钢中夹杂物形貌特征的定量描述方法及其与上浮速度的关系

本文依据分形理论分析,举例探讨了不规则形貌夹杂物分形维数及动力直径的计算方法,且通过水模拟实验验证了采用分形维数和动力直径来定量描述不规则形貌凝聚体上浮速度的可靠性及准确度。结果表明：通过对钢中不规则形貌非金属夹杂物的扫描电子显微镜图像和金相图像进行计算机图像处理后,采用单一像素点覆盖和盒维数求斜率法均可精确地求出其分形维数及其相应的动力直径;采用分形维数和动力直径计算的凝聚体上浮速度与实验值基本一致;利用分形维数和动力直径来定量描述不规则形貌夹杂物是准确可行的。     

去除钢水中非金属夹杂物方法研究

介绍了一种去除钢水中非金属夹杂物的方法,探讨了它对中间包内腔结构改进的作用。经过计算,本方法能够满足10μm以上非金属夹杂物的上浮时间要求。实验证明,通过整流的作用,降低了钢水流动速度,流动更加平稳,可降低注流区的湍流强度,同时使钢液流动路线延长,钢液平均停留时间增加,夹杂物上浮增多,利于提高钢液洁净度。钢水均匀慢速流动减轻了钢水短路流动造成的耐火材料熔损,由耐火材料熔损造成的夹杂物减少。     

基于FBRM和PVM技术的尾矿浓密过程絮团演化规律

在初始泥层高75 cm和耙架转速为0、0.1、1和10 r·min?1条件,以及耙架转速为0.1 r·min?1和初始泥层高度为75、45和25 cm条件下,采用FBRM和PVM实时在线监测技术,对动态浓密系统泥层脱水过程絮团结构演化进行原位连续观测,获得了泥层脱水过程中,絮团直径、数量分布特征和实时图像。研究结果表明,尾矿浓密过程中絮团直径和数量随剪切时间延长呈现先增长后降低,再保持稳定的状态。根据絮团直径变化程度,将絮团密实化过程分为絮团生长期、絮团重构期和絮团破碎期3个阶段。在剪切速率0.1 r·min?1和初始泥层高度75 cm实验条件下,有利于絮团生长和絮团快速破裂重构,并提高絮团密实化程度,但过高的剪切速率作用对絮团结构影响程度下降。剪切速率的增加造成絮团平均直径减小,同时絮团平均直径减小的速率上升。随着初始泥层高度增大,絮团生长阶段时间更长,絮团直径峰值更大,重构期较长,絮团平均直径随初始泥层高度增加而增大。尾矿絮团分形维数可以反映絮团结构变化特征,结合PVM图像的分形维数和孔隙率计算,分析了剪切破坏力与絮团凝聚力存在的相互平衡关系,基于这种动态平衡对絮团破裂程度的影响,研究了尾矿浓密过程中的絮团密实化规律。      

钢中夹杂物的分形维数及其与形貌特征的关系

 利用Matlab图像处理功能计算了钢中夹杂物SEM图像的边缘、二维和三维分形维数,并讨论了边缘分形维数与夹杂物颗粒微观凝聚机制和三维分形维数与其融入顶渣中动力学之间的关系。结果表明：边缘分形维数可定量地表征夹杂物边界轮廓线的曲折复杂程度;对非润湿夹杂物颗粒来说,其边缘分形维数越大,表明气泡易于在其表面生成,从而更加有力于夹杂物的碰撞凝聚长大;夹杂物颗粒的三维分形维数越小,更有利于夹杂物融入渣中而被去除;分形维数是一个影响不规则夹杂物颗粒碰撞、凝聚和去除的重要参数。     

Definition of Raceway Boundary Using Fractal Theory

The particle velocity contours were obtained by tracking the tracer particles in the raceway region of the COREX melter gasifier model and the contours were irregular.According to the fractal theory,the fractal dimensions of different particle velocity contours were determined.Through the analysis of the fractal dimensions,a new method for precise determination of the raceway boundary was proposed.The results show that,when the velocity is less than 0.18m/s,the particles are located in the stagnant zone and the fractal dimensions of particle velocity contours are almost constant as 1.41;when the velocity increases from 0.18 to 0.83m/s,the particles are located in the rapid movement zone and the fractal dimensions decrease gradually from 1.41 to 1.05;when the velocity is greater than 0.83m/s,the particles are located in the cavity zone and the fractal dimensions are again almost constant as approaching to 1.00.Therefore,the velocity contour of 0.18m/s,which is critical to distinguish the rapid movement zone and stagnant zone,can be used to define the raceway boundary.Based on this method,the effect of blowing rate on raceway size was calculated and the results show that the penetration depth and height of the raceway increase with the increase of blowing rate.     

Al2O3夹杂物在钢-渣界面处的运动特性及去除率

通过理论计算和分析,研究了夹杂物颗粒在钢-渣界面处夹杂物去除层内的运动特性及去除率。结果表明:在夹杂物去除层内,Al2O3夹杂物颗粒的布朗扩散上浮临界尺寸为1.33μm,直径小于临界尺寸的夹杂物颗粒很难上浮去除;布朗碰撞的优势区域主要是直径为2.5μm以下的夹杂物颗粒之间以及直径为2.5～5μm夹杂物颗粒与0.5μm以下的微小颗粒之间的碰撞;直径为20～150μm的夹杂物颗粒在钢-渣界面去除层中9min内很容易完全上浮去除,而直径小于10μm的夹杂物颗粒去除率很低且升高缓慢,是提高钢液洁净度的主要控制对象。     

应用格子 Boltzmann方法直接数值模拟研究钢中夹杂物上浮及碰撞行为

采用格子Boltzmann方法对钢液中夹杂物上浮及上浮过程中的碰撞行为进行直接数值模拟研究.结果表明,不同尺寸夹杂物颗粒上浮速度的模拟结果和理论值基本一致,表明本文所采用的数值算法能够精确有效地对钢液中固相夹杂物颗粒运动行为进行研究.当钢液中直径为80μm的夹杂物颗粒位于直径为40μm的下方并一起上浮时,直径为80μm的夹杂物颗粒会逐渐追赶上直径为40μm的夹杂物颗粒并发生碰撞形成大尺寸凝聚体,凝聚体的上浮速度显著大于二者单独上浮时的上浮速度.对于直径为40μm的夹杂物来说,形成凝聚体后的上浮速度比单独上浮时的上浮速度增加300%.实际炼钢过程中,采取必要的措施增加夹杂物颗粒之间上浮过程中的碰撞凝聚,对于提高夹杂物颗粒的上浮速度,尤其是小尺寸夹杂上浮去除速度,提高钢液的洁净度具有重要的意义.      

气泡和液滴的碰撞和聚合现象

采用水模型实验和高速摄像技术模拟了钢液中气泡与液滴碰撞聚合的现象和机理。根据韦伯数We和碰撞参数B的关系,气泡和液滴的碰撞结果分为聚合、反弹和拉伸分离3种。聚合分为靠近碰撞、形成液膜、形成稳定接触面、滑移、稳定上浮等过程;反弹分为靠近碰撞、形成液膜、滑移分离等过程;拉伸分离分为靠近碰撞、形成液膜、形成接触面和共同体、形成颈部、断裂等过程。当We很小时,气泡和液滴会发生聚合。随着We的增大,B适中时,两者聚合;B过小,两者反弹;B过大,两者拉伸分离。在实验的We范围内,3种结果中聚合情况最多。由此,根据相似性可以解释在钢液中少见液滴夹杂物的原因。     

Finite element analysis of the bulge defect forming and eliminating on tube continuous rolled by full floating mandrel mill

Based on the ABAQUS explicit dynamic simulation platform,the finite element model of single stand mill with restrained mandrel was adopted to research the influence of mandrel - roller velocity ratio (MRVR),mandrel friction and tension between stands on rolling force.The analysis results show that when the MRVR is lower than 1,the rolling force increases obviously with the increase of MRVR and reaches the peak value when the MRVR is about 1.The rolling force increase induced by the MRVR increase is the main reason of the formation of the bulge defect on the tube head and tail at the entering and exiting stage during tube continuous rolling process by full floating mandrel mill,which can be intensified by the increase of mandrel friction coefficient.The rolling force decreases with the increase of tension.As the tension is larger, the rolling force decrease amplitude is larger.The influence of backward tension on rolling force is greater than that of forward tension distinctly.Tension control can be used to decrease the rolling force increase induced by the MRVR increase,which is imposing tension at the same time when the MRVR increases,in order to improve even eliminate the bulge defect,and enhance the tube dimension precision.     

超声搅拌和气体搅拌去除夹杂物

 通过水模型实验，对同一容器内相同比搅拌功率条件下，超声搅拌和气体搅拌对去除夹杂物的影响进行了对比研究。结果表明：超声搅拌的空化作用可产生的大量小气泡增大了吸附面积，延长了气泡的上浮时间，有利于夹杂物的去除，可以充分发挥容器器壁粘附夹杂物的作用，保护液体不受外界污染；气体搅拌时，夹杂物去除速率快、效率高。两种搅拌方式去除夹杂物的效率均随比搅拌功率的提高而增大，但比搅拌功率对气体搅拌的影响更加显著。     

超重力场下钢液中夹杂物上浮行为的数值模拟

 超重力技术可以有效提高固液两相间的重力差,在冶金领域,超重力场的引入可以大幅度增加金属熔体中夹杂物的去除效率。基于超重力冶金装置模型,根据动网格与流-固耦合理论,建立了不同重力场下固态夹杂物在钢液中上浮的流体动力学模型。该模型模拟了夹杂物在不同系数的重力场中上浮的运动状态,研究了超重力场中的重力系数与夹杂物尺寸等因素对颗粒上浮和流场分布的影响。模拟结果表明,在重力场系数恒定时,夹杂颗粒经短暂的加速上浮过程后,后续的上浮运动将趋于匀速,夹杂物的上浮速度会随着施加重力场的增大而增长,夹杂物附近的钢液也会被更快地“推开”,从而出现改变流动状态的趋势。尺寸d为1、10 μm的夹杂物颗粒由于其尺寸较小,在施加一定的超重力场后仍满足Stokes上浮模型;尺寸d为100 μm的大尺寸夹杂物则仅在约10倍重力场作用下符合Stokes上浮模型,当施加更大的重力场时,夹杂物附近的流场会由层流流动转变为湍流流动,不再满足Stokes定律。在研究不同系数重力场中夹杂物上浮的模型时发现,当重力场的系数大小随时间变化时,尺寸为1 μm量级的小尺寸夹杂上浮速度的变化幅度与重力场的变化幅度呈正比;而尺寸为10、100 μm的夹杂物在脱离层流流场后,上浮速度与重力场不再呈线性关系。     

Inclusion Composition Control During LF Refining for SPCC Using FactSage Combined With Industrial Trials

Steel plate cold common (SPCC) is a Al-killed steel with Ca-treatment. The control of Al2O3 inclusion into low melting point liquid region is beneficial for inclusion removal, cast-ability promotion and defects reduction during rolling. Thus it is essential to understand steel-inclusion equilibrium since inclusion composition is determined by composition of liquid steel directly through steel-inclusion reaction. Thermodynamic calculation software FactSage is performed to understand how to control inclusion composition during ladle furnace (LF) refining, and industrial trials are carried out to verify calculated results. Firstly, target region for controlling CaO-Al2O3-MgO ternary inclusion is analyzed on the basis of the ternary phase diagram and the relationship between activities related to pure solid and activities related to pure liquid was fixed by thermodynamic analysis in order to obtain reliable activities for components of inclusions in the target region by FactSage. In addition, inclusions in steel samples are detected by scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS). It is found that most of Al2O3 inclusions are modified into lower melting point region but a number of them are still located in high melting point region at the end of LF refining after Ca-treatment. Moreover, the composition of liquid steel equilibrating with liquid CaO-Al2O3-MgO inclusion is obtained by steel-inclusion equilibrium calculation when w[Al]s is approximating 0.03% as: a[O] is 1.0×10-6 to 4.0×10-6, w[Ca] is 20×10-6 to 50×10-6 and w[Mg] is 0.1×10-6 to 3.0×10-6. At last, stability diagrams of various calcium aluminates and CaS are established and they show that liquid calcium aluminate inclusions form when w[Ca] is more than 20×10-6, but CaS precipitation is difficult to prevent because sufficiently low w[S] (<0.003%) is required.     

连铸中间包钢液中凝聚态氧化铝夹杂物运动行为的数值模拟

在Euler-Lagrange框架下,基于应用分形理论对凝聚态Al₂O₃夹杂物形貌结构进行定量分析的基础上,数值模拟研究了连铸中间包钢液中不同形貌凝聚态Al₂O₃夹杂物的运动行为.研究发现中间包钢液流场和夹杂物形貌尺寸共同影响夹杂物在钢液中的运动行为.随着尺寸的变大,簇群状和致密球形两种形貌Al₂O₃夹杂物上浮去除率都逐渐增加.在相同尺寸下,簇群状Al₂O₃夹杂物上浮去除率比致密球形Al₂O₃夹杂物低;随着尺寸的增加,簇群状Al₂O₃夹杂物上浮去除率相比于同尺寸致密球形Al₂O₃夹杂物降低得就越多.计算结果显示,与同尺寸的致密球形Al₂O₃夹杂物相比,直径为20、40、60和80μm的簇群状Al₂O₃夹杂物上浮去除率分别降低了4.8%、5.7%、6.4%和12.5%.      

模具钢电渣重熔铸坯凝固组织形貌的分形特征

为了更为精细化地表达及控制铸坯质量,以H13模具钢电渣重熔铸坯凝固组织为研究对象,引入分形维数对其主体形貌特征进行定量描述。结果表明,基于数盒子法计算得到的分形维数可定量表征凝固组织形貌的自相似复杂程度,其值从柱状晶向中心等轴晶先减小后增大;凝固组织分形维数可作为衡量铸坯偏析程度（偏析率大小）的指标,且分形维数越大,对应区域偏析率越小,偏析越轻;通过凝固组织分形维数、偏析率和偏析点平均面积与二次枝晶间距关系的研究发现,使用二次枝晶间距表征铸坯凝固组织形貌差异并由此反映偏析程度的方法存在局限性。     

莱钢连铸20CrMnTiH钢非金属夹杂物研究

利用大样电解法、LEO-1450型能谱分析仪和NEOPHOT-32型金相显微镜对连铸生产的20CrMnTiH钢中非金属夹杂物的种类、含量、来源、形状、尺寸及分布等进行了研究。结果表明,精炼前夹杂物数量多,颗粒较大,类型主要为硅钙、硅锰酸盐等;中间包中主要为硅酸盐类型的球形和玻璃状夹杂物;铸坯中主要为硅铝酸盐球形夹杂物。经LF精炼后,非金属夹杂物去除率可达99％以上。     

Interactions of elastin fibers with fibroblasts a time-lapse cinemicrographic study

Adhesion of cells to the extracellular matrix is mediated by structural glycoproteins such as fibronectin and laminin, and also elastonectin, whose role is to ensure binding of elastin fibers to cells. Interactions between elastin fibers and human skin fibroblasts cultured in a Rose chamber were investigated by using cinemicrography to observe elastin fiber attachment, detachment, and displacement over a five-day period. Elastin fiber displacement over the cell layer resulted in aggregation, which was measured using morphometry. The total number of isolated elastin fibers or aggregates decreased between 1 h and 8 h and remained stable thereafter. During the same time interval, significant decreases occurred in the numbers of isolated fibers and small aggregates (perimeter < 0.268 mm; surface area < 894 microns 2), whereas larger aggregates were formed. After 15 hours of interaction, none of the aggregates had a perimeter greater than 0.536 mm, consistent with an increase in aggregate compacting. These data demonstrate that elastin-cell interactions do not occur at random. These interactions may play a pivotal role in morphogenesis and in maintaining the integrity of elastic tissues such as the arterial wall, lungs, and skin.     

等离子喷涂氧化钇稳定氧化锆涂层的分形特征与断裂韧性

采用超音速等离子喷涂和普通大气等离子喷涂制备了微米级氧化钇稳定氧化锆（yttria-stabilized zirconia,YSZ）基热障涂层,使用SprayWatch-2i系统测试喷涂过程中粒子飞行速度及表面温度,通过扫描电镜和图像分析技术表征涂层微观结构,利用压痕法测试了断裂韧性和弹性模量,采用基于分形思想的面积-周长幂率定量表征两种工艺条件下孔隙不规则形态,并研究了分形维数对涂层断裂韧性的影响。结果表明:超音速等离子喷涂和普通大气等离子喷涂YSZ涂层孔隙都具有分形特性;超音速等离子喷涂YSZ涂层分形维数是普通等离子喷涂涂层的1.12倍,孔隙结构更复杂,涂层断裂韧性更高。     

Ce对2.9%Si-0.8%Al无取向硅钢夹杂物变质的影响

研究了添加单一稀土元素Ce后2.9%Si-0.8%Al无取向硅钢中夹杂物的变质机理。依据冶金热力学理论计算了Ce添加后,钢液中可能生成的夹杂物种类,分析了各种夹杂物存在的稳定性和相互转化的条件。在此基础上,利用SEM、EDS研究了Ce对无取向硅钢中夹杂物数量、尺寸、形貌及类型的影响。结果表明:适量的Ce显著降低了无取向硅钢中微细夹夹杂物(小于1μm)的数量,增加了粗大夹杂物(2~5μm)数量;Ce使AlN、Al_2O_3等夹杂物变性为球状的CeO_2S_2+AlN、CeS+CeAlO_3和CeS+Al_2O_3等复合夹杂物,有效抑制了钢中MnS的析出。     

不同氧化镁含量烧结矿粒度分布的分形研究

通过对不同MgO含量烧结矿破碎体的筛上、筛下物分布规律的研究,计算得出了烧结矿粒度分布的分形维数,线性相关系数均大于0.97,说明使用分形维数定量表征烧结矿在不同MgO含量条件下的粒度组成是可行的.结果表明:分形维数随着MgO含量的增加而增加,在一定程度上可以定量估测烧结矿中MgO含量的范围,并结合微观结构,合理解释了转鼓强度、成品率和分形维数之间的关系.为更加深入表达不同MgO含量的烧结矿的有关数值模型提供了新的理论依据和研究方法.     

Aggregation Kinetics of Inclusions in Swirling Flow Tundish for Continuous Casting

 The mechanism of inclusion aggregation in liquid steel in swirling flow tundish is analyzed by applying the theory of flocculation which was developed in the field of colloid engineering. The gas bridge forces due to the micro bubbles on hydrophobic inclusion surfaces were considered responsible for the inclusion collision and agglomeration, which can avoid the aggregation to breakup. The quantity of micro bubbles on hydrophobic inclusion particle is more than that on hydrophilic one. The trend of forming gas bridges between micro bubbles on particles is strong in the course of collision. The liquid film on hydrophobic particles is easy to break during collision process. Hydrophobic particles are liable to aggregate in collision. According to the analysis of forces on a non-metallic inclusion particle in swirling chamber, the chance of inclusion collision and aggregation can be improved by the centripetal force. Hydrophobic particles in water are liable to aggregate in collision. Hydrophilic particles in water are dispersed although collision happens. The wettabiliy can be changed by changing solid-liquid interface tension. The non-metallic inclusion removal in swirling flow tundish is studied. It shows that, under certain turbulent conditions, the particle concentration and the wettability between particles and liquid steel are the main factors to induce collision and aggregation.