JP2009144178A - Aluminum alloy casting and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy casting which has improved strength and simultaneously improved thermal conductivity, by dissolving magnesium in the matrix, and to provide a production method therefor. <P>SOLUTION: The aluminum alloy casting contains, at least magnesium dissolved therein and a crystallized product of Al<SB>3</SB>Mg<SB>2</SB>. An amount of magnesium dissolved in the aluminum alloy casting is 0.7 wt.% or more and the crystallized product of Al<SB>3</SB>Mg<SB>2</SB>occupies 3.2% or less by an area rate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aluminum alloy casting and a manufacturing method thereof, and more particularly to an aluminum alloy casting containing at least magnesium and a manufacturing method thereof.

  2. Description of the Related Art Conventionally, a casting method for producing a cast product by injecting a molten metal such as a molten aluminum alloy into a cavity formed by a fixed mold and a movable mold is generally known. The molten aluminum alloy to be cast contains, for example, silicon to improve the fluidity, mold filling, hot cracking, etc. of the molten metal, or elements such as copper and magnesium for solid solution strengthening. It is included.

  Thus, in the aluminum alloy casting cast by the molten metal containing the additive element in the aluminum, the second phase crystallized substance (for example, eutectic silicon) other than the aluminum base which is the first phase is included in the structure. Etc.) is generated. The crystallized product has poor ductility compared to the base aluminum (matrix). For example, when eutectic silicon is coarse, the crystallized product becomes a starting point of crack propagation in the aluminum alloy casting, and the aluminum alloy Castings could be destroyed.

  In view of these points, it is common to improve metal properties such as ductility of aluminum alloy castings by appropriately adjusting the elements to be contained in aluminum and the amount thereof, heat treatment conditions during casting and after casting, and the like. is there.

For example, as an example, by weight ratio, Si: 1.65 to 4.0%, Mg: 0.2 to 0.4%, Fe: 0.2% or less, the balance contains the composition of aluminum and inevitable impurities There has been proposed a method of manufacturing an aluminum alloy casting in which a cast aluminum alloy casting is subjected to a solution treatment in which it is rapidly cooled after reaching a high temperature near the eutectic temperature, and then subjected to an aging treatment (see, for example, Patent Document 1). ). According to the manufacturing method, by setting the elements to be contained in the aluminum alloy casting, the amount thereof, and the heat treatment conditions after casting, the area ratio of eutectic Si is 15% or less, the elongation is 15% or more, the impact An aluminum alloy casting having a value of 30 to 40 × 10 ⁴ J / m ² or more can be obtained.
Japanese Patent Laid-Open No. 9-272942

  Thus, the crystallized substance in the aluminum alloy casting has a great influence on the metal characteristics of the aluminum alloy casting depending on the type and content of the element to be contained, the heat treatment conditions during casting or solution treatment, and the like. For example, in the case of the aluminum alloy casting described in Patent Document 1, magnesium is contained in addition to silicon, and the aluminum alloy casting is solid solution strengthened by dissolving the magnesium in the aluminum alloy casting. The tensile strength of the aluminum alloy casting can be improved.

  However, when magnesium is contained in an aluminum alloy casting, magnesium not only dissolves but also crystallized material containing magnesium is crystallized, and the crystallinity greatly reduces the thermal conductivity of the aluminum alloy casting. There are things to do.

  As described above, when magnesium is contained in an aluminum alloy casting, it is difficult to simultaneously increase the tensile strength of the aluminum alloy casting and increase the thermal conductivity of the aluminum alloy casting. Met.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an aluminum alloy casting capable of improving solid-solution strengthening and improving thermal conductivity by dissolving magnesium. It is in providing the manufacturing method.

In order to solve the above-mentioned problems, the inventor has conducted extensive studies and experiments. As a result, when magnesium is contained in the aluminum alloy casting, the decrease in the thermal conductivity of the aluminum alloy casting causes the aluminum base to be in the first phase ( Of the Al ₃ Mg ₂ crystallized material constituting the second phase in the aluminum alloy casting and the Al ₃ Mg ₂ contained in the aluminum alloy casting. We obtained new knowledge that the thermal conductivity of aluminum alloy castings can be dramatically improved by limiting the amount of crystallized material.

The inventors then focused on the fact that the crystallized product of Al ₃ Mg ₂ , which is the second phase crystallized product in the aluminum alloy casting, is slower to solidify than the aluminum base, and the crystal in the aluminum alloy cast product. By sucking out and sucking out the material from the surface of the casting, the ratio of the crystallized material is reduced to a predetermined ratio or less, thereby dramatically improving the thermal conductive metal characteristics of the aluminum alloy casting. I also got new knowledge that I can do it.

The present invention is based on the new knowledge of the inventors, to solve the above problems, a manufacturing method of an aluminum alloy casting according to the present invention, at least the magnesium has dissolved, the Al ₃ Mg ₂ A step of solution treatment of an aluminum alloy casting containing a crystallized product so that magnesium dissolved in the aluminum alloy casting is 0.7% by weight or more, and an aluminum alloy casting while maintaining the solutionized state. A step of immersing the aluminum alloy casting in the molten metal so that the surface of the aluminum alloy is immersed in a pure aluminum melt and a non-immersed surface not immersed in the molten metal; and at least one of the non-immersed surfaces negative pressure is generated in the facing in a space separate component, the Al ₃ in the aluminum alloy casting in a state in which the solution from at least a portion of the non-immersion surface until crystallized substances g ₂ becomes less 3.2% by area ratio, by sucking from the immersion surface with suck crystallized substances of Al ₃ Mg ₂ in the space the melt in said aluminum alloy casting, And a step of replacing the Al ₃ Mg ₂ crystallized product in the aluminum alloy casting with the pure aluminum.

  In the method for producing an aluminum alloy casting according to the present invention, first, a solution treatment is performed on the aluminum alloy casting. The “solution treatment” referred to in the present invention is a treatment in which the aluminum alloy casting is heated to a temperature equal to or higher than the melting limit of the alloy element in the solid phase of the aluminum alloy casting, and various alloy elements are dissolved in aluminum. . In the present invention, magnesium solid solution means that magnesium atoms are present in an aluminum alloy casting in a state in which a compound such as alloying is not purified.

  In the present invention, in the solution treatment step, the solution treatment is performed so that the magnesium dissolved in the aluminum alloy casting is 0.7% by weight or more. Therefore, the tensile strength of the aluminum alloy casting can be improved. Magnesium that is solid-solved in the aluminum alloy casting may be dissolved up to an amount that is the solid solubility limit of magnesium. However, when the upper limit value of tensile strength is taken into consideration by experiments of the inventor described later, More preferably, it is 4% by weight or less.

  The “crystallized product” as referred to in the present invention is crystallized during casting (specifically during cooling), and the second phase other than the base when the parent phase as the first phase is an aluminum base. It is a component that constitutes a phase and is in a molten state or a semi-molten state when it is subjected to a solution treatment of an aluminum alloy casting and when immersed in a pure aluminum molten metal described later, and it can flow.

The crystallized product varies depending on the element contained in the aluminum alloy and the amount thereof, and examples thereof include eutectic Si, β-AlFeSi crystallized product, Al ₂ Cu crystallized product, and Mg ₂ Si crystallized product. In the method for producing an aluminum alloy casting according to the present invention, at least the crystallized product contains a crystallized product of Al ₃ Mg ₂ .

  Note that the aluminum alloy casting prepared before the solution treatment is an alloy casting that is cast by pouring a molten metal containing a predetermined amount of an element that is a predetermined alloy component into aluminum into a mold. Examples thereof include a die casting method. As another aspect, the aluminum alloy casting may be a casting obtained by, for example, a thixocasting method in which an aluminum billet is cast in a semi-molten state or a rheocasting method.

  Examples of the alloy of the aluminum alloy casting include, for example, an Al—Mg based aluminum alloy, an Al—Cu—Mg based aluminum alloy, an Al—Cu—Mg—Ni based aluminum alloy, an Al—Si—Mg based aluminum alloy, Al An aluminum alloy casting containing a magnesium element such as a -Si-Cu-Mg based aluminum alloy can be mentioned, and the alloy further contains at least one element of Fe, Mn, Ti, Zi, and the like. Also good.

  Next, the aluminum alloy casting in which the solution is maintained, that is, the aluminum alloy casting in which the crystallized material can flow is immersed in a molten pure aluminum. At this time, a part of the surface of the aluminum alloy casting is left as a non-immersed surface, and the remaining surface is immersed in the molten pure aluminum. The pure aluminum referred to in the present invention means aluminum composed of aluminum and inevitable impurities, and more preferably contains at least 98.5% by mass or more of an aluminum element.

And maintaining the attitude of the aluminum alloy casting partially immersed in the molten pure aluminum in the dipping process, generating a negative pressure in the space facing at least a part of the non-immersed surface, and a part of the non-immersed surface from at least crystallizate of the _Al 3 Mg ₂ in the aluminum alloy castings, until less 3.2% in area ratio, suck _Al 3 Mg ₂ crystallizate. More specifically, the crystallized material in the aluminum alloy casting forms a network-like skeleton dispersed in the aluminum alloy casting to form a network (forms a network structure of the crystallized product). Therefore, the crystallized material in the aluminum alloy casting is sucked out using the crystallized material network formation space as the crystallized material suction passage.

  At the same time, due to the negative pressure, the formation space of the network structure from which the crystallized material has been sucked out is used as a suction flow path for the melt of pure aluminum, and the melt of pure aluminum is sucked from the immersion surface. Is filled.

  Note that “generating a negative pressure in a space facing at least a part of a non-immersed surface” according to the present invention refers to sucking out a crystallized substance in the casting from at least a part of the non-immersed surface, and The suction pressure for sucking aluminum is generated in the space, and so-called vacuum suction is performed on the at least part of the non-immersed surface.

In this way, the crystallized material in the aluminum alloy casting is replaced with pure aluminum. As a result, the Al ₃ Mg ₂ crystallized matter that hinders thermal conductivity is reduced to a predetermined amount, and in the space where the crystallized product is present, the thermal conductivity is higher than the crystallized product, and the formability is high. Since pure aluminum with good corrosion resistance is also placed, the aluminum alloy castings before the solution treatment are used for the thermal conductivity, formability (for example, ductility), and corrosion resistance of the aluminum alloy castings. Compared to In particular, since the Al ₃ Mg ₂ crystallized material in the aluminum alloy casting is sucked into the space until the area ratio becomes 3.2% or less, the thermal conductivity of the aluminum alloy casting can be improved. Therefore, when the area ratio of the Al ₃ Mg ₂ crystallized product exceeds 3.2%, the Al ₃ Mg ₂ crystallized product has low thermal conductivity with respect to aluminum (aluminum base). There is a possibility that the thermal conductivity of the alloy casting is hindered.

On the other hand, it is desirable that all of the Al ₃ Mg ₂ crystallized product is sucked out, but since it is difficult to completely suck out all the crystallized product, the lower limit of the area ratio of the Al ₃ Mg ₂ crystallized product is More preferably, it is larger than 0%.

Moreover, the area ratio of the crystallized product of Al ₃ Mg ₂ referred to in the present invention is a crystal of Al ₃ Mg ₂ with respect to the entire area of the metal cross section when an arbitrary cross section of the aluminum alloy casting before the substitution step is observed. It refers to the ratio of the area occupied by the second phase that is the product.

  Further, by performing quenching and aging treatment on the aluminum alloy casting after the replacement step, the primary crystal portion which is the first phase of the aluminum alloy casting is strengthened by aging precipitation.

  In the replacement step of the method for producing an aluminum alloy casting according to the present invention, it is more preferable that the negative pressure in the space facing at least a part of the non-immersed surface is 75 kPa or less. According to the present invention, since the air in the space facing at least a part of the non-immersed surface is degassed to a pressure of 75 kPa or less, the crystallization is preferably performed from the surface of the aluminum alloy casting. A product can be sucked, and a molten pure aluminum can be suitably introduced and filled into the formation space in the aluminum alloy casting in which the sucked crystallized material is present. The space is more preferably a complete vacuum, and the lower limit is a pressure greater than 0 kPa.

Further, in the method for producing an aluminum alloy casting according to the present invention, in the replacing step, the temperature of the molten metal is such that the kinematic viscosity of the molten aluminum of the pure aluminum is 0.18 × 10 ⁻² cm ² / s or less. It is more preferable to adjust.

According to the present invention, the molten alloy is heated so that the kinematic viscosity of the pure aluminum melt is 0.18 × 10 ⁻² cm ² / s or less, so that the aspirated crystallized substance is present. The space within the casting can be suitably filled with molten pure aluminum. In order to obtain the kinematic viscosity, it is preferable to heat at least pure aluminum to 450 ° C. or higher.

That is, when the kinematic viscosity of the molten metal is lower than 0.18 × 10 ⁻² cm ² / s, the fluidity of the molten pure aluminum is lowered, and it becomes easy to inhibit the molten metal from being sucked into the aluminum alloy casting. The lower limit value of the kinematic viscosity of the molten metal is more preferably 0.15 × 10 ⁻² cm ² / s or more. Even when it is smaller than the kinematic viscosity, no further effect can be expected, and when the aluminum alloy casting is immersed, a part of the aluminum alloy casting may be melted. .

As the present invention, an aluminum alloy casting produced by the method for producing an aluminum alloy casting is also disclosed below. The aluminum alloy casting according to the present invention is an aluminum alloy casting in which at least magnesium is solid-solved and contains a crystallized product of Al ₃ Mg ₂ , and the magnesium solid-dissolved in the aluminum alloy casting is 0.7 weight. %, And the crystallized product from Al ₃ Mg ₂ is 3.2% or less in terms of area ratio.

  According to the present invention, by making magnesium dissolved in the aluminum alloy casting 0.7% by weight or more, it is strengthened by solid solution with magnesium, and the tensile strength of the aluminum alloy casting can be improved. That is, if it is less than 0.7% by weight, the effect of solid solution strengthening by magnesium cannot be sufficiently obtained, and the tensile strength cannot be sufficiently improved.

  On the other hand, magnesium dissolved in the aluminum alloy casting may be dissolved to the so-called solid solution limit, but more preferably 1.4 wt% or less. This is because even if it exceeds 1.4% by weight, no further improvement in tensile strength can be expected.

Moreover, the thermal conductivity of an aluminum alloy casting can be improved by making the area ratio of the crystallized product of Al ₃ Mg ₂ contained in the aluminum alloy casting 3.2% or less. That is, when the area ratio of the crystallized product of Al ₃ Mg ₂ exceeds 3.2%, as described above, the thermal conductivity is lowered. On the other hand, since the crystallized product of Al ₃ Mg ₂ has magnesium dissolved in the aluminum alloy casting, it is difficult to completely crystallize the Al ₃ Mg ₂ crystallized product or to eliminate it completely. Therefore, it is more preferable that the lower limit value of the area ratio of the crystallized product of Al ₃ Mg ₂ is larger than 0%.

  According to the present invention, the aluminum alloy casting can enhance solid solution and improve thermal conductivity by dissolving magnesium in solid solution.

  Hereinafter, a preferred method for producing an aluminum alloy casting according to the present invention and a production apparatus suitable for carrying out the method will be described with reference to the drawings.

  FIG. 1 shows an overall configuration diagram of an apparatus for suitably performing a method for producing an aluminum alloy casting according to the present embodiment.

  As shown in FIG. 1, an aluminum alloy casting manufacturing apparatus 10 according to this embodiment is an apparatus for modifying the metal structure of an aluminum alloy casting manufactured from an aluminum alloy by a casting apparatus. The manufacturing apparatus 10 includes a molten metal accommodating part 20 that accommodates a molten pure aluminum melt, a molten metal immersion part 30 that immerses an aluminum alloy casting W that is a material to be treated in the molten metal of the molten metal accommodating part 20, and an aluminum alloy casting. And a suction unit 40 that holds and vacuum-sucks the surface of the aluminum alloy.

  The molten metal storage unit 20 includes at least a storage tank 21 that stores molten pure aluminum, a heater (heater) 22 that heats pure aluminum stored in the storage tank 21, and a storage tank 21. And a molten metal temperature measuring device 23 for measuring a molten metal temperature of the pure aluminum.

  The storage tank 21 is made of a material having a heat resistance temperature higher than the melt temperature of pure aluminum, and an opening having a size into which an aluminum alloy casting W as a material to be processed can be inserted from above is formed.

  The heater 22 is an apparatus that heats the molten metal L to a temperature corresponding to the kinematic viscosity so that the contained pure aluminum melt L has a desired kinematic viscosity. The heater 22 is configured such that the temperature of the molten aluminum L of pure aluminum can be adjusted based on the molten aluminum temperature measured by the molten metal temperature measuring device 23.

  Note that the molten metal storage unit 20 is configured so that the operator can adjust the temperature of the molten metal using the heater 22 while checking the display temperature of the measured temperature of the molten metal temperature measuring device 23 when performing the temperature adjustment. It may be. As another aspect, the molten metal storage unit 20 sets a target temperature of the molten metal in advance, and adjusts the amount of heat generated by the heater 22 so that the measured temperature measured by the molten metal temperature measuring instrument 23 is equal to or higher than the target temperature. It may be configured.

  The molten metal immersion part 30 is formed of an aluminum alloy casting W so that the surface of the aluminum alloy casting W is composed of an immersion surface fd in which the surface of the aluminum alloy casting W is immersed in a molten pure aluminum in the molten metal storage part and a non-immersed surface fn that is not immersed in the molten metal. It is comprised so that it can hold | maintain and it can be immersed in the molten metal in the molten metal accommodating part 20. FIG.

  In this embodiment, the molten metal immersion part 30 is connected to a suction holder 41 of a suction part 40 described later and is configured to hold the aluminum alloy casting W indirectly by holding the suction holder 41. However, a gripping mechanism that can directly grip the casting may be provided separately. Moreover, the molten metal immersion part 30 includes an elevating mechanism that elevates and lowers the suction holder 41 so that the aluminum alloy casting W in the held state can secure the above-described immersed state posture.

  The suction part 40 generates a negative pressure in the space S facing at least a part (upper surface) of the non-immersed surface fn, and the crystallized material in the aluminum alloy casting W formed into a solution from the upper surface of the non-immersed surface is spaced. This is a device for sucking into S and sucking molten metal L from the immersion surface fd into the aluminum alloy casting W. The suction part 40 includes at least a suction holder 41, a pressure measuring device 42, and a suction pump 44. .

  The suction holder 41 has a space S inside, an opening 41a that covers an upper surface that is a part of the non-immersed surface fn of the aluminum alloy casting W, and air in the space S at a position facing the opening 41a. A deaeration port 41b for taking care of is formed. Further, a sealing material 41c for allowing the space S to be sealed is disposed on the periphery of the opening 41a.

  The suction pump 44 is connected to the deaeration port 41b so as to deaerate the air in the space S of the suction holder 41 and generate a negative pressure in the space S. The suction holder 41 is disposed so that the pressure in the space S of the tool 41 can be measured.

  Using the apparatus 10, the aluminum alloy casting according to this embodiment is manufactured. FIG. 2 is a flowchart for explaining each step of the manufacturing method of the aluminum alloy casting according to the present embodiment, and FIG. 3 is a diagram showing a cross-sectional view of the structure of the aluminum alloy casting cast in the casting step. is there.

  First, as a previous step (casting step S11) for manufacturing the aluminum alloy casting of the present embodiment, a predetermined amount of magnesium was added so that at least 0.7 wt% magnesium was contained in the solution treatment described later. Cast from aluminum alloy to cast aluminum alloy. As a casting method, casting is performed by a known casting method using a die cast casting apparatus, a semi-molten casting apparatus, or the like.

As shown in FIG. 3, the structure of the cast aluminum alloy is as follows. As shown in FIG. 3, the first phase (parent phase) that becomes the aluminum base and the second phase consisting of the crystallized structure such as the Al ₃ Mg ₂ crystallized substance. Will be formed. This second-phase crystallized product generally forms a three-dimensional network (network-like) skeleton in an aluminum alloy casting (forms a network structure of crystallized product).

  Then, at least the following series of steps S12 to S14 are carried out as the manufacturing method according to the present embodiment in order to modify the metal structure of the casting for the aluminum alloy casting prepared in the casting step S11. .

First, the solution treatment step S12 shown in FIG. 2 is performed on the prepared aluminum alloy casting. The solution treatment process is performed by putting the cast aluminum alloy casting into a heating furnace (not shown). By this treatment, in the solid phase of the aluminum alloy casting, the aluminum alloy casting is heated to a temperature equal to or higher than the melting limit of the alloy element, and at least 0.7% by weight or more of magnesium is dissolved in aluminum. On the other hand, the crystallized product of Al ₃ Mg ₂ constituting the second phase of the aluminum alloy casting becomes a molten or semi-molten state and changes into a form having fluidity.

The solution treatment step S12 maintains a state where at least the crystallized Al ₃ Mg ₂ can flow (maintains the solution state), and the following immersion step S13 and substitution step S14 are performed. The dipping process S13 and the replacement process S14 are performed using the manufacturing apparatus 10 shown in FIG.

  First, in the immersing step S13, as shown in FIG. 1, the surface of the solution-treated aluminum alloy casting W is immersed in the molten aluminum L of pure aluminum melted in the storage tank 21, and immersed in the molten metal. The aluminum alloy casting W is immersed in the molten metal L by the molten metal immersion part 30 so as to consist of the non-immersed surface fn that is not performed. Specifically, one surface (lower surface) of the aluminum alloy casting W is immersed in the molten metal L in the storage tank 21, and the other surface (upper surface) located on the opposite side is not immersed.

  In the dipping step S13, the suction holder 41 is disposed on the upper surface of the aluminum alloy casting W in advance through the sealing material 41c so that the upper surface is covered with the opening 41a, and the degassing port 41b is used. The suction pump 44 generates a negative pressure in the space S in the suction holder 41 facing the upper surface. Thereby, the aluminum alloy casting W can be adsorbed by the suction holder 41, and the suction holder 41 to which the casting W has been adsorbed can be moved by the molten metal immersion unit 30 to perform the immersion. However, the immersion method is not limited to this method. For example, a mechanism for gripping the aluminum alloy casting W is provided in the molten metal immersion portion 30, and the casting W gripped by the gripping mechanism is moved downward. The casting W may be immersed in the molten metal L.

  And substitution process S14 is performed after immersion process S13. Specifically, in the dipping step S13, the posture in which the aluminum alloy casting W is dipped is maintained, and in the space S facing the upper surface of the casting W adsorbed to the suction holder 41 (a part of the non-immersed surface fn), A negative pressure is further generated by the suction pump 44. That is, since the space S becomes a sealed space by the sealing material 41 c arranged in the opening 41 a of the suction holder 41, air in the space S is deaerated by the suction pump 44 from the deaeration port 41 b of the suction holder 41. As a result, a further negative pressure is generated in the space S. At this time, the pressure due to the negative pressure in the space S measured by the pressure measuring device 42 is more preferably 75 KPa or less.

Then, because of the negative pressure, at least the crystallized material such as Al ₃ Mg ₂ in the aluminum alloy casting W forms a network structure, so the formation space of the network structure of the crystallized material is the suction flow of the crystallized material. It acts as a path and the crystallized material in the aluminum alloy casting W is sucked out. At this time, the crystallized product is sucked out until the Al ₃ Mg ₂ crystallized product has an area ratio of 3.2% or less. It should be noted that by setting the magnitude of the pressure at the time of suction by the suction pump 44 (pressure due to the negative pressure) and the suction time of the suction pump 44 (suction time) in advance by experiments or the like, crystals of Al ₃ Mg ₂ The product can be reduced to 3.2% or less by area ratio.

  Further, since the aluminum alloy casting W is immersed in the molten metal L, the formation space of the network structure from which the crystallized material has been sucked out acts as a suction flow path for the molten aluminum L, and the pure aluminum is melted from the immersed surface fd. Molten metal L is sucked. As a result, pure aluminum is replaced in the space where the crystallized material was present in the sucked aluminum alloy casting W.

In addition, based on the measured temperature which the molten metal temperature measuring device 23 measured, the kinematic viscosity of the molten aluminum L of pure aluminum is 0.18 * 10 ^<-2 > cm ^{< 2} > // by heating a molten metal to desired temperature with the heater 22. FIG. It is desirable to adjust the temperature of the molten metal so as to be s or less.

  Thereafter, quenching and aging treatment step S15 are performed. As a result, the aluminum alloy casting can be strengthened by aging precipitation.

Thus, at least magnesium is a solid solution, and is an aluminum alloy casting containing a crystallized product of Al ₃ Mg ₂ , and the magnesium dissolved in the aluminum alloy casting is 0.7% by weight or more, An aluminum alloy casting in which the crystallized Al ₃ Mg ₂ is 3.2% or less in area ratio can be manufactured.

  The aluminum alloy casting thus obtained can be solid-solution strengthened by dissolving magnesium in solid solution and can improve thermal conductivity.

That is, the aluminum alloy casting according to the present embodiment is solid solution strengthened by magnesium by making magnesium dissolved in the casting 0.7% by weight or more, thereby improving the tensile strength of the aluminum alloy casting. Can do. On the other hand, when the area ratio of the Al ₃ Mg ₂ crystallized material contained in the aluminum alloy casting is set to 3.2% or less, the thermal conductivity of the aluminum alloy casting can be improved.

Hereinafter, the present invention will be described based on examples. The present invention is not limited to the following examples.
Example 1
<Specimen>
First, as a casting process, an aluminum alloy having a composition of Al-0.6Mg (containing 0.5% Fe as impurities) is heated and melted at a melting temperature of 740 ° C. ± 5 ° C. to form a molten metal. In a standard state, argon gas was allowed to flow at ² L / min × 0.4 kgf / cm ² × 5 min, a flux for removal was added to the molten metal by 0.3 (% by weight), and the molten metal was stirred for 2 minutes. Left to stand. Then, the molten metal after stripping is reheated at 740 ° C. ± 5 ° C., and a die casting apparatus is used to set the gate speed to 1.0 m / sec, the pressure to 700 kgf / cm ² , and the cooling speed to 12 ° C./sec. A plate-shaped aluminum alloy casting having a thickness of 10 mm was produced.

Next, as a solution treatment step, the cast aluminum alloy casting was put into a heating furnace under a heating condition of 500 ° C. for 10 hours, so that at least 0.7 wt% of magnesium was dissolved. At this time, the aluminum alloy casting contains a crystallized product of Al ₃ Mg ₂ . In Example 1, magnesium having different solid solution amounts is obtained by changing the amount of magnesium during casting and the heat treatment conditions during solution treatment.

Further, the aluminum alloy casting is held in the solution-treated state, and using the apparatus shown in FIG. 1 described above, first, one surface of the plate-like aluminum alloy casting is heated to 700 ° C. as a dipping process. It was immersed in a molten metal of aluminum (purity 99.7% by weight). Then, the molten metal from dipping the surface with this solution heat state the crystallized substances of Al ₃ Mg ₂ in the aluminum alloy casting until 3.2% or less in area ratio, suck crystallized substances of Al ₃ Mg ₂ Was sucked into the aluminum alloy casting to replace the crystallized Al ₃ Mg ₂ in the aluminum alloy casting with pure aluminum. In the replacement step, a negative pressure was generated from the other surface on the opposite side so that the pressure (vacuum degree) of the space including the surface was 65 kPa.

  Then, T6 process prescribed | regulated to JIS specification was performed as a heat treatment process. Specifically, the aluminum alloy casting after the replacement process is water-quenched at 70 ° C., and further subjected to aging treatment at 160 ° C. for 5 hours to produce the aluminum alloy casting according to the present example. did.

The area ratio of the Al ₃ Mg ₂ crystallized product in the aluminum alloy casting is the area of the Al ₃ Mg ₂ crystallized product with respect to the entire cross-sectional area of the cast product obtained by cutting a part of the aluminum alloy cast. The area ratio within the above range shown in FIG. 4 was confirmed by image analysis using a microscope.

<Evaluation method 1>
Tensile test pieces were manufactured so that the parallel part had a diameter of 6 mm and a length of 25 mm from the thickness center part of the manufactured aluminum alloy casting, and the tensile strength was measured by a tensile test. As a result, the obtained elongation is shown in FIG.

<Evaluation method 2>
A test piece was cut out from the center part of the manufactured aluminum alloy cast piece, and the thermal conductivity was measured by a laser flash method according to JIS R 1611. The result is shown in FIG.

(Comparative Example 1)
In the same manner as in Example 1, an aluminum alloy casting was produced. The difference from Example 1 is that the content of magnesium in the aluminum alloy casting and the heat treatment conditions for the solution treatment were changed to reduce the solid solution amount of magnesium to less than 0.7% by weight. .

Incidentally, the aluminum alloy castings of these Comparative Example 1, all the crystallized substances of _Al 3 Mg ₂ until 3.2% or less in area ratio, from the immersion surface with suck crystallized substances of _Al 3 Mg ₂ By sucking the molten metal into the aluminum alloy casting, the crystallized Al ₃ Mg ₂ in the aluminum alloy casting is replaced with pure aluminum. In the same manner as in Example 1, the tensile strength was measured by a tensile test according to the evaluation method 1. The result is shown in FIG.

(Comparative Example 2)
In the same manner as in Example 1, an aluminum alloy casting was produced. Different from Example 1, in the substitution step, not 3.2% or less crystallizate the area ratio of _Al 3 Mg ₂ (area ratio is more than 3.2%) as, _Al 3 Mg ₂ The crystallized product of Al ₃ Mg ₂ in the aluminum alloy casting was replaced with pure aluminum by sucking out the crystallized product and sucking the molten metal from the immersion surface into the aluminum alloy casting.

  In all of the aluminum alloy castings of Comparative Example 2, the solid solution amount of magnesium is 0.7% by weight. In the same manner as in Example 1, the thermal conductivity was measured according to the evaluation method 2. The result is shown in FIG.

[Result 1]
As shown in FIG. 4, the tensile strength of the test piece of the aluminum alloy casting of Example 1 is 200 MPa or more, and the tensile strength of the test piece of the aluminum alloy casting of Comparative Example 1 is less than 180 MPa. Compared with the comparative example 1, the thing of No. had a greater strength.

[Result 2]
As shown in FIG. 5, the thermal conductivity of the test piece of the aluminum alloy casting of Example 1 is 220 W / m · K or more, and the thermal conductivity of the test piece of the aluminum alloy casting of Comparative Example 2 is 160 W / m. m · K or less. The thermal conductivity of Example 1 was higher than that of Comparative Example 2.

[Discussion 1]
From the result 1, as shown in FIG. 4, the aluminum alloy casting of Example 1 was solid-solution strengthened with magnesium by setting magnesium dissolved in the aluminum alloy casting to 0.7 wt% or more. It is thought that the tensile strength of the alloy casting could be improved. That is, as in the aluminum alloy casting of Comparative Example 1, when the amount of aluminum dissolved in the aluminum alloy casting is less than 0.7% by weight, the effect of solid solution strengthening with magnesium cannot be sufficiently obtained, It seems that the strength cannot be improved.

  Furthermore, as shown in FIG. 4, even if the change in tensile strength with respect to the solid solution amount of magnesium in the aluminum alloy casting of Example 1 is taken into account, the solid solution magnesium in the aluminum alloy casting is solid solution up to the so-called solid solution limit. However, it is more preferable that the content is 1.4% by weight or less. Even when the amount exceeds 1.4% by weight, it is considered that further improvement in tensile strength cannot be expected.

[Discussion 2]
From the result 2, as shown in FIG. 5, the aluminum alloy casting of Example 1 has an area ratio of Al ₃ Mg ₂ crystallized material contained in the aluminum alloy casting of 3.2% or less. It is considered that the thermal conductivity of the aluminum alloy casting could be improved. That is, as in the case of the aluminum alloy casting of Comparative Example 2, when the area ratio of the Al ₃ Mg ₂ crystallized product of the aluminum alloy casting exceeds 3.2%, the thermal conductivity decreases as described above. It is thought that it will end.

Further, as shown in FIG. 5, the Al ₃ Mg ₂ crystallized product has magnesium dissolved in the aluminum alloy casting, so that the Al ₃ Mg ₂ crystallized product is not crystallized at all, or Since it is difficult to eliminate completely, it is considered that the lower limit value of the area ratio of the crystallized product of Al ₃ Mg ₂ is preferably more than 0%.

From the above, the aluminum alloy casting according to Example 1 in which at least gnesium is in solid solution and the crystallized product of Al ₃ Mg ₂ is 0.7% by weight or more of magnesium dissolved in the aluminum alloy casting. It is considered that when the Al ₃ Mg ₂ crystallized product was 3.2% or less in terms of area ratio, magnesium could be dissolved to enhance the solid solution, and the thermal conductivity could be improved. .

  As mentioned above, although embodiment of this invention has been explained in full detail using drawing, a concrete structure is not limited to this embodiment, Even if there is a design change in the range which does not deviate from the gist of the present invention. These are included in the present invention.

  For example, in the present embodiment, a series of steps from a casting step, a solution treatment step, a dipping step, a replacement step, and a heat treatment step has been described, but it is possible to prepare an aluminum alloy casting in the above-described range before the solution treatment step. If possible, the casting step may be omitted, and the heat treatment step may be omitted if the metal characteristics according to the intended use can be obtained.

  The manufacturing method according to the present invention is not only for aluminum alloy castings but also for castings in which a crystallized product that is a second phase is crystallized on a base such as a magnesium alloy casted product. This is particularly effective when the purpose is to suppress the decrease.

The whole apparatus block diagram for performing suitably the manufacturing method of the aluminum alloy casting which concerns on this embodiment. The structure sectional drawing of the aluminum alloy casting before solution treatment after casting. The flowchart for demonstrating each process of the manufacturing method of the aluminum alloy casting which concerns on this embodiment. The figure which showed the result of the tension test of the aluminum alloy casting which concerns on Example 1 and Comparative Example 1. FIG. The figure which showed the result of the heat conduction test of the aluminum alloy casting which concerns on Example 1 and Comparative Example 2. FIG.

Explanation of symbols

  10: Aluminum alloy casting production apparatus, 20: molten metal storage unit, 21: storage tank, 22: heater (heater), 23: molten metal temperature measuring device, 30: molten metal immersion unit, 40: suction unit, 41: suction holding 41c: sealing material, 42: pressure measuring device, 44: suction pump, S: space, S11: casting process, S12: solution treatment process, S13: immersion process, S14: replacement process, S15: heat treatment process, W : Aluminum alloy casting, fd: immersion surface, fn: non-immersion surface

Claims (2)

A solution treatment of an aluminum alloy casting containing at least magnesium in solid solution and containing a crystallized product of Al ₃ Mg ₂ so that the magnesium dissolved in the aluminum alloy casting is 0.7% by weight or more; ,
While maintaining the solution state, the surface of the aluminum alloy casting is composed of an immersion surface immersed in a molten pure aluminum and a non-immersed surface not immersed in the molten metal. Dipping in,
The Al ₃ Mg ₂ crystallized product in the aluminum alloy casting in a state of solution formation from at least a part of the non-immersed surface by generating a negative pressure in a space facing at least a part of the non-immersed surface Until the area ratio becomes 3.2% or less, the Al ₃ Mg ₂ crystallized material is sucked into the space and the molten metal is sucked into the aluminum alloy casting from the immersion surface. Replacing the Al ₃ Mg ₂ crystallized product with the pure aluminum;
A method for producing an aluminum alloy casting, characterized by comprising at least At least magnesium is a solid solution, and is an aluminum alloy casting containing a crystallized product of Al ₃ Mg ₂ ,
Magnesium dissolved in the aluminum alloy casting is 0.7 wt% or more,
The aluminum alloy casting, wherein the Al ₃ Mg ₂ crystallized product has an area ratio of 3.2% or less.

Images