KR101217845B1 - Gradient heat treatment equipment by radiation for shape memory alloys - Google Patents

Abstract

The present invention provides a radiation heat treatment apparatus for manufacturing a shape memory alloy, the heating element to generate heat by applying a constant voltage inside the heat insulating material; A heat storage unit accommodating a sample, storing heat generated from the heating element, and transferring the sample to the sample; A cooling unit formed outside the heat storage unit to prevent conduction of heat transferred to the sample; A heat shield blocking heat dissipation between the heat storage unit and the cooling unit; And a sample moving unit for moving a sample to the outside through the heat storage unit and the cooling unit according to a predetermined time gradient. Radiation-type proportional control heat treatment apparatus according to the present invention is effective in proportional control heat treatment of the shape memory alloy by the cooling device to block the heat transmitted to the outside through the metal specimen in the heat storage unit. In particular, the wide range of phase transformation temperature can be precisely adjusted the transformation strain according to the temperature, it is possible to control the continuous and gradual displacement rather than simple on-off control.

Description

Radiant heat treatment equipment by radiation for shape memory alloys

The present invention relates to a radiation-type proportional control heat treatment apparatus for shape memory alloys, and more particularly, in the manufacture of shape memory alloys, a time gradient and a temperature gradient are simultaneously applied to a single sample by a heat treatment time or a temperature change, and the transformation strain is precisely determined. It relates to a radiation type proportional heat treatment apparatus for shape memory alloy that can be controlled easily.

In order to control the shape memory characteristics of the existing shape memory alloy, heat treatment is performed by using a furnace of uniform temperature using radiant heat. In this case, shape memory characteristics are uniform throughout the specimen.

In the case of a uniformly heat treated sample, it has a rapid transformation strain in a narrow temperature section as shown in FIG. Factors that determine the shape memory characteristics of shape memory alloys include the amount of dislocations introduced during cold working, the distribution state (size and density) of precipitates, and the Ni concentration in the matrix. It is applied to the industrial field.

The shape memory alloy heat treated by the existing heat treatment method enables on / off drive control and is used for various sensors, alternative bimetals and actuators. However, the on-off driving control has a limitation in application, and in particular, there is a problem that it is almost impossible to use the actuator which requires precise transformation strain (displacement) control according to the temperature change.

Therefore, in order to overcome the above problems and to precisely control the transformation strain (displacement) according to the temperature change of the shape memory alloy, a sample having a different transformation temperature in each section may be manufactured by performing heat treatment under different conditions for each section of a single sample. There is a need.

An object of the present invention is to provide a radiation-type proportional heat treatment apparatus for shape memory alloy that can perform heat treatment under different conditions for each section of length of a single sample.

In addition, an object of the present invention is to provide a method of manufacturing a shape memory alloy by using a radiation-type proportional control heat treatment apparatus for shape memory alloy to have different transformation temperature for each section even in the same sample.

In addition, an object of the present invention is to provide a shape memory alloy manufactured using a radiation type proportional heat treatment apparatus for the shape memory alloy.

In order to achieve the above object,

In the radiation type heat treatment apparatus for manufacturing a shape memory alloy,

Heating element to generate a heat by applying a constant voltage inside the heat insulating material;

A heat storage unit accommodating a sample and transferring and storing heat generated from the heating element to the sample;

A cooling unit formed outside the heat storage unit to prevent conduction of heat transferred to the sample;

A heat shield for blocking heat dissipation between the heat storage unit and the cooling unit; And

It provides a radiation-type proportional heat treatment apparatus for a shape memory alloy including a sample moving unit for moving the sample to the outside through the heat storage unit and the cooling unit according to a predetermined time gradient.

The heat storage unit is preferably a metal body having a higher specific heat than air.

The sample is preferably a shape memory alloy.

The voltage applied to the heating element may be increased at regular intervals as time passes to increase the internal temperature of the heat storage unit.

The moving means may automatically move the sample by a predetermined distance at a predetermined time.

To achieve these and other objects,

In the radiation heat treatment method for manufacturing a shape memory alloy,

Applying a constant voltage to the heating element inside the heat insulating material to heat up the inner and heat storage parts to a predetermined temperature;

Inserting a sample therein when the heat storage unit reaches a predetermined temperature;

Moving the sample toward a cooling part formed outside the heat storage part to prevent thermal conduction of the sample; And

When the heat treatment is completed to the final portion of the sample provides a method for producing a shape memory alloy using a radiation-type proportional control heat treatment apparatus comprising the step of withdrawing the sample.

In the step of moving the sample may increase the temperature applied to the heating element to increase the temperature of the heat storage and the inside.

According to another aspect of the present invention,

It provides a shape memory alloy manufactured using the radiation proportional control heat treatment apparatus.

Radiation-type proportional control heat treatment apparatus according to the present invention can block the heat transmitted to the outside through the metal sample from the inside of the cooling apparatus is effective in proportional control heat treatment of the shape memory alloy. That is, the cooling apparatus is a method of heating and heat-treating only the sample located inside by preventing the metal sample having a high temperature inside from transferring heat to a portion of the sample located outside. In addition, a time gradient and a temperature gradient can be simultaneously given to a single metal sample of the shape memory alloy. In particular, the wide range of phase transformation temperature can be precisely adjusted the transformation strain according to the temperature, it is possible to control the continuous and gradual displacement rather than simple on-off control.

1 shows a schematic diagram of a temperature and strain curve of a shape memory alloy annealed according to the prior art.
FIG. 2 shows a schematic diagram of the temperature and strain curves of (a) annealing shape memory alloy and (b) proportional control heat treatment shape memory alloy.
3 and 4 show a schematic diagram of a radiation type proportional heat treatment apparatus for shape memory alloy according to an embodiment of the present invention.
Figure 5 shows the temperature distribution inside the radiation proportional heat treatment apparatus for shape memory alloy according to an embodiment of the present invention.
FIG. 6 shows the results of temperature and strain curves of (a) the annealing shape memory alloy according to the comparative example and (b) the proportionally controlling heat treatment shape memory alloy according to the embodiment.
FIG. 7 shows the results of temperature and strain curves of shape memory alloys subjected to proportional control heat treatment according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 (a) shows a schematic diagram of a static load thermal cycle test result (strain-temperature curve) which is generally used to investigate the shape memory characteristics of the shape memory alloy. Referring to FIG. 2, when the shape memory alloy is subjected to a constant load in the tensile direction at a temperature in which the shape-memory alloy is present in a high temperature state and then cooled, the sample undergoes a phase transformation into martensite at a specific temperature and a sudden transformation strain in the tensile direction (displacement) ) When it is heated again, it transforms back into its mother phase at a certain temperature and returns to its original form. That is, it shows the change of transformation strain with temperature under a constant load. When uniformly heat-treated using radiant heat to a sample according to the prior art, the strain-temperature curve is shown in FIG.

In the radiation type heat treatment method according to the prior art, as shown in FIG. 2 (a), the phase transformation temperature (temperature at which deformation occurs) and transformation strain can be controlled in one sample by changing the heat treatment temperature and time after cold processing. Therefore, it is difficult to control the transformation strain due to temperature change by rapid transformation in narrow temperature range.

In order to control the transformation strain according to the temperature change, a strain-temperature curve such as (b) of FIG. 2 is required. In order for the shape memory alloy to exhibit the same behavior as shown in FIG. 2 (b), a difference in heat treatment conditions (eg, heat treatment temperature and time) should be applied to a single sample.

In the present invention, the heat treatment in this manner is defined as 'proportional control heat treatment', and when the proportional control heat treatment is performed, various phase transformation behaviors are continuously performed to show the behavior as shown in FIG. When continuous phase transformation behavior appears, the transformation rate per temperature (% / ℃) is lowered to facilitate position control.

Figure 3 shows a radiation type proportional heat treatment apparatus for shape memory alloy to perform the proportional control heat treatment according to the present invention. 4 illustrates a heat treatment apparatus in a state in which a sample is moved to a large portion outside the heat generating unit according to one embodiment of the present invention. 3 and 4, the heat treatment apparatus of the present invention is a heat generator 11 to generate heat by applying a constant voltage inside the heat insulating material (14); A heat storage unit 12 accommodating the sample 13 and transferring the heat generated from the heating element 11 to the sample; A cooling unit 15 formed on one side of the heat storage unit 12 to prevent conduction of heat transferred to the sample 13; A heat shield 16 for blocking heat dissipation of the heat storage unit 12 between the heat storage unit 12 and the cooling unit 15; And sample moving parts 19 and 19 'for moving the sample out through the heat storage part 12 and the cooling part 15 according to a predetermined time gradient.

Similar to the furnace using general radiant heat, the outside of the apparatus is treated with a heat insulator 14 to maintain the temperature inside uniformly, and the heating element 11 generates heat when a constant voltage is applied to the inside of the furnace. It is provided. The heat generator 11 material is a material that generates heat by application of a predetermined voltage. The heat storage unit 12 serves to store heat and transfer heat to the sample while heat generated from the heating element 11 is released as radiant energy, and generally, it is preferable to use a metal material having a larger specific heat than air. Specifically, the heat storage unit 12 is located in the furnace interior 17 as a metal mass, and may be slightly less or almost similar to the volume inside the furnace, and the sample 13 passes between the heat storage units 12. It is preferable that the hole which can be formed is formed.

In a furnace that does not normally have a separate cooling device, the heat in the interior flows out through the insulation and the metal sample. In particular, the heat conducted through the sample makes it difficult to perform an effective proportional control heat treatment. That is, since the heat of the heat storage unit 12 is conducted through the sample 13, even after passing through the heat storage unit 12, the outer sample 13 of the heat insulating agent is continuously affected by the heat conducted inside. Will be.

In the present invention, the cooling unit 15 is installed to solve this problem. By installing the cooling unit 15, it is possible to effectively block heat radiated inside the heat insulating material and heat conducted by the sample 13 to enable more precise proportional control heat treatment. That is, the sample 13 out of the furnace 17 is not affected by the heat transferred in the furnace 17 through the sample 13 to give a single heat treatment time or temperature gradient to the single sample 13. It is possible. The cooling unit 15 is typically distinguished from a cooling device in which the entire sample is cooled for the purpose of cooling in order to prevent overheating of a specific part in the annealing process.

Figure 5 shows the temperature distribution inside the radiation proportional heat treatment apparatus according to an embodiment of the present invention. Each graph shows a different voltage applied to the heating element, and specifically, measured by applying voltages of (a) 28V, (b) 32V, (c) 42V, (d) 46V, and (e) 49V to the heating element. The temperature result inside one heating unit is shown. Referring to FIG. 5, when a constant voltage is applied to the heating element, the temperature of the heat storage unit and the inside may be set to a random temperature. In addition, when the distance is very close to the sample removal direction, the temperature is hardly high, and it can be seen that the temperature of the sample rises rapidly above a certain distance. This means that the cooling unit is installed in the radiation type proportional heat treatment apparatus according to the present invention.

The present invention includes a heat shield 16 for partitioning between the heat generating unit 11 and the cooling unit 15 to block heat dissipation of the heat storage unit 12 and the inside of the furnace 17. One side of the heat shield 16 is maintained at an arbitrary high temperature set as the heat storage unit 12 and the inside of the furnace 17, and the other side is kept at room temperature as the cooling unit 15.

Although the sample 13 includes most of the inside of the furnace 17, in order to perform the proportional control heat treatment according to the present invention, the sample 13 is moved from the inside of the furnace 17 to the outside. It includes a sample moving unit 19 for moving the sample to the outside through the heat storage unit 12 and the furnace interior 17 and the cooling unit 15 as the time passes. It is preferable that the sample moving unit 19 automatically move the sample 12 by a predetermined distance at a predetermined time. The sample moving part 19 has a part 19a fixed to the sample 13 part and a part 19c fixed to the heat insulating material 14, and a part whose length is increased as the sample 13 is moved to the outside ( 19b). The configuration of the moving unit 19 is not limited to a specific shape or configuration as long as the sample 13 can be moved, and can be implemented in various forms such as using an actuator.

When the sample is removed at a constant rate at any temperature set using the proportional heat treatment apparatus according to the present invention, proportional control heat treatment is possible. According to the present invention, both a time gradient proportional control and a temperature gradient proportional control are possible, and a method of operating a specific apparatus is as follows.

First, the time gradient proportional control heat treatment applies a voltage to the heating element and raises it to an arbitrary temperature at which the heat treatment is to be performed. When the temperature is reached, the sample is inserted and moved out of the furnace at a constant speed. That is, the first part that passes through the furnace is heat-treated for a short time, and the finally removed part is heat-treated for a long time, so that one sample is continuously heat-treated along the length and has a time gradient.

Second, the temperature gradient proportional control heat treatment is applied to the heating element to increase the temperature up to the initial temperature to perform the heat treatment. When the initial temperature is reached, after a certain time, the sample is moved outside to a certain length and the temperature is increased again. If this process is repeated until the entire sample passes through the inside of the furnace 17, the part that first passed through the heating part is heat-treated at low temperature, and finally the part that passes through the inside of the furnace is heat-treated at high temperature so that one sample is As a result, they are continuously heat treated to have a temperature gradient.

Hereinafter, preferred embodiments of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

Example

Example 1

A sample of a shape memory alloy (Ti-50.9Ni) was introduced into a radiation-type proportional heat treatment apparatus equipped with a heating element, and a predetermined voltage was applied so that the temperature inside the furnace and the heat storage unit was 500 ° C. After 500 ° C, 100mm of sample was moved by 20mm at the rate of 5mm / min every minute to perform proportional controlled heat treatment, and the strain curve according to temperature was measured while applying a stress of 50 MPa to the sample. It was.

Example 2

The same procedure as in Example 1 was conducted except that a stress of 100 MPa was applied to the sample.

Example 3

The same procedure as in Example 1 was conducted except that a stress of 200 MPa was applied to the sample.

Example 4

A sample of the shape memory alloy (Ti-Ni-5Cu) was introduced into a radiation type proportional heat treatment apparatus equipped with a heating element, and a predetermined voltage was applied so that the temperature inside the furnace and the heat storage part was 500 ° C. After 500 ° C, 100mm of sample was moved by 20mm at the rate of 5mm / min every minute to perform proportional controlled heat treatment, and the strain curve according to temperature was measured while applying a stress of 50 MPa to the sample. It was.

Comparative Example 1

A sample of shape memory alloy (Ti-50.9Ni) was introduced into a furnace of a heat treatment apparatus equipped with a heating element, and a predetermined voltage was applied so that the temperature of the heat storage unit and the furnace was 500 ° C. Annealing heat treatment was performed for 20 minutes after reaching 500 ° C., and a strain curve with temperature was measured while applying a stress of 50 MPa to the sample.

Comparative Example 2

The same procedure as in Example 1 was conducted except that a stress of 100 MPa was applied to the sample.

Comparative Example 3

The same procedure as in Example 1 was conducted except that a stress of 200 MPa was applied to the sample.

Comparative Example 4

A sample of a shape memory alloy (Ti-Ni-5Cu) was introduced into a heat treatment apparatus furnace having a heating element, and a predetermined voltage was applied so that the temperature of the heat storage portion was 500 ° C. Annealing heat treatment was performed for 20 minutes after reaching 500 ° C., and a strain curve with temperature was measured while applying a stress of 50 MPa to the sample.

Evaluation and Results

Static load thermal cycle between the samples of Comparative Examples 1 to 3, which were annealed at 500 ° C. for 20 minutes, and the samples of Examples 1 to 3, which were proportionally controlled heat treated at a rate of 5 mm / min at 500 ° C. using a radiant proportional control heat treatment machine. The test was performed and the results are shown in FIGS. 8A and 8B, respectively. The samples of Examples 1 to 3 subjected to proportional control heat treatment showed a lower slope than the samples annealed after the static load thermal cycle test. The transformation strain per unit temperature was calculated quantitatively and is shown in Table 1.

number One 2 3 Comparative example 0.048 0.132 0.327 Example 0.022 0.043 0.104

Referring to Table 1, it can be seen that the sample of Examples 1 to 3 subjected to the proportional control heat treatment has a lower transformation strain per unit temperature.

In addition, in Example 4 and Comparative Example 4, the results of the annealing treatment and the radiative proportional control heat treatment are shown in FIG. 9. Referring to FIG. 9, the transformation strain per unit temperature of the Example 4 sample subjected to the radiative proportional control heat treatment was lower than that of the Comparative Example 4 sample subjected to the annealing treatment. The lower the transformation strain per unit temperature, the better the proportional control characteristic and the easier displacement control according to temperature.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is provided only to help a more general understanding of the present invention, and the present invention is not limited to the above-described embodiments, which are common in the art. Those skilled in the art can make various modifications and variations from this description.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

11: heating element 12: heat storage unit
13: Sample 14: Insulation
15: cooling unit 16: heat shield
17: Inside 18: Sample
19, 19 ': Sample moving part

Claims (8)

In the radiation type heat treatment apparatus for manufacturing a shape memory alloy,
Heating element to generate a heat by applying a constant voltage inside the heat insulating material;
A heat storage unit accommodating a sample, storing heat generated from the heating element, and transferring the sample to the sample;
A cooling unit formed outside the heat storage unit to prevent conduction of heat transferred to the sample;
A heat shield for blocking heat dissipation between the heat storage unit and the cooling unit; And
Including a sample moving unit for moving the sample to the outside through the heat storage unit and the cooling unit according to a predetermined time gradient,
Increasing the voltage applied to the heating element at regular intervals with the passage of time to increase the temperature inside the heat storage unit, the sample moving unit is characterized in that for automatically moving the sample by a predetermined distance at a predetermined time,
A radiation-type proportional control heat treatment apparatus for a shape memory alloy, which is capable of simultaneously giving a time gradient and a temperature gradient to a single sample and controlling deformation amount.
The radiation-type proportional heat treatment apparatus for a shape memory alloy according to claim 1, wherein the heat storage part is a metal body having a specific heat higher than that of air.
The radiation-type proportional heat treatment apparatus for a shape memory alloy according to claim 1, wherein the sample is a shape memory alloy.
delete delete In the radiation heat treatment method for manufacturing a shape memory alloy,
Heating the heat storage unit to a predetermined temperature by applying a constant voltage to the heating element inside the insulation;
Inserting a sample into a heating part when the heat storage part reaches a predetermined temperature;
Moving the sample toward a cooling part formed outside the heat storage part to prevent thermal conduction of the sample; And
A shape memory alloy is manufactured by using a radiation-type proportional heat treatment apparatus for a shape memory alloy according to any one of claims 1 to 3, which includes drawing out a sample when the heat treatment is completed to the final part of the sample. How to. 7. The method of claim 6, wherein the temperature of the heat storage unit is increased in the moving of the sample. A shape memory alloy manufactured using a radiation-type proportional control heat treatment apparatus for a shape memory alloy according to any one of claims 1 to 3.

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