JP2017209716A - Friction agitation joining tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of attaining high durability.SOLUTION: In a friction agitation joining tool, which is a friction agitation joining tool containing silicon nitride, particles formed of a carbide, a nitride or a boride belonging to group 4-6, and a grain boundary phase, Vickers hardness is 14 GPa or higher, and at least a part of the grain boundary phase is formed from oxynitride of a rare-earth element and silicon, and in the oxynitride, an X-ray intensity ratio to silicon nitride is 0.05 or higher and 1.0 or lower.SELECTED DRAWING: Figure 1

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 (for example, Patent Document 1). As a friction stir welding tool used for friction stir welding, Patent Document 1 discloses a friction stir welding tool formed of ceramics.

JP 2011-98842 A International Publication No. 2016/047376

  In recent years, friction stir welding has been used as a method of joining using frictional heat generated from a joining member. Application to aluminum alloy bonding has progressed, and future expansion to steel bonding is expected. In order to obtain excellent weldability in the friction stir welding, it is necessary to sufficiently plastically flow steel. Therefore, the friction stir welding tool is required to have excellent heat resistance and wear resistance. Silicon nitride is a promising candidate material for friction stir welding of steel, and for silicon nitride, its composition has been studied for the purpose of improving fracture toughness and chemical resistance. However, in the friction stir welding tool described in Patent Document 1, the grain boundary phase of silicon nitride is made of a glass phase having low heat resistance and mechanical properties. Durability was not sufficient simply by improving the fracture toughness of the sintered body by dispersing the second phase and by dispersing the dispersed particles in the structure and improving the chemical resistance. . Such a problem is not limited to the friction stir welding tool used for joining steel, but is a problem common to the friction stir welding tool.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms.

(1) According to one aspect of the present invention, a friction stir welding tool is provided. This friction stir welding tool is a friction stir welding tool including silicon nitride, particles formed from a group 4-6 carbide, nitride, or boride, and a grain boundary phase, and has a Vickers hardness. Is 14 GPa or more, and at least a part of the grain boundary phase is formed of an oxynitride of a rare earth element and silicon, and the oxynitride has an X-ray intensity ratio of 0.05 or more to the silicon nitride. It is 1.0 or less. According to the friction stir welding tool of this embodiment, high durability can be realized.

(2) In the friction stir welding tool of the above aspect, the oxynitride is YSiO ₂ N,
The oxynitride may have an X-ray intensity ratio of 0.3 to 1.0 with respect to the silicon nitride. According to the friction stir welding tool of this embodiment, higher durability can be realized.

(3) The friction stir welding tool of the above aspect may be used for friction stir welding of steel materials. According to this form of friction stir welding tool, it can be used for friction stir welding of steel materials.

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 perspective view which illustrated the whole structure of the tool for friction stir welding. It is the figure which illustrated the use condition of the tool. It is the flowchart which showed an example of the manufacturing method of a tool. It is explanatory drawing which shows the composition of each sample, a physical property, and a test result. It is a figure which shows the test result when not grinding.

A. Embodiment:
A-1. Tool configuration:
FIG. 1 is a perspective view illustrating the overall configuration of a friction stir welding tool. 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). When the tool 10 is used, first, the probe unit 12 is disposed above the stacked members 21 and 22 (see FIG. 2A), and the probe unit 12 is rotated about the axis X. The probe portion 12 of the tool 10 receives pressure from the joining device and is pushed into the joined members 21 and 22 while being rotated from above (see FIG. 2B). After that, by continuing to rotate the probe unit 12 around the axis X while the probe unit 12 is pushed into the bonded members 21 and 22, the region of the bonded members 21 and 22 near the probe unit 12 is Plastic flow due to frictional heat. When the probe portion 12 agitates the plastic flowed portions of the members to be joined 21 and 22, a joining region is formed (see FIG. 2C). The joined members 21 and 22 are joined to each other by the joining region. Then, the friction stir welding is completed by pulling out the probe portion 12 from the members 21 and 22 to be joined. In the present embodiment, the joined members 21 and 22 are steel plates, but may be other arbitrary metals such as aluminum instead of steel.

The tool 10 includes (i) silicon nitride (Si ₃ N ₄ ), (ii) particles formed from a group 4-6 carbide, nitride, or boride, and (iii) a grain boundary phase. Here, the “grain boundary phase” refers to a portion where a boundary between crystal grains appears. The grain boundary phase is a portion that looks like a mesh when observed with an optical microscope. Note that particles formed from Group 4-6 carbide, nitride, or boride are also simply referred to as “dispersed particles”.

  In the present embodiment, titanium nitride (TiN) particles are used as particles (dispersed particles) formed from Group 4-6 group carbide, nitride, or boride. From the viewpoint of improving the durability of the tool 10, the content of the dispersed particles is preferably 0.1% by volume or more, and preferably 60% by volume or less. In this specification, “volume%” means the ratio of each substance when the total volume of all the substances contained in the sintered body or the 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.

  Examples of the group 4 element include titanium (Ti), zirconium (Zr), hafnium (Hf), and the like. Examples of Group 5 elements include vanadium (V), niobium (Nb), and tantalum (Ta). Examples of the group 6 element include chromium (Cr), molybdenum (Mo), tungsten (W), and the like. For this reason, examples of particles formed from Group 4-6 carbide, nitride, or boride include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and titanium boride (TiB2). ), Zirconium carbide (ZrC), zirconium nitride (ZrN), zirconium carbonitride (ZrCN), niobium carbide (NbC), tantalum carbide (TaC), tantalum nitride (TaN), tantalum carbonitride (TaCN), chromium nitride (CrN) ) And tungsten carbide (WC).

At least a part of the grain boundary phase of the tool 10 is formed of an oxynitride of a rare earth element and silicon. Oxynitrides of rare earth elements and silicon can be represented as ReSiO ₂ N, Re ₂ Si ₃ O ₃ N ₄ (rare earth elements are denoted as Re). Here, the rare earth element is an element formed from scandium (Sc), yttrium (Y), and a lanthanoid. Examples of lanthanoids include lanthanum (La), cerium (Ce), and praseodymium (Pr). Examples of oxynitrides of rare earth elements and silicon include YSiO ₂ N, Y ₂ Si ₃ O ₃ N ₄ , YbSiO ₂ N, Yb ₂ Si ₃ O ₃ N ₄ , DySiO ₂ N, and Dy ₂ Si ₃ O _{3. N 4, ErSiO 2 N, Er} 2 Si 3 O 3 N 4, LuSiO 2 N, and the like _{Lu 2 Si 3 O 3 N 4} . In the present embodiment, YSiO ₂ N is used as the oxynitride of rare earth elements and silicon.

The oxynitride of rare earth element and silicon has an X-ray intensity ratio with respect to silicon nitride (Si ₃ N ₄ ) of 0.05 or more and 1.0 or less. In this specification, the X-ray intensity ratio R with respect to silicon nitride (Si ₃ N ₄ ) is calculated by the following equation (1).
R = P1 / P2 (1)
(P1 is a peak measured by an X-ray diffractometer, and shows the intensity of the peak showing the highest intensity among peaks showing oxynitrides of rare earth elements and silicon. P2 is an X-ray diffractometer. (It shows the intensity of the peak measured by the above and showing the highest intensity among the peaks showing β silicon nitride (Si ₃ N ₄ ).)

By setting the X-ray intensity ratio R to silicon nitride (Si ₃ N ₄ ) to be 0.05 or more, the wear resistance and high temperature characteristics of the tool 10 can be improved, so that the chemical wear resistance of the tool 10 is improved. Can be improved. On the other hand, when the X-ray intensity ratio R with respect to silicon nitride (Si ₃ N ₄ ) is 1.0 or less, the chemical wear resistance and the strength of the tool 10 can be compatible.

The X-ray intensity ratio R with respect to silicon nitride (Si ₃ N ₄ ) can be adjusted, for example, by changing the temperature and time of heat treatment when the tool 10 is manufactured. For example, the X-ray intensity ratio R with respect to silicon nitride (Si ₃ N ₄ ) can be increased by increasing the heat treatment temperature or increasing the heat treatment time. On the other hand, the X-ray intensity ratio R with respect to silicon nitride (Si ₃ N ₄ ) can be reduced by lowering the heat treatment temperature or shortening the heat treatment time. The X-ray intensity ratio R with respect to silicon nitride (Si ₃ N ₄ ) is preferably 0.3 or more from the viewpoint of further improving the durability of the tool 10.

  The tool 10 has a Vickers hardness of 14 GPa or more. In this specification, the Vickers hardness indicates a value measured at room temperature (25 ° C.) by a measurement method defined in JIS R1610. The test load when measuring the Vickers hardness is 10 kgf.

  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 chemical 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 sintering aid preferably contains at least one of aluminum oxide (Al ₂ O ₃ ) and aluminum nitride (AlN). By containing aluminum oxide, since aluminum and oxygen are dissolved in silicon nitride and silicon nitride is sialonized, 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 (Y ₂ O ₃ ), ytterbium oxide (Yb ₂ O ₃ ), dysprosium oxide (Dy ₂ O ₃ ), and the like. In this embodiment, yttrium oxide (Y ₂ O ₃ ) and aluminum oxide (Al ₂ O ₃ ) are used as sintering aids.

  According to the friction stir welding tool 10 of the present embodiment, chemical wear and mechanical wear due to a chemical reaction with the material to be joined can be reduced. That is, according to the friction stir welding tool 10 of the present embodiment, both chemical wear resistance and strength can be achieved, and thus durability can be improved.

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.

Titanium nitride (TiN) powder as particles (dispersed particles) formed from silicon nitride (Si ₃ N ₄ ) powder as a main raw material of ceramic sintered body and 4-6 group carbide, nitride, or boride And yttrium oxide (Y ₂ O ₃ ) and aluminum oxide (Al ₂ O ₃ ) powder as sintering aids are weighed (step S110). Thereafter, the raw material powders are mixed and pulverized to produce a slurry (step S120). For 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. Test results:
Hereinafter, the present invention will be described in detail using a sample of a friction stir welding tool, but the present invention is not limited to these examples.

[Production of sintered bodies and tools]
FIG. 4 is an explanatory diagram showing the composition, physical properties, and test results of each sample. Silicon nitride (Si ₃ N ₄ ) raw material having an average particle diameter of 0.1 μm as a main raw material, titanium nitride (TiN) raw material having an average particle diameter of 0.6 μm as dispersed particles, and an average particle diameter of 1.0 μm as a sintering aid The yttrium oxide (Y ₂ O ₃ ) raw material and the aluminum oxide (Al ₂ O ₃ ) raw material having an average particle diameter of 0.7 μm 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. For example, when yttrium oxide is 7% by volume, it is blended so that 3% by volume of aluminum oxide is contained. FIG. 4 shows the total volume% of yttrium oxide and aluminum oxide.

  Each sample was produced as follows. First, 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 cold isostatic pressing (CIP treatment) to produce a molded body.

Thereafter, primary firing (1650 ° C. to 1750 ° C., 2 hours) is performed in a nitrogen atmosphere of 1 kPa to 9 kPa, and then hot isostatic pressing (HIP treatment) (1650 ° C. to 1750) in a nitrogen atmosphere of 1 MPa. The sintered compact was produced by performing 2 degreeC). Thereafter, heat treatment (1500 ° C. to 1700 ° C., 2 hours) was performed in a nitrogen atmosphere. By this heat treatment, a YSiO ₂ N phase or a Y ₂ Si ₃ O ₃ N ₄ phase was generated as a grain boundary phase. The prepared sintered body was ground to prepare a sample. The number of samples for each sample was 1. Sample 16 was subjected to a heat treatment temperature of 1800 ° C. higher than other samples in order to reduce the Vickers hardness.

[Measurement of physical properties of sintered body]
The Vickers hardness was measured for the prepared sample. This measurement was performed by the same method as in the above-described embodiment.

[Evaluation test]
An evaluation test was performed on the prepared samples. Similarly to the state shown in FIG. 2, the steel plates as the members to be joined were stacked, and spot welding was performed by pressing a tool against these steel plates. The evaluation test was performed under the following conditions.
<Test conditions>
-Member to be joined: SUS304 (thickness 2 mm)
・ Shielding gas: Argon (Ar)
・ Descent speed: 0.5 mm / s
・ Tool push-in amount: 1 × 10 ³ kgf
・ Rotation speed: 600rpm
・ Retention time: 1 sec
・ RBI: 60
Here, the “shield gas” refers to a gas disposed in the test space in order to break the contact between the material to be joined and air during the test. “Descent speed” indicates a speed at which the tool 10 is brought close to the member to be joined. The “tool indentation load” indicates an indentation load of the tool 10 on the member to be joined. “Rotational speed” indicates the rotational speed of the tool 10. “Holding time” indicates the time during which the tool 10 is held in a state where the pressing load of the tool 10 on the member to be joined is involved. “RBI” indicates the number of repetitions of this test.

<Evaluation method>
The tool state after the test was evaluated. The tool state was evaluated by measuring the length along the axis X before and after the test of the tip portion 11e and the probe portion 12. Judgment criteria are shown below. As the determination, ◎ is the highest evaluation, and the evaluation is decreased in the order of ◯, Δ, ×.
-A: The wear amount of the tip portion 11e is 0.2 mm or less, and the wear amount of the probe portion 12 is 0.05 mm or less.-: The wear amount of the tip portion 11e is greater than 0.2 mm and less than 0.3 mm, and The wear amount of the probe portion 12 is larger than 0.05 mm and less than 0.2 mm. Δ: The wear amount of the tip portion 11 e is 0.3 mm or more and less than 0.5 mm, and the wear amount of the probe portion 12 is 0.2 mm or more and 0.2 mm. Less than 5 mm x: (i) Wear amount of tip portion 11e is 0.5 mm or more and wear amount of probe portion 12 is 0.5 mm or more, or (ii) Sample is damaged

[Results of composition and physical property measurement of each sample]
In FIG. 4, those satisfying the following requirements are shown as examples, and those not satisfying the following requirements are shown as comparative examples.
・ Containing particles formed from group 4-6 carbide, nitride, or boride ・ Vickers hardness of 14 GPa or more ・ At least part of the grain boundary phase is an oxynitride of a rare earth element and silicon The oxynitride of rare earth element and silicon has an X-ray intensity ratio with respect to the silicon nitride of 0.05 to 1.0.

  As shown in FIG. 4, samples 4, 6-9, and 11-15 satisfy the above requirements, and samples 1-3, 5, 10, and 16 do not satisfy the above requirements. That is, Samples 1 and 2 are comparative examples because they do not contain titanium nitride (TiN), which is a particle formed from a Group 4-6 carbide, nitride, or boride, and Sample 3 is a grain boundary phase. This is a comparative example because it does not include a phase formed from an oxynitride of a rare earth element and silicon. Samples 5 and 10 are comparative examples because the X-ray intensity ratio R is less than 0.05 or greater than 1.0, and sample 16 is a comparative example because the Vickers hardness is less than 14 Gpa.

  Examples satisfying the requirements of the present embodiment were evaluated as “◯” or “も し く は” in the joining test. This result shows that the durability of the friction stir welding tool 10 corresponding to the example is high. The reason for this is that a part of the grain boundary glass phase of silicon nitride having low heat resistance or the like is made into a grain boundary phase of an oxynitride of a rare earth element and silicon, resulting in a chemical reaction with the material to be joined. It is considered that chemical wear and mechanical wear can be reduced and durability can be improved.

FIG. 5 is a diagram showing a test result when grinding is not performed on at least one of the tip portion 11e and the probe portion 12 with respect to the manufactured sintered body. Specifically, (i) the sample 17 is a sample that is not ground at both the tip portion 11e and the probe portion 12, and (ii) the sample 18 is a sample that is not ground only at the tip portion 11e. Yes, (iii) The sample 19 is a sample in which only the probe portion 12 is not ground. YSiO ₂ N was formed as the grain boundary phase in the part subjected to the cutting process, but Y ₂ Si ₃ O ₃ N ₄ was added to the part not subjected to the cutting process in addition to the YSiO ₂ N phase as the grain boundary phase. A phase was formed. Since the strength of Y ₂ Si ₃ O ₃ N ₄ is larger than the strength of YSiO ₂ N in the portion where the samples 17 to 19 are not ground, the X-ray intensity ratio R is Y ₂ Si ₃ O ₃ N _4. Was calculated using the intensity of. From this result, it can be seen that good durability can be obtained without cutting. When cutting is not performed, the number of steps is reduced, which is preferable because the manufacturing cost can be reduced.

  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.

C. Variations:
In the above-described embodiment, the friction stir welding tool 10 is used for friction stir welding of steel materials, but the present invention is not limited to this. The friction stir welding tool 10 may be used for friction stir welding of materials other than steel materials. Examples of the material other than the steel material include aluminum.

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

Claims (3)

Silicon nitride,
Particles formed from Group 4-6 carbides, nitrides, or borides;
A friction stir welding tool including a grain boundary phase,
Vickers hardness is 14 GPa or more,
At least a part of the grain boundary phase is formed of an oxynitride of a rare earth element and silicon,
The tool for friction stir welding, wherein the oxynitride has an X-ray intensity ratio with respect to the silicon nitride of 0.05 to 1.0. The friction stir welding tool according to claim 1,
The oxynitride is YSiO ₂ N;
The friction stir welding tool, wherein the oxynitride has an X-ray intensity ratio of 0.3 to 1.0 with respect to the silicon nitride. The friction stir welding tool according to claim 1 or 2,
A friction stir welding tool used for friction stir welding of steel materials.

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