If you could provide a couple more details. such as material type, material thickness and product form, I'd feel much more comfortable giving an opinion. Generally speaking ASME requires the use of the higher post weld heat treatment temperature when joining materials of different P-no. groups. There are exceptions, i.e.: when non pressure parts are welded to pressure parts, the pressure part PWHT controls.
By -
Date 08-04-2001 17:52
I want to agree with DPWeber regarding the amount of information, but here are a couple of "fundamentals" to keep in mind:
1) Different materials and alloys have differing temperatures at which phase changes take place. This means that if you use the higher temperature, you have to understand what is happening with the structure of the other material.
2) All post weld heat treatment (PWHT) is NOT stress relieving. There are different reasons for performing PWHT. Sometimes the temperatures are similar, but normally they vary widely depending on the particular heat treatment that is required.
When looking at the temperatures that you supply, the 746°C looks like an annealing temperature for a Cr-Mo (or similar) steel, or possibly for a martensitic stainless steel. Here the PWHT temperature is below the critical temperature at which phase changes take place. The 1063°C looks like either a normalising temperature for C/Steel, (A bit on the high side) or possibly a homoginisation treatment (Also called solution treatment.) for an austenitic material. (I do not have my books handy to get exact figures.)
If your materials have a temperature range that spans the temperatures at which phase changes take place, then you really need to know what you are doing to get suitable results. This is often a problem when welding materials that air harden, to austenitic materials, because the PWHT of the austenitic material leads to hardening in the other material while the tempering treatment often leads to sensitization in the austenitic material.
Give us more info, and we could possibly help. Also what code, if any, are you working to? Also, what do you mean by "Crack welding at different locations"?
Regards
Niekie
