镀铬及超精加工对减振器连杆耐蚀性的研究

汽车减振器连杆耐蚀性是影响汽车减振器质量和寿命的主要因素之一，连杆电镀工艺参数的选择决定了其镀铬层的质量及其耐腐蚀性能，通过对汽车减振器连杆电流密度与镀铬层组织形态的研究找到其对应关系，进行盐雾试验得到了优化的电流密度参数，不同表面质量的连杆盐雾试验对比表明．：镀前对汽车减振器连杆进行表面超精加工可显著提高连杆的耐蚀性，研究结果为优化企业现行电镀生产工艺并提高汽车减振器的制造水平提供了一条有效途径。     

基于正交试验设计与人工神经网络优化镀铬工艺

提出了一种正交试验设计与人工神经网络相结合的镀铬工艺参数优化方法。样本极差结果表明,对镀铬层的厚度及阴极电流效率影响因素依次为电流密度、电镀时间、电镀温度;且最佳电镀温度为45℃。通过神经网络建立电镀工艺参数与性能之间的模型,预测得出的镀铬层的厚度和阴极电流效率与实际试验的结果接近,训练精度较高,预测值与试验值的相对误差小于1.20%。通过建立镀铬层多指标综合评价模型,对镀铬层的厚度及阴极电流效率两个指标进行综合评价,通过对两个指标权重值的调整,确定镀铬层的综合性能值,得出最优的工艺参数。     

电镀铬对300M钢疲劳性能影响研究

对多次电镀铬的300M钢试样的疲劳性能、氢脆倾向、疲劳断口进行了测试和分析,以研究镀铬次数、镀铬层厚度对300M钢疲劳性能的影响规律。结果表明:镀铬层对300M钢的疲劳性能影响很大,在试验条件下,带镀层试样较未电镀试样的疲劳强度和相同应力条件下的疲劳寿命降低约60%,且镀层越厚疲劳寿命越低;这种影响与电镀次数无明显关系,只要执行正常的除氢工艺,重复电镀多达15次的300M钢仍未发现氢脆倾向。断口分析表明:疲劳裂纹主要起源于镀铬层或镀层与基体的界面处,疲劳性能的大幅降低主要与镀铬层本身的特性有关。     

电流密度对镀铬钢板表面特性的影响

电镀工艺对镀铬钢板的性能具有决定性影响.通过电化学试验、热振试验、X射线光电子能谱(XPS)以及扫描电镜(SEM)等,研究了电流密度对镀铬低碳钢板耐蚀性、镀铬层组成及其与有机膜结合力的影响.结果表明:电流密度过大将加剧铬及其氧化物和氢氧化物在基板的沉积,镀铬板的耐蚀性能较差.以5 A/dm2的电流密度镀铬的低碳钢板的耐...     

不锈钢镀铬液有机添加剂新工艺

往常规镀铬溶液中加入有机添加剂,采用不同的电流密度、镀液温度、pH值和电镀时间进行镀铬,经过对镀层的形貌、厚度及结合力等性能进行比较取舍,获得了最佳镀液配方和工艺:CrO3250g/L,H2SO42.5g/L,Cr3 3g/L,甲醛8~10g/和丁二酸8~10g/L;在室温(20℃),镀液pH值为1.5,电流密度30A/dm2,电镀时间60min。该法既提高镀铬液的阴极电流效率又降低生产能耗,可获得光亮平滑、硬度高、结合力好的镀铬层。     

脉冲频率对15-5PH不锈钢电镀铬层微观结构的影响

采用自制的脉冲电镀装置对15-5PH不锈钢电镀铬层进行研究.结果表明,在标准镀铬液中,镀液温度为55℃,平均电流密度70 A/dm2,在占空比30％的条件下,随频率升高,镀铬层致密度增大,产生微裂纹的倾向性减小,表面粗糙度降低.但当频率大于3.0 Hz时,镀层致密度降低,产生裂纹的倾向性增大,表面粗糙度升高.     

铝硅合金表面电沉积铬工艺的优化

研究了在铝硅合金样品表面电镀硬铬的工艺。用正交试验法对含纳米氧化铈添加剂的镀铬配方进行成分优化,并采用不同的电流密度、镀液温度和电镀时间进行镀铬,经过对镀层的形貌、厚度及结合力等性能进行比较取舍,得出了低铬酸电镀硬铬的工艺配方:80g/LCrO3,0.7g/LH2SO4,3g/LCr3 ,3g/LCeO2;电镀温度为40℃,电流密度为30A/dm2,电镀时间120min。结果表明:纳米氧化铈添加剂的加入,在获得光滑致密镀层的基础上,大大降低了镀液中铬酐的含量,从而降低了对自然环境的污染。     

镀铅锡合金的镀铬阳极腐蚀原因的探讨

为了探明甲基磺酸盐电镀铅锡合金镀层作为镀铬阳极时腐蚀的原因,用A、B、C、D四种溶液(A溶液即现在生产中已使用过的旧溶液;B溶液即把A溶液调整至规范的溶液;C溶液即按照原工艺新配制成的溶液;D溶液即在新配制的溶液中加入0.2g/L铜离子),分别在相同的电镀条件下通过霍尔槽进行对比试验,把四种溶液中所镀出的霍尔槽试片在同一条件下的镀铬溶液中进行腐蚀.研究结果表明:镀铅锡合金溶液中混入铜离子后,加速了铅锡镀层在镀铬溶液中的腐蚀速度,且随电流密度的减少呈下降趋势.试验证明:电流密度在0.2～0.5A/dm2之间时腐蚀速度最小.     

镀银铜棒的制备与表面形貌的研究

采用无氰电镀银的工艺在纯铜基体上沉积具有纳米尺寸晶粒结构的银层。在不同的电流密度和电镀时间工艺下制备出一系列镀银试样。利用SEM、EDS和XRD对镀层的表面形貌和晶体结构进行分析。结果表明:优化后的电流密度为0.10 A/dm~2、电镀时间为40 min。在该参数下,所制备的镀层光亮、晶粒圆润均匀,(220)晶面为最优取向晶体面。     

采煤液压支架立柱堆焊修复研究

研究了不同手工电弧堆焊工艺下D212堆焊层的组织形貌,并与电镀Cr层相对比研究了堆焊层的硬度及耐磨性.结果表明,D212堆焊层组织主要为细小针状马氏体和部分残余奥氏体.堆焊层的硬度随焊接电流的增大而降低,采用双层堆焊比单层堆焊的堆焊层硬度高,堆焊层硬度较高时其耐磨性也较好.采用100 A、44V双层堆焊时,堆焊层硬度和耐磨性与电镀铬相当,可以作为电镀铬局部修补材料.     

Integration of Gas Nitrocarburising and Oxidising in a Mass Production Line for Brake Pistons

The combination of wear- and corrosion resistance is a demand to a multitude of automotive parts. Several metallic coatings as hard/soft chromium or electroless nickel have been the conventional surface protection e.g. on parts as brake pistons and shock absorber or gas spring piston rods. The Corr-I-Dur^R process - a special gasnitrocarburising and oxidising technology - has a huge potential not only in substituting those coatings but also in delivering surfaces with higher quality.The benefits of the replacement of soft chromium with Corr-I-Dur^R and the implementation of the process in the customers production line with an annual capacity of 17 million brake pistons is described in this presentation. Starting with the demands on wear- and corrosion resistance the way of process development and the design of applicative equipment is shown. The result is a tailor-made surface solution with superior quality for deep drawn brake pistons. Two main disadvantages -outgassing of the chromium layer and reduced corrosion resistance on the inner diameter - are eliminated by the replacement with Corr-I-Dur^R. The process-sure achievement of enhanced corrosion resistance, uniform layer thickness, negligible distortion as well as environmental and economical advantages make Corr-I-Dur^R an excellence choice for this application.     

发动机活塞环化学镀Ni—P

研究了发动机活塞环表面化学沉积Ｎｉ－Ｐ非晶镀层及其热处理工艺。结果表明，整个工艺过程控制稳定，化学镀Ｎｉ－Ｐ活塞环可以取代镀Ｃｒ环。     

Preparation and characterization of Cr-P coatings by electrodeposition from trivalent chromium electrolytes using malonic acid as complex

Cr-P coatings were prepared by electrodeposition from trivalent chromium plating bath using malonic acid as complex. The influences of bath composition on the trivalent chromium electrodeposition process and deposited coating properties were studied. The effects of plating parameters such as current density, bath pH and plating time on structure and morphology of deposited coatings were investigated in detail. XRD, SEM, EDAX and XPS techniques were used to characterize the Cr-P deposited coatings. Results show that the composition, microstructure and surface morphology of the Cr-P coatings depend on bath composition and plating conditions including bath pH, current density, plating time, etc. Results of EDAX and XPS indicate that the deposited coatings contain Cr(s), Cr(III), phosphorus, oxygen and carbon. The optimum bath composition was obtained using malonic acid as complex and the mechanism of Cr-P electrodeposition was analyzed. The optimum plating parameters for good-quality chromium deposited coating are pH 2-3, current density 3-12 dm², temperature 35 °C and Ti/IrO₂ as anode. These results may be of great practical and theoretical significance for further improvement of trivalent chromium plating process.     

汽车减震器活塞杆断裂失效分析

通过光学显微镜、扫描电子显微镜和能谱仪等分析手段,对汽车减震器活塞杆压弯检验过程中的异常断裂原因进行了分析。结果表明,活塞杆表面镀Cr层厚度约为24 μm,次表层淬硬层深度约为0.8 mm,次表层组织为回火马氏体+少量铁素体,心部基材组织为铁素体+珠光体;压弯试验时,活塞杆首先在最大弯曲应力一侧的高频淬火区发生氢脆开裂,裂纹形成后,活塞杆在外加应力作用下发生快速失稳断裂。在此基础上,提出了消除活塞杆氢脆隐患的改进措施。     

铬镀层及其阴极化修饰镀层的钝化行为

用电沉积方法在ＡＩＳＩ ４３０不锈钢上得到铬、铬钯交替镀层和铬钯复合镀层，凭借钯的阴极修饰效应，含钯的铬镀层在除氧的非氧化性酸中具有自钝化能力，极化曲线和阻抗频谱测定表明，在相庆铬镀层处于活化－钝化的电位区间，含钯镀层都表现出净阴极电流；活化溶解与钝化过程随电位的相对发展变化可由低频段容抗圈的演变来推定，铬钯复合镀层具有更大的钝化膜阻抗。     

镀铬对模具维护的影响

拉伸模及翻边刀块、整形刀块等一般使用镀硬铬工艺来提高模具光洁度和耐磨性,以降低零件拉伤风险、提升零件质量稳定性、延长模具使用寿命。本文仅就目前车间使用模具镀铬的情况阐述模具镀硬铬的优缺点及使用过程中维护镀层及延长模具镀铬寿命的方法。     

Electro-deposition behaviors of trivalent chromium during pulse plating

Thick trivalent chromium layers were prepared in a modified chromium sulfate bath by pulse plating to replace hexavalent hard chromium coating in industrial fields; layer microstructure development was systematically studied by using electron microscopy and small angle neutron scattering (SANS) to give a model for nucleation and growth behaviors during the pulse plating. Finer columnar grain was formed by pulse plating due to its high nucleation rate at the same current density. Average deposition rate of the trivalent chromium layers is in the range of 32.4 μm/h to 49.7 μm/h. The deposition rate increases as the diameter of cylindrical shape of chromium cluster in a columnar grain is reduced. The highest deposition rate in this study was observed under the conditions of direct current density of 0.4 Acm⁻², combined with a rectangular shape pulse current density of 1.5 Acm⁻² with a 10/2 on-off time ratio. Most of the inner-cracks of the trivalent chromium layers have dimensions in the range of about 39 nm. Ultrasonic agitation during pulse plating resulted in an increase of neutral salt fog spray life, which is related to smaller crack size and broader size distribution in the trivalent chromium.     

晶化温度对非晶态Cr-Fe-C合金镀层的影响

采用三价铬电镀液,在4Cr10Si2Mo钢工件表面电沉积非晶态Cr-Fe-C合金镀层.通过改变络合剂的含量、电流密度和电镀时间,在阴极上沉积了不同厚度的非晶态Cr-Fe-C层.用扫描电子显微镜和光学显微镜、X射线衍射仪、能谱仪测定、显微硬度计研究了从三价铬镀液中电沉积Cr-Fe-C镀层的工艺以及镀层的形貌、结构与性能.结果表明,利用该工艺获得了厚度为30 μm、27 wt%Fe的非晶态Cr-Fe-C合金镀层.该镀层耐蚀性较好,经600℃×1 h晶化处理后硬度最高可达1 800 HV0.05.     

基于CFD的车辆减振器阻尼特性研究

为了设计高品质的车辆减振器,分析研究了减振器在不同工况下的阻尼特性及其影响因素。对减振器的阀系结构进行分析,基于CFD数值方法,建立了较高精度的减振器三维流体模型和流体网格模型,在FLUENT流体软件中进行了仿真分析,获得了减振器复原阀阻尼力特性曲线和内部阀系在不同工况下的压力场特性,并分析研究了在不同工况下影响减振器阻尼特性的最大因素,并进行了试验验证。结果表明:减振器低速工作时,其阀系内部压力场分布均匀,减振器叠加阀多槽面积是影响减振阻尼特性的最大因素;高速工作时,减振器阀系内部压力场波动明显,活塞孔直径是影响减振阻尼特性的最大因素。此方法对减振器内部阀系的优化设计提供了一定的理论依据。