JP5023995B2 - Heat-resistant material testing equipment and test piece - Google Patents

Description

The present invention relates to a heat resistance test for a heat resistant material, and more particularly to a heat resistant material testing apparatus and a test piece suitable for conducting a thermal fatigue test by causing repeated temperature changes and mechanical stress changes in a material to be evaluated.

In general, when a member subjected to repeated rapid temperature changes causes repeated stress or distortion due to the restraining force from its surroundings, for example, the rapid temperature change is restrained by the fastening portion to the internal combustion engine and the exhaust pipe collecting portion. In a member such as an exhaust manifold, repeated temperature changes are made to the test piece made from the material of the member so that the limit of strain allowed for that member can be set appropriately for the required number of thermal cycles. And thermal fatigue tests that cause mechanical stress changes.
Conventionally, as a heat-resistant material testing apparatus for performing this type of thermal fatigue test, a portion between two reference points that are heated and cooled and made of a material to be evaluated is held between the two reference points and a gripping tool. One using a test piece having a portion is known (see, for example, Patent Document 1). In this thermal fatigue test apparatus, in order to reduce the internal temperature distribution and evaluate the appropriate heat resistance, the part held between the two gauge points and other than between the two gauge points, and the part held by the gripping tool are made hollow. The thickness of the test piece is reduced. Moreover, in order to accelerate | stimulate a cooling effect, while circulating cooling water inside a hollow, the cooling gas is sprayed with respect to the part between two gauge points. In addition, the material to be evaluated is heated by high-frequency induction heating, which has a short repetition period and facilitates external observation of the material to be evaluated.
Furthermore, local high stress is generated between the part between the two reference points that are heated rapidly by the induction heating coil and the part other than the two reference points, causing cracks and expansion due to bulging, and normal heat In order to prevent the fatigue from being evaluated, this thermal fatigue test apparatus is provided with a cooling device for portions other than between the two gauge points, and is cooled from the outside by a cooling gas from a ring-shaped cooling nozzle having a large number of discharge holes. Thus, the difference in temperature distribution between the portion other than the two benchmarks and the portion between the two benchmarks is reduced.
Japanese Utility Model Publication No. 5-71754

  However, in the conventional heat-resistant material testing apparatus and the heat-resistant material testing method as described above, the evaluated portion of the test piece is directly heated by the induction heating coil. The test piece cannot be reliably prevented from undergoing deformation such as bulging or necking, and cracks due to other factors, not cracks due to thermal fatigue that should be evaluated originally, should be applied to the material being evaluated. It was easy to occur. Therefore, there has been a problem that proper thermal fatigue strength cannot be evaluated.

The present invention has been made to solve the above-described conventional problems, and can prevent deformation and cracks from being caused by factors other than thermal fatigue in a material to be evaluated. An object of the present invention is to provide a heat-resistant material testing apparatus and a test piece that can evaluate the above.

In order to achieve the above object, the heat-resistant material testing apparatus according to the present invention is (1) a heat-resistant material testing apparatus that heats a material to be evaluated to be evaluated by an induction heating coil. A heat-resistant member that is heated by the induction heating coil to heat the material to be evaluated, the material to be evaluated is formed by a rod-shaped member, and the heat-resistant members are both ends in the axial direction of the material to be evaluated. It is characterized by having been joined to .

With this configuration, heat is transmitted from the heat-resistant member heated by the induction heating coil to the material to be evaluated. Therefore, the heat-resistant member is directly heated by the induction heating coil, and the material to be evaluated is not directly heated by the induction heating coil. Therefore, local thermal expansion (bulging or Necking) and cracks do not occur. On the other hand, even if the heat-resistant member is directly heated by the induction heating coil, since the heat-resistant member has higher heat resistance than the material to be evaluated, the heat-resistant member is locally affected by the occurrence of local steep temperature distribution. Thermal expansion (bulging and necking) and cracks do not occur. As a result, an unexpected abnormal crack does not occur before a crack due to the original thermal fatigue strength occurs in the material to be evaluated, and an appropriate thermal fatigue strength is evaluated.
Further, when each heat-resistant member is heated by the induction heating coil, heat is evenly transmitted from each heat-resistant member to the material to be evaluated through both end portions of the material to be evaluated.

  The heat-resistant material testing apparatus according to (1) is preferably configured such that (2) the heat-resistant member is provided inside the radiation of the induction heating coil so as to be surrounded by the induction heating coil.

  With this configuration, since the heat-resistant member provided inside the radiation of the induction heating coil is surrounded by the induction heating coil, a magnetic field is generated in the induction heating coil when an alternating current of a predetermined frequency is passed through the induction heating coil. When this is done, the heat-resistant member is heated uniformly, and the material to be evaluated is heated via the heat-resistant member.

In order to achieve the above object, the test piece according to the present invention is (3) a material to be evaluated for heat resistance, a first holding member connected to one end of the material to be evaluated, and the object to be evaluated. A test piece in which the material to be evaluated is heated by an induction heating coil, and one end portion of the material to be evaluated and the first holding member. A first heat-resistant member having higher heat resistance than the material to be evaluated is interposed therebetween, and the first heat-resistant member is joined to the first holding member and the material to be evaluated. A second heat-resistant member having higher heat resistance than the material to be evaluated is interposed between the other end portion of the evaluation material and the second holding member, and the second heat-resistant member is connected to the second holding member. It is bonded to the material to be evaluated.

With this configuration, when the first heat-resistant member and the second heat-resistant member are directly heated by the induction heating coil, heat is evenly transmitted from the joint portion between each heat-resistant member and the material to be evaluated to the material to be evaluated. The material to be evaluated is not directly heated by the induction heating coil.

In the test piece according to (3), preferably, (4) the material to be evaluated, the first holding member, and the second holding member are formed of a hollow pipe.

With this configuration, a hollow passage is defined inside the material to be evaluated, the first holding member, and the second holding member, and a refrigerant such as compressed gas or cooling water is circulated in the passage. Cooling in the temperature cycle is accelerated. In addition, when the material to be evaluated is formed of a hollow pipe, the thickness of the material to be evaluated can be reduced, and the difference in temperature distribution between the surface portion and the inside of the material to be evaluated is reduced, and appropriate thermal fatigue is achieved. An evaluation of strength is made.

In the test piece according to (3) or (4), preferably, (5) the heat-resistant member is made of a high thermal conductive material having a higher thermal conductivity than the material to be evaluated.

With this configuration, when the heat-resistant member is formed of a highly heat conductive material, heat can be efficiently transferred from the heat-resistant member to the evaluation target material when heated by the induction heating coil.

According to the present invention, since the heat-resistant member is directly heated by the induction heating coil, and the material to be evaluated is not directly heated by the induction heating coil, the local heat generated by the occurrence of a local temperature distribution with a steep slope is not applied to the material to be evaluated. There is no expansion or cracking. Since the heat-resistant member has higher heat resistance than the material to be evaluated, the local heat expansion and cracking due to the occurrence of a local temperature distribution with a steep slope do not occur even in the heat-resistant member. The heat of the heat-resistant member heated by the induction heating coil is transmitted to the material to be evaluated, and the material to be evaluated is appropriately heated. As a result, there is no unexpected abnormal crack before the crack due to the original thermal fatigue strength occurs in the material to be evaluated, and there is provided a heat-resistant material testing apparatus and test piece capable of evaluating an appropriate thermal fatigue strength. Can be provided.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a configuration diagram showing an outline of the configuration of a heat-resistant material testing apparatus equipped with a test piece according to the first embodiment of the present invention, and FIG. 2 is related to the first embodiment of the present invention. It is sectional drawing which shows the AA cross section of FIG. 1 of a test piece, FIG. 3 is a graph which shows the relationship between temperature and time at the time of applying heat to the test piece which concerns on the 1st Embodiment of this invention. FIG. 4 is a graph showing the restraint rate when restraining the end portion of the test piece according to the first embodiment of the present invention and the number of thermal cycles when a crack occurs.

  First, the configuration of the heat-resistant material testing apparatus and the heat-resistant material testing method according to the first embodiment of the present invention will be described.

  In addition, the heat-resistant material test method according to the present invention can be carried out by the heat-resistant material test apparatus and the test piece according to the present invention, and details of the heat-resistant material test method are also clarified through the description of the heat-resistant material test apparatus and the test piece. I will make it. Specifically, the heating step in the heat-resistant material test method according to the present invention can be performed by the control unit, the high-frequency power source, and the output matching unit in the heat-resistant material test apparatus according to the present invention, and the heat-resistant material according to the present invention. The heat transfer step in the test method can be performed by heating the test piece in the heat-resistant material testing apparatus according to the present invention with an induction heating coil.

  As shown in FIG. 1, the heat-resistant material testing apparatus according to the first embodiment of the present invention includes an apparatus main body 11, a controller 12, a high frequency power supply 13, an output matching unit 14, and a compressed gas supply. The Coffin-type thermal fatigue test apparatus 1 including the section 15 is configured. In the thermal fatigue test apparatus 1, a material to be evaluated (described later) that constitutes a part of the test piece 16 by repeatedly applying a heat cycle of heating and cooling to the test piece 16 held in the apparatus main body 11. The thermal fatigue strength is evaluated by measuring the number of thermal cycles until cracks occur. The presence or absence of cracks in the test piece 16 can be confirmed visually, for example, by spraying silicon or the like on the surface. Further, it is also possible to confirm by performing an appearance inspection when the strain of the test piece 16 is greatly changed by a measuring instrument such as a strain gauge.

  The apparatus main body 11 includes an upper fixing plate 21, a lower fixing plate 22, support columns 23 and 24 that support the upper fixing plate 21 and the lower fixing plate 22, and an upper end holding that holds the upper end portion of the test piece 16. The mechanism 25, the lower end holding mechanism 26 that holds the lower end of the test piece 16, the strain sensor 27 that measures the amount of axial deformation of the test piece 16, and the test piece 16 that measures the temperature of the test piece 16. Includes a thermocouple 28, an upper high-frequency induction coil 31 (induction heating coil) that heats the upper part of the test piece 16, and a lower high-frequency induction coil 32 (induction heating coil) that heats the lower part of the test piece 16. It consists of

  The upper end holding mechanism portion 25 is composed of a pull rod configured to fix the upper side of an elastic body such as a spring and hold the test piece 16 on the lower side, and can absorb the amount of axial deformation of the test piece 16. Yes. The upper end holding mechanism unit 25 may be a hydraulic servo mechanism that can absorb deformation by hydraulic pressure. The deformation amount absorbed by the upper end holding mechanism unit 25 is controlled by the control unit 12 so that a so-called restraint rate (%) representing the degree of restraint in the axial direction of the test piece 16 is controlled. ing. For example, if the restraint rate is 100%, it means a completely fixed holding that does not absorb the amount of deformation of the test piece 16 in the axial direction, and if it is 0%, it means a completely open state that is not held, and 80%. If so, it means that the amount of deformation can be absorbed somewhat. In addition, it is preferable that the restraint rate is set so that the restraint state approximates the actual mounting state in consideration of the design conditions of the parts in which the material evaluated by the thermal fatigue test is used. Further, the inside of the upper end holding mechanism portion 25 has a passage penetrating in the vertical direction so that a refrigerant such as compressed gas supplied from the compressed gas supply portion 15 is circulated.

The lower end holding mechanism portion 26 is configured by a holding mechanism such as a chuck mechanism that holds the test piece 16, and the test piece 16 is held so as not to move in the axial direction.
Similarly to the upper end holding mechanism unit 25, the lower end holding mechanism unit 26 has a passage penetrating in the vertical direction so that a refrigerant such as compressed gas supplied from the compressed gas supply unit 15 is circulated. It has become.
As shown in FIG. 2, the strain sensor 27 includes two upper pressing rods 27 a that are in contact with the upper center portion of the test piece 16 and lower pressing rods 27 b that are in contact with the lower center portion of the test piece 16. The sensor portion is configured to measure the amount of deformation of the test piece 16 in the axial direction and output a detection signal corresponding to the amount of deformation to the control unit 12.

  The thermocouple 28 includes, for example, a contact obtained by joining different metals such as nickel and chromium, and a voltmeter connected to the contact. The thermocouple 28 measures a thermoelectromotive force generated at the contact with the voltmeter and outputs a signal corresponding to the temperature. 12 is output. The thermocouple 28 is joined to the surface portion of the test piece 16 by, for example, spot welding so as to accurately measure the temperature of the surface portion of the test piece 16. The thermocouple 28 may be installed at a plurality of locations so that the temperature of the surface portion of the test piece 16 can be measured more accurately.

The upper high-frequency induction coil 31 is made of, for example, a metal tube such as a copper tube, and the shape, the number of turns, and the like are determined according to the thermal fatigue test conditions and the shape and size of the test piece 16.
As shown in FIGS. 1 and 2, the upper high-frequency induction coil 31 is formed of a coil having an inner diameter larger than the outer diameter of the test piece 16 and a length L1 in the axial direction and having three turns. The both ends 31a and 31b are connected to the output matching unit 14 so that an alternating current of a predetermined frequency flows. The upper high-frequency induction coil 31 surrounds the test piece 16 and is disposed so as to radiate outward. When an alternating current is applied, a magnetic field is generated and an eddy current is generated in the test piece 16. The surface portion of the test piece 16 is heated. Further, a resistance against a steep change in the magnetic field generated in the upper high frequency induction coil 31 is generated, and the test piece 16 is also heated by the resistance.

The lower high-frequency induction coil 32 is configured in the same manner as the upper high-frequency induction coil 31, and is spaced apart from the upper high-frequency induction coil 31 by a distance L2, as shown in FIG. As a result, the portion of the tubular member to be evaluated 17 located at the center in the axial direction of the test piece 16 is not directly heated from the upper high-frequency induction coil 31 and the lower high-frequency induction coil 32.
The lower high-frequency induction coil 32 is connected to the output matching unit 14 at both ends 32a and 32b so that an alternating current of a predetermined frequency flows.

  The control unit 12 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) that stores processing programs, a RAM (Random Access Memory) that temporarily stores data, and a rewritable nonvolatile memory. An input interface circuit including an EEPROM (Electronically Erasable and Programmable Read Only Memory), an A / D converter and a buffer, and an output interface circuit including a drive circuit and the like are included.

  The input interface circuit of the control unit 12 is connected to the strain sensor 27, the thermocouple 28, and the upper end holding mechanism unit 25. Information output from the strain sensor 27 and the thermocouple 28 is transmitted via the input interface circuit. Are taken into the control unit 12.

  Further, based on the strain of the test piece 16 detected by the strain sensor 27, the control unit 12 keeps the constraint rate (%) for the test piece 16 constant at, for example, 80% set according to the test condition. Thus, the degree of absorbing the distortion of the test piece 16 in the upper end holding mechanism 25 is feedback-controlled.

  The CPU includes an electronic circuit such as an integrated circuit, and controls the voltage and current of the upper high-frequency induction coil 31 and the lower high-frequency induction coil 32 in the output matching unit 14 together with the ROM and RAM, and the compressed air in the compressed gas supply unit 15. The feed amount control and the feedback control in the upper end holding mechanism unit 25 are executed.

The high-frequency power supply unit 13 is composed of switching elements such as thyristors, MOSFETs, and IGBTs (Insulated Gate Bipolar Transistors). It is supposed to be generated.
In the high frequency power supply unit 13, an optimal high frequency power supply such as output power and frequency is selected based on the test conditions of the test piece 16.

  The output matching unit 14 is configured to perform matching of the output according to the voltage and power source required for the upper high-frequency induction coil 31 and the lower high-frequency induction coil 32, which are loads, of the high-frequency energy generated in the high-frequency power supply unit 13.

  The compressed gas supply unit 15 includes an air pump or the like, and is configured to supply compressed air to the test piece 16 via the upper end holding mechanism unit 25.

  As shown in FIG. 2, the test piece 16 includes a material 17 to be evaluated for heat resistance such as thermal fatigue strength, a first heat-resistant member 18 that is directly heated by an upper high-frequency induction coil 31, and a lower high-frequency induction. The second heat-resistant member 19 that is directly heated by the coil 32, the first holding member 35, and the second holding member 36 are configured.

Further, the first holding member 35 and one end portion of the first heat-resistant member 18 are connected, and the other end portion of the first heat-resistant member 18 and one end portion of the evaluated material 17 are connected, and the evaluated material 17 The other end of the second heat-resistant member 19 is connected to the other end of the second heat-resistant member 19, and the other end of the second heat-resistant member 19 is connected to the second holding member 36 so that they are integrated. A mold test piece 16 is constructed.
Each connecting portion in the test piece 16 is joined by fillet welding such as laser welding, and is polished so that the surface of the joined portion becomes smooth, and thermal stress is generated in the test piece 16. At this time, the distortion generated in the test piece 16 is made uniform.

  The interiors of the evaluation object 17, the first heat-resistant member 18, the second heat-resistant member 19, the first holding member 35, and the second holding member 36 that are integrally formed are hollow, and an internal passage 47 (Cooling fluid passage) is formed. The internal passage 47 is supplied with compressed air from the compressed gas supply unit 15 and is cooled from the inside of the test piece 16.

Further, a thermocouple 28 is joined to the surface portion in the center in the axial direction of the evaluation target material 17 by spot welding or the like, and the temperature of the surface portion of the evaluation target material 17 is detected. A plurality of thermocouples 28 may be provided at equal intervals in the circumferential direction at the center in the axial direction of the material 17 to be evaluated.
Further, an upper pressing rod 27a and a lower pressing rod 27b are arranged on the surface portion of the evaluation target material 17 in the axial direction center so as to abut on the surface portion of the evaluation target material 17 in the axial direction center. The deformation amount that the evaluation material 17 expands due to the thermal stress generated by heating is detected.

The evaluated material 17 is made of, for example, stainless steel as a heat resistant material having high heat fatigue resistance such as high heat crack resistance and heat deformation used for an exhaust manifold of an automobile, and has an outer diameter D ₂ and an inner diameter D _3. It is formed in a pipe shape having a predetermined thickness. The thickness (thickness) of the material 17 to be evaluated is preferably approximate to the thickness of a component such as an exhaust manifold to be used, but is appropriately selected depending on test conditions, component design conditions, and the like.
Further, the evaluated material 17 conducts heat conduction from the first heat-resistant member 18 that is directly heated by the upper high-frequency induction coil 31 and heat conduction from the second heat-resistant member 19 that is directly heated by the lower high-frequency induction coil 32. It is heated indirectly by the main heat transfer.

Here, the first heat-resistant member 18 and the second heat-resistant member 19 are highly heat-conductive materials that are easy to heat and heat is easily transmitted, and that are highly resistant to cracking and deformation even at high temperatures. The material is made of a material having high heat fatigue strength such as, for example, a ferritic heat resistant steel such as SUH446. Moreover, the evaluated material 17 is obtained by cutting a steel pipe made of ferritic stainless steel such as SUS444 to a specific test length.
The first holding member 35 and the second holding member 36 is, for example, a metal having a high mechanical strength, is formed by an outer diameter D _1, is held in the upper holding mechanism 25 and the lower holding mechanism 26 It is like that.

Hereinafter, specific examples of the test conditions of the thermal cycle applied to the evaluated material 17 will be described.
It is considered that such a test condition is easy to obtain a proper evaluation by applying an environmental condition similar to the environment applied to the actual part to be evaluated. Not right. The test condition is a kind of accelerated test, and the thermal strength is evaluated by applying a thermal cycle load assuming an actual environment.

  Specifically, as shown in FIG. 3, the material to be evaluated 17 is raised from 200 ° C. at a low temperature to 900 ° C. during a second, maintained at 900 ° C. at a high temperature for b second, The heating and cooling thermal cycle in which the temperature is lowered over a period of c seconds to a low temperature of 200 ° C. is one cycle, and a plurality of cycles are tested. Here, one cycle varies depending on various conditions such as the material and size of the material to be evaluated, but is performed in about 4 to 5 minutes, for example. Then, this thermal cycle is repeatedly applied to the evaluation target material 17 until a crack occurs in the evaluation target material 17, and the thermal fatigue strength is evaluated by measuring the number of thermal cycles until the crack occurs. The target number of thermal cycles varies depending on various conditions such as the material and size of the material to be evaluated, but in the present embodiment, for example, it exceeds at least 2,000 times and further exceeds 5,000 times.

  Further, the restraint rate (%) held by the upper end holding mechanism 25 of the test piece 16 is maintained constant by feedback control while the thermal cycle is loaded, and is set to 80%, 70%, for example. Is done. In general, the higher the restraint rate, the smaller the number of thermal cycles until cracks occur in the test piece to be evaluated, and the lower the restraint rate, the greater the number of thermal cycles until cracks occur. The number of thermal cycles (times) and restraint rate (%) as shown in FIG. 4 are selected as appropriate according to various conditions such as the material and size of the material to be evaluated, and a thermal fatigue test is performed with at least 3 kinds of restraint rates. ) Curve graph can be created, and the material to be evaluated can be evaluated.

Next, the operation of the thermal fatigue test apparatus 1 according to the first embodiment of the present invention will be described.
First, the test piece 16 is produced, and as shown in FIG. 2, the test piece 16 is positioned so that the first heat-resistant member 18 is surrounded by the upper high-frequency induction coil 31 and the second heat-resistant member 19 is the lower high-frequency induction. It arrange | positions so that it may become a position which is surrounded by the coil 32 and opposes. Next, the second holding member 36 of the test piece 16 is held so as not to move by the lower end holding mechanism portion 26, and the first holding member 35 is held movably by the upper end holding mechanism portion 25.

When the test piece 16 is set in the thermal fatigue testing apparatus 1, an alternating current is loaded on the upper high-frequency induction coil 31 and the lower high-frequency induction coil 32 by the output matching unit 14, and the first heat-resistant member 18 and the second heat-resistant member 19 is heated directly from a low temperature state to a high temperature state.
That is, when an alternating current is applied to the upper high-frequency induction coil 31 and the lower high-frequency induction coil 32, the first test piece 16 has a first direction in a direction that cancels the magnetic flux change that occurs in the vicinity of the upper high-frequency induction coil 31 and the lower high-frequency induction coil 32. An induced current (eddy current) flows through the heat resistant member 18 and the second heat resistant member 19 to generate heat due to electrical resistance.
At this time, the material 17 to be evaluated is not heated by induction as a whole, but is heated by heat conduction from the first heat-resistant member 18 and the second heat-resistant member 19, and as shown in FIG. A preset high temperature is reached.
In this state, the temperature is successively monitored by the thermocouple 28 provided on the evaluation target material 17 and output to the control unit 12. At the same time, the strain sensor 27 operates, the strain of the test piece 16 is sequentially detected, and feedback control is executed by the control unit 12 so that the test piece 16 has a set constant restraint rate.
When the material to be evaluated 17 is indirectly heated in this way and maintained at a high temperature for b seconds as shown in FIG. 3, the compressed gas is then supplied to the internal passage 47 of the test piece 16 by the compressed gas supply unit 15. Supply is made and the test piece 16 is cooled. As a result, the test piece 16 reaches a low temperature over c seconds.

  Such one cycle is repeatedly executed based on a command from the control unit 12 and is continued until the material to be evaluated 17 is cracked. For example, when the operator visually observes that a crack has occurred in the material 17 to be evaluated, the thermal fatigue test is stopped, and the number of thermal cycles from the start to the stop is measured. Next, the thermal fatigue test is similarly performed by changing the restraint rate, and similarly, the number of thermal cycles from the start to the stop is measured. At least the thermal fatigue test is performed with each of the three different constraint rates.

  By the way, in the thermal fatigue testing apparatus 1 according to the present embodiment, the test piece 16 includes an evaluated material 17 to be evaluated, a first holding member 35 on one end side of the evaluated material 17, and an evaluated material. 17 and a second holding member 36 on the other end side, and further, a heat resistance higher than that of the evaluated material 17 is provided between the one end portion of the evaluated material 17 and the first holding member 35. One heat-resistant member 18 and a second heat-resistant member 19 having higher heat resistance than the material to be evaluated 17 are provided between the other end portion of the material to be evaluated 17 and the second holding member 36, respectively. . The first heat-resistant member 18 is integrally bonded to the first holding member 35 and the evaluated material 17, and the second heat-resistant member 19 is integrated to the second holding member 36 and the evaluated material 17. It is joined to.

  The test piece 16 has a heat resistance higher than that of the material to be evaluated 17, and when the high-frequency induction heating is performed by the upper high-frequency induction coil 31, a first heat-resistant member 18 that heats the material to be evaluated 17 by heat conduction, A second heat-resistant member 19 that has higher heat resistance than the evaluation material 17 and heats the evaluated material 17 by heat conduction when subjected to high-frequency induction heating by the lower high-frequency induction coil 32 is included.

  Therefore, when an alternating current of a predetermined frequency is passed through the upper high-frequency induction coil 31 and the lower high-frequency induction coil 32 of the thermal fatigue test apparatus 1, the direction in which the alternating magnetic flux excited by the upper high-frequency induction coil 31 and the lower high-frequency induction coil 32 is canceled out. Thus, an eddy current is generated in the first heat-resistant member 18 and the second heat-resistant member 19 to generate Joule heat, or heat due to hysteresis heating is further generated, so that the first heat-resistant member 18 and the second heat-resistant member 19 are Directly heated. At this time, the material to be evaluated 17 is indirectly heated by heat conduction from the first heat-resistant member 18 and the second heat-resistant member 19, resulting in a local temperature distribution with a steep slope in the material to be evaluated 17. There will be no problems such as bulging, necking or cracking. In addition, the first heat-resistant member 18 is disposed so as to be opposed to the upper high-frequency induction coil 31 and the second heat-resistant member 19 is disposed so as to be opposed to the lower high-frequency induction coil 32. The test piece 16 can be easily attached and detached.

  On the other hand, even if the first heat-resistant member 18 and the second heat-resistant member 19 are directly heated by the upper high-frequency induction coil 31 and the lower high-frequency induction coil 32, the first heat-resistant member 18 and the second heat-resistant member 19 are evaluated. Since it has higher heat resistance than the material 17, bulging, necking, cracking, and the like due to local steep temperature distribution do not occur in the first heat-resistant member 18 and the second heat-resistant member 19. As a result, an unexpected abnormal crack due to other factors does not occur before the material 17 to be cracked due to the original thermal fatigue strength, and an appropriate thermal fatigue strength is evaluated.

  Moreover, since the test piece 16 has the internal channel | path 47 and can supply the compressed air and can cool the test piece 16 effectively, a thermal cycle can be implemented efficiently. In addition, when the material 17 to be evaluated is formed of a hollow pipe, the thickness of the material 17 to be evaluated can be reduced, and the difference in temperature distribution between the surface portion and the inside of the material 17 to be evaluated is reduced. It is possible to evaluate the thermal fatigue strength.

  In addition, since the first heat-resistant member 18 and the second heat-resistant member 19 are formed of a high heat conductive material, the heating effect is enhanced when heated by the upper high-frequency induction coil 31 and the lower high-frequency induction coil 32.

  In the test piece 16 in the thermal fatigue testing apparatus according to the present embodiment, the first heat-resistant member 18 and the second heat-resistant member 19 are connected to both ends of the material 17 to be evaluated, and the material to be evaluated is indirectly heated. However, the test piece in the thermal fatigue testing apparatus according to the present invention may be configured such that a heat-resistant member surrounding the material to be evaluated 17 is disposed in the vicinity of the material to be evaluated 17. Hereinafter, a second embodiment in which the test piece is provided with such an outer heat-resistant member will be described.

(Second Embodiment)
FIG. 5 is a configuration diagram showing an outline of the configuration of a thermal fatigue test apparatus equipped with a test piece according to the second embodiment of the present invention, and FIG. 6 is according to the second embodiment of the present invention. It is sectional drawing which shows the BB cross section of FIG. 5 of a test piece.
In addition, in the thermal fatigue test apparatus 10 which concerns on 2nd Embodiment, although the test piece in the thermal fatigue test apparatus 1 which mounted | wore with the test piece which concerns on 1st Embodiment differs, other structures are the same. It is configured. Therefore, the same configuration will be described using the same reference numerals as those of the first embodiment shown in FIGS. 1 to 4, and only differences will be described in detail.

First, the configuration of the thermal fatigue test apparatus 10 according to the second embodiment of the present invention will be described.
As shown in FIG. 5, the thermal fatigue test apparatus 10 according to the second embodiment includes an apparatus main body 51, a control unit 12, a high frequency power supply unit 13, an output matching unit 14, and a compressed gas supply unit. 15 and a Coffin type thermal fatigue testing apparatus. In this thermal fatigue test apparatus 10, heating and cooling thermal cycles are repeatedly applied to the test piece 46 held in the apparatus main body 51, and the number of thermal cycles until the test piece 16 is cracked is measured to measure the heat. Fatigue strength is evaluated.

  The apparatus main body 51 includes an upper fixing plate 21, a lower fixing plate 22, support columns 23 and 24 that support the upper fixing plate 21 and the lower fixing plate 22, and an upper end holding that holds the upper end of the test piece 16. The mechanism 25, the lower end holding mechanism 26 that holds the lower end of the test piece 16, the strain sensor 27 that measures the amount of axial deformation of the test piece 16, and the test piece 16 that measures the temperature of the test piece 16. And a high-frequency induction coil 41 (induction heating coil) that heats the test piece 16.

  Similarly to the upper high-frequency induction coil 31, the high-frequency induction coil 41 is made of a metal tube such as a tube, and the shape and the number of turns are determined according to the thermal fatigue test conditions, the shape and size of the test piece 46, and the like.

As shown in FIG. 6, the high-frequency induction coil 41 has a larger inner diameter than the outer diameter D ₄ of the test piece 46, in the axial direction has a length of L3, it is formed number of turns in six of the coil, The both ends 41a and 41b are connected to the output matching unit 14 so that an alternating current of a predetermined frequency flows. The high frequency induction coil 41 is disposed so as to surround the test piece 46 and to radiate outward from the test piece 46. When an alternating current is applied, a magnetic field is generated to generate an eddy current in the test piece 16, and the eddy current causes a test. The surface portion of the piece 46 is heated. Further, a resistance against a steep change in the magnetic field generated in the high frequency induction coil 41 is generated, and the test piece 16 is also heated by the resistance.

  As shown in FIG. 6, the test piece 46 includes a material 52 to be evaluated for heat resistance such as thermal fatigue strength, an outer heat-resistant member 53 directly heated by the high-frequency induction coil 41, and a first holding member. 55 and a second holding member 56.

The end portion of the first holding member 55 and one end portion of the evaluation target material 52 are connected, and the other end portion of the evaluation target material 52 and the end portion of the second holding member 56 are connected so that they are integrated. Is formed.
Each connecting portion is joined by fillet welding by laser welding or the like, and is subjected to polishing so that the surface of the joined portion becomes smooth, and when a thermal stress is generated in the test piece 46, the test piece The distortion generated in 46 is made uniform.

  The outer heat-resistant member 53 is disposed so as to surround the material to be evaluated 52 in close proximity, and is formed integrally with the material to be evaluated 52, the first holding member 55, and the second holding member 56. A slit hole 53a is formed in the central portion in the direction to allow the upper pressing rod 27a and the lower pressing rod 27b of the strain sensor 27 to pass through and the connection line of the thermocouple 28 to pass therethrough. The outer heat-resistant member 53 is fixed to a stationary member (not shown) of the apparatus main body 51 so as not to move within the test piece 46. The interiors of the evaluation object 52, the first holding member 55, and the second holding member 56 that are integrally formed are hollow, and an internal passage 57 (cooling fluid passage) is formed. The internal passage 57 is supplied with compressed air from the compressed gas supply unit 15 and is cooled from the inside of the test piece 46.

Further, a thermocouple 28 is joined to the surface portion in the center in the axial direction of the evaluated material 52 by spot welding or the like, and the temperature of the surface portion of the evaluated material 52 is detected. A plurality of thermocouples 28 may be provided at equal intervals in the circumferential direction at the center in the axial direction of the material 52 to be evaluated.
Further, an upper pressing rod 27a and a lower pressing rod 27b are arranged in contact with the axially central surface portion of the evaluated material 17 on the axially central surface portion of the evaluated material 52. The deformation amount that the evaluation material 52 extends due to the thermal stress generated by heating is detected.

The material 52 to be evaluated is made of, for example, stainless steel having high heat resistance used for an exhaust manifold of an automobile as in the case of the material 17 to be evaluated. The pipe 52 has an outer diameter D ₂ and an inner diameter D ₆ and has a predetermined thickness. It is formed in a shape. This thickness is preferably approximate to the thickness of a part such as an exhaust manifold to be used, but is appropriately selected depending on test conditions, part design conditions, and the like.

Further, the evaluated material 52 is heated by the heat transmitted from the heat generated in the outer heat-resistant member 53 directly heated by the high-frequency induction coil 41.
The outer heat-resistant member 53 is formed of a material having high heat resistance, such as a superconducting material, which is easily heated and easily transmitted.
The first holding member 55 and the second holding member 56 is, for example, a metal having a high mechanical strength, formed by the outer diameter D _4, is held in the upper holding mechanism 25 and the lower holding mechanism 26 It is like that.

Next, the operation of the thermal fatigue test apparatus 10 according to the second embodiment of the present invention will be described.
First, as in the first embodiment, the test piece 46 is manufactured, and the test piece 46 is positioned so that the outer heat-resistant member 53 is surrounded by the high-frequency induction coil 41 and is opposed to the test piece 46 as shown in FIG. Deploy. Next, the second holding member 56 of the test piece 46 is held so as not to move by the lower end holding mechanism portion 26, and the first holding member 55 is held movably by the upper end holding mechanism portion 25. When the test piece 46 is set in the thermal fatigue test apparatus 10, an alternating current is loaded on the high frequency induction coil 41 by the output matching unit 14, and the outer heat-resistant member 53 is directly heated until it changes from a low temperature state to a high temperature state.

  Further, the temperature is successively monitored by the thermocouple 28 provided on the evaluation target material 52 and is output to the control unit 12. At the same time, the strain sensor 27 operates, the strain of the test piece 46 is sequentially detected, and feedback control is executed by the control unit 12 so that the test piece 46 has a set constant restraint rate.

  Next, the heat generated in the outer heat-resistant member 53 is uniformly transmitted to the evaluated material 52, and the evaluated material 52 is indirectly heated uniformly. After the material to be evaluated 52 is maintained at a high temperature by heating, compressed air is supplied to the internal passage 57 of the test piece 46 by the compressed gas supply unit 15, and the test piece 46 is cooled to reach a low temperature.

  Such one cycle is repeatedly executed based on the command of the control unit 12 and is continued until the test piece 46 is cracked. When the operator visually observes that a crack has occurred in the test piece 46, the thermal fatigue test stops and the number of thermal cycles from start to stop is measured. Next, the thermal fatigue test is similarly performed by changing the restraint rate, and similarly, the number of thermal cycles from the start to the stop is measured. At least thermal fatigue tests are carried out with three different restraints.

  In the thermal fatigue testing apparatus 10 according to the present embodiment, the test piece 46 includes an evaluated material 52 to be evaluated, a first holding member 55 connected at one end of the evaluated material 52, and an evaluated material. And an outer heat-resistant member 53 having higher heat resistance than the evaluated material 52 so as to surround the evaluated material 52 close to each other. . Further, the heat-resistant member 53 outside the test piece 46 is disposed so as to be opposed to the high-frequency induction coil 41.

Therefore, when an alternating current of a predetermined frequency is passed through the high-frequency induction coil 41 of the thermal fatigue testing apparatus 10, eddy current or further heat due to hysteresis heating is generated in the outer heat-resistant member 53, and the outer heat-resistant member 53 is directly heated. The
At this time, the heat generated in the outer heat-resistant member 53 is transmitted to the material to be evaluated 52 by any one of heat conduction, heat transfer, and heat radiation. Distribution does not occur, and bulging, necking, cracks, etc. do not occur.
Further, even if the outer heat-resistant member 53 is directly heated by the high-frequency induction coil 41, the outer heat-resistant member 53 has higher heat resistance (higher heat fatigue strength) than the material 52 to be evaluated. No bulging, necking, cracking or the like occurs in 53. As a result, an unexpected abnormal crack due to other factors does not occur before the material 52 to be cracked due to the original thermal fatigue strength, and an appropriate thermal fatigue strength can be evaluated.

Moreover, since the test piece 46 has the internal channel | path 57 and can supply the compressed air and can cool the test piece 46 effectively, a thermal cycle can be implemented efficiently. Further, when the evaluated material 52 is formed of a hollow pipe, the thickness of the evaluated material 52 can be reduced, and the difference in temperature distribution between the surface portion and the inside of the evaluated material 52 is reduced. It is possible to evaluate the thermal fatigue strength.
Further, since the outer heat-resistant member 53 is formed of a high heat conductive material, the heating effect is enhanced when heated by the high frequency induction coil 41.

  FIG. 7 shows another embodiment of a test piece according to the present invention, (a) shows a solid test piece with a circular cross section, (b) shows a test piece with a rectangular cross section, (C) shows a test piece provided with a high heat conduction member surrounding a round bar evaluation material having a circular cross section, and (d) shows a test piece provided with a high heat conduction member around a square member having a rectangular cross section. .

  In the thermal fatigue test apparatus 1 and the thermal fatigue test apparatus 10 according to the present embodiment, the case where the test piece 16 and the test piece 46 are formed of a hollow pipe shape has been described, but the thermal fatigue test according to the present invention is described. The apparatus and test piece may be configured in other shapes. For example, as shown in FIG. 7A, a test piece 81 is formed of a round bar, and an evaluation object 86, heat-resistant members 84 and 85 that are directly heated by a high-frequency induction coil, and a first holding member 82 The second holding member 83 may be used. In this case, you may make it cool by spraying the compressed gas supplied by the compressed gas supply part 15 from the exterior of the test piece 81. FIG.

  Further, as shown in FIG. 7B, a test piece 91 is formed of a plate material, a material 94 to be evaluated, heat-resistant members 93 and 95 that are directly heated by a high-frequency induction coil, a first holding member 92, You may comprise with the 2nd holding member 96. FIG. Also in this case, the compressed gas supplied from the compressed gas supply unit 15 may be blown from the outside of the test piece 91 to be cooled.

  Further, as shown in FIG. 7C, the test piece 101 is formed of a round bar, the material to be evaluated 105, the outer heat-resistant member 104 directly heated by the high frequency induction coil, the first holding member 102, The second holding member 106 may be used. Also in this case, the compressed gas supplied from the compressed gas supply unit 15 may be blown from the outside of the test piece 101 to be cooled.

  Further, as shown in FIG. 7 (d), the test piece 111 is formed of a plate material, the evaluated material 115, the outer heat-resistant member 114 directly heated by the high-frequency induction coil, the first holding member 112, You may comprise with the 2nd holding member 116. FIG. Also in this case, the compressed gas supplied from the compressed gas supply unit 15 may be blown from the outside of the test piece 111 to be cooled.

  In the thermal fatigue test apparatus 1 and the thermal fatigue test apparatus 10 according to the present embodiment, the first heat-resistant member 18 and the second heat-resistant member 19 of the test piece 16 are made of a high heat conductive material, and the test piece 46 However, the thermal fatigue test apparatus and test piece according to the present invention may be made of other materials. For example, it may be formed of stainless steel having high heat resistance or a metal material having high heat conductivity, and the thickness thereof may be larger than the thickness formed of the high heat conductive material.

  As described above, according to the present invention, the heat-resistant member is directly heated by the high-frequency induction coil, and the material to be evaluated is indirectly heated. Therefore, the material to be evaluated has a local steep temperature distribution. It is possible to prevent thermal expansion and cracks from occurring, prevent unexpected abnormal cracks from occurring before the cracks due to the original thermal fatigue strength occur, and perform appropriate thermal fatigue strength tests. Heat resistance test for heat-resistant materials, especially suitable for conducting thermal fatigue tests by causing repeated temperature changes and mechanical stress changes in the material being evaluated Useful for test equipment, heat-resistant material test methods, and test pieces in general.

It is a block diagram which shows the outline of a structure of the thermal fatigue testing apparatus equipped with the test piece which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the AA cross section of FIG. 1 of the test piece which concerns on the 1st Embodiment of this invention. It is a graph which shows the relationship between temperature and time at the time of applying heat to the test piece which concerns on the 1st Embodiment of this invention. It is a graph which shows the thermal cycle number when the restraint rate at the time of restraining the edge part of the test piece which concerns on the 1st Embodiment of this invention, and a crack arises. It is a block diagram which shows the outline of a structure of the thermal fatigue testing apparatus equipped with the test piece which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the BB cross section of FIG. 5 of the test piece which concerns on the 2nd Embodiment of this invention. Fig. 4 shows another embodiment of the test piece according to the present invention, (a) shows a solid test piece with a circular cross section, (b) shows a test piece with a rectangular cross section, and (c) shows The test piece which provided the high heat-conduction member surrounding the round-bar evaluation material with a circular cross section is shown, (d) shows the test piece which provided the high heat-conduction member around the square member whose cross section is a rectangle.

Explanation of symbols

1, 10 Thermal fatigue test equipment (heat resistant paper surface equipment)
DESCRIPTION OF SYMBOLS 11, 51 Apparatus main body part 12 Control part 13 High frequency power supply part 14 Output matching part 15 Compressed gas supply part 16, 46, 81, 91, 101, 111 Test piece 17, 52, 86, 94, 105, 115 Evaluated material 18 First heat-resistant member (heat-resistant member, heat-resistant fatigue strength member)
19 Second heat-resistant member (heat-resistant member, heat-resistant fatigue strength member)
DESCRIPTION OF SYMBOLS 21 Upper side fixing plate 22 Lower side fixing plate 23, 24 Support | pillar 25 Upper end holding mechanism part 26 Lower end holding mechanism part 27 Strain sensor 28 Thermocouple 31 Upper high frequency induction coil (induction heating coil)
32 Lower high frequency induction coil (induction heating coil)
35, 55, 82, 92, 102, 112 First holding member 36, 56, 83, 96, 106, 116 Second holding member 41 High-frequency induction coil (induction heating coil)
47, 57 Internal passage (cooling fluid passage)
53, 104, 114 Outside heat resistant member (heat resistant member)
84, 85, 93, 95 Heat resistant member

Claims (5)

In a heat-resistant material testing apparatus that heats an evaluation target material to be evaluated for heat resistance using an induction heating coil,
A heat-resistant member that has higher heat resistance than the material to be evaluated and is heated by the induction heating coil to heat the material to be evaluated ;
The heat-resistant material testing apparatus , wherein the material to be evaluated is formed of a rod-shaped member, and the heat-resistant member is joined to both end portions in the axial direction of the material to be evaluated .   The heat-resistant material testing apparatus according to claim 1, wherein the heat-resistant member is provided inside the radiation of the induction heating coil so as to be surrounded by the induction heating coil. A material to be evaluated for heat resistance, a first holding member connected to one end of the material to be evaluated, and a second holding member connected to the other end of the material to be evaluated A test piece in which the material to be evaluated is heated by an induction heating coil;
A first heat-resistant member having higher heat resistance than the material to be evaluated is interposed between one end of the material to be evaluated and the first holding member, and the first heat-resistant member is the first holding member. And the material to be evaluated
A second heat-resistant member having higher heat resistance than the material to be evaluated is interposed between the other end of the material to be evaluated and the second holding member, and the second heat-resistant member is the second holding member. A test piece which is bonded to a member and the material to be evaluated. The test piece according to claim 3, wherein the material to be evaluated, the first holding member, and the second holding member are formed of a hollow pipe. The test piece according to claim 3, wherein the heat-resistant member is formed of a high thermal conductive material having a higher thermal conductivity than the material to be evaluated.

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