Scrap/mystery steel.

Ok folks, I thought I'd kick this off with a few words about scrap/mystery steel? Can you make a good knife from mystery steel? Of course you can. Can you waste a lot of time and consumables and end up with a knife that is not worth the effort? You bet. By its very nature, we can't keep mystery steels totally fact based but I will try my best. Here is my opinion on the best ways to handle mystery steel. Please remember that this is just my OPINION but I hope most people will agree.
If you have a large amount of said steel and you're sure its all the same, your best bet is to find a company to test it and give you the chemistry. This will give you a much better idea of whether or not it will make a good blade and also some ideas of how to heat treat it. Use your Google-Fu to find someone in your area who can/will test it, find out what size they need for the sample, & go from there. Once you have the chemistry and you're fairly certain that it will make good knives then start working up a heat treat recipe through trial & error.
If you have some scrap steel but not enough to justify the cost of a chemical analysis then the best thing to do is harden a small blade sized piece and break it. If it snaps like a piece of glass and has a small grain structure then it might make a decent knife. The next step is to make a test blade, heat treat it, & test it. You may have to adjust hardening temps. & times in order to get the best hardness out of the quench. You'll almost definitely have to play with the tempering temps. in order to find the "sweet spot".
I also want to add that its commonly believed that files are 1095, W1, or W2, saw blades are L6, bandsaw blades are 15N20, & automobile springs are 5160. Sometimes this is the case but often it is not.
Spark testing will tell you a lot about the carbon content in a steel. Steel with enough Carbon will make a complex or "forked" spark when grinding it. If you don't have any experience in doing a spark test, you can look at the sparks from a known steel and compare them to the sparks of your mystery steel.
Some people hate the thought of mystery steel but many people love making something useful from a piece of "junk". People also enjoy the trial & error process of getting the most out of something unknown. If thats what floats your boat, by all means, go for it & have fun.
If any of you feel that I've left out something important on this subject then by all means let me know.
 

Archer Moon

Well-Known Member
I would like to add some thoughts. Keep in mind why You are making the knives. Not what the knife will be used for but the reason for making the knife. Is it for money, or just your hobby? Working with known steel is a better way to go when selling your knives. Use the unknown for you. Make fun! If it is not what you enjoy then this is your job and let your boss get you the steel. I like to use 5160. There is a local supplier that sells it cheap. I do have a lot of unknown steel that I have not done anything with. Maybe someday.
 

One

Banned
I'll add that scrap steel isn't necessarily mystery steel or unknown. Sometimes you can salvage known steels in unused condition. Machine shops that mark their drops are a good example.

If it is unknown, the first most important thing is to "know" what you are looking for and weed out the types that aren't what you are looking for. This could be stainless steel and/or low carbon, cast iron etc., or unsuitable sizes that won't be right for the knives you want to make. It's basically a process of elimination. You should be able to narrow the steels down into basic categories... low, medium or high carbon,.. stainless or non stainless,... air, oil or water hardening.

For quench and hardness testing I think starting with air first and if that doesn't work try oil,... then trying water last, makes good sense. Generally speaking however, if oil won't harden pieces under 3/16 inch thick it's probably not a desirable knife steel. Quenching can also help determine if it's a shallow hardening steel, by checking it for a quench line.

The easiest way to determine the general carbon content through spark testing is the distance from the wheel that the sparks burn out. Low carbon steels will throw sparks furthest from the wheel and with high carbon steels the sparks will burn out much closer to the wheel. Forking and branching of the sparks can be misleading. Low/medium carbon steels can fork and branch like some high carbon and some high carbon steels show no branching of forking at all depending on the alloy. Comparison spark testing is fairly reliable, if you know what you are looking for.

Once you determine the general category of the steel, for example, "high carbon/shallow hardening" it will give you important clues into the chemistry and how to go about heat treating it. From there, it usually takes some experimenting and testing to optimize as has been mentioned.

With a good deal of experience, you can become quite proficient at it,... but for newbies you are probably much better off starting with a known steel and eliminating all the variables of mystery steel.

Lastly, I think it is a misconception that salvaging and recycling steels is the same thing as using "unknown" steels. It doesn't necessarily mean that you pick up a random piece of steel, not knowing anything about it, and proceed to try and make a knife blade out of it. You need to do some testing on the steel first and narrow it down, or salvage it as a known alloy. Also, salvaging steels may or may not be about saving money. Environmental concerns can be a big part of the reason for it. It can be fun, interesting and educational to play scientist in your shop and experiment with the "junk" you can find. It can also tie in quite well with the "found object" art genre or concept.
 
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One

Banned
One approach that can work well is first decide what type of steel or steels you want. This decision often has to do with the type of heat treating equipment you have or want to use,... experience, skill level, performance preferences etc. For example, let's say you are looking for 5160. First find out what 5160 is used for. This could be automobile leaf springs, although not all of them are 5160.

In order for 5160 to respond to heat treating the way it's supposed to, the heat treating regime must be in keeping with the alloy. You can take this and turn it around,... if the steel responds to the heat treating regime for a particular alloy the way it's supposed to, then it must be that alloy or one with very similar requirements.

Another way of looking at it is, instead of trying to determine the alloy and then heat treating it accordingly, is to use a regime that fits your set up etc., and find steels that work within that basic regime. This could be as simple as heating to 100 degrees or so above non magnetic, soaking for 5-10 minutes, quenching in 130 canola and tempering as needed. I think this is also a good "baseline regime" for many of the popular bladesmithng steels. Of course, with this approach you'll still probably (unless you get lucky) need to do some experimenting, tweaking and testing to optimize it. However, if it does respond within acceptable standards (according to the end use of the tool) to begin with, you can shorten the learning curve quite a bit and at least start out with a blade that will do a lot of cutting. If it doesn't respond to the regime well, toss it out and try a different steel.

... There's two basic approaches to it, but in the long run,... a good deal of both will probably be the most rewarding.
 
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bubba-san

Well-Known Member
I agree with One . Whats life without a little intrigue . Another point nearly all 5160 and 9260 , used in car springs all have a rounded edge on each side of the flat leaf springs .......... Bubba-san
 

One

Banned
… I love a good mystery....... steel. :)

I think the first most important thing is just,... knowing what you are looking for?
 
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scott.livesey

Dealer - Purveyor
I'll add that scrap steel isn't necessarily mystery steel or unknown. Sometimes you can salvage known steels in unused condition. Machine shops that mark their drops are a good example.
I agree. by "shopping" the scrap bin at the office and the machine shop across the street, I have found all sorts of good "known" stuff. my only problem is most of it is not "blade" steel. so far I have found a 1" thick drop of 7" diameter 440C stainless and a small piece of 420V.
scott
 

One

Banned
There was a place in Phoenix where I got a truck load of drops for free. I loaded it up to where the rear bumper was almost dragging. They were glad just to have it taken away. All good stuff,... O1, A2, A6, D2, etc., and even some H13 for hot working tools. Long time ago, but I still have some.
 
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