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The amount of martensite in austenitic stainless steels produced during plastic deformation at low temperatures is related to the reduction in hydrogen embrittlement resistance. A pre-strain at 4 K was employed in this work to produce strain-induced martensite (SIM) in the microstructure of SUS316L and its weldment to verify the changes in hydrogen embrittlement susceptibility through slow strain tensile (SSRT) tests in a high-pressure hydrogen environment. As the base metal specimens, the weld metal specimens, manufactured by gas tungsten arc welding (GTAW or TIG) were pre-strained at different levels (5%, 10%, and 15%) for comparison with the non-pre-strained condition. Analysis of the most degraded samples tested from -150 °C to 0 °C is conducted through fracture surface observations, lateral crack length measurement, and crack densities. It was possible to indicate that the pre-strain effect induced earlier crack nucleation in comparison to the situation observed in the non-pre-strained material. Moreover, the pre-existing martensite produced by the pre-strain at 4 K is responsible for earlier crack nucleation, leading to a loss in the hydrogen embrittlement resistance for the SSRT pre-strained base metal specimens.

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.

This paper reviews studies on the prediction of ductile fracture during metal forming using an ellipsoidal void model and some other models proposed by the author and some relevant studies. Section 2 discusses the research on the theory of voids for predicting ductile fracture during metal forming. Section 3 summarizes the simulation method for predicting ductile fracture during metal forming using the ellipsoidal void model, and Section 4 summarizes the simulation result on the ductile fracture prediction during metal forming using the ellipsoidal void model. Section 5 shows the applicability of the ellipsoidal void model and the simulation result on the ductile fracture prediction during metal forming using some other models.

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.

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.

Friction stir welding (FSW) is expected to be applied as a welding technique of materials with relatively high melting temperature such as steel materials. Silicon nitride is one of the inexpensive and attractive tool materials for FSW of the thick steel plate. Therefore, in this study, the capability of the silicon nitride tool without groove scroll to weld a low carbon steel plate with a thickness of 15 mm was investigated. The suitability of a tool shape was confirmed by FSW of a thick A5052 plate using a SKD61 tool with same shape as the silicon nitride tool. The defect-free welded specimen of the thick steel plate was obtained using the silicon nitride tool under the optimum welding condition. The silicon nitride tool could be used for FSW of the 15 mm thick steel plate until the welding length of 200 mm without breaking the tool. The groove defect area in the stir zone of the thick steel plate was decreased with decreasing of the tool rotation speed and tool tilt angle. Especially, the tool tilt angle was effective to increase the heat input and the material flow velocity. It is considered that the defect-free weld specimen of the thick steel plate was obtained to sufficient material supply to the RS of the stir zone by decreasing tool tilt angle to 1°.

This study examines the effect of container size on coal briquette’s internal structure using the Discrete Element Method. It found that when the frictional resistance between particle and wall was large and the inner diameter small, the difference in particle filling ratio between the upper and lower parts of the briquette was significant. Conversely, with a larger inner diameter, this difference nearly disappeared. The distribution of contact force indicated that the frictional force’s inhibiting effect on force transmission lessened with a larger container’s inner diameter. The study also revealed that the height of the container affects the briquette’s internal structure, and these results can be summarized by the container’s height to diameter ratio. Essentially, a larger ratio led to a linear increase in the difference in filling ratio between the upper and lower parts of the briquette.

In the gas wiping process used in hot-dip galvanizing, the coating thickness has two thinning limits. The first is the limit due to splashing of the liquid film of molten zinc, and the second is the thinning limit of the wiping capacity of the equipment.

In this study, we investigated the possibility that wiping efficiency is reduced by the effect of zinc solidification due to gas jet cooling by conducting a gas wiping experiment under various temperature conditions.

A galvanized steel strip with a width of 100 mm was immersed in a molten zinc bath in the air atmosphere. The steel strip was heated by induction heating or a gas burner, and the wiping gas was also heated.

The results clarified the fact that high temperature conditions improved gas wiping efficiency. It is suggested that high wiping efficiency is prevented by an increase in viscosity due to an increasing solid volume fraction in the liquid zinc film surface caused by microscopic solidification. In addition, it was also found that the development of the initial alloy layer reduced the amount of liquid phase, which inhibits wiping.

Thermal mixing during the gas stirring operation and arc heating in a steel ladle is analyzed through the modern tools of a physical model using PIV (Particle Image Velocimetry) and thermal PLIF (Planar Laser Induced Fluorescence), whose velocity and temperature fields were used to fine-tune and validate a multiphase Eulerian two-phase mathematical model. Agreement on both fluid dynamics and thermal evolution is reasonably good between experiments and the predictions obtained by the mathematical model of the physical model. The analysis coming from the numerical model validated by the physical model measurements included the thermal mixing and energy efficiency of single nozzle injection in centric and eccentric (4/5R) gas injection. It turned out that energy efficiency in the centric gas injection is 20% more efficient than in eccentric injection. Then, under the same heat flux provided, the maximum temperature of the water in the centric gas injection would be higher than the maximum temperature reached in the eccentric mode with the same gas flow rate. Good heat transfer happens when the heat source impinges in a fluid region with high circulation and turbulent dispersion.

Air-quenched electric arc furnace slag (AEAFS) is a black sphere or spheroid particle prepared by an air quenching theology using electric arc furnace steelmaking slag as raw materials, possessing the characteristics of small particle size, moderate density and high hardness Combined with the tight supply and demand of the existing abrasive market and the continuous increase in price, AEAFS is tried to be used as a free abrasive for sandblasting processing according to its physical characteristics. In order to make sure that the AEAFS meets the requirement of free abrasive blasting, it is necessary to conduct a comprehensive and in-depth analysis of its physical and chemical properties. The research shows that the AEAFS is a spherical particle with weak magnetism and particle size being mainly 2.8 mm (accounting for more than 90%). Its Vickers hardness is in the range of 600–1000 HV; its compressive strength is between 20 and 465 N and increases first and then decreases with particle size. The water content is more than 0.019%, except that the particle size is less than 0.5 mm. All the others meet the requirements of ISO-11126-6: 2018 standard. The content of f-CaO is between 1.122% and 1.612% increasing with the particle size, AEAFS has good chemical stability and weak acid resistance. In summary, AEAFS meets the performance requirements of the medium used in the sandblasting process and is a potential alternative product for sandblasting abrasives.