JPH05195016A - Vacuum sintering furnace - Google Patents

Abstract

PURPOSE:To uniformize flows of gas in a retort set in a vacuum sintering furnace. CONSTITUTION:In this vacuum sintering furnace 1 in which products 21 to be treated are housed in a retort 5 set in the furnace shell 2 and they are heated with a heater 17 set at the outside of the retort 5, many ventholes 8 are pierced in a side wall 5a of the retort 5 at one end and gas is fed from the outside of the furnace 1 to the outside of the side wall 5a through an air inlet 14 in the furnace 1. The fed air is discharged into the outside of the furnace 1 from the inside of a side wall 5b of the retort 5 at the other end through an exhaust port 10 in the furnace 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum sintering furnace for sintering metal powder.

[0002]

2. Description of the Related Art Generally, in a vacuum sintering furnace, a molded product is heated before a sintering process to remove wax, which is a stamping lubricant such as zinc stearate contained in the molded product which is a processed product. Dewaxing is performed. At this time, in order to prevent the wax content from vaporizing and adhering to the low temperature inner wall of the furnace and remaining in the furnace, a container-shaped retort has recently been installed in the furnace and the processed products are stored in this retort. A vacuum sintering furnace having a structure in which a heater provided outside the retort is used and a carrier gas such as N ₂ gas is circulated in the retort during dewaxing to take out the wax component outside the furnace is used.

[0003]

However, in the vacuum sintering furnace having the above structure, the carrier gas is supplied directly into the retort through a single air supply pipe, or the carrier gas supplied into the furnace is supplied to the retort body and its lid. Since the gas was introduced into the retort through the gap and exhausted outside the furnace from the exhaust port at the end of the retort, the gas flow in the retort was uneven, especially when processing a large number of products at once. Due to the uneven flow of the gas flow, a defective dewax is apt to occur and a defective sintered product having poor sintering strength is liable to be generated, and in order to avoid this, dewaxing is required for a long time, resulting in a decrease in productivity.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a vacuum sintering furnace which can make the gas flow in the retort uniform.

[0005]

A vacuum sintering furnace according to the first invention of the present application stores a processed product in a retort provided in the furnace, and a processed product is provided by a heater provided outside the retort. In a vacuum sintering furnace for heating, a plurality of vent holes are formed in the side wall of one end of the retort, an air supply port for supplying gas from outside the furnace to the outside of the side wall, and the other end of the retort. An exhaust port for exhausting the gas from the inside of the side wall of the part to the outside of the furnace is provided.

The vacuum sintering furnace of the second invention of this application is a vacuum sintering in which a processed product is housed in a retort provided in the furnace and the processed product is heated by a heater provided outside the retort. In the furnace, a large number of vent holes are formed in both side walls of the retort that face each other, and a gas supply port for supplying gas to the outside of one of the side walls from outside the furnace and a furnace from the outside of the other side wall. An exhaust port for exhausting the gas to the outside is provided.

The vacuum sintering furnace according to the third aspect of the present invention is a vacuum sintering furnace in which a processed product is housed in a retort provided inside the furnace and the processed product is heated by a heater provided outside the retort. In the furnace, an inlet for supplying gas to the inside of the side wall at one end of the retort and an outlet for exhausting the gas from the inside of the side wall at the other end of the retort are provided, and inside the retort. In the retort, there is provided a straightening vane having a plurality of vent holes that are inserted into and removed from the retort in such a manner as to partition the treated product housed in the refueling tank from the air supply port.

[0008]

In the vacuum sintering furnace of the present invention, the gas supplied from the air supply port is provided in a large number of vent holes (in the case of the first and second inventions) provided in the side wall of the retort or in the current plate. By passing through a large number of ventilation holes (in the case of the third invention), the gas flows into the retort in a rectified state, flows in the retort as a substantially uniform flow, and then is discharged from the exhaust port to the outside of the furnace.

In the second aspect of the invention, the gas flow in the retort is made to flow out to the outside of the retort while being rectified by the ventilation hole provided in the side wall on the gas outflow side of the retort, so that the gas flow in the retort is made more uniform. It

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. In the figure, 1 is a batch type vacuum sintering furnace,
An insulating chamber 4 surrounded by a cylindrical insulating wall 3 made of graphite is provided in a cylindrical furnace shell 2, and a retort 5 made of graphite and having a rectangular box shape is provided in the insulating chamber 4. Reference numeral 6 denotes a furnace lid, which is supported by the furnace shell 2 by a hinge mechanism (not shown) and is opened and closed.
Reference numeral 7 denotes a graphite door of the heat insulation chamber 4, which is fixed to the furnace lid 6. A side wall 5a at one end of the retort 5 is fixed to the door 7 and functions as a loading / unloading door of the retort 5. A large number of vent holes 8 are formed in the side wall 5a.

On the other hand, on the side wall 5b at the other end of the retort 5,
Exhaust port 10 that penetrates the heat insulating wall 3 and the furnace shell 2 to reach the outside of the furnace
Is provided. Reference numeral 11 is an exhaust pipe line connected to the exhaust port 10, 12 is a vacuum strap, and 13 is a vacuum pump. Further, 14 is an air supply port, which connects the inlet of the heat insulation chamber 4 to the outside of the furnace, and an air supply line 15 connected to the inlet.
Is connected to a carrier gas supply source (not shown).
Reference numeral 16 denotes a partition wall that is stretched between the outer circumference of the inlet of the heat insulation chamber 4 and the inner circumference of the furnace shell 2. Also, 17 is an electric heat type heater, 18
Is a hearth fixed to the furnace shell 2 by the supporting legs 19, and a pallet 23 in which trays 22 on which the processed products 21 are placed are stacked in multiple stages.
Is placed on the hearth 18 for dewaxing and vacuum sintering. Reference numeral 24 is a wax reservoir for storing the dropped wax due to insufficient vaporization.

The processed product 2 in the vacuum sintering furnace 1 having the above structure
In order to perform dewaxing No. 1, heating is performed by the heater 17 and carrier gas is supplied into the heat insulating chamber 4 from the air supply port 14 and the vacuum pump 13 is operated in the state shown in FIG. The carrier gas passes through a large number of vent holes 8 in the side wall 5a and flows into the retort 5 in a straightened state, and flows as a substantially uniform flow in the vicinity of each treated product 21 part, and the vaporized wax component is generated from each treated product 21. About exhaust port 10
It is sucked and exhausted from the vacuum trap 12, and the wax portion is collected by the wax strap 12.

Since the carrier gas flows in the retort 5 as a substantially uniform flow in this manner, the dewaxing of the processed product 21 is small, and the dewaxing can be sufficiently carried out in a short time.

Next, FIG. 3 and FIG. 4 show a second embodiment of the present invention, in which an exhaust port 10 is provided in a floor wall 5c near the side wall 5b of the retort 5 to serve as a wax portion outlet pipe to a wax reservoir 24. The second embodiment is different from the first embodiment only in that the furnace structure is used in common and the partition plate 26 is inserted into and removed from the gas inlet side of the retort 5.

The partition plate 26 has a large square hole 27 facing the front surface of the group of trays 22 stacked in multiple stages, and blocks the gas flow to the upper and lower parts of the tray 22 group and the unnecessary gas flow areas on the left and right sides. To improve the gas utilization efficiency, after loading the pallet 23 loaded with the tray 22 into the retort,
It is inserted into the retort 5 by hand and the pallet 23
It is to be removed before taking it out. Also in this vacuum sintering furnace 28, the gas rectifying action by the vent holes 8 of the side wall 5a at the time of dewaxing is the same as that of the first embodiment.

FIG. 5 shows a third embodiment of the present invention, in which a large number of vent holes 31 are formed also in the side wall 5b of the retort 5 on the gas outflow side.
Is provided and the exhaust port 32 is provided in the end wall 3a of the heat insulating chamber 4, which is different from the first embodiment.

In the vacuum sintering furnace 33 of this embodiment,
The carrier gas that has circulated in the retort 5 during dewaxing is sucked and exhausted from the ventilation holes 31 that are dispersed and arranged in each part of the end wall 3a, so that the gas flow in the retort 5 is made more uniform.

Next, FIG. 6 shows a fourth embodiment of the present invention.
The side wall 5a of the retort 5 is not provided with a vent hole, and instead of the partition plate 26, a number of vent holes 42 are bored in a straightening plate 41 that is inserted into and removed from the retort 5, and an air supply port 43 is provided in the retort 5. The second embodiment is different from the second embodiment in that the carrier gas is supplied between the straightening vane 41 and the side wall 5a by connecting to the inlet of the above, and the partition wall 16 is omitted.

In the vacuum sintering furnace 44 of this embodiment,
The carrier gas supplied into the retort 5 is rectified by the rectifying plate 41.
Is rectified by and circulates in the retort 5. Treated product 21
Depending on the size and number of trays, the number of trays 22 and processed products 21
Even if the arrangement on the tray 22 is changed, it is possible to easily obtain an optimum gas flow state by using the rectifying plates 41 having different sizes and numbers of the ventilation holes 42 according to the change. is there.

The dewaxing by the carrier gas has been described above. The vacuum sintering furnace of the present invention is shown in FIG.
As shown as an example, it can also be used in the case of forcibly cooling each processed product 21 with a cooling gas in the cooling step of the processed product 21 after sintering. In the figure, 51 is a cooling gas circulation pipe, one end of which is connected to the air supply port 14 of the vacuum sintering furnace 1 and the other end of which is connected to the exhaust port 10. Reference numeral 52 is a circulation pump having a suction port connected to the exhaust port 10 side, 53 is a gas cooler, and 54a to 54d are electromagnetic opening / closing valves. The other structure is the same as that of the first embodiment.

In the vacuum sintering furnace 1 of this embodiment, the electromagnetic opening / closing valves 54c and 54d are closed and the electromagnetic opening / closing valves 54a and 54b are opened during dewaxing, and dewaxing is performed in the same manner as in the first embodiment. .. In the cooling process after the sintering process, the solenoid on-off valves 54c and 54d are opened to make them 54a and 54b.
And the circulation pump 52 and the gas cooler 53 are operated, the cooled cooling gas is supplied from the air supply port 14 to the side wall 5a.
Since the gas is supplied into the retort 5 through the ventilation holes 8 in a straightened state, each processed product 21 can be cooled substantially uniformly and quickly.

The present invention is not limited to the above embodiments, and the partition plate 26 in FIG. 3 may be omitted. Further, the vacuum sintering furnaces of the first to fourth embodiments can also be used for cooling the processed product with the same cooling gas as in the fifth embodiment. The present invention can also be applied to a vacuum sintering furnace having a cylindrical retort.

[0023]

As described above, according to the present invention,
The gas flow in the retort can be made uniform by the vent holes on the side wall of the retort or the flow straightening plate that is inserted into and removed from the retort, and the dewaxing and cooling of the processed products in the vacuum sintering furnace can be performed uniformly and in a short time. Can be done at.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a vacuum sintering furnace showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a vertical sectional view of a vacuum sintering furnace showing a second embodiment of the present invention.

FIG. 4 is a sectional view taken along line BB of FIG.

FIG. 5 is a vertical sectional view of a vacuum sintering furnace showing a third embodiment of the present invention.

FIG. 6 is a vertical sectional view of a vacuum sintering furnace showing a fourth embodiment of the present invention.

FIG. 7 is a vertical sectional view of a vacuum sintering furnace showing a fifth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum sintering furnace, 2 ... Furnace shell, 4 ... Thermal insulation chamber, 5 ... Retort, 5a ... Side wall, 5b ... Side wall, 8 ... Vent hole, 10 ... Exhaust port, 11 ... Exhaust pipe line, 12 ... Wax strap, 13 ...
Vacuum pump, 14 ... Air supply port, 15 ... Air supply line, 17 ... Heater, 21 ... Processed product, 22 ... Tray, 23 ... Pallet,
26 ... Partition plate, 27 ... Square hole, 28 ... Vacuum sintering furnace, 31 ...
Vent hole, 32 ... Exhaust port, 33 ... Vacuum sintering furnace, 41 ... Rectifier plate, 42 ... Vent hole, 43 ... Air inlet, 44 ... Vacuum sintering furnace,
51 ... Circulation pipeline, 52 ... Circulation pump, 53 ... Gas cylinder
La.

Claims (3)

[Claims] 1. A vacuum sintering furnace in which a processed product is housed in a retort provided in a furnace and the processed product is heated by a heater provided outside the retort, and a large number of side walls are provided at one end of the retort. An air supply hole having a plurality of ventilation holes for supplying gas from outside the furnace to the outside of the side wall, and an exhaust port for discharging the gas from inside of the side wall at the other end of the retort to the outside of the furnace. A vacuum sintering furnace characterized by being provided with. 2. In a vacuum sintering furnace in which a processed product is housed in a retort provided inside the furnace and the processed product is heated by a heater provided outside the retort, a large number are provided on opposite side walls of the retort. Individual ventilation holes are provided, and an air supply port for supplying gas from outside the furnace to the outside of the one side wall and an exhaust port for exhausting the gas from outside of the other side wall to the outside of the furnace are provided. A vacuum sintering furnace characterized by that. 3. In a vacuum sintering furnace in which a processed product is housed in a retort provided inside the furnace and the processed product is heated by a heater provided outside the retort, inside a side wall of one end of the retort. A gas supply port for supplying gas to the other side, and an exhaust port for discharging the gas from the inside of the side wall of the other end of the retort, and a treatment product housed in the retort and the air supply port A vacuum sintering furnace comprising a straightening vane having a plurality of vent holes that are inserted into and removed from the retort in a partitioning manner.