强磁场对Fe-0．12C合金在顺磁居里温度以上先共析铁素体等温转变的影响

利用光学显微镜研究了强磁场对高纯度Fe—0．12C合金在顺磁居里温度以上先共析铁素体等温转变的影响。结果表明：在铁素体呈顺磁性且磁化率很低的顺磁居里温度以上进行等温转变,强磁场能够显著促进Fe-0．12C合金的块状先共析铁素体的转变,增加块状先共析铁素体的转变量。在顺磁居里温度以上,随等温转变温度的降低,块状先共析铁素体晶粒沿磁场方向伸长且呈链状形式排列。这是因为强磁场作用下先共析铁素体在较低温度等温转变时的磁偶极子相互作用增强所致。     

强磁场对Fe-0.28%C-3.0%Mo合金中退化铁素体转变的影响

采用等温热处理时外加12T 强磁场对Fe-0.28%(质量分数,下同)C-3.0%Mo合金中退化铁素体的转变进行研究.在有、无强磁场条件下,港湾温度附近及以下都得到了退化铁素体.强磁场加速了退化铁素体的转变,升高了退化铁素体转变TTT(temperature-time-transformation)曲线的港湾温度.没有磁场时的港湾温度大概为610℃左右,外加强磁场后港湾温度为640℃左右,这主要是由于强磁场降低了退化铁素体的自由能.     

强磁场对铁基合金中奥氏体分解的影响

简要回顾了强磁场在铁基材料领域的发展和应用历史.简述了强磁场影响奥氏体分解的基本原理.强磁场升高铁基材料中马氏体、贝氏体、珠光体、铁素体的转变起始温度,加速其转变行为.强磁场作为材料热处理的新手段,对于材料组织和性能控制具有重要作用.如何定量控制强磁场对铁基材料的相变与析出等还有待于更深入的研究.     

热变形奥氏体状态对珠光体转变动力学的影响

本文在40Cr 钢上研究了热变形奥氏体状态对珠光体转变运力学的影响,所得结论如下:1)在本文的试验条件下,高温形变有促使珠光体转变的作用;2)奥氏体状态必然对以后的相变动力学及相变产物的组织与性能有显著影响,研究形变对钢的相变以及相变后的组织与性能的影响,必须明确相变前奥氏体所处的状态,即加工硬化状态或再结晶状态等等;3)于再结晶状态下,形变对珠光体转变的促进作用,是再结晶细化晶粒作用的反映。晶粒愈细小,单位体积内的晶界面积愈大,从而使相变的核心数目增多,导致转变速度的加快。     

强磁场下冷却速度对Fe-0.12%C合金显微组织的影响

研究了强磁场(12T)下冷却速度对Re-0.12%C合金中的珠光体组织形貌的影响,结果表明:强磁场下珠光体团的长轴方向与磁场方向平行且伸长的程度随其冷却速度的提高而减弱,板平面平行于磁场方向比垂直于磁场方向放置的试样的珠光体面积分数低,同时珠光体团长轴方向与磁场方向平行且伸长的程度也低,最后,探讨了强磁场下珠光体组织形貌的演变机理.     

V-Ti钢热变形奥氏体的连续冷却转变行为

为研究V—Ti微合金钢热变形奥氏体的连续冷却转变行为,在对V—Ti徽合金钷进行Gleeble3800热模拟后,建立了连续冷却转变曲线（CCT图）,探讨了变形量和高温停留对CCT曲线和相变组织的影响．研究表明：变形量的增大,促进了先共析铁素体和珠光体转变,使其孕育期缩短,一定程度上也促进了高冷速下的贝氏体转变,但使低冷速下的贝氏体转变受阻;马氏体转变温度的降低说明变形量的增大在一定程度上使马氏体相变受阻;变形后若高温停留,组织发生静态回复,对扩散型相变的先共析铁素体和珠光体转变以及半扩散型相变的贝氏体转变均不利,使先共析铁素体转变量和珠光体转变量都有相对减少,而对马氏体转变影响不大．     

强磁场作用下材料扩散型固态相变的微观机理

为探讨强磁场对物质原子尺度行为(电子运动、离子扩散)的影响,采用光学显微镜研究强磁场作用下Fe-0.12%C合金的扩散型固态相变;采用数字多用表测量强磁场作用下的纯铝板电阻研究其电子分布.结果表明:随磁感应强度增强,Fe-0.12%C合金室温显微组织中,铁素体晶粒平行于磁场方向伸长并呈链状排列的趋势增强,珠光体团的长轴方向平行于磁场方向伸长的程度也增强;纯铝板的电阻在平行于磁场方向放置时减小,垂直于磁场方向放置时电阻有增加趋势.这是由于组成金属晶体的自由电子和排列成晶格状的金属离子在磁场作用下受到洛伦兹力的作用,随磁感应强度增强,沿磁场方向的电子浓度、金属离子扩散有增强趋势,导致磁场作用下材料扩散型相变的室温组织出现形状各向异性.     

差示扫描量热法测定22Mn2SiVBS钢CCT曲线

在STA-409PC型同步热分析仪上,利用差示扫描量热法对自行设计的低碳空冷贝氏体钢（22Mn2SiVBS钢）进行相变点的测定和显微组织观察,并结合相变点的计算公式对比分析,绘制钢的CCT曲线,验证理论计算公式的正确性。结果表明：该钢的奥氏体转变开始温度A1点为732℃,转变终了温度A3点为836℃;珠光体临界冷却速度是（vp）0．667℃／s,铁索体临界冷却速度（vF）1．16℃／s,与理论计算结果符合较好;控制该钢的轧（锻）后空冷速度为：vF≤v实际〈vB,可以得到以粒状贝氏体为主的显微组织,钢具有强韧性配合良好的力学性能。     

V对H13型压铸模具钢相变特性的影响

本研究采用热膨胀仪测定了不同钒(V)含量的H13型压铸模具钢的连续冷却转变(Continuous cooling transformation,CCT)曲线及等温转变(Time temperature transformation,TTT)曲线,并结合扫描电镜、显微硬度仪、X射线衍射仪分别探究了V元素含量对H13型压铸模具钢相变点(加热过程中珠光体转变为奥氏体的温度A_(c1),加热过程中渗碳体和碳化物完全溶入奥氏体的温度A_(ccm)和奥氏体化后冷却过程中奥氏体向马氏体转变开始温度M_s)、连续冷却转变规律、等温转变规律以及硬度的影响。结果表明:随着V元素含量的增加,试样的M_s点升高,CCT和TTT曲线中的珠光体及贝氏体相区出现左移,CCT曲线中珠光体和贝氏体相区的临界冷却速度加快,试样的淬火态硬度降低。这主要是因为随着V含量的升高,试样中形成了更多稳定的V系碳化物,从而降低了奥氏体化过程中溶入基体的碳含量,进而降低了过冷奥氏体的稳定性,最终促进珠光体及贝氏体相变的发生,即CCT和TTT曲线中珠光体及贝氏体相区左移。     

热处理冷却速率与Cr掺杂对Heusler合金Mn_(50-x)Cr_xNi_(40)In_(10)相变、磁性以及磁热效应的影响

本文采用电弧熔炼方法制备了两组Mn_(50-x)Cr_xNi_(40)In_(10)(x=0,1,2)多晶系列样品,通过改变热处理的冷却速率与Cr掺杂量对样品的相变、磁性以及磁熵变进行了研究。结果表明,与淬火样品相比,慢冷合金的马氏体相变温度较高。随着Cr含量的增加,奥氏体的磁化强度逐渐降低,而马氏体的磁化强度逐渐增强。与淬火样品相比,慢冷样品在相变温度附近,奥氏体和马氏体的磁化强度增强。这主要是由于慢冷样品的原子有序度较高,从而导致其较高马氏体相变温度以及强磁性。不同的热处理冷却速率对Mn_(49)Cr_1Ni_(40)In_(10)合金的磁熵基本没有影响。此外,施加3 T磁场时,在Mn_(49)Cr_1Ni_(40)In_(10)合金中观察到约为13 J/(kg·K)的大的熵变。     

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.……     

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.     

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.     

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.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...