JP2946020B2 - Prevention of outside air inflow when opening and closing the door of the nitrocarburizing furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing outside air from flowing into a nitrocarburizing furnace for nitrocarburizing a surface of a steel plate or the like.

[0002]

2. Description of the Related Art In general, when a surface of a steel plate or the like (work) is industrially soft-nitrided, a shift furnace gas and an ammonia gas are introduced into a heat treatment chamber, and the surface of the work is reacted by the shift furnace gas and the ammonia gas. A gas nitrocarburizing method for nitriding is used.

[0003]

However, the nitrocarburizing method using the gas in the shift furnace requires maintenance of the shift furnace for generating the shift gas, and the maintenance of the shift furnace is troublesome. . Further, although the nitriding ability is affected by the amount of hydrogen in the heat treatment chamber, since the shift furnace gas is basically a hydrocarbon gas, the shift furnace gas contains a large amount of hydrogen components and the nitriding ability is low. For this reason, there is a problem that a large amount of the gas for the conversion furnace is required to perform the treatment in a short time, and the processing time is prolonged with a small amount of the gas for the conversion furnace.

In a nitriding apparatus, a carbon monoxide gas and a hydrogen gas are filled in a heat treatment chamber, and when a negative pressure is caused by a reaction in the heat treatment chamber, when a loading / unloading port is opened at the time of loading or unloading a work, the outside air is opened. May flow into the heat treatment chamber and explode. For this reason, it is necessary to supply a gas for keeping the pressure inside the heat treatment chamber always to the positive pressure to the heat treatment chamber, and there is a problem that the amount of gas used increases and it is uneconomical. The present invention has been made in view of such a point, and an object of the present invention is to provide an outside air inflow prevention method capable of reliably preventing the inflow of outside air with a small amount of processing gas.

[0005]

To achieve the above object, the present invention provides a nitrocarburizing furnace using nitrogen gas, carbon dioxide gas and ammonia gas as atmosphere gas.
A carry-in room is arranged on the carry-in side of the heat treatment room, and a carry-out room is arranged on the carry-out side of the heat treatment room, so that the space between the carry-in room and the heat treatment room and between the heat treatment room and the carry-out room can be raised and lowered, respectively. A door is configured to be openable and closable, and the outer openings of the loading chamber and the unloading chamber are configured to be openable and closable by an outer door that can be raised and lowered, and the inner and outer doors of the loading chamber are controlled to be opened and closed alternately.
Controlling the inner and outer doors of the carry-out chamber to open and close alternately, connecting a purge nitrogen gas ejection path to each of the carry-in chamber and the carry-out chamber,
A flow path opening / closing valve is arranged in each of the purge nitrogen gas ejection paths, and the opening operation of the flow path opening / closing valve arranged in the purge nitrogen gas ejection path on the carry-in side is linked to the opening / closing operation of the inner and outer doors of the carry-in chamber. At the same time, the opening operation of the flow path opening / closing valve arranged in the nitrogen gas ejection path for purge on the discharge chamber side is linked with the opening / closing operation of the inner and outer doors of the discharge chamber, and the corresponding flow path opening / closing valve is opened and closed during each door opening / closing operation. By maintaining the valve open and injecting nitrogen gas into the carry-in and carry-out chambers respectively, the carry-in and carry-out chambers are formed in a nitrogen gas atmosphere to prevent outside air from entering the heat treatment chamber. And

[0006]

According to the present invention, the loading chamber and the loading / unloading chamber are arranged before and after the heat treatment chamber in a state where the loading chamber and the loading / unloading chamber are separated from each other by doors, and doors are also provided on both outer sides of the loading chamber and the loading / unloading chamber. The nitrogen gas spouting path is connected to each of the pipes, and the flow path opening / closing valves arranged in each nitrogen gas spouting path are opened / closed in conjunction with the opening / closing operation of the corresponding front and rear doors of the loading chamber and the unloading chamber. In this case, nitrogen gas is blown out to the carry-in room or carry-out room when one of the front and rear doors is open, and the carry-in room and carry-out room are maintained at a positive pressure when the door is open. Therefore, it is possible to reliably prevent the outside air from flowing into the heat treatment chamber.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a gas nitriding apparatus showing one embodiment of the present invention. This gas nitriding device is
A loading chamber (2) is arranged on the inlet side of (1), and an unloading chamber (3) is arranged on the outlet side of the heat treatment chamber (1), so that it is possible to move up and down between the heat treatment chamber (1) and the loading chamber (2). Partition with inner door (4) and heat treatment room
The space between (1) and the carry-out room (3) is also partitioned by an inner door (5) that can be moved up and down.

An outer door (6) is arranged at the entrance of the loading chamber (2) so as to be able to move up and down, and an outer door (7) is also arranged at the exit of the unloading chamber (3) so as to be able to move up and down. It is. Each door (4) (5)
(6) and (7) are air cylinders (8) that operate independently
(9) It is configured to open and close in (10) and (11). The inner door (4) and the outer door (6) of the loading room (2) are selectively opened and closed,
The inner door (5) and the outer door (7) of the unloading chamber (3) are also selectively opened and closed, so that the heat treatment chamber (1) does not face the outside directly. It is. Both inner doors (4)
In (5), a communication hole (12) having a small opening area is formed.

In the heat treatment chamber (1), a processing gas jet nozzle is provided.
A processing gas supply path (14) to the processing gas ejection nozzle (13) includes a nitrogen gas supply path (15), a carbon dioxide supply path (16), and an ammonia gas supply path (17). ), And each gas supply path (15), (16), (17) has a flow control valve (1).
8) (19) (20), flow meter (21) (22) (23) and pressure regulating valve (24) (25) (2
6) is located.

Purge nitrogen gas ejection paths (27) and (28) branch out from the nitrogen gas supply path (15) to the carry-in chamber (2) and the carry-out chamber (3), respectively. (27) (28)
Are provided with flow passage opening / closing valves (29) and (30). Then, a purge nitrogen gas ejection path (27) connected to the carry-in chamber (2).
The opening / closing valve (29) disposed in the opening and closing operation is linked to the opening / closing operation of the inner door (4) and the outer door (6) of the loading room (2). (4) The flow path opening / closing valve (29) is kept open while the (6) is in the open state, and the purge nitrogen gas ejection path ( The flow path opening / closing valve (30) arranged in (28) is opened / closed in conjunction with the opening / closing operation of the inner door (5) and the outer door (7) of the carry-out chamber (3). When the doors (5) and (7) are open, the flow path on-off valve (30) is kept open.

The processing gas supply path (14) has an atmosphere gas obtained by mixing nitrogen gas and carbon dioxide gas at a flow ratio of 9: 1, and a flow ratio of 1: 1 to the atmosphere gas. A mixed gas obtained by mixing ammonia gas is supplied. Therefore, the component ratio in the mixed gas is 45 Vol% of nitrogen gas, 5 Vol% of carbon dioxide gas, and 50 Vol% of ammonia gas. The mixing ratio of the atmosphere gas is increased depending on the carbon content of the material to be treated, by increasing the carbon dioxide mixing ratio to about 10 vol% in the case of a material having a high carbon content, and Reduces the mixing ratio of carbon dioxide to about 2.5%.

In the drawing, reference numeral (31) denotes an exhaust pipe derived from the ceiling wall of the carry-in room (2) and the carry-out room (3), and (32) denotes a carry-out room (3).
The oil tank for cooling arranged in (3), (33), (34), (35) and (36) are the operation control arranged in the working air supply path to each door opening / closing control air cylinder (8) (9) (10) (11) It is a valve.

In such a nitriding apparatus, the work is introduced into the loading chamber (2) by opening the outer door (6) of the loading chamber (2). At this time, the operation control valve of the air cylinder (10) that drives the outer door (6)
In conjunction with the opening operation of (33), the opening / closing valve (29) of the nitrogen gas ejection path for purging (27) on the loading chamber side is opened to open the outer door (6).
The nitrogen gas for purging is continuously jetted into the carry-in chamber (2) from the start of opening to the closing thereof to prevent the outside air from flowing into the carry-in chamber (2).

When the work is carried into the carry-in room (2), the outer door
(6) is closed, the inner door (4) is opened, and the work is introduced into the heat treatment chamber (1). At this time, the carry-in side purge nitrogen gas ejection path (27) is kept open from the start of opening of the inner door (4) to the closing thereof. Therefore, the outer door
When the inner door (4) is opened and operated after the (6) is completely closed, of course, the inner door (4) must be closed before the outer door (6) is completely closed.
Even if the opening of (4) is started, the outside air component does not flow into the heat treatment chamber (1) because the loading chamber (2) is filled with the nitrogen gas for purging.

In the heat treatment chamber (1), a processing gas obtained by mixing a gas obtained by mixing nitrogen gas and carbon dioxide at a ratio of 9: 1 with the same amount of ammonia gas is applied to the work. Is subjected to a soft nitriding treatment. At this time, communication holes (12) are formed in the inner doors (4) and (5), which define the heat treatment chamber (1), the carry-in chamber (2), and the carry-out chamber (3), respectively. A part of the processing gas in the heat treatment room (1) flows into the carry-in room (2) and the carry-out room (3), and is carried into the carry-in room (2) and the carry-out room.
It is discharged from the discharge tube (31) arranged on the ceiling of (3).

Next, the inner door (5) between the heat treatment room (1) and the unloading room (3) is opened, and the work in the heat treatment room (1) is unloaded.
At this time, the nitrogen gas for purging is discharged into the discharge chamber (3) in conjunction with the opening operation of the inner door (5). After immersing the work in the cooling oil bath (32) and cooling it,
The work is carried out after opening the outer door (7) of the carry-out room (3). Then, purging nitrogen gas is jetted into the discharge chamber (3) in conjunction with the opening operation of the outer door (7).

[0017]

According to the present invention, the loading chamber and the loading / unloading chamber are arranged in front and rear of the heat treatment chamber in a state where the loading chamber and the loading / unloading chamber are separated by doors, and doors are also provided on both outer sides of the loading chamber and the loading / unloading chamber. The nitrogen gas ejection path is connected to each of the chambers by piping, and the flow path on-off valves arranged in each nitrogen gas ejection path are opened and closed in conjunction with the opening and closing operations of the corresponding front and rear doors of the loading chamber and the unloading chamber. Operate and, when any of the front and rear doors are open, blow out nitrogen gas into the carry-in room or carry-out room, and keep the carry-in room and carry-out room at positive pressure with the doors open. Therefore, it is possible to reliably prevent the outside air from flowing into the heat treatment chamber.

In addition, the nitrogen gas supplied to the carry-in chamber and the carry-out chamber may be obtained by branching a part of the nitrogen gas used for the atmospheric gas introduced into the heat treatment chamber. Can be

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a gas nitriding apparatus showing one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat treatment room, 2 ... Carry-in room, 3 ... Carry-out room, 4.5 ... Inner door, 6.7 ... Outer door, 27/28 ... Nitrogen gas ejection path for purging,
29 ・ 30… Flow path open / close valve.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 8/20-8/32 C21D 1/06 C21D 1/74-1/76

Claims (1)

(57) [Claims] 1. An atmosphere gas and an ammonia gas are injected into a heat treatment chamber (1), and a nitrogen gas, a carbon dioxide gas, and an ammonia gas are used as atmosphere gases when a steel sheet to be treated in the heat treatment chamber (1) is subjected to nitrocarburizing treatment. In the nitrocarburizing furnace, a loading chamber (2) is arranged on the loading side of the heat treatment chamber (1), and a loading chamber (3) is placed on the loading side of the heat treatment chamber (1). ) And the heat treatment room (1) and between the heat treatment room (1) and the carry-out room (3) can be opened and closed by inner doors (4) and (5) which can be raised and lowered, respectively. ) And the unloading room (3) can be opened and closed by the outer doors (6) and (7) that can be moved up and down, and the inner and outer doors (4) and (6) of the loading room (2) are opened and closed alternately. The opening and closing doors (5) and (7) of the carry-out chamber (3) are controlled to open and close alternately, and a nitrogen gas discharge passage for purging is provided to the carry-in chamber (2) and the carry-out chamber (3) respectively. 27 ) (28), and connect the nitrogen gas
7) (28) are provided with flow path on-off valves (29) and (30), respectively, and the opening operation of the flow path on-off valve (29) arranged in the nitrogen gas ejection path for purging (27) on the loading chamber side is carried in. In conjunction with the opening and closing operations of the inner and outer doors (4) and (5) of the chamber (2), the opening and closing operation of the flow path opening and closing valve (30) disposed in the purge nitrogen gas ejection path (28) on the discharge chamber side is discharged. The opening / closing doors (5) and (7) of the chamber (3) are linked to the opening / closing operation of the doors, and the flow path opening / closing valves (29) / (30) arranged in the nitrogen gas ejection paths (27) / (28) for purging are carried into the chamber. (2) During the opening and closing operation of the inner and outer doors of the carry-out room (3), the valve is kept open, and the carry-in room (2) and the carry-out room (3)
Injecting nitrogen gas into each of the loading rooms (2)
And unloading chamber (3) in the outside air inflow preventing method in a door opening and closing the circulation of nitrocarburizing furnace so as to prevent the inflow of outside air of the heat treatment chamber formed in a nitrogen gas atmosphere to (1).