Types of Steel and Other Materials

Note that steel grades are specific to different countries and do not have direct equivalents.  

• AISI Steel Grading System
• What steel is best for swords?
• High Carbon Steel  (1055, 1065, 1080)
• Powdered Steel (K120C)
• Tool Steel (L6, T10, SK-5)
• Spring Steel (5160)
• Stainless Steel (VG-1 , 4116 KRUPP, AUS 8A)
• Other Materials (GRIVORY, KRATON, ZYTEL)
• Steel Composition Comparison Chart

AISI Steel Grading System

The first digit of the designation indicates the steel group (1 meaning unalloyed steel, 2 nickel steel, 3 nickel-chromium steel and so on). The second digit indicates the approximate percentage of the average carbon content multiplied by 100.

Tool and Special Purpose Steels

What steel is best for swords?

Selecting the best steel for a sword is a question of trading durability, and edge retention.  The answer is all about personal preference and what the sword will be subjected to.  Heavy dojo use focusing on tatami is going to call for good edge retention.  Occasional cutting with a lot of different target materials is going to call for durability.  Proper forging and heat treatment can affect the performance much more that which steel is used, so only use swords from forges you can trust.

High Carbon Steel

High Carbon Steel (1055, 1065, 1080)

High-carbon steels are extremely strong but more brittle than medium-carbon steels. This composition allows better responses to heat treatment and longer service life than medium-carbon steels. High-carbon steels have superior surface hardness resulting in high wear resistance. The AISI designations for High-carbon steel are: AISI 1055-1095, 1137-1151, and 1561-1572. 

The first digit of the designation indicates the steel group (1 meaning unalloyed steel, 2 nickel steel, 3 nickel-chromium steel and so on). The second digit indicates the approximate percentage of the mean carbon content multiplied by 100.

Examples:
AISI 1055 = Unalloyed Steel with 0.55% Carbon
AISI 1065 = Unalloyed Steel with 0.65% Carbon
AISI 1080 = Unalloyed Steel with 0.80% Carbon

1055 CARBON (From the Cold Steel® Catalog)

1055 steel is right on the border between a medium and a high carbon steel, with a carbon content between 0.50%-0.60% and with manganese between 0.60%-0.90% as the only other component. The carbon content and lean alloy make this a shallow hardening steel with a quenched hardness between Rc 60-64 depending on exact carbon content. These combination of factors make this one of the toughest steels available because, when quenched, it produces a near saturated lathe martensite with no excess carbides, avoiding the brittleness of higher carbon materials. This steel is particularly suited to applications where strength and impact resistance is valued above all other considerations and will produce blades of almost legendary toughness.

Powdered Steel

K120C Swedish powdered steel

Wrought powder metallurgy tool steels offer improved wear resistance, higher hardness, greater heat resistance, increased toughness, and better dimensional stability than conventional tool steels. It has a more refined and more homogeneous microstructure and have smaller, more uniformly distributed carbide particles and a uniform fine grain size. The most significant benefits of P/M technology are manifested in high-speed steels for tooling. Compared with cast/wrought steel, P/M tool steels provide:

• Improved machinability in the final annealed condition
• Improved grindability in the hardened and tempered condition, with no reduction in the abrasion resistance of the finished tool or part
• Increased toughness of the finished tool
• Less out-of-round distortion after going through heat treatment
• Use of higher alloy-content steels possessing higher wear resistance and improved cutting performance

Wrought high-speed steels made by powder metallurgy are primarily for metal-cutting and metal-forming operations.

Tool Steel

L6 Tool Steel

L6 is a lightly alloyed medium carbon steel which allows oil hardening and has a slight improvement in wear resistance over the plain carbon steels and gives deeper hardening. It has very low corrosion resistance. It can readily reach full martensite hardness of 65/66 HRC.

• Principal Features: This is one of the Special Purpose, low alloy tool steel grades, similar to the W group of low alloy tool steels. L6 contains nickel, chromium and molybdenum for a good combination of toughness and hardenability.
• Applications: Typically used in machine tool applications such as bearings, springs, rollers or chuck parts.
•  Heat slowly to 1500 F and hold at temperature for 10 to 30 minutes. Oil or water quench. 
  Forging: Forge at 1975 F down to 1600 F. Do Not forge below 1550 F.
•  Anneal at 1450 F and slow cool at a maximum of 40 F per hour. 
• Tempering is done in the range of 350 F to 1000 F for Rockwell C 62 to 45 range. 

L6 / Bainite Steel (From CAS/Hanwei)

Bainite is a structure of high-carbon steel that combines great strength with excellent flexibility and shock absorption characteristics. It has been known as an exemplary Katana blade component for a number of years but its use has been restricted to a few top-class master smiths, due to the difficulties involved in performing the exacting heat treatment procedures necessary for the production of a Bainite blade body in combination with the very hard Martensite Yakiba (edge section) required for Katana blades.

Hanwei has now mastered this difficult process, using billets of L-6 tool steel (a very tough high-carbon low-alloy steel) as a starting point. Blades are forged and shaped in the normal way, then carefully heat treated to achieve the required Bainite and Martensite structures before final polishing.

T10 Tool Steel

T10 is a Chinese designation for a water hardening high carbon tool steel with about 1% carbon content.  The US designation of this steel is W1.  The W series of tool steels are a very simple alloy group, low cost, and responsive to simple heating and water quenching for hardening. The alloy does undergo considerable distortion during quenching.  This alloy is one of the common Water Hardening tool steel grades available. W1 is basically a simple high carbon steel and is easily hardened by heating and quenching in water, just as with plain carbon steel alloys.

• Applications: W1 is commonly used for hand operated metal cutting tools, cold heading, embossing taps and reamers as well as cutlery.
•  Heat treatment is somewhat dependent upon section size, or intricacy of the part. For large sections, or intricate shapes, slowly preheat to 1100 F and then slowly increase temperature to 1500 F. Hold for 10 to 30 minutes and then quench in water or brine.
•  Forge at 1900 F down to 1550 F. Do not forge below 1500 F.
•  Anneal at 1400 F and slow cool in the furnace at 40 F per hour or less.
•  Temper at 350 to 650 F for Rockwell C of 64 to 50.

SK-5 High Carbon (From the Cold Steel® Catalog)

SK-5 is the Japanese equivalent of American 1080, a high carbon steel with carbon between 0.75%-0.85% and 0.60%-0.90% manganese. As quenched, it has a hardness near Rc 65 and produces a mixture of carbon rich martensite with some small un-dissolved carbides. The excess carbide increases abrasion resistance and allows the steel to achieve an ideal balance of very good blade toughness with superior edge holding ability. Due to these characteristics, this grade of steel has been used traditionally for making a variety of hand tools, including chisels and woodcutting saws, and has stood the test of time and use over many years in many countries.

Spring Steel

5160 Spring Steel

5160 is a carbon-chromium spring steel. It exhibits excellent toughness and high ductility, with a high tensile-yield ratio.

• Applications: Commonly employed in heavy spring applications primarily in the automotive field for leaf springs. 
• Heat Treatment: 5160 is normally hardened in oil. Recommended quenching temperature is 1525 F, with a wide range of mechanical available by tempering between 800 and 1300 F. 
•  Forge this grade between 2100 and 2200 F.
• Annealing: Heat to 1450 F and air cool. 

Stainless steel

Stainless steel is an alloy of iron, chromium, nickel, carbon, and other materials. The principal benefit of this product is its resistance to corrosion and/or oxidation. Series 300 stainless steels are chrome-nickel, non-hardening, and austenitic (nonmagnetic). Series 400 steels can be chrome, hardenable martensitic or non-hardenable ferritic (both magnetic).

VG-1 (From the Cold Steel® Catalog)

When considering a new material for a performance upgrade for the Cold Steel® Tanto, we tested seven different grades of steel including Shiro 2, V-SP-2, 10A, 440C, VG-10, ATS 34, and VG-1. Physical testing for sharpness, edge retention, point strength, shock, and ultimate blade strength showed that while many of the steels had increased performance in one or two testing categories, only one, VG-1, showed the greatest performance increases in the most critical categories. With an outstanding ability to retain an edge and proven strength in point and blade tests, VG-1 will provide Cold Steel® customers with superior performance previously unavailable in a stainless steel blade.

4116 KRUPP STAINLESS (From the Cold Steel® Catalog)

4116 is a fine grained, stainless steel made by ThyssenKrupp in Germany and is used for hygienic applications (medical devices and the pharmaceutical industry) and food processing which make it a superb material for kitchen cutlery. The balance of carbon and chromium content give it a high degree of corrosion resistance and also impressive physical characteristics of strength and edge holding. Edge retention in actual cutting tests exceeded blades made of the 420 and 440 series of stainless steels. Other alloying elements contribute to grain refinement which increase blade strength and edge toughness and also allow for a finer, sharper edge.

AUS 8A STAINLESS (From the Cold Steel® Catalog)

The words "stainless steel" are misleading, because, in fact, all steel will stain or show discoloration if left in adverse conditions for a sufficient time. Steel is made "stainless" by adding Chromium and reducing its Carbon content during the smelting process. There is a serious performance trade-off with stainless steel. As the Chromium increases and the Carbon decreases, the steel becomes more "stainless". But, it also becomes more and more difficult to sharpen, and the edge-holding potential is seriously impaired. This is usually why most stainless knives are rarely razor-sharp and quickly lose what little edge they have. In contrast, at Cold Steel® we use AUS 8A Stainless, a high carbon, low chromium steel that has proven itself to be the ultimate compromise between toughness and strength, edge holding, and resistance to corrosion.

Other Materials

GRIVORY®

Grivory is the trade name for an advanced polyphthalamide reinforced with fiberglass.  It is used in the automotive industry to replace metal parts.  Cold Steel® uses this reinforced plastic for various knife components including the blades in their Nightshade® series.  Grivory is UV/heat stabilized, making it impervious to the elements.

KRATON®

Kraton is the trade name given to a number of high performance elastomers manufactured by Kraton Polymers, and used as synthetic replacements for rubber. Kraton offers many of the properties of natural rubber, such as flexibility, high traction, and sealing abilities, but with increased resistance to heat, weathering, and chemicals. It was first made by the chemical division of the Shell Oil Company in the 1960s. The use of Kraton in knife handles provides a superior, slightly tacky, gripping surface that is unaffected by heat, cold, or moisture. It never rusts, warps, cracks or splits even in the most extreme environments.

ZYTEL®

Zytel is a trademark owned by DuPont and used for a number of different high strength, abrasion and impact resistant thermoplastic polyamide formulations of the family more commonly known as nylon, often with varying degrees of fiberglass, from 13% to 60%, added in for additional stiffness. Zytel® is a tough, stiff nylon and fiberglass composite that contains no metal and is impervious to the elements.

Steel Composition Comparison Chart