M2 Tool Steel | 1.3343 | HS-6-5-2C| SKH51
Short Description:
AISI M2 Tool Steel is molybdenum based high-speed steel in tungsten–molybdenum series. HSS grade steel M2 is a medium alloyed high speed steel which has good machinability. The H-SS M2 chemical composition gives a good combination of well-balanced toughness, wear resistance and red hardness properties. Widely used for cutting tools such as twist drills, taps, milling cutters, saws, knives etc. Also commonly used in cold work punches and dies and cutting applications involving high speed...
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AISI M2 Tool Steel is molybdenum based high-speed steel in tungsten–molybdenum series. HSS grade steel M2
is a medium alloyed high speed steel which has good machinability. The
H-SS M2 chemical composition gives a good combination of well-balanced
toughness, wear resistance and red hardness properties. Widely used for
cutting tools such as twist drills, taps, milling cutters, saws, knives
etc. Also commonly used in cold work punches and dies and cutting
applications involving high speed and light cuts.
Grade M2 High Speed Steel is by far the most popular high speed steel replacing high speed steel grade T1 in most applications because of its superior properties and relative economy.
1. Common M2 Tool Steel Related Specifications and Equivalents
| Country | USA | German | Japan |
| Standard | ASTM A600 | DIN EN ISO 4957 | JIS G4403 |
| Grades | M2 | 1.3343 | SKH51 |
2. ASTM M2 Tool Steel Chemical Composition Properties
| ASTM A600 | C | Mn | P | S | Si | Cr | V | Mo | W | |||||||
| M2 regular C | 0.78 | 0.88 | 0.15 | 0.40 | 0.03 | 0.03 | 0.20 | 0.45 | 3.75 | 4.50 | 1.75 | 2.20 | 4.50 | 5.50 | 5.50 | 6.75 |
| DIN ISO 4957 | C | Mn | P | S | Si | Cr | V | Mo | W | |||||||
| 1.3343 | 0.86 | 0.94 | … | … | … | … | … | 0.45 | 3.80 | 4.50 | 1.70 | 2.10 | 4.70 | 5.20 | 5.90 | 6.70 |
| JIS G4403 | C | Mn | P | S | Si | Cr | V | Mo | W | |||||||
| SKH51 | 0.80 | 0.88 | … | 0.40 | 0.03 | 0.03 | … | 0.45 | 3.80 | 4.50 | 1.70 | 2.10 | 4.70 | 5.20 | 5.90 | 6.70 |
3. AISI HSS M2 Tool Steel Mechanical Properties
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Physical Properties of HSS M2 Material
| Density | 0.294 lb/in3 (8138 kg/m3) |
| Specific Gravity | 8.15 |
| Modulus of Elasticity | 0.294 lb/in3 (8138 kg/m3) |
| Thermal conductivity | 24 Btu/ft/hr/°F 41.5 W/m/°K |
| Machinability | 65% of a 1% carbon steel |
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AISI M2 Tool Steels Properties Mechanical
| Mechanical properties | Metric | Imperial |
| Hardness, Rockwell C (tempered at 1150°F, quenched at 2200°F) | 62 | 62 |
| Hardness, Rockwell C (as hardened, quenched at 2200°F) | 65 | 65 |
| Compressive yield strength (when tempered at 300°F) | 3250 MPa | 471000 psi |
| Izod impact unnotched (when tempered at 300°F) | 67 J | 49.4 ft-lb |
| Abrasion (loss in mm3, as-hardened; ASTM G65) | 25.8 | 25.8 |
| Abrasion (loss in mm3, tempered at 1275°F; ASTM G65) | 77.7 | 77.7 |
| Poisson’s ratio | 0.27-0.30 | 0.27-0.30 |
| Elastic modulus | 190-210 GPa | 27557-30458 ksi |
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M2 Steels Thermal Properties
| Thermal properties | Metric | Imperial |
| CTE, linear (@20.0 – 100°C/ 68.0 – 212°F) | 10 μm/m°C | 5.56 μin/in°F |
| CTE, linear (@20.0 – 500°C/68.0 – 932°F) | 12.2 μm/m°C | 6.78 μin/in°F |
| CTE, linear (@20.0 – 850°C/68.0 – 1560°F) | 12.6 μm/m°C | 7 μin/in°F |
4. Forging of AISI M2 High Speed Steel
Pre
heat M2 HSS steel slowly and uniformly to 850-900°C. The heat should
then be increased more quickly to the forging temperature of
1050-1150°C. If during the forging
the temperature of the M2 high speed tool steel material drops below
880-900°C, re-heating will be necessary. Cool the M2 steel component
very slowly after forging.
5. Heat Treatment of M2 Steel HSS
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Anneal
Heat
to 1600° F, soak thoroughly at heat. Furnace cool 25° F per hour to
900° F, air cool to room temperature. Approximate annealed hardness 241
Maximum Brinell.
Stress Relief of Unhardened Material: Heat slowly
to 1200 to 1250° F. Soak for two hours per inch of thickness at heat.
Slow cool (furnace cool if possible) to room temperature.
-
Hardening
Preheat: Heat slowly to 1550° F, soak thoroughly, heat to 1850° F, soak thoroughly.
-
Harden
Soak
time in the furnace varies from a few minutes to a 15 minutes,
depending tool size, heat capacity of the furnace, and the size of the
charge. – Heat to 2150 to 2200° F for max. toughness and minimum
distortion. – Heat to 2250 to 2275° F for max. hardness and abrasion
resistance.
-
Quench
For full
hardness, oil quench to 150-200° F. Air quench to 150° F. When quenching
in hot salt maintain the quench just above the Ms temperature. After
equalizing withdraw parts from the hot salt and air cooled to 150° F.
-
Temper
Double
temper is mandatory, three tempers are sometimes preferred. Soak for 2
hours per inch of thickness. Air cool to room temperature between
tempers. The best tempering range for hardness, strength and toughness
is 1000 to 1050° F.
| Temper° F | Rockwell “C” | Temper° F | Rockwell “C” |
| As-quenched | 64 | 900 | 64 |
| 400 | 63 | 1000 | 65.5 |
| 500 | 62.5 | 1050 | 63.5 |
| 600 | 62.5 | 1100 | 61.5 |
| 700 | 62.5 | 1150 | 60 |
| 800 | 63.5 | 1200 | 53 |
6. Machinability of AISI M2 Tool Steel H-SS
Shaping
of HSS M2 tool steels can be carried out using grinding methods.
However, they have poor grinding capability and hence they are regarded
as “medium” machinability tool steel under annealed conditions. The
machinability of these tool steels M2 is only 50% of that of the easily
machinable W group or water hardening tool steels.
7. M2 Tool Steel Applications
The main use of high-speed steels continues to be in the manufacture of various cutting tools.
Typical
applications for M2 high speed steel are twist drills, reamers,
broaching tools, taps, milling tools, metal saws. M2 is suitable for
cold forming tools such as extrusion rams and dies, also widely used in
all kinds of cutting tools, knife and punches and die applications,
plastic moulds with elevated wear resistance and screws.
