Should the coupon welded by the welder for his performance qualification undergo PWHT as well?<\/strong><\/li><\/ul>\n\n\n\nIt makes logical sense. Some weldments attain their desired properties only after heat treatment. So, if you subject a coupon to mechanical tests without giving it that heat treatment, and the tests do not pass, you cannot be certain about whether it was the welder\u2019s skill that impacted the test result, or something else?<\/p>\n\n\n\n
So, thinking logically, you should give PWHT to your welder qualification coupon. <\/p>\n\n\n\n
Also, QW 301.2 requires that only a qualified WPS (or SWPS) be used to weld a performance qualification coupon. And PWHT is an essential variable for Procedure Qualifications. So, if the WPS that you use for qualifying your welder requires it, it follows that you must do PWHT for your coupon too.<\/p>\n\n\n\n
However, there is an exception given in QW 301.2 that permits us to forego PWHT for welder qualification test. <\/p>\n\n\n\n
The wording in QW 301.2 goes something like this: Test coupon shall be welded in accordance with a qualified WPS or SWPS, “except that when performance qualification is done in accordance with a WPS or SWPS that requires a preheat or postweld heat treatment, these may be omitted.”<\/p>\n\n\n\n
The wording used here is “may be omitted”, which means that it is choice <\/em>in the hands of welding engineer. <\/p>\n\n\n\nIf the base material chosen for the test coupon is a high alloyed metal such as P91 or P92, it would be unwise to leave it without PWHT. However, if the coupon is made up of carbon steel of 15 mm thickness, then it is not necessary to do PWHT of the test coupon, even though the WPS used for welding the coupon might have been qualified with PWHT. <\/p>\n\n\n\n
Leaving the coupon without PWHT would not violate the Code.<\/p>\n\n\n\n
In my shop, like I said \u2013 almost all production jobs undergo PWHT. Hence the available WPS is with PWHT as well. However, for welder qualification we do not subject the coupons to PWHT. Post welding, we send them straight for RT. We don\u2019t see any point in doing PWHT.<\/p>\n\n\n\n
PWHT is not going to change the soundness of performance qualification coupon in anyway (proven through experience). The authorized inspector agrees with this.<\/p>\n\n\n\n
Note: If you were qualifying the welder through mechanical tests, and welding has been done in accordance with a WPS that requires<\/em> PWHT, I would recommend subjecting the coupon to PWHT too!<\/p>\n\n\n\n