"2013 is the last year of the implementation period of the project for the development of key automotive lightweight technology and the integrated application of the entire vehicle. Some key automotive lightweight technologies are expected to be promoted and applied." A few days ago, the National Automotive Lightweight Technology Innovation Strategic Alliance was held. The National "Twelfth Five-Year" Science and Technology Support Program "Development of Key Lightweight Automotive Technologies and Integrated Application of Vehicles" project promotion meeting. Participants revealed that at present, my country has basically broken through the lightweight design technology and evaluation method of car body, high-strength steel parts stamping and hot forming technology, high-strength steel parts advanced forming technology, fiber-reinforced plastic modular design and application technology, deformed aluminum alloy parts The development and integration of multiple lightweight technologies aimed at reducing the weight of the entire vehicle and other key automotive lightweight technologies.
New materials continue to emerge
Wang Zhiwen, deputy secretary-general of the National Automotive Lightweight Technology Innovation Strategic Alliance, believes that cars are not that heavier cars are safer. Even if the car uses very light materials, if the high-strength processing technology is adopted, the elasticity is very good, and the safer it is. In recent decades, steel sheets for automobiles have become thinner and thinner, and steel strength and corrosion resistance have also been greatly enhanced. The car bodies are tailor-welded by steel plates of different strengths, and steel plates of different strength grades are used in different positions of the stress environment. For safety reasons, high-strength steels are mostly used in places where the stress conditions are harsh and thick steel plates cannot be used (such as anti-collision beams and some reinforced parts).
However, the increase in material strength also brings some problems, mainly the difficulty of processing. Generally, cars are manufactured by stamping, that is, they are formed by extruding materials with molds. The increased strength of automotive steel plates puts forward higher requirements on the stamping process, and now there are many deep-drawn parts, and the materials are prone to cracks and wrinkles. In order to avoid the above situation, manufacturers must study the deformation of the steel plate during stamping to prevent the steel plate from tearing during stamping. However, the better the strength of the steel plate, the more difficult it is to stamp.
In order to fundamentally solve the stamping problem of high-strength steel, a new type of steel is used in the production of car bodies. The matrix of this kind of steel is relatively soft and tough ferrite, which is inlaid with martensite with good hardness, which is easier to form during stamping and has considerable strength after forming. Therefore, this new type of automobile steel will make cars safer.
At present, the thickness of steel plates for vehicles has been reduced to 0.6mm. Analyst Luo Baihui said that this may have reached the limit of the thickness of the steel plate. No matter how thin the steel plate is, no matter how strong it is, it also loses the structural stability of many materials. Now automotive steel plates are increasingly challenged by new materials. The atomic weight of iron determines that its density cannot be changed, and the road to weight loss through thinning seems to have come to an end.
It is understood that the National Automotive Lightweight Technology Innovation Strategic Alliance is cooperating with Changan Automobile Group to jointly develop and promote the "aluminum instead of steel" engine cover. According to Wang Zhiwen, this research is based on the consideration of protecting pedestrians in the event of an accident. Because the application of aluminum alloy in the hood and other parts can reduce the secondary injury caused by the impact. Although the weight of aluminum plate is about 1/3 of that of steel plate, the collision energy it can absorb is twice that of steel plate. Aluminum alloy has a higher safety factor when encountering an impact, because its material has a very good energy absorption effect. Now aluminum alloys are gradually being widely used in high-end cars. All-aluminum SUVs have appeared, and high-end cars with aluminum as the front structure are also being imitated by the industry.
For some steel companies, automotive steel accounts for about 1/3 of current product sales. In order to ensure the automotive steel market and respond to the impact of new materials, many steel companies are actively cooperating with automotive companies to develop a new generation of lightweight and high-strength steel, hoping to compete with aluminum alloys, plastics, and carbon fiber composite materials.
Composite materials still need time
According to the data of the American Chemical Industry Association, the total weight of automobile plastic parts is less than 1/10 of the total weight of automobiles. Therefore, the space for expansion and application is still very broad. The only disadvantage of composite materials is poor flame retardancy, but it can be improved by adding flame retardant materials. In recent years, in order to enhance market competitiveness, various car companies have developed and launched models with lightweight designs. BMW will mass-produce BMWi3 pure electric vehicles this fall. The major feature of this car is that the outer shell is made of plastic and the chassis is made of aluminum alloy. Compared with traditional similar models, it can achieve a weight reduction of 250 kg to 350 kg.
Among local car companies, Great Wall Motor Co., Ltd. and Chery Automobile Co., Ltd. are the two car companies that have gone the farthest in this research field. The front fenders of Chery's A3CC Coupe are made of Noryl GTX resin. At the 2012 Beijing Auto Show, the seven window components of the Haval E concept car exhibited by Great Wall were all made of Bayer Makrolon polycarbonate and equipped with a large panoramic sunroof. This is the first time that my country's local automakers have applied polycarbonate windows on such a large scale. In addition, in addition to the family car market, the lightweight of trucks has already been put on the agenda. Beiqi Foton has changed the bumpers of medium and heavy-duty trucks from steel to plastic, and used glass fiber reinforced plastics in some auto parts, and also replaced some steel engine parts with plastic parts.
However, although foreign vehicle companies have become increasingly mature in lightweighting, Chinese local car companies are still in the stage of learning or catching up. "This is because the domestic composite material industry is still relatively backward, especially high-end materials are completely monopolized by some foreign chemical manufacturers, who master material design technology, analysis technology and component design technology. Because of high-end materials such as high-strength carbon fiber Materials have been monopolized by foreign technology for a long time, leading to high product costs. Some companies can only abandon the use of high-end materials in automobiles.” said Zhao Honghan, deputy secretary general of the China Unsaturated Polyester Resin Industry Association.
In the gap of the 2nd International Automotive Lightweight Innovative Materials and Molding Technology Application Summit Forum held not long ago, Jiang Dingfeng, a senior engineer of Haiyuan Machinery, also told the media that his company is investigating the carbon fiber auto parts complete equipment market. "The time of the official launch of the equipment is still uncertain. We still need to make some investment in technology and find an entry point in the market. Personally, it will be released in 2017 and 2018." He said that there are very few companies in the world for the time being. The ability to mass-produce carbon fiber auto parts and equipment is "BMW has just developed." In addition, he said that only carbon fiber materials can reduce car weight by 50% to 60%, while current materials can only reduce car weight by about 25%.