1. Definition: Components made of metal materials through specific processes, with specific shapes, dimensions, and functions.
2. Classifications:
   • By Material: There are steel parts, aluminum alloy parts, copper alloy parts, etc. Steel parts feature high strength, good toughness, and wear resistance. Aluminum alloy parts are lightweight and corrosion - resistant. Copper alloy parts have excellent electrical and thermal conductivity.
   • By Function: They include structural parts (such as steel beams in buildings and mechanical brackets), transmission parts (such as crankshafts and gears), and connection parts (such as bolts and nuts).

II. Manufacturing Processes

1. Casting: Pour liquid metal into a casting mold cavity and solidify it. There are sand casting (low - cost, suitable for complex - shaped and high - volume parts) and investment casting (high - precision, used for precision parts), etc.
2. Forging: Apply pressure to the blank to make it plastically deformed. It is divided into free forging (high flexibility, for single - piece and small - batch production) and die forging (used for mass - producing complex and high - precision parts).
3. Machining: Use machine tools for cutting. Common methods include turning (for machining rotating parts), milling (for machining planes, grooves, etc.), drilling (for making holes), and grinding (for precision finishing of parts).

III. Application Fields

1. Automotive Industry: A large number of metal parts are used in components such as engines and chassis, such as pistons, connecting rods, and suspension system parts, affecting the performance and safety of vehicles.
2. Aerospace: Metal parts like engine blades, casings, airframe frames, and landing gears work in extreme environments, with extremely high requirements for performance and precision.
3. Electronic Devices: Used for heat dissipation and electromagnetic interference shielding. For example, the metal shell of a mobile phone dissipates heat, and the aluminum alloy radiator of a computer conducts heat.

IV. Development Trends