At present, the dimensional accuracy of cold extruded parts developed in China can reach 8-9 grades. If the ideal lubrication is used (referring to pure aluminum and copper parts), it is second only to the polished surface. Therefore, the parts produced by the cold extrusion method generally do not need to be reprocessed, and a small amount only needs finishing (grinding).
The material utilization rate of cold extruded parts can usually reach more than 80%. For example, the Jiefang automobile piston pin machining material utilization rate is 43.3%, and when cold extrusion is used, the material utilization rate is increased to 92%; and if the universal joint bearing sleeve is changed to cold extrusion, the material utilization rate is changed from the past. 27.8% to 64%. It can be seen that using cold extrusion to produce mechanical parts can save a lot of steel and non-ferrous metal materials.
The efficiency of producing mechanical parts by cold extrusion is very high, especially for large-volume parts. The production of cold extrusion can be several times, dozens of times, or even hundreds of times higher than cutting. For example, the cold extrusion method for automobile piston pins is 3.2 times faster than the manufacturing process by cutting. At present, cold extrusion piston pin automata are used to further increase productivity. The productivity of one cold extrusion automatic machine is equivalent to that of 100 ordinary lathes or 10 four-axis automatic lathes.
Such as special sections, internal teeth, special holes and blind holes, these parts are difficult to complete by other processing methods, but cold extrusion processing is very convenient.
Because cold extrusion uses the cold working strengthening characteristics of cold deformation of metal materials, that is, the metal blank is in a three-way compressive stress state during extrusion, and the material structure is dense after deformation and has continuous fiber flow direction, so the strength of the product is greater. improve. In this way, low-strength materials can be used instead of high-strength materials. For example, in the past, 20Cr steel was used to manufacture Jiefang brand piston pins through cutting. Now, 20 # steel is used to manufacture piston pins through cold extrusion. After measuring various indicators of performance, the cold extrusion method is higher than the cutting method to manufacture piston pins.
From the above characteristics, it can be seen that the cold extrusion technology has outstanding advantages compared with various current processing methods. This opens up a broad path for cold extrusion instead of cutting, forging, casting and drawing processes to manufacture machine parts.