Influence Of Deep Drawing Plastic Deformation And Annealing Treatment On The Microstructure And Three-body Abrasive-wear Mechanisms Of 70 Steel

Microstructure characteristics and three-body abrasive-wear resistance change in the course of deep drawing plastic deformation and anneal treatment of 70 steel were investigated by TEM and SEM methods. The investigation involves: (1) Influence of deep drawing plastic deformation and anneal treatment on mechanical properties of 70 steel; (2) Influence of deep drawing plastic deformation and anneal treatment on microstructure characteristics of 70 steel; (3) Strengthen mechanism of deep drawing plastic deformation of 70 steel; (4) Influence of deep drawing plastic deformation and anneal treatment on three-body abrasive-wear resistance of 70 steel; (5) The three-body abrasive-wear mechanism of 70 steel by means of deep drawing plastic deformation.The results show that the strength and the hardness of 70 steel increase as a result of deep drawing plastic deformation. They show a linear relationship with the strain. The tensile strength and hardness increase firstly, and then reduce with the rise of annealing temperature.Under the deep plastic deformation, the microstructure of 70 steel has been changed gradually. The distance between the pearlite slices reduces gradually. In this process, the pearlite groups rotate and tend to be consistent with the direction of the drawing axis. At the same time, cementite plates are broken, bend and draw, dispersive finally with the severe deformation. After a 200℃ annealing, it shows that the size of ferrite lamellae, as well as the microscope internal strain inside these lamellae, is approximately constant. When the annealing temperature rises, cementite precipitate as particles, and the grain size grows up. When the annealing temperature is up to 700℃, the ductility of steel is improved remarkably, while the strength decreases a lot.Wear resistance of 0.7%C steel can be improved partly by means of deep plastic deformation under the condition of abrasive wear by using quartz. In another word, the strain has little effect on the wear resistance. By using the abrasive of glass, wear resistance can be enhanced almost 2.25 times when the strain amount reaches 2.77.The main wear mechanisms of all samples are fixed. There are micro-cutting , micro-ploughing and fatigue wear in the 70 steel in the work condition of quartz. Micro-cracks will appear if the samples work under the high load. By using the abrasive of glass, the wear mechanism of 0.7%C steeel changes from micro-cutting and ploughing to fatigue wear with the growth of plastic deformation.From the microstructure of the composites, the grooves in the high-speed steels are becoming narrower and lower than the grooves in the 70steel. Then increasing the amount of high-speed steel can improve the wear resistance of the materials in the small load . Under the condition of high load , wear resistance of composites increase first and then reduce with the increasing of high-speed steel because of the more cracks of the reinforcements. By using the abrasive of glass, the grooves of the high-speed steels are narrow and low, so the high-speed steels can protect the matrix materials from the wear and improve the wear resistance of the composites.Through the wear model of the composites, we can explain why the wear resistance increase first and then reduce with the increasing of high-speed steel under the hard abrasive.