4130 to 4340 With PWHT

Date 03-26-2009 17:21

I have to qualify and write a WPS to weld (GTAW) grade 4130 sheet to grade 4340 bar. The weldment is then heat treated to 180-200 KSI in tensile. I would like to use ER4130 as a filler. My questions are:

1. Will the greater carbon content of the 4340 create the possibility of cracking due to dilution of the 4130 filler?

2. How hot should my preheat be?

3. Does anyone have a better recommendation for filler?

Thank you, gentlemen.

By ravi theCobra (**)

Date 03-26-2009 19:08

My first question is do you have to meet the tensile strength ?

By RonG

Date 03-26-2009 20:24

180-200 KSI sounds like it will require Heat Treat (Quench & Temper)(45-48 RC) rather than PWHT.

By 803056

Date 03-27-2009 02:49

Provided you use sufficient preheat and interpass temperature, you should be able to weld without cracking. The postweld heat treatment above the critical temperature, i.e.,, lower A1, will serve to relieve any residual stresses and if quenched, will require a tempering operation to temper the Martensite present after quenching.

The PWHT should be performed immediately after the welding. Cracking, if it occurs, would most likely occur within the first few hours after cooling down to ambient temperatures.

You may pick up a little carbon through dilution with the 4340, but the dilution will be minimal using GTAW. Again, sufficient preheat is the silver bullet that will make this work.

Best regards - Al

By bozaktwo1 (***)

Date 03-27-2009 13:43

Thanks Al, that's what I needed.

I think I'll have to perform a controlled cool down, because the heat treat vendor is out of town. Maybe allow it to cool in air to 350 or so, then hold it to 50 deg./hour.