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Oxide inclusion behavior at the steel/slag interface.

机译：钢/渣界面处的氧化物夹杂行为。

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摘要

The presence of nonmetallic inclusions in steel, particularly oxides such as alumina and calcia-alumina, contribute to problems during steelmaking and can negatively affect the appearance and mechanical properties of final products. A cleaner steel has better formability and is less prone to fatigue and corrosion. Furthermore, during steel production in the melt state, a cleaner steel is less prone to cause process control problems such as clogging during pouring and teeming.; The removal of inclusions has been studied previously in both experimental dissolution in slags and in steel melt flow models, where the positions of simulated inclusions are tracked computationally. This study is an examination of the steps between these, where inclusions approach the steel/slag interface and separate across it. Because the interface is known to be of high energy, often with a chemistry different from the bulk, the effect on any inclusions close to that interface is of critical importance. The near-interface behavior of inclusions during removal is separated into two parts, (i) the actual separation across the interface, and (ii) the approach to the interface and the interface's resulting deformation.; In this research, previous models for the removal of inclusions, as it relates to the steel/slag interface, are studied and expanded upon to include alternate shapes and reactions between phases. It is observed that aluminum oxide inclusions of 5 to 100 mum are typically not impeded by the interface during the separation step using ladle, tundish, and mold slags of moderate viscosity (0.06 to 0.6 kg/m/s), requiring only microseconds to milliseconds (respectively) to separate. Certain values of the interfacial tension between slag and inclusion, sigmaIS, can however cause spherical inclusions to become trapped at the interface due to the change in overall energy (interfacial tensions between a calcia-silica-alumina slag and the liquid metal are on the order of 1 N/m, but are typically 0.2 N/m or less between solid alumina and similar slags). This value is studied experimentally, finding that for typical situations, sigmaIS is not large enough to directly cause settling of alumina inclusions at the interfaces of ladle, tundish, or mold slags. The expanded separation model considers the effect of shape on separation for octahedrons and plates, and the effect of dissolution occurring alongside separation. In this manner, the limiting factors and 'lifetime' of an inclusion at the steel/slag interface is described, so that inclusions that do not fully separate (and settle in local energy minimums) are limited by the dissolution due to the inclusion surface exposed to the slag, and does not remain trapped indefinitely. A high slag viscosity can slow an inclusion during this transition to a settled state several times compared with lower viscosities, and the initial speed, which for high values causes a small delay due to the transition to a preferred speed. However, neither of these effects cause separation to reach critically important times. The other shapes examined have similar separation times, though do not have settling points. This would appear to indicate that for most situations, the removal of alumina inclusions are not impeded by their separation at the steel-slag interface, except in unlikely situations.; Because previous models only considered inclusions already in contact with - or very close to - the interface, a description of the initial approach of an inclusion to the interface is described via fluid dynamics, wherein the particle decelerates in the bounded fluid and eventually deforms the interface. Micrometer-sized particles are slowed considerably (1.7 seconds) due to a limited drag field, while larger inclusions cause more significant deformation, which can delay the final point of rupture by almost two seconds, even if their initial slowdown due to a limited drag field is small.; To verify these results, a water-oil tank
机译：钢中非金属夹杂物的存在，特别是氧化铝和氧化钙-氧化铝之类的氧化物，会在炼钢过程中造成问题，并对最终产品的外观和机械性能产生负面影响。清洁的钢具有更好的可成形性，并且不易疲劳和腐蚀。此外，在熔融状态的钢生产过程中，较纯净的钢不易引起工艺控制问题，例如在浇铸和浇铸过程中发生堵塞。先前已经在炉渣和钢水流动模型中的实验溶出中研究了夹杂物的去除，其中通过计算跟踪了模拟夹杂物的位置。这项研究是对这两个步骤之间的步骤的检查，其中夹杂物接近钢/炉渣界面并在其中分开。由于已知该界面具有高能量，通常具有与本体不同的化学性质，因此对靠近该界面的任何夹杂物的影响至关重要。夹杂物在去除过程中的近界面行为可分为两部分：（i）跨界面的实际分离，以及（ii）接触界面的方法和界面引起的变形。在这项研究中，与钢/矿渣界面相关的先前消除夹杂物的模型得到了研究和扩展，以包括相之间的交替形状和反应。观察到，在使用中等粘度（0.06至0.6 kg / m / s）的钢包，中间包和铸型渣的分离步骤中，界面通常不会阻碍5至100微米的氧化铝夹杂物，仅需几微秒至几毫秒的时间（分别）分开。矿渣与夹杂物之间的某些界面张力sigmaIS值可能会导致球形夹杂物由于总能的变化而被截留在界面处（氧化钙-硅铝氧化物矿渣和液态金属之间的界面张力约为固体氧化铝和类似的炉渣之间的最大粘度为1N / m，但通常为0.2N / m或更小。通过实验研究该值，发现在典型情况下，sigmaIS不足以直接导致钢包，中间包或铸模渣界面处的氧化铝夹杂物沉降。扩展的分离模型考虑了八面体和板的形状对分离的影响，以及在分离过程中发生溶解的影响。以这种方式，描述了钢/炉渣界面处夹杂物的限制因素和“寿命”，因此由于夹杂物表面暴露，溶解不充分限制了夹杂物不能完全分离（并以局部最低能量沉降）。渣，并且不会无限期地被困住。与较低的粘度相比，高的炉渣粘度可在此过渡到沉降状态的过程中使夹杂物减慢几倍，并且初始速度（初始值较高）会因过渡到最佳速度而导致较小的延迟。但是，这些影响均不会导致分离达到至关重要的时间。尽管没有沉降点，但检查的其他形状具有相似的分离时间。这似乎表明，在大多数情况下，铝夹杂物的去除不受钢渣界面处分离的阻碍，除非在极少数情况下除外。因为先前的模型仅考虑已经与界面接触或非常接近界面的夹杂物，所以通过流体动力学描述界面夹杂物的初始方法的描述，其中粒子在结合流体中减速并最终使界面变形。微米大小的颗粒由于有限的阻力场而显着减慢（1.7秒），而较大的夹杂物会引起更大的变形，即使由于有限的阻力场而使它们的初始速度变慢，也可以将破裂的最终点延迟近两秒钟是小。;为了验证这些结果，水油箱

著录项

  • 作者

    Shannon, George Newlin.;

  • 作者单位

    Carnegie Mellon University.;

  • 授予单位 Carnegie Mellon University.;
  • 学科 Engineering Metallurgy.; Physics Fluid and Plasma.; Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 126 p.
  • 总页数 126
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 冶金工业;等离子体物理学;工程材料学;
  • 关键词

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