Interpass temperature for 17-4 PH

By Doug_Smith Date 04-27-2005 05:00

I'm writing a technical specification for a "trunnion collar," which is a device that will be used to move, locate and transport briefly the waste package that will be used to store high-level nuclear waste. I'm a metallurgist, welding engineer and generally jack of all trades. However, I've been reading a number of articles that suggest that the interpass temperature for 17-4 PH be kept as low as 200F. Understanding the martensite transformation in this material and the fact that we will require that the final welded product be solution heated and hardened to condition H900, is this "low" preheat warranted?

Incidentally the thickness of the material will be on the order of 3 1/2 to 4 inches thick and the "stubs" (trunnions) will probably be welded onto the ring. All fabrication has to be done to ASME Section III requirements and several forms of NDE performed.

If anyone has significant experience with this I'd appreciate any insight.

By - Date 04-27-2005 12:41

Doug,
17-4 is a martensitic type of PH material. When the 17-4 is solution annealed at about 1900F., the structure is mostly austenite. As it cools down to between 300 and 200F, the austenite transforms to martensite. After being quenched to this matrensitic structure, the 17-4 is strengthened by a precipitation mechanism during the aging heat treatment. Normally, in my experience, the interpass for a 17-4, using the 630 filler metal, which is recommended for welding the 17-4, is 150C (300F).

Chuck