What's the material for the brake drum?

The brake drum is a brittle gray cast iron material. A brake drum is a cast iron piece shaped like a tambourine that is fixed to the tire and rotates at the same speed. When braking, oil pressure is used to push the Brake shoe to contact the inner edge of the Brake drum, and the friction generated by the contact is used to restrain the rotation of the tire to achieve the purpose of braking. The drum brake is composed of a brake floor plate, a brake pump, a brake shoe and other relevant connecting Rod, a spring, a pin and a brake drum. Currently only commonly used in the rear wheel. Drum brakes, which are cheaper and have higher absolute braking power, are more commonly used in the rear wheels of small cars. But its attrition rate is higher, therefore at the same time the overall cost is higher