Polished Carbon Steel Blade

Blade materials are materials used to make the blade of a knife or other simple edged hand tool or weapon, such as a hatchet or sword – Polished Carbon Steel Blade

Blades can be made from a variety of materials. The most common being carbon steel, stainless steel, tool steel and alloy steel. Other less common materials in blades include: cobalt and titanium alloys, ceramics, obsidian, and plastic.

The hardness of steel is usually stated as a number on the Rockwell C scale (HRC). The Rockwell scale is a hardness scale based on the resistance to indentation a material has. This differs from other scales such as the Mohs scale (scratch resistance testing), which is used in mineralogy. As hardness increases, the blade becomes more capable of taking and holding an edge, but is more difficult to sharpen and increasingly more brittle (commonly called less “tough”).[citation needed] Laminating harder steel between softer steel is an expensive process, though it gives the benefits of both “hard” and “soft” steels, to some extent (see Damascus steel) – Polished Carbon Steel Blade

Alloy steels

Main article: Alloy steel
5160, a spring steel. Popular steel for forging swords and large knives, with high toughness and good wear resistance.[1] Popular sword manufacturers that use 5160 spring steel include Hanwei and Generation 2.[citation needed] 5160 spring steel is mainly used on Medieval type swords.[2]
6150, a chromium-vanadium alloy. Similar to 4140, 6150 is a tough steel with high impact resistance. It can be hardened to the mid-50s on the HRC scale.[citation needed] While a common material for swords or hatchets, it is less than ideal for most knives because of its limited attainable hardness. It tolerates less than ideal temperature control in forging and heat-treating (As does 5160). While it does not hold an edge as well as 1095, it is tough and easy to sharpen – Polished Carbon Steel Blade
V-toku1 / V-toku2, alloyed steel with W/Cr’s original characteristics.[3]
Tool steels
Main article: Tool steel
Tool steel grades used in cutlery: A, D, O, M, T, S, L, W. See also AISI Tool Steel Grades.
The following are tool steels, which are alloy steels commonly used to produce hardened cutting tools:

A2,[4] a steel that trades wear resistance for toughness. It is used in custom made fighting knives by makers such as Phill Hartsfield, Rob Criswell, Mike Snody and John Fitzen (Razor Edge US) and one of the latest to standardize his camp/survival knives in A2 tool steel is Aaron Gough from Gough custom, Canada.[1][5] A2 was the standard baseline steel used by Bark River Custom Knives. A2 is used as the standard tool steel for the Black Wolf Knives range of Hunting Knives by Marc Godwin, Japan
A3
A4
A5
A6, this grade of tool steel air-hardens at a relatively low temperature (approximately the same temperature as oil-hardening grades) and is dimensionally stable. Therefore, it is commonly used for dies, forming tools, and gauges that do not require extreme wear resistance but do need high stability.[6]
A7[7] Tool Steel is a A7 type air-hardening tool steel that exhibits exceptional wear resistance. The high carbon and vanadium contents result in numerous, hard vanadium carbide particles in the steel. These carbides exhibit a hardness that is equivalent to approximately 80 to 85 Rockwell C. Resists wear from sliding contact with other steels as well as from contact with dry and wet slurries of hard abrasive particles such as sand, shot blast media, and ceramics.It is Carbon 0.55% Manganese 0.30% Silicon 0.30% Chromium 5.00% Molybdenum 1.25% Vanadium 1.25%
A8
A9
A10, this grade contains a uniform distribution of graphite particles to increase machinability and provide self-lubricating properties. It is commonly used for gauges, arbours, shears, and punches.[8]
D2 is a high carbon, high chromium die steel and is the highest carbon alloy tool and die steel typically used in knife making.[9] With a chrome content of 12.00%, some call it a “semi-stainless”, because of the lack of free Chromium in solution, even though it is defined by ASM and ANSI as stainless which contains at least 11.5% by weight of chromium.[10] It deserves the informal myth: “D2 knives hold an edge forever, and are impossible to sharpen.”[11] While not as tough as premium carbon steel, it is much tougher than premium stainless steel.[1] D2 knife blades were popularized by Jimmy Lile, and later by Bob Dozier. ( AISI D2 / BOHLER K110 / ISO X153CrMoV12 / W. 1,2379 / GB-CINA Cr12MoV / JIS G4404 / SKD11 )
O1, a popular forging steel. Good wear resistance and excellent edge retention. Very tough, but not as much as 5160.[12] It is most commonly used by Randall Knives, Mad Dog Knives,[13] and many other custom knife makers.[1]
M2, is slightly tougher than D-2. As high-speed tool steel, it is capable of keeping a tempered edge at high temperatures generated in various machining processes. However, it isn’t used as widely in factory production knives, as CPM M4 has become more popular. Custom knife makers still use it for knives intended for fine cutting with very thin edges.[1][12]
M4, see High-speed CPM REX M4.
SAF 2507 is a Sandvik trademarked steel containing 25% chromium, 7% nickel, 4% molybdenum and other alloying elements such as nitrogen and manganese.
T1[14]
T2[15]
S1, a medium carbon shock-resistant steel tool steel which combines moderate hardness with good impact toughness. Carbon content .40 – .55%.[16]
W1, a water hardening tool steel. High carbon content.[1]
W2, tool steel that holds its edge quite well but is not very tough. Has a carbon content of 1.5.[1] Most readily available W2 has a carbon content of no more than 1-1.1%. It can be left at high hardness levels (it can attain a quenched hardness of 67 Rc) and still be quite tough especially in larger knives with thicker spines as the core of the thick portion of the blade does not attain full hardness because of the shallow hardening nature of the steel. Bill Moran considered it to be almost as tough as 5160, but it was unavailable for a period of time. W2 is one of the carbon steels that can produce a nice Hamon in heat treating.[17]
SK3, SK4, SK5 – Japanese carbon steels. SK stands for “Steel Kougu” meaning “Steel Tool”. The lower number indicates fewer impurities.
CPM Tool Steel
Crucible Industries[18] produces Crucible Particle Metallurgy (CPM) tool steels using a powder metal forge process.[19]

CPM 1V,[20] a proprietary steel, very high toughness, several times higher than A2 with same level of wear resistance.[1]
CPM 3V,[21] a proprietary steel, very high toughness, less than CPM 1V, but more than A2, and high wear resistance, better than CPM 1V. Used by several custom knives makers and factories, including Jerry Hossom, Mike Stewart [Bark River], Reese Weiland, Nathan Carothers, and Dan Keffeler. Makes good choice for swords and large knives.[1]
CPM 4V,[22] a proprietary steel, high-impact toughness and a very good wear resistance. Gaining popularity in Bladesports Competition Cutting knives.
CPM 9V,[23] a modification of CPM 10V with lower carbon and vanadium to improve toughness and heat check resistance.
CPM 10V (AISI A11),[24] highly wear-resistant tool steel, toughness comparable with D2 tool steel. Currently used by a few custom knife makers. Phil Wilson pioneered the use of CPM 10V and numerous other CPM steels in sporting knives.[1]
CPM 15V,[25] a proprietary steel, extremely high wear-resistant tool steel, thanks to 14.5% Vanadium content. Found only in custom knives.[1]
CPM CRU-WEAR,[26] a proprietary steel designed as a CPM upgrade to conventional Cru-Wear and D2 steels, it offers better wear resistance, toughness, and hardness than ingot made Cru-Wear.
CPM S7, a shock-resistant medium carbon tool steel, with outstanding impact toughness and high strength, along with medium wear resistance. It has maximum shock resistance and high compression strength, which gives it good deformation resistance in use while retaining good toughness.