Heat Treating 410 Stainless Steel

Date 03-10-2006 19:42

We are in the process of qualifying a welding procedure for welding 410 Stainless with inconel 625. The thickness of the base material is .9375". the process is GTAW/SMAW. My question is during the heat treat of the parts which is going to be around 1260 deg. F, will slow cooling be preferable than faster cooling rate to obtain the required hardness levels in the HAZ of 22 HRC? Any information on this would be greatly appreciated.
Thanks again

By - Date 03-10-2006 21:36

At the 1260F temperature, you are doing what is considered a Subcritical PWHT Temperature Range. The recommended range for the 410 martensitic steel is from 1200-1400F range. The lower hardness will be obtained by heating near the top of the range and then air cool from temperature.

Chuck

By Richard V. Roch (**)

Date 03-10-2006 22:14

When air cool is implied, does this mean using forced air (like compressed air)? Currently we are doing 400 deg. F on the down ramp from 1269 deg. F.
Many thanks for your response Chuck, hope to hear from you again.

Richard

By - Date 03-11-2006 15:02

Richard,
Generally, "forced air" is not recommended for the 410. Also, ramping down to 400F is normally not necessary, although it should not have any detrimental effects on the steel or the HAZ. Once the necessary PWHT has been fulfilled, the weldment is taken out of the oven and cooled to ambient air temperature. But, let me bring up one more point...The martensitic stainless steels are most commonly given the Subcritical PWHT (1200-1400F for the 410) followed by a Supercritical Full Annealing (1525-1625F for the 410) if maximum softness is required. The full annealing transforms a multiple-phase weld zone to a largely ferritic structure (softer) with scattered carbides. But, in the case of a 410 SS (C=0.15% max) the Subcritical PWHT is the most recognized.

Chuck

By Richard V. Roch (**)

Date 03-13-2006 15:19

Again, many thanks for your information. I'ts been very helpful.