Excessive hardness on 9 Chrome Pipe Welds
Excessive hardness on 9 Chrome Pipe Welds
(OP)
Have welded piping 9 chrome using electric preheat to contol and monitor interpass temperatures with approved and demonstated weld procedure. Many hardness readings after PWHT are in excess of Code allowable of 241 BHN. All the obvious variables have been checked, ie materials & welds PMI'd as well as calibration of all equipment.
Looking for someone that has seen this problem in the past, determined the cause, and and how it was resolved.
Looking for someone that has seen this problem in the past, determined the cause, and and how it was resolved.





RE: Excessive hardness on 9 Chrome Pipe Welds
RE: Excessive hardness on 9 Chrome Pipe Welds
RE: Excessive hardness on 9 Chrome Pipe Welds
RE: Excessive hardness on 9 Chrome Pipe Welds
RE: Excessive hardness on 9 Chrome Pipe Welds
RE: Excessive hardness on 9 Chrome Pipe Welds
1) There were some problems in the last few years with mismarked filler material coming from out of the country (Mexico, if I remember right).
2) There are 2 types of 9Cr materials, P9 and P91 (or if dealing with tubing, T9 or T91), with the appropriate filler material for each. The difference between them is P9 (or T9) contains NO vanadium while the P91 (or T91) does.
We ran across the second case about 5 or 6 years ago and found that some filler material manufacturers made no distinction in the AWS designation for these very different materials. Some manufacturers labeled the vanadium containing rod E505-Mod (or ER505-Mod for GTAW) while some just called it E505, the same as for P9 (non-vanadium) base material. Even a little vanadium will greatly increase the hardness of the weld, even after proper PWHT.
RE: Excessive hardness on 9 Chrome Pipe Welds
From 1375ºF to 1175ºF at 100ºF/hour
From 1175ºF to 800ºF at 200ºF/hour
From 800ºF to 400ºF at 300ºF/hour
If you need a procedure, i can send a copy.
Elvis.