镀锌板冲压成形性的模拟与实验研究

镀锌板冲压成形时,常常由于镀锌层失效而使成形性下降.本文采用杯突实验和有限元分析相结合的方法,将镀层和基板看作两种材料,运用固连失效接触模型将镀锌板的基板和镀层连接,建立一系列镀锌板的冲压成形极限图.研究结果表明:由于镀锌层本身材料较软以及摩擦导致镀锌层的粉化、剥落,镀锌板的成形极限小于裸板5％～10％左右.研究结果为...     

镀锌板冲压成形过程中表面形貌演变规律的研究

镀锌板冲压成形时,由于塑性变形的诱发作用和接触摩擦的显著影响,表面形貌会随着时间和空间发生动态变化。采用Wyko NT1100非接触光学轮廓仪测量了镀锌板杯突实验各变形区的表面形貌,基于统计学方法建立了各变形区的形貌模型。分析结果表明,镀锌板冲压成形时,表面形貌会随着变形增大而发生表面粗糙化,不同的变形区域粗糙化的程度不一样。变形量大的凸模圆角区的微峰高度分布函数曲线较扁平,扁平的曲线表示微峰高度数据分布分散,粗糙化大,锌层脱落;变形量小的顶点区微峰高度分布函数较瘦高,高度分布集中,粗糙化小,锌层完整。同时,接触摩擦也影响着表面形貌的变化。     

基于DEFORM-2D的304奥氏体不锈钢拉深过程应力应变的数值模拟

不锈钢板材在拉深成形过程中应变硬化严重,影响因素复杂,易出现起皱、破裂、黏模等现象.运用DEFORM-2D的有限元软件,对不同拉深工艺条件下304奥氏体不锈钢圆筒件的拉深成形过程进行了数值模拟,分析了不同工艺条件下的应力应变情况.结果表明:工件凸缘处的摩擦因数越大,拉深成形极限高度hmax越小;提高拉深速度或降低摩擦因数,拉深成形极限高度hmax增大.通过几种不同条件下的模拟分析发现,在模拟实验条件范围内,304奥氏体不锈钢圆形件拉深成形的最佳成形条件为:凸模圆角rp=3mm、凹模圆角rd=3mm、凸缘处的摩擦因数μ=0.08、拉深速度v拉=30mm/s.这与实际生产中的情况相吻合,产生破裂的部位也与实际一致.     

基于厚度变化的杯形件拉延凹模圆角成形模拟

在模拟软件中,建立带压边圈的杯形件拉延模具模型,设杯形件材料为弹塑体本构模型,考虑厚度的应力、应变变化,通过数值模拟拉延成形,在不同压下位移时,求得凹模圆角处及附近的板料厚度截面等效应变、等效应力以及厚度变化值的分布;在此基础上,对压下位移不同阶段的凹模圆角成形区及附近区域的应力、应变值进行分析.其数值分别沿凹模圆角由外径向内径方向数值增大;另外得出在不同位置厚度发生变化曲线.总之,研究厚度方向的成形状态变化的方法,对揭示板料成形时凹模圆角厚度变化的机理具有一定理论和工程实用意义.     

高强钢冲压过程凹模圆角摩擦功数值分析

通过建立高强钢钢板弯曲的静态隐式仿真模型,对凹模圆角区摩擦功数值进行分析,获得关键参数与摩擦功的对应关系,研究结果表明:在凹模待成形材料流入处位置的摩擦功最大,随着凹模圆角角度增加,摩擦功呈减小趋势,在凹模圆角中部附近,摩擦功出现了较小峰值,随后在凹模圆角出口之前降为零,随着凹模相对圆角半径减小、冲压速度增加、材料强度增加,摩擦功会增大,压边力对摩擦功没有影响。     

摩擦因数对AA6111铝合金热冲压的影响（英文）

通过有限元分析和试验的方法分三种情况研究了摩擦因数对AA6111铝合金热冲压筒形件的影响。结果表明,摩擦因数和润滑位置对铝合金热冲压成形件的最小厚度、厚度均匀性和失效形式影响显著。热冲压过程中,由于不同的润滑条件,试件的失效形式主要有拉-压失效、拉-拉失效和等双拉失效。基于对成形性的考虑,摩擦因数的最优值为0.15。同时,有限元仿真和试验结果具有较高的一致性。破裂通常发生在筒形件底部中心和底部圆角附近,断裂形式分别为韧性断裂和韧性脆性混合断裂。     

前防撞梁拉延成形过程分析及工艺参数优化

采用Dynaform软件对某汽车前防撞梁成形过程进行了模拟,分析了不同形式的工艺补充面对零件成形的影响,以减薄率为评价标准,最终选取凸模圆角半径25 mm、凹模圆角半径15 mm的两端补充形式和符合零件形状的非平面压料面.采用正交试验法研究了压边力、冲压速度、摩擦因数和模具间隙4个工艺参数对成形结果的影响,获得了工艺参...     

浅孔杯形件挤压工艺研究及模具涂层应用

以某浅孔杯形件为研究对象,依据塑性成形理论,设计了4种挤压成形工艺,即上冲头反挤压、浮动凹模上冲头反挤压、上冲头正挤压以及浮动凹模上冲头正挤压工艺,采用DEFORM软件分析了4种挤压成形工艺下杯形件的成形质量及各主冲头的磨损情况,并确定了成形工艺。为降低主冲头磨损,研究了在TiN、TiCN、TiN-TiCN涂层下各主冲头的磨损情况,并确定了合理的镀层材料。通过正交试验法,研究了冲头圆角半径、摩擦因数、冲压速度、涂层厚度对冲头表面磨损深度的影响,并确定了最佳工艺参数。结果表明:在保证零件质量的条件下,采用浮动凹模上冲头正挤压工艺,冲头涂层材料选择TiN-TiCN复合涂层,工艺参数选择涂层厚度为4μm、摩擦因数为0.08、冲压速度为10 mm·s~(-1)和冲头圆角半径为6 mm时,主冲头完成单次挤压后的磨损量较小。     

成形工艺参数对U形件回弹影响的仿真分析

针对U形件弯曲回弹问题,在Abaqus软件中建立6061铝合金薄板U形件拉延成形二维有限元模型,使用Numisheet’ 2011会议回弹测量方法和成形极限图缺陷判据,研究U形件成形过程中单工艺参数对回弹量的影响,通过L_9(3~4)正交试验获取U形件回弹控制最优工艺参数组合。结果表明:不改变其他成形工艺参数,U形件回弹量随着凸、凹模圆角半径或拉延深度的加大,总体呈上升趋势,随凸、凹模间隙值的减小总体呈下降趋势;U形件回弹量随"凸模-板料"摩擦因数的增大而增大,随"凹模、压边圈-板料"摩擦因数或压边力的增大而减小;成形工艺参数影响U形件回弹量的主次顺序依次为"凹模、压边圈-板料"摩擦因数、"凸模-板料"摩擦因数、凸、凹模间隙值、压边力,以优水平工艺参数组合A_2B_3C_1D_3进行成形模拟,U形件法兰端部最大位移偏移量为0.84 mm,回弹控制效果明显。     

热镀锌合金化镀层相结构对摩擦特性与粉化量的影响

利用XRD、SEM、摩擦因数测量仪及双杯突试验机,研究了热镀锌合金化钢板(GA)镀层的相结构对摩擦特性与粉化量的影响。结果表明,随着GA镀层表面ζ相含量的增加,表面铁含量的降低,镀层表面的摩擦因数逐渐增加。相反,随着镀层中铁含量的增加,合金化镀层的粉化量逐渐增加。     

电镀锌板摩擦系数的影响因素分析

采用销盘摩擦试验研究了正压力和速度对电镀锌板摩擦系数的影响规律,运用正交试验及方差分析的方法研究了正压力、速度、镀锌层对摩擦系数的影响水平。结果表明：当速度在5654．86～9424．78mm／min,正压力在0．3～5N的范围内,随着正压力的增大,镀锌板的摩擦系数逐渐降低,随着速度的增大,摩擦系数也逐渐增大,镀锌层对镀锌板摩擦系数影响最大。     

锌层对镀锌钢板力学性能指标的影响

通过对热镀纯锌、电镀纯锌、预磷化电镀纯锌和热镀锌铁4种钢板去锌前后力学性能的对比研究，定量分析了锌层对镀锌钢板力学性能指标的影响规律。在此基础上探讨了镀锌钢板冲压成形的变形机理，结果显示：与电镀纯锌、预磷化电镀纯锌和热镀纯锌镀层相比，锌铁合金镀层的延展性较差，变形过程中镀层和基板之间的不协调显著降低了钢板的整体成形性能。     

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。     

热镀锌铁合金钢板冲压成形过程表面特性研究

热镀锌铁合金钢板在冲压过程中经常出现锌层的粉化和剥落等质量缺陷,加大了质量控制的难度.本文分析了不同预变形条件下热镀锌铁合金镀层的表面形貌和断面金相的演化,同时研究了正压力对摩擦系数的影响.结果表明:锌铁合金层镀层裂纹的萌生和发展是导致锌层粉化的根本原因.随着正压力的增大,锌铁合金钢板的摩擦系数明显降低,但当压力较大时降幅明显放缓.     

A Study of the Corrosion Resistance of Pump–Compressor Pipes with a Diffusion Zinc Coating under the Complicated Conditions of Gas-Producing Wells

The results of corrosion tests of diffusion zinc coatings under the complicated corrosion and erosion conditions of gas-production wells are presented. The slowdown of the anodic process of the solution of a coating and its salt passivation in model solutions was shown by the electrochemical research. It was established that the corrosion rates of diffusion zinc-coated 36G2F steel samples were 4.1–6.1 times lower than those of samples without coating. The corrosion resistance and the operational reliability of pump–compressor pipes can be increased by using protective duplex system combining a diffuse zinc coating (protective layer) and an upper layer of a polymer coating (barrier layer).     

Surface roughness changes on a hot-dipped galvanized sheet steel during deformation at low strain levels

During a study on surface roughening as a function of deformation, an anomalous behavior of the surface roughening for hot-dipped galvanized sheet steel was observed during low levels of imposed strain. A mechanistic model, which explains this surface roughening behavior, is presented. Surface topography parameters, including surface roughness, and relative zinc crystal orientation data, were measured after different amounts of deformation were imposed on the sheet. The proposed model is consistent with both sets of data. The model indicates that the zinc crystals on the surface of the coated sheet steel will initially deform by twinning, which causes a slight increase in surface roughness. The twin regions of the zinc crystals are then favorably oriented for dislocation glide, and the roughness during further deformation will slightly decrease. Once the zinc crystal orientations have homogenized, standard surface roughening due to adjacent grain constraint occurs. Further evidence to support the model include: (1) Twinning in a single crystal of zinc causes a roughness increase of the same magnitude as that found in the zinc coated steel after low strain deformation, (2) twinning of zinc has been observed in other studies of zinc-coated sheet steels, and (3) discontinuous yielding of the steel and recrystallization of the zinc during the sheet deformation did not occur and are not the cause for both the surface roughness and crystal orientation results.     

镀锌板单旁路耦合电弧GMAW高速焊接方法

为了解决镀锌板上锌层易受热烧损,无法使用大电流MIG焊接方法进行高速焊接的问题,采用了一种低热输入高效率的焊接方法——单旁路耦合电弧GMAW(DE-GMAW)用于镀锌板的焊接。搭建了该焊接方法的试验平台,对镀锌板堆焊和搭接接头的高速焊接方法进行试验研究。结果表明,通过调整旁路电流值,单旁路耦合电弧GMAW方法降低了镀锌板上的焊接热输入,并可以在大电流和高焊速的条件下实现镀锌板堆焊和搭接接头的焊接,所得焊缝成形良好,母材变形小,焊接过程稳定无飞溅。焊后镀锌层的烧损与同等热输入条件下的普通MIG焊相比明显降低,保证了镀锌板焊后的耐腐蚀性能。     

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 通过对纯锌镀层（GI）、5%Al-Zn合金镀层（GF）以及55%Al-Zn合金镀层（GL）这三种不同镀层产品进行杯突试验,以及用扫描电子显微镜对变形后镀层表面形态进行观察,得出了镀层的抗加工成形性的区别;在0.02mol/L NaCl溶液中,用电化学测量系统测定了三种镀层在不同杯突变形量条件下的线性极化电阻。结果表明,在相同变形情况下,对GI镀层耐腐蚀性能影响较小,而对GF及GL镀层的耐腐蚀性能影响较大。     

Relation between microstructure and adhesion of hot dip galvanized zinc coatings on dual phase steel

The microstructure of hot dip galvanized zinc coatings on dual phase steel was investigated by electron microscopy and the coating adhesion characterized by tensile testing. The zinc coating consists of a zinc layer and columnar ζ-FeZn₁₃ particles on top of a thin inhibition layer adjacent to the steel substrate. The inhibition layer is a thin compact and continuous layer that consists of η-Fe₂Al_5–xZn_x fine and coarse particles. The coarse faceted particles are on top and fine faceted particles are at the bottom. The steel surface is covered with small fraction manganese oxides, which may impair adhesion of the zinc coating. The adhesion at various interfaces that exist in zinc-coated steel was quantitatively estimated using a so-called “macroscopic atom” model. In addition, the adhesion at the interfaces in zinc-coated steel was qualitatively assessed by examining the fracture and delamination behavior upon tensile testing. In accordance with this model, fracture along zinc grain boundaries preceded fracture along the zinc layer/inhibition layer and ζ-FeZn₁₃ particle/inhibition layer interfaces.     

Effect of Zinc Coatings on Joint Properties and Interfacial Reactions in Aluminum to Steel Ultrasonic Spot Welding

Dissimilar joining of aluminum to steel sheet in multimaterial automotive structures is an important potential application of ultrasonic spot welding (USW). Here, the weldability of different zinc-coated steels with aluminum is discussed, using a 2.5-kW USW welder. Results show that soft hot-dipped zinc (DX56-Z)-coated steel results in better weld performance than hard (galv-annealed) zinc coatings (DX53-ZF). For Al to hard galv-annealed-coated steel welds, lap shear strengths reached a maximum of ~80% of the strength of an Al-Al joint after a 1.0 s welding time. In comparison, welds between Al6111-T4 and hot dipped soft zinc-coated steel took longer to achieve the same maximum strength, but nearly matched the Al-Al joint properties. The reasons for these different behaviors are discussed in terms of the interfacial reactions between the weld members.