Preparation method of ductile iron

Abstract

The invention discloses a preparation method of a spheroidal graphite cast iron. The method comprises the steps as follows: using expandable copolymer resin particles with a grain diameter of 0.2 to 0.3 mm as original granular materials; performing pre-foaming and secondary foaming molding to obtain casting models, molding, drying and then combining the dried models to obtain a model group; performing sand filling and modelling on the model group, and butting the molded model group with an over mold spheroidizing device on a pouring cup; adding a spheroidizing agent into a reactor of the over mold spheroidizing device, wherein the spheroidizing agent is rare earth magnesium ferrosilicon alloy containing 6% to 8% of magnesium, and the quantity of the spheroidizing agent added into the reactor is 0.6% to 0.9% of the weight of molten iron; pouring the molten iron, namely molten metal obtained by melting QT400-18 spheroidal graphite cast iron raw materials into the over mold spheroidizing device; and then enabling the molten metal to flow into a casting mold cavity with modelling; cooling the product material alloy liquid for above 1 hour, and then turning over and cleaning the mold cavity to obtain the spheroidal graphite cast iron. The preparation method of spheroidal graphite cast iron can effectively realize the effect of inoculation treatment, and the obtained spheroidal graphite cast iron contains no white microstructure; besides, the processing steps are simplified, and the production cost is low.

Description

technical field [0001] The invention relates to a preparation method of nodular cast iron. Background technique [0002] At present, in the production process of ductile iron, the material needs to be spheroidized and inoculated. The function of spheroidized treatment is to make graphite grow into a spherical shape during crystal growth to improve the matrix morphology and improve the mechanical properties of castings. The purpose of inoculation is to eliminate White mouth, increasing eutectic groups and graphite balls and refining, eliminating segregation, eliminating the tendency of crystallization to be supercooled, etc. [0003] Especially in the production process of nodular cast iron, in the prior art, the above-mentioned spheroidizing treatment and inoculation treatment are generally required to obtain nodular cast iron with excellent mechanical properties. However, the above two treatment processes take a long time, and in the inoculation process, the inoculant is m...

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Problems solved by technology

However, the above two treatment processes take a long time, and in the inoculation process, the inoculant is mostly Si-Fe, and in order to improve the inoculation effect, special inoculation elements such as strontium, cerium, barium, titanium, and zirconium are added. agent

However, most of the above-mentioned elements belong to the field of precious metals, which increases the cost of incubation

[0004] In addition, during the two steps of spheroidization treatment and inoculation treatment, if the types and addition amounts of nodulizers and inoculants are not suitable, it is easy to cause the defects of spheroidization and inoculation decline, which seriously affect the quality and performance of products.

However, the current improvement schemes often focus on the formulas of nodulizers and inoculants. They did not expect to omit one of the steps to achieve the technical effect achieved by the original two steps. This is because, in the spherical In the process of spheroidization, the focus is often on the spheroidization, such as the performance of desulfurization and deoxidation capabilities. As for whether the spheroidizer itself can achieve the effect of eliminating white spots, and how to adjust the type and amount of nodulizer and the used The structural characteristics of the spheroidizing device itself to realize the spheroidizing and inoculating effects at the same time have not been reported or recorded in the prior art

It is difficult for those skilled in the art to think of how to control the reaction conditions to realize the two functions in the spheroidization process according to the prior art

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