JP3964537B2

JP3964537B2 - Austenitic stainless steel with excellent hot workability

Info

Publication number: JP3964537B2
Application number: JP09638598A
Authority: JP
Inventors: 洋幸東; 猛桧山; 和郎福田; 正純平居
Original assignee: 大平洋金属株式会社
Priority date: 1998-04-08
Filing date: 1998-04-08
Publication date: 2007-08-22
Anticipated expiration: 2018-04-08
Also published as: JPH11293412A

Description

【０００１】
【発明の属する技術分野】
本発明は熱間加工性に優れたオーステナイト系ステンレス鋼に関するものである。
【０００２】
【従来の技術】
ステンレス鋼はＮｉ，Ｃｒ，Ｍｏ，Ｃｕなど高価な元素を多量に含有しているため、歩留を向上し製造コストを低減させることが最重要項目である。特に製造工程での疵発生を防止することによる歩留向上が望まれている。すなわち、耐食性、耐酸化性および強度の点から、Ｎｉ，Ｃｒ，Ｍｏ，Ｃｕなどを多量に含有したステンレス鋼は熱間での加工性が劣り、熱間加工中にデンドライト粒界で割れが発生し、へげ状疵となって歩留低下の原因となっていた。
【０００３】
連続鋳造鋳片の熱間加工性を向上する対策として、例えば特公昭５４−２４３６４号、特公平２−１４４１９号、特公平５−７４５７号、特開平４−１１０４１９号等の公報では、Ｃａ，Ｍｇ，希土類元素（Ｙ，Ｌａ，Ｃｅなどで以下ＲＥＭと呼ぶ），Ｂなどの単独か併用添加することが開示されている。
特公昭５４−２４３６４号公報ではＣａ単独添加またはＣａとＢの併用添加、特公平２−１４４１９号公報および特公平５−７４５７号公報ではＣａ，ＣｅなどのＲＥＭを単独または併用添加、特開平４一１１０４１９公報ではＭｇ単独添加またはＭｇとＢの併用添加法である。
【０００４】
しかし、ＣａやＲＥＭは酸化され易い元素のため、添加歩留が不安定であり、例えば特公平２一１４４１９号公報に開示されているように、Ａｌ脱酸と併用しても十分な効果を得るためにはＣａやＲＥＭの添加量を多くする必要があり、ＣａＯ系やＲＥＭ系介在物による表面疵や地疵などの内部欠陥が多発し、製品歩留低下および品質劣化の問題があった。また、Ｍｇ添加では圧延製品に有害な硬質のＭｇＯ系やＡｌ₂Ｏ₃・ＭｇＯスピネル系介在物を生成し、表面疵や地疵などの内部欠陥が多発し、製品歩留低下および品質低下の原因となる。
【０００５】
一方、Ｂについては、例えば図２（ＣＡＭＰ−ＩＳＩＪ，Vol.６（１９９３）一７３３の開示）に示すように、耐食性など材質特性への影響から添加できない製品があるため、全ての品種に適用できないことや、他製品の不純物元素管理対策として、Ｂ添加品種の発生屑に対し煩雑な特別管理が必要となるという問題がある。
【０００６】
【発明が解決しょうとする課題】
本発明は、上記のような問題点を解決し、熱間加工性が悪い成分系の鋼種も熱間加工で割れ疵がなく、かつ、地疵などの介在物性欠陥の少ない、耐食性の良好なオーステナイト系ステンレス鋼製品を歩留良く製造することを目的とするものである。
【０００７】
【課題を解決するための手段】
本発明者らは、この問題を解決するために種々の製造実験を行い、検討を重ねた結果、ＣａとＭｇを同時に適量含有させることによって、Ｃａ，Ｍｇの歩留を安定させると共に、熱間加工性を安定向上させ、かつ地疵などの介在物性欠陥がないオーステナイト系ステンレス鋼圧延製品を歩留良く製造することができることを見い出した。
【０００８】
すなわち、本発明は熱間加工性の優れたオーステナイト系ステンレス鋼であって、その要旨は以下のとおりである。
質量％で、
Ｃ：０．２％以下、Ｓｉ：０．１〜２％、
Ｍｎ：０．３〜３％、Ｐ：０．０４％以下、
Ｃｒ：１５〜３０％、Ｎｉ：３〜３０％、
Ｎ：０．０１〜０．３％、Ｓ：０．００３％以下、
Ｏ：０．００７％以下、Ａｌ：０．００２〜０．０５％、
Ｃｕ：０．０６％以下、Ｍｏ：０．０５％以下
を含有し、残部はＦｅおよび不可避的不純物成分からなり、かつ、
Ｃｒeq＝（Ｃｒ％）＋１．５（Ｓｉ％）＋（Ｍｏ％）＋０．５（Ｎｂ％）
Ｎｉeq＝（Ｎｉ％）＋３０（Ｃ％十Ｎ％）＋０．５（Ｍｎ％）
δ％＝−０．０８１６（Ｃｒeq）^２＋５．９７５（Ｃｒeq）
−３．７８６（Ｎｉeq）＋０．０５８７（Ｃｒeq）・（Ｎｉeq）
−４６．２３
で計算されるδが３％以下、または７％以上となるオーステナイト系ステンレス鋼において、Ｃａ：０．０００５〜０．００５％、Ｍｇ：０．０００５〜０．００％の範囲で（Ｍｇ％／Ｃａ％）の値が１以下となるＣａとＭｇを併用添加することを特徴とする熱間加工性の優れたオーステナイト系ステンレス鋼。
【０００９】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明者らは、熱間加工性改善のための種々の製造実験を行った結果、
質量％で、
Ｃ：０．２％以下、Ｓｉ：０．１〜２％、
Ｍｎ：０．３〜３％、Ｐ：０．０４％以下、
Ｃｒ：１５〜３０％、Ｎｉ：３〜３０％、
Ｎ：０．０１〜０．３％、Ｓ：０．００３％以下、
Ｏ：０．００７％以下、Ａｌ：０．００２〜０．０５％、
Ｃｕ：０．０６％以下、Ｍｏ：０．０５％以下
を含有し、残部はＦｅおよび不可避的不純物成分からなるオーステナイト系ステンレス鋼において、熱間加工性の改善のためにＣａのみの添加では、Ｃａ歩留のばらつきが大きく、Ｃａ含有量が不安定となり、安定した熱間加工性の改善が得られないことが判った。
【００１０】
安定して熱間圧延時の割れを防止できるように十分な熱間加工性の改善を得るためには、例えば特公平２−１４４１９号公報に開示されているように、Ｓ＋Ｏ含有量との関係から、安定して効果を得るために通常０．００３％以上のＣａ添加が必要であるが、Ｃａが酸化され易いため、Ｃａ含有量が多くなると鋼中のＣａＯ系介在物量が多くなり、地疵欠陥の発生による製品不良率が高くなった。
また、Ｍｇは少量添加でも、Ａｌが０．００３％以上では硬質の有害なＭｇＯまたはＡｌ₂Ｏ₃・ＭｇＯスピネル系介在物が生成され、それによる地疵欠陥が発生し製品不良率が高くなる問題があった。
【００１１】
一方、ＣａとＭｇの併用添加ではＣａ，Ｍｇ歩留は安定し、ＣａまたはＭｇのそれぞれの単独添加よりも熱間加工性改善効果が安定して得られると共に、清浄度が改善され、かつ（Ｍｇ％／Ｃａ％）の比を１以下にすることによって介在物組成は低融点化して、圧延製品に有害となるスピネル系介在物など硬質介在物の生成が防止され、地疵欠陥の発生がなくなることを見い出した。
【００１２】
まず、本発明が含有する合金元素の含有量を限定する理由を以下に説明する。
Ｃは強力なオーステナイト相形成元素で、かっ固溶している場合は強度を高める元素であるが、耐食性の点から低い方が良く、０．２％以下とする。
【００１３】
Ｓｉはステンレス鋼溶製時の脱酸のために添加するが、０．１％未満ではＣｒ歩留が著しく低下するので、その下限を０．１％とする。また、ステンレス鋼の耐食性、耐酸化性を増すが、２％を超えると高温での熱間加工性を害する共に、熱間圧延での圧延負荷が増大し製造上好ましくないので、上限を２％とする。
【００１４】
Ｍｎはオーステナイト相安定化元素で、かつ脱酸に役立ち、また鋼中Ｓと結びつきＭｎＳとして熱間加工性を改善するが、耐食性を低下させるので０．３〜３％とする。
【００１５】
Ｐは耐食性、熱間加工性の点では少ない方が良好で、０．０４％以下とする。
Ｓは熱間加工性改善のため低い方が良く、０．００３％以下とする。
【００１６】
Ｃｒはステンレス鋼の基本成分で耐食性、耐酸化性の点から１５％以上とするが、含有量が多くなると高価になるので３０％を上限とする。
【００１７】
Ｎｉは強力なオーステナイト相形成元素で、かっ耐食性、耐熱性を向上させる。３％未満では耐食性、耐熱性が低く実用的でなく、３０％を超えると高価になるため、３〜３０％とする。
【００１８】
Ｎはオーステナイト相安定化元素であり、かつ、ステンレス鋼の強度と耐食性を改善し、０．０１％以上で効果を示すが、０．３％を超えると熱間加工性を著しく低下させ、また、オーステナイト相固溶限界を超え気泡が発生するので、０．０１〜０．３％とする。
【００１９】
Ｏは熱間加工性および介在物性欠陥防止に対し低い方が良好であり、０．００７％以下とする。
Ａｌは強力な脱酸剤として添加されるが、Ａｌ₂Ｏ₃介在物の生成による品質上の問題、かつ連続鋳造におけるノズル閉塞や耐食性低下の防止のため、０．００２〜０．０５％とする。
【００２０】
Ｍｏ，Ｃｕは表１に示すように、Ｍｏにあっては０．０５％を上限とし、Ｃｕにあっては０．０６％を上限として含有しているので、これに基づいて含有量を限定した。
【００２３】
Ｃａは熱間加工性改善と連続鋳造のノズル閉塞防止や介在物欠陥として有害なＡｌ₂Ｏ₃介在物生成防止のために添加するが、０．０００５〜０．００５％とした理由は、０．０００５％未満ではその効果がなく、また０．００５％を超えると酸化が激しくＣａＯ系介在物が多く生成され、地疵などの介在物性欠陥を多く発生させるほか、清浄度を悪化させ耐食性も悪く有害となるためである。
【００２４】
Ｍｇは熱間加工性改善のためにＣａ添加効果の補完として添加するが、０．０００５％未満では効果がなく、０．００３％超ではＭｇＯ系やＡｌ₂Ｏ₃・ＭｇＯスピネル系介在物の生成による介在物原因の表面疵や地疵などの内部欠陥が多発し、製品歩留低下および品質低下の原因となるので、０．０００５〜０．００３％とする。
【００２５】
かつ、該溶鋼がＡｌ_２Ｏ_３系耐火物内で処理される場合や、Ａｌが０．００３％以上含有される場合、Ｍｇ含有量とＣａ含有量の比（Ｍｇ／Ｃａ）が１超では、有害なＡｌ_２Ｏ_３・ＭｇＯスピネル系介在物が生成されるので、Ａｌ_２Ｏ_３・ＭｇＯスピネル系介在物の生成防止のため、（Ｍｇ／Ｃａ）の比は１以下に規制する必要がある。
図１は熱間加工性、地疵に対するＣａ，Ｍｇの影響を示す。
【００２６】
また、

で計算されるδが３〜７％では、熱間加工性はＣａやＭｇの添加がなくても特に問題がないので、δは熱間加工性の悪い３％以下と７％以上を対象とする。
【００２７】
本発明は上記のように構成することにより、熱間加工性と介在物性欠陥の問題点が解決され、熱間加工性に優れたオーステナイト系ステンレス鋼を、表面品質、内部品質ともに安定して歩留良く製造することが可能になった。
【００２８】
【実施例】
次に本発明の実施例について説明する。
表１は本発明鋼と比較鋼の取鍋下化学成分組成を示すもので、電気炉−ＡＯＤ炉で溶製し、連続鋳造の通常条件でスラブまたはビレット鋳片に鋳造した。また、該鋳片を通常通り手入れ後、ホットストリップ、または厚板または線材にそれぞれ通常のステンレス鋼用の条件で熱間圧延し、熱間圧延後の鋼板の表面疵および介在物性欠陥の地疵発生状況の結果を表２に示した。実施例１、３は板厚４ｍｍの熱延鋼板で、実施例６は３０ｍｍ丸棒で、また実施例８はφ５．５ｍｍ線材の結果である。
【００２９】
これに対し比較例１，２はＣａ量が少なくＭｇの添加がないこと、および比較例３，４は（Ｍｇ／Ｃａ）＞１、また、比較例５はＣａ添加量が多いこと、比較例６，７はＭｇ単独添加の場合で、本発明範囲外の成分で構成されている。
本発明実施例は比較例に比べ、いずれも圧延表面疵が少なく地疵の少ない製品が歩留良く製造できた。なお本発明実施例は、Ｃａ，Ｍｇを添加せずに製造された製品と遜色のない耐食性が得られた。
【００３０】
【表１】

【００３１】
【表２】

【００３２】
【発明の効果】
本発明に従って製造されたオーステナイト系ステンレス鋼は、経済的に表面品質および内部品質ともに良好な製品が安定して得られるので、産業上に及ぼす効果は極めて大きい。
【図面の簡単な説明】
【図１】熱間加工性、地疵に対するＣａ，Ｍｇの影響を示す図。
【図２】（ａ）：Ｒ−ＳＵＳ３０４ＵＬＣの腐食に及ぼすＢ含有量の影響を示す図（６５％ＨＮＯ₃沸騰水中４８ｈ×１０，溶体化熱処理材）。
（ｂ）：Ｒ−ＳＵＳ３０４ＵＬＣのＢ含有量に及ぼす腐食処理回数と腐食速度との関係を示す図（６５％ＨＮＯ₃沸騰水，溶体化熱処理材）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an austenitic stainless steel excellent in hot workability.
[0002]
[Prior art]
Since stainless steel contains a large amount of expensive elements such as Ni, Cr, Mo, and Cu, it is most important to improve the yield and reduce the manufacturing cost. In particular, it is desired to improve the yield by preventing the generation of wrinkles in the manufacturing process. That is, in terms of corrosion resistance, oxidation resistance and strength, stainless steel containing a large amount of Ni, Cr, Mo, Cu, etc. is inferior in hot workability and cracks occur at the dendrite grain boundaries during hot working. However, it became a beard-like ridge and caused a decrease in yield.
[0003]
As measures for improving the hot workability of continuously cast slabs, for example, Japanese Patent Publication No. 54-24364, Japanese Patent Publication No. 2-14419, Japanese Patent Publication No. 5-7457, Japanese Patent Application Laid-Open No. 4-110419, etc. It is disclosed that Mg, rare earth elements (Y, La, Ce, etc., hereinafter referred to as REM), B or the like are added alone or in combination.
In Japanese Patent Publication No. 54-24364, Ca alone or in combination with Ca and B is added. In Japanese Patent Publication No. 2-14419 and Japanese Patent Publication No. 5-7457, REM such as Ca and Ce is added alone or in combination. Japanese Patent Publication No. 1110419 discloses a method of adding Mg alone or using Mg and B together.
[0004]
However, since Ca and REM are easily oxidizable elements, the addition yield is unstable. For example, as disclosed in Japanese Examined Patent Publication No. 2144419, a sufficient effect can be obtained even in combination with Al deoxidation. In order to obtain it, it is necessary to increase the addition amount of Ca and REM, and internal defects such as surface defects and earth defects due to CaO-based and REM-based inclusions frequently occur, resulting in problems of product yield reduction and quality deterioration. . In addition, the addition of Mg produces hard MgO-based and Al ₂ O ₃ .MgO spinel-based inclusions that are harmful to rolled products, and many internal defects such as surface defects and ground defects occur, reducing product yield and quality. Cause.
[0005]
On the other hand, as for B, for example, as shown in FIG. 2 (disclosed in CAMP-ISIJ, Vol. 6 (1993) 1733), there is a product that cannot be added due to the influence on material properties such as corrosion resistance. There is a problem that complicated special management is required for the waste generated from the B-added varieties as a countermeasure against impurity elements in other products.
[0006]
[Problems to be solved by the invention]
The present invention solves the problems as described above, and the component steel types with poor hot workability are also free from cracks due to hot working, have few interstitial property defects such as ground, and have good corrosion resistance. The object is to produce austenitic stainless steel products with good yield.
[0007]
[Means for Solving the Problems]
In order to solve this problem, the present inventors have conducted various manufacturing experiments, and as a result of repeated studies, by adding Ca and Mg in appropriate amounts at the same time, the yield of Ca and Mg is stabilized and hot. It has been found that an austenitic stainless steel rolled product can be manufactured with good yield, which improves the workability stably and has no defects in the inclusion physical properties such as ground.
[0008]
That is, the present invention is an austenitic stainless steel excellent in hot workability, and the gist thereof is as follows.
% By mass
C: 0.2% or less, Si: 0.1-2%,
Mn: 0.3-3%, P: 0.04% or less,
Cr: 15-30%, Ni: 3-30%,
N: 0.01 to 0.3%, S: 0.003% or less,
O: 0.007% or less, Al: 0.002-0.05% ,
Cu: 0.06% or less, Mo: 0.05% or less , with the balance consisting of Fe and inevitable impurity components, and
Creq = (Cr%) + 1.5 (Si%) + (Mo%) + 0.5 (Nb%)
Nieq = (Ni%) + 30 (C% + N%) + 0.5 (Mn%)
δ% = − 0.0816 (Creq) ² +5.975 (Creq)
-3.786 (Nieq) +0.0587 (Creq) · (Nieq)
-46.23
In the austenitic stainless steel in which δ calculated by the above is 3% or less, or 7% or more, Ca: 0.0005 to 0.005%, Mg: 0.0005 to 0.00% (Mg% / An austenitic stainless steel excellent in hot workability, characterized in that Ca and Mg having a value of (Ca%) of 1 or less are added together.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
As a result of conducting various production experiments for improving hot workability, the present inventors have
% By mass
C: 0.2% or less, Si: 0.1-2%,
Mn: 0.3-3%, P: 0.04% or less,
Cr: 15-30%, Ni: 3-30%,
N: 0.01 to 0.3%, S: 0.003% or less,
O: 0.007% or less, Al: 0.002-0.05% ,
An austenitic stainless steel containing Cu: 0.06% or less, Mo: 0.05% or less , the balance being Fe and inevitable impurity components, only Ca for improving hot workability It was found that with the addition of, the Ca yield variation was large, the Ca content became unstable, and stable hot workability improvement could not be obtained.
[0010]
In order to obtain a sufficient improvement in hot workability so that cracking during hot rolling can be prevented stably, for example, as disclosed in JP-B-2-14419, the relationship with the S + O content Therefore, in order to obtain a stable effect, 0.003% or more of Ca is usually necessary. However, since Ca is easily oxidized, when the Ca content increases, the amount of CaO-based inclusions in the steel increases.不良 Product defect rate due to the occurrence of defects increased.
In addition, even if Mg is added in a small amount, hard harmful MgO or Al ₂ O ₃ .MgO spinel inclusions are generated when Al is 0.003% or more, resulting in ground defects, resulting in a high product defect rate. There was a problem.
[0011]
On the other hand, when Ca and Mg are added together, the Ca and Mg yield is stable, and the hot workability improving effect is more stably obtained than when Ca or Mg is added alone, and the cleanliness is improved, and ( By making the ratio of (Mg% / Ca%) 1 or less, the inclusion composition has a low melting point, the formation of hard inclusions such as spinel inclusions that are harmful to the rolled product is prevented, and ground defects are generated. I found it disappeared.
[0012]
First, the reason for limiting the content of alloy elements contained in the present invention will be described below.
C is a strong austenite phase-forming element, and is an element that enhances the strength when it is in solid solution, but it is better from the viewpoint of corrosion resistance, and is 0.2% or less.
[0013]
Si is added for deoxidation at the time of melting stainless steel, but if it is less than 0.1%, the Cr yield is remarkably lowered, so the lower limit is made 0.1%. In addition, the corrosion resistance and oxidation resistance of stainless steel are increased, but if it exceeds 2%, hot workability at high temperatures is impaired, and the rolling load in hot rolling increases, which is not preferable for production. Therefore, the upper limit is 2%. And
[0014]
Mn is an austenite phase stabilizing element and is useful for deoxidation, and is combined with S in the steel to improve hot workability as MnS, but it decreases the corrosion resistance, so is 0.3 to 3%.
[0015]
P is preferably as small as possible in terms of corrosion resistance and hot workability, and is set to 0.04% or less.
S is preferably low for improving hot workability, and is made 0.003% or less.
[0016]
Cr is a basic component of stainless steel and is made 15% or more from the viewpoint of corrosion resistance and oxidation resistance. However, if the content increases, it becomes expensive, so 30% is made the upper limit.
[0017]
Ni is a strong austenite phase-forming element and improves corrosion resistance and heat resistance. If it is less than 3%, the corrosion resistance and heat resistance are low and impractical, and if it exceeds 30%, it becomes expensive, so 3-30%.
[0018]
N is an austenite phase stabilizing element and improves the strength and corrosion resistance of stainless steel, and shows an effect at 0.01% or more, but when it exceeds 0.3%, the hot workability is significantly reduced. , Since the austenite phase solid solution limit is exceeded and bubbles are generated, the content is made 0.01 to 0.3%.
[0019]
The lower O is better for hot workability and prevention of inclusion physical defect, and it is 0.007% or less.
Al is added as a strong deoxidizer, but in order to prevent quality problems due to the formation of Al ₂ O ₃ inclusions, and to prevent nozzle clogging and deterioration of corrosion resistance in continuous casting, 0.002 to 0.05% To do.
[0020]
As shown in Table 1, Mo and Cu contain 0.05% as the upper limit for Mo and 0.06% as the upper limit for Cu, so the content is limited based on this. did.
[0023]
Ca is added to improve hot workability, to prevent nozzle clogging in continuous casting, and to prevent the formation of Al ₂ O ₃ inclusions that are harmful as inclusion defects. If it is less than 0.005%, the effect is not obtained, and if it exceeds 0.005%, the oxidation is severe and many CaO inclusions are generated, which causes many inclusion physical defects such as earth, and also improves the cleanliness and corrosion resistance. It is bad and harmful.
[0024]
Mg is added as a supplement to the Ca addition effect to improve hot workability. However, if it is less than 0.0005%, there is no effect, and if it exceeds 0.003%, MgO-based and Al ₂ O ₃ .MgO spinel-based inclusions are not effective. Since internal defects such as surface defects and ground defects caused by inclusions frequently occur and cause a decrease in product yield and quality, 0.0005 to 0.003%.
[0025]
And when this molten steel is processed in an Al ₂ O ₃ refractory or when Al is contained in an amount of 0.003% or more, the ratio of Mg content to Ca content (Mg / Ca) is more than 1. Since harmful Al ₂ O ₃ .MgO spinel inclusions are generated, the ratio of (Mg / Ca) must be regulated to 1 or less in order to prevent the formation of Al ₂ O ₃ .MgO spinel inclusions. is there.
FIG. 1 shows the effects of Ca and Mg on hot workability and ground.
[0026]
Also,

When δ calculated in (3) is 3 to 7%, there is no particular problem with hot workability even without the addition of Ca or Mg. Therefore, δ is targeted for 3% or less and 7% or more with poor hot workability. To do.
[0027]
By configuring the present invention as described above, the problems of hot workability and interstitial property defects are solved, and austenitic stainless steel having excellent hot workability is stably manufactured in terms of both surface quality and internal quality. It became possible to manufacture well.
[0028]
【Example】
Next, examples of the present invention will be described.
Table 1 shows the chemical composition under the ladle of the steel of the present invention and the comparative steel, which was melted in an electric furnace-AOD furnace and cast into a slab or billet slab under the normal conditions of continuous casting. In addition, after the slab is normally treated, it is hot-rolled on a hot strip, a thick plate or a wire under normal conditions for stainless steel, and the surface defect of the steel sheet after hot rolling and the surface of inclusion physical defect The results of the occurrence situation are shown in Table 2. Examples 1 and 3 in the hot-rolled steel sheet having a thickness of 4 mm, Example 6 with 30mm round bar, also Example 8 is the result of φ5.5mm wire.
[0029]
On the other hand, Comparative Examples 1 and 2 have a small amount of Ca and no addition of Mg, Comparative Examples 3 and 4 have (Mg / Ca)> 1, and Comparative Example 5 has a large amount of Ca addition. 6 and 7 are cases where Mg is added alone, and are composed of components outside the scope of the present invention.
Compared with the comparative example, each of the inventive examples could produce a product with less rolling surface defects and less ground. In the examples of the present invention, corrosion resistance comparable to products manufactured without adding Ca and Mg was obtained.
[0030]
[Table 1]

[0031]
[Table 2]

[0032]
【The invention's effect】
The austenitic stainless steel produced according to the present invention has a great effect on the industry because products with good surface quality and internal quality can be stably obtained economically.
[Brief description of the drawings]
FIG. 1 is a graph showing the influence of Ca and Mg on hot workability and ground.
FIG. 2 (a) is a view showing the effect of B content on corrosion of R-SUS304ULC (48 h × 10 in 65% HNO ₃ boiling water, solution heat treatment material).
(B): R-SUS304ULC corrosion treatment times on the B content and shows the relationship between the corrosion rate FIG (65% HNO ₃ boiling water, solution heat treatment material).

Claims

% By mass
C: 0.2% or less, Si: 0.1-2%,
Mn: 0.3-3%, P: 0.04% or less,
Cr: 15-30%, Ni: 3-30%,
N: 0.01 to 0.3%, S: 0.003% or less,
O: 0.007% or less, Al: 0.002-0.05% ,
Cu: 0.06% or less, Mo: 0.05% or less , with the balance consisting of Fe and inevitable impurity components, and
Creq = (Cr%) + 1.5 (Si%) + (Mo%) + 0.5 (Nb%)
Nieq = (Ni%) + 30 (C% + N%) + 0.5 (Mn%)
δ% = − 0.0816 (Creq) ² +5.975 (Creq)
-3.786 (Nieq) +0.0587 (Creq) · (Nieq)
-46.23
In the austenitic stainless steel in which δ calculated by the above is 3% or less, or 7% or more, Ca: 0.0005 to 0.005%, Mg: 0.0005 to 0.003% (Mg% / An austenitic stainless steel excellent in hot workability, characterized in that Ca and Mg having a value of (Ca%) of 1 or less are added together.