steel research international最新文献

To control the superheat, a key parameter in the continuous casting process, and stabilize it at a predefined optimal value, it is necessary to predict the superheat corresponding to the casting start temperature. This article proposes a molten steel superheat prediction model comprising two submodels for ladle and tundish exit temperatures. The two submodels are developed using a hybrid approach combining both mechanistic and data-driven methods, with a serial connection in structure and end-to-end training for data backpropagation. To improve model accuracy by capturing the time-varying thermal properties of the working layer, this article proposes a forward-inverse physics-informed neural network (fi-PINN) based on the traditional PINN algorithm. The fi-PINN simultaneously solves partial differential equations and estimates parameters. Production data from multiple casting sequences at a steel plant are used to validate the model's performance. The results show that the proposed model improves the accuracy by ≈3.07 and 1.62 K, compared to the mechanistic and data models that do not account for the time-varying thermal properties. Furthermore, the model's ability to capture the variation of the working layer's thermal properties provides strong physical interpretability.

The study systematically elucidates the mechanism by which the initial electrode distance affects the thermal–mechanical coupling effect and microstructural properties of flash butt welded joints of 600 MPa grade high-strength corrosion-resistant steel. A dynamic temperature field flash butt welding is constructed based on real-time thermocouple measurement data at multiple locations, combined with testing, to establish a quantitative correlation mechanism among the initial electrode distance parameter, phase transformation behavior, and mechanical properties. The experimental results indicated that increasing the initial electrode distance reduces the peak weld temperature, effectively suppressing abnormal grain growth in the coarse-grained heat-affected zone (CGHAZ). Microstructural evolution analysis reveals similarly that the weld zone primarily consists of acicular ferrite and bainite, the CGHAZ exhibits a mixed structure of lath bainite and granular bainite, while the fine-grained heat-affected zone comprises a composite structure of polygonal ferrite and granular bainite. Fractographic analysis shows that the fracture surfaces of joints with an initial electrode distance of 14 mm exhibit tough-brittle mixed fractures and the minimum impact energy. In contrast, the initial electrode distance increases 16 mm, and the impact toughness enhances to over 60 J, which is an increase of 21%, exhibiting superior mechanical properties.

Large-scale steel storage tanks for liquid CO₂ are critical elements in Carbon Capture and Storage infrastructure. This study investigated the weldability and mechanical performance of 34 mm thick joints made from cold-resistant microalloyed steel grade P460NL1. The main welded joints are produced using automatic submerged arc welding (SAW 121-2) with a V-groove and heat input of 1.5 ±  0.1 kJ mm⁻¹. Microstructural analysis revealed stable zoning with bainitic structures, maximum hardness of 222 HV₅, and microhardness values not greater than 323 HV_0.3 in the heat-affected zone (HAZ). In the as-welded condition, Charpy impact energy exceeded 186 J at −40 °C and remained above 88 J at −50 °C. Post-weld heat treatment increased yield strength from 452–453 MPa to 465–468 MPa, while slightly reducing tensile strength and impact energy in the fusion line. Additional weldability tests included controlled thermal severity and bead-on-plate welding tests, both confirming the absence of cracking and acceptable HAZ hardness. Strain aging tests showed retention of ductile behavior down to −60 °C. High-temperature tensile testing up to 450 °C confirmed structural stability over a wide operating range. These findings support the use of P460NL1 steel for high-integrity welded structures in demanding CO₂ storage conditions.

Large-scale steel storage tanks for liquid CO₂ are critical elements in Carbon Capture and Storage infrastructure. This study investigated the weldability and mechanical performance of 34 mm thick joints made from cold-resistant microalloyed steel grade P460NL1. The main welded joints are produced using automatic submerged arc welding (SAW 121-2) with a V-groove and heat input of 1.5 ±  0.1 kJ mm⁻¹. Microstructural analysis revealed stable zoning with bainitic structures, maximum hardness of 222 HV₅, and microhardness values not greater than 323 HV_0.3 in the heat-affected zone (HAZ). In the as-welded condition, Charpy impact energy exceeded 186 J at −40 °C and remained above 88 J at −50 °C. Post-weld heat treatment increased yield strength from 452–453 MPa to 465–468 MPa, while slightly reducing tensile strength and impact energy in the fusion line. Additional weldability tests included controlled thermal severity and bead-on-plate welding tests, both confirming the absence of cracking and acceptable HAZ hardness. Strain aging tests showed retention of ductile behavior down to −60 °C. High-temperature tensile testing up to 450 °C confirmed structural stability over a wide operating range. These findings support the use of P460NL1 steel for high-integrity welded structures in demanding CO₂ storage conditions.

The evolution and formation mechanism of slag shells during the process of electroslag remelting (ESR) is crucial for optimizing the conditions of heat transfer and enhancing both the surface and internal quality of the ingot. This study uses Maxwell and Fluent software to develop a 3D model for ESR with two series-connected electrodes, exploring the slag shell formation mechanism. During the process, when the mold diameter is Φ130 mm and the initial slag shell thickness is 5 mm, slag on the mold sidewall solidifies into a slag shell. Intense water cooling forms a crescent-shaped slag shell near the slag–metal interface. As the temperatures of the slag bath and molten metal rise, the slag shell melts and thins. When the thickness of the slag shell reaches 2.6 mm, it enters a dynamic equilibrium state, thereby forming a homogeneous slag shell. As the steel ingot grows and is withdrawn, the slag shell continues to thin. Compared with two-dimensional models, the three-dimensional model exhibits higher heat transfer efficiency. Moreover, the curved morphology of the solidification boundary of the slag shell in the three-dimensional model is more complex and asymmetric.

This study investigates the effect of drawing process parameters on friction properties of AISI 304 steel sheet. In sheet metal forming, friction-related aspects directly influence the process performance and quality of the manufactured products. In this context, the present study aims to investigate the effect of drawing process parameters on the friction properties of AISI 304 austenitic steel sheets under lubricated conditions. For this purpose, strip-shaped samples with dimensions of 0.8 × 25 × 450 mm are tested in a device developed and adapted to a sheet metal tribosimulator for performing the strip drawing test. The influence of parameters such as the strip-sliding speed, normal force, and tool roughness on the average value of the coefficient of friction is analyzed. Several characterization techniques are applied to the strip surfaces after the tests, including hardness tests, roughness analysis, scanning electron microscopy, and X-ray diffraction. The results demonstrate that an increase in the normal force under lubricated conditions reduces the coefficient of friction by 6–21%. The adhesive and abrasive friction mechanisms are predominant under a low force, whereas plastic deformation of the surface asperities dominates at high normal forces.

A novel Fe-18.17Mn-10.51Al-1.04C-5.88Ni duplex steel composition is designed for reduced density and enhanced strength. The alloy is vacuum induction melted, cast into a plate in a copper mold, hot rolled, water quenched, and cold rolled for 80% reduction in thickness (PD1-CR). The deformed material contains 57.3 and 42.7% austenite and ferrite, respectively. Ferrite depicted higher dislocation density, microstrain, with deformed texture components of cube and rotated Goss. Austenite showed A-type and rotated copper texture components. The deformed duplex steel is annealed at 930 °C for 5 (PD1-CA5) and 15 min (PD1-CA15). With annealing time, an increased amount of austenite is recrystallised with the signature of enhanced intensity of Goss/Brass texture component, higher fraction of high-angle grain boundary, and enhanced misorientation angle. Continued annealing, delta ferrite is recovered with an increased low-angle grain boundary fraction. Part of the delta ferrite transformed into austenite and got ordered to B2. Higher yield strength (1430 MPa) of PD1-CA5 than that of PD1-CA15 is mainly due to the increased contribution from higher residual dislocation density. PD1-CA15 displayed enhanced ductility because of partial recrystallisation of austenite, but precipitation of B2 increased strain hardening.

In this study, the relationship between microstructure and mechanical properties of Cr–Mn–Ni low-alloy ultrahigh-strength steel subjected to different tempering processes is studied. The results indicate that with increasing tempering temperature, quenched martensite undergoes gradual decomposition. The strength and hardness gradually decrease, while elongation does not exhibit a clear trend. Impact energy initially declines and later increases, with noticeable tempering brittleness observed at 450 °C and 550 °C. The microstructure and properties of two-step tempering are basically the same as that of conventional tempering. However, extended tempering time leads to a 125% improvement in elongation and superior tensile strength (1760 MPa). The tempering transformation of quenched martensite in the tempering process directly dominates the changes of mechanical properties. The decomposition of supersaturated martensite during tempering is the primary factor affecting grain boundary distribution; however, it has no significant impact on the microstructural orientation relationship or texture evolution. In the tempering brittleness of 550 °C, the distribution of band contrast values, elevated kernel average misorientation at grain boundaries, localized concentration of crystal orientations along <101> and <111>, and the pronounced Brass texture may collectively contribute to the onset of tempering brittleness.

In this study, the relationship between microstructure and mechanical properties of Cr–Mn–Ni low-alloy ultrahigh-strength steel subjected to different tempering processes is studied. The results indicate that with increasing tempering temperature, quenched martensite undergoes gradual decomposition. The strength and hardness gradually decrease, while elongation does not exhibit a clear trend. Impact energy initially declines and later increases, with noticeable tempering brittleness observed at 450 °C and 550 °C. The microstructure and properties of two-step tempering are basically the same as that of conventional tempering. However, extended tempering time leads to a 125% improvement in elongation and superior tensile strength (1760 MPa). The tempering transformation of quenched martensite in the tempering process directly dominates the changes of mechanical properties. The decomposition of supersaturated martensite during tempering is the primary factor affecting grain boundary distribution; however, it has no significant impact on the microstructural orientation relationship or texture evolution. In the tempering brittleness of 550 °C, the distribution of band contrast values, elevated kernel average misorientation at grain boundaries, localized concentration of crystal orientations along <101> and <111>, and the pronounced Brass texture may collectively contribute to the onset of tempering brittleness.

Herein, the 20Cr3MoWVA steel is subjected to carburizing and plasma nitriding composite heat treatment for strengthening. Ball-disk friction wear tests are conducted on three states (Untreated, C, C + PN) of the samples. The results show that after the composite heat treatment, a composite diffusion layer composed of γ′-Fe₄N phase and ε-Fe_2-3N phase is obtained. This diffusion layer has no compound layer and no vein-like grain boundaries, and its thickness is 150 micrometers. The surface hardness of the C + PN sample (1004 HV) is 4.2 times and 1.3 times that of the Untreated sample and the C sample, respectively, and its wear rate decreases by 97.34% and 74.38% compared to the untreated sample and the C sample, respectively. The C + PN sample has the lowest friction coefficient (0.5887), and the surface residual compressive stress reaches −883 MPa. During the plasma nitriding process, Cr-rich M₇C₃ carbides and V-rich MC carbides transform into M_2-3(C, N) and M(C, N) carbonitrides, respectively. The wear mechanisms of the three specimen states involve oxidative wear and adhesive wear, with abrasive wear also present in the untreated and C specimens. During the wear process of the C + PN samples, nanocomposite self-lubricating oxides with excellent wear resistance are formed.