Effect of direct quenching on microstructure and mechanical properties of copper-bearing high-strength alloy steels

Microstructure, properties, and age hardening behavior of a thermomechanically processed ultralow-carbon Cu-bearing high-strength steel

“…[37] For this present steel, a considerably high strength (950 to 980 MPa YS, 1025 to 1085 MPa UTS) is obtained by thermomechanical-controlled processing followed by accelerated cooling (Figure 12(a)). In a DQ HSLA-100 steel, Hwang et al [11] obtained 1125 and 1075 MPa UTS values at 760 °C and 855 °C FRTs, and the YS respectively, values were almost equal to 925 MPa. The lath sizes obtained by them at 760°C and 855 °C FRTs were 190 and 240 nm, respectively, and, in the present study, the average lath widths at different FRTs were in the range of 274 to 248 nm (Figure 5).…”

“…The marginal difference in hardness values among the various FRTs of steels prevailed over the aging-temperature region of 400 °C to 700 °C, and this difference was within the range of 4 to 10 VHN at various aging temperatures. Hwang et al [11] have reported that hardness values in DQ-760 (finish rolling temperature) & tempered(T) and DQ-855 & T steels have become similar after aging at different temperatures. The strength values, i.e., the UTS and YS, have also been increased from the hot-rolled condition to the 400 °C aging temperature (Figure 14(a)).…”

“…The peak hardness values obtained in the present steel are higher than those of HSLA-100 steels reported in the literature. [10][11][12][13][14][15] A plateau in peak hardness is obtained from 450 °C to 550 °C. Yoo et al [10] have observed a similar type of plateau region in the temperature range of 550 °C to 600 °C in the HSLA-100 steel (DQ).…”

“…The peak-strength values (1273 MPa UTS and 1216 MPa YS) obtained in the present steel are higher than those of HSLA-100-grade steels reported in the literature. [10][11][12][13][14] The increase in hardness, UTS, and YS from the hot-rolled condition to the 500 °C aging temperature is 70 VHN (21 pct increase), 206 MPa (19 pct increase), and 251 MPa (26 pct increase), respectively. Simultaneously, the reduction in area is decreased from 54 to 42 (20 pct decrease).…”

“…[8,9] The Age-hardening behavior of Cu-bearing HSLA steels has been reported in the literature, and the carbon content of these steels is in the range of 0.04 to 0.06 wt pct. [10][11][12][13][14][15][16] By reducing the carbon content to an extremely low level in HSLA steels, weldability and toughness can be improved. However, studies on the structure and properties of ultralow-carbon HSLA steels have not been reported much in the literature.…”