钢中非金属夹杂物的相关基础研究（Ι）——非稳态浇铸中的大颗粒夹杂物及夹杂物的形核、长大、运动、去除和捕捉

 从几个方面对多年来在钢中非金属夹杂物基础研究方面做的工作做简单介绍：钢中夹杂物和钢水洁净度的评估方法、稳态浇注和非稳态浇注的定义、非稳态浇注过程中形成的大颗粒夹杂物、总氧和大颗粒夹杂物的对应关系、脱氧过程夹杂物形成的热力学基础、钢水中夹杂物形核及长大的动力学研究和钢水中流体流动和夹杂物的运动、去除及被凝固前沿的捕捉。并讨论了钢中夹杂物研究下一步应该继续进行的工作,对洁净钢的生产提出了一些指导性意见。     

Addition of Titanium Oxide Inclusions into Liquid Steel to Control Nonmetallic Inclusions

Titanium oxide inclusions in steel are well known to inhibit grain growth and act as nucleation sites for acicular ferrite because of absorbing manganese from the surrounding steel resulting in a manganese depleted zone around the inclusion. In this article, the inclusions resulting from TiO₂ additions to low-alloyed C-Mn-Cr steel were studied. Different types of TiO₂ containing materials were added to liquid steel before or during casting to get small titanium-oxide–rich inclusions in steel. The main goals were to find out what happens to TiO₂ in liquid steel after addition and during cooling and to study further what type of inclusions are formed in the steel as a result of the TiO₂ addition. Based on the thermodynamic calculations and the results of scanning electron microscope (SEM)-energy dispersive spectroscope (EDS) and SEM-electron backscatter diffraction (EBSD) analysis, TiO₂ is first reduced to Ti₃O₅ in liquid steel at high temperatures and then to Ti₂O₃ during cooling at around 1573 K (1300 °C). Both reactions liberate oxygen, which reacts with Ti, Mn, and Al forming complex Ti₂O₃-rich inclusions. The results also show that TiO₂ additions result in more TiO_x + MnO inclusions compared with experiments with Ti addition and that the absolute amount of manganese present in the inclusions is much higher in experiments with TiO₂ addition than in experiments with Ti additions.     

轴承钢中TiN夹杂的形成机理及控制措施

针对鞍钢股份有限公司炼钢总厂轴承钢中存在大颗粒TiN夹杂物的问题,分析了TiN夹杂析出的热力学条件。通过优化转炉及精炼操作、加强连铸保护浇铸、控制钢铁料及合金料中的钛含量、优化钢中酸溶铝及精炼渣中氧化钛的含量,最终将轴承钢中的氮含量由0.0050%降至0.0038%,钛含量由0.0045%降至0.0013%。     

超低碳钢钢中夹杂物的研究

为控制超低碳钢中的簇状夹杂物,对超低碳钢中的夹杂物和与全氧含量的关系进行了研究.钢中的夹杂物主要是Al2O3夹杂和Al2O3-TiN复合夹杂,独立夹杂物尺寸大部分小于10 μm.铸坯中w(TO)小于0.003 0%时,钢中仍存在簇状Al2O3夹杂;Al2O3簇状夹杂物与铸坯中全氧含量没有直接关系,所以钢中的全氧含量不能完全代表钢中夹杂物的水平.钢中的簇状Al2O3夹杂物与RH脱碳结束活度氧有关,要控制超低碳钢中簇状Al2O3夹杂物必须稳定生产工艺,减少RH加铝升温,使RH脱碳结束活度氧保持在一定范围.     

On the Relationship Between Inclusions and Pores, Part I: Precipitation

Formation mechanism and clustering of TiN?CAl₂O₃ inclusions precipitated during solidification of austenitic stainless steel is analyzed in this paper. Steel sample are taken from a continuously cast bloom. Clustering of inclusions was examined with a hypothesis that inclusions gather inside the pores. Precipitation of the inclusions occurs through segregation in the residual melt in the interdendritic area. Size and mean distance of the inclusion particles are calculated with mass balance. Impact fracture test in cryogenic temperature reveals clusters of inclusions inside pores on the fracture surface. Size and distribution of the inclusions are examined using light optical microscopy and scanning electron microscopy. Inclusion??s composition is investigated with energy dispersive X-ray spectroscopy analysis. Differential thermal analysis and differential scanning calorimetry Tests determined the transformation temperatures. Results of the experiments are in good agreement with theoretical analysis.     

抗疲劳应力钢中的夹杂物控制

 为了有效控制抗疲劳应力钢中夹杂物危害,通过对钢中典型有害夹杂物进行分析,从脱氧工艺、精炼渣系、钙处理工艺、软吹工艺和连铸保护浇铸等方面进行了优化改进,并取得相应效果。实现了钢中夹杂物有效控制,钢中夹杂物形状主要以小尺寸球状和块状为主,夹杂物成分主要以钙铝酸盐和MnS复合夹杂物为主,夹杂物尺寸控制在20 μm以内,其中90%以上夹杂物都控制在7 μm以内。     

连铸板坯夹杂及其控制途径

阐述柳钢连铸铸板坯内现在的非金属夹杂物的类型、分布及其对钢板性能的影响，并提出了控制非金属夹杂物的途径。     

铝熔体中的气体及夹杂

本文对铝熔体中气体及夹杂的来源、形成机理、影响因素做了系统的分析，对其危害做了说明，最后提出了对铝熔体中气及夹杂的预防措施及去除方法。     

无取向电工钢中夹杂物的分析

对无取向电工钢中的夹杂进行了系统的分析。利用小样电解,采取不同电解液,不同的分离方法对无取向电工钢中稳定和不稳定夹杂物进行了提取、分离和收集。利用扫描电镜(SEM)、X-射线衍射、ICP等对电解分离收集的夹杂物进行了定性和定量分析。     

铝酸钙夹杂物的生成机制研究

运用异质形核理论解释了钢中钙对夹杂物变性的机制过程,计算得出1 873 K下w[Al]s为0.03%时,均质形核生成Al2O3钢中溶解氧的质量分数需达到39.2×10-6,而当反应达到平衡后钢中溶解氧的质量分数为3.3×10-6。脱氧后加入钙靠均质形核很难生成CaO,钙、氧原子主要以Al2O3质点为核心在其表面上生成,生成反应为:[Ca]+(x+1/3)Al2O3=CaO.xAl2O3+2/3[Al],生成过程为Al2O3→CA6→CA2→CA→CxAy液相,并通过SEM/EDS验证了夹杂物变性的机制过程。     

State of the Art in Control of Inclusions, Their Characterization, and Future Requirements

Because of the growing demand of cleaner and defect-free steels, faster and more reliable offline steel cleanliness determination methods combined with online techniques are finding increasing usage to study steel refining and casting issues. Because a single-steel characterization technique is not sufficient to provide answers to all process problems, a combination of these techniques is often used to find a customized solution of the problem. This article reviews the past experiences on steel cleanliness examination to standardize the inclusion-characterization techniques and their applications for both experienced and novice researchers. The article also proposes a suite of techniques as a reference tool to facilitate clean steelmaking research at ArcelorMittal Group more effectively in the future. Examples of use of automated scanning electron microscopy and pulse discrimination analysis are provided.     

高强钢焊缝金属的化学成分和组织及非金属夹杂物

高强钢的应用带来很多潜在的优势.然而,钢铁技术的进步不断地需要新焊接工艺和焊接材料的,以使焊缝金属具有与母材等同的力学性能.为达到这一目的,需要更好地了解高强钢焊缝金属的成分和组织与性能之间的关系.对采用不同的焊接工艺和名义强度为490～840 MPa(70～120 ksi)之间的市售焊接材料获得的高强钢焊缝金属进行试验,试验表征了包括非金属夹杂物在内的常规成分和组织.     

RH精炼过程非金属夹杂物

 以200t钢包RH精炼装置为原型建立了1∶5水模型,分析了实际工艺条件下RH上升管吹气量对卷渣的影响。结果表明,当上升管吹起量为120m3/h时,发生平稳、均匀的卷渣,有利于钢渣反应,根据水模型结果在RH上进行了试验,并通过系统取样,采用金相显微镜、图像分析仪和扫描电镜对比研究了用和不用预熔渣处理的无取向硅钢在精炼过程的夹杂物的数量、尺寸分布以及夹杂物的类型演变情况。经过定量比较发现,在有预熔渣的情况下,RH真空处理后,钢中Al2O3夹杂物变性为CaO-MgO-A12O3的复合夹杂物,并且夹杂物数量和尺寸明显变小。     

Nonmetallic Inclusions in Low-Alloy Tube Steel

Study of the nonmetallic phase of unalloyed tube steel 10G2FB has shown that the steel contains four types of nonmetallic inclusions. Relatively fine (no coarser than 12 µm) calcium aluminates of variable composition are the main type of nonmetallic inclusion (NI) in such steel. It was established that a decrease in the point rating for NI contamination of the steel from 3.5 to 1.5 leads to an increase in the steel’s impact toughness from 235 to 318 J/cm².__________Translated from Metallurg, No. 4, pp. 67–72, April, 2005.     

铝镇静钢夹杂物形态控制工艺研究

通过热力学分析结合现场试验,采用金相分析、扫描电镜、能谱分析等方法,研究了铝镇静钢中氧化物夹杂的变性处理工艺。热力学计算结果表明,当钢中的[Al]s质量分数为0.025%,钙处理时控制钢中钙质量分数高于22 10-6,硫质量分数低于0.008%时,可较容易地将Al2O3夹杂变性为低熔点的C12A7。对天津钢厂生产石油套管钢的LF精炼工艺进行了优化,通过强化钢水钙处理,使钢中钙含量有了显著提高,使夹杂物形态的控制大为改善。     

高强度船板氧、氮及夹杂含量的测定

测定了AH32高强度船板冶炼过程中的氧、氮含量和夹杂物表现行为，定性和定量分析了此钢种各工序点夹杂物的变化规律，为同类型钢种及更高级别船板工艺路线的制定提供了借鉴。     

Ferromagnetic Inclusions in Geomaterials: Implications

Various laboratory and field techniques used to study geomaterials utilize the principles of electromagnetism. Applications in geotechnical engineering such as resistivity profiling, induced polarization, ground-penetrating radar, and time-domain reflectometry, focus on the electrical properties of the materials and neglect the magnetic component. Yet the a priori assumption that the medium is nonferromagnetic may lead to significant errors in data interpretation because the presence of ferromagnetic materials affects the propagation of electromagnetic waves. An experimental study is conducted using kaolinite with ferromagnetic inclusions. Results show that magnetic permeability is a function of the volume fraction and spatial distribution of ferromagnetic inclusions; the interaction among inclusions increases with increasing volume fraction and proximity. These results and published data show that a relaxation due to “wall bowing” occurs at kilohertz frequencies, and a relaxation due to “wall displacement” occurs at megahertz frequencies. It is shown that the relative permittivity (real and imaginary components) inferred from wave-propagation measurements is larger than the actual value by a factor approximately equal to the real relative magnetic permeability. Corrections for ferromagnetic effects must be computed using parameters measured at the same frequency.     

Non-Metallic Inclusions in HSLA Steel-Origin,Detection and Refractory Systems to Improve Cleanness

HSLA steels need extremely low levels of tramp elements like P,S,H and O t.During tapping the steel is deoxidized with aluminum and in the secondary metallurgy sulphur (< 10 ppm) and hydrogen (< 1 ppm) are extracted.After tank degassing the steel is strongly Ca-treated by wire feeding to form CaS instead of MnS.Non-metallic inclusions in the steel and centre segregation with MnS are sinks for hydrogen which result in HIC (Hydrogen Induced Cracking).Therefore these steels ask for excellent oxide cleanness and S-contents of < 10 ppm.Macro inclusions of > 50 μm are harmful for the product.These large inclusions are seldom and difficult to be detected.Small inclusions of < 15 μm do no harm to the product.The origin of non-metallic inclusions is,roughly spoken,one third each of de-oxidation-/reoxidation products,refractory and casting powder.Slag carry-over is mainly avoided by sensitive electronic devices.Slag covers and shrouding systems of the steel stream during the transfer of metal between ladle,tundish and mold are effective to avoid reoxidation.Systems to control the flow of steel in tundish and mold favor the floatation of inclusions and their even distribution in the strand.