JPH09273864A - Heat treatment furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively perform quick cooling in a furnace after heat treatment. SOLUTION: Nitrogen is stored in a liquefied nitrogen gas bomb 7 in a liquefied state, and, after taking it out as necessary, the liquefied nitrogen is put into the easily gasifiable condition by an atomizer 6 to be introduced into a container 1. Accordingly, even in the case where the internal volume of the liquefied nitrogen gas bomb 7 and an introduction pipe are made smaller in size, the liquefied nitrogen is explosively expanded in the container 1 after introduction, and the container 1 can be quickly filled with a nitrogen gas having a predetermined pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment furnace capable of effectively performing rapid cooling in the furnace after heat treatment.

[0002]

2. Description of the Related Art In a heat treatment furnace, a method for quenching, such as quenching, by using a cooling gas has been conventionally established. Such a heat treatment furnace, an exhaust system for evacuating the inside of the furnace, a heating means for heating the processed material charged in the furnace, a gas introduction system path for introducing a cooling gas into the furnace after heating, A cooling fan that blows the introduced cooling gas is provided, and by blowing the cooling gas from the cooling fan to the processed product that has undergone the heat treatment, it is possible to efficiently remove heat from the processed product and cool it.

[0003]

In order to supply such cooling gas, a conventional heat treatment furnace is provided with a surge tank at the beginning of a gas introduction system passage, and the surge tank is filled with the cooling gas in a high pressure state. After the heat treatment is completed, the valve is opened to send the cooling gas inside into the furnace.

However, in such a method, since the furnace pressure is determined by the relative volume relationship between the furnace and the surge tank, it is necessary to install a large surge tank in order to increase the furnace pressure and increase the cooling efficiency. is there. For this reason, there is a problem that not only the size of the entire apparatus is increased, but also various problems such as a reduction in space factor and an increase in cost are involved. Also,
Even if the surge tank is made large, it is not possible to generate a pressure higher than the internal pressure of the tank in the furnace. In addition, in order to complete the gas introduction in a short time, it is practiced to thicken the pipe, but when this is done, the gas pressure suddenly enters the furnace and the wind pressure caused by the gas causes the furnace internal components, for example, fragile gas. There is a risk that the heat insulating material such as graphite felt may be easily damaged.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention stores a refrigerant in a liquefied state, takes it out if necessary, and then puts it in a state in which it is easily vaporized into a furnace. I am going to guide you.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION That is, the heat treatment furnace of the present invention is
An exhaust system for evacuating the inside of the furnace, a heating means for heating the processed material charged in the furnace, a refrigerant introduction system path for introducing a refrigerant into the furnace after heating, and the introduced refrigerant to the processed material. A cooling fan that blows air toward the cooling fan is connected to the refrigerant introduction system path through an atomizer so that a refrigerant container in which the refrigerant is stored in a liquefied state can be switched between open and closed.

With such a construction, the volume ratio of the refrigerant when liquefied and when the gas is vaporized is utilized to make the refrigerant container much more effective than the conventional surge tank even though the refrigerant storage amount is substantially the same. It can be done with a small internal volume. Moreover, by introducing the refrigerant in a mist state into the high-temperature furnace, the refrigerant can be explosively expanded after the introduction while suppressing the volume at the time of introduction to instantly create a high-pressure gas atmosphere. In addition to efficient gas introduction, it is possible to effectively avoid generation of wind pressure that locally damages the components inside the furnace. Moreover, when the refrigerant vaporizes in the furnace, the heat of vaporization is taken from the surroundings, so the cooling capacity of the refrigerant can be utilized to the maximum extent as compared with the case of introducing the refrigerant in the gas state from the beginning. Becomes

[0008]

An embodiment of the present invention will be described below with reference to the drawings. In this heat treatment furnace, an exhaust system 2 for evacuating the inside of the container 1, a heating means 3 for heating a processed material W loaded in the container 1, and a refrigerant for introducing nitrogen as a refrigerant into the container 1 after heating. It is provided with an introduction system passage 4 and a cooling fan 5 for blowing the introduced nitrogen toward the processed material W.

More specifically, the container 1 has a cylindrical shape and a heat insulating main body 11 having a nozzle 11a formed on its peripheral wall toward the core, and a heat insulating cover for sealing both open ends of the heat insulating main body 11. It has 12 and 13 inside. Insulated body 1
1 and the heat insulating lids 12 and 13 are made of, for example, graphite felt, and have a heat treatment space S1 closed therein, and one heat insulating lid is used to load a treatment object W into the heat treatment space S1. A container 12 is attached to and detached from the opening of the heat insulating main body 11 together with a door 1a for loading and unloading the processed material provided at one end of the container 1. The heat insulating lids 12 and 13 also serve as dampers that are opened and closed by being driven by an opening / closing cylinder (not shown) during cooling. Also, the heat insulating body 11
A gas cooling space S2 partially surrounded by a guide 14 is formed between the container 1 and the container 1, and a heat exchanger 15 is arranged in a part of the gas cooling space S2. The gas cooling space S2 communicates with the heat treatment space S1 when the heat insulating lids 12, 13 are opened. On the other hand, the nozzle 11a is the guide 1
4 communicates with the blower space S3 outside the heat insulating main body 11 through a part of the openings 4.

In this embodiment, the exhaust system 2 has a structure in which a mechanical booster pump 21 and an oil rotary vacuum pump 22 are connected in series, and a container 1 is provided via a valve 23.
It is connected inside so that it can be switched on and off. The heating means 3 is composed of a sheathed heater, a graphite heater, or the like having the ability to heat the object to be processed to a temperature (for example, about 1,000 degrees) corresponding to the heat treatment, and is inside the heat treatment space S1 and is an object to be processed. It is arranged at a position surrounding W.

The refrigerant introducing passage 4 is for feeding nitrogen gas, which is a refrigerant, into the heat treatment space S1 in the furnace after the heat treatment, and its end is connected to a position facing the gas cooling space S2. An atomizer 6 having a venturi-nozzle structure is connected to the refrigerant introduction path 4 via a valve 41 in the middle of the path, and the venturi portion 61 of the atomizer 6 is connected via a valve 71 to nitrogen gas. Is connected to a liquid phase portion of a liquid nitrogen gas cylinder 7 which is a refrigerant container for storing in a liquefied state, and a small surge tank 8 is connected to a venturi inlet portion 62 of the atomizer 6. The outlet side of the small surge tank 8 is connected to the gas phase portion of the liquid nitrogen gas cylinder 7 via a valve 81 so that nitrogen gas is stored at a predetermined pressure.

The cooling fan 5 is arranged at a position facing the heat exchanger 15 in the gas cooling space S2, and its shaft portion penetrates the container 1 and is connected to a motor 51 outside the furnace. Then, by driving the motor 51, the gas existing in the gas cooling space S2 is sucked in from the core direction,
It is designed to discharge in the radial direction.
The discharged gas, after flowing through the air blowing space S3, is jetted toward the processed material W arranged in the heat treatment space S1 through the nozzle 11a provided in the heat insulating main body 11, and at this time, the heat insulating lid 1
By opening 2 and 13, the heat is returned to the heat exchanger 15 through the cooling space S2. Hereinafter, this system is referred to as a gas circulation system.

Next, a description will be given of the manner in which the workpiece W charged in the furnace is subjected to various heat treatments under the vacuum created by the exhaust system 2 through the heating means 3 and then subjected to rapid cooling. By the time the heat treatment is completed, the valve 81 of the liquefied nitrogen gas cylinder 7 is opened and the small surge tank 8 is about 10 kg.
Pressurize to f / cm ² . After the heating process is completed, the exhaust valve 23 is closed, the motor 51 is started, the cooling fan 5 is rotated, and the valves 41 and 71 that were originally closed are opened. Liquid nitrogen in the liquefied nitrogen gas cylinder 7 is supplied to the venturi portion 61 of the atomizer 6 by gas pressure, and high pressure nitrogen gas flows into the venturi inlet portion 62 from the small surge tank 8 in that state, so that the nitrogen gas When passing through the venturi portion 61 of the atomizer 6, the liquid nitrogen is atomized and poured into the container 1. The venturi outlet 63 has a ventilation space S3 that is a vacuum.
While communicating directly with the Venturi inlet section 62
Is connected to the surge tank 8, the venturi 61
A sonic flow is generated inside, and the maximum possible flow rate is obtained.
On the other hand, the atomized liquid nitrogen introduced into the gas cooling space S2 inside the container 1 is vaporized by the heat inside the container 1 and explosively expands, causing the pressure inside the container 1 to rise rapidly. The gas pressure in the container 1 is controlled by opening and closing the valve 71 by a timer or setting the pressure controller 16 attached to the container 1 so that the internal pressure of the furnace becomes about 8 kgf / cm ^{2 in} about 1 to 2 seconds. Control the amount of. Then, the cycle in which the nitrogen gas is blown to the processed material W along the above-described gas circulation system, while being cooled by the heat exchanger 15 and blown to the processed material W again, is repeated. During this time, the processed material W is cooled by directly blowing nitrogen gas, and also indirectly by cooling the vaporization heat when the atomized liquid nitrogen is vaporized at the time of introduction from the respective furnace materials. .

In the heat treatment furnace having the cooling function as described above, the liquid nitrogen that substantially controls most of the cooling is utilized by utilizing the volume ratio between the liquefaction and the vaporization of the refrigerant nitrogen. It is possible to make the internal volume of the liquid nitrogen gas cylinder 7 in which is stored much smaller than that of the conventional surge tank. That is, when the refrigerant storage amount is substantially the same, the theoretical internal volume ratio can be set to 1/666. In this embodiment, nitrogen gas is used to promote atomization, and a surge tank 8 is provided for storing the pressurized gas, but this surge tank 8 is filled with nitrogen gas. It is not necessary to store the entire amount of the above, and it is sufficient to provide an internal volume that is a fraction of or less than the conventional internal volume, as long as the amount necessary for atomization is sufficient. Therefore, even if the liquid nitrogen gas cylinder 7 and the surge tank 8 are used together, it is possible to cover with a much smaller volume than the conventional surge tank. Moreover, by introducing liquid nitrogen into the high-temperature container 1 in a mist state, it is possible to explosively expand the refrigerant after introduction while suppressing the volume at the time of introduction, and to instantly create the required high-pressure gas atmosphere. Gas can be introduced with extremely high efficiency even with a small pipe, and the pressure inside the container 1 can be raised to a predetermined pressure in a shorter time than before (in the past, it took about 7 seconds to bring the inside of the furnace to the same predetermined pressure). Was needed). In addition, the relatively fragile insulation 11, 12, 13
It is also possible to effectively avoid the generation of wind pressure that locally damages the components inside the furnace such as. Further, since vaporization occurs in the furnace, it is possible to raise the furnace pressure above the supply pressure by appropriately controlling the opening / closing timing of the valve 41. Further, when the liquid nitrogen vaporizes in the container 1, the heat of vaporization is taken from the surroundings, so that the cooling efficiency can be more effectively enhanced as compared with the case of introducing the nitrogen gas.

As described above, when the heat treatment furnace of this embodiment is used, the inside of the container 1 is brought into a high-pressure gas atmosphere suitable for rapid cooling within a short time, and at the same time, the heat of vaporization is also used to perform quenching treatment and the like. Not only can the performance of the furnace be effectively improved, but also the structure of the furnace can be made compact, and at the same time, the durability of the furnace material can be effectively improved.

The specific configuration of each section is not limited to the illustrated embodiment. For example, it goes without saying that the present invention can be applied to a cooling chamber in a multi-chamber type heat treatment furnace in which a heating chamber and a cooling chamber are separated. Further, although the surge tank is charged from the gas phase portion of the liquid nitrogen gas cylinder in the above embodiment, the gas temperature in the surge tank may be kept low by directly feeding and evaporating the liquid nitrogen. Further, it is also possible to install only the liquid nitrogen gas cylinder without using the surge tank and use the pressurized gas in the cylinder in the range where the atomizing gas can be obtained in the venturi part of the atomizer. . This configuration is extremely effective in reducing the cooling rate of a general heat treatment furnace including a sintering furnace.

Other configurations can be variously modified without departing from the spirit of the present invention.

[0018]

Since the heat treatment furnace of the present invention is constructed as described above, the inside of the furnace is brought into a high-pressure gas atmosphere suitable for rapid cooling within a short time, and at the same time, the heat of vaporization is used to quench the heat treatment. It is possible to effectively improve performance such as processing. Further, the structure of the furnace can be made compact, and at the same time, the durability of the furnace can be effectively improved.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the same.

FIG. 3 is a diagram showing a main part of the embodiment.

[Explanation of symbols]

 W ... Treated material 1 ... Furnace 2 ... Exhaust system 3 ... Heating means 4 ... Refrigerant introduction system path 5 ... Cooling fan 6 ... Atomizer (spray nozzle) 7 ... Refrigerant container (liquid nitrogen gas cylinder)

Claims (1)

[Claims] 1. An exhaust system for evacuating the inside of a furnace, a heating means for heating a processed material charged in the furnace, and a refrigerant introducing system passage for introducing a refrigerant into the furnace after heating. In a device comprising a cooling fan for blowing the refrigerant toward the processed material, a refrigerant container in which the refrigerant is stored in a liquefied state is connected to the refrigerant introduction system passage via an atomizer in a disconnectable and switchable manner. A heat treatment furnace characterized by: