Advanced Welding Processes: Technologies and Process Control

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High-energy density processes 153 Most of the metallurgical problems experienced with laser welding are common to other fusion welding processes; for example, cold cracking in high-carbon and alloy steels, porosity and solidification cracking in aluminium alloys, but, with suitable precautions, these problems may be restricted. Some common application areas are described below. Austenitic stainless steel Austenitic stainless steels have been laser welded in a range of thicknesses. Typical conditions for 13.3 mm keyhole welds are given in the figures above, but speeds of up to 1 m min –1 can be achieved with a CO2 laser at 11 kW. As with other welding techniques, care is needed to avoid solidification cracking and sensitization although the thermal cycle may restrict thermal damage in the HAZ. Low-carbon steel Low-carbon steel is readily joined with a range of common welding processes, including GMAW and GTAW. The primary reasons for using high-capitalcost processes such as lasers is to increase productivity and to improve quality. There are no specific problems with the laser welding of uncoated plain carbon steels and both CO 2 and Nd:YAG systems have been used successfully as the following applications confirm. In thin-section sheet material, laser welding has been used for fabrication of high-precision pressings [166] to fabricate beams for the carriages for a CNC punch press. A 5 kW CO 2 laser was used and the main objective was to limit distortion and weld finishing operations. Lasers are being adopted for many carbon steel welding applications in the automotive industry, [167] including the welding of floor panels and engine support frames. In most cases, robotic automation is involved and integrated beam delivery systems have been developed. The use of 1 kW Nd:YAG lasers with optical fibre delivery systems have also been applied to robotic welding. Coated steels, particularly zinc-coated or galvanized materials, are difficult to weld and, even if satisfactory parameters are developed, they are prone to batch variation. Some success has, however, been reported using a Nd:YAG laser with a multiple laser (Multilase) system. [144, 168] Laser welding has also been evaluated for fabrication of thicker section, higher-strength steels such as ASTM A36 (0.29% C, 0.8–1.2% Mn, 0.15– 0.40% Si) [169] and it was found that welding speeds of up to 1 m min –1 could be achieved in 19 mm thick plate using a 15 kW CO 2 laser. A cost analysis indicated a three-year payback period for the laser system in this application.
154 Titanium alloys Advanced welding processes Titanium alloys can be laser welded if due care is taken to prevent atmospheric contamination and the resultant embrittlement that occurs in these materials. Welding speeds up to 6 m min –1 have been reported for 3.0 mm thick material using a CO 2 laser at 4.6 kW output power. [170] Nickel alloys A range of nickel alloys has been successfully laser welded, and welding speeds of 0.5 m min –1 have been reported for Inconel 600 8 when using a continuous-wave CO2 laser at 11 kW. C263 and Jethete M152 are also readily welded. 8.3.6 Practical considerations Joint configurations and accuracy Square butt, stake/lap, spot, edge, and T butt joints as shown in Fig. 8.14 are the normal joint configurations used for laser welding. Due to the small focal spot size, alignment of butt joints is critical and joint preparation must be accurate. In addition, any automatic positioning, work and beam-handling equipment must be made to high levels of precision. Safety Direct or reflected laser light from the workpiece and surrounding fixtures can be extremely dangerous, particularly with high-power systems, and 8.14 Typical laser weld joint configurations. 8 Inconel 600: nominal composition 75%Ni, 15%Cr, 8%Fe.
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Advanced welding processes i
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Advanced welding processes Technolo
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Contents Preface ix Acknowledgement
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Contents vii 10.4 Automated control
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Welding has traditionally been rega
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Acknowledgements I would like to ac
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1.1 Introduction Welding and joinin
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An introduction to welding processe
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Stage 1 Stage 2 An introduction to
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Slag deposit on weld surface An int
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∑ no heavy slag - reduced post-we
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Electro slag SAW multi wire SAW FCA
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Weld metal used (kg m -1 ) 40 35 30
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Advanced process development trends
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% consumed 70 60 50 40 30 20 10 Adv
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Advanced process development trends
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Mains input Power regulation Contro
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Welding power source technology 29
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Three-phase transformer Three-phase
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Mains input Welding power source te
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Off line storage Operator interface
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4.2.1 Improved toughness Filler mat
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Filler materials for arc welding 47
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Flat strip Solidified slag on weld
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Gases for advanced welding processe
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CVN impact energy (J) 200 150 100 5
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∑ argon plus 15-25% carbon dioxid
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25 23 21 19 17 15 13 11 9 7 20 18 1
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Ozone emission (ml min -1 ) 4 3 2 1
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Table 5.3 Continued Argon + 1 to 7%
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Advanced gas tungsten arc welding 7
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Power source Advanced gas tungsten
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Number of arc starts 35 30 25 20 15
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Water cooling 6.7 Dual-shielded GTA
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∑ low current: 0.1-15 A; ∑ inte
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Surface tension Surface tension Adv
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7.2.1 Globular drop transfer Metal
Page 116 and 117: Gas metal arc welding 103 projected
Page 118 and 119: Droplet forming 7.6 Drop spray tran
Page 120 and 121: Number of counts 100 80 60 40 20 0
Page 122 and 123: Metal cored Rutile Basic Self-shiel
Page 124 and 125: F d Fem F v F st F g 7.13 Balance o
Page 126 and 127: Gas metal arc welding 113 is the cu
Page 128 and 129: Stick out Dip transfer Pulse/spray
Page 130 and 131: Gas metal arc welding 117 V = M + A
Page 132 and 133: Voltage (V) 50 40 30 20 10 Gas meta
Page 134 and 135: Pulse current t p 7.23 Pulsed trans
Page 136 and 137: Gas metal arc welding 123 The mean
Page 138 and 139: Wire feed rate (m min -1 ) 11 10.5
Page 140 and 141: Gas metal arc welding 127 Improveme
Page 142 and 143: Gas metal arc welding 129 and a num
Page 144 and 145: Current (A) 500 400 300 200 100 0 G
Page 146 and 147: Pulse amplitude (A) 500 400 300 200
Page 148 and 149: Gas metal arc welding 135 otherwise
Page 150 and 151: High-energy density processes 137
Page 152 and 153: High-energy density processes 139 P
Page 154 and 155: Arc voltage 30 25 20 15 10 High-ene
Page 156 and 157: High-energy density processes 143 N
Page 158 and 159: Reflecting mirror Laser cavity Powe
Page 160 and 161: High-energy density processes 147 H
Page 162 and 163: Laser beam Gas lens Plasma control
Page 164 and 165: High-energy density processes 151 P
Page 168 and 169: High-energy density processes 155 a
Page 170 and 171: High-energy density processes 157 l
Page 172 and 173: High-energy density processes 159 p
Page 174 and 175: 8.4.5 Practical considerations High
Page 176 and 177: Sliding particle stop Undeflected b
Page 178 and 179: 9.1 Introduction 9 Narrow-gap weldi
Page 180 and 181: 6-16 mm Parallel-sided with backing
Page 182 and 183: Water cooling Main Shielding-gas po
Page 184 and 185: Narrow-gap welding techniques 171 T
Page 186 and 187: 9.7 ‘Twist arc’ narrow-gap GMAW
Page 188 and 189: GMAW torch The NOW process GMAW tor
Page 190 and 191: Narrow-gap welding techniques 177 T
Page 192 and 193: 10.1 Introduction 10 Monitoring and
Page 194 and 195: Monitoring and control of welding p
Page 196 and 197: PROJECT: WELDING CODE : WELDING PRO
Page 198 and 199: TYPE TOUGHNESS TEST TYPE No. TEMP R
Page 204 and 205: Data RAM ADC I/O device Monitoring
Page 208 and 209: Current I(A) 150 140 130 120 110 Mo
Page 210 and 211: Table 10.5 Stability criteria Monit
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Monitoring and control of welding p
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CCD camera Travel direction Torch M
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Welding automation and robotics 219
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Table 11.1 Robot applications Weldi
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∑ evaluate alternatives; ∑ eval
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Option Manual metal arc Gas metal a
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Appendices Appendices 247
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Arc Metal arc Manual metal arc Resi
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Tensile strength Appendices 251 Des
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Appendices 253 Exx16 Basic low-hydr
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GMAW stainless steel c Wire feed sp
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Appendix 4 American, Australian and
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Appendices 259 Carbon Manganese ste
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Consumable type Features Applicatio
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Appendix 7 Plasma keyhole welding o
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References [1] British Standards In
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References 267 [40] Anon, 1989 ‘S
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References 269 [88] Boughton P and
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References 271 Century Conference (
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References 273 [178] Benn B, 1988
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References 275 [224] Philpott M L,
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References 277 [269] UK Patent 8411
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Activated TIG (A-TIG) 91, 97 adapti
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digital measuring systems 189-90 di
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high-frequency high-voltage arc ini
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current measurement 194-6 determina
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carbon dioxide 63-4, 64-6 chlorine
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Advanced Welding Processes: Technologies and Process Control

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