(1) Roughing of hardened steel: In the production process of gears and ring gears that have undergone heat treatment during turning, some gears, ring gears are quenched or carburized and quenched. The hardness is generally above HRC55, and some hardness reaches HRC60 or even HRC65. Some gears have serious deformation after heat treatment, especially the large ring gear and large gear after carburizing and quenching (such as high-speed iron gears, large ring gears for construction machinery, and large gear rings for heavy industry, etc.). These large gear ring gears are deformed after quenching. Very large, this involves hardened steel roughing.

 (2) Intermittent processing of quenched steel: Indiscriminate cutting has always been a problem, not to mention high-hardness quenched steels with HRC60. Especially when high-speed turning hardened steel, if the workpiece has intermittent cutting, the tool will be subjected to more than 100 impacts per minute to finish processing when intermittently cutting hardened steel, which is a great challenge to the impact resistance of the tool. Taking the processing of automotive gears as an example, it has become a trend to use hardened gears instead of grinding wheels. It is understood that, as one of the three major markets for the gear industry, vehicle gears account for 62% of the total gear market, among which automotive gears also occupy The market share of vehicle gears is 62%. In other words, the gears used in automobiles account for nearly 40% of the entire gear market, showing the importance of gears for the automotive industry. Although hardening and hard turning of hardened steels have been popular, there are still many problems encountered in the processing of automotive hardened gears. For example, some automotive gears have oil holes in their inner holes, and cutters can easily collapse during high-speed operation. Knife, gear position tolerance is difficult to guarantee and so on.

 (3) Grooving of hardened steels: For example, the hard turning after quenching of synchronizer sleeve engagement grooves, although tool manufacturers have developed special grooved tools for synchronizer sleeves, the tool life is still not satisfactory. (4) The finish of hardened steel turning: If the bearing steel after quenching generally requires a good surface finish, Gcr15 steel is commonly used bearing steel, hardness after quenching is generally around HRC62, in the production and processing of weighing, due to the bearing The precision and finish requirements are very high. If the design is to adjust the cutting edge of the tool, the turning finish can reach Ra0.4 when machining hardened steel with CBN tools.