Comparison of Semi-Metal Brake Pads and Ceramic Brake Pads

Nov. 11, 2020


Semi-metal friction material is a new type of automobile brake material developed in the 1970s. The formula usually contains about 20%-45% of ferrous metal components. By adding these components, the materials have good thermal stability and good thermal conductivity, which overcomes the serious thermal decline of asbestos friction materials at high temperatures and the friction surface is easy to crack At present, semi-metal friction materials are still the most widely used in China, but for foreign or domestic, semi-metal friction materials still have many shortcomings. For example, steel fiber is easy to rust, and it is easy to adhere to the counterpart after rust. There is greater damage, which reduces the strength of the friction material and intensifies wear. At the same time, the hardness of the steel fiber is high, and the hardness difference with the dual is too large, which is easy to damage the dual and accelerate the wear of the dual. These kinds of problems are like "stubborn diseases" that plague many manufacturers and have not been effectively resolved.


In order to solve many problems of semi-metal friction materials, ceramic brake pads are presented as a new formula. Ceramic brake pads are based on the principle of cermet rather than non-metal ceramics. When the brake pads are braked at high speed and vigorously, high temperatures are generated on the friction surface. At this high temperature, a similar reaction of cermet sintering will occur on the surface of the Brake Pad, so that the brake pad has good stability at this temperature. The semi-metal brake pads will not produce a sintering reaction at this temperature. The sharp increase in surface temperature will cause the surface material to melt and even produce air cushion, which may cause the brake performance to drop sharply after continuous braking or the brakes are completely lost.


Because steel fiber will rust, produce noise and dust, it cannot meet the requirements of ceramic formula. Therefore, ceramic brake pads are composed of ceramic fiber, non-ferrous filler material, adhesive and a small amount of metal, including mineral fiber, aromatic Compared with other brake pads, ceramic type brake pads are cleaner and quieter than other brake pads, and provide excellent braking performance without wearing the mating parts.


 Ceramic brake pads have the following advantages over other types of brake pads:


(1) The biggest difference between Ceramic Brake Pads and semi-metal brake pads is that there is no metal. The metal in the semi-metal brake pads is the material that mainly produces friction. The braking force is large, but the wear is large and noise is prone to occur. After installing the ceramic brake pads, there will be no abnormal squeal during normal driving. Because the ceramic brake pads do not contain metal components, it avoids the metal squeal similar to the friction between the semi-metal brake pads and the counterpart.


(2) Stable friction coefficient. The friction coefficient is the most important performance index of any friction material, and it is related to the braking ability of the brake pad. In the braking process, due to the heat generated by friction, the working temperature increases, and the friction material of the semi-metal brake pad is affected by the temperature, and the friction coefficient begins to decrease. In actual applications, friction will be reduced, thereby reducing the braking effect. The friction material of semi-metal brake pads is immature, and the friction coefficient is too high, causing unsafe factors such as loss of direction, burning of pads, and scratching of brake discs during braking. Even when the temperature of the brake disc is as high as 650 degrees, the friction coefficient of the ceramic brake pads is still about 0.45-0.55, which can ensure that the vehicle has good braking performance.


Brake Pad

Brake Pad


(3) Ceramics have good thermal stability and low thermal conductivity, and good wear resistance. The long-term use temperature is 1000 degrees. This feature makes ceramics suitable for the high-performance requirements of various high-performance brake materials, and can meet the technical requirements of brake pads for high speed, safety, and high wear resistance.


(4) It has good mechanical strength and physical properties. Can withstand greater pressure and shear.


(5) It has very low thermal attenuation. When the temperature of the brake disc reaches 650 degrees, the friction coefficient of the ceramic brake pads is still around 0.45-0.55, which can still ensure that the vehicle has good braking performance to ensure safety, and the thermal attenuation of the brake pads is small.


(6) Improve the performance of brake pads. Due to the fast heat dissipation of ceramic materials, its friction coefficient is higher than that of Semi-Metal Brake Pads in the manufacture of brakes.


(7) Security. The brake pads will generate instantaneous high temperature when braking, especially when driving at high speed or when braking emergency. At high temperatures, the friction coefficient of the friction plate will decrease, which is called thermal decay. Semi-metal brake pads have low thermal decay, high temperature conditions and increased brake oil temperature during emergency braking, which delays braking and even loses braking effect. The safety factor is low.


(8) Comfortability. In the comfort index, car owners are often most concerned about the noise of the brake pads. In fact, noise is also a problem that ordinary brake pads cannot solve for a long time. The noise is caused by abnormal friction between the friction plate and the friction disc. The cause of the noise is very complicated. The braking force, the temperature of the brake disc, the speed of the vehicle and the weather conditions may all be the causes of the noise.


(9) Excellent material properties. The high-tech materials such as large particles of graphite/brass/advanced ceramics and semi-metal used in ceramic brake pads have the advantages of high temperature resistance, wear resistance, brake stability, repair of brake discs, environmental protection, noise-free and long service life, and overcome semi-metal brakes. The defects in the material and craftsmanship of the disc are currently the most advanced advanced ceramic brake discs in the world. In addition, the ceramic slag ball content is low, the reinforcement is good, and the dual wear and noise of the brake pad can also be reduced.


(10) Long service life. Service life is an indicator that everyone is very concerned about. The service life of semi-metal brake pads is below 25,000-40,000 kilometers, while the service life of ceramic brake pads is above 60,000-80,000 kilometers. That's because the unique formula material used in the ceramic brake pads is only one or two kinds of electrostatic powder, and the other materials are non-static materials, so that the powder will be taken away by the wind with the movement of the vehicle and will not stick. Affect the appearance on the wheel hub. The life of ceramic materials is 50% longer than that of ordinary semi-metals. After using ceramic brake pads, there will be no scratching grooves on the brake disc, which extends the service life of the original brake disc by 20%.


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