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M4 High Speed Tool Steel: Properties, Process, Uses
- John
M4 Tool Steel is a critical material for industries requiring high-performance cutting tools. At SteelPro Group, we focus on providing this high-speed steel in its best forms, including the advanced PM M4. In this guide, we will dive into M4 tool steel, helping you choose best materials.
What Is M4 Tool Steel?
W4 tool steel is a high-speed steel (HSS) known for its excellent wear resistance, high hardness, and ability to maintain cutting performance at elevated temperatures. It is commonly used for cutting tools, drills, and taps in high-speed machining applications. Compared to other HSS grades like M2, W4 offers superior wear resistance and hardness retention but with slightly lower toughness.
Conventional M4 tool steel is prone to abrasive tool wear and poor surface finish in its annealed state, and becomes brittle after quenching. However, PM M4, made through powder metallurgy, has a more uniform microstructure and consistent hardness. This reduces wear, improves machinability, and preserves toughness in the hardened state.
What Is M4 Tool Steel Equivalent To?
Here is the equivalent information for M4 tool steel:
| Standard/System | Equivalent Grade |
| ASTM A681, A600 | M4 |
| QQ-T-59 | M4 |
| DIN | 1.3343 |
| EN ISO 4957 | X20CrWMoV 12 1 |
| JIS | SKH51 |
| GB | W18Cr4V |
Chemical Composition of M4 Tool Steel
The chemical composition of M4 is designed to optimize its high hardness, wear resistance, and thermal stability. The tungsten, molybdenum, and vanadium content significantly enhance its ability to withstand high temperatures and resist abrasive wear, while chromium and carbon improve overall strength and durability.
The table below shows the detailed chemical composition of M4 tool steel.
| Element | Composition |
| Carbon (C) | 1.25 – 1.4 % |
| Chromium (Cr) | 3.75 – 4.75 % |
| Copper (Cu) | ≤ 0.25 % |
| Iron (Fe) | 75.9 – 81.4 % |
| Manganese (Mn) | 0.15 – 0.40 % |
| Molybdenum (Mo) | 4.25 – 5.5 % |
| Nickel (Ni) | ≤ 0.30 % |
| Phosphorus (P) | ≤ 0.030 % |
| Silicon (Si) | 0.20 – 0.45 % |
| Sulfur (S) | ≤ 0.030 % |
| Tungsten (W) | 5.25 – 6.5 % |
| Vanadium (V) | 3.75 – 4.5 % |
Physical Properties of M4 Tool Steel
M4 tool steel is characterized by high density and strong resistance to thermal expansion, making it stable under fluctuating temperatures. Its excellent thermal conductivity ensures efficient heat dissipation, while its specific heat capacity supports performance in high-heat environments.
The table below presents the detailed physical properties of M4 tool steel.
| Property | Metric | Imperial |
| Density | 7.8 g/cm³ | 0.282 lb/in³ |
| Melting Point | 1410 – 1450°C | 2570 – 2642°F |
| Thermal Conductivity | 27 W/m·K | 19.0 BTU·ft/h·°F·ft² |
| Specific Heat Capacity | 0.46 J/g·K | 0.11 BTU/lb·°F |
| Coefficient of Thermal Expansion | 11.5 µm/m·K | 6.39 µin/in·°F |
Mechanical Properties of M4 Tool Steel
M4 tool steel offers excellent hardness and tensile strength, making it highly resistant to wear and deformation. Its ability to withstand high forces and impacts ensures long-lasting performance, while its stiffness helps maintain shape under load.
The table below presents the detailed mechanical properties of M4 tool steel.
| Property | Metric | Imperial |
| Hardness (HRC) | 62 – 64 HRC | 62 – 64 HRC |
| Tensile Strength | 2100 – 2500 MPa | 305 – 363 ksi |
| Yield Strength | 1700 – 2100 MPa | 246 – 305 ksi |
| Elongation | 8 – 12 % | 8 – 12 % |
| Modulus of Elasticity | 210 GPa | 30.5 x 10⁶ psi |
| Impact Toughness (Charpy) | 20 – 30 J | 15 – 22 ft-lb |
| Poisson’s Ratio | 0.27 – 0.30 | 0.27 – 0.30 |
Heat Treatment of M4 Tool Steel
SteelPro Group ensures precise temperature and cooling rate control during the heat treatment of M4 tool steel. Our production process strictly adheres to standards, delivering M4 tool steel products with consistent quality. Below is the detailed heat treatment process for M4 tool steel.
Annealing
Annealing is important for relieving internal stresses in the steel, making the steel easier to machine. It is especially useful after forging, casting, or welding. After annealing, the hardness can reach approximately 240-255 HB.
Process: Heat M4 to a temperature of 850-900°C (1,562-1,652°F) and hold at that temperature for 1 hour per 25.44 cm (1 in). Then, slowly cool the steel in the furnace at a rate of approximately 20°C (36°F) per hour.
Hardening
Preheating
Preheating is recommended to reduce thermal shock. For complex-shaped tools, preheating should be performed in two stages to prevent thermal gradients:
- First stage: 500–600°C (932–1,112°F)
- Second stage: 800–900°C (1,472–1,652°F)
Austenitizing
Heat the M4 tool steel to 1,200–1,250°C (2,192–2,282°F). Soak for 30-45 minutes per 25.44 cm (1 in) of thickness.
Quenching
After austenitizing, M4 tool steel must be rapidly cooled (quenched) to lock in hardness. This can be performed in oil for higher hardness and a more uniform microstructure, or in air for reduced distortion and less risk of cracking.
Tempering
Tempering is crucial to reduce brittleness caused by quenching and to balance hardness and toughness. After tempering, the hardness range is typically 58-62 HRC.
Tempering is usually carried out at 540-650°C (1,004-1,202°F), with a double tempering process recommended at 600–650°C (1,112–1,202°F) for optimal results.
M4 Tool Steel Product Forms
Our products comply with international standards such as ASTM and ISO, and we also offer customized size options. If you require pre-hardened or annealed bars with specific hardness, please contact us for customized solutions.
| Product Form | Dimension Range (Metric) | Dimension Range (Imperial) |
| Round Bars | Diameter: 10 mm to 100 mm | Diameter: 0.39 in to 3.94 in |
| Length: 1000 mm to 3000 mm | Length: 39.37 in to 118.11 in | |
| Flat Bars | Thickness: 5 mm to 50 mm | Thickness: 0.20 in to 1.97 in |
| Width: 20 mm to 200 mm | Width: 0.79 in to 7.87 in | |
| Length: 1000 mm to 3000 mm | Length: 39.37 in to 118.11 in | |
| Plates | Thickness: 10 mm to 50 mm | Thickness: 0.39 in to 1.97 in |
| Width: 200 mm to 1500 mm | Width: 7.87 in to 59.06 in | |
| Length: 1000 mm to 3000 mm | Length: 39.37 in to 118.11 in |
M4 Tool Steel Applications
- Blades: Circular saw blades, Knives for metalworking
- Broaches: Internal broaching tools, Surface broaching tools
- Gear Hobs: Spur and helical gear hobs, Internal gear hobs
- Thread Rolls: Cold-forming thread rolls for bolts and screws
- Milling Cutters: End mills, Face mills
- Shaper Cutters: Used in shaping metal parts and components
- Shaving Cutters: Precision tools for finishing gears and other components
PM M4 steel (or CPM M4 steel) made using powder metallurgy processes offers improved wear resistance, toughness, and dimensional stability. These enhanced properties make it suitable for complex, high-stress machining applications.
M4 Tool Steel for Peak Performance
At SteelPro Group, we provide M4 and other high-speed tool steel in various forms, from bars to custom profiles, tailored to your machining needs. With our precision cutting and heat treatment services, we ensure that every product meets your exact specifications.
