Melting furnace

1. A melting furnace including:

a melting portion to which a metal material is supplied, the melting portion having a sloping floor inclined downwardly;

a burner for melting the metal material in the melting portion into a molten material;

a heating portion that receives the molten material from the melting portion through the sloping floor of the melting portion, which is inclined downwardly toward the heating portion, wherein the molten material is heated by radiant heat of combustion gas injected from the burner in the melting portion to raise the temperature of the molten material;

a temperature regulating portion that receives the molten material from the heating portion and stores the molten material;

a connecting path from the heating portion toward the temperature regulating portion, such that the molten material in the heating portion flows on the connecting path into the temperature regulating portion;

a separator that separates the heating portion and the temperature regulating portion, wherein the lower portion of the separator is immersed in the molten material; and

an inlet that connects the heating portion and the temperature regulating portion, formed between the lower portion of the separator and the connecting path, to allow introduction of the molten material from the heating portion into the temperature regulating portion;

an immersion heater wherein at least part of the immersion heater is immersed in the molten material in the temperature regulating portion to thereby heat the molten material; and

a gas introduction path that is formed in the separator to connect the melting portion and the temperature regulating portion, and that introduces combustion gas injected from the burner in the melting portion into a space above the molten material in the temperature regulating portion;

wherein the burner is configured so that the combustion gas has an oxygen concentration of 5% or less.

2. The melting furnace according to claim 1 , wherein the gas introduction path is inclined so that an outlet on the side of the temperature regulating portion is disposed in a higher position than an inlet on the side of the melting portion.

3. The melting furnace according to claim 1 , further including:

an inner wall or ceiling of the temperature regulating portion,

a first exhaust port on the inner wall or ceiling, and

an adjustment damper in the first exhaust port, for adjusting an exhaust amount;

wherein:

the adjustment damper is configured such that the combustion gas introduced into the temperature regulating portion via the gas introduction path is 10% or more and 20% or less of the gas combustion amount of the burner.

4. The melting furnace according to claim 3 , wherein the melting furnace further includes a preheating portion that includes a material supplying path and a lid, and that is positioned above the melting portion,

the temperature regulating portion is further provided with a first open/close damper at the first exhaust port, and

the preheating portion is provided with a second exhaust port on the lid, and the second exhaust port is provided with a second open/close damper.

5. The melting furnace according to claim 2 , further including:

an inner wall or ceiling of the temperature regulating portion,

a first exhaust port on the inner wall or ceiling, and

an adjustment damper in the first exhaust port, for adjusting an exhaust amount; wherein:

the adjustment damper is configured such that the combustion gas introduced into the temperature regulating portion via the gas introduction path is 10% or more and 20% or less of the gas combustion amount of the burner.