Summary for stainless steel welding blackening Discussion
Avoiding blackening during stainless steel welding is the central issue in this thread. Vish. S of Fortuna Associates in Bangalore asks how to prevent the stainless surface from turning black during welding. John Rendleman explains that carbide precipitation can occur when stainless steel is heated to about 1600 degrees, separating chrome from the ferrite grains. He says the normal welding process reverses this on quenching, but if the metal cools too slowly, the reversal may not happen, leaving the stainless black and more likely to rust. His practical advice is to reduce the welding temperature, increase travel speed, or do both so the material cools faster and avoids discoloration.
Q. What is the best way to avoid blackening of stainless steel surface during welding?
Vish.S
Fortuna Associates – Bangalore, India
2001
A. Carbide precipitation occurs when stainless steel is heated to 1600 degrees. That is the separation of the chrome from the ferrite grains. In the normal welding process the process reverses upon quenching. If the metal cools too slowly the process will not reverse and the stainless will turn black. It will also rust. Try a lower welding temperature or faster travel speed or both.
John Rendleman
– Grand Tower, Illinois, U.S.A.
2002