JP2656839B2 - Vacuum heat treatment furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vacuum heat treatment furnace used for quenching a product made of high alloy steel such as high speed tool steel or alloy tool steel.

[Conventional technology]

As is well known, a vacuum heat treatment furnace can be roughly classified from its heating method by providing a processing chamber comprising a heat insulating layer in which a heating element is disposed on an inner surface side in a vacuum tank, and directly heating an article to be processed. There are a thermal type and an external heat type in which a heat source is provided outside the vacuum processing chamber disposed in the furnace to indirectly heat the article to be processed.

In order to cool an object to be processed after heating in these vacuum heat treatment furnaces, a configuration in which cooling is performed by using a refrigerant gas introduced into a processing chamber from the outside is most widely adopted.

On the other hand, for quenching of high alloy steel products that require a quenching temperature exceeding 1000 ° C, such as high-speed steel and alloy tool steel, decarburization can be achieved by heating under vacuum or an inert gas atmosphere. There is no concern about deterioration of the properties of the product due to oxidation or oxidation.
An internal heat type vacuum heat treatment furnace capable of easily obtaining a high temperature exceeding 00 ° C. is most commonly used.

In the quenching process, usually, after a workpiece is heated to a predetermined high temperature under vacuum, a low-temperature inert gas is introduced as a refrigerant into the processing chamber, and the quenching is performed by heat exchange with the refrigerant gas. This is done by quenching the product, but at this time, without causing cracks or distortion in the workpiece, cooling at a cooling rate sufficient to obtain the desired quenching hardness, and the quenching process is ensured. In order to achieve this, it is necessary not only to introduce the refrigerant gas into the processing chamber but also to make the refrigerant gas flow so that it can uniformly contact the entire surface of the article to be processed and rapidly exchange heat. Become.

Therefore, in the vacuum heat treatment furnace used for the quenching process, various studies have been conventionally made on the control of the gas flow of the refrigerant gas introduced into the furnace. For example, as shown in FIG. A processing chamber (54) comprising a heat insulating layer (52) containing a heating element (53) is provided in the processing chamber (51), and upper and lower gas doors (55) and (56) are provided above and below the processing chamber (54). The cooling coil (57) is disposed above the processing chamber (54) so as to be openable and closable.
4) The upper and lower gas doors (55) and (56) are opened, and the refrigerant gas introduced from the outside is raised in the processing chamber (54) by the fan (58) provided at the top of the furnace, and the upper cooling coil (57)
After being cooled in the processing chamber (54), a forced circulating flow is returned to the lower part of the processing chamber (54) through the outside thereof, thereby forming an upward flow of the refrigerant gas in the processing chamber (54) and heating the processing target. Equality of
As shown in FIG. 6, a vacuum heat treatment furnace configured to achieve rapid cooling, and a tubular heating element (63) provided in a vacuum tank (61), which is circumferentially arranged in a longitudinal direction, are included. A processing chamber (64) comprising a heat insulating layer (62) is provided, and upper and lower gas flow ports (65) and (66) are provided in the upper and lower portions of the processing chamber (64) so as to be openable and closable. A heat exchanger (67) is provided around the outside, and a plurality of gas injection holes (6) are opened in the tubular heating element (63) toward the center of the processing chamber (64).
8), and these heating elements (63)
4) By connecting to the refrigerant gas distribution device (69) communicating with the outside, the upper and lower gas doors (6
5) Open (66) and circulate the refrigerant gas introduced from the outside by gas circulation means (70) provided at the top of the furnace through the distributor (69) through the gas injection holes (63) of each heating element (63). 68), the refrigerant gas is sprayed toward the outer peripheral surface of the article in the processing chamber (64), and the refrigerant gas is guided from the processing chamber (64) to the outer heat exchanger (67) and forcedly circulated. A vacuum heat treatment furnace (Japanese Patent Laid-Open Publication No. 1-142018) and the like, which are configured to cool and evenly cool a heated article to be processed, has been proposed and put to practical use.

[Problems to be solved by the invention]

However, each of the above-mentioned conventional vacuum heat treatment furnaces has the following problems.

For example, when a long workpiece to be processed such as a broach is suspended and quenched in order to prevent the occurrence of bending, in the former vacuum heat treatment furnace, the refrigerant gas rising in the processing chamber is used. However, as the temperature rises due to contact and heat exchange with the heated article to be processed and the temperature increases, the cooling capacity decreases as the temperature increases, that is, a difference occurs in the cooling capacity at the top and bottom of the processing chamber. There is a problem that as the length is longer, a larger difference in quenching hardness is more likely to occur between the upper and lower sides.

On the other hand, in the latter conventional vacuum heat treatment furnace, a low-temperature refrigerant gas is blown from the outer peripheral side toward the heated article to be processed through the gas injection holes of the heating element. When the quenching process is performed by suspending a single workpiece without causing a difference in cooling capacity, the entire surface can be rapidly and uniformly cooled. In the case where the quenching process is performed by suspending a plurality of hangers, there is a problem in that the hanged one positioned outside is cooled quickly, and the hanged one positioned inside is cooled slowly.
In addition, the article to be treated located on the outside is also cooled unevenly between the surface facing the heating element and the surface on the opposite side, so that in addition to the difference in quenching hardness in the circumferential direction, bending occurs. easy. In addition, since the refrigerant gas that collides with the outer processed object forms a turbulent flow and comes into contact with the inner processed object, quenching hardness unevenness is also likely to occur on the inner processed object, and a plurality of processed objects are required. One having a uniform hardness distribution has a problem that quenching is difficult.

In addition, these conventional vacuum heat treatment furnaces are configured to circulate and cool the refrigerant gas introduced during quenching in the furnace, such as a fan for circulating the refrigerant gas in the furnace and a heat exchanger for cooling. Is disposed, the internal structure thereof is complicated, and there is a disadvantage that a complicated procedure and many man-hours are required for maintenance and inspection and disassembly and maintenance.

The present invention has been made in view of the above-mentioned problems of the related art, and it is possible to set or easily change the flow of the refrigerant gas introduced at the time of cooling after heating to the one most suitable for the shape and the set state of the article to be processed, and thus the heating is performed. The product can be cooled rapidly and evenly, the quenching process can be assured, and the product quality can be improved.
The purpose is to provide a vacuum heat treatment furnace that is easy to maintain.

[Means for solving the problem]

In order to achieve the above object, the present invention is configured as follows. That is, the vacuum heat treatment furnace according to the present invention comprises: a vacuum tank; a cylindrical processing chamber including a heat insulating layer provided in the vacuum tank and provided with gas flow ports that can be opened and closed at upper and lower portions; And a flow path cylinder disposed between the flow path cylinder and the vacuum tank inner wall and between the flow path cylinder and the heat insulation layer outer wall of the processing chamber. And a heat treatment element provided around the inner periphery of the processing chamber, wherein the heat insulating layer of the processing chamber has a double configuration in which a gas flow gap is provided in the layer. While forming, on the inner side wall of the heat insulating layer, a plurality of injection nozzles that communicate the gas flow gap in the layer and the processing chamber are provided,
In each of the upper and lower portions between the processing chamber and the flow path cylinder, a gas permeable gap between the processing chamber and the flow path cylinder, and a gas flow between the vacuum tank inner wall and the flow path cylinder A first gas supply pipe provided with a gas flow path switching valve capable of alternately opening and closing the gap and communicating with the vacuum tank in a gap between the processing chamber and the flow tube; A second gas supply pipe is provided in communication with a gas flow gap in the layer, and a gas discharge pipe is provided in communication with a gap between the inner wall of the vacuum tank and the channel tube.

[Action]

In the vacuum heat treatment furnace according to the present invention having the above-described configuration, at the time of cooling after heating, when the refrigerant gas from the refrigerant gas supply source is introduced into the furnace to cool the heated workpiece, the refrigerant gas Is introduced into the gap between the processing chamber and the flow path cylinder via the first gas supply pipe, and the upper gas flow path switching valve is actuated to close the gap between the processing chamber and the flow path cylinder. While the upper end portion allows gas flow, the gas flow in the gap between the upper end of the flow path cylinder and the inner wall of the vacuum tank is closed, and at the same time, the lower gas flow path switching valve is operated, so that the processing chamber and the flow path cylinder While closing the gas flow at the lower end of the gap between, the gas flow through the gap between the upper end of the flow path cylinder and the inner wall of the vacuum tank,
In addition, by opening the gas flow openings at the upper and lower portions of the processing chamber, the gas flows into the furnace through the first gas supply pipe, and is guided upward through the gap between the processing chamber and the flow path tube, and the processing is performed. The gas flows in from the upper gas flow port of the chamber, flows down while contacting and exchanging heat with the heated article to be processed in the processing chamber, and flows out of the lower gas flow port. A coolant gas flow discharged from the gas discharge pipe to the outside of the furnace can be formed through the gap between the flow path cylinder and the inner wall of the vacuum tank.

Further, by operating the upper and lower gas flow switching valves in the opposite manner to the above, the refrigerant gas flows in from the lower gas flow port of the processing chamber and flows out of the upper gas flow port, and into the processing chamber, It is possible to form an ascending flow of refrigerant gas that rises while contacting and exchanging heat with the heated workpiece,
Further, while continuing to introduce the refrigerant gas through the first gas supply pipe, the direction of the refrigerant gas flow in the processing chamber is switched by operating the upper and lower gas flow path switching valves in reverse at any time. A refrigerant gas flow that alternates in the vertical direction can be formed in the room.

In addition, the refrigerant gas from the refrigerant gas supply source is introduced into the gas flow gap in the heat insulating layer of the processing chamber through the second gas supply pipe, and the upper and lower gas flow path switching valves are operated to operate the processing chamber. By closing the gas flow at the upper and lower ends of the gap between the and the flow path cylinder, and by opening the gas flow ports at the upper and lower parts of the processing chamber, the gas flows into the furnace through the second gas supply pipe. The gas is injected into the processing chamber from a gas flow gap in the heat insulating layer of the processing chamber through a plurality of injection nozzles provided on an inner wall of the processing chamber, and is sprayed on the workpiece heated in the processing chamber to contact / heat. While being exchanged, it is divided in the vertical direction and flows out from the upper and lower gas flow ports, through the upper and lower gaps between the upper and lower ends of the flow path cylinder and the vacuum tank inner wall and the gap between the flow path cylinder and the vacuum tank inner wall,
A refrigerant gas stream discharged from the gas discharge pipe to the outside of the furnace can be formed.

In the vacuum processing furnace according to the present invention, as described above, the switching operation of the upper and lower gas flow path switching valves causes the refrigerant gas flow in the processing chamber to flow downward, a single flow of the upward flow and the injection flow, or Since the flow can be switched at a desired time interval such as a downward flow and an upward flow, the flow of the refrigerant gas corresponding to the shape and size of the heated workpiece and the set state in the processing chamber can be obtained. As a result, the heated article to be processed can be cooled uniformly and rapidly, and the heat taken out can be efficiently discharged to the outside of the system, so that the cooling effect can be further ensured.

In addition, the injection nozzles provided on the inner wall of the heat insulating layer of the processing chamber are arranged evenly in the vertical direction and the inner circumferential direction, and the tip thereof faces the processing chamber side beyond the heating element, so that the processing object It is desirable to achieve uniform cooling and to prevent the formation of turbulence due to collision of the refrigerant gas with the heating element.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a front sectional view showing the outline of the vacuum heat treatment furnace of the present embodiment.

In FIG. 1, (1) is a vacuum tank, and the vacuum tank (1) is a vertical steel pressure vessel having a cylindrical body, and is connected to a vacuum pump not shown here. Have been.

(2) is a heat insulating layer, and the heat insulating layer (2) is a cylindrical member made of a heat insulating material such as glass fiber, and is disposed in the vacuum tank (1) with a gap therebetween. A heater (3) is provided on the surface, and a processing chamber (4) for accommodating a processing object is formed therein. The heat insulation layer (2)
Is a cylindrical inner heat insulating layer (2a), a cylindrical outer heat insulating layer (2b) that deflects the inner heat insulating layer (2a) with a gap through which gas can flow, and an inner and outer heat insulating layer (2a). (2b) annular upper and lower heat insulating layers (2c) and (2d) disposed at the upper and lower ends, and closing the upper and lower ends of the gap between them.

Here, the inner holes of the upper and lower heat insulating layers (2c) and (2d) of the heat insulating layer (2) are provided with upper and lower gas flow ports (11) and (12) into the processing chamber (2).
The upper and lower heat-dissipating lids (5) and (6) are disposed freely in these upper and lower gas flow ports (11) and (12). The upper and lower heat insulating lids (5) and (6) are connected to the output shafts of upper and lower cylinders (7) and (8) provided at the upper and lower portions of the vacuum tank (1), respectively. It is opened and closed by the operation of (8). On the other hand, on the inner peripheral surface of the heat insulating layer (2), the heater (3) is made of rod-like graphite, and is circumferentially arranged at equal intervals in the vertical direction. It is connected to energization and input control means.

The nozzle (9) is made of a tubular molybdenum material, and its base end penetrates through the inner heat insulating layer (2a) of the heat insulating layer (2). ), And the front end of the heater (3) passes through the gap of the heater (3).
And a plurality of processing chambers (4) are arranged at equal pitches in the vertical and circumferential directions of the processing chamber (4).

(10) is a flow path tube, and the flow path tube (10) is a cylindrical shape made of a thin nonmagnetic stainless steel plate, which surrounds the heat insulating layer (2) and has an inner wall of a vacuum tank (1). The heat-insulating layer (2) is disposed with a gap through which gas can flow between the outer wall and the outer wall.

(13) and (14) are upper and lower gas flow path switching valves,
These upper and lower gas flow path switching valves (13) and (14) are annular ones made of magnetic stainless steel, and are provided in upper and lower annular gaps between the heat insulating layer (2) and the flow path cylinder (10). The heat insulating layer (2) and the flow tube (10) are arranged so that they can be freely inserted and removed, and are activated by inputting power to upper and lower electromagnetic rings (15) and (16) provided on the upper and lower inner walls of the vacuum tank (1). ) And the gap between the upper and lower ends of the flow tube (10) and the inner wall of the vacuum tank (1) are selectively closed.

(17) is a first gas supply pipe. The first gas supply pipe (17) communicates with a gap between the heat insulation layer (2) and the flow path tube (10) to form a vacuum tank (1). ) It is provided substantially at the center in the vertical direction of the trunk.

(18) is a second gas supply pipe. The second gas supply pipe (18) communicates with a gap between the inner and outer heat insulating layers (2a) and (2b) of the heat insulating layer (2) to form a vacuum tank. (1) It is provided at a substantially central portion in the up-down direction of the body, which is different from the position of the first gas supply pipe (17) in the circumferential direction.

The first gas supply pipe (17) and the second gas supply pipe (18) are connected to a branch pipe (20) having on-off valves (21) and (22).
Here, it is connected to a nitrogen gas supply means as a refrigerant gas not shown here.

(19) is a gas exhaust pipe, and the gas exhaust pipe (19)
Is connected to the gap between the inner wall of the vacuum tank (1) and the flow path tube (10), and the vertical portion of the body of the vacuum tank (1) on the side opposite to the gas supply pipes (17) and (18). It is provided in the center. The gas exhaust pipe (19) is connected to a heat exchanger (not shown) via a connecting pipe (23) having an on-off valve (24). This heat exchanger is connected to the nitrogen gas supply means.

In the vacuum heat treatment furnace of the present embodiment having the above-described configuration, when the object to be processed heated in the processing chamber (4) is rapidly cooled with the refrigerant gas, the following patterns of refrigerant gas are stored in the processing chamber (4). A flow can be formed.

This will be described with reference to FIGS. 2 to 4, which are explanatory diagrams of the operation. The first pattern is the formation of a downward flow, as shown in FIG. The refrigerant gas from the means is introduced into the gap between the heat insulating layer (2) and the channel tube (10) via the first gas supply pipe (17), and the upper gas channel switching valve (13) is operated. To open the upper end of the gap between the heat insulating layer (2) and the flow channel tube (10), while opening the flow channel tube (10).
By closing the gap between the upper end and the inner wall of the vacuum tank (1), and simultaneously operating the lower gas flow switching valve (14),
While closing the lower end of the gap between the flow path tube (10) and the lower end of the flow path tube (10) and the inner wall of the vacuum tank (1).
By opening the upper and lower heat-insulating lids (5) and (6) together, the refrigerant gas is supplied from the first gas supply pipe (17) to the heat-insulating layer (2) and the flow path as indicated by the arrow in FIG. The gas flows into the processing chamber (4) from the upper gas flow port (11) through the gap between the cylinders (10), forms a downward flow in the processing chamber (4), and passes through the lower gas flow port ( This is achieved by discharging from 12) to the outside via a gas discharge pipe (19) through a gap between the flow path tube (10) and the inner wall of the vacuum tank (1).

The second pattern is the formation of an upward flow, which, as shown in FIG.
As described above, the gas is introduced into the gap between the heat insulating layer (2) and the flow path tube (10) via the first gas supply pipe (17), while the gas flow path switching valves (13) and (14) at the upper and lower portions are respectively provided. By operating the refrigerant gas in the reverse manner, the refrigerant gas is supplied from the first gas supply pipe (17) to the space between the heat insulating layer (2) and the flow path tube (10) as shown by the arrow in FIG. The gas flows into the processing chamber (4) from the lower gas flow port (12) through the gap, forms an ascending flow in the processing chamber (4), and flows through the upper gas flow port (13). This is achieved by discharging the gas to the outside through the gas discharge pipe (19) through the gap between the (10) and the inner wall of the vacuum tank (1).

The third pattern is the formation of an alternating flow in the vertical direction,
This is achieved by inverting the upper and lower gas flow switching valves (13) and (14) at appropriate times while continuing to introduce the refrigerant gas through the first gas supply pipe (17).
This is achieved by changing the direction of the refrigerant gas flow in the processing chamber (4) by alternating the operation of the first pattern and the operation of the second pattern.

In the first to third patterns described above, the gas flow of the second gas supply pipe (18) is closed.

The fourth pattern is the formation of a jet flow from the outer peripheral direction, which, as shown in FIG. 4, transfers refrigerant gas from an external supply means via a second gas supply pipe (18). Into the gap between the inner and outer heat-insulating layers (2a) and (2b) of the heat-insulating layer (2), and actuate the gas flow switching valves (13) at the upper and lower portions to thereby allow the heat-insulating layer (2) and the flow path cylinder While the upper and lower ends of the gap between (10) are closed, the gap between the upper and lower ends of the flow tube (10) and the inner wall of the vacuum tank (1) is opened, and the upper and lower heat insulating lids (5) are combined.
By opening (6), the refrigerant gas is supplied from the first gas supply pipe (17) to the inner and outer heat insulating layers (2a) and (2b) of the heat insulating layer (2) as shown by arrows in FIG. Through a gap between the nozzles, the fuel is injected toward the processing chamber (4) through a nozzle (9) provided around the inner heat-insulating layer (2a), and is divided vertically in the processing chamber (4). The gas is discharged from the upper and lower gas flow ports (11) and (12) to the outside via the gas discharge pipe (19) through the gap between the flow path cylinder (10) and the inner wall of the vacuum tank (1). Achieved. In this pattern, the gas flow of the first gas supply pipe (17) is closed.

Next, a specific heat treatment example using the vacuum heat treatment furnace of the present embodiment will be described.

First, a small-diameter broach made of high-speed tool steel with an outer diameter of 50 mm and a length of 1400 mm was suspended in a jig, 16 pieces were inserted into the processing chamber, and heated to 1200 to 1220 ° C. Based on the pattern, an alternating flow of nitrogen gas whose direction was changed up and down at a pitch of 20 to 40 seconds was formed in the processing chamber, and the quench treatment was performed by rapid cooling with the alternating flow. When the surface hardness and bending of each broach after the quenching treatment were measured, they had uniform hardness distribution in the longitudinal direction, and the bending was very good quality with a total length of 0.3 mm or less.

Next, insert one large-diameter broach made of high-speed tool steel with an outer diameter of 100 mm and a length of 2000 mm into the center of the processing chamber.
After suspending and heating to 1200 to 1220 ° C., based on the above-described fourth pattern, a refrigerant gas was blown onto the outer peripheral surface of the broach in the processing chamber, and the quenching treatment was performed by rapid cooling with the jet flow. When the surface hardness and bending of the broach after the quenching treatment were measured, the hardness distribution in the longitudinal direction was uniform, and the bending was very good quality with a total length of 0.4 mm or less.

As described above, in the vacuum heat treatment furnace of the present embodiment, the flow of the refrigerant gas in the processing chamber can be arbitrarily set and changed to the downward flow, the upward flow, the vertical alternating flow, and the injection flow from the outer peripheral side. In cooling the heated article to be processed, the refrigerant gas flow can uniformly and rapidly cool the article to be processed according to the shape and the set state of the article to be treated. Further, since the heat taken from the article to be processed is carried out of the system by discharging the refrigerant gas from the gas discharge pipe, the forced circulation means and the cooling means of the refrigerant gas are provided in the furnace as in a conventional heat treatment furnace. There is no need to provide them, the configuration is simple, and maintenance and inspection and maintenance are easy.

In the heat treatment furnace of the present embodiment, the upper and lower gas flow path switching valves (13) and (14) are made to be annular, and these are operated by an electromagnetic ring. However, this is an example. A plurality of flow holes are provided between the upper and lower ends of the flow channel tube (10) and the vacuum tank (1), and the heat insulating layer (2) and the flow channel tube (1) are provided.
0) While a plurality of flow holes are provided at the upper and lower ends of the gap between
Other configurations such as providing a plurality of butterfly valves that rotate between them to selectively open and close the gas flow can be employed.

〔The invention's effect〕

As described above, the heat treatment furnace according to the present invention sets or easily changes the flow of the refrigerant gas introduced into the processing chamber at the time of cooling after heating to the one most suitable for the shape and set state of the article to be processed. Therefore, the heated workpiece can be cooled rapidly and evenly, and the quenching process can be assured and the product quality can be improved.In addition, the internal structure is simple and its maintenance and inspection and maintenance are easy. It's easy.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an outline of a vacuum heat treatment furnace according to an embodiment of the present invention, FIGS. 2 to 4 are explanatory views of the operation of the vacuum heat treatment furnace according to the embodiment of the present invention, and FIG. FIG. 6 is a front sectional view showing a heat treatment furnace, and FIG. 6 is a front sectional view showing a conventional vacuum heat treatment furnace. (1) ... Vacuum tank, (2) ... Heat insulation layer, (2a) ...
Inner heat insulating layer, (2b) ... outer heat insulating layer, (3) ... heater, (4) ... processing chamber, (5) ... upper heat insulating lid, (6) ...
... Lower thermal insulation lid, (7) ... Upper cylinder, (8) ... Lower cylinder, (9) ... Nozzle, (10) ... Flow path cylinder, (11) ...
... Upper gas outlet, (12) ... Lower gas outlet, (13) ...
Gas flow switching valve, (14) ... Gas flow switching valve, (15) ...
… Upper electromagnetic ring, (16) …… Lower electromagnetic ring, (17)…
First gas supply pipe, (18) ... Second gas supply pipe, (19) ...
... gas exhaust pipe.

Claims (1)

(57) [Claims] A cylindrical processing chamber comprising a vacuum tank, a heat insulating layer provided in the vacuum tank, and having a gas flow opening which can be opened and closed at upper and lower portions, and a heat insulating layer between the inner wall of the vacuum tank and the processing chamber. A flow path cylinder disposed between the processing chamber and a flow path cylinder disposed between the flow path cylinder and the vacuum tank inner wall and between the flow path cylinder and the heat insulating layer outer wall of the processing chamber; And a heating element provided on the inner periphery of the vacuum heat treatment furnace,
The heat insulating layer of the processing chamber is formed in a double configuration in which a gas flow gap is provided in the layer, and a plurality of jets communicating the gas flow gap in the layer and the processing chamber are formed on the inner wall of the heat insulating layer. A nozzle is provided, on the other hand, in each of the upper and lower portions between the processing chamber and the flow path cylinder, a gas permeable gap between the processing chamber and the flow path cylinder, the vacuum tank inner wall, and the flow path cylinder. Provide a gas flow path switching valve that can alternately open and close the gap through which gas can flow,
A first gas supply pipe communicating with a gap between the processing chamber and the flow path tube, and a second gas supply pipe communicating with a gas flow gap in a heat insulating layer of the processing chamber. And a gas exhaust pipe communicating with a gap between the inner wall of the vacuum tank and the flow channel tube.