With the rapid development of China's automobile industry and the strengthening of ecological and environmental protection, hot-dip galvanized low-alloy high-strength steel is an effective means to solve the problem of lightweight vehicle bodies. It not only reduces the weight of the vehicle body, reduces fuel consumption, and reduces carbon dioxide emissions, but also effectively Improve corrosion resistance and safety performance. The composition of low-alloy high-strength steel is designed with trace amounts of strong carbide-forming elements, such as niobium, vanadium and titanium. The structure is composed of ferrite and a small amount of pearlite. The second phase precipitates are dispersed and distributed, mainly relying on carbides and nitrides. The precipitation strengthening on the ferrite matrix hinders dislocation movement and increases the yield strength. Cold-rolled HC420LAD+Z hot-dip galvanized automotive sheet is one of the most typical grades of cold-rolled low-alloy high-strength steel. It is widely used in seats of automobiles and buses due to its high yield strength and good forming, welding and anti-corrosion properties. parts, brackets, connecting plates and other reinforced structural parts to achieve the purpose of lightweighting the car.
At present, most domestic steel mills adopt advanced smelting and rolling equipment and process technologies, such as LF+RH tandem, hot continuous rolling, continuous pickling-cold continuous rolling, American Steel Co., Ltd. hot-dip galvanizing process, etc. Among them, the US Steel Union method uses degreasing cleaning to replace the oxidation furnace in the Sendzimir method, which can obtain galvanized strip steel with high surface quality. It is currently the most widely used galvanizing process. This work conducts research and development on hot-dip galvanized HC420LAD+Z produced by the US Steel Union hot-dip galvanizing process in a steel plant to enhance the coating performance of cold-rolled HSLA series steel grades and better meet the high-quality requirements of automotive sheets. And reduce energy consumption, painting costs and VOCs (volatile organic compounds) emissions. Through the rational design of chemical composition and the optimized control of key rolling production processes, the development of low-cost and high-quality hot-dip galvanized HC420LAD+Z steel strip for automobiles has been achieved, and has the characteristics of (0.5～2.5)mm×(1 000～1 Stable batch production capacity of 850)mm specifications.
