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)解液(ye)(ye)表面(mian)淬(cui)火(huo)原理是將工(gong)(gong)(gong)件置于電(dian)(dian)(dian)解液(ye)(ye)中（局部或(huo)全部）作為陰(yin)極(ji)，金屬電(dian)(dian)(dian)解槽作為陽(yang)極(ji)。電(dian)(dian)(dian)路接通后，電(dian)(dian)(dian)解液(ye)(ye)發生(sheng)電(dian)(dian)(dian)離(li)，在陽(yang)極(ji)上放出(chu)氧，在陰(yin)極(ji)上放出(chu)氫(qing)。氫(qing)圍繞工(gong)(gong)(gong)件形成(cheng)氣膜(mo)，產生(sheng)很大(da)的電(dian)(dian)(dian)阻，通過的電(dian)(dian)(dian)流轉化(hua)為熱能將工(gong)(gong)(gong)件表面(mian)迅速加熱到臨界點以(yi)上溫度。電(dian)(dian)(dian)路斷開氣膜(mo)消失，加熱的工(gong)(gong)(gong)件在電(dian)(dian)(dian)解液(ye)(ye)中即實現淬(cui)火(huo)冷(leng)卻。此方法所用(yong)設備簡單，淬(cui)火(huo)變形小，適用(yong)于形狀簡單、小工(gong)(gong)(gong)件的批量生(sheng)產。
電(dian)解液(ye)溫度(du)(du)(du)不(bu)能超(chao)過(guo)60℃。溫度(du)(du)(du)過(guo)高，氫氣(qi)膜不(bu)穩定(ding)(ding)，影響加(jia)熱過(guo)程，還會(hui)加(jia)速(su)溶液(ye)的蒸發。常用電(dian)壓為160～180V，最高不(bu)超(chao)過(guo)260V，電(dian)流密(mi)(mi)度(du)(du)(du)的范圍是4～10A／c㎡，通常可選(xuan)用6A／c㎡。電(dian)流密(mi)(mi)度(du)(du)(du)過(guo)大時(shi)，加(jia)熱速(su)度(du)(du)(du)快(kuai)，淬硬層(ceng)薄。在加(jia)熱過(guo)程中(zhong)(zhong)，應將工件的位置加(jia)以(yi)固定(ding)(ding)，否則會(hui)造成電(dian)流密(mi)(mi)度(du)(du)(du)的變化，使淬硬層(ceng)質(zhi)量惡(e)化。加(jia)熱時(shi)間可通過(guo)試驗確(que)定(ding)(ding)。工件在電(dian)解液(ye)中(zhong)(zhong)可采用端部自(zi)由加(jia)熱、端部絕緣加(jia)熱、回轉加(jia)熱和(he)連續加(jia)熱等方式。
