Control Of Microstructure And Properities Of The High Strength Coiled Reinforeced Bar For Building

The rapid development of construction industry in our country brings on more increasing demand of high strength coiled reinforeced bar for building and more strict quality requirements. Reinforced Concrete is main material widely used in building construction at present and in the long run in China. In order to meet the needs of building structure,we can predict that the demand and output of the high strength coiled reinforeced bar will continue to maintain a high level. The mechanical properties(include yield strength, tensile strength, elongation percentage,etc.) of coiled reinforeced bar must conform to the standard before come into use.In order to find the reason of low mechanical properties produced by Hanzhong Steel Company of Shannxi Iron and Steel Group, sample pointedly, protect the samples,process them into fracture surface, spectroscopic and metallographic samples. Analysis the macro-fracture, detect the chemical composition of the samples by the spectrum analyzer, observe the inclusion and metallographic structure by using metallographic microscope, the tensile fracture and the metallographic surface were microscopically analyzed and their micro area composition was studied by SEM and EDS.This paper synthetically analyzes the properties of high strength coiled reinforeced bar produced by Han Hong Steel Company with the above methods found the causes of low mechanical properties of steel are that large number of bainite structure and widmanstatten structure, component unsteady. Combined with field technical parameters analysis and laboratory analysis, this paper presents improving measurements for mechanical properties of steel, to optimize the rolling temperature parameters are benefited to the control of microstructure,combing with the control of components and inclusions to have a better mechanical properties. For(37)6、(37)8 and(37) 10 400 Mpa coiled reinforeced bar,control the component close to C:0.235%,Si:0.38%,Mn:1.13%,V:0.015%, and(37) 12 colse to C:0.235%,Si:0.43%, Mn:1.18%,V:0.018%. Extend the argon blowing time helps inclusion floating into the slag,prevent slag involved in steel during continuous casting, at the same time, using the electromagnetic stirring can effectively reduce the inclusion content. Carry out the TMCP ruels strictly, expecially the finsh-rolling temperature and cooling speed, it`s not only benefit to the formation of ferrite and pearlite and make them distribute evenly as well, but also avoid the formaton of bainite and widmanstatten. We can set the temperature parameters are as follows: holding zone temperature on 1070±10℃, rolling temperature on 980±20℃,finishing temperature on 910±20℃, shearing temperature on900±20℃, spitting temperature on 890±20℃, cooling temperature on 670±10℃.