What is Stainless Alloy Steel ?
Stainless steel spoons and tableware often have inconspicuous markings such as “18-8” or “18-10” on them. These markings indicate the amount of chromium (Cr) and nickel (Ni) contained in the iron-based stainless alloy. For example, “18-8” means that the alloy contains 18% chromium and 8% nickel. The 18-8 stainless steel is referred to as SUS304 in JIS standards and is classified as austenitic stainless steel. It does not harden through quenching and is therefore not used for cutlery.
Stainless steels that harden through quenching and are used for knives are classified as martensitic stainless steels with a high carbon content. Generally, stainless steels used in knives contain 0.6-1.0% carbon and 13-16% chromium.
Types and Characteristics
Chromium-Nickel Series (Austenitic Stainless Steel)
– SUS304, SUS316, etc.
– Excellent corrosion resistance.
– Does not harden through heat treatment.
– Generally non-magnetic (does not stick to magnets).
– Contains chromium and nickel, with almost no carbon.
– Used in spoons and tableware.
Chromium Series (Ferritic Stainless Steel)
– SUS304, SUS316, etc.
– Less corrosion-resistant than austenitic but cheaper.
– Does not harden through heat treatment.
– Magnetic at room temperature (sticks to magnets).
– Contains chromium, with a small amount of carbon (generally less than 0.12%).
– Used in bolts, nuts, and household appliance parts.
Chromium Series (Martensitic Stainless Steel)
– SUS420J2, SUS440C, etc.
– Less corrosion-resistant than other types.
– Hardens through heat treatment (quenching).
– Magnetic at room temperature (sticks to magnets).
– Contains chromium and a high amount of carbon.
– Used in knives, bearings, and gauges.
Molybdenum Steel (Molybdenum Vanadium Steel)
The type of steel used varies by retailer, but the AUS series is often used for high-end cutlery, scissors, pocket knives, medical instruments, food machinery, and machine parts.
AUS-6M
– Carbon content: 0.55-0.65%
– Rockwell Hardness (HRC): ~58.0
– Hardening temperature range: ~1050°C
– Hardening method: oil/air cooling
– Manufacturer: Aichi Steel Corporation
AUS-8
– Carbon content: 0.70-0.80%
– Rockwell Hardness (HRC): ~59.0
– Hardening temperature range: ~1050°C
– Hardening method: oil/air cooling
– Manufacturer: Aichi Steel Corporation
AUS-10
– Carbon content: 0.95-1.10%
– Rockwell Hardness (HRC): ~60.0
– Hardening temperature range: ~1050°C
– Hardening method: oil/air cooling
– Manufacturer: Aichi Steel Corporation
VG Series
VG-1
– Carbon content: ~1.00%
– Rockwell Hardness (HRC): 61+
– Hardening temperature range: ~1050°C
– Hardening method: oil/air cooling
– Manufacturer: Takefu Special Steel Co., Ltd.
VG-2 & 5
– Carbon content: 0.65% (VG2) / 0.75% (VG5)
– Rockwell Hardness (HRC): 58+ (VG2) / 59+ (VG5)
– Hardening temperature range: ~1050°C
– Hardening method: oil/air cooling
– Manufacturer: Takefu Special Steel Co., Ltd.
VG-10
– Carbon content: ~1.00%
– Rockwell Hardness (HRC): 60+
– Hardening temperature range: ~1050°C
– Hardening method: oil/air cooling
– Manufacturer: Takefu Special Steel Co., Ltd.
Silver Series
Silver-1
– Carbon content: 0.80-0.90%
– Rockwell Hardness (HRC): 57+
– Hardening temperature range: 1040-1090°C
– Hardening method: oil/air cooling
– Manufacturer: Hitachi Metals, Ltd.
Silver-3 (Gin-san)
– Carbon content: 0.95-1.10%
– Rockwell Hardness (HRC): 59+
– Hardening temperature range: 1040-1090°C
– Hardening method: oil/air cooling
– Manufacturer: Hitachi Metals, Ltd.
Elemental Effects
**Carbon (C)**: Essential for steel, increasing hardness and strength.
**Silicon (Si)**: Removes oxygen from molten steel, also increasing strength and hardness.
**Manganese (Mn)**: Removes sulfur from molten steel, improves hardening and toughness.
**Phosphorus (P)**: Generally harmful, causing cold brittleness.
**Sulfur (S)**: Harmful, causing hot brittleness.
Added Element Effects
**Chromium (Cr)**: Improves hardenability and corrosion resistance. Stainless steel contains at least 13% Cr.
**Molybdenum (Mo)**: Forms carbides, improving wear resistance and corrosion resistance.
**Vanadium (V)**: Forms very hard carbides, improving wear resistance and refining grain structure.
**Tungsten (W)**: Forms carbides, improving wear resistance and high-temperature strength.
**Cobalt (Co)**: Strengthens martensite, preventing carbide separation, and improving wear resistance at high temperatures.
**Copper (Cu)**: Occasionally added for its antibacterial properties.
Please note that the information provided is for reference only. The hardness and performance of the same material can vary significantly depending on the manufacturer and production methods. The price of a knife is not solely determined by the material used, so please understand this important point.