The Development And Research Of Cr-Mo Alloy Steel Liner For Super-large Semi-autogenous Grinding Mill

In this paper,a kind of Cr-Mo alloy steel liner for ultra-large semi-autogenous grinding mill with a diameter of more than 10 m was studied.SEM,TEM,and mechanical property tests are used to study the mechanics properties,microstructure and precipitated carbides of different heat treatment processes on the Cr-Mo series alloy steel lining.Combined with the analysis of microstructure and mechanical properties,it is confirmed that the optimal heat treatment process is 920 ? quenching and 600 ? tempering.The quenching structure is acicular martensite,and the quenched structure is tempered sorbite and a small part of twins.Its mechanical properties are hardness 388 HBW,impact energy 55 J,tensile strength 1295 MPa,elongation 4.5%.The types of precipitated carbides are M2 C,M3C,M7C3 and M23C6,and the main forms are small particle,long strip and block.The effects of Ni and V alloy elements on the microstructure and mechanical properties of Cr-Mo alloy steel liner were analyzed.The results showed that the fine grain and solid solution strengthening of Ni and V alloy elements increased the tensile strength of the material by 12%,the hardness by 20% and the impact energy reduced by 6 J.Mechanical properties of large castings of Cr-Mo alloy steel liner 322 mm×446mm×240 mm were tested in different parts after heat treatment.The surface tensile strength of the liner is 1205 MPa,the yield strength is 958 MPa,the elongation after fracture is 6%,the reduction of area is 15%,the hardness is 348 HBW,and the Impact energy is 57 J.The core tensile strength of the liner decreased by 27%,the elongation after fracture decreased by 64%,the reduction of area decreased by 93%,the impact energy decreased by 38%,and the hardness decreased by 2%.From the surface to the core,the strength and toughness gradually decayed,but the hardness was not affected.The nano-indentation hardness of Cr-Mo alloy steel liner matrix reached 5.6 GPa,and the young's modulus was 234 GPa.Three groups of test steels containing Ni and V alloy elements at 600 ?tempering and 620 ? tempering,without Ni and V alloy elements at 600 ? tempering were subjected to abrasion tests at an impact energy of 3.5 J by an impact wear tester.The results show that the abrasion resistance of the test steel containing Ni and V alloy elements is the best,and the relative wear resistance is 1.13 times that of the test steel without Ni and V alloy elements.Fatigue wear is the main form of wear in impact wear tests.