Interpass Temperature

The interpass temperature is the temperature of the weld before you lay the next pass. If you go too hot on multi-pass welds, the structure overheats, the grain becomes coarse, and the weld loses toughness. If it's too cold, the next bead won't bond properly and you get cold lap defects. So you have to choose the temperature so that the weld doesn't cool down too much, but also doesn't glow. With higher-strength or alloyed steels, you have to be especially careful not to get too hot. As a rule of thumb: if you briefly hold the back of your glove against the weld and it's bearable, but the weld is already noticeably warm, you're usually on the safe side.