Welding A706 Rebar

[Lion06]

I have always shown E80 electrodes to be used when welding A706 rebar to steel. I received a question from a fabricator recently that caused me to look into this much more closely.

Looking at AWS D1.4 Section 5.1.2 - the filler metal should be selected based on the lower tensile strength base metal. A706 grade 60 reinforcing steel has a tensile strength of 80 ksi. A36 plate has a tensile strength of 58-80 ksi. To me, this means that they have the same tensile strength (using the upper end of the range for the plate).

Table 5.1 reads to use E80 electrodes for the reinforcing steel. This is consistent with the PCI Design Manual, which states that E70 electrodes are not permitted for grade 60 reinforcement (this note is new in the 7th edition - previous additions showed E70 as an option, but the fillet weld sizes were larger). I came across an AWS interpretation document (

http://www.aws.org/technical/interps/d1.4-98-i1.pdf)

that seems to state the exact opposite.

Does anyone have any literature or code road map that can shed some light on this?

 

[bridgebuster]

Lion06,

Attached is the NYSDOT Steel Construction Manual - which incorporates AWS. There is a section with a procedure for welding reinforcing bars; NYSDOT uses E70 rods.

 

[Lion06]

bridgebuster,

Thank you for that document. It seems very similar to AWS D1.4.

I'm trying to understand the big inconsistency between PCI and other publications. Clearly, the AWS would trump PCI, but I would like to understand why such a big difference exists.

I would also love to see something more explicit from AWS, because my interpretation is that the E80 electrodes should be used based on my reading of the text.

 

[TLHS]

I've specifically stopped calling out required electrodes. I calculate based on the matching electrode for the weaker steel and refer the contractor to the appropriate code. At some point while checking something I caught a person calling out the wrong electrode and realized we were specifying something that's defined in the welding codes. The only thing we really do by specifying it in the notes is introduce the possibility of a screw up on our part.

 

[TLHS]

So I guess my answer is that I would have just referred them the CSA W186 (or whatever the US equivalent is)

 

[Lion06]

I thought I proofread my post, but, obviously, additions should be editions.

TLHS, so you always size your welds based on electrodes to match the lower tensile strength and stay silent regarding the electrodes on your drawings? How do you arrive at E70 electrodes for welding A706 to A36? Both have an Fu of 80 ksi (A36 has a range, but the top of the range is 80).