The invention provides a tunnel kiln for firing ceramic porous bodies which can fire ceramic porous bodies containing organic binders in a shorter period of time than in conventional methods without producing breaks or requiring nitrogen gas. The tunnel kiln includes a preheating zone 1, a firing zone 2, and a cooling zone 3 and fires the ceramic porous bodies loaded on a carriage 7 by driving it in a furnace. A heat storage regenerative burner 10 is used as means of heating the firing zone 2 so that low-oxygen-concentration exhaust gas discharged from the heat storage regenerative burner 10 may be returned to an exhaust gas return line 14 and supplied into the preheating zone 1. The exhaust gas return line 14 may be provided with a combustion device 17 that reduces the oxygen concentration by consuming oxygen contained in the exhaust gas.

The invention provides a tunnel kiln for firing ceramic porous bodies which can fire ceramic porous bodies containing organic binders in a shorter period of time than in conventional methods without producing breaks or requiring nitrogen gas. The tunnel kiln includes a preheating zone 1, a firing zone 2, and a cooling zone 3 and fires the ceramic porous bodies loaded on a carriage 7 by driving it in a furnace. A heat storage regenerative burner 10 is used as means of heating the firing zone 2 so that low-oxygen-concentration exhaust gas discharged from the heat storage regenerative burner 10 may be returned to an exhaust gas return line 14 and supplied into the preheating zone 1. The exhaust gas return line 14 may be provided with a combustion device 17 that reduces the oxygen concentration by consuming oxygen contained in the exhaust gas.

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.

In a method for producing in particular structural components or chassis components for a motor vehicle by hot or semi-hot forming, a sheet metal blank is heated in a heating station at least in a first region from a starting temperature to a target temperature, and then the warm blank is transferred to a cooled pressing tool and is formed and press-hardened. The heating station includes at least one burner zone which includes at least one burner, in which zone the sheet metal blank is heated from the starting temperature to the target temperature, and at least one burner is operated with a combustion gas and an oxygen-containing gas and the sheet metal blank comes into direct contact with the burner flame.

In a method for producing in particular structural components or chassis components for a motor vehicle by hot or semi-hot forming, a sheet metal blank is heated in a heating station at least in a first region from a starting temperature to a target temperature, and then the warm blank is transferred to a cooled pressing tool and is formed and press-hardened. The heating station includes at least one burner zone which includes at least one burner, in which zone the sheet metal blank is heated from the starting temperature to the target temperature, and at least one burner is operated with a combustion gas and an oxygen-containing gas and the sheet metal blank comes into direct contact with the burner flame.

The heat treatment method of the present invention includes: a first step of mist cooling a treatment object retained at a prescribed temperature by supplying mist-like coolant, to a target temperature near to and higher than a first transformation point at which a structure of the treatment object begins to be transformed into a prescribed structure; a second step, following the first step, of retaining the treatment object for a prescribed time in a state where supply of mist-like coolant is stopped; and a third step, following the second step, of cooling the treatment object to a temperature lower than or equal to the first transformation point. According to the present invention, it is possible to provide a heat treatment method capable of suppressing irregularity and deformation in the structure of the treatment object.

The heat treatment method of the present invention includes: a first step of mist cooling a treatment object retained at a prescribed temperature by supplying mist-like coolant, to a target temperature near to and higher than a first transformation point at which a structure of the treatment object begins to be transformed into a prescribed structure; a second step, following the first step, of retaining the treatment object for a prescribed time in a state where supply of mist-like coolant is stopped; and a third step, following the second step, of cooling the treatment object to a temperature lower than or equal to the first transformation point. According to the present invention, it is possible to provide a heat treatment method capable of suppressing irregularity and deformation in the structure of the treatment object.

A shell (10) acts as a transporting shoe for steel ingots, which are pushed through a preferably tubular induction furnace for inductive heating for the purpose of producing seamless tubes by the extrusion process. The shell (10) is formed in such a way that it partially reaches around the contour of the steel ingot to be heated. The shell is provided at one end leading in the pushing-through direction or transporting direction, with a shoulder (12), which extends at an angle to the transporting direction, against which the steel ingot rests in such a way that the pushed-through steel ingot takes the shell (10) along with it. A method for inductively heating steel ingots uses a shell (10) as described.

A shell (10) acts as a transporting shoe for steel ingots, which are pushed through a preferably tubular induction furnace for inductive heating for the purpose of producing seamless tubes by the extrusion process. The shell (10) is formed in such a way that it partially reaches around the contour of the steel ingot to be heated. The shell is provided at one end leading in the pushing-through direction or transporting direction, with a shoulder (12), which extends at an angle to the transporting direction, against which the steel ingot rests in such a way that the pushed-through steel ingot takes the shell (10) along with it. A method for inductively heating steel ingots uses a shell (10) as described.