Thermodynamic analysis of steel deoxidization processes during tapping and refining operations

A thermodynamic model based on the interaction parameter approach for molten metal solutions and a quasi‐chemical model for molten slags and non‐metallic inclusions was employed to analyze steel deoxidization during tapping and refining operations in a ladle furnace. This model is able to predict the mineralogical nature of non‐metallic inclusions and their amount through thermodynamics and mass balances. It was found that the addition sequence of deoxidizers during a tapping procedure influences the nature and amount of the different inclusions. Besides, the metal‐slag equilibrium is readily reached after tapping and at the end of steel treatment in the ladle furnace. The model proved to be useful for steel cleanliness assessments and the design of steel deoxidization practices.     

不同铝含量的脱氧剂对钢液洁净度的影响

铝具备较强的脱氧能力,被广泛应用于炼钢过程中钢液的脱氧。然而铝脱氧产生的高熔点、大尺寸Al₂O₃夹杂物不仅会严重降低钢液的洁净度、恶化钢材韧性和疲劳寿命,还容易造成水口结瘤,影响连铸工艺的顺行。考虑到局部过饱和度对夹杂物的形核和长大等有着重要的影响,采用纯铝和Fe-30%Al合金(质量分数)对钢液进行脱氧,且实际加入的铝量保持一致,通过对不同脱氧时间(30、60 s)的钢液成分和夹杂物特征进行分析,研究了不同铝含量的合金对钢液洁净度的影响。结果表明,相较于纯铝脱氧,Fe-30%Al合金在相同时间节点下脱氧效果更好,合金中铝元素溶解速度更慢。此外,在目前试验条件下使用纯铝脱氧的钢样中夹杂物尺寸可达到9μm,而使用Fe-30%Al合金脱氧的夹杂物尺寸最大只有4μm。采用纯铝脱氧60 s后钢中夹杂物平均尺寸为Fe-30%Al合金脱氧的1.35倍,且单位面积夹杂物数量多了23%。两种合金在脱氧过程中残留在钢液中的夹杂物均以多面体夹杂为主,并有少量碰撞聚集形成的松散型团簇状夹杂。使用Fe-30%Al合金脱氧比纯铝脱氧更有利于钢液洁净度的提高,这取决于两...     

RH精炼工艺对无取向电工钢质量的影响

为了在保证产品质量的前提下降低无取向电工钢的生产成本,分析了RH精炼工艺在不同钢水循环流量下各工序夹杂物的演变规律、成品磁性能和表面质量的变化.结果 显示,RH精炼工艺的变化对钢液中夹杂物组成、热轧材样夹杂物数量和成品磁性能无明显影响,对表面质量有负相关影响,钢水循环流量越大,表面夹杂物降低等级的比例越低.RH出站,钢液中夹杂物当量面积,尤其是5μm以上较大夹杂物与钢水循环流量呈负相关的影响,热轧材样中夹杂物(包括第二相析出物)主要是第二相析出物AlN和MnS、少量的氧化物夹杂,其数量与RH精炼工艺无相关性.在保证质量满足要求的前提下,RH工序可适当调整钢水循环流量,降低生产成本.     

稀土处理的无取向硅钢夹杂物控制研究进展

 冷轧无取向硅钢磁性能受钢材化学成分、夹杂物分布、再结晶组织等因素的影响,对炼钢工艺技术具有很高的依赖性。长条状或带有棱角的夹杂物通常比球形夹杂物对矫顽力和磁滞损耗的影响更大,而对磁性能影响较大的夹杂物主要为尺寸小于0.5 μm的夹杂物。总结分析了稀土处理对无取向硅钢夹杂物的影响,包括粗化夹杂物、减少钢中微细夹杂物数量和对夹杂物的球化作用。稀土元素具有很强的脱氧能力,能够有效净化钢液。添加稀土后,钢中生成的稀土氧化物或稀土氧硫化物通常呈球状或近似球状,并且由于稀土元素具有较高的表面活性,生成的微细夹杂物在钢液中更容易聚合长大,可以达到夹杂物改性和粗化的效果。稀土硫化物和稀土氧硫化物熔点高、固溶难,在再加热过程中能够有效减少硫元素的固溶量,抑制冷却过程中细小MnS的析出。此外,AlN、MnS等容易在稀土夹杂物表面析出,由此进一步减少了细小析出物数量。稀土还有改善成品织构的作用,存在最佳的添加量。同时对国内外无取向硅钢冶炼过程中的稀土添加工艺也进行了分析,当前以钢包加入法为主,通过真空下添加稀土,添加稀土前使用Al、Si等对钢水预先脱氧并喷吹脱硫剂,加入稀土后对钢水进行充分搅拌,可以保证稀土处理效果,但在连铸过程中仍存在因稀土夹杂物导致的水口结瘤问题有待研究解决。     

氧化物冶金在高强度低合金钢生产中的试验研究

通过对氧化物冶金技术在高强度低合金钢生产中的试验研究,探索采用氧化物冶金技术冶炼过程中转炉终点及LF精炼过程钢中的氧含量控制、正确的脱氧方式、脱氧合金元素的加入时机等,通过调节钢液成分,确保形核诱导粒子的生成;同时,利用扫描电镜分析了钢中夹杂物的成分、形貌、尺寸及夹杂物周围的组织形貌,并对试验钢板的性能进行了取样检测。结果表明,试验炉次氧化物冶金的效果良好且试验钢板性能很好。     

钢包内衬用耐火材料对钢中非金属夹杂物的影响

 炉外精炼是炼钢流程中控制钢中非金属夹杂物的重要转折点,作为整个精炼过程中与钢液实时接触的钢包内衬用耐火材料,因为高温物理化学反应易向钢中引入夹杂物,导致精炼效果达不到预期。通过对典型现役钢包内衬用耐火材料与不同脱氧钢之间的界面反应归纳发现,钢包内衬用耐火材料会对钢中夹杂物的形貌、成分和理化性能产生影响,既可向钢中引入夹杂物,也能够吸附去除夹杂物。提出未来钢包内衬用耐火材料应被赋予更多净化钢液等功能指标的发展方向。     

中间包微孔MgO耐火材料与钢液反应行为

为了评估新型中间包微孔MgO耐火材料与钢液的反应性,系统测定了不同钢液与微孔MgO耐火材料表观接触角,研究了界面化学反应产物以及钢中夹杂物组成的变化.结果 表明:含硫钢在微孔MgO耐火材料上铺展性最好,帘线钢次之,模具钢最差,主要是表面活性元素S降低了钢液表面张力所致;熔钢与耐火材料的界面行为中既包含了物理渗透又包含了...     

Theory and Practice of Oxide Inclusion Composition and Morphology Control in Spring Steel Production

Theoxideinclusionsinspringsteelcomemainlyfromtheproductsofdeoxidizationofmoltensteel .Ifthemoltensteelisalloyedwithferrosiliconandfinal lydeoxidizedwithaluminum ,thepropertiesofde oxidization productsarenotdeterminedbythechemicalcompositionofmoltensteel,butbythepropertiesofalloysanddynamicconditionsofdeoxi dization .Forspringsteel ,theoriginaldeoxidizationproductsfoundinfinishedproductsaretridymite ,a luminumsilicateandalumina[1] .Inordertoreducetheamountandthesizeofinclusionswhichdeterio rate…     

Inclusion Characteristics of Bearing Steel in a Runner after Ingot Casting

In the uphill teaming method of ingot casting molten metal from the ladle goes into the runner system, which feeds one or several ingot moulds. This method is still important for production of bearing steel. In order to make clean steel, which has a controlled amount of inclusions, good understanding of inclusions characteristics is necessary. In this work non‐metallic inclusions of steel left in the runner part of an ingot casting system were studied. Inclusion type, size, and morphology were the main focus of this study. A scanning electron microscope (SEM) was used to assess inclusion size and morphology. The chemical composition of inclusions was determined by SEM equipped with EDS. An automated program called ‘INCAFeature’ was used to collect statistics of inclusion characteristics. Based on the statistical analysis of inclusion composition, four types of inclusions including oxides, sulfides, carbonitrides and complex inclusions were defined. The inclusion characteristics in the runner were also compared to literature data of inclusions found in ladle and mould samples.     

Application of Thermodynamic Model for Inclusion Control in Steelmaking to Improve the Machinability of Low Carbon Free Cutting Steels

Oxide inclusions formed during steelmaking processes influence the machinability of steel products. At moderate and high cutting speeds, the tool life is dominated by chemical wear. However this wear can be suppressed by engineering exogenous and indigenous glassy oxide inclusions in steel. The present work demonstrates a method to engineer glassy oxide inclusions in a low carbon free cutting steel applying a new thermodynamic model for deoxidation control of steel based on slag‐melt as well as melt‐oxide inclusion equilibration. The model is used online in an industrial production line for the controlled production of glassy inclusions. These inclusions are shown to improve machinability by lubricating the tool‐chip interface during machining of the steel at high cutting speeds. Using an inclusion engineered work piece, the crater wear of an uncoated P10 tool is significantly improved and the tool life is tripled at cutting speeds in the range between 200 and 400 m/min. The industrial results show that thermodynamic modelling is a powerful tool to produce free cutting steels with consistently good machinability behaviour.     

超低氧精炼时钙处理对氧化物夹杂的影响

 研究了采用LF精炼顶渣控制技术对钢液进行超低氧冶炼时,钙处理对钢中非金属夹杂物的影响。试验在转炉出钢时采用铝终脱氧,LF精炼过程采用强脱氧、高碱度、强还原性精炼顶渣对钢液进行超低氧冶炼,比较了钙处理和不钙处理的钢液中非金属夹杂物转变的情况。结果表明,采用精炼顶渣控制技术冶炼超低氧钢时,钢液不需要进行钙处理就能实现铝脱氧产物Al2O3→MgO·Al2O3尖晶石→CaO-MgO-Al2O3类复合夹杂物的转变,得到炼钢温度下呈液态的复合氧化物夹杂,这些液态的夹杂物容易通过碰撞长大上浮去除,得到高洁净度的钢液,且残留在钢液的氧化物夹杂为较低熔点的复合氧化物,在浇注过程中不会产生水口结瘤。     

用酸溶法研究钢中超细氧化物夹杂的三维形貌

 钢中超细氧化物夹杂对提高钢材性能有重大意义。介绍了用稀盐酸溶解铁基体后，利用配有特殊滤膜的专用溶剂过滤器，将钢中某些非金属夹杂物与溶液分离的方法。利用带有EDS(Energy Dispersive Spectrometer)的扫描电镜(SEM)对夹杂物形貌进行了观察。结果表明，该方法可以把耐酸的超细氧化物夹杂从钢基体中提取出来，同时可以得到夹杂物的三维形貌、尺寸、化学成分等详细信息，是一种研究钢中超细氧化物夹杂的有效方法。     

新一代自润滑无铅易切削钢的开发

 应用炼钢过程中夹杂物控制的热力学模型预测钢包精炼和钢液凝固后钢中氧化物夹杂的成分,在模型预测指导下进行了自润滑易切削钢工业生产试验,并对开发的易切削钢进行了切削性能测试。结果表明,钢中氧化物夹杂预测结果与实测结果一致;用无涂层P10刀具进行的切削试验结果也表明,与传统含铅易切削钢相比,自润滑易切削钢在高速(v≥200 m/min)切削条件下,后刀面磨损降低200%;切削速度v=100 m/min时,二者相当;v=200 m/min时,前刀面月牙洼磨损降低200%,且月牙洼离刀刃较远。说明在高速切削条件下,开发的新一代自润滑易切削钢的切削性能明显优于传统含铅易切削钢,完全可替代传统含铅易切削钢。     

A Comparison of a Two‐Dimensional and a Three‐Dimensional Method for Inclusion Determinations in Tool Steel

To produce clean commercial tool steel the non‐metallic inclusions characteristics have to be known, since they influence the mechanical properties of steel. In this work, inclusion characteristics in steel samples from plant trials were studied. The samples were collected in the steel plant according the two following methods: (a) 2D investigations of inclusions by a cross sectional method and (b) 3D investigations of inclusions collected on a film filter after electrolytic extraction. More specifically, the chemical composition, morphology, number and size distribution of inclusions in tool steel samples taken from ladle during melt treatment were determined by both methods. In both methods SEM equipped with EDS was used for compositional analysis of inclusions. In addition, in the cross sectional method an automated detection program called ‘INCAFeature’ was used to collect more statistics of non‐metallic inclusions. The composition of inclusions larger than 5 µm was found to contain 49% CaO based on the results from both methods. However, for smaller inclusions it was found that the accuracy of the 2D method was less than that of the 3D method due to the influence of the metal matrix on the results. In addition, it was found that a critical inclusion size of 4 µm could be defined for the 3D method, above which the standard deviation in composition determination was very low.     

无缝钢管钢采用复合脱氧的效率

本文总结了为提高钢管钢的质量，采用硅锰（铝）合金和硅锰（钛）合金对钢水进行复合脱氧所产生的效果及质量化检验结果。     

等离子体光谱仪定量分析低合金钢中稳定氧化夹杂物

钢中非金属夹杂物对钢的力学性能和工艺性能的影响,主要是降低材料的塑性、韧性和疲劳性能,尤其当夹杂物以不利的形状及分布特征存在时,对材料机械性能的影响更为严重。以往氧化夹杂物分量测定采用化学法和原子吸收法,测定周期长,且Ca、Cr、Mn、Fe等元素的氧化物含量很低,化学法测定有一定局限性。而采用等离子体光谱分析(ICP-AES)定量测定氧化夹杂物,由于夹杂物含量低,相对干扰少,此法具有速度快,灵敏度高,并可同时测定多元素等特点,从而大大缩短了分析周期,降低了分析成本和劳动强度。     

渣组成对钢水洁净度的影响

 在实验室基础上对比研究了w(CaO)/w(SiO2)为5、w(Al2O3)为25%的渣系A,w(CaO)/w(SiO2)为8、w(Al2O3)为46%的渣系B,与高强度合金结构钢液在1600 ℃条件下反应90 min后钢水洁净度的变化,研究结果表明：随着渣系由A到B,钢中总氧质量分数平均值由12.25×10-6降低到9.25×10-6,硫质量分数平均值由19×10-6降低到8.63×10-6,炉渣的硫分配系数LS由7~17增加到120~260;渣系A、渣系B与合金钢液反应后钢中夹杂物大部分是钙镁铝硅酸盐类夹杂,并且得出渣系B精炼条件下钢中这类夹杂熔点明显低于渣系A精炼条件下的此类夹杂。     

Inclusion evolution after calcium addition in Ti-bearing Al-kill steel

In current article, experiments with different calcium addition were carried out in an Al₂O₃ crucible at 1873?K to investigate the variation of inclusion in Ti-bearing Al-kill Steel. It was found that calcium significantly influenced the morphology, composition distribution and size of oxide inclusions in Ti-bearing Al-kill Steel. Liquid oxide inclusions were modified promptly after calcium addition. Meanwhile, calcium could also modify solid titanium aluminate inclusions to spherical ones similarly, but there were a number of multilayer inclusions in molten steel at the initial stage. Different calcium treatment level should be adopted in different titanium content steel production process. As for the production practice, to achieve the full liquid inclusions in molten steel, the amount of calcium and titanium should be controlled simultaneously during the production process.     

Effect of Calcium Treatment on Non-Metallic Inclusions in Ultra-Low Oxygen Steel Refined by High Basicity High Al2O3 Slag

 The influence of calcium treatment on non-metallic inclusions had been studied when control technology of refining top slag in ladle furnace was used in ultra-low oxygen steelmaking. A sufficient amount aluminium was added to experimental heats for final deoxidizing during BOF tapping, and the refining top slag with strong reducibility, high basicity and high Al2O3 in ladle furnace was used to produce ultra-low oxygen steel and the transformation of non-metallic inclusions in molten steel was compared by calcium treatment and no calcium treatment. The results show that the transformation of Al2O3→MgO·Al2O3 spinel→CaO-MgO-Al2O3 complex inclusions has been completed for aluminum deoxidation products and calcium treatment to molten steel is unnecessary when using the control technology of ladle furnace refining top slag to produce ultra-low oxygen steel, and the complex inclusions are liquid at the temperature of steelmaking and easily removable to obtain very high cleanliness steel by flotation. Furthermore, the problems of nozzle clogging in casting operations do not happen and the remaining oxide inclusions in steel are the relatively lower melting point complex inclusions.     

含钡合金对冷镦钢脱氧的试验研究

在250kg感应炉上对冷镦钢进行了含钡合金脱氧的试验研究。试验中钡系合金主要选取SiAlBaCa和SiAlBaCaSr及用于钙处理的SiCa、SiCaBa包芯线。选用FeSiAl作为对比脱氧剂，考察了钡系合金脱氧的全氧含量，脱氧产物的分布、尺寸和形貌，探讨了钡系合金脱氧和对夹杂物的变质作用的机理。试验中发现，含钡合金用于钢液脱氧，可获得较低的氧含量，其脱氧产物易于上浮且速度很快，钢中的夹杂物形态发生改善呈球形，而且均匀分布于钢中。