JPH10280044A - Manufacture of pipe sample with scc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a pipe sample forming an SCC under no restriction on a diameter, shape and material of the metallic pipe and also, to surely form the SCC in the pipe axial direction without applying the load under condition of simulating the generated environment. SOLUTION: While forming a part of treating surface 3 in the metallic pipe 1 to molten state by heating, the heated position is rapidly cooled just after heating to shrink the molten position 5 and by this method, the side part in the shrinkage position is made to be under condition of developing a tensile residual stress in the peripheral direction. Defect is grown under condition of bringing the treating surface 3 in the metallic pipe 1 into contact with corrosive liquid and the SCC is formed in the pipe axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a pipe sample containing SCC, and more particularly to introducing intragranular stress corrosion cracking inside a metal pipe.

[0002]

2. Description of the Related Art As a method of manufacturing a pipe sample containing SCC into which stress corrosion cracking has been introduced, a technique disclosed in Japanese Patent Application Laid-Open No. 3-81089 (a method of manufacturing a pipe sample containing SCC) has been proposed. In this technical example, a metal pipe (for example, SUS30 which is a kind of austenitic stainless steel pipe) is used.
4 steel pipe), when a girth weld joint is formed, the girth weld joint is deleted in a groove shape along the circumferential direction to form a welding groove,
A weld bead is superimposed on the welding groove to form a repair overlay girth weld joint, the direction of the residual welding stress is set, and the inside of the metal pipe is filled with a corrosive liquid to grow a crack.

[0003] By this method, stress corrosion cracking (SCC) having a deep, large and set length direction is formed on the inner surface of a metal tube.
In particular, to produce pipe samples intentionally introducing standard intergranular stress corrosion cracking.

[0004]

However, according to the prior art described above, intergranular corrosion cracking and intragranular stress corrosion cracking (hereinafter collectively referred to as SCC) can be generated in the internal structure of the metal tube. Nevertheless, there is a part to be improved in that a pipe sample is formed in which the SCC is formed in an appropriate amount in the pipe axis direction.

The present invention has been made in view of such circumstances, and aims to achieve the following objects. When manufacturing a pipe sample on which an SCC is formed, it is difficult to be restricted by the diameter, shape, and material of the metal tube. Forming SCC in a pipe sample without imposing a load under conditions simulating the generation environment. To provide a pipe sample formed with an appropriate amount of SCC to contribute to the development of inspection equipment and improvement of accuracy. The SCC must be formed securely in the pipe axis direction.

[0006]

Means for Solving the Problems As one technical means,
A part of the surface to be treated in the metal tube is heated by a heating means such as a laser beam, a gas burner, a TIG welding torch, etc., and is brought into a molten state. After being rapidly cooled by jetting cold water and shrinking the melting point, a tensile residual stress in the circumferential direction is generated on the side of the shrinking part, and then the surface of the metal pipe to be treated is brought into contact with the corrosive liquid. In this state, a defect is grown and an SCC is formed in the tube axis direction. As another technical means, a welding groove in the pipe axis direction is formed in advance on a part of the surface to be processed of the metal pipe, and a welding bead is sequentially formed on the welding groove, and welding is performed by shrinking the welding bead. A state in which a tensile residual stress in the circumferential direction is generated on the side of the bead, and the surface to be processed of the metal tube is brought into contact with the etchant to grow a defect. As the surface to be treated,
The outer surface or inner surface of the metal tube is selected, and high-temperature high-pressure water containing chlorine ions or the like is applied as a corrosive liquid.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a method for manufacturing a pipe sample containing SCC according to the present invention will be described with reference to FIG.
A description will be given based on FIG. Hereinafter, the processing steps for generating the SCC will be described in order.

[Applicable metal pipe] For example, when SCC is generated in an austenitic stainless steel pipe,
Those having a carbon content of 0.04% or less are applied.

[Surface to be Treated] In the example shown in FIGS. 1 and 2, when a girth weld joint 2 is formed on a metal pipe (steel pipe) 1,
Surface 3 (outer surface 3A) in the vicinity of girth weld joint 2
And an SCC in the tube axis direction is formed on the inner surface 3B).

As shown in FIG. 3, by operating the heating means 4, for example, a combustion gas is supplied from a combustion gas supply system 4A to a gas burner 4B and ignited.
Is melted 5 by partially heating the surface 3 to be processed by the gas burner 4B.

[Heating Conditions] According to many empirical values, the heating conditions for the melting point 5 and the heating conditions for efficiently applying SCC in the process described below are as follows. Heating width: W ≧ thickness of tube wall: t (Rt) ^0.5 ≧ L ≧ 2 (Rt) ^0.5 where L: heating length, R: radius to center of tube wall.

[Quenching of the melting point] While forming the melting point 5 on the surface 3 to be treated, the heating point is sequentially moved in the axial direction of the tube so as to move away from the girth welded joint 2, and the cooling means 6 operates, for example. Cold water is supplied from the cooling water supply system 6A and is jetted from the jet nozzle 6B, and the melting point 5 immediately after the heated point is rapidly cooled with the cold water.

[Application of Tensile Residual Stress] When the melted portion 5 is rapidly cooled, the melted portion 5 shrinks rapidly with cooling, and a tensile residual stress in the circumferential direction is applied to the surface 3 to be processed located on the side of the shrunk portion. Stress is applied.

[Generation of SCC by Corrosion Solution] The surface 3 to be treated of the metal tube 1 to which the tensile residual stress is applied is brought into contact with a corrosion solution such as high-temperature water containing chlorine ions. A gap is formed by bringing graphite wool and the like close to each other. Corrosion conditions such as formation of a sensitized region due to thermal influence at the time of forming the molten portion 5, application of tensile residual stress, presence of a corrosive liquid, formation of a gap, etc. Assuming a proper corrosion environment, a defect near the melting point 5 grows, and an SCC in the tube axis direction is formed. Note that the environment of the etchant is kept at a high pressure. Further, the corrosive fluid, that is, water containing chlorine ions, for example, tap water,
Or obtained by diluting tap water with pure water,
It is desirable that the chloride ion concentration be 50 PPb or more.

Next, the SC according to the present invention will be described with reference to FIG.
A second embodiment of a method for manufacturing a pipe sample containing C will be described.

In the technical means shown in FIG. 4, a metal pipe (steel pipe) is used.
As shown in FIG. 4 (a), a welding groove 11 in the tube axis direction is formed in advance on a part of the surface 3 to be treated in FIG. 1 and, as shown in FIG. 11, a weld bead 12 is sequentially formed, and the quenched weld bead 12 is formed.
4 (c), a circumferential tensile residual stress X is generated on the side near the weld bead 12, as shown in FIG. 4 (c). According to the first embodiment, the surface 3 to be processed of the metal tube 1 is brought into contact with a corrosive liquid to grow defects. The welding groove 11 forms the surface 3 to be processed of the metal tube 1 (the outer surface 3A and the inner surface 3B can be used in a normal case).
The groove is formed by machining or grinder along the tube axis direction.

[Other Embodiments] The method of manufacturing a pipe sample containing SCC according to the present invention includes the following techniques. a) The metal pipe is a pipe having similar characteristics other than a carbon steel pipe and a stainless steel pipe. b) A part of the surface to be treated is heated by a laser beam, a TIG welding torch or the like instead of a gas burner, and is brought into a molten state. c) The quenching means immediately after heating is a fluid other than cold water. d) As the corrosive liquid, water containing no chloride ions, high-temperature high-pressure pure water, or the like is applied.

[0018]

According to the method of manufacturing a pipe sample containing SC according to the present invention, the following effects are obtained. (1) A part of the surface to be treated in a metal tube is brought into a molten state, quenched immediately after heating, brought into a state where tensile residual stress in the circumferential direction is generated, and brought into contact with a corrosive liquid to grow defects. In addition, a pipe sample on which an SCC is formed can be manufactured by making it hard to be restricted by the diameter, shape, and material of the metal tube. (2) Since tensile residual stress is generated by heating, quenching, or the like, an SCC can be formed in a pipe sample without imposing a load under conditions that simulate the generation environment. (3) With these, it is possible to provide a pipe sample in which an appropriate amount of SCC is formed, thereby contributing to the development of an inspection apparatus and improvement in accuracy. (4) SCC with tensile residual stress applied in the circumferential direction
Can be reliably formed in the tube axis direction.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a processing state of an outer surface in a first embodiment of a method of manufacturing an SCC-containing pipe sample according to the present invention.

FIG. 2 is a partially cutaway perspective view showing a processing state of an inner surface in the first embodiment of the method of manufacturing an SCC-containing pipe sample according to the present invention.

FIG. 3 is a model diagram together with a block diagram showing a heating and cooling state in the first embodiment of the method of manufacturing the SCC-containing pipe sample according to the present invention.

4A and 4B show a second embodiment of a method for manufacturing a pipe sample containing SCC according to the present invention, wherein FIG. 4A shows a state of forming a welding groove, FIG. 4B shows a state of forming a weld, and FIG. FIG. 4 is a model diagram showing a stress generation state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal pipe (steel pipe) 2 Girth weld joint 3 Surface to be treated 3A Outer surface 3B Inner surface 4 Heating means 4A Combustion gas supply system 4B Gas burner 5 Melting point 6 Cooling means 6A Cooling water supply system 6B Spout nozzle 11 Welding groove 12 Welding Bead X tensile residual stress

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G01N 1/28 G01N 1/28 K (72) Inventor Tsutomu Saegashi 1 Shinnakaharacho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Ishikawajima-Harima Heavy Industries Co., Ltd. Inside the Yokohama Engineering Center

Claims (4)

[Claims] 1. A surface to be treated (3) in a metal tube (1)
Heating a part of the tube to a molten state, moving the heated portion in the axial direction of the tube, and rapidly cooling the heated portion immediately after heating to shrink the molten portion (5) to the side of the contracted portion. A step of generating a tensile residual stress in the circumferential direction, and
Contacting the surface of the metal tube to be treated with a corrosive liquid to grow defects. 2. The S according to claim 1, wherein the surface to be treated (3) is an outer surface (3A) of the metal tube (1).
How to make a pipe sample with CC. 3. The S according to claim 1, wherein the surface to be treated (3) is the inner surface (3B) of the metal tube (1).
How to make a pipe sample with CC. 4. A surface (3) to be treated in a metal tube (1).
Forming a weld groove (11) in the pipe axis direction on a part of the weld bead and forming a weld bead (12) on the weld groove to generate a circumferential tensile residual stress on the side of the weld bead. A method for producing a pipe sample containing SCC, comprising: a step of bringing a surface to be treated in a metal tube into contact with a corrosive liquid to grow a defect.