KR0154401B1 - Aluminum alloy and the manufacturing method thereof - Google Patents

Abstract

The present invention relates to a high ductility aluminum alloy having excellent high temperature ductility, and a method for manufacturing the same, and a method of adding a large amount of a special alloy element generally used or powder metallurgy has a defect that is uneconomical and low in practicality because of high manufacturing cost. .

Accordingly, the present invention is carried out in the order of melting, the complete dissolution of Mn and Zr in the alloying elements, the temperature is constantly lowered and the melting of the alloying element by adding Mg, and casting And a method of producing high ductility aluminum, and an aluminum alloy in which the alloying elements are added in an amount of 3-7% Mg, 0.3-1.2% Mn, and 0.05-0.25% Zr. It is to be able to manufacture an alloy having excellent hot ductility without adding a large amount of alloying elements such as expensive Li, Sc, Cr, Zr and Cu or using a special equipment.

Description

Highly ductile aluminum alloy and its manufacturing method

The accompanying drawings are manufacturing process diagrams of the aluminum alloy according to the present invention.

The present invention relates to a high ductility aluminum alloy having excellent high temperature ductility, and a method for manufacturing the same, in particular, a high ductility aluminum alloy capable of increasing the addition efficiency without using a large amount of alloying elements in the aluminum alloy and having a very excellent elongation at high temperature. And to a method for producing the same.

In general, the manufacturing method of aluminum alloy with high ductility is based on the principle of grain refinement and the resulting sliding of grain boundary at high temperature, and a large amount of special alloy element is added or powder metallurgy is mainly used. come.

The method for adding a large amount of the special alloy element is Li, Sc addition alloy (EL Bradley, RA Emigh and JW Morris, Jr: Scripta Metallurgica et Materialia, Vol. 25, pp. 717-721, 1991) and has a brand name Supral Al-6Cu-0.4Zr alloy (see Alcan Aerospace company brochure) is a typical example, in which a large amount of alloying elements form a second phase to suppress grain growth, resulting in finer grains and higher hot ductility. It is.

However, the Li and Sc addition alloy is not only expensive, but also has a problem in that it is difficult to manufacture the alloy because of its high reactivity in the atmosphere and harmful to the human body, and Supral has a high melting point of Cu and Zr added in excess of the equilibrium high capacity. It is difficult to dissolve, has a low recovery rate of alloying elements, and forms a coarse secondary phase, thereby degrading mechanical properties.

In addition, these alloys require metal coagulation equipment to make the alloy element into supersaturated solid solution state during casting, which makes it difficult to manufacture large ingots. There is this.

On the other hand, the method of powder metallurgy (see K. Higashi et al .: 7 Scripta Metallurgica et Materialia, Vol. 26 pp. 191 to 196, 1992) is produced by sintering the finely prepared powder, so that the crystal grains are very fine. Although there is an advantage, an expensive powder manufacturing equipment is required separately, and the surface of the powder is easily contaminated with an oxide film, so that a large amount of pores are generated at high temperature tension.

The object of the present invention devised in view of such a conventional problem is that the high temperature without the addition of a large amount of alloying elements such as expensive Li, Sc, Cr, Zr and Cu by using the appropriate alloy design and manufacturing conditions or using a special equipment It is to provide a high ductility aluminum alloy having a ductility and a method of manufacturing the same.

The above object of the present invention is to provide a high ductility aluminum alloy, characterized in that the addition of alloying elements in the content of Mg 3-7%, Mn 0.3-1.2%, Zr 0.05-0.25%, and also dissolving Al And completely dissolving Mn and Zr in the alloying elements, lowering the temperature constantly and adding and dissolving Mg, an alloying element, performing casting, homogenizing, hot rolling and cold rolling. It is achieved by providing a method for producing a high ductility aluminum alloy, characterized in that performed in the order of the rolling step.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and various embodiments.

The alloy element of the Al alloy according to the present invention is characterized in that the type and amount of Mg 3-7%, Mn 0.3-1.2%, and Zr 0.05-0.25% are added.

In other words, the components of the alloy element is to replace Cr, which is easy to form a coarse secondary phase, in a 5000-based Al alloy containing Mg, Mn, and Cr as the main alloy element with a small amount of Zr having a greater effect of generating fine precipitates. When the element is added in each range, the alloy has a high hot ductility, out of this range the hot ductility is bad or the appropriate manufacturing conditions can be changed.

The Mg is added to increase the strength and refine the structure as a solid solution strengthening and dynamic recrystallization promoting element, but less than 3%, such effect is less, and at 7% or more, cold workability is deteriorated due to grain boundary precipitation and excessive work hardening effect 3 ~ The addition amount is limited to 7%.

In addition, the Mn and Zr as a fine precipitate generating element inhibits grain growth and contributes to the refinement and stabilization of the tissue, and when the addition of 0.3% and 0.05% or more, respectively, sufficient precipitates are generated and the effect is high. When excessively added in excess of 1.2% and 0.25%, a crude object may be generated and the high temperature ductility may be lowered.

Next, the manufacturing method of the high ductility aluminum alloy of the present invention as described above will be described.

The accompanying drawings are manufacturing process diagrams of the aluminum alloy according to the present invention. As shown in the drawing, after Al is dissolved, Mn and Zr are first added among the alloying elements, and then heated to a high temperature in the temperature range of 770 to 880 ° C. to completely dissolve them. The temperature of the molten metal is lowered to 680 to 770 ° C, and Mg is added to dissolve, followed by casting. At this time, the alloying element may be used a mother alloy previously dissolved in high concentration in Al.

As mentioned above, the reason why the melting temperature of Mn and Zr is set in a range higher than about 750 ° C., which is the melting temperature of a conventional Al alloy, is that the melting point of these elements is so high that the temperature melts at least 770 ° C. to melt completely in a short time. This is because the high and fine phase is formed, and when the temperature is low, complete dissolution is not achieved, or even when dissolved, a crude object is formed, which deteriorates high temperature ductility, and takes a long time to completely dissolve, thereby decreasing productivity and recovery rate. Because. However, when excessively heated above 880 ° C., oxidation is severe and the recovery rate is lowered again. Therefore, the appropriate melting temperature range of these elements is limited to 770 ° C. to 880 ° C.

In addition, the melting temperature of Mg is set in a low temperature range. The melting point of this element is low, and the vapor pressure is large, so that the oxidation and evaporation is low when the temperature is 770 ° C or higher, and the recovery rate is low. This is because the recovery rate is reduced. Therefore, the appropriate dissolution temperature of Mg is limited to the range of 680 ~ 770 ℃, and the casting temperature is also limited to this range in order to refine the casting structure and increase the solid solution of Mn, Zr.

As described above, in the present invention, the dissolution order of the alloying elements is efficiently distributed as the dissolution and casting conditions, and the melting temperature is differently performed in various stages according to the type of elements, and the final dissolution temperature is dissolved at the same temperature as the casting temperature. While maximizing the suppression of the production of the target and to promote the generation of microphases to achieve the miniaturization of tissues.

After casting, the manufacturing process is cold rolled into a plate with a desired thickness through the usual homogenization treatment and hot rolling. The surface of the rolled sheet may be shaved a few millimeters at an appropriate time in order to improve the surface condition. A hot rolling process may be put between rolling and cold rolling, or cold rolling may be omitted when the amount of hot rolling is large. In addition, although recrystallization heat treatment may be performed during or after cold rolling, it is not necessarily required.

When the cold rolled sheet produced by such a process is subjected to a tensile test at a temperature range of 450 to 530 ° C., it shows excellent hot ductility. Even though the temperature is outside this range, the ductility of this alloy is higher than that of general Al alloy, but the above range It is considerably lower than when you are inside. The elongation is lowered outside this temperature range because the grain boundary friction is increased at 450 ° C. or lower, and the grain slippage is slowed, and the grain growth rate is increased at 530 ° C. or higher, resulting in coarse texture.

The manufacturing process and general characteristics of the alloy of the present invention will be more clearly understood by the following examples.

Example 1

Table 1 below shows the relationship between dissolution temperature, casting temperature, Zr recovery rate and high temperature elongation of Al alloy, Zr is dissolved after Al, 0.15∼0.25% added with Mn and heated to the highest temperature, then completely dissolved. The temperature of the molten metal was lowered, Mg was added, completely melted, and immediately cast. The cast alloys were subjected to the usual homogenization treatment and hot rolling at 430 to 540 ° C., and then cold rolled to 60% or more to prepare a sheet having a thickness of about 2 mm. Tensile test specimens with a gauge distance of 25 mm were made from this sheet and subjected to a tensile test at a temperature range of 450 to 530 ° C., followed by high temperature ductility.

As shown in the above table, the higher the melting temperature, the Zr recovery is improved and the high temperature elongation is also increased. That is, when the melting temperature is 770 ℃ or more, Zr recovery shows a high level of 80% or more, high temperature elongation can be obtained 450% or more. If the melting temperature is 700 ° C. or lower, the Zr recovery rate is significantly reduced to 50% or less, which is uneconomical. When it is dissolved at 750 ° C. or lower, a crude object is generated and the high temperature ductility is lowered. In order to suppress evaporation of Mg and to speed up the solidification rate, the casting temperature was set to 770 ° C. or lower to obtain almost 100% Mg recovery. In addition, since the dendritic structure became fine, Mn and Zr were dissolved in a supersaturated state and precipitated as a fine phase during the heat treatment process, a fine recrystallized structure of 10 μm or less was obtained, and as a result, excellent high temperature elongation was achieved.

On the other hand, the relationship between the analysis value and the high temperature elongation, which is the amount of Zr contained in the alloy, the higher the Zr content, the better the high temperature elongation. That is, when the Zr content is in the range of 0.05 to 0.25%, a high temperature elongation of at least 600% is obtained when the Zr content is high. The high temperature elongation when Zr was not added at all was 150% or less.

Example 2

Table 2 below is an example of the results of Mg content on high temperature ductility when the amount of Mg alloy element is changed in Al-Mg-0.5 / 1.0Mn-0.05 / 0.2Zr alloy system. The melting temperature and the casting temperature were in the range of 780 ~ 860 ℃ and 680 ~ 770 ℃, respectively, after casting the plate was manufactured in the same manner as in Example 1 and the high temperature ductility was measured by the same method. In this table, hot ductility tends to increase gradually as the Mg content increases. In other words, if the Mg content is 0.5% or less, the hot ductility does not exceed 200%, but if it exceeds 2%, the hot ductility is obtained at 200% or more, and if it exceeds 3.5%, the excellent high ductility is obtained. .

Example 3

Table 3 below is an example of measuring the high-temperature ductility after manufacturing the plate material in the same manner as in Example 2 by changing the amount of alloying elements, such as Mn, Cu in the Al alloy. When Mn is alone without Cu, Mn content of more than 0.5% yields a high temperature elongation of 250% or more.In the case where only Cu is 0.8 to 1.5% without Mn, overall high temperature ductility is compared with that of Mn alone. Not good. If Mn is cavities with 0.5 to 1% Cu, high ductility of 250% or more can be obtained when the Mn content exceeds 0.25%, but the effect of improving hot ductility is not so high compared to the amount added. The reason is that as the amount of added Cu increases, the amount of coarse secondary phase increases, making it difficult to homogenize the tissue and increasing the amount of pore generated at high temperature deformation. Therefore, Cu does not necessarily need to be added, and in terms of homogenization and pore generation, it is necessary to suppress the amount of addition as much as possible.

As described above, the present invention enhances the effect of forming a microphase by adding Zr instead of Cr to a commercial 5000-based Al alloy composed of Al-Mg-Mn-Cr. In the manufacturing method, high Zr, Mn melting temperature and low Mg melting temperature are used to make each alloy element dissolve quickly and efficiently. By promoting the heat treatment, the microstructure of the structure is effectively achieved even with a small alloy element has an advantage that can be obtained excellent hot ductility.

As described in detail above, according to the manufacturing method of the aluminum alloy according to the present invention, by adding a large amount of alloying elements such as expensive Li, Sc, Cr, Zr and Cu, or special equipment by appropriate alloy design and manufacturing conditions It is possible to manufacture an alloy having a high temperature ductility of several hundred percent without using, so as to enable the production of articles of a complex shape that is impossible with ordinary metal with excellent moldability, such as plastic.

Claims (2)

By weight%, Mg: 4.1-7%, Mn: 0.3-1.2%, Zr: 0.05-0.25% and the remainder consisting of unavoidable impurities, and have an elongation of up to 640% at 450-530 ° C. High ductility aluminum alloy with excellent high temperature ductility. Al was dissolved, Mn and Zr were added during alloy combustion, and completely dissolved at 770 to 880 ° C. At 680 to 770 ° C, Mg was added and dissolved at 680 to 770 ° C, and casting was performed to obtain Mg: A method for producing a high ductility aluminum alloy having excellent high temperature ductility, characterized by producing an alloy consisting of 4 to 7%, Mn: 0.3 to 1.2%, Zr: 0.05 to 0.25% and the remainder of unavoidable impurities.