KR101514265B1 - Low electrical resistance and high strength aluminum alloy manufacturing methods - Google Patents

Abstract

A method for producing an aluminum alloy, comprising the steps of adding an essential additive element containing 0.05 to 0.5 wt.% Of Fe, 0.05 to 0.5 wt.% Of Zr and 0.01 to 0.5 wt.% Of MM (misch metal) and 0.001 to 0.05 wt. At least one element selected from the group consisting of 0.01 to 0.2 wt.% Of Si, 0.01 to 0.1 wt.% Of Mg, 0.005 to 0.05 wt.% Of Be, 0.01 to 0.1 wt.% Of Ti and 0.005 to 0.05 wt. A first step of selectively adding at least two of the essential additive elements and the optional additional elements and maintaining the total added amount of the additive element to 0.6 wt% or less and the remainder of the aluminum to dissolve the aluminum alloy; A third step of forming the rod into a multi-stage rolling and molding the rod into a rod; and a fourth step of heat-treating the rod, characterized in that a high strength aluminum alloy is obtained in addition to a high conductivity Strength aluminum alloy with low electrical resistance characteristics.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a high strength aluminum alloy,

The present invention relates to a method of manufacturing a high strength aluminum alloy having a low electrical resistance characteristic, and more particularly, to a method of manufacturing a high strength aluminum alloy which is capable of obtaining a high strength aluminum alloy with high electrical conductivity by adding an element of strength strengthening alloy to pure aluminum ≪ / RTI >

Aluminum has a low electric resistance property and various strength characteristics can be obtained according to various alloying elements. Therefore, aluminum is widely used as an industrial base material which is very important now, and its usage is also rapidly increasing.

In addition, various kinds of aluminum alloys are used in accordance with the applications required in various industrial fields, and new aluminum alloys suitable for the new requirements are still being developed.

Aluminum is considered to be the most advantageous because of its light weight and low electrical resistance. In recent years, there has been an increasing demand for high strength properties which are difficult to be compatible with the original physical properties of aluminum, and new advanced alloying design techniques are required. For example, heat-resistant aluminum alloy materials used in high-capacity processed transmission lines that can transmit twice as much current as conventional processing transmission lines are required to have both high electrical conductivity and high strength. Particularly, it is assumed that the refrigerating air conditioner for home use and automobile is always required to have a high performance and high efficiency. If the use of new refrigerant gas, The strength of the inner pressure of the tube must be increased by about twice as much as the present time, and the heat conduction characteristics should not be lowered.

After the condenser tube is manufactured, it is assembled with a heat exchanger together with a fin material, a head pipe, and the like, and then is brazed to complete a final product. Considering that the brazing process is usually performed at 600 to 630 ° C , At very high temperatures. That is, by the brazing treatment, recovery of microstructures such as dislocation and abrupt disappearance of dentine grains and formation and recrystallization of recrystallized grains proceed, and the strength of the material itself is inevitably reduced. Aluminum alloy system (AA3003) has been proposed as a candidate for overcoming the material limitations. However, high efficiency of the air conditioner can not be achieved because the heat conduction characteristic is rapidly reduced due to the addition of a large amount of alloying elements.

For this reason, there is a need to develop an aluminum alloy manufacturing technology capable of simultaneously realizing high electric conductivity characteristics and high strength characteristics that can be applied in extreme manufacturing processes.

Korean Registered Patent No. 10-1198324 (October 31, 2012)

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above-mentioned problems, and it is an object of the present invention to provide a method of manufacturing a high-strength aluminum alloy which can achieve high strength without deteriorating electrical resistance characteristics by adding pure aluminum, And an object of the present invention is to provide a method of manufacturing a high strength aluminum alloy having low electrical resistance characteristics.

In order to accomplish the above object, the present invention provides a method of manufacturing a high strength aluminum alloy having a low electrical resistance characteristic, comprising the steps of: 0.05 to 0.5 wt.% Of Fe; 0.05 to 0.5 wt.% Of Zr; , 0.01 to 0.5 wt.% Of Ti, 0.001 to 0.05 wt.% Of Ni, 0.01 to 0.2 wt.% Of Si, 0.01 to 0.1 wt.% Of Mg, 0.005 to 0.05 wt. 0.01 to 0.1 wt.% Of Sr, and 0.005 to 0.05 wt.% Of Sr, and the total added amount of the indispensable element and the optional element is maintained at 0.6 wt.% Or less A second step of molding the aluminum alloy into a cast steel bar; a third step of multi-step rolling the casting bar to form a rod into a rod; and a third step of heat- And a fourth step.

The alloying in the first step is performed at 740 ° C to 850 ° C.

The forming of the casting bar in the second step is performed at 450 ° C to 550 ° C, and the casting bar is supplied to the multi-stage rolling mill while being maintained at 490 ° C to 550 ° C.

In addition, the third step is characterized in that the rolling is started at 450 ° C to 550 ° C and the rolling is finished at 250 ° C to 350 ° C.

Finally, the heat treatment in the fourth step is performed at a temperature of 300 ° C to 450 ° C.

As described above, according to the present invention, the following effects can be expected.

It is possible to provide an aluminum alloy in which the high conductivity and the high strength are realized at the same time, and the improved characteristics can be expected by heat treatment after the processing, which is advantageous in various industrial fields.

Hereinafter, preferred embodiments of the present invention will be described in detail.

A method of manufacturing a high strength aluminum alloy having a low electrical resistance characteristic according to the present invention is characterized by comprising the steps of: (a) providing a solution containing 0.05 to 0.5 wt.% Of Fe, 0.05 to 0.5 wt.% Of Zr and 0.01 to 0.5 wt.% Of MM % Of Ni, 0.01 to 0.1 wt.% Of Ba, 0.005 to 0.05 wt.% Of Be, 0.01 to 0.1 wt.% Of Ti, and 0.01 to 0.1 wt.% Of Ti, To 0.05% by weight, and the total amount of the additive element and the optional additive element is maintained at 0.6 wt% or less, and the remainder is aluminum alloy to dissolve the aluminum alloy . Thereafter, the aluminum alloy is cast through a casting machine, and then the casting bar is rolled into a section of a predetermined size through a multi-stage rolling mill to form a rod, followed by heat treatment.

Alloying in the melting furnace is performed at 740 ° C to 850 ° C and molding of the casting bar is performed at 450 ° C to 550 ° C and rolling is started at 450 ° C to 550 ° C and rolling is finished at 250 ° C to 350 ° C And the heat treatment is preferably performed at a temperature of 300 ° C to 450 ° C.

Hereinafter, the present invention will be described in more detail.

First, an additional element for forming a high-strength aluminum alloy manufacturing method having a low electrical resistance characteristic includes an essential additive element including Fe, Zr, and MM and a selective additive element including Ni, Si, Mg, And the remainder is aluminum, which is an alloy containing a small amount of an additive element added to an aluminum alloy. These additional elements are additive elements that form a large number of intermetallic compounds such as Al ₃ Fe, Al ₃ Zr, and Al ₃ MM together with aluminum during the dissolution or solidification process. Some of the additional elements promote the formation of intermetallic compounds . In particular, MM is composed of La, Ce, Pr, Nd and Sm, which are rare earth elements, and such La, Ce, Pr, Nd and Sm bond with aluminum to form various intermetallic compounds.

In general, the ingot used as the dissolving raw material is often divided into 99.9% of virgin ingot, and the EC (electrical commercial) ingot with a small amount of B added to the virgin ingot. When B is added, boride is formed by reacting with Ti, V, etc. which greatly decrease the electric conductivity per unit amount of addition. By replacing the atomic defect caused by these elements with defects of intermetallic compounds, the relative electrical conductivity is prevented from lowering, Aluminum) EC (Electrical Commercial) ingot is used because it is precipitated and separated by the specific gravity difference between the molten metal and the boride.

The effect of the additive element on the aluminum alloy is as follows.

It plays a role in increasing the strength and accelerating the aging in the Fe - aluminum alloy, and it produces a precipitate of Al ₃ Fe, and the addition amount is limited to 0.05 to 0.5 wt%.

Zr - Aluminum alloys are fine precipitate forming elements, which increase the yield strength and tensile strength as well as improve the heat resistance. They form precipitates of fine Al ₃ Zr during casting and heat treatment, and the addition amount is limited to 0.1-0.5 wt%.

MM - is a constituent of rare earth elements such as La, Ce, Pr, Nd and Sm. It is an element that improves the yield strength and tensile strength as well as heat resistance. It is an element which produces fine precipitates during casting and heat treatment. %.

Ni - As an element contributing to improvement in heat resistance and strength, the addition amount is limited to 0.001 to 0.05 wt%.

Si - Al ₃ Zr to form various intermetallic compounds. As a result, it contributes to the improvement of the strength, but when it is added in an excessive amount, the conductivity is decreased and the material The content thereof is limited to 0.01 to 0.2 wt%.

Mg - aging is promoted to contribute to the improvement of strength, thereby improving the heat resistance. However, when the added amount is excessive, the heat resistance is deteriorated. Therefore, the addition amount is limited to 0.01 to 0.1 wt%.

The precipitation of Be - Al ₃ Zr is accelerated and the decrease of the conductivity is not great even if the addition amount is increased. And has an effect of improving the corrosion resistance, and the addition amount is limited to 0.005 to 0.05 wt%.

Ti - casting promotes nucleation to refine the casting structure and reduce the disconnection at the time of drawing, but the addition amount is limited to 0.01 to 0.1 wt% in order to lower the conductivity at the time of addition.

Sr - It helps the fine precipitation of metal nursing product during casting. Its addition amount is limited to 0.005 ~ 0.05wt.

The addition of each element described above improves the strength and heat resistance of aluminum but does not significantly increase the electrical resistivity, so the additive element should be used within the range of the optimum addition amount. The additive element in the present invention is present in the form of precipitates mostly because of a small amount of a small amount of the additive element, and has little influence on the electric conductivity or the thermal conductivity, but has a large effect on the increase in strength and heat resistance. On the other hand, the concentration of elements such as Ti and V is strictly limited because it has a large effect on the electric conductivity and the thermal conductivity. Since Ti and V have a large solubility limit and a large increase in resistivity, boron is added to the molten aluminum in the form of Al-B or potassium borofluoride to precipitate in the form of TiB2 and VB2.

Next, the production method of the present invention will be described.

The method of manufacturing a high strength aluminum alloy having a low electrical resistance characteristic according to the present invention can be applied to all aluminum alloy manufacturing processes whether they are manufactured by a batch type process or a rod by a continuous casting method (Properzi method) .

 Wherein an essential additive element including 0.05 to 0.5 wt.% Of Fe, 0.05 to 0.5 wt.% Of Zr and 0.01 to 0.5 wt.% Of MM (misch metal) is added through a melting furnace, 0.001 to 0.05 wt. At least two of the optional elements including 0.01 to 0.2 wt.%, Mg 0.01 to 0.1 wt.%, Be 0.005 to 0.05 wt.%, Ti 0.01 to 0.1 wt.% And Sr 0.005 to 0.05 wt. % Of the total amount of the additive element and the optional additive element is less than 0.6 wt.%, And the remainder is aluminum to produce an aluminum alloy. The aluminum alloy is cast through the casting machine, The casting bar is rolled into a section of a predetermined size through a multi-stage rolling mill, and then subjected to a heat treatment. In each process step, the continuous casting process is optimized according to the solidification analysis of the aluminum casting rod temperature gradient, solidification rate, and additive elements.

In the process of continuous casting, the above-mentioned trace amount of the additive element including aluminum is put into a melting furnace and melted and alloyed at 740 캜 to 850 캜. When the melting and alloying temperature was 800 ℃, the Zr amount was not decreased and the recrystallization temperature was the highest. On the other hand, the amount of Zr decreased considerably at 700 ℃, and the recrystallization temperature was the lowest when partial segregation was severe. The amount of added elements such as Zr, Sc, and MM did not decrease as the melting and alloying temperature increased, the addition of elements did not occur, and the recrystallization temperature was high. This is in order to improve the heat resistance by forcibly solving the addition elements as much as possible such as Zr in aluminum.

Then, the molten metal spouted from the melting furnace flows along the bath and then flows into the casting machine, and cooling water is injected from the inside and outside of the casting machine to solidify the square casting. The casting bar is formed at 450 ° C to 550 ° C and supplied to the multi-stage rolling mill at a high temperature of 490 ° C to 550 ° C. When the temperature of the casting bar is too low, the risk of cracking due to the poor adhesion is increased in the next step of the multistage rolling. When the temperature of the casting bar is too high, rolling is easy. However, And thus it can not be squeezed during the rolling process, it may cause disconnection of the central part in the subsequent process.

The casting bar is supplied to a continuous multistage mill by a three-directional roll while being maintained at a high temperature of 490 ° C to 550 ° C. The rolling is started at 450 ° C to 550 ° C and the rolling is finished at 250 ° C to 350 ° C, And rolled to a rod having a diameter of about 9.5 mm to about 12.5 mm. The hot rolling of the casting bar destroys the casting structure, crushes the coarse crystals containing Zr, Fe, and the like, and uniformly and finely distributes it to improve the strength. In addition, in the post-drawing treatment, (site).

The reason why the hot rolling temperature is started at 550 DEG C or less and finishes at 350 DEG C or less is that when the hot working start temperature exceeds 550 DEG C, a hardly alloyed element such as Zr is precipitated to a great extent and heat resistance and strength And when the end temperature of the hot working is 350 DEG C or more, the potential for the Zr precipitation site is not sufficiently increased. Also, the section reduction ratio was 92% in hot working. This is because, when the sectional reduction ratio is less than 80%, the fracture of the cast structure and the crushing of the coarse crystallized product and the proliferation of the dislocation do not occur sufficiently.

On the other hand, the rolling temperature can be adjusted to prevent cracking in the manufacturing process, and a hot-worker can be used to cut the segregation layer.

The continuously rolled rod is maintained at a temperature of 300 to 450 DEG C for 50 to 80 hours to perform a heat treatment, which optimizes the precipitation amount of the intermetallic compound in the above production process. If the precipitation amount of the intermetallic compound is small, the heat resistance can not be improved. If the precipitation amount is large, the intermetallic compound crystals become large in the cooling process and the uniform dispersion does not occur in the aluminum matrix, Heat treatment is carried out within the above temperature and time range so as to be uniformly dispersed in the mother body by optimizing with particulates.

Hereinafter, embodiments of the present invention will be described.

In order to produce a high strength aluminum alloy having a low electrical resistance characteristic according to the present invention, dissolution and alloying were carried out using an electric furnace. The casting process consisted of melting of EC Grade aluminum, alloying of added elements, agitation and tapping, and was performed at 800 ° C for 1 hour. This is to enhance strength and heat resistance by forcibly adding an additional element to aluminum, and at a temperature of 740 캜 or less, coarse crystals were crystallized and segregated. The temperature of the casting machine was adjusted to 490 ℃ to prepare a cast bar.

The manufactured casting bar was rolled into a section of a predetermined size through a multi-stage rolling mill, and the rolling start temperature was set at 490 ° C and the end temperature was set at 280 ° C. 3-way rolls are continuously fed from a 13-stage to a 15-stage multistage mill. The processing rate of each stage is 20% and the final machining rate is 93.4%. Hot rolling destroys the casting structure, Are uniformly and finely distributed to improve strength and heat resistance.

When the hot-rolling start temperature is 550 ° C or lower and the hot-working starting temperature exceeds 550 ° C, Zr or the like is not precipitated to a large extent or contributes to improvement in heat resistance and strength characteristics, and the hot- The growth of dislocations or the like is not sufficiently generated at 350 DEG C or more. The reduction rate of the cross section during hot rolling is 80% or more. When the reduction ratio of the cross section is less than 80%, the fracture of the cast structure, crushing of the coarse crystallized product, and dislocation growth do not occur sufficiently. When the final rolling process is completed, it is rolled into a rod having a diameter of about 9.5 mm to 12.5 mm.

Continuous multi-stage rolling changes the internal structure. The order of rolling changes into casting structure of casting bar, transformation structure by continuous multi-stage rolling, and recrystallized structure of final aluminum rod. In the case of continuous triple-stage rolling, strain is preferentially increased at the surface portion, and when the shape of each end is triangular, the strain is increased and the strain rate is increased as the stage is increased. At the end of multi- Respectively. In the present invention, the change in the thermal conductivity increases with the progress of the multi-step rolling while the continuous multi-step rolling is performed, and decreases with the deformation of the microstructure during the multi-step rolling and then increases again. As a result, the thermal conductivity increased due to the fracture of the cast structure, and the thermal conductivity temporarily decreased due to the formation of the deformed structure. After that, a recrystallized structure was formed by processing and the grain was elongated in the working direction, Respectively.

The continuously rolled rod was maintained at a temperature of 300 to 450 ° C for 50 to 80 hours for heat treatment. Thus, the precipitated intermetallic compound was optimally dispersed in particulate form in the aluminum matrix to be evenly dispersed.

Table 1 below summarizes alloy compositions showing excellent properties obtained according to the present invention and their characteristic values in composition.

Table 1

As can be seen from Table 1, it can be seen that conductivity characteristics and high strength characteristics, which are difficult to achieve in an aluminum alloy, are simultaneously realized. The characteristics shown in Table 1 are the characteristics of the alloy cast after melting, and further improved characteristics can be expected if the alloy is subjected to a heat treatment process after processing.

As described above, according to the present invention, an aluminum alloy is designed so that the total amount thereof is not more than 0.6 wt.%, Based on pure aluminum, optionally combined with the essential additional elements and optional additional elements, It should be appreciated that many other modifications are possible for those of ordinary skill in the art.

Claims (5)

In an aluminum alloy manufacturing method,
0.05 to 0.5 wt.% Of Fe, 0.05 to 0.5 wt.% Of Zr, and 0.01 to 0.5 wt.% Of MM (misch metal)
, 0.001 to 0.05 wt.% Of Ni, 0.01 to 0.2 wt.% Of Si, 0.01 to 0.1 wt.% Of Mg, 0.005 to 0.05 wt.% Of Be, 0.01 to 0.1 wt.% Of Ti and 0.005 to 0.05 wt. At least two of the selectively added elements are selectively added,
A first step of maintaining an added total amount of the indispensable element and the optional additional element at 0.6 wt.% Or less and the remainder being aluminum to produce an aluminum alloy;
A second step of molding the aluminum alloy into a cast steel bar;
A third step of multi-step rolling the casting bar and molding it into a rod; And
And a fourth step of heat-treating the rod. The method of manufacturing a high-strength aluminum alloy having low electrical resistance characteristics. The method according to claim 1,
Wherein the alloying in the first step is performed at a temperature of 740 ° C to 850 ° C. The method according to claim 1,
Wherein the molding of the casting bar in the second step is carried out at 450 ° C to 550 ° C and the casting bar is supplied to the multi-stage rolling mill while being maintained at 490 ° C to 550 ° C. A method for producing an alloy. The method according to claim 1,
Wherein the step of starting the rolling in the third step is performed at 450 ° C to 550 ° C and the step of rolling is performed at 250 ° C to 350 ° C. The method according to claim 1,
Wherein the heat treatment in the fourth step is performed at a temperature of 300 ° C to 450 ° C.