High-strength bolt processing technology


Drawing The drawing process has two purposes. One is to […]

The drawing process has two purposes. One is to change the size of the raw material; the other is to obtain basic mechanical properties of the fastener through deformation strengthening. For medium carbon steel and medium carbon alloy steel, there is another purpose, that is, to make wire rod The flake cementite obtained after controlled cooling is cracked as much as possible during the drawing process to prepare for the subsequent spheroidization (softening) annealing to obtain granular cementite. However, some manufacturers arbitrarily reduce the drawing to reduce the cost. For passes, the excessive reduction in surface area increases the work hardening tendency of the wire rod wire and directly affects the cold heading performance of the wire rod wire. If the distribution of the reduction ratio of each pass is not appropriate, it will also cause torsion cracks in the wire rod wire during the drawing process. This kind of cracks distributed along the longitudinal direction of the wire and with a certain period are exposed during the cold heading process of the wire. In addition, if the lubrication is not good during the drawing process, it can also cause the cold drawn wire rod wire to regularly appear transverse cracks. The tangential direction of the wire rod wire exiting and winding die mouth is not concentric with the drawing die, which will increase the wear of the unilateral pass of the drawing die, make the inner hole out of round, and cause uneven drawing deformation in the circumferential direction of the wire. The roundness of the steel wire is too poor, and the cross-sectional stress of the steel wire is uneven during the cold heading process, which affects the cold heading qualification rate. During the drawing process of wire rod wire, the excessive surface reduction rate deteriorates the surface quality of the steel wire, while the excessively low surface reduction rate is not conducive to the crushing of flaky cementite, and it is difficult to obtain as much granular cementite as possible , That is, the spheroidization rate of cementite is low, which is extremely detrimental to the cold heading performance of the steel wire. The bar and wire rod steel wire produced by the drawing method has a partial surface reduction rate directly controlled within the range of 10%-15%

Contact Us