Research Of Casting Process And Heat Treatment System Of High Chromium Cast Iron-Ductile Iron Composite Roll Material

Composite roll is the main consumption components of rolling mill in the rolling process which requires the abrasion resistance of the working layer and the toughness of the roll core at the same time.As one of the most commonly used composite roll,high chromium cast iron-ductile cast iron bimetallic composite roll has good prospects for development.In this paper,the thermodynamics calculation software was used to study the variation of the precipitates and the elements in the composites during the change of temperature and holding time.A 10kg—intermediate frequency vacuum induction furnace was used to study the effect of different process parameters on the compounding of liquid-solid bimetallic composites by changing the pouring temperature and volume ratio.The influence of heat treatment process on the composites was studied by heat treatment and microstructure and property tests.Specific studies are as follows:(1)Thermo-Calc calculation software was used to calculate the phase diagrams and properties of high-chromium cast iron with C and Cr elements respectively.The experimental results show that with the decrease of temperature,the final balance solidified structure of the high chromium cast iron is composed with a small amount of martensite and austenite and M7C3 type eutectic carbides.With the increase of Cr/C ratio in high chromium cast iron,the eutectic M7C3 type carbide and its transformation,M23C6 type carbides,are obviously increased.At the same time,the initial precipitation temperature of M7C3 carbides is not affected by carbon content or chromium content.The initial precipitation temperature of M23C6 carbides decreases with increasing carbon content and increases with the increase of Cr content.The results show that with the increase of C and Cr content,the content of austenite in high chromium cast iron decreases gradually and the higher the temperature is,the higher the austenite content is and the M7C3 type carbide content in high chromium cast iron increased gradually and the higher the temperature is,conversely the lower the M7C3 type carbide content is.(2)The experiments of bimetallic liquid-solid composite experiments were carried out by using 10kg vacuum induction furnace.The diameter of ductile iron was selected as ?30mm,?35mm,?40mm,and the casting temperature was 1520 ?,1550 ?,1580 ? and 1600 ?.The results show that the smaller the diameter of the core material is and the higher the pouring temperature is,the better the combination of the two materials is,but both the core material diameter being too small or the pouring temperature being too high are not conducive to the actual production.(3)The experiments show that cast structure of high chromium cast iron is austenite and M7C3 type carbide and a small amount of martensite with the metallographic microscope,which is in accordance with the thermodynamic calculation results.Using the box type resistance furnace for the composites being heat-treated to study the effects of quenching process and tempering process on the microstructure and properties of the composites shows that the high temperature quenching at 925 ? for 2h and the quenching by fog can not only make the outer high chromium cast iron reach a high hardness but also allow the strength and impact toughness of roll core ductile iron tensile to still meet the target and make the elements of the bonding interface spread and the interface width enlarged which thereby enhance the interface performance.450 ? tempering after quenching can ensure high-chromium cast iron still maintain a high hardness and does not affect the performance of ductile iron and interface.