Minimum Preheat Temperature 1

[chowhk]

Dear Sirs,

I would like to seek your advise on below matter:

I have a WPS/PQR (GTAW) states that the minimum temperature is 23 deg C. In ASME IX 406.1 says that:
"A decrease of more than 55 deg C in the preheat temperature qualified. The minimum temperature for welding shall be specified in the WPS."

Q: If I would like to weld using this WPS/PQR under 10 deg C, it is within the range or I have to requalify the WPS/PQR.

Thank you.

 

[weldstan]

What was the preheat on the PQR? That is the temp which governs the permitted decrease.

 

[chowhk]

Same as the WPS, minimum preheat temperature -> 23 deg C (ambient).

Q: If the metal (A106 Gr B, 10 mm thk) surface is 10 deg C (below the stated minimum preheat temperature in the WPS), can I weld using this WPS without preheat?

 

[Duwe6]

10°C / 50°F is an adequate preheat for A-106 steel, a P-1 material. If the pipe is less than 25mm thick.

If it is 25mm or greater in thickness, minimum preheat should be 175°F / 80°C.

 

[weldstan]

Yes; but amend your WPS accordingly.

 

[weldstan]

I also advise preheating to expell moisture.

 

[steakman911]

weldstan is Right. It looks to me that your WPS would need changing to weld at 10C.

As it stands, if your WPS states a minimum preheat of 23c, then you cannot weld at 10C..it must be pre-heated to 23C. (which is kinda of a weird number for preheat if I may say so...but I think I understand why) A106B does not usually need preheat unless as a precaustion due to thickness or its sitting out side in colder weather. Typical Minimum on the WPS's I use is normally at 10C. (am in Alberta where right now it is averaging -15C all the time.)

But I will also add that preheat will never hurt. Many times I will advise my welders expecially if we are welding A106B/C in Sch100 to Sch160 to go to 200F for Preheat...l just like to be safe and sure we do not get any cracking when tacking or cracking in the root-regardless of process used. Especially if its Boiler External piping or B31.1 product. Am Ddaling with that as we speak.

Max preheat would be determined by your max interpass temp.

Rgds,