ã€China Aluminum Network】 1. Problems to be Considered in Mold Design The design of the mold must meet the calculation requirements for stiffness and strength in order to reduce the amount of elastic deformation when the mold is under pressure. When determining the working belt, the length of the working belt, the form of the air knife, the neck of the mold, and the form of the welding chamber must all be taken into account in selecting the preferred values ​​for the parameters. The selection of factors such as the diversion hole and diverter hole of the die should be selected as large as possible within the allowable range to achieve the purpose of reducing the pressure. Aluminum templates generally use hard alloys such as 6061, which makes the production technology more difficult. During the extrusion process, the material discharge, pressure, and discharge are often too slow. Therefore, the mold design plays a role in the production process. Great key role.
2. Die design diversion hole, diverted hole Design and design of the die when the diversion hole, diversion hole location should be evenly distributed, so that all parts of the profile can absorb the same amount of metal. The size of the diversion hole and the diverging hole is proportional to the area of ​​the profile. If the strength of the die and the surface quality of the profile are not affected, the diversion hole and the diverging hole should be made as large as possible. When the metal is extruded, the metal flows into the welding chamber and leads. The bigger the flow hole and the diverging hole, the smaller the force of the bridge area, the displacement of the metal flow from the bridge will reduce the resistance and the discharge speed will increase, but it will not affect the strength of the mold. Therefore, molds with small inlet holes and large bridge positions do not necessarily have stronger strength than those with larger inlet holes.
The bridge position design bridge position is an important part of the mold organization, it is the support bridge of the mold, must consider it to have sufficient support force to the mold when designing the mold bridge position. In order to meet the support strength of the mold, the general bridge angle is designed to be between 18-25°C. Too large angle will increase the friction between the metal flow and the bridge position, which will slow down the flow of the metal flow. The smaller the angle, the easier the metal will be for welding. The speed of discharge will increase. At the same time, design bridge point angle intersections as smooth as possible to avoid or reduce the welding dead angle.
The welding room design welding room should not be too deep, the welding room too deep will increase the metal volume of the welding room, welding room increases volume when the welding process is also lengthened, the extrusion pressure will then increase.
Work belt design mold work with polishing to be careful, to ensure flatness, verticality, can not appear Turtle or uneven, a reasonable calculation of the working belt length, uniform metal flow.
3. Extrusion process flow:
Aluminum rod heating (440-460°C)
Mold heating (420-460°C, 3-6h) → Extrusion (outlet temperature 530-570°C) → Spray air-cooled quenching → Take heat from the ingot (410-420°C)
Plate self-testing (below 200°C)→stretch straightening (below 70°C, elongation ≤1.5%)→cutting sawing→ringing (checking)→aging→hardness testing→removal (or oxidation, spraying) ).
Aluminum rod heating on the 6061 alloy, must be heated to above 500 °C, Mg and Si can be completely solid solution, extrusion ingot above 440 °C, due to the role of extrusion heat to make the temperature rise, through the die hole metal temperature reached 530-570 °C, to achieve solution treatment state, therefore, aluminum rod must be heated to between 440 ~ 460 °C before extrusion.
The temperature of the mould before heating on the mould is: 410-440°C for flat mould and 430-460°C for diverting mould; the heating time of the mould in the furnace is not allowed to exceed 10 hours, and the working time of the mould hole is easy to produce point corrosion.
The extrusion speed must be carefully controlled during extrusion. The extrusion speed has an important influence on the thermal effect of deformation, the uniformity of deformation, the process of recrystallization and solution, the mechanical properties of the product and the surface quality of the product. In order to increase production efficiency, according to many years of production exploration and experience accumulation, at present our main extrusion methods follow the “low-temperature and high-speed†production process, that is, the aluminum rod temperature is inversely proportional to the extrusion speed, and the aluminum rod has a high temperature and extrusion. The speed is appropriately slowed, the temperature of the aluminum rod is low, and the extrusion speed is appropriately accelerated. Through this adjustment mode, the extrusion production is adjusted to a better state. Under normal circumstances, the temperature can be accelerated when the upper mold is produced to the third stick, and the temperature of the flat die is kept at 390-410°C; the temperature of the split die is kept at 410-430°C. good.
In-line quenching is used to rapidly dissolve Mg2Si dissolved in a matrix metal at a high temperature and rapidly cooled to room temperature after being ejected. 6061 containing Mg2Si0.6-0.9%, from 500 degrees to 204 degrees to the critical cooling temperature range, a smaller cooling rate of not less than 180 °C/min, water-cooled, 6061 alloy aluminum template hardness requirements of ≥ 15HW, its large section Quench cooling, recommended at 549°C/min. Extrusion line quenching, the cooling rate should be able to ensure that the supersaturated solid solution is condensed on the principle of straightening the product, the quenching caused by quenching can be corrected to the limit.
Aging 6061 alloy aluminum profiles, its mechanical properties generally require tensile strength: 265 (σь) MPa or so, Vickers hardness ≥ 15HW. Therefore aging temperature is generally 180-200 °C, time 5-6h; sometimes in order to improve its strength properties, can also be used (170-180) °C × (6-8) h process.