Study On The Influence Of Steel Bar’s Organization And Performance By Gradual Cooling

Control cooling technology can alter cooling processes to obtain the requiredmechanical properties in the premise of adding less or nor micro-alloying elements.With resources environment was more serious and ecological economic developmentand increasingly seeking，it had great significance to study the impact of controlcooling on reinforcement steel.At present the cooling of the control technology afterrooled had widely been applied to the steel productions,such as rolled plates and steelbars,under adding less or nor micro-alloying elements it could obtain highermechanical properties.This paper was in order to use control cooling technology toobtain good plastic organization in the surface and core,high strength organization inthe transition region with adding nor Nb、V、Ti and low1%Mn conditions.Then itensures that the bar could be improved the mechanical properties in the condition ofgood plasticity.This experiment studyed the impacts of the organization and performance byusing the control cooling technology of firstly air cooling and then water quenchingwith the low carbon steel Q235and medium-carbon steel35K in880℃and920℃austenitic temperature.And the experiment investigated the four factors of carbonquality score、austenitic transition temperature、the surface temperature of accusedcold process and specifications control how to influent the performance andorganization during the process of control cooling.According to it,the paper obtainsthe result how each factor influents the organization and performance in coolingprocess,finally it can provide test parameters and basis for the experiment.The test proved that Q235could obtain good plastic organization with the majorproeutectoid ferrite in the surface and core，and high strength organization with martensite primarily in the transition austenitic region after the control coolingtechnology of firstly air cooling and then water quenching.However35K could notget the expected organization after the control cooling technology.At the same timethe technology could significantly enhance the mechanical properties of thesamples.When Q235sample cooling down640℃and600℃then water quenching，the mechanical property of R_m and R_p0.2(R_el) could be improved greatly with goodplastic nature.The mechanical property of R_m and R_p0.2(R_el) of35K still could beimproved，but the plastic nature was poorer，and sample is easy to appear brittlefracture phenomena.The paper simulated the temperature distribution of the cross section during theair cooling process by ANSYS software.According to the simulation of thermalanalysis in the process of the air cold,it can be found that the temperature distributionof the cross section is non-uniform.The temperature in the surface was lower than thecore temperature,and with the temperature decrease,the temperature differencebetween the surface and central department was minish.The simulate result providethe theoretical basis for the control cooling technology.