Heat resistant cast iron is a kind of cast iron used at high temperature, because of its good oxidation resistance, growth resistance and heat fatigue resistance. Usually, Cr, Si, Al are the main elements to maintain its heat resistance, especially when the use temperature is about 1200K, Al seems to be essential. The application of aluminum refractory cast iron is limited due to its brittleness and poor heat and fatigue resistance. The influence of rare earth elements on the tissue and mechanical properties of ordinary cast iron has been reported, but the influence of Ce on the tissue and mechanical properties of aluminum refractory cast iron has still been rarely studied
"Growth" refers to the oxidation caused by the penetration of the oxidizing gas along the boundary of the graphite sheet and the cracks, and the volume expansion of the casting caused by the graphitization due to decomposition. Adding aluminum, silicon, chromium and other elements to the cast iron forms a dense layer of silica, aluminum oxide film on the surface of the cast, which can significantly improve the antioxidant capacity at high temperature and make the matrix of cast iron into a single phase ferrite. In addition, silicon and aluminum can improve the phase change point, so that they do not undergo a solid phase change at the working temperature, and can reduce the resulting volume changes and micro-cracks. Chromium can form a stable carbide and improve the thermal stability of cast iron. The commonly used heat-resistant cast iron has medium silicon cast iron, high chromium cast iron, nickel chromium silicon cast iron, etc., mainly used in the manufacture of heating furnace accessories, such as furnace bottom plate, chain components, heat exchanger, etc.
1. Silicon system is heat-resistant to cast iron(RTSi5)
This material is the oldest kind of silicon cast iron in sheet graphite, the mechanical properties decreases with the increase of silicon content at room temperature, and decreases sharply with Si> 6.5%. However, the total amount of carbon and silicon is a constant value. If Si is high, C will be discharged, which should be paid special attention to.
2. Chromium system is heat-resistant to cast iron
With heat resistant cast iron, improving the carbon content is conducive to the heat resistance under wear conditions; increasing the silicon content will increase the antioxidant capacity, but reduce the high temperature strength and thermal stability, so the Si content generally does not exceed 4%.
3. Aluminum system is heat-resistant to cast iron
Aluminum heat-resistant cast iron, with the increase of Al content, heat resistance is also increasing, but the range of use is not large, because there is no satisfactory processing performance, with the lowest mechanical properties and great brittleness.
4. Nickel-series of heat-resistant cast iron
High nickel austenitic cast iron, due to good heat impact resistance, high temperature strength and creep resistance, as well as good heat resistance, has attracted more and more attention in China. And because it has good impact toughness at room temperature and high temperature, can prevent brittle break, with it to replace silicon, silicon aluminum and chromium system heat-resistant cast iron is promising
