Nb-Ti-Cr-Si基超高温合金有坩埚整体定向凝固组织的演化

分析了Nb-Ti-Cr-Si基超高温合金有坩埚整体定向凝固试样不同区域的组织,结果表明未熔区的组织由初生相Nbss、块状的(Nb,X)5Si3和少量的小块状Cr2Nb组成。在过渡区初生相Nbss依附在未熔区的Nbss优先生长,Nbss/(Nb,X)5Si3共晶组织生长比较混乱,在初生相Nbss枝晶间出现了富Ti的Nbss/Cr2Nb共晶团。稳态区组织中Nbss和(Nb,X)5Si3定向排列,实现了整体定向凝固。固/液界面形态为树枝状,在糊状区出现了Nbss/(Nb,X)5Si3、富Ti的Nbss/(Nb,X)5Si3和Nbss/Cr2Nb三种共晶组织,根据组织分析的结果并总结了其凝固路径,测试了不同区域组织的显微硬度,结果表明稳态区的(Nb,X)5Si3的显微硬度最高。     

热处理对定向凝固Nb-Ti-Si基超高温合金组织及显微硬度的影响

对以2.5μm/s和50μm/s抽拉速率定向凝固的Nb-Ti-Si基超高温合金试样,分别进行了在1250,1350℃和1400℃保温50h的均匀化热处理。结果表明:均匀化热处理后的组织主要由Nbss,β(Nb,X)5Si3及γ(Nb,X)5Si3相组成,在以2.5μm/s抽拉速率定向凝固的试样中还出现了针状Cr2(Nb,Ti)析出相。随均匀化热处理温度的升高,针状析出相的数量增多;经均匀化热处理后定向凝固试样中的大块六边形硅化物的平直边界和尖锐的棱角逐渐圆润;共晶胞中心的细小硅化物逐渐球化,而共晶胞内板条状的硅化物部分碎化,逐渐变成小岛状。热处理后并没有发生β(Nb,X)5Si3向α(Nb,X)5Si3的晶型转变。同定向凝固态相比较,均匀化热处理后合金的显微硬度显著提高,并且随着均匀化热处理温度的升高,合金及各相的显微硬度先升高后降低,在1350℃/50h热处理后显微硬度值最高。     

Nb基超高温合金定向凝固组织及其共晶凝固机理研究进展

Nb-Si基共晶体系超高温合金是目前最有希望应用于超高温环境的材料之一.目前的研究还仅仅停留在合金化改善其综合性能及抗氧化涂层的制备等方面,而对其共晶凝固机理等更深层次的研究还较少.从Nb基超高温合金铸态、定向凝固态组织及相组成等角度入手对该合金的微观组织变化规律进行了分析和总结;并对Nb基超高温合金共晶凝固机理的研究进展进行了综述;此外,还讨论了该合金目前仍需解决的问题.     

Nb基超高温合金制备及定向凝固用坩埚的选择

目前Nb基超高温合金的制备主要是通过多次电孤熔炼得到成分均匀的铸锭.其定向凝固或者是在水冷铜坩埚内采用Czochralski技术进行,或者是采用不需要坩埚的悬浮区熔法实现,但这两种方法都不能得到较高的温度梯度.为了获得更好的定向凝固组织,需要在超高温超高真空定向凝固设备上进行有坩埚的整体定向凝固.结合国内外共晶自生复合材料常用的制备技术,提出了适用于铌基超高温合金整体定向凝固技术的坩埚材料及其涂层技术.     

铌硅化物基超高温合金电弧熔炼态组织和成分分布

采用真空非自耗电弧熔炼后再真空自耗电弧熔炼的方法制备了Nb-Ti-Si-Cr-Al-Hf-Mo-B-Y超高温合金的母合金锭,分析了合金锭不同位置的组织形貌、相组成和成分分布特点.结果表明:母合金锭主要由Nbss, (Nb,X)5Si3和(Nb,X)3Si三相组成.母合金锭组织主要由初生Nbss枝晶,花瓣状Nbss+(Nb,X)5Si3共晶和块状(Nb,X)3Si组成;但在母合金锭底部和顶部的中心部位组织却由分布均匀的Nbss+(Nb,X)5Si3共晶组成,没有出现初生树枝状Nbss和块状(Nb,X)3Si.母合金锭中的成分分布特点为Si由锭边缘向中央逐渐升高,Ti由边缘向中央逐渐递减.     

Cr含量对Nb-Si基超高温合金组织和室温断裂韧性的影响

采用真空非自耗电弧熔炼的方法制备了4种名义成分为Nb-22Ti-16Si-4Hf-3Al-x Cr(x=0,3,5和10,原子分数,%)的合金,并于1450℃保温50 h进行了均匀化处理,研究Cr含量对Nb-Si基超高温合金电弧熔炼态和热处理后组织,及其电弧熔炼态下室温断裂韧性的影响。结果表明:添加Cr没有改变硅化物的晶型(均为γ(Nb,X)5Si3),但其含量随Cr含量的增加而增加,而Nbss/γ(Nb,X)5Si3共晶的含量则逐渐降低;添加Cr还促进了Nbss/(Nb,X)5Si3/Cr2(Nb,X)三相共晶的形成,且该共晶的含量随合金中Cr含量的增加而增加。经1450℃/50 h热处理后,原电弧熔炼态的Nbss枝晶和共晶组织消失,且合金组织明显变得均匀。Cr含量为0,3%和5%的合金组成相为Nbss和γ(Nb,X)5Si3,而在Cr含量为10%的合金中则出现了Nbss,γ(Nb,X)5Si3和Cr2(Nb,X)的三相平衡组织。电弧熔炼态下合金的室温断裂韧性随Cr含量的增加呈现降低的趋势。     

电弧熔炼Nb-Ti-Si-Cr-Hf-Al-B-Y超高温合金母合金锭的组织形成和成分分布特点

采用真空非自耗电弧熔炼然后再真空自耗电弧熔炼的方法制备了Nb-Ti-Si-Cr-Hf-Al-B-Y超高温合金的母合金锭,分析了其在不同位置的组织组成及成分分布特点.发现母合金锭的组织主要由Nbss与(Nb,X)5Si2两相组成.在母合金锭的边缘部位,组织主要由(Nbss (Nb,X)5Si3)共晶团组成,此外还有少量的Nbss枝晶;但在母合金锭的中央部位,组织由初生(Nb,X)5Si3块或板条以及(Nbss (Nb,X)5Si3)共晶团组成.母合金锭中的成分分布特点为Si含量由锭边缘向中央逐渐升高,而由锭下部到上部逐渐降低;Ti含量的变化则为由锭边缘向中央,由锭下部到上部逐渐减少.     

铌-硅基超高温合金定向凝固及相组成的热力学研究进展

铌-硅基超高温合金作为有望在1200℃以上温度使用的结构材料而受到广泛研究。综述了铌-硅基超高温合金中合金化元素的作用以及熔体过热处理技术在该合金定向凝固中的应用,并评述了对铌-硅基多元合金相组成等的热力学研究进展。     

Nb-Si基超高温合金的定向凝固研究进展

主要论述水冷铜坩埚内的Czochralski定向凝固、电子束定向凝固、光悬浮定向凝固、整体定向凝固和电磁冷坩埚定向凝固5种定向凝固的基本原理,优缺点以及研究定向凝固Nb-Si基超高温合金所取得的进展。现阶段,基本不用Czochralski定向凝固和电子束定向凝固研究Nb-Si基超高温合金了;到目前为止,光悬浮定向凝固是制备研究Nb-Si基超高温合金的主要手段;整体定向凝固制备的Nb-Si基超高温合金的断裂韧性已达20MPa·m1/2左右;电磁冷坩埚定向凝固制备的Nb-Si基超高温合金的高温拉伸强度已达200MPa(1250℃)。     

Fe-C-Cr合金定向凝固组织

对经定向凝固的共晶 Fe—2.94％C—29.1％Cr 合金及过共晶 Fe—3.12％C—35.9％Cr、Fe—2.80％C—33.1％Cr 合金的凝固组织作了研究。上述三种合金中的初晶及共晶碳化物均为(Fe,Cr)_7C_3它们都以小面状析出,其中初晶在与凝固方向垂直的截面上为六角形块。初晶碳化物在定向凝固时以六角形状进行包抄式的凝固,然后再从六角形壳向内凝固,最终生成完整六角形。随着凝固速度变小,初晶(Fe,Cr)_7C_3的截面尺寸及间距增大,且从实心的六角形棒变成空心的六角形棒。过共晶合金的液固两相区长度约为1.5mm。共晶合金凝固时,碳化物的形貌为不规则多边形棒,且在凝固速度大时,组织细小。上述三种合金,当凝固速度 R>2m/sec 时,液固界面将变得凹凸不平。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from