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DL/T 884-2019: Power plant metallography inspection and assessment guideline
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Power plant metallography inspection and assessment guideline
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Basic data | Standard ID | DL/T 884-2019 (DL/T884-2019) | | Description (Translated English) | Power plant metallography inspection and assessment guideline | | Sector / Industry | Electricity & Power Industry Standard (Recommended) | | Classification of Chinese Standard | F24 | | Word Count Estimation | 20,235 | | Date of Issue | 2019-06-04 | | Date of Implementation | 2019-10-01 | | Older Standard (superseded by this standard) | DL/T 884-2004 | | Regulation (derived from) | Natural Resources Department Announcement No. 7 of 2019 | | Issuing agency(ies) | National Energy Administration | DL/T 884-2019: Power plant metallography inspection and assessment guideline---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Power plant metallography inspection and assessment guideline
ICS 27.100
F 24
People's Republic of China Electric Power Industry Standard
Replace DL/T 884-2004
Technical Guidelines for Metallographic Inspection and Evaluation of Thermal Power Plants
2019-06-04 released
2019-10-01 implementation
Issued by National Energy Administration
Table of contents
Foreword...II
1 Scope...1
2 Normative references...1
3 Terms and definitions...2
4 General requirements...2
5 Macro Metallographic Inspection...2
6 Microscopic Metallographic Inspection...3
7 Analysis and Evaluation...6
8 Records and reports...10
Appendix A (informative appendix) commonly used low-power etchants...11
Appendix B (informative appendix) commonly used sandpaper, polishing abrasives and their use...12
Appendix C (informative appendix) commonly used chemical etching reagents for microstructure...14
Appendix D (informative appendix) on-site metallographic preparation...16
Appendix E (informative appendix) Preparation and use of metallographic complex materials...18
Appendix F (Informative Appendix) Color Metallographic Method...19
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009 "Guidelines for Standardization Work Part 1.Standard Structure and Compilation".
Compared with DL/T 884-2004 "Technical Guidelines for Metallographic Inspection and Evaluation of Thermal Power Plants", this standard has major technical changes except for editorial changes.
Change as follows.
-Made some adjustments in the content and arrangement of chapters;
-Added the interpretation and definition of the terms "microstructure aging" and "metallographic complex";
--- Increase the macroscopic grain size inspection method and evaluation, and macroscopic defect evaluation of welded joints in the macroscopic structure inspection;
-Delete the contents of the "General Guidelines and Requirements" section and re-formulate the contents of the new "General Requirements" clauses;
--Added microscopic inspection and analysis. polished state inspection morphology characteristics, post-etching inspection organization and morphology characteristics, image acquisition, quantification
Metallographic survey items, etc.;
- Delete the entire content of "4.3 Quantitative Metallographic Method" (4.3.1 Image Analyzer, 4.3.2 Main Measurement Parameters, 4.3.3 Grain Size Measurement
Fixed), adding the content of measurement and analysis using image analysis software;
--Delete "Embritishment Analysis" and "Creep Hole Damage Rating" in the "Qualitative Analysis" section of the "Power Plant Metallographic Analysis" chapter, and "Definite
The whole content of "Quantity Analysis";
--Add the general rules of microstructure aging assessment);
--Add all levels of groups for bainite microstructure aging evaluation, martensite microstructure aging evaluation, and austenite microstructure aging evaluation
Texture aging characteristics;
-Delete the original Appendices B T91 steel structure aging assessment grade chart and appendix steel creep damage assessment grade chart;
--Commonly used low-magnification etchants as Appendix A, adding low-magnification etchants for cast aluminum alloy and deformed aluminum alloy;
--Chemical etching reagents commonly used in microstructure are listed as Appendix C, and 9-12% Cr steel and other materials are added to show δ ferrite, 700 ℃ electricity
Chemical etching agent for the microstructure, austenite structure of nickel-based and nickel-iron-based superalloys, aluminum and aluminum alloys, copper and copper alloys for station use;
--- Added Appendix E. Preparation and use of metallographic complex materials;
-Added Chapter 8 Records and Reports.
This standard was proposed by the China Electricity Council.
This standard is under the jurisdiction of the Power Station Metal Materials Standardization Technical Committee.
Drafting organizations of this standard. Xi'an Thermal Power Research Institute Co., Ltd., Thermal Power Research Institute of China Datang Group Science and Technology Research Institute, North China Electric Power Science
Research Institute Co., Ltd., State Grid Shaanxi Electric Power Research Institute, China Datang Group Science and Technology Research Institute Co., Ltd. Central China
Branch, Zhejiang Zheneng Technology Research Institute Co., Ltd.
The main drafters of this standard. Wang Caixia, Jia Jianmin, Cai Wenhe, Zhang Bing, Song Li, Li Xichao, Wang Zhichun, Lou Yumin, He Xipeng,
Ma Hong, Liu Shutao, Dong Shuqing, and Ju Guangyu.
This standard was first issued on June 1,.2004, and this is the first revision.
This standard replaces DL/T 884-2004 "Technical Guidelines for Metallographic Inspection and Evaluation of Thermal Power Plants" from the date of implementation.
The opinions or suggestions during the implementation of this standard are fed back to the Standardization Management Center of the China Electricity Council (Baiguang Road, Beijing
No. 100761).
Technical Guidelines for Metallographic Inspection and Evaluation of Thermal Power Plants
1 Scope
This standard specifies the basic requirements, main operating steps, basic processes and evaluation standards for the metallographic inspection of thermal power plant components.
This standard applies to the metallographic inspection and evaluation of high-temperature components in thermal power plants. The metallographic inspection and evaluation of other metal parts can refer to this standard.
Row.
2 Normative references
The following documents are indispensable for the application of this document. For dated reference documents, only the dated version applies to this document.
For undated references, the latest version (including all amendments) applies to this document.
GB/T 224 Steel Decarburization Depth Measurement Method
GB/T 226 Steel Macrostructure and Defect Inspection Method
GB/T 1979 Structural steel macrostructure defect rating chart
GB/T 4236 Steel Sulfur Mark Inspection Method
GB/T 6462 Metal and oxide coating thickness measurement microscope method
GB/T 6394 Method for determination of average grain size of metals
GB/T 10121 Steel tower-shaped hairline magnetic particle inspection method
GB/T 10561 Determination of the content of non-metallic inclusions in steel, grading chart, microscopic inspection method
GB/T 13298 Metal Microstructure Inspection Method
GB/T 13299 Steel Microstructure Evaluation Method
GB/T 13305 Metallographic determination of α-phase area content in stainless steel
GB/T 15711 Test Tower Shaped Hairline Acid Leaching Method for Non-metallic Inclusions in Steel
GB/T 15749 Quantitative Metallographic Determination Method
GB/T 20410 Steel for high temperature bolts of turbines
DL/T 439 Technical Guidelines for High Temperature Fasteners in Thermal Power Plants
DL/T 674 No. 20 steel pearlite spheroidization rating standard for thermal power plants
DL/T 773 12Cr1MoV steel spheroidization rating standard for thermal power plants
DL/T 786 Carbon steel graphitization inspection and rating standard
DL/T 787 15CrMo steel pearlite spheroidization rating standard for thermal power plants
DL/T 999 2.25Cr-1Mo steel spheroidization rating standard for power station
DL/T 1422 18Cr-8Ni series austenitic stainless steel boiler tube microstructure aging rating standard
DL/T 1603 Austenitic stainless steel boiler tube inner wall shot blasting quality inspection and acceptance technical conditions
3 Terms and definitions
The following terms and definitions apply to this standard.
3.1
Microstructure aging
When steel is operated for a long time under certain high temperature conditions, its microstructure gradually disperses, its orientation gradually disappears, alloy elements migrate, carbides precipitate and aggregate
It gathers, grows, and gradually assumes a spherical shape, tends to be evenly distributed in the crystal (inside the slats), and slowly gathers at the grain boundary (the gap between the slats), and is in a chain
The process of shape distribution. These changes in the microstructure reduce the performance of materials and reduce the safety of parts.
3.2
Metallographic surface replica
A method of copying the microstructure with the prefabricated replica material and the metal surface.
4 General requirements
4.1 The metallographic inspection personnel shall undergo corresponding professional skills training and have the ability of metallographic inspection and evaluation.
4.2 The micrometer scale of the metallurgical microscope should be verified according to the measurement requirements, and within the validity period; the eyepiece scale and the microscope equipped with image analysis software
Mirror, the scale and the system scale of the image analysis software need to be verified and calibrated regularly. The portable metallurgical microscope used for field observation should meet
Observe the requirement of clear image.
4.3 The metallographic samples should be representative, and the sample interception (including the interception direction, position, quantity) should be based on the metal manufacturing method, inspection purpose,
Relevant standards or the provisions of the mutual agreement.
4.4 Where sampling is difficult or unsuitable, and where sampling will affect the integrity of components, on-site metallographic inspection or metallographic replication should be used
Method for testing. During on-site inspection, the impact of vibration, dust, temperature, humidity and other environmental factors on the inspection results should be minimized.
4.5 Samples and replica samples should be kept clean and dry. Samples to be retained should be placed in a drying dish after observation and analysis for proper preservation and records.
4.6 Metallographic inspection personnel should master relevant safety protection knowledge and have safety protection awareness to prevent personal injury caused by sample preparation equipment and hazardous chemicals.
Hazards; should master relevant environmental protection knowledge, comply with relevant national laws and regulations, and avoid environmental pollution caused by hazardous chemicals.
5 Macroscopic metallographic inspection
5.1 Macroscopic grain size inspection
5.1.1 Grinding, polishing and etching of the sample shall be carried out in accordance with the requirements of GB/T 13298.
5.2 Microstructure inspection
5.2.1 Macrostructure inspection is used to check the macroscopic quality of metal materials, assess macroscopic defects, and distinguish dendrites, welded areas, segregation, porosity, and macroscopic
View coarse crystals and so on.
5.2.2 Grind the test surface of the sample with No. 400 ~ No. 600 sandpaper, and then etch it. Commonly used etching methods include hot acid attack, cold acid attack and electrolytic corrosion
For the etching method, see Appendix A for the commonly used macrostructure etchant, and the specific operation should be carried out in accordance with the requirements of GB/T 226.
5.2.3 The evaluation of macrostructure defects of structural steel shall be in accordance with the requirements of GB/T 1979, the requirements of GB/T 20410 for macrostructure evaluation of bolts, and the
5.3 The hairline inspection adopts tower-shaped turning specimens, which shall be inspected by acid etching method or magnetic flaw detection method. The specific requirements shall be in accordance with GB/T 15711 or GB/T 10121.
Seek execution.
5.4 The sulfur mark inspection shall be carried out in accordance with GB/T 4236.Glossy printing paper impregnated with 2%-10% sulfuric acid aqueous solution, close to the finely ground steel
Check the section for 2min～5min, then peel it off, fix, wash and dry to get the sulfur mark. According to the size and number of brown spots on the photo paper,
The shape, distribution state, and color depth can be used to assess the distribution and concentration of sulfur.
6 Microscopic metallographic inspection
6.1 Sample preparation
6.1.1 The metallographic sample is required to be able to characterize the characteristics of the material itself, and at the same time, it requires a clear structure and a smooth edge. It is not allowed to be cited due to improper preparation methods.
Defects such as phase change, deformation, peeling, scratches, and blurring.
6.1.2 Sample preparation
6.1.2.1 The preparation of metallographic samples shall be implemented in accordance with GB/T 13298.
6.1.2.2 Refer to Appendix B for commonly used sandpaper, polishing abrasives and their use, and refer to Appendix C for commonly used chemical etching reagents for microstructure.
6.1.2.3 The samples should be cleaned between each sandpaper grinding process and after polishing. The etched metallographic surface should be dried quickly after thorough cleaning.
6.1.3 On-site sample preparation
6.1.3.1 Preparation
On-site metallographic equipment and supplies are shown in Appendix D.1, and polishing and preparation are shown in Appendix D.2.
6.1.3.2 Inspection location
It should be selected where the operating temperature is high, the stress is high, the component damage is serious or the defect is prone to
It is recommended to select the inspection site.
6.1.3.3 Grinding
6.1.3.3.1 Smoothing
Use an electric angle grinder equipped with a grinding wheel to thoroughly remove the oxide scale, rust, and decarburized layer of the inspected part, requiring a relatively flat surface.
The grinding depth should ensure that the remaining thickness of the part is not less than the minimum required wall thickness of the part.
6.1.3.3.2 Polishing
Use sandpaper to polish in order from coarse to fine, and change the direction after each sandpaper is polished. The difference in particle size of each sandpaper should be between 100-200.
Until all scratches and deformed layers are completely removed.
6.1.3.4 Polishing
Polishing can use mechanical polishing, chemical polishing, electrolytic polishing and other methods.
a) During mechanical polishing, the polishing paste is polished from coarse to fine, changing the direction after each polishing, and polishing for 2 to 3 passes until it meets the requirements. Last one
The particle size of the polishing paste should be 2.5μm or 1μm. The final polishing direction of the weld should be perpendicular to the weld fusion line.
b) During chemical polishing, select a chemical polishing reagent suitable for the material, and continue to wipe the surface of the sample repeatedly until it meets the requirements. Polishing time
It should not be too long to avoid the appearance of pits. Common chemical polishing reagents are shown in the attached table D.1.
c) When electropolishing, choose electropolishing reagent, current, voltage and polishing time suitable for the material. Common electrolytic polishing reagents see the attached table
D.2.
d) After polishing, the polishing surface should be thoroughly cleaned, and there should be no water stains and pollutants remaining.
6.1.3.5 Erosion
6.1.3.5.1 The etching agent and etching method of the on-site metallographic samples are the same as those of the sampled samples. The on-site re-etching time should consider the influence of environmental factors.
The degree of eclipse should be slightly deeper.
6.1.3.5.2 After etching, clean and blow dry the etched surface to avoid water stains and pollutants. Should be able to observe a clear group with a portable metallurgical microscope
Texture morphology.
6.1.4 Duplicate
6.1.4.1 See Appendix E for the preparation and use of metallographic complex materials.
6.1.4.2 Thoroughly clean the etched surface with a solvent before replicating, use a dropper to drop an appropriate amount of solvent on the surface of the prepared replica sample, and remove the AC paper (or organic
Cover the surface of the sample flatly with a glass sheet, and apply proper pressure with your thumb to squeeze out the bubbles in the replica to make it fit tightly. If the part
Or the ambient temperature is too high, and methanol solvents with low volatility can be used.
6.1.4.3 After the replica material is dried, peel off from one corner to get the metallographic replica (sheet).
6.1.4.4 The replica samples should be properly stored in time. The plexiglass replicas should be wrapped in lens paper or sandwiched between clean papers; AC paper replicas should be used
Use double-sided tape to paste the back of the complex film on the marked glass slide, cover it with sealing paper and flatten it, clamp it with another glass slide, and tie it tightly with a rubber band.
6.1.4.5 The duplicate samples shall be uniquely identified.
6.1.5 Color metallographic method
Color metallography can be dyed by chemical dyeing method, constant potential method, and thermal oxidation method. See Appendix F for details.
6.2 Microscopic observation and inspection
6.2.1 Selection of metallurgical microscope observation methods (brightfield illumination, darkfield illumination, polarized light illumination, differential interference contrast adjustment prism), color filter types
For class selection, aperture diaphragm adjustment, field diaphragm adjustment, light source adjustment, etc., please refer to GB/T 13298 requirements and instrument instructions.
6.2.2 Observe, inspect and analyze the prepared sample/replica under a metallographic microscope with a suitable magnification. Generally use 50 times to 100 times
Observe the entire sample and observe the details at high magnification.
6.2.3 The following morphological feature inspections should be carried out in the polished state.
a) Micro cracks, voids, etc.;
b) Oxide scale morphology and thickness;
c) Creep holes;
d) Corrosion pits on the inner and outer walls;
e) Evaluation of non-metallic inclusions;
f) Graphitization inspection;
g) Coating and plating thickness.
6.2.4 The following organization and morphological feature inspections should be carried out after etching.
a) Evaluation of matrix microstructure and its spheroidization and aging;
b) Free cementite, low carbon deformation pearlite, band structure, Widmanstatten structure, δ ferrite, α-phase in stainless steel and other intermetallic compounds
Things
c) Creep holes, deformed layers, coatings, coatings, infiltration layers, oxide scales, corrosion pits, microcracks
Mixed crystal crack) etc.;
d) Graphitization inspection;
e) Decarburization layer and shot peening layer inspection;
f) Grain size;
g) Microstructure of welded joints.
6.2.5 Image acquisition
a) Choose an appropriate magnification according to the requirements of the inspection area or microstructure characteristics, and add a scale with obvious contrast to the collected images;
b) On-site metallography can directly observe and collect images with a portable metallographic microscope on the etched inspection surface, and the images should clearly show the tissue characteristics.
6.3 Quantitative metallographic analysis
6.3.1 Quantitative metallographic determination can refer to the requirements of GB/T 15749.
6.3.2 A representative field of view should be selected during measurement. The measurement field/position depends on the uniformity of the object to be measured, generally no less than five fields/positions,
Take the average value as the measurement result.
6.3.3 When using image analysis software for quantitative metallographic analysis, it should be determined under the actual magnification.
6.3.4 The following items can be quantitatively analyzed by image analyzer.
a) Average grain size of metal;
b) The size and distribution of α-phase, pores, etc. in carbide, graphite, δ ferrite, and stainless steel;
c) Evaluation of non-metallic inclusions;
d) Decarburization layer, carburizing layer, shot peening layer depth, thickness measurement of coating, plating layer, oxide scale, etc.;
e) The depth of corrosion pits and microcracks.
7 Analysis and evaluation
7.1 Organizational routine analysis and assessment
7.1.1 The methods of free cementite evaluation, low-carbon deformation pearlite evaluation, band structure evaluation, and Widmanstatten structure evaluation should be in accordance with GB/T 13299;
7.1.2 Graphitization evaluation shall be implemented in accordance with the requirements of DL/T 786;
7.1.3 Inspection of the decarburized layer shall be carried out in accordance with the requirements of GB/T 224;
7.1.4 The shot peening layer inspection shall be carried out in accordance with the requirements of DL/T 1603;
7.1.5 Bolt microstructure inspection shall be carried out in accordance with the requirements of DL/T 439;
7.1.6 The average grain size inspection shall be evaluated in accordance with the requirements of GB/T 6394.The finished part/steel tube should be measured as the actual grain size, when the microstructure is Martensite
In the case of full bainite whose body or grain boundary is not easy to appear, the grain size of original austenite shall be inspected;
7.1.7 The shape, distribution and grade inspection of non-metallic inclusions shall be carried out in accordance with the requirements of GB/T 10561;
(Newly developed standard)
7.1.9 The determination of the area content of α-phase in stainless steel shall be carried out in accordance with the requirements of GB/T 13305;
7.1.10 The thickness measurement of oxide scale, coating, plating, etc. can be carried out with reference to GB/T 6462.
7.2 Microstructure aging assessment
7.2.1 Observe and evaluate the prepared sample/replica at a high magnification under a metallurgical microscope. The magnification is generally 500 times to 1000 times.
Use higher magnification (such as laser confocal microscope) for evaluation.
7.2.2 When assessing the aging of the microstructure, the service time, use temperature, stress and the original microstructure state of the components shall be considered comprehensively.
7.2.3 The two basic characteristics of microstructure aging are the changes in microstructure morphology and the distribution and size changes of intragranular and grain boundary carbides.
Divided into 5 levels. Schematic diagram of different state changes of carbides in the pearlite structure, bainite structure and austenite structure at levels 1 to 5 in the intragranular and grain boundary regions
As shown in Figure 1, the different state changes of carbides in the martensite structure in the lath bundle, lath boundary and grain boundary region can also refer to Figure 1.
Figure 1 Schematic diagram of different state changes of intragranular and grain boundary carbides
7.2.4 When assessing the level of aging (spheroidization) of microstructure, the number of selected fields of view on the same inspection surface should not be less than 3.If the sample microstructure is old (ball)
There is unevenness in chemical transformation, which should be treated differently according to the unevenness. For individual unevenness, the field of view area of the same level should account for 90% of the total observation area
The above old (ball) level is used as the evaluation result. For general inhomogeneities, the spheroidization level with severe aging (spheroidization) should be used as the evaluation result.
And in the evaluation conclusion, express its unevenness in words.
7.2.5 In the evaluation of microstructure aging by metallographic replication, the observed carbide particles are slightly larger than the actual carbide particles, and the creep holes
The size may be smaller than the actual hole size.
7.2.6 Evaluation of spheroidization of pearlite tissue
7.2.6.1 The microstructure of pearlite steel includes four types. ferrite plus pearlite, ferrite plus bainite, ferrite plus bainite plus pearlite or bainite.
The degree of spheroidization is divided into 5 grades, and the spheroidization characteristics of microstructures of grades 1 to 5 are shown in Table 1 and Table 2.
7.2.6.2 The evaluation of microstructure spheroidization of No. 20 steel, 12Cr1MoV steel, 15CrMo steel, and 2.25Cr-1Mo steel can be in accordance with Table 1 and Table 2, or in accordance with its
Corresponding standards, using the method of comparison with the standard map to evaluate.
a) Nodularization of the microstructure of No. 20 steel can also be assessed in accordance with DL/T 674;
b) The spheroidization of the microstructure of 12Cr1MoV steel can also be assessed in accordance with DL/T 773;
c) 15CrMo steel microstructure spheroidization can also be assessed in accordance with DL/T 787;
d) The microstructure spheroidization of 2.25Cr-1Mo steel can also be assessed in accordance with DL/T 999.
7.2.7 Bainite structure aging assessment
The microstructure of bainite steel is tempered bainite or ferrite plus tempered bainite. It is divided into 5 gr...
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