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1、吉 林 大 学本科毕业设计 翻译 学生姓名：* 班 级：*班 学 号：* 学 院：材料科学与工程学院 专 业：材料成型及控制工程 指导教师：* 副教授 2011年3月25日吉林大学材料科学与工程学院本科生毕业设计 翻译16吉林大学材料科学与工程学院本科生毕业设计 翻译Section 4 Die Design and Construction Guidelines for HSS DiesGeneral Guidelines for Die Design and ConstructionDraw DiesHigher than normal binder pressure and press t
2、onnage is necessary with H.S.S. in order to maintain process control and to minimize buckles on the binder. Dies must be designed for proper press type and size. In some cases, a double action press or hydraulic press cushion may be required toachieve the necessary binder forces and control. Air cus
3、hions or nitrogen cylinders may not provide the required force for setting of draw beads or maintaining binder closure if H.S.S. is of higher strength or thickness.Draw beads for H.S.S. should not extend around corners of the draw die. This will result in locking out the metal flow and cause splitti
4、ng in corners of stamping. Draw beads should “run out” at the tangent of the corner radius to minimize metal compression in corners, as shown in figure 16 on page 47.Better grades of die material may be necessary depending on the characteristics of the HSS, the severity of the part geometry, and the
5、 production volume. A draw die surface treatment, such as chrome plating, may be recommended for outer panel applications.Form and Flange DiesPart setup in form and flange dies must allow for proper overbend on all flanges for springback compensation. Springback allowance must be increased as materi
6、al strength increases; 3 degrees for mild steels, but 6 degrees or more for HSS.Punch radii must be fairly sharp. 1t for lower strength steels. Higher strength steels may require larger radii, but keeping them as small as practical will reduce springback in the sidewalls. Flange steel die clearance
7、must be held to no more than one metal thickness clearance to reduce springback and sidewall curl.Form and flange steels should be keyed or pocketed in the casting to avoid flexing.Flange steels should be designed to wrap over and coin the flange break in order to set the break and reduce springback
8、. See figure 17 on page 48. Die strength must not be compromised with light-weight die construction. High strength steel will require a stiffer die to resist flexing and the resultant part distortions, especially for channel or “hat-section” parts. This type of part can also cause serious die damage
9、 if double blanks occur.Cutting DiesTo reduce press tonnage requirements and extend die life, a minimum shear of four to six times metal thickness in twelve inches of trim steel length is recommended.To reduce die maintenance, maximum trim angles should be about 5 to 10 less than those used for mild
10、 steel. Trim steels should be keyed or pocketed in casting to avoid flexing. Die clearance should be 7 to 10% of metal thickness.Drawbead Types Conventional Drawbeads Run-out Drawbeads For H.S.S. Lock Beads for Stretch-Form DieFigure 161. Providing a vertical step in the flange stiffens and straight
11、ens the flange, stopping sidewall curl as well as springback.2. The addition of stiffening darts helps maintain a 90-degree flange.3. By adding a horizontal step along the flange, the flange is stiffened, resulting in reduced springback.4. Back relief on the upper flange steel allows for extra press
12、ure to be applied futher out on the formed radius.Section 5 Die Tryout Guidelines for High Strength Steel DiesGeneral Guidelines for Die TryoutDraw DiesHigher draw die binder pressure and press tonnage will be necessary in order to maintain process control and draw parts without buckles. A double ac
13、tion press or a press with hydraulic cushion may be required in some cases to achieve the required binder forces.HSS draw die operations will require sheet steel lubricants that are formulated for extreme pressures. Mill oils will not provide sufficient lubricity for most applications. Pre-lubes or
14、dry film lubricants may be necessary for process control.Die plan view punchline corner radii should be larger than with mild steels to avoid buckling in the corners of the binder.Stretch Form DiesLock beads may require modification to avoid cracking or tearing with higher strength grades of HSS. Op
15、ening side walls of beads and enlarging corner radii will avoid cracking of high strength sheet steel. Lock beads should be continuous around the punchline for stretch form dies.For large panels from stretch-form dies, such as a roof panel or hood outer, elastic recovery may result in a shrunken pan
16、el that does not fit well on the male die member of the trim or flange dies. This problem is corrected by adding a “plus” factor to the overall part dimensions of the draw die or stretch form die punch. This “plus” is usually no more than 2.5 mm at the center of the sides and the front, tapering to
17、0.0mm at the corners of the part profile on the punch. Finish part profile is defined, and plus is removed, in the main flange die.Form and Flange DiesThe punch radius should be fairly sharp with 1 or 2t used for lower strength steel. HSS may require larger radii, but as small as practical to reduce
18、 springback of sidewalls.The flange steel radius affects sidewall curl and springback on any offset flanges. This radius should also be small to reduce springback of side flanges.Overbend for springback compensation must be increased as tensile strength increases: 3 degrees is standard for mild stee
19、ls, but 6 degrees or more will be required for HSS.Flange steel die clearance should be tight, maintaining no more than one metal thickness clearance to reduce springback and sidewall curl.Cutting DiesTo reduce press tonnage requirements and extend die life, a minimum shear of four to six times meta
20、l thickness in twelve inches of trim steel length is required.Die clearance should be 7 to 10% of metal thickness for HSS.To reduce trim steel maintenance, reduce maximum trim angles by about 5 to 10 from those used for mild steel. Trim steels should be keyed or pocketed in the casting to avoid flex
21、ing.Die Tryout When Using Bake Hardenable SteelIn order to obtain the maximum benefits of BHS, tryout of the dies should be performed as follows: Circle grid analysis must be performed on a panel before any die rework is attempted. With the gridded panel as a reference, the die can be modified to pr
22、ovide a minimum biaxial stretch of 2.0%. Stretch-form or draw dies are best for this material.For rough or functional tryout, it is possible to use mild steel with a 6% to 8% gauge increase to perform the normal process of die preparation. This alleviates complications when the BHS strengthens betwe
23、en each die being tried out. The reason for this is the time lag that normally occurs between a panel being formed and its use in the next operation.When the entire line of dies is ready for approval, all dies must be set in line. Panels should be run through all the die operations consecutively. Th
24、is will avoid some of the strengthening effects of time delays between stamping operations that can cause variation in panels. Dimensional approval of the panel will be most difficult if this procedure is not followed.The strengthening reaction in the BHS can cause dimensional variation in flanges s
25、ince springback will vary with time as the strength increases. This is why running the panel through all die operations consecutively is crucial to a successful buyoff.Part BuyoffTo reduce the part buyoff time and eliminate many hours of tryout time, the benefits of functional build must be consider
26、ed. This procedure has been proven to save time and money by concentrating on an acceptable sub-assembly rather than making each stamping to part specifications. Those parts that are easiest to change are revised to suit the sub-assembly dimensional targets. Those parts that do not affect the sub-as
27、sembly quality are not changed, but the detail part specifications are revised. The functional build process will eliminate excessive tryout hours if used for part buyoff on HSS stampings.In addition to saving tryout time and die rework costs with functional build, lower part variation can also be r
28、ealized. Two dimensional challenges faced by the die maker when first trying out dies are to reduce the dimensional variation from nominal specifications, and to reduce the short term variationfrom part to part. The typical priority is to first minimize part-to-part variation and later address nomin
29、al deviation. A strong argument for this strategy is that the deviation from nominal is not precisely known until a dimensionally consistent part can be evaluated. The results are a dimensionally consistent part even though a number of checkpoints may deviate from nominal, and perhaps even be out of
30、 tolerance. In many situations when dimensions on the die are reworked to shift them closer to nominal, they become less stable and result in higher part-to-part variation. The functional build philosophy evaluates the acceptability of the part after it becomes stable, and before minor dimensional s
31、hifts are made. Large deviant or critical dimensions may be identified for rework even with functional build. There are dimensions that can often be spared rework based on a functional build approach. In these cases, the part remains more stable and the die more robust because less rework occurs whi
32、le attempting to shift dimensions.For more information on functional build, refer to the Auto/Steel Partnership publication. “Event-Based Functional Build: An Integrated Approach to Body Development”. 第四节-高强度钢模具设计和制造指南对模具设计和制造的一般准则拉深模具为了控制高强度钢的成形并减少板料边缘的弯曲，高强度钢成型时的压力和吨位高于一般情况是必要的。模具设计必须考虑适当的压力类型和尺寸。
33、在某些情况下，为了达到需要的压边力和控制力可以用一种双动压力垫或液压垫。如果高强度钢有更高的强度和厚度，空气垫子或氮气缸可能提供不了固定拉深筋或保持边缘固定的力。高强度钢拉深筋不应该在拉伸模具的转角处延长，这将会导致金属流动被锁定和在冲压件角落处产生开裂。拉深筋应该“远离”转角半径切线以减小金属在转角处压缩,如图16。 基于高强度钢的特性、重要部位的几何结构和生产量，选用好的材料制造模具是必要的。拉深模的表面处理,例如电镀，可推荐用于外板的应用。胀形和翻边模 为了能补偿回弹量，用胀形和翻边模生产的零件必须允许适当的过度弯曲。回弹极限必须随材料强度增加而增加;3度适用于低度钢,但6度或以上适用于
34、高强度钢。 冲床半径必须相当尖锐。低强度钢1吨位。高强度钢可以要求更大半径,但使保持和实际生产时一样小，可以降低侧壁的回弹。 翻边模具间隙必须不超过一个金属厚度间隙以降低回弹及侧壁发生的卷曲。 胀形和翻边板材要固定在铸件里以避免发生挠曲。 翻边板材应设计时应包住和压住边缘断处以设置中断和减少回弹。见图17。 模具强度不能小于低强度模具结构的强度。高强度钢将会需要一个坚硬的模具来抵抗屈曲和相应部分的扭曲,尤其是对集中力处或冒形截面部分。这部分在成形多个毛坯时也会引起严重的模具损坏剪切模具 为了降低吨位要求和延长模具寿命,十二英寸长的金属至少修剪四到六次。 为了减少模具的维修,最大修剪角应该在5角
35、到10，应该低于使用低碳钢的角度。修剪钢材要固定在铸件中以避免铸件挠曲。模具间隙应该是7%到10%的金属厚度。拉延筋的类型传统的拉延筋 高强度拉延筋带压边圈拉延模具1.提供一个垂直的台阶来强化和压制边缘,同时防止侧壁的卷曲以及回弹。2.增加强化暗褶有助于维持一个90度边。3.通过沿边缘添加一个横向的台阶、能强化边缘并减少回弹。4.上边缘金属的补充使得额外的压力能够进一步应用于形成的半径上。第五节 高强钢模具的模具调试对模具调试的一般准则拉深模具为了控制高强度钢成型控制并减少板料边缘的弯曲，在高强度钢成型时压力和吨位高于一般情况是必要的。在某些情况下，为了达到需要的压边力和控制力可以用一种双作用
36、压力垫或液压垫。 高强度钢拉深模操作时需要用于制定极端的压力钢板润滑剂，机油对于大多数应用将不提供足够的润滑性。预先润滑或干膜润滑油对拉深过程控制有必要的作用。拉伸成型对于有高强度的高强度钢定位调整杆可能需要修改以避免断裂或撕裂。开放侧面转角半径的筋和扩大转角半径将避免高强度钢板的开裂。定位调整杆应连续围绕在延伸模的延伸方向上。 延伸模对于大型嵌板,如车顶或外罩，弹性的回复可能导致板面的收缩,以至于与凸模和翻边模不匹配。通过添加一个因素的来增大拉深模具或翻边部分尺寸来纠正这个问题。这个“添加的因素”是在该中心的侧面和前面增加不超过2.5毫米,冲头上转角处部分的锥度是0，在总的翻边模中，通过边界
37、部分的剖面,增加的部分被移走。胀形和翻边模 冲头半径应比较突出尖锐，低强度钢用1或2吨位。H.S.S.可能需要更大半径,但减小到使用时能减少侧壁回弹。 在任何平板翻边中翻边钢材会影响回弹和侧壁的卷曲。半径应该也小到可以减少边缘的回弹。 过度弯曲时回弹补偿必须随抗拉强度增加而增加:3度对于低强度钢是一种标准,但6度或以上将会被用于H.S.S。 翻边模模具间隙应该紧凑,保持间隙不超过一个金属厚度以减少回弹及侧壁的卷曲。剪切模 降低吨位要求和延长模具寿命,十二英寸长的金属至少修剪四到六次。 对于高强度钢模具间隙应在7% - 10%的金属厚度。 减少模具的维修,最大修剪角应该在5角到10，应该低于对低
38、碳钢的使用角度。修剪钢材要固定在铸件中以避免在铸件挠曲。当使用加热可硬化钢材的模具试用 为了获得使用BHS的最大值,模具应进行如下:在行任何模具重新工作前都必须尝试分析圆网格。模具可作为一个参考网格板料、模具可修改提供的最小二轴的伸展2.0%。延伸模或拉伸模具最适合该材料。 粗糙度或功能调试,它可以用低碳钢增加6% -8%标准来来表现通常模具的准备过程。这能减轻在每个模具调试时BHS得到强化时的复杂情况。这一现象的原因可能是时间滞后,通常一个板料之间发生的形成及其用于下一个操作。当整个系列的模具已准备就绪，所有的模具必须设置在一条线上。板料能在所有的模具连续操作。这将避免一些加固效果的时间延迟
39、操作,可以引起冲压件之间变化。如果这个过程是不被允许的那么尺寸的延伸将是最困难的。 BHS的变化会导致边缘尺寸的变化,因为随时间回弹将随强度的增加而增加。这就是为什么让板料能连续通过模具各部分，对一个成功的检查来说是至关重要的。部分新产品引入 为了减少新产品引入时间和消除几个小时的调试时间,就要考虑功能建设所有的优势。这个应用程序被证明能节省时间和金钱通过专注于一个可接受的半成品,而不是迫使每个冲压分开进行。这些零件是最容易改变来适应半成品进行相应的修正尺寸的目标。这些部分并不足以影响半成品质量，但是细节部分规格被修改。如果将这种程序用于高强度钢冲压件新产品引入将会消耗过多时间。 在功能的建立
40、中除了节省时间和模具调试成本,降低零件变化都有可能实现。模具制造商所面临两个尺寸上的挑战：当第一次尝试模具时相对于公称规格降低尺寸上的变化,降低了各部分间的短期尺寸变化。首要任务是要先减小零件间变化和偏差。这个策略一个强有力的论点认为偏离标称是被允许的直到零件尺寸上一致可以评估。尽管很多测试点偏离标准位置有的甚至超过偏差极限但在结果上它们尺寸上是一致的。在许多情况下当改变模具尺寸使它接近标准值,它们变得不稳定甚至导致部分间更大的变化。这功能建设理论评估零件变稳定后可接受程度,在小尺寸上的进行改变。即使功能的建立在模具重做时也会有大偏差或临界尺寸出现。基于功能性建设的方法重做时经常有些备用尺寸。在这些情况下,模具零件仍然更加稳定和模具具有更强的性能，因为在改变模具尺寸上有相对少的调整。 更多的信息,请参阅功能建设汽车/钢合作出版。“基于事件的功能建设:一套综合的方法来发展部件”。