Why is E6010 used for root pass on materials higher than 60,000 psi 2

[engr2GW]

Hi,
Other than ease of penetration, why is E6010 used for root pass on materials higher than 60,000 psi tensile strenght, I thought the strenght of the electrode should be that of the material or higher.
I've seen WPS with E6010 root and 7010 or 7018 fill and cap on a material of 70,000 psi

 

[metengr]

Because certain users feel that they can pull successful roots using E6010 on higher strength base materials. As long as the weld procedure specification is qualified, this is acceptable.

 

[stanweld]

Many high strength micro-alloyed steels (X65 & X70) exhibited root bead cracking when welded with matching strength E7010 or E8010 electrodes due to dillution with the base metal. Welding the root with the lower carbon equivalent E6010 electrodes mitigated cracking without reducing strength of the welded joint.

 

[engr2GW]

Thanks all

@ Stanweld; could you please explain what you mean by dillution when E7010 and E8010 is used on 70k and 80k materials, and how the cracking resulting from that is mitigated by the use of E6010 root instead or how the dillution in the former did not happen in or affect the use of E6010 electrode for root bead.

Thanks.

 

[stanweld]

Typically 30% and more of the base metal alloy constituents are deposited into the deposited weld metal in the root due to the combined melting of the welding filler metal and both sides of the base metal. This increases the effective carbon equivalent of the deposited weld metal in the root pass. If the filler metal has a relatively high C.E. to begin with, the addition of alloying elements like carbon, manganese, molybdenum, vanadium and niobium from the base metal increase the potential for hydrogen cracking in the deposited weld metal. Lowering the C.E. in the electrode (E6010)lowers the C.E. in the deposited weld metal which reduces the potential for cracking.

This