Nodular cast iron inoculant and preparation method thereof and application in smelting nodular cast iron

Abstract

The invention relates to a nodular cast iron inoculant and a preparation method thereof and an application in smelting nodular cast iron. The nodular cast iron inoculant consists of 3-6% of Bi, 40-50% of Si, 0.5-3% of Ba, 0.1-3% of La, 10-18% of Ca, 1-3% of O, 0.5-3% of S and the balance of Fe and unavoidable trace elements. The nodular cast iron inoculant is prepared by the steps of mechanically mixing a metal oxide, a metal sulfide and a silicon iron-based alloy; adding an adhesive into a grinding device, and pressing the mixture into a cluster; breaking the cluster, screening and wrapping with an aluminum foil. In use, when the output molten iron accounts for about 1/2 of the lip-pour ladle, the inoculant is added to perform inoculation treatment on the nodular cast iron once or multiple times. The inoculant provided by the invention contains the trace elements such as O, S, Bi and the like and is low-silicon and efficient, and multiple heterogeneous nucleation mass points are formed in the iron liquid, thereby increasing the graphite quantity, improving the shock resistance, mechanical property and yield, increasing the utilization rate of foundry returns, and increasing the economic benefits.

Description

technical field [0001] The invention relates to a molten iron treatment technology for smelting ductile iron, in particular to a nodular cast iron inoculant, a preparation method thereof and an application in smelting ductile iron. Background technique [0002] Ductile iron is an important engineering material. Because the mechanical properties of ductile iron are close to those of steel, many steel castings and forgings are replaced by ductile iron. Therefore, ductile iron has been widely used in industry. In order to achieve good mechanical properties, the following methods can be used: heat treatment, alloying, and inoculation treatment. Among them, inoculation treatment is a relatively simple, economical and effective method. It not only promotes graphitization, prevents free cementite and white pits from appearing, but also helps spheroidization, making graphite smaller and more rounded. The distribution is more uniform, thereby improving the comprehensive mechanical p...

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Problems solved by technology

[0003] There are two types of inoculants for cast iron: carbon-based and silicon-based. Carbon-based inoculants have the advantages of strong graphitization ability and slow decay, but their melting point is high, and they have to be processed above 1450 ° C. It is difficult to use them in production. Therefore, at present, they are mainly Ferrosilicon is used as the basic inoculant. 75SiFe is commonly used in production, but its inoculation effect is poor. In order to eliminate free cementite, a large amount needs to be added. In order to control the final silicon content, the silicon content of the original molten iron must be reduced. This brings certain difficulties to the application and batching of recycled materials, which seriously restricts the utilization rate of recycled materials in the production process, resulting in a large backlog of recycled materials, which causes a lot of waste in industrial production; in addition, the inoculation of 75SiFe The decay speed is fast, and the thick and large parts or the thick parts of the same casting are prone to thick and distorted graphite balls due to slow cooling rate and long solidification time, and even form vermicular graphite or fragmented graphite, thereby significantly reducing the mechanical properties

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