1. 不銹鋼工件在電化學拋光前必須徹底除油,并用去污粉擦洗,以免油污污染拋光槽液。
2. 在使用過程中需要(yao)經常(chang)測(ce)量(liang)電(dian)化學(xue)拋光液(ye)(ye)的(de)相對(dui)密(mi)(mi)度。如(ru)果(guo)相對(dui)密(mi)(mi)度小于配方(fang)規(gui)定值,表(biao)明電(dian)化學(xue)拋光液(ye)(ye)含水(shui)過多,可(ke)用蒸發(fa)法將溶(rong)液(ye)(ye)加熱至80℃以上(shang),將多余水(shui)分(fen)除去,體積不足部分(fen)可(ke)按(an)配方(fang)比例補(bu)充(chong)磷(lin)酸和硫酸。在工件進(jin)入電(dian)化學(xue)拋光槽前(qian),最(zui)好將工件上(shang)所附著的(de)水(shui)分(fen)瀝干(gan)(gan)或吹干(gan)(gan)。如(ru)果(guo)相對(dui)密(mi)(mi)度太高(gao),超過配方(fang)規(gui)定值,表(biao)示水(shui)分(fen)過少,要(yao)適當補(bu)充(chong)少量(liang)水(shui),使相對(dui)密(mi)(mi)度降至規(gui)定值。有條(tiao)件的(de)最(zui)好按(an)周期化驗分(fen)析溶(rong)液(ye)(ye),根據結果(guo)及(ji)時進(jin)行(xing)調整。
3. 溶液的(de)老化
由于拋光過程中不銹鋼表面的溶解,溶液中的鐵、鎳、鉻含量將逐漸升高,此時溶液逐漸失去拋光能力。無論如何增高溫度,開大電流,均無助于恢復拋光能力。分析溶液,如鐵含量超過60g/L,三價鉻含量超過25g/L,說明溶液已經老化,在高濃度磷酸的存在下,鐵、鉻(三價)均呈酸式磷酸二氫鐵[Fe(H2PO4)3]或磷酸二氫鉻[Cr(H2PO4)3]形式存在,不易沉淀,只有當形成磷酸鐵(FePO4)或磷酸鉻(CrPO4)時才會沉淀于槽底。磷酸濃度較低的溶液具有自凈化能力。對于拋光溶液再生,恢復拋光能力,有兩種方法可供選擇。一個方法是適當用水稀釋溶液,降低酸度,鐵、鉻、鎳等雜質可局部呈磷酸鹽沉淀,除去槽底沉淀,然后再加熱蒸發除去水分,恢復原有的相對密度,此法操作起來較繁瑣,需要消耗較大的能源和時間。另一方法是更換部分溶液,最好保留20%的舊溶液,補充80%的新溶液。可以少通電或不通電處理,很快即可實現正常拋光。
4. 清理陰極(ji)鉛板
在拋光過(guo)程中(zhong)陰極(ji)鉛板表面會(hui)沉積出一(yi)層厚厚的鐵、鎳(nie)等(deng)雜質(zhi),影響(xiang)(xiang)陰極(ji)表面導電,導致(zhi)電流下降,使拋光表面的陽極(ji)電流密度也上不去(qu),嚴(yan)重影響(xiang)(xiang)拋光質(zhi)量。因此(ci),要(yao)及時(shi)將陰極(ji)板上的沉積物除去(qu),有(you)時(shi)形成硬質(zhi)厚膜,要(yao)強力(li)敲打才能除下,最后沖洗(xi)干凈(jing),以保持整個電路通暢。
5. 陰極(ji)與(yu)陽極(ji)面積比(bi)
陰極面(mian)積控制在陽極面(mian)積的(de)1/2~1/3.5.在此情(qing)況下,可(ke)以防止三價(jia)鉻的(de)增長,過多的(de)三價(jia)鉻在陽極表面(mian)被氧化(hua)成六價(jia)鉻。三價(jia)鉻含(han)量過多,易(yi)使拋光液老化(hua)。
6. 陰(yin)陽極(ji)之間的(de)極(ji)距
陰極(ji)(ji)與(yu)陽(yang)極(ji)(ji)之間的(de)(de)距(ju)離過大、電(dian)阻(zu)增大,電(dian)能消耗增大,溶液容易升溫,影響拋光質量。距(ju)離過小,易造(zao)成短路打火(huo),燒黑制(zhi)品。陰極(ji)(ji)與(yu)陽(yang)極(ji)(ji)之間的(de)(de)距(ju)離以100~300mm為宜(yi)。
7. 象形陰(yin)極
對(dui)(dui)拋光(guang)一些復雜的大(da)型工(gong)件(jian),可制作(zuo)象形(xing)陰(yin)極(ji)(ji),以保持(chi)陽極(ji)(ji)電流分布均勻,特別是對(dui)(dui)內(nei)腔工(gong)件(jian),有適當的象形(xing)陰(yin)極(ji)(ji)安置在內(nei)腔中,才能使內(nei)腔各部位拋光(guang)一致。
8. 進出(chu)槽要切斷電源
在(zai)電(dian)化學拋光時,由于(yu)電(dian)流密度較高,給電(dian)流較大,因此,工件在(zai)進出拋光槽(cao)時,要先切斷電(dian)源,不(bu)可(ke)帶(dai)電(dian)掛(gua)或摘夾具,以(yi)防止產生電(dian)火(huo)花(hua),引起電(dian)解(jie)產生,并(bing)會使聚集在(zai)槽(cao)面上的(de)氫氣和氧氣混合氣發生爆炸。
9. 控(kong)制(zhi)槽液溫度
由于強大的電流通過槽液,會使槽液升溫,在連續操作中要采取冷卻措施,使用冷凍機冷卻不斷升溫的槽液。拋光液的溫應適度維持在規定的工藝范圍內,使不銹鋼表面拋光整平速率維持正常,以便有效降低電解液的黏度,減少陽極黏膜的厚度,加速陽極溶解產物的擴散,使溶液對流加快,有利于陽極上滯留氣泡脫附,避免產生斑點、麻點。溫度過高,會導致溶液過熱,加速六價鉻向三價鉻的轉變(Cr6++3e→Cr3+),易產生表面腐蝕。溫度過低,使溶液黏度增大,陽極表面黏膜增厚,不利于陽極溶解物的擴散,使拋光整平效果明顯降低。
10. 控制合適(shi)的陽極(ji)電(dian)流密度(du)
不銹鋼零(ling)(ling)件電(dian)(dian)(dian)化(hua)(hua)學拋光(guang)時,陽(yang)(yang)極(ji)電(dian)(dian)(dian)流密度與(yu)金屬的溶解幾乎呈(cheng)正比。只(zhi)有選擇(ze)好(hao)(hao)陽(yang)(yang)極(ji)電(dian)(dian)(dian)流密度,并(bing)控(kong)制(zhi)在(zai)(zai)一(yi)定的陽(yang)(yang)極(ji)電(dian)(dian)(dian)位(wei)(wei)區間(jian),才能獲得(de)良(liang)好(hao)(hao)的電(dian)(dian)(dian)化(hua)(hua)學拋光(guang)質量,陽(yang)(yang)極(ji)電(dian)(dian)(dian)流密度的最佳(jia)值,要根(gen)據(ju)不同的電(dian)(dian)(dian)解液配方,通過(guo)實際(ji)拋光(guang),觀察拋光(guang)所得(de)最佳(jia)值確定。在(zai)(zai)合適的陽(yang)(yang)極(ji)電(dian)(dian)(dian)流密度下,根(gen)據(ju)黏膜理論,微(wei)觀表(biao)面凸出(chu)部(bu)位(wei)(wei)優(you)先(xian)溶解,有利于整平(ping)精飾表(biao)面。陽(yang)(yang)極(ji)電(dian)(dian)(dian)流密度過(guo)小,零(ling)(ling)件表(biao)面發生一(yi)般的陽(yang)(yang)極(ji)溶解,起不到拋光(guang)效果。陽(yang)(yang)極(ji)電(dian)(dian)(dian)流密度過(guo)大,黏膜被(bei)擊穿,氧氣猛烈析(xi)出(chu)呈(cheng)氣流狀,表(biao)面過(guo)熱,導致(zhi)電(dian)(dian)(dian)拋光(guang)液擴散(san)加(jia)劇,黏膜被(bei)破壞,不復存在(zai)(zai),發生電(dian)(dian)(dian)化(hua)(hua)學腐蝕。所以在(zai)(zai)電(dian)(dian)(dian)拋光(guang)過(guo)程中必須控(kong)制(zhi)陽(yang)(yang)極(ji)電(dian)(dian)(dian)流密度在(zai)(zai)最佳(jia)值,也就是在(zai)(zai)確定的工(gong)藝范圍(wei)內。
11. 陽極移動
陽(yang)(yang)(yang)極(ji)(ji)移(yi)動(dong)使陽(yang)(yang)(yang)極(ji)(ji)溶(rong)解產(chan)(chan)物加(jia)快擴(kuo)散出去,起(qi)到(dao)攪拌作(zuo)用,有(you)效地排除陽(yang)(yang)(yang)極(ji)(ji)表(biao)面滯留的氣泡(pao),避(bi)免產(chan)(chan)生的氣流(liu)生成(cheng)條紋,防止(zhi)局部(bu)過熱造成(cheng)表(biao)面過腐蝕(shi)。陽(yang)(yang)(yang)極(ji)(ji)移(yi)動(dong)有(you)助于(yu)提高(gao)陽(yang)(yang)(yang)極(ji)(ji)電(dian)流(liu)密度,提高(gao)不銹(xiu)鋼(gang)零(ling)件的電(dian)化學拋光(guang)表(biao)面質量。
12. 氯離子的(de)危害
在電(dian)化(hua)學拋光(guang)液中不允許有活(huo)性氯(lv)(lv)離子(zi)(zi)存在,氯(lv)(lv)離子(zi)(zi)能破(po)壞電(dian)化(hua)學拋光(guang)中表面形(xing)成(cheng)(cheng)的保護性黏膜,使不銹鋼表面形(xing)成(cheng)(cheng)過腐蝕性的麻點。氯(lv)(lv)離子(zi)(zi)可(ke)(ke)在陽極高(gao)電(dian)流(liu)密度上氧化(hua)成(cheng)(cheng)氯(lv)(lv)氣逸出而除去。氯(lv)(lv)離子(zi)(zi)的來(lai)源(yuan)可(ke)(ke)能是用鹽酸酸洗后(hou)未(wei)洗凈(jing)而帶(dai)入(ru)槽(cao)液,或(huo)原料中的不純物氯(lv)(lv)離子(zi)(zi)引入(ru)。
13. 六價鉻和三價鉻的最(zui)佳配比
在(zai)電(dian)(dian)(dian)(dian)化學(xue)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)液(ye)(ye)(ye)(ye)(ye)中(zhong)(zhong)(zhong)六(liu)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)有(you)(you)(you)(you)(you)氧化性(xing),對不銹鋼表(biao)面起鈍化保護作(zuo)(zuo)用,三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)對維護電(dian)(dian)(dian)(dian)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)有(you)(you)(you)(you)(you)作(zuo)(zuo)用。新配(pei)成的(de)電(dian)(dian)(dian)(dian)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)液(ye)(ye)(ye)(ye)(ye)如(ru)果(guo)沒(mei)有(you)(you)(you)(you)(you)化學(xue)反應(ying)產(chan)(chan)生(sheng)三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge),還不能(neng)獲得良好(hao)(hao)的(de)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)表(biao)面。只(zhi)有(you)(you)(you)(you)(you)當電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)到溶(rong)(rong)(rong)(rong)液(ye)(ye)(ye)(ye)(ye)中(zhong)(zhong)(zhong)有(you)(you)(you)(you)(you)一定量(liang)(liang)的(de)三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)存在(zai)時(shi),才(cai)能(neng)出現理想的(de)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)表(biao)面。如(ru)果(guo)配(pei)方中(zhong)(zhong)(zhong)加(jia)有(you)(you)(you)(you)(you)鉻(ge)(ge)(ge)(ge)(ge)酐(gan)(gan),即六(liu)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge),通過(guo)電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)反應(ying),在(zai)陰(yin)(yin)極上產(chan)(chan)生(sheng)氫氣還原部分(fen)六(liu)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)成為(wei)(wei)(wei)三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge);如(ru)果(guo)配(pei)方中(zhong)(zhong)(zhong)沒(mei)有(you)(you)(you)(you)(you)鉻(ge)(ge)(ge)(ge)(ge)酐(gan)(gan),則三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)要靠陽(yang)(yang)極溶(rong)(rong)(rong)(rong)解(jie)(jie)(jie)(jie)不銹鋼所含的(de)鉻(ge)(ge)(ge)(ge)(ge)而得。這就(jiu)是為(wei)(wei)(wei)什么(me)新配(pei)的(de)電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)液(ye)(ye)(ye)(ye)(ye)要充分(fen)電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)后才(cai)能(neng)進行(xing)正(zheng)常的(de)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)工作(zuo)(zuo)。在(zai)含有(you)(you)(you)(you)(you)鉻(ge)(ge)(ge)(ge)(ge)酐(gan)(gan)的(de)溶(rong)(rong)(rong)(rong)液(ye)(ye)(ye)(ye)(ye)中(zhong)(zhong)(zhong),加(jia)入(ru)明(ming)膠或(huo)甘油,它們能(neng)和鉻(ge)(ge)(ge)(ge)(ge)酐(gan)(gan)起強烈(lie)的(de)還原反應(ying),部分(fen)六(liu)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)轉(zhuan)(zhuan)變(bian)為(wei)(wei)(wei)三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(Cr3+)。六(liu)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)是黃色(se)的(de),三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)是綠色(se)的(de)。它們在(zai)電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)液(ye)(ye)(ye)(ye)(ye)中(zhong)(zhong)(zhong)使溶(rong)(rong)(rong)(rong)液(ye)(ye)(ye)(ye)(ye)呈(cheng)(cheng)黃綠色(se)。這就(jiu)是為(wei)(wei)(wei)什么(me)通電(dian)(dian)(dian)(dian)處理后才(cai)可電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)。最(zui)佳(jia)的(de)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)質量(liang)(liang)是在(zai)電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)過(guo)程的(de)中(zhong)(zhong)(zhong)間階(jie)段。在(zai)生(sheng)產(chan)(chan)過(guo)程中(zhong)(zhong)(zhong)電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)液(ye)(ye)(ye)(ye)(ye)要保持黃綠色(se)。此時(shi),根據(ju)化學(xue)分(fen)析數據(ju),六(liu)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)與三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)的(de)配(pei)比是:含Cr6+30%,含Cr3+70%.為(wei)(wei)(wei)了(le)維持該配(pei)比,可觀察(cha)電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)液(ye)(ye)(ye)(ye)(ye)的(de)顏色(se),如(ru)果(guo)顏色(se)呈(cheng)(cheng)黃色(se)為(wei)(wei)(wei)主,表(biao)明(ming)電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)液(ye)(ye)(ye)(ye)(ye)含Cr6+偏(pian)高,可加(jia)入(ru)適(shi)量(liang)(liang)的(de)明(ming)膠或(huo)甘油,使其部分(fen)六(liu)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)還原為(wei)(wei)(wei)三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge),或(huo)通過(guo)大陰(yin)(yin)極小(xiao)陽(yang)(yang)極電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)產(chan)(chan)生(sheng)三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)。如(ru)果(guo)顏色(se)呈(cheng)(cheng)深綠色(se),表(biao)明(ming)電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)液(ye)(ye)(ye)(ye)(ye)含Cr3+高了(le),按比例適(shi)量(liang)(liang)加(jia)入(ru)用水溶(rong)(rong)(rong)(rong)解(jie)(jie)(jie)(jie)好(hao)(hao)的(de)鉻(ge)(ge)(ge)(ge)(ge)酐(gan)(gan)溶(rong)(rong)(rong)(rong)液(ye)(ye)(ye)(ye)(ye),或(huo)通過(guo)大陽(yang)(yang)極小(xiao)陰(yin)(yin)極電(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)液(ye)(ye)(ye)(ye)(ye),使三(san)(san)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)部分(fen)轉(zhuan)(zhuan)變(bian)成六(liu)價(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)。同時(shi)可改善溶(rong)(rong)(rong)(rong)液(ye)(ye)(ye)(ye)(ye)的(de)拋(pao)(pao)(pao)光(guang)(guang)(guang)(guang)(guang)質量(liang)(liang)。
14. 金屬拋除量
如果電解拋(pao)(pao)光(guang)時(shi)(shi)陽極電流密度為20A/d㎡,時(shi)(shi)間為4min時(shi)(shi),用(yong)工具金相(xiang)顯微鏡(jing)觀測,不(bu)銹(xiu)鋼零件的(de)螺紋內徑(jing)的(de)金屬(shu)拋(pao)(pao)除(chu)量(liang)為每分鐘(zhong)約0.001mm,螺紋外徑(jing)的(de)金屬(shu)拋(pao)(pao)除(chu)量(liang)為0.002mm,齒形基本無變化,僅齒的(de)頂部略有拋(pao)(pao)鈍。陽極電流密度增(zeng)加,其(qi)金屬(shu)拋(pao)(pao)除(chu)量(liang)呈比例增(zeng)大。對于精(jing)密尺寸的(de)不(bu)銹(xiu)鋼零件的(de)尺寸應考慮電化學拋(pao)(pao)光(guang)后的(de)金屬(shu)拋(pao)(pao)除(chu)量(liang)(損耗)。
15. 電焊或(huo)熱處(chu)理(li)后零件的電化(hua)學拋光
凡電焊或熱處理(li)后(hou)的零件在電化學拋(pao)(pao)光時按兩次(ci)(ci)進行,第(di)一次(ci)(ci)進槽(cao)拋(pao)(pao)光3~5min后(hou)取出(chu),將已(yi)疏松(song)了(le)的焊渣和熱處理(li)氧化皮用(yong)金屬絲刷將它刷掉(diao),或用(yong)小(xiao)錘(chui)敲掉(diao),再第(di)二次(ci)(ci)進槽(cao)再拋(pao)(pao)光3~5min,可獲得較好的效果。
16. 中(zhong)和工序
經過電化(hua)學(xue)拋光后(hou)的(de)零件,如果不再進(jin)行(xing)(xing)后(hou)續加工(gong),如電鍍(du)、著(zhu)色等其他(ta)工(gong)序,要(yao)進(jin)行(xing)(xing)鈍(dun)(dun)化(hua)和中和。中和的(de)作用(yong)是(shi)充分(fen)地消除在電化(hua)學(xue)拋光和鈍(dun)(dun)化(hua)后(hou)表(biao)面(mian)所吸附的(de)酸(suan)(suan)性物質。中和一般(ban)是(shi)在碳酸(suan)(suan)鈉20~30g/L的(de)溶液(ye)中進(jin)行(xing)(xing)的(de)。路(lu)云(yun)鶴認為(wei),經過電化(hua)學(xue)拋光后(hou)的(de)零件表(biao)面(mian)有一層均勻的(de)鈍(dun)(dun)化(hua)膜,可(ke)(ke)不需要(yao)再進(jin)行(xing)(xing)鈍(dun)(dun)化(hua)處理(li)。不銹(xiu)鋼零件電化(hua)學(xue)拋光后(hou),經過40℃的(de)溫水(shui)清(qing)洗,再冷水(shui)清(qing)洗,中和并清(qing)洗后(hou)用(yong)壓縮空(kong)氣吹干,才可(ke)(ke)以有效地避免殘留酸(suan)(suan)液(ye)腐蝕拋光表(biao)面(mian)。

