Research On The Structure And Property Of The New Kind Heat-resistant Grate

Grates as an important part in reciprocating grate is used for MSW incineration. Toproducing grates with high-performance is one of the key technologies to the manufacture ofa massive MSW incinerator. The current domestic grates are mainly reling on imports,whichcasuse a large cost.While the domestic grates does not meet the conditions of MSWincineration or with a higher costs. The working conditions,main failure mechanism of gratesin the MSW incinerator and researching status of heat and wear resistant alloys with highpercent of Cr,both at home and abroad,were investigated.Based on these,the wear resistantalloys with high percent of Cr is choosed to be research object for grates matrial incombination with the mineral resources reserves in China.And then,the effect of elements onthe structure and performance of this heat and wear resistant alloy were analysised. Combinedwith the schaeffler diagram,three kinds of grate material were designed according to theworking condition of grate.The grate materials designed were made by Medium-frequencyinduction furnaces and sand casting.The morphology,chemical composition, organizational stability, thermal expansioncoefficient, hardness, toughness, tensile strength at room temperature and high temperature,high-temperature oxidation performance and wear characteristics of alloys were tested andanalysed using universal tensile testing machine, LeicaDMI5000M metallographicmicroscope, scanning electron microscopy, electron microprobe, x-ray diffraction, differentialthermal analysis and other research methods.The results indicates that, in actual castingcondition, the structure of ZG30Cr26Ni4consists of ferritic matrix,small amount of austeniteand very small amount of （Cr,Fe）₂₃C₆and （Cr,Fe）₇C₃, the structure is stable at hightemperature; the structure of RTCr28Ni4consists of austenite matrix, and （Cr,Fe）₂₃C₆distributes along anstenite’ crystal boundary discontinuity,and small amount of （Cr,Fe）₇C₃,the structure is stable at high temperature; the structure of RTCr18consists of alloypearlite matrix, more amount of （Cr,Fe）₇C₃,less amount of （Cr,Fe）₂₃C₆distributes alongpearlite’ crystal boundary discontinuity and a small amount of residual austenite,the structureis not so stable at high temperature. Three types of alloy’s coefficient of thermal expansion arein the same level and all with high tensile strength at room temperature.The hardness and hightemperature tensile strength of ZG30Cr26Ni4is lowest, but has best toughness; RTCr18hasthe highest hardness, lowest toughness and high temperature tensile strength; the hardness andtoughness of RTCr28Ni4is between ZG30Cr26Ni4and RTCr18, also has the highest hightemperature tensile strength. The oxidation kinetics curves at950℃of the three alloys are accord with parabola, the content of chromium and Silicon casuse major impact to thecomposition of oxide film and its formation mechanism,by contrast, the RTCr28Ni4has abest antioxidate performance at950℃due to its dense oxide film and the oxide film attachedto the matrix strongiy, followed by ZG30Cr26Ni4and RTCr18. The alloy of RTCr28Ni4has aexcellent wear resistance performance most than ZG30Cr26Ni4and RTCr18.Among the three kinds of grate material, RTCr28Ni4is a good material with excellentcomprehensive properties on tensile strength at room or high temperature, toughness,structure stability at high temperature, high temperature oxidation resistance and wearresistance.