GTAW 304SS to 410SS w/o preheat & w/o PWHT 1

[tc7]

I have the unfortunate job of field repairing equipment that involves 302/304 threaded fasteners that were originally GTAW welded to a 410 base plate (the base plate was originally heat treated to HRC35-40). The attached fasteners need to be removed and replaced.

All guidance I have seen so far indicates that I should preheat the 410 and then stress relieve after welding - neither will be practical or possible in my present circumstance.

I am tentatively selecting a 309L filler as my calculations show a resulting FN of ~10, not bad (I think). This is based on WRC-92 and Dr Kotecki calculations with the assumption of 15% dilution with each base material. Same calculation with 310 welding rod shows an FN off the chart so I assume this indicates a fully austenitic weld will result(not good, I think).

There is no governing welding code for this job, so a full blown procedure qualification is not required.

Any advice/comment/criticism from the board is invited please.

Thank you.

 

[tc7]

Hi DekDee and metengr-
In the OP I said it is not 'required' in the sense that I am not strictly bound to meet any Code minimums which is semantically different than "not needed". As you may have noticed, I am not marching blindly into this and obviously am giving this much thought and research. It's always my custom to brainstorm these odd ball jobs and conduct trials of some form. In my application I don't think I need tensiles or bends as the construction is fillet welds only. This is likely to be a one time effort and so I'll place my available resources where best served which is, in my own opinion, in macros and traverses of the mock-ups I said I was going to do.

Please stay tuned and please continue to offer any advice that might be useful to me.
Best Regards.

 

[metengr]

Good, and use 309L versus 308L for your butter layer.

 

[tc7]

Can certainly do that metengr,
But what is your reason for urging the 309L ?

 

[metengr]

tc7;
Take a good look at a Schaeffler Delong diagram and you will see that using 308L will result in a dilution zone within the weld deposit that I think will result in cracking concerns from/during solidification. Again, for DMW, you stay away from 308, 316 type electrodes, and go with 309, 310 or even 312 electrodes.

 

[tc7]

Got it!
Thank you.

 

[CoryPad]

tc7,

Thank you, that makes perfect sense. I can state from experience that sulfur concentration around 0.035 % in base metals is enough to cause centerline segregation and cracking when welding with NiCr-3 filler metal.


metengr,

Would you consider a joint between ductile iron and low alloy steel to be dissimilar metal welding? Fraunhofer Institute in Dresden recommended 308LSi for that application.

 

[metengr]

CoryPad;
For the family of ferritic ductile irons I would not for the simple reason it would behave similar to a higher carbon, higher silicon version of low alloy steel in terms of weldability. If you are talking about the family of austenitic ductile irons, this would be a DMW to low alloy steel.

 

[EdStainless]

Can you drill a sample from the base plate an d really check the carbon?
If it is under 0.10% then any small amount of preheat will be good enough.

I like the sound of 309 filler. If you are thinking of buttering it only needs to be done on the 410.
And if the fitting really is 303 throw it away and force them to make a new one. You can't trust the strength (fatigue) of 303 anyway.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[tc7]

Here is an update as promised, if anyone is interested:

We pursued the welding recipe as listed in the 28 Sep post except I chose to follow metengr's urging to use 309L instead of the 308L.
After a few trials, we quickly decided to give up the use of the NiCr-3 (Alloy 82) filler because it was absolutely a nightmare to weld with as it was very sticky and hard to flow deeply into the corner of the root. Outside of the root we had good penetration but our cross sections showed very little penetration into the corner.
So we proceeded to run out a few more mockups with purely 309L and had very good success. We applied the sledge hammer test to a single 303 bar welded to a 410 plate and smashed it into destruction. It took about 15 hits with a 10lb sledge in a variety of directions before the bar separated. Attached pics are testimony to the effort. Other samples were sent to the lab for macros and traverses and I'll post them later for interests sake.

 

[tc7]

I can't figure out how to attach more than one file at a time. I thought this additional photo was important to the story so added it with a new post. This is what we started with.

 

[EdStainless]

Did you look at the failure with a magnifying glass?
Was it ductile?
That is the real issue here. Over all it doesn't look bad.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube