JP2008137048A - Friction spot welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve joining strength inexpensively by promoting with a simple structure the plastic flow of metal caused by frictional heat with a rotary tool. <P>SOLUTION: With a lubricant Z interposed between the respective joining faces of a first metallic member (11) and a second metallic member (12), both metallic members (11, 12) are superimposed on each other. Then, the rotary tool 16 is brought in contact with the first metallic member (11), softening and plastically fluidizing the first metallic member (11) through the frictional heat generated by the rotating motion and the pressurizing motion of the rotary tool 16, and thereby joining both metallic members (11, 12) in a solid state. Further, the lubricant Z is eliminated by the frictional heat generated therein. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method in which a rotary tool is pushed in from one side of a plurality of stacked metal members, and the metal members are spot-joined with frictional heat generated thereby.

  Conventionally, in order to reduce the weight for the purpose of improving the fuel consumption of automobiles, aluminum alloy materials have been frequently used as body materials for automobiles and the like. Along with this, there are increasing opportunities to join a member made of, for example, an aluminum alloy and a member made of an iron material or the like.

  However, when members made of such dissimilar metal materials are joined by fusion welding such as arc welding, there is a problem that a brittle intermetallic compound is generated and joint strength is lowered. For this reason, mechanical joining methods using rivets and the like have been used in the past. However, such methods have a problem in that the cost is increased because secondary materials such as rivets are required.

Therefore, a joining method called friction spot joining has attracted attention as a method capable of joining members made of different metal materials at low cost. In this joining method, for example, as shown in Patent Document 1 below, an aluminum alloy plate and a steel plate are overlapped, and the tip of the rotary tool is pushed in from the side of the aluminum alloy plate. The aluminum alloy plate is softened and plastically flowed by frictional heat generated by rotating operation and pressurizing operation, so that the aluminum alloy plate and the steel plate are solid phase welded (solid phase bonding) at a temperature below the melting point. is there.
JP 2005-34879 A

  By the way, in the said patent document 1, for the purpose of the improvement of joining strength, rust prevention, etc., the surface of a steel plate is beforehand given rust prevention plating, such as galvanization, and this plating steel plate and an aluminum alloy plate are joined. Has been done. However, depending on the use environment etc. of the product, there is a thing that originally does not need to apply such antirust plating on the surface of the steel sheet. In such a case, the antirust plating is not applied. It is desirable to perform friction point welding using a steel plate.

  Therefore, the present inventors conducted an experiment in which a steel plate (non-plated steel plate) that has not been plated for rust prevention and an aluminum alloy plate are joined by a friction point joining method. Then, unlike the conventional method using a steel plate on which rust-preventive plating was applied, it was found that the rotating tool could not be pushed into the aluminum alloy plate to a sufficient depth, and sufficient bonding strength could not be obtained. This is presumably because the plastic flow of the aluminum alloy plate caused by frictional heat with the rotating tool does not occur sufficiently. Of course, if the rotary tool is pushed to a sufficient depth by increasing the pressing force of the rotary tool, the bonding strength can be improved, but in this case, a drive source such as a motor for driving the rotary tool can be provided. It becomes necessary to increase the cost, resulting in an increase in cost.

  The present invention has been made in view of the circumstances as described above, and in the friction point joining method for joining the metal members by pushing a rotary tool from one side of a plurality of metal members stacked, the rotation is performed. The object is to promote the plastic flow of the metal caused by frictional heat with the tool with a simple configuration and to improve the joint strength between the metal members at a lower cost.

  In order to solve the above-mentioned problem, the present invention is a method of joining a first metal member and a second metal member having a higher melting point than the first metal member in a solid state, A preparatory step of superimposing both metal members in a state where a lubricant is interposed between the joint surfaces of the first metal member and the second metal member, and after this preparatory step, a rotating tool is provided on the first metal member side. A joining step of joining the two metal members in a solid state by causing the first metal member to soften and plastically flow by frictional heat generated by rotating and pressing operations of the rotating tool. In the joining step, joining is performed while the lubricant is lost by the frictional heat generated in the process (claim 1).

  According to the present invention, before the first and second metal members are overlapped and the rotary tool is pushed into the first metal member, a lubricant is interposed between the joint surfaces of the two metal members in advance. Since it did in this way, the plastic flow of the 1st metal member which arises by pushing in of the said rotation tool can be promoted effectively by the lubrication effect | action of the said lubricant. Therefore, it is possible to generate a sufficient plastic flow with a simple configuration without taking measures such as increasing the pushing force of the rotating tool, and it is possible to smoothly perform friction point joining of the two metal members. Become. Moreover, since the lubricant is lost due to frictional heat generated at the time of joining, it is possible to effectively avoid a situation in which the joining of the two metal members is hindered by remaining the components of the lubricant when joining is completed, There is an advantage that the bonding strength can be effectively improved.

  As the lubricant, for example, grease or highly viscous oil can be preferably used (claims 2 and 3).

  As described above, when grease or highly viscous oil is used as the lubricant, it is possible to sufficiently eliminate the components of the lubricant when the joining is completed while promoting plastic flow of the first metal member. The joint strength between the two metal members can be effectively improved.

  The friction point joining method of the present invention can be suitably applied, for example, when the first metal member is an aluminum alloy plate and the second metal member is a steel plate.

  In this case, it is preferable to remove beforehand the oxide film formed on the joining surface of the steel plate as the second metal member before performing the preparation step.

  In this way, since the aluminum alloy plate and the steel plate can be joined with no oxide film interposed therebetween, a solid solid state joined state can be created between these two metal members. The bonding strength can be effectively improved.

  As described above, according to the present invention, in the friction point joining method in which the metal members are joined by pressing the rotary tool from one side of the plurality of stacked metal members, the frictional heat with the rotary tool is used. The resulting plastic plastic flow can be promoted with a simple configuration, and the joint strength between the metal members can be improved at a lower cost.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, the apparatus (friction point joining apparatus) used in order to implement the friction point joining method concerning this invention is demonstrated roughly.

  FIG. 1 is a diagram schematically illustrating an example of the friction point joining apparatus. The friction point joining apparatus shown in this figure is an apparatus for joining an aluminum alloy plate 11 (corresponding to a first metal member according to the present invention) and a steel plate 12 (corresponding to a second metal member according to the present invention). As a constituent element, the rotary tool 16 is pressed against the joint P (part to be joined) in a state where the aluminum alloy plate 11 and the steel plate 12 are overlapped as shown in the figure. . Then, frictional heat is generated by pushing the rotary tool 16 into the joint portion P while rotating at a high speed, and the metal members 11 and 12 are joined to each other by the frictional heat. Hereinafter, the aluminum alloy plate 11 is simply abbreviated as the aluminum plate 11, and the aluminum plate 11 and the steel plate 12 may be collectively referred to as a workpiece 10.

  The rotary tool 16 is formed of a substantially cylindrical member that is driven to rotate about the central axis X, and is pressed against the joint P from the side of the aluminum plate 11 having a low melting point in the workpiece 10. FIG. 2 is an enlarged view showing the tip of the rotary tool 16. In FIG. 2, the left half shows the cross section of the rotary tool 16, and the right half shows the outer shape. As shown in the figure, the distal end portion (lower end portion in the figure) of the rotary tool 16 has a small-diameter cylindrical pin portion 16a projecting from the center portion thereof, and a portion radially outside the pin portion 16a. And a shoulder portion 16b formed such that the height of the bottom surface decreases toward the outside. The pin portion 16a is formed such that the lower end portion protrudes a predetermined distance below the height of the peripheral edge portion of the shoulder portion 16b.

  The specific dimension of such a rotary tool 16 is determined to an appropriate value depending on the thickness of the workpiece 10, etc. As an example of a suitable value, the diameter D1 of the shoulder portion 16b is 10 mm, and the diameter of the pin portion 16a. D2 is 2 mm, the protrusion length h of the pin portion 16a with respect to the peripheral portion of the shoulder portion 16b is 0.3 to 0.35 mm, and the inclination angle θ (shoulder inclination angle) of the bottom surface of the shoulder portion 16b is 5 ° to 7 °. The

  On the opposite side of the rotary tool 16 with the workpiece 10 interposed therebetween, a receiving tool 17 having a diameter substantially the same as or larger than that of the rotary tool 16 is provided in a coaxial arrangement. The receiving member 17 moves in a direction approaching the rotary tool 16 with the workpiece 10 interposed therebetween, and at least a tip thereof abuts on the steel plate 12 until pressing by the rotary tool 16 is started. When the rotary tool 16 is pressed, the workpiece 10 is supported against the pressing force.

  The rotating tool 16 and the receiving tool 17 as described above are mounted on a drive control device (not shown) composed of an articulated robot or the like so that the rotation speed, pressing position, pressing force, pressing time, and the like are appropriately controlled. It is configured. Although omitted in FIG. 1, a jig such as a spacer or a lift prevention plate is appropriately used to prevent the aluminum plate 11 from being lifted when the workpiece 10 is fixed in advance and the rotary tool 16 is pressed.

  Next, the specific content of the friction point joining method of this embodiment performed using the above friction point joining apparatuses is demonstrated. In this embodiment, as the steel plate 12, a non-plated steel plate, that is, a steel plate on which no rust prevention plating such as galvanization is applied is used. For this reason, as shown in FIG. 3A, a thin oxide film S is formed on the surface of the steel plate 12 in the initial state.

  In order to join such a steel plate 12 and the aluminum plate 11, first, as shown in FIG. 3 (b), the oxide plate S formed on the surface of the steel plate 12 is joined to the aluminum plate 11. The oxide film S corresponding to the portion (the portion corresponding to the joint P in FIG. 1 in the overlapping surface with the aluminum plate 11) is removed by surface polishing or the like. Then, the lubricant Z shown in FIG. 3C is applied to the portion from which the oxide film S has been removed. As the lubricant Z, a lubricant having a viscosity that can promote plastic flow of an aluminum plate 11 to be described later and having a property of disappearing due to frictional heat generated during joining is used. Although details will be described later, as a suitable example of such a lubricant Z, for example, high-viscosity oil and grease can be exemplified.

  Next, as shown in FIG. 4, the aluminum plate 11 and the steel plate 12 are overlapped. As a result, the lubricant Z is interposed between the joint surfaces of the aluminum plate 11 and the steel plate 12. Then, as shown in FIG. 1, a rotating tool 16 (see arrow A1) that rotates about the axis is brought close to the workpiece 10 as indicated by arrow A2, and the lower end portion of the rotating tool 16 is a low melting point metal. It is made to contact | abut to the junction part P from the aluminum plate 11 side. In accordance with this, the support 17 is approached from the side of the steel plate 12 as indicated by an arrow A3, and the workpiece 10 is supported so that the joint P is sandwiched between the rotary tool 16.

  Then, as described above, the rotary tool 16 is pushed into the aluminum plate 11 to a predetermined depth while rotating the rotary tool 16 at a high speed with the workpiece 10 being sandwiched between the rotary tool 16 and the receiving member 17, and the friction generated accordingly. The aluminum plate 11 and the steel plate 12 are spot-bonded by heat. More specifically, this joining process is divided into three processes, a first pressing process, a second pressing process, and a third pressing process which will be described below.

  First, in the first pressing step, as shown in FIG. 5, while rotating the rotary tool 16 at a preset first rotation speed, the aluminum plate 11 is applied to the aluminum plate 11 with a first pressing force during a first pressurizing time. Press and touch. The values of the first rotation speed, the first pressurizing time, and the first pressurizing force are as follows: the pushing depth of the rotary tool 16 against the aluminum plate 11 is determined by the tip of the pin portion 16a and the peripheral portion of the shoulder portion 16b The depth is determined so that the radial inner region of the shoulder portion 16b does not contact the aluminum plate 11 while contacting the aluminum plate 11. Specifically, for example, the first rotation speed is set to 1500 rpm to 3500 rpm, the first pressurization time is set to 0.2 seconds to 2.0 seconds, and the first pressure is set to 2.45 kN to 3.43 kN, respectively. It is preferable.

  Then, as described above, the rotary tool 16 is pressed around the aluminum plate 11 while rotating around the central axis X, so that two positions of the lower end portion of the pin portion 16a and the peripheral portion of the shoulder portion 16b in the rotary tool 16 are provided. The frictional heat is generated at the contact portion of the aluminum plate 11, and this frictional heat is promptly applied to the entire joint P including the portion between the two contact portions of the aluminum plate 11 (the portion where the bottom surface of the shoulder portion 16b is not in contact). As a result, the entire joint P is softened quickly. At this time, by setting the first rotation speed, the first pressurizing time, and the first pressurizing force to the above values, the aluminum plate 11 can be favorably softened without being sheared.

  Further, in the initial stage of the first pressing step, the narrow-diameter pin portion 16a protruding by a predetermined length h from the peripheral portion of the shoulder portion 16b comes into contact with the aluminum plate 11 before the shoulder portion 16b. The rotary tool 16 is positioned with a small frictional resistance, and rotational runout in the direction perpendicular to the central axis X is suppressed (anchor function).

  In the subsequent second pressing step, as shown in FIG. 6, while rotating the rotary tool 16 at the second rotation speed, the aluminum is applied with a second pressure greater than the first pressure during the second pressurization time. Push into plate 11. In this second pressing step, the pressing force is increased as compared with the first pressing step, so that the pin portion 16a and the shoulder portion 16b of the rotary tool 16 gradually enter deeper into the aluminum plate 11, and these pin portions The entire surface of 16a or shoulder portion 16b contacts the aluminum plate 11. Along with this, plastic flow occurs in addition to softening of the aluminum plate 11 (this plastic flow is schematically indicated by a broken line Q in the figure).

  During the generation of the plastic flow Q, the flow of the softened aluminum plate 11 is promoted by the presence of the lubricant Z interposed between the joint surfaces of the aluminum plate 11 and the steel plate 12. That is, the lubricant Z is configured to have a function of promoting the plastic flow Q of the aluminum plate 11. At this time, the bottom surface of the shoulder portion 16b inclined so as to decrease in height toward the outer side in the radial direction suppresses the softened aluminum plate 11 from flowing out from the portion immediately below the rotating tool 16 (joint portion P). Therefore, the plastic flow Q is intensively generated at the joint P. Although an oxide film (not shown) is formed on the surface of the aluminum plate 11, the oxide film is broken at the portion where the plastic flow Q occurs (joint portion P). Eleven new surfaces are exposed.

  The values of the second rotation speed, the second pressurizing time, and the second pressurizing force are determined by the pressing depth of the rotary tool 16 with respect to the aluminum plate 11, and the entire surface of the pin portion 16 a and the shoulder portion 16 b being the aluminum plate 11. The aluminum plate 11 is determined to have such a depth that it can come into contact with the aluminum plate 11 and that the aluminum plate 11 is not too thin to be torn off. Specifically, for example, the second rotation speed is set to 2000 rpm to 3000 rpm, the second pressurization time is set to 1.0 second to 2.0 seconds, and the second applied pressure is set to 3.92 kN to 5.88 kN, respectively. It is preferable.

  In the subsequent third pressing step, as shown in FIG. 7, while rotating the rotary tool 16 at the third rotation speed, the aluminum is applied with a third pressing force that is smaller than the second pressing force during the third pressurizing time. The plate 11 is pressed and contacted. In the third pressing step, the pressing force is reduced more than in the second pressing step, so that the rotary tool 16 is not pushed deeper than the depth at the completion of the second pressing step, and at the same position as that time. The aluminum plate 11 is continuously pressed. As a result, the aluminum plate 11 is prevented from being excessively thin and torn and the temperature of the joint P is maintained at the same level as in the second pressing step, and good plastic flow is maintained for a long time. Done.

  As specific examples of the third rotation speed, the third pressurization time, and the third pressurizing value, the third rotation speed is 1500 rpm or more and 3500 rpm or less, and the third pressurization time is 0.5 second or more and 2.5. The second applied pressure is preferably set to 0.49 kN or more and 1.47 kN or less.

  During the plastic flow of the aluminum plate 11 in the second pressing step and the third pressing step, the lubricant Z (FIG. 6) interposed between the aluminum plate 11 and the steel plate 12 is It gradually disappears due to vaporization due to frictional heat, and at the time when the third pressing step is finally finished, most of it disappears as shown in FIG. Then, the new surface of the steel plate 12 is exposed at the portion where the lubricant Z has disappeared, and the exposed new surface is a new surface on the side of the softened aluminum plate 11 (new surface formed by breaking the oxide film during plastic flow). , The mating surfaces of the aluminum plate 11 and the steel plate 12 are firmly solid-phase bonded.

  When the third pressing step is completed and the joining at one joining portion P is completed, the rotary tool 16 and the receiving member 17 are separated from the workpiece 10. Then, in the joint P after such friction point joining is completed, as shown in FIG. 8, the marks of the shoulder portion 16b and the pin portion 16a remain on the surface of the aluminum plate 11, and the shoulder portion 16b A burr R protruding upward in the periphery is formed. When proper bonding is performed, the burrs R are formed substantially uniformly over the entire circumference with an appropriate radial thickness.

  The aluminum plate 11 and the steel plate 12 are overlapped as described above, and the rotary tool 16 is pushed in from the side of the aluminum plate 11 having a low melting point, and the aluminum plate 11 is softened and plastically flowed by the frictional heat generated at that time. Thus, in the friction point joining method for joining both the metal members 11 and 12 in a solid state, the lubricant Z is interposed in advance between the joining surfaces of the aluminum plate 11 and the steel plate 12 before the rotary tool 16 is pushed. Therefore, since the plastic flow of the aluminum plate 11 generated during the joining is promoted by the presence of the lubricant Z, it is possible to achieve a simple configuration without taking measures such as increasing the pushing force of the rotating tool 16. Sufficient plastic flow can be generated, and there is an advantage that the friction point joining of both the metal members 11 and 12 can be performed smoothly. In addition, by using a lubricant having a property that disappears due to frictional heat at the time of joining as the lubricant Z, the components of the lubricant Z remain when joining is completed, and the metal members 11 and 12 are connected to each other. Therefore, it is possible to effectively avoid the situation in which the joining of the two metal members 11 and 12 is effectively inhibited.

  Moreover, after removing beforehand the oxide film S (oxide film S formed in the part joined to the aluminum plate 11 among the surfaces of the steel plate 12) formed in the joining surface of the steel plate 12 like the said embodiment. When the friction spot welding is performed, the aluminum plate 11 and the steel plate 12 can be joined in a state where the oxide film S is not interposed, and a strong solid-phase joining state can be created between the two. There is an advantage that the joint strength between the two metal members 11 and 12 can be improved more effectively.

  Next, an experimental example was carried out to confirm the effect of friction point joining of the two metal members 11 and 12 with the lubricant Z interposed between the aluminum plate 11 and the steel plate 12 as described above. Is described below.

  In this experiment, an aluminum plate 11 having a predetermined thickness and a steel plate (non-plated steel plate) 12 having a predetermined thickness that is not plated on the surface are used. In the state where various lubricants Z were interposed, friction point welding was performed. Then, confirmation tests such as measurement of tensile shear strength were performed on the various test pieces thus obtained. Further, as a comparative example, a test piece in which an aluminum plate 11 and a non-plated steel plate 12 are joined without using the lubricant Z, and an aluminum plate 11 and a plated steel plate (steel plate having a galvanized surface) are lubricated. The test piece joined without using the agent Z was prepared, and the tensile shear strength was measured for each of them.

  FIG. 9 shows a list of test pieces prepared for this experiment. In FIG. 3-No. 7 is an aluminum plate 11 having a thickness of 1.4 mm as an upper plate on the side into which the rotary tool 16 is pushed, and an unplated steel plate 12 having a thickness of 1.0 mm as a lower plate superimposed on the lower side of the upper plate. Used, the metal members 11 and 12 are molded by performing friction point bonding with various lubricants Z interposed therebetween. On the other hand, test piece No. 2 is the above-mentioned test piece No. 3-No. 7 is a comparative example in which these two members are joined without using the lubricant Z while using the same upper plate and lower plate as in FIG. Furthermore, test piece No. 1 is a comparative example in which a galvanized steel sheet with a thickness of 1.0 mm is used as a lower plate and bonding is performed without using the lubricant Z. In addition, when using the non-plated steel plate 12 as a lower board (test piece No.2-No.7), it joined so that the oxide film S of the joining surface was removed, and it joined.

The above test piece No. As the material of the lubricant Z used in No. ³ , high viscosity oil having a kinematic viscosity of 5.7 mm ² / s (40 ° C.) was used. In addition, test piece No. No. 4 is a silicone grease. No. 5 is a graphite spray containing graphite powder. 6 is a BN spray containing a powder of boron or a compound thereof (boron nitride, etc.). In No. 7, molybdenum spray containing molybdenum powder was used as the lubricant Z, respectively.

  Each test piece No. 1-No. 7 is formed by friction point joining under the same joining conditions. The joining conditions are shown in the table of FIG.

  And each test piece No. obtained in this way. 1-No. 7, a test for measuring the average value of the remaining thickness of the aluminum plate 11 as the upper plate (the thickness of the portion where the indentation marks of the rotary tool 16 remain), and the joint between the upper plate and the lower plate Each of the tests for measuring the tensile shear strength was conducted. The results are shown in FIG. 11 and FIG. The tensile shear strength was measured by pulling the upper plate and the lower plate in a direction perpendicular to the thickness direction and measuring the load when the joint between the upper plate and the lower plate was broken.

  According to FIG. 12, test piece No. using a plated steel plate (steel plate with a galvanized surface) as the lower plate. It can be seen that 1 is the most excellent in tensile shear strength. This is because most of the galvanized layer softened or melted by frictional heat is pushed out of the joint P by the plastic flow of the aluminum plate 11, and a part of the galvanized layer is mixed into the aluminum plate 11. In this state, it is considered that the aluminum plate 11 and the plated steel plate are solid-phase bonded. On the other hand, test piece No. using a non-plated steel plate having no plating as described above as a lower plate. 2 is the above-mentioned test piece No. Compared to 1, the bonding strength (tensile shear strength) is greatly reduced. This is presumably because the pushing resistance when pushing the rotary tool 16 into the aluminum plate 11 increased and the plastic flow of the aluminum plate 11 did not occur sufficiently. That is, according to FIG. The remaining plate thickness of the aluminum plate 11 in FIG. It can be seen that the rotation tool 16 could not be pushed deeply into the aluminum plate 11 by that amount (that is, the pushing resistance of the rotation tool 16 increased). And it is thought that due to this, the plastic flow of the aluminum plate 11 does not sufficiently occur and the bonding strength is lowered.

  On the other hand, a test piece No. using a lubricant Z at the time of joining was used. 3-No. For No. 7, the above test piece No. It can be seen from FIG. 12 that the tensile shear strength is higher than 2. The main reason for this is considered to be that the plastic flow of the aluminum plate 11 is promoted by the presence of the lubricant Z, and the pushing resistance of the rotary tool 16 is lowered accordingly. As shown in FIG. 3-No. In most cases, the remaining plate thickness of the aluminum plate 11 is the above-mentioned test piece No. It is also estimated from the fact that it is considerably smaller than 2 (that is, the rotary tool 16 can be pushed deeper).

  And the above-mentioned test piece No. 3-No. 7 in comparison with the tensile shear strength, test piece No. using a high-viscosity oil or grease as the lubricant Z was obtained. 3, No. Compared to the other test pieces No. 4 5-No. It can be seen that the tensile shear strength of No. 7 is greatly reduced. Thus, other test pieces No. 5-No. The tensile shear strength of No. 7 is relatively low because the lubricant Z used in these test pieces contains inorganic components such as graphite, boron nitride, and molybdenum, and these inorganic components are Even if frictional heat is applied at the time of joining, it remains because it does not disappear due to vaporization or the like, so this remaining component is considered to reduce the joining strength between the aluminum plate 11 and the steel plate 12 (non-plated steel plate). .

  On the other hand, the test piece No. using an organic lubricant such as highly viscous oil or grease as the lubricant Z was used. 3, No. 4, the lubricant Z is sufficiently lost by vaporization or the like due to frictional heat at the time of joining, so that the remaining components as described above are not generated and the joining between the aluminum plate 11 and the steel plate 12 is not hindered. . For this reason, the above-mentioned test piece No. 3, No. 4, the aluminum plate 11 and the steel plate 12 are firmly joined. 5-No. Compared with the test piece of No. 7, the joint strength is greatly improved. Of course, these test pieces No. 3, No. No. 4, test piece No. using a plated steel plate (steel plate on which galvanization was applied). Compared to 1, the bonding strength is low, but the strength is sufficiently satisfactory depending on the use conditions of the product, and such strength can be obtained without applying rust-proof plating such as galvanization. Therefore, the above test piece No. 3, No. The bonding method corresponding to No. 4 (method of bonding using high-viscosity oil or grease as the lubricant Z) has a great merit as a method for obtaining necessary bonding strength at low cost.

The test piece No. The kinematic viscosity of the high-viscosity oil used in No. ³ was 5.7 mm ² / s (40 ° C.). However, as this high-viscosity oil, the kinematic viscosity that can promote the plastic flow of the aluminum plate 11 well. If it is oil which has this, it can use suitably not only the oil of the above kinematic viscosity. However, when a similar experiment was conducted using an oil having a kinematic viscosity of 2.5 mm ² / s (40 ° C.), a significant effect could not be obtained. From this, it can be said that it is necessary to use an oil having a kinematic viscosity larger than at least 2.5 mm ² / s (40 ° C.) as the high-viscosity oil. However, as to how much kinematic viscosity oil is actually used with respect to this value, it should be appropriately determined according to the required bonding strength and the like. On the other hand, it has been found that even when an oil having a kinematic viscosity of 440 mm ² / s (40 ° C.) is used as the highly viscous oil, the effect of promoting the plastic flow can be sufficiently obtained. For this reason, it is possible to use an oil having a wide range of kinematic viscosities including a range of at least 5.7 to 440 mm ² / s (40 ° C.) as the high-viscosity oil.

  Moreover, in the said embodiment, although the example which joins the aluminum plate 11 and the steel plate 12 was shown, the friction point joining method of this invention will be the above metal members if two metal members with different melting | fusing points are mutually. Not limited to combinations, it is applicable. For example, a magnesium alloy can be used as the metal member (first metal member) on the side into which the rotary tool 16 is pushed.

It is a figure which shows typically an example of an apparatus suitable for the friction point joining method concerning one Embodiment of this invention. It is a figure which expands and shows the front-end | tip part of a rotary tool. It is a figure for demonstrating the condition which removes the oxide film of the surface of a steel plate as a preparatory process of friction point joining, and applies a lubricant | lubricant to the said surface. It is a figure which shows the condition which piled up the steel plate and the aluminum plate. It is a figure for demonstrating the 1st press process in friction point joining. It is a figure for demonstrating the 2nd press process in friction point joining. It is a figure for demonstrating the 3rd press process in friction point joining. It is a figure for demonstrating the condition when friction point joining is completed. It is a table | surface which shows the kind of test piece used for the experiment for confirming the effect of this invention. It is a table | surface which shows the joining conditions at the time of shape | molding each said test piece. It is a table | surface which shows the result of having measured the remaining board thickness of the aluminum plate with respect to each test piece. It is a graph which shows the result of having measured the tensile shear strength with respect to each test piece.

Explanation of symbols

11 Aluminum alloy plate (first metal member)
12 Steel plate (second metal member)
16 Rotating tool S Oxide film Z Lubricant

Claims (5)

A method of superimposing a first metal member and a second metal member having a higher melting point to join both metal members in a solid state,
A preparatory step of superimposing both metal members in a state where a lubricant is interposed between the joint surfaces of the first metal member and the second metal member;
After this preparation step, a rotating tool is brought into contact with the first metal member, and the first metal member is softened and plastically flowed by frictional heat generated by the rotating operation and the pressurizing operation of the rotating tool. And a joining step for joining both the metal members in a solid phase state,
In the joining step, the friction point joining method is characterized in that joining is performed while the lubricant is lost by the frictional heat generated in the process. In the friction point joining method according to claim 1,
A friction point joining method, wherein grease is used as the lubricant. In the friction point joining method according to claim 1,
A friction point joining method characterized by using high-viscosity oil as the lubricant. In the friction point joining method according to any one of claims 1 to 3,
The friction point joining method, wherein the first metal member is an aluminum alloy plate and the second metal member is a steel plate. In the friction point joining method according to claim 4,
Before performing the said preparatory process, the oxide film currently formed in the joining surface of the steel plate as said 2nd metal member is removed beforehand, The friction point joining method characterized by the above-mentioned.

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