410 Stainless

Date 04-11-2006 18:40

Having trouble achieving the required hardness requirements per the old NACE of 22HRC. Welded the test coupons (15/16" thk.) using alloy 625 filler. Process GTAW root and hot pass, SMAW fill and cap. Preheat temperature 400 Deg. F. Interpass temperatures 400-600 Deg. F. PWHT at 1260 Deg. f for 6 hours. Hardness at the HAZ between 23 & 25 HRC. I was told that if I increase the PWHT by 10 Deg. this would make a difference. Does anyone know if that would make that much difference? Any help would be appreciated.
Thanks in advance.

By - Date 04-11-2006 18:55

Richard,
For 410 SS, the recommended Subcritical PWHT is 1200-1400F. The lowest hardness is obtained by heating to these upper limits. 1340F has been used to gain minimum hardness in the 410 SS.

By Richard V. Roch (**)

Date 04-11-2006 18:59

Thanks. One of the problems we are having is that the material was tempered at 1283 Deg. F, and I am told that we cannot go higher than this temperature without violating the existing tempering of the base materials. I guess going to 1270 Deg. F would be worth the effort to bring the HRC 2 or 3 points.
Thanks Meadows.

By Richard V. Roch (**)

Date 04-11-2006 19:52

Are there any particulars other than what I stated in the first posting i.e. preheat/interpass temperatures, that I need to adjust to achieve best hardness results?
thanks

By GRoberts (***)

Date 04-11-2006 20:42

Some other things you might look into that might help:

Did you cool the part before PWHT? Do you know what the martensite finish temperature is? Anyhow, make sure you cool it down below the Mf temperature before PWHT. You probably did, but it doesn't hurt to check.

If you can't get it hotter, you can hold it at temperature longer. Take the sample you did the original hardness check on and give it an extra 4 hours or more at temperature and see if it comes down any.

I can't say whether your application will benefit a whole lot by increasing the temperature 10F, but I've seen 25F and some extra hours make a big difference on Cr-Mo alloys.

By Richard V. Roch (**)

Date 04-11-2006 21:06

Thanks Roberts.