The 440 series and 420HC: what hides behind a cheap stamp

A “440” stamp on a blade is not a grade but a family, and the spread inside it is wider than the distance between the family and its neighbours. Knowing that a knife is “440” is about as useful as knowing that a car is “German.”

How the designations work

440A, 440B and 440C are American AISI designations that differ mainly in carbon: from A to C there is more of it. More carbon means higher hardness and wear resistance, and less reserve of toughness and corrosion resistance. All three have plenty of chromium.

420 follows the same logic with even less carbon. The letters after the number mark variants inside the family: HC means high carbon, “more carbon than in the base 420”; J2 is an index of the Japanese standard. The stamp promises nothing beyond that: no heat treatment, no hardness, no geometry.

The 420 series

Carbon is below 0.3–0.5%, which makes the steel too soft for a useful cutting tool in the kitchen. Wear resistance is low, but rust resistance is very high. A good choice for a diving knife, a poor one for the kitchen. It mostly goes into very cheap kitchen knives.

A concrete example: SUS420J2 — 14% chromium, 0.3% carbon, hardness 56 ± 1 HRC. No mistake and no fraud: the steel honestly does what it was designed for. The trouble starts when it is sold as “professional.”

A similar story with 1K6, a relatively soft steel used in budget lines of kitchen knives. Very clean stainless, high chromium content, hardness around 56–58 HRC. Slightly more carbon than the base 420, and it holds an edge correspondingly slightly better.

440A and 440B

A large share of inexpensive mass-market kitchen knives — the ones sold in hardware and furniture chains — is made from these and their like. 440A also turns up at well-known makers: Cutco, for instance, uses it.

The verdict is simple and cheerless: for a cutting tool this steel is not strong enough. It is not defective and not dangerous, it is just not about cutting.

440C

Twenty years ago 440C counted as a good knife steel. Today it is obsolete and does not compete with modern grades, but it still goes into plenty of kitchen knives.

And here is the main point. If 440C is hardened properly, it is an excellent steel for a kitchen knife: good strength, good rust resistance, a decent edge. If it was heat-treated badly, it is entirely unusable.

One stamp, two different knives. The difference is not in the grade or the country but in the workshop, and it is not printed on the box.

Indirect evidence that chemistry is not the issue: the Austrian N690 corresponds roughly to 440C in composition, differing by a higher molybdenum content and an addition of cobalt — and it is a perfectly modern steel. On the same base you can build both a good knife and rubbish.

Surgical steel

A genre of its own is the “surgical steel” stamp. No official grade with that name exists. The term refers to the soft steels used in medicine: 17-4, 17-4 PH, stainless 455, the implant alloys 316L and titanium 6AL4V, which is not a steel at all. None of them has the properties a knife needs. All of them resist rust beautifully — which is enough in medicine.

In practice, knives labelled “surgical steel” are made of 420 or something worse. The advice in the source is given without ceremony:

Don’t buy them, and if you have them at home, just throw them out.

Chinese stamps

5Cr15MoV and 5Cr14MoV decode mechanically: the number to the left of Cr is the carbon content in tenths of a per cent, the number to the right is the chromium percentage rounded to a whole number. So 5Cr15MoV is roughly 0.5% carbon and 15% chromium, and it is essentially the same as the German X50CrMoV15, also known as 1.4116. In its properties it is compared to AUS-8, possibly with slightly better corrosion resistance.

Cheap knives sold as a set in a wooden block usually have a hardness of about 52 HRC. Every two HRC points roughly double the life of an edge: 52 HRC stays sharp for about a week, 62 HRC for about a year under regular use. That is the whole difference between a supermarket block and the talk about Japanese steel, converted into days.

Who needs what

A well-hardened 440C in the kitchen is a perfectly normal working option, nothing to be ashamed of. A 420 in a diver’s sheath is also in its place: it is there for corrosion resistance, not for cutting.

Exactly one purchase is pointless — paying extra for a word. “Surgical steel,” “German steel,” “Japanese technology” on the box of a twenty-euro knife describe neither the composition nor the heat treatment. They describe the marketing department.