Effect Of Different Temperature On Mechanical Properties Of Refractory Steel

Fire-resistant steel belongs to the fire-resistant lean alloy steel which can keep a high intensity after the fire breaking out for a period.The fire-resistant steel is widely applied in the constructive engineering field of prefabricated steel building due to the function of fire prevention and collapse resistance in the high temperature,which has greatly solved structural problems of being damaged by the fire,and casualties and economic losses.At present,the research of refractory steel mainly focuses on its alloying elements and microstructure,This paper researched the mechanical property towards the Q235 FRB and Q345 FRB these two steels in order to study the mechanical property in the fire and that after the temperature getting lower after the fire.This research got the strength reduction factor of Q235 FRB and Q345 FRB in different high temperatures,comparing and analyzing the influences of different cooling methods after high temperatures towards the mechanical property of Q235 FRB and Q345 FRB,and fit the performance to get the calculation formula.This paper carried on tension test towards the Q235 FRB and Q345 FRB and explored the effects of after-fire temperature and different cooling methods(natural cooling and immersion cooling)on the mechanical property of Q235 FRB and Q345 FRB,basing on the testing methods of high temperature and steady state in order to get the mechanical property of the Q235 FRB and Q345 FRB under the high temperature and after the high temperature,and got the stress-strain curve of Q235 FRB and Q345 FRB under different temperatures and the reduction factor of metrics(elastic modulus,yield strength,tensile strength and ultimate elongation)of mechanical property under and after the high temperature,compared and analyzed the results with the present results in the literature.The result shows that the elastic modulus,yield strength and tensile strength of Q235 FRB and Q345 FRB decrease along with the increasing of testing temperature under the high temperature.When the temperature raising to 400℃,the reduction speed of yield strength and tensile strength is faster;when the temperature reached to 800℃,all the mechanical index are inefficient and reducing to 10% of the mechanical property under general temperatures.The cooling method after high temperature has a slight influence towards the elastic modulus of Q235 FRB and Q345 FRB.The reduction factor of elastic modulus only fluctuates among small scope under the condition of natural cooling and immersion cooling with the increasing of the temperature after fire,while the method hasa great effect on the yield strength,tensile strength and extensibility.The tensile strengths of these two steels constantly decrease with the increasing of the temperature after fire under the natural cooling,and it reduces by around 10% under 900℃ comparing with that under general temperature while the yield strength shows an increasing trend before the decreasing with the increasing of temperature and when it is 900℃,it reduces by 40% of that under general temperature.Under the immersion cooling,the tensile strengths of these two materials increase with the increasing of the fire temperature.When it is 900℃,the tensile strength develops by around 20% comparing with that of the general temperature.The yield strengths Q235 FRB and Q345 FRB increase with the development of the temperature.When it is 900℃,the yield strength increases by about 30% of that under the general temperature.At low temperature,the impact toughness is not different from that at room temperature.Through finite element simulation,it is found that fire resistant steel has better deformation resistance than ordinary steel in fire accident.