Development Of Bimetal Wear-Resistant Hammerhead

Abrasion is one of the main reasons for the failures of mechanical parts during the operation of mechanical equipment.It not only wastes resources,reduces the safety and reliability of equipment,but also reduces productivity and increases the cost of production.Hammer is a sort of accessory widely used in mining machines.Developing of high-performance wear-resistant hammer has always been an important content in the field of materials.In this paper focuses on the actual questions of poor wear resistance and bad toughness of the existing high manganese steel hammer in enterprise and combined with the low hardness of the supplies,then developed a double liquid bimetal composite casting wear-resistant hammer.The experiment project of this paper is the orthogonal test method with four factors and three levels.Based on the test of Rockwell hardness and impact toughness,the impact of four factors on the comprehensive score has been determined as follows:Cr（wt.%）>tempering temperature>quenching temperature>C（wt.%）.The influence of sample microstructure on the wear-resistant performance was analyzed by means of metallographic,SEM,EDS and XRD.By experiments,the alloy composition with the best performance is2.8%C,20%Cr,0.8%Si,1.0%Mn,1.5%Mo,0.8%Cu.And the heat treatment process is that holding at 710°C for 0.5 h,then austenitizing at 1040°C for 2 h,air cooling,and low temperature tempering at 250°C for 2 h.The phase composition under the above conditions becomes（Fe,Cr）₇C₃,martensite,retained austenite and pearlite.And the corresponding properties of the alloy are:60.17 HRC,andαk=9.88 J/cm².Based orthogonal test,the effect of rare earth addition on the properties of high chromium cast iron was studied by single factor method.It had a certain adsorption effect about O and S element.But it would reduce the wear resistance of high chromium cast iron.According to the shape and size of the product,the ProCAST software was used to analyze the temperature field of the filling and solidification process of the wear-resistant end of the hammer,and the defects were analyzed also.The results shows that both the integrated design of casting and riser and the separate design of casting and riser can effectively reduce casting defects and meet process performance requirements.Considering the production costs,the process scheme with integrated pouring and pouring design is optimal,and the possibility of shrinkage defects was low.On the basis of composition and process optimization and modeling results,the high chromium cast iron-high manganese steel dual liquid bimetal composite hammer head was prepared by continuous casting using the lost foam casting process.The pouring temperature of high manganese steel is 1550℃,and the pouring temperature of high chromium cast iron is 1450℃.The metallographic and SEM images and EDS was analyzed on the composite hammerhead,it is founded that the bimetal achieves good metallurgical bonding,and the average thickness of the bonding layer is 555μm.Heat treatment has no effect on the thickness of the bonding layer of the double liquid bimetal composite hammer,but the elements of C,Cr and Mn have diffusion certainly.The bimetal wear-resistant hammer developed in this experiment has a unit wear rate of 0.40 g/m²·h at room temperature.Compared with the samples provided by the manufacturer,the wear resistance is improved by nearly four times.The test results have been applied to production and have started trial use.