An important method for manufacturing metal parts-cold extrusion

With China's entry into the WTO, the development of global economic integration will inevitably have a huge impact on the technology of China's traditional industries. We must reform the traditional processing methods to adapt to the market. In order to participate in international competition, it is necessary to be in line with international standards in the form and means of technical exchanges, and corporate innovation capabilities have increasingly become an important part of corporate competitiveness.

Cold extrusion forming refers to the shape and size of the formed part reaching or close to the finished part. It is a new technology developed on the basis of traditional metal plastic processing. In recent years, cold extrusion technology is one of the new technologies that have been rapidly developed in various industries and is an important method in the processing of product parts. Compared with other manufacturing processes (such as cutting, casting, and forging), it has a "high quality , High yield, low consumption, low cost ". At present, it plays an extremely important role in the manufacturing industries of automobiles, electronic communications, light industry, construction, aerospace, military, and daily hardware. Especially in the parts manufacturing industry in the 21st century, after China's entry into the WTO, market competition for product prices has become increasingly fierce, and cold extrusion technology has become one of the important indicators for continued development and development of various enterprises. It is generally believed that the level of cold forming (cold extrusion, cold forging, cold heading, stamping, etc.) processing technology in a country is an important sign and reflection of the country's automotive industry level, industrialization level, and even modernization level.

Cold extrusion technology is closely related to the automotive industry. According to foreign auto industry reports, the cold extruded parts on each car have reached 80kg, replacing the cutting method used in the past. It is expected that in 2010, the number of cold extrusion products in automobiles will continue to increase. Why should the advanced technology of cold extrusion be widely used in the mechanical manufacturing process, because it has the following significant advantages technically and economically?

1. Significantly reduce the consumption of raw materials

Cold extrusion is a metal plastic forming processing method. Under the premise of not destroying the metal, the metal volume is plastically transferred, so that the metal is formed with fewer chips and no chips, and parts of the required shape and size are obtained. In this way, a large amount of metal scraps formed during the cutting process are avoided, and the raw materials of steel and non-ferrous metals are greatly saved, so that 1t of metal materials can be used for 2t or even 3 to 5t.

2. Improve labor productivity

Cold extruded parts are carried out on a press, which is easy to operate, easy to grasp and has high productivity. For example: pure iron base material is soft, poor cutting performance, and difficult to machine. After cold extrusion, it not only saves raw materials significantly, but also increases productivity by 30 times. Another example is automobile engine piston pin, cold extrusion can improve productivity 3.2 times than turning. At present, a cold extrusion piston pin automaton has been produced to further increase productivity. The productivity of a cold extrusion automaton is equivalent to 100 horizontal lathes or 10 four-axis automatic lathes.

3.Parts with complex shapes can be formed

Under the reciprocating linear motion of the press, complete the complex processing procedures, and can be made into parts with complex shapes. Such as thin-walled special-shaped pieces, cylindrical pieces with reinforcing ribs, etc., the shape is complex, the size is small, and strict requirements are imposed. If it is manufactured by cutting, it will not only have low productivity and large material consumption, but also be very difficult in the manufacturing method; but it will be very convenient to use cold extrusion processing.

4.Improve the mechanical properties of parts

During the cold extrusion process, the metal material is under three-way compressive stress. After extrusion deformation, the grain structure of the metal material is more dense, and the metal flow lines are not cut, becoming a metal flow line continuously distributed along the contour of the extrusion. At the same time, because cold extrusion uses the work hardening characteristics of cold deformation of metal materials, the strength of cold extrusion parts is greatly improved, thereby providing the possibility of replacing low strength steel with high strength steel. For example, in the past, China used cutting machining to produce automotive engine piston pins. The raw material used was low-alloy structural steel 20Cr. Because the cold extrusion method is used to improve the mechanical properties of the piston pin parts, the material is 20 low carbon steel.

5.Parts that can obtain higher dimensional accuracy and smaller surface roughness values

The surface quality of the cold extruded parts is very good. During the cold extrusion process, the surface of the metal material is ironed by the smooth surface of the mold under high pressure, so the surface roughness value of the part is very small, and the surface strength is also greatly improved. Generally, the surface roughness value Ra of a cold-extruded part is at least 0.63 to 1.25 μm. It can be seen that some parts processed by the cold extrusion method can leave less machining allowance, or even meet the technical requirements on the product drawings without leaving machining allowance.

The dimensional accuracy of cold extruded parts can generally reach the precision level IT8 ～ IT9, and the individual dimensional tolerance range can be controlled within 0.015mm. The cold extrusion process can obtain the ideal surface roughness and dimensional accuracy of the part. Some parts can no longer be cut after cold extrusion, so that the cold extrusion method can be used instead of forging, casting and cutting of some parts. Opened a broad road.

6. Reduce process and shorten production cycle

The cold extrusion process is to plastically deform the metal in the cavity of the closed mold. The obtained extruded part has no flashing, so the subsequent process of cutting (or punching) is no longer needed, thereby shortening the production cycle.

7. Reduce equipment investment

Compared with the die forging process, because cold extrusion does not produce flashing, the cutting die and the cutting press can be omitted, which significantly reduces the equipment investment. In addition, the cold extrusion production and processing can be carried out on a dedicated cold extrusion press, or on a general hydraulic press, or on a general press that is not specifically designed for cold extrusion, such as a general punch or friction press. .

8. Reduce the production cost of parts

Since cold extrusion can greatly save raw materials and metal cutting man-hours, it is bound to reduce the manufacturing cost of parts. For example, there are three methods for producing automotive piston pins: cold extrusion, round steel cutting, and seamless steel tube cutting. The cost of cold extruded piston pins is the lowest, which is 45% lower than that of round steel cutting and 29% lower than the processing cost of using seamless steel pipes as raw materials.

1. The difference between cold extrusion and hot extrusion

2. The difference between hot forged parts and cold extruded parts

3. The difference between hot forging drawing and cold extrusion drawing The difference between hot forging drawing and cold extrusion drawing

1. The difference between cold extrusion and hot extrusion

2. The difference between hot forged parts and cold extruded parts

3. The difference between hot forging drawing and cold extrusion drawing The difference between hot forging drawing and cold extrusion drawing