Filler Metals, Tensile Strength and Code

By SteveTN Date 04-15-2009 15:05

I am a student in welding engineering and I have a multi-part question to ask. This may cross several forum lines, but my question culminates in d1 code application so I am asking it here. Why are filler metals rated in minimum tensile strength (ie 60 ksi for 60xx, 70ksi for 70xx etc.) and not yield strength? Why is it in D1.1 Chapter 2 Table 2.3 that the allowable shear stress need to be .3 times the tensile strength of the filler and not the yield strength? Yield strength is used for the base metal. Wouldn't using yield strength for the weld be more conservative and allow for more welding discontinuities? The same question applies to D1.5 when calculating allowable weld stress in flange to web / stiffener to web welds; tensile strength of the filler is used again and not yield. Rattling around in my head is weld ductility/weld yielding and it may be the answer here, but I can't seem to make any sense of that. I am also confined by the fact that I do not have access to complete D1.1 - D1.5 codes. If anyone can help or point me in the right direction, I would very much appreciate it.

By 803056

Date 04-15-2009 16:48

I've often though about the same question and came to the conclusion that when a procedure is qualified using a grooved joint only tensile strength is determined. Yield strength and ductility (reduction in area or elongation) are not usually determined and are not typically included as criteria for the acceptance or rejection of the welded test piece. That being the case, the tensile strength of the weld serves as the basis of the allowable stess on the weld.

The base metal in the other hand is tested and ultimate tensile strength, yield point, and ductility are typically determined as part of the testing regiment. As you noted, the yield point is used as the basis of design calculations for the base metal, but tensile strength is used for sizing the weld.

Best regards - Al