JP6693130B2 - Method for evaluating hydrogen embrittlement resistance - Google Patents
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Description
本発明は、耐水素脆化特性評価方法に関する。特に、遅れ破壊など水素脆化を発生する可能性のある金属材料（例えば、鋼）の耐水素脆化特性を評価する方法に関する。 The present invention relates to a hydrogen embrittlement resistance evaluation method. In particular, the present invention relates to a method for evaluating the hydrogen embrittlement resistance property of a metal material (for example, steel) that may cause hydrogen embrittlement such as delayed fracture.
自動車、各種産業機械などには、軽量化、高性能化などが求められている。特に、機械構造用部品には、土木・建築構造物の建設費削減のため、高強度化が進められている。しかし、鋼などの金属材料は、高強度であるほど、遅れ破壊などの水素脆化を引き起こす可能性が高いという問題がある。 Lighter weight and higher performance are required for automobiles and various industrial machines. In particular, mechanical structural parts are being strengthened to reduce the construction cost of civil engineering and building structures. However, there is a problem that the higher the strength of a metal material such as steel, the higher the possibility of causing hydrogen embrittlement such as delayed fracture.
「遅れ破壊」は、静的応力下に置かれた部品が、ある時間経過後に突然、脆性的に破壊する現象である。このような破壊が生じると、重大な事故につながる危険性が高いことから、使用環境において遅れ破壊が生じない材料を選択する必要がある。一般的に水素脆化抑制のためには高合金鋼を用いるのが有効であるが、経済性の観点からは安価な材料の選択が望まれる。したがって、耐遅れ破壊特性に優れ、かつ安価な材料を選択するためには、より詳細に耐水素脆化特性を評価できる方法が必要となる。 "Delayed fracture" is a phenomenon in which a component placed under static stress suddenly and brittlely fractures after a certain period of time. When such destruction occurs, there is a high risk of causing a serious accident, so it is necessary to select a material that does not cause delayed destruction in the use environment. Generally, it is effective to use a high alloy steel for suppressing hydrogen embrittlement, but it is desirable to select an inexpensive material from the viewpoint of economy. Therefore, in order to select a material that is excellent in delayed fracture resistance and inexpensive, a method that enables more detailed evaluation of hydrogen embrittlement resistance is required.
従来、遅れ破壊などの水素脆化特性を評価する方法が種々提案されている。特許文献１には、水素侵入した試験片で低歪み速度の引張試験における破断時伸びを測定し、その値から求めた水素脆化危険度指数（％）と鋼中に存在する拡散水素量との相関関係を求め、この相関関係から鋼材の水素脆化危険度を評価する方法が開示されている。また、非特許文献１には、限界拡散性水素量と侵入水素量を比較することによって耐水素脆化特性を評価する方法が開示されている。 Conventionally, various methods for evaluating hydrogen embrittlement characteristics such as delayed fracture have been proposed. In Patent Document 1, a hydrogen embrittlement risk index (%) obtained by measuring the elongation at break in a tensile test at a low strain rate with a hydrogen-penetrated test piece and the amount of diffused hydrogen present in the steel Is disclosed, and a method for evaluating the risk of hydrogen embrittlement of a steel material from this correlation is disclosed. Further, Non-Patent Document 1 discloses a method for evaluating the hydrogen embrittlement resistance by comparing the critical diffusible hydrogen content and the penetrating hydrogen content.
たとえば、自動車は、世界各地で販売され、利用されており、実際に、どのような環境で使用されるのかを知るのは難しく、また、その中で最も厳しい使用環境を正確に把握することも難しい。さらに、日本で使用される部品であっても、部品形状によっては構造上常時塩水がたまる可能性がある場合など、想定を超える厳しい環境となることもあり、その際に遅れ破壊などの水素脆化発生リスクがある。
特許文献１および非特許文献１に記載の水素脆化評価方法は、使用される環境が変化した際の水素侵入特性について明らかにできないため、想定範囲外の使用環境がどこまで許容できるかについて把握することができない。
For example, automobiles are sold and used all over the world, and it is difficult to know what kind of environment they are actually used in, and it is also possible to accurately understand the most severe environment in which they are used. difficult. Furthermore, even for parts used in Japan, depending on the shape of the parts, there may be a severe environment that exceeds expectations, such as when salt water may accumulate due to the structure. There is a risk of occurrence.
Since the hydrogen embrittlement evaluation methods described in Patent Document 1 and Non-Patent Document 1 cannot clarify hydrogen penetration characteristics when the environment in which they are used change, the extent to which the operating environment outside the assumed range can be tolerated is understood. I can't.
本発明は、従来技術の問題を解決するためになされたものであり、任意の部材に関し、使用環境の許容範囲という指標によって、その部材の耐水素脆化特性を評価する方法を提供することを目的とする。 The present invention has been made to solve the problems of the prior art, and provides a method for evaluating the hydrogen embrittlement resistance of any member by an index of the allowable range of the operating environment. To aim.
本発明は、下記の耐水素脆化特性評価方法を要旨とする。 The gist of the present invention is the following method for evaluating hydrogen embrittlement resistance.
（Ａ）耐水素脆化特性を評価する方法であって、
（１）試験対象材の試験体を陰極として電解を行い、侵入水素量ＨＥに対応する陰極水素チャージ条件を求めるステップ、
（２）前記試験対象材の試験体を陰極として電解を行い、水素をチャージした後、遅れ破壊試験を行い、限界拡散性水素量ＨＣを測定するステップ、
（３）前記侵入水素量ＨＥが前記限界拡散性水素量ＨＣを下回る陰極水素チャージ条件の広さによって耐水素脆化特性を判定するステップ、
を備える、耐水素脆化特性の評価方法。
(A) A method for evaluating hydrogen embrittlement resistance, comprising:
(1) a specimen to be tested materials perform electrolysis as the cathode, obtaining the cathode hydrogen charging conditions corresponding to absorbed hydrogen amount H E step,
(2) A step of performing electrolysis using the test body of the test object material as a cathode, charging hydrogen, and then performing a delayed fracture test to measure a critical diffusible hydrogen amount H C ,
(3) the absorbed hydrogen amount H E is determining hydrogen embrittlement resistance by the width of the cathode hydrogen charging condition is below the critical diffusible hydrogen amount H C,
A method for evaluating hydrogen embrittlement resistance, comprising:
（Ｂ）陰極水素チャージ条件が、電位差である、
上記（Ａ）の耐水素脆化特性の評価方法。
(B) The cathode hydrogen charging condition is a potential difference,
The method for evaluating hydrogen embrittlement resistance of (A) above.
（Ｃ）前記（１）のステップにおいて、
前記試験片を陰極とし、電解質を含む水溶液中で、銀塩化銀電極に対して−０．８〜１．５Ｖの範囲において定電位を付与して電解を行い、侵入水素量ＨＥに対応する電位差を求める、
上記（Ｂ）の耐水素脆化特性の評価方法。
(C) In the step (1) above,
The test piece as a cathode, in an aqueous solution containing an electrolyte, in the range of -0.8~1.5V against a silver-silver chloride electrode by applying a constant potential perform electrolysis, corresponding to absorbed hydrogen amount H E Find the potential difference,
The method for evaluating hydrogen embrittlement resistance according to the above (B).
（Ｄ）前記（２）のステップにおいて、
前記試験片の応力集中係数が３以上である、
上記（Ａ）〜（Ｃ）のいずれかの耐水素脆化特性の評価方法。
(D) In the step (2),
The stress concentration factor of the test piece is 3 or more,
The method for evaluating hydrogen embrittlement resistance according to any of (A) to (C) above.
本発明によれば、任意の部材について使用することができる環境を把握するとともに、その際の侵入水素量を把握することができるので、水素脆化の観点から安全に使用できる材料を選択する際に有用な情報を提供することが可能である。さらに、使用可能な環境の範囲で評価することで材料の水素脆化特性優劣の判定を容易にする。このため、本発明は、産業上の貢献が極めて顕著である。 According to the present invention, it is possible to understand the environment in which any member can be used and the amount of invading hydrogen at that time. Therefore, when selecting a material that can be used safely from the viewpoint of hydrogen embrittlement. It is possible to provide useful information to In addition, evaluation in the range of usable environment facilitates determination of superiority or inferiority of hydrogen embrittlement characteristics of the material. Therefore, the present invention makes a very significant industrial contribution.
本実施形態に係る耐水素脆化特性評価方法は、下記のステップ（１）〜（３）を備える。
（１）試験対象材の試験体を陰極として電解を行い、侵入水素量ＨＥに対応する陰極水素チャージ条件を求めるステップ、
（２）前記試験対象材の試験体を陰極として電解を行い、水素をチャージした後、遅れ破壊試験を行い、限界拡散性水素量ＨＣを測定するステップ、
（３）前記侵入水素量ＨＥが前記限界拡散性水素量ＨＣを下回る陰極水素チャージ条件の広さによって耐水素脆化特性を判定するステップ。
The method for evaluating hydrogen embrittlement resistance according to this embodiment includes the following steps (1) to (3).
(1) a specimen to be tested materials perform electrolysis as the cathode, obtaining the cathode hydrogen charging conditions corresponding to absorbed hydrogen amount H E step,
(2) A step of performing electrolysis using the test body of the test object material as a cathode, charging hydrogen, and then performing a delayed fracture test to measure a critical diffusible hydrogen amount H C ,
(3) determining the hydrogen embrittlement resistance by the width of the cathode hydrogen charging conditions the absorbed hydrogen amount H E is below the critical diffusible hydrogen amount H C.
ステップ（１）について
このステップは、試験対象材の試験体についての侵入水素量ＨＥに対応する陰極水素チャージ条件を把握する。なお、侵入水素量ＨＥとは、ある環境において試験片に侵入する最大の拡散性水素量である。このとき、陰極水素チャージ条件は、任意の部材が実際の使用環境で用いられた場合の水素侵入の厳しさを示すことになる。陰極水素チャージ条件として用いる物性値には制約がなく、電位差、電流などが挙げられるが、中でも電位差を用いるのがよい。なお、陰極電解によってチャージを行う理由は、試験片の損傷がなく、短時間で試験片中に水素侵入させることができるためである。
This step for step (1) is to grasp the cathode hydrogen charging conditions corresponding to absorbed hydrogen amount H E for the test of the tested material. Here, the absorbed hydrogen amount H E, the largest amount of diffusible hydrogen entering the specimen in some circumstances. At this time, the cathode hydrogen charge condition indicates the severity of hydrogen invasion when an arbitrary member is used in an actual use environment. There is no restriction on the physical property value used as the cathode hydrogen charging condition, and a potential difference, a current, etc. may be mentioned, but among them, the potential difference is preferably used. The reason for charging by cathodic electrolysis is that hydrogen can penetrate into the test piece in a short time without damaging the test piece.
まず、予備試験として、陰極水素チャージ時間と拡散性水素量の関係を調査し、試験片中に均一に水素が拡散し、拡散性水素量が最大となるまでの時間（水素チャージ時間）を明らかにする。予備試験に用いる試験片は、侵入水素量ＨＥを測定する試験片と材質が同じであるだけでなく、形状も同じものを使用することが望ましい。なぜならば、均一に水素がチャージされるまでの時間は、材質および形状に影響されるからである。拡散性水素量は、試験片中の水素濃度の平均値を表す。よって、水素チャージ時間が短い時は、試験片表面近くは水素濃度が高く、中心近くは水素濃度が低い状態となり、拡散性水素量は低い値を示す。一方、水素チャージ時間が長くなると、中心近くの水素濃度も高くなり、拡散性水素量が高くなる。そして、チャージ時間がある長さを超えると、試験片中にチャージされる水素濃度は飽和し、最大値に達する。陰極水素チャージの電位に応じた値で一定となる。以上の予備試験結果より、拡散性水素量が一定となる水素チャージ時間を求め、侵入水素量ＨＥの測定の際の水素チャージ時間とする。 First, as a preliminary test, the relationship between the cathode hydrogen charging time and the diffusible hydrogen content was investigated, and the time until the diffusible hydrogen content reached its maximum (hydrogen charge time) was clarified. To Test piece used in the preliminary test, not only the test piece and the material to measure the absorbed hydrogen amount H E is the same, the shape may be desirable to use the same. This is because the time until the hydrogen is uniformly charged depends on the material and shape. The diffusible hydrogen amount represents the average value of the hydrogen concentration in the test piece. Therefore, when the hydrogen charging time is short, the hydrogen concentration is high near the surface of the test piece and low near the center, and the diffusible hydrogen amount is low. On the other hand, when the hydrogen charging time becomes long, the hydrogen concentration near the center also becomes high and the diffusible hydrogen amount becomes high. Then, when the charging time exceeds a certain length, the hydrogen concentration charged in the test piece becomes saturated and reaches the maximum value. It becomes constant at a value according to the potential of the cathode hydrogen charge. From preliminary results described above, we obtain the hydrogen charging time diffusible hydrogen amount is constant, the hydrogen charging time for the measurement of the absorbed hydrogen amount H E.
侵入水素量ＨＥを求める試験では、予備試験で決定したチャージ時間において、ある電位について水素量が飽和するまで水素チャージを行い、昇温脱離分析（Ｔｈｅｒｍａｌ Ｄｅｓｏｒｐｔｉｏｎ Ａｎａｌｙｓｉｓ：ＴＤＡ）により試験片中の拡散性水素量を求めるのがよい。試験片中に侵入した微量な拡散性水素量を精度良く測定することが重要である。このため、試験片中の拡散性水素量は、ＴＤＡによって求めることとするのがよい。ＴＤＡは、ガスクロマトグラフまたは四重極質量分析計を用いた試験機にて行う。これらの装置を使うことにより微量な拡散性水素量を分析することができる。 In the test for determining the amount H E of penetrating hydrogen, hydrogen charging is performed until the amount of hydrogen is saturated at a certain potential at the charge time determined in the preliminary test, and the temperature of the sample in the test piece is measured by thermal desorption analysis (Thermal Desorption Analysis: TDA). The amount of diffusible hydrogen should be calculated. It is important to accurately measure the minute amount of diffusible hydrogen that has penetrated into the test piece. Therefore, the amount of diffusible hydrogen in the test piece is preferably determined by TDA. TDA is performed by a testing machine using a gas chromatograph or a quadrupole mass spectrometer. By using these devices, a minute amount of diffusible hydrogen can be analyzed.
ここで、ＴＤＡのグラフの例を図１に示す。試験片を室温から昇温すると水素放出量が増加し、１００℃から２００℃程度でピークとなり、その後減少する。この曲線の積分値が試験片中に侵入した拡散性水素量（侵入水素量）となる。なお、素材によってはピークが２つとなることもあるが、室温から始まる第一ピークが水素脆化の原因となる拡散性水素であり、第二ピークに含まれる水素は水素脆化に関与しない非拡散性水素である。したがって、本発明では拡散性水素のみ対象とするため、第一ピークのみ積算し、第二ピークは積算しない。第一ピークの温度範囲は、測定開始温度からＴＤＡ曲線の傾きが正から負になった後、再度０となる温度までである。 Here, an example of a graph of TDA is shown in FIG. When the temperature of the test piece is raised from room temperature, the amount of released hydrogen increases, peaks at about 100 ° C to 200 ° C, and then decreases. The integrated value of this curve becomes the amount of diffusible hydrogen that has penetrated into the test piece (amount of penetrated hydrogen). Depending on the material, there may be two peaks, but the first peak starting at room temperature is diffusible hydrogen that causes hydrogen embrittlement, and the hydrogen contained in the second peak does not contribute to hydrogen embrittlement. It is diffusible hydrogen. Therefore, in the present invention, since only diffusible hydrogen is targeted, only the first peak is integrated and the second peak is not integrated. The temperature range of the first peak is from the measurement start temperature to the temperature at which the slope of the TDA curve changes from positive to negative and then becomes 0 again.
様々な電位において侵入水素量ＨＥを調査することで、陰極水素チャージ電位と侵入水素量ＨＥとの関係を示す曲線が得られる。この際、電位は、銀塩化銀参照極において−０．８以下の範囲に設定することが望ましい。なぜならば、−０．８Ｖ超では鋼に水素を侵入させることが難しいからである。また、電位は銀塩化銀参照極において−１．５Ｖ以上の範囲に設定することが望ましい。なぜならば、−１．５Ｖで鋼における侵入水素量は飽和し、それを下回る電位を付加しても侵入水素量ＨＥを増加させることができないからである。 By investigating the amount H E of penetrating hydrogen at various potentials, a curve showing the relationship between the cathode hydrogen charge potential and the amount H E of penetrating hydrogen is obtained. At this time, the potential is in silver-silver reference electrode chloride - it is desirable to set 0.8 or less. Because, - 0.8 V because it is difficult to penetrate the hydrogen ultra in steel. The potential in the silver-silver reference electrode chloride - it is desirable to set to 1.5V or more ranges. Because - absorbed hydrogen amount in the steel in 1.5V is saturated, it is impossible to increase the also absorbed hydrogen amount H E by adding a potential below it.
このステップは、電解質を含む水溶液中で行うのがよいが、その水溶液は、評価する材料の耐水素脆化特性によって選択する。すなわち、評価する材料が例えば高強度ボルト用鋼程度の材料であれば中性のＮａＣｌ水溶液が適当である。それより低い耐水素脆化特性の材料であればアルカリ性のＮａＯＨ水溶液を用い、それより高い耐水素脆化特性の材料であればＮａＣｌにＮＨ４ＳＣＮなどの水素侵入促進物質を添加した水溶液を用いるのが良い。ただし、材料間の評価をする際は同じ水溶液を用いなければならない。 This step is preferably carried out in an aqueous solution containing an electrolyte, which is selected according to the hydrogen embrittlement resistance of the material to be evaluated. That is, if the material to be evaluated is a material such as steel for high strength bolts, a neutral NaCl aqueous solution is suitable. If the material has a lower hydrogen embrittlement resistance, an alkaline aqueous NaOH solution is used, and if the material has a higher hydrogen embrittlement resistance, an aqueous solution obtained by adding a hydrogen penetration promoting substance such as NH 4 SCN to NaCl is used. Is good. However, the same aqueous solution must be used when evaluating materials.
ステップ（２）について
このステップは、前記試験対象材の試験体に遅れ破壊試験を行い、限界拡散性水素量ＨＣを測定するステップである。ここで、遅れ破壊試験方法としては、公知の方法を採用すればよく、例えば、定荷重試験、低ひずみ速度試験（Ｓｌｏｗ Ｓｔｒａｉｎ Ｒａｔｅ Ｔｅｓｔ：ＳＳＲＴ）、通常ひずみ速度試験（Ｃｏｎｖｅｎｔｉｏｎａｌ Ｓｔｒａｉｎ Ｒａｔｅ Ｔｅｓｔ：ＣＳＲＴ）によって求めることができる。ただし、ＣＳＲＴの場合は、水素の応力誘起拡散による局所水素量で評価する方法であるため、局所応力の計算を必要とする。また、ＳＳＲＴの場合は、破断応力と限界拡散性水素量ＨＣの関係が求まるので、本発明の評価においては想定される部品に負荷される応力値における限界拡散性水素量ＨＣを採用する。
About Step (2) This step is a step of performing a delayed fracture test on the test body of the test target material and measuring the critical diffusible hydrogen amount H C. Here, as the delayed fracture test method, a known method may be adopted, for example, a constant load test, a low strain rate test (Slow Strain Rate Test: SSRT), a normal strain rate test (Conventional Strain Rate Test: CSRT). Can be sought by. However, in the case of CSRT, since it is a method of evaluating the amount of local hydrogen due to stress-induced diffusion of hydrogen, calculation of local stress is required. Further, in the case of SSRT, the relationship between the fracture stress and the limit diffusible hydrogen amount H C is obtained, so in the evaluation of the present invention, the limit diffusible hydrogen amount H C at the stress value assumed for the component is adopted. ..
いずれの試験方法においても、基本的な試験手順は、水素チャージ、応力負荷、ＴＤＡからなる。これらの試験により、負荷応力と試験片中の限界水素量の関係、または試験片中の水素量と破断応力の関係を調査する。 In both test methods, the basic test procedure consists of hydrogen charging, stress loading, and TDA. By these tests, the relationship between the load stress and the limit hydrogen content in the test piece, or the relationship between the hydrogen content in the test piece and the breaking stress is investigated.
試験片は、ボルトなどの実部品または切欠き付きのものを利用する。その理由は、遅れ破壊などの水素脆化は応力集中部で発生する可能性が高いため、それを模擬するためである。 Use real parts such as bolts or those with notches as the test piece. The reason is that hydrogen embrittlement such as delayed fracture is likely to occur in the stress concentration portion, and therefore it is simulated.
試験片に水素をチャージする方法については、ステップ（１）と同様である。 The method of charging the test piece with hydrogen is the same as in step (1).
試験の際に注意すべき点は、定荷重試験やＳＳＲＴのように試験中に水素が拡散することを想定した試験方法では水素飛散防止処置をすることである。その方法は、Ｚｎ、Ｃｄなどの水素飛散防止めっきを水素チャージ後に施す、または応力負荷を水素チャージセル付帯で水素チャージさせながら行う、などの処置が必要である。水素飛散防止めっきを使用した場合は、ＴＤＡの前にそのめっきを除去する。 A point to be noted at the time of the test is to prevent the hydrogen from scattering in the test method such as the constant load test and the SSRT which is supposed to diffuse hydrogen during the test. The method requires treatment such as performing hydrogen scattering prevention plating of Zn, Cd or the like after hydrogen charging, or performing stress load while hydrogen charging with a hydrogen charge cell. If hydrogen shatterproof plating is used, remove the plating before TDA.
ステップ（３）について
このステップでは、前記侵入水素量ＨＥと前記限界拡散性水素量ＨＣとを比較し、ＨＥ＜ＨＣとなる陰極水素チャージ条件の広さを調査する。この広さが水素脆化なく使用できる範囲を示し、その範囲が広い材料ほど耐水素脆化特性に優れていると評価することができる。評価基準である、陰極水素チャージ条件としては、電位差を用いるのが好ましい。最も、侵入水素量のばらつきが小さく、再現性が高いからである。
また、部品の抜き取り調査などによって実環境における侵入水素量ＨＥの値を採取できれば、各試験条件における侵入水素量ＨＥの変化と比較することにより、実環境においてその部品が遅れ破壊に対してどれぐらい余裕があるかを把握することができる。
Step (3) In this step, the amount H E of invading hydrogen is compared with the amount H C of the limit diffusible hydrogen, and the range of the cathode hydrogen charging condition satisfying H E <H C is investigated. This width indicates a range that can be used without hydrogen embrittlement, and it can be evaluated that a material having a wider range is more excellent in hydrogen embrittlement resistance. It is preferable to use a potential difference as a cathode hydrogen charging condition which is an evaluation criterion. This is because the variation in the amount of invading hydrogen is the smallest and the reproducibility is high.
Also, if taking the value of the absorbed hydrogen amount H E in the real environment, such as by parts of the sampling survey, by comparing the change in the absorbed hydrogen amount H E in each test condition, with respect to the part is delayed fracture in a real environment You can understand how much you can afford.
以下、本件発明に係る水素脆化特性の評価方法について実施例を挙げて更に具体的に説明するが、本件発明は以下の実施例に限定されるものではない。 Hereinafter, the method for evaluating hydrogen embrittlement characteristics according to the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.
表１に示す鋼を焼入れ焼戻しして引張強さ（Ｔｅｎｓｉｌｅ Ｓｔｒｅｎｇｔｈ：ＴＳ）を１２００〜１４００ＭＰａに調質した丸棒（鋼材Ａ〜Ｆ）を準備した。鋼材Ａ〜Ｆそれぞれについて、以下のとおり、ＨＥおよびＨＣの測定、ならびに、従来の評価試験をおこなった。 The steels shown in Table 1 were quenched and tempered to prepare round bars (steel materials A to F) whose tensile strength (Tensile Strength: TS) was adjusted to 1200 to 1400 MPa. For each steel to F, as follows, the measurement of H E and H C, and it was subjected to conventional evaluation test.
＜ＨＥ（侵入拡散性水素量）測定試験＞
前記丸棒から、機械加工により切り出した試験片（φ５×５０ｍｍＬ）について、陰極水素チャージをおこない、ＨＥ測定のための予備試験およびＨＥ測定試験を行った。いずれの試験においても、陰極水素チャージのセルは、３％ＮａＣｌ水溶液、銀−塩化銀（Ａｇ/ＡｇＣｌ）参照極、白金（Ｐｔ）対極で構成されたものであった。
<H E (penetration diffusible hydrogen content) measurement test>
From the round bar, the test piece cut by machining (φ5 × 50mmL), performed cathode hydrogen charging was carried out a preliminary test and H E measurement test for H E measurements. In each test, the cathode hydrogen charging cell was composed of a 3% NaCl aqueous solution, a silver-silver chloride (Ag / AgCl) reference electrode, and a platinum (Pt) counter electrode.
鋼材Ｂおよび鋼材Ｅの試験片について行った予備試験の結果を図２に示す。予備試験は、試験片に陰極水素チャージを行い、試験片中に侵入する 拡散性水素量が飽和するまでの時間を調査した。侵入水素量の測定は、前述の昇温脱離分析（ＴＤＡ）によりおこなった。図２に示す結果から、ＨＥ測定試験での水素チャージ時間を次の通りとすることとした。
鋼材Ａ〜Ｃ（ＳＣＭ４３５）：４８時間
鋼材Ｄ〜Ｆ（Ｖ添加鋼）：１６８時間
The result of the preliminary test performed on the test pieces of the steel materials B and E is shown in FIG. In the preliminary test, the test piece was charged with cathode hydrogen, and the time until the amount of diffusible hydrogen penetrating into the test piece was saturated was investigated. The amount of invading hydrogen was measured by the above-mentioned thermal desorption analysis (TDA). From the results shown in FIG. 2, it was decided to the hydrogen charging time in H E measurement test as follows.
Steel materials A to C (SCM435): 48 hours Steel materials DF (V added steel): 168 hours
予備試験の後、ＨＥ測定試験を、鋼材Ａ〜Ｆの試験片についておこなった。−０．９Ｖ、−１．１Ｖ、−１．３Ｖおよび−１．５Ｖの電位で、予備試験により決めた上記時間の水素チャージをおこない、試験片中の拡散性水素量を測定した。拡散性水素量の測定は、前述の昇温脱離分析（ＴＤＡ）によりおこなった。 After preliminary tests, the H E measurement test was performed for the test piece of steel to F. - 0.9V, - 1.1V, - 1.3V and - at 1.5V potential performs the time of hydrogen-charged decided by a preliminary test were measured amount of diffusible hydrogen in the specimen. The amount of diffusible hydrogen was measured by the above-mentioned thermal desorption analysis (TDA).
＜ＨＣ（限界拡散性水素量）測定試験＞
前記丸棒から、機械加工により試験片（φ７×７０ｍｍＬ）を切り出し、その中央部に応力集中係数が約３．５の環状切欠きを設けた。上記の試験片に、２４時間の陰極水素チャージにより拡散性水素を導入し、さらにＺｎめっきを施した。試験片内の拡散性水素量を均一にするため、試験片を室温に次の時間保持した。
鋼材Ａ〜Ｃ（ＳＣＭ４３５）：２４時間
鋼材Ｄ〜Ｆ（Ｖ添加鋼）：９６時間
<H C (critical diffusible hydrogen content) measurement test>
A test piece (φ7 × 70 mmL) was cut out from the round bar by machining, and an annular notch having a stress concentration factor of about 3.5 was provided at the center thereof. Diffusible hydrogen was introduced into the above test piece by cathode hydrogen charging for 24 hours, and further Zn plating was performed. The test piece was kept at room temperature for the next time in order to make the amount of diffusible hydrogen in the test piece uniform.
Steel materials A to C (SCM435): 24 hours Steel materials DF (V added steel): 96 hours
室温保持後の試験片に、ＴＳの９０％の公称応力を負荷する定荷重試験を行い、破断直後または１００時間耐久後に試験片を回収した。回収した試験片について、めっきを逆電解により除去した後、ガスクロマトグラフを用いて試験片中の水素量を求めた。様々な拡散性水素量の水準において、以上の試験を行い、試験片が破断しない最大の水素量をＨＣとした。 The test piece after being kept at room temperature was subjected to a constant load test in which a nominal stress of 90% of TS was applied, and the test piece was recovered immediately after breaking or after 100 hours of durability. After the plating was removed by reverse electrolysis on the recovered test piece, the amount of hydrogen in the test piece was determined using a gas chromatograph. The above tests were conducted at various diffusible hydrogen content levels, and the maximum hydrogen content at which the test piece did not break was defined as H C.
＜従来の評価試験＞
非特許文献１に示される条件での評価を行った。すなわち、ＪＡＳＯ Ｍ ６０９（日本自動車技術協会規格）のＣＣＴを最大１８０サイクル行い、その条件での侵入水素量ＨＥ＿ＣＣＴも求めた。
<Conventional evaluation test>
The evaluation was performed under the conditions shown in Non-Patent Document 1. That performed up to 180 cycles CCT of JASO M 609 (Japan Automobile Technology Association standard), was determined also absorbed hydrogen amount H E _ CCT in that condition.
以上の結果を、表２に示す。また、図３には、鋼材ＢおよびＥについて、「陰極水素チャージ電位とＨＥの関係」と「ＨＣ」とを比較した結果を示す。 The above results are shown in Table 2. Further, in FIG. 3, for steel B, and E, shows the results of a comparison with the "relation cathodic hydrogen charging potential and H E" and "H C".
図３において、それぞれの鋼材のＨＥ曲線とＨＣの交点が限界電位となり、それ以上の高い電位の環境においては遅れ破壊しないと判定できる。したがって、引張強さが同じＴＳ１２００ＭＰａ級の鋼材であるＢとＥでは、Ｅの方が限界電位が低く、ＨＣ＞ＨＥとなる電位範囲が広いため、鋼材Ｄ〜Ｆ（Ｖ添加鋼）の方が鋼材Ａ〜Ｃ（ＳＣＭ４３５）より耐水素脆化特性に優れている、と評価できる。 3, the intersection of H E curve and H C of each steel becomes critical potential, can be determined that no delayed fracture in more high potential environment. Accordingly, the tensile strength of the same TS1200MPa class in steel in which B and E, who E is lower limit potential, the potential range of the H C> H E is wide, steel D~F of (V added steel) It can be evaluated that the steel has better hydrogen embrittlement resistance than the steel materials A to C (SCM435).
表２に示すように、比較法（非特許文献１に提案されている（ＨＣ−ＨＥ＿ＣＣＴ）／ＨＣを指標とする方法）は、ＣＣＴ環境において遅れ破壊するかどうかについては正負で判定できるが、ＣＣＴ環境で遅れ破壊を生じないと判定される（ＨＣ−ＨＥ＿ＣＣＴ）／ＨＣ＞０を満たす試料間での比較は難しい。一方、本発明法は、陰極チャージ電位とＨＥの関係を示すことで、水素侵入環境の厳しい範囲についても評価可能であり、詳細な鋼種間の差を限界電位という指標で評価可能である。
なお、Ｖ添加鋼は、耐遅れ破壊特性に優れている実績がある。しかし、比較法による評価では、鋼材Ｄ〜Ｆ（Ｖ添加鋼）と鋼材Ａ〜Ｃ（ＳＣＭ４３５）との差異が明確ではない。一方、本発明法による評価では、限界電位の範囲が広く、鋼材Ｄ〜Ｆ（Ｖ添加鋼）の方が鋼材Ａ〜Ｃ（ＳＣＭ４３５）より耐水素脆化特性に優れていることを明確に示すことができた。
As shown in Table 2, comparison method (proposed in Non-Patent Document 1 (H C -H E_CCT) / H C of an index method) is determined by positive and negative about whether the delayed fracture in the CCT environment possible, comparisons between samples satisfying is determined to not cause delayed fracture in CCT environment (H C -H E_CCT) / H C> 0 is difficult. On the other hand, the present invention method, by showing the relationship between cathodic charging potential and H E, is also evaluable for demanding range of hydrogen penetration environment can be evaluated by the index of the limit on the potential difference between the detailed grades.
It should be noted that the V-added steel has a track record of being excellent in delayed fracture resistance. However, in the evaluation by the comparative method, the difference between the steel materials D to F (V-added steel) and the steel materials A to C (SCM435) is not clear. On the other hand, in the evaluation by the method of the present invention, the range of the limit potential is wide, and it is clearly shown that the steel materials D to F (V-added steel) are superior to the steel materials A to C (SCM435) in hydrogen embrittlement resistance. I was able to do it.
本発明によれば、任意の部材について使用することができる環境を把握するとともに、その際の侵入水素量を把握することができので、水素脆化の観点から安全に使用できる材料を選択する際に有用な情報を提供することが可能である。さらに、使用可能な環境の範囲で評価することで材料の水素脆化特性優劣の判定を容易にする。このため、本発明は、産業上の貢献が極めて顕著である。
According to the present invention, it is possible to understand the environment in which any member can be used and the amount of invading hydrogen at that time. Therefore, when selecting a material that can be used safely from the viewpoint of hydrogen embrittlement. It is possible to provide useful information to In addition, evaluation in the range of usable environment facilitates determination of superiority or inferiority of hydrogen embrittlement characteristics of the material. Therefore, the present invention makes a very significant industrial contribution.
Claims (4)
（２）前記試験対象材の試験体を陰極として電解を行い、水素をチャージした後、遅れ破壊試験を行い、限界拡散性水素量ＨＣを測定するステップ、
（３）前記物性値において、前記侵入水素量ＨＥが前記限界拡散性水素量ＨＣを下回る陰極水素チャージ条件の広さによって耐水素脆化特性を判定するステップ、
を備える、耐水素脆化特性の評価方法。 (1) Specimens to be tested material was subjected to electrolytic as a cathode, to charge the hydrogen, the cathode hydrogen charging is performed a plurality of times while changing the affect physical properties in the cathode hydrogen charging conditions, and the absorbed hydrogen amount H E Determining a relationship with the physical property value ,
(2) A step of performing electrolysis using the test body of the test object material as a cathode, charging hydrogen, and then performing a delayed fracture test to measure a critical diffusible hydrogen amount H C ,
(3) In the physical property value, determining resistance to hydrogen embrittlement by the width of the cathode hydrogen charging conditions the absorbed hydrogen amount H E is below the critical diffusible hydrogen amount H C,
A method for evaluating hydrogen embrittlement resistance, comprising:
請求項１に記載の耐水素脆化特性の評価方法。 The physical property value is a potential difference,
The method for evaluating hydrogen embrittlement resistance according to claim 1.
前記試験体を陰極とし、電解質を含む水溶液中で、銀塩化銀電極に対する電位差が−１．５〜−０．８Ｖとなるように定電位を付与して電解を行い、侵入水素量ＨＥに対応する電位差を求める、
請求項２に記載の耐水素脆化特性の評価方法。 In the step (1) above,
Said specimen as a cathode, in an aqueous solution containing an electrolyte, performs imparting to the electrolyte a constant potential such that a potential difference to pair the silver-silver chloride electrode is -1.5 to-0.8 V, absorbed hydrogen amount H Find the potential difference corresponding to E ,
The method for evaluating hydrogen embrittlement resistance according to claim 2.
前記試験体の応力集中係数が３以上である、
請求項１から３までのいずれかに記載の耐水素脆化特性の評価方法。 In the step (2) above,
The stress concentration factor of the test body is 3 or more,
The method for evaluating hydrogen embrittlement resistance according to any one of claims 1 to 3.
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