Welding Precautions for T-1 Steels

What precautions should I take when welding T-1 steels?

T-1 is a quenched and tempered steel. Welding quenched and tempered steels may be difficult due its high strength and hardenability. The base steel around the weld is rapidly being heated and cooled during welding, resulting in a heat affected zone (HAZ) with high hardness. Hydrogen in the weld metal may diffuse into HAZ and cause hydrogen embrittlement, resulting in delayed underbead or toe cracking outside of the weld. To minimize heat affected zone cracking:

Use a low hydrogen consumable, like a -H4 or -H2
Preheat. This slows the cooling rate. Note that excessive preheat may anneal the base material
Slow cool. More time at elevated temperatures allows the dissolved hydrogen to escape
Peen the weld beads to minimize residual weld stresses
Use the lowest strength filler metal meeting design requirements. If making fillet welds, the weld can be oversized to give the specified strength 
Minimize weld restraint