The process of steel heating is a thermal activation process. The austenite transformation of carbon steel includes four processes: austenite nucleation, carbide dissolution, austenite homogenization, and austenite grain growth. When alloy steel is heated, the austenitization process is the same as that of carbon steel. The whole process is closely related to the diffusion of carbon in steel. The alloying elements in alloy steel have an influence on the diffusion of carbon, and the influence is as follows:

1. Carbide forming elements such as Cr, Mo, W, Ti, and V have a greater affinity with carbon, which hinders the diffusion of carbon in steel and slows down the formation of austenite. Only Ni can increase the diffusion rate of carbon in austenite and increase the formation rate of austenite.

2. After the formation of austenite, there are still some undissolved carbides in the alloy steel. In order to increase the dissolution of carbides, it is necessary to increase the heating time.

3. Most alloying elements hinder the growth of austenite grains.

4. Carbides in steel also reduce the thermal conductivity of steel.

Therefore, it takes longer for the alloy steel to complete these four processes. When calculating the heating time, a relatively large heating coefficient is used.