JP2020066751A - Al-Mg-Si-BASED ALUMINUM ALLOY PLASTICALLY WORKED MATERIAL, AND METHOD FOR MANUFACTURING Al-Mg-Si-BASED ALUMINUM ALLOY EXTRUSION MATERIAL - Google Patents

Abstract

To provide an Al-Mg-Si-based aluminum alloy plastically worked material excellent in self-pierce rivet bond strength.SOLUTION: A plastically worked material used for self-pierce rivet bond contains Si: 0.95 mass%-1.25 mass%, Mg: 0.80 mass%-1.05 mass%, Cu: 0.30 mass%-0.50 mass%, Mn: 0.40 mass%-0.60 mass%, Fe: 0.15 mass%-0.30 mass%, Cr: 0.09 mass%-0.21 mass%, B: 0.0001 mass%-0.03 mass%, has a percentage content of Zn of 0.25 mass% or less, a percentage content of Zr of 0.05 mass% or less and a percentage content of Ti of 0.10 mass% or less, and the balance Al with impurities, in which a shearing tensile maximum load measured according to JIS Z3136-1999 of a self-pierce rivet joined body of the aluminum alloy plastically worked materials is 8.5 kN or more.SELECTED DRAWING: Figure 2

Description

  TECHNICAL FIELD The present invention relates to a method for producing an Al—Mg—Si-based high-strength aluminum alloy plastic material having excellent self-piercing rivet bonding strength and an Al—Mg—Si-based aluminum alloy extruded material having excellent self-piercing rivet bonding strength.

  The Al-Mg-Si-based aluminum alloy is a practical alloy in that it has strength and is excellent in corrosion resistance and recyclability, so that it is used in vehicles, ships, automobiles, motorcycles, etc., that require high strength and corrosion resistance. It is used as a structural material for transport aircraft.

  Among the Al-Mg-Si-based aluminum alloys, 6061 is particularly often used, but further weight reduction is required in order to improve transportation efficiency by reducing the weight of the vehicle body structure. Strengthening is required. In order to achieve such high strength, improvement by changing the additive metal species of the aluminum alloy and the content thereof is being studied.

Further, when an Al-Mg-Si based aluminum alloy is used as a structural material, MIG welding or the like has been used for joining, but since HAZ (heat affected zone) causes strength reduction, joining by friction stir welding is used. Has also been done. On the other hand, attention is focused on a joining method by mechanical fastening, which can perform joining more easily than MIG welding and friction stir welding. Joining with self-piercing rivets is a typical example, and has already been used for joining automobile frame members. For example, in Patent Document 1, Mg: 0.40 to 0.60% (mass%, the same applies hereinafter), Si: 0.50 to 0.70%, Cu: 0.05 to 0.40%, Mn: 0. .05 to 0.30%, Zr: 0.05 to 0.20%, Ti: 0.005 to 0.2%, Al-Mg-Si based aluminum alloy extruded material consisting of balance Al and unavoidable impurities In addition, a self-piercing rivet-bonded aluminum alloy extruded material for automobile frames, which has been subjected to aging treatment after press quenching by air cooling, has a proof stress of 200 N / mm ² or more, and has a local elongation of 3.5% or more, is described. Has been done.

Japanese Patent No. 4540209

The aluminum alloy extruded material described in Patent Document 1 has a proof stress value of about 240 MPa (N / mm ² ), and the weight is reduced by replacing the iron-based material generally used for the frame material with this aluminum alloy material. When trying to realize it, it was difficult to secure strength and rigidity equivalent to those of iron-based materials. Further, in Patent Document 1, regarding self-piercing rivet joining, the self-piercing rivet joining property is evaluated only by the presence or absence of a through crack penetrating through the front and back of the material to be joined on the receiving die side after self-piercing rivet joining. However, there is no disclosure about the joint strength, and therefore, no knowledge about what structure should be adopted to sufficiently improve the joint strength of the self-piercing rivet joint is not obtained from Patent Document 1.

  The present invention has been made in view of the above technical background, and is an Al-Mg-Si-based aluminum alloy plastically worked material having excellent self-pierce rivet bonding strength and an Al-Mg-Si system having excellent self-piercing rivet bonding strength. It is an object to provide a method for manufacturing an aluminum alloy extruded material.

  In order to achieve the above object, the present invention provides the following means.

[1] A plastic work material used for self-piercing rivet joining,
Si: 0.95 mass% to 1.25 mass%, Mg: 0.80 mass% to 1.05 mass%, Cu: 0.30 mass% to 0.50 mass%, Mn: 0.40 mass% to 0.60% by mass, Fe: 0.15% by mass to 0.30% by mass, Cr: 0.09% by mass to 0.21% by mass, B: 0.0001% by mass to 0.03% by mass. , Zn content is 0.25 mass% or less, Zr content is 0.05 mass% or less, Ti content is 0.10 mass% or less, and the balance is aluminum alloy plasticity consisting of Al and unavoidable impurities. It is a processed material,
The maximum shear tensile load measured according to JIS Z3136-1999 for the self-piercing rivet joint between the aluminum alloy plastically worked materials is 8.5 kN or more, and the Al-Mg-Si based aluminum alloy plastically worked. Material.

[2] A plastically worked material used for self-piercing rivet joining,
Si: 0.95 mass% to 1.25 mass%, Mg: 0.80 mass% to 1.05 mass%, Cu: 0.30 mass% to 0.50 mass%, Mn: 0.40 mass% to 0.60% by mass, Fe: 0.15% by mass to 0.30% by mass, Cr: 0.09% by mass to 0.21% by mass, B: 0.0001% by mass to 0.03% by mass. , Zn content is 0.25 mass% or less, Zr content is 0.05 mass% or less, Ti content is 0.10 mass% or less, and the balance is aluminum alloy plasticity consisting of Al and unavoidable impurities. It is a processed material,
The self-piercing rivet joint between the aluminum alloy plastic working materials has a maximum cross-tension load of 5.0 kN or more measured according to JIS Z3137-1999. Material.

  [3] The Al-Mg-Si-based aluminum alloy plastically worked material according to item 1 or 2 used as a structural member for an automobile frame.

[4] Si: 0.95 mass% to 1.25 mass%, Mg: 0.80 mass% to 1.05 mass%, Cu: 0.30 mass% to 0.50 mass%, Mn: 0.40 Mass% to 0.60 mass%, Fe: 0.15 mass% to 0.30 mass%, Cr: 0.09 mass% to 0.21 mass%, B: 0.0001 mass% to 0.03 mass% Zn content is 0.25 mass% or less, Zr content is 0.05 mass% or less, Ti content is 0.10 mass% or less, and the balance is Al and inevitable impurities. A molten metal forming step of obtaining a molten aluminum alloy;
A casting step of obtaining a billet by casting the obtained molten metal;
A homogenizing heat treatment step of performing a homogenizing heat treatment of holding the billet at a temperature of 480 ° C. to 530 ° C. for 2 hours to 15 hours;
A cooling step of cooling the billet after the homogenizing heat treatment to 200 ° C. or less at an average cooling rate of 150 ° C./hour or more;
An extrusion step of obtaining an extruded material by performing hot extrusion at an extrusion speed of 3 m / min to 25 m / min in a state where the billet that has undergone the cooling step is at 500 ° C to 560 ° C.
A quenching step of quenching the temperature of the obtained extruded material from 500 ° C. to 570 ° C. to 150 ° C. or less at a cooling rate of 100 ° C./sec to 500 ° C./sec;
An aging treatment step of obtaining an aluminum alloy extruded material by heating the extruded material that has been subjected to the quenching step at a temperature of 160 ° C. to 200 ° C. for 1 hour to 24 hours,
The obtained aluminum alloy extruded material has a maximum shear tensile load of 8.5 kN or more measured in accordance with JIS Z3136-1999 for a self-piercing rivet joined body of the aluminum alloy extruded materials. -Mg-Si system aluminum alloy extruded material manufacturing method.

[5] Si: 0.95 mass% to 1.25 mass%, Mg: 0.80 mass% to 1.05 mass%, Cu: 0.30 mass% to 0.50 mass%, Mn: 0.40 Mass% to 0.60 mass%, Fe: 0.15 mass% to 0.30 mass%, Cr: 0.09 mass% to 0.21 mass%, B: 0.0001 mass% to 0.03 mass% Zn content is 0.25 mass% or less, Zr content is 0.05 mass% or less, Ti content is 0.10 mass% or less, and the balance is Al and inevitable impurities. A molten metal forming step of obtaining a molten aluminum alloy;
A casting step of obtaining a billet by casting the obtained molten metal;
A homogenizing heat treatment step of performing a homogenizing heat treatment of holding the billet at a temperature of 480 ° C. to 530 ° C. for 2 hours to 15 hours;
A cooling step of cooling the billet after the homogenizing heat treatment to 200 ° C. or less at an average cooling rate of 150 ° C./hour or more;
An extrusion step of obtaining an extruded material by performing hot extrusion at an extrusion speed of 3 m / min to 25 m / min in a state where the billet that has undergone the cooling step is at 500 ° C to 560 ° C.
A quenching step of quenching the temperature of the obtained extruded material from 500 ° C. to 570 ° C. to 150 ° C. or less at a cooling rate of 100 ° C./sec to 500 ° C./sec;
An aging treatment step of obtaining an aluminum alloy extruded material by heating the extruded material that has been subjected to the quenching step at a temperature of 160 ° C. to 200 ° C. for 1 hour to 24 hours,
The obtained aluminum alloy extruded material has a cross tensile maximum load of 5.0 kN or more measured according to JIS Z3137-1999 for a self-piercing rivet joined body of the aluminum alloy extruded materials. -Mg-Si system aluminum alloy extruded material manufacturing method.

  According to the inventions [1] and [2], it is possible to provide an Al—Mg—Si based aluminum alloy plastically worked material having excellent bonding strength in self-piercing rivet bonding.

  According to the invention [3], it is possible to provide a structural member for an automobile frame, which is excellent in the bonding strength of the self-piercing rivet bonding.

  In the inventions [4] and [5], it is possible to manufacture an Al-Mg-Si-based aluminum alloy extruded material having excellent bonding strength in self-piercing rivet bonding.

It is explanatory drawing of the joining method by a self-piercing rivet, Comprising: (A) is sectional drawing which shows the punching start state of a punch, (B) is sectional drawing which shows the state which the rivet penetrated the upper side board | plate, (C) of punch It is a sectional view showing the completed state where self-piercing rivet joining was performed by further driving. It is sectional drawing which shows one Embodiment of the extruded material which is an example of the Al-Mg-Si system aluminum alloy plastic working material which concerns on this invention. It is a perspective view which shows the test piece (self-pierce rivet joined body) for a tensile shear test. It is a perspective view which shows the test piece (cross-shaped self-pierce rivet joined body) for a cross tension test.

  The aluminum alloy plastically worked material according to the present invention is a plastically worked material used for self-piercing rivet joining, and Si: 0.95 mass% to 1.25 mass% and Mg: 0.80 mass% to 1. 05 mass%, Cu: 0.30 mass% to 0.50 mass%, Mn: 0.40 mass% to 0.60 mass%, Fe: 0.15 mass% to 0.30 mass%, Cr: 0. 09% by mass to 0.21% by mass, B: 0.0001% by mass to 0.03% by mass, Zn content is 0.25% by mass or less, Zr content is 0.05% by mass or less. , Ti content is 0.1 mass% or less, and the balance is an aluminum alloy plastically worked material consisting of Al and unavoidable impurities. Regarding a self-piercing rivet joined body of the aluminum alloy plastically worked materials, JIS Z3136 (1999) ) Was measured according to N cross-sectional maximum tensile load is characterized in that it is not less than 8.5kN. Examples of the aluminum alloy plastically worked material include an aluminum alloy extruded material and an aluminum alloy rolled material.

  The aluminum alloy plastically worked material (extruded material or rolled material) having the above-described configuration is excellent in the joining strength of self-piercing rivet joining, and is used as a structural material (frame, etc.) of a vehicle body of a vehicle such as an automobile, a motorcycle, or a railway. It is suitable.

  The composition of the aluminum alloy (the significance of limiting the content range of each component, etc.) will be collectively described in detail in the paragraph after the description of the manufacturing method of the present invention.

  In the present invention, two aluminum alloy plastically worked materials according to the present invention are prepared, and a self-pierce rivet joined body obtained by self-piercing rivet joining these two aluminum alloy plastically worked materials is based on JIS Z3136-1999. The maximum shear tensile load measured by the method is 8.5 kN or more. By providing the above-described aluminum alloy composition, it is possible to obtain a self-piercing rivet joined body having an excellent joining strength with a maximum shear tensile load of 8.5 kN or more.

  The self-piercing rivet joining will be described with reference to FIG. As shown in FIG. 1 (A), two plate-shaped aluminum alloy plastic working materials to be joined below the self-piercing rivet 11 in which a tubular shaft portion 11b is connected to the lower surface of the upper head portion 11a. 1 are arranged in an overlapping manner, a die (receiving die) 12 is arranged below the aluminum alloy plastically worked material 1, and the upper surface of the upper head portion 11a of the self-piercing rivet 11 is pushed downward by a punch 13 to make a self-piercing rivet 11. When the piercing rivet 11 is driven, as shown in FIG. 1 (B), the shaft portion 11b is punched out of the upper aluminum alloy plastically worked material 1 and is then expanded by the central convex portion of the die 12, The upper and lower aluminum alloy plastic working materials 1 and 1 are locked to each other (see FIG. 1C). The self-piercing rivet joining is joining of the upper and lower aluminum alloy plastic working materials 1 and 1 by the locking structure using the self-piercing rivet 11. In FIG. 1, 14 is a plate pressing member.

  FIG. 2 shows an embodiment of the aluminum alloy plastically worked material 1 according to the present invention. The aluminum alloy plastically worked material 1 shown in FIG. 2 has a so-called V-shaped cross section, but the shape is not particularly limited to such a shape. The cross-sectional shape of the plastically worked material 1 is not particularly limited, but a cross-sectional shape that can realize weight reduction of the vehicle structural member and can secure sufficient rigidity and strength as the structural material is adopted. Specifically, the cross-sectional shape may be, for example, a hollow cross-sectional shape such as a mouth shape or a square shape, or a solid body.

  Next, a method for manufacturing the aluminum alloy extruded material 1 according to the present invention will be described. This manufacturing method uses Si: 0.95% by mass to 1.25% by mass, Mg: 0.80% by mass to 1.05% by mass, Cu: 0.30% by mass to 0.50% by mass, Mn: 0. 40 mass% to 0.60 mass%, Fe: 0.15 mass% to 0.30 mass%, Cr: 0.09 mass% to 0.21 mass%, B: 0.0001 mass% to 0.03. The content of Zn is 0.25 mass% or less, the content of Zr is 0.05 mass% or less, the content of Ti is 0.1 mass% or less, and the balance is Al and unavoidable impurities. And a casting step for obtaining a billet by casting the obtained molten metal.

(Molten metal forming process)
In the molten metal forming step, Si: 0.95 mass% to 1.25 mass%, Mg: 0.80 mass% to 1.05 mass%, Cu: 0.30 mass% to 0.50 mass%, Mn: 0.40 mass% to 0.60 mass%, Fe: 0.15 mass% to 0.30 mass%, Cr: 0.09 mass% to 0.21 mass%, B: 0.0001 mass% to 0. The content of Zn is 0.25 mass% or less, the content of Zr is 0.05 mass% or less, the content of Ti is 0.1 mass% or less, and the balance is Al and unavoidable. An aluminum alloy melt prepared by melting so as to have a composition of impurities is obtained.

(Casting process)
Next, a casting material is obtained by casting the obtained molten metal (casting step). The casting method is not particularly limited, and a conventionally known method may be used, and examples thereof include a continuous casting and rolling method, a hot top casting method, a float casting method, and a semi-continuous casting method (DC casting method). To be In this casting step, it is preferable to reduce the crystal grain size of the metal structure or crystallized substances formed in the ingot (billet) by performing a casting process with a high cooling rate.

  Hereinafter, a homogenization heat treatment step, a cooling step, an extrusion step, a quenching step, and an aging treatment step are sequentially performed.

(Homogenization heat treatment process)
The obtained billet is subjected to homogenizing heat treatment. That is, the homogenizing heat treatment of holding the billet at a temperature of 480 ° C to 530 ° C for 2 hours to 15 hours is performed. If the temperature is lower than 480 ° C, the ingot billet is insufficiently softened, the pressure during the hot extrusion process is significantly increased, the appearance quality is deteriorated, and the productivity is also decreased. On the other hand, when the temperature exceeds 530 ° C., the effect of suppressing recrystallization is reduced due to coarsening of Mn and Cr precipitates, and the occurrence of recrystallization reduces the toughness of the extruded material and also provides high strength. hard. Above all, it is preferable to set the temperature of the homogenizing heat treatment to 485 ° C to 525 ° C.

  Further, if the homogenizing heat treatment time is less than 2 hours, the ingot billet is insufficiently softened, the pressure during hot extrusion becomes extremely high, the appearance quality deteriorates, and the productivity also decreases. Further, if it is less than 2 hours, it becomes insufficient to eliminate the segregation in the crystal grains in the ingot structure and to homogenize it, and the toughness of the extruded material decreases, and it is difficult to obtain high strength. On the other hand, when the homogenizing heat treatment time exceeds 15 hours, no further effect of the homogenizing heat treatment can be obtained, and the productivity is rather reduced.

(Cooling process)
Next, the billet after the homogenization heat treatment is cooled to a temperature of 200 ° C. or less at an average cooling rate of 150 ° C./hour or more. The larger the average cooling rate, the more preferable. The cooling method in this cooling step is not particularly limited, but examples thereof include fan cooling and mist cooling. The reason for forcibly cooling the billet at an average cooling rate of 150 ° C./hour or more is to suppress coarse growth of solid solution precipitates in the cooling process after the homogenizing heat treatment. By suppressing the coarse growth, the strength can be sufficiently improved by the subsequent aging treatment, and the toughness of the extruded material can be sufficiently ensured.

(Extrusion process)
An extruded material is obtained by performing hot extrusion processing at an extrusion speed of 3 m / min to 25 m / min in a state where the billet that has undergone the cooling step is at 500 ° C to 560 ° C. If the heating temperature is lower than 500 ° C., the elements added to the ingot remain unmelted in the matrix, and the strength cannot be improved by the aging treatment. On the other hand, when the heating temperature exceeds 560 ° C., the exothermic heat after the extrusion may cause local eutectic melting (burning) in the extruded material. Therefore, the heating temperature during hot extrusion is set to 500 ° C to 560 ° C. Above all, the heating temperature during hot extrusion is preferably set to 510 ° C to 550 ° C. The billet heating time is not particularly limited, but considering that the heating device is installed online in the extrusion process, it is set to a time that can ensure good productivity, It is preferably set within 30 minutes, and particularly preferably set within 15 minutes.

  The extrusion speed at the time of the hot extrusion processing is set to 3 m / min to 25 m / min. In consideration of productivity, the higher the extrusion speed, the better, but if the extrusion speed exceeds 25 m / min, peeling or cracking may occur on the surface of the extruded material. On the other hand, if the extrusion speed is less than 3 m / min, the productivity will decrease.

(Quenching process)
The temperature of the extruded material after the hot extrusion processing is required to be 500 ° C to 570 ° C. The temperature of the extruded material immediately after being discharged from the mold is measured with a non-contact thermometer or a contact thermometer. If the measured temperature is less than 500 ° C., the elements added to the ingot remain unmelted in the matrix, and the strength cannot be improved by the aging treatment. If the measured temperature exceeds 570 ° C., eutectic melting (burning) may occur locally in the extruded material. Above all, it is preferable that the temperature of the extruded material after the hot extrusion is 510 ° C to 560 ° C.

  Immediately after the hot extrusion process, the extruded material at a temperature of 500 ° C to 570 ° C is rapidly cooled to 150 ° C or less at a cooling rate of 100 ° C / sec to 500 ° C / sec. Such rapid cooling can be performed using, for example, a cooling device installed on the extrusion outlet side. Quenching under such conditions forms a metal structure in which the metal structure of the extruded material has a fibrous structure and the ratio of the area of the fibrous structure to the entire cross-sectional area of the extruded material is 95% or more. This is an important step above. In this rapid cooling step, if the cooling rate is less than 100 ° C./sec, quenching during cooling becomes insufficient, the toughness of the extruded material decreases, and it is difficult to obtain high strength. On the other hand, if the cooling rate exceeds 500 ° C./sec, the thick portion and the thin portion are deformed due to the difference in thermal shrinkage and the dimensional accuracy is deteriorated.

  The cooling method in the rapid cooling step is not particularly limited, but examples thereof include fan air cooling, mist cooling, shower cooling, liquid nitrogen cooling, and water cooling. Further, rapid cooling may be performed by appropriately combining the cooling methods illustrated above.

  In the quenching step, the cooling rate of the extruded material is preferably set to 150 ° C / sec to 450 ° C / sec, and particularly preferably set to 200 ° C / sec to 400 ° C / sec.

(Aging treatment process)
Next, the extruded material that has undergone the quenching process is heated at a temperature of 160 ° C. to 200 ° C. for 1 hour to 24 hours to perform an aging treatment. If the aging temperature is less than 160 ° C., the precipitate becomes too fine and the age hardening is not sufficient, so that a high-strength extruded material cannot be obtained. On the other hand, when the aging treatment temperature exceeds 200 ° C., overaging treatment causes coarsening of precipitates, making it impossible to obtain a high-strength extruded material. Further, if the aging treatment time is less than 1 hour, it becomes a sub-aging treatment and a high strength extruded material cannot be obtained. When the aging treatment time exceeds 24 hours, the overaging treatment is performed and a high-strength extruded material cannot be obtained. Above all, it is preferable to set the aging treatment temperature to 170 ° C to 190 ° C. Further, the aging treatment time is preferably set to 1 hour to 16 hours.

  The aluminum alloy extruded material obtained through the above-mentioned molten metal forming step, casting step, homogenizing heat treatment step, cooling step, extrusion step, quenching step, and aging treatment step is a self-piercing rivet joint between the aluminum alloy extruded materials. The shear tensile maximum load measured according to JIS Z3136-1999 is 8.5 kN or more, and the obtained aluminum alloy extruded material is a self-piercing rivet joined body of the aluminum alloy extruded materials according to JIS Z3137-1999. The maximum cross tensile load measured according to the above is 5.0 kN or more, and the self-piercing rivet bonding strength is excellent.

  In the manufacturing method of the present invention, after the extrusion step, if a solution treatment or a quenching treatment is performed, the formed fibrous structure will be impaired, so such a solution treatment or a quenching treatment is performed. Not desirable to do.

  Further, in the manufacturing method of the present invention, for example, in order to be applied as a vehicle body structural material (frame or the like) of vehicles such as automobiles, motorcycles, and railways, if necessary, after the extrusion step, a drawing process, a cutting process. One or more types of processing, bending, crushing, welding, machine fastening, etc. may be performed.

  Next, the composition of the “aluminum alloy” in the above-described aluminum alloy plastically worked material according to the present invention and the method for manufacturing an aluminum alloy extruded material according to the present invention will be described in detail below. The aluminum alloy has Si: 0.95% by mass to 1.25% by mass, Mg: 0.80% by mass to 1.05% by mass, Cu: 0.30% by mass to 0.50% by mass, Mn: 0. 40 mass% to 0.60 mass%, Fe: 0.15 mass% to 0.30 mass%, Cr: 0.09 mass% to 0.21 mass%, B: 0.0001 mass% to 0.03. The content of Zn is 0.25 mass% or less, the content of Zr is 0.05 mass% or less, the content of Ti is 0.10 mass% or less, and the balance is Al and unavoidable impurities. Is an aluminum alloy.

The Si coexists with Mg to form a Mg ₂ Si-based precipitate, which contributes to improving the strength of the extruded material. As described above, Si is added to the Mg content in excess of the amount that produces Mg ₂ Si, so that the strength can be sufficiently improved by the aging treatment. Therefore, the Si content is 0.95. Set to mass% or more. On the other hand, if the Si content exceeds 1.25 mass%, the grain boundary precipitation of Si increases, the toughness of the extruded material decreases, and the extrudability during hot extrusion processing deteriorates. Therefore, the Si content is set to 0.95% by mass to 1.25% by mass. Among them, the Si content is preferably set to 1.00% by mass to 1.20% by mass, and more preferably set to 1.05% by mass to 1.15% by mass.

The Mg coexists with Si to form a Mg ₂ Si-based precipitate, which contributes to improving the strength of the extruded material. If the Mg content is less than 0.80% by mass, the effect of precipitation strengthening cannot be sufficiently obtained and high strength cannot be secured. On the other hand, if the Mg content exceeds 1.05 mass%, the toughness of the extruded material will be reduced due to an excessive increase of Mg ₂ Si-based precipitates, and the extrusion pressure during hot extrusion will be significantly increased. This deteriorates the appearance quality and also reduces the productivity. Therefore, the Mg content is set to 0.80 mass% to 1.05 mass%. Among them, the Mg content is preferably set to 0.85 mass% to 1.00 mass%.

  The Fe has the effect of preventing the coarsening of crystal grains by crystallizing out as an AlFeSi phase. If the Fe content is less than 0.15 mass%, the effect of preventing coarsening of crystal grains cannot be sufficiently obtained. On the other hand, when the Fe content exceeds 0.30 mass%, a coarse intermetallic compound is generated, the toughness of the extruded material is reduced, and an appearance defect called a pickup may occur during hot extrusion processing. Therefore, the Fe content is set to 0.15% by mass to 0.30% by mass. Above all, the Fe content is preferably set to 0.15% by mass to 0.25% by mass.

  The Mn crystallizes as an AlMnSi phase, and Mn that does not crystallize has the effect of suppressing recrystallization. Due to the effect of suppressing this recrystallization, the structure after hot extrusion can be made into a fibrous structure, so that high strength can be realized. When the Mn content is less than 0.40% by mass, the above recrystallization suppressing effect cannot be obtained, the recrystallized structure becomes coarse and grows, and the strength decreases (high strength cannot be secured). It becomes difficult to control, and the toughness deteriorates due to the structure state in which the fibrous structure and the recrystallized structure are mixed. On the other hand, if the Mn content exceeds 0.60% by mass, a coarse intermetallic compound is generated and the toughness of the extruded material is reduced. Therefore, the Mn content is set to 0.40% by mass to 0.60% by mass. Among them, the Mn content is preferably set to 0.44% by mass to 0.56% by mass. It should be noted that Mn can synergistically improve the above effects by being added in a complex manner with Cr having the same effect.

The Cu increases the apparent supersaturation amount of the Mg ₂ Si-based precipitate and increases the Mg ₂ Si precipitation amount, thereby significantly promoting the age hardening of the extruded material of the final product. When the Cu content is less than 0.30% by mass, sufficient age hardening cannot be obtained. On the other hand, if the Cu content exceeds 0.50% by mass, the toughness of the extruded material decreases and the extrudability during hot extrusion processing deteriorates. On the other hand, if the addition amount is excessively increased, the corrosion resistance may be lowered, the susceptibility to intergranular corrosion may be increased, and stress corrosion cracking may be caused. Therefore, the Cu content is set to 0.30 mass% to 0.50 mass%. Among them, the Cu content is preferably set to 0.35% by mass to 0.50% by mass, more preferably 0.40% by mass to 0.50% by mass.

  The Cr crystallizes as an AlCrSi phase, and Cr that does not crystallize has the effect of suppressing recrystallization. Due to the effect of suppressing this recrystallization, the structure after hot extrusion can be made into a fibrous structure, so that high strength can be realized. When the Cr content is less than 0.09% by mass, the above recrystallization suppressing effect cannot be obtained, the recrystallized structure becomes coarse and grows, and the strength decreases (high strength cannot be secured). It becomes difficult to control, and the toughness deteriorates due to the structure state in which the fibrous structure and the recrystallized structure are mixed. On the other hand, if the Cr content exceeds 0.21% by mass, a coarse intermetallic compound is generated and the toughness of the extruded material is reduced. Therefore, the Cr content is set to 0.09 mass% to 0.21 mass%. Above all, the Cr content is preferably set to 0.11% by mass to 0.19% by mass. It should be noted that the above effects can be synergistically improved by adding Cr in combination with Mn having the same effect.

The B (boron) is an element effective in coordinating with Ti to refine the crystal grains. If the B content is less than 0.0001% by mass, the effect of refining the crystal grains may not be sufficiently obtained. On the other hand, if the B content exceeds 0.03% by mass, TiB ₂ is excessively produced, which may deteriorate the machinability. Therefore, the B content is set to 0.0001% by mass to 0.03% by mass.

  Although Ti is an element effective in refining the crystal grains, if the Ti content exceeds 0.10 mass%, a coarse Ti compound crystallizes and the toughness of the extruded material is reduced. Therefore, the Ti content is set to 0.10 mass% or less (not containing Ti; that is, including the Ti content of 0 mass%).

  Zr is an element having an effect of suppressing recrystallization like Mn and Cr, and the content ratio of Zr is set to 0.05% by mass or less. When the Zr content exceeds 0.05% by mass, the effect of refining the crystal grains of Ti described above is hindered and the toughness of the extruded material is reduced. Therefore, the Zr content is set to 0.05% by mass or less. It may be Zr-free (Zr content may be 0% by mass). Above all, the Zr content is preferably set to 0.01% by mass or less (including 0% by mass; that is, including Zr-free).

  Zn is an element effective in improving the castability, but if the Zn content exceeds 0.25 mass%, the corrosion resistance and toughness may be reduced. Therefore, the Zn content is set to 0.25% by mass or less (Zn is not contained; that is, the Zn content is 0% by mass is included).

  Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

<Example 1>
Si: 0.95% by mass, Fe: 0.18% by mass, Cu: 0.30% by mass, Mn: 0.44% by mass, Mg: 0.80% by mass, Cr: 0.09% by mass, B: Aluminum alloy melt containing 0.005% by mass, Zn: 0.03% by mass, Zr: 0.01% by mass, Ti: 0.02% by mass, the balance being Al and inevitable impurities. After that, an ingot billet having a diameter of 156 mm and a length of 450 mm was produced by the hot top casting method using the molten aluminum alloy.

  Next, the ingot billet was subjected to homogenizing heat treatment at 495 ° C. for 8 hours (homogenizing heat treatment step). The ingot ingot after the homogenization heat treatment step was forcibly cooled at a ingot cooling rate of 220 ° C./hour until the ingot reached a temperature of 150 ° C. or less (cooling step). Next, the ingot billet that has undergone the cooling step is subjected to hot extrusion processing under the conditions of an ingot heating temperature of 535 ° C. and an extrusion speed of 12 m / min, so that it has a day-like shape of length 17 mm × width 80 mm and a square shape. A hollow extruded material (see FIG. 2) having an R of 1.0 mm and a tube wall thickness (wall thickness) T of 3.0 mm was obtained (extrusion step). Next, the hollow extruded material of 550 ° C. obtained by the hot extrusion process (the temperature of the hollow extruded material at the exit of the extrusion die was measured by a contact thermometer) was cooled to 400 ° C./sec at a temperature of 100 ° C. or lower. It was rapidly cooled until it reached (quick cooling step). The hollow extruded material that had been subjected to the quenching step was cut into a length of 300 mm, and then heated at 170 ° C. for 8 hours to perform an aging treatment (aging treatment step). Thus, the Al-Mg-Si based aluminum alloy hollow extruded material 1 shown in FIG. 2 was obtained.

<Examples 2 to 15>
As the above-mentioned aluminum alloy molten metal, except that an aluminum alloy molten metal having an aluminum alloy composition shown in Table 1 (an aluminum alloy containing the elements shown in Table 1 in the content ratios shown in the table and the balance being Al and inevitable impurities) is used In the same manner as in Example 1, the Al-Mg-Si based aluminum alloy hollow extruded material 1 shown in FIG. 2 was obtained.

<Comparative Example 1>
Si: 1.00 mass%, Fe: 0.15 mass%, Cu: 0.05 mass%, Mn: 0.70 mass%, Mg: 0.85 mass%, Cr: 0.11 mass%, B: Aluminum alloy melt containing 0.005% by mass, Zn: 0.03% by mass, Zr: 0.01% by mass, Ti: 0.02% by mass, the balance being Al and inevitable impurities. After that, an ingot billet having a diameter of 156 mm and a length of 450 mm was produced by the hot top casting method using the molten aluminum alloy.

  Next, the ingot billet was subjected to homogenizing heat treatment at 495 ° C. for 8 hours (homogenizing heat treatment step). The ingot billet after the homogenization heat treatment step was forcibly cooled at a ingot cooling rate of 250 ° C./hour until the ingot reached a temperature of 150 ° C. or less (cooling step). Next, the ingot billet that has undergone the cooling step is subjected to hot extrusion processing under the conditions of an ingot heating temperature of 530 ° C. and an extrusion rate of 12 m / min, so that it has a day-like shape of length 17 mm × width 80 mm. A hollow extruded material (see FIG. 2) having an R of 1.0 mm and a tube wall thickness (wall thickness) T of 3.0 mm was obtained (extrusion step). Next, the hollow extruded material of 545 ° C. obtained by the hot extrusion processing (the temperature of the hollow extruded material at the exit of the extrusion die was measured by a contact thermometer) was cooled to 400 ° C./second at a temperature of 100 ° C. or lower. It was rapidly cooled until it reached (quick cooling step). The hollow extruded material that had been subjected to the quenching step was cut into a length of 300 mm, and then heated at 180 ° C. for 6 hours to perform an aging treatment (aging treatment step). Thus, an Al-Mg-Si based aluminum alloy hollow extruded material was obtained.

<Comparative example 2>
As the aluminum alloy molten metal, an aluminum alloy molten metal having an aluminum alloy composition shown in Table 2 (an aluminum alloy containing the elements shown in Table 1 in the content rates shown in the table and the balance being Al and inevitable impurities) is used, An Al-Mg-Si based aluminum alloy hollow extruded material was obtained in the same manner as in Comparative Example 1 except that the ingot billet was subjected to homogenizing heat treatment at 565 ° C for 8 hours.

<Comparative example 3>
Si: 1.10% by mass, Fe: 0.18% by mass, Cu: 0.40% by mass, Mn: 0.50% by mass, Mg: 0.95% by mass, Cr: 0.15% by mass, B: Aluminum alloy melt containing 0.004% by mass, Zn: 0.03% by mass, Zr: 0.01% by mass, Ti: 0.02% by mass, the balance being Al and inevitable impurities. After that, an ingot billet having a diameter of 156 mm and a length of 450 mm was produced by the hot top casting method using the molten aluminum alloy.

  Next, the ingot billet was subjected to homogenizing heat treatment at 495 ° C. for 7 hours (homogenizing heat treatment step). The ingot ingot after the homogenization heat treatment step was forcibly cooled at a ingot cooling rate of 220 ° C./hour until the ingot reached a temperature of 150 ° C. or less (cooling step). Next, the ingot billet that has undergone the cooling step is subjected to hot extrusion processing under the conditions of an ingot heating temperature of 535 ° C. and an extrusion speed of 12 m / min, so that it has a day-like shape of length 17 mm × width 80 mm and a square shape. A hollow extruded material (see FIG. 2) having an R of 1.0 mm and a tube wall thickness (wall thickness) T of 3.0 mm was obtained (extrusion step). Then, the hollow extruded material of 550 ° C. obtained by the hot extrusion processing (the temperature of the hollow extruded material at the exit of the extrusion die was measured by a contact thermometer) was cooled to 50 ° C./sec at a temperature of 100 ° C. or lower. It was rapidly cooled until it reached (quick cooling step). The hollow extruded material that had been subjected to the quenching step was cut into a length of 300 mm, and then heated at 180 ° C. for 6 hours to perform an aging treatment (aging treatment step). Thus, an Al-Mg-Si based aluminum alloy hollow extruded material was obtained.

<Comparative example 4>
Si: 1.10 mass%, Fe: 0.20 mass%, Cu: 0.40 mass%, Mn: 0.50 mass%, Mg: 0.85 mass%, Cr: 0.15 mass%, B: Aluminum alloy melt containing 0.004% by mass, Zn: 0.03% by mass, Zr: 0.01% by mass, Ti: 0.02% by mass, the balance being Al and inevitable impurities. After that, an ingot billet having a diameter of 80 mm and a length of 80 mm was produced by the hot top casting method using the molten aluminum alloy.

  Next, the ingot billet was subjected to homogenizing heat treatment at 500 ° C. for 7 hours (homogenizing heat treatment step). The ingot billet after the homogenization heat treatment step was forcibly cooled at a ingot cooling rate of 150 ° C./hour until the ingot reached a temperature of 150 ° C. or less (cooling step). Next, the ingot billet that has undergone the cooling step is heated to an ingot heating temperature of 530 ° C., and hot forged, thereby forging a cylindrical body having a diameter of 80 mm and a height of 80 mm to a height of 16 mm. It processed and obtained the forged material. Next, the forged material was subjected to a solution heat treatment at a temperature of 530 ° C. for 4 hours, water-quenched, and then heated at 180 ° C. for 6 hours to perform an aging treatment. Thus, an Al-Mg-Si based aluminum alloy forged material was obtained.

<Comparative Examples 5 to 14>
As the above-mentioned aluminum alloy molten metal, an aluminum alloy molten metal having an aluminum alloy composition shown in Table 2 (an aluminum alloy containing the elements shown in Table 2 in the content rates shown in the table and the balance being Al and inevitable impurities) is used. In the same manner as in Example 1, an Al-Mg-Si based aluminum alloy hollow extruded material was obtained.

  For each aluminum alloy extruded material obtained as described above, the metal structure was observed by the following method, and various evaluations were performed based on the following evaluation methods.

<Method of observing metal structure>
Regarding the extruded material, after cutting out a cross section parallel to the extrusion direction of the extruded material, the cross section (cut surface) of the extruded material is mirror-polished and then electrolytically etched, and then the cross section (cut surface) is observed with an optical microscope. did. In a metallographic photograph of the cross section (cut surface) of each extruded material using an optical microscope, the ratio of the area of the fibrous structure to the entire area of the cross section was obtained from image analysis in multiple fields of view, and the ratio was 90%. The above is judged to be a "fibrous structure" (see Tables 1 and 2), and the above ratio is 20% or more and less than 90% (a structure other than the fibrous structure is a recrystallized structure). It was judged as "mixed structure", and those having the above ratio of less than 20% (structures other than fibrous structure being recrystallized structure) were judged as "recrystallized structure" (see Tables 1 and 2).

  Regarding the forged material of Comparative Example 4, after cutting out in a cross section parallel to the processing direction of the forged material, the cross section (cut surface) of the forged material was mirror-polished, and then electrolytic etching was performed, and then the cross section (cut surface) Was observed with an optical microscope. As in the case of the extruded material, the judgment was made by obtaining the morphology and proportion of the metal structure (see Table 2).

<Tensile property evaluation method (tensile strength and 0.2% proof stress measurement method)>
The tensile strength (MPa) and 0.2% proof stress (MPa) of the extruded material (or forged material) were measured by performing a tensile test at room temperature (25 ° C.) according to JIS Z2241-2011. That is, a JIS No. 5 test piece was sampled from the extruded material (or forged material) by the method described in JIS Z2201-1998. The size of this JIS No. 5 test piece (solid body) was 25 mm in width of the parallel part × 60 mm in length of the parallel part × 2.5 mm in thickness. In addition, the distance between the gauge points in the test piece was set to 50 mm. A tensile test was performed on the test piece using an Instron type tensile tester. The tensile test speed was set to 2 mm / min, and after the proof stress measurement was set to 10 mm / min. The number of n of JIS No. 5 test piece was three, and the average value of the three test pieces was “0.2% proof stress” (see Tables 3 and 4). In Tables 3 and 4, those having a 0.2% proof stress of 380 MPa or more are represented by “⊚”, and those having a 0.2% proof stress of 350 MPa or more and less than 380 MPa are represented by “◯”. Those having a 2% proof stress of less than 350 MPa were expressed as “x”.

<Workability evaluation method>
The workability during extrusion (or forging) was evaluated. In the extrusion process, products with appearance defects such as cracks and surface peeling on the extruded product (extruded material) are described as "x", and products that do not have such appearance defects are described as "○". did. In the forging process, similar to the extrusion process, the product (forged material) after forging that has a defective appearance such as cracks or wrinkles is described as “x”, and the product that does not have such a defective appearance is described. It was written as "○".

<Self-piercing rivet bondability (SPR bondability) evaluation method>
According to JIS Z3136-1999, an extruded material (or a forged material) is cut to a thickness of 2.5 mm to obtain two cut plates (solid plates) having a shape as shown in FIG. These two cut plates are overlapped with each other (in the case of Example 1, two cut plates obtained from the hollow extruded material obtained in Example 1 are overlapped with each other) and self-piercing riveting is performed. Thus, a self-pierce rivet joined body was obtained, and this was used as a test piece for a tensile shear test (see FIG. 3). In addition, in accordance with JIS Z3137-1999, an extruded material (or a forged material) is cut into a thickness of 2.5 mm to obtain two cut plates (solid plates) having a shape as shown in FIG. Then, these two cut plates were superposed in a cross shape and self-pierce rivet joined at the center to obtain a self-pierce rivet joined body, which was used as a test piece for cross tension test (see FIG. 4). ). An Atlas Copco self-piercing rivet joining device was used for the self-piercing rivet joining. A rivet having an outer diameter of the head of 5 mm and a vertical length of 6.5 mm was used, and the lower die had a flat shape with a depth of 1.2 mm.

  A test piece for the tensile shear test and a test piece for the cross tension test, each of which has a lower die side extruded material (or forged material) is visually inspected for occurrence of a through crack, and a through crack is not generated. Was evaluated as “◯” (good SPR bondability), and those in which penetration cracking had occurred were evaluated as “x”.

<Method of measuring maximum shear tension and maximum cross tension of self-piercing rivet joints>
With respect to the test piece for the tensile shear test, the maximum shear tensile load was measured according to JIS Z3136-1999. In addition, the maximum cross tension load was measured for the above-mentioned test piece for cross tension test according to JIS Z3137-1999. Both tests were performed with the tensile test speed set to 10 mm / min. In both of the above tests, the number of n (the number of test pieces) was set to 3, and the average value of the maximum loads was used as data (test result value).

  In addition, in Tables 3 and 4, those having a maximum shear tensile load of 8.5 kN or more were described as “◯”, and those having a maximum shear tensile load of less than 8.5 kN were described as “x”. In addition, a cross tension maximum load of 5.0 kN or more was described as “◯”, and a cross tension maximum load of less than 5.0 kN was described as “x”.

<Comprehensive evaluation>
Of the five evaluation items "0.2% proof stress", "workability", "SPR bondability", "shear tension maximum load" and "cross tension maximum load", one or more items have an evaluation result of "x" If there was such a result, it was judged as "fail", and if there was no evaluation result of "x" in all five evaluation items, it was judged as "pass".

  As is clear from the table, the Al-Mg-Si based aluminum alloy extruded materials of Examples 1 to 15 according to the present invention have a 0.2% proof stress of 350 MPa or more and high strength, and a shear tensile maximum load. It was 8.5 kN or more, the maximum cross tension load was 5.0 kN or more, and the self-piercing rivet joining strength was excellent. In addition, the Al-Mg-Si-based aluminum alloy extruded materials of Examples 1 to 15 had good self-pierce rivet bondability (no penetration crack occurred).

  On the other hand, in Comparative Examples 1 to 14 that deviate from the scope of the present invention, the comprehensive evaluation was unsuccessful.

  The Al-Mg-Si based aluminum alloy plastically worked material (extruded material or rolled material) according to the present invention and the Al-Mg-Si based aluminum alloy extruded material obtained by the manufacturing method of the present invention have high strength and self Since it has excellent pierce rivet joint strength, it can be suitably used as a substitute for conventional iron-based materials. For example, it can contribute to weight reduction of a vehicle body by using it as a structural material (frame or the like) of a vehicle body of a transportation machine such as a vehicle, a ship, an automobile or a motorcycle.

1 ... Aluminum alloy plastic processed material (extruded material or rolled material)
11 ... Self-piercing rivets

Claims (5)

A plastic work material used for self-piercing rivet joining,
Si: 0.95 mass% to 1.25 mass%, Mg: 0.80 mass% to 1.05 mass%, Cu: 0.30 mass% to 0.50 mass%, Mn: 0.40 mass% to 0.60% by mass, Fe: 0.15% by mass to 0.30% by mass, Cr: 0.09% by mass to 0.21% by mass, B: 0.0001% by mass to 0.03% by mass. , Zn content is 0.25 mass% or less, Zr content is 0.05 mass% or less, Ti content is 0.10 mass% or less, and the balance is aluminum alloy plasticity consisting of Al and unavoidable impurities. It is a processed material,
The maximum shear tensile load measured according to JIS Z3136-1999 for the self-piercing rivet joint between the aluminum alloy plastically worked materials is 8.5 kN or more, and the Al-Mg-Si based aluminum alloy plastically worked. Material. A plastic work material used for self-piercing rivet joining,
Si: 0.95 mass% to 1.25 mass%, Mg: 0.80 mass% to 1.05 mass%, Cu: 0.30 mass% to 0.50 mass%, Mn: 0.40 mass% to 0.60% by mass, Fe: 0.15% by mass to 0.30% by mass, Cr: 0.09% by mass to 0.21% by mass, B: 0.0001% by mass to 0.03% by mass. , Zn content is 0.25 mass% or less, Zr content is 0.05 mass% or less, Ti content is 0.10 mass% or less, and the balance is aluminum alloy plasticity consisting of Al and unavoidable impurities. It is a processed material,
The self-piercing rivet joint between the aluminum alloy plastic working materials has a maximum cross-tension load of 5.0 kN or more measured according to JIS Z3137-1999. Material.   The Al-Mg-Si system aluminum alloy plastic working material according to claim 1 or 2, which is used as a structural member for an automobile frame. Si: 0.95 mass% to 1.25 mass%, Mg: 0.80 mass% to 1.05 mass%, Cu: 0.30 mass% to 0.50 mass%, Mn: 0.40 mass% to 0.60% by mass, Fe: 0.15% by mass to 0.30% by mass, Cr: 0.09% by mass to 0.21% by mass, B: 0.0001% by mass to 0.03% by mass. , Zn content is 0.25% by mass or less, Zr content is 0.05% by mass or less, Ti content is 0.10% by mass or less, and the balance is aluminum and unavoidable impurities. A molten metal forming step of obtaining a molten metal;
A casting step of obtaining a billet by casting the obtained molten metal;
A homogenizing heat treatment step of performing a homogenizing heat treatment of holding the billet at a temperature of 480 ° C. to 530 ° C. for 2 hours to 15 hours;
A cooling step of cooling the billet after the homogenizing heat treatment to 200 ° C. or less at an average cooling rate of 150 ° C./hour or more;
An extrusion step of obtaining an extruded material by performing hot extrusion at an extrusion speed of 3 m / min to 25 m / min in a state where the billet that has undergone the cooling step is at 500 ° C to 560 ° C.
A quenching step of quenching the temperature of the obtained extruded material from 500 ° C. to 570 ° C. to 150 ° C. or less at a cooling rate of 100 ° C./sec to 500 ° C./sec;
An aging treatment step of obtaining an aluminum alloy extruded material by heating the extruded material that has been subjected to the quenching step at a temperature of 160 ° C. to 200 ° C. for 1 hour to 24 hours,
The obtained aluminum alloy extruded material has a maximum shear tensile load of 8.5 kN or more measured in accordance with JIS Z3136-1999 for a self-piercing rivet joined body of the aluminum alloy extruded materials. -Mg-Si system aluminum alloy extruded material manufacturing method. Si: 0.95 mass% to 1.25 mass%, Mg: 0.80 mass% to 1.05 mass%, Cu: 0.30 mass% to 0.50 mass%, Mn: 0.40 mass% to 0.60% by mass, Fe: 0.15% by mass to 0.30% by mass, Cr: 0.09% by mass to 0.21% by mass, B: 0.0001% by mass to 0.03% by mass. , Zn content is 0.25% by mass or less, Zr content is 0.05% by mass or less, Ti content is 0.10% by mass or less, and the balance is aluminum and unavoidable impurities. A molten metal forming step of obtaining a molten metal;
A casting step of obtaining a billet by casting the obtained molten metal;
A homogenizing heat treatment step of performing a homogenizing heat treatment of holding the billet at a temperature of 480 ° C. to 530 ° C. for 2 hours to 15 hours;
A cooling step of cooling the billet after the homogenizing heat treatment to 200 ° C. or less at an average cooling rate of 150 ° C./hour or more;
An extrusion step of obtaining an extruded material by performing hot extrusion processing at an extrusion speed of 3 m / min to 25 m / min in a state where the billet that has undergone the cooling step is at 500 ° C. to 560 ° C .;
A quenching step of quenching the temperature of the obtained extruded material from 500 ° C. to 570 ° C. to 150 ° C. or less at a cooling rate of 100 ° C./sec to 500 ° C./sec;
An aging treatment step of obtaining an aluminum alloy extruded material by heating the extruded material that has been subjected to the quenching step at a temperature of 160 ° C. to 200 ° C. for 1 hour to 24 hours,
The obtained aluminum alloy extruded material has a cross tensile maximum load of 5.0 kN or more measured according to JIS Z3137-1999 for a self-piercing rivet joined body of the aluminum alloy extruded materials. -Mg-Si system aluminum alloy extruded material manufacturing method.

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