Automobile Casting Process Knowledge And Its Casting Technology Development Trend
1. The direction of development of automotive castings
1.1 integrated design of automotive castings
With the automotive energy saving and reduce the cost of production requirements continue to increase, make full use of the advantages of casting, the original stamping, welding, forging and casting forming several parts, through reasonable design and structural optimization, to achieve integrated parts casting Forming, can effectively reduce the weight of parts and reduce the unnecessary processing of the process, in order to achieve the weight of parts and high performance.
The development trend of automobile casting integration is more obvious in the development of nonferrous alloy castings. In order to make full use of the casting process to achieve the characteristics of the complex structure of the castings, there has been an integrated design of the door plate,
Seat skeleton, dashboard skeleton, front frame and firewall, the size of which is significantly larger than the castings currently produced, requires the production of 4 000 to 5 000 t or even larger tonnage die casting machines.
1.2 The weight of automotive castings
To ensure the strength and safety of the car under the premise of the car as much as possible to reduce the quality of the preparation, to achieve light weight, thereby enhancing the car's power, reduce fuel consumption and reduce exhaust pollution. Car reduction of 100 kg per 100 grams, 100 km fuel consumption can be reduced by 0.3 ~ 0.6 L, if the vehicle weight reduction of 10%, fuel efficiency can be increased by 6% to 8%. With the needs of environmental protection and energy conservation, the weight of the car has become the world's automobile development trend, the weight of automotive castings has become one of the important direction of development of automotive castings.
1.2.1 Lightweight design of automobile castings
For the overall safety factor of the castings, the equal thickness design is one of the main design methods for automotive castings. However, the main drawback of the equal thickness design is that the structural performance can not be fully exploited and the weight of the casting is increased. Using CAE analysis, topology optimization and other means to optimize the design of parts, so that parts of the stress value of various parts close to the various parts of the wall thickness is inconsistent, small parts of the thinner material thickness or not to reduce the material the weight of. Taking into account the casting forming can achieve the formation of complex structure castings, you can achieve a variety of irregular shaped cross-section. Design, the use of CAE or topology optimization and other means of stress analysis of parts. According to the distribution of the force, determine the shape of the parts and the specific local material thickness. Through the casting reinforcement, digging holes and thickening, can greatly reduce the weight of parts.
1.2.2 Light alloy car castings
The use of aluminum and magnesium and other light alloy materials are the main weight loss measures of current automobile manufacturers. The density of aluminum is only 1/3 of steel, and has excellent corrosion resistance and ductility. The density of magnesium is smaller, only 2/3 of aluminum, excellent in high pressure casting conditions. Aluminum and magnesium specific strength (strength and quality ratio) are quite high, to reduce the weight, improve fuel efficiency plays a decisive role. US auto industry in the past two years to improve competitiveness, with its substantial use of aluminum and magnesium castings and integrated casting is closely related.
1.2.3 High performance of automotive castings
Improve the performance of the material, so that the weight of the unit parts can withstand higher loads, is one of the ways to effectively reduce the weight of castings. Stent-type castings account for a significant proportion of castings, and the development of castings has also become one of the focuses. Through the heat treatment and other measures to make the material microstructure changes, thereby enhancing the strength of parts, stiffness or toughness, can effectively reduce the weight of parts.
Isotonic quenched ductile iron, not only the strength of steel than ordinary steel has improved, and the density is lower than the steel, the density of 7.1 g / cm3, while the cast steel density of 7.8 g / cm3, is widely recommended in recent years, the material The The use of isothermal quenching ductile iron, in the same size of the castings under the conditions of light, 10% lighter than steel. Dongfeng Motor Company in a certain type of commercial vehicles were used to cool the ductile iron cast iron instead of steel light weight verification work,
And for the isothermal quenching ductile iron pieces of high strength characteristics of the 14 suspension parts into the expert forum line redesign. Table 1 is the use of isothermal quenching ductile iron material after the replacement of the lightweight effect, the total weight reduction of nearly 40%, the effect is significant. It should be noted that the light weight effect in Table 1 is not only the material substitution, but also the contribution of the lightweight design. In general, the replacement of materials for automotive castings is often accompanied by lightweight design of parts.
In the aluminum alloy and magnesium alloy castings also use high strength, high tough materials to replace the original light alloy weight loss on the basis of the application of high-performance materials for further weight loss, the United States General Motors Corporation to replace the high-performance AE44 alloy The original aluminum alloy, the use of high-pressure casting method of production sub-frame, in the aluminum alloy weight loss on the basis of further weight loss 6 kg.
2. The development direction of automobile casting technology
2.1 Thin wall complex structure castings production technology
With the development of the automobile industry and the demand for energy saving and emission reduction, the weight of automobile parts is becoming more and more lightweight. Through thin-walled design, it is an important development direction of engine block. FAW Casting Co., Ltd. for the FAW Volkswagen production cast iron cylinder, for example, the early production of 06A cylinder wall thickness 4.5mm ± 1.5 mm, EA111 cylinder wall thickness 4 mm ± 1 mm, the current mass production of EA888Evo2 cylinder wall thickness 3.5 mm ± 0.8 mm, the next generation EA888Gen.3 cylinder product structure is more complex, the wall thickness of only 3mm ± 0.5 mm, is the thinnest gray cast iron cylinder. In the mass production, there are some problems such as broken core, drift core and wall thickness fluctuating. However, by controlling the quality of sand core and sand, But can not meet the EA888Gen.3 cylinder production requirements, must be used as a whole group of core pouring process.
2.2 Aluminum-magnesium alloy large-scale structural parts manufacturing technology
With the increasing demand for energy saving, environmental protection and cost reduction, aluminum-magnesium alloy large-scale structural casting has become an important development trend, and its manufacturing technology has become the current development of hot spots. At present, the main production technology of aluminum-magnesium alloy large-scale structural parts is high-pressure casting, extrusion casting and low-pressure casting. As the high-pressure casting production efficiency, product quality has become the main production process, the development of its manufacturing technology is mainly concentrated in the high-pressure casting process is easy to curl, easy to form a stomata inside the casting, can not heat treatment problems.