| The grinding roller of large-scale standing grinding machines would undergomultidirectional impact and repeated abrasive wear during grinding, for which urgesthe materials used have enough ductility as well as high strength and hardness.However, the single kind of material present applied in the above grinding roller, isdifficult to satisfy the properties requirements. Thus, the aim of this research is todevelop a kind of composite grinding roller of steel bonded carbide embeddedmulti-element low alloyed wear-resistant steel by duplex metal composite technology,in which a low alloyed wear-resistant steel ZG32MnCrMoNi is used for matrixmaterial and WC-based hard alloy for the embedded materials.The effects of heat treatment on microstructure and mechanical properties of thelow alloyed wear-resistant steel ZG32MnCrMoNi were investigated and thecorresponding heat treatment parameters were optimized. Moreover, according to theworking condition, thickness and characteristic of effective rolling area, the test blockstructure of embedded hard alloy on multi-element low alloyed wear-resistant steelwas analyzed and designed, as well as its embedding composite processing wasstudied.Multi-element low alloyed wear-resistant steel was respectively heat treatedthrough following two kinds of techniques: normalizing+quenching+tempering andannealing+quenching+tempering. The results have shown that the microstructuresof the samples heat treated with normalizing as preheat treatment are more tiny andhomogeneous. And the mechanical properties and wear resistance are improved.However, tensile strength and hardness gradually decrease with the temperingtemperature increasing, while impact toughness and wear resistance increase firstlyand then decline.According to the above experimental results, the optimized heat treatmenttechnique of multi-element low alloyed wear-resistant steel ZG32MnCrMoNi is900°C normalizing+900°C quenching+300°C tempering. The microstructure ofZG32MnCrMoNi steel after the mentioned heat treatment is mainly composed of martensite, retained austenite and a quite small amount of carbides, and the tensilestrength, elongation, impact toughness and hardness of the steel are1532.5MPa,5.5%,19.0J/cm2and46.3HRC, respectively.The carbide rod was designed to be cone-bar shape with a dimension of Φ12（13）×40mm according to the effective rolling zone characteristics of the prototypeof cone rod roller. The end with larger dimension of the carbide rod is toward to theinside of the roller which was preset into water glass sand. The results have shownthatWhen the pouring temperature is1550~1570°C and volume rate of embeddedhard alloy to base steel is1.7:10, the cracks were found at the bottom surface of theembedded hard alloy and the bonding mode between hard alloy and steel belongs tomechanical bond. When lowing the volume rate of embedded hard alloy and baseplant to1.1:10, the bottom quality of embedded hard alloy was improved evidentlyand the combined interface between hard alloy and steel have obvious metallurgicalbonding area of the average thickness about150μm. When further declining thevolume rate of embedded hard alloy and base plant to0.8:10, good bottom qualitywas obtained, in addition, the combined interface has obvious metallurgical bondingarea, belongs to the metallurgical bond.When the volume rate of embedded hard alloy and steel is1.1:10, and thepouring temperature is1520~1540°C, bottom quality of embedded hard alloy waspoor, which belongs to the mechanical bond. When rises the pouring temperature to1550~1570°C, embedded hard alloy showed a preferable bottom quality, in whichthe combination interface have obvious metallurgical bonding area. When furtherincreases the pouring temperature to1580~1600°C, the bottom quality of embeddedhard alloy was poor with adhering sand. Moreover, the combined interface hasobvious metallurgical bonding area, belongs to the metallurgical bond.The composite grinding rollers blank were experimentally manufactured by theabove optimized embedding process parameters of carbide embedded multi-elementlow alloyed wear-resistant steel technology in Zhengzhou Dingsheng EngineeringTechnology Co., Ltd., which were heat treated with900°C normalizing+900°Cquenching+300°C tempering. The manufactured grinding rollers were applied by cement plant of Dengfeng Electricity Group Co., Ltd. and Shanxi TianshiConstruction Materials Co., Ltd. and the results show that the service life of the abovegrinding roller is2times higher than that of grinding roller produced by building-upwelding technology of multi-element low alloyed wear-resistant steel. |
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