JPH0616896Y2 - Heating furnace equipment - Google Patents

Description

[Detailed description of the device]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating furnace device used for manufacturing, for example, a base material for optical fibers or quartz glass.

[Prior art]

BACKGROUND ART A heating furnace is used as an apparatus for converting a porous member on which glass particles are deposited into a transparent glass in a manufacturing process of an optical fiber preform and quartz glass. FIG. 4 shows an example of the heating furnace. In this heating furnace, a heater 4 made of carbon or silicon carbide is arranged inside a furnace body 1 composed of a body 2 made of stainless steel and lids 3 at both ends thereof. A heat insulating material 5 is arranged around the heater 4. Cooling jackets 6 are provided on the outer sides of the body 2 and the lid 3, respectively, and a cooling water inlet / outlet 7 is provided on an outer wall 6a thereof.
Is attached. On the side surface of the furnace body 1, a temperature measuring port 8 penetrating the body 2 and the cooling jacket 6, a peep window 9 and the like are attached. The body 2 and the lid 3 have a welded structure. For example, the body 2 and the flange 2a at the end of the body 2 are welded at a welded portion 10 inside the furnace body 1. Further, the ends of the temperature measuring port 8 and the observation window 9 attached to the side surface of the furnace body 1 are also welded inside the body 2. This device is used as follows. For example, a porous member having glass particles deposited therein is placed in the center of the heating furnace, and the heater 4 is energized to raise the temperature. The temperature of the heater 4 is 1400-1600 ℃
Therefore, the body 2 and the lid 3 are cooled by pouring water through the cooling jacket 6.

[Problems to be solved by the device]

However, in this heating furnace device, stress corrosion cracking (SCC) may occur in the welded portion 10. This is a form of damage in which when a metal material is stressed in a corrosive environment, pitting or crevice corrosion is a starting point to generate a crack, which propagates through a grain boundary or inside the grain to cause a crack. SCC is particularly likely to occur in an environment containing a cyclized product. In the case of this heating furnace apparatus, thermal stress and chlorine ions in cooling water cause stress corrosion cracking. FIG. 3 shows the SCC region in the relationship between the temperature and the chloride ion concentration of the stainless metal material (JIS SUS316). Since tap water or industrial water used as cooling water has a chlorine ion concentration of 6 to 15 ppm, SUS316 is used as a metal material.
When using, the temperature of the welded part 10 is 100
It can be seen that when the temperature exceeds ℃, it enters the SCC region. In the case of this heating furnace apparatus, the temperature of the outer surface of the furnace body 1 is cooled to 100 ° C. or lower. However, the furnace body 1 in which the welded portion 10 is located
The temperature of the inner wall reaches 120 to 250 ° C. even though the heat insulating material 5 is arranged around the heater 4 and the body 2 and the lid 3 are cooled by the cooling jacket 6. The present invention has been made to solve the above problems,
An object of the present invention is to provide a heating furnace device in which stress corrosion cracking does not occur.

[Means for Solving the Problems]

A heating furnace apparatus of the present invention made to achieve the above object will be described with reference to FIG. 1 corresponding to an embodiment. As shown in the figure, the heating furnace apparatus of the present invention comprises a furnace body 1, a heat insulating material surrounding the heater 4 and the heater 5 arranged inside the furnace body 1, and a cooling jacket provided outside the furnace body 1. 6 and the portion 10 joined by welding is located outside the cooling jacket 6.

【Example】

Embodiments of the present invention will be described below. FIG. 1 is a vertical sectional view of an embodiment of a heating furnace apparatus to which the present invention is applied. A furnace body 1 of this heating furnace device is composed of a cylindrical body 2 and lids 3 on the upper and lower surfaces thereof. A heater 4 is provided in the center of the body 2, and a heat insulating material 5 is arranged around the heater 4. A cooling jacket 6 is provided outside the body 2 and the lid 3. Further, a temperature measuring port 8 penetrating the body 2 and the cooling jacket 6 and a viewing window 9 are attached to the side surface of the furnace body 1. The body 2 and lid 3 of this heating furnace are made by cutting a relatively large metal ingot made of SUS316. A flange 2a is integrally formed on the end of the body 2, and a projection 2b is integrally formed around the opening on the side surface (see FIG. 2). The outer wall 6a of the cooling jacket 6, the temperature measuring port 8 and the like are welded by the flange 2a and the protrusion 2b. All of these welded portions 10 are located outside the cooling jacket 6, and there is no welded portion on the inner wall surface of the furnace body 1, that is, in the vicinity of the heater 4. This device is used as follows. The workpiece is placed on the center of the furnace body 1, and the heater 4 is energized to raise the temperature to 1400 to 1600 ° C. At the same time, cooling water is flown through the cooling jacket 6 to cool the furnace body 1. At this time, the temperature on the inner surface side of the body portion 2 and the lid body 3 reaches 120 to 250 ° C., but since each welding portion 10 is located outside the cooling jacket 6 and is away from the high temperature heater 4, the welding portion 10 The temperature is kept below 100 ° C. Therefore, even if the cooling water of the cooling jacket 6 contains chlorine ions of about 6 to 15 ppm, the welded portion 10 of SUS316 does not enter the SCC region and cracks do not occur. The welding structure of the heating furnace apparatus of the present invention can be applied to a high temperature apparatus such as a drawing furnace other than the heating furnace.

[Function and effect of the device]

As described in detail above, in the heating furnace device of the present invention, the welding portion of each component is located outside the cooling jacket,
Separated from the hot part of the furnace. Therefore, the temperature of the welded portion does not enter the stress corrosion cracking region, and stress corrosion cracking due to thermal stress or chlorine ions in the cooling water does not occur.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a heating furnace apparatus to which the present invention is applied, and FIG. 2 is a schematic vertical sectional view showing a welding portion thereof.
FIG. 3 is a diagram showing a stress corrosion cracking region, and FIG. 4 is a partial cross-sectional view showing a conventional heating furnace apparatus .. 2 Body ... 2a ... Flange 2b ... Projection, 3 ... Lid 4 ... Heater, 5 ... Insulation material 6 ... Cooling jacket, 6a ... Outer wall 7 ... Cooling water inlet / outlet, 8 ... Temperature measurement port 9 ... Viewing window, 10 ... Welded part

Claims (3)

[Scope of utility model registration request] 1. A furnace body, a heater disposed inside the furnace body, a heat insulating material surrounding the heater, and a cooling jacket provided outside the furnace body, and a portion joined by welding is a cooling jacket. A heating furnace device which is located outside. 2. The heating furnace apparatus according to claim 1, wherein parts cooled to 100 ° C. or less by the cooling jacket are joined by welding. 3. The heating furnace apparatus according to claim 1, wherein the chamber, the flange and the portion joined by welding are formed of stainless steel.