|project||High pressure casting||Low pressure casting||High and low pressure casting comparison results|
(1) The essence of high pressure casting (referred to as die casting) is to fill the cavity of a die-casting mold (die-casting mold) with liquid or semi-liquid metal at a higher speed under high pressure, and form and solidify under pressure to obtain castings. ；
(2) Die casting has two characteristics of high pressure and high speed filling die casting. Its commonly used injection pressure is from several thousand to several tens of thousands kPa, even as high as 2×105kPa. The filling speed is about 10~50m/s, sometimes even more than 100m/s. The filling time is very short, generally in the range of 0.01~0.2s;
(1) The pressure and speed during pouring can be adjusted, so it can be applied to various casting molds (such as metal molds, sand molds, etc.), casting various alloys and castings of various sizes;
(2) Bottom injection type filling is adopted, the filling of molten metal is stable, and there is no splash phenomenon, which can avoid the entrapment of gas and the erosion of the mold wall and core, which improves the qualification rate of castings;
(3) Castings crystallize under pressure, with dense structure, clear contours, smooth surface and high mechanical properties, which are particularly advantageous for the casting of large and thin-walled parts.
(4) Eliminate the need to feed the riser;
(5) Low labor intensity, good working conditions, simple equipment, easy to realize mechanization and automation;
1. Low pressure casting can cast all kinds of complex castings. High pressure cannot produce complex castings. Low pressure casting is mainly used to produce automobile wheels in the automobile industry, cylinder blocks of internal combustion engines, cylinder heads, pistons, missile shells, impellers, wind guide wheels, etc. Castings with complex shapes and high quality requirements.
2. The cost of low-pressure mold and equipment is 1/3 of the cost of high-pressure casting, and the low-pressure development cycle is shorter than the high-pressure development cycle 1/3.
3. Special-shaped complex parts can be manufactured using sand core technology to reduce the difficulty of subsequent processing and process errors. High pressure cannot use sand core technology;
4. During the use of low-pressure products, it is denser and has higher noise reduction and shock absorption than high-pressure castings;
5. The high-pressure complex parts adopt multi-batch split combination, and the low-pressure adopts integrated molding technology to reduce the combination error and reduce the processing difficulty;
6. The low-pressure casting can meet the design requirements without being restricted by the process, and is convenient for production;
1). Due to the high speed of liquid metal filling the cavity during die-casting, the fluid state is unstable, so the general die-casting method is adopted, which is easy to produce pores inside the casting, and the elongation is not good, so heat treatment cannot be performed;
2). Die casting is more difficult for castings with complex recesses;
3). High melting point alloys (such as copper, ferrous metals), die-casting mold life is relatively low;
4). It is not suitable for small batch production. The main reasons are the high manufacturing cost of die-casting molds, the high production efficiency of die-casting machines, and the uneconomical production of small batches;
5). High equipment and mold costs.
1) The degree of freedom of the gate plan is small, which limits the product. (Restrictions on gate location and quantity, changes in product internal wall thickness, etc.;
2) Long casting cycle and poor productivity. In order to maintain directional solidification and melt fluidity, the mold temperature is higher and the solidification speed is slow.
3) The structure near the gate is relatively thick, and the mechanical properties of the lower profile are not high.
4) Need comprehensive and strict management (temperature, pressure, etc.)
1. High pressure casting pores, serious slag holes, poor density, and casting air leakage need to be impregnated;
2. Low-pressure castings have no porosity and slag holes, and the castings are dense and do not require impregnation;
3. The low-pressure development cycle is shorter than the high-pressure development cycle by 1/3
JIS tensile strength (MPa) 228±41;
Yield strength bai (MPa) 154±14;
Elongation (%) 1.4±0.8;
Hardness (HB) test bar requirements 74.1±1.5 castings cut;
Tensile strength σb (MPa): 275;
Yield strength (MPa) ≥ 170;
Elongation (%): ≥2-8;
Hardness (HB): ≥80;
The tensile strength of low pressure is higher than high pressure: 47 (MPa);
The yield strength of low pressure is higher than high pressure: 20 (MPa);
Low elongation is higher than high pressure: 6.2%;
Hardness Low pressure is higher than high pressure: ≥6 (HB) can be adjusted and controlled according to process performance requirements;
|Thermal Conductivity||96W/MK||159W/MK||Low thermal conductivity is higher than high pressure: 63W/MK|
|Aluminum utilization rate||50-65%||85-95%||Low-pressure aluminum utilization rate is higher than high-pressure: 30%|
|Heat treatment||no||T6||Improve mechanical properties and corrosion resistance, improve machinability and weldability, eliminate casting stress of castings and internal stress caused by machining, stabilize the shape and size of processed parts, and make some Si crystals of Al-Si alloys spherical To improve the plasticity of the alloy, the ability of the product to adapt to high and low temperature environments is strengthened, and the product stability is improved. |