Purpose:

It is primarily used in curtain walls, architecture, machinery manufacturing, steel construction projects, shipbuilding, solar power generation supports, steel structure engineering, electrical engineering, power plants, agricultural and chemical machinery, glass curtain walls, automobile chassis, airports, etc

Square and rectangular tubes are collectively referred to as square and rectangular cold-formed hollow sections. They are formed by uncoiling, flattening, curling, and welding strip steel into round tubes, which are then rolled into shape. The codes are divided into F (square tube) and J (rectangular tube). The wall thickness deviation range is ±10% or ±8% depending on the thickness. The delivery length is usually 4-12 meters (customizable), and short tubes longer than 2 meters are allowed. The bending degree should not exceed 2 millimeters per meter [1] [3]. According to the production process, they can be divided into hot-rolled, cold-drawn, extruded seamless square tubes and welded square tubes (including processes such as arc welding, resistance welding, and high-frequency welding). The main materials are plain carbon steel (such as Q195, Q215, Q235, 20# steel) and low alloy steel (such as Q345, 16Mn, Q390) [2] [4-5]. The types of cross-sections include simple types (square, rectangular) and complex types (corrugated, irregular), and the surface can be treated with galvanizing, oil coating, etc. The product implementation standards cover national standards, American standards, European standards, and collective standards such as "Square and Rectangular Tubes for Building Structures", in which the collective standards adjust the theoretical weight calculation formula and add parameter requirements such as weld flattening tests [2] [7].

Square and rectangular tubes are produced using cold-bending high-frequency welding technology, featuring high precision, uniform wall thickness, and high internal and external wall smoothness. The theoretical weight calculation formula is adjusted according to corporate standards. The specification range covers square tubes from 15*15 to 900*900mm and rectangular tubes from 10*20 to 800*10000mm, with wall thicknesses ranging from 1.5 to 40mm. We maintain a stock of 200,000 tons and support customization within a length of 24 meters [3] [5] [7]. In 2025, Tianjin Youfa Dezhong Steel Pipe Co., Ltd. developed a patent for a laser cutting machine that can reduce deformation issues in cut products. This technology achieves precise positioning through the cooperation of clamping components and adjustment components [10]. The products are widely used in building curtain walls (such as international airports, grand theaters), rail transit (Wuxi light rail), machinery manufacturing (computer embroidery machines), and shipbuilding, with specific applications including steel structure skeletons, equipment support frameworks, and fluid conveying pipelines