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Method for measuring P91 steel weld brinell hardness

A Brinell hardness and Brinell hardness tester technology, applied in the direction of testing material hardness, etc., can solve the problems of large gap between measured values, complicated operation, misjudgment of safe operation of boilers, etc., and achieves small errors and accurate measurement results. Effect

Active Publication Date: 2015-05-20
STATE GRID CORP OF CHINA +1
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AI Technical Summary

Problems solved by technology

The existing testing technical standards are all based on the Brinell hardness value. The portable Brinell hardness tester is large in size, complicated to operate and has too many limitations, which cannot meet the requirements of on-site inspection. The portable Leeb hardness tester is small in size and easy to operate. And it can detect a variety of hardness values, and is widely used in the detection of metal parts of power plant boilers
In the existing technical standards, there is only carbon steel and low alloy steel Leeb hardness (HL)-Brinell hardness (HB) conversion, there is no HL-HB conversion of high alloy steel P91, therefore, the portable Leeb hardness tester detects The Brinell hardness value (HBHLD) is quite different from the Brinell hardness value (HB) detected by the Brinell hardness testing machine used in the laboratory, and it is very easy to cause unqualified hardness values ​​in the on-site inspection and cause serious damage to the safe operation of the boiler. Misjudgment
[0004] In addition, during the on-site inspection of the power plant boiler, it was found that the same type of Leeb hardness tester had a small gap in the measured values ​​when the calibration test block was used for calibration, but a large gap in the measured values ​​when the production pipes were measured. cause uncertainty in test results
This is because the Leeb hardness value of the existing portable Leeb hardness tester calibration test block is mostly 780-800HL, while the Leeb hardness value range of the P91 steel base material and weld seam used for power plant boilers is generally between 450HL-600HL. Different hardness intervals cause large measurement errors

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  • Method for measuring P91 steel weld brinell hardness
  • Method for measuring P91 steel weld brinell hardness
  • Method for measuring P91 steel weld brinell hardness

Examples

Experimental program
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Embodiment 1

[0028] Embodiment 1: The manufacture of P91 steel hardness test block and the establishment of the conversion relationship between Leeb hardness and Brinell hardness:

[0029] The P91 material used in the high temperature header is selected, and the specification is Φ273×28mm. In order to meet the requirements of GB / T17394-1998 "Metal Leeb Hardness Test Method" for hardness samples: the minimum thickness of the sample measured by the impact device type D and DC type Leeb hardness tester is 5mm, and the quality of the sample placed stably > 5kg, according to the density of P91 steel at 20°C is 7.78t / m 3 , the calculated sample size meeting the standard requirements is 210×116×17mm.

[0030] In order to meet the requirements of welding technology, the processing of the groove of the hardness test block is as follows: figure 1 shown.

[0031] The hardness test block is welded by manual arc welding SMAW, the welding machine model is ZX7-400STG, the welding material is Thyssen C...

Embodiment 2

[0045] Example 2: On-site detection of Brinell hardness of P91 steel weld seam

[0046] The P91 steel base material and weld seam used in power plant boilers are inspected on site, and the area to be inspected is polished to make it have a metallic luster, no scale and other dirt, and the surface roughness is ≤1.6. Utilize the portable Leeb hardness meter to measure the Leeb hardness of the P91 steel weld area to be measured, and obtain the Brinell hardness value according to the linear relational formula determined in embodiment 1, and compare with the actual measured Brinell hardness value, the result See Table 4.

[0047] Table 4 Comparison table of measured Brinell hardness value and calculated Brinell hardness value of P91 steel weld seam

[0048]

[0049] As can be seen from Table 4, according to the conversion relationship formula of HB-HL established by the present invention, the error between the calculated value of the calculated Brinell hardness and the measured...

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Abstract

The invention discloses a method for measuring P91 steel weld brinell hardness. The method comprises the following steps: (1) welding P91 steel, and adjusting a heat treatment temperature and a heat preservation time to prepare test specimens with different brinell hardness values; (2) respectively detecting the Leeb hardness value HL and the brinell hardness value HB of each test specimen weld prepared in the step (1) by using a Leeb hardness tester and a Brinell hardness tester; (3) with the brinell hardness value of the test specimen with the tested hardness as a horizontal coordinate and the Leeb hardness value as a vertical coordinate, establishing an HB-HL hardness correlation curve to obtain a linear relation; (4) selecting a P91 steel weld region to be measured, measuring the Leeb hardness of the P91 steel weld region to be measured by using a portable Leeb hardness tester so as to obtain the Leeb hardness value according to the linear relation in the step (3). The method disclosed by the invention can be used for accurately detecting the brinell hardness value of the P91 steel weld and providing forceful guarantee for the safe operation of boilers.

Description

technical field [0001] The invention relates to a method for measuring the Brinell hardness of P91 steel welds, belonging to the technical field of material detection. Background technique [0002] P91 steel is widely used in subcritical and supercritical high-temperature and high-pressure steam pipelines due to its high oxidation resistance and high-temperature steam corrosion performance, good impact toughness, high and stable long-lasting plasticity and heat strength. [0003] Hardness is one of the commonly used indicators to evaluate the mechanical properties of metal materials. Hardness testing is widely used in the inspection of metal materials in power plant boilers because of its convenient, fast and non-destructive materials. After the release of DL / T438-2009 "Metal Technology Supervision Regulations for Thermal Power Plants", there are clear regulations on the hardness of P91 materials: the hardness range of P91 steel base material is 180-250HB, and the weld seam ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/42G01N3/52
Inventor 邵明星胡新芳赵永宁杜宝帅张鸿武马永泉张志彬荆象阳刘蕊
Owner STATE GRID CORP OF CHINA
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