JP3248263B2 - Al-Mn alloy for cryogenic forming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an Al-Mn alloy having excellent moldability when applied to a cryogenic molding method, which has attracted attention as a new molding method for Al and Al alloys.
It relates to a series alloy material.

[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.

[0003] Under these circumstances, along with the development of an Al alloy material having excellent press formability, improvement of the forming technique has been promoted. First, in terms of material development, the conventional Al alloy material had a strength of 30 kgf / cm ² and an elongation of 30%, but recently an Al alloy material having a strength of 30 kgf / cm ² and an elongation of more than 35% has been developed. Improvements in moldability have been observed. On the other hand, with respect to molding technology, technologies such as hydraulic facing molding and warm molding have been developed, and improvement in molding ability has been recognized.

[0004] The present applicant has been studying 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 A
This is a processing method developed based on new findings that the alloy exhibits excellent mechanical properties such as tensile strength and elongation at extremely low 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.

[0005]

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 an Al alloy material having excellent formability at extremely low temperatures.

[0006]

Means for Solving the Problems The present invention which has achieved the above object is an Al-Mn alloy material which is press-formed at an extremely low temperature of -40 ° C or less after applying a press lubricating oil. , Mn: 0.2 to 2% by weight, the balance being Al and unavoidable impurities, and having an average crystal grain size of 150 μm
Al-M for cryogenic molding having the gist of the following points
It is an n-based alloy material.

[0007]

The present inventors have studied the optimum Al alloy sheet from various angles when applying the cryogenic forming method. First, it has been found that a material that is unlikely to cause grain boundary fracture at cryogenic temperatures significantly improves the workability at cryogenic temperatures, and the Al-Mg alloy rolled sheet in which the content and proportion of the Al alloy and the crystal grains are strictly adjusted. (Japanese Patent Application No. 3-98291). However, although this rolled Al alloy is excellent in corrosion resistance, it is a high Mg-containing Al alloy based on Al-2.5 to 8.5 wt% Mg, and the Al alloy will be used for melting in the future. When recycled as scrap, there is a problem that it is difficult to convert it to other alloys because Mg is high, which is disadvantageous in recyclability.

Accordingly, the present inventors have further studied an Al alloy material suitable for a cryogenic forming method in consideration of recyclability and the like. As a result, the Al-Mn system containing a predetermined amount of Mn has the same corrosion resistance as pure Al and good recyclability, and strictly adjusts the Mn content and crystal grains in the Al alloy material. As a result, the present inventors have found that an Al alloy capable of obtaining excellent formability at an extremely low temperature can be realized, and completed the present invention. First, the reasons for limiting the component range of the Al-Mn alloy material for cryogenic forming of the present invention are as follows.

Mn: 0.2 to 2% by weight Mn has the effect of improving the strength without lowering the moldability. If the Mn content is less than 0.2% by weight, the above effects cannot be obtained, while if the Mn content exceeds 2% by weight, a coarse compound is formed, and the moldability decreases. The Al alloy material of the present invention is composed of Mn as a basic component and the balance of Al and unavoidable impurities.
Elements such as n, Cr, and Zr may be contained in a predetermined amount. The reasons for limiting the component ranges when these elements are contained are as follows.

Mg: 0.2-2.5% by weight, Cu: 1.
One or more elements selected from the group consisting of 5% by weight or less and Zn: 2% by weight or less. All of these elements are effective in improving strength. Mg
Increases the work hardening ability of the Al alloy as the content increases, so that the ductility and the strength are improved. In order to exhibit this effect, the Mg content needs to be 0.2% by weight or more. Cu improves the strength and ductility similarly to Mg, and also promotes the formation of fine precipitates by aging to improve the strength. On the other hand, Zn is also effective in promoting age hardening. However, when the content of Mg exceeds 2.5% by weight, the solid solubility of Mn is sharply reduced, a coarse compound is formed, the moldability is reduced, and the recyclability is disadvantageous. If the Cu content exceeds 1.5% by weight, the solid solubility of Mn decreases, and the moldability decreases. Further, when the content of Zn exceeds 2% by weight, grain boundary destruction is apt to occur at an extremely low temperature, and the formability is reduced.

Cr: 0.5% by weight or less and / or Z
r: 0.5% by weight or less These elements refine crystal grains to prevent grain boundary destruction,
It is an element that improves cryogenic molding workability. However, when the content is excessive, a large amount of Al-Cr-based or Al-Zr-based compounds is generated, which becomes a starting point of destruction during molding,
Decreases cryogenic formability. Therefore, the content must be 0.5% by weight or less. The Al of the present invention
The alloy may inevitably contain impurity elements such as Fe and Si, but it is preferable that the total content of Fe and Si is suppressed to 1% by weight or less. That is, these elements are insoluble impurities, and when their content exceeds 1% by weight in total, an insoluble compound is generated at the time of melting and casting, and this becomes a starting point of destruction at the time of forming and improves the formability. Extremely low. It is also effective to add Ti or B to the Al alloy material of the present invention in a range of 0.2% by weight or less from the viewpoint of refining the cast structure.

On the other hand, the Al-
When the average crystal grain size of the Mn-based alloy material exceeds 150 μm,
Grain boundary fracture occurs and extremely deteriorates moldability at extremely low temperatures. Therefore, the average crystal grain size of the Al—Mn alloy material of the present invention needs to be 150 μm or less.

By the way, in producing the Al alloy material of the present invention, it is only necessary to perform normal casting and homogenizing treatments and then to perform hot rolling, but there is a possibility that crystal grains become coarse in a usual production method. For example, Invention Association Open Technical Report 89-1
No. 5623, JIS110 for cryogenic processing
Alloy No. 0 and JIS 5182 alloy are manufactured by a normal manufacturing method.
All alloys may have an average crystal grain size exceeding 150 μm, in which case the effect of improving the formability at extremely low temperatures cannot be sufficiently achieved. Therefore, in producing the Al alloy material of the present invention, care must be taken to make the crystal grains fine (not coarse) in each of the steps of casting, homogenization, and hot rolling. In order to further exhibit the effect of improving the strength and ductility due to solid solution hardening of Mg or Cu after rolling,
Hot rolling and / or cold rolling after the homogenization treatment,
It is effective that these elements are sufficiently dissolved by annealing. In order to exert such an effect by annealing, the temperature is preferably set to 300 ° C. or more.
If the temperature is lower than 00 ° C., the above-mentioned elements are not sufficiently dissolved.

[0014]

EXAMPLE An Al-Mn alloy having the chemical composition shown in Table 1 was melted by an ordinary smelting method, and then subjected to ingot forming, soaking, hot rolling and cold rolling to obtain a 1 mm thick plate. Made. These sheet materials were annealed using a continuous annealing furnace or a batch furnace to adjust the grain size. Table 1 also shows the results (average crystal grain size).

[0015]

[Table 1]

Using these plate materials, liquid nitrogen (−19)
6 ° C.), a tensile test is carried out, and after cooling in liquid nitrogen, -196 ° C. and -100 ° C.
The Erichsen test was carried out. Table 2 shows the test results.

[0017]

[Table 2]

No. 1 to No. Sample No. 10 satisfies the requirements of the present invention, and it can be seen that all of them show excellent cryogenic molding workability. On the other hand, no. 11
-19 are comparative examples lacking any of the requirements defined in the present invention, and are inferior to the examples. That is, No. of the comparative example. No. 11 has a large crystal grain and thus has low moldability. In Nos. 11 to 17, the moldability was reduced due to the insoluble compound due to the large content of the additional element. Since Nos. 18 and 19 contain a large amount of impurities, they are insoluble compounds and the moldability is reduced.

[0019]

The present invention is constituted as described above, and an Al-Mn alloy material excellent in cryogenic workability is obtained.

Continuation of front page (56) References JP-A-58-224141 (JP, A) JP-A-4-300032 (JP, A) JP-A-4-308055 (JP, A) JP-A-5-339668 (JP) Yanagawa et al., "Factors Governing the Ductility of AI-Mg Alloy", Kobe Steel Engineering Reports, Vol. 42, No. 1, P. 28-33, (1992) Miyagi et al. “Characteristics and applications of aluminum alloys at cryogenic temperatures” Kobe Steel Engineering Reports, Vol. 34, no. 3, p. 67-71, (1984) (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-Mn-based alloy material press-formed at extremely low temperature below
And containing Mn: 0.2 to 2% by weight, with the balance being Al
And an unavoidable impurity having an average crystal grain size of 15
A for cryogenic molding, characterized in that it is not more than 0 μm.
l-Mn alloy material. 2. Mg: 0.2-2.5% by weight, C
The Al-Mn alloy material for cryogenic forming according to claim 1, wherein the Al-Mn alloy material contains at least one selected from the group consisting of u: 1.5 wt% or less and Zn: 2 wt% or less. 3. The composition according to claim 1, further comprising:
3. The Al-Mn alloy material for cryogenic forming according to claim 1, wherein the Al-Mn alloy material contains Zr: 0.5% by weight or less. 4. Fe and S contained in unavoidable impurities
The Al-Mn alloy material for cryogenic forming according to any one of claims 1 to 3, wherein i is suppressed to 1% by weight or less in total.