Subjecting 307 (18-8-6 Cr-Ni-Mn) to extensive preheat?

[kingnero]

Is there a detrimental effect on weld deposit of stainless steel type 307, when it is subjected to preheat of 350°C = 660°F for 1h?

We've got high carbon steel (CEv = 1) that was surfaced with 13% Mn FCAW years ago. Now the piece needs resurfacing.
This steel needs preheat of 350°C, whereas the Mn layer cannot withstand 200°C (due to carbide precipition).

As you cannot tell what parts or what depth has been resurfaced with the Mn wire, I would suggest preheating to 350°C, then a butter layer of 307, then resurfacing with hardfacing rods 350HB.
This would mean that the 307 would be subjected to high temps for quite some time (30 minutes to 1 hour, the duration of the welding operation).

Any thoughts on the use of 307 as a butter layer at these temps?


For your information, the workpiece is a switch crossing of little importance made from rail steel.

 

[EdStainless]

you are talking about 218 stainless? Anything with 8% Mn is not a 3xx alloy.
You are looking to use this a weld overlay on steel, correct?
E307 weld filler is only 4%Mn, 20Cr, 9Ni.
If your filler is low C (not more than 0.03%) and you don't have a lot of dilution then the overlay should not sensitize significantly at 660F.
But I don't see why you don't directly apply the hardfacing?

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P.E. Metallurgy, Plymouth Tube

 

[kingnero]

Ed, thx for your response.

google for AISI 307: you'll find most suppliers have a composition of 18 (or 19)% Cr - 8 (or 9) % Ni - about 6% Mn (At least in Europe, we do).

Yes, this is weld overlay. Problem is that the underlying surface is possibly (or highly likely, depending on the exact location) Hadfield or 13% Mn steel.
This cracks and fissures enormously when heated. Hence a ductile butter layer (elongation = more than 35%) to stop the underlying cracks from mounting upto the surface, causing more chipping/spalling.

The hardfacing rods we're currently using have 0.10%C.

 

[EdStainless]

There is a UNS designation W30710, that is what I referred to.
It sounds like you are stuck.
I am guessing that they ignored perheat (or used a much lower temp) when they overlayed the Hadfield.
Grinding it off is your only real option, since you obviously don't want to start over on a new part.

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P.E. Metallurgy, Plymouth Tube