Sec. IX, QW-407.2 (T&T range)

By locolito Date 09-25-2008 10:41

Dear all
Let me ask you the following question;
If any client spec. calls for impact requirements, then the supplementary essential QW-407.2 (T&T range) (Sec. IX) becomes for both the GTAW and SMAW process essential.
The text of QW-407.2 says: "A change in the postweld heat treatment temperature and time range".
How is this to be understood, how narrow (what temp./time tolerance plus/minus) would "a change in the postweld heat treatment temperature and time range" have to be in order not to exceed the "range" ?
My thinking is that since a WPS can be qualified for quite a range of base metal thickness, the holding time would for 1" (1 hour) however be different than for 2" (2 hours) (B31.1, Table 132 - 1hr/in.).
I will be very glad about your clarification. Thanks and regards Roli

By js55

Date 09-25-2008 12:59

Time at temp ranges are essentially an engineering decision, exemplified by the language "essentially equivelent" in QW-407.2. However, the text of QW-407.2 says specifically that your qual time must be at least 80% of the production time. This essentially means your HT qual should be a fairly long time to cover repairs and thicker materials.
As for temp, this is an engineering decision altogether. The ranges specified in the code of consturction is a good place to start.
Whatever engineering decision you make willl need to be justified to your customer base dupon alloy and service.