Study On Microstructure And Properties Of High Porformance Steel For Grinding Rod

As the grinding medium in the rod mill,the grinding rod is widely used in the production process of metal and nonmetal ore.At present,most domestic grinding rod exist many problems,such as poor wear resistance,large amount of wear,adding and taking out the rods frequently when the rod mill is in operation and so on.These problems will increase the cost of grinding process and reduce the production efficiency of the rod mill.For these reasons,it is significant to develop a new type of high performance grinding rod by designing the rational alloy component and developing the reasonable microstructure control technology in order to improve the operation efficiency of the rod mill and reduce the production cost.Based on the thermodynamic theory of Fe-Cr-C system and the basic principle of phase equilibrium calculation,this paper carried out the thermodynamic calculation of the equilibrium of austenite and M7C3 in the Fe-Cr-C system and determined the variation relationship between the amount of M₇C₃ carbide and the composition of austenite with the austenitizing temperature in the alloy steel.And the composition design and the heat treatment process of the test steel were carried out on this basis.In this research,the microstructure and properties of different chromium and manganese content of the test steel after forging and different heat treatment were studied and the regulation of controlling the quantity and morphology of the carbide in high performance steel for grinding rod is analyzed and summarized.And then the wear resistance of the test steel was evaluated by the wear resistance test.The results showed that the coarse austenite grains formed during the high temperature heating for forge has been well refined by forging at large forging ratio.As the forging ratio increased from 1.2 to 4.8,the grain size of austenite grains have increased by more than 4;the hardness distribution and impact toughness of the test steel have been also significantly improved.Taking the test steel rods with 100 mm diameter that forged and air cooled as the specimen,this paper established the optimizing technology to control the microstructure of the test steel.After the treatment by this optimizing technology,a large number of dispersed M₇C₃ carbide can be obtained in the matrix structure of 2#and 3#test steel and the microstructure of fine and uniform martensite matrix can be obtained by air cooling,which meets the requirements of the microstructure and performance of the grinding rod.The phase structure of the test steel was identified by XRD,and the microstructure of 2#and 3#steel was mainly composed of martensite and M₇C₃.Among the all three kinds of test steel,1#has poor hardenabibility because of its low content of chromium and manganese,so the large quantity of the non martensite in 1#test steel rod with 100 mm diameter is exhibited after air cooling.Because of the high chromium content in 3#test steel,using 3#as a grinding rod will raise the production cost.Therefore,considering these reasons,2#test steel is the most suitable test steel as a grinding rod in all three types of test steel.Under the same wear conditions,the wear resistance of 2#test steel is much larger than the current wear-resistant grinding rods.