Advanced Welding Processes: Technologies and Process Control

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Water cooling Main Shielding-gas ports 9.4 Narrow-gap GTAW torch. Telescopic gas shield Forward gas shield Narrow-gap welding techniques 169 Secondary gas supply 9.5 Additional gas-shielding facilities. Trailing shield Electrode Gas diffuser
170 Advanced welding processes be increased to levels similar to those of GMAW. Many commercial applications of narrow-gap GTAW employ hot wire addition and an interesting example is the Roboweld system which was designed for welding transmission pipelines both on land and on pipe lay barges. Seam tracking and accurate positioning of the electrode may be achieved by one of the methods described in Chapter 10, but some systems also include facilities for video monitoring of the arc and torch position with the ability for the operator to override the automatic control to correct the torch position. To improve the sidewall fusion the electrode may be oscillated or alternatively the arc may be deflected magnetically. 9.3.2 GMAW The potential for using narrower weld preparations and smaller included angles for GMAW has often been claimed as an advantage of the process when compared with SMAW. However, although some concessions are allowed in the construction standards, this advantage has not been fully exploited in manual welding probably due to the difficulty of maintaining consistent fusion with reduced access. Reduced preparation widths are, however, used in automatic welding where improved control is possible. The developments in narrow-gap GMAW fall into two categories: ∑ the use of conventional automatic systems and narrower gaps; ∑ the use of special narrow-gap GMAW systems and narrow gaps. Reduced gap/angle GMAW A major application in the first category are the systems developed for transmission pipeline welding. The CRC Evans system, [184] for example, uses a compound bevel of the type shown in Fig. 9.2. In comparison with a standard American Petroleum Institute (API) bevel, this preparation reduces the weld metal volume by more than 20%. The pipe position is fixed with its longitudinal axis in the horizontal plane and welding must therefore be carried out in the 5G position (i.e. with the welding system rotating around the pipe). This is achieved by using a tractor equipped with an oscillator and typical operating conditions are shown in Table 9.1. Systems such as this have been used successfully for welding pipe diameters of 600–1500 mm with wall thicknesses of 8–22 mm. Narrow-gap GMAW developments The use of narrow-gap GMAW for the welding of submarine hulls was reported as early as 1966 [185] and, by the mid 1970s, a range of developments of the process were being used on production applications in Japan.
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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
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Gas metal arc welding 103 projected
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Droplet forming 7.6 Drop spray tran
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Number of counts 100 80 60 40 20 0
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Metal cored Rutile Basic Self-shiel
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F d Fem F v F st F g 7.13 Balance o
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Gas metal arc welding 113 is the cu
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Stick out Dip transfer Pulse/spray
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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 166 and 167: High-energy density processes 153 M
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 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
Page 224 and 225: 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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