A graphitization furnace has a furnace structure including a support part within a furnace chamber, and a gate valve. The gate valve in an open state thereof after a graphitization process dumps a pack material within the furnace chamber in a state in which carbon bodies are located within the furnace chamber, and the support part catches the carbon bodies as a level of the carbon bodies lowers with a decrease in an amount of the pack material remaining within the furnace chamber.

Provided are a heat treatment apparatus for carbonaceous grains and a method therefor allowing drifts and internal clogging in a direct energizing furnace to not occur, allowing heat treatment of the carbonaceous grains to be continued uniformly at high temperatures for a prolonged period of time, and allowing productivity and workability to be improved. A conductive tubular structure 14 is electrically connected to an upper part of a lower electrode 13 in a manner of surrounding an upper electrode 12. The rate of change between the specific electrical resistivity of grains when grains are lightly filled and the specific electrical resistivity of grains when the grains are tap filled is defined (1-tap filling/lightly filling)100, and the rate of change is equal to less than 70%.

A method of driving conductive molten metal and a melting furnace, the method including making direct current flow vertically between a first electrode, and applying a magnetic field radially toward the center of a melting chamber from the outside of the melting furnace or toward the outside of the melting furnace from the center of the melting chamber to apply torque. The method further includes rotating the molten metal by the torque to discharge the molten metal to a holding furnace, which is provided on the melting chamber, from an outlet opening of a partition plate provided between the melting chamber and the holding furnace and to suck the molten metal, which is present in the holding furnace, from an inlet opening of the partition plate.

A method of producing a spring which reduces time required for a heat treatment step of eliminating a machining strain generated by a forming step is provided. This production method is provided with a forming step (S10) of forming a spring steel material into a spring shape and a heat treatment step (S12) of eliminating a machining strain generated in the spring steel material by the forming step. The heat treatment step is executed by electrically heating the spring steel material by applying a current thereto. The heat treatment step has a first step of heating the spring steel material to a predetermined set temperature and a second step of keeping the spring steel material at the set temperature for a predetermined set time period subsequent to the first step. The set temperature is set to be higher than 430 C. but not higher than 500 C.

A method of producing a spring which reduces time required for a heat treatment step of eliminating a machining strain generated by a forming step is provided. This production method is provided with a forming step (S10) of forming a spring steel material into a spring shape and a heat treatment step (S12) of eliminating a machining strain generated in the spring steel material by the forming step. The heat treatment step is executed by electrically heating the spring steel material by applying a current thereto. The heat treatment step has a first step of heating the spring steel material to a predetermined set temperature and a second step of keeping the spring steel material at the set temperature for a predetermined set time period subsequent to the first step. The set temperature is set to be higher than 430 C. but not higher than 500 C.

A method of producing a spring which reduces time required for a heat treatment step of eliminating a machining strain generated by a forming step is provided. This production method is provided with a forming step (S10) of forming a spring steel material into a spring shape and a heat treatment step (S12) of eliminating a machining strain generated in the spring steel material by the forming step. The heat treatment step is executed by electrically heating the spring steel material by applying a current thereto. The heat treatment step has a first step of heating the spring steel material to a predetermined set temperature and a second step of keeping the spring steel material at the set temperature for a predetermined set time period subsequent to the first step. The set temperature is set to be higher than 430 C. but not higher than 500 C.

Graphite is produced from powder as a carbon source by means of a graphitization furnace. The graphitization furnace is comprised of: an electrically conductive crucible including a hollow configured to house the powder; an electrode including a columnar shaft and a head provided at an end of the shaft, the head having a shape selected from the group consisting of a sphere, a hemisphere, a column with a rounded edge, a cone, and a cone with a rounded tip; and a power source configured to apply electric current to the powder through the crucible and the electrode.

Graphite is produced from powder as a carbon source by means of a graphitization furnace. The graphitization furnace is comprised of: an electrically conductive crucible including a hollow configured to house the powder; an electrode including a columnar shaft and a head provided at an end of the shaft, the head having a shape selected from the group consisting of a sphere, a hemisphere, a column with a rounded edge, a cone, and a cone with a rounded tip; and a power source configured to apply electric current to the powder through the crucible and the electrode.

The invention relates to a dental furnace wherein a firing chamber is heated up in a first heating-up period at a first heating-up rate of more than 501 K/min, in particular more than 1001 K/min, which heats the furnace to at least 10001 C, in particular to 1100-12501 C. The first heating-up period is followed by an intermediate heating period, which is at least five minutes long, in particular at least ten minutes long, the gradient or heating-up rate of which is adapted to the material to be sintered in the dental furnace (10), and wherein this is followed by an end heating-up period (44) during which heating up is effected at a heating-up rate of more than 301 K/min, in particular approximately 501 K/min, and wherein during this the furnace temperature is held for at least five minutes, in particular for at least 25 minutes, above the temperature toward the end of the first heating-up period, and wherein forced cooling of the furnace (10) is performed after this.

The invention relates to a dental furnace wherein a firing chamber is heated up in a first heating-up period at a first heating-up rate of more than 501 K/min, in particular more than 1001 K/min, which heats the furnace to at least 10001 C, in particular to 1100-12501 C. The first heating-up period is followed by an intermediate heating period, which is at least five minutes long, in particular at least ten minutes long, the gradient or heating-up rate of which is adapted to the material to be sintered in the dental furnace (10), and wherein this is followed by an end heating-up period (44) during which heating up is effected at a heating-up rate of more than 301 K/min, in particular approximately 501 K/min, and wherein during this the furnace temperature is held for at least five minutes, in particular for at least 25 minutes, above the temperature toward the end of the first heating-up period, and wherein forced cooling of the furnace (10) is performed after this.