China custom aluminum profile | Extrusion technology of radiator profile



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Aluminum alloy is widely used in heat dissipation equipment because of its light and beautiful quality, good thermal conductivity and easy to be processed into complex shape. Aluminum alloy heat dissipation equipment mainly has three types: flat width, comb or fish thorn; The heat sink outside the circle or oval is radial and branch shaped. Their common features are: the distance between the fins is short, and a groove is formed between the adjacent two fins, and the ratio of depth to width is large; The wall thickness difference is large, the heat sink is thin in general, and the thickness of the bottom plate at the root is large. Therefore, it is very difficult to design, manufacture and produce the die of the heat dissipating profile.
Some products with smaller size and symmetrical shape are easy to produce. Most of the radiator profiles are flat and wide, with large size and some asymmetry. The ratio of groove depth to width between fins is very big, and it is difficult to produce. It is necessary to cooperate with ingot, mold and extrusion technology to produce radiator profile smoothly. The alloy used for extrusion radiator profile must have good compressibility and heat conductivity, and the alloy 1a30, 1035 and 6063 are generally used. At present, 6063 alloy is widely used, because it has good extrusion and heat conductivity, and has good mechanical properties.
The production of aluminum alloy radiator profile should be started from the quality of ingot, material and design of mold, reduction of extrusion pressure and extrusion technology.
1. Quality requirements for ingots
The alloy composition of ingot should strictly control impurity content to ensure the purity of alloy melt. For 6063 alloy, the content of Fe, Mg and Si should be controlled. The content of Fe should be less than 0.2%. The content of Mg and Si is generally controlled at the lower limit of national standard, Mg content is 0.45% ~ 0.55%, Si content is 0.25% ~ 0.35%. The ingot should be well homogenized to make the structure and performance of ingot uniform.
The surface of ingot shall be smooth, and segregation tumor or sand mud shall not be allowed. The end face of ingot shall be flat, and it shall not be cut into steps or cut too much (the cutting angle shall be within 3mm). Because the step or cutting angle is too large, when extruding the heat dissipating profile with plane die, if there is no design guide, the ingot directly touches the mold. Because the end face of ingot is uneven, some places first contact the mold, which causes stress concentration, which is easy to crush the tooth shape of the mold, or the discharging sequence is different, which is easy to produce the phenomenon of blocking or extrusion forming.
2. Requirements for mold
Because the die of radiator profile is many slender teeth, it is necessary to bear a great extrusion pressure, each tooth must have a high strength and toughness. If there is a great difference in the performance between them, it is easy to break the teeth with poor strength or toughness. Therefore, the quality of die steel must be reliable, the best use of H13 steel produced by reliable manufacturers or the selection of high-quality imported steel. The heat treatment of the die is very important. It is better to use vacuum heating quenching, and the high pressure pure nitrogen quenching is the best way to ensure the uniform performance of all parts of the die after quenching. After quenching, three tempering shall be adopted to ensure the hardness of the die is enough toughness under the premise of hrc48-52. This is an important condition to prevent the die from breaking teeth.
The key to the successful extrusion of radiator profile is to design the die reasonably and make it accurately. Generally, it is necessary to avoid ingot directly pressing on the working belt of the mold. For the flat and wide comb radiator profile, a small middle and larger guide die is designed to make the metal flow to both sides, reduce the extrusion pressure on the working belt of the mold, and make the pressure distribution even. Because of the large wall thickness difference of the section of radiator profile, the difference between them should be kept correspondingly when designing the working belt of the die. That is, the working belt in the place with large wall thickness should be increased especially, which can be up to 20mm-30mm, and the position of the tooth tip should break through the normal and reduce the working belt to the minimum. In short, the uniformity of metal flow should be ensured everywhere. For flat and wide radiator, in order to ensure the rigidity of the die, the thickness of the die should be increased appropriately. The thickness increase is about 30% ~ 60%. The die should be made very fine. The empty knife should keep symmetry between the upper and lower, the left and right, and the middle. The machining error between the teeth and the teeth should be less than 0.05mm. The machining error is easy to produce the deviation of the teeth, that is, the thickness of the heat sink is uneven, and even the tooth will be broken.
For the section with mature design, it is also a better method to use inlaid alloy steel die, because the alloy steel mold has better rigidity and wear resistance, and it is not easy to produce deformation, which is conducive to the forming of radiator profile.
3. Reduce extrusion pressure
In order to prevent the tooth breaking of the mould, the extrusion pressure should be reduced as much as possible, and the extrusion pressure is related to the length of ingot, the size of alloy deformation resistance, the state of ingot and the degree of deformation. Therefore, the cast rod of extruded heat dissipating aluminum profile should not be too long, which is about 0.6-0.85 times of the normal casting rod length. Especially in the process of mould test and extrusion of the first casting rod, it is better to use shorter casting rod, i.e. the casting rod with normal length (0.4-0.6) times to test the mold in order to ensure the production of qualified products.
For the section of radiator profile with complex shape, besides shortening the length of the casting rod, the first trial extrusion with pure aluminum short casting can be considered. After the successful extrusion, the normal ingot can be used for extrusion production.
The homogenization annealing of ingots can not only make the structure and properties uniform, but also improve the extrusion performance and reduce the extrusion pressure. Therefore, it is required that the ingot must be annealed uniformly. As for the influence of deformation degree, the fracture area of radiator profile is generally large, and the extrusion coefficient is generally within 40, so the influence is small.
4. Extrusion process
The key to the production of radiator profile is the first test of extrusion die. If necessary, simulation test can be done on computer to see whether the working belt of die design is reasonable, and then on the extruder. The first die test is very important. The operator should make the main plunger move forward and press slowly under the low pressure of less than 8Mpa. It is better for someone to take care of the exit of the die with the light of a flashlight. Only after each heat sink of the extrusion die is evenly squeezed out of the mold hole can the pressure accelerate the extrusion. When the die is successfully tested, the extrusion speed should be controlled to ensure smooth operation. When producing radiator profile, attention should be paid to the heating temperature of the mold, so that the mold temperature and ingot temperature are similar. If the temperature difference is too large, the metal temperature will decrease due to the slow extrusion speed when pressing up, which will easily cause the phenomenon of mold blocking or uneven flow rate.

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