電解液的加熱是以直流電為電源在電解液中進行的，適用于表面加熱淬火的電解液很多，一般采用質量分數為8％～10％的Na2CO3水溶液。
電(dian)(dian)(dian)解(jie)液(ye)表面淬(cui)火(huo)(huo)(huo)原(yuan)理是將工件(jian)(jian)置于(yu)電(dian)(dian)(dian)解(jie)液(ye)中（局部(bu)或(huo)全(quan)部(bu)）作為陰極，金(jin)屬(shu)電(dian)(dian)(dian)解(jie)槽作為陽極。電(dian)(dian)(dian)路接通(tong)(tong)后，電(dian)(dian)(dian)解(jie)液(ye)發生電(dian)(dian)(dian)離，在陽極上(shang)(shang)放出(chu)氧(yang)，在陰極上(shang)(shang)放出(chu)氫(qing)(qing)。氫(qing)(qing)圍(wei)繞工件(jian)(jian)形成氣膜(mo)(mo)，產生很大的(de)電(dian)(dian)(dian)阻，通(tong)(tong)過的(de)電(dian)(dian)(dian)流轉化為熱能將工件(jian)(jian)表面迅速加(jia)熱到臨界點以上(shang)(shang)溫度。電(dian)(dian)(dian)路斷(duan)開(kai)氣膜(mo)(mo)消失，加(jia)熱的(de)工件(jian)(jian)在電(dian)(dian)(dian)解(jie)液(ye)中即(ji)實現淬(cui)火(huo)(huo)(huo)冷卻。此方法(fa)所用(yong)設備(bei)簡單，淬(cui)火(huo)(huo)(huo)變形小(xiao)，適(shi)用(yong)于(yu)形狀簡單、小(xiao)工件(jian)(jian)的(de)批量生產。
電(dian)(dian)解液(ye)溫度(du)不能超過(guo)(guo)60℃。溫度(du)過(guo)(guo)高，氫氣膜不穩定，影響加(jia)(jia)熱(re)(re)(re)過(guo)(guo)程，還會(hui)加(jia)(jia)速溶液(ye)的(de)蒸(zheng)發。常(chang)(chang)用(yong)電(dian)(dian)壓為(wei)160～180V，最高不超過(guo)(guo)260V，電(dian)(dian)流密度(du)的(de)范圍是4～10A／c㎡，通常(chang)(chang)可選用(yong)6A／c㎡。電(dian)(dian)流密度(du)過(guo)(guo)大時，加(jia)(jia)熱(re)(re)(re)速度(du)快，淬(cui)硬(ying)層薄。在(zai)加(jia)(jia)熱(re)(re)(re)過(guo)(guo)程中(zhong)，應將工(gong)件的(de)位置(zhi)加(jia)(jia)以(yi)固定，否則(ze)會(hui)造成電(dian)(dian)流密度(du)的(de)變(bian)化，使淬(cui)硬(ying)層質量惡化。加(jia)(jia)熱(re)(re)(re)時間可通過(guo)(guo)試驗(yan)確定。工(gong)件在(zai)電(dian)(dian)解液(ye)中(zhong)可采(cai)用(yong)端部自由加(jia)(jia)熱(re)(re)(re)、端部絕緣(yuan)加(jia)(jia)熱(re)(re)(re)、回(hui)轉加(jia)(jia)熱(re)(re)(re)和(he)連(lian)續加(jia)(jia)熱(re)(re)(re)等方式(shi)。
