Some car lovers once said that just replacing a set of carbon ceramic brake system for their sports car is enough to buy another B-class car. For example, to enjoy the carbon ceramic brake system optional service provided by Ferrari, you may need Pay more than RMB 250,000 in fees. Such expensive pricing is not an exaggeration to call carbon ceramic brakes the "big man" in the brake industry. What is the opportunity for the emergence of the carbon ceramic brake system and why is it so expensive?
This also starts with the car's braking system. As a process tool of energy conversion, the automobile brake system needs to convert the kinetic energy possessed by the automobile into heat energy. It takes a lot of energy to drive a one-ton car to a speed of hundreds of kilometers per hour. Conversely, it takes a similar amount of energy to decelerate a car with a speed of hundreds of kilometers per hour to zero in a short time. This requires a car. Kinetic energy can be converted into heat energy and quickly dissipated into the air. This whole process is completed by the automobile braking system. Therefore, when such a huge capacity is converted through the friction of the brake disc, and then the heat energy of the brake disc is dissipated to the outside world, its own temperature is quite high when the car is braking, and it will become red if it is severely overheated. Therefore, the requirements for high-quality brake discs in terms of high temperature resistance and heat dissipation are not low.
Traditional brake discs are made of metal materials and have poor heat resistance. If the surface temperature rises too high and approaches the melting point of the metal itself, the engineering strength of the entire metal brake disc will be weakened, leading to the weakening of the braking effect of the entire car. If this kind of thermal degradation is to be fundamentally solved, the heat resistance of brake discs and brake pads must be improved. Research has shown that carbon ceramic materials can improve these problems, and carbon ceramic brake systems have emerged.
As a new type of brake material developed in recent years, carbon ceramic (C/SiC) brake material has the advantages of low density, high temperature resistance, high friction performance and stability. The core of the carbon ceramic brake system lies in the brake disc. Its material is reinforced composite ceramic synthesized with carbon fiber and silicon carbide at a high temperature of 1700°C. Not only is it extremely resistant to high temperatures, but also weighs in the same size. It is also more than half lighter than traditional brake discs.
At present, the brake materials widely used in high-speed trains, automobiles and airplanes are mainly powder metallurgy and C/C composite materials. However, powder metallurgy brake materials have shortcomings such as easy bonding at high temperature, easy degradation of friction performance, significant reduction in high temperature strength, poor thermal shock resistance, and short service life; while C/C brake materials have low static and wet friction coefficients (wet Relative to dry state attenuation by about 50%), large thermal storage, long production cycle (about 1200h) and high production costs, etc., restrict its further development and application.
Examples of practical applications of carbon ceramic brake materials:
· The German Academy of Aeronautics and Astronautics (DLR) Walter Krenkel and others have studied C/SiC brake materials with high-end car brake discs as the application target. It has been applied in high-end cars such as Porsche 911, Audi A8L, and Ferrari.
· The American Starfire Company researched the precursor conversion method to prepare C/SiC brake materials and applied them to motorcycle brake pads.
·The scientific research team of Academician Zhang Litong of Northwestern Polytechnical University in China took the lead in researching carbon-ceramic brake materials in 2001. By the end of 2014, carbon-ceramic brake discs have been finalized on two key models of fighters and entered the batch production stage. Test flight verification has been carried out on multiple models of fighters. .
Carbon ceramic brake material is a high-performance brake material developed in recent years following powder metallurgy materials and C/C composite materials. Compared with traditional metal and semi-metal brake materials, it has the advantages of low density, high strength, stable friction performance, small friction, large braking ratio, high temperature resistance, and long service life. Compared with C/C composite materials, due to the introduction of an appropriate amount of SiC ceramic hard material as the matrix, the oxidation resistance and friction coefficient of the material are improved, and the friction performance is not sensitive to external environmental media (mold, oil, moisture, etc.). Therefore, carbon ceramic C/SiC brake materials have broad application prospects in high-speed trains, automobiles, airplanes and other fields.
The reason why carbon ceramic brake discs can improve the thermal decay phenomenon that occurs during automobile braking is because as a ceramic modified brake pad, it changes the sliding friction method and the traditional shear friction method, so that it will not scratch the brake during braking. Moving plate. During use, a carbon film will be produced. The surface of the brake disc is as smooth as a mirror, and there will be no friction furrows and become smoother, thereby increasing the friction surface to make the friction more stable and the braking performance stronger. In addition to the weight advantage, another major advantage of the wear-resistant carbon ceramic brake system is that there is a large amount of silicon carbide on its surface, and silicon carbide, as the hardest substance known to man, can make the life of carbon ceramics up to 30 Years.
Disadvantages: Although the advantages of carbon ceramic brakes are abundant, the production process is extremely complicated. The raw materials need to be die-casted under high temperature and high pressure for a long time. The strict production process makes it difficult for the output to increase significantly, so the price rises. It also limits the large-area application of carbon ceramics.