Understand the relevant dynamics of car brake discs

Casting is the process of pouring molten metal liquid into the mold, cooling and solidifying to obtain the required shape and performance of parts. Casting is a commonly used manufacturing method with low manufacturing costs and high process flexibility, which can obtain complex shapes and large castings. It occupies a large proportion in mechanical manufacturing, such as machine tools accounting for 60-80%, automobiles accounting for 25%, and tractors accounting for 50-60%.

Due to the increasing requirements for casting quality, casting accuracy, casting cost, and casting automation, casting technology is developing towards high precision, large-scale, high-quality, automation, and cleanliness. For example, in recent years, China has developed rapidly in high-precision casting technology, continuous casting technology, special casting technology, casting automation, and casting molding simulation technology

The high-strength automobile brake drum casting process involves adding three new elements, chromium, vanadium, and titanium, in addition to carbon, silicon, manganese, phosphorus, sulfur, and other elements already present in the raw material during the melting of gray cast iron. The addition amounts are chromium 0.5-0.8%, vanadium 0.05-0.09%, and titanium 0.05-0.09% by weight. These elements are obtained through melting, pouring, forming, annealing, sand cleaning, and mechanical processing.

In addition to the existing elements of carbon, silicon, manganese, phosphorus, sulfur, and chromium in the raw material, two new elements of copper and molybdenum are added, with a weight percentage of 0.3-0.8% for copper and 0.1-0.2% for molybdenum, which are obtained through melting, casting, forming, annealing, sand cleaning, and mechanical processing. The molybdenum is added together with the iron material during melting to overcome the aforementioned obstacles to ferrite nucleation and growth. However, during the solidification process, the role of chromium in promoting cementite is also strong, which can easily enhance the white tendency of cast iron; Vanadium is an element that strongly forms carbides, and the addition of vanadium to gray cast iron greatly enhances its tendency towards white cast iron; Titanium is also a strong carbide forming element. Therefore, the automobile brake hub manufactured by this method has high pearlite and hardness, and is prone to premature cracking during use, especially during the braking process, which can cause defects such as abnormal noise and shaking.