steel research international最新文献

This study aims to understand the fracture mechanisms within the hot ductility trough by investigating four microalloyed steels with varying Ti content and balanced Nb. Variations in the cooling rate and Ti content significantly influence intergranular cracking by affecting proeutectoid ferrite formation and TiNb(CN) precipitation. Thermomechanical tests are conducted at three critical temperatures (700, 800, and 900 °C), under cooling rates of 10 and 1 K·s⁻¹, and a strain rate of 0.001 s⁻¹. The effect of cooling rate on hot ductility is examined by analyzing ferrite thickness, and TiNb(CN) precipitates through microstructural investigation and MatCalc simulation. At 700 °C, a thin ferrite layer at grain boundaries causes intergranular cracking. A slower cooling rate increases ferrite thickness, thereby, reducing crack susceptibility. At 800 and 900 °C, precipitation behavior and dynamic recrystallization dominate the hot ductility. Coarser precipitates formed under slow cooling result in lower microvoid density at TiNb(CN)-grain boundary interfaces, thereby limiting crack propagation. Among the Ti-containing steels, steel S1 exhibits the highest ductility recovery, while steel S2 demonstrates the most favorable overall hot ductility performance. The high Ti content in S3 promotes excessive TiNb(CN) formation, which increases microvoids and suppresses the recovery of hot ductility.

Efficient oxide scale removal is critical for maintaining surface quality and process efficiency in steel manufacturing. This study optimizes water jet descaling by evaluating the performance of flat and rotary jet nozzles under varying process parameters. Using a combined approach of experimental analysis and computational fluid dynamics, it investigates the influence of pressure (138–275 bar), lead angle (0°, 15°, 25°), working distance (50–100 mm), and spray angle (15°–25°) on descaling efficiency. Findings indicate that flat jet nozzles achieve superior performance at short working distances due to concentrated impact forces, while rotary jet nozzles sustain efficiency over extended distances through dynamic droplet attack angles. A critical threshold for flat jet nozzles is identified, beyond which scale removal efficiency declines sharply. The study confirms an optimal 15° lead angle for flat jets, aligning with industrial best practices. By integrating principles of fluid mechanics, impact dynamics, and erosion mechanics, it establishes a robust framework for nozzle parameter optimization. These insights contribute to the development of adaptive descaling systems capable of real-time adjustments for challenging steel grades, enhancing scale removal effectiveness in continuous casting and hot rolling operations.

Herein, disordered special quasirandom structure models of Fe_20−x−yCr₅Ni₇Al_xTi_y (x, y = 1, 2, 3, 4, 5) are established for the single-phase austenitic structure of low-magnetic stainless steel through first-principles calculations. The alloy volume exhibits linear expansion with increasing Al and Ti content, affected by the combined effects of doping atomic radius and interatomic interactions. The Fe₁₄Cr₅Ni₇Al₂Ti₄ alloy demonstrates the smallest volume and higher structural stability. Energy analysis reveals that the total energy, cohesive energy, and formation energies of all systems are negative, confirming the structural stability of the crystals with varying Al and Ti content. With increasing Ti/Al atomic ratios, the bulk modulus gradually decreases, while the shear modulus and Young's modulus increases, suggesting reduced resistance to volumetric deformation but enhanced resistance to shear and tensile/compressive deformation. Low-magnetic stainless steels with Ti/Al ratios of 1/5, 3/3, and 5/1 are fabricated to verify the calculated results. These alloys maintain stable austenitic structures and paramagnetic behavior, with yield strength, tensile strength, and elongation ranging in 476–834 MPa, 896–1139 MPa, and 14.6–41.2%. Relative magnetic permeabilities are measured as 1.00457, 1.00474, and 1.00557. This study provides theoretical guidance for the compositional optimization and technological development of high-strength stable austenitic Fe–Cr–Ni–Al–Ti alloys.

Herein, disordered special quasirandom structure models of Fe_20−x−yCr₅Ni₇Al_xTi_y (x, y = 1, 2, 3, 4, 5) are established for the single-phase austenitic structure of low-magnetic stainless steel through first-principles calculations. The alloy volume exhibits linear expansion with increasing Al and Ti content, affected by the combined effects of doping atomic radius and interatomic interactions. The Fe₁₄Cr₅Ni₇Al₂Ti₄ alloy demonstrates the smallest volume and higher structural stability. Energy analysis reveals that the total energy, cohesive energy, and formation energies of all systems are negative, confirming the structural stability of the crystals with varying Al and Ti content. With increasing Ti/Al atomic ratios, the bulk modulus gradually decreases, while the shear modulus and Young's modulus increases, suggesting reduced resistance to volumetric deformation but enhanced resistance to shear and tensile/compressive deformation. Low-magnetic stainless steels with Ti/Al ratios of 1/5, 3/3, and 5/1 are fabricated to verify the calculated results. These alloys maintain stable austenitic structures and paramagnetic behavior, with yield strength, tensile strength, and elongation ranging in 476–834 MPa, 896–1139 MPa, and 14.6–41.2%. Relative magnetic permeabilities are measured as 1.00457, 1.00474, and 1.00557. This study provides theoretical guidance for the compositional optimization and technological development of high-strength stable austenitic Fe–Cr–Ni–Al–Ti alloys.

Post processing of tool steels often requires an elevated tempering resistance, enabled by the precipitation of tempering carbides, increasing the hardness. This necessitates sufficient solute contents of alloying elements in a supersaturated iron matrix after austenitizing and quenching. Both, carbide-forming refractory elements (i.e., tungsten, molybdenum, or vanadium) as well as elements like manganese or silicon influence the tempering carbide precipitation. This study investigates the influence of the alloying elements tungsten, vanadium, silicon, and manganese on the tempering behavior of boride rich high boron cold work tool steels (HBTS). Thus, alloys with varying compositions and element contents are cast, swaged, and heat treated. The hardness after tempering at different temperatures is measured. Microstructural investigations by electron microscopy and atom probe tomography (APT) are performed to contextualize the findings. It is found that tungsten influences the tempering hardness negligibly, whereas vanadium significantly enhances secondary hardness. APT analysis reveals the precipitation of VC tempering carbides. Silicon and manganese, both individually and in combination, increase the tempering hardness. These insights pave the way for the adaptation and utilization of HBTS in future applications that necessitate high tempering resistance due to postprocessing or elevated operating temperatures.

In this study, the final rolling temperatures (FRTs) are the key process parameters in the control of precipitates, microstructure, and mechanical properties of V–N microalloyed X70 pipeline steels. As the FRTs decrease from 890 to 780 °C, the yield strength (YS) , −20 °C impact energy and drop-weight tear test (DWTT) properties first increase to 565 ± 7 MPa, 273 ± 10 J, and 95 ± 2% at 830 °C, and finally decreased to 545 ± 5 MPa, 221 ± 6 J, and 85 ± 3% at 780 °C. The ductile-brittle transition temperature (DBTT) is −71, −73, −79, and −69 °C, respectively, at FRTS of 890 , 860 , 830, and 780 °C. The diameter of the precipitates was in the range between 5–80 nm under all the FRTs. The optimum microstructure and mechanical properties were obtained at a FRT of 830 °C. The main effect of the FRT on the yield strength was fine grain strengthening, dislocation strengthening and precipitation strengthening in this steel. The significant enhancement in low-temperature toughness is primarily attributed to transformation strengthening from acicular ferrite (AF) and precipitation hardening from high fraction of 5-20 nm V(C, N) precipitates. The fine non-parallel AF with high degree of misorientation could improve the low-temperature toughness by impeding the dislocation crack propagation.

High-Mo super-austenitic stainless steels exhibit pronounced Mo segregation along grain boundaries (GBs) during thermomechanical processing, promoting Mo-rich precipitate formation during hot rolling. Atomic-level understanding of the fundamental mechanisms governing this precipitation behavior is essential for material performance optimization. First-principles calculations are employed to systematically investigate the segregation behavior in the Σ9 (114) GB region of fcc-Fe, and strain effects on solute aggregation dynamics and precipitate nucleation are assessed. The results reveal that Mo preferentially segregates to specific sites within the Σ9 (114) GB, though the GB exhibits limited solute accommodation capacity. Progressive Mo segregation reduces GB cohesive strength, with incremental bond weakening correlating with Mo accumulation. Notably, Mo-induced atomic size mismatch generates substantial lattice distortions. Applied microstrain enhances Mo aggregation by thermodynamically stabilizing segregation and altering local atomic environments. The interplay between solute clustering and strain-induced distortions produces significant atomic displacements, creating localized strain fields conducive to precipitate nucleation via preferential phase formation pathways.

High-Mo super-austenitic stainless steels exhibit pronounced Mo segregation along grain boundaries (GBs) during thermomechanical processing, promoting Mo-rich precipitate formation during hot rolling. Atomic-level understanding of the fundamental mechanisms governing this precipitation behavior is essential for material performance optimization. First-principles calculations are employed to systematically investigate the segregation behavior in the Σ9 (114) GB region of fcc-Fe, and strain effects on solute aggregation dynamics and precipitate nucleation are assessed. The results reveal that Mo preferentially segregates to specific sites within the Σ9 (114) GB, though the GB exhibits limited solute accommodation capacity. Progressive Mo segregation reduces GB cohesive strength, with incremental bond weakening correlating with Mo accumulation. Notably, Mo-induced atomic size mismatch generates substantial lattice distortions. Applied microstrain enhances Mo aggregation by thermodynamically stabilizing segregation and altering local atomic environments. The interplay between solute clustering and strain-induced distortions produces significant atomic displacements, creating localized strain fields conducive to precipitate nucleation via preferential phase formation pathways.

The relevance of research on lightweight Fe–Mn–Al–C alloys is continuously increasing. This is justified by their good comprehensive mechanical properties, as well as their potential to improve fuel efficiency and reduce CO₂ emissions due to their low density. This work examines the effect of alloying elements on the structure and properties of austenitic Fe–Mn–Al–C steels, the trend of formation and distribution of κ-carbides depending on the content of the main alloying elements. Special attention is paid to the manufacturing process, strengthening methods, and challenges associated with their production. Some issues that require more detailed study for the implementation of lightweight Fe–Mn–Al–C steels in production are also discussed.

The relevance of research on lightweight Fe–Mn–Al–C alloys is continuously increasing. This is justified by their good comprehensive mechanical properties, as well as their potential to improve fuel efficiency and reduce CO₂ emissions due to their low density. This work examines the effect of alloying elements on the structure and properties of austenitic Fe–Mn–Al–C steels, the trend of formation and distribution of κ-carbides depending on the content of the main alloying elements. Special attention is paid to the manufacturing process, strengthening methods, and challenges associated with their production. Some issues that require more detailed study for the implementation of lightweight Fe–Mn–Al–C steels in production are also discussed.