pre heat and post heat EB welding for aisi4340

[Kulungi]

Eb welding of material AISI 4340 in accordance with ASTM A519 does this require a pre heat? Also after EB welding does this material require post heat and what at temperatures is required?

 

[metengr]

For 4340 steel, I would recommend preheat as a minimum for any fusion welding process because of the hardenability of this steel. The preheat should be 400 deg F minimum.

Regarding PWHT, this depends on several factors; weld joint geometry, materials being joined, etc, and service duty.

If you provide more information, we can determine if PWHT is necessary.

 

[Kulungi]

I have two different joint configurations
1st joint is a overlap joint with a .200 deep weld on a round 5 1/2 diameter.
2 nd weld is 100% penetration with .400 deep weld that joins 3 details together. This diameter is 4 3/8 round. An end cover and two layers inner and outer (one slides over the other) approx. .200 each joined in the first weld at the other end of the part.
So first weld is to be done, the parts get machined and second weld is to be done. What process should I use to avoid cracking?

 

[metengr]

Kulungi;
I thought that you were using electron beam (EB) welding for the entire job (both welds). Is this the case?

Based on your second weld joint configuration, I would perform a post weld heat treatment to assure some level of stress relief and softening in the base metal heat affected zone.

The selection of PWHT temperature will be based on your original heat treatment condition for the 4340 steel. Can you review the mill certifications and determine what the tempering temperature was for the material? If you have this information, the PWHT temperature should be 50 deg F below the original heat treatment tempering temperature to avoid changing the bulk properties of the parts.

 

[Kulungi]

Yes both welds are EB. I will check on the material to verify its original condition but the part have been machined would that change heat treatment condition?

 

[metengr]

No.