WO2012026469A1 - 成形用アルミニウム合金板 - Google Patents
成形用アルミニウム合金板 Download PDFInfo
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- WO2012026469A1 WO2012026469A1 PCT/JP2011/068979 JP2011068979W WO2012026469A1 WO 2012026469 A1 WO2012026469 A1 WO 2012026469A1 JP 2011068979 W JP2011068979 W JP 2011068979W WO 2012026469 A1 WO2012026469 A1 WO 2012026469A1
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- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 88
- 238000005204 segregation Methods 0.000 claims abstract description 110
- 238000005259 measurement Methods 0.000 claims abstract description 51
- 229910052710 silicon Inorganic materials 0.000 claims description 11
- 239000012535 impurity Substances 0.000 claims description 9
- 229910052796 boron Inorganic materials 0.000 claims description 7
- 229910052804 chromium Inorganic materials 0.000 claims description 7
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- 229910045601 alloy Inorganic materials 0.000 abstract description 43
- 239000000956 alloy Substances 0.000 abstract description 43
- 229910018134 Al-Mg Inorganic materials 0.000 abstract description 40
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- 238000001556 precipitation Methods 0.000 abstract description 15
- 238000000034 method Methods 0.000 description 60
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- 238000009749 continuous casting Methods 0.000 description 35
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 229910018084 Al-Fe Inorganic materials 0.000 description 2
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- 229910018192 Al—Fe Inorganic materials 0.000 description 2
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- 241001391944 Commicarpus scandens Species 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
- B22D11/003—Aluminium alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
- B22D11/055—Cooling the moulds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
- B22D11/059—Mould materials or platings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
- B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
- C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
- C22F1/047—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with magnesium as the next major constituent
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
- B21B2003/001—Aluminium or its alloys
Definitions
- the present invention relates to an aluminum alloy sheet for forming which is a high Mg content Al—Mg alloy sheet and has high formability.
- Al—Mg alloy As is well known, various aluminum alloy plates have conventionally been used for each alloy for transporting machines such as automobiles, ships, airplanes or vehicles, machines, electrical products, architecture, structures, optical instruments, and components and parts of equipment. It is widely used depending on the characteristics. In many cases, these aluminum alloy plates are formed by press molding or the like, and are used as members and parts for the above-described applications. From the viewpoint of high formability, among aluminum alloys, an Al—Mg alloy having an excellent balance between strength and ductility is advantageous. As this Al—Mg alloy, for example, JIS A5052, 5182 and the like are typical alloys. However, this Al—Mg alloy sheet is inferior in ductility and inferior in formability as compared with conventional cold-rolled steel sheets. For this reason, conventionally, examination of the component system of Al—Mg-based alloy plates and optimization of manufacturing conditions have been performed.
- the strength ductility balance is improved.
- the aluminum alloy plate for automobiles described in Patent Document 1 is a high Mg content Al—Mg alloy plate having a Mg content of 6 to 10% by mass, manufactured by a twin roll continuous casting method.
- the average size of the Al—Mg intermetallic compound is 10 ⁇ m or less.
- the aluminum alloy sheet for automobile body sheets described in Patent Document 2 is an Al—Mg alloy sheet having a Mg content of 2.5 to 8% by mass, manufactured by a continuous casting method.
- the number of Al—Mg intermetallic compounds of 10 ⁇ m or more is 300 pieces / mm 2 or less, and the average crystal grain size is 10 to 70 ⁇ m.
- Patent Document 3 describes an Al—Mg-based alloy plate having an Mg content of 8 to 14% by mass, manufactured by a twin-roll continuous casting method.
- the maximum value of the deviation width of each Mg concentration from the average Mg concentration is 4% by mass or less in absolute value.
- the average value is 0.8 mass% or less in absolute value.
- the Al—Mg-based intermetallic compound that crystallizes during casting tends to be a starting point of fracture during press molding. Therefore, in order to improve the press formability of the Al-Mg alloy plate having a high Mg content, the Al-Mg intermetallic compound (also referred to as ⁇ phase) is made finer or the coarse ⁇ phase is reduced. It is effective to do.
- the cooling rate (casting rate) in the casting process is increased to suppress Al—Mg-based intermetallic compounds that crystallize during casting.
- the higher the Mg content of the Al—Mg alloy plate the more difficult it is to reduce the ⁇ phase to the extent that it does not adversely affect the press formability only by controlling the cooling rate in the casting process.
- Patent Document 3 an Al—Mg-based intermetallic compound caused by Mg segregation (unevenness in concentration) is suppressed by suppressing the degree of Mg segregation (Mg concentration distribution) over the thickness direction by homogenization heat treatment and final annealing conditions. Precipitation of ( ⁇ phase) is suppressed.
- a high Mg-containing Al—Mg alloy plate produced by using the conventional twin-roll continuous casting method causes Mg segregation even in the plate width direction. Therefore, there is a problem that it is difficult to reduce the ⁇ phase of the high Mg-containing Al—Mg alloy plate to such an extent that it does not adversely affect the press formability only by suppressing the degree of Mg segregation in the plate thickness direction. .
- the present invention has been made to solve such problems, and the problem is to reduce the precipitation of ⁇ phase inside the high Mg-containing Al—Mg alloy plate and improve the press formability. It is intended to provide an aluminum alloy sheet for forming.
- a forming aluminum alloy plate according to the present invention is a forming aluminum alloy plate containing Mg: 6.0% by mass or more and 15.0% by mass or less, with the balance being Al and impurities.
- a plurality of plate width direction measurements set at predetermined intervals in the plate width direction and the plate length direction in a square region having the entire plate width set as one side on the surface of the forming aluminum alloy plate.
- the Mg concentration is measured at a point, and the average value of the Mg concentration measured at the plurality of measurement points in the plate width direction is defined as the plate width direction average Mg concentration (Co).
- the Mg concentration is measured at a plurality of plate thickness direction measurement points set over the entire plate thickness at predetermined intervals, and the average value of the Mg concentration measured at the plurality of plate thickness direction measurement points is the plate thickness direction average Mg concentration When (Ci), the plate thickness
- the absolute value of the region Mg segregation degree (X) defined by the difference (Ci-Co) between the direction average Mg concentration (Ci) and the plate width direction average Mg concentration (Co) is 0.5 mass. % Or less, and the average value is 0.1 mass% or less.
- region Mg segregation degree (X) defined by the difference of the board thickness direction average Mg density
- the plate thickness In the aluminum alloy sheet for forming according to the present invention, in calculating the region Mg segregation degree (X) in addition to the region Mg segregation degree (X), at least one of the measurement points in the sheet width direction, the plate thickness
- Mg concentration Mg concentration
- Ct plate thickness direction Mg concentration
- Ci plate thickness direction average Mg concentration
- the absolute value of the thickness direction Mg segregation degree (Y) defined by the difference (Ct ⁇ Ci) is preferably such that the maximum value is 4 mass% or less and the average value is 0.8 mass% or less.
- the board defined by the difference of the board thickness direction Mg density
- the thickness direction Mg segregation degree (Y) is a maximum value or an average value of a predetermined value or less, the segregation of Mg is further suppressed. For this reason, the precipitation of the ⁇ phase inside the forming aluminum alloy plate is further reduced, and non-uniform deformation at the time of forming and strain concentration due to the non-uniform deformation are further suppressed.
- the content of Mg is preferably more than 8% by mass and 14% by mass or less. According to the said structure, by prescribing
- the impurities are Fe: 1.0 mass% or less, Si: 0.5 mass% or less, Ti: 0.1 mass% or less, B: 0.05 mass%.
- Mn 0.3 mass% or less
- Cr 0.3 mass% or less
- Zr 0.3 mass% or less
- V 0.3 mass% or less
- Cu 1.0 mass% or less
- Zn 1 It is preferably at least one element having a mass of 0.0% or less.
- an Al—Mg-based intermetallic compound composed of Al—Mg— (Fe, Si) or the like inside the aluminum alloy plate for forming Precipitation of intermetallic compounds other than Al—Mg, such as Al—Fe and Al—Si, is suppressed.
- fracture toughness and press formability are improved.
- press formability is not inhibited by regulating the contents of Ti, B, Mn, Cr, Zr, V, Cu, and Zn as impurities.
- the formation of ⁇ phase is reduced by suppressing the segregation of Mg, and excellent press formability can be obtained.
- the aluminum alloy sheet for forming is restricted to a narrower Mg content, or in addition to Mg, at least one element of Fe, Si, Ti, B, Mn, Cr, Zr, V, Cu, Zn Is contained as an impurity, and the press formability is further improved by regulating the content thereof.
- FIG. 2 shows a plurality of measurement points of Mg concentration used when calculating the degree of Mg segregation of a forming aluminum alloy sheet according to the present invention
- (a) is a plan view
- (b) is a cross-sectional view taken along line AA in (a).
- FIG. It is sectional drawing which shows typically the structure of the thin plate continuous casting apparatus used in the case of manufacture of the aluminum alloy plate for shaping
- the forming aluminum alloy plate according to the present invention (hereinafter referred to as an aluminum alloy plate) is an aluminum alloy containing a high content of Mg, and is defined by a plate width direction average Mg concentration Co and a plate thickness direction average Mg concentration Ci.
- the region Mg segregation degree X is restricted to a predetermined value or less.
- the aluminum alloy plate according to the present embodiment includes Mg: 6.0% by mass or more and 15.0% by mass or less, and the balance is made of an aluminum alloy containing Al and impurities, that is, a high Mg content Al—Mg alloy.
- the aluminum alloy plate according to the present embodiment includes Fe: 1.0 mass% or less, Si: 0.5 mass% or less, Ti: 0.1 mass% or less, and B: 0.05 as elements other than Mg.
- Mn 0.3% by mass or less
- Cr 0.3% by mass or less
- Zr 0.3% by mass or less
- V 0.3% by mass or less
- Cu 1.0% by mass or less
- Zn It is preferably composed of a high Mg-containing Al—Mg alloy containing at least one element of 1.0% by mass or less as an impurity.
- Mg Mg is an important alloy element that increases the strength and ductility of the Al alloy sheet.
- the Mg content is less than 6.0% by mass, the strength and ductility are insufficient, the characteristics of the high Mg-containing Al—Mg alloy are not obtained, and the press formability is insufficient.
- the Mg content exceeds 15.0% by mass, the segregation of Mg in the aluminum alloy plate, that is, the degree of Mg segregation in the region can be regulated within a predetermined range even if the manufacturing method and conditions are controlled. It becomes difficult.
- the Mg content is 6.0% by mass or more and 15.0% by mass or less, preferably more than 8% by mass and 14% by mass or less.
- Fe and Si are elements to be regulated to the smallest possible amount. Fe and Si are precipitated as an Al—Mg-based intermetallic compound such as Al—Mg— (Fe, Si), or an intermetallic compound other than Al—Mg based such as Al—Fe, Al—Si.
- the Fe content exceeds 1.0% by mass, or when the Si content exceeds 0.5% by mass, the amount of precipitation of these intermetallic compounds becomes excessive, and fracture toughness and formability are reduced. It greatly inhibits. As a result, press formability is significantly reduced. Therefore, the Fe content is 1.0 mass% or less, preferably 0.5 mass% or less, and the Si content is 0.5 mass% or less, preferably 0.3 mass% or less.
- Ti and B have the effect of refining the cast plate (ingot) structure
- Mn, Cr, Zr and V have the effect of refining the rolled plate structure
- Cu and Zn also have the effect of improving strength. For this reason, in the range which does not inhibit the press formability which is the characteristic of the alloy plate of the present invention, it is allowed to contain one or more of these elements aiming at these effects.
- the allowable amounts of these elements are Ti: 0.1 mass% or less, B: 0.05 mass% or less, Mn: 0.3 mass% or less, Cr: 0.3 mass% or less, Zr: 0.3 mass% % Or less, V: 0.3 mass% or less, Cu: 1.0 mass% or less, and Zn: 1.0 mass% or less are preferable.
- a square region having the entire plate width W as one side is set on the surface of the aluminum alloy plate 60. .
- this square region that is, a region surrounded by the total plate width W and the plate length L having the same length as the total plate width W, a predetermined interval a in the plate width direction and the plate length
- a plurality of plate width direction measurement points Px are set at predetermined intervals b in the direction.
- the Mg concentration on the surface of the aluminum alloy plate 60 is measured at the plurality of plate width direction measurement points Px.
- the average value of these measured Mg concentrations is the average Mg concentration Co in the plate width direction, and serves as an index of the degree of Mg segregation in the plate width direction on the surface of the aluminum alloy plate 60. Further, for the measurement of the Mg concentration, EPMA (electron beam probe microanalyzer) capable of line analysis is used, and the Mg concentration is measured by scanning in the plate width direction of the aluminum alloy plate 60.
- EPMA electron beam probe microanalyzer
- a square region having a total plate width W as one side is set on the surface of the aluminum alloy plate 60, and the region It is necessary to measure the Mg concentration on the surface of the inner aluminum alloy plate 60.
- the number (points) of the measurement points Px in the plate width direction set in the region is 5 points or more without including the plate end in the plate width direction, and 5 points or more in the plate length direction, for a total of 25 points or more. preferable.
- the interval a in the plate width direction and the interval b in the plate length direction are set so that the number of measurement points Px in the plate width direction is 25 or more.
- the interval b in the plate length direction is preferably set to 0.5 to 2 times the interval a in the plate width direction.
- Thickness direction average Mg concentration: Ci As shown in FIG. 1B, in order to calculate the plate thickness direction average Mg concentration Ci, first, at all of the plurality of plate width direction measurement points Px set in the region, a predetermined value in the plate thickness direction is set. A plurality of plate thickness direction measurement points Py are set over the entire plate thickness T at an interval c. And Mg density
- the interval c in the thickness direction is preferably set to 0.2 mm or less.
- the initial measurement point of the plate thickness direction measurement point Py is the already measured plate width direction measurement point Px.
- the region Mg segregation degree X is defined by the difference (Ci-Co) between the plate thickness direction average Mg concentration (Ci) and the plate width direction average Mg concentration (Co). This is an index of the degree of Mg segregation in both the plate width directions.
- region Mg segregation degree X is 0.5 mass% or less in the maximum value, and is 0.1 mass% or less in the average value.
- the plate width direction average Mg concentration Co, the plate thickness direction average Mg concentration Ci, and the region Mg segregation degree X are the chemical component composition of the aluminum alloy plate 60, manufacturing conditions described later, specifically, cooling conditions during casting, It is controlled by the cast plate thickness or the amount of face cutting, the homogenization heat treatment condition, and the final annealing condition.
- the maximum value or average value of the region Mg segregation degree X becomes larger on the plus side, the ⁇ phase due to Mg segregation tends to precipitate.
- the ⁇ phase that is the starting point of fracture increases, strength and elongation decrease, and moldability decreases.
- the maximum value or average value of the region Mg segregation degree X is increased to the minus side, there are many portions where the Mg concentration is significantly reduced. In the portion where the Mg concentration is significantly low, the strength is low. Therefore, at the time of tensile deformation in molding, only the portion where the Mg concentration is low is preferentially deformed, resulting in nonuniform deformation. For this reason, the distortion at the time of shaping
- molding will concentrate partially, especially elongation will fall and a moldability will fall.
- the formability in the aluminum alloy plate 60 falls.
- the plate thickness direction Mg segregation degree Y defined by the plate thickness direction Mg concentration Ct and the plate thickness direction average Mg concentration Ci is a predetermined value. It is preferable to be regulated as follows.
- the plate thickness direction Mg concentration Ct is the Mg concentration measured at the plurality of plate thickness direction measurement points Py described in FIG.
- the plate thickness direction average Mg concentration Ci is an average value of the measured plate thickness direction Mg concentration Ct.
- the plate thickness direction Mg concentration Ct and the plate thickness direction average Mg concentration Ci are the plate thicknesses measured at at least one plate width direction measurement point Px in the region when calculating the region Mg segregation degree X. Mg concentration in the direction.
- the plate thickness direction Mg concentration Ct is preferably calculated from a value measured at one of the plate width direction measurement points Px at the plate width central portion, and at three points in the vicinity of the plate width central portion and both ends of the plate width. More preferably, it is measured and calculated by averaging them.
- the sheet thickness direction Mg segregation degree Y is defined by the difference (Ct ⁇ Ci) between the sheet thickness direction Mg concentration (Ct) and the sheet thickness direction average Mg concentration (Ci). It is an index of the degree of segregation.
- the sheet thickness direction Mg segregation degree Y can be well reproduced by using the region Mg segregation degree X together with the Mg segregation degree of the entire aluminum alloy sheet 60. And in the aluminum alloy plate 60 which concerns on this invention, it is preferable that the absolute value of sheet thickness direction Mg segregation degree Y is 4 mass% or less at a maximum value, and is 0.8 mass% or less on an average value.
- the plate thickness direction Mg concentration Ct, the plate thickness direction average Mg concentration Ci, and the plate thickness direction Mg segregation degree Y are the chemical composition of the aluminum alloy plate 60, the manufacturing conditions described later, specifically, the cooling conditions during casting.
- the thickness is controlled by the thickness of the cast plate or the amount of face cutting, the homogenization heat treatment condition, and the final annealing condition.
- the maximum value or average value of the Mg segregation degree Y in the plate thickness direction is increased to the plus side, the ⁇ phase due to Mg segregation is likely to precipitate. For this reason, the ⁇ phase that is the starting point of fracture increases, the strength and elongation decrease, and the moldability decreases. Further, when the maximum value or average value of the Mg segregation degree Y in the plate thickness direction is increased to the minus side, there are many portions where the Mg concentration is significantly reduced. For this reason, the strength is lowered in such a portion where the Mg concentration is significantly lowered.
- the aluminum alloy plate according to the present invention preferably has an average crystal grain size of 100 ⁇ m or less on the surface thereof.
- the press formability is improved.
- the average crystal grain size exceeds 100 ⁇ m and becomes coarse, the press formability tends to decrease, and defects such as cracks and rough skin during molding tend to occur.
- SS stripcher strain
- the average crystal grain size is preferably 20 ⁇ m or more.
- the crystal grain size referred to in the present invention is the maximum diameter of crystal grains in the plate length direction.
- the crystal grain size is measured by the line intercept method in the L direction by mechanically polishing an aluminum alloy plate to 0.05 to 0.1 mm and then observing the electrolytically etched surface with a 100 ⁇ optical microscope. Is done.
- the length of one measurement line is 0.95 mm, and the total measurement line length is 0.95 ⁇ 15 mm by observing a total of five fields with three lines per field.
- the aluminum alloy sheet of the present invention is manufactured through a melt casting process, a homogenization heat treatment process, a cold rolling process, and a final annealing process. Hereinafter, each step will be described.
- the melt casting process is a process of melting a high Mg content Al—Mg alloy having the above-described chemical composition and manufacturing a cast plate from the molten metal using a thin plate continuous casting method.
- a thin plate continuous casting method a graphite fixed mold type continuous casting method is preferable.
- the graphite fixed mold type continuous casting method is performed using a thin plate continuous casting apparatus 10 as shown in FIG.
- the molten metal 2 stored in the holding furnace 1 is poured into the continuous mold 3 (graphite fixed mold 4) from the casting port 1a.
- the molten metal 2 is solidified by the graphite fixing mold 4 while the graphite fixing mold 4 is cooled by the water cooling jacket 5.
- the cast plate 6 with a thin plate thickness is obtained.
- the produced cast plate 6 is carried out to the next process by the roll 7.
- the cooling rate is higher than that in the DC casting method, a fine cast structure is obtained, and the press formability is improved.
- a relatively thin plate thickness of about 5 mm can be obtained, processes such as hot rough rolling and hot finish rolling after casting, which have been performed with conventional DC ingots (thickness 200 to 600 mm), can be omitted. .
- the cooling rate is determined by a method known from the dendrite arm spacing (Dendrite secondary branch interval: DAS) of the cast plate 6 (for example, published by the Japan Institute of Light Metals, August 20, 1988, “Aluminum dendrite arm spacing and cooling”). The method described in “Measurement method of speed” and the like). That is, the average interval d between adjacent dendrite secondary arms (secondary branches) in the cast structure of the cast plate 6 is measured by the intersection method (number of fields of view of 3 or more, number of intersections of 10 or more).
- DAS dendrite arm spacing
- intersection method number of fields of view of 3 or more, number of intersections of 10 or more.
- the pouring temperature when the molten metal 2 is poured into the graphite fixed mold 4 is in the range of liquidus temperature + 50 ° C. or higher and liquidus temperature + 250 ° C. or lower, preferably It is liquidus temperature +100 degreeC or more and liquidus temperature +150 degreeC or less.
- the pouring temperature is lower than the liquidus temperature + 50 ° C.
- the molten metal is solidified in the mold, and the cast plate breaks easily.
- the pouring temperature exceeds the liquidus temperature + 250 ° C., the cooling rate during casting becomes slow and the degree of Mg segregation increases. In this case, it becomes difficult to suppress the Mg segregation degree within the range of the present invention, and it is impossible to suppress the precipitation of ⁇ phase and the decrease in formability due to the Mg segregation degree.
- the roll 7 for feeding the casting plate 6 in the casting direction is periodically rotated in the direction opposite to the casting direction to retract the casting plate 6.
- the backward stroke length is in the range of 0.5 mm to 5 mm, preferably 1 mm to 3 mm.
- the holding time of 1 s or less is set before the retreat, the castability becomes more stable.
- the reverse stroke length is in the range of 0.5 mm to 5 mm.
- the average casting speed is in the range of 100 mm / min to 500 mm / min, preferably 250 mm / min to 350 mm / min. It is below min.
- the average casting speed is less than 100 mm / min, the molten metal 2 rapidly solidifies in the vicinity of the casting port 1a, so that the drawing resistance at that portion increases when the roll 7 is drawn. Is easy to break.
- the average casting speed exceeds 500 mm / min, a molten metal leak due to insufficient cooling occurs near the cast plate outlet 4a.
- the thickness of the cast plate 6 to be continuously cast is in the range of 5 mm to 20 mm.
- the plate thickness is less than 5 mm, the molten metal 2 rapidly solidifies in the vicinity of the casting port 1a, so that when the roll 7 is pulled out, the drawing resistance at that portion increases, so the cast plate 6 breaks. easy.
- the plate thickness exceeds 20 mm, the cooling rate of casting becomes remarkably slow, and the degree of segregation of Mg increases. In this case, it is difficult to suppress the Mg segregation degree within the range of the present invention, and there is a possibility that the precipitation of ⁇ phase due to the Mg segregation degree cannot be suppressed. Further, the ⁇ phase as a whole tends to become coarse or precipitate in large quantities. As a result, there is a high possibility that the press formability is significantly lowered.
- the thin plate continuous casting method has been described above by taking the graphite fixed mold type continuous casting method as an example, but is not limited thereto. Any method can be used as long as it can suppress the Mg segregation degree of the aluminum alloy sheet within the scope of the present invention, and for example, a twin roll continuous casting method may be used.
- the twin-roll continuous casting method is performed using a thin plate continuous casting apparatus 100 as shown in FIG.
- the molten metal 300 is poured from the hot water supply nozzle 400 of the holding furnace 200 between a pair of rotating water-cooled copper molds (double rolls 500) and solidifies.
- a thin cast plate 600 is obtained.
- the Hunter method, the 3C method and the like are known.
- processes such as hot rough rolling and hot finish rolling after casting, which have been performed with conventional DC ingots (thickness 200 to 600 mm), are performed. Can be omitted.
- the homogeneous heat treatment step is a step of performing a predetermined homogenization heat treatment on the cast plate 6 produced in the above step.
- the homogenization heat treatment is performed for a required time at a temperature of 400 ° C. or higher and a liquidus temperature or lower.
- the heat treatment time is 1 second (1 s) or less.
- the temperature range in which the ⁇ phase is highly likely to occur is a temperature range from 200 to 400 ° C. at the center of the cast plate when the temperature is raised, and a temperature range from homogenization heat treatment temperature to 100 ° C. when the temperature is cooled. Therefore, in order to suppress the generation of the ⁇ phase, the average rate of temperature increase in the range of the temperature of the cast plate center portion from 200 to 400 ° C. is 5 ° C./s or more when heating to the homogenization heat treatment temperature. Is preferred. In cooling from the homogenization heat treatment temperature, the average cooling rate in the range from the homogenization heat treatment temperature to 100 ° C. is preferably 5 ° C./s or more.
- the cold rolling process is a process in which the cast plate 6 that has been subjected to the homogenization heat treatment is cold-rolled to a thickness of the product plate, for example, 0.1 mm to 13 mm.
- the cast structure is made into a processed structure by cold rolling. Therefore, when the plate thickness of the cast plate 6 to be cold-rolled is thick, it is preferable that intermediate annealing is performed in the middle of cold rolling so that the cold rolling rate in the final cold rolling is 60% or less.
- the degree of work organization in cold rolling depends on the cold rolling rate of cold rolling, so that the cast structure may remain for the above-mentioned texture control. It is allowed as long as the characteristics are not impaired.
- the final annealing step is a step of applying a predetermined final annealing to the cold-rolled sheet produced in the above step.
- final annealing is performed on the cold-rolled sheet at a temperature of 400 ° C. or higher and lower than the liquidus temperature (° C.).
- the final annealing temperature is less than 400 ° C., there is a high possibility that a solution effect will not be obtained, and there is no effect of reducing the degree of Mg segregation.
- the final annealing temperature is preferably 450 ° C. or higher.
- the average cooling rate after the final annealing is as low as less than 10 ° C./s, the degree of Mg segregation increases in the cooling process.
- the average cooling rate is preferably 15 ° C./s or more.
- melts of Al—Mg alloys having various chemical composition shown in Table 1 were obtained by the above-described graphite fixed mold type continuous casting method and twin roll type continuous casting method. Under the conditions shown in Table 2, casting was performed to each plate thickness shown in Table 2. Each cast plate is selectively subjected to chamfering treatment and homogenization heat treatment under the conditions shown in Table 2, and then to a plate thickness of 1.0 mm or 11.0 mm without hot rolling. Cold rolled. In addition, intermediate annealing was not performed during cold rolling.
- each cold-rolled sheet is subjected to final annealing in a continuous annealing furnace at a temperature and cooling conditions shown in Table 2 (the holding time at the annealing temperature is 1 second or less), and an aluminum alloy sheet for forming (Example) No. 1-5 and Comparative Examples No. 6-20).
- the forming aluminum alloy plate (Comparative Example No. 6) is manufactured by a manufacturing method using a twin-roll continuous casting method described in Patent Document 3.
- the conditions of the graphite fixed mold type continuous casting method are the retreat stroke length: 3 mm, the average casting speed: 300 mm / min, the casting temperature (the pouring temperature): the liquidus temperature + 140 ° C.
- the peripheral speed of the twin rolls was 70 m / min
- the pouring temperature when pouring the molten metal into the twin rolls was the liquidus temperature + 20 ° C.
- the twin roll surface was not lubricated.
- Thermodynamic calculation software Thermo-Calc Ver.R Al-DATA Ver.6 is used to calculate the liquidus temperature of each alloy.
- Example Nos. 1 to 5 Comparative Examples Nos. 6 to 22
- the region Mg segregation degree X and the thickness direction Mg segregation degree Y of each alloy sheet were calculated by the following procedure. And evaluated. The results are shown in Table 2.
- Example No. The calculation result of the region Mg segregation degree X in FIG.
- the calculation result of the region Mg segregation degree X of 6 is shown in FIG.
- the calculation result of the sheet thickness direction Mg segregation degree Y of Example 1 is shown in FIG.
- FIG. 7 shows the calculation results of the thickness segregation degree Y of 16 in the plate thickness direction.
- a plurality of plate thickness direction measurement points Py are set at intervals of 0.01 mm in the plate thickness direction (interval c) at each of the measurement points Px (No. 1 to 25) in the plate width direction (see FIG. 1 (b)). Then, the Mg concentration of the aluminum alloy plate at each measurement point (predetermined plate thickness position (predetermined depth position)) is measured, the average value of the Mg concentration at each measurement point is calculated, and the plate thickness direction average Mg concentration Ci It was.
- the plate thickness direction average Mg concentration Ci and the plate width direction average Mg concentration Co at each measurement point of the plate width direction measurement point Px are defined by the difference between them (Ci-Co).
- a region Mg segregation degree X is calculated (see FIGS. 4 and 5).
- EPMA JEOL X-ray microanalyzer: JXA-8800RL
- JXA-8800RL is used to measure the Mg concentration.
- the maximum value of the region Mg segregation degree X was determined to be satisfactory ( ⁇ ) when the absolute value was 0.5% by mass or less, and unsatisfactory (x) when exceeding 0.5% by mass. Further, the average value of the region Mg segregation degree X was satisfied ( ⁇ ) when the absolute value was 0.1% by mass or less, and was unsatisfactory (x) when the absolute value exceeded 0.1% by mass.
- One point (No. 13) is selected from the plate width direction measurement points (No. 1 to 25), and the plate thickness direction (a plurality of plate thickness direction measurement points Py) measured at the measurement point is selected.
- the Mg concentration was defined as the Mg concentration Ct in the plate thickness direction.
- the plate thickness direction Mg segregation degree Y defined by the difference (Ct ⁇ Ci) between the two is obtained. Calculated. If the plate thickness direction measurement point Py is 0.01 mm or 1.0 mm, the plate thickness direction measurement point Py is located on the surface of the alloy plate (see FIGS. 6 and 7).
- the maximum value of the sheet thickness direction Mg segregation degree Y was satisfied ( ⁇ ) when the absolute value was 4% by mass or less, and unsatisfactory ( ⁇ ) when exceeding 4% by mass. Further, the average value of the thickness direction Mg segregation degree Y was satisfied ( ⁇ ) when the absolute value was 0.8% by mass or less, and was unsatisfactory ( ⁇ ) when exceeding 0.8% by mass.
- Example No. 1-5 Comparative Example No.
- the average crystal grain sizes of 6 to 10, 12 to 17, and 19 to 22 were in the range of 30 to 60 ⁇ m. Comparative Example No.
- the average crystal grain sizes of 11 and 18 exceeded 100 ⁇ m.
- a tensile test was performed using a test piece collected from the alloy plate, and the tensile strength (TS (MPa)) and the total elongation (EL (%)) were measured.
- the press formability is evaluated by a strength ductility balance value defined by (TS) ⁇ (EL), and when the strength ductility balance value is 11000 or more, it is evaluated as pass ( ⁇ ), and when it is less than 11000, it is evaluated as reject ( ⁇ ). Is done.
- the specimens were collected from five arbitrary positions with a distance of 100 mm or more in the longitudinal direction of the alloy plate.
- the (TS) value and (EL) value the average value of the measured values of five test pieces was used.
- the tensile test is performed according to JISZ2201, and the shape of the test piece is performed with a JIS No. 5 test piece. A test piece is produced so that a longitudinal direction may correspond with the rolling direction of an alloy plate. The crosshead speed was 5 mm / min, and the test was performed at a constant speed until the test piece broke.
- Example No. satisfying the requirements of the present invention were superior in press formability as compared with Comparative Examples Nos. 6 to 22 that do not satisfy the requirements of the present invention.
- Comparative Example No. 6 is an alloy plate described in Patent Document 3, but the Mg segregation degree (region Mg segregation degree) cannot be suppressed within the scope of the present invention, so press formability. It was inferior to.
- Comparative Examples Nos. 7 and 14 the Mg segregation degree can be suppressed within the range of the present invention, but since the Mg content is below the lower limit, the strength ductility balance is low and the press formability is poor. It was.
- Comparative Examples No. 8 and 15 since the Mg content exceeded the upper limit, the degree of Mg segregation was large and the press formability was poor. Comparative Example No.
- the comparative example 21 performed the face-cutting process which cuts both plate
Abstract
Description
例えば、特許文献1に記載された自動車用アルミニウム合金板は、双ロール式連続鋳造法で製造された、Mg含有量が6~10質量%である高Mg含有Al-Mg系合金板である。ここでは、Al-Mg系金属間化合物の平均サイズが10μm以下である。
前記構成によれば、Mg含有量を所定範囲に規定することによって、成形用アルミニウム合金板の強度、延性が向上すると共に、成形用アルミニウム合金板の内部でのβ相の析出が低減される。
本発明に係る成形用アルミニウム合金板(以下、アルミニウム合金板と称す)は、高含有量のMgを含むアルミニウム合金であって、板幅方向平均Mg濃度Coおよび板厚方向平均Mg濃度Ciで定義される領域Mg偏析度Xをが所定値以下に規制されていることを特徴とする。
本実施形態に係るアルミニウム合金板は、Mg:6.0質量%以上15.0質量%以下を含み、残部がAlおよび不純物であるアルミニウム合金、すなわち、高Mg含有Al-Mg系合金から構成される。また、本実施形態に係るアルミニウム合金板は、Mg以外の元素として、Fe:1.0質量%以下、Si:0.5質量%以下、Ti:0.1質量%以下、B:0.05質量%以下、Mn:0.3質量%以下、Cr:0.3質量%以下、Zr:0.3質量%以下、V:0.3質量%以下、Cu:1.0質量%以下、Zn:1.0%質量以下の少なくとも1種以上の元素を不純物として含有する高Mg含有Al-Mg系合金から構成されることが好ましい。
MgはAl合金板の強度、延性を高める重要合金元素である。Mg含有量が6.0質量%未満であると、強度、延性が不足して、高Mg含有Al-Mg系合金の特徴が出ず、プレス成形性が不足する。一方、Mg含有量が15.0質量%を超えると、製造方法や条件の制御を行なっても、アルミニウム合金板のMgの偏析、すなわち、前記領域Mg偏析度を所定範囲内に規定することが難しくなる。領域Mg偏析度が所定範囲内に規定されない場合、アルミニウム合金板でのβ相の析出が多くなり、プレス成形性が著しく低下するほか、加工硬化量が大きくなり、冷間圧延性も低下する。したがって、Mg含有量は、6.0質量%以上15.0質量%以下、好ましくは8質量%を超え14質量%以下である。
FeおよびSiは、できるだけ少ない量に規制されるべき元素である。FeおよびSiは、Al-Mg-(Fe、Si)などからなるAl-Mg系金属間化合物や、Al-Fe、Al-SiなどのAl-Mg系以外の金属間化合物となって析出する。Fe含有量が1.0質量%を超える場合、または、Si含有量が0.5質量%を超える場合には、これらの金属間化合物の析出量が過大となって、破壊靱性や成形性を大きく阻害する。その結果、プレス成形性が著しく低下する。したがって、Fe含有量は1.0質量%以下、好ましくは0.5質量%以下であり、Si含有量は0.5質量%以下、好ましくは0.3質量%以下である。
TiおよびBは鋳板(鋳塊)組織の微細化効果を有し、Mn、Cr、ZrおよびVには圧延板組織の微細化効果を有する。また、CuおよびZnは、強度を向上させる効果も有する。このため、本発明の合金板の特性であるプレス成形性を阻害しない範囲で、これらの効果を狙ってこれらの元素を一種以上含有させることは許容される。これらの元素の許容量は、Ti:0.1質量%以下、B:0.05質量%以下、Mn:0.3質量%以下、Cr:0.3質量%以下、Zr:0.3質量%以下、V:0.3質量%以下、Cu:1.0質量%以下、Zn:1.0質量%以下が好ましい。
図1(a)に示すように、板幅方向平均Mg濃度Coを算出するためには、まず、アルミニウム合金板60の表面に、全板幅Wを1辺とする正方形状の領域を設定する。この正方形状の領域、すなわち、全板幅Wと、全板幅Wと同じ長さの板長さLと、により囲まれた領域において、板幅方向に所定の間隔a、かつ、板長さ方向に所定の間隔bで、複数の板幅方向測定点Pxを設定する。これら複数の板幅方向測定点Pxで、アルミニウム合金板60の表面でのMg濃度を測定する。これらの測定されたMg濃度の平均値が、板幅方向平均Mg濃度Coであり、アルミニウム合金板60の表面での板幅方向におけるMgの偏析度合いの指標となる。また、Mg濃度の測定には、線分析が可能なEPMA(電子線プローブマイクロアナライザ)が用いられ、アルミニウム合金板60の板幅方向に走査することによりMg濃度が測定される。
図1(b)に示されるように、板厚方向平均Mg濃度Ciを算出するためには、まず、前記領域に設定された複数の板幅方向測定点Pxの全てにおいて、板厚方向に所定の間隔cで全板厚Tにわたって複数の板厚方向測定点Pyを設定する。そして、各板厚方向測定点Pyの、板深さ位置でのMg濃度(後記する板厚方向Mg濃度Ctと同義)を測定する。これらの測定されたMg濃度の平均値が、板厚方向平均Mg濃度Ciであり、アルミニウム合金板60の板厚方向(板深さ方向)におけるMgの偏析度合いの指標となる。また、Mg濃度の測定には、前記と同様にEPMAが用いられ、板幅方向の断面を板厚方向に走査することにより、全板厚Tの範囲における各厚み位置部分でのMg濃度が測定される。
領域Mg偏析度Xは、板厚方向平均Mg濃度(Ci)と板幅方向平均Mg濃度(Co)との差(Ci-Co)で定義され、アルミニウム合金板60全体、すなわち、板厚方向および板幅方向の両方でのMgの偏析度合いの指標となる。そして、本発明に係るアルミニウム合金板60においては、領域Mg偏析度Xの絶対値が、その最大値で0.5質量%以下、かつ、その平均値で0.1質量%以下である。なお、板幅方向平均Mg濃度Co、板厚方向平均Mg濃度Ciおよび領域Mg偏析度Xは、アルミニウム合金板60の化学成分組成、後記する製造条件、具体的には鋳造の際の冷却条件、鋳板板厚または面削量、均質化熱処理条件、最終焼鈍条件で制御される。
板厚方向Mg濃度Ctは、前記したように、図1(b)に記載された複数の板厚方向測定点Pyで測定されたMg濃度である。板厚方向平均Mg濃度Ciは、測定された板厚方向Mg濃度Ctの平均値である。
板厚方向Mg偏析度Yは、板厚方向Mg濃度(Ct)と板厚方向平均Mg濃度(Ci)との差(Ct-Ci)で定義され、アルミニウム合金板60の板厚方向のMgの偏析度合いの指標となるものである。板厚方向Mg偏析度Yは、前記領域Mg偏析度Xと併用することによって、アルミニウム合金板60の板全体のMgの偏析度合いを良好に再現できる。そして、本発明に係るアルミニウム合金板60においては、板厚方向Mg偏析度Yの絶対値が、最大値で4質量%以下、且つ、平均値で0.8質量%以下であることが好ましい。なお、板厚方向Mg濃度Ct、板厚方向平均Mg濃度Ciおよび板厚方向Mg偏析度Yは、アルミニウム合金板60の化学成分組成、後記する製造条件、具体的には鋳造の際の冷却条件、鋳板板厚または面削量、均質化熱処理条件、最終焼鈍条件で制御される。
本発明に係るアルミニウム合金板は、その表面の平均結晶粒径が100μm以下であることが好ましい。
アルミニウム合金板表面の平均結晶粒径を100μm以下に微細化させることによって、プレス成形性が向上する。平均結晶粒径が100μmを超えて粗大化した場合、プレス成形性が低下しやすく、成形時の割れや肌荒れなどの不良が生じ易くなる。一方、平均結晶粒径があまり細か過ぎても、5000系アルミニウム合金板に特有の、SS(ストレッチャーストレイン)マークがプレス成形時に発生する。この観点からは、平均結晶粒径は20μm以上であることが好ましい。
本発明のアルミニウム合金板は、溶解鋳造工程と、均質化熱処理工程と、冷間圧延工程と、最終焼鈍工程と、を経て製造される。以下、各工程について説明する。
溶解鋳造工程は、前記した化学成分組成を有する高Mg含有Al-Mg系合金を溶解し、薄板連続鋳造法を用いて溶湯から鋳板を製造する工程である。薄板連続鋳造法としては、黒鉛固定鋳型式連続鋳造法が好ましい。
黒鉛固定鋳型式連続鋳造法では、鋳板6の板厚が5~20mmの範囲であれば、鋳造における冷却速度は15℃/sとする。冷却速度が遅いと、Mgの偏析度合いが大きくなり、Mg偏析度(前記した領域Mg偏析度Xおよび板厚方向Mg偏析度Yを、以下、Mg偏析度と称す)を本発明の範囲内に抑制することが難しくなり、これに起因するβ相の析出を抑制できない可能性がある。また、β相全般が粗大化し、多量に析出する傾向がある。この結果、アルミニウム合金板のプレス成形性が著しく低下する可能性が高くなる。
黒鉛固定鋳型式連続鋳造法では、溶湯2を黒鉛固定鋳型4に注湯する際の注湯温度は、液相線温度+50℃以上、且つ液相線温度+250℃以下の範囲であり、好ましくは液相線温度+100℃以上、且つ液相線温度+150℃以下である。注湯温度が、液相線温度+50℃未満の場合には、鋳型内で溶湯が凝固し、鋳板破断が発生しやすくなる。注湯温度が液相線温度+250℃を超える場合には、鋳造の際の冷却速度が遅くなり、Mgの偏析度合いが大きくなる。この場合には、Mg偏析度を本発明の範囲内に抑制することが難しくなり、Mg偏析度に起因するβ相の析出や成形性の低下を抑制することができない。
黒鉛固定鋳型式連続鋳造法では、鋳造の安定化を図るために、鋳造方向に鋳板6を送るロール7を周期的に鋳造方向とは反対方向に回転させて鋳板6を後退させる。後退ストローク長さは0.5mm以上5mm以下の範囲であり、好ましくは1mm以上3mm以下である。また、後退前に1s以下の保持時間が入れられると、より鋳造性が安定する。
黒鉛固定鋳型式連続鋳造法では、溶湯2を黒鉛固定鋳型4で鋳造する際、平均鋳造速度は100mm/min以上、且つ500mm/min以下の範囲であり、好ましくは250mm/min以上、且つ350mm/min以下である。平均鋳造速度が100mm/min未満である場合には、鋳込口1aの付近で溶湯2が急速に凝固することにより、ロール7で引き抜く際にその部位の引出抵抗が増大するため、鋳板6が破断し易い。平均鋳造速度が500mm/minを超える場合には、鋳板出口4aの付近で、冷却不足による溶湯漏れが発生する。
黒鉛固定鋳型式連続鋳造法では、連続鋳造する鋳板6の板厚は5mm以上20mm以下の範囲である。板厚が5mm未満の場合には、鋳込口1aの付近で溶湯2が急速に凝固することにより、ロール7で引き抜く際に、その部位の引出抵抗が増大するため、鋳板6が破断し易い。板厚が20mmを超える場合には、鋳造の冷却速度が著しく遅くなり、Mgの偏析度合いが大きくなる。この場合には、Mg偏析度を本発明の範囲内に抑制することが難しくなり、Mg偏析度に起因するβ相の析出を抑制できない可能性がある。また、β相全般が粗大化したり、多量に析出する傾向がある。この結果、プレス成形性が著しく低下する可能性が高くなる。
黒鉛固定鋳型式連続鋳造法では、鋳板6の表面でMg偏析が発生しやすい。そのため、作製された鋳板6の板両面を所定量削る面削処理を行うことが好ましい。面削処理により板両面のMg偏析部を取り除くことで、Mg偏析度を本発明の範囲内に抑制することができる。Mg偏析部の深さは後退ストローク長さに対応するため、面削量は、前記した引き抜き方法の後退ストローク長さとする。
均質加熱処理工程は、前記工程で作製された鋳板6に所定の均質化熱処理を施す工程である。均質化熱処理は、400℃以上液相線温度以下で、必要時間行なわれる。連続熱処理炉を使用して、薄板連続鋳造法による鋳板6に均質化熱処理を施す場合、熱処理時間は、1秒(1s)以下が目安である。この均質化熱処理によって、Mgの偏析度合いが小さくなり、Mg偏析度を本発明の範囲内に抑制することができる。
冷間圧延工程は、均質化熱処理が施された鋳板6を、製品板の板厚、例えば、0.1mm以上13mm以下に冷延処理する工程である。冷間圧延によって、鋳造組織が加工組織化される。したがって、冷間圧延される鋳板6の板厚が厚い場合には、冷延途中に中間焼鈍を入れて、最終の冷間圧延における冷延率を60%以下とすることが好ましい。なお、冷間圧延における加工組織化の程度は、冷間圧延の冷延率にも依存するため、上記した集合組織制御のために鋳造組織が残留する場合もあるが、成形性や機械的な特性を阻害しない範囲内において許容される。
最終焼鈍工程は、前記工程で作製された冷延板に、所定の最終焼鈍を施す工程である。最終焼鈍工程では、400℃以上、且つ液相線温度(℃)未満の温度で冷延板に最終焼鈍を施す。この最終焼鈍によって、Mgの偏析度合いが小さくなり、Mg偏析度を本発明の範囲内に抑制することができ、これに起因するβ相の析出やプレス成形性の低下を抑制することができる。
表1に示される種々の化学成分組成のAl-Mg系合金(実施例A~E、比較例F、G)の溶湯を、前記した黒鉛固定鋳型式連続鋳造法および双ロール式連続鋳造法により、表2に示される条件で、表2に示される各板厚へと鋳造した。そして、各鋳板が、表2に示される条件で選択的に面削処理、均質化熱処理を施された後、熱間圧延することなしに、板厚1.0mmまたは板厚11.0mmまで冷間圧延された。なお、冷間圧延中、中間焼鈍は行なわれなかった。次に、これら各冷延板を、表2に示される温度と冷却条件で、連続焼鈍炉で最終焼鈍(焼鈍温度での保持時間は1秒以下)を行い、成形用アルミニウム合金板(実施例No.1~5、比較例No.6~20)とした。ここで、成形用アルミニウム合金板(比較例No.6)は、特許文献3に記載された双ロール式連続鋳造法を用いた製造方法によって作製されている。
各合金の液相線温度の算出には、熱力学計算ソフトThermo-Calc Ver.R(Al-DATA Ver.6)が用いられる。
また、実施例No.1の領域Mg偏析度Xの算出結果を図4、比較例No.6の領域Mg偏析度Xの算出結果を図5に示す。そして、実施例1の板厚方向Mg偏析度Yの算出結果を図6、比較例No.16の板厚方向Mg偏析度Yの算出結果を図7に示す。
まず、成形用アルミニウム合金板の表面に、一辺の長さが100mmの正方形状の領域を設定した。次いで、その領域内の板幅方向に、16.6mm間隔(間隔a)で板端を含まずに5点設定し、板長さ方向に、25mm間隔(間隔b)で5点設定した。これにより、合計で25点の板幅方向測定点Px(No.1~25)が設定される(図1(a)参照)。そして、各測定点でのアルミニウム合金板の表面でのMg濃度を測定し、各測定点でのMg濃度の平均値を算出して板幅方向平均Mg濃度Coとした。
前記板幅方向測定点(No.1~25)のうちから1点(No.13)を選択して、その測定点で測定された板厚方向(複数の板厚方向測定点Py)でのMg濃度を、板厚方向Mg濃度Ctとした。そして、各測定点でのMg濃度の平均値として前記で算出された板厚方向平均Mg濃度Ciを用いることにより、両者の差(Ct-Ci)で定義される板厚方向Mg偏析度Yが算出される。なお、板厚方向測定点Pyが0.01mmまたは1.0mmであれば、板厚方向測定点Pyは合金板の表面に位置している(図6、図7参照)。
また、得られた成形用アルミニウム合金板(実施例No.1~5、比較例6~22)について、前記した測定方法にしたがって、各合金板の平均結晶粒径を測定した。
さらに、得られた成形用アルミニウム合金板(実施例No.1~5、比較例No.6~22)について、各合金板のプレス成形性を下記手順で評価した。その結果を表2に示す。
L 板長さ
W 板幅
T 板厚
Px 板幅方向測定点
Py 板厚方向測定点
1 保持炉
1a 鋳込口
2 溶湯
3 連続鋳造鋳型
4 黒鉛固定鋳型
4a 鋳板出口
5 水冷ジャケット
6 鋳板
7 ロール
10 薄板連続鋳造装置
100 薄板連続鋳造装置
200 保持炉
300 溶湯
400 給湯ノズル
500 双ロール
600 鋳板
Claims (4)
- Mg:6.0質量%以上15.0質量%以下を含み、残部がAlおよび不純物である成形用アルミニウム合金板であって、
前記成形用アルミニウム合金板の表面に設定された全板幅を1辺とする正方形状の領域において、板幅方向および板長さ方向に所定の間隔で設定された複数の板幅方向測定点でMg濃度を測定し、複数の前記板幅方向測定点で測定されたMg濃度の平均値を板幅方向平均Mg濃度(Co)とし、
複数の前記板幅方向測定点について、板厚方向に所定の間隔で全板厚にわたって設定された複数の板厚方向測定点でMg濃度を測定し、複数の前記板厚方向測定点で測定されたMg濃度の平均値を板厚方向平均Mg濃度(Ci)としたとき、
前記板厚方向平均Mg濃度(Ci)と前記板幅方向平均Mg濃度(Co)との差(Ci-Co)で定義される領域Mg偏析度(X)の絶対値は、その最大値が0.5質量%以下、かつ、その平均値が0.1質量%以下であることを特徴とする成形用アルミニウム合金板。 - 前記領域Mg偏析度(X)に加えて、
前記領域Mg偏析度(X)の算出に際して、前記板幅方向測定点の少なくとも1つにおいて、板厚方向に所定の間隔で全板厚にわたって測定されたMg濃度を板厚方向Mg濃度(Ct)としたとき、
前記板厚方向Mg濃度(Ct)と前記板厚方向平均Mg濃度(Ci)との差(Ct-Ci)で定義される板厚方向Mg偏析度(Y)の絶対値は、その最大値が4質量%以下、かつ、その平均値が0.8質量%以下であることを特徴とする請求項1に記載の成形用アルミニウム合金板。 - 前記Mgの含有量が、8質量%を超えて14質量%以下であることを特徴とする請求項1または請求項2に記載の成形用アルミニウム合金板。
- 前記不純物が、Fe:1.0質量%以下、Si:0.5質量%以下、Ti:0.1質量%以下、B:0.05質量%以下、Mn:0.3質量%以下、Cr:0.3質量%以下、Zr:0.3質量%以下、V:0.3質量%以下、Cu:1.0質量%以下、Zn:1.0%質量以下の少なくとも1種以上の元素であることを特徴とする請求項1または請求項2に記載の成形用アルミニウム合金板。
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