The production flowsheet of 20mm plate of tested steel EH420 (/% : 0.20C
0.38Si
1.63Mn
0.007P
0.001S
0.062V
0.017Nb
0.009Ti
0.021 Alt
0.38Ni
0.015Cu) is 210t BOF-LF-RH-230 mm slab casing-rolling. The tensile test of steel EH420 is carried out at ambient temperature
450 °C
480 °C
500 °C and 600 °C
the morphology of fracture of steel tensile specimen is observed by scanning electron microscope and the fracture mechanism of steel is analyzed. Results show that the yield strength of steel at ambient temperature is 443 MPa and the yield strength of the steel at 480°C is 270 MPa which is basically equal to two-thirds of the yield strength of steel at ambient temperature
therefore the steel EH420 has fire resistance at less than 480 °C.