JP4152095B2 - Method for producing semi-molten billet of aluminum alloy for transportation equipment - Google Patents

Description

【００２６】
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。
【００２７】
【表２】

【００２８】
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の良好なものを○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。
【００２９】
図２は、初晶α（Ａｌ）相の微細均一化が○評価の代表例写真を示す。
【００３０】
【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５０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 segregation and defects and a longer die life compared to conventional die casting methods. The billet casting method used for this is a method (method) in which electromagnetic and mechanical stirring is performed in the semi-melting temperature range in order to spheroidize the primary crystal α (Al) phase in the billet stage, known as the Pennecy Almax method A) or a method of adding a larger amount of Al-Ti-B than the amount normally added at the time of casting, and raising the temperature to the latter half melting temperature range to spheroidize 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.
Moreover, in method B, since a large amount of Al—Ti—B is added, quality instability occurs due to TiB ₂ sedimentation in the melting furnace, and the method of introducing strain by rolling in method C introduces uniform strain. In addition, the extrusion process is cumbersome due to room temperature extrusion, and it is difficult to introduce uniform strain, and both strain introduction methods require product processing after processing, and mass production and cost reduction cannot be achieved. there were.
[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-stage 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 the aluminum alloy for transportation equipment of the present application is as follows: Si 0.15 to 1.5 wt%, Mg 0.20 to 2.0 wt%, Zn 0.30 wt% or less, Fe1 .2 wt% or less, at least one of Ti 0.001 to 0.5 wt% and B 0.0001 to 0.5 wt%, Cu 0.05 to 0.50 wt%, Mn 0.10 to 1.0 wt% and Cr 0. An aluminum alloy containing at least one or more of 03 to 0.50 wt%, the balance being substantially composed of Al, and having a dendrite branch interval (DAS) of 200 μm or less is manufactured, and then a strain rate of 5 to 50 %, Processing introduction speed 50 mm / sec. In the following, at a temperature lower than the recrystallization temperature, processing strain is introduced by cold mold forging, and then the temperature is raised above the eutectic temperature or the solidus temperature, so that the liquid phase ratio becomes 20 to 80%. It is a method of holding and semi-melting.
[0007]
In this case, for homogenization of component segregation and release of casting stress, it is preferable to perform a homogenization treatment at a temperature of 450 to 600 ° C. for 1 to 10 hours before introducing processing strain.
[0008]
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.
[0009]
When Si component coexists with Mg component, Mg ₂ Si is precipitated by heat treatment and contributes to improvement of mechanical properties. However, if it is less than 0.15 wt%, the effect is small, whereas if it exceeds 1.5 wt%, Since cold forging workability deteriorates, it was set to 0.15 to 1.5 wt%.
[0010]
The Mg component contributes to the improvement of the mechanical properties by coexisting with the Si component, but the effect is small if it is less than 0.20 wt%, while the cold forgeability becomes worse if it exceeds 2.0 wt%. 0.20 to 2.0 wt%.
[0011]
The Zn component is set to 0.30 wt% or less in order to reduce the corrosion resistance.
[0012]
The Fe component produces an intermetallic compound with Al, and if it is contained in a large amount, it becomes an Al—Fe—Si compound and adversely affects elongation, toughness, and corrosion resistance.
[0013]
The Ti component refines the structure of the ingot and prevents the occurrence of ingot cracking, but the effect is small if it is less than 0.001 wt%, whereas the giant crystallized TiAl ₃ is present if it exceeds 0.5 wt%. Of 0.001 to 0.5 wt% because it promotes the generation of cracks and leads to cracks during cold forging and deterioration of mechanical properties of transport equipment parts.
[0014]
The B component also refines the ingot structure together with the Ti component and prevents the occurrence of ingot cracking, but the effect is small if it is less than 0.0001 wt%, and cracking during cold forging if it exceeds 0.5 wt%. In addition, the mechanical properties of transport equipment parts are reduced, so 0.0001 to 0.5 wt% was set.
[0015]
The Cu component is useful for improving the mechanical properties, but the effect is small if it is less than 0.05 wt%, and if it exceeds 0.50 wt%, it causes cracking during cold forging and a decrease in corrosion resistance. It was 0.50 wt%.
[0016]
The Mn component contributes to the improvement of strength and elongation by suppressing recrystallization and refining of recrystallized grains, but the effect is small if it is less than 0.10 wt%, and the ductility is lowered if it exceeds 1.0 wt%. 0.10 to 1.0 wt%.
[0017]
The Cr component, like the Mn component, suppresses recrystallization grain refinement or recrystallization and improves strength, elongation, and toughness. However, the effect is small at less than 0.03 wt%, and when it exceeds 0.50 wt%. Since it has an adverse effect on ductility, it was set to 0.03 to 0.50 wt%.
[0018]
Billets with a dendrite branch spacing (DAS) of 200 μm or less are cast. When the dendrite branch spacing (DAS) exceeds 200 μm, the primary α (Al) phase becomes uniform and fine spheroidized when heated to the semi-melting temperature range. Is difficult to obtain, and it takes time to perform the homogenization, so the dendrite branch interval (DAS) is set to 200 μm or less.
[0019]
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. 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 the removal of casting distortion is insufficient. However, at a processing temperature exceeding 600 ° C., partial melting occurs and workability during forging is also impaired. When the heating time exceeds 10 hours, the homogenization effect corresponding to the long heating time is not increased, and heating energy is lost. For this reason, the homogenization treatment conditions were heating at a temperature of 450 to 600 ° C. for 1 to 10 hours.
[0020]
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%, the introduction of strain 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. The change in the α (Al) phase size is not recognized, and cracks are generated 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.
[0021]
The processing introduction speed can be greatly increased by adding grain refinement and homogenization of the billet ingot. In terms of productivity, it is preferable that the processing introduction speed is as fast as possible. However, 50 mm / sec. Exceeds 50 mm / sec because cracks occur during forging, forged dead zones occur, and strain is not uniformly introduced. It was as follows. Further, when the billet temperature during cold mold forging is higher than the recrystallization temperature, the introduction of strain for the predetermined processing rate is insufficient, and even when the temperature is raised to the semi-melting temperature, the primary α (Al) phase has a granular structure. Therefore, it was set below the recrystallization temperature.
[0022]
Thereafter, the billet is heated to a temperature equal to or higher than the eutectic temperature or the solidus temperature and held at a temperature at which the liquid phase ratio becomes 20 to 80%, and semi-molten molding is performed. Uniform spheroidization of the (Al) phase cannot be achieved, and the deformation resistance of semi-molten molding is large, making it difficult to perform pressure molding. 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 equal to or higher than the eutectic temperature or the solidus temperature was set to 20 to 80%.
[0023]
【Example】
Specific examples of the present invention are shown below.
FIG. 1 is a schematic diagram of cold die forging used in the method of the present invention, in which reference numeral 1 denotes a forging die, 2 denotes a forging die punch, and 3 denotes an aluminum alloy billet.
[0024]
A molten metal was prepared so that each of Si, Mg, Zn, Fe, Ti, B, Cu, Mn, and Cr had a composition as shown in Table 1 below, and an aluminum alloy billet was cast by continuous casting.
[0025]
[Table 1]

[0026]
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. .
[0027]
[Table 2]

[0028]
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 had good moldability. . Regarding the moldability of the semi-melt molding, a good one was evaluated as “good”, and a poor one was determined as “poor”. The shape of the primary crystal α (Al) phase after semi-melt molding was evaluated as “◯” when spheroidization was observed, and “×” when the spheroidization was insufficient. In the fine homogenization of the primary crystal α (Al) phase after the semi-melt molding, the primary crystal α (Al) phase size 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.
[0029]
FIG. 2 shows a photograph of a representative example in which fine homogenization of the primary crystal α (Al) phase is evaluated as o.
[0030]
【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 mold forging.
FIG. 2 is a photomicrograph of a representative example of evaluation of fine homogenization of primary crystal α (Al) phase, with a magnification of 50 times.
[Explanation of symbols]
1 Forging die 2 Forging die punch 3 Aluminum alloy billet

Claims (3)

Si 0.15 to 1.5 wt%, Mg 0.20 to 2.0 wt%, Zn 0.30 wt% or less, Fe 1.2 wt% or less, and Ti 0.001 to 0.5 wt% and B0.0001 to 0.5 wt% and one or more, and Mn0.10～1.0Wt% and Cr0.03～0.50Wt% of at least one or more of, and a Cu0.05～0.50Wt%, the balance being inevitable impurities and Al An aluminum alloy having a dendrite branch interval of 200 μm or less is manufactured, and then a strain rate of 5 to 50% and a processing introduction speed of 50 mm / sec. In the following, at a temperature lower than the recrystallization temperature, processing strain is introduced by cold mold forging, and then the temperature is raised above the eutectic temperature or the solidus temperature, so that the liquid phase ratio becomes 20 to 80%. A method for producing a semi-molten molded billet of an aluminum alloy for transport equipment, characterized by being held and semi-molten processed. Si 0.15-1.5 wt%, Mg 0.20-2.0 wt%, Zn 0.30 wt% or less, Fe 1.2 wt% or less, and at least Ti0.001-0.5 wt% and B0.0001-0.5 wt% 1 type or more, Cu0.05-0.50 wt% and at least 1 sort (s) in Mn 0.10-1.0 wt%, Cr0.03-0.50 wt%, and balance is unavoidable impurities and Al An aluminum alloy having a dendrite branch interval of 200 μm or less is manufactured, and then a strain rate of 5 to 50% and a processing introduction speed of 50 mm / sec. In the following, at a temperature lower than the recrystallization temperature, processing strain is introduced by cold mold forging, and then the temperature is raised above the eutectic temperature or the solidus temperature, so that the liquid phase ratio becomes 20 to 80%. A method for producing a semi-molten molded billet of an aluminum alloy for transportation equipment, characterized by being held and semi-molten processed. The aluminum alloy for transportation equipment according to claim 1 or 2 , wherein the aluminum alloy is subjected to a homogenization treatment at a temperature of 450 to 600 ° C for 1 to 10 hours before the processing strain is introduced. Manufacturing method of semi-melt molded billet.

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