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)使用過(guo)程中需要經(jing)常測量電化(hua)(hua)學拋(pao)光(guang)液的相對(dui)密度(du)(du)。如(ru)果相對(dui)密度(du)(du)小于配(pei)方(fang)規定值(zhi)(zhi)(zhi),表(biao)明電化(hua)(hua)學拋(pao)光(guang)液含水過(guo)多,可(ke)用蒸(zheng)發法(fa)將(jiang)溶(rong)液加熱至80℃以上(shang),將(jiang)多余水分除去,體積不(bu)足部分可(ke)按配(pei)方(fang)比例補(bu)充磷酸和硫酸。在(zai)工件(jian)進入電化(hua)(hua)學拋(pao)光(guang)槽前,最(zui)好將(jiang)工件(jian)上(shang)所附著的水分瀝干或吹干。如(ru)果相對(dui)密度(du)(du)太高,超過(guo)配(pei)方(fang)規定值(zhi)(zhi)(zhi),表(biao)示(shi)水分過(guo)少,要適當(dang)補(bu)充少量水,使相對(dui)密度(du)(du)降(jiang)至規定值(zhi)(zhi)(zhi)。有條件(jian)的最(zui)好按周期化(hua)(hua)驗分析溶(rong)液,根(gen)據結果及時進行調整。
3. 溶液的老化
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. 清理陰極鉛板(ban)
在(zai)拋(pao)光(guang)過程中陰極(ji)鉛板表(biao)面會沉(chen)(chen)積出一層厚厚的鐵、鎳(nie)等(deng)雜質(zhi),影(ying)響陰極(ji)表(biao)面導電(dian),導致電(dian)流(liu)下降,使拋(pao)光(guang)表(biao)面的陽極(ji)電(dian)流(liu)密度也上(shang)不去,嚴重(zhong)影(ying)響拋(pao)光(guang)質(zhi)量。因(yin)此,要(yao)及時將陰極(ji)板上(shang)的沉(chen)(chen)積物除去,有(you)時形(xing)成硬質(zhi)厚膜,要(yao)強力敲打才能除下,最后沖洗干凈,以保(bao)持(chi)整(zheng)個(ge)電(dian)路通暢。
5. 陰極與陽極面積比
陰極(ji)面積控制在陽(yang)極(ji)面積的1/2~1/3.5.在此情(qing)況下,可以防止三(san)價鉻(ge)的增長(chang),過(guo)多(duo)的三(san)價鉻(ge)在陽(yang)極(ji)表面被氧化成六(liu)價鉻(ge)。三(san)價鉻(ge)含量(liang)過(guo)多(duo),易(yi)使拋光液老化。
6. 陰陽極(ji)之間(jian)的極(ji)距
陰極與陽(yang)極之間的距離(li)(li)過(guo)大、電阻(zu)增大,電能消耗增大,溶液容易升(sheng)溫(wen),影響(xiang)拋光(guang)質量。距離(li)(li)過(guo)小,易造成短路打火,燒黑制品。陰極與陽(yang)極之間的距離(li)(li)以100~300mm為(wei)宜。
7. 象形陰極(ji)
對(dui)拋(pao)光一些復雜的大型工(gong)件(jian),可制(zhi)作象形陰極,以保持陽極電流分布均勻,特(te)別(bie)是對(dui)內腔工(gong)件(jian),有適(shi)當(dang)的象形陰極安置(zhi)在內腔中,才能使內腔各部位(wei)拋(pao)光一致。
8. 進出槽要切斷電源
在(zai)電(dian)(dian)化學(xue)拋(pao)光(guang)(guang)時,由于電(dian)(dian)流(liu)密(mi)度較高,給電(dian)(dian)流(liu)較大,因此,工(gong)件(jian)在(zai)進(jin)出拋(pao)光(guang)(guang)槽時,要(yao)先切斷電(dian)(dian)源,不可帶電(dian)(dian)掛或摘夾具,以防止產生(sheng)電(dian)(dian)火花(hua),引起電(dian)(dian)解產生(sheng),并會使聚(ju)集(ji)在(zai)槽面上的(de)氫氣和氧(yang)氣混合氣發生(sheng)爆炸。
9. 控制槽液溫度
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(kong)制合適的陽極(ji)電(dian)流密度
不(bu)銹鋼零件電(dian)(dian)化學拋(pao)(pao)(pao)光(guang)時,陽(yang)(yang)極(ji)(ji)電(dian)(dian)流(liu)密(mi)(mi)(mi)度(du)(du)(du)(du)與金屬的(de)溶解(jie)幾乎呈(cheng)正比。只有(you)選擇好陽(yang)(yang)極(ji)(ji)電(dian)(dian)流(liu)密(mi)(mi)(mi)度(du)(du)(du)(du),并控制在(zai)(zai)(zai)一(yi)定的(de)陽(yang)(yang)極(ji)(ji)電(dian)(dian)位(wei)區(qu)間,才能(neng)獲得良(liang)好的(de)電(dian)(dian)化學拋(pao)(pao)(pao)光(guang)質量,陽(yang)(yang)極(ji)(ji)電(dian)(dian)流(liu)密(mi)(mi)(mi)度(du)(du)(du)(du)的(de)最(zui)佳值(zhi),要(yao)根(gen)據(ju)不(bu)同(tong)的(de)電(dian)(dian)解(jie)液配方,通過(guo)實際拋(pao)(pao)(pao)光(guang),觀(guan)察拋(pao)(pao)(pao)光(guang)所得最(zui)佳值(zhi)確定。在(zai)(zai)(zai)合適的(de)陽(yang)(yang)極(ji)(ji)電(dian)(dian)流(liu)密(mi)(mi)(mi)度(du)(du)(du)(du)下,根(gen)據(ju)黏膜理(li)論,微觀(guan)表面(mian)凸(tu)出部位(wei)優先溶解(jie),有(you)利于整平精飾表面(mian)。陽(yang)(yang)極(ji)(ji)電(dian)(dian)流(liu)密(mi)(mi)(mi)度(du)(du)(du)(du)過(guo)小,零件表面(mian)發生(sheng)一(yi)般(ban)的(de)陽(yang)(yang)極(ji)(ji)溶解(jie),起(qi)不(bu)到拋(pao)(pao)(pao)光(guang)效果。陽(yang)(yang)極(ji)(ji)電(dian)(dian)流(liu)密(mi)(mi)(mi)度(du)(du)(du)(du)過(guo)大,黏膜被(bei)擊穿,氧(yang)氣(qi)(qi)猛烈析出呈(cheng)氣(qi)(qi)流(liu)狀,表面(mian)過(guo)熱,導致電(dian)(dian)拋(pao)(pao)(pao)光(guang)液擴散加劇(ju),黏膜被(bei)破壞,不(bu)復存(cun)在(zai)(zai)(zai),發生(sheng)電(dian)(dian)化學腐蝕(shi)。所以在(zai)(zai)(zai)電(dian)(dian)拋(pao)(pao)(pao)光(guang)過(guo)程中必須(xu)控制陽(yang)(yang)極(ji)(ji)電(dian)(dian)流(liu)密(mi)(mi)(mi)度(du)(du)(du)(du)在(zai)(zai)(zai)最(zui)佳值(zhi),也(ye)就是在(zai)(zai)(zai)確定的(de)工藝(yi)范圍(wei)內。
11. 陽極移動
陽極移動(dong)使(shi)陽極溶解產物(wu)加快(kuai)擴散出(chu)去,起到(dao)攪拌作(zuo)用,有(you)效地排除陽極表面滯留的氣(qi)泡,避(bi)免產生的氣(qi)流生成條紋,防(fang)止(zhi)局部過熱造成表面過腐蝕。陽極移動(dong)有(you)助于提高陽極電流密度,提高不銹鋼零(ling)件的電化學(xue)拋(pao)光(guang)表面質量。
12. 氯離子的危(wei)害(hai)
在(zai)電化學拋光液(ye)中(zhong)(zhong)不允(yun)許(xu)有活(huo)性(xing)氯(lv)(lv)離(li)子存(cun)在(zai),氯(lv)(lv)離(li)子能破(po)壞電化學拋光中(zhong)(zhong)表(biao)面形(xing)(xing)成(cheng)的保護性(xing)黏膜(mo),使不銹鋼(gang)表(biao)面形(xing)(xing)成(cheng)過腐(fu)蝕性(xing)的麻點。氯(lv)(lv)離(li)子可在(zai)陽極高(gao)電流(liu)密度上氧化成(cheng)氯(lv)(lv)氣逸出而(er)(er)除去(qu)。氯(lv)(lv)離(li)子的來源可能是用鹽酸酸洗后未洗凈而(er)(er)帶入槽液(ye),或原(yuan)料中(zhong)(zhong)的不純物氯(lv)(lv)離(li)子引入。
13. 六價(jia)鉻和三價(jia)鉻的最(zui)佳配比
在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)化(hua)(hua)學拋(pao)(pao)光(guang)(guang)液(ye)(ye)(ye)(ye)(ye)中(zhong)(zhong)(zhong)六(liu)(liu)(liu)價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)有(you)(you)氧化(hua)(hua)性,對不銹鋼表(biao)面(mian)起鈍化(hua)(hua)保護(hu)作用,三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)對維(wei)護(hu)電(dian)(dian)(dian)(dian)(dian)拋(pao)(pao)光(guang)(guang)有(you)(you)作用。新(xin)配(pei)(pei)成(cheng)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)拋(pao)(pao)光(guang)(guang)液(ye)(ye)(ye)(ye)(ye)如(ru)(ru)(ru)果(guo)沒有(you)(you)化(hua)(hua)學反(fan)(fan)應(ying)產生(sheng)三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge),還不能獲得良好的(de)(de)(de)拋(pao)(pao)光(guang)(guang)表(biao)面(mian)。只有(you)(you)當電(dian)(dian)(dian)(dian)(dian)解(jie)到溶(rong)液(ye)(ye)(ye)(ye)(ye)中(zhong)(zhong)(zhong)有(you)(you)一定量(liang)(liang)的(de)(de)(de)三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)存在(zai)(zai)時,才(cai)能出現理(li)想(xiang)的(de)(de)(de)拋(pao)(pao)光(guang)(guang)表(biao)面(mian)。如(ru)(ru)(ru)果(guo)配(pei)(pei)方中(zhong)(zhong)(zhong)加(jia)(jia)有(you)(you)鉻(ge)(ge)(ge)(ge)(ge)(ge)酐(gan),即六(liu)(liu)(liu)價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge),通(tong)過電(dian)(dian)(dian)(dian)(dian)解(jie)反(fan)(fan)應(ying),在(zai)(zai)陰(yin)極(ji)上產生(sheng)氫(qing)氣還原部分(fen)六(liu)(liu)(liu)價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)成(cheng)為(wei)三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge);如(ru)(ru)(ru)果(guo)配(pei)(pei)方中(zhong)(zhong)(zhong)沒有(you)(you)鉻(ge)(ge)(ge)(ge)(ge)(ge)酐(gan),則(ze)三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)要靠陽(yang)極(ji)溶(rong)解(jie)不銹鋼所(suo)含(han)的(de)(de)(de)鉻(ge)(ge)(ge)(ge)(ge)(ge)而得。這就是(shi)(shi)為(wei)什(shen)么新(xin)配(pei)(pei)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)解(jie)拋(pao)(pao)光(guang)(guang)液(ye)(ye)(ye)(ye)(ye)要充分(fen)電(dian)(dian)(dian)(dian)(dian)解(jie)后才(cai)能進行正常(chang)的(de)(de)(de)拋(pao)(pao)光(guang)(guang)工作。在(zai)(zai)含(han)有(you)(you)鉻(ge)(ge)(ge)(ge)(ge)(ge)酐(gan)的(de)(de)(de)溶(rong)液(ye)(ye)(ye)(ye)(ye)中(zhong)(zhong)(zhong),加(jia)(jia)入明膠(jiao)或甘油(you),它們能和鉻(ge)(ge)(ge)(ge)(ge)(ge)酐(gan)起強烈的(de)(de)(de)還原反(fan)(fan)應(ying),部分(fen)六(liu)(liu)(liu)價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)轉變為(wei)三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)(Cr3+)。六(liu)(liu)(liu)價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)是(shi)(shi)黃(huang)色(se)(se)(se)(se)(se)的(de)(de)(de),三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)是(shi)(shi)綠色(se)(se)(se)(se)(se)的(de)(de)(de)。它們在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)解(jie)液(ye)(ye)(ye)(ye)(ye)中(zhong)(zhong)(zhong)使(shi)溶(rong)液(ye)(ye)(ye)(ye)(ye)呈(cheng)(cheng)黃(huang)綠色(se)(se)(se)(se)(se)。這就是(shi)(shi)為(wei)什(shen)么通(tong)電(dian)(dian)(dian)(dian)(dian)處理(li)后才(cai)可(ke)電(dian)(dian)(dian)(dian)(dian)解(jie)拋(pao)(pao)光(guang)(guang)。最佳的(de)(de)(de)拋(pao)(pao)光(guang)(guang)質量(liang)(liang)是(shi)(shi)在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)解(jie)過程(cheng)的(de)(de)(de)中(zhong)(zhong)(zhong)間階(jie)段(duan)。在(zai)(zai)生(sheng)產過程(cheng)中(zhong)(zhong)(zhong)電(dian)(dian)(dian)(dian)(dian)解(jie)拋(pao)(pao)光(guang)(guang)液(ye)(ye)(ye)(ye)(ye)要保持(chi)(chi)黃(huang)綠色(se)(se)(se)(se)(se)。此時,根據(ju)化(hua)(hua)學分(fen)析數據(ju),六(liu)(liu)(liu)價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)與三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)的(de)(de)(de)配(pei)(pei)比是(shi)(shi):含(han)Cr6+30%,含(han)Cr3+70%.為(wei)了(le)維(wei)持(chi)(chi)該配(pei)(pei)比,可(ke)觀察電(dian)(dian)(dian)(dian)(dian)解(jie)液(ye)(ye)(ye)(ye)(ye)的(de)(de)(de)顏色(se)(se)(se)(se)(se),如(ru)(ru)(ru)果(guo)顏色(se)(se)(se)(se)(se)呈(cheng)(cheng)黃(huang)色(se)(se)(se)(se)(se)為(wei)主,表(biao)明電(dian)(dian)(dian)(dian)(dian)解(jie)液(ye)(ye)(ye)(ye)(ye)含(han)Cr6+偏高(gao),可(ke)加(jia)(jia)入適量(liang)(liang)的(de)(de)(de)明膠(jiao)或甘油(you),使(shi)其部分(fen)六(liu)(liu)(liu)價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)還原為(wei)三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge),或通(tong)過大陰(yin)極(ji)小陽(yang)極(ji)電(dian)(dian)(dian)(dian)(dian)解(jie)產生(sheng)三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)。如(ru)(ru)(ru)果(guo)顏色(se)(se)(se)(se)(se)呈(cheng)(cheng)深綠色(se)(se)(se)(se)(se),表(biao)明電(dian)(dian)(dian)(dian)(dian)解(jie)液(ye)(ye)(ye)(ye)(ye)含(han)Cr3+高(gao)了(le),按比例適量(liang)(liang)加(jia)(jia)入用水(shui)溶(rong)解(jie)好的(de)(de)(de)鉻(ge)(ge)(ge)(ge)(ge)(ge)酐(gan)溶(rong)液(ye)(ye)(ye)(ye)(ye),或通(tong)過大陽(yang)極(ji)小陰(yin)極(ji)電(dian)(dian)(dian)(dian)(dian)解(jie)拋(pao)(pao)光(guang)(guang)液(ye)(ye)(ye)(ye)(ye),使(shi)三價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)部分(fen)轉變成(cheng)六(liu)(liu)(liu)價(jia)(jia)(jia)(jia)(jia)鉻(ge)(ge)(ge)(ge)(ge)(ge)。同時可(ke)改善(shan)溶(rong)液(ye)(ye)(ye)(ye)(ye)的(de)(de)(de)拋(pao)(pao)光(guang)(guang)質量(liang)(liang)。
14. 金屬拋除量
如(ru)果電(dian)解(jie)拋(pao)(pao)(pao)光時(shi)(shi)陽極(ji)電(dian)流(liu)密(mi)(mi)度為(wei)(wei)20A/d㎡,時(shi)(shi)間為(wei)(wei)4min時(shi)(shi),用工具金(jin)(jin)相(xiang)顯(xian)微鏡觀測,不(bu)銹(xiu)鋼零件的螺(luo)紋內徑的金(jin)(jin)屬(shu)拋(pao)(pao)(pao)除量(liang)為(wei)(wei)每分鐘(zhong)約0.001mm,螺(luo)紋外徑的金(jin)(jin)屬(shu)拋(pao)(pao)(pao)除量(liang)為(wei)(wei)0.002mm,齒形基本無變化(hua),僅齒的頂部略(lve)有拋(pao)(pao)(pao)鈍(dun)。陽極(ji)電(dian)流(liu)密(mi)(mi)度增(zeng)加,其金(jin)(jin)屬(shu)拋(pao)(pao)(pao)除量(liang)呈比例增(zeng)大。對于精密(mi)(mi)尺(chi)寸(cun)(cun)的不(bu)銹(xiu)鋼零件的尺(chi)寸(cun)(cun)應考慮電(dian)化(hua)學(xue)拋(pao)(pao)(pao)光后(hou)的金(jin)(jin)屬(shu)拋(pao)(pao)(pao)除量(liang)(損耗)。
15. 電(dian)焊或熱處理后零(ling)件的電(dian)化學拋光
凡電焊(han)或(huo)熱處(chu)理(li)后的零件在電化學拋光時(shi)按兩次進行,第一(yi)次進槽拋光3~5min后取出(chu),將已疏松了的焊(han)渣和熱處(chu)理(li)氧化皮用(yong)金屬絲刷將它刷掉,或(huo)用(yong)小錘(chui)敲(qiao)掉,再第二次進槽再拋光3~5min,可獲得較好(hao)的效果。
16. 中和(he)工序
經(jing)過電(dian)化學拋(pao)光(guang)后(hou)的零(ling)件(jian),如果不(bu)再(zai)進行后(hou)續加(jia)工,如電(dian)鍍(du)、著色等其他工序,要(yao)進行鈍(dun)化和(he)(he)中和(he)(he)。中和(he)(he)的作用(yong)是(shi)充分地消(xiao)除在電(dian)化學拋(pao)光(guang)和(he)(he)鈍(dun)化后(hou)表面所(suo)吸附的酸性(xing)物(wu)質。中和(he)(he)一般是(shi)在碳酸鈉20~30g/L的溶液中進行的。路云鶴(he)認為(wei),經(jing)過電(dian)化學拋(pao)光(guang)后(hou)的零(ling)件(jian)表面有(you)一層(ceng)均(jun)勻的鈍(dun)化膜,可不(bu)需(xu)要(yao)再(zai)進行鈍(dun)化處(chu)理。不(bu)銹鋼零(ling)件(jian)電(dian)化學拋(pao)光(guang)后(hou),經(jing)過40℃的溫水清洗,再(zai)冷水清洗,中和(he)(he)并清洗后(hou)用(yong)壓縮(suo)空(kong)氣吹干,才可以有(you)效地避免殘(can)留酸液腐蝕拋(pao)光(guang)表面。