JP2016194109A - Austenite stainless steel with taper shape for manufacturing pipe and manufacturing method therefor - Google Patents
Austenite stainless steel with taper shape for manufacturing pipe and manufacturing method therefor Download PDFInfo
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 229910001220 stainless steel Inorganic materials 0.000 title abstract description 9
- 229910001566 austenite Inorganic materials 0.000 title abstract description 8
- 239000010935 stainless steel Substances 0.000 title abstract description 6
- 238000005482 strain hardening Methods 0.000 claims abstract description 12
- 238000000034 method Methods 0.000 claims abstract description 11
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 5
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 5
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 5
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 229910000963 austenitic stainless steel Inorganic materials 0.000 claims description 25
- 238000012545 processing Methods 0.000 claims description 12
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 2
- 238000000465 moulding Methods 0.000 abstract description 8
- 230000008719 thickening Effects 0.000 abstract description 2
- 239000000203 mixture Substances 0.000 abstract 1
- 229910000831 Steel Inorganic materials 0.000 description 11
- 239000010959 steel Substances 0.000 description 11
- 238000002347 injection Methods 0.000 description 9
- 239000007924 injection Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 6
- 239000011162 core material Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 238000005260 corrosion Methods 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 238000009864 tensile test Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 238000005097 cold rolling Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000007542 hardness measurement Methods 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 238000011946 reduction process Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 238000005336 cracking Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 229920001187 thermosetting polymer Polymers 0.000 description 1
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Abstract
Description
本発明は、テーパー形状付きパイプ、とりわけシームレス極細パイプ、を製造するのに適したオーステナイト系ステンレス鋼及び該ステンレス鋼を用いたパイプの製造方法に関する。 The present invention relates to an austenitic stainless steel suitable for producing a tapered pipe, particularly a seamless extra-fine pipe, and a method for producing a pipe using the stainless steel.
近年、痛くない注射針として、根本より先端の細いテーパー形状付きの極細パイプが知られている。このようなテーパー付きパイプは、一般に、母材である板材を金属プレス加工でテーパー形状付きパイプ状にカーリング加工し、継ぎ目をレーザー溶接加工後、歪みを取り、プレスレイアウトから切り離すことにより製造されている。継ぎ目に溶接加工を施さないと、針が曲がった時、隙間が発生し薬液が漏れるといった問題が発生するため、継ぎ目の溶接加工は必要不可欠な作業工程であるが、その溶接加工は細管部を対象とするために高精度を要し、また、専用の生産設備が必要となるため、設備費の増加により製品単価が上がってしまうという問題がある。 In recent years, as an injection needle that does not hurt, an extremely fine pipe with a tapered shape whose tip is narrower than the root is known. Such tapered pipes are generally manufactured by curling a base plate, which is a base material, into a tapered pipe shape by metal pressing, removing the strain after laser welding, and separating it from the press layout. Yes. If welding is not performed at the seam, there will be a problem that when the needle is bent, a gap will occur and chemicals will leak, so the seam welding is an indispensable work process. Since high accuracy is required for the target, and a dedicated production facility is required, there is a problem that the unit price of the product increases due to an increase in the facility cost.
そこで、シームレスパイプを素材として用い、これをつぼめ成形することにより、継ぎ目のないテーパー形状付きパイプを製造することが試みられている（特許文献１）。
しかし、パイプをつぼめ成形してテーパー形状にした場合、先端にいくほど増肉して内径が極端に小さくなり、注射針として使用する際の薬液の流動抵抗が大きくなるという問題がある。
Therefore, an attempt has been made to produce a seamless pipe with a tapered shape by using a seamless pipe as a raw material and then forming the seamless pipe (Patent Document 1).
However, when the pipe is formed into a tapered shape, there is a problem in that the thickness increases toward the tip, the inner diameter becomes extremely small, and the flow resistance of the drug solution when used as an injection needle increases.
また、上記の問題に対しては、パイプの内側に芯材を入れた状態でつぼめ成形を行うことが検討されている（特許文献２）。
このような方法によれば必要な内径は確保できるが、芯材の挿入、引抜といった特別な工程が別途必要となり、製造工程数が増加する。
Further, for the above-mentioned problem, it has been studied to perform squeeze molding with a core material inside the pipe (Patent Document 2).
According to such a method, a necessary inner diameter can be secured, but a special process such as insertion and extraction of a core material is required separately, and the number of manufacturing processes increases.
本発明は、パイプをつぼめ成形してテーパー形状を付与する場合において、特別な方法によらずに十分な内径を確保することを目的とする。 An object of the present invention is to ensure a sufficient inner diameter without depending on a special method when a taper is formed by squeezing a pipe.
本発明者らは、上記課題を解決するためにつぼめ成形時の材料組織を分析した結果、パイプを構成する材料として、高歪み領域で適度に加工硬化するオーステナイト系ステンレス鋼を用いると、つぼめ成形する際、歪が軸方向に分散し、先端部の増肉が抑えられることを見出した。
そして、具体的には、公称歪み３０〜４０％の高歪み領域における加工硬化指数が０．２５以上であると、つぼめ成形しても先端部での増肉が起こりにくいことを見出し、本発明に到達した。
As a result of analyzing the material structure at the time of forming the pot to solve the above-mentioned problems, the present inventors have used austenitic stainless steel that is moderately work-hardened in a high strain region as the material constituting the pipe. In doing so, the present inventors have found that the strain is dispersed in the axial direction and the increase in thickness at the tip is suppressed.
And specifically, when the work hardening index in a high strain region having a nominal strain of 30 to 40% is 0.25 or more, it has been found that even if it is squeeze molded, it is difficult to increase the thickness at the tip. Reached.
すなわち、本発明は以下のとおりである。
本発明のテーパー形状付きパイプ製造用オーステナイト系ステンレス鋼は、質量％において、Ｃ：０．１％以下，Ｓｉ：１．５％以下，Ｍｎ：２．０％以下，Ｎｉ：７〜１１％，Ｃｒ：１５〜２１％，Ｎ：０．１５％以下、Ｃ＋Ｎ：０．０２％以上であって、残部がＦｅおよび不可避的不純物である組成を有し、公称歪み３０〜４０％の高歪み領域での加工硬化指数（Ｎ値）が０．２５以上である。
また、本発明のオーステナイト系ステンレス鋼は、Ｃｕ及びＭｏの少なくとも１種以上をさらに含有し、質量％において、Ｃｕ：３．０％以下，Ｍｏ：３．０％以下であると好ましい。
本発明のテーパー形状付きパイプの製造方法は、オーステナイト系ステンレス鋼からなるパイプを用意する工程と、前記パイプの先端を、縮径加工金型を用いて、無回転でつぼめ成形する工程と、パイプを回転させながらダイスを動作し加工する工程と、を含む。
That is, the present invention is as follows.
The austenitic stainless steel for producing tapered pipes of the present invention is, in mass%, C: 0.1% or less, Si: 1.5% or less, Mn: 2.0% or less, Ni: 7-11%, Cr: 15 to 21%, N: 0.15% or less, C + N: 0.02% or more, with the balance being Fe and inevitable impurities, and a high strain region with a nominal strain of 30 to 40% The work hardening index (N value) at 0.25 is 0.25 or more.
Moreover, the austenitic stainless steel of this invention further contains at least 1 or more types of Cu and Mo, and it is preferable in Cu: 3.0% or less and Mo: 3.0% or less in the mass%.
The method of manufacturing a pipe with a tapered shape of the present invention includes a step of preparing a pipe made of austenitic stainless steel, a step of forming the tip of the pipe with a reduced diameter mold without rotation, and a pipe Moving and processing the die while rotating.
本発明のオーステナイト系ステンレス鋼を用いれば、肉厚が均一なテーパー形状付パイプを製造することができる。そのため、薬液の流動抵抗の小さいテーパー形状付低痛型注射針を、特別な方法によらずに安定して量産することができる。 When the austenitic stainless steel of the present invention is used, a tapered pipe with a uniform thickness can be manufactured. Therefore, it is possible to stably produce a taper-shaped low-pain type injection needle having a small flow resistance of a chemical solution without using a special method.
以下に、本発明について具体的に説明する。
まず、本発明のテーパー形状付きパイプ製造用オーステナイト系ステンレス鋼について詳しく説明する。
本発明のオーステナイト系ステンレス鋼は、質量％で、Ｃ：０．１％以下，Ｓｉ：１．５％以下，Ｍｎ：２．０％以下，Ｎｉ：７〜１１％，Ｃｒ：１５〜２１％，Ｎ：０．１５％以下であって、残部がＦｅおよび不可避的不純物である組成を有する。
また、本発明の別の態様においては、さらに、Ｃｕ：３．０％以下，Ｍｏ：３．０％以下のうちの１種以上を含有する。
The present invention will be specifically described below.
First, the austenitic stainless steel for manufacturing a tapered pipe according to the present invention will be described in detail.
The austenitic stainless steel of the present invention is, in mass%, C: 0.1% or less, Si: 1.5% or less, Mn: 2.0% or less, Ni: 7-11%, Cr: 15-21% , N: 0.15% or less, with the balance being Fe and inevitable impurities.
Moreover, in another aspect of this invention, 1 or more types in Cu: 3.0% or less and Mo: 3.0% or less are contained further.
Ｃはオーステナイト形成元素であり、高温で生成するδフェライトの抑制、冷間加工で誘発されたマルテンサイト相の強化に極めて有効に作用する。しかし、Ｃ含有量を高くし過ぎると粒界にＣｒ炭化物が析出し、耐粒界腐食や靭性が低下するので、Ｃ含有量は０．１質量％以下とする。 C is an austenite-forming element and acts extremely effectively on the suppression of δ ferrite formed at high temperatures and the strengthening of the martensite phase induced by cold working. However, if the C content is too high, Cr carbide precipitates at the grain boundaries and the intergranular corrosion resistance and toughness are reduced, so the C content is set to 0.1 mass% or less.
Ｓｉは鋼の脱酸に必要な成分である。しかし、過剰に添加してもその効果は飽和し、製造コストの上昇を招くことにもなる。したがって、その上限は１．０質量％とする。 Si is a component necessary for deoxidation of steel. However, even if added excessively, the effect is saturated and the manufacturing cost is increased. Therefore, the upper limit is 1.0% by mass.
Ｍｎはオーステナイト相の安定度を支配する元素で、その活用は他の元素とのバランスのもとに行うものである。もっとも、過剰な添加はステンレス鋼の延性を低下させ、製造コストの上昇を招くことにもなる。したがって、その上限は２．０質量％とする。 Mn is an element that governs the stability of the austenite phase, and its utilization is performed in a balance with other elements. However, excessive addition reduces the ductility of the stainless steel and leads to an increase in manufacturing cost. Therefore, the upper limit is made 2.0% by mass.
Ｎｉはオーステナイト相を得るために必須の元素であり、必要な量としてＮｉ含有量は７〜１１質量％とする。 Ni is an essential element for obtaining an austenite phase, and the Ni content is 7 to 11% by mass as a necessary amount.
Ｃｒは耐食性を付与するために必要な成分である。意図する耐食性を付与するのには少なくとも１２質量％のＣｒが必要である。しかし、Ｃｒはフェライト形成元素でもあるので含有量を高くしすぎると高温でδフェライト相が多量に生成し、また、過剰な添加は製造コストの上昇を招くので、上限を２１質量％とする。 Cr is a component necessary for imparting corrosion resistance. At least 12% by mass of Cr is necessary to provide the intended corrosion resistance. However, since Cr is also a ferrite forming element, if the content is too high, a large amount of δ ferrite phase is generated at a high temperature, and excessive addition causes an increase in production cost, so the upper limit is made 21 mass%.
Ｎはオーステナイト形成元素であるとともに、オーステナイト相およびマルテンサイト相を硬化させるのに有効な元素である。もっとも、過剰な添加は製造時のブローホールの原因となるので０．１５質量％以下とする。 N is an austenite forming element and an element effective for hardening the austenite phase and the martensite phase. However, excessive addition causes blowholes during production, so the content is made 0.15% by mass or less.
ＣとＮは互いに同様な硬化作用を示し、公称歪み３０〜４０％の高歪み領域での加工硬化指数（Ｎ値）は０．２５以上とするためにＣ＋Ｎの含有量を０．０２質量％以上とする。 C and N have the same hardening effect, and the work hardening index (N value) in a high strain region with a nominal strain of 30 to 40% is 0.25 or more, so the content of C + N is 0.02% by mass. That's it.
Ｃｕはオーステナイト形成元素であるとともに、冷間鍛造性を改善させるのに有効な元素である。もっとも、過剰な添加は熱間加工性を低下させ、割れ発生の原因となる。したがって、その上限は３．０質量％とする。 Cu is an austenite forming element and an element effective for improving cold forgeability. However, excessive addition reduces hot workability and causes cracking. Therefore, the upper limit is 3.0% by mass.
Ｍｏは耐食性を向上させるとともに、固溶強化元素としてステンレス鋼の強度を向上させる。もっとも、過剰な添加は熱間加工性を低下させる。したがって、その上限は３．０質量％とする。 Mo improves corrosion resistance and improves the strength of stainless steel as a solid solution strengthening element. However, excessive addition reduces hot workability. Therefore, the upper limit is 3.0% by mass.
本発明において、オーステナイト系ステンレス鋼の公称歪み３０〜４０％の高歪み領域での加工硬化指数（Ｎ値）は０．２５以上とする。
オーステナイト系ステンレス鋼のＮ値は、０．２５〜０．４４であることが好ましく、より好ましくは０．２５〜０．４０、さらに好ましくは０．２５〜０．３５である。
Ｎ値が０．２５未満であると、パイプをつぼめ成形する際に先端部での増肉が起こる。一方、Ｎ値が０．４４を超えると、任意の形状への加工が困難になる傾向にある。
In the present invention, the work hardening index (N value) in the high strain region of 30-40% nominal strain of austenitic stainless steel is 0.25 or more.
The N value of the austenitic stainless steel is preferably 0.25 to 0.44, more preferably 0.25 to 0.40, and still more preferably 0.25 to 0.35.
If the N value is less than 0.25, thickening at the tip occurs when the pipe is squeezed. On the other hand, when the N value exceeds 0.44, processing to an arbitrary shape tends to be difficult.
本発明において、オーステナイト系ステンレス鋼の公称歪み３０〜４０％の高歪み領域での加工硬化指数（Ｎ値）は、ＣとＮの含有量の合計や、Ｍｎ、Ｎｉ、Ｃｒ、Ｃｕ等の元素の量を調整することにより所望の値にすることができる。一般に、オーステナイト系ステンレス鋼のＮ値は、ＣやＮの含有量を多くするほど大きくなる傾向にある。 In the present invention, the work hardening index (N value) in a high strain region of 30-40% nominal strain of austenitic stainless steel is the sum of the contents of C and N, elements such as Mn, Ni, Cr, Cu, etc. The desired value can be obtained by adjusting the amount of. Generally, the N value of austenitic stainless steel tends to increase as the content of C or N increases.
本発明において、オーステナイト系ステンレス鋼の加工前の硬さには限定はない。一般に、オーステナイト系ステンレス鋼の加工前の硬度は、１５０〜２００（ＨＶ）程度であり、この程度の範囲の硬度を有するものであれば、Ｎ値を０．２５以上とすることにより、パイプをつぼめ成形する際の先端部での増肉が抑制できる。 In the present invention, the hardness of the austenitic stainless steel before processing is not limited. Generally, the hardness of austenitic stainless steel before processing is about 150 to 200 (HV), and if it has a hardness in this range, the N value is made 0.25 or more, so that the pipe It is possible to suppress the increase in thickness at the tip when the pot is formed.
次に、本発明のオーステナイト系ステンレス鋼を用いてテーパー形状付きパイプの製造する方法について説明する。
テーパー形状付きパイプは、本発明のオーステナイト系ステンレス鋼を用いて、予めパイプを用意する工程、及び、用意したパイプをつぼめ成形（テーパー成形）する工程（パイプの軸方向に沿って外径が小さくなるように成形加工する工程）を経て製造することができる。
Next, a method for producing a tapered pipe using the austenitic stainless steel of the present invention will be described.
A pipe with a taper shape is prepared by using the austenitic stainless steel of the present invention in advance, and a process of preparing the pipe in advance (taper forming) (the outer diameter is small along the axial direction of the pipe). It can be manufactured through a molding process).
予め用意するパイプは、外径が軸方向に均一なものであってよい。また、テーパー形状付きパイプを注射針として使用する場合には、予め用意するパイプは、継ぎ目のないシームレスなものであることが好ましい。
予め用意するパイプの外径、内径にも限定はなく、注射針の場合、例えば、外径を０．３〜０．８ｍｍ、内径０．２〜０．６ｍｍ程度にすることができる。
The pipe prepared in advance may have a uniform outer diameter in the axial direction. Moreover, when using a pipe with a taper shape as an injection needle, it is preferable that the pipe prepared in advance is seamless and seamless.
There is no limitation on the outer diameter and inner diameter of the pipe prepared in advance, and in the case of an injection needle, for example, the outer diameter can be about 0.3 to 0.8 mm and the inner diameter can be about 0.2 to 0.6 mm.
また、つぼめ成形の方法に限定はなく、例えば、縮径加工金型（特殊円形ダイス）を用いて無回転でプレス成形してもよい。この方法は、金型の構成が単純であるため、一層優れた加工精度での成形ができ、一度で複数個の加工成形が可能になるので、生産性も向上し、加工速度を更に高めることができる。
つぼめ成形の後、必要に応じて、パイプを回転させながら縮径加工金型を動作させる。より具体的には、パイプを回転させて縮径加工金型とパイプの中心とを揃えながら、分割可能な縮径加工金型を任意のタイミングで開いたり（すなわち、分割した縮径加工金型を互いに近づける方向に移動させたり）、閉じたり（すなわち、分割した縮径加工金型を互いに離れる方向に移動させたり）することで、テーパー形状の長さや径を任意に変更するなどして、パイプの曲がりを矯正する工程を設けてもよい。
Moreover, there is no limitation in the method of squeeze molding, For example, you may press-mold without rotation using a diameter-reduction processing die (special circular die). Since this method has a simple mold configuration, it can be molded with even better processing accuracy, and multiple processing moldings can be performed at once, improving productivity and further increasing the processing speed. Can do.
After squeeze molding, if necessary, the diameter-reducing mold is operated while rotating the pipe. More specifically, while the pipe is rotated to align the diameter-reducing mold and the center of the pipe, a separable diameter-reducing mold is opened at any timing (ie, the divided diameter-reducing mold is divided). By moving the taper shape closer to each other) or by closing (that is, moving the divided diameter reducing dies in directions away from each other) to arbitrarily change the length and diameter of the tapered shape, etc. A step of correcting the bending of the pipe may be provided.
以下に実施例を挙げて本発明を詳細に説明するが、本発明は以下の実施例に限定されない。
表１に実施例で用いた供試材の化学成分値（質量％）を示した。表中の１〜５は本発明鋼、ａ〜ｃは比較鋼である。
EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.
Table 1 shows the chemical component values (mass%) of the test materials used in the examples. In the table, 1 to 5 are steels of the present invention, and ac are comparative steels.
（テーパー形状付きパイプの作製）
実施例においては、以下のようにして注射針用のテーパー形状付きパイプを作製した。
供試材を真空溶解炉にて溶解して鋼塊に鋳造した後、得られた鋼塊に熱間圧延を施して板厚３．０ｍｍの熱延板を製造した。その後、溶体化処理、冷間圧延を繰り返し、得られた冷延板から外径０．３５ｍｍのシームレス極細パイプ（芯引き管）を作製した。その後、パイプを所望の長さに切断し、バフ研磨した後、つぼめ成形（プレス加工）し、曲がりの矯正、洗浄、針先研磨、電解研磨、洗浄作業を経て、先端外径０．２ｍｍ以下のテーパー形状付きのシームレス極細パイプを作製した。
(Production of tapered pipe)
In Examples, a tapered pipe for an injection needle was produced as follows.
After the test material was melted in a vacuum melting furnace and cast into a steel ingot, the obtained steel ingot was hot-rolled to produce a hot-rolled sheet having a thickness of 3.0 mm. Thereafter, solution treatment and cold rolling were repeated, and a seamless extra-fine pipe (core drawing pipe) having an outer diameter of 0.35 mm was produced from the obtained cold-rolled sheet. After that, the pipe is cut to a desired length, buffed, then squeezed (pressed), bent, corrected, cleaned, polished by the tip of the needle, electropolished, and cleaned, with a tip outer diameter of 0.2 mm or less A seamless extra-fine pipe with a tapered shape was prepared.
つぼめ成形は、縮径加工金型（特殊円形ダイス）を用いて、パイプ先端を無回転でプレス加工することにより行った。
また、曲がりの矯正は、パイプを回転させながらダイスを上述のようにして動作し加工することにより行った。
The squeeze molding was performed by pressing the pipe tip without rotation using a reduced diameter die (special circular die).
Further, the bending was corrected by operating and processing the die as described above while rotating the pipe.
（断面硬さ測定）
テーパー形状付きパイプの断面硬さは、次のようにして測定した。
テーパー形状付きパイプの芯引き管部（つぼめていない部分）および縮径加工部を切り出し、中心軸に対して垂直な円形断面が底面となるように熱硬化性樹脂に埋め込み、研磨により鏡面仕上した。その後、図１に示すような周方向４等分位置の肉厚方向の中心点（Ａ〜Ｄ）における硬さを、マイクロビッカース硬さ試験機により測定し、その平均を平均断面硬さとした。
そして、縮径加工部の平均断面硬さから芯引き管部の平均断面硬さを差し引いたΔ硬さを求めた。
(Cross section hardness measurement)
The cross-sectional hardness of the tapered pipe was measured as follows.
The cored pipe part (the part that has not been squeezed) and the diameter-reduced part of the tapered pipe are cut out, embedded in a thermosetting resin so that the circular cross section perpendicular to the central axis is the bottom, and polished to a mirror finish . Thereafter, the hardness at the center point (A to D) in the thickness direction at the four equal positions in the circumferential direction as shown in FIG. 1 was measured with a micro Vickers hardness tester, and the average was taken as the average cross-sectional hardness.
And (DELTA) hardness which deducted the average cross-sectional hardness of the core drawing pipe part from the average cross-sectional hardness of the diameter reduction process part was calculated | required.
（肉厚測定）
テーパー形状付きパイプの肉厚は、次のようにして測定した。
断面硬さ測定に供したテーパー付きシームレス極細パイプの芯引き管部および縮径加工部を光学顕微鏡で１００倍に拡大し、図２に示すような周方向１６等分位置（１〜１６）の肉厚を測定し、その平均を平均肉厚とした。
そして、縮径加工部の平均肉厚から芯引き管部の平均肉厚を差し引いたΔ肉厚を求めた。なお、注射針として用いる場合、Δ肉厚は１５μｍ以下であることが好ましい。
(Thickness measurement)
The wall thickness of the tapered pipe was measured as follows.
The cored tube portion and the diameter-reduced portion of the tapered seamless ultra-thin pipe subjected to the cross-section hardness measurement are magnified 100 times with an optical microscope, and the circumferential direction is divided into 16 equal positions (1 to 16) as shown in FIG. The wall thickness was measured and the average was taken as the average wall thickness.
And (DELTA) thickness which deducted the average thickness of the core drawing pipe | tube part from the average thickness of the diameter reduction process part was calculated | required. When used as an injection needle, the Δ wall thickness is preferably 15 μm or less.
（加工硬化指数測定）
オーステナイト系ステンレス鋼の公称歪み３０〜４０％の高歪み領域での加工硬化指数（Ｎ値）は、次のようにして測定した。
供試材を真空溶解炉で溶解して鋼塊に鋳造した後、得られた鋼塊に熱間圧延を施して板厚３．０ｍｍの熱延板を製造した。その後、板厚０．８ｍｍとなるまで溶体化処理、冷間圧延を繰り返して冷延板を作製し、引張方向が圧延方向と平行になるようにＪＩＳ１３Ｂ号引張試験片を作製した。該ＪＩＳ１３Ｂ号引張試験片を用いて、ＪＩＳＺ２２０１に準じて引張試験を行い、得られた応力−歪み曲線からσ＝Ｃεn（真応力（σ）、真歪み（ε）、Ｃ（定数））を満足するｎを求め、Ｎ値とした。
(Measurement of work hardening index)
The work hardening index (N value) in a high strain region of 30-40% nominal strain of austenitic stainless steel was measured as follows.
After the test material was melted in a vacuum melting furnace and cast into a steel ingot, the obtained steel ingot was hot-rolled to produce a hot-rolled sheet having a thickness of 3.0 mm. Thereafter, solution treatment and cold rolling were repeated until the plate thickness reached 0.8 mm to produce a cold rolled sheet, and a JIS No. 13B tensile test piece was prepared so that the tensile direction was parallel to the rolling direction. Using this JIS No. 13B tensile test piece, a tensile test was performed according to JISZ2201, and σ = Cε n (true stress (σ), true strain (ε), C (constant)) was obtained from the obtained stress-strain curve. Satisfactory n was determined and used as the N value.
本発明鋼１〜５、比較鋼ａ〜ｃのＮ値と、各オーステナイト系ステンレス鋼を用いて製造したテーパー形状付きパイプの諸物性を表２に示す。本発明鋼１〜４のオーステナイト系ステンレス鋼は、Ｎ値が０．２６以上であり、これらのオーステナイト系ステンレス鋼を用いて製造したテーパー形状付きパイプにおいては、縮径加工部のΔ硬さが４１〜５５（ＨＶ）と加工硬化が高いことにより、Δ肉厚が３〜１３μｍと増肉が抑制された。
これに対し、比較鋼ａ〜ｃのオーステナイト系ステンレス鋼は、Ｎ値が０．１８〜０．２０と低いために、縮径加工部のΔ硬さが２７〜３３（ＨＶ）と低く、Δ肉厚が１８〜２２μｍと縮径加工部が増肉していた。
このように、本発明のオーステナイト系ステンレス鋼からなるパイプにつぼめ成形を施してテーパー形状を付与した場合には、縮径加工部の増肉を抑制することができた。これは、本発明のオーステナイト系ステンレス鋼は、高歪み領域での加工硬化指数（Ｎ値）が大きいので、縮径加工時にパイプの先端部の加工がある程度進むと、軸方向に歪みが分散するためであると推測される。
Table 2 shows the N values of
On the other hand, the austenitic stainless steels of the comparative steels a to c have a low N hardness of 0.18 to 0.20, and therefore the Δ hardness of the reduced diameter processed portion is as low as 27 to 33 (HV). The wall thickness was 18-22 μm and the reduced diameter processed part was thickened.
As described above, when the pipe made of the austenitic stainless steel of the present invention is subjected to the squeeze forming to give the tapered shape, the increase in the thickness of the reduced diameter processed portion can be suppressed. This is because the austenitic stainless steel of the present invention has a large work hardening index (N value) in a high strain region, and therefore, when the processing of the tip of the pipe proceeds to some extent during diameter reduction processing, strain is dispersed in the axial direction. This is presumed.
本発明のオーステナイト系ステンレス鋼を用いて製造された縮径加工部の増肉が抑制されたテーパー形状付きパイプは、肉厚が均一であるので、先端部で極端に内径が小さくなるということがなく、注射針として用いた場合の薬液の流動抵抗を抑えることができる。よって、本発明のオーステナイト系ステンレス鋼は注射針の製造に好適に用いることができる。 Since the pipe with a tapered shape, which is manufactured by using the austenitic stainless steel of the present invention and the thickness increase of the reduced diameter processed portion is suppressed, is uniform in thickness, the inner diameter is extremely small at the tip. In addition, the flow resistance of the chemical solution when used as an injection needle can be suppressed. Therefore, the austenitic stainless steel of this invention can be used suitably for manufacture of an injection needle.
Claims (3)
前記パイプの先端を、縮径加工金型を用いて、無回転でつぼめ成形する工程と、
パイプを回転させながらダイスを動作し加工する工程と、
を含む、テーパー形状付きパイプの製造方法。 Preparing a pipe made of the austenitic stainless steel according to claim 1 or 2,
A step of forming the tip of the pipe without rotation using a reduced diameter die; and
The process of working and processing the die while rotating the pipe,
The manufacturing method of the pipe with a taper shape including this.
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