The argon and carbon dioxide co-injection tests were carried out with low carbon steel melts of 100 kg in a multi-function direct current ladle furnace (DC-LF) equipped with a hollow graphite electrode. It is shown that, the heating rates of the heats with argon or Ar-CO2 injection are higher than that of the normal solid graphite electrode heat. The average heating rate of the heat with argon injection is 1.59 times than that of the normal solid graphite electrode heat. The minimal average heating rate of the heat with Ar-CO2 co-injection is 3 times than that of the latter, and the maximum is 5.51 times. When argon or Ar-CO2 is injected into LF, the electric current isn’t change, but the voltage is lower.