JP2011174182A - Method for producing aluminum alloy ingot - Google Patents

Abstract

An aluminum alloy ingot manufacturing method, an aluminum alloy ingot, and an aluminum alloy material in which generation of oak tree structure is stably suppressed are provided.
SOLUTION: Fe: 0.03-2.5 mass%, Si: 1.0 mass% or less, Mg: 5.5 mass% or less, Cu: 0.5 mass% or less, Mn: 1.0 mass% Hereinafter, Cr: 0.35 mass% or less, Ca: 0.0005-0.05 mass%, Ti: 0.0005-0.1 mass%, B: 0.0001-0.02 mass%, In this method, an aluminum alloy ingot in which an Al—Fe intermetallic compound is crystallized inside the ingot is manufactured through a melting step, a molten metal holding step, and a casting step. At the time of adding Ca, Ti, and B to the molten metal in the molten metal holding step, the molten metal temperature at the time of addition is 675 to 740 ° C., or the time from the addition to the end of casting is within 160 minutes, at least any of them It shall be satisfied.
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Description

  The present invention relates to a method for producing an aluminum alloy ingot used for rolling or the like.

  As is well known, when JIS 1000 series aluminum alloy or JIS 5000 series aluminum alloy is cast by molten alloy by a semi-continuous casting method or the like, it is often found in the resulting ingot as shown in FIG. A unique cast structure (A) called a tree structure is generated.

  This oak tree structure refers to the structure unevenness generated in the ingot due to the difference in the crystallization state of the Al—Fe intermetallic compound crystallized in the cast structure.

  And the oak tree structure once generated in the ingot does not disappear even after various processes such as extension processing and heat treatment, and when it is subjected to chemical conversion treatment or anodizing treatment, Patterns are generated on the surface due to different colors. For this reason, it cannot be used for products that require chemical conversion treatment, anodization treatment, or the like, and there has been a problem in that significant material loss occurs or delivery time trouble occurs.

  Therefore, as a countermeasure for preventing the occurrence of oak tree structure, as shown in Patent Documents 1 and 2 below, adding appropriate amounts of Ca, Ti, and B has been conventionally performed.

Japanese Patent Publication No.58-38502 Japanese Patent Publication No.58-10455

  However, the addition of Ca, Ti and B may still cause oak tree texture, and further measures are desired.

  This invention is made in order to solve such a problem, Comprising: It aims at provision of the manufacturing method of the aluminum alloy ingot which suppressed generation | occurrence | production of the oak tree structure stably.

  In order to solve the above-mentioned problems, the inventor has conducted intensive research. As a result, the operating conditions when adding Ca, Ti, and B in the ingot manufacturing process, or the time from the addition to the end of casting, The present inventors have found that it has a great influence on the occurrence of the tree structure, and based on this knowledge, have completed the present invention.

That is, this invention has the structure described below.
(1) Fe: 0.03-2.5 mass%, Si: 1.0 mass% or less, Mg: 5.5 mass% or less, Cu: 0.5 mass% or less, Mn: 1.0 mass% or less , Cr: 0.35 mass% or less, Ca: 0.0005-0.05 mass%, Ti: 0.0005-0.1 mass%, B: 0.0001-0.02 mass%, An aluminum ingot in which an Al—Fe intermetallic compound is crystallized is manufactured through a melting step, a molten metal holding step, and a casting step, and in the molten metal holding step, Ca, Ti, and B are mixed into the molten metal. A method for producing an aluminum alloy ingot, wherein the molten metal temperature at the time of addition is 675 to 740 ° C.
(2) The manufacturing method of the aluminum alloy ingot of the preceding clause 1 whose molten metal temperature when adding Ca, Ti, and B is 715-740 degreeC.
(3) The manufacturing method of the aluminum alloy ingot of the preceding clause 1 whose molten metal temperature when adding Ca, Ti, and B is 720-730 degreeC.

It is explanatory drawing which shows the melt | dissolution casting process which concerns on one Embodiment of this invention. It is explanatory drawing which shows the oak tree structure which appears in the cross section of the conventional aluminum alloy ingot.

  The aluminum alloy ingot produced in this embodiment is a composition having a risk of generating a oak tree structure, that is, an aluminum alloy ingot that crystallizes an Al-Fe intermetallic compound inside the ingot, Such alloy ingots are: Fe: 0.03-2.5 mass%, Si: 1.0 mass% or less, Mg: 5.5 mass% or less, Cu: 0.5 mass% or less, Mn: 1 0.0 mass% or less, Cr: 0.35 mass% or less, Ca: 0.0005-0.05 mass%, Ti: 0.0005-0.1 mass%, B: 0.0001-0.02 mass% And an aluminum alloy ingot in which an Al—Fe intermetallic compound is crystallized.

In the above, when the Fe content is less than 0.03% by mass, the oak tree structure is practically not generated, so that the present invention is not meaningful. On the other hand, if the amount exceeds 2.5% by mass, a large primary crystal of an Al—Fe-based intermetallic compound such as Al ₃ Fe crystallizes, and the workability such as rolling deteriorates, or the corrosion resistance of the rolled product or the like deteriorates. Therefore, it is not suitable as an alloy for obtaining a rolled product. Therefore, the Fe content in the ingot is 0.03 to 2.5 mass%, preferably 0.05 to 2.0 mass%.

  The contents of Si, Mg, Cu, Mn, and Cr other than Fe take into consideration the workability such as rollability and deep drawability, strength, corrosion resistance, surface light brightness, and color tone of the anodized film according to the application of the product. And determined within the above range.

  Suitable alloys having the above composition include JIS 1000 series alloys and JIS 5005 alloys having an aluminum purity of 99.0% by mass or more and less than 99.9% by mass.

  When Ca is contained in the aluminum alloy ingot, the outer area (B) of the oak tree structure (see FIG. 2) can be remarkably enlarged, and the inner area (A) of the oak tree structure The hue contrast with the external region (B) can be reduced. If the outer region becomes larger, the oak tree structure disappears or even if it exists, it is not exposed to the surface by rolling, so even if anodizing treatment is performed after rolling, an anodized pattern does not appear. In addition, when the hue contrast between the inner region (A) and the outer region (B) becomes small, even if an anodized pattern appears, this pattern becomes inconspicuous. However, when the Ca content is less than 0.0005 mass% or more than 0.05 mass%, the above effect cannot be obtained. Therefore, the content of Ca should be selected within the range of 0.0005 to 0.05% by mass, but the range of 0.001 to 0.01% by mass is particularly preferable.

  Ti and B have the property of reducing the crystal grain size of the lower layer of the coarse cell layer on the surface of the ingot by adding them to the alloy ingot. That is, it functions as a crystal grain refining material. When this crystal grain size is reduced to 150 μm or less, the effect produced by the inclusion of Ca is increased. If the Ti content is less than 0.0005 mass% and the B content is less than 0.0001 mass%, it is difficult to make the crystal grain size 150 μm or less, and the Ti content is 0.1 mass%. % And B contents exceeding 0.02% by mass lead to an increase in cost, saturation of crystal grain refinement, and anodization when the alloy is anodized. . Therefore, the Ti content needs to be 0.0005 to 0.1 mass%, and the B content needs to be 0.0001 to 0.02 mass%.

  As shown in FIG. 2, the aluminum alloy ingot having the above composition is manufactured through a melting step by the melting furnace 1, a molten metal holding step by the holding furnace 3, and a casting step by the casting machine 5.

  In the melting step, the aluminum alloy is melted to produce a molten metal having Fe, Si, Mg, Cu, Mn, and Cr in the above composition range. Next, the molten metal is transferred to the holding furnace 3 through the transfer rod 2 and held in the holding furnace 3.

  In the holding furnace 3, Ca, Ti, and B are added to the molten metal. The method of adding these Ca, Ti, and B to the molten metal is arbitrary, and a single element may be added, or an Al—Ca master alloy, an Al—Ti master alloy, an Al—B master alloy, and an Al—Ti—B master. The alloy may be continuously added in the form of a wire or the like. Preferably, an Al-4-6 mass% Ca master alloy, an Al-4-6 mass% Ti master alloy, and an Al-4-6 mass% Ti-0.5-2 mass% B master alloy are used.

  After the addition of Ca, Ti, and B, the molten metal is supplied to the casting machine 5 through the casting rod 4. In this embodiment, a degassing tank 6 is provided in the middle of the casting rod 4 to perform a known degassing process on the molten metal.

  The molten metal transferred to the casting machine 5 is cast by known semi-continuous casting or continuous casting.

  Thus, in this embodiment, the molten metal temperature at the time of addition of Ca, Ti, B to the molten metal in the holding furnace 3 is 675-740 ° C., or the time from the addition of the Ca, Ti, B to the end of casting. Must be within 160 minutes, or at least one of the conditions must be satisfied.

  When the molten metal temperature at the time of addition of Ca, Ti, B to the molten metal in the holding furnace 3 is less than 675 ° C., the added Ca, Ti, B, especially Al-4-6 mass% Ca master alloy, Al-4-6 mass % Ti master alloy, Al-4-6 mass% Ti-0.5-2 mass% B master alloy becomes difficult to melt, so the composition of the molten metal and hence the composition of the ingot becomes non-uniform. As a result, Ca, Ti, B becomes difficult to act effectively, and the oak tree structure is likely to occur. Further, when the molten metal temperature at the time of addition of Ca or the like exceeds 740 ° C., the oxidation of Ca becomes intense, and not only the effective amount of solid solution Ca decreases, but also the crystal grain refining ability itself of Ti and B decreases at a high temperature. Therefore, an oak tree structure is likely to occur. The preferable lower limit of the molten metal temperature when adding Ca, Ti, and B is 680, more preferably 715 ° C, most preferably 720 ° C, and the preferable upper limit of the molten metal temperature is 730 ° C. A melt temperature range of 720 to 730 ° C. is particularly preferable.

  On the other hand, when the time from the addition of Ca, Ti, B to the end of casting is longer than 160 minutes, the ability of refining Ti and B crystal grains decreases and Ca does not work effectively, and the oak tree structure becomes It tends to occur. Preferably, the time from the addition of Ca, Ti, B to the end of casting is within 130 minutes.

  As described above, if any one of the molten metal temperature condition at the time of addition of Ca, Ti, and B or the time condition from the addition to the end of casting is satisfied, the effect of suppressing the occurrence of oak tree structure can be obtained. By satisfying both conditions, the best oak tree structure generation suppression effect can be obtained.

  The aluminum ingot cast by the casting machine 5 is processed into a predetermined product shape through a process such as rolling, and then anodization is performed as necessary. The rolling and anodizing treatment may be performed under known conditions.

  According to this embodiment, since the occurrence of oak tree structure in the aluminum alloy ingot is suppressed, the occurrence of an anodized pattern due to the oak tree structure is suppressed even when anodized. Become.

  A JIS1050 aluminum alloy was used, and after melting this alloy in the melting furnace 1, it was transferred to the holding furnace 3 by the transfer rod 2 and held in the holding furnace 3. In the holding furnace 3, Ca, Ti, and B were added. At the time of this addition, the melt temperature at the time of addition was set as shown in Table 1 from Group 1 to Group 11. In addition, addition is performed using what shape | molded Al-5 mass% Ca master alloy and Al-5 mass% Ti-1 mass% B master alloy in the shape of a wire, and is the last of Ca, Ti, and B in an ingot. The content was Ca: 0.006% by mass, Ti: 0.03% by mass, and B: 0.002% by mass.

  After the addition of Ca or the like, the molten metal was supplied to the casting machine 5 with the casting rod 4, and semi-continuous casting was performed with the casting machine 5. In addition, the degassing process by the conventional method was performed during the transfer of the casting iron 4.

  In this process, the time from the addition of Ca, Ti, B to the end of casting in the holding furnace 3 was set as in the first group to the eleventh group in Table 1.

  Then, casting was performed with the number of castings set as shown in Table 1 for each of the first group to the eleventh group in Table 1.

  After casting, the presence or absence of oak tree structure in the ingot was examined. Table 1 shows the ratio (occurrence rate) at which the oak tree structure was generated relative to the number of castings.

  As understood from the results in Table 1, the molten metal temperature at the time of addition of Ca, Ti, B to the molten metal in the holding furnace 3 is 675-740 ° C., from the addition of the Ca, Ti, B to the end of casting. Group 1 to 10 satisfying at least one of the following conditions is clearly lower in incidence of oak tree structure than Group 11 that deviates from any of the conditions. It was confirmed that the oak tree structure can be suppressed.

DESCRIPTION OF SYMBOLS 1 Melting furnace 2 Transfer rod 3 Holding furnace 4 Casting rod 5 Casting machine 6 Degassing tank 10 Aluminum alloy ingot

Claims (3)

Fe: 0.03-2.5 mass%, Si: 1.0 mass% or less, Mg: 5.5 mass% or less, Cu: 0.5 mass% or less, Mn: 1.0 mass% or less, Cr: 0.35 mass% or less, Ca: 0.0005 to 0.05 mass%, Ti: 0.0005 to 0.1 mass%, B: 0.0001 to 0.02 mass%, and Al— A method for producing an aluminum alloy ingot from which an Fe-based intermetallic compound is crystallized, through a melting step, a molten metal holding step, and a casting step,
When adding Ca, Ti, and B to a molten metal in the molten metal holding step, the molten metal temperature when added is 675 to 740 ° C.   The manufacturing method of the aluminum alloy ingot of Claim 1 whose molten metal temperature when adding Ca, Ti, and B is 715-740 degreeC.   The manufacturing method of the aluminum alloy ingot of Claim 1 whose molten metal temperature when adding Ca, Ti, and B is 720-730 degreeC.

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