Square steel: It is solid and is a bar. Different from square tubes, it is hollow and belongs to pipes. Steel: It is a material made of various shapes, sizes and properties required by steel ingots, billets or steel through pressure processing. Steel is an important material indispensable for national construction and the realization of the four modernizations. It is widely used and has a wide variety of varieties. According to the different cross-sectional shapes, steel is generally divided into four categories: profiles, plates, pipes and metal products. In order to facilitate the organization of steel production, ordering and supply, and to do a good job in business management, it is divided into heavy rails, light rails, large-sized steel, medium-sized steel, small-sized steel, steel cold-bent steel, high-quality steel, wire rods, medium and thick steel plates, thin steel plates, electrical silicon steel sheets, strip steel, seamless steel pipes, welded steel pipes, metal products and other varieties.