Production method of vermicular graphite cast iron

Abstract

The invention discloses a production method of vermicular graphite cast iron. The production method includes the following steps that vermicularizing treatment is performed on one bag of molten iron by the aid of a rare-earth alloy, and vermicular graphite is formed; spheroidizing treatment is performed on the other bag of molten iron by the aid of a magnesium alloy, and spheroidal graphite is formed; the two bags of molten iron are mixed, the residue amount of magnesium in the mixed molten iron is smaller than that of rare-earth, and thus the vermicular graphite cast iron is produced. According to the technical scheme, flake graphite in the cast iron is eliminated, the vermicularity is stable, the high vermicularity and the high strength are ensured to coexist, and the extensibility of the vermicular graphite cast iron is greatly improved.

Description

technical field [0001] The invention relates to the technical field of casting, in particular to a production method of vermicular graphite cast iron. Background technique [0002] The mechanical properties of compacted graphite cast iron are between gray cast iron and ductile iron, and have good comprehensive properties. For castings that work under hot conditions such as cylinder blocks and cylinder heads of high-power engines, it has become a development trend to use vermicular graphite cast iron instead of gray cast iron for production. In the production of vermicular graphite cast iron, the requirements of high vermicularization rate and high strength must be guaranteed at the same time. The vermicularization methods currently used include: adding in furnace, pouring into ladle, feeding wire and inoculating with secondary tapping liquid treatment. According to the traditional creeping treatment method, it is difficult to ensure high creeping rate and good comprehensive...

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Problems solved by technology

According to the traditional creeping treatment method, it is difficult to ensure high creeping rate and good comprehensive performance at the same time. Foreign countries generally use high-precision thermal analyzers to control creeping rate

However, this method is costly, the creep rate changes rapidly, and the control range of residual rare earth and residual magnesium is narrow

Without high-quality raw materials and high-precision analytical instruments, it is difficult to ensure the stable production of high creep rate and high performance compacted graphite iron castings

At present, in the metallographic structure of vermicular graphite cast iron with high vermicularization rate, flake graphite often appears, and the appearance of flake graphite will reduce the strength of vermicular graphite cast iron, thus causing the production of vermicular graphite cast iron in my country, it is difficult to ensure high vermicularity The coexistence of high efficiency and high strength limits the development of vermicular graphite cast iron in my country

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