JP5291354B2 - Gas nitriding furnace and gas soft nitriding furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel gas nitriding furnace and gas soft nitriding furnace capable of preventing generation of solid matter caused by outflowing of treatment gas. <P>SOLUTION: The gas nitriding furnace 100 includes a standby chamber 30 for passage and standby of an object S to be treated, between a heating chamber 10 for nitriding the object S to be treated and a pre/post-treatment chamber 20 for carrying out pretreatment and posttreatment of the object S to be treated. The standby chamber 30 has a heating means 38 for heating an interior of the standby chamber 30 to a predetermined temperature or more, and an exhaust means L3 for exhausting gas in the standby chamber 30. Since the treatment gas flowing out to the standby chamber 30 is discharged without solidifying thereby, deterioration of treatment efficiency of the whole treatment furnace is prevented which is due to generation of solid matter caused by outflowing of the treatment gas. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a gas nitriding furnace and a gas soft nitriding furnace for batch-type gas nitriding treatment of workpieces such as steel machine parts.

Conventionally, ammonia (NH ₃ ) gas and carbonic acid (CO ₂ ) gas are added at a predetermined ratio in a nitrogen gas (N ₂ ) atmosphere in nitriding treatment, which is one of surface hardening treatment methods for machine metal parts and the like. Gas soft nitriding using gas as a source gas promotes the diffusion of nitrogen due to the presence of carbon, so it has superior wear resistance, seizure resistance, fatigue resistance, etc. compared to nitriding with NH ₃ alone, etc. It is known to exert.

As a heat treatment apparatus (furnace) for performing such a gas soft nitriding treatment, ones having various configurations have been proposed. For example, in Patent Document 1 below, a cooling chamber and a purge chamber are attached to a heating chamber for heat-treating a heated object, and the heated object is moved between the cooling chamber and the purge chamber by an elevator. Are disclosed in a batch process. Patent Document 2 below discloses an apparatus that performs efficient processing by providing a conveyance mechanism between heating chambers and between cooling chambers.
Japanese Unexamined Patent Publication No. 7-90361 JP 2003-183728 A

By the way, as described above, when a gas obtained by mixing ammonia (NH ₃ ) gas and carbonic acid (CO ₂ ) gas with nitrogen gas (N ₂ ) is used as a processing gas, these gases react to react with ammonium carbonate (( A gas of ammonia compound such as NH ₄ ) ₂ CO ₃ ) is generated.
Further, when ammonia nitrate (NH ₄ NO ₃ ), ammonium chloride (NH ₄ Cl) or the like is appropriately added to the above gas for the purpose of activating the surface of the object to be processed, these ammonia compound gases are also generated.
Then, it flows out from the heating chamber to the carry-in / out chamber etc. and is cooled to solidify (gas → solid), and accumulates as powder in the carry-in / out chamber.
Therefore, when such a phenomenon occurs, the furnace must be temporarily stopped to remove the accumulated solid matter, and the removal work and cleaning work must be performed, thereby reducing the processing efficiency of the entire processing furnace. There is a problem of inviting.
Therefore, the present invention has been devised in order to effectively solve such problems, and an object of the present invention is to provide a novel gas nitriding furnace and gas softening which can prevent generation of solidified substances due to outflow of processing gas. A nitriding furnace is provided.

In order to solve the above-mentioned problem, the invention of claim 1
A gas nitriding furnace comprising a standby chamber for waiting for the object to be processed between a heating chamber for nitriding the object to be processed and a pre- and post-processing chamber for performing pre- and post-processing of the object to be processed. Provided in the vicinity of the bottom of the waiting chamber on the front and rear processing chamber side, heating the waiting chamber to a temperature higher than the solidification temperature of the ammonia compound, and the ammonia compound gas flowing out from the heating chamber into the waiting chamber. heating means for heating a gas nitriding furnace, characterized in that an exhaust means for exhausting the waiting room of the gas.
The gas nitriding furnace according to claim 2 is:
2. The gas nitriding furnace according to claim 1, wherein the standby chamber includes a lifting platform that is vertically movable, and the lifting platform has a bottom and an upper portion that are configured to convey an object to be processed. Each of the bottom part and the upper part of the base is a gas nitriding furnace configured to horizontally connect the heating chamber and the front and rear processing chambers .
The gas soft nitriding furnace of claim 3 is:
A gas soft nitriding furnace provided with a standby chamber for passing and waiting for the object to be processed between a heating chamber for nitriding the object to be processed and a pre- and post-processing chamber for performing pre- and post-processing of the object, The standby chamber is provided near the bottom of the standby chamber on the front and rear processing chamber side , heats the standby chamber above the solidification temperature of ammonium carbonate ((NH4) 2CO3) gas, and flows out of the heating chamber into the standby chamber. heating means for heating the ammonium carbonate ((NH4) 2CO3) gas, the ammonium carbonate waiting room ((NH4) 2CO3) is characterized in that an exhaust means for exhausting gas.

According to the gas nitriding furnace and the gas soft nitriding furnace of the present invention, since the heating means is provided in the standby chamber adjacent to the heating chamber, the standby chamber has a predetermined temperature, specifically, at least ammonium carbonate ((NH ₄ ) It can be heated to a temperature higher than the solidification temperature of the ammonia compound such as ₂ CO ₃ ).
As a result, even if an ammonia compound gas such as ammonium carbonate ((NH ₄ ) ₂ CO ₃ ) flows out from the heating chamber to the standby chamber, the gas is solidified to be solidified and deposited in the standby chamber. Therefore, it is possible to prevent a reduction in the processing efficiency of the entire processing furnace.
Further, since the standby chamber is further provided with exhaust means, the gas flowing into the standby chamber can be safely exhausted by the exhaust means, so that harmful gas leaks out from the standby chamber. There is nothing.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.
(Constitution)
FIG. 1 shows an embodiment of a gas nitrocarburizing furnace 100 according to the present invention.
As shown in the figure, the gas nitrocarburizing furnace 100 includes a heating chamber 10 that performs gas soft nitriding treatment on an object S such as mechanical metal parts, and a vacuum purge / cooling chamber that performs before and after treatment of the object S (front and rear treatment). Chamber) 20, a standby chamber 30 located between the heating chamber 10 and the vacuum purge / cooling chamber 20, and a control for controlling a series of processes in the heating chamber 10, the vacuum purge / cooling chamber 20, and the standby chamber 30. It is mainly comprised from the part 40. FIG.

  First, the vacuum purging / cooling chamber 20 includes a roller conveyor 24 that horizontally conveys the workpiece S to a processing chamber main body 21 that includes hermetic inlets 22 and 23, and a heat exchanger 25 that cools the inside of the housing 21. And an agitation fan 26 for agitating the atmosphere in the processing chamber main body 21, a vacuum purge line L1 for vacuum purging the processing chamber main body 1, and the like. In addition to carrying in / out to the side, the pre- and post-processing necessary for carrying in / out the workpiece S is carried out.

More specifically, before processing the object to be processed S in the heating chamber 10, the object S is once accommodated in the vacuum purge / cooling chamber 20, and its entrances 22 and 23 are opened and closed. In a state of being sealed by the lids 22a and 23a, vacuum purge is performed for a predetermined time by a vacuum purge line L1 to remove impurities such as oxygen.
A vacuum pump P1, a surge tank 50, a decomposition furnace 60, and the like are sequentially attached to the vacuum purge line L1, and the gas (air, ammonia gas, etc.) in the vacuum purge / cooling chamber 20 is forced by the vacuum pump P1. In addition to being temporarily stored in the surge tank 50, harmful ammonia gas stored in the surge tank 50 is decomposed into nitrogen and hydrogen by the decomposition furnace 60 and combusted and exhausted. The cracking furnace 60 is filled with a Ni catalyst, and has a structure capable of efficiently decomposing ammonia even at a relatively low temperature.

  On the other hand, after the object to be processed S is processed in the heating chamber 10, the object to be processed S is returned to the vacuum purge / cooling chamber 20 and sealed in the same manner by the liftable open / close lids 22a and 23a. The workpiece S is cooled to, for example, about 100 ° C. to near room temperature by driving the stirring fan 26 while flowing a coolant such as cooling water through 25 to stir the atmosphere.

The open / close lids 22a and 23a for opening and closing the entrances 22 and 23 of the vacuum purge / cooling chamber 20 can be moved up and down by the air cylinder mechanisms 22b and 23b, respectively, and the entrances 22 and 23 can be sealed by the link mechanisms 22c and 23c. It is like that. The roller conveyor 24 is provided with a drive motor (not shown) so that the workpiece S can be conveyed in the direction of the entrances 22 and 23.
Further, since the object to be processed S is usually mostly small mechanical metal parts (separate objects) such as gears, shafts, rings, plates, etc., a transport tray (not shown) whose size is standardized is not shown. ) Are placed in a plurality of upper and lower stages, and are transported between the chambers in units of trays so that each process is performed in a batch manner.

  Next, the heating chamber 10 includes a loading / unloading port 12 for loading / unloading the workpiece S, a roller conveyor 13 for horizontally conveying the workpiece S, a radiant heater, and the like to / from a heating chamber body 11 made of refractory. A plurality of heaters 14, a stirring fan 15 for stirring the atmosphere in the heating chamber 10, a source gas supply line L 2 for supplying source gas, and the like.

Then, after loading the object to be treated S in the heating chamber body 11, the carry-out the inlet 12 therein to close the lid 12a raw gas from the supply line L2 N ₂ and NH ₃ and a mixed gas of CO _2, etc. While the atmosphere is being stirred by the stirring fan 15 and the atmosphere is heated uniformly by, for example, 400 to 600 ° C. × 1.5 to 2 hours, the workpiece S is gasified. Soft nitriding is performed.

The opening / closing lid 12a of the carry-in / out port 12 of the heating chamber body 11 is also made of a refractory material, and is moved up and down by an air cylinder mechanism 12b to open and close the carry-in / out port 12.
Next, the standby chamber 30 includes a standby chamber main body 31 positioned so as to communicate between the heating chamber 10 and the vacuum purge / cooling chamber 20, an elevating mechanism 32 that moves up and down in the standby chamber main body 31, and the standby chamber. The heating unit 38 including a heating wire to heat the inside of the main body 31 and an exhaust line (exhaust unit) L3 for exhausting the gas in the standby chamber main body 31 are mainly provided.

The elevating mechanism 32 includes a rectangular elevating table 33 that conveys the workpiece S, and an elevating cylinder 34 and a cylinder rod 35 that elevate and lower the rectangular elevating table 33 in the vertical direction.
The bottom and top of the lift 33 are respectively constituted by roller conveyors 36 and 37. As shown in the figure, the lift 33 is moved up and down, so that the roller conveyor 13 on the heating chamber 10 side and the vacuum purge / cooling chamber 20 are provided. The roller conveyor 24 is located at the same height with respect to the roller conveyor 24 on the side, and the roller conveyor 13 and the roller conveyor 24 are connected at the same level by either one of the roller conveyors 36 and 37.

  That is, as shown by the solid line in the figure, when the elevator platform 33 is lowered, the roller conveyor 36 on the upper side is located between the roller conveyor 13 and the roller conveyor 24 and is connected horizontally, and the broken line in the figure. As shown in FIG. 2, when the elevator platform 33 is raised, the lower roller conveyor 37 is positioned between the roller conveyor 13 and the roller conveyor 24 and is connected horizontally.

On the other hand, the heating means 38 is provided in the portion where the temperature is lowest in the standby chamber main body 31 during normal operation, that is, in the vicinity of the bottom of the standby chamber main body 31 near the vacuum purge / cooling chamber 20 side as illustrated. The interior of the standby chamber 30 is always above a predetermined temperature. Specifically, when only nitrogen gas, ammonia gas, or carbon dioxide is used, the solidification temperature of ammonium carbonate ((NH ₄ ) ₂ CO ₃ ) is about 60 ° C. When the addition of ammonium nitrate (NH ₄ NO ₃ ), ammonium chloride (NH ₄ Cl), or the like is performed at a higher temperature (about 150 to 250 ° C.) It has become.

On the other hand, the exhaust line (exhaust means) L3 is connected to the cracking furnace 60, and decomposes, burns and discharges ammonia and ammonia compound gas flowing into the standby chamber body 31.
Next, the control unit 40 is a control mechanism in which a predetermined control circuit, a control sequencer, and the like are housed in a control panel having a control panel (not shown), and the operator adjusts the processing temperature and processing time of the workpiece S. In addition, the functions and operations of the respective sections of the chambers 10, 20, and 30 described above are controlled along a predetermined sequence.

(Function and effect)
In the gas soft nitriding furnace 100 of the present invention having such a configuration, when the gas soft nitriding treatment of the workpiece S in the heating chamber 10 is completed, the carry-in / out port 12 of the heating chamber 10 is opened. It is taken out to the standby chamber 30 and further passed through the standby chamber 30 and conveyed to the vacuum purge / cooling chamber 20 side, where it is cooled.
When nitrogen gas, ammonia gas, carbon dioxide gas and, if necessary, ammonium nitrate (NH ₄ NO ₃ ) are supplied to the heating chamber 10, ammonium carbonate ((NH ₄ ) ₂ CO ₃ ) generated in the heating chamber 10 Then, an ammonia compound gas such as ammonium nitrate (NH ₄ NO ₃ ) flows out into the standby chamber 30.
However, as described above, since the inside of the standby chamber 30 is constantly heated to a temperature higher than the solidification temperature of these ammonia compounds by the heating means 38, these ammonia compounds are solidified in the standby chamber 30. There is nothing.

FIG. 2 shows the temperature distribution (upper and lower part average value) of each part in the standby chamber 30.
As shown in the figure, in the conventional example (dotted line in the figure) that does not include the heating means 38 as in the present invention, the temperature on the heating chamber 10 side is the highest, and as it goes to the vacuum purge and cooling chamber 20 side. The temperature is low. This is because the gas soft nitriding process at a high temperature is performed on the heating chamber 10 side as described above, whereas the cooling process by the heat exchanger 25 is performed on the vacuum purge / cooling chamber 20 side.

Therefore, in the conventional example, the temperature on the vacuum purge / cooling chamber 20 side from the central portion of the standby chamber 30 is lower than the solidification temperature of the ammonia compound (about 60 ° C.), and the ammonia compound that has flowed out solidifies. As a result, it was deposited in the chamber 30.
On the other hand, in the present invention, the portion (purge / cooling chamber 20) where the temperature is lowest in the standby chamber 30 is always heated by the heating means 38 such as a heating wire, so that the solid line in the figure shows. In addition, the temperature in the standby chamber 30 exceeds the solidification temperature of the ammonia compound at any location.

As a result, it is possible to prevent inconveniences such as the ammonia compound flowing out into the standby chamber 30 solidifying and adhering to the lifting platform 33 or being deposited on the bottom of the standby chamber 30.
Further, according to the present invention, the standby chamber 30 is provided with exhaust means (exhaust line L3), so that the ammonia compound gas that has not solidified and remains in the standby chamber 30 is quickly exhausted from the exhaust line L3 for decomposition. The gas can be sent to the furnace 60 for decomposition, and no harmful gas leaks out of the standby chamber 30.

As described above, in the gas nitrocarburizing furnace 100 of the present invention, since the solidification of the gas flowing out to the standby chamber 30 can be prevented in advance, inconvenience due to the solidified product and removal / cleaning work of the solidified product are not required. The reliability and operating efficiency of the nitrocarburizing furnace can be improved.
In the present embodiment, the gas soft nitriding furnace 100 for performing the gas soft nitriding treatment has been described as an example, but it is needless to say that the present invention can be similarly applied to other various gas nitriding furnaces.

1 is a cross-sectional view showing an embodiment of a gas (soft) nitriding furnace 100 according to the present invention. It is a figure which shows the temperature distribution of each part in a waiting room.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Gas (soft) nitriding furnace 10 ... Heating chamber 20 ... Vacuum purge and cooling chamber (front and back processing chamber)
DESCRIPTION OF SYMBOLS 30 ... Standby chamber 38 ... Heating means 40 ... Control part L1 ... Vacuum purge line L2 ... Raw material gas supply line L3 ... Exhaust line (exhaust means)
S: Object to be processed

Claims (3)

A gas nitriding furnace provided with a standby chamber for passing and waiting for the object to be processed between a heating chamber for nitriding the object to be processed and a pre- and post-processing chamber for performing pre- and post-processing of the object to be processed,
Ammonia that is provided in the standby chamber near the bottom of the standby chamber on the front and rear processing chamber side , heats the standby chamber to a temperature higher than the solidification temperature of the ammonia compound, and flows out from the heating chamber into the standby chamber A gas nitriding furnace comprising heating means for heating a compound gas and exhaust means for exhausting the gas in the standby chamber.   In the gas nitriding furnace according to claim 1,
  The waiting room includes a lifting platform that can move up and down in a vertical direction,
  The lifting platform has a bottom portion and an upper portion configured to convey an object to be processed, and each of the bottom portion and the upper portion of the lifting platform is configured to horizontally connect the heating chamber and the front and rear processing chambers. A gas nitriding furnace characterized by that. A gas soft nitriding furnace provided with a standby chamber for passing and waiting for the object to be processed between a heating chamber for nitriding the object to be processed and a pre- and post-processing chamber for performing pre- and post-processing of the object to be processed,
The standby chamber is provided near the bottom of the standby chamber on the front and rear processing chamber side, and heats the standby chamber to a temperature higher than the solidification temperature of ammonium carbonate ((NH4) 2CO3) gas and flows out of the heating chamber into the standby chamber. A gas soft nitriding furnace comprising heating means for heating the ammonium carbonate ((NH4) 2CO3) gas and exhaust means for exhausting the ammonium carbonate ((NH4) 2CO3) gas in the standby chamber.

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