Heating temperature is too high or too low, the body is not conducive to the formation of the ball. When the heating temperature is too high, the majority of dissolved carbon in austenite, the carbon in austenite is more evenly distributed, increasing the tendency to form lamellar pearlite, bearing steel annealing temperature is raised to 840 ℃, after annealing all been clear lamellar lamellar pearlite; heating temperature is too low, so that the original organization lamellar pearlite carbide has not completely dissolved off, as the ball of the residual carbide core crystallization decreases cooling, the residual sheet along carbide carbide precipitation and the formation of thin sheet-like fine point of orientation chain carbide. Annealing cooling rate in the sphere of the main body of the size of the impact is large, the cooling rate generally increases, diffusion of the carbon and iron difficulties, the formed carbide particles is reduced, were densely packed shape and directional. Spheroidizing abnormal lumps etched deep tissue analysis of the characteristics of organizations can be seen dots, fine granular carbides with the parallel arrangement of intermittent flakes carbides coexist, which retains the carbon flakes water cooling pearlite formation of fine features, combined with the heating temperature on the ball of the quality of analysis, you can determine the organization of the ball due to thermal anomalies organization, wear water- cooled capillary sampling carried out on the ball annealing the results also confirmed that, when the heating temperature is lower than 760 ℃ decreased effect when the ball fell to 740 ℃ annealing organization is to retain a large number of water cooling the formation of fine pearlite.
With a short pull mandrel system, the process includes steel cold drawn steel tip into the outer mold starts reducing, pipe wall and the mandrel contacts and put it into the deformation zone, at the same time, gradually reduce the pipe wall, and finally fixed pipe diameter and the outer mold prolapse, so in a stable phase-drawn steel parts of the axial tensile stress deformation, radial and tangential compressive stress, which is pulled along by the compressive stress state of two, because the presence of tensile stress, when the metal-drawn plastic poor. Annealing of the ball body in the presence of a small amount of lamellar pearlite, their pearlite plastic deformation is different from the particulate, granular pearlite lamellar pearlite as compared with less phase interface, hardness, low intensity, far higher than the plastic lamellar pearlite and ferrite pearlite lamellar plastic deformation resistance is low, the tensile stress in the pearlite lamellar ferrite first began plastic deformation, plastic deformation of ferrite formed with the induction of the slip, certain orientation and the direction of tensile stress parallel to or nearly parallel to the brittle carbide layer rupture, fracture shear zone formed through adjacent layers of ferrite, thereby first, the crack generation in lamellar pearlite region, the role of stress in the drawing expanded into transverse cracks.
