[ASME Section VIII Division 1]

Procedure qualification requirement of unequal thickness joint with taper transition :

When the thicker test coupon is tapered to provide a transition at the Weld,

the qualified range shall be based on the base metal thickness adjacent to

the toe of the Weld at the thinnest end of the transition. 

The test specimen for the tensile and bent test may be machined to the thickness

required for the thinner base metal prior to testing.

[AWS D1.2] Table 3.4
Test on Plate, CJP Groove Welds, T : Thickness of Test Coupon Welded

T less than 1/8 in. (3 mm) :
Qualified Thickness Range: T Min., 2T Max.

T from 1/8 in. (3 mm), to 3/8 in. (10 mm), incl. :
Qualified Thickness Range: 1/8 in. (3 mm) Min., 2T Max.

T over 3/8 in. (10 mm), to less than 1 in. (25 mm) :
Qualified Thickness Range: 0.5T Min., 2T Max.

T 1 in. (25 mm) and over :
Qualified Thickness Range: 0.5T Min., Unlimited

이종두께 완전용입 맞대기 용접시에는, 용접두께(Weld Thickness) 기준을 WPS/PQR에

적용하는게 일반적이므로,  용접 두께가 얇은 모재 두께 18mm와 동일하다는 가정하에

WPS 두께허용범위는 9~36mm가 맞을듯 합니다.

이종 두께의 경우 통상적으로 3:1 Taper를 적용하여 용접시험편을 제작하고 용접 두께부분을 

모재 두께로 인정하여 두께허용범위를 적용하게 됩니다.