JPH06323972A - Creep rupture tester for tubular test piece - Google Patents

Abstract

PURPOSE:To reproduce the stress state, which is actually applied on a tubular device, to discern the degree of the true damage in a tubular test piece and to make the structure of a tester compact. CONSTITUTION:A wedge-shaped jig 5, which is inserted into a tubular test piece 4 whose inner surface is machined in the tapered shape and in contact with the inner surface at the entire surface, and a plate-shaped jig, which is in contact with the outer surface of the tubular test piece 4 in the inserting direction of the wedge-shaped jig 5 are pulled in the reverse directions to each other, and the tubular test piece is broken in this constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a creep rupture tester for tubular test pieces, which is used for testing materials such as tubes of heat exchangers.

[0002]

2. Description of the Related Art Conventionally, when performing a material test on a tubular material subject to internal pressure stress at a high temperature such as a tube of a heat exchanger, a rod-shaped test piece is cut out from the tubular material, and a uniaxial creep rupture test is performed. In addition to this, an internal pressure creep rupture test is performed in which both ends of this tubular material are closed by welding, a gas is sealed at a predetermined pressure inside, and the time required for rupturing by heating to a high temperature is determined.

[0003]

When a rod-shaped test piece is cut out from the above-mentioned tubular material and subjected to a uniaxial creep rupture test, the actual tubular material is subjected to stress due to internal pressure, and therefore the tubular material is tubular. The stress state that acts on the equipment is a multiaxial stress state, whereas in the uniaxial creep rupture test, the stress state is a uniaxial stress state, and the stress state is different from the actual stress state. In addition, the tubular equipment that has been used for a long period of time often has accumulated damage due to long-term use near the outer surface rather than the inside, but when cutting out rod-shaped test pieces from such tubular equipment. These areas have been removed and the extent of the true damage cannot be determined. Also, when conducting an internal pressure creep rupture test, it is possible to simulate the actual stress state,
A compressor that loads the gas pressure equivalent to the actual stress state is required inside the rod-shaped test piece, and the gas heated to high temperature spouts from the inside when the tubular equipment breaks, so The structure of the testing machine is very large because it requires a protective device against gas so that the testing machine is not destroyed.

[0004]

The creep rupture tester for a tubular test piece according to the present invention is intended to solve the above-mentioned problems, and the inner surface is inserted into the tubular test piece whose inner surface is processed into a tapered shape. With a wedge-shaped jig, a plate-shaped jig that is held in contact with the outer surface of the tubular test piece in the direction in which the wedge-shaped jig is inserted, and the wedge-shaped jig and the plate. And a means for breaking the tubular test piece by pulling the jigs in the directions opposite to each other.

[0005]

That is, in the creep rupture tester for a tubular test piece according to the present invention, a wedge-shaped jig and a wedge-shaped jig which are inserted into the inside of the tubular test piece whose inner surface is processed into a taper shape and contact the entire inner surface are formed. The plate-shaped jig that is held in contact with the outer surface of the tubular test piece in the direction in which the jig is inserted is pulled in opposite directions to break the tubular test piece,
The state of the force acting from the wedge-shaped jig that is in contact with the inner surface of the tubular test piece whose inner surface is processed into a tapered shape is almost equivalent to the stress state due to the internal pressure, and the gas pressure is applied inside the tubular test piece. It does not require a compressor to be loaded or a protective device against gas ejected from inside. In addition, the creep rupture test can be performed on the tubular equipment almost as it is, and the vicinity of the outer surface of the tubular test piece where damage is accumulated is not deleted.

[0006]

1 and 2 are explanatory views of a creep rupture tester according to an embodiment of the present invention. In the figure, the creep rupture tester according to the present embodiment is used for a material test of a tubular material subject to internal pressure stress at high temperature such as a tube in a heat exchanger. As shown in FIG. 1, the inner surface is tapered. Wedge-shaped jig 5, which is made of the same material as the processed tubular test piece 4 and is in contact with the entire inner surface of the tubular test piece 4 and pulls it downward, abuts on the bottom surface of the tubular test piece 4 and pulls it upward. A jig 6, a tubular electric furnace (not shown) for heating the tubular test piece 4, a jig 6 for pulling the tubular test piece 4 upward, and a lever type load applying device (not shown) for giving a pulling force to the wedge-shaped jig 5. Etc. When performing a material test using this tester, a wedge-shaped jig 5 made of the same chemical composition as the test material is manufactured, and the wedge-shaped jig 5 is mounted on the tubular test piece 4, Further, a jig 6 for pulling the bottom of the tubular test piece 4 upward is attached. And
These wedge-shaped jigs 5 are mounted on the lever-type load-loading device so that the wedge-shaped jigs 5 are pulled downward, and the jigs 6 for pulling the bottom of the tubular test piece 4 upward are pulled upward. To install.

As described above, using this tester, a steel tube 1 made of 21 / 4Cr-1Mo used for about 20 years as a heat transfer tube of the boiler for thermal power generation shown in FIG. A breaking test was performed. The outer surface of the steel pipe 1 is deteriorated due to exposure to combustion gas, and due to creep damage due to long-term use, minute cracks 2 and cavities are formed near the outer surface as shown in FIGS. 3 is generated. As shown in FIG. 2B, such a steel pipe 1 was left as it was in the vicinity of the outer surface where creep damage had accumulated, and only the inner surface was processed into a taper shape to form a tubular test piece 4. Then, the tubular test piece 4 was placed in the central portion of the tubular electric furnace and a load corresponding to an internal pressure stress of 5 kgf / mm ² was applied at 620 ° C., whereupon it broke at 4325 hr. In addition, a test piece similar to that for the conventional internal pressure creep rupture tester was manufactured from the same heat transfer tube of a boiler for thermal power generation, and when the same load was applied at the same temperature, it broke at 4287 hr, and the rupture time by this tester was almost the same. It was equivalent. Also, a rod-shaped creep rupture test piece was manufactured from the same heat transfer tube of a boiler for thermal power generation, and a uniaxial creep rupture test was conducted under the same conditions using a conventional uniaxial creep rupture tester. It was longer than the breaking time of the tubular test piece 4 by this tester and the breaking time by the conventional internal pressure creep rupture tester. It is considered that this is because in the conventional uniaxial creep rupture tester, the damaged region near the outer surface was deleted during the production of the creep rupture test piece.

[0008] When a rod-shaped test piece is cut out from a conventional tubular equipment and subjected to a uniaxial creep rupture test, the actual tubular equipment is subjected to internal pressure stress.
The stress state acting on the tubular material is the stress state in the multiaxial direction, whereas in the uniaxial creep rupture test, the stress state becomes the uniaxial stress state, and the stress state is different from the actual stress state. In addition, the tubular equipment that has been used for a long time often accumulates damage due to long-term use near the outer surface rather than the inner surface, but when cutting out a rod-shaped test piece from the tubular equipment like this. In addition, these areas are cut and removed during processing, and the true degree of damage cannot be determined. Also, when performing an internal pressure creep rupture test, it is possible to simulate the actual stress state, but it is necessary to have a compressor, etc., that loads the gas pressure equivalent to the actual stress state inside the rod-shaped test piece, and the tubular shape. The gas heated to high temperature spouts from the inside when the equipment breaks, so a protective device for the gas is required so that the spouting gas does not destroy the testing machine, and the structure of the testing machine is very large. In the present creep rupture testing machine, the inner surface of the tubular test piece 4 is processed into a taper shape, and the wedge-shaped jig 5 made of the same material as the tubular test piece 4 is entirely in contact with the inner surface. The creep rupture test is performed by inserting and pulling the tubular test piece 4, and the entire inner surface of the tubular test piece 4 having the tapered inner surface is processed. Stress due to force acting from the wedge-shaped jig 5 for bonding state is substantially equal to the stress state due to internal pressure, it is possible to reproduce the actual stress distribution steel pipe 1 is subjected. In addition, since the tubular test material can be tested almost as it is, the vicinity of the outer surface where a lot of local damage has accumulated due to long-term use is not deleted, and the extent of damage can be accurately estimated. be able to. Also, conventional single-axis creep rupture testing machines can be used as is for heating devices, load loading devices, etc., and large-scale devices such as compressors and protective devices, such as conventional internal pressure creep rupture testing machines, are required. Instead, the stress simulating the internal pressure can be easily applied. In this way, it does not require a large-scale device such as the conventional internal pressure creep rupture tester, and the same stress distribution creep rupture test as the internal pressure creep rupture tester with the same device as the conventional uniaxial creep rupture tester. By doing so, it becomes possible to easily estimate the damage accumulated in the tubular equipment used under high temperature and stress due to internal pressure for a long time, and improve the reliability and inspection of these tubular equipment. It can contribute to cost reduction. In addition, since the creep rupture test can be performed easily under the stress of internal pressure at high temperature and in a state close to the stress condition actually used, the cost of collecting the material data necessary for the development of new materials By reducing the value, the data can be enriched and it can contribute to the improvement of the reliability of various devices using new materials.

[0009]

The creep rupture tester for tubular test pieces according to the present invention is constructed as described above, and the state of the force acting from the wedge-shaped jig on the inner surface of the tubular test piece is the stress state due to the internal pressure. Since they are almost the same, it is possible to reproduce the stress state actually applied to the tubular material. Moreover, since the vicinity of the surface on the outer side of the tubular test piece where damage is accumulated is not deleted, the true degree of damage can be determined. Further, since the compressor for loading the gas pressure inside the tubular test piece and the protective device for the gas ejected from the inside are not required, the structure of the tester becomes compact.

[Brief description of drawings]

FIG. 1 is a front view of a test piece mounting portion in a creep rupture tester according to an embodiment of the present invention.

2 (a) is a perspective view of a steel pipe of the test material, FIG. 2 (b) is a front view of a tubular creep rupture test piece, and FIG. 2 (c) is a C- in FIG. 2 (b). View from arrow C, same figure (d)
[Fig. 4] is a detailed view of a portion d in Fig. 7C.

[Explanation of symbols]

1 Steel pipe of test material 2 Micro crack 3 Micro cavity 4 Tubular test piece 5 Wedge jig 6 Creep rupture Jig for pulling the bottom of test piece upward

Claims (1)

[Claims] 1. A wedge-shaped jig, which is inserted into the inside of a tubular test piece whose inner surface is processed into a taper shape and is in contact with the entire inner surface, and the tubular test piece in a direction in which the wedge-shaped jig is inserted. A plate-shaped jig that is held in contact with the outer surface to suppress it, and means for breaking the tubular test piece by pulling the wedge-shaped jig and the plate-shaped jig in opposite directions to each other are provided. A creep rupture tester for characteristic tubular test pieces.