JPH0664094U - Electric heating furnace with separate heating chamber - Google Patents

Abstract

(57) [Summary] [Purpose] In a firing furnace for ceramics, etc., volatile matter emitted from the processed material deteriorates the heating element in a short time, so the heating element and volatile gas do not come into direct contact as a method of extending the life of the heating element. Provide a furnace structure. [Structure] In a firing furnace for ceramics or the like, a heating element chamber is provided with ceiling partition bricks so that the heating element mounted in the upper part of the furnace does not come into direct contact with the volatile matter generated from the processed material.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a furnace structure of a continuous electric furnace for firing ceramics and the like.

[0002]

[Prior art]

 In recent years, application development of fine ceramics has progressed, and sintered ceramics have been used for members such as electronic parts and mechanical parts. After firing such a ceramics sintered body, a firing process is performed. For example, in the case of firing electronic parts, it is common to perform firing in a large amount and in a continuous electric furnace to reduce the cost. However, when firing ceramic mix, not only the firing temperature is high, but there are various volatiles from the binder for molding and the treated product itself, which significantly shortened the life of the resistance heating element.

[0003]

[Problems to be solved by the device]

 A conventional continuous electric furnace is equipped with resistance heating elements at the top and bottom of the furnace, and pushes the base plate on which the material to be processed is pushed with a pusher to perform a continuous baking process. The furnace body is divided into pre-tropical zone, warming zone, holding zone and cooling zone. The resistance heating elements are arranged in the upper and lower parts of the furnace, but the resistance heating element chamber at the bottom of the furnace is partitioned by rail bricks and hearth floor plates, while the resistance heating element at the top of the furnace is the same as the treated product inside the furnace. Therefore, it was directly exposed to volatile substances such as alkali which are harmful to the resistance heating element, and caused a chemical reaction with the material of the resistance heating element to shorten the life of the resistance heating element. The short life of the heating element deteriorates the yield of treated products and raises the firing cost, which is a serious problem. As a method of solving this problem, a muffle made of a refractory material was put in a furnace and fired in the muffle so that harmful volatiles did not come into contact with the resistance heating element. This method is certainly effective, but there is a limit to the size of the muffle. For example, when a large amount of material is to be fired in a furnace whose furnace width exceeds 800 mm, the heating element chamber cannot be separated. It was unsuitable. Furthermore, since the muffle is composed of multiple refractory materials, there is a risk that harmful gas may leak from the seams in some cases.

[0004]

[Means for Solving the Problems]

 The present invention provides an unprecedented furnace structure in order to solve these problems. That is, in a continuous firing furnace that fires ceramics, etc., the chamber through which the processed product passes and the heating element chamber are partitioned by refractory bricks, and the atmosphere gas is introduced into the partitioned heating element chamber to create a gas in the heating element chamber. It is characterized by making the pressure higher than others. The atmosphere gas introduced into the heating element chamber may be any gas that protects the resistance heating element, and the gas pressure may be such that the volatile matter of the processed material does not enter the heating element chamber.

[0005]

[Action]

 The electric furnace of the present invention will be described with reference to FIG. The furnace chamber is composed of side wall bricks 6, ceiling partition bricks 4 and hearth bricks 8, and resistance heating elements 3 are attached above and below the furnace chamber. The resistance heating element 3 in the upper part of the furnace is placed in a heating element chamber composed of a ceiling brick 5 and a ceiling partition brick 4. Further, a resistance heating element chamber is also formed under the hearth brick 8. The sheath 1 containing the processed product is loaded on the base plate 2 and continuously passes through the furnace chamber by the pusher. Atmospheric gas introduction pipes 9 are attached to the upper and lower resistance heating chambers from the outside of the furnace to increase the internal pressure of the heating chamber. The pillar pillars at the bottom of the furnace have holes 11 for passing atmospheric gas. The atmospheric gas enters the upper and lower heating element chambers through the inlet pipe 9, is introduced into the furnace chamber through the gap between the ceiling partition bricks 4 and the hearth bricks 8, and is discharged from the exhaust stack 10 together with the volatile matter from the treated material. It is discharged outside the furnace.

[0006]

【Example】

 The present invention will be described in detail based on embodiments.

(Example) In order to investigate the effect of the present invention, an electric furnace of the present invention in which the upper part of the temperature rising zone was modified was manufactured. The electric furnace of the present invention has a preheating zone, a temperature rising zone, a holding zone, and a cooling zone, and is continuously fired by a pusher. The silicon carbide heating elements (diameter x heating portion length x end length: 25 mm × 850 mm × 400 mm) was mounted. Among these, the temperature rising zone was 24 KW / 8 lines for the upper circuit and 20 KW / 8 lines for the lower circuit, and the furnace temperature was set to 600 ° C. Further, air was introduced into the heating element chamber as an atmospheric gas at 50 liters / min. The maximum temperature in the furnace of this furnace was set to 1350 ° C and the transfer speed was 1470 mm / h, and 5 rows and 2 rows of sheath (337 x 225 x 60) containing ceramic molded products as the processed products were placed on the base plate. It was conveyed by a pusher and fired continuously. Table 1 shows the life expectancy of the heating element and the amount of baking treatment per hour, which was found as a result.

(Comparative Example) A conventional electric furnace, that is, an electric furnace having a structure in which the upper heating element in the temperature rising zone in the furnace is in the same furnace chamber as the processed material Ceramics were continuously fired at an inner maximum temperature of 1350 ° C. and a conveying speed of 1450 mm / h. Table 1 shows the average life of the heating element and the amount of baking treatment per hour, which were found in the baking test for 12 months. As a result, in the conventional electric furnace, the silicon carbide heating element has reached the end of its life in a short time due to water vaporized from the processed material, alkali vapor, fluoride, etc., and has been replaced. In addition, the bricks that make up the furnace chamber deteriorated, and it was necessary to stop the furnace and replace the bricks. On the other hand, in the electric furnace of the present invention, the upper heating element was inserted into the heating element chamber so as not to come into contact with the volatile gas, so it could be used for about 7,000 hours. Furthermore, there was little damage to the furnace room bricks, and there was no need to repair the furnace or replace the bricks, which was good.

[0009]

[0010]

[Effect of device]

 As is clear from the examples, when the electric furnace of the present invention is used, the life of the resistance heating element is significantly extended, which is incomparable with that of the conventional electric furnace. It is expected that the yield of treated products will be dramatically improved and that the product cost will be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electric furnace showing a heating element chamber separation type structure of the present invention.

FIG. 2 is a cross-sectional view of an electric furnace showing a conventional furnace structure.

[Explanation of symbols] 1 Saya 2 plate 3 Silicon carbide heating element 4 Ceiling partition brick 5 Ceiling brick 6 Side wall 7 Bottom brick 8 Hearth floor brick 9 Atmosphere gas introduction pipe 10 Exhaust cylinder 11 Hole for passing atmospheric gas

Claims (1)

[Scope of utility model registration request] 1. In a continuous firing furnace for firing ceramics or the like, a chamber through which a processed product passes and a heating element chamber are partitioned by refractory bricks, and an atmosphere gas is introduced into the partitioned heating element chamber to generate a heating element. Electric furnace with separated heating element chamber, characterized in that the gas pressure in the chamber is higher than others.