JPS62270732A - Heating furnace - Google Patents

Abstract

PURPOSE:To hermetically maintain the inside of a reaction vessel so as to improve the thermal efficiency of a heating furnace and to obviate the generation of strain by thermal stress by providing a heat resistant sealing material to the outside of a through-hole formed to a receiving base and imposing the reaction vessel on such sealing material. CONSTITUTION:A shell 2 of the heating furnace 1 and the reaction vessel of the type opened in the lower part are supported by the receiving base 25. The receiving base 25 is provided with the recess 27 formed in the core part and is integrally formed with a flange 29 on the outside periphery thereof. The refractory blocks 50, 51, 52 made of graphite, etc., are fitted into such recess 27 of the receiving base 25. The refractory block 50 of the upper inside part is formed of the heat resistant sealing material and an annular groove 55 is formed on the top surface side thereof. The reaction vessel 3 is imposed in the groove 55. There is no need for cooling the sealing part and the generation of the large thermal strain is obviated according to the above-mentioned constitution. The condensation of the vapor of a low melting metal onto the sealing part is obviated as well.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a heating furnace suitable for use in the recovery treatment of cemented carbide.

[Prior art] Cemented carbide scrap such as worn cutting tool tips is once crushed and then reused as a raw material for powder metallurgy, but this scrap is made of cobalt matrix with carbides such as tungsten carbide firmly bound together. Therefore, it is difficult to crush it as it is, and it is necessary to perform embrittlement treatment prior to crushing.

A conventional method for this embrittlement treatment, as shown in Japanese Patent Application Laid-open No. 58-84932, uses a treatment device equipped with a heating hood as an outer shell and a container as a reaction vessel. A method in which a low-melting point metal, such as zinc, which has a melting point lower than that of the cemented carbide matrix, is reacted at high temperature in a container with a high-pressure inert gas atmosphere to melt the matrix, and then the low-melting point metal is evaporated by reducing the pressure. be. This treatment turns the cemented carbide chip into a porous body that is extremely easy to break.

[Problems to be Solved by the Invention] The conventional treatment equipment used for the embrittlement treatment of the cemented carbide described above has an annular flange that projects outwardly formed integrally at the lower end of a container that is a reaction vessel. The inside of the container was kept airtight by fixing the annular flange part with a sealing material in between, but the upper part of the container was heated to a high temperature (reaction temperature) and the lower part (sealing part) was cooled for sealing. However, there were problems in that the seal part deformed due to thermal stress and leakage occurred at the seal part due to creep. Another problem was that zinc vapor that entered the cooled seal part solidified and eroded the container wall.

[Means for Solving the Problems] In order to solve the above problems, the present invention employs the following configuration.

That is, the heating furnace according to the present invention includes a reaction vessel formed as a hollow body with an opening on one side, an outer shell provided with a heater for heating the reaction vessel and disposed outside the reaction vessel, and the reaction vessel and the outer shell. A heating furnace is provided with a cradle for supporting a shell, and the pedestal is provided with a through hole leading to the inside of a reaction vessel, and the reaction vessel is arranged so that the opening thereof faces downward. It is characterized in that the inside is kept airtight from the outside by being placed on a heat-resistant sealing material provided on the outside of the hole.

[Operation] A material to be heated, such as carbide scrap, is placed in a reaction container placed on a sealing material with the opening facing downward, and heated by a heater in an outer shell that can be covered on the outside.

Since the interior of the reaction container is kept airtight by the sealing material, the object to be heated can be heated in an atmosphere of an inert gas or the like or in a vacuum.

Since the reaction vessel is simply placed on the sealing material, there is no need to specifically cool the sealing part. Therefore, unlike conventional devices, distortion due to thermal stress does not occur, and low melting point metal vapor does not adhere to the seal portion.

[Example] The figure shows one example of the present invention, and this heating furnace 1
comprises a bell-shaped outer shell 2 and a reaction vessel 3. outer shell 2
The first large-sized material (rock wool) is placed inside the metal outer skin 5.
A layer 6 and a second refractory (ceramic wool) layer 7 are provided,
Its inner surface is lined with a sheet-like refractory material (wet felt) 8 that is free of fluff. These refractories are held in the shell by pins 9, .

On the inner surface of the outer shell 2, chrome heaters bent in a zigzag manner up and down are provided in multiple stages (six stages in the illustrated example) along the circumferential direction. The heaters 10 are provided independently for each stage, and both ends of each heater 10 are connected to a pair of terminals 12, 12. The lead rod 13 of each terminal 12 is insulated by a ceramic tube 14. By energizing these terminals 12, 12, the heaters 10 at each stage can be heated individually.

In addition, the outer shell 2 is equipped with thermometers 1 in multiple stages (5 stages in the illustrated example).
5. ... are inserted, and these thermometers 15 can measure the temperature inside the furnace at each position in the vertical direction.

At the top of the outer shell 2 there is a hanging fitting 16. ... are provided, and an outward flange 17 is provided integrally with the outer skin 5 at the lower end. This 7 flange 17 has a plurality of fasteners 19 with notches 18. ...is installed protrudingly.

The reaction vessel 3 is made of heat-resistant steel and has a bell shape that opens downward like the outer shell, and has a hanging fitting 21 at the top like the outer shell. ...is provided. Reaction vessel 3
As shown in FIG. 3, the lower end of the opening is slightly thicker, and the opening peripheral edge 23 is formed in the shape of a bullet that bulges out to have a roughly circular cross section.

Although the radius R in the figure is larger than 1/2 of the thickness of the thick walled portion 24 directly above, the lower end of the reaction vessel 3 is not formed in this way and is simply formed as shown in FIG. It may also be formed as a curved surface.

The outer shell 2 and the reaction vessel 3 are supported by a pedestal 25. The pedestal 25 has a recess 27 formed in the core thereof with a through hole 26 passing vertically therethrough, and a flange 29 is integrally formed on the outer periphery of the recess 27 . A mounting bracket 30 is attached to the outer circumference of the flange portion 29. ... are provided protrudingly, and a fixing bolt 31 is attached to this metal fitting 30 with a pin 32 so as to be freely rotatable up and down. A partitioning protrusion is provided in the middle of the recess 27 in an annular shape. In addition, legs 3 are provided on the lower surface of the pedestal 25.
3. ... is provided, and this leg 33. ... supports the pedestal 25 on the floor surface.

A connecting flange 36 is provided at the lower end of the peripheral wall 35 of the through hole 26, and an annular cooling water pipe 38 is attached near the connecting flange 36. An inlet portion 41 of a condenser 40 is connected to the connection flange 36 . The condenser 40 is formed in the shape of a hollow container, and can be divided into two members, an upper and a lower member, by a horizontal plane including an axial center line.

Seven flange 43.43 are provided at the joint between the upper and lower members, and a cooling water pipe 45 is attached so as to sandwich these seven flange 43.43. Also, inside the condenser 40, there are a plurality of cooling water pipes 46. ... are provided through the pipes, and cooling water is supplied to these cooling water pipes from a pump (not shown).

A refractory block 50.51.5 is placed in the recess 27 of the pedestal 25.
2 is fitted. As these refractories, graphite or the like can be suitably used.The refractory block 50 disposed on the inside upper part serves as a heat-resistant sealing material. The reaction container 3 is placed in the groove 55.

A funnel 57 also made of graphite is placed on the top surface of the heat-resistant sealing material 50. The lower end opening of the funnel 57 is located within the through hole 26 and faces the inlet of the condenser 40.

When recovering cemented carbide scrap using this heating furnace 1, scrap as a workpiece and zinc as a low melting point metal (or other low melting point metals that form an alloy with the cemented carbide matrix) are used. (good) is placed in a suitable tray and held in the reaction vessel 3. Graphite trays are preferably used as the trays, and these may be stacked in multiple stages.

The reaction vessel 3 is placed with its opening peripheral portion fitted into the groove 55 of the block 5o, which is a sealing material. At this time, its lower end is in close contact with the bottom surface of the groove 55 of the sealing material, and the inside and outside of the reaction container 3 are sealed at this portion. Hermetically sealed. In addition, as shown in the figure, the reaction vessel 3
If a packing material such as ceramic wool (carbon wool is also acceptable) is interposed between the lower outer circumferential surface of the groove 55 and the circumferential wall of the groove 55, the seal will be more or less complete. In this case, it is more convenient for the opening periphery 23 of the reaction vessel 3 to bulge outward as shown in FIG.

After loading the work into the reaction vessel 3, cover the outer shell 2 and tighten the fixing bolts 31. ... as a fixture 19. engages with...
It is firmly fixed to the pedestal 25 by tightening with a nut. Next, the interior of the reaction vessel 3 and the gap 60 between the reaction vessel 3 and the outer shell 2 are filled with an inert gas such as nitrogen gas or argon gas through a pipe (not shown). The pressure inside the reaction vessel 3 is preferably higher than twice the partial pressure of zinc during heating. Moreover, the pressure in the gap 60 is
Approximately 10. It is preferable to lower it by AΩ.

For this purpose, it is preferable to provide a differential gauge that can detect the difference in pressure between the inside of the reaction vessel 3 and the gap 60.

Once the furnace is filled with inert gas, the heater 10 is energized and heated to 900'C or higher. Since the heaters 10 are independently provided in a plurality of stages, the temperature distribution in the furnace can be made most preferable by controlling the amount of electricity supplied to the heaters 10.

This heating causes low melting point metals such as zinc to diffuse into the matrix and form an alloy, causing the cemented carbide scrap to expand.

After a sufficient heating time has elapsed, the pressure is reduced from the condenser 40 side to evacuate the inside of the reaction vessel.

At the same time, the pressure inside the outer shell 2 is also reduced. Due to this reduced pressure, the zinc in the reaction vessel 3 is evaporated and guided to the condenser 40, but since the condenser 40 is cooled by cooling water, the zinc vapor is condensed here and recovered as the original zinc lump. Ru. If heating is stopped after sufficient zinc has been removed, a sponge-like, porous cemented carbide block is obtained that is extremely easy to crush. If this block is crushed by a known method, it can be reused as a raw material powder for powder metallurgy.

In this heating furnace 1, the reaction vessel 3 heated to a high temperature is sealed by simply placing it on a sealing material.
There is no need to cool the sealing part, and large thermal stress does not occur. Therefore, the reaction vessel 3 is less likely to be damaged or deformed, and therefore leakage from the seal portion is less likely to occur. Moreover, since the seal part is not cooled, there is no loss due to heat transfer.
Good thermal efficiency. Since the inside of the reaction vessel is maintained above the boiling point of zinc (903° C.), corrosion due to adhesion and liquefaction does not occur.

Further, since there is no need to provide a special fixing member to the reaction vessel 3 made of heat-resistant steel, the shape can be simple and the manufacturing cost can be reduced.

[Effects of the Invention] As is clear from the above description, the heating furnace according to the present invention has excellent thermal efficiency, is resistant to distortion or damage due to thermal stress, and is free from corrosion due to adhesion of low-melting point metals. It became something.

It is clear that this heating furnace can be used for pulverizing alloys containing cobalt other than cemented carbide, and for separating and recovering various alloys and mixtures.

[Brief explanation of the drawing]

FIG. 1 is a partial front view of one embodiment of the present invention;
Figure 2 is a partially broken plan view, Figure 3,
FIG. 4 is an enlarged sectional view of essential parts in different embodiments, and FIGS. 5 and 6 are a plan view and a partially sectional front view of the pedestal. 1...Heating furnace 2...Outer shell 3...
Reaction vessel 50...Sealing material patent applicant Osaka Lead-Tin Refinery Co., Ltd. Sumitomo Electric Industries, Ltd.

Claims (1)

[Claims] (1) A reaction vessel formed as a hollow body with an opening on one side, an outer shell provided with a heater for heating the reaction vessel and placed outside the reaction vessel, and a pedestal for supporting the reaction vessel and the outer shell. The heating furnace is equipped with a heating furnace, wherein the pedestal is provided with a through hole leading to the inside of the reaction vessel, and
The reaction container is configured such that the inside thereof is kept airtight from the outside by placing the reaction container with the opening facing downward on a heat-resistant sealing material provided outside the through hole. A heating furnace featuring: