Welded steel pipes, also known as welded pipes, are made by welding steel plates or strips after they are curled and formed into tubes. The production process of welded steel pipes is simple, with high efficiency, diverse specifications, and low equipment costs. However, their strength is generally lower than seamless steel pipes. Since the 1930s, with the rapid development of high-quality continuous rolling of steel strips and advancements in welding and inspection technologies, the quality of welding seams has continuously improved, leading to an increase in the variety and specifications of welded steel pipes. These pipes have gradually replaced seamless steel pipes in many fields. Welded steel pipes can be classified into straight seam welded pipes and spiral welded pipes based on the form of the weld seam.
Straight Seam Welded Steel Pipes for Low-Pressure Liquid Delivery (GB/T 3092-2008), also commonly known as ordinary welded pipes or black pipes, are used for transporting water, gas, air, oil, heating steam, and other low-pressure fluids, as well as for other purposes. These pipes are classified into regular and thickened pipes based on wall thickness, and into non-threaded (plain) and threaded pipes based on end form. The size of the pipe is indicated by its nominal diameter (mm), which is an approximation of the inner diameter. The size is often expressed in inches, such as 11/2. Besides direct use for fluid transportation, these pipes are also widely used as raw materials for galvanized welded steel pipes for low-pressure fluid delivery.
Welded Steel Pipes for Low-Pressure Fluid Transportation (GB/T 3091-2015), also known as galvanized electric welded steel pipes or white pipes, are hot-dip galvanized (furnace-welded or electric-welded) steel pipes used for transporting water, gas, air, oil, heating steam, hot water, and other low-pressure fluids or for other purposes. They are categorized into regular and thickened galvanized pipes based on wall thickness, and into non-threaded and threaded galvanized pipes based on end form. The size of the pipe is expressed in nominal diameter (mm), which approximates the inner diameter, and is often expressed in inches, such as 11/2.
Ordinary Carbon Steel Electrical Conduit Pipes (GB 3640-88) are used in electrical installation projects of industrial and civil buildings, machinery, and equipment to protect electrical wires.
Straight Seam Electric Welded Steel Pipes (GB/T 13793-2016) have welds 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 coiled as pipe billets, formed into spirals at room 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 transport efficiency, they can save investment costs in pipeline laying. They are primarily used for oil and gas pipelines.
High-Frequency Welded Spiral Steel Pipes for Pressure Fluid Transmission (SY 5038-83) are made from hot-rolled steel strips coiled as pipe billets, formed into spirals at room temperature, and welded using the high-frequency lap welding method. These pipes are used for transporting pressurized fluids. They have strong pressure-bearing capabilities, good plasticity, and are easy to weld and form. They have undergone rigorous scientific inspections and tests, ensuring safe and reliable use. With large diameters and high transport efficiency, they can save investment costs in pipeline laying. They are primarily used for laying oil and gas pipelines.
Spiral Submerged Arc Welded Steel Pipes for General Low-Pressure Fluid Transportation (SY5037-83) are made from hot-rolled steel strips coiled as pipe billets, 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 transporting water, gas, air, steam, and other low-pressure fluids.
High-Frequency Welded Spiral Steel Pipes for General Low-Pressure Fluid Transportation (SY 5039-83) are made from hot-rolled steel strips coiled as pipe billets, formed into spirals at room temperature, and welded using the high-frequency lap welding method. These pipes are used for transporting general low-pressure fluids.
Spiral Welded Steel Pipes for Piles (SY 5040-83) are made from hot-rolled steel strips coiled as pipe billets, formed into spirals at room temperature, and welded using double-sided submerged arc welding or high-frequency welding methods. These pipes are used as foundation piles in civil engineering structures, docks, bridges, and other construction projects.
