JPH0523540Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a pressure sintering furnace for sintering molded products made of powder raw materials such as ceramics, cemented carbide (superalloy), and the like.

(Prior art) Conventionally, ceramics, cemented carbide, etc. are difficult to machine, so they are made into powder, mixed with a binder such as wax, and molded using injection molding or metal molding. A generally adopted process is to perform a so-called wax removal process to completely remove the wax after forming the shape, followed by sintering.

In the dewaxing process, as illustrated in FIG. At the same time, a valve 2 is installed in the exhaust passage 23 of the sintering furnace 21 to evaporate and diffuse the wax into the sintering furnace 21.
4. The wax is guided out of the furnace by a vacuum pump 26 or the like provided through a wax strap device 25, and the wax is agglomerated and collected by the wax strap device 25.

By the way, in order to prevent wax from coagulating and adhering to the exhaust passage 23 and valve 24 during the wax removal process, a method is adopted in which the piping and valve 24 are heated from the outside to near the temperature inside the furnace using heating means ( (Refer to Utility Model Application Publication No. 113333/1983). In addition, in a pressure sintering furnace, the inner walls of the furnace are also heated by gas convection, so in order to prevent excessive temperature rise of the furnace structure,
As illustrated in FIG. 5, a water cooling jacket 27 is provided, and during the wax removal process,
Hot water is passed through the water cooling jacket 27 and a heating device 28 is inserted therein.

(Problems to be solved by the invention) In the conventional method, in which the piping is heated from the outside, due to the heat capacity of the piping, there is a delay in controlling the temperature of the vaporized wax, and sufficient wax removal cannot be performed. There is a problem in that wax adheres to the inner wall and inside the valve 23. The only way to remove wax adhering to the inner walls of the pipes is to remove the pipes and clean them, and maintenance work is difficult because the pipes are installed at the bottom of the furnace body.

Further, the method of circulating hot water through the water cooling jacket 27 has problems such as complicated piping and a considerable amount of time required to heat the water to a predetermined temperature.

The present invention was devised in view of the above-mentioned circumstances, and aims to provide a pressure sintering furnace that can efficiently heat vaporized wax without causing any delay in temperature control.

(Means for solving the problems) In order to solve the above problems, the present invention takes the following technical measures.

That is, the present invention provides a pressurized sintering furnace 1 in which a gas containing wax vapor evaporated from a body 3 to be sintered is guided to a wax trap 10 through exhaust gas passages 7 and 12. , is characterized in that a heating means 14 is provided.

(Function) According to the present invention, when the gas containing wax vapor generated in the furnace body 2 of the pressure sintering furnace 1 passes through the exhaust gas passage 7, the heating means 14 provided in the exhaust gas passage 7 The wax is brought into the wax strap 10 while being held at a predetermined temperature (close to the furnace temperature). Therefore, the wax vapor is heated in a timely and efficient manner, so that there is no risk of solidification and adhesion in the middle of the piping or near the valve, and the wax vapor can be reliably led to the wax strap 10 and recovered.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 shows a first embodiment of the present invention, in which 1 is a pressure sintering furnace, 2 is a furnace body, 3 is a body to be sintered, and 4 is a body to be sintered.
5 is a heating device for the sintered body, 6 is an exhaust port for gas containing wax vapor provided at the bottom of the furnace, 7 is an exhaust gas furnace connected to the exhaust port 6, and 8 is a sintered body 2 on the outer periphery thereof. A water cooling jacket is provided.

9 is a valve connected to the outer end of the exhaust gas passage 7;
0 is a wax strap, 11 is a vacuum pump for sucking out exhaust gas, and these are connected in series by exhaust gas passages 12 and 13.

Reference numeral 14 denotes an exhaust gas heating means (electric heater), which is directly input into the exhaust port 6 through the exhaust gas path 7.

Reference numeral 15 denotes an electrode outlet through which an electrode 16 provided on the heating means 14 passes.

Reference numeral 17 denotes an atmosphere release valve, which is connected to the exhaust gas path 13 on the upstream side of the vacuum pump 11.

According to the first embodiment of the present invention, the object to be sintered 3 set on the mounting table 4 in the furnace body 2 is heated by the heating device 5.
As a result, the wax is heated to a temperature higher than the wax evaporation temperature, and the wax mixed in the body 3 to be sintered is evaporated and diffused into the furnace body 2. Wax vapor and furnace gas are sucked by the vacuum pump 11, reach the discharge port 6 from the lower side of the mounting table 4, pass through the exhaust gas path 7, the valve 9, and the exhaust gas path 12, and then reach the wax strap 1.
0, the wax vapor is condensed and collected in the wax trap 10. The gas containing the wax vapor is maintained at the furnace temperature by the heating means 14 disposed in the exhaust port 6 and the exhaust gas passage 7, and therefore passes through the exhaust gas passage 7 portion that penetrates the water cooling jacket 8. In particular, the wax does not solidify due to the temperature drop and is smoothly guided to the wax strap 10. Furthermore, since the wax vapor etc. comes into direct contact with the heating element of the heating means 14, the heat transfer efficiency is good and rapid heating can be performed, allowing for rapid response without delay in temperature control. .

FIG. 2 shows a second embodiment of the present invention.
Wax strap 1 from gas outlet 6 of furnace body 2
When the exhaust gas path 7 to 0 is long, the heating means 7 is divided into a plurality of zones and the other configurations are the same as in the first embodiment. Therefore, detailed explanation will be omitted.

FIG. 3 shows a third embodiment of the present invention, in which a temperature detection means 18 is provided in the exhaust gas passage 7 in the first embodiment.
(for example, a thermocouple) to detect the temperature inside the exhaust gas passage 7 and control the temperature of the heating means 14,
In addition to maintaining the temperature at a predetermined value, it is possible to control the temperature to accommodate a variety of waxes.
Therefore, according to the third embodiment, since the heating of the gas containing wax vapor can be precisely controlled, wax removal can be carried out reliably and efficiently by maintaining an appropriate temperature corresponding to each type of wax. It is possible.

Note that the heating means 14 is not limited to an electric heater, and it goes without saying that other heating devices may be used.

(Effects of the invention) As mentioned above, the heating sintering furnace according to the invention has the following features:
Since the heating means 14 is disposed in the exhaust gas passage 7 following the gas discharge passage 6 of the furnace body, the temperature inside the exhaust gas passage 7 can be maintained at approximately the same temperature as the inside temperature of the furnace, and the wax vapor containing wax vapor can be maintained. Since the gas comes into direct contact with the heating means 14, there is no delay in controlling the gas temperature, allowing for quick response, preventing wax vapor from solidifying in the exhaust gas passage 7 and the valve 9, and achieving complete wax removal. It is possible,
There is no need to frequently clean the exhaust gas passage 7, valve 9, etc., and the inside of the exhaust gas passage 7 is also easy to clean, and the heating means 14 comes into direct contact with the gas, which improves thermal efficiency and improves economic efficiency. can be increased.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention;
Fig. 2 is a sectional view of main parts showing the second embodiment, Fig. 3 is a sectional view of main parts showing the third embodiment, Fig. 4 is an explanatory diagram showing an example of the arrangement of the conventional example, and Fig. 5 is a sectional view of main parts showing the second embodiment. FIG. 3 is a vertical cross-sectional view of a conventional example. 1... Pressure sintering furnace, 3... Sintered body, 7, 12
... Exhaust gas path, 10 ... Wax strap, 14
...Heating means.

Claims (1)

[Claims for Utility Model Registration] In a pressurized sintering furnace 1 in which a gas containing wax vapor evaporated from a body 3 to be sintered is guided to a wax strap 10 through exhaust gas passages 7 and 12, the exhaust gas passage 7 A pressure sintering furnace characterized in that a heating means 14 is disposed therein.