三元磷酸盐体系无机预润滑试剂的研发及其在改善热镀锌汽车板成形方面的应用

目的旨在合成一种用于改善热镀锌汽车板材料成形性能的无机预润滑试剂,以期降低热镀锌板表面摩擦系数,进而减少冲压过程中开裂等缺陷的发生。方法以磷酸、金属硝酸盐等为主要试剂合成机预润滑试剂,在热镀锌汽车板材料表面得到均匀、连续的无机预润滑薄膜。采用扫面电子显微镜、辉光光谱仪等手段对材料表面所形成的无机预润滑薄膜的基本形貌、厚度等进行表征。采用平板摩擦、深冲实验对材料涂覆预润滑膜后的表面摩擦系数及冲压性能进行分析。同时,根据汽车板材料认证特点,对无机预润滑处理后的热镀锌汽车板材料的焊接/胶接、涂装性能进行分析。结果采用辊涂法在热镀锌汽车板材料表面可形成厚度为50～60 nm连续、均匀的薄膜。较之普通热镀锌材料,上述表面涂覆无机预润滑薄膜后的热镀锌材料表面摩擦系数可有效下降13%。,且伴随板面温度升高,无机预润滑热镀锌材料表面摩擦系数的下降愈发明显;同时,无机预润滑处理热镀锌材料的焊接性能(包括焊接窗口、焊接寿命)符合同等厚度汽车板材料的认证需求。涂覆无机预润滑薄膜热镀锌板表面与汽车结构胶具有良好的兼容性;此外,汽车主机厂挂片实验结果证实,现有的脱脂工艺可将材料表面无机预润滑膜彻底脱除,所得磷化膜厚度、晶粒大小与普通热镀锌板无异。结论当前所研发的无机预润滑试剂在热镀锌板表面形成薄膜,在不影响材料其他各项性能的前提下,可有效降低材料摩擦系数,为减少冲压缺陷的发生提供保证。     

无机固体润滑处理热镀锌板在汽车中的应用

目的降低汽车生产成本,提高汽车生产效率。方法采用平板拉延法测定无机固体润滑处理热镀锌板与普通热镀锌板等在拉延过程中摩擦系数,分析其随时间变化的趋势;采用SEM观察拉延后各钢板的表面形貌差异;采用拉深试验对比无机固体润滑处理热镀锌板与普通热镀锌板的最大拉深力和最大杯高;采用模拟焊接法对比两者的可焊电流区间、可焊电流宽度、最大剪切力和纽扣直径;采用随车挂片的方法对比两者的磷化、电泳性能。即分别评价无机固体润滑处理热镀锌板和普通热镀锌板在冲压、焊接、涂装性能的差异性。结果冲压性能方面,无机固体润滑处理热镀锌板的摩擦系数较普通热镀锌板降低23%,且微区表面与其他工艺表面的钢板相比几乎无磨损、划伤存在。拉深试验中最大拉深力下降4.5%,最大杯高增加9.5%,无机固体润滑处理热镀锌板具有更优的冲压性能。焊接性能方面,前者较后者的可焊电流区间下降0.6 k A,可焊电流宽度都为1.2 k A,前者的最大剪切力为2.75 k N,后者剪切力为2.6 k N,前者的纽扣直径为5.8 mm,后者的纽扣直径为5.2 mm,焊接性能相差不大。涂装性能方面,前者磷化膜重为3.12 g/mm~2,后者磷化膜重为3.09 g/mm~2,磷化性能相当,且两者的电泳膜性能试验全部通过。经试冲500次发现,无机固体润滑处理热镀锌板可有效防止模具粘锌。结论无机固体润滑处理热镀锌板和普通热镀锌板相比,有更优的冲压性能,焊接、涂装性能相当,且能有效改善锌层脱落。而且,无机固体润滑处理热镀锌板替换普通热镀锌板,可降低整车生产成本,提高生产效率。     

Friction analysis of thermally sprayed coatings finished by ball burnishing and grinding

Thermally sprayed coatings offer a promising approach as efficient method to increase the wear-resistance of sheet metal forming tools. However, the roughness of thermally sprayed surfaces is quite high. The use of these coatings for deep drawing tools results in poor sheet surface qualities and low drawing ratios. Because it is suspected that high friction is the reason for the low drawability, hard metal coatings (WC–12Co), deposited by high velocity oxygen fuel flame-spraying, were machined by grinding and ball burnishing to improve their friction behavior and the accuracy of the tool shape. The investigation was conducted by plane strip drawing tests. Strips of high strength steel were mated with these novel and effective coatings at different normal contact pressures and drawing velocities. Uncoated friction elements made of C60 steel were considered as reference during the analysis. The results revealed that coated but unmachined friction elements showed high friction values, which led to scratch marks on the sheet surface after drawing. Applying the finishing processes, the friction coefficient could be reduced significantly. Additionally, deep drawing tests were carried out to determine the drawing ratio for coated, unmachined as well as for processed, coated dies. Thermally sprayed and ball burnished as well as thermally sprayed and ground coatings are feasible for deep drawing. Due to the post treatment, the drawing ratio β = 1.8 was increased to 2.0. This is consistent to the results of the friction tests.     

Determination of tribological conditions within hot stamping

Innovative hot sheet metal forming technologies are gaining an increasing significance in the scope of application of more and more innovative high and ultra high strength steels in the automotive industry. With respect to a numerical process design beside the mechanical and the thermal material characteristics the friction coefficient represents an important input parameter for finite element (FE) simulation. Within the scope of this paper an evaluation method for the determination of the friction coefficient μ for the direct hot stamping process of boron-manganese steels will be presented. Therefore cup deep drawing tests at elevated temperatures following the time-temperature-characteristic of the hot stamping process are carried out. For the calculation of the friction coefficient the approach according to Siebel for the modeling of the maximum drawing force is used.     

Performance of W-TI-(N) coated pins in lubricated pin-on-disk tests

W-Ti-(N) thin films were deposited on polished bearing steel balls by dc magnetron sputtering varying the partial pressure ratio, pN₂/pAr. The tribological behaviour was accessed by pin-on-disk testing with contact geometry of uncoated and coated 100Cr6 balls sliding against uncoated different disk materials used as stamping sheet. Different types and amounts of lubricants were used in the tests.In non-lubricated tests, friction coefficients (μ) as high as 0.8 were achieved. For the more ductile sheet materials (Al alloy and Zn-coated steel) strong adhesion was observed. The best compromise between low wear rate and low friction coefficient was achieved for N-containing coatings deposited without ion gun assistance.In lubricated conditions, a significant decrease of the friction coefficient down to 0.05 and a reduction of the wear coefficient in more than one order of magnitude down to < 10^− 16 m²N^− 1 were reached in relation to non-lubricated tests. Very good tribological results were achieved using the corrosion protection oil as lubricant, with amounts usually applied for protection of sheet materials (2 g/m²). It was found that the wear coefficient of the coated ball decreased linearly with increasing hardness of the coating, being the best that deposited with N contents in the range from 35 at.% to 40 at.%. The tribological performance of the coated samples was approximately constant even when the amount of used lubricant was reduced to only 25% of the initial value (0.5 g/m²).     

Tribological properties of TiAlN-coated cermets

Ti(C,N)-based cermets were coated with TiAlN using multi-arc ion plating technology. Sliding wear tests were performed on the coated cermets. The microstructure and morphologies of the coated cermets before and after friction and wear tests were characterized. The results show that the TiAlN coating surface was smooth and its root mean square roughness was 16.6 nm. The hardness (HK) of TiAlN coating layers reached approximately 3200 and the critical load (L _c) under which the coating failure occurred was 59 N. The sliding wear test results show that the friction coefficients of the TiAlN-coated cermets were lower than that of the cermets without any coating. Under the same load, the adhesion phenomenon of the counterpart materials on the specimens was improved and the mean friction coefficient increased with increasing sliding velocity. When the sliding velocity was 0.26 m·s⁻¹, the mass of the coated cermets reduced. At the same sliding velocity, the average friction coefficient of the TiAlN-coated cermets was lower under a higher load. The wear mechanisms of the TiAlN-coated cermets were mainly adhesive and abrasive wear.     

基于凹模压边区摩擦学性能的冲压仿真分析

通过改善凹模压边区摩擦学性能以提高冲压成形件质量,分别利用YLP-20型激光加工系统和多弧离子镀沉积设备在试样表面制备三角形微织构和TiN薄膜,采用UMT-3摩擦磨损试验机开展摩擦学性能试验;通过Dynaform软件建立有限元模型,以凹模压边区为研究对象,根据试验所得摩擦因数对冲压过程进行仿真分析。结果表明:镀膜和织构两种表面处理技术均能降低凹模压边区与板料间的摩擦因数,且先织构后镀膜技术具有最佳减摩效果;板料的减薄率随摩擦因数的减小而降低,增厚率则相反,并在摩擦因数减小到0.150后板料厚度变化趋于稳定;增大压边力会导致板料减薄率增加,减小凹模压边区与板料间的摩擦因数可抑制这一负面效果;将表面织构和镀膜技术应用于凹模压边区改善板料成形性能是可行的。     

基于AutoForm的阶梯盒形件冲压工艺模拟及优化

阶梯盒形件是汽车制造业中的典型零件,但是由于其拉伸成形困难,废品率较高.针对某阶梯盒形件进行了工艺性分析,规划了冲压生产工艺,并利用AutoForm软件对拉伸成形过程进行了仿真模拟,选取板料尺寸、摩擦系数及压边力为研究对象,对比分析了3个参数对拉伸质量的影响规律,最后给出了优化成形质量的建议,对指导实际生产有一定的意义...     

板材成形拉延摩擦试验机系统设计与实践

文章在系统研究板材拉延成形中摩擦系数测定、拉延筋约束阻力测试以及镀锌板粘附性测试等3种试验方法的基础上,自主开发了专用的板材成形拉延摩擦试验机系统。该试验机系统由机械系统、控制系统、控制软件以及相应的规范等组成。开发了拉延摩擦高温试验模具系统,实现了板材成形高温拉延摩擦试验测定,建立了基于PID调节技术实现提高试验机载荷控制精度的方法。实际应用表明,该试验机性能稳定、可靠,为促进板料拉延成形试验水平的提高,及国产汽车板的开发和应用提供了保障。     

Evaluation of stamping lubricants using the deep drawing test

This paper presents a practical methodology that uses the deep drawing test and finite element (FE) analysis to evaluate stamping lubricants under near production conditions. In stamping operations good lubrication helps to reduce wrinkling, premature fracture, and localized thinning. Furthermore, lubrication also reduces tool wear in large-volume production. Determination of reliable friction data associated with a given lubrication system is also important for successful process design and simulation by FE analysis. In this study, five stamping lubricants (four dry film lubes and one wet lube) were evaluated using the deep drawing test. The performance of the lubricants were evaluated based on: (a) maximum punch force measured, (b) the maximum applicable blank holder force (BHF), (c) the draw-in length, (d) the perimeter of flange after test, (e) the change of surface roughness, and (f) the inspection of surface topography. The coefficient of friction for each lubricant tested was determined through the FE-based inverse analysis by matching the predicted and measured values of the load-stroke curve and the draw-in length. This study showed that one of the tested lubricants was most effective, regardless of test speed and the magnitude of BHF. The methodology used was shown to be effective in evaluating various lubricants for sheet metal forming and accurately differentiating their performances.     

摩擦系数对圆筒形件拉深成形性能的影响

应用有限元软件PAM-STAMP 2G研究了圆筒形件拉深成形过程中不同摩擦系数条件下硬化指数n值对板料拉深性能的影响.结果表明,随着摩擦系数的增大,板料的极限拉深比减小.在小摩擦系数的情况下,硬化指数对板料的拉深性能影响不大.随着摩擦系数的增加,硬化指数对板料的拉深性能影响越来越大.当摩擦系数较大时,可以通过增加板料的...     

汽车覆盖件拉深过程中的压边力预测

结合数值模拟与人工神经网络技术研究了汽车内覆盖件承载地板在冲压成形中压边力的预测。将板料模型零件导入到Dynaform中进行网格划分并对其拉深过程进行模拟仿真,结合正交试验获取不同参数条件下最佳压边力的数据样本,然后运用Matlab软件中的GRNN神经网络工具箱对数据进行训练学习,采用训练好的神经网络对板料成形过程中的压边力进行预测,获得了板料拉深过程中的压边力变化曲线。通过预测结果和模拟结果对比,预测误差在10%以内。将预测的曲线对零件模拟仿真,结果显示零件最大减薄率在25%以内,并对板料进行实际冲压验证。结果显示成形效果良好,无起皱、破裂缺陷,符合实际生产的要求,说明GRNN神经网络可以用于零件冲压过程中压边力的预测。     

应用均匀设计方法提高筒形件的成形质量

均匀设计是试验设计方法的一种。采用有限元技术和均匀设计方法对筒形件在拉深成形过程中的摩擦系数、压边力、凹模口圆角半径等工艺参数进行优化设计。优化后的仿真结果在提高成形裕度和抑制厚度的变化方面取得很好的效果。该方法还可以明显减少模拟计算次数，提高优化效率，改善板料冲压成形的仿真计算精度。     

汽车座椅外侧板单动拉延成形工艺分析及优化

以某型号汽车座椅外侧板为例,采用Auto Form软件对座椅外侧板拉延成形过程进行模拟分析,并根据分析结果预测出拉延过程中的拉裂风险。通过调整零件的圆角半径和修改局部结构,消除了开裂风险,降低了最大减薄率。为取得更好的成形效果,选取压边力、摩擦系数、冲压速度、凸凹模间隙4个重要成形工艺参数进行正交试验及参数优化,得出最优工艺方案为:压边力250 k N、摩擦系数0.13、冲压速度1000 mm·s-1和凸凹模间隙2.42 mm,最终零件的最大减薄率为24.33%,最大增厚率为6.54%。采用优化后方案进行实际拉深试模,得出零件的成形性能与有限元模拟结果一致,工件质量完全符合设计要求。     

超级钢板材冲压性能的试验研究

超级钢的化学成分与普通的碳素结构钢相近,但其力学性能有大幅度的提高.将超级钢应用于国产汽车冲压件的生产中不仅可以提高汽车质量,而且可以降低汽车的成本、减小汽车重量、降低能源消耗和减少环境污染.概述了板材的冲压性能的评价指标,介绍了拉伸试验值对板材冲压性能的影响,对超级钢板材进行了拉伸试验、冷弯试验和金相组织检验,研究了超级钢板的硬化指数、塑性应变比、屈服强度、极限强度、均匀延伸率等力学性能,并分析了超级钢板的冲压成形性能,了解这些性能对超级钢冲压件的生产具有一定的指导作用.     

Development of tribo-simulator for hot stamping

Coefficients of friction were measured at elevated temperatures using a hot flat strip drawing test machine newly developed by the authors for the purpose of confirming the coefficients of friction used for the FEM simulation of hot stamping. To examine the functions of the tribo-simulator, the coefficients of friction are measured using hot rolling oil with an emulsion, which is supplied continuously, while varying the drawing speed, drawing pressure and temperature. From the experimental results, it was shown that the coefficient of friction in hot stamping can be measured using this tribo-simulator. The measured coefficients of friction can be used as values in the FEM simulation of hot stamping. Moreover, the tribological behavior at the interface between the die and strip in hot stamping can be evaluated from the coefficient of friction, because it is one of the quantitative values used to represent the tribological behavior between the die and blank.     

Study of the influence of phase composition and iron content on the formability characteristics of zinc-iron electroplated sheet steel

This study focuses on the relationship between coating composition and deformation and friction behavior of zinc-iron electroplated sheet steel. The influence of phase composition and microhardness of the deposits and the electrodeposition process parameters on the mechanical properties of the material were determined. The influence of coating composition on the friction and galling behavior was also investigated. Both V-bend test and cup test were used to evaluate the influence of the iron content on the powdering and flaking behavior of the deposits. Finally, the adhesion of the coating to the substrate was studied by lap shear tests. Although the soft η phase appears to be the main component in zinc-iron coatings with less than 16 wt% Fe, Γ₁ particles were observed even at low iron contents. As the iron content in the coating increases, the Γ₁ fraction increases and the coating becomes harder and more brittle. Above 16 wt% Fe the deposits start to show substantial powdering and flaking during deformation. At iron contents above 30 wt%, bending of the coated product results in total coating delamination. At low iron contents, zinc-iron electroplated sheet steel exhibits a superior deformation behavior, and both cup tests and flat die tests proved the suitability of the coating for deep drawing.     

基于Fastamp和正交试验的汽车门框冲压工艺参数优化

针对某汽车门框冲压工艺复杂、容易出现破裂和起皱的特点,选择对成形质量影响最大的拉延工序进行分析,并基于国产Fastamp软件建立了汽车门框拉延仿真模型.然后,选取压边力、摩擦系数、冲压速度及模具间隙作为正交试验的主要影响因素,建立了4因素4水平的正交试验表.采用综合评分法和极差分析法,获得了最优的工艺参数组合:摩擦系数...     

汽车钢板快速冲压中模温对成形性能影响

模具温度在快速冲压工艺中对板材的成形性能有着重要的影响。文章在自行开发的差温拉深实验装置上,运用正交分析方法,针对影响典型汽车用钢电镀锌钢板快速冲压成形性能的参数(凸模、凹模和压边圈温度)进行正交实验,得出各模具温度对电镀锌钢板拉深成形性能的显著性指标和模具温度最优化组合,分析了模具温度差对拉深成形性能的影响以及温度对破裂方式的影响。为研究汽车钢板快速冲压成形工艺提供了依据。     

Friction behavior of aluminum-coated 22MnB5 in hot stamping under dry and lubricated conditions

The coefficient of friction of aluminum-coated 22MnB5 in hot stamping under dry condition is measured for various surface roughnesses of the die using a flat drawing test machine developed by the authors. The surfaces of the die after drawing are photographed and then analyzed using EDX in the SEM. On the basis of the experimental results, the friction behavior under dry condition is discussed. Moreover, the coefficient of friction of aluminum-coated 22MnB5 in hot stamping under lubricated condition is measured for various surface roughnesses of the dies and the effect of the lubrication on the coefficient of friction is discussed.