JPS5928554A - Ultra-plastic aluminum alloy and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain an ultra-plastic Al alloy more enhanced in characteristics, in a method for obtaining the ultra-plastic Al alloy from an Al alloy containing Mg, Mn and Cr by permitting a small amount of Si to be present in the alloy. CONSTITUTION:This ultra-plastic Al alloy contains 4.0-6.0% Mn, 0.4-1.5% Mn, 0.05-0.3% Cr and more than 0.15%- less than 0.5% Si and the remainder Al. This molten alloy is continuously cast and rolled to form a strip like plate with a thickness of about 3-20mm. and, after said strip like plate is annealed at about 420-530 deg.C, pre-stage cold rolling and intermediate annealing are performed and post-stage cold rolling is subsequently carried out until a draft reaches about 60% or more. In this case, Si contributes like pig to dynamic recrystallization to form fine particle of Mg2Si and contributes to the development of self-ultraplasticity and further has effect improving the flowability of the molten alloy at the time of casting.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a superplastic aluminum alloy.

Specifically, the present invention relates to a method for industrially easily manufacturing superplastic aluminum alloys. When mechanical force is applied to the material from the outside, the material can be deformed by several hundred moduli without causing local deformation (constriction). Metals and alloys that exhibit extraordinary elongation ranging from 1,000 cm to 1,000 cm are known as superplastic metals or superplastic alloys. Two types of aluminum superplastic alloys are known: recrystallized fine-grained superplastic alloys and eutectic microstructured superplastic alloys. A recrystallized fine-grained superplastic alloy is one in which recrystallized grains newly generated by annealing a cold-rolled alloy plate are controlled to be fine. In addition, a eutectic microstructure superplastic alloy is one in which the eutectic (mixed phase) structure is controlled to be fine during casting and is carried through to rolling. In any of these superplastic alloys, the structure ranges from a diameter of o, s microns or less to a maximum of 10
Composed of micron-sized crystal grains, smooth grain boundary movement or sliding occurs, allowing the material to easily undergo plastic deformation. In recrystallized fine-grained superplastic alloys, it is necessary to add special elements to prevent grain coarsening. In many cases, transition elements are used as additive elements that exhibit such effects. In addition, when a superplastic tetite alloy is continuously deformed, work hardening occurs within the crystal grains, and finally the plastic deformation becomes L. In order to reduce such work hardening, in addition to the above elements, Furthermore, steel,
It is also known to add magnesium, zinc, etc. These elements (-i) have the effect of dynamic recrystallization, that is, causing recrystallization simultaneously with the deformation of the material, and constantly regenerating the structure of the material before deformation.

The present inventors previously developed a method for producing superplastic properties by annealing and cold rolling an aluminum alloy sheet produced by continuously casting and rolling an aluminum alloy bath containing magnesium, manganese, and chromium. proposed a method for producing aluminum alloy sheets that was much improved
L million and! ;b-//9waOθ) The present inventors have now discovered that the presence of a small amount of silicon in the alloy in the above method improves the properties of the alloy, and has achieved the present invention.

That is, the present invention provides Da, 0 to 1. ．． 0'% magnesium, 0. q~eight manganese, o, o t -o, 3
A superplastic aluminum alloy containing more than 0.15% but less than 0.3% of silicon, and the remainder consisting essentially of aluminum, and a molten alloy having the above composition, which is continuously cast and rolled. A strip plate with a thickness of 3 to 20 WM is made, and after annealing at a temperature of 1I20 to 530 C, it is subjected to first-stage cold rolling and intermediate annealing, and then second-stage cold rolling until a rolling reduction of 1.0% or more is reached. The gist of this paper is a method for producing a superplastic aluminum alloy, which is characterized by carrying out the following steps.

To explain the present invention in more detail, the superplastic aluminum alloy according to the present invention is composed of magnesium, O0j~/ , S attack manganese, O1
θ5~0.3% chromium and more than 0.15% and 0. % silicon, with the remainder consisting essentially of aluminum. As mentioned above, magnesium is an effective element for promoting dynamic recrystallization or recovery. The larger the amount of magnesium, the more effective it is, and at least θ%tj is necessary. However, 6. When the amount exceeds θ, coarsened β phase (Mg-Al compound) crystallizes at grain boundaries, making cold rolling difficult.

Manganese and chromium have the effect of inhibiting coarsening of recrystallized grains. Manganese is added in an amount of S% or less, that is, in a range where it is almost dissolved in solid solution during casting.

However, if it is less than 0.17%, the effect of its addition is small.

If more manganese is added than can be solid-dissolved during casting, coarse crystallized substances will be produced during casting. This crystallized material id not only does not contribute to the refinement of recrystallized grains, but also has an adverse effect on cold rolling. Similarly, when chromium is added in a large amount, it becomes easier to form coarse compounds with manganese, which causes the refinement effect of manganese and chromium to be lost, so the upper limit is 0.
．． 3%, preferably 0.2%. Moreover, the amount added is 0. If it is less than the OS level, the effect of addition is small.

Silicon is an inevitable impurity in aluminum, but the amount present in the base metal used for normal drawing does not contribute to superplasticity. However, when its abundance exceeds a certain level, it contributes to dynamic recrystallization like magnesium. In addition, silicon reacts with magnesium to form an intermetallic compound (
MgtSl) is formed in the form of fine particles, which itself contributes to the development of superplasticity.

Furthermore, silicon has the effect of improving the fluidity of molten metal during casting. In order to achieve this effect, silicon is added to the molten metal θ:/! more than r% and 0. ! ; be present in an amount less than %. If the amount of silicon present is too large, segregation tends to occur on the surface of the strip plate obtained by casting.

The preferred presence of silicon is 0.2 to -0.

The superplastic aluminum alloy according to the present invention may further contain other transition elements, such as zirconium, which interact with the above additive elements and do not reduce their effects. Further, small amounts of titanium and boron may be added by a conventional method to make the crystals finer. Furthermore, impurities such as iron and copper contained in general aluminum alloys are within the allowable range for normal alloys, that is, 0.70% iron or less.
Particularly 0.20 ratio 1 under, copper 0. /θ or less, there is no problem even if it exists.

Therefore, in order to produce the superplastic aluminum alloy according to the present invention, magnesium, manganese, chromium, and silicon are added to aluminum with a purity of q q, q 0% or more (JIS / species), and a molten alloy of a predetermined composition is prepared. It is preferable to prepare Then, the molten metal is continuously cast and rolled to directly reach 3 to 20 mTn, preferably da~/! ;mm
Manufacture strips with a thickness of . Continuous casting and rolling methods are well known, and several methods such as the Hunter method and the 30 method are known. According to these continuous casting pressures and treatments, a nozzle is placed between a mold made up of two rotating casting rolls, and the molten alloy is introduced into the mold through this nozzle, and is then cooled in the mold. A strip plate is manufactured by rolling at the same time. According to this method, the solid solution amount of manganese and chromium increases during casting, so that manganese can be added within the range of manganese and chromium added. As the rate increases, rolling becomes progressively more difficult. Therefore, it is preferable to perform cold rolling separately in the first stage and second stage, and perform annealing in the middle. The intermediate annealing removes the work hardening that occurred during the cold rolling in the previous stage, making the cold rolling in the latter stage easier. In intermediate annealing, softening progresses as the annealing temperature increases, but especially at 2
00'Q-2! ; Softening progresses significantly at 0υ. Softening reaches almost saturation at 2SθC, and even if heated to a higher temperature, the improvement in the degree of softening is relatively small. If the temperature is too high, the precipitates in the alloy plate will become coarse and the superplastic properties of the product will be impaired. Therefore, intermediate annealing is usually
It is preferable to carry out at -1IOθC.

The annealing time is also preferably short, and is usually 7 to 7 hours.

When intermediate dulling is performed, the subsequent cold rolling is performed until the rolling reduction reaches 60% or more. If the rolling ratio in the subsequent stage is smaller than this, it is difficult to obtain a rolled sheet exhibiting excellent superplastic properties. The preferred rolling rate in the latter stage is t, 3% or more, and generally the higher the rolling rate, the better the superplastic properties of the rolled plate. However, if the rolling rate is high, rolling becomes difficult again due to the increased stress, so the subsequent rolling rate is appropriately determined in consideration of all the superplastic properties required of the rolled plate. In general, it is appropriate that the rolling rate in the second stage is less than the go coefficient.

When the overall rolling rate is K and the rolling rate of the latter stage is 2, the rolling rate of the first stage is given by the following formula.

Usually, the rolling reduction in the first stage is 30% or more. If the pre-rolling ratio is smaller than this, the effect of intermediate annealing will be small. A suitable first stage rolling ratio is 3O-40%. When the 1111-stage rolling ratio is higher than this, it is preferable to perform additional intermediate annealing during the first stage rolling to remove work hardening, and then further perform the first stage rolling. The rolling itself in both the first and second stages is carried out in a conventional manner.

The superplastic aluminum alloy according to the present invention exhibits excellent superplastic properties at temperatures of 300 π or higher, particularly qoo'6 or higher. Therefore, by utilizing this property, various types of superplastic materials applied to general superplastic materials can be used. Typical examples include vacuum forming and bulge processing, in which a female mold is used and the material is brought into close contact with the female mold using fluid pressure.The strain rate during processing is usually / ×10'″3~t×10
- It is preferable to carry out the elongation in the range of 7 seconds and the uniaxial elongation in the range of 100 to 500%.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example / Alloy with the composition shown in Table / (contains less than 0% of iron, i, copper θ, 0 / % as impurities, other impurities total θ, θ
2 inches or less) in a gas furnace, and the temperature of the molten metal is so
It was fully degassed as C. An aluminum master alloy containing S% titanium and boron/q6 was added to this molten metal so that the titanium content was 0.03%. Using a driving mold consisting of water-cooled rolls with a diameter of 30 cm, the above molten metal was continuously cast and rolled at 730 C and a casting speed of /θ00 n/min to a thickness of 4.0 cm. A strip of Am was manufactured.

This strip plate was annealed at 1I70~qgθC for 7:1 hours, and then cold rolled into an alloy plate with a thickness of 3.3mm (
rolling ratio 50). This was intermediately annealed for 2 hours at 35Oυ, and then cold rolled again to a thickness of 80wn (total rolling ratio: 70%). A tensile test piece (parallel length 2!
The parallel part width/Om) was cut out. This test piece was tested in accordance with the JIB Zyukottt "Tensile Test Method" with a gauge length of 23 mm, a test temperature of 5OOC, and S2
A tensile test was conducted at an initial strain rate of θC1/, 3X/θ-3/sec. The results are shown in the table below.

Claims (1)

[Claims] ro < z, θ ~ 4.0 ti magnesium, o, lI
A superplastic material containing up to 5% manganese, 0.3% chromium and 0.3% chromium and 15% silicon in an amount less than 0.5%, the remainder consisting essentially of aluminium. Aluminum alloy. (2) +', θ~4.0mm magnesium, 0. '
l-/,,! Manganese, O, O! r~θ, 3% chromium and o,ls more than % and 0. A molten aluminum alloy containing silicon in an amount less than
After annealing at a temperature of IIO2-130C, pre-stage cold rolling and intermediate annealing were performed, followed by 60°C.
1. A method for producing a superplastic aluminum alloy, which comprises performing post-stage cold rolling until a rolling reduction of 1 or more is reached. A manufacturing method according to claim 1, characterized in that: (4) Intermediate annealing Sθ~da. The manufacturing method according to claim 1 or 3, characterized in that the manufacturing method is carried out in oc. (5) Pure knotweed, made by adding magnesium, manganese, chromium and silicon to aluminum with a purity of 7% or more.
6.0% magnesium, o, l/, ~/,! r% manganese, O,OS~0.3% chromium and 0. / ,
! ! According to any one of claims 1 to 9, the method comprises preparing a molten aluminum alloy containing silicon in an amount of more than -%, less than t%, and casting and rolling the molten aluminum alloy. Manufacturing method described.