Harry.C Posted September 11, 2019 Share Posted September 11, 2019 What is the difference between ferritic, austenitic and martensitic stainless steels? I've not done much metalwork and I'm looking to get some stainless steel to experiment with. Harry Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted September 11, 2019 Share Posted September 11, 2019 There are four major groups of stainless steel defined according to the crystal structure of the steel: austenitic, ferritic, martensitic and duplex. This microstructure of these alloys depends on the alloying elements present in them; these alloys have different alloying elements as well. Ferritic steels are high chromium, magnetic stainless steels that have a low carbon content. Known for good ductility, resistance to corrosion and stress corrosion cracking, ferritic steels are commonly used in automotive applications, kitchenware, and industrial equipment. An example is most 400 series Austenitic steels are non-magnetic stainless steels that contain high levels of chromium and nickel and low levels of carbon. Known for their formability and resistance to corrosion, austenitic steels are the most widely used grade of stainless steel. Example is the 300 series Martensitic stainless steels are a group of chromium steels ordinarily containing no nickel developed to provide steel grades that are both corrosion resistant and hardenable via heat treating to a wide range of hardness and strength levels. 431 and 440 are examples. Duplex and Super Duplex Stainless Steel Duplex stainless steels have a two-phase microstructure that consists of grains of 50% austenitic and 50% ferritic stainless steel. This type of steel has a selection of benefits, and it is often chosen over regular ferritic or austenitic stainless steels due to its increased strength - it is about twice as strong as these metals. Examples are 2205 and 32750 None of these make a good starting point for learning how to forge Quote Link to comment Share on other sites More sharing options...
Steve Shimanek Posted September 15, 2019 Share Posted September 15, 2019 I have a 7 foot SS hex shaft about 2.5 inches across that looks to have been used as a drive shaft for some kind of machinery, probably from the tuna packing plant here, that broke and was found in the local scrap yard. It is non magnetic and i have not tested it yet for hardenability, but will cut off a piece and see how it works as a dive knife. Are there any field tests beyond the magnet and hardenabilty to try to ID SS series? Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted September 16, 2019 Share Posted September 16, 2019 If it is nonmagnetic I wouldn't even waste my time trying to harden it. You can probably work harden it, but not with heat. SS will work harden enough to stop a HSS drill from drilling it. SS is also not an easy metal to forge - tough. I would think of some other use for that hex you have. Quote Link to comment Share on other sites More sharing options...
Steve Shimanek Posted September 19, 2019 Share Posted September 19, 2019 Good points; I will try a chunk just to see how it works, to at least see what i might use it for. Thanks for your response. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted September 19, 2019 Share Posted September 19, 2019 If you read my last post where I explained this, you can save yourself some time testing it for hardenability if its not magnetic Quote Link to comment Share on other sites More sharing options...
Harry.C Posted September 27, 2019 Author Share Posted September 27, 2019 Thanks for the material breakdown. I'm going to visit an old friend this weekend who is going to build a forge for his new workshop. I'm going to see if I can pick up some tips from him and have a go at it too. Quote Link to comment Share on other sites More sharing options...
arftist Posted October 4, 2019 Share Posted October 4, 2019 Non-magnetic stainless would make a dive knife useless for anything but stabbing sharks. I would want a knife that can cut. Quote Link to comment Share on other sites More sharing options...
Steve Shimanek Posted October 6, 2019 Share Posted October 6, 2019 I have thousands of dives, saw plenty of sharks on some of them; the only thing i have stabbed is fish after I have speared them. Everyone will have their own perspective on the subject. Quote Link to comment Share on other sites More sharing options...
arkie Posted October 6, 2019 Share Posted October 6, 2019 Steve (Sells), thanks for posting the info on various types of stainless steels. I recently had a magnet stick to a pair of stainless medical forceps which surprised me. I guess they were made of ferric stainless. Quote Link to comment Share on other sites More sharing options...
Zane Posted October 7, 2019 Share Posted October 7, 2019 With some types of Ferritic and Martensitic stainless steel being magnetic and others not, I was wondering what makes them magnetic? Is it the level of iron or is it the crystalline structure? Quote Link to comment Share on other sites More sharing options...
Harry.C Posted October 7, 2019 Author Share Posted October 7, 2019 Both the material properties and their structure make it magnetic. Here is a breakdown of their structure: https://www.accu.co.uk/en/p/112-difference-between-ferritic-austenitic-and-martensitic-stainless-steels 18 hours ago, arkie said: Steve (Sells), thanks for posting the info on various types of stainless steels. I recently had a magnet stick to a pair of stainless medical forceps which surprised me. I guess they were made of ferric stainless. Arkie, I've recently discovered that cold working Austentic steel (even just bending it) changes the structure of the iron atoms, which turns some of it into Martensitic. So I wonder if perhaps your medical forceps were stainless steel grade 304? Does anyone know if there is a better method of testing stainless steel to see what type it is? Quote Link to comment Share on other sites More sharing options...
arkie Posted October 8, 2019 Share Posted October 8, 2019 I have not a clue what type of stainless the forceps are. I have noticed that a lot of disposable surgical instruments are coming from India and other third world countries. No telling what their "stainless" composition is. Quote Link to comment Share on other sites More sharing options...
Harry.C Posted October 8, 2019 Author Share Posted October 8, 2019 Maybe someone on here knows how they would examine metals to test the composition? I'm curious to see how metal recycling companies would sort metals, but nothing came up on Google search. Quote Link to comment Share on other sites More sharing options...
pnut Posted October 8, 2019 Share Posted October 8, 2019 (edited) Scrapyards usually use a handheld spectrometer for specific alloys, but some just eyeball it and separate it into Al, magnetic, and non magnetic ferrous material. Depends really on the scrapyard and the type of scrap they deal with mostly. Pnut Edited October 8, 2019 by pnut Quote Link to comment Share on other sites More sharing options...
JHCC Posted October 8, 2019 Share Posted October 8, 2019 My local scrapyard was kind enough to test some shaft segments for me (turned out to be 4140, as expected) with their handheld XRF spectrometer. It helps if you ask politely and sell them your scrap. Quote Link to comment Share on other sites More sharing options...
Harry.C Posted October 8, 2019 Author Share Posted October 8, 2019 Thanks JHCC Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted October 8, 2019 Share Posted October 8, 2019 My local scrapyard does: copper/brass/etc, Al, Stainless and everything else. They stopped sorting and differentiating between cast iron and steel as it all sold for the same when it got shipped to China. Large pile of almost anything, (cars, washing machines old farm stuff, dock weights, galvanized, wiring still in place), all mixed up. Probably ends up as A-36 Quote Link to comment Share on other sites More sharing options...
pnut Posted October 8, 2019 Share Posted October 8, 2019 Or miles of rebar. Pnut Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.