1. Quality requirements of ingot
The surface of the ingot should be smooth, and no segregation nodules or sand should be allowed. The end face of the ingot should be flat, and it should not be cut into a step shape or the cutting slope is too large (the cutting slope should be within 3㎜). Because the step shape or tangential inclination is too large, when extrusion heat dissipation profile with a plane die, if no conductive jay is designed, the ingot directly touches the mold, due to the uneven end face of the ingot, some places contact the mold first, resulting in stress concentration, easy to break the tooth shape of the mold, or cause different discharge, easy to produce a bad phenomenon of plugging or extrusion molding.
2, the requirements for the mold
Because the mold of the radiator profile is a lot of elongated teeth, to withstand a lot of extrusion pressure, each tooth must have a high strength and toughness, if there is a great difference between the performance of each other, it is easy to make those teeth with poor strength or toughness fracture. Therefore, the quality of the mold steel must be reliable, it is best to use H13 steel produced by reliable manufacturers, or choose high-quality imported steel. The heat treatment of the mold is very important, to use vacuum heating quenching, it is best to use high pressure pure nitrogen quenching, which can ensure the uniform performance of each part of the mold after quenching. After quenching, three times of tempering should be taken to ensure that the hardness of the mold has enough toughness under the premise of HRC48 ~ 52. This is an important condition to prevent mold tooth breakage.
3, reduce extrusion pressure
In order to prevent mold teeth from breaking, extrusion pressure should be reduced as much as possible, and extrusion pressure is related to the length of the ingot, the size of the alloy deformation resistance, the state of the ingot, the size of the deformation degree and other factors. Therefore, the casting rod of the extruded cooling aluminum profile should not be too long, about the length of the normal casting rod (0.6 to 0.85 times). Especially in the test mold and extrusion of the first casting rod, in order to ensure the smooth production of qualified products, it is best to use a shorter casting rod, that is, the normal length of the casting rod (0.4 ~ 0.6) times to test the mold. For the radiator profile section with complex shape, in addition to shortening the length of the casting rod, it can also be considered to use pure aluminum short casting for the first test extrusion, and then use normal ingots for extrusion production after successful test extrusion.
4, extrusion process
The key to the production of radiator profiles is the first test of the extrusion mold. If conditions are available, you can first do a simulation test on the computer to see whether the working belt of the mold design is reasonable, and then test the mold on the extrusion machine. The first test mold is very important, the operator should let the main plunger forward pressure under the low pressure of less than 8MPa slow forward, it is best to use the flashlight light to look after the mold exit, such as extrusion mold each heat sink is evenly extruded out of the mold hole, in order to gradually pressure accelerated extrusion. When continuing extrusion after successful mold test, attention should be paid to controlling the extrusion speed to achieve smooth operation. When producing radiator profiles, attention should be paid to the heating temperature of the mold, so that the mold temperature is similar to the ingot temperature. If the temperature difference is too large, due to the slow extrusion speed during the upper pressure, the metal temperature will drop, and it is easy to produce the phenomenon of blocking or uneven flow rate.
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