(I) Welded steel pipes

Welded steel pipes, also known as seam steel pipes, are generally welded from steel plates or steel strips. The hydraulic press is divided into galvanized and non-galvanized according to the appearance of the pipe. The appearance of galvanized white is also called white iron pipe or galvanized steel pipe; the appearance of non-galvanized steel is generally welded steel pipe, also known as black iron pipe. Galvanized welded steel pipes are often used to transport pipes that require relatively clean media, such as domestic water, purified air, and instrument air. Non-galvanized welded steel pipes can be used to transport steam, gas, compressed air, and condensate.

According to user requirements, welded steel pipes can be divided into two types at the factory, one with threaded pipe ends and the other without threaded pipe ends. The length of each welded steel pipe with thread at the pipe end is 4-9m, and the length of each welded steel pipe without thread is 4-12m.

Welded steel pipes are divided into thin-walled steel pipes, thickened steel pipes, and general steel pipes according to different wall thicknesses. The most used on process pipes is general steel pipe, whose experimental pressure is 2.0MPa. The experimental pressure of the thickened steel pipe was 3.0 MPa.

There are many connection methods for welded steel pipes, including screw connection, flange connection and welding. The flange connection is divided into threaded flange connection and welding flange connection, and the welding method is divided into gas welding and arc welding.

The standard scale of commonly used welded steel pipes is 6 ~ 150mm in nominal diameter.

(Two) seamless steel pipe

Seamless steel pipe is a large amount of industrial pipes with various specifications. It is basically divided into two types: seamless steel pipe for fluid transportation and seamless steel pipe with speciality. The former is a commonly used steel pipe for process pipelines and the latter Such as boiler special steel pipe, cracking furnace pipe and heat exchanger steel pipe. According to the material, it can be divided into carbon seamless steel pipe, chrome molybdenum seamless steel pipe and stainless, acid-resistant seamless steel pipe. According to the nominal pressure, it can be divided into three types: low pressure (0≤1.0MPa), medium pressure (1.0 <10MPa =, high pressure (≥10MPa). Process pipes are usually seamless steel pipes for fluid transportation.