JP3248254B2 - Method for producing Al-Mg based alloy rolled sheet for cryogenic forming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al-M having excellent formability when applying a cryogenic forming method, which has attracted attention as a new forming method for Al and Al alloys.
The present invention relates to a method for producing a rolled g-based alloy sheet.

[0002]

2. Description of the Related Art Al and Al alloys are widely used as component materials in various fields such as household goods, automobiles, aircrafts, railway vehicles, ships, and buildings. Al
And Al alloys have excellent properties as metal materials, but there is a limit to the formability of applying normal press forming, and it is difficult to form into complex shapes by press forming. There was a disadvantage that it was. For these reasons, along with the development of an Al alloy material having excellent press formability, improvements in forming technology have been actively pursued.

[0003] The present applicant has been studying the molding technology for some time, and has developed a cryogenic molding method as a part of the research. This cryogenic forming method uses Al or Al
This is a processing method developed based on the discovery of new knowledge that the alloy exhibits excellent mechanical properties such as tensile strength and elongation at cryogenic temperatures, and its technical significance was recognized. (Japanese Patent Application No. 2-416279)
issue). That is, the cryogenic forming method described above involves applying a press lubricating oil to an Al or Al alloy plate, and then immersing the plate in liquid nitrogen.
Press forming is carried out at extremely low temperatures, and it has become possible to form parts having complicated shapes that could not be formed conventionally. This is because lubricating oil deteriorates when lubricating oil is cooled down to -40 ° C or lower, and lubricity is impaired. This is due to the fact that it has been found that it is rather improved.

[0004]

However, if a conventional Al alloy material is used as it is in the cryogenic processing method, it is not sufficient even if it can be formed into a complicated shape. However, development of an Al alloy material suitable for cryogenic forming has been desired. The present invention has been made under such circumstances, and its purpose is to
An object of the present invention is to provide a method for producing a rolled aluminum alloy sheet exhibiting excellent formability at extremely low temperatures.

[0005]

Means for Solving the Problems The method of the present invention, which has achieved the above object, refers to an Al-Mg alloy rolled sheet which is press-formed at an extremely low temperature of -40 ° C or less after applying a press lubricating oil. A production method, wherein: Mg: 1.5 to 8.5% by weight.
And the balance of Al-
After casting and agglomerating the Mg-based alloy, (a) hot rolling is performed, or (b) after hot rolling and / or cold rolling.
This is a method for producing an Al-Mg alloy rolled sheet for cryogenic forming, which has a feature in adjusting the average crystal grain size of the rolled alloy sheet to 100 µm or less by annealing at a temperature of 0 ° C or higher.

[0006]

The present inventors have studied from various angles the conditions for obtaining an optimum Al alloy rolled sheet when applying the cryogenic forming method. As a result, using an Al alloy whose components and component ratios are strictly adjusted, and casting and ingoting this Al alloy, (a) hot rolling is performed, or (b) hot rolling and / or If it is annealed at a temperature of 300 ° C. or more after cold rolling, it exhibits excellent formability at extremely low temperatures.
The present inventors have found that a rolled 1-alloy plate can be obtained and completed the present invention. First, the reasons for limiting the component range of the Al alloy used in the present invention are as follows.

Mg: 1.5-8.5% by weight Mg is an element effective for improving strength and ductility. If the content of Mg is less than 1.5% by weight, the above effect cannot be sufficiently exerted, and the cryogenic molding workability is deteriorated. On the other hand, when Mg exceeds 8.5 weight, hot rolling becomes impossible in the manufacturing process.

The Al alloy used in the present invention is composed of Mg as a basic component and the balance of Al and unavoidable impurities. However, if necessary, a predetermined amount of elements such as Cu, Zn, Mn, Cr and Zr may be contained. good. The reasons for limiting the component ranges when these elements are contained are as follows.

Cu: 1.5% by weight or less and / or Z
n: 2% by weight or less All of these elements are effective for improving the strength. Further, Cu promotes the formation of fine precipitates and contributes to hardening during the coating baking treatment after the forming process. On the other hand, Zn is also effective in improving stress corrosion cracking resistance. However, when the Cu content exceeds 1.5% by weight, Al—Mg
-Cu-based coarse compounds are inevitably generated, which extremely deteriorates cryogenic molding processability. If the Zn content exceeds 2% by weight, grain boundary destruction is likely to occur at extremely low temperatures.

At least one element selected from the group consisting of Mn: 1.5% by weight or less, Cr: 0.5% by weight or less and Zr: 0.5% by weight or less These elements refine crystal grains to form grain boundaries. Prevent destruction,
It is an element that improves cryogenic molding workability. However, when the content becomes excessive, Al—Mn system, Al—Cr
And Al-Zr-based compounds are generated in large amounts, and serve as starting points for destruction during molding, deteriorating cryogenic molding workability. Therefore, the content of Mn must be 1.5% by weight or less, the content of Cr must be 0.5% by weight or less, and the content of Zr must be 0.5% by weight or less.

The Al alloy used in the present invention contains 0.2% by weight of Ti or B from the viewpoint of refining the cast structure.
It is also effective to add it in the following range. From the viewpoint of preventing oxidation of the molten metal before casting, it is also effective to add Be in an amount of 0.1% by weight or less. Further, the Al alloy used in the present invention may contain a small amount of Fe or Si as an unavoidable impurity, and when these elements are used in a small amount, crystal grains are refined to improve cryogenic workability, but excessively contained. When a large amount of Al-Fe or Al-Mg-Si compound is crystallized, extremely low temperature workability is extremely reduced.
The total content of these elements should be kept below 0.5% by weight.

Next, the manufacturing conditions of the present invention will be described. In carrying out the present invention, it is only necessary to cast and homogenize an Al alloy having the composition adjusted as described above and then hot-roll the aluminum alloy. However, in a normal production method, the crystal grains may be coarsened. There is. For example, JIS1100 alloy and JIS5182 alloy for cryogenic processing disclosed in Hatsumei Kyokai Disclosure No. 89-15623 are manufactured by a normal manufacturing method. Therefore, the average crystal grain size of 1100 alloy is 150 μm, Even 5182 alloy
It exceeds 00 μm, deteriorating the moldability at extremely low temperatures. That is, in the above-mentioned technology, there is a possibility that the improvement of the moldability at the cryogenic temperature is not sufficiently achieved. Therefore, in carrying out the present invention, it is necessary to pay attention to making the crystal grains fine (not coarsening) in each of the steps of casting, homogenization, and hot rolling. From such a viewpoint, the average crystal grain size of the rolled Al alloy sheet manufactured by the present invention is 100 μm or less (more preferably 10 to 5 μm).
(About 0 μm). In order to further improve the strength and ductility by solid solution hardening of Mg (and Cu) after rolling, hot rolling and / or cold rolling are performed after the homogenization treatment, and these elements are subsequently annealed. It is effective to make a solid solution sufficiently. In order to exert such an effect by annealing, the temperature is preferably set to 300 ° C. or higher. If the temperature is lower than 300 ° C., the above-mentioned elements are not sufficiently dissolved.

In performing the annealing treatment, excellent cryogenic workability can be imparted by using a normal batch furnace. However, a short-time treatment using a continuous annealing furnace and forced cooling are performed. And water quenching, the crystal grains are refined,
In addition, since the additive element is sufficiently dissolved, more excellent cryogenic molding workability can be provided.

[0014]

EXAMPLES Al- having the chemical composition shown in Tables 1 and 2 was used.
After melting the Mg-based alloy by the usual smelting method, ingot forming, soaking heat treatment, hot rolling and cold rolling are performed to a thickness of 1 mm.
Was manufactured. These sheets were annealed at various temperatures in a continuous annealing furnace. The annealing temperature and the average crystal grain size are also shown in Tables 1 and 2.

[0015]

[Table 1]

[0016]

[Table 2]

After applying lubricating oil to these plates, they were immersed in liquid nitrogen and immediately subjected to the Erichsen test. The test results are shown in Tables 3 and 4.

[0018]

[Table 3]

[0019]

[Table 4]

No. Examples 1 to 15 (Tables 1 and 3) are examples satisfying the requirements of the present invention, and all show excellent cryogenic molding workability. On the other hand, no. 16 to 30 (Tables 2 and 4) are comparative examples lacking any of the requirements specified in the present invention, and are inferior to the examples. That is, No. 16-22, 24-3
In the case of No. 0, the component composition range was out of the specified range of the present invention. Sample No. 23 has an annealing temperature of less than 300 ° C., and none of them has sufficient properties. In the case of No. 1 having a Mg content exceeding 8.5% by weight. No. 17 could not be tested because of hot rolling cracks. No. In the case of 25 to 30, coarsening of crystal grains was observed.

[0021]

According to the present invention, the rolled Al-Mg alloy sheet having excellent cryogenic formability can be manufactured.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI C22F 1/00 684 C22F 1/00 684 691 691B (56) References JP-A-4-176837 (JP, A) JP-A-4 147936 (JP, A) JP-A-4-300032 (JP, A) JP-A-4-308055 (JP, A) JP-A-5-339668 (JP, A) Miyagi et al. Characteristics and Applications ”Kobe Steel Engineering Reports, Vol. 34, no. 3, p. 67-71, (1984) Yanagawa et al., "Factors Governing the Ductility of AI-Mg Alloy", Kobe Steel Engineering Reports, Vol. 42, No. 1, P. 28-33, (1992) Japan Institute of Invention and Innovation Public Technical Report No. 89-15623 (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 21/00-21/18 C22F 1/04-1/057

Claims (4)

(57) [Claims] (1) After applying a press lubricating oil, the temperature is -40 ° C or less.
Al-Mg based alloy pressure pressed at cryogenic temperature below
A method for producing a rolled sheet, comprising : casting and ingoting an Al-Mg-based alloy containing 1.5 to 8.5% by weight of Mg, the balance being Al and unavoidable impurities, and then (a) hot rolling. Or (b) annealing at a temperature of 300 ° C. or more after hot rolling and / or cold rolling.
A method for producing an Al-Mg based alloy rolled sheet for cryogenic forming , wherein the average grain size of the rolled alloy sheet is adjusted to 100 µm or less . 2. Cu: 1.5% by weight or less and / or
2. The method according to claim 1, wherein an Al—Mg alloy containing Zn: 2 wt% or less is used. 3. 3. Mn: 1.5% by weight or less, Cr:
The method according to claim 1, wherein an Al—Mg alloy containing at least one member selected from the group consisting of 0.5% by weight or less and Zr: 0.5% by weight or less is used. 4. The production method according to claim 1, wherein an Al—Mg alloy is used in which Fe and Si contained as unavoidable impurities are suppressed to 0.5% by weight or less in total.