Introduction of basic knowledge of cold heading and cold extrusion（冷镦、冷挤压基础知识介绍）.doc

Introduction of basic knowledge of cold heading and cold extrusion（冷镦、冷挤压基础知识介绍） Sufficient impact toughness and abrasion resistance are also required. In addition, the metal blank in the mold in a strong plastic deformation, the mold temperature will rise to 250 degrees Celsius to about 300 degrees, so the mold material needs a certain tempering stability. As a result of the above, the life of cold extrusion die is much lower than that of stamping die. 2) a large tonnage press is required. Because of the large deformation resistance of the blank when cold extrusion, it needs hundreds of tons or even thousands of tons of press. 3) due to the high cost of cold extrusion dies, they are only suitable for mass production of parts. The minimum batch size is 5~10. 4) the blank needs surface treatment before extrusion. This not only increases the process, but also takes up a larger production area, and it is difficult to realize the automation of production. 5) not suitable for high strength material processing. 6) the plasticity and impact toughness of the cold extrusion parts become worse, and the residual stress of the parts is great, which will cause the deformation and corrosion resistance of the parts to decrease (produce stress corrosion) Development process of cold extrusion technology at home and abroad Modern cold extrusion technology began in the late eighteenth Century, when the French pushed the lead from small holes into bullets in the French Revolution and began a cold extrusion. In France in 1830 has been started by the mechanical press, the anti extrusion manufacturing method of tin lead pipe and tube. In 1906, in order to make brass suit buttons, the United States had patented the hollow hollow cup. In 1909 American Hooker method patent -- positive impact extrusion method, the metal flow direction is the same as the extrusion direction, is developed in 1906 after buying the patent, the patent in the cup shape blank, is manufactured by drawing method. The