M4, 1.3351, HS6–5–4, High-speed Tool Steel
Designation by Standards
| Mat. No. | EN | AISI/SAE |
| 1.3351 | HS6-5-4 | M4 |
Chemical Composition (in weight %)
| C | Si | Mn | P | S | Cr | Mo | W | V |
| 1.25 – 1.4 | max 0.45 | max 0.4 | max 0.03 | max 0.03 | 3.8 – 4.5 | 4.2 – 5 | 5.2 – 6 | 3.7 – 4.2 |
Description
M4 Molybdenum High Speed Tool Steels. It has a relatively high 1.3% carbon content for high hardness and excellent wear resistance.
Applications
Used for cutting tools of all types for machining operations. Heavy duty milling cutters, broaches, broaches.
Physical properties (average values) at ambient temperature
Density [g/cm3]: 7.97
Transformation temperatures (oC): Ac1=803, Ac3=895
Coefficient of Linear Thermal Expansion 10-6 oC-1
| 20-100oC | 20-200oC | 20-300oC | 20-400oC | 20-500oC | 20-600oC | 20-700oC | 20-800oC |
| 9.4 | 10.4 | 10.9 | 11.3 | 11.5 | 11.8 | 12.0 | 12.1 |
Soft Annealing
Heat to 820-848oC, cool slowly in furnace. This will produce a maximum Brinell hardness of 255.
Hardening
Heat up to 450-600oC, 1st pre-heating: 850oC, 2nd pre-heating: 1050oC. Harden from a temperature of 1190- 1230oC followed by oil, air quenching or warm bath quenching at 400oC.
Tempering
Tempering temperature: 540-560oC, 3x for 1 hour.
Tempering Temperature (oC) vs. Hardness (HRC)
| 200oC | 300oC | 400oC | 500oC | 525oC | 550oC | 575oC | 600oC | 650oC | 700oC |
| 63 | 62 | 62 | 64 | 64.5 | 65 | 64 | 62 | 57 | 47 |
Forging
Hot forming temperature: 1100-900oC.
Cold Working
Cold working may be accomplished by conventional methods with the alloy in the annealed condition.
Machinability
Machinability is relatively low, rating 40% that of the water hardening (W group) tool steels which are relatively easy to machine.
