JP2014181383A - High corrosion resistance high strength stainless steel, structure in atomic furnace and manufacturing method of high corrosion resistance high strength stainless steel - Google Patents
High corrosion resistance high strength stainless steel, structure in atomic furnace and manufacturing method of high corrosion resistance high strength stainless steel Download PDFInfo
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Description
本発明は、照射誘起応力腐食割れ等の発生感受性を低減した高耐食性高強度ステンレス鋼と、それを利用した原子炉内構造物、ならびに高耐食性高強度ステンレス鋼の製造方法に関する。 The present invention relates to a high-corrosion-resistant high-strength stainless steel with reduced susceptibility to radiation-induced stress corrosion cracking, a reactor internal structure using the same, and a method for producing a high-corrosion-resistant high-strength stainless steel.
原子炉の内部のように高度の放射線照射を受ける環境中において使用するためのオーステナイト系ステンレス鋼の合金組成物の一例として、特許文献1に記載されたものがある。
この特許文献1に記載の技術は、タイプ304オーステナイト系ステンレス鋼の改良を成すものであって、かかる標準のオーステナイト系ステンレス鋼の特定成分に一定の制限を加えると共に正確な比率の追加合金成分を含有させて成るような特定の合金組成物に関する。具体的には、約18〜20重量%のCr、約9〜11重量%のNi、約1.5〜2重量%のMn、並びに残部のFeおよび偶発不純物から成っている。タイプ304のオーステナイトステンレス鋼に準じるためであるかかる合金組成物の炭素含量は約0.02〜約0.04重量%に制限される。また、NbおよびTaの合計量は炭素含量の最低14倍に相当すると共に、合金組成物全体の最高約0.65重量%までに制限される。更に、Nbの含量は合金組成物全体の約0.25重量%以下に制限され、Taの含量は合金組成物全体の約0.4重量%までの値を取り得るものとなっている。
As an example of an alloy composition of austenitic stainless steel for use in an environment that receives a high level of radiation irradiation such as the inside of a nuclear reactor, there is one described in Patent Document 1.
The technique described in Patent Document 1 is an improvement of type 304 austenitic stainless steel, which adds certain restrictions to the specific components of such standard austenitic stainless steel and provides additional alloy components in the correct proportions. The present invention relates to a specific alloy composition. Specifically, it consists of about 18-20% by weight Cr, about 9-11% by weight Ni, about 1.5-2% by weight Mn, and the balance Fe and incidental impurities. The carbon content of such alloy compositions, which is to comply with Type 304 austenitic stainless steel, is limited to about 0.02 to about 0.04 weight percent. Also, the total amount of Nb and Ta corresponds to a minimum of 14 times the carbon content and is limited to a maximum of about 0.65% by weight of the total alloy composition. Further, the Nb content is limited to about 0.25% by weight or less of the entire alloy composition, and the Ta content can take a value up to about 0.4% by weight of the entire alloy composition.
一般に、オーステナイト系ステンレス鋼は耐食性に優れた材料である。しかし、原子力発電プラントの原子炉炉内、例えば軽水炉での炉心で高温高圧水および中性子照射環境におかれると、照射誘起応力腐食割れの発生感受性が高まることが指摘されている。また、原子力プラントの高経年化に応じて、より強度の高い構造材料が要求されている。
また、溶接熱による鋭敏化を抑制するために、含有する炭素量を低減したSUS316LやSUS304Lの低炭素オーステナイト系ステンレス鋼が使用されている。しかし、近年、中性子照射量の高い環境で使用される制御棒のSUS316L製シースやタイロッドでは、照射誘起によると考えられる応力腐食割れが確認されている。これは、材料が中性子照射を受けることによる硬化や照射誘起粒界偏析が原因と考えられており、中性子照射損傷の抑制が必要である。
In general, austenitic stainless steel is a material excellent in corrosion resistance. However, it has been pointed out that the susceptibility to irradiation-induced stress corrosion cracking increases when exposed to high-temperature high-pressure water and neutron irradiation environments in a nuclear reactor nuclear reactor, for example, a core of a light water reactor. In addition, with the aging of nuclear power plants, structural materials with higher strength are required.
In order to suppress sensitization by welding heat, SUS316L or SUS304L low carbon austenitic stainless steel with a reduced carbon content is used. However, in recent years, stress corrosion cracking, which is considered to be due to irradiation induction, has been confirmed in SUS316L sheaths and tie rods of control rods used in environments with high neutron irradiation. This is considered to be caused by hardening or irradiation-induced grain boundary segregation due to neutron irradiation of the material, and neutron irradiation damage must be suppressed.
上述の特許文献1に記載の技術では、NbおよびTaの添加により溶体化熱処理後でもNbおよびTaが炭素を安定化して、応力腐食割れや照射誘起応力腐食割れを抑制すること、およびNb添加量を少なくしてTa添加量を多くすることで、中性子吸収により生成する長半減期のNb94に代わり短半減期のTa182として取扱を容易にする効果がある、としている。
しかし、特許文献1に記載のステンレス鋼では、制御棒を始めとした原子炉内構造物として要求される耐食性と強度特性を満足できない可能性がある。
In the technique described in Patent Document 1 described above, Nb and Ta stabilize carbon even after solution heat treatment by adding Nb and Ta, thereby suppressing stress corrosion cracking and irradiation-induced stress corrosion cracking, and the amount of Nb added By reducing the amount of Ta and increasing the amount of Ta added, it is said that it has the effect of facilitating handling as a short half-life Ta182 instead of the long half-life Nb94 generated by neutron absorption.
However, the stainless steel described in Patent Document 1 may not be able to satisfy the corrosion resistance and strength characteristics required for a reactor internal structure such as a control rod.
本発明は、中性子照射環境に曝される環境において、応力腐食割れ、照射誘起応力腐食割れ、すき間腐食などが発生することが抑制された高耐食性高強度ステンレス鋼とそれを利用した原子炉内構造物ならびに高耐食性高強度ステンレス鋼の製造方法を提供する。 The present invention relates to a high corrosion resistance high strength stainless steel in which the occurrence of stress corrosion cracking, irradiation induced stress corrosion cracking, crevice corrosion, etc. is suppressed in an environment exposed to a neutron irradiation environment, and a reactor internal structure using the same Provided is a method for producing a high-strength stainless steel with high corrosion resistance.
上記課題を解決するために、例えば特許請求の範囲に記載の構成を採用する。
本発明は、上記課題を解決する手段を複数含んでいるが、その一例を挙げるならば、C:0.04質量%以下,Mn:1.0〜2.0質量%,Ni:9.0〜13.0質量%,Cr:17.0〜20.0質量%,Ta:Cの13倍以上で0.50〜0.65質量%を含有し、残部がFeおよびNbを含む不可避不純物からなる化学組成で、JISG0551で規定されるオーステナイト平均結晶粒度番号が10.0〜13.0である、ことを特徴とする。
In order to solve the above problems, for example, the configuration described in the claims is adopted.
The present invention includes a plurality of means for solving the above-mentioned problems. For example, C: 0.04% by mass or less, Mn: 1.0 to 2.0% by mass, Ni: 9.0 -13.0% by mass, Cr: 17.0-20.0% by mass, Ta:
本発明によれば、中性子照射環境に曝される環境において、応力腐食割れ、照射誘起応力腐食割れ、すき間腐食などが発生することが抑制された高耐食性高強度ステンレス鋼を提供することができる。そして、このような本発明の高耐食性高強度ステンレス鋼の照射誘起応力腐食割れの発生感受性の低減、かつ微細結晶組織による高強度との材料特性を生かして、0.1MeV以上のエネルギーを持つ中性子が0.5×1021n/cm2以上照射されるような過酷な環境で使用される原子炉炉内構成機器あるいは構造物に適用することにより、原子力プラントの信頼性を向上させ、長寿命化することができる。 According to the present invention, it is possible to provide a high-corrosion-resistant high-strength stainless steel in which occurrence of stress corrosion cracking, irradiation-induced stress corrosion cracking, crevice corrosion, and the like is suppressed in an environment exposed to a neutron irradiation environment. And, by taking advantage of the material characteristics of such high corrosion resistance high strength stainless steel of the present invention, the reduction in the susceptibility to irradiation-induced stress corrosion cracking, and the high strength due to the fine crystal structure, neutrons having energy of 0.1 MeV or more Is applied to nuclear reactor components or structures that are used in harsh environments that are irradiated by 0.5 × 10 21 n / cm 2 or more, improving the reliability of nuclear power plants and extending the service life Can be
本発明の高耐食性高強度ステンレス鋼および原子炉内構造物ならびに高耐食性高強度ステンレス鋼の製造方法の実施形態を、図1乃至図12を用いて説明する。
図1は本発明の高耐食性高強度ステンレス鋼の製造方法の実施例1の比較のための冷間圧延率と結晶粒径との相関を示す図、図2は本発明の高耐食性高強度ステンレス鋼の製造方法の実施例1における冷間圧延率と結晶粒径との相関を示す図、図3は本発明の高耐食性高強度ステンレス鋼の製造方法の実施例1における冷間圧延率と結晶粒径との相関を示す図、図4は本発明の高耐食性高強度ステンレス鋼の製造方法の実施例1における冷間圧延率と結晶粒径との相関を示す図、図5は本発明の高耐食性高強度ステンレス鋼の製造方法の実施例2における平均結晶粒度番号と時効熱処理時間との相関を示す図、図6は本発明の高耐食性高強度ステンレス鋼の製造方法の実施例2における平均結晶粒度番号と時効熱処理温度との相関を示す図、図7は本発明の高耐食性高強度ステンレス鋼の製造方法の実施例3における本発明の材料および比較材の100℃における0.2%耐力を示す図、図8は本発明の高耐食性高強度ステンレス鋼の製造方法の実施例3における本発明の材料および比較材の100℃における引張強さを示す図、図9は実施例3におけるすき間腐食試験における試験片の概要の側面図および上面図、図10は本発明の高耐食性高強度ステンレス鋼の製造方法の実施例3における本発明の材料および比較材のすき間腐食による最大粒界腐食深さを比較した図、図11は本発明の高耐食性高強度ステンレス鋼の製造方法の実施例3における本発明の材料と比較材のすき間腐食による粒界腐食箇所数を比較した図、図12は本発明の高耐食性高強度ステンレス鋼を適用した制御棒の斜視図である。
Embodiments of the high corrosion resistance high strength stainless steel and the reactor internal structure and the high corrosion resistance high strength stainless steel manufacturing method of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing the correlation between the cold rolling rate and the crystal grain size for comparison with Example 1 of the production method of the high corrosion resistance high strength stainless steel of the present invention, and FIG. 2 is the high corrosion resistance high strength stainless steel of the present invention. FIG. 3 is a diagram showing the correlation between the cold rolling rate and crystal grain size in Example 1 of the steel production method, and FIG. 3 is a diagram showing the cold rolling rate and crystal in Example 1 of the production method of the high corrosion resistance high strength stainless steel of the present invention. FIG. 4 is a diagram showing the correlation with the grain size, FIG. 4 is a diagram showing the correlation between the cold rolling rate and the crystal grain size in Example 1 of the production method of the high corrosion resistance high strength stainless steel of the present invention, and FIG. FIG. 6 is a diagram showing the correlation between the average grain size number and the aging heat treatment time in Example 2 of the method for producing high corrosion resistance high strength stainless steel, FIG. 6 shows the average in Example 2 of the method for producing high corrosion resistance high strength stainless steel of the present invention. Figure showing the correlation between grain size number and aging heat treatment temperature, 7 is a diagram showing the 0.2% proof stress at 100 ° C. of the material of the present invention and the comparative material in Example 3 of the production method of the high corrosion resistance high strength stainless steel of the present invention, and FIG. 8 is the high corrosion resistance high strength stainless steel of the present invention. The figure which shows the tensile strength at 100 degrees C of the material of this invention and the comparative material in Example 3 of the manufacturing method of steel, FIG. 9 is the side view and top view of the outline | summary of the test piece in the crevice corrosion test in Example 3, FIG. 10 is a diagram comparing the maximum intergranular corrosion depth due to crevice corrosion of the material of the present invention and the comparative material in Example 3 of the production method of the high corrosion resistance high strength stainless steel of the present invention, and FIG. 11 is a diagram showing the high corrosion resistance of the present invention. FIG. 12 is a diagram comparing the number of intergranular corrosion sites due to crevice corrosion between the material of the present invention and the comparative material in Example 3 of the method for producing high-strength stainless steel. FIG. It is a perspective view of a control rod.
本発明に係る高耐食性高強度ステンレス鋼は、オーステナイト系ステンレス鋼であり、Cが0.04質量%以下、Mnが1.0〜2.0質量%、Niが9.0〜13.0質量%、Crが17.0〜20.0質量%、TaがCの13倍以上でかつ0.50〜0.65質量%、残部がFeと、Nbを含む不可避不純物からなる化学組成となっているものである。
また、本発明に係る高耐食性高強度ステンレス鋼は、JIS G 0551で規定されるオーステナイト平均結晶粒度番号が10.0〜13.0の範囲にあるステンレス鋼である。
The high corrosion resistance high strength stainless steel according to the present invention is an austenitic stainless steel, C is 0.04% by mass or less, Mn is 1.0 to 2.0% by mass, and Ni is 9.0 to 13.0% by mass. %, Cr is 17.0 to 20.0 mass%, Ta is 13 times or more of C and 0.50 to 0.65 mass%, and the balance is Fe and an inevitable impurity containing Nb. It is what.
Moreover, the high corrosion resistance high-strength stainless steel according to the present invention is a stainless steel having an austenite average grain size number defined by JIS G 0551 in the range of 10.0 to 13.0.
以下、本発明にかかる高耐食性高強度ステンレス鋼の各物性値について説明する。 Hereinafter, each physical property value of the high corrosion resistance high strength stainless steel according to the present invention will be described.
1.化学成分について
本発明にかかる高耐食性高強度ステンレス鋼では、Cは、強度を得るために有効な元素である。一方、Cの含有量が0.04質量%を超えると、溶接熱影響部の粒界に炭化物が生成しやすく、耐応力腐食割れ性が低下する。したがって、C含有量の上限を0.04質量%とする。
1. About chemical components
In the high corrosion resistance high strength stainless steel according to the present invention, C is an element effective for obtaining strength. On the other hand, if the C content exceeds 0.04 mass%, carbides are likely to be generated at the grain boundaries of the weld heat affected zone, and the stress corrosion cracking resistance is reduced. Therefore, the upper limit of the C content is 0.04% by mass.
本発明にかかる高耐食性高強度ステンレス鋼において、Mnの含有量は、材料の靭性を与えるために1.0〜2.0質量%とする。 In the high corrosion resistance high strength stainless steel according to the present invention, the Mn content is set to 1.0 to 2.0% by mass in order to give toughness of the material.
本発明にかかる高耐食性高強度ステンレス鋼において、Niは、鋼の耐食性を維持するために必要な元素である。また、オーステナイトの安定化元素として、9.0質量%以上の含有量が必要である。一方、その含有量が13.0質量%を超えると、熱間加工性が著しく悪化する。したがって、Niの含有量は9.0〜13.0質量%とする。 In the high corrosion resistance high strength stainless steel according to the present invention, Ni is an element necessary for maintaining the corrosion resistance of the steel. Further, a content of 9.0% by mass or more is necessary as a stabilizing element for austenite. On the other hand, when the content exceeds 13.0% by mass, the hot workability is remarkably deteriorated. Therefore, the Ni content is 9.0 to 13.0 mass%.
本発明にかかる高耐食性高強度ステンレス鋼において、Crは、鋼の耐食性を維持するために必要な元素である。耐食性を確保するために、その含有量を17.0質量%以上確保する必要がある。一方、その含有量が20.0質量%を超えると、材料が脆化されやすくなり、かつ材料コストも著しく上昇する。したがって、Crの含有量は17.0〜20.0質量%とする。 In the high corrosion resistance high strength stainless steel according to the present invention, Cr is an element necessary for maintaining the corrosion resistance of the steel. In order to ensure corrosion resistance, it is necessary to secure the content of 17.0% by mass or more. On the other hand, when the content exceeds 20.0 mass%, the material is easily embrittled and the material cost is significantly increased. Therefore, the Cr content is 17.0 to 20.0 mass%.
本発明にかかる高耐食性高強度ステンレス鋼において、Taは、材料構成元素の平均原子半径に比べ原子半径が大きいため、材料中に固溶している場合に照射によって生成された原子空孔を捕獲し、格子間原子との再結合確率を上昇させて照射損傷を抑制することができる。
ここで、原子空孔が拡散により結晶粒界へ流入する場合、粒界近傍のCr原子が粒界から離れる方向に拡散し、粒界近傍でのCr濃度がマトリックスのCr濃度より低下する、いわゆるCr欠乏を生じる。しかし、Taが原子空孔を捕獲する場合は、原子空孔の粒界への拡散が抑制され、粒界Cr欠乏が抑制されることになる。一方、TaがTaCとして存在する場合も、TaCとマトリックスの界面が原子空孔の消滅サイトとなるため、Taが固溶した場合と同様に、粒界Cr欠乏を抑制することができる。このようにTaの存在は、単独で固溶している場合も、TaCとして存在している場合でも、照射誘起による粒界Cr欠乏を抑制することができ、照射誘起応力腐食割れの抑制に効果があると考えられる。ただし、Cが必要以上にマトリックス中に存在する場合、溶接熱を受けた場所では、粒界上にCr炭化物を形成してCr欠乏を生じる、いわゆる熱鋭敏化を生じ、応力腐食割れ感受性が高まる。そのため、固溶しているC濃度を低減するために、TaCを形成する必要がある。
上述の原理を踏まえて、TaはC含有量の13倍含み、かつ0.50質量%以上が必要である。また、溶接性などの特性劣化を鑑み、上限を0.65質量%とする。
更に、TaがCを安定化した場合、全Ta量のうち30%以上がTaCとして析出していると、耐応力腐食割れ性の効果が期待される。また、析出し分散するTaCは強度的には析出硬化として作用し、強度向上に寄与するため、全Ta量のうち30%以上がTaCとして析出していることが望ましい。なお、TaCとして析出しているTa量の評価は、定電流電解法により採取した電解抽出残渣を定量分析することにより測定することができる。
In the high corrosion resistance high strength stainless steel according to the present invention, Ta captures atomic vacancies generated by irradiation when dissolved in the material because Ta has a larger atomic radius than the average atomic radius of the constituent elements. In addition, irradiation damage can be suppressed by increasing the recombination probability with interstitial atoms.
Here, when atomic vacancies flow into the crystal grain boundary by diffusion, Cr atoms near the grain boundary diffuse in a direction away from the grain boundary, and the Cr concentration in the vicinity of the grain boundary is lower than the Cr concentration in the matrix. Causes Cr deficiency. However, when Ta captures atomic vacancies, diffusion of atomic vacancies into grain boundaries is suppressed, and grain boundary Cr deficiency is suppressed. On the other hand, when Ta is present as TaC, the interface between TaC and the matrix becomes an atomic vacancy annihilation site, so that grain boundary Cr deficiency can be suppressed as in the case where Ta is dissolved. Thus, the presence of Ta can suppress irradiation-induced grain boundary Cr deficiency, whether it is dissolved alone or as TaC, and is effective in suppressing irradiation-induced stress corrosion cracking. It is thought that there is. However, when C is present in the matrix more than necessary, in a place where welding heat is applied, so-called thermal sensitization occurs, which forms Cr carbide on the grain boundary and causes Cr deficiency, and stress corrosion cracking susceptibility increases. . Therefore, it is necessary to form TaC in order to reduce the concentration of dissolved C.
Based on the above principle, Ta needs to be 13 times the C content and 0.50% by mass or more. In view of deterioration in characteristics such as weldability, the upper limit is set to 0.65% by mass.
Further, when Ta stabilizes C, if 30% or more of the total amount of Ta is precipitated as TaC, an effect of stress corrosion cracking resistance is expected. In addition, since the precipitated and dispersed TaC acts as precipitation hardening in terms of strength and contributes to strength improvement, it is desirable that 30% or more of the total amount of Ta is precipitated as TaC. The amount of Ta deposited as TaC can be measured by quantitatively analyzing the electrolytic extraction residue collected by the constant current electrolysis method.
更に、Nbについては、中性子吸収により生成する長半減期のNb94が生成され、取扱いに問題が生じることから、不可避不純物として含まれる程度に抑制する。 Furthermore, Nb 94 having a long half-life produced by neutron absorption is produced and Nb94 is problematic in handling, so Nb is suppressed to the extent that it is included as an inevitable impurity.
2.平均結晶粒度番号について
さらに、本発明にかかる高耐食性高強度ステンレス鋼においては、原子炉炉内を構成する材料として、100℃での引張強度が470MPa以上であることが望ましい。
この強度要求を達成するためには、JIS G 0551で規定されるオーステナイト平均結晶粒度番号が、10.0以上の微細な結晶組織を形成させる必要がある。ただし、結晶粒の成長を抑えすぎると不均一な混粒組織になりやすいため、製法上、平均結晶粒度番号13.0以下が現実的である。
2. About average grain size number
Furthermore, in the high corrosion resistance high strength stainless steel according to the present invention, it is desirable that the tensile strength at 100 ° C. is 470 MPa or more as a material constituting the reactor.
In order to achieve this strength requirement, it is necessary to form a fine crystal structure having an austenite average grain size number defined by JIS G 0551 of 10.0 or more. However, if the growth of crystal grains is suppressed too much, a non-uniform mixed grain structure tends to be formed. Therefore, an average crystal grain size number of 13.0 or less is realistic in terms of manufacturing method.
以下、このような平均結晶粒度番号10.0〜13.0の微細な結晶組織を形成させるための高耐食性高強度ステンレス鋼の製造方法について説明する。 Hereinafter, a method for producing a high-corrosion-resistant high-strength stainless steel for forming such a fine crystal structure having an average grain size number of 10.0 to 13.0 will be described.
まず、Cが0.04質量%以下,Mnが1.0〜2.0質量%,Niが9.0〜13.0質量%,Crが17.0〜20.0質量%,TaがCの13倍以上で0.50〜0.65質量%を含有し、残部がFeと、Nbを含む不可避不純物からなる化学組成のオーステナイト系ステンレス鋼を用意する。 First, C is 0.04 mass% or less, Mn is 1.0 to 2.0 mass%, Ni is 9.0 to 13.0 mass%, Cr is 17.0 to 20.0 mass%, Ta is C An austenitic stainless steel having a chemical composition comprising 0.50 to 0.65% by mass at 13 times or more, the balance being Fe and inevitable impurities including Nb is prepared.
次いで、準備したオーステナイト系ステンレス鋼に対して、1050℃〜1150℃で1分〜60分の溶体化熱処理を施し、その後水冷する。
ステンレス鋼中に均質な固溶体組織を得るためには、1050℃〜1150℃の温度で溶体化熱処理が必要である。また、材料の板厚により条件の調整が必要ではあるが、1分〜60分の溶体化熱処理を行うことが適切である。
Next, the prepared austenitic stainless steel is subjected to solution heat treatment at 1050 ° C. to 1150 ° C. for 1 minute to 60 minutes, and then water-cooled.
In order to obtain a homogeneous solid solution structure in stainless steel, solution heat treatment is required at a temperature of 1050 ° C to 1150 ° C. Further, although it is necessary to adjust the conditions depending on the thickness of the material, it is appropriate to perform solution heat treatment for 1 minute to 60 minutes.
この溶体化熱処理後のステンレス鋼に、圧延率30%〜80%の冷間圧延を実施する。
オーステナイト系ステンレス鋼の平均結晶粒度番号は、一般的に10.0未満である。そこで、平均結晶粒度番号10.0以上の微細結晶を形成させるためには、まず、溶体化熱処理後の元材料の結晶粒内に、再結晶の核生成サイトを増やすために冷間加工で加工転位を導入して大きな塑性変形を起こさせることが必要である。ただし、圧延率が大き過ぎると、施工効率が低下する。一方、圧延率が低い場合は、その後の時効熱処理では、再結晶となるサイトが不十分のため、転位の回復が抑えられるのと、導入した加工転位を駆動力に結晶粒の粗大化を引き起こすことが懸念される。以上の諸要因を考慮して、圧延率30%〜80%の冷間圧延率とする。
Cold rolling with a rolling rate of 30% to 80% is performed on the stainless steel after the solution heat treatment.
The average grain size number of austenitic stainless steel is generally less than 10.0. Therefore, in order to form fine crystals with an average grain size number of 10.0 or more, first, cold processing is performed to increase the number of recrystallization nucleation sites in the crystal grains of the original material after solution heat treatment. It is necessary to introduce dislocations to cause large plastic deformation. However, if the rolling rate is too large, the construction efficiency decreases. On the other hand, when the rolling rate is low, the subsequent aging heat treatment has insufficient sites for recrystallization, so that the recovery of dislocations can be suppressed, and the coarsening of the grains is caused by the introduced processing dislocations as the driving force. There is concern. Considering the above factors, the cold rolling rate is 30% to 80%.
次いで、この冷間圧延後に、850℃〜1050℃で30分〜120分の時効熱処理を実施し、空冷する。
先の冷間圧延によって生成した転位を回復により消滅させて、再結晶化を促すために、850℃〜1000℃で30分〜120分の時効熱処理を行い、空冷することが必要である。
また、この時効熱処理には、TaCの析出を安定化させる役割もある。
Next, after this cold rolling, an aging heat treatment is performed at 850 ° C. to 1050 ° C. for 30 minutes to 120 minutes, and air cooling is performed.
In order to eliminate the dislocations generated by the previous cold rolling by recovery and promote recrystallization, it is necessary to perform an aging heat treatment at 850 ° C. to 1000 ° C. for 30 minutes to 120 minutes and air-cool.
The aging heat treatment also has a role of stabilizing the precipitation of TaC.
以下、実施例1〜4を参照して、本発明のステンレス鋼が良好な特性を有する材料であることを、具体例を示して説明する。 Hereinafter, with reference to Examples 1-4, it demonstrates that a stainless steel of this invention is a material which has a favorable characteristic, showing a specific example.
(実施例1および比較例1)
まず、表1に示す化学組成(質量%)をもつ供試材を真空溶解で作製した。
No.1〜4の材料は、いずれも熱間圧延の後、1050℃で30分および水冷の溶体化熱処理を施した。
また、Taの含有量の影響を検討するため、Ta含有量が0.65質量%以上のNo.5,No.6の2種類の試作材(比較材)を作製して、No.1〜No.4の材料と同様の条件で溶体化熱処理を施した。
No.10は比較材として用意された市販のSUS316Lであり、No.11は比較材としてのSUS304Lである。
(Example 1 and Comparative Example 1)
First, specimens having the chemical composition (mass%) shown in Table 1 were prepared by vacuum melting.
No. All the materials 1 to 4 were subjected to solution heat treatment at 1050 ° C. for 30 minutes and water cooling after hot rolling.
Further, in order to examine the influence of the Ta content, a No. 1 content of Ta of 0.65% by mass or more was used. 5, no. No. 6 two types of prototype materials (comparative materials) were prepared. 1-No. Solution heat treatment was performed under the same conditions as in the material No. 4.
No. 10 is a commercially available SUS316L prepared as a comparative material. 11 is SUS304L as a comparative material.
冷間圧延率の適切な範囲を検討するため、No.1の材料から数個の板材試験片を作製し、それぞれ溶体化熱処理を行った。
その後、圧延率25%,35%,50%,75%の冷間圧延を施した後に、950℃の温度で120分の時効熱処理を実施した。時効熱処理後に、電子線後方散乱回折法(Electron BackScatter Diffraction:以下EBSDと記載)によって結晶粒径の分布を測定した。圧延率25%における測定結果を図1に,圧延率35%における測定結果を図2に,圧延率50%における測定結果を図3に,圧延率75%における測定結果を図4に示す。
EBSD測定は、日立ハイテックノロジー社製のFE−SEM(S−4300SE)に装着したTSL社製の方位顕微鏡(OIM)を用いて行った。測定領域は1×1mm、測定step=2μmとした。図1〜図4中の横軸は結晶粒径で、縦軸は合計結晶数に占める割合、即ち粒径の頻度である。各試験片の結晶粒径に対応する結晶粒度番号の分布範囲および平均結晶粒度番号を演算した。
また、平均結晶粒度番号Gは、JIS G 0551の定義により、次式(1)で表される。式(1)において、mは断面積1mm2当たりの結晶の数である。
In order to examine the appropriate range of the cold rolling rate, No. Several plate material test pieces were prepared from one material, and each was subjected to solution heat treatment.
Then, after performing cold rolling with a rolling rate of 25%, 35%, 50%, and 75%, aging heat treatment was performed at a temperature of 950 ° C. for 120 minutes. After the aging heat treatment, the crystal grain size distribution was measured by an electron backscatter diffraction method (hereinafter referred to as EBSD). FIG. 1 shows the measurement result at a rolling rate of 25%, FIG. 2 shows the measurement result at a rolling rate of 35%, FIG. 3 shows the measurement result at a rolling rate of 50%, and FIG. 4 shows the measurement result at a rolling rate of 75%.
The EBSD measurement was performed using an orientation microscope (OIM) manufactured by TSL, which was attached to an FE-SEM (S-4300SE) manufactured by Hitachi High-Technology. The measurement area was 1 × 1 mm and measurement step = 2 μm. 1 to 4, the horizontal axis is the crystal grain size, and the vertical axis is the ratio of the total number of crystals, that is, the frequency of the grain size. The distribution range of the crystal grain size number corresponding to the crystal grain size of each test piece and the average crystal grain size number were calculated.
The average grain size number G is represented by the following formula (1) according to the definition of JIS G 0551. In the formula (1), m is the number of crystals per 1 mm 2 cross-sectional area.
従って、結晶粒径をdとすると、次式(2)よりmを表すことができる。dの単位はμmである。つまり、結晶粒径dが小さいほど、平均結晶粒度番号Gが大きいことになる。 Therefore, when the crystal grain size is d, m can be expressed by the following formula (2). The unit of d is μm. That is, the smaller the crystal grain size d, the larger the average crystal grain size number G.
以上の計算式(1),(2)に基づき、JIS G 0551の方法に従って平均結晶粒度番号を計算した。表2に、各圧延率下での結晶粒径および平均結晶粒度番号をまとめて示す。 Based on the above formulas (1) and (2), the average grain size number was calculated according to the method of JIS G 0551. Table 2 summarizes the crystal grain size and the average grain size number under each rolling rate.
図1および表2に示すように、圧延率25%の試験片の結晶粒径は2.5μm〜80μmの広い範囲に分布しており、組織の均一性が低いことがわかった。これは、圧延が不十分で、転位サイトにより不均一な再結晶が生じたためと考えられる。
一方、図2〜図4および表2に示す圧延率35%,50%,75%での試験片の結晶粒径は、全体的に0.5μm〜30μmの小さい範囲に分布しており、良い組織の均一性が現れていることがわかった。
以上の平均結晶粒度番号の結果から、10.0〜13.0の平均結晶粒度番号のステンレス鋼を得るためには、30%以上の圧延率が必要と考えられる。また、実際の製造効率や図2〜図4に示した結晶粒径の分布状態を考慮すると、圧延率を80%以下にした方が良い操作性が期待されるとともに、微細結晶が得られる効率を高く維持することができることがわかった。
As shown in FIG. 1 and Table 2, the crystal grain size of the test piece having a rolling rate of 25% was distributed in a wide range of 2.5 μm to 80 μm, and it was found that the uniformity of the structure was low. This is presumably because rolling was insufficient and non-uniform recrystallization occurred due to dislocation sites.
On the other hand, the crystal grain sizes of the test pieces at the rolling rates of 35%, 50%, and 75% shown in FIGS. 2 to 4 and Table 2 are distributed over a small range of 0.5 μm to 30 μm as a whole. It was found that tissue uniformity appeared.
From the result of the above average grain size number, in order to obtain stainless steel having an average grain size number of 10.0 to 13.0, it is considered that a rolling rate of 30% or more is necessary. Considering the actual production efficiency and the distribution of crystal grain size shown in FIGS. 2 to 4, it is expected that the operability is better when the rolling rate is 80% or less, and the efficiency with which fine crystals are obtained. Can be maintained high.
以上の結果に基づき、冷間圧延の最適施工範囲は圧延率30%〜80%であることがわかった。 Based on the above results, it was found that the optimum construction range for cold rolling was a rolling rate of 30% to 80%.
(実施例2および比較例2)
更に、実施例1の表1における本発明材のNo.3の材料から数個の板材試験片を製作し、溶体化熱処理後50%の冷間圧延を施した。その後、900℃および1000℃の温度で固定して、10分〜150分と時間を変化させた時効熱処理を実施した。時効熱処理後の冷却は空冷とした。その後、各試験片の平均結晶粒度番号を測定した。図5に50%の冷間圧延後、900℃で10分〜150分の時効熱処理における平均結晶粒度番号の変化を示す。比較のために、溶体化熱処理のみを施し時効熱処理を施さなかったNo.1の平均結晶粒度番号を測定した。その結果を、図5中の熱処理時間0分のプロットで表す。
(Example 2 and Comparative Example 2)
Furthermore, in Table 1 of Example 1, the No. of the material of the present invention. Several plate specimens were produced from the three materials, and 50% cold-rolled after solution heat treatment. Then, it fixed at the temperature of 900 degreeC and 1000 degreeC, and implemented the aging heat processing which changed time from 10 minutes to 150 minutes. Cooling after aging heat treatment was air cooling. Thereafter, the average grain size number of each test piece was measured. FIG. 5 shows the change in the average grain size number in the aging heat treatment at 900 ° C. for 10 minutes to 150 minutes after 50% cold rolling. For comparison, No. 1 was subjected only to solution heat treatment and not subjected to aging heat treatment. An average grain size number of 1 was measured. The result is represented by a plot of the heat treatment time of 0 minutes in FIG.
図5に示すように、時効熱処理時間が10分〜30分の間では、熱処理時間の増加につれて、平均結晶粒度番号が上昇するという傾向が見られた。これは、30分以下の短時間熱処理では、再結晶がまだ完全に完了しておらず、微細結晶と元材料の粗大結晶と混在して、不均一な微細組織となっているためであると考えられる。
一方、時効熱処理時間が30分〜120分の間では、平均結晶粒度番号がほぼ12.5と一定で、安定な微細組織が得られることがわかった。
しかし、時効熱処理時間が120分〜150分の間では、時効熱処理により結晶粒の成長が加速され、平均結晶粒度番号が10.0より小さくなり、低下する傾向が表れた。
As shown in FIG. 5, when the aging heat treatment time was between 10 minutes and 30 minutes, the average crystal grain size number tended to increase as the heat treatment time increased. This is because recrystallization has not been completely completed in a short-time heat treatment of 30 minutes or less, and a fine crystal and a coarse crystal of the original material are mixed to form a non-uniform microstructure. Conceivable.
On the other hand, it was found that when the aging heat treatment time was between 30 minutes and 120 minutes, the average grain size number was constant at approximately 12.5 and a stable microstructure was obtained.
However, when the aging heat treatment time was between 120 minutes and 150 minutes, the growth of crystal grains was accelerated by the aging heat treatment, and the average grain size number became smaller than 10.0, and a tendency to decrease was exhibited.
また、図5に示すように、1000℃の熱処理では、平均結晶粒度番号は900℃より低い傾向となったが、熱処理時間が30分〜120分の間であれば、10.0以上の平均結晶粒度番号を維持できていることがわかった。 Further, as shown in FIG. 5, in the heat treatment at 1000 ° C., the average grain size number tended to be lower than 900 ° C., but if the heat treatment time was between 30 minutes and 120 minutes, the average of 10.0 or more It was found that the grain size number could be maintained.
以上の結果から、冷間圧延後に、900℃付近の温度で30分〜120分の時効熱処理を行った後に空冷することにより、平均結晶粒度番号が10.0〜13.0で、かつ均一的な微細結晶組織を有するオーステナイト系の高耐食性高強度ステンレス鋼を作製できることがわかった。 From the above results, the average grain size number is 10.0 to 13.0 and uniform by performing air-cooling after performing aging heat treatment at a temperature near 900 ° C. for 30 minutes to 120 minutes after cold rolling. It was found that an austenitic high corrosion resistance high strength stainless steel having a fine crystal structure can be produced.
(実施例3および比較例3)
実施例1の表1における本発明材のNo.1の材料において、溶体化熱処理後に50%の冷間圧延を施し、さらにそれぞれ850℃〜1050℃の温度で120分と空冷の時効熱処理を実施した。図6に各温度での平均結晶粒度番号を示す。
(Example 3 and Comparative Example 3)
No. 1 of the present invention material in Table 1 of Example 1. The material 1 was subjected to 50% cold rolling after the solution heat treatment, and further subjected to air-cooling aging heat treatment at a temperature of 850 ° C. to 1050 ° C. for 120 minutes. FIG. 6 shows the average grain size number at each temperature.
図6に示すように、850℃〜1000℃の温度範囲では、顕著な平均結晶粒度番号の低下は現れておらず、良好な結晶粒径を有していることがわかった。
しかし、1000℃より高温になると、再結晶後の粒成長が促進され、平均結晶粒度番号が低下することがわかった。
以上の結果から、850℃〜1000℃の温度で120分および空冷の時効熱処理により、平均結晶粒度番号10.0〜13.0の微細結晶組織を本発明材の化学組成のステンレス鋼中に形成できることがわかった。
As shown in FIG. 6, it was found that in the temperature range of 850 ° C. to 1000 ° C., no significant decrease in the average grain size number appeared, and the crystal grain size was good.
However, it has been found that when the temperature is higher than 1000 ° C., grain growth after recrystallization is promoted, and the average grain size number decreases.
From the above results, a fine crystal structure having an average grain size number of 10.0 to 13.0 is formed in stainless steel having the chemical composition of the present invention by aging heat treatment at a temperature of 850 ° C. to 1000 ° C. for 120 minutes and air cooling. I knew it was possible.
(実施例4および比較例4)
本発明材は、原子炉炉内で使用される構造物を主な適用対象としている。また、原子炉炉内で使用される構造物に用いる一部の材料では、高い強度が必要なものもある。このため、少なくとも100℃での0.2%耐力は175MPa以上、引張強度は475MPa以上の機械的特性が必要である。
そこで、50%の冷間圧延後に900℃で120分および空冷の時効熱処理を施した実施例1の表1における本発明材のNo.1〜4の材料に対して、100℃で引張試験を行い、機械的特性を求めた。比較のため、冷間圧延および時効熱処理を行なわず、溶体化熱処理のみを施したNo.1の材料と、比較材No.10のSUS316Lも同条件で引張試験を実施した。すべての引張試験の繰り返し数は2とした。図7に各材料の100℃での0.2%耐力の平均値を、図8に各材料の100℃での引張強さの平均値を示す。
(Example 4 and Comparative Example 4)
The material of the present invention is mainly applied to structures used in a nuclear reactor. In addition, some materials used for structures used in nuclear reactors may require high strength. For this reason, the mechanical properties of 0.2% proof stress at least at 100 ° C. are 175 MPa or more and tensile strength is 475 MPa or more.
Therefore, No. of the material of the present invention in Table 1 of Example 1 subjected to aging heat treatment at 900 ° C. for 120 minutes and air cooling after 50% cold rolling. Ten to four materials were subjected to a tensile test at 100 ° C. to obtain mechanical properties. For comparison, no cold rolling and no aging heat treatment were performed, and no solution No. was subjected to only solution heat treatment. 1 and comparative material No. Ten SUS316L was also subjected to a tensile test under the same conditions. The number of repetitions of all tensile tests was 2. FIG. 7 shows an average value of 0.2% proof stress of each material at 100 ° C., and FIG. 8 shows an average value of tensile strength of each material at 100 ° C.
図7,図8に示すように、比較材であるSUS316Lに比べて、本発明材は0.2%耐力と引張強さのいずれも高い水準になっている。特に、No.1は、溶体化熱処理のみでも、0.2%耐力と引張強さが要求値を満足している。しかしながら裕度が殆どない。
一方、溶体化熱処理後に冷間圧延および時効熱処理を施したNo.1〜4の材料は、0.2%耐力と引張強さにおいて各要求値から100MPa以上の裕度を有しており、確率論を考慮した高い安全率の設計にも満足でき、実用性が十分に期待される。以上の結果から、確率論を考慮した設計に必要な裕度を満足するためには、表1に示す本発明材の化学組成のステンレス鋼に対して上述のような条件の溶体化熱処理と冷間圧延、時効熱処理を施すことで平均結晶粒度番号を10.0以上にする必要があることがわかった。
As shown in FIGS. 7 and 8, both the 0.2% proof stress and the tensile strength of the material of the present invention are higher than those of SUS316L, which is a comparative material. In particular, no. For No. 1, 0.2% proof stress and tensile strength satisfy the required values even with only solution heat treatment. However, there is almost no margin.
On the other hand, No. 1 was subjected to cold rolling and aging heat treatment after solution heat treatment. The materials 1 to 4 have a tolerance of 100 MPa or more from each required value in 0.2% proof stress and tensile strength, can be satisfied with a high safety factor design considering probability theory, and have practicality Expected enough. From the above results, in order to satisfy the tolerance required for the design considering the probability theory, the solution heat treatment and cooling under the above-mentioned conditions are applied to the stainless steel having the chemical composition of the present invention shown in Table 1. It was found that the average grain size number needs to be 10.0 or more by performing hot rolling and aging heat treatment.
次に、高温高圧水中でのすき間腐食特性を評価した。
実施例1の表1における本発明材のNo.1〜4の材料と、試作材のNo.5,No.6から、縦10mm×横50mm×板厚1.5mmの短冊試験片を各2枚(合計12枚)採取し、表面を耐水研磨紙で600番まで仕上げた。同材の試験片1同士を図9に示すように向かい合わせ、スポット溶接部2でスポット溶接して接合した。また、比較のため、本発明材と同様な作製方法で、No.10のSUS316LおよびNo.11のSUS304Lから各4枚(合計8枚)の短冊試験片を作製して、スポット溶接2により同材の試験片同士1を2枚結合させた。これにより、2枚の試験片間にすき間を形成した。
それらの試験片を、288℃,溶存酸素濃度8ppm,導電率1.0〜1.2μS/cm2,γ線線量率20kGy/hの環境に静置し、1000時間の浸漬試験を実施した。浸漬試験後、試験片長手方向に平行に試験片中央で切断し、その断面の腐食状態を観察した。各試験片の粒界腐食の最大深さを図10に、腐食の箇所数を図11に示す。
Next, crevice corrosion characteristics in high-temperature and high-pressure water were evaluated.
No. 1 of the present invention material in Table 1 of Example 1. 1 to 4 and the prototype No. 5, no. Two strip test pieces each having a length of 10 mm, a width of 50 mm and a plate thickness of 1.5 mm were collected from No. 6 (12 sheets in total), and the surface was finished to 600 with water-resistant abrasive paper. The test pieces 1 made of the same material were faced to each other as shown in FIG. For comparison, the same manufacturing method as that for the material of the present invention was used. 10 SUS316L and no. Four strip test pieces (total 8 pieces) were prepared from 11 SUS304L, and two test pieces 1 of the same material were joined by spot welding 2. Thereby, a gap was formed between the two test pieces.
These test pieces were left in an environment of 288 ° C., dissolved oxygen concentration of 8 ppm, conductivity of 1.0 to 1.2 μS / cm 2 and γ-ray dose rate of 20 kGy / h, and a 1000 hour immersion test was performed. After the immersion test, the specimen was cut at the center of the specimen parallel to the longitudinal direction of the specimen, and the corrosion state of the cross section was observed. The maximum depth of intergranular corrosion of each test piece is shown in FIG. 10, and the number of corrosion locations is shown in FIG.
図10および図11に示すように、いずれの材料においても粒界腐食は観察された。
図10において、比較材のSUS316Lは、4個の試験片とも腐食の最大深さが130μmを超えており、またSUS304Lは腐食の最大深さが平均で約100μmとなり、いずれも深い粒界腐食が観察された。
一方、本発明材No.1〜4は、各試験片における粒界腐食深さは、最大でも60μm未満、平均で35μmとなり、それぞれSUS316Lの約3分の1以下、SUS304Lの約2分の1以下であった。
As shown in FIG. 10 and FIG. 11, intergranular corrosion was observed in all materials.
In FIG. 10, SUS316L as a comparative material has a maximum corrosion depth of more than 130 μm for all four test pieces, and SUS304L has an average maximum corrosion depth of about 100 μm. Observed.
On the other hand, the present invention material No. In Nos. 1 to 4, the intergranular corrosion depth in each test piece was less than 60 μm at the maximum and 35 μm on average, which was about 1/3 or less of SUS316L and about 1/2 or less of SUS304L, respectively.
更に、図11において、SUS316Lの粒界腐食の箇所数は平均で試験片ごとに75箇所であり、SUS304Lは平均で試験片ごとに52箇所であった。
これに対して、本発明材No.1〜4は、平均で試験片ごとに17箇所となり、それぞれ、SUS316Lの約4分の1以下、SUS304Lの約2分の1以下であり、良好な耐食性を有していることがわかった。
一方、Taの含有量を高めた試作材No.5およびNo.6の試験片では、図10に示す粒界腐食深さは、本発明材とほぼ同等な粒界腐食深さが現れていた。しかし、図11に示した腐食の箇所数は、No.1〜4の本発明材の約1.5倍となり、Taの含有量が高すぎると腐食密度が上昇する傾向があることがわかった。
以上の結果から、本発明材は、通常のオーステナイト系ステンレス鋼に比べて良好な耐すき間腐食性を有していることがわかった。また、粒界腐食密度を低減させるためには、Taの含有量は0.65質量%以下にするべきであることがわかった。
Furthermore, in FIG. 11, the number of locations of intergranular corrosion of SUS316L was 75 on average for each test piece, and SUS304L was 52 on average for each test piece.
On the other hand, this invention material No. 1 to 4 averaged 17 locations for each test piece, which were about ¼ or less of SUS316L and ½ or less of SUS304L, respectively, and were found to have good corrosion resistance.
On the other hand, prototype material No. with increased Ta content was obtained. 5 and no. In the test piece of No. 6, the intergranular corrosion depth shown in FIG. However, the number of corrosion locations shown in FIG. It became about 1.5 times that of the present invention material of 1-4, and it was found that if the Ta content is too high, the corrosion density tends to increase.
From the above results, it was found that the material of the present invention has better crevice corrosion resistance than ordinary austenitic stainless steel. It was also found that the Ta content should be 0.65% by mass or less in order to reduce the intergranular corrosion density.
(実施例5)
以上説明した高耐食性高強度ステンレス鋼を、0.1MeV以上のエネルギーをもつ中性子が0.5×1021n/cm2以上照射される原子炉炉内構造物に使用することができる。
(Example 5)
The high-corrosion-resistant high-strength stainless steel described above can be used for a reactor internal structure irradiated with 0.5 × 10 21 n / cm 2 or more of neutrons having an energy of 0.1 MeV or more.
実施例1の高耐食性高強度ステンレス鋼を、原子炉炉内構造物および機器の中で最も中性子照射損傷速度の速い制御棒に使用した場合について以下説明する。 The case where the high corrosion resistance high-strength stainless steel of Example 1 is used for a control rod having the fastest neutron irradiation damage rate among reactor internal structures and equipment will be described below.
図12は中性子吸収材にボロン・カーバイドを使用した制御棒を示す。
この制御棒は、主に、ローラー3、冷却孔4、中性子吸収棒5、シース6、コネクター7、コネクター・ソケット8、ハンドル9、タイロッド10を有している。これらにはいずれも実施例1に記載の高耐食性高強度ステンレス鋼が用いられている。
FIG. 12 shows a control rod using boron carbide as a neutron absorber.
The control rod mainly includes a
制御棒はすき間を有するため、すき間腐食の可能性があり、かつ照射誘起応力腐食割れを発生する可能性もある。そこで、耐すき間腐食性、耐応力腐食割れ性に優れ、かつ照射損傷抑制にも効果がある本発明の高耐食性高強度ステンレス鋼を使用することにより、制御棒のすき間腐食および照射誘起応力腐食割れを抑制し、長寿命かつ信頼性の高い制御棒とすることができる。 Since the control rod has a gap, there is a possibility of crevice corrosion, and there is also a possibility of generating irradiation-induced stress corrosion cracking. Therefore, by using the high corrosion resistance high strength stainless steel of the present invention, which is excellent in crevice corrosion resistance and stress corrosion cracking resistance and also effective in suppressing irradiation damage, control rod crevice corrosion and radiation induced stress corrosion cracking. This makes it possible to provide a long-life and highly reliable control rod.
なお、本発明の高耐食性高強度ステンレス鋼は、棒、薄板、管など様々な形状の部材として製造可能であるので、ボロン・カーバイドを使用する制御棒だけでなく、ハフニウムを中性子吸収材に使用した制御棒にも適用できる。 In addition, since the high corrosion resistance high strength stainless steel of the present invention can be manufactured as members of various shapes such as rods, thin plates, tubes, etc., not only control rods using boron carbide but also hafnium is used for neutron absorbers It can also be applied to control rods.
また、原子炉炉内で従来から使用されているオーステナイト系ステンレス鋼は、0.1MeV以上のエネルギーを持つ中性子が0.5×1021n/cm2以上照射されると照射誘起応力腐食割れを発生する可能性がある。
そこで、制御棒に限らず、原子炉炉内構造物および機器、たとえば沸騰水型原子炉の炉心シュラウド、上部格子板、炉心支持板などや、加圧水型原子炉のバッフル板、フォーマ板、バッフル・フォーマ・ボルトなどに、本発明のオーステナイト系ステンレス鋼を使用することにより、長期信頼性に優れる原子炉および原子力発電プラントとすることができる。
In addition, austenitic stainless steels conventionally used in nuclear reactors cause irradiation-induced stress corrosion cracking when neutrons having an energy of 0.1 MeV or more are irradiated by 0.5 × 10 21 n / cm 2 or more. May occur.
Therefore, not only control rods, but also reactor internal structures and equipment, such as boiling water reactor core shrouds, upper lattice plates, core support plates, pressurized water reactor baffle plates, former plates, baffles, By using the austenitic stainless steel of the present invention for former bolts, a nuclear reactor and a nuclear power plant having excellent long-term reliability can be obtained.
なお、本発明は上記の実施形態に限られず、種々の変形、応用が可能なものである。 In addition, this invention is not restricted to said embodiment, A various deformation | transformation and application are possible.
1…すき間腐食試験片、
2…スポット溶接部、
3…ローラー、
4…冷却孔、
5…中性子吸収棒、
6…シース、
7…コネクター、
8…コネクター・ソケット、
9…ハンドル、
10…タイロッド。
1 ... crevice corrosion test piece,
2 ... Spot weld,
3 Roller
4 ... cooling holes,
5 ... Neutron absorber rod,
6 ... sheath,
7 ... Connector,
8 ... Connector socket,
9 ... handle,
10 ... Tie rod.
Claims (5)
JISG0551で規定されるオーステナイト平均結晶粒度番号が10.0〜13.0である
ことを特徴とする高耐食性高強度ステンレス鋼。 C: 0.04 mass% or less, Mn: 1.0 to 2.0 mass%, Ni: 9.0 to 13.0 mass%, Cr: 17.0 to 20.0 mass%, Ta: 13 of C It contains 0.50 to 0.65% by mass at least twice, and the chemical composition composed of inevitable impurities including Fe and Nb in the balance,
An austenite average grain size number specified in JIS G0551 is 10.0 to 13.0. A high corrosion resistance and high strength stainless steel.
前記高耐食性高強度ステンレス鋼は、100℃での0.2%耐力が175MPa以上、引張強さが475MPa以上である
ことを特徴とする高耐食性高強度ステンレス鋼。 In the high corrosion resistance high strength stainless steel according to claim 1,
The high corrosion resistance high strength stainless steel has a 0.2% proof stress at 100 ° C. of 175 MPa or more and a tensile strength of 475 MPa or more.
0.1MeV以上のエネルギーをもつ中性子が0.5×1021n/cm2以上照射される前記原子炉内構造物に請求項1または2に記載の高耐食性高強度ステンレス鋼を用いた
ことを特徴とする原子炉内構造物。 A reactor internal structure disposed inside the nuclear reactor,
The high-corrosion-resistant high-strength stainless steel according to claim 1 or 2 is used for the reactor internal structure irradiated with 0.5 × 10 21 n / cm 2 or more of neutrons having energy of 0.1 MeV or more. Characteristic reactor internal structure.
前記原子炉内構造物が、制御棒である
ことを特徴とする原子炉内構造物。 In the nuclear reactor structure according to claim 3,
The reactor internal structure is a control rod.
この溶体化熱処理後に圧延率30%〜80%の冷間圧延を実施する工程と、
この冷間圧延後に、850℃〜1050℃で30分〜120分の時効熱処理を実施する工程と、
この熱処理後に空冷する工程と
を備えることを特徴とする高耐食性高強度ステンレス鋼の製造方法。 C: 0.04 mass% or less, Mn: 1.0 to 2.0 mass%, Ni: 9.0 to 13.0 mass%, Cr: 17.0 to 20.0 mass%, Ta: 13 of C 1 to 60 minutes at 1050 ° C. to 1150 ° C. with respect to the austenitic stainless steel having a chemical composition comprising 0.50 to 0.65% by mass and the balance being inevitable impurities including Fe and Nb Performing a water-cooled solution heat treatment;
A step of performing cold rolling at a rolling rate of 30% to 80% after the solution heat treatment;
A step of performing an aging heat treatment at 850 ° C. to 1050 ° C. for 30 minutes to 120 minutes after the cold rolling;
And a step of air-cooling after the heat treatment. A method for producing a high corrosion-resistant high-strength stainless steel.
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