JPH0892722A - Method of preventing outside air inflow when opening and closing the soft nitriding furnace door - Google Patents

Abstract

(57) [Summary] [Object] To provide an outside air inflow prevention method capable of reliably preventing outside air inflow in a metal soft nitriding furnace with a small amount of processing gas. [Structure] Heat treatment room for soft nitriding the steel sheet to be treated (1)
Then, a mixed gas of nitrogen gas, carbon dioxide gas, and ammonia gas is supplied. Loading room (2) on the loading side of heat treatment room (1)
The unloading chamber (3) is arranged on the unloading side of the heat treatment chamber (1). Inner doors that can be raised and lowered between the carry-in chamber (2) and the heat treatment chamber (1) and between the heat treatment chamber (1) and the carry-out chamber (3), respectively.
(4) and (5) are arranged, and outer doors (6) and (7) which can be moved up and down are arranged at the outer openings of the carry-in chamber (2) and the carry-out chamber (3), respectively. Nitrogen gas ejection passages for purging in the carry-in chamber (2) and the carry-out chamber (3) respectively
Connect (27) and (28). Nitrogen gas ejection passages for both purges (27) (2
Each of the doors (4), (5), (6) is equipped with the flow path on-off valves (29) (30) arranged in (8).
When (7) is open, the valve open state is maintained.

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 the inflow of outside air in a soft nitriding furnace for soft nitriding the surface of a steel sheet or the like.

[0002]

2. Description of the Related Art Generally, when industrially soft-nitriding the surface of a steel sheet or the like (workpiece), a shift furnace gas and ammonia gas are introduced into a heat treatment chamber, and the surface of the workpiece is removed by a reaction between the shift furnace gas and ammonia gas. Gas soft nitriding methods of nitriding have been used.

[0003]

However, in the soft nitriding method using the shift converter gas, there is a problem that the shift furnace for generating the shift converter gas needs to be maintained and managed, and the maintenance of the shift furnace is troublesome. . Further, the nitriding ability is affected by the amount of hydrogen in the heat treatment chamber, but since the metamorphic furnace gas is basically a hydrocarbon gas, the nitriding ability is low due to the large amount of hydrogen components in the metamorphic furnace gas. Therefore, there is a problem that a large amount of the metamorphic furnace gas is required for processing in a short time, and that a small amount of the metamorphic furnace gas increases the processing time.

Further, in the nitriding apparatus, when the heat treatment chamber is filled with carbon monoxide gas and hydrogen gas and the pressure inside the heat treatment chamber becomes negative due to the reaction, the outside air is opened when the loading / unloading port is opened when loading or unloading the work. May flow into the heat treatment chamber and explode. For this reason, it is necessary to supply gas to the heat treatment chamber so that the pressure inside the heat treatment chamber is always maintained at a positive pressure, which increases the amount of gas used and is uneconomical. The present invention has been made in view of such a point, and an object thereof 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]

In order to achieve the above-mentioned object, the present invention provides a soft nitriding furnace using nitrogen gas, carbon dioxide gas and ammonia gas as atmosphere gas,
A carry-in chamber is arranged on the carry-in side of the heat treatment chamber, and a carry-out chamber is arranged on the carry-out side of the heat treatment chamber. The carry-in chamber and the heat-treat chamber can be moved up and down between the carry-in chamber and the heat-treat chamber. The doors can be opened and closed, and the outer openings of the carry-in chamber and the carry-out chamber can be opened and closed by outer doors that can be moved up and down, and the inner and outer doors of the carry-in chamber are controlled to be opened and closed alternately.
It controls to open and close the inner and outer doors of the carry-out chamber alternately, and connects the purging nitrogen gas ejection path to the carry-in chamber and the carry-out chamber respectively,
A flow path opening / closing valve is arranged in each of the purging nitrogen gas ejection paths, and the opening operation of the flow path opening / closing valve arranged in the purging nitrogen gas ejection path 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 passage opening / closing valve arranged in the purging nitrogen gas ejection passage on the side of the discharge chamber is linked to the opening / closing operation of the inner and outer doors of the discharge chamber, and the corresponding flow passage opening / closing valve is opened during the opening / closing operation of each door. By keeping the valve open and injecting nitrogen gas into the carry-in and carry-out chambers respectively, a nitrogen gas atmosphere is created in the carry-in and carry-out chambers to prevent outside air from entering the heat treatment chamber. I am trying.

[0006]

In the present invention, the carrying-in chamber and the carrying-out chamber are arranged in front of and behind the heat treatment chamber in the state of being partitioned by doors, and the doors are also arranged at both outer sides of the carrying-in chamber and the carrying-in / carrying-out chamber. The nitrogen gas ejection passages are connected to each of the pipes, and the flow passage opening / closing valves arranged in each nitrogen gas ejection passage are opened / closed in conjunction with the opening / closing operations of the corresponding front and rear doors of the carry-in chamber and the front and rear doors of the carry-out chamber. When either the front or back door is open, nitrogen gas is ejected to the loading or unloading chamber to maintain positive pressure in the loading and unloading chambers with the door open. Therefore, it is possible to reliably prevent the outside air from flowing into the heat treatment chamber.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawings are schematic diagrams of a gas nitriding apparatus showing an embodiment of the present invention. This gas nitriding device is used in the heat treatment room
A carry-in chamber (2) is arranged on the inlet side of (1) and a carry-out chamber (3) is arranged on the outlet side of the heat treatment chamber (1) so that the space between the heat treatment chamber (1) and the carry-in chamber (2) can be raised and lowered. It is divided by the inner door (4) and the heat treatment room
The (1) and the carry-out chamber (3) are 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 carry-in chamber (2) so that it can be moved up and down, and an outer door (7) is also arranged so that it can be moved up and down at the exit of the carry-out chamber (3). There is. Each door (4) (5)
(6) (7) are air cylinders that operate independently (8)
(9) (10) (11) is configured to open and close. The inner door (4) and outer door (6) of the carry-in chamber (2) are selectively opened and closed,
Further, the inner door (5) and the outer door (7) of the carry-out chamber (3) are selectively opened and closed so that the heat treatment chamber (1) does not directly face the outside. There is. Both inner doors (4)
A communication hole (12) having a small opening area is formed in (5).

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

Purging nitrogen gas ejection passages (27) and (28) are branched from the nitrogen gas supply passage (15) to the carry-in chamber (2) and the carry-out chamber (3). (27) (28)
The flow path opening / closing valves (29) and (30) are arranged in the. Then, the purging nitrogen gas ejection passage (27) connected to the carry-in chamber (2)
The flow passage opening / closing valve (29) arranged at the opening / closing valve is adapted to be opened / closed in conjunction with the opening / closing operation of the inner door (4) and the outer door (6) of the carry-in chamber (2). (4) The flow path opening / closing valve (29) is kept open while the valves (6) are open, and the purging nitrogen gas injection passage (() is connected to the discharge chamber (3). The flow passage opening / closing valve (30) arranged in 28) is designed to be 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). While the doors (5) and (7) are open, the flow path opening / closing valve (30) is kept open.

In the processing gas supply passage 14, an atmosphere gas in which nitrogen gas and carbon dioxide gas are mixed at a flow ratio of 9: 1 and a flow ratio of this atmosphere gas to be 1: 1. A mixed gas, in which ammonia gas is mixed, is allowed to flow. Therefore, the component ratio in the mixed gas is 45 vol% nitrogen gas, 5 vol% carbon dioxide gas, and 50 vol% ammonia gas. In addition, the mixing ratio of this atmosphere gas increases the mixing ratio of carbon dioxide to about 10 vol% in the case of a material containing a large amount of carbon depending on the carbon content of the material to be treated, and in the case of a material containing a small amount of carbon, Reduces the mixing ratio of carbon dioxide to about 2.5%.

In the figure, reference numeral (31) is an exhaust pipe drawn out from the ceiling walls of the carry-in chamber (2) and the carry-out chamber (3), and (32) is the carry-out chamber (3).
The oil tank for cooling placed in, and (33) (34) (35) (36) are the operation controls placed in the working air supply passages to the air cylinders (8) (9) (10) (11) for controlling the opening / closing of each door. It is a valve.

In such a nitriding apparatus, the outer door (6) of the carry-in chamber (2) is opened to introduce the work into the carry-in chamber (2). At this time, the operation control valve of the air cylinder (10) that drives the outer door (6)
In conjunction with the valve opening operation of (33), the flow path opening / closing valve (29) of the purging nitrogen gas injection path (27) on the carry-in chamber side is opened, and the outer door (6)
The nitrogen gas for purging continues to be jetted into the carry-in chamber (2) from the beginning of opening to the time of closing it to prevent the outside air from flowing into the carry-in chamber (2).

When the work is loaded into the loading chamber (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 loading chamber side purging nitrogen gas ejection passage (27) is kept open from the beginning of opening the inner door (4) to the closing of the inner door (4). Therefore, the outer door
Not only when the inner door (4) is opened and operated after (6) is completely closed, the inner door (6) can be opened before it is completely closed.
Even when (4) starts to open, since the purging nitrogen gas is filled in the carry-in chamber (2), outside air components do not flow into the heat treatment chamber (1).

In the heat treatment chamber (1), a processing gas obtained by mixing the same amount of ammonia gas with a gas obtained by mixing nitrogen gas and carbon dioxide at a ratio of 9: 1 is applied to the work, Soft nitriding the surface. At this time, communication holes (12) are formed in the inner doors (4) and (5) that define the heat treatment room (1), the carry-in room (2), and the carry-out room (3). 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 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 chamber (1) and the discharge chamber (3) is opened, and the work in the heat treatment chamber (1) is discharged from the discharge chamber.
Although it is carried out to (3), at this time also, purging nitrogen gas is jetted into the carry-out chamber (3) in conjunction with the opening operation of the inner door (5). After immersing the work in the cooling oil tank (32) and cooling it,
The work is carried out by opening the outer door (7) of the carry-out chamber (3). Then, purging nitrogen gas is ejected into the carry-out chamber (3) in conjunction with the opening operation of the outer door (7).

[0017]

According to the present invention, the carry-in chamber and the carry-out chamber are arranged in front of and behind the heat treatment chamber, and the doors are arranged at both outer sides of the carry-in chamber and the carry-in / out chamber. Nitrogen gas ejection passages are connected to the chamber by piping, and the flow passage on-off valves arranged in each nitrogen gas ejection passage are opened and closed in conjunction with the opening and closing operations of the front and rear doors of the loading chamber and the front and rear doors of the loading chamber. Operate it, and when either the front or rear door is open, spout nitrogen gas into the carry-in chamber or carry-out chamber, and keep the carry-in and carry-out chamber at positive pressure with the door open. Therefore, it is possible to reliably prevent the outside air from flowing into the heat treatment chamber.

Moreover, the nitrogen gas supplied to the carry-in chamber and the carry-out chamber can be obtained by branching a part of the nitrogen gas used as the atmospheric gas introduced into the heat treatment chamber. Can be converted.

[Brief description of drawings]

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

[Explanation 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 passage for purging,
29 ・ 30… Flow passage opening / closing valve.

Claims (1)

[Claims] 1. A nitrogen gas, a carbon dioxide gas, and an ammonia gas are used as atmosphere gases when injecting an atmosphere gas and an ammonia gas into the heat treatment room (1) to soft-nitrid the steel sheet to be treated in the heat treatment room (1). In a soft nitriding furnace that uses gas, a carry-in chamber (2) is arranged on the carry-in side of the heat treatment chamber (1), and a carry-out chamber (3) is arranged on the carry-out side of the heat treatment chamber (1). 2) and the heat treatment chamber (1) and between the heat treatment chamber (1) and the carry-out chamber (3) can be opened and closed by inner doors (4) and (5) that can be moved up and down, respectively. 2) and the carry-out chamber (3) are configured so that the outer openings 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 carry-in chamber (2) are opened and closed alternately. In addition, it controls to open and close the inner and outer doors (5) and (7) of the carry-out chamber (3) alternately, and ejects nitrogen gas for purging into the carry-in chamber (2) and the carry-out chamber (3) respectively. Routes (27) and (28) are connected, and the nitrogen gas injection route (2
7) (28) are equipped with the flow path on-off valves (29) and (30) respectively, and the opening operation of the flow path on-off valve (29) located in the purging nitrogen gas injection path (27) on the loading chamber side is loaded. In conjunction with opening and closing operations of the inner and outer doors (4) and (5) of the chamber (2), carry out the opening operation of the flow passage opening / closing valve (30) arranged in the purging nitrogen gas ejection passage (28) on the carrying-out chamber side. The flow passage opening / closing valves (29) and (30) arranged in the purging nitrogen gas ejection passages (27) and (28) are interlocked with the opening and closing operations of the inner and outer doors (5) and (7) of the chamber (3). (2) -While the inner and outer doors of the carry-out chamber (3) are being opened and closed, the open state is maintained, and the carry-in chamber (2) -carry-out chamber (3)
By injecting nitrogen gas into each of them, the loading room (2)
-A method of preventing outside air from flowing into the heat treatment chamber (1) by forming a nitrogen gas atmosphere in the carry-out chamber (3) to prevent outside air from entering the heat treatment chamber (1) when opening and closing the door of the nitrocarburizing furnace.