Recognize When Rebar Is High Carbon?

Andrew Colglazier

Andrew Colglazier

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Sep 14, 2006
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I have a fair amount of 1" rebar which I suspect is high carbon. The reason I think this is that I have been using a length of it to heat my oil quenchant. After being heated to bright orange/yellow and being quenched, it is quite hard and resistant to cutting with a file.

How can I discover for sure?

If it is high carbon, any way to find out what steel it is? Has anyone worked with this kind of material? It does have some numbers stamped into it, if this is any kind of indicator.

Thanks!

Andy
 
Rebar varies pretty widely in content, and the content can vary even in a single bar. There are some high-tensile grades of rebar which might be decent material (for some applications at least), but a lot of the run-of-the-mill stuff is pretty crappy. You have to take it on a stick by stick basis and experiment to see if it will work for your purposes. I would not recommend making blades from any of it.
 
ive heard that a lot of it is made from recycled railway scrap, spikes and straps and such which is usually a medium carbon steel. i use rebar when im not sure how forging a particular shape is going to go so i dont ruin my high carbon stuff. its good to have around for that kind of thing. plus it might make a decent center punch or chisel.
 
The person to ask would be Raymond Richard. He uses rebar frequently and has stated some specs for different grades. I remember something about grade 60 on his last rebar build.
 
Find ASTM standard A 615 and A 706. These govern the most commonly used types of rebar, like all I've ever seen except that which was older than 60 years. It comes in grades 40, 60, and 90, which are the approximate yield strengths in ksi. Tensile strength will be 30 to 40 ksi higher. AFAIK, none of the standard stuff is what we on a knife forum would call high carbon. In fact, there are limits on carbon and carbon equivalence for the A 706 grade to ensure weldability. Grade 60 is the usual grade found now for construction. I've seen some grade 40 pulled from old buildings, but its rare now, except maybe at home depot or lowes. A 615 is kind of a crap shoot for any property we would desire here and for weldability. Carbon equivalence can be upwards of 0.4, so there can definately be some hardening if quenched, but again, nothing like knifenuts are trying to find.
 
I've made a few grade 60 blades- I specify that they are rebar knives and not superior type blade stock. however, the most used utility beater knife in my kitchen is a rebar blade I forged out 2 years ago - the first one- and it's has gone through total hell and manages to hold up, hold an edge as well as most production stainless kitchen knives I've used, and has a good prybar quotient. Nothing wrong with beating on a beater.
 
koyote makes an extremely good point. i know im guilty of this, as im sure lots of us here are, of getting caught up with steels and different heat treats and all that mess. a knife is essentially a sharp piece of metal or a sharp piece of anything for that matter. if your making one for someone else, you should use the highest quality materials available, but that doesnt mean you cant make a knife out of a piece of rebar scrap, or a tire iron or an old spring. if your having fun doing it, who cares if its a masterpiece. maybe ill go hammer out a rebar knife tomorrow.
 
Sorry but your wasting your time usually you get what you pay for and if I bought a knife made from rebar and it wouldnt hold a edge ide be some mad. Might be ok for practice but thats about it.
 
I have made many a metal chisel out of rebar, but I only use the one that has the raised seams on each side, heat treated it as I would 5160 and I have used it for years. I may try a knife as a test in my new gas forge.

Richard
 
Just for reference, A-996-60 grade rebar is rail and axle steel. It will harden and make knives similar to 1070-1080 . Most other rebar is low carbon. If you don't know the grade, it is best used for handles on damascus billets, and for making tongs.

Heating it up and quenching it to see if it gets hard ,or will break, won't tell you much. Most mild steel will harden somewhat.
Stacy
 
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