The bar shearing machine uses the shearing method to segment the raw materials in a certain size. It has the advantages of high cutting productivity, simple operation no metal loss in the incision, so it is widely used.
The process of cutting can be divided into three stages. In the first stage of shearing, the blade is pressed into the bar, the plastic deformation zone is large. Because of work hardening, cracks appear at the contact with the edge. In the second stage, the crack expands with the depth of the blade. In the third stage of shearing, under the action of the edge, the metal between the upper lower cracks is broken, forming an S-shaped section.
The cutting quality is related to the cutting edge's sharpness, blade clearance, support, material performance shear speed. When the edge is round blunt, the shear billet will be enlarged, the crack at the edge will appear later, resulting in the uneven shear section. As a result, the cross section axis are perpendicular to each other, the burr on the end will be pulled out for soft materials. The edge clearance is too small. It is only easy to damage the cutting edge, but also the upper lower cracks do coincide, the cross section is serrated. When the material with poor plasticity is cold cut, the end face crack is produced. If the blank supporting force is enough. Because the directions of the upper lower cracks are parallel to each other, the fracture surface is inclined. The results show that the shear rate is high, the plastic deformation zone work hardening are concentrated, the crack directions on the upper lower sides are the same, the smooth fracture surface can be obtained. When the shear speed is slow, the situation is opposite.
According to the different temperature of shearing billet, it can be divided into cold shear hot shear. The production efficiency of cold shear is high, but it needs large shear force. The steel with high strength poor plasticity will produce great stress during cold shearing, which may lead to crack even crack. Therefore, hot cutting method should be used. The medium carbon steel with large section diameter greater than 120mm should be pre heated sheared. High carbon steel alloy steel should be preheated sheared. The chemical composition size of high carbon steel alloy steel determine the preheating temperature. Selected 400 to 730 degrees Celsius.