青冶小編給大家講解一下熱鍍鋅加工的原理

熱(re)(re)鍍鋅(xin)(xin)也稱(cheng)熱(re)(re)浸(jin)鍍鋅(xin)(xin)，是鋼(gang)鐵(tie)構件浸(jin)入熔融的鋅(xin)(xin)液中(zhong)獲(huo)得金屬(shu)覆蓋層(ceng)的一(yi)種方法。隨高壓輸電、交通、通訊事業迅速(su)發(fa)展，對(dui)鋼(gang)鐵(tie)件防護(hu)要求(qiu)越來(lai)越高，熱(re)(re)鍍鋅(xin)(xin)需求(qiu)量也不斷增加。

防護性能

通常電(dian)(dian)鍍鋅(xin)(xin)層(ceng)(ceng)(ceng)厚度(du)5～15μm，而(er)熱(re)鍍鋅(xin)(xin)層(ceng)(ceng)(ceng)一般(ban)在35μm以上，甚至(zhi)高(gao)達(da)200μm。熱(re)鍍鋅(xin)(xin)覆蓋能力好，鍍層(ceng)(ceng)(ceng)致密，無有機(ji)物夾(jia)雜。眾所(suo)周知，鋅(xin)(xin)的抗大(da)氣(qi)腐蝕(shi)的機(ji)理有機(ji)械保護及電(dian)(dian)化學保護，在大(da)氣(qi)腐蝕(shi)條件(jian)下鋅(xin)(xin)層(ceng)(ceng)(ceng)表面有ZnO、Zn(OH)2及堿式(shi)碳(tan)酸鋅(xin)(xin)保護膜(mo)，一定程度(du)上減緩鋅(xin)(xin)的腐蝕(shi)，這層(ceng)(ceng)(ceng)保護膜(mo)(也稱白銹(xiu))受(shou)到(dao)破(po)壞(huai)又會形成(cheng)新的膜(mo)層(ceng)(ceng)(ceng)。當鋅(xin)(xin)層(ceng)(ceng)(ceng)破(po)壞(huai)嚴(yan)重，危及到(dao)鐵(tie)基體(ti)時，鋅(xin)(xin)對基體(ti)產生(sheng)電(dian)(dian)化學保護，鋅(xin)(xin)的標(biao)準電(dian)(dian)位-0.76V，鐵(tie)的標(biao)準電(dian)(dian)位-0.44V，鋅(xin)(xin)與鐵(tie)形成(cheng)微電(dian)(dian)池時鋅(xin)(xin)作為陽極被溶解，鐵(tie)作為陰極受(shou)到(dao)保護。顯然熱(re)鍍鋅(xin)(xin)對基體(ti)金屬(shu)鐵(tie)的抗大(da)氣(qi)腐蝕(shi)能力優于電(dian)(dian)鍍鋅(xin)(xin)。

鍍鋅(xin)層(ceng)形成(cheng)過程

熱鍍(du)鋅(xin)(xin)(xin)(xin)(xin)層形(xing)成(cheng)(cheng)(cheng)過(guo)程是鐵(tie)(tie)(tie)基體(ti)(ti)與最(zui)外面(mian)的純(chun)鋅(xin)(xin)(xin)(xin)(xin)層之間形(xing)成(cheng)(cheng)(cheng)鐵(tie)(tie)(tie)-鋅(xin)(xin)(xin)(xin)(xin)合(he)金的過(guo)程，工件(jian)(jian)表面(mian)在熱浸鍍(du)時形(xing)成(cheng)(cheng)(cheng)鐵(tie)(tie)(tie)-鋅(xin)(xin)(xin)(xin)(xin)合(he)金層，才使得(de)鐵(tie)(tie)(tie)與純(chun)鋅(xin)(xin)(xin)(xin)(xin)層之間很(hen)好結合(he)，其過(guo)程可簡(jian)單(dan)地敘述為(wei)(wei)：當鐵(tie)(tie)(tie)工件(jian)(jian)浸入(ru)熔(rong)融(rong)(rong)的鋅(xin)(xin)(xin)(xin)(xin)液(ye)(ye)時，首先在界面(mian)上形(xing)成(cheng)(cheng)(cheng)鋅(xin)(xin)(xin)(xin)(xin)與α鐵(tie)(tie)(tie)(體(ti)(ti)心)固(gu)熔(rong)體(ti)(ti)。這是基體(ti)(ti)金屬鐵(tie)(tie)(tie)在固(gu)體(ti)(ti)狀態下溶有(you)鋅(xin)(xin)(xin)(xin)(xin)原子(zi)所(suo)形(xing)成(cheng)(cheng)(cheng)一種晶體(ti)(ti)，兩種金屬原子(zi)之間是融(rong)(rong)合(he)，原子(zi)之間引力比(bi)較小。因此，當鋅(xin)(xin)(xin)(xin)(xin)在固(gu)熔(rong)體(ti)(ti)中(zhong)達到(dao)(dao)飽和后(hou)，鋅(xin)(xin)(xin)(xin)(xin)鐵(tie)(tie)(tie)兩種元素原子(zi)相(xiang)互擴(kuo)散(san)，擴(kuo)散(san)到(dao)(dao)(或(huo)叫滲入(ru))鐵(tie)(tie)(tie)基體(ti)(ti)中(zhong)的鋅(xin)(xin)(xin)(xin)(xin)原子(zi)在基體(ti)(ti)晶格中(zhong)遷移，逐(zhu)漸與鐵(tie)(tie)(tie)形(xing)成(cheng)(cheng)(cheng)合(he)金，而(er)擴(kuo)散(san)到(dao)(dao)熔(rong)融(rong)(rong)的鋅(xin)(xin)(xin)(xin)(xin)液(ye)(ye)中(zhong)的鐵(tie)(tie)(tie)就與鋅(xin)(xin)(xin)(xin)(xin)形(xing)成(cheng)(cheng)(cheng)金屬間化合(he)物FeZn13，沉入(ru)熱鍍(du)鋅(xin)(xin)(xin)(xin)(xin)鍋(guo)底，即為(wei)(wei)鋅(xin)(xin)(xin)(xin)(xin)渣。當工件(jian)(jian)從(cong)浸鋅(xin)(xin)(xin)(xin)(xin)液(ye)(ye)中(zhong)移出時表面(mian)形(xing)成(cheng)(cheng)(cheng)純(chun)鋅(xin)(xin)(xin)(xin)(xin)層，為(wei)(wei)六方(fang)晶體(ti)(ti)。其含鐵(tie)(tie)(tie)量不(bu)大于(yu)0.003%。

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