The material degree for brake drums is gray iron class 35 (HT250, FC250, GG25, ISO300, G250) with 1% copper (Cu). Their Brinell Hardness should be HB 180-250. Their weights are usually from 10kg to 45kg. They are widely used for the many kinds of vehicles such as cars, trucks, tractors etc.
What is brake drum?
Brake drum is shaped like a tambourine in the cast iron pieces, with the tire fixed and the same rotation speed. Promote the use of hydraulic brake shoes contacts the inner drum brakes, the friction generated by exposure to suppress the rotating tire to achieve the purpose of the brakes. Floor from the brake drum brake, brake wheel cylinder, brake shoe and other relevant connecting rod, spring, shoot nails, brake drums formed. Currently only used in the rear general. Lower the cost of drum brakes, braking force is absolutely higher, is more use of small cars in the rear. But the wear rate was higher overall costs so high at the same time.
The problems with brake drum production.
According to the experiences of Dandong Ruiding Foundry in China, for the large brake drums, they should be made by resin sand casting process. This casting process can keep the good dimensional requirements, and most importantly, they can keep a good dynamic balance. However, green sand casting process can also be an alternative choice, but the casting workshop must have the experience for making them. For the small brake drums, the automatic molding line and molding machines will be the good choice for making them. The automatic molding line can meet the large bulk demand, and keep a good technical requirements.
However, there were some problems when Dandong Foundry made brake drums. Firstly, for the 1% copper, the added copper will increase the material costs. If you did not add it, it will reduce the wear-resisting property, which will reduce the lifetime of brake drums. Secondly, for the surface quality, sometime, we may think the surface quality is not important for the brake drums since they are not visible after assembly, but good surface quality will mean the good dimensions, which will affect the dynamic balance property for the brake drums. The clients usually do not require the dynamic testing (dynamic-balancing experiment), but you could inspect the dimensions such as wall thickness. Good dimensions will guarantee the good dynamic balance. Of course, for the small brake drums used on the small cars, the dynamic testing will be necessary.