Abstract
Heat-resistant cast iron, also known as heat resistant cast iron or heat resistant alloy cast iron, is a kind of cast iron material with strong heat resistance and high strength at high temperature. Its basic components are 2.5%-4.5% carbon and 11%-30% chromium, and some other impurities. Heat-resistant cast iron is mainly used in areas where high temperature requirements or extreme temperature changes exist, such as turbine casing of thermal power plants and exhaust pipe of internal combustion engines. The introduction of GB 9437-88 standard for heat-resistant cast iron parts describes the material requirements, testing methods, technical requirements and other information related to heat resistant cast iron parts.
Introduction
Heat-resistant cast iron (also known as chromium cast iron or heat-resistant alloyed cast iron) is a kind of cast iron material with strong heat resistance, high strength at high temperature and wear resistance. The main components of it are 2.5% ~ 4.5% carbon and 11% ~ 30% chromium, plus some other impurities. Heat-resistant cast iron has the characteristics of good thermal fatigue resistance, crack resistance and wear resistance, so it is used in areas where the requirements of high temperature or rapid temperature changes exist (such as turbine casings of thermal power plants and exhaust pipes of internal combustion engines). To standardize the production process, the national standard (GB 9437-88) for heat-resistant cast iron parts has been formulated to ensure the quality of heat-resistant cast iron parts.
Material Requirements
According to GB 9437-88, the materials for heat-resistant cast iron parts shall be the sub-class of chilled cast iron AJ40, AJ40-M, AJ46 or AJ46-M. These cast irons contain 2.5% - 4.5% carbon, 11% - 30% chromium, 0.15% - 2.0% silicon, and aluminum, manganese and molybdenum in small quantities. The gray cast iron SFM, SFHT and JM grade cast irons may also be used as specified.
Testing Methods
The tensile strength, yield strength, Brinell hardness and impact value of heat-resistant cast iron parts shall be tested according to specified test methods, and the test results shall meet the requirements of GB 9437-88. Metallographic examination shall be performed to detect chemical composition and spheroidization rate of the material.
Technical Requirements
GB 9437-88 specifies that the allowable deviation range of the cast iron parts dimensions, axis ratio and relative position of the adjacent surfaces shall meet the pre-designed scale. The appearance of the cast iron parts shall be clean and without sand holes, burrs and cracks. Heat treatment processes such as normalizing and tempering shall be carried out. The residual ash of cast iron parts shall not exceed 0.15%.
Conclusion
Heat-resistant cast iron has excellent mechanical properties and good heat-resistance, so it is widely used in high-temperature or rapid-temperature-change areas. GB 9437-88 is the national standard for heat-resistant cast iron parts, which regulates the material requirements, testing methods and technical requirements of heat-resistant cast iron parts. The production of heat-resistant cast iron parts shall strictly conform to the requirements of GB 9437-88 to ensure the quality of the parts.
