Strip formation and process stability in twin roll strip casting

Process stability in the thin strip casting process of steel has been investigated with a laboratory pilot caster. Depending on the steel grade and the process parameters irregular process states could be observed. It has been proved experimentally that the observed behaviour is not caused by the regulation system. Investigations of microsections on the cast strips have shown evidence of periodical changes in heat flux during solidification and strip formation as the reason for observed oscillating process variables. Similar to conventional flat rolling forward and backward slip between strip and casting rolls during the joining of the shells can occur. Under certain combinations the process parameters and the cast material a backward‐slip can lead to local lift‐offs of the solidified shells. This circumstance significantly disturbs the heat flux and consequently the solidification, even periodically.     

双辊薄带连铸生产不锈钢技术探讨

不锈钢是双辊薄带连铸工艺重点开发的钢种之一.综述了不锈钢的分类和性能特点,简要介绍了不锈钢的几种生产型式,详细讨论了双辊薄带连铸生产不锈钢的技术要点和难点.     

Microstructure of shot-blasting casting roll and effect on strip solidification during strip-casting process

In the strip-casting process,the surface topography of the casting roll has a significant influence on the solidification microstructure and surface quality of the as-cast strip. Shot-blasting treatment is an important way to achieve a suitable surface topography on the casting roll. In this study,a casting roll of beryllium copper alloy was shot blasted using steel pellets in the laboratory,resulting in a randomly distributed discontinuous peak and dent surface topography,in which cold deformation-slip bands and fine-deformation twins were formed. The thickness of the deformed copper alloy was about 100 μm during the shot-blasting process,and the copper hardness value increased significantly within 40 μm of the surface,with a maximum increase of more than 20% compared to the mean substrate hardness value. Within 60-100 μm of the surface,the hardness at the peak position was still higher than the copper substrate mean value,but the hardness at the dents was not,which was mainly due to the copper alloy slip and twinning deformation mechanisms. The surface hardness was similar to that of the substrate after the shot-blasted sample had been subjected to thermal shock. The molten steel first chilled and nucleated at the surface peaks of the casting roll;furthermore,fine dendrites grew and crossed over the middle of the dents. Therefore,the peak intervals of the shot-blasted surface are an important factor in solidification quality control.     

Simple model for thermal calculation in twin-roll strip casting process

The numerical model for the solidification process of metal in the twin-roll type strip caster is presented in this paper. In the model the temperature change as well as the eliminating process of latent heat is calculated along the stream lines obtained by a comparatively simple velocity field. The calculations are carried out on the strip casting of type 304 stainless steel under various casting parameters. The results so obtained show a good fit to the experimental ones, and suggest that the control of the height of molten pool is of importance to the establishment of the optimal operation.     

Transient thermal model of the continuous single-wheel thin-strip casting process

A transient heat-transfer model (STRIP1D) has been developed to simulate the single-roll continuous strip-casting process. The model predicts temperature in the solidifying strip coupled with heat transfer in the rotating wheel, using an explicit finite difference procedure. The model has been calibrated using strip thickness data from a test caster at ARMCO Inc. (Middletown, OH) and verified with a range of other available measurements. The strip/wheel interface contact resistance and heat transfer were investigated in particular, and an empirical formula to calculate this heat-transfer coefficient as a function of contact time was obtained. Wheel temperature and final strip thickness are investigated as a function of casting speed, liquid steel pool depth, superheat, coatings on the wheel hot surface, strip detachment point, wheel wall thickness, and wheel material.     

Effect of electric current pulse on solidification of silicon steel pertinent to twin roll casting

Abstract

An experimental study with respect to the influence of electric current pulse (ECP) on the solidification structure of molten silicon steel was investigated with a copper mould designed to simulate the twin roll casting process. The experimental results showed that the application of ECP can increase the proportion of equiaxed grains up to 67·5%. The mechanism of exerting ECP is also discussed. It can be confirmed that the application of ECP on twin roll casting could effectively improve the solidification structure of silicon steel strip.     

水平连铸引拉铸紫铜工艺的初探

探讨水平连铸拉铸紫铜熔炼、铸造的工艺特点,分析拉铸工艺参数对铸坯质量的影响．     

A mathematical model of the thermal field in continuous hot rolling of strip and simulation of the process

Development of a mathematical model of the thermal process and flowchart of simulation. Application of the model to start of rolling when the rolls have a homogeneous temperature and to rolls having a temperature profile brought about during the previous revolution. Interpretation of the results in terms of design parameters of a strip rolling mill. Application of the model for estimating physical constants. Further development.     

双辊薄带钢连铸侧封技术研究

侧封问题是双辊薄带连铸技术的一个关键性问题。分固体板侧封和电磁侧封两个方面综述了侧封技术的发展状况,分析了它们的优缺点。     

Modelling molten flux layer thickness profiles in compact strip process moulds for continuous thin slab casting

Abstract

The important functions promoted by powdered flux added over the liquid steel surface in continuous casting moulds are strongly affected by the thickness of the liquid layer that forms as a result of the heat absorbed. The present work discusses the results of a three-dimensional steady state model, developed to represent the coupled fluid flow and heat transfer phenomena that determine thickness profiles of the liquid flux layer. Since the laminar flow of the liquid slag layer depends on the shearing imposed on it by the turbulent motion of the liquid steel beneath it, and since additionally this motion is strongly influenced by the flow characteristics of the steel stream poured into the mould through the submerged entry nozzle (SEN), separate turbulent flow models for the liquid steel in the SEN and the mould were also developed. The consistency among the models and their accuracy was judged by comparing thickness and temperature flux profiles measured in plant against predicted ones; the comparison showed good agreement. The effects of casting speed, mould width, and flux viscosity and heat of melting on the liquid layer thickness were investigated. The last variable was found to exert the most marked influence. Different from conventional casting moulds, where the liquid layer thickness increases with increasing casting speed, in compact strip process moulds the thickness remains almost constant with increasing casting speed. This difference is well accounted for by the model, which suggests that this behaviour stems from the different slag flow patterns generated in straight, wide moulds and in thin moulds having a central upper funnel shaped section.     

双辊铸轧薄带钢工艺参数检测系统的建立与结果分析

设计和建立了双辊铸轧机的工艺参数在线检测系统，介绍了数据处理方法并对测量数据进行了分析处理，其结果对双辊铸轧薄带钢的过程控制和薄带质量的提高提供了可靠的依据。     

The future of the twin-roll strip casting and rolling process

Twin-roll strip casting and rolling is a typical near-net-shape steel manufacturing process. The twin-roll strip casting and rolling of low-carbon steel strips has made a number of breakthroughs and achieved significant results during the past 20 years. Baosteel has been paying close attention to the development of this technology and set up a research and development project focused on its industrialization in 2001. The Ningbosteel-Baosteel strip casting industrialization demo project( NBS),which was launched in 2016,marks the strip-casting technology( registered as Baostrip) developed by Baosteel as having reached an advanced international level after 15 years of effort. This paper summarizes the results obtained in the industrialized demonstration plant and considers the future development of strip casting and rolling.     

带钢连续酸洗机组辊式矫直机关键结构参数研究

分析了矫直机常用辊系结构,并结合连续酸洗机组原料特点与矫直工艺要求,详细介绍了酸洗机组矫直机关键结构参数,如辊系结构与辊数计算、辊径与辊距等参数的选取及计算方法。以某钢厂酸洗原料数据为例,完成了矫直机关键结构参数的计算,并将计算结果与工程实际进行了比较说明。实践表明,该计算选型方法对矫直机的设计具有一定的指导作用。     

A unified computational model for surface texturing process of strip casting rollers

A new unified computational method is proposed for modeling the relationship between the parameters of the high-speed particle-impact texturing process and the final surface morphology of the casting roller. The whole surface-texturing process is divided into three parts. The first part is the acceleration process of particles inside and outside the nozzle,which can be analyzed using the computational fluid dynamics method to obtain the particle impact velocities. The second part is a simulation of the bombardment process of particles onto the roller surface using the LS-DYNA software as the analysis tool and the results obtained in the first part as input parameters. The last part is the continuously random impact process of particles on the casting roller surface to form a functional surface,which is characterized by a simplified roughness model. Finally,the above three parts are combined to establish a unified computational model,the performance of which is successfully verified in a series of experiments.     

A mathematical model of a drum and ring horizontal strip casting process

A mathematical formulation has been developed to represent the heat transfer and the solidification process in a drum and ring type horizontal strip casting machine. This system involves a ring shaped trough, containing a molten metal pool into which a drum is partially immersed. Both the ring and the drum are made to rotate and their surfaces are cooled with water sprays; as a result, solidified shells are formed on both the internal surface of the ring and on the outer surface of the drum. These two shells are welded together to form the strip. In the formulation equations were developed to represent the temperature profiles in the system and the build-up of the solidified shells as a function of position. The principal usefulness of the analysis is to provide guidance regarding the interrelationships between the key process variables, such as the depth of the metal pool, the system geometry, the angular velocities, and heat transfer coefficients. One may also define the safe limits of operation, in terms of these parameters.     

带钢热连轧设定及组织性能预报软件开发

针对连轧工艺设计和生产管理的需要,开发了带钢热连轧设定及组织性能预报软件.该软件具有使用方便、功能强大、计算精度高、适用范围广等优点,可满足带钢热连轧工艺设计、设备选择、现场生产管理等的需要.     

神经元网络技术在连铸漏钢预报中的应用

介绍在连铸神经元网络漏钢预报系统中开发应用的人工神经元网络技术。对人工神经元网络的结构选型和训练进行了说明。现场运行结果表明：该系统对于不同的生产条件和工艺参数均具有良好的性能。     

双辊连铸无取向硅钢铸带特征及常化作用研究

双辊连铸技术是冶金及材料领域内的一项前沿技术,对于生产高品质硅钢具有独特优势.本实验研究了一种双辊铸轧w[Si]=4.5%的无取向硅钢,考察其铸态和常化处理后样品的组织、织构及析出相尺寸特征.结果表明：铸带组织以与铸带法向成5~20（°）倾角的柱状晶为主,晶内存在少量0.3~0.4μm的AlN析出相,铸带织构以λ（〈001〉//ND）织构为主,表层织构漫散.950℃/10 min常化处理后,析出相尺寸增大,表层λ织构增强.