154CM, ATS-34 and CPM-154: one steel with three biographies

In price lists these three names sit side by side and are regularly passed off as one another. Their chemistry is the same: 154CM is the original American steel, ATS-34 is its Japanese version from Hitachi, CPM-154 is the same formula made by powder metallurgy. The difference is not in the recipe but in the way it is made. This is precisely the case where the method matters more than the recipe.

The confusion starts with the names. 154CM and CPM-154 differ by three characters and by a whole generation of metallurgy, and knife descriptions mix them up regularly — sometimes through carelessness, sometimes because it suits the seller.

154CM: the steel that barely reached the kitchen

Rather more has been written about 154CM than has been made from it in kitchen knives. The steel’s reputation is good: a high-quality stainless with very high wear resistance. Price gets in the way. Production kitchen knives don’t use 154CM simply because it is expensive. Small makers turn out short runs of it, such knives are hard to find, and they start at around three hundred euros.

The second feature is the flip side of wear resistance. At high hardness 154CM can be brittle. This is a general property of steels whose wear resistance rests on chromium carbides: the carbide is hard and therefore resists abrasion well, but it is also brittle and makes a convenient starting point for a crack. In the kitchen this shows up not as dulling but as chipping — small pieces break off the edge.

It is worth understanding separately why such a steel never made it into mass production at all. Large manufacturers producing knives in volume tend to take stainless — the average buyer expects a knife to be stainless, and that requirement outranks all the others. 154CM meets the condition but costs so much that the whole arithmetic of series production falls apart. As a result a steel with a good reputation lives in the small-batch segment, and the mass buyer meets it only in texts.

ATS-34: the same composition, a different mill

ATS-34 is a version of the same steel made by Hitachi. In knives it turns up at around 60–61 HRC. Formally it is a Japanese steel, in fact an American formula made in Japan, and in Japanese catalogues it long served as a reference point: other grades were described through it. Gingami (also known as GIN-1), for instance, is described plainly as having slightly less carbon, slightly more chromium and noticeably less molybdenum than ATS-34.

For the user there is no practical difference between 154CM and ATS-34. The difference is in the name and the country in which the steel became available to a knifemaker. One formula acquired two biographies simply because it was melted on two continents, and it has lived in catalogues as two separate lines ever since.

CPM-154: the same steel, made differently

CPM-154 is Crucible’s powder version of 154CM. The composition is identical to the original steel, apart from a little added vanadium, which makes wear resistance slightly higher. The rest of the difference is metallurgy.

The point of the powder process is carbide size. In conventional melting the carbides have time to grow large, and every large carbide is a potential chip. In powder steel the melt is atomised, the metal solidifies as fine particles, and the carbides stay small. They still grow slowly during hot pressing and rolling, but they start from an incomparably smaller size. The result for CPM-154 is predictable: a cleaner steel, finer carbides, higher toughness and better workability. It is easier for the maker to work with.

It got no easier for the user. CPM-154 is hard to sharpen — wear resistance works both ways, and the steel resists your stone as readily as it resists food. On the other hand it can be sharpened very keen and holds an edge for a long time. Hardness is taken up to 61 HRC, though that is not often chosen.

The ceiling of this approach is worth naming too. Any powder stainless contains a substantial quantity of chromium carbides — no less than nine or ten per cent, with total carbide no less than fifteen. Fifteen per cent carbide is already the threshold beyond which high toughness is not to be expected. So even a carefully made powder stainless loses on the balance of properties to powder carbon steels, where the entire carbide budget went to vanadium. CPM-154 is a good steel in its class, but the class is set by the requirement not to rust.

Who needs it

Factory kitchen knives in CPM-154 don’t exist. It is a material for small workshops: knives are made from it one at a time, mostly fillet and chef’s knives. Buying such a knife, you are buying not so much the steel as a particular maker and his heat treatment — and that is the honest way to put it.

With 154CM and ATS-34 the picture is soberer. It is a good steel for a kitchen knife, but not an outstanding one: for a little more money there are better steels. The nearest example is VG-10, close to 154CM in alloy but better at holding an edge and better at resisting corrosion, and incomparably easier to find. If you are choosing a knife rather than collecting names, the difference in a given maker’s heat treatment will matter more than the difference between these three lines in a catalogue.