Steel Temperature Research Articles

Research on temperature prediction model of molten steel of tundish in continuous casting

To achieve the desired superheat of molten steel during the continuous casting process, optimization of process parameters such as molten steel temperature in ladle furnace, casting speed, and baking temperature is necessary. Therefore, obtaining the superheat corresponding to these process parameters in advance is particularly important. To address this issue, a model for predicting the temperature of molten steel in the tundish during continuous casting is designed. The model adopts a combined modeling approach of mechanistic model and data model. To address the issue of the mechanism model’s inability to capture the variation of the lining’s thermal parameters, this article improves the traditional physics-informed neural network (PINN) algorithm. It combines the constraints from both the forward and inverse problems, allowing for obtaining solutions to the equations while capturing the variation of equation parameters. Actual data from multiple casting sequences at a steel plant are collected to validate the accuracy and interpretability of the model. The results show that the error of the model is about 2.1k which has better accuracy compared to pure mechanistic model and pure data model. Additionally, it can capture the variation patterns of tundish lining thermal parameters under different operating conditions. Therefore, the model designed in this article can provide both profound physical interpretation ability and more practical predictions of molten steel temperature.

Explainable machine learning model for predicting molten steel temperature in the LF refining process

Explainable machine learning model for predicting molten steel temperature in the LF refining process

Effect of Heat Treatment on Impact Transition Temperature of High Strength Low Alloy Steel (HSLA) Steel Rods

Effect of Heat Treatment on Impact Transition Temperature of High Strength Low Alloy Steel (HSLA) Steel Rods

Flow, Heat‐Transfer, and Mixing Behaviors of Scrap Steel in a Refining Ladle with Bottom Blowing

The flow, heat‐transfer, and mixing behaviors of steel scraps with different amounts, positions, and sizes added from the top of the bottom‐blown 300 t ladle are numerically investigated and compared through a coupled model. In the results, it is shown that it takes 59 s to mix the temperature of molten steel after adding scrap steel at the position of x = 0 mm, y = 553.5 mm, and z = 3375 mm. The further the addition position is from the axial position of the permeable brick, the shorter the mixing time of the speed and temperature of molten steel. For the scrap amount of 0.5, 1.5, and 2.5 t, the mixing time of molten steel temperature is 44, 78, and 47 s, correspondingly, which exhibits a pattern of initial increase followed by decrease, with an ≈8 K decline in molten steel temperature for every additional 1.0 t of scrap. When considering the scrap size of 10, 30, and 50 mm, the average temperature mixing time of molten steel is 44, 61, and 45 s, respectively. In this research, theoretical guidance can be can be provided for the addition of scrap in ladle during practical production processes.

Optimization of Inclusion and Microstructure of As‐Cast Nonquenched and Tempered Steel F38MnVS with Trace Ce

Various techniques, such as optical microscopy, high‐temperature confocal laser scanning microscopy, scanning electron microscopy, electron backscatter diffraction, and thermodynamic calculations, are employed to analyze the optimization mechanism of Ce on the inclusions and microstructures in F38MnVS as‐cast samples. The results show that the addition of Ce inhibits MnS precipitation at the grain boundaries and significantly reduces the diameters and aspect ratios of the inclusions. After Ce treatment, a new type of composite inclusion appears in the steel. The modification of the inclusions by Ce promotes the optimization of the as‐cast microstructure during solidification, which mainly exhibits austenite grain refinement and polygonal ferrite formation in the grains. Based on the misfit degree theory, the refinement of the austenite grains is because of the nucleation of austenite grains facilitated by Ce2O2S and CeAlO3. The increased nucleation of the intragranular polygonal ferrite is mainly attributed to Ce2O2S, Ce2S3, CeAlO3, and VC, which can promote the nucleation of α‐Fe. Simultaneously, the addition of Ce reduces the phase transition temperature, increases the driving force of the phase transition, and increases the nucleation rate. This study's results can provide a reference for the application of Ce treatment in the preparation of nonquenched tempered steel for automobiles.

A novel route of carburizing through microwave hybrid heating

Abstract Carburizing is a surface treatment process by diffusing carbon into the steel. These days, manufacturing industries demand highly efficient processes that consume low power. Microwave processing is a newly evolving process that consumes low power. This study proposes a novel route for carburizing mild steel (substrate) through experimental and simulation studies using a microwave heating. Charcoal powder was used as a susceptor to convert microwave energy into heat energy and to deposit carbon on the surface of the specimen. The mild steel specimens were exposed to the microwave power input of 900 W and 360 W for exposure time of 1500 s and 1980 s naming it as S2 and S3 respectively. The microstructural analysis of specimens S2 and S3 confirms the formation of pearlite structures at the surface. However, the amount of pearlite structure was significantly higher for the S3. The higher carbon content is confirmed through energy-dispersive x-ray spectroscopy (EDS) analysis of specimen S3. The average hardness of the S3 specimen was determined to be 220.8 HV, which shows an increase of 38.36% compared to the S1 (base metal). x-ray diffraction (XRD) results indicate the additional cementite peaks (Fe3C) and ferrite-confirming phase transformations for carburized samples. The wear analysis of S2 and S3 was conducted through pin-on-disk testing. The peak COF of 0.73 and 0.64 was observed for S2 and S3 respectively. The hard surface of S3 resists the penetration of the counter body to a greater extent due to the fine morphology of pearlite. From the FEM study, the maximum value of 7.96 × 10 3 (V/m) was determined at the center region for the electric field distribution in the microwave cavity, which is the optimum value for efficient heating. The maximum temperature of the mild steel obtained during the carburization process was 900 °C in 1800 s. The microwave carburizing process requires relatively less time than the conventional carburizing process which will save energy consumption.

Al Alloy Melting Behavior and Interfacial Reactions with Steel Under Natural Convection.

The Al alloy melting behavior and interfacial reactions during the steelmaking process of high-Al automotive steel were investigated in this study. The total dissolution time of Al bars (20 × 20 × 80 mm) in molten steel was quite short, decreasing from 21.4 s to 10.0 s with an increase in bath temperature from 1580 to 1620 °C. The Al alloy melting process at the molten steel temperature of 1600 °C included the formation of a solidified steel layer, the latter's rapid melting, and Al alloy normal melting, while at 1600 °C, the process included a second increase in the thickness of the solidified layer. Because steel elements such as [Fe], [C], [O], and [N] could diffuse during the whole Al alloy melting process, an Fe (Al)-FeAl-FeAl2-Fe2Al5-Al diffusion layer along the direction of the Al-rich matrix could be found at the Fe-Al interface. Moreover, FexO, Al2O3, and unstable AlN inclusions could be observed in the FeAl layer. This study also investigated how to reduce the number of these easily formed inclusions. Decreasing the pre-heating process time and dissolved oxygen content could be useful in decreasing FexO and Al2O3 inclusion formation. Some small-sized AlN inclusions formed in the center of the Al bars where they could not come into contact with the molten steel directly during the melting process; even for the immersion time of only 1 second, these inclusions were not stable in molten steel at the refining temperature and disappeared during the melting process.

Reduced spheroidization in rail flash-butt welding by selective alloying

Thermal cycle (welding simulations) at the inter-critical region were performed on an Si and V micro-alloyed (not heat-treated) rail steel. The beginning of austenitization temperature (Ac1) in the micro-alloyed rail steel occurred significantly above that observed in an alternative heat-treated rail steel. Very little pearlite alteration was observed until austenitization at a temperatures above 750°C, where there was a reduction in hardness and onset of spheroidization. The maximum spheroidization together with the lowest observed hardness occurred at 760°C. It was also observed that there is a linear correlation between hardness and volume fraction of spheroidization of cementite. By the dilatometric variation, contraction due to austenitization was observed only from 760°C onwards in the 60 s isothermal period at the austenitization temperature. These results may lead to a new approach to weldability and reduction of the softened region concerning rail welding.

Impact of CO2 as an oxidant on the decarburization and chromium retention and an approach for CO2 recycling

This study explores the unique role of CO2 as an oxidant in stainless steel smelting, focusing on its effectiveness in decarbonization and chromium retention. The research begins by theoretically demonstrating that although the introduction of CO2 increases the CO partial pressure in the reaction system, the decarburization and chromium (Cr) retention capabilities of CO2 can still be stably maintained through the rational adjustment of the molten steel composition, temperature, and inert gas proportions. Further experimental findings indicate that chromium does not exhibit significant oxidation losses when the carbon (C) content exceeds 1.0% (mass). Finally, a novel CO2 recovery and utilization approach is proposed, integrating CO2 capture from smelting flue gas and recycling it for smelting, reducing O2 consumption and energy costs. This innovative process, compatible with existing smelting plants, presents a promising pathway towards carbon neutrality in the iron and steel industry, bridging theoretical insights with practical applications.

Effect of Initial Intergranular Ferrite Size on Induction Hardening Microstructure of Microalloyed Steel 38MnVS6

In this study, we investigated the effect of grain size of an initial microstructure (pearlite + ferrite) on a resulting microstructure of induction-hardened microalloyed steel 38MnVS6, which is one topical medium carbon vanadium microalloyed non-quenched and tempered steel used in manufacturing crankshafts for high-power engines. The results show that a coarse initial microstructure could contribute to the incomplete transformation of pearlite + ferrite into austenite in reaustenitization transformation by rapid heating, and the undissolved ferrite remains and locates between the neighboring prior austenite grains after the induction-hardening process. As the coarseness level of the initial microstructure increases from 102 μm to 156 μm, the morphology of undissolved ferrite varies as granule, film, semi-network, and network, in sequence. The undissolved ferrite structures have a thickness of 250–500 nm and appear dark under an optical metallographic view field. To achieve better engineering applications, it is not recommended to eliminate the undissolved ferrite by increasing much heating time for samples with coarser initial microstructures. It is better to achieve a fine original microstructure before the induction-hardening process. For example, microalloying addition of vanadium and titanium plays a role of metallurgical grain refinement via intragranular ferrite nucleation on more sites, and the heating temperature and time of the forging process should be strictly controlled to ensure the existence of fine prior austenite grains before subsequent isothermal phase transformation to pearlite + ferrite.

Analysis of Thermophysical Properties of Electro Slag Remelting and Evaluation of Metallographic Cleanliness of Steel.

Improving the competitiveness of steel companies is linked to sustainable, quality-compliant steel production. Therefore, new steel production technologies contributing to increased cleanliness of steel are continuously being developed and optimized. One way to achieve a high steel quality is to use electro slag remelting (ESR) technology. In this paper, the principle of ESR technology and the importance of fused slags for optimizing the process are outlined. The aim of this work was to analyze the main thermophysical properties of steel and fused slags used in the ESR process. Determination of the properties of steel and slags was performed using the FactSage calculation software, which involved the calculation of the liquid and solid temperature of steel and slags, the calculation and construction of quaternary diagrams, and the calculation of viscosity. The resulting quaternary diagrams revealed the substantial influence of chemical composition on melting temperatures of slags. In order to validate the acquired results, a CrNiMoV-type steel was subjected to investigation of its metallographic cleanliness and evaluation of its mechanical properties; the ESR process was shown to significantly improve the cleanliness of the steel and improve the mechanical properties of the steel compared to its cleanliness and quality when produced via vacuum degassing (VD) technology. During the ESR process, the average size of non-metallic inclusions was reduced from 20 μm to 10 μm, and the maximum size of non-metallic inclusions was reduced from 50 μm to 28 μm. The mechanical properties of the steel produced using ESR technology were impacted as follows: the ductility increased by 10%, contraction increased by 18%, notched toughness at 20 °C increased by 46%, and at -40 °C (respectively -50 °C) it increased by 30%.

Classified dataset, regression and machine learning modeling for prediction of phase transformation temperatures in steels

The prediction of the characteristic Martensite Start (Ms) temperature and Austenitic Nose Tip Temperature (ANTT) in steels is of scientific and technological importance; however, it faces significant challenges due to multiphysical complexity.In this study, we introduced a structured framework for data classification and hierarchical iterations aimed at predicting Ms (Martensite start temperature) and ANTT (Austenite non-transforming temperature). This framework was incorporated into two optimization models, leading to enhancements in accuracy, extrapolation capabilities, and generalization performance. First, we classified the collected Ms datasets hierarchically based on the alloying elements presented in steels, including carbon, austenite stabilizers, non-austenitization elements, and data credibility. Regression analyses of Ms temperatures concerning chemical compositions were then carried out using phenomenological variables from binary systems to multi-component systems in alignment with the spirit of CALPHAD modeling, which is renowned for its robust extrapolation abilities. By iteratively fitting the hierarchically classified datasets and implementing hierarchical iterations, we developed the CALPHAD-guided phenomenological variable (CGPV) Ms regression model. This model achieved improved accuracy levels, with R2 values of 0.9 for training and 0.87 for testing, surpassing most conventional regression models that do not account for compositional interactions. Furthermore, the CALPHAD-guided machine learning (CGML) model, constructed based on the classified datasets and hierarchical iterations but without utilizing phenomenological variables, demonstrated strong performance with R2 values of 0.98 and 0.86 for training and testing, respectively. The CGML model was demonstrated not only to reliably filter out problematic data in a dataset but also to unveil the unnoticed coupling between carbon and other alloying elements on Ms. Finally, the CGML method has been readily transferred to predict ANTT with high accuracy as well.

Rapid Identification of Liquid Steel Temperature in Tundish Based on Blackbody Cavity Sensor

Rapid Identification of Liquid Steel Temperature in Tundish Based on Blackbody Cavity Sensor

A versatile steel belt casting equipment for in situ synchrotron radiation x-ray scattering measurement of polymer films.

A steel belt casting equipment, weighing approximately ∼6-7 tons and measuring ∼5m in length, has been designed and developed for simulating the industrial processing of polymer films and being combined with synchrotron radiation in situ x-ray scattering measurements. Through modification of its modules, it is feasible to implement two distinct film casting modes, namely the wet and the dry casting processes. The speed of a steel belt can span from 0.5 to 8 m/min. The highest experimental temperature and drying wind speed are 300 °C and 6m/s, respectively. All film casting parameters, such as extrusion speed, distance between die and steel belt, casting speed, temperature, and wind speed, can be adjusted independently. Especially, the control accuracy of the temperature and casting rate can reach ±0.1 °C and ±0.01 m/min, respectively. The feasibility of this equipment has been validated through in situ x-ray scattering tests at the BL10U1 industrial beamline of the Shanghai synchrotron radiation facility. With the assistance of this equipment, the understanding of the physical mechanism behind the film casting process should be improved so that the development of advanced functional polymer films.

Effects of carbon content and heat treatment on wear-resistance and impact properties of novel cast steels with bainitic and martensitic structure

Abstract The traditional material for caterpillar boards is mainly Hadfield steel. The wear resistance of the Hadfield steel cannot be fully exerted due to insufficient work hardening during the operation of the caterpillar board. The effects of carbon content and heat treatment on the wear-resistant and impact properties of a novel caterpillar board cast steels with bainitic and martensitic structures have been investigated. The microstructural observation of worn surface topography was performed by scanning an electronic microscope, and the impact toughness was carried out by an impact tester, in a bid to improve the wear-resistant properties and its impact toughness. The results demonstrate that the hardness and wear-resistant properties of cast steels increase with the increase of carbon content, whereas the impact properties reduce because the brittle phases, such as the carbide precipitation and the martensite, are more. The heat treatment temperature of steels can change the relative ratio of bainitic and martensitic structures, thus affecting the wear-resistant properties of the steels. By controlling the carbon content and heat treatment processing of the steels, the optimal combination of toughness and wear-resistant properties can be achieved. The wear mechanism of dual-phase cast steel was analyzed through wear resistance tests, and it also shows that dual-phase cast steel with bainitic and martensitic structures had better wear-resistance properties compared to the Hadfield steel at low-impact wear conditions.

Post-fire structural material behaviour of high- and ultra-high-strength steels – Experimental study and aids for assessment for further use and potential reuse after fires

A thorough understanding and realistic modelling of the essential post-fire material behaviour is crucial for a safe assessment of the residual structural performance of steel components and the reliable further usage of steel structures after fires. This paper presents a comprehensive experimental study of the constitutive material behaviour after heating-cooling cycles of two quenched and tempered high-strength steels (S690QL, S960QL) as well as two thermomechanically rolled steels (S960M, S1100M). The results are compared to both the behaviour of grade S355J2+N mild steels and a comprehensive database of existing post-fire tests. Except for high- and ultra-high-strength steels, which are exposed to very high temperatures above the A1-phase-transformation-temperature during fires, the assumption of reversibility of the mechanical properties for structural designs of steel structures has been confirmed. At high and very high steel temperatures, the microstructure changes and the strength properties after fire are significantly lower than those of virgin high-strength steel specimens. The study thus provides the basis for reliable structural designs and future normative guidance of the post-fire structural steel designs.

Smith GA-PID feedback control of hot strip final rolling temperature

Abstract At present, the hot strip finishing temperature control system generally adopts a computer model or mechanism model to predict the strip’s final rolling temperature, which is open-loop control. To realize the precise control of the final rolling temperature of high-performance steel, this paper introduces the PID feedback control strategy at the end of the finishing zone, to realize the high-precision temperature control of the strip steel. The Smith compensator is used to predict the compensation for the large hysteresis problem of the final rolling temperature, and various intelligent algorithms are used to optimize the three parameters of the PID controller, eliminate the nonlinear problem, and obtain better dynamic performance. After the experiment, it is concluded that the Smith GA-PID optimization control strategy system has a small overshoot, the peak time and regulation time are the shortest, and the dynamic response is the fastest. Compared with the traditional PID control method, the overshoot is reduced by 97.6%, and the required regulation time is reduced by 7.85 s.

The influence of coupling effect between stress and high temperature on the degradation of microstructure and hardness in P91 steel

Interrupted aging and creep tests were performed in the condition of 650 °C/70 MPa for P91 steel. The mechanisms of hardness and microstructure evolution during aging and creep were studied through hardness test, SEM/EBSD and TEM/EDS. By comparing the difference between aging and creep, the coupling effect of temperature and stress in P91 steel was elucidated. Results show that creep stress could accelerate the entire degradation process in P91 steel. Firstly, the dislocation density increased rapidly at the beginning of creep, and then decreased also at a high rate after reaching its peak value. On the other hand, the dislocation density decreased slowly in aging condition. Additionally, with the migration of grain boundaries under creep stress, some intergranular M23C6 entered inside grains and afterwards dissolved into matrix. On the other hand, other M23C6 which remained intergranular continuously ripened and congregated with time, and finally turned into large ones at triple junctions of grain boundaries. Furthermore, stress had the greatest impact on dislocation density, whereas temperature affected volume fraction of M23C6 the most. In creep condition, the degradation of mechanical properties of P91 steel was mainly caused by the reduction of dislocation strengthening which was followed by grain boundary strengthening.

Two-stage rolling and partial annealing enables heterogeneous structure and strength-ductility enhancement for austenitic stainless steel

Austenitic stainless steels are widely used in civil and defense industries. However, its low yield strength severely limits its fields of application. Under conventional processing routes, uniform grain refinement improves strength but unfortunately sacrifices ductility. In order to achieve the balance of strength and ductility, a new processing route of cold rolling and cryogenic rolling combined with partial annealing was proposed in this work. The results showed that the two-stage rolling and annealing produced dual-phase heterogeneous microstructure containing micron-sized grains (>1 μm), submicron-sized grains (500–1000 nm), and ultra-fine grains (100–500 nm) arranged in lamellar structures. Compared with the single-stage cold rolled and annealed steel, the tensile strength increased to 1.1 GPa, which was slightly higher than the single-stage cryogenic rolled and annealed steel. Furthermore, the elongation was improved to 25 %. The improvement of tensile properties was mainly due to the contribution of persistent hetero-deformation induced (HDI) hardening and twining induced plasticity (TWIP) effect to work hardening. This study not only proposed a simple and effective way to improve the mechanical properties of austenitic stainless steels, but also provided guidance for the design and development of high performance heterostructured materials.

Coupled CFD-FEM modeling of fluid–thermal–structural interaction in a single-strand tundish

A mathematical model has been developed to study the fluid–thermal–structural interaction in a single-strand tundish based on a coupled computational fluid dynamics (CFD) and finite element method (FEM) approach. The flow pattern and temperature distribution of the molten steel were predicted by the CFD calculation. Heat transfer and thermal stress profiles in the solid layers were investigated by the FEM analysis. Case studies were carried out comparatively to investigate the effect of tundish preheating and thermal insulation. The results show that tundish preheating can maintain the desired temperature of the molten steel at the exit. The heating efficiency drops significantly after 3 h of preheating. Reducing the thermal conductivity of the insulation material will reduce the temperature of the tundish shell and increase the thermal stress on the working lining. The modeling results can be used to improve the reliability and lifetime of the tundish and reduce production costs.