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)為異向性(xing)的材料(liao)深拉深成形特性(xing)評價的重要指標。鐵素體系列不銹鋼中,其平均r值(zhi)越大,其極限(xian)拉深比就越高。
c. 拉(la)深皺折-鐵素(su)體系(xi)列(lie)不(bu)銹鋼(gang)在沖床(chuang)上進(jin)行深拉(la)深加工時,在其表面上容(rong)易(yi)產生凹(ao)凸不(bu)平的皺折。可(ke)認為是組合結構不(bu)同(tong)而引起的塑性異向性。
d. 時效性斷裂(lie)-奧氏(shi)(shi)體(ti)系(xi)列不銹鋼SUS304等準穩定型(xing)奧氏(shi)(shi)體(ti)系(xi)列不銹鋼,在(zai)加工后有發生時效性裂(lie)紋的(de)現象。它(ta)與晶界晶粒無關(guan)。一般(ban)認為(wei)是由于加工感應而(er)引起(qi)的(de)馬氏(shi)(shi)體(ti)、氫和(he)殘余應力所(suo)致。
1. 沖壓加工
沖(chong)壓加(jia)(jia)(jia)(jia)(jia)(jia)工(gong)(gong)(gong)行業(ye)(ye)是(shi)家庭式(shi)作坊(fang)工(gong)(gong)(gong)業(ye)(ye)的(de)(de)代表性產(chan)業(ye)(ye),多(duo)是(shi)從單獨(du)一個(ge)一個(ge)地加(jia)(jia)(jia)(jia)(jia)(jia)工(gong)(gong)(gong)西(xi)餐(can)(can)具、器皿等(deng)所(suo)謂的(de)(de)“洋(yang)人(ren)筷子”等(deng)開(kai)始,發展到餐(can)(can)飲業(ye)(ye)的(de)(de)廚房(fang)用具以(yi)(yi)(yi)及廚房(fang)中所(suo)使(shi)(shi)用的(de)(de)水槽(cao)、洗滌盆、深(shen)(shen)拉(la)(la)深(shen)(shen)加(jia)(jia)(jia)(jia)(jia)(jia)工(gong)(gong)(gong)的(de)(de)澡(zao)盆以(yi)(yi)(yi)及汽車、電機領域中的(de)(de)零部件等(deng)。主要工(gong)(gong)(gong)藝(yi)方(fang)法(fa)是(shi)采(cai)用剪切、沖(chong)孔(kong)、拉(la)(la)深(shen)(shen)等(deng)進(jin)行連續(xu)加(jia)(jia)(jia)(jia)(jia)(jia)工(gong)(gong)(gong)。洋(yang)餐(can)(can)具、器皿和鍋的(de)(de)沖(chong)壓加(jia)(jia)(jia)(jia)(jia)(jia)工(gong)(gong)(gong),基(ji)本上是(shi)屬于(yu)圓筒拉(la)(la)深(shen)(shen)制成。原材料(liao)板直徑(jing)D對容器(產(chan)品(pin)(pin))直徑(jing)d之比,D/d稱為(wei)拉(la)(la)深(shen)(shen)比。以(yi)(yi)(yi)可能拉(la)(la)深(shen)(shen)的(de)(de)最大原材料(liao)板直徑(jing)為(wei)Dmax時(shi),則Dmax/d稱為(wei)極限(xian)拉(la)(la)深(shen)(shen)比(LDR: Limiting Drawing Ratio)作為(wei)衡量加(jia)(jia)(jia)(jia)(jia)(jia)工(gong)(gong)(gong)性的(de)(de)指標。不(bu)銹(xiu)鋼(gang)產(chan)品(pin)(pin)得(de)(de)以(yi)(yi)(yi)大幅度的(de)(de)增加(jia)(jia)(jia)(jia)(jia)(jia)需(xu)求與沖(chong)壓加(jia)(jia)(jia)(jia)(jia)(jia)工(gong)(gong)(gong)技術的(de)(de)發展有(you)很大關系(xi)。不(bu)銹(xiu)鋼(gang)產(chan)品(pin)(pin)生產(chan)廠家在深(shen)(shen)拉(la)(la)深(shen)(shen)加(jia)(jia)(jia)(jia)(jia)(jia)工(gong)(gong)(gong)等(deng)方(fang)面,由于(yu)塑性加(jia)(jia)(jia)(jia)(jia)(jia)工(gong)(gong)(gong)技術和材料(liao)技術的(de)(de)進(jin)展。使(shi)(shi)得(de)(de)鐵素體系(xi)列(lie)不(bu)銹(xiu)鋼(gang)高(gao)加(jia)(jia)(jia)(jia)(jia)(jia)工(gong)(gong)(gong)性鋼(gang)種(zhong),已(yi)經產(chan)品(pin)(pin)化(hua)了。可以(yi)(yi)(yi)選定平(ping)均r值在1.2~1.8,LDR為(wei)2.2~2.5的(de)(de)鋼(gang)種(zhong)。
在不銹(xiu)鋼制品的(de)沖壓加(jia)工中,如果使用奧(ao)氏體系(xi)(xi)列不銹(xiu)鋼或鐵素體系(xi)(xi)列不銹(xiu)鋼的(de)高加(jia)工性能鋼種時,可以(yi)進(jin)行(xing)一定程(cheng)度的(de)深(shen)拉(la)深(shen)加(jia)工。奧(ao)氏體系(xi)(xi)列不銹(xiu)鋼的(de)代表型(xing)鋼種 SUS 304(18Cr -18Ni),因為它的(de)LDR為2.5,可以(yi)進(jin)行(xing)相(xiang)對(dui)較大的(de)深(shen)拉(la)深(shen)加(jia)工。
但由于加(jia)工(gong)(gong)(gong)硬化傾向大而急劇地(di)增加(jia)了加(jia)工(gong)(gong)(gong)難度,有時(shi)竟(jing)發生(sheng)裂紋(wen)或斷裂。為此(ci),沖壓(ya)廠家就(jiu)在中間加(jia)上一道熱處理工(gong)(gong)(gong)序之后(hou)(hou)再進行深拉(la)深加(jia)工(gong)(gong)(gong)。還(huan)必須注意(yi),奧氏體系(xi)列不(bu)銹鋼(gang)的奧氏體穩定度低的鋼(gang)種經過拉(la)深后(hou)(hou),有可能發生(sheng)時(shi)效(xiao)斷裂現(xian)象。
近年來,新(xin)潟縣(xian)(xian)燕市的(de)沖壓(ya)加(jia)工(gong)廠和新(xin)鴻縣(xian)(xian)工(gong)業技術中心共同開發不銹鋼熱沖壓(ya)技術,實(shi)現了超深(shen)(shen)拉深(shen)(shen)加(jia)工(gong)。熱沖壓(ya)技術就是將(jiang)凹模或者凸模其中之一進行加(jia)熱,這(zhe)樣不銹鋼原(yuan)來的(de)拉深(shen)(shen)程度就可(ke)以提(ti)高1.5~2.0倍。熱沖壓(ya)加(jia)工(gong)設(she)備的(de)工(gong)作原(yuan)理如(ru)圖(tu)6-9所示。其加(jia)工(gong)特(te)性如(ru)圖(tu)6-10所示。
2. 彎曲與連續沖裁
奧氏體(ti)系列(lie)不(bu)(bu)(bu)銹(xiu)(xiu)(xiu)(xiu)鋼(gang)(gang)進行彎(wan)(wan)曲(qu)加(jia)(jia)工(gong)是件簡(jian)單之事,可以制作(zuo)角鋼(gang)(gang)、槽(cao)鋼(gang)(gang)等(deng)(deng)型材(cai)(cai)(cai)使用。鐵素(su)體(ti)系列(lie),馬氏體(ti)系列(lie)不(bu)(bu)(bu)銹(xiu)(xiu)(xiu)(xiu)鋼(gang)(gang)作(zuo)為型材(cai)(cai)(cai)加(jia)(jia)工(gong),一(yi)(yi)般情(qing)況(kuang)下沒有(you)問題(ti),但(dan)當彎(wan)(wan)曲(qu)半(ban)(ban)徑(jing)R小的(de)(de)(de)時候,在(zai)(zai)折彎(wan)(wan)處(chu)有(you)時會發生斷裂。在(zai)(zai)JIS標準(zhun)中(zhong),對鐵素(su)體(ti)、馬氏體(ti)系列(lie)的(de)(de)(de)不(bu)(bu)(bu)銹(xiu)(xiu)(xiu)(xiu)鋼(gang)(gang)彎(wan)(wan)曲(qu)試驗(yan)標準(zhun)規定(ding),彎(wan)(wan)曲(qu)半(ban)(ban)徑(jing)R為1.0t(t為板材(cai)(cai)(cai)厚度(du))不(bu)(bu)(bu)應發生彎(wan)(wan)曲(qu)斷裂。還(huan)有(you),必須(xu)注(zhu)意不(bu)(bu)(bu)銹(xiu)(xiu)(xiu)(xiu)鋼(gang)(gang)彎(wan)(wan)曲(qu)加(jia)(jia)工(gong)回(hui)彈量大(da)的(de)(de)(de)特點。落料(liao)(liao)(俗稱下料(liao)(liao))或(huo)稱為沖(chong)(chong)(chong)裁加(jia)(jia)工(gong),大(da)多(duo)數(shu)是采用沖(chong)(chong)(chong)床連續加(jia)(jia)工(gong)的(de)(de)(de)方式,有(you)時在(zai)(zai)沖(chong)(chong)(chong)切斷面上,發生塌邊(bian)(bian)(bian)現象(即(ji)沖(chong)(chong)(chong)切面與基準(zhun)平面不(bu)(bu)(bu)垂直)。精(jing)密落料(liao)(liao)是從變壓(ya)(ya)器等(deng)(deng)使用疊層的(de)(de)(de)電磁鋼(gang)(gang)板的(de)(de)(de)加(jia)(jia)工(gong)技術開展起來(lai)的(de)(de)(de)技術,對粒子加(jia)(jia)速器的(de)(de)(de)套環(huan)(collar)或(huo)電子零部件中(zhong)的(de)(de)(de)引(yin)線(xian)(xian)框(lead frame)等(deng)(deng)等(deng)(deng),從較厚的(de)(de)(de)板材(cai)(cai)(cai)到(dao)超薄(bo)材(cai)(cai)(cai),精(jing)密落料(liao)(liao)得到(dao)廣泛(fan)應用。沖(chong)(chong)(chong)壓(ya)(ya)加(jia)(jia)工(gong)機械(xie)亦可以進行精(jing)密沖(chong)(chong)(chong)壓(ya)(ya)(落料(liao)(liao))加(jia)(jia)工(gong),但(dan)由(you)于沖(chong)(chong)(chong)壓(ya)(ya)塌邊(bian)(bian)(bian)的(de)(de)(de)問題(ti),一(yi)(yi)般不(bu)(bu)(bu)能作(zuo)為成(cheng)品直接使用。在(zai)(zai)精(jing)密沖(chong)(chong)(chong)壓(ya)(ya)中(zhong),為控制塌邊(bian)(bian)(bian),就需加(jia)(jia)一(yi)(yi)道機械(xie)控制的(de)(de)(de)工(gong)藝措施,這需要按產(chan)品用途以及成(cheng)本兩方面來(lai)權衡。在(zai)(zai)加(jia)(jia)工(gong)方法(fa)競爭上,還(huan)有(you)一(yi)(yi)種(zhong)“蝕刻”方法(fa),在(zai)(zai)電子產(chan)品的(de)(de)(de)接線(xian)(xian)框等(deng)(deng)超薄(bo)產(chan)品中(zhong),在(zai)(zai)加(jia)(jia)工(gong)廠家的(de)(de)(de)技術競爭中(zhong),兩者幾乎各占一(yi)(yi)半(ban)(ban)。
3. 加工油、表面保(bao)護薄膜(mo)和(he)其(qi)他潤滑(hua)
a. 表面(mian)保護薄膜(mo)-為了(le)保持不銹鋼(gang)的(de)匠(jiang)藝性、防止產生瑕(xia)疵以(yi)及作為潤滑而敷于(yu)材(cai)料表面(mian)的(de)聚氯(lv)乙(yi)烯或聚乙(yi)烯等薄膜(mo)。
b. 揮(hui)發性(xing)加(jia)(jia)(jia)工(gong)油--加(jia)(jia)(jia)工(gong)時有潤滑效果(guo)而后(hou)又能揮(hui)發掉的(de)加(jia)(jia)(jia)工(gong)油。使用完全揮(hui)發型的(de),可以(yi)省掉清洗工(gong)序。
c. 潤滑不銹鋼板-具(ju)有(you)透明(ming)石(shi)蠟(la)涂裝的(de)不銹鋼,它比加工油或表面保護膜有(you)更好的(de)加工性。
在(zai)沖(chong)床上進(jin)行(xing)不銹鋼(gang)板彎曲(qu)、沖(chong)裁(落料(liao))等加(jia)(jia)工(gong)時,可使用加(jia)(jia)工(gong)油(you)、表(biao)(biao)面(mian)保(bao)(bao)(bao)(bao)護(hu)(hu)薄膜(mo)(mo)(mo)或(huo)直接(jie)使用潤(run)(run)滑鋼(gang)板。在(zai)表(biao)(biao)6-1中(zhong)(zhong),對(dui)(dui)加(jia)(jia)工(gong)油(you)、表(biao)(biao)面(mian)保(bao)(bao)(bao)(bao)護(hu)(hu)薄膜(mo)(mo)(mo)和潤(run)(run)滑鋼(gang)板進(jin)行(xing)比較。表(biao)(biao)面(mian)保(bao)(bao)(bao)(bao)護(hu)(hu)薄膜(mo)(mo)(mo)是不銹鋼(gang)保(bao)(bao)(bao)(bao)持(chi)匠(jiang)藝性的(de)一項重(zhong)要(yao)措施。所用樹(shu)脂為聚氯乙烯系(xi)列(lie)或(huo)聚乙烯系(xi)列(lie)。材(cai)料(liao)運轉(zhuan)自(zi)始至終都是用表(biao)(biao)面(mian)保(bao)(bao)(bao)(bao)護(hu)(hu)薄膜(mo)(mo)(mo)對(dui)(dui)材(cai)料(liao)表(biao)(biao)面(mian)施行(xing)保(bao)(bao)(bao)(bao)護(hu)(hu)。使用表(biao)(biao)面(mian)保(bao)(bao)(bao)(bao)護(hu)(hu)薄膜(mo)(mo)(mo),最容易發生的(de)問題就(jiu)是殘留(liu)糊狀物(wu),貼附后(hou)長期保(bao)(bao)(bao)(bao)存在(zai)倉(cang)庫內的(de)或(huo)者是不具備耐候性能(neng)的(de)薄膜(mo)(mo)(mo)放置在(zai)室(shi)外的(de),則容易發生損壞。表(biao)(biao)面(mian)保(bao)(bao)(bao)(bao)護(hu)(hu)薄膜(mo)(mo)(mo)要(yao)根(gen)據用途和加(jia)(jia)工(gong)方(fang)法選(xuan)定。主要(yao)廠家生產的(de)表(biao)(biao)面(mian)保(bao)(bao)(bao)(bao)護(hu)(hu)薄膜(mo)(mo)(mo)性能(neng)及(ji)其有關事項如表(biao)(biao)6-2所示。不使用表(biao)(biao)面(mian)保(bao)(bao)(bao)(bao)護(hu)(hu)薄膜(mo)(mo)(mo)時,一般情況下(xia)要(yao)使用加(jia)(jia)工(gong)油(you)。當使用加(jia)(jia)工(gong)油(you)加(jia)(jia)工(gong)后(hou),需進(jin)行(xing)洗(xi)(xi)凈(jing)。洗(xi)(xi)凈(jing)的(de)方(fang)法有多(duo)種(zhong),最近(jin)在(zai)保(bao)(bao)(bao)(bao)護(hu)(hu)地球環境問題當中(zhong)(zhong),規(gui)定了(le)保(bao)(bao)(bao)(bao)護(hu)(hu)環境條例,對(dui)(dui)于破壞臭(chou)氧層(ceng)的(de)清洗(xi)(xi)劑做出(chu)了(le)限制(zhi)。
因此,當使(shi)用(yong)加(jia)(jia)工(gong)油(you)(you)時,要(yao)(yao)考慮到(dao)洗凈和存放問題。在加(jia)(jia)工(gong)油(you)(you)選定方面,從前認為(wei)(wei)由于不(bu)銹鋼硬度比普(pu)通鋼要(yao)(yao)高,加(jia)(jia)工(gong)不(bu)銹鋼比普(pu)通鋼困難(nan),所以要(yao)(yao)選用(yong)有黏性(xing)的(de)加(jia)(jia)工(gong)油(you)(you)。具(ju)有黏性(xing)的(de)加(jia)(jia)工(gong)油(you)(you)往往是黏糊糊的(de),在加(jia)(jia)工(gong)過程中(zhong)不(bu)但(dan)變(bian)黑而且難(nan)以清洗。另外,其中(zhong)多(duo)數情況下(xia)加(jia)(jia)入氯系列添加(jia)(jia)劑(ji)。因此,更有必要(yao)(yao)進行(xing)充分地清洗。近年來(lai),開發了許(xu)多(duo)水溶性(xing)加(jia)(jia)工(gong)油(you)(you),在深拉深等加(jia)(jia)工(gong)中(zhong),其潤滑性(xing)堪比原(yuan)用(yong)油(you)(you)性(xing)的(de)加(jia)(jia)工(gong)油(you)(you)。水溶性(xing)加(jia)(jia)工(gong)油(you)(you)比較容易(yi)清洗,應用(yong)效果很好(hao)。作為(wei)(wei)新技術,雖然加(jia)(jia)工(gong)條件受到(dao)某種程度的(de)限(xian)制,免清洗的(de)揮發型加(jia)(jia)工(gong)油(you)(you)仍得到(dao)推廣。
在揮(hui)(hui)發(fa)性(xing)加工(gong)(gong)油(you)中,有完全(quan)揮(hui)(hui)發(fa)型和部(bu)分殘留型等產品。需根據加工(gong)(gong)條件選(xuan)擇,使用完全(quan)揮(hui)(hui)發(fa)型的(de)可以省(sheng)掉加工(gong)(gong)后(hou)的(de)清(qing)洗。在家電生產廠中,沖(chong)制全(quan)自動洗衣機不銹鋼(gang)洗衣桶時就是采用完全(quan)揮(hui)(hui)發(fa)型加工(gong)(gong)油(you)。在其他領域中,完全(quan)揮(hui)(hui)發(fa)型加工(gong)(gong)油(you)已實際運(yun)用到沖(chong)孔、內緣翻(fan)邊(bian)、壓(ya)(ya)制筋板(ban)、彎曲和卷邊(bian)等沖(chong)壓(ya)(ya)工(gong)(gong)藝中。
由于使(shi)用揮(hui)發(fa)性加工(gong)(gong)(gong)(gong)(gong)油(you)可(ke)以省(sheng)掉(diao)清洗工(gong)(gong)(gong)(gong)(gong)序,在流水加工(gong)(gong)(gong)(gong)(gong)作(zuo)(zuo)業線(xian)上(shang)使(shi)用,可(ke)以降低成(cheng)本。主要生產廠家的揮(hui)發(fa)性加工(gong)(gong)(gong)(gong)(gong)油(you)產品如表6-3所(suo)示。如將(jiang)揮(hui)發(fa)性加工(gong)(gong)(gong)(gong)(gong)油(you)的涂敷方式和(he)加工(gong)(gong)(gong)(gong)(gong)條件(jian)進(jin)行(xing)改(gai)進(jin)時,即可(ke)以完全省(sheng)掉(diao)清洗工(gong)(gong)(gong)(gong)(gong)作(zuo)(zuo)。但是,揮(hui)發(fa)性加工(gong)(gong)(gong)(gong)(gong)油(you)涂敷方式、加工(gong)(gong)(gong)(gong)(gong)條件(jian)及(ji)加工(gong)(gong)(gong)(gong)(gong)夾(jia)具的質量(liang)管理不善時,由于加工(gong)(gong)(gong)(gong)(gong)夾(jia)具的磨損等可(ke)能(neng)產生對不銹(xiu)(xiu)鋼的鐵粉(fen)銹(xiu)(xiu)蝕事故。關于鐵粉(fen)銹(xiu)(xiu)蝕檢(jian)查方法,可(ke)參照本書后部章(zhang)節中的“使(shi)用時注意重占日(ri)惠執處理”由的說(shuo)明。
先(xian)前(qian)在沖壓加工(gong)過程中使(shi)用(yong)加工(gong)油。為了(le)洗(xi)(xi)凈(jing)這些加工(gong)油而使(shi)用(yong)了(le)破壞臭氧(yang)層的(de)三氯乙烷,三氯乙烯(xi)等(deng)。后來,洗(xi)(xi)凈(jing)方法改為堿(jian)性洗(xi)(xi)凈(jing)方法。在1995年,考慮到(dao)保護地球環(huan)境(jing)問題,開發了(le)潤(run)滑(hua)(hua)不(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)。在汽車、電機、燃氣器具(ju)領域中,積極推廣(guang)了(le)省掉清洗(xi)(xi)工(gong)序的(de)潤(run)滑(hua)(hua)不(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)。特別是在汽車領域中的(de)排氣分支管的(de)不(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)化過程中,實踐(jian)證明,加工(gong)這種形狀復雜的(de)工(gong)件(jian),認為潤(run)滑(hua)(hua)不(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)比(bi)以前(qian)使(shi)用(yong)潤(run)滑(hua)(hua)油的(de)加工(gong)性更優越(yue)。所以,潤(run)滑(hua)(hua)不(bu)(bu)銹(xiu)(xiu)鋼(gang)(gang)板(ban)的(de)需要量大幅度(du)增加。
潤滑不(bu)(bu)銹鋼板(ban),根據用(yong)途亦有不(bu)(bu)涂薄膜(mo)(mo)(mo)的(de)。非脫膜(mo)(mo)(mo)型(xing)和(he)(he)脫膜(mo)(mo)(mo)型(xing)兩(liang)類(lei)已經產(chan)品化了。潤滑不(bu)(bu)銹鋼板(ban)種類(lei)和(he)(he)特(te)性如表(biao)6-4所示。在建(jian)筑材料領域中,使用(yong)潤滑不(bu)(bu)銹鋼板(ban)做屋(wu)頂時,非脫膜(mo)(mo)(mo)型(xing)和(he)(he)脫膜(mo)(mo)(mo)型(xing)一樣,其薄膜(mo)(mo)(mo)經過1~2年的(de)紫外線照射就消失(shi)了。作為工(gong)程實(shi)(shi)例,用(yong)于(yu)西武百(bai)貨大(da)樓和(he)(he)福岡機場候機大(da)廳(ting)。實(shi)(shi)踐證明(ming),潤滑不(bu)(bu)銹鋼板(ban)的(de)加工(gong)性比(bi)加工(gong)油還要優(you)越,見(jian)表(biao)6-5。
不銹鋼板生產廠(chang)家的潤滑不銹鋼板產品,在(zai)透明涂裝不銹鋼項(xiang)目中有介紹(shao)。