Method of case hardening gears

A method of making gears of a gear modulus m greater than 5 mm for continuous bending and contact loads in the range of 400-600 N/mm2 fatigue point and higher short term loads, comprising making said gears from low hardenability (LH) or specified hardenability (SH) steel having a carbon content of 0.5 to 1.2% and of a critical diameter Dcr in mm equal to the gear modulus m times 1.5 to 2.0, and through surface hardening (TSH) said gears so formed,

• whereby a hardened depth in mm at the tooth root bottom and radius is equal to 0.2 to 0.25 times the gear modulus m;
• a hardened depth in mm at a pitch line is equal to 0.25 to 0.32 times the gear modulus m;
• and,
• a hardened depth in mm at a tooth tip is equal to 0.25 to 0.75 times the gear modulus m;
• and,
• a surface hardness (HRC) at a surface is equal to 56 to 65 and at a gear tooth core equal to 30 to 45.

A method of making gears of a gear modulus m from 3 to 4.5 mm for continuous bending loads in the vicinity of 300-600 N/mm2 fatigue point, comprising making said gears from low hardenability (LH) or specified hardenability (SH) steel having a carbon content of 0.5 to 1.2% and of a critical diameter Dcr in mm equal to the gear modulus m times 1.5 to 2.5, and through surface hardening (TSH) said gears so formed, whereby:

• a hardened depth in mm at a tooth root bottom and radius is equal to 0.2 to 0.45 times the gear modulus m;
• a hardened depth in mm at the pitch line is equal to 0.25 to 0.78 times the gear modulus m;
• a hardened depth mm at the tooth tip is equal to 0.25 to 1.25 times the gear modulus m, and,
• a surface hardness (HRC) is equal to 56-61 and at a gear tooth core of 30-45.

A method of making gears of a gear modulus m of 3.0 to 4.5 mm for continuous bending in the range of 300 N/mm2 fatigue point, comprising making said gears from low hardenability (LH) or specified hardenability (SH) steel having a carbon content of 0.35 to 1.2% and having critical diameter Dcr in mm equal to the gear modulus m times 1.5 to 3.0, and through surface hardening (TSH) said gears so formed, whereby:

• a hardened depth in mm at the tooth root bottom and a radius equal to 0.2 to 0.75 times the gear modulus m;
• a hardened depth in mm at the pitch line equal to 0.25 to 0.78 times the gear modulus m;
• a hardened depth in mm at the tooth tip equal to 0.25 to 2.0 times the gear modulus m;
• and
• a surface hardness (HRC) at the surface equal to 50-61 and at a gear tooth core equal to 30-45.