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To ensure the quality of aluminum extruded heat sink. We should start from the following four aspects:

1. Quality Requirements For Ingots

The alloy composition of ingots should be strictly controlled. To ensure the purity of the alloy melt. The ingot should be fully homogenized so that the structure and properties are uniform. The surface of ingot must be smooth and no segregation or sand. The end of the INGOT should be flat, not cut into steps. 


2. Requirements For Mold

Because the aluminum heat sink mold has a lot of verminous fins. They will be under great pressure when extruding process. Each fin has to be very strong and tough. So the quality of steel die must be reliable. We recommend H13/521  Tool Steel.

Tool Heat treatment is very important. To use vacuum heating quenching. And it is best to use high-pressure pure nitrogen quenching. That can ensure the uniform performance of each part of the die after quenching. After quenching, three times of tempering should be adopted. To ensure that the hardness of the tool has enough toughness under the premise of HRC48 ~ 52. This is an important condition to prevent the broken fins.
 

To prevent the fins broken, the extrusion pressure should reduce as far as possible. The extrusion force relates to the length of the aluminum rod, the deformation resistance of the alloy, and the degree of deformation. So, the length of the cast bar should not be too long, which is about 0.6 ~ 0.85 times of the normal length.

For the section of aluminum heat sink with complex shape. Besides shortening the length of casting bar. Considering to use pure aluminum short casting for the first extrusion test. Then use normal casting bar for extrusion production after successful extrusion test.

Homogenization annealing of ingot can not only make micro-structure and properties uniform. But also improve extrusion properties and reduce extrusion pressure. So, uniform annealing is necessary for ingot casting.

4. Extrusion Process

The key to the production of aluminum heat sink profile is the first trial of extrusion die. The operator should allow the main plunger to advance at a low pressure of less than 8MPa. After each fin of the die is uniformly extruded out. It can gradually pressurize to speed up the extrusion. Pay attention to the heating temperature of the tool/die when extrusion process. The die temperature should be close to the cast bar's.