inoculants for cast iron
According to the form of carbon in cast iron and the form of graphite, cast iron can be divided into five categories: white cast iron, gray cast iron, malleable cast iron, ductile cast iron, and vermicular graphite cast iron. The fracture of white cast iron is bright white, brittle, and hard, and it is rarely used alone. It is an intermediate product in the manufacture of malleable cast iron. Most of the carbon exists in the form of cementite; while the carbon in the other four types of cast iron is mainly in the form of graphite, But there is a big difference in performance.
According to different casting requirements, the commonly used inoculant for cast iron is as follows:
1. 75/72% Ferrosilicon in the particle size 3-8mm/1-3mm/0.2-0.8mm is the most commonly used inoculant. The content of aluminum and calcium plays an important role in the inoculation effect. It is generally believed that molten iron, aluminum, and calcium will react with oxygen and nitrogen to form compounds with high melting points and become graphite The core of crystallization. Moreover, after adding the inoculant, local silicon-rich micro-regions can be formed in the molten iron, which is conducive to graphite precipitation. When purchasing ferrosilicon for incubation, the content of aluminum and calcium cannot be ignored.
2. Barium-containing ferrosilicon inoculant for cast iron also has a strong ability to promote graphitization, which can improve the shape and distribution of graphite in thin-walled castings, and it also has the effect of slowing down the growth and decline. The amount of treatment is less than 75 ferrosilicon. , my country’s existing barium-containing ferrosilicon generally contains 2 to 6% of barium and size 3-8mm.
3. Using 20-30% barium-containing silicon-barium alloy as an inoculant can significantly reduce the white mouth tendency of cast iron and increase the time for maintaining the inoculation effect to about 30 minutes, especially suitable for use For large castings, the amount of alloy added during processing is about 0.1%.
4. Silicon carbide is a substance with the reputation of "rich core". As an additive inoculant for cast iron, it reduces the tendency of castings to white mouth, enhances the graphite nucleation ability and increases the graphite nucleation center, and obtains a moderate number of eutectic clusters. The shape and distribution of graphite that meets the requirements. After the synthetic cast iron smelting process is applied, when the proportion of scrap in the furnace charge is too high and the number of molten iron cores is too small, the nucleation effect of silicon carbide can play a key role. The silicon carbide inoculant for cast iron is generally with the content of SiC 88-90%, and the particle size is relatively small 0.1-0.5mm, which can be used for smelting small tonnage ladle.
If you do not know how to choose or use inoculant can contact Anyang Huatuo Metallurgy who has in such materials for cast iron for more than 20 years.