Overview of Iron Casting Process

Iron casting is a process of injecting molten iron into the cavity of a prefabricated mold and obtaining a metal part of the desired shape after cooling and solidification. Its core advantages are low cost, strong adaptability, and the ability to produce complex geometric parts. It is widely used in the fields of automobiles, machinery, energy, etc. According to the differences in mold materials and processes, iron casting is mainly divided into sand casting, metal mold casting, and investment casting, among which sand casting occupies a dominant position due to its flexibility and economy.

Core process flow

1.Mold preparation

Sand casting: using quartz sand, clay or coated sand (resin coated sand) as materials, the mold is made by hand or machine (such as static pressure molding line), and the accuracy can reach CT8-CT10 level. Coated sand casting (shell casting) is suitable for precision small and medium-sized parts, while clay sand wet mold casting is mostly used for large structural parts.

Metal mold casting: using steel or cast iron molds, it can be reused, has a high surface finish, and is suitable for mass production, but the cost is relatively high.

2.Melting and molten iron treatment

Melting equipment: electric furnace (medium frequency furnace, electric arc furnace) or cupola, smelting temperature is controlled at 1400-1550℃.

Composition adjustment: Add carbon, silicon, manganese and other elements according to casting requirements. For example, ductile iron needs to be spheroidized by adding magnesium or rare earth elements to make graphite spherical; gray cast iron needs to control the carbon equivalent (CE=3.0-4.5%) to form a flake graphite structure.

Purification of molten iron: remove impurities through slag remover or inert gas purge to improve the purity of the material.

3.Pouring and solidification control

Pouring temperature: gray cast iron is usually 1250-1400℃, ductile iron needs to be reduced to 1300-1350℃ to reduce magnesium burning.

Solidification optimization: Use chills or insulation risers to adjust the cooling rate to avoid shrinkage and shrinkage defects.

4.Post-processing

Cleaning: Remove sand molds, pouring heads and burrs, usually by shot blasting, sand blasting or mechanical cutting.

Heat treatment: Annealing to eliminate internal stress, normalizing to increase strength, quenching + tempering to enhance wear resistance.

Surface treatment: Painting, galvanizing or nitriding to improve corrosion resistance.