Research On Corrosion Active Inclusions And Corrosion Resistance Of High-grade Ship Plate Steel

With the acceleration of Arctic development,the demand of steel for low temperature environment in national economy is more and more vigorous.Under the condition of maintaining its existing mechanical and physical properties,improving the corrosion resistance of steel has become an important engineering problem in the research and development of high-grade ship plate steel.In order to clarify the corrosion mechanism of ultra-low temperature shipbuilding steel,in addition to testing the chemical composition and mechanical properties of a batch of ordinary shipbuilding steel provided by a steel plant,the microstructure of inclusions and electrochemical corrosion test were carried out.Furthermore,in order to facilitate the characterization of inclusions,the corrosion reagent was upgraded.At the same time,in order to explore the influence of deoxidization process on the inclusion composition,the high-grade shipbuiding steel was treated with Zr deoxidization process(steel A)and Al deoxidation process(steel B),and the third batch of steel(steel C)with the same composition as steel A but treated by Al deoxidization process were tested by electrochemical test method.According to the electrochemical test results of ordinary shipbuilding steel,it can be concluded that the number of corrosive active nonmetalic inclusions(CANI)is directly proportional to the saturation current density.In order to improve the corrosion resistance of shipbuilding steel produced by this plant,it is necessary to reduce the amount of CANI in the steel.The corrosion resistance of EH36 steel plate was analyzed by electrochemical corrosion test and accelerated corrosion test in simulated seawater.The results show that the main composition of active inclusions is Al and Mg composite oxides,and the main composition is Mg O·2Al₂O₃.There is a positive correlation between saturated current density,corrosion weight loss rate and corrosion active inclusion density.At the meanwhile,the electrochemical test results of different deoxidization processes show that the effective deoxidization process can reduce the number of CANI and improve the corrosion resistance.In the future manufacturing for this steel plant,in order to improve the corrosion resistance of high-grade shipbuilding steel,appropriate Ca treatment and appropriate deoxidation process can be utilized to reduce the amount of CANI in steel.