Pre-treatment Process Optimization And Process Simulation Analysis To 20 Steel

Because of the good comprehensive properties, cold drawn tubes are used in various industries of the national economy. The rapid development of industry put forward higher requirements on the service performance of cold drawn pipe. Since the traditional drawing technology is difficult to achieve request of the precision, it is significant to analyze and optimize all the aspects of cold drawing production. Therefore, enterprises need to study and solve the problem of how to improve the production efficiency as well as the quality of products in each process. The rationality of the existing pickling process was verified. The key parameters of normal temperature phosphating process were optimized by orthogonal test. According to the numerical simulations, the distributions of the stress and strain of the tube have been obtained and distributions of the axial stress and radial stress have been drawn. The forming mechanism of pipe in cold drawing process and the influence of different process parameters on drawing force were studied.The main contents of this paper are as follows:(1) The plastic deformation index of the pickled sample that from different time in a pickling cycle, such as tensile strength, yield strength and the specimen section shrinkage and elongation of the cross-section, were validated through tensile test. The experimental results show that all the plastic deformation indexes were qualified, no defects such as hydrogen embrittlement were observed and the plastic deformation indexes of the pickled sample were descended.(2) The technology for normal-temperature multiple phosphating of 20 steel was analyzed by conducting orthogonal tests. The better parameters of phosphating process were determined as follows: the total acidity is 120, the phosphating time is 30 min and the promotion agent is 6. It was found by SEM that the surface morphology of the zinc system phosphating was better under the optimized parameters. The phosphate film was stripped with coarse grains. The corrosion resistance was increased and surface quality of the phosphating was more compact when using surface conditioning agent.(3) In this paper, the cold drawn forming processes of steel tube with conical die was simulated by the finite element analysis software ANSYS, which including the stages of steel tube into the die, stable drawn and away from die. According to the numerical simulations, the distributions of the axial stress and radial stress as of the steel tube at different areas have been drawn. Based on the stress and strain of the tube with conical die drawing, the forming mechanism of the precision of both the diameter and wall thickness had been explained. Drawing force was divided into several phases according to its distribution law.(4) Through plenty of simulation result, the paper studied the mainly influent factors on the drawing force, such as friction, modular angle, wall thickness of rigid pipe and drawing speed. The optimized cold drawing die was proposed according to the stress characteristics and the relationship between the drawing force and the different process parameters. The size precision of the diameter and wall thickness of the finished product is improved by the new cold drawing die.