The Development Of High-strength Steel And The Research Of Anti-corrosion Resistance

HRB500 hot rolled ribbed steel bar with high intensity,good toughness and good seismic performance.Replacing HRB335 reinforced with HRB500 steel bar,can be saved more than 28% of the amount of steel used in construction,replace the HRB400 reinforced can be saved about 14% of the amount of construction steel.VN micro-alloying is a major producer process of high-strength steel,make full use of inexpensive nitrogen elements to achieve the precipitation strengthening,and finally to its strength and reach 500 MPa level.Therefore,the use of water cooling and micro-alloying combine to produce ingredients reasonable designed,excellent mechanical properties of high strength steel,optimized production processes,reduced costs,protected the environment,and to promote the development of the national economy is of great significance.In the process of placing,high strength steel tend to produce different degree of surface corrosion after roll forming,which leads to the loss of the materials,also greatly reduces the product quality of high strength steel.However the surface of steel will naturally be formed a thin layer of iron oxide after rolling and air cooling process.It has an important influence that the formation and properties of tin oxide layer on the corrosion resistance of high strength steel.So it has an important significance that the research of high strength steel in the rolling process of high temperature oxidation mechanism and stability properties of the oxide layer in the process of storage,transportation and use of the corrosion resistance of steel.VN micro-alloying technologies combined with controlled rolling and controlled cooling technology were used to develop different specifications of HRB500 steelbar.Metallographic microscope and electronic universal testing machine were applied to observe and analyse the micro-structure,grain size,mechanical properties and strong mechanism of samples.The results show that the VN micro-alloying technologies combined with controlled rolling technology in different specifications HRB500 steel bar,Increasing dosage of VN micro-alloying or enhance water cooling intensity can significantly enhance strength of steel,but can be also reduced yield stronger than steel;VN micro-alloying technology combined with controlled rolling and cooling process to produce large-sized 25 mm HRB500 steel,the ideal vanadium content is0.060%~0.090%,in 0.8~1.2MPa water pressure,the water flow is 380~680m3/h,of reinforcing strength enhance the effect is remarkable,the strong yield than qualified and mechanical performance to meet national standards;for 16 mm small specification HRB500 steel bar,it should be reduced the amount of vanadium-nitrogen alloy,use of weak water cooling process to produce the best results.Wear water-cooling process were carried out to study different cooling bed temperature on high strength steel surface oxide film on the composition and structure,through the microscope,scanning electron microscope,XRD diffraction and tensile testing machine steel metallurgical micro structure and various parts of the surface oxide scale the morphology,thickness and structural composition were analyzed.The results show that the steel surface oxide layer and the steel substrate binding compact,reinforced tissue are F+P and no abnormal tissue appears when the temperature of cooling bed is higher than 840℃,the oxide layer structure loose and easy off,reinforced tissue transition occurs,and there is abnormal tissue B+widmanstatten when the temperature is below 840℃;the greater the cooling intensity,the rebar surface oxide layer growth rate faster,less in proportion to the outer Fe2O3,the thickness of oxide layer becomes thinner;the steel surface oxidation iron consists of Fe2O3,Fe4O3 and Fe O when the temperature of cooling bed is below720℃,the oxide layer composed only of Fe2O3 and Fe O when the temperature is higher than 720℃.