JP2009221566A - Aluminum alloy material for high pressure gas vessel having excellent hydrogen embrittlement resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a 7,000 series aluminum alloy material for a high pressure gas vessel jointly having hydrogen embrittlement resistance, mechanical properties or the like. <P>SOLUTION: An aluminum alloy material for a high pressure gas vessel is composed of a 7,000 series alloy material having a specific composition, and whose strength is made high, and while dispersed grains in the aluminum alloy material structure thereof are secured by a fixed amount as the trap site of hydrogen, a proof stress of ≥275 MPa is set as members such as a liner, a nozzle and a gas pipe, and then its hydrogen embrittlement resistance is improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention has excellent hydrogen embrittlement resistance and is suitable for peripheral members such as liners of high-pressure gas containers, caps or gas pipes, and Al-Zn-Mg-Cu alloys. Material (hereinafter referred to as 7000 series aluminum alloy material). In the present invention, the term “for a high-pressure gas container” is used collectively, including all uses of a high-pressure gas container member such as a liner and a high-pressure gas container peripheral member such as a base or a gas pipe.

  As a high-pressure gas container, for example, there is a gas cylinder such as natural gas mounted in an automobile or the like. These gas cylinders are mainly made of iron, but in order to reduce weight, reinforcing fibers are wrapped around the outer surface of an aluminum liner (filament winding), and reinforcing fibers are applied to the outer surface of a plastic liner. Various wraps have been proposed.

  For example, Patent Document 1 discloses a method for manufacturing a high-pressure gas container using such an aluminum liner from an aluminum alloy extruded material. That is, a 7000 series aluminum alloy extruded material is subjected to a drawing process, the drawn material is subjected to a solution treatment, and then an impact process is performed to form a bottomed cylindrical body. Thereafter, a gas outlet is formed by cold die forging and aging treatment is performed to manufacture a small high-pressure gas container.

  Further, Patent Documents 2 and 3 propose that the proof stress of an aluminum liner as disclosed in Patent Document 1 is further improved and the manufacturing method described above is also improved. In Patent Document 2, an aluminum material made of a precipitation hardening type aluminum alloy such as 7000 series is subjected to a solution treatment, and then the cylindrical portion or all of the material having a shape made up of a cylindrical portion and hemispherical portions at both ends of the cylindrical portion. It has been proposed to apply a plastic strain by squeezing and then forming a liner shape by spinning the end opening to remove the aging treatment after the solution treatment.

Furthermore, Patent Document 3 discloses a method for producing an aluminum liner that can improve the yield strength, can eliminate the aging treatment, and can be processed with high accuracy without leaving the deformation of the container due to the solution treatment. Although this patent document 3 also includes 7000 series, it desirably intends an aluminum extrusion material such as a seamless pipe made of a precipitation hardening type aluminum alloy such as 6061 series such as 6061. And after giving solution treatment to this aluminum extrusion raw material, plastic strain is provided by ironing etc., and an end mouth part is shape | molded after that and it is made a liner shape.
JP-A-6-63681 Japanese Patent No. 3750449 JP 2000-233245 A

  In recent years, hydrogen as a fuel for fuel cells has attracted attention as clean energy. However, since this hydrogen causes hydrogen embrittlement of metal materials such as iron and aluminum, it is difficult to efficiently store at high pressure using a high-pressure gas container. This point is the same not only for high-pressure gas containers made of iron, which is a general material, but also for high-pressure gas containers using an aluminum liner, and is excellent in hydrogen embrittlement resistance due to its reliability as a high-pressure gas container. Is required.

  However, in the high-pressure gas container using an aluminum liner, there are not so many proposals for excellent hydrogen embrittlement resistance, and an aluminum 6000 series alloy such as 6061 is mainly used at present. This is also related to the fact that the aluminum 6000 series alloy material does not have hydrogen embrittlement, and this has become common technical knowledge.

  However, in a fuel cell vehicle equipped with a hydrogen fuel cell, the hydrogen filling pressure is increasing in order to meet the demand for increasing the cruising distance per hydrogen filling. In the application of the conventional material, the thickness of the hydrogen container material and its peripheral members are increased, resulting in an increase in weight. For this reason, higher strength materials are required for the hydrogen container material and its peripheral members in order to reduce the thickness and weight. As a material having higher strength than a 6000 series alloy, there is a 7000 series alloy. However, it is generally known that stress corrosion cracking (SCC) involving hydrogen embrittlement is a problem in high-strength 7000 series alloys. It is obvious that the hydrogen embrittlement resistance is further lowered in the high-strength 7000 series alloys that have a high content of other main elements such as Zn and Mg and have increased the strength by the peak aging treatment or the like against the overaging treatment. is there.

  Therefore, when the 7000 series alloy aluminum material with increased strength is used for the high-pressure gas container and its peripheral members, the high-pressure gas container, its peripheral members, Moreover, the reliability as a high-pressure gas container for hydrogen storage is not increased. This applies not only to the above-described aluminum alloy liner but also to a high-pressure gas container in which reinforcing fibers are wound around the outer surface of a plastic liner, or when the base or gas pipe is made of an aluminum 7000 series alloy material.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a 7000 series aluminum alloy material for high-pressure gas containers that has mechanical properties such as hydrogen embrittlement resistance and strength.

  In order to achieve this object, the gist of the aluminum alloy material for high-pressure gas containers excellent in hydrogen embrittlement resistance according to the present invention is, in mass%, Zn: 4.0 to 6.7%, Mg: 0.00. 75 to 2.9%, Cu: 0.001 to 2.6%, Si: 0.05 to 0.40%, Ti: 0.005 to 0.20%, Fe: 0.01 to 0.5% Further, Mn: 0.01-0.7%, Cr: 0.02-0.3%, Zr: 0.01-0.25%, V: 0.01-0.10% One type or two or more types are included after satisfying the relationship of 1.0% ≧ Fe + Mn + Cr + Zr + V ≧ 0.1%, and the balance has an aluminum alloy composition composed of Al and inevitable impurities, and the conductivity (% IACS) is In relation to the total content of Fe, Mn, Cr, Zr and V, conductivity (%) ≧ −4.9 × ( Satisfy the relation of e + Mn + Cr + Zr + V) +40.0, and assumed that 0.2% proof stress is not less than 275 MPa.

Here, it is preferable that the aluminum alloy material is subjected to a tempering selected from a peak aging treatment and an overaging treatment. Further, the electrical conductivity of the aluminum alloy material is related to the total content of Fe, Mn, Cr, Zr, and V, and the relationship of electrical conductivity (%) ≧ −4.9 × (Fe + Mn + Cr + Zr + V) +41.5 It is preferable to satisfy. Further, the hydrogen embrittlement resistance of the aluminum alloy material is 10% when the strain rate is 1.0 × 10 ⁻⁶ s ⁻¹ or less and only the atmospheric conditions are changed and the aluminum alloy material is tensile deformed. Embrittlement susceptibility represented by [(δ1-δ2) / δ1] × 100% as the rate of decrease of the elongation value δ2 in a highly humid atmosphere of 90% RH or higher with respect to the elongation value δ1 in a dry atmosphere of RH or lower. The index is preferably 10% or less. Moreover, it is preferable that the said aluminum alloy material is for high pressure gas containers for hydrogen storage.

  In the present invention, in order to improve the hydrogen embrittlement resistance, attention was paid to dispersed particles of a 7000 series aluminum alloy material. In order to use the dispersed particles in the grains as hydrogen trapping sites, the present invention secures a certain amount of dispersed particles in the grains.

  Conventionally, in Ni alloy materials, steel materials, and the like, precipitates are regulated as a starting point of hydrogen embrittlement and crack generation, or conversely, they are treated as effective hydrogen trapping (capturing) sites.

  However, in the field of aluminum 7000 series alloy materials, the relationship between such dispersed particles and the resistance to hydrogen embrittlement has not been well known. This is presumably due to the fact that high-pressure gas containers (gas cylinders) using an aluminum 7000 series alloy liner have not received much attention as high-pressure hydrogen storage containers.

  On the other hand, according to the present invention, hydrogen embrittlement resistance of a 7000 series aluminum alloy material used as a member such as a liner, a base or a gas pipe of a high-pressure gas container is controlled by controlling the amount of dispersed particles in the grain. The characteristics can be remarkably improved.

(Aluminum alloy material composition)
First, the chemical component composition of the aluminum alloy material of the present invention will be described below, including reasons for limiting each element. In addition,% display of element content means the mass% altogether. The chemical composition of the aluminum alloy material of the present invention is as follows: Al—Zn—Mg alloy material and 7000 series aluminum alloy material, which is an Al—Zn—Mg—Cu alloy material, such as liners, caps or gas pipes of high pressure gas containers It is determined in order to guarantee mechanical properties such as strength and ductility that are required for the members. Further, when the content of the main element is large, or when the peak aging treatment (T6) is applied to the overaging treatment (T7) as the tempering, the strength becomes higher. In order to improve hydrogen embrittlement resistance, as will be described later, it is determined by the content and tempering of Fe, Mn, Cr, Zr, V, etc., measured by conductivity, and a hydrogen trapping site. It is necessary to control the amount of dispersed particles more accurately.

  From these viewpoints, the chemical composition of the aluminum alloy material of the present invention is, in mass%, Zn: 4.0 to 6.7%, Mg: 0.75 to 2.9%, Cu: 0.001 to 2 .6%, Si: 0.05-0.40%, Ti: 0.005-0.20%, Fe: 0.01-0.5%, and Mn: 0.01-0. 1% or more of 7%, Cr: 0.02-0.3%, Zr: 0.01-0.25%, V: 0.01-0.10%, 1.0% ≧ Fe + Mn + Cr + Zr + V ≧ An aluminum alloy composition containing 0.1% of the relationship and the balance of Al and inevitable impurities is included.

(Zn, Mg)
The essential alloy elements Zn and Mg improve the strength by forming fine dispersed phases such as η ′ phase and T ′ phase called GP zone or intermediate precipitation phase by artificial aging treatment of the alloy material. In particular, Zn has a high effect of improving the balance between strength and ductility. If the Zn and Mg contents are too small, such as Zn less than 4.0 and Mg less than 0.75%, the fine dispersed phase becomes insufficient and the strength decreases.

  On the other hand, if the Zn and Mg contents are too high, such as Zn exceeding 6.7% and Mg exceeding 2.9%, the strength becomes too high, and the corrosion resistance and hydrogen embrittlement resistance deteriorate. Further, if the Zn and Mg contents are too large, they cannot be dissolved in aluminum, so that coarse crystallized products are formed, which causes a decrease in the strength and elongation of the aluminum alloy material, and the workability also decreases. . Therefore, the contents of Zn and Mg are set to Zn: 4.0 to 6.7% and Mg: 0.75 to 2.9%, respectively.

(Cu)
Inclusion of Cu brings about improvement in strength and corrosion resistance. However, if Cu is added in excess of 2.6%, the strength becomes too high, and the workability is lowered due to the formation of coarse crystals. On the other hand, when the Cu content is less than 0.001%, the effects of improving strength and corrosion resistance are reduced. Therefore, the Cu content is in the range of 0.001 to 2.6%.

(Ti)
Ti has the effect of reducing the crystal grains of the ingot, preventing cracking during casting, improving workability during hot working, preventing cracking during product processing, and improving the surface appearance. If the content is too small, such an effect cannot be expected. If the content is too large, a coarse Ti compound is formed, resulting in cracking, deterioration of workability, and poor surface appearance. Therefore, Ti is contained in the range of 0.005 to 0.20%.

(Si)
Si easily forms an Al-Fe-Si-based crystallized product during casting. Addition of Si exceeding 0.40% causes a coarse crystallized substance that becomes a starting point of fracture, and causes deterioration in workability, elongation, fatigue characteristics, toughness, and hydrogen embrittlement resistance. On the other hand, since part of Si is also expected to form dispersed particles, addition of 0.05% or more is desirable. Therefore, Si is contained in the range of 0.05 to 0.40%.

(Fe, Mn, Cr, Zr, V)
Fe is essential to contain 0.01 to 0.5%, Mn: 0.01 to 0.7%, Cr: 0.02 to 0.3%, Zr: 0.01 to 0.25% V: 0.01 to 0.10% of one kind or two or more kinds are contained. These Fe, Mn, Cr, Zr, and V form dispersed particles that serve as hydrogen trap sites during holding during heating during soaking. These dispersed particles have an effect of suppressing the movement of grain boundaries, and are effective in non-recrystallization and refinement of recrystallized grains. Moreover, these dispersed particles contribute to the formation of fibers in the microstructure and have the effect of improving the strength.

  Usually, when the amount of other main elements such as Zn and Mg is large, or when the strength is increased by the peak aging treatment relative to the overaging treatment, the hydrogen embrittlement resistance decreases. However, even in such a case, by increasing the amount of dispersed particles formed by these Fe, Mn, Cr, Zr, and V elements, it functions as a hydrogen trapping (trapping) site, and is resistant to hydrogen embrittlement. The chemical property can be improved.

  In order to exhibit this effect reliably, the inclusion of Fe is essential, and Mn, Cr, Zr, and V are selectively contained, and the elements are contained in the above lower limit values or more. On the other hand, if each content is too large, it may cause coarse crystallized substances that become the starting point of fracture, resulting in deterioration of workability, elongation, fatigue properties, toughness, hydrogen embrittlement resistance, and a large amount. The dispersed particles also increase the quenching sensitivity. For this reason, it is made to contain below the said upper limit of each of these elements.

  However, in order to improve the hydrogen embrittlement resistance with certainty, as described above, the dispersed particles are determined by the content and tempering of each element, measured by conductivity, and become hydrogen trapping sites. There is a need to control the amount of more accurately.

  For this reason, if the total content (total amount) of these elements is too large, the hydrogen embrittlement resistance is lowered, so the total content of Fe + Mn + Cr + Zr + V is 1.0% or less. On the other hand, if the total content (total amount:%) of these elements is too small, the effect of improving hydrogen embrittlement resistance is not expected, so the total content of Fe + Mn + Cr + Zr + V is 0.1% or more.

  Furthermore, in order to improve the hydrogen embrittlement resistance with certainty, the content of each element and the tempered state are optimized in relation to the conductivity (% IACS). That is, the total content of Fe, Mn, Cr, Zr, and V [total amount (%) of these elements indicated by (Fe + Mn + Cr + Zr + V)] satisfies the following relationship (formula) together with the individual contents. That is, the electrical conductivity (%) ≧ −4.9 × (Fe + Mn + Cr + Zr + V) +40.5 is satisfied. In order to improve the hydrogen embrittlement resistance more reliably, it is preferable that the electrical conductivity (%) ≧ −4.9 × (Fe + Mn + Cr + Zr + V) +41.5 is satisfied.

(impurities)
Other elements other than the elements described above are impurities and are usually included in Al-Zn-Mg and Al-Zn-Mg-Cu-based 7000 series aluminum alloy materials as long as they do not impair the intended characteristics of the present invention. To the extent allowed. However, an impurity element such as oxygen, which tends to cause inclusions, is likely to cause inclusions in the aluminum alloy material structure and become a starting point of destruction, thereby reducing strength and elongation. Therefore, it is preferable to reduce these impurities as much as possible.

(Micro structure)
Based on the above 7000 series aluminum alloy material composition, in the present invention, characteristically, in order to improve the hydrogen embrittlement resistance, the amount of dispersed particles in the microstructure of the 7000 series aluminum alloy material is controlled. A certain amount is secured as a hydrogen trapping site.

  As described above, the dispersed particles (intragranular precipitates) improve the hydrogen embrittlement resistance as hydrogen trap sites. However, it is difficult to quantitatively define the amount of the dispersed particles by an amount that improves the hydrogen embrittlement resistance (an amount that functions as a hydrogen trap site). This is because it is assumed that the dispersed particles improve the hydrogen embrittlement resistance as hydrogen trap sites, including sizes that can be analyzed by SEM, TEM, etc., and fine particles that are difficult to analyze. . In other words, there is no reason why fine intragranular precipitates that are difficult to analyze the structure do not improve the hydrogen embrittlement resistance as hydrogen trap sites.

(conductivity)
Therefore, in the present invention, the amount of intragranular precipitate that improves the hydrogen embrittlement resistance as a hydrogen trap site, the content and total amount of each element as the component, and the conductivity (% of 7000 series aluminum alloy material) IACS). Further, when the amount of the main composition is large, or when the strength is high in the peak aging treatment relative to the overaging treatment, more dispersed particles are required to improve the hydrogen embrittlement resistance. Therefore, the electrical conductivity to be defined is not limited to the electrical conductivity alone, but as described above, the total content of Fe, Mn, Cr, Zr, and V [(Fe + Mn + Cr + Zr + V)] (total amount of these elements (%)) ], The electric conductivity (%) ≧ −4.9 × (Fe + Mn + Cr + Zr + V) +40.5 is satisfied. In order to improve the hydrogen embrittlement resistance more reliably, it is preferable that the electrical conductivity (%) ≧ −4.9 × (Fe + Mn + Cr + Zr + V) +41.5 is satisfied.

(Production method)
Next, a method for producing a 7000 series aluminum alloy material for high-pressure gas containers according to the present invention will be described below. For 7000 series aluminum alloy materials, extrudates, rolled plate materials, forged materials, etc. are appropriately obtained by extruding, rolling (hot, cold), forging, etc., each of the ingots produced by the usual melt casting method. You can choose. That is, a manufacturing method and a processing method suitable for obtaining the shape and characteristics of a member such as a liner, a die, or a gas pipe in a high-pressure gas container can be appropriately selected. Here, general-purpose production as a production method of the liner will be described below including preferable conditions.

Melting and casting:
First, an aluminum alloy ingot having the above 7000 series component composition is cast into a slab. In this melting and casting process, the molten aluminum alloy melt-adjusted within the above-mentioned 7000 series component composition range is cast by appropriately selecting a normal melting casting method such as a continuous casting method or a semi-continuous casting method (DC casting method). To do.

Homogenization heat treatment:
Next, the ingot (slab) is subjected to a homogenization heat treatment. The temperature of the homogenization heat treatment itself is selected from a homogenization temperature range of 400 ° C. or higher and lower than the melting point, and optimally a temperature range of 420 to 520 ° C., as usual. The purpose of this homogenization heat treatment (soaking) is to homogenize the structure, that is, to eliminate segregation in the crystal grains in the ingot structure and to sufficiently dissolve the alloy elements and coarse compounds. When this soaking temperature is low, segregation in the crystal grains cannot be sufficiently eliminated, and this acts as a starting point of fracture, so that workability and the like are lowered.

  In the case of a rolled material, the ingot after the homogenization heat treatment is cooled to the hot rolling temperature, or once cooled to room temperature and then reheated to the hot rolling temperature, hot rolled to obtain a plate material having a predetermined thickness. Thereafter, heat treatment is performed as necessary to obtain a soft material. In addition, between hot rolling and annealing, you may perform annealing and cold rolling as needed.

  In the case of an extruded material, the ingot after the homogenization heat treatment is reheated, extruded into a predetermined shape by hot extrusion, and then heat-treated as necessary to obtain a soft material. In addition, you may perform a core extraction and annealing between hot extrusion and annealing as needed.

  In the case of a forged material, the ingot after the homogenization heat treatment is reheated, forged into a predetermined shape by hot forging, and then heat-treated as necessary to obtain a soft material. In addition, between a hot forging and annealing, you may perform reheating, hot forging, and cold forging as needed.

  When producing a container material such as a liner for a high-pressure gas container or a peripheral member from these rolled material, extruded material, or forged material, the above-mentioned soft material is squeezed while being heated as necessary. Perform necessary processing such as ironing, spinning, cutting, drilling. However, it is desirable to select and perform tempering according to the required characteristics of each member of the high-pressure gas container after the container material and peripheral members are manufactured. This tempering is performed by, for example, T6 (solution treatment and quenching treatment + peak aging treatment), T7 (solution treatment and quenching treatment +) within the heat treatment conditions described in JIS-H-0001. Each tempering is called “overaging treatment”.

  In addition, you may perform room temperature aging and distortion correction as needed between the said quenching process and high temperature aging processes, such as a peak aging process and an overaging process. Moreover, any of a batch furnace, a continuous furnace, and a molten salt bath furnace may be used as the heat treatment furnace used for the solution treatment. The quenching treatment after the solution treatment may be any of water immersion, water jetting, mist jetting, air jetting, and air cooling. Furthermore, any of a batch furnace, a continuous furnace, an oil bath, a hot water bath, etc. may be used for the high temperature aging treatment performed after the solution treatment and the quenching treatment.

Moreover, before preparing the member for high-pressure gas containers with respect to these plate material, extruded material, and forged material, the above-described tempering may be selected and performed. In the case of an extruded material, the cast billet is reheated and hot extruded so that the temperature of the extruded material on the extrusion outlet side is in the solution temperature range. Quenching is performed by forced cooling by injection, mist injection, air injection, or the like. Thereafter, if necessary, after room temperature aging and distortion correction, high temperature aging treatment is performed (T6, T7). Moreover, after performing the drawing process as necessary, for example, in the heat treatment conditions described in JIS-H-0001, solution treatment, quenching, if necessary, room temperature aging, distortion correction, high temperature An aging treatment (T6, T7) may be performed.

  Next, examples of the present invention will be described. Assuming a liner in a high-pressure gas container, a 7000 series aluminum alloy plate (rolled plate) is manufactured under the conditions shown in Table 2 with each component composition shown in Table 1, and as shown in Table 2, mechanical properties, Conductivity and hydrogen embrittlement resistance were investigated and evaluated. In Table 2, the total content (total amount: mass%) of Fe, Mn, Cr, Zr, and V in the item of conductivity is abbreviated as (Fe to V).

  More specifically, in the production of the plate material, first, each slab was cast from each molten aluminum alloy having each component composition shown in Table 1. This slab was cooled to room temperature after homogenizing heat treatment at each temperature (° C.) × each time (hr) shown in Table 2. Then, after chamfering to a thickness of 50 mm, reheating, hot rolling to a thickness of 2 mm at a starting temperature of 400 ° C., and then a plate having a thickness of 1.0 mm by cold rolling. . And after solution treatment at each temperature (° C.) × each time (hr) shown in Table 2, quenching is performed by water quenching or forced air cooling, and after aging for 3 days at room temperature (15 to 35 ° C.), a leveler is used. After correcting the distortion of the plate, peak aging treatment, overaging treatment, tempering symbols, T6 (peak aging treatment after solution treatment and quenching), T7 (solution treatment and overaging treatment after quenching) Each tempered material was produced. An air furnace was used for soaking, heating to hot rolling temperature, and high temperature aging treatment. Cooling means for quenching immediately after solution treatment shown in Table 2 and cooling rate in the case of water quenching (described as WQ in Table 2) is about 250 ° C./second, and forced air cooling with a fan (Table 2 is described as forced air cooling), the cooling rate is about 50 ° C./min. Inventive Examples 3, 5 to 9, and Comparative Examples 12 and 16 are subjected to high temperature aging treatment in two stages under the temperature and time conditions described in Table 2. In Table 2, the “×” notation of the temperature × time of each heat treatment is indicated by “*”.

(Sample material properties)
The external dimensions of the prepared tempered plate materials were 1.0 mm in thickness and 200 mm in width in common with each example. Then, from the plate materials after room temperature aging for 30 days after these high temperature aging treatments, the test materials (plate-like test pieces) are cut out, and the conductivity, tensile properties, and hydrogen embrittlement resistance properties of these test materials are measured and evaluated. did. These results are shown in Table 2.

conductivity:
The electrical conductivity (% IACS) on both sides of the test material was measured by a commercially available eddy current type conductivity measuring device, 5 points for each side, 10 points in total, and the average value of these was measured for the conductivity of each test material. Rate.

Tensile test:
In the tensile test, a JISZ2201 No. test piece (parallel portion 25 mm width × 50 mm length) was taken from the test material so that the longitudinal direction of the test piece was perpendicular to the rolling direction, and the crosshead A tensile test was performed at a speed of 5 mm / min. The measured N number was 5, and each mechanical property was an average of these values.

Hydrogen embrittlement resistance test:
The hydrogen embrittlement resistance of the test material is 10% RH or less when the strain rate is 1.0 × 10 ⁻⁶ s ⁻¹ or less and only the atmospheric conditions are changed and the aluminum alloy material is tensile deformed. As the rate of decrease of the elongation value δ2 in a high-humidity atmosphere of 90% RH or higher with respect to the elongation value δ1 in the dry atmosphere, [(δ1-δ2) / δ1] × 100% Sensitivity index (%) was used. Specifically, a small tensile test piece having a width of 5 mm, a length of 12 mm, and a shoulder radius of 7.5 mm from the test material is set so that the longitudinal direction of the test piece is perpendicular to the rolling direction of the plate. Tensile tests were performed until breakage at two initial strain rates of 1.4 × 10 −6 s-1 and atmospheric conditions in a dry atmosphere of 10% RH or less and a highly humid atmosphere of 90% RH or more. Went. The reduction rate of the elongation value δ2 in the high-humidity atmosphere of 90% RH or more relative to the elongation value δ1 in the dry atmosphere of 10% RH or less was calculated by the above formula. It can be evaluated that the hydrogen embrittlement resistance is excellent as the decrease rate of these elongation values is 10% or less, more preferably 5% or less.

  Here, the rate of decrease in elongation value of 5% means that a 6061-T6 material that has been proven to be excellent in hydrogen embrittlement resistance in a hydrogen container member was tested for hydrogen embrittlement resistance under the same conditions described above. The obtained reference value. Further, the elongation rate decrease rate of 10% is not a hydrogen container member, but was obtained by testing the hydrogen embrittlement resistance test under the same conditions as described above for a 7050-T7 material that has been proven as a structural member with excellent corrosion resistance. This is the reference value.

  As can be seen from Tables 1 and 2, Invention Examples 1 to 11 have both high strength and hydrogen embrittlement resistance. That is, the invention example has the composition of the aluminum alloy of the present invention, the composition and the tempering are appropriate, and the conductivity (% IACS) is related to the composition of the contents of Fe, Mn, Cr, Zr, and V. Is pleased. As a result, it has both high strength with 0.2% proof stress of 275 MPa or more and excellent hydrogen embrittlement resistance with an embrittlement susceptibility index of 10% or less.

  In Examples 1 and 2, the embrittlement susceptibility index is negative. This is because the elongation value δ2 in a highly humid atmosphere of 90% RH or more is 10% RH or less in a dry atmosphere. This is because it is larger than δ1, and it can be said that this is one characteristic that shows excellent resistance to hydrogen embrittlement.

  On the other hand, as can be seen from Tables 1 and 2, Comparative Examples 12 to 15 do not have both high strength and hydrogen embrittlement resistance. In Comparative Examples 12 and 15, the Mg content is too small. In Comparative Examples 13 and 14, the conductivity (%) does not satisfy the relationship of conductivity (%) ≧ −4.9 × (Fe + Mn + Cr + Zr + V) +40.5.

  Therefore, the results of the above examples support the critical significance or effect of combining the requirements of the components and structures in the present invention, or the preferable production conditions, such as hydrogen embrittlement resistance and mechanical properties. .

  As described above, according to the present invention, it is possible to provide a 7000 series aluminum alloy material for high-pressure gas containers that has excellent hydrogen embrittlement resistance. Therefore, the 7000 series aluminum alloy material can be applied as a member such as a liner, a cap or a gas pipe to a high pressure gas container in which reinforcing fibers are wound around the outer surface of an aluminum alloy or plastic liner.

Claims (5)

  In mass%, Zn: 4.0 to 6.7%, Mg: 0.75 to 2.9%, Cu: 0.001 to 2.6%, Si: 0.05 to 0.40%, Ti : 0.005 to 0.20%, Fe: 0.01 to 0.5%, respectively, Mn: 0.01 to 0.7%, Cr: 0.02 to 0.3%, Zr: One or two or more of 0.01 to 0.25%, V: 0.01 to 0.10% are satisfied while satisfying the relationship of 1.0% ≧ Fe + Mn + Cr + Zr + V ≧ 0.1%, and the balance is Al And an aluminum alloy composition composed of inevitable impurities, and the conductivity (% IACS) is related to the total content of Fe, Mn, Cr, Zr, and V in terms of conductivity (%) ≧ −4.9 ×. The relationship of (Fe + Mn + Cr + Zr + V) +40.0 is satisfied, and the 0.2% proof stress is 275 MPa or more. High-pressure gas container for an aluminum alloy material excellent in hydrogen embrittlement resistance characterized by.   The aluminum alloy material for a high-pressure gas container excellent in hydrogen embrittlement resistance according to claim 1, wherein the aluminum alloy material is tempered selected from peak aging treatment and overaging treatment.   The electrical conductivity of the aluminum alloy material satisfies the relationship of electrical conductivity (%) ≧ −4.9 × (Fe + Mn + Cr + Zr + V) +41.5 in relation to the total content of Fe, Mn, Cr, Zr, and V. The aluminum alloy material for a high-pressure gas container excellent in hydrogen embrittlement resistance according to claim 1 or 2. The hydrogen embrittlement resistance of the aluminum alloy material is 10% RH or less when the strain rate is 1.0 × 10 ⁻⁶ s ⁻¹ or less and only the atmospheric conditions are changed and the aluminum alloy material is subjected to tensile deformation. As the rate of decrease of the elongation value δ2 in a high-humidity atmosphere of 90% RH or higher with respect to the elongation value δ1 in the dry atmosphere, an embrittlement susceptibility index represented by [(δ1-δ2) / δ1] × 100% is obtained. The aluminum alloy material for a high-pressure gas container excellent in hydrogen embrittlement resistance according to any one of claims 1 to 3, which is 10% or less.   The aluminum alloy material for a high-pressure gas container excellent in hydrogen embrittlement resistance according to any one of claims 1 to 4, wherein the aluminum alloy material is for a high-pressure gas container for hydrogen storage.