不断扩大流化床淬火的应用范围

<正> 近几年来对改进淬火工艺、提高其再现性及控制方法给予了很大的关注。钢制件的淬火硬化与钢合金的相变特征、制件尺寸和形状、淬火介质的冷却特性等有关。钢合金的相变特征是冶金学变数——含碳量、化学成分、奥氏体晶粒大小等的函数,这可由钢合金的“TTT”相图来很好的描述。然而,淬火介质的冷却特性却难以分析描述,这是     

适度硬化表面淬火钢的加工和应用(一)

表面淬火钢的硬化程度对变速器零件的加工和应用起到决定性的作用.硬化程度主要取决于材料的化学成分,是选择表面淬火钢淬火温度的主要标准,因为稳定的材料质量是高效率大规模生产的保证.顶端淬火样品的变形和热处理条件对测量结果具有决定性的影响.由于明显的不确定性,必须考虑到顶端淬火试验测定的硬化程度和材料化学成分之间的不同.在狭窄的硬化程度范围内对表面淬火钢的热处理确保了可预测和可再现的大规模生产.一些实例表明,由于稍稍偏离所需的硬化程度范围造成不规则的热处理变形,并因成本问题而被放弃.     

适度硬化表面淬火钢的加工和应用(二)

表面淬火钢的硬化程度对变速器零件的加工和应用起到决定性的作用.硬化程度主要取决于材料的化学成分,是选择表面淬火钢淬火温度的主要标准,因为稳定的材料质量是高效率大规模生产的保证.顶端淬火样品的变形和热处理条件对测量结果具有决定性的影响.由于明显的不确定性,必须考虑到顶端淬火试验测定的硬化程度和材料化学成分之间的不同.在狭窄的硬化程度范围内对表面淬火钢的热处理确保了可预测和可再现的大规模生产.一些实例表明,由于稍稍偏离所需的硬化程度范围造成不规则的热处理变形,并因成本问题而被放弃.     

汽车转向器传动齿轮断裂失效分析

为确定某转向器传动齿轮断裂原因,对该转向器齿轮进行了断IJ＇宏观分析、SEM电镜分析、化学成分分析、金相组织、硬度检测分析及故障再现试验。试验表明：由于转向齿轮淬火和高温回火边缘区硬度较大,并且该处容易应力集中,在受到外力时容易产生裂纹,从而最终导致断裂,并根据断裂原因制定了相应的解决方案。     

磁场淬火原理与应用

所谓磁场淬火就是工件在淬火槽中淬火时,外加磁场的作用,从而改善淬火质量的一种淬火工艺方法。其工艺原理图如图1所示。磁场淬火与常规淬火相比,具有下列优点: 1.可以降低淬火时的组织应力,防止淬     

大力推广应用新型淬火介质

1推广应用新型淬火介质的意义新型淬火介质通常指各种专用淬火油和优质水溶性淬火剂。和普通机油相比，专用淬火油具有更强的冷却能力、更合理的冷却速度分布、更长的使用寿命，或者更能保持工件的光亮性。优质水性淬火剂能不同程度地降低钢件在水中淬火时的低温冷却速度，因而能防止淬裂，或获得更高的淬火硬度和更深的淬硬深度。由于有这些优点，推广应用新型淬火介质可获得以下收效。（1）改善和提高淬火工件的内在质量优质水性淬火剂能有效地降低水的低温冷却速度，因此能防止工件的淬火开裂。专用淬火油及水性淬火液具有高于普通机油的…     

精密轴承套圈淬火油的选择

减少轴承套圈淬火变形是热处理工作者的永恒课题,而淬火油的选择是解决淬火变形的重要环节.选择冷却速度介于快速淬火油(冷油)和等温淬火油(热油)之间的温油作为淬火油,解决壁厚小于16mm套圈的淬火变形问题.     

一种较为理想的淬火槽

为了使淬火槽内的淬火介质温度均匀,能迅速进行循环冷却,使淬火工件的质量提高,我们对淬火槽进流管的位置进行了改革。通常的淬火槽进出水管(或油管)及淬火介质在槽内的流动情况如图1。这种淬火槽使淬火介质在槽内上下翻滚,热流不能顺利排出,而冷流又由于上     

球销自动淬火工艺在汽车设备加工中的应用

为解决传统汽车球销手工感应淬火法存在淬火不均匀、生产效率较低的不足,提出了球销自动淬火工艺在汽车设备加工中的应用,分析汽车球销自动淬火设备运行机理,基于汽车球销淬火上料下料方式的优化,以及感应淬火汽车球销的搬运结构的改进,实现球销自动淬火工艺在汽车设备加工中的应用,实验数据表明,提出的汽车球销自动感应淬火工艺较传统手工感应淬火方法,淬火效率提高76.75%,淬硬层合格率提高17.10%,适合于大批量汽车球销的自动化感应淬火生产。     

结构合理的淬火槽

淬火槽的结构影响淬火介质的均匀性,对淬火工件的质量有影响。我厂淬火槽结构如图所示。这种淬火槽的进流管由槽底分三处进入,淬火介质较平稳地向上浮,槽内热介质由槽上四周均匀地排入溢流槽,淬火槽内同一横截面     

Determination of metal strain-hardening curves from conical-indenter impression results

A new technique to determine the strain resistance of metal with a pronounced yield strength is proposed. As an approximation of the curves of the strain-hardening resistance of metals, a three-parameter function is used, which optimally describes the form of real curves. Three conical indenters with different taper angles are used. Multiple simulations of indenter impression into a metal by the finite-element method are carried out. As a result, a functional correlation is found between the parameters of the function approximating the hardening curves and the diagrams of conical-indenter impression into an elastoplastic medium. It is experimentally shown that the curves of strain hardening can be quite accurately determined by the proposed technique.     

Shape control in micro borehole generation by EMM with the assistance of vibration of tool

Electrochemical micromachining (EMM) is gaining importance day by day due its advantages that include no tool wear, absence of stress/burr, high MRR, bright surface finish and ability to machine complex shapes regardless of hardness. Overcut and taper formation is the main problem during micro borehole machining. In this paper, an electrical circuit model of EMM is presented for better understanding of the process and experimental MRR is found to be in good agreement with theoretical MRR. In the present set up variation of overcut with voltage, pulsed frequency, vibration amplitude of tool and vibration frequency of tool are investigated. To reduce overcut and taper angle of micro borehole, machining zone is simulated with a reversed taper tool and verified by practical experiments for proper shape control during micro borehole generation. Variation of micro nozzle angle with different feed rates and different times of machining are also investigated for the shape control during micromachining with conical tool. Finally, it has been shown that both reversed taper and forward taper tool can be used for generation of taper less micro features i.e. boreholes.     

Effect of taper tension profile on the telescoping in a winding process of high speed roll to roll printing systems

Winding is an integral operation in almost every roll to roll system. A center-wound roll is one of the suitable and general schemes in a winding mechanism. In general, the quality of wound roll is known to be related to the lateral displacement error and starring defect of a wound roll. Especially, a telescoping within a center-wound roll can cause damages such as misalignment between layers, folding, wrinkle, etc. Taper tension is known to be one of the major factors which affect the shape of a wound roll. It is therefore necessary to analyze the relationship between taper tension profile and telescoping within the center-wound roll to prevent winding failure and to sustain high quality of the printed materials. It is hard to compensate for undesirable winding roll shapes such as telescoping, because a winding is commonly a final process in roll to roll systems and has no feedback control mechanism to correct winding roll shape directly during winding operation. Therefore, an optimal taper tension profile and the accurate control of it in a winding section could be one way to shape the fail-safe of a wound roll. Through the correlation between taper tension profile and telescoping in a winding process, a mathematical model for the telescoping due to tension distribution in cross machine direction was developed, and verified by experimental study. A new logic to determine the proper taper tension profile was designed by combining and analyzing the winding mechanism which includes nip induced tension model, relationship between taper tension profile and telescoping, relationship between taper value and telescoping. Numerical simulations and experimental results show that the proposed method is very useful for determining the desirable taper tension profile during the winding process and preventing defects of winding roll shape such as telescoping.     

A taper tension profile maker in a converting machine

Winding is an integral operation in almost every web handling process, and a center-wound roll is one of the suitable and general schemes in a winding system. However, improper internal stresses within a center-wound roll can cause damage such as buckling, spoking, cinching, etc. Wound roll quality and performance are known to be related to the distribution of in-roll stresses. It is therefore necessary to analyze the relationship between taper tension in the winding section and internal stress distribution within the center-wound roll to prevent winding failure. But it is hard to compensate for an undesirable winding roll shape such as starring, buckling, and telescoping. This is because the winding section is the final process in a roll to roll system and has no feedback control system to correct winding roll shape directly. A time varying tension profile and accurate control of it in a winding section is one way to shape the fail-safe in-roll stress distribution of a winding roll. In this study, a new taper tension profile making method is aimed for designing high quality wound rolls. A new method to determine the proper taper tension profile was designed by analyzing the winding mechanism which includes the stress model in center-wound rolls, nip induced tension model, relationship between taper tension profile and telescoping, relationship between taper tension type and internal stress distribution. An auto taper tension profile making method was proposed not only to optimize radial stress distribution but also to minimize lateral error (telescoping). Simulation results show that the proposed method is very useful for determining the desirable taper tension profile during the winding process and preventing defects of winding roll shape such as telescoping, starting, and dishing and so on.     

锥面活塞环锥度方向的快速识别方法

为提高普通锥面活塞环锥度方向的检测效率 ,提出一种可快速判别多片同直径锥面活塞环锥度方向的方法 ,并介绍了测量过程中传感器最佳采样步距的选取方法和活塞环之间间隙的判别原则。     

低周循环应力-应变关系和损伤

引入硬化状态变量表征微结构变化对材料循环变形行为的影响，提出应变控制下材料的循环应力一应变关系，由此导出的疲劳损伤演变方程与材料的损伤和硬化状态有关，考虑加载历史的影响。其结果可以为分析多级疲劳加载时，损伤演变过程和剩余寿命估算提供新的思路。     

Analysis of taper produced in side zone during ecd

The full capabilities of electrochemical machining (ecm) have not been utilized in production, mainly due to some inherent problems associated with tool design. For example, the side wall generated during electrochemical drilling (ecd) of a cylindrical hole is tapered. To study the effect of process parameters on the taper produced during ecd, experiments were performed using brass as cathode, low alloy steel forgings and castings as anode and aqueous solution of NaCl as electrolyte. From the analysis of the results, some useful conclusions have been derived that would be helpful in controlling the taper produced by bare tool, bare bit tool or coated tool.     

Analysis of taper produced in side zone during ecd

The full capabilities of electrochemical machining (ecm) have not been utilized in production, mainly due to some inherent problems associated with tool design. For example, the side wall generated during electrochemical drilling (ecd) of a cylindrical hole is tapered. To study the effect of process parameters on the taper produced during ecd, experiments were performed using brass as cathode, low alloy steel forgings and castings as anode and aqueous solution of NaCl as electrolyte. From the analysis of the results, some useful conclusions have been derived that would be helpful in controlling the taper produced by bare tool, bare bit tool or coated tool.     

MODELLING OF HOLE TAPER AND HEAT AFFECTED ZONE DUE TO LASER BEAM PERCUSSION DRILLING

Determination of hole taper and extent of heat affected zone is a challenging task for manufacturing engineers from the quality and accuracy point of view of the laser-drilled hole especially in reflecting materials like aluminum. In this article, an axisymmetric finite element method-based thermal model has been developed for the determination of the transient temperature distribution in the aluminum sheet, which is further used for determination of hole profile, hole taper and extent of heat-affected zone during laser beam percussion drilling. Simulation results showing the effect of pulse width, pulse frequency, and peak power on hole taper and extent of heat affected zone incorporating the temperature dependent thermal properties and phase change have been presented. The developed model is also capable of predicting the hole profile through the isotherm generated along the depth of hole due to repeated laser pulses. The predicted values of hole taper are compared with the experimental results. It is found that the effect of pulse width on hole taper is more prominent than the peak power and extent of heat affected zone increases with the increase of pulse width, pulse frequency but it decreases with the increase of peak power.     

471型管端车丝机外圆加工刀具的改进

为解决 471型管端车丝机加工石油套管时管端螺纹锥度不规则变化的问题 ,对外圆加工刀具几何参数作了合理改进 ,从而减小了外圆加工时钢管所受径向切削力 ,保证了管端螺纹锥度的精度稳定性