Q. Another question on 4130. Andy, I am a certified welder at NASA in Houston. We never weld carbon steels. Recently an engineer came to me about welding/manufacturing an aircraft part out of 4130. My experience in the past is that 4130 filler metal does not perform or look very good. I read your past responses on this topic and you made reference to a preferred filler metal, but I don't think you gave the full name or number type for these filler metals. Could you be more specific so we can make this purchase?Also is it necessary to normalize the heat-affected zone with an open flame when you TIG weld 4130 with this wire? Thank you. (Submitted by: Alan Weible from ****inson , Texas )

A. The 4130 filler I use is a Tig-tectic brand 680 stock number. They don't give the composition of the filler. However, it welds like a cross between ER 80S-D2 and a 312 filler. It has great appearance and great strength. Other good filler options are ER70S-2, ER70S-6 and ER80S-D2. These do not give as good of coloring as the Tig-tectic 680 but has good strength and elongation percentages needed for small aircraft and race cars. If your fit-up is tight enough you do not need to stress relieve the heat zone. Keep as tight of an arc length as possible to reduce total heat input to the parent metal. If you feel you need to stress relieve because of poor fit up or excessive heat input, use a 900deg. temp marker and mark about 3/4 to 1 " away from the weld area. Use a neutral flame and avoid any hot spotting.