If you are not sure which filler metal to use, a good general rule is that a lower strength or grade can be used successfully, but a little stronger or higher grade seldom works.

Question

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Using a filler metal that is stronger or of a higher grade than the base metal can lead to issues such as cracking due to the differences in material properties. It's important to match the filler metal's strength and composition closely to that of the base metal for optimal welding results.

If You Are Not Sure Which Filler Metal to Use