Effect Of Deep Drawing Plastic Deformation And Annealing Treatment On The Microstructure And Wear Resistance Of 70 Steel

Microstructure evolution and wear resistance transform in the course of deep drawing plastic deformation and anneal treatment of 0.7%C steel were studied through FESEM and SEM testing methods. The investigation involves: (1) Effect of deep drawing plastic deformation and anneal treatment on mechanical properties of 0.7%C steel;(2) Effect of deep drawing plastic deformation and anneal treatment on microstructure of 0.7%C steel;(3)The strengthening mechanism of deep drawing plastic deformation and lower temperature anneal treatment of 0.7%C steel;(4) Effect of deep drawing plastic deformation and anneal treatment on abrasive wear resistance of 0.7%C steel;(5) The wear mechanism of 0.7%C steel by means of deep drawing plastic deformation.The results show that the tensile strength and the microhardness of 0.7%C steel increase gradually with the increase of deformation and show a linear relationship with the strain. With the rise of annealing temperature, the tensile strength and the micro-hardness of 0.7%C steel increase at first, and then reduce gradually.During the process of deep plastic deformation, the microstructure of 0.7%C steel can be refined gradually. Space between the pearlite slices reduces by degrees .The pearlite groups rotate and tropisms of the pearlite tend to be consistent with the direction of the drawing axis. Cementite plates are broken and refined after deformations of cut, bend and draw, and the dissolution of cementite occurs heavily with the severe deformation. On the condition of low annealing temperature, the microstructure of cold drawing steel wire changes little, the microstructure is more well-proportioned, and the dissolution amount of cementite increases. When the annealing temperature rises, cementite precipitate as particles, and the grain size grows up with the rise of the annealing temperature, as well as the grain size of ferrite. The microstructure of 0.7%C steel transforms to pearlite after recrystallization annealing atthe temperature of 680 °C.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 aluminium oxide and quartz. The wear resistance of 0.7%C steel increases first and then reduces with the rise of annealing temperature, and wear losses of samples are similar.By using the abrasive of glass, wear resistance of the steel can be improved greatly with the increase of strain. Wear resistance can be enhanced over 6 times when the strain amount reaches 3.58, the wear resistance of 0.7%C steel also increases first and then reduces with the rise of annealing temperature, but the difference of wear losses are remarkable.Micro-cutting and micro-ploughing are the main wear mechanisms of all samples in the work condition of aluminium oxide and quartz. By using the abrasive of glass, the wear mechanism of 0.7%C steel changes from micro-cutting and ploughing to low cycle fatigue with the growth of plastic deformation. When in the low annealing temperature, low cycle fatigue wear is the main wear mechanism, while in the high annealing temperature, micro-cutting and ploughing is the main wear mechanism.