JP3414436B2 - Aluminum alloy for extrusion - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial age hardening treatment after forcibly air-cooling a high-temperature material extruded from a mold of a hot extruder. , An aluminum alloy for extrusion having a strength comparable to that of a medium-strength aluminum alloy subjected to T6 treatment. [0002] Al-Mg-Si based alloys have an appropriate strength, extrudability and good corrosion resistance.
Generally, it is widely used as a medium strength alloy for extrusion. Typical alloys of these include Si 0.4-0.8%
(% By weight, the same applies hereinafter), Cu 0.15 to 0.4%, Mg
0.8-1.2%, Cr 0.04-0.35%, balance A
JIS 606 having a composition consisting of 1 and unavoidable impurities
One alloy can be mentioned. However, JIS6061
Al alloys represented by alloys have high quenching sensitivity,
Since a large amount of water must be used for cooling during the hot extrusion press, the extruded material is liable to be twisted, warped, etc., and has problems in workability and production yield. [0003] On the other hand, there are also alloys having low quenching sensitivity, such as JIS6063 and 6N01 alloys, which are alloys that can process extruded high-temperature profiles only by forced air cooling and artificial aging treatment (T5 treatment). is there. However, this kind of alloy has difficulties in strength and toughness, and does not have the properties of about 6061 alloy required for structural materials such as building materials. SUMMARY OF THE INVENTION An object of the present invention is to provide an alloy having mechanical properties equivalent to or better than JIS6061 alloy by T5 treatment which is highly advantageous in terms of productivity. According to the present invention, the following alloy is provided to achieve the above object. That is, Si0.2
0.5%, Mg 1.73 [Si] to 1.73 [Si]
+ 0.4% (where [Si] is the Si content (% by weight)
), Cu 0.5-1.5%, Mn 0.05-
0.2% contained, impurity Fe is regulated to 0.2% or less,
The balance is an aluminum alloy for extrusion composed of Al and inevitable impurities. Hereinafter, the reason why the range of the component composition of the aluminum alloy of the present invention is limited as described above will be described. Si: Si imparts strength mainly by precipitation hardening of the aging precipitate β'-MgSi. In general, if the content is less than 0.4%, sufficient strength cannot be obtained.
₂ Si crystallized out, greatly reducing elongation. Also theory Mg
_An alloy containing excess Si exceeding the amount of 2Si improves extrudability and increases tensile strength and proof stress. However, it has the property of easily causing grain boundary cracking and reducing bending workability, toughness, and weldability. On the other hand, theoretical Mg of about 6061 alloy
_The amount of 2Si extremely impairs press hardenability. Therefore, considering the hardenability of press, the theoretical amount of Mg ₂ Si is reduced to 1.4%.
And the amount of Si corresponding thereto was set to 0.5%. Although the strength cannot be sufficiently obtained when the Si content is 0.4% or less, it can be supplemented by a Cu intermetallic compound described later.
The lower limit of the amount of Si was set to 0.2%. [0007] Mg: Mg imparts strength by strengthening its own solid solution and by precipitation hardening of aging precipitate β'-Mg ₂ Si and aging precipitate S'-CuMgAl ₂ combined with Cu described later. is there. However, in general, if the content is less than 0.6%, sufficient strength cannot be obtained, and if the amount of Si is sufficient to form Mg ₂ Si, adding Mg in excess of 1.2% will cause It is said that the equilibrium phase Mg ₂ Si grows as a crystallized product, and the formability is greatly reduced as seen in the decrease in elongation. On the other hand, the alloy of the present invention
₂ Si content was suppressed to about JIS6063 alloy, and its strength was strengthened by Cu or S'-
This is to be performed with a CuMgAl ₂ -based compound.
Further, the extrudability is also taken into consideration, and if the crystallization amount of these compounds is too large, the extrusion pressure becomes excessive. Therefore, the amount of Mg is 1.73 [Si] to 1.73 [Si] + 0.4% (where [Si] is the Si content (% by weight), depending on the amount of Si necessary for the formation of Mg ₂ Si. To show). [0008] Cu: Cu is generally said to increase the nucleation of Al-Mg-Si-based Mg ₂ Si, but does not lead to elongation or deterioration of toughness. Cu in the alloy of the present invention
Is to enhance the mechanical properties of the alloy in a solid solution S'-CuMgAl ₂ or Al-Cu-based compounds. On the other hand, if Cu itself is less than 0.5%, sufficient strength cannot be obtained, and if it exceeds 1.5%, the extrusion pressure sharply increases, and the corrosion resistance deteriorates. Therefore, the addition amount of Cu is 0.1.
5 to 1.5%. Mn: Mn is A during the homogenizing heat treatment after casting.
By generating an intermetallic compound of l and submicron size and pinning low-angle and high-angle grain boundaries to prevent recrystallization and prevent Si grain boundary precipitation to improve mechanical properties . Further, this element has a negative effect on mechanical properties during the soaking treatment of the Al-Fe-Si alloy.
It is also said to accelerate the transformation from -AlFeSi to a more preferable α-AlFeSi phase. It is considered that transition elements such as Cr and Zr also show the same effect, but the negative effects of these elements including Mn make the quenching sensitivity more sensitive and the mechanical properties after artificial aging cannot be sufficiently obtained. Is the result. This negative effect is much smaller in Mn than in Cr and Zr, and Mn is more advantageous in T5 treatment. The effect on hardenability is
When Mn is not more than 0.2%, it is not so large in forced air cooling immediately after extrusion. On the other hand, if the addition is less than 0.05%, the above effect cannot be sufficiently obtained. Therefore, Mn was adopted in the alloy of the present invention, and the amount was set to 0.05 to 2.0%. Fe: Fe is originally contained in Al metal as an impurity, and Al—Fe—Si or Al—Fe—
Crystals such as Cu are formed, coarsen with the content, and adversely affect mechanical properties. Therefore, although it should be strictly restricted by nature, it is compromised to 0.2% or less in view of production cost and quality maintenance. The alloy of the present invention has the above characteristics even if it contains one or more of Ti 0.2% or less and B 0.01% or less for the purpose of refining the cast structure of the billet as the material for extrusion. Nothing is harmed. The extruded material made of an Al alloy of the present invention is prepared by casting a molten metal adjusted to a predetermined composition into a billet by a semi-continuous casting method or the like.
A homogenization treatment is performed under the conditions of time keeping to finely disperse and precipitate the Mn-based intermetallic compound,
To form a solid solution.
System and a structure in which Al-Cu and Al-Mg-Cu intermetallic compounds were partially precipitated.
After heating at a temperature of about 520 ° C. and extruding in a state where a part of the intermetallic compound precipitated was dissolved, the extruded material was quenched by forcible air cooling with air to obtain Mg, S
i, Cu is re-dissolved and finally maintained at a temperature of 160 to 200 ° C. for 2 to 24 hours to make the Mg-Si and Al-Cu, Al-Mg-Cu intermetallic compounds fine and uniform It can be manufactured by a main process consisting of forming a structure dispersed and precipitated. Next, embodiments of the present invention will be described in detail. A melt having the component composition shown in Table 1 is prepared by a normal melting method, then cast into a billet having a diameter of 177 mm by semi-continuous casting, and then subjected to a homogenization heat treatment at 570 ° C. for 4 hours. As a result, alloys 1 to 8 of the present invention were produced. For comparison, a conventional alloy 6N01 (JIS) -equivalent alloy and a 6N01 alloy had Mn of 0.1% and Cu of 0.5%.
%, An alloy containing Si in excess of the theoretical amount of Mg ₂ Si was also produced. Table 1 shows that 6N01, 6061
JIS component specification ranges are also shown. [Table 1] Then, the mixture was extruded at a temperature of about 500 ° C. into a plate having a width of 130 mm and a thickness of 2.9 mm.
After forced cooling at / sec, artificial aging was performed under the aging conditions shown in Table 2. Cut out JIS No. 7 test pieces from these samples,
The tensile strength, proof stress, and elongation were measured. Table 2 shows the results. [Table 2] As is clear from the results in Table 2, it can be seen that the alloys in the predetermined range of the alloy of the present invention are equivalent to the 6N01 alloy in the same test and superior to the standard mechanical properties of JIS of 6N01. . The tensile strength is 60
It can also be seen that this is superior to the standard properties of 61. Although some of the proof stresses were slightly inferior, they were found to be excellent in elongation and high in toughness. Theoretical Mg
₂ Si amount than excess alloy containing the enhanced Si and Cu, as shown in this comparative example, showing very high tensile strength, the yield strength. However, as can be seen from Table 2, it has a low elongation and has a brittle property as compared with the alloy of the present invention. As described above, according to the present invention, according to the present invention, the T5 treatment can be used to improve the mechanical properties and equivalents of at least 6061 alloy, which is a conventional typical Al-Mg-Si alloy, or its equivalent. An alloy having workability can be obtained, and as a structural material or the like requiring toughness, it is possible to overcome both the low mechanical properties, which is a problem of the conventional T5 material, and the low productivity, which is a problem of the T6 material. It is possible.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-341546 (JP, A) JP-A-59-215453 (JP, A) JP-B-49-1369 (JP, B1) International Publication 93/002220 (WO, A1) (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 21/00-21/18

Claims (1)

(57) [Claims 1] 0.2 to 0.5% of Si, 1.73 of Mg
[Si] to 1.73 [Si] + 0.4% (however, [S
i] represents the content (% by weight) of Si), Cu0.5
-1.5%, Mn 0.05-0.2%, impurity F
e is controlled to 0.2% or less (more than weight%), and the balance is Al
And an aluminum alloy for extrusion, comprising an unavoidable impurity.