JPH0488151A - Duplex stainless steel excellent in hot workability - Google Patents
Duplex stainless steel excellent in hot workabilityInfo
- Publication number
- JPH0488151A JPH0488151A JP20442790A JP20442790A JPH0488151A JP H0488151 A JPH0488151 A JP H0488151A JP 20442790 A JP20442790 A JP 20442790A JP 20442790 A JP20442790 A JP 20442790A JP H0488151 A JPH0488151 A JP H0488151A
- Authority
- JP
- Japan
- Prior art keywords
- weight
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- content
- stainless steel
- hot workability
- 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
- 229910001039 duplex stainless steel Inorganic materials 0.000 title claims abstract description 29
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 17
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 6
- 229910001566 austenite Inorganic materials 0.000 abstract description 19
- 229910000859 α-Fe Inorganic materials 0.000 abstract description 12
- 229910001220 stainless steel Inorganic materials 0.000 abstract description 8
- 229910052726 zirconium Inorganic materials 0.000 abstract description 7
- 229910052804 chromium Inorganic materials 0.000 abstract description 3
- 230000001105 regulatory effect Effects 0.000 abstract description 3
- 239000010935 stainless steel Substances 0.000 abstract description 3
- 229910052750 molybdenum Inorganic materials 0.000 abstract description 2
- 229910052799 carbon Inorganic materials 0.000 abstract 1
- 229910052802 copper Inorganic materials 0.000 abstract 1
- 229910052748 manganese Inorganic materials 0.000 abstract 1
- 229910052759 nickel Inorganic materials 0.000 abstract 1
- 229910052757 nitrogen Inorganic materials 0.000 abstract 1
- 229910052698 phosphorus Inorganic materials 0.000 abstract 1
- 229910000831 Steel Inorganic materials 0.000 description 19
- 230000007797 corrosion Effects 0.000 description 19
- 238000005260 corrosion Methods 0.000 description 19
- 239000010959 steel Substances 0.000 description 19
- 238000005336 cracking Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 10
- 230000007423 decrease Effects 0.000 description 6
- 238000005098 hot rolling Methods 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000012535 impurity Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000006477 desulfuration reaction Methods 0.000 description 2
- 230000023556 desulfurization Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 230000005501 phase interface Effects 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 208000009205 Tinnitus Diseases 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000010420 art technique Methods 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は、熱間加工性、特に熱間圧延時における耳割れ
抵抗性に優れたフエライトーオーステナイト二相ステン
レス鋼に関する。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a ferrite-austenite duplex stainless steel that has excellent hot workability, particularly excellent edge cracking resistance during hot rolling.
［従来の技術ｌ
５ＵＳ３２９Ｊ２Ｌ等の二相ステンレス鋼は、オーステ
ナイト系ステンレス鋼、フェライト系ステンレス鋼等に
比較し耐応力腐食割れ性や溶接性に優れている。この性
質を利用して、各種構造用材料として二相ステンレス鋼
が広範な分野で使用されるようになってきている。特に
、最近では、ステンレス鋼貯水槽用の材料として注目さ
れている。[Prior Art 1 Duplex stainless steels such as 5US329J2L are superior in stress corrosion cracking resistance and weldability compared to austenitic stainless steels, ferritic stainless steels, and the like. Taking advantage of this property, duplex stainless steel has come to be used in a wide range of fields as a variety of structural materials. In particular, recently, stainless steel has attracted attention as a material for water storage tanks.
二相ステンレス鋼は、このように優れた性質を備えてい
るものの、熱間加工性が悪い。これは、二相ステンレス
鋼の組織がフェライト相及びオーステナイト相の混合組
織であることに由来する。Although duplex stainless steel has such excellent properties, it has poor hot workability. This is because the structure of duplex stainless steel is a mixed structure of a ferrite phase and an austenite phase.
すなわち、変形抵抗が異なる二相が共存しているため、
熱間圧延時に加えられた応力がフェライト相とオーステ
ナイト相の境界に集中し、相界面に亀裂、破断等の欠陥
が生じる。これら欠陥は、熱延板に耳割れとなって現れ
、製品歩留りを低下させる原因となる。In other words, since two phases with different deformation resistances coexist,
The stress applied during hot rolling concentrates on the boundary between the ferrite phase and austenite phase, causing defects such as cracks and fractures at the phase interface. These defects appear as edge cracks in the hot-rolled sheet and cause a decrease in product yield.
この熱間加工性を改善するため、従来から種々の方法が
提案されている。Various methods have been proposed to improve this hot workability.
たとえば、特公昭５７−１５６６０号公報においては、
オーステナイト相の変形能に悪影響を及ぼすＳ、０等の
不純物含有量を低下させ、相界面に偏析する不純物の濃
度を低下させることが開示されている。For example, in Japanese Patent Publication No. 57-15660,
It is disclosed that the content of impurities such as S and 0, which adversely affect the deformability of the austenite phase, is reduced, and the concentration of impurities segregated at the phase interface is reduced.
また、特公昭５９−１４０９９号公報では、粒界に偏析
し割れ発生の原因となるＳ含有量を０６００５重量％以
下に低減すると共に、Ｂの添加によって熱間加工性を向
上させている。Furthermore, in Japanese Patent Publication No. 59-14099, the S content, which segregates at grain boundaries and causes cracking, is reduced to 06005% by weight or less, and the hot workability is improved by adding B.
更に、特公平１−１９４６５号公報では、Ｓ含有量を０
．００３重量％以下に下げた二相ステンレス鋼にＣａを
添加することによって固溶Ｓを著しく低く抑えると共に
、ＡＩ２添加によって熱間加工性を改善することが紹介
されている。Furthermore, in Japanese Patent Publication No. 1-19465, the S content is set to 0.
．． It has been introduced that by adding Ca to duplex stainless steel at a concentration lower than 0.003% by weight, the solid solution S can be kept extremely low, and that hot workability can be improved by adding AI2.
これら先行技術は、何れもＳ含有量を低減するものであ
って、そのための手段として稀土類金属ＲＥＭ、Ｃａ等
の脱硫元素を添加している。或いは、Ｓを単独で低減す
ることが困難であるため、０含有量の低減及びそのため
の脱酸剤であるＡＩ２の添加等の手段が採用されている
。These prior art techniques all reduce the S content, and as a means for this purpose, desulfurization elements such as rare earth metals REM and Ca are added. Alternatively, since it is difficult to reduce S by itself, measures such as reducing the 0 content and adding AI2, which is a deoxidizing agent, are adopted.
［発明が解決しようとする課題］
ところが、Ｓ含有量を０．００３％以下に規制した５Ｕ
Ｓ３２９Ｊ２Ｌ相当の二相ステンレス鋼を溶製し、熱間
圧延を施したところ、耳割れが発生する場合と、発生し
ない場合があった。そのため、安定した熱間加工性を得
ることが困難であった。また、逆にＳ含有量が０．００
３％を超えた二相ステンレス鋼を熱間圧延したときにも
、耳割れが発生した場合と、発生しない場合があった。[Problem to be solved by the invention] However, in 5U, the S content is regulated to 0.003% or less.
When duplex stainless steel equivalent to S329J2L was produced and hot rolled, edge cracking occurred in some cases and not in others. Therefore, it has been difficult to obtain stable hot workability. Moreover, on the contrary, the S content is 0.00
Even when duplex stainless steel containing more than 3% was hot rolled, there were cases where edge cracking occurred and cases where it did not occur.
更に、前掲の先行文献で開示されている第３元素を添加
して溶製した二相ステンレス鋼を熱間圧延したところ、
無添加材に比較して熱間加工性に若干の改善がみられる
ものの、必ずしも安定した熱間加工性が得られなかった
。Furthermore, when the duplex stainless steel prepared by adding a third element disclosed in the above-mentioned prior document was hot-rolled,
Although there was a slight improvement in hot workability compared to the additive-free material, stable hot workability was not necessarily obtained.
そこで、本発明は、このような問題を解消すべ（案出さ
れたものであり、フェライト相及びオーステナイト相の
間のバランスをＳ含有量との関係において定量的に調整
することにより、安定して熱間加工性を改善し、歩留り
良く熱間加工することが可能な二相ステンレス鋼を提供
することを目的とする。Therefore, the present invention has been devised to solve such problems, and by quantitatively adjusting the balance between the ferrite phase and the austenite phase in relation to the S content, it is possible to stably The purpose of the present invention is to provide a duplex stainless steel that has improved hot workability and can be hot worked with a good yield.
［課題を解決するための手段］
本発明の二相ステンレス鋼は、その目的を達成するため
、次の成分・組成をもつものである。[Means for Solving the Problems] In order to achieve the object, the duplex stainless steel of the present invention has the following components and composition.
Ｃ：０．０３重量％以下。C: 0.03% by weight or less.
Ｓｉ：１．０重量％以下。Si: 1.0% by weight or less.
Ｍｎ：１．５０重量％以下。Mn: 1.50% by weight or less.
Ｐ ：０．０４重量％以下。P: 0.04% by weight or less.
Ｓ ：０．００３重量％以下。S: 0.003% by weight or less.
Ｎｉ：４．０〜９，０重量％。Ni: 4.0 to 9.0% by weight.
Ｃｒ ： ２０．０−３０．０重量％ Ｍｏ ： ２．０〜４．０重量％ Ｃｕ：１．Ｏ重量％以下。Cr: 20.0-30.0% by weight Mo: 2.0-4.0% by weight Cu:1. O weight% or less.
Ｎ ：０．０８〜０．３０重量％
必要に応じＴｉ：０．５重量％以下、Ｚｒ：０．５重量
％以下、Ｌａ／Ｃｅ＜１．０を満足する稀土類金属ＲＥ
Ｍ：０．１重量％以下の一種又は二種以上
また、これら成分間では、次式で定義されたＡ値が２０
≦Ａ≦７Ｏ−６７００Ｘ （Ｓ％） となるように成分
調整されている。N: 0.08 to 0.30% by weight Ti: 0.5% by weight or less, Zr: 0.5% by weight or less, rare earth metal RE satisfying La/Ce<1.0
M: 0.1% by weight or less of one or more types, and among these components, the A value defined by the following formula is 20
The components are adjusted so that ≦A≦7O-6700X (S%).
Ａ ＝ ２１０ ｆｃ％）−５，８（Ｓ ｉ％） ＋３
．５ ｆＭ ｎ％）＋１１．５（Ｎ ｉ％）−５，８［
Ｃｒ％） −６（Ｍ ｏ％）÷４．５ｆＣｕ％ｌ＋２６
［ｆＴ ｉ％）＋［Ｚｒ％）÷（ＲＥＭ％）１÷２３５
（Ｎ％）＋１００［作 用］
Ｓ含有量を低下させた二相ステンレス鋼の熱間加工性が
良い場合と悪い場合とに分かれるのは、熱間加工性に影
響を与えているのはＳ含有量だけではないことに原因が
ある。そこで、本発明者等は、熱間加工性を安定的に向
上させるため、鋼中のＳ含有量以外に熱間加工性に影響
を与える因子を調査した。その結果、次の知見を得た。A = 210 fc%) -5,8 (Si%) +3
．． 5 fM n%) + 11.5 (N i%) - 5,8 [
Cr%) -6(Mo%)÷4.5fCu%l+26
[fT i%) + [Zr%) ÷ (REM%) 1 ÷ 235
(N%)+100 [Effect] The reason why the hot workability of duplex stainless steel with reduced S content is good and bad is that it is the S that affects the hot workability. The cause is not just the content. Therefore, in order to stably improve hot workability, the present inventors investigated factors other than the S content in steel that affect hot workability. As a result, we obtained the following knowledge.
二相ステンレス鋼の熱間加工性を左右するものは、トー
タルのＳ含有量ではなく、フェライト−オーステナイト
の粒界に偏析したＳである。この粒界に析出するＳｉを
低減するとき、二相ステンレス鋼の熱間加工性が改善さ
れることが推測される。また、フェライト相は、オース
テナイト相に比較してＳの固溶度が大きい。そこで、フ
ェライト相が多量に生成される組成に成分調整すると、
フェライト−オーステナイト粒界に偏析するＳｉが少な
くなり、熱間加工性に優れた二相ステンレス鋼が得られ
る。What influences the hot workability of duplex stainless steel is not the total S content but the S segregated at the ferrite-austenite grain boundaries. It is presumed that when the Si precipitated at the grain boundaries is reduced, the hot workability of the duplex stainless steel is improved. Furthermore, the ferrite phase has a higher solid solubility of S than the austenite phase. Therefore, by adjusting the composition to produce a large amount of ferrite phase,
Less Si is segregated at the ferrite-austenite grain boundaries, resulting in a duplex stainless steel with excellent hot workability.
また、従来から、Ｓｉの低減或いはフェライト量の増加
によって二相ステンレス鋼の熱間加工性が改善されるこ
とは、定性的には知られていた。Furthermore, it has been qualitatively known that the hot workability of duplex stainless steel is improved by reducing the amount of Si or increasing the amount of ferrite.
しかし、その両者の相互の効果が定量的に把握されてい
なかったため、安定的に耳割れを防止することができず
、特公昭５９−１４０９９号公報で示されているように
Ｂ添加等の対策が必要であった。However, because the mutual effects of the two were not quantitatively understood, it was not possible to stably prevent ear cracking, and as shown in Japanese Patent Publication No. 59-14099, countermeasures such as B addition were taken. was necessary.
本発明は、このような鋼中におけるＳの挙動に着目し、
鋼中のトータルＳ含有量を低減すると共に、フェライト
−オーステナイトの比率をＳ含有量との関係において定
量的にコントロールすることによって、熱間加工性の改
善を図ったものである。そのため、特公昭５９−１４０
９９号公報で示されているようなり添加の必要もなくな
る。The present invention focuses on the behavior of S in such steel,
The hot workability is improved by reducing the total S content in the steel and quantitatively controlling the ferrite-austenite ratio in relation to the S content. For this reason, the special public
As shown in Japanese Patent No. 99, there is no need for addition.
つまり、実験的に得られたＡ値を用いることにより、二
相ステンレス鋼の相比（オーステナイト量）を定量的に
把握することができる。また、Ａ値とＳｉとの関係を２
０≦Ａ≦７Ｏ−６７００Ｘ（Ｓ％）という関係式で特定
することによって、安定的に耳割れを防止することが可
能となった。That is, by using the experimentally obtained A value, it is possible to quantitatively understand the phase ratio (austenite content) of duplex stainless steel. Also, the relationship between A value and Si is 2
By specifying using the relational expression 0≦A≦7O-6700X (S%), it has become possible to stably prevent edge cracking.
以下、本発明二相ステンレス鋼の成分・組成及びＡ値の
限定理由を説明する。The ingredients and composition of the duplex stainless steel of the present invention and the reasons for limiting the A value will be explained below.
Ｃ：０．０３重量％以下 Ｃは、鋼中に不可避的に含まれる元素である。C: 0.03% by weight or less C is an element inevitably contained in steel.
Ｃ含有量を低減すると、炭化物の生成が少なくなり、加
工性が向上する。また、耐食性及び耐粒界腐食性も向上
する。この点で、Ｃ含有量を０．０３重量％以下にした
。Reducing the C content reduces the formation of carbides and improves processability. Corrosion resistance and intergranular corrosion resistance are also improved. In this respect, the C content was set to 0.03% by weight or less.
Ｓｉ：１．０重量％以下
Ｓｉは、脱酸剤として鋼に添加される元素である。しか
し、含有量が１．０重量％を超えると、０相生成能が高
くなり、靭性や耐食性等を劣化させる。そこで、Ｓｉ含
有量は、その上限を１．０重量％に定めた。Si: 1.0% by weight or less Si is an element added to steel as a deoxidizing agent. However, if the content exceeds 1.0% by weight, the ability to form 0 phase increases, resulting in deterioration of toughness, corrosion resistance, etc. Therefore, the upper limit of the Si content was set at 1.0% by weight.
Ｍｎ：１．５０重量％以下
Ｍｎは、溶接性を向上させる上で有用な元素である。し
かし、Ｍｎ含有量が１．５０重量％を超えるようになる
と、耐食性が低下する。そこで、Ｍｎ含有量の上限を、
１．５０重量％とした。Mn: 1.50% by weight or less Mn is a useful element for improving weldability. However, when the Mn content exceeds 1.50% by weight, corrosion resistance decreases. Therefore, the upper limit of Mn content is
The content was 1.50% by weight.
Ｐ：０．０４重量％以下
Ｐは、不可避的に混入する不純物であり、熱間加工性や
耐応力腐食割れ性に有害な元素である。P: 0.04% by weight or less P is an impurity that is inevitably mixed in, and is an element harmful to hot workability and stress corrosion cracking resistance.
しかし、Ｐ含有量を極めて低（抑えることは、製鋼上か
ら製造コストの上昇を招く。そこで、Ｐ含有量の上限を
、０．０４重量％に定めた。However, keeping the P content extremely low leads to an increase in manufacturing costs from the viewpoint of steel manufacturing. Therefore, the upper limit of the P content was set at 0.04% by weight.
Ｓ：０．００３重量％以下
Ｓは、フェライト−オーステナイト粒界に偏析し鋼の熱
間加工性を低下させるだけでなく、鋼中のＭｎと硫化物
を形成し、耐孔食性や耐隙間腐食性を低下させる有害な
元素である。この点からＳ含有量は可能な限り低いほど
よく、本発明においてはその上限を０．００３重量％に
設定した。S: 0.003% by weight or less S not only segregates at ferrite-austenite grain boundaries and reduces the hot workability of steel, but also forms sulfides with Mn in steel, improving pitting corrosion resistance and crevice corrosion resistance. It is a harmful element that reduces sex. From this point of view, the S content should be as low as possible, and in the present invention, the upper limit is set at 0.003% by weight.
Ｎｉ：４．０〜９．０重量％
Ｎｉは、耐食性向上に対して有効な元素であると共に、
二相組織形成のために不可欠なものである。このＮｉ含
有量に関しては、Ｃｒ含有量等との関係で適切な二相組
織を得るため、その含有範囲を４．０〜９．０重量％と
じた。Ni: 4.0 to 9.0% by weight Ni is an effective element for improving corrosion resistance, and
It is essential for the formation of a two-phase structure. Regarding the Ni content, in order to obtain an appropriate two-phase structure in relation to the Cr content and the like, the content range was set to 4.0 to 9.0% by weight.
Ｃｒ ： ２０．０〜３０．０重量％
Ｃｒは、耐食性の向上及び二相組織の形成の上で、必要
不可欠な元素である。２０．０重量％よりもＣｒ含有量
が少ないと、二相ステンレス鋼が使用される過酷な腐食
環境下における耐食性が十分でなく、またフェライト相
の比率も低下する。Cr: 20.0 to 30.0% by weight Cr is an essential element for improving corrosion resistance and forming a two-phase structure. If the Cr content is less than 20.0% by weight, the corrosion resistance in the harsh corrosive environment in which duplex stainless steel is used will not be sufficient, and the ratio of ferrite phase will also decrease.
逆に、Ｃｒ含有量が３０．０重量％を超えて多くなると
、Ｏ相が析出し易くなり、靭性、溶接性等が劣化する。On the other hand, when the Cr content increases beyond 30.0% by weight, O phase tends to precipitate, and toughness, weldability, etc. deteriorate.
そこで、Ｃｒ含有量を２０．０〜３０．０重量％の範囲
に設定した。Therefore, the Cr content was set in the range of 20.0 to 30.0% by weight.
Ｍｏ：２．０〜４．０重量％
Ｍｏは、Ｃｒと共同してＣＩ２イオンを含む腐食環境に
おける局部腐食に対する抵抗性を高める元素である。し
かし、本発明のように高Ｃｒ鋼において、Ｍｏ含有量が
２．０重量％未満であると、ＣｒとＭＯとの相乗効果が
少な（、耐局部腐食の改善が十分でない。しかし、ＭＯ
を４．０重量％を超えて添加すると、σ相析出に起因し
た脆化が生じ、加工性、靭性等を劣化させる。そこで、
Ｍｏ含有量は、２．０〜４．０重量％の範囲に定めた。Mo: 2.0 to 4.0% by weight Mo is an element that works together with Cr to increase resistance to local corrosion in a corrosive environment containing CI2 ions. However, in high Cr steel as in the present invention, if the Mo content is less than 2.0% by weight, the synergistic effect between Cr and MO is small (improvement in local corrosion resistance is not sufficient.
When more than 4.0% by weight is added, embrittlement occurs due to σ phase precipitation, resulting in deterioration of workability, toughness, etc. Therefore,
Mo content was set in the range of 2.0 to 4.0% by weight.
Ｃｕ：１．０重量％以下
Ｃｕは、耐応力腐食割れ性や耐亜硫酸ガス腐食性を向上
させる上で有効な元素である。しかし、１．０重量％を
超えてＣｕを含有させると、熱間加工性が低下する。そ
こで、Ｃｕ含有量の上限を１．０重量％と定めた。Cu: 1.0% by weight or less Cu is an effective element for improving stress corrosion cracking resistance and sulfur dioxide gas corrosion resistance. However, when Cu is contained in an amount exceeding 1.0% by weight, hot workability decreases. Therefore, the upper limit of the Cu content was set at 1.0% by weight.
Ｎ：０．０８〜０．３０重量％
Ｎは、Ｃと同様にオーステナイト形成元素であり、オー
ステナイト相に固溶して耐食性を向上させる。その結果
、フェライト相に比較しＣｒ及びＭｏ含有量が若干少な
いことに起因するオーステナイト相の耐食性低下が抑制
される。この点、特に二相ステンレス鋼の耐食性をバラ
ンスよく保持する上で、Ｎは必須の成分である。また、
σ相の析出を抑制し、靭性を向上させる作用も呈する。N: 0.08 to 0.30% by weight N, like C, is an austenite-forming element, and is dissolved in the austenite phase to improve corrosion resistance. As a result, a decrease in corrosion resistance of the austenite phase, which is caused by the slightly lower Cr and Mo contents than the ferrite phase, is suppressed. In this respect, N is an essential component, especially in maintaining the corrosion resistance of duplex stainless steel in a well-balanced manner. Also,
It also has the effect of suppressing the precipitation of the σ phase and improving toughness.
以上の効果を発現させるため、Ｎ含有量を０．０８重量
％以上に維持することが必要である。しかし、０．３０
重量％を超えてＮを含有させても、固溶度を超えてしま
い、過剰のＮがガスとなって鋼塊に欠陥を生じさせる。In order to exhibit the above effects, it is necessary to maintain the N content at 0.08% by weight or more. However, 0.30
Even if N is contained in an amount exceeding % by weight, the solid solubility will be exceeded, and the excess N will turn into gas and cause defects in the steel ingot.
したがって、Ｎ含有量を０．０８〜０．３０重量％の範
囲に定めた。Therefore, the N content was set in the range of 0.08 to 0.30% by weight.
Ｔｉ、Ｚｒ：０．５重量％以下
Ｔｉ及びＺｒは、脱酸作用と共に脱硫作用を呈し、熱間
加工性に悪影響を与えるＳを低減する有効な元素である
。しかし、Ｔｉ、Ｚｒを０．５重量％を超えて添加する
とき、ストリーク状の表面傷を発生させる原因となる。Ti, Zr: 0.5% by weight or less Ti and Zr exhibit a deoxidizing effect and a desulfurizing effect, and are effective elements for reducing S, which adversely affects hot workability. However, when Ti or Zr is added in an amount exceeding 0.5% by weight, it causes streak-like surface scratches.
この欠陥を抑えるため、Ｔｉ、Ｚｒの含有量を最高０．
５重量％までとした。In order to suppress this defect, the content of Ti and Zr should be increased to a maximum of 0.
The content was up to 5% by weight.
稀土類金属ＲＥＭ：０．１重量％以下
稀土類金属ＲＥＭは、Ｔｉ、Ｚｒと同様にＳを補助的に
低減する作用を呈する。このＲＥＭによる脱硫作用は、
Ｌａ＜Ｃｅの場合により効果的になる。しかし、０．１
重量％を超えてＲＥＭを添加するとき、鋼中に多数の非
金属介在物が生成して、鋼の清浄度を低下させる。した
がって、ＲＥＭ含有量の上限を０．１重量％とした。Rare earth metal REM: 0.1% by weight or less Rare earth metal REM, like Ti and Zr, exhibits the effect of supplementarily reducing S. This desulfurization effect by REM is
It becomes more effective when La<Ce. However, 0.1
When adding more than % by weight of REM, a large number of non-metallic inclusions are formed in the steel, reducing the cleanliness of the steel. Therefore, the upper limit of the REM content was set to 0.1% by weight.
Ａ値：２０〜［７Ｏ−６７００Ｘ （Ｓ％）］Ａ値は、
フェライト相とオーステナイト相の比率を推定するため
の指標として実験的に確認されたものである。このＡ値
が２０〜［７０−６７００×（Ｓ％）］の範囲にあるよ
うに、各合金成分を前述した範囲で調整する。Ａ値が２
０未満であると、組織がフェライト単相に近くなり、溶
接部の靭性や耐食性において問題を生じる。他方、Ａ値
が［７Ｏ−６７００Ｘ （Ｓ％）］を超えると、Ｓ含有
量を０．００３重量％以下に低減した場合でも耳割れを
生じる場合があり、熱間加工性が不安定になる。そのた
め、Ａ値を、２０〜［７Ｏ−６７００Ｘ （Ｓ％）コの
範囲に設定した。A value: 20 ~ [7O-6700X (S%)] A value is
This was experimentally confirmed as an index for estimating the ratio of ferrite phase to austenite phase. Each alloy component is adjusted within the range described above so that the A value is within the range of 20 to [70-6700×(S%)]. A value is 2
When it is less than 0, the structure becomes close to a ferrite single phase, which causes problems in the toughness and corrosion resistance of the welded part. On the other hand, if the A value exceeds [7O-6700X (S%)], edge cracking may occur even if the S content is reduced to 0.003% by weight or less, making hot workability unstable. . Therefore, the A value was set in the range of 20 to [7O-6700X (S%).
［実施例］ 次いで、実施例によって本発明を具体的に説明する。[Example] Next, the present invention will be specifically explained with reference to Examples.
第１表に示す成分・組成を持つステンレス鋼を高周波溶
解炉で溶製し、この溶湯から得られたインゴットを中心
部に沿って二分割した。次いで、鋼塊の表面疵を取り除
いた後、大気中で１２５０’ＣＸ２時間の加熱を施し、
１バス当りの圧延率３０％で７パスの熱間圧延を行った
。Stainless steel having the components and composition shown in Table 1 was melted in a high-frequency melting furnace, and the ingot obtained from this molten metal was divided into two along the center. Next, after removing surface flaws from the steel ingot, it was heated at 1250'CX for 2 hours in the atmosphere,
Seven passes of hot rolling were performed at a rolling rate of 30% per bus.
（以下、このページ余白）
第１表のＡ、〜Ａ、は、比較鋼で、組織的にはフエライ
トーオーステナイト二相ステンレス鋼の動噴にある。Ａ
、はＳ含有量が０．００３重量％を超えており、Ａ２は
Ｓ含有量が０，００３重量％以下であるものの、Ａ値が
［７Ｏ−６７００Ｘ（Ｓ％）］を超えている。また、Ａ
３〜Ａ６は、特公昭５７−１５６６０号公報、特公昭５
９−１４０９９号公報及び特公平１−１９４６５号公報
で開示されている二相ステンレス鋼にそれぞれ相当する
が、何ｆｉもＡ値が［７Ｏ−６７００ｘ （Ｓ％）］を
超すように成分調整されている。(Hereinafter, the margins of this page) A and A in Table 1 are comparative steels, which are structurally in the dynamic jet type of ferrite-austenite duplex stainless steel. A
, has an S content exceeding 0.003% by weight, and although A2 has an S content of 0,003% by weight or less, the A value exceeds [7O-6700X (S%)]. Also, A
3 to A6 are published in Japanese Patent Publication No. 57-15660, Japanese Patent Publication No. 57-15660.
These correspond to the duplex stainless steels disclosed in Japanese Patent Publication No. 9-14099 and Japanese Patent Publication No. 1-19465, but the composition of any fi is adjusted so that the A value exceeds [7O-6700x (S%)]. ing.
これに対し、Ｂ１〜Ｂ６は、本発明の動噴にある二相ス
テンレス鋼であって、フェライト−オーステナイトの二
相組織をもつ。このうち、Ｂ４〜Ｂ６は、請求項２に相
当するものであり、第３元素としてそれぞれＲＥＭ、Ｔ
ｉ及びＺｒを含有している。On the other hand, B1 to B6 are duplex stainless steels in the dynamic jetting of the present invention, and have a ferrite-austenite duplex structure. Of these, B4 to B6 correspond to claim 2, and are REM and T as the third element, respectively.
Contains i and Zr.
また、第２表は、第１表の各種鋼のＡ値及びＳ含有量と
の関係で熱延後の耳割れ状態を表したものである。Further, Table 2 shows the edge cracking state after hot rolling in relation to the A value and S content of the various steels shown in Table 1.
第２表：
Ｓ含有量及びＡ値と熱間加工性との関係性：熱間加工性
は、最大耳側れ深さで判定し、２ｍｍ以下のものを○、
２〜５ｍｍのものをΔ、５ｍｍ≧のものを×で表した。Table 2: Relationship between S content and A value and hot workability: Hot workability is determined by the maximum edge depth, and those with a depth of 2 mm or less are rated ○,
Those with a diameter of 2 to 5 mm are indicated as Δ, and those with a diameter of 5 mm≧ are indicated as ×.
第２表から明らかなように、比較鋼Ａ、−Ａ。As is clear from Table 2, comparative steels A and -A.
は、何れも２ｍｍ以上の耳割れが発生している。In all cases, ear cracks of 2 mm or more have occurred.
これに対し、本発明鋼Ｂ１〜Ｂ６では、耳割れが全く生
じていないか、或いは若干生じている程度である。また
、ＲＥＭ及びＣａ＋Ａρをそれぞれ添加した比較鋼Ａ、
及びＡ、では、第３元素の添加に起因するものと考えら
れる熱間加工性改善効果がみられる。しかし、Ｂを添加
した比較鋼Ａ４においては、熱間加工性改善効果は微々
たるものである。On the other hand, in the steels B1 to B6 of the present invention, no edge cracking occurred at all or only a slight amount of edge cracking occurred. In addition, comparative steel A to which REM and Ca+Aρ were added,
In and A, an effect of improving hot workability is observed, which is considered to be due to the addition of the third element. However, in comparative steel A4 to which B was added, the effect of improving hot workability is slight.
熱間加工性に与えるＳ含有量及びＡ値の影響を図示する
と、第１図の通りである。この図から、熱間加工性は、
Ｓ含有量で一義的に定まるものではな（、同一のＳ含有
量レベルであってもＡ値が上昇すると熱間加工性が低下
していることが判かる。逆に、同じＡ値であっても、高
Ｓ材の熱間加工性が悪いことも判かる。The influence of S content and A value on hot workability is illustrated in FIG. 1. From this figure, hot workability is
It is not determined uniquely by the S content (it can be seen that even at the same S content level, as the A value increases, the hot workability decreases. However, it is also clear that the hot workability of the high S material is poor.
すなわち、熱間加工性は、フェライト相とオーステナイ
ト相との比率を規定するＡ値とＳ含有量によって定まる
臨界値を境に、大きく変化している。そして、第１図の
斜線で示した本発明の領域にＳ含有量及びＡ値を維持す
ることにより、良好な熱間加工性をもつ二相ステンレス
鋼が得られている。That is, the hot workability changes greatly after reaching a critical value determined by the A value and the S content, which define the ratio of the ferrite phase to the austenite phase. By maintaining the S content and A value within the region of the present invention indicated by the hatched area in FIG. 1, a duplex stainless steel with good hot workability is obtained.
［発明の効果］
以上に説明したように、本発明においては、Ｓ含有量を
低減させると共に、Ｓ含有量との関連においてフェライ
ト−オーステナイトの相比率を所定範囲に維持するよう
に成分調整することによって、熱間加工性を高めな二相
ステンレス鋼を得ている。この二相ステンレス鋼は、熱
間加工性が安定して高い状態に維持されているため、熱
間圧延時に耳割れを発生することが抑制され、高い歩留
りで熱延板を製造することが可能となる。[Effects of the Invention] As explained above, in the present invention, the S content is reduced and the components are adjusted so as to maintain the ferrite-austenite phase ratio within a predetermined range in relation to the S content. As a result, a duplex stainless steel with improved hot workability was obtained. This duplex stainless steel maintains stable and high hot workability, which suppresses the occurrence of edge cracks during hot rolling, making it possible to manufacture hot rolled sheets with a high yield. becomes.
第１図は、Ｓ含有量及びＡ値が二相ステンレス鋼の熱間
加工性に与える影響を表したグラフである。FIG. 1 is a graph showing the influence of S content and A value on hot workability of duplex stainless steel.
Claims (2)
％）＋１１．５（Ｎｉ％）−５．８（Ｃｒ％）−６（Ｍ
ｏ％）＋４．５（Ｃｕ％）＋２３５（Ｎ％）＋１００で
定められるＡ値を２０≦Ａ≦７０−６７００×（Ｓ％）
の範囲に維持する関係が成立していることを特徴とする
熱間加工性に優れた二相ステンレス鋼。(1) C: 0.03% by weight or less, Si: 1.0% by weight or less, Mn: 1.50% by weight or less, P: 0.04% by weight or less, S: 0.003% by weight or less, Ni: 4.0-9.0% by weight, Cr: 20.0-30.0% by weight, Mo: 2.0-4.0% by weight, Cu: 1.0% by weight or less, N: 0.08-0 .30% by weight, and between these components, the following formula A=210(C%)-5.8(Si%)+3.5(Mn
%)+11.5(Ni%)-5.8(Cr%)-6(M
o%)+4.5(Cu%)+235(N%)+100 A value determined by 20≦A≦70-6700×(S%)
A duplex stainless steel with excellent hot workability that maintains a relationship within the range of .
重量％以下、Ｌａ／Ｃｅ＜１．０を満足する稀土類金属
ＲＥＭ：０．１重量％以下の一種又は二種以上を含有し
、且つこれら成分の間に、次式 Ａ＝２１０（Ｃ％）−５．８（Ｓｉ％）＋３．５（Ｍｎ
％）＋１１．５（Ｎｉ％）−５．８（Ｃｒ％）−６（Ｍ
ｏ％）＋４．５（Ｃｕ％）＋２６［（Ｔｉ％）＋（Ｚｒ
％）＋（ＲＥＭ％）］＋２３５（Ｎ％）＋１００で定め
られるＡ値を２０≦Ａ≦７０−６７００×（Ｓ％）の範
囲に維持する関係が成立していることを特徴とする熱間
加工性に優れた二相ステンレス鋼。(2) C: 0.03% by weight or less, Si: 1.0% by weight or less, Mn: 1.50% by weight or less, P: 0.04% by weight or less, S: 0.003% by weight or less, Ni: 4.0-9.0% by weight, Cr: 20.0-30.0% by weight, Mo: 2.0-4.0% by weight, Cu: 1.0% by weight or less, N: 0.08-0 .30% by weight, furthermore Ti: 0.5% by weight or less, Zr: 0.5
% by weight or less, rare earth metal REM satisfying La/Ce<1.0: Contains 0.1% by weight or less of one or more kinds, and between these components, the following formula A = 210 (C% )-5.8(Si%)+3.5(Mn
%)+11.5(Ni%)-5.8(Cr%)-6(M
o%)+4.5(Cu%)+26[(Ti%)+(Zr
%) + (REM%)] + 235 (N%) + 100, a relationship is established that maintains the A value in the range of 20≦A≦70-6700×(S%). Duplex stainless steel with excellent workability.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20442790A JP3266247B2 (en) | 1990-08-01 | 1990-08-01 | Duplex stainless steel with excellent hot workability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20442790A JP3266247B2 (en) | 1990-08-01 | 1990-08-01 | Duplex stainless steel with excellent hot workability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0488151A true JPH0488151A (en) | 1992-03-23 |
| JP3266247B2 JP3266247B2 (en) | 2002-03-18 |
Family
ID=16490361
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP20442790A Expired - Lifetime JP3266247B2 (en) | 1990-08-01 | 1990-08-01 | Duplex stainless steel with excellent hot workability |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100389323B1 (en) * | 1998-12-29 | 2003-11-12 | 주식회사 포스코 | Heat-resistant austenitic stainless steel with excellent hot workability |
| JP2007270265A (en) * | 2006-03-31 | 2007-10-18 | Sumitomo Metal Ind Ltd | Method for manufacturing duplex stainless steel seamless pipe |
| JP2012207301A (en) * | 2011-03-17 | 2012-10-25 | Nippon Steel & Sumikin Stainless Steel Corp | Stainless steel with high n content excellent in surface flaw resistance and method for producing the same |
| CN103205653A (en) * | 2013-03-27 | 2013-07-17 | 宝钢不锈钢有限公司 | Duplex stainless steel with excellent thermoplasticity and corrosion resistance and manufacturing method thereof |
| CN107385360A (en) * | 2017-07-06 | 2017-11-24 | 钢铁研究总院 | A kind of two phase stainless steel reinforcing bar and preparation method thereof |
-
1990
- 1990-08-01 JP JP20442790A patent/JP3266247B2/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100389323B1 (en) * | 1998-12-29 | 2003-11-12 | 주식회사 포스코 | Heat-resistant austenitic stainless steel with excellent hot workability |
| JP2007270265A (en) * | 2006-03-31 | 2007-10-18 | Sumitomo Metal Ind Ltd | Method for manufacturing duplex stainless steel seamless pipe |
| JP2012207301A (en) * | 2011-03-17 | 2012-10-25 | Nippon Steel & Sumikin Stainless Steel Corp | Stainless steel with high n content excellent in surface flaw resistance and method for producing the same |
| CN103205653A (en) * | 2013-03-27 | 2013-07-17 | 宝钢不锈钢有限公司 | Duplex stainless steel with excellent thermoplasticity and corrosion resistance and manufacturing method thereof |
| CN107385360A (en) * | 2017-07-06 | 2017-11-24 | 钢铁研究总院 | A kind of two phase stainless steel reinforcing bar and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3266247B2 (en) | 2002-03-18 |
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