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Resources/Materials & grades/M2 / HS6-5-2C

Materials & grades

M2 / HS6-5-2C / 1.3343 / SKH51 high-speed steel: equivalents BM2 and W6Mo5Cr4V2

M2 is the most widely used molybdenum high-speed steel, with about 0.85–0.9 % carbon, 6 % tungsten, 5 % molybdenum, 4 % chromium and 2 % vanadium. It is hardened to 62–65 HRC for drills, taps, milling cutters, broaches and cold-work punches and is also sold as HS6-5-2C (1.3343), SKH51 and BM2.

Names by standard

What it is called in each region

RegionSystemDesignationStandardMatch
USAAISI/SAEM2A600 lists a regular-carbon M2 (about 0.78–0.88 % C) and a high-carbon variant.ASTM A600Same material
UNST11302—Same material
UKBS 4659BM2Superseded British standard, withdrawn in favour of EN ISO 4957. Listed against M2 and 1.3343 by West Yorkshire Steel and Total Materia.BS 4659:1971Equivalent
EUEN 10027-1 nameHS6-5-2CCarbon 0.86–0.94 %. The prefix HS marks a high-speed steel and the digits give W-Mo-V-Co.EN ISO 4957Equivalent
EN 10027-2 number1.3343EN ISO 4957Equivalent
DIN (legacy)S 6-5-2 / SC 6-5-2Superseded German names. Total Materia also lists the older numbers 1.3339 and 1.3342 and X82WMoCrV6-5-4 against this steel.DIN 17350Equivalent
IndiaIS 3748:2022 (ISO 4957 name)HS6-5-2CIS 3748:2022 is an identical adoption of ISO 4957 and absorbed IS 7291.IS 3748:2022Equivalent
IS 7291:1981XT87W6Mo5Cr4V2Superseded Indian designation. Carbon 0.82–0.92 %, a wider range than ASTM A600 regular M2.IS 7291:1981Closest equivalent
JapanJIS G 4403SKH51Carbon 0.80–0.88 %, chromium 3.80–4.50 %.JIS G 4403Equivalent
JIS (old designation)SKH9Superseded Japanese name that Proterial and steeldata list alongside SKH51 for the same steel.—Closest equivalent

On equivalence

  • Regular-carbon M2 (0.78–0.88 % C) in ASTM A600 and SKH51 (0.80–0.88 % C) are very close; EN ISO 4957 HS6-5-2C is higher in carbon (0.86–0.94 %). Mill sheets show typical carbon around 0.85–0.90 %.
  • ASTM A600 also lists a high-carbon M2 (about 0.95–1.05 % C). Treat steeldata ranges of 0.78–1.05 % C as covering both versions.
  • The older Indian grade XT87W6Mo5Cr4V2 (IS 7291:1981) has a carbon range of 0.82–0.92 %. IS 3748:2022 now adopts ISO 4957, so new Indian orders use HS6-5-2C.
  • Total Materia lists the older DIN numbers 1.3339 and 1.3342 against the 6-5-2 family; confirm the carbon band if an old drawing quotes one of these.
  • Powder-metallurgy and remelted brands such as Böhler S600 ISORAPID or Erasteel E M2 share the M2 analysis but have finer carbides and different toughness.

Chemical composition

Composition limits, mass %

ElementM2 regular carbon (T11302)USA · ASTM A600HS6-5-2C (1.3343)EU · EN ISO 4957HS6-5-2CIndia · IS 3748:2022 (identical to ISO 4957)XT87W6Mo5Cr4V2India · IS 7291:1981 (superseded)SKH51Japan · JIS G 4403
C0.78–0.880.86–0.940.86–0.940.82–0.920.80–0.88
Si0.20–0.45≤0.45≤0.45—≤0.45
Mn0.15–0.40≤0.40≤0.400.15–0.40≤0.40
P≤0.030————
S≤0.030————
Cr3.75–4.503.80–4.503.80–4.503.75–4.503.80–4.50
Mo4.50–5.504.70–5.204.70–5.20—4.70–5.20
V1.75–2.201.70–2.101.70–2.10—1.70–2.10
W5.50–6.755.90–6.705.90–6.70—5.90–6.70

Mechanical properties

Strength and hardness

ConditionTensile strengthYield strengthElongationHardness
Soft annealed (delivery), 1.3343MaximumDörrenberg 1.3343 data sheet———≤269 HB
Soft annealed (delivery), Böhler S600Maximum; tensile strength limited to 950 MPaBöhler S600 data sheet≤950 MPa≤138 ksi——≤280 HB
Soft annealed, stockist typicalMaximum annealed hardness quoted by USCTI (Griggs Steel)USCTI M2 steel sheet———≤255 HB
Hardened and tempered (bars delivered hardened and tempered)Minimum, Böhler S600 hardened at 1100–1210 °C and tempered 550–570 °CBöhler S600 data sheet———≥62 HRC
Hardened and tempered, typical working hardnessTypical, austenitized 1204–1232 °C (2200–2250 °F), tempered 552–566 °C (1025–1050 °F)USCTI M2 steel sheet———about 64 HRC

In practice

Behaviour, heat treatment and uses

Characteristics

  • General-purpose high-speed steel with well-balanced toughness, wear resistance and red hardness; replaced tungsten grade T1 in most uses (USCTI).
  • Red hardness (hot hardness) is rated high by Böhler. Because the standard temper is 550–570 °C, edges keep their hardness at temperatures approaching that range.
  • Machinability when annealed is about 50–60 % of a 1 % carbon steel (USCTI).
  • Sensitive to decarburization in hardening; use a salt bath, vacuum or protective atmosphere (Böhler preheats in three stages and limits time at austenitizing temperature).
  • Suitable base for PVD and CVD coatings (Dörrenberg).
  • Density about 8.1 g/cm³ and elastic modulus about 207 GPa (USCTI).

Heat treatment

  • Annealing: 770–840 °C (1420–1545 °F), controlled furnace cooling at 10–20 °C/h to about 600 °C, then air (Böhler); 780–860 °C (Dörrenberg).
  • Stress relieving: 600–650 °C (1110–1200 °F), furnace cooled.
  • Preheating: three stages at about 500, 850 and 1050 °C (930, 1560, 1920 °F) (Böhler); USCTI preheats at 1500–1550 °F (815–845 °C).
  • Austenitizing: 1100–1210 °C (2010–2210 °F) with a very short hold of 80–150 seconds (Böhler); 1180–1230 °C (Dörrenberg). For cutting tools USCTI uses 2200–2250 °F (1204–1232 °C) in a furnace; lower temperatures (about 1175–1190 °C) give more toughness for punches and dies.
  • Quench: oil, a warm salt bath at 500–550 °C (930–1020 °F), or pressurized gas, cooled quickly below 540 °C.
  • Tempering: 550–570 °C (1020–1060 °F) immediately after quenching; hold at least 2 hours and repeat. Böhler recommends three tempering cycles; USCTI requires two and recommends three for large sections.

Typical uses

  • Twist drills, taps and reamers
  • Milling cutters, end mills and broaches
  • Gear-cutting tools and thread-rolling dies
  • Saw blades and knives
  • Cold-work punches and dies for blanking and cold extrusion
  • Cold forming and coining tools

Tool steels

Similar grades compared

GradeC %Mn %Cr %Ni %Tensile, first listed condition
M2 / HS6-5-2C0.78–0.880.15–0.403.75–4.50—≤950 MPa
M42 / HS2-9-1-81.05–1.150.15–0.403.50–4.25—≤1010 MPa
A2 / 1.23630.95–1.050.40–1.004.75–5.50——
D2 / 1.23791.40–1.600.10–0.6011.00–13.00——
D3 / 1.20802.00–2.350.10–0.6011.00–13.50——
O1 / 1.25100.85–1.001.00–1.400.40–0.70——
S70.45–0.550.20–0.903.00–3.50——
H11 / 1.23430.33–0.430.20–0.504.75–5.50—1790–1845 MPa
H13 / 1.23440.32–0.450.20–0.604.75–5.50—1730–1845 MPa
P20 / 1.23110.28–0.400.60–1.001.40–2.000.90–1.20950–1100 MPa

Composition from the US standard where one exists, otherwise the first standard listed on each grade's page. Strength conditions differ between grades; open a grade for its full table.

Questions answered

Common questions

What is the equivalent of M2 high-speed steel?

M2 corresponds to HS6-5-2C (1.3343) in Europe and, since IS 3748:2022, in India, to BM2 in the withdrawn British BS 4659, and to SKH51 in Japan. The Chinese W6Mo5Cr4V2 is also used as a name for the same steel.

Is SKH51 the same as M2?

SKH51 (JIS G 4403) is the Japanese equivalent of M2. It has 0.80–0.88 % carbon and 3.80–4.50 % chromium, which fits ASTM A600 regular M2 closely.

What hardness does M2 reach?

After hardening and tempering, M2 is normally 62–65 HRC. Böhler guarantees at least 62 HRC for S600 bars delivered hardened and tempered, and USCTI quotes a typical 64 HRC.

What is the difference between M2 and M42?

M42 is a cobalt high-speed steel with about 8 % cobalt, 9.5 % molybdenum and 1.1 % carbon. It reaches higher hardness (up to about 68 HRC) and holds it hotter, which suits cutting hard materials, but it is more expensive and less tough.

What temperature is M2 hardened at?

About 1180–1230 °C (2150–2250 °F) for cutting tools, held only briefly. It is then quenched and tempered two or three times at about 550–570 °C (1020–1060 °F).

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Keep reading

M42 / HS2-9-1-8M42 is a cobalt-molybdenum high-speed steel with about 1.1 % carbon, 9.5 % molybdenum and 8 % cobalt, hardened to 65–68 HRC for tools that cut hard or heat-resistant materials.D2 / 1.2379D2 is a high-carbon, 12 % chromium cold-work tool steel that is hardened to about 58–62 HRC for dies, punches, shear blades and thread-rolling tools.A2 / 1.2363A2 is an air-hardening 5 % chromium cold-work tool steel with about 1 % carbon, hardened to about 57–63 HRC for punches, dies and gauges that need good dimensional stability.O1 / 1.2510O1 is an oil-hardening manganese–chromium–tungsten tool steel with about 0.9–1.0 % carbon, hardened to about 58–64 HRC for cutting tools, gauges and general-purpose dies.H13 / 1.2344H13 is the standard 5 % chromium hot-work tool steel, used for die-casting dies, forging dies and extrusion tooling that see repeated heating and cooling.AnnealingAnnealing heats steel to a set temperature, holds it and cools it slowly to make it softer, more ductile and easier to machine or cold form.Quenching and temperingQuenching and tempering hardens steel by cooling it rapidly from the austenite range to form martensite, then reheats it below Ac1 to trade some hardness for toughness.EN 10027 names and numbersEuropean steels carry two identifiers under EN 10027: a steel name (Part 1) such as S235JR, C45 or 42CrMo4 that describes the steel's use or chemistry, and a material number (Part 2) such as 1.0503 or 1.7225.JIS steel designationsJapanese JIS steel symbols start with S for steel and add letters for the steel family or its use, but the number means different things in different standards.SAE / AISI numbersA four-digit SAE/AISI number such as 1045 or 4140 names a carbon or alloy steel by its chemistry: the first two digits identify the steel family and the last two give the nominal carbon content in hundredths of a percent.

References

Sources

  1. Böhler S600 (1.3343 / HS6-5-2C) data sheet — EN ISO 4957 HS6-5-2C, typical analysis, annealed hardness max 280 HB, hardening 1100–1210 °C, tempering 550–570 °C, min 62 HRC.
  2. Dörrenberg 1.3343 HS6-5-2C (DMO5) data sheet — Typical analysis, soft annealed max 269 HB, annealing 780–860 °C, hardening 1180–1230 °C; similar to AISI M2.
  3. Carpenter Technology: M2 high-speed steel (UNS T11302) — Type analysis; UNS T11302, ASTM A600 and QQ-T-590.
  4. Total Materia: IS XT87W6Mo5Cr4V2 (IS 7291:1981) — Superseded Indian grade with visible C, Cr and Mn limits; cross-reference to HS6-5-2.
  5. Total Materia: KS SKH 51 (equivalents list) — SKH51 C and Cr limits; equivalents JIS SKH 51, BS BM 2, EN HS6-5-2C, DIN 1.3343 and older numbers.
  6. eFunda: AISI M2 tool steel — A600 M2 limits (C 0.78–1.05 spanning regular and high carbon, Mn, Si, Cr, Mo, W, V, P, S, Cu).
  7. Total Materia: ASTM A 600 M2 regular C — C 0.78–0.88 and Cr 3.75–4.50 visible; equivalents list includes 1.3339, 1.3342, SC 6-5-2, HS6-5-2C, SKH 51, BM 2.
  8. steel-grades.com: ISO HS6-5-2C — HS6-5-2C limits: C 0.86–0.94, Si ≤0.45, Cr 3.80–4.50, Mo 4.70–5.20, V 1.70–2.10, W 5.90–6.70.
  9. Akrostal: HS6-5-2C / 1.3343 (SW7M) — ISO 4957 limits including Mn ≤0.40, P/S ≤0.030; soft-annealed ≤269 HB, 790–840 °C.
  10. Marks GmbH: 1.3343 material sheet — Analysis limits for HS 6-5-2 C (W 5.9–6.7, V 1.7–2.1).
  11. Sekidou Kouhan: SKH51 (JIS G 4403:2025, Table 2) — SKH51 limits; annealed hardness 262 HBW max; page says values checked against the JISC viewer.
  12. Otai Steel: M2 tool steel (SKH51, 1.3343) — Limits by standard (ASTM, DIN 17350, JIS G 4403); annealed 255 HB max.
  13. Bureau of Indian Standards: IS 3748:2022 Tool Steels (standard of the week) — IS 3748:2022 is an identical adoption of ISO 4957 and merges IS 3748:1990 and IS 7291:1980.
  14. USCTI: M2 high-speed steel sheet (Griggs Steel) — Known names (HS 6-5-2, 1.3343, SKH 51), typical analysis, heat treatment in °F.
  15. West Yorkshire Steel: tool steel international standards table — Cross-reference row for BS 4659 BM2, M2, 1.3343.
  16. ASTM A600 Standard Specification for Tool Steel High Speed — Governing US standard for M2 (UNS T11302); limits recorded in our own structure and verified against eFunda, Total Materia (C, Cr) and Otai listings; the standard text itself was not read.
  17. EN ISO 4957:2018 Tool steels — Governing European and international standard for HS6-5-2C; limits verified against steel-grades.com, Marks and Akrostal listings (tungsten 5.90–6.70, vanadium 1.70–2.10); the standard's own table was not read.
  18. JIS G 4403 High speed tool steels — Governing Japanese standard for SKH51; limits verified against the JIS G 4403:2025 table as reproduced by Sekidou Kouhan (vanadium 1.70–2.10, tungsten 5.90–6.70), Otai and zknives; Total Materia confirms C and Cr.

Values summarize published limits and typical data. The governing standard and the current edition control; check them before specifying.