A vacuum carburization process and a vacuum in the direction of the carburization

摘要

A method is provided between a diffusion process and a quenching process, a normalization process for carrying out a stages cooling, in which a temperature lowering treatment and a temperature maintaining treatment are alternatingly repeated several times, so that a temperature history of a first temperature to a predetermined temperature a predetermined condition is fulfilled; a according to - normalization - maintaining process for maintaining the temperature of the entire workpiece for a predetermined period of time after the normalization process, so that the entire workpiece the predetermined temperature, in order thus to produce fine crystal grains in the workpiece; and a back heating-up process for increasing the temperature of the workpiece on the second temperature after the according to - normalization - maintaining process are provided. Even if, according to the invention, a process temperature is set high, in order to obtain a rapid progress of the carburization and the diffusion, and thus to shorten the process time, a uniformity of the temperature of between a surface and an interior of the workpiece by means of the high temperature process is achieved, and crystal grains are prevented from being to be as coarse grains, as a result of which a workpiece with a predetermined value is obtained.