JP4607133B2 - Friction stir processing tool and method of manufacturing friction stir processed product - Google Patents

Description

  The present invention relates to a friction stir processing tool used for friction stir processing of titanium or a titanium alloy, and a method of manufacturing a friction stir processed product made of titanium or a titanium alloy using the tool. Here, the friction stir processing includes processing technologies for both friction stir welding and friction stir modification.

  Titanium and titanium alloys are lightweight and have high specific strength, heat resistance, high corrosion resistance, non-magnetic properties, and biocompatibility, so they are used as a very useful metal material in many applications such as aircraft, chemical plants, and artificial bones. It has been. Titanium and titanium alloy welding is not easy due to its high affinity with oxygen, and TIG welding using tungsten and an inert gas is usually used for this welding. However, TIG welding requires a high level of welding technology, yet is not sufficient in terms of processing quality such as joint defects and flatness of the joint surface, and there is still room for improvement.

  On the other hand, the probe of the tool is pushed firmly into the work piece and rotated at a high speed, and the work material (made of metal) in the vicinity of the probe is plasticized by the frictional heat generated at that time, and stirred and fluidized. Techniques for joining processed materials or processing techniques for controlling the crystal grain size to be small and thereby improving the strength and hardness of the processed materials have been developed. The former is called Friction Stir Welding, and the latter is called Friction Stir Processing (see Patent Documents 1 and 2).

  According to the friction stir welding, since the frictional heat between the tool and the material to be joined is used for joining, the highest temperature does not reach the melting point and the joining is performed in a solid state, so arc welding (TIG welding) or the like. Compared to fusion welding, there are advantages such as less strength reduction at the joint, fewer joint defects such as thermal distortion, pores and cracks, and a relatively flat joint surface. It has been put to practical use in the fields of railway vehicles, ships, civil engineering structures and automobiles.

Hard tool steel is mainly used for friction stir processing of relatively low melting point metal materials such as aluminum and its alloys, but application to friction stir processing for high melting point metal materials is also being developed. . For example, for joining steel plates, an example using a tungsten-rhenium alloy tool, an example using sialon which is a composite material of Si ₃ N ₄ and Al ₂ O ₃ , and polycrystalline cubic boron nitride were used. Examples have been reported. In these tool materials, tool wear, breakage, mixing of the tool material into the work material, and the like are problems.

In particular, as a tool material suitable for friction stir processing of titanium and titanium alloy, which are very useful high melting point metal materials, the following Non-Patent Document 1 proposes a tool material made of a tungsten-rhenium alloy. However, since both tungsten and rhenium are expensive metals, they are problematic in practical use as tool materials used for friction stir processing.
Japanese Patent No. 2712838 JP 2003-64458 A Zachary Loftus, Jennifer Takeshita, Dr. Anthony Reynolds, Dr. Wei Tang 'An Overview of Friction Stir Welding TIMETAL 213 Beta Titanium', 5th International Symposium on Friction Stir Welding, Metz, TWI, 2004.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide an inexpensive tool for friction stir processing of titanium or titanium alloy and titanium or titanium alloy using the tool. Another object of the present invention is to provide a method for producing a friction stir processed product made of titanium or a titanium alloy that can be bonded or modified at low cost.

  The above object can be achieved by a friction stir processing tool for titanium or a titanium alloy having the following characteristics and a method for manufacturing a friction stir processed product.

  That is, the invention according to claim 1 is a friction stir processing tool for titanium or a titanium alloy, wherein the surface of a friction stir processing tool made of a nickel alloy is surface-treated by fluorine ion implantation. .

  The invention according to claim 2 is the friction stir processing tool according to claim 1, wherein the nickel alloy is made of an alloy containing nickel and containing at least chromium and iron. It is a tool for stirring processing.

  The invention according to claim 3 is the friction stir processing tool according to claim 1 or 2, wherein the fluorine ion implantation is performed at a pulse frequency of 1 to 2 kHz at room temperature under an implantation time of 150 to 400 minutes. This is a friction stir processing tool for titanium or a titanium alloy.

  The invention according to claim 4 is the friction stir processing tool according to claim 1 or 2, wherein the fluorine ion implantation is performed at a pulse frequency of 1 to 2 kHz at room temperature under an implantation time of 300 to 400 minutes. This is a friction stir processing tool for titanium or a titanium alloy.

  The invention according to claim 5 is a method for producing a friction stir processed product, characterized in that titanium or a titanium alloy is friction stir processed using the friction stir processing tool according to any one of claims 1 to 4. It is.

Hereinafter, the present invention will be described in detail with reference to the drawings.
1A and 1B show an example of a friction stir processing tool of the present invention, in which FIG. 1A is a plan view viewed from the tip side of the tool, and FIG. 1B is a cross-sectional view taken along line bb in FIG. In FIG. 1, the friction stir processing tool 1 includes a gripping portion 2, a flange portion 3, a protruding portion 4 having a shoulder surface 4a, and a probe 5. The grip part 2 is a part for attaching the friction stir processing tool 1 to the friction stir processing apparatus. The flange portion 3 is provided for improving the handleability and strength of the friction stir processing tool 1, but is not necessarily required.

  The protruding portion 4 is usually cylindrical, and is provided so that the probe 5 protrudes from the central portion of the distal end surface. A portion of the tip surface of the protruding portion 4 excluding a portion where the probe 5 is provided is a shoulder surface 4a. The shoulder surface 4a is a surface that comes into contact with the surface of the workpiece during the friction stir processing, and a surface that is slightly conical with respect to the probe 5 is used. A slightly conical protrusion can also be used.

  The probe 5 may have a truncated cone shape instead of a cylindrical shape. The screw may be cut off, or the side surface or the slope may be chamfered. The diameter of the protrusion 4 is preferably about 12 to 25 mm, and the height is preferably about 9 to 10 mm. The diameter of the probe 5 is about 5 to 10, and the length depends on the thickness of the workpiece, but the tip of the probe 5 is processed. The tip of the probe 5 is preferably inserted deeply into the workpiece so as not to come into contact with the surface plate that supports the material. For example, when a workpiece having a thickness of about 3 to 6 mm is used, a probe having a length of about 2.8 to 5.9 mm is preferably used.

  In the present invention, at least the protruding portion 4 and the probe 5 of the friction stir processing tool 1 are made of a nickel alloy, and the surface thereof is surface-treated by fluorine ion implantation. Here, the fluorine ion implantation uses an ion implantation apparatus such as an omnidirectional ion implantation apparatus, accelerates the fluorine ions to collide with the surface of the tool 1, and causes the fluorine ions to penetrate into the surface portion of the tool 1. The object is to improve the physical properties of the surface portion of the tool 1.

  Here, the nickel alloy is an alloy containing nickel as a main component, and has high hardness and high heat resistance. The nickel alloy includes a multiphase intermetallic compound based on nickel. The nickel alloy is preferably an alloy based on nickel and containing at least chromium and iron. As an alloy containing nickel and containing at least chromium and iron, for example, Inconel (trade name) of International Nickel Company is preferable.

  Inconel is based on nickel and can be classified into various types such as Inconel 600, Inconel 625, Inconel 718, and Inconel X750, depending on the amount of alloying elements such as iron, chromium, niobium, molybdenum, titanium, and aluminum. As the inconel alloy, one having a composition of 76Ni-16Cr-8Fe is particularly preferable. The reason why Inconel alloy is particularly suitable is that it has high strength at high temperatures, has toughness, has moderate workability in tool fabrication, is inexpensive, and is easily available.

  In order to prevent wear and wear of the tool during friction stir processing, it is essential for the tool in the present invention that the surface of the tool made of nickel alloy is surface-treated by fluorine ion implantation. Surface hardening is performed by fluorine ion implantation, and high hardness is developed. Due to this high hardness, a higher hardness is obtained compared to nitrogen ion implantation and carbon ion implantation, the wear resistance is remarkably improved, and the tool can withstand long-time friction stir processing. For the fluorine ion implantation process, a normal ion implantation apparatus such as an omnidirectional ion implantation apparatus and conditions can be used. As the fluorine ion source, methane tetrafluoride is usually used, but is not limited thereto.

  In particular, in the surface treatment by fluorine ion implantation, the amount of ion implantation and the depth of ion implantation that have a significant effect on the physical properties of the hardened surface are important. If the surface modification is insufficient, the probe wears out during friction stir welding. However, the friction stir zone does not reach the bottom of the workpiece, and a linear unbonded portion called a kissing bond due to poor stirring may occur on the back side of the workpiece. For this reason, surface modification is important.

In the surface modification by fluorine ion implantation, if the ion implantation time is less than 150 minutes, the surface modification tends to be insufficient when processing a long distance. On the other hand, if the fluorine ion implantation time exceeds 400 minutes, the occurrence of kissing bonds can be avoided, but restrictions on the ion implantation apparatus and operating conditions arise. In particular, a by-product in the ion implantation operation is generated, and there is a risk that a defect may occur in the surface modification by the ion implantation. Also in the ion implantation apparatus used in the experiment of the present invention, it is possible to maintain a normal surface modified layer by performing the apparatus maintenance for 400 minutes as a limit. Not to do.
Therefore, the fluorine ion implantation time is preferably 150 to 400 minutes, more preferably 300 to 400 minutes. However, if the above limitations on the ion implantation apparatus are solved, fluorine ion implantation exceeding 400 minutes is possible. The ion implantation depth is preferably about 3 to 5 μm, and the ion implantation amount is preferably about 10 ¹⁶ to 10 ¹⁷ ions / cm ^2, but is not particularly limited.

  FIG. 2 is a partially cutaway perspective view showing an example of a method for producing a friction stir processed product of the present invention. In FIG. 2, the ends of two plate-like bodies 6 a and 6 b made of titanium or a titanium alloy are abutted with each other and placed on the surface plate 9 and fixed. The probe 5 of the friction stir processing tool 1 of the present invention as shown in FIG. 1 is press-fitted into the abutting portions 7 of the plate-like bodies 6a and 6b, and the shoulder surface 4a of the protruding portion 4 of the tool 1 and the plate-like body 6a and 6b are brought into contact with each other, and the vicinity of the abutting portion 7 of the plate-like bodies 6a and 6b is heated and softened by friction between the probe 5 and the shoulder surface 4a rotating at high speed.

  The tool 1 is continuously rotated while the probe 5 is press-fitted to stir the vicinity of the abutting portion 7 of the plate-like bodies 6a and 6b in the vicinity of the probe 5 while moving the tool 1 on the abutting portion 7 in the direction of arrow A. Let When the tool 1 moves, the portions including the abutting portions 7 of the plate-like bodies 6a and 6b generate frictional heat and are softened and stirred. And the part including the abutting part 7 of the plate-like bodies 6a and 6b after the projecting part 4 of the tool 1 is moved is joined, and the part is extremely shallow near a substantially circular shape due to the contact with the shoulder surface 4a. Lined arcuate scars 8 remain, as depressions are created and they are successively displaced and overlapped one after another.

  The probe advance angle of the tool 1 is generally set to about 1 to 5 °. The rotation speed of the tool 1 is generally set to appropriate conditions within a range of several hundred to several thousand rotations / minute, and the joining speed is generally within a range of several tens to several hundred mm / minute. In particular, in the present invention, the rotation speed of the tool 1 is preferably 600 to 800 rpm, and the joining speed is preferably 100 to 200 mm / min.

  The titanium or titanium alloy constituting the plate-like bodies 6a and 6b is pure titanium mainly composed of titanium or an alloy containing other components (Al, V, Sn, Cr, Mo, Zr, Ni, etc.), For example, industrial pure titanium having an α structure, Ti-6Al-4V alloy having an α-β structure, Ti-6Al-3Cr-3Sn-3Al alloy having a β structure, and the like may be titanium or a titanium alloy. There is no particular limitation.

  The tool 1 is used by being attached to a known friction stir welding apparatus composed of three machine axes including a platen axis (X), a transverse axis (Y), and a lifting / lowering axis (Z). Further, in processing of a workpiece having a three-dimensional curved surface, the machine axis of the surface plate axis (X), the transverse axis (Y), the lifting axis (Z), the swing axis (A), and the pivot axis (C). It is used by being attached to a known five-axis frame type friction stir welding apparatus comprising two tools. It can also be used by attaching it to a machine head mounted at the tip of a known robot arm having three joint axes and two rotation axes.

  In the above example, friction stir welding (FSW) for joining workpieces made of titanium or a titanium alloy has been described, but instead of two workpieces, one piece of titanium or titanium similar to this is used. Using a workpiece made of an alloy, the probe 5 of the tool 1 that rotates at a high speed is inserted with a strong force on the surface thereof, and the tool 10 is moved to the other end along the processing portion while rotating at a high speed. It can also be applied to friction stir reforming (FSP) in which a workpiece is reformed by plasticizing the processed portion by frictional heat and moving it while applying pressure by the shoulder surface 4a of the tool 1.

  In the friction stir processing tool of the present invention, the surface of the friction stir processing tool made of a nickel alloy is surface-treated by fluorine ion implantation. Since the tool is made of a nickel alloy, it has high hardness and high heat resistance. It is inexpensive compared to a conventional friction stir processing tool made of a tungsten-rhenium alloy. In addition, the surface of the tool made of nickel alloy is surface-treated by fluorine ion implantation, so that the surface is hardened, high hardness is developed and wear resistance is improved, and the tool can withstand long-time friction stir processing. Can do.

  Therefore, when the friction stir processing tool of the present invention is used, titanium or a titanium alloy, which is a high melting point metal material, can be satisfactorily friction stir processed. In particular, when fluorine ion implantation is performed at a pulse frequency of 1 to 2 kHz and at room temperature under conditions of implantation time of 150 to 400 minutes, preferably 300 to 400 minutes, surface hardening is reliably performed and high hardness is ensured. It develops and the wear resistance is remarkably improved, and the tool can withstand long-time friction stir processing.

  Further, the manufacturing method of the friction stir processed product of the present invention is a friction stir processing of titanium or a titanium alloy using the friction stir processing tool as described above, so that the friction stir processing made of a conventional tungsten-rhenium alloy is performed. A friction stir processed product made of titanium or a titanium alloy can be manufactured at a lower cost than that using a processing tool.

  Specific examples of the present invention will be given below. The present invention is not limited to these examples.

(Production of friction stir processing tool)
A tool was manufactured by cutting the INCONEL625 alloy into the shape shown in FIG. The protruding portion 4 of this tool is a cylindrical shape having a height of 9 mm and a diameter of 24 mm, and the probe 5 is provided at the center of the distal end surface of the protruding portion 4, and has a slightly tapered truncated cone shape. Rather, the three sides are chamfered and have a length of 2.8 mm and a diameter of 9.1 mm. The shoulder surface 4a has a slightly conical shape with the probe 5 at the center.

  On the surface of the tool manufactured in this way, using an omnidirectional ion implantation apparatus, gas type: methane tetrafluoride, gas pressure: 0.5 Pa, RF output 0.5 kW, pulse voltage: −20 kV, pulse frequency: Fluorine ions were injected under the conditions of 1 kHz, tool temperature: normal temperature, injection time: 300 minutes, and a friction stir processing tool 1 was produced.

(Comparative Example 1)
In Example 1, except that ammonia gas was used in place of tetrafluoromethane gas, nitrogen ions were implanted into the tool surface in the same manner as in Example 1 to produce a friction stir processing tool.

(Comparative Example 2)
A friction stir processing tool made of INCONEL625 alloy having the same shape as that of Example 1 was prepared. In this case, the surface treatment of fluorine ion implantation was not performed.

(Comparative Example 3)
A tool for friction stir processing made of a tungsten-rhenium alloy (rhenium content: 5% by weight) having the same shape as in Example 1 was prepared. In this case, the surface treatment of fluorine ion implantation was not performed.

(Friction stir welding test 1)
Using the friction stir processing tools obtained in Example 1 and Comparative Examples 1 to 3, friction stir welding was performed by the method shown in FIG. As plate-like bodies 6a and 6b to be friction stir welded, JIS class 2 industrial pure titanium plates (JIS H 4600, 2 types) having a length of 300 mm, a width of 75 mm and a thickness of 3 mm were used.

  The two plate-like bodies 6a and 6b are attached to the surface plate 9 of the friction stir welding apparatus (not shown) of the machine 3 axes of the surface plate axis (X), the transverse axis (Y), and the lifting and lowering axis (Z). The sides of 300 mm in length were butted together and fixed. Thereafter, the friction stir welding tool 1 of Example 1 was attached to the above friction stir welding apparatus, and argon was applied under the conditions of the rotation speed of the tool 1 of 600 rpm, the moving speed of 100 mm / min, the load load of 2 tons, and the advance angle of 3 degrees. The butt 7 was subjected to friction stir welding over a distance of 230 mm in a gas injection environment.

  Thereafter, the plate-like bodies 6a and 6b are removed from the platen 9 of the friction stir welding apparatus, and then the plate-like bodies 6a and 6b similar to the above are newly attached to the platen 9 in the same manner as described above. Friction stir welding was performed in the same manner as above except that the rotation speed was 800 rpm and the moving speed was 50 mm / min.

  Next, in place of the friction stir processing tool 1 of Example 1, the tool rotation speed was 600 rpm and moved in the same manner as above except that the friction stir processing tool prepared in Comparative Examples 1, 2, and 3 was used. Friction stir welding was performed under conditions of a speed of 100 mm / min, a rotation speed of 800 rpm, and a moving speed of 50 mm / min.

  The external appearance photograph of the butted part of the plate-like body obtained by friction stir welding is shown in FIGS. FIG. 3 shows a friction stir weld with a rotational speed of 600 rpm and a moving speed of 100 mm / min, and FIG. 4 shows a friction stir weld with a rotational speed of 800 rpm and a moving speed of 50 mm / min.

  The appearance photograph of the butted portion is the front side viewed from the side where the probe 5 is press-fitted (front side), and the side viewed from the side opposite to the side where the probe 5 is pressed-in (back side) as back side. Indicated. The friction stir processing tool (Tool) used was shown as Inconel (Fion injected) in Example 1, Inconel (N + C ion injected) in Comparative Example 1, and simply Inconel in Comparative Example 2.

  As can be seen from FIG. 3, in the front side, the butt portion is joined in any of the tools of Example 1, Comparative Example 1 and Comparative Example 2. However, in the back side, using the tool of Comparative Example 2 (shown as simply Inconel at the left end), the joining of the butt portion is insufficient, and the butt line is clearly observed. However, in the Inconel (Fion injected) of Example 1 and the Inconel (N + Cion injected) of Comparative Example 1, the butt line is not clearly observed, and It can be seen that the joining is sufficiently advanced.

  Referring to FIG. 4, in the front side, the butt portion is joined in any of the tools of Example 1, Comparative Example 1, and Comparative Example 2. However, in the back side, the one using the tool of Comparative Example 2 (shown simply as Inconel on the left end) is insufficient in joining the butt portion of the circled portion near the right end, Although the line is clearly observed, in the case of Inconel (Fion injected) of Example 1, the butt line is not observed, and it can be seen that the joining of the butt portion is sufficiently advanced.

  In the case of Inconel (N + C ion injected) of Comparative Example 1, a butting line is observed in the circled portion near the right end, but it is not clearer than that of the tool of Comparative Example 2, and Although the joining of the butt portion is proceeding more than that of the first embodiment, it can be seen that the joining state of the butt portion is inferior to that of Example 1.

(Friction stir welding test 2)
The friction stir processing tool 1 of Example 1 that was the best in the friction stir welding test 1 was used as it was, and the welding conditions that were the best in the friction stir welding test 1 above, that is, the rotation speed of the tool was 600 rpm. Friction stir welding was performed on the butt 7 over a distance of 230 mm under an argon gas injection environment under the conditions of a moving speed of 100 mm / min, a load of 2 tons, and a forward angle of 3 degrees. After cooling, remove the tool 1 from the friction stir welding apparatus, replace the plate-like bodies 6a and 6b with new ones, perform the same operation, repeat this operation twice, and perform friction stir welding over a total distance of 690 mm. It was.

  In addition, the friction stir welding tool tool made of the tungsten-rhenium alloy of Comparative Example 3 was used instead of the tool of Example 1, and the friction stir welding was performed over a total distance of 690 mm in the same manner as above. .

  The appearance of the abutting part of the plate-like bodies 6a and 6b is that the surface side where the probe 5 is press-fitted and the back side opposite to the side where the probe 5 is pressed-in are both joined by friction stirring. No difference was found between the one using the friction stir processing tool of Example 1 and the one using the tungsten-rhenium alloy tool of Comparative Example 3. Moreover, when the external appearance of the tool after completion | finish of friction stir welding was observed, the tool which consists of the tungsten-rhenium alloy of the comparative example 3 used what also used the tool for friction stir processing of Example 1 for the abrasion state of a tool. There was no difference between the two.

  Aiming at optimization of fluorine ion implantation conditions, gas type: tetrafluoromethane, gas pressure: 0.5 Pa, RF output 0.5 kW, pulse voltage: -20 kV, tetrafluoromethane injection time, pulse frequency, By changing the tool temperature as shown in Table 1 below, four types of friction stir processing tools were prepared under four conditions 1 to 4, and the welding conditions that were considered to be the best in the first embodiment, that is, the tool Friction stir welding was performed in a single operation over a distance of 230 mm under the argon gas injection environment under the conditions of a rotational speed of 600 rpm, a moving speed of 100 mm / min, a load of 2 tons, and a forward angle of 3 degrees. An external view photograph of the butted portion of the obtained plate-like body is shown in FIG.

The tensile strength test of the butted part of the obtained plate-like body was performed.
As shown in FIG. 6, the numbers 1 to 5 were cut from the bonded sample into the sample shape shown in FIG. 7 with the longitudinal axis direction perpendicular to the bonding line. This was set in a tensile strength tester and measured at room temperature under the condition of a crosshead speed of 3 mm / min. Table 1 shows the average values of the samples of Nos. 1 to 5 (collecting positions). In addition, the tensile strength of the JIS class 2 industrial pure titanium plate (JIS H 4600 type 2) itself was 374 MPa.

  In addition, the weight loss of the tool was measured. As described above, the friction stir welding was performed on the butt portion 7 over a distance of 230 mm under the argon gas injection environment under the conditions of the rotational speed of the tool of 600 rpm, the moving speed of 100 mm / min, the applied load of 2 tons, and the forward angle of 3 degrees. However, after cooling, the tool 1 was removed from the friction stir welding apparatus and the weight of the tool before and after the friction stir welding was measured to determine the weight loss. The amount of wear (g) is shown in Table 1. In addition, in condition 1 (injection time 300 minutes), the friction stir welding operation was repeated three times and the friction stir welding was performed over a total distance of 690 mm. It was 796 g. Further, in the condition 3 (injection time 150 minutes), when the friction stir welding operation was repeated three times and the friction stir welding was performed over a total distance of 690 mm, the tool wear amount was 0.995 g.

  Surface treatment by fluorine ion implantation focuses on the ion implantation amount and ion implantation depth that have a significant effect on physical properties, and condition 2 (standard condition) is used as a reference, and condition 2 has a larger fluorine ion implantation amount than condition 1 Condition 3, Condition 3 is a condition in which the amount of fluorine ion implantation is smaller than that in Condition 1, Condition 4 is a condition in which the amount of fluorine ion implantation is smaller than that in Condition 1, but the diffusion distance is wide (condition where the ion implantation depth is deep) )It was set.

  In FIG. 5, F1 condition is a friction stir welding photograph according to condition 1 in Table 1. The front viewed from the side where the probe 5 is press-fitted (front side) is the front side, and the side opposite to the side where the probe 5 is press-fitted (back side) The side viewed from the side is shown as back. Similarly, F2 condition represents condition 2 in Table 1, F3 condition represents condition 3 in Table 1, and F4 condition represents condition 4 in Table 1. As is apparent from FIG. 5, the appearance of joining the front side and the back side is good, and no significant difference is observed between the conditions. However, as is apparent from Table 1, Condition 1 is the best when the measurement results of tensile strength, elongation, and tool wear amount are taken into consideration.

  Furthermore, with the aim of optimizing the fluorine ion implantation conditions, gas type: tetrafluoromethane, gas pressure: 0.5 Pa, RF output 0.5 kW, pulse voltage: -20 kV, pulse frequency: 1 kHz, tool temperature: Four types of friction stir processing tools were prepared under four conditions of normal temperature and injection time of chlorotetrafluoromethane of 150 minutes, 200 minutes, 250 minutes, and 300 minutes. Friction stir welding was performed over a distance of 230 mm in an argon gas injection environment under the conditions, that is, the rotational speed of the tool was 600 rpm, the moving speed was 100 mm / min, the applied load was 2 tons, and the advance angle was 3 degrees.

  The external appearance photograph of the butted part of the obtained plate-like body is shown in FIGS. Here, FIG. 8 is a front side photograph after friction stir welding when the injection time is 150 minutes, and FIG. 9 is a back side photograph thereof. FIG. 10 is a front side photograph after friction stir welding when the injection time is 200 minutes, and FIG. 11 is a back side photograph thereof. FIG. 12 is a front side photograph after friction stir welding when the injection time is 250 minutes, and FIG. 13 is a back side photograph thereof. FIG. 14 is a front side photograph after friction stir welding when the injection time is 300 minutes, and FIG. 15 is a back side photograph thereof.

  As is apparent from FIGS. 8 to 15, the appearance of bonding between the front surface side and the back surface side was good in all cases. In observing the butt line on the back side, it becomes a problem whether the butt line is clear or not. When the bonding is good, the agitation is sufficiently performed even on the back surface, which is the surface farthest from the tool, and the butt line is not completely lost, but is not clear. 9, 11, 13, and 15, as the fluorine ion implantation time becomes longer, the range in which the butt line disappears becomes longer and the joining operation in which the butt line is recognized is seen. Even in the second half, the range becomes shorter and the butt line becomes unclear. From these results, it can be said that a better bonding state can be obtained with a tool having a longer fluorine ion implantation time.

  As described above, the longer the fluorine ion implantation time, the better the bonding state. However, when the implantation time exceeds 400 minutes, there are restrictions on the ion implantation apparatus and operating conditions. In particular, by-products are generated in the ion implantation operation, and there is a risk that defects may occur in surface modification by ion implantation. Also in this ion implantation apparatus, it is possible to maintain a normal surface modified layer by performing maintenance of the apparatus for 400 minutes as a limit. Therefore, it is preferable not to exceed 400 minutes.

Further, the shoulder surface 4a of the tool after performing the friction stir welding operation under the condition of 300 minutes of the fluorine ion implantation time was measured at five locations with a Vickers hardness tester under a load of 0.49N. The average Vickers hardness was 790 (Hv). In addition, when fluorine ion implantation was not performed, the average Vickers hardness was 233 (Hv).
Considering the above test results comprehensively, the optimum fluorine ion implantation time is determined to be 150 to 400 minutes, preferably 300 to 400 minutes.

An example of the tool for friction stir processing of this invention is shown, (a) is the top view seen from the front end side of the tool, (b) is sectional drawing in the bb line of (a). It is a partially cutaway perspective view showing an example of a method for producing a friction stir processed product of the present invention. It is an external appearance photograph of the butting part of the plate-like body obtained by friction stir welding of the friction stir processing tool at a rotational speed of 600 rpm and a moving speed of 100 mm / min. It is an external appearance photograph of the butting part of the plate-like body obtained by friction stir welding with a rotational speed of 800 rpm and a moving speed of 50 mm / min of the friction stir processing tool. It is an external appearance photograph of the butt | matching part of the plate-shaped body obtained using the tool for friction stirring processing by 4 conditions which changed injection | pouring time, pulse frequency, and tool temperature. It is drawing which shows the collection position at the time of cutting out the test piece for a tensile test from the joined plate-shaped object. It is drawing which shows the shape of the test piece for a tensile test. It is the surface side photograph of the butt | matching part of the plate-shaped body obtained using the tool for friction stir processing by the conditions for injection | pouring time for 150 minutes. It is a back surface side photograph in FIG. It is the surface side photograph of the butt | matching part of the plate-shaped body obtained using the tool for friction stir processing by the conditions for injection | pouring time for 200 minutes. It is a back surface side photograph in FIG. It is the surface side photograph of the butt | matching part of the plate-shaped body obtained using the tool for friction stir processing on condition of injection | pouring time for 250 minutes. It is a back surface side photograph in FIG. It is the surface side photograph of the butt | matching part of the plate-shaped body obtained using the tool for friction stirring processing by the conditions for injection | pouring time for 300 minutes. It is the back side photograph in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Friction stirring processing tool 2 Gripping part 3 Flange part 4 Protrusion part 4a Shoulder surface 5 Probe 6a Titanium plate 6b Titanium plate 7 Butting part 8 Scar 9 Surface plate

Claims (5)

  A friction stir processing tool for titanium or a titanium alloy, wherein the surface of a friction stir processing tool made of a nickel alloy is surface-treated by fluorine ion implantation.   2. The friction stir processing tool for titanium or titanium alloy according to claim 1, wherein the nickel alloy is made of an alloy containing nickel and containing at least chromium and iron.   3. The friction stir processing for titanium or titanium alloy according to claim 1 or 2, wherein the fluorine ion implantation is performed at a pulse frequency of 1 to 2 kHz at room temperature under an implantation time of 150 to 400 minutes. Tools.   3. The friction stir processing for titanium or titanium alloy according to claim 1 or 2, wherein the fluorine ion implantation is performed at a pulse frequency of 1 to 2 kHz and at room temperature under an implantation time of 300 to 400 minutes. Tools.   A method for producing a friction stir processed product, characterized by subjecting titanium or a titanium alloy to friction stir processing using the friction stir processing tool according to any one of claims 1 to 4.