1. The material that often used in machine parts
There are four major materials. They are ferrous metal, non-ferrous metal, non-metallic material and different kinds of composite material. Steel and iron casting of ferrous metal, copper alloy and aluminum alloy of non-ferrous metal are the most widely used.
2. The principle of choosing materials
How do you choose appropriate material? That is very important. When you choose materials of parts, three factors should be taken into consideration: usage, technique and economic effect.
Usage: Meeting the demand of usage is the most fundamental principle of choosing materials, including working condition, size and restriction of parts and importance of parts.
Generally speaking, reducing weight is one of major tasks of machine design. If the size of parts depends on strength, the size and weight are limited, materials with high strength will be applied. Parts under sliding friction should be made of materials with good anti-friction properties or wear-resistant materials. Parts that work at high temperatures should be made of heat-resistant materials, and parts that work in corrosive media should be made of corrosion-resistant materials.
Technique: Technique requirements refer to good cold and hot workability of welding materials. For example, box body parts adopt large-scale castings or molding parts. It depends on the production size whether casting or welding parts are used for box parts. Castings should be used for large batches and welding parts should be used for small batches. Materials with good fluidity should be selected for casting blanks and materials with good weldability should be selected for welding parts
The processability of material heat treatment should be considered.
Since general parts must be machined, cutting performance (easy chip breaking, smooth surface, small tool wear, etc.) should also be considered in the selection of materials.
Economic performance: Economy is first reflected in price of materials. On the basis of meeting the above two selection principles, materials with low prices should be selected as far as possible. Secondly, economy should not be considered only from the price, but also from the processing and manufacturing costs and use and maintenance costs. In short, economy should be comprehensively considered.