CN114383917B - Method for etching original austenite grain boundary of microalloyed carbon steel - Google Patents
Method for etching original austenite grain boundary of microalloyed carbon steel Download PDFInfo
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- CN114383917B CN114383917B CN202111508165.6A CN202111508165A CN114383917B CN 114383917 B CN114383917 B CN 114383917B CN 202111508165 A CN202111508165 A CN 202111508165A CN 114383917 B CN114383917 B CN 114383917B
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- 238000005530 etching Methods 0.000 title claims abstract description 57
- 229910001566 austenite Inorganic materials 0.000 title claims abstract description 45
- 229910000975 Carbon steel Inorganic materials 0.000 title claims abstract description 31
- 239000010962 carbon steel Substances 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000010438 heat treatment Methods 0.000 claims abstract description 54
- 238000005260 corrosion Methods 0.000 claims abstract description 40
- 230000007797 corrosion Effects 0.000 claims abstract description 37
- OXNIZHLAWKMVMX-UHFFFAOYSA-N picric acid Chemical compound OC1=C([N+]([O-])=O)C=C([N+]([O-])=O)C=C1[N+]([O-])=O OXNIZHLAWKMVMX-UHFFFAOYSA-N 0.000 claims abstract description 31
- 238000005498 polishing Methods 0.000 claims abstract description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 23
- 238000010791 quenching Methods 0.000 claims abstract description 21
- 230000000171 quenching effect Effects 0.000 claims abstract description 21
- 238000005496 tempering Methods 0.000 claims abstract description 17
- 239000005457 ice water Substances 0.000 claims abstract description 13
- 239000003945 anionic surfactant Substances 0.000 claims abstract description 7
- 239000012153 distilled water Substances 0.000 claims abstract description 7
- 238000003756 stirring Methods 0.000 claims description 19
- 238000004140 cleaning Methods 0.000 claims description 11
- 238000005520 cutting process Methods 0.000 claims description 6
- 238000000227 grinding Methods 0.000 claims description 6
- 239000013543 active substance Substances 0.000 claims description 2
- 238000000861 blow drying Methods 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 16
- 238000002360 preparation method Methods 0.000 abstract description 8
- 238000004458 analytical method Methods 0.000 abstract description 7
- 229910000831 Steel Inorganic materials 0.000 abstract description 3
- 239000000463 material Substances 0.000 abstract description 3
- 239000010959 steel Substances 0.000 abstract description 3
- 238000001514 detection method Methods 0.000 abstract description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 20
- 238000001035 drying Methods 0.000 description 10
- 238000010587 phase diagram Methods 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 7
- 238000001816 cooling Methods 0.000 description 6
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- 230000002708 enhancing effect Effects 0.000 description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 4
- 239000010931 gold Substances 0.000 description 4
- 229910052737 gold Inorganic materials 0.000 description 4
- 239000003518 caustics Substances 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 238000005464 sample preparation method Methods 0.000 description 3
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000010835 comparative analysis Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/32—Polishing; Etching
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
- C23F1/10—Etching compositions
- C23F1/14—Aqueous compositions
- C23F1/16—Acidic compositions
- C23F1/28—Acidic compositions for etching iron group metals
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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Abstract
The invention belongs to the technical field of steel material microstructure grain boundary etching, and particularly discloses a method for etching a microalloyed carbon steel prior austenite grain boundary. The prior austenite grain boundary corrosive comprises the following components: based on the 1L consumption, picric acid 20-25g, HCL solution 0.5-0.75ml, anionic surfactant 5-10ml, distilled water to 1000ml; the sample etching method is characterized by adopting heat treatment (higher than austenitizing temperature), ice water quenching, tempering, normal temperature quenching, sample preparation, grain boundary corrosion, return light polishing and grain boundary re-corrosion; the method has the advantages that the etching effect of the prior austenite grain boundary of the micro-alloyed carbon steel can be obviously improved, the method is simple and easy to operate, and the application requirements of industrial detection and analysis of the prior austenite grain size and the like of the micro-alloyed carbon steel are met.
Description
Technical Field
The invention belongs to the technical field of metallographic structure corrosion characterization preparation, and particularly relates to a method for etching a prior austenite grain boundary of micro-alloyed carbon steel.
Background
The microalloyed carbon steel is a main high-strength metal material at present, has wide application in the fields of civil use, military use, traffic, construction and the like, and with the development of various microalloying element adding technologies, for example, one or more microalloying elements such as Nb, V, ti, mo and the like are added into low-carbon steel, so that the strength and other mechanical properties of the microalloyed carbon steel are obviously improved to be suitable for higher-end requirement standards; the microalloyed high-strength steel is heated to above the austenite temperature and is kept for a plurality of time periods, austenite is recrystallized in a thermal deformation mode to achieve the purpose of grain refinement, and meanwhile, steel products with required shapes, such as plates, profiles, bars and the like, are obtained; according to different product requirements, the micro-alloyed carbon steel after heat treatment and thermal deformation adopts different cooling modes to obtain different room temperature microstructures, for example, the cooling speed is high to obtain a martensitic structure, the cooling speed is low to obtain a ferrite+pearlite structure, or a proper cooling speed can obtain a bainite structure and the like, and all room temperature structure grain changes depend on the prior austenite grain size, namely, the prior austenite grain size determines the room temperature structure grain size of the micro-alloyed carbon steel, so that the mechanical property of a final material is affected. Therefore, the etching technique of the prior austenite grain boundaries has an important influence in scientific research and industrial analysis.
At present, the prior austenite grain boundary etching mostly adopts picric acid solution for corrosion, but the prior austenite grain boundary etching requirement of partial microalloyed low carbon steel cannot be met by the technology, the efficiency is lower, and the effect is not obvious; therefore, a general prior austenite grain boundary etching technology needs to be further improved, so as to meet the industrial analysis and scientific research work, and the main technical difficulty of improving the prior austenite grain boundary etching technology is concentrated in: improvement of corrosive agent and improvement of metallographic preparation technology.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a corrosion and treatment method for etching the prior austenite grain boundary of the microalloyed carbon steel, which improves the metallographic corrosion efficiency while obviously improving the etching effect of the prior austenite grain boundary so as to solve the problem of poor etching efficiency of the prior austenite grain boundary of the microalloyed carbon steel.
The object of the invention is achieved by the following scheme.
Firstly, most of corrosive agents suitable for etching the prior austenite grain boundaries of the microalloyed carbon steel are picric acid solution, and as part of prior austenite grain boundaries of the alloy are corroded by picric acid, the etching effect of the grain boundaries is poor, so that the conventional picric acid solution is improved, the conventional picric acid solution is upgraded from normal-temperature corrosion type to heating type picric acid solution, and meanwhile, the conventional metallographic sample preparation method is improved to match with the heating type picric acid corrosion effect, so that the effect of clearly etching the prior austenite grain boundaries of the microalloyed carbon steel is achieved.
The preparation method of the micro-alloyed carbon steel metallographic sample is characterized by comprising the following main steps of:
(1) Preparing a metallographic etching corrosive: based on the 1L consumption, picric acid 20-25g, HCL solution 0.5-0.75mL, anionic surfactant 5-10mL, distilled water to 1000mL;
(2) Austenitizing heat treatment and ice water quenching: firstly, heating a micro-alloyed carbon steel sample to an austenite temperature of above 920 ℃, preserving heat for 0.5-3 hours, taking out the sample after finishing heat treatment, rapidly stirring in ice water for 30-60s, and finishing ice water quenching to obtain a treated sample;
(3) Tempering heat treatment and water quenching: tempering the sample treated in the step (2) at 400-600 ℃, preserving heat for 3-6 hours, taking the sample out of the furnace, rapidly stirring in warm water for 20-30s, and completing water quenching to obtain a tempered sample;
(4) Preparing a metallographic sample: cutting, mounting, grinding and polishing the sample subjected to tempering treatment in the step (3) to obtain a metallographic sample with a scratch-free surface;
(5) Sample grain boundary etching: placing the metallographic sample prepared in the step (4) into the metallographic etching corrosive prepared in the step (1), heating to 50-70 ℃, and simultaneously adopting a magnetic rod stirring mode to ensure that the solution temperature is uniform; the metallographic sample is boiled for 30-90 seconds, the surface of the sample is changed from smooth to a corrosion surface, then primary corrosion is completed, the metallographic sample is taken out, and the preliminary corrosion sample is obtained after cleaning and blow drying;
(6) And (3) carrying out return polishing and re-etching on the corroded sample: and (3) manually polishing the preliminary corrosion sample obtained in the step (5) on a polishing disk for a plurality of times to obtain a polished sample, then performing grain boundary etching again, placing the polished sample in the metallographic etching corrosive prepared in the step (1), heating to 50-70 ℃ for 20-40s, and starting to aggravate the corrosion surface on the sample surface to finish secondary corrosion, thereby realizing the prior austenite grain boundary etching of the microalloyed carbon steel.
Preferably, the anionic surfactant in step (1) comprises a TEEPOL active agent.
Preferably, the heating temperature in the step (2) is 1100-1200 ℃, and the heat preservation time is 1-1.5h.
Preferably, the tempering treatment in the step (3) is performed at 550 ℃ for 6 hours.
Preferably, the heating in step (5) is at a temperature of 60 ℃ for a period of 60s.
Preferably, the polishing in step (6) is performed several times, specifically 3 to 5 times.
Preferably, the heating temperature in step (6) is 60 ℃ and the heating time is 30s.
The beneficial effects of the invention are as follows:
(1) The invention improves the traditional picric acid solution, improves the traditional metallographic sample preparation method from normal temperature corrosion type to heating picric acid solution, and particularly adopts tempering mode to reprocess the experimental sample so as to match with the heating picric acid corrosion effect, thereby achieving the effect of clearly etching the microalloyed carbon steel prior austenite grain boundary; the invention has remarkable effect on the prior austenite grain boundary etching of the micro-alloyed carbon steel, and meets the scientific research and industrial detection analysis requirements in the aspect of metallographic analysis and microstructure improvement;
(2) The method has the advantages of simplicity, low operation requirement, easy realization and good application prospect.
Drawings
FIG. 1 is a golden phase diagram of a metallographic sample after etching in example 1.
Fig. 2 is a golden phase diagram of a metallographic sample after etching of comparative example 1.
FIG. 3 is a golden phase diagram of a metallographic sample after etching in example 2.
FIG. 4 is a golden phase diagram of a metallographic sample of comparative example 2 after etching.
The specific embodiment is as follows:
the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
Example 1:
the chemical composition of the micro-alloyed carbon steel prepared in the example 1 is (in mass percent): 0.1% of C, 0.29% of Si, 1.42% of Mn, 0.018% of P, 0.004% of S, 0.01% of Cr, 0.005% of Mo, 0.32% of Ni, 0.057% of Al, 0.008% of N, 0.019% of Nb, 0.001% of Ti, 0.052% of V and the balance of Fe, and a sample having a size of 20mm×20mm was prepared. The required picric acid solution comprises the following components: based on the consumption of 1L, 20g of picric acid, 0.7mL of HCl solution, 5mL of anionic surfactant and distilled water to 1000mL;
(1) Austenitizing heat treatment and ice water quenching: firstly, placing an experimental sample in an alumina crucible, heating to 1200 ℃ in a muffle furnace, preserving heat for 1 hour, adopting an external K-type thermocouple to detect the temperature of the sample, accurately adjusting the temperature of the muffle furnace along with experimental requirements, placing the sample in ice water for 30 seconds after the expected austenitizing heat treatment is completed, enhancing stirring and enhancing cooling effect, and obtaining a martensitic structure;
(2) Tempering heat treatment and water quenching: placing the sample subjected to the heat treatment in the step (1) in a low-temperature muffle furnace, heating to 550 ℃, preserving heat for 6 hours, then placing the sample in water for 30 seconds, and stirring to finish water quenching;
(3) Preparing a metallographic sample: performing metallographic cutting on the experimental sample subjected to tempering heat treatment, then performing hot inlaying, sample grinding and polishing operations, and cleaning and drying by using ethanol solution to obtain a metallographic sample with a smooth mirror surface on the surface;
(4) Sample grain boundary etching: placing the prepared metallographic sample into picric acid solution, heating to 60 ℃ and stirring, soaking and corroding for 60 seconds, and stirring the solution in a magnetic rod stirring mode to ensure that the solution temperature is uniform; after the surface of the metallographic sample is gradually changed into a corrosion surface from a smooth mirror surface, stopping corrosion, and cleaning and drying by using an ethanol solution to obtain a preliminary corrosion sample;
(5) And (3) carrying out return polishing and re-etching on the corroded sample: and (3) carrying out manual light polishing on the sample subjected to preliminary corrosion for 5 times by using a flannelette polishing disc, placing the sample in a picric acid solution after the corrosion surface of the metallographic sample is improved, heating to 60 ℃ and stirring for 30 seconds, and then washing and drying by using an ethanol solution to obtain the etched metallographic sample.
To illustrate the effect of the present invention, comparison is further made with comparative example 1;
comparative example 1: adopting a traditional prior austenite grain boundary etching method; the corrosive agent is a common picric acid solution, and comprises the following components: the volume of the distilled water is fixed to 1000mL by using 20g of picric acid according to the amount of 1L.
The preparation method adopts the traditional metallographic sample preparation technical method and comprises the following steps:
(1) Austenitizing heat treatment and water quenching: placing an experimental sample in an alumina crucible, heating to 1200 ℃ in a muffle furnace, preserving heat for 1 hour, detecting the temperature of the sample by adopting an external K-type thermocouple, accurately adjusting the temperature of the muffle furnace along with experimental requirements, placing the sample in the water after the expected austenitizing heat treatment is completed, and enhancing stirring;
(2) Preparing a metallographic sample: performing metallographic cutting on the experimental sample subjected to tempering heat treatment, then performing hot inlaying, sample grinding and polishing operations, and cleaning and drying by using ethanol solution to obtain a metallographic sample with a smooth mirror surface on the surface;
(3) Sample grain boundary etching: and placing the prepared metallographic sample in a heated and stirred picric acid solution (60 ℃) for 60 seconds, stopping corrosion after the surface of the metallographic sample is gradually changed into a corrosion surface from a smooth mirror surface, and cleaning and drying by using an ethanol solution to obtain a preliminary corrosion sample.
Compared with the new treatment technology of the invention, the traditional technology lacks ice water quenching, tempering heat treatment, secondary manual polishing and re-corrosion and improved picric acid solution after austenitizing heat treatment.
As can be seen from comparison of the gold phase diagrams, for corrosion analysis of the same micro-alloyed carbon steel sample, the conventional prior austenite grain boundary etching method is adopted, the micro-alloyed carbon steel has poor corrosion effect, the prior austenite grain boundary cannot be clearly displayed by the gold phase diagrams, and related microstructure information such as the prior austenite grain size and the like is difficult to obtain, as shown in fig. 2.
The same sample is subjected to metallographic preparation treatment by adopting the method, and the prior austenite grain boundaries are etched by using the modified picric acid, so that compared with the traditional method, the prior austenite grain boundaries with a clearer degree can be obtained in the embodiment 1, and the prior austenite grain boundaries are shown in figure 1.
According to the comparative analysis of the micro-alloyed carbon steel sample in the example 1, the traditional prior austenite grain boundary corrosion method is adopted, the effect is poor, the metallographic analysis is difficult to meet, and the problem of researching the maximum structural performance of the alloy material is solved. Through the comparative analysis, the grain boundary etching of the material sample in the example 1 is clear, which shows that the invention has a remarkable effect on the prior austenite grain boundary etching of the microalloyed carbon steel.
Example 2:
the chemical composition of the micro-alloyed carbon steel prepared in the example 2 is (in mass percent): 0.105% of C, 0.23% of Si, 0.99% of Mn, 0.002% of P, 0.001% of S, 0.005% of Cr, 0.005% of Mo, 0.005% of Ni, 0.031% of Al, 0.006% of N, 0.028% of Nb, 0.001% of Ti, 0.001% of V and the balance of Fe, and a sample having a size of 20mm by 20mm was prepared. The required picric acid solution comprises the following components: based on the 1L consumption, 20g of picric acid, 0.7mL of HCL solution, 5mL of anionic surfactant and distilled water to 1000mL;
(1) Austenitizing heat treatment and ice water quenching: firstly, placing an experimental sample in an alumina crucible, heating to 1100 ℃ in a muffle furnace, and preserving heat for 1 hour; after the expected austenitizing heat treatment is completed, quenching by ice water, strengthening stirring, and improving the cooling speed of the sample to obtain a martensitic structure;
(2) Tempering heat treatment and water quenching: heating the heat-treated sample to 550 ℃ by using a low-temperature muffle furnace, preserving heat for 6 hours, then placing the sample in water, and enhancing stirring to finish water quenching;
(3) Preparing a metallographic sample: cutting the experimental sample after heat treatment to finish metallographic preparation operations such as hot inlaying, sample grinding, polishing and the like, and cleaning and drying the experimental sample by using ethanol solution to obtain a metallographic sample with a smooth mirror surface;
(4) Sample grain boundary etching: heating picric acid solution to 60 ℃, placing the prepared metallographic sample in the picric acid solution for corrosion for 60s, and stirring the solution in a magnetic rod stirring mode to ensure that the temperature of the solution is uniform; stopping etching after the surface of the metallographic sample is gradually changed into an etching surface from a smooth mirror surface, and cleaning and drying by using ethanol solution to obtain a preliminary etching sample;
(5) And (3) carrying out return polishing and re-etching on the corroded sample: and slightly polishing the sample subjected to preliminary corrosion by using a flannelette polishing disk for 3 times by adopting a manual light polishing method, then placing the sample in a picric acid solution, heating to 60 ℃, stirring by using a magnetic rod, soaking and corroding for 30 seconds, and finally cleaning and drying by using an ethanol solution to obtain the etched metallographic sample.
To further illustrate the importance of the metallographic sample preparation method of the present invention to the etching effect of the microalloyed carbon steel prior austenite grain boundaries, comparison is further made with comparative example 2;
comparative example 2: adopts the traditional prior austenite grain boundary etching method and the common picric acid solution, and comprises the following components: in terms of 1L consumption, picric acid 20g and distilled water to 1000mL;
the specific procedure of comparative example 2 is as follows:
(1) Austenitizing heat treatment and water quenching: and placing the experimental sample in an alumina crucible, heating to 1100 ℃ in a muffle furnace, preserving heat for 1 hour, detecting the temperature of the sample by adopting an external K-type thermocouple, and accurately adjusting the temperature of the muffle furnace according to experimental requirements. After the desired austenitizing heat treatment was completed, the sample was placed in warm water and stirring was enhanced.
(2) Preparing a metallographic sample: and (3) carrying out metallographic cutting on the experimental sample subjected to tempering heat treatment, then finishing the operations of hot inlaying, sample grinding and polishing, and cleaning and drying by using ethanol solution to obtain a metallographic sample with a smooth mirror surface on the surface.
(3) Sample grain boundary etching: and placing the prepared metallographic sample in a heated and stirred picric acid solution (60 ℃) for 60 seconds, stopping corrosion after the surface of the metallographic sample is gradually changed into a corrosion surface from a smooth mirror surface, and cleaning and drying by using an ethanol solution to obtain a preliminary corrosion sample.
The results show that the traditional prior austenite grain boundary etching method lacks ice water quenching, tempering heat treatment, secondary light polishing and re-corrosion after austenitizing heat treatment and modified picric acid solution in the invention; the gold phase diagram (fig. 4) obtained cannot clearly show the prior austenite grain boundaries, but the gold phase diagram (fig. 3) of example 2 obtained by the method of the present invention can clearly show the prior austenite grain boundaries, so as to demonstrate that the method provided by the present invention has very remarkable effects.
Description: the above embodiments are only for illustrating the present invention and not for limiting the technical solution described in the present invention; thus, while the invention has been described in detail with reference to the various embodiments described above, it will be understood by those skilled in the art that the invention may be modified or equivalents; all technical solutions and modifications thereof that do not depart from the spirit and scope of the present invention are intended to be included in the scope of the appended claims.
Claims (5)
1. The prior austenite grain boundary etching method for the micro-alloyed carbon steel is characterized by comprising the following steps of:
(1) Preparing a metallographic etching corrosive: based on the 1L consumption, picric acid 20-25g, HCL solution 0.5-0.75mL, anionic surfactant 5-10mL, distilled water to 1000mL;
(2) Austenitizing heat treatment and ice water quenching: firstly, heating a micro-alloyed carbon steel sample to an austenite temperature of above 920 ℃, preserving heat for 0.5-3 hours, taking out the sample after finishing heat treatment, rapidly stirring in ice water for 30-60s, and finishing ice water quenching to obtain a treated sample;
(3) Tempering heat treatment and water quenching: tempering the sample treated in the step (2) at 400-600 ℃, preserving heat for 3-6 hours, taking the sample out of the furnace, rapidly stirring in warm water for 20-30s, and completing water quenching to obtain a tempered sample;
(4) Preparing a metallographic sample: cutting, mounting, grinding and polishing the sample subjected to tempering treatment in the step (3) to obtain a metallographic sample with a scratch-free surface;
(5) Sample grain boundary etching: placing the metallographic sample prepared in the step (4) into the metallographic etching corrosive prepared in the step (1), heating to 50-70 ℃, and simultaneously adopting a magnetic rod stirring mode to ensure that the solution temperature is uniform; the metallographic sample is boiled for 30-90 seconds, the surface of the sample is changed from smooth to a corrosion surface, then primary corrosion is completed, the metallographic sample is taken out, and the preliminary corrosion sample is obtained after cleaning and blow drying;
(6) And (3) carrying out return polishing and re-etching on the corroded sample: manually polishing the preliminary corrosion sample obtained in the step (5) on a polishing disk for 3-5 times to obtain a polished sample, then performing grain boundary etching again, placing the polished sample in the metallographic etching corrosive prepared in the step (1), and heating again to 50-70 ℃ for 20-40s, wherein the surface of the sample begins to aggravate the corrosion surface, and finishing secondary corrosion, so as to realize the grain boundary etching of the microalloyed carbon steel prior austenite;
the anionic surfactant in step (1) comprises a TEEPOL active agent.
2. The method for etching a prior austenite grain boundary of a microalloyed carbon steel according to claim 1, wherein the heating temperature in the step (2) is 1100-1200 ℃, and the holding time is 1-1.5h.
3. The method for etching a prior austenite grain boundary of a microalloyed carbon steel according to claim 1, wherein the tempering treatment in the step (3) is performed at a temperature of 550 ℃ for a period of 6 hours.
4. The method of claim 1, wherein the heating in step (5) is performed at a temperature of 60 ℃ for a period of 60 seconds.
5. The method of claim 1, wherein the heating in step (6) is performed at a temperature of 60 ℃ for a period of 30 seconds.
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| PCT/CN2022/133251 WO2023103758A1 (en) | 2021-12-10 | 2022-11-21 | Micro-alloyed carbon steel original austenite grain boundary etching method |
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| CN117871218B (en) * | 2024-03-13 | 2024-05-31 | 南昌航空大学 | Subregion division and microstructure display method of ferrite heat-resistant steel heat affected zone |
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