鋼模型腔超塑成形與電火花復合加工

1、鋼模型腔超塑成形與電火花復合加工楊蘊林 , 王長生 , 盧根基 , 馬仰峽大量機械畢業(yè)設計，專業(yè)訂做模具畢業(yè)設計、聯(lián)系QQ:365066922模具畢業(yè)設計網(wǎng)：摘要:鋼模型腔的電火花加工是常用的型腔加工技術,但加工效率較低。型腔超塑成形是型腔加工新技術之一,但需用高溫合金凸模,且成形后需淬火強化而影響已成形型腔的精度。介紹了將2 種技術優(yōu)化組合的復合加工原理、實施方案及應用實例。該技術尤其適用于有批量要求的復雜高精度型腔的加工。 關鍵詞:鋼模型腔;超塑成形;電火花加工;復合加工1 引言鋼模型腔的現(xiàn)有加工技術主要是機加工和電加工, 而復雜高精度型腔的加工主要靠電火花加工。型腔超塑成形技術雖有良好的

2、應用前景,但因其適用范圍的局限性而未被廣泛采用。事實上任何一種加工技術都有局限性, 因此若將某些現(xiàn)有技術優(yōu)化組合, 則往往有更好的效果。鋼模型腔的電火花加工和超塑成形主要工藝特點對比見表1 , 可以看出, 2 種技術有一定互補性。如電火花加工效率低, 但可加工淬火后的模坯。超塑成形快, 但成形后淬火強化會影響已成形型腔的精度?；谝陨戏治? 將2 種技術優(yōu)化組合的超塑成形與電火花復合加工技術, 即以超塑成形為主, 輔以電火花加工,可獲得意想不到的效果。表1 鋼模型腔電火花加工和超塑成形主要工藝特點對比2 復合加工技術工藝方案圖1 對比了復合加工與超塑成形的主要工藝流程。以下以復合加工為主予以說

3、明:(1) B 1 與A 1 相同。模坯下料后一般都要經(jīng)過鍛造及熱處理,以改善組織提高使用壽命,這在一定程度上也起到了為B 3 或A 2、A 4 作組織準備的作用。(2) B 2 與A 3 區(qū)別在于對工藝凸模的精度要求。B 2 對凸模精度要求可降低, 這樣可減少難加工的高溫合金凸模的加工工序、工時和成本,并增長凸模使用壽命。(3) B 3 與A 4 區(qū)別在于對超塑成形的精度要求。超塑成形的型腔精度完全取決于A 3 和A 4 , A 2 是為A 4 服務的,復合加工的型腔精度由B 2、B 3 及B 6 保證, 且最終精度由B 6 保證, 因而復合加工中可降低B 2、B 3 的精度要求。對B 3

4、精度要求的降低, 使A 2可以省略, 這是由于模具鋼大多是以熱軋球化退火態(tài)供應的, 要求較高的模具還要對模坯進行鍛造和熱處理以進一步改善組織, 因而成形前模坯組織基本上是鐵素體基體與均勻分布的粒狀碳化物, 已基本滿足超塑成形的組織條件2 ,3 。超塑成形精度要求的降低則意味著超塑成形可以在普通壓機上、在較寬的溫度范圍、較高的應變速率范圍內進行,對模坯的組織要求也可降低(省略A 2) ,從而可降低工藝成本并提高加工效率。(4) B 4 由于無需考慮淬火變形(最終精度由B 6保證) , 故可采用多種熱處理方式以提高模坯強韌性, 也可將超塑成形后仍處于成形溫度的模坯迅速調整至淬火溫度淬火, 無需重新

5、加熱并有形變熱處理的效果。(5) B 5 只是精加工電極的設計與制備。(6) B 6 的加工余量很小,某些部位的型腔加工余量甚至為零,故可明顯減少電火花工時及電極損耗,并使壓印成形后仿型腔分布的流線基本不被破壞,型腔表面過熱過燒層趨于零。綜上所述, 復合加工技術兼有電火花加工和超塑成形技術的優(yōu)點而避開了各自的缺點。圖1 型腔超塑成形與復合加工主要工藝流程3 應用實例某離合器掛檔軸端部梅花瓣形齒冷擠壓模, 材料為Cr12MoV ,硬度要求5961HRC。原制造工藝: 下料鍛造球化退火機加工淬火回火磨削梅花形型腔的電火花加工裝配, 其中僅電火花加工型腔就需46h ,工時費用達300 元。模具使用中

6、梅花形型腔端口易發(fā)生局部崩塊而早期失效。該模具型腔形狀復雜,精度要求較高,并有批量要求,宜采用復合加工技術。復合加工的工藝凸模采用鎳基高溫合金K3 ,其形狀尺寸精度是根據(jù)該冷擠模圖紙要求, 經(jīng)適當調整后確定的(如圖2 所示) , 采用精鑄棒料慢走絲線切割加工而成。超塑成形是在YB32- 100A 液壓機上采用反擠壓半開式成形, 成形溫度780800 , 壓下速度0. 61. 2mm/ min , 成形時間10min , 型腔深度5. 55. 8mm。成形后迅速將模坯頂出并轉移到1 000 的爐內, 透燒后熱油分級淬火, 180200 回火。電火花精加工的電極尺寸除取決于模具圖紙要求外還要考慮超

7、塑成形及淬火后型腔的實際形狀尺寸, 為此, 對模擬試樣進行了批量檢測, 發(fā)現(xiàn)型腔自根部至端口略呈喇叭口變形。經(jīng)電火花試加工, 最終確定紫銅電極主要尺寸(參見圖2) 為R3. 1 0- 0. 05mm , <19 0- 0. 05mm , <15. 8 0 - 0. 05mm。電火花精加工工時1h , 加工后型腔形狀尺寸精度、粗糙度、硬度等完全符合設計要求, 加工后的模具實物見圖3。圖2 工藝凸模復合加工與原電火花加工相比, 省去了電火花粗加工工序及電極; 電火花精加工工時減少, 電極使用壽命延長; 模坯組織缺陷少, 流線仿型腔分布;型腔表面粗糙度值降低,表面過熱過燒層趨于零。復合加

8、工與超塑成形相比, 降低了對工藝凸模形狀尺寸精度及超塑壓印成形精度的要求, 因而本實例中省去了模坯的組織預處理、工藝凸模的磨削加工,并可在普通液壓機上、較快速度下完成型腔成形。經(jīng)測評, 該模具批量達20 件時, 復合加工比原電火花加工的工藝成本降低約15 % , 制造周期縮短近50 % , 且提高了模具使用壽命, 模具批量大于20 件時,則工藝成本和制造周期優(yōu)勢更明顯。圖3 復合加工技術制造的冷擠壓模4 結束語對于形狀比較復雜、精度較高、有批量要求的鋼模型腔, 采用超塑成形與電火花復合加工有更好的綜合效益,是可供首選的型腔加工技術。參考文獻: 1 盧存?zhèn)? 電火花加工工藝學M . 北京:國防工

9、業(yè)出版社,1998. 2 楊蘊林,席聚奎. 超塑技術在模具制造中的應用J .兵器材料科學與工程,1996 ,19(1) : 3743. 3 林兆榮. 金屬超塑性成形原理與應用M . 北京:航空工業(yè)出版社,1990.附 錄B(外文翻譯)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齒冷, 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