Mechanical parts refer to the inseparable basic units […]
Mechanical parts refer to the inseparable basic units that make up the machine, such as bolts, screws, keys, belts, gears, shafts, springs, pins, etc. Mechanical parts are divided into general parts and special parts. General-purpose parts refer to parts that can be widely used in various machines, and special-purpose parts refer to parts that can only be used in a certain type of specific machine.
1. Commonly used materials for mechanical parts
Materials for mechanical parts include metallic materials, non-metallic materials and composite materials.
Metal materials are divided into ferrous metal materials and non-ferrous metal materials. Ferrous metal materials include various steels, cast steels and cast irons, which have good mechanical properties (such as strength, plasticity, toughness, etc.), are relatively cheap and easily available, and can meet the requirements of a variety of properties and uses. Among all kinds of ferrous metals, alloy steel is often used to manufacture important parts due to its excellent performance. Non-ferrous metal materials include copper alloys, aluminum alloys, bearing alloys, etc., which have the advantages of low density, good thermal and electrical conductivity, etc., and can usually be used in occasions where friction reduction, wear resistance and corrosion resistance are required.
Non-metallic materials refer to polymer materials such as plastics, rubber, synthetic fibers, and ceramics. Polymer materials have many advantages, such as abundant raw materials, low density, good elasticity in an appropriate temperature range, and good corrosion resistance. The main disadvantage is that it is easy to age, and many of the materials have poor flame retardancy. Generally speaking, they have poor heat resistance. The main characteristics of ceramic materials are extremely high hardness, wear resistance, corrosion resistance, high melting point, high rigidity, and lower density than steel. At present, ceramic materials have been used in structures such as seals, rolling bearings, and cutting tools. Its main disadvantages are relatively brittle, low fracture toughness, expensive, and poor processing technology.
Composite material refers to a new type of material that uses two or more materials with significantly different physical and mechanical properties to obtain the required properties through a composite process. For example, glass, graphite (carbon), boron, plastic and other non-metallic materials can be compounded into various fiber-reinforced composite materials. By attaching plastic to the surface of ordinary carbon steel plate, a high-strength and corrosion-resistant plastic composite steel plate can be obtained. The main advantage is that it has higher strength and elastic modulus, and the quality is particularly small, but it also has poor heat resistance, heat conductivity and The disadvantage of poor electrical conductivity. In addition, composite materials are more expensive. Therefore, composite materials are currently mainly used in high-tech fields such as aviation and aerospace. In civilian products, composite materials also have some applications.
2. The principle of material selection for mechanical parts
Selecting suitable materials from a variety of materials is a task restricted by many factors. Commonly used materials for mechanical parts include steel, cast iron, non-ferrous metals and non-metals, etc. The brand, performance and heat treatment knowledge of common materials can be found in the mechanical design manual. The selection of materials in mechanical design is an important part. With the continuous development of materials science, the requirements for parts in the machinery manufacturing industry are increasing. Therefore, when selecting materials, designers should fully understand the properties and applicable conditions of the materials, and consider the use of parts, process and economic requirements. The following is an introduction to the general selection principles of metal materials (mainly steel).
The principle of selecting mechanical parts materials is: the required materials should meet the requirements of the parts, and have good manufacturability and economy.