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Resources/Materials & grades/M42 / HS2-9-1-8

Materials & grades

M42 / HS2-9-1-8 / 1.3247 / SKH59 cobalt high-speed steel: equivalents BM42

M42 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. It is sold as HS2-9-1-8 (1.3247) in Europe, BM42 in the UK and SKH59 in Japan.

Names by standard

What it is called in each region

RegionSystemDesignationNormaMatch
USAAISI/SAEM42ASTM A600Same material
UNST11342—Same material
UKBS 4659BM42Superseded British standard, withdrawn in favour of EN ISO 4957. Listed by West Yorkshire Steel against M42 and 1.3247.BS 4659:1971Equivalent
EUEN 10027-1 nameHS2-9-1-8The digits give W-Mo-V-Co: about 1.5 % W, 9 % Mo, 1 % V and 8 % Co.EN ISO 4957Equivalent
EN 10027-2 number1.3247EN ISO 4957Equivalent
DIN (legacy)S 2-10-1-8Superseded German name. USCTI also lists the older form HS 2-10-1-8.DIN 17350Equivalent
ÍndiaIS 3748:2022 (ISO 4957 name)HS2-9-1-8IS 3748:2022 is an identical adoption of ISO 4957. A pre-2022 Indian XT designation for M42 was not found.IS 3748:2022Equivalent
JapanJIS G 4403SKH59Maxis and Misumi cross-reference tables list SKH59 against M42, HS2-9-1-8 and BM42.JIS G 4403Equivalent

On equivalence

  • Mill analyses differ slightly from the standard ranges: Böhler S500 is 1.1 % C, 3.9 % Cr, 9.2 % Mo, 1.1 % V, 1.5 % W, 7.8 % Co; Zapp quotes 9.4 % Mo; Carpenter 9.5 % Mo and 8 % Co.
  • Cobalt differs between standards: ASTM A600 allows 7.75–8.75 %; EN ISO 4957 and JIS G 4403 allow 7.50–8.50 %.
  • Annealed hardness sources disagree by a few HB: Total Materia gives 277 HB maximum for the DIN listing, Böhler 280 HB, Zapp about 280 HB.
  • Annealing temperature sources also differ: 830 °C (Zapp), 770–840 °C (Böhler), about 857–899 °C (USCTI). Follow the supplier's data sheet for the brand in use.
  • IS 3748:2022 now adopts ISO 4957 in full; an earlier Indian XT designation for M42 was not found.

Chemical composition

Composition limits, mass %

ElementM42 (T11342)USA · ASTM A600HS2-9-1-8 (1.3247)EU · EN ISO 4957HS2-9-1-8Índia · IS 3748:2022 (identical to ISO 4957)SKH59Japan · JIS G 4403
C1.05–1.151.05–1.151.05–1.151.05–1.15
Si0.15–0.65≤0.70≤0.70≤0.70
Mn0.15–0.40≤0.40≤0.40≤0.40
P≤0.030———
S≤0.030———
Cr3.50–4.253.50–4.503.50–4.503.50–4.50
Mo9.00–10.009.00–10.009.00–10.009.00–10.00
V0.95–1.350.90–1.300.90–1.300.90–1.30
W1.15–1.851.20–1.901.20–1.901.20–1.90
Co7.75–8.757.50–8.507.50–8.507.50–8.50

Mechanical properties

Strength and hardness

ConditionTensile strengthYield strengthElongationHardness
Soft annealed (delivery), Böhler S500Maximum; drawn material max 300 HB; tensile strength limited to 1010 MPaBöhler S500 data sheet≤1010 MPa≤146 ksi——≤280 HB
Soft annealed, typicalZapp states about 280 HB; USCTI quotes a maximum of 277 HBZapp M42 – 1.3247 data sheet; USCTI M42 steel sheet———about 277–280 HB
Hardened and tempered, typicalTypical working hardness, austenitized about 1180 °C (2160 °F), tempered 1025–1050 °F (551–565 °C)USCTI M42 steel sheet———about 67 HRC
Hardened and tempered, maximumMaximum hardness Zapp states is possibleZapp M42 – 1.3247 data sheet———up to 68 HRC

In practice

Behaviour, heat treatment and uses

Characteristics

  • Cobalt raises hot hardness: Carpenter describes M42 as a premium cobalt steel with high hardness and superior hot hardness, and Böhler rates the red hardness of S500 as very high.
  • Böhler rates S500 toughness as good and compressive strength as very high; it is less tough than M2.
  • Used for heavy-duty and high-production cutting of high-strength steels, hard alloys and nonferrous superalloys (Carpenter).
  • Can be less prone to chipping in interrupted cuts than carbide and is cheaper (USCTI).
  • Machinability when annealed is about 35–40 % of a 1 % carbon steel (USCTI).
  • Density about 7.8–8.0 g/cm³ and elastic modulus about 207–220 GPa (USCTI, Zapp).
  • Decarburizes readily in air; protect it during austenitizing.

Heat treatment

  • Annealing: 770–840 °C (1420–1545 °F) with slow furnace cooling (Böhler); 830 °C for about 4 hours (Zapp); USCTI quotes 1575–1650 °F (857–899 °C), then furnace cooling at no more than 50 °F/h (28 °C/h) to 1000 °F.
  • Stress relieving: 600–650 °C (1110–1200 °F) for about 2 hours, furnace cooled (Böhler, Zapp).
  • Preheating: three stages at about 500, 850 and 1050 °C (930, 1560, 1920 °F) (Böhler).
  • Austenitizing: 1130–1180 °C (2065–2155 °F) with a short hold of 80–150 seconds (Böhler); USCTI gives 2150–2175 °F (1177–1191 °C) in a furnace or 2125–2150 °F (1163–1177 °C) in salt. Use the lowest temperature for toughness and the highest for hot hardness.
  • Quench: oil, a warm salt bath at 500–550 °C (930–1020 °F), or pressurized gas, cooled quickly below 540 °C (1000 °F).
  • Tempering: 550–570 °C (1020–1060 °F), three cycles recommended, each at least 1 hour per 20 mm of thickness (Böhler); USCTI gives 1025–1050 °F with a 2 hour hold and three cycles required.

Usos típicos

  • End mills, drills, reamers and taps for hard or heat-resistant materials
  • Broaches, form tools and gear-cutting tools
  • Saw blades
  • Thread-rolling dies and header tooling
  • Punches

Tool steels

Similar grades compared

GrauC %Mn %Cr %Ni %Tensile, first listed condition
M42 / HS2-9-1-81.05–1.150.15–0.403.50–4.25—≤1010 MPa
M2 / HS6-5-2C0.78–0.880.15–0.403.75–4.50—≤950 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.

Perguntas respondidas

Common questions

What is the equivalent of M42 high-speed steel?

M42 corresponds to HS2-9-1-8 (1.3247) in Europe and, since IS 3748:2022, in India, to BM42 in the withdrawn British BS 4659, and to SKH59 in Japan.

What is the difference between M2 and M42?

M42 adds about 8 % cobalt and raises molybdenum to about 9.5 %. That gives higher hardness (up to about 68 HRC) and better red hardness than M2, which is 62–65 HRC and cobalt-free. M2 is tougher and cheaper.

What hardness can M42 reach?

Typically about 67 HRC after hardening and tempering, and up to about 68 HRC according to Zapp. Annealed M42 is soft enough to machine at roughly 277–280 HB.

What temperature is M42 hardened at?

Böhler gives 1130–1180 °C (2065–2155 °F) with a very short hold of 80–150 seconds. Tempering follows three times at about 550–570 °C (1020–1060 °F).

Is SKH59 the same as M42?

SKH59 (JIS G 4403) is the Japanese equivalent of M42. Both are 1.1 % carbon, 9–10 % molybdenum and 7.5–8.5 % cobalt steels; small differences in silicon, chromium and cobalt limits exist between standards.

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Keep reading

M2 / HS6-5-2CM2 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.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.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 S500 (1.3247 / HS2-9-1-8) data sheet — EN ISO 4957 HS2-9-1-8, typical analysis, annealed hardness max 280 HB, hardening 1130–1180 °C, tempering 550–570 °C.
  2. Zapp: M42 – 1.3247 high-speed steel data sheet — Typical analysis, soft annealing ~830 °C, delivery ~280 HB, hardness up to 68 HRC.
  3. Carpenter Technology: M42 high-speed steel (UNS T11342) — Type analysis; UNS T11342, ASTM A600 and QQ-T-590; superior hot hardness.
  4. Total Materia: ISO HS2-9-1-8 tool steel — Standard listing with C 1.05–1.15 and Co 7.5–8.5; annealed hardness about 277 HB.
  5. AZoM: M42 molybdenum high speed tool steel (UNS T11342) — A600 M42 limits for all elements; annealing 871 °C; temper 538–593 °C three times.
  6. eFunda: AISI M42 tool steel — A600 M42 limits for all elements.
  7. Total Materia: IS HS2-9-1-8 (IS 3748:2022) — IS 3748:2022 entry for HS2-9-1-8: C 1.05–1.15, Co 7.5–8.5, Cr 3.5–4.5 visible; lists S 2-10-1-8 (DIN) among equivalents.
  8. Marks GmbH: 1.3247 material sheet — EN ISO 4957 limits for HS 2-10-1-8 (Si 0.70, Mn 0.40, Co 7.5–8.5, Cr 3.5–4.5, Mo 9–10, V 0.9–1.3, W 1.2–1.9).
  9. Oberste-Beulmann: 1.3247 HS2-9-1-8 data sheet — Si <0.70, Mn <0.40; BM 42, M 42; soft-annealed max 277 HB.
  10. Songshun Steel: M42 / SKH59 / 1.3247 — Limits by standard: ASTM A600, EN ISO 4957 and JIS G 4403:2006.
  11. H2ABC: SKH 59 (JIS G 4403-2022) — SKH59 limits: C 1.05–1.15, Si ≤0.7, Mn ≤0.4, Cr 3.5–4.5, Mo 9–10, W 1.2–1.9, V 0.9–1.3, Co 7.5–8.5.
  12. Sekidou Kouhan: SKH59 (JIS G 4403:2025, Table 2) — SKH59 limits as above; page says values checked against the JISC viewer.
  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: M42 high-speed steel sheet (Griggs Steel) — Other names (1.3247, HS 2-10-1-8, S500), typical analysis, annealed 277 HB max, tempered 67 HRC, heat treatment in °F.
  15. West Yorkshire Steel: tool steel international standards table — Cross-reference row for BS 4659 BM42, M42, 1.3247, HS2-9-1-8, SKH59.
  16. ASTM A600 Standard Specification for Tool Steel High Speed — Governing US standard for M42 (UNS T11342); limits recorded in our own structure and verified against AZoM and eFunda; the standard text itself was not read.
  17. EN ISO 4957:2018 Tool steels — Governing European and international standard for HS2-9-1-8; limits verified against Marks, Oberste-Beulmann and Songshun listings, and C, Cr and Co against the Total Materia IS 3748:2022 page; the standard's own table was not read.
  18. JIS G 4403 High speed tool steels — Governing Japanese standard for SKH59; limits verified against the JIS G 4403:2025 and 2022 tables as reproduced by Sekidou Kouhan and H2ABC, and the 2006 values on Songshun.

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