Non-Chemical non-ferrous magnetism

[Harold_V]

I have sold quite a lot of stainless Harold. And as I recall all of what tested out at the scrapyard or was marked 316, was slightly magnetic. 304 generally is not.

That is not a method of determining grade, for both of those materials are slightly magnetic in the work hardened condition, and both are not when annealed. The same thing applies to all of the 300 series, so they can not be sorted by their magnetic properties. However, you can sort the 300 series in the annealed condition from all other grades, for they are magnetic in all states.

This information is provided in (material) stock books and is readily available for those that deal with such materials. It is common knowledge amongst machinists.

I'm not suggesting that you didn't sort by the method, but I am saying that it is not reliable, so you well could have been passing 304 for 316. They are identical in appearance and other properties. They are difficult, if not impossible, to sort by machining, while some grades are not. For example, one can discern 303 S from 303 Se, and all 303 types are readily sorted from all other 300 series by a simple cut with a lathe. That's assuming you are familiar with the properties of the materials, which I am.

If you have something that is strongly magnetic but looks like stainless it probably is one of the 400 series of stainless. Some of this has chrome but no nickel.

That isn't reliable, either. 17-4 PH and 17-7 PH are both magnetic, and are not in the 400 series. You may be able to include 13-8 and 15-5 with those two, but I hesitate to say with certainty because I am not familiar with the properties of those two. I do know that they all contain both nickel and chromium, but in varying amounts.

These materials are all precipitation hardening, and do not rely on carbon content to achieve their hardness.

Harold

 

[goldsilverpro]

I found quite a few lists of the chemical composition of superalloys on the internet and could find none containing PGMs. Here is a fairly complete list.

http://www.dynamicmet.com/sp4.htm

 

[jimdoc]

There was talk of using ruthenium and rhenium in super alloys.

http://www.lipmann.co.uk/articles/will_aero_engine_makers.html

 

[goldsilverpro]

I stand corrected. I just found this quote:

"The superalloys of the first generation were intended for operation up to 700 °C (973 K). The up-to-date superalloys of the fourth generation are used as single crystals and are extra alloyed, especially with ruthenium. They can operate up to 1100 °C (1373 K)."

And:

http://www.google.com/search?q=ruthenium+superalloys&sourceid=navclient-ff&ie=UTF-8&rlz=1B3GGGL_enUS259US259

http://www.google.com/search?q=rhenium+superalloys&sourceid=navclient-ff&ie=UTF-8&rlz=1B3GGGL_enUS259US259

 

[qst42know]

Assuming one could find this exotic alloy containing approximately 5% to 10% Ruthenium, by what method would the recovery of this metal from a nickel chromium base be possible for a small scale refiner?

 

[Platdigger]

If you go back to my post Harold, I didn't say it was 400 only.

I think you took ....I mean, in a way, you pulled a quote out of context.

As far as I know, all the 304 I ran into was non magnetic.

I am sure there could be exceptions to that also.

If it was slightly magnetic.....or even somewhat strong and not marked, then I had it tested.

It could also be our use of the word "slightly" could be different.

Are you saying there is 316 that is non magnetic?
Randy

 

[Harold_V]

If you go back to my post Harold, I didn't say it was 400 only.

I just wanted to assure readers that being magnetic is not a sign of stainless being a 400 series. You said:

If you have something that is strongly magnetic but looks like stainless it probably is one of the 400 series of stainless.

That stainless is magnetic is no more an assurance of it being a 400 series than one being slightly magnetic being 316. That is not the case in either example. The point is that stainless alloys are incredibly complex and tend to not fall in categories. Not all of them that are not magnetic can't be heat treated, so even that feature isn't acceptable for grading. An example of a non-magnetic stainless that can be heat treated is A-286. To the uneducated, it could easily be confused with a 300 series stainless.

I think you took ....I mean, in a way, you pulled a quote out of context.

I don't think so. I simply read what you said and knew that it was not true in all cases. I think readers should understand that there are differences, that you can't generalize. As I said, unless you know and understand the stainless family exceedingly well, there are exceptions to almost all of the rules, so you can inadvertently provide misleading information.

As far as I know, all the 304 I ran into was non magnetic.

Any of the 300 series materials will acquire minimal magnetic properties as they are cold worked. I mentioned that previously----it's called work hardening. Not only does the item become mildly magnetic, it also becomes harder. It's to do with alignment of the atoms of the material. It's not speculation-----as I said, this is published information. A ready reference is the Jorgensen Stock Book, which details the magnetic properties of these alloys.

Are you saying there is 316 that is non magnetic?

No, I'm not saying it----the stock book is. It is published information, coming from a source that is an accepted authority in the machining world. All 316 is non magnetic. Only when it has been cold worked does it assume magnetic properties, with the degree of magnetic attraction related to the degree of cold working. It becomes mildly magnetic, never achieving the same degree of magnetic attraction as do other materials we accept as being magnetic.

As I said, you can not determine if a material is any given grade judging by magnetic properties. You can't even assume a stainless alloy is a 300 series if it is NOT magnetic-----there are exceptions to that, too. Again, I offer you as an example, A286. It is not magnetic under any condition, yet it can be heat treated. That tends to go against everything you know and understand about heat treatment of stainless, but, remember, I already mentioned the fact that carbon is generally not the reason these alloys heat treat.

A286, like 17-4 PH, 17-7 PH, 13-8 and 15-5 are all precipitation hardening materials. Some are magnetic, some are not.

Harold

 

[EVO-AU]

To one and all:

Boy, did I ever open up a pandoras' box. Ask a man if a traffic light is red or green and he will, most assuredly, state the orange is what counts. Oh well, I doubt if I will ever come across any of the sophisticated alloys of which you gentlemen speak, but thanks for all your work.

Phill

 

[Anonymous]

Try taking some "slighty magnetic" SS to the scrap yard and selling it as stainless. Talk about a pandora's box... And I am not talking about something that is chromed either...