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(zai)使用(yong)過程(cheng)中需要經常(chang)測量(liang)電化(hua)學(xue)拋光液(ye)(ye)的相(xiang)對密(mi)(mi)度(du)。如(ru)果相(xiang)對密(mi)(mi)度(du)小于配(pei)方(fang)規定(ding)(ding)值,表明電化(hua)學(xue)拋光液(ye)(ye)含水(shui)過多,可用(yong)蒸發法將(jiang)溶液(ye)(ye)加(jia)熱至(zhi)80℃以上,將(jiang)多余(yu)水(shui)分(fen)(fen)除去,體積不足(zu)部分(fen)(fen)可按配(pei)方(fang)比例補充(chong)磷(lin)酸和硫(liu)酸。在(zai)工件進入電化(hua)學(xue)拋光槽前,最好將(jiang)工件上所附著的水(shui)分(fen)(fen)瀝干(gan)或吹干(gan)。如(ru)果相(xiang)對密(mi)(mi)度(du)太高(gao),超(chao)過配(pei)方(fang)規定(ding)(ding)值,表示水(shui)分(fen)(fen)過少(shao),要適(shi)當補充(chong)少(shao)量(liang)水(shui),使相(xiang)對密(mi)(mi)度(du)降至(zhi)規定(ding)(ding)值。有條件的最好按周期化(hua)驗分(fen)(fen)析溶液(ye)(ye),根據結果及(ji)時進行調(diao)整。
3. 溶液(ye)的(de)老(lao)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. 清理陰極鉛板(ban)
在拋光(guang)過(guo)程中(zhong)陰(yin)極(ji)(ji)(ji)鉛板表面會沉積(ji)出一層厚厚的(de)(de)鐵(tie)、鎳(nie)等雜質(zhi),影響陰(yin)極(ji)(ji)(ji)表面導電(dian)(dian),導致(zhi)電(dian)(dian)流下降,使拋光(guang)表面的(de)(de)陽極(ji)(ji)(ji)電(dian)(dian)流密度也上不去(qu),嚴重(zhong)影響拋光(guang)質(zhi)量(liang)。因此(ci),要及(ji)時將陰(yin)極(ji)(ji)(ji)板上的(de)(de)沉積(ji)物除去(qu),有時形成硬質(zhi)厚膜,要強力敲(qiao)打才(cai)能除下,最后沖洗干凈,以保(bao)持整(zheng)個(ge)電(dian)(dian)路通暢。
5. 陰極(ji)與陽極(ji)面積比
陰極(ji)面(mian)積控制在(zai)陽極(ji)面(mian)積的(de)1/2~1/3.5.在(zai)此(ci)情況下,可以防止三(san)(san)價鉻(ge)(ge)的(de)增長,過(guo)多的(de)三(san)(san)價鉻(ge)(ge)在(zai)陽極(ji)表面(mian)被氧化(hua)成六價鉻(ge)(ge)。三(san)(san)價鉻(ge)(ge)含(han)量過(guo)多,易使(shi)拋光液老化(hua)。
6. 陰陽極(ji)之(zhi)間(jian)的極(ji)距
陰極(ji)與(yu)陽極(ji)之(zhi)間的(de)距離過(guo)大、電阻(zu)增大,電能消耗增大,溶液(ye)容易升溫,影響拋光質量。距離過(guo)小(xiao),易造成(cheng)短(duan)路打火,燒黑制(zhi)品。陰極(ji)與(yu)陽極(ji)之(zhi)間的(de)距離以100~300mm為(wei)宜。
7. 象形陰極(ji)
對拋光一些復雜的大型工件,可制作象形陰極(ji)(ji)(ji),以保持(chi)陽極(ji)(ji)(ji)電(dian)流分(fen)布均勻(yun),特別是(shi)對內腔(qiang)工件,有適當(dang)的象形陰極(ji)(ji)(ji)安置在內腔(qiang)中,才能使內腔(qiang)各部位(wei)拋光一致。
8. 進出槽要切斷電源
在(zai)電(dian)(dian)(dian)化學拋(pao)光時,由(you)于電(dian)(dian)(dian)流密度(du)較(jiao)高(gao),給電(dian)(dian)(dian)流較(jiao)大,因此,工件在(zai)進出拋(pao)光槽時,要先切斷電(dian)(dian)(dian)源,不(bu)可帶電(dian)(dian)(dian)掛或摘夾具,以防止產生電(dian)(dian)(dian)火花,引起電(dian)(dian)(dian)解(jie)產生,并會使聚集在(zai)槽面上的氫氣(qi)和(he)氧氣(qi)混(hun)合氣(qi)發生爆炸。
9. 控制槽液溫(wen)度(du)
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. 控制合適的陽極電流密度
不銹鋼零件電(dian)(dian)(dian)(dian)(dian)化(hua)(hua)學(xue)拋(pao)光(guang)(guang)時,陽(yang)(yang)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)流密(mi)(mi)度(du)(du)與(yu)金屬的(de)(de)溶(rong)(rong)解幾(ji)乎呈(cheng)正比。只有(you)選擇好陽(yang)(yang)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)流密(mi)(mi)度(du)(du),并控(kong)制(zhi)在(zai)(zai)一定(ding)的(de)(de)陽(yang)(yang)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)位區(qu)間,才能獲得良(liang)好的(de)(de)電(dian)(dian)(dian)(dian)(dian)化(hua)(hua)學(xue)拋(pao)光(guang)(guang)質量,陽(yang)(yang)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)流密(mi)(mi)度(du)(du)的(de)(de)最(zui)佳值,要根據不同的(de)(de)電(dian)(dian)(dian)(dian)(dian)解液配(pei)方,通(tong)過(guo)實際(ji)拋(pao)光(guang)(guang),觀(guan)察拋(pao)光(guang)(guang)所得最(zui)佳值確(que)定(ding)。在(zai)(zai)合適(shi)的(de)(de)陽(yang)(yang)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)流密(mi)(mi)度(du)(du)下,根據黏(nian)膜理論,微觀(guan)表面(mian)凸出部位優先溶(rong)(rong)解,有(you)利(li)于(yu)整平精飾(shi)表面(mian)。陽(yang)(yang)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)流密(mi)(mi)度(du)(du)過(guo)小,零件表面(mian)發生一般(ban)的(de)(de)陽(yang)(yang)極(ji)(ji)溶(rong)(rong)解,起(qi)不到拋(pao)光(guang)(guang)效果。陽(yang)(yang)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)流密(mi)(mi)度(du)(du)過(guo)大,黏(nian)膜被(bei)(bei)擊穿,氧氣猛烈析出呈(cheng)氣流狀,表面(mian)過(guo)熱,導(dao)致電(dian)(dian)(dian)(dian)(dian)拋(pao)光(guang)(guang)液擴散加(jia)劇(ju),黏(nian)膜被(bei)(bei)破壞(huai),不復存在(zai)(zai),發生電(dian)(dian)(dian)(dian)(dian)化(hua)(hua)學(xue)腐蝕。所以(yi)在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)拋(pao)光(guang)(guang)過(guo)程(cheng)中(zhong)必須控(kong)制(zhi)陽(yang)(yang)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)流密(mi)(mi)度(du)(du)在(zai)(zai)最(zui)佳值,也(ye)就是在(zai)(zai)確(que)定(ding)的(de)(de)工(gong)藝范(fan)圍(wei)內。
11. 陽極(ji)移(yi)動
陽(yang)極移動(dong)使陽(yang)極溶解產物加快擴散出去,起到攪(jiao)拌作用,有(you)效地排除陽(yang)極表面滯(zhi)留的氣(qi)泡,避免產生的氣(qi)流生成(cheng)條紋(wen),防止局部(bu)過熱(re)造成(cheng)表面過腐蝕。陽(yang)極移動(dong)有(you)助于提(ti)高陽(yang)極電流密度(du),提(ti)高不銹鋼零件(jian)的電化學拋(pao)光表面質量。
12. 氯離子的(de)危害
在電化(hua)學拋光(guang)液(ye)中(zhong)不(bu)允許有活性(xing)氯(lv)離子(zi)存在,氯(lv)離子(zi)能破壞電化(hua)學拋光(guang)中(zhong)表面形成(cheng)的保(bao)護性(xing)黏(nian)膜,使不(bu)銹鋼表面形成(cheng)過腐(fu)蝕(shi)性(xing)的麻點。氯(lv)離子(zi)可在陽(yang)極高(gao)電流(liu)密度上(shang)氧(yang)化(hua)成(cheng)氯(lv)氣逸出(chu)而除去。氯(lv)離子(zi)的來源(yuan)可能是用鹽酸酸洗后未洗凈而帶(dai)入槽(cao)液(ye),或(huo)原(yuan)料中(zhong)的不(bu)純物氯(lv)離子(zi)引入。
13. 六價鉻(ge)和(he)三價鉻(ge)的(de)最佳配比(bi)
在(zai)電(dian)(dian)(dian)(dian)(dian)化(hua)學拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)液(ye)(ye)(ye)(ye)(ye)中(zhong)六(liu)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)有(you)氧化(hua)性(xing),對(dui)不(bu)(bu)銹鋼表(biao)面起(qi)鈍化(hua)保(bao)護(hu)作(zuo)(zuo)用,三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)對(dui)維(wei)護(hu)電(dian)(dian)(dian)(dian)(dian)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)有(you)作(zuo)(zuo)用。新配(pei)(pei)成(cheng)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)液(ye)(ye)(ye)(ye)(ye)如(ru)果(guo)(guo)沒(mei)有(you)化(hua)學反(fan)應(ying)(ying)產(chan)(chan)生(sheng)三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge),還不(bu)(bu)能(neng)獲(huo)得良好的(de)(de)(de)(de)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)表(biao)面。只有(you)當電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)到溶(rong)(rong)液(ye)(ye)(ye)(ye)(ye)中(zhong)有(you)一(yi)定量(liang)的(de)(de)(de)(de)三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)存在(zai)時(shi),才(cai)能(neng)出(chu)現理想(xiang)的(de)(de)(de)(de)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)表(biao)面。如(ru)果(guo)(guo)配(pei)(pei)方中(zhong)加(jia)有(you)鉻(ge)(ge)(ge)(ge)(ge)(ge)酐(gan),即(ji)六(liu)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge),通(tong)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)反(fan)應(ying)(ying),在(zai)陰(yin)極上產(chan)(chan)生(sheng)氫氣還原部(bu)分六(liu)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)成(cheng)為(wei)三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge);如(ru)果(guo)(guo)配(pei)(pei)方中(zhong)沒(mei)有(you)鉻(ge)(ge)(ge)(ge)(ge)(ge)酐(gan),則(ze)三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)要靠陽極溶(rong)(rong)解(jie)(jie)(jie)(jie)不(bu)(bu)銹鋼所含(han)的(de)(de)(de)(de)鉻(ge)(ge)(ge)(ge)(ge)(ge)而(er)得。這就(jiu)是為(wei)什(shen)么新配(pei)(pei)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)液(ye)(ye)(ye)(ye)(ye)要充(chong)分電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)后才(cai)能(neng)進行正常(chang)的(de)(de)(de)(de)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)工作(zuo)(zuo)。在(zai)含(han)有(you)鉻(ge)(ge)(ge)(ge)(ge)(ge)酐(gan)的(de)(de)(de)(de)溶(rong)(rong)液(ye)(ye)(ye)(ye)(ye)中(zhong),加(jia)入(ru)明(ming)膠或(huo)甘(gan)油,它(ta)們能(neng)和(he)鉻(ge)(ge)(ge)(ge)(ge)(ge)酐(gan)起(qi)強烈的(de)(de)(de)(de)還原反(fan)應(ying)(ying),部(bu)分六(liu)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)轉(zhuan)變(bian)為(wei)三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)(Cr3+)。六(liu)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)是黃色(se)的(de)(de)(de)(de),三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)是綠(lv)色(se)的(de)(de)(de)(de)。它(ta)們在(zai)電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)液(ye)(ye)(ye)(ye)(ye)中(zhong)使(shi)溶(rong)(rong)液(ye)(ye)(ye)(ye)(ye)呈(cheng)黃綠(lv)色(se)。這就(jiu)是為(wei)什(shen)么通(tong)電(dian)(dian)(dian)(dian)(dian)處理后才(cai)可(ke)電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)。最佳的(de)(de)(de)(de)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)質(zhi)(zhi)量(liang)是在(zai)電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)過(guo)(guo)程(cheng)的(de)(de)(de)(de)中(zhong)間階段。在(zai)生(sheng)產(chan)(chan)過(guo)(guo)程(cheng)中(zhong)電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)液(ye)(ye)(ye)(ye)(ye)要保(bao)持(chi)黃綠(lv)色(se)。此(ci)時(shi),根據化(hua)學分析數據,六(liu)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)與三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)的(de)(de)(de)(de)配(pei)(pei)比(bi)是:含(han)Cr6+30%,含(han)Cr3+70%.為(wei)了維(wei)持(chi)該配(pei)(pei)比(bi),可(ke)觀察電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)液(ye)(ye)(ye)(ye)(ye)的(de)(de)(de)(de)顏色(se),如(ru)果(guo)(guo)顏色(se)呈(cheng)黃色(se)為(wei)主,表(biao)明(ming)電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)液(ye)(ye)(ye)(ye)(ye)含(han)Cr6+偏高,可(ke)加(jia)入(ru)適量(liang)的(de)(de)(de)(de)明(ming)膠或(huo)甘(gan)油,使(shi)其部(bu)分六(liu)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)還原為(wei)三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge),或(huo)通(tong)過(guo)(guo)大(da)陰(yin)極小陽極電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)產(chan)(chan)生(sheng)三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)。如(ru)果(guo)(guo)顏色(se)呈(cheng)深綠(lv)色(se),表(biao)明(ming)電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)液(ye)(ye)(ye)(ye)(ye)含(han)Cr3+高了,按比(bi)例適量(liang)加(jia)入(ru)用水溶(rong)(rong)解(jie)(jie)(jie)(jie)好的(de)(de)(de)(de)鉻(ge)(ge)(ge)(ge)(ge)(ge)酐(gan)溶(rong)(rong)液(ye)(ye)(ye)(ye)(ye),或(huo)通(tong)過(guo)(guo)大(da)陽極小陰(yin)極電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)(jie)(jie)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)液(ye)(ye)(ye)(ye)(ye),使(shi)三(san)(san)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)部(bu)分轉(zhuan)變(bian)成(cheng)六(liu)價(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)。同(tong)時(shi)可(ke)改善溶(rong)(rong)液(ye)(ye)(ye)(ye)(ye)的(de)(de)(de)(de)拋(pao)(pao)光(guang)(guang)(guang)(guang)(guang)質(zhi)(zhi)量(liang)。
14. 金(jin)屬(shu)拋(pao)除(chu)量
如果電(dian)(dian)解拋光時陽極電(dian)(dian)流密度(du)為(wei)20A/d㎡,時間為(wei)4min時,用(yong)工具金(jin)相顯微鏡觀(guan)測,不(bu)銹(xiu)鋼零件的(de)螺(luo)紋(wen)內徑的(de)金(jin)屬(shu)拋除量(liang)為(wei)每分鐘約(yue)0.001mm,螺(luo)紋(wen)外徑的(de)金(jin)屬(shu)拋除量(liang)為(wei)0.002mm,齒形基本(ben)無變(bian)化(hua),僅齒的(de)頂(ding)部略有拋鈍。陽極電(dian)(dian)流密度(du)增加,其(qi)金(jin)屬(shu)拋除量(liang)呈比例增大。對于(yu)精密尺(chi)寸的(de)不(bu)銹(xiu)鋼零件的(de)尺(chi)寸應考慮電(dian)(dian)化(hua)學拋光后(hou)的(de)金(jin)屬(shu)拋除量(liang)(損耗)。
15. 電(dian)焊或熱(re)處理后零件的(de)電(dian)化學拋(pao)光(guang)
凡電焊或熱處理(li)后的(de)零件在電化(hua)(hua)學拋光(guang)時按兩次(ci)進行,第一(yi)次(ci)進槽拋光(guang)3~5min后取出,將(jiang)已疏松了的(de)焊渣(zha)和(he)熱處理(li)氧化(hua)(hua)皮用金屬(shu)絲刷將(jiang)它刷掉,或用小錘(chui)敲掉,再第二次(ci)進槽再拋光(guang)3~5min,可獲得較(jiao)好的(de)效果。
16. 中和工序
經(jing)過(guo)電(dian)化(hua)學(xue)拋光后(hou)的(de)(de)零件,如(ru)果不(bu)再進行(xing)后(hou)續加工,如(ru)電(dian)鍍、著色等(deng)其(qi)他工序,要進行(xing)鈍化(hua)和(he)(he)中(zhong)(zhong)和(he)(he)。中(zhong)(zhong)和(he)(he)的(de)(de)作用(yong)是充分地消(xiao)除在(zai)電(dian)化(hua)學(xue)拋光和(he)(he)鈍化(hua)后(hou)表面所(suo)吸附的(de)(de)酸(suan)性(xing)物(wu)質(zhi)。中(zhong)(zhong)和(he)(he)一(yi)般是在(zai)碳酸(suan)鈉20~30g/L的(de)(de)溶(rong)液中(zhong)(zhong)進行(xing)的(de)(de)。路云鶴認(ren)為,經(jing)過(guo)電(dian)化(hua)學(xue)拋光后(hou)的(de)(de)零件表面有一(yi)層均勻的(de)(de)鈍化(hua)膜,可不(bu)需要再進行(xing)鈍化(hua)處理。不(bu)銹鋼(gang)零件電(dian)化(hua)學(xue)拋光后(hou),經(jing)過(guo)40℃的(de)(de)溫水(shui)清洗(xi),再冷水(shui)清洗(xi),中(zhong)(zhong)和(he)(he)并清洗(xi)后(hou)用(yong)壓縮空(kong)氣吹(chui)干(gan),才(cai)可以有效地避免殘留酸(suan)液腐蝕拋光表面。