钢中非金属夹杂物的三维定量表征

以超低碳钢、易切削钢、管线钢为研究对象,通过优化电解萃取法以及夹杂物自动分析技术,完成了钢中大尺寸氧化铝、大尺寸硫化锰、常规氧硫化物等典型夹杂物的三维形态表征及自动定量统计,并就滤膜干扰物、夹杂物分散状态、扫描电镜参数设置等影响夹杂物三维定量表征的因素进行了讨论。与二维分析相结合,夹杂物的三维形态表征及定量统计结果将提供最为全面、真实、准确的夹杂物信息。     

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洁净钢中的非金属夹杂物(non-metallic inclusion,NMI)主要在炼钢工艺过程中产生,对宏观性能有很大影响。分析NMI可以建立钢铁工艺与性能之间的桥梁,为洁净钢产品工艺控制及新品研发提供参考依据。综述NMI表征方法,根据样品制备方法将其分为35种。针对尺寸为1~20μm微观夹杂物采用扫描电镜进行自动分析已经成为当前研究应用热点。对NMI表征方法做了简要介绍,并以具体实践举例说明测试结果可以反映炼钢工艺制度(总氧控制),与最终宏观性能(拉拔断丝率)完全对应。该方法可供国内外同行参考。     

H13钢中非金属夹杂物在LF-VD精炼过程的行为研究

H13钢是热作模具钢中应用最广泛的钢种之一,夹杂物对其性能有严重危害。结合某钢厂生产实际情况,以现场取样为基础,用金相显微镜、扫描电镜系统地研究了LF-VD精炼过程中的夹杂物,计算和分析了H13钢冶炼过程中生成Al2O3、MgO.Al2O3类夹杂物的热力学条件。研究结果表明:钢液经LF精炼、VD处理后,钢中夹杂物的数量和面积明显减少,但随着炉渣中Al2O3活度的增大,炉渣吸附Al2O3类夹杂物的能力减弱,去除Al2O3夹杂物的速度减慢;夹杂物在LF精炼前主要以Al2O3、FeS、MgO.Al2O3类夹杂为主,LF精炼结束后为Al2O3、FeS、CaO.Al2O3类夹杂,VD处理后为Al2O3类夹杂。     

U-Nb合金中夹杂物的纳米压痕表征

采用纳米压痕技术对铸态U-5.5Nb合金中Nb_2C、U(C,N)以及基体力学性能进行了表征,根据获得的硬度值计算了屈服强度和塑性指数。实验结果表明Nb_2C夹杂物的弹性模量和硬度最大,而U(C,N)夹杂物的弹性模量和硬度远小于Nb_2C但明显高于基体;计算结果显示Nb_2C夹杂物屈服强度最高而塑性指数值最小,倾向于发生弹性变形,U(C,N)夹杂物强度低但塑性指数值最大,更容易发生塑性变形并发生破裂。基体多步循环加载获得的弹性模量和硬度值与单次加载基本一致,并且弹性模量值和文献中报道的单向拉伸实验测得的值相符。     

变速器中间轴断齿失效分析

对变速器中间轴的断口形貌、化学成分、硬度、显微组织、非金属夹杂等进行了分析。结果表明,断口处有大量非金属夹杂、夹渣及孔洞,破坏了材料的连续性,导致应力集中,在外力作用下形成疲劳源,造成中间轴在试验中断裂。     

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。     

The effect of microstructure and non-metallic inclusions on corrosion behavior of low carbon steel in chloride containing solutions

The effect of microstructure and inclusions on corrosion of API-5L Х60-Х100 low carbon steel is examined in acetate buffer solutions (pH 6) containing chloride. Microstructure was varied by preliminary heat treatment resulting in following series: ferrite–pearlite, ferrite–bainite, ferrite–martensite, and demonstrated the minor effect on the active dissolution kinetics, as well as oxide and sulfide inclusions. The current in the passive region and breakdown potential appeared to be sensitive to both types of inclusions and steel microstructure. Voltammetric parameters are listed which correlate with corrosion rate under open circuit and can be used to predict both short- and long-term corrosion behavior.     

Thermodynamic aspects of inclusion engineering in steels

Tailoring non-metallic inclusions in accordance to the desired effect on steel properties has gained widespread acceptance in the last decades and has become known as “inclusion engineering”. Effective inclusion engineering involves three steps： （a） a good knowledge of how inclusions influence properties, （b） understanding what is the effect of each type of inclusions on these properties and thus which is the most desirable inclusion in a given product and （c） adjusting the processing parameters to obtain these inclusions. A significant portion of the process adjustment is done during steel refining, where the steel can be tailored so that the desired chemical composition of the non-metallic inclusions that will precipi- tate can be altered. Understanding the relations between steel chemistry, processing variables and inclusion chemical composition requires significant understanding of the thermodynamics of the systems involved. These complex equilibrium calculations are best done using computational thermodynamics. In this work some of the basic techniques used to control inclusion composition are reviewed and the thermodynamic information required to perform this task is presented. Several examples of the application of computational thermodynamics to inclusion engineering of different steels grades are presented and compared with experimental results, whenever possible. The potential and limitations of the method are highlighted, in special those related to thermodynamic data and databases.     

439铁素体不锈钢夹杂物形成热力学计算及形貌分析

对439铁素体不锈钢中各种夹杂物形成的热力学条件进行了分析,采用金相显微镜和扫描电子显微镜结合面扫描对夹杂物的类型和形貌进行分析。结果表明,钢液中少量Al的存在扩大了Al₂O₃的生成优势;少量Mg与Al反应生成镁铝尖晶石;钢中TiN的析出与Ti的氧化都与钢液中Al的含量有关。根据试验观察结果可知,Ti单稳和Ti、Nb双稳定条件下铁素体不锈钢中夹杂物的分布和类型存在一定的差异。     

42CrMo钢螺栓断裂分析

42CrMo钢的B7M螺栓在使用过程中发生了断裂。为了探索断裂原因,应用光电直读光谱仪、光学显微镜、扫描电子显微镜对该螺栓断裂处进行了化学成分、宏观、微观等分析。结果表明,螺栓的化学成分符合产品技术要求,螺栓断裂主要是由于原材料棒中存在中心碳偏析以及严重夹杂物所致。     

The role of inclusions in crevice corrosion of high- alloy austenitic stainless steel tube used in seawater- cooled condensers

In view of the reported superiority of high chromiuni-nickel-molybdenuni austenitic stainless steel tube over copper alloy tube in seawater-cooled condensers, two such compositions were tested for crevice cor-rosion performance in seawater using a Campbell test rig. Tube of one particular alloy composition was free of crevice attack in seawater testing, whereas tube of the other alloy composition experienced exten-sive crevice attack. Anodic cyclic polarization test results carried out in the laboratory were in agreement with the field test results for these alloys. It was thus concluded that inclusion morphology, together with alloy composition, should be considered in the selection of tube materials for condenser applications.     

人造金刚石晶体中气态和固态包裹体的研究

采用光学显微镜对FeNi触媒合成金刚石中包裹体的形态进行了观察,发现金刚石中的气态包裹体主要表现为大小不同的气泡,弥散状分散的小气泡以及云浮状呈现在晶体中;固态包裹体主要为石墨包裹体和金属包裹体;通过对不同包裹体种类和含量的金刚石静压强度、TI、TTI等进行测试分析,发现无包裹体和几乎无包裹体的金刚石的质量最好,金属包裹体对合成金刚石的质量影响不大,气态包裹体次之,石墨包裹体对合成金刚石的质量影响最大。     

分离FGH95合金粉末中陶瓷夹杂物的水淘析法有效性分析

通过对水淘析法的原理分析 ,运用流体力学中的摩擦数群法确定了以陶瓷夹杂物在水中的沉降速度来确定水流速度 ,及在确定的水流速度下 ,所能淘析出的FGH95合金粉末的最大尺寸 ;并以比较淘析出的FGH95合金粉末的实际最大尺寸与理论最大尺寸 ,考察了水淘析法分离FGH95合金粉末中的陶瓷夹杂的有效性     

42CrMo连铸辊裂纹原因分析

通过宏观及微观分析对250 mm的42CrMo钢连铸辊的开裂原因进行分析。结果表明,铸造缺陷、非金属夹杂物含量较多,调质处理温度过高、保温时间较长,以致形成粗大珠光体和大量的魏氏组织,是造成连铸辊开裂的主要原因。另外,存在应力集中,机加工应力过大也导致了连铸辊的开裂。     

Effects of processing variables on melt cleanliness of AZ31B magnesium alloy investigated by quantitative evaluation of Fe and non-metallic inclusions

Impurities such as Fe, Ni and Cu and non-metallic inclusions such as oxides, nitrides, carbides, sulfides and fluorides are harmful to the quality and various properties of magnesium alloy sheets produced by twin-roll casting. In this study, the changes of the content of Fe and non-metallic inclusions in AZ31B magnesium alloys with melt temperature and isothermal holding time were quantitatively evaluated using EPMA and the metallographic method. The Fe content did not increase above the Fe content in the raw material, which implies that the dissolution of Fe from a steel crucible was suppressed effectively. The content of non-metallic inclusions, mainly consisting of oxide, fluoride and Fe-rich intermetallic compounds, did not change remarkably with the melt temperature but it increased with the isothermal holding time due to the continuous oxidation of the magnesium alloy melt on the melt surface.     

含硫金刚石的合成及杂质分析

本文分别用Ni70Mn25Co5合金粉末和含添加剂硫的Ni70Mn25Co5合金粉末作触媒合成了金刚石单晶，通过对比，发现添加剂硫的引入使得金刚石内的包裹体含量增加，使晶体表面出现熔坑；利用X射线荧光光谱对晶体的杂质成分、相对含量进行了分析，发现杂质元素锰、硫的含量随着触媒中硫的添加量的增加呈增加趋势，由此推测在金刚石生长过程中生成了难熔的MnS，MnS以包裹体的形式进入金刚石中，在一定程度上破坏了金刚石的晶格排列，使得表面出现熔坑。     

P110套管静水压试验开裂失效分析

对静水压试验中开裂失效的P110套管进行了断口形貌观察、化学成分和金相分析、能谱分析,结果表明,导致套管失效的原因有两方面,一是管体内壁存在淬火裂纹,二是管体中存在非金属夹杂。为避免此类失效的发生,提出了生产过程中的注意环节及改进措施。     

低碳铝镇静钢QD08中Ds类夹杂物分析与控制

低碳铝镇静钢QD08主要用于制造汽车发动机爪极,Ds类夹杂物超标,严重影响其疲劳寿命。采用电子显微镜、SEM和EDS等方法,对夹杂物形貌、尺寸及成分进行分析。研究认为,提高钢水洁净度,避免连铸卷渣将减少钢水中的夹杂物。并且通过改进生产工艺,有效控制了QD08中的大颗粒Ds类夹杂物,为现场改善Ds夹杂提供技术指导。     

球磨机ZGMn13衬板的失效分析

采用化学成分分析、金相检验等方法,对高锰钢衬板在使用中的碎裂进行分析.分析表明,衬板中存在严重的疏松,晶界上有大量未溶块状碳化物并析出针状碳化物以及球状氧化物;热处理工艺不当、铸造疏松以及非金属夹杂物的超标是导致球磨机衬板早期失效的主要原因,并提出了改进措施.     

Mathematical model of electromagnetic elimination in tubule with high frequency magnetic field

In order to find the ways to improve the elimination efficiency with high frequency magnetic field, a mathematical model of electromagnetic elimination （EME） in the tubule with high frequency magnetic field was set up. The calculated results show that by ignoring the flow of molten metal, when the surface magnetic induction intensity of the metal （B0） is 0.03 T and the diameter of the tubule is 8 mm, the non-metallic inclusions with 30 μm diameter can be wiped offin 7 s from the center of the molten aluminum, whereas the elimination time of the 5 μm non-metallic inclusions is more than 240 s. When B0 is 0.03 T, the diameter of the tubule is 8 mm and elimination time is more than 30 s, the elimination efficiency of 5μm, 10μm and 30 μm non-metallic inclusions is about 60%, 90% and 100%, respectively, the elimination efficiency increases with the decreasing diameter of the tubule. It can be concluded that increasing the magnetic induction intensity or decreasing the diameter of the tubule can decrease the elimination time and improve the elimination efficiency in EME with high frequency magnetic field.