Study On The Heat Treatment And Properties Of A New Alloy Wear Resistant Steel

In mining industry, large economic losses were always caused by the wear of the materials.For example, only for the liner materials of the mill, which would lose up to 20w tons due to the wear and tear every year. In this case,it is becoming more and more important to develop the wear resistant materials for reducing the wear consumption to improve mining productivity, save cost and expand the space of the mining.In the background of wet mill working condition, a new type of alloy wear resistant steel has been designed independently for wet milling. Firstly, the thermodynamic software which can simulate the phase composition of the material and the distribution of the alloy elements was used to design the composition of the new steel in order to understand the existent phase of the material at different temperature. And then, this new type material was prepared by melting and casting methods. The heat treatment process of the material was also designed and optimized. The impact of the different heat treatment process on the structure and mechanical properties such as hardness, impact testing and tensile testing of the designed materials were analyzed by metallographic observation, XRD analysis, SEM and EDS analysis. Finally, the effects of the different microstructure on wear resistant and corrosion resistant of the materials were studied with the part of the optimized materials.The results show that the pearlite transformation incubation period is extended greatly as the addition of the alloying elements. During the annealing process of shorter holding time, no pearlite was discovered. And when materials cooling with furnace temperature, the super-cooled austenitic will transform into the martensite that makes the hardness of the materials rise, not fall. Only the softening annealing without the phase transition can reduce the hardness of the material effectively and improve the machinability of the material. In the quenching process, the precipitation phase dissolve into the austenitic becomes better with the heating temperature rising while the lath martensite becomes bulky. As the doping of the alloy elements to stablelize the austenitic,the granular structure will be obtained during the isothermal quenching. The second phase will be precipitated and secondary hardening will occur in low temperature tempering to improve strength and toughness of the materias.The designed materials contain the elements of C 0.305%, Cr 1.504%, Cu 0.450%, Mo 0.479%,Mn 1.111%,Ni 0.944%,Si 0.695%,Nb 0.045% and V 0.092%. Comparing the consequence of the mechanical property, the optimized heat treatment process was determined to be 700? annealing, 900? oil quenching and 300? tempering. The hardness can be up to 51.6HRC, the tensile strength is 1600MPa, the impact toughness is 57.4J/cm2. The structure of the material is the tempered martensite with second phase. The wear resistant of this structure is better than the one of the granular structure which is obtained by the isothermal quenching, and the corrosion of this structure is also better.