To meet the increasing demand for low-impurity steel products, powder top blowing has been applied to the steelmaking process. Powder reagents penetrating deeper into the molten metal lead to longer resident time and higher efficiency of refining. Many studies have been performed on the basis of cold model experiments with a single liquid phase for clarifying the penetration behavior of the particle. However, the effects of the second liquid phase have been reported little whereas molten slag often exists on the surface of molten metal in the steelmaking process.

In the present work, the sphere was penetrated into the fluids consisting of a silicone oil layer and water bath. The time variation of the penetration depth of the sphere was measured with a high-speed camera. Effects of the type and size of the sphere, entry velocity, and oil depth were estimated. As a result, the stagnation of penetration occurred under the condition of no air column behind the sphere. On the other hand, a thin oil layer led to no stagnation and deeper penetration due to promoting the formation of air or oil columns. However, an oil layer thicker than 2 mm suppressed the penetration by decreasing the kinetic energy under the condition of high viscosity. The same penetration behavior was observed with a smaller sphere. However, the behavior was more sensitive to the effect of buoyant force because the size of the residual bubble on the surface of the sphere became relatively bigger than the sphere.

The influences of SO₂ in the recirculation flue gas on the sintering process are studied through simulating the flue gas recirculation with sinter pot test at room temperature. The results show that, with the increasing concentration of SO₂, the SO₂ is absorbed by CaO, the surface of CaO particles will generate CaSO₄ which affects the formation of binding phase, so the sinter yield and particle size will decrease. The residual sulfur in sinter ore will increase obviously when SO₂ concentration is higher than 500 ppm, the residual sulfur of middle sinter ore in 2000 ppm is 1.54 times higher than that in 500 ppm. Meanwhile, the SO₂ peak concentration in flue gas is enriched, which is conductive for the end-of-pipe treatment of SO₂. The RI of sinter ore is increased and softening and melting properties become better, because the consumption of CaO affects the formation of calcium ferrite and increases the reduction rate and melting point of sinter ore, another reason is that the decomposition of CaSO₄ leads to an increase in the porosity in the sinter, and the higher porosity makes the sinter expose more surface area to the reduced body, and the RI of the sinter increase. Therefore, adding an appropriate amount of SO₂ in the sintering process can improve the quality of the sinter, and if the SO₂ content is too high, it will affect the formation of the binder phase and reduce the strength and yield of the sinter.

The ironmaking process mostly consisting of coke plant, sintering plant and blast furnace accounts for about 80% of total CO₂ emission from steel plants. Out of the total emission by steelmaking companies, the blast furnace is responsible for more than half (55%), followed by sintering plant (12%) and coke plant (10%). The current study aims to apply a developed laboratory-scale technology to sintering test equipment (STE); a low-carbon sintering process. The technology also encompasses the recycling of by-products added to the sinter mix as calcium ferrites. Several morphological changes in views of pore size and phase constitution were made in the sinter containing calcium ferrite compared with the standard sinter. 1 kg STE was employed to check the viability of such technology. The comparison between standard and low-carbon sinters was made in views of sinter strength (tumbler index) and reducibility. The expected reduction in CO₂ emissions follows the reduction of 33% in the coke ratio. Two different methods were performed: the first one by adding calcium ferrite without considering the basicity level, and the second one by maintaining the basicity constant, while decreasing the limestone content. In both cases, the sinter strength and reducibility were maintained at the same level as the standard sinter or improved. These obtained results showed that it is possible to maintain or improve the quality of raw materials used in ironmaking processes while significantly reducing the requirement for coke.

Hot metal temperature was a direct indicator of blast furnace condition. If the operator predicted its trend in advance, it was conducive to the stable operation of the blast furnace. This study combined expert experience and big data technology to propose an intelligent prediction method for hot metal temperature. Based on metallurgical theory and data governance algorithms, outlier processing, data simplification, data standardization and frequency unification of blast furnace data were completed. The blast furnace feature was processed by multiple feature engineering method, 8 rammed residual blast furnace features were eliminated; 36 features were screened by feature selection technique to form the optimal combination of hot metal temperature prediction; 4 derived parameters were constructed by PCA technique. Applying the filtered combination of feature as input, a GSO-DF model was created, which was satisfactory in predicting the hot metal temperature in the next hour. The MAE and MSE of the GSO-DF model was 3.54 and 27.34, respectively. It achieved a hit rate of 92.86% in the ±10°C range. The average hit-rate of the model can reach more than 91% by updating the model every day to test the data of the coming month. Even if the hot metal temperature fluctuated greatly, it was still able to predict the temperature trend well and provide reliable guidance for the field personnel. The hot metal temperature qualified rate increased by 6.8% during the model application period. It contributed to the improvement of hot metal quality at the site, and achieved satisfactory result.

The laying head temperature (LHT) is the crucial for determining the Stelmor air cooling rate of the high-speed wire rod. However, the high ambient temperature and long distance make it challenging to measure this temperature accurately with the current approach. To address this issue, a new method has been developed that involved placing a pyrometer close to the wire rod in a location with lower ambient temperatures in front of the laying head, resulting in a smaller measuring spot. To improve accuracy, two primary issues have been investigated. Firstly, a relationship between oxidation time and emissivity of the wire rod was established. For example, when the HRB400 (8 mm) wire rod was oxidized at 1000°C for 0.625 s, its emissivity was calculated to be approximately 0.69. Secondly, a correlation was established between directional emissivity and the angle between radiation emitted from the measuring spot of the wire rod and its normal to address rapid fluctuations in measured temperature caused by wire rod vibration. As a result, measured temperature was reconstructed when changes in the angle occurred due to wire rod vibration, resulting in a significant reduction in temperature fluctuations.

For the analytical model of rolling force of ultra-thin strip, the iterative conditions of the exit plastic zone are improved to solve the convergence problem of the Fleck model in small reduction rolling. The nonlinear law of friction coefficient in multi-pass rolling is analyzed, and the friction coefficient database for sample data is established through the friction coefficient calculation model, which is used GWO-KELM neural network training friction coefficient prediction model, the Fleck rolling force prediction model based on the modified friction coefficient is established ultimately. A comparative analysis of prediction errors is conducted on three different specifications of strip steel using actual production data from a multifunctional 280 mm 20-high mill. The results show that the best performing MSE, RMSE, MAE, MAPE and R2, with values of 170.48, 13.06 kN, 9.01 kN, 3.30%, and 0.989, respectively. The accuracy of the modified rolling force prediction model is significantly improved, and the data scale of friction coefficient database can be continuously expanded, so the accuracy of the rolling force prediction model can be continuously improved.

The laser welding of 22MnB5 unequal-thickness thin sheets often presents challenges such as incomplete fusion, excessive weld pool width affecting mechanical properties, weld sagging, and splashing. These issues stem from the unique characteristics of laser welding, including deep melting depth, small heat affected zone, and fast welding speed. To address this, ABAQUS software was employed to simulate the welding process of two different thickness of steel sheets under different welding conditions. Using the Box-Behnken Design (BBD) experimental method, welding parameters were optimized, and a response surface model for residual stress and deformation post-welding was established. The effects of laser power, welding speed and beam offset on post-welding deformation and residual stress were studied. In this paper, the residual stress and welding deformation of the weldment after welding are systematically analyzed. Finite element analysis shows that when using optimized welding process parameters for welding, the stress distribution of the welded model is relatively uniform, with a maximum stress value of 547 MPa. The high stress smoothly transitions to the low stress, and deformation occurs at the starting and ending positions of the welding. Experimental results demonstrated that under the optimized parameters, by characterizing the grain structure after laser welding using EBSD, the weld metal exhibits significant fine grain structure and random grain orientation distribution, indicating rapid solidification and crystal growth. In contrast, the grains in the heat affected zone (HAZ) are larger and have a more ordered orientation. The KAM diagram reveals that the strain in the weld metal is higher, the grain interface has a higher dislocation density, and the HAZ dislocation density is lower. EBSD data shows that the grain size of welded joints varies greatly, with an average size of 3.00 µm. There are numerous low angle grain boundaries, joint appearance was enhanced, with no weld sag, bubbles, or splashes. In addition, the yield strength and tensile strength of welded sheet, whether pre-quenching or post-quenching, exhibit good mechanical properties of the welded parts, play an important role in the light-weight work of the automobile.

It is well known that Ni-advanced weathering steels considerably improve the protectiveness of rust layers and drastically reduce corrosion rate compared with the conventional weathering steels. However, unpainted Ni-advanced weathering steels are not suitable for use in high-chloride environments because of no formation of protective rust layers. To expand the application of Ni-advanced weathering steels, it is imperative to understand in detail their corrosion behavior in high-chloride environments. In this study, the effect of Ni addition on the atmospheric corrosion behavior of carbon steels was explored through a wet-dry cyclic corrosion test and potentiodynamic polarization measurements in a simulated high-chloride environment. In particular, the study focused on corrosion morphology and analyzed the distribution of corrosion depth after the corrosion test. During the corrosion test, the protective rust layers did not seem to form on all the specimens due to the high-chloride condition. Nevertheless, the corrosion rates decreased with increasing Ni addition to steels. Corrosion morphology analysis revealed that the Ni addition suppressed relatively uniform corrosions on the entire surface and the growth of deep hole-like corrosions. Anodic polarization curves showed that the Ni addition suppressed the dissolution of the steel matrix, which led to the atmospheric corrosion properties of 2.5Ni-WS and 5Ni-WS in inhibiting relatively uniform corrosion and the growth of deep hole-like corrosions. The change in the electrochemical properties of the steel matrix due to the Ni addition significantly affects the atmospheric corrosion behavior of carbon steels in high-chloride environments.

Hydrogen embrittlement (HE) susceptibility was evaluated on JIS–SUP12-based steel (SB), and V-, Nb- and (Nb+Mo)-added steels (SV, SNb and SNbMo, respectively) under uniaxial tension and high stress triaxiality conditions, to elucidate the roles of the microalloying elements in the HE mechanisms of 2 GPa-grade medium-carbon Si–Cr spring steels, which were obtained via low-temperature tempering. The SV steel contained solute V and undissolved V carbides, the SNb steel undissolved Nb carbides and the SNbMo steel solute Mo and undissolved Nb carbides. The microalloying of V, Nb and Mo decreased the apparent hydrogen diffusivity owing to strong hydrogen attraction by solute V and Mo, and reversible hydrogen trapping with V and Nb carbides. Although all the steels attained the 2 GPa tensile strength in hydrogen-uncharged state, hydrogen significantly reduced the tensile strength through premature failure before the onset of yielding under uniaxial tension condition. In the hydrogen-charged specimens, the strength was strongly correlated with the shear fracture surface area. The HE susceptibility was increased in the following order: SNbMo ≈ SNb < SB < SV. This suggests that hydrogen-induced plasticity mitigates the HE susceptibility in the SNb and SNbMo steels, whereas the solute V facilitates the hydrogen-induced plastic inhomogeneity, which leads to premature fracture. Under high stress triaxiality condition in micro-cantilever specimens, hydrogen decreased the intrinsic fracture resistance to one third compared to the uncharged specimens, regardless of the steels. In the microalloyed specimens, hydrogen suppressed intergranular fracture, whereas the dependence of fracture resistance on the microalloying element was minor.

This study investigated the fundamental aspects of signal enhancement in arc-plasma-assisted laser-induced breakdown spectroscopy (AP-LIBS), as a crucial step towards its potential application for enhanced real-time compositional analysis in electric arc furnaces (EAF). By superimposing a sustained arc discharge with nanosecond laser pulses on molten iron, AP-LIBS achieved significant signal enhancement compared with conventional LIBS. Spatiotemporal characterizations revealed that the enhancement was most pronounced in the peripheral plasma region, characterized by larger plasma size and longer lifetime in AP-LIBS setups. The enhancement factor η, defined as the ratio of AP-LIBS signal intensity to the sum of individual arc and laser-induced plasma intensities, exceeds 10 for most emission species. Spatial distribution analyses show increased emission intensities at greater distances from the laser spot in AP-LIBS, in contrast to the decay observed in standard LIBS. Temporal analysis demonstrated extended high-intensity periods for AP-LIBS compared to the rapid decay in conventional LIBS techniques. The spatiotemporal behavior of the enhancement factor varies significantly among the emission species, thereby providing insights into complex plasma dynamics. Elements with low vapor pressure and ionic species generally exhibited higher enhancement, whereas elements with high vapor pressure exhibited limited enhancement, indicating minimal additional evaporation effects for high vapor pressure element. These findings provide valuable insights into plasma generation and maintenance mechanisms in AP-LIBS, suggesting its potential for improved sensitivity in elemental analysis for electric arc furnace applications.