高碳贝氏体轴承钢滚动接触疲劳性能的研究

以GCr15Si1Mo贝氏体轴承钢为研究对象,在油润滑条件和无润滑条件下,对不同初始碳化物体积分数的试样进行滚动接触疲劳试验,采用扫描电镜观察试验前后试样的表面形貌和碳化物分布,并通过Weibull曲线确定试样滚动接触疲劳性能的优劣性。结果表明,在无润滑条件下,碳化物体积分数为1.9%的试样滚动接触疲劳性能优于碳化物体积分数为5.1%的试样。在油润滑条件下,贝氏体轴承钢的滚动接触疲劳性能的优劣性依次为：无初始碳化物试样、碳化物体积分数为5.1%试样、碳化物体积分数为1.9%试样。碳化物作为基体的硬质相,很容易成为疲劳源,无初始碳化物的贝氏体轴承钢的滚动接触疲劳性能优于有碳化物的贝氏体轴承钢;碳化物脱落后的凹坑增大了润滑油和试样表面的粘着力,有利于增加油膜厚度,从而提高滚动接触疲劳寿命。     

热轧轴承钢球球坯网状碳化物达标的工艺探讨

GB/T18254-2002标准规定:"供热加工用球化退火钢材不检查碳化物网状",而我国目前各大钢厂生产的较大直径GCr15轴承钢普遍存在碳化物网状超标状况,所以各热轧、热镦轴承钢球球坯的企业,必须通过自行生产工艺控制球坯内部碳化物网状达标。本文通过分析试验,确定热轧轴承球坯碳化物网状达标的工艺方法及达标条件。     

4Cr13模具钢的等温相变规律与预处理工艺优化

测试了4Cr13塑料模具钢的过冷奥氏体等温转变曲线,研究了该钢的等温相变规律,分析了经过不同工艺固溶(1 010～1 090℃保温2,3 h)和球化退火(905℃×2 h奥氏体化和700～770℃保温5,8 h等温球化)预处理后的显微组织和硬度,并获得最优工艺。结果表明：在725℃下试验钢的珠光体形核孕育期最短;经1 010℃固溶处理后,组织中存在大量球状碳化物,当固溶温度为1 070～1 090℃时,碳化物基本溶解,马氏体板条束明显粗化,最优固溶工艺为1 050℃×3 h,此时碳化物占比较低且弥散分布;随着等温球化温度升高,链状碳化物数量先减少后增多,并且保温8 h后球状碳化物的分布更均匀;1 050℃固溶3 h+905℃×2 h+750℃×8 h球化退火后试验钢的球化效果最好,直径小于0.5μm的碳化物占比约为78.92%,硬度最低,约为192 HBW。     

GCr15轴承钢的碳化物超细化

研究了传统球化退火、固溶+高温回火、固溶+等温退火3种球化处理工艺及其对GCr15轴承钢淬回火后的组织和性能的影响。试验结果表明,固溶+高温回火和固溶+等温退火工艺均能有效细化碳化物颗粒,后者还能有效球化碳化物颗粒。球化获得的超细化碳化物能细化淬回火后原始奥氏体晶粒,获得双细化效果,提高材料硬度和弯曲强度。     

含氮不锈轴承钢的孪晶碳化物及其对性能的影响

采用光学显微镜、扫描电子显微镜对40Cr15Mo2VN含氮不锈轴承钢中的锻造退火孪晶碳化物组织、淬回火后的孪晶碳化物及淬回火后的断口进行了观察和分析,结果表明,40Cr15Mo2VN含氮不锈轴承钢锻造退火后的孪晶碳化物在随后的淬回火过程中不能消除,并且该组织使材料的断裂模式发生改变,脆性增加,应视为缺陷组织。     

GCr15轴承钢中碳化物的定量分析

为了准确测定GCr15轴承钢中残余奥氏体的含量,必须先测出其碳化物的含量。采用计算法、金相法及电解萃取法分别测定了球化退火态GCr15轴承钢中碳化物的含量,并对这三种方法进行了比较。结果表明:球化退火态GCr15轴承钢中的碳化物体积分数为13.51%~16.61%;金相法只可估算碳化物的含量,准确性较差;计算法模拟计算的是材料在热力学平衡态条件下的相含量,只可作为其它方法的参照;电解萃取法是一种能相对比较准确测定碳化物含量的分析方法。     

轴承部件的显微组织及硬度分析

选用GCr15和GCr18Mo钢材分别制作滚动轴承的滚子和套圈,对两种部件做同样的等温淬火热处理后进行组织及硬度检验。试验结果表明:两部件表面至心部组织及硬度均匀。两部件的组织都由下贝氏体和碳化物组成,但套圈中的下贝氏体组织和碳化物都比滚子中的细小。滚子和套圈中下贝氏体针长宽比分别约为7.5和10,碳化物的平均直径分别约为0.55μm和0.42μm。滚子和套圈的硬度平均值分别为56.2 HRC和60.8 HRC。     

量块热处理工艺

我厂为了解决精度测量问题,曾试制量块,其热处理工艺如下: 一、材料的选择我们选用GCr15轴承钢作为制造量块的材料。二、锻造后的球化退火轴承钢球化退火工艺如图1所示。﹃扣勺翎乓何咖2.检查标准图1 GC月5钢退火工艺 (1)硬度:于IB 187~207; (2)金相组织:球化珠光体2~4级,碳化物偏析《3级,     

低温形变对GCr15钢碳化物球化及细化作用的研究

本文选取GCr15钢球化退火予备组织,探讨在高温奥氏体化后控冷至A_1以下的低温形变对钢中碳化物快速球化与细化的作用。一、试验材料与试验方法试验采用GCr15钢生产用原材料,加工成台阶试样,化学成分及冶金质量符合标准。轧制时台阶试样各分段的形变率为70％     

热处理工艺对纳米贝氏体渗碳轴承钢表层组织和性能的影响

目前渗碳纳米贝氏体轴承钢表层高碳成分组织与性能的演变规律还不是很清楚.设计一种高碳钢模拟G23Cr2Ni2Si1Mo纳米贝氏体渗碳轴承钢表层高碳成分,利用SEM、TEM、硬度和冲击等研究微观组织与力学性能随相变时间的演变规律.结果表明,试样在200℃贝氏体等温相变需要总时间为48 h.随着等温时间从0h延长到48 h,组织中的马氏体含量逐渐降低、贝氏体铁素体含量逐渐升高、残余奥氏体含量先升高后降低,在等温12 h时含量最高38.5％.等温48h后,组织中贝氏体板条平均厚度为48 nm.随等温时间的延长,试验钢的硬度先降低后升高,在等温12 h有最小值58.1 HRC;冲击韧性值逐渐增大,在等温48h达到最大值96.0 J/cm2;抗压强度逐渐降低,断裂应变逐渐增大.该研究结果更清晰地展示了纳米贝氏体渗碳轴承钢表层组织与性能的变化规律,为其工艺优化提供了理论支撑.     

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。     

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.     

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....