Research On Forging And Rolling Combined Process Of Large Diameter Wear-resistant Steel Balls

The large diameter wear-resistant steel ball is a kind of grinding medium.It is mainly used in mining,electric power,metallurgy and other industrial fields to grind and break corresponding materials.Due to the harsh working environment,wear-resistant steel balls have become the large consumed parts in industrial production.The service life of wearresistant steel balls affects the cost of the corresponding fields in which they are used.Therefore,people have been researching and improving the manufacturing process of wearresistant steel balls to continuously improve the quality of wear-resistant steel balls.In this paper,based on the problems existing in the forming process of large-diameter wear-resistant steel balls,the method of forming large-diameter wear-resistant steel balls by forging and rolling combined process is proposed.The process is to manufacture wearresistant steel balls with a diameter of 140 mm as an example,and the forming material is 65 Mn steel.Its excellent wear resistance,toughness,hardness and other properties are the basic conditions for forming high quality wear-resistant steel balls.In the forging and rolling combined process,the bar is first hot forged in forging dies.And then the initially formed wear-resistant steel balls are rolled by means of spiral roller to complete the forming process.And by determining reasonable process parameters to prevent some defects,such as small platforms,flash and so on,and to improve the quality of the surface and core of the steel balls.In the research process,DEFORM-3D software was used to simulate the forming process of wear-resistant steel balls to clarify and optimize the process parameters,and to analyze the forming characteristics,quality and defects of wear-resistant steel balls.Finally,the simulation results are verified by experiments.The process proposed in this paper will provide guidance for the actual production of large-diameter wear-resistant steel balls.The main research contents and conclusions of this paper are as follows:(1)Based on the working environment and market demand of large-diameter wear-resistant steel balls and the analysis of steel balls forming process,the forging and rolling combined process is proposed to be the forming scheme of large-diameter wear-resistant steel balls.(2)In the study,wear-resistant steel balls with a diameter of 140 mm was produced.And the molds required during the forming process is designed.According to the principle of volume invariance and other conditions,the diameter of the spherical cavity of the forging die is designed to be 142.2mm.Meanwhile,the moving condition of wear-resistant steel balls in the rollers and the selection principle of the roller cavity parameters are studied.The rolling molds are designed as spiral rollers.For the roller,the outer diameter is 500 mm,the length is 650 mm,the radius of the spiral hole is 71.7mm,the height of the hole rib is 70 mm,the width of the rib is 10 mm,and the spiral lead is 150 mm.(3)Determine the important process parameters of the forging and rolling combined process in the forming process of wear-resistant steel balls.When the wear-resistant steel ball is produced under the optimal forging and rolling combined process parameters,its stress and strain changes and distribution characteristics,failure coefficient and material flow condition are explored,and its forming quality and defects are analyzed.The results show: The pressing stroke of the die on the forging press is 119.5 mm,and the rollers assembly inclination angle is about 6°,the forming state of the steel ball is most ideal.The material is well filled in the mold,and there is no obvious flash on the surface of the steel ball.During the rolling stage,the steel ball moves stably in the rollers.The surface material of the wear-resistant steel ball is smoother after rolling.And its overall quality is better.Meanwhile,the rolling speed of the wear-resistant steel ball should be controlled to 3r/s ~6 r/s to avoid the wear defects caused by the rollers on the steel balls surface and the problem of rolling effect not obvious.(4)The effectiveness of the simulation results was proved by experiments.The finished wear-resistant steel ball has a good shape,complete surface streamline and high dimensional accuracy.Moreover,the hardness of the wear-resistant steel ball manufactured by this process is higher than that of the wear-resistant steel ball produced by forging in the factory.