Search Results (220)

Due to their characteristics of a high power-to-weight ratio, stringent lightweight requirements, and harsh working environments, straight face gears are prone to issues such as tooth fracture and inadequate fatigue strength. Meanwhile, because of the lack of fatigue information and weak fatigue life prediction method, the fatigue life of face gears cannot be effectively evaluated. In this study, the key technologies involved in the hot rolling forming process, fatigue experiments, and numerical modeling of straight face gears are studied. A technical foundation for straight face gears formed by hot rolling processing is established, and a fatigue experiment of the hot rolling forming of straight face gears is carried out. Due to the lack of information on fatigue experiments, a numerical prediction model is constructed. Sample expansion is carried out using a BP neural network–Bootstrap model to calculate the reliable lifespan of hot-rolled straight face gears, and fatigue life prediction for hot-rolled straight face gears is completed via the improved GM(1,1,λ) model based on the artificial bee colony algorithm, and thus the accurate evaluation of the fatigue life of rolling forming face gears is realized. The feasibility and superiority of the improved fatigue life prediction model are demonstrated by comparing it with the traditional prediction model and experimental results. The theoretical basis and technical support for the research of the fatigue resistance and installation application of face gears are provided. Full article

Equipment wear and assembly clearances can change the longitudinal stiffness of hot strip mills and further affect roll-gap levelling accuracy and asymmetric strip profile control. In this study, the longitudinal stiffness of a 1580 mm four-high hot strip finishing mill was investigated by combining the analytical calculation of the hydraulic press-down system with a three-dimensional mill–strip finite element model. The effects of typical horizontal and vertical gap forms, including work-roll offset, same-side deflection, roll crossing, and unilateral vertical clearance caused by step-pad wear, on total longitudinal stiffness and stiffness difference between the two sides were analysed systematically. The results show that work-roll horizontal offset changes the longitudinal stiffness in a nonlinear manner, whereas work-roll rotation and roll crossing generally reduce the longitudinal stiffness and increase the stiffness asymmetry between the two sides. Unilateral vertical clearance also causes nonlinear variation in both total stiffness and side-to-side stiffness difference. The proposed method was further applied to the stiffness prediction module of the Guangxi BG 1700 mm hot strip mill production line, providing support for equipment maintenance, roll-gap levelling, and stable strip production. Full article

C276 Hastelloy/Q235 Steel cladding plates were prepared by vacuum-sealed hot rolling (VSHR) with a small hole. The effects of different Ni interlayers on the macro-morphology, microstructure, mechanical properties and corrosion resistance of the cladding plates were systematically investigated. The results indicated that without an interlayer, a large number of Mo-rich white M₆C particles formed near the C276 Hastelloy side, along with the formation of black Cr-Mn oxides at the interface. The addition of the Ni interlayer suppressed the diffusion of the C element from the Q235 Steel toward the C276 Hastelloy, consequently reducing the precipitation of M₆C carbides and Cr-Mn oxides. When the Ni interlayer thickness was 0.5 mm, the M₆C carbides on the Hastelloy side disappeared completely. The incorporation of a Ni interlayer increased the hardness of the C276 Hastelloy side and the interface layer, as well as the shear strength of the cladding plate. This was mainly because the Ni interlayer acted as a barrier to suppress the development of a Mo/Cr-depleted zone adjacent to the C276 Hastelloy and decrease interfacial Cr-Mn oxides, thus enhancing interfacial bonding. Under all three conditions, the cladding plates were bent without cracking. Moreover, the addition of a Ni interlayer also improved the corrosion resistance of the cross-section of the C276 Hastelloy. XPS analysis of the passive film revealed that the corrosion resistance was primarily attributed to the formation of Mo- and Cr-containing oxides on the surface. The corrosion resistance reached the optimal with the Ni interlayer thickness of 0.5 mm, in which Mo and Cr played a crucial role. Full article

It is difficult to effectively evaluate the technology used to test fatigue in face gears due to their complexity, the lack of experimental data, and weak life evaluation methods. In this paper, we study fatigue experiment technology and carry out a life evaluation for hot rolling straight face gears. A hot rolling forming test was completed by analyzing and simulating the rolling formation of face gears, and the bending stress and fatigue life of face gears was simulated. We designed an experimental scheme and test bench for testing fatigue in straight face gears; this is the first bending fatigue life experiment carried out on hot rolling straight face gears in China. The BP neural network–Bootstrap sample expansion method and GM(1,1) model were carried out to evaluate the fatigue life of hot rolling straight face gears under information-poor conditions. A comparative analysis was carried out with skiving-formed straight face gears, which verifies the feasibility and superiority of hot rolling forming for straight face gears. This study provides a theoretical basis and technological support for the study of fatigue resistance in face gears, and applications for machine installations are provided. Full article

In this work, measurements of thermal diffusivity, heat capacity and thermal expansion of 40HM (42CrMo4, 1.7225, AISI 4140) steel manufactured conventionally and via Laser Powder Bed Fusion (L-PBF) were carried out in the temperature range from room temperature (RT) to 1000 °C. Thermophysical properties were tested using specialized test stands from NETZSCH. Thermal diffusivity was studied using both the LFA 427 laser flash apparatus and the LFA 467 xenon flash apparatus. Specific heat capacity was investigated using DSC 404 F1 Pegasus differential scanning calorimeter, and thermal expansion was investigated using the DIL 402 C. Inconel 600 and A310 steel were selected as the reference materials during the thermal diffusivity test using LFA467 in the RT÷500 °C range. The conventionally manufactured 40HM steel, in the form of hot-rolled bar stock, was subjected to standard heat treatment for this steel grade—quenching followed by high-temperature tempering. The additively manufactured 40HM steel was subjected to stress-relief annealing. The results revealed no significant differences between the thermophysical properties of the L-PBF-produced samples in the out-of-plane and in-plane build orientations. Furthermore, no substantial differences were observed between the thermophysical properties of the conventionally produced material and the material manufactured using the L-PBF technique. Full article

Duplex-phase low-density steels are attracting interest for lightweight structural applications, as reducing vehicle mass is an effective route to lower fuel consumption and emissions. This review summarizes recent progress in alloy design, processing, microstructure control, and performance of duplex-phase low-density steels. The roles of major alloying elements are discussed in terms of phase stability and precipitation tendency, followed by an overview of typical processing routes from melting to hot and cold rolling and subsequent heat treatments used to tailor phase fractions and defect structures. Strengthening mechanisms are reviewed with emphasis on precipitation control, including the beneficial contribution of fine intragranular κ′ precipitates and the ductility penalty associated with coarse intergranular κ* films, as well as the use of B2-based particles for high specific strength. Deformation behavior is then discussed in terms of transformation-/twinning-induced plasticity (TRIP/TWIP), planar versus wavy slip, and strain partitioning between ferrite and austenite. Finally, key challenges are outlined, including quantitative interface-based mechanism description, gaps in service property data, stable industrial production and compositional uniformity, and the development of forming and welding windows for engineering implementation. Full article

As wind turbines trend toward larger sizes, higher rotational speeds, and extended service lives, higher demands are emerging for the dimensional accuracy, mechanical properties, and service reliability of the main shaft bearings. The hot bulging process is a critical process in bearing ring manufacturing. The stress–strain and dimensional evolution during the hot bulging process are crucial for the fatigue life and dimensional accuracy of rings with non-circular cross-sections. Therefore, based on the residual stress field from rolling as an initial condition, this paper established a coupled finite element model for the entire rolling-to-bulging process of GCr15SiMn bearing steel rings and verified the accuracy of the model. A stepwise rotation hot bulging process was innovatively designed. The stresses, strains, and deformation rates of the rings were thoroughly evaluated at different steps of the bulging process. Additionally, the effect of the bulge amount on the stress–strain uniformity and dimensional accuracy of the fabricated rings was also evaluated. Results indicate that based on the stepwise rotation hot bulging process conducted at 870–930 °C, when the first-step bulging amount is 1.50 mm, the secondary and third-step amounts are both 0.50 mm, and the bulging speed is 1.00 mm/s, while the roundness error of ring #3 stabilizes within 0.28–0.35 mm. The standard deviation of the axial equivalent strain was decreased by 92%, and the stress peak was also decreased by 39%. Above all, the stepwise rotation hot bulging process is an effective approach to improve the distribution uniformity of the stress–strain and the dimensional consistency of the bearing rings. This paper provides theoretical foundations and process guidance for the precision forming of large wind turbine bearing rings with non-standard sections. Full article

Multilayer laminated composites consisting of high-chromium cast iron (HCCI) powder clad with low-carbon steel (LCS) were fabricated via multi-pass hot rolling at a deformation of 70% under three different temperatures: 1100 °C, 1150 °C, and 1200 °C. The microstructure, elemental diffusion, and mechanical properties of the samples processed at these temperatures were systematically investigated. The results indicate that effective metallurgical bonding was achieved between the HCCI powder and the LCS matrix, with the HCCI regions accumulating high strain energy and dislocation density. Hardness testing demonstrated that higher rolling temperatures lead to increased hardness. The dominant wear mechanism was identified as dry sliding wear. The relatively low content of retained austenite contributed to a reduction in tensile strength, while this microstructure further promoted abrasive wear through the spalling of carbides. These findings suggest that hot processing offers a feasible pathway for improving the wear resistance of HCCI-based composites. Full article

Magnesium alloys’ poor corrosion resistance limits their applications as biodegradable bone repair materials. Alloying tailors Mg alloys’ microstructure and properties. The present study investigates the effect of 2 wt.% Ag addition on the microstructure and initial corrosion behavior of hot-rolled Mg-1Ca alloy. Mg-1Ca and Mg-1Ca-2Ag alloys were prepared by melting using Mg-2Ca and Mg-4Ag master alloys, followed by homogenization at 400 °C for 2 h, hot rolling, and stress-relief annealing at 400 °C for 6 h. The alloys were systematically characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). Initial corrosion behavior was evaluated via 3 h immersion tests in simulated body fluid (SBF). Results reveal Ag’s high thermal diffusivity promotes segregation at tensile twin boundaries, forming Ag₃Mg nanoparticles. These nanoparticles hinder grain boundary migration and, with increased deformation, facilitate grain rotation and high-angle grain boundary formation, weakening texture. Internal stress accumulation near twin boundaries—driven by grain orientation variation and nanoparticles—induces ~86° rotation of {10–12} tensile twins around the c-axis, forming double twins. During corrosion, nanoparticles and double twins synergistically promote dense protective film formation, significantly reducing corrosion rates. Full article

By means of characterization techniques such as XRD, TEM, and in situ EBSD, the texture evolution, recrystallization behavior, and their modulation by the Al₃Zr phase in hot-rolled Al-Zn-Mg-Cu-Zr alloys with varied homogenization treatments were investigated. Results show that both the single-stage homogenized (SH) alloy and the double-stage homogenized (DH) alloy acquired a typical β-fiber texture after hot rolling, including brass, S, and copper orientations. The DH alloy experienced suppressed recrystallization (a recrystallization fraction of 6.05%) owing to its higher density of Al₃Zr precipitates. In contrast, the SH alloy exhibited more significant dissolution and agglomeration of Al₃Zr, leading to extensive recrystallization peaking at 78.1%. The primary recrystallization mode was identified as continuous recrystallization, characterized by the growth and coarsening of subgrains. Although dynamically recrystallized (DRx) grains formed during hot rolling could act as potential recrystallization nuclei, most of them exhibited weak growth capability, except the cube-oriented grains. During recrystallization, deformed grains with S orientation tended to transform into cube-oriented grains, while those with brass orientation prefer to convert into Goss-oriented grains. This can be attributed to the presence of highly mobile grain boundaries between these specific orientation pairs. In the DH alloy, subgrain growth and DRx grain consumption during annealing reduced orientation dispersion in deformed grains, promoting marked brass texture strengthening, with its volume fraction reaching 57.7%. Full article

This study investigates the technological and chemical causes of early zinc-coating degradation on cold-formed steel sections produced from DX51D+Z140 galvanized coils. Commercially manufactured products exhibiting early corrosion symptoms were used in this study. The entire processing route, which included strip preparation, cold rolling, hot-dip galvanizing, passivation, multi-roll forming, storage, and transportation to customers, was analyzed with respect to the residual surface chemistry and process-related deviations that affect the coating integrity. Thirty-three specimens were examined using electromagnetic measurements of coating thickness. Statistical analysis based on the Cochran’s and Fisher’s criteria confirmed that the increased variability in zinc coating thickness is associated with a higher susceptibility to localized corrosion. Surface and chemical analysis revealed chloride contamination on the outer surface, absence of detectable Cr(VI) residues indicative of insufficient passivation, iron oxide inclusions beneath the zinc coating originating from the strip preparation, traces of organic emulsion residues impairing wetting and adhesion, and micro-defects related to deformation during roll forming. Early zinc coating degradation was shown to result from the cumulative action of multiple technological (surface damage during rolling, variation in the coating thickness) and environmental (moisture during storage and transportation) parameters. On the basis of the obtained results, a methodology was proposed to prevent steel product corrosion in industrial conditions. Full article

A weak-axis moment connection incorporating a double reduced beam section and a box-reinforced panel zone (WDRBS) is introduced for hot-rolled H-shaped columns. The configuration is intended to shift inelastic demand away from the column face and to constrain weak-axis panel-zone distortion. A series of finite element models is established and calibrated to examine the cyclic response of this connection type. By varying the geometric parameters of the second reduction zone, a closed-form expression for determining its cutting depth (c₂) is formulated, allowing both reduced regions to yield concurrently, i.e., the Optimum State. The numerical investigation demonstrates that connections designed according to this equation exhibit stable hysteresis, limited weld-adjacent plastic ll rightstrain, and sufficient deformation and energy-dissipation capacities. All specimens exhibit plastic rotations greater than 0.03 rad, ductility ratios greater than 3.0, and equivalent viscous damping ratios greater than 0.3. To facilitate engineering implementation using common hot-rolled sections, a simplified method is further proposed to approximate the admissible range of c₂ with practical accuracy. While the length of the second reduction region has only a modest influence on peak strength (approximately 1.5–6%), it markedly affects the failure mechanism and plastic-hinge distribution. A stepwise design procedure for WDRBS connections is accordingly recommended. The study does not consider composite-slab interaction or gravity-load effects, and the findings—based solely on finite element simulations—require future verification through full-scale experimental testing. Full article

The hole expansion process of high-strength steel is influenced by multiple factors, including the deformation path, UTS/YS ratio, uniform elongation, sheet anisotropy, sheet thickness, strain rate, material micro-defects and the work hardening exponent. Based on forming limit curves or instability criteria, the prediction of the hole expansion ratio (HER) often requires extensive initial boundary conditions that complicate the result. In this study, V-Nb bainitic steel was subjected to hot continuous rolling and underwent water quenching with different coiling temperatures, then subsequently followed by thermal simulation and mechanical testing to fit the work hardening exponent (n) and to obtain the necking deformation instability curve. The radial displacement at the hole edge during simulation was predicted with the ratio of ultimate tensile strength to fracture strength. Furthermore, based on the tensile fracture failure criterion, the HER was predicted with the true fracture strain derived from uniaxial tensile tests. Comparison between the simulated results and actual hole expansion tests shows that the crack resistance in the post-uniform stage, strain hardening capacity and deformation compatibility between the microstructure and matrix are critical factors. And the proposed model achieves a prediction accuracy of over 85% for the V-Nb bainitic high-strength steel. Full article

In the manufacturing sector, energy loss often stems mainly from wear. By improving the surface characteristics of alloys, we can substantially cut down on this kind of loss, which in turn boosts the efficiency of energy use. In this study, Fe₄₀Mn₁₉Cr₂₀Ni₂₀Mo₁ high-entropy alloy (HEA) with a face-centered cubic (FCC) structure was subjected to aluminum–nitrogen co-infiltration treatment via pack aluminizing and plasma nitriding, forming an aluminum–nitrogen co-infiltrated layer with a thickness of approximately 17 μm. An analysis was carried out on the microstructure, growth dynamics, and tribological behavior of the Al-N co-infiltrated layer across a broad temperature spectrum. The results showed that the surface hardness of the samples treated by aluminizing and Al-N co-infiltration reached 592 HV and 993 HV, respectively, which were significantly higher than that of the hot-rolled alloy (178 HV). The Al-N co-infiltrated HEA exhibited a low and stable friction coefficient as well as wear rate over a wide temperature range (20–500 °C), which was attributed to the formation of the Al-N co-infiltrated layer composed of AlN, CrN, and FeN phases. This study demonstrates that Al-N co-infiltration treatment is an effective surface modification technique, which can significantly enhance the hardness and tribological properties of high-entropy alloys over a wide temperature range. Full article

In this study, we fabricated Fe-25Ni-15Cr alloy rods via vacuum induction melting, electroslag remelting, forging, hot rolling, and annealing. We systemically investigated the influence of varying cold-drawing deformation levels (10–60%) on microstructure evolution and mechanical properties, which were characterized by a variety of multi-scale characterization techniques, including optical microscopy, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The results show that when the cumulative deformation amount is less than 30%, the hardness, tensile strength, and yield strength increase significantly with the increase in deformation amount, while the elongation continues to decline; when the cumulative deformation amount exceeds 30%, the rates of increase in hardness and strength decrease significantly; and when the deformation amount increases to 50%, dislocation density accumulates preferentially at the grain boundaries and forms a cellular substructure, while the texture orientation gradually stabilizes from random distribution to the <111> direction. This alloy rod exhibits three strengthening mechanisms during cold drawing: grain refinement, second-phase precipitation, and work hardening. A predictive model for tensile strength is derived through theoretical calculations. This work has guiding significance for establishing a cold-drawing process window without intermediate annealing. Full article