JP2001221575A - Vacuum furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of furnace member and products by early detecting defects in a radiant tube and taking counter measure. SOLUTION: An evaporation preventing gas is supplied into a vacuum chamber 12 through a gas supplying source and a gas supplying pipe 44. Inner pressure of the vacuum chamber 12 is detected by means of a vacuum pressure sensor 38, and the pressure data are inputted to a control unit 40. Volume of the evaporation preventing gas supplied into the vacuum chamber 12 is measured by a flow meter 46, and the data are inputted into the control unit 40. The control unit 40 adjusts volume of the evaporation preventing gas so as to keep inner pressure of the vacuum chamber 12 to a predetermined level based on the pressure data from the vacuum pressure sensor 38, and emergency is detected when the flow data from the flow meter 46 becomes less than the abnormal flow set preliminarily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum furnace for heating a processed product using a radiant tube heater.

[0002]

2. Description of the Related Art A vacuum furnace used for powder sintering of various alloy products and firing of ceramic products has a processing chamber surrounded by a heat insulating material in a vacuum chamber. The processing product is configured to be heated using a combustion-type radiant tube heater.

In the vacuum furnace, when a metal is heated as a processed product, an evaporation preventing gas such as N ₂ , Ar, H _{2 is} placed in a vacuum chamber in order to prevent evaporation of, for example, Cr contained in the metal. The operation is performed while the pressure is supplied and the inside of the chamber is maintained at a predetermined pressure (for example, about 1333.22 Pa).

[0004]

In the vacuum furnace,
By opening the door provided in the processing chamber and circulating the inert gas supplied into the vacuum chamber at the time of cooling using a fan while cooling it with a cooler, it is possible to rapidly cool the processed product to the quenching level. is there. The radiant tube heater has a very high temperature during heating. That is, since the radiant tube heater is repeatedly heated and cooled, if used for many years, the tube may be damaged, though extremely rarely.

[0005] When the tube is damaged, air, combustion exhaust gas, or the like enters the vacuum chamber from the damaged portion. If the tube is left undisturbed, it becomes easily oxidized as a furnace material such as a heat insulating material or a C-based material or Mo. If you are using the metal material of
The life of the furnace material may be shortened, or the quality of the processing material during processing may be impaired.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems inherent in the prior art, and has been proposed in order to appropriately solve the problem. The present invention detects early detection of damage to a radiant tube heater. An object of the present invention is to provide a vacuum furnace capable of suppressing deterioration of a furnace material, a processed product, and the like.

[0007]

[MEANS FOR SOLVING THE PROBLEMS]
In order to appropriately achieve the intended purpose, the vacuum furnace according to the present invention is provided with a processing chamber surrounded by a heat insulating wall in a vacuum chamber, and a space between a processing product charged into the processing chamber and the heat insulating wall. A gas supply means for supplying a pressure adjusting gas into the vacuum chamber, a vacuum pressure sensor for detecting an internal pressure of the vacuum chamber, and a pressure supplied by the gas supply means. Flow rate variable means for adjusting the supply flow rate of the adjustment gas, flow rate detection means for detecting the supply flow rate of the pressure adjustment gas, and the inside of the vacuum chamber based on pressure data input from the vacuum pressure sensor. While controlling the flow rate varying means so as to maintain the pressure at the set pressure, the flow rate data input from the flow rate detection means is less than a preset abnormal flow rate Characterized by being composed of a control means for detecting occurrence of abnormality in.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a vacuum furnace according to the present invention will be described below with reference to the accompanying drawings by way of preferred embodiments.

FIGS. 1 and 2 show a vacuum furnace according to an embodiment. In a vacuum chamber 12 of the vacuum furnace 10, a holding material made of a metal material (furnace material) such as Mo is used. A heat-insulating material (furnace material) made of a C-based material is disposed in the housing so that the heat-insulating wall 14 formed in a box shape is housed therein.
A processing chamber 16 is defined by the heat insulating wall 14. A mounting table 20 on which the processing product 18 is mounted is disposed inside the processing chamber 16, and the processing product 18 mounted on the mounting table 20 is set so as to face substantially the center of the processing chamber 16. . Further, the vacuum pump 2 is provided in the vacuum chamber 12.
2 are connected, and the vacuum chamber 12 and the processing chamber 16 are connected.
Is configured to be able to have a substantially vacuum atmosphere inside.

A motor 2 is provided above the vacuum chamber 12.
4 is provided, and the fan 2 rotated by the motor 24 is provided.
6 faces the inside of the chamber, and is configured to circulate an inert gas supplied into the vacuum chamber 12 when the processing article 18 is cooled. Vacuum chamber 12
As shown in FIG. 2, coolers 28 through which cooling water circulates are disposed on both left and right sides of the furnace in the furnace width direction with the heat insulating wall 14 interposed therebetween. It is configured to cool. The insulation wall 14
Openings 30 are respectively formed in the ceiling and the bottom of the vehicle, and an opening / closing door 32 is provided in each opening 30 so as to be openable and closable.
The opening / closing door 32 is opened / closed via a fluid pressure cylinder 34 provided outside the vacuum chamber 12. That is, the opening and closing doors 32 and 32 close the openings 30 and 30 when the processing product 18 is heated, and open the openings 30 and 30 when the processing product 18 is cooled, and the inert gas cooled by the cooler 28 is opened. Is circulated in the processing chamber 16 so that the processed product 18 can be rapidly cooled to the quenching level.

The vacuum furnace 10 includes a vacuum chamber 12.
And a plurality of combustion-type radiant tube heaters 36 penetrating through the heat insulating wall 14 and facing the inside of the processing chamber 16, respectively, in a vertical direction along the furnace wall so as to reach between the heat insulating wall 14 and the processing product 18. It is arranged to extend. That is,
In the vacuum furnace 10, the processing product 18 charged in the processing chamber 16 is
Is heated by a plurality of radiant tube heaters 36.

The vacuum chamber 12 is provided with a vacuum pressure sensor 38 for detecting the internal pressure, and pressure data (pressure signal) from the sensor 38 is input to a control device 40 as control means. It has become. The vacuum chamber 12 contains N ₂ , Ar,
A gas supply pipe 44 derived from a supply source 42 of an evaporation preventing gas (pressure adjusting gas) such as H ₂ is connected to the processing product 18.
At the time of heating, a predetermined amount of an evaporation preventing gas can be supplied into the vacuum chamber 12 in order to prevent evaporation of Cr and the like. That is, in the embodiment, the gas supply means is constituted by the supply source 42 and the gas supply pipe 44. The gas supply pipe 44 is provided with a flow meter 46 as flow detection means provided with a control valve (flow variable means) capable of adjusting the supply flow rate of the evaporation preventing gas. The supply flow rate of the evaporation preventing gas supplied to the vacuum chamber 12 via the supply pipe 44 is detected, and its flow rate data (flow rate signal)
Is input to the control device 40. In addition,
As the flow meter 46, for example, a high-precision mass flow meter is used, and a small flow rate fluctuation can be detected.

The control device 40 controls the opening and closing of the control valve of the flow meter 46 based on the pressure data relating to the internal pressure of the vacuum chamber 12 input from the vacuum pressure sensor 38, so that when the processing product 18 is heated, Is set to keep the internal pressure of the vacuum chamber 12 at a preset pressure (small pressure) set in advance. In the control device 40, a reference flow rate of the evaporation preventing gas required to maintain the internal pressure of the vacuum chamber 12 at a set pressure is set.

An auxiliary supply pipe 48 branches from the supply source side of the gas supply pipe 44 from the interposition position of the flow meter 46, and the auxiliary supply pipe 48 is connected to the vacuum chamber 12 via an on-off valve 50. It is connected. The on-off valve 50 is always kept closed, and is opened when an abnormal situation described later occurs, so that the control device supplies a large amount of evaporation preventing gas into the vacuum chamber 12 through the auxiliary supply pipe 48. At 40, the opening and closing are controlled.

When the radiant tube heater 36 is damaged as described above, air, combustion exhaust gas, and the like enter the vacuum chamber 12 and the processing chamber 16 from the damaged portion. In this case, since the internal pressure of the vacuum chamber 12 is increased by the amount of invasion of air, combustion exhaust gas, and the like, the supply flow rate of the evaporation preventing gas required to maintain the above-described set pressure is smaller than the reference flow rate. Become. Therefore,
In the embodiment, the abnormal flow rate is set to be smaller than the reference flow rate by a predetermined amount, and when the flow rate data fed back from the flow meter 46 becomes smaller than the abnormal flow rate, the controller 40 detects that an abnormal situation has occurred. It is configured as follows. Then, when an abnormal situation occurs, the on-off valve 50 is immediately opened to supply a large amount of the evaporation preventing gas into the vacuum chamber 12, thereby suppressing deterioration of the furnace material and the processing product 18.

Since the set pressure itself in the vacuum chamber 12 is extremely low, the supply flow rate of the evaporation preventing gas due to the intrusion of the air and the combustion exhaust gas fluctuates early. Damage can be detected early.

[0017]

Next, the operation of the vacuum furnace according to the embodiment will be described. Upper and lower openings 30, 30 of the heat insulating wall 14
Are closed by the open / close doors 32, 32, and the processing product 18 is stored in the processing chamber 16
And placed on the mounting table 20 described above. Next, the inside of the processing chamber 16 is set to a substantially vacuum atmosphere by the vacuum pump 22, and the radiant tube heater 36 is burned to heat the processed product 18. Further, the evaporation preventing gas is supplied into the vacuum chamber 12, and based on the pressure data and the flow rate data input from the vacuum pressure sensor 38 and the flow meter 46, the control device 40 controls opening and closing of a control valve in the flow meter 46. By adjusting the supply flow rate of the evaporation preventing gas, the inside of the vacuum chamber 12 is maintained at a preset pressure in the evaporation preventing gas atmosphere. This prevents evaporation of Cr and the like contained in the processed product 18 during heating.

When the heat treatment of the processed product 18 is completed,
The combustion of the radiant tube heater 36 is stopped, and the doors 32, 32 are operated to open the openings 30, 30.
To release. In addition, the inert gas is cooled by contacting the coolers 28, 28 by rotating the fan 26 while supplying the inert gas into the vacuum chamber 12,
This gas circulates inside the processing chamber 16 through the openings 30, 30. As a result, the processed product 18 is rapidly cooled to the quenching level.

As described above, if the operation of repeating heating and rapid cooling in the vacuum furnace 10 is performed for many years, the tubes of the radiant tube heater 36 may be damaged. If the tube is damaged during the heating of the processing product 18, air or combustion exhaust gas enters the vacuum chamber 12 or the processing chamber 16 from the damaged portion. If the tube is left untreated, the room becomes an oxidizing atmosphere. Sisters,
There is a possibility that the furnace material and the processed product 18 that are easily oxidized may deteriorate.

Therefore, in the vacuum furnace 10 of the embodiment, before the inside of the vacuum chamber 12 or the processing chamber 16 becomes an oxidizing atmosphere, the damage of the tube or the like is detected, and the deterioration of the furnace material and the processing product 18 is suppressed. It has become.

That is, when air or combustion exhaust gas enters the vacuum chamber 12, the internal pressure increases, and in the control device 40 to which the pressure data from the vacuum pressure sensor 38, which has detected this, is input, By controlling the opening and closing of the control valve in 46, the supply flow rate of the evaporation preventing gas is adjusted, and the internal pressure of the vacuum chamber 12 is maintained at the set pressure. In this case, the supply flow rate of the evaporation preventing gas becomes smaller than the reference flow rate by the amount of the air and the combustion exhaust gas entering the vacuum chamber 12. When the supply flow rate becomes smaller than the preset abnormal flow rate, the control device 40 detects that an abnormal situation has occurred, and opens the on-off valve 50 to supply a large amount of the evaporation preventing gas into the vacuum chamber 12. To supply. That is, before the inside of the vacuum chamber 12 becomes completely oxidizing atmosphere due to the invasion of air or combustion exhaust gas, the inside of the chamber 12 can be set to the high-pressure evaporation preventing gas atmosphere. Is prevented. Further, by supplying a large amount of the evaporation preventing gas, intrusion of air and combustion exhaust gas from the damaged portion of the tube is suppressed.

When the control device 40 detects an abnormal situation, the combustion of the radiant tube heater 36 is stopped, or an alarm means such as an alarm buzzer or an alarm lamp is activated to notify the operator of the abnormal situation. Preferably, the occurrence is recognized.

Although the embodiment has been described using a combustion type radiant tube heater, an electric resistance type radiant tube heater may be employed. Further, in the embodiment, the flow meter as the flow rate detection means,
Although the control valve as the flow rate varying means is provided, a configuration in which the flow meter and the control valve are formed separately can be adopted. Further, in the embodiment, the evaporation preventing gas for maintaining the inside of the vacuum chamber at the set pressure is supplied into the vacuum chamber when an abnormal situation occurs. An oxidizing gas may be supplied.

[0024]

As described above, in the vacuum furnace according to the present invention, the intrusion of air or combustion exhaust gas into the vacuum chamber due to the damage of the radiant tube heater can be detected at an early stage. Therefore, it is possible to prevent furnace materials and processed products from deteriorating.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram also showing a vacuum furnace and a control system thereof according to a preferred embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a vacuum furnace according to an example.

[Explanation of symbols]

 Reference Signs List 12 vacuum chamber 14 heat insulating wall 16 processing chamber 18 processed product 26 fan 38 vacuum pressure sensor 40 controller (control means) 42 supply source (gas supply means) 44 gas supply pipe (gas supply means) 46 flow meter (flow rate detection means) )

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiharu Shimizu 19-18, Sakurada-cho, Atsuta-ku, Nagoya City, Aichi Prefecture Inside Higashi Kokugas Co., Ltd. 64-1 Address (72) Inventor Kenjiro Sato 945 F term at 1 Sonemachi, Sakae-cho, Toyoake-shi, Aichi (reference) 4K061 AA05 BA02 BA09 DA05 FA12 GA03 GA04 4K063 AA07 AA12 AA16 BA01 BA04 BA15 CA03 CA05 DA05 DA19 DA20 DA33

Claims (4)

[Claims] A processing chamber (16) surrounded by a heat insulating wall (14) is provided in a vacuum chamber (12), and a processing product (18) charged into the processing chamber (16) and a heat insulating wall (14) are provided. And a gas supply means (42, 44) for supplying a pressure adjusting gas into the vacuum chamber (12), wherein the vacuum chamber (12) A vacuum pressure sensor (38) for detecting the internal pressure of the gas; a flow rate variable means for adjusting a supply flow rate of the pressure adjustment gas by the gas supply means (42, 44); and a supply flow rate of the pressure adjustment gas. Flow detection means
(46), based on the pressure data input from the vacuum pressure sensor (38), while controlling the flow rate variable means to maintain the internal pressure of the vacuum chamber (12) at a set pressure,
A vacuum furnace characterized by comprising flow rate data input from the flow rate detection means (46) and control means (40) for detecting occurrence of an abnormal situation when the flow rate becomes lower than a preset abnormal flow rate. . 2. The vacuum furnace according to claim 1, wherein a large amount of a non-oxidizing gas is supplied into said vacuum chamber when said control means detects the occurrence of an abnormal situation. . 3. The vacuum furnace according to claim 1, wherein the alarm means is activated when the control means detects the occurrence of an abnormal situation. 4. An inert gas is supplied into the vacuum chamber (12) when the processing product (18) is cooled, and the inert gas is circulated by a fan (26) provided in the chamber (12) for processing. Goods (1
The vacuum furnace according to any one of claims 1 to 3, wherein the vacuum furnace is configured to rapidly cool (8).