Steel pipes are classified into two types:
seamless steel pipes and welded steel pipes according to their manufacturing methods. The seamless steel pipe is made of high-quality carbon steel or alloy steel and has hot rolling and cold rolling (extraction). The welded steel pipe is formed by welding a steel plate rolled into a tubular shape by a seam or a spiral seam. In terms of the manufacturing method, it is further divided into a welded steel pipe for low-pressure fluid transportation, a spiral-welded electric steel pipe, a direct-wound welded steel pipe, an electric welded pipe, and the like. Seamless steel tubes can be used in a variety of liquids, gas pipelines, and the like. Welded pipes can be used for water pipes, gas pipes, heating pipes, etc.
1. Welded steel pipe
1.1 Welded steel pipe and galvanized welded steel pipe for low pressure fluid transportation
The welded steel pipe for low-pressure fluid transportation is made of carbon soft steel. It is the most commonly used small-diameter pipe in pipeline engineering. It is suitable for conveying water, gas, steam and other media. It is divided into plated according to its surface quality. Zinc pipes (commonly known as white iron pipes) and non-galvanized pipes (commonly known as black iron pipes). The inner and outer walls are coated with a zinc protective layer about 3% to 6% less than the non-galvanized. According to the different wall thickness of the pipe, it is divided into three types: thin-walled pipe, ordinary pipe and thickened pipe. Thin-walled tubes are not suitable for conveying media and can be used as casings.
1.2
LSAW steel pipe can be divided into electric welded steel pipe and straight seam welded steel pipe which is rolled and rolled by field steel plate. Can make several wall thicknesses.
1.3 Spiral seam welded steel pipe is divided into automatic submerged arc welded steel pipe and high frequency welded steel pipe.
a.
SSAW steel pipe is divided into Class A pipe and Class B pipe according to the pressure of the conveying medium. Class A pipes are generally welded with ordinary carbon steel Q235, Q235F and ordinary low-alloy structural steel 16Mn. Class B pipes are welded with Q235, Q235F, Q195 and other steel materials and used as low-pressure fluid conveying pipes.
b. Spiral seam high-frequency welded steel pipe has no uniform product standard, generally made of ordinary carbon steel Q235, Q235F and other steel.
2. Seamless steel pipe
The seamless steel tubes are divided into hot rolled tubes and cold drawn (rolled) tubes according to the manufacturing method. The cold-rolled (rolled) pipe has a maximum nominal diameter of 200 mm and the hot-rolled pipe has a maximum nominal diameter of 600 mm. In pipeline engineering, hot-rolled pipes are often used when the pipe diameter exceeds 57 mm, and cold-drawn (rolled) pipes are often used when the pipe diameter is less than 57 mm. There are three types of seamless steel pipes commonly used in pipeline engineering:
2.1 General seamless steel pipe
General seamless steel pipe is referred to as seamless steel pipe. It is made of ordinary carbon steel, high quality carbon steel, ordinary low alloy steel and alloy structural steel. It is used to make liquid pipelines or to make structures and parts. Seamless steel pipes are available in outer diameter and wall thickness, with a variety of wall thicknesses at the same outer diameter and a wide range of pressures. Usually the length of the steel pipe is 3-12.5 m for hot rolled pipes and 1.5-9 m for cold drawn (rolled) pipes.
2.2 Seamless steel tubes for low and medium pressure boilers: Seamless steel tubes for low and medium pressure boilers are made of high quality carbon steel No. 10 and No. 20.
