Advanced Welding Processes: Technologies and Process Control

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Reflecting mirror Laser cavity Power supply Gas cooling and recirculating system 8.7 Principles of the CO 2 laser. High-energy density processes 145 Partially reflecting mirror Beam focus system workpiece by a series of mirrors and lenses. Since glass lenses are unsuitable at the operating wavelength, lenses for CO 2 systems are usually made from ZnSe whilst mirrors are normally made from copper coated with a gold reflecting surface. A beam with low divergence is essential if long-delivery systems and flexibility of layout are required. Even with these constraints beam delivery systems have been incorporated into robot welding and cutting installations where flexible positioning of the welding head is required. Whilst CO 2 is the gas which is responsible for the emission of radiation, industrial lasers use gas mixtures which may contain up to 80% helium and 15% nitrogen. In the process of stimulating emission, heat is generated in the cavity and, to avoid overheating and instability, the gas is continuously circulated through a cooling system. The beam power delivered by CO 2 laser systems is commonly between 0.1 and 45 kW and the output may be pulsed or continuous. The overall efficiency is normally less than 10% and large chillers are required to remove excess heat from the system.
146 Advanced welding processes 8.3.2 Nd:YAG lasers The operating principle of the Nd:YAG laser is shown in Fig. 8.8. In this case, the active laser material is made up of a solid yttrium aluminium garnet crystal, which is doped with neodymium. Stimulation of the neodymium atoms is achieved by excitation with high-power flash lamps for pulsed operation or arc lamps for continuous wave output. Typically, the YAG rod has a fully reflective mirror at one end and a partially reflective mirror at the beam discharge end. The energy is amplified within the cavity and a beam of radiation in the near infrared range, 1064 nm in wavelength, is emitted through the partially reflecting mirror. Beam delivery can be made much simpler since normal optical glass can be used at Nd:YAG laser wavelengths. The cost of the optical components can be reduced and fibre optic cables may be used to provide efficient, flexible distribution systems. Fibre delivery offers considerable advantages compared with mirror systems; for example they reduce the need for accurate mirror alignment, allow safe delivery of the laser without bulky enclosures and enable variations in laserto-workpiece distance to be more easily accommodated. For this reason, Nd:YAG lasers are more suitable for robotic applications. In addition, the Nd:YAG radiation is absorbed more easily by most metal surfaces and allows improved process efficiency. Mirror Flash lamp Flash lamp power supply Cooling system Nd:YAG rod 8.8 Principle of the Nd:YAG laser. Partially reflecting mirror Beam delivery system
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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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Page 108 and 109: Advanced gas tungsten arc welding 9
Page 110 and 111: Surface tension Surface tension Adv
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Page 114 and 115: 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
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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 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 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
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Current I(A) 150 140 130 120 110 Mo
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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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