The rocker arm of a coal mining machine is a key component that connects the spiral drum and the body. Under service load, the rocker arm shell is in a state of energy excitation under tension compression cyclic stress and complex impact stress for a long time, which leads to residual stress being concentrated in areas such as weak stiffness and variable cross-section, causing local or partial deformation or fracture of the shell. As a large and complex shaped steel casting, the shape stability and fatigue strength of the rocker arm shell are directly influenced by theof the casting products manufacturers. ZHY Casting et al. pointed out through on-site testing and finite element analysis that optimizing the casting process of material and casting products manufacturers can effectively improve the quality of rocker arm casting. ZHY Casting has proposed a casting process plan for the rocker arm shell of the 3050 coal mining machine. Lv Ruilin and others have made a series of improvements to the material of the coal mining machine rocker arm shell and the casting process of casting products manufacturers, improving the tensile and yield strength of the rocker arm shell. Wang et al. designed a casting process plan for a certain type of coal mining machine rocker arm shell by casting products manufacturers through multiple process analyses and selection of various process parameters.
ZG20SiMn cast steel has high strength, good plasticity and toughness, and is mainly used in the manufacturing of heavy machinery parts that bear large loads, such as frames, body shells, etc. ZHY Casting improved the microstructure and mechanical properties of steel castings by increasing the cooling rate after normalizing, and developed a reasonable heat treatment process for ZG20SiMn cast steel. ZHY Casting studied the fatigue behavior of ZG20SiMn cast steel under strain control mode and determined the effect of applied strain amplitude on the cyclic deformation and fracture behavior of the material.
In order to avoid quality problems such as deformation and cracking of large and complex shell components, and to improve equipment service safety, casting products manufacturers have conducted extensive research and optimization on the casting process of large and complex components by domestic and foreign scholars. Wang Chengjun and others proposed an optimization plan for the process of coal mining machinerail cast steel parts using the innovative solution tool of the material field model. Jiang Jufu et al. used ProCAST software to simulate the temperature field, stress field, and defect distribution during the filling and solidification process of A356.2 aluminum alloy car wheels under local casting technology. Ma Zhengyu used the joint simulation technology of ProCAST and ABAQUS software to study the dynamic evolution process of residual stress in marine diesel engine body from casting to heat treatment. Cheng Yazhen et al. analyzed the temperature and stress distribution characteristics of a thin-walled complex titanium alloy steel casting and proposed the process requirements for thin-walled complex castings. Liu Yang et al. verified through simulation of the stress field of steel castings after sand drop that the casting process can generate a large amount of residual stress on the machine bed. Bohacek et al. simulated the filling and solidification process of a large centrifugal casting work roll shell and explained the behavior of metal liquid filling and spraying. Aneesh et al. proposed a thermal simulation model that effectively eliminates steel casting defects generated during the gravity casting process of engine cylinder blocks. Kermanpur et al. used k- ɛ The turbulence model and D’Arcy model are used to simulate the filling and solidification processes of automotive steel castings. Aravind et al. effectively reduced casting defects in the centrifugal pump crankcase by changing process variables and modifying the position of the core pin. Reddy conducted simulation research on the casting process of automotive wheels using ProCAST software, exploring the solidification behavior of materials and the detection of hot spots in steel castings.
Foundry product manufacturers are concerned about the large volume and obvious irregular structure of the rocker arm shell. The temperature and stress evolution laws during the casting process are not yet clear, and casting defects still need to be improved. Therefore, taking the MG325 coal mining machine rocker arm shell in the thin coal seam of Yangcun coal mine in Yanzhou mining area as the research object, the casting products manufacturers designed the top and bottom injection rocker arm shell casting process schemes, and used ProCAST software to numerically simulate the filling and solidification process of the rocker arm shell steel castings. The casting products manufacturers analyzed the temperature field, stress field, and defect distribution of the rocker arm shell, and analyzed the pouring system using the Niyama criterion. Foundry product manufacturers optimize the structure and parameters based on casting process schemes with lower defect rates, providing a basis and technical support for reducing casting defects and residual stress control of the coal mining machine rocker arm shell.
1) During the filling process of rocker arm shell steel castings by casting products manufacturers, the filling temperature of the bottom injection process scheme is lower than that of the top injection process scheme; When the solid-phase ratio during the solidification process exceeds 80%, the temperature rapidly drops to the solid-phase line.
2) Casting products manufacturers have shown through simulation that there are obvious isolated liquid phase zones at the bottom of the output end hole in the rocker arm shells cast by both process schemes. According to the Niyama criterion analysis, there is a significant amount of shrinkage and porosity at the bottom of the output end hole after solidification of the steel casting. The top pouring process scheme has a shrinkage volume of 0.0775% of the rocker arm shell, while the bottom pouring process scheme has a shrinkage volume of 0.0721% of the rocker arm shell. The defect rate of the bottom pouring process scheme is relatively low.
3) After optimizing the casting process by casting products manufacturers, the casting defects of steel castings are significantly reduced, and the stress field distribution is significantly improved. The shrinkage volume has decreased from 0.0721% of the rocker arm shell volume before optimization to 0.0049%; The stress optimization of the thin-walled area at the end of the motor hole in steel castings is 38.47%, and the stress optimization of the output end hole area is 91.08%.
4) For the steel castings of the rocker arm shell of the coal mining machine, the casting products manufacturers can improve the riser structure and size, add cold iron as a process method, which can maintain an increasing temperature gradient from the bottom to the riser of the steel castings, and enhance the effect of local simultaneous solidification and overall sequential solidification of the steel castings.