AISI high speed steel material M42 tool steel is a molybdenum-series high-speed steel alloy with an additional 8% cobalt. (HSS Steel M42) 8% Cobalt tool bits are designed for machining work hardening alloys and other tough materials. They have increased water resistance and tool life. This improves performance and retention of the cutting edge. M42 steel composition makes for a good combination of toughness and hardness.
High-speed steel M42 steel is widely used in metal manufacturing industries and in cutting tools manufacturing because of its superior red-hardness as compared to more conventional high-speed steels, allowing for shorter cycle times in production environments due to higher cutting speeds or from the increase in time between tool changes. HSS M42 tool steel is also less prone to chipping when used for interrupted cuts and costs less when compared to the same tool made of carbide. Tools made from cobalt-bearing high speed steels can often be identified by the letters HSS-Co.
AISI M42 tool steel is a conventionally manufactured cobalt alloyed high-speed steel. The various stages of the manufacturing process are chosen and controlled so that an end product is obtained with a good structure in terms of carbide size and distribution. This is a distinct advantage for the finished tool.
M42 high speed steel is characterised by
- all-round applicability
- good machine-ability
- good performance
- good hot hardness
- good wear resistance
1. Supply Range of AISI M42 Tool Steel High Speed
M42 Steel Round Bar: diameter 2mm – 200mm
M42 Steel Flat: thickness 2-1000mm x width 10-100mm
M42 Steel Plate: thickness 2-200mm x width 200-610mm
Surface Finish: Black, Rough Machined, Turned or as per given requirements.
2. Common M42 Tool Steel Related Specifications and M42 High Speed Steel Equivalents
| Country | USA | German | Japan |
| Standard | ASTM A600 | DIN EN ISO 4957 | JIS G4403 |
| Grades | M42 | 1.3247/HS2-9-1-8 | SKH59 |
3. AISI M42 Tool Steel Chemical Composition Properties Comparison
| ASTM A600 | C | Mn | P | S | Si | Cr | V | Mo | W | Co | ||||||||
| M42 | 1.05 | 1.15 | 0.15 | 0.40 | 0.03 | 0.03 | 0.15 | 0.65 | 3.50 | 4.25 | 0.95 | 1.35 | 9.00 | 10.00 | 1.15 | 1.85 | 7.75 | 8.75 |
| DIN ISO 4957 | C | Mn | P | S | Si | Cr | V | Mo | W | Co | ||||||||
| 1.3247/HS2-9-1-8 | 1.05 | 1.15 | … | … | … | … | … | 0.70 | 3.50 | 4.50 | 0.90 | 1.30 | 9.00 | 10.00 | 1.20 | 1.90 | 7.50 | 8.50 |
| JIS G4403 | C | Mn | P | S | Si | Cr | V | Mo | W | Co | ||||||||
| SKH59 | 1.05 | 1.15 | … | 0.40 | 0.03 | 0.03 | … | 0.70 | 3.50 | 4.50 | 0.90 | 1.30 | 9.00 | 10.00 | 1.20 | 1.90 | 7.50 | 8.50 |
4. Mechanical Properties of AISI M42 Tool Steel HSS
| Properties | Unit | TEMPERATURE °C / °F | ||
| 20 / 70 | 400 / 750 | 600 / 1110 | ||
| DENSITY | Kg/m³ lbs/in³ | 8.03 .290 | 7.93 .286 | 7.87 .284 |
| MODULUS OF ELASTICITY | kN/mm³² psi | 225 33 · 10 6 | 200 29 · 10 6 | 180 26 · 10 6 |
| COEFFICIENT OF THERMAL
EXPANSION FROM 20°C / 70°F |
per °C per °F | — | 11.5 · 10-6 6.4 · 10-6 | 11.8 · 10-6 6.6 · 10-6 |
| THERMAL CONDUCTIVITY | W/m °C Btu/sq. ft. h °F/in. | 24 166 | 28 194 | 27 187 |
| SPECIFIC HEAT | J/kg °C Btu/lb °F | 420 0.10 | 510 0.12 | 600 0.14 |
- Mechanical Properties of M42 Steel
| Mechanical Properties | Metric | Imperial |
| Hardness, Rockwell C (oil quenched from 1204°C, 5 minutes) | 64.3 | 64.3 |
| Hardness, Rockwell C (oil quenched from 1177°C, 5 minutes) | 65.5 | 65.5 |
| Hardness, Rockwell C(oil quenched from 1163°C) | 65.8 | 65.8 |
| Izod impact unnotched (oil quenched at 1191°C; 510°C temper temperature) | 13.6 J | 10.0 ft- lb |
| Izod impact unnotched (oil quenched at 1191°C; 622°C temper temperature) | 24.4 J | 24.4 J |
| Machinability (1% carbon steel) | 35.0 – 40.0% | 35.0 – 40.0% |
| Poisson’s ratio | 0.27-0.30 | 0.27-0.30 |
| Elastic modulus | 190-210 GPa | 27557-30457 ksi |
5. Forging of High Speed M42 Tool Steel
Pre heat the M42 high speed steel slowly and uniformly to 650-760°C and equalise. Then increase more quickly to the forging temperature of 1010-1150°C and equalise prior to forging. Do not allow the forging temperature to drop below 980°C, if this occurs re heating will be necessary. Always cool the m42 high speed steel very slowly after forging.
6. Machinability
AISI Steel grade M42 tool steel can be drilled, turned, threaded, broached, milled and tapped when it is in its annealed condition and rated at 45% of 1% carbon steel.
7. Heat Treatment of M42 Tool Steel High-speed steel material
- Annealing
AISI M42 high speed steel is heated at 871°C (1599°F) and then cooled slowly in a furnace.
- Stress Relieving
To relieve stresses created by extensive machining or tooling with complex geometries. Heat in a neutral atmosphere for 1 to 2 hours after reaching a temperature of 1110 to 1200°F (600 to 650°C), followed by slow cooling in the furnace.
- Hardening
AISI M42 high speed steel is preheated to 871°C (1599°F), soaked and finally heated to 1204°C (2199°F).
- Tempering
Tempering M42 tool steel at 560°C / 1040°F or higher 3 times for at least 1 hour at full temperature is recommended.
8. Application of M42 Tool Steel High Speed
AISI M42 tool steel is a high-speed steel suitable for cutting tools such as, twist drills, broaches, taps, milling, cutters, saws, reamers etc. In terms of performance, HSS grade M42 is a steel to be used in conditions where the demand for hot hardness is of great importance i.e. where high performance is essential.
Typically employed to machine the super alloys and exotic, AISI HSS M42 tool steel is employed in drills, hobs, taps, end mills, milling cutters, form and gear cutters, broaches and chasers.
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