What Tom said may surprise you....

What is interpass temperature?

I want to thank Tom Helm for his overview of FCAW (flux core wire feed) at last Thursday's WeldComm. Almost anyone who welds for a living, needs to know flux core. Flux core is always in demand. In this photo, I thought Tom was warning us about dropping sparks down your gloveā€¦ that REALLY hurts.. The truth is he was giving us some useful information about interpass temperature. What he is saying is that the back of your hand is very sensitive. So here is how you check your temperature: Place the back of your hand a few inches from your last weld, pull your hand away if it's TOO HOT. If you can hold it for up to 10 seconds, then you have the CORRECT interpass temperature of about 450-500 degrees. This is not to be confused with the minimum or PRE-HEAT tempurature, which is at least 50 -100 degrees Fahrenheit.

Check out this article on interpass temperature (The James F. Lincoln Arc Welding Foundation)
and this article on preheating