The aluminum shell is produced and cast under high temperature conditions. The aluminum shell is produced too fast and the cooling intensity is relatively large, resulting in some elements in the alloy cannot be transformed into required elements

In the process of developing from a big country to a powerful country, the number of enterprises in China's hardware accessories industry, whether manufacturing or circulation, will become smaller and smaller, and the scale and strength of enterprises will become larger and larger. It is bound to follow a path of cross regional, transnational, collectivization and chain operation relying on brands, technology content and strong capital.

From visual inspection to simple measurement and then to precision measurement, the progress of measurement technologymust ensure the progress of manufacturing technology to a certain extent. Mr. Qian Xuesen, a famous scientist, also pointed