Mixed weld electrodes design question

[jay156]

I specified 1/4" E70XX fillet welds for a pipe rack, but the guys who did it only had a pressure piping spec for a full penetration groove weld that called for one pass with an E60XX then the top pass with an E70XX.

So these guys tried to apply that technique to the fillet weld and they mixed E60 and E70 electrodes, I guess by making the first pass with the E60, then filling the rest out with the E70.

I'm not totally up to speed when it comes to welding procedures in the first place. I just say, "Make a 1/4" fillet weld, you follow AWS or whatever you need to do to conform to the standards, and don't bother me about it." But now they did this weird thing and I need to figure out if it's okay. Should I just check the welds assuming a 60 ksi Fw?

 

[connectegr]

A 1/4" fillet weld is a single pass weld. So there should be no combination of 60ksi and 70ksi weld metal. Depending on your base metal, AWS D1.1 Table 3.1 will provide the required filler metal. Note that the minimum fillet weld Table 5.8, depends on the use of E70 filler metal.

http://www.FerrellEngineering.com

 

[Ron]

Agree with connectegr....this should be a single pass with E70xx. No need for the E60xx to get the extra root "bite"....not needed for a small fillet weld.

 

[TLHS]

Why would they try to use a different qualified weld procedure, anyway? Fillet welds on prequalified materials should be prequalified as far as I'm aware.

 

[jay156]

Thanks, I know it's not necessary, but I'm just asking how do I determine if it's okay?

They just did it this way because someone doesn't know what they're doing over there.

 

[dhengr]

I agree with the posts above. However, the throat size of the fillet will normal control your design requirements. So, check the fillet weld cap’y., using Fy = 60ksi filler metal and if they are o.k. let it go at that. Depending on the weld configuration and the base metal you may also have to check the base metal at the weld leg dimension. But, prequalified AWS welds generally avoid the need for this. You also do tend to get some mixing in the welding process so the actual weld strength is somewhere in between that of the filler metal and the base metal. Also, check the sizes of the actual welds. If they did what they say they did, you probably have at least a 5/16th or 3/8th inch fillet. They would have needed at least several passes if it’s a nice balanced weld.

Since the welders normally weld pressure piping, there is some logic to their process and procedure. On a highly restrained joint they often want to use a slightly softer filler metal for the root pass, to prevent root cracking. Then they switch to the higher strength filler metal for the joint strength, knowing that the mixing will bring the root pass up a bit, in strength. The reasoning is that you loose very little in strength but prevent cracking in that difficult first pass region.