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On-site test method for pearlite spheroidization grade of No.20 steel

An on-site inspection and grade technology, applied in the direction of testing material hardness, etc., can solve the problems of cumbersome inspection procedures, high requirements for operator knowledge and experience, and damage to working parts, achieving low knowledge and experience requirements, low cost, and damage. small effect

Inactive Publication Date: 2011-09-14
YANGZHOU UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to overcome the above-mentioned various shortcomings of the traditional pearlite spheroidization grade detection method of No. 20 steel, to provide an on-site detection method for the pearlite spheroidization grade of No. 20 steel, and to solve the problem of working parts caused by the traditional metallographic method. The destruction and detection procedures are cumbersome, and the requirements for the operator's knowledge level and experience are relatively high.

Method used

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  • On-site test method for pearlite spheroidization grade of No.20 steel
  • On-site test method for pearlite spheroidization grade of No.20 steel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0017] Select the steel parts to be tested on site, generally steel parts that are prone to overtemperature and overpressure, and then use an angle grinder equipped with a grinding wheel to remove the high-temperature anti-rust paint, surface oxide layer and decarburization layer on the surface to be exposed. The state of organization within the metal. After the decarburized layer is completely removed, stop the mechanical grinding work immediately. Use an angle grinder to install a self-stick polishing disc, and then replace it with 180, 400, and 600 water sandpaper for rough grinding in sequence. Then replace it with No. 01 and No. 02 metallographic sandpaper for fine grinding to ensure that the surface roughness Ra≤1.6μm. The grinding surface should be cleaned before each replacement of different types of sandpaper. During the entire mechanical grinding process, water should be sprayed at the same time to reduce the temperature of the grinding surface, so as to prevent th...

Embodiment 2

[0019] In 2008, a superheater tube was selected as the tested part in a thermal power plant in Yangzhou. The material of the superheater tube was No. 20 steel, and the design temperature was 450°C. At that time, the steel pipe had been in service for 100,000 hours. Use an angle grinder with a grinding wheel to remove the high-temperature anti-rust paint, surface oxide layer and decarburization layer on the surface to be tested. After the decarburization layer is completely removed, stop the mechanical grinding work immediately. Use an angle grinder to install a self-stick polishing disc, and then replace it with 180, 400, and 600 water sandpaper for rough grinding in sequence. Then replace it with No. 01 and No. 02 metallographic sandpaper for fine grinding to ensure that the surface roughness Ra≤1.6μm. Clean the grinding surface before changing different types of sandpaper each time. Spray water at the same time during the whole mechanical grinding process to reduce the te...

Embodiment 3

[0021] In 2009, a superheater tube was selected as the tested part in a thermal power plant in Taizhou. The material of the superheater tube was No. 20 steel, and the design temperature was 450°C. At that time, the steel pipe had been in service for 80,000 hours. Use an angle grinder with a grinding wheel to remove the high-temperature anti-rust paint, surface oxide layer and decarburization layer on the surface to be tested. After the decarburization layer is completely removed, stop the mechanical grinding work immediately. Use an angle grinder to install a self-stick polishing disc, and then replace it with 180, 400, and 600 water sandpaper for rough grinding in sequence. Then replace it with No. 01 and No. 02 metallographic sandpaper for fine grinding to ensure that the surface roughness Ra≤1.6μm. Clean the grinding surface before changing different types of sandpaper each time. Spray water at the same time during the whole mechanical grinding process to reduce the temp...

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Abstract

The invention discloses an on-site test method for pearlite spheroidization grade of No.20 steel, which solves the problems of damage on work parts, complex test process, higher demand on knowledge level and experience of operators and the like in a conventional metallographical method. The on-site test method provided by the invention comprises the following steps of: mechanically clearing a surface of an objective steel piece, then, mechanically grinding and polishing the surface of the objective steel piece while spraying water, orderly testing the hardness of a same part for 20-40 times by a Leeb hardness tester when the surface roughness Ra is controlled to be not more than 1.6 mum, respectively reading a Brinell hardness number of the same part, and performing data processing on the Brinell hardness numbers obtained after many tests to obtain the pearlite spheroidization grade of the No.20 steel piece, wherein the whole data processing procedure is finished by a computer program. The on-site test method for the pearlite spheroidization grade of the No.20 steel is less in damage to work pieces, simple in test process, simple in used devices, low in demand on the knowledge level and experience of the operators, high in test efficiency and degree of automation, higher in accuracy, excellent in repeatability and the like.

Description

technical field [0001] The invention relates to an evaluation method of pearlite spheroidization grade, in particular to an on-site detection method of pearlite spheroidization grade of No. 20 steel. Background technique [0002] No. 20 steel is a high-quality carbon structural steel, which can be used to manufacture boiler superheaters, boiler water-cooled wall tubes, and coke towers with operating temperatures not exceeding 450°C. It is widely used in electric power and petrochemical fields. However, during the long-term use of No. 20 steel at high temperature, the pearlite in its structure will undergo spheroidization, that is, the cementite (carbide) form of pearlite will gradually change from the initial lamellar shape to spherical shape, and the mechanical properties of the material will also be reduced. And then down. The spheroidization phenomenon is essentially a diffusion process, and it is also a material aging process. [0003] The pearlite spheroidization char...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/48
Inventor 程宏辉曹磊黄新秦康生
Owner YANGZHOU UNIV
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