JP4322733B2 - Magnesium sheet for extending excellent in formability and manufacturing method thereof - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a magnesium thin plate for stretching, which is excellent in formability at a temperature of 80 ° C. or higher, particularly excellent in press formability at a temperature in the range of 150 to 300 ° C.

  Conventionally, a magnesium alloy sheet for drawing is made into a thin sheet by repeatedly heat-treating, hot-rolling and warm-rolling a cast slab having a thickness of several mm to several tens of mm or a thick plate by extrusion. In this way, the thin Mg alloy sheet produced by repeated heat treatment, hot rolling, warm rolling, etc. is inferior in workability at a temperature between room temperature and warm range, that is, cold, and economical. It is also expensive in terms, and has not been widely used.

  In recent years, Mg alloys have a lower specific gravity than Al, have high non-rigidity, and can be reduced in weight, so there is an increasing demand for Mg alloy plates that are inexpensive and excellent in formability, and magnesium alloys that are excellent in press formability. Patent Documents 1 to 3 are available. Patent Document 1 shows the composition and rolling conditions for improving the press formability in warm at 200 ° C. Patent Documents 2 and 3 improve the ductility and bending workability in cold by adding lithium to magnesium and forming part of the β phase of the bcc structure in the α phase of the hcp structure or by forming a β single phase. However, since lithium is an active metal, there are not only safety problems in handling a large amount industrially, but also there is a problem that it is expensive and significantly reduces the corrosion resistance of magnesium.

  Although some have been proposed for hot working of magnesium, for example, Patent Documents 4 to 7 are intended to efficiently perform hot working, and are not intended to improve moldability. In Patent Document 6, the processing method and conditions for imparting a large strain are studied for the purpose of crystal grain refinement, and the crystal grain size is refined to 1 μm or less. Not mentioned. Further, the shape is limited or it is necessary to repeatedly perform hot forging, and a thin magnesium alloy plate cannot be produced.

  Prior art document information relating to the present application includes the following.

JP-A-6-293944 JP-A-6-25788 JP-A-9-41066 JP-A-5-293529 JP-A-6-81089 JP 2000-271893 A JP 2001-252703 A

  The present invention has been made in view of these points, and is excellent in press formability such as workability of 80 ° C. or higher, particularly overhang workability in the range of 150 to 300 ° C., and bendability, and is economical. In view of this, it is an object of the present invention to provide a spreading magnesium thin plate having excellent formability made of an inexpensive thin Mg alloy plate and a method for producing the same.

  As a result of intensive studies, the present inventor has found that the following magnesium alloys are excellent in workability.

  2 to 8.0% by weight of Al according to claim 1, 0.5 to 2.0% by weight of Zn, 0.05 to 2.0% by weight of Mn, the balance being Mg and inevitable The extruded Mg alloy sheet made of the above impurities is subjected to warm rolling or cold rolling after warm rolling in a range where the rolling rate exceeds 35% and not more than 70%, and then 170 to 450 Heat treatment is performed in a temperature range of ° C., the plate thickness is 0.05 to 2 mm, and the X-ray intensity ratio in X-ray diffraction [X-ray intensity of (0002) plane] / [(101 (upper bar) 1) plane X-ray intensity] is 0.1 to 5.0, and the crystal grain size is 2 to 7 μm.

  The manufacturing method of the magnesium sheet for extending | stretching of Claim 2 is 2.0 to 8.0 weight% for Al, 0.5 to 2.0 weight% for Zn, and 0.05 to 2.0 weight for Mn. Extruded Mg alloy sheet containing Mg and the balance of Mg and inevitable impurities, with the rolling rate exceeding 35% and 70% or less, warm rolling or cold rolling after warm rolling Then, heat treatment is performed in a temperature range of 170 to 450 ° C., the plate thickness is 0.05 to 2 mm, and the X-ray intensity ratio in X-ray diffraction [X-ray intensity of (0002) plane] / [(101 (Upper bar) 1) X-ray intensity of the surface] is 0.1 to 5.0, and the crystal grain size is 2 to 7 μm.

  The magnifying magnesium thin sheet having excellent formability according to the present invention and a method for producing the same are as follows. The extruded material of slab or pillet is 80 ° C. or higher as compared with a commercially available material produced in the process of warm rolling and heat treatment at a high pressure ratio Excellent in press formability such as overworkability, especially in the range of 150 to 300 ° C., and in the press formability such as bendability, and can be manufactured at low cost in terms of economy. It is effective.

  The above-described magnesium thin sheet for extensibility excellent in formability according to the present invention is composed of 2.0 to 8.0% by weight of Al, 0.5 to 2.0% by weight of Zn, and 0.05 to 2.0% by weight of Mn. By directly extruding a cast billet containing Mg and the balance consisting of Mg and inevitable impurities, a plate excellent in workability such as a warm overhang value is produced while suppressing ear cracks and breakage. The appropriate concentration range of each component is as follows.

[Al content]
The greater the amount of Al added, the more effective the strength is, and it is necessary to add 2.0% by weight or more in terms of strength. If it exceeds 8.0% by weight, the crystallized product does not form a solution, becomes brittle, and there is a problem in extrudability.
[Zn content]
The more Zn is added, the more effective the corrosion resistance is, and it is necessary to add 0.5% by weight or more from the viewpoint of corrosion resistance. If it exceeds 2.0% by weight, a crystallized product is generated and embrittled, which is problematic in terms of extrudability.
[Mn amount]
Mn has an effect of improving the corrosion resistance and workability as the amount added is increased, but if it is too much, it becomes brittle and there is a problem in extrudability, so 0.05 to 2.0% by weight.

[Fe, Si, Cu, Nb, Ca amount]
It is a harmful component in terms of extrudability and processability, and it is desirable that it be as small as possible. Regarding the contents inevitably included, Fe is preferably less than 0.035 wt%, Si is less than 0.1 wt%, Cu is less than 0.1 wt%, and Nb is less than 0.005 wt%.

  A billet of Mg alloy having the above composition is extruded. Extrusion conditions include an extrusion temperature range of 350 to 500 ° C., an extrusion rate of 1 to 100 m / min, an extrusion ratio of 50 or more, desirably 100 or more, and a thickness of 0.3 to 2.5 mm.

  The extruded magnesium alloy is warm-rolled or cold-rolled after warm rolling so that the thickness after rolling is in the range of 0.05 to 2 mm. The total rolling ratio exceeds 35% and is preferably in the range of 70% or less, and more preferably in the range of 40 to 60%. This warm rolling or cold rolling after warm rolling is performed two or more times. When performing cold rolling after warm rolling, it is desirable that the cold rolling be performed at a rolling rate of 30% or less. In addition, by performing heat treatment after rolling, the warm stretchability of 80 ° C. or higher is greatly improved, and when the stretch rate is 0.3 mm / min, the value becomes 11 mm or higher at a molding temperature of 250 ° C. Excellent in properties.

  If it exceeds 35% and 70%, the warm overhang value at 80 to 300 ° C. after the subsequent heat treatment is not good. For example, the warm overhang value at 250 ° C. is 10 mm or less.

  After performing rolling twice or more, heat treatment is performed. The heat treatment temperature is preferably in the range of 170 to 450 ° C. By this heat treatment, it is considered that strain recovery and recrystallization occur, the crystal orientation becomes appropriate, and workability is improved. Outside this temperature range, for example, the warm overhang value at 250 ° C. is 10 mm or less, and sufficient workability cannot be obtained.

  The crystal orientation of the wrought magnesium alloy having excellent workability thus produced, that is, the X-ray intensity ratio by X-ray diffraction [X-ray intensity of (0002) plane] / [X of 101 (upper bar) 1) plane Line strength] is in the range of 0.1 to 5.0, and the crystal grain size is suitably 2 to 7 μm. If the crystal grain size is less than 2 μm, it is difficult to produce economically. Conversely, if it exceeds 7 μm, for example, the warm overhang value at 250 ° C. is 10 mm or less, and the workability is inferior.

The present invention will be further specifically described with reference to the following examples.
Example 1
A billet having a composition of Mg-3.0 wt% Al-0.9 wt% Zn-0.10 wt% Mn was extruded under the conditions of a temperature of 400 ° C. and an extrusion speed of 5 m / min, and the plate thickness was 1.60 mm. It was. Further, the sheet was passed through 3 to 4 times to perform warm rolling or cold rolling after warm rolling, and heat treatment was performed at 170 to 450 ° C. to obtain a magnesium alloy sheet for stretching with a thickness of 0.8 mm. .

  As described above, the characteristics of the produced magnesium alloy were evaluated. The production conditions are shown in Table 1, and the evaluation results are shown in Table 2. Comparative Example 1 is an Mg alloy produced by extrusion of billet, warm rolling, cold rolling, or heat treatment. The evaluation method is as shown below.

[Evaluation of warm overhang height]
The overhang height was determined by measuring the maximum overhang height (mm) before rupturing at 250 ° C. by extending a magnesium alloy sheet using an Erichsen tester.

[Evaluation of X-ray intensity ratio]
Using Cu as the tube, the X-ray intensity was measured under the conditions of a voltage of 50 kV and a current of 190 mA, and the X-ray intensity ratio [X-ray intensity of (0002) plane] / [(101 (upper bar) 1) X of plane Line strength] was determined.

  The evaluation results are shown in Table 2. As shown in Table 2, the stretched magnesium alloy sheet of the present invention is superior in stretch workability as compared with the Mg alloy sheet manufactured outside the scope of the present invention. When the total rolling rate is less than 36%, the crystal grain size is larger than 7 μm. When the total rolling rate is 70% or more, the crystal grain size is as small as 7 μm or less, but the X-ray intensity ratio [(0002 ) Plane X-ray intensity] / [(101 (upper bar) 1) plane X-ray intensity] is greater than 5.0, but the extrusion degree is increased and the rolling conditions are controlled (warm and cold). By controlling the total rolling rate of the hot rolling, a texture with fine crystal grains and a small proportion of the bottom surface parallel to the plate surface can be obtained.

  This is inferred from the cross-sectional observation of the crystal grain size and the X-ray diffraction result, and shows values as shown in Table 2. It is assumed that the difference between the crystal grain size and the texture influences the warm overhang value.

  The wrought magnesium alloy sheet of the present invention has a composition containing Al of 2.0 to 8.0% by weight, Zn of 0.5 to 2.0% by weight, and Mn of 0.05 to 2.0% by weight. Then, the extruded Mg alloy sheet with the balance being Mg and inevitable impurities is subjected to warm rolling in the range where the rolling rate exceeds 35% and not more than 70%, or after cold rolling after warm rolling, 170 The heat treatment is performed in a temperature range of ˜450 ° C. X-ray intensity ratio in X-ray diffraction [X-ray intensity of (0002) plane] / [X-ray intensity of (101 (upper bar) 1) plane] is 0.1 to 5.0, and crystal grain size is It is 2-7 micrometers, It is characterized by the above-mentioned. This expanded magnesium according to the present invention has an exaggerated workability significantly higher than that of a commercially available material manufactured by a hot rolling and heat treatment process using a slab or billet extruded material. .

Claims (2)

  Extruded Mg containing 2.0 to 8.0% by weight of Al, 0.5 to 2.0% by weight of Zn, 0.05 to 2.0% by weight of Mn, the balance being Mg and inevitable impurities The alloy sheet is subjected to a heat treatment in a temperature range of 170 to 450 ° C. after being subjected to warm rolling or cold rolling after warm rolling in a range where the rolling rate exceeds 35% and is 70% or less. The plate thickness is 0.05 to 2 mm, and the X-ray intensity ratio [X-ray intensity of (0002) plane] / [X-ray intensity of (101 (upper bar) 1) plane] in X-ray diffraction is A thin magnesium sheet for extending excellent in formability, characterized by being 0.1 to 5.0 and having a crystal grain size of 2 to 7 μm.   Extruded Mg containing 2.0 to 8.0% by weight of Al, 0.5 to 2.0% by weight of Zn, 0.05 to 2.0% by weight of Mn, the balance being Mg and inevitable impurities The alloy sheet is subjected to a heat treatment in a temperature range of 170 to 450 ° C. after the rolling rate exceeds 35% and is subjected to warm rolling or cold rolling after warm rolling in a range of 70% or less, The plate thickness is 0.05 to 2 mm, and the X-ray intensity ratio in X-ray diffraction [X-ray intensity of (0002) plane] / [X-ray intensity of (101 (upper bar) 1) plane] is 0.1. A method for producing a magnesium thin plate for stretching, which is excellent in formability, characterized by being produced so that the crystal grain size is 2 to 7 μm.