How much do you know about semi-metallic brake pads?
Semi-metallic brake pads are a new type of friction material developed on the basis of organic friction materials and traditional powder metallurgy friction materials. It uses metal fibers instead of asbestos fibers. It is a non-asbestos friction material developed by Bendis Company of the United States in the early 1970s.
"Semi-metal" hybrid brake pads (Semi-met) mainly use rough steel wool as the reinforcing fiber and important compound. Asbestos and non-asbestos organic brake pads (NAO) can be easily distinguished from the appearance (fine fibers and particles), and they also have certain magnetic properties.
Semi-metallic friction materials have the following main characteristics:
(l) Very stable below the coefficient of friction. No heat decay occurs. Good thermal stability;
(2) Good wear resistance. The service life is 3-5 times that of asbestos friction materials;
(3) It has good friction performance and stable friction coefficient under relatively high load;
(4) Good thermal conductivity. The temperature gradient is small. Especially suitable for disc brakes with small size;
(5) Braking noise is small.
The United States, Europe, Japan and other countries began to promote and use it on a large scale in the 1960s. The wear resistance of the semi-metal sheet is more than 25% higher than that of the asbestos sheet. At present, it occupies a dominant position in the brake pad market in my country. And most cars in the United States. Especially cars and vans. Semi-metallic brake linings already account for more than 80%.
However, the product still has the following disadvantages: ①Steel fiber is easy to rust, and it is easy to stick or damage the pair after rusting, and the strength of the product is reduced after rusting, and the wear is increased; ②The thermal conductivity is high, and it is easy to cause air resistance in the braking system at high temperatures The friction disc layer is separated from the steel plate: ③The hardness is high, which will damage the dual material, resulting in chatter and low-frequency braking noise; ④The density is high.
Although semi-metallic brake pads have many disadvantages, they are still the preferred material for automotive brake pads due to their good production stability and low price.
