Welded steel pipes, also known as welded pipes, are steel tubes formed by welding steel plates or steel strips after they have been curled into shape. The production process of welded steel pipes is simple, with high production efficiency, a wide range of specifications, and low equipment investment. However, their strength is generally lower than that of seamless steel pipes. Since the 1930s, with the rapid development of high-quality strip steel continuous rolling production and advancements in welding and inspection technologies, the quality of weld seams has continued to improve, leading to an increasing variety of welded steel pipe specifications, which have gradually replaced seamless steel pipes in many fields. Welded steel pipes are classified into longitudinal welded pipes and spiral welded pipes based on the form of their weld seams.
Longitudinal welded pipes have a simple production process, high production efficiency, low cost, and rapid development. Spiral welded pipes generally have higher strength than longitudinal welded pipes, allowing for the production of larger-diameter pipes from narrower billets, and pipes of different diameters from the same width of billet. However, compared to longitudinal pipes of the same length, the length of the weld seam increases by 30-100%, and the production speed is lower. Therefore, smaller-diameter welded pipes mostly adopt longitudinal welding, while larger-diameter pipes typically employ spiral welding.
Longitudinal Welded Steel Pipes for Low-Pressure Fluid Transmission (GB/T 3092-2008), also known as common welded pipes or black pipes, are used for conveying water, gas, air, oil, heating steam, and other low-pressure fluids, as well as for other purposes. The pipes are classified into regular and thickened wall types based on their wall thickness, and into plain-end and threaded-end pipes based on their end configurations. The specifications of the pipes are expressed in nominal diameters (mm), which are approximate values of the inner diameters. These diameters are often expressed in inches, such as 1½, etc. Besides being directly used for fluid transmission, these pipes are also widely used as the base pipes for galvanized welded steel pipes for low-pressure fluid transmission.
Galvanized Electric Welded Steel Pipes for Low-Pressure Fluid Transmission (GB/T 3091-2015), commonly known as white pipes, are hot-dip galvanized welded (furnace-welded or electric-welded) steel pipes used for conveying water, gas, air, oil, heating steam, hot water, and other low-pressure fluids or for other purposes. These pipes are categorized into regular and thickened galvanized types based on wall thickness, and into plain-end and threaded-end galvanized pipes based on end configurations. The specifications are indicated by nominal diameters (mm), which are approximations of the inner diameters, often expressed in inches, such as 1½, etc.
Ordinary Carbon Steel Wire Casing (GB 3640-88) is used in electrical installation projects for industrial and civil buildings, machinery installations, and other applications to protect electrical wires.
Longitudinal Electric Welded Steel Pipes (GB/T 13793-2016) are pipes with weld seams parallel to the longitudinal direction of the pipe. They are typically classified into metric electric welded steel pipes, electric welded thin-wall pipes, transformer cooling oil pipes, etc.
Spiral Submerged Arc Welded Steel Pipes for Pressure Fluid Transmission (SY 5036-83) are made from hot-rolled steel strips, formed into spirals at room temperature, and welded using the double-sided submerged arc welding method. These pipes are used for transmitting pressurized fluids. They exhibit strong pressure-bearing capabilities, excellent welding performance, and are reliable and safe for use after undergoing rigorous scientific inspections and tests. With large diameters and high transmission efficiency, they can save costs on pipeline installation and are primarily used for oil and natural gas pipelines.
Spiral High-Frequency Welded Steel Pipes for Pressure Fluid Transmission (SY 5038-83) are made from hot-rolled steel strips, formed into spirals at room temperature, and welded using the high-frequency lap welding method. These pipes have strong pressure-bearing capabilities, good plasticity, and are convenient for welding and processing. They are reliable and safe for use after undergoing various rigorous scientific inspections and tests. With large diameters and high transmission efficiency, they can save costs on pipeline installation and are primarily used for laying oil and natural gas pipelines.
Spiral Submerged Arc Welded Steel Pipes for General Low-Pressure Fluid Transmission (SY5037-83) are made from hot-rolled steel strips, formed into spirals at room temperature, and welded using double-sided automatic submerged arc welding or single-sided welding methods. These pipes are used for transmitting low-pressure fluids such as water, gas, air, and steam.
Spiral High-Frequency Welded Steel Pipes for General Low-Pressure Fluid Transmission (SY 5039-83) are made from hot-rolled steel strips, formed into spirals at room temperature, and welded using the high-frequency lap welding method. These pipes are intended for transmitting general low-pressure fluids.
Spiral Welded Steel Pipes for Piles (SY 5040-83) are made from hot-rolled steel strips, formed into spirals at room temperature, and welded using double-sided submerged arc welding or high-frequency welding methods. These pipes are used in civil engineering structures, docks, bridges, and other foundation piles.
