JP2011148005A - Metallic material for friction stir welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic material that excels in joining strength after friction stir welding. <P>SOLUTION: The metallic material is a metallic material for friction stir welding. The metallic material is characterized in that it is an aluminum material of A6N01 specified in JIS H 4000 and that the average grain size of the aluminum material is ≤1.76 μm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a metal material for friction stir welding.

  The strength of the metal material can be increased by refining the crystal grains. For the joining of such metal materials, friction stir welding (FSW = Friction Stir Welding) with low heat input is used for the purpose of preventing coarsening of refined crystal grains (for example, Patent Document 1). See).

JP 2002-346770 A

  By the way, the metal material used for friction stir welding is requested | required that the joining strength of a junction part may not fall.

  Then, this invention aims at providing the metal material excellent in the joint strength after friction stir welding.

  As described above, Patent Document 1 describes that it is necessary to prevent coarsening of crystal grains in the joining of metal materials whose strength is increased by refining crystal grains. That is, Patent Document 1 suggests that the crystal grains are preferably smaller in order to improve the strength of the metal material.

  On the other hand, as a result of intensive studies, the present inventor has found that the strength of the metal material at the bonded portion after friction stirring is lowered even if the crystal grains are too small or too large.

  The first metal material of the present invention based on such knowledge is a metal material for friction stir welding, and the metal material is an aluminum material of A1050 defined in JIS H4000, and the crystal grains of the aluminum material The average particle size is 0.95 μm or more and less than 2.3 μm.

  Further, the second metal material of the present invention is a metal material for friction stir welding, and the metal material is an aluminum material of A6N01 defined in JIS H4000, and the average grain size of the crystal grains of the aluminum material The diameter is 1.76 μm or less.

  The third metal material of the present invention is a metal material for friction stir welding, and the metal material is IF steel, and the average grain size of the IF steel crystal grains is 0.6 μm or more and 7 It is characterized by being 0.0 μm or less. The crystal grain size of the third metal material is more preferably 1.0 μm or more and 2.2 μm or less.

  Such first to third metal materials are excellent in the strength of the joined portion after the friction stir welding.

  Moreover, it is preferable that the 1st and 2nd metal material of this invention is heated by 150 degreeC or more and 225 degrees C or less. Moreover, it is preferable that the 3rd metal material is heated by 575 degreeC or more and 650 degrees C or less, especially 575 degreeC or more and 625 degrees C or less. When the metal material is heated to a temperature in the above-described range, the dislocation is reduced and the crystal grain size is controlled to an appropriate value, so that a metal material having excellent strength at the joint portion after friction stir welding can be obtained. it can.

  The metal material of the present invention is a metal material for friction stir welding, and the average particle size of crystal grains of the metal material is 1.0 μm or more and 1.76 μm or less. In addition, the metal material is preferably heated at an absolute temperature of a ratio of 0.468 or more and 0.510 or less with respect to the melting point at the absolute temperature of the metal material. The metal material having the above average particle diameter is excellent in the strength of the joined portion after the friction stir welding. Further, by heating to the above temperature, dislocations are reduced and the crystal grain size is controlled to an appropriate value, so that a metal material having excellent strength at the bonded portion after friction stir welding can be obtained. .

  ADVANTAGE OF THE INVENTION According to this invention, the metal material excellent in the joining strength after friction stir welding is provided.

FIG. 1 is a diagram for explaining friction stir welding. FIG. 2 is a plan view showing a test piece for a tensile test. FIG. 3 is a graph showing the tensile strength of the metal material according to Experimental Example 1. FIG. 4 is a graph showing the tensile strength of the metal material according to Experimental Example 1. FIG. 5 is a graph showing the tensile strength of the metal material according to Experimental Example 1. FIG. 6 is a graph showing the relationship between the heating temperature and tensile strength of the metal material of Experimental Example 1. FIG. 7 is a graph showing the tensile strength of the metal material according to Experimental Example 2. FIG. 8 is a graph showing the relationship between the heating temperature of the metal material of Experimental Example 2 and the tensile strength.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a diagram for explaining friction stir welding. 1A shows a state of friction stir welding, and FIG. 1B shows a side view of a rotary tool used for friction stir welding.

  In the friction stir welding, as shown in FIG. 1A, the ends of the metal material 1a and the metal material 1b are brought into contact with each other, and the pin 11 provided at the tip of the rod-shaped rotary tool 10 is inserted between the ends. Then, the pin 11 is moved along the end portion while rotating. Here, the friction stir welding includes a spot FSW.

  As shown in FIG. 1 (b), the rotary tool 10 is composed of a substantially cylindrical shoulder 12 and a pin 11 at the tip of the shoulder 12 and inserted between the ends of the metal material. The pin 11 has a substantially cylindrical shape having a smaller diameter than the shoulder 12.

  The metal material of the present embodiment that is preferably used as the metal materials 1a and 1b for friction stir welding has a particle size in a predetermined range in order to improve the strength of the bonded portion after the friction stir welding. It is.

  One of the metal materials of the present embodiment is an A1050 aluminum material defined in JIS H4000, and the average grain size of the crystal grains is 0.95 μm or more and less than 2.3 μm. Another metal material of the present embodiment is an A6N01 aluminum material specified in JIS H4000, and the average grain size of the crystal grains is 1.76 μm or less. Further, another one of the metal materials of the present embodiment is IF steel, and the average grain size of the crystal grains is 1.0 μm or more and 2.2 μm or less. Such A1050 material, A6N01 material, and IF steel are excellent in the strength of the bonded portion after friction stir welding.

  Further, as is clear from the preferable average particle diameters of these A1050 material, A6N01 material, and IF steel, the metal material having an average particle diameter of 1.0 μm or more and 1.76 μm or less is effective in the strength of the bonded portion after the friction stir welding. It will be excellent.

  As a method for setting the particle size of the metal material of the present embodiment to a particle size in the predetermined range, for example, a method of arbitrarily combining repeated lap joint rolling (ARB = Accumulative Roll-Bonding) processing and heating for the O material is used. However, the present invention is not limited to this. For example, it is possible to use a low-temperature large-pressure rolling annealing method using liquid nitrogen, a shear extrusion method (ECAP method), a high-pressure torsion method (High Pressure Torsion), a powder mechanical milling method, or the like.

  The A1050 material and the A6N01 material are preferably heated to a predetermined temperature of 150 ° C. or higher and 225 ° C. or lower. In addition, 150 degreeC is the temperature of the fatigue limit of A1050 material. The IF steel is preferably heated to a predetermined temperature of 575 ° C. or more and 625 ° C. or less. In addition, the heating here means that substantially the entire A1050 material, A6N01 material, and IF steel are heated for a sufficient time until reaching a predetermined temperature. When the A1050 material, the A6N01 material, and the IF steel are each heated to the predetermined temperature, the dislocation is reduced and the grain size of the crystal grains is controlled to an appropriate value. As a result, A1050 material, A6N01 material, and IF steel excellent in the strength of the joint portion after friction stir welding are obtained.

  Here, the melting point at the absolute temperature of the aluminum material is 933 K (Kelvin), and the ratio of the suitable heating temperature (absolute temperature) of the aluminum material to the melting point is 0.453 or more and 0.534 or less. The melting point of IF steel at the absolute temperature is 1811K, and the ratio of the suitable heating temperature (absolute temperature) of the IF steel to this melting point is 0.468 or more and 0.510 or less. Therefore, when the metal material is heated at an absolute temperature of a ratio of 0.468 or more and 0.510 or less with respect to the melting point at the absolute temperature of the metal material, the dislocation is reduced and the grain size of the crystal grains is reduced. Is controlled to an appropriate value. As a result, the strength of the joint portion after friction stir welding is excellent.

  Hereinafter, experimental examples performed in accordance with the present embodiment will be described.

  [Experimental Example 1]

Sample No. 1 prepared in this experimental example 1 1-No. Table 1 shows the manufacturing conditions, crystal grain size, and friction stir welding conditions for each of the 19 metal materials.

  As shown in Table 1, sample no. 1-No. In order to produce 14 metal materials, the ARB processing of the number of cycles shown in Table 1 was performed on the O material of A1050 material. In the ARB processing, a plate having a thickness of 2 mm, a width of 60 mm, and a length of 400 mm is used as a starting material. The plate material obtained by rolling was water-cooled and then divided into two equal parts to obtain a plate material having the same size as the starting material. The above is one cycle of ARB processing. Note that the rolling was performed using a two-stage rolling mill with a roll diameter of 255 mm at a roll peripheral speed of 0.17 m / s and under non-lubricating conditions.

  Sample No. 5-No. Each of the metal materials of 8 was heated at 200 ° C., 225 ° C., 250 ° C., and 300 ° C. for 30 minutes in an Ar gas atmosphere after the ARB processing in the tubular electric furnace. Sample No. 12-No. Each of the 14 metal materials was heated at 225 ° C., 275 ° C., and 300 ° C. for 30 minutes in an Ar gas atmosphere using an inside of a tubular electric furnace after ARB processing.

  Sample No. 15-No. In order to produce 19 metal materials, the ARB processing of the number of cycles shown in Table 1 was performed on the O material of the A6N01 material. Sample No. About 19 metal materials, 275 degreeC heating was further performed for 30 minutes.

  Sample No. 1-No. The average grain size of the crystals of each of the 19 metal materials is as shown in Table 1. In addition, the average particle diameter of the crystal is the same as the manufactured sample No. 1-No. Each of the 19 metal materials is subjected to electropolishing, and a crystal grain boundary map is obtained by EBSP (EBSP = Electron Back Scattering Pattern) image method of each metal material after electropolishing. And obtained by measuring the distance between the intersections of the crystal grain boundaries.

  Sample No. obtained in this way. 1-No. Friction stir welding was performed on each of the 19 metal materials under the conditions shown in Table 1 (the rotational speed of the rotating tool and the moving speed of the rotating tool), and the tensile strength of the joint portion (joint) was measured. The sample No. used for friction stir welding was used. 15-No. The 19 metal material has a thickness of 2.0 mm, a width of 60 mm, and a length of 300 mm. For the friction stir welding, a rotating tool having a shoulder diameter of 12 mm, a pin diameter of 4 mm, and a pin length of 1.7 mm was used.

  In the tensile test, as shown in FIG. 2, a test piece in which the joint portion J in the stirring portion S crosses the center was used. Each parameter of this test piece is L1: 45mm, W1: 12mm, L2: 10mm, L3: 4mm, L4: 4mm, W2 = 4mm, R = 4mm. The test piece was subjected to a tensile test at a tensile speed of 1 mm / min at room temperature using a tensile tester manufactured by INSTRON.

  3 to 6 show the tensile strength of the metal material according to Experimental Example 1. FIG. In FIG. 1-No. The relationship between the particle size of 8 metal material and the tensile strength is shown. As shown in FIG. 3, it was confirmed that the strength of the bonded portion of the A1050 material is improved when the crystal grain size is 0.95 μm or more and less than 2.3 μm.

  In FIG. 9-No. The relationship between the particle size of 14 metal materials and tensile strength is shown. The sample shown in FIG. 3 is friction stir welded at a rotational speed of 400 rpm of the rotary tool, whereas the sample shown in FIG. 4 is friction stir welded at a rotational speed of 1000 rpm of the rotary tool. As shown in FIG. 4, the absolute value of the tensile strength becomes small as the rotational speed of the rotary tool increases, but the A1050 material has a crystal grain size of 0.95 μm or more and less than 2.3 μm. It has been confirmed that the tendency that the strength of the bonded portion is improved is the same.

  In FIG. 15-No. The relationship between the particle size of 19 metal materials and the tensile strength is shown. As shown in FIG. 5, it was confirmed that the A6N01 material was improved in strength at the bonded portion when the crystal grain size was 1.75 μm or less.

  FIG. 6 is a graph showing the relationship between the heating temperature and tensile strength of the metal material of Experimental Example 1. In FIG. 5-No. 8 shows the relationship between the heating temperature and the tensile strength of the metal material. As shown in FIG. 6, it was confirmed that the metal material, particularly the A1050 material, was heated to 150 ° C. or higher and 225 ° C. or lower, whereby the strength of the bonded portion was improved.

  [Experiment 2]

Sample No. 2 prepared in Experimental Example 2 20-No. Table 2 shows the production conditions, crystal grain size, and friction stir welding conditions for each of the 25 metal materials.

  As shown in Table 2, sample no. 20-No. In order to produce 24 metal materials, ARB processing of the number of cycles shown in Table 2 was performed on O material of IF steel (Ti-added ultra-low carbon IF steel). In ARB processing, a plate having a thickness of 1.6 mm, a width of 35 mm, and a length of 400 mm is used as a starting material, and the surface of the starting material is degreased with acetone, and two sheets obtained by wire brushing are stacked and pressed. The plate was rolled at a rate of 50%, and the plate obtained by rolling was water-cooled and then divided into two equal parts to obtain a plate of the same size as the starting material. The above is one cycle of ARB processing. Note that the rolling was performed using a two-stage rolling mill with a roll diameter of 255 mm at a roll peripheral speed of 0.17 m / s and under non-lubricating conditions.

Sample No. 25 metal materials are IF steel O materials. Table 3 shows the composition of the O material of the IF steel. Sample No. 21-No. Each of the 24 metallic materials was further heated in a tubular electric furnace at 575 ° C., 600 ° C., 625 ° C., and 650 ° C. for 30 minutes in an Ar gas atmosphere.

  Sample No. 20-No. Table 2 shows the average crystal grain size of each of the 25 metal materials. The average crystal grain size was obtained by the same method as in Experimental Example 1.

  Sample No. obtained in this way. 20-No. Friction stir welding was performed on each of the 25 metal materials under the conditions shown in Table 2 (the rotational speed of the rotating tool and the moving speed of the rotating tool), and the tensile strength of the joint portion (joint) was measured. The sample No. used for friction stir welding was used. 20-No. The metal material 25 has a thickness of 1.6 mm, a width of 30 mm, and a length of 300 mm. For friction stir welding, a rotating tool having a shoulder diameter of 12 mm, a pin diameter of 4 mm, and a pin length of 1.4 mm was used.

  Moreover, in the tensile test, as shown in FIG. 3, a test piece in which the joining portion J in the stirring portion S crosses the center was used. Each parameter of this test piece is L1: 60mm, W1: 16mm, L2: 10mm, L3: 7.5mm, L4: 25mm, W2 = 12mm, R = 15mm. The test piece was subjected to a tensile test at a tensile speed of 1 mm / min at room temperature using a tensile tester manufactured by INSTRON.

  7 and 8 show the tensile strength of the metal material according to Experimental Example 2. FIG. In FIG. 20-No. The relationship between the particle size of 25 metal materials and tensile strength is shown. As shown in FIG. 7, it was confirmed that the IF steel has an improved strength at the bonded portion when the crystal grain size is 0.6 μm or more and 7.0 μm or less. In addition, it was confirmed that the strength of the joint portion of IF steel is further improved when the crystal grain size is 1.0 μm or more and 2.2 μm or less.

  FIG. 8 is a graph showing the relationship between the heating temperature and the tensile strength of the metal material according to Experimental Example 2. In FIG. 20-No. The relationship between the heating temperature of 25 metal materials and tensile strength is shown. As shown in FIG. 8, it was confirmed that the IF steel was heated to 575 ° C. or more and 650 ° C. or less, particularly 575 ° C. or more and 625 ° C. or less, whereby the strength of the joint portion was improved.

  1a, 1b ... metal material, 10 ... rotating tool, 11 ... pin, 12 ... shoulder.

Claims (2)

A metal material for friction stir welding,
The metal material is an A6N01 aluminum material defined in JIS H 4000,
The average grain size of the crystal grains of the aluminum material is 1.76 μm or less.
A metal material characterized by that.   The metal material according to claim 1, wherein the metal material is heated to 150 ° C. or more and 225 ° C. or less.

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