JP2020041837A - Hydrogen embrittlement characteristic evaluation method - Google Patents
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 111
- 239000001257 hydrogen Substances 0.000 title claims abstract description 110
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 110
- 238000011156 evaluation Methods 0.000 title claims abstract description 14
- 239000000463 material Substances 0.000 claims abstract description 95
- 238000012360 testing method Methods 0.000 claims abstract description 72
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 56
- 239000010959 steel Substances 0.000 claims abstract description 56
- 238000000034 method Methods 0.000 claims abstract description 52
- 238000007906 compression Methods 0.000 claims abstract description 13
- 230000006835 compression Effects 0.000 claims abstract description 13
- 238000005096 rolling process Methods 0.000 claims abstract description 10
- 230000035882 stress Effects 0.000 description 21
- 238000012545 processing Methods 0.000 description 8
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000005452 bending Methods 0.000 description 5
- 239000008151 electrolyte solution Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 239000002344 surface layer Substances 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 239000011780 sodium chloride Substances 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000012085 test solution Substances 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 230000006355 external stress Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 125000000896 monocarboxylic acid group Chemical group 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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Abstract
Description
本発明は、水素脆化特性評価方法に関する。 The present invention relates to a method for evaluating hydrogen embrittlement characteristics.
鉄鋼材料では、材料中に水素が導入され引張応力が負荷されると、水素脆化と呼ばれる現象が生じることがある。水素脆化が生じると、材料の破断強度、伸びおよび絞りが低下する。また、材料中の水素濃度が極めて高い場合には、引張応力または残留応力が付与されていない状態であっても、材料内部で水素脆化割れが生じることがある。その一例が、油井・ガス井の湿潤硫化水素環境で使用される炭素鋼・低合金鋼で生じる、水素誘起割れ（Ｈｙｄｒｏｇｅｎ Ｉｎｄｕｃｅｄ Ｃｒａｃｋｉｎｇ：ＨＩＣ）である。 In a steel material, when hydrogen is introduced into the material and a tensile stress is applied, a phenomenon called hydrogen embrittlement may occur. When hydrogen embrittlement occurs, the breaking strength, elongation and drawing of the material decrease. Further, when the hydrogen concentration in the material is extremely high, hydrogen embrittlement cracking may occur inside the material even in a state where no tensile stress or residual stress is applied. One example is Hydrogen Induced Cracking (HIC) that occurs in carbon steel and low alloy steel used in wet hydrogen sulfide environments in oil and gas wells.
一般に、材料強度が高くなるほど、鉄鋼材料の水素脆化感受性は増大することが知られている。したがって、材料に対する塑性ひずみ（永久ひずみ）の付与は、転位を生成し材料強度を上昇させるため、水素脆化感受性に対して悪影響を与える可能性が高いと考えられる。 In general, it is known that the higher the material strength, the higher the hydrogen embrittlement susceptibility of the steel material. Therefore, it is considered that the application of plastic strain (permanent strain) to the material generates dislocations and increases the strength of the material, and thus has a high possibility of adversely affecting the hydrogen embrittlement susceptibility.
鉄鋼材料には、製管またはプレスといった成形時に加えて、施工時、使用時等の種々の段階において、塑性ひずみが付与される。上述のとおり、塑性ひずみは水素脆化感受性に大きく影響を与えるため、製品の最終的な水素脆化感受性を適正に評価するためには、塑性ひずみ付与後の性能評価が必要である。 A plastic strain is imparted to the steel material at various stages such as construction and use, in addition to forming at the time of forming a pipe or pressing. As described above, since plastic strain greatly affects hydrogen embrittlement susceptibility, it is necessary to evaluate the performance after plastic strain is applied in order to properly evaluate the final hydrogen embrittlement susceptibility of a product.
例えば、鋼板をパイプ状に成形して継目を溶接することで製造する溶接鋼管においては、製管時に塑性変形が加わることとなる。ここで、最終製品である溶接鋼管を用いて水素脆化感受性を評価することは可能である。しかしながら、この方法では製管した後でないと最終製品の性能が分からないため、工業的にはその前段階である鋼板を用いて適正な評価ができることが望まれる。 For example, in a welded steel pipe manufactured by forming a steel plate into a pipe shape and welding seams, plastic deformation is applied during pipe production. Here, it is possible to evaluate hydrogen embrittlement susceptibility using a welded steel pipe as a final product. However, in this method, the performance of the final product cannot be known until after the pipe has been produced. Therefore, industrially, it is desired that a proper evaluation can be performed using a steel plate which is the preceding stage.
また、鋼板をプレス成形する場合、塑性ひずみは局所に集中する。このような材料に外部応力を負荷して水素脆化特性を評価することは容易ではない。材料が大きく変形してしまっていること、歪み分布により強度分布が同時に生じ均一な応力負荷が困難なことが挙げられる。したがって、塑性ひずみの影響を正しく評価できる手法が必要である。 Further, when a steel sheet is press-formed, plastic strain is locally concentrated. It is not easy to evaluate the hydrogen embrittlement characteristics by applying an external stress to such a material. The material is greatly deformed, and the strength distribution is simultaneously generated due to the strain distribution, and it is difficult to uniformly apply a stress. Therefore, there is a need for a method capable of correctly evaluating the effect of plastic strain.
例えば、特許文献１には、高強度鋼板の耐遅れ破壊性の評価方法（水素脆化評価法）が開示されている。特許文献１に記載される方法では、高強度鋼板の試験片に対して、この高強度鋼板の伸び量に対して２０〜８０％の塑性歪みを伴う引張加工を加えた後に、曲げ部の半径が５〜３０ｍｍとなるようなＵ曲げ加工か、曲げ部の角度が３０〜９０度となるようなＶ曲げ加工のいずれかを加え、更に、この曲げ加工を加えた試験片の両辺部分に対して５００〜２０００ＭＰａの圧縮応力を付加した状態で、電解溶液に陰極として浸漬し、陰極及び陽極に定電流を通電して水素チャージを行い、陰極試験片に割れが生じるまでの時間で高強度鋼板の耐遅れ破壊性を評価することとしている。 For example, Patent Literature 1 discloses a method for evaluating delayed fracture resistance of a high-strength steel sheet (hydrogen embrittlement evaluation method). In the method described in Patent Literature 1, a test piece of a high-strength steel sheet is subjected to a tensile processing with a plastic strain of 20 to 80% with respect to the elongation of the high-strength steel sheet, and then a radius of a bent portion is obtained. Is 5 to 30 mm or V-bending so that the angle of the bent portion is 30 to 90 degrees. Furthermore, the bending is performed on both sides of the test piece. In a state where a compressive stress of 500 to 2000 MPa is applied, the cathode is immersed in the electrolytic solution as a cathode, a constant current is applied to the cathode and the anode, and hydrogen charging is performed. Is to be evaluated for delayed fracture resistance.
しかしながら、特許文献１に記載される方法では、塑性歪みを伴う引張加工に加えて、評価時にＵ曲げ加工またはＶ曲げ加工により塑性ひずみを付与するため、塑性ひずみ量と水素脆化特性との関係を定量的に評価することができないという問題がある。また、引張加工では、塑性ひずみが局部に集中するおそれがあり、付与する塑性ひずみ量の制御が困難であるという問題もある。 However, in the method described in Patent Document 1, since a plastic strain is imparted by U-bending or V-bending at the time of evaluation, in addition to tensile processing accompanied by plastic strain, the relationship between the amount of plastic strain and hydrogen embrittlement properties is evaluated. Cannot be quantitatively evaluated. Further, in the tensile working, there is a possibility that the plastic strain may be concentrated in a local area, and there is a problem that it is difficult to control the amount of the applied plastic strain.
本発明は、上記の問題を解決し、鋼材の水素脆化特性に及ぼす塑性ひずみ量の影響を定量的に評価することが可能な方法を提供することを目的とする。 An object of the present invention is to solve the above problems and to provide a method capable of quantitatively evaluating the effect of the amount of plastic strain on the hydrogen embrittlement characteristics of a steel material.
本発明は、上記の問題を解決するためになされたものであり、下記の水素脆化特性評価方法を要旨とする。 The present invention has been made to solve the above-mentioned problem, and has a gist of the following method for evaluating hydrogen embrittlement characteristics.
（１）塑性ひずみが付与される鋼材の水素脆化特性を評価する方法であって、
（ａ）前記塑性ひずみが付与される前の前記鋼材と同一の鋼からなる試験材に対して、冷間または温間の圧縮加工または圧延を施す工程と、
（ｂ）前記圧縮加工または圧延が施された前記試験材に対して、水素を導入する工程と、
（ｃ）前記水素が導入された前記試験材を用いた水素脆化特性の評価結果に基づいて、前記鋼材の水素脆化特性を評価する工程と、を備える、
水素脆化特性評価方法。
(1) A method for evaluating the hydrogen embrittlement property of a steel material to which plastic strain is applied,
(A) performing a cold or warm compression working or rolling on a test material made of the same steel as the steel material before the plastic strain is applied;
(B) introducing hydrogen into the compression-processed or rolled test material;
(C) evaluating a hydrogen embrittlement property of the steel material based on an evaluation result of the hydrogen embrittlement property using the test material into which the hydrogen has been introduced,
Method for evaluating hydrogen embrittlement characteristics.
（２）上記（ｂ）の工程において、水素導入の前、後または同時に、前記試験材に対して、弾性域での引張応力を付与する、
上記（１）に記載の水素脆化特性評価方法。
(2) In the step (b), a tensile stress in an elastic region is applied to the test material before, after or simultaneously with the introduction of hydrogen.
The method for evaluating hydrogen embrittlement characteristics according to the above (1).
（３）上記（ａ）の工程において、前記鋼材に付与される塑性ひずみの最大値の見積もり結果に基づいて、前記試験材に対して、前記塑性ひずみの最大値以上の塑性ひずみを付与する、
上記（１）または（２）に記載の水素脆化特性評価方法。
(3) In the step (a), a plastic strain equal to or more than the maximum value of the plastic strain is applied to the test material based on the estimation result of the maximum value of the plastic strain applied to the steel material.
The method for evaluating hydrogen embrittlement characteristics according to the above (1) or (2).
本発明によれば、鋼材の水素脆化特性に及ぼす塑性ひずみ量の影響を定量的に評価することが可能となる。 According to the present invention, it is possible to quantitatively evaluate the effect of the amount of plastic strain on the hydrogen embrittlement characteristics of a steel material.
本発明の一実施形態に係る水素脆化特性評価方法について、詳細に説明する。 The method for evaluating hydrogen embrittlement properties according to one embodiment of the present invention will be described in detail.
本発明の一実施形態に係る水素脆化特性評価方法は、製造時、施工時または使用時に塑性ひずみが付与される鋼材の水素脆化特性を評価する方法であり、（ａ）塑性ひずみ負荷工程、（ｂ）水素導入工程、および（ｃ）水素脆化特性評価工程を備える。各工程について詳しく説明する。 The hydrogen embrittlement property evaluation method according to one embodiment of the present invention is a method for evaluating the hydrogen embrittlement property of a steel material to which a plastic strain is imparted at the time of production, construction, or use. , (B) a hydrogen introduction step, and (c) a hydrogen embrittlement property evaluation step. Each step will be described in detail.
（ａ）塑性ひずみ負荷工程
塑性ひずみ負荷工程においては、まず塑性ひずみが付与される前の、水素脆化特性の評価対象となる鋼材と同一の鋼からなる試験材を準備する。ここで、同一の鋼とは、工業的に同一の工程により製造された鋼を意味する。すなわち、塑性ひずみが付与される前の鋼材と試験材とは、化学組成および金属組織が略同一である。
(A) Plastic Strain Loading Step In the plastic strain loading step, first, a test material made of the same steel as a steel to be evaluated for hydrogen embrittlement characteristics before plastic strain is applied is prepared. Here, the same steel means steel manufactured industrially by the same process. In other words, the steel material before the plastic strain is applied and the test material have substantially the same chemical composition and metal structure.
そして、上記の試験片に対して、冷間または温間の圧縮加工または圧延を施す。ここで、冷間または温間の圧縮加工または圧延とは、５０℃程度までの温度で行う圧縮加工または圧延を指すものとする。５０℃を超える温度では、鋼の回復が生じるおそれがある。その場合、塑性ひずみの水素脆化特性への影響が低減されるため、狙い通りの塑性ひずみを付与しても、その塑性ひずみの水素脆化特性への影響の適切な評価が難しくなるおそれがある。 Then, the test piece is subjected to cold or warm compression or rolling. Here, cold or warm compression processing or rolling refers to compression processing or rolling performed at a temperature up to about 50 ° C. At temperatures above 50 ° C., steel recovery may occur. In that case, the influence of plastic strain on hydrogen embrittlement properties is reduced, so even if the intended plastic strain is applied, it may be difficult to properly evaluate the influence of plastic strain on hydrogen embrittlement properties. is there.
本発明者らが、鋼材に付与される塑性ひずみ量と水素脆化特性との関係を調査した結果、塑性ひずみの付与方法に依存せずに、塑性ひずみ量と水素脆化割れの感受性との間に正の相関関係が認められることが分かった。すなわち、圧縮加工であっても引張加工であっても、それにより生じる塑性ひずみ量の水素脆化特性に及ぼす影響が同等であることを見出した。 The present inventors have investigated the relationship between the amount of plastic strain and the hydrogen embrittlement characteristics imparted to steel, without depending on the method of imparting plastic strain, the amount of plastic strain and the susceptibility of hydrogen embrittlement cracking It was found that there was a positive correlation between them. That is, it has been found that the effect of the amount of plastic strain caused by the compression processing and the tensile processing on the hydrogen embrittlement characteristics is the same.
上述のように、試験材に対して引張加工を施す場合には、塑性ひずみが局部に集中するおそれがあり、特に大きな塑性ひずみを付与したい場合には、付与する塑性ひずみ量の制御が困難である。そのため、本発明においては、塑性ひずみを付与するため、圧縮加工または圧延を行う。塑性ひずみ量は、断面圧下率などにより容易に調整することが可能である。 As described above, when performing tensile processing on the test material, there is a risk that the plastic strain is concentrated in a local area, and particularly when it is desired to apply a large plastic strain, it is difficult to control the amount of the plastic strain to be applied. is there. Therefore, in the present invention, compression or rolling is performed to impart plastic strain. The amount of plastic strain can be easily adjusted by the cross-sectional reduction ratio or the like.
また、試験材の形状について特に制限はないが、厚さが一定の板状の試験材に対して圧縮加工または圧延を施すことにより、全面に均一な塑性ひずみを付与することが可能である。また、試験材の大きさについても特に制限はなく、小型のものから大型のものまで自由に適用することが可能である。 Although there is no particular limitation on the shape of the test material, it is possible to apply uniform plastic strain to the entire surface by subjecting a plate-like test material having a constant thickness to compression processing or rolling. Further, the size of the test material is not particularly limited, and can be freely applied from small to large.
さらに、試験材に付与する塑性ひずみ量についても、適宜調整すればよい。例えば、評価対象となる鋼材に付与される塑性ひずみの最大値を見積もり、その見積り結果に基づいて、試験材に付与する塑性ひずみ量を決定することができる。塑性ひずみが付与された後の鋼材の水素脆化特性を厳しく評価する観点からは、見積もられた塑性ひずみの最大値以上の塑性ひずみを試験材に付与することが好ましい。 Further, the amount of plastic strain applied to the test material may be appropriately adjusted. For example, it is possible to estimate the maximum value of the plastic strain to be applied to the steel material to be evaluated, and to determine the amount of plastic strain to be applied to the test material based on the estimation result. From the viewpoint of strictly evaluating the hydrogen embrittlement characteristics of the steel material after the plastic strain is applied, it is preferable to apply a plastic strain equal to or more than the estimated maximum plastic strain to the test material.
（ｂ）水素導入工程
水素導入工程においては、上記（ａ）の工程で圧縮加工または圧延を施し、塑性ひずみを付与した試験材に対して、水素を導入する。
(B) Hydrogen Introducing Step In the hydrogen introducing step, hydrogen is introduced into the test material which has been subjected to compression or rolling in the step (a) to give plastic strain.
水素を導入する方法については特に制限はなく、公知の方法を適宜採用すればよい。例えば、電解液中で電解チャージを行う方法、高圧水素ガス雰囲気下で保持する方法、腐食液中に浸漬する方法等が挙げられる。 The method for introducing hydrogen is not particularly limited, and a known method may be appropriately employed. For example, a method of performing electrolytic charging in an electrolytic solution, a method of maintaining the same in a high-pressure hydrogen gas atmosphere, a method of immersing it in a corrosive solution, and the like can be given.
電解チャージを行う方法では、試験材および白金等の対極を電解液に浸漬し、試験材と対極との間に電位差を生じさせて、試験材に水素発生電位より卑の電位となる電圧を印加することで、試験材中に電気化学的に水素を導入することが可能である。 In the method of performing electrolytic charging, a test material and a counter electrode such as platinum are immersed in an electrolytic solution to generate a potential difference between the test material and the counter electrode, and a voltage that is lower than the hydrogen generation potential is applied to the test material. By doing so, it is possible to electrochemically introduce hydrogen into the test material.
電解液としては、硫酸（Ｈ２ＳＯ４）水溶液または塩酸（ＨＣｌ）水溶液等の酸性溶液、塩化ナトリウム（ＮａＣｌ）水溶液等の中性溶液、水酸化ナトリウム（ＮａＯＨ）水溶液等のアルカリ性溶液を用いることができる。 As the electrolytic solution, an acidic solution such as an aqueous solution of sulfuric acid (H 2 SO 4 ) or hydrochloric acid (HCl), a neutral solution such as an aqueous solution of sodium chloride (NaCl), or an alkaline solution such as an aqueous solution of sodium hydroxide (NaOH) is used. Can be.
また、高圧水素ガス雰囲気下で保持する方法では、例えば、水素分圧が０．１ＭＰａ以上、好ましくは１ＭＰａ以上である水素含有雰囲気中に試験材を保持することで、水素を導入することが可能である。 In the method of holding under a high-pressure hydrogen gas atmosphere, for example, hydrogen can be introduced by holding the test material in a hydrogen-containing atmosphere having a hydrogen partial pressure of 0.1 MPa or more, preferably 1 MPa or more. It is.
さらに、腐食液中に浸漬する方法では、酸溶液中に単純浸漬し、腐食反応で発生した水素を材料中に導入してもよいし、ＮＡＣＥ ＴＭ０２８４−２０１６に規定される酸性溶液中に硫化水素ガスを飽和させた環境に試験材を浸漬し、腐食反応によって試験材表面で水素を発生させることで、試験材中に水素を導入してもよい。 Further, in the method of immersion in a corrosion liquid, hydrogen may be simply immersed in an acid solution and hydrogen generated by the corrosion reaction may be introduced into the material, or hydrogen sulfide may be introduced into an acid solution specified in NACE TM0284-2016. Hydrogen may be introduced into the test material by immersing the test material in a gas-saturated environment and generating hydrogen on the surface of the test material by a corrosion reaction.
水素導入工程においては、水素導入の前後または同時に、試験材に対して、弾性域での引張応力を付与してもよい。引張応力を付与することにより、水素の導入量を増加させることが可能である。付与する引張応力を弾性域のものとするのは、新たな塑性ひずみが付与されるのを避けるためである。 In the hydrogen introduction step, a tensile stress in the elastic range may be applied to the test material before, after or simultaneously with the introduction of hydrogen. By applying a tensile stress, the amount of hydrogen introduced can be increased. The reason why the applied tensile stress is in the elastic range is to avoid applying new plastic strain.
（ｃ）水素脆化特性評価工程
水素脆化特性評価工程においては、まず上記（ｂ）の工程で水素が導入された試験材を用いて、当該試験材の水素脆化特性の評価を行う。水素脆化特性の評価方法については特に制限はなく、試験材に含まれる水素濃度を測定する方法、割れの発生状態を評価する方法、水素透過試験を行う方法などが挙げられる。
(C) Hydrogen embrittlement property evaluation step In the hydrogen embrittlement property evaluation step, first, the hydrogen embrittlement property of the test material is evaluated using the test material into which hydrogen has been introduced in the step (b). The method for evaluating the hydrogen embrittlement characteristics is not particularly limited, and examples thereof include a method for measuring the concentration of hydrogen contained in the test material, a method for evaluating the state of occurrence of cracks, and a method for performing a hydrogen permeation test.
試験材中の水素濃度の測定方法については特に制限はなく、例えば、ガスクロマトグラフ式昇温脱離水素分析装置（ＴＤＡ）を用いて、試験材を１００℃／ｈの昇温速度で４００℃まで加熱した後、放出された水素量を測定することにより求めることができる。 The method for measuring the hydrogen concentration in the test material is not particularly limited. For example, the test material is heated to 400 ° C. at a rate of 100 ° C./h using a gas chromatograph-type thermal desorption / hydrogen analyzer (TDA). After heating, it can be determined by measuring the amount of hydrogen released.
なお、水素濃度の測定は、上述の方法によって試験材に水素を導入した後に行ってもよいし、水素導入の前後の両方で行ってその差を評価してもよい。水素脆化特性を評価するための重要なパラメータの１つである試験材中の水素濃度を測定することにより、試験材の水素脆化特性を評価することが可能となる。 The measurement of the hydrogen concentration may be performed after introducing hydrogen into the test material by the above-described method, or may be performed both before and after introducing hydrogen to evaluate the difference. By measuring the hydrogen concentration in the test material, which is one of the important parameters for evaluating the hydrogen embrittlement characteristics, the hydrogen embrittlement characteristics of the test material can be evaluated.
また、割れの発生状態を評価する方法についても特に制限はなく、水素導入後の試験材について、目視で評価するか、光学顕微鏡もしくは電子顕微鏡等を用いて表面観察を行うか、または超音波探傷法を用いて内部の割れの測定を行い、水素導入によって割れが生じたか否か、またはどの程度の割れが発生したかの調査を行うことができる。 Also, there is no particular limitation on the method of evaluating the state of occurrence of cracks, and the test material after hydrogen introduction is visually evaluated, or surface observation is performed using an optical microscope or an electron microscope, or ultrasonic flaw detection. The internal crack is measured by using the method, and it is possible to investigate whether or not the crack has been generated by the introduction of hydrogen or how much the crack has been generated.
さらに、試験材に対して応力を負荷した後に、割れの発生状態を評価してもよい。試験材に負荷する応力の種類については特に制限されず、引張応力、圧縮応力、曲げ応力、ねじり応力のいずれであってもよい。そして、例えば、破断が生じた際の応力を測定することによって、試験材の水素脆化特性を直接的に評価することが可能である。試験材に対する応力の負荷は、上述の方法によって試験材に水素を導入した後に行ってもよいし、水素を導入しながら行ってもよい。塑性ひずみの影響を調査することが目的であるため、試験片全体に負荷される応力については弾性応力以下とすることが望ましいが、切欠き底またはき裂先端等の応力集中が生じる局所においては、弾性応力を超え塑性ひずみが生じてもよい。 Furthermore, after applying stress to the test material, the state of occurrence of cracks may be evaluated. The type of stress applied to the test material is not particularly limited, and may be any of tensile stress, compressive stress, bending stress, and torsional stress. Then, for example, it is possible to directly evaluate the hydrogen embrittlement characteristics of the test material by measuring the stress at the time when the fracture occurs. The loading of the stress on the test material may be performed after introducing hydrogen into the test material by the above-described method, or may be performed while introducing hydrogen. Since the purpose is to investigate the effect of plastic strain, it is desirable that the stress applied to the entire test piece be equal to or less than the elastic stress, but in places where stress concentration occurs, such as the notch bottom or crack tip. Alternatively, a plastic strain exceeding the elastic stress may occur.
また、水素透過試験とは、板状の試験片を採取し、その一方から水素を導入し、他方から試験片中を透過した水素を検出する手法である。水素導入方法について特に制限はなく、上述した電解液中で電解チャージを行う方法、高圧水素ガス雰囲気下で保持する方法、腐食液中に浸漬する方法等を採用することができる。一方、水素検出側についても、透過してきた水素を電気化学的に測定してもよいし、ガスクロマトグラフ等を用いてガスとして評価してもよい。用いる手法によっては、試験片上にＮｉまたはＰｄのメッキを施すこともある。水素透過試験では、材料中への水素の侵入速度および拡散速度を評価することができる。 In addition, the hydrogen permeation test is a method in which a plate-shaped test piece is sampled, hydrogen is introduced from one of the test pieces, and hydrogen transmitted through the test piece is detected from the other. The method for introducing hydrogen is not particularly limited, and a method of performing electrolytic charging in the above-described electrolytic solution, a method of maintaining the same in a high-pressure hydrogen gas atmosphere, a method of immersing in an etching solution, and the like can be employed. On the hydrogen detection side, on the other hand, the permeated hydrogen may be measured electrochemically or may be evaluated as a gas using a gas chromatograph or the like. Depending on the technique used, the test piece may be plated with Ni or Pd. In the hydrogen permeation test, the rate of penetration and diffusion of hydrogen into a material can be evaluated.
上述の方法により試験材を用いた水素脆化特性の評価が終了した後、当該評価結果に基づいて、評価対象となる鋼材の水素脆化特性の評価を行う。鋼材の水素脆化特性の評価方法については特に制限はない。例えば、鋼材に付与されると見積もられた塑性ひずみの最大値を試験材に付与した場合には、試験材の水素脆化特性が、塑性ひずみが付与された後の鋼材の水素脆化特性であると評価することができる。 After the evaluation of the hydrogen embrittlement characteristics using the test material is completed by the above-described method, the hydrogen embrittlement characteristics of the steel to be evaluated are evaluated based on the evaluation results. There is no particular limitation on the method for evaluating the hydrogen embrittlement properties of steel. For example, when the maximum value of the plastic strain estimated to be applied to steel is given to the test material, the hydrogen embrittlement property of the test material becomes the hydrogen embrittlement property of the steel material after the plastic strain is applied. Can be evaluated.
以下、実施例によって本発明をより具体的に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.
０．０５％のＣおよび１．５％のＭｎを含み、異なる工程で製造された３種類の炭素鋼（鋼Ａ〜Ｃ）からなる鋼板をそれぞれ試験材とした。試験材の寸法は、厚さ２０ｍｍ、幅２０ｍｍ、長さ１００ｍｍとした。また、いずれの鋼板も引張強さは、約６００ＭＰａであった。 Steel sheets containing 0.05% of C and 1.5% of Mn and made of three types of carbon steels (steels A to C) manufactured in different processes were used as test materials. The dimensions of the test material were 20 mm in thickness, 20 mm in width, and 100 mm in length. Each of the steel sheets had a tensile strength of about 600 MPa.
本実施例においては、鋼板を製管する際に付与される塑性ひずみの最大値を５％と見積もった。そして、当該見積もり結果に基づき、上記の３つの試験材のそれぞれに対して冷間圧延を施して、５％の圧縮塑性ひずみを付与し、厚さを１９ｍｍとした。 In the present example, the maximum value of the plastic strain applied when producing a steel sheet was estimated to be 5%. Then, based on the estimation result, each of the above three test materials was subjected to cold rolling to give 5% compression plastic strain, and the thickness was set to 19 mm.
そして、塑性ひずみを付与する前後の試験材を用いて、ＮＡＣＥ ＴＭ０２８４−２０１６の規定に準拠したＨＩＣ試験を実施した。具体的には、５％ＮａＣｌおよび０．５％ＣＨ３ＣＯＯＨを含有し、窒素ガスを用いて酸素を除去した後、１気圧のＨ２Ｓを飽和させた水溶液を試験液として準備した。 Then, an HIC test in accordance with the provisions of NACE TM0284-2016 was performed using the test materials before and after the plastic strain was applied. Specifically, an aqueous solution containing 5% NaCl and 0.5% CH 3 COOH and removing oxygen using nitrogen gas and saturated with 1 atm of H 2 S was prepared as a test solution.
そして、上記の試験液に各試験材を２５℃で９６時間浸漬することで、水素の導入を行った。その後、試験材を試験液から取り出し、内部に発生したＨＩＣを超音波探傷法（Ｃスキャン）により測定し、インディケーション部分（ＨＩＣ割れ発生部分）の面積率（ＣＡＲ）を求めた。塑性ひずみ付与後の試験材のＣＡＲについては、試験材の板厚中央部および表層部のそれぞれについて求めた。 Then, hydrogen was introduced by immersing each test material in the test liquid at 25 ° C. for 96 hours. Thereafter, the test material was removed from the test solution, and the HIC generated inside was measured by an ultrasonic flaw detection method (C scan) to determine the area ratio (CAR) of the indication portion (the HIC crack occurrence portion). The CAR of the test material after the plastic strain was applied was determined for each of the central portion and the surface layer of the test material.
その結果を表１に示す。なお、各試験材について、９試料ずつＨＩＣ試験を実施した。表１には、測定されたＣＡＲの最大値を示している。 Table 1 shows the results. In addition, about each test material, 9 samples performed the HIC test. Table 1 shows the maximum value of the measured CAR.
表１に示すように、塑性ひずみを付与する前では、鋼Ａ、Ｂ、ＣのＣＡＲは、いずれも３％以下であり、水素脆化特性に差はない結果となった。それに対して、５％の圧縮塑性ひずみを付与した後では、結果に大きく差が生じた。具体的には、鋼Ａでは板厚中央部の割れが顕著であったが、それ以外での割れはなかった。また、鋼Ｂでは板厚中央部にも表層部にも割れが確認された。鋼Ｃでも板厚中央部および表層部の両方で割れが確認されたが、特に表層部において割れが顕著であった。 As shown in Table 1, before the plastic strain was applied, the CARs of the steels A, B, and C were all 3% or less, and there was no difference in the hydrogen embrittlement characteristics. On the other hand, there was a large difference in the results after applying 5% compression plastic strain. Specifically, in steel A, cracks were noticeable at the center of the sheet thickness, but there were no cracks other than that. In the case of steel B, cracks were confirmed both in the central part and in the surface layer. Although cracks were confirmed both in the central part of the sheet thickness and in the surface layer of Steel C, cracks were particularly remarkable in the surface layer.
以上の結果から、これらの材料が板厚方向に対し均一に塑性ひずみを付与されて用いられる場合には、鋼Ｂが最も良好な鋼材と考えられる。しかし、鋼板に曲げ加工を施し、管状に成形する場合においては、塑性ひずみは表面で最も大きく、板厚中央部で小さくなるため、表層部において割れが生じない鋼Ａが最も良好な鋼材であると評価された。 From the above results, it is considered that when these materials are used after being given a plastic strain uniformly in the thickness direction, steel B is the best steel material. However, when a steel sheet is bent and formed into a tubular shape, the plastic strain is largest at the surface and small at the center of the sheet thickness, so that steel A that does not crack at the surface layer is the best steel material. Was evaluated.
本発明によれば、鋼材の水素脆化特性に及ぼす塑性ひずみ量の影響を定量的に評価することが可能となる。 According to the present invention, it is possible to quantitatively evaluate the effect of the amount of plastic strain on the hydrogen embrittlement characteristics of a steel material.
Claims (3)
（ａ）前記塑性ひずみが付与される前の前記鋼材と同一の鋼からなる試験材に対して、冷間または温間の圧縮加工または圧延を施す工程と、
（ｂ）前記圧縮加工または圧延が施された前記試験材に対して、水素を導入する工程と、
（ｃ）前記水素が導入された前記試験材を用いた水素脆化特性の評価結果に基づいて、前記鋼材の水素脆化特性を評価する工程と、を備える、
水素脆化特性評価方法。 A method for evaluating the hydrogen embrittlement properties of steel material to which plastic strain is applied,
(A) performing a cold or warm compression working or rolling on a test material made of the same steel as the steel material before the plastic strain is applied;
(B) introducing hydrogen into the compression-processed or rolled test material;
(C) evaluating a hydrogen embrittlement property of the steel material based on an evaluation result of the hydrogen embrittlement property using the test material into which the hydrogen has been introduced,
Method for evaluating hydrogen embrittlement characteristics.
請求項１に記載の水素脆化特性評価方法。 In the step (b), a tensile stress in an elastic range is applied to the test material before, after or simultaneously with the introduction of hydrogen.
The method for evaluating hydrogen embrittlement characteristics according to claim 1.
請求項１または請求項２に記載の水素脆化特性評価方法。 In the step (a), a plastic strain equal to or more than the maximum value of the plastic strain is applied to the test material based on the estimation result of the maximum value of the plastic strain applied to the steel material.
The method for evaluating hydrogen embrittlement characteristics according to claim 1 or 2.
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