The material to be welded has a different base chemistry, processing, or coating than that specified for the part.
The metal type and coating have a large affect on weldability. Any of the following conditions may require weld schedule changes:
- Substitution of any material by another that has different base metal characteristics (such as base metal chemistry, hardness, or processing).
- Substitution of a coated steel (electrogalvanized, hot dip galvanized, or galvannealed) for another steel with the same base metal, but a different coating material or thickness.
- Substitution of a bare steel (no coating) for a coated steel, or vice versa.
- Substitution of a plated steel part for a coated or unplated part, or vice versa.
- The above considerations should also be applied to aluminum and its coatings (conversion coatings, etc.)
Detectable evidence may include:
- Cracks and Holes
- Expulsion/Burn Through
- Inconsistent Weld Quality
- Nonround Weld
- Poor Class A Appearance
- Sticking/Stuck Tips
- Stuck Weld
- Undersized Weld
- Surface appearance of the material
Quality, Workplace Issues, Cost, Downtime, Maintenance, Throughput (cycle time; PPH), are all potentially affected by this condition. Special considerations are noted below:
Cost: Substitution of an incorrect metal and/or coating can affect all of the welds made on the part, so weld repair may be extensive, and, in the worst case, require scrapping of the parts.
- Material substitution not reported throughout process/plant
- Substitution necessary because of a shortage of the specified material
- Parts erroneously made of the incorrect material
- Parts have been plated because of corrosion concerns
- Parts should have been plated, but this step was erroneously omitted