lec 12 fundamentals of joining, oxyfuel-gas and arc welding processes

8/15/2019 Lec 12 Fundamentals of Joining, Oxyfuel-gas and Arc Welding Processes

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Introduction to Consolidation Processes

• Consolidation Processes consist of – Welding – Brazing – Soldering – Fasteners – Adhesives –

Shrink Fits – Slots and Tabs

Soldering Brazing Welding

Low- High Temperature


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Types of Fusion Welds

• Bead welds : Limitedpenetration so used on thinmaterials , or surfacemodifications

• Groove welds : Used on thickmaterials , requires jointpreparation, used for singleand multiple passes

• Fillet welds : Use for tee, lapand corner joints

• Plug welds : Used apermanent replacement forrivets or bolts


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Weld Procedures

Various weldprocedures used toproduce welded

joints. (CourtesyRepublic SteelCorporation,Youngstown, OH).


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Heat Effects

• In fusion welding , the heat melts some of thebase material, which is then rapidly cooled,creating changes in the granular structure.

• The pool of metal bonding the base material isa blend of each material, and forms a caststructure in the joint zone.

•

Surrounding the pool of metal is the heataffected zone , where metallurgical propertieshave been changed.


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Butt Weld with Backing Plate

Schematic of a butt weld between a plate ofmetal A and a plate of metal B, with abacking plate of metal C and filler of metalD. The resulting weld nugget becomes a

complex alloy of all four metals.


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Heat Affected Zone


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AWS Weldability


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Summary

• Proper weld considerations – Selection of the process and fillers – Design of the Joint – Effects of heating and cooling on weld and parent

materials• Parallel considerations apply to brazing and

soldering


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Oxyacetylene FlameTemperatures

Typicaloxyacetylene flame and the

associated temperaturedistribution.

Preheat the metal and provide

shielding from oxidation

Maximum temperature andfirst stage of combustion iscomplete.


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Oxyfuel-Gas Welding Process


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Oxygen Torch Cutting

• Oxy-fuel gas cutting (flame cutting) – Most common thermal cutting process – Metal is melted by the flame of the oxyfuel gas

torch


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ARC WELDING


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Consumable-electrode ArcWelding


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Schematic of SMAW

Schematic diagram of shielded metal arc welding (SMAW).(Courtesy of American Iron and Steel Institute, Washington, DC.)


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Flux-Cored Arc Welding

• Best used for welding steels• Equipment cost greater than SMAW• Needs good ventilation to remove fumes

generated by the vaporizing flux


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lec 12 fundamentals of joining, oxyfuel-gas and arc welding processes

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