Joining Processes: Welding, Brazing, Soldering Brazing and Soldering: Melting of filler rod only
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Transcript of Joining Processes: Welding, Brazing, Soldering Brazing and Soldering: Melting of filler rod only
Joining Processes: Welding, Brazing, Soldering
1. Brazing and Soldering: Melting of filler rod only
• Brazing: higher temperature, ~brass filler, strong
• Soldering: lower temp, ~tin-lead filler, weak
2. Welding: Melting of filler rod and base metals
3. Both: Join inexpensive parts to form complex product
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Types of Joints
Brazing• Steel base metal + Brass filler rod is common
• Lower temp than welding: retains heat treatment (if present), minimizes grain growth.
• Strong but slow (careful preparation, cleanup)
• Furnace brazing is easily automated
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en.wikipedia.org
www.kirkframeworks.com
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Shielded Metal Arc Welding (SMAW): “Stick welding”
• Older, simple technology
• The electrode is also the filler rod
• Only for steel
• Strong welds if done properly (but often not)
• Very high heat input: good for thick parts, bad for grain growth and distortion
Gas Metal Arc Welding (GMAW): “MIG” (Metal-Inert-Gas)• ~Complex mechanism but simple to perform and easy to automate
• The electrode is also the filler rod, fed continuously from a spool. It melts in the arc.
• For steel or aluminum
• Low skill level can achieve good weld
• Medium heat input: distortion and grain growth are significant
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www.difflock.com
www.scenta.co.uk
www.mig-welding.co.uk
Gas Metal Arc Welding (GMAW): “MIG” (Metal-Inert-Gas)
A fair/typical quality MIG weld (still hot!)
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Gas Tungsten Arc Welding (GTAW): “TIG” (Tungsten-Inert-Gas)
• The electrode is tungsten (not consumed)
• The filler rod is separate and fed manually
• High skill level required to achieve good weld
• Difficult to automate
• Low heat input and small weld bead: distortion and grain growth are minimized
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Gas Tungsten Arc Welding (GTAW): “TIG” (Tungsten-Inert-Gas)
• Typical good quality TIG welds
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Resistance Spot Welding (RSW): “Spot Welding”
• No filler rod: electrical current is passed through metal under pressure
• Low skill level required
• Easy to automate
• Low heat input and no weld bead: distortion and grain growth are minimized
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Distortion from Welding Processes
• Non-uniform shrinkage of weld bead
• Difficult to maintain alignments
• Solution: Rigid fixtures, pre-compensate for warping, loose tolerances
Weld bead profile: Convex or Concave?
• Solidification of molten bead leads to shrinkage
• Shrinkage of a concave bead leads to tension on surface tends to crack
• Shrinkage of a convex bead leads to compression on surface does not crack
• Generally, slightly convex beads are preferred.
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Welding Flaws
www.ndt-ed.org/EducationResources
www.mig-welding.co.uk
Welding Flaws:
Incomplete Penetration
(not enough heat input)
References
Kalpakjian: http://www.nd.edu/~manufact/index3.htm