Solve the problem of heat treatment deformation of thin-shell cast aluminum parts

With the rapid development of my country's equipment manufacturing industry, the processing of aluminum parts has become more and more important, and many of them are common equipment shells and most of them are large thin-walled shells. Such parts are commonly used in aluminum ingot casting. After casting, in order to make the material structure of the parts meet the cutting performance and physical properties, heat treatment, quenching and aging are generally required. Due to the structural particularity, this kind of parts will produce obvious deformation after heat treatment, as thin-walled parts, if the deformation after heat treatment is too large, it cannot meet the requirements of use. After the parts are deformed, the general solution is to perform heat treatment and annealing on the parts first, and then let the fitter calibrate the shape, so that although the fitter can calibrate the part, the strength and hardness of the part material will greatly decrease and affect the performance of the part. Annealed parts are difficult to shape. The solution is to fix the shape of the part without annealing. The author has been engaged in the preparation of mechanical processing technology for a long time, and now we will discuss and communicate with you on such problems encountered in actual production and some solutions through experiments. Figure 1 shows that the outer shell of a certain model of equipment has a wall thickness of 4mm. It requires that all parts are directly casted except for the large flat surface and the flat peripheral contour casting allowance. The external dimensions of the parts are 500mm wide and 800mm high. The radius of the two arcs are 500mm and 400mm. Because it belongs to the thin-walled shell, in order to ensure the casting accuracy and surface quality of the parts combined with the casting cost, the metal mold sand casting is adopted. The heat treatment state of the parts is required to be T6 (quenching + artificial aging). In order to reduce the deformation of the parts during quenching, it is required to add support ribs to the parts from a technological perspective during casting (see Figure 1). However, the parts undergoing quenching and artificial aging during heat treatment are seriously deformed and cannot meet the requirements of use. The author tried to set the parts back to the thick steel plate for heat treatment (see Figure 2), but the parts still deformed seriously after loosening the splint after heat treatment. It is believed that the thermal expansion coefficient of the steel plate and aluminum material is different. Then the author investigated the whole process of heat treatment and found that the deformation of the parts mainly occurred in the quenching process, and the deformation was very small during the artificial aging of the parts. The purpose and principle of heat treatment (T6 state) of cast aluminum parts: T6 state is to make the parts get higher strength. The principle is that quenching is to allow the material to produce a large amount of supersaturated back solution and supersaturated solid solution to separate out the crystal structure of the material structure. Then the artificial aging is to increase the aggregation and dispersion of the body to make the material meet the performance requirements in a short time. If after quenching, the material of the part is allowed to form a solid body at room temperature (that is, natural aging, this process requires 100~150h, so the natural crystallization process is relatively slow, and the purpose of artificial aging is to accelerate its development. After quenching, the aluminum parts are in the crystal Before forming, the material has not hardened, but has become softer and more plastic than before. It looks like an annealing effect. According to the above principle, the author adopts the process to let the fitter correct the shape of the part within a short time after quenching, and then perform Artificial aging is a measure to reduce the heat treatment deformation of parts. Specific method: after quenching, when the temperature of the parts drops below 40

(That is, when a person wears gloves to touch the mosquito), let the fitter adjust the shape according to the size of the part. Because it is a thin-walled part and the material of the part is relatively soft at this time, a wooden hammer is generally used for shape correction. If necessary, tooling can be used to clamp the shape to be adjusted After the shape meets the size of the drawing, perform artificial aging or visual aging so that the deformation of the part is very small. Normally, after quenching, about h parts can be calibrated. If the time delay is too long, because the solid solution precipitation structure begins to crystallize, the part material begins to harden, which makes it difficult to align. Solve the problem of heat treatment deformation of thin-shell cast aluminum parts @陈办波$Hanguang Heavy Industry Co., Ltd. Military Products Center! Hebei Handan 056028 With the rapid development of my country's equipment manufacturing industry, the processing of aluminum parts has become more and more important, and many of them are common equipment shells and mostly large thin-walled shells. Such parts are commonly used in aluminum ingot casting. After casting, in order to make the material structure of the parts meet the cutting performance and physical properties, heat treatment and quenching are generally required.