Edge Retention/Rolling Test Stand

[Mark Reich]

 We're sure that this revelation comes as quite a surprise to Mark Reich but as we said in an earlier post (remark) about Mark. Even an old dog can learn new tricks.

Not that I'm not an old dog. I am. Not that I'm not choosy about what tricks I will or won't learn. I may be  persnickety in my old age as well.

I just don't know which of my many blunders you're referring to at the moment. I'm pretty sure I voted hardening will make a difference.

Don't worry, I may be an old dog, but I can still chew through several crows without any heartburn.

[KnifeGrinders]

Hi Jan and Mark,
Could you explain me in plain language the Carbon contents please? - as I am totally confused when they talk about the Carbon %.
They talk of the unhardened steel Carbon contents in the order of 5% and more, but when I read knives composition Carbon is 0.4% to 1%.

[Jan]

We're sharpening now non-hardened A2 now. Looks to us like 260-275 is going to be the number. Lower numbers can be squeezed out but not on a consistent level throughout the edge. Don't know what the 30° chisels are going to turn out to be yet because we haven't tried them yet. To the right is a micro pic of a sharpened and deburred edge. We've done the minimum amount of grinding here. The bevel is 15° and all we've done is created a 19° micro-bevel on the edge.

                                               

We did run another test prior to shipping these off. We ran a roll test on this now sharpened but non-hardened A2 steel. As you may recall we did something similar with a piece of cold rolled sheet goods that was .050 thick a few weeks ago. That non-hardened material was sharpened to 275 and then placed in the SET for rolling...and roll it did, all the way to 818 (one series of five back and forths). This as compared to hardened steels that roll in the 200 - 250 point range (ending sharpness level minus beginning sharpness level). The non-hardened A2 began at 259 and ended at 720 so it seems that hardening must have some considerable and beneficial effect with regard to rolling of edges. We're sure that this revelation comes as quite a surprise to Mark Reich but as we said in an earlier post (remark) about Mark. Even an old dog can learn new tricks.

Of course we have just presented strong evidence of something we had all suspected was true so "why do it?" We are about to harden A2 steel at different levels and then measure the effect of these various hardness levels on edge rolling. Now we have established the far end of the hardening spectrum as well... no hardening at all.  Our conclusion is that "non-hardened steels roll a lot and now we know, fairly precisely, how much "a lot" is. "

Annealed A2 steel may have hardness some 20 HRC only.

Jan

[EOU]

We're posting this because the Exchange is screwed up. Who's running this place anyhow? It seems that the last post isn't visible until someone (or yourself) post the next post. We see that Jan was the last poster but don't believe we can see it until we post this message. Anyway looks like that is the problem until it is fixed.

[EOU]

Test Post - we have problems with displaying recently composed posts in this thread. I can see the posts if I view them as a guest but not logged in as a member.

[Mike Brubacher]

Now EOU can't see their posts but I can. Someone should be canned. Of course we were just pulling your leg a bit Mark. You are neither old nor a dog. You do perform tricks with knife metals though. Maybe not tricks, maybe just magic.

[admin]

Test post - please ignore

[Mark Reich]

Cast iron may have close to 5% carbon, but that's the only thing that comes to mind. Not very many common blade steels have much more than 1%. A2 has about 1%.

Medium carbon steel, which is the vast majority of knives, are up to 0.5% carbon.

High carbon steels go up to about 0.84 percent carbon.

Above that, hypereutectoid steels basically have an abundance of carbon, in the 1% range.

Elmax and D2 are exceptionally high for common tool steels at about 1.7% and 1.5% respectively. They also have a lot of chromium, which ties up the extra carbon in chromium carbides.

The higher grades of Japanese steel are very high as well, with about 1.2-1.5%. Super Blue is even higher.  

Most of the modern powdered steels have very high carbon, from about 1.3% to 3%, but that is like a different category IMHO.  

That's about the most I can say off the top of my head.

[Jan]

KG, an oversimplified answer to your question may be:

If the amount of carbon in molten iron is below 2.1% we have steel, but if it is above 2.1% we have cast iron.

Typically we distinguish between:
Low carbon steel with less than 0.25% carbon content,
Medium carbon steel with some 0.3 to 0.5% carbon content,
High carbon steel with some 0.55% to 0.95% carbon content and
Very high carbon steel with some 1 to 2% carbon content.

The highest possible carbon content has a chemical compound called cementite (Fe3C) which has 6.7 weight % of carbon. Often the excess of carbon in high carbon steels is present as separate cementite grains.

Jan

[KnifeGrinders]

KG, an oversimplified answer to your question may be:

If the amount of carbon in molten iron is below 2.1% we have steel, but if it is above 2.1% we have cast iron.

Typically we distinguish between:
Low carbon steel with less than 0.25% carbon content,
Medium carbon steel with some 0.3 to 0.5% carbon content,
High carbon steel with some 0.55% to 0.95% carbon content and
Very high carbon steel with some 1 to 2% carbon content.

The highest possible carbon content has a chemical compound called cementite (Fe3C) which has 6.7 weight % of carbon. Often the excess of carbon in high carbon steels is present as separate cementite grains.

Jan

Thank you Mark and Jan, all clear now.