Reducing Hardness in SA 516-gr 70 welds

[OSUengr]

I need to qualify a WPS and the PQR coupon needs to be 1" thick SA516 gr 70 material. The processes to be qualified are FCAW, SMAW, GTAW, SAW. The welds need to obtain Vickers hardness of 200HV or less without performing a PWHT. We have done tests in the past but we had hardness levels over 200HV in the HAZ and WM. Does anyone have any parameters or recommendations, such as pre-heat temperature, amps, volts, heat input?

Thank you.

 

[vesselfab]

what weld filler metals/flux are you using for each process

 

[metengr]

OSUengr;
For starters, I would use a generous preheat of 250 deg F for 1" thick plate. I would limit the interpass temperature to 600 deg F. For plate thicknesses 3/4" and greater, I really doubt that you can achieve a consistent BM HAZ below 200 VHN because this is will be a function of carbon equivalent.

Why are you performing this work? This sounds like a weld related research project for a university, in lieu of a job specific activity.

 

[stanweld]

In terms of HAZ hardness, preheat and interpass temp is most important as well as carbon equivalent of the base SA-516 Gr70. metengr's recommendations should be followed. You should also be able to obtain SA-516 Gr 70 with restricted C.E. I've seen many heats with CE < 0.35.

 

[OSUengr]

Filler metals
SAW - electrod-flux combo F7A2-EM14K-H8
SMAW - E7018
FCAW - E71T-1C
GTAW - ER70S-2

This is a customer spec requirement.

CE for the base metal is .41







It is a customer requirement

 

[gtaw]

If all else fails, use a temper bead technique so the HAZ is tempered by the last weld bead.

High heat input will reduce the cooling rate and thus reduce the hardness. This should work provided toughness isn't a concern. Weave beads will increase the heat input (by reducing the travel speed) and increasing the amperage.

Best regards - Al

 

[vesselfab]

boy you've got a hard nut to crack. 200Hv is what a lot of the steels will be from mill.

You may have to look around for some extra low CE steels.

 

[Mr168]

May want to have a talk with the customer about alternatives.

You may be able to generate a PQR that eventually meets the requirements, but what are the odds of consistently replicating these results in the field?

 

[OSUengr]

Thanks for all the help...

 

[weldtek]

For Welds the only consumable likely to be problematic is ER70S-2.
The HAZ's may pose issues, especially with a CE of .41. The best advice has already been given.

 

[unclesyd]

If you are using high preheat on of the older approaches is to wrap the weld area with insulation lagging. I have used this approach on highly constrained weldments.