At present, in the production of small cars, ordinary galvanized sheets are widely used. Galvanized steel sheet has good plastic deformation processing properties, and its strength and bending stiffness can also meet the requirements of car bodies. It can also meet the requirements of car body tailor welding, so it is widely used in automobile bodies. In order to meet the requirements of lightweight in the machinery manufacturing industry, the steel industry launched a series of high-strength stainless steel plates for small vehicles. This kind of high-strength steel plate is obtained by strengthening the method on the basis of high-carbon steel plate, and the strength is greatly improved. Utilizing high toughness characteristics, the physical performance requirements of the car body can be maintained even when the thickness is reduced, thereby reducing the weight of the car. For example, BH steel plates are under low-strength conditions. After being stamped, they are spray-painted and tempered to increase their strength. In comparison, the strength of steel plates produced in the past with a strength of 440MPa can be increased to 500MPa after using this processing technology. Originally, 1 mm thick steel plates were used as side panels, while high-strength steel plates only need 0.8 mm thick steel plates. The use of high-strength steel plates can also effectively improve the impact resistance of the car body, avoid dents caused by impact from sand and gravel on the ground during driving, and extend the service life of the car.
High-strength steel plates for automobiles should have the characteristics of high toughness and good ductile plastic deformation. At present, high-strength steel plates include BH steel (paint-hardened thick steel plate), dual-phase DP steel, change-induced plastic deformation steel (TRIP), micro-aluminum alloy M steel, high toughness void-free solid solution IF steel, etc. They are generally used for parts that require high toughness, adjust impact absorption energy, and have strict molding requirements, such as wheels, lifting components, bumpers, and anti-skid bars. With the development of performance and forming technology, high-strength steel plates are used Take the internal and external parts of the car, such as the car roof panel, the internal and external door panels, the diesel engine hood, the trunk lid, etc. Nowadays, many mid- to high-end cars use high-strength steel plates.
After more than 20 years of industrial development and production, high-strength steel plates now have standardized and basically manufactured product series and are widely used in the manufacture of prefabricated components for many cars. The average utilization rate of Japanese automobile high-strength steel plates was 25% in 1993 and 36% in 2001. The British Iron and Steel Institute AISI researched and developed the "Ultra-Light Body Body Research" (ULSAB) with 13 steel plants around the world. In March 1999, it exhibited a high-strength steel body in Michigan. The high-strength steel body used in the car body The steel plate is about 86%, and its average weight is 25% lighter than the general steel frame car body, which is very attractive to automobile manufacturers. In January 1998, 34 major steel companies in the world invested in each other to launch the high-strength steel body research and development project ULSAB-AVC. Through the use of high-quality stainless steel and new production technology, the weight of the car was reduced and the rationality was improved. Consider the more stringent impact regulations in 2005 and the European IV environmental standards implemented in 2006. It can be seen from this that the development of high-strength steel for automobiles is no longer simply a matter of upgrading car body materials, it also involves the issue of whether the car can meet new environmental protection and testing standards.
The development and application of high-strength steel are closely related to related technologies such as forming, spraying and welding. Stamping molding is an important forming method in the automobile industry. Car body prefabricated components, door frames, fenders, etc. are all produced through stamping molding. Some prefabricated components have very complex shapes. For example, high toughness, void-free solid solution IF steel has excellent deep drawing and drawing capabilities and is used in stamping dies to produce various complex shapes of automotive stamping parts. The ferrite inside it will not have any voids to solidify. Molten carbon and nitrogen atoms, so that the stainless steel plate can obtain a low yield ratio and high tensile strength after cold rolling and continuous quenching. In other words, it has very high "ductility" and will not break easily and can withstand various Deformation of stamping dies for various abrasive tools.
In recent years, a "tailored welding" technology has become popular, which is a kind of steel plate that is cut and welded by steel plates of different thicknesses and different properties. This kind of tailor-welded steel plate can be processed into stamping parts. The use of tailor-welded thick steel plates can be matched with different plates according to different positions of the trolley, so as to maximize its effect. For example, thicker high-strength steel plates are used in areas with heavy loads, while thicker high-strength steel plates are used in other positions. Thin high-strength steel plate. The use of tailor-welded steel plates simplifies the production process, improves the performance of prefabricated components and reduces weight. The components that use "tailor welding" on the prefabricated components of the car often include side frames, door beams, body bottoms, side rails, windshield windows, neutral poles, etc. Therefore, there are also high requirements for electric welding of high-strength steel plates.
Spraying is an important process in the automotive industry, including galvanized steel. At present, the body-in-white of mid-to-high-end cars generally uses galvanized sheets. Galvanized sheets can ensure that the car body will not rust after ten years of use. However, the roughness and cleanliness of the steel plates produced by the steel mill during the cold rolling process will directly affect the adhesion of the hot-dip galvanized zinc layer. In addition, the precision control of the thickness of the steel plate will also affect the working accuracy of the intelligent automobile production line. Since the intelligent automobile production line is welded by intelligent robots, plate thickness deviations will often cause virtual connections. Therefore, the intelligent automobile industry has very strict regulations on thick steel plates. For example, for a 0.8mm thick steel plate that is 1.5 meters wide and 3 kilometers long, the dimensional tolerance of the thickness and thickness cannot exceed 20 μm.
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