Aluminum, magnesium and other are more active metal elements, aluminum content is ranked third in the earth's crust. Magnesium and aluminum are both important raw materials for industrial production. Because of their chemical properties are too lively, soft and volatile nature, so the common industrial production is commonly used alloy raw materials.
When designing the structure of aluminum alloy and magnesium alloy castings, you should usually pay attention to the following matters:
1 Because of the low melting point of aluminum alloy and magnesium alloy, a variety of casting methods can be used to produce aluminum alloy and magnesium alloy castings. Therefore, when designing their structures, the casting method used for the casting should first be considered in order to take into account the corresponding structural manufacturability.
(2) Aluminum alloy and magnesium alloy castings should adopt a thin-walled structure as much as possible to achieve uniform wall thickness. This is beneficial to prevent shrinkage porosity and increase the strength of the casting metal. However, for the uneven thickness of the wall, it is necessary to set up aluminum alloy and magnesium alloy castings for feeder feeding, and thickening of some parts may be used to achieve solidification in order to facilitate favorable feeding and ensure quality.
8 Aluminum alloys and magnesium alloys are easily oxidized and inhaled, and the density is small (2/3 to 3/4 smaller than cast steel and cast iron), making the metal liquid static pressure small and difficult to exhaust. Therefore, aluminum alloys and magnesium alloy castings are prone to generate pores and oxidized slags, which reduce the mechanical properties and airtightness. In the design of casting structures, large horizontal planes should be avoided, the transition should be smooth, and no turbulence of molten metal should be caused. '
4 Because of the low melting point of aluminum alloy and magnesium alloy, for the castings with certain airtightness requirements, special care should be taken when designing the casting structure to avoid the use of core support to fix the core, otherwise the core support and the casting body do not fuse, Oil leak.
5 As the aluminum alloy and magnesium alloy wire shrink more, the elastic modulus is lower, and the local stress concentration is sensitive, so it is easy to produce deformation and crack in the casting and use. Therefore, attention should be paid to the design of the casting structure.
a) Using I-shaped, slotted and Box-shaped cross-sections with larger moments of inertia to enhance the casting wall;
b) The structural shape of the reinforcing ribs should be appropriate. Otherwise, a large stress concentration is likely to occur at the edges of the ribs. In addition, the ribs should not be too thick, otherwise shrinkage holes can easily occur at the junction with the wall.
c) In order to avoid the edge of the hole should be built should be strengthened, such as the use of flange reinforcement;
d) Reinforcement ribs are often used for wheel castings to strengthen the connection between the hub and the web. For =-: between the heat three and the cast wall, a thicker wall connection with a slope is often used;
e) Thin-walled castings can be reinforced with ribs or stepped sections; large diameter bolts with relatively long distances are not required to fasten aluminum alloys and magnesium alloy castings, otherwise shadowing may occur due to excessive local forces. Reasonable The casting design should use a large number of small-diameter bolts to fasten the castings so that the fastening force of each bolt will not cause deformation of the softer aluminum alloy and the magnesium castings, in addition to the use of larger nuts. Washers to reduce the pressure of the mother to the boss;
f) As far as possible, the forces on the castings are transmitted along the axis so as to avoid additional bending or torsional stress. An inch of thin-walled shell-shaped aluminum alloy and magnesium alloy castings should not have abrupt shapes;
g) Since the elasticity of aluminum alloy and magnesium alloy is small and easily deformable, the aluminum alloy and magnesium alloy castings with press-fitting relationship must be considered when designing the casting structure, and the clearance generated after j deformation and multiple disassembly and assembly must be considered. Similarly, the threaded holes in the aluminum alloy and magnesium alloy castings should be longer than those in the cast iron and steel casting hatches. For the aluminum alloy castings, the L (length) of the brain (diameter) is 2 and for the magnesium alloy casting, L is taken. /d:2.5.
6 Magnesium alloys have higher compressive strength than tensile strength. Therefore, when designing magnesium alloy casting structures, asymmetric cross-sections and compressive stresses should be used.
7 Magnesium alloys have poor corrosion resistance, and commonly used surface treatment to improve the corrosion resistance of magnesium alloy castings. In addition, the structural design of castings should pay attention to the following: in the use of magnesium alloy castings (such as water pump castings) in contact with flowing water, try not to have Pits that can retain water; To avoid damage to the corrosion-resistant lacquer layer, there should be no sharp corners on the casting.
8 should pay attention to using bimetal casting, insert casting and other methods to solve the aluminum alloy and magnesium alloy casting structural design problems.
When designing the structure of aluminum alloy and magnesium alloy castings, you should usually pay attention to the following matters:
1 Because of the low melting point of aluminum alloy and magnesium alloy, a variety of casting methods can be used to produce aluminum alloy and magnesium alloy castings. Therefore, when designing their structures, the casting method used for the casting should first be considered in order to take into account the corresponding structural manufacturability.
(2) Aluminum alloy and magnesium alloy castings should adopt a thin-walled structure as much as possible to achieve uniform wall thickness. This is beneficial to prevent shrinkage porosity and increase the strength of the casting metal. However, for the uneven thickness of the wall, it is necessary to set up aluminum alloy and magnesium alloy castings for feeder feeding, and thickening of some parts may be used to achieve solidification in order to facilitate favorable feeding and ensure quality.
8 Aluminum alloys and magnesium alloys are easily oxidized and inhaled, and the density is small (2/3 to 3/4 smaller than cast steel and cast iron), making the metal liquid static pressure small and difficult to exhaust. Therefore, aluminum alloys and magnesium alloy castings are prone to generate pores and oxidized slags, which reduce the mechanical properties and airtightness. In the design of casting structures, large horizontal planes should be avoided, the transition should be smooth, and no turbulence of molten metal should be caused. '
4 Because of the low melting point of aluminum alloy and magnesium alloy, for the castings with certain airtightness requirements, special care should be taken when designing the casting structure to avoid the use of core support to fix the core, otherwise the core support and the casting body do not fuse, Oil leak.
5 As the aluminum alloy and magnesium alloy wire shrink more, the elastic modulus is lower, and the local stress concentration is sensitive, so it is easy to produce deformation and crack in the casting and use. Therefore, attention should be paid to the design of the casting structure.
a) Using I-shaped, slotted and Box-shaped cross-sections with larger moments of inertia to enhance the casting wall;
b) The structural shape of the reinforcing ribs should be appropriate. Otherwise, a large stress concentration is likely to occur at the edges of the ribs. In addition, the ribs should not be too thick, otherwise shrinkage holes can easily occur at the junction with the wall.
c) In order to avoid the edge of the hole should be built should be strengthened, such as the use of flange reinforcement;
d) Reinforcement ribs are often used for wheel castings to strengthen the connection between the hub and the web. For =-: between the heat three and the cast wall, a thicker wall connection with a slope is often used;
e) Thin-walled castings can be reinforced with ribs or stepped sections; large diameter bolts with relatively long distances are not required to fasten aluminum alloys and magnesium alloy castings, otherwise shadowing may occur due to excessive local forces. Reasonable The casting design should use a large number of small-diameter bolts to fasten the castings so that the fastening force of each bolt will not cause deformation of the softer aluminum alloy and the magnesium castings, in addition to the use of larger nuts. Washers to reduce the pressure of the mother to the boss;
f) As far as possible, the forces on the castings are transmitted along the axis so as to avoid additional bending or torsional stress. An inch of thin-walled shell-shaped aluminum alloy and magnesium alloy castings should not have abrupt shapes;
g) Since the elasticity of aluminum alloy and magnesium alloy is small and easily deformable, the aluminum alloy and magnesium alloy castings with press-fitting relationship must be considered when designing the casting structure, and the clearance generated after j deformation and multiple disassembly and assembly must be considered. Similarly, the threaded holes in the aluminum alloy and magnesium alloy castings should be longer than those in the cast iron and steel casting hatches. For the aluminum alloy castings, the L (length) of the brain (diameter) is 2 and for the magnesium alloy casting, L is taken. /d:2.5.
6 Magnesium alloys have higher compressive strength than tensile strength. Therefore, when designing magnesium alloy casting structures, asymmetric cross-sections and compressive stresses should be used.
7 Magnesium alloys have poor corrosion resistance, and commonly used surface treatment to improve the corrosion resistance of magnesium alloy castings. In addition, the structural design of castings should pay attention to the following: in the use of magnesium alloy castings (such as water pump castings) in contact with flowing water, try not to have Pits that can retain water; To avoid damage to the corrosion-resistant lacquer layer, there should be no sharp corners on the casting.
8 should pay attention to using bimetal casting, insert casting and other methods to solve the aluminum alloy and magnesium alloy casting structural design problems.
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