大规格电镦成形过程解析及端面凹陷改善方法

本文主要针对超大规格气阀在电镦成形过程中的蒜头端面凹陷问题,提出设计新型曲面接触式凹型砧子的方法以降低蒜头端面下沉深度,为实际电镦生产中获得较好的电镦成形形状提供方法依据。在MSC.Marc分析平台构建电镦有限元模型进行电镦模拟分析,根据有限元模拟电镦成形过程,针对性采用曲面接触式凹型砧子对电镦成形过程中的端面凹陷进行改善,分析凹型砧子对电镦成形过程中的蒜头端面下沉深度、蒜头直径、电镦温度的影响,发现新型曲面接触式凹型砧子能有效降低蒜头端面凹陷程度和改善电镦聚料形状。     

电镦机的改造

我们在使用原电镦机时,常常出现坯料电镦完后,夹紧缺不能及时泄荷松开。有时要让镦粗缸复位到止点时,夹紧缺才猛然松开。这时有些坯料温度已下降到终锻温度以下,对下道工序的模压成形很不利。因此,常常使电镦件大头前端出现叠层和裂纹,应力组织很不理想。改造后的电镦机在通往砧子缸和镦粗缸的油路中分别加了减压阀和压力继电器(含时间继电器)从而使电     

触底式镦粗工艺研究

利用Deform-3D对触底式镦粗和悬漏式镦粗两种工艺方案进行数值模拟,对比分析镦粗变形过程中应力、应变在轴向和径向上的分布情况,以及坯料心部的静水压力的分布规律。通过在坯料轴线方向设置追踪点分析坯料心部金属的流动及压实效果。分析结果表明:触底式镦粗时坯料内部的等效应变、静水压力状态更好,分布更均匀,压实效果更显著,更有助于锻合坯料心部的空洞缺陷,改善坯料内部质量。     

转向油泵定子的反挤压成型实验研究

研究了转向油泵定子的反挤压成型工艺,分析了工件产生端面高低不平以及底部缺料等缺陷的原因.通过改进凸模结构,有效地消除了这些缺陷,并找出了该类壁厚不均匀件在反挤压成型时的变形规律,为最终实现非均匀壁厚件的反挤压成型工艺的实用化提供了必要的实验依据.     

开式筒模锻造中坯料镦歪矫正方法

在自由锻锤上用开式筒模锻造时,由于法兰大,所需坯料也大,坯料的高径比有时很大。当高径比达到2.5～3时,镦粗时坯料容易镦歪。常用的矫正方法,一般是用垫铁把筒模的一边垫高,锤击坯料,使金属向另一边流动,或用赶铁将坯料赶向最需要的方位。当H/D<1时(H为坯料高度,D为坯料直径),镦歪的坯料用上述方法很难矫正,如继续镦粗,坯料就会严重分布不均,造成一边有很多飞边,另一边充不满模膛的观象,使锻件报     

台阶杆形件冷镦模的设计

在多工位自动冷镦机上生产台阶杆形工件易产生如图1A所示的缺陷。怎样才能解决这一问题呢?几年来我们结合生产进行试验,取得了一定经验。一、镦锻过程中的金属流动规律图2表示冷镦锻汽车轮壳螺柱(毛坯)时金属在模具内的流动情况。由于选用的坯料与凹模腔直径d接近(略小0.05～0.1毫米),所以在镦锻过程中,坯料首先在凹模端面形成环     

100Cr6轴承钢镦粗过程的微观组织模拟研究

为获得合理的100Cr6轴承钢镦粗工艺和优良的成形质量,通过simufact.forming软件对100Cr6轴承钢的镦粗过程进行数值模拟,得到坯料镦粗过程的等效应变、等效应力及温度分布等场量信息,并研究了坯料温度、上模速度、模具温度、摩擦因数等不同工艺参数对其镦粗成形的动态再结晶及晶粒尺寸等微观组织的影响。结果表明:坯料变形大的心部区域晶粒尺寸最小,坯料周边自由变形表层区域晶粒尺寸次之,与上下模具接触的坯料难变形表层区域晶粒尺寸最大;在其他条件相同的情况下,升高坯料温度,坯料平均晶粒尺寸减小,动态再结晶体积分数增大;提高上模速度,坯料平均晶粒尺寸增大,动态再结晶体积分数减小;增大摩擦因数,坯料平均晶粒尺寸减小,动态再结晶体积分数增大;升高模具温度,坯料平均晶粒尺寸减小,动态再结晶体积分数减小。     

怎样进行镦粗

六、怎样预防和矫正镦粗的缺陷?镦粗的主要缺陷是弯曲和歪斜。为防止发生弯曲,镦粗前可以先将坯料回转倒棱,即采用“铆镦法”镦粗。这样能增加坯料两端与锤砧的接触面,使变形困难锥体积加大,把镦粗变形尽可能推向坯料中间部位(见图6)。这种方法操作难度大,锤击次数多,变形时间长,并不十分理想。最常用的是“预弯曲镦粗法”(砧边矫正法),即先将竖立在锤砧上的坯料轻击一锤,观察出坯料可能发生弯曲的趋势后,     

超细长毛坯的镦粗

<正> 通常为保证坯料镦粗能够顺利进行,不产生任何缺陷,圆柱体坯料镦粗时,其高与直径(H/D)之比不应超过2.5—3,在2—2.2内更好.对于平行六面体毛坯,其高度与较小基边之比应小于3.6—4。这就是坯料镦粗规则. 但是,对于某些锻件,由于材料缺乏(所需直     

圆锥滚子单工位冷镦模具

长期以来 ,我公司圆锥滚子毛坯采用单工位卧式冷镦工艺 ,其特点是效率及自动化程度较高 ,但由于金属只经过一次镦压成型 ,材料变形急剧 ,造成模具寿命低 ,这就要求在设计模具时充分考虑模具的寿命问题。滚子在单击自动冷镦机上镦压成型 ,要经过进料、切断、打入凹模、成型及推出凹模等五个工步才能完成 ,而整套冷镦圆锥滚子所使用的工具中影响冲压质量的主要是凹模 ,凹模是将坯料冲压成型中的静止零件 ,在冲压过程中 ,要承受很大的压力 ,容易产生磨损、下沉或开裂。为了提高模具的使用寿命 ,降低工具费用 ,提高经济效益 ,圆锥滚子凹模型腔的…     

Spring back phenomenon exhibited in the process of hollow cylinder upsetting

Spring back of the end surfaces of the billet and the elastic deflection of the dies in the process of hollow cylinder upsetting between elastic platens is investigated using a thermo-elastic-plastic coupling model. The finite-element method and the finite-difference method are adopted to simulate the forming process, and the unloading process is performed on the elements of the workpiece in response to the spring back phenomenon accounted for in this study. Therefore, the effect of die elasticity on the variation of the inner surface profile of the hollow cylinder, predictions of forging load, and the distributions of temperature and strain components may be examined. The surface asperity of the billet and the forging load obtained by simulation agree quite well with the results of the upsetting experiment.     

电镦机智能化改造

常规电镦机各工艺参数多为恒值，在镦粗过程中不能实进控制。本文介绍一种新型电镦机计算机控制系统。在对镦粗速度、加热电流、镦粗压力等主要工艺参数分析的基础上，建立了工艺过程的优化控制系统。优化目标为最佳成形温度，而温度的控制主要通过压力控制来实现。     

Matrix-presentation linear least square error method of inverse elastic-plastic large deformation finite element model for upsetting

The main purpose of this paper is to develop the matrix presentation linear least square error method of inverse elastic-plastic large deformation finite element model for upsetting to obtain the friction coefficients during the upsetting process. This inverse model assumed the linear material and based on the modified experimental loading increments using the linear modified experimental upsetting loading standard proposed in this paper. Then the friction coefficients of contact boundary between the workpiece and the die at specific finite element analysis stages can be derived. Finally, using the cubic spline fitting, the history of friction coefficient during the upsetting process can be obtained. It is demonstrated that the workpiece profile of upsetting experiment is quite identical to the workpiece profile of simulation using the result obtained in this paper as the history of friction coefficient of contact boundary, and furthermore the distribution of stress and strain of the workpiece during upsetting process can be understood.     

不锈钢管接头精密成形的工艺分析与实验研究

不锈钢管接头截面积变化大，成形和脱模困难。本文对其塑性加工工艺方案进行分析比较，并通过工艺实验，验证工艺分析结果。该零件采用温挤压成形可以获得较好的技术经济效益；一次正挤压效率高，工艺力大；正挤-镦粗复合工艺则工艺力小，但效率较低。     

Analysis of the dissimilar interface frictional constraints during the upsetting process

A thermo-elastic-plastic coupling model combined with frictional functions is proposed to analyse the plastic upsetting of a cylinder, accounting for dissimilar interface frictional constraints. The flow stress of the deforming workpiece is considered as a function of strain, strain rate and temperature, and the properties of the interface frictional constraints are approached through the use of two continuously varying functions which are presented in terms of the amount of the workpiece deformation.The effects of various combinations of dissimilar interface frictional constraints at the top and bottom die surfaces on the temperature, strain and strain rate distributions are investigated. The asymmetrical flow inducing uneven billet profiles, together with the variations in top and bottom die surface loads, are predicted. The results obtained are consistent with the observations of upsetting experiments.     

Rational parameters of profiled workpieces for an upsetting process

An upsetting process of specially profiled workpieces was proposed. Modeling of a workpiece upsetting, profiled as a cylinder with conical and cylindrical ledges was done using a finite element method. During the upsetting of these workpieces, buckling occurs. Schemes of upsetting a workpiece with conical ledges result in a decrease in the irregularity of the equivalent strain distribution in the longitudinal section. This scheme produces a zone of minimal equivalent strain decrease in the workpiece. It was found that during the upsetting process of the workpiece with a conical ledge on the lateral surface and in the center, compressive stresses appear. These stresses contribute to the closure of voids in an ingot during the upsetting process. Rational workpiece parameters were found which allow the production of forgings with minimal irregularity of equivalent strain distribution, minimal formation of a barrel, and a favorable stress state in the workpiece. Experimental research, which confirms the advantages of upsetting specially profiled workpieces, was done.     

Study on the progressive forming mechanism of multi-step shafts based on convex-end billet in the cross wedge rolling technology

The deforming process is complicated and both the end concave and the central defect can be easily formed in multi-step shafts shaped by the cross-wedge rolling technology. To realize the accurate forming of multi-step shafts without stub bar, this article breaks the bondage of traditional flat-end billet, and introduces into convex-end billet. Based on established mechanical models and the damage computation principles, the distribution and change features of stress fields, strain fields and microstructures in different segments of the multi-step shaft during the progressive forming process are analyzed, and the location of the central defect is predicted. It is found that the concave depth of shaft ends decreases as the length of the convex-end of billet increases, the microcosmic grains are affected by the section shrinkage of the shaft segments and the larger the section shrinkage is, the smaller the size of the microcosmic grain will be. It records the longest duration of maximum stress, the largest fluctuation of lateral stress and the most frequent cycle of transverse strain in the multi-step shaft end and therefore the central defect is most likely to occur. The research findings settle a dependable theoretical basis for enhancing the molding quality and realizing the accurate forming for multi-step shafts in cross wedge rolling.

     

长钢管的大变形量镦粗工艺及模具设计

针对长钢管大变形量镦压加工难等问题,开展了镦压工艺计算与设计,建立了钢管的高径比、镦压变形量与镦压质量之间的关系。在镦压工艺和模具设计上对坯料可能产生的失稳和制品内、外径保证问题进行了评价,并进行了镦压试验,提出了解决因长钢管大变形量镦压而导致失稳倾向和制品易折叠的镦压加工方法,规定了模具工作过程及注意事项。研究结果表明,长钢管接受镦压加工时,若其高径比和镦压总变形量大大超过镦压加工规范时,采取两次镦压、在毛坯内径中加装芯棒和在外径外部设计模圈及对坯料进行酸洗、磷化、浸涂固体润滑剂等技术,可以有效地解决长钢管大变形量镦压加工难的问题。     

In situ 3D measurement of lubrication behavior at interface between tool and workpiece by direct fluorescence observation technique

A new direct observation method, which is based on an optical microscopy and a conventional fluorescence method, is developed in order to measure the oil film thickness at the interface between the tool and the workpiece in lubricated upsetting. The oil film thickness is measured using this method. The oil film thickness and the distribution at the interface during lubricated upsetting can be measured three dimensionally. The calculated central thicknesses at the instant of entrapment are in good agreement with the measured ones for lubricants with higher viscosity at higher compression speed. The 3D surface topography of workpiece at the end surface can be clearly visualized.     

再生核质点法模拟金属镦粗过程

介绍再生核质点法的基本原理及其在刚塑性可压缩材料体积成形中的应用,采用罚函数法处理边界条件,为使结果收敛于精确值,对积分过程采用积分修正和稳定化技术,采用Newton-Raphson方法使非线性方程线性化,对下一时间步工件的形状可以用更新的节点坐标计算,模拟了二维平面镦粗过程,模拟结果与实际变形情况相符,说明该方法的有效性。