high silicon cast iron
Adding a certain amount of certain alloying elements to cast iron can obtain alloy cast iron with higher corrosion resistance in some media. High silicon cast iron is one of the most widely used. A series of alloy cast irons containing 10% to 16% silicon are called high-silicon cast irons. Except for a few varieties with silicon content of 10% to 12%, the silicon content is generally 14% to 16%. When the silicon content is less than 14.5%, the mechanical properties can be improved, but the corrosion resistance is greatly reduced. If the silicon content reaches more than 18%, although the alloy is resistant to corrosion, the alloy becomes very brittle, so that it is not suitable for casting. Therefore, the most widely used industrially is high-silicon cast iron containing 14.5% to 15% silicon.
Adding some alloying elements to high-silicon cast iron can improve its machining performance. Adding rare earth magnesium alloy to high silicon cast iron with 15% silicon can purify and degas, improve the matrix structure of cast iron, and spheroidize graphite, thereby improving the strength, corrosion resistance and processing performance of cast iron; Performance has also improved. In addition to grinding, this high-silicon cast iron can also be turned, tapped, drilled, and repaired under certain conditions, but it is still not suitable for sudden cooling and heating; its corrosion resistance is better than ordinary high-silicon cast iron , the adapted medium is basically similar.
Adding 6.5% to 8.5% copper in high silicon cast iron containing 13.5% to 15% silicon can improve the machining performance. The corrosion resistance is similar to that of ordinary high silicon cast iron, but it is worse in nitric acid. This material is suitable for making pump impellers and shaft sleeves with strong corrosion resistance and wear resistance. The method of reducing the silicon content and adding alloying elements can also be used to improve the machining performance. Adding chromium, copper and rare earth elements to silicon cast iron containing 10% to 12% silicon (called medium ferrosilicon) can improve its brittleness and processing properties. It can be turned, drilled, tapped, etc., and in many media, the corrosion resistance is still close to that of high silicon cast iron.
In medium silicon cast iron with a silicon content of 10% to 11%, 1% to 2.5% molybdenum, 1.8% to 2.0% copper and 0.35% rare earth elements are added to improve the machining performance, which can be turned and is resistant to Corrosion is similar to high silicon cast iron. Practice has proved that this cast iron is used as the impeller of the dilute nitric acid pump in the production of nitric acid and the impeller of the sulfuric acid circulating pump for the drying of chlorine, and the effect is very good.
The above-mentioned high-silicon cast irons have poor corrosion resistance to hydrochloric acid, and they are generally only resistant to corrosion in low-concentration hydrochloric acid at room temperature. In order to improve the corrosion resistance of high silicon cast iron in hydrochloric acid (especially hot hydrochloric acid), the content of molybdenum can be increased, such as adding 3% to 4% molybdenum to high silicon cast iron with a silicon content of 14% to 16%. Molybdenum-containing high-silicon cast iron will form a protective film of molybdenum oxychloride on the surface of the casting under the action of hydrochloric acid. It is insoluble in hydrochloric acid, which significantly increases the ability to resist hydrochloric acid corrosion at high temperatures. The corrosion resistance remains unchanged in other media. This kind of high silicon cast iron is also called anti-chlorine cast iron.
Due to its superior acid resistance and corrosion resistance, high-silicon cast iron has been widely used in chemical corrosion protection. The most typical grade is STSil5, which is mainly used to manufacture acid-resistant centrifugal pumps, pipes, towers, heat exchangers, containers, valves and cocks.
There are related to much more alloy elements for the high silicon cast iron, Anyang Huatuo Metallurgy can supply various type of ferro alloys such as FeSiMg,BaSi, etc, if you have any interests please contact us.