Welding of 415/425 martensitic stainless steel 2

[kingnero]

Situation: large casting of cast X5 CrNi 13 4 (werkstoff nr. 1_4313) needs repair welding due to surface defects.
Base material:
.025 % C
.45 Si
.55 Mn
.012 P
.004 S
12.60 Cr
4.62 Ni
.45 Mo
.012 N
310HV20
900 MPa f_y
944 MPa f_u
Application: impeller vanes repair (surface damage).

I see two options:
(1) Welding above M_S temp
(2) Welding below M_F temp
In both cases, taking precautions against hydrogen introduction.
Filler: 410 NiMo, regular 420 (? , see below)

My idea is to go with option (1), so I need to calc or obtain from literature the M_S temp, apply a 30°C safety margin, and use preheat and interpass minimum temperature of that value. Slow cooling. How would I selectively temper several repair locations of a multi tonne casting? Calling in an induction heating specialist? Will they have PWHT procedures ready to go, or where would I find those?

However, %C in the base material is very low. Do any of you have recommendations for this? Would Zeron 100 "X" grade filler be an option in order to not apply PWHT?

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[EdStainless]

Was the entire casting heat treated? If so, how and what temp?
If this is really a martensitic alloy it would respond to Q&T, but with this low of a carbon (and high Ni and N) I doubt that it is martensitic.
A reasonable amount of pre-heat and controlled cooling should be adequate.

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

 

[kingnero]

Ed, thx for your reply. I didn't even consider the option of this not being martensitic.
The part is 20 yrs old, all they have are the mill certs and reports of balancing. No mention of any heat treatment, however hardness is given. I'll consult with a metallurgist and see if they can offer any help regarding the welding and PWHT (if necessary) procedure.

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[metengr]

If this material is X5 CrNi 13 4, it is similar to a CA 6NM, a cast martensitic stainless steel. Low carbon controls the hardness of martensite. I would follow the welding requirements for welding CA6 NM, there is also a similar composition filler metal.

http://www.kubotamaterials.com/alloys/corrosion_resistant/CA6NM.pdf

 

[kingnero]

Thanks for the document, googling CA6NM gives again some interesting reading material.

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[weldstan]

Depending on corrosion service, repairs to this material have often been done with E/ER309L filler metal.

 

[metengr]

thread338-304849

 

[kingnero]

Extremely helpful thread!
Thx Weldstan, both 308 and 309 have already been mentioned in the discussions...

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As mentioned by metengr, this material is similar to CA-6NM. Fortunately for you, the carbon is reasonably low, for hardness of this alloy is extremely sensitive to C content.

Your filler metal choices are:
(i) Matching = E/ER410NiMo if you need strength; or
(ii) non-matching = E/ER308L or E/ER309L if you just need to make up dimensions.

With (ii) you might get away without PWHT if you preheat and use small stringer beads similar to temper bead technique. For PWHT follow ASME VIII-D1 (P-No. 6, Gr-No. 4).

Since this alloy is susceptible to hydrogen cold cracking, I recommend a low-hydrogen process (GTAW if small, GMAW if bigger). If you must use stick, follow extreme moisture control practice (including austenitic fillers).

When using E/ER410NiMo filler, the weld will actually be harder than the HAZ, and is at least equally prone to cold cracking. If you can, purchase 410NiMo filler with 0.03% max carbon (0.02% max preferred). Preheat but not more than 300°F and do not let interpass temperature run too high or you may run into this alloy's low ceiling for austenite reversion. Preheat does not have to be as high as for Alloy 410 (a quite different martensitic SS). A post-weld soak is recommended.

 

p.s., Austenitic weld deposits have reasonably good cavitation resistance. 308 is better than 309 in that respect.

 

[kingnero]

Thanks to the man with the best username - ever

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haha, thanks kingnero.
I wanted it for a twitter handle but it was too long, so I guess the world will have do be deprived of my fake news.

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