JPH10237602A - Niobium-containing ferritic stainless steel excellent in low temperature toughness of hot rolled sheet - Google Patents
Niobium-containing ferritic stainless steel excellent in low temperature toughness of hot rolled sheetInfo
- Publication number
- JPH10237602A JPH10237602A JP5857997A JP5857997A JPH10237602A JP H10237602 A JPH10237602 A JP H10237602A JP 5857997 A JP5857997 A JP 5857997A JP 5857997 A JP5857997 A JP 5857997A JP H10237602 A JPH10237602 A JP H10237602A
- Authority
- JP
- Japan
- Prior art keywords
- stainless steel
- hot
- mass
- ferritic stainless
- temperature toughness
- 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.)
- Granted
Links
Landscapes
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、連続鋳造片を熱間
圧延したままの、Ｎｂ含有フェライト系ステンレス鋼の
鋼帯（以下，焼鈍を施した熱延焼鈍板と区別するため、
熱延板と称す）の低温靭性に関するものである。BACKGROUND OF THE INVENTION The present invention relates to a steel strip of Nb-containing ferritic stainless steel (hereinafter referred to as an annealed hot-rolled annealed sheet) in which a continuously cast piece is hot-rolled.
(Referred to as hot-rolled sheet) at low temperature.
【０００２】[0002]
【従来の技術】フェライト系ステンレス鋼は、オーステ
ナイト系に比べて熱膨張係数が低いため、熱疲労特性や
高温酸化特性に優れており、熱ひずみが問題となる耐熱
用途に使用されている。自動車排ガス経路部材において
は、エキゾーストマニホールド、フロントパイプ、触媒
担体外筒、センターパイプなどにフェライト系ステンレ
ス鋼が使用されている。近年、排ガス浄化効率の向上や
高出力化の観点から排ガスの温度は上昇する傾向にあ
り、より耐熱性の優れたフェライト系ステンレス鋼が求
められている。これに対応するために、Ｎｂ、Ｍｏなど
を含有した鋼が開発されており、これらの合金元素の含
有量も高くなる傾向にある。2. Description of the Related Art Ferritic stainless steel has a lower coefficient of thermal expansion than austenitic stainless steel, and therefore has excellent thermal fatigue properties and high-temperature oxidation properties, and is used for heat-resistant applications where thermal strain is a problem. In automobile exhaust gas path members, ferrite-based stainless steel is used for exhaust manifolds, front pipes, catalyst carrier outer cylinders, center pipes, and the like. In recent years, the temperature of exhaust gas has tended to increase from the viewpoint of improving exhaust gas purification efficiency and increasing output, and a ferritic stainless steel having more excellent heat resistance has been demanded. To cope with this, steels containing Nb, Mo and the like have been developed, and the content of these alloying elements tends to be high.
【０００３】一般に，フェライト系ステンレス鋼は、延
性脆性遷移温度を有し、遷移温度域よりも低温側では、
脆性的な割れが発生する場合がある。とくに、耐熱性に
有効な合金元素である、Ａｌ、Ｓｉ、ＲＥＭ（希土類元
素）、Ｎｂ、Ｔｉ、Ｚｒ、Ｍｏ、Ｗ、Ｃｕなどを多量に
含む場合には、遷移温度が上昇する。一方、遷移温度
は、素材の板厚や金属組織によっても変動し、板厚の薄
い冷延焼鈍板よりも冷間圧延前の厚板の熱延焼鈍板の方
が、また、再結晶組織である熱延焼鈍板よりも加工組織
の残る熱延板の方がそれぞれ高く、低温靭性に劣ってい
る。このため、製品としては優れた耐熱性を有する鋼で
あっても、製造する段階では低温靭性が低いため、曲げ
等が加わる工程で脆性破壊を起こす場合があり、このよ
うな鋼は、通板前に、１００℃付近まで加温する必要が
ある。[0003] Generally, ferritic stainless steel has a ductile brittle transition temperature, and at a lower temperature side than the transition temperature range,
Brittle cracks may occur. In particular, when a large amount of alloy elements effective for heat resistance, such as Al, Si, REM (rare earth element), Nb, Ti, Zr, Mo, W, and Cu, is included, the transition temperature increases. On the other hand, the transition temperature varies depending on the thickness and the metal structure of the material, and the hot-rolled annealed sheet before cold rolling is more recrystallized than the cold-rolled annealed sheet having a small thickness. Each of the hot-rolled sheets with the processed structure remains higher than a certain hot-rolled annealed sheet, and is inferior in low-temperature toughness. For this reason, even if the steel has excellent heat resistance as a product, the low-temperature toughness is low at the manufacturing stage, so that brittle fracture may occur in the process where bending is applied. Needs to be heated to around 100 ° C.
【０００４】熱延板の靭性改善に対しては、おもに、
Ｃ、Ｎ量の低減や、熱間圧延条件の規制（例えば熱間圧
延後の冷却速度の規制）などの措置が講じられる。前者
は、脆性破壊の起点となりうる炭窒化物の量そのものを
低減することを、後者は、冷却速度を速めることによる
炭窒化物生成の抑制を目的としている。これらの対策
は、ＳＵＨ４０９系、ＳＵＳ４３０ＬＸ系、ＳＵＳ４３
６系などの比較的合金元素量の少ないＪＩＳ規定の鋼種
に対しては有効であると考えられる。[0004] In order to improve the toughness of a hot-rolled sheet,
Measures such as reduction of C and N contents and regulation of hot rolling conditions (for example, regulation of cooling rate after hot rolling) are taken. The former aims at reducing the amount of carbonitride which can be a starting point of brittle fracture, and the latter aims at suppressing carbonitride production by increasing the cooling rate. These measures are for SUH409, SUS430LX, SUS43
It is considered to be effective for JIS-specified steel grades with relatively small alloying element contents such as series 6.
【０００５】[0005]
【発明が解決しようとする課題】しかしながら、上述し
た措置は、ＪＩＳ規定以外の高合金化したフェライト系
ステンレス鋼に対しては、必ずしも有効であるとは言い
難い。例えば、Ｎｂを多く含むフェライト系ステンレス
鋼では、熱間圧延中およびその後の冷却中に金属間化合
物であるＬａｖｅｓ相（Ｆｅ2 Ｎｂが主成分）が析出し
やすいため、上述した方法では必ずしも十分な低温靭性
の改善は期待できない。したがって、これらの鋼種は、
熱間圧延を行った後の製造工程において、加温を余儀な
くされているのが実状である。本発明は、このような現
状に対応すべく、現有設備の一般的な製造方法を用い、
なおかつ、合金成分の調整だけで、優れた低温靭性を有
する熱延板を製造しうるＮｂ含有フェライト系ステンレ
ス鋼を提供することを目的とする。However, the measures described above are not necessarily effective for ferritic stainless steels with high alloying other than those specified in JIS. For example, in a ferritic stainless steel containing a large amount of Nb, the Laves phase (mainly composed of Fe 2 Nb), which is an intermetallic compound, tends to precipitate during hot rolling and subsequent cooling. No improvement in low temperature toughness can be expected. Therefore, these steel grades
In the manufacturing process after hot rolling, heating is inevitably required. The present invention uses a general manufacturing method of existing equipment to cope with such a current situation,
In addition, an object of the present invention is to provide an Nb-containing ferritic stainless steel capable of producing a hot-rolled sheet having excellent low-temperature toughness only by adjusting alloy components.
【０００６】[0006]
【課題を解決するための手段】本発明の目的とする、優
れた低温靭性を有する熱延板が製造できるＮｂ含有フェ
ライト系ステンレス鋼は、質量％で、Ｃ：０．０２０％
以下、Ｓｉ：０．１０〜０．５０％、Ｍｎ：０．７０〜
１．５０％、Ｓ：０．００６％以下、Ｃｒ：１７．０〜
２０．０％、Ｍｏ：１．７５〜２．５０％、Ｎｂ：０．
５５〜０．８０％、Ｃｕ：０．０２〜０．３％未満、
Ｎ：０．０２０％以下を含有し、更に、Ｃ＋Ｎ：０．０
１５〜０．０２５％の条件を満足し、残部をＦｅおよび
製造上の不可避的不純物からなる組成にすることによっ
て達成される。SUMMARY OF THE INVENTION The object of the present invention is to produce a hot rolled sheet having excellent low-temperature toughness in Nb-containing ferritic stainless steel.
Hereinafter, Si: 0.10 to 0.50%, Mn: 0.70 to
1.50%, S: 0.006% or less, Cr: 17.0 to
20.0%, Mo: 1.75 to 2.50%, Nb: 0.
55-0.80%, Cu: less than 0.02-0.3%,
N: 0.020% or less, and C + N: 0.0
It is achieved by satisfying the condition of 15 to 0.025%, with the balance being a composition comprising Fe and unavoidable impurities in production.
【０００７】[0007]
【発明の実施の形態】本発明者らは、Ｎｂ含有フェライ
ト系ステンレス鋼の熱延板の低温靭性を改善すべく種々
の検討を行った結果、化学成分を上記成分範囲に厳密に
規定することにより、低温靭性の優れた鋼を得ることが
できることが判った。すなわち、Ｎｂ含有フェライト系
ステンレス鋼の熱延板の低温靭性は、炭窒化物の生成量
とＦｅ2 Ｎｂを主体とするＬａｖｅｓ相の生成量に左右
されること、両者を比較した場合には、本発明の成分系
においては後者の方がより靭性に悪影響を及ぼすことを
明らかにした。更に、ＣやＮの低減や熱間圧延方法の調
整だけでは靭性の改善は困難なこと、むしろＣとＮを若
干含有させることによって低温靭性を改善できることを
明らかにした。BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted various studies to improve the low-temperature toughness of a hot-rolled Nb-containing ferritic stainless steel, and have determined that the chemical components are strictly defined within the above-mentioned ranges. As a result, it was found that a steel having excellent low-temperature toughness can be obtained. That is, the low-temperature toughness of the hot-rolled sheet of Nb-containing ferritic stainless steel depends on the amount of carbonitride formed and the amount of Laves phase mainly composed of Fe 2 Nb. It has been clarified that the latter has a more adverse effect on toughness in the component system of the present invention. Furthermore, it has been clarified that it is difficult to improve toughness only by reducing C and N and adjusting the hot rolling method, but rather that low-temperature toughness can be improved by adding a small amount of C and N.
【０００８】ＣとＮは、一般的にはクリープ強さやクリ
ープ破断強さなどの高温強度を向上させるために有効な
元素であるものの、古くからフェライト系ステンレス鋼
の低温靭性に対しては有害であるとされており、可能な
限りの低減化がなされてきた。本発明に至る過程におい
ても、ＣとＮの低減化を図ったものの、熱延板の低温靭
性を改善できる結果が必ずしも得られなかった。そこ
で、発明者等はＮｂ含有フェライト系ステンレス鋼の熱
延板の低温靭性に及ぼすＣ＋Ｎの影響を詳細に検討し
た。Although C and N are generally effective elements for improving high-temperature strength such as creep strength and creep rupture strength, they have long been harmful to the low-temperature toughness of ferritic stainless steel. It has been reduced as much as possible. Also in the process leading to the present invention, although the reduction of C and N was attempted, the result of improving the low-temperature toughness of the hot-rolled sheet was not always obtained. Therefore, the present inventors have studied in detail the effect of C + N on the low-temperature toughness of a hot-rolled Nb-containing ferritic stainless steel sheet.
【０００９】図１はＦｅ−１８Ｃｒ−１．０Ｍｎ−２．
１Ｍｏ−０．７Ｎｂ−０．２Ｃｕを基本成分としたＮｂ
含有フェライト系ステンレス鋼の熱延板の低温靭性に及
ぼす（Ｃ＋Ｎ）量の影響を示す結果である。供試材に
は、４００ｋｇの真空溶解にて作製した厚さ７５ｍｍの
インゴットを、１２５０℃で３時間の加熱の後熱間圧延
し、厚さ４．５ｍｍ、仕上げ温度８３０℃で熱間圧延を
終了した後に水冷したものを用いた。そして、ＪＩＳ
Ｚ ２２０２（金属材料衝撃試験片）の４号試験片に準
拠して、幅４．５ｍｍのサブサイズ試験片を、衝撃方向
が圧延方向に平行になるように採取し、ＪＩＳ Ｚ ２
２４２（金属材料衝撃試験方法）に準拠してシャルピー
衝撃試験を行った。低温靭性は、２５℃でのシャルピー
衝撃値で評価した。なお、熱延板のシャルピー衝撃値
は、製造性に支障のない２５Ｊ／ｃｍ2 以上を目標値と
した。FIG. 1 shows Fe-18Cr-1.0Mn-2.
Nb with 1Mo-0.7Nb-0.2Cu as a basic component
It is a result which shows the influence of (C + N) amount on the low temperature toughness of the hot-rolled sheet of the containing ferritic stainless steel. The test material was hot rolled at a temperature of 1250 ° C. for 3 hours and then hot rolled at a thickness of 4.5 mm at a finishing temperature of 830 ° C. After the completion, water-cooled one was used. And JIS
In accordance with No. 4 test piece of Z 2202 (metallic material impact test piece), a 4.5 mm wide sub-size test piece was sampled so that the impact direction became parallel to the rolling direction, and JIS Z 2
A Charpy impact test was performed according to 242 (metallic material impact test method). The low temperature toughness was evaluated by the Charpy impact value at 25 ° C. The target value of the Charpy impact value of the hot-rolled sheet was 25 J / cm 2 or more which did not hinder the productivity.
【００１０】図１の結果から、シャルピー衝撃値は、
（Ｃ＋Ｎ）量の増加に伴い大きくなり、０．０２質量％
付近を最大値としてそれ以降の（Ｃ＋Ｎ）量では小さく
なる傾向にある。目標値である、２５Ｊ／ｃｍ2 以上の
値を得るためには、（Ｃ＋Ｎ）量を０．０１５〜０．０
２５質量％に厳密に規定する必要があることがわかる。
（Ｃ＋Ｎ）量の多い領域での衝撃値の低下は、これまで
に良く知られているように、固溶Ｃ、Ｎの増大および炭
窒化物の面積率の増大によるものと思われる。一般に、
（Ｃ＋Ｎ）量の低減は，低温靭性の改善に有効であると
言われているが、本発明の成分系においては，逆に低温
靭性を劣化する結果となった。この理由は、（Ｃ＋Ｎ）
量を低減すると、Ｌａｖｅｓ相（Ｆｅ2 Ｎｂが主体）を
生成しやすいこと、Ｌａｖｅｓ相はｈｃｐ型構造の棒状
析出物であるため破壊の起点となりやすいことなどが考
えられる。したがって、（Ｃ＋Ｎ）量を若干増加させる
ことによって、Ｌａｖｅｓ相の量に対して相対的に球状
の炭窒化物が増え、靭性低下を緩和するものと思われ
る。これは、従来にない新しい知見である。また、製鋼
効率の点からは、（Ｃ＋Ｎ）量を極端に低減する必要が
無くなるため、製鋼段階での脱Ｃ、Ｎに要する時間は短
くなる利点がある。以下に、本発明において条件、各成
分の範囲を限定した理由を説明する。From the results of FIG. 1, the Charpy impact value is
(C + N) increases with an increase in the amount, and becomes 0.02% by mass.
There is a tendency that the value becomes smaller as the (C + N) amount becomes the maximum value in the vicinity. In order to obtain a target value of 25 J / cm 2 or more, the (C + N) amount is set to 0.015 to 0.0
It is understood that it is necessary to strictly define the content at 25% by mass.
It is considered that the decrease in impact value in the region with a large amount of (C + N) is due to an increase in solid solution C and N and an increase in the area ratio of carbonitride, as is well known. In general,
It is said that the reduction of the (C + N) content is effective for improving the low-temperature toughness. However, in the component system of the present invention, the low-temperature toughness is degraded. The reason for this is (C + N)
When the amount is reduced, it is considered that a Laves phase (mainly Fe 2 Nb) is easily formed, and that the Laves phase is a rod-like precipitate having an hcp type structure and thus easily becomes a starting point of fracture. Therefore, it is considered that by slightly increasing the (C + N) amount, the spherical carbonitrides increase relative to the amount of the Laves phase, thereby alleviating the decrease in toughness. This is an unprecedented new finding. Further, from the viewpoint of steel making efficiency, there is no need to extremely reduce the (C + N) amount, and thus there is an advantage that the time required for de-C and N in the steel making stage is shortened. Hereinafter, the reasons for limiting the conditions and the range of each component in the present invention will be described.
【００１１】Ｃ＋Ｎ：０．０１５〜０．０２５質量％ 上述したように、熱延板の低温靭性はＣ、Ｎ含有量に大
きく影響される。熱延板の低温靭性が良好であるシャル
ピー衝撃値２５Ｊ／ｃｍ2 以上の値は、（Ｃ＋Ｎ）量が
０．０１５〜０．０２５質量％の範囲で達成される。C + N: 0.015 to 0.025% by mass As described above, the low-temperature toughness of a hot-rolled sheet is greatly affected by the contents of C and N. The Charpy impact value of 25 J / cm 2 or more at which the hot-rolled sheet has good low-temperature toughness is achieved when the (C + N) content is in the range of 0.015 to 0.025% by mass.
【００１２】Ｃ、Ｎ：それぞれ０．０２０質量％以下 （Ｃ＋Ｎ）量の規制が示すように、Ｃ、Ｎの含有量が、
０．０２５質量％以上になると固溶量の増大や炭窒化物
量の増大によって低温靭性が低下する。一方、一般の製
鋼段階においてＣ又はＮを０．００５質量％以下に低減
することはコスト的に高くなる。そこで、（Ｃ＋Ｎ）量
の範囲を満足させるために、それぞれ０．０２０質量％
以下に規定する。C and N: 0.020% by mass or less, respectively As shown in the regulation of (C + N) content, the content of C and N is
If it exceeds 0.025% by mass, the low-temperature toughness decreases due to an increase in the amount of solid solution and an increase in the amount of carbonitride. On the other hand, reducing C or N to 0.005% by mass or less in a general steelmaking stage increases costs. Therefore, in order to satisfy the range of the amount of (C + N), 0.020 mass%
It is specified below.
【００１３】Ｓｉ：０．１０〜０．５０質量％ 高温酸化特性の改善に有効な元素である。その効果は
０．１０質量％以上で顕著になる。しかし、過剰に添加
すると、鋼の脆化を招く。このため、Ｓｉの含有量は
０．１０〜０．５０質量％とした。Si: 0.10 to 0.50 mass% Si is an element effective for improving high-temperature oxidation characteristics. The effect becomes remarkable at 0.10% by mass or more. However, excessive addition causes brittleness of the steel. For this reason, the content of Si is set to 0.10 to 0.50% by mass.
【００１４】Ｍｎ：０．７０〜１．５０質量％ 適量添加すると高温酸化特性，特に表層酸化物の密着性
を著しく改善し，とくに０．７０質量％以上の添加でそ
の効果は著しくなる。しかし、過剰に含有すると硬質と
なり、低温靱性や加工性の低下を招く。そこで、Ｍｎの
含有量は、１．５０質量％以下とした。Mn: 0.70 to 1.50% by mass When added in an appropriate amount, the high-temperature oxidation characteristics, especially the adhesion of the surface oxide, are remarkably improved, and the effect becomes remarkable especially when added in an amount of 0.70% by mass or more. However, if it is contained excessively, it becomes hard, resulting in lowering of low-temperature toughness and workability. Therefore, the content of Mn is set to 1.50% by mass or less.
【００１５】Ｓ：０．００６質量％以下 溶接高温割れに対して有害であるので可能な限り低い方
が望ましいが、低くおさえるには、原料の厳選や脱硫に
時間がかかり、製造コストの上昇を招く。本発明におい
ては、Ｓは０．００６質量％まで許容しても十分な耐溶
接高温割れ性を有するため、Ｓの範囲を０．００６質量
％以下とした。S: 0.006% by mass or less Since it is harmful to hot cracking at welding, it is desirable to keep it as low as possible. However, to keep it low, it takes time for careful selection of materials and desulfurization, which leads to an increase in production cost. Invite. In the present invention, S has sufficient welding hot crack resistance even if it is allowed up to 0.006% by mass. Therefore, the range of S is set to 0.006% by mass or less.
【００１６】Ｃｒ：１７．０〜２０．０質量％ 耐食性および高温酸化特性の確保に必要不可欠な元素で
ある。Ｓｉ、Ａｌなどの高温酸化特性を改善する元素を
多く含まない場合には、酸化特性を確保するために少な
くとも１７．０質量％以上の添加が必要となる。一方、
Ｃｒを多量に添加すると硬質となり、鋼の低温靭性に悪
影響を及ぼす。高温酸化特性を確保し、なおかつ靭性を
損なわないように、Ｃｒの含有量は１７．０〜２０．０
質量％の範囲とした。Cr: 17.0 to 20.0 mass% Cr is an element indispensable for ensuring corrosion resistance and high-temperature oxidation characteristics. When a large amount of elements that improve high-temperature oxidation characteristics such as Si and Al are not contained, at least 17.0% by mass or more must be added to secure oxidation characteristics. on the other hand,
If a large amount of Cr is added, the steel becomes hard and has an adverse effect on the low-temperature toughness of the steel. The Cr content is 17.0 to 20.0 so as to ensure high-temperature oxidation characteristics and not impair toughness.
% By mass.
【００１７】Ｍｏ：１．７５〜２．５０質量％ 高温強度の改善に有効な元素である。高温強度の面から
１．７５質量％以上の添加が必要である。しかし、多量
に添加すると鋼の脆化を招く。また、これらの元素は非
常に高価であるため材料のコスト高を招く。高温強度を
確保し、なおかつ，靭性を損なわないように、Ｍｏの含
有量は、１．７５〜２．５０質量％の範囲とした。Mo: 1.75 to 2.50 mass% Mo is an element effective for improving high-temperature strength. From the viewpoint of high-temperature strength, 1.75% by mass or more must be added. However, when added in large amounts, the steel becomes brittle. In addition, these elements are very expensive, so that the cost of the material is increased. The Mo content is set in the range of 1.75 to 2.50% by mass so that high-temperature strength is ensured and toughness is not impaired.
【００１８】Ｎｂ：０．５５〜０．８０質量％ フェライト系ステンレス鋼の高温強度を改善するのに最
も有効な合金元素の１つである。通常のＮｂ含有フェラ
イト系ステンレス鋼は、最大で０．４質量％程度含有し
ているが、十分な高温強度を得るためには、少なくとも
０．５５質量％以上の添加が必要となる。一方、Ｎｂは
靭性に悪影響を及ぼす元素であり、０．８０質量％を超
えると、連続鋳造片や熱延板の靭性を著しく劣化させ
る。そこでＮｂの含有量は、０．５５〜０．８０質量％
の範囲とした。Nb: 0.55 to 0.80% by mass Nb is one of the most effective alloying elements for improving the high-temperature strength of ferritic stainless steel. Ordinary Nb-containing ferritic stainless steel contains at most about 0.4% by mass, but at least 0.55% by mass or more is required to obtain sufficient high-temperature strength. On the other hand, Nb is an element that has an adverse effect on toughness, and if it exceeds 0.80% by mass, the toughness of a continuously cast piece or a hot-rolled sheet is significantly deteriorated. Therefore, the content of Nb is 0.55 to 0.80% by mass.
Range.
【００１９】Ｃｕ：０．０２〜０．３質量％未満 適量の添加で低温靱性と加工性の両方を向上させるのに
有効な元素であり、その効果は０．０２質量％以上の添
加で顕著となる。しかし、Ｃｕを過剰に添加すると加工
性に支障をきたす。そこで、Ｃｕの含有量は、０．０２
〜０．３質量％未満とした。Cu: less than 0.02 to 0.3% by mass It is an element effective for improving both low-temperature toughness and workability by adding an appropriate amount, and its effect is remarkable by adding 0.02% by mass or more. Becomes However, an excessive addition of Cu impairs workability. Therefore, the content of Cu is 0.02
To less than 0.3% by mass.
【００２０】なお、熱延板を得るまでの連続鋳造片の冷
却条件や、熱間圧延方法については、本発明ではとくに
規定しないが、析出物を過剰に生成させない方法が好ま
しい。すなわち、スラブの冷却条件については、水冷に
より粗大析出物の生成を抑制し、熱間圧延前の加熱は、
１２００℃以上で２時間以上の均熱を行ってスラブ中の
析出物を固溶させ、熱間圧延は、８００℃以上で終了し
てそののち少なくとも６００℃以下まで水冷を施して、
析出物の生成を可能な限り抑制するのが好ましい。The conditions for cooling the continuous cast pieces until the hot-rolled sheet is obtained and the hot rolling method are not particularly specified in the present invention, but a method that does not excessively generate precipitates is preferable. That is, regarding the cooling conditions of the slab, the generation of coarse precipitates is suppressed by water cooling, and the heating before hot rolling is
The precipitate in the slab is solid-dissolved by performing soaking at 1200 ° C. or more for 2 hours or more, and hot rolling is completed at 800 ° C. or more and then water-cooled to at least 600 ° C. or less.
It is preferable to suppress generation of precipitates as much as possible.
【００２１】また、本発明では熱間圧延以降の製造方法
についてもとくに規定はしないが、低温靭性を損なわな
い範囲で加工熱処理を施して製品とするのが好ましい。
すなわち、熱延板および冷延板の焼鈍は１０００℃以上
の結晶粒が粗大化しない温度域で行い、析出物を可能な
限り固溶させるのが好ましい。また、焼鈍後は、強制空
冷もしくは水冷によって冷却中の再析出を抑制するのが
好ましい。なお、本発明鋼の製品としての形態はとくに
制約されるものでなく、熱延焼鈍板および鋼帯、冷延焼
鈍板および鋼帯、鋼管、溶接構造物のいずれにも適用可
能である。In the present invention, the production method after hot rolling is not particularly limited, but it is preferable to apply a thermomechanical treatment within a range that does not impair the low-temperature toughness to obtain a product.
That is, it is preferable that annealing of the hot-rolled sheet and the cold-rolled sheet is performed in a temperature range of 1000 ° C. or more where crystal grains are not coarsened, and the precipitates are dissolved as much as possible. After annealing, it is preferable to suppress re-precipitation during cooling by forced air cooling or water cooling. The form of the steel of the present invention as a product is not particularly limited, and is applicable to any of a hot-rolled annealed plate and a steel strip, a cold-rolled annealed plate and a steel strip, a steel pipe, and a welded structure.
【００２２】[0022]
【実施例】高周波真空溶解炉にて４００ｋｇのインゴッ
トを作製し、７５ｍｍ厚とした後、熱間圧延を施して、
板厚４．５ｍｍの熱延鋼帯とした。熱間圧延は、１２３
０℃で２時間加熱したのちに、８００℃〜８５０℃で熱
間圧延を終え、その後水槽に浸漬して冷却した。その合
金の化学成分を表１に示す。これらの板は、所定の試験
片に加工したのち、前述したシャルピー衝撃試験を実施
した。また、ＪＩＳＺ ２２０４（金属材料曲げ試験
片）で規定されている３号試験片を用い、ＪＩＳ Ｚ
２２４８（金属材料曲げ試験方法）の押曲げ法にて曲げ
試験を行った。なお、曲げ試験は熱間圧延方向に垂直方
向に試験片を採取して曲げ半径４．５ｍｍで密着までの
曲げ（以下１ｔ曲げと称す）と、曲げ半径１８０ｍｍで
９０°に曲げた後に反対側に９０°に曲げるのを１０回
繰り返す曲げ（以下１０回曲げと称す）の２種類の方法
で行った。その結果を表２に示す。EXAMPLE A 400 kg ingot was produced in a high-frequency vacuum melting furnace, and after having a thickness of 75 mm, hot rolling was performed.
A hot-rolled steel strip having a thickness of 4.5 mm was obtained. Hot rolling is 123
After heating at 0 ° C for 2 hours, hot rolling was completed at 800 ° C to 850 ° C, and then immersed in a water bath and cooled. Table 1 shows the chemical components of the alloy. After processing these plates into predetermined test pieces, the above-described Charpy impact test was performed. In addition, using the No. 3 test piece specified in JISZ 2204 (metal material bending test piece), JIS Z
The bending test was performed by the press bending method of 2248 (metal material bending test method). In the bending test, a test piece was taken in a direction perpendicular to the hot rolling direction and bent to a close contact with a bending radius of 4.5 mm (hereinafter referred to as 1t bending), and after bending to 90 ° with a bending radius of 180 mm, the opposite side was used. This was performed by two kinds of bending (hereinafter, referred to as bending 10 times) in which bending to 90 ° was repeated 10 times. Table 2 shows the results.
【００２３】[0023]
【表１】 [Table 1]
【００２４】[0024]
【表２】 [Table 2]
【００２５】鋼種Ｎｏ．１〜１０は本発明鋼である。い
ずれの鋼もシャルピー衝撃値および曲げ特性に優れてお
り、熱延板において良好な低温靭性を有している。これ
は、上述したように、ＣとＮの含有量を厳密に調整した
ことによる。鋼種Ｎｏ．１１〜１５は比較鋼であり、い
ずれの鋼も（Ｃ＋Ｎ）量が本発明の請求範囲から上又は
下に外れるため、シャルピー衝撃値の基準（２５Ｊ／ｃ
ｍ2 以上）を満足しない。そして、鋼種Ｎｏ．１１、鋼
種Ｎｏ．１３、鋼種Ｎｏ．１５は１t 曲げ試験において
も割れが発生する。ただし、鋼種Ｎｏ．１２及び鋼種Ｎ
ｏ．１４はＮｂ含有量が比較的低いため１t 曲げ試験で
は割れは発生していない。１０回曲げ試験では、（Ｃ＋
Ｎ）量が本発明の請求範囲から多い方に外れた鋼種Ｎ
ｏ．１５のみに割れが発生しており、曲げ半径が大きい
場合には割れ傾向が小さくなる。Steel type No. 1 to 10 are steels of the present invention. All steels are excellent in Charpy impact value and bending characteristics, and have good low-temperature toughness in a hot-rolled sheet. This is because the contents of C and N were strictly adjusted as described above. Steel type No. 11 to 15 are comparative steels. Since the (C + N) amount of any of the steels falls outside or above the claims of the present invention, the standard of Charpy impact value (25 J / c)
m 2 or more) is not satisfied. And steel type No. 11, steel type No. 13, steel type No. In No. 15, cracking occurs even in the 1t bending test. However, steel type No. 12 and steel type N
o. Since No. 14 has a relatively low Nb content, no crack is generated in the 1t bending test. In the ten-fold bending test, (C +
N) steel type N whose amount deviates from the claims of the present invention
o. No. 15 has cracks, and when the bending radius is large, the tendency of cracks is small.
【００２６】[0026]
【発明の効果】本発明によれば、現有設備の一般的な製
造方法を用い、なおかつ、合金成分の調整だけで、熱延
板の低温靭性が優れたＮｂ含有フェライト系ステンレス
鋼を提供することができる。したがって、排ガス経路部
材などに使用される、Ｎｂを多く含有する耐熱用フェラ
イト系ステンレス鋼を、特別な手法を用いることなく、
安定して製造することができる。According to the present invention, there is provided an Nb-containing ferritic stainless steel having excellent low-temperature toughness of a hot-rolled sheet by using a general manufacturing method of existing equipment and adjusting only alloy components. Can be. Therefore, heat-resistant ferritic stainless steel containing a large amount of Nb, which is used for exhaust gas path members and the like, can be used without using a special method.
It can be manufactured stably.
【図１】２５℃のシャルピー衝撃値に及ぼす（Ｃ＋Ｎ）
量の影響を示す図。FIG. 1. Effect on (C + N) Charpy impact value at 25 ° C.
The figure which shows the influence of quantity.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 名越 敏郎 山口県新南陽市野村南町4976番地 日新製 鋼株式会社技術研究所内 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiro Nagoshi 4976 Nomura Minami-cho, Shinnanyo-shi, Yamaguchi Pref. Nisshin Steel Co., Ltd.
Claims (1)
０．１０〜０．５０％、Ｍｎ：０．７０〜１．５０％、
Ｓ：０．００６％以下、Ｃｒ：１７．０〜２０．０％、
Ｍｏ：１．７５〜２．５０％、Ｎｂ：０．５５〜０．８
０％、Ｃｕ：０．０２〜０．３％未満、Ｎ：０．０２０
％以下を含有し、更に、Ｃ＋Ｎ：０．０１５〜０．０２
５％の条件を満足し、残部をＦｅおよび製造上の不可避
的不純物からなる組成を有する、熱延板の低温靭性に優
れたＮｂ含有フェライト系ステンレス鋼。(1) In mass%, C: 0.020% or less, Si:
0.10 to 0.50%, Mn: 0.70 to 1.50%,
S: 0.006% or less, Cr: 17.0 to 20.0%,
Mo: 1.75 to 2.50%, Nb: 0.55 to 0.8
0%, Cu: less than 0.02 to 0.3%, N: 0.020
%, And C + N: 0.015 to 0.02
An Nb-containing ferritic stainless steel which satisfies the condition of 5% and has a balance of Fe and inevitable impurities in production, and is excellent in low-temperature toughness of a hot-rolled sheet.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP05857997A JP3705391B2 (en) | 1997-02-27 | 1997-02-27 | Nb-containing ferritic stainless steel with excellent low temperature toughness of hot-rolled sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP05857997A JP3705391B2 (en) | 1997-02-27 | 1997-02-27 | Nb-containing ferritic stainless steel with excellent low temperature toughness of hot-rolled sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10237602A true JPH10237602A (en) | 1998-09-08 |
| JP3705391B2 JP3705391B2 (en) | 2005-10-12 |
Family
ID=13088374
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP05857997A Expired - Fee Related JP3705391B2 (en) | 1997-02-27 | 1997-02-27 | Nb-containing ferritic stainless steel with excellent low temperature toughness of hot-rolled sheet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3705391B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1176220A1 (en) * | 2000-07-25 | 2002-01-30 | Kawasaki Steel Corporation | Ferritic stainless steel sheet having superior workability at room temperatures and mechanical characteristics at high temperatures, and method of producing the same |
| WO2013085005A1 (en) * | 2011-12-09 | 2013-06-13 | 新日鐵住金ステンレス株式会社 | Hot-rolled ferritic stainless steel sheet with excellent cold cracking resistance and manufacturing process therefor |
| WO2017135240A1 (en) | 2016-02-02 | 2017-08-10 | 日新製鋼株式会社 | HOT ROLLED Nb-CONTAINING FERRITIC STAINLESS STEEL SHEET AND METHOD FOR PRODUCING SAME, AND COLD ROLLED Nb-CONTAINING FERRITIC STAINLESS STEEL SHEET AND METHOD FOR PRODUCING SAME |
| US9885099B2 (en) | 2012-03-09 | 2018-02-06 | Nippon Steel & Sumikin Stainless Steel Corporation | Ferritic stainless steel sheet |
| US10385429B2 (en) | 2013-03-27 | 2019-08-20 | Nippon Steel & Sumikin Stainless Steel Corporation | Hot-rolled ferritic stainless-steel plate, process for producing same, and steel strip |
-
1997
- 1997-02-27 JP JP05857997A patent/JP3705391B2/en not_active Expired - Fee Related
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1176220A1 (en) * | 2000-07-25 | 2002-01-30 | Kawasaki Steel Corporation | Ferritic stainless steel sheet having superior workability at room temperatures and mechanical characteristics at high temperatures, and method of producing the same |
| US6521056B2 (en) | 2000-07-25 | 2003-02-18 | Kawasaki Steel Corporation | Ferritic stainless steel sheet having superior workability at room temperatures and mechanical characteristics at high temperatures |
| WO2013085005A1 (en) * | 2011-12-09 | 2013-06-13 | 新日鐵住金ステンレス株式会社 | Hot-rolled ferritic stainless steel sheet with excellent cold cracking resistance and manufacturing process therefor |
| CN103857812A (en) * | 2011-12-09 | 2014-06-11 | 新日铁住金不锈钢株式会社 | Hot-rolled ferritic stainless steel sheet with excellent cold cracking resistance and manufacturing process therefor |
| JPWO2013085005A1 (en) * | 2011-12-09 | 2015-04-27 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel hot-rolled steel sheet with excellent cold cracking property and method for producing the same |
| CN103857812B (en) * | 2011-12-09 | 2017-05-31 | 新日铁住金不锈钢株式会社 | The excellent ferrite-group stainless steel hot rolled steel plate of cold crack and its manufacture method |
| US9885099B2 (en) | 2012-03-09 | 2018-02-06 | Nippon Steel & Sumikin Stainless Steel Corporation | Ferritic stainless steel sheet |
| US10385429B2 (en) | 2013-03-27 | 2019-08-20 | Nippon Steel & Sumikin Stainless Steel Corporation | Hot-rolled ferritic stainless-steel plate, process for producing same, and steel strip |
| WO2017135240A1 (en) | 2016-02-02 | 2017-08-10 | 日新製鋼株式会社 | HOT ROLLED Nb-CONTAINING FERRITIC STAINLESS STEEL SHEET AND METHOD FOR PRODUCING SAME, AND COLD ROLLED Nb-CONTAINING FERRITIC STAINLESS STEEL SHEET AND METHOD FOR PRODUCING SAME |
| KR20180109865A (en) | 2016-02-02 | 2018-10-08 | 닛신 세이코 가부시키가이샤 | Nb-containing ferritic stainless steel hot-rolled steel sheet and manufacturing method thereof, Nb-containing ferritic stainless steel cold-rolled steel sheet and manufacturing method thereof |
| EP3708690A1 (en) | 2016-02-02 | 2020-09-16 | Nippon Steel Stainless Steel Corporation | Cold rolled nb-containing ferritic stainless steel sheet and method for producing same |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3705391B2 (en) | 2005-10-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| TWI465587B (en) | Ferritic stainless steel having excellent oxidation resistance | |
| CN104662188A (en) | Ferritic stainless steel | |
| WO2011111871A1 (en) | Highly oxidation-resistant ferrite stainless steel plate, highly heat-resistant ferrite stainless steel plate, and manufacturing method therefor | |
| WO2003106722A1 (en) | Heat-resistant ferritic stainless steel and method for production thereof | |
| JP2005015909A (en) | High-strength low-specific-gravity steel sheet and method for manufacturing the same | |
| CN111989417A (en) | Duplex stainless steel clad steel sheet and method for manufacturing same | |
| TWI553129B (en) | Ferrous iron-type stainless steel hot-rolled steel sheet, its manufacturing method and fat iron-based stainless steel cold-rolled steel plate | |
| TWI625398B (en) | Ferrous iron-based stainless steel | |
| JP5125600B2 (en) | Ferritic stainless steel with excellent high-temperature strength, steam oxidation resistance and workability | |
| JP7009278B2 (en) | Ferritic stainless steel sheets with excellent heat resistance and exhaust parts and their manufacturing methods | |
| JP4185425B2 (en) | Ferritic steel sheet with improved formability and high temperature strength, high temperature oxidation resistance and low temperature toughness at the same time | |
| JP3269799B2 (en) | Ferritic stainless steel for engine exhaust parts with excellent workability, intergranular corrosion resistance and high-temperature strength | |
| JP3705391B2 (en) | Nb-containing ferritic stainless steel with excellent low temperature toughness of hot-rolled sheet | |
| JP4457492B2 (en) | Stainless steel with excellent workability and weldability | |
| JP6624345B1 (en) | Ferritic stainless steel | |
| JP2923825B2 (en) | Ferritic stainless steel sheet for heat resistance with excellent high-temperature strength and weldability | |
| JP3591486B2 (en) | High Cr ferritic heat resistant steel | |
| JP4167166B2 (en) | High Al content ferritic stainless steel hot rolled steel strip with excellent toughness and method for producing the same | |
| WO2018116792A1 (en) | Ferritic stainless steel | |
| CN114959444B (en) | Low-temperature acid dew point resistant steel and preparation method thereof | |
| JPH0353026A (en) | Manufacture of ferritic stainless steel sheet having excellent heat resistance and corrosion resistance | |
| JP6624347B1 (en) | Ferritic stainless steel | |
| JP2506243B2 (en) | Method for producing oxidation-resistant ferritic stainless steel | |
| JPH0353025A (en) | Manufacture of high heat-resistant and high-corrosion resistant ferritic stainless steel sheet | |
| JP3752523B2 (en) | Ferritic heat resistant steel |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Effective date: 20040227 Free format text: JAPANESE INTERMEDIATE CODE: A621 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20050421 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20050426 |
|
| A521 | Written amendment |
Effective date: 20050627 Free format text: JAPANESE INTERMEDIATE CODE: A523 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20050720 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20050720 |
|
| R150 | Certificate of patent (=grant) or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090805 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Year of fee payment: 5 Free format text: PAYMENT UNTIL: 20100805 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Year of fee payment: 5 Free format text: PAYMENT UNTIL: 20100805 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Year of fee payment: 6 Free format text: PAYMENT UNTIL: 20110805 |
|
| LAPS | Cancellation because of no payment of annual fees |