M390, Elmax and the Other Austrians

Böhler-Uddeholm AG is a steel group, one of the world’s leading suppliers of high-grade tool steel. Sheet steel, tubes, wire, forging equipment, gas turbine components, FOX welding electrodes. Plants in Austria, Germany, North and South America, sales companies on every continent. Knife steel on that list is a rounding error.

The group was formed in 1991 by the merger of the Austrian state-owned Böhler Ges.m.b.H. and the Swedish Uddeholm AB; a quarter of the shares stayed with an Austrian industrial holding. Hence a small muddle in the words: “Austrian steels” is a colloquial shortcut. Elmax, Vanax and AEB-L are Swedish by birth; they became Austrian through a deal.

M390

M390 is a powder stainless with 20% chromium, and that figure is almost always read wrongly. About thirteen of those twenty percent are in solution. The rest is locked up in carbides, and locked-up chromium no longer works for corrosion resistance: it is busy with carbon and forms no oxide film on the surface.

That is why S110V with 15.25% chromium has exactly the same level of corrosion resistance as M390 with twenty. What matters is the whole composition, not the number opposite Cr in the table.

For edge retention M390 sits in the top group — above S30V, which in turn holds an edge better than Elmax, S35VN, CPM-154 and BG42.

Its limitation is shared by all powder stainless steels: they carry a lot of carbide. No less than 9–10% chromium carbide and no less than 15% carbide in total. Above 15% carbide, high toughness is off the table. This is exactly why powder non-stainless steels are close to twice as tough as powder stainless ones at the same edge retention.

Elmax

Elmax is a powder stainless from Uddeholm with 1.7% carbon and about 0.1% nitrogen. The design is classic: plenty of carbon, plenty of carbides, decent wear resistance, good stain resistance. For edge retention it sits below S30V — that is not a verdict, just a position in the line.

Vanax

Vanax is more interesting. It is a third-generation powder steel in which carbon has largely been replaced by nitrogen: 1.55% nitrogen against 0.35% carbon. Elmax is the other way round — 1.7% carbon and about 0.1% nitrogen. Two very similar steels with two elements swapped mirror-fashion.

Nitrogen in the lattice works roughly like carbon but does less damage to corrosion resistance. Nitrides and carbonitrides coarsen more slowly than carbides, so the particles come out finer. The result is exceptional corrosion resistance, excellent edge stability, and a steel that sharpens fairly easily, which is rare for a high-carbide stainless.

Technically none of this is free. Liquid steel dissolves nitrogen poorly, so the powder is atomised with a low nitrogen content and then nitrided — before hot pressing into an ingot. Knife steel here turned out to be a by-product of knowing how to handle a gas.

The rusting half of the catalogue

Drop the “stainless” requirement and the more interesting part of the same group’s price list begins. Among the steels with the best combination of toughness and wear resistance stand Vanadis 4 Extra, Vanadis 8 and K390 — powder, alloyed mainly with vanadium, and non-stainless.

The reason is simple. Chromium added for the sake of stainlessness gets locked into chromium carbides: they are softer than vanadium carbides and larger. Softer means you need more of them for the same edge retention. Larger means toughness drops. In knife steel, stainlessness is always bought at the expense of other properties; the only question is whether you are willing to wipe the blade.

A patent that isn’t on the shelf

Böhler holds a patent on powder steels with a high niobium content. The trouble with niobium is that it forms carbides right in the liquid steel, before atomisation: the carbides come out coarse, and the nozzle through which the melt passes into jets of nitrogen gas can simply clog. That usually caps the addition at around three percent.

The workaround is elegant: the steel is first atomised with no carbon at all, so that FeNb forms instead of niobium carbide, and only then is the powder mixed with graphite and pressed. One of the compositions contained just 12% chromium — and showed better corrosion resistance than M390 at higher wear resistance.

The application was filed in 2009. There are still no products. Worth remembering when you read about “the steel of the future”: between a patent and a shelf lie fifteen years and the question of whether the extra processing step pays for itself.

Who needs this

What you buy in an M390 kitchen knife is not sharpness but the interval between sharpenings. If you touch the knife up on a steel every day, you don’t need the interval, and you will pay for it twice: at the till, and later, when you have to sharpen a high-carbide steel.

Vanax makes sense where the environment really is aggressive: salt, acid, constant moisture. In a home kitchen it is usually the solution to a problem you don’t have.