Fusion welding is a collective of processes where the parent metal is heated to a molten state before any filler or pressure is applied, then the weld cools rapidly.
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What does the act of heating the parent metal up to molten temperatures cause?
Metallurgical problems with the final weld which must be dealt with or accommodated in the design.
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What can localised heating cause?
High residual stresses and differential shrinkage stresses that lead to distortion or warpage.
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What can happen when two materials with different co-efficients of expansion are welded together?
The weld can become stressed and cracked.
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What can cracking be caused by?
A reduction of ductility or a degree of hardening in the HAZ.
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What can tolerance problems be caused by?
Volumetric changes caused by the weld cooling from molten.
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Explain issues of gas solubility in a weld.
Hydrogen can be dissolved into a weld and if this is not released it can become brittle.
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Why does a shielding gas need to be used in fusion welding?
Fusion welding encourages oxidation of the weld therefore the shielding gas is used to protect the weld pool from oxidation.
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Name a problem the welding process has associated with it.
Fumes can be given off from the flux and the molten metal which could be dangerous.
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What does multi-layer welds have the possibility of?
**** inclusions
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Name another problem the welding process has associated with it.
Unless an autogenous weld is used the filler metal must be matched to the base metal, it is not always possible to get an identical match this will cause metallurgical problems.
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Why is overhead welding and issue?
Gravity affects fusion welding as the metal is molten, the weld will try and pull away from the base metal.
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How is issue of oxidation combated in fusion welding?
By using fluxes of shield gases.
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How are metallurgical changes in the HAZ combatted in fusion welding?
The changes are combatted with pre and post heat treatment.
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How is shrinkage combatted?
By leaving excess material at the edges that can be machined afterwards.
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What technique of welding would be a good choice if fusion welding cannot be accepted in design?
Solid state welding.
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Other cards in this set
Card 2
Front
What does the act of heating the parent metal up to molten temperatures cause?
Back
Metallurgical problems with the final weld which must be dealt with or accommodated in the design.
Card 3
Front
What can localised heating cause?
Back
Card 4
Front
What can happen when two materials with different co-efficients of expansion are welded together?
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