Japanese Steel Types Explained: White, Blue, VG-10, SG2 & More

Stainless examples

VG10, VG MAX, AUS-10

Carbon examples

Shirogami #2, Aogami Super

HRC range

About 58-68

Price range

$50-$500+

The steel is the soul of a Japanese knife. Understanding steel types is the key to choosing a knife that matches your cooking style and maintenance preferences. This guide covers every major Japanese knife steel — from traditional carbon steels forged for centuries to cutting-edge powdered steels.

What Is Japanese Steel?

There is no single "Japanese steel". On a kitchen knife the phrase means one of a family of blade steels made by Japanese mills. Most of the steels in this guide come from three mills: Proterial (called Hitachi Metals until January 2023^[13]), whose Yasugi works sell Shirogami, Aogami, Kigami, Ginsan, ZDP-189 and HAP40 under the Yasugi Specialty Steel (YSS) name^[1][10]; Takefu Special Steel in Echizen, Fukui, which makes VG-10 and SG2^[14][15]; and Aichi Steel, which makes the AUS series^[17].

The -gami in Shirogami (白紙), Aogami (青紙) and Kigami (黄紙) is the Japanese word for paper, so the names translate as white paper, blue paper and yellow paper steel. For the white-vs-blue choice in depth, see Aogami vs Shirogami.

The older meaning is tamahagane (玉鋼), the steel of Japanese swords, smelted from iron sand and charcoal in a clay furnace called a tatara^[24]. It is still made: the Society for the Preservation of Japanese Art Swords revived tatara smelting in Okuizumo, Shimane, as the Nittoho Tatara, which now runs with technical cooperation from Proterial to supply the tamahagane that Japanese swords need^[23]. Proterial says its Yasugi works draw on that tatara tradition and the region's high-purity iron sand^[11], but its production today combines that heritage with electric and vacuum furnaces and modern refining^[12]. Shirogami and Aogami are made to a published chemical specification^[1][5], so they are not the same material as sword tamahagane.

Japanese Knife Steel Chart

This chart lists the main Japanese knife steels with their maker, published hardness, rust resistance and ease of sharpening. "Mill" hardness is the minimum the steelmaker publishes after its standard heat treatment; the figure "on knives" is the range retailers or knife makers list for finished blades, which depends on each maker's heat treatment. Rust resistance follows the chromium content the mill publishes — stainless steel needs at least about 10.5% chromium^[28]. Ease of sharpening is what the steelmaker, knife maker or a specialist retailer says; "not stated" means none of our sources gives it.

Proterial was called Hitachi Metals until January 2023^[13], so older listings may name Hitachi as the maker of the Shirogami, Aogami, Ginsan, ZDP-189 and HAP40 grades. The full alloy figures for each steel are in the mill data table below.

VG-10 vs SG2 (R2): Which Is Better?

SG2 is the harder steel and holds an edge a little longer; VG-10 is easier to sharpen and costs less, and the two resist rust about equally. Both are stainless steels made by Takefu Special Steel in Echizen, Fukui^[14][15]. Takefu lists VG-10 at HRC 60 or more and SG2 at HRC 62 or more; knife makers typically finish VG-10 at about 60–61 and SG2 at about 62–64, according to a retailer that stocks both^[26].

Which to choose: Knives and Stones, which sells both, recommends VG-10 for most home cooks and for a first Japanese knife, because it is the kinder steel to learn to sharpen on, and SG2 for cooks who sharpen rarely and want the longest stretch between touch-ups. Neither is stain-proof: rinse and dry either blade after use^[26].

SG2 or R2? Knives are often listed as "SG2/R2"^[30], but Knives and Stones reports finding no steelmaker page for a steel called R2, so it cannot be confirmed from a mill that the two names describe identical steel^[29]. Check the knife maker's hardness figure rather than the name.

For VG-10 on its own, see our VG-10 steel guide.

Overview: Carbon vs Stainless vs Powdered

Carbon Steel (Hagane) — Traditional Japanese Steels

Carbon steels are the traditional choice for Japanese knives, prized for their ability to take an incredibly sharp edge and the satisfying cutting feel they provide. In the tables below, HRC is Proterial's published minimum after its standard heat treatment, which is the same (60) for every grade; a finished knife's hardness depends on the maker's heat treatment, so the grades differ mainly in carbon and alloy content.

Shirogami (White Steel)

Key trait: White steel is the purest — almost no alloying elements. This makes it exceptionally easy to sharpen and capable of a razor-fine edge. However, it has zero rust resistance.

Aogami (Blue Steel)

Key trait: Blue steel adds tungsten and chromium to improve edge retention. It holds an edge longer than white steel but is slightly harder to sharpen. Still not rust-resistant.

Stainless Steel — Modern Performance

HRC here is the mill's published minimum where the mill gives one; otherwise it is the published spec of the named knife.

Powdered Steel — Premium Performance

Complete Comparison Chart

The stars are an editorial ranking, not measurements. For the published hardness, chromium and retailer descriptions, see the steel chart above.

Who Makes Each Steel: Mill Data at a Glance

This table takes each steel's chemistry and hardness from the mill that makes it. Mills publish a minimum hardness after their standard heat treatment; the figure on a finished knife is set by the knife maker's quench and temper. Where the mill gives no figure, the hardness comes from a published spec for a knife made in that steel.

Carbon vs stainless, in numbers. Proterial lists no chromium at all for Shirogami and Kigami, and only 0.20–0.50% for the Aogami grades^[1][4][6], which is why they rust. The stainless grades carry far more: Ginsan 13.00–14.50%^[8], VG-10 15%^[14] and ZDP-189 20%^[9]. HAP40 sits between them at 3.70–4.70%^[10]; it is sold as a semi-stainless steel that may darken and form a patina, although it will not rust as easily as carbon steel^[22].

Heat treatment matters as much as the grade. Proterial's own sheet for Shirogami #3 shows it: water-quenched and tempered at 180–220 °C it reaches HRC 60 or more, but oil-quenched and tempered at 280–340 °C only 52 or more^[3]. The same grade can therefore leave different workshops at quite different hardness.

Check the label. Takefu warns that knives falsely advertised as VG10 are being sold online, and that their quality differs significantly from genuine VG10^[14]. See how to spot a fake Japanese knife.

Core Steel vs Cladding: What the Steel Name Refers To

Most Japanese kitchen knives are not one solid piece of the steel on the label. Takefu Special Steel, which also makes laminated blade stock, describes three-layer (3-ply) material, a high-grade blade steel combined with lower-cost cladding, as the most popular for kitchen knives, and two-layer (2-ply) material as mainly used for single-edged knives^[16]. Two published examples: the Shun Classic chef's knife has a VG-MAX core inside 34 layers of stainless Damascus on each side^[19], and the Hatsukokoro Hayabusa nakiri has a HAP40 core with stainless cladding^[22].

So the named steel is the cutting edge: it sets the hardness, edge retention and how the knife sharpens. With stainless cladding the core is exposed only along the edge, and that is where a carbon or semi-stainless core needs care; the retailer of the HAP40 nakiri notes that the edge area may darken and form a patina^[22]. A Damascus pattern belongs to the cladding, not the core. See Damascus vs mono-steel, and single vs double bevel for the single-edged knives that use two-layer steel.

Which Steel Should You Choose?