Industrial developed countries, such as the United States, Japan, Germany, etc. all have a large number of modern hot-rolled steel pipe equipment, mainly automatic rolling pipe mill and cycle rolling pipe mill. The steel pipe produced by them accounts for 92% of the world's hot-rolled pipe production, and the steel pipe growth rate reaches 7.5%. Their hot-rolled pipe production accounts for about 15 percent of the world's steel production.

 

 

In recent years, tube billet continuous casting has developed greatly, gradually replaced the rolled tube billet. Increase metal yield by 10%-15% and save energy cost by more than 40%, greatly reducing the cost. Since the 1980s, cone-shaped roll piercing system and limited-action mandrel continuous rolling mill have been widely used. The limited-action mandrel continuous rolling pipe mill can produce steel pipe with diameter of 426mm and length of 50m. High production efficiency, the maximum output per machine can be up to 80-1 million t/a; Product quality is good, outside diameter tolerance can reach + / -0.02%-0.4%, wall thickness deviation within + / -03%-6.5% range. On the basis of two - roll mandrel continuous rolling mill, three - roll adjustable mandrel continuous rolling mill is developed abroad.

 

 

In recent years, the output of welded pipes in major steel-producing countries has exceeded the output of seamless pipes. For example, Japanese welded pipes accounted for 80% of the output of steel pipes in 1973. With the development of long-distance industrial transportation routes, the proportion of large diameter welded pipe is increasing. In the 1970s, the maximum outside diameter of u-o forming welded pipe in foreign countries increased to 1626mm, and its o-type press was as high as 6000MN, and the maximum wall thickness increased to 40mm. The annual capacity of u-o forming welding pipe machine is 1.1 million tons.

 

 

The spiral welded pipe USES a molding machine to shape the strip immediately after the spot welding position, cuts into the ruler and then sends several welding machine to carry on the double-face welding, makes one molding machine top several to use.

 

 

As the demand for precision, thin wall and high strength special steel pipe grows continuously, the production of cold rolling and cold drawing steel pipe develops rapidly

 

 

Cold rolling mill has cycle type, multi-roll type, vertical type, planetary type and continuous type and so on. Among them, the cycle cold mill is the most common. Cold drawing is the main method of production of precision steel pipe, there are three kinds of cold drawing machines including pendulum, rotary and drum. The rolling tube drawing machine covers a small area and has high drawing speed.