Influence of melt-treatment on material constants of aluminum sheet used for easy-open can during hot deformation

The isothermal compression test at elevated temperature was carried out for aluminum sheets prepared by different melt-treatment methods with aid of dynamic hot/mechanical simulation experimental technology. The material constants of hot deformation have been solved by multivariate regression directly. Influence of metallurgy factors on the constants was analyzed. The results show that at some strain, the relationship of sheets’ flow stress with deformation temperature and strain rate can be expressed more suitably with Arrhenius equation modified by hyperbolic sine function. Structure factor A1, stress-level coefficient α, strain rate sensibility exponent m and deformation activation energy Q all increase with increment of strain, while stress exponent n decreases gradually. The bigger α value or the smaller n value is, the more obvious the dynamic softening is, but the α value will increase for the metallurgy defects existing in the sheets. Influence of melt-treatment on Q depends upon the synthesis effect of all kinds of metallurgy defects. The Q and n values of the sheet prepared by high-efficient melt-treatment are the least, while the m value is the biggest, and the sheet can deform easily and evenly.

Research on technological parameters of pressure forming with hot granule medium on AA7075 sheet

Hot granule medium pressure forming （HGMF） process is a new process in which granule medium replaces the medium in existing flexible-die hot forming process, such as liquids, gases or viscous medium. Hot forming of light alloy sheet parts can be realized based on the properties of granule medium, such as withstanding high temperature and pressure, filling well, sealing and loading easily. In this work, the forming of AA7075 cylindrical parts by HGMF process is taken as an example to establish the constitutive relation and forming limit diagram （FLD） of AA7075 sheet which is related to temperature by hot uniaxial tensile test of sheet metal. Based on the assumption that granule medium is applied to extended Drucker-Prager linear material model, the finite element model of HGMF process is established and the effect of technological parameters, such as forming temperature, blank-holder gap and drawing ratio, on the sheet metal formability, is studied. The limit drawing ratio curve of AA7075 cylindrical parts at forming temperature of 175-300 ℃ is obtained by HGMF process test, and the limit drawing ratio reaches the maximum value of 1.71 at 250 ℃. The results of numerical simulation are consistent with the results of process test, and the forming force, distribution of wall thichness and form of instability are predicted correctly, which provides reference for the application of HGMF process.

Discrete element and finite element coupling simulation and experiment of hot granule medium pressure forming

The granule medium of discreteness is supposed to be continuous（Drucker-Prager model） in the existing finite element simulation analysis on the hot granule medium pressure forming（HGMF） process, so the granule medium may produce tensile stress in the process of pressure-transferring and flowing, which does not coincide with the reality. The analysis method, discrete element and finite element（DE-FE） coupling simulation, is proposed to solve the problem. The material parameters of simulation model are obtained by the pressure-transfer performance test of granule medium and the hot uniaxial tensile test of sheet metal. The DE-FE coupling simulation platform is established by adopting Visual Basic language. The features in the process that AA7075-T6 conical parts are formed by the HGMF process are analyzed and verified by the process test. The studies show that the results of DE-FE coupling simulation coincide well with the test results, which provides a new analysis method to solve the mechanics problem in the coupling of discrete and continuum.

Hot Granules Medium Pressure Forming Process of AA7075 Conical Parts

High strength aluminum alloy plate has a low elongation at room temperature, which leads to the forming of its components need a high temperature. Liquid or gas is used as the pressure-transfer medium in the existing flexible mould forming process, the heat resistance of the medium and pressurizing device makes the application of aluminum alloy plate thermoforming restricted. To solve this problem, the existing medium is replaced by the heat-resisting solid granules and the general pressure equipments are applied. Based on the pressure-transfer performance test of the solid granules medium, the feasibility that the assumption of the extended Drucker-Prager linear model can be used in the finite element analysis is proved. The constitutive equation, the yield function and the theoretical forming limit diagram（FLD） of AA7075 sheet are established. Through the finite element numerical simulation of hot granules medium pressure forming（HGMF） process, not only the influence laws of the process parameters, such as forming temperature, the blank-holder gap and the diameter of the slab, on sheet metal forming performance are discussed, but also the broken area of the forming process is analyzed and predicted, which are coincided with the technological test. The conical part whose half cone angle is 15° and relative height H/d0 is 0.57, is formed in one process at 250℃. The HGMF process solves the problems of loading and seal in the existing flexible mould forming process and provides a novel technology for thermoforming of light alloy plate, such as magnesium alloy, aluminium alloy and titanium alloy.

Stress-strain analysis on AA7075 cylindrical parts during hot granule medium pressure forming

Hot granule medium pressure forming(HGMF) is a technology in which heat-resistant granules are used to replace liquids or gases in existing flexible-die forming technology as pressure-transfer medium. Considering the characteristic of granule medium that seals and loads easily, the technology provides a new method to realize the hot deep-drawing forming on high strength aluminum alloy sheet. Based on the pressure-transfer performance test of granule medium and the material performance test of AA7075-T6 sheet, plastic mechanics analysis is conducted for the areas, such as the flange area, force-transfer area and free deforming area, of cylindrical parts deep-drawn by HGMF technology, and the function relation of forming pressure is obtained under the condition of nonuniform distribution of internal pressure. The comparison between theoretical result and experimental data shows that larger deviation occurs in the middle and later period of forming process, and the maximum theoretical forming force is less than the experimental value by 24.6%. The variation tendency of the theoretical thickness curve is close to the practical situation, and the theoretical value basically agrees well with experimental value in the flange area and the top area of spherical cap which is in the free deforming area.

汽车车身常用板材耐腐蚀性能研究

车身常用板材的耐腐蚀性能是车身板材选用的重要参考标准,因此,对已加工为零件的热浸镀铝硅镀层板、未加工为零件的热浸镀铝硅镀层板、电镀锌板、热镀锌板、热成型钢裸板和冷轧板分别进行裸板材板和电泳板的中性盐雾对比试验。结果表明:有镀层的板材耐腐蚀性能明显优于无镀层板材;热浸镀铝硅镀层板加工成零件后其镀层会被破坏,导致其裸板耐腐蚀性能下降,但其电泳板的耐腐蚀性能加工前后变化不大,划痕扩蚀情况反而提升;热成型钢裸板因加工过程形成的氧化膜和脱碳层,在中性盐雾条件下4 h即出现锈蚀,其电泳板和电泳划痕板中性盐雾试验均出现严重的起泡问题。

热浸镀锌铝镁镀层钢板硅烷涂装性能评价

以热浸镀纯Zn镀层板为对比,对具有不同表面状态(涂油或钝化)的热浸镀锌铝镁(ZM)镀层平板及双拉变形板在汽车主机厂进行了硅烷电泳处理,随后对其硅烷膜和电泳漆膜的品质进行了评价。结果表明:ZM镀层板的硅烷涂装性能优于纯Zn镀层板;变形对纯Zn镀层和ZM镀层的涂装性能无明显影响,但表面钝化会明显降低电泳漆膜的附着力和耐蚀性。

热镀锌及锌铝镁合金钢在不同大气环境下的腐蚀行为

选用热镀锌(GI)钢和热镀锌铝镁合金(ZM)钢,分别在吐鲁番、江津、青岛和万宁4种典型环境地区中进行大气腐蚀试验。通过分析镀层腐蚀后的形貌、微观组织结构和腐蚀产物成分,探究了纯Zn镀层和Zn–Al–Mg合金镀层在不同大气环境下的腐蚀行为。结果表明,在相同大气环境下服役时,ZM具有比GI更优异的耐蚀性。两者在干燥大气中的腐蚀速率都较低,在潮湿工业大气环境和近海高氯大气环境中的腐蚀速率较高,腐蚀产物以Zn(OH)_(2)、ZnO、ZnCO_(3)及Zn5(CO_(3))_(2)(OH)_(6)为主。

易拉罐盖料及拉环料用铝合金板带材生产概述

文章概述了易拉罐盖料及拉环料用铝合金板带材的主要生产工艺,包括热轧、冷轧、涂层、成型生产工艺,并展望了生产工艺的发展方向。

设备精度对铝热连轧板形的影响及改善措施

热连轧作为铝合金轧制变形的首道工序,其初始板形的好坏对后续工序的影响深远,甚至影响最终用户的产品体验。本文主要以河南中孚高精铝材有限公司热连轧卷材的板凸度指标为研究对象,指出热连轧关键设备精度对板凸度的影响程度。精轧机每个机架标定后HGC缸的位置偏差会导致工作辊两侧实际辊缝出现偏差,从而影响热轧卷的板凸度控制。关键设备出现不同程度的局部磨损是引起板凸度变化的主要原因。通过对轧机标定数据的跟踪,制定合理的维护计划,保证热连轧机设备的精度和稳定性,才能为冷轧提供板形良好的热轧坯料。

镁铝叠层板的热轧成形及热冲压成形性能研究

镁铝叠层板密度低、表面耐蚀性好,是一种新型板材。应用热轧法将5052铝合金板坯和AZ31镁合金板坯叠层组料加热、轧制成形出镁铝叠层板;采用单向拉伸试验测定力学性能,优选了轧后热处理工艺;通过热成形极限实验对镁铝叠层板进行热冲压成形性能测定;运用回归分析法得到了镁铝叠层板的成形极限散点图、曲线型成形极限图和条带型成形极限图。结果表明,轧后经200℃×60min的退火处理能明显提高其塑性,获得良好的综合性能。200℃下镁铝叠层板冲压成形性能与镁合金板材相当。

基于Φ函数的铝热连轧防打滑轧制规程优化

针对铝材轧制过程中的打滑现象提出了预防热轧打滑的判断条件,并提出了预防打滑为主的综合电机功率剩余程度相近的目标函数,建立了轧制规程多目标优化的数学模型,并应用果蝇优化算法对压下率进行了优化。在河南某铝热连轧厂对5052铝合金加工进行轧制规程优化,将Φ函数负荷分配法应用到轧制规程中,结果表明:合理的负荷分配能较好地实现各电机在功率上的剩余程度相近,并有很好的预防打滑效果,证明Φ函数负荷分配法制定轧制规程是合理有效的。

经不同熔体处理的易拉罐用铝材的热压缩变形组织

采用动态热／力模拟实验技术对经不同熔体处理的易拉罐用铝材进行高温压缩变形实验，并用光学显微镜、透射电镜分析探讨其热变形组织特征。结果表明：冶金质量影响易拉罐用铝材的动态再结晶组织特征，在未处理或常规熔体处理状态下存在枝晶网胞结构，晶粒组织不均匀；高效熔体处理使易拉罐用铝材在较低的温度下即可通过亚晶合并方式发生动态再结晶，并在变形温度573～673K、应变速率0．1～1、0 s^-1、变形量约0、7的较宽的热变形工艺条件下可获得细小且分布较均匀的再结晶晶粒组织。

ICP-AES测定彩涂镀铝锌板镀层中铝的含量

本文着重研究了样品前处理和用电感耦合等离子体 -原子发射光谱仪测定彩涂镀铝锌板镀层中 Al含量的最佳方法 ,测定结果表明 ,方法的回收率和精密度分别为 99.8%和 1.13% ,该方法快速、准确、可靠 。

钛-铝复合板加工性能研究

对钛-铝复合板在380～470℃、应变速率10-3～10-1/s下进行高温拉伸试验,制定了复合板的热轧工艺,确定了复合板的应力应变本构方程。结果表明,钛-铝复合板在单向拉伸时,出现翘曲现象;并发现随变形速率的增大,其伸长率增大。

铝合金板材热成形-淬火一体化工艺研究进展

为解决铝合金室温塑性差和成形后热处理变形的问题,发展起来了一种铝合金板材热成形-淬火一体化新工艺。该工艺是将热处理和热成形在同一工步完成,即固溶后板材快速转移到模具中成形,然后完成模内淬火,最后通过时效来提高其强度。高温成形可提高板材成形性能,模内淬火能够保证其强度和尺寸精度。重点介绍了铝合金板材热成形-淬火一体化工艺关键技术及最新研究进展,总结了铝合金板材热成形-淬火一体化工艺实验研究和数值模拟的研究现状。

基于灰色预测的MFAC在铝热连轧张力控制中的仿真研究

针对重庆某铝加工厂双机架铝带热连轧机机架间张力波动问题,分析了影响张力波动的原因。为提高张力系统的控制精度,对传统PID控制器进行了算法改进,采用无模型自适应算法进行控制器设计,并加入灰色预测模型,通过超前预测来补偿系统延时及参数时变,形成新的控制律作用在被控对象上。仿真结果显示,基于灰色预测的无模型自适应控制在跟踪性、适应性、克服大时滞能力方面与传统的PID控制相比有很大的优越性。

热镀55%Al-Zn钢板的耐热性能

对热镀55%Al-Zn钢板分别进行了300,350,400,450℃的烘烤处理,研究了不同温度烘烤24h后其表面镀层的光泽度、单位面积质量、形貌、化学成分、结合性能等的变化,分析了该钢板的耐热性能。结果表明:在不超过350℃下烘烤24h后,镀层未发生任何变化;当在400℃烘烤24h后,镀层的光泽度略微下降,表面出现裂纹,但表面形貌、化学成分、单位面积质量和结合性能均未发生明显变化;当在450℃烘烤24h后,镀层的光泽度显著降低,单位面积质量明显减小,结合性能变差,部分镀层脱落。

基于最小二乘支持向量机的反向建模的铝合金变形抗力模型

根据某1＋4铝热连轧厂现场采集的大量轧制数据对几种铝合金变形抗力利用最小二乘支持向量机进行了反向建模回归分析，用细菌觅食优化算法对支持向量机的参数进行了优化。将回归后的变形抗力模型用于二级设定计算中的轧制力预报，结果表明回归后的模型适用于轧制现场，精度优于传统模型。

AA7075-T6圆筒形零件热态颗粒介质压力成形过程的力学分析

基于颗粒介质传压性能试验和AA7075-T6板材材料性能试验,对采用热态颗粒介质压力成形(HGMF)工艺拉深成形圆筒形件的法兰区、传力区和自由变形区进行了塑性力学分析,求解得到内压非均匀分布条件下成形压力的函数关系式,并与实测数据进行比对。分析结果表明,在成形中后期产生较大的偏差,理论求解最大成形力低于实测值24.6%。工艺试验研究表明,在成形温度为250℃条件下,采用HGMF工艺可一道次成形AA7075-T6圆筒形零件(底部为自由变形区)的极限拉伸比(LDR)为1.71。HGMF工艺操作便捷,装置简单,可在通用压力设备上实现轻合金板材件热成形,适用于航空、航天和军工等领域中小批量产品。