Questions on figuring out HT for "recycled steel"

D

deker

Joined
Nov 14, 2005
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Just at the start, let me say that this is not another "I found a rusty chunk of stuff in my yard, will it make a good knife?" thread.

What I'm wondering is how folks go about deciphering a HT for a decent sized quantity of known good steel when the composition isn't known. I've come across a supply of identical spring harrow teeth (all from the same harrow actually) that are known to be some decent steel (the guy who provided it had personally run the harrow and had seen these teeth catch on roots, etc and almost completely straighten out before returning to their original shape). Each one when un-coiled works out to about 1/4"x2"x4' and I will be able to get my hands on more of them in trade for some time teaching bladesmithing.

I've done some of the basic testing of heat, quench, break and even when seemingly overheated and not normalized afterward the grain looks decent and it certainly hardens VERY well in Parks #50. What I'm looking for though is some input on methodology to decipher how I can put a good HT on this stuff. What are other tests I can perform? What of those tests will actually prove useful? Where can I send a sample for analysis? Once I have an analysis, how do I divine some baseline HT process to use as a starting point?

So, what say you all? How do you do it? I generally don't bother with recycled steels, but this is an exceptional case because I will likely be able to get my hands on a large enough quantity to make the effort worthwhile.

-d
 
when i use any mystery steel, which is rarely, i simply do some testing... 1- how does it forge/react to the hammer 2- how does it act when normalized/thermal cycled (seen strange things here). 3- does it harden enough to be used as a "blade" 4- How does it react to the tempering cycle.

If all of the above are acceptable, i do some cutting test, flex test etc... Usually at the end of all the testing and crap Ive gone through to see if its a suitable material to use, Im reminded why I like 1095 and W2 so much.
 
Sometimes a medium carbon steel with a little bit of vanadium in it is used for springy and tough applications like that. I'm talking a little out of my ass here, but I believe that below a certain carbon content the martensite forms a lathe structure rather than a more drastic plate structure, making it a lot tougher. But sadly, not hard enough for certain knife applications. I'd be sure to test the hardness of this stuff with some sort of penetrative test before making a thin skinner out of it etc...
 
I think what Matt is trying to say is correct. Test the steel and see what it's actual working properties are.

Some things you can try are spark testing followed by, quench testing for the quenching medium, (air, oil or water), and hardness testing. Check it for a quench line. You can use a magnet to find critical. Do some hot malleability testing, like "torque" or twist testing, and also observe the scale how it forms and reacts to forging. For tempering, start with a low temper, like 350, test it and temper it higher if needed. If you do all this you should be able to get a good general idea of the type of alloy, actual working properties and be able to make a good serviceable blade from it... if the steel is worth it.
 
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send a sample to matt doyle and he can test it for you. that way you know for sure what it is or at least what it contains.
 
Testing and analyzing steel yourself can be fun and educational... :)
 
Tai Goo said:
I think what Matt is trying to say is correct. Test the steel and see what it's actual working properties are.

Some things you can try are spark testing followed by, quench testing for the quenching medium, (air, oil or water), and hardness testing. Check it for a quench line. You can use a magnet to find critical. Do some hot malleability testing, like "torque" or twist testing, and also observe the scale how it forms and reacts to forging. For tempering, start with a low temper, like 350, test it and temper it higher if needed. If you do all this you should be able to get a good general idea of the type of alloy, actual working properties and be able to make a good serviceable blade from it... if the steel is worth it.
Click to expand...

Everything Tai is suggesting makes sense but the magnet part, all that a magnet will tell you is that your metal is at 1414f (Curie point) it will not tell you what your steel's critical point is. With many steels the Curie point is close enough for shootin' so you may not be too far off if you hold it at that for 15-20 minutes to allow for carbide dissollution (you might get lucky and actually wander into AC1 by accident)

here's a thread on that from Don Fogg's forum

http://forums.dfoggknives.com/index.php?showtopic=5872

If you want to guess and make knives that do not take advantage of everything the steel can give you you can do all of the abovementioned testing, if you have a large enough pile of the stuff to be worth the expense, send it out for analysis (then using your analysis as guidelines make educated tests)

-Page
 
sunshadow said:
Everything Tai is suggesting makes sense but the magnet part, all that a magnet will tell you is that your metal is at 1414f (Curie point) it will not tell you what your steel's critical point is. With many steels the Curie point is close enough for shootin' so you may not be too far off if you hold it at that for 15-20 minutes to allow for carbide dissollution (you might get lucky and actually wander into AC1 by accident)

here's a thread on that from Don Fogg's forum

http://forums.dfoggknives.com/index.php?showtopic=5872

If you want to guess and make knives that do not take advantage of everything the steel can give you you can do all of the abovementioned testing, if you have a large enough pile of the stuff to be worth the expense, send it out for analysis (then using your analysis as guidelines make educated tests)

-Page
Click to expand...


That's right!
You can't rely on just one test... and it takes a basic understanding in heat treating and blade performance to be able to do the tests correctly.

Any test is subject to error and/or misinterpretation.... that's a given!

The steel is only "worth it", if you are curious enough...

... and why take anyone else's word for it?
 
I'd also recommend running some "in shop tests" on any new store bought steel!...
 
Having an analysis is the best bet. I had some rake tines tested and turned out .55 carbon, much lower than I expected for the toughness. I have 90ft of it out back, on top of the leaf spring pile!!:jerkit::o

[the good stuff's inside!:D:D]
 
The question was, "deciphering a HT for a decent sized quantity of known good steel when the composition isn't known."

I assumed that meant through do it yourself in shop tests.

The question was also, "will it make a good knife?",... not a great knife or necessarily the best knife...

... Yes, it is possible and really not that hard, IF you have a basic understanding of steel and heat treating. In other words any competent smith “should” be able to do it.
 
I have never failed to get an answer as to what kind of steel from a farm implement maker.I simply call and ask for engineering.The bigger the company the longer it takes,but someone will have an answer.Nathan is right about the vanadium and lower carbon on the newer stuff.Old stuff is usually better.Vermeer had an answer in less than 5 minutes,Case all day.Never call on monday morning or friday afternoon,otherwise they are usually interested in what you plan to do.
 
If trial and error are in the works, why not do it the old fashioned way and watch the decalescence? (I'm sure I spelled that one wrong.) If you have a thermocouple in your forge, that makes it even easier to get a range of temperature for soak / hardening.

Once you have an idea of austenizing temp, you can quench some samples, and temper them at progressively higher tempers until you get a combo of toughness and hardness that is to your liking.

Fine tuning from there is a matter of testing little changes.
 
Thanks for the responses so far. I have indeed watched the decalescense, and it was more apparent than on any other steel I've ever used. The blade began to cool, then the entire thing began to brighten from the ends toward center, then all cooled at the same rate. It was a 1/4" thick cross section.

What I plan to do is quench test pieces at just above the point of decalescense and go from there. The one piece I've quenched so far seems to have gotten somewhat harder (based on the "file test") than some of my 1095/15n20 damascus. I take this as a good sign :)

-d
 
There was a thread sometime ago on harrow teeth like you are describing. I can't seem to locate it now. But it said to treat as 1095. The reason I remember it is I have a pile of those teeth.
 
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