Application of silicon in cast iron

1. Effect of silicon on promoting graphitization in cast iron: in cast iron, silicon is the alloy element with the strongest effect on promoting graphitization, and its talent for promoting graphitization is three times that of nickel and five times that of copper. In addition, whether in liquid or solid cast iron, the effect of silicon and iron is stronger than carbon. Silicon in liquid cast iron will reduce the solubility of carbon. The higher the content of silicon in molten iron, the lower the carbon content, and more carbon will be overhead. In addition, oxygen and nitrogen in cast iron can stabilize carbides. The silicon contained in cast iron can reduce the content of oxygen and nitrogen in it, thus indirectly enhancing the effect of silicon on graphitization.

2. Solid-solution strengthening effect of silicon in ferrite: in solid cast iron, silicon is almost completely dissolved in austenite and ferrite, and does not enter into carbide. Silicon atoms and iron atoms can be linked to form silicon-containing ferrites with strong covalent bonds, which not only promote the formation of ferrite, but also strengthen the effect of ferrite. In order to understand the talent of silicon strengthening ferrite, foreign researchers in the 1950s

Different amounts of silicon are added to the steel with% content and no other alloying elements to compare the effect of silicon on mechanical function. In the production of cast iron, the solid solution strengthening effect of silicon can reduce or eliminate copper, nickel, tin, molybdenum, chromium and other alloy elements with advanced strength, which is beneficial to reduce production costs and avoid the negative effects of alloying elements.

3. Other effects of silicon in cast iron

The effect of silicon in cast iron is multifaceted. In addition to "promoting graphitization" and "solid solution strengthening", silicon has many important effects. Here, two are briefly introduced:

1) Silicon dissolved in liquid cast iron greatly enhances the oxidation resistance of molten iron, and silicon can also reduce the solubility of nitrogen in molten iron. Among all kinds of casting alloys, only cast iron can use cupola, oxygen rotary furnace and other smelting equipment to smelt in oxygen-rich and nitrogen-rich atmosphere, precisely because of this effect of silicon.

2) The silicon content in cast iron will be increased to more than%, and the anti-oxidation ability and anti-heat growth function of cast iron will be greatly improved. In the early stage, the trademark of silicon series heat-resistant cast iron was used in the standards of heat-resistant cast iron in various countries. In recent years, due to the consideration of energy conservation, various internal combustion engines have improved the temperature of exhaust gas. In the automotive industry of various countries, great attention has been paid to the application of heat-resistant silicon molybdenum nodular cast iron and the application of silicon solid solution strengthening effect.