金沙集团1862cc

Metallurgy refers to the process and process of extracting metals or metal compounds from minerals and making metals into metal materials with certain properties by various processing methods. Metallurgy has a long history of development, from the Stone Age to the subsequent Bronze Age, and then to the large-scale development of modern steel smelting. The history of human development is fused with the history of metallurgy.

Papermaking is one of the four great inventions of China. In the Western Han Dynasty, people already understood the basic method of making paper. In the Eastern Han Dynasty, the eunuch CAI Lun summed up the experience of his predecessors, improved the papermaking process, and used plant fibers such as bark, hemp heads, rags, and old fish nets as raw materials to make paper, which greatly improved the quality of paper.

Due to the harsh working conditions of petroleum underground, many downhole tools bear the load for a long time and are used in the working conditions of corrosion and wear, resulting in premature failure and failure, and thus shortening their life. For example: oil plunger, large rotor journal, sleeve, bearing bush, oil drill collar, wear plate, wear band, etc., but these parts are often very expensive.