The steel casting process generally includes the following main steps:

Raw Material Preparation

Scrap steel: Suitable scrap steel is selected as the main raw material. The source of the scrap steel must be clear, the composition relatively stable, and free of excessive impurities and oil stains. Different types of scrap steel may require different process adjustments in subsequent processing to ensure the quality of the molten steel.

Ferroalloys: According to the required composition of the cast steel, corresponding ferroalloys such as ferromanganese, ferrosilicon, and ferrochromium are prepared to adjust the content of alloying elements in the steel to obtain the desired properties.

Slag-forming materials: Commonly used slag-forming materials include limestone and fluorspar. They are used to form slag during smelting, remove impurities and harmful elements from the molten steel, adjust the composition and properties of the slag, and ensure the smooth progress of the smelting process.
Smelting

Charging: The prepared scrap steel and other raw materials are charged into an electric furnace or other furnace in a certain order and proportion. The charging method and order will affect the smelting efficiency and molten steel quality. Generally, large pieces of scrap steel are charged first, followed by small pieces and ferroalloys.

Melting: The raw materials in the furnace are gradually melted using the electric energy of the electric furnace or other energy sources. During the melting process, the temperature and furnace conditions need to be closely monitored, and parameters such as power need to be adjusted as needed to ensure that the furnace materials melt evenly and quickly.

Refining: After the furnace materials are completely melted, the refining stage begins. By adding refining agents to the molten steel, blowing in oxygen or other gases, etc., impurities, gases, and harmful elements in the molten steel are further removed, the composition and temperature of the molten steel are adjusted, and the purity and quality of the molten steel are improved.

Casting

Mold preparation: According to the shape and size of the required casting, the corresponding mold is made. The mold can be a sand mold, a metal mold, etc. Sand molds have the advantages of low cost and flexible shaping, while metal molds have the advantages of high dimensional accuracy and good surface quality. Before casting, the mold needs to be dried and coated to improve the strength and permeability of the mold and prevent defects in the casting.

Molten steel adjustment: Before casting, the temperature and composition of the molten steel are finally adjusted and tested to ensure that the molten steel temperature is appropriate and the composition meets the requirements. Too high a temperature may cause the casting to have defects such as pores and shrinkage, while too low a temperature may cause insufficient pouring or cold shuts.

Casting operation: The adjusted molten steel is slowly and steadily poured into the mold. The casting speed and height need to be reasonably controlled according to the structure and requirements of the casting. During the casting process, care should be taken to prevent splashing and air entrainment.

Cooling and Solidification

Natural cooling: After casting, the molten steel in the mold gradually cools and solidifies in the natural environment. The cooling rate affects the microstructure and properties of the casting. Generally speaking, when the cooling rate is faster, the grains of the casting will be smaller, and the strength and hardness will be relatively higher, but the toughness may be reduced; when the cooling rate is slower, the grains will be relatively larger, the strength and hardness may be lower, but the toughness will be better.

Controlled cooling: For some castings with higher performance requirements, controlled cooling methods may be used, such as setting cooling water pipes around the mold or using air cooling, to precisely control the cooling rate of the casting and obtain the ideal microstructure and properties.

Post-processing

Sand removal and cleaning: After the casting cools to a certain temperature, sand removal is performed to remove the casting from the mold. Then, the casting is cleaned to remove surface sand grains, burrs, and flash. Common cleaning methods include shot blasting and sand blasting.

Heat treatment: According to the performance requirements of the casting, the casting undergoes appropriate heat treatment, such as quenching, tempering, normalizing, and annealing. Heat treatment can improve the microstructure of the casting, improve the strength, toughness, and hardness of the casting, eliminate casting stress, and stabilize the size and performance of the casting.

Machining: The casting undergoes necessary machining, such as turning, milling, drilling, and grinding, to achieve the design requirements for size and accuracy and meet the performance requirements.

Inspection: Various inspection methods are used to inspect the quality of the casting, such as visual inspection, dimensional measurement, non-destructive testing (such as ultrasonic testing, radiographic testing, magnetic particle testing, etc.), and mechanical property testing, to ensure that the quality of the casting meets the standards and customer requirements.