Heat treatment of Austenitic SS

[JohnPhillimore]

I need some advise on the heat treatment of 1.4404 Austenitic stainless steel welded link chain. This is required to restore the strength of the material following cold working and welding.

As I see it we can either stress relieve it at a temp of around 375 C, or solution anneal it at around 1100 C.

My problem is that I'm not too sure what effect the proccess have on the steel (particularly stress relieving) and what effect the higher temperature in solution annealing will have on the weld.

The chain is to be used in a fairly high stress area suffering much shock loading.

 

[swall]

What specific alloy was used and what was the welding process?

 

[EdStainless]

First of all, what is the design strength?
If you anneal you will be back to 30ksi yield or so.

Why are you heat treating at all? Any heat treatment will lower the strength, but it will increase the ductility.
Typically with these alloys you either leave as is or do a full solution anneal.

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[JohnPhillimore]

Thanks for the prompt replies

swall: the alloy being used is X2CrNiMo17-12-2 No. 1.4404 to EN 10088-2 which I believe to be a 316 SS. The welding process being used can be either resistance butt or flash (the manufacturers choice) using filler rod 19.12.3.L.S1 to EN 12072.

EdStainless: The design strength is a mean stress of 800 N/mm2. The simple answer to why are we heat treating is because our drawings say it should be! I am lead to believe that there has been problems with them in the past and concerns regarding inclusions.

A bit more background info:
Our drawing states that they should be "stress relieve at 700/750C after welding" (as it has done for many many years), but our current supplier has questioned this (quite correctly IMHO) suggesting that this may be damaging to the SS.
These chains are used to link a team of horses to a heavy gun carriage which is then pulled at high speed in a public display arena, and should a link fail it could potentially have fatal consequences with a gun carriage going into the audience!!

 

[EdStainless]

You are correct. The 700-750C would probably lead to sensitization of the material and reduce its toughness.
The 800KPa strength level is for cold worked material, if you anneal you will be at a fraction of that.

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Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net

 

[arunmrao]

I guess your requirement can be met by using low alloy steel chain links which can be comfortably formed,welded,heat treated and then for aesthtics and corrosion resistance be chrome plated.

The cost will be several times lower and as you have rightly ponted 700-750C tempering only aggravates your problem.

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

 

[metengr]

Agree with arunmaro, you should not be using stainless steel chain in this application.

 

[JohnPhillimore]

Unfortunately a plaited chain is likely to suffer from the repeated buffeting it will receive whilst in service resulting in the plaiting failing prematurely. As these are used in a ceremonial role it is an essential requirement that they have a polished finish.

I am looking at specifying grade 8 chain complying with EN 818-2.

 

[swall]

What you could do is make the chain out of 17-4 PH stainless, then give it an H-1100 heat treat after welding.
Finish up by electropolishing for a nice appearance.

 

[EdStainless]

If I was doing this I would look at using a duplex stainless like LDX2101 or 2205. Weld with 2209 and no heat treatment. Good corrosion resistance, good strength, and good resistance to SCC. Your minimum tensile strength would be about 660MPa (memory).

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Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net

 

[unclesyd]

Here is one supplier of SS chain. They list the Working Load Limits for their 316 chain. Nearly all chain used around people should be certified as to the WLL. I think this is an OSHA requirement that says the chain should meet NACM guide lines.

http://www.1st-chainsupply.com/chain/stainlessus/38-338US.html

There is a place in Georgia that will test your chain to
certify/recertify it.