Rolling and heat treatment process of SM490YB test steel plate

For the SM490YB test steel plate, in order to obtain uniform and fine ferrite and pearlite structure and appropriate hardness, and to obtain the required properties, the continuous cooling rate after normalizing should be controlled at 0.3-1.0 ℃/s.

For the SM490YB test steel plate, the microstructure in the normalized state is ferrite + pearlite. As the normalizing temperature increases from 900 ℃ to 940 ℃, the yield strength and tensile strength of the steel plate show a downward trend, and the yield strength is from 358 to 367 MPa is reduced to 334~340MPa, tensile strength is reduced from 509~511 MPa to 490~492MPa, and the holding time has no obvious effect on the strength; when the normalizing temperature is 900 ℃, -50 ℃ longitudinal and transverse Charpy V-shaped notch impact absorption The energy is between 153~289J, but when the normalizing temperature increases to 920~940 ℃, the longitudinal and transverse Charpy V-notch impact absorption energy at -50℃ shows a low value of 24~38J.

By optimizing the composition design and rolling and heat treatment process, the ultra-thick wind power structure SM490YB steel plate with a thickness of 115 mm and excellent low-temperature impact performance at -50 °C in the core is developed by using a 370 mm thick continuous casting slab. The process is feasible; the internal quality of the SM490YB steel plate reaches NB/T 47013.3-2015 standard level 1 flaw detection level, the transverse and longitudinal properties of different positions in the thickness direction all meet the design requirements, the yield strength margin of SM490YB steel plate is > 30 MPa, and the tensile strength margin of the whole plate is greater than > 15 MPa; -50 ℃ The impact toughness is good, and the impact value is between 153 and 315 J.