WO2014142199A1 - Aluminum alloy plate for structural material - Google Patents
Aluminum alloy plate for structural material Download PDFInfo
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- WO2014142199A1 WO2014142199A1 PCT/JP2014/056567 JP2014056567W WO2014142199A1 WO 2014142199 A1 WO2014142199 A1 WO 2014142199A1 JP 2014056567 W JP2014056567 W JP 2014056567W WO 2014142199 A1 WO2014142199 A1 WO 2014142199A1
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- 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
- C22C21/10—Alloys based on aluminium with zinc as the next major constituent
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- 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
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- 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
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- 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
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- 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
- C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
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- 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
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- 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
- C22F1/053—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 zinc as the next major constituent
Definitions
- the present invention relates to a high-strength aluminum alloy plate for a structural material that has improved workability and excellent corrosion resistance.
- the aluminum alloy plate of the present invention is a rolled plate, which is a plate obtained by subjecting a plate produced by rolling to aging at room temperature for 2 weeks or more after solution treatment and quenching treatment, before forming into a structural material and artificial This refers to the plate before age hardening.
- the composition and tempering (solution treatment and quenching) of the JIS to AA6000 series aluminum alloy plates which are used in the above-mentioned automobile panels, are excellent in formability, strength, corrosion resistance, low alloy composition and recyclability. Control of the treatment, and further, the artificial age hardening treatment, is far from achieving the high strength.
- the 7000 series aluminum alloy which is an Al—Zn—Mg series aluminum alloy
- SCC stress corrosion cracking
- composition control for example, in Patent Document 1, Mg added in excess of Zn and Mg content (stoichiometry ratio of MgZn 2 ) of a 7000 series aluminum alloy extruded material that forms MgZn 2 without excess or deficiency. but by utilizing the fact that contributes to high strength by adding Mg to excess over stoichiometric ratio of MgZn 2, to suppress the MgZn 2 amount, without reducing the SCC resistance, and high strength Yes.
- Patent Document 2 As a typical example of the structure control of precipitates and the like, for example, in Patent Document 2, a 7000 series aluminum alloy extruded material after artificial age-hardening treatment is used for a precipitate having a particle diameter of 1 to 15 nm in crystal grains. As a result of observation by (TEM), it is made to exist at a density of 1000 to 10000 / ⁇ m 2 to reduce the potential difference between the grains and the grain boundaries, thereby improving the SCC resistance.
- TEM TEM
- composition control to improve both the strength and SCC resistance of a 7000 series aluminum alloy extruded material and examples of structure control such as precipitates are many practical applications in extruded materials. There are many in proportion to On the other hand, there are very few examples of conventional structure control such as composition control and precipitates in a 7000 series aluminum alloy plate according to the small practical use of the plate.
- Patent Document 3 in a structural material made of a clad plate in which 7000 series aluminum alloy plates are welded together, the diameter of an aging precipitate after artificial age hardening treatment is 50 mm (angstrom) or less in order to improve strength. It has been proposed that a certain amount exists as a spherical shape. However, there is no disclosure about the SCC resistance performance, and there is no corrosion resistance data in the examples.
- Patent Document 4 the molten metal is cold-rolled after rapid solidification, and the crystal precipitates in the crystal grains of the 7000 series aluminum alloy plate after artificial age hardening treatment are measured by a 400 times optical microscope.
- Strength equivalent to equivalent circle diameter with equivalent area
- average area fraction is set to 4.5% or less, and strength and elongation are improved.
- Patent Documents 5 and 6 in order to increase the strength and SCC resistance of a 7000 series plate for a structural material, the ingot is forged and rolled repeatedly in a warm working region after being forged. Is fine. This is because, by making the structure finer, a large tilt grain boundary having an orientation difference of 20 ° or more, which causes a potential difference between the grain boundary and the grain boundary, which causes a decrease in SCC resistance, is suppressed. This is to obtain a texture having a small angle grain boundary of 25 ° or more.
- such warm rolling is repeated because the conventional hot rolling and cold rolling methods cannot obtain a texture in which such a low-angle grain boundary is 25% or more. ing. Therefore, since the process is greatly different from the conventional method, it is difficult to say that it is a practical method for producing a plate.
- the extruded material is completely different from the rolled plate in its manufacturing process such as a hot working process, and the resulting structure of crystal grains and precipitates is, for example, a fibrous form in which the crystal grains are elongated in the extrusion direction.
- the crystal grains are basically different from a rolled plate having equiaxed grains.
- the object of the present invention is to provide a 7000 series aluminum for structural members such as automobile members, which has both strength and formability and is excellent in corrosion resistance as a rolled plate produced by the conventional method. It is to provide an alloy plate.
- the gist of the aluminum alloy sheet for structural material of the present invention is, in mass%, Zn: 3.0 to 6.0%, Mg: 1.5 to 4.5%, Cu: 0.00.
- the Zn content [Zn] and the Mg content [Mg] satisfy the relationship [Zn] ⁇ ⁇ 0.3 [Mg] +4.5, and the balance Is the maximum endothermic peak temperature in the differential scanning calorimetry curve when Al—Zn—Mg-based aluminum alloy plate having a composition consisting of Al and inevitable impurities is subjected to solution aging and quenching at room temperature.
- the maximum exothermic peak height in the temperature range of 200 to 300 ° C. is 50 ⁇ W / mg or more, and the work hardening index n value (10 to 20%) is 0.22 or more. To do.
- the aluminum alloy plate referred to in the present invention is a plate produced by rolling, and the ingot is hot-rolled after soaking, further cold-rolled into a cold-rolled plate, and further subjected to solution treatment and quenching treatment, etc.
- the aluminum alloy plate referred to in the present invention defines a room temperature aged structure of the 7000 series aluminum alloy plate produced as described above, and is processed into a structural material for use as a material aluminum alloy plate. It is. For this reason, it refers to a plate after the plate manufactured as described above is aged at room temperature (room temperature standing), and before being formed into a structural material as an application and before artificial age hardening treatment.
- the present invention analyzed the room temperature aged structure of a 7000 series aluminum alloy plate having a composition in which the Mg content was increased in order to ensure strength while suppressing the Zn content in order to improve corrosion resistance, using a differential scanning calorimetry curve. .
- the composition and action of the cluster formed by aging at room temperature are different in the 7000 series aluminum alloy plate having such a composition as compared with the 7000 series aluminum alloy sheet having a high Zn content.
- the clusters (atomic aggregates) generated by aging at room temperature are not only the artificial age-hardening properties (BH properties) after forming into the structural material that is used. They have also found that it contributes to the ductility (work hardening characteristics) required during the forming of structural materials. Therefore, by controlling these clusters, it is possible to improve not only the corrosion resistance but also the balance between strength and ductility (formability), and as a rolled plate manufactured by a conventional method, it has both strength and formability.
- a structural 7000 series aluminum alloy plate excellent in corrosion resistance such as SCC resistance can be provided.
- composition, size, or density of such clusters cannot be directly identified using ordinary observation means such as SEM or TEM at the present time. Difficult to define quantitatively.
- the room temperature aged structure of the manufactured 7000 series aluminum alloy plate is controlled by indirectly defining the clusters by analysis using a differential scanning calorimetry curve. More specifically, in the analysis based on the differential scanning calorimetry curve, the work hardening characteristics as ductility are improved as the temperature of the endothermic peak corresponding to the re-solution of clusters formed by room temperature aging is lowered. On the other hand, the higher the maximum height of the exothermic peak in the temperature range of 200 to 300 ° C. corresponding to the precipitate after the artificial age hardening treatment, the greater the amount of artificial age precipitate and the higher the strength.
- the measurement of the differential scanning calorimetry curve is not the state of the plate that has not been aged at room temperature immediately after the tempering treatment, but as a guide for two weeks or more. This is performed on the plate after aging at room temperature (room temperature standing), before forming into a structural material and before artificial age hardening.
- Aluminum alloy composition First, the chemical component composition of the aluminum alloy sheet of the present invention will be described below, including reasons for limiting each element. In addition,% display of content of each element means the mass% altogether.
- the chemical composition of the aluminum alloy sheet of the present invention combines strength and formability, which are required characteristics for structural materials such as automobile members intended in the present invention, as a rolled sheet produced by a conventional method. It is a prerequisite for satisfying corrosion resistance.
- the Al-Zn-Mg-Cu-based 7000 series aluminum alloy composition in the present invention is a composition in which the Mg content is increased in order to secure strength while suppressing the Zn content in order to improve the corrosion resistance. .
- the chemical composition of the aluminum alloy sheet of the present invention is, in mass%, Zn: 3.0 to 6.0%, Mg: 1.5 to 4.5%, Cu: 0.05 to 0.5. %, And the Zn content [Zn] and the Mg content [Mg] satisfy a relationship of [Zn] ⁇ ⁇ 0.3 [Mg] +4.5, the balance being Al and inevitable It shall consist of impurities.
- Zr 0.05 to 0.3%
- Mn 0.1 to 1.5%
- Cr 0.05 to 0.3%
- Sc 0.05
- One type or two or more types of up to 0.3% may be selectively included.
- Ag 0.01 to 0.2% may be selectively contained.
- Zn 3.0-6.0% Zn, which is an essential alloying element, together with Mg, forms clusters during aging of the manufactured tempered plate to improve work hardening characteristics and improve the workability of the structural material.
- an aging precipitate is formed to improve the strength during the artificial aging treatment after the forming process to the structural material. If the Zn content is less than 3.0%, the strength after the artificial aging treatment is insufficient. However, if the Zn content increases and exceeds 6.0%, the grain boundary precipitate MgZn 2 increases and intergranular corrosion tends to occur, and the corrosion resistance deteriorates. Therefore, in the present invention, the Zn content is suppressed to be relatively small. For this reason, the minimum of Zn content is 3.0%, Preferably it is 3.5%. Moreover, the upper limit of Zn content is 6.0%, Preferably it is 4.5%.
- Mg 1.5-4.5% Mg, which is an indispensable alloy element, together with Zn forms clusters during room temperature aging of the manufactured tempered plate to improve work hardening characteristics.
- an aging precipitate is formed during the artificial aging treatment after the forming process to the structural material, thereby improving the strength.
- the Mg content is made relatively large. If the Mg content is less than 1.5% by mass, the strength is insufficient and the work hardening characteristics are deteriorated. However, if it exceeds 4.5 mass%, the rollability of the plate is lowered, and the SCC sensitivity is enhanced. Therefore, the lower limit of the Mg content is 1.5%, preferably 2.5%. Moreover, the upper limit of Mg content is 4.5%.
- Balance formula of Zn and Mg In the present invention, in order to ensure high strength due to the inclusion of Zn and Mg, not only the content of Zn and Mg but also the Zn content [Zn] (mass%) and the Mg content [ It is important to control the balance with [Mg] (mass%). For this reason, as a control of this balance, [Zn] and [Mg] have a balance formula of [Zn] ⁇ ⁇ 0.3 [Mg] +4.5, preferably [Zn] ⁇ ⁇ 0.5 [Mg]. The balance equation of +5.75 is satisfied.
- the 0.2% proof stress of the structural material after the artificial age hardening treatment can be set to 350 MPa or more by a preferable manufacturing method described later. It becomes. Further, by satisfying [Zn] ⁇ ⁇ 0.5 [Mg] +5.75, the 0.2% proof stress of the structural material after artificial age hardening treatment is set to 400 MPa or more by a preferable manufacturing method described later. It becomes possible.
- Cu 0.05 to 0.5%
- Cu has the effect of suppressing the SCC sensitivity of the Al—Zn—Mg alloy and improving the SCC resistance. It also improves general corrosion resistance.
- the Cu content is less than 0.05%, the effect of improving SCC resistance and general corrosion resistance is small.
- the lower limit of the Cu content is 0.05%.
- the upper limit of the Cu content is 0.5%, preferably 0.4%.
- Zr 0.05 to 0.3%
- Mn 0.1 to 1.5%
- Cr 0.05 to 0.3%
- Sc 0.05 to 0.3% Since the transition elements of Zr, Mn, Cr, and Sc contribute to improvement in strength by refining the crystal grains of the ingot and the final product, they are selectively contained when necessary. When any one or two or more of these are contained, if the content of Zr, Mn, Cr, or Sc is less than the lower limit, the content is insufficient and the strength is lowered. On the other hand, when the contents of Zr, Mn, Cr, and Sc exceed the respective upper limits, the elongation decreases because coarse crystals are formed.
- the contents are as follows: Zr: 0.05 to 0.3%, Mn: 0.1 to 1.5%, Cr: 0.05 to 0.3%, Sc: 0.05 -0.3%, preferably Zr: 0.08-0.2%, Mn: 0.2-1.0%, Cr: 0.1-0.2%, Sc: 0.1- Each range is 0.2%.
- Ag 0.01-0.2% Ag has an effect of closely and finely precipitating aging precipitates that contribute to strength improvement by artificial aging treatment after forming processing into a structural material, and has the effect of promoting high strength. Therefore, Ag is selectively contained as necessary. . If the Ag content is less than 0.01%, the effect of improving the strength is small. On the other hand, even if the Ag content exceeds 0.2%, the effect is saturated and expensive. Therefore, the Ag content is in the range of 0.01 to 0.2%.
- Other elements are basically inevitable impurities. As a melting raw material, in addition to pure aluminum ingots, the inclusion of these impurity elements due to the use of aluminum alloy scrap is assumed (allowed), and each content within the range specified by the JIS standard of 7000 series alloys is allowed. .
- Ti and B are impurities as a rolled plate, but also have the effect of refining the crystal grains of the ingot, so the upper limit of Ti is 0.2%, preferably 0.1%, and the upper limit of B is 0.05% or less, preferably 0.03%.
- Fe and Si are allowed to be contained without affecting the characteristics of the aluminum alloy rolled sheet according to the present invention as long as Fe: 0.5% or less and Si: 0.5% or less.
- the 7000 series aluminum alloy sheet structure of the present invention has the maximum endothermic peak temperature in the differential scanning calorimetry curve after room temperature aging for 2 weeks or more after solution treatment and quenching of the sheet. Is 130 ° C. or less, and the maximum exothermic peak height in the temperature range of 200 to 300 ° C. is 50 ⁇ W / mg or more.
- the maximum endothermic peak temperature corresponds to the re-solution of clusters formed during aging of this plate at room temperature.
- the lower the maximum endothermic peak temperature the lower the thermal stability of the cluster (which tends to decompose), and the easier it is to decompose by cutting dislocations during plastic deformation besides heat. Therefore, the lower the cluster stability is, the less likely it is to cause dislocation movement failure or strain concentration during plastic deformation, such as forming a plate into a structural material.
- the maximum endothermic peak temperature is 130 ° C. or less.
- the higher the stability of the cluster the higher the maximum endothermic peak temperature is higher than 130 ° C., the work hardening property is lowered, and the work hardening index n value (10 to 20%) is reduced to 0. Cannot be over 22.
- the higher the stability of this cluster the more difficult it is to move dislocations during plastic deformation, such as forming a plate into a structural material. Since the movement of dislocations is concentrated, strain concentration is likely to occur and work hardening characteristics are deteriorated.
- the maximum height of the exothermic peak in the temperature range of 200 to 300 ° C. corresponds to the precipitation of artificial aging precipitates (artificial aging precipitates) that contribute to the improvement of strength. Therefore, the higher the exothermic peak height, the greater the amount of artificial aging precipitates deposited (density) and the higher the strength.
- This guideline is that the maximum height of the exothermic peak in the temperature range of 200 to 300 ° C. is 50 ⁇ W / mg or more. When the maximum height of the exothermic peak is less than 50 ⁇ W / mg, There is a high possibility that the 0.2% proof stress of the structural material cannot be 350 MPa or more.
- a work hardening index n value (10 to 20%) is defined. That is, a 7000 series aluminum alloy plate manufactured by the above-described composition and structure and a preferable manufacturing method described later, and after hardening and quenching the plate, a work hardening index n value after aging at room temperature for 2 weeks or more as a standard (10 to 20%) is 0.22 or more.
- Work hardening is a phenomenon in which hardness increases due to plastic deformation when stress is applied during molding, and is also called strain hardening. As the deformation progresses due to the molding process, the resistance increases and the hardness increases, which is work hardening.
- This is a characteristic value that is an index of the molding processability and is called “n value”.
- This n value is an index n obtained by approximating the relationship between the stress ⁇ and the strain ⁇ in the plastic region above the yield point.
- the approximate expression is a Voc's expression that matches aluminum well.
- n value the easier the work is hardened, and the hardened part that has undergone plastic deformation by molding such as bending becomes harder and the surrounding area is more easily deformed, so that molding processability such as bending is improved.
- the n value the harder the work is hardened, and the part that is initially subjected to plastic deformation, the most stressed part does not become harder, but it becomes more plastically deformed and is more likely to be constricted and fractured. Low formability such as bending.
- the 7000 series aluminum alloy plate can be manufactured by a manufacturing method according to a normal manufacturing process. That is, an aluminum alloy hot-rolled sheet having a thickness of 1.5 to 5.0 mm is manufactured through normal manufacturing processes such as casting (DC casting or continuous casting), homogenization heat treatment, and hot rolling. The Subsequently, it is cold-rolled to obtain a cold-rolled sheet having a thickness of 3 mm or less. At this time, one or more intermediate annealings may be selectively performed before cold rolling or in the middle of cold rolling.
- an ordinary molten casting method such as a continuous casting method or a semi-continuous casting method (DC casting method) is appropriately selected for the aluminum alloy melt adjusted within the above-mentioned 7000-based component composition range. Cast.
- homogenization heat treatment Next, the cast aluminum alloy ingot is subjected to a homogenization heat treatment prior to hot rolling.
- the purpose of this homogenization heat treatment (soaking) is to homogenize the structure, that is, eliminate segregation in crystal grains in the ingot structure.
- the soaking process is performed in two or two soaking steps.
- Two-stage soaking means cooling after the first soaking, but it is not cooled to 200 ° C. or lower, and after stopping the cooling at a higher temperature, after maintaining at that temperature, Hot rolling is started after reheating to a high temperature.
- the two-time soaking is once cooled to a temperature of 200 ° C. or less including room temperature, reheated and maintained at that temperature for a certain period of time. Start.
- the transition element compound is finely dispersed, aiming to refine the compound that affects the moldability to the structural material.
- solid solution of Zn, Mg, and Cu is promoted, aiming at work hardening characteristics at room temperature aging and strength improvement at artificial aging treatment.
- the soaking temperature in the first stage or the first time is controlled to 400 to 450 ° C., preferably 400 to 440 ° C.
- a Zr compound or a compound composed of Mn, Cr, or Sc can be finely dispersed. If this soaking temperature is less than 400 ° C., a sufficient effect of miniaturization cannot be obtained, and work hardening characteristics cannot be improved during aging at room temperature. On the other hand, if it exceeds 450 ° C., these compounds are coarsened, and it is impossible to improve the work-hardening characteristics at the time of aging at room temperature.
- the holding time of the first or first soaking may be about 1 to 8 hours.
- the second or second soaking temperature is controlled to 450 ° C. to the solidus temperature, preferably 470 ° C. to the solidus temperature.
- the solid solution of Zn, Mg and Cu can be promoted, and the strength at the time of artificial aging treatment after solution treatment can be improved.
- the soaking temperature is less than 450 ° C., sufficient dissolution of these elements cannot be obtained, and the work-hardening characteristics at room temperature aging and the strength after artificial aging do not increase.
- the solidus temperature is exceeded, partial melting occurs and the mechanical properties deteriorate, so the upper limit is made the solidus temperature or lower.
- the holding time during the second or second soaking may be about 1 to 8 hours.
- the hot rolling start temperature is selected from the range of 350 ° C. to the solidus temperature and hot rolled to obtain a hot rolled sheet having a thickness of about 2 to 7 mm. Annealing (roughening) of the hot-rolled sheet before cold rolling is not necessarily required, but may be performed.
- Cold rolling In cold rolling, the hot-rolled sheet is rolled into a cold-rolled sheet (including a coil) having a desired final thickness of about 1 to 3 mm. Intermediate annealing may be performed between cold rolling passes.
- solution treatment After cold rolling, solution treatment is performed as a tempering.
- the solution treatment is not particularly limited and may be heating and cooling using a normal continuous heat treatment line. However, in order to obtain a sufficient solid solution amount of each element and refinement of crystal grains, the holding time is predetermined at a solution treatment temperature of 450 ° C. to a solidus temperature, preferably 480 to 550 ° C. After reaching the solution treatment temperature, it is carried out in the range of 2 to 3 seconds and 30 minutes or less.
- the average cooling (temperature decrease) speed after solution treatment is not particularly limited.
- forced cooling means such as air cooling such as fans, water cooling means such as mist, spraying, and immersion are selected or combined. Or use in hot water from room temperature to 100 ° C.
- the solution treatment is basically only one time, but when the room temperature age hardening has progressed too much, the solution treatment and the restoration treatment are made the above-mentioned preferable conditions in order to ensure the moldability to the automobile member. It may be applied again, and this excessive room temperature age hardening may be canceled once.
- the aluminum alloy plate of the present invention is molded into an automobile member as a material and assembled as an automobile member. Further, after being molded into an automobile member, it is subjected to a separate artificial age hardening treatment to obtain an automobile member or an automobile body.
- the 7000 series aluminum alloy plate of the present invention is made to have a desired strength as a structural material such as an automobile member and a 0.2% proof stress of 350 MPa or more, preferably 400 MPa or more by an artificial age hardening treatment after forming into a structural material.
- the time point at which this artificial age hardening treatment is performed is preferably after the forming process of the material 7000 series aluminum alloy plate to the automobile member. This is because the 7000 series aluminum alloy plate after the artificial age hardening treatment has high strength but has low formability, and may not be formed depending on the complexity of the shape of the automobile member.
- the temperature and time conditions of this artificial age hardening treatment are within the range of general artificial aging conditions (T6, T7) from the desired strength, the strength of the 7000 series aluminum alloy plate of the material, or the progress of room temperature aging. It is decided freely.
- T6, T7 general artificial aging conditions
- aging treatment at 100 to 150 ° C. is performed for 12 to 36 hours (including an overaging region).
- the first-stage heat treatment temperature is in the range of 70 to 100 ° C. for 2 hours or longer
- the second-stage heat treatment temperature is in the range of 100 to 170 ° C. for five hours or longer (overaging region). Select from).
- the structure of the cold-rolled sheet was mainly controlled by changing various soaking conditions shown in Tables 3 and 4. Specifically, in common with each example, a 7000 series aluminum alloy molten metal having each component composition shown in Tables 1 and 2 below was DC-cast to obtain an ingot of 45 mm thickness ⁇ 220 mm width ⁇ 145 mm length. The ingot was subjected to two-stage soaking or twice soaking under the conditions of Tables 3 and 4. After the first soaking, the second stage soaking is cooled to 250 ° C., once the cooling is stopped at that temperature, reheated and held at the second stage soaking temperature, and cooled to the hot rolling start temperature. The hot rolling was started.
- the second soaking was once cooled to room temperature, reheated and held at the second soaking temperature, cooled to the hot rolling start temperature, and then started hot rolling.
- the only soaking process in Tables 3 and 4 does not perform the second reheating after being cooled once, but keeps the soaking temperature and time as usual, and then cools to the hot rolling start temperature. Started.
- hot rolling was performed at the starting temperatures shown in Tables 3 and 4 to produce hot rolled sheets having a thickness of 5 mm.
- the hot-rolled sheet was subjected to a roughing treatment in which forced air cooling was performed after holding at 500 ° C. for 30 seconds, and cold rolling was performed to 2 mm.
- This cold-rolled sheet was subjected to a solution treatment at 500 ° C. for 1 minute in common with each example, and after this solution treatment, forced air cooling was performed to cool to room temperature to obtain a T4 tempered material.
- a plate-like test piece was collected from the solution-treated aluminum alloy plate that had been aged at room temperature for two weeks in common with each example, and subjected to DSC measurement and tensile test. Each characteristic was investigated as follows.
- DSC measurement differential thermal analysis: The DSC measurement (differential thermal analysis) conditions were the same under the following conditions in common with each example.
- Test apparatus Seiko Instruments DSC220C, Standard material: pure aluminum, Sample container: pure aluminum, Temperature rising condition: 15 ° C./min, Atmosphere (in sample container): Argon gas (gas flow rate 50 ml / min), Test sample weight: 24.5 to 26.5 mg.
- the sampling by differential thermal analysis is performed from 10 points including the front end, the center, and the rear end in the longitudinal direction of the aluminum alloy plate after aging at room temperature, and the measured values are averaged. Turned into.
- the differential thermal analysis profile was horizontal in the 0-100 ° C. section of the differential thermal analysis profile.
- N value The n value was measured by performing a room temperature tensile test in the direction perpendicular to the rolling direction, using the plate-like test piece after the artificial age hardening treatment as a JIS No. 5 tensile test piece (distance between gauge points 50 mm). Then, the true stress and true strain are calculated from the end point of yield elongation, plotted on a logarithmic scale with the horizontal axis being strain and the vertical axis being stress, and the gradient of the straight line represented by the measurement point is the nominal strain of 10% and 20%. The n value (10 to 20%) was calculated from the two points.
- a current having a current density of 1 mA / cm 2 was allowed to flow for 24 hours in a state immersed in an aqueous sodium chloride solution (5% by mass), and then the sample was pulled up, and then the cross section of the test piece was cut and polished.
- the magnification was x100, and a corrosion depth of 200 ⁇ m or less was evaluated as “ ⁇ ” as minor corrosion. Moreover, the case where it exceeded 200 micrometers was evaluated as "x" as big corrosion.
- each invention example is within the composition range of the aluminum alloy of the present invention, and is manufactured within the range of the preferable manufacturing conditions described above.
- the maximum endothermic peak temperature was 130 ° C. or lower, and the maximum exothermic peak in the temperature range of 200 to 300 ° C.
- the height is 50 ⁇ W / mg or more and satisfies the tissue regulations analyzed by the DSC curve.
- the work hardening index n value (10 to 20%) is as high as 0.22 or more, excellent in ductility, and excellent in workability to a structural material.
- the BH property is excellent and the strength is high. It also has excellent corrosion resistance.
- the composition example satisfying [Zn] ⁇ ⁇ 0.3 [Mg] +4.5 has a 0.2% proof stress of 350 MPa or more after artificial age hardening, and [Zn] ⁇ ⁇ .
- Invention Examples 2, 4, 6, 8-12, 16-19, and 21 that satisfy both 0.5 [Mg] +5.75, the 0.2% proof stress after artificial age hardening is 400 MPa or more. is there.
- each comparative example does not have both workability and strength because the alloy composition is out of the scope of the present invention or the manufacturing condition is out of the preferred range.
- Comparative Example 26 in Table 4 As shown in Alloy No. 26 in Table 2, Zn is outside the lower limit.
- Zn exceeds the upper limit as shown by Alloy No. 27 in Table 2.
- Comparative Example 28 Cu is outside the lower limit as shown by Alloy No. 28 in Table 2.
- Comparative Example 29 Cu exceeds the upper limit as shown by Alloy No. 29 in Table 2.
- Comparative Examples 30 to 32 in Table 4 are manufactured out of the preferable manufacturing condition range although the invention example aluminum alloy of Alloy No. 2 in Table 1 is used.
- Comparative Example 30 is a soaking treatment only once (corresponding to the second soaking). In Comparative Example 31, the first soaking temperature is too low. In Comparative Example 32, the second soaking temperature is too low. For this reason, the comparative example in which these soaking conditions deviate from the preferable range does not satisfy the structure rule analyzed by the DSC curve, and the work hardening index n value (10 to 20%) after aging at room temperature is less than 0.22. In other words, the 0.2% proof stress after the artificial age hardening treatment is less than 350 MPa, so that both workability and strength are not achieved.
- Comparative Examples 40 to 43 in Table 4 the Mg content is outside the upper limit as shown in Alloy Nos. 37 to 40 in Table 2. Therefore, even if both of the relations [Zn] ⁇ ⁇ 0.3 [Mg] +4.5 and [Zn] ⁇ ⁇ 0.5 [Mg] +5.75 are satisfied, including soaking, Even if it is manufactured within the preferable manufacturing conditions, it does not satisfy the tissue regulations analyzed by the DSC curve. As a result, Comparative Examples 40 and 41 having relatively high Zn have a work hardening index n value (10 to 20%) after room temperature aging as low as 0.21 level, and do not have both workability and strength.
- the present invention can provide a 7000 series aluminum alloy plate for automobile members having both strength, formability, and corrosion resistance. Therefore, the present invention is also suitable for automobile structural materials such as frames and pillars that contribute to weight reduction of the vehicle body, and structural materials for other uses.
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Abstract
Description
先ず、本発明アルミニウム合金板の化学成分組成について、各元素の限定理由を含めて、以下に説明する。なお、各元素の含有量の%表示は全て質量%の意味である。 Aluminum alloy composition:
First, the chemical component composition of the aluminum alloy sheet of the present invention will be described below, including reasons for limiting each element. In addition,% display of content of each element means the mass% altogether.
必須の合金元素であるZnは、Mgとともに、製造された調質後の板の室温時効時にクラスタを形成して加工硬化特性を向上させ、構造材への成形加工性を向上させる。また、構造材への成形加工後の人工時効処理時に、時効析出物を形成して強度を向上させる。Zn含有量が3.0%未満では人工時効処理後の強度が不足する。但し、Zn含有量が多くなって6.0%を超えると、粒界析出物MgZn2が増えて粒界腐食が起こりやすくなり、耐食性が劣化する。従って、本発明ではZn含有量は比較的少なめに抑制する。このため、Zn含有量の下限は3.0%であり、好ましくは3.5%である。また、Zn含有量の上限は6.0%であり、好ましくは4.5%である。 Zn: 3.0-6.0%
Zn, which is an essential alloying element, together with Mg, forms clusters during aging of the manufactured tempered plate to improve work hardening characteristics and improve the workability of the structural material. In addition, an aging precipitate is formed to improve the strength during the artificial aging treatment after the forming process to the structural material. If the Zn content is less than 3.0%, the strength after the artificial aging treatment is insufficient. However, if the Zn content increases and exceeds 6.0%, the grain boundary precipitate MgZn 2 increases and intergranular corrosion tends to occur, and the corrosion resistance deteriorates. Therefore, in the present invention, the Zn content is suppressed to be relatively small. For this reason, the minimum of Zn content is 3.0%, Preferably it is 3.5%. Moreover, the upper limit of Zn content is 6.0%, Preferably it is 4.5%.
必須の合金元素であるMgは、Znとともに、製造された調質後の板の室温時効時にクラスタを形成して加工硬化特性を向上させる。また、構造材への成形加工後の人工時効処理時に時効析出物を形成して強度を向上させる。本発明ではZn含有量は比較的低目に抑制するため、逆にMg含有量は比較的多めにする。Mg含有量が1.5質量%未満では強度が不足し、加工硬化特性が低下する。但し、4.5質量%を超えると、板の圧延性が低下し、SCC感受性も強くなる。従って、Mg含有量の下限は1,5%であり、好ましくは2.5%である。また、Mg含有量の上限は4.5%である。 Mg: 1.5-4.5%
Mg, which is an indispensable alloy element, together with Zn forms clusters during room temperature aging of the manufactured tempered plate to improve work hardening characteristics. In addition, an aging precipitate is formed during the artificial aging treatment after the forming process to the structural material, thereby improving the strength. In the present invention, since the Zn content is suppressed to a relatively low level, the Mg content is made relatively large. If the Mg content is less than 1.5% by mass, the strength is insufficient and the work hardening characteristics are deteriorated. However, if it exceeds 4.5 mass%, the rollability of the plate is lowered, and the SCC sensitivity is enhanced. Therefore, the lower limit of the Mg content is 1.5%, preferably 2.5%. Moreover, the upper limit of Mg content is 4.5%.
本発明では、ZnとMgとの含有による高強度化を保障するために、前記したZnとMgとの含有量だけではなく、Znの含有量[Zn](質量%)とMgの含有量[Mg](質量%)とのバランスを制御することが重要となる。このために、このバランスの制御として、[Zn]と[Mg]とが、[Zn]≧-0.3[Mg]+4.5のバランス式、好ましくは[Zn]≧-0.5[Mg]+5.75のバランス式を満たすようにする。 Balance formula of Zn and Mg:
In the present invention, in order to ensure high strength due to the inclusion of Zn and Mg, not only the content of Zn and Mg but also the Zn content [Zn] (mass%) and the Mg content [ It is important to control the balance with [Mg] (mass%). For this reason, as a control of this balance, [Zn] and [Mg] have a balance formula of [Zn] ≧ −0.3 [Mg] +4.5, preferably [Zn] ≧ −0.5 [Mg]. The balance equation of +5.75 is satisfied.
Cuは、Al-Zn-Mg系合金のSCC感受性を抑え、耐SCC性を向上させる作用がある。また、一般耐食性も向上させる。Cu含有量が0.05%未満では、耐SCC性や一般耐食性の向上効果が小さい。一方、Cu含有量が0.5%を超えると、圧延性及び溶接性などの諸特性を却って低下させる。従って、Cu含有量の下限は0.05%である。また、Cu含有量の上限は0.5%であり、好ましくは0.4%である。 Cu: 0.05 to 0.5%
Cu has the effect of suppressing the SCC sensitivity of the Al—Zn—Mg alloy and improving the SCC resistance. It also improves general corrosion resistance. When the Cu content is less than 0.05%, the effect of improving SCC resistance and general corrosion resistance is small. On the other hand, if the Cu content exceeds 0.5%, various properties such as rollability and weldability are reduced. Therefore, the lower limit of the Cu content is 0.05%. Further, the upper limit of the Cu content is 0.5%, preferably 0.4%.
Zr、Mn、Cr、Scの遷移元素は、鋳塊及び最終製品の結晶粒を微細化して強度向上に寄与するので、必要な場合には選択的に含有させる。これらをいずれか一種、或いは二種以上を含有する場合、Zr、Mn、Cr、Scの含有量がいずれも下限未満では、含有量が不足して、強度が低下する。一方、Zr、Mn、Cr、Scの含有量がそれぞれの上限を超えた場合には、粗大晶出物を形成するため伸びが低下する。従って、これらを含有させる場合の含有量は、Zr:0.05~0.3%、Mn:0.1~1.5%、Cr:0.05~0.3%、Sc:0.05~0.3%の各範囲、好ましくはZr:0.08~0.2%、Mn:0.2~1.0%、Cr:0.1~0.2%、Sc:0.1~0.2%の各範囲とする。 One or more of Zr: 0.05 to 0.3%, Mn: 0.1 to 1.5%, Cr: 0.05 to 0.3%, Sc: 0.05 to 0.3% Since the transition elements of Zr, Mn, Cr, and Sc contribute to improvement in strength by refining the crystal grains of the ingot and the final product, they are selectively contained when necessary. When any one or two or more of these are contained, if the content of Zr, Mn, Cr, or Sc is less than the lower limit, the content is insufficient and the strength is lowered. On the other hand, when the contents of Zr, Mn, Cr, and Sc exceed the respective upper limits, the elongation decreases because coarse crystals are formed. Therefore, when these are contained, the contents are as follows: Zr: 0.05 to 0.3%, Mn: 0.1 to 1.5%, Cr: 0.05 to 0.3%, Sc: 0.05 -0.3%, preferably Zr: 0.08-0.2%, Mn: 0.2-1.0%, Cr: 0.1-0.2%, Sc: 0.1- Each range is 0.2%.
Agは、構造材への成形加工後の人工時効処理によって強度向上に寄与する時効析出物を緊密微細に析出させ、高強度化を促進する効果があるので、必要に応じて選択的に含有させる。Ag含有量が0.01%未満では強度向上効果が小さい。一方、Ag含有量は0.2%を超えて含有させてもその効果が飽和し、高価となる。従って、Ag含有量は0.01~0.2%の範囲とする。 Ag: 0.01-0.2%
Ag has an effect of closely and finely precipitating aging precipitates that contribute to strength improvement by artificial aging treatment after forming processing into a structural material, and has the effect of promoting high strength. Therefore, Ag is selectively contained as necessary. . If the Ag content is less than 0.01%, the effect of improving the strength is small. On the other hand, even if the Ag content exceeds 0.2%, the effect is saturated and expensive. Therefore, the Ag content is in the range of 0.01 to 0.2%.
これら以外のその他の元素は基本的に不可避的不純物である。溶解原料として、純アルミニウム地金以外に、アルミニウム合金スクラップの使用による、これら不純物元素の混入なども想定(許容)して、7000系合金のJIS規格で規定する範囲での各々の含有を許容する。例えば、Ti、Bは、圧延板としては不純物であるが、鋳塊の結晶粒を微細化する効果もあるので、Tiの上限は0.2%、好ましくは0.1%、Bの上限は0.05%以下、好ましくは0.03%とする。Fe、Siは、Fe:0.5%以下、Si:0.5%以下であれば、本発明に係るアルミニウム合金圧延板の特性に影響せず、含有が許容される。 Other elements:
Other elements other than these are basically inevitable impurities. As a melting raw material, in addition to pure aluminum ingots, the inclusion of these impurity elements due to the use of aluminum alloy scrap is assumed (allowed), and each content within the range specified by the JIS standard of 7000 series alloys is allowed. . For example, Ti and B are impurities as a rolled plate, but also have the effect of refining the crystal grains of the ingot, so the upper limit of Ti is 0.2%, preferably 0.1%, and the upper limit of B is 0.05% or less, preferably 0.03%. Fe and Si are allowed to be contained without affecting the characteristics of the aluminum alloy rolled sheet according to the present invention as long as Fe: 0.5% or less and Si: 0.5% or less.
以上の組成を前提として、本発明の7000系アルミニウム合金板組織は、この板の溶体化および焼入れ処理後、目安として2週間以上室温時効した後の示差走査熱分析曲線において、最大の吸熱ピーク温度が130℃以下であるとともに、200~300℃の温度範囲における発熱ピークの最大高さが50μW/mg以上とする。 Organization:
Based on the above composition, the 7000 series aluminum alloy sheet structure of the present invention has the maximum endothermic peak temperature in the differential scanning calorimetry curve after room temperature aging for 2 weeks or more after solution treatment and quenching of the sheet. Is 130 ° C. or less, and the maximum exothermic peak height in the temperature range of 200 to 300 ° C. is 50 μW / mg or more.
以上の組成や組織および後述する好ましい製造方法によって、本発明の7000系アルミニウム合金板は、成形加工性が向上するが、特に構造材への成形加工の際に用いられる、曲げ加工性を保障するために、本発明では加工硬化指数n値(10~20%)を規定する。すなわち、以上の組成や組織および後述する好ましい製造方法によって製造した7000系アルミニウム合金板であって、この板の溶体化および焼入れ処理後、目安として2週間以上室温時効した後の加工硬化指数n値(10~20%)を0.22以上とする。 Work hardening characteristics:
The above-described composition and structure and the preferable manufacturing method described later improve the forming processability of the 7000 series aluminum alloy plate of the present invention, but particularly ensure the bending processability used when forming a structural material. Therefore, in the present invention, a work hardening index n value (10 to 20%) is defined. That is, a 7000 series aluminum alloy plate manufactured by the above-described composition and structure and a preferable manufacturing method described later, and after hardening and quenching the plate, a work hardening index n value after aging at room temperature for 2 weeks or more as a standard (10 to 20%) is 0.22 or more.
本発明における7000系アルミニウム合金板の製造方法について、以下に具体的に説明する。 (Production method)
The method for producing a 7000 series aluminum alloy plate in the present invention will be specifically described below.
先ず、溶解、鋳造工程では、上記7000系成分組成範囲内に溶解調整されたアルミニウム合金溶湯を、連続鋳造法、半連続鋳造法(DC鋳造法)等の通常の溶解鋳造法を適宜選択して鋳造する。 (Dissolution, casting cooling rate)
First, in the melting and casting process, an ordinary molten casting method such as a continuous casting method or a semi-continuous casting method (DC casting method) is appropriately selected for the aluminum alloy melt adjusted within the above-mentioned 7000-based component composition range. Cast.
次いで、前記鋳造されたアルミニウム合金鋳塊に、熱間圧延に先立って、均質化熱処理を施す。この均質化熱処理(均熱処理)は、組織の均質化、すなわち、鋳塊組織中の結晶粒内の偏析をなくすことを目的とする。 (Homogenization heat treatment)
Next, the cast aluminum alloy ingot is subjected to a homogenization heat treatment prior to hot rolling. The purpose of this homogenization heat treatment (soaking) is to homogenize the structure, that is, eliminate segregation in crystal grains in the ingot structure.
熱間圧延は、熱延開始温度が固相線温度を超える条件では、バーニングが起こるため熱延自体が困難となる。また、熱延開始温度が350℃未満では熱延時の荷重が高くなりすぎ、熱延自体が困難となる。したがって、熱延開始温度は350℃~固相線温度の範囲から選択して熱間圧延し、2~7mm程度の板厚の熱延板とする。この熱延板の冷間圧延前の焼鈍 (荒鈍) は必ずしも必要ではないが実施しても良い。 (Hot rolling)
In the hot rolling, the hot rolling itself becomes difficult because burning occurs under conditions where the hot rolling start temperature exceeds the solidus temperature. On the other hand, when the hot rolling start temperature is less than 350 ° C., the load during hot rolling becomes too high, and the hot rolling itself becomes difficult. Therefore, the hot rolling start temperature is selected from the range of 350 ° C. to the solidus temperature and hot rolled to obtain a hot rolled sheet having a thickness of about 2 to 7 mm. Annealing (roughening) of the hot-rolled sheet before cold rolling is not necessarily required, but may be performed.
冷間圧延では、上記熱延板を圧延して、1~3mm程度の所望の最終板厚の冷延板 (コイルも含む) に製作する。冷間圧延パス間で中間焼鈍を行っても良い。 (Cold rolling)
In cold rolling, the hot-rolled sheet is rolled into a cold-rolled sheet (including a coil) having a desired final thickness of about 1 to 3 mm. Intermediate annealing may be performed between cold rolling passes.
冷間圧延後は調質として溶体化処理を行う。この溶体化処理については、通常の連続熱処理ラインによる加熱、冷却でよく、特に限定はされない。ただ、各元素の十分な固溶量を得ることや結晶粒の微細化のためには、450℃~固相線温度以下、好ましくは480~550℃の溶体化処理温度で、保持時間は所定の溶体化処理温度に到達後、2秒か3秒以上、30分以下の範囲で行う。 (Solution treatment)
After cold rolling, solution treatment is performed as a tempering. The solution treatment is not particularly limited and may be heating and cooling using a normal continuous heat treatment line. However, in order to obtain a sufficient solid solution amount of each element and refinement of crystal grains, the holding time is predetermined at a solution treatment temperature of 450 ° C. to a solidus temperature, preferably 480 to 550 ° C. After reaching the solution treatment temperature, it is carried out in the range of 2 to 3 seconds and 30 minutes or less.
本発明の7000系アルミニウム合金板は、構造材への成形加工後に人工時効硬化処理によって、自動車部材などの構造材としての所望の強度、0.2%耐力で350MPa以上、好ましくは400MPa以上とされる。この人工時効硬化処理を行う時点は、素材7000系アルミニウム合金板の自動車部材への成形加工後が好ましい。人工時効硬化処理後の7000系アルミニウム合金板は、強度は高くなるものの、成形性は低下しており、自動車部材の形状の複雑化によっては成形できない場合も生じるからである。 Artificial age hardening treatment:
The 7000 series aluminum alloy plate of the present invention is made to have a desired strength as a structural material such as an automobile member and a 0.2% proof stress of 350 MPa or more, preferably 400 MPa or more by an artificial age hardening treatment after forming into a structural material. The The time point at which this artificial age hardening treatment is performed is preferably after the forming process of the material 7000 series aluminum alloy plate to the automobile member. This is because the 7000 series aluminum alloy plate after the artificial age hardening treatment has high strength but has low formability, and may not be formed depending on the complexity of the shape of the automobile member.
DSC測定(示差熱分析)条件は、各例とも共通して下記の同一条件で行った。
試験装置:セイコ-インスツルメンツ社製DSC220C、
標準物質: 純アルミ、
試料容器: 純アルミ、
昇温条件:15℃/min、
雰囲気(試料容器内): アルゴンガス(ガス流量50ml/min)、
試験試料重量:24.5~26.5mg。
なお、示差熱分析での試料採取は、前記室温時効後のアルミニウム合金板の長手方向に亙る先端部、中央部、後端部とを各々必須で含む10箇所から行って、測定値を各々平均化した。 DSC measurement (differential thermal analysis):
The DSC measurement (differential thermal analysis) conditions were the same under the following conditions in common with each example.
Test apparatus: Seiko Instruments DSC220C,
Standard material: pure aluminum,
Sample container: pure aluminum,
Temperature rising condition: 15 ° C./min,
Atmosphere (in sample container): Argon gas (gas flow rate 50 ml / min),
Test sample weight: 24.5 to 26.5 mg.
In addition, the sampling by differential thermal analysis is performed from 10 points including the front end, the center, and the rear end in the longitudinal direction of the aluminum alloy plate after aging at room temperature, and the measured values are averaged. Turned into.
各例とも機械的特性は、共通して、各板状試験片の圧延直角方向の室温引張試験を行い、0.2%耐力(MPa)、全伸び(%)を測定した。室温引張り試験はJIS2241(1980)に基づき、室温20℃で試験を行った。引張り速度は5mm/分で、試験片が破断するまで一定の速度で行った。 (Mechanical properties)
In each example, the mechanical properties were commonly measured by performing a room temperature tensile test in the direction perpendicular to the rolling direction of each plate-like specimen, and measuring 0.2% yield strength (MPa) and total elongation (%). The room temperature tensile test was performed at a room temperature of 20 ° C. based on JIS2241 (1980). The tensile speed was 5 mm / min, and the test was performed at a constant speed until the test piece broke.
n値は、前記人工時効硬化処理後の板状試験片を、JIS5号引張試験片(標点間距離50mm)として、圧延直角方向の室温引張試験を行い測定した。そして、降伏伸びの終点から真応力と真歪みを計算し、横軸を歪み、縦軸を応力とした対数目盛上にプロットし、測定点が表す直線の勾配を、公称ひずみ10%、20%の2点で計算して、n値(10~20%)とした。 (N value)
The n value was measured by performing a room temperature tensile test in the direction perpendicular to the rolling direction, using the plate-like test piece after the artificial age hardening treatment as a JIS No. 5 tensile test piece (distance between gauge points 50 mm). Then, the true stress and true strain are calculated from the end point of yield elongation, plotted on a logarithmic scale with the horizontal axis being strain and the vertical axis being stress, and the gradient of the straight line represented by the measurement point is the nominal strain of 10% and 20%. The n value (10 to 20%) was calculated from the two points.
一般的な耐食性評価のために、旧JIS-W1103の規定に準じた粒界腐食感受性試験を、前記人工時効硬化処理後の板状試験片(試験片3個)に対して行った。試験条件は、試験片を硝酸水溶液(30質量%)に室温で1分間浸漬した後、水酸化ナトリウム水溶液(5質量%)に40℃で20秒浸漬した後、硝酸水溶液(30質量%)に室温で1分間浸漬することによって試験片の表面を洗浄した。その後、塩化ナトリウム水溶液(5質量%)に浸漬した状態で、1mA/cm2の電流密度の電流を24時間流した後、試料を引き上げ、その後、試験片の断面を切断・研磨し、光学顕微鏡を用いて、試料表面からの腐食深さを測定した。倍率は×100とし、腐食深さが200μm以下までを軽微な腐食として「○」と評価した。また、200μmを超える場合を大きな腐食として「×」と評価した。 (Intergranular corrosion sensitivity)
For general corrosion resistance evaluation, a grain boundary corrosion susceptibility test in accordance with the provisions of the former JIS-W1103 was performed on the plate-like test pieces (three test pieces) after the artificial age hardening treatment. The test condition was that the test piece was immersed in an aqueous nitric acid solution (30% by mass) for 1 minute at room temperature, then immersed in an aqueous sodium hydroxide solution (5% by mass) at 40 ° C. for 20 seconds, and then immersed in an aqueous nitric acid solution (30% by mass). The surface of the test piece was cleaned by dipping for 1 minute at room temperature. Thereafter, a current having a current density of 1 mA / cm 2 was allowed to flow for 24 hours in a state immersed in an aqueous sodium chloride solution (5% by mass), and then the sample was pulled up, and then the cross section of the test piece was cut and polished. Was used to measure the depth of corrosion from the sample surface. The magnification was x100, and a corrosion depth of 200 μm or less was evaluated as “◯” as minor corrosion. Moreover, the case where it exceeded 200 micrometers was evaluated as "x" as big corrosion.
これら発明例のうち、組成が[Zn]≧-0.3[Mg]+4.5を満足する発明例は人工時効硬化処理後の0.2%耐力が350MPa以上であり、[Zn]≧-0.5[Mg]+5.75を両方満足する発明例2、4、6、8~12、16~19、21の場合には、人工時効硬化処理後の0.2%耐力が400MPa以上である。 For this reason, even after aging at room temperature, the work hardening index n value (10 to 20%) is as high as 0.22 or more, excellent in ductility, and excellent in workability to a structural material. At the same time, even after room temperature aging, the BH property is excellent and the strength is high. It also has excellent corrosion resistance.
Of these invention examples, the composition example satisfying [Zn] ≧ −0.3 [Mg] +4.5 has a 0.2% proof stress of 350 MPa or more after artificial age hardening, and [Zn] ≧ −. In Invention Examples 2, 4, 6, 8-12, 16-19, and 21 that satisfy both 0.5 [Mg] +5.75, the 0.2% proof stress after artificial age hardening is 400 MPa or more. is there.
本出願は、2013年3月14日出願の日本特許出願(特願2013-051608)に基づくものであり、その内容はここに参照として取り込まれる。 Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on March 14, 2013 (Japanese Patent Application No. 2013-051608), the contents of which are incorporated herein by reference.
Claims (4)
- 質量%で、Zn:3.0~6.0%、Mg:1.5~4.5%、Cu:0.05~0.5%を各々含み、かつZnの含有量[Zn]とMgの含有量[Mg]とが [Zn]≧-0.3[Mg]+4.5を満足する関係にあり、残部がAlおよび不可避的不純物からなる組成のAl-Zn-Mg系アルミニウム合金板であって、この板を溶体化および焼入れ処理後に室温時効させた際の示差走査熱量分析曲線において、最大の吸熱ピーク温度が130℃以下であるとともに、200~300℃の温度範囲における発熱ピークの最大高さが50μW/mg以上であり、加工硬化指数n値(10~20%)が0.22以上であることを特徴とする構造材用アルミニウム合金板。 In mass%, Zn: 3.0-6.0%, Mg: 1.5-4.5%, Cu: 0.05-0.5%, respectively, and Zn content [Zn] and Mg The content [Mg] of the Al—Zn—Mg based aluminum alloy plate having a composition satisfying [Zn] ≧ −0.3 [Mg] +4.5, with the balance being Al and inevitable impurities. In the differential scanning calorimetry curve when this plate is aged at room temperature after solution treatment and quenching treatment, the maximum endothermic peak temperature is 130 ° C. or less, and the maximum exothermic peak in the temperature range of 200 to 300 ° C. An aluminum alloy plate for a structural material having a height of 50 μW / mg or more and a work hardening index n value (10 to 20%) of 0.22 or more.
- 前記アルミニウム合金板が、更に、質量%で、Zr:0.05~0.3%、Mn:0.1~1.5%、Cr:0.05~0.3%、Sc:0.05~0.3%の1種又は2種以上を含む請求項1に記載の構造材用アルミニウム合金板。 The aluminum alloy plate is further, in mass%, Zr: 0.05 to 0.3%, Mn: 0.1 to 1.5%, Cr: 0.05 to 0.3%, Sc: 0.05 The aluminum alloy plate for a structural material according to claim 1, comprising one or more of ˜0.3%.
- 前記アルミニウム合金板が、更に、質量%で、Ag:0.01~0.2%を含む請求項1または2に記載の構造材用アルミニウム合金板。 The aluminum alloy plate for a structural material according to claim 1 or 2, wherein the aluminum alloy plate further contains Ag: 0.01 to 0.2% by mass.
- 前記アルミニウム合金板のZnの含有量[Zn]とMgの含有量[Mg]とが[Zn]≧-0.5[Mg]+5.75を満足する関係にあり、人工時効硬化処理後の0.2%耐力が400MPa以上である、請求項1乃至3のいずれか1項に記載の構造材用アルミニウム合金板。 The aluminum content [Zn] and the Mg content [Mg] in the aluminum alloy plate satisfy the relationship [Zn] ≧ −0.5 [Mg] +5.75, and 0 after the artificial age hardening treatment. The aluminum alloy plate for a structural material according to any one of claims 1 to 3, having a 0.2% proof stress of 400 MPa or more.
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