JPH02236216A - Method and apparatus for heat treatment - Google Patents

Abstract

PURPOSE:To make uniform inner temp. of a material to be treated and to reduce the residual stress by dipping the heated material to be treated into cooling water together with a tray and shifting bubbles covering surface of the material to be treated. CONSTITUTION:A cooling lightening body 11 is arranged at bottom face of the tray 1, and inner part of the tray 1 is parted with wire nets 13, and the materials 9 to be treated are set in the sections, respectively. This is charged into a heat treatment furnace 91 and heated at hot temp., and after that, the materials 9 to be treated are dipped into the cooling water together with the tray 1. The water coming into contact with the surface of the cooling lightening body 11 is boiled with the heated cooling lightening body 11, and vapor bubbles 72 are generated. The bubbles 72 rise while covering the materials 9 to be treated. Further, the bubbles 71 generate from the materials 9 to be treated itself. The materials 9 to be treated are cooled in the cooling water under condition of being covered with the bubbles 71, 72 shifted upward. As a cooling adjusting material is not used, the heat treatment operation and control are facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and an apparatus for heat treating castings 5@remains of aluminum materials, m-materials, etc.

[Prior art]

Metal materials such as aluminum and steel are cast. After being processed into the desired shape by forging etc. Heat treatment is performed as necessary. That is. Objects to be processed made of these metal materials. After being heated to a predetermined high temperature, it is immersed in cooling water for heat treatment. As for this heat treatment. For example, solution treatment is used for aluminum materials, and quenching is used for steel materials.

However. 20 In heat treatment, 2. The surface and interior of the object to be treated. The upper and lower ends should maintain the same temperature as possible, that is, the temperature difference between them should be as small as possible. Must be cooled evenly. This is because if the temperature difference between the two is large, thermal stress will occur within the object to be processed. Thermal strain occurs. This is because residual stress is generated.

However, as shown in Figure 22. When the heated object 9 is immersed in cooling water, the cooling water that comes into contact with the surface of the object 9 boils and generates bubbles. Then, the generated bubbles move upward, and the upper part of the object to be treated 9 becomes in a film boiling state with a vapor film formed on the surface, as shown in FIG. 23A. It is covered by a film boiling part i with a high bubble density, and the outside thereof is further covered by a region j with a relatively low bubble density,
Furthermore, cooling water surrounds it. On the other hand, as shown in the figure, the lower part of the object to be processed is covered with a nucleate boiling zone h where bubble density is low, where bubbles are generated from the surface. Cooling water surrounds it. Therefore, the upper part of the object to be treated has a high bubble density and there is little infiltration of cooling water. This is because the cooling rate is slow, and on the other hand, the lower part of the object to be processed has a low bubble density, and there are many parts that come into contact with the cooling water. Cooling speed is fast. In addition, in the nucleate boiling zone h, the temperature boundary layer on the surface of the object to be treated is destroyed by the generation of bubbles. The heat transfer coefficient increases and the cooling rate becomes even faster. Therefore, a large temperature difference occurs between the lower part and the upper part of the object to be processed 9, as well as between the surface and the inside thereof, and the above-mentioned uniform cooling cannot be achieved.

As cooling progresses further and the temperature of the object to be processed falls, the nucleate boiling part h moves to the upper part of the object to be processed, as shown in FIG. 23B, and only the upper part of the object to be processed 9 is covered by the nucleate boiling part h with a low bubble density. The heat transfer coefficient increases and cooling occurs rapidly. On the other hand, since the lower part is directly surrounded by cooling water, a temperature boundary layer is formed on the surface of the object to be processed, which reduces the heat transfer coefficient and causes gradual cooling, causing a difference in cooling rate and making it impossible to cool the object uniformly. .

Regarding the above. As an example, the object to be processed 9 is an aluminum casting (hereinafter referred to as aluminum casting). This is explained below. That is. Conventionally, in the solution treatment of aluminum castings (for example, cylinder heads of automobiles), a large number of objects 9 to be treated are placed in one tray 8, as shown in FIG. processing at the same time. This tray 8 is designed to heat and cool a large amount of objects 9 at the same time, so its bottom and surrounding area are breathable. It has a mesh shape with good water permeability. That is, as shown in FIGS. 17 and 18, the tray 8 is made of metal and has a wire mesh 8L on the bottom surface. It has a frame 82 on the side and has good water permeability. and. The money in tray 8! Forty objects 9 to be processed are placed on the il 81. The heat treatment process for aluminum castings is generally performed at T6 as shown in Figure 16.
After the treatment is performed, the object 9 heated in the heat treatment furnace 91 as shown in FIG. 15 is sent to the upper part of the cooling water tank 93 together with the tray 8 when the door 92 at the furnace outlet is opened. It is immersed in cooling water 931 in a few seconds. Due to this. Aluminum castings are cooled to water temperature and converted into a solid solution.

At this time, the tip (lower edge) of the object to be treated that comes into contact with the cooling water first
cooling is very fast. and. As shown in FIG. 22, a large amount of steam bubbles 7L are generated on the surface of the casting due to the boiling phenomenon in the direction in which the object 9 is submerged. A large temperature difference occurs inside the object to be processed 9 due to these air bubbles. Next, in FIGS. 19A to 19C, a thermocouple is attached to the object to be processed 9. This is an example in which temperature changes were measured at positions A, B, and C (Fig. 19A). Figure 19A is a diagram showing how bubbles are generated. The bubble area becomes wider as you move upwards, which is opposite to the direction of submersion. Therefore. As shown in Figure 19B, the temperature curves at points A, B, and C in the longitudinal direction indicate that point A relative to the cooling water is the fastest (cooled down). Subsequently, the upper points B and C are cooled, and a large temperature difference occurs between points A, B, and C. At points B, D, and E on the central section. The temperature difference between the three points is small because they come into contact with the cooling water at almost the same time. Generally, when a maximum temperature difference of 8T occurs within an object, a thermal stress σ expressed as σ=±(0.3 to 1.2)·E·β·8T occurs within the object. Note that E above is Young's modulus. β is the coefficient of linear expansion. In the case of the cooling method shown in Fig. 19A above. A in the longitudinal direction,
Since a maximum of 8 T occurs between B and C (Figure 19B),
A cooling method that keeps 8T small is required. Note that the temperature difference between central sections B, D, and E is small, and the thermal stress difference is also small (Fig. 19C).

Next, FIGS. 20A to 20C show an example in which an aluminum casting object 9 to be processed is placed horizontally in the tray 8.

In this case, they are cooled almost simultaneously. The temperature difference in the longitudinal direction (Figure 20B) is small. Shigashi 2 cross sections B, D, E
In this case, the lower part B is cooled faster, and the upper part B is cooled more slowly because the surface heat transfer coefficient decreases due to air bubbles, and the temperature difference between the cross sections is large (Fig. 2 OC). In addition, Figure 20B. The dashed line in Figure 20C is . It uses a cooling adjustment agent. The cooling rate is very slow regardless of the amount of bubbles.

next. FIG. 21 illustrates the generation of residual stress when no structural transformation occurs during the heat treatment process. The object to be treated had a diameter of 100III1 and was water quenched at 850'C. The figure shows the cooling temperature, thermal stress, and residual stress at the outer surface and center of the object to be processed. When a temperature difference occurs between the outer surface and the center of the object to be processed. In the cooling method shown in FIG. 19A, a temperature difference is created in the longitudinal direction, which causes residual stress, which can cause stress cracks in the object to be processed, and an improvement in the cooling method is required.

Also. Stretch until the temperature difference reaches the maximum point W in Figure 21 above. Compressive stress increases.

After passing through W, the stress in both parts decreases as the temperature difference decreases. In the time until W. The outer surface receives tensile stress at that temperature and undergoes plastic deformation. In the figure, a indicates elastic deformation, and b and c indicate actual stress. After passing through W, the stress distribution reverses at U as the temperature difference decreases. The final state is a compressive residual stress in the outer surface and a tensile stress in the center. When this residual stress exceeds the descending stress of the material, it causes cracks and fractures due to stress concentration. Therefore, what controls the magnitude of residual stress is the temperature difference in W.
It is the strength of the material.

Conventionally, in the heat treatment of long items such as cylinder heads, the objects to be treated are placed vertically as shown in Figs. The difference is large, thermal stress and thermal strain are observed, and residual stress occurs. Also, the second
When placed horizontally as shown in figure 0A. The internal temperature during cooling is fairly uniform, and the residual stress is small. It is not a practical heat treatment method because it is not possible to heat treat a large amount at once, and temperature differences occur depending on the position of the object to be treated, making uniform cooling impossible. As an example of such a countermeasure, as shown by the dotted lines in Figures 20B and 20C, a cooling regulator is mixed into the cooling water to slow down the overall cooling and reduce the internal temperature difference. ．． but. It is necessary to control the concentration of the cooling regulator in the cooling water.

Also. Since the cooling adjustment agent may adhere unevenly to the work surface, it may not be possible to reduce the internal temperature difference, and the cooling adjustment agent must be washed with water before proceeding to the next process.

Also. Aluminum castings such as cylinder heads can withstand even severe durability tests. A heat treatment that does not cause cracks due to thermal stress is required. In particular, residual stress during solution treatment is caused by the extremely large internal temperature difference during the quenching process. [Problems to be Solved] In view of the above-mentioned conventional problems, the present invention aims to provide a heat treatment method and an apparatus therefor that can equalize the internal temperature of the object to be treated and reduce residual stress during heat treatment. It is something. [Means for Solving the Problems] The present invention involves immersing a heated object together with a tray in cooling water. The method of heat treating the object to be processed is characterized in that the heat treatment is performed while moving bubbles covering the surface of the object to be processed.

What should be noted in the present invention is that the heated object to be treated is immersed together with the tray in cooling water for heat treatment.
Heat treatment is performed while moving air bubbles covering the object in the cooling water.

As a means for supplying air bubbles, as mentioned above, air bubbles are supplied by boiling of the cooling water from the surface of the tray placed in the cooling water together with the object to be treated, or air, etc. is supplied from the outside into the cooling water in the cooling water tank. gas may be supplied. As a means for generating air bubbles from the surface of the tray itself, there is a heat treatment device described below.

In addition, the equipment for carrying out the above heat treatment method is as follows:
In a heat treatment device comprising a cooling water tank and a tray for carrying a heated object into the cooling water in the cooling water tank,
At least the tray above is at its bottom. There is a heat treatment apparatus characterized by including a cooling relaxation body that generates bubbles when immersed in cooling water.

In this apparatus, when the cooling relaxation body and the object to be treated are immersed in cooling water in a heated state, bubbles are generated by the boiling of the cooling water in contact with the surface of the cooling relaxation body. The cooling relaxation body includes a metal body. and. The cooling relaxation body is necessary to keep the bubbles generated for a long time.
It is best to use one with as large a heat capacity as possible. In addition, a cooling relaxation body is provided at least at the bottom of the tray. this is. For the object to be processed placed in the tray. This is to send air bubbles from below. In addition, the cooling relaxation body must be formed on the bottom of the tray itself (
(first to third embodiments), or it may be provided separately on the net-like bottom of the tray (fourth and fifth embodiments). Moreover, it can also be provided on the side of the tray together with the bottom.

In order to make it easier for cooling water to enter the tray during heat treatment, the cooling relaxation body described above can be arranged in a honeycomb shape or other shape that facilitates water circulation. [Function] In the method of the present invention, when a heated object to be treated is placed in cooling water and subjected to heat treatment, air bubbles covering the surface of the object to be treated are moved. Therefore, the entire surface of the object to be processed is almost uniformly surrounded by bubbles, and as the bubbles move, the surrounding cooling water is brought into uniform contact with the surface of the object to be processed, and the amount of cooling water that comes into contact with the object to be processed is adjusted appropriately. It will be cooled while being maintained. Therefore, the entire object to be processed comes into contact with the cooling water appropriately through the bubbles, and the entire object is cooled uniformly and at an appropriate rate, reducing the temperature difference inside the object. Furthermore, in this method, by adjusting the density of the bubbles covering the surface of the object to be processed, the amount of cooling water that enters between the bubbles can be adjusted, and the cooling rate can be optimized. Also. According to the device, a cooling relaxation body is provided on the bottom of the tray. When the tray containing the object to be processed is immersed in cooling water, the cooling water that comes into contact with the surface of the cooling relaxation body immediately boils, and its vapor bubbles surround the surface of the object to be processed.

Therefore, as shown in FIG. 24A, the object 9 to be processed is covered by a film boiling region i having a high bubble density, and the outside thereof is further covered by a region j having a relatively low bubble density. Cooling water surrounds it. In the film boiling part i, the density of bubbles is high.
Since there is little infiltration of cooling water, the cooling rate is slow. The entire object to be processed is cooled uniformly and gradually. As cooling progresses further, the temperature of the object to be processed decreases. As shown in FIG. 24b, the object 9 to be treated is covered with a nucleate boiling zone h having a low bubble density. Cooling water surrounds a region j with relatively low bubble density, and the cooling rate gradually increases. The entire object to be processed is cooled uniformly and gradually and quickly.

As mentioned above, the cooling rate of the entire object to be processed is relaxed in the early stage of cooling. After that, the cooling rate is gradually increased and
This allows the cooling rate to be adjusted appropriately throughout the entire cooling process. The temperature difference inside the object to be processed becomes smaller.

〔effect〕

Therefore, according to the above method. The movement of air bubbles brings the surrounding cooling water into uniform contact with the surface to be treated. It is possible to equalize the internal temperature of the object to be treated during heat treatment. Therefore, without generating residual stress. Furthermore, the bubbles keep the amount of cooling water in contact with the object to be treated at an appropriate level, optimizing the cooling rate, making it possible to effectively achieve the desired heat treatment. Also, as usual. Since no cooling agent is used, there is no need to control its concentration or wash the object with water after heat treatment. Furthermore, there is no problem with wastewater treatment of cooling water.

Also, according to the device. You can obtain the same effect as the above method. This is because the cooling relaxation body on the bottom of the tray generates bubbles at the same time as the heat treatment begins. No special equipment is required for bubble supply.

〔Example〕

First Example Regarding the heat treatment method and apparatus according to the present invention, the first example
This will be explained using FIGS. 3 to 3 and 4A to 4c. That is, in this example. Heat treatment is performed using tray 1 shown in Figure 1. The tray 1 has a cooling relaxation body 11 on the bottom surface. The side surface is a frame surrounded by shelves 12. Moreover, in the tray 1, one object to be processed 9 is arranged. Similar to the conventional FIGS. 17 and 18, the wire mesh 1
Separated by 3.

Therefore, the cooling relaxation body 11 has a honeycomb shape, as shown in FIG. 2 as a vertical cross-section, and as shown in FIG. 3 as a cross-section. It has a zero body 111 and a space 112. and. The main body is made of steel. The thickness of the main body 111 is approximately 20
uw. The width is approximately 60mm. The space 112 is a rectangle with 40 cylinders on each side.

Next, when performing heat treatment using the above tray l. As shown in Figure 1. Cooling relaxation body l1 in the tray 1
A large number of objects 9 to be processed (for example, 40 objects) are placed on top,
As shown in FIG. 15, it is placed in a heat treatment furnace 91. Then, it is heated to a high temperature for a predetermined time, and then the tray 1 and the object 9 to be processed are immersed in cooling water. As a result of this immersion, as shown in FIG. 4A, the water that has come into contact with the surface of the cooling relaxation body 1l is boiled by the heated cooling relaxation body, and steam bubbles 72 are generated. Then, the bubble 7
2 rises while covering the object 9 to be processed. In addition, bubbles 71 are generated from the object 9 itself, as in the case of the conventional method.

Therefore. The object to be processed 9 has the above-mentioned upwardly moving air bubbles 71.
．． covered by 72. It is cooled in cooling water. Therefore. The object to be processed 9 is gradually cooled while the internal temperature difference is small.

FIGS. 4A to 4C show the above-mentioned cooling state.

This figure is explained in the prior art (Figures 19A to 19C).
Similarly to Figure 4A, each point A, B, and C in the longitudinal direction of the object to be processed 9 in Figure 4A. The temperature changes at points B, D, and H in the central cross-sectional direction were measured. FIG. 4B and the above-mentioned FIG. 19B showing temperature changes in the longitudinal direction,
Also, when comparing Fig. 4C in the central cross-sectional direction and Fig. 19C, respectively. In the case of this example (FIGS. 4B and 4C), it can be seen that the temperature difference between the measurement points is very small. This is particularly noticeable for A, B, and C in the longitudinal direction. Also, according to this example. It can be seen that the cooling rate is slower than in the conventional method (Figures 19B and 19C). Note that the above Figures 4A to 4C are the same as the above Figures 19A to 1.
As in the case of Fig. 9C, an aluminum casting cylinder head is used as the object to be processed.

Also. The heat treatment is a solution treatment and is heated to approximately SOO°C in a heat treatment furnace. As described above, according to this example, the heat treatment can be performed while reducing the temperature difference inside the object to be processed 9.

Therefore, heat treatment can be performed effectively without generating residual stress inside the cylinder head as the object to be treated. Also. In this example. Since the cooling relaxation body 1l is in a honeycomb state (Fig. 3) having a space, through the space,
Cooling water easily enters the tray and has good water permeability. Second Embodiment In this embodiment, as shown in FIGS. 5 and 6, the tray 1 of the first embodiment is provided with a cooling relaxation body 15 on its side surface as well.

The cooling relaxation body 15 has a honeycomb shape similar to the cooling relaxation body 11 disposed on the bottom surface of the tray 1, and has a zero body 151 and a space 152.

According to this example, the same effects as the first example can be obtained.
In addition to the cooling relaxation body 11 on the bottom, bubbles are also generated from the cooling relaxation body 15 on the side. Even better heat treatment can be performed.

Also, in this example, instead of the cooling relaxation body 15 on the side surface. A cooling relaxation body 16 shown in FIG. 7 may also be used. The cooling relaxation body 16 is . Zero body 16l and space 162
but. It is rising toward the inside of the tray 1. Therefore. The air bubbles generated by the cooling relaxation body 16 are. It is guided by the inclined space 162 and advances into the tray 1. Therefore, the effect of the bubbles can be further obtained.

Third Embodiment This example is shown in Figure 8. In the tray 1 of the first embodiment, a wire mesh 17 is placed above the cooling relaxation body 11 with a space of about 3 at apart. And gold 41
The object to be processed 9 is placed upright on the il17.

According to the tree example, there is a space between the cooling relaxation body 11 and the object to be treated 9. The lower end portion of the object to be processed 9 can be covered with more air bubbles. Therefore, a sudden drop in temperature at the lower end portion can be prevented, and the temperature difference between the objects to be processed can be further reduced.

Fourth Embodiment In this example, as shown in FIGS. 9 and 10Ii1, a plate-shaped cooling relaxation body 21 is prepared separately from the tray 1, and the cooling relaxation body 2l is placed on the bottom wire mesh 1B of the tray 1. This is an example of setting Then, the object to be processed 9 is placed il2 on the cooling relaxation body 2l on the tray, and heat treatment is performed in the same manner as in the first embodiment.

The cooling relaxation body 21 is a thick plate having an upper surface slightly larger than the bottom surface of the first object to be processed 9, and has a space hole 211 in the center thereof for inlet of cooling water. The size of this cooling relaxation body 21 is. For example, length 200ffl. Width 250mm, space hole 211
The diameter is 15-20m and the tentative thickness is 20-30mm.
Also. The bottom surface of the object to be processed 9 is slightly smaller than the length and width of the cooling relaxation body 21. The height is 400-500m+. Further, the cooling relaxation body 2l and the object to be processed 9 have approximately equivalent heat capacities.

In this example. In the initial cooling, the cooling relaxation body 21 and the object to be processed 9 are used. Boiling bubbles are generated from the entire surface, and the object to be treated 9
The rapid cooling of the water is alleviated. Then, as the cooling time further elapses, the surface of the object 9 to be processed reaches a nucleate boiling region where the surface becomes bubble nuclei and bubbles are generated therefrom.

Therefore, the rapid cooling of the lower part of the object to be processed at the initial stage of cooling is alleviated by the heat capacity of the cooling relaxation body. In addition, bubble generation at the upper and lower parts of the object to be treated weakens at approximately the same time. Then, the object 9 to be treated undergoes nucleate boiling in both the lower part and the upper part, enters the quenching region, and gains strength. After that, it enters the convection area where the temperature of the cooling water is close to that of the cooling water, and the heat treatment is completed. therefore. As in this example, by placing a cooling relaxation body with the same thermal capacity as the object to be processed on the bottom surface of the object to be processed. Expansion of bubble boiling. Fully uniform boiling of Maki. Simultaneous entry into the convective region can be obtained. Therefore, heat treatment can be performed without trying to equalize the internal temperature of the object to be treated. Fifth Embodiment This example is. In place of the plate-shaped cooling relaxation body of the fourth embodiment, a container-shaped cooling relaxation body 23 is used as shown in FIGS. 11 to 13. The cooling relaxation body 23 is placed on the bottom wire meshwork 8 of two trays. The object to be treated 9 is placed in the cooling relaxation body 23 and heat treated in the same manner as in the first embodiment. The cooling relaxation body 23 is. It has a square container shape consisting of a bottom plate 232 and a side plate 231. The bottom plate 232 has five space holes 233 for water intrusion. The size of the cooling relaxation body 23 is . For example, it has an inner surface with a length of 200 am, a width of 250 mm, and a height of 60 mm, and the bottom plate and side walls are loan thick. Object to be processed 9
is the same as the fourth embodiment. In this example, compared to the fourth example, since the side plate 23 of the cooling relaxation body 23 is located on the lower side of the object to be processed 9, air bubbles are generated from the bottom plate 232 and... The side plate 23
A large amount of bubbles are generated even from 1. Therefore, compared to the fourth embodiment, the amount of bubbles rising up the side surface of the object to be processed 9 is large.
The object to be processed 9 will be covered with many bubbles. Therefore, in this example as well, the entire object 9 to be treated undergoes nucleate boiling at approximately the same time, similar to the fourth example. Further, since the amount of bubbles on the side surface of the object to be processed 9 is larger than that in the fourth embodiment, the object to be processed can be uniformly heat-treated more effectively than in the same example. Also, for this reason, when trying to obtain the same effect as the fourth embodiment. The cooling relaxation body 23 can be made lighter than the cooling relaxation body 2l.

Sixth Embodiment In this embodiment, as shown in FIG. 14, an air nozzle 15 is provided below the device 93. From the air nozzle 75, cooling water 93
Compressed air is jetted into the air bubble 1 to supply air bubbles 76.

The tray 8 is similar to the conventional one shown in FIGS. 17 and 18. However, in this example. In the cooling water 931, bubbles 76 are generated by the compressed air. The heated object 9 to be processed is immersed in the tray 8.

The bubble 76 is. It passes through the wire mesh 81 on the bottom of the tray 8 and rises, wrapping the object to be processed inside the tray 8 as it rises. Therefore, the 3 objects to be processed are. As mentioned above, under conditions where there is little difference in internal temperature. Cool down gradually.

According to this example, since the bubbles are supplied from the outside, the object to be processed can be wrapped in the bubbles and cooled for the required time. Furthermore, since no cooling adjustment agent is used as in the conventional method, heat treatment operations and management are easy.

Note that the heat treatment can also be performed using the air supply and the cooling relaxation body in combination. For example, it is possible to initially supply only steam bubbles from the cooling relaxation body without supplying air, and then supply air when the number of steam bubbles decreases.

[Brief explanation of drawings]

Figures 1 to 4C show the tray of the first embodiment. Figure 1 is its front view, Figure 2 is a dark blue sectional view of the cooling relaxation body, Figure 3 is a sectional view taken along the line A-A in Figure 2, and Figures 4A to 4C are conceptual diagrams of the heat treatment state. and cooling curves, Figures 5 to 7 show the tray of the second embodiment, Figure 5 is a front view, Figure 6 is a sectional view of the side cooling relaxation body, and Figure 7 is another cooling relaxation body. 8 is a front view of the tray of the third embodiment, and FIG. 9 is a sectional view of the body.
Figures 1 and 10 show the fourth embodiment, and Figure 9 is a perspective view of the cooling relaxation body. Figure 10 is a side view showing the state during heat treatment.
11 to 13 show the fifth embodiment, and FIG. 11 is a perspective view of the cooling relaxation body. Figure 12 is a plan view of the cooling relaxation body. 1st
3 is a side view showing the state during heat treatment, FIG. 14 is a conceptual diagram of the sixth embodiment, and FIGS. 15 to 22 are conventional examples.5 FIG. 15 is a conceptual diagram of the heat treatment apparatus. is an explanatory diagram of a heat treatment pattern, FIGS. 17 and 18 are a partially cut-out plan view and front view of a conventional tray, and FIGS. 19A to 19C are state diagrams and cooling curve No. 20A of conventional vertical cooling. Figures 20C to 20C are state diagrams and cooling curves of conventional horizontal cooling, Figure 21 is a diagram explaining the occurrence of thermal stress during cooling, and Figure 22 is a diagram showing the state during cooling. Figures 23A and 23B are schematic diagrams of the cooling process of the conventional method, and Figure 24A. FIG. 24B is a schematic diagram of the cooling process of the present invention. Figure 1 1, 8. ．． ．． }Leh 11. 15, 16, 21, 23. ．． ．． Cooling relaxation body. 71,72.76,. ．． ．． Bubbles, 9. ．． ．． Processed object

Claims (2)

[Claims] (1) A method of heat-treating the heated object by immersing the heated object together with a tray in cooling water, characterized in that the heat treatment is performed while moving air bubbles covering the surface of the object. heat treatment method. (2) In a heat treatment apparatus consisting of a cooling water tank and a tray for transporting the heated object into the cooling water of the cooling water tank, the tray has at least a cooling section at the bottom that generates air bubbles when immersed in the cooling water. A heat treatment apparatus characterized by having a relaxation body.