JP2017039979A - Aluminum alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy having excellent various qualities such as mechanical properties and corrosion resistance compared to a standard material even in substantial compliance with general standard.SOLUTION: The aluminum alloy contains at least one kind of element consisting of Cu, Si, Mg, Zn, Cr, Mn and the balance inevitable impurities consisting of elements other than the elements contained in the element group and Al with total content of the inevitable impurities of 0.01 wt.% or less.SELECTED DRAWING: None

Description

  The present invention relates to an aluminum alloy. More specifically, the present invention relates to an aluminum alloy having various qualities such as mechanical properties and corrosion resistance superior to standard materials, almost in accordance with general standards.

  Conventionally, aluminum alloys have been used in various fields from the viewpoint of lightness and workability, and most of them are manufactured as standard materials conforming to domestic standards such as Japanese Industrial Standards (JIS) and overseas standards. Has been.

  However, in such a standard material, since elements other than the additive elements are only limited to a predetermined content or less as unavoidable impurity elements, a relatively large number of unavoidable impurity elements are included in the actual alloy. It is included.

  For this reason, in actual alloys, inevitable impurity elements are combined with additive elements and other inevitable impurity elements to form coarse compounds, and various qualities such as mechanical properties and corrosion resistance are deteriorated. However, there are cases where the excellent properties inherently possessed cannot be fully exhibited.

  On the other hand, a technique for improving the specific quality by limiting the content of each inevitable impurity element in the standard material (JIS6061 series aluminum alloy) to a lower level is known (for example, see Patent Document 1). ).

Japanese Patent Laid-Open No. 5-279778

  However, in the aluminum alloy described in Patent Document 1, some of the unavoidable impurity elements are newly added to increase the content in the actual alloy. The quality deteriorates and the raw material cost increases by the amount of added elements.

  The present invention was devised in view of the above points, and an object thereof is to provide an aluminum alloy having various qualities such as mechanical properties and corrosion resistance superior to standard materials, almost in accordance with general standards. To do.

  In order to achieve the above object, the aluminum alloy of the present invention contains at least one additive element in the element group consisting of Cu, Si, Mg, Zn, Cr, and Mn, and the remainder is included in the element group. It consists of inevitable impurity elements (hereinafter simply referred to as “inevitable impurity elements”) composed of elements other than the elements to be added and Al, and the total content of the inevitable impurity elements is 0.01 wt% or less.

  Here, main aluminum alloys of JIS include high-strength alloys 2000 series, 5000 series and 6000 series excellent in toughness and corrosion resistance, and 7000 series having the highest strength among aluminum alloys.

  Of the additive elements described above, Cu is added to the 2000 series, 6000 series, and 7000 series, and the strength is increased by aging precipitation of the intermediate phase of the intermetallic compound, the aging precipitation rate is increased, and the stress corrosion cracking is suppressed. Is an effective element.

  Si is an element that is added to the 2000 series and 6000 series and is effective in increasing the strength by aging precipitation of the intermediate phase of the intermetallic compound.

  Mg is an element that is added to all of these four alloy systems and is effective in increasing the strength by aging precipitation and solid solution strengthening of the interphase of the intermetallic compound.

  Zn is an element that is added only to the 7000 series and is effective for increasing the strength by aging precipitation of the intermediate phase of the intermetallic compound.

  Cr is an element that is added to the 5000 series, 6000 series, and 7000 series, and is effective for increasing the strength by refining crystal grains, improving corrosion resistance, and particularly suppressing stress corrosion cracking.

  Mn is added to the 2000 series and 5000 series, and is an element effective for increasing the strength by refining crystal grains, improving corrosion resistance, and particularly suppressing stress corrosion cracking, similar to Cr.

  Further, in addition to these additive elements, trace amounts of inevitable impurity elements inevitably contained in the mother alloy of aluminum include Fe, Ti, Ni, Pb, Bi, Na, and the like. The total content of impurity elements is limited to 0.01 wt% or less.

  This is because if the total content of unavoidable impurity elements exceeds 0.01 wt%, the unavoidable impurity elements are combined with some of the additive elements, and the additive elements are consumed wastefully and a sufficient additive effect cannot be obtained. This is because a coarse intermetallic compound is formed and workability, toughness, fatigue strength, and the like are lowered.

  Moreover, the additive element in the element group mentioned above is Cu: 4.0-5.0%, Mg: 0.4-0.8%, Si: 0.2-1.0%, Mn: 0.5 -1.0%. An aluminum alloy having this composition range (hereinafter referred to as “A alloy”) substantially corresponds to a heat treatment type JIS 2000 series, specifically, an Al—Cu—Mg series 2014 alloy.

In this alloy A, Cu is added to increase the strength by aging precipitation of the initial precipitation phase or intermediate phase of the intermetallic compounds CuAl ₂ and CuMgAl ₂ , and the content thereof is 4.0 wt% or more, and 5. 0 wt% or less.

This is because when the Cu content is less than 4.0 wt%, the initial precipitation phase and the intermediate phase precipitation amount of the intermetallic compounds CuAl ₂ and CuMgAl ₂ are small, and sufficient strength cannot be obtained. On the other hand, if the Cu content exceeds 5.0 wt%, the θ phase may be precipitated beyond the maximum solid solubility limit of Cu in Al (5.7 wt%), and a homogeneous α-supersaturated solid solution cannot be obtained. This is because stable aging precipitation cannot be performed, the strength variation increases, and the raw material cost also increases.

Mg is also added to increase the strength by aging precipitation of the intermetallic compound CuMgAl _{2 in} the initial phase or the intermediate phase, and the content thereof is 0.4 wt% or more and 0.8 wt% or less.

This is because if the Mg content is less than 0.4 wt%, the initial precipitation phase or the intermediate phase precipitation amount of the intermetallic compound CuMgAl ₂ is small and sufficient strength cannot be obtained. On the other hand, if the Mg content exceeds 0.8 wt%, the intermetallic compound Al ₂ CuMg may be precipitated beyond the solid solubility limit of Mg in Al, and a homogeneous α-supersaturated solid solution cannot be obtained and is stable. This is because aging precipitation cannot be performed and the variation in strength increases, and the raw material cost also increases.

Si is added to increase the strength by aging precipitation of an intermediate phase of the intermetallic compound Mg ₂ Si, and the content thereof is set to 0.2 wt% or more and 1.0 wt% or less.

This is because when the Si content is less than 0.2 wt%, the amount of intermediate phase precipitation of the intermetallic compound Mg ₂ Si is small and sufficient strength cannot be obtained. On the other hand, when the Si content exceeds 1.0 wt%, coarse Si crystallization increases, and mechanical properties such as extrusion processability deteriorate.

  Mn is added to increase the recrystallization temperature by, for example, forming an Al-Cu-Mn compound in an aluminum alloy that has few impurities and is likely to coarsen the recrystallized grains, and to supplement the strength by refining the crystal grains. The content is 0.5 wt% or more and 1.0 wt% or less.

This is because when the Mn content is less than 0.5 wt%, the precipitation amount of the Al—Cu—Mn compound is small, and sufficient strength complementation is not performed. On the other hand, when the Mn content exceeds 1.0 wt%, Mn is combined with other additive elements, and the formation of initial precipitation phases and intermediate phases of intermetallic compounds CuAl ₂ and CuMgAl ₂ effective for increasing the strength is suppressed. Because it is done.

  Note that the upper limit of the Mn content is 1.2 wt% in the JIS 2014 alloy, whereas the lower content is set to 1.0 wt% in the A alloy. This is because the total content of inevitable impurity elements in the alloy A is limited to 0.01 wt% or less, and Mn is consumed wastefully because Fe and Cr forming a compound with Mn are very small. This is because even if the amount of Mn added is reduced, a sufficient amount of Al—Cu—Mn compound can be formed.

  Further, the additive element in the element group may be wt%, Mg: 4.0-5.0%, Mn: 0.5-1.2%, Cr: 0.05-0.10%. An aluminum alloy having this composition range (hereinafter referred to as “B alloy”) substantially corresponds to a non-heat treatment type JIS 5000 series, more specifically, an Al—Mg series 5083 alloy.

  In this B alloy, Mg is added to increase the strength by solid solution strengthening in Al, and the content thereof is 4.0 wt% or more and 5.0 wt% or less.

  This is because if the Mg content is less than 4.0 wt%, the amount of solid solution in Al is small and sufficient strength cannot be obtained. On the other hand, if the Mg content exceeds 5.0 wt%, excess Mg precipitates at the grain boundaries, causing intergranular corrosion and stress corrosion cracking, resulting in a decrease in corrosion resistance and workability. This is because, particularly during rolling, crocodile cracks that break from the approximate center in the thickness direction of the plate and ear cracks that crack in the plate width direction near the edge of the plate are likely to occur.

  Mn is added in order to supplement the strength by refining crystal grains, and the content thereof is 0.5 wt% or more and 1.2 wt% or less.

  This is because when the Mn content is less than 0.5 wt%, sufficient strength complementation is not performed. On the other hand, if the Mn content exceeds 1.2 wt%, Mn combines with Fe and other inevitable impurity elements to form coarse intermetallic compounds, and workability, toughness, fatigue strength, and the like decrease. .

  Note that the upper limit of the Mn content is 1.0 wt% in the JIS 5083 alloy, whereas the upper limit is 1.2 wt% in the B alloy. This is because the total content of inevitable impurity elements in the B alloy is limited to 0.01 wt% or less, and Fe and other inevitable impurity elements that form coarse intermetallic compounds with Mn are very small. This is because a coarse intermetallic compound is not formed even if the amount of addition is increased.

  Cr, like Mn, is added together with Mn to supplement the strength by refining crystal grains, and its content is 0.05 wt% or more and 0.10 wt% or less.

  This is because when the Cr content is less than 0.05 wt%, sufficient strength complementation is not performed. On the other hand, when the Cr content exceeds 0.10 wt%, Cr is combined with Al to form a coarse intermetallic compound, and workability, toughness, fatigue strength, and the like are reduced.

  The upper limit of the Cr content is 0.25 wt% in the JIS 5083 alloy, whereas the lower content is set to 0.10 wt% in the B alloy. This is because, as described above, the upper limit of the Mn content can be increased by limiting the total content of inevitable impurity elements to 0.01 wt% or less. This is because sufficient strength complementation can be performed.

Further, the additive element in the element group is wt%, Mg: 0.8 to 1.2%, Si: 0.5 to 1.0%, Cu: 0.15 to 0.35%, Cr: 0 It may be 0.05 to 0.20%. An aluminum alloy having this composition range (hereinafter referred to as “C alloy”) is approximately JIS6000 type of heat treatment type, more specifically, Al—Mg—Si type 6061 alloy regarded as an Al—Mg ₂ Si pseudo binary system. It is equivalent.

In this C alloy, Mg is added in order to increase the strength by aging precipitation of an intermediate phase of the intermetallic compound Mg ₂ Si, and the content thereof is 0.8 wt% or more and 1.2 wt% or less.

This is because if the Mg content is less than 0.8 wt%, the amount of intermediate phase precipitation of the intermetallic compound Mg ₂ Si is so small that sufficient strength cannot be obtained. On the other hand, when the Mg content exceeds 1.2 wt%, the solid solubility of the intermetallic compound Mg ₂ Si decreases conversely by the amount of a large amount of Mg dissolved in Al, so this intermetallic compound Mg ₂ Si This is because the amount of aging precipitation in the intermediate phase is reduced and the strength cannot be further increased.

Si is also added to increase the strength by aging precipitation of the intermediate phase of the intermetallic compound Mg ₂ Si, and the content thereof is set to 0.5 wt% or more and 1.0 wt% or less.

This is because when the Si content is less than 0.5 wt%, the amount of precipitation of the intermediate phase of the intermetallic compound Mg ₂ Si is small and sufficient strength cannot be obtained.

Specifically, since the composition ratio Si / Mg of the intermetallic compound Mg ₂ Si is 0.578, it is necessary for forming an intermediate phase of the intermetallic compound Mg ₂ Si when the Mg content is the lower limit of 0.8 wt%. The Si content is 0.5 wt% (= 0.8 × 0.578).

Therefore, by defining the lower limit of the Si content as 0.5 wt%, both Mg and Si are consumed without excess or deficiency in forming the intermediate phase of the intermetallic compound Mg ₂ Si.

  On the other hand, when the Si content exceeds 1.0 wt%, coarse Si crystallization increases, and mechanical properties such as extrusion processability deteriorate.

Specifically, since the composition ratio Si / Mg of the intermetallic compound Mg ₂ Si is 0.578, when the Mg content is 1.2 wt% at the upper limit, the Si content necessary for forming the intermediate phase of the intermetallic compound Mg ₂ Si The amount is 0.7 wt% (= 1.2 × 0.578).

  Here, the surplus of 0.3 wt% (= 1.0-0.7) Si has a crystal solubility limit of 1.65 wt% (> 0.3). It is dissolved in Al without taking out.

Further, the intermediate phase of the intermetallic compound Mg ₂ Si formed is 1.9 wt% (= 1.2 + 0.7) from the above description, but the solid solubility limit of the intermetallic compound Mg ₂ Si in Al Since it is the same as 1.9 wt%, it is dissolved in Al without precipitation.

  In addition, since the total content of inevitable impurity elements in the C alloy is limited to 0.01 wt% or less, the amount of Fe or the like that forms coarse intermetallic compounds with Mg or Si is very small.

Therefore, by defining the upper limit of Mg content to 1.2 wt% and the upper limit of Si content to 1.0 wt%, mechanical properties such as extrudability are not lowered, and Mg and Si are wasted. Without being consumed, it is possible to secure a sufficient amount of aging precipitation of the intermediate phase of the intermetallic compound Mg ₂ Si, and to ensure high strength.

Cu is added to increase the aging precipitation rate of the intermetallic compound Mg ₂ Si, and the content thereof is set to 0.15 wt% or more and 0.35 wt% or less.

  This is because if the Cu content is less than 0.15 wt%, the effect of increasing the aging precipitation rate is small and sufficient strength cannot be obtained. On the other hand, when the Cu content exceeds 0.35 wt%, the aging precipitation rate hardly increases and only the raw material cost increases.

  Cr is added in order to supplement strength by refining crystal grains, and the content thereof is 0.05 wt% or more and 0.20 wt% or less.

  This is because when the Cr content is less than 0.05 wt%, sufficient strength complementation is not performed. On the other hand, when the Cr content exceeds 0.20 wt%, Cr is combined with Al, a coarse intermetallic compound is formed, and workability, toughness, fatigue strength, and the like are reduced.

The upper limit of the Cr content is 0.35 wt% in the JIS6061 alloy, whereas the upper limit is 0.20 wt% in the C alloy. This is because the addition of Cr, 1) increases the quench sensitivity during extrusion, hardenability is deteriorated, 2) Cr functions as precipitation sites of the intermetallic compound Mg 2 _Si, intermetallic compounds Mg 2 _Si This is because the amount of aging precipitation in the intermediate phase is reduced and the strength is lowered, and further, 3) the total content of unavoidable impurity elements in the C alloy is limited to 0.01 wt% or less, and Cr and the compound are reduced. This is because the amount of inevitable impurity elements to be formed is small, so that Cr is not consumed unnecessarily and the amount added is small.

  Further, the additive element in the element group is wt%, Zn: 5.0 to 5.5%, Mg: 2.5 to 3.0%, Cu: 1.2 to 2.5%, Cr: 0 It is good also as 15 to 0.25%. An aluminum alloy having this composition range (hereinafter referred to as “D alloy”) substantially corresponds to a heat treatment type JIS7000 series, specifically, an Al—Zn—Mg—Cu—Cr series 7075 alloy.

In this D alloy, Zn is added in order to increase the strength by aging precipitation of the intermediate phase of the intermetallic compound MgZn ₂ (η ′ phase), and its content is 5.0 wt% or more and 5.5 wt%. The following.

This is because if the Zn content is less than 5.0 wt%, the amount of intermediate phase precipitation of the intermetallic compound MgZn ₂ is so small that sufficient strength cannot be obtained. On the other hand, when the Zn content exceeds 5.5 wt%, the strength cannot be further increased.

Mg is also added to increase the strength by aging precipitation of the intermediate phase of the intermetallic compound MgZn ₂ (η ′ phase), and the content thereof is 2.5 wt% or more and 3.0 wt% or less.

This is because if the Mg content is less than 2.5 wt%, the amount of intermediate phase precipitation of the intermetallic compound MgZn ₂ is so small that sufficient strength cannot be obtained. On the other hand, when the Mg content exceeds 3.0 wt%, the strength cannot be further increased.

  Cu is added to improve corrosion resistance by suppressing stress corrosion cracking, and the content thereof is set to 1.2 wt% or more and 2.5 wt% or less.

  Here, the cause of this stress corrosion cracking is thought to be due to the large potential difference between the grains and the grain boundaries, and Cu seems to relieve this potential difference and suppress stress corrosion cracking. . Table 1 shows electrode potentials of solid solutions and compounds in aluminum alloys (Light Metal Society, Research Group Report No. 15, 1985. 9).

According to Table 1, for example, the electrode potentials of 99.95% Al (high purity aluminum), Al + 4% MgZn ₂ (intermetallic compound MgZn ₂ in Al), and Al + 2% Cu (Al—Cu solid solution) are − 0.85V, -1.07V, and -0.75V, and Cu and Zn are likely to cause a large potential difference with Al. And it is thought that the electrode potential in the D alloy is made uniform when the Al-Cu solid solution having the most potential among them is uniformly dispersed in the grains and grain boundaries.

  Therefore, if the Cu content is less than 1.2 wt%, the dispersion amount of the Al—Cu solid solution is small and sufficient potential difference relaxation cannot be performed by Cu, and stress corrosion cracking cannot be suppressed, while the Cu content exceeds 2.5 wt%. Then, it is because Al-Cu solid solution aggregates and a noble part is formed locally, and conversely stress corrosion cracking is promoted.

  Cr is added in order to supplement strength by refining crystal grains, and the content thereof is 0.15 wt% or more and 0.25 wt% or less.

  This is because when the Cr content is less than 0.15 wt%, sufficient strength complementation is not performed. On the other hand, if the Cr content exceeds 0.25 wt%, the quenching sensitivity at the time of extrusion processing becomes high, and the hardenability deteriorates.

  The aluminum alloy according to the present invention has various qualities such as mechanical properties and corrosion resistance, which are superior to standard materials, almost in accordance with general standards.

It is a cross-sectional microscope picture which shows the microstructure of the various alloys concerning this invention. FIG. 2A is an appearance photograph of the sample after the press test, FIG. 2A is an appearance photograph of the invention material 1, and FIG. It is the external appearance photograph of the chip extract | collected at the time of cutting.

  Hereinafter, an embodiment of the present invention relating to an aluminum alloy will be described with reference to the drawings for understanding of the present invention.

  The aluminum master alloy used in the aluminum alloy according to the present invention is usually made of high-purity aluminum of 3N (99.9 wt%) or more with a very low content of inevitable impurity elements.

  Furthermore, in order to fully exhibit the excellent properties inherent in each standard material, it is preferable to use high-purity aluminum of 4N (99.99 wt%) or more as in this embodiment.

  Thereby, the content of each inevitable impurity element contained in the mother alloy of aluminum is kept low, and the inevitable impurities contained in the A alloy, B alloy, C alloy, and D alloy which are aluminum alloys according to the present invention after production. The total content of elements can be limited to 0.01 wt% or less.

  Also, for the additive elements Cu, Si, Mg, Zn, Cr, and Mn, a master alloy is prepared for each element or a plurality of elements and added to the molten metal obtained by melting the high-purity aluminum described above. Thus, an aluminum alloy according to the present invention was produced.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to such examples.

[Manufacture of aluminum alloys]
In the aluminum alloy according to the present invention, an ingot is produced from aluminum of higher purity than usual and additive elements of various alloys.
Specifically, in the alloy A, a 4N high-purity aluminum ingot is heated and melted at 750 to 780 ° C. to obtain a molten aluminum, and then, in this molten aluminum, a predetermined amount of an additive element Cu, while maintaining the same temperature, A molten metal of Invention Material 1 was obtained by adding each mother alloy of Mg, Si, and Mn.

  Similarly, with respect to the molten aluminum obtained by heating and melting a 4N high-purity aluminum ingot at 750 to 780 ° C., in the B alloy, a predetermined amount of each of the master alloys of additive elements Mg, Mn, and Cr is added, In the C alloy, a predetermined amount of each of the master alloys of additive elements Mg, Si, Cu, Cr is added. In the D alloy, by adding a predetermined amount of each of the master alloys of the additive elements Zn, Mg, Cu, Cr, Each melt of Invention Material 2, Invention Material 3, and Invention Material 4 was obtained. And each ingot of diameter 192 mm x length 1800 mm was manufactured from each molten metal of these inventive materials 1 to 4 by a so-called vertical semi-continuous casting method.

  In addition, instead of the 4N high-purity aluminum described above, each mother alloy of the same type and amount as the inventive materials 1 to 4 was added to a molten aluminum obtained by heating and melting a normal pure aluminum (99 wt% or more) metal. Was added to each of the melts of Comparative Materials 1 to 4 having compositions of a alloy, b alloy, c alloy, and d alloy respectively corresponding to the A alloy, B alloy, C alloy, and D alloy. And each ingot of diameter 192 mm x length 1800 mm was manufactured from each molten metal of these comparative materials 1-4 by the vertical semi-continuous casting method mentioned above.

  Table 2 shows the chemical compositions of inventive materials 1 to 4 and comparative materials 1 to 4 of the aluminum alloy produced as described above.

  According to Table 2, the inevitable impurity elements are 0.1 to 0.3 wt% in the comparative materials 1 to 4, whereas in the inventive materials 1 to 4, the high purity aluminum is always used. It turns out that it is restrict | limited to 0.01 wt% or less.

  Furthermore, the processed material was manufactured by extruding each ingot of these invention materials 1-4 and the comparative materials 1-4.

Next, various test methods for these ingots and processed materials will be described.
However, the ingot was tested after performing a predetermined tempering treatment at an arbitrary temperature. Regarding the processed material, the heat treatment material A invented material 1, a alloy comparison material 1, C alloy invention material 3, c alloy comparison material 3, D alloy invention material 4, d alloy comparison material 4 The test was conducted after the so-called T6 (solution treatment → quenching → artificial aging treatment), and the test was conducted. The invention material 2 of the B alloy and the comparison material 2 of the b alloy which were non-heat treated materials were extruded. The test was conducted without any tempering.

[Micro observation]
A test piece was cut out from the surface layer portion and the center portion only for the ingot, and immersed in a phosphoric acid solution, and the cross section was observed with an optical microscope.

[Mechanical test]
The tensile test was performed in accordance with JISZ2241 by preparing JIS4220 test pieces of ingots and workpieces. The Charpy impact test was performed in accordance with JISZ2242 by preparing a JIS5 test piece (V notch standard test piece) of JISZ2202. The Brinell hardness test was performed in accordance with JISZ2243 by preparing a 50 mm square × 10 mm long test piece.

[Conductivity test]
Test specimens of 50 mm square x 10 mm length were prepared for ingots and processed materials, and the standard annealed copper wire, the so-called IACS conductivity (% IACS) was taken as the eddy current conductivity. It was measured by a meter.

[Workability test]
A cylindrical test piece having a diameter of 10 mm and a height of 10 mm was produced only for the ingot, and the sample was reduced at a reduction speed of 2.0 mm / min in a state where the upper and lower portions were not restrained and no lubricant was applied. The limit upsetting rate e and the maximum load were measured.

Here, the limit upsetting rate e (%) means that the initial height of the test piece is h ₀ (mm), and cracks 1 and 2 as shown in FIG. If the height of the test piece when the can was _h 1 and (mm), it was determined by _{e (%) = (h 0} -h 1) / h 0 × 100.

  In addition, a block-shaped test piece is produced only for the ingot, and the industrial alcohol is used as the cutting oil at a feed speed of 0.29 mm / rev, a rotation speed of 400 rpm, and a cutting angle of 90 degrees. The appearance of chips generated when cutting a thickness of 0.03 mm was observed.

[Corrosion resistance test]
The test piece is immersed for 30 minutes in a solution in which an acidic solution consisting of 10% HCl or an alkaline solution consisting of 10% NaOH is kept at 50 ° C. for only the processed material, and the amount of aluminum dissolved in the solution is dissolved. The amount of Al was measured by atomic absorption, and the surface appearance was observed.

  Next, the test results of the various tests described above will be described while comparing the inventive materials 1 to 4 in which the total content of inevitable impurity elements is limited with comparative materials 1 to 4 that are normal standard materials of JIS standards. .

[Microstructure]
FIG. 1 is a cross-sectional photomicrograph showing the microstructure of each ingot of invention materials 1 to 4 with few inevitable impurity elements and comparative materials 1 to 4 containing inevitable impurity elements of a conventional level.

  According to FIG. 1, a large number of coarse intermetallic compounds are recognized in the comparative materials 1 to 4 as compared with the inventive materials 1 to 4 regardless of the sampling position (surface layer portion, center portion) from the ingot.

  Here, Table 3 shows the forms of typical intermetallic compounds formed in the aluminum alloy.

  According to Table 3, it can be seen that when the content of inevitable impurity elements is large, various intermetallic compounds are formed, and in particular, many types of intermetallic compounds are formed with Fe in aluminum. Further, according to Table 2, the content ratio of the comparative materials 1 to 4 and the inventive materials 1 to 4 is the highest among the inevitable impurity elements, and the comparative materials 1 to 4 are about the same as the inventive materials 1 to 4. It can be seen that 100 to 300 times as much Fe is contained. Therefore, it is presumed that the difference in microstructure described above is largely caused by the difference in Fe content.

[Mechanical properties, conductivity (ingot)]
Table 4 shows the results of mechanical tests and conductivity tests of the ingots of the inventive materials 1 to 4 and the comparative materials 1 to 4.

  The invention material 1 of the alloy A and the comparison material 1 of the alloy a are so-called duralumin, and the elongation tends to decrease as the tensile strength and the proof stress increase. Although tensile strength and proof stress are increasing compared with the material 1, elongation is also increasing.

  Inventive material 2 of B alloy and comparative material 2 of b alloy, inventive material 2 slightly decreases in tensile strength, proof stress, and hardness compared to comparative material 2, but elongation and impact values increase remarkably. ing. In particular, the impact value of the inventive material 2 is more than twice as large as that of the comparative material 2.

  Inventive material 3 of the C alloy and comparative material 3 of the c alloy, the inventive material 3 has a slight decrease in tensile strength and hardness as compared with the comparative material 3, but there is almost no difference in mechanical properties.

  Inventive material 4 of D alloy and comparative material 4 of d alloy are so-called ultra-super duralumin and are known as high-strength materials as described above. Inventive material 4 has a tensile strength, Although the yield strength and hardness are almost the same, the elongation and impact value are remarkably increased.

  That is, in the ingot of the aluminum alloy according to the present invention, except for the Al-Mg-Si-based C alloy, the elongation and impact value increased compared to the standard material, and the workability during forging and rolling was improved. .

  Moreover, about the electrical conductivity, invention materials 1-4 were substantially the same as comparative materials 1-4, respectively, and the electroconductivity equivalent to a standard material was obtained.

[Mechanical properties, conductivity (processed material)]
Table 5 shows the results of mechanical tests and conductivity tests of the processed materials of the inventive materials 1 to 4 and the comparative materials 1 to 4.

  According to Table 5, the tensile strength and proof stress of Inventive Materials 2 and 4 are slightly smaller than those of Comparative Materials 2 and 4, respectively. Has also increased. That is, the aluminum alloy processed material according to the present invention has an elongation and impact value that are higher than those of the standard material in all alloy systems, and characteristics suitable for the structural material of the transport system are obtained.

  In addition, in addition to the elongation and impact values described above, an increase in tensile strength was also observed for the invention material 3 of the C alloy in which almost no difference from the comparative material 3 was observed in the ingot.

  Moreover, about the electrical conductivity, like the ingot, the inventive materials 1 to 4 were substantially the same as the comparative materials 1 to 4, respectively, and the electrical conductivity almost equivalent to the standard material was obtained.

[Machinability]
Table 6 shows the results of the press test of the processed materials of the inventive materials 1 to 4 and the comparative materials 1 to 4.

  According to Table 6, the limit upsetting rate and the maximum load are higher than those of the comparative materials 1 to 4 in all the inventive materials 1 to 4. That is, in the aluminum alloy processed material according to the present invention, the limit upsetting rate and the maximum load increased in all alloy systems as compared with the standard material, and the workability, particularly forgeability, was improved.

  Moreover, in FIG. 3, the external appearance photograph of the chip which shows the machinability of each ingot of invention materials 1-4 and comparative materials 1-4 is shown.

  According to FIG. 3, the appearance of the chips is not significantly different from the comparative materials 1 to 4 in all the inventive materials 1 to 4. That is, in the ingot of aluminum alloy according to the present invention, chip fractionability almost equal to that of the standard material was obtained in all alloy systems.

  Here, in general, when the purity of aluminum increases, the chip becomes seized or entangled with a cutting tool for machining due to softening of the substrate, making machining difficult, and the appearance of the chip changes greatly. . On the other hand, as described above, since the difference in hardness between the inventive materials 1 to 4 and the comparative materials 1 to 4 is small, it is considered that the change in the appearance of the chips is also reduced.

[Corrosion resistance]
Table 7 shows the results of the corrosion resistance test of the processed materials of the inventive materials 1 to 4 and the comparative materials 1 to 4.

  According to Table 7, the dissolved Al content in all of the invention materials 1 to 4 is lower than that of the comparative materials 1 to 4 in both the acidic solution and the alkaline solution. That is, in the processed material of the aluminum alloy according to the present invention, the corrosion amount was reduced and the corrosion resistance was improved in all alloy systems as compared with the standard material.

  Specifically, the amount of decrease in the amount of dissolved Al in the acidic liquid is larger than that in the alkaline liquid. This is because, in an alkaline solution, “overall corrosion,” where corrosion progresses uniformly on the entire surface of the alloy surface, is likely to occur, whereas in acidic solution, corrosion progresses locally from the defective portion of the alloy surface in the form of pores. This is considered to be because the effect of the difference in the amount of precipitation of coarse intermetallic compounds that can become defective portions appears more greatly in the acidic liquid than in the alkaline liquid.

  Furthermore, when compared in this acidic solution, the inventive material 1 of Al—Cu—Mg system, the inventive material 4 of Al—Zn—Mg—Cu—Cr system, the inventive material 2 of Al—Mg system, Al—Mg— Compared to the Si-based invention material 3, the amount of decrease in the dissolved Al amount relative to the comparative material is small.

  This is presumably because the effect of reducing the potential difference due to Cu appeared significantly more than the effect of corrosion due to the intermetallic compound, as described above.

  As described above, the aluminum alloy to which the present invention is applied has various qualities such as mechanical properties and corrosion resistance, which are superior to standard materials, almost in accordance with general standards.

Claims (5)

Including at least one additive element in the element group consisting of Cu, Si, Mg, Zn, Cr, Mn,
The remainder consists of inevitable impurity elements consisting of elements other than the elements included in the element group and Al,
An aluminum alloy having a total content of the inevitable impurity elements of 0.01 wt% or less. The additive element is
In wt%, Cu: 4.0-5.0%, Mg: 0.4-0.8%, Si: 0.2-1.0%, Mn: 0.5-1.0%. Item 2. The aluminum alloy according to Item 1. The additive element is
The aluminum alloy according to claim 1, wherein wt% is Mg: 4.0-5.0%, Mn: 0.5-1.2%, Cr: 0.05-0.10%. The additive element is
wt%, Mg: 0.8-1.2%, Si: 0.5-1.0%, Cu: 0.15-0.35%, Cr: 0.05-0.20%. Item 2. The aluminum alloy according to Item 1. The additive element is
In wt%, Zn: 5.0-5.5%, Mg: 2.5-3.0%, Cu: 1.2-2.5%, Cr: 0.15-0.25%. Item 2. The aluminum alloy according to Item 1.

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