General Requirements for the Surface Quality of Hot Rolled Steel Sheets
Hot-rolled steel sheets are widely used in construction engineering and other industries due to their excellent characteristics. To ensure a good performance, it is necessary to meet the surface quality requirements. General requirements for surface quality of hot rolled steel plates are specified in GB T14977-94.
GB T14977-94 stipulates basic requirements for the surface quality of hot rolled steel sheets, including the cleanliness of the surface, the roughness of the surface, the quality of the oxide film and the defects of the surface.Cleanliness refers to the degree of cleanness and freedom from foreign matter on the steel plate surface. Cleanliness is judged by visual inspection. According to the requirements of GB T14977-94, the surface of hot rolled steel plates shall be clean, free from defects and foreign matter, and shall not be contaminated by spots, stains, crackle or other blemishes.
The roughness of the steel surface refers to the size of the surface scratches. According to the hot rolled steel plate surface according to GB T14977-94 requires the surface scratches range between 20-25μm. The surface shall be uniform and there shall be no deep ridges and deep pits.
The quality of the oxide film of hot rolled steel plates refers to the continuity of the oxide film on steel surface, which is judged by the texture, density and thickness of the oxide film. Before delivery, they must meet the requirements of GB T14977-94.
Steel plate surface defects refer to the degree of acceptance of small cracks, large cracks and porosities at the surface. According to the regulations of GB T14977-94, these defects should be less than 5mm2, and cracks should be less than 15mm.
In addition, GB T14977-94 specifies restrictions on the size of slag inclusion and misshapen parts on the surface of hot rolled steel sheet, as well as requirements for shape change, twist, straightness and size deviation.
In short, the surface quality of hot rolled steel plates affects the performance and quality of the product.Therefore, surface quality of hot rolled steel sheets should meet the requirements of GB T14977-94. All indicators, such as cleanliness, roughness, oxide film quality and surface defects, should meet certain requirements.
