Study of Nanometer-Sized Precipitation and Properties of Fire Resistant Hot-Rolled Steel

• Published in: Metals (Basel ) 2019-11, Vol.9 (11), p.1230
• Main Authors: Xie, Zhenjia, Song, Zhendong, Chen, Kun, Jiang, Minghong, Tao, Ya, Wang, Xuemin, Shang, Chengjia
• Format: Article
• Language: English
• Subjects: Air cooling; Bearing steels; Carbides; Carbon; Cooling; Diameters; Elongation; Fire resistance; Grain boundaries; Grain size; High temperature; high temperature strength; Hot rolling; Hot-rolled steel; interphase precipitation; low alloy steel; low carbon; Low carbon steels; Microhardness; Molybdenum; Precipitation; Rolling resistance; Room temperature; Scanning electron microscopy; Shear modulus; stability; Steel; Tempering; Tensile strength; Titanium; Yield strength; Yield stress
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met9111230

Nanometer-sized precipitated carbides in a low carbon Ti-V-Mo bearing steel were obtained through hot rolling and air cooling and were investigated by transmission electron microscopy (TEM). The nanometer-sized interphase-precipitated carbides have been found to exhibit an average diameter of ~6.1 ± 2.7 nm, with an average spacing of ~24–34 nm. Yield strength of 578 ± 20 MPa and tensile strength of 813 ± 25 MPa were achieved with high elongation of 25.0 ± 0.5% at room temperature. The nanometer-sized precipitation exhibited high stability after annealing at high temperatures of 600 °C and 650 °C for 3 h. Average diameters of carbides were statistically measured to be ~6.9 ± 2.3 nm and 8.4 ± 2.6 nm after tempering at high temperatures of 600 °C and 650 °C, respectively. The micro-hardness was ~263–268 HV0.1 after high temperature tempering, which was similar to the hot-rolled sample (273 HV0.1), and yield strength of 325 ± 13 MPa and 278 ± 4 MPa was achieved at elevated temperatures of 600 °C and 650 °C, respectively. The significant decrease of yield strength at 650 °C was attributed to the large decrease in shear modulus.