Welded steel pipes, also known as welded pipes, are steel pipes manufactured by welding steel plates or strips after they have been curled and formed. The production process of welded steel pipes is simple, with high production efficiency, diverse specifications, and low equipment costs. 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 welding seams has continuously improved, leading to an increasing variety of welded steel pipe specifications, which have replaced seamless steel pipes in numerous fields. Welded steel pipes are classified into longitudinal welded pipes and spiral welded pipes based on the form of their welding seams.

Longitudinal Welded Steel Pipes for Low-Pressure Liquid Transportation (GB/T 3092-2008), also known as ordinary 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. These pipes are categorized into regular and thickened pipes based on wall thickness, and into plain-end and threaded-end pipes based on the form of their ends. The specifications of these pipes are expressed in nominal diameters (mm), which are approximate values of the inner diameters. Customarily, they are also expressed in inches, such as 1½ inches. In addition to direct use in fluid transportation, these pipes are widely used as raw materials for galvanized welded steel pipes for low-pressure fluid transportation.

Galvanized Welded Steel Pipes for Low-Pressure Liquid Transportation (GB/T 3091-2015), also known as galvanized electric welded pipes or white pipes, are hot-dip galvanized welded steel pipes (furnace-welded or electric-welded) used for conveying water, gas, air, oil, heating steam, hot water, and other low-pressure fluids or for other purposes. They are divided into regular and thickened galvanized pipes based on wall thickness, and into plain-end and threaded-end galvanized pipes based on the form of their ends. The specifications are expressed in nominal diameters (mm), which are approximate values of the inner diameters, and are also commonly expressed in inches, such as 1½ inches.

Ordinary Carbon Steel Electrical Conduit (GB 3640-88) is used in electrical installation projects for industrial and civil buildings, machinery installation, and other applications to protect electrical wires.

Longitudinal Electric Welded Steel Pipes (GB/T 13793-2016) are steel pipes with welds parallel to the longitudinal direction of the pipe. They are generally classified into metric electric welded steel pipes, electric welded thin-walled pipes, transformer cooling oil pipes, etc.

Spiral Submerged Arc Welded Steel Pipes for Pressure Pipelines (SY 5036-83) are produced from hot-rolled steel coils, spirally formed at ambient temperature, and welded using the double-sided submerged arc welding method. These pipes are used for transporting pressurized fluids. They exhibit strong pressure-bearing capabilities, excellent welding performance, and have undergone rigorous scientific inspections and tests, ensuring safe and reliable use. With large diameters and high transportation efficiency, they can save investment in pipeline laying and are primarily used for oil and natural gas pipelines.

High-Frequency Welded Spiral Steel Pipes for Pressure Pipelines (SY 5038-83) are produced from hot-rolled steel coils, spirally formed at ambient temperature, and welded using the high-frequency lap welding method. These pipes are used for transporting pressurized fluids and possess high pressure-bearing capabilities, good plasticity, and ease of welding and processing. They have undergone strict scientific inspections and tests, ensuring safe and reliable use. With large diameters and high transportation efficiency, they can save investment in pipeline laying and are primarily used for oil and natural gas pipelines.

General Spiral Submerged Arc Welded Steel Pipes for Low-Pressure Fluid Transportation (SY5037-83) are produced from hot-rolled steel coils, spirally formed at ambient temperature, and welded using the double-sided or single-sided automatic submerged arc welding method. These pipes are used for transporting water, gas, air, and steam under general low-pressure conditions.

General High-Frequency Welded Spiral Steel Pipes for Low-Pressure Fluid Transportation (SY 5039-83) are produced from hot-rolled steel coils, spirally formed at ambient temperature, and welded using the high-frequency lap welding method. These pipes are used for general low-pressure fluid transportation.