JPH0456744A - High conductivity al-mg-si alloy tube and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the external cylindrical conductor of a compressed gas insulated transmission line for bulk power conduction excellent in electrical conductiv ity by subjecting an Al-Mg-Si alloy having a specified compsn. to homogenizing treat ment and precipitation treatment, thereafter subjecting it to hot extrusion into the shape of a tube and executing hardening and aging treatment. CONSTITUTION:At the time of manufacturing as air transmission line of which an internal cylindrical conductor 2 is housed in an external cylindrical conductor 1 made of an Al alloy pipe, a stranded conductor 3 is housed in the internal cylindrical conduc tor 2 and the space thereamong is filled with an insulating SF6 gas, the external cylindrical conductor 1 is manufactured by an Al-Mg-Si alloy. The ingot of the Al-Mg- Si alloy contg., by weight, 0.3 to 0.8% Mg, 0.3 to 0.8% Si, <=0.10% Fe, 0.0003 to 0.0030% B and each <=0.0030% and total <=0.0100% of Mn, Cr, Ti, V and Zr as transi tion metals with total <=0.0050% impurities is subjected to homogenizing treatment at 450 to 600 deg.C for 8 to 24hr, is subjected to precipitation treatment at 300 to 400 deg.C for 8 to 24hr, is thereafter subjected to hot extruding into the shape of a pipe and is subjected to hardening and aging treatment to regulate the size of Mg2Si precipitates to <=5mum. The external cylindrical conductor 1 for an air transmission line excellent is electrical conductivity can be manufactured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an aluminum alloy tube with excellent electrical conductivity and a method for manufacturing the same, particularly for use in external cylindrical conductors of large-capacity conductive conduits and aerial power transmission lines. The present invention relates to a highly conductive Al-Mg-3i alloy extruded tube and a method for manufacturing the same.

[Prior Art] A conduit aerial power transmission line is a power transmission line that has recently been put into practical use as a new type of underground power transmission cable. Figures 3 and 4 show cross sections of the conduit aerial power transmission line, in which an aluminum alloy vibrator is used for the inner cylindrical conductor 1 and the outer cylindrical conductor 2, and the space between the conductors 1 and 2 is insulated. Sulfur hexafluoride (SF6) gas is used as the gas.

A stranded conductor 3 is housed inside the inner cylindrical conductor l.

Although the material for such aluminum alloy pipes has not yet been established, it is required to have good conductivity, workability, and on-site weldability. For this purpose, alloys such as JIS 8063.6101, which is a typical alloy for extrusion, are used.

In addition, the present applicant previously disclosed Mg in Japanese Patent Application No. 1-19836.
, an aluminum alloy material with excellent electrical conductivity in which SiSFe and other impurities are controlled, the remainder substantially consists of A1, and the area ratio of Mg2Si precipitates is 1.2% or less, and an alloy having the above composition is homogeneously After treatment, lO~70℃/
We proposed a manufacturing method in which hot extrusion is performed after cooling at a cooling rate of hr.

Furthermore, the following have been proposed as wire rods of aluminum alloy materials with excellent conductivity and methods for producing the same.

■ S1SGes An aluminum alloy with regulated Mg and Fe, which precipitates Mg2Ge and improves strength without reducing conductivity (Japanese Patent Laid-Open No. 48-539)
18) ■ Fe, Mg5S i (Be or sb) regulated aluminum alloy, Mg, S in electric aluminum base metal.
It is obtained by adding iSSb, and Mg5SisFe increases the strength without reducing the conductivity, and reduces the deterioration of corrosion resistance.
Or those prevented by sb (JP-A-49-49814 and ■ Regulation of Mgs Si, 60% rough drawn wire
After the above cold working, a method of making Mg2Si precipitates fine and increasing strength by performing a 15% or more cold working after a primary heat treatment at 120 to 180°C, and a secondary heat treatment at 130 to 240°C. (Japanese Unexamined Patent Publication No. 53-78114) ■ A method for preventing cracking of ingots by controlling Mg5SiSTiSB, degassing with chlorine gas or fluorocarbon gas, and further treating with Ti and B (Unexamined Japanese Patent Application No. 53-78114)
35814)■ Zrs Sis Mg is regulated and the ingot is cooled to 200°C at a rate of 5°C/sec or more.
A method of achieving heat resistance and high strength by performing 80% or more processing, then 65% or more cold working, and then heat treatment at 300 to 450°C for 20 to 100 hours (Unexamined Japanese Patent Publication) (Sho 56-65968).

[Problem to be solved by the invention] The conventional JIS 8063 alloy has an electrical conductivity of 53 to 5.
5% (lAC3,%), which is lower than the 57-59% of ordinary aluminum with a purity of 99.5%, and the power loss during power transmission was large. Furthermore, since the JIS 6101 alloy has poor weldability, it has the disadvantage that a method for joining pipes must be devised.

Furthermore, the previously proposed invention described in Japanese Patent Application No. 1-19836 has the disadvantage that a cooling furnace is required since it must be cooled at a cooling rate of 10 to 70°C/hr after homogenization treatment. be. Furthermore, the products proposed in ■ to ■ are all manufactured by a continuous casting method (Bloperch method) using a steel belt and a casting wheel, and cannot be used for pipes, which is the object of the present invention. be.

Therefore, the purpose of the present invention is to obtain an electric conductivity of 6 in lAC3 expression.
The purpose of the present invention is to provide an aluminum alloy extruded tube and a method for manufacturing the same, which can obtain 0% or more.

[Means for Solving the Problem] In order to achieve the above object, the present invention provides Mg: 0.3 to 0.
．． 8%, Si: 0.3-0.8%, Fe:≦0
．． 10%, B: 0.0003-0.0030%, Mn.

All transition metals of Cr5Ti, V, and Zr are o and ooa
o% or less, and the total of these is o, otoo% or less, and the sum of other impurities is 0.0050% or less, the balance consists essentially of Al, and the Mg2Si precipitate is 5 μm or less. Highly conductive Al - A Mg-Si alloy tube is the first invention, and an alloy material having the above composition is heated to 8 to 2
After homogenizing for 4 hours, at 300-400℃
The second invention is a method for manufacturing a highly conductive Al-Mg-Si alloy tube, which performs hot extrusion quenching and aging treatment under normal conditions after 4 hours of precipitation treatment.

[Function] The reasons for limiting the range of ingredients and manufacturing conditions of the alloy in the present invention are as follows.

Mg: Mg coexists with Si to form Mg2Si precipitates and contributes to improving strength, but as Mg content increases, electrical conductivity decreases.

Therefore, when the Mg content is less than 0.3%, the strength as a conductor is insufficient, and when it exceeds 0.8%, the electrical conductivity decreases. Therefore, the Mg content is 0.3 to 0.
It was set at 8%. In addition, due to the balance between both performances, 0.35 ~
0.5% is more preferred.

St:Si coexists with Mg to form Mg2Si precipitates and contributes to improving strength, but as the Si content increases, electrical conductivity and weldability decrease. Si content is 0.3%
If it is less than 0.8%, the strength as a single unit is insufficient and
If it exceeds , the electrical conductivity decreases. Therefore, 0.3
It was set at ~0.8%. In addition, considering both performances, 0.3
More preferably 5% to 0.5%.

Fe: Fe is set to 0.10% or less in order to lower the electrical conductivity of the aluminum alloy.

B: B refines the crystal structure of the alloy ingot, and at the same time,
Impurity elements (M n
It has the effect of precipitating and removing Mnx CrST as a boron compound.
It has the effect of reducing i, V, and Zr contents and increasing electrical conductivity. If the amount is less than 0.0003%, there is no effect, and if it exceeds 0.0030%, the boron compound remains and lowers the conductivity. Gatte, B content 0.0
It is necessary to set it to 0.003-0.0030%.

Mns Crs Tis V% Zr: Mns Cr
.

Ti and VSZr are contained in aluminum base metal, and both have the effect of lowering electrical conductivity. Therefore, the maximum content of each is 0.0030
% or less, and the total content of these is preferably 0.0100% or less.

Other impurities: All other impurities have the effect of lowering electrical conductivity. Therefore, the smaller the content, the more preferable it is, and the total content is preferably 0.0050% or less.

Mg2Si precipitates: Mg2Si precipitates are necessary to ensure strength, but when their shape becomes large, they have the effect of lowering electrical conductivity. In order to ensure strength and conductivity, the length of the precipitate is preferably 5 μm or less.

Homogenization treatment conditions: Homogenization treatment conditions for ingots are 450 to 60
A temperature range of 0°C is preferred. If this temperature is lower than 450°C, Mg-Si crystallized substances crystallized during casting will not be sufficiently infused, resulting in a decrease in strength. The same applies when the processing time is less than 8 hours. Furthermore, if the homogenization treatment temperature exceeds 600°C, the strength will increase, but the electrical conductivity will decrease. The same applies when the processing time exceeds 24 hours. The homogenization treatment of the ingot is performed in order to aggregate Al-Fe-Si and Al-Mg-Si eutectic compounds and improve extrudability.

If the temperature is less than 450°C, the diffusion rate of Fe5Si and Mg atoms will be low and the eutectic compound will not aggregate, resulting in a decrease in extrudability. Moreover, when the temperature exceeds 600°C, a part of the ingot starts to melt.

Precipitation treatment: The Mg and Si dissolved in solid solution by the homogenization treatment are precipitated uniformly and finely within the crystal grains as MgzSi compounds by the precipitation treatment, making extrusion easier and at the same time making the recrystallized grains of the material after extrusion finer. , has the effect of increasing strength. If this temperature is less than 300°C, precipitation of the Mg2Si compound will be insufficient, and the effect of increasing strength will be reduced. Furthermore, if the temperature exceeds 400°C, the precipitates of the Mg2Si compound become large, making it impossible to obtain fine recrystallization, and the effect of improving strength is lost. In addition, if the extrusion temperature is lower than 350°C, the extrusion pressure will not be high, and if it exceeds 550°C, the surface condition of the extruded material will deteriorate, and impurity elements (Mn, Cr, Ti, V,
, Zr) etc., the conductivity decreases due to re-solid solution, which is not preferable. After extrusion, quenching from 450 to 500℃ and 25
Aging treatment is performed at 0 to 300°C to finely precipitate Mg2Si compounds.

[Example 1 Table 1: After filtering a molten aluminum alloy having the composition shown to remove nonmetallic inclusions, the outer diameter was 520 mm.
A hollow ingot with an inner diameter of 150 mm was cast, and the outer circumference was made to have an outer diameter of 500 mm on the face side. This was heated to 470℃ for 10
After time homogenization treatment, precipitation treatment at 350℃ for 8 hours, extrusion processing at 450℃, outer diameter 150fflf
A tube material with a wall thickness of 18 mm+ was obtained.

After further aging treatment at 280°C for 7 hours, test pieces were cut out and tested for Mg2Si precipitates, mechanical properties, and electrical conductivity.

The size of the Mg2Si precipitates was determined from optical micrographs at a magnification of 400 times. Specifically, FIG. 1 is a photograph of the precipitation-treated material, and FIG. 2 is a photograph of the material not subjected to the precipitation treatment. This photograph was subjected to an image analysis device, and the particle size distribution of the precipitates was statistically processed to determine the size (maximum value) of the Mg2Si precipitates.

The conductivity was measured according to JIS H0505r "Method for Measuring Volume Resistivity and Conductivity of Nonmetallic Materials."

Mechanical properties were determined using JIS Z 2201 r Metal Material Tensile Test Piece No. 4 test piece. These results are shown in Table 1.

From the results in Table 1, it can be seen that the inventive materials N011~ et al.
The size of g2Si precipitates is 5μm or less, the tensile strength is 10kgf/mta2 or more, and the 0.2% proof stress is 6
lAC with kg/+am 2 or more and conductivity of 60% or more
Three values were obtained.

On the other hand, comparative material No. 6 has an Mg content of 8.
22%, the yield strength was slightly low at 5.8 kgf/mm2 (the size of the MgzSi precipitates was 8 μ■, and the conductivity was low at 59.2%. No. 7 had a Mg content of 1 ,02%, the size of M g 2 Si precipitates was 10 μm, and the conductivity was low at 59.8%.No. 8 had a low Si content of 0.24%, so The tensile strength was slightly lower at 9.8 kgf/mm2.No.9 has a high Si content of 0.98%, so M
The size of the g2Si precipitates was 10 μm and there were single Si precipitates, and the electrical conductivity was as low as 58.6%. No, l
O has a high B content of 0.0040%, so B compounds remain, resulting in a low conductivity of 58.7%. No, 11~
No. 15 had high contents of Mn5 (: 1S7 i, V, and Zr), and the conductivity was 80% or less in all cases.

In No. 1B, the sum of M n −, (: rSTi, V, and Zr contents was high at 0.0105%, and the electrical conductivity was low at 58%.

Example 2 No. of the aluminum alloy composition shown in Table 1.

After casting and facing the shiraishi material in the same manner as in Example 1, homogenization treatment and precipitation treatment were performed under the conditions shown in Table 2, extrusion processing was performed at 450°C, and then at 480°C. After being held in water for 2 hours and quenched in water, a test material was obtained by aging at 280° C. for 8 hours. These were subjected to various tests in the same manner as in Example 1, and the results are shown in Table 2.

Invention examples Nos. 17 to 23 all have the size of Mg2Si precipitates of 5μ or less and the tensile strength of 11.9k.
gf/gm2 or more, 0.2% proof stress is 6.9kgf'/m
A lAC3 value of m' or more and a conductivity of 60% or more was obtained.

On the other hand, in comparative example No. 24, the homogenization temperature was 4.
Since the temperature was as low as 00°C, the size of the M g 2 Si precipitates was 10 μm, the electrical conductivity was as low as 55.8%, and the yield strength was as low as 5.3 kgf/mg'.

Since the precipitation treatment temperature for No. 25 is as low as 250°C, M
The size of g2Si precipitates becomes IOμ group, and the conductivity is 5.
It was as low as 5.2%. Nos. 28 to 29 have different aluminum alloy compositions, but the precipitation treatment temperature is 45%.
Because the temperature is as high as 0°C, the size of MgzSi precipitates is 15 to 2
The conductivity was as low as 55.9 to 57.8%.

C Effect of the Invention] In this way, the present invention reduces transition metal elements to extremely small amounts by boron-treating an aluminum alloy whose Mg2Si content is regulated to 0.3 to 0.8%. By restricting and precipitating after homogenization,
By making the Mg2Si precipitates fine, the conductivity can be increased to 60
% or more was obtained, and an aluminum alloy useful for use in conduit power transmission lines was obtained.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph of a precipitation-treated material of the present invention, FIG. 2 is an electron micrograph of a material not subjected to precipitation treatment, and FIGS. 3 and 4 are cross-sectional views of a power transmission line to which the present invention is applied. l...Inner cylindrical conductor, 2...Outer cylindrical conductor, 3...
・Twisted conductor. Patent Applicant Sumitomo Light Metal Industries Co., Ltd. Agent Patent Attorney Hide Komatsu Agent Patent Attorney Hiroshi Asahi

Claims (2)

[Claims] (1) Mg: 0.3 to 0.8% (same as below weight%), S
i: 0.3-0.8%, Fe: ≦0.10%, B: 0.
0003~0.0030%, Mn, Cr, Ti
, V, and Zr are all 0.0030% or less, and the total of these is 0.0100% or less, and the total of other impurities is 0.0050% or less, and the balance is substantially composed of Al. , a highly conductive Al-Mg-Si alloy tube, characterized in that Mg_2Si precipitates are 5 μm or less. (2) Mg: 0.3-0.8%, Si: 0.3-0.8
%, Fe:≦0.10%, B:0.0003-0.00
30%, Mn, Cr, Ti, V, Zr transition metals are all 0.0030% or less, and the total of these is 0.0100% or less, and the total of other impurities is 0.0
After homogenizing the aluminum alloy at 450 to 600°C for 8 to 24 hours and precipitating it at 300 to 400°C for 8 to 24 hours, A method for manufacturing a highly conductive Al-Mg-Si alloy tube, characterized by performing hot extrusion, quenching, and aging treatment under certain conditions.