Welding, Stainless Steel S310, and Magnetic Permeability

What is the application that you are worried about magnetism?

316 has properties added to it to make it magnetic.

With 304 there shouldn't be any problems with it becoming magnetic unless you are using abrasives or something with contaminates in it.

Actually if you use an inertial weld or friction weld you may avoid these difficulties. Thats what many solenoid manufacturers do. milo

SS304 and 316, in the usual as-delivered status are austenitic, but a small percentage of delta ferrite is present, which makes those steels slightly ferromagnetic.

Ferrite (alfa and delta) are ferromagnetic and therefore have a very high relative magnetic permeability (μ = B/H) which can be more than 100.

Austenite is paramagnetic and has a relative magnetic permeability slightly above 1.

Delta ferrite content in as welded SS304 and 316 be in the order of 3 to 10%.

As welded 310S is fully austenitic, so the magnetic permeability must be lower than 304 and 316.

But care should be taking during welding due to susceptibility to hot cracking of all fully austenitic SS.

Best regards

We have used S316, however, the magnetic permeability increased significantly after welding process.

As S310 is a full autenitic, and in terms of Schaeffler Constitution diagram, it should not has the problem. I wonder if anyone has the experience of welding S310, if the magnetic permeability is increased after welding?

What kind of welding process can avoid increase magnetic permeability for S310?

You can use similar welding electrodes. For example, if you use stick welding (SMAW), you can use AWS A5.4 E310-16 electrode which has 0 FN (fully austenitic structure) or if you prefer TIG or MIG welding you can use a ER 310 rod with the same result.

Best regards.

Do i need to consider the welding temperature to avoid affecting the magnetic permeability?

I think you mean interpass temperature and/or preheating. I think this would have no effects on magnetic permeability, but as I posted previously, fully austenitic steels are prone to hot cracking and even I don't know the exact application, sure you will not want cracks in the welds. Then follow the recommendations of welding filler metal manufacturer.

would u like to introduce some document about welding for me? I know nothing about the welding.

is a cold work needed after welding? The ER310 rod is filler metal or electrode type?

There is a lot of information on the web about welding from free access articles to on line courses, according to your needs.

You can start having a look on wikipedia typing "welding" the article has a long list of references and will serve to familiarize with process and terminology.

If you want a bit more advanced knowledge, here is one of the links you can find easily by googling a bit:

http://www.lincolnelectric.com/knowledge/articles/list.asp

It has a lot of free access articles about welding, from basic knowledge to specific applications.

Regarding your other questions, no cold work is needed after welding. ER310 is a bare rod used as filler metal and electrode (one of the pieces between which an electric arc is established) in those processes in which the electrode is a bare consumable rod (GMAW, SAW). On TIG (GTAW) process, it's used just as filler metal, as the electrode is a Wolfram (Tungsten for americans) short rod, non consumable.

If you mean by "electrode" those covered electrodes for manual stick welding, the the designation is E310-16.

Best regards

Thank you very much, I really appreciate your help :)

What is your application? Just interested.

For low magnetic permeability and corrosion resistance comparable to 304 and 316, opt for 316LN or 20Cb3 both are lower than 316L. I don't know about "hardness". Hardness in refernece to stainless steel is usually not an issue except for the hardenable stainless steels like the 400 series which are very magnetic.

Another option is to use Inconel 625. Inconel 625 is significantly more expensive but also has very low permeability.

I have built superconducting magnet cryostats where very uniform magnetic fields are required and where residual magneticism becomes very important. If the materials above are not available in the forms you need, there is a way to screen heats of 316L stainless steel for suitable magnetic properties.

Both 304 & 316 stainless steel become magnetic after welding or cold working or after thermal cycling to cryogenc temperatures. There are several suitable filler metals good for welding 316L stainless steel to minimize residual magnetism in the weld metal but that does not always solve the problem of permeability in the heat affected zone.

Inconel 625 is a good choice. If we can not find a low magnetic permeability material after welding process with low price. We have to think about Inconel 625 at final stage.

Inconel 625 has very low magnetic permeability, about 1.0006 before welding. I wonder if the magnetic permeability increased after welding process. what is the value?

Magnetic permeability of Inconel 625 does not change after welding.

Some of this has been covered in this thread, our experience has been that welding 304 does leave residual magnetism in the weld joint which is then quite difficult to remove. The level of magnetism is quite low (~300milligauss in our case) but persistent.