Welding on X20CrMoV12-1 (simialr to 422 SS) 1

[vg1122]

Dear Members,
I would appreciate your comments and guidance.
We are going to perform a weld repair on a coupling fit on the LP end of a shaft made of X20CrMoV12-1 (chemically similar to 422 stainless steel). We could not find the same material here in US. Hence we are thinking of qualifying the weld process with 422 Stainless steel. The hardness of the shaft is around 20.5 HRC.

Are we doing the right thing? I am concerned about the hardness.

Also, I could not find MTS 4Si filler wire. Should we use E410NiMo?
There had been some interesting discussions on welding of this material some time back (metengr) in this forum. Any comments from your experience and knowledge would be appreciated.

Thanks,
Vg1122

 

[metengr]

vg1122;
This is the thread you were thinking about

thread1135-113298

Are you sure about this material for use as a LP shaft material? 422 stainless is a martensitic stainless steel that contains alloying elements like vanadium and tungsten that create carbides for elevated temperature strength (to about 1050 deg F) in comparison to 410 stainless steel.


Despite the above, I would at least obtain hardness readings of the LP shaft end to be welded to decide on the method of heat treatment for the 422 stainless steel coupon for weld qualification. The base material selection for the coupon seems correct based on the similarity between materials. I would qualify the weld procedure using ASME Section IX guidelines and with an automatic GTAW process using circumferential stringer beads. Bends, tensile and hardness testing (metallographic examination of the fusion zone).


Item 2; filler metal
You did not mention the service temperature. I would be hesitant to use 410 NiMo because this is not really an elevated temperature filler metal. It is more suitable for ambient to lower temperature service. If you need elevated temperature strength and ductility, I would use an Inconel 82 filler metal for this repair.

 

[vg1122]

Thank you for the post.
The hardness value of 20.5 HRC was obtained on the LP end area to be weld repaired. It is going to be a weld build up with SAW.
We found a supplier who can provide MTS 4Si filler wire.
We will not be able to perform the hardening process at 1877F (the recommended for martensitic stainless steel) as it may cause dimensional changes. I am considering the following PWHT as remmended in the attached datasheet on Thermanit MTS 4 Si.

*Intermediate stress-releiving at first from welding temperature for 2 hours at 1022F followed by cooling to 248F.
*Tempering for 4 hours between 1328-1400F
(The current base metal hardness 20.5 corresponds 422 SS oil quenched from 1900 F followed by 1400F tempering for 8 hours - ASM alloy digest).

Will I be able to acheive consistency in hardness with this PWHT?

Thank you.

 

[vg1122]

Metengr,
Could you enlighten me on this:
The AUstenetizing temperature of 422 SS is 1905F. However, as we do not intend to go for that temperature in the suggested PWHT, what would be the effect on the weld material (whose chemical composition is closer to 422SS)?
(ie martensitic structure will not be acheived in the weld material.?)
Is there a way to get around this problem?
We will be doing local heat treatment only and even that will not allow us into 1900F range.

Thanks.
vg1122.

 

[metengr]

vg1122;
You know that the filler metal datasheet only pertains to the GTAW process, which as I mentioned above is what I would strongly recommend. If you intend to use the SAW process, you need to determine if the filler metal supplier can provide this and the recommended flux for the SAW process.

The post weld heat treatment will consist of only tempering the weld build-up and surrounding base metal using the recommended tempering temperature range as specified in the datasheet. I would suggest using 1350 deg F as the maximum temperature to avoid altering the hardness of the base metal (this is the hardness from the original quench and temper heat treatment of the LP shaft).

The quench and temper heat treatment listed in the filler metal datasheet should not be followed for this weld build-up repair, it could be if you wanted to remove the weld heat affected zone from the shaft base metal, but this is not practical.

The quench and temper for the 422 stainless coupon that you intend to qualify the weld procedure is appropiate and must be done, prior to welding.

 

[metengr]

[/quote]Will I be able to acheive consistency in hardness with this PWHT?[/quote]

Yes, I would expect a narrow hardness range by following the recommended tempering temperature (not the quench and temper). At a 1350 deg F tempering temperature, I would expect the hardness range would be above 21 HRc (maybe closer to 25 HRc). Also, this is why you need to qualify the weld procedure before welding to assure you have zeroed in on the essential variables.

 

[vg1122]

Thank you metengr.

I have found this site and the forums to be very much helpful.

vg1122.