Effect of Coiling Conditions on Microstructure and Mechanical Property Characteristic of a C–Mn–Si–Cr Steel

Coiling condition in thermal mechanical control process can affect the final microstructure and mechanical property significantly. To achieve the ferrite–martensite dual-phase steel with less alloy content and lower cost, a C–Si–Mn–Cr steel was designed and air-cooled to 750 °C after hot rolling and then coiled on four conditions: (i) water cooling to 300 °C and coiling, (ii) quench to room temperature, (iii) water cooling to 90 °C and coiling at 250 °C, and (iv) water cooling to 90 °C and coiling at 170 °C. After uniaxial tensile test, specimens 2# and 4# present better formability than the other two specimens. By using optical microscopy, SEM and TEM, 2#, 3#, and 4# acquired ferrite–martensite dual-phase microstructure. 1# is composed of ordinary ferrite–pearlite microstructure.