Bimetallic cylinder liner, also known as composite material cylinder liner or thermal expansion cylinder liner, is a key component used in internal combustion engines. Its main purpose is to protect the cylinder surface of the engine, preventing high-temperature gas from directly contacting the metal and causing overheating and wear. The bimetallic cylinder liner is made of two layers of metal materials with different coefficients of expansion. The inner layer is usually a high-temperature resistant alloy, and the outer layer is a metal with good thermal conductivity. When the engine is running, high-temperature gas will cause the inner metal to expand, while the outer metal will transfer heat due to its good thermal conductivity, thereby maintaining the cylinder wall temperature within an appropriate range and extending the service life of the engine. In addition, it can also absorb some mechanical impacts and improve the stability of the engine's operation. Therefore, bimetallic cylinder liners are widely used in power equipment such as automobiles, ships, and airplanes.