首先想了解不銹鋼沖壓、彎曲和連續沖裁加工工藝,必須要知道以下幾點:
a. 極限拉深比--拉深加工時,相對于容器直徑d可能拉深的最大原料板直徑為Dmax時,Dmax/d則稱為極限拉深比(LDR).
b. 平(ping)均r值--塑性為(wei)異(yi)向性的(de)材料深(shen)拉深(shen)成(cheng)形特性評價的(de)重要指標。鐵素(su)體系列不銹鋼中(zhong),其平(ping)均r值越大,其極(ji)限拉深(shen)比就越高。
c. 拉深皺(zhou)(zhou)折(zhe)(zhe)-鐵素體系(xi)列不(bu)銹(xiu)鋼在沖床上(shang)進行深拉深加(jia)工(gong)時,在其表面上(shang)容(rong)易產生凹凸不(bu)平的皺(zhou)(zhou)折(zhe)(zhe)。可認(ren)為是組(zu)合結構不(bu)同而(er)引起的塑(su)性異向性。
d. 時效性(xing)斷(duan)裂-奧氏體(ti)系列不銹(xiu)鋼(gang)SUS304等(deng)準穩定型奧氏體(ti)系列不銹(xiu)鋼(gang),在加工后有發生(sheng)時效性(xing)裂紋的現象。它(ta)與晶界晶粒(li)無關。一般(ban)認為是由于加工感應(ying)而引起的馬氏體(ti)、氫和殘余應(ying)力(li)所致。
1. 沖壓加工
沖壓加工(gong)(gong)(gong)(gong)(gong)(gong)行(xing)業(ye)是家庭式作(zuo)坊工(gong)(gong)(gong)(gong)(gong)(gong)業(ye)的(de)(de)(de)代表性(xing)產(chan)業(ye),多是從單獨一(yi)個(ge)一(yi)個(ge)地加工(gong)(gong)(gong)(gong)(gong)(gong)西餐(can)具、器(qi)皿等(deng)(deng)所謂(wei)的(de)(de)(de)“洋人筷子”等(deng)(deng)開始(shi),發展(zhan)(zhan)到(dao)餐(can)飲業(ye)的(de)(de)(de)廚房用(yong)具以(yi)(yi)及廚房中所使(shi)用(yong)的(de)(de)(de)水槽(cao)、洗滌盆、深(shen)(shen)(shen)拉(la)(la)(la)深(shen)(shen)(shen)加工(gong)(gong)(gong)(gong)(gong)(gong)的(de)(de)(de)澡盆以(yi)(yi)及汽車、電機領域中的(de)(de)(de)零部件等(deng)(deng)。主要工(gong)(gong)(gong)(gong)(gong)(gong)藝方(fang)法是采用(yong)剪切、沖孔、拉(la)(la)(la)深(shen)(shen)(shen)等(deng)(deng)進行(xing)連續加工(gong)(gong)(gong)(gong)(gong)(gong)。洋餐(can)具、器(qi)皿和鍋的(de)(de)(de)沖壓加工(gong)(gong)(gong)(gong)(gong)(gong),基本上是屬(shu)于圓筒拉(la)(la)(la)深(shen)(shen)(shen)制成。原(yuan)材料(liao)板直(zhi)徑D對容器(qi)(產(chan)品(pin))直(zhi)徑d之比,D/d稱(cheng)為拉(la)(la)(la)深(shen)(shen)(shen)比。以(yi)(yi)可(ke)能拉(la)(la)(la)深(shen)(shen)(shen)的(de)(de)(de)最大(da)原(yuan)材料(liao)板直(zhi)徑為Dmax時,則Dmax/d稱(cheng)為極限(xian)拉(la)(la)(la)深(shen)(shen)(shen)比(LDR: Limiting Drawing Ratio)作(zuo)為衡量加工(gong)(gong)(gong)(gong)(gong)(gong)性(xing)的(de)(de)(de)指(zhi)標。不銹(xiu)鋼(gang)(gang)(gang)產(chan)品(pin)得(de)以(yi)(yi)大(da)幅度的(de)(de)(de)增加需求與沖壓加工(gong)(gong)(gong)(gong)(gong)(gong)技術的(de)(de)(de)發展(zhan)(zhan)有很(hen)大(da)關系(xi)。不銹(xiu)鋼(gang)(gang)(gang)產(chan)品(pin)生產(chan)廠家在深(shen)(shen)(shen)拉(la)(la)(la)深(shen)(shen)(shen)加工(gong)(gong)(gong)(gong)(gong)(gong)等(deng)(deng)方(fang)面,由于塑性(xing)加工(gong)(gong)(gong)(gong)(gong)(gong)技術和材料(liao)技術的(de)(de)(de)進展(zhan)(zhan)。使(shi)得(de)鐵素體系(xi)列不銹(xiu)鋼(gang)(gang)(gang)高加工(gong)(gong)(gong)(gong)(gong)(gong)性(xing)鋼(gang)(gang)(gang)種,已經產(chan)品(pin)化了。可(ke)以(yi)(yi)選定平均r值在1.2~1.8,LDR為2.2~2.5的(de)(de)(de)鋼(gang)(gang)(gang)種。
在不(bu)銹(xiu)(xiu)鋼制(zhi)品的(de)沖壓(ya)加工(gong)(gong)中,如果(guo)使用奧氏體系列不(bu)銹(xiu)(xiu)鋼或鐵(tie)素體系列不(bu)銹(xiu)(xiu)鋼的(de)高加工(gong)(gong)性能鋼種時(shi),可以進(jin)行(xing)一定程度(du)的(de)深(shen)(shen)拉(la)深(shen)(shen)加工(gong)(gong)。奧氏體系列不(bu)銹(xiu)(xiu)鋼的(de)代表(biao)型鋼種 SUS 304(18Cr -18Ni),因為(wei)它的(de)LDR為(wei)2.5,可以進(jin)行(xing)相對較大的(de)深(shen)(shen)拉(la)深(shen)(shen)加工(gong)(gong)。
但由(you)于加工(gong)(gong)硬化(hua)傾(qing)向大而急劇地增加了加工(gong)(gong)難(nan)度,有時竟發生裂(lie)紋(wen)或斷(duan)裂(lie)。為此,沖(chong)壓廠家就(jiu)在中間(jian)加上一道熱處(chu)理(li)工(gong)(gong)序(xu)之后再進(jin)行深拉深加工(gong)(gong)。還(huan)必須注意,奧(ao)氏體系列不銹鋼(gang)的(de)奧(ao)氏體穩(wen)定度低的(de)鋼(gang)種(zhong)經(jing)過拉深后,有可(ke)能發生時效(xiao)斷(duan)裂(lie)現象。
近年來,新潟縣燕市的(de)沖壓(ya)加(jia)工廠和新鴻縣工業技術中心(xin)共同(tong)開(kai)發不銹(xiu)鋼(gang)熱沖壓(ya)技術,實現了超深拉深加(jia)工。熱沖壓(ya)技術就(jiu)是將凹(ao)模(mo)(mo)或者凸模(mo)(mo)其(qi)中之一進(jin)行加(jia)熱,這樣不銹(xiu)鋼(gang)原(yuan)(yuan)來的(de)拉深程(cheng)度就(jiu)可以提(ti)高1.5~2.0倍。熱沖壓(ya)加(jia)工設備的(de)工作原(yuan)(yuan)理(li)如圖6-9所示。其(qi)加(jia)工特(te)性如圖6-10所示。
2. 彎曲與連續沖裁
奧氏(shi)體(ti)系(xi)列(lie)(lie)不(bu)(bu)銹(xiu)鋼(gang)進行(xing)彎(wan)曲(qu)(qu)加(jia)工(gong)是(shi)(shi)件簡單之事,可以制(zhi)作(zuo)角(jiao)鋼(gang)、槽鋼(gang)等(deng)(deng)型材(cai)使用(yong)。鐵素(su)體(ti)系(xi)列(lie)(lie),馬氏(shi)體(ti)系(xi)列(lie)(lie)不(bu)(bu)銹(xiu)鋼(gang)作(zuo)為(wei)型材(cai)加(jia)工(gong),一(yi)(yi)般情(qing)況下(xia)沒有(you)(you)問題(ti),但當彎(wan)曲(qu)(qu)半(ban)徑R小的(de)(de)(de)時(shi)(shi)(shi)候,在(zai)(zai)折(zhe)彎(wan)處(chu)有(you)(you)時(shi)(shi)(shi)會發(fa)生斷(duan)裂。在(zai)(zai)JIS標(biao)準(zhun)中,對鐵素(su)體(ti)、馬氏(shi)體(ti)系(xi)列(lie)(lie)的(de)(de)(de)不(bu)(bu)銹(xiu)鋼(gang)彎(wan)曲(qu)(qu)試(shi)驗標(biao)準(zhun)規定,彎(wan)曲(qu)(qu)半(ban)徑R為(wei)1.0t(t為(wei)板(ban)材(cai)厚度)不(bu)(bu)應(ying)發(fa)生彎(wan)曲(qu)(qu)斷(duan)裂。還有(you)(you),必須注意不(bu)(bu)銹(xiu)鋼(gang)彎(wan)曲(qu)(qu)加(jia)工(gong)回彈量大的(de)(de)(de)特(te)點(dian)。落(luo)(luo)料(liao)(俗稱(cheng)下(xia)料(liao))或稱(cheng)為(wei)沖(chong)裁加(jia)工(gong),大多數是(shi)(shi)采用(yong)沖(chong)床連續加(jia)工(gong)的(de)(de)(de)方(fang)式,有(you)(you)時(shi)(shi)(shi)在(zai)(zai)沖(chong)切(qie)斷(duan)面(mian)(mian)上(shang),發(fa)生塌(ta)邊現象(即沖(chong)切(qie)面(mian)(mian)與基準(zhun)平面(mian)(mian)不(bu)(bu)垂直)。精(jing)密落(luo)(luo)料(liao)是(shi)(shi)從(cong)變壓器等(deng)(deng)使用(yong)疊層(ceng)的(de)(de)(de)電磁鋼(gang)板(ban)的(de)(de)(de)加(jia)工(gong)技(ji)(ji)術開展(zhan)起來(lai)的(de)(de)(de)技(ji)(ji)術,對粒(li)子加(jia)速(su)器的(de)(de)(de)套環(collar)或電子零部(bu)件中的(de)(de)(de)引線框(lead frame)等(deng)(deng)等(deng)(deng),從(cong)較厚的(de)(de)(de)板(ban)材(cai)到超薄材(cai),精(jing)密落(luo)(luo)料(liao)得到廣泛應(ying)用(yong)。沖(chong)壓加(jia)工(gong)機(ji)械(xie)亦可以進行(xing)精(jing)密沖(chong)壓(落(luo)(luo)料(liao))加(jia)工(gong),但由于(yu)沖(chong)壓塌(ta)邊的(de)(de)(de)問題(ti),一(yi)(yi)般不(bu)(bu)能作(zuo)為(wei)成品直接使用(yong)。在(zai)(zai)精(jing)密沖(chong)壓中,為(wei)控制(zhi)塌(ta)邊,就需加(jia)一(yi)(yi)道機(ji)械(xie)控制(zhi)的(de)(de)(de)工(gong)藝措施,這需要按產品用(yong)途以及成本兩(liang)方(fang)面(mian)(mian)來(lai)權衡。在(zai)(zai)加(jia)工(gong)方(fang)法(fa)競爭上(shang),還有(you)(you)一(yi)(yi)種“蝕刻(ke)”方(fang)法(fa),在(zai)(zai)電子產品的(de)(de)(de)接線框等(deng)(deng)超薄產品中,在(zai)(zai)加(jia)工(gong)廠家(jia)的(de)(de)(de)技(ji)(ji)術競爭中,兩(liang)者幾乎各占一(yi)(yi)半(ban)。
3. 加工油、表面保護薄(bo)膜和(he)其他潤滑
a. 表(biao)面(mian)保護薄膜-為(wei)了保持不銹鋼的(de)匠(jiang)藝性、防止產生瑕疵(ci)以及作為(wei)潤滑而敷于材料表(biao)面(mian)的(de)聚氯乙(yi)(yi)烯或聚乙(yi)(yi)烯等薄膜。
b. 揮發(fa)(fa)性加工(gong)油--加工(gong)時有潤(run)滑效果而后又(you)能(neng)揮發(fa)(fa)掉的(de)(de)加工(gong)油。使(shi)用完全揮發(fa)(fa)型的(de)(de),可以省(sheng)掉清(qing)洗(xi)工(gong)序(xu)。
c. 潤滑不銹(xiu)鋼板-具有透明(ming)石蠟涂裝的不銹(xiu)鋼,它(ta)比加工油或表面保(bao)護膜有更(geng)好(hao)的加工性。
在沖(chong)床上進(jin)行不銹鋼(gang)板(ban)彎曲、沖(chong)裁(落料)等加(jia)(jia)工(gong)時,可(ke)使(shi)用(yong)(yong)(yong)加(jia)(jia)工(gong)油(you)、表(biao)(biao)(biao)(biao)面(mian)(mian)保(bao)(bao)(bao)(bao)護薄(bo)膜(mo)(mo)或直接使(shi)用(yong)(yong)(yong)潤(run)滑鋼(gang)板(ban)。在表(biao)(biao)(biao)(biao)6-1中,對加(jia)(jia)工(gong)油(you)、表(biao)(biao)(biao)(biao)面(mian)(mian)保(bao)(bao)(bao)(bao)護薄(bo)膜(mo)(mo)和潤(run)滑鋼(gang)板(ban)進(jin)行比較。表(biao)(biao)(biao)(biao)面(mian)(mian)保(bao)(bao)(bao)(bao)護薄(bo)膜(mo)(mo)是(shi)不銹鋼(gang)保(bao)(bao)(bao)(bao)持匠藝性(xing)的(de)(de)一項重要措施(shi)。所(suo)用(yong)(yong)(yong)樹脂(zhi)為聚(ju)氯(lv)乙烯系列或聚(ju)乙烯系列。材料運轉自(zi)始至終都是(shi)用(yong)(yong)(yong)表(biao)(biao)(biao)(biao)面(mian)(mian)保(bao)(bao)(bao)(bao)護薄(bo)膜(mo)(mo)對材料表(biao)(biao)(biao)(biao)面(mian)(mian)施(shi)行保(bao)(bao)(bao)(bao)護。使(shi)用(yong)(yong)(yong)表(biao)(biao)(biao)(biao)面(mian)(mian)保(bao)(bao)(bao)(bao)護薄(bo)膜(mo)(mo),最容易(yi)發生(sheng)(sheng)的(de)(de)問(wen)題就是(shi)殘留糊狀(zhuang)物,貼附后長(chang)期保(bao)(bao)(bao)(bao)存(cun)在倉(cang)庫內的(de)(de)或者(zhe)是(shi)不具(ju)備耐候性(xing)能(neng)的(de)(de)薄(bo)膜(mo)(mo)放置(zhi)在室外的(de)(de),則容易(yi)發生(sheng)(sheng)損(sun)壞。表(biao)(biao)(biao)(biao)面(mian)(mian)保(bao)(bao)(bao)(bao)護薄(bo)膜(mo)(mo)要根據用(yong)(yong)(yong)途(tu)和加(jia)(jia)工(gong)方(fang)(fang)法選定。主要廠(chang)家生(sheng)(sheng)產的(de)(de)表(biao)(biao)(biao)(biao)面(mian)(mian)保(bao)(bao)(bao)(bao)護薄(bo)膜(mo)(mo)性(xing)能(neng)及其有關事項如表(biao)(biao)(biao)(biao)6-2所(suo)示(shi)。不使(shi)用(yong)(yong)(yong)表(biao)(biao)(biao)(biao)面(mian)(mian)保(bao)(bao)(bao)(bao)護薄(bo)膜(mo)(mo)時,一般情況下要使(shi)用(yong)(yong)(yong)加(jia)(jia)工(gong)油(you)。當使(shi)用(yong)(yong)(yong)加(jia)(jia)工(gong)油(you)加(jia)(jia)工(gong)后,需進(jin)行洗(xi)(xi)凈(jing)。洗(xi)(xi)凈(jing)的(de)(de)方(fang)(fang)法有多種,最近在保(bao)(bao)(bao)(bao)護地球環境(jing)問(wen)題當中,規(gui)定了保(bao)(bao)(bao)(bao)護環境(jing)條例,對于破壞臭(chou)氧層的(de)(de)清洗(xi)(xi)劑做出了限制。
因(yin)此,當使用加(jia)工(gong)油(you)(you)時,要考慮到(dao)洗凈(jing)和存放問題。在加(jia)工(gong)油(you)(you)選定方面,從(cong)前認為由于不(bu)(bu)銹(xiu)鋼硬度(du)比普通(tong)(tong)鋼要高,加(jia)工(gong)不(bu)(bu)銹(xiu)鋼比普通(tong)(tong)鋼困難,所以要選用有(you)黏性(xing)(xing)的(de)加(jia)工(gong)油(you)(you)。具有(you)黏性(xing)(xing)的(de)加(jia)工(gong)油(you)(you)往往是黏糊糊的(de),在加(jia)工(gong)過程(cheng)中(zhong)不(bu)(bu)但變黑(hei)而且(qie)難以清(qing)洗。另外,其中(zhong)多(duo)數(shu)情況下加(jia)入氯系列添加(jia)劑。因(yin)此,更有(you)必要進行充分地清(qing)洗。近(jin)年來,開發(fa)了(le)許多(duo)水(shui)溶(rong)性(xing)(xing)加(jia)工(gong)油(you)(you),在深拉深等加(jia)工(gong)中(zhong),其潤(run)滑性(xing)(xing)堪比原用油(you)(you)性(xing)(xing)的(de)加(jia)工(gong)油(you)(you)。水(shui)溶(rong)性(xing)(xing)加(jia)工(gong)油(you)(you)比較容(rong)易清(qing)洗,應用效果很好。作為新技術,雖然加(jia)工(gong)條件受到(dao)某(mou)種程(cheng)度(du)的(de)限制,免(mian)清(qing)洗的(de)揮發(fa)型(xing)加(jia)工(gong)油(you)(you)仍(reng)得(de)到(dao)推(tui)廣。
在揮(hui)發(fa)性加(jia)工(gong)(gong)油(you)中,有完全(quan)(quan)揮(hui)發(fa)型和(he)部分殘留型等產(chan)品。需根據加(jia)工(gong)(gong)條件選擇(ze),使(shi)用(yong)完全(quan)(quan)揮(hui)發(fa)型的(de)可(ke)以省(sheng)掉加(jia)工(gong)(gong)后的(de)清洗(xi)。在家電(dian)生產(chan)廠中,沖(chong)制(zhi)全(quan)(quan)自動洗(xi)衣機不(bu)銹鋼洗(xi)衣桶時就是采(cai)用(yong)完全(quan)(quan)揮(hui)發(fa)型加(jia)工(gong)(gong)油(you)。在其他(ta)領域中,完全(quan)(quan)揮(hui)發(fa)型加(jia)工(gong)(gong)油(you)已實際運用(yong)到沖(chong)孔(kong)、內緣翻邊、壓(ya)制(zhi)筋板、彎曲(qu)和(he)卷邊等沖(chong)壓(ya)工(gong)(gong)藝中。
由于(yu)使(shi)用(yong)揮發(fa)性加工(gong)油(you)可以(yi)省(sheng)掉清洗工(gong)序,在流水(shui)加工(gong)作業線(xian)上(shang)使(shi)用(yong),可以(yi)降低成本(ben)。主要生(sheng)(sheng)產(chan)(chan)廠(chang)家(jia)的(de)揮發(fa)性加工(gong)油(you)產(chan)(chan)品如表6-3所示。如將揮發(fa)性加工(gong)油(you)的(de)涂(tu)敷方(fang)式(shi)和加工(gong)條件(jian)進行改進時(shi),即可以(yi)完全省(sheng)掉清洗工(gong)作。但是,揮發(fa)性加工(gong)油(you)涂(tu)敷方(fang)式(shi)、加工(gong)條件(jian)及加工(gong)夾具的(de)質量管(guan)理不(bu)善時(shi),由于(yu)加工(gong)夾具的(de)磨損等可能產(chan)(chan)生(sheng)(sheng)對不(bu)銹(xiu)鋼的(de)鐵粉銹(xiu)蝕事故(gu)。關于(yu)鐵粉銹(xiu)蝕檢查方(fang)法,可參照本(ben)書后(hou)部章節中的(de)“使(shi)用(yong)時(shi)注(zhu)意重占日(ri)惠(hui)執處理”由的(de)說(shuo)明。
先前(qian)在(zai)(zai)沖壓加(jia)工(gong)過程(cheng)(cheng)中(zhong)使用(yong)加(jia)工(gong)油(you)(you)。為(wei)了洗凈這些加(jia)工(gong)油(you)(you)而(er)使用(yong)了破壞臭氧(yang)層的(de)三(san)氯乙烷,三(san)氯乙烯等。后來,洗凈方(fang)法(fa)改為(wei)堿性洗凈方(fang)法(fa)。在(zai)(zai)1995年,考慮到保護地球環(huan)境問題(ti),開發(fa)了潤滑(hua)不(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)。在(zai)(zai)汽(qi)車、電機(ji)、燃氣(qi)器具(ju)領域(yu)中(zhong),積極推(tui)廣了省掉清洗工(gong)序(xu)的(de)潤滑(hua)不(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)。特別是在(zai)(zai)汽(qi)車領域(yu)中(zhong)的(de)排氣(qi)分(fen)支管的(de)不(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)化過程(cheng)(cheng)中(zhong),實踐證明,加(jia)工(gong)這種形狀(zhuang)復雜的(de)工(gong)件(jian),認為(wei)潤滑(hua)不(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)比以前(qian)使用(yong)潤滑(hua)油(you)(you)的(de)加(jia)工(gong)性更優越(yue)。所以,潤滑(hua)不(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)的(de)需要量大幅度(du)增加(jia)。
潤滑不(bu)銹鋼(gang)板,根據用(yong)途亦(yi)有不(bu)涂薄膜的。非脫膜型(xing)和(he)脫膜型(xing)兩類已經產品化了。潤滑不(bu)銹鋼(gang)板種類和(he)特性(xing)如(ru)表6-4所示。在建筑(zhu)材料領域中,使用(yong)潤滑不(bu)銹鋼(gang)板做屋頂時(shi),非脫膜型(xing)和(he)脫膜型(xing)一(yi)樣,其(qi)薄膜經過1~2年的紫外(wai)線(xian)照射就(jiu)消失了。作為工程(cheng)實(shi)例,用(yong)于西武百貨大樓和(he)福岡機場候機大廳。實(shi)踐(jian)證明,潤滑不(bu)銹鋼(gang)板的加工性(xing)比(bi)加工油還要優(you)越,見(jian)表6-5。
不(bu)銹鋼板(ban)生產廠家的潤滑不(bu)銹鋼板(ban)產品,在(zai)透明涂裝不(bu)銹鋼項(xiang)目中有(you)介(jie)紹(shao)。