Shortened working tap

The friction force that needs to be overcome when aluminum alloy is extruded through the die working belt surface is an important part of extrusion pressure. According to the formula of friction force, the size of friction force is proportional to the length of the working belt. Therefore, when designing the work belt, the length of the work belt should be shortened as much as possible to reduce friction while meeting the strength of the work belt itself. At the same time, the working belt should not have a transition or reduce the transition as far as possible, fully reflecting the role of the working belt as a "sizing belt", and trying to avoid the common idea of using the working belt to adjust the flow rate in the design work. Figure 4a and b show the work belt plan before optimization. According to the wall thickness of each part of the profile and the distance from the center of the mold, work belts of different lengths are used to adjust the flow rate of each part of the profile, so as to achieve the effect of balanced outflow. The length of the working belt of the mold is generally 2mm ~ 8mm, and the longest can reach 20mm. After optimization, the "equal sizing belt" scheme as shown in Figure 4c and d is adopted: The working belt is all set to equal length, and the length value is taken within the range of 2.5mm~3.5mm according to the profile size and wall thickness. The flow rate adjustment is carried out instead of the traditional working belt through the unequal length flow rate adjustment chamber in front, which greatly reduces the extrusion friction and greatly improves the extrusion speed of aluminum tube and aluminum square tube.

How to eliminate the processing stress of aluminum alloy square tube?

Aluminum alloy square tube is a class of non-ferrous metal structural materials used in industry, aluminum alloy density is low, but the strength is relatively high, plasticity is good, can be processed into various profiles, with electrical conductivity, thermal conductivity and corrosion resistance, in aviation, aerospace, automotive, machinery manufacturing, shipbuilding and chemical industry in a large number of applications.

Aluminum alloy square pipe in the process processing, especially in the machining process is easy to produce large stress deformation resulting in size out-of-tolerance scrap, some did not deformation out-of-tolerance at the time also often produce deformation after installation, leading to greater system problems. Several existing stress relieving methods of aluminum alloy include thermal aging, vibration aging, mechanical drawing, mold correction and cryogenic composite stress relieving methods.

Thermal aging stress relief is generally for small and medium-sized parts, is a traditional stress relief method, because many aluminum alloy materials are very sensitive to temperature, so the aging temperature can not be too high, otherwise it will reduce the strength of the material. Therefore, thermal aging is usually carried out at temperatures not higher than 200 ° C, so the stress removal effect can only remove about 10-35%.

Vibration aging stress removal is to use a controlled vibration energy to act on the machined product through the exciter held on the surface of the machined product, and carry out vibration treatment at a specific frequency, so as to release and reduce the residual stress of the workpiece. This processing method is commonly used in the stress relief treatment of large structural parts, welding and casting parts, and the removal effect is about 50-60%.

The principle of mechanical tensile stress elimination is to apply a certain amount of long-term tensile plastic deformation to the quenched aluminum alloy plate along the rolling direction, so that the tensile stress and the original quenching residual stress superimposed plastic deformation, so that the residual stress can be alleviated and released. The results show that the mechanical tensile method can eliminate more than 90% of the residual stress. However, this method is only suitable for parts with simple shapes, and requires higher organizational uniformity of aluminum alloy sheets before stretching, and is mostly used in aluminum processing factories.

Loading correction cold pressing method is in a special finishing mold, through strictly controlled limited cold shaping to eliminate the residual stress in the complex shape of aluminum alloy die forging, this method is to adjust rather than eliminate the overall stress level of the parts, it makes the residual stress on some parts of the aluminum alloy product is released at the same time, it is possible to increase the residual stress in other parts. In addition, in view of the large residual stress already existed in the workpiece, too much molding deformation may cause cold work hardening, cracking and fracture; However, if the deformation is too small, the stress relief effect is not good, and the cost of making the plastic mold is also high, and the difficulty of the plastic operation is larger, so the limitation of this method is difficult to apply in actual operation.

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