Method and device for testing environmental fracture toughness of petroleum pipe

A technology for oil pipes and fracture toughness, which is applied in the direction of applying stable tension/pressure to test the strength of materials, etc. It can solve the problems of large dispersion of experimental results, inability to accurately obtain the value of fracture toughness, accuracy of loading stress, and poor parallelism. , to achieve the effect of a reliable experimental method

Inactive Publication Date: 2015-04-22
SOUTHWEST PETROLEUM UNIV
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Problems solved by technology

[0004] (A) The structure of the DCB sample is complex, the processing of prefabricated cracks is difficult, the dimensional accuracy is not easy to control, and the size effect of the sample seriously affects the experimental results;
[0005] (B) The experiment uses a wedge to load the sample, the accuracy and parallelism of the loading stress are poor, and the experimental results are highly discrete;
[0006] (C) The sample with double cantilever beam structure is greatly affected by the plasticity of the metal material when it is split, and the load when the crack starts to expand cannot be accurately measured, and the fracture toughness calculation results are biased
[0007] In order to solve the problem that conventional fracture toughness test methods cannot accurately obtain the value of fracture toughness, the present invention simulates the service environment of oil pipes with the help of high-temperature autoclave, proposes a new experimental method for testing fracture toughness of oil pipes, and designs fracture toughness test samples and devices to form a A new experimental method suitable for testing the fracture toughness of oil pipes, which can solve the above problems well

Method used

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  • Method and device for testing environmental fracture toughness of petroleum pipe
  • Method and device for testing environmental fracture toughness of petroleum pipe
  • Method and device for testing environmental fracture toughness of petroleum pipe

Examples

Experimental program
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Effect test

example 1

[0038] Use oil pipe A to process the sample according to the requirements, determine the corrosive medium and the loading stress according to the service conditions, and the relationship between loading deflection and stress is as follows: image 3 , the detailed loading data is shown in Table 1.

[0039] After 168 hours of corrosion, it was found that the impact toughness of oil pipe A after the corrosion test was significantly lower than that of the original state, the reduction rate was 14.8%, and the fracture toughness was reduced by 48.8%. 2 S and CO 2 The partial pressures were 1MPa and 1.5MPa respectively, and the toughness and impact resistance decreased to a certain extent after 168 hours of testing under the condition of loading 80% of the nominal yield stress. There is a certain risk in this corrosive environment. The detailed results are shown in Table 2. Figure 4 .

example 2

[0041] Utilize the present invention to test the environmental fracture toughness of oil pipe B, the experimental conditions are temperature 60°C, total pressure 10MPa, H 2 S and CO 2 The partial pressure was 1MPa and 1.5MPa respectively, and the test was carried out under the condition of loading 80% of the nominal yield stress for 14 days. The experimental data and results are shown in Table 3. After the corrosion test, the impact performance and fracture toughness of oil pipe B decreased by 90.5% and 93.5% respectively compared with the original state. , indicating that oil pipe B has poor resistance to stress corrosion cracking in this environment, and cracks initiate and grow rapidly, which greatly reduces the toughness and impact resistance of oil pipe B, and the possibility of environmental fracture is very high, so it is not suitable for this environment.

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Abstract

The invention discloses a method and a device for testing the environmental fracture toughness of a petroleum pipe. The method comprises the following steps of: detecting the size of the fracture toughness of the petroleum pipe under the service environment, processing the petroleum pipe into a sample, determining the experimental temperature, pressure and gas-liquid phase corrosive medium according to the service working condition of the pipe, loading the sample by the device for testing the environmental fracture toughness of the petroleum pipe, calculating the fracture toughness according to the load size and the crack expansion length after experiment, and obtaining stress-corrosion-cracking resistance, notch sensitivity and the action mechanism of the metal material in the service environment. The method and the device disclosed by the invention has the advantages that the size of the fracture toughness of the metal material of the petroleum pipe in any load and corrosion environment can be determined, the impact-toughness damage degree of the metal material in the service environment can be detected, so that the preference of the petroleum pipe is carried out and the experimental base is provided for designing the strength of the petroleum pipe.

Description

technical field [0001] The invention relates to a method and device for testing the environmental fracture toughness of petroleum pipes, more specifically, it relates to a method for testing the environmental fracture toughness of petroleum pipes, and also relates to an experimental device for testing the fracture toughness using the method. Background technique [0002] In the petroleum industry, in order to avoid unforeseen accidents and disasters such as pipe cracking, performance attenuation, and intergranular fracture due to stress corrosion, it is necessary to carry out environmental fracture evaluation experiments on petroleum pipes. The applicability and reliability in the research and evaluation. At present, the method of evaluating the environmental fracture of metal materials at home and abroad is mainly the constant load stress corrosion test method, that is, the A method experiment is carried out by using the stress ring under normal temperature and pressure, wh...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/08
Inventor 曾德智侯铎张智施太和任建邓文良
Owner SOUTHWEST PETROLEUM UNIV
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