Welding practice

Welding Practice Welding Practice Brian D Smith Tech Eng, Tech Weldl, MITO, CGIA Registered Welding Education Technician Acknowledgements The author expresses his thanks to the following organizations supply of information and illustrations: for their support and their Air Products PLC Arc Speed Services, Derbyshire Arco Ltd: safety signs (colour plates) The British Oxygen Company (BOC), Guildford and Derby: gas cylinder identification chart (colour plates and Figure 1.1) The British Standards Institute, Milton Keynes CENTRA, Manchester Chubb Fire Ltd: fire extinguishers (colour plates) East Midlands Further Education Council, Nottingham ESAB Group (UK) Ltd, Waltham Cross Gas Control Equipment, Skelmerdale The Health and Safety Executive Migatronic Welding Equipment Ltd, Loughborough C S Milne Ltd, Leicester Trueweld, Derby The Welding Institute, Abington, Cambridge Special thanks to Mr Len Gourd, BSe FWeldI, for his continuing support Every possible effort has been made to trace copyright holders Any rights not acknowledged here will be acknowledged in subsequent printings if notice is given to the publisher Butterworth-Heinemann An imprint of Elsevier Science Linacre House, Jordan Hill, Oxford 0X2 8DP 225 Wildwood Avenue, Woburn MA 01801-2041 First published 1996 Transferred to digital printing 2002 Copyright © 1996, Brian D Smith All rights reserved The right of Brian D Smith to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 Nopartofthispublicationmaybereproducedinanymaterialfonn (includingphotocopyingorstoringinanymedium byelectronicmeansand whetheror not transientlyor incidentallytosomeother use ofthispublication)without the writtenpermissionofthecopyrightholderexceptinaccordancewiththeprovisionsoftheCopyright,Designsand Patents Act1988or under the termsofa licenceissuedby theCopyrightLicensingAgencyLtd,90TottenhamCourtRoad,London EnglandWIT4LP.Applicationsforthecopyrightholder'swrittenpermissionto reproduceanypart ofthispublication shouldbeaddressedtothepublisher British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 340 61406 For information on all Butterworth-Heinemann visit our website at www.bh.com publications Printed and bound in Great Britain by Antony Rowe Ltd, Eastbourne Contents Underpinning information Arc welding safety Welding terminology Weld symbols (BS499 part 1980) Types of joints Features of a welded joint Distortion control Weld defects Inspection Welding procedure and welder qualifications Manual metal arc welding 29 Manual metal arc welding equipment Striking the arc Stop/starts Electrode angles Weaving Electrode classification Electrode size and current capacity Electrode coatings Welding positions for plates Positional welding Plate positions Summary Metal arc gas-shielded welding MAGS welding process Choice of shielding gas Electrode wires Wire feed system Metal transfer modes The self-adjusting arc Contact tip, nozzle settings Electrode extension Burn back Current and voltage settings British Standards for wires and fillers Features of the process Weaving Flux-cored arc welding Self-shielded flux-cored arc welding 47 vi CONTENTS Gas-shielded flux-cored arc welding MAGS positional welding Tungsten arc gas-shielded welding 61 TAGS welding equipment Equipment selection Surge injector DC suppressor Contactor Arc striking Electrode types and diameters Gas nozzles Gas lens Torches Shielding gas AC/DC non-consumable electrode arcs Oxyacetylene welding and cutting Standard welding/cutting equipment Safety precautions to be observed when using oxygen and acetylene cylinders Regulators Safety Flashback arrestors Hoses (BSS120) Purging Hose connectors Hose check valves '0' clips Welding torches Nozzles Equipment assembly (welding and cutting) Lighting-up procedure Flame settings Extinguishing the flame Welding techniques High- and low-pressure systems Filter glasses Plate edge preparation Oxyacetylene positional welding Bronze welding Fluxes Oxyfuel gas cutting Torches Fuel gases 77 CONTENTS Nozzles Hand cutting Quality of cut Supporting materials Cutting techniques Questions 99 Health and safety MMA welding MAGS welding TAGS welding Gas welding and cutting Answers to questions Appendix 1: Welding processes Welding processes and their numerical 107 representation Appendix 2: Useful information 109 Index 113 vii Underpinning information Arc welding safety Under the Health and Safety at Work Act 1974 welders have a responsibility to take reasonable care for their safety and that of others by cooperating with safety requirements Welding and the welding environment can create many hazards, but can be carried out quite safely if you play your part and observe some basic safety rules There are a number of factors to be considered; a few of these are listed below Personal protection Personal protection for the welder is most important, apart from the most obvious dangers of burns, stray sparks and falling objects, the arc gives off ultraviolet and infrared rays These will affect the skin and eyes much in the same way as long periods of exposure to the sun Suitable protection must be worn at all times to guard against these and other dangerous occurrences Protective clothing comes in the form of gauntlets, leather coats, aprons, sleeves, spats and capes The eyes should always be protected by a shade of filter glass suitable for the welding operation and amperage being used, or a clear glass for the chipping of slag Table 1.1 details the recommended filter glasses Protection for the feet in the form of safety boots with a toecap is an essential part of the welder's protective clothing Boots protect the Table 1.1 Recommended filter glasses for welding Filter glasses for manual metal arc welding EWF up to 100 amps 8-9 EWF 100-300 amps 10-11 over 300 amps EWF 12-13-14 Filter glasses for oxyfuel gas welding: GWF Aluminium and alloys GWF Brazing and bronzing welding GWF Copper and alloys GWF Thick plate and pipe Filter glasses are usually protected on the outside by a separate, clear plastic cover lens This will give protection from spatter particles and prolong the life of the filter lens toes from damage by falling objects, while also giving the best protection against sparks entering the footwear Some boots have a flap up the front, others may be one piece with high legs giving good protection to the foot and leg Low shoes or trainers are not the ideal footwear for the welder Many types of eye protection are available in the form of spectacles, goggles, face visors, clear glasses for use with welding helmets/ shields, etc The most important aspect when choosing any form of eye protection is that it must conform to British Standard (BS)2092 Eye protection must be worn for all cutting, grinding, chipping and welding operations Working at heights In your profession as a welder it is possible that you may have to work off scaffolding, UNDERPINNING INFORMATION trestles, elevated platforms and so on In most instances these elevated platforms will be erected or operated by qualified people eliminating the possible risk of collapse As a welder working from such platforms, extra care must be taken to avoid even the slightest risk of electric shock Although the effects of the shock may be dismissed, it could lead to loss of balance and falling with serious or fatal results b er a 1ways Remem wor k mg a t h eig ht s t a k e ex t care w h en Responsibilities of the welder Under the Health and Safety at Work Act 1974, individuals are held responsible for their own safety as well as that of colleagues and those working in close proximity Always ensure you have taken all reasonable, practical precautions to avoid the risk of accidents and fires, for example: a) good housekeeping; keep a tidy work area b) wear protective clothing on feet, body and eyes c) screening of workstation to protect passers-by d) use and position extraction equipment correctly e) carry out safety checks on equipment f) not tamper with safety posters or signs These are just a few points to consider before work commences How many more can you think of? Welding fumes Welding fumes are virtually impossible to eliminate from the welding process However, fumes can be rendered harmless by observing the following simple rules: a) the welder positlOnmg hIm/herself out of th e fume pa th b) using adequate ventilation either natural or mechanical - fans and extraction equipment, for instance c) correct positioning of source of ventilation some gases are heavier than air and will sink to the bottom of a confined area; in these cases extraction should be at a low level d) placing the source of extraction as close to the point of welding as possible without disturbing the gas shield e) siting the source of extraction to pull the fumes away from the welder f) avoid welding on contaminated surfaces, such as oil, grease, paint, galvanised metal, etc R b f h' h' I d emem ~r, urnes:, IC mc u e POlS?~oUS gases whIch asphyxIate are not always vIsIble IS not possIble to use the above methWhere It ods, then breathmg apparatus may be required, supplied either from an airline or a personal body pack If in doubt ask! Storage and handling of gas cylinders The most com~on method of ~upplying gases use.d for weldmg IS from c~hnders All gas cyhnders should be treated wIth respect, handled carefully and stored in well-ventilated conditions Never allow cylinders to come into contact with heat, contaminants containing oil and grease, and observe the following handling and storage conditions: a) always keep cyhnders, flttmgs and connections fre~ from oil ~nd grease b) store cyhnde~s upnght c) transport cyhnders upnght d) store flammable and non-flammable gases separately e) store full and empty cylinders separately f) avoid cylinders coming into contact with heat g) secure cylinders by 'chaining up' during storage, transport and use h) open cylinder valves slowly i) only use recommended leak-detection sprays j) report damaged cylinders to the supplier k) always check for leaks h ff gas supp Iyater I) SWltC f use Gas cylinders find their way into many different environments from schools and colleges to heavy fabrication Wherever gases are used the operator, supervisor and management should be aware of the dangers and familiar with the operating conditions, safety requirements, handling and storage conditions Gas suppli- 100 A9 AI0 QUESTIONS A satisfactory permanent method of connecting return lead clamps to workbenches is by A) soldering B) brazing C) bolting D) clamps MAGS welding A1 The cable connecting the work to the power source unit is called the welding A) earth B) mains C) return It is an advantage to carry out manual metal-arc welding in the flat position rather than the horizontal-vertical position because the electrodes used may be A) bare wire B) shorter C) larger diameter D) output A2 The glass tube situated adjacent regulator of a MAGS unit is a A) contents gauge B) heater unit C) filter unit D) flowmeter D) smaller diameter State the purpose of a fuse in an electric circuit A3 When using liquid CO2 for the MAGS welding process, it is necessary to incorporate into the system a B12 Name TWO welding power units which supp Iy d·nec t curren t to a we Id·mg arc B13 State TWO reasons why electrodes for manual metal-arc welding need careful storage B14 State TWO reasons why the correct arc length should be maintained during manual metal-arc welding A) filter B) h eater C) coo Ier D) by-pass valve · · A4 A cy Im d er pamte d bl ac k WIt h aver t lCaI · · w h Ite Ime tams A) oxygen gas B) CO2 gas C) CO2 liquid BIS Give ONE reason why it is essential that correct joint preparations are used when manual metal-arc welding D) argon gas AS The gas supplied in blue cylinders with a green band contains a mixture of argon B16 Give TWO reasons for using the multirun technique when producing a horizontal-vertical tee-fillet weld B17 Give TWO reasons why slag should be removed before depositing the next run of weld metal Bl1 B18 Name TWO items of protection to be worn by the welder during manual metal-arc welding operations B19 State ONE cause cable connection use B20 of a bolted electrical overheating during State TWO items of information which may be obtained from a macro-exam in ation of a welded joint to the and A) ox~gen B) helIum C) hydrogen D) CO2 A6 The filler wire used in MAGS welding fed to the weld pool from a A) spool B) heater C) pool A7 is D) solenoid The slope angle of a MAGS gun when making a bead in the flat position should be A) 30: B) 40 C) 50° D) 70° GAS WELDING AND CUTTING A2 Oxygen is supplied are painted A) blue B) red C) maroon D) black A3 The flame setting used for fusion welding low carbon steel by the oxy-acetylene process is A) oxidizing B) carburizing C) neutral AlOA macro-examination involves polishing and A) etching B) bending C) heating D) fracturing D) normalizing ' ' Ace t y Iene f1tt mgs are A) left hand B) right hand C) square D) round Bll Sketch the end face of an oxy-acetylene cutting nozzle and indicate the orifice through , whiCh the cuttmg stream of oxygen IS emIt- A4 AS A6 A7 in cylinders which A9 · h ave th rea d s w h ICh B12 B13 The oxygen hose on a blowpipe acetylene welding is co loured A) red B) blue C) green D) grey Gas pressures used welding are measured A) new t ons B) bars C) grams D) tonnes in in for oxyB14 The size of filler wire diameter for welding 1.6 mm low carbon A) 1.6 mm B) 2.4 mm C) 3.2 mm D) 4.0 mm 103 ted State two arrester functions required steel is of a butt of a weld flashback State why copper must never be used on an acetylene supply State a safe method generally used for testing for leaks on oxy-fuel gas welding or cutting systems BIS State why acetylene cylinders must always be stored and used standing in the vertical position B16 Sketch a neutral B17 On the shown of A) the B) the oxy-acetylene The angle of filler wire to the work when oxy-acetylene flame sketch of the acetylene cylinder in Fig 6.7, indicate the position safety valve fusible plug oxy-acetylene welding by the leftward technique in the fIat position range of A) 10/20° is in the » 20/30° C 30/40° D) 60/70° B A8 The angle of the nozzle to the work when oxy-acetylene welding by the leftward technique in the flat position is in the range of A) 10/20° B) 20/30° C) 30/40° D) 60/70° BI8 State the main advantage oE a two-stage regulator regulator compared with B19 Name two weld defects B20 State two hazards acetylene welding a single-stage associated with oxy- Welding processes and • their numerical representation Arc welding 11 Metal arc welding without 111 112 113 114 115 118 12 121 122 Metal arc welding with gas protection covered electrode Gravity arc welding with covered electrode Bare wue metal arc weldmg Flux cored metal arc weldmg Coated wue metal arc weldmg Fuecracker weldmg Submerged arc weldmg Submerged arc welding with wire electrode Submerged metal arc weldmg wIth stnp electrode 13 Gas shielded metal arc welding 131 o • o o o o o 0 MIC welding 135 MAG welding: metal arc welding with non-inert gas shield 14 Gas-shielded welding with non-con sumable electrode 141 149 TIC welding Atomic-hydrogen welding o 15 Plasma arc weldmg 18 Other arc weldmg processes o o 181 Carbon arc welding o 185 Rotatmg arc weldmg 915 Salt bath brazmg o Resistance 21 22 welding Spot welding Seam welding 221 Lap seam welding 225 Seam welding with strip 23 24 25 29 29 943 31 Projection welding Flash welding Resistance butt welding 311 312 313 32 321 97 Other resistance welding HF resistance welding Furnace soldering G Id' as 10g ld' xy ue g,as we l.ng Oxyace ty ene we ld mg xypropane we ld mg xy h y d rogen we ld mg · Au- fue I gas we ld Ing Au-acety Iene we ld mg Bid' 953 F nctlOn so l denng 41 42 43 44 45 47 48 71 72 73 74 75 751 752 753 76 78 processes reI o o o o o r~z~ we g In Solid phase welding; Ultrasonic welding Friction pressure welding Force welding Welding by high mechanical Diffusion welding Gas pressure welding Cold welding Oth er we ld' Ing processes ° t ld l~ Th EIec t ros Iag we ld mg EI ec t rogas we ld mg In d uc t IOn we ld Ing LIght d la t IOn we ld mg Laser welding Arc image welding Infrared welding Electron beam welding Stud welding o ~/~ o o o o welding o o o o energy 108 APPENDIX 781 Arc stud welding 78 Resistance stud welding Brazing, soldering and braze welding 91 Brazing 911 Infrared brazing 912 Flame brazing 913 914 916 917 918 919 923 924 93 94 Furnace brazing Dip brazing Induction brazing Ultrasonic brazing Resistance brazing Diffusion brazing Vacuum brazing Vacuum brazing Other brazing processes Soldering 941 942 944 945 946 947 948 949 951 952 954 96 322 971 72 441 Infrared soldering Flame soldering Dip soldering Salt bath soldering Induction soldering Ultrasonic soldering Resistance soldering Diffusion soldering Flow soldering Soldering with soldering iron Vacuum soldering Other soldering processes Air-propane welding Gas braze welding Arc braze welding Explosive welding Appendix Useful informa tion Chemical Al C Cb Aluminium Carbon Columbium (Niobium) Co Cobalt Cr Chromium Cu Copper Hydrogen H Fe Iron Mg Magnesium Mn Manganese Mo Molybdenum Nitrogen N Electrode symbols Nb Ni P Pb S Si Sn Ta Ti V W Zn Niobium Nickel Oxygen Phosphorus Lead Sulphur Silicon Tin Tantalum Titanium Vanadium Tungsten Zinc Diameters mm 1.6 2.5 3.25 diameters - metric, imperial approximate lengths SWG in 16 14 12 10 1/16 5/64 3/32 1/8 5/32 3/16 1/4 5/16 - and Lengths mm in 250 300 350 400 450 600 700 10 12 14 16 18 24 28 Length metre centimetre inch foot yard kiJometre mile nautical mile Bar m em in ft yd 0.01 0.0254 0.3048 0.9144 100 2.54 30.48 91.44 39.3701 0.393701 12 36 3.28084 0.0328084 0.0833333 1.0936 0.0109361 0.0277778 0.3333333 km mi n.mi 1.60934 1.85200 Atmosphere 0.986923 0.621371 1.15078 Ib/in2 14.6959 0.539957 0.868976 110 APPENDIX Units and metric Weight 16 drams 160z 14 pounds stones quarters 20 cwt 10 mg 10 cg 10 dg 0.035 oz 1000 g 1000 kg grain dram ounce pound stone quarter hundredweight (long) ton milligram centigram decimgram gram 64.8 mg 1.772 g 28.35 g 0.4356 kg 6.35 kg 12.7 kg 50.8 kg 1.016 tonnes 0.015 grain 0.154 grain 1.543 grain 15.43 grain kilogram tonne (metric ton) 2.205 Ib 0.984 (long) ton Area are hectare km2 acre rood mi2 100 m 100 are 100 hectares 0.4047 hectare 1011.7 m2 2.59 km2 119.6 yd2 2.471 acres 0.387 mi2 4840 yd 1/4 acre 640 acres m g t N J W s M k c m Jl 1728 cu in 27 cu ft 1000 cu em 1000 cu dm Capacity 4 fl oz gill pt qt 10 m! 10 cl 10 dl 16.4 cm3 0.0283 m3 0.765 m3 0.061 in3 0.035 ft3 1.308 yd2 Ilbf tonf kgf IN Conversions mass units fluid ounce gill pint quart gallon millilitre cen tili tre decilitre Iitre 28.4 ml 0.142 0.568 1.136 4.546 0.002 pt 0.018 pt 0.176 pt 76 pt 4.448 N 9.964 kN 9.807 N 0.2248 Ibf between Ibf, kgf, etc are as for Pressure or stress Ibf/in2 kgf/cm2 kN/m2 MN/m2 0.0703 kgf/cm2 6.895 kN/m2 1.575 kgf/mm2 15.444 MN/m2 14.223 Ibf/in2 98.067 kN/m2 0.145 Ibf/in2 0.06475 ton/in2 Energy (work, heat) ft Ibf kgf m measure metre gramme tonne (or metric ton) newton (SI unit of force) joule (SI unit of energy) watt (SI unit of power) second mega (x million) kilo (x thousand) centi (1 hundredth) milli (1 thousandth) micro (1 millionth) Force tonf/in2 cubic inch cubic foot cubic yard cu centimetre cu decimetre cu metre factors Abbreviations Cubic measure 1 1 1 conversion kW h Btu 1J lkW 0.1383 kgf m 1.356 J 7.233 ft lbf 9.81 J 3412 Btu 3.6 MJ 1.055 kJ 0.102 kgf m/s J/sl N m/s 1.341 hp Basic conversion factors To convert in mm ft m Ib kg ton (long) tonne gallon (imp.) ml cu ft into mm in m ft kg Ib tonne kg (litre) ml cm-1 Compound tonf/in2 Ibf/in2 N/mm2 N/mm2 ft.lbf kgf.m kgf.m ft.lbf J in/min m/hr eu.ft/hr l/min Ib/cu.ft g/em3 Multiply by 25.40 0.0393 701 0.304 3.280 839 0.453592370 2.204 62 1.01605 1000.0 4.545.96 1000.0 1.000 028 28.3161 conversion factors N/mm2 N/mm2 tonf/in2 Ibf/in2 J(joules) J ft.lbf kgf.m ft.lbf m/hr in/min l/min cu.ft/hr g/em3 Ib/cu.ft 15.444 006 894 777 0.064 749 145.037 76 1.355 82 9.806 650 7.23301 0.138255 0.737562 1.524 0.656 168 0.471 95 2.118936 0.01602 62.43 Index AC/DC non-consumable electrode arcs 67 Arc striking 31, 63 Arc welding safety correct earthing electrical hazards fire prevention fuses personal protection responsibilities of the welder storage and handling of gas cylinders welding fumes working at heights British Standards for wires and filters 53 Bronze welding 91 Burn back 52 Carburising flame 85 Closed corner joint 90 Collets 66 Common gases and their application Contact tip, nozzle settings 52 Contactor 63 Current and voltage settings 53 Cutting techniques 96 DC suppressor 63 Direction of travel 69 Distortion control 16 methods of controlling 50 17 Earthing see Arc welding safety, correct earthing Electrode angles 32 basic or hydrogen-controlled 37 cellulosic 37 classification 35 coatings 37 extension 52 grinding 65 iron powder 36 rutile 36 size, current capacity 35 wires 48 Equipment 30 assembly (welding and cutting) selection 61 Examination dye-penetrant 23 magnetic particle 23 radiographic 23 ultrasonic 24 visual 20 Extinguishing the flame 85 Features of the process 53 Filler rods 68 Fillet weld 58 closed corner joint 87 lap joint 87 profiles 16 Filter glasses 1, 86 Flame settings 84 Flashback arrestors 80 Flat position 39 Flux-cored arc welding 54 Fluxes 91 Footpedal 65 Fusion runs 69 Gas cylinders identification storage and handling 83 114 INDEX Gas le~s 66 mixtures and their applications nozzles 66 welding 105 welding and cutting 102 Gases, fuel 92 Generators 30 Plate edge preparation 86 Positional welding 38 Process applications 70 Purging 81 68 Quality of cut 95 Rectifier 30 Regulator and flowmeter Hand cutting 93 Health and Safety at Work Act 1, High- and low-pressure systems 85 Horizontal-vertical butt joints 59 corner joint 71 position 41 single 'V' butt joint 73 'T' fillet joint 57, 71,88 Hoses (BS5120) 80 check valves 81 connectors 81 Inspection Regulators 79 Safety 77, 79 see also Arc welding safety Scratch start 64 Self-adjusting arc 52 Shielding gas 67 choice of 48 Single 'V' butt joint 57, 74 Slope and tilt angle 54 Slope down 64 up 19 64 Square edge butt joint 72, 88, 89, 90 Standard welding/cutting equipment 77 Stops and starts 32, 53, 69 Supporting materials 96 Surge injector 63 Joint features 16 types 13 Lift start 64 Lighting-up procedure 67 84 Macro-examination 25 Manual metal arc welding 29, 99, 104 Metal arc gas-shielded welding 47, 100, 104 positional welding 56 Metal transfer modes 50 Neutral flame 84 Non-destructive testing 20 Nozzle sizes and material thicknesses Nozzles 82, 92 '0' clips 81 Open circuit voltage 31 Operating conditions 94 Outside corner joint 72 Overhead IT' fillet 44 IV' butt welds 44 Oxidising flame 84 Oxyacetylene positional welding 86 welding and cutting 77 Oxyfuel gas cutting 91 83 IT' fillet and square edge butt joints 56 TAGS positional welding 70, 101 equipment 61 Testing bend 24 destructive 24 nick-break 25 impact 25 tensile 25 Torch high-pressure 82 low-pressure 82 Torches 67, 92 Transfomer 30 Transformer/rectifier 30 Tungsten arc gas-shielded welding 61 Vertical corner joint 74 fillet weld 74 position 42 'T' fillet 42 IV' butt welds 44 Weaving 34, 53, 70 INDEX Weld defects 19 features 16 symbols 10 Welded joint, features 14 Welder qualifications 26 Welding positions for plates 37 procedure 26 procedure approval 27 processes and their numerical representation 107 techniques 8S terminology S torches 82 Wire feed system 49 115 ... Flux-cored arc welding Self-shielded flux-cored arc welding 47 vi CONTENTS Gas-shielded flux-cored arc welding MAGS positional welding Tungsten arc gas-shielded welding 61 TAGS welding equipment... techniques Questions 99 Health and safety MMA welding MAGS welding TAGS welding Gas welding and cutting Answers to questions Appendix 1: Welding processes Welding processes and their numerical 107... electric arc welding be trained in the basic practice of mouth-to-mouth resuscitation Welding terminology Welding, gas and arc, is a widely used process to join metals by fusion welding, brazing