Contents
M42 High-Speed Tool Steel: Properties, Process, Uses
- John
What Is M42 Tool Steel?
M42 tool steel is a high-speed alloy with 8-10% cobalt. It offers excellent red-hardness, staying hard at high temperatures, and great wear resistance for longer tool life. Ideal for cutting tough materials like high-strength steel and aerospace alloys, M42 is more cost-effective than carbide tools and resists chipping. With a hardness of 68-70 HRC after heat treatment, it’s perfect for cutting tools, dies, and molds.
What Is M42 Tool Steel Equivalent To?
Below is a list of the most common equivalents for M42 tool steel across various standards:
| GB | ISC | JIS | ASTM | UNS | ISO |
| W2Mo9Cr4VCo8 | T72948 | SKH59 | M42 | T11342 | HS 2-9-1-8 |
M42 Tool Steel Chemical Composition
M42 tool steel’s chemical composition, with high levels of cobalt (Co), molybdenum (Mo), and tungsten (W), gives it excellent hardness and heat resistance. Chromium (Cr) and vanadium (V) improve its toughness and wear resistance. The table below shows its chemical composition.
| Element | Composition |
| Carbon (C) | 1.05 – 1.15 % |
| Chromium (Cr) | 3.5 – 4.25 % |
| Cobalt (Co) | 7.75 – 8.75 % |
| Copper (Cu) | ≤ 0.25 % |
| Iron (Fe) | 71.0 – 76.3 % |
| Manganese (Mn) | 0.15 – 0.40 % |
| Molybdenum (Mo) | 9.0 – 10 % |
| Nickel (Ni) | ≤ 0.30 % |
| Phosphorus (P) | ≤ 0.030 % |
| Silicon (Si) | 0.15 – 0.65 % |
| Sulfur (S) | ≤ 0.030 % |
| Tungsten (W) | 1.15 – 1.85 % |
| Vanadium (V) | 0.95 – 1.35 % |
- The sulfur content can be adjusted to 0.06% to 0.15% to enhance machinability.
M42 Tool Steel Physical Properties
M42 tool steel offers a high density, strong thermal conductivity, and low thermal expansion, making it ideal for high-performance and heat-resistant applications. The table below presents the key physical properties of M42 tool steel.
| Property | Metric Value | Imperial Value |
| Density | 7.8 g/cm³ | 0.282 lb/in³ |
| Thermal Conductivity | 27.0 W/m·K | 18.7 BTU/hr·ft·°F·in |
| Specific Heat | 460 J/kg·K | 0.11 BTU/lb·°F |
| Coefficient of Thermal Expansion | 11.7 µm/m·°C | 6.5 × 10⁻⁶ in/in·°F |
| Melting Point | 1400 – 1450 °C | 2552 – 2642 °F |
M42 Tool Steel Mechanical Properties
M42 tool steel is very hard (62-64 HRC) and strong, making it great for tough jobs like cutting and drilling. It also offers good toughness, though it is less impact-resistant compared to some other high-speed steels, like M2 or M4 steel. The table below shows the main mechanical properties of M42 tool steel.
| Property | Metric Value | Imperial Value |
| Hardness (after heat treatment) | 62-64 HRC | 62-64 HRC |
| Tensile Strength | 3000-3200 MPa | 435,000-464,000 psi |
| Yield Strength | 2200-2400 MPa | 319,000-348,000 psi |
| Elongation | 3-4% | 3-4% |
| Impact Toughness (Charpy) | 15-20 J/cm² | 11-15 ft·lbf/in² |
| Modulus of Elasticity | 210 GPa | 30.5 × 10³ ksi |
| Poisson’s Ratio | 0.27 – 0.30 | 0.27 – 0.30 |
M42 Tool Steel Heat Treatment
Our heat treatment process is designed to enhance hardness, strength, and toughness, ensuring that M42 meets the demanding requirements of industries like manufacturing, automotive, and tooling.
Annealing
To soften the steel, heat it slowly to 1575-1650°F (857-899°C). Hold the steel at this temperature for 1 hour per inch (25.4 mm) of thickness, with a minimum of 2 hours.
Cool the steel slowly in the furnace at no more than 50°F (28°C) per hour until it reaches 1000°F (538°C). Once cooled, let it cool to room temperature in the furnace or air.
Hardening
- Preheating
First, heat the steel gradually to a temperature between 816-871°C (1500-1600°F). Keep the temperature steady before moving to the next step.
- Austenitizing
In this step, heat the steel quickly to the desired austenitizing temperature. If using a furnace, heat it to 2150-2175°F (1177-1191°C). If using a salt bath, heat the steel to a slightly lower range of 2125-2150°F (1163-1177°C). This ensures that the steel reaches the required hardness and hardenability.
- Quenching
After austenitizing, the steel must be quenched to lock in its hard properties. There are three main quenching methods: pressurized gas, warm oil, and salt.
The steel should cool rapidly, ideally below 1000°F (538°C) to retain its hardness. For oil quenching, the steel should be cooled until it turns black (around 900°F or 482°C) and then air-cooled to about 150-125°F (66-51°C). If using salt, quench at 1000-1100°F (538-593°C), then allow it to cool in air.
Tempering
Immediately after quenching, temper the steel to reduce brittleness while maintaining strength. Heat the steel to 1025-1050°F (551-565°C) and hold it for 2 hours. Afterward, allow it to cool to room temperature in air.
Tempering should be performed three times to reduce internal stresses, enhance toughness, and achieve the optimal balance between hardness and ductility.
M42 Tool Steel Product Forms
At SteelPro Group, we provide an extensive selection of M42 tool steel products, designed to fulfill the varied requirements of our clients. Whether you require round bars, square bars, flat bars, plates, drill rods, or custom tooling blanks, we provide various sizes to suit your specific application.
| Product Form | Size Range (Metric) | Size Range (Imperial) |
| Round Bars | Diameter: 10 mm to 500 mm | Diameter: 0.39 in to 19.7 in |
| Length: 1000 mm to 4000 mm | Length: 3.3 ft to 13.1 ft | |
| Square Bars | 10 mm x 10 mm to 300 mm x 300 mm | 0.39 in x 0.39 in to 11.8 in x 11.8 in |
| Length: 1000 mm to 4000 mm | Length: 3.3 ft to 13.1 ft | |
| Flat Bars | Thickness: 5 mm to 100 mm | Thickness: 0.2 in to 3.9 in |
| Width: 20 mm to 500 mm | Width: 0.79 in to 19.7 in | |
| Length: 1000 mm to 4000 mm | Length: 3.3 ft to 13.1 ft | |
| Plate | Thickness: 10 mm to 150 mm | Thickness: 0.39 in to 5.9 in |
| Width: 200 mm to 2000 mm | Width: 7.9 in to 78.7 in | |
| Length: 1000 mm to 4000 mm | Length: 3.3 ft to 13.1 ft | |
| Drill Rods | Diameter: 3 mm to 30 mm | Diameter: 0.12 in to 1.18 in |
| Length: 300 mm to 1000 mm | Length: 11.8 in to 39.4 in |
M42 Tool Steel Applications
Below is a classification of the common uses of M42 tool steel based on different industries:
Cutting Tools
- Twist Drills
- Taps (e.g., Thread Taps)
- End Mills
- Reamers
- Boring Tools
- Cutting Saws
- Threading Dies
Forming and Shaping Tools
- Molding Tools
- Broaches
- Shaper Tools
- Tapping Tools
Precision Machinery Components
- Gear Cutting Tools
- Spindle Components
- Punches and Dies for Stamping
- Knives (for high wear resistance)
Tooling and Production Equipment
- Drill Bits
- Milling Tools
- Gear Blanks
- Shearing Blades
Custom Solutions & Precision Machining For M42 Steel
Our M42 products come in a wide range of forms, including round bars, square bars, flat bars, plates, and drill rods. We also provide other grades like T1 steel.
Our grinding, turning, milling, and cutting services ensure your products are crafted with the highest quality standards, providing reliable and long-lasting results. SteelPro Group is your trusted partner for durable, high-performance M42 steel solutions.
