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. 平均r值(zhi)--塑性(xing)為(wei)異向性(xing)的材(cai)料深(shen)拉深(shen)成形特性(xing)評價的重要(yao)指標(biao)。鐵素體系列不(bu)銹鋼中(zhong),其平均r值(zhi)越大,其極限(xian)拉深(shen)比就越高。
c. 拉深皺折-鐵素體系列(lie)不銹鋼在沖床上進行深拉深加工時,在其表面上容易產生凹凸不平的皺折。可認為是組合(he)結構(gou)不同而引起(qi)的塑性異(yi)向性。
d. 時效性(xing)斷裂(lie)-奧氏體系列(lie)不(bu)銹(xiu)鋼SUS304等準穩定型奧氏體系列(lie)不(bu)銹(xiu)鋼,在(zai)加工后有發生時效性(xing)裂(lie)紋(wen)的現(xian)象(xiang)。它與(yu)晶(jing)界晶(jing)粒無關。一(yi)般(ban)認為(wei)是由于加工感應而引(yin)起的馬氏體、氫和殘余應力所致。
1. 沖壓加工(gong)
沖(chong)壓加(jia)(jia)(jia)工(gong)(gong)(gong)行業(ye)是家庭式作坊工(gong)(gong)(gong)業(ye)的(de)(de)(de)代表性(xing)產(chan)業(ye),多是從單獨一個一個地加(jia)(jia)(jia)工(gong)(gong)(gong)西(xi)餐(can)(can)具(ju)(ju)、器(qi)皿(min)等(deng)(deng)所謂的(de)(de)(de)“洋(yang)(yang)人筷子(zi)”等(deng)(deng)開始(shi),發展到餐(can)(can)飲業(ye)的(de)(de)(de)廚房(fang)(fang)用具(ju)(ju)以(yi)及廚房(fang)(fang)中(zhong)所使(shi)用的(de)(de)(de)水槽、洗滌盆、深(shen)(shen)拉(la)深(shen)(shen)加(jia)(jia)(jia)工(gong)(gong)(gong)的(de)(de)(de)澡盆以(yi)及汽車、電機(ji)領域中(zhong)的(de)(de)(de)零部件(jian)等(deng)(deng)。主要(yao)工(gong)(gong)(gong)藝方法是采用剪切、沖(chong)孔、拉(la)深(shen)(shen)等(deng)(deng)進行連續加(jia)(jia)(jia)工(gong)(gong)(gong)。洋(yang)(yang)餐(can)(can)具(ju)(ju)、器(qi)皿(min)和鍋的(de)(de)(de)沖(chong)壓加(jia)(jia)(jia)工(gong)(gong)(gong),基本上(shang)是屬于圓筒拉(la)深(shen)(shen)制(zhi)成。原(yuan)材(cai)料板(ban)直(zhi)(zhi)徑(jing)D對容器(qi)(產(chan)品(pin))直(zhi)(zhi)徑(jing)d之比(bi),D/d稱為(wei)(wei)拉(la)深(shen)(shen)比(bi)。以(yi)可能(neng)拉(la)深(shen)(shen)的(de)(de)(de)最大原(yuan)材(cai)料板(ban)直(zhi)(zhi)徑(jing)為(wei)(wei)Dmax時(shi),則Dmax/d稱為(wei)(wei)極限拉(la)深(shen)(shen)比(bi)(LDR: Limiting Drawing Ratio)作為(wei)(wei)衡量加(jia)(jia)(jia)工(gong)(gong)(gong)性(xing)的(de)(de)(de)指標。不(bu)銹(xiu)鋼(gang)(gang)(gang)產(chan)品(pin)得(de)以(yi)大幅(fu)度的(de)(de)(de)增加(jia)(jia)(jia)需求與(yu)沖(chong)壓加(jia)(jia)(jia)工(gong)(gong)(gong)技(ji)(ji)術(shu)的(de)(de)(de)發展有很大關系。不(bu)銹(xiu)鋼(gang)(gang)(gang)產(chan)品(pin)生產(chan)廠家在深(shen)(shen)拉(la)深(shen)(shen)加(jia)(jia)(jia)工(gong)(gong)(gong)等(deng)(deng)方面(mian),由于塑性(xing)加(jia)(jia)(jia)工(gong)(gong)(gong)技(ji)(ji)術(shu)和材(cai)料技(ji)(ji)術(shu)的(de)(de)(de)進展。使(shi)得(de)鐵(tie)素體系列(lie)不(bu)銹(xiu)鋼(gang)(gang)(gang)高加(jia)(jia)(jia)工(gong)(gong)(gong)性(xing)鋼(gang)(gang)(gang)種(zhong),已(yi)經產(chan)品(pin)化了。可以(yi)選定平(ping)均(jun)r值在1.2~1.8,LDR為(wei)(wei)2.2~2.5的(de)(de)(de)鋼(gang)(gang)(gang)種(zhong)。
在不銹(xiu)鋼(gang)制品的(de)(de)沖壓加(jia)工(gong)(gong)中(zhong),如(ru)果(guo)使用奧氏(shi)體(ti)系(xi)列不銹(xiu)鋼(gang)或鐵素(su)體(ti)系(xi)列不銹(xiu)鋼(gang)的(de)(de)高加(jia)工(gong)(gong)性能鋼(gang)種(zhong)時,可以進行一定程度的(de)(de)深(shen)(shen)拉深(shen)(shen)加(jia)工(gong)(gong)。奧氏(shi)體(ti)系(xi)列不銹(xiu)鋼(gang)的(de)(de)代表型鋼(gang)種(zhong) SUS 304(18Cr -18Ni),因為(wei)它的(de)(de)LDR為(wei)2.5,可以進行相對較(jiao)大的(de)(de)深(shen)(shen)拉深(shen)(shen)加(jia)工(gong)(gong)。
但由于(yu)加(jia)工硬化(hua)傾向(xiang)大而急劇地(di)增加(jia)了加(jia)工難度,有時竟發生(sheng)裂紋或斷(duan)裂。為此,沖(chong)壓廠家(jia)就在中(zhong)間加(jia)上一道熱處理工序之后再進(jin)行(xing)深(shen)拉深(shen)加(jia)工。還必須注意(yi),奧氏體系列不銹鋼的奧氏體穩定度低(di)的鋼種經過拉深(shen)后,有可能發生(sheng)時效斷(duan)裂現(xian)象。
近年來,新潟縣燕市的(de)沖壓(ya)加(jia)工(gong)廠(chang)和新鴻縣工(gong)業技(ji)術中心共同開發(fa)不銹鋼(gang)熱(re)沖壓(ya)技(ji)術,實(shi)現了超深(shen)拉深(shen)加(jia)工(gong)。熱(re)沖壓(ya)技(ji)術就(jiu)是將凹模(mo)(mo)或者凸模(mo)(mo)其(qi)中之一進行加(jia)熱(re),這樣(yang)不銹鋼(gang)原來的(de)拉深(shen)程度就(jiu)可以提高(gao)1.5~2.0倍。熱(re)沖壓(ya)加(jia)工(gong)設備(bei)的(de)工(gong)作(zuo)原理如圖6-9所(suo)(suo)示(shi)。其(qi)加(jia)工(gong)特(te)性如圖6-10所(suo)(suo)示(shi)。
2. 彎曲與連續(xu)沖裁
奧氏體系列不銹鋼(gang)(gang)進(jin)行彎(wan)曲(qu)加(jia)(jia)工(gong)(gong)(gong)(gong)(gong)是(shi)件簡單之事(shi),可(ke)(ke)以(yi)制(zhi)作(zuo)角鋼(gang)(gang)、槽鋼(gang)(gang)等(deng)型材使(shi)用(yong)。鐵(tie)素體系列,馬氏體系列不銹鋼(gang)(gang)作(zuo)為型材加(jia)(jia)工(gong)(gong)(gong)(gong)(gong),一(yi)般(ban)情況下沒有問題(ti)(ti),但當彎(wan)曲(qu)半徑R小的(de)(de)時(shi)候,在(zai)(zai)(zai)折彎(wan)處有時(shi)會(hui)發生(sheng)斷(duan)(duan)裂(lie)。在(zai)(zai)(zai)JIS標(biao)準(zhun)中(zhong),對鐵(tie)素體、馬氏體系列的(de)(de)不銹鋼(gang)(gang)彎(wan)曲(qu)試驗標(biao)準(zhun)規定,彎(wan)曲(qu)半徑R為1.0t(t為板材厚度)不應發生(sheng)彎(wan)曲(qu)斷(duan)(duan)裂(lie)。還有,必須注意不銹鋼(gang)(gang)彎(wan)曲(qu)加(jia)(jia)工(gong)(gong)(gong)(gong)(gong)回(hui)彈量大的(de)(de)特點(dian)。落(luo)料(liao)(liao)(liao)(俗(su)稱下料(liao)(liao)(liao))或稱為沖(chong)(chong)(chong)(chong)裁加(jia)(jia)工(gong)(gong)(gong)(gong)(gong),大多數是(shi)采(cai)用(yong)沖(chong)(chong)(chong)(chong)床連續加(jia)(jia)工(gong)(gong)(gong)(gong)(gong)的(de)(de)方式,有時(shi)在(zai)(zai)(zai)沖(chong)(chong)(chong)(chong)切斷(duan)(duan)面(mian)(mian)上,發生(sheng)塌(ta)邊現象(即沖(chong)(chong)(chong)(chong)切面(mian)(mian)與基(ji)準(zhun)平(ping)面(mian)(mian)不垂直)。精密(mi)落(luo)料(liao)(liao)(liao)是(shi)從(cong)變壓(ya)(ya)器等(deng)使(shi)用(yong)疊層的(de)(de)電(dian)磁鋼(gang)(gang)板的(de)(de)加(jia)(jia)工(gong)(gong)(gong)(gong)(gong)技(ji)術(shu)開展起(qi)來(lai)的(de)(de)技(ji)術(shu),對粒子(zi)加(jia)(jia)速器的(de)(de)套(tao)環(collar)或電(dian)子(zi)零部(bu)件中(zhong)的(de)(de)引線(xian)框(kuang)(lead frame)等(deng)等(deng),從(cong)較厚的(de)(de)板材到(dao)(dao)超薄(bo)材,精密(mi)落(luo)料(liao)(liao)(liao)得到(dao)(dao)廣泛應用(yong)。沖(chong)(chong)(chong)(chong)壓(ya)(ya)加(jia)(jia)工(gong)(gong)(gong)(gong)(gong)機械亦可(ke)(ke)以(yi)進(jin)行精密(mi)沖(chong)(chong)(chong)(chong)壓(ya)(ya)(落(luo)料(liao)(liao)(liao))加(jia)(jia)工(gong)(gong)(gong)(gong)(gong),但由(you)于沖(chong)(chong)(chong)(chong)壓(ya)(ya)塌(ta)邊的(de)(de)問題(ti)(ti),一(yi)般(ban)不能作(zuo)為成(cheng)品(pin)直接使(shi)用(yong)。在(zai)(zai)(zai)精密(mi)沖(chong)(chong)(chong)(chong)壓(ya)(ya)中(zhong),為控制(zhi)塌(ta)邊,就需加(jia)(jia)一(yi)道(dao)機械控制(zhi)的(de)(de)工(gong)(gong)(gong)(gong)(gong)藝(yi)措施,這需要(yao)按產品(pin)用(yong)途以(yi)及(ji)成(cheng)本(ben)兩方面(mian)(mian)來(lai)權衡。在(zai)(zai)(zai)加(jia)(jia)工(gong)(gong)(gong)(gong)(gong)方法競爭(zheng)上,還有一(yi)種“蝕刻”方法,在(zai)(zai)(zai)電(dian)子(zi)產品(pin)的(de)(de)接線(xian)框(kuang)等(deng)超薄(bo)產品(pin)中(zhong),在(zai)(zai)(zai)加(jia)(jia)工(gong)(gong)(gong)(gong)(gong)廠家的(de)(de)技(ji)術(shu)競爭(zheng)中(zhong),兩者幾乎各(ge)占一(yi)半。
3. 加工油(you)、表面保護薄膜(mo)和其他潤滑
a. 表(biao)面保護薄膜-為了保持不銹鋼的匠藝性(xing)、防(fang)止產(chan)生瑕疵以及作為潤滑(hua)而敷于材料(liao)表(biao)面的聚氯乙烯(xi)(xi)或(huo)聚乙烯(xi)(xi)等(deng)薄膜。
b. 揮發性加(jia)工油--加(jia)工時(shi)有潤(run)滑效果(guo)而后又(you)能揮發掉的加(jia)工油。使用(yong)完全揮發型的,可以省掉清洗工序(xu)。
c. 潤滑不銹(xiu)鋼板-具有透(tou)明石蠟涂裝的(de)不銹(xiu)鋼,它(ta)比加工油或表面保(bao)護膜有更好的(de)加工性。
在(zai)沖(chong)床上進行(xing)(xing)不銹(xiu)(xiu)鋼(gang)板(ban)彎曲、沖(chong)裁(落料(liao))等加(jia)(jia)工(gong)時,可使用(yong)加(jia)(jia)工(gong)油、表(biao)面保(bao)(bao)(bao)(bao)護(hu)(hu)薄(bo)(bo)膜(mo)(mo)(mo)或直接使用(yong)潤滑鋼(gang)板(ban)。在(zai)表(biao)6-1中,對(dui)加(jia)(jia)工(gong)油、表(biao)面保(bao)(bao)(bao)(bao)護(hu)(hu)薄(bo)(bo)膜(mo)(mo)(mo)和潤滑鋼(gang)板(ban)進行(xing)(xing)比(bi)較(jiao)。表(biao)面保(bao)(bao)(bao)(bao)護(hu)(hu)薄(bo)(bo)膜(mo)(mo)(mo)是(shi)不銹(xiu)(xiu)鋼(gang)保(bao)(bao)(bao)(bao)持匠藝性(xing)的(de)(de)一項(xiang)重要(yao)措(cuo)施。所(suo)用(yong)樹脂為聚氯乙烯系(xi)列或聚乙烯系(xi)列。材料(liao)運轉自(zi)始至終(zhong)都(dou)是(shi)用(yong)表(biao)面保(bao)(bao)(bao)(bao)護(hu)(hu)薄(bo)(bo)膜(mo)(mo)(mo)對(dui)材料(liao)表(biao)面施行(xing)(xing)保(bao)(bao)(bao)(bao)護(hu)(hu)。使用(yong)表(biao)面保(bao)(bao)(bao)(bao)護(hu)(hu)薄(bo)(bo)膜(mo)(mo)(mo),最(zui)容(rong)易(yi)發生的(de)(de)問題就是(shi)殘留糊狀物(wu),貼附后長期保(bao)(bao)(bao)(bao)存在(zai)倉庫內(nei)的(de)(de)或者是(shi)不具備耐候性(xing)能的(de)(de)薄(bo)(bo)膜(mo)(mo)(mo)放置在(zai)室外的(de)(de),則容(rong)易(yi)發生損壞(huai)。表(biao)面保(bao)(bao)(bao)(bao)護(hu)(hu)薄(bo)(bo)膜(mo)(mo)(mo)要(yao)根據用(yong)途和加(jia)(jia)工(gong)方法(fa)選定(ding)。主要(yao)廠(chang)家生產的(de)(de)表(biao)面保(bao)(bao)(bao)(bao)護(hu)(hu)薄(bo)(bo)膜(mo)(mo)(mo)性(xing)能及(ji)其(qi)有關事項(xiang)如表(biao)6-2所(suo)示(shi)。不使用(yong)表(biao)面保(bao)(bao)(bao)(bao)護(hu)(hu)薄(bo)(bo)膜(mo)(mo)(mo)時,一般(ban)情況(kuang)下要(yao)使用(yong)加(jia)(jia)工(gong)油。當(dang)使用(yong)加(jia)(jia)工(gong)油加(jia)(jia)工(gong)后,需進行(xing)(xing)洗(xi)凈。洗(xi)凈的(de)(de)方法(fa)有多種,最(zui)近在(zai)保(bao)(bao)(bao)(bao)護(hu)(hu)地球環境(jing)問題當(dang)中,規定(ding)了保(bao)(bao)(bao)(bao)護(hu)(hu)環境(jing)條例,對(dui)于破壞(huai)臭氧層的(de)(de)清洗(xi)劑做出了限制。
因此,當使用(yong)加(jia)工(gong)油(you)(you)時(shi),要(yao)考(kao)慮(lv)到(dao)(dao)洗凈和存放問題。在(zai)加(jia)工(gong)油(you)(you)選定(ding)方面,從前認為由于(yu)不(bu)銹(xiu)鋼硬(ying)度比(bi)普通(tong)鋼要(yao)高,加(jia)工(gong)不(bu)銹(xiu)鋼比(bi)普通(tong)鋼困難,所以(yi)要(yao)選用(yong)有(you)黏(nian)性的(de)加(jia)工(gong)油(you)(you)。具有(you)黏(nian)性的(de)加(jia)工(gong)油(you)(you)往往是(shi)黏(nian)糊糊的(de),在(zai)加(jia)工(gong)過程中不(bu)但(dan)變黑而且難以(yi)清(qing)洗。另外,其(qi)中多數情(qing)況下加(jia)入(ru)氯系列添加(jia)劑。因此,更有(you)必要(yao)進行(xing)充分(fen)地清(qing)洗。近年(nian)來,開發(fa)了許多水(shui)溶性加(jia)工(gong)油(you)(you),在(zai)深(shen)拉深(shen)等加(jia)工(gong)中,其(qi)潤(run)滑性堪比(bi)原用(yong)油(you)(you)性的(de)加(jia)工(gong)油(you)(you)。水(shui)溶性加(jia)工(gong)油(you)(you)比(bi)較容易清(qing)洗,應用(yong)效果(guo)很好(hao)。作(zuo)為新技(ji)術,雖然加(jia)工(gong)條(tiao)件(jian)受到(dao)(dao)某(mou)種(zhong)程度的(de)限制,免清(qing)洗的(de)揮發(fa)型加(jia)工(gong)油(you)(you)仍得(de)到(dao)(dao)推廣。
在揮發性加(jia)工(gong)油(you)中,有完(wan)全揮發型(xing)(xing)(xing)和部分殘留型(xing)(xing)(xing)等(deng)產品。需根據加(jia)工(gong)條(tiao)件選(xuan)擇,使用(yong)完(wan)全揮發型(xing)(xing)(xing)的可以省(sheng)掉加(jia)工(gong)后的清洗(xi)。在家電生產廠中,沖制全自動(dong)洗(xi)衣(yi)機不(bu)銹鋼洗(xi)衣(yi)桶時(shi)就(jiu)是采用(yong)完(wan)全揮發型(xing)(xing)(xing)加(jia)工(gong)油(you)。在其他領域中,完(wan)全揮發型(xing)(xing)(xing)加(jia)工(gong)油(you)已(yi)實際(ji)運(yun)用(yong)到沖孔、內緣翻邊、壓制筋板、彎曲和卷邊等(deng)沖壓工(gong)藝中。
由于使用揮(hui)發性(xing)加(jia)(jia)工油(you)可(ke)(ke)以省掉清洗工序,在(zai)流水加(jia)(jia)工作(zuo)業線上使用,可(ke)(ke)以降低成本。主要生產(chan)(chan)廠家的(de)揮(hui)發性(xing)加(jia)(jia)工油(you)產(chan)(chan)品如表6-3所示。如將揮(hui)發性(xing)加(jia)(jia)工油(you)的(de)涂(tu)敷方(fang)式和加(jia)(jia)工條件進(jin)行改(gai)進(jin)時,即(ji)可(ke)(ke)以完(wan)全省掉清洗工作(zuo)。但是(shi),揮(hui)發性(xing)加(jia)(jia)工油(you)涂(tu)敷方(fang)式、加(jia)(jia)工條件及加(jia)(jia)工夾具的(de)質(zhi)量管理不(bu)善時,由于加(jia)(jia)工夾具的(de)磨(mo)損等(deng)可(ke)(ke)能產(chan)(chan)生對不(bu)銹鋼的(de)鐵(tie)粉(fen)銹蝕(shi)事故(gu)。關于鐵(tie)粉(fen)銹蝕(shi)檢查方(fang)法,可(ke)(ke)參照本書后部(bu)章節中的(de)“使用時注意重占日惠執處(chu)理”由的(de)說明(ming)。
先(xian)前在(zai)沖(chong)壓加(jia)工(gong)(gong)(gong)過(guo)程中(zhong)使用(yong)(yong)加(jia)工(gong)(gong)(gong)油。為了(le)(le)洗(xi)(xi)凈(jing)這(zhe)些加(jia)工(gong)(gong)(gong)油而使用(yong)(yong)了(le)(le)破壞臭氧層的三(san)氯(lv)乙烷,三(san)氯(lv)乙烯等。后來(lai),洗(xi)(xi)凈(jing)方法(fa)改為堿性洗(xi)(xi)凈(jing)方法(fa)。在(zai)1995年,考慮到保護地球環境(jing)問(wen)題,開發了(le)(le)潤滑不(bu)(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)。在(zai)汽(qi)車、電機、燃氣器具領域中(zhong),積極推廣(guang)了(le)(le)省掉清洗(xi)(xi)工(gong)(gong)(gong)序的潤滑不(bu)(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)。特別是(shi)在(zai)汽(qi)車領域中(zhong)的排(pai)氣分支管的不(bu)(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)化過(guo)程中(zhong),實踐證明,加(jia)工(gong)(gong)(gong)這(zhe)種形狀復雜的工(gong)(gong)(gong)件,認為潤滑不(bu)(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)比以前使用(yong)(yong)潤滑油的加(jia)工(gong)(gong)(gong)性更(geng)優越。所以,潤滑不(bu)(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)的需要(yao)量(liang)大幅度增加(jia)。
潤滑(hua)不銹(xiu)鋼(gang)(gang)板(ban),根據用(yong)(yong)(yong)途亦(yi)有不涂薄膜(mo)的(de)。非(fei)脫(tuo)(tuo)膜(mo)型(xing)(xing)和脫(tuo)(tuo)膜(mo)型(xing)(xing)兩類(lei)已經產品(pin)化了。潤滑(hua)不銹(xiu)鋼(gang)(gang)板(ban)種類(lei)和特性(xing)如表6-4所示。在建筑材(cai)料領域中,使用(yong)(yong)(yong)潤滑(hua)不銹(xiu)鋼(gang)(gang)板(ban)做屋頂時,非(fei)脫(tuo)(tuo)膜(mo)型(xing)(xing)和脫(tuo)(tuo)膜(mo)型(xing)(xing)一樣,其薄膜(mo)經過1~2年的(de)紫(zi)外線照(zhao)射就消失了。作為工程實例,用(yong)(yong)(yong)于西(xi)武百(bai)貨大(da)樓和福岡機場(chang)候機大(da)廳。實踐證明,潤滑(hua)不銹(xiu)鋼(gang)(gang)板(ban)的(de)加工性(xing)比加工油還要優越,見(jian)表6-5。
不(bu)銹(xiu)鋼板(ban)生產廠家的潤(run)滑不(bu)銹(xiu)鋼板(ban)產品,在(zai)透明涂裝不(bu)銹(xiu)鋼項目中(zhong)有(you)介(jie)紹。