计算热力学在钢中非金属夹杂物研究中的应用

简要介绍了采用计算热力学方法分析钢中非金属夹杂物形成过程中涉及到的多元多相体系的热力学模拟。尝试应用Thermo-Calc软件系统对非金属夹杂物的形成热力学进行了探讨。指出,尽管Thermo-Calc软件具有较强的实用性,但为了拓宽该软件的工业应用前景,应对其中的SLAG数据库进行必要的完善。     

The Application of Computational Thermodynamics in the Understanding and Control of Clogging and Scum in Continuous Casting of Steel

Non-metallic inclusions are present in small volume fractions in steel products. A significant portion of them is associated to the deoxidation process. The type and form of inclusions is, in general, directly connected to the deoxidation practice and to eventual reoxidation during processing. Besides influencing the steel properties, non-metallic inclusions can have an important effect on their processability. In this work, we review the processability questions associated with inclusions in the continuous casting of steel, with emphasis on long products. When solid inclusions are present during the casting of steel they may agglomerate and clog the valves used in the continuous casting equipment, limiting the number of sequential heats that can be casted and reducing casting speeds. Additionally, in some conditions, solid non-metallic inclusions may agglomerate and form surface defects in the continuous casting products, sometimes referred to as scum. As productivity and quality are essential to the profitability of steelmaking, avoiding these conditions is of paramount importance. Thus, we review the main thermodynamic conditions that may lead to the clogging of continuous casting valves, and discuss, from the thermodynamic point of view, the measures that can be taken to avoid the occurrence of these various conditions. Furthermore, we discuss the conditions that might cause to the formation of scum and the thermodynamics of its formation and elimination. It is concluded that the analysis of steelmaking conditions via computational thermodynamics can have an important role in avoiding problems in continuous casting and helping ensure productivity and quality in the process.     

Q195热轧带钢凝固冷却过程非金属夹杂物生成热力学及工业实践

为了控制Q195钢中非金属夹杂物在凝固冷却过程的转变,采用ASPEX自动扫描电镜研究了实际生产凝固冷却过程夹杂物的转变,并用FactSage软件理论计算了这一过程夹杂物转变的热力学原理。研究结果表明:Si-Mn-Al复合脱氧Q195热轧带钢中间包内夹杂物主要成分为SiO2-MnO-Al2O3,连铸坯中硫化物夹杂质量分数急剧升高,氧化物夹杂中SiO2质量分数升高,MnO质量分数下降。钢中夹杂物成分与尺寸有明显对应关系,中间包内夹杂物尺寸越大,Al2O3质量分数越多,SiO2质量分数越低;铸坯中夹杂物尺寸越小,MnS质量分数越高,氧化物夹杂尺寸越小,SiO2质量分数越高。FactSage热力学计算表明,在钢凝固冷却过程,钢中会析出SiO2相、Mn2Al4Si5O18相和MnS相,析出相尺寸一般较小,使小尺寸夹杂物中SiO2和MnS质量分数升高,热力学理论计算可以较好地解释夹杂物成分在凝固冷却过程的转变。     

调质45钢主轴机加工性能异常的原因分析

本文针对某批调质45钢制的主轴存在局部难以机加工的问题,进行了成分、金相组织、扫描电镜和能谱等方面的检验和分析。结果表明,该批调质45钢的组织不均匀,存在网状铁素体,局部存在金属或非金属夹杂,因而造成钢中局部硬度偏高。     

稀土处理HRB400E钢洁净度研究

为了研究稀土对HRB400E螺纹钢中夹杂物成分和形貌的影响,对稀土处理后螺纹钢中可能存在的夹杂物进行热力学计算,并通过扫描电镜及能谱仪对稀土处理前后 HRB400E钢中夹杂物进行了表征和分析。结果表明,稀土可在现场冶炼时加入到螺纹钢中并且质量分数达到0.003 2%;稀土有净化钢液的作用,使钢中S质量分数从0.018%降低到0.004%,降低了77.78%;热力学计算表明,稀土质量分数为0.003 2%时,夹杂物生成的可能性由高到低为REAlO₃、RE₂O₂S、Al₂O₃。稀土对HRB400E钢中硫、氧化夹杂物有良好的改质效果,将夹杂物变质为RE₂O₂S和REAlO₃,稀土元素与S结合使钢中MnS夹杂的析出减少,有利于钢材综合性能的提升。     

采用高频磁场去除太阳能级硅熔体中的SiC粒子(英文)

高质量硅材料在光伏太阳能和电子设备中具有重要应用,然而原料中的非金属颗粒和金属杂质严重影响其电学性能和力学性能。由于SiC粒子会降低光伏电池的力学性能并导致分流问题,因此在制备太阳能电池之前必须将这些杂质从硅材料中去除。利用磁场去除液态金属中的非金属杂质是制备高纯金属的一项尖端技术。利用该方法去除冶金级硅材料中的SiC粒子,并结合杂质去除经典模型和计算流体力学对熔体中粒子浓度和分离效率进行计算。为检验该方法的有效性,采用感应炉进行多次实验。结果表明:该方法能有效去除非金属杂质,提纯硅熔体,且实验结果与模型的预测结果相符。     

应用极值分析法推测车轮钢中最大夹杂物尺寸

随着钢纯净度的提高,钢中大尺寸脆性非金属夹杂物出现概率逐渐降低,常规的夹杂物检测方法很难捕捉到,但这些大尺寸脆性夹杂物对其疲劳寿命有重要影响。介绍了一种钢中最大夹杂物尺寸的分析方法——极值分析法,采用该方法推测车轮钢中的最大脆性夹杂物尺寸,并用能谱仪分析了大尺寸脆性夹杂物的元素成分。结果表明：基于Gumbel分布函数的极值分析法可以作为估计车轮钢中最大夹杂物尺寸的一种方法;当该方法用在实际大生产检验中,应注意累积分布概率F(x)的选取,即样本总量对评估结果影响较大;车轮钢中大尺寸B类夹杂物的化学成分一般为CaO+Al₂O₃。     

45钢棒料的质量检验和重结晶退火工艺研究

45钢棒料制成的工件经正火或调质处理后存在局部难以加工的问题,通过硬度、化学成分、金相、扫描电镜和能谱等方法对其进行了检验和分析。结果表明,该棒料组织不均匀,有网状铁素体及带状偏析,局部存在屈氏体组织和金属或非金属夹杂。采用重结晶退火可以改善原有组织的缺陷,满足工件的加工性能要求。     

A STUDY OF SIDE-BLOWN BASIC BESSEMER STEEL

通过150余炉钢的度验,指出了为着提高侧吹硷性转炉钢材性能应考虑下列几点: 1.侧吹硷性转炉钢的常温机械性能是完全符合而远为超过部颁标准甲类钢性能规定之最低数据。但由于钢中含氮较高,平均在0.008％左右,故而就钢材的应变时效、兰脆、应变硬化以及低温性能而言,显著地较酸性转炉钢及平炉钢为低劣。过去选取按平炉钢化学成分的规格,是不合适的,因为忽略了氮气含量的影响。试验提出钢的化学成分修改的意见。 2.钢中含氧量的多寡与成品非金属夹杂物的含量,当吹风深浅的程度不变时,在颇大的程度上决定于吹炼终点的炭分高低,且比较显著地影响着钢材的性能,今后应避免吹炼时过分的降炭、出钢后包中增炭以调整成分的操作。     

Computer aided design of free-machinability prehardened mold steel for plastic

In order to improve the machinability but not to impair other properties of the prehardened mold steel for plastic, the composition was designed by application of Thermo-Calc software package to regulate the type of nonmetallic inclusion formed in the steel. The regulated non-metallic inclusion type was also observed by SEM and EDX. Then the machinability assessment of the steel with designed composition under different conditions was studied by the measurement of tool wear amount and cutting force. The results show that the composition of free cutting elements adding to mold steel for plastic can be optimized to obtain proper type of non-metallic inclusion in the aid of Thermo-Calc, compared with the large volume fraction of soft inclusion which is needed for promoting ductile fracture at low cutting speeds, the proper type of inclusion at high cutting speeds is glassy oxide inclusion. All those can be obtained in the present work.     

碱性电弧炉冶炼ZG25MnCrNiMo钢化学成分的控制

为控制碱性电弧炉冶炼ZG25MnCrNiMo钢的化学成分,总结了熔炼过程中合金化元素、杂质元素及非金属夹杂物的变化趋势,分析了ZG25MnCrNiMo{N4~学成分的影响因素,并阐述了冶炼过程中各元素的控制方法。通过合理操作,有效控制ZG25MnCrNiMoSN冶炼过程,改善钢液质量,进而提高产品质量。     

包钢U75V重轨钢夹杂物演变规律分析

为了研究重轨钢冶炼过程中夹杂物的演变规律,以U75V重轨钢为研究对象,通过全流程取样,分析了夹杂物的组分、尺寸、数密度等变化特征。研究结果表明,硅铁等合金中的残余元素对重轨钢中的非金属夹杂物有重要影响。此外,本研究对重轨钢典型夹杂物的演变规律有了明确的认识,有效识别了冶炼各个工序的夹杂物去除能力,并找到了限制性的环节。     

大理石、萤石对不锈钢焊条熔滴过渡及熔滴中夹杂物的影响

采用水中收集熔滴、光学显微分析、电子扫描能谱分析、计算机图像分析及平板堆焊等试验方法，分别研究了大理石、萤石对不锈钢焊条熔熵过渡行为，以及它们对熔滴中非金属夹杂物及焊缝中气孔的影响。结果表明焊缝和熔滴中的非金属夹杂物呈圆球形，它们是熔滴反应区化学反应的产物，属“内生”性质；药皮中大理石含量增大时，熔滴尺寸与熔滴中夹杂物含量的波动变化存在对应关系，焊条工艺性变差，焊缝中气孔敏感性未减小；药皮中氟化稀土和萤石比值增大，熔滴细化，熔滴中夹杂物含量增大，焊条工艺性能有所改善，焊缝中气孔倾向未减小。     

38CrMoAlA钢传动主轴失效分析

借助光谱仪、蔡司光学显微镜和洛氏硬度计等分析手段对38CrMoAlA钢主轴失效件的化学成分、非金属夹杂物、断口裂纹形貌、显微组织和硬度进行检测与观察,分析并讨论了造成该工件裂纹产生的影响因素。结果表明:38CrMoAlA钢主轴的化学成分、硬度、渗氮层、非金属夹杂物、带状组织均符合标准要求;显微组织晶粒粗大,为贝氏体+珠光体,非预期使用态组织(回火索氏体),故工件硬度高、内应力较大、脆性较大,在应力的作用下易产生裂纹,导致脆性断裂失效。     

热轧硬线钢中夹杂物分布特征的研究

采用光学显微分析法在不同直径硬线钢的不同部位,分析了非金属夹杂物的数量、大小和分布特征。检测分析说明,夹杂物的尺寸与热轧硬线钢的直径相对应,多数夹杂物分布在硬线钢的中间部位。单向变形过程中氧化物类夹杂物普遍破碎,沿变形方向成串分布。。     

Influence of Ti on non-metallic inclusion formation and acicular ferrite nucleation in high-strength low-alloy steel weld metals

The phase transition behaviors of non-metallic inclusions as a function of Ti content were investigated by monitoring changes in the microstructure and mechanical properties of high-strength low-alloy steel multipass weld metals. Weld metals with Ti contents ranging from 0.007 to 0.17 wt% were prepared using a gas metal arc welding process. The inclusion analysis was performed based on thermodynamic calculations and transmission electron microscopy, accompanied by energy-dispersive spectrometry and selected area electron diffraction. With increase in the Ti content of weld metals, the chaotic arrangement of ferrite laths in the columnar zone was transited to a well aligned arrangement and the impact toughness of the weld metals drastically deteriorated in response to the decrease in the Mn content of the inclusion. The effective inclusion phase for intragranular nucleation contained considerable amounts of Mn and a Mn depleted zone was observed around the effective nucleant.     

The modeling of structure and properties of carburized low-chromium hypereutectoid steels

Research of carburized high-carbon bearing LH15 (52100) steel is presented. Problems analyzed include thermodynamic and kinetic basis of carburizing in two-phase field (austenite-cementite), carbon content influence in diffusive layer on utilization properties of the examined steel, and functional carbon content influence on chemical and phase composition of carbonized layer. An understanding of these problems enables modeling of functional properties and chemical and phase composition diffusion layers, obtained at definite carburizing parameters. That is the choice of carburizing process parameters (temperature, time, carbon potential) for the best utilizable properties.     

渗碳齿轮钢18CrNiMo7-6的疲劳性能及其影响因素

以18CrNiMo7-6齿轮钢为研究用基础钢,在传统真空脱气冶炼方式基础上,采用Nb微合金化和电渣重熔冶炼相结合获得一种对比试验钢,通过旋转弯曲疲劳试验表征了两种试验钢的疲劳性能,并利用显微组织、硬度分布、疲劳断口表征以及夹杂物分析等手段,探究了两种试验齿轮钢疲劳性能的影响因素。结果表明,采用电渣重熔方法冶炼并Nb微合金化的试验钢的疲劳极限较基础钢提高90 MPa,且相同载荷下寿命显著提高,渗碳层晶粒度由基础钢的7.5级细化至9级,而残留奥氏体含量的增加导致其表面硬度降低。通过Aspex夹杂物表征发现试验钢中夹杂物数量较基础钢大幅度降低,且硬质氧化物夹杂较少,与断口表征结果相一致。综合分析可知,晶粒细化和非金属夹杂物水平下降是提升试验钢疲劳性能的主要因素。     

电磁过滤钢液中非金属夹杂物的运动速度和去除效率的理论分析

电磁过滤原理是根据非金属夹杂物与熔体导电性的差异,在电磁场作用下非金属夹杂物与熔体的运动规律不同,使非金属夹杂物与熔体分离,经流体力学分析、采用柱塞流及轨线模型研究电磁过滤水平流动钢液中非金属夹杂物的运动速度和去除效率,结果表明,非金属夹杂物的去除效率随着熔体流速（u)和过滤器的高度（2h)的降低而增加;随着电磁力（f)、电磁力作用区长度（x)和非金属夹杂物的粒径（dp)的增加而增加,经分析表明,采用电磁过滤法可有效去除粒径小于10um的非金属夹杂物,该模型可用来设计过滤器的结构和确定电磁过滤工艺参数,为电磁去除钢液中的非金属夹杂物技术的工业应用提供理论基础。     

Effects of CeF3 on properties of self-shielded flux cored wire

0 IntroductionSelf-shielded flux cored wire is a newly developedwelding material used without gas protection. Use of suchcored wires has grown rapidly in developed countriesbecause of the following advantages: simple use, goodwind resistance ability, lower cost resulted from highproductivity and strong desulfurization ability[1]. Self-shielded flux cored wires are preferred for on-site weldingsuch as ship and barge building, storage tank, bridge,offshore oil platform buildings and so on[2 -3].…