Cr12MOV钢的隐晶马氏体及其强韧化

文章对Cr12MoV 钢的隐晶码氏体及其强韧化进行了研究。电镜分析表明,Cr12MoV 钢的淬火隐晶马氏体的微观形态与亚结构随淬火奥氏体化温度不同而异。950℃及其以下奥氏体化温度淬火,可获得单一的板条状位错融隐晶马氏体;而经950～1100℃奥氏体化温度淬火,则获得了由针(片)状孪晶马氏体与板条状位错马氏体构成的混合隐晶马氏体组织,并且孪晶马氏体随奥氏体化温度升高而增多。经机械性能试验发现,隐晶马氏体的微观形态与亚结构对钢的强韧性有直接影响。因此,为了使Cr12MoV 钢得到最有效的强韧化效果,不仅要均匀化和细化钢中的碳化物,而且要控制钢中隐晶马氏体的微观形态与亚结构。     

提高40 Cr钢强度和韧性的新途径

本文通过实验,研究了提高40Cr 钢强度和韧性的问题,即进行两次淬火,第一次高温淬火能够增加位错亚结构,减少孪晶,消除未溶碳化物,减少偏析;第二次常规淬火,获得第一次淬火所得位错马氏体的遗传,细化了晶粒,从而提高了强度和韧性。     

在线淬火对高强度钢板组织转变及力学性能的影响

对高强度钢板分别进行在线淬火+600℃回火以及离线淬火+600℃回火处理,对比研究了两种工艺下的组织和力学性能.结果表明:两种工艺下试验钢板的显微组织均为回火马氏体,在线淬火+回火后的马氏体板条间距更小,板条更长;在线淬火+回火后的马氏体具有更高的位错密度和更多的大角度晶界,且碳化物析出相的尺寸更加细小;在线淬火+回火后试验钢板的强度更高,但塑性和韧性略低于离线淬火+回火工艺下的.     

高强度低碳马氏体型钢的组织结构与疲劳性能的关系

本文对高强度低碳马氏体型钢的组织结构和疲劳性能间的关系进行了系统的研究。试验表明,在低温回火状态下,典型钢种25Si2Mn2CrNiMoV具有优良的疲劳强度和疲劳裂纹扩展抗力。试验钢中板条马氏中的位错亚结构,弥散分布的e碳化物以及良好的微观塑性延长了疲劳裂纹的萌生期。马氏体板条束,马氏体板条晶间的位向差以及马氏板条间的残余奥氏体薄膜则是控制疲劳裂纹扩展速率的组织结构因素。文中对在回火马氏体脆性区造成疲劳性能恶化的原因也进行了分析讨论。     

淬回火工艺对N-Mo合金化Cr13型耐蚀塑料模具钢组织与力学性能的影响

对N-Mo合金化Cr13型耐蚀塑料模具钢进行925～1 150℃保温0.5 h的油淬处理,再分别进行150～300℃保温2 h或者350～600℃保温1 h的回火处理,研究了淬回火工艺对该钢组织与力学性能的影响。结果表明：试验钢淬火后的组织主要为淬火马氏体,随着淬火温度的升高,晶粒长大,第二相逐渐固溶进基体,试验钢的硬度先增大后降低,当淬火温度为1 050℃时,硬度达到峰值,为57.7 HRC,此时第二相基本固溶进基体,残余奥氏体体积分数仅为8.49%。随着回火温度的升高,试验钢组织由回火马氏体向索氏体转变,第二相逐渐析出并长大;硬度呈先降低后升高再迅速降低的趋势,冲击吸收能量随回火温度的变化规律与回火硬度的变化规律相反,抗拉强度的变化规律与硬度的变化规律一致,屈服强度呈先增大后降低的趋势,并在回火温度为480℃时达到最大值,为1 445 MPa;在200℃以上温度回火后试验钢的塑性均保持在一个较好的水平。试验钢获得优异综合性能的热处理工艺为1 050℃×0.5 h淬火+200～300℃×2 h回火,此时组织为回火马氏体,硬度为48～53 HRC,抗拉强度为1 752～2 050 MP...     

淬火温度和回火工艺对4Cr5Mo2V钢高温耐磨性能的影响

将4Cr5Mo2V钢在1 000～1 090℃下淬火,并通过不同温度2次回火处理将相同淬火温度下试验钢的回火硬度分别调整至55,52 HRC,研究了淬火温度和回火工艺对显微组织、冲击韧性和高温(350℃)耐磨性能的影响。结果表明：回火硬度相同时,淬火温度过高或过低均会降低试验钢的韧性而加剧磨损表面材料剥落,从而降低耐磨性能;相同回火硬度下,1 030℃淬火条件下试验钢的韧性和高温耐磨性能最好,1 090℃淬火条件下最差;淬火温度相同时,较低温度回火试验钢因具有较高回火硬度,能够起到支撑表面氧化层的作用,其耐磨性能比较高温度回火时好;4Cr5Mo2V钢的推荐热处理工艺为1 030℃×30 min油淬+560℃×2 h×2次回火。     

热处理工艺对工程机械用1000MPa级高强钢组织与性能的影响

对工程机械用1 000MPa级高强钢进行不同温度的淬火和回火热处理,研究了热处理工艺对其力学性能和显微组织的影响,并得到了试验钢较佳的淬火和回火温度。结果表明:随着淬火温度升高,试验钢的强度先增大后降低,并在900℃时达到最大;830℃以下淬火后,组织中存在未溶铁素体,组织为铁素体和板条马氏体;900℃以上淬火后,组织为板条马氏体;随着回火温度的升高,试验钢的强度下降,塑、韧性提高,当回火温度达到450℃以上时,组织转变为回火索氏体,冲击韧性大幅提高;较优的热处理工艺为900℃淬火后在500℃回火。     

粒状贝氏体组织对热锻模具钢性能的影响

本文研究了4SiMnMoV钢连续和等温转变形成的粒状贝氏体组织的性能,回火后粒状贝氏体组织的室温和高温性能。粒状贝氏体组织回火后在室温时的韧性低于回火马氏体,但高温时具有较高的韧性。随着试验温度的升高(至250℃左右)回火后的拉状贝氏体韧性接近或超过回火马氏体组织的韧性,并没有兰脆产生(或不明显)。试验温度超过550℃时,各种回火组织的韧性均急剧上升。在100℃～500℃时回火后粒状贝氏体除具有良好的韧性外,强度也稍高于回火马氏体。从而指出大型锻模予热到100℃～250℃是十分必要的。     

ASTM 4130钢的局部脆化研究

利用焊接热模拟试验以及金相和透射电镜技术研究了中碳调质钢ASTM 4130钢的组织转变与冲击性能的关系。结果表明,一次热循环的粗晶区和二次热循环的临界粗晶区是调质态ASTM 4130钢焊接热影响区的2个局部脆化区,相对母材韧性损失分别达94.5%和96.6%。粗晶区脆化的主要原因是大量上贝氏体和未回火马氏体的生成以及晶粒粗大;沿晶分布的"项链"状M-A组元和块状铁素体的存在是临界粗晶区脆化的主要组织因素。     

基于V型缺口试样冲击性能确定1Cr17Ni2不锈钢的热处理工艺

对1Cr17Ni2不锈钢进行了不同温度的淬火+回火热处理,研究了其V型缺口试样冲击性能与淬火和回火温度的关系;基于V型缺口试样冲击性能确定了较佳热处理工艺,并测试了该工艺热处理后试验钢的拉伸性能。结果表明:V型缺口试样的冲击吸收功随淬火温度和回火温度的升高而增大;回火温度对其断裂方式的影响大于淬火温度的,随回火温度升高,断裂方式从沿晶和解理的脆性开裂向韧窝型韧性开裂转变;当淬火温度为980℃或1 020℃,回火温度大于650℃时,该钢可满足螺柱冲击韧性和强度的要求,如需二次回火,则推荐二次回火温度应高于620℃。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.