JP3676723B2 - Method for producing semi-melt molded billet of aluminum alloy for transportation equipment - Google Patents

Description

【００３０】
上記表１に示すアルミニウム合金ビレットを、表２に示す条件で処理し、半溶融成型の成型性、半溶融成型後の初晶α（Ａｌ）相の形状を評価した結果も表２に併記した。
【００３１】
【表２】

【００３２】
表２に示した加工歪導入時の成型性は、表２で示す成型条件で成型した際に割れが発生せず成型性が良好なものを○とし、割れが見られるものを×で判定した。半溶融成型の成型性は、良好なものを○とし、成型性の悪いものを×と判定した。半溶融成型後の初晶α（Ａｌ）相の形状は、球状化が認められているものを○とし、球状化が不充分であるものを×と判定した。半溶融成型後の初晶α（Ａｌ）相の微細均一化では、初晶α（Ａｌ）相のサイズが１００μｍ以下を○とし、１００μｍを越えるサイズのものを×と判定した。
【００３３】
図２は、初晶α（Ａｌ）相の微細均一化が○評価の代表例顕微鏡組織写真を示し、図３は、微細均一化が×評価の代表例顕微鏡組織写真を示している。
【００３４】
【発明の効果】
以上述べて来た如く、本発明方法によれば、従来の半溶融ビレットよりも工程が簡素化され低コスト化が図れる。また、得られる組織も初晶α（Ａｌ）相サイズが平均１００μｍ以下で、かつ初晶α（Ａｌ）相の面積率５０％の均一球状化組織となっており、自動車部材等の輸送機器用として使用が可能である。
【図面の簡単な説明】
【図１】冷間型枠鍛造の模式図である。
【図２】初晶α（Ａｌ）相の微細均一化が○評価の代表例の顕微鏡組織写真であり、倍率は９２倍である。
【図３】初晶α（Ａｌ）相の微細均一化が×評価の代表例の顕微鏡組織写真であり、倍率は９２倍である。
【符号の説明】
１ 鍛造用金型
２ 鍛造用金型ポンチ
３ アルミニウム合金ビレット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a semi-melt molded billet of an aluminum alloy used for transportation equipment.
[0002]
[Prior art]
The thixocast method using a semi-molten billet is a technology that has recently been attracting attention because it has advantages such as fewer casting segregations, gas entrainment, shrinkage and other defects, and a longer die life compared to conventional die casting methods. It is. The billet casting method used for this is a method in which the primary α (Al) phase is spheroidized in the billet stage, known as the Pennessy Almax method, so that electromagnetic stirring is performed in the semi-melting temperature range (method A). ) And a method of adding a larger amount of Al-Ti-B than the amount normally added at the time of casting, raising the temperature to the latter half melting temperature range, and spheroidizing the primary crystal α (Al) phase (Method B) There is. Further, a method (method C) in which strain is introduced by extrusion / rolling and then heated and spheroidized as in method B is widely known.
[0003]
[Problems to be solved by the invention]
In the case of the conventional semi-molten production method, the method A has a problem that the process is very complicated and the production cost is high.
Further, in method B, since a large amount of Al-Ti-B is added, quality instability occurs due to TiB2 sedimentation in the melting furnace, and the method of introducing strain by rolling in method C introduces uniform strain. Extrusion is difficult, and the working process is complicated due to room temperature extrusion, and it is difficult to introduce uniform strain. Both strain methods require product processing after processing, and mass production and cost reduction cannot be achieved. It was.
[0004]
Japanese Patent No. 2976073 discloses an improved method. That is, in the first item, there is described in “the step of deforming a fully solidified metal or metal alloy material at a temperature below its recrystallization temperature, heating the deformable material to cause recrystallization of the microstructure of the material. And partially melting the recrystallized structure to form independent particles in a liquid matrix that exhibits thixotropic behavior by raising the temperature of the material above its solidus temperature. It is a method including the step of
In this method, the deformation material is heated to cause recrystallization of the microstructure of the material, and heating that is called so-called two-step heating in which the temperature of the material is raised to a temperature above the solidus temperature. Is done. Such a method can be said to be an improved technique as compared with the conventional technique, but it still requires two steps of heating, and has a problem that the process is complicated and heating control is difficult.
[0005]
An object of the present invention is to provide a method for producing a semi-molten molded billet of an aluminum alloy for transportation equipment in which the disadvantages of the above prior art are eliminated, the process is simple and cost reduction can be promoted, and the resulting product is homogeneous. To do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the manufacturing method of the semi-molten molded billet of aluminum alloy for transportation equipment of the present application is Cu 4.0 wt% or less, Si 5.0 to 10 wt%, Mg 0.2 to 0.7 wt%, Zn 0.35 wt% Hereinafter, Fe 0.55 wt% or less, Mn 0.5 wt% or less, Ti 0.005 to 0.5 wt% and at least one of B 0.0001 to 0.5 wt%, with the balance being substantially composed of Al. An aluminum alloy having an eutectic Si average particle size of 40 μm or less and a dendrite branch interval (DAS) of 200 μm or less is manufactured, and then a strain rate of 5 to 50% and a processing introduction speed of 11 to 50 mm / sec. In this method, processing distortion is introduced by cold mold forging at a temperature of 200 ° C. or less, and then the temperature is raised to the eutectic temperature or higher, and the liquid phase ratio is maintained at a temperature of 20 to 80% and semi-molten molding is performed. It is.
[0007]
In this case, homogenization for 1 to 10 hours at a temperature of 450 to 550 ° C. is performed before processing strain is introduced in order to homogenize component segregation, spheroidization of eutectic Si and release of casting stress. Preferably it is done.
[0008]
Moreover, in order to achieve the said objective, the manufacturing method of the semi-molten shaping | molding billet of the aluminum alloy for transportation apparatuses of this application is Cu4.0 wt% or less, Si5.0-10 wt%, Mg0.2-0.7 wt%, Zn0. 35 wt% or less, Fe 0.55 wt% or less, Mn 0.5 wt% or less, at least one of Ti 0.005 to 0.5 wt% and B0.0001 to 0.5 wt%, Sr0.001 to 0.10 wt%, It contains at least one of Na 0.003-0.02 wt% and Sb 0.05-0.3 wt%, the balance is substantially composed of Al, and the average grain size of eutectic Si is 40 μm or less. An aluminum alloy having a dendrite branch interval (DAS) of 200 μm or less is manufactured, and then a strain rate of 5 to 50% and a processing introduction speed of 11 to 50 mm / sec. In this method, processing distortion is introduced by cold mold forging at a temperature of 200 ° C. or less, and then the temperature is raised to the eutectic temperature or higher, and the liquid phase ratio is maintained at a temperature of 20 to 80% and semi-molten molding is performed. It is.
[0009]
In this case, homogenization for 1 to 10 hours at a temperature of 450 to 550 ° C. is performed before processing strain is introduced in order to homogenize component segregation, spheroidization of eutectic Si and release of casting stress. Preferably it is done.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, various numerical limitation reasons such as numerical limitation of the amount of aluminum alloy components used in the present invention will be described in detail.
[0011]
The Cu component contributes to the strengthening of the matrix by solid solution hardening, but if it exceeds 4.0 wt%, the corrosion resistance deteriorates, so it was made 4.0 wt% or less.
[0012]
Si component improves the flow of hot water during casting, improves casting cracks and shrinkage cavities, and improves wear resistance. However, if the amount is less than 5.0 wt%, these effects are small, while 10 wt% is reduced. If it exceeds, the elongation and toughness deteriorate and the cold forging workability deteriorates.
[0013]
The Mg component precipitates Mg ₂ Si and contributes to improving the strength. However, if it is less than 0.2 wt%, the effect is small, while if it exceeds 0.7 wt%, the precipitation amount of Mg ₂ Si is excessive and the toughness is reduced. Therefore, the content was set to 0.2 to 0.7 wt%.
[0014]
The Zn component has an upper limit of 0.35 wt% in order to deteriorate the corrosion resistance.
[0015]
The Fe component becomes an Al—Fe—Si compound and adversely affects elongation, toughness, and corrosion resistance. However, if it is 0.55 wt% or less, substantially no adverse effect is observed.
[0016]
The Mn component improves the strength, elongation and toughness, but if it exceeds 0.5 wt%, the brittle intermetallic compound of the Al-Fe-Si-Mn compound increases, and the workability is adversely affected. % Was the upper limit.
[0017]
The Ti component refines the structure of the ingot and prevents the occurrence of ingot cracking, but the effect is less if it is less than 0.005 wt%, while the TiAl ₃ giant crystallized product if it exceeds 0.5 wt%. Of 0.005 to 0.5 wt% in order to promote generation of cracks and cause cracks during cold forging.
[0018]
The B component also refines the structure of the ingot together with the Ti component and prevents the occurrence of ingot cracking. However, the effect is small if it is less than 0.0001 wt%, while it is less than 0.5 wt% during cold forging. Since it causes cracking, the content was set to 0.0001 to 0.5 wt%.
[0019]
Sr component refines eutectic Si and improves impact value / elongation, but if its amount is less than 0.001 wt%, these effects are small, while if it exceeds 0.10 wt%, workability decreases, The amount is set to 0.001 to 0.10 wt% because it causes inclusion inclusion.
[0020]
The Na component refines the eutectic Si to improve the impact value and elongation. However, when the amount is less than 0.003 wt%, the effect is small. On the other hand, when the amount exceeds 0.02 wt%, the fluidity and degassing properties are reduced. Since it causes a decrease, the amount is set to 0.003 to 0.2 wt%.
[0021]
The Sb component also refines the eutectic Si, but if its amount is less than 0.05 wt%, it is insufficient to exhibit its effect, while if it exceeds 0.3 wt%, the toughness decreases, so its amount Was set to 0.05 to 0.3 wt%.
[0022]
A billet having an average particle size of eutectic Si of 40 μm or less and a dendrite branch interval (DAS) of 200 μm or less is cast, but the average particle size of eutectic Si exceeds 40 μm and the dendrite branch interval (DAS) is If it exceeds 200 μm, it becomes difficult to make the primary α (Al) phase into uniform fine spheroids when heated to the semi-melting temperature range, and it takes time for the homogenization process to take place. The average grain size of crystal Si was 40 μm or less, and the dendrite branch interval (DAS) was 200 μm or less.
[0023]
By homogenizing the billet obtained by casting, crystallized substances such as Al ₂ Cu and Mg ₂ Si crystallized at the crystal grain boundaries during casting are dissolved in the matrix. Further, the eutectic Si is spheroidized by homogenization treatment to reduce deformation resistance during cold forging. When the homogenization temperature is less than 450 ° C. or when the heating time does not reach 1 hour, sufficient solid solution cannot be obtained, and eutectic Si spheroidization and removal of casting strain are insufficient. However, if the processing temperature exceeds 550 ° C., eutectic melting occurs and the workability during forging is impaired. On the other hand, when the heating time exceeds 10 hours, no increase in homogenization effect corresponding to the long heating time is observed, resulting in a loss of heating energy. For this reason, the homogenization treatment conditions were heating at a temperature of 450 to 550 ° C. for 1 to 10 hours.
[0024]
Next, processing strain is introduced by cold forging so that the process can be simplified and strain is effectively introduced at a low processing rate, and strain is uniformly introduced into the entire forging billet. Formwork forging. When the strain rate is less than 5%, strain introduction is small, so even if the temperature is raised to the semi-melting temperature range, uniform spheroidization of the primary crystal α (Al) phase cannot be achieved. In addition to no change in the α (Al) phase size, cracks occur during cold forging, so the content was set to 5 to 50%. The distortion rate here is (L ₁ −L ₂ ) / L ₁ × 100 (%), where L ₁ is the original length of the forging billet and L ₂ is the length of the billet after forging. Defined.
[0025]
The processing introduction speed can be greatly increased by adding crystal grain refining and homogenization treatment of the billet ingot. From the viewpoint of productivity, the processing introduction speed is preferably as fast as possible. 11 mm / sec. The productivity is inferior at less than 50 mm / sec. Exceeds 50 mm, cracks occur during cold forging, forging dead zones occur, and strain is not uniformly introduced, so that the thickness is 11 to 50 mm / sec. It was. In addition, when the billet temperature during cold die forging exceeds 200 ° C., strain introduction for a predetermined processing rate becomes insufficient, and even when the temperature is raised to a semi-melting temperature, the primary α (Al) phase has a granular structure. Therefore, the temperature was set to 200 ° C. or lower.
[0026]
Thereafter, the billet is heated to a temperature equal to or higher than the eutectic temperature and held at a temperature at which the liquid phase ratio becomes 20 to 80%, and semi-molten molding is performed, but if the liquid phase ratio is less than 20%, the primary crystal α (Al) phase Uniform spheroidization cannot be achieved, and the deformation resistance of semi-molten molding is large, making pressure molding difficult. On the other hand, if it exceeds 80%, a molded product having a uniform structure cannot be obtained. For this reason, the liquid phase ratio in the semi-melting temperature range above the eutectic temperature was set to 20 to 80%.
[0027]
【Example】
Specific examples of the present invention are shown below.
FIG. 1 is a schematic view of cold mold forging used in the method of the present invention, in which 1 is a forging die, 2 is a forging die punch, and 3 is an aluminum alloy billet.
[0028]
A molten metal was prepared so that Cu, Si, Mg, Zn, Fe, Mn, Ti, B, and Sr each had a composition as shown in Table 1 below, and an aluminum alloy billet was cast by continuous casting.
[0029]
[Table 1]

[0030]
The aluminum alloy billet shown in Table 1 was processed under the conditions shown in Table 2, and the results of evaluating the moldability of semi-melt molding and the shape of the primary crystal α (Al) phase after semi-melt molding are also shown in Table 2. .
[0031]
[Table 2]

[0032]
The moldability at the time of introducing the processing strain shown in Table 2 was judged as “Good” when the mold did not generate a crack when molded under the molding conditions shown in Table 2 and the moldability was good, and “C” was judged as cracked. . Regarding the moldability of the semi-melt molding, a good one was evaluated as “good”, and a poor one was determined as “poor”. As for the shape of the primary crystal α (Al) phase after the semi-melt molding, a case where spheroidization was recognized was evaluated as ◯, and a case where the spheroidization was insufficient was determined as X. In the fine homogenization of the primary crystal α (Al) phase after semi-melt molding, the size of the primary crystal α (Al) phase was set to ○ when the size of the primary crystal α (Al) phase was 100 μm or less, and × when the size exceeded 100 μm.
[0033]
FIG. 2 shows a representative example microstructure photograph in which fine homogenization of the primary crystal α (Al) phase is evaluated as “good”, and FIG. 3 shows a representative example microstructure photograph in which fine homogenization is evaluated as “x”.
[0034]
【The invention's effect】
As described above, according to the method of the present invention, the process is simplified and the cost can be reduced as compared with the conventional semi-molten billet. The resulting structure also has a uniform spheroidized structure with an average primary crystal α (Al) phase size of 100 μm or less and an area ratio of primary crystal α (Al) phase of 50%. It can be used as
[Brief description of the drawings]
FIG. 1 is a schematic diagram of cold form forging.
FIG. 2 is a microstructural photograph of a representative example of evaluation where fine homogenization of the primary α (Al) phase is ○, and the magnification is 92 times.
FIG. 3 is a microstructural photograph of a representative example in which fine homogenization of the primary crystal α (Al) phase is x evaluation, and the magnification is 92 times.
[Explanation of symbols]
1 Forging die 2 Forging die punch 3 Aluminum alloy billet

Claims (4)

Cu 4.0 wt% or less, Si 5.0 to 10 wt%, Mg 0.2 to 0.7 wt%, Zn 0.35 wt% or less, Fe 0.55 wt% or less, Mn 0.5 wt% or less, Ti 0.005 to 0.5 wt%, and Aluminum alloy containing at least one of B0.0001 to 0.5 wt%, the balance being substantially composed of Al, the average grain size of eutectic Si being 40 μm or less, and the dendrite branch interval being 200 μm or less Next, the strain rate is 5 to 50%, the processing introduction speed is 11 to 50 mm / sec. At a billet temperature of 200 ° C. or less at the billet temperature, work distortion is introduced by cold forging, and then the temperature is raised to the eutectic temperature or higher, and the liquid phase ratio is kept at a temperature of 20 to 80% and semi-molten molding A method for producing a semi-molten molded billet of an aluminum alloy for transportation equipment.   The semi-molten molding of an aluminum alloy for transport equipment according to claim 1, wherein the aluminum alloy is manufactured and homogenized for 1 to 10 hours at a temperature of 450 to 550 ° C before introducing processing strain. Billet manufacturing method. Cu 4.0 wt% or less, Si 5.0 to 10 wt%, Mg 0.2 to 0.7 wt%, Zn 0.35 wt% or less, Fe 0.55 wt% or less, Mn 0.5 wt% or less, Ti 0.005 to 0.5 wt%, and Including at least one of B0.0001 to 0.5 wt% and at least one of Sr0.001 to 0.10 wt%, Na 0.003 to 0.02 wt% and Sb 0.05 to 0.3 wt% In addition, an aluminum alloy in which the balance is substantially composed of Al, the average particle diameter of eutectic Si is 40 μm or less, and the dendrite branch interval is 200 μm or less is manufactured, and then the strain rate is 5 to 50%, the processing introduction speed 11-50 mm / sec. Then, processing distortion is introduced by cold mold forging at a billet temperature of 200 ° C. or lower, and then the temperature is raised to the eutectic temperature or higher, and the liquid phase ratio is maintained at a temperature of 20 to 80%, and semi-molten molding is performed. A method for producing a semi-molten molded billet of an aluminum alloy for transportation equipment.   The semi-molten molding of an aluminum alloy for transportation equipment according to claim 3, wherein the aluminum alloy is manufactured and homogenized for 1 to 10 hours at a temperature of 450 to 550 ° C before introducing processing strain. Billet manufacturing method.

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