7 TWI VOL THE WELDING INSTITUTE 20. A copper bar is placed inside a 5 mm coil, the amperage required to magnetically saturate it will be: a. In the range of 500 to 100 amps. b. Generally less than steel. c. Not enough information given to give a correct value. d. It is not possible to magnetically saturate a copper bar. 21. Which of the following is the most common method for demagnetising a component? a. AC. b. DC straight polarity. ( )c. HW DC d. The above currents cannot be used for dernagnetising. 2?-. What is coercive force? a. The magnetic force required to magnetically saturate a part. b. The magnetic force required to magnetise a part. c. The reverse magnetic force required to demagnetise a part. d. The reverse magnetic force required to cause the poles of a magnet to rotate 180. 23. How is the strength of a permanent magnet usually measured? a. By lifting a specified weight of any material. ( b. By lifting a specified weight of steel. c. By ampere-turns. d. By comparing it against the readings of a magnetometer. e. Both a and b. 24. What sort of magnetic field is produced when using a permanent magnet? . a. Longitudinal. b. Circular. c. Reversing poles. d. None of the above. WS 10 Qu paper MSR-SWI-MT-l issue 3 Date: 28/051103 5 on TWI VOL THE WELDING INSTITUTE 25. When considering AC. yokes, which of the following is applicable? a. Can be used for the detection of both surface and slight sub-surface defects. b. No power source required. c. Must be used with at least a 400 mm pole spacing to ensure adequate coverage. d. None of the above. 26. An example of an instrument use to determine the direction of a magnetic field is called a: a. Burmah-Castrol strip. -, b. ASME penetrameter. ) c. Berthold penetrameter. d. All of the above. e. None of the above. 27. Why is H.W.D.C. often used with dry powders, as opposed to D.C.? a. Because dry powders are not attracted to leakage fields caused by direct current. b. Because the powder retains a residual field with direct current. c. Because greater powder mobility is achieved on the test surface. d. A.C. of H.W.D.C. is not used with dry powders. 28. When checking a weld for defects with a permanent magnet, the magnet should be ) placed: a. Transversely over the weld to look for longitudinal defects. b. Longitudinal with the weld to look for transverse defects. c. At 45to the weld to look for both transverse and longitudinal defects at the same time. d. Normally in positions A and B if specification does not state otherwise. 29. Which of the following statements is always true? a. MPI is better than dye penetrant testing. b. Fluorescent inks used in MPI are always green/yellow. c. MPI'can only be used on ferromagnetic materials. d. All of the above. WIS 10 Qu paper MSR-SWI-MT-1 issue: 3 Date: 28/05//03 60f7 TWI VOL THE WELDING INSTITUTE 30. Which of the following surface breaking defects are best detected using MPI? a. Equiaxed defects. b. Planar defects. c. All types of entrapped gas defects. d. All surface defects are detected using MPI. WIS 10 Qu paper MSR-SWI-MT-l issue 3 Date: 28/05//03 70f7 u o u o o d s u j J ! U O S 1 U n n 1 U O n ; ) ~ S TWIVOI. _ THE WELDING INSTITUTE Magnetic Particle Testing: Basic Procedure: l) Test method for the detection of surface and sub-surface defects in ferromagnetic materials. 2) Magnetic field induced in component. (Permanent magnet, electromagnet (Y6 Yoke) or current flow (Prods). 3) Defects disrupt the magnetic flux. 4) Defects revealed by applying ferromagnetic particles. (Background contrast paint may be required) Method: 1) Apply contrast paint. 2) Apply magnet & ink. 3) Result. ( . ? ' < " ; , ~ - ' I , lVi';--'" , Advantage Disadvantages 1) Pre-cleaning not as critical as with DPL 1) Ferromagnetic materials only. 2) Will detect some sub-surface defects. 2) Demagnetisation may be required. 3) Relatively low cost. 3) Direct current flow may produce Arc strikes. 4) Simple equipment. 4) No permanent record. 5) Possible to inspect through thin coatings. 5) Required to test in 2 directions. Senior Welding Inspection - Non-Destructive Testing 15.4 Rev 09-09-02 Copyright 2002 TWI Ltd TWI VOl. THE WELDING INSTITUTE Senior Welding Inspection - WIS 10 Multi - Choice Question Paper (MSR-SWI-MT-1) Narne: . Answer all questions 1. A desirable property of magnetic particles used for the inspection medium for either the dry or wet method, is that they: a. Posses high permeability. b. Posses high retentively. c. Must be non-magnetic d. None of the above 2. The accumulation of particles held at a leakage field on a components surface is called: a. A discontinuity. b. A defect. c. An indication. d. Magnetic writing 3. Which of the following methods my be considered for the magnetic particle inspection of a large casting, both for surface and subsurface defects: a. A.C. yolk b. Permanent magnet. c. D.C. prods. d. All of the above. 4. A magnetising force of one oersted produces: a. 1 gauss. b. 1 Tesla. c. 1 Weber. d. 104 Tesla. WIS 10 Qu paper MSR-SWI-MT-l issue 3 Date: 28/05//03 1 on TWI VOL THE WELDING INSTITUTE 4. Which of the following probes under most circumstances would be best suited for the detection of plate laminations, on thin plate: a. 1.5 MHz twin shear wave, 45. b. 4 MHz single shear wave, 60c. 4 MHz twin compression wave. d. 1.5 MHz single compression wave. 5. The number of complete waves which pass a give point in a give period of time (usually one second) is referred to as: ) a. Amplitude of wave motion. b. Pulse length of wave motion. c. Frequency of wave motion. d. Wave length of wave motion. 6. Which of the following are unique to an ultrasonic test report. a. Type of couplant, scanning pattern and attenuation checks. b. Surface preparation, scanning pattern and type of couplant used. c. Pre-cleaning method, probes used and couplant used. d. Calibration, probes used and test sensitivity. (- 7. 25 million cycles per second can also be stated as: a. 25 kilohertz. b. 250 kilohertz. c. 25 megahertz. d. 2.5 megahertz. WIS 10 Qu paper MSR-SWI-UT-l issue 3 Date: 28/06/03 20f8 TWI VOL THE WELDING INSTITUTE 8. In A scan presentation, the amplitude of the vertical indications on the screen represents the: a. Amount of ultrasonic energy returning back to the probe. b. Distance travelled by the probe. c. Thickness of the material. d. Elapsed time since the ultrasonic pulse was generated. 9. In A scan presentation, the horizontal base line represents the: a. The amount of reflected ultrasonic energy b. Distance travelled by the probe. ( \ c. Elapsed time or distance. d. None of the above. 10. Which of the following are important considerations for the ultrasonic examination of a fusion butt weld a. Material thickness. b. Surface condition. c. Joint configuration. d. Both a and b. e. All of the above. ( 11. Which of the following probe combinations would you expect to be used on a carbon steel weld joining two plates 12mm thick (cap left as welded)? a. 45single crystal shear wave, 85single crystal shear wave, 60single crystal shear wave and a single crystalcompression. b. 45single crystal shear wave, 70single crystal shear wave, 60single crystal shear wave and a twin crystal compression. c. 0single crystal shear wave, 45single crystal compression, 60single crystal compression and a combined double longitudinal wave. d. 45twin crystal transverse wave, 60single crystal transverse wave, 70twin crystal transverse wave and a 00 twin crystal compression. WIS 10 Qu paper MSR-SWI-UT-l issue 3 Date: 28/06/03 30r8 TWI VOL THE WELDING INSTITUTE 12. The angle of incidence is: a. Greater than the angle of reflection. b. Less than the angle of reflection. c. Equal to the angle of reflection. d. Not related to the angle of reflection. 13. The gradual loss of sonic energy as the ultrasonic vibrations travel through the material is referred to as: a. Reflection. J b. Refraction. c. Attenuation d. None of the above. 14. The phenomenon whereby an ultrasonic wave changes direction when the wave crosses a boundary between materials with different velocities is called: a. Refraction. b. Reflection. c. Penetration. d. Rarefaction. ( \ 15. How many echoes would be present on the CRT if a V1 (A2) block is used to calibrate a normal probe 0 to 50 mm, on the 25-mm dimension? a. 2. b. 4. c. 8. d. As many echoes as possible to ensure good test sensitivity. WIS 10 Qu paper MSR-SWI-UT-l issue 3 Date: 28/06/03 40f8 TWI VOL THE WELDING INSTITUTE 16. The 1.5 mm hole in a V1 (A2) test block may be used to: a. Determine the resolution of the probe. b. Determine the pulse width of the probe. c. Set test sensitivity. d. All of the above. 17. An echo is set at full screen height on' a vertically calibrated CRT, then the sound is reduced by 6dB: a. The echo will drop by 50% of its initial height. b. The echo will drop to 20% of its initial height. c. The echo under most circumstance disappears off the screen. d. The echo will drop to 10% of its initial height. 18. What is the thickness of a V2 (A4) test block? a. 12.5 mm. b. 20 mm. c. 25 mm. d. Both a and b e. All of the above. \, 19. What does 23 mm of Perspex represent in a V1 (A2) block when using compression probes: a. 100 mm of steel. b. 23 mm of steel. c. 50 mm of steel. d. 200 mm of steel. WIS 10 Qu paper MSR-SWI-UT-l issue 3 Date: 28/06/03 50[8 TWI VOL THE WELDING INSTITUTE 20. Which of the following NDE methods is best to use when testing ferromagnetic materials? a. Magnetic particle. b. Radiography. c. Ultrasonic. d. All of the above may be used, it depends on many factors. 21. Which of the following statements are true? a. The higher the probe frequency the faster the sound travels through a given ! J material. b. The higher the probe frequency the slower the sound travels through a given material. c. The higher the probe frequency the more sound is lost due to attenuation. d. The higher the probe frequency less sound is lost through attenuation. 22. Which of the following wave types travels the fastest in steel a. Longitudinal. b. Shear. c. All wave types travel at the same velocity in steel. d. Longitudinal and shear waves will not travel in steel. ( , 23. Which of the following single crystal probes would contain the thinnest crystal? a. 2.5 MHz compression probe. b. 5 MHz compression probe. c. 5 MHz angle probe. d. 10 MHz angle probe. WIS 10 Qu paper MSR-SWI-UT-1 issue 3 Date: 28/06/03 6 of8 TWI VOl. THE WELDING INSTITUTE 24. Which of the following transducers produces the least beam spread in the far zone? a. 1 MHz, 10 mm diameter crystal. b. 5 MHz, 25mm diameter crystal. c. 2 MHz, 25 rnm diameter crystal. d. 5 MHz, 10 mm diameter crystal. 25. Sound attenuation in a material is due to: a. Absorption and scattering. b. Reflection and refraction. c. Density and velocity. d. Density and elasticity. 26. Which of the following probes would be best suited for the detection of near surface plate lamination on 12mm thick plate? a. 5 MHz, twin compression probe. b. 2.5 Mhz, twin compression probe. c. 5 Mhz single 0probe. d. 5 Mhz twin 60probe. 27. Calculate the wavelength for a frequency of 4.25 MHz at a velocity of 5800 meters (per second: a. 0.73 mm. b. 1.36 mm. c. 0.073 mm. d.0.136mm. WIS 10 Qu paper MSR-SWI-UT-l issue 3 Date: 28/06/03 70f8 TWI VOL THE WELDING INSTITUTE 28. Which of the following scan types produces a plan view of any defective areas under test? a. A-scan. b. B-scan. c. C-scan. d. D-scan. 29. When testing a specimen, using a compression probe, a decrease in a wave frequency (obtained by changing the probe) will result in: a. An increase in sound velocity. b. A decrease in sound velocity. c. No change in velocity. d. No change in wavelength. 30. Which of the following is acceptable test sensitivity when using a compression probe? a. 2nd BWE 80% FSH at test depth. b. 1st BWE 100% FSH at any depth. c. Echo from 1.5 rnm hole 100% FSH (V1 test block). d. Echo from 5 mm hole 80% FSH (V2 test block). ( . WIS LaQu paper MSR-SWI-UT-l issue 3 Date: 28/06/03 80f8 ) ( ) () ..-.--.... _------_._---.._... _.-----_... _... _..-../" ~ .: Image Quality Indicators ~ ~ Ifhickness (mm) 0.050 0.063 0.08 0.10 0.125 0.15 0.16 0.20 0.25 0.30 0.32 0.35 0040 0.50 0.60 0.63 0.75 . 0.80 0.90 1.00 1.20 1.25 1.50 1.60 1.80 2.00 2.50 3.00 3.20 4.00 5.00 6.30 1-6 6 5 4 3 2 1 STEP 7-12 6 5 4 3 2 1 8S 3971 13-18 6 5 4 3 2 1 4-10 7 6 5 4 3 2 1 -._------_. 'WIRE 9-15 15-21 7 6 5 4 3 2 1 7 6 5 4 3 2 1 DIN 54 109 WIRE (DIN 62) 1-7 7 6 5 4 3 2 1 6-12 7 6 5 4 3 2 1 10-16 7 6 5 4 3 2 1 H 1 6 5 4 3 2 1 8S EN 462-2 STEP/HOLE H5 6 5 4 3 2 1 H9 6 5 4 3 2 1 H 13 6 5 4 3 2 1 --------_... _..__... W1 7 6 5 4 3 2 1 8S EN 462-1 WIRE W6 W10 W 13 7 6 5 7 4 6 3 2 4 5 1 7 3 2 5 6 1 4 3 2 1 , - -- . -_. TWIV!7!7I. --__THE WELDING INSTITUTE Annex B (nonnative) Minimum image quality values Single-wall technique; rQ{ on source side Table 13.2 Steplhole IQI (Illal.ity cluss A Nomlrial Utickncss t IQI "llluc l) Jnrn I'fa,Me B.1 \\fire IQI [lImge lllU1Jity class A Numinal thlekncss t. 111m IQI Up to 1,2 W 18 above 1,2 to 2,0 \V 17 above 2,0 to ;'l,5 \\1 16 above 3,5 to 5,0 \V 15 above 5,0 to 7 W 14 above 7 to 10 'ltY 13 above 10 to It') W 12 above lG to 25 Wll above 25 to 32 WlO above 32 to 40 W9 above 40 to 55 \V8 above 55 to 85 W7 above 85 to 160 WI) above 150 to 250 'W5 above 2fJO W4 1) When using Ir W2 sources, IQI values WO(1iC than the values can be accepted as fQUQWS; 10rmn to 24 111m: up to two values; abovo 24 10m lQ :30mm: up to one V'.lIU{l. 'fuble n.is Step/hole IQI llIlllge tlulllit)' C!l...., 11 Penetrated In lUllIIQI valuel ) Iup to 2,5 above 2,5 to 0,5 above 5,5 to 9,5 above 9,5 to 15 above 15 to 24 above 2-1 to "0 above 40 to 60 above 60 to 80 HZ 113 H4 H5 116 Hi HS UO I) \\11(:11 using Ir W:! sources, IQI worse than ULI! listt1(! ''nhw,:'l C"MI be ;lcce[>lc,l ,L'; followa; &15 HUll to U"S mm; up to two values; :t.hu\.'." fJ/", nuu to :!l hUll.: UJllU unc \,Lhw.....up to 2,0 above 2,0 to 3,5 above 3,5 to 6 above 6 10 10 above 10 to 15 above 15 to 24 above 2'1 to 30 above 30 to 40 above 40 to 60 above 60 to 100 above 100 to 150 above 150 to 200 above 200 to 250 above 250 to 320 . above 320 to 400 ahove 400 110 H4 H5 no H7 118 H9 HID lIll H 12II 13 H 14 II 15 H 16 1117 H 18 !) When using Ir Hl2 sources, IQI values W01SC UI,I.(I 1I11: listed values can be accepted as fOUI)\\'!;: 10rom t.) 24 nun: UJl to two values; above 24 nun to 30 mm: up to one value. Single-wall technique; IQI on source side \ 1able B.3 Wire IQI Image quality class B Nominal thickne.'iS t mm IQI value I) Up to 1,5 WIg above 1,5 to 2,5 WI8 above 2,5 to 4 V.[17 above 4 to 6 W16 above 600 8 W 15 above 8 Lo 12 W 14 above 12 to 20 W 13 above 20 to 30 W 12 above 30 to 35 Wll above 35 to 45_ W 10 above 45 to 65 W9 above 65 to 120 WB above 120 to 200 W7 above 2.00 to 350 W6 above 350 W5 1) When using Ir 192 sources, IQI values worse than UIC li>.1.ed Vlllues can be accepted as (ollom;: 12' mm to 40 miu; up to one value. Senior Welding Inspection - Non-Destructive Testing 15,1 Rev 09-09Copyright 2002 TWr Ltd I TWIV!J[lI. _ THE WELDING INSTITUTE r TabLe R.l' Step/hole IQI ITable BA ror . l mugc qual it.y d.1.S.Q B Nominal [ mm [Q[ vn.Iue 1) Up to 2,5 1I2 above 2,5 tn 4 H3 above '1 to g H4 above 15% silicon. In the correct application, a brazed, or bronze welded joint may be stronger than a fusionwelded joint, as the surface area of bonding is much higher, as shown below; Area of fusion welds .' . Area of braze weld Fusion welded T joint Brazed T joint Senior Welding Inspection - Oxy - Fuel Gas Welding /CuttiI1l:9.3 Rev 09-09-02 Copyright 2002 TWI Ltd TWII[J[JI. _ THE WELDING INSTITUTE Oxy Fuel Gas Cutting: lu oxy-fuel gas cutting we do not need to melt the steel, but simply heat it until il reaches its ignition temperature. (Appears bright cherry red) At this temperature the iron will react with pure oxygen to produce an exothermic chemical reaction, the product being FE3 0 4 or magnetic oxide of iron. A jet of pure oxygen is sent from an orifice in the centre of the nozzle that reacts with the iron at its ignition temperature. The velocity of the oxygen jet removes the magnetic iron oxide from the cut face (The kerf), As we do not require to reach the high temperatures needed for fusion welding, we do not need to use acetylene gas. Therefore propane, butane and other cheaper gases may be used for oxy-fuel gas cutting. Temperature reached during the chemical exothermic reaction of oxygen with iron is sufficient to melt most metals, though a restriction of oxy-fuel gas cutting is that it cannot be used successfully in its conventional form to cut metals with high melting point oxides (i.e. Stainless Steels). By the addition of an iron " \-/) powder injection system, the iron-oxygen reaction can be produced ahead of the materials surface by the exothermic reaction of the heated iron powder within the oxygen jet. The thickness of steel that may be cut using the Oxy-Fuel gas cutting method is solely dependant on the nozzle size and gas pressure available. The oxy-fuel gas cutting system may be simply mechanised and used to cut plates (Photograph 1) and preparations on pipe to be welded. (Photographs 2.3. & 4). It must be recognised that the cut face may be hardened up to a depth of 3mm, therefore dressing is normally required to remove this hardened region as well as removing oxide. The main inspection points of conventional oxy fuel gas cutting will include: SAFETY POINTS + 1) Cutting nozzle type, and size. 2) Nozzle distance from work. 3) Cutting oxygen pressure. 4) Speed of travel of the cutting head. S) Angle of cut. 6) Fuel gas type and flame setting. \, 7) Pre-heat, if specified. 8) The condition of the kerf. If all the above parameters are set correctly then the cut face or kerf should appear as in photograph 4 below -;t.. ":", ,,,"X',,,_ '". ' I Main oxygen cutting jet ,:{f. ';i Fuel gas & oxygen Fe304 Jet Senior Welding Inspection - Oxy - Fuel Gas Welding /Cuttirt9.4 Rev 09-09-02 Copyright 2002 TW[ Ltd () TWIV!lOI. _ THE WELDING INSTITUTE Questions QU1. Oxy Fuel Gas Welding and Cutting What is the principal limitation of oxy/fuel gas cutting? lJ QU2. Give three flame types and their respective applications QU3. What is the flame temperature of acetylene in Oxygen? \ QU5. Why is preheat some times required prior to oxy-gas cutting. QU6. Give any major limitations of oxy-acetylene welding Senior Welding Inspection - QU Oxy Fuel Gas Welding & Cutting Sec 19 Copyright 2003 TWI Ltd . ) B W S B l d p U B O Z TWIVOI. _ THE WELDING INSTITUTE Arc and Plasma Cutting Processes: All thermal cutting processes that we use in fabrication must satisfy 2 major functions to be successfully used as a cutting/gouging process. 1)A high temperature. (Capable of melting the materials being cut) 2) A high Velocity. (Capable of removing the molten materials in the cut) In oxy-fuel gas cutting described in the previous section the temperature is achieved by the exothermic reaction of iron at its ignition temperature and pure oxygen. The product of iron oxide is removed from the cut edge, or kerf by the velocity of the oxygen gas jet. Plasma Cutting: Plasma cutting utilises the temperatures reached from the production of the plasmas from certain types of gases. Nitrogen gas plasma can reach a temperature of over 20,000C but temperature of air plasma is much lower. Air however is freely available and therefore cheaper and can be compressed by a compressor in the equipment, but is restricted in the depth of cut attainable. ~ - ) The velocity for plasma cutting is produced by the expansion of the plasma in the torch chamber, which is then forced through a constricting orifice at the torch head, producing the velocity required. There are 2 different types of the plasma cutting process, which are: 1) 2) Transferred arc. (Used for cutting conductive materials) Non-transferred arc. (Used for cutting non-conductive materials) Air Plasma Cutting Equipment ( ----, Power source Shielding gas-.. ~ -.-.J Senior Welding Inspection - Arc and Plasma Cutting 20.1 Rev 09-09-02 Copyright 2002 TWI Ltd. TWIVlJOI. _ THE WELDING INSTITUTE Arc Cutting & Gouging: We can use the temperature attained by an electric arc in cutting processes to reach the temperatures required to melt the metal or alloy to be cut. There are 3 types of process that are generally used, the main differences being in the consumables and the gas used in producing the velocity required. 1) Conventional cutting/gouging electrodes. 2) Oxy-Arc cutting/gouging. 3) Arc-Air cutting/gouging. Conventional cutting/gouging electrodes: (,J In conventional arc gouging there is no requirement for any additional equipment other than that required for MMNSMAW welding. The consumables consist of a light alloy central core wire, which is mainly to give rigidity, and a heavy flux coating, which provides elements that produce arc energy. The arc is struck in a conventional way to MMA welding, however the arc melts the base material, which is then pushed away by using a pushing action with the electrode. The process generates a great volume of welding fume and is not very effective, but is suitable for the occasional need to remove old welds, or gouge grooves in base metal. Oxy-Arc cutting/gouging: In oxy-arc cutting we require a special type of electrode holder. The consumables are tubular in section and are coated with a very light flux coating. The electrode is located in the special electrode holder to which is attached a power cable and gas hose. The power cable is attached to the power source and the gas hose is attached to a source of compressed oxygen. The arc is struck and the compressed oxygen may be activated at the torch head. The heat of the electric arc will melt the base metal or alloy and the velocity to remove it is provided by the compressed oxygen. When cutting ferritic alloys, a similar effect can be produced to the exothermic reaction found when using conventional oxy-fuel gas cutting. This process is generally used for decommissioning/scrapping plant as the cut surface is generally not consistent. Arc-Air cutting/gouging: Arc-air cutting is the most commonly used method of arc cutting/gouging and is used extensively for gouging old welds and removing materials. The consumable is a copper coated carbon electrode. The gas used is of course compressed air. The' process is basically a "melt and blow process" in that no exothermic reaction is involved The main disadvantages include the high level of high-pitched noise produced and the volume of fumes generated. The cut face will require dressing due to potential carbon pick up and the rapid heating/ cooling cycle involved. A major safety inspection point in the use of all arc processes is that correct ear protection is in use and also that an efficient fully isolated breathing supply system is also being used. Senior Welding Inspection - Arc and Plasma Cutting Rev 09-09-0220.2 Copyright 2002 TWI Ltd. TWIV!lOI. _ THE WELDII\JG II\JSTITUTE 1) \J Light flux coating Cross Section Tubular steel core wire containing compressed oxygen Oxy-Arc Gouging. Gouged metal 2) Arc-Air Gouging. Jet of compressed air supplied from holes in the electrode holder ----. 0 .'.' ... ;., Copper covered carbon electrode Senior Welding Inspection - Arc and Plasma Cutting 20.3 Rev 09-09-02 Copyright 2002 TWI Ltd. TWIV!7/lI. _ THE WELDING INSTITUTE Questions QU1. QU2. QU3. QU4. QU5. Arc and Plasma Cutting What are the two types of the plasma cutting process? State what each cutting process is used for. Name three types of arc cutting and gouging processes. What is the main application area for arc gouging, with regards to welding related activities? At what temperature is reached during Nitrogen gas plasma cutting? State at least one advantage of plasma arc cutting over conventional thermal cutting (oxy-fuel gas). . Senior Welding Inspection - QU Arc and Plasma cutting Sec 20 Copyright 2003 TWI Ltd TWIV!lOI. _ THE WELDING INSTITUTE Welding Safety: As a respected officer, it is a duty of a welding inspector to ensure that safe working practices are strictly followed. Safety in welding can be divided into several areas, some of which are as follows: 1) Welding/cutting process safety. 2) Electrical safety. 3) Welding fumes & gases. (Use & storage of gases.) 4) Safe use of lifting equipment. ( ) 5) Safe use of hand tools and grinding machines. 6) General welding safety awareness. 1) \Velding/cutting process safety: Consideration should be given to safety when using gas, or arc cutting systems by: a) Removing any combustible materials from the area. b) Checking all containers to be cut or welded are fume free. (Permits to work etc.) c) Providing ventilation and extraction where required. l d) Ensuring good gas safety is being practised. e) Keeping oil and grease away from oxygen. f) Appropriate PPE is worn at all times Senior Welding Inspection - Welding Related Safety 21.1 Rev 09-09-02 Copyright 2002 TWI Ltd TWIrllOI. _ ~ ) (- \ THE WELDING INSTITUTE 2) Electrical Safety: Safe working with electrical power is essential. Ensure that insulation is used where required and that cables and connections are in good condition. Be especially vigilant in wet or damp conditions. Low voltage supply (110 v) must be used where appropriate for all power tools etc. All electrical equipment must be regularly tested and identified as such accordingly. 3) Gases & Fume Safety: The danger of exposure to dangerous fumes and gases in welding cannot be over emphasised. Exposure to these welding fumes and gases may come from electrodes, plating, base metals and gases used in and produced during the welding process. Dangerous gases that may be produced during the welding process include ozone, nitrous oxides, and phosgene (caused by the breakdown of Trichloroethlylene based degreasing agents in arc light); all of which are extremely poisonous and will result in death when over-exposure occurs. Other gases used in welding can also cause problems by displacing air, or reducing the oxygen content. Most gases are stored under high pressure, and therefore the greatest care should be exercised in the storage and use of such gases. All gases should be treated with respect and are considered a major hazard area in welding safety. Cadmium, chromium, and other metallic fumes are extremely toxic and again will result in death if over-exposure results. Know the effects of a coating fume and always use correct extraction or breathing systems, which are essential items in safe welding practice. If in doubt stop the work! Until a health and safety officer takes full responsibility. 4) Lifting Equipment: It is essential that correct lifting practices are used for slinging and that strops of the correct load rating are used for lifts. All lifting equipment is subject to regular inspection according to national regulations in the country concerned. In the UK this is governed by the HSE under the LOLER requirements, which are mandatory for all operations within the UK. Cutting comers is an extremely dangerous practice when lifting and often leads to fatalities. (Never stand beneath a load) Senior Welding Inspection - Welding Related Safety Rev 09-09-02 21.2 Copyright 2002 TWI Ltd TWIV!lul. _ THE WELDING INSTITUTE 5) Hand tools and grinding machines: Hand tools should always be in a sate and serviceable condition (grinding machines should have wheels changed by an approved person) and should always be used in a safe and correct manner. Use cutting discs for cutting, and grinding discs for grinding only. 6) General: Accidents do not just happen, but are usually attributable to someone's neglect, or ignorance of a hazard. Be aware of the hazards in any welding job, and always minimise the risk. Always refer to your safety advisor if any doubt exists. ~ . Senior Welding Inspection - Welding Related Safety 21.3 Rev 09-09-02 Copyright 2002 TWI Ltd TWIV!lOI. _ THE WELDING INSTITUTE Exercise: Complete the table below, by inserting any specific safety issues that will need to be considered: l) ~ Material Process Other Information Issues to be considered Stainless Steel MAG Vessel contained explosive & toxic compounds Stainless Steel Silver braze Cd braze alloy Steel Gas Welding Galvanized Steel MMA Cadmium plated Steel TIG Degreased with Trichloroethylene, but still damp Steel Arc Air Gouging Confined space Steel Overhead Lift 500 tonnes Steel MMA Site work Wet conditions Stainless Steel TIG Confined space In an area containing combustibles I . Steel Oxy- Fuel cutting Senior Welding lnspection - Welding Related Safety 21.4 Rev 09-09-02 Copyright 2002 TW[ Ltd ) TWIV!l!ll. _ THE WELDING INSTITUTE Questions Welding Safety QU1. How can the welder protect himself against UVA light: QU2. Occasional accidental exposure to the eye can produce an extremely painful condition known as: cJ QU3. To reduce the possibility of electric shock, a correctly wired welding circuit should contain three leads these leads are: a). b). c). QU4. Arc welding produce fumes and dust particles, state the precautions a welder must take to protect against fumes and dust particles: ( QU5 When welding on items, which have been degreased particular precautions, must be made, why? Senior Welding Inspection - QU Arc Welding Safety Sec 21 Copyright 2003 TWI Ltd ---- ------- ---------) s l a a l S J O A n n q u P l a M . a q l . z z U O n J a s TWIIll!ll. _ THE WELDING INSTITUTE The Weldabilitv of Steels: 0/ In general, the term weldability of materials can be defined as: "The ability of a material to be welded by most of the common welding processes, and retain the properties for which it has been designed" The weldability of steels can involve many factors depending on the type of steel, the process and the mechanical properties required. Welding engineers involved only with the welding of C/Mn structural steel could probably define weldability as carbon equivalent, however this is a narrow application of the term. Poor weldability generally results in the occurrence of some sort of cracking problem, though most steels have a degree of weldability. When considering any type of weld cracking mechanism, three elements must be present for it's occurrence: 1) Stress. 2) Restraint. 3) Susceptible microstructure. 1. Residual stress is always present in weldments, through local expansion & contraction. 2. Restraint may be a local restriction, or through plates being welded to others. 3. The microstructure is often made susceptible to cracking by the process of welding. The types of cracking mechanism prevalent in steels in which the CSWIP 3.1 Welding Inspector should have some knowledge are: ( 1. Hydrogen induced HAZ cracking. (elMn steels) 2. Hydrogen induced weld metal cracking. (HSLA steels) 3. Solidification cracking. (All steels) 4. Lamellar tearing. (All steels) 5. Inter-crystalline corrosion. (Stainless steels) Senior Welding Inspection - The Weldability of Steels 22.1 Rev 09-09-02 Copyright 2002 TW[ Ltd TWIVlJOI. _ THE WELDING INSTITUTE Definitions: To compliment this section it is important to understand the following terms. Solubility: Maximum Solubility: Steel: Plain Carbon Steels: Low Carbon Steel: lVIedium Carbon Steel: High Carbon Steels: Low Alloy Steels: High Alloy Steels: Ferrite: Austenite: Martensite: Diffusion: To be able to dissolve one substance in another, like sugar in tea. The maximum % of a substance that can be dissolved in another. An alloy of the iron with the non-metal carbon. (0.01 - 1.4% C) Stee