Section 5 Conduction electric resistance furnace.ppt

Section 5 Conduction electric resistance furnace 1 Electric slag furnace Application: refining/ remelting of metals ① Working principle Slag(CaF2): resistance (liquid element) Electric-thermal conversion: slag resistance electric energy heat energy Slag is the heating element. Heat transfer process conduction slag electrode Slag is liquid and its thermal conductivity is very large. Smelting process melting refining cooling electrode droplet melt ingot Slag is not only the heating element ,but also the refining agent. ② Advantages (1) High refining quality; (2) Lower investment in equipments than that of the vacuum arc furnace. ③ Furnace type 1) Electric slag furnace with cooling jacket 2) Electric slag furnace with lining 2 Electrode salt bath furnace Application: heat treatment of machine parts ① Working principle Electric-thermal conversion process electric energy--- heat energy salt resistance Salt composition: NaNo3, KCl,.. Salt has resistance, acting as heating element Heat transfer process Salt------- charge Mainly by conduction ② Furnace type By installation mode of electrode inserting mode of electrode: oxidation submerging mode of electrode By layout mode of electrode ③ Characteristic 1) Advantages (1) High heating speed (2) Protection of oxidation 2) Disadvantages (1) Salt produces harmful gases (2) Salt + water explosion submerged electrode (3) Salt on the surface of metal parts must be washed off (4) Difficult to start (assistant electrode) Summary of electric resistance furnaces The most widely used electric furnace in industry and laboratory Simple structure, easy operation Issues: Energy loss in th