JPH08269646A - Boron-containing stainless steel excellent in oxidation and corrosion resistance and its production - Google Patents
Boron-containing stainless steel excellent in oxidation and corrosion resistance and its productionInfo
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- JPH08269646A JPH08269646A JP7146695A JP7146695A JPH08269646A JP H08269646 A JPH08269646 A JP H08269646A JP 7146695 A JP7146695 A JP 7146695A JP 7146695 A JP7146695 A JP 7146695A JP H08269646 A JPH08269646 A JP H08269646A
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- stainless steel
- boron
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、耐酸化性および耐食性
に優れた含ボロンステンレス鋼とその製造方法に関し、
とくに、中性子を放射する原子力廃棄物の貯蔵、輸送あ
るいは中性子遮蔽材などの原子力関連設備材料としてと
りわけ有効に用いられる含ボロンオーステナイト系ステ
ンレス鋼に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boron-containing stainless steel having excellent oxidation resistance and corrosion resistance and a method for producing the same.
In particular, the present invention relates to boron-containing austenitic stainless steel that is particularly effectively used as a nuclear-related facility material such as storage and transport of neutron-emitting nuclear waste or neutron shielding material.
【０００２】[0002]
【従来の技術】中性子遮蔽能を有しかつ耐食性を有する
材料としては、ボロン（Ｂ）を含有したオーステナイト
系ステンレス鋼が有効であり、広く利用されている。し
かしながら、この鋼種では、加熱時にボライド〔( Cr,
Fe)2Ｂ〕を生成するためにCrが消費され、マトリックス
中の有効Cr濃度が１wt％以上も低下し、そのためにボロ
ンを添加しないステンレス鋼に比べると、耐食性、耐酸
化性がともに劣化するという問題点があった。従来、こ
うした問題点を克服する方法として、例えば、特開昭62
−222049号公報に見られるように、上記ボライド生成に
よるCr減量を見込んで予めCr量(22 〜30wt％) を高くす
る一方で、極低Ｃにした材料などが提案されている。2. Description of the Related Art Austenitic stainless steel containing boron (B) is effective and widely used as a material having neutron shielding ability and corrosion resistance. However, in this steel type, the boron [(Cr,
Cr is consumed to produce Fe) 2 B], and the effective Cr concentration in the matrix is lowered by 1 wt% or more. Therefore, both corrosion resistance and oxidation resistance are deteriorated as compared with stainless steel containing no boron. There was a problem. Conventionally, as a method for overcoming these problems, for example, Japanese Patent Laid-Open No. 62-62
As disclosed in Japanese Patent Laid-Open No. 222049, a material in which the amount of Cr (22 to 30 wt%) is increased in advance in consideration of the decrease in Cr due to the formation of the above-mentioned boron, while the amount of ultra-low C is proposed.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、上記従
来技術は、極低Ｃにしなければならないことに加え、多
量のCrの添加を必要とすることから、コスト高になる
他、製造上困難を伴うという欠点があった。そこで、本
発明は、ボロン添加ステンレス鋼における耐酸化性なら
びに耐食性が、等量のCrを含むボロン無添加ステンレス
鋼と比べて同等もしくはそれ以上に優れている含ボロン
ステンレス鋼ならびに、その製造方法を提案することを
目的とする。However, the above-mentioned prior art requires an extremely low C and also requires the addition of a large amount of Cr, resulting in high cost and difficulty in production. There was a drawback. Therefore, the present invention, the oxidation resistance and corrosion resistance in the boron-added stainless steel, boron-containing stainless steel is equal to or more excellent than boron-free stainless steel containing an equal amount of Cr, and a method for producing the same. The purpose is to propose.
【０００４】[0004]
【課題を解決するための手段】上記課題解決のために本
発明では、下記の要旨構成にかかる手段を提案する。 Ｂを0.05〜5.0 wt％含有するステンレス鋼であっ
て、その表層部に厚さ10μｍ以上の有効クロム濃化層を
有することを特徴とする耐酸化性および耐食性に優れた
含ボロンステンレス鋼。 Ｂを0.05〜5.0 wt％含有するステンレス鋼であっ
て、その表層部に厚さ10μｍ以上の有効クロム濃化層を
有し、かつその直下には、ボライド〔( Cr, Fe)2Ｂ〕の
生成に伴う有効クロムが希釈したマトリックス層を有す
ることを特徴とする耐酸化性および耐食性に優れた含ボ
ロンステンレス鋼。 Ｃ：0.15wt％以下、 Si：0.10〜1.0 wt％、Mn：
0.10〜2.00wt％、 Cr：11.0〜27.0wt％、Ni：5.0 〜2
5.0wt％、 Ｂ：0.05〜5.0 wt％、およびＮ：0.3 wt％
以下を含有し、残部がFeおよび不可避的不純物からなる
ステンレス鋼であって、その表層部に厚さ10μｍ以上の
有効クロム濃化層を有すること、また、この濃化層直下
には、ボライドの生成に伴う有効クロムが希釈したマト
リックス層を有すること、を特徴とする耐酸化性および
耐食性に優れた含ボロンステンレス鋼。 Ｃ：0.15wt％以下、 Si：0.10〜1.0 wt％、Mn：
0.10〜2.00wt％、 Cr：11.0〜27.0wt％、Ni：5.0 〜2
5.0wt％、 Ｂ：0.7 〜2.0 wt％、Mo：0.1 〜3.0 wt％
およびＮ：0.3 wt％以下を含有し、残部がFeおよび不可
避的不純物からなるステンレス鋼であって、その表層部
に厚さ10μｍ以上の有効クロム濃化層を有すること、ま
た、この濃化層直下には、ボライドの生成に伴う有効ク
ロムが希釈したマトリックス層を有すること、を特徴と
する耐酸化性および耐食性に優れた含ボロンステンレス
鋼。 Ｃ：0.15wt％以下、 Si：0.10〜1.0 wt％、Mn：
0.10〜2.00wt％、 Cr：18.0〜25.0wt％、Ni：5.0 〜1
2.0wt％、 Ｂ：0.05〜2.0 wt％、Mo：1.0 〜3.0 wt％
およびＮ：0.3 wt％以下を含有し、残部がFeおよび不可
避的不純物からなるステンレス鋼であって、その表層部
に厚さ10μｍ以上の有効クロム濃化層を有すること、ま
た、この濃化層直下には、ボライドの生成に伴う有効ク
ロムが希釈したマトリックス層を有すること、を特徴と
する耐酸化性および耐食性に優れた含ボロンステンレス
鋼。 上記有効クロム濃化層は、凝固時にマトリックス中
に生成したボライド〔(Cr, Fe)2Ｂ〕中のボロン（Ｂ）
が揮発することによってCr量が該マトリックス層よりも
１wt％以上高い表層部である上記〜のいずれかに記
載の含ボロンステンレス鋼。 Ｂを0.05〜5.0 wt％含有するステンレス鋼スラブ
を、酸素分圧 PO2：１％〜21％、加熱温度：800 〜1100
℃の範囲内にて30 min〜２hrの加熱保持を行い、その
後、熱間圧延を行うことを特徴とする耐酸化性および耐
食性に優れた含ボロンステンレス鋼の製造方法。In order to solve the above problems, the present invention proposes the following means. A boron-containing stainless steel having excellent oxidation resistance and corrosion resistance, which is a stainless steel containing 0.05 to 5.0 wt% of B, and has an effective chromium concentration layer having a thickness of 10 μm or more on a surface layer portion thereof. A stainless steel containing B in an amount of 0.05 to 5.0 wt%, having an effective chromium concentration layer having a thickness of 10 μm or more on the surface layer thereof, and immediately below that, a boron [(Cr, Fe) 2 B] A boron-containing stainless steel having excellent oxidation resistance and corrosion resistance, characterized by having a matrix layer in which effective chromium generated is diluted. C: 0.15 wt% or less, Si: 0.10 to 1.0 wt%, Mn:
0.10-2.00wt%, Cr: 11.0-27.0wt%, Ni: 5.0-2
5.0 wt%, B: 0.05-5.0 wt%, and N: 0.3 wt%
A stainless steel containing the following, with the balance being Fe and unavoidable impurities, having an effective chromium concentration layer with a thickness of 10 μm or more in the surface layer portion, and immediately below this concentration layer, boron A boron-containing stainless steel having excellent oxidation resistance and corrosion resistance, characterized in that it has a matrix layer in which effective chromium accompanying formation is diluted. C: 0.15 wt% or less, Si: 0.10 to 1.0 wt%, Mn:
0.10-2.00wt%, Cr: 11.0-27.0wt%, Ni: 5.0-2
5.0 wt%, B: 0.7-2.0 wt%, Mo: 0.1-3.0 wt%
And N: 0.3 wt% or less, the balance being Fe and unavoidable impurities, and stainless steel having an effective chromium concentration layer having a thickness of 10 μm or more in the surface layer portion, and this concentration layer A boron-containing stainless steel excellent in oxidation resistance and corrosion resistance, which has a matrix layer in which effective chromium due to the formation of boride is diluted immediately below. C: 0.15 wt% or less, Si: 0.10 to 1.0 wt%, Mn:
0.10 ~ 2.00wt%, Cr: 18.0 ~ 25.0wt%, Ni: 5.0 ~ 1
2.0 wt%, B: 0.05 to 2.0 wt%, Mo: 1.0 to 3.0 wt%
And N: 0.3 wt% or less, the balance being Fe and unavoidable impurities, and stainless steel having an effective chromium concentration layer having a thickness of 10 μm or more in the surface layer portion, and this concentration layer A boron-containing stainless steel excellent in oxidation resistance and corrosion resistance, which has a matrix layer in which effective chromium due to the formation of boride is diluted immediately below. The effective chromium enriched layer is composed of boron (B) in boron [(Cr, Fe) 2 B] formed in the matrix during solidification.
The boron-containing stainless steel according to any one of the above 1 to 3, which is a surface layer portion in which the amount of Cr is higher than the matrix layer by 1 wt% or more by volatilization. A stainless steel slab containing 0.05 to 5.0 wt% B was prepared with oxygen partial pressure PO 2 : 1% to 21% and heating temperature: 800 to 1100.
A method for producing a boron-containing stainless steel having excellent oxidation resistance and corrosion resistance, which comprises performing heating and holding for 30 min to 2 hours within a range of ° C, and then performing hot rolling.
【０００５】[0005]
【作用】ボロンを含有するオーステナイト系ステンレス
鋼については、一般に、熱間圧延時に表面疵（鳥の足跡
状の欠陥）が発生することが指摘されていた。このこと
について発明者らは、その原因を詳細に研究した。その
結果、この表面疵は、一般的な熱間加工性劣化の原因の
他に、耐酸化性が低いことも大きく起因していることを
突き止めた。すなわち、熱間加工性が劣る場合の割れ状
の欠陥とは異なる筋状（鳥の足跡状）の疵が残ることが
認められ、この疵の原因についてさらに調べたところ、
Crの濃度が低い部分での異常酸化によるものであること
が判ったのである。It has been pointed out that austenitic stainless steels containing boron generally have surface defects (bird-like defects) during hot rolling. With respect to this, the inventors have studied the cause in detail. As a result, it was found that this surface flaw is largely caused by low oxidation resistance in addition to the general cause of deterioration in hot workability. That is, it was observed that streaky (bird's footsteps) flaws different from crack-like defects when hot workability was inferior were left, and further investigation into the cause of these flaws revealed that
It was found that this was due to abnormal oxidation in the portion where the Cr concentration was low.
【０００６】そこで発明者らは、種々の条件にてボロン
含有ステンレス鋼の耐酸化特性を調査した。その結果、
室温から通常の熱間圧延温度である1150〜1200℃にボロ
ン含有ステンレス鋼を加熱すると、上述したように、鋼
（マトリックス）中にボライド〔( Cr, Fe)2Ｂ〕が析出
して固定される結果、耐酸化性や耐食性の維持に必要な
有効Cr濃度が低下し、そのために、同等のCr量を有する
オーステナイト系ステンレス鋼と比較して耐食性および
耐酸化性が著しく劣化することが判った。しかし、発明
者らの研究によると、上記の加熱に際し、まず1000〜11
00℃の温度に30min 〜２hrの間保持し、その後、熱間圧
延温度である1150〜1200℃に昇温した場合には、同等の
Cr量を有するオーステナイト系ステンレス鋼よりもむし
ろ耐食性ならびに耐酸化性に優れることがわかったので
ある。Therefore, the inventors investigated the oxidation resistance of boron-containing stainless steel under various conditions. as a result,
When boron-containing stainless steel is heated from room temperature to a normal hot rolling temperature of 1150 to 1200 ° C., as described above, boron [(Cr, Fe) 2 B] is precipitated and fixed in the steel (matrix). As a result, it was found that the effective Cr concentration necessary for maintaining the oxidation resistance and the corrosion resistance is lowered, and therefore the corrosion resistance and the oxidation resistance are remarkably deteriorated as compared with the austenitic stainless steel having the same Cr amount. . However, according to the research conducted by the inventors, when the above-mentioned heating is performed, first, 1000 to 11
If the temperature is maintained at 00 ° C for 30 min to 2 hours and then raised to the hot rolling temperature of 1150 to 1200 ° C, the same
It was found that they are superior in corrosion resistance and oxidation resistance to austenitic stainless steel having a Cr content.
【０００７】このような現象が生じる理由について、発
明者らは、以下のように考えている。それは、通常のボ
ロン含有ステンレス鋼においては、ボライド〔( Cr, F
e)2Ｂ〕の生成により、マトリックス中の有効Cr量が消
費され、同等のCr量を有するステンレス鋼と全Cr量では
同じであっても、マトリックス中の有効Cr量を比較する
と、明らかにボロン含有ステンレス鋼の方がその量が少
なく、従って、耐酸化性や耐食性に貢献するフリーの有
効Cr量が少ないために高温では異常酸化を生じやすく、
先に述べたような欠陥発生の原因となってしまう。The inventors consider the reason why such a phenomenon occurs as follows. In ordinary boron-containing stainless steel, it is the boron [(Cr, F
e) The formation of 2 B] consumes the amount of effective Cr in the matrix, and even if the total amount of Cr is the same as that of stainless steel having the same amount of Cr, it is clear that the amount of effective Cr in the matrix is compared. Boron-containing stainless steel has a smaller amount, and therefore the amount of free effective Cr that contributes to oxidation resistance and corrosion resistance is small, so abnormal oxidation easily occurs at high temperatures,
This causes the defects described above.
【０００８】ところが、発明者らの知見では、酸化の過
程において、その酸化反応をゆっくりと進行させると、
異常酸化を起こしてボライドを生成する前にボロンが酸
化物となり、優先的に表面から揮散し、結局、ボロンと
結合していたCrのみが取り残されて拡散することで、ス
テンレス鋼の表層部分に10μｍ〜100 μｍ厚の均一な有
効Cr濃化層が出現することがわかった。このような処理
をした含ボロンステンレス鋼の場合、有効クロム濃化層
のために、同等のCr量を含有するステンレス鋼よりも、
表層近傍ではむしろ有効Cr濃度がマトリックス層に比べ
て高く(1wt％以上) なり、耐酸化性, 耐食性がともに優
れたステンレス鋼となるのである。つまり、熱間圧延に
先立つ加熱の前に、まず適当な熱処理条件で前処理（予
備加熱）することにより、ゆっくりとした酸化反応を進
行させることで該ステンレス鋼の表層部に有効Cr濃化層
を形成することができる。その結果、なんら余分なCrを
添加することなく、耐食性, 耐酸化性の両方を高めた含
ボロンステンレス鋼が得られるのである。However, according to the knowledge of the inventors, in the process of oxidation, if the oxidation reaction is slowly advanced,
Boron becomes an oxide before it abnormally oxidizes to produce boride and volatilizes preferentially from the surface.In the end, only Cr that has bound to boron is left behind and diffuses, so that the surface layer of stainless steel diffuses. It was found that a uniform effective Cr-enriched layer having a thickness of 10 μm to 100 μm appeared. In the case of boron-containing stainless steel that has been subjected to such treatment, due to the effective chromium concentration layer, stainless steel containing an equivalent amount of Cr,
In the vicinity of the surface layer, the effective Cr concentration is rather higher than that of the matrix layer (1 wt% or more), and the stainless steel has excellent oxidation resistance and corrosion resistance. In other words, before heating prior to hot rolling, first, pretreatment (preheating) is performed under appropriate heat treatment conditions to allow a slow oxidation reaction to proceed, and thereby an effective Cr-enriched layer is formed on the surface layer portion of the stainless steel. Can be formed. As a result, boron-containing stainless steel with improved corrosion resistance and oxidation resistance can be obtained without adding any extra Cr.
【０００９】次に、本発明にかかる含ボロンステンレス
鋼において、鋼成分の組成の限定理由について説明す
る。 Ｃ：0.15wt％以下 Ｃは、ステンレス鋼中でCr炭化物を形成し、耐食性, 耐
酸化性に寄与するCrを減少させてしまう。従って、Ｃ
は、0.15wt％以下に限定する。Next, the reasons for limiting the composition of the steel components in the boron-containing stainless steel according to the present invention will be described. C: 0.15 wt% or less C forms Cr carbide in stainless steel and reduces Cr that contributes to corrosion resistance and oxidation resistance. Therefore, C
Is limited to 0.15 wt% or less.
【００１０】Si：0.10〜1.0 wt％ Siは、脱酸元素であり精錬上必要な元素である。また、
ステンレス鋼の耐食性、耐酸化性を向上させる元素であ
るが、1.0 wt％を超えると熱間加工性を悪くする。これ
らのことからSiは、0.10〜1.0 wt％に限定する。Si: 0.10 to 1.0 wt% Si is a deoxidizing element and is an element necessary for refining. Also,
It is an element that improves the corrosion resistance and oxidation resistance of stainless steel, but if it exceeds 1.0 wt%, it deteriorates hot workability. From these things, Si is limited to 0.10 to 1.0 wt%.
【００１１】Mn：0.10〜2.00wt％ Mnは、Siと同様に脱酸元素として有効であり0.10wt％以
上を添加する。また、Niの代替成分として利用される元
素であるが、多量に添加すると誘導放射能の残留が多く
なるので2.00wt％以下とした。Mn: 0.10 to 2.00 wt% Mn is effective as a deoxidizing element like Si, and 0.10 wt% or more is added. In addition, it is an element used as a substitute component of Ni, but if it is added in a large amount, the amount of residual induced radioactivity increases, so the content was made 2.00 wt% or less.
【００１２】Cr：11.0〜27.0wt％ Crは、ステンレス鋼における基本成分であり、耐食性を
向上させる。顕著な耐食性の向上を得るには少なくとも
11wt％を超えるCr量が必要であり、このCr量が高いほど
耐食性に優れる。しかしながら、Crを27wt％を超えて添
加した場合、材料の脆化が著しくなり、実用上好ましく
ない。従って、Crの範囲は11.0〜27.0wt％と限定する
が、好ましくは、優れた耐食性を示す18wt％以上、脆化
の生じる25wt％以下の範囲が望ましい。Cr: 11.0 to 27.0 wt% Cr is a basic component in stainless steel and improves corrosion resistance. At least to get a noticeable improvement in corrosion resistance
A Cr amount exceeding 11 wt% is required, and the higher the Cr amount, the better the corrosion resistance. However, when Cr is added in an amount of more than 27 wt%, embrittlement of the material becomes remarkable, which is not practically preferable. Therefore, the range of Cr is limited to 11.0 to 27.0 wt%, but it is preferable that the range of 18 wt% or more showing excellent corrosion resistance and 25 wt% or less where embrittlement occurs is desirable.
【００１３】Ni：5.0 〜25.0wt％ Niは、Crとともにステンレス鋼の基本成分であり、オー
ステナイト相を安定にするために必須の元素である。と
りわけＢ含有ステンレス鋼においては、Niがボロン化合
物中にほとんど固溶せず消費されないため、5.0wt ％の
添加で十分オーステナイトを安定化させる。しかしなが
ら、25wt％を超えて添加した場合、コスト高となるため
上限は25wt％とする。好ましくは、オーステナイトが安
定となる5.0 〜12.0wt％の範囲が望ましい。Ni: 5.0 to 25.0 wt% Ni is a basic component of stainless steel together with Cr, and is an essential element for stabilizing the austenite phase. Especially in B-containing stainless steel, Ni is hardly dissolved in the boron compound and is not consumed. Therefore, addition of 5.0 wt% sufficiently stabilizes austenite. However, if added in excess of 25 wt%, the cost will increase, so the upper limit is 25 wt%. Preferably, the range of 5.0 to 12.0 wt% at which austenite becomes stable is desirable.
【００１４】Mo：0.1 〜3.0 wt％ Moは、Crに比較して約３倍の耐食性付加作用を有し、耐
食性の向上にきわめて有効な元素である。はっきりとし
た耐食性向上の効果を得るには、少なくとも0.1 wt％以
上の添加が必要である。しかしながら、3.0 wt％を超え
て添加した場合、コストが高くなるうえ脆化が著しくな
り実用上好ましくない。従って、Moは、0.1 〜3.0 wt％
の範囲に限定する。好ましくは、1.0 〜3.0 wt％であ
る。Mo: 0.1 to 3.0 wt% Mo has an effect of adding corrosion resistance about three times that of Cr, and is an extremely effective element for improving the corrosion resistance. In order to obtain a clear effect of improving corrosion resistance, it is necessary to add at least 0.1 wt% or more. However, if it is added in excess of 3.0 wt%, the cost becomes high and the embrittlement becomes remarkable, which is not preferable in practice. Therefore, Mo is 0.1-3.0 wt%
It is limited to the range of. Preferably, it is 1.0 to 3.0 wt%.
【００１５】Ｂ：0.05〜5.0 wt％ Ｂは、中性子吸収能を確保するために必要不可欠な元素
であり、中性子吸収能を発現させるためには少なくとも
0.05wt％の添加を必要とする。しかしながら、このＢを
5.0 wt％よりも多く添加した場合、材料強度、耐摩耗
性、加工性などの面において実用上多くの問題が発生す
るため、5.0 wt％が上限となる。ただし、加工性に着目
した場合、好ましくは0.05〜2.0 wt％が望まれる。な
お、このＢは、本発明においてはとりわけ重要な役割を
担う元素であり、このＢの添加によってまず、ボライド
〔( Cr, Fe)2Ｂ〕を積極的に生じさせ、次いで熱間圧延
に先立つ予備処理（熱処理）によって、表層部に有効ク
ロム濃化層を生成させるために必要な成分である。従っ
て、Ｂは、オーステナイトマトリックス中に固溶してい
るものを除いて、予備熱処理の前は少なくとも表層部の
ものは全てボライド〔( Cr, Fe)2Ｂ〕の形態で存在して
いることが好ましいと言える。B: 0.05 to 5.0 wt% B is an essential element for ensuring the neutron absorbing ability, and at least to express the neutron absorbing ability.
Addition of 0.05 wt% is required. However, this B
If more than 5.0 wt% is added, practically many problems occur in terms of material strength, wear resistance, workability, etc., so 5.0 wt% is the upper limit. However, when paying attention to workability, 0.05 to 2.0 wt% is preferable. Note that B is an element that plays an especially important role in the present invention, and the addition of B first causes boride [(Cr, Fe) 2 B] to be positively generated, and then precedes hot rolling. It is a component necessary for forming an effective chromium concentrated layer on the surface layer by pretreatment (heat treatment). Therefore, except for B as a solid solution in the austenite matrix, at least all of the surface layer is present in the form of boride [(Cr, Fe) 2 B] before the preheat treatment. It can be said that it is preferable.
【００１６】Ｎ：0.3 wt％以下 Ｎは、ステンレス鋼の強度と耐食性を向上させる元素で
あるが、0.3 wt％を超えて添加した場合、強度の上昇に
よる加工性の劣化が問題となる。また、ＢＮを形成し、
前記クロムボライドの生成を妨げるため0.3 wt％以下に
規定する。N: 0.3 wt% or less N is an element that improves the strength and corrosion resistance of stainless steel, but if added in excess of 0.3 wt%, deterioration of workability due to an increase in strength becomes a problem. Also, forming BN,
It is specified to be 0.3 wt% or less in order to prevent the formation of the chrome boride.
【００１７】有効クロム濃化層：10μｍ以上 上述したように本発明においては、ステンレス鋼表層部
に10μｍ以上の厚さの有効クロム濃化層を設けることが
必要である。好ましくは50μｍ以上、より好ましくは 1
00μｍ以上の厚さにするのがよい。この層は、マトリッ
クス層のCr濃度よりも１wt％以上高いCrを有し、それは
後述する本発明に特有な酸化熱処理により、表層部にあ
るボライド〔( Cr, Fe)2Ｂ〕のＢとCrとを分解し、Ｂを
揮散させて、Cr濃度が相対的に高い層としたものであ
る。Effective Chromium Concentration Layer: 10 μm or More As described above, in the present invention, it is necessary to provide an effective chromium concentration layer having a thickness of 10 μm or more on the surface layer of stainless steel. Preferably 50 μm or more, more preferably 1
It is recommended that the thickness be 00 μm or more. This layer has a Cr content higher than the Cr concentration of the matrix layer by 1 wt% or more. This is due to the oxidative heat treatment peculiar to the present invention described below, which results in B and Cr of the boride [(Cr, Fe) 2 B] in the surface layer portion. Is decomposed and B is volatilized to form a layer having a relatively high Cr concentration.
【００１８】次に、本発明製造方法, 特に予備処理条件
すなわち酸化熱処理について説明する。 加熱条件： 800〜1100℃ ボロンの酸化による脱ボロン反応を促進させるには、少
なくとも 800℃以上の温度に保持する必要がある。しか
し、800 ℃近傍では反応が極めて緩慢であるため、実用
上は1000℃以上が好ましい。ただし、1100℃以上の温度
で加熱保持した場合、ボロンの酸化のみならずクロムの
酸化も進行するため、有効クロム濃化層を形成して酸化
の進行を妨げる前にCr含有量の少ない部分から優先的に
異常酸化が進行し、そのまま酸化反応が続いてしまう。
従って、加熱条件は 800℃から1100℃、より好ましくは
1000〜1100℃の温度範囲が望ましい。Next, the manufacturing method of the present invention, particularly the pretreatment conditions, that is, the oxidative heat treatment will be described. Heating conditions: 800 to 1100 ℃ To accelerate the deboron reaction due to the oxidation of boron, it is necessary to maintain the temperature at least 800 ℃ or higher. However, since the reaction is extremely slow near 800 ° C, it is preferably 1000 ° C or higher for practical use. However, when heated and maintained at a temperature of 1100 ° C or higher, not only the oxidation of boron but also the oxidation of chromium progresses.Therefore, from the portion with a small Cr content before forming an effective chromium concentration layer and hindering the progress of oxidation. The abnormal oxidation progresses preferentially, and the oxidation reaction continues as it is.
Therefore, the heating conditions are from 800 ℃ to 1100 ℃, more preferably
A temperature range of 1000-1100 ° C is desirable.
【００１９】保持時間：30 min〜２hr 上記加熱のための保持時間については、必要な有効クロ
ム濃化層の厚さ、処理温度に依存する。しかし、有効ク
ロム濃化層形成が最も速くなる1100℃でも、少なくとも
30min 以上の保持をしなければ前処理効果が現れない。
また、最も濃化層の形成が遅い800 ℃で処理した場合、
２hr以上の保持を必要とする。２hr以上の保持ではこの
有効クロム濃化層の厚さ変化は急激に少なくなり、時間
を長くしても 150μｍ以上の有効クロム濃化層は得られ
ないため、工業上の実用性からは２hr以内が好ましい。
従って、保持時間は30min 以上から２hrと限定した。Holding time: 30 min to 2 hours The holding time for the above heating depends on the required thickness of the effective chromium concentration layer and the processing temperature. However, even at 1100 ° C, where the formation of the effective chromium concentration layer is the fastest, at least
The pretreatment effect does not appear unless it is held for 30 min or longer.
In addition, when treated at 800 ° C, where the thickest layer is formed,
Hold for 2 hours or more is required. When kept for 2 hours or more, the change in the thickness of the effective chromium-enriched layer is drastically reduced, and even if the time is extended, an effective chromium-enriched layer of 150 μm or more cannot be obtained. Is preferred.
Therefore, the holding time was limited to 30 minutes or more and 2 hours.
【００２０】雰囲気：酸素分圧 PO2：1.0 〜21％ ステンレス鋼表面の酸化を進行させるためには、少なく
とも1.0 ％の酸素分圧を必要とし、それよりも少ない場
合、酸化反応に極めて時間がかかり実用上問題がある。
また、酸素分圧を20％以上に安定させるのは工業上危険
でもあり、また、安定した制御が困難であるため安定し
た処理条件を得るのが難しい。従って、酸素分圧の範囲
を1.0 〜21％とした。好ましくは２〜10％、より好まし
くは３〜５％とする。Atmosphere: Oxygen partial pressure PO 2 : 1.0 to 21% In order to promote the oxidation of the stainless steel surface, an oxygen partial pressure of at least 1.0% is required. There is a problem in practice.
Further, it is industrially dangerous to stabilize the oxygen partial pressure to 20% or more, and it is difficult to obtain stable treatment conditions because stable control is difficult. Therefore, the oxygen partial pressure range is set to 1.0 to 21%. It is preferably 2 to 10%, more preferably 3 to 5%.
【００２１】[0021]
【実施例】表１に示す成分組成の鋼を同表に示す条件で
酸化熱処理をした後、1150〜1200℃に昇温したのち熱間
圧延し、その後常法に従って熱処理し、酸洗し、矯正し
て製品を得た。その結果も同表に示す。酸化増量は、実
験室的に雰囲気 PO2＝３％から、大気中(PO2＝21％) ま
で制御して前処理を施した後、1200℃×２hr・大気中の
酸化試験を行った後に測定した。また、有効クロム濃化
層は断面をEPMAにて分析し、Cr濃度がマトリックスのCr
濃度より１％以上高い領域として定義、測定した。耐食
性は、酸洗によって表面のスケールを除去した後、孔食
電位を測定した結果である。[Examples] Steels having the chemical compositions shown in Table 1 were subjected to oxidative heat treatment under the conditions shown in the same table, heated to 1150 to 1200 ° C and hot-rolled, and then heat-treated and pickled according to a conventional method, It was straightened to obtain the product. The results are also shown in the table. The amount of oxidation increase is controlled experimentally from the atmosphere PO 2 = 3% to the atmosphere (PO 2 = 21%) after pretreatment, and then 1200 ° C × 2hr after the oxidation test in the atmosphere. It was measured. The cross section of the effective chromium concentration layer was analyzed by EPMA.
It was defined and measured as a region higher than the concentration by 1% or more. The corrosion resistance is the result of measuring the pitting potential after removing the surface scale by pickling.
【００２２】[0022]
【表１】 [Table 1]
【００２３】表１に示す結果に明らかなとおり、Ｂを含
有しないステンレス鋼および前処理を全くせず有効クロ
ム濃化層の生成していない比較例では、酸化増量が激し
くかつ耐食性もよくない。これに対し、酸化熱処理を施
した発明例は、いずれも酸化増量は小さく耐食性も優れ
ている。但し、Ｂは含有していても低酸素濃度雰囲気(P
O2＝３％, 10％)の発明例No.3, 4 では、耐食性があま
り高くない。これに対して、有効クロム濃化層の厚い発
明例No.7, 8 などは、耐酸化性, 耐食性とも極めて良好
である。As is clear from the results shown in Table 1, in the case of a stainless steel containing no B and a comparative example in which an effective chromium-enriched layer was not formed without any pretreatment, the amount of oxidation increase and the corrosion resistance were not good. On the other hand, in each of the invention examples subjected to the oxidative heat treatment, the oxidative increase is small and the corrosion resistance is excellent. However, even if B is contained, the atmosphere with low oxygen concentration (P
Invention Examples Nos. 3 and 4 with O 2 = 3%, 10%) do not have very high corrosion resistance. On the other hand, Invention Examples Nos. 7 and 8 having a thick effective chromium concentration layer have extremely good oxidation resistance and corrosion resistance.
【００２４】図１は、上記実施例No. 2 （相当の18.2Cr
−1.0 Ｂ）ステンレス鋼の表層部のＥＰＭＡマッピング
の写真（加速電圧15.0KV, ビーム電流2000×10-7Ａ，測
定間隔１μｍ, 測定時間0.03秒) である。表層部に約 1
00μｍの有効クロム濃化層が生成しており、本発明組織
構造を確認できた。FIG. 1 shows the above embodiment No. 2 (corresponding to 18.2Cr).
-1.0 B) A photograph of EPMA mapping of the surface layer of stainless steel (accelerating voltage 15.0 KV, beam current 2000 × 10 -7 A, measurement interval 1 μm, measurement time 0.03 seconds). About 1 on the surface
An effective chromium-concentrated layer of 00 μm was formed, confirming the structure of the present invention.
【００２５】[0025]
【発明の効果】以上説明したとおり本発明によれば、熱
間圧延に先立つ予備的な酸化熱処理を行うだけで、ボロ
ン無添加のステンレス鋼と同等かそれ以上に優れた耐酸
化性と耐食性を有するボロン含有ステンレス鋼を製造す
ることができる。As described above, according to the present invention, it is possible to obtain the oxidation resistance and the corrosion resistance which are equal to or better than those of the boron-free stainless steel only by performing the preliminary oxidative heat treatment prior to the hot rolling. Boron-containing stainless steel can be manufactured.
【図１】図１は、Ｂ含有ステンレス鋼の有効クロム濃化
層の生成のもようを示すＥＰＭＡ法に基づく金属組織写
真である。FIG. 1 is a photograph of a metallographic structure based on EPMA showing the formation of an effective chromium-enriched layer of B-containing stainless steel.
フロントページの続き (72)発明者 谷内 俊彦 神奈川県川崎市川崎区小島町４番２号 日 本冶金工業株式会社技術研究所内Front page continued (72) Inventor Toshihiko Taniuchi 4-2 Kojima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Nihon Metallurgical Industry Co., Ltd.
Claims (7)
であって、その表層部に厚さ10μｍ以上の有効クロム濃
化層を有することを特徴とする耐酸化性および耐食性に
優れた含ボロンステンレス鋼。1. A stainless steel containing 0.05 to 5.0 wt% of B, which has an effective chromium-concentrating layer having a thickness of 10 μm or more on the surface layer portion thereof, which is excellent in oxidation resistance and corrosion resistance. Boron stainless steel.
であって、その表層部に厚さ10μｍ以上の有効クロム濃
化層を有し、かつその直下には、ボライド〔( Cr, Fe)2
Ｂ〕の生成に伴う、耐酸化性, 耐食性に有効な有効クロ
ムが希釈したマトリックス層を有することを特徴とする
耐酸化性および耐食性に優れた含ボロンステンレス鋼。2. A stainless steel containing 0.05 to 5.0 wt% of B, which has an effective chromium-concentrated layer having a thickness of 10 μm or more on the surface layer thereof, and a boron [(Cr, Fe ) 2
[B] is formed, and a boron-containing stainless steel having excellent oxidation resistance and corrosion resistance is characterized by having a matrix layer in which effective chromium effective for oxidation resistance and corrosion resistance is diluted.
ンレス鋼の成分組成が、 Ｃ：0.15wt％以下、 Si：0.10〜1.0 wt％、Mn：0.10
〜2.00wt％、 Cr：11.0〜27.0wt％、Ni：5.0 〜25.0wt
％、 Ｂ：0.05〜5.0 wt％、およびＮ：0.3 wt％以下を
含有し、 残部がFeおよび不可避的不純物からなるステンレス鋼か
らなることを特徴とする耐酸化性および耐食性に優れた
含ボロンステンレス鋼。3. The composition of the boron-containing stainless steel according to claim 1 or 2, wherein C: 0.15 wt% or less, Si: 0.10 to 1.0 wt%, Mn: 0.10.
~ 2.00wt%, Cr: 11.0 ~ 27.0wt%, Ni: 5.0 ~ 25.0wt
%, B: 0.05 to 5.0 wt%, and N: 0.3 wt% or less, the balance being made of stainless steel consisting of Fe and inevitable impurities. Boron stainless steel having excellent oxidation resistance and corrosion resistance. steel.
ンレス鋼の成分組成が、 Ｃ：0.15wt％以下、 Si：0.10〜1.0 wt％、Mn：0.10
〜2.00wt％、 Cr：11.0〜27.0wt％、Ni：5.0 〜25.0wt
％、 Ｂ：0.7 〜2.0 wt％、Mo：0.1 〜3.0 wt％および
Ｎ：0.3 wt％以下を含有し、 残部がFeおよび不可避的不純物からなるステンレス鋼か
らなることを特徴とする耐酸化性および耐食性に優れた
含ボロンステンレス鋼。4. The composition of the boron-containing stainless steel according to claim 1 or 2, wherein C: 0.15 wt% or less, Si: 0.10 to 1.0 wt%, Mn: 0.10.
~ 2.00wt%, Cr: 11.0 ~ 27.0wt%, Ni: 5.0 ~ 25.0wt
%, B: 0.7 to 2.0 wt%, Mo: 0.1 to 3.0 wt% and N: 0.3 wt% or less, the balance being made of stainless steel consisting of Fe and unavoidable impurities. Boron-containing stainless steel with excellent corrosion resistance.
ンレス鋼の成分組成が、 Ｃ：0.15wt％以下、 Si：0.10〜1.0 wt％、Mn：0.10
〜2.00wt％、 Cr：18.0〜25.0wt％、Ni：5.0 〜12.0wt
％、 Ｂ：0.05〜2.0 wt％、Mo：1.0 〜3.0 wt％および
Ｎ：0.3 wt％以下を含有し、 残部がFeおよび不可避的不純物からなるステンレス鋼か
らなることを特徴とする耐酸化性および耐食性に優れた
含ボロンステンレス鋼。5. The boron-containing stainless steel according to claim 1 or 2, wherein the composition is C: 0.15 wt% or less, Si: 0.10 to 1.0 wt%, Mn: 0.10.
~ 2.00wt%, Cr: 18.0 ~ 25.0wt%, Ni: 5.0 ~ 12.0wt
%, B: 0.05 to 2.0 wt%, Mo: 1.0 to 3.0 wt% and N: 0.3 wt% or less, the balance being made of stainless steel consisting of Fe and unavoidable impurities. Boron-containing stainless steel with excellent corrosion resistance.
ックス中に生成したボライド〔( Cr, Fe)2Ｂ〕中のボロ
ン（Ｂ）が揮発することによってCr量が該マトリックス
層よりも１wt％以上高い表層部である請求項１〜５項の
いずれか１項に記載の含ボロンステンレス鋼。6. The effective chromium enriched layer has a Cr content of 1 wt% than that of the matrix layer due to volatilization of boron (B) in boron [(Cr, Fe) 2 B] formed in the matrix during solidification. The boron-containing stainless steel according to any one of claims 1 to 5, which has a surface layer portion having a high percentage by at least%.
スラブを、酸素分圧 PO2：１％〜21％、加熱温度：800
〜1100℃の範囲内にて30 min〜２hrの加熱保持を行い、
その後、熱間圧延を行うことを特徴とする耐酸化性およ
び耐食性に優れた含ボロンステンレス鋼の製造方法。7. A stainless steel slab containing 0.05 to 5.0 wt% of B, oxygen partial pressure PO 2 : 1% to 21%, heating temperature: 800
Heat and hold for 30 min to 2 hr within the range of ~ 1100 ℃,
Then, a method for producing boron-containing stainless steel having excellent oxidation resistance and corrosion resistance, which is characterized by hot rolling.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07146695A JP3636500B2 (en) | 1995-03-29 | 1995-03-29 | Boron-containing stainless steel slab with excellent oxidation and corrosion resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07146695A JP3636500B2 (en) | 1995-03-29 | 1995-03-29 | Boron-containing stainless steel slab with excellent oxidation and corrosion resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08269646A true JPH08269646A (en) | 1996-10-15 |
| JP3636500B2 JP3636500B2 (en) | 2005-04-06 |
Family
ID=13461408
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP07146695A Expired - Fee Related JP3636500B2 (en) | 1995-03-29 | 1995-03-29 | Boron-containing stainless steel slab with excellent oxidation and corrosion resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3636500B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19937255B4 (en) * | 1999-08-06 | 2004-05-06 | Ballard Power Systems Inc., Burnaby | Corrosion resistant bipolar plate for PEM fuel cells and use |
| US10991954B2 (en) | 2015-12-23 | 2021-04-27 | Posco | Stainless steel for polymer fuel cell separation plate having improved hydrophilicity and contact resistance and method for manufacturing same |
| US11923580B2 (en) | 2015-09-22 | 2024-03-05 | Posco Co., Ltd | Stainless steel for fuel cell separator plate and manufacturing method therefor |
-
1995
- 1995-03-29 JP JP07146695A patent/JP3636500B2/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19937255B4 (en) * | 1999-08-06 | 2004-05-06 | Ballard Power Systems Inc., Burnaby | Corrosion resistant bipolar plate for PEM fuel cells and use |
| US11923580B2 (en) | 2015-09-22 | 2024-03-05 | Posco Co., Ltd | Stainless steel for fuel cell separator plate and manufacturing method therefor |
| US10991954B2 (en) | 2015-12-23 | 2021-04-27 | Posco | Stainless steel for polymer fuel cell separation plate having improved hydrophilicity and contact resistance and method for manufacturing same |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3636500B2 (en) | 2005-04-06 |
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