JP2004010913A - Heat treatment method in sodium bath, and device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove moisture and oxygen in an atmospheric gas for heating, only by piping without using extra facilities, while making use of the advantages of heat treatment in a sodium bath. <P>SOLUTION: The heat treatment method comprises a gas purification step for removing the moisture and the oxygen in the atmospheric gas, by contacting the atmospheric gas with liquid metallic sodium, a heating step for heating a solid metallic material 40 in the atmospheric gas treated in the gas purification step, and a cooling step for cooling the solid metallic material in the liquid metallic sodium. The heat treatment device comprises a heating part 4 for heating the solid metallic material in the atmospheric gas, a sodium bath chamber 7 for accommodating the liquid metallic sodium for cooling the solid metallic material by immersing it therein, and a bubbling line 16 for introducing the atmospheric gas into the liquid metallic sodium in the sodium bath chamber. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for heating a heat treatment material as a solid metal material and performing a heat treatment using liquid sodium, and more particularly to a method and an apparatus involving removal of oxygen, moisture and the like in a gas atmosphere in a heating section.
[0002]
[Prior art]
Techniques for performing heat treatment of a solid metal material using liquid sodium are disclosed in, for example, JP-A-2002-12917 and JP-A-2000-345236.
[0003]
When heat-treating a steel material, it is general to heat it to 800 ° C. or more after carburizing. At this temperature, if oxygen and moisture are present in the atmosphere gas, an oxide layer is formed and decarburization occurs. In the case where the carburized heat-treated material is immediately heat-treated, the temperature is generally raised to the heat treatment temperature in a carburizing gas atmosphere and the heat treatment is performed. Since the carburizing gas is a reducing gas, it does not cause formation of an oxide layer and decarburization.
[0004]
However, when rapidly cooling without carburizing steel and metals other than steel, or when heating and heat-treating a carburized heat treatment material again, oxygen and moisture must be removed from the atmosphere gas in the heating section. , Generates an oxide layer, and in the case of steel materials, causes decarburization. Therefore, it is necessary to remove oxygen and moisture from the atmosphere gas of the heating unit.
[0005]
Conventionally, two types of methods have been used as a method for removing oxygen and moisture from the atmosphere gas of a heating unit. One is a method in which the atmosphere gas in the heating unit is used as a reducing gas, and the other is a method using only nitrogen gas evaporated from liquid nitrogen.
[0006]
[Problems to be solved by the invention]
When a reducing gas is used, a reducing gas generator or a cylinder is required. Further, since the reducing gas is often flammable, a combustion device is required when exhausting the gas. On the other hand, when using nitrogen evaporated from liquid nitrogen, a tank for liquid nitrogen and a tank for evaporating liquid nitrogen to nitrogen gas are required. As described above, when quenching the steel material and metals other than the steel material without carburizing, or when heating and heat-treating the carburized heat treatment material again, respective facilities other than the heat treatment apparatus are required.
[0007]
The present invention provides a sodium bath treatment method and apparatus with simple gas purification that removes oxygen and moisture in a heated atmosphere gas by taking advantage of the characteristics of a sodium bath heat treatment, and only by laying out piping without using extra equipment. The purpose is to:
[0008]
[Means for Solving the Problems]
The present invention achieves the above object, and the invention according to claim 1 includes a gas refining step of removing oxygen and moisture in the atmospheric gas by bringing the atmospheric gas into contact with liquid metallic sodium; The method includes a heating step of heating the metal material in an atmosphere gas having undergone the gas purification step, and a cooling step of cooling the solid metal material in liquid metallic sodium. According to the first aspect of the present invention, it is possible to remove oxygen and moisture in the atmosphere gas of the heating section only by laying pipes without providing new equipment, thereby preventing generation of an oxide layer and decarburization on the surface of the heat-treated material.
[0009]
According to a second aspect of the present invention, in the sodium bath heat treatment method of the first aspect, metallic sodium used in the gas purification step and the cooling step is common. According to the second aspect of the present invention, the operation and effect of the first aspect of the present invention can be obtained, and the sodium used for the heat treatment is diverted to the purification of the atmosphere gas, so that the equipment can be used efficiently.
[0010]
According to a third aspect of the present invention, in the sodium bath heat treatment method according to the first or second aspect, in the gas refining step, the atmospheric gas is supplied to a liquid surface of metallic sodium inside a container containing the metallic sodium. Is passed through the gaseous phase part above. According to the third aspect of the invention, the operation and effect of the first or second aspect of the invention can be obtained, and the pipe through which the atmospheric gas flows does not need to be always in contact with the liquid sodium, so that the liquid sodium flows into the pipe. The possibility of such an accident is low, and safe driving is possible.
[0011]
According to a fourth aspect of the present invention, in the sodium bath heat treatment method according to the first or second aspect, the atmosphere gas is released into the metallic sodium in the gas purification step. According to the fourth aspect of the present invention, in addition to the functions and effects of the first or second aspect of the present invention, a large contact area between the atmospheric gas and the liquid sodium can be obtained, and a stirring effect due to the movement of bubbles can be expected. Therefore, the effect of removing oxygen and moisture in the atmosphere gas is great.
[0012]
The invention according to claim 5 is a heating section for heating a solid metal material in an atmosphere gas, a sodium bath for containing liquid metal sodium for immersing and cooling the solid metal material, and a sodium bath for storing the liquid metal sodium. A bubbling line for releasing the atmospheric gas into the liquid metallic sodium. According to the fifth aspect of the present invention, it is possible to remove oxygen and moisture in the atmosphere gas of the heating section only by laying pipes without providing new equipment, thereby preventing generation of an oxide layer and decarburization on the surface of the heat-treated material. In addition, a stirring effect due to the movement of the bubbles can be expected.
[0013]
According to a sixth aspect of the present invention, in the sodium bath heat treatment apparatus according to the fifth aspect, a means for monitoring and controlling the oxygen concentration and the dew point in the atmospheric gas is further provided. According to the sixth aspect of the invention, the operation and effect of the fifth aspect of the invention can be obtained, and the timing of heating the heat-treated material can be appropriately selected.
[0014]
According to a seventh aspect of the present invention, in the sodium bath heat treatment apparatus according to the sixth aspect, a dew point at which heating of the solid metal material is started is set to −60 ° C. or less.
[0015]
According to the seventh aspect of the present invention, the operation and effect of the fifth or sixth aspect of the present invention can be obtained, and the generation and decarburization of an oxide layer of the heat-treated material can be effectively prevented or suppressed. Here, the reason why the dew point at which the heating of the heat-treated material is started is -60 ° C (moisture concentration 11 ppm) is based on the fact that the oxygen concentration actually performed by the inventors is 1 ppm or less and the dew point is -52 ° C (moisture concentration 30 ppm). No formation of oxidized layer and no decarburization occurred in the test.
[0016]
According to an eighth aspect of the present invention, in the sodium bath heat treatment apparatus according to any one of the fifth to seventh aspects, the atmosphere gas cooled by being brought into contact with the sodium is supplied to the atmosphere which is still at the heat treatment temperature. A heat exchanger for heating using gas is provided. According to the invention of claim 8, the operation and effect of any of the inventions of claims 5 to 7 can be obtained, and the thermal efficiency can be improved.
[0017]
According to a ninth aspect of the present invention, in the sodium bath heat treatment apparatus according to any one of the fifth to eighth aspects, a check valve for preventing a backflow of the liquid metallic sodium in the bubbling line is provided. Is characterized in that: According to the ninth aspect of the invention, the operation and effect of any one of the fifth to eighth aspects of the invention can be obtained. In addition, the pressure in the bubbling line is higher than the pressure of the sodium bath gas phase due to a change in temperature or erroneous operation of a valve. Even if it becomes low, the backflow of sodium in the bubbling line can be stopped.
[0018]
According to a tenth aspect of the present invention, in the sodium bath heat treatment apparatus according to any one of the fifth to ninth aspects, a level gauge for detecting a sodium level is provided in the middle of the bubbling line. And According to the tenth aspect, in addition to the effects and advantages of the fifth to ninth aspects, when the sodium in the sodium bath flows backward through the bubbling line, this is sensed and an alarm is issued. To improve safety in the event of an erroneous operation.
[0019]
According to an eleventh aspect of the present invention, in the sodium bath heat treatment apparatus according to the tenth aspect, the liquid level gauge is installed in a buffer tank provided in the middle of the bubbling line. I do. According to the eleventh aspect of the present invention, the operation and effect of the tenth aspect of the present invention can be obtained, and the flow velocity when the liquid sodium in the sodium bath flows backward through the bubbling line can be reduced. It is possible to increase the time margin from when the alarm is issued until the countermeasure against the backflow of liquid sodium.
[0020]
According to a twelfth aspect of the present invention, in the sodium bath heat treatment apparatus according to any one of the fifth to eleventh aspects, the introduction of the atmosphere gas into the metallic sodium in the sodium bath chamber through the bubbling line is stopped. The same pressure pipe is provided for communicating between the level of metallic sodium in the sodium bath and the bubbling line.
[0021]
According to the twelfth aspect of the invention, in addition to the functions and effects of any of the fifth to eleventh aspects, the following functions and effects can be obtained. That is, when the pressure in the sodium bath gas phase and the pressure in the bubbling line are different due to a change in temperature or the like, opening the valve provided in the bubbling line requires that the pressure in the sodium bath gas phase and the bubbling line be different. The difference from the pressure may cause a danger because the liquid level of the liquid sodium in the bubbling line goes up and down. According to the twelfth aspect of the present invention, the pressure difference is eliminated by connecting the inside of the bubbling line and the sodium bath gas phase with the same pressure pipe, and the liquid level of the liquid sodium in the bubbling line does not change only by opening the valve of the bubbling line. , Safety can be improved.
[0022]
According to a thirteenth aspect of the present invention, in the sodium bath heat treatment apparatus according to the twelfth aspect, a portion of the bubbling line connected to the metallic sodium in the sodium bath is made of metal in the sodium bath. A three-way cock is provided so as to be able to selectively communicate above the liquid level of sodium and one of the same pressure tubes. According to the thirteenth aspect of the present invention, the operation and effect of the twelfth aspect of the present invention can be obtained. In addition, erroneous operations such as bubbling while opening the same-pressure pipe and forgetting to close the same-pressure pipe even after the bubbling is completed can be prevented. Can be prevented.
[0023]
According to a fourteenth aspect of the present invention, in the sodium bath heat treatment apparatus according to any one of the fifth to thirteenth aspects, a vapor trap for removing sodium vapor in the atmosphere gas is provided. . According to the fourteenth aspect, the operation and effect of any one of the fifth to thirteenth aspects can be obtained, and in addition, sodium vapor (sodium vapor) is prevented from adhering to the piping of the sodium bath heat treatment apparatus. can do.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of a sodium bath heat treatment apparatus according to the present invention will be described with reference to FIGS.
In FIG. 1, a sodium bath 7 contains liquid metal sodium as a coolant. In this specification, "sodium" includes not only pure sodium but also one containing potassium or lithium. A heating unit 4 is provided above the sodium bath 7, and a heat treatment material exchanging unit 3 is provided above the heating unit 4. A vertically extending support bar 1 is disposed so as to reach the sodium bath 7 from above the heat treatment material exchange unit 3 through the heat treatment material exchange unit 3 and the heating unit 4, and a solid metal material is provided at the lower end of the support bar 1. A certain heat treatment material (quenched material) 40 is held.
[0025]
The support bar 1 is driven up and down by a drive unit 2. In the state shown by the solid line in FIG. 1, the heat treatment material 40 is located in the heating unit 4. When the support bar 1 is driven downward, the heat treatment material 40 (indicated by a dotted line) is immersed in the liquid sodium in the sodium bath 7. When the support bar 1 is driven upward, the heat treatment material 40 (shown by a dotted line) reaches the heat treatment material exchange unit 3.
[0026]
An upper gate valve 5 is provided between the heat-treated material exchange unit 3 and the heating unit 4, and the heat-treated material exchange unit 3 is heated by closing the upper gate valve 5 when the heat-treated material 40 is in the heat-treated material exchange unit 3. The part 4 can be pressure separated and the heat treatment material 40 can be replaced. In addition, a heat shield plate 6 is provided between the upper gate valve 5 and the heating unit 4, so that the upper gate valve 5 can be prevented from being overheated.
[0027]
There is a lower gate valve 8 between the heating unit 4 and the sodium bath 7, and by closing the lower gate valve 8 when the heat treatment material 40 is in the heating unit 4, the heating unit 4 and the sodium bath 7 are pressured. Can be separated.
[0028]
A vapor trap 9 is connected to the sodium bath 7 via a pipe, and is configured to remove sodium vapor in the atmospheric gas exiting from the sodium bath 7.
[0029]
A circulation pump 10 for circulating the atmosphere gas, a flow meter 11 connected to the discharge side of the circulation pump 10 for adjusting the circulation flow rate are connected, and a heat exchanger 12 is connected further downstream of the flow meter 11. Have been. In the heat exchanger 12, the cooled atmosphere gas flowing out of the sodium bath 7 exchanges heat with the uncooled atmosphere gas, so that the thermal efficiency can be improved.
[0030]
A dew point meter 13 for monitoring the dew point of the atmosphere gas; an oxygen meter 14 for monitoring the oxygen concentration of the atmosphere gas; a passage line 15 for passing the atmosphere gas through the sodium bath 7 gas phase; A bubbling line 16 for releasing atmospheric gas into liquid sodium in the bathroom 7 is connected. Further, a buffer tank 18 having a liquid level gauge 17 is installed in the bubbling line 16. The liquid level gauge 17 is configured to generate an alarm when liquid sodium in the sodium bath 7 flows back through the bubbling line 16. Have been. The buffer tank 18 is set to have a capacity for securing a time for responding to the backflow of liquid sodium after the liquid level gauge 17 issues an alarm.
[0031]
An isobar 19 for communicating the bubbling line 16 with the gas phase of the sodium bath 7 and a three-way cock 20 for controlling the direction of conduction of the isobar 19 are arranged. The three-way cock 20 will be described later with reference to FIG.
[0032]
Further, the heat treatment apparatus has a vacuum system 21 for drawing a vacuum in the heat treatment apparatus and a gas system 22 for supplying an inert gas into the heat treatment apparatus. Here, the "inert gas" is a gas which does not easily react with sodium. For example, argon or nitrogen is suitable. Further, a pipe 23 for leading the vacuum system 21 and the gas system 22 to the heat treatment material exchange unit 3, a pipe 24 for leading the vacuum system 21 and the gas system 22 to the heating unit 4, and a vacuum system 21 and a gas system 22 are provided. A pipe 25 for leading to the gas phase portion of the sodium bath 7 is connected.
[0033]
Further, a check valve 26 for preventing sodium in the sodium bath 7 from flowing back to the bubbling line 16, sodium oxide generated by the reaction of oxygen and sodium in the sodium bath 7, and water generated by the reaction of water with sodium A purification system 27 for removing sodium oxide (hereinafter, sodium oxide and sodium hydroxide is referred to as “impurities”) is provided.
[0034]
The sodium storage tank 28 is connected to the sodium bath 7 and has a capacity to transfer and store all of the sodium in the sodium bath 7, although shown small in the figure.
[0035]
Here, the procedure of heat treatment using this heat treatment apparatus will be described. First, the heat treatment material 40 is attached to the heat treatment material exchange unit 3, and the entire heat treatment apparatus is evacuated using the vacuum system 21. Then, using an inert gas supply system 22, the pressure is slightly higher than the atmospheric pressure (0.03 to 0.05 kgf / cm). ² Pressure). In this operation, since the heat treatment apparatus was opened to the atmosphere in order to mount the heat treatment material 40, a large amount of oxygen and moisture were mixed in the heat treatment apparatus. In)).
[0036]
Next, the inside of the heat treatment apparatus is evacuated and degassed. This is to remove oxygen and moisture contained in the heat treatment material exchange unit 3, the heating unit 4, and the heat treatment material 40. As for the flow of the gas, the inert gas is sent from the inert gas supply system 22 to the sodium bath 7 via the vapor trap 9 using the pipe 25. The inert gas sent to the sodium bath 7 passes through the heating unit 4, passes through the specimen exchange unit 3, passes through the heat exchanger 12, and reaches the piping of the dew point meter 13 and the oxygen meter 14. In this heat treatment apparatus, the dew point was continuously monitored, and the oxygen concentration was measured in batches. Thereafter, the air is exhausted to the outside of the system via the buffer tank 18 such as air. The flow of gas at this time is shown by arrows in FIG.
[0037]
The heating unit 4 is heated to 400 ° C., and the parts other than the heating unit 4 above the lower gate valve 8 are heated to 200 ° C., thereby being included in the heat treatment material exchange unit 3, the heating unit 4, and the heat treatment material 40. Helps release oxygen and moisture. This operation is because if the oxygen concentration and the water concentration are high and the liquid sodium in the sodium bath 7 is removed, a large amount of impurities are generated. The melting point of these impurities is higher than that of sodium. If a large amount of impurities is generated, the injection into the sodium bath 7 and the drain pipe may be blocked, so that a large amount of oxygen and moisture are prevented from dissolving into the liquid sodium. Incidentally, the inert gas used at this time was an argon gas having an oxygen concentration of 0.05 ppm or less and a dew point of −80 ° C. (water content of 0.53 ppm).
[0038]
In the present heat treatment apparatus, the method of injecting sodium into the sodium bath 7 employs a method in which the sodium bath 7 is evacuated and injected with a pressure difference from the sodium storage tank 28. And heating and deaeration are continued during the sodium injection. The flow of gas is supplied from the inert gas supply system 22 to the lower gate valve 8 and the heating unit 4 by using a pipe 24 to keep the lower gate valve 8 closed. Same as ki. The gas flow at this time is shown by arrows in FIG.
[0039]
This heating deaeration is performed until the dew point becomes -40 ° C (water content 130 ppm). The minimum scale of the oxygen meter 14 of the heat treatment apparatus was 1 ppm, and the main deaeration was performed at a dew point of −40 ° C., and the oxygen concentration was less than 1 ppm.
[0040]
When the dew point is lower than −40 ° C. and liquid sodium is injected into the sodium bath 7, heat deaeration is performed by a circulation method. The pressure inside the heat treatment apparatus is slightly higher than the atmospheric pressure, and the circulation pump is started. The gas flow is heated by the heat exchanger 12 from the circulation pump 10, and then supplied between the closed lower gate valve 8 and the heating unit 4, passed through the heating unit 4 and the heat treatment material exchange unit 3, 12 and heat the gas.
[0041]
From the heat exchanger 12, through the dew point meter 13, if necessary, through the oxygen meter 14, via the buffer tank 18, to the sodium bath 7 via the passage line 15 or the bubbling line 16. It returns from the sodium bath 7 to the circulation pump 10 through the vapor trap 9. The flow of gas at this time is shown by arrows in FIG. The dew point is monitored until the dew point is less than −60 ° C. (11 ppm water) by circulating degassing.
[0042]
In the tests performed so far by the inventors, the oxygen concentration was less than 1 ppm before the dew point reached -40 ° C. Therefore, only the dew point was monitored after the oxygen concentration became less than 1 ppm. In the heat treatment test performed at a dew point of -52 ° C (30 ppm of water), neither formation of an oxide layer nor decarburization occurred. However, in consideration of safety margin, it is desirable that the dew point is lower than -60 ° C.
[0043]
When the passing line 15 was used in the test apparatus, the time required for the dew point to change from -40 ° C to -52 ° C was about 1 hour. At this time, the flow rate was 5 L / min, the volume of the sodium bath 7 other than the gas phase and the volume of the sodium bath 7 were both about 100 L, and the surface area of the liquid sodium was 0.28 m. ² It is. Under these conditions, three ventilation cycles were required to lower the dew point from -40C to -52C. In addition, it has been confirmed that the dew point is lower than −60 ° C. regardless of whether the passing line 15 or the bubbling line 16 is used.
[0044]
FIG. 5 shows an enlarged view of the vicinity of the bubbling line 16, the same pressure pipe 19, and the three-way cock 20. At the time of bubbling, by setting the three-way cock 20 in the direction shown in FIG. 5, the bubbling line 16 and the buffer tank 18 are connected, and the pressure tube 19 is closed. When the bubbling is stopped, the three-way cock is rotated and set in the direction of the three-way cock 20b indicated by the dotted line in the figure, thereby disconnecting it from the buffer tank 18 and conducting the bubbling line 16 and the same-pressure pipe 19. Thereby, it is possible to correct the imbalance in the pressure between the bubbling line 16 and the gas phase in the sodium bath 7 due to a temperature change or the like.
[0045]
When the dew point reaches a predetermined temperature, the heating unit 4 is heated to a predetermined temperature. At this time, heating of portions other than the heating unit 4 is stopped and the heat shield plate 6 is closed, but the circulation of the inert gas is continued. When the heating unit 4 reaches a predetermined temperature, the heat shield plate 6 is opened, the heat treatment material 40 is moved to the heating unit 4, and the heat shield plate 6 is closed until it hits the support rod 1. The state at this point is shown in FIGS. Here, as shown in FIG. 7, the heat shield plate 6 has two semi-circular plates 6a and an operation rod 6b fixed to them, and the heat shield plate 6 is The heat shield plate 6 can be opened and closed by moving it laterally.
[0046]
When the temperature of the heat treatment material 40 reaches the heat treatment temperature, the circulation pump 10 is stopped to stop the circulation of the inert gas. When the bubbling line 16 is used, the three-way cock 20 is set to the bubbling stop position, The heat shield plate 6 is opened, and the lower gate valve 8 is opened. Thereafter, the support bar 1 is driven downward to immerse the heat treatment material 40 in the liquid sodium in the sodium bath 7. This state is shown in FIG.
[0047]
After the heat-treated material 40 is immersed in liquid sodium in the sodium bath 7 for a predetermined time, the heat-treated material 40 is pulled up to the heat-treated material exchange section 3 and the lower gate valve 8, the heat shield plate 6, and the upper gate valve 5 are closed. The state at this point is shown in FIG. The heat treatment material exchange unit 3 is pressure-isolated by the upper gate valve 5 and an inert gas is supplied from the pipe 23 while opening the atmosphere, thereby cooling the heat treatment material 40 using the inert gas. When it is confirmed that the temperature of the heat-treated material 40 is equal to or lower than the melting point of sodium (98 ° C.) and that the temperature of the heat-treated material 40 has been cooled to a safe level when handling the heat-treated material 40, the heat-treated material 40 is replaced with the heat-treated material 40 for heat treatment. .
[0048]
After exchanging the heat treatment material 40, the inside of the heat treatment material exchange unit 3 is replaced with vacuum gas using the pipe 23, and circulating deaeration is performed as in FIG. When the dew point becomes equal to or lower than a predetermined temperature, the heat treatment material 40 is heated by the heating unit 4 to perform heat treatment. Thereafter, heat treatment is performed in the same procedure.
[0049]
When removing oxygen and moisture by bubbling the atmosphere gas into the liquid sodium in the sodium bath 7, when there is a temperature change in the gas phase of the sodium bath 7, or before applying pressure in the bubbling direction, a three-way cock is required. When an operation error such as opening the 20 to the sodium bath 7 side is performed, the liquid sodium in the sodium bath 7 may flow back through the bubbling line 16. In that case, a check valve 26 provided in the bubbling line 16 prevents backflow. When the check valve 26 does not operate normally, the liquid level gauge 17 issues a sodium backflow warning. The liquid level gauge 17 is provided in a buffer tank 18. The buffer tank 18 suppresses the rising speed of the liquid level, so that there is sufficient time to perform an operation such as closing the sodium bath side of the three-way cock 20.
[0050]
Next, an embodiment of the present invention assuming an actual machine will be described with reference to FIG. However, parts that are the same as or similar to those in the above-described embodiment are given the same reference numerals, and redundant description is omitted.
[0051]
In a general heat treatment apparatus, the position where the heat treatment material 40 is set, the heating unit 4 and the bath container (sodium bath 7) for the coolant are horizontally arranged. Therefore, the support bar 1 is not used. The heat-treated material 40 is set in the inlet-side air lock 30, and after gas replacement, is moved by a driving roller to the heating unit 4 partitioned by a heat-resistant door instead of the upper gate valve 5. Therefore, there is no heat shield plate 6. Thereafter, through a process similar to that of the heat treatment apparatus of the above embodiment, it is taken out of the heat treatment apparatus from the outlet side air lock 31.
[0052]
【The invention's effect】
As described above, according to the sodium bath heat treatment method and apparatus of the present invention, oxygen and moisture in the atmosphere gas of the heating section are removed only by laying pipes, without providing new equipment, and the surface of the heat treated material is removed. Oxidation layer formation and decarburization can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic system diagram of an embodiment of a sodium bath heat treatment apparatus according to the present invention.
FIG. 2 is a schematic system diagram showing a state of heating and degassing with evacuation performed before injecting sodium into the sodium bath of the sodium bath heat treatment apparatus of FIG. 1;
FIG. 3 is a schematic system diagram showing a state of heating and degassing while evacuation is performed during evacuation / injection of sodium for injecting sodium into the sodium bath of the sodium bath heat treatment apparatus of FIG.
FIG. 4 is a schematic system diagram showing a state of heating and degassing while circulating when heating a heating unit after injecting sodium into a sodium bath of the sodium bath heat treatment apparatus of FIG. 1;
FIG. 5 is an enlarged partial system diagram showing the vicinity of a bubbling line, the same pressure tube, and a three-way cock in FIG. 4;
FIG. 6 is a schematic system diagram showing a state in which a heat treatment material is heated by a heating unit of the sodium bath heat treatment apparatus of FIG. 1;
FIG. 7 is an enlarged schematic perspective view showing the vicinity of the heat shield plate in the state of FIG. 6;
FIG. 8 is a schematic system diagram showing a state in which a heat treatment material is being rapidly cooled in a sodium bath of the sodium bath heat treatment apparatus of FIG. 1;
FIG. 9 is a schematic system diagram showing a state when a processing material is replaced in the sodium bath heat treatment apparatus of FIG. 1;
FIG. 10 is a schematic system diagram of an embodiment when the present invention is applied to a general heat treatment apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Support rod, 2 ... Drive part, 3 ... Heat treatment material exchange part, 4 ... Heating part, 5 ... Upper gate valve, 6 ... Heat shield plate, 6a ... Semi-disc part, 6b ... Operation rod, 7 ... Sodium bath , 8 ... lower gate valve, 9 ... vapor trap, 10 ... circulation pump, 11 ... flow meter, 12 ... heat exchanger, 13 ... dew point meter, 14 ... oxygen meter, 15 ... passing line, 16 ... bubbling line, 17 ... Liquid level gauge, 18: buffer tank, 19: same pressure pipe, 20: three-way cock, 21: vacuum system, 22: gas system, 23, 24, 25 ... piping, 26 ... check valve, 27 ... purification system, 28 ... Sodium storage tank, 29: outlet gate valve, 30: inlet side air lock, 31: outlet side air lock, 40: heat treatment material.

Claims (14)

A gas purification step of contacting the atmosphere gas with liquid metallic sodium to remove oxygen and moisture in the atmosphere gas;
A heating step of heating the solid metal material in an atmosphere gas that has undergone the gas purification step,
A cooling step of cooling the solid metal material in liquid metallic sodium,
A sodium bath heat treatment method comprising: The sodium bath heat treatment method according to claim 1, wherein metal sodium used in the gas purification step and the cooling step is common. The method for heat treating a sodium bath according to claim 1 or 2, wherein, in the gas refining step, the atmosphere gas is passed through a gas phase portion above a liquid level of metallic sodium inside a vessel containing the metallic sodium, Sodium bath heat treatment method characterized by the above-mentioned. 3. The sodium bath heat treatment method according to claim 1, wherein the atmosphere gas is released into the metallic sodium in the gas purification step. A heating unit for heating the solid metal material in an atmosphere gas;
A sodium bath containing liquid metallic sodium for immersing and cooling the solid metallic material,
A bubbling line for releasing the atmospheric gas into liquid metallic sodium in the sodium bath;
A sodium bath heat treatment apparatus comprising: The sodium bath heat treatment apparatus according to claim 5, further comprising a unit for monitoring and controlling an oxygen concentration and a dew point in the atmospheric gas. The sodium bath heat treatment apparatus according to claim 6, wherein a dew point at which heating of the solid metal material is started is set to -60C or less. The heat exchanger for sodium bath according to any one of claims 5 to 7, wherein the atmosphere gas cooled by being brought into contact with the sodium is heated using the atmosphere gas which is still at a heat treatment temperature. A sodium bath heat treatment apparatus comprising: The sodium bath heat treatment apparatus according to any one of claims 5 to 8, further comprising a check valve for preventing a backflow of the liquid metallic sodium in the bubbling line. apparatus. The sodium bath heat treatment apparatus according to any one of claims 5 to 9, further comprising a liquid level gauge for detecting a sodium liquid level in the middle of the bubbling line. The sodium bath heat treatment apparatus according to claim 10, wherein the liquid level gauge is installed in a buffer tank provided in the middle of the bubbling line. The sodium bath heat treatment apparatus according to any one of claims 5 to 11, wherein the introduction of the atmospheric gas through the bubbling line into the metallic sodium in the sodium bath is stopped. A sodium bath heat treatment apparatus, wherein a pressure equalizing pipe is provided for communicating the liquid level above the bubbling line. 13. The sodium bath heat treatment apparatus according to claim 12, wherein a portion of the bubbling line connected to the metallic sodium in the sodium bath is above a liquid level of the metallic sodium in the sodium bath and the same pressure pipe. A sodium bath heat treatment apparatus characterized in that a three-way cock is provided so that one of the two can be selectively contacted. The sodium bath heat treatment apparatus according to any one of claims 5 to 13, further comprising a vapor trap for removing sodium vapor in the atmosphere gas.

Images