Effect of rolling end-cooling temperature 880 ~320 °C of experiment of Q355B hot-rolled H-beam steel on the strength

toughness and structure of the H-beam steel flange is studied. The results show that as the temperature after controlled cooling is 570 °C

the yield strength of the steel increases by 73 MPa compared to that of the air cooling process

and the elongation after fracture is 23. 5% ； as the temperature after controlled cooling is 320 °C

the yield strength of the steel increases by 228 MPa compared to that of the air cooling process

and the elongation after fracture is 16. 0%

which shows that the elongation rate is not qualified. The microstructure and ferrite grain size of Q355B hot rolled H beam steel obtained by normalizing after rolling are F + P and 11. 0. When the temperature drop rate of controlled cooling process is 73. 9 °C/s and the end-cooling temperature is 570 °C

B appears on the surface of die jet flange

the structure of the inner and core of the flange is F + P

and the grain size is 12. 0 ~ 12. 5 ； as the cooling temperature drop rate is 91. 4 °C/s

and the end-cooling temperature is 320 °C

M appears on the surface at the spraying side

and B appears at the core and inner side

at this time

the strength of steel is too high and the plasticity is seriously insufficient.