Steel pipes are divided into two types according to their manufacturing methods: seamless steel pipes and welded steel pipes. Seamless steel pipes are made of high-quality carbon steel or alloy steel, and can be either hot-rolled or cold-rolled (drawn). Welded steel pipes are made of rolled steel plates welded with butt or spiral seams. In terms of manufacturing methods, they are further divided into welded steel pipes for low-pressure fluid transportation, spiral seam welded steel pipes, directly rolled welded steel pipes, welded pipes, etc. Seamless steel pipes can be used for various liquid, gas pipelines, etc. Welded pipes can be used for water pipelines, gas pipelines, heating pipelines, etc.
1. Welded steel pipe
1.1 Welded steel pipes and galvanized welded steel pipes for low-pressure fluid transportation
Welded steel pipes for low-pressure fluid transportation are made of carbon mild steel and are the most commonly used small diameter pipes in pipeline engineering. They are suitable for conveying media such as water, gas, steam, etc. According to their surface quality, they are divided into galvanized pipes (commonly known as white iron pipes) and non galvanized pipes (commonly known as black iron pipes). The inner and outer walls coated with a zinc protective layer are about 3% -6% heavier than non galvanized ones. According to the different wall thicknesses of their pipes, they are divided into three types: thin-walled pipes, ordinary pipes, and thickened pipes. Thin walled pipes are not suitable for conveying media and can be used as casing.
1.2 Straight seam rolled welded steel pipes
Straight seam rolled welded steel pipes can be divided into welded steel pipes and straight seam rolled welded steel pipes made by welding steel plates in sections on site. Can produce several pipe wall thicknesses.
1.3 Spiral seam welded steel pipes
Spiral seam welded steel pipes are divided into two types: automatic submerged arc welded steel pipes and high-frequency welded steel pipes.
a. Spiral seam automatic submerged arc welded steel pipes are divided into two categories based on the pressure of the conveying medium: Class A pipes and Class B pipes. Class A pipes are generally welded with ordinary carbon steel Q235, Q235f, and ordinary low alloy structural steel 16mn, while Class B pipes are welded with steel materials such as Q235, Q235f, and Q195, used as low-pressure fluid conveying pipes
b. Spiral seam high-frequency welded steel pipe There is no unified product standard for spiral seam high-frequency welded steel pipe, and it is generally made of ordinary carbon steel such as Q235 and Q235f.
2. Seamless steel pipe
Seamless steel pipes are divided into hot-rolled pipes and cold drawn (rolled) pipes according to their manufacturing methods. The maximum nominal diameter of cold drawn (rolled) pipes is 200mm, and the maximum nominal diameter of hot-rolled pipes is 600mm. In pipeline engineering, hot-rolled pipes are often used when the pipe diameter exceeds 57mm, and cold drawn (rolled) pipes are commonly used when the pipe diameter is less than 57mm. There are three types of seamless steel pipes commonly used in pipeline engineering:
2.1 General seamless steel pipes
Seamless steel pipe, commonly referred to as seamless steel pipe, is made of ordinary carbon steel, high-quality carbon steel, ordinary low alloy steel, and alloy structural steel. It is used for making liquid conveying pipelines or for making structures and parts. Seamless steel pipes are supplied according to their outer diameter and wall thickness. They have multiple wall thicknesses under the same outer diameter and can withstand a wide range of pressures. The usual length of steel pipes is 3-12.5m for hot-rolled pipes and 1.5-9m for cold drawn (rolled) pipes.
2.2 Seamless steel pipes for low and medium pressure boilers
Seamless steel pipes for low and medium pressure boilers are made of high-quality carbon steel grades 10 and 20, with operating temperatures.