Steel casting process is the process of heating iron in a crucible container to produce a metal.
What Is Cast Steel?
Cast steel is steel that can be used for casting.
Cast steel is a general term for iron-based alloys used to produce castings that do not undergo eutectic transformation during solidification, and is a type of cast alloy.
Cast steel is an alloy with iron and carbon as the main elements, and the carbon content is 0-2%.
Cast steel results in a more uniform composition of steel with fewer impurities than any previous manufacturing process.
The Flow of The Steel Casting Process
1. Put the qualified materials into the smelting equipment according to the corresponding proportion, and sample and analyze the liquid. After passing the inspection, pour according to the pouring principle. When pouring, the method of rapid pouring at low temperature should be selected, and the time and temperature should be recorded at the same time.
2.Before the casting of steel castings, use computer software to analyze and predict the quality of the entire casting process of the product, and strictly optimize the entire casting process. Throughout the process, the dimensions of the casting are tightly controlled to prevent cracking.
3.After the preliminary work is completed, polishing and sampling inspection are required. Generally, high-precision surface grinders are used to accurately grind and polish steel castings to improve the dimensional accuracy of products. The purpose of sampling inspection is to improve the yield of products, remove some unqualified products from finished products, and ensure the quality of products.
(1) Smelting of cast steel.
Cast steel must be smelted by electric furnaces, mainly electric arc furnaces and induction furnaces. According to the different lining materials and slag system used, it can also be divided into acid furnace and alkaline furnace. Carbon and low alloy steels can be smelted in any type of furnace, but high alloy steels can only be smelted in alkaline furnaces.
(2) Casting process.
The melting point of cast steel is high, the fluidity is poor, and the molten steel is easily oxidized and inhaled. At the same time, its volume shrinkage rate is 2 to 3 times that of gray cast iron. Therefore, the casting performance of cast steel is poor, and defects such as insufficient pouring, pores, shrinkage cavities, hot cracks, sand sticking, and deformation are prone to occur. In order to prevent the occurrence of the above-mentioned defects, corresponding measures must be taken in the process.
① The molding sand used for the production of steel castings should have high refractoriness and sand resistance, as well as high strength, air permeability and concession. The raw sand usually uses silica sand with larger and uniform particles;
In order to prevent sand sticking, the surface of the cavity is mostly coated with coatings with higher refractoriness;
When producing large pieces, it is mostly used in sand molds or water glass sand, which is faster than casting molds. In order to improve the strength and concession of the casting mold, various additives are often added to the molding sand.
②In the design of gating system and riser. Since the cast carbon steel tends to solidify layer by layer and has a large shrinkage, the principle of rigid sequential solidification is used to set the gating system and riser. To prevent the occurrence of shrinkage cavities and shrinkage porosity. Generally speaking, steel castings should be provided with risers. Cold iron is also used more. In addition, the bottom pour pouring system with simple shape and large cross-sectional area should be used as much as possible, so that the molten steel can fill the mold quickly and smoothly.
(3) Heat treatment.
The heat treatment of cast steel is usually annealing or normalizing. Annealing is mainly used for steel castings with w(C)≥0.35% or particularly complex structure. Such castings have poor plasticity, large casting stress and easy cracking. Normalizing is mainly used for steel castings with w(C)≤0.35%. Such steels have low carbon content, good plasticity, and are not easy to crack when cooled.
(4) Liquid steel fluidity
Due to the poor fluidity of molten steel, in order to prevent cold insulation and insufficient pouring of steel castings, the wall thickness of steel castings should not be less than 8mm;
The structure of the gating system is simple, and the section size is larger than that of cast iron;
In the casting process, dry casting or hot casting is used, and the pouring temperature is appropriately increased, generally 1520° to 1600°C.
Because the pouring temperature is high, the superheat degree of molten steel is large, and the liquid remains for a long time, and the fluidity can be improved.
However, if the pouring temperature is too high, it will cause defects such as coarse grains, thermal cracking, pores and sticky sand. Therefore, for small, thin-walled and complex-shaped castings, the pouring temperature is about the melting point temperature of steel + 150 °C; The pouring temperature of large, thick-walled castings is about 100°C higher than the melting point.
Through the above analysis, I believe that everyone has a more professional and detailed understanding of the steel casting process and characteristics, and I hope it will be helpful to everyone. It is also recognized that correct operating procedures can not only make equipment smoother and more reliable, but also improve work efficiency.
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