GTAW filler rod selection

[10secBu]

I have been welding Mild steel with ER70-S6 and chromoly with ER70-S2. I understand that Er80-s2 (?) is the recommended rod for 4130 chromoly tubing.

Is there any negative effect of using the ER80...rod on mild steel?

I'm just wondering if it's possible to use one rod for both mild steel and chromoly without any negative strength effects on either?

Maybe this should be asked a different way...

What filler rods should be one have on hand for different materials...most commonly used?

Lastly, I understand that some welders choose a silicon-bronze rod for Tig welding sheetmetal to limit heat input/warpage. What is the numerical designation for this wire?

thanks
Todd

[Kevin Disney]

Todd,

ER80-S2 is a higher strength rod, the 80 means 80,000 psi tensile strength. This is a good choice for welding chrome moly but not necessarily for mild steel. The finished weld will have a significantly higher strength than the mild steel base metal. You also lose some ductility which makes fatigue cracking more likely to occur near the toe of the weld (the point where the weld metal and base metal meet). Recommend you stay with ER70-S6 on mild steel and ER70-S2 or ER80-D2 on chrome moly.

[ASKANDY]

Excellent Kevin!