Research And Development Of Corrosion Resistant Bridge Steel

Bridge construction is an important national infrastructure in China and can greatly promote local economic development.Corrosion-resistant bridge steel is a kind of bridge steel used in harsh environments such as high chloride ion concentration,high temperature,high humidity and high salt.It has high requirements on strength,toughness and corrosion resistance.There is still a big gap between bridge steel and foreign countries.Therefore,it is necessary to study corrosion-resistant bridge steel and develop a new type of corrosion-resistant bridge steel with excellent mechanical properties.In this paper,two-component low-carbon bainitic steels of 3Ni 3%nickel(Mass fraction)and 0.4Ni 0.4%nickel(Mass fraction)were designed.Through the thermal simulation experiment machine,the austenite continuous cooling transition behavior of 3Ni and 0.4Ni steel was studied,and the CCT curve was drawn.The controlled rolling and controlled cooling experiments were carried out in a laboratory rolling mill to study the influence of hot rolling process parameters on the microstructure and properties of the test steel plate.Weekly immersion experiments were conducted to study the corrosion resistance of 3Ni and 0.4Ni steels.The main research of this paper are as follows:(1)When the cooling rate of 3Ni steel is between 0.5?/s and 7?/s,the microstructure consists of ferrite and bainite.When the cooling rate is greater than 7?/s,the microstructure consists entirely of bainite.When the cooling rate of 0.4Ni steel is between 0.5?/s and 10?/s,the microstructure consists of ferrite and bainite.As the nickel element increases,the ferrite transformation process is hindered,and the CCT curve of the test steel moves to the lower right.(2)For the 3Ni steel,the test steel is controlled at a soaking temperature of about 1200?,the rough rolling temperature is controlled at 940-1120?,the finishing rolling temperature is controlled at 830-890?,and the open cooling temperature is controlled at 710-730?,when the final cooling temperature is controlled at 540-570?,the microstructure,mechanical properties and corrosion resistance of the developed corrosion resistant bridge steel meet the standard requirements.(3)For the test steel 0.4 Ni steel,the test steel is controlled at a soaking temperature of about 1200?,the rough rolling temperature is controlled at 940-1120?,the finishing rolling temperature is controlled at 800-870?,and the open cooling temperature is controlled at 690-710? when the final cooling temperature is controlled at 540-560?,the microstructure,mechanical properties and corrosion resistance of the developed corrosion resistant bridge steel meet the standard requirements.(4)Compared with the test steel 3 Ni steel and 0.4 Ni steel,the corrosion rate before 96 hours is not much different,but after 96 hours the corrosion depth and rate of 3 Ni steel are much lower than that of 0.4Ni steel.(5)The relative corrosion rates of two groups of test steels with 3Ni and 0.4Ni rolled according to the above rolling process are 0.6,0.59,0.87 and 0.88,which are obviously better than that of 09CuPCrNi,and the relative corrosion rates of the two groups of test steels with 3%Ni are less than 0.6.