Mystery steel identified... A8

Self Made Knives

Self Made Knives

Well-Known Member
I have some mystery steel that I've made a couple of test blades out of and it seems to perform pretty well. I was originally told it was D2, but found out today from the factory sales rep that it is in fact A8 tool steel. I tried searching the forum but couldn't find anybody talking about it.

Several sources online state that is tougher than D2 and CPM 3V, but less wear resistant. Sounds like some extreme duty, tough combat type knives have been made out of it. Sales rep said it had 8% chromium, but most online sources are showing more like 5.5%. It will rust, but not easily. I found heat treating instructions for 60 Rockwell.

Sooooo..... I can get nearly all of the A8 steel I could possibly use for free. It is about 3/16" thick, so that's a problem for some designs, but if its free.... I can put it on the mill with a fly cutter and thin if down without too much trouble. What do you guys think? Ever used it? Seems pretty good to me, but I'd like to hear other opinions.
 
There is A8 (~5% Cr) and then A8 Modified (~9% Cr). The carbon content is good for extreme duty type applications, as it is only .5% or .6%. Extremely tough knives, these steels will make.
"air-hardening, 8% chromium tool steel which exhibits very good wear resistance and toughness. exhibits wear resistance which is better than that of S7, and toughness which is better than that of D2. Typical applications include wood chipper knives, slitter knives, scrap shears, plastic granulator knives, tire shredding knives, shear blades, planer knives, punches, and fineblanking dies." -matweb.

Not used too terribly much by knife makers, but looks like it offers good apex stability and wear resistance too. Go for it!
 
The pieces I get are left overs from shredder blades. They are about 24" long and 1.5 - 2" wide. I knew they were really tough from my own testing, as far as chopping. Haven't really tried any edge retention tests, not sure what's the best way to test that. I'm just worried that if offering a blade for sale and it's labeled A8 steel, would I get any push back from customers. Its just really hard to pass on free steel, especially now that I know what it is.
 
Apparently not much interest or experience with A8 tool steel, but maybe one of you metal gurus can help me understand this graph. How about this Charpy V notch impact test? It looks like the toughness is maxed out at a temper temp of about 625 and again at 1000. Looks like a temper anywhere between 600-900 doesn't change Rockwell significantly, but toughness curve doesn't make sense to me. If I temper at 400 to get about 58-59 Rockwell, is a toughness of 4.5 good? In comparison to other common blade steels, how is 4.5?
A8.JPG
 
Bark River Knives uses mostly A8.
It's a good steel that is very tough and can be sharpened by the user easily.
 
i know several folks who use this steel for swords/machetes. would probably make a good "Rambo" blade. in your case, it is the best kind of steel there is, FREE. why not make a couple of 4" basic blades and work em till they fail?
 
Self Made Knives said:
Apparently not much interest or experience with A8 tool steel, but maybe one of you metal gurus can help me understand this graph. How about this Charpy V notch impact test? It looks like the toughness is maxed out at a temper temp of about 625 and again at 1000. Looks like a temper anywhere between 600-900 doesn't change Rockwell significantly, but toughness curve doesn't make sense to me. If I temper at 400 to get about 58-59 Rockwell, is a toughness of 4.5 good? In comparison to other common blade steels, how is 4.5?
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What doesn't make sense about the graph for toughness? You've pretty much nailed it so far. It's hard to tell how this compares to other steels, as this is the first chart I've seen of toughness in a blade steel using v-notch testing. Most steels won't register on that test, blade steels at least. So in that sense, a 4.5 is very tough. Based on that graph, you have a steel that is intended for extremely rough use and resistance to gross failure at high strength, rougher than a human can be with bare hands.
 
Meant to post this earlier, but think of this as an air hardening version of 5160 with better wear resistance, particularly with the A8 Modified.
 
Thanks guys for your thoughts, I've read everything there is on the web about this steel. That didn't take very long, not very many people talking about it. One of the questions about the graph was about how the toughness curve peaks, then dips, then climbs again. Would there be in difference in tempering at 625 or 975? And, I guess I've never noticed a steel that had the same hardness at such a wide temp range, basically the same from 550 to 1000 degrees.

I've decided from reading and from my 2 test blades that is a pretty decent steel. I'm going to make a couple more "finished" blades with it. My main worry now is that if I label the blades as A8, will I get steel snobs shying away from them. My brother made a big bowie style chopper out of this steel and has been testing it on brush, bones, meat, fish, etc. The edge has dulled, but no chips, rolls, or damage at all so far.
 
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