Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallurgy ( Physical Metallurgy ) > Analytical tests of the metal (Metal Testing and Materials )

Microstructure and Properties of chromium cast iron grinding balls

Author MiaoShuSen
Tutor LiuYaoDong
School Changchun University of
Course Materials Processing Engineering
Keywords Alloying elements White Cast Heat treatment Microstructure Mechanical properties
Type Master's thesis
Year 2010
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In this paper, based on the role of chromium in the chromium wear-resistant cast iron, designed in three diameters of 110mm, different chromium content of chromium anti-wear cast iron ball; With metallurgical technology, electron microscopy, TEM technology, X-ray diffraction techniques and other analytical tools, macroscopic hardness, micro-hardness, impact toughness and wear performance comparison and analysis to explore the impact on the material properties of different chromium content; improved by two different means of heat treatment and high chrome anti- grinding microstructure and properties of cast iron, analysis of the organization and performance of the material after heat treatment changes on two different heat treatment processes on materials discussed and summarized. The results show that: the cast three-chromium cast iron eutectic structure are ledeburite low in chromium cast iron eutectic structure is relatively thick, high chromium cast iron eutectic structure is relatively small. With the increase in the chromium content, the three-chromium cast iron carbide type experienced by M3C to the M7C3 transition process, low-chromium cast iron carbide type M3C carbide honeycomb mesh distribution of chromium cast iron carbide type a mixture of M3C and M7C3 carbides lower number of chromium cast iron increased significantly, multi-needle distribution. High chromium cast iron carbide type to of M7C3 this high hardness carbide-based macro hardness of the material, the austenite transformation products and carbide micro hardness than low, high chromium, M 7 C 3 type carbide hexagonal rod-shaped and lath-shaped distribution in the matrix, continuous greatly reduced. Cast under high chromium cast iron hardness was significantly higher than the low in chromium cast iron, the surface hardness value reaches 53HRC, the three chromium cast iron impact toughness, no more than 4.73 J/cm2. On this basis, we designed two types of heat treatment programs heat treatment process on the microstructure of high chromium cast iron. The research shows that: the chromium content of about 15% of the high chromium cast iron using conventional heat treatment process, when the quenching temperature of 850 ° C, tempering temperature is 350 ℃, the microstructure and properties of high chromium cast iron, get to martensite Lord matrix, carbide type M7C3-based and more content was broken block, strip distribution. The surface hardness values ​​can be achieved 60HRC impact toughness 6.3J/cm2; isothermal quenching, austempering heat treatment process allows the high chromium cast iron martensite and acicular bainite matrix organization, Lower Bayesian close to the hardness of martensite, while the toughness than martensite, so that the high chromium cast iron, a good impact toughness. At a temperature of 320 ° C, such as quenching 1.5h, Earn ideal matrix organization, the hardness value of the material reaches 63HRC, impact toughness value of 8.4 J/cm2. By comparison, the isothermal quenching can effectively improve the performance of the organization of the material, can get better material impact toughness. Analysis found that fracture morphology of worn surface observation by the impact of high chromium cast iron, high chromium cast iron fracture is a brittle fracture, wear mechanism to abrasive wear. Etc. the austempering high chromium cast iron samples wear better performance than conventional heat treatment after the sample has good wear resistance.

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