The Application of Wollastonite in Brake Shoes Production
Wollastonite, a naturally occurring calcium – silicate mineral, has become an important component in the production of brake shoes. As the key friction – generating elements in braking systems, brake shoes rely on high – performance friction materials to ensure reliable braking. Wollastonite, when incorporated into brake shoes friction materials, brings about a series of changes in the performance of brake shoes mixtures or brake shoes mixes.
Function in brake shoes mixture
Wollastonite plays multiple crucial roles in the brake shoes mixture. Firstly, it serves as a reinforcing filler. In a typical brake shoes friction material composition, when wollastonite accounts for 10 – 15% by mass, it can increase the tensile strength of the material by approximately 10 – 15MPa. This enhanced strength allows the brake shoes to endure the intense mechanical forces during braking without structural failure.
Secondly, wollastonite contributes to improving the thermal stability of the friction material. During the braking process, large amounts of heat are generated. Brake shoes with wollastonite – containing friction materials can dissipate heat more effectively. For instance, experiments show that the surface temperature of brake shoes with wollastonite can be reduced by 20 – 30°C compared to those without it under the same braking conditions, which helps to maintain the braking performance and prevent thermal fade.
Advantages
1. Stable Friction Performance
Wollastonite – added brake shoes demonstrate excellent friction stability. In the SAE J661 standard friction test, the coefficient of friction of brake shoes with wollastonite remains relatively stable within a range of 0.3 – 0.5 under different braking speeds (from 50 km/h to 150 km/h). This stability ensures consistent braking force, providing drivers with better control over the vehicle during braking.
2. High Wear Resistance
The wear resistance of brake shoes is significantly improved by the addition of wollastonite. Laboratory wear – testing results show that the linear wear rate of brake shoes with wollastonite is only about 0.2 – 0.3 mm/1000 cycles, while that of traditional brake shoes without wollastonite is 0.4 – 0.5 mm/1000 cycles. This means that the service life of brake shoes with wollastonite can be extended by about 30 – 50%, reducing the frequency of replacement and maintenance costs.
Disadvantages
1. High Cost
The main drawback of using wollastonite in brake shoes production is its relatively high cost. High – quality wollastonite powder suitable for brake – shoe manufacturing is 2 – 3 times more expensive than some common mineral fillers such as talc or mica. This cost factor may increase the overall production cost of brake shoes, making it less attractive for price – sensitive markets.
2. Processing Difficulties
Wollastonite has certain processing difficulties. Its needle – like crystal structure may cause problems during the mixing process in brake shoes mixes. For example, it is prone to agglomeration, which is difficult to disperse evenly in the matrix of the friction material. Uneven dispersion may lead to inconsistent performance of the brake shoes, such as local over – wear or inconsistent friction.
In summary, although wollastonite offers remarkable advantages in terms of friction stability and wear resistance in the production of brake shoes, its high cost and processing challenges need to be carefully addressed to fully realize its potential in the brake – shoe industry.