JPS6411685B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-oxidation hardening method and a hardening device used for hardening to improve the mechanical strength of processed metal parts by making the structure of the material fine and uniform. .

B. Prior Art After various components of automobiles and machine tools are processed into a predetermined shape, they are hardened to improve their mechanical strength. During this hardening, so-called non-oxidation hardening is generally performed in which a protective atmosphere is used to prevent oxidation of the part to be hardened (workpiece).

Conventionally, the protective gas used in the non-oxidizing quenching is a mixture of raw material gas and a theoretical amount of air, which is then placed in a high-temperature shift furnace, and nickel is filled in a retrel that is externally heated in the shift furnace. Hardening is performed using an endothermic modified gas (RX gas) that has been transformed by contact with a catalyst, and by adjusting the carbon potential in the gas to be equal to the carbon content of the workpiece material, while avoiding an increase or decrease in the surface carbon content of the workpiece. It was on.

However, since the RX gas is an active gas,
If there is a large amount of air mixed in, there is a high risk of explosion, so a large amount (10m ³ /Hr) of RX gas is supplied into the quenching furnace to increase the pressure inside the furnace and prevent air from entering the furnace. We are trying to prevent this. Therefore, a large amount of RX gas is consumed, and since the unit price of this RX gas is high, running costs are high, which poses a problem in terms of energy saving measures.

Therefore, a method of quenching using an inert gas as a protective gas without the risk of explosion may be considered. As the inert gas, exothermic modified gas (NX gas) is used, which is obtained by mixing raw material gas with excess air and using the combustion heat to transform the mixture.

By using NX gas, there is no danger of explosion even if air gets mixed in, so the pressure inside the quenching furnace can be lowered, and the amount of NX gas supplied can be reduced (1~
3 m ³ /Hr), and the unit price of NX gas is low, so the running cost is low and it is also preferable in terms of energy saving.

However, if only NX gas is used, the carbon potential is lower than the carbon content of the workpiece, and decarburization may occur. The carbon potential must be adjusted by mixing heated city gas (hereinafter referred to as 13A low-pressure city gas) as enrichment gas.

When NX gas is used as a protective gas in this way, a small amount of methane is mixed in with it, so if a large amount of air gets mixed in, there is a risk of explosion. It is necessary to take measures to prevent air from entering the furnace when transporting workpieces from the furnace.

B. Purpose of the Invention The present invention aims to provide a non-oxidizing quenching method that prevents air from entering the quenching furnace during loading and unloading of workpieces, and a quenching device used to carry out the method.

C. Structure of the Invention The present invention provides a method for quenching by supplying NX gas (exothermic gas) as a protective gas to a quenching furnace and mixing various methane-based gases as an enrichment gas. In a quenching furnace where a chamber and a heating chamber are installed side by side and an intermediate door is provided between the two chambers, the supply of enrichment gas is stopped when the workpiece is carried into and out of the heating chamber through the intermediate door. This is a non-oxidation quenching method in which quenching is performed by increasing the amount of NX gas supplied.

Further, the second invention provides a heating chamber 2 of the quenching furnace 1 in which a front chamber 3 equipped with a quenching tank and a heating chamber 2 are arranged side by side, and an intermediate door 9 is provided between both chambers 2 and 3 so as to be openable and closable. A first gas supply pipe 11 for supplying NX gas to and a second gas supply pipe 13 for supplying enrichment gas are provided, and a third gas supply pipe 15 for supplying NX gas to the front chamber 3 of the quenching furnace 1 is provided. The second gas supply pipe 13 is provided with a normally open solenoid valve 17 that closes the pipe line when the intermediate door 9 is opened, and the third gas supply pipe 15 is provided with a normally open solenoid valve 17 that closes the pipeline when the intermediate door 9 is opened.
Normally closed solenoid valve 18 that opens the pipeline when the
The first gas supply pipe 1 is installed during quenching.
NX gas and enrichment gas are supplied from the first and second gas supply pipes 13 to the heating chamber 2 of the quenching furnace for quenching, and the supply of enrichment gas from the second gas supply pipe 13 is stopped when loading and unloading the workpiece. , 3rd
The first gas supply pipe 15 is opened, and the first gas supply pipe 1 is opened.
NX gas is supplied from the first and third gas supply pipes 15 to the heating chamber 2 and the front chamber 3.

D. Example FIG. 1 is a diagram showing an example of a hardening apparatus used in carrying out the method of the present invention, and in the same figure,
1 is a quenching furnace in which a heating chamber 2 and a front chamber 3 are arranged side by side. The heating chamber 2 has a structure with excellent heat resistance and heat insulation, and is provided with an appropriate heating means (not shown) for heating the interior of the room, and has a ceiling surface 2a that is designed to speed up heating and control temperature distribution and atmospheric effects. An RC fan 4 is provided for uniformity. The front chamber 3 is provided with a front door 5 for loading a workpiece in the front part thereof, which can be opened and closed in the vertical direction, and a quenching tank, for example, an oil tank 6 is integrally formed in the lower part. A quenching elevator 7 is provided in the oil tank 6 so as to be movable up and down, and is filled with quenching oil 8.

An intermediate door 9 is vertically movable between the heating chamber 2 and the front chamber 3, and its upper end is connected to the piston rod 10a of the air cylinder 10 disposed above the quenching furnace 1. It opens and closes by expanding and contracting, and opens and closes the heating chamber 2.

11 is NX that has been metamorphosed in a metamorphosis furnace (not shown)
This is a first gas supply pipe that supplies gas to the heating chamber 2 of the quenching furnace 1, and its tip is introduced into the heating chamber 2. 12 is a first flow meter provided in the first gas supply pipe 11. A second gas supply pipe 13 supplies enrichment gas to the heating chamber 2, and its tip is connected to the first gas supply pipe 11 downstream of the first flowmeter 12. 14 is the second gas supply pipe 1
This is the second flowmeter provided at No. 3. As the enrichment gas, for example, 13A low-pressure city gas made from liquefied natural gas containing methane as a main component is used. Reference numeral 15 denotes a third gas supply pipe for supplying NX gas to the front chamber 3 of the quenching furnace 1, the rear end of which is connected to the first gas supply pipe 11, and the tip thereof introduced into the front chamber 3. 16 is a third flow meter installed in the third gas supply pipe 15.

17 is a first gas supply pipe provided in the second gas supply pipe 13;
This is a solenoid valve that keeps the pipeline open at all times, and switches to close the pipeline when energized. Reference numeral 18 denotes a second electromagnetic valve provided in the third gas supply pipe 15, which normally closes the pipe line, and switches to open the pipe line when energized. Reference numeral 19 denotes a limit switch provided above the intermediate door 9, which is turned on at the rising end when the intermediate door 9 rises. This limit switch 19
is turned on, the first solenoid valve 17 and the second solenoid valve 17 are turned on.
The electromagnetic valve 18 is energized to close the second gas supply pipe 13 and open the third gas supply pipe 15.

In the above configuration, the quenching operation is explained as follows.
The heating means in the heating chamber 2 of the quenching furnace 1 is activated to bring the temperature inside the furnace to a predetermined temperature, and the first
Pour the required amount of NX gas (1 to 3
13A low-pressure city gas (m ³ /Hr) is supplied to create a protective atmosphere in the heating chamber 2 and to match the carbon potential to the carbon content of the workpiece 20. In this state, first, the front door 5 is opened by an appropriate means, and a large number of works 20 are hardened in the front chamber 3 and placed on the elevator 7. After that, the front door 5 is closed, and then the air cylinder 10 is shortened, the intermediate door 9 is raised, the heating chamber 2 is opened, and the workpiece 20 is carried into the heating chamber 2. After being carried in, the air cylinder 10 is extended, the intermediate door 9 is lowered, the heating chamber 2 is closed, and the workpiece 20 is heated. During this heating, the front door 5 is opened and a new work 20 is loaded and placed on the elevator 7. When the workpiece 20 is heated to a predetermined temperature in the heating chamber 2, the intermediate door 9 is opened and the high-temperature workpiece 20 is removed from the heating chamber 2, as shown in FIG.
is carried out and placed on the elevator 7, and a new work 20 is carried from the elevator 7 into the heating chamber 2. After this, the intermediate door 9 is closed and the next heating is performed.
On the other hand, in the front room, after carrying out the work 20, the elevator 7
to lower the workpiece 20 into the quenching oil 8 in the oil tank 6.
The material is immersed in water and quenched. When the hardening is completed, the elevator 7 is raised, then the front door 5 is opened to take out the hardened workpiece 20 from the front chamber 3, and then a new workpiece 20 is loaded and placed on the elevator 7. Thereafter, the above-described operations are repeated to continuously harden the workpiece 20.

During the above operation, the workpiece 20 is carried into the heating chamber 2.
When the intermediate door 9 rises during unloading, the limit switch 19 is pushed up at the rising end and turned on.
Then, the first and second solenoid valves 17 and 18 are energized and switched, closing the second gas supply pipe 13 and stopping the supply of 13A low-pressure city gas to the heating chamber 2, and at the same time supplying the third gas to the heating chamber 2. Open supply pipe 15 and NX
Gas is supplied to the front chamber 3, and a large amount (4
~8m ³ /Hr) of NX gas is supplied to fill the inside of the furnace with NX gas. This is because when the pressure inside the furnace is low, when the intermediate door 9 is opened, the temperature of the heating chamber 2 decreases, and the inside of the quenching furnace 1 becomes negative pressure, so air flows in from the outside even when the front door 5 is closed. This prevents air from entering the heating chamber 2 and prevents an explosion even if air does enter. When the loading and unloading of the workpiece 20 into and out of the heating chamber 2 is completed and the intermediate door 9 is lowered, the limit switch 19 is activated.
OFF, the first and second solenoid valves 17 and 18 return after a predetermined period of time, the third gas supply pipe 15 is closed, the supply of NX gas to the front chamber 3 is stopped, and the second gas The supply pipe 13 is opened and 13A low pressure city gas is supplied to the heating chamber 2.

Note that the first solenoid valve 17 is kept energized for 30 to 45 minutes after being energized, and is switched when the heating chamber 2 reaches a certain heating temperature after the intermediate door 19 is closed.
Set to resupply 13A low pressure city gas to heating chamber 2. The second electromagnetic valve 18 is set to maintain the energized state for 1 to 5 minutes after being energized, and to supply NX gas to the front chamber 3 only while the intermediate door 9 opens the heating chamber 2.

The temperature of the heating chamber 2 during the above-mentioned quenching and the timing of supply of NX gas and 13A low pressure city gas are shown in FIG. Note that point A in FIG. 3 indicates the starting point of the intermediate door 9 to rise, and point B indicates the time of descent.

In the above description, 13A low-pressure city gas was used as the enrichment gas, but other gases such as methane and butane may also be used. In addition, the first and second solenoid valves 17,
Although the switching operation 18 was performed using the limit switch 19, it may also be performed manually or by using a timer.

E. Effects of the Invention This invention uses NX gas as a protective gas during quenching, so the pressure inside the furnace can be kept low, reducing the amount of gas used and also reducing the unit price of gas, reducing running costs. can be done. In addition, a small amount of methane-based enrichment gas is mixed in to prevent decarburization of the workpiece during quenching, so there is a risk of an explosion due to air being mixed in when the workpiece is brought in and out of the heating chamber. Stop the supply of enrichment gas, and
By increasing the amount of NX gas supplied, it prevents air from entering the heating chamber, and by filling the heating chamber with NX gas, even if air gets mixed in, it will not explode, greatly improving safety.

Furthermore, if 13A low-pressure city gas is used as the enrichment gas, special storage equipment is not required and the equipment can be made smaller. Furthermore, since the supply amount of NX gas and the supply of enrichment gas are controlled as the intermediate door that opens and closes the heating chamber is opened and closed, the supply of enrichment gas can be reliably stopped when the heating chamber is opened.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the hardening device according to the present invention, FIG. 2 is a sectional view showing its operating state, and FIG. 3 is a time chart showing the timing of supply of protective gas. 1... Quenching furnace, 2... Heating chamber, 3... Front chamber, 9... Intermediate door, 11... First gas supply pipe, 13... Second gas supply pipe, 15... Third gas supply pipe, 17, 18...
Solenoid valve, 19...limit switch.

Claims (1)

[Claims] 1. A method for quenching in a non-oxidizing atmosphere by supplying exothermic modified gas as a protective gas to a quenching furnace and mixing methane-based gas as an enrichment gas, comprising: a front chamber equipped with a quenching tank; In a quenching furnace in which a heating chamber is installed in parallel with a heating chamber, and an intermediate door is provided between the two chambers so that the intermediate door can be freely opened and closed, the supply of enrichment gas is stopped when the workpiece is carried into and out of the heating chamber through the intermediate door. A non-oxidizing quenching method characterized in that the amount of protective gas supplied is increased. 2. A quenching furnace with a front chamber equipped with a quenching tank and a heating chamber installed side by side, an intermediate door that can be opened and closed between the two chambers, and a quenching furnace that supplies exothermic gas to the heating chamber of the quenching furnace. 1 gas supply pipe, a second gas supply pipe that supplies enrichment gas, a third gas supply pipe that supplies exothermic transformed gas to the front chamber of the quenching furnace, and an intermediate gas supply pipe that is provided in the second gas supply pipe and Consisting of a normally open solenoid valve that closes the pipeline when the door opens, and a normally closed solenoid valve that is installed on the third gas supply pipe and opens the pipeline when the intermediate door opens. A quenching device featuring: