JPH067038B2 - Heavy-duty insulated hearth of industrial furnace - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heavy-duty adiabatic hearth of an industrial furnace suitable for heat treatment of heavy objects.

[Prior Art] When annealing a coiled thin steel sheet in a box-type annealing furnace, there are two types of coil of the thin steel sheet: a tight coil wound without a gap and an open coil with a gap.

The tight coil steel plate can handle the coil as one steel ingot, but the open coil steel plate has a low rigidity as a coil, so to prevent deformation during heating, load the coil on the hearth. Sufficient flatness is required for the surface. In addition, since the hearth is required to have a function of withstanding a coil load at high temperatures, heat-resistant steel ribs mainly made of stainless steel have been conventionally used as a hearth filled with a heat insulating material. There is. In such a conventional hearth, the space formed between the ribs is filled with a heat insulating material to reduce the heat dissipation from the hearth, and to reduce the cross-sectional area of the ribs to the hearth as much as possible. I try to reduce the heat.

Although many stainless steel materials are used as the rib material, and they are subjected to a large load under a high temperature of about 800 ° C, creep deformation of the rib material cannot be avoided. In order to reduce the creep deformation, it is necessary to increase the rib shape so as to reduce the load on the rib material, but increasing the rib shape increases heat conduction to the hearth, which is against energy saving. .

Moreover, bricks are laid as the hearth used in the past,
There is one that has fireproof insulation and can withstand the load. However, the brick is a small piece for the entire hearth area,
In addition, there are generally tolerances in shape and dimensions. Therefore, laying bricks to make a hearth satisfying the required flatness requires a great deal of labor. When performing heat treatment in a box-type annealing furnace, heating and cooling are repeated in the same furnace, and therefore, it is preferable that the hearth constituting the furnace has a smaller heat storage amount. As the bricks laid on the hearth, refractory bricks with relatively high density and thermal conductivity are used because of their limited heat resistance. For this reason, the amount of heat stored in the hearth and discharged and the amount of heat passing through are large, which causes a decrease in thermal efficiency.

[Object of the Invention] The present invention is excellent in heat insulating property at low material cost and operating cost,
An object of the present invention is to provide a heavy-duty adiabatic hearth of an industrial furnace that can easily secure the flatness of the upper surface.

[Structure of the Invention] The present invention forms a packed layer of fire-resistant heat-insulating powdery particles in which the lower layer particles are coarse particles and the upper layer particles are small particles in the hearth, and the non-heat treated material is formed on the upper surface of the upper layer particles. A pedestal can be placed, and a fireproof and heat-insulating cloth is interposed between the upper layer and the lower layer.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a box-shaped furnace 1 as an example of an industrial furnace. The box-shaped furnace 1 has a furnace shell made of a steel plate and a reinforcing steel material in a rectangular parallelepiped shape. The hearth 2 has a rectangular floor, and a door 3 is attached to the front of the hearth 2 so that the door 3 can be opened and closed to put in and take out a thin steel plate coil to be heat-treated.

As shown in the enlarged vertical cross-sectional view of FIG. 2, the hearth 2 has a hearth steel plate 4 at the bottom, and the hearth steel plate 4 has a partition formed on the upper surface of the hearth steel plate 4 in a grid pattern of about 1 m square. 5 are arranged.
The height of the partition 5 is smaller than the depth of the filling layer, which will be described below, and is a height that does not project to the surface of the filling layer.

A plate-shaped heat insulating plate 6 having a high heat insulating property is laid on the upper surface of the hearth steel plate 4. The heat insulating plate 6 is intended to improve the heat insulating performance of the entire hearth 2. The heat insulating plate 6 needs strength because the load from the upper surface is transmitted, but heat resistance is not required.

On the upper surface of the heat insulating plate 6, a layer filled with coarse particles 7 having a relatively large particle size and having a fire resistant heat insulating property is formed. As the coarse particles 7, it is possible to use bricks that are crushed to have a particle shape that is close to a spherical shape without an acute angle. In order to reduce the change in the layer thickness between the initial filling of the coarse particles 7 and the high temperature load, a brick with crushed parts with an acute angle part may be broken and the layer may be reduced. It is desirable that the shape be close to a spherical shape without any.

On the upper surface of the layer of coarse particles 7, a fireproof and heat-insulating cloth 8 such as asbestos cloth is laid, and a layer of small particles 9 of a fireproof substance is further filled thereon. As described above, the layer thickness of the small particles 9 is determined on the upper surface of the small particles 9 so that the partition 5 partitioning the hearth 2 does not project. When a ruler-shaped object is passed through the upper surface of the small particles 9, the upper surface of the small particles 9 becomes a highly precise horizontal surface, which is suitable for mounting the coil receiving base 10.

The fireproof heat insulating cloth 8 is for preventing the small particles 9 in the upper layer from entering the gaps between the coarse particles 7.

When the load on the hearth 2 is locally extremely biased, the load on the strength of the lower packing layer is reduced (which generally improves the heat insulating property), and the coarse particles 7 and the small particles 9 as the filler are used. In order to facilitate the selection of, a pillar made of refractory material may be provided under an unbalanced load. Since the pillars are minute compared to the area of the entire hearth, the heat insulation is not impaired as a whole.

[Effect of the Invention] The heat insulation of the industrial furnace is improved, it is easy to secure the flatness of the upper surface of the hearth, and the bulk density of the packed bed is smaller than that of the conventional brick-laid hearth, so the heat storage amount is higher. There is less, the energy-saving effect as a furnace is large, and since the fire-resistant heat-insulating cloth is interposed between the particles of the upper layer of the small particles and the particles of the lower layer of the coarse particles, the particles of the small particles are difficult to move, and therefore, It is possible to maintain the flatness of the upper surface of the hearth much better than in the case where the whole packed bed is formed of a single layer of coarse particles.

[Brief description of drawings]

FIG. 1 is a perspective view of a box-type furnace which is an example of an industrial furnace, and FIG. 2 is a longitudinal sectional view of an embodiment of the present invention. In the figure, 1 indicates a box furnace, 2 indicates a hearth, 7 indicates coarse particles, and 9 indicates small particles.

Claims (1)

[Claims] 1. A packed bed of refractory heat-insulating powder particles in which the lower layer particles are coarse particles and the upper layer particles are small particles is formed on the hearth, and a heat treatment target pedestal is mounted on the upper surface of the upper layer particles. A heavy-duty heat-insulating hearth of an industrial furnace, characterized in that a fire-resistant heat-insulating cloth is interposed between the upper layer and the lower layer.