JP2013204741A - Stainless steel pipe joint - Google Patents
Stainless steel pipe joint Download PDFInfo
- Publication number
- JP2013204741A JP2013204741A JP2012075672A JP2012075672A JP2013204741A JP 2013204741 A JP2013204741 A JP 2013204741A JP 2012075672 A JP2012075672 A JP 2012075672A JP 2012075672 A JP2012075672 A JP 2012075672A JP 2013204741 A JP2013204741 A JP 2013204741A
- Authority
- JP
- Japan
- Prior art keywords
- stainless steel
- steel pipe
- less
- ring
- corrosion resistance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Landscapes
- Joints With Sleeves (AREA)
Abstract
Description
この発明は、温水器やエコキュートなどに用いられる温水、給湯配管において、耐食性を有するステンレス鋼管継手に関する。 The present invention relates to a stainless steel pipe joint having corrosion resistance in hot water and hot water supply pipes used for water heaters and Ecocutes.
温水器やエコキュートなど温水缶体を有する給湯機器にはＣｕ製の給水・給湯配管が一般的に用いられている。しかし、地下水などを用いた場合に硫酸イオンやカルシウムイオンの存在によりＣｕ特有の孔食を生じ、早期に漏水にいたる場合がある。またＣｕ管の腐食により溶出したＣｕイオンは給水、給湯環境における電位を貴化させるために、缶体など付帯設備の腐食を誘発する可能性がある。さらには近年のＣｕの価格の上昇にともないシステムのコスト上昇も招いている。 A water supply / hot water supply pipe made of Cu is generally used for a hot water supply apparatus having a hot water can body such as a water heater or an eco-cute. However, when groundwater or the like is used, pitting corrosion peculiar to Cu occurs due to the presence of sulfate ions or calcium ions, leading to water leakage early. Further, Cu ions eluted by corrosion of the Cu pipe may cause corrosion of incidental equipment such as a can body in order to make potential in a water supply and hot water supply environment noble. In addition, the cost of the system is increased with the recent increase in the price of Cu.
耐食性を有する配管材料としてステンレス鋼管がある。ステンレス鋼はＣｒを含有しているため、腐食環境において表面に不働態皮膜を形成し、優れた耐食性を示す。このことから、耐食用途に幅広く用いられている。ステンレス鋼の中でもオーステナイト系ステンレス鋼は、一般にフェライト系ステンレス鋼と比較して高い耐食性を有する。しかし、温水環境では応力腐食割れ（ＳＣＣ）が発生すること、Ｎｉを多量に含有するためコストが高いことから、温水配管用途にはフェライト系ステンレス鋼が多く使用されている。 There is a stainless steel pipe as a piping material having corrosion resistance. Since stainless steel contains Cr, it forms a passive film on the surface in a corrosive environment and exhibits excellent corrosion resistance. For this reason, it is widely used for corrosion resistance. Among stainless steels, austenitic stainless steel generally has higher corrosion resistance than ferritic stainless steel. However, since stress corrosion cracking (SCC) occurs in a warm water environment and Ni is contained in a large amount, the cost is high. Therefore, ferritic stainless steel is often used for warm water piping applications.
図１は、温水配管用途における代表的な継手の模式図である。温水配管用途においては、例えば特許文献１に代表されるような現場でも手軽に施工可能なメカニカル継手が広く採用されている。 FIG. 1 is a schematic view of a typical joint in a hot water piping application. In hot water piping applications, for example, mechanical joints that can be easily constructed even in the field as represented by Patent Document 1 are widely used.
温水環境において、単純に浸漬する限り、一般的なフェライト系ステンレス鋼は耐食性を有する。しかしながら、実機において、ステンレス鋼管は、継手における隙間構造内面において隙間腐食が発生し、漏水に繋がる重大な問題となる。特にステンレス鋼管が溶接により製造されており、端部にフレア加工が施されている場合、端部かつ溶接ビード部は、溶接時の入熱ならびに加工による不働態皮膜の損傷により耐食性が低下しており、更に、過酷な腐食環境である隙間構造内面となることから、高い耐食性が要求される。 As long as it is simply immersed in a warm water environment, general ferritic stainless steel has corrosion resistance. However, in an actual machine, the stainless steel pipe is a serious problem in which crevice corrosion occurs on the inner surface of the gap structure in the joint, leading to water leakage. In particular, when stainless steel pipes are manufactured by welding and the ends are flared, the ends and weld bead portions have reduced corrosion resistance due to heat input during welding and damage to the passive film due to processing. In addition, since the inner surface of the gap structure is a severe corrosive environment, high corrosion resistance is required.
フェライト系ステンレス鋼は、一般に、特に隙間部の耐食性がオーステナイト系ステンレス鋼と比較して劣る。溶接隙間部においては、特にその傾向が蹄著である。故に、継手部の耐食性を確保することのみのためにＣｒ、Ｍｏを多量に含有した高価で加工性の低いフェライト系ステンレス鋼を適用しているのが現状である。 Ferritic stainless steel is generally inferior to austenitic stainless steel in particular in terms of the corrosion resistance of the gaps. In the weld gap, the tendency is particularly remarkable. Therefore, in order to ensure only the corrosion resistance of the joint portion, the present situation is that an expensive and low workability ferritic stainless steel containing a large amount of Cr and Mo is applied.
本発明の課題は、安価で配管部分の耐食性に優れたステンレス鋼管継手を提供することである。 An object of the present invention is to provide a stainless steel pipe joint that is inexpensive and excellent in corrosion resistance of a pipe portion.
本発明の構成は以下の通りである。
（１）ＴＩＧ溶接、高周波溶接、またはレーザー溶接により製造されたステンレス鋼管の端部にフレア加工を施し、Ｚｎを２０質量％以上含むＣｕ合金製のＯリングおよび漏水防止のための樹脂またはゴム製のＯリングを取り付けたことを特徴とする温水用途向けステンレス鋼管継手。
The configuration of the present invention is as follows.
(1) The end of a stainless steel pipe manufactured by TIG welding, high frequency welding, or laser welding is subjected to flaring, and an O-ring made of Cu alloy containing 20% by mass or more of Zn and a resin or rubber for preventing water leakage Stainless steel pipe fittings for hot water applications, characterized by having an O-ring attached.
（２）鋼管として用いるフェライト系ステンレス鋼が質量％で、Ｃ：０．０３％以下、Ｎ：０．０４％以下、Ｓｉ：２．０％以下、Ｍｎ：２．０％以下、Ｐ：０．０５％以下、Ｓ：０．０３％以下、Ｃｒ：１６〜２５％、Ｍｏ：４％以下、Ａｌ：０．００１〜０．１０％を含有し、残部がＦｅおよび不可避不純物からなり、式（１）で示す耐孔食指数（ＰＩ）が１８以上であることを特徴とする温水用途向けステンレス鋼管継手。
ただし、ＰＩは以下の式で与えられる。
ＰＩ＝Ｃｒ＋３Ｍｏ・・・・・（１）
(2) Ferritic stainless steel used as a steel pipe in mass%, C: 0.03% or less, N: 0.04% or less, Si: 2.0% or less, Mn: 2.0% or less, P: 0 0.05% or less, S: 0.03% or less, Cr: 16 to 25%, Mo: 4% or less, Al: 0.001 to 0.10%, with the balance being Fe and inevitable impurities, A stainless steel pipe joint for hot water applications, wherein the pitting corrosion index (PI) shown in (1) is 18 or more.
However, PI is given by the following equation.
PI = Cr + 3Mo (1)
（３）ステンレス鋼が、Ｆｅの一部に代えて、更に、質量％で、Ｎｉ：４％以下を含有することを特徴とする（１）または（２）の温水用途向けステンレス鋼管継手。 (3) The stainless steel pipe joint for hot water applications according to (1) or (2), wherein the stainless steel further contains Ni: 4% or less in mass% instead of part of Fe.
（４）ステンレス鋼が、Ｆｅの一部に代えて、更に、質量％で、Ｔｉ：２５×（Ｃ％＋Ｎ％）以下およびＮｂ：２５×（Ｃ％＋Ｎ％）以下の一種以上を含有することを特徴とする（１）ないし（３）の温水用途向けステンレス鋼管継手。 (4) In place of a part of Fe, the stainless steel further contains one or more of Ti: 25 × (C% + N%) or less and Nb: 25 × (C% + N%) or less in mass%. (1) to (3), a stainless steel pipe joint for hot water use.
（５）ステンレス鋼管継手における接合部の隙間構造内にＺｎを２０質量％以上含むＣｕ合金部品を配置し、漏水防止のための樹脂またはゴム製のＯリングと併用していることを特徴とするステンレス鋼管継手施工方法。 (5) A Cu alloy part containing 20% by mass or more of Zn is disposed in the gap structure of the joint in the stainless steel pipe joint, and is used in combination with a resin or rubber O-ring for preventing water leakage. Stainless steel pipe fitting construction method.
低コストかつ加工性の良いステンレス鋼管継手を提供できる。この継手は温水配管用途一般に適用でき、低コスト化、省スペース化に寄与できる。 It is possible to provide a stainless steel pipe joint with low cost and good workability. This joint can be applied to general hot water piping applications, and can contribute to cost reduction and space saving.
本発明者らは、温水配管用途で耐食性を有し、かつ施工性の良いステンレス鋼継手を開発するため種々の検討を行った結果、以下の知見を得た。 As a result of various investigations to develop a stainless steel joint having corrosion resistance and good workability for use in hot water piping, the present inventors have obtained the following knowledge.
ａ）ステンレス鋼を溶接により銅管として加工する際に、溶接ビード部は溶接時の入熱を受ける。この結果、Ｃｒ主体の酸化スケールが形成され、スケール直下のＣｒ濃度が減少することにより耐食性が低下する。配管内面の溶接ビード部には、内面形状を整えるためのビードカットを施すことがあるが、この場合も強加工と研磨焼けにより耐食性が低下している。したがって、ステンレス鋼管の耐食性は、継手を考慮しない場合、溶接ビード部の耐食性に支配される。なお、オーステナイト系ステンレス鋼の場合、溶接時の残留応力が原因で溶接ビード部に応力腐食割れ（ＳＣＣ）が発生して漏水に繋がるため、基本的に本用途には適用不可能である。 a) When processing stainless steel as a copper pipe by welding, the weld bead portion receives heat input during welding. As a result, an oxide scale mainly composed of Cr is formed, and the corrosion resistance is lowered by decreasing the Cr concentration immediately below the scale. The weld bead portion on the inner surface of the pipe may be subjected to bead cut for adjusting the inner surface shape, but in this case as well, the corrosion resistance is lowered due to strong processing and polishing burn. Therefore, the corrosion resistance of the stainless steel pipe is governed by the corrosion resistance of the weld bead portion when the joint is not considered. In the case of austenitic stainless steel, stress corrosion cracking (SCC) occurs in the weld bead due to residual stress at the time of welding, which leads to water leakage, and thus is basically not applicable to this application.
ｂ）ステンレス鋼管の継手としては、溶接継手とメカニカル継手が一般的である。溶接は現場での施工性が悪いため、温水配管用途ではメカニカル継手が多く採用されている。 b) As a joint of a stainless steel pipe, a welded joint and a mechanical joint are common. Since welding has poor workability on site, many mechanical joints are used in hot water piping applications.
ｃ）ステンレス鋼管のメカニカル継手においては、多くの場合、端部に拡管フレア加工が施される。更に、ステンレス鋼管をソケットに差し込み、ステンレス鋼管とソケットの間には、漏水防止のため、樹脂または金属のＯリング（またはパッキン）が組み込まれる。すなわち、メカニカル継手においては、ステンレス鋼管とソケットまたはＯリングとの隙間構造が形成される。 c) In many cases, a stainless steel pipe mechanical joint is subjected to a tube-flaring process at the end. Further, a stainless steel pipe is inserted into the socket, and a resin or metal O-ring (or packing) is incorporated between the stainless steel pipe and the socket to prevent water leakage. That is, in the mechanical joint, a gap structure between the stainless steel pipe and the socket or O-ring is formed.
ｄ）ソケットとの隙間構造、Ｏリングまたはパッキンとの隙間構造は共に過酷な隙間腐食環境が形成されるが、詳細な検討の結果、密着隙間となるＯリングとの隙間構造が最も過酷な環境であるとの知見を得た。この部位において腐食が発生すると、漏水に繋がる危険性があるため、実用上も重要な部位である。 d) Although the gap structure with the socket and the gap structure with the O-ring or packing together form a severe crevice corrosion environment, as a result of detailed studies, the gap structure with the O-ring that forms the tight adhesion gap is the most severe environment. The knowledge that it is. If corrosion occurs in this part, there is a risk of leaking water, so this part is also practically important.
ｅ）以上の知見から、ステンレス鋼管のメカニカル継手において、最も耐食性が必要となるのは、溶接ビード部かつＯリングとの隙間構造を形成している部分である。これまで、温水配管用途のステンレス鋼は、耐隙間腐食性の問題から、ＣｒやＭｏを多く含有する、高コストで加工性の低い高合金フェライト系ステンレス鋼が適用されていた。 e) From the above knowledge, in the stainless steel pipe mechanical joint, the most corrosion resistance is required in the portion where the weld bead portion and the O-ring are formed. Up to now, high-alloy ferritic stainless steel containing a large amount of Cr and Mo and having low workability has been applied to stainless steel for hot water piping because of the problem of crevice corrosion resistance.
ｆ）そこで、隙間構造が形成されている継手部を、Ｚｎの犠牲防食作用により、局所的に防食することで、これまで適用できなかった、低コストで加工性の良いフェライト系ステンレス鋼が温水配管用途に適用可能となる。また、加工性が悪く、端部の拡管フレア加工が困難であった鋼種についても、強加工による耐食性の低下を招くことなく、継手とすることができる。Ｚｎを用いてステンレス鋼管を犠牲防食する具体的な方法は、黄銅製のＯリングをメカニカル継手内部に配置することによる。 f) Therefore, the ferritic stainless steel with low workability and good workability, which could not be applied so far, is obtained by locally preventing the joint portion in which the gap structure is formed by the sacrificial anticorrosive action of Zn. Applicable to piping applications. Moreover, it can be set as a coupling, without inviting the fall of the corrosion resistance by a strong process also about the steel type with which workability was bad and the pipe-flaring process of the edge part was difficult. A specific method for sacrificing corrosion protection of stainless steel pipes using Zn is by placing a brass O-ring inside the mechanical joint.
ｇ）Ｚｎは、犠牲防食作用を有し、腐食生成物によるバリア効果も期待できる材料であり、主にめっきとして広く用いられている。しかし、温水配管用途においては、消耗が速く、生成した腐食生成物も温水流により溶出してしまう欠点がある。 g) Zn is a material that has a sacrificial anticorrosive action and can be expected to have a barrier effect due to corrosion products, and is widely used mainly as a plating. However, in hot water piping applications, there is a drawback that consumption is fast and the generated corrosion products are also eluted by the hot water flow.
ｈ）Ｚｎを含有する黄銅の場合、Ｚｎ単体と比較してＺｎの消耗が遅い。また、Ｚｎが犠牲防食する際に、スポンジ状のＣｕが腐食生成物を保持した状態で残存するため、Ｚｎ単体と比較して強度を保持でき、腐食生成物の消耗も少ない。更に、Ｏリングとして隙間構造内部に配置した場合、腐食生成物が直接、温水流に曝されないため、腐食生成物のバリア効果がより発揮できる。ゴム製Ｏリングと併用することで、漏水も防止可能である。 h) In the case of brass containing Zn, consumption of Zn is slower than that of Zn alone. In addition, when Zn is sacrificial and corrosion-proof, sponge-like Cu remains in a state where the corrosion product is retained, so that the strength can be maintained as compared with Zn alone, and the corrosion product is less consumed. Further, when the O-ring is arranged inside the gap structure, the corrosion product is not directly exposed to the hot water flow, and therefore, the barrier effect of the corrosion product can be further exhibited. Water leakage can also be prevented by using it together with a rubber O-ring.
１）図２に黄銅製Ｏリングを採用した継手の構造例を示す。（ａ）は黄銅製Ｏリングを１個適用した構造である。（ｂ）は黄銅製Ｏリングを２個配置した構造であり、ステンレス鋼管端部のフレア加工が（ａ）と比較して容易であるため、金型費用が低減でき初期投資の点でメリットがあり、また、加工性が悪いステンレス鋼にも本発明が適用可能となる。このように、隙間構造内部に黄銅部品を配置することにより、最も耐食性の要求される溶接ビード部かつＯリングとの密着隙間形成部を局所的に防食することで、これまで適用できなかった、低コスト、高加工性のフェライト系ステンレス鋼が適用可能となった。これにより、原材料費、加工費を低減した低コストの継手を提供できるのみならず、曲げ加工が容易であるため、省スペース化も期待できる。 1) FIG. 2 shows a structural example of a joint adopting a brass O-ring. (A) is a structure to which one brass O-ring is applied. (B) is a structure in which two brass O-rings are arranged, and the flaring of the end of the stainless steel tube is easier than in (a), so the mold cost can be reduced and there is an advantage in terms of initial investment. In addition, the present invention can be applied to stainless steel having poor workability. Thus, by arranging the brass parts inside the gap structure, it was not possible to apply so far by locally preventing the weld bead part and the adhesion gap forming part with the O ring that are most required for corrosion resistance. Low-cost, high workability ferritic stainless steel is now applicable. As a result, not only can a low-cost joint with reduced raw material costs and processing costs be provided, but also bending can be easily performed, so that space saving can also be expected.
本発明を適用可能なステンレス鋼管は、継手部を局部的に防食することにより、配管全体の寿命を大幅に延長できるもの、すなわち、継手部の隙間構造外では温水環境で耐食性を有するフェライト系ステンレス鋼を素材とする必要がある。隙間構造外において、温水環境において耐食性を有するには、耐孔食指数（ＰＩ＝Ｃｒ＋３Ｍｏ）にて１８以上が必要である。それに伴い、必要とされる犠牲防食の効果量、すなわち黄銅中のＺｎ含有量も規定される。以下、本発明における黄銅およびフェライト系ステンレス鋼を構成する各元素について説明する。 The stainless steel pipe to which the present invention can be applied is one that can significantly extend the life of the entire pipe by locally preventing the joint portion, that is, a ferritic stainless steel having corrosion resistance in a hot water environment outside the gap structure of the joint portion. It is necessary to use steel as the material. Outside the gap structure, in order to have corrosion resistance in a hot water environment, a pitting corrosion index (PI = Cr + 3Mo) of 18 or more is required. Accordingly, the effective amount of sacrificial protection required, that is, the Zn content in brass is also defined. Hereinafter, each element which comprises the brass in this invention and a ferritic stainless steel is demonstrated.
黄銅に含有されるＺｎの比率が多いほど、犠牲防食の効果が大きくなる。隙間構造外では温水環境で耐食性を有するステンレス鋼管を犠牲防食する場合、２０％以上のＺｎを含有している必要がある。また、Ｚｎ含有量が３０％まではＺｎ含有量が多いほど伸びが大きく加工性が良い。３０％以上となるとα単相からα＋βの二相構造となり、伸びが急激に減少するだけでなく、β相の選択溶解が発生するようになる。Ｚｎを４０％以上含有する場合、この傾向が特に顕著である。選択溶解が発生した場合も、ステンレス鋼管に対する犠牲防食作用は発揮されるものの、その効果が低下する。したがって、本発明におけるＣｕ合金中のＺｎ含有量は２０％以上、好ましくは２０〜４０％である。 The greater the proportion of Zn contained in brass, the greater the effect of sacrificial protection. Outside the gap structure, when sacrificial corrosion protection is performed on a stainless steel pipe having corrosion resistance in a warm water environment, it is necessary to contain 20% or more of Zn. Further, when the Zn content is up to 30%, the larger the Zn content, the larger the elongation and the better the workability. When it is 30% or more, the α single phase changes to a α + β two-phase structure, and not only the elongation decreases rapidly but also the selective dissolution of the β phase occurs. This tendency is particularly remarkable when Zn is contained in an amount of 40% or more. Even when selective dissolution occurs, the sacrificial anticorrosive action for the stainless steel pipe is exhibited, but the effect is reduced. Therefore, the Zn content in the Cu alloy in the present invention is 20% or more, preferably 20 to 40%.
Ｃ（炭素）およびＮ（窒素）は、ステンレス鋼中に不可避的に含まれる元素である。ＣおよびＮの含有量を低減すると、炭化物および窒化物の生成が少なくなり、溶接性および溶接部の耐食性を向上できるので、ＣおよびＮの含有量は少ない方が好ましい。しかしながら、ＣおよびＮの含有量を低減するには精錬時間を長くする必要があり、精錬時間が長くなるとステンレス鋼の製造コストが高騰してしまう。そこで、耐食性とコストのバランスを考慮して、Ｃの含有量の上限を０．０３％以下とし、Ｎの含有量の上限を０．０４％とした。 C (carbon) and N (nitrogen) are elements inevitably contained in stainless steel. If the C and N contents are reduced, the formation of carbides and nitrides is reduced, and the weldability and corrosion resistance of the welded portion can be improved. Therefore, it is preferable that the C and N contents are low. However, in order to reduce the contents of C and N, it is necessary to lengthen the refining time, and if the refining time becomes long, the production cost of stainless steel increases. Therefore, considering the balance between corrosion resistance and cost, the upper limit of the C content is set to 0.03% or less, and the upper limit of the N content is set to 0.04%.
Ｓｉ（ケイ素）は、脱酸剤として添加される。しかしながら、２％を超えるとフェライト相の硬質化を招き、加工性や靭性を悪化させる要因となる。したがって、Ｓｉ含有量の上限を２％とした。 Si (silicon) is added as a deoxidizer. However, if it exceeds 2%, the ferrite phase is hardened, which causes deterioration of workability and toughness. Therefore, the upper limit of the Si content is 2%.
Ｍｎ（マンガン）は、ステンレス鋼に不純物として含まれるＳと結合し、化学的に不安定なＭｎＳを形成して耐食性を低下させる。したがって、Ｍｎ含有量は低いほど好ましく、本発明においては２％を上限とする。 Mn (manganese) combines with S contained as an impurity in stainless steel to form chemically unstable MnS, thereby reducing the corrosion resistance. Therefore, the lower the Mn content, the better. In the present invention, the upper limit is 2%.
Ｐ（りん）は、靭性を損なうため低い方が望ましい。ただし、含Ｃｒ鋼の溶製において精錬により脱りんは困難であることから、Ｐ含有量を極低化するには原料の厳選など過剰なコスト増大を伴う。したがって、本発明では一般的なフェライト系ステンレス鋼と同様に０．０５％までのＰ含有を許容する。 P (phosphorus) is preferably low because it impairs toughness. However, since dephosphorization is difficult by refining in the smelting of Cr-containing steel, excessive cost increase such as careful selection of raw materials is involved in extremely reducing the P content. Therefore, in the present invention, the P content up to 0.05% is allowed as in the case of general ferritic stainless steel.
Ｓ（硫黄）は、孔食の起点となりやすいＭｎＳを形成して耐食性を阻害する元素である。Ｓ含有量は０．０３％以下とする。 S (sulfur) is an element that inhibits corrosion resistance by forming MnS that tends to be a starting point of pitting corrosion. The S content is 0.03% or less.
Ｃｒ（クロム）は、不働態皮膜の主要構成元素であり、耐孔食性、耐隙間腐食性の向上をもたらす。しかし、Ｃｒ含有量が多くなるとＣ、Ｎの低減が難しくなり、機械的性質やコストを増大させる要因となる。したがって、本発明では、Ｃｒ含有量を１６〜２５％とする。 Cr (chromium) is a main constituent element of the passive film, and improves pitting corrosion resistance and crevice corrosion resistance. However, when the Cr content increases, it becomes difficult to reduce C and N, which increases the mechanical properties and cost. Therefore, in this invention, Cr content shall be 16-25%.
ＭｏはＣｒと共に耐食性を向上させるために有効な元素である。しかし、Ｍｏの添加効果は４％以上添加してもほぼ変化なく、過剰な添加はコスト増大を招くため、本発明では、Ｍｏ含有量を４％以下とした。 Mo is an effective element for improving the corrosion resistance together with Cr. However, the effect of addition of Mo is substantially unchanged even when 4% or more is added, and excessive addition causes an increase in cost. Therefore, in the present invention, the Mo content is set to 4% or less.
Ａｌ（アルミニウム）は脱酸剤として用いる元素である。過剰に添加した場合、ステンレス鋼管を製造する際に溶接性を悪化させるため、本発明ではＡｌ含有量を０．００１〜０．１０％とした。 Al (aluminum) is an element used as a deoxidizer. When adding excessively, when manufacturing a stainless steel pipe, in order to deteriorate weldability, in this invention, Al content was made into 0.001-0.10%.
Ｎｉ（ニッケル）はステンレス鋼の耐酸性を向上させ、腐食を抑制する元素である。用途により適切な量を添加しても良いが、４％を超えて添加した場合、オーステナイト相を含む二相組織となり、加工性が低下する。したがって、適切な添加量は４％以下である。 Ni (nickel) is an element that improves the acid resistance of stainless steel and suppresses corrosion. An appropriate amount may be added depending on the application, but when added in excess of 4%, a two-phase structure including an austenite phase is formed, and workability is deteriorated. Therefore, the appropriate addition amount is 4% or less.
Ｔｉ（チタン）およびＮｂ（ニオブ）はＣ、Ｎを固定し、ステンレス鋼で問題となる粒界腐食を防止するのに有効な元素である。ただし、過剰に添加した場合、Ｔｉは表面疵の発生により製造性を悪化させ、Ｎｂはフェライト相を硬質化し加工性を悪化させる。したがって、本発明ではＴｉ：２５×（Ｃ％＋Ｎ％）以下およびＮｂ：２５×（Ｃ％＋Ｎ％）以下の一種以上を含有するものとする。 Ti (titanium) and Nb (niobium) are effective elements for fixing C and N and preventing intergranular corrosion which is a problem in stainless steel. However, when excessively added, Ti deteriorates productivity due to generation of surface defects, and Nb hardens the ferrite phase and deteriorates workability. Therefore, in this invention, Ti: 25 * (C% + N%) or less and Nb: 25 * (C% + N%) or less shall be contained.
以下、本発明の実施例について詳しく解説する。
表１に示す化学組成を有するステンレス鋼を溶製し、熱間圧延にて板厚３ｍｍの熱延板を作製した。その後、冷間圧延にて１．０ｍｍとし、仕上焼鈍を１０００〜１０７０℃で行い、酸洗を施すことによって供試材とした。
Examples of the present invention will be described in detail below.
Stainless steel having the chemical composition shown in Table 1 was melted, and a hot-rolled sheet having a thickness of 3 mm was produced by hot rolling. Then, it was set as 1.0 mm by cold rolling, finish annealing was performed at 1000-1070 degreeC, and it was set as the test material by performing pickling.
得られた鋼材を用いて、ＴＩＧ溶接によりステンレス銅管を作製した。ステンレス鋼管の端部に二種類のフレア加工を施し、一方にはゴム製のＯリングのみを、他方にはゴム製のＯリングおよびＺｎを３５質量％含有する黄銅製のＯリングを装着し、樹脂製のソケットに差し込んで固定し、継手サンプルとした。継手の構造は図２（ｂ）と同様の形状とした。 Using the obtained steel material, a stainless copper pipe was produced by TIG welding. Two kinds of flares are applied to the end of the stainless steel pipe, and only one rubber O-ring is attached to the other, and the other rubber O-ring and brass O-ring containing 35% by mass of Zn are attached. It was inserted into a resin socket and fixed to obtain a joint sample. The structure of the joint was the same as that shown in FIG.
図３に耐食性評価として行ったループ試験装置の概略を示す。作製した継手サンプル（５）内に温水を一定の流速で流し、各部位での腐食の有無を調査した。試験液槽（６）（容量２７０Ｌ）には腐食促進のため２０００ｐｐｍＣｌ―に加え２ｐｐｍのＣｕ２＋を添加した温水を用いた。ヒーター（７）により、試験中は温水を８０℃に保持し、ポンプ（８）にて温水を循環させた。Ｃｌ―は上水の残留塩素起因により、Ｃｕ２＋は熱交換器等に使用されているＣｕからの溶出により、それぞれ混入しうる腐食促進成分である。試験期間は７０日とし、７日ごとにループさせる温水を交換した。
FIG. 3 shows an outline of a loop test apparatus performed as a corrosion resistance evaluation. Hot water was allowed to flow through the produced joint sample (5) at a constant flow rate, and the presence or absence of corrosion at each part was investigated. For the test solution tank (6) (capacity 270 L), hot water to which 2 ppm of Cu 2+ was added in addition to 2000
ループ試験後、隙間構造外の溶接ビード部（以下、溶接部）、溶接ビード部かつＯリングとの密着隙間部（以下、隙間部）の腐食状態を観察した。温水用途においては、配管以外にも多くの部位にステンレス鋼が使用されており、設備全体での寿命は、最も寿命の短い部位で決定される。最も寿命の短い部位は溶接隙間部であり、温水用途にて、従来、一般的に使用されているフェライト系ステンレス鋼の溶接隙間を本試験にて評価したところ、板厚約０．８ｍｍに対して、侵食深さは約２００μｍであった。温水配管の板厚は、薄いもので０．４ｍｍ程度である。そこで、各部位における侵食深さが１００μｍ以下のものを合格（○）、１００μｍを超えるものを不合格（×）とした。 After the loop test, the corrosion state of the weld bead portion outside the gap structure (hereinafter referred to as a weld portion), the weld bead portion and the close contact gap portion (hereinafter referred to as the gap portion) with the O-ring was observed. In hot water applications, stainless steel is used in many parts other than piping, and the life of the entire equipment is determined at the part with the shortest life. The part with the shortest life is a weld gap, and when the weld gap of ferritic stainless steel, which has been conventionally used in hot water applications, was evaluated in this test, the thickness was about 0.8 mm. The erosion depth was about 200 μm. The thickness of the hot water piping is thin and is about 0.4 mm. Then, the thing whose erosion depth in each site | part is 100 micrometers or less was set as the pass ((circle)), and the thing exceeding 100 micrometers was set as the disqualification (x).
表２にループ試験結果を示す。鋼種Ａ、Ｂは、温水環境において従来一般的に使用されているフェライト系ステンレス鋼であり、黄銅製Ｏリング無しでも溶接部、隙間部共に耐食性を有する。鋼種Ｃ、Ｄは、黄銅製Ｏリング無しでは溶接部のみ耐食性を有するが、黄銅製Ｏリング有りでは隙間部も耐食性を有するようになる。すなわち、本発明により新たに適用可能となった鋼種である。Ｅ鋼は、請求項の成分範囲外の比較例であり、溶接部の耐食性が劣るため、継手部を局所的に防食しても、温水配管用途には適用不可能である。 Table 2 shows the loop test results. Steel types A and B are ferritic stainless steels that are generally used in a hot water environment and have corrosion resistance in both the welded portion and the gap portion even without a brass O-ring. Steel types C and D have corrosion resistance only in the welded part without the brass O-ring, but the gap part also has corrosion resistance with the brass O-ring. That is, it is a steel type newly applicable by the present invention. Steel E is a comparative example outside the component range of the claims, and since the corrosion resistance of the welded portion is inferior, even if the joint portion is locally anticorrosive, it is not applicable to hot water piping applications.
以上説明したように、本発明を用いることで、低コストかつ加工性の良いステンレス鋼管継手を提供できる。この継手は温水配管用途一般に適用でき、低コスト化、省スペース化に寄与できる。 As described above, by using the present invention, it is possible to provide a stainless steel pipe joint with low cost and good workability. This joint can be applied to general hot water piping applications, and can contribute to cost reduction and space saving.
１ ソケット
２ Ｏリング
３ ステンレス
４ 黄銅リング
５ 試料
６ 試験液槽
７ ヒーター
８ ポンプ
1 Socket 2 O-
Claims (5)
ただし、ＰＩは以下の式で与えられる。
ＰＩ＝Ｃｒ＋３Ｍｏ・・・・・（１） Ferritic stainless steel is mass%, C: 0.03% or less, N: 0.04% or less, Si: 2.0% or less, Mn: 2.0% or less, P: 0.05% or less, S: 0.03% or less, Cr: 16 to 25%, Mo: 4% or less, Al: 0.001 to 0.10%, the balance is made of Fe and inevitable impurities, and is represented by the formula (1) 2. The stainless steel pipe joint according to claim 1, wherein the pitting corrosion index (PI) is 18 or more.
However, PI is given by the following equation.
PI = Cr + 3Mo (1)
A stainless steel pipe joint characterized in that a Cu alloy part containing 20 mass% or more of Zn is disposed in the gap structure of the joint in the stainless steel pipe joint, and is used in combination with a resin or rubber O-ring for preventing water leakage .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2012075672A JP2013204741A (en) | 2012-03-29 | 2012-03-29 | Stainless steel pipe joint |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2012075672A JP2013204741A (en) | 2012-03-29 | 2012-03-29 | Stainless steel pipe joint |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2013204741A true JP2013204741A (en) | 2013-10-07 |
Family
ID=49524046
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2012075672A Pending JP2013204741A (en) | 2012-03-29 | 2012-03-29 | Stainless steel pipe joint |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2013204741A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101831160B1 (en) | 2015-12-10 | 2018-02-22 | 주식회사 태성 | Water pipe connection structure and connection method |
| JP2021085056A (en) * | 2019-11-26 | 2021-06-03 | 日鉄ステンレス株式会社 | Ferritic stainless steel member for water-use facility |
| JP2021515140A (en) * | 2019-01-30 | 2021-06-17 | 上海衆源燃油分配器製造有限公司Ｓｈａｎｇｈａｉ Ｚｈｏｎｇｙｕａｎ Ｆｕｅｌ Ｒａｉｌ Ｍａｎｕｆａｃｔｕｒｅ Ｃｏ．， Ｌｔｄ | High pressure rigid flexible pipeline connection sealing system |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5725227A (en) * | 1980-07-21 | 1982-02-10 | Nisshin Steel Co Ltd | Joining method of stainless steel pipe |
| JPS5745379A (en) * | 1980-08-30 | 1982-03-15 | Sansha Electric Mfg Co Ltd | Ultrasonic washer |
| JPH04198493A (en) * | 1990-11-28 | 1992-07-17 | Sumitomo Metal Ind Ltd | Connecting structure of steel material and gasket |
| JP2000120974A (en) * | 1998-10-21 | 2000-04-28 | Mitsubishi Heavy Ind Ltd | Force feeding pipe for dewatered sludge |
| JP2002285300A (en) * | 2001-01-18 | 2002-10-03 | Kawasaki Steel Corp | Ferritic stainless steel sheet and production method therefor |
| JP2005256869A (en) * | 2004-03-09 | 2005-09-22 | Sun Rise Kogyo Kk | Structure of end portion of pipe, and method for manufacturing end portion of pipe |
| JP2011184731A (en) * | 2010-03-08 | 2011-09-22 | Nippon Steel & Sumikin Stainless Steel Corp | Ferritic stainless steel having excellent corrosion resistance in condensed water environment generated from hydrocarbon combustion exhaust gas |
-
2012
- 2012-03-29 JP JP2012075672A patent/JP2013204741A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5725227A (en) * | 1980-07-21 | 1982-02-10 | Nisshin Steel Co Ltd | Joining method of stainless steel pipe |
| JPS5745379A (en) * | 1980-08-30 | 1982-03-15 | Sansha Electric Mfg Co Ltd | Ultrasonic washer |
| JPH04198493A (en) * | 1990-11-28 | 1992-07-17 | Sumitomo Metal Ind Ltd | Connecting structure of steel material and gasket |
| JP2000120974A (en) * | 1998-10-21 | 2000-04-28 | Mitsubishi Heavy Ind Ltd | Force feeding pipe for dewatered sludge |
| JP2002285300A (en) * | 2001-01-18 | 2002-10-03 | Kawasaki Steel Corp | Ferritic stainless steel sheet and production method therefor |
| JP2005256869A (en) * | 2004-03-09 | 2005-09-22 | Sun Rise Kogyo Kk | Structure of end portion of pipe, and method for manufacturing end portion of pipe |
| JP2011184731A (en) * | 2010-03-08 | 2011-09-22 | Nippon Steel & Sumikin Stainless Steel Corp | Ferritic stainless steel having excellent corrosion resistance in condensed water environment generated from hydrocarbon combustion exhaust gas |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101831160B1 (en) | 2015-12-10 | 2018-02-22 | 주식회사 태성 | Water pipe connection structure and connection method |
| JP2021515140A (en) * | 2019-01-30 | 2021-06-17 | 上海衆源燃油分配器製造有限公司Ｓｈａｎｇｈａｉ Ｚｈｏｎｇｙｕａｎ Ｆｕｅｌ Ｒａｉｌ Ｍａｎｕｆａｃｔｕｒｅ Ｃｏ．， Ｌｔｄ | High pressure rigid flexible pipeline connection sealing system |
| JP2021085056A (en) * | 2019-11-26 | 2021-06-03 | 日鉄ステンレス株式会社 | Ferritic stainless steel member for water-use facility |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR101339484B1 (en) | High-strength stainless steel pipe | |
| EP2562284B1 (en) | Cr-CONTAINING STEEL PIPE FOR LINE PIPE AND HAVING EXCELLENT INTERGRANULAR STRESS CORROSION CRACKING RESISTANCE AT WELDING-HEAT-AFFECTED PORTION | |
| KR20130123463A (en) | Ferrite stainless steel exhibiting excellent corrosion resistance and strength in weld zones, and tig-welded structure | |
| JP2007302995A (en) | Ferritic stainless steel for warm water vessel with welded structure and warm water vessel | |
| JP2014084493A (en) | AUSTENITIC Fe-Ni-Cr ALLOY FOR COATED TUBE EXCELLENT IN WELDABILITY | |
| JP2014114466A (en) | Cladding material of duplex stainless clad steel having excellent pitting-corrosion resistance, duplex stainless clad steel using the same, and method for producing the same | |
| EP2500444A1 (en) | Duplex stainless steel having excellent alkali resistance | |
| JP4400423B2 (en) | Martensitic stainless steel pipe | |
| JP2011105976A (en) | Drain pipe | |
| JP2013204741A (en) | Stainless steel pipe joint | |
| JP4502131B2 (en) | Duplex stainless steel with excellent hot workability | |
| JP5640777B2 (en) | Cr-containing steel pipe for line pipes with excellent intergranular stress corrosion cracking resistance in weld heat affected zone | |
| JP2007321181A (en) | Method for forming martenstic stainless steel material welded part | |
| JP5780660B2 (en) | Welded structure of ferritic stainless steel can | |
| JP5045178B2 (en) | Method for manufacturing bend pipe for line pipe and bend pipe for line pipe | |
| JP2009114471A (en) | High strength stainless steel pipe | |
| AU758316B2 (en) | High Cr steel pipe for line pipe | |
| JP2013204128A (en) | Ferritic stainless steel excellent in corrosion resistance in welded portion | |
| JP5467673B2 (en) | Ferritic stainless steel for corrugated tubes | |
| JP4765283B2 (en) | Method for producing martensitic stainless steel pipe circumferential welded joint | |
| JP2011068967A (en) | Water storage tank constructed by welding panel made from stainless steel | |
| JP5040973B2 (en) | Method for producing martensitic stainless steel pipe circumferential welded joint | |
| JP2009167439A (en) | Ferritic stainless steel for welding gap structural warm-water vessel | |
| JP5365499B2 (en) | Duplex stainless steel and urea production plant for urea production plant | |
| JP4823534B2 (en) | Low Ni austenitic stainless steel with excellent stress corrosion cracking resistance |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20140704 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20150416 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20150602 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20150730 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20151215 |
|
| A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20160510 |