1% Cr, 1% Ni and 1% Mo steel ?

[kingnero]

I got a request for surface repair welding (build-up for bearing mounting surface on a shaft) on a material that has been analyzed with:

.15%C
.3%Mn
Si between .15 and .80
1.15%Cr
.8%Ni
1%Mo
.15%Cu
.3%V

Hardness 250 HB

This chemistry is something I haven't encountered yet. Anybody cares to give his opinion about weldability, filler material, heat treatment, ... ?

 

This does not correspond to any SAE low alloy steel. How was this analysis done? I would not proceed without being certain the analysis is reasonably exact, especially carbon. (NOTE: PMI, or portable X-ray analysis, is NOT adequate.)
The hardness seems low, indicating the steel is hot finished or annealed.
.
If this analysis is anywhere near accurate then the potential for very high hardness is there along with the potential for cold cracking, unless steps are taken to mitigate. This includes ample preheat, strict moisture control practices, appropriate welding techniques and heat input, and post-weld soaking. All while minimizing shaft distortion, which actually could be your biggest risk.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[kingnero]

Thanks for your quick reply. One of my previous questions on this forum was about the accuracy of analysing equipment. Having spent some time and discussions about this subject (with real experts), I'm bound to believe even the carbon content is reasonably accurate.
I hope this answers your question, due to contractual agreements I cannot elaborate much further on this subject.

Thanks also for the warning, I suspected cold cracking might be an issue.
Shaft distortion is under control due to much experience with repair welding of rotating equipment. Automated GTAW welding will be used.

Any ideas about filler material? As I've got no sample material to perform tests on, this is my major concern. I'd much prefer some testing, however this does not seem possible for the time being.

 

[EdStainless]

The chemistry sort of reminds me of A734 typeA, or a low C version (older version?) of D-6a.
In either case it would be a high strength material.

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P.E. Metallurgy, Plymouth Tube

 

[Dhurjati Sen]

Dear kingnero,

Weldability : Moderate

Filler Wire : ERNiCrFe3

Heat Treatment: None

Regards.

DHURJATI SEN

 

DS,
Why recommend a filler metal here, and why nickel? Adding different metallurgy unnecessarily complicates the situation.
The application is recovery of metal by build-up, so the objective here is to match the mechanical properties and basic metallurgy while maintaining dimensional integrity.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Tmoose]

"Bearing mounting" = ball or roller bearing mounted on the shaft?

I'd be some concerned with why the bearing journal/seat is damaged.

If the application bearing is secured by silly setscrews or eccentric collar, and the equipment is belt drive, then typical fits with .002" or so clearance are likely to "fail" via bearing loosening again despite excellent workmanship on your part.

If ball/roller bearings with tapered adapters are used, then the bearing loosening and tearing up the shaft likely originated with improper installation techniques. Repairs are likely to "fail" via bearing loosening again despite excellent workmanship on your part.

If instead this is the journal for a plain / sliding bearing, then the failure was likely due to a lubrication issue, and if those are not resolved, repairs are likely to "fail" again despite excellent workmanship on your part.

I am sure you are aware of weld induced distortion, and the possibility that the damaged bearing seat can be full of stresses that already may have put a hard bend/kink in the shaft, requiring heroic measures including multiple shaft straightening efforts and remachining other regions of the shaft to maintain runouts ~ .001" or so.

 

[kingnero]

There is wear to due age (we're talking about revision of gas turbine rotors). Bearing work (inner race to be mounted directly on the shaft) is done by a team of the bearing manufacturer.

Also, Hastelloy and such are not considered as filler material. Trying to match base metal as much as possible.

 

[EdStainless]

There are some weld fillers that are closer to your chem.
Such as 10018-N1, 12018M, or HY-100.
Good luck.

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P.E. Metallurgy, Plymouth Tube

 

Careful EdS, those are overkill.
The alloy in the filler + the carbon dilution from the base metal will give a deposit much harder than the substrate. Matching the final properties is the bottom line, not matching composition.
Normally I tone down the filler metal by at least one strength class to mitigate the hardness, even if stress relieved.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Sparweb]

As I've got no sample material to perform tests on, this is my major concern. I'd much prefer some testing, however this does not seem possible for the time being.

Then your material selection is even more dependent upon determining the right base alloy than it would be if you could test and confirm before reworking the part.
Are you sure the chemical test wasn't contaminated? You've given a detailed chemical analysis but 3 clever guys are still guessing. That's a clue to me that something is wrong, or missing.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

 

[kingnero]

Yes, I'm convinced the analysis is done correctly. In this sector, custom made alloys are common (anyway, more common than elsewhere). That's why the fabricator also invested in a state of the art in-house materials analysis laboratory complete with trained guys to operate the equipment.

I agree however this is a funny alloy with lower than axpected hardness. That's why I asked here.

 

[EdStainless]

That is the problem, do you match strength with a low carbon non-alloyed grade.
Or do you start adding some alloying knowing that you will get stronger.
Even HY-100 filler is under 0.15% C, and the others are a little lower in C.

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

 

[kingnero]

Busy with this at the moment. Will keep you updated.

 

[kingnero]

Performing tests with X70 filler wire after consulting with a materials engineer.
Taken into account: current microstructure of the material, heat treatment before (initial production) and after welding, application, hardenability of the filler, ...