Continuous casting is an industrial process whereby molten metal is solidified into a semi-finished billet, bloom, or slab for subsequent rolling in finishing mills; it is the most frequently used ...process to cast not only steel, but also aluminium and copper alloys. Since its widespread introduction for steel in the 1950s, it has evolved to achieve improved yield, quality, productivity and cost efficiency. It allows lower-cost production of metal sections with better quality, due to the inherently lower costs of continuous, standardized production of a product, as well as providing increased control over the process through automation. Nevertheless, challenges remain and new ones appear, as ways are sought to minimize casting defects and to cast alloys that could originally only be cast via other means. This Special Issue of the journal "Metals" consists of 14 research articles that cover many aspects of experimental work and theoretical modelling related to the ongoing development of continuous casting processes.
In this study, Cu-0.8Cr-0.1Zr alloy was prepared by vacuum horizontal continuous casting method. The effect of different thermo-mechanical treatment processes on the properties was studied, and the ...microstructure evolution at different stages of thermo-mechanical treatment were observed by SEM, EBSD and (HR)TEM. The results showed that the optimal comprehensive performance of tensile strength (803 MPa) and conductivity (76% IACS) was obtained by three-stage drawing and thermal treatment (primary 43.75% drawing and solution treatment at 950 °C for 60 min + secondary 97.2% drawing and aging at 500 °C for 30 min + tertiary 75% drawing). Through the microstructure characterization, it was found that the morphology and distribution of the Cr-rich primary phase can be regulated by solution treatment, and inherited during the thermo-mechanical treatment. It acts as a nucleation point and hard point, thereby refining the grain and improving the strength of the alloy. Additionally, it reduces the number of solid solution atoms in the matrix and prevents the loss of conductivity. Furthermore, drawing with a large amount of deformation can produce a nano-lamellar structure with high temperature stability, and drawing after high temperature aging can induce substructure formation. The combination of nano-lamellar structure and substructure further improves the strength.
•The Cu-Cr-Zr alloy was prepared by vacuum horizontal continuous casting.•A high performance of UTS (803 MPa) and conductivity (76% IACS) was obtained.•Cr-rich primary phase has genetic characteristics and can improve the properties.•Large deformation drawing produce nanostructures with high temperature stability.•Substructural strengthening is a reason for strength increase after drawing.
All 61 sticker breakouts and 183 false sticker breakouts were obtained based on the on-line mould monitoring system during the conventional slab continuous casting. The 16-dimensional temperature ...characteristics and temperature velocity characteristics of the sticker breakout were extracted. The sticker breakout recognition based on the XGBoost forward iterative model was developed and optimized by the mean square error algorithm. The results show that the prediction probability of the sticker breakout after optimization is in the range of 0.72–1.00. The smallest output value is 0.5 higher than that before optimization. When the threshold is set to 0.65, the optimized XGBoost model can correctly predict all sticker breakouts and has a 99.5% accuracy rate. The XGBoost model has a stronger generalization ability and higher prediction accuracy, which promotes the intelligent production of continuous casting.
•C70250 plate with columnar grains along casting direction were produced by HCCM continuous casting.•Solid-liquid interface location is a key factor to control precipitate content in columnar ...grains.•Columnar grain plate had better plasticity than equiaxed grain plate due to grain orientation.
C70250 (Cu-2.6 wt%Ni-0.5 wt%Si) alloy plates with straight columnar grains, inclined columnar grains and equiaxed grains were produced by a heating-cooling combined mold (HCCM) horizontal continuous casting, respectively, and the influences of microstructure on the mechanical properties of the alloy were studied. The results showed that, when the casting speed was 30 mm/min, the straight columnar grains along the casting direction formed in the C70250 alloy plate and the precipitate content was relatively high, ～ 10%. When the casting speed was 50 mm/min and 80 mm/min, inclined columnar grains and equiaxed grains formed, respectively, with a low precipitate content of 6%. The high casting speed made the solid-liquid interface at the entrance of the cold mold and the solidified plate was cooled rapidly due to strong cooling effect, which suppressed formation of precipitated phase. The yield strength of the alloy plate with equiaxed grains were 219 MPa and the elongation to failure was 36%. For the plate with inclined columnar grains, its yield strength (76 MPa) were obviously lower than that of the other two plates and the elongation reached 45%. Compared with the equiaxed grain plate, the columnar grain plate had smaller grain orientation difference, better intergranular deformation compatibility and intergranular deformation uniformity, which was mainly responsible for its better plasticity.
This article studies a steelmaking-continuous casting (SCC) scheduling problem by considering ladle allocation. It takes technological rules in steel manufacturing and ladle-related constraints into ...account. A scheduling problem is formulated to determine allocation equipment for jobs, production sequence for jobs processed by the same equipment, and modification operations for empty ladles after their service for jobs. To ensure the fastest production and least energy consumption, we present a mixed integer mathematical programming model with the objectives to minimize the maximum completion time, idle time penalties, and energy consumption penalties related to waiting time. To solve it, we develop a two-stage approach based on a combination of scatter search (SS) and mixed integer programming (MIP). The first stage applies an SS algorithm to determine the assignment and sequence variables for charges. For the obtained solution, we construct a temporal constraint network and establish an MIP model at the second stage. We apply ILOG.CPLEX to solve the model and find the final solution. We analyze and compare the performance of the proposed approach with a hybrid method that combines a genetic algorithm with MIP on instances constructed from a real iron-steel plant. To further verify the effectiveness of the proposed algorithm, we compare its results with optimal solutions of the constraint-relaxed original problem. The experimental results show the effectiveness of the proposed approach in solving the SCC-scheduling problem. Note to Practitioners -This article deals with a scheduling problem arising from a steelmaking-continuous casting process in steel manufacturing. It integrates ladles allocation into the scheduling problem to reduce the energy consumption as much as possible. Such a problem in the existing work is handled, respectively, and its solutions tend to cause much energy waste and some mismatched plans. This article takes complex technological constraints into full account and minimizes the maximum job completion time, idle time of equipment, and waiting time of jobs. It establishes a mixed integer mathematical model and proposes a hybrid algorithm that combines scatter search and mixed integer programming to solve it. The extensive results demonstrate that the proposed approach can effectively solve the studied scheduling problem. The obtained solution gives decision makers some desired reference to determine a right schedule when an actual production process is conducted.
All 61 sticker breakouts and 183 false sticker breakouts were obtained based on the on-line mould monitoring system during the conventional slab continuous casting. The 16-dimensional temperature ...characteristics and temperature velocity characteristics of the sticker breakout were extracted. The sticker breakout recognition based on the XGBoost forward iterative model was developed and optimized by the mean square error algorithm. The results show that the prediction probability of the sticker breakout after optimization is in the range of 0.72∼1.00. The smallest output value 0.5 higher than that before optimization. When the threshold is set to 0.65, the optimized XGBoost model can correctly predict all sticker breakouts and has a 99.5% accuracy rate. The XGBoost model has a stronger generalization ability and higher prediction accuracy, which promotes the intelligent production of continuous casting.
The internal structure of casting billets directly affects the performance of steel products, but in practice, it cannot be detected online. Macro images (low-magnification snapshots of the casting ...billet sample cross sections) can visualize the structure, but obtaining them is lagging and costly. Numerical simulation methods are time-consuming to calculate, and only corrected for a few steel grades, making accuracy difficult to guarantee under other working conditions. Thus, we propose a model based on generative adversarial networks (GANs) to quickly predict the internal structure of billets, which can synthesize macro images from production parameters. However, the macro images are less visually varied and have small and dense features. Conventional GANs struggle to generate macro images of casting billets. Therefore, this model is based on the attentional GAN (AttnGAN) to learn different level features through the supervision of multiresolution images. The generators apply three-branch residual blocks to predict new pixels by multiscale information, which improves the realism of details. Additionally, considering the ordering property of continuous casting (CC), a series model of the deep neural network (DNN) and recurrent neural network (RNN) is designed to encode input parameters. It is combined with image information pretraining to simplify the learning of the mapping relationship in the macro image synthesis model. After comparison with other text-to-image generation models, our model performs better in terms of evaluation metrics and visual effects. The prediction results are verified using two samples from SCM435-M steel. The obtained results have a high consistency with the real data, with the absolute error of the equiaxed crystal rate (ECR) being 0.84% and 0.6%, respectively. Moreover, the inference speed of our model is fast, which is of reference value for the optimization of the CC process.
Cu-Al bimetallic composite plates with a thickness of 2 mm were prepared by a horizontal continuous composite casting-rolling process. The effects of rolling parameters on the forming performance of ...Cu-Al composite plates and the interface evolution mechanisms were investigated. The results reveal that a suitable deformation temperature and an increase in first-pass deformation are both conducive to enhancing bimetallic deformation coordination. For cold rolling, the first-pass reduction should exceed 60 % to avoid delamination cracking. When the rolling temperature rises to 200–300 °C, the first-pass reduction can be decreased to 55 % due to the better deformation coordination of bimetallic. However, an excessive rolling temperature results in the formation of a continuous layer of intermetallic compounds at the new interface, and the formability of the plates is decreased significantly. In the rolling process of Cu-Al composite plates, the original Cu-Al interface is first shattered, and then the matrix metal flows into the gaps of the broken interface. Finally, a new oxidation-free interface at the atomic scale is developed, which is beneficial to the bonding strength of the composite plates. The Cu-Al composite sheets prepared by the above reasonable parameters exhibit a tensile strength of 180–191 MPa, an elongation of 8%–12 %, and an excellent interfacial bonding strength of 66–89 MPa.
The carbonisation of energy structures is a principal reason for the high carbon levels of carbon dioxide (CO2) emissions in the steel industry. The implementation of an energy substitution policy in ...the Chinese steel industry has important practical significance for this industry in terms of reducing CO2 emissions. Based on this, this paper divides 20 types of energy-saving and emission-reduction (ESER) technologies into 4 categories: coal-saving technology, electricity-saving technology, comprehensive energy-saving technology, and linkage technology according to the energy-saving effect of different technology on energy varieties. Considering the energy substitution constraints on energy structures within the steel industry, we construct a bottom-up optimisation model based on a scenario analysis to analyse the emission reductions under 3 different scenarios: the baseline scenario (BAU), policy scenario (PS), and strengthened policy scenario (SPS). Results show that the emission reduction of coal-saving technology and comprehensive energy-saving technology in 2030 is 102 million tons CO2 (MtCO2) and 129 MtCO2, respectively, in the PS, and 116 MtCO2 and 130 MtCO2, respectively, in the SPS. Compared with these types of technology, electricity-saving technology is maintained at the level of the BAU. Linkage technology is developed in the latter period of the SPS. The emission reduction of linkage technology in the SPS in 2030 will be 4.1 MtCO2. During the period of 2015–2020, priority should be given to the development of thin slab continuous casting technology in comprehensive energy-saving technology and the development of blast furnace thick phase high efficiency coal injection technology in coal-saving technology. During the period 2020–2030, priority should be given to the development of thick layer sintering technology, hot delivery & hot charging technology of continuous casting slab, online treatment technology in comprehensive energy-saving technology and low temperature rolling technology, converter ‘negative energy steelmaking’ technology, and double preheating technology for hot stove of blast furnace in coal-saving technology.
Roll‐gap deviation (RGD) is commonly observed in the slab continuous caster, which means the thicknesses of the right and left sides are different. The RGD amounts and positions on the solute ...redistribution are investigated. In the RGD zone, slab thickness decreases from the left to the right side. Dynamic grid technology is used to consider the mesh deformation in the model. When RGD is set before the solidification end of the slab middle part, the center segregation in the right‐edge part decreases but that in the left‐edge part increases. That is because the solute‐enriched liquid moves from the right to the left side with solid compression. When RGD is set after the slab middle part is solidified, the center segregation in the right‐edge part is deteriorated, while that in the left‐edge part is reduced. This is because the slab right‐edge part is fully solidified in the RGD zone, and the segregation cannot be reduced in the later stage. With the RGD position moving from 15.5 to 18.0 m from the meniscus, the center segregation in the right‐edge part decreases first and then increases, while that in the left‐edge part increases slightly and then declines.
When the roll‐gap deviation (RGD) exists before the solidification end of the slab middle part, the center segregation in the right‐edge part decreases, but that in the left‐edge part increases. As RGD is set after the middle part is solidified, the center segregation in the right‐edge part is deteriorated, while that in the left‐edge part is reduced.
