JP6740176B2 - Hydrogen permeation test device - Google Patents

Description

The present invention relates to a hydrogen permeation trial KenSo location in the metal, such as high strength steel.

High-strength steel materials such as high-strength steel lose their ductility when hydrogen is contained, resulting in a marked decrease in strength. This phenomenon is called hydrogen embrittlement (see Non-Patent Document 1). Since hydrogen that has penetrated into the steel material is involved in the occurrence of hydrogen embrittlement, it is important to know the hydrogen penetration behavior in the steel material, which is the initial process of hydrogen embrittlement. The hydrogen permeation test is widely used to understand this hydrogen penetration behavior. Conventionally, in a hydrogen permeation test, first, a flat steel material is sandwiched between a cathode tank and an anode tank. In this state, hydrogen is generated on the hydrogen entry surface of the cathode tank to penetrate hydrogen into the steel material, and hydrogen that has permeated through the high-strength steel material is detected on the hydrogen detection surface of the anode tank (see Patent Document 1).

JP, 2016-095146, A

Tetsuo Shirakami, "Hydrogen Embrittlement in Steel Materials", Materials and Environment, vol. 60, No. 5, 236-240, 2011. Michihiko Nagumo, "Basics of Hydrogen Embrittlement, Behavior of Hydrogen and Embrittlement Mechanism", published by Uchida Lao Tsuruga Co., Ltd., 2008.

By the way, in the steel material to which the tensile stress is applied, defects are generated in the steel material, and the hydrogen penetration behavior changes as compared with the state in which the tensile stress is not applied (see Non-Patent Document 2). Since high-strength steel materials used for structures are often subjected to tensile stress during use, hydrogen penetration under high-strength steel materials can be measured in order to measure the behavior of hydrogen penetration into high-strength steel materials in actual environments. It is important to measure the behavior. However, in the hydrogen permeation test described above, the test cannot be performed while applying tensile stress to the steel material.

The present invention has been made to solve the above problems, and an object of the present invention is to make it possible to measure the hydrogen penetration behavior of a steel material to which tensile stress is applied.

Hydrogen permeation test method comprises a first step of adding a tensile stress in the metal sample to be measured, a second step of measuring the state of the hydrogen permeable metal sample while applying a tensile stress in the metal sample, the second A third step of evaluating the hydrogen permeation behavior in the metal sample based on the measurement result of the step.

In the above hydrogen permeation test method, in the second step, the tensile stress is changed within a range of less than the lower limit stress due to hydrogen embrittlement of the metal sample to measure the hydrogen diffusion coefficient or the hydrogen permeation rate, and in the third step, The measurement results of the two steps are extrapolated to evaluate the hydrogen diffusion coefficient or hydrogen permeation rate above the hydrogen embrittlement lower limit stress.

The hydrogen permeation test apparatus according to the present invention includes a hydrogen intrusion part for injecting hydrogen into a columnar metal sample to be measured, a hydrogen detection part for detecting hydrogen that has permeated the metal sample, and a metal sample by pulling in the direction of the sample extends, and a stress applying portion to apply a tensile stress to the metal sample, the hydrogen penetration portion and hydrogen detection unit that is arranged in series in the direction in which the metal sample extends.

In the above hydrogen permeation test apparatus, the hydrogen penetration part includes a first tank containing the first electrolyte solution, a first counter electrode housed in the first tank together with the first electrolyte solution, and a part of the first tank. A first sample fixing part, which is provided on the first sample fixing part to which a metal sample serving as a working electrode is fixed, and a metal sample formed in the first tank of the first sample fixing part and fixed to the first sample fixing part And a first power source for flowing an electric current between the metal sample and the first counter electrode, the hydrogen detection unit includes a second tank in which the second electrolyte solution is housed, A reference electrode housed in the second tank with the second electrolyte solution, a second counter electrode housed in the second tank with the second electrolyte solution, and provided in a part of the second tank to fix the metal sample. A second sample fixing part, a second opening formed in the second tank of the second sample fixing part and capable of contacting the second electrolyte solution with the metal sample fixed to the second sample fixing part; A measuring unit is provided that controls the electric potential to be constant with respect to the reference electrode and measures a current flowing between the metal sample and the second counter electrode.

As described above, according to the present invention, since the state of hydrogen that permeates the metal sample in the state where the tensile stress is applied to the metal sample is measured, the hydrogen entry behavior of the steel material to which the tensile stress is applied is The excellent effect of being measurable is obtained.

FIG. 1 is a flowchart for explaining a hydrogen permeation test method according to an embodiment of the present invention. FIG. 2 is a configuration diagram showing a configuration of the hydrogen permeation test device according to the embodiment of the present invention. FIG. 3 is a characteristic diagram showing the relationship between the tensile stress and the hydrogen permeation rate obtained by extrapolating the measurement results of the hydrogen permeation test method according to the embodiment. FIG. 4 is a configuration diagram showing a configuration of another hydrogen permeation test device according to the embodiment of the present invention. FIG. 5 is a configuration diagram showing a partial configuration of another hydrogen permeation test apparatus according to the embodiment of the present invention.

Hereinafter, the hydrogen permeation test method according to the embodiment of the present invention will be described with reference to FIG. First, in the first step S101, tensile stress is applied to the metal sample to be measured. Next, in the second step S102, the state of hydrogen that permeates the metal sample in a state where tensile stress is applied to the metal sample is measured. In this measurement, the tensile stress may be changed within the range of less than the lower limit stress due to hydrogen embrittlement of the metal sample to measure the hydrogen diffusion coefficient or the hydrogen permeation rate.

Next, in the third step S103, the hydrogen permeation behavior of the metal sample is evaluated based on the measurement result of the second step S102. Here, the measurement result of the second step S102 is extrapolated to evaluate the hydrogen diffusion coefficient or the hydrogen permeation rate above the hydrogen embrittlement lower limit stress.

Next, a hydrogen permeation test apparatus for carrying out the above hydrogen permeation test method will be described with reference to FIG. The hydrogen permeation test apparatus includes a hydrogen intrusion part 101 for injecting hydrogen into the metal sample 104 to be measured, and a hydrogen detection part 102 for detecting hydrogen that has permeated the metal sample 104. The metal sample 104 is made of, for example, high strength steel material such as high strength steel. The metal sample 104 may have a columnar shape such as a prism or a cylinder.

Further, the hydrogen permeation test apparatus includes a stress applying unit 103 that applies tensile stress to the metal sample 104. The stress applying unit 103 applies tensile stress to the metal sample 104 by pulling the columnar metal sample 104 in the extending direction.

The hydrogen penetration part 101 includes a first tank 111 that stores a first electrolyte solution 112, and a first counter electrode 114 that is stored in the first tank 111 together with the first electrolyte solution 112. In addition, in the embodiment, a reference electrode 113 housed in the first tank 111 is also provided together with the first electrolyte solution 112. The reference electrode 113 may be omitted. In addition, a first sample fixing portion 115 to which the metal sample 104 serving as a working electrode is fixed is provided in a part of the first tank 111. Further, in the first sample fixing portion 115, the first tank 111 is formed with a first opening portion 116 that allows the first electrolyte solution 112 to come into contact with the metal sample 104 fixed to the first sample fixing portion 115. There is. The first electrolyte solution 112 is, for example, a 0.1 M NaOH aqueous solution containing 1% ammonium thiocyanate.

Further, the hydrogen intrusion unit 101 includes a power supply control unit 117 that causes an electric current to flow between the metal sample 104 and the first counter electrode 114. The power supply controller 117 controls the potential of the metal sample 104 to be constant with respect to the reference electrode 113, for example, and causes a predetermined current to flow between the metal sample 104 and the first counter electrode 114.

The hydrogen detection unit 102 includes a second tank 121 containing a second electrolyte solution 122. In the second tank 121, the reference electrode 123 and the second counter electrode 124 are housed together with the second electrolyte solution 122. In addition, a second sample fixing portion 125 to which the metal sample 104 is fixed is provided in a part of the second tank 121. Further, in the second sample fixing part 125, the second tank 121 is provided with a second opening 126 that allows the second electrolyte solution 122 to come into contact with the metal sample 104 fixed to the second sample fixing part 125. There is. The second electrolyte solution 122 is, for example, a 0.1 M NaOH aqueous solution containing 1% ammonium thiocyanate.

The hydrogen detection unit 102 also includes a measurement unit 127 that controls the potential of the metal sample 104 to be constant with respect to the reference electrode 123 and measures the current flowing between the working electrode and the second counter electrode 124. The measurement unit 127 is, for example, a potentiostat.

In the hydrogen intrusion part 101, a negative potential that is equal to or lower than the hydrogen generation potential is applied to the metal sample 104 to inject hydrogen into the metal sample 104. Instead of applying the potential, the first tank 111 may be filled with an acidic solution to cause a corrosion reaction in the metal sample 104 to generate hydrogen, and thus hydrogen may enter.

The hydrogen that has entered the metal sample 104 as described above moves in the metal sample 104 by diffusion and reaches the hydrogen detection unit 102. In the second tank 121 accommodating the second electrolyte solution 122, each electrode is set to a potential sufficient to immediately oxidize the hydrogen that has arrived, and in the measurement unit 127, the amount that the hydrogen has reached is taken as the current value. To detect. For example, the measurement unit 127 measures the current flowing between the metal sample 104 and the second counter electrode 124 in a state where the potential of the metal sample 104 is constant with respect to the reference electrode 123. Obtain (electrochemical hydrogen permeation method).

From the change with time of the current value thus measured, it is possible to know the hydrogen penetration behavior in the metal sample 104 in the state where tensile stress is applied by the stress applying section 103. For example, the hydrogen permeation rate is obtained by dividing the obtained current value (current density) by the Faraday constant. Further, as is well known, the hydrogen diffusion coefficient can be obtained from the change in the current value (current density) described above (see Patent Document 1 and the like).

By the way, it is considered that hydrogen embrittlement in a steel material or the like does not occur below a certain tensile stress, and this tensile stress is called a lower limit stress. When hydrogen is introduced into a steel material in a state where a tensile stress exceeding the lower limit stress is applied, the steel material breaks due to hydrogen embrittlement. In this case, only hydrogen penetration behavior data for a short time before hydrogen embrittlement fracture can be obtained, and the hydrogen diffusion coefficient or hydrogen permeation rate in a steady state cannot be measured.

Therefore, the tensile stress applied by the stress applying unit 103 is changed within a range of less than the lower limit stress due to hydrogen embrittlement of the metal sample 104, and under this condition, the state of hydrogen permeating the metal sample 104 (hydrogen diffusion coefficient Or hydrogen permeation rate) is measured. This measurement result is extrapolated to obtain the relationship between tensile stress and hydrogen permeation rate as shown in FIG. In the relationship between the tensile stress thus obtained and the hydrogen permeation rate, the hydrogen diffusion coefficient or the hydrogen permeation rate is evaluated (determined) in the range of the embrittlement lower limit stress due to hydrogen or more.

By the way, in the hydrogen permeation test device, as shown in FIGS. 4 and 5, the hydrogen intrusion part 101 and the hydrogen detection part 102 may be arranged in a state of sandwiching the metal sample 104. The metal sample 104 is sandwiched by the surface of the first tank 111 on which the first opening 116 is formed and the surface of the second tank 121 on which the second opening 126 is formed. In order to prevent the first electrolyte solution 112 and the second electrolyte solution 122 from leaking, the contact portion (first sample fixing portion 115) between the metal sample 104 and the first tank 111, the metal sample 104 and the second tank 121, It is advisable to provide a seal portion 105 made of a rubber material on each of the contact portions (second sample fixing portion 125), and bring them into close contact with each other. With this configuration, it is easy to expand the areas of the first opening 116 and the second opening 126 in the extending direction of the metal sample 104 even if the metal sample 104 has the same length. As described above, the measurement sensitivity (S/N ratio) can be improved by increasing the area where hydrogen is detected in contact with the electrolyte solution.

As described above, according to the present invention, since the state of hydrogen that permeates the metal sample in the state where the tensile stress is applied to the metal sample is measured, the hydrogen penetration behavior of the steel material to which the tensile stress is applied is determined. Can be measured.

The present invention is not limited to the embodiments described above, and many modifications and combinations can be implemented by a person having ordinary knowledge in the field within the technical idea of the present invention. That is clear.

101... Hydrogen intrusion part, 102... Hydrogen detection part, 103... Stress application part, 104... Metal sample, 111... First tank, 112... First electrolyte solution, 113... Reference electrode, 114... First counter electrode, 115... 1 sample fixing part, 116... 1st opening part, 117... power control part, 121... 2nd tank, 122... 2nd electrolyte solution, 123... reference electrode, 124... 2nd counter electrode, 125... 2nd sample fixing part, 126... 2nd opening part 127... Measuring part.

Claims (2)

A hydrogen intrusion part for injecting hydrogen into the columnar metal sample to be measured,
A hydrogen detector for detecting hydrogen that has passed through the metal sample;
A stress applying unit that applies tensile stress to the metal sample by pulling the metal sample in a direction in which the metal sample extends ,
Wherein the hydrogen penetration portion and the hydrogen detector, hydrogen permeation test apparatus characterized that you have been placed in series in a direction in which the metal sample extends. The hydrogen permeation test apparatus according to claim 1 ,
The hydrogen penetration part is
A first tank containing a first electrolyte solution;
A first counter electrode housed in the first tank together with the first electrolyte solution,
A first sample fixing part, which is provided in a part of the first tank and to which the metal sample serving as a working electrode is fixed,
A first opening for allowing the first electrolyte solution to come into contact with the metal sample fixed to the first sample fixing part formed in the first tank of the first sample fixing part;
A power source for passing an electric current between the metal sample and the first counter electrode,
The hydrogen detector is
A second tank containing a second electrolyte solution;
A reference electrode housed in the second tank together with the second electrolyte solution;
A second counter electrode housed in the second tank together with the second electrolyte solution;
A second sample fixing part which is provided in a part of the second tank to fix the metal sample;
A second opening for allowing the second electrolyte solution to come into contact with the metal sample fixed to the second sample fixing part formed in the second tank of the second sample fixing part;
A hydrogen permeation test apparatus, comprising: a measurement unit that controls the potential of the metal sample to be constant with respect to the reference electrode and measures a current flowing between the metal sample and the second counter electrode.