Welding 316l to Super 13 Martensitic UNS S41426 (SM13CRS) 1

[acrmnsm]

Further to the very helpful response to thread330-393368 I have now been asked to look at welding 316L to Super 13 Martensitic UNS S41426 (SM13CRS)with 110ksi yield - I am trying to understand the recommendations for this - the weld spec says 309 filler wire, is that Ok.
Secondly the recommended PWHT is heat to 1400F and cool to 360F over 3 hrs. The UNS S41426 is a Q&T martensitic steel - so I assume that we will not get anything like the 110ksi yield? What is the yield likely to be then? I don't think we can quench and temper with the 316L material welded to it can we?

 

[metengr]

In lieu of using 309 filler, I would use a nickel-base filler metal, like Inco 82 or equivalent. This type of weld joint will require buttering the SM13CRS using the Inconel filler followed by a subcritcal PWHT to temper the HAZ in the SM13CRS. Once this is step is completed, you can finish the butt weld to the 316L using low preheat and interpass of 300 deg F with Inconel. If you follow the above, the bulk properties of the SM13CRS will not be affected.

 

[weldstan]

Why do you care about matching the tensile properties of the higher strength material? As long as the strength of the weld metal is equal to or greater than the lower strength material is all that really matters. I also concur with mwtengr's recommendations.

 

[acrmnsm]

I see your point, but there are situations, like this one, where the higher strength material is loaded and lower strength is not.
EDIT- Sorry i mean to say that the loads through the higher strength material are different than those through the lower strength material.

 

[metengr]

acrmnsm
As a point to weldstan's comment, you better be sure the weld joint design is such that it is truly located in a low stress region or otherwise problems will develop. I can't tell how many times folks were fixated on how to weld rather than to design for DMW's in service.

 

[weldstan]

Even so the deposited weld metal would not be subject to the full load. You would then need to determine the minimum strength required or increase the thickness of the higher strength material to compensate for any loss of strength due to welding.

 

[acrmnsm]

Ace, i think you understand my problem now. Imagine a flat plate in tension, of SM13CRS, with a bar of 316 welded perpendicular to the plate, the bar experiences no other external loading.
So we would like
either
1) The weld process including PWHT to not affect the SM13CRS plate yield strength significantly (which I do not think is possible, hence my question)
or
2) To estimate the reduction in yield strength so that we can redesign the plate to take the required load.

 

[metengr]

acrmnsm
If you perform a sub-critical PWHT for the SMSS after buttering it will not reduce the bulk mechanical properties. The sub-critical PWHT should be performed 50 deg F below the original tempering temperature. The purpose for the sub-critical PWHT is to reduce only the HAZ hardness in this application and residual stress.