Some of the heat sink profiles are relatively small in size and symmetrical in shape. It is relatively easy to produce. Most heat sink profiles are flat and wide, with large dimensions and some asymmetries. The grooves between the fins have a large aspect ratio. Difficult to produce. In order to produce the heat sink profile smoothly, heat sink manufacturers need to cooperate with the ingot, mold and extrusion process. The alloys used for extruding heat sink profiles must have good extrudability and thermal conductivity. Generally, alloys such as 1A30, 1035, and 6063 are used. At present, 6063 alloy is commonly used because it has good mechanical properties in addition to good extrudability and thermal conductivity.
The production of aluminum alloy heat sink profiles should start from the quality of the ingot, the material and design of the mold, the reduction of the extrusion force, and the extrusion process.
Extrusion Aluminum Heat Sink
1.Quality requirements of ingots
The alloy composition of the ingot must strictly control the impurity content to ensure the purity of the 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 are generally controlled at the lower limit of national standards, the content of Mg is 0.45% to 0.55%, and the content of Si is 0.25% to 0.35%. The ingot must be fully homogenized to make the structure and properties of the ingot uniform.
The surface of the ingot should be smooth, and no segregation knobs or sandy mud are allowed. The end face of the ingot should be flat, and can not be cut into steps or the cutting slope is too large (the cutting slope should be within 3㎜). Because the step shape or the cutting slope is too large, when the heat-dissipating aluminum profile is extruded with a flat die, if the diversion bar is not designed, the ingot directly touches the mold. Due to the uneven end face of the ingot, some places first contact the mold and stress concentration occurs , It is easy to squeeze the tooth shape of the mold, or cause the material to be discharged in a different order, and it is easy to cause the phenomenon of plugging or poor extrusion molding.
2. Reduce squeezing force
In order to prevent the mold from breaking teeth, the pressing force should be reduced as much as possible, and the pressing force is related to the length of the ingot, the resistance to alloy deformation, the state of the ingot, and the degree of deformation. Therefore, the casting rod of the extruded aluminum profile should not be too long, which is about 0.6 to 0.85 times the normal casting rod length. Especially when testing the die and extruding the first casting rod, in order to ensure the successful production of a qualified product, it is best to use a shorter casting rod, that is, a casting rod that is twice the normal casting rod length (0.4 to 0.6). mold.
In addition to shortening the length of the casting rod, for the section of the aluminum extrusion heat sink profile with a complex shape, pure aluminum short casting can be considered for the first trial extrusion. After successful trial extrusion, the normal ingot is used for extrusion production.
The ingot homogenization annealing can not only make the structure and properties uniform, but also can improve the extrusion performance and reduce the extrusion force, so the ingot must be uniformly annealed. As for the influence of the degree of deformation, the cross-sectional area of the heat sink profile is generally large, and the extrusion coefficient is generally within 40, so its impact is small.