Determining Steel type….

[BaitMaster]

Wondering if anyone has some tricks of the trade for knowing what kind of steel you have if from an unknown source.

I recently acquired an abundance of 2 1/8” shafting for free….

It was used as a driveshaft for a large machine, driving hundreds of HP….

I don’t know if it’s just mild steel or some sort of alloy? Any tips appreciated.

Cuts easily with a bandsaw. Has a machined finish under the rust, not too deep of rust. Was sitting outside for years and years before I got it.

 

[ducdon]

There is no good way short of lab analysis. A magnet will tell you if it's one of many kind of stainless. Some folks claim they can get an idea by grinding it and observing the sparks ( check spark test on YouTube). If in your stock of metals you have some 1018 and 4140 do some comparison sample cuts on the lathe. higher grade steels are tougher and cut with a finer finish. -OR- just use it as though it were ordinary low carbon steel and you'll have a long term supply. It's a great find regardless.

 

[lucsimoneau]

Being a teacher at our local college, you can always take a piece of metal and bring to a physics department if they have a metal spectrometer - most colleges and universities should have this equipment. We have also used our scrap metal supplier who also has this type of analysis tool.

 

[ducdon]

Years ago I attended a Saturday morning coffee meet. One of the attendees was a retired steel salesman and he brought his ANSI catalogue of steels. The catalogue is about 2 inches thick and includes many many types of steels. If your willing to order in steel mill batch sizes you can get anyone of them. For guys like us the list is limited to a few common types. Depending on the origin of what you have it could be anything. In common usage I think 1045 medium carbon is often used for shafting.

 

[whydontu]

Most alloy metals suppliers will have an x-ray fluorescence spectrometer, they need them for quick testing of incoming material shipments. Ask nicely and bring donuts and the QA person might test for free. Where are you located?

 

[BaitMaster]

@whydontu a small town in southern Alberta. No big city type fancy metal distributors within a few hundred KM to my knowledge. Calgary likely has one.

 

[YYCHM]

@whydontu a small town in southern Alberta. No big city type fancy metal distributors within a few hundred KM to my knowledge. Calgary likely has one.

Try the U of L Engineering Dept.

 

[mbond]

In addition to the comments from others:

If you _need_ to know, then start with an XRF. The machines cost about 50K USD I think, so all the suggestions for how to beg or borrow make sense. This kind of machine sends X-rays (the same ones they take pictures of your teeth etc.) into the material. Normal X-ray film shows where the rays have been absorbed (bones and high density tissues) and where they have just passed through (cavities, fractures, ordinary skin, fat, and other low density tissues). XRF works differently. Every atom in the periodic table has a standard or stable electron shell. That is both the number of electrons that must go around the nucleus so that they aren't ions (equal to the number of protons or the atomic number) and all at their minimum energy levels. When bombarded by EM radiation (not particle radiation), the electrons in the shell will move to elevated energy levels. But because those elevated levels are unstable, they will fall back again. Unlike what we can do on purpose or by accident on a lathe or mill, these cannot occupy arbitrary levels. In my SAE wrench set, I have a 1/2, 5/8, 3/4, but there are lots of dimensions in between. With electrons there aren't. To move from one level to another they must gain or loose one quanta of energy (I don't want to go into the rest of quantum theory, so even if you are interested don't ask here. PM and maybe). As the electrons fall back to their minimum energy positions, they 'fluoresce' or emit a characteristic EM radiation signature. That tells which elements are present, and that can be checked against a reference

But XRF cannot tell the difference between hot rolled and cold rolled for example. Or any other difference in the crystallin structure of the metal like strain hardening or exotic treatments.

My advise is don't try to figure this out exactly. just use the metal for what you think it seems good for and count your blessings that you have so much. I have only a tiny stock and none of it is stuff i know much about

 

[BaitMaster]

@YYCHM U of L doesn’t have an engineering dept.

Ya, I am thankful I stumbled into a bunch of it. I mean, obviously I’m not going to spend 50k USD on a fancy piece of instrumentation to figure out what kind a metal I got.

I was more looking for a “trick” that I could do at home to tell the general type it was. Like is this a 41xx or a 43xx piece of bar that I could use for something demanding? A medium carbon? Or is it a mild steel for general purpose stuff. Not looking for exact percentages of elements or anything.

 

[Dan Dubeau]

Short of looking up the manufacture, and finding a print of the shaft in question with a material callout, you're going to have to guess. I treat mystery metal as an unknown and it doesn't go into critical projects where I would need a specific material. Spark test back to back with a few known steels is your best bet. You can sort it into mild steel, med carbon, and high carbon pretty easily. Which should be good enough for most projects. If you need more specific than that for a project buy it.

At work we have a big rack full of mystery offcuts etc. Some labeled, some not, but when making pins it can be a guessing game sometimes if I need something bigger than a fresh bar so the spark test comes in handy. Is it o1, 4140, 1018? We don't stock a big variety of types of steel, o1, 4140, 17-4, and 1018, so it's relatively easy to discern

 

[Dan Dubeau]

@YYCHM U of L doesn’t have an engineering dept.

Ya, I am thankful I stumbled into a bunch of it. I mean, obviously I’m not going to spend 50k USD on a fancy piece of instrumentation to figure out what kind a metal I got.

I was more looking for a “trick” that I could do at home to tell the general type it was. Like is this a 41xx or a 43xx piece of bar that I could use for something demanding? A medium carbon? Or is it a mild steel for general purpose stuff. Not looking for exact percentages of elements or anything.

If I had to guess, I'd say a 4340 or similar. The application it came from should give some clue as to the alloy. I doubt an engineer would spec mild steel for a shaft of that size in a high HP application.

 

[Tomc938]

@YYCHM U of L doesn’t have an engineering dept.

Ya, I am thankful I stumbled into a bunch of it. I mean, obviously I’m not going to spend 50k USD on a fancy piece of instrumentation to figure out what kind a metal I got.

I was more looking for a “trick” that I could do at home to tell the general type it was. Like is this a 41xx or a 43xx piece of bar that I could use for something demanding? A medium carbon? Or is it a mild steel for general purpose stuff. Not looking for exact percentages of elements or anything.

Does it machine nicely?

In that case - SCORE!

If not, well, you can likely find a use for it somewhere.

 

[Matt-Aburg]

I usually can tell just by doing a simple taste test.................

 

[mbond]

that sounds like the best test!

 

[BaitMaster]

so I had a couple minutes after work here and I threw that cookie in the lathe and did a couple operations on it.

The surface finish is consistently excellent, especially on facing cuts.

Known Mild steel I’ve noticed is a little bit “gummy” looking when I face it, but this stuff faces beautifully. See attached mild steel face picture as well.

It likes a lower rpm to be cut at then the mild steel I did in a similar diameter when making a part for my mill.

I drilled through the center drill hole and I burnt a drill bit up in the process. Lowered RPM and tried again with sharp bit, worked.

Not sure what to think.

I don’t have a known bar of alloy steel to experiment with and I’m new to machining so I’ve never machined it before to compare to mild.

Any thoughts?

 

[Dan Dubeau]

My guess is a 4*** steel of around 30-40rc hardness.

 

[Ironman]

I just found out the hard way that a shaft was stainless. Cutting a 3/16" keyway cost me 4 endmills.
The chips were magnetic, but the shaft was not.

 

[PeterT]

OK you peaked my interest because I noticed that same thing milling some stainless before. The endmill was covered in magnetic swarf 'fur'. How does that happen?

 

[Bandit]

I interested in that too. Note, some stainless is magnetic, depends? on amount of Crome and other alloys. I think some of the 304 alloys are magnetic, but changing after cutting???
BaitMaster, just run with that shafting! Start your ENGINE! Use it. You have already found out a few things just by turning it.

 

[whydontu]

Without going down that rabbit hole, heating austenitic 300-series stainless steel will tend to increase its ferrite content, making it magnetic. 400-series ferritic and martensitic stainless steels will normally be magnetic. Think of stainless steel as stew. Not every spoonful of stew has the same ratio of potato, beef, and parsnip. Not every crystal of stainless has the same ratio of iron, chrome, and nickel. Heating stainless will alter the crystal structure, and if the chips are coming off blue then the machining process has exceeded the critical temperature and ferrite will form.