一种新型润滑剂在扩孔成形中的应用研究

通过分别在植物粉一水基润滑剂、聚乙烯薄膜、机油和油脂4种润滑条件下进行的薄钢板扩孔成形试验，研究了植物粉一水基润滑剂的应用性能。结果表明：在4种润滑剂中，使用植物粉一水基润滑剂的薄钢板平均扩孔率最高，凸模极限行程最大，扩孔成形性最好；植物粉一水基润滑剂的减摩润滑效果与板料种类有关，σa／σh较低和δ较高的板料效果较差。     

深冲用电镀钢板的摩擦特性及表面损伤的研究

采用扳成形动卷摩擦因数测试装置对两种铡扳(热浸镀 电镀,即GA-E钢板;IF钢电镀锌钢扳,即EG钢板）以及未电镀的裸板进行摩擦特性研究,着重研究了成形模具温度对摩擦的影响,并对两种镀层钢板经拉深后的表面损伤进行了分析。研究结果表明：(1)在相同的变形条件下,与EG钢板相比,GA-E钢板的摩擦因数随温度增加的变化幅度较小;(2)两种镀层钢板的摩擦因数均随冲头速度的增加而降低;(3)GA-E钢板接触表面损伤的主要形式为微裂纹,而EG钢板的接触表面损伤为犁划痕。     

Effect of coating material and lubricant on forming force and surface defects in wire drawing process

A pilot wire drawing machine as well as wire end-pointing roller was developed. Using these machines, a wire drawing test for four different coating materials and two different lubricants was performed as the reduction ratio increased from 10% to 30%. Materials used for a substrate in this study are plain carbon steel (AISI1045) and ultra low carbon bainite steel. To compute the friction coefficient between the coating layer of wire and the surface of die for a specific lubricant, a series of finite element analyses were carried out. SEM observations were also conducted to investigate the surface defects of wire deformed. Results show that the behavior of drawing force varies with the lubricant-type at the initial stage of drawing. The powder-typed lubricant with a large particle causes the retardation of full lubrication on the entire contact surface and the local delamination of coating layer on the wire surface. As the flow stress of a substrate increases, the delamination becomes severe.     

基于热混合润滑的钢/橡胶接触表面水润滑增强调控

目的 增强钢/橡胶摩擦副的润滑性能,为提高混合润滑状态下水润滑轴承的性能提供参考。方法 建立水润滑条件下钢/橡胶摩擦副的热混合润滑模型,讨论热效应对润滑性能的影响,并在此基础上进一步研究表面粗糙度、水基润滑剂黏度和供水压力对水润滑增强调控的作用。结果 与等温解相比,热效应使Stribeck曲线发生了右移,摩擦因数和载荷比增大,膜厚比降低。最高水膜温度随着转速的增加而升高,热效应对混合润滑性能的影响显著。减小摩擦副表面粗糙度,Stribeck曲线向左移动。在相同转速下,载荷比随着表面粗糙度的减小而降低,膜厚比反之。表面粗糙度越大,水膜温度越高,最高温度位于出口区,且钢的表面温度低于水膜和橡胶的表面温度。当水基润滑剂的黏度增大时,膜厚比增大,载荷比和最高水膜温度降低,Stribeck曲线发生左移。增加供水压力可以改善水膜压力分布,使水膜承载区增大、压力减小,粗糙峰接触压力和承载区减小,导致载荷比减小、膜厚比增加,Stribeck曲线向左偏移,水膜最高温度降低。当接触区由边界润滑向混合润滑过渡时,水膜最高温度出现拐点,且水膜最高温度拐点随着供水压力的增加而左移。结论 热效应会降低摩擦副的混合润滑性能,因此在混合润滑中不能忽略。考虑热效应时,通过减小表面粗糙度,或增加水基润滑剂黏度和供水压力,均有利于增强钢/橡胶接触表面水润滑的混合润滑性能。     

The effect of process and material parameters on the coefficient of friction in the flat-die test

The effects of process and material parameters on the coefficient of friction in the flat-die test were examined. Low carbon steel, a hot-dip galvanized steel and ExtraGal?,¹ another hot-dip galvanized steel were used in the tests. As the die surface roughness increased, the coefficient of friction increased most of the time. Under some conditions an optimum roughness was evident. The bare steel produced the highest coefficient of friction in the majority of the tests. The hot-dip galvanized steel and the ExtraGal? alternated as the material that produced the lowest coefficient. The speed and load effects, found in other applications, have been confirmed, in general: the coefficient decreased for increases in load and speed in most cases. The contact rarely appeared to be starved of lubricants. In most instances the die made of the hardened tool steel created lower coefficients of friction than the cast iron dies. The results can be best understood in terms of micro-plasto-hydrodynamic lubrication, aided by the flow of the lubricants in micro-channels.     

热镀锌铁合金和有机覆膜钢板成形特性的对比研究

通过单轴拉伸试验和模拟成形试验深入研究了锌铁合金镀层和有机覆膜层成形特性的差异，在此基础上分析了不同变形量条件下锌铁合金镀层和有机覆膜层的表面粗化规律。结果表明：有机覆膜钢板表面涂覆的有机膜层可以有效改善试样表面和冲头表面的摩擦状态，使钢板上的应变更趋于均匀化。     

计入表面吸附膜的热弹流润滑体系建模及分析

目的 研究表面吸附膜在热弹流润滑中的作用机理.方法 构建考虑表面吸附膜的非牛顿流体点接触热弹流润滑模型,分析润滑剂的非牛顿性、吸附膜及钢的热传导系数对热弹流润滑性能的影响.结果 润滑剂的非牛顿性及吸附膜的计入对油膜压力和厚度的影响很小.与牛顿流体相比,非牛顿流体可以得到较低的温升和摩擦系数.同时,随着非牛顿流体特征剪应...     

温模条件下镀锌钢板摩擦行为研究

开发了温模条件下钢板摩擦行为的评估装置,在此基础上研究了模具温度变化对镀锌钢板成形表面摩擦行为的影响。结果表明,不同镀层特性的镀锌钢板的摩擦系数随模具温度变化呈现出不同的变化规律。当模具温度升高时,热镀纯锌、电镀纯锌和热镀锌铁合金的摩擦系数均有所升高。由于预磷化膜的存在,预磷化电镀锌钢板的摩擦系数随模具温度变化有所波动,且总体维持在较低的数值。电镀纯锌钢板表面摩擦系数在模具温度较低时变化不大,但在模具温度较高时大幅度上升。     

粉末润滑界面边界层状态微观形态观察和分析

目的粉末润滑边界层状态预示着润滑条件的优劣。粉末颗粒以其良好的润滑性能和承载能力以及对极端工况的适应性,被广泛应用于诸多领域,因此需对粉末润滑界面的摩擦润滑性能展开深入研究。方法利用UMT-2多功能摩擦磨损测试仪,结合形状测量激光显微系统对粉末润滑界面边界层的微观形态进行观察和机理分析。重点研究载荷(1、2、4、6 MPa)、速度(2、4、8、16 r/min)、粉末层厚度(1.5、3.5、5.5、7.5μm)以及表面粗糙度(0.389、0.745、1.751、3.112μm)等工况条件对粉末润滑的影响机制。结果较大的接触载荷有利于形成致密的边界层,提高润滑性能。在速度较低时,不利于形成完整、致密的边界层,润滑较差,甚至产生爬行现象,随着速度的增加,润滑效果改善,但过大的速度又会加快粉末耗散。适量的粉末层厚度能够使摩擦界面间形成完整、厚实的边界层,提供良好的润滑能力。粗糙度适当的表面有利于粉末润滑剂存储、边界层的形成以及润滑作用的维持。结论合理选择接触载荷、速度、粉末层厚度以及试样表面粗糙度有助于提高粉末颗粒的润滑性能。     

Evolution of through-thickness texture gradients in various steel sheets

In order to investigate the evolution of through-thickness texture gradients in various ferritic steel sheets, samples of a deep drawing steel, a ferritic stainless steel and a low carbon steel were deformed by cold rolling with and without application of a lubricant during the deformation process. The hot band texture of all samples examined showed notable through-thickness texture gradients. The evolution of the cold rolling texture in the ferritic stainless steel and the low carbon steel in a solution-treated state was nearly independent of the lubrication during rolling. However, in the deep drawing steel and the as-received low carbon steel, the lubrication played an important role in the formation of the through-thickness texture gradients. Whereas the samples rolled with lubrication showed uniform textures throughout the sheet thickness, in the samples rolled without lubrication pronounced shear textures were observed on the sheet surface. The evolution of these through-thickness texture gradients is discussed in terms of inhomogeneous strain states computed by an FEM model. This article is based on a presentation made in the symposium “ ’99 International Symposium on Textures of Materials”, held at Sunchun National University, Sunchun, April 21–22, 1999 under the auspices of The Korean Institute of Metals and Materials and The Research and Development Center for Automobile’s Parts and Materials.     

Determination of frictional behavior in sheet metals using orthogonal arrays

Frictional behavior of two sheet materials, aluminum-killed drawing-quality steel (AKDQ) and electro-galvanized (zinc) drawing-quality steel (AKDQ-EG), is examined under conditions of varying die material, die radius, crosshead speed, and lubricant. Tests are conducted using a special apparatus designed to measure front and back tension on uniform tensile strip specimens pulling over a circular die, simulating both frictionless and frictional conditions under certain sheet-metal-forming conditions. Use of a specially designed test apparatus with four contact angles for the same test condition minimizes the error associated with the use of single measurements for the determination of friction coefficient. Lubricant and die material play important roles among different factors examined in determining the coefficient of friction. Die radius has the most pronounced effect on the coefficient of friction. Implication of these results on actual sheet forming processes are discussed.     

薄板深冲成形过程中摩擦系数的测定

采用作者设计的一种新型测量薄板深冲成形过程中工具与工件之间摩擦系数的模拟装置 ,测定了相同材质的带材在不同条件下的摩擦系数。测试过程中改变润滑条件、辊距及带材的表面取向 ,测试结果表明摩擦系数与润滑和冲头的几何形状有很大关系。为计算机有限元模拟提供真实摩擦边界条件 ,为有限元模拟结果的可靠性奠定了坚实的基础     

热镀锌带钢表面色差缺陷形成机理及改进措施

为了消除热镀锌板卷的色差缺陷,从热轧、镀锌、冲压工艺对色差缺陷形成机理进行分析。导致热镀锌板卷色差缺陷的主要原因有原料表面粗糙度不均匀、锌层厚度不均、冲压导致锌层开裂。针对这3种不同原因,制定了相应措施在热轧工序冷却装置上进行边部遮蔽;提高沉没辊安装精度、调节镀后冷却段移动风箱上下表面的风量;冲压模具表面强化、润滑等,有效减少了色差缺陷的不合格率。     

基于Archard修正模型的角接触球轴承磨损有限元分析

在分析轴承受力和运动的基础上,研究了轴承运行时球与滚道接触区的滑动,计算了一定条件下接触区滑动速度的分布,指出了球在滚道上运动时纯滚动点的存在。开展了球盘摩擦磨损试验,得到了轴承钢在边界润滑条件下的摩擦因数和磨损系数。利用有限元方法和Archard磨损计算模型,建立了球与内圈磨损的仿真计算模型,并分析了运行时间、径向载荷、接触角等因素对轴承磨损的影响。     

The friction modeling of different tribological interfaces in extrusion process

Friction and lubrication are of great importance in many important metal forming processes such as sheet metal forming, forging and extrusion. With the products being more complex, it may utilize different lubrication medium in different tool/workpiece interface in which the metal flow could be controlled more effectively. While there is a substantial body of published research on friction modeling in metal forming processes, there has been relatively little work on forming process in which different tribological interfaces such as lubricant/grease, lubricant/dry and dry/grease are existed. The objective of this research is to investigate the friction distribution in combined forward and backward extrusion process. A realistic model of friction is developed to determine the friction coefficient of lubricated tool/workpiece interface. The friction coefficient of the other interface in which grease or different lubricant may applied is then determined by a coupled FEM and experiment investigation. Both the simulation and experimental data will be presented.     

矩形盒拉深时摩擦润滑条件与压边力的有限元分析

建立了矩形盒拉深的有限元模型，进行了数值模拟分析，讨论了摩擦润滑条件和压边力对板料拉深过程的影响，两者对拉深过程的影响都比较大。从数值模拟结果分析中得知，在实际拉深过程中要尽量减小模具和板料的摩擦，通过有限元模拟分析方法得到最佳压边力数值。     

高润滑皮膜钢板的成形特性及在汽车覆盖件中的应用

高润滑皮膜钢板通过固化手段在合金化熔融镀锌钢板(GA钢板)表面的GA层形成固态润滑皮膜,紧密附着在钢板表面,从而降低钢板的表面摩擦系数,改善润滑性能,达到提高钢板成形性、削减原材料成本的目的。本研究采取适当方法对高润滑皮膜钢板和普通GA钢板的滑动性能、拉伸性能以及胀形性能进行了对比试验,并提出以成形余裕度作为成形性的评价参数,结合在实际汽车覆盖件生产中的成形余裕度测试。结果表明:高润滑皮膜钢板的各项性能对比普通GA钢板均有较大地提高;在成形稳定性方面,对比普通GA钢板提升了60%以上。目前,高润滑皮膜钢板已经在丰田、本田等汽车制造厂中被广泛使用。     

固态塑性成形过程中界面接触换热的实验研究

文章通过自制的接触换热系数测量设备对纯铜与3Cr2W8V合金钢、不锈钢与不锈钢间的接触换热系数进行了实验研究。分析了温度和载荷对接触换热系数的影响,并且分析了在铝合金和模具钢的接触面间加入玻璃润滑剂后对接触换热系数的影响。实验结果发现,接触换热系数与温度的关系并不是简单的正比关系,而与载荷的指数近似成正比关系,且在接触面涂上玻璃润滑剂后,接触换热系数可大大降低。     

一种植物粉-水基润滑剂在锥杯成形中的应用

通过4种润滑条件下薄钢板的锥杯拉深成形试验，研究了植物粉-水基润滑剂的应用性能。结果表明：植物粉-水基润滑剂减摩润滑效果最好，润滑效果与板料种类有关，塑性较高的搪瓷板应用效果较好。     

压铸模乳液涂料的润滑机理

压铸模乳液涂料的润滑机理在于它的润滑剂大部分受热分解而释出气体。在整个压铸过程中，在模具型腔和金属间形成持久而又适度的气隙，润滑层由释放出的气体和残留的润滑剂所构成，所以润滑剂的发气特性和高温摩擦因数是控制乳液涂料的关键性能。在压铸过程开始时同温摩擦因数起主导作用。接着气体润滑的作用控制着整个过程。对于大型铝合金和镁合金铸件来说，必须在配方中加入高耐热性的成分，在整个压铸过程中才能够持久而且稳定地释放出气体。