Hereditary Effect Of Needle-Like Carbide In Primary Material On Low Chromium White Cast Irons

In this paper, the history and present status of metal heredity were introduced and the reason that the low chromium cast iron showed high rate of reduction owing to the needle-like carbide were analyzed. Then, on the basis of studying the influence of the needle-like carbide heredity in the primary material on the structure and property of the low chromium cast iron, the hereditary mechanics of the needle-like carbide were analyzed and the poor hereditary effect of needle-like carbide were improved. The morphosis, constitution and micro structure of primary material and low chromium cast iron were detailedly investigated by means of optical microscope, SEM, TEM etc. The measures for removing the heredity of needle-like carbide were investigated using different technology, such as remelting, overheating and electromagnetic stirring. The theory was provided for studying the hereditary effect of casting alloy and increasing the service life of wear resistant material.Through the research of the hereditary mechanism of needle-like carbide, it was found that the same structures were also found in the low chromium cast iron when there was needle-like carbide in the primary material. In particular, the hereditary effect of needle-like carbide in low chromium cast iron were most obvious when primary material was the complete chill pig iron or the returns. The constitution and the microstructure of the primary material were analyzed as well as the low chromium cast iron sample. The results showed that the elements in primary material were C and Fe and the needle-like carbides in the low chromium cast iron samples contains C, Fe and Cr. It is important the microstructure of needle-like carbide were both the orthorhombic in the primary material and low chromium cast iron sample. It was proved that needle-like carbide possessed the visible hereditary effect.The improvement of hereditary effect of the needle-like carbide was studied by means of remelting, overheating and electromagnetic stirring. The results showed the above three kind of technologies all weakened the hereditary effect to some degrees, the needle-like carbide sizes were lessened and the quantities were increased with the remelting times. And also, the sizes and quantities of the needle-like carbides were decreased by increasing the melting temperature and the magnetic density. It was found that the influence of electromagnetic stirring on improving the heredity of needle-like carbides and the mechanical property of the low chromium cast iron was better than the remelting times and overheating temperature.