吹氩连铸中间包内钢液流动特性的水模型实验研究

建立了模拟连铸中间包底吹氩流动过程的水模型.通过测定分析水模型的RTD（停留时间分布）曲线研究了吹气流量、吹气位置及控流元件对中间包内流动特性的影响规律,并对此进行优化.结果表明：条形透气梁安放位置对中间包内的流动特性影响最为显著,均匀开孔的多孔挡墙和条形透气梁喷吹氩气二者的配合使用能获得理想的流动特性.     

气幕挡墙中间包内渣钢界面卷混现象

 中间包内采用气幕挡墙是有效去除钢水中细小夹杂的新技术。采用物理模拟方法,研究了连铸中间包采用气幕挡墙时其内流动行为和渣钢界面卷混现象,考察了吹气流量、气幕位置以及与湍流控制器组合对中间包内的渣钢界面的影响规律。结果表明,气幕挡墙的位置和吹气量是影响中间包卷渣的主要因素。     

热轧卷板表面夹渣缺陷来源分析及控制现状

热轧卷板的表面夹渣缺陷对热轧板的质量及产品性能会产生极其恶劣的影响,会导致产品品级的下降乃至报废等问题,并对产品的服役期限及性能造成一定影响.随着冶炼过程中钢液洁净度的不断提高,夹渣缺陷所造成的质量问题显得尤为严重.而不同生产工艺下表面夹渣缺陷的来源方式略有差异,缺陷的来源主要有精炼过程中钢包渣的卷渣、非稳态浇注时期的...     

连铸中间包湍流控制器水模实验研究

通过水模实验，研究了湍流控制器对连铸中间包流体流动的影响。合理结构的湍流控制器能够改善中间包流体流动特性，最小停留时间增加，活塞流体积提高，死区体积下降。实验观察发现，中间包采用湍流控制器后，在两块上渣堰之间的液面流动平稳，可以减少卷渣现象。     

高速连铸结晶器内卷渣机理及其控制研究

利用物理模型研究了高拉速条件下结晶器内的卷渣机理,考察了保护渣粘度、操作参数对结晶器内弯月面波动和卷渣行为的影响。研究结果表明：在高拉速条件下,表面回流卷混是引起卷渣的主要方式,表面速度可以作为判断卷渣发生的特征参数。此外,本研究还给出卷渣发生时的临界表面速度,提出了避免卷渣的改进措施     

多模式全连续铸轧产线卷渣缺陷分析及控制

通过扫描电镜和能谱分析仪对低碳低硅铝镇静钢表面卷渣缺陷微观形貌进行观察和能谱分析。结果表明,低碳低硅铝镇静钢表面较短条状卷渣缺陷的主要成分为钙、铝和氧,为典型的钙铝酸盐夹杂物;较长条状卷渣缺陷的主要成分为钙、硅、氟、钠和氧,为典型的保护渣成分。针对不同类型的卷渣缺陷及其成因,分别在炼钢工艺的挡渣出钢、精炼工艺的升温时间和钙含量以及连铸工艺的中间包控流装置、中间包保护气氛、结晶器液面波动、钢包下渣和结晶器保护渣等方面进行改造、控制和优化。采取上述措施后,因低碳低硅铝镇静钢表面卷渣缺陷造成的产品降级率由大于10.0%降至1.5%以下,产品质量得到明显提升。     

Effects of several casting parameters on slag entrapment in mould( part A: water modeling)

The mechanism of slag entrapment in the mould was analyzed and the water modeling experiment was done according to the industrial manufacturing. The results show that the flow of the liquid steel becomes more active and the level fluctuation in the mould becomes bigger when the casting speed increases from 1. 0 m / min to 1. 2 m / min. So the control of slag entrapment in the mould becomes more difficult. When the depth of the nozzle increases from 30mm to 42. 5mm and the angle increases from 15° downward to 30° downward,the level fluctuation in the mould becomes smaller and the slag entrapment in the mould also decreases. But the impact depth increases and the circumfluence vortex center moves downward,which is unfavorable for the flotation of gas bubbles and inclusions. Furthermore,the impact depth with side holes a ( 16. 3 × 20 mm 2 ) and b ( 10 ×10 mm 2 ) is almost equal,but a smaller level fluctuation can be obtained with side hole a.     

多模式全连续铸轧产线卷渣缺陷分析及控制

通过扫描电镜和能谱分析仪对低碳低硅铝镇静钢表面卷渣缺陷微观形貌进行观察和能谱分析。结果表明,低碳低硅铝镇静钢表面较短条状卷渣缺陷的主要成分为钙、铝和氧,为典型的钙铝酸盐夹杂物;较长条状卷渣缺陷的主要成分为钙、硅、氟、钠和氧,为典型的保护渣成分。针对不同类型的卷渣缺陷及其成因,分别在炼钢工艺的挡渣出钢、精炼工艺的升温时间和钙含量以及连铸工艺的中间包控流装置、中间包保护气氛、结晶器液面波动、钢包下渣和结晶器保护渣等方面进行改造、控制和优化。采取上述措施后,因低碳低硅铝镇静钢表面卷渣缺陷造成的产品降级率由大于10.0%降至1.5%以下,产品质量得到明显提升。     

Physical and mathematical simulations for molten steel flow in a large ingot casting process with double bottom argon bubbling porous beams

The effects of gas bubbling with double bottom porous beams on the flow during the filling process at different filling levels in a large ingot mould were investigated. Mixing time is long in the mould without gas bubbling. In the case of bottom gas bubbling with a small gas flow rate, the mixing time can be decreased by about 50–70%. Favourable bubbling position is 102–142?mm from the bottom centre. Large granular slag drops are entrapped at a lower filling level less than 60?mm and the slag drops entrapped become small with an increase in filling height without gas bubbling. Gas bubbling with reasonable flow rates does not cause strong slag entrapment during the initial stage of the filling process. Bottom gas bubbling in filling process of large ingot casting is beneficial to achieve simultaneously uniform temperature and composition, and to remove inclusions in the bath.     

Steel Thermo‐Fluid‐Dynamics at Tundish Drainage and Quality Features

In steelmaking and casting, transient operations are very critical for product quality and process regularity. This holds especially for the tundish. Typical drawbacks can occur at ladle change, where, for example, refilling high flow rates induce flow short‐circuits risky for dispersed oxides (“inclusions”) dragging towards the strands. At drainage, vortices formation can affect steel cleanliness via slag entrapment. Such topics were investigated for an industrial tundish with computational fluid dynamics validated tools. The focus was given on a multi‐strand layout more prone to unevenness features. As a matter of fact, the different steel path to reach different strands causes often too high temperature differences and different strand cleanliness levels. Strands closer to the tundish center, are generally hotter and less clean; the others, slightly colder but cleaner. Multiphase models, together with advanced meshing techniques and validated boundary conditions, were used to describe tundish refilling and drainage. Within the operating conditions of concern, a bath height of 300 mm was found as a best compromise between the need of avoiding slag entrapment through vortices and to have maximum yield. Once applied into operating practice, no rejection for cleanliness or customer claims were achieved. As refers to temperature loss from ladle to tundish, a drop at strands of about 2 and of 4°C from tundish inlet to strand, in agreement with plant data over about 700 heats and literature experiments under the same operating conditions, were found.     

Emulsification of Top Slags during Argon Stirring through a Porous Plug in the Ladle of Si Deoxidised Carbon Steels

Intensive experiments with 170‐t heats of carbon steels in the LD steel plant of Saarstahl AG were performed to study the emulsification of an acid top slag during different stirring conditions in this research project. During ladle treatment samples were taken from steel for the analysis of the composition of the inclusions together with the top slag. Within these investigations gas flow rates and stirring times were systematically varied in order to study their influence on the entrapment of top slag in the steel melt. At the same time a model was developed for the evaluation of the performance of the porous plug with regard to gas flow rate and gas pressure or finally for blockades and leakages. According to the experiments of this project the following results were established. Small top slag particles are discovered nearly in all steel samples together with endogenous SiO₂‐Al₂O₃ deoxidation products. But emulsified phases or parts of the top slag generating larger inclusions with a size of 30 – 60 μm show the low melting eutectic composition. On the other hand, this emulsification process leads simultaneously to CaO depletion and SiO₂ accumulation of the top slag particularly when a longer stirring period is applied as shown during these experimental trials. The whole process requires low melting top slags and low melting emulsified inclusions in combination with a low viscosity level. To meet the emulsification requirements the gas flow is characterised by high gas flow rates in the order of 30 – 40 STP m³/h and high pressures with 8 – 12 bar indicating a blockade of the porous plug and the existence of a gas jet.     

中间包夹杂物的去除与控制新技术

通过对中间包中不同去除夹杂物的手段进行综合分析,得到各环节中间包均应保护浇注和防止卷渣卷气,中间包应具有合理的控流装置（上下挡墙、湍流抑制器、旋涡抑制器）以得到理想的流场;利用钢包注流生成的小气泡、中间包气幕挡墙和电磁搅拌离心流动可以有效去除中间包内钢水中夹杂物;连续真空处理对脱气和去除夹杂物有良好效果但其可调性差,电磁过滤可作为辅助方法去除夹杂物。     

四流中间包气幕挡墙水模拟研究

采用不同参数的多孔透气砖进行了25 t四流中间包的底部吹气水模拟实验,结合RTD曲线和标准差分析,研究透气砖面积(210～105 mm×56～28 mm) 、4种吹气位置和吹气量(60～120 L/h)对中间包液体流动特性的影响,并与不吹气的情况进行了对比。结果表明,中间包吹气能改善液体的流动特性,均衡其在不同水口间的停留时间,并能延长峰值时间和降低死区体积。透气砖靠近挡墙,采用小气量和小面积更有利于改善现有中间包流场。     

钢包卷渣临界底吹流量规律的水力学模拟研究

用水模拟钢水、油模拟钢渣,通过水力模型研究了底吹钢包中的临界卷渣流量.结果表明,临界卷渣流量随渣层厚度的增加而减小,随粘度的增加而增大,通过分析渣-钢界面的速度分布和能量平衡,对以临界流量作为卷渣发生的判定条件的准确性进行了检验.采用因次分析得到了底吹钢包临界卷渣流量的无因次表达式Qcr∝(Δρσ/ρ2s)0.35(μs/μm)0.3(Hs/Hm)-0.42,利用该表达式计算了实际钢包卷渣的临界流量,分析了影响因素,建议110 t钢包进行钢水弱搅拌净化操作时最大底吹流量为QN＝240 L/min.     

上水口环形吹氩对中间包内渣眼形成的影响

 中间包上水口环形吹氩可以在塞棒周围形成清洗钢液的环形气幕,同时部分氩气泡随钢液进入上水口内,可以减少非金属夹杂物在水口内壁的黏附,起到防止水口堵塞的作用。然而,不合理的吹氩量会导致中间包内液面渣层受过强的气液羽流冲击而形成渣眼,使得钢液裸露并发生二次氧化,严重影响铸坯质量。采用标准 k ε 湍流模型研究中间包内流体流动,采用DPM模型和VOF模型耦合方法,研究上水口环形吹氩条件下渣眼的形成及演化规律。结果表明,上水口环形吹氩在塞棒周围形成较强的上升流,塞棒上部邻近区域存在多个涡流区;在钢液涡流的影响下,中间包液渣下层远离塞棒区域,上层向塞棒区域迁移;随着吹氩量的增大,平均湍动能增大,塞棒附近钢液速度逐渐增大,钢渣界面钢液速度先增大后减小,渣眼边缘钢液速度先增大后减小然后再增大,速度与垂直方向夹角逐渐减小;增大吹氩量,中间包熔池液面形成以塞棒为中心的渣眼,渣眼面积逐渐增大。试验条件下不产生渣眼的临界吹氩量为4.2 L/min,对应的钢渣界面最大速度为0.247 m/s,与垂直方向夹角为70°。     

1 500 mm x230 mm板坯结晶器液面波动与卷渣行为水力学模型试验和应用

基于相似理论,以钢厂1 500 mmx230 mm板坯结晶器为原型建立1 ：2的结晶器水力学模型。结果 表明,吹气量一定时,水口中心处到窄边的液面波动先增大后减小,吹气量大于0. 8 lymin时,开始发生卷渣现象, 并且结晶器内的气泡数量变多。浸人深度的增加使液面波动减弱,浸入深度在65 - 95 mm时对卷渣影响的效果不 显著;拉速增加使流股的冲击深度增大,拉速大于LI m/min时有大渣滴被卷入;当结晶器的拉速为1.0 ~ 1.1 m/min, 吹气量为0.6~0.8 I/min,浸入深度为75 - 85 mm时较合理。C45E钢生产实践表明,当拉速由0.9-1.2 m/min调整 至1.0 ~ 1.1 m/min,浸入深度由130 ~ 190 mm改进为150 ~ 170 mm时,铸坯缺陷率由6%降至1.9%。     

非对称中间包稳态浇铸与换包操作的冶金效果

??To rationally assess and optimize the metallurgical effect of an industrially used three- strand asymmetric tundish?? the mixing characteristics of molten steel with different tundish configurations were investigated by residence time distribution??RTD??curves based on the analysis of fluid flow and temperature distribution at four flow control schemes?? and the behavior of the tundish level was tracked by employing volume- of- fluid??VOF??model. The fluid dynamics behavior of the tundish was studied in term of both steady and unsteady service situations with and without fluid flow control devices?? which made it possible to assess comprehensively the metallurgical effect of the given tundish. The results show that the flow control effect of bare tundish is weak. It is observed that there are distinct short- circuit flow and large proportion of dead zone?? together with the non- uniform temperature distribution and the flow state discrepancy among the three strands?? which will accordingly lead to the quality difference of the bloom castings. The improvements on the fluid flow characteristics and the temperature distribution have been observed in tundish with the combined application of baffles and turbulence inhibitor. The proportion of dead zone is decreased by 13. 28%?? the temperature difference is only 0. 5K among three outlets?? along with an improved fluid flow consistency. Additionally?? studies also show that this arrangement may have large steel level velocity and level fluctuation during ladle change period. That is likely to bring about exposure?? reoxidation and even slag entrainment of molten steel. Attentions should be paid to the control of the ladle change interval?? inlet flowrate and the moment height of liquid level.     

抑旋板条件下多流中间包流动特性的数值模拟

以某厂35 t对称四流方坯中间包为研究对象,采用数值模拟方法研究了抑旋板对中间包流场特征的影响.结果表明:未加入抑旋板时,在端部的4流水口上方易形成逆时针旋涡,钢液面降至69 mm时便出现卷渣现象;在4流水口附近加入抑旋板,可以破坏水口处逆时针旋转流场,降低水口附近钢液流速,提高液面稳定性,对抑制汇流旋涡形成效果明显.改变抑旋板安放角度及高度,可使中间包内钢液均沿径向流入水口,钢液表面无明显旋涡形成,卷渣液位降低了40.6%,金属收得率显著提高.     

Effects of several casting parameters on slag entrapment in mould (part B:numerical modeling)

Based on the effects of several casting parameters on slag entrapment in the mould (water modeling),the numerical modeling was researched. The results show that the flow field with a submerged nozzle section dimension of 65 mm×80 mm is better than that with a submerged nozzle section dimension of 40 mm×40 mm and is favorable for avoiding slag entrapment. In this paper,low surface velocity,small level fluctuation and proper impact depth can be achieved with a nozzle of an outlet angle of 25° and an immersion depth of 150 mm,or with a prototype nozzle of an outlet angle of 15° angle and an immersion depth of 150 mm.     

120t钢包汇流卷渣的物理模拟

通过水模试验,对某厂120 t钢包浇铸过程中汇流卷渣现象进行了观察,研究了钢包渣量、钢包水口直径对卷渣高度的影响。结果表明,钢包从无渣到1.0%的渣量时,开始卷渣高度降低了57%,稳定贯穿漩涡的高度降低了56%;渣量从1.0%增加到7.0%,开始卷渣高度增加了63%,稳定漩涡高度增加了62%;钢包水口流量由2.884 m3/h增加到22.465 m3/h,开始卷渣高度增加60%,钢包水口出流流量由2.361 m3/h增加到19.211 m3/h,稳定漩涡高度增加了75%。