JP2021008961A - Aluminum alloy bolt - Google Patents
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本発明は、頭部と、該頭部の下端面から下方に伸びる首下部とを有し、頭部と首下部の境界領域に首下丸み部が形成されているアルミニウム合金製のボルトに関するものである。 The present invention relates to an aluminum alloy bolt having a head and a lower neck extending downward from the lower end surface of the head, and a rounded portion under the neck is formed in a boundary region between the head and the lower neck. Is.
一般に、機械的な構造物を構成する複数の部材の連結ないしは締結にはボルトが用いられるが、例えば自動車などといった軽量化の要求が強い構造物を構成する複数の部材の連結ないしは締結には、軽量であることからアルミニウム合金ボルトが広く用いられている。アルミニウム合金ボルトは、典型的には、工具等と係合させるための頭部と、該頭部の下端面から下方に伸びその一部又は全部にねじが切られた首下部ないしは軸部とを有している（例えば、特許文献１、２参照。）。 Generally, bolts are used for connecting or fastening a plurality of members constituting a mechanical structure, but for connecting or fastening a plurality of members constituting a structure having a strong demand for weight reduction such as an automobile, for example, Aluminum alloy bolts are widely used because of their light weight. An aluminum alloy bolt typically has a head for engaging with a tool or the like and a lower neck or shaft that extends downward from the lower end surface of the head and is partially or partially threaded. Has (see, for example, Patent Documents 1 and 2).
一方、アルミニウム合金は、一般に、強度が高くなればなるほど応力腐食割れへの感受性が高くなるといった特徴を有する。このため、アルミニウム合金ボルトを製造する場合、応力腐食割れへの対策が不可欠となる。そして、このような対策の１つとして、アルミニウム合金ボルトを形成しているアルミニウム合金材料の結晶粒を微細化することより耐応力腐食割れ性を強化するといった手法が知られている。 On the other hand, aluminum alloys generally have a characteristic that the higher the strength, the higher the sensitivity to stress corrosion cracking. Therefore, when manufacturing aluminum alloy bolts, it is indispensable to take measures against stress corrosion cracking. Then, as one of such measures, a method of strengthening the stress corrosion cracking resistance by refining the crystal grains of the aluminum alloy material forming the aluminum alloy bolt is known.
一般に、アルミニウム合金は、加工歪を付与した後に溶体化処理や時効処理などの熱処理を施せば、その結晶粒が微細化するといったことが知られている。したがって、アルミニウム合金ボルトを製造する際に、ボルト素材に加工歪を付与した上で熱処理を施せば、ボルト素材の結晶粒を微細化することができ、ひいてはアルミニウム合金ボルトの耐応力腐食割れ性を向上させることができる。 In general, it is known that the crystal grains of an aluminum alloy become finer when it is subjected to a heat treatment such as a solution treatment or an aging treatment after applying processing strain. Therefore, when manufacturing aluminum alloy bolts, if the bolt material is subjected to processing strain and then heat-treated, the crystal grains of the bolt material can be made finer, which in turn improves the stress corrosion cracking resistance of aluminum alloy bolts. Can be improved.
しかしながら、従来のボルトの製造手法では、首下丸み部（首下Ｒ部）ないしは首下部に十分に加工歪を付与することができず、これらの部位では熱処理を施しても結晶粒を十分に微細化することができない。このため、従来のアルミニウム合金ボルトでは、とくに応力集中部である首下丸み部に応力腐食割れが生じるおそれがあるといった問題がある。 However, with the conventional bolt manufacturing method, it is not possible to sufficiently apply processing strain to the rounded part under the neck (R part under the neck) or the lower part of the neck, and even if heat treatment is applied to these parts, the crystal grains are sufficiently produced. It cannot be miniaturized. For this reason, the conventional aluminum alloy bolt has a problem that stress corrosion cracking may occur particularly in the rounded portion under the neck which is a stress concentration portion.
本発明は、上記従来の問題を解決するためになされたものであって、首下丸み部ないしは首下部に十分に加工歪を付与することができ、この後の熱処理によりこれらの部位の結晶粒を微細化して、応力集中部における耐応力腐食割れ性を向上させることを可能にする手段を提供することを解決すべき課題とする。 The present invention has been made to solve the above-mentioned conventional problems, and it is possible to sufficiently impart processing strain to the rounded portion under the neck or the lower portion of the neck, and the crystal grains of these portions are subjected to the subsequent heat treatment. It is an issue to be solved to provide a means capable of improving the stress corrosion cracking resistance in the stress concentration portion by refining the above.
前記課題を解決するためになされた本発明に係る、頭部（ボルトヘッド）と、該頭部の下端面から下方に伸びる首下部（軸部）とを有し、頭部と首下部の境界領域に首下丸み部（首下Ｒ部）が形成されているアルミニウム合金製のボルトの製造方法は、線材作製工程と、歪付与工程と、ボルト素材作製工程と、熱処理工程と、ねじ形成工程とを有する。 It has a head (bolt head) and a lower neck (shaft) extending downward from the lower end surface of the head according to the present invention made to solve the above problems, and is a boundary between the head and the lower neck. The manufacturing method of the aluminum alloy bolt in which the rounded portion under the neck (R portion under the neck) is formed in the region is a wire rod manufacturing process, a strain applying process, a bolt material manufacturing process, a heat treatment process, and a screw forming process. And have.
そして、線材作製工程では、ボルトの形状及び寸法に相応ないしは対応するアルミニウム合金製の線材（円柱形部材）を作製する。歪付与工程では、線材の、首下丸み部が形成される部位を含む領域（該部位の上下の所定の領域）に、据え込み加工又は絞り加工（絞り成型加工）を施して加工歪を付与する。ボルト素材作製工程では、線材に塑性加工を施して、頭部と首下部と首下丸み部とを有するボルト素材を作製する。熱処理工程では、ボルト素材に熱処理（例えば、溶体化処理及び時効処理）を施す。ねじ形成工程は、ボルト素材作製工程の実施後において熱処理工程の前又は後に実施され、このねじ形成工程では、ボルト素材の首下部の一部又は全部の領域にねじ部を形成する。かかるボルトでは、頭部、首下丸み部（任意的に首下部の、首下丸み部との隣接領域）を構成するアルミニウム合金の第１結晶粒の平均結晶粒径は、首下部を構成するアルミニウム合金の第２結晶粒の平均結晶粒径より小さくなる。
ここで、「隣接領域」は、ボルトの首下丸み部に接する首下部のうち、第１結晶粒を有する領域をいう。図１０（ａ）に示すように、首下部の一部が隣接領域の場合もあれば、図１０（ｂ）に示すように、第１結晶粒の領域が広いときは、首下部の大部分が隣接領域となる場合もある。隣接領域は、図１１に示すように、少なくとも、ねじ端部からねじの呼び径Ｄと等しい距離の位置まで延びることが好ましい。構造物をボルトで締結する場合、頭部から、ねじ端部から距離Ｄの位置までの部分には大きな応力が集中するが、ねじ端部から距離Ｄの位置から、ねじ端部までの部分には、それほど大きな応力がかからないためである。
Then, in the wire rod manufacturing step, a wire rod (cylindrical member) made of an aluminum alloy corresponding to or corresponding to the shape and size of the bolt is manufactured. In the strain applying step, processing strain is applied by performing stationary processing or drawing processing (drawing processing) on the region of the wire rod including the portion where the rounded portion under the neck is formed (predetermined region above and below the portion). To do. In the bolt material manufacturing process, the wire rod is subjected to plastic working to produce a bolt material having a head, a lower part of the neck, and a rounded portion under the neck. In the heat treatment step, the bolt material is heat-treated (for example, solution treatment and aging treatment). The screw forming step is carried out after the bolt material manufacturing step and before or after the heat treatment step, and in this screw forming step, a screw portion is formed in a part or all of the lower neck portion of the bolt material. In such a bolt, the average crystal grain size of the first crystal grains of the aluminum alloy constituting the head and the rounded portion under the neck (optionally, the region adjacent to the rounded portion under the neck) constitutes the lower neck. It is smaller than the average crystal grain size of the second crystal grains of the aluminum alloy.
Here, the "adjacent region" refers to a region having a first crystal grain in the lower part of the neck in contact with the rounded portion under the neck of the bolt. As shown in FIG. 10A, a part of the lower part of the neck may be an adjacent region, and as shown in FIG. 10B, when the region of the first crystal grain is wide, most of the lower part of the neck. May be an adjacent area. As shown in FIG. 11, the adjacent region preferably extends from the screw end to a position equal to the nominal diameter D of the screw. When fastening a structure with bolts, a large amount of stress is concentrated from the head to the position from the screw end to the distance D, but from the position from the screw end to the distance D to the screw end. This is because a large amount of stress is not applied.
本発明に係るボルトの製造方法においては、線材作製工程で、横断面の直径が首下部の横断面の直径と同一である円柱形の線材を作製し、歪付与工程で、線材の頭部が形成される側（上側）の端部から首下丸み部が形成される部位より下側の所定の部位まで、頭部を形成するための据え込み加工を施し、この後首下丸み部が形成される部位から前記所定の部位まで絞り加工を施すようにしてもよい（第１の実施態様）。 In the method for manufacturing a bolt according to the present invention, a cylindrical wire whose cross-sectional diameter is the same as the diameter of the cross section of the lower part of the neck is manufactured in the wire rod manufacturing step, and the head of the wire rod is formed in the strain applying step. From the end on the side to be formed (upper side) to a predetermined part below the part where the rounded part under the neck is formed, an embedding process is performed to form the head, and then the rounded part under the neck is formed. The drawing process may be performed from the portion to be formed to the predetermined portion (first embodiment).
本発明に係るボルトの製造方法においては、線材作製工程で、横断面の直径が首下部の横断面の直径より大きい円柱形の線材を作製し、歪付与工程で、首下丸み部が形成される部位より上側の部位から線材の下端部まで、首下部を形成するための絞り加工を施し、この後に線材の頭部が形成される側（上側）の端部から首下丸み部が形成される部位より下側の所定の部位まで、頭部を形成するための据え込み加工を施すようにしてもよい（第２の実施態様）。この場合、絞り加工と据え込み加工とを複数回繰り返して実施するようにしてもよい（第３の実施態様）。 In the method for manufacturing a bolt according to the present invention, a cylindrical wire whose cross-sectional diameter is larger than the diameter of the cross section of the lower part of the neck is manufactured in the wire rod manufacturing step, and a rounded portion under the neck is formed in the strain applying step. From the part above the part to the lower end of the wire, drawing processing is performed to form the lower part of the neck, and after that, the rounded part under the neck is formed from the end on the side (upper side) where the head of the wire is formed. The embedding process for forming the head may be performed up to a predetermined portion below the portion to be formed (second embodiment). In this case, the drawing process and the stationary process may be repeated a plurality of times (third embodiment).
本発明に係るアルミニウム合金製のボルトによれば、歪付与工程で首下丸み部ないしは首下部に十分に加工歪を付与することができ、この後の熱処理工程で溶体化処理や時効処理などといった熱処理を施すことで、これらの部位のアルミニウム合金材料の結晶粒が微細化される。このため、首下丸み部等の応力集中部における耐応力腐食割れ性を大幅に向上させることができ、ボルトの信頼性を高めることができる。 According to the aluminum alloy bolt according to the present invention, sufficient processing strain can be applied to the rounded portion under the neck or the lower part of the neck in the strain applying step, and in the subsequent heat treatment step, solution treatment, aging treatment, etc. By applying the heat treatment, the crystal grains of the aluminum alloy material at these parts are made finer. Therefore, the stress corrosion cracking resistance in the stress concentration portion such as the rounded portion under the neck can be significantly improved, and the reliability of the bolt can be improved.
以下、添付の図面を参照しつつ、本発明の実施形態を具体的に説明する。まず、本願出願人に係るアルミニウム合金製のボルトの普通の製造方法を説明する。
図１（ａ）〜（ｃ）は、横断面が円形であり、その直径が製造すべきボルトの首下部の横断面の直径と同一であるアルミニウム合金製のコイル材からボルトを製造するための普通の手法を示している。
Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. First, an ordinary method for manufacturing an aluminum alloy bolt according to the applicant of the present application will be described.
1 (a) to 1 (c) are for manufacturing a bolt from a coil material made of an aluminum alloy having a circular cross section and having the same diameter as the diameter of the cross section of the lower part of the neck of the bolt to be manufactured. It shows the usual method.
このボルトの製造方法によれば、図１（ａ）に示すように、アルミニウム合金製のコイル材（図示せず）を、製造すべきボルトの形状及び寸法に相応ないしは対応する長さに切断して円柱形の線材１（円柱形部材）を作製し、この線材１を所定の形状（後記の大径部及びテーパ部に対応する形状）を有する金型２内に配置する。なお、この種のボルトに適したアルミニウム合金としては、例えば６０００系（Al-Mg-Si）のアルミニウム合金（ＪＩＳ規格ではＡ６０００番台）や７０００系（Al-Zn-Mg-(Cu)）のアルミニウム合金（ＪＩＳ規格ではＡ７０００番台）などを用いることができる。６０００系、７０００系のアルミニウム合金の引張り強さは、それぞれ、４００ＭＰａ以上、５００ＭＰａ以上となる。 According to this bolt manufacturing method, as shown in FIG. 1A, an aluminum alloy coil material (not shown) is cut to a length corresponding to or corresponding to the shape and size of the bolt to be manufactured. A cylindrical wire rod 1 (cylindrical member) is produced, and the wire rod 1 is placed in a mold 2 having a predetermined shape (shape corresponding to a large diameter portion and a tapered portion described later). Examples of aluminum alloys suitable for this type of bolt include 6000 series (Al-Mg-Si) aluminum alloys (A6000 series in JIS standard) and 7000 series (Al-Zn-Mg- (Cu)) aluminum. An alloy (A7000 series in JIS standard) or the like can be used. The tensile strengths of the 6000 series and 7000 series aluminum alloys are 400 MPa or more and 500 MPa or more, respectively.
本明細書では、線材ないしはボルト素材における位置関係を簡潔に示すため、適宜、これらの中心軸方向に関して頭部が形成される側を「上」といい、これと反対側（首下部ないしは軸部が形成される側）を「下」ということにする。本明細書において、コイル材、線材、ボルト素材等における「横断面」は、これらの中心軸と垂直な面で切断した断面を意味する。また、本明細書において「首下部」は、頭部の下端面からボルト下端部まで伸びる軸部（ねじ部及び非ねじ部を含む）を意味する。図１において（図２〜図６も同様）、仮想線Ｌは、後で説明する首下丸み部８の位置ないしは該首下丸み部８に対応する位置を示している。 In the present specification, in order to briefly show the positional relationship between the wire rod or the bolt material, the side on which the head is formed with respect to the central axis direction thereof is appropriately referred to as "upper", and the opposite side (lower neck or shaft portion). The side on which is formed) is referred to as "bottom". In the present specification, the "cross section" of the coil material, wire material, bolt material, etc. means a cross section cut on a plane perpendicular to the central axis thereof. Further, in the present specification, the "lower neck" means a shaft portion (including a threaded portion and a non-threaded portion) extending from the lower end surface of the head to the lower end of the bolt. In FIG. 1 (the same applies to FIGS. 2 to 6), the virtual line L indicates the position of the lower neck rounded portion 8 or the position corresponding to the lower neck rounded portion 8, which will be described later.
そして、金型２内に配置された線材１に対して、ハンマー等（図示せず）で下向きの押圧力を加えて据え込み加工を施し、線材１の上端近傍部を塑性変形させ、図１（ｂ）に示すように、大径部３及びテーパ部４を形成する。なお、これらの大径部３及びテーパ部４は、後で説明するように最終的には頭部６（ボルトヘッド）となる。一方、線材１のテーパ部４より下側の部分は塑性変形せず、そのままの状態で首下部５となる。 Then, the wire rod 1 arranged in the mold 2 is subjected to a stationary process by applying a downward pressing force with a hammer or the like (not shown) to plastically deform the portion near the upper end of the wire rod 1, and FIG. As shown in (b), the large diameter portion 3 and the tapered portion 4 are formed. The large diameter portion 3 and the tapered portion 4 will eventually become the head 6 (bolt head) as will be described later. On the other hand, the portion of the wire rod 1 below the tapered portion 4 is not plastically deformed and becomes the lower neck portion 5 as it is.
さらに、大径部３とテーパ部４とに頭部成型加工（プレス加工）を施して、図１（ｃ）に示すように、頭部６と首下部５とを備えたボルト素材７を作製する。その際、頭部６と首下部５の境界領域に首下丸み部８（首下Ｒ部）が形成される。なお、この製造方法においては、線材１の直径ｄ１と首下部５の直径ｄ２は同一である。この後、首下部５の周面の一部又は全部に、転造等によりねじが形成され、ボルトが完成する。この普通のボルトの製造方法では、図１（ｂ）、（ｃ）中のＲ１、Ｒ２で示す領域では加工歪は比較的小さくなる。 Further, the large diameter portion 3 and the tapered portion 4 are subjected to head molding processing (press processing) to produce a bolt material 7 having a head 6 and a lower neck 5 as shown in FIG. 1 (c). To do. At that time, a rounded portion 8 under the neck (R portion under the neck) is formed in the boundary region between the head 6 and the lower neck 5. In this manufacturing method, the diameter d 1 of the wire rod 1 and the diameter d 2 of the lower neck 5 are the same. After that, a screw is formed on a part or all of the peripheral surface of the lower part of the neck 5 by rolling or the like, and the bolt is completed. In this ordinary bolt manufacturing method, the machining strain is relatively small in the regions shown by R1 and R2 in FIGS. 1B and 1C.
図１（ｄ）〜（ｆ）は、それぞれ、図１（ａ）〜（ｃ）に示す線材１又はボルト素材７に、熱処理（溶体化処理及び時効処理）を施した場合のアルミニウム合金材料の結晶粒の大きさを模式的に示している。ただし、実際のボルトの製造工程では、このような個別の熱処理は施さず、ボルト素材７を作製した後に熱処理を施す。なお、このような結晶粒径の変化は、加工歪の付与だけでは起こらず、熱処理によって生じる。図１（ｄ）〜（ｆ）において、線材１内又はボルト素材７内のおおむね円形の多数の図形は、アルミニウム合金材料の結晶粒の大ききを比喩的ないしは誇張的に示している。これらの円形の図形は、線材１内又はボルト素材７内の各部位における結晶粒の相対的な大小関係を示すためのものであり、結晶粒の実際の寸法を示すものではないのはもちろんである。なお、このような結晶粒の大きさの表示は、後で説明する図２〜図６においても同様である。 1 (d) to 1 (f) show the aluminum alloy material obtained by subjecting the wire rod 1 or the bolt material 7 shown in FIGS. 1 (a) to 1 (c) to heat treatment (solution treatment and aging treatment), respectively. The size of the crystal grains is schematically shown. However, in the actual bolt manufacturing process, such individual heat treatment is not performed, but the heat treatment is performed after the bolt material 7 is manufactured. It should be noted that such a change in crystal grain size does not occur only by applying processing strain, but occurs by heat treatment. In FIGS. 1 (d) to 1 (f), a large number of substantially circular figures in the wire rod 1 or the bolt material 7 show the size of the crystal grains of the aluminum alloy material figuratively or exaggeratedly. Of course, these circular figures are for showing the relative magnitude relationship of the crystal grains in each part in the wire rod 1 or the bolt material 7, and do not show the actual dimensions of the crystal grains. is there. The display of the size of such crystal grains is the same in FIGS. 2 to 6 described later.
このボルトの製造方法によれば、首下部５には塑性変形を伴う加工は施されないので、この領域ではアルミニウム合金材料の流動は起こらず、これらの領域には加工歪を付与することができない。このため、図１（ｆ）から明らかなとおり、熱処理を施しても、ボルト素材７の首下部５では、アルミニウム合金材料の結晶粒を微細化することができず（結晶粒径大）、耐応力腐食割れ性を確保することができない。また、首下丸み部８（ないしは、その隣接領域）では、ある程度の加工歪を付与することができるので、熱処理を施すことによりアルミニウム合金材料の結晶粒を多少は微細化することができるが（結晶粒径中）、耐応力腐食割れ性を十分に確保することはできない。なお、頭部６の大部分（下端近傍部以外の部分）では、アルミニウム合金材料の結晶粒は十分に微細化される（結晶粒径小）。 According to this bolt manufacturing method, since the lower part of the neck 5 is not processed with plastic deformation, the aluminum alloy material does not flow in this region, and processing strain cannot be applied to these regions. Therefore, as is clear from FIG. 1 (f), even if the heat treatment is performed, the crystal grains of the aluminum alloy material cannot be refined at the lower neck 5 of the bolt material 7 (large crystal grain size), and the resistance to resistance. Stress corrosion cracking cannot be ensured. Further, since a certain amount of processing strain can be applied to the rounded portion 8 under the neck (or an adjacent region thereof), the crystal grains of the aluminum alloy material can be made slightly finer by performing the heat treatment ( Sufficient stress corrosion cracking resistance cannot be ensured (in grain size). In most of the head portion 6 (a portion other than the portion near the lower end), the crystal grains of the aluminum alloy material are sufficiently finely divided (small crystal grain size).
図２（ａ）〜（ｄ）は、横断面が円形であり、その直径が製造すべきボルトの首下部の直径より大きいアルミニウム合金製のコイル材からボルトを製造するための本願出願人に係るもう１つの普通の手法を示している。このボルトの製造方法によれば、図２（ａ）に示すように、アルミニウム合金製のコイル材（図示せず）を、製造すべきボルトの形状及び寸法に相応ないしは対応する長さに切断して円柱形の線材１１を作製する。ここで、コイル材には、その円形の横断面の直径が製造すべきボルトの首下部の横断面の直径より大きいものが用いられる。 FIGS. 2 (a) to 2 (d) relate to the applicant for manufacturing a bolt from a coil material made of an aluminum alloy having a circular cross section and a diameter thereof larger than the diameter of the lower neck of the bolt to be manufactured. It shows another common technique. According to this bolt manufacturing method, as shown in FIG. 2A, an aluminum alloy coil material (not shown) is cut to a length corresponding to or corresponding to the shape and dimensions of the bolt to be manufactured. To produce a cylindrical wire rod 11. Here, a coil material having a circular cross-sectional diameter larger than the cross-sectional diameter of the lower part of the neck of the bolt to be manufactured is used.
次に、図２（ｂ）に示すように、線材１１の、首下丸み部（ないしは、頭部と首下部の境界領域）に対応する部位から下端部にわたって絞り加工（絞り成型加工）を施して首下部１２を形成した上で、この線材１１を所定の形状を有する金型１３内に配置する。この場合、絞り加工が施される部位では、横断面の直径がｄ３である線材１１が縮径され、首下部１２の横断面の直径ｄ４はｄ３よりも小さくなる。このため、首下部１２内ではアルミニウム合金材料の流動が起こり、首下部１２に十分な加工歪を付与することができる。 Next, as shown in FIG. 2B, drawing processing (drawing processing) is performed from the portion of the wire rod 11 corresponding to the rounded portion under the neck (or the boundary region between the head and the lower part of the neck) to the lower end portion. After forming the lower part of the neck 12, the wire rod 11 is arranged in a mold 13 having a predetermined shape. In this case, the wire rod 11 having a cross-sectional diameter of d 3 is reduced in diameter at the portion to be drawn, and the cross-sectional diameter d 4 of the lower neck 12 is smaller than d 3 . Therefore, the aluminum alloy material flows in the lower part of the neck 12, and sufficient processing strain can be applied to the lower part of the neck 12.
そして、金型１３内に配置された線材１１に対して、ハンマー等（図示せず）で下向きの押圧力を加えて据え込み加工を施し、線材１１の上端近傍部（絞り加工が施されていない部分の上側部分）を塑性変形させ、図２（ｃ）に示すように、大径部１４及びテーパ部１５を形成する。なお、テーパ部１５と首下部１２の間には、絞り加工が施されていない未加工部１６が存在する。さらに、大径部１４とテーパ部１５と未加工部１６とに頭部成型加工（プレス加工）を施して、図２（ｄ）に示すように、頭部１７と首下部１２とを備えたボルト素材１８を作製する。その際、頭部１７と首下部１２の境界領域に首下丸み部１９（首下Ｒ部）が形成される。この後、首下部１２の周面の一部又は全部に、転造等によりねじが形成され、ボルトが完成する。この普通のボルトの製造方法では、図２（ｃ）、（ｄ）中のＲ３、Ｒ４で示す領域では加工歪は比較的小さくなる。 Then, a downward pressing force is applied to the wire rod 11 arranged in the mold 13 with a hammer or the like (not shown) to perform stationary processing, and a portion near the upper end of the wire rod 11 (drawing is performed). The upper portion of the non-existent portion) is plastically deformed to form the large diameter portion 14 and the tapered portion 15 as shown in FIG. 2 (c). There is an unprocessed portion 16 that has not been drawn between the tapered portion 15 and the lower neck portion 12. Further, the large diameter portion 14, the tapered portion 15, and the unprocessed portion 16 are subjected to head molding processing (press processing), and as shown in FIG. 2 (d), the head 17 and the lower neck portion 12 are provided. The bolt material 18 is produced. At that time, a rounded portion 19 under the neck (R portion under the neck) is formed in the boundary region between the head 17 and the lower neck 12. After that, a screw is formed on a part or all of the peripheral surface of the lower part of the neck 12 by rolling or the like, and the bolt is completed. In this ordinary bolt manufacturing method, the machining strain is relatively small in the regions shown by R3 and R4 in FIGS. 2C and 2D.
図２（ｅ）〜（ｈ）は、それぞれ、図２（ａ）〜（ｄ）に示す線材１１又はボルト素材１８に熱処理（溶体化処理及び時効処理）を施した場合のアルミニウム合金材料の結晶粒の大きさを、図１（ｄ）〜（ｆ）と同様の形態で比喩的ないしは誇張的に示している。図２（ｈ）から明らかなとおり、このボルトの製造方法によれば、ボルト素材１８の首下部１２には絞り加工によって加工歪を付与することができ、この後の熱処理により首下部１２のアルミニウム合金材料の結晶粒を微細化することができる（結晶粒径小）。 2 (e) to 2 (h) show the crystals of the aluminum alloy material when the wire rod 11 or the bolt material 18 shown in FIGS. 2 (a) to 2 (d) is heat-treated (solution treatment and aging treatment), respectively. The grain size is shown figuratively or exaggerated in the same form as in FIGS. 1 (d) to 1 (f). As is clear from FIG. 2 (h), according to this bolt manufacturing method, processing strain can be applied to the lower neck 12 of the bolt material 18 by drawing, and the aluminum of the lower neck 12 is subjected to the subsequent heat treatment. The crystal grains of the alloy material can be made finer (small crystal grain size).
しかしながら、首下丸み部１９（ないしは、その隣接領域）では、十分に加工歪を付与することができないので、熱処理を施してもアルミニウム合金材料の結晶粒を十分には微細化することができず（結晶粒径中）、耐応力腐食割れ性を十分には確保することができない。なお、頭部１７の大部分（下端近傍部以外の部分）では、アルミニウム合金材料の結晶粒は十分に微細化される（結晶粒径小）。 However, since the processing strain cannot be sufficiently applied to the rounded portion 19 under the neck (or the adjacent region thereof), the crystal grains of the aluminum alloy material cannot be sufficiently refined even if heat treatment is performed. (In crystal grain size), stress corrosion cracking resistance cannot be sufficiently ensured. In most of the head portion 17 (a portion other than the portion near the lower end), the crystal grains of the aluminum alloy material are sufficiently finely divided (crystal grain size is small).
以下、本発明に係るアルミニウム合金製のボルトの製造方法を説明する。
＜実施形態１＞
図３（ａ）〜（ｄ）は、本発明の実施形態１に係るボルトの製造方法を示している。このボルトの製造方法は、図１（ａ）〜（ｆ）に示す普通のボルトの製造方法と同様に、横断面が円形であり、その直径が製造すべきボルトの首下部の横断面の直径と同一であるアルミニウム合金製のコイル材からボルトを製造する。すなわち、実施形態１に係るボルトの製造方法は、図１（ａ）〜（ｆ）に示す普通のボルトの製造方法を改良したものである。
Hereinafter, a method for manufacturing an aluminum alloy bolt according to the present invention will be described.
<Embodiment 1>
3 (a) to 3 (d) show a method for manufacturing a bolt according to the first embodiment of the present invention. The method for manufacturing this bolt is the same as the method for manufacturing ordinary bolts shown in FIGS. 1A to 1F, and the cross section is circular, and the diameter thereof is the diameter of the cross section of the lower part of the neck of the bolt to be manufactured. Manufacture bolts from the same aluminum alloy coil material as. That is, the bolt manufacturing method according to the first embodiment is an improvement of the ordinary bolt manufacturing method shown in FIGS. 1A to 1F.
そして、実施形態１に係るボルトの製造方法では、図１（ａ）〜（ｆ）に示す普通のボルトの製造方法に比べて、線材の据え込み加工を施す部分を、線材の伸びる方向（上下方向）に長くしている。すなわち、普通のボルトの製造方法に比べて、線材を下向きに深く据え込むようにしている。具体的には、首下丸み部に対応する部位よりやや下側の部位まで、アルミニウム合金材料が塑性流動する程度に線材に据え込み加工を施すようにしている。 Then, in the bolt manufacturing method according to the first embodiment, as compared with the ordinary bolt manufacturing methods shown in FIGS. 1 (a) to 1 (f), the portion where the wire rod is embedded is in the direction in which the wire rod extends (up and down). It is lengthened in the direction). That is, the wire rod is installed deeply downward as compared with the ordinary bolt manufacturing method. Specifically, the wire rod is embedded to the extent that the aluminum alloy material plastically flows to a portion slightly below the portion corresponding to the rounded portion under the neck.
実施形態１に係るボルトの製造方法においては、図３（ａ）に示すように、アルミニウム合金製のコイル材（図示せず）を、製造すべきボルトの形状及び寸法に相応ないしは対応する長さに切断して円柱形の線材２１を作製し、この線材２１を所定の形状を有する金型２２内に配置する。そして、線材２１にハンマー等（図示せず）で下向きの押圧力を加えて据え込み加工を施し、線材２１の上端近傍部を塑性変形させ、図３（ｂ）に示すように、大径部２３及びテーパ部２４を形成する。なお、テーパ部２４より下側の塑性変形しない部分は首下部２５となる。この場合、大径部２３には加工歪が十分に付与される。なお、テーパ部２４の下部では、加工歪はやや小さくなる。図３（ｂ）から明らかなとおり、この大径部２３の中心軸方向（上下方向）の長さは、図１（ｂ）に示す普通のボルトの製造方法における大径部３の中心軸方向の長さに比べてかなり長くなっている。 In the method for manufacturing a bolt according to the first embodiment, as shown in FIG. 3A, a coil material made of an aluminum alloy (not shown) has a length corresponding to or corresponding to the shape and size of the bolt to be manufactured. A cylindrical wire rod 21 is produced, and the wire rod 21 is placed in a mold 22 having a predetermined shape. Then, a downward pressing force is applied to the wire rod 21 with a hammer or the like (not shown) to perform stationary processing, and the portion near the upper end of the wire rod 21 is plastically deformed, and as shown in FIG. 3B, a large diameter portion is formed. 23 and the tapered portion 24 are formed. The portion below the tapered portion 24 that is not plastically deformed is the lower neck portion 25. In this case, processing strain is sufficiently applied to the large diameter portion 23. At the lower part of the tapered portion 24, the machining strain becomes slightly smaller. As is clear from FIG. 3 (b), the length in the central axial direction (vertical direction) of the large diameter portion 23 is the central axial direction of the large diameter portion 3 in the ordinary bolt manufacturing method shown in FIG. 1 (b). It is considerably longer than the length of.
次に、図３（ｃ）に示すように、大径部２３の下側部分及びテーパ部２４に絞り加工を施して縮径する。なお、大径部２３の上側部分は縮径されず、非縮径部２３ａとなる。この絞り加工により、絞り加工が施されなかった非縮径部２３ａの下側には、比較的縮径の度合いが小さい第１縮径部２６と、首下部２５と同一径となるまで縮径されて該首下部２５の一部をなす第２縮径部２５ａとが形成される。これにより、図１（ａ）〜（ｆ）に示す普通のボルトの製造方法ではアルミニウム合金材料の流動が起こらなかった、テーパ部２４に対応する部位、すなわち最終的に首下丸み部となる部分ないしはその隣接領域にもアルミニウム合金材料の流動を起こさせて十分に加工歪を付与することができる。 Next, as shown in FIG. 3C, the lower portion of the large diameter portion 23 and the tapered portion 24 are drawn to reduce the diameter. The upper portion of the large diameter portion 23 is not reduced in diameter and becomes a non-reduced diameter portion 23a. By this drawing process, the diameter of the first reduced diameter portion 26, which has a relatively small degree of diameter reduction, and the diameter of the first reduced diameter portion 26, which is relatively small, are reduced to the same diameter as the lower neck portion 25 on the lower side of the non-reduced diameter portion 23a that has not been drawn. A second reduced diameter portion 25a forming a part of the lower neck portion 25 is formed. As a result, the portion corresponding to the tapered portion 24, that is, the portion that finally becomes the rounded portion under the neck, in which the flow of the aluminum alloy material did not occur in the ordinary bolt manufacturing methods shown in FIGS. 1 (a) to 1 (f). Alternatively, the aluminum alloy material can flow in the adjacent region to sufficiently impart processing strain.
前記のとおり、このボルトの製造方法では、図１（ａ）〜（ｆ）に示す普通のボルトの製造方法に比べて線材２１を下向きに深く据え込むようにしているので、頭部の形成に必要な量を超えて余分に据え込み加工を施すことになる。すなわち、完成製品であるボルトには不必要なものである、過剰に据え込んだ比較的大径の部分が生じる。そこで、この大径の部分に対して絞り加工を施すようにしている。このように絞り加工が施される部分では、据え込み加工及び絞り加工の２度の加工により加工歪を付与することができるので、熱処理後におけるアルミニウム合金材料の結晶粒の微細化をより促進することができる（結晶粒径小）。 As described above, in this bolt manufacturing method, the wire rod 21 is set deeply downward as compared with the ordinary bolt manufacturing methods shown in FIGS. 1 (a) to 1 (f), so that it is necessary for forming the head. Excessive amount of embedding processing will be performed. That is, there is an over-installed, relatively large-diameter portion that is unnecessary for the finished bolt. Therefore, drawing is performed on this large diameter portion. In the portion where the drawing process is performed in this way, processing strain can be applied by two processes of the stationary processing and the drawing process, so that the refinement of the crystal grains of the aluminum alloy material after the heat treatment is further promoted. Can be (small grain size).
さらに、非縮径部２３ａと第１縮径部２６とに頭部成型加工（プレス加工）を施して、図３（ｄ）に示すように、頭部２７と首下部２５（第２縮径部２５ａを含む）とを備えたボルト素材２８を作製する。その際、頭部２７と首下部２５（第２縮径部２５ａ）の境界領域に首下丸み部２９（首下Ｒ部）が形成される。この後、首下部２５の一部又は全部の周面に、転造等によりねじが形成され、ボルトが完成する。このボルトの製造方法では、図３（ｂ）中のＲ５で示す領域では据え込み加工により加工歪が付与され、図３（ｃ）中のＲ６で示す領域では絞り加工により加工歪が付与される。かくして、図３（ｄ）中のＲ７で示す領域では、据え込み加工及び絞り加工により加工歪が付与されるので、加工歪は非常に大きくなる。 Further, the non-diameter portion 23a and the first diameter reduction portion 26 are subjected to head molding processing (press processing), and as shown in FIG. 3D, the head 27 and the lower neck portion 25 (second diameter reduction portion) are subjected to head molding processing (press processing). A bolt material 28 including the portion 25a) is produced. At that time, the lower neck rounded portion 29 (lower neck R portion) is formed in the boundary region between the head 27 and the lower neck 25 (second reduced diameter portion 25a). After that, a screw is formed on a part or all of the peripheral surface of the lower part of the neck 25 by rolling or the like, and the bolt is completed. In this bolt manufacturing method, machining strain is applied by embossing in the region shown by R5 in FIG. 3 (b), and machining strain is applied by drawing in the region shown by R6 in FIG. 3 (c). .. Thus, in the region shown by R7 in FIG. 3D, the machining strain is applied by the stationary machining and the drawing machining, so that the machining strain becomes very large.
図３（ｅ）〜（ｈ）は、それぞれ、図３（ａ）〜（ｄ）に示す線材２１又はボルト素材２８に熱処理（溶体化処理及び時効処理）を施した場合のアルミニウム合金材料の結晶粒の大きさを、図１（ｄ）〜（ｆ）と同様の形態で比喩的ないしは誇張的に示している。図３（ｈ）から明らかなとおり、このボルトの製造方法によれば、熱処理後には首下丸み部２９（ないしは、その隣接領域）でアルミニウム合金材料の結晶粒（第１結晶粒）を十分に微細化することができ（結晶粒径小）、首下丸み部２９の耐応力腐食割れ性を十分に確保することができる。さらに、首下部２５の上側部分（すなわち、第２縮径部２５ａ）でも、熱処理によりアルミニウム合金材料の結晶粒を十分に微細化することができ、首下部２５の上側部分の耐応力腐食割れ性を確保することができる。なお、頭部２７でも、アルミニウム合金材料の結晶粒は十分に微細化される（結晶粒径小）。頭部２７、首下丸み部２９、首下部２５の上部部分２５ａのアルミニウム合金の結晶粒の平均結晶粒径は、約４０μｍ以下、好適には、約１０μｍ〜約３０μｍ、より好適には約１０μｍ〜約２０μｍとなり、首下部２５（上部部分２５ａを除く）の結晶粒の平均結晶粒径（例えば１５０μｍ）より小さくなっている。ここでは、首下部２５の上部部分２５ａも微細化したが、頭部２７と首下丸み部２９のみ微細化されても良い（以下の実施の形態において同様）。 3 (e) to 3 (h) show the crystals of the aluminum alloy material when the wire rod 21 or the bolt material 28 shown in FIGS. 3 (a) to 3 (d) is heat-treated (solution treatment and aging treatment), respectively. The grain size is shown figuratively or exaggerated in the same form as in FIGS. 1 (d) to 1 (f). As is clear from FIG. 3 (h), according to the method for manufacturing this bolt, after the heat treatment, the crystal grains (first crystal grains) of the aluminum alloy material are sufficiently formed in the rounded portion 29 (or the adjacent region thereof) under the neck. It can be miniaturized (grain grain size is small), and the stress corrosion cracking resistance of the rounded portion 29 under the neck can be sufficiently ensured. Further, even in the upper portion of the lower neck portion 25 (that is, the second reduced diameter portion 25a), the crystal grains of the aluminum alloy material can be sufficiently refined by heat treatment, and the stress corrosion cracking resistance of the upper portion of the lower neck portion 25 is resistant. Can be secured. Even at the head 27, the crystal grains of the aluminum alloy material are sufficiently finely divided (crystal grain size is small). The average crystal grain size of the aluminum alloy crystal grains of the head 27, the rounded portion 29 under the neck, and the upper portion 25a of the lower neck 25 is about 40 μm or less, preferably about 10 μm to about 30 μm, more preferably about 10 μm. It is about 20 μm, which is smaller than the average crystal grain size (for example, 150 μm) of the crystal grains in the lower neck 25 (excluding the upper portion 25a). Here, the upper portion 25a of the lower neck 25 is also miniaturized, but only the head 27 and the rounded portion 29 under the neck may be miniaturized (the same applies to the following embodiments).
図４（ａ）〜（ｄ）は、図３（ａ）〜（ｄ）に示す実施形態１に係るボルトの製造方法に比べて、線材２１をさらに下向きに深く据え込むようにしたボルトの製造方法を示している。具体的には、首下丸み部に対応する部位よりかなり下側の部位、例えばねじ部の切り上がり位置まで、アルミニウム合金材料が塑性流動する程度に、線材２１に据え込み加工を施すようにしている。また、図４（ｅ）〜（ｈ）は、それぞれ、図４（ａ）〜（ｄ）に示す線材２１又はボルト素材２８に熱処理（溶体化処理及び時効処理）を施した場合のアルミニウム合金材料の結晶粒の大きさを、図１（ｄ）〜（ｆ）と同様の形態で比喩的ないしは誇張的に示している。なお、図４（図５も同様）において、仮想線Ｍは、ねじ部の切り上がり位置を示している。 4 (a) to 4 (d) show the manufacture of bolts in which the wire rod 21 is installed deeper downward as compared with the method for manufacturing bolts according to the first embodiment shown in FIGS. 3 (a) to 3 (d). Shows the method. Specifically, the wire rod 21 is embedded to the extent that the aluminum alloy material plastically flows to a portion considerably below the portion corresponding to the rounded portion under the neck, for example, to the cut-up position of the screw portion. There is. Further, FIGS. 4 (e) to 4 (h) are aluminum alloy materials obtained by subjecting the wire rod 21 or the bolt material 28 shown in FIGS. 4 (a) to 4 (d) to heat treatment (dissolution treatment and aging treatment), respectively. The size of the crystal grains of No. 1 is shown figuratively or exaggeratedly in the same form as in FIGS. 1 (d) to 1 (f). In FIG. 4 (the same applies to FIG. 5), the virtual line M indicates the rounded-up position of the threaded portion.
図４（ａ）〜（ｈ）に示すボルトの製造方法は、線材２１の据え込みの深さが異なる点を除けば、図３（ａ）〜（ｈ）に示すボルトの製造方法と同様であるので、図４（ａ）〜（ｈ）では、線材２１ないしはボルト素材２８の各構成要素には、図３（ａ）〜（ｈ）の場合と同様の参照番号を付している。このボルトの製造方法では、図４（ｂ）中のＲ８で示す領域では据え込み加工により加工歪が付与され、図４（ｃ）中のＲ９で示す領域では絞り加工により加工歪が付与される。かくして、図４（ｄ）中のＲ１０で示す領域では、据え込み加工及び絞り加工により加工歪が付与されるので、加工歪は非常に大きくなる。 The bolt manufacturing method shown in FIGS. 4 (a) to 4 (h) is the same as the bolt manufacturing method shown in FIGS. 3 (a) to 3 (h), except that the installation depth of the wire rod 21 is different. Therefore, in FIGS. 4A to 4H, each component of the wire rod 21 or the bolt material 28 is given the same reference number as in the case of FIGS. 3A to 3H. In this bolt manufacturing method, machining strain is applied by embossing in the region shown by R8 in FIG. 4 (b), and machining strain is applied by drawing in the region shown by R9 in FIG. 4 (c). .. Thus, in the region shown by R10 in FIG. 4D, the machining strain is applied by the stationary machining and the drawing machining, so that the machining strain becomes very large.
図４（ｈ）から明らかなとおり、このボルトの製造方法によれば、首下丸み部２９（ないしは、その隣接領域）でアルミニウム合金材料の結晶粒を十分に微細化することができ、首下丸み部２９の耐応力腐食割れ性を十分に確保することができる。さらに、首下部２５の上側部分（第２縮径部２５ａ）、すなわちねじ部の切り上がり位置より上側の部分でアルミニウム合金材料の結晶粒を十分に微細化することができ、首下部２５のこの部分の耐応力腐食割れ性を向上させることができる。すなわち、図３（ａ）〜（ｄ）に示すボルトの製造方法に比べて、より広い領域でアルミニウム合金材料の結晶粒を微細化することができ、首下部２５の上側部分の耐応力腐食割れ性を向上させることができる。 As is clear from FIG. 4 (h), according to this bolt manufacturing method, the crystal grains of the aluminum alloy material can be sufficiently refined at the rounded portion 29 (or the adjacent region thereof) under the neck, and the crystal grains under the neck can be sufficiently refined. Sufficient stress corrosion cracking resistance of the rounded portion 29 can be ensured. Further, the crystal grains of the aluminum alloy material can be sufficiently refined in the upper portion (second reduced diameter portion 25a) of the lower neck portion 25, that is, the portion above the cut-up position of the screw portion, and this of the lower neck portion 25. The stress corrosion cracking resistance of the portion can be improved. That is, as compared with the bolt manufacturing methods shown in FIGS. 3A to 3D, the crystal grains of the aluminum alloy material can be made finer in a wider area, and stress corrosion cracking resistance cracking in the upper portion of the lower neck 25 can be achieved. The sex can be improved.
＜実施形態２＞
図５（ａ）〜（ｄ）は、本発明の実施形態２に係るボルトの製造方法を示している。このボルトの製造方法は、図２（ａ）〜（ｈ）に示す普通のボルトの製造方法と同様に、横断面が円形であり、その直径が製造すべきボルトの首下部の横断面の直径より大きいアルミニウム合金製のコイル材からボルトを製造する。さらに、図２（ａ）〜（ｈ）に示す普通のボルトの製造方法と同様に、線材に絞り加工を施して首下部を形成した上で、線材の上部に据え込み加工を施すようにしている。すなわち、実施形態２に係るボルトの製造方法は、図２（ａ）〜（ｈ）に示す普通のボルトの製造方法を改良したものである。そして、実施形態２に係るボルトの製造方法では、図２（ａ）〜（ｈ）に示す普通のボルトの製造方法に比べて、絞り加工を施す領域を上側に広げている。したがって、絞り加工を施した部分の上部では、絞り加工に加えて据え込み加工を施すことになる。
<Embodiment 2>
5 (a) to 5 (d) show a method for manufacturing a bolt according to the second embodiment of the present invention. The method for manufacturing this bolt is the same as the method for manufacturing ordinary bolts shown in FIGS. 2A to 2H, and the cross section is circular, and the diameter thereof is the diameter of the cross section of the lower part of the neck of the bolt to be manufactured. Manufacture bolts from larger aluminum alloy coil materials. Further, in the same manner as the ordinary bolt manufacturing methods shown in FIGS. 2 (a) to 2 (h), the wire rod is drawn to form the lower part of the neck, and then the wire rod is stationary. There is. That is, the bolt manufacturing method according to the second embodiment is an improvement of the ordinary bolt manufacturing method shown in FIGS. 2A to 2H. Then, in the bolt manufacturing method according to the second embodiment, the area to be drawn is expanded upward as compared with the ordinary bolt manufacturing methods shown in FIGS. 2A to 2H. Therefore, in addition to the drawing process, the stationary processing is performed on the upper part of the drawn portion.
実施形態２に係るボルトの製造方法においては、図５（ａ）に示すように、アルミニウム合金製のコイル材（図示せず）を、製造すべきボルトの形状及び寸法に相応ないしは対応する長さに切断して円柱形の線材３１を作製する。ここで、コイル材には、その円形の横断面の直径が製造すべきボルトの首下部の横断面の直径より大きいものが用いられる。 In the method for manufacturing a bolt according to the second embodiment, as shown in FIG. 5A, a coil material made of an aluminum alloy (not shown) has a length corresponding to or corresponding to the shape and size of the bolt to be manufactured. To produce a cylindrical wire rod 31. Here, a coil material having a circular cross-sectional diameter larger than the cross-sectional diameter of the lower part of the neck of the bolt to be manufactured is used.
次に、図５（ｂ）に示すように、線材３１の、首下丸み部（ないしは、頭部と首下部の境界領域）に対応する部位より上側の部位から線材３１の下端部にわたって絞り加工（絞り成型加工）を施して首下部３２を形成した上で、この線材３１を所定の形状を有する金型３３内に配置する（図５（ｆ）参照）。この場合、絞り加工が施された部分では線材３１が縮径され、アルミニウム合金材料の流動が起こり、加工歪が付与される。ここで、線材３１の絞り加工が施された部分の上端近傍部は、金型３３の空洞３４内に位置する（図５（ｆ）参照）。すなわち、この絞り加工により、首下丸み部に対応する部分に加工歪が付与される。 Next, as shown in FIG. 5B, drawing is performed from the portion of the wire rod 31 above the portion corresponding to the rounded portion under the neck (or the boundary region between the head and the lower neck) to the lower end portion of the wire rod 31. (Drawing and molding) is performed to form the lower neck portion 32, and then the wire rod 31 is placed in a mold 33 having a predetermined shape (see FIG. 5 (f)). In this case, the diameter of the wire rod 31 is reduced in the portion where the drawing process is performed, the aluminum alloy material flows, and processing strain is applied. Here, the portion near the upper end of the drawn portion of the wire rod 31 is located in the cavity 34 of the mold 33 (see FIG. 5 (f)). That is, by this drawing process, processing strain is applied to the portion corresponding to the rounded portion under the neck.
そして、金型３３内の線材３１に対して、ハンマー等（図示せず）で下向きの押圧力を加えて据え込み加工を施し、線材３１の絞り加工が施されていない部分と、絞り加工が施された部分の上端近傍部とを塑性変形させ、図５（ｃ）に示すように、大径部３５及びテーパ部３６を形成する。この場合、大径部３５及びテーパ部３６にはもれなく据え込み加工が施されるが、大径部３５の下端近傍部及びテーパ部３６には、すでに絞り加工が施されているので、これらの部分には絞り加工及び据え込み加工の両方が施される。なお、首下部３２には、前記のとおり絞り加工が施されている。かくして、大径部３５とテーパ部３６と首下部３２とに十分に加工歪が付与される。 Then, a downward pressing force is applied to the wire rod 31 in the mold 33 with a hammer or the like (not shown) to perform stationary processing, and the portion of the wire rod 31 that has not been drawn and the drawing process are performed. As shown in FIG. 5C, the large-diameter portion 35 and the tapered portion 36 are formed by plastically deforming the portion near the upper end of the applied portion. In this case, the large-diameter portion 35 and the tapered portion 36 are completely embedded, but the portion near the lower end of the large-diameter portion 35 and the tapered portion 36 have already been drawn. Both drawing and stationary processing are applied to the portion. The lower part of the neck 32 is drawn as described above. Thus, sufficient machining strain is applied to the large diameter portion 35, the tapered portion 36, and the lower neck portion 32.
さらに、大径部３５とテーパ部３６とに頭部成型加工（プレス加工）を施して、図５（ｄ）に示すように、頭部３７と首下部３２とを備えたボルト素材３８を作製する。その際、頭部３７と首下部３２の境界領域に首下丸み部３９（首下Ｒ部）が形成される。この後、首下部３２の周面の一部又は全部に、転造等によりねじが形成され、ボルトが完成する。このボルトの製造方法では、図５（ｂ）中のＲ１１で示す領域では絞り加工により加工歪が付与され、図５（ｃ）中のＲ１２で示す領域では据え込み加工により加工歪が付与される。かくして、図５（ｄ）中のＲ１３で示す領域では、据え込み加工及び絞り加工により加工歪が付与されるので、加工歪は非常に大きくなる。なお、図５において、仮想線Ｍは、ねじ部の切り上がり位置を示している。 Further, the large diameter portion 35 and the tapered portion 36 are subjected to head molding processing (press processing) to produce a bolt material 38 having a head 37 and a lower neck portion 32 as shown in FIG. 5 (d). To do. At that time, a rounded portion 39 under the neck (R portion under the neck) is formed in the boundary region between the head 37 and the lower neck 32. After that, a screw is formed on a part or all of the peripheral surface of the lower part of the neck 32 by rolling or the like, and the bolt is completed. In this bolt manufacturing method, machining strain is applied by drawing in the region shown by R11 in FIG. 5 (b), and machining strain is applied by stationary machining in the region shown by R12 in FIG. 5 (c). .. Thus, in the region shown by R13 in FIG. 5D, the machining strain is applied by the stationary machining and the drawing machining, so that the machining strain becomes very large. In FIG. 5, the virtual line M indicates the rounded-up position of the threaded portion.
図５（ｅ）〜（ｈ）は、それぞれ、図５（ａ）〜（ｄ）に示す線材３１又はボルト素材３８に熱処理（溶体化処理及び時効処理）を施した場合のアルミニウム合金材料の結晶粒の大きさを、図１（ｄ）〜（ｆ）と同様の形態で比喩的ないしは誇張的に示している。図５（ｈ）から明らかなとおり、このボルトの製造方法によれば、熱処理により首下丸み部３９（ないしは、その隣接領域）でアルミニウム合金材料の結晶粒を微細化することができ（結晶粒径小）、首下丸み部３９の耐応力腐食割れ性を十分には確保することができる。さらに、首下部３２でもアルミニウム合金材料の結晶粒を微細化することができ（結晶粒径小）、首下部３２の耐応力腐食割れ性を十分には確保することができる。なお、頭部３７でも、アルミニウム合金材料の結晶粒は十分に微細化される（結晶粒径小）。 5 (e) to 5 (h) show the crystals of the aluminum alloy material when the wire rod 31 or the bolt material 38 shown in FIGS. 5 (a) to 5 (d) is heat-treated (solution treatment and aging treatment), respectively. The grain size is shown figuratively or exaggerated in the same form as in FIGS. 1 (d) to 1 (f). As is clear from FIG. 5 (h), according to this bolt manufacturing method, the crystal grains of the aluminum alloy material can be refined at the rounded portion 39 (or the adjacent region thereof) under the neck by heat treatment (crystal grains). The diameter is small), and the stress corrosion cracking resistance of the rounded portion 39 under the neck can be sufficiently ensured. Further, the crystal grains of the aluminum alloy material can be made finer even in the lower neck 32 (the crystal grain size is small), and the stress corrosion cracking resistance of the lower neck 32 can be sufficiently ensured. Even at the head 37, the crystal grains of the aluminum alloy material are sufficiently finely divided (crystal grain size is small).
＜実施形態３＞
図６（ａ）〜（ｅ）は、本発明の実施形態３に係るボルトの製造方法を示している。このボルトの製造方法は、線材に対して、まずその上端近傍部より下側の部位に絞り加工を施し、この後に線材の上端近傍部に据え込み加工を施すことにより、大径部とテーパ部を形成する点では、図５（ａ）〜（ｈ）に示す実施形態２に係るボルトの製造方法と同様である。
<Embodiment 3>
6 (a) to 6 (e) show a method for manufacturing a bolt according to the third embodiment of the present invention. In the method of manufacturing this bolt, the wire rod is first drawn in a portion below the upper end portion thereof, and then installed in the vicinity of the upper end portion of the wire rod to form a large diameter portion and a tapered portion. Is the same as the method for manufacturing bolts according to the second embodiment shown in FIGS. 5 (a) to 5 (h).
しかしながら、実施形態３に係るボルトの製造方法では、絞り加工と据え込み加工とを交互に複数回繰り返し、首下丸み部に対応する部分及び首下部の上部に対応する部分に加工歪を蓄積させて、熱処理後にアルミニウム合金材料の結晶粒をより細かく微細化するようにしている。この実施形態３に係るボルトの製造方法によれば、絞り加工と据え込み加工の繰り返し回数を変える（調節）ことにより、アルミニウム合金材料の結晶粒の粒径を調整ないしは制御することができる。 However, in the method for manufacturing a bolt according to the third embodiment, drawing processing and stationary processing are alternately repeated a plurality of times, and processing strain is accumulated in a portion corresponding to a rounded portion under the neck and a portion corresponding to an upper portion of the lower neck. After the heat treatment, the crystal grains of the aluminum alloy material are made finer. According to the bolt manufacturing method according to the third embodiment, the particle size of the crystal grains of the aluminum alloy material can be adjusted or controlled by changing (adjusting) the number of repetitions of the drawing process and the stationary process.
実施形態３に係るボルトの製造方法においては、図６（ａ）に示すように、アルミニウム合金製のコイル材（図示せず）を、製造すべきボルトの形状及び寸法に相応ないしは対応する長さに切断して円柱形の線材４１を作製する。ここで、コイル材には、その円形の横断面の直径が製造すべきボルトの首下部の横断面の直径より大きいものが用いられる。 In the method for manufacturing a bolt according to the third embodiment, as shown in FIG. 6A, a coil material made of an aluminum alloy (not shown) has a length corresponding to or corresponding to the shape and size of the bolt to be manufactured. To make a cylindrical wire rod 41. Here, a coil material having a circular cross-sectional diameter larger than the cross-sectional diameter of the lower part of the neck of the bolt to be manufactured is used.
次に、図６（ｂ）に示すように、線材４１の、首下丸み部（ないしは、頭部と首下部の境界領域）に対応する部分よりやや上側の部位から線材４１の下端部にわたって絞り加工（絞り成型加工）を施して首下部４２を形成する。この場合、線材４１の上端近傍部には、絞り加工が施されていない未加工部４３が存在する。続いて、この線材４１を所定の形状を有する金型（図示せず）内に配置し、未加工部４３と首下部４２の上端近傍部とに据え込み加工を施して拡径部４４を形成する。この据え込み加工では、絞り加工が施されなかった未加工部４３と、絞り加工が施された首下部４２の上端近傍部とが塑性変形して拡径される。このとき、首下部４２の上端近傍部には、絞り加工と据え込み加工とが施されるので、より大きい加工歪を付与することができ、この部分では熱処理が施されたときに、アルミニウム合金材料の結晶粒は非常に小さくなる。 Next, as shown in FIG. 6B, the wire rod 41 is squeezed from a portion slightly above the portion corresponding to the rounded portion under the neck (or the boundary region between the head and the lower neck) to the lower end portion of the wire rod 41. Processing (drawing processing) is performed to form the lower neck portion 42. In this case, in the vicinity of the upper end of the wire rod 41, there is an unprocessed portion 43 that has not been drawn. Subsequently, the wire rod 41 is placed in a mold (not shown) having a predetermined shape, and the unprocessed portion 43 and the portion near the upper end of the lower neck portion 42 are embedded to form the enlarged diameter portion 44. To do. In this embedding process, the unprocessed portion 43 that has not been drawn and the portion near the upper end of the neck lower portion 42 that has been drawn are plastically deformed to increase the diameter. At this time, since the drawing process and the stationary process are performed on the portion near the upper end of the lower neck portion 42, a larger processing strain can be applied, and when the heat treatment is applied to this portion, the aluminum alloy is applied. The crystal grains of the material become very small.
さらに、線材４１に対して、前記の絞り加工と据え込み加工とを（図６（ｂ）、（ｃ）中に破線Ａで示す工程）、予め設定された回数だけ交互に繰り返して実施する。この場合、拡径部４４に対応する部分では、繰り返し塑性変形が生じ、大きな加工歪が付与される。ここで、絞り加工と据え込み加工の繰り返し回数を多くすればするほど、線材４１の上部により大きな加工歪を付与することができ、熱処理を施すことにより、アルミニウム合金材料の結晶粒径を小さくすることができる。したがって、絞り加工と据え込み加工の繰り返し回数を調節ことにより、アルミニウム合金材料の結晶粒の粒径を制御ないしは調節することができる。 Further, on the wire rod 41, the drawing process and the stationary process (step shown by the broken line A in FIGS. 6B and 6C) are alternately repeated a preset number of times. In this case, the portion corresponding to the enlarged diameter portion 44 is repeatedly plastically deformed, and a large machining strain is applied. Here, as the number of repetitions of drawing and embossing increases, a larger processing strain can be applied to the upper part of the wire 41, and the crystal grain size of the aluminum alloy material is reduced by performing heat treatment. be able to. Therefore, the particle size of the crystal grains of the aluminum alloy material can be controlled or adjusted by adjusting the number of repetitions of drawing and embossing.
このように、図６（ｂ）、（ｃ）中に破線Ａで示す絞り加工と据え込み加工とを交互に繰り返し実施した後、線材４１に対してさらなる据え込み加工又は絞り加工を施して、図６（ｄ）に示すように、大径部４５及びテーパ部４６を形成する。さらに、大径部４５とテーパ部４６とに頭部成型加工（プレス加工）を施して、図６（ｅ）に示すように、頭部４７と首下部４２とを備えたボルト素材４８を作製する。その際、頭部４７と首下部４２の境界領域に首下丸み部４９（首下Ｒ部）が形成される。 In this way, after the drawing process and the stationary process shown by the broken line A are alternately and repeatedly performed in FIGS. 6 (b) and 6 (c), the wire rod 41 is further subjected to the stationary process or the drawing process. As shown in FIG. 6D, the large diameter portion 45 and the tapered portion 46 are formed. Further, the large diameter portion 45 and the tapered portion 46 are subjected to head molding processing (press processing) to produce a bolt material 48 having a head 47 and a lower neck 42 as shown in FIG. 6 (e). To do. At that time, a rounded portion 49 under the neck (R portion under the neck) is formed in the boundary region between the head 47 and the lower neck 42.
この後、首下部４２の周面の一部又は全部に、転造等によりねじが形成され、ボルトが完成する。このボルトの製造方法では、図６（ｂ）中のＲ１４で示す領域では絞り加工により加工歪が付与され、図６（ｃ）中のＲ１５で示す領域では据え込み加工により加工歪が付与される。かくして、図６（ｅ）中のＲ１６で示す領域では、据え込み加工及び絞り加工が繰り返し実施されて加工歪が蓄積されるので、加工歪は非常に大きくなる。 After that, a screw is formed on a part or all of the peripheral surface of the lower part of the neck 42 by rolling or the like, and the bolt is completed. In this bolt manufacturing method, machining strain is applied by drawing in the region shown by R14 in FIG. 6B, and machining strain is applied by stationary machining in the region shown by R15 in FIG. 6C. .. Thus, in the region shown by R16 in FIG. 6 (e), the stationary processing and the drawing processing are repeatedly performed and the processing strain is accumulated, so that the processing strain becomes very large.
図６（ｆ）〜（ｊ）は、それぞれ、図６（ａ）〜（ｅ）に示す線材４１又はボルト素材４８に熱処理（溶体化処理及び時効処理）を施した場合のアルミニウム合金材料の結晶粒の大きさを、図１（ｄ）〜（ｆ）と同様の形態で比喩的ないしは誇張的に示している。図６（ｊ）から明らかなとおり、このボルトの製造方法によれば、頭部４７と、首下部４２の上端近傍部（首下丸み部４９を含む）とでは、絞り加工と据え込み加工とが繰り返されるので、その繰り返し回数に応じてアルミニウム合金材料の結晶粒径が非常に小さくなり（結晶粒径微小）、耐応力腐食割れ性が大幅に向上する。なお、線材４１の、前記上端近傍部より下側の部分は、最初に絞り加工が施されるだけであるので、アルミニウム合金材料の結晶粒径は、実施形態２における首下部３２の場合と同様である（結晶粒径小）。 6 (f) to 6 (j) show the crystals of the aluminum alloy material when the wire rod 41 or the bolt material 48 shown in FIGS. 6 (a) to 6 (e) is heat-treated (solution treatment and aging treatment), respectively. The grain size is shown figuratively or exaggerated in the same form as in FIGS. 1 (d) to 1 (f). As is clear from FIG. 6 (j), according to the method of manufacturing this bolt, the head 47 and the portion near the upper end of the lower neck 42 (including the rounded portion 49 under the neck) are subjected to drawing and embedding. As the above is repeated, the crystal grain size of the aluminum alloy material becomes very small (the crystal grain size is very small) according to the number of repetitions, and the stress corrosion cracking resistance is significantly improved. Since the portion of the wire rod 41 below the upper end portion is only first drawn, the crystal grain size of the aluminum alloy material is the same as in the case of the lower neck portion 32 in the second embodiment. (Small crystal grain size).
図７（ａ）、（ｂ）に、据え込み加工を施した複数のアルミニウム合金製の試験片を作製した上で、これらの試験片に熱処理（溶体化処理及び時効処理）を施し、該試験片中のアルミニウム合金材料の平均結晶粒径を測定した結果を示す。なお、据え込み加工を施さず、熱処理のみを施した試験片についても同様の測定を行っている。具体的には、図７（ａ）に示すように、アルミニウム合金材料からなる高さ（中心軸方向の長さ）がｈ０（２０ｍｍ）であり直径がＤ（１２ｍｍ）である複数の円柱形部材を準備し、これらの円柱形部材を、高さが所定値ｈ１（＜ｈ０）となるように上下方向（中心軸方向）に押圧して塑性変形させ、圧縮率αが互いに異なる試験片を作製した。ここで、試験片の圧縮率αは、下記の式１で定義される値である。
α＝１００×（ｈ０−ｈ１）／ｈ０……………………………………………式１
α ：圧縮率（％）
ｈ０：円柱形部材の加工前の高さ（ｍｍ）
ｈ１：円柱形部材の加工後の高さ（ｍｍ）
In FIGS. 7 (a) and 7 (b), a plurality of test pieces made of aluminum alloy that have been subjected to embedding processing are prepared, and then heat treatment (solution treatment and aging treatment) is performed on these test pieces to perform the test. The result of measuring the average crystal grain size of the aluminum alloy material in one piece is shown. The same measurement is performed on the test piece that has been subjected to only heat treatment without embedding. Specifically, as shown in FIG. 7A, a plurality of cylindrical shapes made of an aluminum alloy material having a height (length in the central axis direction) of h 0 (20 mm) and a diameter of D (12 mm). A test in which members are prepared and these cylindrical members are plastically deformed by pressing them in the vertical direction (central axis direction) so that the height becomes a predetermined value h 1 (<h 0 ), and the compression ratios α are different from each other. Pieces were made. Here, the compressibility α of the test piece is a value defined by the following equation 1.
α = 100 × (h 0 -h 1) / h 0 ................................................... Formula 1
α: Compression rate (%)
h 0 : Height (mm) of cylindrical member before processing
h 1 : Height after processing of cylindrical member (mm)
図７（ｂ）は、圧縮率αが０〜８０％の範囲内の複数の試験片に対して熱処理を施した後で、各試験片中のアルミニウム合金材料の平均結晶粒径を測定した結果を示している。図７（ｂ）から明らかなとおり、据え込み加工を施さない試験片（α＝０）では、平均結晶粒径は３０μｍであるが、圧縮率αが２０％の試験片では平均結晶粒径が２０μｍとなり、とくに圧縮率αが４０％以上の試験片では平均結晶粒径は１０μｍ以下となっている。 FIG. 7B shows the results of measuring the average crystal grain size of the aluminum alloy material in each test piece after heat-treating a plurality of test pieces having a compressibility α in the range of 0 to 80%. Is shown. As is clear from FIG. 7B, the average crystal grain size of the test piece (α = 0) not subjected to the embedding process is 30 μm, but the average crystal grain size of the test piece having a compression ratio α of 20% is 30 μm. It is 20 μm, and the average crystal grain size is 10 μm or less, especially in the test piece having a compression ratio α of 40% or more.
図９（ａ）は、据え込み加工を施さず熱処理のみを施した試験片（α＝０）中のアルミニウム合金材料の結晶構造を示す顕微鏡写真である。また、図９（ｂ）は、圧縮率αが８０％の据え込み加工を施した後で熱処理を施した試験片中のアルミニウム合金材料の結晶構造を示す顕微鏡写真である。図９（ａ）と図９（ｂ）を対比すれば、据え込み加工を施して熱処理を施した試験片では、据え込み加工を施さず熱処理のみを施した試験片に比べて、アルミニウム合金材料の結晶粒径が大幅に小さくなっていることが分かる。 FIG. 9A is a photomicrograph showing the crystal structure of the aluminum alloy material in the test piece (α = 0) that has been subjected to only heat treatment without embedding. Further, FIG. 9B is a micrograph showing the crystal structure of the aluminum alloy material in the test piece which has been subjected to a stationary process having a compression ratio α of 80% and then heat-treated. Comparing FIGS. 9 (a) and 9 (b), the test piece subjected to the stationary processing and heat treatment is made of an aluminum alloy material as compared with the test piece obtained by only heat treatment without the stationary processing. It can be seen that the crystal grain size of is significantly smaller.
図８（ａ）、（ｂ）に、部分的に絞り加工を施した複数のアルミニウム合金製の試験片を作製した上で、これらの試験片に熱処理（溶体化処理及び時効処理）を施し、該試験片中の絞り部分におけるアルミニウム合金材料の平均結晶粒径を測定した結果を示す。なお、絞り加工を施さず、熱処理のみを施した試験片についても同様の測定を行った。具体的には、図８（ａ）に示すように、アルミニウム合金材料からなる高さ（中心軸方向の長さ）がｈ（２０ｍｍ）であり直径がＤ０（１２ｍｍ）である複数の円柱形部材を準備し、これらの円柱形部材の下部に、直径が所定値Ｄ１（＜Ｄ０）となるように絞り加工を施して塑性変形させ、断面減少率β（絞り率、押し出し率）が互いに異なる試験片を作製した。ここで、試験片の断面減少率βは、下記の式２で定義される値である。
β＝１００×（Ｄ０ ２−Ｄ１ ２）／Ｄ０ ２………………………………………式２
β ：断面減少率（％）
Ｄ０：円柱形部材の加工前の直径（ｍｍ）
Ｄ１：円柱形部材の絞られた部分の直径（ｍｍ）
In FIGS. 8A and 8B, a plurality of aluminum alloy test pieces partially drawn are prepared, and then heat treatment (solution treatment and aging treatment) is performed on these test pieces. The result of measuring the average crystal grain size of the aluminum alloy material in the squeezed portion in the test piece is shown. The same measurement was performed on the test piece that had been subjected to only heat treatment without drawing. Specifically, as shown in FIG. 8A, a plurality of cylindrical shapes made of an aluminum alloy material having a height (length in the central axis direction) of h (20 mm) and a diameter of D 0 (12 mm). Members are prepared, and the lower part of these cylindrical members is drawn and plastically deformed so that the diameter becomes a predetermined value D 1 (<D 0 ), and the cross-sectional reduction rate β (drawing rate, extrusion rate) is obtained. Different test pieces were prepared. Here, the cross-sectional reduction rate β of the test piece is a value defined by the following equation 2.
β = 100 × (D 0 2- D 1 2 ) / D 0 2 …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
β: Cross-section reduction rate (%)
D 0 : Diameter (mm) of cylindrical member before processing
D 1 : Diameter (mm) of the narrowed part of the cylindrical member
図８（ｂ）は、断面減少率βが０〜８０％の範囲内の複数の試験片に対して熱処理を施した後で、各試験片中の絞られた部分（β＝０の場合を除く）のアルミニウム合金材料の平均結晶粒径を測定した結果を示している。図８（ｂ）から明らかなとおり、絞り加工を施さない試験片（β＝０）では、平均結晶粒径は約３０μｍであるが、断面減少率βが大きくなればなるほど平均結晶粒径が小さくなり、とくに断面減少率βが８０％の試験片では平均結晶粒径は１０μｍとなっている。 FIG. 8B shows a case where a plurality of test pieces having a cross-sectional reduction rate β in the range of 0 to 80% are heat-treated and then the narrowed portion (β = 0) in each test piece. The results of measuring the average crystal grain size of the aluminum alloy material (excluding) are shown. As is clear from FIG. 8B, the average crystal grain size of the test piece (β = 0) not subjected to the drawing process is about 30 μm, but the larger the cross-sectional reduction rate β, the smaller the average crystal grain size. In particular, the average crystal grain size of the test piece having a cross-sectional reduction rate β of 80% is 10 μm.
図９（ｃ）は、絞り加工を施さず熱処理のみを施した試験片（β＝０）中のアルミニウム合金材料の結晶構造を示す顕微鏡写真である。また、図９（ｄ）は、断面減少率βが８０％の絞り加工を施した後で熱処理を施した試験片中の絞り部分のアルミニウム合金材料の結晶構造を示す顕微鏡写真である。図９（ｃ）と図９（ｄ）を対比すれば、絞り加工を施して熱処理を施した試験片では、絞り加工を施さずに熱処理のみを施した試験片に比べて、アルミニウム合金材料の結晶粒径が大幅に小さくなっていることが分かる。 FIG. 9C is a photomicrograph showing the crystal structure of the aluminum alloy material in the test piece (β = 0) that has been subjected to only heat treatment without drawing. Further, FIG. 9D is a photomicrograph showing the crystal structure of the aluminum alloy material in the drawn portion in the test piece which has been subjected to the drawing process having a cross-sectional reduction rate β of 80% and then heat-treated. Comparing FIGS. 9 (c) and 9 (d), the test piece subjected to drawing and heat treatment is made of an aluminum alloy material as compared with the test piece obtained by only heat treatment without drawing. It can be seen that the crystal grain size is significantly smaller.
図７（ｂ）、図８（ｂ）及び図９（ａ）〜（ｄ）によれば、本発明の実施形態１〜３に係るボルトの製造方法を用いることにより、ボルトの首下丸み部ないしは首下部でアルミニウム合金材料の結晶粒を十分に微細化することができ、首下丸み部等の応力集中部における耐応力腐食割れ性を向上させることができることが分かる。 According to FIGS. 7 (b), 8 (b) and 9 (a) to 9 (d), the rounded portion under the neck of the bolt is formed by using the method for manufacturing the bolt according to the first to third embodiments of the present invention. It can be seen that the crystal grains of the aluminum alloy material can be sufficiently refined at the lower part of the neck, and the stress corrosion cracking resistance at the stress concentration part such as the rounded part under the neck can be improved.
以上、本発明の実施形態１〜３に係るアルミニウム合金製のボルトの製造方法によれば、歪付与工程で首下丸み部ないしは首下部に十分に加工歪を付与することができ、この後の熱処理工程で熱処理（溶体化処理及び時効処理）を施して、これらの部位のアルミニウム合金材料の結晶粒を十分に微細化することができるので、首下丸み部等の応力集中部における耐応力腐食割れ性を大幅に向上させることができ、ボルトの信頼性を高めることができる。 As described above, according to the method for manufacturing an aluminum alloy bolt according to the first to third embodiments of the present invention, it is possible to sufficiently apply processing strain to the rounded portion under the neck or the lower portion of the neck in the strain applying step. Since heat treatment (solution treatment and aging treatment) can be performed in the heat treatment step to sufficiently refine the crystal grains of the aluminum alloy material in these parts, stress corrosion cracking resistance in stress-concentrated parts such as rounded parts under the neck. The cracking property can be significantly improved, and the reliability of the bolt can be improved.
１ 線材、２ 金型、３ 大径部、４ テーパ部、５ 首下部、６ 頭部、７ ボルト素材、８ 首下丸み部、１１ 線材、１２ 首下部、１３ 金型、１４ 大径部、１５ テーパ部、１６ 未加工部、１７ 頭部、１８ ボルト素材、１９ 首下丸み部、２１ 線材、２２ 金型、２３ 大径部、２３ａ 非縮径部、２４ テーパ部、２５ 首下部、２５ａ 第２縮径部、２６ 第１縮径部、２７ 頭部、２８ ボルト素材、２９ 首下丸み部、３１ 線材、３２ 首下部、３３ 金型、３４ 空洞、３５ 大径部、３６ テーパ部、３７ 頭部、３８ ボルト素材、３９ 首下丸み部、４１ 線材、４２ 首下部、４３ 未加工部、４４ 拡径部、４５ 大径部、４６ テーパ部、４７ 頭部、４８ ボルト素材、４９ 首下丸み部。 1 Wire, 2 Mold, 3 Large Diameter, 4 Tapered, 5 Lower Neck, 6 Head, 7 Bolt Material, 8 Rounded Under Neck, 11 Wire, 12 Lower Neck, 13 Mold, 14 Large Diameter, 15 Tapered part, 16 Raw part, 17 Head, 18 Bolt material, 19 Rounded part under neck, 21 Wire rod, 22 Mold, 23 Large diameter part, 23a Non-reduced diameter part, 24 Tapered part, 25 Lower neck, 25a 2nd reduced diameter part, 26 1st reduced diameter part, 27 head, 28 bolt material, 29 rounded part under the neck, 31 wire rod, 32 lower part of the neck, 33 mold, 34 cavity, 35 large diameter part, 36 tapered part, 37 Head, 38 Bolt material, 39 Rounded under neck, 41 Wire, 42 Lower neck, 43 Unprocessed part, 44 Expanded part, 45 Large diameter part, 46 Tapered part, 47 Head, 48 Bolt material, 49 Neck Lower rounded part.
Claims (6)
該頭部および該首下丸み部を構成するアルミニウム合金の第１結晶粒の平均結晶粒径は、該首下部を構成するアルミニウム合金の第２結晶粒の平均結晶粒径より小さいことを特徴とするアルミニウム合金製ボルト。 A bolt made of an aluminum alloy having a head and a lower neck extending downward from the lower end surface of the head, and a rounded portion under the neck is formed in a boundary region between the head and the lower neck.
The average crystal grain size of the first crystal grains of the aluminum alloy constituting the head and the rounded portion under the neck is smaller than the average crystal grain size of the second crystal grains of the aluminum alloy constituting the lower neck portion. Aluminum alloy bolts.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03229009A (en) * | 1989-11-21 | 1991-10-11 | Nippon Steel Corp | Set of high strength bolt, nut and washer |
| JPH07180714A (en) * | 1993-12-24 | 1995-07-18 | Nippon Steel Corp | Manufacture of bolt excellent in fatigue strength |
| JP2010046704A (en) * | 2008-08-25 | 2010-03-04 | Daiichi Kogyo Co Ltd | Method, apparatus and die for manufacturing bolt |
| JP2012101247A (en) * | 2010-11-10 | 2012-05-31 | Topura Co Ltd | Method for manufacture fastening component made from aluminum-based alloy, and fastening component made from aluminum-based alloy |
| JP2015074009A (en) * | 2013-10-08 | 2015-04-20 | Sus株式会社 | Bolt and production method thereof |
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- 2020-11-04 JP JP2020184198A patent/JP7018616B2/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03229009A (en) * | 1989-11-21 | 1991-10-11 | Nippon Steel Corp | Set of high strength bolt, nut and washer |
| JPH07180714A (en) * | 1993-12-24 | 1995-07-18 | Nippon Steel Corp | Manufacture of bolt excellent in fatigue strength |
| JP2010046704A (en) * | 2008-08-25 | 2010-03-04 | Daiichi Kogyo Co Ltd | Method, apparatus and die for manufacturing bolt |
| JP2012101247A (en) * | 2010-11-10 | 2012-05-31 | Topura Co Ltd | Method for manufacture fastening component made from aluminum-based alloy, and fastening component made from aluminum-based alloy |
| JP2015074009A (en) * | 2013-10-08 | 2015-04-20 | Sus株式会社 | Bolt and production method thereof |
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