Current coke quality evaluation relies predominantly on the Nippon Steel Corporation test method. However, its simplified experimental conditions cannot fully reproduce the complex environment of the blast furnace (BF), thereby limiting the reliability of coke quality assessment. In this paper, two metallurgical cokes (Coke A (CA) and Coke B (CB)) with different blending ratios were selected for comparison, of which CA had a higher proportion of high-quality coking coal. The effects of annealing temperatures and pressure on the degradation behaviour and evolution of pore structure, crystalline structure, and optical texture of cokes were investigated using a self-developed Si–Mo furnace, optical microscopy, and X-ray diffraction. The results indicate that coke degradation exhibits various characteristics in different BF zones. In the lump zone (1000 °C–1100 °C), coke undergoes limited weight loss and particle-size reduction while maintaining relatively low gasification reactivity. The cohesive zone (1200 °C–1300 °C) represents a critical transition stage for coke degradation, during which gasification rate accelerates markedly. In the dripping zone (>1300 °C), coke degradation continues to intensify. Furthermore, the inherent structural differences between the two cokes lead to distinct degradation behaviours. Compared with CB, CA has a lower porosity, smaller equivalent pore diameter, and a higher proportion of high-order anisotropic optical textures. These features are expected to restrict CO 2 diffusion and reduce the effective carbon–CO 2 reaction area, thereby limiting carbon consumption. Additionally, at 1600 °C, cokes exhibit greater weight loss and particle-size degradation under the pressurised condition than under the corresponding non-pressurised condition. Based on these findings, it is proposed to consider preferentially distributing CB near the furnace walls and to concentrate CA in the central region to balance gas permeability and supporting capacity of the burden. The study provides valuable insights for evaluating coke quality and optimising coke utilisation in low-carbon ironmaking.
34CrNiMo6 steel is widely used in heavy-duty transmission components, and improving its bloom surface quality is important for increasing product yield and reducing downstream processing costs. To address transverse corner cracking during continuous casting, mould flux evaluation, optimisation and industrial validation were conducted based on the steel's solidification characteristics, thermophysical properties and casting conditions. Calculations indicated a relatively low risk of peritectic transformation shrinkage, but low thermal conductivity increased corner shell sensitivity to non-uniform cooling and heat-flux fluctuations, demanding continuous liquid slag film lubrication and stable interfacial heat transfer. The existing Flux A exhibited a long melting time and high viscosity, break temperature and crystallisation temperature, resulting in a thin liquid slag layer and a shortened effective lubrication range that contributed to frequent cracking. Following the concept of ‘stable lubrication and controlled heat transfer’, Flux B was developed by reducing basicity, Al 2 O 3 and carbon contents, increasing Na 2 O content and introducing a small amount of Li 2 O. Optimisation reduced the melting temperature from 1185 °C to 1081 °C and the viscosity measured at 1300 °C from 0.59 to 0.36 Pa·s. Shorter melting time and lower break and crystallisation temperatures indicated improved melting and rheological properties and controlled high-temperature crystallisation. A parallel two-strand comparative trial over two consecutive heats showed that replacing Flux A with Flux B increased the liquid slag layer thickness from approximately 5 to 9 mm and mould flux consumption from 0.35 to 0.68 kg·t −1 . The number of transverse corner crack indications detected by magnetic particle inspection in the sampled blooms decreased from 20 to 3, representing a reduction of approximately 85%. These results demonstrate that mould flux optimisation based on steel solidification characteristics and thermophysical properties provides an effective approach to improving the bloom surface quality of Cr–Ni–Mo quenched-and-tempered steels.
The mould fluxes with appropriate viscosity and crystallisation are crucial materials in the continuous casting for rare earth alloyed steel. In this study, a novel mould fluxes, (36-0.5 x )CaO-(36-0.5 x )Al 2 O 3 -8SiO 2 - x CeO 2 -5Li 2 O-5B 2 O 3 -10BaO (CASCLBB), was proposed. The effect of CeO 2 content on viscosity, structure and crystallisation were systematically investigated. The viscosity value at 1400 °C was first increased from 0.62 Pa·s to 0.71 Pa·s with an increased CeO 2 content from 0 wt.% to 4 wt.%. This was because the oxidation state of Ce ions shifted from Ce 4+ to Ce 3+ when CeO 2 content was increased, accompanied by enhanced precipitation of crystalline phases such as Ca 2 Al 2 SiO 7 , BaAl 2 O 4 , and BaCeO 3 . The appearance of these crystalline phases induced phase separation, which became dominant from 0 wt.% to 4 wt.% CeO 2 and consequently increased viscosity. However, the viscosity value decreased to 0.51 Pa·s when CeO 2 content further increased 12 wt.%, which was attributed to decreased fractions of Q 2 , Q 3 , BO, [BO 3 ] and [AlO 4 ] units. The increasing structural depolymerisation may have become dominant, resulting in a more depolymerised melt network and consequently reduced viscosity. Additionally, the mechanism of viscosity variation with temperature for a sample containing 8 wt.% CeO 2 was discussed.
Slab camber is a critical shape-defect problem in hot strip rough rolling and directly affects slab centring, side-guide interaction and subsequent rolling stability. Excessive slab camber is especially problematic during transient threading stages, particularly at the head end, where asymmetric rolling conditions are more pronounced. To address this problem, this article proposes a physics-guided analysis and fast control method based on asymmetric deformation modelling. A mathematical model of slab camber motion is established by considering the combined effects of incoming wedge, initial curvature, centre offset, and stiffness difference. Based on this model, the influences of different asymmetric factors on exit wedge evolution and transient lateral motion are quantitatively analysed in an interpretable manner. Accordingly, an auto-tuning method for fast model predictive control (F-MPC) with an adaptive time horizon is proposed to dynamically suppress slab camber. The optimal time-horizon combination is obtained by particle swarm optimisation (PSO) for offline optimisation, and the online computational burden is reduced by an interior-point method with warm-start initialisation to satisfy control-cycle requirements. Simulations and mill trials show that the F-MPC controller effectively reduces slab camber at the roughing-mill exit and is suitable for industrial online implementation.
Formation of carbon deposits during coal carbonisation is a persistent problem in coke ovens. The nature of carbon deposits depends on the type of oven and how the deposits are formed under the operating conditions of the oven. The situation is even more complicated in the Indian scenario considering the higher content of mineral matter in coal. A comparative study on the characteristics of carbon deposits originating from different ovens is essential to develop an efficient solution for their removal. In the present study, a deposit from the base of stamp charged coke oven was compared with the goose neck deposit of top charge oven using multiple analytical techniques. Relatively higher graphitisation was observed in the carbon deposit from stamp charge oven as proven by Raman and X-ray diffraction analysis. The same deposit contained higher mineral matter (8.9%), particularly Fe2O3 (8.54%) which could act as the catalyst for the graphitisation process. Higher thermal reactivity was observed in carbon residue from stamp charge oven, which resulted in higher mass loss (37%) compared to top charge oven one (28%). Petrographic and morphological analysis confirmed the abundance of spherulitic carbons in both deposits, however, owing to the increased residence time for the gaseous by-products in the stamp charge oven, the molecular arrangement of carbon structure was highly compact and globular. Solubility tests revealed that the organic solvents were more efficacious in solubilising similar to 20% to 25% of the carbonaceous clinker at ambient temperatures. To summarise, this article characterised and demonstrated the catalytic graphitisation potential of Fe-rich deposits isolated from coke ovens and their attainable downstream application.
