metal identification

[JimH]

I picked some round up at the scrap yard. When I got home I noticed it had "4140" painted on it. I have done the grinder spark test and strongly suspect that it is not 4140. I was wondering if there is any other simple (read cheap and at home) test that will not necessarily identify what the steel type is, but rule out that it is an alloy steel?
Jim

[bspooh]

How do you know it isn't 4140?? Tell me what sparks were....

I use a lot of 1018 and a lot of 4140...I can't tell the difference in sparks, but I can tell the difference when I machine it...sometimes My material rack will get mixed up....I usually can't tell the difference even when I machine it ...so I just assume it is mild steel...even if it is not...

brent

[JimH]

Hi Brent,
I'm certainly not a spark evaluation expert, rookie would be more appropriate. I read the book(s), looked at the pictures, and then put some to the grinder. For comparison, I also ground a piece of 1018. Both had a spark pattern that I expected for the 1018 (from the pictures and color). Could not tell any spark pattern difference between the two pieces. From my reading I expected a difference.

From your statement, you tell the difference by how it reacts when machining. I haven't machine it yet.
Thanks,
Jim

[Indexer]

I'm no expert either, but you might be able to tell somethings about your stock with a heat treatment test. If it is 4140, it has 0.38 - 0.42 percent carbon, which would mean that it would harden considerablly on heating to cherry-red (non-magnetic) and quenching. A small sample of it might be cut off for the purpose to simplify the heating/quenching. A low carbon steel like 1018 would not harden much at all. As for the 41 part, 4100's are low alloy steels . . . a small bit of Cr and Mo . . . strengthens the steel, but you're not going to be able to identify their presence in the home shop very well. For details on alloy steels, you might try:
http://www.efunda.com/materials/allo...eels/alloy.cfm

I guess I would say that if it responds to the hardening test like a medium carbon steel then you should accept the 4140 marking as your best guess. If it doesn't harden, it might as well be used as a mild steel anyway.



------------------
Rich Kuzmack

Pi = 355/113 . . . to
<85 parts per billion

[snorman]

As I recall 4140 grinds much like crs. Nice orange spark with very few bursts. It's been a long time however. I was grinding a variety of chisels and punches today and noticed a lot of difference in the sparks from one to another. Reminded me of that spark test.

The cherry red and quench test will tell you if your steel is 1018 or something else. 4140 should get pretty hard and you'll probably notice no difference if it's the mild stuff. Just run the corner of a file across it after it's cool. Preferably not your best file. Machining in the lathe should give some indication too although they're both stringy as hell.

[spope14]

The grind test will show 4140 a bit brighter, the chrome.

It is hard to tell, however, here are two ways to possibly tell.

1. turn then sand the diameter (unless CRS, then just sand). 4140 will be brighter in color, just enough to tell, and will sand real nice!!!! This is about a 60% good method.

2. Run at a higher speed than normal for the material, and a feed of .006. The 1018 still looks poor, the 4140 starts to improve in finish (nose rad .015 to .032 on the tool). 41 series likes to be "pushed" a bit in feed. Depth of cut .030 Example here - 1" diameter - run at 1200 rpm. Just did this experiment with my class today to show this effect on why you would actually turn 41 series a bit faster and higher feed than 1018. (Speeds and feeds at work here).

3. Run the material real fast (within common sense limits) - example 1" diameter at 2000 RPM with a depth of .015. 41 series will start to harden a bit, some fuzzing at the shoulder of the cut, or full blown hardening.

Using carbide in all of this, HSS will work but the tool will junk up.

Just some crazy ideas I have done, and have proved good. Sure some will raise eyebrows.

By the way, safety throughout all of this, and remember to stay within machine capacity and limits, and within common sense.

[JimH]

I heated a piece of the metal til non-magnetic and quenched it. File won't mark it. So it must be a high carbon steel. Sanding a non-hardened piece does seem to make it shine brighter than plain old steel.
Thanks for the suggestions!
Jim

BTW, I was at the scrap yard (again) Saturday. Next to where I got my piece is 15 feet of round marked 4140. It's 6 3/4 inch diameter. Laying there just rusting.

[Thrud]

Jim

You think you could sneak that baby in without the "boss" noticing? ;-)

[JimH]

Boss (wife) is heading out of town shortly. Unfortunately, she is taking the PU. Don't think I could get into my Subaru after I tied it to the ski rack.

Jim

[spope14]

Have truck, generator, chop saw, will travel. Where is this mammoth piece of iron gold?