The battle of surface quality is like the battle of porcelain and mirror. The surface of the hot-rolled material is covered with a 10-15μm thick oxide sheet, and the roughness Ra value is between 12.5-25μm, like a warrior's armor; After electrolytic degreasing and polishing rolling, the surface roughness of cold-rolled products can be controlled at 0.1-0.8μm, and the reflectivity can reach more than 80%, which is comparable to precision optical components.
The difference in mechanical properties is like the competition between bronze and fine steel. The tensile strength of hot rolled low carbon steel is about 370MPa, and the elongation is 30%, which is suitable for large deformation requirements of structural parts. The tensile strength of cold-rolled SPCC steel strip rises to more than 400MPa, but the elongation is reduced to 15%, becoming the ideal choice for precision stamping. This performance scissors difference is particularly pronounced in automotive manufacturing: the body frame requires the toughness of hot-rolled material, while the hood relies on the high strength precision of cold-rolled sheet.
The battle of dimensional accuracy is a battle between millimeters and microns. Thickness tolerance of hot rolled wide strip steel ±0.2mm, width fluctuation ±5mm; The thickness deviation of cold-rolled sheet is ±0.01mm, and the width accuracy is ±0.5mm. This jump in accuracy has made cold-rolled materials popular in the field of electronic components, and the 0.3mm thin sheet in the frame of smartphones has a flatness error of no more than one-fifth the diameter of a human hair.
