JP2790702B2 - Metal bolt for measuring permeated hydrogen - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for detecting intrusion of hydrogen from a usage environment into a metal bolt used in a building or a bridge. Therefore, it is used for quality control of bolts by a manufacturer of metal bolts or safety management by a construction company using bolts or the like.

[Conventional technology]

For example, high-tensile steel 100 kg / cm ² or more strength is used in the construction or the like, to become very brittle when exposed to hydrogen in the state of the stressed as hydrogen embrittlement or hydrogen delayed cracking, well-known I have. In addition, hydrogen embrittlement occurs not only in high-strength steel but also in general metals. Naturally, metal embrittlement such as high-tension bolts used in construction and the like also causes hydrogen embrittlement under the use environment.

Therefore, it is meaningful to detect hydrogen invading a practically used metal member from its use environment and to grasp or estimate the degree of hydrogen embrittlement of the metal member. In view of such importance, several methods for detecting or quantifying hydrogen in a metal member have been proposed.

For example, Be, published in Metal Progress, 58, May, 1979
In the article by rman, the hydrogen concentration is determined from the electrode current value detected by bringing the burner electrode into close contact with the metal member (prior art 1). Further, in Japanese Patent Application Laid-Open No. 56-24563, a hydrogen collection container is brought into close contact with a metal member to collect hydrogen released from the member surface, and the amount of hydrogen is determined by a hydrogen gas detector (prior art 2). ).

Japanese Patent Application No. 1-77117 by the present inventors specifically discloses bolts as metal members. This cuts out the metal bolts and covers it to form a cavity,
This device measures the degree of hydrogen embrittlement by obtaining the amount of hydrogen that has penetrated into the cavity with a built-in hydrogen sensor or an external gas analyzer via a gas sampling needle (prior art 3).

[Problems to be solved by the invention]

In the above-mentioned prior art 3, hydrogen atoms generated by corrosion or the like outside the bolt enter the bolt, reach the hollow portion, become hydrogen molecules, that is, hydrogen gas, are collected in the hollow portion, and the hydrogen concentration is measured. That is. Therefore, strict sealing of the cavity inside the bolt is a very important factor,
Prior art 3 was not always sufficient.

For these reasons, the present invention provides a metal bolt for measuring permeated hydrogen, which secures hermeticity over a long period of time under the use environment of the bolt.

[Means for solving the problem]

The metal bolt for measuring permeated hydrogen of the present invention has a head (1)
Opening at the end face of the head, extending from the head (1) to the shaft (2), and the metal plate (5) or the central thin metal plate (1) on the head (1) side.
It has a cavity (4) hermetically sealed by joining 1), and a rubber plate (8), a perforated ring (9) and a cap (10) are placed on a metal plate (5) for sealing. It is composed of the provided structure.

The symbols in parentheses indicate the corresponding elements of the embodiment shown in the drawings and described later.

[Action]

The permeated hydrogen measurement metal bolt is made of the same material as possible to detect the amount of invading hydrogen.
Attach near the bolts that are practically used. If the bolt surface is subject to corrosion, for example, in the operating environment,
Due to the corrosion reaction, hydrogen atoms penetrate from the bolt shaft portion (2) and the screw portion (3) toward the inside of the bolt, reach the hollow portion (4) and are collected as hydrogen molecules. Once the hydrogen gas reaches the hollow portion (4) and becomes hydrogen gas, the hydrogen gas does not return to the shaft portion (2) or the screw portion (3) of the bolt and diffuses. Also, if the connection with the bolt body is ensured even from the metal plate (5) portion of the bolt head, it does not diffuse outside.

Therefore, the hydrogen that has entered the bolt is accumulated in the bolt cavity (4). When measurement is required, remove the cap (10) from the bolt, pierce the metal plate (5) and rubber plate (8) of the head 1 of the bolt (3) with a gas sampling needle and pass it through the cavity (4). Then, an argon gas or the like is sent as a carrier gas, and the hydrogen gas collected in the cavity is transported to a hydrogen analyzer for analysis. For the hydrogen analysis, a gas chromatograph equipped with a thermal conductivity detector or a semiconductor gas sensor may be used.

The hydrogen gas collected in the cavity (4) as described above is
It is very important not to leak outside. The metal plate (5) is directly joined to the opening end face (6) of the bolt without using an O-ring or the like as in the related art. There are various methods for joining, but the method must be a method that ensures airtightness and does not cause hydrogen permeation at the joint.
For example, the operation of bonding with an adhesive is easy,
Even if the bonding is complete, there is a concern about hydrogen transmission loss from the adhesive material on the bonding surface. Also, for example, in soldering, there is a problem that the airtightness tends to be uncertain.

As a result of conducting research to avoid these problems, various welding methods were successfully used, but laser beam welding was the most suitable. The cross-section of the joint surface between the metal plate (5) on which laser beam welding was performed and the end surface (6) of the opening of the bolt was inspected, and the materials were completely fused together. There was no need.

Further, the metal plate (5) is made of a material that is easy to weld,
It is required that the material be a soft material through which the gas sampling needle can easily pass, and a material through which hydrogen gas cannot pass. Therefore, generally, metal materials such as iron, copper, and aluminum are suitable. The material of the metal plate (5) for iron bolts is the same as that of the bolts for laser welding. Had to be used. If the material is thinner than this, welding becomes difficult because the material itself melts. In such a case, a method is adopted in which the thickness is increased by, for example, overlapping a metal ring only on the welded portion to enable welding. Alternatively, a method is used in which a thick metal disk is used, and only the central portion through which the gas sampling needle passes is etched or polished to reduce the thickness.

When the gas sampling needle is pierced through the metal plate, a resilient rubber plate (8) is installed to prevent leakage of hydrogen gas from around the needle, and this rubber plate (8) is placed on the metal plate (5). ) Is provided with a perforated ring (9). In addition, rubber plate (8) depending on bolt usage environment
In order to prevent the elasticity from decreasing due to aging, a cap (10) for shutting off the use environment is installed on the bolt head.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the cross-sectional views shown in FIGS.

FIG. 1 shows a case where a circular plate having a constant thickness is used as a metal plate 5 used for sealing the bolt cavity portion 4, and FIG. 2 shows a case where a circular plate having only a central portion is used as the metal plate 5. It is shown.

A hollow portion 4 extending from the end face of the bolt head portion 1 to the screw portion 3 through the shaft portion 2 is opened, and a female screw hole 7 larger than the diameter of the hollow portion 4 is connected to the head portion 1. A hole 7 opens out at the end face of the head 1. An iron thin disk 5 is placed on an opening end face 6 serving as a ring-shaped shoulder between the hole of the cavity 4 and the female screw hole 7 having a larger diameter, and a peripheral portion in contact with the opening end face 6 of the disc 5 Is irradiated with a laser beam for welding.

FIG. 1 shows a case where an iron disk 5 having a thickness of about 0.1 mm or more is used as a metal disk. In the case of such a thickness, the iron disk 5 is not melted completely by the laser beam, but it may be necessary to apply force to pass the gas sampling needle or it may be difficult to pass the gas sampling needle. . In such a case, as shown in FIG. 2, a central thin iron disk 11 made by a method such as electrolytic etching or polishing in advance only at the central portion of the iron disk 5 through which the gas sampling needle passes is adopted. . Or the iron disk 5
Using a thin material such as 0.05 mm, for example, a washer-shaped iron ring having a thickness of about 0.1 mm is superimposed on the peripheral portion of the disk 5 to be irradiated with a laser beam and welded to make the thickness thick, so that laser beam welding is easy. To do.

Silicon resin disk 8 is placed on this welded iron disk 5.
A perforated ring 9 screwed into the female screw hole 7 tightens the peripheral edge of the resin disk 8. A hole at the center of the perforated ring 9 is provided for inserting a gas sampling needle for analyzing hydrogen gas collected in the bolt. Since the silicon resin disk 8 has elasticity, when the gas sampling needle is inserted into the iron disk 5, it functions to seal the hydrogen gas from leaking from around the needle. However, the environment in which bolts are generally used is harsh due to exposure to wind, rain, and high temperatures.
When the silicone resin disk 8 is opened to the use environment, there is a concern that the elasticity is impaired. Therefore, an iron cap 10 is further screwed into the female screw hole 7 on the perforated ring 9 to protect the silicon resin disc 8.

The illustrated permeated hydrogen measurement metal bolt is a processed one of those practically used as bolts for joining structural materials, and is bolted to structural materials together with practical bolts, and is substantially similar to practical bolts. It is placed under the same environment. When installed in this manner, in the metal bolt for measuring permeated hydrogen of the present invention, hydrogen gradually penetrates into the bolt from the environment and finally reaches the cavity 4 and is collected as in the case of a practically used bolt. You.

When it becomes necessary to measure hydrogen, the bolt is removed from the place of use, the cap 10 is removed with a spanner or the like, and a gas sampling needle is inserted into the center of the perforated ring 9. The needle penetrates through the silicon resin disk 8 and the iron disk 5 to reach the cavity 4. A small hole is formed at the base and the tip of the needle inserted into the cavity 4, respectively, and the carrier gas is discharged from the hole at the tip, and the hydrogen gas in the cavity 4 is led to the hole at the base and connected by piping. Transported to the analyzer where the hydrogen concentration was determined. From the obtained hydrogen concentration, it is possible to estimate how much hydrogen has penetrated from the environment into the practical bolt bolted to the structural material.

In this way, the concentration of invading hydrogen in the bolt can be easily measured, and thereafter, it can be arbitrarily measured at a required point in time. By measuring, it is possible to estimate the hydrogen embrittlement of the bolts used in practical use.

〔The invention's effect〕

As described above, according to the measuring bolt of the present invention, it is possible to collect the intrusion hydrogen that the practical bolt receives from the use environment without touching the practical bolt. By quantifying the amount of collected hydrogen, it is possible to easily know the amount of intrusion of hydrogen received by the practical bolt, and therefore to understand the state of hydrogen embrittlement of the bolt, and to be effective in bolt quality evaluation or safety measures Can be demonstrated.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are cross-sectional explanatory views showing the configuration of an apparatus according to an embodiment of the present invention. 1: Bolt head, 2: Shaft 3: Screw, 4: Cavity 5: Iron disc, 6: Open end face 7: Female screw hole, 8: Silicon resin disc 9: Perforated ring, 10: Cap 11: Central thin steel disc

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-24563 (JP, A) JP-A-64-77117 (JP, A) JP-B-56-44369 (JP, B2) (58) Field (Int.Cl. ⁶ , DB name) G01N 17/00-17/04 G01N 27/00 G01N 27/12

Claims (2)

(57) [Claims] 1. An opening provided in an end face of a head, a cavity extending from the opening to a shaft and closed at a shaft end, a metal plate hermetically sealed in the opening, and a metal plate mounted on the metal plate. It is characterized by comprising a rubber plate which is placed one above another, a ring-shaped member which is provided on the rubber plate and whose center is perforated, and a cap which is placed on the ring-shaped member and hermetically closes a bolt head. Metal bolt for measuring permeated hydrogen. 2. The metal plate according to claim 1, wherein the thickness of the joint portion with the inner surface of the metal bolt is increased, as the metal plate sealingly joined inside the opening provided in the end face of the head. A metal bolt for measuring permeated hydrogen, wherein a metal plate having a reduced thickness at the center is used.