5.8 PWHT

Date 03-06-2007 20:43

I need some input on the Stress-relieving topic in D1.1's-5.8. Heres my dilemma; I
have qualified a PQR using 8630 Mod. and 4130 (both Q&T[temper temp. 1200]) with
FCAW, the test coupon was stressed relieved at 1125 F for 4.5 hrs. This coupon
was tested at the lab and passed all of its mechnical requirements (tensile, bends, CVN's,
hardness, etc.). I am now in the process of writing the WPS, but now I'm at
a stand still; upon closer reading of 5.8, I now wonder if the WPS is worth anything
at all. In 5.8.1 it states that stress relief treatment SHALL conform to the following
requirements, and one of those requirements is that of a maximum 1100 F for Q&T
steels. I'm I not to surpass 1100 F, didn't I prove that 1125 F on the PQR works,
and if need be can I utilize the +/- 25 F on the WPS to lower to 1100 F and still have
a legitimate WPS.

By GRoberts (***)

Date 03-07-2007 04:56

Even if you did PWHT above the AWS limitation, if you have a sophisticated customer, they should be willing to listen to your stance that the WPS has prooved itself. In other codes, and company specifications, the more common stance on Q&T steels is to limit the PWHT temperature to either 50F or 25F below the previous tempering temperature, which you did. I'm not sure how the +/-25F would work in your case without D1.1 in front of me to see the specific language. Someone else may have an answer for you there.

By castle

Date 03-08-2007 19:08

I do not think the +/- 25 F tolerance is stated in D1.1, but I believe the 25 F tolerance
has something to do with furnace calibration. The calibration sticker on the furnace that
we use shows the specific temperatures tested (ex. 1000, 1050, 1100, 1125, 1500, 1175),
and then it also shows +/- 25 F for the temperatures listed.

When our WPSs require PWHT we state in the PWHT section +/- 25 F next to the
temperature (assuming this is common). If the wrong program was punch in or the furnace
was acting squirrelly, then I can see were the +/- tolerance would help out. As long as
the temper temperature was not exceeded as you stated, then I do not see the harm in
utilizing the tolerance. Don't get me wrong though, I understand that the PQR was tested
at a specific temperature, and a major increase or decrease would change the mechanicals,
but I don't see what +/- 25 F would hurt. Any other input on this would be greatly appreciated.

Thanks GRoberts, you always reassure me that I'm on the right path.