M7 1.3348 T11307 HS2-9-2 SKH58 High Speed Tool Steel

M7 Steel Description

M7 is one of the High Speed Tool Steels in the molybdenum alloy family, with tungsten, chromium and vanadium for strengthening. It has good hardenability and is very wear resistant. Very high resistance to softening at elevated temperatures and good toughness. Deep hardening response.

M7 Steel Applications

M7 is widely used for cutting tools in machining operations. Sendzimir rolls, segment and circular cutters, profile cutting tools, thread cutting drills and cold forming tools.  M7 high-speed steel is used for making heavier construction drills where flexibility and extended drill life are extremely important. M7 molybdenum high-speed tool steels are mainly used for cutting tools in all machining operations. This steel exhibits good abrasion-resistance because of its carbon and vanadium contents. It is an excellent choice for premium tools which require an outstanding balance of red hardness, edge toughness and wear-resistance. It is especially suited for machining semi-hard, heat-treated steel at about 300-350 Brinell Hardness.

M7 Steel Chemical composition

Physical properties (average values) at ambient temperature

Modulus of elasticity [103 x N/mm2 ]: 217

Density [g/cm3 ]: 8.30

Thermal conductivity [W/m.K]: 19.0

Electric resistivity [Ohm mm2 /m]: 0.65

Specific heat capacity[J/g.K]: 0.46

Soft Annealing

Heat to 820-880℃, cool slowly in furnace. This will produce a maximum Brinell hardness of 230-280.

Hardening

Heat up to 450-600℃, preheat to 850℃ and then to 1050℃. Harden from a temperature of 1180-1220℃ followed by oil, air quenching or warm bath at 550℃. Hardness after quenching is 64-66 HRC.

Tempering

Tempering temperature: 3 x 1 hour at 540-560℃. Hardness after tempering is min 64 HRC.

Forging

Hot forming temperature: 1100-900℃.

Cold Working

In the annealed condition M7 may be cold worked by conventional methods.

Machinability

Machinability is medium, rating about 60% that of the W group water hardening low alloy tool steels at 100% for comparison.

Corrosion Resistance

Although this alloy contains chromium and molybdenum it is still a steel and thus will corrode. It should be protected from rusting.