The radiator profile is small in size, and products with symmetrical shapes are easier to manufacture. Most radiator profiles are flat and wide, with larger external dimensions, and some are asymmetrical. The depth and width between the fins are large, making it difficult to manufacture. In the ingot, mold, and extrusion process, many aspects are needed to cooperate in order to successfully produce the radiator profile. The alloy used for extruding heat sink profiles should have good extrusion force and thermal conductivity. Commonly used alloys are 1A30, 1035, 6063, etc. 6063 alloy has good mechanical properties in addition to good extrusion performance, so 6063 alloy is widely used at present.
The production of aluminum radiator profiles should start with the quality of ingots, mold materials and design, reduction of extrusion force and extrusion process.
1. Ingot quality requirements
During the casting process, the impurity content in the alloy should be strictly controlled to ensure the purity of the alloy melt. To control the Fe.Mg.Si content in 6063 alloy. The potassium sulfate content should be less than 0.2%, and the potassium sulfate content is generally controlled within the lower limit specified by the state, the Mg content is 0.45%~0.55%, and the Si content is 0.25%~0.35%. In the casting process, sufficient homogenization treatment should be carried out to ensure the uniformity of the structure and properties of the ingot.
The surface of the ingot should be smooth and free of segregation tumors and sand sticking. The end face of the ingot should be flat, and it should not be cut into a step shape or the cutting slope should be too large (the cutting slope should be within 3mm). Due to the stepped shape or the cutting slope is too large, when the flat die is used to extrude the heat-dissipating profile, the end faces of the ingot and the die are not uniform without the design of the baffle. Some parts contact the mold first, causing stress concentration, which is easy to squeeze the tooth profile of the mold, or cause inconsistent discharge sequence, which is easy to cause mold blockage or poor extrusion molding.
2. Mold requirements
Since most of the radiator profiled surface molds are slender teeth, they have to withstand greater squeezing force, and each tooth must have higher strength and toughness. If the performance differs greatly from each other, it is easy to cause poor tooth surface strength or toughness. . Therefore, the quality of die steel must be reliable, and it is best to choose H13 steel produced by a reliable quality manufacturer, or choose high-quality imported steel. The heat treatment of the mold is very important. It is necessary to use vacuum heating and quenching, preferably high-pressure pure nitrogen quenching, to ensure that the performance of each part of the mold is uniform after quenching. On the basis of HRC48~52, it is quenched and tempered three times to make the mold hardness have sufficient toughness. This can effectively prevent broken teeth.
The key to successful extrusion is reasonable mold design and high processing accuracy. In general, direct extrusion of the ingot onto the mold belt should be avoided as much as possible. For the wide flat comb radiator profile, the small middle and large guide dies on both sides can make the metal flow to both sides, reduce the extrusion pressure of the die working belt, and the pressure is evenly distributed. Because the wall thickness difference of the radiator section is large, the difference should be properly maintained when designing the mold working belt, that is, the radiator section must be particularly enlarged, which can be as large as 20mm~30mm, and the position of the tooth tip must break the convention. Minimize its working band. All in all, it is necessary to ensure that all metals flow evenly. For flat and wide radiators, the thickness of the mold should be appropriately increased to ensure that the mold has a certain degree of rigidity. The thickness of the skin increases by about 30% to 60%. The mold must be very fine. The empty knife must be up, down, left, and right, and the middle must be symmetrical. The machining error between the tooth and the tooth must be less than 0.05mm. The large machining error is likely to produce eccentric teeth, that is, the thickness of the heat sink is different. Evenly, even broken teeth will occur.
On more mature sections, it is also a good method to use alloy steel nested molds, which have good rigidity, wear resistance, and are not prone to deformation, which is beneficial to the molding of radiator profiles.
3. Reduce extrusion pressure
In order to avoid tooth breakage, the extrusion pressure should be reduced as much as possible, and the extrusion pressure should be proportional to the length of the ingot. The alloy deformation resistance value is related to factors such as the state of the ingot and the degree of deformation. Therefore, the cast rods of heat-dissipating aluminum profiles should not be too long, which is about 0.6 to 0.85 times the length of ordinary cast rods. Especially in the casting rod trial and extrusion process, in order to ensure the quality of the casting rod, it is best to use a shorter casting rod, that is, the length of the general casting rod (0.4~0.6) times to ensure the quality of the casting rod.
For radiator profiles with complex shapes, in addition to shortening the length of the cast rods, pure aluminum short casting can be used as a trial extrusion test, and after success, ordinary ingots can be used for extrusion production.
During annealing, the uniform annealing of the ingot not only has uniform structure and performance, but also improves the extrusion performance and reduces the extrusion force. Therefore, the ingot must be uniformly annealed. As for the influence of deformation, because the fracture area of the radiator profile is generally relatively large, and the extrusion coefficient is generally within 40, the effect is not large.
4. Extrusion process
The key to the production of heat-dissipating parts is the initial test of the extrusion die. If possible, you can first perform a simulation test on the computer to see if the working belt of the die design is reasonable, and then try the die on the extruder. The first trial of the mold is very important. The operator should make the main plunger move slowly below 8MPa when the main plunger is pushed forward. It is best if someone looks at the exit of the mold with a flashlight, and waits for each heat sink of the extrusion mold to be evenly squeezed out of the mold. After the hole, pressure can be gradually accelerated to accelerate the extrusion. After the pressure test is successful, pay attention to controlling the speed of the extrusion force to make the operation smooth. When processing the special-shaped surface of the radiator, pay attention to the mold heating temperature, which is close to the ingot temperature. If the temperature difference is too large, the temperature of the metal will decrease due to the slow extrusion speed during upward pressure, which will easily cause mold blockage or uneven flow rate.
