Gear steel 20CrMnTiH isothermal normalizing treatment method

Abstract

The invention discloses a gear steel 20CrMnTiH isothermal normalizing treatment method, and belongs to the field of material thermal treatment. The gear steel 20CrMnTiH isothermal normalizing treatment method comprises the steps: adopting a warm-air district cooling technology after austenitizing heating: in district I, the warm air temperature is 50 to 55 DEG C, the air speed is controlled to be 8 to 12 m / s, and the air cooling time of parts is controlled to be 2 to 3 minutes; in district II, the air temperature is 55 to 60 DEG C, the air speed is 5 to 8 m / s, and the air cooling time of parts is controlled to be 3 to 4 minutes; regulating an isothermal normalizing furnace to be in two-stage control: first stage, the temperature is controlled to be 550 to 570 DEG C, and the heat preservation time is 1 to 1.5 hours; second stage, the temperature is controlled to be 570 to 600 DEG C, and the isothermal control time is 1 to 1.5 hours; after isothermal normalizing, entering an air cooling chamber, controlling the air temperature to be 30 to 40 DEG C and the air speed to be 5 to 8 m / s, and carrying out air cooling after cooling to 200 to 250 DEG C. The hardness of gear blank treated by the technology can be up to 165 to 180 HB, the pearlite interlamellar spacing is controlled to be 0.18 to 0.24 mu m, the grade of a banded structure is controlled to be 1 to 1.5, the cutting performance is good, deformation after quenching can be stably controlled, and the reject ratio is basically zero.

Description

technical field [0001] The invention belongs to the field of material heat treatment, and in particular relates to a gear steel 20CrMnTi isothermal positive treatment method. After this heat treatment process, the structure and hardness of the gear steel blank parts are optimized, which is very suitable for chip processing and is a subsequent part. Advanced finishing and heat treatment provide tissue performance guarantee. Background technique [0002] In automobile production, gears are essential and basic parts. When the quality of the gears, especially the gears of the rear axle gear transmission is low, there will be problems such as difficult assembly, high noise and tooth surface wear. Carburizing and quenching deformation is one of the reasons that affect the quality of the assembly. Among the factors affecting deformation, it is often concentrated on carburizing and quenching, and it is easy to ignore the influence of pre-heat treatment of forging billet on deforma...

AI Technical Summary

Problems solved by technology

[0005] The normalizing process of automotive gear blanks is generally austenitized at 930°C. It takes 50 minutes to cool the steel evenly to 550°C, and then cools the steel evenly to 250°C for 100 minutes and then air-cools. The control is difficult, and the process is generally unstable.

For example, Chinese patent CN101429587A discloses a car differential gear isothermal normalizing treatment, which only cools the forging to 600-720 degrees Celsius under the condition of nitrogen air cooling, and does not limit the cooling rate, nitrogen temperature, nitrogen speed and other conditions , resulting in unstable final material properties, uneven hardness, and low pass rate

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