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25

Technical Services

Weld Cracking

Image 3A

Image 3B

Different alloying elements affect the melting temperatures and ranges of aluminum. Alloys with a larger liquid to solid range

will have a greater tendency to hot crack. The graph shows where each chemistry’s peak of crack sensitivity will be based

on the percentage of the major alloying element.

Crater cracks

may occur as a result of stress and/or chemistry. Crater cracks that are caused by stress typically occur

when the weld termination point (crater) has a smaller cross section than the rest of the weld and simply cannot withstand

the forces applied during the solidification process (see Images 3A and 3B).

Because of their chemistry, some base materials are more susceptible to hot cracking than others. Welds made on these

alloys need to be “flooded” with enough of the filler alloy to change the chemistry and move it away from the crack sensitive

range. Since the crater is typically smaller in cross-section, there is often not enough filler alloy added to change the weld

pool chemistry and it becomes prone to hot cracking, even though the remainder of the weld is not.

Since weld cracks can be the result of stress, chemistry, or a combination, determining the root cause can be difficult.

For assistance in troubleshooting weld cracking concerns, please contact AlcoTec Technical Services at 1-800-228-0750.