JP2006283138A - Aluminum or aluminum alloy material and structure using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide aluminum or an aluminum alloy from which a structure can be produced at a low cost, and which is excellent in bending workability and press moldability, is high in threshold surface pressure in the case of fastening by mechanical means, and can be made higher in axial force, and a structure using the same. <P>SOLUTION: When the portion of 1/4 the plate thickness from the surface is defined as a surface layer and the portion of l/3 the plate thickness making 1/6 thicknesses respectively from the center in the thickness direction toward both surfaces is defined as a central layer, the difference between the average hardness of the surface layer and the average hardness of the central layer is ≥4 Hv and ≤12 Hv in Vickers hardness. When the portion up to the position where the hardness from the surface attains a mean value X is defined as a surface part when the mean value of the hardness distribution in the plate thickness direction is defined as X, the thickness in the surface layer part is ≥1/4 the plate thickness. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used when a structural material is manufactured by joining aluminum or aluminum alloy materials or by joining aluminum or aluminum alloy materials and steel materials by a mechanical fastening method such as bolts, nuts and rivets. Relates to aluminum or aluminum alloy material.

  When mechanically fastening aluminum or aluminum alloy members or parts with bolts, nuts, rivets, etc. in civil engineering or building structures such as ships, railway vehicles, automobiles, aircraft, etc. or bridges, etc., aluminum or aluminum The alloy material has a problem that the vicinity of the fastening portion is easily deformed as compared with the steel material. In particular, there is a problem in that the seating surface of aluminum or an aluminum alloy material is depressed due to mechanical fastening, and the axial force (fastening force) is likely to be reduced. To solve this problem, (1) a method of increasing the strength of aluminum or aluminum alloy material to be fastened and increasing the limit surface pressure (limit surface pressure) at which the seat surface begins to sink, (2) bolts, A method is conceivable in which the bearing surface area is expanded by increasing the outer diameter of the seating surface such as a nut and a rivet, and the surface pressure of the seating surface with respect to a predetermined axial force is lowered.

  Further, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2002-339990), a method of providing a hard plating layer on the surface of a material to be fastened to increase the limit surface pressure of the material to be fastened, Patent Document 2 (Japanese Patent Laid-Open No. 6-122950). No. 2) and Patent Document 3 (Japanese Patent Laid-Open No. 2004-149893) have proposed a method in which the material is improved and strengthened only in the vicinity of the bolt hole or the rivet hole to prevent the seat surface from being depressed.

JP 2002-339990 A JP-A-6-122950 JP 2004-149893 A

  However, the method of increasing the limit surface pressure of the material to be fastened by increasing the strength of the aluminum or aluminum alloy material can suppress the depression of the seating surface, but the workability (formability) of the member by bending or press molding is reduced. There is a problem that it is lowered. In order to increase the strength of aluminum or aluminum alloy materials, it is necessary to increase the amount of alloy elements such as magnesium. However, if the amount of alloy elements such as magnesium is increased, the corrosion resistance of the material, particularly stress corrosion cracking, is increased. Sensitivity becomes sensitive, and some parts of the corrosive environment such as high temperature and high humidity have to be subjected to some anticorrosion treatment such as painting, and the cost becomes extremely high. In order to eliminate the anticorrosion treatment, it is necessary to use an aluminum alloy material having a relatively low strength with a small amount of addition of an alloy element such as magnesium. These aluminum or aluminum alloy materials are machined by bolts, nuts, rivets, etc. When fastened, the vicinity of the fastened portion is likely to be deformed, and in particular, there is a high possibility that the seating surface is depressed and the axial force is reduced. For this reason, not only a high axial force cannot be applied and a high-strength fastening portion cannot be obtained, but also there is a concern that the seat surface may collapse during use, resulting in a reduction in axial force, leading to destruction.

  On the other hand, the method of reducing the surface pressure of the seating surface for a given axial force by increasing the seating surface area or using a washer, etc. uses special bolts, nuts and rivets that have a large seating surface area. It is necessary to do this, and the fastening cost becomes high. Moreover, since this also increases weight, even if it uses lightweight aluminum or aluminum alloy material, there exists a problem that the lightweight effect will reduce.

  Further, as disclosed in JP-A-2002-339990, a method of providing a hard plating layer on the surface of a material to be fastened and increasing the limit surface pressure of the material to be fastened has low bending workability and press formability, There is a problem that the plating process is necessary and the material cost becomes high.

  Furthermore, as disclosed in JP-A-6-122950, the method for melting and strengthening the periphery of a bolt hole with high-density thermal energy and reforming and strengthening the aluminum or aluminum alloy material adds one step to the modification step, and the bolt fastening portion In order to fabricate a structure in which a large number of is present, the cost is remarkably increased.

  Even in the technique described in Japanese Patent Application Laid-Open No. 2004-149893, in order to produce a structure having a large number of fastening parts such as bolts, nuts, rivets, etc., a device in which holes are made one by one or provided with a number of tools It is necessary to drill holes at a time using one of them, and the method of drilling holes one by one is costly and is not suitable for mass-produced products. There is a problem that the cost increases and the manufacturing cost of the structure also increases.

  The present invention has been made in view of such a problem, and can produce a structure at a low cost, has excellent bending workability and press formability, and is a limit for fastening by mechanical means. An object is to provide an aluminum or aluminum alloy material having a high surface pressure and a high axial force, and a structure using the same.

  In the aluminum or aluminum alloy material according to the first invention of the present application, the surface of the aluminum or aluminum alloy material used for fastening by mechanical means is harder than the central portion in the plate thickness direction, and the hardness in the plate thickness direction is high. When the average value of the thickness distribution is X, the thickness of the surface layer portion from the surface to the position where the hardness becomes the average value X is ¼ or more of the plate thickness.

  In the aluminum or aluminum alloy material according to the second invention of the present application, the surface of the aluminum or aluminum alloy material used for fastening by mechanical means is harder than the central portion in the plate thickness direction, There is a difference between the average hardness of the 1/4 surface layer and the average hardness of the center layer whose thickness is 1/6 of the plate thickness from the center in the plate thickness direction to both surfaces. Vickers hardness is 4 Hv or more and 12 Hv or less.

  In the aluminum or aluminum alloy material according to the second aspect of the present invention, it is preferable that the average value of the hardness distribution in the thickness direction is not less than 60 Hv and not more than 85 Hv in terms of Vickers hardness. Moreover, these aluminum or aluminum alloys are structural 3000 series or 5000 series aluminum alloys, for example.

  The structure according to the present invention is characterized in that the above-described aluminum or aluminum alloy materials, or the aluminum or aluminum alloy and other kinds of materials are fastened by mechanical means.

  According to the present invention, since the central portion (center layer, etc.) in the thickness direction including the central portion of aluminum or aluminum alloy material has low hardness (Vickers hardness), bending workability of aluminum or aluminum alloy material and press There is no loss of moldability. For this reason, a large number of holes can be drilled at a time by pressing. On the other hand, since the surface (surface layer portion or surface layer) of aluminum or aluminum alloy material has high hardness (Vickers hardness), aluminum or aluminum alloy materials or aluminum or aluminum alloy materials and steel materials are fastened with bolts and nuts. In this case, it is possible to prevent the traces of bolts or nuts from remaining on the surface of the aluminum or aluminum alloy material. In other words, when a depression (a trace) of 0.004 mm, for example, is generated on the surface of the aluminum or aluminum alloy material when the bolts and nuts are tightened, the pressure acting on the surface of the aluminum or aluminum alloy material is Or if it is the limit surface pressure at the time of fastening of an aluminum alloy material, this limit surface pressure can be raised. Thus, in the present invention, since the limit surface pressure is high, it is possible to fasten the aluminum or aluminum alloy material with a higher axial force.

  For this reason, according to this invention, the structure which consists of lightweight aluminum or aluminum alloy material can be manufactured at low cost using mechanical fastening methods, such as a volt | bolt nut and a rivet. Further, since it is not necessary to use bolts, nuts and rivets having a large seating surface area, the light weight effect can be maintained.

  And since the aluminum or aluminum alloy material of the present invention has a high hardness of the surface layer portion or the surface layer, the surface of the aluminum or aluminum alloy is not easily deformed during use as a structure, and the bearing surface is depressed during use of the structure. Accordingly, it is possible to suppress a decrease in the axial force of the bolt, nut and rivet.

  According to the present invention, while maintaining high bending workability and press formability, it is possible to increase the critical surface pressure when fastening aluminum or an aluminum alloy material by mechanical means, and to increase the axial force. There is an effect that can be done. Thereby, the structure of aluminum or aluminum alloy material with a high limit surface pressure can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present invention, the hardness (Vickers hardness) is controlled as follows in the plate thickness direction of aluminum or aluminum alloy material. However, in any embodiment, the surface is harder than the central portion in the thickness direction.

(1) 1st Embodiment When the average value of the hardness distribution of a plate | board thickness direction is set to X, the part from the surface to the position where hardness becomes the average value X is defined as a surface layer part. This average value is obtained by measuring the hardness at a constant pitch from the surface to the center in the thickness direction of the aluminum or aluminum alloy material, and dividing the sum of the measured values by the number of measurement points. For example, when the plate thickness is 4 to 6 mm, the number of measurement points is 7 to 11 points. In the first embodiment, the thickness of the surface layer portion is ¼ or more of the plate thickness.

(2) Second Embodiment In the second embodiment, a quarter of the plate thickness from the surface is defined as the surface layer. Further, a portion where 1/6 of the plate thickness from the center in the plate thickness direction toward both surfaces is 1/3 of the plate thickness is defined as a central layer. In the second embodiment, the difference between the average hardness of the surface layer and the average hardness of the center layer is 4 Hv or more and 12 Hv or less in terms of Vickers hardness.

(3) Preferred aspect of the second embodiment In the second embodiment, it is preferable that the average value of the hardness distribution in the thickness direction is not less than 60 Hv and not more than 85 Hv in terms of Vickers hardness. Moreover, these aluminum or aluminum alloys are structural 3000 series or 5000 series aluminum alloys, for example.

  FIG. 1 is a graph showing the hardness distribution in the thickness direction of an aluminum or aluminum alloy plate according to an embodiment of the present invention, where the horizontal axis represents the distance from the plate surface and the vertical axis represents Vickers hardness. . The plate thickness is 6 mm, the Vickers hardness is lowest at the center (including the position 3 mm from the plate surface), and the Vickers hardness is highest at the front and back surfaces. FIG. 2 shows an annealed aluminum or aluminum alloy plate, and the Vickers hardness is approximately constant at about 65 Hv (64.8 Hv). The material of FIG. 1 is the same material as FIG. 3C, and the material of FIG. 2 is the same material as FIG. That is, a JIS A5454Al alloy with a magnesium addition amount of 2.7% by mass was cast by a conventional method, the thickness was changed to 6 mm by hot rolling and cold rolling, and then annealed at 350 ° C. The material of FIG. 1 is the material of FIG. 1 that is subjected to rolling (skin pass) to change the surface processing rate (5%).

  In the present invention, as shown in FIG. 1, since the central portion including the central layer has a lower hardness than the front and back surfaces of the plate, the workability such as bending workability and press formability is excellent. In addition, since the surface layer portion or surface layer on the front and back surfaces of the plate is high in hardness, it is possible to suppress the depression of the seating surface when mechanically fastened with bolts, nuts, rivets, etc. Can be increased. Further, even when used as a structure, it is possible to prevent the vicinity of the fastening portion from being deformed by an external force and the seating surface from being depressed to reduce the axial force. The limit surface pressure is the seat surface pressure (pressure at the contact portion between the aluminum or aluminum alloy material and the bolt / nut or rivet) when the amount of depression of the seat surface exceeds 0.004 mm. If tightened below, there will be virtually no effect due to a reduction in axial force. Therefore, a material having a higher limit surface pressure has an advantage that it can be tightened with a bolt, nut, rivet or the like with a higher fastening force. The axial force is a tightening force of a bolt / nut or a driving force of a rivet, and both are forces acting in the axial direction of the bolt or rivet against aluminum or an aluminum alloy material.

  Such an effect can be obtained when the thickness of the surface layer portion is ¼ or more of the plate thickness as in (1).

  Further, as described in (2), the above-described effects can also be obtained when the difference between the average hardness of the surface layer and the average hardness of the center layer is 4 Vv or more and 12 Hv or less in terms of Vickers hardness.

  In order to manufacture the above-mentioned aluminum or aluminum alloy material, the raw material is melted, cast and homogenized by a conventional method, and then subjected to a hot rolling process as it is to obtain an aluminum or aluminum alloy plate as a predetermined thickness. obtain. Then, by controlling the hot rolling finishing temperature at that time, the surface layer of the aluminum or aluminum alloy plate is maintained to be soft, and in the central portion of the plate thickness, it is softened so as to be easily processed. . For example, the above-described characteristics can be obtained by controlling the hot rolling coiling temperature to be in the range of 250 ° C to 300 ° C.

  Or after melting, casting, and homogenizing the material by a conventional method, hot rolling and cold rolling are performed to obtain a predetermined plate thickness, and then the aluminum or aluminum alloy plate is annealed at a predetermined temperature. Thereafter, the surface is slightly rolled (skin pass) to increase the hardness of the surface layer of the aluminum or aluminum alloy plate. For example, in the rolling (skin pass) after the annealing treatment, the above-described characteristics can be obtained by setting the surface processing rate to 2 to 8%.

  Next, the results of experiments conducted to verify the effects of the present invention will be described. First, a JIS A 5454 Al alloy having an additive amount of magnesium as a main additive element of 2.7% by mass and good resistance to stress corrosion cracking is manufactured by a conventional method, and a thickness of 6 mm is obtained by hot rolling and cold rolling. After that, annealing was performed at 350 ° C., and the surface processing rate was changed to perform rolling (skin pass) to obtain four types of A5454 aluminum alloy plates (1) to (4). 3 (a) shows the distribution of Vickers hardness in the thickness direction of the annealed material, and FIGS. 3 (b) to 3 (e) show four types of A5454 aluminum alloy plates (1) to (4) subjected to skin pass rolling. The Vickers hardness distribution in the thickness direction is shown. The hardness distribution of each aluminum alloy plate was measured with a Vickers hardness tester (test load 0.29 N) at a pitch of 0.5 mm from the plate surface.

  Next, as shown to Fig.4 (a), these materials were cut out to 50 square mm, and it was set as the test aluminum plate 1. FIG. A bolt hole having a diameter of 13 mm (JIS B1001 grade 1) is drilled in the center of the test aluminum plate 1, and an M12 hexagon socket head bolt 2 (JIS B1176), a hexagon nut 3 (JIS B1181), and a plain washer 4 (JIS). B1256), and as shown in FIG. 4, the aluminum plate 1, the bolt 2, the nut 3 and the washer 4 are arranged, and a torque of 40 N · m is set by a preset type torque wrench. A bearing surface pressure was applied. After applying this seating surface pressure and leaving it to stand for more than 5 hours, the fastening is released, and the thickness of the test material at the site where the seating surface pressure is applied is measured with a micrometer with a sharp tip at the measurement part. Then, the amount of depression of the seat surface was measured. FIG. 4B shows the depressed area 5 remaining on the aluminum plate 1. The depressed area 5 is a trace of the bolt 2.

  Further, as shown in FIG. 5, in order to investigate the bending workability, a plate having a width of 50 mm and a length of 250 mm was prepared, and a 90 ° bending test with a bending radius of 5.0 mm was performed. That is, the 90 ° bending test (bending radius) was performed by placing the test aluminum plate 1 on the 90 ° bending block 6 and bending the aluminum plate 1 with the punch 7 having a tip radius of 5 mm.

  The above test results are shown in Table 1 below. The amount of depression on the bearing surface was measured with a tightening torque of 40 N · m.

  In the case of the aluminum alloy plates (2) and (3), which are examples of the present invention, the difference in average Vickers hardness (α−β) between the surface layer and the center layer is 4 to 12 Hv, Since the thickness of the hardened layer was ¼ or more of the plate thickness, the amount of depression of the bearing surface was as extremely small as 0.001 mm or less, and the bending test result was also good.

  On the other hand, in the case of the comparative example aluminum material (1) with a low processing rate of the annealed material and the skin pass, the difference in average Vickers hardness (α-β) between the surface layer and the center layer is less than 4 Hv. The amount of depression on the bearing surface was as large as 0.009 mm or more. Further, when the hardness distribution was high over the entire thickness in the plate thickness direction as in the aluminum alloy plate (4) of the comparative example, the amount of depression on the seat surface was low, but it was too hard and cracks occurred in the bending test.

  Using the aluminum alloy plate (2) (Example) in Example 1 and the annealed material (Comparative Example), the set torque is changed by a preset type torque wrench, and various seating surfaces are applied to the test aluminum alloy plate. After applying pressure and leaving the seating surface pressure for 5 hours or longer, release the fastening and measure the thickness of the specimen at the part where the seating surface pressure was applied using a micrometer with a sharp tip at the measuring section. Then, the amount of depression of the seat surface was obtained. The results are shown in Table 2 below.

  In the case of the aluminum alloy plate (2), even if the tightening torque is 40 nm, the seating surface depression amount is 0.001 mm, and the critical surface pressure is the value when the seating surface depression amount exceeds 0.004 mm. Since it is a bearing surface pressure, the limit surface pressure of the aluminum alloy plate (2) is 40 N · m or more. On the other hand, in the case of the annealed material, when the tightening torque is 20 N · m, no depression occurs, but when the tightening force is 40 N · m, the amount of depression becomes 0.012 mm, which is the limit pressure. Has been exceeded. In addition, when the tightening force is high torque of 60 N · m or 80 N · m and a high surface pressure is applied to the fastening seat surface, the aluminum alloy plate (2) of the embodiment of the present invention is significantly more depressed than the annealed material. Less is.

  The applicability of the present invention to aluminum alloys other than JIS A5454P alloy was investigated. Four types of alloys A3004, A5052, A5154, and A5083 manufactured by ordinary methods were hot rolled and cold rolled to a plate thickness of 4 mm, and then annealed at 350 ° C., and the surface processing rate was 2 to 8%. Rolling (skin pass) was applied. After that, as in Example 1, each alloy was rolled (skin pass) so that the surface processing rate was 2 to 8%, and the comparative example was not subjected to rolling (skin pass) as it was annealed. With respect to the comparative material (A5083P-H32) that has not been annealed with the work hardening material, the amount of depression of the bearing surface and the bending workability due to the bolt axial force were obtained.

  The measurement of the cross-sectional hardness, the amount of depression of the bearing surface due to the bolt axial force, and the investigation of the bending workability were the same as the test method used in Example 1. The bolt tightening torque was tested at two levels of 40 N · m and 80 N · m, and the bending radius was tested at two levels of 5 mm and 10 mm. The results are shown in FIG. 7 and Tables 3 and 4 below.

  After the annealing treatment, the aluminum alloy plate of the embodiment of the present invention that was rolled (skin pass) so that the processing rate of the surface was 2 to 8%, the seating surface depression did not occur at a tightening torque of 40 N · m ( Even when tightened with a torque of 80 N · m (limit surface pressure 0.004 mm or less), the amount of depression is relatively small. However, in the case of A5083, since the material strength was high and the average hardness was high, a slight decrease in bending workability was recognized. When the present invention is applied to this relatively high strength A5083 material, the minimum bending radius is increased and the design shape is restricted, but an effect is recognized in suppressing the seat surface depression.

  On the other hand, in the case of the comparative example in which the annealing process is not performed and the skin pass is not applied, even when the tightening torque is 40 N · m, at least 0.006 mm or more of the seat surface is depressed, and when tightened with the torque of 80 N · m, The amount of depression of the bearing surface was 0.099 mm or more, which was significantly larger than that in the example of the present invention. In addition, although the A5083-H32 material that has not been annealed with the work-hardening material does not show a depression of the seating surface, cracking occurred even in a bending test with a bending radius of 10 mm, and the bending workability was poor. .

It is a graph which shows the hardness distribution (Vickers hardness) for demonstrating the structure of this invention. It is a graph which shows the hardness distribution of the conventional annealing material. (A) thru | or (e) are graphs which show the hardness distribution of aluminum alloy plate (1) thru | or (4) of Table 1, and an annealing material. (A), (b) is a figure which shows the fastening test method by a torque wrench. It is a figure which shows the bending test method by a pinch. It is a graph which shows the hardness distribution of the aluminum plate of the Example which performed the skin pass about various materials, and an annealing material.

Explanation of symbols

1: Aluminum alloy plate 2: Bolt 3: Nut 4: Plain washer 5: Recessed area 6: Bending block 7: Punch

Claims (5)

In aluminum or aluminum alloy materials used for applications that are fastened by mechanical means, the surface is harder than the central part in the thickness direction, and the average value of the hardness distribution in the thickness direction is X. An aluminum or aluminum alloy material, characterized in that the thickness of the surface layer portion up to a position where the hardness is an average value X is ¼ or more of the plate thickness. In aluminum or aluminum alloy materials used for applications that are fastened by mechanical means, the surface is harder than the central portion in the plate thickness direction, and the average hardness of the surface layer that is 1/4 of the plate thickness from the surface, and the plate thickness The difference from the average hardness of the central layer having a thickness of 1/6 of the plate thickness from the center in the direction to both surfaces to 1/3 of the plate thickness is 4 Hv or more and 12 Hv or less in terms of Vickers hardness. Characteristic aluminum or aluminum alloy material. 3. The aluminum or aluminum alloy material according to claim 2, wherein the average value of the hardness distribution in the thickness direction is not less than 60 Hv and not more than 85 Hv in terms of Vickers hardness. The aluminum or aluminum alloy material according to claim 3, wherein the aluminum or aluminum alloy material is a structural 3000 series or 5000 series aluminum alloy. A structure characterized in that the aluminum or aluminum alloy material according to any one of claims 1 to 4, or the aluminum or aluminum alloy, and another kind of material are fastened by mechanical means.

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