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Magnetization intensity based TP304H boiler pipe material damage degree detection method

A TP304H, magnetization technology, applied in the direction of material magnetic variables, etc., can solve the problem of not considering material damage, etc., to achieve the effect of small demand, small sample size, and simple sample preparation

Inactive Publication Date: 2016-08-10
XIAN THERMAL POWER RES INST CO LTD
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Problems solved by technology

[0003] At present, TP304H boiler tubes are mainly rated according to the map and second phase precipitation in DL / T 1422-2015 "18Cr-8Ni Series Austenitic Stainless Steel Boiler Tube Microstructure Aging Rating Standard", without considering the γ→ Factors of Material Damage Caused by Phase Transformation Stress During α′ Transformation

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  • Magnetization intensity based TP304H boiler pipe material damage degree detection method
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  • Magnetization intensity based TP304H boiler pipe material damage degree detection method

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Embodiment Construction

[0020] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0021] The materials used in the implementation cases of the present invention are ASME SA213 TP304H boiler tube new samples and high-temperature service samples, and their chemical compositions are shown in Table 1.

[0022] Table 1: Chemical composition (wt%) of TP304H steel in the implementation case

[0023]

[0024] Firstly, a sample with a diameter of Φ3mm and a length of about 15mm is prepared from the fire surface of the new TP304H sample and the TP304H high-temperature service sample, and the magnetic test is carried out in the VSM vibrating sample magnetometer to obtain the magnetization curve of the sample, see figure 1 with figure 2 . It can be seen from the figure that there is no inflection point on the magnetization curve of the TP304H new sample, and the magnetization intensity corresponding to the inflection point on the...

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Abstract

The invention discloses a method for detecting the damage degree of the TP304H boiler tube material based on the magnetization intensity, which comprises the following steps: (1) A round bar-shaped sample is prepared from the TP304H boiler tube sample to the fire side after service, with a diameter of about Φ3 mm and a length of About 15mm, the surface of the sample has been ground and polished; (2) Use the VSM vibrating sample magnetometer to test the magnetic properties of the sample, obtain the magnetization curve of the sample, and obtain the magnetization value at the inflection point, which is used as the material of the TP304H boiler tube sample damage indicator. The invention uses the magnetization intensity to indicate the material damage degree of the TP304H boiler tube after service, considers the material damage factor caused by the phase transition stress, and improves the accuracy of evaluating the material state of the TP304H boiler tube. The invention requires small sample size, simple sample preparation and low cost.

Description

Technical field: [0001] The invention belongs to the technical field of metallographic analysis in iron and steel, and in particular relates to a method for detecting the damage degree of TP304H boiler tube material based on magnetization. Background technique: [0002] TP304H austenitic heat-resistant steel began to be used in high-temperature heating surface tubes of power plant boilers in my country in the early 1980s. With the prolongation of the service time of TP304H boiler tube, the second phase of the grain boundary is gradually precipitated and coarsened, resulting in the lack of chromium in the area adjacent to the grain boundary and the existence of α'-martensite structure in the microstructure after shutdown and cooling. The austenite (γ) structure of the TP304H boiler tube matrix is ​​paramagnetic, and the α′-martensite structure is ferromagnetic; in addition, the volume expands during the phase transformation of γ→α′, resulting in a large internal stress (phase...

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Application Information

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IPC IPC(8): G01N27/82
CPCG01N27/82
Inventor 史志刚马红何晓东
Owner XIAN THERMAL POWER RES INST CO LTD
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