Search Results (3)

The interfacial bonding properties of stainless steel clad (SSC) rebars determine whether they can be widely used. In the industrial production of SSC rebars, the process of intermediate and finish rolling of the microstructure evolution, element diffusion behavior, and interfacial bonding properties of bimetallic interfaces are investigated. In this paper, 316L seamless stainless steel (SS) tube and HRB400E carbon steel (CS) bar were prepared by a vacuum oxidation-free composite round billet, and the industrial emergency stopping of SSC rebars’ hot rolling was carried out. The metallographic results showed that the thicknesses of the carburized austenite zone (CAZ) varied greatly (832–238 μm) and showed a parabolic downward trend, while the thicknesses of the decarburized ferrite zone (DFZ) varied little (85–99 μm). The elemental line scans showed that Fe and Cr had the same parabolic downward trend. The intermediate-rolling had a great influence on element diffusion, and, in S6–9, the diffusion distance of Fe and Cr decreased significantly. The diffusion distances of the elements in the intermediate-rolling back stage and finishing-rolling front stage (S9–12) were basically balanced. The elemental diffusion distances and interfacial bonding strength were not consistent. Among them, the shear strength (τ) of S13 was 410.7 MPa. Compared with ordinary rebars, the yield strength (Re) and tensile strength (Rm) of finished SSC rebars were increased by 7.05% (30.9 MPa) and 7.10% (43.0 MPa), respectively. The tensile properties exceed those of mixture effects. The paper provides a theoretical basis for the improvement of the interfacial bonding strength and optimization of the rolling process system for the industrial production of SSC rebars. Full article

The characteristics of flow field distribution and temperature variation of an inclined jet impinging on a steel tube surface at different positions in circumferential directions were studied via numerical simulation. By analyzing the local convective heat transfer coefficient in circumferential direction, it was shown that the downstream and upstream regions had the characteristics of typical asymmetry. As the inclination angle increases, the local convective heat transfer coefficient gradually increases in the downstream region and gradually decreases in the upstream region. When the θ of the top and bottom jet is 30°, the increases in the downstream region are 40.2% and 54.6%, respectively. Based on the study of the local convective heat transfer coefficient and temperature distribution in the circumfluence direction of a steel tube during the cooling process, it was shown that the optimal inclination angle is 0~10°. With the increase in inclination angle, the average heat transfer coefficient shows a decreasing trend overall. With the increase in jet Reynolds number, the decrease in the average heat transfer coefficient gradually decreases. When the inclination angle increases to 30°, the effect of inclination angle on steel tube cooling is obviously stronger than that of jet position. Full article

Large residual stress occurs during the quenching process of hot-rolled seamless steel tubes, which results in bending, cracking, and ellipticity exceeding standards and seriously affects the quality of hot-rolled seamless steel tubes. In addition, the stress generation mechanism of hot-rolled seamless steel tubes is different from that of steel plates due to the characteristics of annular section. In this research, the finite element simulation method was used to study the quenching residual stress of seamless steel tubes with different cooling intensities. The variation law of temperature and stress on the steel tube under different cooling intensities were analyzed. The results show that the radial stress was close to 0, and the circumferential and axial stresses were the main factors affecting the quality of the steel tube. With the increase in the cooling time, the magnitude and direction of each stress component of the steel tube changed simultaneously. Finally, a typical stress distribution state of “external compressive stress, internal tensile stress” was presented in the thickness direction of the steel tube. Furthermore, with the increase in the cooling intensity, the residual stress of the steel tube gradually increased and was mainly concentrated on the near wall of the steel tube. Full article