Optimization of Intensified Silicon Deoxidation

For demanding wire applications steel cleanliness should be very high and the inclusions inevitably found in steel should be harmless. This means strict control of inclusions' size, quantity, and composition, pursuing deformable inclusions in rolling conditions. Primary inclusions are formed during steel treatment in the ladle. Most of these are removed to the ladle slag or on the lining. However, the rest of the inclusions still remain through the successive process stages, and some new inclusions are formed during casting and solidification. Conventionally, deformable inclusions are produced by Si–Mn deoxidation resulting in MnO–SiO₂–Al₂O₃ inclusions. This leaves, however, the oxygen content too high for demanding applications. In order to get really clean steel, the Si deoxidation needs to be strengthened by lowering the activity of SiO₂ forming in steel. This can be done by bringing the steel in intimate contact with a slag containing SiO₂–MnO–Al₂O₃ and additionally CaO and some MgO. With this kind of intensified Si deoxidation it is possible to produce steels with low oxygen content having inclusions that will elongate at rolling. In this paper thermodynamic examination of potential slag systems and compositions to equilibrate with steels having medium carbon and high silicon were scrutinized. The optimal slag composition for producing low‐O steels with deformable inclusions was evaluated by using FactSage thermodynamic calculation program. The lowest SiO₂ activities at the region in which slag is still liquid at 1400°C, can be found when slag composition is approximately 36–40 wt% SiO_2, 6–18 wt% Al₂O_3, 30–40 wt% CaO, 6–8 wt% MgO, and 2–4 wt% MnO. Industrial heats using intensified Si deoxidation and slag based inclusion engineering were produced in a steel mill with 60 tons heat size. Inclusions and slag compositions were in satisfactory accordance with the theoretical examinations, though some scattering was discovered.     

20SiMn合金结构钢精炼渣系优化

为控制20SiMn锻件用结构钢中氧含量和钢中夹杂物，首先采用热力学软件FactSage 8.1计算了1 600℃下CaO-SiO₂-Al₂O₃-5%MgO系精炼渣与20SiMn钢液平衡时的等氧线，并优化了精炼渣成分。同时，计算了不同氧含量下钢中Fe-Mg-Al-O体系优势区图。其次，实验室中设计了4组精炼渣成分，并在1 600℃下采用高温电阻炉进行渣-钢平衡试验，试验后采用X射线荧光光谱分析测定渣成分，采用等离子体光谱仪对钢样成分进行分析，采取红外碳硫分析仪、氧氮联合分析仪分别测定钢中碳硫和全氧含量，采用场发射扫描电子显微镜对试样中的夹杂物进行成分和形貌分析，并对钢中夹杂物数量与成分进行统计，试验研究了不同精炼渣对钢中氧含量、夹杂物组成、数量和尺寸的影响。最后，建立了动力学模型来描述“钢渣”界面上的夹杂物去除行为。试验和热力学模型结果揭示了钢中典型Al₂O₃、MgO·Al₂O₃夹杂物与钢中氧、镁和铝含量的关系，动力学模型描述了夹杂物分...     

30Cr1Mo1V汽轮机转子钢的精炼渣优化

摘要：为有效控制30Cr1Mo1V汽轮机转子钢中非金属夹杂物和有害杂质元素含量,利用热力学软件FactSage 8.1,计算了1873K下CaO-SiO2-Al2O3-5%MgO系精炼渣与30Cr1Mo1V钢液平衡时的等［O］线、等［S］线,以获得最优精炼渣成分范围。研究了不同精炼渣对钢中氧、硫含量,夹杂物特性的影响,继而揭示了钢中典型MgO·Al2O3夹杂物的热力学形成机制以及夹杂物与精炼渣之间的成分关系,并构建了“钢 渣”界面MgO·Al2O3夹杂物运动模型。实验和模型结果表明,优化渣系50.4%CaO-40-3%Al2O3-4.3%SiO2-5%MgO对钢液脱氧、脱硫和非金属夹杂物控制的效果明显,模型预测结果与夹杂物去除率对应关系良好。     

H08A焊丝钢夹杂物演变规律分析

为了提高H08A焊丝钢的拉拔性能和焊接性能,对该钢种全流程进行取样分析,利用扫描电镜观察夹杂物的形貌,统计数密度,利用夹杂物自动分析系统对夹杂物成分变化和成分分布进行分析,利用FactSage热力学软件分析夹杂物低熔点区域分布。结果表明,钢中全氧含量可间接反映出夹杂物数密度水平,若没有LF精炼和中间包保护浇铸,铸坯中全氧很难达到要求的0.005%。夹杂物类型主要是硅锰铝氧化物的复合夹杂物,脱氧合金化后,夹杂物成分趋于稳定,大尺寸夹杂物多为MnO-SiO₂-Al₂O₃,尺寸最大达到70 μm。钙收得率不高,在夹杂物中没有发现典型钙氧化物夹杂物。夹杂物主要是球形,大尺寸夹杂物总量较多,中间包和铸坯中80 μm以下大尺寸夹杂物占比较小,80 μm以上大尺寸夹杂物占比为87.6%~87.9%。     

国内外油井管钢中非金属夹杂物的对比分析

 为了提高国内油井管钢质量,采用扫描电镜对比了日本和国内油井管钢中夹杂物成分和形貌,统计了夹杂物尺寸分布、夹杂物间距和夹杂物分布等参数,基于FactSage热力学软件平衡凝固模型分析了冷却过程中夹杂物的演变过程,基于夹杂物碰撞数量平衡模型,讨论了油井管钢中夹杂物碰撞率。结果表明,日本油井管钢中夹杂物主要为CaS包裹的镁铝尖晶石,国内油井管钢中夹杂物主要为钙铝酸盐包裹的镁铝尖晶石夹杂物和纯镁铝尖晶石夹杂物。日本油井管钢夹杂物比国内油井管钢夹杂物数量少、尺寸小、分布更均匀。日本油井管钢中夹杂物数量密度达到7.5个/mm2,国内油井管钢中夹杂物数量密度达到28.3个/mm2。日本油井管钢中夹杂物最大尺寸不超过5 μm,国内油井管钢中夹杂物最大尺寸达到20 μm。FactSage计算冷却过程中夹杂物演变结果与试验结果吻合。国内油井管钢中夹杂物碰撞率比日本油井管钢中夹杂物的碰撞率高2个数量级。     

钢中微细夹杂物的评价方法

为了对钢中微细夹杂物进行有效的分析评价,本文以氧化物冶金工艺引入的小粒径、均匀且弥散分布的夹杂物为例,建立了一种对微细夹杂物的粒径及分布、成分和形貌进行分析评价的方法。以扫描电子显微镜、透射电子显微镜和能谱分析仪相结合对钢中微细夹杂物进行分析,发现了采用氧化物冶金工艺的钢中夹杂物主要成分所生成的粒子为以MgO、CaO为核心,外层包缚着MnS的细小夹杂物;含Mg的氧化物粒子的形状为长方体, 表面平整光滑,边缘处棱角分明, 大小约为1 μm×0.8 μm×0.3 μm。同时还发现用氧化物冶金工艺的钢其微细夹杂物数量明显高于用常规冶炼工艺的钢。采用本方法可以对钢中微细夹杂物进行较为系统、全面的评价分析。     

Thermodynamics for Precipitation of CaS Bearing Inclusion and Their Deformation During Rolling Process for Al‐Killed Ca‐Treated Steel

Thermodynamics for CaS bearing inclusions precipitation and their deformative behaviors during compact strip production (CSP) rolling process for Al‐killed calcium treatment steel were researched using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) combined with the results of industrial trials. In addition, thermodynamic software FactSage was applied to calculate component activities of an inclusion and to analyze properties of sulfide‐oxide duplex inclusions. It is possible for CaS bearing inclusion precipitation during secondary refining and continuous casting in two manners: the first is that Ca and S react directly after calcium treatment; the other is as the well modified calcium aluminates react with dissolved sulfur and aluminum in liquid steel. Correspondingly, two types of sulfide‐oxide duplex inclusion were observed in casting slab. For the first type duplex inclusion, nearly no chemical reactions occur between outer CaS layer and solid inclusion core, thus the outer CaS rich layer is easily separated even taken off from the inner core during rolling process, and a crack may be generated correspondingly. The later one performs a better deformation during rolling process.     

高碱度精炼渣对GCr15轴承钢洁净度的影响

 利用实验室渣-钢平衡试验研究了高碱度精炼渣对GCr15轴承钢中[w(T[O])]和夹杂物的影响。结合试验结果和热力学分析,探讨了钢中[w(T[O])、]夹杂物尺寸分布和粒径大小的变化规律,以及氧化物夹杂的转变过程。研究结果表明,碱度为6时,精炼渣(59.4%CaO-24.8%Al2O3-9.8%SiO2-6%MgO)可将钢中[w(T[O])]控制在0.000 6%以内,氧化物夹杂平均尺寸最小为2.26 μm。随着钢中[w([Ca])]和[w([Mg])]的增加,钢中氧化物夹杂转变过程为Al2O3→MgO·Al2O3→MgO→CaO-Al2O3-MgO复合夹杂物(核心为MgO,外围包裹着CaO-Al2O3)。渣-钢反应前期钢中以MgO·Al2O3为主,后期以MgO和CaO-Al2O3-MgO复合夹杂物为主。氧化物夹杂转变的试验结果与热力学分析结果相一致,大多数氧化物夹杂尺寸小于5 μm。     

低碳低硅钢连铸过程的非金属夹杂物研究

采用扫描电镜、金相法对湘钢连铸坯生产过程中非金属夹杂物的数量、类型、组成及分布等进行了研究找出了目前生产工艺中外来非金属夹杂物的来源,即钢包中炉渣对钢水的污染、无长水口保护时空气对钢水的二次氧化以及注流冲击卷渣产生的非金属夹杂物.保护状态下铸坯中非金属夹杂物数量为3.7~6.5个/mm2;敞开状态下数量为 4.1~7.3个/mm2.提出应加强炉渣控制、完善钢水保护条件及优化中间包流场等措施,进一步提高低碳低硅钢质量的思路.     

石油套管钢管壁内缺陷的形成机理

针对某石油套管钢管壁内缺陷,采用扫描电镜?能谱仪（SEM-EDS）分析,并结合FactSage8.0软件计算进行研究,结果表明缺陷纵向面主要由浅条纹及深条纹组成,浅条纹处存在大量MgO·Al₂O₃夹杂物,深条纹处有大量的Al₂O₃、MgO·Al₂O₃、CaO·Al₂O₃·SiO₂等夹杂物聚集在一起。缺陷横截面上的夹杂物主要为CaO·Al₂O₃·SiO₂、CaO·Al₂O₃·MgO和CaO·Al₂O₃·MgO·SiO₂ 3类。推测钢管壁内缺陷形成机理主要为:①大包钢水在浇注末期钢水卷带钢包渣进入中间包钢水中,该渣滴随后吸附钢中高Al₂O₃含量的微细xAl₂O₃·yCaO或Al₂O₃夹杂物,导致渣滴中的Al₂O₃含量升高;②大包钢水在真空脱气（VD）精炼过程大Ar气搅拌下卷入了钢包渣,该渣滴随后吸附钢中的微细Al₂O₃夹杂物,导致渣滴中的Al₂O₃含量升高;以上两种形式形成的渣滴在凝固冷却过程中,转变为CaO·Al₂O₃·SiO₂, CaO·Al₂O₃·MgO,CaO·Al₂O₃·SiO₂·MgO 3种类型的夹杂物。圆管坯在穿孔变形过程中,在纵向拉应力和横向切应力作用下,使卷入的大型渣滴沿纵向及横截面延伸扩展,最终形成钢管壁内的缺陷。      

铝脱氧轴承钢GCr15精炼渣最优成分的分析与实践

为了研究铝脱氧轴承钢GCr15最适合的精炼渣系,利用FactSage热力学计算软件对MgO对精炼渣熔点的影响、精炼渣对平衡钢液成分的影响及精炼渣的脱硫能力等进行热力学计算,得出最适合的渣系成分,并将优化结果应用于国内某厂"100tEAF→LF→VD→CC"流程生产轴承钢GCr15的工业试验。结果表明,优化后的精炼渣系的主要成分(质量分数)为CaO 50%~55%,Al2O325%~33%,SiO26%~10%,MgO 5%~7%,R=5~7;使用该渣系进行工业试验,VD出站时全氧质量分数可达到0.001 1%~0.001 3%;铸坯中主要夹杂物为Al_2O_3、MgO-Al_2O_3、MnS、TiN、钙铝酸盐和硅酸盐等,其中氧化物类夹杂的个数密度在3个/mm~2以下,平均等效直径在4μm以下。     

X80管线钢精炼过程夹杂物形成与演变

通过工业试验取样研究了X80管线钢精炼过程夹杂物的类型、尺寸、成分等变化规律,并结合FactSage8.1软件对钙处理和钢液冷却凝固过程夹杂物的演变机理进行了热力学计算分析.试验结果表明,LF精炼结束时夹杂物主要为MgO–Al₂O₃和MgO–Al₂O₃–CaO,数量占比分别为25%、75%,其尺寸主要分布在1～5μm之间,且1～2μm和2～5μm的夹杂物比例分别为56.0%、37.3%;RH精炼中T[O]、[N]质量分数分别由LF精炼结束时的0.0022%、0.0059%降低至0.0010%、0.0035%,夹杂物数量密度由LF结束约23.07 mm–2降低至7.44 mm–2,夹杂物去除率约67.8%;钙处理时,夹杂物主要为MgO–Al₂O₃–CaO和CaS–Al₂O₃–CaO系,夹杂物中CaS平均质量分数由RH精炼结束时的8%增加至36%,CaO平均质量分数由24%减少至12%;软吹结束时,尺寸<40μ...     

Research Status of Numerical Simulation of Nonmetallic Inclusions Interfacial Removal

The removal of inclusions in liquid steel has always been the focus of research, and the removal of inclusions is mainly through the process of the inclusion through the slag–steel interface. The inclusion removal process can be subdivided into inclusions in molten steel grew up rise, in steel–slag interface through separation, adsorb dissolved in molten slag 3 steps. Based on the microscopic process of three steps, this article summarizes and discusses the mathematical model, fluid mechanics model, and experimental verification method of inclusion removal process, analyzes limiting and influencing factors of inclusion removal process, and comprehensively describes the numerical simulation research progress of inclusion removal process. With the development of numerical simulation techniques and experimental equipment, some progress has been made in the study of interfacial removal of inclusions. The inclusion interface removal behavior can be analyzed semiquantitatively based on dynamic force model. The computational fluid dynamics model has advantages in studying the phenomena of the inclusion interface, and the phase-field method is often used to simulate the removal process of the inclusion interface. The combination of water model and numerical simulation, high-temperature laser confocal method, and other methods is of great help to explore the interface behavior of inclusions.     

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.     

In situ studies of agglomeration between Al2O3–CaO inclusions at metal/gas,metal/slag interfaces and in slag

Abstract

Studies of inclusion behaviour at the metal/slag interface is of great importance for the steel industry in order to achieve better control of both the size and amount of the inclusions, as well as improving the steel quality and the casting process. In this work agglomeration of liquid Al₂O₃–CaO particles at both steel/argon gas and steel/slag interfaces was studied with a confocal scanning laser microscope. In addition, agglomeration of liquid Al₂O₃–CaO–SiO₂ inclusions present in the slag was investigated. The results showed that liquid inclusions more easily agglomerated to semiliquid inclusions than to liquid inclusions. Moreover, the agglomeration of liquid particles was found to be improved remarkably when the particles were present in the slag compared to when they were in the steel/slag interface.     

碲处理控制Y15易切削钢中MnS夹杂物形貌

 为了研究碲对钢中MnS夹杂物形貌的影响,针对Y15高硫易切削钢,利用SEM-EDS扫面电镜,结合FactSage热力学计算,分析了不同碲质量分数对钢中MnS夹杂物形貌、尺寸、长宽比的影响,同时探讨了稀散金属碲对MnS夹杂物形貌控制的机理。研究结果表明,钢液中加碲后,在MnS夹杂物的外环形成了碲、锰、铁的复合相。钢中加碲后MnS夹杂物的形貌和分布大幅度改变,当碲硫比为0.05时,链状MnS夹杂物大幅度减少,球状MnS夹杂物数量增加;当碲硫比增加到0.2时,链状MnS夹杂物基本消失;当碲硫比增加到0.5时,MnS夹杂物形貌的变化不再明显。钢中加碲显著降低了MnS夹杂物的长宽比,控制MnS夹杂物长宽比最合适的碲硫比为0.2。FactSage计算结果表明,MnTe的生成温度为1 900 ℃,在MnS的析出温度下,MnTe是作为液态夹杂物存在的。在凝固过程中,MnTe和MnS发生固溶现象,由于MnTe为液态,两者形成的固溶体会趋于球形生长。     

Effect of Top Slag Composition on Inclusion Characteristics during Vacuum Degassing of Tool Steel

The focus of the study was to investigate the effect of the chemical composition of the top slag on the inclusion chemical composition during vacuum treatment of a plastic mould tool steel. Sampling was done before and after vacuum degassing. The chemical composition of the inclusions was determined by using SEM combined with EDX. The results showed that several inclusion compositions were found before vacuum degassing, while only one main composition of inclusions was present after vacuum degassing. Furthermore, the composition of the top slag was found to have a great influence on the composition of the inclusions found in samples taken after vacuum degassing. The present study also shows that the vacuum degassing effectively reduces the number of inclusions in steel. Finally, the thermodynamic calculations of the activities using Wagner's equation were found to predict a lower oxygen activity value than the calculations made using the Thermo‐Calc software.     

Computational Thermodynamic Study of Inclusions Formation in the Continuous Casting of SAE 8620 Steel

The general purpose of this work is a thermodynamic study of non‐metallic inclusions in the CC tundish for SAE 8620 steel. Specific purposes are: (1) Obtaining the phases formed and their composition in inclusions by applying computational thermodynamics for SAE 8620 steel; (2) Establishing conditions of steel composition for the improvement of SAE 8620 castability, including the plant validation in terms of the castability index. Thermodynamic studies were performed with the commercial software FactSage and databases. Simulations were carried out by the global chemical composition of SAE 8620 steel in the CC tundish, resulting in both steel composition and non‐metallic inclusions (oxides and sulphides) at the desired temperature. Furthermore, results showed both different solid oxides and liquid phase formation in inclusions by varying calcium content in the steel. Thus, it was possible to determine the inclusion composition as a function of aluminium and calcium content of SAE 8620 steel, and moreover, to establish a range of calcium content in which the inclusions are predominantly formed by liquid phase. In addition, the percentages of liquid and solid phase in inclusions, as well as, oxide compositions could be calculated.     

Industrial Application of Desulfurization Using Low Basicity Refining Slag in Tire Cord Steel

Desulfurization performance with low binary basicity refining slag in 72 grade tire cord steel was calculated using FactSage and it is found that sulfur content in steel decreases with the increase of basicity of slag, MgO content in slag and slag/steel ratio while sulfur partition ratio between slag and steel increases gradually with the increase of basicity of slag as well as MgO content. Experiments were carried out and the results are of great agreements with theoretical calculation. Then industrial application tests were performed in a domestic plant and good results were achieved. Sulfur content in steel decreases gradually during refining process, as a result, sulfur content in the billets is controlled in the range of 0.007 1%-0.008 1%. Sulfur content in steel refined with slag basicity of 1.21 is lower than that of 1.02, while the plasticity of oxide compound inclusions is a little better controlled in low basicity heats. Using refining slag with basicity of 1.0-1.2 and MgO content of 5%-10% and reducing the slag takeover of LD are favorable for improving the desulfurization performance and the plasticity of inclusions during the industrial production.     

长水口吹氩生成微小气泡工业实验研究

在连铸生产中采用大流量长水口吹氩,并采用“冷钢片沾钢法”沾取中间包钢液试样,成功沾取了中间包钢液中微小氩气泡。冷钢片沾样表面气泡为中间包上部钢/渣界面和炉渣中氩气泡,尺寸主要位于1.0~3.0 mm,但该尺寸不能反映中间包钢液内部长水口吹氩生成气泡,冷钢片沾样内部气泡为钢液内部长水口吹氩生成的气泡。结合扫描电镜和共聚焦显微镜对沾取试样内部气泡形貌、尺寸和数量进行了分析,结果表明大部分气泡为独立圆形气泡,偶见少量粘连和聚合气泡;钢液内部氩气泡尺寸主要位于100~1000 μm,平均尺寸为500 μm左右;气泡在长水口出口及其下方较为弥散,气泡数量可达15.2 cm?2。采用扫描电镜结合能谱分析,发现部分气泡内粘附有夹杂物,有些气泡粘附多个夹杂物;气泡粘附Al₂O₃夹杂物的几率高于粘附CaO(?MgO)?Al₂O₃?SiO₂复合夹杂物的几率。