20CrMnTi齿轮钢中TiN夹杂物的特征与分布

为了研究含钛齿轮钢中TiN夹杂物的析出与控制,利用扫描电镜对20CrMnTi齿轮钢两个端淬试样中TiN夹杂的分布与形貌进行了观察,通过夹杂物自动分析系统统计了试样中TiN夹杂的尺寸、数量,建立了数学模型,对试样中TiN夹杂的析出与长大进行了计算。结果表明,较高钛含量的试样凝固过程中TiN析出更早,析出量也更大,由于析出了更多数量的TiN夹杂,从而使得析出TiN夹杂的最终尺寸更小,当TiN夹杂的数量密度由37.28增加为58.65个/mm2时,TiN平均尺寸由2.33减小为1.49 μm。通过在凝固过程中为TiN夹杂提供充足数量的氧化物颗粒作为析出核心,提高异质形核率,从而增大TiN的析出数量,就可以降低析出TiN的整体尺寸,这为含钛齿轮钢中TiN夹杂物的控制提供了一种新的思路。     

脱氧后氧化铝夹杂物的特征

许多冶金工作者在去除钢中的非金属夹杂物的工作中做了很多努力，但是，近年来，用户对钢质的洁净度要求越来越高。为了满足用户的需求，不仅需要考虑去除夹杂物的有效方法，而且需要考虑如何使夹杂物尺寸保持较小的对策。因此，研究调整夹杂物在钢中分布尺寸的控制因素至关重要，根据上述观点，在试验室规模的试验中，当铝和氧含量不同的范围时，用一种新的取样方法研究钢水脱氧反应后氧化铝夹杂物的初始尺寸分布。在Tammann炉内，将2kg钢熔化，试验温度为1873K，用Ar作为保护气体，然后调整碳和氧的浓度。加铝后方可进行取样操作，用电子探针显微分析仪测量钢中氧化铝夹杂物尺寸分布，该分析仪带有LaB6的电子射线枪，同时配有用于微粒分析的最新开发软件：结果表明：氧化铝夹杂物的尺寸分布受钢中氧含量影响，并且其在脱氧后1s内的长大过程被认为是由氧扩散控制。     

45A钢方坯夹杂物行为研究

为了了解45A钢铸坯夹杂物行为,利用显微镜、电子探针和大样电解等分析方法对45A钢铸坯中夹杂物分布、数量和种类做了分析。结果表明:铸坯夹杂物整体控制水平较好,其中铸坯夹杂物指数平均为22.2个/mm2,铸坯中心夹杂物指数为25.8个/mm2;铸坯大样电解结果表明大型夹杂物总量平均为2.23 mg/(10 kg),夹杂物直径都大于300μm;大型夹杂物主要来源于结晶器卷渣、氧化产物和中间包覆盖剂等。     

帘线钢小方坯夹杂物的控制

阐述了帘线钢对夹杂物的要求,及夹杂物对盘条性能的影响。针对本钢北营炼钢厂小方坯连铸机生产的帘线钢出现的夹杂物断丝的问题,通过检测分析得出其主要夹杂物为钛夹杂、铝夹杂、铝镁复合夹杂、氧化钾及氧化钠等。从夹杂物的产生机理入手,通过对钛来源进行控制、炼钢全流程控氮降低氮化钛析出,精炼渣系调整及铝含量控制避免纯Al2O3析出,精炼过程碱度的调整和萤石量降低避免耐材侵蚀MgO析出,连铸液面自动控制改进避免卷渣后钾钠氧化物夹杂带入,工艺优化后再未出现钛夹杂超标以及夹杂物引起的断丝率超标问题。     

原位生成六铝酸钙对刚玉质多孔材料结构和性能的影响

为解决多孔透气材料力学强度与透气性能两者之间的矛盾, 以纯铝酸钙水泥为钙源, 在刚玉质多孔材料中原位生成六铝酸钙相, 研究了六铝酸钙生成量对多孔材料显微结构、物相组成及物理性能的影响。结果表明: 在1700℃保温3 h处理后, 添加纯铝酸钙水泥的试样中均有板状片六铝酸钙生成。当纯铝酸钙水泥添加量(质量分数)不超过3%时, 六铝酸钙的原位生成不仅提高了多孔材料的常温耐压强度和高温抗折强度(1400℃保温0.5 h), 还能改善材料的透气性能; 继续增加纯铝酸钙水泥的加入量, 多孔材料的上述性能降低。当纯铝酸钙水泥添加量(质量分数)为3%时, 试样常温耐压强度为33.6 MPa, 高温抗折强度为6.2 MPa, 达西渗流系数及非达西渗流系数分别为2.54×10-10 m2和1.46×10-6 m。     

Formation of Low-Melting-Point Inclusions in Al-Deoxidized Steel Refined by High-Basicity Calcium Aluminate Slag in ZrO2 Crucible Experiments

ZrO₂ crucible experiments were carried out in the laboratory to study the formation of low-melting-point inclusions in steel, during which aluminum deoxidization and a high-basicity calcium aluminate refining slag (CaO/SiO₂: 6 to 8, Al₂O₃ 40 to 45 pct) were used. Four experiments were done with different slag/steel reaction times (30, 60, 90, and 180 minutes). It was found that inclusions were mainly composed of CaO-Al₂O₃-ZrO₂ with very limited SiO₂, in spherical morphology and with sizes mainly less than 5 μm. They can be classified into two types according to the ZrO₂ content. The first type contained much lower ZrO₂, whereas a much higher level of ZrO₂ was detected in the other type. An evolution of inclusions with the reaction time was observed and studied. The obtained results indicated that chemical compositions of inclusions were widely scattered in the CaO-Al₂O₃-ZrO₂ phase diagram after 30 min reaction. However, the composition of inclusions became much more uniform and concentrated in low-melting-temperature regions at 60, 90, and 180 minutes, which would be favorable to prevent nozzle clogging and fatigue problems. Compared with the authors’ previous results obtained in MgO crucible experiments, it was found that low-melting-temperature inclusions can be targeted in shorter time in ZrO₂ crucible experiments, without any degradation of cleanliness.     

铝酸钙炉渣冶金性能研究进展

简单介绍了炉渣在冶炼过程中的作用与重要性。分别对四元、五元、六元及六元以上铝酸钙炉渣冶金性能的研究现状归纳和总结。并提出了应加强对高碱度、高元铝酸钙炉渣冶金性能的研究。     

Transformation of Alumina Inclusions by Calcium Treatment

The objectives of this study were to investigate reactions of calcium with Al₂O₃ by different model experiments both on the laboratory and on the industrial scale. Experiments with solid Al₂O₃ and CaO were performed between 1350 °C and 1600 °C. Reaction rate constants were determined based on scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) observations of reaction products and weight measurements of the Al₂O₃ reacted via dissolution of the CaO bearing phases from the specimens after the annealing period. The results showed that the formation of calcium aluminate phases proceeded rapidly at temperatures greater than 1405 °C when a liquid calcium aluminate was formed. In the lowest temperature range (1350 °C–1405 °C), when the formation of liquid phase ceased, the reaction rate was several orders of magnitude lower. Industrial trials including Ca-alloy injection into steel, sampling and SEM/EDS analyses, as well as an inclusion rating in the samples show the concept of rapid transformation of the alumina inclusions with Ca treatment.     

<Emphasis Type="Italic">In Situ</Emphasis> Observation of Calcium Aluminate Inclusions Dissolution into Steelmaking Slag

The dissolution rate of calcium aluminate inclusions in CaO-SiO₂-Al₂O₃ slags has been studied using confocal scanning laser microscopy (CSLM) at elevated temperatures: 1773 K, 1823 K, and 1873 K (1500 °C, 1550 °C, and 1600 °C). The inclusion particles used in this experimental work were produced in our laboratory and their production technique is explained in detail. Even though the particles had irregular shapes, there was no rotation observed. Further, the total dissolution time decreased with increasing temperature and decreasing SiO₂ content in the slag. The rate limiting steps are discussed in terms of shrinking core models and diffusion into a stagnant fluid model. It is shown that the rate limiting step for dissolution is mass transfer in the slag at 1823 K and 1873 K (1550 °C and 1600 °C). Further investigations are required to determine the dissolution mechanism at 1773 K (1500 °C). The calculated diffusion coefficients were inversely proportional to the slag viscosity and the obtained values for the systems studied ranged between 5.64 × 10^?12 and 5.8 × 10^?10 m²/s.     

Desulphurization of Hot Metal and Ferronickel With Calcium Aluminate Fluxes

Traditionally, fluxes containing calcium fluoride and other additives are used for the treatment of hot metal and molten steel. Recently, magnesium powder or lime-Mg mixture is used more popularly in hot metal desulphurization. However, the use of calcium fluoride has been restricted due to environmental concerns, and the supply of magnesium is uncertain for the countries, which are short of magnesium resource. For those reasons, calcium aluminate fluxes are a possible alternative to replace slags containing calcium fluoride or magnesium. Calcium aluminate fluxes can be produced from three different raw materials: (1) high-quality bauxite, (2) residuals from aluminum dross treatment processes and (3) waste products from alumina production. Due to the limited amount and high cost associated with high-quality bauxite, the other two sources are preferred based on both economic and environmental considerations. The objective of this paper is to examine the use of waste slags and by-products from the aluminum industry as potential refining fluxes for the steel industry so that waste disposal from the aluminum industry can be reduced with economical and environmental benefits for both industrial sectors.     

微波加热技术在铝酸钙炉渣浸出过程中的应用

在微波辐射加热条件下考察了微波辐射功率、浸出用液的Na2Oc质量浓度、液固比等对高炉铝酸钙渣的浸出过程的影响,并与传统加热浸出进行了比较。结果表明,氧化铝浸出率和反应体系的温度随着微波辐射功率的提高而增加。在温度未达到溶液沸点之前,反应体系为非恒温反应过程。微波辐射浸出与传统加热浸出相比较,微波辐射加热下炉渣中氧化铝浸出速率较传统加热方式浸出快得多,微波浸出可降低浸出用液的Na2Oc质量浓度,缩短浸出时间。     

Mechanism Study on the Formation of Liquid Calcium Aluminate Inclusion from MgO‐Al2O3 Spinel

A study on the formation mechanism of liquid calcium aluminate inclusions from MgO‐Al₂O₃ spinel was carried out. It was found that spinel reacted with dissolved Ca in liquid steel forming liquid calcium aluminate phase. Stability calculations showed good agreement with the experimental result. According to the thermodynamic calculation, liquid calcium aluminate inclusions would form from spinel even at very low level of dissolved Ca content at 1873 K. At lower temperatures, the compound CaO‐2Al₂O₃ was found to be the stable phase at the spinelmetal interface. Potential sources of dissolved Ca during ladle processes were also discussed.     

Calcium Modification of Inclusions via Slag/Metal Reactions

Metallurgical and Materials Transactions B - This paper examines the consistency between experiments and thermodynamic predictions of the modification of non-metallic inclusions by dissolved Ca in...