Square steel: solid, bar. It is different from square tube, hollow and belongs to pipe. Steel: it is a material with various shapes, sizes and properties required by ingot, billet or steel through pressure processing. Steel is an essential material for national construction and the realization of the four modernizations. It is widely used and has a wide variety. According to the different section shapes, steel is generally divided into four categories: profile, plate, pipe and metal products. In order to facilitate the organization of steel production, order supply and business management, it is also divided into heavy rail, light rail, large section steel, medium section steel, small section steel Steel cold-formed section steel, high-quality section steel, wire rod, medium and thick steel plate, sheet steel, electrical silicon steel sheet, strip steel, seamless steel pipe, welded steel pipe, metal products, etc.