JP2016132004A - Friction agitation jointing tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat-resistance and the heat input of a friction agitation junction tool to be used in a friction agitation junction for jointing the members to be jointed by pushing a tool having a projection (or a probe part) while rotating the tool, by softening a portion of the member to be jointed by a frictional heat, and by agitating the softened part with the projection.SOLUTION: A friction agitation jointing tool is characterized by ceramics having a thermal conductivity of 34 W/mK or lower and a thermal shock fracture resistance coefficient of 8 kW/m or larger.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a friction stir welding tool.

  Conventionally, a friction stirrer in which a tool provided with a protruding portion is pushed into a member to be bonded while rotating, a part of the member to be bonded is softened by frictional heat, and the softened portion is stirred by the protruding portion to join the members to be bonded. Joining is known. As friction stir welding tools used for friction stir welding, Patent Literature 1 and Patent Literature 2 disclose friction stir welding tools formed of steel and cemented carbide, respectively. Patent Literature 3 and Patent Literature 4 disclose a friction stir welding tool formed of ceramics.

JP 7-505090 Gazette JP 2001-314983 A JP 2010-194591 A JP 2011-98842 A

  In recent years, the demand for friction stir welding for steel joining has increased. Since steel has high strength at high temperatures, high heat resistance is required for friction stir welding tools used for joining steel. Moreover, in order to obtain excellent bondability, it is necessary to cause the steel to flow sufficiently plastically. For this reason, the friction stir welding tool has high heat input, that is, it can give a lot of heat to the steel. Required. However, ceramics that have been studied as a conventional tool material cannot achieve both heat resistance and heat input and cannot obtain good bonding properties. For this reason, the technique which improves the heat resistance and heat input property of the tool for friction stir welding was calculated | required.

  In order to solve the above problems, the present invention can be realized as the following forms.

(1) According to one aspect of the present invention, there is provided a friction stir welding tool characterized by comprising a ceramic having a thermal conductivity of 34 W / mK or less and a thermal shock fracture resistance coefficient of 8 kW / m or more. The According to the friction stir welding tool of this embodiment, the heat resistance and heat input property of the tool can be improved.

(2) In the friction stir welding tool, the ceramic is composed of at least one of sialon and silicon nitride, a sintering aid, a periodic table group 4 element, a group 5 element, or a group 6 element. , At least one of carbide, nitride, and carbonitride. According to this configuration, the thermal conductivity is 34 W / mK or less and the thermal shock fracture resistance coefficient is 8 kW / m or more, so that the heat resistance and heat input property of the tool can be improved.

(3) In the friction stir welding tool, the content of at least one of the carbide, the nitride, and the carbonitride may be 0.1 volume% or more and 25 volume% or less. According to this configuration, the thermal shock fracture resistance coefficient is 8 kW / m or more, and the heat resistance is high enough to withstand the joining of steel.

(4) In the friction stir welding tool, the content of at least one of the carbide, the nitride, and the carbonitride may be 0.1 volume% or more and 10 volume% or less. With this configuration, not only tool breakage but also wear can be suppressed.

(5) In the friction stir welding tool, the content of the sintering aid may be not less than 0.7% by volume and not more than 15% by volume. According to this configuration, the thermal conductivity is 34 W / mK or less and the thermal shock fracture resistance coefficient is 8 kW / m or more, so that the heat resistance and heat input property of the tool can be improved.

(6) In the friction stir welding tool, the content of the sintering aid may be not less than 3.5% by volume and not more than 15% by volume. With this configuration, tool wear can be further suppressed.

(7) In the friction stir welding tool, at least one of the carbide, the nitride, and the carbonitride is titanium nitride, titanium carbide, titanium carbonitride, tungsten carbide, chromium nitride, zirconium nitride, carbonized. It may contain at least one of tantalum and niobium carbide. With this configuration, the iron resistance can be improved, so that the wear of the tool can be suppressed and the joined state of the members to be joined can be improved.

The present invention can be realized in various modes, for example, in the form of a friction stir welding apparatus including a friction stir welding tool, a method of manufacturing a friction stir welding tool, a friction stir welding method, and the like. Can be realized.
The friction stir welding tool includes a substantially cylindrical main body portion and a substantially cylindrical probe portion that is formed at the distal end portion of the main body portion and is pressed against a member to be joined during friction stir welding. It may be a stir welding tool.

It is the figure which illustrated the whole structure of the tool for friction stir welding. 2 is a diagram illustrating a usage state of the tool 10. FIG. 3 is a flowchart showing an example of a method for manufacturing the tool 10. It is explanatory drawing which shows a composition, physical property, and test result of sample # 1- # 11. It is explanatory drawing which shows a composition, physical property, and test result of sample # 12- # 22. It is explanatory drawing which shows a composition, physical property, and test result of sample # 23- # 32.

A. Embodiment:
A-1. Tool configuration:
FIG. 1 is a diagram illustrating the overall configuration of a friction stir welding tool. 1A to 1D are a front view, a bottom view, a top view, and a perspective view of a friction stir welding tool, respectively. The friction stir welding tool 10 (hereinafter also simply referred to as “tool 10”) is formed of a ceramic sintered body. The tool 10 includes a main body portion 11 having a substantially cylindrical shape and a probe portion 12. The probe portion 12 is configured by a substantially cylindrical protrusion, and is formed at the center portion of the distal end portion 11 e of the main body portion 11. The axis line of the probe unit 12 coincides with the axis line X of the main body unit 11. In this embodiment, the diameter of the main body 11 is 12 mm, the diameter of the probe 12 is 4 mm, the length of the main body 11 along the axis X is 18.5 mm, and the length of the probe 12 is 1.5 mm. Each dimension may be an arbitrary value.

  FIG. 2 is a diagram illustrating the usage state of the tool 10. The tool 10 is used by being attached to a joining device (not shown). The probe portion 12 of the tool 10 receives pressure from the joining device and is pushed into the joining line WL that is a boundary between the members 21 and 22 while being rotated. Thereafter, the members to be joined 21 and 22 move relative to the tool 10 in the direction indicated by the white arrow in the drawing while the probe portion 12 is pushed into the members to be joined 21 and 22. Thereby, the tool 10 moves relatively along the joining line WL. In this embodiment, the to-be-joined members 21 and 22 are steel plates, but may be other arbitrary metals instead of steel. The vicinity of the joining line WL of the members to be joined 21 and 22 plastically flows due to frictional heat with the probe portion 12. When the probe part 12 agitates the plastic flowed portions of the members to be joined 21 and 22, the joining area WA is formed. The joined members 21 and 22 are joined to each other by the joining region WA.

The tool 10 is preferably formed of a ceramic sintered body mainly containing at least one of sialon and silicon nitride (Si ₃ N ₄ ). The average particle size of sialon and silicon nitride is preferably 0.1 μm or more and 1.5 μm or less. Since sialon and silicon nitride are excellent in heat resistance, the durability of the tool 10 can be improved by using at least one of sialon and silicon nitride as a main component. The content of at least one of sialon and silicon nitride is more preferably 65% by volume or more and 90% by volume or less. By doing in this way, durability of the tool 10 can fully be ensured, ensuring content of another component. Note that the ceramic sintered body may be other types of ceramics instead of the silicon nitride ceramics mainly composed of silicon nitride. Further, the tool 10 may have a substance other than ceramics in a part of the main body 11.

  The sintered body preferably has a thermal conductivity of 34 W / mK or less and a thermal shock fracture resistance coefficient of 8 kW / m or more. By setting it as such a structure, the heat resistance and heat input property of the tool 10 can be improved. Conventionally, it has been considered that a general tool including a friction stir welding tool has a higher thermal conductivity and is preferable from the viewpoint of heat resistance. However, if the thermal conductivity is high, the amount of heat (amount of heat drawn) transmitted to the tool 10 side increases, and a sufficient amount of heat cannot be given to the members to be joined. Therefore, by setting the thermal conductivity of the tool 10 to 34 W / mK or less, a sufficient amount of heat can be given to the members to be joined, and excellent jointability can be realized. The thermal conductivity is more preferably 27 W / mK or less from the viewpoint of wear of the tool 10, and preferably 5 W / mK or more from the viewpoint of improving the thermal shock resistance. Moreover, since the heat shock fracture resistance coefficient of a sintered compact is 8 kW / m or more, since heat resistance which can endure joining of steel can be provided, the defect | deletion of the tool 10 can be suppressed. The thermal shock breakdown resistance coefficient may be 40 kW / m or less.

In the present embodiment, the thermal shock fracture resistance coefficient is obtained by the following equation (1).
Thermal shock fracture resistance coefficient R (kW / m) = k (1-v) · σ / (E · α) (1)
However, k is thermal conductivity (W / mK), v is Poisson's ratio, σ is bending strength (MPa), E is Young's modulus (GPa), and α is thermal expansion coefficient (ppm / K). As a measuring method, the method described in JIS R 1611 for thermal conductivity, JIS R 1602 for Poisson's ratio and Young's modulus, JIS R 1601 for bending strength, and JIS R 1618 for thermal expansion coefficient can be applied mutatis mutandis. . The thermal conductivity is a measured value at room temperature.

  The sintered body contains at least one of carbide, nitride, and carbonitride including at least one of Group 4 element, Group 5 element and Group 6 element of the periodic table. It is preferable to do. These carbides, nitrides, and carbonitrides (hereinafter also referred to as “dispersed particles”) can be dispersed in sialon and silicon nitride, thereby improving the iron resistance and strength of the sintered body. By improving the iron-resistant reactivity of the sintered body, wear of the tool 10 can be suppressed and the joined state of the members to be joined can be improved. The content of the dispersed particles is preferably 0.1% by volume or more from the viewpoint of improving iron resistance and bending strength and improving the joined state of the joined members. Moreover, it is preferable that it is 25 volume% or less from a viewpoint of improving a thermal shock resistance, and it is more preferable that it is 10 volume% or less from a viewpoint of the abrasion property of the tool 10. FIG. The upper limit of the content of the dispersed particles in terms of improving the thermal shock resistance is due to the following reason. As the content of dispersed particles increases, the thermal expansion coefficient and Young's modulus increase. Moreover, when there is too much content of a dispersed particle, bending strength will fall. All of these factors reduce the thermal shock fracture resistance coefficient. In addition, the Young's modulus and Poisson's ratio increase depending on the type of dispersed particles. An increase in Poisson's ratio also causes a decrease in the thermal shock resistance coefficient.

  In the present embodiment, “volume%” means the ratio of each material when the total volume of all materials contained in the sintered body or tool 10 is 100%. The content of each substance in the sintered body or tool 10 can be calculated by determining the amount of each element by fluorescent X-ray analysis or the like.

Periodic table Group 4 elements include Ti, Zr, Hf and the like, Group 5 elements include V, Nb, Ta and the like, and Group 6 elements include Cr, Mo, W and the like. Specific examples of the dispersed particles include TiC, ZrC, HfC, V ₃ C ₂ , NbC, TaC, Cr ₃ C ₂ , Mo ₂ C, WC, TiN, ZrN, HfN, VN, NbN, TaN, CrN, Mo ₂ N, WN, TiCN, ZrCN, HfCN, VCN, NbCN, TaCN, CrCN, Mo ₂ CN, WCN and the like can be exemplified. From the viewpoint of iron resistance, TiN (titanium nitride), TiC (titanium carbide), TiCN (titanium carbonitride), WC (tungsten carbide), CrN (chromium nitride), ZrN (zirconium nitride), TaC (tantalum carbide) And at least one of NbC (niobium carbide). Further, from the viewpoint of further improving the iron resistance and the wearability of the tool 10, at least one of CrN (chromium nitride), ZrN (zirconium nitride), TaC (tantalum carbide) and NbC (niobium carbide). It is more preferable to contain. Further, two or more substances may be contained as dispersed particles. The average particle size of the dispersed particles is preferably 0.4 μm or more and 1.5 μm or less.

  The sintered body preferably contains a sintering aid in order to increase the strength of the tool 10. The content of the sintering aid is 0.7% by volume or more from the viewpoint of reducing the thermal conductivity of the sintered body (tool 10) and imparting sufficient heat input and improving iron resistance. From the viewpoint of wear of the tool 10, it is more preferably 3.5% by volume or more. Further, from the viewpoint of improving the thermal shock resistance, it is preferably 15% by volume or less. The average particle diameter of the sintering aid is preferably 0.4 μm or more and 1.5 μm or less.

  The sintering aid preferably contains at least one of aluminum oxide and aluminum nitride. By containing aluminum oxide, aluminum and oxygen are dissolved in silicon nitride and silicon nitride is sialonized, so that the strength of the sintered body can be improved. The sintering aid preferably contains a rare earth element. By containing the rare earth element, the sialon and silicon nitride particles can be formed into needles, so that the strength and thermal shock resistance of the sintered body (tool 10) can be improved. Specific examples of sintering aids containing rare earth elements include yttrium oxide, ytterbium oxide, dysprosium oxide, and the like.

A-2. Tool manufacturing method:
FIG. 3 is a flowchart showing an example of a method for manufacturing the tool 10. Various materials and numerical values used in the following description (for example, average particle diameter of powder, mixing time, heating time, heating temperature, etc.) are examples of such, and values other than these are arbitrarily adopted. be able to.

Silicon nitride powder as a main raw material of ceramic sintered body, titanium nitride (TiN) powder as dispersed particles, yttrium oxide (Y ₂ O ₃ ) and aluminum oxide (Al ₂ O ₃ ) powder as sintering aids Are weighed (step S110). The raw material powder is mixed and pulverized to produce a slurry (step S120). In the mixing and pulverization, particles of each raw material powder may be pulverized using a ball mill while mixing the raw material powder together with a solvent (for example, ethanol). Although there is no limitation in particular about grinding | pulverization time, For example, about 20 hours-about 30 hours can be illustrated. Thereby, a slurry containing the raw material powder is obtained. The obtained slurry is degassed by hot water drying to obtain a mixed powder (step S130).

The obtained mixed powder is press-molded and fired (step S140). After press molding of the mixed powder, a cold isostatic pressing process (CIP process) may be performed. Although there is no limitation in particular about the shape of a molded object, forming in a substantially cylindrical shape is preferable. A sintered body can be obtained by performing a hot isostatic pressing process (HIP process) after primary firing of the obtained molded body. The firing temperature during primary firing is preferably 1550 to 1950 ° C., and the firing time is preferably 1 to 3 hours. The HIP treatment is preferably performed at a firing temperature of 1500 to 1800 ° C., a firing time of 1 to 3 hours, a gas pressure of 10 to 200 MPa, and an N ₂ atmosphere. The obtained ceramic sintered body is processed into a tool shape (step S150). In addition, in this embodiment, although it processes by a grinding process, you may process by another arbitrary system. Thus, the friction stir welding tool 10 is completed.

B. Example:
Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. Samples # 1 and # 23 indicate the same sample. Samples # 5, # 20, and # 24 are all the same sample.

B-1. Example 1 (Evaluation regarding content of dispersed particles):
[Production of sintered bodies and tools]
FIG. 4 is an explanatory diagram showing the composition, physical properties, and test results of Samples # 1 to # 11. Silicon nitride (Si ₃ N ₄ ) raw material having an average particle diameter of 0.1 μm as a main raw material, yttrium oxide (Y ₂ O ₃ ) raw material having an average particle diameter of 1.0 μm and an average particle diameter of 0.7 μm as a sintering aid An aluminum oxide (Al ₂ O ₃ ) raw material and a titanium nitride (TiN) raw material having an average particle size of 0.6 μm as dispersed particles were blended so as to obtain a sintered body having the composition shown in FIG. However, the ratio of yttrium oxide and aluminum oxide in the sintering aid was 7: 3 in all samples. That is, it mix | blended so that yttrium oxide might contain 7 volume% and aluminum oxide 3 volume%. The blended raw material powder and ethanol were placed in a resin pot and mixed and ground for 24 hours. After mixing and pulverizing, the slurry was hot-water dried to remove the ethanol to produce a powder. The obtained powder was press-molded and then subjected to CIP to produce a molded body. Thereafter, primary sintering was performed (1650 ° C. to 1750 ° C., 2 hours), and HIP treatment (1600 ° C., 2 hours, gas pressure 150 MPa) was performed to produce a sintered body. The firing was performed in an N ₂ atmosphere. Moreover, the grinding process was performed with respect to the produced sintered compact, and the tool 10 was produced. The number of samples for each sample was 1.

[Measurement of physical properties of sintered body]
The produced sintered body was measured for thermal conductivity, Poisson's ratio, bending strength, Young's modulus, and thermal expansion coefficient. These measurements were performed by the same method as in the above-described embodiment. Moreover, the thermal shock fracture resistance coefficient was calculated | required based on Formula (1) in embodiment mentioned above.

[Tool test]
The manufactured tool 10 was subjected to a friction stir welding test. Similarly to the state shown in FIG. 2, the steel plates as the members to be joined were butted together, and a tool was pressed against the boundary portion to move the members to be joined relative to each other. The friction stir welding test was performed under the following conditions.
<Friction stirring test conditions>
Joined member: rolled steel plate (SPCC), rotation speed: 600 rpm
Tool push-in amount: 1.5 mm, descending speed: 2 mm / min.
Movement speed: 200 mm / min. Traveling distance: 100 / pass Note that “rotational speed” indicates the rotational speed of the tool 10, and “tool pressing amount” indicates the pressing amount of the tool 10 against the member to be joined. “Descent speed” indicates a speed when the tool 10 is brought close to the member to be joined, and “moving speed” indicates a speed when the tool 10 relatively moves on the member to be joined, and “movement distance”. Indicates the distance that the tool 10 has moved relative to the member to be joined.

<Evaluation method>
The tool state after the friction stir welding test and the joining state of the steel plates were evaluated. The tool state was evaluated by projecting the tool 10 and measuring various dimensions including the main body part 11, the tip part 11e, and the probe part 12. ◎ when the wear is minimal (highest evaluation), ○ when the wear is relatively small (second highest evaluation), △ when the wear is relatively large (third highest evaluation), The case where the defect occurred was marked as x (lowest evaluation). The bonding state was evaluated by visual observation of the bonding surface. A case where no void was recognized on the joint surface and the surface was a homogeneous joint surface was evaluated as ◯ (high evaluation), and a case where a void was observed on the joint surface was evaluated as x (low evaluation). In addition, about the sample (tool sample whose tool state was x) in which the tool 10 is missing, the evaluation of the joining state of the steel plates could not be performed.

[Results of composition and physical property measurement of each sample]
As shown in FIG. 4, samples # 1 to # 11 are different from each other in content of titanium nitride (TiN) as dispersed particles and silicon nitride (Si ₃ N ₄ ) as a main raw material, and other compositions are the same. It is. Sample # 1 differs from Samples # 2- # 11 in that it lacks dispersed particles. The content of the dispersed particles of Samples # 2 to # 11 is different from each other in the range of 0.1% by volume to 30.0% by volume. Sample # 1 lacking dispersed particles and Samples # 2 to # 9 having a content of dispersed particles of 0.1% to 25.0% by volume had a thermal shock fracture resistance coefficient of 8 kW / m or more. On the other hand, Samples # 10 and # 11 in which the content of dispersed particles was 26.0% by volume to 30.0% by volume had a thermal shock fracture resistance coefficient of less than 8 kW / m. In addition, the thermal conductivity of all the samples in Example 1 was 34 W / mK or less.

[Test results]
In Samples # 2 to # 9, the evaluation result of the bonding state was “◯”. On the other hand, the evaluation result of the joining state of the sample # 1 was “x”, which was inferior to the samples # 2 to # 9. Samples # 2 to # 6 were all good in the evaluation results of the tool state and the joining state as “◯”. On the other hand, all of samples # 1, # 7 to # 9 have a tool state evaluation result of “Δ”, and samples # 10 and # 11 have the tool 10 missing during the test.

  The following can be understood from the results of Example 1 described above. By containing the dispersed particles in an amount of 0.1% by volume or more, the joined state of the members to be joined can be improved. Moreover, by setting the content of the dispersed particles to 25.0% or less, a sintered body having a thermal shock fracture resistance coefficient of 8 kW / m or more can be obtained. Since a tool using a sintered body having a thermal shock fracture resistance coefficient of 8 kW / m or more has high heat resistance that can withstand the joining of steel, the tool 10 can be prevented from being broken.

B-2. Example 2 (Evaluation of content and type of combustion aid):
FIG. 5 is an explanatory diagram showing the composition, physical properties, and test results of Samples # 12 to # 22. A sintered body and a tool 10 were produced by the same raw materials and methods as in Example 1. However, the sintering aid of sample # 19 was made entirely of yttrium oxide so that the main raw material silicon nitride was not sialonized. The other samples were blended so that yttrium oxide and aluminum oxide were contained in a ratio of 7: 3 as a sintering aid. Moreover, the physical property measurement of the sintered compact and the friction stir welding test of the tool 10 were performed and evaluated by the same method as in Example 1.

[Results of composition and physical property measurement of each sample]
Samples # 13 to # 18 and # 20 to # 22 are different from each other in the content of silicon nitride as the sintering aid and the main raw material, and the other compositions are the same. Sample # 12, unlike the other samples, lacks dispersed particles. Sample # 19 is different from Sample # 18 in terms of the type of sintering aid, and the other compositions are the same as Sample # 18. Samples # 12 and # 13 having a sintering aid content of 0.5% by volume had thermal conductivity exceeding 34 W / mK. Samples # 14 to # 22 having a sintering aid content of 0.7 vol% or more had a thermal conductivity of 34 W / mK or less. Sample # 22 having a sintering aid content of 20.0% by volume had a thermal shock resistance coefficient of less than 8 kW / m. On the other hand, the thermal shock fracture resistance coefficients of Samples # 12 to # 21 were all 8 kW / m or more. Sample # 18 had a bending strength greater than that of sample # 19.

[Test results]
Samples # 14 to # 21 all had a bonding state evaluation result of “◯”. In contrast, Samples # 12 and # 13 have an evaluation result of the bonding state of “x”, which is inferior to Samples # 14 to # 21. In Samples # 12 and # 13, the voids observed on the joint surface of the steel plates are presumed to be due to insufficient heat input. In Samples # 14 to # 21, the evaluation result of the tool state was “◯” or “Δ”, which was good. In particular, Samples # 17 to # 21 had a better evaluation result of the tool state “◯”, which was better. On the other hand, sample # 22 lost the tool 10 during the test.

  The following can be understood from the results of Example 2 described above. By containing 0.7% by volume or more of a sintering aid, a sintered body having a thermal conductivity of 34 W / mK or less can be obtained. The tool 10 using a sintered body having a thermal conductivity of 34 W / mK or less has high heat input and can give a sufficient amount of heat to the members to be joined. It can be improved. Moreover, by setting the content of the sintering aid to 15.0% or less, a sintered body having a thermal shock fracture resistance coefficient of 8 kW / m or more can be obtained. Since a tool using a sintered body having a thermal shock fracture resistance coefficient of 8 kW / m or more has heat resistance that can withstand the joining of steel, the tool 10 can be prevented from being broken.

B-3. Example 3 (Evaluation regarding the type of dispersed particles):
FIG. 6 is an explanatory diagram showing the composition, physical properties, and test results of Samples # 23 to # 32. A sintered body and a tool 10 were produced in the same manner as in Example 1. However, as dispersed particles, TiN (titanium nitride), TiC (titanium carbide), TiCN (titanium carbonitride), SiC (silicon carbide) having an average particle diameter of 0.6 μm, WC (tungsten carbide) having an average particle diameter of 0.4 μm Any one of CrN (chromium nitride), ZrN (zirconium nitride), TaC (tantalum carbide) and NbC (niobium carbide) having an average particle size of 1.5 μm was used. The other raw materials were the same as in Example 1. Moreover, the physical property measurement of the sintered compact and the friction stir welding test of the tool 10 were performed and evaluated by the same method as in Example 1. In addition, an iron resistance test was performed on the sintered body by the following method.
<Iron resistance test conditions>
SUS304 of 5 mm × 5 mm × 3 mmt was placed on a 12 mm × 12 mm × 5 mmt sintered body, and heated at 1000 ° C. for 30 minutes in a reducing atmosphere.

<Evaluation method>
The state of the sintered body after the iron resistance test was evaluated by visual observation. The case where there is no adhesion between the sintered body and SUS304 and separation is possible (highest evaluation), and the case where there is adhesion between the sintered body and SUS304, but the case where separation is possible is Δ (second evaluation) High), the case where there was welding between the sintered body and SUS304, and separation was impossible, was marked as x (lowest evaluation).

[Results of composition and physical property measurement of each sample]
As shown in FIG. 6, samples # 24 to # 32 are different from each other in the type of dispersed particles, and the other compositions are the same. Sample # 23 differs from the other samples in that it lacks dispersed particles. In all the samples of Example 3, the thermal conductivity was 34 W / mK or less, and the thermal shock fracture resistance coefficient was 8 kW / m or more.

[Test results]
In the iron resistance test, the samples # 24 to # 31 had good evaluation results of “◯” or “Δ”. In particular, Samples # 28 to # 31 had a better evaluation result of “◯”. On the other hand, Sample # 23 lacking dispersed particles and Sample # 32 containing silicon carbide as dispersed particles had an evaluation result of “X” in the iron resistance test, which was inferior to Samples # 24 to # 31. . Regarding the tool state, Samples # 24 to # 31 had good evaluation results of “◎” or “「 ”. In particular, Samples # 28 to # 31, in which the results of the iron resistance test were good, were also better because the evaluation result of the tool state was “◎”. On the other hand, the samples # 23 and # 32 both had a tool state evaluation result of “Δ”. Regarding the joined state, the evaluation results of all the samples # 24 to # 31 were “◯”. On the other hand, both of the samples # 23 and # 32 have an evaluation result of the bonding state of “x”, which is inferior to the samples # 24 to # 31.

  The following can be understood from the results of Example 3 described above. As the dispersed particles, any one of carbides, nitrides, and carbonitrides including any one of Group 4 elements, Group 5 elements, and Group 6 elements of the periodic table is used. By making it contain, the iron-resistant reactivity of a sintered compact can be improved. Moreover, the iron-resistant reactivity of a sintered compact can be improved more by containing any one of chromium nitride, zirconium nitride, tantalum carbide, and niobium carbide as dispersed particles. By improving the iron-resistant reactivity of the sintered body, wear of the tool 10 can be suppressed and the joined state of the members to be joined can be improved.

  As mentioned above, although embodiment and the Example of this invention were described, this invention is not limited to such an embodiment and an Example, A various structure can be taken in the range which does not deviate from the meaning. For example, the technical features in the embodiments and examples corresponding to the technical features in the embodiments described in the summary section of the invention are used to solve part or all of the above-described problems, or In order to achieve some or all of the effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Tool for friction stir welding 11 ... Main-body part 11e ... Tip part 12 ... Probe part 21 ... Joined member 22 ... Joined member X ... Axis WA ... Joining area WL ... Joining line

Claims (7)

A friction stir welding tool,
A friction stir welding tool comprising a ceramic having a thermal conductivity of 34 W / mK or less and a thermal shock fracture resistance coefficient of 8 kW / m or more. The friction stir welding tool according to claim 1,
The ceramics are
At least one of sialon and silicon nitride;
A sintering aid,
At least one of a carbide, nitride, and carbonitride of a Group 4 element, a Group 5 element, or a Group 6 element in the periodic table;
A friction stir welding tool, comprising: The friction stir welding tool according to claim 2,
The content of at least one of the carbide, the nitride, and the carbonitride is:
A friction stir welding tool characterized by being 0.1 volume% or more and 25 volume% or less. The friction stir welding tool according to claim 3,
The content of at least one of the carbide, the nitride, and the carbonitride is:
A friction stir welding tool characterized by being 0.1 volume% or more and 10 volume% or less. The friction stir welding tool according to any one of claims 2 to 4,
The content of the sintering aid is
A friction stir welding tool characterized by being 0.7 volume% or more and 15 volume% or less. The friction stir welding tool according to claim 5,
The content of the sintering aid is
A friction stir welding tool characterized by being in a range of 3.5% by volume to 15% by volume. The friction stir welding tool according to any one of claims 2 to 6,
At least one of the carbide, the nitride, and the carbonitride is:
A friction stir welding tool comprising at least one of titanium nitride, titanium carbide, titanium carbonitride, tungsten carbide, chromium nitride, zirconium nitride, tantalum carbide, and niobium carbide.

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