After any workpiece is mechanically processed, there will be residual prestress on the surface. The residual compressive stress on the hot-dip galvanized rectangular tube can improve its wear resistance and the fatigue of the tensile stress. The residual tensile stress on the square tube is actually the opposite of the compressive stress. Next, let me introduce to you the reason for the residual prestress on the galvanized rectangular tube.

The residual stress caused by deformation caused by cold plasticity. When the galvanized rectangular tube is processed, due to the cutting force, the processed surface of the square tube is deformed by strong cold plasticity. The most prominent cause of this cold plastic deformation is the tool: The upper knife faces the plastic deformation caused by the extrusion and friction of the surface of the square tube, because the base metal of the square tube is in an elastic state at this time. After the cutting force disappears, the metal of the base body tends to recover. At this time, the galvanized rectangular tube has been restricted by the surface of the shaping, causing the base body to not recover its original shape, so that it will remain on the surface. Under stress, the residual stress on it will cause its wear resistance and fatigue strength to decrease.