1, motor shell process structure analysis
Motor shell parts, the product is characterized by: (1) uneven wall thickness, thinner in the middle, surrounded by thicker; (2) the shape is very complex, the shape of the near-cylindrical, multi-hole, rib. Parts structure roughly along the through-hole diameter to the expansion, profile size of about 420mmX390mmX150mm, casting thickness is concentrated in 6-8mm, 28mm thick, thin 4mm, the product wall thickness suitable for extrusion casting technology, indirect extrusion casting of small wall thickness of 1-6mm. parts performance requirements: (1) gas tightness requirements are high, the motor shell extrusion casting at (1.6-2.0) (1.6-2.0MPa) pressure to maintain 3min without leakage; (2) alloy properties: tensile strength ≥ 240MPa elongation ≥ 1.0%, hardness ≥ 80HBW; (3) motor casing parts machined surface is not allowed to have cracks, cold segregation, shrinkage, undercasting and other defects.
Although the motor shell parts are non-axisymmetric parts, the pressure application position can be adjusted in the center to achieve rough symmetry. In order to make the casting wall thickness as uniform as possible, the upper and lower end faces of the motor shell opened a number of grooves, because the more uniform wall thickness of the casting, the liquid metal filling smooth and uniform distribution of extrusion force, to avoid the product partially over-thickness, the liquid metal aggregation contraction caused by the shrinkage; in order to avoid the deep and thin bore, the casting of the first short and thin bore, and then in the machining of the molding, because of the long and thin core in the casting of the temperature rise fast, low strength, molding Experiments are prone to fracture, often change the inlay core task is cumbersome; shell around the strength of the parts through the reinforcement, the shape of the surrounding by the slider extract core with the completion. Considering the surface quality of the motor shell longitudinal and not machined surface, as well as mold service life, draw mold slope 1.5 ° on one side.
Extrusion casting method to produce uneven thickness of the shell parts, due to the good fluidity of the liquid metal, coupled with the pressure to solidify under the action of molding and plastic deformation, the parts of the densification and performance to improve, can meet the uneven thickness of the shell parts of the shape and performance requirements. Through the above elaboration, the motor shell product manufacturing suitable for extrusion casting method, material selection ADC12.
2, squeeze casting process design
2.1 Squeeze casting method selection
The choice of extrusion casting method determines the ease of mold design and product quality behind. Direct squeeze casting is suitable for simple structure of the parts; and indirect squeeze casting to low-speed smooth, large flow of liquid metal will be pushed into the mold cavity and solidified under high pressure, the shape of the parts depends on the closed mold chamber, its size. Indirect squeeze casting of the sprue is generally a short distance, large cross-section, sufficient pressure retention process, the pressure transfer between the loss of less, and therefore suitable for the manufacture of structurally complex parts. Motor shell parts structure is very complex, direct extrusion casting is difficult to realize the shape of the parts, suitable for indirect extrusion casting process.
2.2 The number of castings in the mold cavity is determined
According to the characteristics of indirect extrusion casting, the production of parts, for large and complex parts of a mold a relatively reasonable. For the projected area of small parts, under the conditions of the equipment allows, can be selected into a mold more than one, and the number of cavities is good to use an even number, symmetrical distribution, so that as far as possible each position of the casting of the casting is subjected to a more uniform squeeze casting effect. Motor shell parts of larger size, and the outer perimeter of the bore and protruding parts, molding and demolding need to rely on core extraction to complete, a mold can not be realized, in summary, the motor shell castings using a mold a piece.
