Knives Illustrated
Frequently
Asked Questions
What
is “AEB-L” steel?
AEB-L is a stip steel made in Sweden by Uddeholm. Composition:
C Si
Mn max P max S Cr
0.68 0.4 0.65
0.025 0.015 12.8
Few know what AEB-L steel is, and those that do, only have heard that
it is similar to 440B or 440A. The only similarities between AEB-L and
440B or 440A is the amount of carbon. The fact that AEB-L has only
12.8% chromium by volume compared to the 16-17% in 440A and 440B makes
the steels almost as different as night and day. This makes AEB-L very
balanced, it still has excellent corrosion resistance, in the same area
as 440C or other popular stainless steels used in knives today. It gets
very hard, up to 64 as quenched. Though AEB-L is not a powder
metallurgy steel, it contains very tiny carbides, its average carbide
size is six-tenths of one micron, powder metallurgy steels have a
carbide size of 2-4 microns. This gives AEB-L excellent toughness,
great ease of sharpening, ease in grinding and polishing, great wear
resistance, and a very keen edge to a knife. 440C has some carbides as
large 50 microns. A very keen edge is about one half of one micron, so
when cutting, carbide pullout happens with large carbides,
the carbides are pulled like a tooth out of the blade, this makes for a
toothy and hard to sharpen edge, not to mention that the carbides are
virtually worthless. AEB-L also naturally forms what is called the K2
carbide, the harder of the two chromium carbides, compared to the K1
carbide, which is formed in steels such as 440C. The K2 carbide is
about 79 on the Rockwell C scale, compared to 72 for the K1 carbide.
Through proper heat treatment, AEB-L has fine, evenly distributed K2
carbides. AEB-L lies almost perfectly on what is called the “Carbon
Saturation Line”, which means that all of the carbides formed are
precipitated carbides, not primary carbides like are formed in 440C,
and there is more carbon and a similar amount chromium in solution as
compared to 440C. Primary carbides are very large. So, through a
balanced composition, AEB-L has excellent toughness, edge retention,
workability, ease of sharpening, and ease of polishing.
Does the nickel
or 304 in some of your damascus effect the edge retention of the steel?
There is nearly zero carbon migration when using nickel or 304 in
damascus, so the two metals are almost unchanged, other than that they
have been mechanically forged, which can bring benefits in and of
itself. This means that the steel along with the nickel is essentially
the same, other than the fact that it has nickel or 304 along with it.
Nickel and 304, since they are unhardenable, will wear down faster,
giving the steel a slightly "toothy" cut to it after the first initial
uses. We use the minimum amount of nickel or 304 to minimize this, our
steels contain only 8-11% nickel or 304, depending on the pattern.
Is damascus better than a single steel?
In short, we don't know, though there are plenty of theories to wonder
about, there has been no major testing done on damascus to find out.
Any testing that has been done hasn't been extensive enough to prove
anything, but there has been extremely little testing done. There are
many possible advantages; for example, O1 is a very wear resistant
steel, while 15N20 is very tough. When O1 and 15n20 are used together,
it gets a
combination of toughness and wear resistance not found in either steel.
There is also the possibility of increased edge retention with damascus
steels. Two steels that have high edge retention with different
compositions, and possibly for different compositional reasons, may
have the best of both worlds when used together. An example is our
AEB-L/154CM damascus, one is a steel with very small carbides (AEB-L),
and the other has large carbides (154CM). The AEB-L is going to be fine
grained and have small carbides, giving it a fine, polished edge, good
for certain cuts, while 154CM is convential, meaning it will have some
large, bulky carbides, which, try as you might, generally means your
knife edge is going to be slightly toothy after some cutting, even if
you get a fine polish in the first place, which is good for many
different cuts than those good for a polished edge. Together, you may
get some of the best properties of both. We plan on doing testing on
this, either with a CATRA machine or another method, though it might be
difficult to show that there is an increase in performance with general
testing methods. Another interesting thing about high-alloy double high
carbon damascus is that the steels respond to heat treatment better
after being forge welded together into damascus, meaning they get
harder, which shows that there are benefits to forging stainlesses and
to forge welding that are as of yet unknown.
In addition to the fine/coarse combinations of AEB-L/154CM, 3V/154CM,
etc. we also make coarse/coarse: D2/154CM or fine/fine: AEB-L/CPM-154
and 3V/CPM-154. In double high carbon mixes, we are limited to steels
with high nickel in carbon steels (15N20), or high molybdenum in
stainless steels (BG42, 154CM/ATS-34, CPM-154) to provide a bright
layer for contrast. Those stainless mixes containing high molybdenum
such as 154CM are not as easy to etch as those with 302, and require
etching with muriatic (swimming pool acid or HCl) or sulfuric acid
rather than Ferric Chloride. These high performance mixes are also
limited to certain patterns, call for more information.
We
are also considering providing san-mai material such as stainless
laminated CPM-M4 to give some stain resistance and ease of finishing to
CPM-M4.
