Effect of Nb-V Microalloying 0.15 - 0.35Mo Content and Rolling Temperature on Properties of Fire-Resistant Steel for Building

Tested steels are melting by a 50 kg medium induction furnace and rolling to 13 mm plate. The effect of rolling temperature (1 010 ~ 1 050 ℃) of tested steel 0.15Mo,R2- 0.15MoV, R3- 0.35MoNbV, R4- 0.35MoNbVB and R5- 0.35MoNbVTiB on properties of the steels has been tested. Results show that the R3 steel (/% : 0.04C,l. 12Mn, 0.32Si,0.018P,0.023S,0. 35Cr,0.35Mo,0.025Nb,0.15V) rolled at 1 030 T has excellent comprehensive properties i. e. tensile strength 598 MPa,yield strength 514 MPa,elongation 28% ,ratio of yield-tensile strength 0. 86,the HV hardness scale before and after tempering at the temperature of 600 ℃ respectively being 215 and 204, and impact energy of steel at 0 ℃ being 124 J,and the yield strength of steel at 600 ℃ being 355 MPa with ratio of yield-tensile strength 0. 69 to meet the requirement of state standard for fire-resistant steel.