The Source Of "High Weathering" In spa-c Weathering Steel
JIS G3125 SPA-C steel plate is a kind of high weathering steel. GNH is the "high weathering" Chinese phonetic alphabet (the principle of national standard naming, most of which is now in line with international standards), D is the grade, indicating that low temperature impact toughness is required, standard: GB/T 4171-2008 "weathering structural steel". High weathering steels are more resistant to atmospheric corrosion. Q345 series high weather resistant structural steel plates include 09CuPCrNi, Q345GNHL, SPA-H, Q355NH and other steel grades. Theseweatheringsteels are alloyed by Cu, P, Cr, Ni, etc., forming a protective layer on the surface of the metal substrate, thus having a higher Resistance to atmospheric corrosion. The weather resistance of this type of steel is better than that of weathering steel for welded structures, so it is called high weathering structural steel. This type of steel is widely used in railway vehicles, various weather-resistant building structures (especially for industrial atmospheric environments), and bridge auxiliary structural components.
Cold Rolled SPA-CWeathering Steel
The SPA-C cold-rolled steel is an abbreviation for ordinary carbon structural steel cold-rolled sheet. Also known as cold rolled sheet, commonly known as cold plate, sometimes mistakenly written as cold rolled sheet. The cold plate is made of a common carbon structural steel hot-rolled steel strip, which is further cold-rolled into a steel sheet having a thickness of less than 4 mm. Since it is rolled at normal temperature, it does not produce iron oxide high weathering steel (SPA-H), which is mainly used in hot rolling, and is widely used in the container industry. Since ordinary carbon steel is highly corrosive in the atmosphere and causes serious economic losses, the development of weathering steel has broad market prospects.
SPA-C Weathering Steel Element
Cu is more resistant to atmospheric corrosion when used in combination with other elements such as P and Cr. When the Cu content is 0.25%, the steel has good weather resistance. When the content exceeds 0.30%, the corrosion resistance is improved slowly, and the effect of continuously increasing Cu is not large. At the same time, Cu-containing steel has the problem of hot processing sensitivity, and it is easy to produce mesh cracks. Therefore, in order to improve the atmospheric corrosion resistance and prevent cracks in the steel, the Cu content is designed to be 0.25 to 0.35%. 3.2.3 P is an effective element for improving atmospheric corrosion resistance in alloying elements. It is generally not used alone, and it is better to use it in combination with Cu, Cr, etc. When the P content is increased from 0.01% to 0.08%, the steel plate is resistant to the atmosphere. Corrosion performance is greatly improved, and after the P content exceeds 0.08%, the resistance to atmospheric corrosion is not significantly improved. At the same time, excessive addition will reduce the ductility of the steel.
The carbon of the SPA-C weathering steel sheet is in the sub-peritectic range, which is liable to cause cracks. At the same time, the weathering steel also contains high elements such as Cu, P, Ni, etc. These elements tend to embrittle the grain boundary of the steel during the crystallization process, resulting in large thermal stress and tissue stress of the steel during cooling. If strong cooling is used in the continuous casting process, the crack is easily spread, and the cooling is too weak, which is liable to cause P segregation, resulting in internal cracking of the cast slab. Therefore, the steel grade should be moderately cooled during continuous casting. Therefore, in the production of weathering steel, the heat flow of the mold can not be high. According to the research on the production of weathering steel by Baosteel, the heat flux of the wide surface of the crystallizer is 1.4 to 1.6 MW/m2, and the weathering steel is not prone to longitudinal cracks. Compared with the cooling water volume of our company's crystallizer, the cooling water volume of the mold wide surface is reduced from 85-95m3/h to 80-85m3/h, so that the temperature difference between the inlet and outlet water is increased from 6-8 °C to 8-10 °C. .
SPA-CWeathering Steel Welding
TheSPA-C weathering steel sheet is a steel that requires high welding performance. Steel sheets tend to limit the P content to less than 0.04%, while other corrosion-resistant alloying elements are used instead of P in steel. In this experiment, a low alloy steel A588 was selected as the experimental steel. Compared with SPA-H steel, the P content in steel was reduced and the content of alloying elements Mn and Ni in steel was increased. Through the wet-wet-week immersion experiment, the corrosion behavior under simulated atmospheric conditions and industrial atmospheric conditions was studied, which provided a theoretical basis for its production and use. In the case where the composition and structure of the steel are basically unchanged, the initial corrosion of the steel may be different in different environments. The influence of different environments on the corrosion resistance is first manifested in the initial stage of corrosion in which the protective rust layer has not been formed and the steel matrix is directly in contact with the corrosive medium. Therefore, the observation of the evolution of the microstructure in the initial stage of corrosion reveals the different environments to the microscopic The impact mechanism of the organization is of great significance
