ZrO_(2)-C质浸入式水口渣线耐火材料的侵蚀机制分析

针对目前连铸浸入式水口渣线部位耐火材料的侵蚀造成水口服役失效与连铸生产效率无法提升的难题,以某钢厂低碳铝镇静钢连铸常用的ZrO_(2)-C质浸入式水口为例,对其侵蚀后的水口渣线部位耐火材料进行取样,详细分析了水口渣线部位耐火材料的侵蚀原因与机制。结果表明:保护渣对水口外部渣线材料的冲刷、溶解与反应是导致浸入式水口渣线部位侵蚀和缩颈的核心问题。因此,如何有效防止或避免渣线部位耐火材料与保护渣间的接触与反应对抑制渣线侵蚀至关重要。

长水口吹氩对中间包流场和渣层行为影响的数值模拟研究

通过建立中间包内多相流非稳态数学模型,研究了长水口吹氩对中间包内流场的影响,分析了吹氩流量与渣眼面积和卷渣量之间的关系。结果表明,在扩张型长水口吹氩时,氩气泡流容易聚集于长水口的喇叭口处。由于浮力作用,吹氩造成的气泡流在湍流抑制器上方会产生较强的上升流,钢液涡度分析显示,这有利于夹杂物的碰撞长大和上浮去除。对于该50 t两流中间包,在拉坯速度为1.2 m/min条件下,当长水口吹氩流量为1.5×10^(-4)Nm^(3)/s时,既能有效促进夹杂物的上浮去除,也可使渣眼面积控制在较低范围内;而吹氩流量大于2.5×10^(-4)Nm^(3)/s时,会加剧渣眼形成和卷渣程度,导致钢液发生严重的二次氧化。

In-situ Formation of MgAl_(2)O_(4):A Method of Tailoring Microstructure and Properties for Development of High-performance Refractories

The in-situ formation mechanism of MgAl_(2)O_(4) was introduced,focusing on the formation process by solid phase reaction and gas phase reaction as well as the phenomenon of secondary spinelization.The influencing factors of the in-situ MgAl_(2)O_(4) formation and its effect on the microstructure and the properties of materials were systematically summarized for the Al2O3-MgO-MgAl_(2)O_(4) system and the carbon-containing refractories systems.It was pointed out that the in-situ formation of MgAl_(2)O_(4),including secondary spinelization,can regulate the microstructure and the service performance of materials.Its expansion effect can not only offset the shrinkage caused by sintering to improve the corrosion resistance of refractories,but also seriously restrict the reliability of functional refractories.The composition,the particle size,the atmosphere,and the temperature are important factors affecting the in-situ formation of MgAl_(2)O_(4).In the carbon-containing materials systems,the solid-solid reaction and the gas-solid reaction coexist to produce MgAl_(2)O_(4),which provides an effective way to further regulate the microstructure and the properties of materials through the reaction process.

Analysis of Corrosion Behavior of ZrO_(2)-C Slag-line Materials in Continuous Casting

In view of the service failure and low continuous casting production efficiency due to the corrosion of refractories at the slag-line in submerged entry nozzles,a submerged entry nozzle for low-carbon aluminum killed steel continuous casting in one steel plant was sampled and taken as the research object to analyze the causes and the mechanism of refractory corrosion at the slag-line.The results show that the core issue of the corrosion and necking of the slag-line materials is that the slag-line material are eroded,dissolved,and reacted by the mold flux gradually.Therefore,it is important to suppress or avoid the contact and reaction between the mold flux and slag-line materials.

Indispensability and Vulnerability of Magnesia-carbon Bricks for Steelmaking Process

The manufacturing techniques of magnesia-carbon bricks in China have been documented from raw materials,production(process and facilities)to performance and wear issues in the ladle.Magnesia-carbon bricks made of ordinary fused magnesia is the prevailing material used in the slagline of the ladle,but its service life is substantially lower than the bricks based on large-periclase-crystal fused magnesia.In two types of fused magnesia,the average values of periclase crystal size are in double for their difference.It is suggested that large-periclase-crystal fused magnesia should be used for manufacturing magnesia-carbon bricks for the slagline of the ladle by abandoning ordinary fused magnesia,in order to have a prolonged service life,increase the availability of the ladle and reduce the number of downtimes of the ladle.Free phenol in resin produced in China should be as low as that of resin made in Europe,to improve production environment and reduce smoke emission during the ladle preheating.There are large spaces to promote the productivity of magnesia-carbon bricks in China,with high intensity mixers and hydraulic presses.Expansion controlled magnesia-carbon bricks in the ladle depend on the optimized combination of sintered magnesia,Carbores and antioxidants as the matrix,to minimize the premature wear of vertical cracks and joint opening formed in the ladle lining.

A Retrospective Review of Aluminamagnesia-carbon Refractories

The residual expansion of in-situ spinel formation in using of alumina-magnesia-carbon(AMC)bricks monolizes the lining of steel-making ladles with the closure of their joints,which has been an effective solution avoiding washing out of the joints in ladle lining by the reduction of the penetration of liquid slag and molten steel.Alumina-magnesiacarbon refractories are overall reviewed,in terms of major raw materials,thermal evolution,corrosion and oxidation,and thermomechanical behavior,as well as type,addition and fraction of magnesia used.General commercial products contain 5%-10%MgO and 5%-10%C with a certain amount of metallic aluminum powder,which is believed to facilitate spinel formation at early stage of heating-up,although high magnesia containing AMC bricks are studied and used sometimes.With low ratio of Al_(2)O_(3)/C=12.9 and the carbon content of 6.4%C,AMC brick exhibits the highest corrosion resistance.It is important to determine the type,addition and fraction of magnesia used in AMC refractories for demonstrating high corrosion resistance and superior thermomechanical behavior.

Advanced green refractory technologies for coke ovens at Baosteel

To construct world-class iron and steel enterprises, Baosteel has adopted a strategy of environmental management that emphasizes environmental protection in the low-carbon and ecological manufacturing of steel products. In recent years, Baosteel has developed a series of advanced green refractory technologies （including composite refractory precast blocks with a unique ceramic glaze, and high-thermal-conductivity/high-density silica brick） for use in Baosteel coke ovens. The results of these applications not only reduce production costs and increase production efficiency, but also facilitate clean production by coke ovens. Baosteel＇ s coke oven has become China＇ s leading example of the application of green refractories.

Multifunctional Refractory-lined Vessel: Ladle Aggregate

A ladle primarily is a container used to transport molten steel from the steelmaking unit to the casting facility.The essential requirements are heat resistant,insulative and strong enough to hold molten steel up to 300 t,with a structure of multilayered refractory lining in a steel shell vessel.When a ladle is assembled with three-phase graphite electrodes,a ladle furnace forms,starting steel refining process with/without the vacuum tank degasser and RH circulating degasser,in order to meet the growing demand on high purity and higher quality steel.The working lining is under aggressive conditions that comprise the chemical reaction with molten steel,the severe corrosion of liquid slag,the disaggregation through oxidation,and the strong stress due to the impacting of the melts and gases and the effects of thermomechanical behaviors.Magnesiacarbon brick is one of the major materials,being indispensable for the slagline of a ladle furnace.Alumina-magnesiacarbon brick has played an important role to substantially increase the service life in the metal zone,from the early lining materials of high alumina and doloma bricks.The permanent lining must assume sufficient responsibility to allow finishing the process of the engaged charge in case of a failure in the working lining.The insulation layer must be as thin as possible in order to maximize the ladle’s capacity,and reduce the shell temperature for saving energy.In this issue,several integrant refractories are reviewed or investigated in order to compile a lining overview,and to contribute a prolonged service life under aggressive working conditions of the ladle furnace.

Study and Application of Sealing Material for Coke Oven Chamber

A kind of dry refractory sealing material has been developed to repair the fine cracks in coke oven chamber. With silica sand as the main raw material, the sealing material is blown into coke oven chamber by compressed air while being applied, and bonded to brick surface or filled in fine cracks of chamber under right pressure. The physical properties of the material are similar to those of silica bricks during its application. So it can be adapted to conditions of coke oven and has good service life. The study and application results of the sealing material are described in this paper.

Insulating Permanent Lining of Calcium Hexaluminate Based Castable for 300t Ladle in Baosteel

Minimizing of heat loss of liquid steel through the ladle lining led to the integration of increasing insulation function of the permanent lining and high-quality insulating layer between the permanent lining and the ladle steel shell.In this paper,a study was made on physical and thermomechanical properties and corrosion resistance of calcium hexaluminate based castables.The chemical and physical properties of CA6 based castables fabricated in this work can fulfill general requirements of the permanent lining in ladle.The permanent linings of CA6 based castables offer superb thermal insulation and corrosion resistance,compared to conventional refractory systems of 300t ladle in Baosteel.Both functions of insulation and safety work effectively in whole process of ladle operation.

Innovative Lining of Unburnt Al_(2)O_(3)-MgO Brick for 300t Steel Ladle in Baosteel

The manufacture of clean steel needs high performance carbon-free bricks for ladle lining.Based on long term application experiences of the prefab Al_(2)O_(3)-MgO blocks,unburnt Al_(2)O_(3)-MgO brick has been developed by pressing a mix of alumina,spinel and magnesia as major raw materials and Al_(2)O_(3)-MgO gel powder as binder.In addition to low open porosity and high strength,the unburnt Al_(2)O_(3)-MgO brick shows superior corrosion resistance and thermal shock resistance to the prefab block.Field trials in a 300t steel ladle have indicated the residual lining of unburnt Al_(2)O_(3)-MgO bricks showed smooth surface without large spalling and seldom steel infiltration,consequently longer service life than the prefab blocks.The reliable,unburnt Al_(2)O_(3)-MgO bricks have more advantages of high efficiency,energy-saving and eco-friendly production.It will be one of the best options for ladle lining in the manufacture of high-purity steel.

Corrosion of Magnesia-chrome Brick by Smelting Reduction Slag with Iron Bath

Effects of FeO content （0, 5%, 10%, and 15% in mass, respectively ） in lab-synthesized smelting redttc- tion slag with iron bath and test temperature （1 450, 1 500, 1550, anti 1 600 ℃ ） on corrosion am,amount and microstructure of fused rebonded magnesia - chrome brick with 26.02 massqc of Cr2O3 were researched by rotary cylinder method. The results show that ： （ 1 ） the corro- sion amolult of magnesia -chrome brick by slag without FeO is higher than that by the slag with 5% FeO, and the vorrosion amount increases when FeO content increa- ses from 5% to 15% ; （2） the test temperature is one of the important factors affecting the slag corrosion resist- ance of magnesia - chrome brick, and the corrosion of smelting reduction slag to brick increases with the temperature rising.

开浇过程湍流抑制器消能行为的数值模拟

中间包开浇过程中钢液流速大,极易造成钢液飞溅。有关开浇过程钢液流场的研究较少,缺乏相关机理性研究。根据钢液流动特性,引入水力学消能的概念,对中间包开浇过程中钢液流场变化以及内旋型湍流抑制器对开浇钢液的消能效果进行研究,并对不同结构湍流抑制器的消能效果及影响因素进行分析,得出开浇过程中钢液流场变化情况和内旋型湍流抑制器消能效果的作用机理。方形湍流抑制器通过挑流消能方式消能;波浪形湍流抑制器主要通过底流消能,次级消能方式为挑流消能;月牙形湍流抑制器通过形成表面旋流的面流、窄缝式消能等消能方式对钢液进行消能;内旋型湍流抑制器通过面流、窄缝式消能、旋滚流消能和孔流消能等结合的方式对钢液进行消能。内旋型湍流抑制器多种消能机理相结合的方式,对钢液的消能效果最明显。研究结果表明,内旋型湍流抑制器的综合消能表现最佳,可以有效降低开浇过程中钢液飞溅的高度,降低卷入的空气量。研究结果为湍流抑制器优化设计提供了理论基础及参考数据,可以有效提高湍流抑制器的利用率,降低生产成本,有较好的应用前景。

无挡墙中间包内流动状况数值模拟研究

利用数学模型研究了国内某厂的中间包不设置挡墙对中间包流场的影响,并用水模型验证了数学模型的有效性。结果表明,在设置挡墙的中间包内,夹杂物碰撞长大的区域主要是湍流抑制器内和上方空间及上下挡墙之间区域。中间包不设挡墙将出现大面积的超低速流区,死区扩大,平均停留时间大幅延长。改造湍流抑制器,将残钢孔改成直径为φ75 mm、孔宽为150 mm的导流孔,可减少死区和超低流速区,平均停留时间大幅延长,长水口吹氩流量可以提高至2.5×10^(-4)Nm^(3)/min而不出现渣眼现象,有利于夹杂的去除,但是去除挡墙后有利于夹杂物碰撞长大的区域将大幅缩减。