JP3235536B2 - Processing furnace and processing method for sintered hard alloy scrap - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace and a method for heat treatment of a sintered hard alloy scrap, and more particularly to a furnace for a heat treatment for facilitating pulverization for reuse of a sintered hard alloy scrap. And about the method.

[0002]

2. Description of the Related Art For example, a sintered hard alloy such as a cemented carbide is used as a throw-away tip (disposable tip) for a cutting edge of a cutting tool. The cemented carbide scrap recovered from the wear at the cutting edge of such a cutting tool is once pulverized and then reused as a powder metallurgy raw material. However, in general, cemented carbide scrap is made of cobalt as a matrix and carbide powder particles of tungsten carbide or the like are firmly bonded, and thus it is difficult to grind the scrap as it is. Therefore, in order to pulverize cemented carbide scrap, it is necessary to perform embrittlement treatment for facilitating pulverization prior to the pulverization.

FIG. 2 schematically illustrates an example of a furnace used for the embrittlement treatment of such a cemented carbide, the details of which are disclosed in JP-A-58-84932. In the processing furnace of FIG. 2, a reaction vessel 103 and a heating hood 112 that covers the reaction vessel 103 are provided on a substrate 101. Reaction vessel 10
A packing 102 is arranged between the lower end flange of the heating hood 3 and the substrate 101, and a packing 113 is similarly arranged between the lower end flange of the heating hood 112 and the lower end flange of the reaction vessel 103. You. The reaction vessel 103 and the heating hood 112 are integrated and fixed to the substrate 101 by bolts or the like.

[0004] The inner wall of the heating hood 112 is
5 coated. Insulation member 115 and reaction vessel 103
The heater 116 and the temperature sensor 143 are arranged in the space between the two, and the space can be evacuated through the port 137.

[0005] The substrate 101 has an opening at the center thereof communicating with the inside of the reaction vessel 103, and a connecting member 105 is formed continuously below the opening. Water cooling pipe 1
09 is cooled by the coupling member 10.
5 is fixed to a flange 106 at a lower end of the fifth member by a bolt or the like via a packing 107. Condenser 108 and reaction vessel 1
The interior of 03 can be evacuated via port 130 and from which an inert gas can be introduced.

In the lower part of the reaction vessel 103, the support 1
The support 118 is supported by the substrate 101 in such a manner that the opening at the center of the substrate 101 is not completely closed. That is, the ventilation inside the reaction vessel 103 and the inside of the condenser 108 is maintained through the plurality of partial recesses 119 provided in the support 118. The support 118 also includes a steam guide tube 12 integrally formed therewith.
One.

A plurality of ring groove crucibles 122 made of, for example, graphite are stacked on the support 118, and a lid 127 is put on the uppermost crucible 122. Crucible 122
, Another temperature sensor 146 is arranged.

[0008] The processing furnace shown in FIG.
7, changeover switch 147, pressure regulator 148, valve 13
5, 139, 149, vacuum pumps 136, 140, pressure gauge 132, filter 134 and check valve 142.

In the processing furnace of FIG. 2 configured as described above, a cemented carbide scrap is set in a ring groove of the crucible 122 together with a low melting point metal such as zinc (or cadmium), and Ar (or N). ₂ ) under an inert gas atmosphere such as at about 850 ° C.
At a temperature of This molten zinc alloys with the cemented carbide matrix by diffusion. At this time, the pressure in the reaction vessel 103 at the time of heating is 2 vapor pressures of zinc.
It is maintained in the range of about 1200-2000 mbar which is more than double.

Thereafter, the condenser 10 is connected through the port 130.
If the pressure inside the reactor vessel 8 and the reaction vessel 103 is reduced, zinc once alloyed with the cemented carbide matrix evaporates, leaving a sponge-like porous cemented carbide block that is easily crushed. At this time, the vaporized zinc vapor is introduced into the condenser 108 through the central opening 126 of the crucible 122, the funnel-shaped hollow chamber 118a of the support body 118, and the vapor guide tube 121, which are contained in the Ar gas. It precipitates as 129. Ar gas after the condensation of zinc vapor is passed through vent 1
19, into the reaction vessels 103 and penetrate into the crucibles 122 through the capillary gaps 128 between the stacked ring groove crucibles 122. And crucible 12
The Ar gas returned into 2 serves to transport zinc vapor again into condenser 108, and by repeating this, a sponge-like cemented carbide containing almost no zinc and easy to pulverize is obtained.

FIG. 3 schematically illustrates another example of a furnace used for embrittlement of a cemented carbide, the details of which are disclosed in Japanese Patent Application Laid-Open No. 62-270732. The processing furnace in FIG. 3 includes a bell-shaped furnace shell 202 and a bell-shaped reaction vessel 203 housed therein. Furnace shell 202
Includes a metal skin 205, a rock wool layer 206, a ceramic wool layer 207, and a sheet-like refractory 208, which are pinned by a pin 209.
Is held in. A plurality of ribbon heaters 210 are provided on the inner periphery of the furnace shell 202 along the circumferential direction thereof. These heaters 210 can be heated independently for each stage, and are connected to corresponding terminals 212. The lead bar 213 of each terminal 212 is insulated by a ceramic tube 214. Further, a plurality of thermometers 215 are inserted into the furnace shell 202 corresponding to the plurality of ribbon heaters 210.

The furnace shell 202 and the reaction vessel 203
5 supported. At the lower end of the furnace shell 202,
A flange 217 is formed integrally with the outer skin 205,
A plurality of fixing notches 219 are provided along the outer periphery of the flange. Bolts 231 that can rotate around pins 232 are fitted into these fixing notches 219, whereby the furnace shell 202 is fixed on the receiving base 225.

The pedestal 225 has a concave portion on its upper surface, in which the refractory blocks 250, 251 and 252 are arranged. The upper inner refractory block 250 serves as a heat-resistant seal and has an annular groove 255 on its upper surface.
Are formed. The bell-shaped reaction vessel 203 has an increased thickness at its lower end, and is simply placed on the heat-resistant sealing material 250 such that the lower end of the thick wall abuts against the bottom surface of the groove 255. On the heat-resistant sealing material 250,
The funnel 257 is placed.

A connection flange 236 is provided below the receiving base 225 below the funnel 257. The connection flange 236 is connected to the inlet flange 24 of the condenser 240.
1 are connected by bolts. Thereby, the inside of the reaction vessel 203 and the inside of the condenser 240 communicate in an airtight state. The condenser 240 can be split up and down along its flange 243. The condenser 240 is cooled by cooling pipes 245 along the flange 243 and by a number of cooling pipes 246 penetrating therethrough.

Also in the processing furnace of FIG. 3 configured as described above, cemented carbide scrap is set together with zinc on an appropriate tray in the reaction vessel 203, and about 1 hour.
About 800 in an Ar atmosphere of 200 to 2000 mbar
By heating to ９００900 ° C., zinc is alloyed with the cemented carbide matrix. Thereafter, the pressure in the reaction vessel 203 is reduced by evacuating the inside of the reaction vessel 203 from the condenser 240 side, and Ar gas containing zinc vapor is drawn into the condenser 240, and the zinc vapor is solidified in the condenser 240. In this manner, by sufficiently evaporating and removing zinc from the tray in the reaction vessel 203, a sponge-like cemented carbide block that can be easily pulverized is left on the tray.

[0016]

In the processing furnace of FIG. 2 according to the prior art as described above, the reaction vessel 103 and the heating hood 112 have the substrate 101 at their lower end flanges.
However, there is a problem that the reaction vessel 103 and the heating hood 112 are deformed due to thermal strain. Further, since artificial rubber packings 102 and 113 are interposed at their lower end flanges, the flanges must be cooled to about 200 ° C. or less at least in the vicinity of the packings. There is also a problem that zinc is condensed and fixed in the low temperature portion of the flange.

In the processing furnace shown in FIG. 3, the furnace shell 202 is fixed to the pedestal 225 by bolting.
The problem of thermal strain 2 still remains. On the other hand, the reaction vessel 203 is independent without being integrated with the furnace shell 202 by bolting or the like, and is independent of the groove 255 of the seal member 250.
Is simply placed along the
3 is not deformed by thermal strain. However, since the reaction vessel 203 is simply placed on the groove 255, it is inevitable that zinc vapor leaks from the lower end of the reaction vessel 203 into the space between the furnace shell 202 and the reaction vessel 203. The zinc vapor leaked into the furnace shell 202 in this manner
It reacts with the heater 210 and the refractory layers 206, 207, 208, etc., so that the deterioration of the furnace shell 202 is remarkably accelerated.

In view of the above-mentioned problems in the prior art, the present invention provides a reactor vessel and a reaction vessel accommodated therein, which are individually supported on a receiving table so as not to cause mutual thermal strain and to provide a reaction vessel. It is a primary object of the present invention to provide a processing furnace in which zinc vapor does not leak into the furnace shell.

[0019]

SUMMARY OF THE INVENTION A processing furnace for a sintered hard alloy scrap according to the present invention comprises a reaction vessel for causing an alloying reaction between a binder in a sintered hard alloy scrap and a low melting point metal, and the reaction vessel. A furnace shell that is covered so as to heat it, and a condenser for solidifying and recovering the low-melting-point metal evaporated after the alloying reaction.The reaction vessel has an opening at the bottom, and the lower end thereof has heat. It is connected to a lower end flange via a skirt-shaped connection part for reducing distortion and increasing heat dissipation efficiency, and the lower end flange is fixed to a receiving stand via a heat-resistant seal, and a furnace shell put on the reaction vessel Is characterized in that the skirt-shaped connection portion is simply placed without being fixed on the support base so as to be exposed below the lower end surface of the furnace shell.

That is, in the processing furnace according to the present invention, since the lower end flange of the reaction vessel is fixed to the pedestal via the heat-resistant seal, the vapor of the low melting point metal does not leak into the furnace shell. Since the lower end of the reaction vessel is connected to the lower end flange through a skirt-shaped connecting portion for reducing thermal distortion and increasing heat radiation efficiency, the lower end is not deformed by thermal distortion. Further, the furnace shell is also simply placed without being fixed on the support base, so that the furnace shell is not deformed by thermal strain.

The lower opening of the reaction vessel is connected to the interior of the condenser by a connection pipe extending downward, and the connection pipe is used to guide the vapor of the low melting point metal from the reaction vessel to the interior of the condenser. Preferably, a steam conduit is inserted, and further includes a temperature sensor and a heater for controlling the temperature of the steam conduit to be equal to or higher than the melting point of the low melting point metal.

By providing a temperature sensor and a heater for controlling the temperature of the steam conduit so as to maintain it at a temperature equal to or higher than the melting point of the low melting point metal, the vapor of the low melting point metal is condensed and solidified in the steam conduit. By doing so, it is possible to prevent the steam conduit from being clogged.

Further, it is preferable that a gas inlet for introducing an inert gas into the inside of the reaction vessel is provided at the skirt-shaped connection portion.

This can prevent the low-melting-point metal from condensing and solidifying inside the skirt-shaped connection portion and adhering.

Further, the condenser has a double-walled structure for passing cooling water, a cassette type collecting vessel for collecting a condensed ingot of a low melting point metal below the steam pipe, and further, an exhaust port. It is preferable to provide a bar-shaped structure for obstructing the flow of the steam flowing toward and condensing the steam.

Thus, the condensed ingot of the low-melting-point metal can be efficiently collected in the cassette-type collection container, and the vapor of the low-melting-point metal that cannot be condensed in the collection container can also flow through the barrier structure. During the inhibition, it is condensed and solidified into a powder.

On the other hand , in the method of heat treatment of the sintered hard alloy scrap, the pressure in the reaction vessel containing the protective gas for preventing oxidation is preferably set to a pressure not higher than the atmospheric pressure and not lower than 600 mmHg. By heating while maintaining the binder, the binder and the low melting point metal in the sintered hard alloy scrap are alloyed, and after the alloying,
By reducing the pressure while heating the inside of the reaction vessel, the alloyed low-melting metal is evaporated and removed from the sintered hard alloy scrap, and the vapor of the low-melting metal is introduced into the condenser to reduce the solid content of the original solid. It is characterized in that it is recovered as a melting point metal and that a porous, spongy, easily crushed sintered hard alloy scrap is obtained in the reaction vessel.

According to a pressurized heat treatment method of this, since preferably a pressure below atmospheric pressure is used as the pressure condition at which to a binder and a low melting point metal sintered hard alloy scrap alloyed, in that case The reaction vessel does not need to be inspected and certified as a pressure vessel in the High Pressure Gas Control Law, while the pressure is set to a pressure of 600 mmHg or more, so that the low-melting-point metal and the binder in the sintered hard alloy scrap can be reliably used. To be alloyed.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically illustrates a heat treatment furnace for scrap of a sintered hard alloy according to an embodiment of the present invention. This processing furnace comprises, as main parts, a bell-shaped furnace shell 2, a bell-shaped reaction vessel 3, a pedestal 4 for supporting them, and a condenser 5.

The furnace shell 2 includes a metal shell 19, a heat insulating material 20 inside the metal shell 19, and a heating element 21. The heating element 21 is divided into a plurality of stages, and a plurality of temperature sensors 22 are inserted into the furnace shell 2 correspondingly. That is, each stage of the heating element 21 can be individually controlled according to the corresponding temperature sensor 22, whereby the temperature distribution of the externally heated portion of the reaction vessel 3 can be controlled more uniformly.

The reaction vessel 3 made of heat-resistant steel is a bell type having an opening at a lower end, and the lower end is connected to a lower end flange 14 via a skirt-like connecting portion 15 for reducing thermal strain and increasing heat radiation efficiency. It is connected. The substrate 9 positioned by the guide pins 12 is arranged on the receiving table 4. The reaction vessel 3 has a flange 1 on a heat-resistant seal 11.
4 is placed on the substrate 9 so as to abut, and its flange 14 is pressed and fixed against the substrate 9 by the tightening mechanism 13. Thereby, the reaction vessel 3 is air-tightly fixed to the substrate 9.

On the other hand, the furnace shell 2 is placed on a support column 10 integrated with the receiving base 4 so that the lower end thereof is separated from the substrate 9 by a predetermined space. At this time, since the lower end of the furnace shell 2 is simply placed on the support column 10 without being fixed by bolting or the like, the furnace shell 2 is not deformed by thermal strain. Further, since the flange 14 at the lower end of the reaction vessel 3 is exposed to the space below the furnace shell 2 and is connected to the reaction vessel 3 via a skirt-shaped connection portion 15 for improving heat radiation efficiency, the heat-resistant seal 11 is The flange 14 is not heated so much as to deteriorate. Further, even if the flange 14 is pressed and fixed to the substrate 9, the skirt-shaped connection portion 15 reduces thermal distortion, so that the reaction container 3 is not thermally deformed. In order to prevent the vapor of the low melting point metal from condensing and solidifying in the vicinity of the relatively low temperature flange 14, it is preferable to provide a plurality of inert gas inlets 16 around the skirt-shaped connection portion 15.

The substrate 9 has an opening in the center, and the opening is air-tightly connected to the condenser 5 via a connecting pipe 26.
In order to make the inside of the reaction vessel 3 communicate with the inside of the condenser 5, a steam conduit 6 fixed to a central opening of the substrate 9 is inserted into the connection pipe 26. A temperature sensor 7 and a heater 8 are arranged near the outer wall of the steam conduit 6 in order to prevent the vapor of the low melting point metal from condensing and adhering the solidified metal in the steam conduit 6.

The condenser 5 preferably has a double-walled structure through which cooling water can pass through the entire surface so that the entire inner surface can be efficiently and uniformly cooled. Inside the condenser 5, a cassette type recovery vessel 18 is arranged below the vapor conduit 6 extending from the reaction vessel 3. That is, the vapor of the low melting point metal transported from the reaction vessel 3 through the vapor conduit 6 is condensed and solidified in the recovery vessel 18 and recovered. Note that a fence 17 is also provided in the condenser 5 in order to prevent a gas containing a vapor of the low melting point metal from being short-circuited to the exhaust port 23 connected to the vacuum pump.

When processing a sintered hard alloy scrap using a heat treatment furnace as shown in FIG. 1, first, at a position where the reaction vessel 3 is covered on the substrate 9, the scrap is placed on a suitable tray together with zinc. Set on top. The material of the tray is preferably graphite, and a plurality of trays can be stacked. The zinc mixed with the scrap on the tray is not limited to this, and any other low-melting metal that can be easily alloyed with cobalt, nickel, etc. used as a binder for the sintered hard alloy may be replaced with zinc. Can also be used.

The reaction container 3 is put on the tray on which the scrap is set. That is, the flange 14 at the lower end of the reaction vessel 3 is brought into contact with the heat-resistant sealing material 11, and is pressed and fixed to the substrate 9 by the tightening mechanism 13. The reaction vessel 3 thus mounted is covered with the furnace shell 2, and the lower end of the furnace shell 2 is placed on the support column 10 on the pedestal 4.

Thereafter, exhaust is performed by a vacuum pump through the exhaust port 23 of the condenser 5, and the inside of the condenser 5 and the inside of the reaction vessel 3 communicating with it through the vapor conduit 6 are evacuated. . An inert gas such as Ar or nitrogen gas is introduced from the gas inlet 16 into the reaction vessel 3 and the condenser 5 once evacuated, and the inside of the reaction vessel 3 is adjusted by adjusting the exhaust capability of the vacuum pump. 600mmHg
As described above, the pressure is set and maintained within the range below the atmospheric pressure. 6
Is being more than the pressure 00MmHg, in order to perform alloying of the binder and the low melting point metal sintered hard alloy scrap efficient pressure above 600mmHg is <br/> because a required. On the other hand, the pressure in the reaction vessel 3 is set to be equal to or lower than the atmospheric pressure in order to avoid the necessity for the reaction vessel 3 to be inspected and certified as a pressure vessel. However, it goes without saying that the pressure in the reaction vessel 3 may be set to be equal to or higher than the atmospheric pressure if the reaction vessel 3 is inspected and certified as a pressure vessel according to the High Pressure Gas Control Law.

When the above preparation is completed, the heating element 21 is energized to heat the reaction vessel 3 to about 800 to 850 ° C. This heating is performed by independently controlling each of the divided sections of the heating element 21 based on the plurality of temperature sensors 22, so that the uniformity of the temperature in the reaction vessel 3 is maintained. Also,
During the heating, the pressure in the reaction vessel 3 is maintained at the pressure set before the heating by finely adjusting the evacuation capacity of the vacuum pump.

By such heating, zinc diffuses into a binder made of cobalt, nickel or the like in the sintered hard alloy scrap to form an alloy, and the sintered hard alloy scrap expands. After a sufficient heating time has elapsed to alloy the zinc and expand the sintered hard alloy scrap, the evacuation capacity of the vacuum pump is gradually increased to start reducing the pressure in the reaction vessel 3 via the condenser 5. I do. Prior to the start of the decompression, the heater 8 near the steam conduit 6 is energized, and the temperature of the steam conduit 6 is constantly maintained at a temperature equal to or higher than the melting point of zinc based on the temperature sensor 7.

As the pressure in the reaction vessel 3 progresses, zinc which has diffused into the binder of the sintered hard alloy scrap and alloyed is evaporated. Then, the zinc vapor is sucked into the condenser 5 through the vapor conduit 6 together with the inert gas,
It is condensed and solidified in the cassette type recovery container 18 and recovered as an original zinc lump. On the other hand, the zinc vapor that has not been completely condensed in the collection container 18 is drawn toward the exhaust port 23, but its flow is obstructed by the fence-like structure 17 provided in front thereof, and during that time it condenses and solidifies, , In the condenser 5 as zinc powder. The temperature in the reaction vessel 3 during the decompression is about 800 to 850 when zinc is alloyed.
The temperature may be the same in the range of ° C., but may be increased to, for example, about 900 ° C. to promote the evaporation of zinc.
When the pressure in the reaction vessel 3 increases and reaches a certain degree of vacuum (for example, 10 mmHg or less), the introduction of the inert gas from the gas inlet 16 is stopped, and a high vacuum is applied to further evaporate the remaining zinc. Exhausted.

By heating and evacuating the reaction vessel 3 until the zinc is sufficiently removed (for example, 50 ppm or less in the scrap) in this way, the sintered hard alloy scrap becomes porous and spongy. Blocks, which are easily crushed. Therefore, by grinding this sponge-like block by a known method, it becomes possible to reuse it as a powder raw material for a sintered hard alloy.

[0042]

As described above, according to the present invention, there is provided a heat treatment furnace for a sintered hard alloy scrap, in which a furnace shell and a reaction vessel housed therein are individually supported on a receiving table. It is possible to provide a processing furnace that does not cause mutual thermal strain and does not allow zinc vapor to leak from the reaction vessel into the furnace shell. Preferably , the pressure in the reaction vessel is 600 mm
Is set to sub-atmospheric pressure above Hg, the reaction vessel, it is not necessary to undergo testing and certification as a pressure vessel in the High Pressure Gas Control Law.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a processing furnace for a sintered hard alloy scrap according to an example of an embodiment of the present invention.

FIG. 2 is a schematic view showing one example of a processing furnace for a sintered hard alloy scrap according to the prior art.

FIG. 3 is a schematic view showing another example of a processing furnace for a sintered hard alloy scrap according to the prior art.

[Explanation of symbols]

 2 Furnace shell 3 Reaction vessel 4 Cradle 5 Condenser 6 Steam conduit 7 Temperature sensor 8 Heater 9 Substrate 10 Support post 11 Heat-resistant seal 12 Guide pin 13 Tightening mechanism 14 Flange 15 Skirt-like connection part 16 Gas inlet 17 Fence structure Object 18 Cassette type collection container 19 Metal outer skin 20 Insulation material 21 Heating element 22 Temperature sensor 23 Exhaust port 26 Connecting pipe

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Norimitsu Kimoto 1-1-1, Kunyokita, Itami-shi, Itami-shi, Hyogo Itami Works, Sumitomo Electric Industries, Ltd. (56) References JP-A-58-84932 (JP) JP-A-62-270732 (JP, A) JP-A-6-145816 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22B 1/00-61/00

Claims (4)

(57) [Claims] 1. A reaction vessel for causing an alloying reaction between a binder in a sintered hard alloy scrap and a low-melting metal, a furnace shell put on the reaction vessel for heating the reaction vessel, and the alloying. A condenser for solidifying and recovering the low-melting-point metal evaporated after the reaction, wherein the reaction vessel has an opening at a lower portion, and a lower end portion for reducing thermal strain and increasing heat radiation efficiency. The lower end flange is connected to a lower end flange via a skirt-shaped connection portion, the lower end flange is fixed to a receiving table via a heat-resistant seal, and the furnace shell put on the reaction vessel has the skirt-shaped connection portion. A processing furnace for a sintered hard alloy scrap, wherein the processing furnace is simply placed without being fixed on a support so as to be exposed below a lower end surface of a furnace shell. 2. The lower opening of the reaction vessel is connected to the interior of the condenser by a connection pipe extending downward, and the connection pipe has a low melting point metal from the reaction vessel to the interior of the condenser. A steam conduit for guiding the steam is inserted, and further comprising a temperature sensor and a heater for controlling the temperature of the steam conduit so as to maintain the temperature of the low melting point metal or higher. Item 2. A processing furnace for a sintered hard alloy scrap according to item 1. 3. The sintered hard alloy according to claim 1, wherein a gas inlet for introducing an inert gas into the inside of the reaction vessel is provided in the skirt-shaped connecting portion. Processing furnace for scrap. 4. The condenser has a double-walled structure for allowing cooling water to pass therethrough, and further includes a cassette-type collection container for collecting the low-melting-point metal condensed ingot below the steam conduit. 4. A fence-like structure for obstructing a flow of the steam flowing toward an exhaust port without being condensed in the collection container and condensing the steam. A processing furnace for a sintered hard alloy scrap according to any one of the preceding claims.