钢模型腔超塑成形与电火花复合加工

1、钢模型腔超塑成形与电火花复合加工杨蕴林 , 王长生 , 卢根基 , 马仰峡大量机械毕业设计，专业订做模具毕业设计、联系QQ:365066922模具毕业设计网：摘要:钢模型腔的电火花加工是常用的型腔加工技术,但加工效率较低。型腔超塑成形是型腔加工新技术之一,但需用高温合金凸模,且成形后需淬火强化而影响已成形型腔的精度。介绍了将2 种技术优化组合的复合加工原理、实施方案及应用实例。该技术尤其适用于有批量要求的复杂高精度型腔的加工。 关键词:钢模型腔;超塑成形;电火花加工;复合加工1 引言钢模型腔的现有加工技术主要是机加工和电加工, 而复杂高精度型腔的加工主要靠电火花加工。型腔超塑成形技术虽有良好的

2、应用前景,但因其适用范围的局限性而未被广泛采用。事实上任何一种加工技术都有局限性, 因此若将某些现有技术优化组合, 则往往有更好的效果。钢模型腔的电火花加工和超塑成形主要工艺特点对比见表1 , 可以看出, 2 种技术有一定互补性。如电火花加工效率低, 但可加工淬火后的模坯。超塑成形快, 但成形后淬火强化会影响已成形型腔的精度。基于以上分析, 将2 种技术优化组合的超塑成形与电火花复合加工技术, 即以超塑成形为主, 辅以电火花加工,可获得意想不到的效果。表1 钢模型腔电火花加工和超塑成形主要工艺特点对比2 复合加工技术工艺方案图1 对比了复合加工与超塑成形的主要工艺流程。以下以复合加工为主予以说

3、明:(1) B 1 与A 1 相同。模坯下料后一般都要经过锻造及热处理,以改善组织提高使用寿命,这在一定程度上也起到了为B 3 或A 2、A 4 作组织准备的作用。(2) B 2 与A 3 区别在于对工艺凸模的精度要求。B 2 对凸模精度要求可降低, 这样可减少难加工的高温合金凸模的加工工序、工时和成本,并增长凸模使用寿命。(3) B 3 与A 4 区别在于对超塑成形的精度要求。超塑成形的型腔精度完全取决于A 3 和A 4 , A 2 是为A 4 服务的,复合加工的型腔精度由B 2、B 3 及B 6 保证, 且最终精度由B 6 保证, 因而复合加工中可降低B 2、B 3 的精度要求。对B 3

4、精度要求的降低, 使A 2可以省略, 这是由于模具钢大多是以热轧球化退火态供应的, 要求较高的模具还要对模坯进行锻造和热处理以进一步改善组织, 因而成形前模坯组织基本上是铁素体基体与均匀分布的粒状碳化物, 已基本满足超塑成形的组织条件2 ,3 。超塑成形精度要求的降低则意味着超塑成形可以在普通压机上、在较宽的温度范围、较高的应变速率范围内进行,对模坯的组织要求也可降低(省略A 2) ,从而可降低工艺成本并提高加工效率。(4) B 4 由于无需考虑淬火变形(最终精度由B 6保证) , 故可采用多种热处理方式以提高模坯强韧性, 也可将超塑成形后仍处于成形温度的模坯迅速调整至淬火温度淬火, 无需重新

5、加热并有形变热处理的效果。(5) B 5 只是精加工电极的设计与制备。(6) B 6 的加工余量很小,某些部位的型腔加工余量甚至为零,故可明显减少电火花工时及电极损耗,并使压印成形后仿型腔分布的流线基本不被破坏,型腔表面过热过烧层趋于零。综上所述, 复合加工技术兼有电火花加工和超塑成形技术的优点而避开了各自的缺点。图1 型腔超塑成形与复合加工主要工艺流程3 应用实例某离合器挂档轴端部梅花瓣形齿冷挤压模, 材料为Cr12MoV ,硬度要求5961HRC。原制造工艺: 下料锻造球化退火机加工淬火回火磨削梅花形型腔的电火花加工装配, 其中仅电火花加工型腔就需46h ,工时费用达300 元。模具使用中

6、梅花形型腔端口易发生局部崩块而早期失效。该模具型腔形状复杂,精度要求较高,并有批量要求,宜采用复合加工技术。复合加工的工艺凸模采用镍基高温合金K3 ,其形状尺寸精度是根据该冷挤模图纸要求, 经适当调整后确定的(如图2 所示) , 采用精铸棒料慢走丝线切割加工而成。超塑成形是在YB32- 100A 液压机上采用反挤压半开式成形, 成形温度780800 , 压下速度0. 61. 2mm/ min , 成形时间10min , 型腔深度5. 55. 8mm。成形后迅速将模坯顶出并转移到1 000 的炉内, 透烧后热油分级淬火, 180200 回火。电火花精加工的电极尺寸除取决于模具图纸要求外还要考虑超

7、塑成形及淬火后型腔的实际形状尺寸, 为此, 对模拟试样进行了批量检测, 发现型腔自根部至端口略呈喇叭口变形。经电火花试加工, 最终确定紫铜电极主要尺寸(参见图2) 为R3. 1 0- 0. 05mm , <19 0- 0. 05mm , <15. 8 0 - 0. 05mm。电火花精加工工时1h , 加工后型腔形状尺寸精度、粗糙度、硬度等完全符合设计要求, 加工后的模具实物见图3。图2 工艺凸模复合加工与原电火花加工相比, 省去了电火花粗加工工序及电极; 电火花精加工工时减少, 电极使用寿命延长; 模坯组织缺陷少, 流线仿型腔分布;型腔表面粗糙度值降低,表面过热过烧层趋于零。复合加

8、工与超塑成形相比, 降低了对工艺凸模形状尺寸精度及超塑压印成形精度的要求, 因而本实例中省去了模坯的组织预处理、工艺凸模的磨削加工,并可在普通液压机上、较快速度下完成型腔成形。经测评, 该模具批量达20 件时, 复合加工比原电火花加工的工艺成本降低约15 % , 制造周期缩短近50 % , 且提高了模具使用寿命, 模具批量大于20 件时,则工艺成本和制造周期优势更明显。图3 复合加工技术制造的冷挤压模4 结束语对于形状比较复杂、精度较高、有批量要求的钢模型腔, 采用超塑成形与电火花复合加工有更好的综合效益,是可供首选的型腔加工技术。参考文献: 1 卢存伟. 电火花加工工艺学M . 北京:国防工

9、业出版社,1998. 2 杨蕴林,席聚奎. 超塑技术在模具制造中的应用J .兵器材料科学与工程,1996 ,19(1) : 3743. 3 林兆荣. 金属超塑性成形原理与应用M . 北京:航空工业出版社,1990.附 录B(外文翻译)Die Manufacturing Technology:Superplastic Forming and EDM Compound Processingof the Steel Die CavityYang YunLin, Wang Changsheng, Lu GengJi, Ma YangxiaAbstract: Steel EDM cavity model

10、 is a commonly used cavity processing technology, but less efficient processing. Superplastic forming cavity is a cavity, one of the processing of new technologies, but need to punch high-temperature alloy, and quenching after forming and strengthening the impact of the precision forming cavity. Int

11、roduced the technology to optimize the combination of two kinds of processing of complex theory, and application examples of the implementation of the program. In particular, the technical requirements applicable to the complexity of bulk high-precision processing cavity.Key words: steel model cavit

12、y; superplastic forming; EDM; composite processing1 IntroductionCavity model of the existing steel processing technology is the machining and electrical processing, and complex high-precision processing cavity mainly by EDM. Superplastic forming cavity despite a good prospect, but because of the lim

13、itations of the scope of application has not been widely adopted. In fact any kind of processing technology has limitations, so if some of the existing technology portfolio optimization is often a better result. Steel cavity model and the EDM process of superplastic forming characteristics of the ma

14、in comparison in Table 1, we can see that there are two kinds of technology will certainly complement each other. EDM, such as low efficiency, but the mold after hardening machinable blanks. Superplastic forming soon, but the shape will be affected after the quenching has been formed to strengthen t

15、he accuracy of the cavity. Based on the above analysis, two kinds of technology to optimize the combination of superplastic forming and spark compositeprocessing technology, that is, superplastic forming, supplemented by EDM, get unexpected results.Table 1 EDM cavity steel model and the process of s

16、uperplastic formingcharacteristics of the main contrast2 composite processing technology programFigure 1 Comparison of the composite processing and the main superplastic forming process. Complex processing in the following be described mainly: (1)B 1 and A 1 the same. Die cutting blanks generally ha

17、ve to go through after forging and heat treatment to improve the organization to increase service life, which to some extent, also played for the B 3 or A 2, A 4 to prepare for the role of organizations. (2) B 2 and A 3 is to process the difference between the accuracy of punch. B 2 on punch accurac

18、y can be reduced, this can be difficult to reduce the processing of high-temperature alloy processing punch, working hours and costs and increase service life of punch. (3) B 3 and A 4 is the difference between the superplastic forming of precision. Superplastic forming of the cavity accuracy depend

19、s entirely on the A 3 and A 4, A 2 for A 4 services, composite cavity machining accuracy by the B 2, B 3 and B 6 assurance, and ultimately to ensure the accuracy of the B 6, processing complex and thus can reduce the B 2, B 3 of accuracy. B 3 of the reduced accuracy, so that A 2 can be omitted, whic

20、h is mostly as a result of die steel is hot-rolled annealed state of the supply of the ball, requiring a high modulus blank mold but also to forging and heat treatment to further improve the organization, thus forming billet organization the former mode is essentially ferrite matrix with uniformly d

21、istributed granular carbide, has been basically to meet the organization superplastic forming conditions 2, 3. Superplastic forming of the lower precision means that superplastic forming can be in the general press, in a wide temperature range, high strain rate carried out within the framework of th

22、e Organization of the billet mold can reduce the demands (omit A 2), process which can reduce costs and improve processing efficiency. (4) B 4 as there is no need to consider the deformation hardening (the ultimate guarantee the accuracy of the B 6), it can be a variety of treatment methods to impro

23、ve strength and toughness of die blanks can also be super plastic forming after forming in a billet mold temperature quickly adjusted to quenching temperature quenching, without re-heating and the effect of thermomechanical treatment.(5) B 5 is just finishing the design and preparation of the electr

24、ode.(6) B 6 of the allowance is very small, some parts of the cavity allowance or even zero, it can significantly reduce working hours and the EDM electrode wear and tear, and after stamping forming cavity imitation streamline the distribution of basic not be destroyed, burned off overheating cavity

25、 surfacelayer tends to zero.In conclusion, both complex EDM processing technology of superplastic forming technology and the advantages and avoid their shortcomings.Figure 1 superplastic forming cavity and composite processing of the main process 3 Application ExampleShaft end of a file linked to th

26、e Ministry of clutch petal plum-shaped extrusion die齿冷, materials for Cr12MoV, hardness 59 61HRC. The original manufacturing process: material under forging spheroidizing machining grinding quenching and tempering plum-shaped cavity of the assembly EDM, EDM and only on the cavity to be 4 6h, working

27、 hours, the cost of up to 300 yuan. The use of plum-shaped mold cavity-prone port block partial collapse and early failure. The mold cavity the shape of complex, high precision and volume requirements, should adopt the composite processing technology.Composite processing technology used punch Ni-bas

28、e superalloy K3, itsshape is based on the dimensional accuracy of cold extrusion die drawings requested, with appropriate adjustments to be determined (as shown in Figure2), the use of walking cast bar cutting thread formed. Superplastic forming in the hydraulic press YB32-100A using the anti-extrus

29、ion forming semi-open, forming temperature of 780 800 , the rate reduction 0. 6 1. 2mm / min, forming time 10min, cavity depth5. 5 5. 8mm. Formed quickly after the top of a blank mold and transferred to 1 000 of the furnace, hot oil, after burning through grade quenching, 180 200 tempered. EDM finis

30、hing electrode size depends on the mold in addition to drawing requirements should also be considered superplastic forming and quenching after the actual shape of the cavity size, to that end, to simulate the bulk sample testing and found that cavity from the roots to the port slightly deformed bell

31、. Examination by the EDM processing, the final copper electrode to determine the main dimensions (see Figure 2) for the R3. 1 0 - 0. 05mm, <19 0 - 0. 05mm, <15. 8 0- 0. 05mm. EDM finishing time 1h, after the cavity shape processing dimensional accuracy, roughness, hardness, such as compliance

32、with thedesign requirements of the mold after processing in kind see Figure 3.Figure 2 Process punchComplex processing compared with the original EDM, EDM rough machining process eliminates the need and the electrode; EDM finish to reduce working hours, extended service life of electrodes; modulus l

33、ess defects billet organizations, streamline the distribution of imitation cavity; cavity surface roughness value lower than the overheated surface layer tends to zero burning. Complex processing and superplastic forming, compared to thetechnology reduces the size of punch shape precision and accuracy of superplastic forming stamping requirements, thus eliminating the need for this example in the organization of pre-processing module blanks, craft punch grinding p