SA285-C vs SA516-70 1

[jghtech]

Have previously used SA285 Grade C plate for the construction of miniature boilers. A quantity of SA516 Grade 70 plate has been made available to me for the construction of another miniature boiler. Would a list member please advise if there are any welding considerations to be taken into account when using SA516-70 vs. SA285-C?

 

[metengr]

The SA 516 Grade 70 is excellent pressure vessel steel plate material to weld and fabricate. For miniature boilers, my preference would be ASME SA 515 Grade 70 because it is more suitable for elevated temperature service. Follow the preheat and post weld heat treatment requirements as defined in ASME B&PV Code, Section I. Both steel plate materials are P-No1 designation.

 

[chaulklate]

Although both materials are P1, they are different sub groups. The 516-70 material is G2 and the SA-285-C is G1. The lower the group number, the lower the yield stress. It will depend on what the stress value of your weld rod/wire/consumable is. If you used 65 KSI rod to qualify your 285-C weld procedures and want to use the same procedure for 516-70, you would want to derate your seams to the lower stress value. It is not common practice to use a lower yield consumable than the base metal. Check your weld procedures, your consumable should be 70 KSI or greater to use it on 516-70 or else you are looking at the material stress derate. Or else do your calculations based on the lower stress values of 285-C and use the 516-70 as a higher substitute.

Or at least that's what I believe to be true.

 

[metengr]

chaulklate;
Yes, you are correct. The ultimate tensile strength for the SA 285 Grade C plate material varies from 55Ksi up to 75 Ksi. However, Section II will only credit the 55ksi for design purposes. I doubt that one would use an AWS 5.1 E6010 weld rod to qualify for a full penetration groove weld, but you never know. I would expect that the OP's WPS would have been qualified using E7018 for the SA 285 Grade C plate.

 

[deanc]

I would also suggest SA-516 Gr70. It forms better and will not fire check as bad.

Lots of times E6010 is used for tacks and roots,fill and cap with E7018.

If you are joining a replacement part on to something that is old or has been in service E6010 works much better for your first layer.

 

[JoeTank]

I often see E6010 used for SA285 Grade C material. I think deanc is correct that more often E6010 is used for root pass only. Strength wouldn't be an issue with SA285 C, but E6010 does tend to have lower toughness than E7018.

Joe Tank

 

[jghtech]

Thank you to all respondents. Calculations will be based on 285C with 516-70 used as a higher substitute.

 

[deanc]

jghtech

Nice thought....but I would want to see calcs. for what is used. There are other considerations.