Thread: Best Stainless for Razors ?

Originally Posted by AndreGrobler

Appreciated... but you are dealing with cpm154m which has larger carbides ... This will be lessened by a tougher matrix, but mostly smaller carbides...

Please expand a little more. I thought the point of crucible particle metallurgical steels (CPM) was to have the smallest carbides possible at manufacture. How does that translate into larger carbides, then tougher and smaller? It's confusing the way your statement reads, to me anyway.

Larger carbides usually occur because of overheating. Maybe I missed something.

Larger carbides does occur with overheating, but primarily the chemistry (available carbon and other carbide formers) makes the size and the hardness of the carbides. PM just tends to make the variation in the size of the carbides less. So they are all more or less the same size... no big clunky ones.

The stainless with the smallest carbides are not pm steels. They are aebl and 13c26n and 14c28n and 12c27... these are the industrial razor steels. They have just enough carbon to get hard enough with due care that there is no excess carbon to form carbides.

Please note i am not an expert... this is the information i got from recognised experts... i may get stuff and explanations wrong.

Oh yes 440a and 420 hc has the same tiny carbides... but to get it hard enough to be useful requires huge amounts of care to reduce ra...

And now that i think about it becut has the same amount of carbon as aebl et al so would also not have large carbides...

The most common stainless razor steels are B-U AEB-L and Sandvik 13C26 which are pretty much identical. The problem is that you can't really find them in the thicknesses needed for a straight razor. The knife steel suppliers in the US had enough trouble getting 1/8 inch stock and I don't know if anyone had ever seen the rumored 3/16 stuff over here. Some of the other steels mentioned like Niolox are highly abrasion resistant when HT'ed to their full potential, which seems to be an undesirable;le thing for razors from what I have read on here.

Originally Posted by AndreGrobler

Oh yes 440a and 420 hc has the same tiny carbides... but to get it hard enough to be useful requires huge amounts of care to reduce ra...

The question with those is do they have the requisite fine edge stability like AEB-L/13C26? If there was ever an application that requires that, it is a razor. AEB-L will get to 61 Rc easily with a low temperature temper and you don't have to use LN to finish it. Dry ice and acetone will work just fine.

IF you do a heat treat that minimizes retained austinite... you can get a good solid 59 apparently...

440A has more silicon than AEB-L and considerable more chromium, like 3-5 points more. The problem with it may be one of quality control in some cases. That is not an issue with the Uddeholm and Sandvik products. It should be noted that only the HC version of 420 stainless is suitable for blades and it still has only about 75% of the carbon of 12C27, only slightly more than some of the "engineering" grades of steel like 4140. The regular 420 only has like .15% carbon, no more than the 410 or 416 steel that many knife makers use for guards and fittings. That makes me wonder if the bit of extra chrome or one of the other alloying elements are what allow you to get to 59 with that stuff. I typically think of plain carbon steels with that carbon content as being ones where you only see like 54-55 Rc or so. Do you have any info on that, Andre?

Chromium does increase hardenability... but you only need .7% carbon to get to 65-68 right after the quench... the alloying elements will tend to make that more... i think...

But with strongly alloyed steels... retained austinite is often what has a large determining factor in final hardness... the more the softer...

This topic is very interesting, a lot to learn for themselves.