Impact of slag–refractory lining reactions on the formation of inclusions in steel

Abstract

The present study was carried out to investigate the impact of slag– refractory lining reactions on the formation of inclusions during ladle treatment of steel. The experiments were conducted on an industrial scale in the ladle at Uddeholm Tooling AB in Hagfors, Sweden. The inclusion chemistry and population during ladle treatment were studied along with the composition of the ladle glaze, taken from the ladle lining. The inclusions in the steel were classified into four groups according to the Swedish standard SS 111116. SEM/EDS analyses were carried out to identify the phases present in both the inclusions and the ladle glaze. The number of inclusions in the steel before deoxidation was found to increase with the ladle age, i.e. the number of times the ladle had been in use. A similar increase was also found after vacuum degassing and before casting. A great portion of inclusions before casting was found to be supplied by ladle glaze. This observation was further confirmed and explained by thermodynamic analysis. The present results show that ladle glaze is a major source of inclusions in the ladle at Uddeholm Tooling.     

炼钢 精炼 连铸过程钢包热状态测试研究

测试了宝钢炼钢厂炼钢 精炼 连铸过程钢包的热状态;研究了钢包在各个周转阶段的包衬温度分布及其变化规律。测试结果表明,在钢包的第1和第2个周转过程包衬吸热和蓄热明显,该阶段应考虑钢水温降的热补偿。在钢包的第3和第4个周转过程中,包衬各点的温度变化较为平缓,表明从第4个周转开始,包衬温度变化处于一种动态平衡的循环过程。     

Transition section in continuous bar casting during the serial casting of different steels

In continuous slab casting at OAO Magnitogorskii Metallurgicheskii Kombinat (MMK), metal of different grades in a series is separated by leaving an appropriate quantity of steel from the previous melt in the intermediate ladle. The losses of metal are least on leaving around 12 t of steel in the intermediate ladle. The mass of the transition sections of mixed composition in the bar billet is 2.5 times the mass of the steel left in the ladle.     

钢包底温度场和应力场数值模拟

钢包是连铸生产线上的重要设备，其内衬的热应力是影响钢包寿命的主要因素。本文运用有限单元法，对钢包底的温度场和应力场进行了数值模拟。计算结果表明，新包预热后仍处于吸热状态，经数次热循环后才达到“准稳态”；包底工作层应力值在预热完成后，钢水注入瞬时达到最大；包底工作层热面靠近包壁处的应力比靠近中心部位高，可在靠近包壁处增设保温装置降低该处应力。     

Production of 180 × 180 mm continuous-cast billet from high-carbon steel

The introduction of the continuous casting of high-carbon steel into 180 × 180 mm billet is described. Measures are developed to increase the production series in the intermediate ladle from 3.5 to 10 melts. The basic factors that affect the development of microstructural defects—central porosity, as well as liquation bands and cracks extending over the cross section—are identified. The technology is corrected so as to hinder the development of such defects.     

炼钢-连铸过程300t钢包热状态测试研究

对宝山钢铁集团公司炼钢厂炼钢-精炼-连铸过程钢包的热状态进行了测试,研究了钢包在各个周转阶段的包衬温度分布及其变化规律.测试结果表明,在钢包的第1和第2个周转过程包衬吸热和蓄热明显,该阶段应考虑钢水温降的热补偿.在钢包的第3和第4个周转过程中,包衬各点的温度变化较平缓,表明从第4个周转开始,包衬的温度变化处于一种动态平衡的循环过程.     

A Model for Predicting the Melt Temperature in the Ladle and in the Tundish as a Function of Operating Parameters during Continuous Casting

A mathematical model for predicting the melt temperatures in the ladle and in the tundish during continuous casting has been developed. First of all, a chain of models was created for the following stages of the ladle cycle; the preheating of the empty ladle, filling of the ladle, period in the ladle furnace, waiting period prior to casting, the casting period, and, finally, the free cooling period of the empty ladle. Models, written in CFD code, were used in sequence so that each simulation continued from the results of the simulation of the previous stage. An intermediate model was constructed to estimate the outlet temperature of melt drained from the ladle. Then the work was continued by performing simulations in the tundish, using as input the temperature of the simulated melt feed from the ladle and, as an initial condition, the temperature field of the remaining melt in the tundish. The final model “TEMPARV3” was created and tested by means of measured tundish data received from a steel plant. By means of statistical analysis the coefficients of correlation between the test data and model data at the start, in the middle period, and at the end of casting were calculated to be 0.9, 0.92 and 0.87, respectively. So, the most effective predictive power of the model in the tundish by means of a sequential casting schedule is realized during the middle period of the casting process. The model is applied interactively by a user interface, which expresses the predicted melt temperatures numerically and with graphical curves. The predictive model can be used off‐line as a tool for scheduling the stage operations in advance. The program may be utilized on‐line to estimate the superheat needed and to control periods of the operation. In extreme cases, when the model alerts the operator about the danger of superheat loss having a critical effect on casting, the operator has a chance to take adjustment measures. In addition to production work, the model could be of benefit for studying changes in operating parameters, for training operators, and for use as a “low‐cost computational pilot plant” in process development in general.     

连铸用钢包的耐火内衬优化及疲劳寿命预测

摘要：连铸技术对钢包的性能要求越来越高，而传统钢包炉衬构件普遍存在使用寿命短、消耗高等问题。通过研究耐火材料特性，优化内衬结构布置，设计出一种长寿命、超保温的新型钢包，并基于数值模拟技术，对新型钢包与传统钢包在典型工况下的温度与应力进行对比分析。温度场模拟结果表明，新型钢包在保温性能上有较大的提升，钢包壳最高温度较传统钢包降低54℃。同时，应力场结果表明，新型钢包壳的最大应力减小了66.7MPa且整体应力分布更加均匀。最后将温度场和应力场的分析结果反馈到钢包的生产、制造、维护上，并进行实验验证。实验结果表明，新型钢包在保温与长寿等性能方面表现更好，内衬寿命提高了119炉次，达到了钢包设计、制造、维护一体化的效果。     

RH精炼终点-中间包浇铸过程超低碳钢水增碳的影响因素

通过数据统计,分析了钢厂180 t RH精炼结束到45 t中间包浇铸过程中钢包衬、中间包涂料和覆盖剂等对MA超低碳钢水(≤0.005%C)增碳的影响。结果表明,连续浇铸第1炉增碳较大,增碳量5×10^-6~10×10^-6,其余炉次增碳量≤3×10^-6。通过第1炉缓缓加入覆盖剂控制中间包液面波动,加Al₂O₃减少钢包渣线侵蚀,减少钢包砖衬、中间包涂料和覆盖剂游离碳含量,可使RH精炼终点-中间包浇铸过程中钢水增碳量≤3×10^-6。     

钢包整体筑衬技术

钢包整体筑衬技术可以使用浇注法和湿式喷射法,浇柱法用材料主要有Ａ１２Ｏ３－尖晶石系和Ａｌ２Ｏ３－ＭｇＯ系,湿式喷射法用材要注意改进其传送性、耐蚀性和耐爆裂性,尽管钢包整体筑衬的侵蚀速度比砌砖法稍快,但是差别不大。     

Modelling of ladle glaze interactions

Abstract

A potential source of inclusions in liquid steel is ladle glaze, the slag/inclusion coating on the refractory lining of the ladle which is always present after casting and before reuse of the ladle. The composition and quantity of this glaze can vary considerably, depending on the range of steel qualities being made and, in order to model the effect of glaze on inclusion/top slag formation, a combined fluid flow-thermodynamic model has been developed. The behaviour of ladle glaze for various different steels has been studied under pilot plant conditions and the results incorporated into the mathematical model. The implications of the pilot plant and model results are discussed in the context of the production of clean steel.     

连铸铝镇静钢时中间包钢水氧含量预测模型

针对国内某厂６０ｔ中间包浇注低碳铝镇静钢的多次试验数据，从理论上建立了浇注过程中中间包钢水氧含量的预测模型，模型中综合考虑了钢包渣中ＦｅＯ及ＭｎＯ含量，耐火材料ＳｉＯ２含量，钢包到中间包钢水吸氮量，浇注时间，拉速，铸坯断面积等因素的影响，并对改进中间包操作进行了讨论。     

Thermomechanical Modelling for Refractory Lining of a Steel Ladle Lifted by Crane

Numerical methods can be applied on metallurgical processes like engineering design of a steel ladle. In this study, the thermomechanical behaviour of refractory lining of a steel ladle which is lifted by a crane was investigated. To simulate this behaviour coupled heat transfer – structural analysis was made by using FEM (Finite‐Elements‐Method). For these calculations a two‐dimensional, an axially symmetrical geometric model and a FE‐model of a steel ladle with wear lining consisting of MgO‐C brick in the slag zone and castable MgO‐Al₂O₃–spinel in the working zone were created. Thermal stresses, hydrostatic pressure, gravity of molten steel and slag and refractory lining were used as boundary conditions. The results gained from the calculations showed that the maximum total displacements were observed at the bottom lining of the ladle.     

高寿命中间包干式工作衬技术的研究与应用

为了提高连铸机的作业率,缩短中间包周转时间,莱钢炼钢厂研制开发了单包连拉时间大于50h的干式工作衬。应用表明,高寿命中间包干式料烧结层薄、抗浸蚀、单包连拉时间长、操作简单,比应用涂抹料年降成本近300万元。     

攀钢用铝镁碳砖综合砌筑钢包衬

攀钢钢包内衬原为铝镁浇注料，连铸投产后包衬寿命急剧下降，并常在渣线部位出现漏钢事故。为确保连铸正常生产，采用了铝镁碳砖和镁碳砖综合砌包工艺，模铸和连铸的典型试验和扩大试验表明效果良好，平均寿命为７８．３次。     

Simulation of the design of an intermediate ladles in a continuous-casting machine

Physical simulation of various designs for a 27-t intermediate ladle with asymmetric metal supply is undertaken, in steady and unsteady steel casting. The flow rates of the metal, its residence time in the casting chamber, the ascent of nonmetallic inclusions, and their percentage content in the mold are determined. An asymmetric stop for equalizing the flow rate in near and far sections of the mold is developed. The best design is an intermediate ladle with an asymmetric stop and annular tuyeres for argon injection around the casting holes.     

高铝--尖晶石浇注料在连铸钢包上的应用

介绍了高铝－尖晶石浇注料在连铸钢包工作衬的实践。实践证明：高铝尖晶石烧注料具有施工简单,包龄提高、耐材消耗降低优点,对促进连铸生产发展有重要意义。同时也简述了该料剥落的成因。     

Improvement of the thermal operating conditions of steel-teeming ladles

The thermal state of a 30-t steel-teeming ladle is subjected to CFD simulation. The results obtained are verified by direct measurements of the lining and steel temperatures at various stages of technology under the conditions of an operating electric-furnace shop in a miniplant. The simulation results are used to determine the quantitative indices of the effect of the lining heating temperature on the energy consumed in steelmaking. It is shown that an increase in the temperature of the 30-t ladle lining by 100°C leads to a decrease in the temperature of metal tapping from EAF by ~11°C, which is equivalent to a saving of 4 kWh electric power per 1 t liquid steel.     

Model for temperature profile estimation in the refractory of a metallurgical ladle

Modeling of the transient thermal state of metallurgical ladels is motivated by the need for estimating the drop in temperature of the liquid metal in the ladle. On-line estimation of the state is required, since the same ladle is used in a number of casting cycles with rapid changes in boundary conditions for the temperature field, and the conditions in the current as well as previous cycles affect the thermal state. Although a large number of methods for the numerical solution of conduction-diffusion partial differential equations have been developed, there are still advantages to keeping thermal field computations at a relatively simple level, in contrast to the situation in the design process of ladles, where two-dimensional modeling may be required. Extensive computations under nonverifiable boundary and initial parameter values are not especially suited for real-time simulation of industrial processes. This article presents a novel approach to the solution of the one-dimensional transient heat conduction problem applied to ladle linings, relying on classical analytical techniques in combination with numerical methods. The performance of the model was validated by a comparison of predictions to thermocouple measurements from the refractory of a steelmaking ladle during a campaign of 26 casting cycles. Reasonable agreement between the measured and simulated variables could be established, which demonstrates the feasibility of the approach.     

钢包整体浇注设备的研制

为适应钢厂冶炼的需要,研制开发了钢包整体浇注成套设备。使用该设备后,明显提高了钢包的使用寿命和质量,钢包浇注壁质地均匀、致密度高,节约了耐材降低了成本。