JPH08145862A - Method for evaluating delayed break of metallic material - Google Patents

Abstract

PURPOSE: To obtain an evaluation index relating the delayed break of a metallic member with the amount of diffusive hydrogen by impressing a constant load to a test piece while exposing the whole outer peripheral surface of the test piece to an ambience where hydrogen invades and measuring the amount of hydrogen invading a hollow at the same time. CONSTITUTION: A test liquid 23 such as dilute hydrochloric acid or the like is filled in a test tank 21 of a hydrogen-feeding device 20. When a test is started, a constant load is impressed between the test tank 21 and a sample-fixing instrument 30 for a metallic material test piece 1 by a load-impressing device 32 connected to the fixing instrument 30. Hydrogen atoms invading from the outer peripheral surface of the test piece 1 form hydrogen molecules when reaching a hollow 2. The hydrogen molecules are transferred to a hydrogen-detecting device 13 by a carrier gas, and the amount of hydrogen invading the hollow 2 is measured. When the test piece 1 breaks, an integral value of the amount of hydrogen invading the test piece 1 is calculated by a data processor 15 connected to the hydrogen-detecting device 13. The obtained integral value is determined as the limit amount of diffusive hydrogen of the metallic material and set as an evaluation index of the delayed break.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for evaluating delayed fracture of metallic materials. INDUSTRIAL APPLICABILITY The present invention is used in fields such as the iron making industry, various non-ferrous metal industries, and the construction industry using metal members.

[0002]

2. Description of the Related Art The delayed fracture of a metal material is considered to be caused by hydrogen atoms (diffusible hydrogen) in the metal material, but its mechanism has not yet been fully understood.

Since a long-term exposure test is required to evaluate delayed fracture of a metal material, indoor tests have been proposed and carried out by shortening the test period by various methods. However, despite the importance of diffusible hydrogen in delayed fracture, an effective method has not yet been established for the method of evaluating the delayed fracture of a metal member and the amount of diffusible hydrogen in association with each other.

One of the methods currently used to evaluate the delayed fracture and the diffusible hydrogen content in association with each other is the method used in the critical diffusible hydrogen content method. This is because two test pieces of the same metal material are charged with hydrogen under the same conditions, one test piece is subjected to a rupture test in which a tensile stress of 0.9 TS is applied, and the other test piece is subjected to hydrogen thermal analysis. The amount of diffusible hydrogen is measured by applying the device. Here, the upper limit of the amount of diffusible hydrogen in which delayed fracture does not occur for 100 hours is defined as the limit diffusible hydrogen amount, and is used for delayed fracture evaluation of a metal material. If the actual amount of hydrogen penetration in the environment of use of the metal material is less than the limit diffusible hydrogen content of the metal material, it is judged that delayed fracture does not occur. As a method of charging the test piece with hydrogen, there are a method of immersing the test piece in an acid, a method of negatively charging the test piece in an electrolytic solution, and the like. In addition, when carrying out the breaking test, the test was conducted in the atmosphere after hydrogen charging, washing with water and drying.

As a method for measuring the amount of hydrogen penetrating in the use environment, Japanese Patent Laid-Open No. 3-269234 discloses a method of measuring the amount of hydrogen penetrating into the cavity in the use environment. The technology is disclosed.

[0006]

The method used in the conventional limiting diffusible hydrogen content method is to use two test pieces of the same metal material.
This was used, and the breakage test was performed with one, while the amount of diffusible hydrogen was separately measured with the other. However, since the fracture test is performed in the atmosphere, the charged hydrogen was released during the measurement, and it was difficult to accurately grasp the amount of diffusible hydrogen involved in delayed fracture. Moreover, even with the same metal material, the variation due to the test piece was unavoidable, and the reliability of the data was questionable in this respect as well.

[0007]

[Means for Solving the Problems] A rod-shaped metal material test piece having a cavity is prepared, and a constant load is applied to the test piece while exposing the entire outer peripheral surface of the test piece to a hydrogen infiltration atmosphere, and at the same time, hydrogen that has invaded the cavity. A delayed fracture evaluation method for a metal material, comprising measuring the amount of hydrogen and using the amount of invading hydrogen until the test piece breaks as an index of the delayed fracture of the metal material.

A cavity is provided in the rod-shaped metal material test piece,
The opening of the cavity is closed by a seal. A carrier gas supply device and a hydrogen detection device are connected to the seal, and each is connected to the cavity of the test piece.

The amount of invading hydrogen may be continuously measured by a hydrogen detecting device and the integrated value thereof may be calculated after the fracture occurs, or may be collectively detected by the hydrogen detecting device after the fracture occurs.

The metal material test piece may have a cylindrical shape. In this case, a load may be applied to the entire test piece and at the same time, the amount of hydrogen that has entered the cavity may be measured.

A small notch may be provided in the test piece to promote hydrogen charging of the test piece. However, in this case, notches are provided in both the hollow part and the solid part,
Both conditions need to be equal. When using a cylindrical test piece, one notch is sufficient.

[0012]

Function: Since the outer peripheral surface of the metal material test piece is exposed to the hydrogen penetrating atmosphere, hydrogen atoms generated on the outer peripheral surface enter the inside of the test piece. When the hydrogen atoms that have penetrated into the test piece reach the inner surface of the hollow cavity, they form hydrogen molecules and penetrate into the cavity. The hydrogen molecules once entering the cavity do not enter the test piece again and diffuse, and are accumulated in the cavity. A certain load is applied to the solid part, and when delayed fracture occurs, the hydrogen molecules that have entered the cavity are transferred to the hydrogen detection device by the carrier gas supplied from the carrier gas supply device, and the load is applied. To the delayed fracture occurs, the amount of hydrogen that has penetrated into the cavity is measured. In addition, the hydrogen molecules are continuously transferred to a hydrogen detection device by a carrier gas, and the amount of invaded hydrogen is sequentially measured, so that when delayed fracture occurs, an integrated value of the amount of invaded hydrogen is obtained by a data processing device. You may In this way, the total amount of hydrogen that has penetrated into the cavity of the test piece can be obtained before the delayed fracture occurs at a constant load. Here, the hydrogen that has penetrated into the cavity is considered to be diffusible hydrogen that contributed to the delayed fracture. Therefore,
The delayed fracture susceptibility of the metal piece can be evaluated using the thus obtained integrated value of the amount of invading hydrogen as an index.

If delayed fracture does not occur even if a load is continuously applied for a certain period of time, it can be determined that the delayed fracture does not occur in the metal material. If the maximum amount of total penetrating hydrogen when the delayed fracture does not occur under the same load is defined as the limit diffusible hydrogen amount, if the amount of hydrogen that penetrates in the actual environment is less than the limit diffusible hydrogen amount, delayed fracture Can be determined not to occur.

Further, the hollow metal bolt described in JP-A-3-269234 can be used as a test piece. In this case, the amount of hydrogen penetrating in the use environment is also measured by the metal bolt, and if compared with the measured limit diffusible hydrogen amount, the presence or absence of delayed fracture in the use environment is predicted more realistically. You can

[0015]

Embodiments of the invention will be described with reference to the drawings. FIG. 1 shows an example of an apparatus for carrying out the delayed fracture evaluation method for metallic materials according to the present invention.

The metal material test piece 1 comprises a solid portion and a hollow portion having a cavity 2. The cavity 2 is open at one end face. Appropriate sizes of the test piece are an outer diameter of 5 to 300 mm, a hollow wall thickness of 0.5 to 100 mm, and a length of 50 to 500 mm. The opening of the test piece 1 is closed by a test piece seal 5 made of adhesive rubber or the like. A carrier gas introduction pipe 7 and a gas discharge pipe 8 penetrate through the test piece seal 5. The carrier gas introduction pipe 7 connects the carrier gas supply device 10 and the cavity 2. An inert gas such as Ar is used as the carrier gas. The gas discharge pipe 8 connects the hydrogen detection device 13 and the cavity 2. As the hydrogen detector 13, a gas chromatograph analyzer,
A semiconductor gas sensor, a mass spectrometer, etc. are used. A data processing device 15 is connected to the hydrogen detection device 13.

The metal material test piece 1 to which the above apparatus is connected is used as the sample fixtures 30 and 31 in the hydrogen supply apparatus 20.
Then, the outer peripheral surface is exposed to a hydrogen intrusion atmosphere by the hydrogen supply device 20, and the test is started. Hydrogen supply device 2
Reference numeral 0 comprises a test tank 21, a test solution 23 filling the inside thereof, sample fixtures 30 and 31, a test tank seal 27, and a temperature controller 25. The test tank 21 and the metal material test piece 1 are in close contact with each other by the test tank seal 27 to prevent the test liquid 23 from leaking. Dilute hydrochloric acid, salt water, or the like is used as the test liquid 23, and its temperature is kept constant by the temperature controller 25. The sample fixtures 30 and 31 hold both ends of the metal material test piece 1.

At the start of the test, the load test device 32 connected to the sample fixture 30 is used to test the metal material test piece 1.
A constant load is applied between the sample fixtures 30 and 31.
In this embodiment, a tensile load is applied, and its size is 0.9TS.

When the hydrogen atoms penetrating from the outer peripheral surface of the metal material test piece 1 reach the cavity 2, they form hydrogen molecules. The hydrogen molecule is detected by the carrier gas as a hydrogen detector 13
Then, the amount of hydrogen that has entered the cavity 2 is measured. In this example, the amount of hydrogen is continuously measured during the test. When the metal material test piece 1 breaks, the data processing device 15 connected to the hydrogen detection device 13 calculates an integrated value of the amount of hydrogen that has entered the metal material test piece 1.

When no fracture occurs for 100 hours after the start of the test, it is judged that delayed fracture does not occur in the metal material,
By the same method as described above, the metal material test piece 1 was previously used.
Calculate the integrated value of the amount of hydrogen that has penetrated into.

The obtained integrated value is used as the critical diffusible hydrogen content of the metal material and is used as an index for evaluating delayed fracture. If the amount of hydrogen intrusion in the environment where the metal material is actually used is less than this critical diffusible hydrogen amount, it can be determined that the metal material does not undergo delayed fracture in that environment.

FIG. 2 is a cross-sectional view of a metal material test piece used in a method for evaluating delayed fracture of a metal material of a test piece having another shape. The shape of the metal material test piece is cylindrical, and the size is such that the outer diameter is 5 to 300 mm and the wall thickness of the hollow portion is 0.5.
It is suitable that the length is about 100 mm and the length is about 50 to 500 mm.

FIG. 3 is a cross-sectional view of a metal material test piece used in a delayed fracture evaluation method for a metal material of a test piece having another shape. In the metal material test piece 1 shown in FIG. 1, in order to promote the invasion of hydrogen into the test piece, one notch portion 40 of the same size is provided in each of the hollow portion and the solid portion.
Is provided. As for the size of the notch, a width of 2 to 5 mm and a depth of 2 to 5 mm are suitable.

FIG. 4 is a cross-sectional view of a metal bolt having a hollow portion, which is used in the delayed fracture evaluation method for a metal material of a test piece having another shape. The metal bolt includes a cavity 42 opened at the head of the bolt, a metal disc 45 that closes the opening of the cavity 42, and a silicon resin disc 4.
7. A cap 50 for sealing the opening of the cavity 42. When the critical diffusible hydrogen content is measured using the apparatus described in FIG. 1 using this bolt as a test piece, a load is applied to the entire bolt. Further, in order to measure the amount of hydrogen that has entered the cavity 42, the cap is removed so that the carrier gas introduction pipe and the gas discharge pipe penetrate the metal disc 45 and the silicon resin disc 47 to communicate with the cavity 42. .

[0025]

By using the method for evaluating delayed fracture of a metal material according to the present invention, an index for evaluating the delayed fracture of a metal member and the amount of diffusible hydrogen can be obtained. Further, since it is possible to perform both the breaking test and the hydrogen amount measurement using one test piece, it is possible to obtain more reliable data.

[Brief description of drawings]

FIG. 1 is an example of an embodiment of a delayed fracture evaluation method for metal materials according to the present invention.

FIG. 2 is a cross-sectional view of a metal material test piece used in a method for evaluating delayed fracture of a metal material according to a test piece having another shape.

FIG. 3 is a cross-sectional view of a metal material test piece used in a delayed fracture evaluation method for a metal material of a test piece having another shape.

FIG. 4 is a cross-sectional view of a metal bolt having a hollow portion, which is used in a delayed fracture evaluation method for a metal material according to a test piece having another shape.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal material test piece 2 Cavity 5 Sealing material 7 Carrier gas introduction pipe 8 Gas discharge pipe 10 Carrier gas supply device 13 Hydrogen detection device 15 Data processing device 20 Hydrogen supply device 21 Test tank 23 Test liquid 25 Temperature control device 27 Test tank seal 30 Sample Fixing Tool 31 Sample Fixing Tool 32 Load Device 40 Notch 42 Cavity 45 Metal Disk 47 Silicon Resin Disk 50 Cap

Claims (6)

[Claims] 1. A rod-shaped metal material test piece having a cavity is produced, a constant load is applied to the test piece while exposing the entire outer peripheral surface of the test piece to a hydrogen intrusion atmosphere, and at the same time, the amount of hydrogen invading the cavity is measured. A method for evaluating delayed fracture of a metal material, wherein the amount of invading hydrogen until the test piece breaks is used as an index of the delayed fracture of the metal material. 2. The delayed fracture evaluation method for a metal material according to claim 1, wherein the test piece comprises a solid portion and a hollow portion following the solid portion, and a constant load is applied to the solid portion. 3. The delayed fracture evaluation method for a metal material according to claim 1, wherein a constant load is applied from both ends of the cylindrical test piece. 4. The delayed fracture evaluation method for a metal material according to claim 2, wherein notches are provided in the solid portion and the hollow portion of the test piece, respectively. 5. The method for evaluating delayed fracture of a metal material according to claim 2, wherein a notch is provided on the outer peripheral surface of the cylindrical metal material test piece. 6. The delayed fracture evaluation method for a metal material according to claim 1, wherein a metal bolt having a hollow portion is used as the test piece.