High strength spec for non pwht 4130 weldeing

[Ibreakstuffdigitally]

We're in the unfortunate position of being unable to heat treat a 4130 frame. Our design is made from 3" OD 100 wall and 2" OD 65 wall tubing, and is sufficiently large that every heat treater we talk to waxes poetic about how much the thing's going to deform.

As such, I'd like to find a spec for the best mechanical properties I can expect to get from welding pre-treated tubes. We can heat treat to as high a strength as 155 ksi beforehand, but it's what's left in the HAZ after the fact that I'm concerned about. We are also not tied down to any specific weld rod. Since we won't be post weld heat treating, there's no particular requirement for a material match, at least none I can think of.

Unfortunately, I also need ductility. The part will be subject to significant shock loads, which it must withstand without brittle failure, so a 10% elongation is another requirement

Any suggestions on how this might best be accomplished, and the best material properties I might expect, would be very much appreciated!

 

[metengr]

Ibreakstuffdigitally;
If you are going to heat treat the 4130 material, prior to welding, you need to watch your heat input to avoid affecting bulk mechanical properties. I would suggest using the GTAW (TIG) process to assure a more localized heat input. The preheat would be 300 deg F, and keep the interpass below 600 deg F.

Regarding filler metal, I would investigate an ER120S-1 filler metal, as referenced in AWS SFA 5.28. The Ni addition will improve toughness at higher stregnth.

I would qualify a welding procedure using the above information.

 

[Ibreakstuffdigitally]

Thanks,

We often use ESAB Spoolarc 120 for welding astm A514 or HY 100 steel plates, and it's classified as AWS/ASME SFA 5.28 ER120S-1. We've had good experiences with it.

Are there any guidelines with regard to expected degredation of mechanical properties of the material in the HAZ, or is it purely going to be a case of test and see?

 

[metengr]

I try not to predict because I need my day job to pay the bills. Test and see.....