Aluminum alloy is widely used in heat dissipation equipment because of its high quality, good thermal conductivity and easy processing. Aluminum alloy heat sinks are mainly three types: the wide flat form, comb shaped or fishbone shaped; the panels of round or oval outside heat radiating, dendritic.
Their common features: the distance between the heat sink is short, the two of adjacent heat sink to form a groove, its depth width ratio is big, the wall thickness difference is also big, general speaking, the heat sink is thin, and the root of the base plate thickness. So it is very difficult to design, manufacture and produce the mold of radiator profiles.
Radiator profile is more easier to produce for a smaller size and symmetric products, most of the radiator profiles flat width, shape size is larger, and some asymmetry, the groove between the heat sink deep aspect ratio, the difficulty of its production. It needs several aspects of match from the ingot, mold, extrusion process, in order to successfully produce radiator profiles. Extrusion heat sink of the alloy must have good extrusion and thermal conductivity, the general use of 1A30, 1035 and 6063, etc. At present, it is widely used in the 6063 alloys, because it has good mechanical properties except for the good and the heat conduction.
The production of aluminum alloy radiator profiles to proceed from ingot quality and mould of materials and quality, reduce the extrusion force and extrusion technology and other aspects.
1, the quality of ingot
The composition of the alloy ingot should be strictly control the content of impurities, to ensure the purity of the alloy at. For 6063 alloy should control the content of Fe, Mg and Si. The content of Fe should be less than 0.2%, the content of Si and Mg is generally controlled at the lower limit of the national standard, the content of Mg is 0.55% ~ 0.45%, and the content of Si is 0.35% ~ 0.25%. The ingot thoroughly homogenized, uniform performance.
The ingot surface should be smooth, the segregation or sticky sand mud is not allowed. The end of Ingot should be smooth, not cut too large step slope (cut slope should be 3 mm or less). Because the step shape or cut slope is too large, when flat die extrusion radiator, if there is no design of diversion Jian, ingot directly met die, due to the ingot surface uneven, some places first contact with the mould, resulting in stress concentration, easy to the tooth shape of the mold to squeeze off, or cause a material has a, prone to block molding or extrusion forming is not good phenomenon.
2, the requirements of the mold
Because the radiator profiles are many slender teeth, to withstand a lot of pressure, each tooth should has a high strength and toughness, if there is a big difference between the performance, it is easy to make the strength or toughness of those teeth to produce fracture. Therefore, the quality of die steel must be reliable, the best use of the quality and reliability of the production of H13 steel, or the selection of high quality imported steel. The heat treatment of the mould is very important. It is very important to use vacuum heating and quenching, and it is best to use high pressure pure nitrogen quenching, which can guarantee the performance of the mould after quenching. After quenching, the hardness of the mould can be taken for three times, so that the hardness of the mould can be ensured to have enough toughness in the condition of HRC48 ~ 52. This is an important condition for preventing mould breaking.
The heat sink section to be able to smooth extrusion, the key is the design of the mold to be reasonable, manufacturing to accurate. Generally try to avoid direct extrusion ingot to the mold working with. For the flat width of the comb shaped heat sink, the design of a small, two sides of the larger flow, so that the flow of metal to the two sides to reduce the pressure on the work of the mold, but also to make the pressure distribution uniformity. Because of the large wall thickness difference of the section of the radiator, the work of the design of the work with the corresponding to keep their difference, in other words, the wall thickness of the local work with a special increase, can be large to 20mm ~ 30mm, and the position of the tooth tip to break the routine, to minimize the work. In short, we should ensure the uniformity of the flow of metal. For flat wide heat sink, in order to ensure that the mold has a certain rigidity, the thickness of the mold should be appropriately increased. Thickness increased from about 30% to 60%. Mold production has to be very precise, air knife to so that the upper and lower, left and right, middle maintain symmetry, the machining error between the teeth to less than 0.05mm, machining error major prone to partial tooth, namely fin thickness uneven, even will produce the phenomenon of broken teeth.
For more mature design section, mosaic alloy die steel is a good method, because alloy steel die with high rigidity and wear resistance, not easy to deformation, is good for forming radiator.
3, reduce the squeeze pressure
In order to prevent mold broken teeth and we should minimize extrusion pressure, and extrusion pressure is bound up with alloy deformation resistance, the size of the ingot and the degree of deformation and other factors. Therefore, the extruded aluminum profile of the cast rod should not be too long, about the length of normal cast rods (0.85 ~ 0.6 times). Especially in the test mode and the first root casting rod, to ensure that the smooth production of qualified products, the best use of shorter cast rods, that is, the normal cast rod length (0.6 ~ 0.4) times the cast rods to test.
For complex shape of radiating section, in addition to shorten the casting rod length, consider with pure aluminum short cast do first test extrusion, trying to squeeze after the success of using normal ingot of extrusion production.
Ingot homogenizing annealing can not only make the organization and performance of uniform, and can improve the compression performance and reduce extrusion pressure, so the requirements of ingot must homogenizing annealing. As to the extent of deformation, because the size of the radiator section is generally larger, the extrusion coefficient is generally less than 40, so it has little effect.
4, extrusion process
The key to the production of the heat sink profile is the first test mode of the extrusion die, which can be done in the computer simulation test, and the work of the die design is reasonable. First test is very important, hand operation to let the main piston forward pressure under low pressure lower than 8Mpa to slow ahead, it is best to have torch light care at the die exit, extrusion die of each heat sink are uniform extrusion die hole, in order to gradually pressurized accelerated in extrusion. After the success of the test model to continue to squeeze, should pay attention to control the extrusion speed, so that a smooth operation. The production of radiator profiles should be paid attention to when the heating temperature of the mold, mold temperature and temperature to make similar ingot. If the temperature difference is too large, due to the pressure when the extrusion speed is slow, will make the metal temperature drop, easy to produce the phenomenon of blocking or uneven flow velocity.
Radiator profiles extrusion technology is not only related to the above factors, and also extrusion machine ability and level, the rear of the equipment automation degree, the worker's operation skill etc., different radiating section should be to take corresponding measures according to its characteristics, can not be generalized.
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