Preparation method for nodular cast iron

Abstract

The invention relates to a preparation method for nodular cast iron and belongs to the technical field of cast iron smelting. The preparation method comprises the steps that coke, limestone, pig iron, melt down steel and scrap steel with the mass ratio of 100: 30: (58-62): (26-30): (10-14) are smelted into iron liquid; nodulizing agents are made into ultrafine powder with the grain size of 1-25 micrometers, the ultrafine powder is wrapped into a first spherical nodulizing agent and a second spherical nodulizing agent with the diameters of 5-15 mm through steel boards, a first layer of nucleating agent is put into a nodulizing package, the first spherical nodulizing agent covers the first layer of nucleating agent, a pig iron scrap I covers the first spherical nodulizing agent, a second layer of nucleating agent covers the pig iron scrap I, the second spherical nodulizing agent, a pig iron scrap II and a third layer of nucleating agent cover the second layer of nucleating agent in sequence, and the iron liquid is poured for nodulizing and nucleating treatment; and the iron liquid is poured and subjected to heat treatment, and the finished nodular cast iron is obtained. The preparation method is convenient to implement and little in pollution, absorptivity of the nodulizing agents is high, the nodulizing effect is good, and the prepared nodular cast iron is high in intensity and good in toughness and size stability.

Description

technical field [0001] The invention belongs to the technical field of cast iron smelting, and relates to a preparation method of nodular cast iron. Background technique [0002] Ductile iron is spherical graphite obtained through spheroidization and inoculation treatment. Its comprehensive performance is close to that of steel. Based on its excellent performance, it has been successfully used to cast some parts with complex stress, high strength, toughness and wear resistance. [0003] In order to make the white ink in cast iron crystallize into spherical shape, nodularizing agent should be added when smelting molten iron. At present, in the field of industrial production, the main nodulizers are Mg, rare earth elements and Ca. Mg is the element with the strongest nodulizer ability and the most widely used nodulizer, but because the boiling point of Mg is much lower than the temperature of molten iron When used alone, it will violently gasify, resulting in low Mg absorptio...

AI Technical Summary

Problems solved by technology

The traditional process often adopts salt bath isothermal quenching to obtain bainite ductile iron with excellent toughness and wear resistance, and uses salt bath graded quenching to obtain martensitic ductile iron with high strength and high wear resistance. The process is mature and the production stability is high, but the one-time investment in production equipment is large, and the energy consumption in the production process is high

Moreover, the traditional austempering and graded quenching processes cause large deformation due to changes in internal thermal stress, structural stress and phase transformation stress, making it difficult to die-cast castings with more precise dimensions.

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