SKD vs SLD: same hardness, two steel classes

Here is the thing this page exists to say: "SKD" is not one steel. It is a JIS die-steel family, with SKD1, SKD11, SKD12 and others in it, tool steels that share a standards series rather than a recipe. So the SKD stamped on a knife tells you a family, not a chemistry. Every SKD knife in stock today is a Yoshikane, most of them sold as Hatsukokoro x Yoshikane, and our own listings state about 1% carbon and 5% chromium. That chemistry is SKD12's (JIS: carbon 0.95-1.05%, chromium 4.80-5.50%), the Japanese A2, and it is the steel this comparison is actually about.

SLD sits on the other side of the same JIS table. It is the brand name Proterial (formerly Hitachi Metals) uses for one steel: SKD11, the Japanese D2, a high-carbon, high-chromium tool steel that Proterial makes to a narrower band than the JIS spread. SLD is a single producer's version of one family entry, not a family label. That is why the honest pair is SKD12 against SKD11: two different tool-steel classes at the same working hardness, not two names for one steel.

On hardness the two tie: SKD at 62-64 HRC on our listings, SLD at 62-64 HRC on our listings. (For tooling rather than knives, Proterial's heat-treatment table puts SLD at 57-63 HRC after tempering.) The difference hides in the composition rows: SKD12 carries 0.95-1.05% carbon where SLD's typical is 1.50%, and 4.80-5.50% chromium where SLD's typical is 12.00%. The hardness is a tie; the class is not.

SKD12 by its JIS row: carbon 0.95-1.05%, chromium 4.80-5.50%, molybdenum 0.90-1.20%, vanadium 0.15-0.35%, no cobalt, the A2 chemistry under a Japanese number. SLD by Proterial's own typical values: carbon 1.50%, chromium 12.00%, molybdenum 0.90%, vanadium 0.30%, no cobalt, sitting inside the JIS SKD11 range of 1.40-1.60% carbon and 11.00-13.00% chromium. Proterial makes SLD to a narrower band than JIS allows, and says SKD11 is not classified as stainless because of its high carbon.

One caution the table hides: SKD12's chromium is well under half of SLD's, and SLD's own chromium is not what it looks like. Knife Steel Nerds notes that about half of D2's chromium is tied up in carbides, so the free chromium that resists rust is well below the headline number.

Both steels are ingot melts, so nothing here comes from powder atomization; CPM-D2 is the powder version of the D2 story, and SLD is not that. Knife Steel Nerds puts A2, SKD12's class, at about 6% chromium carbide, and says that structure is somewhat coarser than simple steels like 1095 and O1 but finer than a steel like D2. About D2, SLD's class, they describe a large amount of large chromium carbides. Nobody publishes a carbide volume figure for SLD. The schematic below is drawn from those class descriptions, so read it as geometry, not as a measurement.

This is where the classes diverge, and every word here is about A2 and D2, the proxy classes for our steels at the same 62-64 HRC band. Knife Steel Nerds estimates A2, SKD12's class, at about 85% of 440C's edge retention, and they call that number an estimate rather than a measurement. On the D2 side, SLD's class, Böhler-Uddeholm CATRA numbers relayed by Knife Steel Nerds put it somewhat better than 440C, on par with 3V, and below S35VN, S30V, Elmax and M390. We publish no score and no CATRA figure for either steel: the direction, SLD longer, is as far as the evidence goes.

Again labelled by class: Knife Steel Nerds says A2, the class our SKD12 belongs to, has good toughness and compares favorably with higher wear resistance steels like D2. For D2, SLD's class, Crucible, relayed by the same source, rates its toughness worse than 3V, CruWear and A2, and says the large carbides in D2 limit its toughness and also its edge stability. We publish no Charpy figure for either steel. Neither is a cleaver: keep both off frozen food and away from prying.

The label that fits both steels is semi-stainless, and one misconception is worth killing here: SLD is not stainless. Proterial says outright that SKD11 is not classified as stainless because of its high carbon, and Knife Steel Nerds' verdict on D2-class corrosion is good for a tool steel and somewhat over-promoted. On the SKD side, Knife Steel Nerds says A2, SKD12's class, offers a little stain resistance against simple carbon steels but is not stain resistant to the degree of a stainless steel. Wipe and dry either knife; neither forgives a wet overnight.

Same hardness band, very different stone manners, and the reason is carbide. Knife Steel Nerds says the relatively low volume of chromium carbide makes A2, SKD12's class, much easier to grind, polish and sharpen than the common high wear resistance steels. SKD12's about 6% carbide is a light load; SLD's D2 class carries a large amount of large chromium carbides, and those take more work on the stone. SKD gives up some edge life precisely where SLD earns it.

Buy SKD if you sharpen yourself and want the easier knife on the stone, with an edge our Yoshikane listings say behaves similarly to carbon steel for keenness, and a tougher edge for a busy kitchen. Buy SLD if you want longer time between sharpenings from a tool steel and more price points to choose from, and you are happy to spend longer on the stones. Either way, these are semi-stainless tool steels: dry the knife after every use.

One standard SKD 210mm gyuto sits near A$540; standard SLD 210mm gyutos run from A$198 to about A$1,000. A spread that wide inside one steel tells you the price is set by the maker, the line and the finish, not by the alloy. The A$198 Yuepo and the A$999.95 Yorokobi Special share a steel and differ in maker and finish. Read the price rows as catalogue shape, not as a quality ladder for the steel.

Daily life with the two is more alike than different. Neither is stainless: wipe and dry at the sink, no soaking, no dishwasher, and neither will punish you much beyond that. A light patina near the edge is normal on both and comes off with a soft cleaner if it bothers you. Sharpening day is where your lives part: SKD asks for less patience and returns quicker sessions; SLD asks for more time on the stones and gives longer gaps between sessions.

Written by James Zhang for Knives & Stones. Disclosure: we sell both steels. Composition comes from Proterial, the producer of SLD, and from the JIS tables for SKD12; hardness is from our own listings, and prices are a live stock read of standard 210mm gyutos as of 2026-10-03. Performance statements are about the A2 and D2 classes and come from Knife Steel Nerds (Larrin Thomas). We tested nothing ourselves, and where a number does not exist, we left the space empty instead of inventing one.

One habit fixes the whole category: when a knife says SKD, ask which SKD. Our listings state about 1% carbon and 5% chromium, SKD12's chemistry, and that number decides the class. Listings elsewhere sometimes call Yoshikane's steel SKD11; a chemistry line settles in one search what the family name never will. The same habit works for any family name on a blade: ask for the grade.