JPH0514025B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of operating a semi-continuous vacuum carburizing furnace that is equipped with two chambers, a heating chamber and a cooling chamber, and performs carburizing treatment.

<Prior Art> A conventional vacuum carburizing furnace equipped with two chambers, a heating chamber and a cooling chamber, is described in Japanese Patent Application Laid-open No. 130270/1985 as shown in FIG.

This vacuum carburizing furnace 1 has a heating chamber 2 composed of a heating element 2a and a heat insulating material 2b, which are chemically and mechanically stable in high-temperature environments such as vacuum and air, and which covers the heating chamber 2 and has an oil tank 3a. A vacuum container 4 that constitutes the outer wall of the cooling chamber 3 itself is provided, and both the heating chamber 2 and the cooling chamber 3 are connected to a vacuum exhaust source V.
is connected. Further, a carburizing gas source C is connected to the heating chamber 2, and an inert gas source G such as nitrogen gas capable of pressurizing the inside of the cooling chamber 3 to above atmospheric pressure is connected to the cooling chamber 3, respectively.

In addition, 5 is a charging door, 6 is an intermediate vacuum door, 7 is a carry-out door, 8 is an internal transfer device, 9 is a lifting platform, 5a is an internal charging door, and 6a is an internal intermediate door.

The operating method using this vacuum carburizing furnace 1 is as follows (see Table 1).

First, the heating chamber 2 is heated in advance to a predetermined temperature under atmospheric pressure.

First step...The charging doors 5, 5a are opened, the first object to be heated M1 is charged into the heating chamber 2, and immediately the charging doors 5, 5a are opened.
Close 5a.

Second step: While the heating chamber 2 is evacuated by the vacuum evacuation source V, the first heat target M1 is vacuum heated to a predetermined temperature, and then a predetermined carburizing process is performed by the carburizing gas source C. . Then, the material is evacuated again and subjected to diffusion treatment, and then the temperature is lowered and soaked to the quenching temperature.
Meanwhile, the cooling chamber 3 is evacuated.

Third step: The intermediate vacuum doors 6, 6a are opened, the object to be heated M1 is transferred to the lifting platform 9 of the cooling chamber 3 by the internal transfer device 8, and the intermediate vacuum doors 6, 6a are immediately closed.

Fourth step: While supplying gas from the inert gas source G to pressurize the cooling chamber 3 above atmospheric pressure, the elevator platform 9 is lowered to quench the first object to be heated M1.
In the meantime, air is introduced into the high-temperature heating chamber 2 to bring it to atmospheric pressure, and the charging doors 5 and 5a are opened to charge the second heat object M2 into the heating chamber 2, and the charging door is immediately opened. 5, 5a are closed. The reason why the cooling chamber 3 is pressurized above atmospheric pressure is to prevent the air from entering the cooling chamber 3 when air enters the heating chamber 2 .

Fifth step: The lifting platform 9 is raised, the carry-out door 7 is opened, the first object to be heated M1 is carried out of the furnace 1, and the carry-out door 7 is immediately closed to evacuate the cooling chamber 3.
In the meantime, the second heated object M2 is handled in the same manner as in the second step.

Thereafter, in the steady state, the third, fourth, and fifth steps are repeated.

<Problems to be solved by the invention> The conventional method of operating the vacuum carburizing furnace 1 is to
1. When charging M2 into the heating chamber 2, the heating chamber 2 is exposed to the atmosphere, so that the soot adhering to the heating element 1a and the heat insulating material 1b during the carburizing process can be burned off.
This is effective in cleaning the inside of the heating chamber 2.

However, in the conventional method of operating the vacuum carburizing furnace 1,
When transferring the heated object M from the heating chamber 2 to the cooling chamber 3,
In order to prevent the heated object M from being oxidized, the cooling chamber 3 is kept in a vacuum, and it is necessary to make not only the heating chamber 2 but also the cooling chamber 3 a vacuum. Therefore, since the cooling chamber 3, which has a large volume and is equipped with an oil tank 3a, etc. that performs the quenching that is essential for the carburizing process, is evacuated, the number of man-hours for maintenance and inspection during operation to maintain the airtightness of the large vacuum container 4 increases. Moreover, the operating energy of the vacuum evacuation source V increases.

Furthermore, the cooling chamber 3 with a large volume also needs to have a vacuum structure, and a large vacuum container 4, which covers the heating chamber 2 and constitutes the outer wall of the cooling chamber 3 itself, is equipped with various high-strength outer walls and vacuum sealing materials. is required,
Not only does the cost of materials increase when manufacturing the vacuum carburizing furnace 1, it also becomes necessary to control airtightness during manufacturing.
This increased the manufacturing cost and man-hours for the furnace.

Furthermore, since the object to be heated M is transferred from the heating chamber 2 to the cooling chamber 3 in a vacuum state, it is necessary to arrange the internal transfer device 8 and the driving device for the intermediate vacuum doors 6 and 6a inside the vacuum container 4. As a result, this type of drive device must be constructed with special mechanisms and parts, which increases the number of man-hours for maintenance and inspection of the furnace, the number of man-hours for manufacturing, and the manufacturing cost.

The present invention solves the above-mentioned problems, and allows maintenance and inspection to maintain airtightness during operation by allowing operation of a large-volume cooling chamber without creating a vacuum state without interfering with the processing of heated objects. It is an object of the present invention to provide a method for operating a vacuum carburizing furnace that can reduce the number of man-hours and save energy in the vacuum exhaust source, as well as reduce the number of man-hours and manufacturing cost of the furnace itself.

<Means for solving the problems> The operating method according to the present invention includes two chambers, a heating chamber and a cooling chamber, separated by an intermediate vacuum door, and
A method of operating a vacuum carburizing furnace in which a charging door for charging the heated material is provided at the front of the heating chamber, and an ejection door for transporting the heated material at the rear of the cooling chamber, the method comprising: heating the furnace in advance; The chamber is heated to a predetermined temperature at atmospheric pressure, and the cooling chamber is constantly kept in an inert gas atmosphere at atmospheric pressure by supplying inert gas.
It is characterized by performing the following steps 1 to 5.

First step: Open the charging door, charge the first object to be heated into the heating chamber, and close the charging door.

Second step: The first object to be heated is heated in a vacuum in a heating chamber, and then the first object to be heated is carburized, diffused, and heated while lowering and soaking temperature.

Third step: Bring the heating chamber to atmospheric pressure by supplying an inert gas, open the intermediate vacuum door, transfer the first object to be heated to the cooling chamber, and then close the intermediate vacuum door.

Fourth step The first object to be heated is quenched by the cooling means, the charging door is opened, the second object to be heated is charged into the heating chamber, and then the charging door is closed.

Fifth step: The carry-out door is opened to carry out the quenched first heat object from the cooling chamber, and then the carry-out door is closed, during which time the subsequent second heat object is processed in the second and subsequent steps.

<Actions and Effects of the Invention> In the operating method according to the present invention, when the object to be heated is transferred from the heating chamber to the cooling chamber, both the heating chamber and the cooling chamber are kept in an inert gas atmosphere at atmospheric pressure. , the object to be heated is not oxidized and can be transferred without any trouble. Then, the object to be heated is hardened by a cooling means in an inert gas atmosphere at atmospheric pressure in the cooling chamber, and then transported out of the cooling chamber, where it is subjected to a predetermined carburizing treatment without any trouble.

Therefore, in the present invention, it is only necessary to cover only the heating chamber with a vacuum container and keep the cooling chamber in an inert gas atmosphere at atmospheric pressure by constantly supplying inert gas. It is no longer necessary to create a structure.

Therefore, maintenance and inspection to maintain the airtightness of the large volume cooling room can be simplified, and the number of man-hours for maintenance and inspection during operation can be reduced. Further, since it is not necessary to put only the heating chamber in a vacuum state and not put a large cooling room in a vacuum state, it is possible to save energy in the evacuation source.

Furthermore, since it is not necessary to construct a cooling chamber with a large volume that can be evacuated, there is no need for a large vacuum container made of various high-strength outer walls and vacuum sealing materials, which is required in the past. Manufacturing man-hours and manufacturing costs can be reduced.

In addition, it is no longer necessary to install the heated object transfer device and intermediate vacuum door drive device inside the vacuum container as in the past, so these devices can be constructed from commercially available products with normal mechanisms rather than special devices. This can help reduce the manufacturing man-hours and manufacturing cost of the furnace. In particular, since inert gas is always supplied to the cooling chamber at atmospheric pressure, when transferring heated objects from the heating chamber to the cooling chamber, the intermediate vacuum door is opened and the rear transfer device placed on the cooling chamber side is used. It is possible to transfer the material to be heated by using the transfer device, which eliminates the need for a device to transfer the material to be heated in the vacuum container, further reducing the manufacturing man-hours and manufacturing cost of the vacuum carburizing furnace. Maintenance and inspection can also be easily performed.

<Example> An example of the present invention will be described below based on the drawings.

First, to explain the vacuum carburizing furnace used in the examples, this vacuum carburizing furnace 11 is composed of two chambers, a heating chamber 12 and a cooling chamber 13, as shown in FIG. It is covered by 14.

The heating chamber 12 has a heat insulating material 12b inside the vacuum container 14.
and a heating element 12a.

As the heating element 12a, a resistance heating element is used which has high high-temperature strength, does not oxidize and burn when directly exposed to air at high temperatures, does not generate thermal cracks, and does not evaporate even in high-temperature vacuum conditions. For example, a silicon carbide heating element that has undergone recrystallization treatment, an alumina spray coating layer formed on its surface, or a nickel-chromium alloy heating element with a maximum heating temperature of 1000℃ or less and a vacuum pressure of about 0.2 Torr. body, iron/chromium alloy heating element, etc. can be used.

The heat insulating material 12b is made of a refractory material that has low thermal conductivity and is chemically stable even when repeatedly exposed to vacuum ←→ atmosphere at high temperatures, such as high-purity ceramic fiber.

In the front part of the heating chamber 12 (left side in the figure),
A charging door 15 for charging the object to be heated M is provided.
This charging door 15 is a door that serves both the heating chamber 12 and the vacuum vessel 14, and is opened and closed in the vertical direction by a drive device (not shown) disposed in the furnace 11 via a link mechanism 151 and a guide rail 152. It is configured to

At the rear of the heating chamber 12 (on the right side in the figure), there is a heated object M.
An intermediate vacuum door 16 for carrying out is provided. Similar to the charging door 15, this intermediate vacuum door 16 is a door that serves both the heating chamber 12 and the vacuum container 14, and is connected to the link mechanism 161, the guide rail 162, and the chain 16.
3. It is configured to be opened and closed in the vertical direction by a drive device (not shown) outside the furnace 11 that is connected to the shaft of one sprocket 164 via a sprocket 164.

Further, in the heating chamber 12, a vacuum exhaust source V composed of a vacuum pump or the like is connected to a conduit 2 equipped with a solenoid valve 22.
1, and the carburizing gas source C is connected to a conduit 23 equipped with a solenoid valve 24 and a flow regulator 25.
connected via. Furthermore, a nitrogen gas source G that supplies nitrogen gas as an inert gas is connected to the heating chamber 12 via a conduit 28 that includes a solenoid valve 29 .

Note that 18 is a hearth rail, and 20 is a fan for stirring the carburizing gas.

The cooling chamber 13 is connected to the rear part of the heating chamber 12 at the intermediate vacuum door 16, and includes an oil tank 13a serving as a cooling means for quenching inside.

At the rear of the cooling chamber 13 (on the right side in the figure), there is a heated object M.
An unloading door 17 for unloading is provided, and this unloading door 17
Like the charging door 15, it is opened and closed in the vertical direction by a drive device (not shown) disposed outside the furnace 11 via a link mechanism 171 and a guide rail 172.

Further, a nitrogen gas source G is connected to the cooling chamber 13 via a conduit 30 including a flow rate regulator 31 so that the inside of the cooling chamber 13 is always maintained at atmospheric pressure and in a nitrogen gas atmosphere. By the way, in the case of the example, furnace 1
During operation, the pressure inside the cooling chamber 13 is slightly increased (approximately 20 mm) above atmospheric pressure so that the atmospheric pressure can be maintained at all times.
H ₂ O) and causes nitrogen gas to flow out.

Unlike the conventional cooling chamber 3, this cooling chamber 13 does not need to maintain a vacuum state during operation.
Since it is sufficient to maintain the atmospheric pressure state of the nitrogen gas atmosphere, there is no need for the outer wall to have a high-strength structure or to use a vacuum sealing material.

Note that reference numeral 19 denotes a lifting platform for loading and lifting the heated object M into the oil tank 13a, and is driven by an air cylinder 34 provided outside the cooling chamber 13. 32 is a nitrogen gas waste pipe equipped with a flow rate regulator 33.

In addition, a conveyor 35 for charging the object to be heated M is disposed at the front of the furnace 11, corresponding to the position of the charging door 15, and at the rear of the furnace 11, a conveyor 35 for charging the material to be heated M is arranged corresponding to the position of the loading door 17. A conveyor 37 for carrying out the object to be heated M is provided.

In the charging conveyor 35, there is a charging door 1.
A push-out rod 36 is provided as a front transfer device capable of transferring the heated material M on the charging conveyor 35 to a predetermined position on the hearth rail 18 in the heating chamber 12 when the charging conveyor 35 is released. In addition, the distal end of the discharging conveyor 37 is inserted into the cooling chamber 13 through the discharging door 17, and when the intermediate vacuum door 16 is opened, the heating chamber 12
A rear transfer device that transfers the heated object M inside the cooling chamber 13 onto the lifting platform 19, and also transports the heated object M inside the cooling chamber 13 out of the furnace 11 when the carrying-out door 17 is opened. As a drawer rod 38 is provided.

In addition, when transporting the object to be heated M, the extrusion rod 36 and the drawer rod 38 hook the pallet P on which the object to be heated M is placed on the upper surface, and pull out the pallet P.
The object to be heated M is transferred through the .

Next, the operating method of the embodiment using this vacuum carburizing furnace 11 will be explained (see Table 2).

First, the heating chamber 12 is heated in advance to a predetermined temperature at atmospheric pressure, and the flow rate regulator 31 is adjusted to supply a predetermined flow rate of nitrogen gas from the nitrogen gas source G into the cooling chamber 13 for cooling. The inside of the chamber 13 is kept in a nitrogen gas atmosphere at atmospheric pressure. In addition, each door 1
5, 16, and 17 will be closed.

First step: Open the charging door 15, use the extrusion rod 36 to transfer the first heated object M1 on the charging conveyor 35 to a predetermined position on the hearth rail 18, and
1 into the heating chamber 12. Then, the charging door 15 is immediately closed.

Second Step The solenoid valve 22 is opened to reduce the pressure in the heating chamber 12 to a vacuum state, and the first object to be heated M1 is heated and soaked to a predetermined carburizing temperature, and then the solenoid valve 22 is closed.

Then, while maintaining a predetermined carburizing temperature, the solenoid valve 24 is opened to supply carburizing gas at a predetermined flow rate into the heating chamber 12 for a predetermined time, thereby carburizing the first object to be heated M1.

Thereafter, while maintaining the high temperature, the solenoid valve 24 is closed and the solenoid valve 22 is opened again to create a vacuum state in the heating chamber 12, and the carburized first heat target M
Carbon in the surface layer of No. 1 is diffused into the core.

Thereafter, the first object to be heated M1 is heated and soaked so as to reach the optimum temperature for hardening.

Third step: Close the solenoid valve 22 and open the solenoid valve 29 to supply nitrogen gas into the heating chamber 12 to create a nitrogen gas atmosphere at the same atmospheric pressure as the cooling chamber 13, and then create an intermediate vacuum. Door 16 is opened. Then, using the drawer rod 38, the first heated object M1 on the hearth rail 18 is transferred onto the lifting platform 19, the first heated object M1 is transferred to the cooling chamber 13, and then the intermediate vacuum door 16 will be closed. Incidentally, when the first heat target M1 is transferred, since both the heating chamber 12 and the cooling chamber 13 are in a nitrogen gas atmosphere, the first heat target M1 is not oxidized and there is no problem. It will be transferred without any problem.

Fourth step: The air cylinder 34 is operated to lower the elevator platform 19, and the first object to be heated M1 is put into the oil tank 13a and oil quenched.

At the same time, the charging door 15 is opened, and the subsequent second heat object M2 on the charging conveyor 35 is charged into a predetermined position on the hearth rail 18 of the heating chamber 12 via the push rod 36. , and then immediately closes the charging door 15. At that time, since air flows into the heating chamber 12, the soot of the carburizing gas adhering to the heating element 12a and the heat insulating material 12b is burned out, and the heating chamber 12
You can cleanse the inside.

Fifth step: The lifting platform 19 and the first heated object M1 in the oil tank 13a are raised via the air cylinder 34 and returned to their original positions. Then, the carry-out door 17 is opened, and the first heated object M1 is transferred from the elevator platform 19 onto the carry-out conveyor 37 via the drawer rod 38.
1 is carried out from the cooling chamber 13, the carrying-out door 17 is closed. Furthermore, in the heating chamber 12, the second heat target M2 is processed in the same manner as in the second step.

Thereafter, in a steady state, the third, fourth, and fifth steps are repeated. Although a small amount of air enters the cooling chamber 13 during unloading, the intruding air is diluted with an inert gas and discharged before the next heated object M comes to the cooling chamber 13.

Therefore, in the operating method of this embodiment, even if the cooling chamber 13 is not brought into a vacuum state, the heated object M may become a nuisance.
The effects of the invention described above are
The effect is similar to that described in the effect section.

In addition, in this embodiment, movable loading door 15, intermediate vacuum door 16, unloading door 17, and lifting platform 1
9. If the push-out/draw-out rods 36, 38, etc. for transferring the heated material M in the furnace 11 are not all disposed in the vacuum vessel 14, and automatic operation is performed, detection for confirming the position of each movable part. The sensor can be placed outside the vacuum vessel 14, and the mechanism during automatic operation can be simplified, which is advantageous in terms of hardware and software during automatic operation.

By the way, when operating the conventional furnace 1 automatically, cams, cam rods, etc. are placed at the positions of each moving part because operating the various detection switches in a vacuum significantly shortens the life of their contacts. Then, the end of the cam rod or the like needs to be taken out of the vacuum vessel, and the movement of the end must be detected by a detection switch, resulting in a complicated mechanism.

In addition, in the embodiment, an oil tank 13a is used as a cooling means for hardening the object to be heated, but
In addition, a quenching liquid such as water or a water-soluble coolant, or a well-known cooling means such as gas cooling or fluidized bed cooling may be used.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a vacuum carburizing furnace used in an embodiment of the present invention, and FIG. 2 is a sectional view of a furnace used in a conventional example. 11...Vacuum carburizing furnace, 12...Heating chamber, 12a
...Heating element, 12b...Insulating material, 13...Cooling chamber, 13a...Oil tank, 14...Vacuum container, 15...
...Charging door, 16...Intermediate vacuum door, 17...Export door, 36...(Front transfer device) Extrusion rod, 38
... (rear transfer device) drawer rod, M ... heated object, V ... vacuum exhaust source, C ... carburizing gas source, G ...
...(Inert gas source) Nitrogen gas source.

Claims (1)

[Claims] 1. A heating chamber and a cooling chamber separated by an intermediate vacuum door are provided, and a charging door for charging objects to be heated is provided at the front of the heating chamber, This is a method of operating a vacuum carburizing furnace that is equipped with an exit door at the rear for transporting heated materials, in which the heating chamber is heated to a predetermined temperature at atmospheric pressure in advance, and the cooling chamber is supplied with inert gas. to maintain an inert gas atmosphere at constant atmospheric pressure,
A method for operating a vacuum carburizing furnace, comprising performing the following steps 1 to 5. First step: Open the charging door, charge the first object to be heated into the heating chamber, and close the charging door. Second step: The first object to be heated is heated in a vacuum in a heating chamber, and then the first object to be heated is carburized, diffused, and heated while lowering and soaking temperature. Third step: Bring the heating chamber to atmospheric pressure by supplying an inert gas, open the intermediate vacuum door, transfer the first object to be heated to the cooling chamber, and then close the intermediate vacuum door. Fourth step The first object to be heated is quenched by the cooling means, the charging door is opened, the second object to be heated is charged into the heating chamber, and then the charging door is closed. Fifth step: The carry-out door is opened to carry out the quenched first heat object from the cooling chamber, and then the carry-out door is closed, during which time the subsequent second heat object is processed in the second and subsequent steps.