Welding advice:316 stainless to carbon steel 4130 1

[montec]

I am looking for a specification or suggested procedure to cover a welding process joining a 316 SS pipe cap to a 4130 outer ring with a butt and/or fillet weld joint. Post weld, I would like to increase the yield strength of the 4130 by heat treatment. I seek any guidance for a heat treat procedure that won't significantly affect stainless component and weld filler properties. Thanks y'all.
Montec

 

[metengr]

montec;
The filler metal for this dissimilar metal weld joint would be 309. What exactly do you need in terms of strength level for the 4130 versus the weld joint strength? 4130 is a low alloy steel and can be hardened by thermal treatment. However, the heat from welding will have an effect on the 4130 steel properties adjacent to the weld joint, so you need to be specific regarding the base metal (4130 alloy steel) strength requirements, and the limitation associated with the dissimilar metal weld joint strength.

 

[montec]

Thanks metengr:

The yield strength I'm looking for on the 4130 ring is 100 to 150ksi.

-montec

 

[metengr]

montec;
This is considered high strength and would require a quench and temper heat treatment to achieve before welding, not after welding. If you heat treated the 4140 before welding, you would need to factor into your design the location of this dissimilar metal weld joint because the heat from welding will locally soften (reduce the strength) the 4140 base material. Also, the filler metal and 316 ss will be much lower in yield strength in comparison to the heat treated 4140 base material.

I would suggest you carefully review you material selection regarding the use of a dissimilar metal weld.

 

[metengr]

montec;
The above should read 4130 not 4140. Sorry about that, I was involved with a job this morning regarding 4140 steel and for some reason it carried over into my thought processes.

 

[montec]

Thanks again, metengr
I was laboring under the apparent mis-conception that a heat treat could be done after the welding of dissimilar metals to compensate for the effects of weld heat in the 4130 parent metal if it were soft to start with.

It looks like I should prepare a sample welded coupon of these materials and have it tested to failure before going any further.

I am most appreciative of your input, metenger

-Montec

 

[metengr]

montec;
Yes, unfortunately with dissimilar metal weld joints thermal treatment after welding is normally restricted to one of the two base materials being joined. In this case it would be the 316 stainless steel because it cannot be hardened by thermal treatment. In fact, the 316 ss would suffer corrosion performance by subjecting it to a quench and temper heat treatment for the 4130 alloy steel.