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High-strength Hot-dip Galvanized Steel Technology Jul 10, 2017

             Because of high strength steel contains more Si, MN and other alloying elements, these elements on the one hand delayed the GA plate coating the speed of alloying, more important is the annealing on the surface of the plate to form a very stable oxide, during the subsequent hot plating process, the effective aluminum and Zn in the Fe and Zn in the steel are hindered, and the galvanized property of the steel plate is reduced, and the surface defects such as leakage plating on the hot-dip galvanized sheet are made. Therefore, the plating of high strength steel is a hot topic in the research of steel industry.Galvanized Steel

             Through chemical composition adjustment, such as adding CR and Mo to steel, especially using Mo instead of SI, has been developed on the traditional hot galvanizing line of the successful hot-dip galvanized dual-phase GA steel plate, in the same amount, MO than MN can better improve the hardenability of steel, at the same time than MN and Si is difficult to oxidize, in the annealing is hot to the surface of the steel is less inclined to enrichment. The same is due to the enrichment of SI easily lead to plating defects, the traditional cold rolled trip steel is not suitable for production on the hot galvanizing line because of the higher Si content (1.0~1.8%), although the dew point or redox atmosphere in the annealing furnace can change the chemical composition of the plate surface, thus improving the coating quality, but it can not completely eliminate the leaking plating area. For this, X, Vandeneynde and other people proposed that the SI-type trip steel first in the hydrogen-free atmosphere of the nitrogen pre-heating to form a homogeneous oxide layer, the new process of reducing the temperature in the reductive atmosphere with hydrogen and the heat-dip galvanizing trip steel with this process is found to be of good plating property in the laboratory. In addition, the isothermal transition temperature of trip steels is too high due to the limit of the temperature of the zinc pot, so that enough residual austenite can not be obtained. Ooi and so on before annealing on the steel plate surface pre-plating Fe to improve the plating and coating adhesion, also some people have proposed the use of mechanical grinding or pickling method to remove the surface of the alloy elements enrichment layer after the hot-dip galvanizing method. Using hydrochloric acid or sulfuric acid pickling can wash away the surface enrichment of SI, MN and other alloy elements, can improve the high strength steel plating problem.Galvanized Steel

              In a word, with the trend of energy-saving in automobile industry, hot-dip galvanized steel plate is a main development direction of cold-rolled broad-band steel technology, how to ensure the strength of all kinds of high-strength steel at the same time, realize its hot galvanizing process and ensure good quality of zinc plating is the key problem.Galvanized Steel