JP2000237882A - Aluminum alloy plate for super plastic forming, aluminum alloy tube and its super plastic formed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wide width aluminum alloy plate for super plastic forming and to integrally form a large formed body by subjecting rolled plates of super plastic aluminum alloy each other to solid-state welding. SOLUTION: Solid-state welding is a joining method not remaining a solidified structure to a joining part. It is preferable for solid-state welding to use friction agitation welding, flash butt welding, DC butt welding, resistance welding. A super plastic aluminum alloy is either of Al-Mg alloy, Al-Zn-Mg alloy, Al-Zn-Mg- Cu alloy, Al-Cu alloy, Al-Li alloy, Al-Mg-Si alloy, Al-Si alloy, etc., a recrystallization grain is refined, a grain size is preferably <=30 μm. The material, refined by static recrytallization is subjected to a grain refining treatment to have a grain size of <=40 μm, or a cold rolling of a draft of >=40% or softening annealing to a degree not generating recrsytallization in a process to produce a rolled plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for superplastic forming, that is, a wide alloy plate or an alloy pipe formed of a rolled aluminum alloy formed at 300 to 560 DEG C., and a molded product thereof. It is applied to decorative applications such as large integral molded products and building materials, structures such as automobiles and bridges, and pipes with irregular cross sections.

[0002]

2. Description of the Related Art In recent years, 350% of aluminum alloys have been used.
Various studies have been made on superplastic materials exhibiting an elongation of 100% or more at a high temperature of 100 ° C. or more, and Al-78% Zn,
Al-33% Cu, Al-6% Cu-0.4% Zr (S
UPRAL), Al-Zn-Mg-Cu alloy (747
5, 7075) and 5083 are known as superplastic alloys. Since these superplastic alloys can achieve elongation of up to several 100%, complicated molded bodies and structures made of them are proposed and put to practical use. The feature of superplastic forming is that it can be deformed with low stress because it is formed at a high temperature, and is generally formed by blow molding. For this reason, it is often the case that only a female mold is required for the mold, and the material of the mold does not require a high-strength super hard material like a general cold press, and the mold cost is inexpensive. one of. Such superplastic forming has a great effect when applied to a large-sized molded product having a relatively small number of products of medium to small varieties and a high mold cost, such as integral molding of a leisure boat.

[0003] It is also desired to apply superplastic processing to a pipe to form a pipe or a structure having a complicated cross section. In this case, a circular or square pipe is manufactured in advance by extrusion. It has been generally proposed to seal both ends of the tube and perform superplastic forming by blow molding or the like.

[0004]

However, in order to obtain a large molded product by the above-described superplastic forming, a large rolled plate is required as a raw material. However, in practice, a large rolled plate, particularly a wide rolled plate is required. Rolled sheets have limitations in equipment, and there is a limit to widening. As a countermeasure for this, it is usually conceivable to weld the plate, but there is a problem that the superplastic property of this portion is completely lost since the welded portion is once melted to form a solidified structure. In addition, since superplastic forming is generally performed by blow molding, if cracks or breaks occur even at one location due to poor welding, air leakage occurs and molding becomes impossible. Therefore, widening by welding is impossible.

[0005] In producing a tube, alloys that exhibit superplasticity include 5083 and 747 as described above.
5 and the like, but these are often very difficult to extrude alloys, and since the extruded material is cold drawn, it is difficult to perform working heat treatment to refine the crystal grains,
Therefore, it is difficult to provide sufficient superplastic properties.

However, in order to increase the size of the superplastic molded body, it is necessary to increase the width and size of the material that can be superplastically formed. is necessary. Also, if superplastic forming of a pipe becomes possible, it becomes possible to produce a deformed pipe having a complicated cross-sectional shape used for an automobile as shown in FIG. 1, and since superplastic forming is excellent in transferability, it becomes complicated. Applications such as decorative pillars for building materials with surface patterns are also open. For this purpose, it is necessary to produce an aluminum alloy tube capable of superplastic forming, and it is necessary to develop a joining method without lowering the superplastic properties.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a joining method that does not impede the superplastic properties. As a result, the joining portion is not a solidified structure but a solid-phase joining, and the joining portion has as much processing strain as possible. By providing a fine crystal grain by heating at the time of superplastic forming, and by examining a combination of a material and a joining method that does not significantly reduce the superplastic property of the joint, the following invention was reached. .

That is, the present invention relates to a wide aluminum alloy sheet for superplastic forming, characterized in that superplastic aluminum alloy rolled sheets are solid-phase joined, and the superplastic aluminum alloy rolled sheet is solid-phase joined. This is an aluminum alloy tube for superplastic forming. The superplastic aluminum alloy material according to claim 1 or 2, wherein friction stir welding, flash butt welding, DC butt welding, or electric resistance welding is used as the solid phase welding. A superplastic formed body obtained by superplastic forming the joined body according to 2.

[0009]

Embodiments of the present invention will be described below.

First, the superplastic material of the present invention will be described. The material used in the present invention can be basically applied to any aluminum alloy exhibiting superplastic properties. In general, Al-Mg based, Al-Zn-Mg based, A
l-Zn-Mg-Cu, Al-Cu, Al-Li
System, Al-Mg-Si system, Al-Si system and the like, and specifically, 5083, 7475, 2004 and the like are preferable.
Superplastic aluminum alloys generally obtain superplastic properties by making recrystallized grains finer, and the grain size is preferably 30 μm or less. Further, usually, a static recrystallization type (50) for refining crystal grains before performing superplastic deformation.
83, 7475 etc.) and a continuous recrystallization type that dynamically recrystallizes during superplastic deformation. In the present invention, either of these static recrystallization type and dynamic recrystallization type are known. Can also be used. The material of the type that is refined by static recrystallization has a crystal grain size of 40 μm or less even if a crystal grain refinement process is performed in advance in the process of manufacturing a rolled plate. Alternatively, the H1n material is cold-rolled at a rolling ratio of 40% or more, or is made into an H2n or H3n state softened and annealed to such an extent that recrystallization does not occur, and recrystallized by heating during superplastic forming. In the dynamic recrystallization type, it is necessary to form a cold-rolled sheet (H1n) having a cold rolling reduction of 40% or more or a soft-annealed H2n or H3n state so that recrystallization does not occur. Due to the relationship between dynamic strain and temperature during superplastic deformation, dynamic recrystallization occurs during deformation and the size is reduced.

Next, the joining method according to the present invention will be described. It is essential that the bonding method used in the present invention is a solid-phase bonding method. Here, the solid-phase joining method means a joining method in which a solidified structure does not remain in the joint, and even if melting occurs temporarily at the joining interface as in a flash butt welding method, a molten portion is discharged during the joining process. As a result, the present invention can be applied as long as the bonding interface is solid phase bonding. However, spot welding such as spot welding and projection welding is not preferable because air is leaked from the welding points during molding because they are not joined to each other. More specifically, solid phase stir welding (FSW), flash butt welding, DC butt welding, electric resistance welding, and the like are common. This is preferable because the plastic properties are improved.

The operation of the present invention is as follows. In the case of fusion joining, since the joining portion has a solidified structure once melted, the crystal grains are coarsened, and the superplasticity is completely lost.
On the other hand, in the case of solid-phase bonding,
Alternatively, once molten, the molten metal is discharged from the joint, and as a result, a state is obtained in which no large crystal grains exist in the joint. Furthermore, since the joint interface and its vicinity undergo strong plastic working at a high temperature, high strain is introduced, so that the joint part is finely recrystallized or at least finely recrystallized by heating during superplastic forming. Crystallize. That is, the superplastic property of the joint is maintained or improved without lowering. as a result,
The joined body according to the present invention can be sufficiently formed by superplastic working. Therefore, a large superplastic plate having a sufficient size can be obtained by joining a plurality of narrow rolled plates, and a large molded body such as a leisure boat hull can be integrally formed by superplastic forming. It becomes possible. Alternatively, by bending and joining a rolled plate,
Tubes can be easily made even with alloys such as 83, 7475, which are difficult to extrude and draw. In addition, since the superplastic property is not lost, by expanding the tube by superplastic forming using a mold having a modified cross section, it is possible to easily manufacture a tubular molded body having a complicated shape.

In the case of fusion joining, cracks and the like are apt to occur as welding defects in the joints. If such cracks are present, gas leaks during superplastic forming, making molding difficult. Therefore, there is no gap for gas leakage, and there is no such problem during molding.

In the manufacture of the tube, cold drawing may be performed after joining. However, it is not preferable to cold-draw a tube made of a recrystallized plate because the portion is coarsely recrystallized by heating during the next superplastic working. Therefore,
It is desirable that the original plate at the time of pipe making be subjected to a heat treatment of H1n or H2n or H3n which is annealed to the extent that recrystallization does not occur. In this case, the joint has high processing strain introduced,
Further, even when cold drawing is performed, this portion does not cause crystal grains to become coarse during superplasticity.

[0015]

Embodiments of the present invention will be described below.

[First Embodiment] First, an embodiment of a rolled plate joined body suitable for a large molded product will be described. Table 1 shows the alloy composition of the aluminum alloy used in the examples.

[0017]

[Table 1]

The alloys having the chemical components shown in Table 1 were prepared by a usual manufacturing method.
mm H18 material. Alloy 2 was an alloy equivalent to 7475, and was manufactured into a W material having a thickness of 2.0 mm. A base plate having a width of 100 mm and a length of 100 mm was prepared from these plates and joined by various joining methods shown in Table 2 so that the rolling direction was the longitudinal direction to obtain a 100 mm × 200 mm plate.
The joint plate was flattened by removing burrs and excess piles at the joint, and then the width 1 was set so that the joint was at the center in the longitudinal direction of the test piece.
A test piece having a length of 0 mm and a parallel portion length of 30 mm was prepared, and a superplastic tensile test was performed at the temperature and strain rate shown in the table. For comparison, the same test was performed on the unbonded base plate. Table 2 shows the results.

[0019]

[Table 2]

As shown in the table, the TIG-welded test piece had almost no superplastic elongation, whereas the solid-phase-bonded test piece had a small crystal grain size and had no superplastic properties. It is the same or improved level. Therefore, according to the present invention, a wide and long aluminum alloy plate for superplastic forming can be obtained, and a large molded product can be produced by superplastic forming.

Embodiment 2 Next, an embodiment of a superplastic forming tube will be described. Table 3 shows the alloy composition of the aluminum alloy used in Example 2.

[0022]

[Table 3]

The alloy 6 in Table 3 (equivalent to 5083) was made into a H24 material having a thickness of 2.0 mm by a usual manufacturing method. Alloy 7
(Equivalent to 7475) was annealed at 230 ° C. for 5 hours by a normal manufacturing method to obtain an overaged W material having a plate thickness of 2.00 mm. These plate members were bent to have a diameter of 30 mm and a length of 300 mm, and were joined by joining methods shown in Table 4 to form circular pipes. 30m in diameter using alloy 8 (equivalent to 6061)
m T4 extruded pipes were produced. These were put into an air furnace at 500 ° C. corresponding to the superplastic temperature, and after holding for 15 minutes, the crystal grains of the base plate and the joint were measured. Then, using a mold shown in FIG. 2, superplastic forming was performed to expand the tube to 60 mm by air pressure, and the formability was evaluated. Table 4 shows the results.

[0024]

[Table 4]

As shown in the table, in the case of the present invention, it was possible to increase the outer diameter from 30 mm to 60 mm by 100%, whereas in the case of TIG welding, the superplastic elongation almost disappeared, so that joining was performed. Has broken at the part. In addition, the extruded material was cold drawn at the time of pipe making, and as a result, the crystal grains were insufficiently refined, and as a result, a sufficient expanded tube was not obtained and the tube was broken on the way.

[0026]

As described in detail above, according to the present invention,
A wide and long plate can be obtained without losing the superplastic properties of the base plate. Therefore, it is possible to integrally form a large one such as a hull of a leisure boat by superplastic forming having a large forming ability. The use of the tube according to the invention also makes it possible to produce tubes with greatly different diameters or tubes with a complicated cross section. Furthermore, by utilizing the transferability of the plate surface, which is a feature of superplastic forming, it is possible to easily manufacture large building material panels and decorative columns having complicated surface patterns.

[Brief description of the drawings]

FIG. 1 is a perspective view of a complex cross-section tube according to the present invention.

FIG. 2 is a sectional view of a mold and a superplastic forming apparatus used in an embodiment of the present invention.

[Explanation of symbols]

 1 Aluminum tube for superplastic forming 2 Joint 3 Hollow 4 Seal 5 Fluid for forming 6 Mold 7 Tube for superplastic forming

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) // B23K 103: 10 F-term (Reference) 4E028 CA01 CA13 EA04 EA07 4E067 AA05 AB03 BG02 BM00 DC02 DC03 DC05 DC06 EA07 EA09 EB08 4F100 AB02 AB10A AB10B AB11 AB12 AB13 AB14 AB17 AB18 AB19 AB31A AB31B BA02 DA11 EC032 EC172 JK20A JK20B

Claims (4)

[Claims] 1. A wide aluminum alloy sheet for superplastic forming, characterized in that superplastic aluminum alloy rolled sheets are solid-phase bonded. 2. An aluminum alloy tube for superplastic forming in which a superplastic aluminum alloy rolled plate is solid-phase bonded. 3. The superplastic aluminum alloy material according to claim 1, wherein solid phase welding is performed by friction stir welding, flash butt welding, DC butt welding, or electric resistance welding. 4. A superplastic formed body obtained by superplastic forming the joined body according to claim 1.