WO2008065703A1

WO2008065703A1 - Electrical heating unit for heat treatment oven and heat treatment oven

Info

Publication number: WO2008065703A1
Application number: PCT/JP2006/323609
Authority: WO
Inventors: Susumu Uemori
Original assignee: Koyo Thermo Systems Co., Ltd.
Priority date: 2006-11-27
Filing date: 2006-11-27
Publication date: 2008-06-05

Abstract

An electrical heating unit (10) for heat treatment ovens which comprises: a base material (1) which is a ceramic fiber molding comprising alumina and silica; and a coating layer (2) formed by applying a coating material comprising a base ingredient comprising water and a water-soluble aluminum phosphate and a pigment comprising silicon carbide to that surface of the base material (1) which serves as an oven-wall inner side and then drying the coating material. Since the aluminum phosphate contained in the coating layer (2) has a high affinity for the alumina as a component of the base material (1), the coating layer (2) formed on the surface of the base material (1) is adherent thereto at high bond strength. The surface of the base material (1) is hence prevented from generating dust in the oven over long.

Description

Specification

Electric heating unit for heat treatment furnace and heat treatment furnace

Technical field

The present invention relates to a heat treatment furnace heat insulating material used as a furnace wall of a heat treatment furnace such as a firing furnace, an electric heating unit for a heat treatment furnace in which a heating element is embedded in the heat insulating material, and the heat insulating material. It relates to the heat treatment furnace used.

Background art

[0002] A heat insulating material made of a ceramic fiber having a low cost and a low thermal conductivity is used for a furnace wall of a heat treatment furnace such as a firing furnace. Thermal insulation made of ceramic fiber generates a lot of dust. For this reason, for example, when cleanliness is required as in a heat treatment furnace for electronic parts, a heat-resistant glass ceramic plate is placed inside the furnace wall, and the heat insulating material is exposed in the space where the workpiece is transported. (For example, see Patent Document 1.) ₀

[0003] However, if the entire surface of the space in which the workpiece is transported in the heat treatment furnace is partitioned by a heat-resistant glass ceramic plate, the equipment cost increases. In addition, the heat-resistant glass-ceramic plate is complicated to be easily damaged due to repeated temperature rise and fall or impact.

[0004] Therefore, there is a demand for low dust generation of a ceramic fiber heat insulating material that does not require a heat-resistant glass ceramic plate. Therefore, the surface of the insulation ceramic fiber, powdered refractory materials 60 to 90 weight ^_0/0, 5-30% inorganic binder, and a heat-resistant coating layer consists of thickener mosquitoes also coatings There is a method of forming (see, for example, Patent Document 2) ₀

[0005] In addition, a dense SiO 2 made of the same material as the ceramic fiber insulation is introduced from the surface of the insulation.

2

A method of infiltrating the sewage is also proposed.

Patent Document 1: Japanese Patent Laid-Open No. 5-330836

Patent Document 2: Japanese Patent Laid-Open No. 2003-192472

Disclosure of the invention

Problems to be solved by the invention

[0006] In the method disclosed in Patent Document 2, the surface of the heat insulating material is completely covered with the heat-resistant coating layer, and at first glance, it is excellent in low dust generation. However, the heat-resistant coating layer has a weak bond with the surface of the heat insulating material. Due to the difference in expansion coefficient from the heat insulating material, it is difficult to maintain low dust generation over a long period of time when cracking due to thermal stress is likely to occur when heating and cooling are repeated.

[0007] Further, in the method of infiltrating SiO from the surface of the heat insulating material, it penetrates into the heat insulating material.

2

Therefore, the film does not crack due to thermal stress, but the surface of the heat insulating material cannot be reliably covered, so it is impossible to completely prevent dust generation!

[0008] Furthermore, in an electric calorie heat unit for a heat treatment furnace in which a heating element is embedded in a ceramic fiber heat insulating material, it is also necessary to maintain the insulation of the heating element regardless of the furnace temperature.

[0009] An object of the present invention is to fix a ceramic fiber sheet-like heat insulating material on the surface of the ceramic fiber heat insulating material, and then form a coating layer with a coating agent having a composition having a strong bonding force with the ceramic fiber. Accordingly, an object of the present invention is to provide an electric heating unit for a heat treatment furnace and a heat treatment furnace capable of preventing the occurrence of defective insulation while maintaining the low dust generation property of the heat insulating material over a long period of time.

Means for solving the problem

The electric heating unit for a heat treatment furnace of the present invention constitutes a furnace wall of the heat treatment furnace and heats the inside of the heat treatment furnace, and includes a base material, a heating element, a sheet-like heat insulating material, and a coating layer. . The base material is a ceramic fiber molded body containing alumina and silica. The heating element is embedded near one surface in the base material and generates heat when energized. The sheet-like heat insulating material is formed by compressing a ceramic fiber containing alumina and silica and forming it into a sheet shape. The coating layer is formed by applying a coating agent comprising a base containing water and water-soluble aluminum phosphate and a pigment that is silicon carbide on the surface of the sheet-like heat insulating material and then drying.

The heat treatment furnace of the present invention is used for firing electronic components and the like, and is constituted by a furnace wall provided with a base material, a heating element, a sheet-like heat insulating material, and a coating layer. The base material is a ceramic fiber molded body containing alumina and silica. The heating element is embedded near one surface in the base material and generates heat when energized. The sheet-like heat insulating material is formed by compressing a ceramic fiber containing alumina and silica into a sheet shape. The coating layer is formed by applying a coating agent comprising a base containing water and water-soluble aluminum phosphate and a pigment that is silicon carbide on the surface of the sheet-like heat insulating material and then drying it.

[0012] After the sheet-like heat insulating material is fixed to the surface of the base material, the core containing aluminum phosphate is used. A coating layer is formed by the one-tipping agent. Aluminum phosphate is considered to have a high affinity with alumina that forms the sheet-like heat insulating material. The surface of the base material is covered with a sheet-like heat insulating material and then dried and baked, so that the coating layer is formed with a strong bonding force, and the base layer does not crack when repeated heating and cooling. Dust generation into the furnace is also prevented for a long time. In addition, the surface of the base material is coated with a black coating layer containing silicon carbide contained as a pigment, and heat generated from the heating element embedded in the base material is efficiently radiated. Furthermore, a sheet-like heat insulating material with few voids is disposed between the base material and the coating layer, and the penetration of silicon carbide, which is a good conductor at high temperatures, into the base material is prevented. Insulation failure does not occur in the heating element embedded in the base material.

The invention's effect

[0013] According to the present invention, after the sheet-like heat insulating material is fixed to the surface of the base material, the coating layer is formed by the coating agent containing aluminum phosphate, so that the coating layer is formed on the surface of the base material. Can be formed with strong bond strength. Even when the temperature rise and fall is repeated, the surface of the base material, which does not crack the coating layer, can prevent dust from entering the furnace for a long period of time. In addition, the surface of the base material can be covered with a black coating layer, and the heat generated from the heat generator embedded in the base material can be efficiently radiated. Furthermore, by placing a sheet-like heat insulating material with few voids between the base material and the coating layer, the penetration of silicon carbide, which is a good conductor at high temperatures, into the base material is prevented and embedded in the base material. Insulation failure of the heating element can be prevented. Brief Description of Drawings

FIG. 1 is a cross-sectional view showing a configuration of a heat treatment furnace of the present invention.

FIG. 2 is a partially enlarged sectional view of an electric heating unit for a heat treatment furnace according to the present invention.

FIG. 3 is a diagram showing experimental results of an example and a conventional example of an electric heating unit for a heat treatment furnace according to the present invention.

Explanation of symbols

[0015] 1 Base material

2 Coating layer

3 Heating element

4 Sheet insulation 10 Electric heating unit for heat treatment furnace

100 heat treatment furnace

103, 104 furnace wall

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a cross-sectional view showing a configuration of a heat treatment furnace 100 according to an embodiment of the present invention. For example, the heat treatment furnace 100 performs a setterless heat treatment on the glass substrate for plasma display, which is the workpiece 200. The heat treatment furnace 100 includes furnace walls 101 to 104, a conveyance roller 120, and a conveyance motor 124.

[0017] The furnace walls 101 to 104 respectively cover the left and right side surfaces, the upper surface, and the lower surface of the conveyance path through which the workpiece 20 is conveyed. The left and right side furnace walls 101 and 102 are constituted by a heat treatment furnace heat insulating material 10, and the upper and lower side furnace walls 103 and 104 are constituted by a heat treatment furnace electric heating unit 20. At least in the heating region, the furnace walls 103 and 104 are provided with a heater (not shown) on the inner surface.

The transport roller 120 is provided at each of a plurality of positions along the transport path. Both ends of the transport roller 120 pass through the furnace walls 101 and 102, and are rotatably supported by bearings 121 and 122 outside the furnace on the left side and right side. A sprocket 123 is fixed to the conveying roller 120 at the end exposed to the outside of the furnace on the right side surface side. The rotation of the transport motor 124 is transmitted to the sprocket 123 via the chain 125.

FIG. 2 is a partially enlarged cross-sectional view of the electric heating unit 10 for a heat treatment furnace of the present invention. The electric heating unit 10 for the heat treatment furnace is used as the upper and lower furnace walls 103 and 104 in the heat treatment furnace 100. The electric heating unit 10 for a heat treatment furnace includes a base material coating layer 2, a heating element 3, and a sheet-like heat insulating material 4. Base material 1 is a ceramic fiber molded body containing alumina and silica, and is generally used as a material for furnace walls 101-104. The base material 1 is formed by a known method such as a vacuum forming method in accordance with the size of the furnace walls 103 and 104.

[0020] Although the coil-shaped one is illustrated as the heating element 3, not limited to this, for example, a wave-shaped one can be suitably used.

[0021] The sheet-like heat insulating material 4 is formed by compressing a ceramic fiber containing alumina and silica. As an example, a lmm-thick one is commercially available. The sheet-like heat insulating material 4 has less voids than the base material 1 due to the high degree of compression of the ceramic fiber. The sheet-like heat insulating material 4 is fixed to a surface that becomes at least the inner surface of the furnace when used as the furnace walls 101 and 102 in the base material 1. For example, when the base material 1 is manufactured by a vacuum forming method, the sheet is first placed on a suction screen of the mold (mold), for example, by sticking with a ceramic fiber coating cement diluted with an inorganic binder. It is possible to use a method in which the heat insulating material 4 is set, and then the heating element 3 is positioned and set thereon, and vacuum forming is integrally performed with the base material 1. In any case, the sheet-like heat insulating material 4 is firmly fixed to the base material 1 by the chemical bonding force of the inorganic binder through the processes of drying and firing.

[0022] The coating layer 2 is formed by applying a liquid coating agent kneaded with silicon carbide as a pigment in a base containing water and water-soluble aluminum phosphate to the surface of the base material 1 and then drying it. Has been. The coating agent contains 50% of the base and the pigment. The base contains water and aluminum phosphate as main components in a weight ratio of about 2: 1, and can also contain small amounts of amorphous silica, alcohol, nitric acid, aluminum hydroxide, and the like. However, the composition is not limited to this, and can be changed as appropriate.

[0023] The coating layer 2 is applied with a coating agent on the surface of the sheet-like heat insulating material 4, and then dried and fired at an appropriate temperature of 300 ° C to 600 ° C for about 3 hours. ~ 1. Made to Omm thickness. The covering layer 2 may be formed on the entire surface of the base material 1 or on two or more surfaces.

[0024] It is considered that the aluminum phosphate contained in the coating layer 2 composed of the coating agent has a high affinity with the alumina contained in the sheet-like heat insulating material 4. For this reason, the coating layer 2 is formed on the surface of the sheet-like heat insulating material 4 with a strong bonding force.

[0025] In the furnace of the heat treatment furnace 100, the temperature rise and fall is repeated between the normal temperature and the heat treatment temperature of the workpiece. The sheet-like heat insulating material 4 and the coating layer 2 made of different materials have different expansion coefficients. The force by which thermal stress acts on the interface between the sheet-like insulation 4 and the coating layer 2 due to the temperature rise and fall in the furnace The bonding force of the coating layer 2 to the surface of the sheet-like insulation 4 is strong. There is no breakage.

[0026] Base material 1 is formed by molding a ceramic fiber containing alumina and silica. There are many fine voids. When the coating agent is applied directly to the surface of the base material 1, the coating agent penetrates into the base material 1. Silicon carbide contained in the coating agent becomes a good conductor at high temperatures. The heating element 3 embedded in the base material 1 may cause insulation failure due to the coating agent silicon carbide that has penetrated into the base material 1.

[0027] Therefore, by applying the coating agent after fixing the sheet-like heat insulating material 4 to the surface of the base material 1, the penetration of the coating agent into the base material 1 is prevented, and the insulation failure of the heating element 3 is prevented. It is preventing.

FIG. 3 is a diagram showing experimental results of examples and comparative examples of the electric heating unit 10 for heat treatment furnace. Furnace walls 103 and 104 are made from the base material 1 in which the heating element 3 is embedded, and in the embodiment of the electric heating unit 10 for heat treatment furnace, the sheet-like heat insulating material 4 is fixed to the inner side surface, and then the coating layer 12 is formed. The sheet-like heat insulating material 4 was not fixed to the inner side surface of the comparative example, and the coating layer 12 was not formed, but was strong. These examples and comparative examples were individually made as heat treatment furnaces with the upper and lower furnace walls 103, 104, the furnace temperature was controlled at 700 ° C, and 150 liters of air was introduced into the furnace per minute, The number of dust was measured.

[0029] As a result, as shown in FIG. 3, in the implementation f row, it is 5.0 / ζ πι, 2.0 / ζ πι, 1.0 / ζ πι, 0.

Any dust of 0.3 / z m was slightly detected, but in the comparative example, the number of dust was too large to be measured. From this result, it can be seen that the coating layer 2 realizes the low dust generation property of the electric heating unit 10 for the heat treatment furnace.

[0030] By using the electric heating unit 10 for the heat treatment furnace as the furnace walls 103 and 104 on the upper and lower surfaces of the heat treatment furnace 100, a furnace that does not generate dust in the base material 1 even when the temperature in the furnace is repeatedly raised and lowered Dust is not scattered inside. Even when cleanliness is required, such as when heat treating electronic parts, the heat treatment furnace 100 can be manufactured at low cost without the need to partition the space in the furnace where the workpiece is transported by expensive heat-resistant glass ceramic plates. . In addition, it is not necessary to replace the heat-resistant glass ceramic plate, and maintenance can be simplified.

[0031] The coating layer 2 exhibits a black color due to silicon carbide contained as a pigment in the coating agent. For this reason, it has excellent heat dissipation, can prevent abnormal heating of the heating element 13, and can efficiently heat the inside of the furnace to reduce power consumption.

Industrial applicability The present invention can be used to prevent dust generation from the furnace wall in a heat treatment furnace such as a firing furnace.

Claims

The scope of the claims

[1] In a heating unit for a heat treatment furnace in which a heating element is embedded in the vicinity of one surface of a base material of a ceramic fiber containing alumina and silica to constitute a furnace wall of the heat treatment furnace and heat the inside of the heat treatment furnace.

After fixing a sheet-like heat insulating material made of ceramic fino at least on the furnace inner surface of the furnace wall of the base material, from a base containing water and water-soluble aluminum phosphate and a pigment that is silicon carbide A heating unit for a heat treatment furnace, wherein a coating layer is formed by applying a coating agent and then drying.

[2] In a heat treatment furnace having a furnace wall with a heating element embedded in the vicinity of one surface in a ceramic fiber base material containing alumina and silica!

After a sheet-like heat insulating material made of ceramic fino is pasted on at least the inner surface of the furnace wall of the base material, a coating made of a base containing water and water-soluble aluminum phosphate and a pigment made of silicon carbide A heat treatment furnace in which a coating layer is formed by applying an agent and then drying.