Abstract
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.
Highlights
IntroductionHigh-strength low-alloy (HSLA) steel is of great importance for construction materials
As reference a material, high-strength low-alloy (HSLA) steel is of great importance for construction materials
HSLA steel, the strictest requirement is that the yield strength at 600 ◦ C should be guaranteed to be higher than two-thirds of the yield-strength value specified at room temperature [2]
Summary
High-strength low-alloy (HSLA) steel is of great importance for construction materials. Mo steels for fire-resistant applications [1,9,10] In this method, bainite strengthening was obtained by controlled accelerated cooling, and remained microalloying elements of Nb, V, and Ti in solid-solution precipitates as nanometer-sized MC-type carbides at elevated temperature in fire to provide high temperature strength. Interphase precipitation strengthening is generally recognized as an effect and economic approach in developing high-strength low-alloy hot-rolled steels [11,12,13,14]. The objective of the present work is to develop a high-strength low-alloy fire-resistant steel by introducing nanometer-sized interphase precipitation of microalloying element carbides. The findings from the present study may provide an alternative approach for developing high-strength fire-resistant hot-rolled steels
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