JP4124386B2 - Method for producing high-strength aluminum or aluminum alloy rod - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing high-strength aluminum or aluminum alloy rods.
[0002]
[Prior art]
Aluminum or aluminum alloy rods make use of advantages such as light weight, high specific strength, and high corrosion resistance. Electrical parts, mechanical parts, structural parts of motorcycles, automotive parts, structural parts of ships, vehicles, and aircraft, civil engineering and building parts Widely used in Moreover, the cross-sectional shape is prescribed | regulated by JIS, such as a round shape, a rectangle, a square, a regular hexagon, a regular octagon.
[0003]
As the aluminum alloy rod, in the case of a non-heat treatment type alloy, (1) an aluminum alloy cast billet is heated and then extruded to a predetermined diameter by hot extrusion, and (2) a roll immediately after continuous casting. There are three types: continuous cast and rolled rods that are hot rolled to a predetermined diameter by rolling, and (3) drawn rods that have been subjected to cold drawing to further reduce the cross-sectional area of the extruded rod or continuous cast and rolled rod. Extruded bars and continuous cast rolled bars have low strength and hardness due to hot working, but the drawn bars are characterized by high strength and hardness because they are cold worked. The same applies to the case of an aluminum rod.
In the case of a heat-treatable alloy, the strength and hardness are improved by natural or artificial aging treatment after solution treatment of the rod produced as described above.
[0004]
Further, the rod manufactured as described above may be subjected to correction (such as tension or roll correction), final annealing, and stabilization treatment heating as necessary.
[0005]
As aluminum for rods or non-heat-treatable aluminum alloys, pure aluminum such as 1070, 1050 and 1100, Al—Mn alloys such as 3003, and Al—Mg alloys such as 5052, 5056 and 5083 are prescribed in JIS. Yes. Examples of heat-treatable aluminum alloys include Al-Cu- (Mg) alloys such as 2011, 2014, 2024, and 2117, Al-Mg-Si alloys such as 6061 and 6063, and Al-- such as 7003, 7N01, and 7075. A Zn—Mg alloy is defined in JIS.
[0006]
[Problems to be solved by the invention]
In order to obtain a high-strength rod of aluminum or non-heat-treatable aluminum alloy, it is necessary to perform cold drawing to reduce the cross-sectional area as described above. However, in the case of cold drawing, the strength and hardness to be obtained are adjusted according to the reduction in area of the drawing, so in order to obtain a bar with multiple levels of strength and hardness, the hole diameter is different. It is uneconomical to prepare a large number of drawing dies or a large number of extrusion dies having different hole diameters. In particular, the drawing dies are generally made of cemented carbide and are expensive, and it is expensive to prepare a large number of dies.
[0007]
Furthermore, in the case of an Al-Mg alloy with a large amount of Mg added, work hardenability is high, so if drawing with a surface area reduction rate above a certain limit, cracking occurs during drawing or the force required for drawing. There is a problem that machining becomes impossible due to excessively large thickness. In this regard, even in the JIS standard, hard rods of H14 and H18 are defined for the 5052 alloy with a small Mg addition of 2.2 to 2.8%, but the 5056 alloy with a large Mg addition of 4.5 to 5.6% is more processed. Only H12 having a small degree (area reduction rate) is defined. This reflects that it becomes difficult to manufacture a hard drawn rod as the amount of Mg added increases.
[0008]
In view of such problems, an object of the present invention is to provide a method capable of easily producing aluminum or an aluminum alloy rod having desired strength and hardness without using a drawing die.
[0009]
[Means for Solving the Problems]
As a result of various studies on work hardening methods for rods other than the conventional drawing method, the present inventors have found that surface roughness is large in mere twisting and there is a problem in appearance, but twisting in one direction is twisted in the opposite direction. When restored, the present invention has been completed by newly finding that the surface roughness and appearance are restored to the state before twisting, and the surface hardness and strength of the rod are improved.
[0010]
That is, the method for producing a high-strength aluminum or aluminum alloy rod according to the present invention is characterized by twisting an aluminum or aluminum alloy rod in one direction and then twisting it back in the opposite direction (Claim 1). .
In the production method of the present invention, it is preferable that the number of times of twisting in one direction and the number of times of twisting back in the opposite direction are substantially the same.
The production method of the present invention is particularly effective when the aluminum alloy is an Al—Mg alloy (claim 2).
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
First, an aluminum or aluminum alloy rod is prepared as a material. This rod may be any of an extruded rod, a continuous cast rolled rod, a drawn rod, and those obtained by annealing or stabilizing treatment heating. As aluminum, industrially pure aluminum prescribed in JIS, for example, 1060 (Al purity 99.60% or more), 1050 (Al purity 99.50% or more), 1100 (Al purity 99.00% or more), or the like can be used.
[0012]
Moreover, when higher strength is required, it is preferable to use an Al—Mg alloy among aluminum alloys. This is because Mg is an additive element that improves the work hardenability of Al, and the strength and hardness after untwisting are further improved. Examples of the Al-Mg alloy include 5005 alloy (Al-0.50 to 1.0% Mg alloy), 5052 alloy (Al-2.2 to 2.8% Mg alloy), and 5454 alloy (Al-2.4 to 3.0%) defined in JIS. Mg alloy), 5154 alloy (Al-3.1 to 3.9% Mg alloy), 5182 alloy (Al-4.0 to 5.0% Mg alloy), 5083 alloy (Al-4.0 to 4.9% Mg alloy), 5056 alloy (Al-4.5 to 5.6% Mg alloy) and the like are all suitable for the present invention. In order to improve the strength as much as possible, it is more preferable as an embodiment of the present invention to use an alloy having a large amount of Mg addition of 4% or more, such as 5056 alloy, 5083 alloy, and 5182 alloy.
[0013]
The aluminum or aluminum alloy bar is first twisted in one direction. This one-way twisting process is performed by a device that twists the rod by holding both ends of the rod with a chuck and fixing the chuck at one end and rotating the chuck at the other end, or rotating the chucks at both ends in opposite directions. That's fine. Even if this unidirectional twist is applied, the effect of improving the strength can be seen, but the surface roughness becomes large, and the metal flow due to the twist is conspicuous, which is not preferable in practice.
[0014]
The aluminum or aluminum alloy rod twisted in one direction as described above is then twisted back in the opposite direction by the same number of rotations as the one-way torsional rotation, so that the surface roughness and metal flow are It is almost restored to the state, and it can be returned to a state where it cannot be determined at all that it has undergone twisting. The greater the torsional rotational speed, the greater the improvement in strength after untwisting, but the effect is saturated when the value exceeds a certain limit, and the surface hardness decreases. Further, if the number of torsional rotations is further increased, the rod will break. The optimum number of torsional rotations varies depending on the material, diameter, and length of the rod. However, for example, when a 22 mmφ round rod of pure aluminum is 200 mm long, it can be twisted and untwisted about 7 times. The surface has the maximum hardness and breaks after 13 times. If the twist is applied six times or more before the breakage occurs, the metal flow is not completely restored even if the twist is restored. Therefore, in implementing the present invention, it is only necessary to set the number of rotations for twisting and untwisting according to the purpose of use in consideration of the hardness and the surface condition.
[0015]
Further, the rod subjected to the twisting / twisting processing may be subjected to straightening (tensile or roll straightening, mild drawing processing, etc.), final annealing, and stabilization treatment heating according to a conventional method.
[0016]
As described above, according to the manufacturing method of the present invention, it is possible to easily manufacture aluminum or an aluminum alloy rod having a desired strength and hardness without using a drawing die.
[0017]
【Example】
Examples of the present invention will be described below.
[Example 1]
A pure aluminum rod for industrial use (JIS-1060 soft annealed material, outer diameter 22mmφ, length 300mm) with a single-side rotary twist tester (manufactured by Toyama Sumitomo Electric Co., Ltd.) with a chuck distance of 200mm and a rotational speed of 25 After twisting in one direction at a predetermined number of revolutions at rpm, it was twisted back in the opposite direction by the same number of revolutions. Then, the measurement of surface hardness and surface roughness and the measurement of cross-sectional hardness distribution were performed. Further, in order to measure the strength of the untwisting rod, a 30 mm long cylinder was cut out and subjected to a compression test.
[0018]
FIG. 1 shows the rod 1 before processing. The bar 1 is provided with a marker line 2 in the length direction. 2A shows a state in which the rod 1 is twisted three times in one direction (+ direction), and FIG. 2B shows a state in which the rod 1 is twisted back three times in the opposite direction (− direction). FIG. 3A shows a state in which the rod 1 has been twisted six times in one direction, and FIG. 3B shows a state in which the rod 1 has been twisted six times in the opposite direction. FIG. 4 shows a state in which the rod 1 is twisted 12 turns in one direction and then twisted back 12 turns in the opposite direction.
[0019]
According to FIGS. 2 (a) and 3 (a), the marker line 2 looks like a spiral with a constant pitch when twisted in one direction. Further, in this state, the metal flow streak 3 is seen, and it can be seen that the streak 3 is also spiral. When this is twisted back, the marker line 2 returns to a substantially straight line as shown in FIG. In addition, at ± 6 rotations, the marker line 2 is slightly waved as shown in FIG. 3B, but as a whole, it is directed in the length direction. However, when the rotation is ± 12, the marker line M is greatly irregularly twisted as shown in FIG. 4 and cannot be restored.
[0020]
FIG. 5 shows the surface roughness of the pre-twisted annealed material, the unidirectional twisted material, and the unidirectional twisted untwisted material. (3) The surface roughness of the one-way twisted material is considerably large, but the surface roughness of the twisted-back processed materials (2) and (4) is restored to the state before the processing. However, if the torsional rotational speed is excessively ± 12 as in (5), the surface roughness will not be restored even after twisting back.
[0021]
FIG. 6 shows the result of measuring the hardness distribution of the cross-section of the bar that was twisted back after unidirectional twisting. Although the hardness of the center part of the rod is not much different from that of the annealed material, it can be seen that the hardness gradually increases as it approaches the surface, and that the hardness increases as the torsional rotational speed increases.
[0022]
FIG. 7 shows the compression test results of a cylindrical sample cut out to a length of 30 mm from the rod. It can be seen that the annealed material (C) before processing has a 0.2% yield strength of 23.58 MPa, whereas the torsion processed material with a torsional rotational speed of ± 6 turns has a markedly increased 0.2% yield strength of 125.9 MPa. This corresponds to the strength of H18 of the drawn rod.
[0023]
[Example 2]
Next, examples of the Al—Mg alloy will be described. For a JIS-5056 alloy rod (annealed material, outer diameter 22 mmφ, length 300 mm), a single-side rotary twist tester was used in the same manner as in Example 1 with a chuck distance of 200 mm and a rotational speed of 25 rpm. Three rotations were twisted and untwisted. Thereafter, the sample was cut and the hardness distribution of the cross section was measured. As a result, the Vickers hardness near the surface reached 123. Since the Vickers hardness of the annealed material before processing was 73, a significant improvement in strength was observed. Since it is difficult to produce a high-strength material with an aluminum-Mg based alloy, there is no JIS standard as a bar material. Compared to the JIS standard for a plate material for reference, this hardness is H18 ( Or H38) It corresponds to a hard material. Also, the metal flow and surface roughness on the appearance were the same as before processing, and there were no problems at all.
[0024]
As described above, according to the manufacturing method of the present invention, it is possible to easily manufacture high-strength and high-hardness aluminum or an aluminum alloy without using an expensive drawing die, and it is economical especially in a variety of small-quantity production. Great effect. Furthermore, it is possible to easily produce an Al—Mg alloy hard bar with a large amount of Mg added, which was difficult to produce by conventional drawing.
[Brief description of the drawings]
FIG. 1 is a side view showing a rod before twisting with a marker line.
2A is a side view showing a state of a marker line when the rod of FIG. 1 is twisted three times in one direction, and FIG. 2B is a side view showing a state of the marker line when the rod is twisted back three times in the opposite direction thereafter. .
3A is a side view showing the state of the marker line when the rod of FIG. 1 is twisted six turns in one direction, and FIG. 3B is a side view showing the state of the marker line when the rod is twisted back six times in the opposite direction. .
4 is a side view showing a state of a marker line when the rod of FIG. 1 is twisted 12 times in one direction and then twisted back 12 times in the opposite direction.
FIG. 5 is a graph showing the surface roughness of a bar before twisting and a bar twisted by the method of the present invention.
FIG. 6 is a graph showing the hardness distribution of the cross section of the rod before twisting and the rod twisted by the method of the present invention.
FIG. 7 is a graph showing the compressive strength of a bar before twisting and a bar twisted by the method of the present invention.
[Explanation of symbols]
1: Aluminum rod 2: Marking line 3: Metal flow streaks

Claims (2)

A method for producing a high-strength aluminum or aluminum alloy rod, characterized by twisting an aluminum or aluminum alloy rod in one direction and then twisting it back in the opposite direction The method for producing a high-strength aluminum alloy rod according to claim 1, wherein the aluminum alloy is an Al-Mg alloy.

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