MnS inclusions in bearing steel have long been considered to significantly affect the fatigue life of bearing steel. In this paper, the sizes of inclusions in bearing steel with different sulfur contents were analyzed and the precipitation behavior of MnS was calculated using thermodynamics. Furthermore, the positive role of MnS in bearing steel was discussed. Results showed that when the size of inclusions in bearing steel was increased, the proportion of MnS components in composite inclusions gradually decreased. When the sulfur content was increased, the shape of inclusions changed from a particle shape to a strip shape. With increasing MnS content, the inclusion ratio of Al₂O₃ was significantly reduced in the Al₂O₃–CaO–MgO–MnS quaternary inclusion system, particularly for MnS proportions greater than 20%. The content of sulfur in bearing steel significantly affects the precipitation temperature of MnS. When sulfur content increases from 0.001% to 0.007%, the precipitation temperature of MnS increases from 1493 K to 1633 K as the precipitation of MnS moves from the austenite solid phase to the liquid and solid phases, and the precipitation size of MnS inclusions significantly increases. The size of oxide inclusions should be controlled to improve MnS wrap oxide inclusions in steel. Based on these results, a composition control with high sulfur levels and low oxygen levels should be adopted to improve the fatigue performance of steel.

This paper aims at manufacturing stainless steel clad (SSC) rebars by metal deposition and a hot rolling method as well as characterizing its interface features and mechanical properties. The interface of the SSC rebar is relatively flat and clean, exhibiting a metallurgical bonding state at the microscale. Decarburization occurred at the interface in the carbon steel side of the SSC rebar. The diffusion of C, Cr, as well as Mn was measured across the interface of the SSC rebar, and the diffusion distance of Cr and Mn was found at 32 µm and 25 µm, respectively. The Vickers hardness testing in the transition zone of the SSC rebar near the carbon side showed 545 HV^0.2 due to the martensite phase formed by the diffusion of key elements C, Cr, and Mn. The microstructure in the transition zone near the stainless steel reveals the duplex structure of martensite and ferrite. The carbide precipitations were observed near the interface, both in the transition zone and in the base metal of the stainless steel zone. The yield strength, tensile strength, and elongation of the SSC rebar were found as 423 MPa, 602 MPa, and 22%. No macroscopic crack was observed after the positive or negative bending tests.

In this work, duplex stainless steel/low-alloy steel-clad rebars were fabricated using metal deposition and hot rolling. The interfacial characteristics of the rebar, such as element diffusion and phase composition, were investigated using an optical microscope and a scanning electron microscope with an energy-dispersive spectrometer. The mechanical properties of the rebar were evaluated by tensile and bending tests. The results show that the rebar interface is composed of a carburized layer on the duplex stainless steel side and a decarburized layer on the low-alloy steel side; they also show that the rebar exhibits good mechanical properties, with 435 MPa of yield strength, 630 MPa of tensile strength, and a 24.8% percentage elongation. The reduction in the cladding thickness at the rebar’s transverse rib root was studied using the ABAQUS software. The results show that the cladding thickness is reduced due to the effect of the groove shape during the rolling process. The rebar’s transverse rib root cracked after bending due to the thinning of the cladding and brittle fractures in the interfacial martensite layer.

Through calculating the temperature field of billet in the process of reheating furnace, direct rolling and direct rolling with insulating cover, the temperature uniformity of billet obtained by different processes before starting rolling had been analysed. And then the mechanical properties and microstructure of hot rolled rebars in different positions of each process had been examined. The conclusions are as follows: The temperature uniformity of billet before rough rolling can be effectively increased by adding insulation covers in the conveying process of billet. With the decrease of temperature difference between the head and tail of billet, the fluctuation range of mechanical properties of production is narrowed. The process can obviously reduce the difference of grain size between the head and the tail of billet.

In order to solve the problem of heterogeneous deformation in the rolling process of 10Ni5CrMoV heavy plate, the effects of uniform temperature rolling (UTR) and graded temperature rolling (GTR) on the microstructure and deformation uniformity...

Low-alloy steels are widely used in cold-region load-bearing structures, but low temperature restricts dislocation motion and promotes cleavage or quasi-cleavage fracture, resulting in decreased impact toughness and an increased ductile-to-brittle transition temperature. This review summarizes soft/hard phase heterostructures as an effective microstructural strategy for improving low-temperature toughness in low-alloy steels. The toughening mechanisms are discussed from the perspectives of crack initiation, crack propagation, and crack-tip plastic energy dissipation. Available studies indicate that the beneficial effect of heterogeneity does not originate from phase coexistence alone, but depends on the coordinated optimization of structural scale, phase topology, interfacial stability, and metastable-phase behavior. Continuous or semi-continuous soft-phase pathways can accommodate local plastic strain and promote crack-tip blunting, while dispersed non-percolating hard phases provide load-bearing capacity without forming continuous brittle channels. Stable hierarchical interfaces can further deflect, branch, or arrest cracks and support hetero-deformation-induced hardening. However, excessive soft/hard strength mismatch, hard-phase percolation, coarse brittle constituents, weak interfaces, or unstable retained austenite may accelerate strain localization and cleavage initiation. The design window is also sensitive to loading rate and crack-tip constraint; under impact loading or high-constraint conditions, the three-stage hetero-deformation response may be qualitatively retained but quantitatively compressed. These considerations provide practical guidelines for designing low-temperature-tough low-alloy steels with improved fracture resistance in engineering applications.