Justification to not weld 316L and 4140?
Justification to not weld 316L and 4140?
(OP)
Hello,
We have an application with a rotating horizontal shaft with overhung weight. We must weld a corrosion-resistant collar of 316L combination bevel/fillet welded to the 1018 shaft and due to the overhung load these welds are machined and polished. The collar is long enough vs. it's thickness that it is not full penetration welded.
Now we have an esteemed customer who requested 4140 instead of the 1018 carbon steel and our spec review did not catch this stipulation. Unfortunately there are ways to make 4140 and 316L stick together with welding tools (note choice of words) with no discussion of joint strength and I'm seriously concerned that doing this in this application will result in high notch sensitivity, corrosion sensitivity, and fatigue failure. While stress levels are low the stress is pure alternating fatigue.
Is there a welding code that could provide guidance (a categorical "no!" is acceptable) about the proposed 4140/316L design? I see a lot of information out there about how to weld 4140 but not related to 316L and highly stressed joints.
Thanks,
David
We have an application with a rotating horizontal shaft with overhung weight. We must weld a corrosion-resistant collar of 316L combination bevel/fillet welded to the 1018 shaft and due to the overhung load these welds are machined and polished. The collar is long enough vs. it's thickness that it is not full penetration welded.
Now we have an esteemed customer who requested 4140 instead of the 1018 carbon steel and our spec review did not catch this stipulation. Unfortunately there are ways to make 4140 and 316L stick together with welding tools (note choice of words) with no discussion of joint strength and I'm seriously concerned that doing this in this application will result in high notch sensitivity, corrosion sensitivity, and fatigue failure. While stress levels are low the stress is pure alternating fatigue.
Is there a welding code that could provide guidance (a categorical "no!" is acceptable) about the proposed 4140/316L design? I see a lot of information out there about how to weld 4140 but not related to 316L and highly stressed joints.
Thanks,
David





RE: Justification to not weld 316L and 4140?
Whether the design with the intended manufacturing methods will be effective is another matter.
RE: Justification to not weld 316L and 4140?
Above all the extra strength of the 4140 is of no value in this application so the 1018 is preferred for it's familiarity.
RE: Justification to not weld 316L and 4140?
RE: Justification to not weld 316L and 4140?
It is understood that these manufacturing methods are more expensive than those used in your current design. You could inform your customer that whereas you have not manufactured equipment to their design, service life cannot be predicted. Service life of your currently designee equipment is predictive and you will extend your warranty accordingly if they will relent.
RE: Justification to not weld 316L and 4140?
Weld onto the 4140 with a general Ni filler (Inco 82 or similar). Remember your preheat. Then you could even re-temper the shaft at that point for stress relief.
After that you should be able to make your attachment welds for 316 to the Ni patches without damage to the 4140.
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Plymouth Tube
RE: Justification to not weld 316L and 4140?
If for some reason we need to develop and qualify a 4140/316L weld procedure you've provided good starting point for that process.
It's the second part of the question (strength and toughness) that became the determining factor - lacking any data on the structural performance of the 4140/316L welds, we would need to develop a weld process and the joint would have to pass performance tests in order to be found suitable for the design. That is not commercially justifiable for this case. I'm sure I'll be asked again and this information will greatly help frame expectations of the customer.
In many cases we build our shafting out of whatever material the customer prefers for their process, which means switching between low carbon steel / austenitic stainless / duplex stainless / monel/hastelloys. The welding of those materials is trusted and well known here and the materials are fairly tough even after welding.
Rarely are we asked for high carbon alloys like 4140 to be used in a welded application which is why I was hoping to find data that gave me trust in the 4140/316L process. It is dangerous to assume that our product testing and development using low carbon materials can roll over and assure the 4140 will work equally well; I had to tell them no.
RE: Justification to not weld 316L and 4140?
RE: Justification to not weld 316L and 4140?
David
RE: Justification to not weld 316L and 4140?
Weel, just to help you in the future, you can temper bead a butter layer on the 4140 side of the weld joint as mentioned above and through grain refinement (using this controlled bead deposition process) one can obtain toughness in the BM HAZ that can even exceed the Q&T base material notch toughness. There is a time and cost factor involved.
RE: Justification to not weld 316L and 4140?
RE: Justification to not weld 316L and 4140?