age hardening see precipitation hardening alloy elements 35–36 alloying interstitial and substitutional 14 alloy metallurgy 40–46 heat treatable 43–46 non-heat treatable 40–43 aluminium applications 7 characteristics 4, Appendix B history 1 backing bars and strips 78–80 butt welds definitions 75–78 cold work (strain hardening) 15–16 defects 199–205 hot cracking 24–31 oxide filming 22–24 porosity 18–22 ‘suck-back’ in TIG welding 111 degreasing 66–68 mechanical cleaning 66 chemical cleaning (pickling) 67 design backing bars and strips 78–80 edge preparations (joint design) 72–78 edge preparations (joint design) for MIG 136–139 edge preparations (joint design) for TIG 98–99 effect of position 72 for access 70–71 designations 36–40 alloy composition identification 36–38 temper designations 38–40 distortion 84–89 electron beam welding capabilities 157, 160 process principles 155–157 fatigue 89–96 joint classification 92–94 filler metals effect on hot cracking 29–31 selection 46–50 fillet weld definitions 74, 75 friction welding friction stir welding 161–165 capabilities 163, 164, 165 mechanical properties 165 process principles 160–161 rotary motion 161 gamma radiography 213 GMAW see MIG grain size 12–13 effect on hot cracking 30 GTAW see TIG handling of parent metals 51 laser cutting 58–63 health and safety 60–63 parameters 61 principles 58–60 laser welding arc augmented 154–155 CO 2 laser welding 152–153 defects 154 Nd-YAG (solid state) welding 153–154 process principles 150–152 liquation cracking see hot cracking mechanical cutting 64–66 MIG welding arc starting 135 contact tip 129–130 electro-gas welding 143–144 filler wire 133–134 fine wire 124 mechanised and robotic welding 141–143 parameters (argon shielding) 136–137 parameters (helium shielding) 138 power sources 119–121 process principles 116–118 Index 235 pulsed MIG 121–124 shielding gases 130–133 spot welding 144–146 terminating the weld 140–141 torches 125–126 torch positioning 138–140 twin wire 124–125 wire feeders 127–128 non-destructive testing 205–215 eddy current 207–208 penetrant 205–207 radiography 211–215 ultrasonic 208–211 penetrant examination 205–207 plasma arc cutting 52–58 health and safety 56–58 parameters 55 principles 52–54 plasma arc welding parameters 149 plasma MIG 150 process principles 147–149 variable polarity 149 porosity 18–22 in autogenous welds 18 in parent metal 22 effect of cleanliness 21 composition 20 hose type 20 process 20 gas dew point 20 ISO classification 200 precipitation (age) hardening 16–17 resistance welding flash butt welding 176–180 power sources 167–169 seam welding 175–176 spot welding 171–175 surface condition 169–171 236 Index solidification cracking see hot cracking solid solution strengthening see alloying storage of parent metals 52 strengthening mechanisms 10–18 strength loss 31–34 in HAZ 32–34 in weld metal 31–32 TIG welding effects of HF 100 mechanised/ automated welding 114– 115 parameters (argon shielding) 104 parameters (helium shielding) 113 process principles 97–101 shielding gas 102–106 spot and plug welding 115 torches and cables 106–107 torch manipulation 110–112 tungsten electrodes 108–109 ultrasonic examination 208–211 water jet cutting 63–64 weldability 18–31 hot cracking 24–31 oxide film 22–24 porosity 18–22 welder approval ASME IX 193, 196, 197 BS EN 287 Pt 2 191–193 BS EN 1418 197–198 welding procedure 181–182, 183 welding procedure approval ASME IX 188–190 BS EN 288 Pt 4 182–188 alloy grouping 184 range of approval 187–188 test regime 185–187 x-radiography 213 . 129 130 electro-gas welding 143–144 filler wire 133 134 fine wire 124 mechanised and robotic welding 141–143 parameters (argon shielding) 136 137 parameters (helium shielding) 138 power sources 119–121 process. strengthening see alloying storage of parent metals 52 strengthening mechanisms 10–18 strength loss 31–34 in HAZ 32–34 in weld metal 31–32 TIG welding effects of HF 100 mechanised/ automated welding. 116–118 Index 235 pulsed MIG 121–124 shielding gases 130 133 spot welding 144–146 terminating the weld 140–141 torches 125–126 torch positioning 138 –140 twin wire 124–125 wire feeders 127–128 non-destructive