铜锭品位对低压铸造黄铜水暖铸件冶金缺陷的影响

分析了铜锭品位对低压铸造黄铜水暖铸件常见冶金缺陷的影响，结果表明即使原始铜锭的品位相差较大，但当成分相近时，对铸件的结晶组织形态影响不大，夹杂相均为以Pb氧化物为主、混有Cu、Zn或Si等氧化物的复合夹杂；铜锭的冶金质量直接影响铸件的性能，在原工艺中应采取有效措施对铜熔液进行脱氧除渣，并调整铸件中的Al、Si和Sb元素含量，以有效减弱冶金缺陷对铸件性能的影响。     

电磁制动技术的发展及在板坯连铸结晶器中的应用

总结了板坯连铸结晶器中电磁制动技术的发展、研究状况以及冶金效果。电磁制动技术可以控制结晶器内钢液的流动、稳定弯月面、减少卷渣现象,有利于结晶器内夹杂物的上浮及去除,从而提高铸坯的质量,且为提高铸坯拉速创造了条件。结果表明电磁制动的影响因素有板坯宽度、浇注速度、浸入式水口（SEN）的形状等。     

电渣熔铸模拟三峡真机导叶组织性能研究及应用

主要介绍了电渣熔铸模拟三峡真机导叶各部位组织与性能及真机导叶的批量生产情况.模拟三峡真机导叶内部无缩孔、气孔、裂纹等铸造缺陷,残余夹杂物细小、均匀分布,有害元素S含量降低约1/3,钢液纯净,组织致密,大截面(590mm)中心部位成分偏析轻微,力学性能完全符合三峡导叶的技术条件要求.24件三峡真机导叶的力学性能与模拟真机导叶的相比,其韧性及塑性指标有不同程度的提高,表面质量也得到改善.     

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.     

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.     

精冲钢连铸坯角部横裂纹产生原因及控制措施

为了研究精冲钢角部横裂纹形成原因并制定相应控制措施,通过数值模拟计算了二冷区连铸坯温度场分布,在此基础上采用Gleeble 3500热模拟机测定了试验钢种在连铸条件下的断面收缩率。使用金相显微镜、扫描电镜对角部横裂纹附近成分、微观组织以及钢中夹杂物进行观察分析。结果表明,连铸坯角部横裂纹形成是由于钢中大尺寸夹杂形成裂纹源,弯曲过程中连铸坯角部表面温度处于第Ⅲ脆性区710~765 ℃,裂纹进一步扩展形成角部横裂纹。针对裂纹产生原因提出延长软吹时间、控制过程温降、调整二冷水量等措施,有效降低连铸坯角部横裂纹产生概率。     

气体保护熔炼条件下Mg-Gd-Y-Zr合金的夹杂物

本文研究了气体保护条件下,常规熔铸的Mg-Gd-Y-Zr合金中夹杂物的形貌、分布及形成原因,并通过计算分析了夹杂物的沉降行为.结果表明,Mg-Gd-Y-Zr合金中有MgO或Y的氧化物为主的球状、簇状、不规则状、线状的复合夹杂物和含熔剂夹杂物,夹杂物的平均尺寸为12.7μm,平均体积分数为0.26%.夹杂物出现的频率随其尺寸增大而急剧减小,尺寸在20μm以下的夹杂物占夹杂物总体积接近85%,尺寸在45μm以下的夹杂物占96%.计算结果表明,夹杂物沉降速率与其尺寸和密度相关;夹杂物密度增大,可使镁合金中夹杂物的最大尺寸减小,计算得到的合金中最大夹杂物的尺寸与实验结果基本一致.     

锆脱氧对船板EH36夹杂物和耐蚀性能的影响

为研究脱氧方式对船板夹杂物形态和耐蚀性能的影响,采用锆脱氧和铝脱氧,对比两种脱氧条件下钢板晶粒尺寸、夹杂物形态和耐腐蚀性能。结果表明,锆脱氧试验钢夹杂物主要为钙铝酸盐夹杂、球形复合氧化物;其中,大颗粒和长条状MnS夹杂物的密度较低,夹杂物弥散细小,可以阻止晶界迁移带来的晶粒长大,有效细化钢板晶粒尺寸。锆脱氧形成的钢中细小氧化物可以作为MnS异质形核核心,降低了钢基体MnS夹杂微区电化学腐蚀敏感性与扩展速度;这种复合氧化物电化学稳定性好,与铝脱氧方式相比,可以有效提升钢板耐蚀性能。     

Double oxide film defects in Ni-based super-alloy castings

A new class of defects has been recently discovered, which are regarded as double oxide film defects. In this study, a number of Ni-based vacuum-cast test bars were investigated. The fractures in the broken test bars were observed by Scanning Electron Microscopy （SEM）. Energy Dispersive Spectroscopy （EDS）, as well as Wavelength Dispersive Spectroscopy （WDS） were used to characterize the chemical elements of the fracture＇s surface. Observation by SEM revealed the presence of inclusions identified as films that appeared to have initiated the growth of carbides. This study has added to the evidence that oxide film defects do exist in Ni-based super-alloy in certain vacuum casting conditions. It provides a reference for researchers＇ further study on the defects, and provides a possible direction for researchers to improve casting technology so as to remove these defects.     

Structural features of powder materials operating under high temperatures, stresses, and wear

It is known that parts of hot zones of metallurgical plants as well as heavily loaded pressing and forging tools operate under a high temperature, elevated mechanical stresses, the action of a steam ambient, slag, surface wear due to contact with the hot metal, etc. The possibility of providing the requisite properties by using high-temperature alloys has already been exhausted because the complexity of their composition intensifies the segregation inhomogeneity of the ingots which cannot be eliminated in the process of hot deformation and homogenizing annealing. As a rule, fracture starts under the conditions of cyclic loads on local structural defects such as accumulations of coarse particles of the eutecie γ′-phase, borides, carbides, nonmetallic inclusions. The chemical inhomogeneity and the structural defects caused by it can be removed by using methods of powder metallurgy that can provide materials with unique properties unattainable in the conventional metallurgy. The present paper is devoted to the special features of the structure of powder nickel alloys. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 10–16, July, 1998.     

夹杂物对FGH95粉末高温合金切削加工力学特性的影响

FGH95粉末高温合金作为一种高强度、高耐热性的镍基高温合金,常用在制造先进航空发动机的压气机盘、涡轮盘、涡轮轴以及涡轮盘挡板等高温承力转动部件,是一种典型的难加工材料.FGH95粉末高温合金中非金属夹杂物的成分、含量、分类、形貌对粉末高温合金材料性能有着重要的影响.从切削加工角度,采用力学分析和显微镜观察的方法研究了FGH95粉末高温合金中非金属夹杂物对切削加工刀具的影响,分析了切削加工时非金属夹杂物的力学特性,提出了夹杂物在切削加工过程中的变形机理.     

Semisolid casting using a vertical-injection squeeze casting machine: material flow and tensile properties of Al-7Si-0.3Mg alloy

Semisolid die casting of thixotropic Al-7Si-0.3Mg alloy has been carried out using a vertical-injection squeeze casting machine. The flow of the billet surface layer during casting was determined by X-ray examination of embedded markers. Tensile properties of the castings were then evaluated and metallographic observations were made. The original billet surface layer was found to be largely confined to the surface layer in the biscuit, except for the top of the billet surface, which flowed to the upper surface of the casting. As a consequence, the incidence of oxide inclusions within the casting was very low, leading to high elongation values with low scatter. Significantly lower strength and higher elongation values were observed in the biscuit. This effect was attributed to there being a significantly lower concentration of the solute elements in the biscuit compared to the casting.     

Prediction model of austenite growth and the role of MnS inclusions in non-quenched and tempered steel

The austenite growth behavior of non-quenched and tempered steels (casted by continuous casting and molding casting processes) was studied. The austenite grain size of steel B casted by continuous casting process is smaller than that of steel A casted by molding casting process at the same heating parameters. The abnormal austenite growth temperature of the steels A and B are 950 °C and 1000 °C, respectively. Based on the results, the models for the austenite grain growth below and above the abnormal austenite growth temperature of the investigated steels were established. The dispersedly distributed fine particles MnS in steel B is the key factor refining the austenite grain by pinning the migration of austenite grain boundary. The elongated inclusions MnS are ineffective in preventing the austenite grain growth at high heating temperature. For the non-quenched and tempered steel, the continuous casting process should be adopted and the inclusion MnS should be elliptical, smaller in size and distributed uniformly in order to refine the final microstructure and also improve the mechanical properties.     

钛微合金化Q390钢的纯净度研究

针对国内某钢厂生产的含Ti微合金钢Q390（采用BOF-LF-RH-CC工艺流程）,对LF处理前、LF处理后、RH处理后、中间包环节及连铸坯取样,通过光镜、电镜能谱分析及大样电解等手段研究分析了该钢种的纯净度和夹杂物演变行为。结果表明：该钢种工艺生产过程稳定,生产的钢水纯净度较高,铸坯中大型夹杂物数量为1.4 mg/10 kg,夹杂物以CaO-SiO2-Al2O3复合为主,一些大型夹杂物中复合了较高含量的Ti。另外,对钢中一些典型夹杂物的产生机理进行了阐述。     

AN INVESTIGATION OF INTERNAL DEFECTS IN HIGH-CHROMIUM STAINLESS STEEL

在高铬不锈钢的生产中,影响质量最严重的是钢锭中的轴心裂纹和钢材中的髪纹。本文的研究结果指出,这两种缺陷属于同一来源,没有轴心裂纹的钢锭在锻成钢材后也没有髪纹。 钢锭中轴心裂纹是在凝固过程中形成的,因而冷凝条件对它有影响。利用耐火材料做锭模可以得到内部坚实的钢锭,减小锭模模壁厚度,增大钢锭圆锥度或降低浇铸温度等只能减轻而不能完全消除裂纹。 熔炼过程中的脱氧方法对钢中夹杂物的性质和形状分布有影响。改善脱氧方法并采用薄模浇铸,可以大大地减少轴心裂纹和髪纹,从而提高钢的收得率。我们认为夹杂物的性质、多寡及其形状分布可能对钢液的流动性和表面张力有影响;改善钢液的流动性或减小其表面张力可以促进钢液的充填性能,从而弥补凝固过程中由于冷凝收缩而产生的缺陷。 在一定压力以下的真空中熔化和浇铸可以得到内部良好的钢锭。通过真空熔铸所得到的钢锭,其柱状晶区大小缩小,而柱状晶的缩小对避免钢锭中轴心裂纹有利。得到这种效果的原因可能是多方面的,真空有去气作用,在真空中钢锭的凝固散热与在一般情况下有所不同,真空作用使钢液的性质发生变化等等。虽然,上述几方面的理论基础还有待于进一步研究,但从目前实际效果来说,真空熔化和浇铸应该认为是提高不     

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针对某钢厂生产的38B3汽车用钢,探伤时发现棒材表面有纵向裂纹的现象,采用金相显微镜和扫描电镜对裂纹试样进行观察和分析,结果表明,38B3汽车用钢棒材表面纵裂纹的产生,主要是由于A1、Si、Na等氧化物夹渣分布于连铸坯的表层下面,在轧制过程中由于应力作用沿Al、Si、Na等氧化物夹渣集中处产生裂纹.通过采取相应的措施改善工艺以获得高质量的铸坯.     

The use of tantalum in the process industry

Tantalum is one of the refractory metals, so named because of their excellent high-temperature properties. These metals, especially tantalum, have remarkable corrosion-resisting properties due to an inherent, self-healing oxide layer that protects the tantalum against the most hostile environments (except those containing fluorine or fluorides). In this article, the production, fabrication, and applications of tantalum are discussed, as are the advantages and disadvantages of using the material. C.E.D. Rowe earned his B.Sc. in metallurgy from the University of Durham, United Kingdom, in 1963. He is currently technical manager at Special Metals Fabrication Ltd., United Kingdom.     

Mechanical properties of metals for biomedical applications using powder metallurgy process: A review

The uses of biomaterials have been revolutionizing the biomedical field in deployment as implants for humans. During the past five decades, many implant materials made of metals have been put into practical use. Powder metallurgy techniques have been used to produce controlled porous structures, such as porous coatings applied for dental and orthopedic surgical implants, which allow bony tissue ingrowth within the implant surface, thereby improving fixation. This paper examines various important metals using powder metallurgy technology to produce elements of a total hip replacement. These alloys are 316L stainless steel alloy, Co−Cr−Mo alloy, and Ti−6Al−4V alloy. Also, this paper examines current information on the mechanical properties. Mechanical properties are discussed as a function of type of materials and process of fabrication. This article addresses the engineering aspects concerning the advantages and disadvantages of each type of material.     

粉末冶金Nb-35Ti-6Al-5Cr-8V合金组织演变及其力学行为

采用粉末冶金法对不同球磨时间的Nb-35Ti-6Al-5Cr-8V合金机械合金化粉末塑变行为,热压烧结材料的微观组织结构和力学行为进行了研究。研究结果表明：塑性良好的Nb-35Ti-6Al-5Cr-8V粉末随着球磨时间增加首先变形为大尺寸的片状、后经持续的加工硬化破碎成絮状;热压烧结能够制备微观组织可控晶粒细化的Nb-35Ti-6Al-5Cr-8V合金,合金由单一的Nbss相构成,Ti、Al、Cr、V元素固溶引起Nb晶格尺寸减小0.0685 ?;随着球磨时间增加合金晶粒明显细化进而显著提高了合金的维氏硬度和室温压缩强度,其变化符合材料硬度和强度的Hall-Petch规律。粉末冶金制备Nb-35Ti-6Al-5Cr-8V合金的各项力学性能明显优于熔铸法制备合金。     

脉冲电磁场下铝合金半连续铸造技术研究进展

利用脉冲电磁场引起的力效应、热效应及磁势能可显著改善铝合金半连续铸造组织性能,同时,脉冲电磁铸造技术在绿色生产、智能控制等方面紧密契合“低碳冶金”的国家战略要求。综述了脉冲电磁场在铸造晶粒细化、微观结构演变及析出物细化3方面的研究成果,分析了脉冲电磁场特性与材料相变的耦合机制,提出了脉冲电磁场控制凝固、析出相变组织的初步构想,以满足高性能铝合金的质量要求。着重介绍了基于理论指导开发的熔体表面脉冲电磁场技术及其在7XXX(φ203)、6XXX(φ380)、Al-Si(φ120)等多规格半连续铸造的工业实践,脉冲电磁场有望在今后铸造、热处理等多个冶金环节发挥更大作用。