classify Process classificationSquare rectangular tube according to the production process: hot-rolled seamless square pipe, cold-drawn seamless square pipe, extruded seamless square pipe, welded square pipe. Among them, the welded square pipe is further divided into: 1. According to the process - arc welded square pipe, resistance welded square pipe (high frequency, low frequency), gas welded square pipe, furnace welded square pipe 2. According to the weld - straight seam welded square pipe, spiral welded square pipe. Material classificationSquare pipe according to material: carbon steel square tube, low alloy square tube. 1. Pu carbon steel is divided into: Q195, Q215, Q235, SS400, 20# steel, 45# steel, etc. 2. Low alloy steel is divided into: Q345, 16Mn, Q390, ST52-3, etc. Production standard classificationSquare tube according to production standards: national standard square tube, Japanese standard square tube, imperial square tube, American standard square tube, European standard square tube, non-standard square tube. Cross-section shape classificationSquare tubes are classified by cross-sectional shape: 1. Simple cross-sectional square tube: square square tube, rectangular square tube. 2. Complex cross-sectional square tube: flower-shaped square tube, open-shaped square tube, corrugated square tube, special-shaped square tube. Surface treatment classificationSquare tubes are divided according to surface treatment: hot-dip galvanized square pipe, electro-galvanized square pipe, oiled square tube, pickling square tube. Classification of usesSquare pipes are classified according to their use: square pipes for decoration, square pipes for machine tools and equipment, square pipes for machinery industry, square pipes for chemical industry, square pipes for steel structures, square pipes for shipbuilding, square pipes for automobiles, square pipes for steel beams and columns, and square pipes for special purposes. Wall thickness classificationSquare rectangular tubes are classified according to wall thickness: ultra-thick wall square rectangular tube, thick-walled square rectangular tube and thin-walled square rectangular tube.