Heatsink Extrusion and Die (Matrizes de extrusão de alumínio)Disgin
Due to light weight good thermal conductivity and easy processing into complex shape,aluminum is widely used for heatsink. There are three main types: flat, comb-shaped or fishbone-shaped; round or oval circular radiator; and tree shape.They have common features: 1.short distance between the heat sink; 2 large wall thickness difference, generally heat sink is thin. As a result,there are many difficulties for die design and manufacturing.
For heatsink manufacturing,it needs take consideratrion from ingot, die and extrusion tech and other several aspects.Currently 6063 alloy is widely used, because of its good extrudability, thermal conductivityand better mechanical properties.
Aluminum heatsink profiles should think more about ingot quality, die material and design,and extrusion technology and other aspects.
1, Quality Requirements of Aluminium Billet
Aluminium Billet alloy composition should strictly control the impurity content to ensure that the alloy is extremely pure. For 6063 alloy to control the Fe, Mg, Si content. Fe content should be less than 0.2%, Mg, Si content are generally controlled in the national standard of the lower limit, Mg content of 0.45% to 0.55%, Si content of 0.25% to 0.35%. The ingot has to undergo a full homogenization process, so that the ingot organization, performance uniform.
The ingot surface should be smooth, do not allow a segregation tumor or sticky mud. The end of the ingot should be smooth, not cut into a stepped or cut too large (cut inclination should be less than 3 mm). Because the step-like or cut inclination is too large, with the plane die extrusion heat profile, if there is no diversion design , ingot directly hit the mold, the ingot end uneven , Easy to squeeze the die of the tooth profile, or cause the material has different, prone to blocking or extrusion molding bad phenomenon.
2, Die Requirements
Because the heatsink profile die has many slender teeth to withstand big extrusion force, each tooth must have a high strength and toughness, if the performance of each other there is a big difference, it is easy So that the strength or toughness of those teeth are broken. Therefore, the quality of mold steel must be reliable, it is best to use quality and reliable manufacturers of H13 steel, or use high-quality imported steel. Die heat treatment is very important to use vacuum heating and quenching, the best use of high-pressure nitrogen quenching, quenching can guarantee the performance of the various parts of the mold evenly. After quenching to take three tempering, the hardness of the mold to ensure that under the premise of HRC48 ~ 52, with sufficient toughness. This is an important condition to prevent die broken teeth.Heatsin profiles are able to be extruded successfully, the key is a reasonable die design and manufacturing should be accurate. Generally try to avoid the ingot extrusion directly to the die working place.
For the mature section, tungsten insert is also a good method, because the tungsten steel die has good rigidity and wearing resistance, not easy to be deformation.
3, Reduce Extrusion Force
In order to prevent die teeth breaking, should minimize the extrusion pressure, and extrusion pressure has something to do with the long billet, the deformation resistance of ingot,and state,and the degree of deformation and other factors. Therefore,aluminum billet should not be too long, about 0.6 to 0.85 times. Especially in the die trial and first billet extrusion, in order to ensure the production of qualified products, best to use a shorter billet, 0.4 ~ 0.6 times try die.
For the complex shape ,should also consider high pure billet.
4.Extrusion Press and Processing Control
First die trial is very important, you can do the first simulation test on the computer to see whether the die design work a reasonablely, and then try to die on the press. Forward pressure on the low pressure of less than 8MPa ,use a torch light to take care of the die exit port. After the success of extrusion die tral , should pay more attention to the extrusion speed control. Also make the die temperature and billet temperature close,if the temperature difference is too large, due to the pressure on the extrusion speed is slow, will reduce the metal temperature, easy to produce blockage or flow velocity uneven phenomenon.
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