Charles,
Your points are well taken, but the forum does not mention if this a procedural question or not. But 2 important points should be noted here. No. 1 is that a filler metal and a base metal having the SAME chemistry will have the same tensile strength. That is what determines tensile strength, chemistry. No.2 is that the applicable filler metal specification will give the minimum required tensile requirements for any filler metal. Respectfully, QW153.1 and QW-153.1 (c) are referring tensile testing of a "tensile test specimen". This will require a welded specimen to be performed. The forum question specifically asks about a filler metal before weld deposition. This is totally different than what QW-153.1 is referring to. My question to the forum is how can a filler metal, having the same chemistry as the base metal, have a different tensile strength?
CM
I think I have to agree with you on this one Charles. ASME IX does not address what filler metals are or are not allowed to be used with specific base matals, it only requires certain properties of a welded joint, as you mentioned. (QW153, which addresses the properties required from welding procedure qualification) Since the original question was whether or not ASME IX addresses the issue, I think you called it right.
One example of the situation described in the original question I have had to deal with, is welding on a 5 Cr, 1/2 Mo alloy (8018-B6 or 80T5-B6) with a 90 minimum tensile strength. Normally the matching filler metal will not meet 90ksi after stress relief because most alloys in the 5Cr-1/2Mo family are 80Ksi or less, so that is what they are designed for. So you have to pick your filler metal manufacturer and get an electrode with the right chemistry. (In this case higher carbon) By design, most of the time the filler metal is lower in hardenability than the base metal. This is because of the drastic quenching effect that the surrounding base metal has on the weld as compared to the cooling rate experienced by the base metal during heat treatement. So the weld can reach the same strength without having as much alloy. Most of the time this is beneficial from the crack-resistance standpoint, but it can be detemental when higher strengths are required.
If you are talking stainless steels/nickels, etc, (as I think Mr. Meadows is- althought the original question did not indicate what alloys were involved), usually filler metal will over-match the base metal to aid in corrosion resistance. Mr. Meadows points out that before depositing the weld, the electrode overmatches even more to compensate for oxidation in the arc, but mostly we are concerned about the properties of the weld deposit, not the filler metal before welding. (Unless you are manufacturing the filler metal.) Except for solid wire where the chemical analysis is allowed to be determined from the wire, and therefore will be slightly different from the deposited weld metal.
I think the bottom line is that you cannot seperate the filler metal from the procedure qualification, which is how ASME addresses the minimum tensile strength required from the joint, which in turn dictates the minimum tensile strength of the weld metal.