What is the material of a car brake drum?

Automobile brake drum is a kind of brittle gray cast iron material.

A brake drum is a cast iron shaped like a tambourine that is fixed to a tire and rotates at the same speed. When applying the brake, oil pressure is used to push the shoe of the brake to contact the inner edge of the brake drum. The friction force generated by the contact restrains the rotation of the tire for the purpose of braking. Drum brake is composed of brake bottom plate, brake pump, brake shoe and other related connecting rod, spring, pin and brake drum. Currently only commonly used in the rear wheel. Drum brakes, which cost less and have higher absolute braking power, are more widely used in the rear wheels of small cars. But its attrition rate is higher, therefore the whole cost is higher at the same time.