Tempering process of Corten A steel plates

 Isothermal annealing is to heat the Corten-A Steel plate to a temperature higher than Ac3 (or Ac1), and then cool it to a certain temperature within the pearlite temperature range and maintain it isothermally after maintaining for a suitable time, so that the austenite is transformed into a pearlite type. The tissue is then annealed in air. The isothermal annealing process is applied to medium carbon alloy steel and low alloy steel, and its purpose is to refine the structure and reduce the hardness. The heating temperature of the hypoeutectoid steel is Ac3 + (30 ～ 50) ℃, and the heating temperature of the hypereutectoid steel is Ac3 + (20 ～ 40) ℃, which is maintained for a certain time, and the furnace is cooled to a temperature slightly lower than the Ar3 temperature for isothermal transformation, and then released from the furnace for air cooling . Isothermal annealing structure and hardness are more uniform than full annealing.

Purpose of tempering process for Corten-A plates

The heat treatment process is divided into four major steps. Among them, tempering is a relatively common process in heat treatment. The purpose of the heat treatment process is as follows:
1. Reduce brittleness, eliminate or reduce internal stress, there is a lot of internal stress and brittleness after quenching, if it is not tempered in time, the tube will often deform or even crack;
2. Obtain the required mechanical properties of the pipe. After quenching, the pipe has high hardness and brittleness. In order to meet the different performance requirements of various pipes, the hardness can be adjusted through appropriate tempering to reduce the brittleness and obtain the required Toughness, plasticity
3.Stable tube size;
4. For some alloy steels that are difficult to soften during annealing, high temperature tempering is often used after quenching (or normalizing) to properly collect carbides in the pipe and reduce the hardness to facilitate cutting processing.