The Surface Treatment of Sheets and Strips in China
Introduction
Surface treatment of steel sheets and strips has been a popular area of research in the past decades, due to its wide range of applications in engineering and manufacturing. The surface treatments are for the purpose of improving the material properties such as surface hardness and wear resistance, to increase the service life of the material and to reduce overall costs. Surface treatment of China steel sheets and strips is regulated by the General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ), formerly the General Administration of Quality and Technical Supervision (AQT). This document covers the surface treatment process of sheets and strips and its related national standards.
Types of surface treatment
The surface treatments of steel sheets and strips include various techniques such as heat treating, electroplating, chemical treatment, and cold working. Heat treating is a process of changing the chemical and physical properties of a material through the application of thermal energy. It is used to improve the mechanical properties of a material such as hardness, strength, and fatigue strength. Electroplating is a process of coating a metal surface with a thin layer of metal. It is used to protect the metal surface from corrosion, increase the electrical and thermal conductivity, and improve its visual appearance. Chemical treatment is done to improve the properties of a given material through the application of chemicals such as phosphating or galvanizing. Cold working is a process of increasing strength and wear resistance of a material without increasing the temperature of the metal. It is used to increase the hardness and fatigue strength of a material.
General Administration of Quality Supervision, Inspection and Quarantine Regulations
The AQSIQ governs the production of all materials in China, including surface treatments of steel sheets and strips. It has issued a number of regulations for the production of sheet metal and metal strip products, covering the entire production process from raw material to finished product. According to the AQSIQ regulations, all metal sheets and metal strips must pass all the quality inspection before, during and after the surface treatment process. These inspections include visual inspection, tensile tests, hardness tests, corrosion tests and eddy current tests. The AQSIQ also stipulates that the surface finish of steel sheets and strips must be free from any imperfections, and the finish must be uniform over the entire length of the sheet. It also provides detailed requirements for the types of surface treatments that can be applied to the sheet material, such as electroplating, galvanizing, or phosphating.
National Standards
In addition to the AQSIQ regulations, there are also a number of national standards that provide specific requirements for the surface treatment of steel sheets and strips in China. These include GB/T 2867.1, GB/T 2868-2017, GB/T 4031, and GB/T 4032. GB/T 2867.1 is the national standard for the surface treatment of hot rolled steel sheets and strips. It covers the requirements for the surface hardness, chemical composition, and other requirements for this type of steel. GB/T 2868-2017 is the national standard for the surface treatment of cold reduced sheets and strips. It provides requirements for the surface finish and other critical properties for this type of steel. Similarly, GB/T 4031 is the national standard for the surface treatment of hot rolled stainless steel sheets and strips, while GB/T 4032 covers the requirements for the surface treatment of cold reduced stainless steel sheets and strips.
Conclusion
Surface treatment of steel sheets and strips is a critical step in the production process in China, as it affects the mechanical and other properties of the material. It is governed by the AQSIQ and a number of national standards, which outline the requirements for surface hardness, chemical composition, and other important properties of the steel sheets and strips. From heat treating to cold working, various techniques are available for surface treatment of steel sheets and strips in China, and the surface finish must meet all the required standards for quality.
