| Steel ball bearing is used widely as mechanical foundation, and the steel ball is the key which will influence the service life and dynamic performance directly. Cold heading as the first process influences the late process. Cold heading process parameters and the die are important which will influence the ball billet's dimension & shape, material utilization rate, production efficiency and the ball's service life. Ball billet was used in our country ago, and cone ball billet is now popular in foreign countries. Because of the cone angle of the die, it decreases the friction, the zone and 2 poles which can shorten the rough cutting time. So the cone ball billet process parameters and the die should be solved now.Cold heading research is mainly done by production test at home and abroad, and the design cycle is long, the cost of test is high. So this paper designed the virtual orthogonal tests by DEFORM software. Result of simulations and optimization contributes to cold heading process and the die.First of all, by the research of currently cold heading process and the using of DEFROM software, this paper carried out the finite element simulation of cold heading process. This simulation analyzed the stress, strain, damage coefficient, speed, and the laws of the metal flow. These data would provide the reference for the following mathematical modeling and experimental parameters.Second of all, according to the forming characteristic, mathematical model of the cold heading forming is established by upper bound method, and compared with the traditional model this model improved and can express different phase force. The model is accuracy and simulation results shows good agreement. While the traditional model can only calculate the cold heading force in different diameters yet still exists obvious errors. Meanwhile, this paper designed the virtual orthogonal experiments, and stimulated the cold heading deformation of different experiments to propose the evaluation indicator of the degree circle, cold heading force etc. Optimized parameters of the ball-billets can be got, and then try to figure out the influence of every single experimental factor and factors on the trends shaping the level of the ball-billets.At last, in order to deal with the deficiencies which have been found during the vast investigation, such as the short service life of the cold heading die. This paper analyzed the wear distribution of the mould, optimized the locality of the mould, and also designed the virtual orthogonal experiment to get better structure size inside the mould. Ultimately, the service life of the cold heading mould can be predicted according to the wearing depth.In conclusion, this paper did a research in steel ball cold heading process and made a detailed analysis of the cold heading process of corn shaped ball billets. Moreover, it optimized the process parameters and the local size inside the die. This paper has some guidance and reference for actual steel ball production. |
