Pipe nodular cast iron manufacturing method

Abstract

The invention belongs to the technical field of casting and relates to a pipe nodular cast iron manufacturing method. The method comprises iron liquid melting preparation, nodulizing and inoculation treatment. The pipe nodular cast iron greatly improves high temperature creep resistance and creep fracture resistance of a casting, has cyclic failure frequency of 410-440 times at a thermal cyclic temperature of 500-600 DEG C, has high temperature tensile strength of 130-140N/mm<2> at a temperature of 600 DEG C, and has tensile strength of 620-650N/mm<2>, yield strength of 500-530N/mm<2>, elongation percentage of 4.5-5.5%, hardness of 245-255HB and a yield ratio of 0.8-0.9 at a room temperature. The pipe nodular cast iron has a high yield ratio and good heat resistance, reduces casting deformation probability, prolongs a service life and satisfies requirements on high temperature mechanical properties and antioxidation performances of nodular cast iron.

Description

technical field [0001] The invention belongs to the technical field of casting, and in particular relates to a method for manufacturing ductile iron for pipe fittings. Background technique [0002] In recent years, out of the consideration of protecting the environment and saving resources, increasing the compression ratio, improving fuel combustion efficiency and reducing emissions, new requirements have been continuously put forward for automobile engines. In order to adapt to the application of catalytic technology and turbocharging technology And the exhaust temperature of the engine continues to rise, and the requirements for the high-temperature mechanical properties and oxidation resistance of the exhaust manifold of the automobile engine are getting higher and higher. Therefore, the high-temperature resistance requirements of the exhaust manifold of the automobile engine have reached 900 ℃ However, the existing domestic exhaust manifold materials generally can only m...

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Problems solved by technology

[0002] In recent years, out of the consideration of protecting the environment and saving resources, increasing the compression ratio, improving fuel combustion efficiency and reducing emissions, new requirements have been continuously put forward for automobile engines. In order to adapt to the application of catalytic technology and turbocharging technology And the exhaust temperature of the engine continues to rise, and the requirements for the high-temperature mechanical properties and oxidation resistance of the exhaust manifold of the automobile engine are getting higher and higher. Therefore, the high-temperature resistance requirements of the exhaust manifold of the automobile engine have reached 900 ℃ However, the existing domestic exhaust manifold materials generally can only meet the requirements for use at a temperature of about 750°C; with the further improvement of engine performance, especially the continuous improvement of turbocharging technology, the exhaust manifold The working temperature will also increase. In addition, the exhaust manifold has been working in a high temperature cycle for a long time, the heating temperature is uneven, the difference between the surface layer and the inner cavity is hundreds of degrees, and the working conditions are harsh. The oxidation resistance of the exhaust manifold material at high temperature The performance directly affects the service life of the exhaust manifold. The tensile strength of ordinary ductile iron materials is only about 50N / mm2 at a temperature of 650°C. The number of times is about 100 times, and the high-temperature creep resistance and creep fracture resistance are poor, which can no longer meet the high-temperature mechanical properties and oxidation resistance requirements of exhaust manifold materials.

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