Briefly describe the main points of heat treatment process of cast steel

The steel used for castings is a kind of casting alloy. At present, cast steel is mainly used to manufacture some parts with complex shapes, which are difficult to be forged or formed by cutting and require higher strength and plasticity.

Cast steel can be divided into: carbon cast steel and alloy cast steel according to chemical composition. Carbon cast steel is divided into: C≤0.20% is low carbon steel; C0.2～0.5% is medium carbon steel; C≥0.5% is high carbon steel.

Cast steel is divided into: low-alloy steel (generally, the total amount of alloying elements is below 8%) and high-alloy steel (generally, the total amount of alloying elements is above 8%).

Cast steel can be divided into structural cast steel, wear-resistant cast steel, stainless cast steel, heat-resistant cast steel and tool cast steel according to the application.

Cast steel is divided into: pearlite cast steel, ferrite cast steel, martensitic cast steel and austenite cast steel according to the structure.

Cast steel is a type of casting, so forging workpieces can improve the internal structure of the organization, with good mechanical properties and uniform grains. Important and laborious workpieces must be forged. I believe that many casters need to pay attention to the process points of heat treatment of steel castings.

The main process elements of heat treatment of steel castings:

1. The heat treatment of steel castings consists of three stages: heating, heat preservation and cooling. The determination of its process parameters is based on ensuring product quality and saving costs.

2. The heat treatment methods of steel castings are different according to the heating and cooling conditions. The main heat treatment methods of steel castings are: annealing and normalizing, homogenization treatment, quenching, tempering, solution treatment, precipitation hardening, stress relief treatment and hydrogen removal deal with.

3. Annealing is a heat treatment process in which the steel casting is heated above a certain temperature, kept for a certain period of time, and cooled. The purpose of annealing is to eliminate the columnar crystals, coarse equiaxed crystals, Widmanderman structure and dendritic segregation in the cast structure, so as to improve the mechanical properties of the cast steel.

4. The structure of carbon steel after annealing: hypoeutectoid cast steel is ferrite and pearlite, eutectoid cast steel is pearlite, hypereutectoid cast steel is pearlite and carbide. Suitable for all grades of steel castings.