The Influence Of Micro Alloying And Fast Cooling After Rolling On Microstructures And Mechanical Properties Of Hot Ribbed Bars

Hot ribbed bars are important steels. They are used in architecture area. Hot ribbed bars produced in our country are not as good as that produced by steel developed country in terms of mechanic character such as intention. It is very important to produce high intention steel bars for the marketplace and link orbit of international marketplace. Because traditional production technologies have their own shortcomings, they can not satisfy the requirements of producers and consumers contemporarily. So we need a production processing to produce 400MPa grade hot ribbed bars, which is widely applied, low production cost, and well product performances.Through investigation on spot and profound analyzing in many hot ribbed bars producing factories, the Key Laboratory of Rolling and Automation (Northeastern University) improved steel bars cooling after rolling technology. The improved technology made use of fast cooling after rolling to adjust temperature of steel bars on cold bed, and increased many properties by adding a small quantity of vanadium or niobium.This text combined production data on spot, aimed at producing 400MPa grade hot ribbed bars using 20MnSi as material, and using improved cooling technology, researched influence of adding a small quantity of vanadium or niobium, and using fast cooling after rolling on microstructures and mechanical properties of hot ribbed bar. Obtained achievement as follows:(1) Adding a small quantity of vanadium or niobium in 20MnSi can refine ferrite grain and improve mechanical properties obviously. Using fast cooling after rolling technology, the quantities of vanadium or niobium can be reduced in producing 400MPa grade hot ribbed bars.(2) For using 20MnSi to produce 335MPa grade hot ribbed bars, through regulating cooling parameters propriety and carbon equivalent satisfying national standards, the content of Mn can be reduced. The performances of steel bars still satisfy national standards.(3) The temperature of steel bars on cold bed is the mostly factor on deciding mechanical performances of steel bars. Both yield strength and tensile strength reduce along...