JPH07116779A - High-al ferritic stainless steel and its production - Google Patents
High-al ferritic stainless steel and its productionInfo
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- JPH07116779A JPH07116779A JP5262534A JP26253493A JPH07116779A JP H07116779 A JPH07116779 A JP H07116779A JP 5262534 A JP5262534 A JP 5262534A JP 26253493 A JP26253493 A JP 26253493A JP H07116779 A JPH07116779 A JP H07116779A
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、優れた耐高温酸化特性
を呈する高Ａｌフェライト系ステンレス鋼及びその製造
方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high Al ferritic stainless steel exhibiting excellent high temperature oxidation resistance and a method for producing the same.
【０００２】[0002]
【従来の技術】高Ａｌフェライト系ステンレス鋼は、優
れた耐高温酸化特性を呈することから、チムニー材，電
熱材料，排ガス浄化装置の触媒コンバータ基材等として
使用されている。高Ａｌフェライト系ステンレス鋼を基
材に使用したメタリックコンバータは、従来のセラミッ
クコンバータの比較して格段に熱衝撃性が強く、エンジ
ンにより近い場所に設置できる利点をもつ。また、他の
高温酸化性雰囲気に曝される構造用材料等の用途に適し
た材料として注目されている。本発明者等も、この系統
の高Ａｌフェライト系ステンレス鋼の開発を進めてき
た。その一環として、たとえば特開平４−１４７９４５
号公報では、希土類金属，Ｙ，アルカリ土類金属等の合
金元素を添加した高Ａｌフェライト系ステンレス鋼を紹
介した。これらの合金元素は、鋼材表面に形成される酸
化皮膜を強固なものにし、鋼材の耐高温酸化特性を向上
させる。また、鋼中に含まれているＳ等の有害元素を除
去し、或いは固定する作用も呈する。2. Description of the Related Art High Al ferritic stainless steel is used as a chimney material, an electric heating material, a catalytic converter base material of an exhaust gas purifying device, etc. because it exhibits excellent high temperature oxidation resistance. The metallic converter using high Al ferritic stainless steel as a base material has a remarkably strong thermal shock resistance as compared with the conventional ceramic converter and has an advantage that it can be installed closer to the engine. Further, it is attracting attention as a material suitable for other uses such as structural materials exposed to high temperature oxidizing atmosphere. The present inventors have also been developing a high Al ferritic stainless steel of this system. As a part of that, for example, Japanese Patent Laid-Open No. 4-147945
In the publication, high Al ferritic stainless steel to which alloying elements such as rare earth metal, Y, alkaline earth metal, etc. are added is introduced. These alloying elements strengthen the oxide film formed on the surface of the steel material and improve the high temperature oxidation resistance of the steel material. Further, it also acts to remove or fix harmful elements such as S contained in the steel.
【０００３】[0003]
【発明が解決しようとする課題】連続鋳造によって高Ａ
ｌフェライト系ステンレス鋼のスラブを製造する際、ス
ラブ表面近傍に微細な管状気泡が発生し易い。微細な管
状気泡は、高Ａｌフェライト系ステンレス鋼特有の現象
であり、スラブの熱延や冷延，加工工程で肌荒れ，クラ
ック等の表面欠陥を発生させる原因となる。この微細気
泡は、本発明者等の調査によると、Ａｒに起因したピン
ホールとは明らかに異なるパイプ状の形態をもってい
る。本発明は、このような問題を解消すべく案出された
ものであり、微細気泡発生の原因が鋼中Ｍｇ濃度にある
との知見に基づき、鋼中Ｍｇ濃度を低減させる条件下で
所定成分の溶湯を調製し、耐高温酸化特性に優れた高Ａ
ｌ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。[Problems to be Solved by the Invention] High A by continuous casting
When manufacturing a slab of ferritic stainless steel, fine tubular bubbles are likely to occur near the surface of the slab. The fine tubular bubbles are a phenomenon peculiar to high-Al ferritic stainless steel and cause surface defects such as rough skin and cracks in the hot rolling and cold rolling of the slab and the working process. According to the investigation by the present inventors, the fine bubbles have a pipe-like form which is clearly different from the pinholes caused by Ar. The present invention has been devised to solve such a problem, and based on the finding that the cause of the generation of fine bubbles is the Mg concentration in the steel, a predetermined component under the condition of reducing the Mg concentration in the steel. A high-A with excellent high temperature oxidation resistance
l Ferritic stainless steel is intended to be provided.
【０００４】[0004]
【課題を解決するための手段】本発明においては、その
目的を達成するため、Ａｌ：３〜６重量％を含む高Ａｌ
フェライト系ステンレス鋼の溶湯に、５〜３０重量％の
ＣａＦ2 を含むＣａＯ−ＣａＦ2 −Ａｌ2 Ｏ3 系のスラ
グを接触させた後、希土類元素及びＹの１種又は２種以
上を添加し、次いで連続鋳造する。溶湯のＭｇ濃度は、
５〜３０重量％のＣａＦ2 を含むＣａＯ−ＣａＦ2 −Ａ
ｌ2 Ｏ3 系のスラグとの接触によって０．０１５重量％
以下に低減させることが好ましい。或いは、連続鋳造の
前工程で希土類元素やＹの１種又は２種以上を添加する
際、少なくともアルミナ系耐火物でライニングされた容
器に溶湯を収容することにより、鋼中Ｍｇ濃度が低い高
Ａｌフェライト系ステンレス鋼が得られる。アルミナ系
耐火物は、容器の器壁自体を、或いは容器内面にライニ
ングとして施す何れの形態でも使用される。In the present invention, in order to achieve the object, high Al containing 3 to 6% by weight of Al is used.
After bringing CaO—CaF 2 —Al 2 O 3 -based slag containing 5 to 30% by weight of CaF 2 into contact with the molten ferritic stainless steel, one or more rare earth elements and Y are added. Then, continuous casting is performed. The Mg concentration of the molten metal is
5 to 30 wt% of CaO-CaF 2 -A containing CaF 2
0.015 wt% by contact with slag of l 2 O 3 system
It is preferable to reduce the amount to the following. Alternatively, when one or more rare earth elements or Y are added in the pre-process of continuous casting, the molten metal is stored in a container lined with at least an alumina-based refractory so that the high Mg content in the steel is high. Ferritic stainless steel is obtained. The alumina refractory is used in any form in which the vessel wall of the container itself or the inner surface of the container is used as a lining.
【０００５】本発明に従って得られた高Ａｌフェライト
系ステンレス鋼は、Ｃ：０．０３重量％以下と、Ｓｉ：
０．２５重量％以下と、Ｍｎ：０．２５重量％以下と、
Ｐ：０．０３重量％以下と、Ｓ：０．００１重量％以下
と、Ｎ：０．０３重量％以下と、Ｃｒ：１５〜３０重量
％と、希土類金属及びＹの１種又は２種以上：０．０１
〜０．２重量％を含み、Ｍｇ含有量が０．０１５重量％
以下に規制されている。この高Ａｌフェライト系ステン
レス鋼は、更に４重量％以下のＭｏを含んでいても良
い。The high Al ferritic stainless steel obtained according to the present invention contains C: 0.03% by weight or less and Si:
0.25 wt% or less, Mn: 0.25 wt% or less,
P: 0.03% by weight or less, S: 0.001% by weight or less, N: 0.03% by weight or less, Cr: 15 to 30% by weight, and one or more of rare earth metals and Y. : 0.01
~ 0.2 wt%, 0.015 wt% Mg content
It is regulated below. The high Al ferritic stainless steel may further contain 4 wt% or less of Mo.
【０００６】[0006]
【作用】本発明者等は、高Ａｌフェライト系ステンレス
鋼に管状の微細気泡が発生するメカニズムを調査・研究
した。所定の組成をもつスラグ−メタルを誘導溶解炉で
溶解し、希土類金属，Ｙ，アルカリ土類金属等を添加し
た後、定期的に溶湯をサンプリングした。また、成分調
整された溶湯を鋳造し、気泡の発生状況を観察した。鋼
中Ｍｇ濃度［Ｍｇ］及び鋼中水素濃度［Ｈ］で実験結果
を整理したところ、図１に示す関係が成立していること
を見い出した。すなわち、鋼中のＭｇ濃度［Ｍｇ］が１
５０ｐｐｍを超えるとき、得られた鋳片に微細な管状気
泡の発生がみられた。他方、１５０ｐｐｍ以下の［Ｍ
ｇ］では、３〜４ｐｐｍの範囲で［Ｈ］が変動しても、
管状気泡の発生は検出されなかった。このことから、微
細な管状気泡を発生させる主要な原因は、凝固時に溶湯
から放出されるＭｇガスにあるものと推論した。The present inventors investigated and studied the mechanism by which tubular microscopic bubbles are generated in high Al ferritic stainless steel. A slag-metal having a predetermined composition was melted in an induction melting furnace, rare earth metals, Y, alkaline earth metals and the like were added, and then the molten metal was sampled periodically. In addition, the molten metal having the adjusted components was cast and the generation of bubbles was observed. When the experimental results were arranged by the Mg concentration [Mg] in steel and the hydrogen concentration [H] in steel, it was found that the relationship shown in FIG. 1 was established. That is, the Mg concentration [Mg] in steel is 1
When it exceeded 50 ppm, generation of fine tubular bubbles was observed in the obtained slab. On the other hand, 150 ppm or less [M
g], even if [H] varies in the range of 3 to 4 ppm,
The generation of tubular bubbles was not detected. From this, it was inferred that the main cause of the generation of fine tubular bubbles was Mg gas released from the molten metal during solidification.
【０００７】Ａｌ及び希土類金属，Ｙ等を含む高Ａｌフ
ェライト系ステンレス鋼の溶湯においては、Ｍｇに関し
次式（１）〜（３）の反応が生じるものと考えられる。 ２［Ａｌ］＋３（ＭｇＯ）＝（Ａｌ2 Ｏ3 ）＋３［Ｍｇ］ ・・・・（１） ２［Ｙ］＋３（ＭｇＯ）＝（Ｙ2 Ｏ3 ）＋３［Ｍｇ］ ・・・・（２） ２［Ｙ］＋３（ＭｇＯ）＝（Ｙ2 Ｏ3 ）＋３Ｍｇ（ｇ） ・・・・（３） 式（１）の反応は、Ａｌ添加によって［Ｍｇ］が増加す
ることによって確認される。すなわち、溶湯にＡｌを添
加すると、反応式（１）に従ってスラグ中のＭｇＯが還
元され、図２に示すように鋼中Ｍｇ濃度［Ｍｇ］が増加
する。また、Ｙを添加したとき、反応式（２）に従って
［Ｍｇ］が飽和溶解度まで上昇する。更にＹを添加する
と、式（３）に示すようにＭｇガスが発生する。Ｍｇガ
スは、スラグ層を通過して上昇し、空気に接触したとき
燃焼する。本発明者等は、発生した白煙から粉末を回収
し、成分分析した。その結果、白煙粉末の大部分がＭｇ
Ｏであることを確認した。It is considered that in the molten metal of high Al ferritic stainless steel containing Al and rare earth metals, Y, etc., the reactions of the following equations (1) to (3) occur with respect to Mg. 2 [Al] +3 (MgO) = (Al 2 O 3) +3 [Mg] ···· (1) 2 [Y] +3 (MgO) = (Y 2 O 3) +3 [Mg] ···· ( 2) 2 [Y] +3 (MgO) = (Y 2 O 3 ) + 3Mg (g) ... (3) The reaction of the formula (1) is confirmed by the increase of [Mg] by the addition of Al. . That is, when Al is added to the molten metal, MgO in the slag is reduced according to the reaction formula (1), and the Mg concentration [Mg] in steel increases as shown in FIG. Further, when Y is added, [Mg] rises to the saturated solubility according to the reaction formula (2). When Y is further added, Mg gas is generated as shown in formula (3). The Mg gas passes through the slag layer, rises, and burns when it comes into contact with air. The present inventors collected powder from the generated white smoke and analyzed the components. As a result, most of the white smoke powder was Mg.
It was confirmed to be O.
【０００８】他方、溶湯に添加したＹの減少速度を解析
したところ、一次反応で整理できることを見い出した。
たとえば、粘性の小さなスラグと接触する溶湯では、鋼
中Ｙ濃度［Ｙ］が急激に減少する。これは、スラグ層を
Ｍｇガスが盛んに上昇し、それに伴って式（３）に従っ
た［Ｙ］の酸化反応が進行することに由来するものと推
察される。このように、［Ｙ］を減少させる反応は、ス
ラグ中の反応に関与する元素の拡散に律速され、本系に
おいてはＭｇが主要な律速因子である。以上の結果か
ら、高Ａｌフェライト系ステンレス鋼を溶製している状
態では、鋼中Ｍｇ濃度［Ｍｇ］が平衡に達しており、溶
湯を鋳造しスラブとして凝固するときに飽和限界を超え
た鋼中Ｍｇが外部に放出され、Ｍｇの放出跡が微細な管
状気泡となってスラブに残るものと考えられる。したが
って、気泡の主要な原因である［Ｍｇ］を減少させるた
めには、温度及び圧力が一定条件下ではＭｇＯの濃度を
下げること、Ａｌ2 Ｏ3 ，Ｙ2 Ｏ3 等の活量を上げるこ
と等が効果的であるとが、式（１）及び（２）から予想
される。On the other hand, when the decreasing rate of Y added to the molten metal was analyzed, it was found that it could be arranged by the first-order reaction.
For example, the Y concentration [Y] in steel sharply decreases in a molten metal that comes into contact with slag having a low viscosity. It is presumed that this is because Mg gas vigorously rises in the slag layer, and the oxidation reaction of [Y] according to the equation (3) proceeds accordingly. Thus, the reaction that reduces [Y] is rate-controlled by the diffusion of the elements involved in the reaction in the slag, and Mg is the main rate-controlling factor in this system. From the above results, in the state where the high Al ferritic stainless steel is being melted, the Mg concentration [Mg] in the steel reaches the equilibrium, and the steel that exceeds the saturation limit when the molten metal is cast and solidifies as a slab. It is considered that the medium Mg is released to the outside, and the traces of the Mg release remain as fine tubular bubbles in the slab. Therefore, in order to reduce [Mg] which is a main cause of bubbles, it is necessary to reduce the concentration of MgO and increase the activities of Al 2 O 3 , Y 2 O 3 etc. under the conditions of constant temperature and pressure. Are expected to be effective from equations (1) and (2).
【０００９】Ａｌ2 Ｏ3 の活量を上げるためには、Ａｌ
2 Ｏ3 の活量を低下させるＣａＯを相対的に低減するこ
と、換言すればＣａＯ／Ａｌ2 Ｏ3 比を小さくすること
が有効である。しかし、高Ａｌの溶湯を製造する工程で
は、メタルからスラグに移行するＡｌ分が多く、スラグ
中のＣａＯ／Ａｌ2 Ｏ3 比は０．６程度の低いレベルに
ある。これ以上にＣａＯ／Ａｌ2 Ｏ3 比を下げること
は、ＣａＯ−Ａｌ2 Ｏ3−ＭｇＯ三元系状態図における
１６００℃の液相線からみて限界がある。また、Ｙ2 Ｏ
3 等の活量を上げることは、有効であるものの、高価な
Ｙ源を多量に消費し、製造コストを上昇させる原因とな
る。そこで、本発明者等は、ＭｇＯの濃度を低下させる
方法として、スラグ中のＭｇＯ溶解度を下げる手段を検
討した。そして、種々のスラグについて組成との関連で
ＭｇＯ溶解度を調査したところ、５〜３０重量％のＣａ
Ｆ2 を含むＣａＯ−ＣａＦ2 −Ａｌ2 Ｏ3 系のスラグ
は、従来から使用されているＣａＯ−Ａｌ2 Ｏ3 系のス
ラグに比較して、ＭｇＯ溶解度を大幅に減少させる作用
を呈することを見い出した。In order to increase the activity of Al 2 O 3 , Al
It is effective to relatively reduce CaO that reduces the activity of 2 O 3 , that is, to reduce the CaO / Al 2 O 3 ratio. However, in the process of producing a high Al molten metal, a large amount of Al is transferred from the metal to the slag, and the CaO / Al 2 O 3 ratio in the slag is at a low level of about 0.6. Reducing the CaO / Al 2 O 3 ratio beyond this limit is limited in view of the liquidus line at 1600 ° C. in the CaO—Al 2 O 3 —MgO ternary phase diagram. Also, Y 2 O
Increasing the activity such as 3 is effective, but consumes a large amount of expensive Y source, and causes a rise in manufacturing cost. Therefore, the present inventors have examined means for reducing the solubility of MgO in slag as a method of reducing the concentration of MgO. When the MgO solubility was investigated in relation to the composition of various slags, Ca of 5 to 30% by weight was obtained.
CaO-CaF 2 -Al 2 O 3 system slag containing F 2, as compared to CaO-Al 2 O 3 based slag which has been used conventionally, it exhibits the effect of greatly reducing the MgO solubility I found it.
【００１０】具体的には、５重量％以上のＣａＦ2 を含
むＣａＯ−ＣａＦ2 −Ａｌ2 Ｏ3 系スラグでは、ＣａＯ
−Ａｌ2 Ｏ3 系に比較して［Ｍｇ］を０．００５重量％
程度或いはそれ以上に低減することが可能であった。
［Ｍｇ］の減少作用は、ＣａＦ2 含有量が５重量％を超
えたときに顕著であった。しかし、３０重量％を超える
多量のＣａＦ2 を含むＣａＯ−ＣａＦ2 −Ａｌ2 Ｏ3 系
スラグは、耐火物の溶損が激しく、炉材の寿命を低下さ
せる。スラグのＭｇＯ溶解度は、アルミナ系耐火物の使
用により実質的にゼロにできる。すなわち、スラグ中の
ＭｇＯは、ドロマイト系の耐火物から供給される。そこ
で、ドロマイト系に代えアルミナ系耐火物を少なくとも
容器のライニングに使用するとき、耐火物から供給され
るＭｇＯがなく、スラグ中のＭｇＯが極めて低い濃度レ
ベルに規制される。この場合、鋼中Ｍｇ濃度［Ｍｇ］が
５０ｐｐｍ以下に低下し、管状気泡の発生がみられない
スラブが得られる。[0010] Specifically, in the CaO-CaF 2 -Al 2 O 3 slag containing 5% or more by weight of CaF 2, CaO
0.005% by weight of [Mg] in comparison with Al 2 O 3 system
It was possible to reduce it to a degree or more.
The reducing effect of [Mg] was remarkable when the CaF 2 content exceeded 5% by weight. However, CaO—CaF 2 —Al 2 O 3 -based slag containing a large amount of CaF 2 in excess of 30% by weight causes severe melting loss of refractory and shortens the life of the furnace material. The MgO solubility of the slag can be made substantially zero by using an alumina refractory. That is, MgO in the slag is supplied from the dolomite refractory material. Therefore, when an alumina refractory is used instead of a dolomite refractory at least for the lining of the container, there is no MgO supplied from the refractory and the MgO in the slag is regulated to an extremely low concentration level. In this case, the Mg concentration [Mg] in the steel is reduced to 50 ppm or less, and a slab in which tubular bubbles are not generated can be obtained.
【００１１】本発明の溶製方法が適用されるステンレス
鋼は、合金元素を所定の含有量で含んでいることが好ま
しい。以下、各合金元素及びその含有量を説明する。 Ｃ：０．０３重量％以下 高Ａｌフェライト系ステンレス鋼においては、耐酸化性
に悪影響を与える有害元素である。Ｃ含有量の増加に応
じて、異常酸化が発生し易くなる。また、スラブ又はホ
ットコイルの靭性を劣化させる原因ともなる。 Ｓｉ：０．２５重量％以下 Ｓｉは、一般に耐高温酸化特性に対し有効な合金元素で
あるとされている。しかし、高Ａｌフェライト系ステン
レス鋼では、Ｓｉ含有量を低減することにより耐高温酸
化特性が著しく改善される。Ｓｉ含有量低減による影響
は、Ｍｎ含有量の規制と相俟つて顕著になる。 Ｍｎ：０．２５重量％以下 熱間加工性の改善に有効な合金元素であるものの、高Ａ
ｌフェライト系ステンレス鋼においては耐高温酸化特性
に悪影響を及ぼす。そこで、耐高温酸化特性を確保する
ため、Ｍｎ含有量を０．２５重量％未満に低減する。ま
た、Ｍｎ含有量の低減によって、靭性の向上も図られ
る。The stainless steel to which the melting method of the present invention is applied preferably contains a predetermined amount of alloying elements. Hereinafter, each alloy element and its content will be described. C: 0.03 wt% or less In high Al ferritic stainless steel, it is a harmful element that adversely affects the oxidation resistance. Abnormal oxidation is likely to occur as the C content increases. It also causes deterioration of the toughness of the slab or hot coil. Si: 0.25 wt% or less Si is generally considered to be an effective alloying element for high temperature oxidation resistance. However, in high Al ferritic stainless steel, the high temperature oxidation resistance is significantly improved by reducing the Si content. The effect of reducing the Si content becomes significant together with the regulation of the Mn content. Mn: 0.25% by weight or less Although it is an alloying element effective in improving hot workability, it has a high A content.
l Ferritic stainless steel adversely affects high temperature oxidation resistance. Therefore, in order to secure the high temperature oxidation resistance, the Mn content is reduced to less than 0.25% by weight. Further, the toughness can be improved by reducing the Mn content.
【００１２】Ｐ：０．０３重量％以下 耐高温酸化特性に悪影響を与える元素であることから、
Ｐ含有量は低いほど好ましい。また、Ｐ含有量を低減す
るとき、熱延板の靭性も向上する。 Ｓ：０．００１重量％以下 希土類金属，Ｙ等と結合し、非金属介在物となって鋼材
の表面性状を劣化させる。また、耐高温酸化特性に有効
な希土類金属，Ｙ等を消費することから、多量のＳを含
むとき、損失分を見込んで多量の希土類金属，Ｙ等を添
加することが必要になる。しかも、希土類金属，Ｙ等と
の反応が一定化しないため、添加した希土類金属，Ｙ等
の歩留りに大きくバラツキが生じる結果となる。したが
って、本発明においては、Ｓ含有量を０．００１重量％
以下と厳しく規制することが必要である。 Ｎ：０．０３重量％以下 鋼材の靭性を低下させる有害元素である。また、耐高温
酸化特性に有効なＡｌ量をＡｌＮの生成により消費し、
異常酸化発生の原因となる。したがって、Ｎ含有量は、
上限を０．０３重量％に設定する。P: 0.03% by weight or less Since it is an element which adversely affects the high temperature oxidation resistance,
The lower the P content, the more preferable. Further, when the P content is reduced, the toughness of the hot rolled sheet is also improved. S: 0.001% by weight or less Combined with rare earth metals, Y, etc. to form non-metallic inclusions and deteriorate the surface properties of the steel material. Further, since the rare earth metal, Y, etc. effective for high temperature oxidation resistance are consumed, when a large amount of S is contained, it is necessary to add a large amount of rare earth metal, Y etc. in consideration of the loss. In addition, since the reaction with the rare earth metal, Y, etc. is not constant, the yield of the added rare earth metal, Y, etc. greatly varies. Therefore, in the present invention, the S content is 0.001% by weight.
It is necessary to strictly control the following. N: 0.03 wt% or less It is a harmful element that reduces the toughness of steel materials. Also, the amount of Al effective for high temperature oxidation resistance is consumed by the generation of AlN,
It causes abnormal oxidation. Therefore, the N content is
The upper limit is set to 0.03% by weight.
【００１３】Ｃｒ：１５〜３０重量％ 本発明に従った高Ａｌフェライトステンレス鋼における
基本的な合金元素であり、１５重量％以上のＣｒ含有で
耐高温酸化特性の改善に顕著な効果がみられる。しか
し、２５重量％を超える多量のＣｒ含有は、スラブ又は
ホットコイルの靭性を劣化させ、製造性が悪くなる。 Ａｌ：３〜６重量％ Ｃｒと同様に、耐高温酸化特性を確保する上で必要な合
金元素である。箔材料等の形態で使用するとき、異常酸
化の発生を抑制するために３重量％以上のＡｌ含有が必
要とされる。しかし、６重量％を超える多量のＡｌ含有
は、スラブ又はホットコイルの靭性を劣化させ、製造性
を悪くする。希土類金属，Ｙ及びアルカリ土類金属の１
種又は２種以上： ０．０１〜０．２重量％ これら合金元素は、鋼材表面に生成する酸化皮膜の保護
作用を著しく改善し、また下地鋼に対する酸化皮膜の密
着性を向上させる。その結果、高Ａｌフェライトステン
レス鋼の耐高温酸化特性が改善される。このような効果
は、含有量が０．０１重量％以上になると顕著に現れ
る。しかし、０．２重量％を超えて多量に含有される
と、熱間加工性及び靭性の劣化によって製造が困難にな
るばかりでなく、多量の介在物生成により鋼材の表面性
状を劣化させる原因になる。Cr: 15 to 30% by weight It is a basic alloying element in the high Al ferritic stainless steel according to the present invention, and if it contains 15% by weight or more of Cr, a remarkable effect is observed in improving the high temperature oxidation resistance. . However, if a large amount of Cr exceeds 25% by weight, the toughness of the slab or hot coil is deteriorated and the manufacturability is deteriorated. Al: 3 to 6 wt% Like Cr, it is an alloying element necessary for ensuring high temperature oxidation resistance. When used in the form of a foil material or the like, it is necessary to contain 3% by weight or more of Al in order to suppress the occurrence of abnormal oxidation. However, the inclusion of a large amount of Al exceeding 6% by weight deteriorates the toughness of the slab or the hot coil and deteriorates the manufacturability. Rare earth metal, Y and alkaline earth metal 1
Species or two or more: 0.01 to 0.2% by weight These alloy elements remarkably improve the protective action of the oxide film formed on the surface of the steel material and improve the adhesion of the oxide film to the base steel. As a result, the high temperature oxidation resistance of high Al ferritic stainless steel is improved. Such an effect becomes remarkable when the content is 0.01% by weight or more. However, if it is contained in a large amount exceeding 0.2% by weight, not only manufacturing becomes difficult due to deterioration of hot workability and toughness, but also a cause of deteriorating the surface quality of the steel material due to generation of a large amount of inclusions. Become.
【００１４】Ｍｇ：０．０１５重量％以下 希土類金属やＹと同様に耐高温酸化特性を向上させる元
素であるが、鋼中Ｍｇ濃度が上昇するとスラブに管状気
泡が発生し易くなる。本発明においては、管状気泡の発
生を抑え、表面性状が良好なスラブや熱延鋼板を得る上
から、Ｍｇ含有量の上限を０．０１５重量％に規制し
た。 Ｍｏ：４重量％以下 本発明においては、必要に応じて添加される任意元素で
あるが、Ｍｏを添加することによって鋼の耐高温酸化性
が著しく改善され、なおかつ高温強度も改善される。し
かし、Ｍｏの過剰添加は鋼の靭性を劣化させ、清掃性を
悪くする原因ともなるので、最高４重量％までとする。
更に、本発明に従った高Ａｌフェライト系ステンレス鋼
は、Ｃ及び／又はＮを固定するＮｂ，Ｖ，Ｔｉ等を添加
することにより、靭性を向上させることもできる。過酷
な高温雰囲気に曝される用途にあっては、Ｎｂ，Ｖ，Ｔ
ｉ等を０．０５重量％以上添加することにより、高温強
度を改善することが有効である。Mg: 0.015 wt% or less Like rare earth metals and Y, it is an element that improves the high temperature oxidation resistance, but if the Mg concentration in steel increases, tubular bubbles are likely to occur in the slab. In the present invention, the upper limit of the Mg content is restricted to 0.015% by weight in order to suppress the generation of tubular bubbles and obtain a slab or hot-rolled steel sheet having good surface properties. Mo: 4 wt% or less In the present invention, it is an optional element that is added as necessary. However, the addition of Mo significantly improves the high temperature oxidation resistance of steel and also improves the high temperature strength. However, excessive addition of Mo deteriorates the toughness of the steel and deteriorates the cleanability, so the maximum content is 4% by weight.
Further, the high Al ferritic stainless steel according to the present invention can be improved in toughness by adding Nb, V, Ti or the like which fixes C and / or N. For applications exposed to severe high temperature atmosphere, Nb, V, T
It is effective to improve the high temperature strength by adding 0.05% by weight or more of i and the like.
【００１５】[0015]
実施例１：表１に成分を調整したステンレス鋼溶湯８２
トンを溶製した。表２は、このときのスラグ組成を示
す。ＶＯＤを大気に開放し、０．２重量％に相当する４
１０ｋｇのＹを添加した。そして、Ａｒガス吹込みによ
り溶湯を３分間撹拌した後、連続鋳造工程に送り鋳造し
た。組成を表１に併せ示すように得られたスラブのＭｇ
濃度［Ｍｇ］は０．００８重量％であり、スラブ中に管
状気泡は観察されなかった。このスラブを熱延すること
により、肌荒れ等の欠陥がない良好な表面性状を持つ鋼
板が得られた。このときのスラブ研削歩留りは９８％，
酸洗後の疵取り歩留りは９９．５％であった。Example 1: Stainless steel molten metal 82 whose components are adjusted in Table 1
Tons were melted. Table 2 shows the slag composition at this time. VOD is opened to the atmosphere, equivalent to 0.2% by weight 4
10 kg Y was added. Then, after the molten metal was stirred for 3 minutes by blowing Ar gas, it was sent to a continuous casting process for casting. Mg of the slab obtained as shown in Table 1 together with the composition
The concentration [Mg] was 0.008% by weight, and no tubular bubbles were observed in the slab. By hot-rolling this slab, a steel sheet having good surface properties without defects such as rough skin was obtained. The slab grinding yield at this time is 98%,
The flaw removal yield after pickling was 99.5%.
【００１６】[0016]
【表１】 [Table 1]
【００１７】[0017]
【表２】 [Table 2]
【００１８】実施例２：Ａｌ2 Ｏ3 系耐火物でライニン
グした取鍋を使用し、表３に示すように成分調整したス
テンレス鋼溶湯８２トンを溶製した。表４は、このとき
のスラグ組成を示す。ＶＯＤを大気に開放し、実施例１
と同じ条件下でＹを添加し、溶湯を３分間撹拌した後、
連続鋳造工程に送り鋳造した。得られたスラブの組成
を、表３に併せ示す。スラブは、０．０８重量％のＹ及
び０．００４重量％のＭｇを含んでいた。また、スラブ
中に管状気泡は観察されず、実施例１と同様に肌荒れ等
の欠陥がない良好な表面性状を持つ鋼板に圧延できた。
このときのスラブ研削歩留りは９８％，酸洗後の疵取り
歩留りは９９．７％であった。Example 2 Using a ladle lined with Al 2 O 3 refractory, 82 tons of molten stainless steel having the components adjusted as shown in Table 3 were melted. Table 4 shows the slag composition at this time. Example 1 with VOD open to the atmosphere
After adding Y under the same conditions as above and stirring the molten metal for 3 minutes,
It was sent to the continuous casting process and cast. The composition of the obtained slab is also shown in Table 3. The slab contained 0.08 wt% Y and 0.004 wt% Mg. Further, tubular bubbles were not observed in the slab, and similar to Example 1, it could be rolled into a steel sheet having good surface properties without defects such as rough skin.
The slab grinding yield at this time was 98%, and the flaw removal yield after pickling was 99.7%.
【００１９】[0019]
【表３】 [Table 3]
【００２０】[0020]
【表４】 [Table 4]
【００２１】比較例：表５に示すように成分調整したス
テンレス鋼溶湯８２トンを溶製した。表６は、このとき
のスラグ組成を示す。ＶＯＤを大気に開放し、実施例１
と同じ条件下でＹを添加し、溶湯を３分間撹拌した後、
連続鋳造工程に送り鋳造した。得られたスラブの組成
を、表５に併せ示す。スラブは、０．０７重量％のＹ及
び０．０１６重量％のＭｇを含んでいた。スラブ中に
は、微細な管状気泡が発生していた。このスラブから製
造された熱延鋼板には、管状気泡に由来する表面疵が発
生していた。このときのスラブ研削歩留りは９６％，酸
洗後の疵取り歩留りは９４．９％であった。Comparative Example: 82 tons of molten stainless steel having the composition adjusted as shown in Table 5 was melted. Table 6 shows the slag composition at this time. Example 1 with VOD open to the atmosphere
After adding Y under the same conditions as above and stirring the molten metal for 3 minutes,
It was sent to the continuous casting process and cast. The composition of the obtained slab is also shown in Table 5. The slab contained 0.07 wt% Y and 0.016 wt% Mg. Fine tubular bubbles were generated in the slab. The hot-rolled steel sheet produced from this slab had surface defects caused by tubular bubbles. The slab grinding yield at this time was 96%, and the flaw removal yield after pickling was 94.9%.
【００２２】[0022]
【表５】 [Table 5]
【００２３】[0023]
【表６】 [Table 6]
【００２４】実施例３：表７に示す成分に調整したステ
ンレス鋼溶湯８２トンを溶製した。表８は、このときの
スラグ組成を示す。ＶＯＤを大気開放し、０．２重量％
に相当する４１０ｋｇのＹを添加した。Ａｒガス吹き込
みにより３分間撹拌した後、連続鋳造工程に送りスラブ
に鋳造した。得られたスラブは、組成を表７に併せ示す
ように、Ｍｇ濃度［Ｍｇ］が０．００７％であり、スラ
ブ中に管状気泡は観察されなかった。このスラブを熱延
することにより、表面疵の少ない良好な表面性状をもつ
鋼板が得られた。このときのスラブの研削歩留りは９８
％，酸洗後の疵取り歩留りは９９．５％であった。Example 3 82 tons of molten stainless steel adjusted to the components shown in Table 7 were melted. Table 8 shows the slag composition at this time. 0.2% by weight of VOD opened to the atmosphere
Of 410 kg of Y, corresponding to After stirring for 3 minutes by blowing Ar gas, the slab was cast in a continuous casting process. As shown in Table 7, the composition of the obtained slab had a Mg concentration [Mg] of 0.007%, and tubular bubbles were not observed in the slab. By hot-rolling this slab, a steel sheet having good surface properties with few surface defects was obtained. The grinding yield of the slab at this time is 98.
%, And the flaw removal yield after pickling was 99.5%.
【００２５】[0025]
【表７】 [Table 7]
【００２６】[0026]
【表８】 [Table 8]
【００２７】実施例４：Ａｌ2 Ｏ3 系耐火物をライニン
グした取鍋を使用し、表９に示す成分に調整したステン
レス鋼溶湯８２トンを溶製した。表１０は、このときの
スラグ組成を示す。ＶＯＤを大気に開放し、実施例１と
同じ条件下でＹを添加し、溶鋼を３分間撹拌した後、連
続鋳造工程に送り鋳造した。得られたスラブは、組成を
表９に併せ示すように、０．０７重量％のＹ及び０．０
０４重量％のＭｇを含んでいた。また、スラブ中に管状
気泡は観察されず、実施例１と同様に表面疵の少ない良
好な表面性状を持つ鋼板に圧延できた。このときのスラ
ブ研削歩留りは９８％，酸洗後の疵取り歩留りは９９．
５％であった。Example 4 Using a ladle lined with Al 2 O 3 refractory, 82 tons of molten stainless steel having the components shown in Table 9 were prepared. Table 10 shows the slag composition at this time. VOD was opened to the atmosphere, Y was added under the same conditions as in Example 1, the molten steel was stirred for 3 minutes, and then sent to a continuous casting step for casting. The resulting slab had 0.07 wt% Y and 0.0% as shown in Table 9 together.
It contained 04% by weight of Mg. Further, tubular bubbles were not observed in the slab, and as in Example 1, the steel plate could be rolled into a steel sheet having good surface properties with few surface defects. The slab grinding yield at this time was 98%, and the flaw removal yield after pickling was 99.
It was 5%.
【００２８】[0028]
【表９】 [Table 9]
【００２９】[0029]
【表１０】 [Table 10]
【００３０】[0030]
【発明の効果】以上に説明したように、本発明において
は、連続鋳造の前工程で鋼中Ｍｇ濃度を低下させ、微細
な管状気泡がスラブに発生することを抑制している。得
られたスラブは、良好な表面性状をもつ鋼板に圧延され
る。したがって、高Ａｌフェライト系ステンレス鋼本来
の耐高温酸化特性を十分に活用し、構造材，暖房器具の
各種機材，メタリックコンバータ用基材等として広範な
分野で使用される高温用鋼材が提供される。As described above, in the present invention, the Mg concentration in the steel is lowered in the pre-step of continuous casting, and the generation of fine tubular bubbles in the slab is suppressed. The slab obtained is rolled into a steel plate with good surface properties. Therefore, a high temperature steel material that is used in a wide range of fields as a structural material, various equipment for heating appliances, a base material for a metallic converter, etc. is provided by fully utilizing the high temperature oxidation resistance characteristic of high Al ferritic stainless steel. .
【図１】 鋼中Ｈ濃度及び鋼中Ｍｇ濃度が管状気泡の発
生に与える影響FIG. 1 Effect of H Concentration in Steel and Mg Concentration in Steel on Tubular Bubble Generation
【図２】 鋼中Ａｌ濃度が鋼中Ｍｇ濃度に与える影響Fig. 2 Effect of Al concentration in steel on Mg concentration in steel
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｃ２２Ｃ 38/00 ３０２ Ｚ 38/18 38/22 ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI technical display location C22C 38/00 302 Z 38/18 38/22
Claims (5)
イト系ステンレス鋼の溶湯に、５〜３０重量％のＣａＦ
2 を含むＣａＯ−ＣａＦ2 −Ａｌ2 Ｏ3 系のスラグを接
触させた後、希土類元素及びＹの１種又は２種以上を添
加し、次いで連続鋳造することを特徴とする高Ａｌフェ
ライト系ステンレス鋼の製造方法。1. A molten metal of high Al ferritic stainless steel containing 3 to 6% by weight of Al, and 5 to 30% by weight of CaF.
After contacting the CaO-CaF 2 -Al 2 O 3 system slag containing 2, was added one or more of rare earth elements and Y, then the high Al ferritic stainless steel characterized by continuous casting Steel manufacturing method.
−ＣａＦ2 −Ａｌ2Ｏ3 系のスラグを溶湯に接触させ、
溶湯中のＭｇ含有量を０．０１５重量％以下に規制する
請求項１記載の製造方法。 2. CaO containing 5-30% by weight of CaF 2.
-CaF 2 -Al 2 a O 3 based slag is brought into contact with the molten metal,
The manufacturing method according to claim 1, wherein the Mg content in the molten metal is regulated to 0.015% by weight or less.
グされた容器にＡｌ：３〜６重量％を含む高Ａｌフェラ
イト系ステンレス鋼の溶湯を収容し、連続鋳造の前工程
で希土類元素及びＹの１種又は２種以上を添加する高Ａ
ｌフェライト系ステンレス鋼の製造方法。3. A high Al ferritic stainless steel melt containing Al: 3 to 6% by weight is housed in a container lined with at least an alumina refractory material, and a rare earth element and one of Y are used in the preceding step of continuous casting. Or high A to which two or more kinds are added
Method for producing ferritic stainless steel.
２５重量％以下と、Ｍｎ：０．２５重量％以下と、Ｐ：
０．０３重量％以下と、Ｓ：０．００１重量％以下と、
Ｎ：０．０３重量％以下と、Ｃｒ：１５〜３０重量％
と、希土類金属及びＹの１種又は２種以上：０．０１〜
０．２重量％を含み、Ｍｇ含有量が０．０１５重量％以
下に規制されている耐高温酸化性に優れた高Ａｌフェラ
イト系ステンレス鋼。4. C: 0.03 wt% or less and Si: 0.
25 wt% or less, Mn: 0.25 wt% or less, P:
0.03 wt% or less, S: 0.001 wt% or less,
N: 0.03 wt% or less and Cr: 15 to 30 wt%
And one or more rare earth metals and Y: 0.01 to
High Al ferritic stainless steel containing 0.2% by weight and having a Mg content regulated to 0.015% by weight or less and having excellent high temperature oxidation resistance.
２５重量％以下と、Ｍｎ：０．２５重量％以下と、Ｐ：
０．０３重量％以下と、Ｓ：０．００１重量％以下と、
Ｎ：０．０３重量％以下と、Ｃｒ：１５〜３０重量％
と、Ｍｏ：４重量％以下と、希土類金属及びＹの１種又
は２種以上：０．０１〜０．２重量％を含み、Ｍｇ含有
量が０．０１５重量％以下に規制されている耐高温酸化
性に優れた高Ａｌフェライト系ステンレス鋼。5. C: 0.03 wt% or less and Si: 0.
25 wt% or less, Mn: 0.25 wt% or less, P:
0.03 wt% or less, S: 0.001 wt% or less,
N: 0.03 wt% or less and Cr: 15 to 30 wt%
And Mo: 4 wt% or less, and one or more rare earth metals and Y: 0.01 to 0.2 wt%, and the Mg content is controlled to 0.015 wt% or less. High Al ferritic stainless steel with excellent high temperature oxidation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26253493A JP3319832B2 (en) | 1993-10-20 | 1993-10-20 | Manufacturing method of high Al ferritic stainless steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26253493A JP3319832B2 (en) | 1993-10-20 | 1993-10-20 | Manufacturing method of high Al ferritic stainless steel |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2002122141A Division JP2002339048A (en) | 2002-04-24 | 2002-04-24 | HIGH Al FERRITE STAINLESS STEEL HAVING EXCELLENT HIGH TEMPERATURE OXIDATION RESISTANCE |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07116779A true JPH07116779A (en) | 1995-05-09 |
| JP3319832B2 JP3319832B2 (en) | 2002-09-03 |
Family
ID=17377142
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26253493A Expired - Fee Related JP3319832B2 (en) | 1993-10-20 | 1993-10-20 | Manufacturing method of high Al ferritic stainless steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3319832B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11350084A (en) * | 1998-06-11 | 1999-12-21 | Nippon Steel Corp | Corrosion resistant steel |
-
1993
- 1993-10-20 JP JP26253493A patent/JP3319832B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11350084A (en) * | 1998-06-11 | 1999-12-21 | Nippon Steel Corp | Corrosion resistant steel |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3319832B2 (en) | 2002-09-03 |
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