The big difference interpass temperature beetween Root pass and Fill Pass

[Thuhuongengineer]

when we qualify PQR, we will record all the value of interpass in all pass (Root, Hot, Fill, Cap). We will choose the biggest value among all the value (called A) According to ASME IX, in WPS we will add more 56 degree to this biggest value of interpass, so Maximun interpass temperature in WPS is A + 56. This value of interpass will be used in all pass in WPS (Root, hot, fill, cap).

There is one thing I'm not clear : For example, in root pass while qualify PQR,I have interpass temperature 80 degree. Fill pass I hvae interpass 200 degree. So WPS will have interpass 200+56 = 256 degree for all pass. In production weld, my welder performs Root pass with interpass 250 degree. It far over 80 degree in comparision with qualify PQR but is still in the range of WPS. So the quality of root pass is affected or not. There is something unreasonable here or not.

The big difference interpass temperature beetween Root pass and Fill Pass affects the quality of weld joint or not?

 

[metengr]

There is nothing wrong with what you have stated regarding the production welding. The welder is within the maximum interpass temp requirement of 256 deg C. Interpass temperature is more of a concern with impact qualification and with corrosion properties (austenitic stainless and duplex stainless base materials).

 

[stanweld]

The maximum interpass temp measured during qualification + 100 F (55 C) allowable per QW-406.3 is only applicable for where impact testing is required. For temper bead welding the root pass not a temper bead) is excluded from the requirement per QW-406.8, which again is applicable only when impact testing is a requirement.

If the production weld does not require impact testing, you need not be concerned.

Finally, the interpass temperature does not apply to the root bead per the definition of interpass temperature in ASME IX and the definition of "Pass: a single progression of welding or surfacing operation along a joint, weld deposit or substrate. The result of a pass is a weld bead or layer."

 

[racookpe1978]

Well, considering that a root pass is deposited as molten metal and plasma across a gap where there is no previous metal, the root pass temperature is just a few shades closer to 2500 degrees rather than 250 degrees. Once the root is deposited and has cooled to solid metal, then the following passes may need to consider inner temperatures. 8<)