JPH02427B2

JPH02427B2 -

Info

Publication number: JPH02427B2
Application number: JP56168812A
Authority: JP
Inventors: Masanori Ueda; Tadashi Nishi
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 1981-10-23
Filing date: 1981-10-23
Publication date: 1990-01-08
Also published as: JPS5871356A

Description

【発明の詳細な説明】[Detailed description of the invention]

本発明はステンレス鋼の高純精錬技術を活用し
て、耐食性がすぐれかつ製品の加工性がすぐれた
安価なフエライト系ステンレス鋼を提供すること
を目的とするもので、フエライト系ステンレス鋼
の成分系と製造法に関するものである。１７Crを主とするフエライト系ステンレス鋼
は安価な利点を生かして、、従来より主として薄
板として広く使用されて来たが、１８Cr−８Ni
系のオーステナイト系ステンレス鋼に比較すると
耐食性、加工性の点で相当に劣つている。特に耐
食性の点では大気中、あるいは自然に存在する
水、水道水、あるいは温水等の比較的ゆるやかな
条件下で使用されるが、溶接部や加工を受けた部
分では容易に発銹し、又母材部でも耐食性が劣つ
ている。将来の用途拡大のためには耐食性の大巾
改善が切望されている。また、加工性においても
絞り性、張り出し性の点で今一歩である。もちろ
んこれらの耐食性や加工性の改善については従来
より莫大な研究がなされた結果、主として合金添
加の方法で改善されて来た。耐食性に関しては使
用環境により、その要求度合が異なり一律な規準
は決められない。したがつて用途によつてMo、
Cu、Ni、Ti、Nb等の選択添加がよく知られ、
加工性に対してはTi、Ｂ、Alの添加、Ｃ、Ｎの
低減、熱圧間条件、熱処理条件との組合せ等が検
討されて来た。しかしこのようにして、合金添加
を重視するとコストを高くし、プロセスの簡略化
を阻害する。このような現状に対して、本発明者等は、精錬
技術、特に高純化精錬技術に注目し、合金化は極
力少量にして、耐食性の向上、加工性の向上、プ
ロセスの簡略化を実現することをねらいに多くの
研究を実施して来た。その結果、ＰとＳ、ＣとＮ
の低減、すなわち高純化技術がこのねらいに合致
することを見出し本発明を完成させたものであ
る。すなわち本発明の要旨とするところは下記のと
おりである。 (1) 重量％でC0.08％以下、Si0.3％以下、Mn0.3
％以下、Cr13〜26％、N0.03％以下、P0.015％
未満、P0.0010％未満、Al0.02〜0.20％を含み、
必要に応じてさらにNb0.02〜0.30％、Mo3％
以下、Cu1％以下、Ni1％以下、Ti0.6％以下、
B0.010％以下を１種または２種以上を含み残
部実質的にFeからなることを特徴とする耐食
性を主とする使用性能がすぐれたフエライト系
ステンレス鋼。 (2) 重量％でC0.08％以下、Si0.3％以下、Mn0.3
％以下、Cr13〜26％、N0.03％以下、P0.015％
未満、S0.0010％未満、Al0.02〜0.20％を含み、
必要に応じてさらにNb0.02〜0.30％、Mo3％
以下、Cu1％以下、Ni1％以下、Ti0.6％以下、
B0.010％以下を１種または２種以上を含み残
部実質的にFeからなる溶鋼をΔT40℃の鋳造
温度条件下で連続鋳造し、得られた鋳片を1130
℃を超えないように加熱あるいは保熱した後、
熱間圧延することを特徴とする耐食性を主とす
る使用性能がすぐれたフエライト系ステンレス
鋼の製造方法。ここで、ΔT℃＝（連続鋳造時のタンデイシユ
における溶鋼温度℃）−（溶鋼の凝固温度℃）。以下本発明を詳細に説明する。高純化精錬技術はCa系のフラツクス等の吹込
み等によりステンレス鋼でもS10ppm以下、
P150ppm以下が可能なことが報告され、更にＣ
やＮの低減もすでに工業的規模で実現されてい
る。本発明者らはこれらの高純化精錬技術に注目
し、かつ製造のプロセスの検討を加味したわけで
あるが、１７Cr系のフエライト系ステンレス鋼
の耐食性、特に発銹性を電気化学的に検討した結
果、Cl^-による不働態破壊抵抗性に対してＰを低
減することがきわめて有効なことがわかつた。更
にＳを低減することは１７Cr系の不働態化特性
を改善し、更に上述の低Ｐとの相乗効果で、Cl^-
による不働態破壊抵抗性を大巾に向上させること
がわかつた。これらの知見をもとにして、真空溶解炉にて低
Ｐ、低Ｓに注目した合金を溶製すると共に熱間圧
延の加熱温度、熱間圧延条件、熱延板焼鈍条件、
冷間圧延条件、最終焼鈍条件等を加味して検討し
た。製品は0.7mm厚とした。耐食性についてはこ
れらの製品で電気化学的測定はもとより各種浸漬
試験を行なつた。耐食性に対してはプロセス条件
の影響は顕著ではなく、合金組成の影響が大きか
つた。特にＳを10ppm未満、Ｐを150ppm未満と
することでこの種の合金の不働態化特性及びCl^-
等による不働態破壊抵抗性を大巾に向上させ得る
ことを見出した（第１図）。又大気中での耐銹性
の加速テストとして４％NaCl＋0.2％H₂O₂、60
℃の浸漬試験を実施した。これらの結果からCr
量（第２図）、Mo、Cu、Ni、Ti等の添加効果
（第３図）が低Ｓ、低Ｐの合金で一層顕著に現わ
れることが判明した。こうして低Ｐ、低Ｓ等の高
純化はそれ自体も耐食性に効果を示すが、Mo、
Cu、Ni等の合金元素の効果を一層顕著なものと
し、高価なこれら合金元素の添加量を低減し得る
ことがはじめて明らかになつた。フエライト系ステンレス鋼製品の加工性の要請
に関しては、曲げ性更には冷間加工後の曲げ性等
から、用途によつては深絞り性ならびに絞り時の
リジング特性について検討した。まず曲げ性については、プロセスの影響は小さ
く、合金組成の影響が大きい。特に製品板に30％
程度の冷間加工を与えた後、圧延方向に直角方向
の密着曲げをする加工Ｃ曲げテストで合金によつ
て割れが発生した。明らかにS0.001％未満でかつ
Ｐも0.015％未満の合金には密着曲げで割れは全
く発生しなかつた（第４図）。深絞り特性はを求めて評価した。製品板より
圧延方向、圧延方向を直角方向、45゜方向より規
定の引張試験片を採取し、ｒ値を測定し、を求
めた。又圧延方向から採取した引張試験片に20％
の引張歪を与えた後、粗度計にて発生したリジン
グ高さを測定した。フエライト系ステンレス鋼のリジング性、値
については合金組成はもとより熱間圧延条件の影
響やその後の熱処理の影響が大きいことはよく知
られている。高純鋼についても特に熱延板焼鈍の
影響は大きく、連続焼鈍法による850〜1050℃の
温度域に急速加熱する方式が従来のベル型焼鈍に
よる方式よりすぐれていた。又熱延板焼鈍を省略
した場合にも連続焼鈍法と基本的には近い結果が
得られた。こうして高純化効果は熱延法、あるい
は熱延板焼鈍の方法をいかんを問わず効果を示す
ことが判明したが、ここでは通常の熱間圧延法と
連続焼鈍法に注目して検討した結果、高純合金系
では従来のベル型焼鈍方式において知られた知見
とは異なりNbとAlの効果が特に顕著となること
が判明した。又高純合金では特に鋳造時の細粒
化、熱延加熱温度の適正化がリジング、値に関
して重要な管理ポイントであることが判明した。
この点は高純合金が粒成長しやすく粗大化する傾
向を有するためである。高純合金（Ｓ＜0.0010％、Ｐ＜0.015％）にお
けるAlおよびNbの効果は第５図および第６図に
示す通りである。Nbは0.02〜0.30％の添加でリジ
ングの増大を抑えて、値を改善する。Alは0.02
〜0.20％４値を大巾に改善し、かつリジングの
劣化を抑制する。又Ｂの少量添加は高純合金にお
いてもその効果が認められた。以上述べた通り、精錬技術の進歩、特に有害な
不純物であるＰとＳをCa系のフエラツクスで従
来より大巾に低減する方法をベースに溶製された
フエライト系ステンレス鋼において、不働態化能
力が向上し、耐食性がすぐれ、更にMo、Cu、Ni
等の添加の有効性を一層大きなものとし、従来よ
りも少量で大きな効果を発揮する。又きびしい曲
げ加工性を低Ｐ、低Ｓ化は改善する。更に薄板の加工性についても、低Ｐ、低Ｓ合金
においてはNb、Al等の作用効果が顕著で、少量
の添加で大巾な改善効果が得られることが判明し
た。ただ低Ｐ、低Ｓ鋼では鋳造組織の微細化のた
めに鋳造時のΔT℃（タンデイツシユでの溶鋼温
度−溶鋼の凝固温度（計算値））を小さくし、
ΔT℃40℃が必要である。又熱延前の加熱温度
も粗大化防止のため1130℃以下とする必要があ
る。以上の知見はすぐれた品質のフエライト系ステ
ンレス鋼を安価に供給する目的に対して極めて画
期的で大きな効果を発揮するものである。以下に本発明の成分の限定理由について述べ
る。Ｃ：Ｃは耐食性、加工性にとつて有害で低い方
が望ましいが、低Ｐ、低Ｓベースではさほど有害
ではなく、上限を0.08％とした。 Si：Siは耐食性、加工性に対して低い方が望ま
しく、0.3％以下とした。 Mn：Mnは耐食性に対して低い方が望ましく、
0.3％以下とした。Ｐ：Ｐはフエライト系ステンレス鋼の、不働態
特性、特にCl^-による不働態破壊抵抗性を害し、
低ければ低い程望ましく、0.015％未満とした。Ｓ：Ｓはフエライト系ステンレス鋼の不働態化
特性を害し、低ければ低い程望ましく、0.0010％
未満が望ましい。低Ｐ効果と低Ｓ効果は相乗作用
を有し、Cl^-による不働態破壊抵抗性を増し、耐
銹性を改善し、又、曲げ特性を改善する。 Cr：Crはフエライト系ステンレス鋼に不可欠
で13％から26％まで耐食性を大巾に向上する。13
％未満では耐食性が不十分で26％をこえると加工
性が劣化する。 Al：Alは低Ｓ、低Ｐ系フエライトステンレス
鋼で0.02〜0.20％においてを大巾に改善し、か
つリジング特性も改善する。0.02％未満では効果
が小さく、0.20％をこえるとリジング特性を劣化
させる。 Nb：Nbは低Ｓ、低Ｐ系フエライトステンレス
鋼で0.02％〜0.30％においてリジング特性を改善
する。0.02％未満では効果が小さく、0.30％を超
えると効果が飽和し、用途によつて選択添加す
る。Ｎ：Ｎは耐食特性にはさほど影響しないが、加
工性には低い方が望ましい。したがつて通常レベ
ルの0.03％以下とした。 Mo：Moは特に低Ｐ、低Ｓベースで少量添加
で耐食性を顕著に改善し、用途によつて３％以下
で選択添加する。３％をこえるとコストが高くな
るからである。 Cu：Cuは特に低Ｐ、低Ｓベースで少量添加で
耐食性を顕著に改善し用途によつて１％以下で選
択添加する。１％をこえると効果が飽和する。 Ni：Niは低Ｐ、低Ｓベースで少量添加で耐食
性を改善し、用途によつて１％以下で選択添加す
る。１％をこえると効果が飽和する。 Ti：Tiは低Ｐ、低Ｓベースで少量添加で耐食
性、加工性を改善し用途によつて0.6％以内で選
択添加する。0.6％をこえると効果が飽和する。Ｂ：Ｂは低Ｐ、低Ｓベースで少量添加で加工性
を改善し、用途によつて0.010％以内で選択添加
する。0.010％をこえると耐食性を劣化させる。 ΔT：鋳造温度は低Ｓ、低ＰベースではΔT
40℃が望ましい。ΔTが40℃をこえると粗大化し
やすく、所期の加工性が得られない。同じく熱延
の加熱温度あるいは保熱温度は1130℃以下にしな
ければ粗大化しやすく、所期の低Ｓ、低Ｐの効果
が得られない。以下に本発明の実施例について述べる。高純ステンレス合金の溶製は、溶銑予備処理さ
れた溶銑を使用し、Fe−Cr合金を添加して150T
で転炉で溶製し、Ｃレベルが0.2％程度で出鋼し、
取鍋にてCa系のフラツクスを吹込み、、Ｐを0.015
％未満、Ｓを0.001％未満とした後、VOD炉で仕
上脱炭した。出鋼後大半は連続鋳造し200mm厚CC
スラブとし、一部はインゴツトした。連続鋳造の
場合、鋳造条件はΔT40℃を満たすように注入
しスラブとした。インゴツトは分塊圧延したスラ
ブとした。このスラブの熱延加熱温度は1100℃と
し、熱延条件は仕上圧延開始温度を900℃以下に
制御する低温圧延とし、３mmのホツトコイルとし
た。その後連続焼鈍で1000℃に急速加熱すること
からなる熱延板焼鈍を施し、連続酸洗した。冷間
圧延はすべて１回冷延で0.7mmまで圧延し、850℃
の最終焼鈍をし、酸洗し、製品板を得た。比較材
としては通常条件で製造されているステンレス薄
板を使用した。得られた製品の結果は表１の通りである。本発
明鋼はCa系の高純化処理により、すべてＳ＜
0.0010％、Ｐ＜0.015％を満たしている。これら
の製品の特性試験結果は表２の通りで耐食特性を
中心に、すぐれた使用性能が得られ、本発明の効
果が確認された。以上の如く、本発明鋼は基本特性である耐食性
を主とした使用特性に対する合金の高純化の影響
を明らかにした結果得られたものであり、更にそ
の製造方法については連続鋳造に際しての鋳造条
件及び鋳片の加熱温度条件を規制することを要件
とするものであるが、本発明以外の製造条件、例
えば連続鋳造と熱間圧延を直結するCC−DRプロ
セスあるいはCC−ホツトチヤージプロセスによ
り製造されても、本発明鋼の基本特性は変らず所
期の特性を発揮しうることは明らかである。 The purpose of the present invention is to utilize high-purity stainless steel refining technology to provide an inexpensive ferritic stainless steel with excellent corrosion resistance and product workability. and manufacturing methods. Ferritic stainless steel, mainly made of 17Cr, has been widely used mainly as thin plates due to its low cost, but 18Cr-8Ni
Compared to other austenitic stainless steels, it is considerably inferior in terms of corrosion resistance and workability. In particular, in terms of corrosion resistance, it is used under relatively mild conditions such as in the atmosphere, naturally occurring water, tap water, or hot water, but it easily rusts in welded or processed parts. Corrosion resistance is also poor in the base metal. Significant improvements in corrosion resistance are strongly desired for future expansion of applications. In addition, it is a step forward in terms of processability as well as drawability and stretchability. Of course, much research has been done to improve these corrosion resistances and workability, and improvements have been made mainly by adding alloys. Regarding corrosion resistance, the degree of requirement varies depending on the usage environment, and a uniform standard cannot be determined. Therefore, depending on the use, Mo,
The selective addition of Cu, Ni, Ti, Nb, etc. is well known,
For workability, the addition of Ti, B, and Al, the reduction of C and N, and combinations with hot-pressure conditions and heat treatment conditions have been studied. However, placing emphasis on alloy addition in this way increases costs and impedes process simplification. In response to this current situation, the inventors of the present invention have focused on refining technology, especially high-purity refining technology, and have achieved the goal of improving corrosion resistance, improving workability, and simplifying the process by minimizing the amount of alloying. Many studies have been conducted with this aim. As a result, P and S, C and N
The present invention was completed based on the discovery that a reduction in the amount of carbon, that is, a high purification technology meets this aim. That is, the gist of the present invention is as follows. (1) C0.08% or less, Si 0.3% or less, Mn0.3 by weight
% or less, Cr13~26%, N0.03% or less, P0.015%
less than P0.00, containing less than 10%, Al0.02~0.20%,
Further Nb0.02~0.30%, Mo3% as required
Below, Cu1% or less, Ni1% or less, Ti0.6% or less,
A ferritic stainless steel that has excellent usability, mainly corrosion resistance, and is characterized by containing one or more types of B0.010% or less and the remainder essentially consisting of Fe. (2) C0.08% or less, Si0.3% or less, Mn0.3 in weight%
% or less, Cr13~26%, N0.03% or less, P0.015%
Contains less than 0.00%, S less than 10%, Al 0.02~0.20%,
Further Nb0.02~0.30%, Mo3% as required
Below, Cu1% or less, Ni1% or less, Ti0.6% or less,
Molten steel containing one or more types of B0.010% or less and the remainder substantially Fe is continuously cast under a casting temperature condition of ΔT 40℃, and the obtained slab is 1130%
After heating or keeping it warm so as not to exceed ℃,
A method for producing ferritic stainless steel with excellent usability, mainly corrosion resistance, which is characterized by hot rolling. Here, ΔT°C = (molten steel temperature in the tundish during continuous casting in °C) - (solidification temperature of molten steel in °C). The present invention will be explained in detail below. High-purity refining technology uses Ca-based flux injection to reduce S10ppm or less even in stainless steel.
It has been reported that P150ppm or less is possible, and C
Reductions in carbon and nitrogen have already been achieved on an industrial scale. The present inventors focused on these high-purity refining technologies and considered the manufacturing process, and electrochemically investigated the corrosion resistance, especially the rusting property, of 17Cr ferritic stainless steel. As a result, it was found that reducing P was extremely effective in improving resistance to passivation destruction caused by Cl ^- . Furthermore, reducing S improves the passivation properties of the 17Cr system, and furthermore, due to the synergistic effect with the low P mentioned above, Cl ^-
It was found that the resistance to passive state destruction caused by Based on these findings, we melted an alloy with a focus on low P and low S in a vacuum melting furnace, and also changed the heating temperature for hot rolling, hot rolling conditions, hot rolled plate annealing conditions,
The study was conducted taking into account cold rolling conditions, final annealing conditions, etc. The product was 0.7mm thick. Regarding corrosion resistance, these products were subjected to various immersion tests as well as electrochemical measurements. The effect of process conditions on corrosion resistance was not significant, and the effect of alloy composition was significant. In particular, by setting S to less than 10 ppm and P to less than 150 ppm, the passivation properties of this type of alloy and Cl ^-
It has been found that the resistance to passive state destruction caused by such methods can be greatly improved (Fig. 1). Also, as an accelerated test for rust resistance in the atmosphere, 4% NaCl + 0.2% H ₂ O ₂ , 60
A temperature immersion test was conducted. From these results, Cr
It was found that the effect of addition of Mo, Cu, Ni, Ti, etc. (Fig. 3) is more pronounced in low S and low P alloys. In this way, high purification such as low P and low S has an effect on corrosion resistance in itself, but Mo,
It has been revealed for the first time that the effects of alloying elements such as Cu and Ni can be made even more pronounced, and the amount of these expensive alloying elements added can be reduced. Regarding the workability requirements of ferritic stainless steel products, we investigated bendability, bendability after cold working, and depending on the application, deep drawability and ridging characteristics during drawing. First, regarding bendability, the influence of the process is small, and the influence of the alloy composition is large. Especially 30% on product board
After being subjected to a certain amount of cold working, cracking occurred due to the alloy in a process C bending test in which tight bending was performed in a direction perpendicular to the rolling direction. It is clear that the alloy containing less than 0.001% S and less than 0.015% P did not crack at all during close bending (Figure 4). The deep drawing characteristics were determined and evaluated. Specified tensile test pieces were taken from the product sheet in the rolling direction, in a direction perpendicular to the rolling direction, and in a 45° direction, and the r value was measured. In addition, 20% was added to the tensile test piece taken from the rolling direction.
After applying a tensile strain of , the height of the ridging that occurred was measured using a roughness meter. It is well known that the ridging property and value of ferritic stainless steel are greatly influenced by not only the alloy composition but also hot rolling conditions and subsequent heat treatment. High-purity steel is also particularly affected by hot-rolled plate annealing, and the continuous annealing method, which rapidly heats steel to a temperature range of 850 to 1050°C, is superior to the conventional bell-shaped annealing method. Furthermore, even when hot-rolled sheet annealing was omitted, results basically similar to those obtained using the continuous annealing method were obtained. In this way, it has been found that the high purification effect is effective regardless of the method of hot rolling or hot rolled plate annealing, but here, as a result of focusing on the ordinary hot rolling method and continuous annealing method, It was found that in high-purity alloy systems, the effects of Nb and Al are particularly significant, contrary to what is known in the conventional bell-type annealing method. In addition, it has been found that for high-purity alloys, particularly grain refinement during casting and optimization of hot rolling heating temperature are important control points regarding ridging and value.
This is because high-purity alloys tend to grow grains easily and become coarse. The effects of Al and Nb on high purity alloys (S<0.0010%, P<0.015%) are shown in FIGS. 5 and 6. Addition of 0.02 to 0.30% Nb suppresses the increase in ridging and improves the value. Al is 0.02
Significantly improves the 4 value by ~0.20% and suppresses ridging deterioration. The effect of adding a small amount of B was also recognized in high-purity alloys. As mentioned above, progress in refining technology has improved the passivation ability of ferritic stainless steel, which is produced based on a method that uses Ca-based ferrax to reduce the harmful impurities P and S to a greater extent than before. improved, corrosion resistance is improved, and Mo, Cu, Ni
It further increases the effectiveness of additions such as, and achieves a greater effect with a smaller amount than before. Also, severe bending workability is improved by lowering P and S. Furthermore, regarding the workability of thin plates, it was found that the effects of Nb, Al, etc. are remarkable in low P and low S alloys, and that a large improvement effect can be obtained by adding a small amount. However, for low P and low S steel, in order to refine the casting structure, the ΔT°C (molten steel temperature at tundish - solidification temperature of molten steel (calculated value)) during casting is made smaller.
ΔT℃40℃ is required. Also, the heating temperature before hot rolling must be 1130°C or less to prevent coarsening. The above findings are extremely innovative and highly effective for the purpose of supplying ferritic stainless steel of excellent quality at low cost. The reasons for limiting the components of the present invention will be described below. C: C is harmful to corrosion resistance and processability, and a lower content is desirable, but it is not so harmful on a low P, low S base, and the upper limit was set at 0.08%. Si: It is desirable for Si to be low in terms of corrosion resistance and workability, and is set to 0.3% or less. Mn: The lower the Mn content, the better for corrosion resistance.
It was set to 0.3% or less. P: P impairs the passive properties of ferritic stainless steel, especially the resistance to passive breakdown due to Cl ^- .
The lower the content, the more desirable it is, and it is set to less than 0.015%. S: S impairs the passivation properties of ferritic stainless steel, and the lower it is, the more desirable it is, 0.0010%
Less than is desirable. The low P effect and the low S effect have a synergistic effect, increasing resistance to passive failure due to Cl ^- , improving rust resistance, and improving bending properties. Cr: Cr is essential for ferritic stainless steel and greatly improves corrosion resistance from 13% to 26%. 13
If it is less than 26%, corrosion resistance will be insufficient, and if it exceeds 26%, workability will deteriorate. Al: Al significantly improves low S, low P ferrite stainless steel at 0.02 to 0.20%, and also improves ridging properties. If it is less than 0.02%, the effect will be small, and if it exceeds 0.20%, the ridging characteristics will deteriorate. Nb: Nb improves ridging properties in low S, low P ferrite stainless steel at 0.02% to 0.30%. If it is less than 0.02%, the effect is small, and if it exceeds 0.30%, the effect is saturated, so it should be added selectively depending on the application. N: Although N does not significantly affect corrosion resistance, it is desirable for workability to be low. Therefore, it was set at 0.03% or less of the normal level. Mo: Mo can significantly improve corrosion resistance when added in small amounts, especially on a low P and low S basis, and is selectively added in an amount of 3% or less depending on the application. This is because if it exceeds 3%, the cost will increase. Cu: Cu can significantly improve corrosion resistance when added in small amounts, especially on a low P and low S basis, and is selectively added at 1% or less depending on the application. When it exceeds 1%, the effect is saturated. Ni: Ni improves corrosion resistance when added in small amounts based on low P and low S, and is selectively added at 1% or less depending on the application. When it exceeds 1%, the effect is saturated. Ti: Ti improves corrosion resistance and processability by adding a small amount on a low P, low S base, and is selectively added within 0.6% depending on the application. The effect saturates when it exceeds 0.6%. B: B is a low-P, low-S base that improves processability when added in small amounts, and is selectively added within 0.010% depending on the application. If it exceeds 0.010%, corrosion resistance will deteriorate. ΔT: Casting temperature is low S, ΔT based on low P
40℃ is desirable. When ΔT exceeds 40°C, it tends to become coarse and the desired workability cannot be obtained. Similarly, unless the hot rolling heating temperature or heat retention temperature is set to 1130° C. or lower, coarsening tends to occur and the desired low S and low P effects cannot be obtained. Examples of the present invention will be described below. High-purity stainless steel alloy is melted using pre-treated hot metal and Fe-Cr alloy is added to produce 150T.
It is melted in a converter and tapped with a C level of about 0.2%.
Inject Ca-based flux in a ladle, P 0.015
After reducing the S content to less than 0.001%, final decarburization was performed in a VOD furnace. After tapping, most of the steel is continuously cast into 200mm thick CC.
It was made into slabs and some parts were made into ingots. In the case of continuous casting, the casting conditions were to satisfy ΔT40°C and form a slab. The ingot was a slab rolled by blooming. The hot rolling heating temperature of this slab was 1100°C, the hot rolling conditions were low temperature rolling where the finish rolling start temperature was controlled to 900°C or less, and a 3 mm hot coil. Thereafter, hot-rolled plate annealing, which consists of continuous annealing and rapid heating to 1000°C, was performed, followed by continuous pickling. All cold rolling is done once to 0.7mm at 850℃.
A final annealing process was carried out, followed by pickling to obtain a product plate. As a comparison material, a thin stainless steel plate manufactured under normal conditions was used. The results of the obtained products are shown in Table 1. The steel of the present invention has all S<
0.0010%, P < 0.015%. The characteristics test results of these products are shown in Table 2, and excellent usability, mainly in terms of corrosion resistance, was obtained, confirming the effectiveness of the present invention. As described above, the steel of the present invention was obtained as a result of clarifying the influence of high purification of the alloy on the usage characteristics, mainly corrosion resistance, which is a basic property. Although it is a requirement to regulate the heating temperature conditions of the slab, it is not possible to manufacture under manufacturing conditions other than the present invention, such as the CC-DR process or CC-hot charge process that directly connects continuous casting and hot rolling. It is clear that the basic characteristics of the steel of the present invention remain unchanged even if the steel of the present invention is changed, and the desired characteristics can be exhibited.

【表】【table】

【表】【table】【図面の簡単な説明】[Brief explanation of drawings]

第１図ａ，ｂは１７Cr系ステンレス鋼のCl^-を
含む液（３％NaCl＋５％H₂SO₄、30C、Ar脱気）
の中での陽分極曲線に対するＰ、Ｓ量の影響を示
す図、第２図はフエライト系ステンレス鋼の、４
％NaCl＋0.2％H₂O₂液中、60℃×25hrテストに
よる耐食性に対するCr量と高純化の効果を示す
図、第３図は１７Crステンレス鋼の、４％NaCl
＋0.2％H₂O₂液中、60℃×24hrテストによる耐食
性に対する高純度ならびに合金元素の影響を示す
図、第４図は各種フエライト系ステンレス鋼
（Cr：11.5〜26％、２％以下のMo、１％以下の
Niを含む）における加工後のＣ方向曲げ特性と、
Ｐ、Ｓの影響を示す図、第５図は１７Crステン
レス鋼薄板の値に対する高純化合金及びAl、
Nbの影響を示す図、第６図は１７Crステンレス
鋼薄板のリジング高さに対する高純化合金及び
Al、Nbの影響を示す図である。第１図ａ：曲線の鋼中、P50ppm、S5ppm 曲線の鋼中、P50ppm、S9ppm 曲線の鋼中、P50ppm、S60ppm 曲線の鋼中、P50ppm、S140ppm 第１図ｂ：曲線の鋼中、P50ppm、S8ppm 曲線の鋼中、P100ppm、S8ppm 曲線の鋼中、P150ppm、S8ppm 曲線の鋼中、P250ppm、S8ppm 曲線の鋼中、P340ppm、S8ppm 第３図：実用合金Ｐ0.020％、Ｓ0.0050
％〓〓〓高純合金Ｐ＜0.015％、Ｓ＜0.0010％第４図：〇割れ発生なし、△微小割れ、×割れ第５図及び第６図： ‐‐‐実用合金Ｐ0.020％、Ｓ0.0050％ ―――高純合金Ｐ＜0.015％、Ｓ＜0.0010％ Figure 1 a and b are 17Cr stainless steel liquid containing Cl ^- (3% NaCl + 5% H ₂ SO ₄ , 30C, Ar degassing)
Figure 2 shows the influence of P and S amounts on the positive polarization curve of ferritic stainless steel.
%NaCl + 0.2% H ₂ O ₂ solution, 60℃ x 25 hr test showing the effect of Cr content and high purity on corrosion resistance.
Figure 4 shows the effects of high purity and alloying elements on corrosion resistance in +0.2% H ₂ O ₂ solution at 60℃ x 24 hours test. Mo, less than 1%
C-direction bending characteristics after processing in (including Ni),
Figure 5 shows the influence of P, S on the value of 17Cr stainless steel thin plate, highly purified alloy, Al,
Figure 6 shows the effect of Nb on the ridging height of a 17Cr stainless steel thin plate.
FIG. 3 is a diagram showing the influence of Al and Nb. Figure 1 a: Curved steel, P50ppm, S5ppm Curved steel, P50ppm, S9ppm Curved steel, P50ppm, S60ppm Curved steel, P50ppm, S140ppm Figure 1b: Curved steel, P50ppm, S8ppm In the steel of the curve, P100ppm, S8ppm In the steel of the curve, P150ppm, S8ppm In the steel of the curve, P250ppm, S8ppm In the steel of the curve, P340ppm, S8ppm Figure 3: Practical alloy P0.020%, S0.0050
% 〓〓〓 High purity alloy P<0.015%, S<0.0010% Figure 4: 〇 No cracking, △ Microcracking, × Cracking Figures 5 and 6: ---Practical alloy P0.020%, S0 .0050% ---High purity alloy P<0.015%, S<0.0010%

Claims

【特許請求の範囲】１重量％でC0.08％以下、Si0.3％以下、Mn0.3
％以下、Cr13〜26％、N0.03％以下、P0.015％未
満、S0.0010％未満、Al0.02〜0.20％、残部実質
的にFeからなることを特徴とする不働態化特性、
cl^-1による不働態破壊抵抗性、リジング特性、深
絞り性、冷間工後のＣ方向曲げ密着性に優れた高
純化フエライト系ステンレス鋼。２重量％でC0.08％以下、Si0.3％以下、Mn0.3
％以下、Cr13〜26％、N0.03％以下、P0.015％未
満、S0.0010％未満、A0.02〜0.20％含み、さらに
Nb0.02〜0.30％、Mo3％以下、Cu1％以下、Ni1
％以下、Ti0.6％以下、B0.010％以下を１種又は
２種以上を含み、残部実質的にFeからなること
を特徴とする不働態化特性、cl^-1による不働態破
壊抵抗性、リジング特性、深絞り性、冷間加工後
のＣ方向曲げ密着に優れた高純化フエライト系ス
テンレス鋼。３重量％でC0.08％以下、Si0.3％以下、Mn0.3
％以下、Cr13〜26％、N0.03％以下、P0.015％未
満、S0.0010％未満、Al0.02〜0.20％、残部実質
的にFeからなる溶鋼を、ΔT≦40℃の鋳造温度条
件下で連続鋳造し、得られた鋳片を1130℃を超え
ないように加熱あるいは保熱した後、熱間圧延す
ることを特徴とする不働態化特性、cl^-1による不
働態破壊抵抗性、リジング特性、深絞り性、冷間
加工後のＣ方向曲げ密着性に優れた高純化フエラ
イト系ステンレス鋼の製造方法。ここで、ΔT℃＝（連続鋳造時のタンデイシユ
における溶鋼温度℃）−（溶鋼の凝固温度℃）４重量％でC0.08％以下、Si0.3％以下、Mn0.3
％以下、Cr13〜26％、N0.03％以下、P0.015％未
満、S0.0010％未満、A0.02〜0.20％含み、さらに
Nb0.02〜0.30％、Mo3％以下、Cu1％以下、Ni1
％以下、Ti0.6％以下、B0.010％以下を１種又は
２種以上を含み、残部実質的にFeからなる溶鋼
を、ΔT≦40℃の鋳造温度条件下で連続鋳造し、
得られた鋳片を1130℃を超えないように加熱ある
いは保熱した後、熱間圧延することを特徴とする
不働態化特性、cl^-1による不働態破壊抵抗性、リ
ジング特性、深絞り性、冷間加工後のＣ方向曲げ
密着性に優れた高純化フエライト系ステンレス鋼
の製造方法。ここで、ΔT℃＝（連続鋳造時のタンデイシユ
における溶鋼温度℃）−（溶鋼の凝固温度℃）[Claims] 1. C0.08% or less, Si 0.3% or less, Mn 0.3 in weight%
% or less, Cr13-26%, N0.03% or less, P0.015% or less, S0.0010% or less, Al0.02-0.20%, the remainder essentially consisting of Fe,
Highly purified ferritic stainless steel with excellent passive fracture resistance due to cl ^-1 , ridging properties, deep drawability, and C direction bending adhesion after cold working. 2 Weight%: C0.08% or less, Si0.3% or less, Mn0.3
% or less, Cr13~26%, N0.03% or less, P0.015% or less, S0.0010% or less, A0.02~0.20% included, and
Nb0.02~0.30%, Mo3% or less, Cu1% or less, Ni1
% or less, Ti 0.6% or less, B 0.010% or less, the passivation property is characterized by containing one or more types, and the remainder substantially consists of Fe, and resistance to passivation breakdown due to cl ^-1. A highly purified ferritic stainless steel with excellent ridging properties, deep drawability, and C-direction bending adhesion after cold working. 3 Weight%: C0.08% or less, Si0.3% or less, Mn0.3
% or less, Cr13~26%, N0.03% or less, P0.015% or less, S0.0010% or less, Al0.02~0.20%, and the balance substantially consists of Fe at a casting temperature of ΔT≦40°C. Passivation properties characterized by continuous casting under conditions, heating or heat retention of the obtained slab at a temperature not exceeding 1130℃, and then hot rolling, passivation resistance due to cl ^-1 , a method for producing highly purified ferritic stainless steel that has excellent ridging properties, deep drawability, and C-direction bending adhesion after cold working. Here, ΔT℃=(molten steel temperature in tundish during continuous casting in degrees Celsius) - (solidification temperature of molten steel in degrees Celsius) 4 In weight%, C0.08% or less, Si0.3% or less, Mn0.3
% or less, Cr13~26%, N0.03% or less, P0.015% or less, S0.0010% or less, A0.02~0.20% included, and
Nb0.02~0.30%, Mo3% or less, Cu1% or less, Ni1
% or less, Ti 0.6% or less, B 0.010% or less, and the remainder substantially consists of Fe, by continuous casting under a casting temperature condition of ΔT≦40℃,
The obtained slab is heated or kept at a temperature not exceeding 1130℃ and then hot rolled to improve passivation properties, passivity fracture resistance due to cl ^-1 , ridging properties, and deep drawability. , a method for producing highly purified ferritic stainless steel with excellent C-direction bending adhesion after cold working. Here, ΔT℃=(molten steel temperature in tundish during continuous casting in degrees Celsius) - (solidification temperature of molten steel in degrees Celsius)