CN117309537A - Display method of austenite grain boundary of low-carbon quasi-bainitic steel - Google Patents
Display method of austenite grain boundary of low-carbon quasi-bainitic steel Download PDFInfo
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- CN117309537A CN117309537A CN202311194864.7A CN202311194864A CN117309537A CN 117309537 A CN117309537 A CN 117309537A CN 202311194864 A CN202311194864 A CN 202311194864A CN 117309537 A CN117309537 A CN 117309537A
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- 238000000034 method Methods 0.000 title claims abstract description 45
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 37
- 239000010959 steel Substances 0.000 title claims abstract description 37
- 229910001566 austenite Inorganic materials 0.000 title claims abstract description 28
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 14
- 238000010438 heat treatment Methods 0.000 claims abstract description 19
- 238000001816 cooling Methods 0.000 claims abstract description 16
- 238000005498 polishing Methods 0.000 claims abstract description 9
- 238000000227 grinding Methods 0.000 claims abstract description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910002651 NO3 Inorganic materials 0.000 claims abstract description 6
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims abstract description 6
- 238000001035 drying Methods 0.000 claims abstract description 5
- 238000011010 flushing procedure Methods 0.000 claims abstract description 5
- 239000011159 matrix material Substances 0.000 claims abstract description 4
- 238000007599 discharging Methods 0.000 claims abstract description 3
- 238000005096 rolling process Methods 0.000 claims description 6
- 238000003723 Smelting Methods 0.000 claims description 3
- 238000005530 etching Methods 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 3
- 229910003460 diamond Inorganic materials 0.000 claims description 2
- 239000010432 diamond Substances 0.000 claims description 2
- 239000012535 impurity Substances 0.000 claims description 2
- 238000011161 development Methods 0.000 abstract description 2
- 238000007689 inspection Methods 0.000 abstract description 2
- 239000007769 metal material Substances 0.000 abstract description 2
- 238000005088 metallography Methods 0.000 abstract description 2
- 230000008093 supporting effect Effects 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 9
- 239000000243 solution Substances 0.000 description 9
- 244000137852 Petrea volubilis Species 0.000 description 6
- 229910001562 pearlite Inorganic materials 0.000 description 5
- 229910001567 cementite Inorganic materials 0.000 description 4
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 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 description 4
- 238000010791 quenching Methods 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910000639 Spring steel Inorganic materials 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910021591 Copper(I) chloride Inorganic materials 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- OXBLHERUFWYNTN-UHFFFAOYSA-M copper(I) chloride Chemical compound [Cu]Cl OXBLHERUFWYNTN-UHFFFAOYSA-M 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 239000003599 detergent Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000002453 shampoo Substances 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
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- 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
-
- 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
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/20—Metals
- G01N33/204—Structure thereof, e.g. crystal structure
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
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Abstract
The invention discloses a display method of austenite grain boundaries of low-carbon quasi-bainitic steel, and belongs to the technical field of physical inspection of metal materials. The method comprises the steps of firstly placing a low-carbon quasi-bainitic steel sample to be measured in a heat treatment furnace for high-temperature treatment, wherein the heating temperature is 650-750 ℃, preserving heat for 0.5-4 h, cooling to 400-500 ℃ along with the furnace, discharging and air cooling, grinding and polishing the obtained sample to be measured to prepare a metallographic sample, corroding, flushing and drying a surface to be measured of the metallographic sample obtained by adopting a nitrate alcohol solution, and obtaining metallographic images with obvious gray level difference between a matrix and a grain boundary through image acquisition equipment. The display method can accurately display the austenite grain boundary information of the quasi-bainitic steel, and indirectly evaluate the mechanical properties of the quasi-bainitic steel rail by measuring the grain size through quantitative metallography, thereby playing a supporting role in the development and application of the bainitic steel rail.
Description
Technical Field
The invention belongs to the technical field of physical inspection of metal materials, and particularly relates to a display method of austenite grain boundaries of low-carbon quasi-bainitic steel.
Background
The traditional bainitic steel mainly comprises bainitic ferrite and cementite, wherein cementite is easy to form a crack source in specific application and affects the service life of the steel, so that the precipitation of carbide is inhibited by adding alloy elements Si, al and the like in low-carbon steel, the cementite is replaced by carbon-rich residual austenite in the process of structure transformation, a special carbide-free quasi-bainitic structure is formed, and no obvious grain boundary reference property is generated in the process of grain size measurement.
The prior austenite grain boundary display comprises a carburization method, a simulated carburization method, a ferrite net method, an oxidation method, a direct hardening method, a cementite net method and a fine pearlite net method, wherein the carbide is formed to display the grain boundary and no atmosphere is added, but the method is to heat a sample to about the austenitizing temperature of 820 ℃, keep the temperature for 30min, cool the sample to below a lower critical temperature at a sufficiently slow cooling speed, and separate out the carbide from the austenite grain boundary, and the method needs to measure the critical temperature of steel types. The austenite grain size of the pearlite steel rail is usually prepared by adopting a fine pearlite net method and a direct hardening method, wherein the fine pearlite net method is mainly aimed at eutectoid steel, and a sample is incompletely hardened or adopts a gradient hardening method, so that austenite grains are surrounded by fine pearlite; the direct hardening method needs to heat the sample to the complete austenitizing temperature, preserve heat for 1h, quench with a larger cooling speed to obtain a martensitic structure, tempering for 15min at about 230 ℃ before corrosion to improve contrast, finally preparing the sample obtained by heat treatment into a metallographic sample, adopting picric acid aqueous solution, detergent and other active agents to corrode at a certain temperature to display grain boundaries according to a certain concentration ratio.
The invention patent CN201911410944.5 discloses a display method of austenite grains of spring steel, which mainly comprises the steps of preserving heat of the steel for 10-40 min at 850-900, quenching at a cooling speed of complete hardening, tempering and preserving heat of a cooled sample at 400-600 ℃ for more than 8h, cooling to 350 ℃ along with a furnace, and then cooling to room temperature in air; adding 50ml deionized water, 2-2.5 g picric acid, 1.5-2 g shampoo and 1g iron scale produced by high-line steel mill into a water bath beaker at 70 ℃, stirring uniformly to prepare corrosive liquid, standing a sample in the corrosive liquid for 30-60 s, taking out, flushing with alcohol, drying, and clearly showing austenite grain boundaries in the pattern. The invention patent CN201811095252.1 discloses a display method of austenite grains of spring steel, which mainly comprises the steps of preserving heat of the steel for 0.5-1 h at 850-900 ℃, quenching at a cooling speed of complete hardening, tempering and preserving heat of a cooled sample for more than 1-3 h at 400-600 ℃, and cooling to obtain a quenched sample; adding 2-3 g of sodium dodecyl benzene sulfonate into 100ml of saturated picric acid solution in a beaker, stirring until the sodium dodecyl benzene sulfonate is completely dissolved, and dripping 1-3 drops of 2-5% CuCl 2 Preparing a solution into etching solution, and putting a sample into the solution to be corroded for 1-3 min; both methods require heat treatment to quench and temper the sample to form tempered martensite, the austenite grain size is easily changed by complete austenitization, and the corrosion process using saturated picric acid plus an active agent is complex and difficult to control.
Disclosure of Invention
In view of the above, the invention aims to provide a method for displaying austenite grain boundaries of low-carbon quasi-bainitic steel, which utilizes the characteristic that residual austenite in quasi-bainite is thermally and mechanically unstable, and the residual austenite is decomposed at high temperature to form different electrode potentials between the grain boundaries and the grain boundaries, so that strong gray scale difference can be formed in the corrosion process by using a conventional corrosive agent, and the purpose of grain size measurement is achieved.
The invention aims at realizing the following steps:
the invention provides a display method of austenite grain boundaries of low-carbon quasi-bainitic steel, which mainly comprises the following steps:
(1) Placing the low-carbon quasi-bainitic steel sample to be tested in a heat treatment furnace for high-temperature treatment, wherein the heating temperature is 650-750 ℃, preserving heat for 0.5-4 h, cooling to 400-500 ℃ along with the furnace, discharging and air cooling;
(2) Grinding and polishing the sample to be detected obtained in the step (1) to prepare a metallographic sample;
(3) And (3) corroding the surface to be tested of the metallographic specimen obtained in the step (2) by using a nitrate alcohol solution, flushing and drying, and obtaining metallographic images with obvious gray scale difference between a matrix and a grain boundary by using image acquisition equipment.
Based on the technical scheme, the heating temperature in the step (1) is 680-720 ℃, and the temperature is kept for 1-2 h.
Based on the technical scheme, the furnace is further cooled to 450 ℃ in the step (1).
Based on the technical scheme, further, the chemical components and weight percentages of the quasi-bainitic steel in the step (1) are as follows: c:0.20 to 0.3 percent, si:1.5 to 2.0 percent, mn:1.6 to 2.0, cr:0.8 to 1.0 percent, mo:0.2 to 0.5 percent, P: less than or equal to 0.015 percent, S: less than or equal to 0.005 percent, and the balance of Fe and unavoidable impurities.
Based on the technical scheme, further, the quasi-bainitic steel is subjected to smelting, rough rolling, finish rolling and cooling to obtain a quasi-bainitic structure, namely bainitic ferrite plus austenite.
Based on the above technical scheme, further, the grinding in the step (2) is specifically grinding by sequentially using 80# metallographic sand paper, 100# metallographic sand paper, 200# metallographic sand paper, 500# metallographic sand paper, 800# metallographic sand paper and 1200# metallographic sand paper.
Based on the technical scheme, the polishing in the step (2) is specifically polishing by using a diamond polishing agent with the diameter of 1-2.5 μm.
Based on the technical scheme, the concentration of the nitrate alcohol solution in the step (3) is 2-5%.
Based on the technical scheme, further, the etching time in the step (3) is 10-30 s.
Compared with the prior art, the invention has the following beneficial effects:
1. the display method of the austenite grain boundary of the low-carbon quasi-bainitic steel can accurately display the austenite grain boundary information of the quasi-bainitic steel, and the mechanical properties of the quasi-bainitic steel rail can be indirectly evaluated by measuring the grain size through quantitative metallography, so that the display method has a supporting effect on development and application of the bainitic steel rail.
2. The invention successfully solves the problem of displaying the austenite grain boundary of the quasi-bainitic steel, and a method for displaying the austenite grain information of the quasi-bainitic steel is not reported in the prior art.
Drawings
In order to more clearly illustrate the embodiments of the present invention, the drawings to which the embodiments relate will be briefly described.
FIG. 1 shows the morphology of the tissue after heat treatment at 700℃in example 1.
FIG. 2 is a graph showing the morphology of the tissue after heat treatment at 720℃in example 2.
FIG. 3 is a morphology of the tissue before heat treatment in comparative example 1.
FIG. 4 is a graph showing the morphology of the tissue after heat treatment at 350℃in comparative example 2.
FIG. 5 is a graph showing the morphology of the tissue of comparative example 3 after heat treatment at 850 ℃.
Detailed Description
The following detailed description of the invention is provided in connection with examples, but the implementation of the invention is not limited thereto, and it is obvious that the examples described below are only some examples of the invention, and that it is within the scope of protection of the invention to those skilled in the art to obtain other similar examples without inventive faculty.
Examples 1 to 2
Examples 1-2 provide a method for displaying austenite grain boundaries of low-carbon quasi-bainitic steel, which comprises the following steps:
the chemical components and weight percentages of the selected quasi-bainitic steel are as follows: c:0.26%, si:1.57%, mn:1.72%, cr:0.93%, mo:0.34%, P:0.014%, S:0.004% of a quasi-bainitic steel sample, wherein the quasi-bainitic steel is subjected to smelting, rough rolling, finish rolling and cooling to obtain a quasi-bainitic structure, namely bainitic ferrite and austenite, a finished product is selected to cut a metallographic sample, the sample to be measured is placed in a heat treatment furnace for high-temperature treatment, the heating temperature and the heat preservation time are shown in a table 1, and then the steel is cooled to 450 ℃ along with the furnace, and is discharged for air cooling; grinding and polishing the heat-treated sample to be tested to prepare a metallographic specimen, corroding the surface to be tested for 20s by adopting a nitrate alcohol corrosive liquid (the concentration of the corrosive liquid is shown in table 1), flushing and drying, and obtaining metallographic images with obvious gray differences between a matrix and a grain boundary through image acquisition equipment.
Comparative examples 1 to 3
The specific procedures of comparative examples 1 to 3 and example 1 were the same, except that the processing parameters in Table 1 were different.
TABLE 1 heating temperature, holding time and corrosive solution concentration during the display of austenite grain boundaries of low carbon quasi-bainitic steels
| Sample name | Heating temperature (. Degree. C.) | Time of thermal insulation (h) | Concentration of corrosive solution (%) |
| Example 1 | 700 | 1.5 | 3 |
| Example 2 | 720 | 1 | 4 |
| Comparative example 1 | Is not heat treated | Is not heat treated | 3 |
| Comparative example 2 | 350 | 2 | 3 |
| Comparative example 3 | 850 | 1 | 3 |
The metallographic images detected by the display method equipment of examples 1-2 and comparative examples 1-3 are shown in fig. 1-5, respectively, and it can be seen that the display method of examples 1-2 can accurately display the austenite grain boundary information of the quasi-bainitic steel.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (9)
1. The display method of the austenite grain boundary of the low-carbon quasi-bainitic steel is characterized by mainly comprising the following steps of:
(1) Placing the low-carbon quasi-bainitic steel sample to be tested in a heat treatment furnace for high-temperature treatment, wherein the heating temperature is 650-750 ℃, preserving heat for 0.5-4 h, cooling to 400-500 ℃ along with the furnace, discharging and air cooling;
(2) Grinding and polishing the sample to be detected obtained in the step (1) to prepare a metallographic sample;
(3) And (3) corroding the surface to be tested of the metallographic specimen obtained in the step (2) by using a nitrate alcohol solution, flushing and drying, and obtaining metallographic images with obvious gray scale difference between a matrix and a grain boundary by using image acquisition equipment.
2. The display method according to claim 1, wherein the heating temperature in the step (1) is 680 to 720 ℃, and the temperature is kept for 1 to 2 hours.
3. The display method according to claim 1, wherein the furnace is cooled to 450 ℃ in step (1).
4. The display method according to claim 1, wherein the chemical components and weight percentages of the quasi-bainitic steel in the step (1) are: c:0.20 to 0.3 percent, si:1.5 to 2.0 percent, mn:1.6 to 2.0, cr:0.8 to 1.0 percent, mo:0.2 to 0.5 percent, P: less than or equal to 0.015 percent, S: less than or equal to 0.005 percent, and the balance of Fe and unavoidable impurities.
5. The method according to claim 1, wherein the quasi-bainitic steel obtained in the step (1) is subjected to smelting, rough rolling, finish rolling, and cooling to obtain a quasi-bainitic structure.
6. The display method according to claim 1, wherein the grinding in step (2) is specifically grinding with 80#, 100#, 200#, 500#, 800#, 1200# metallographic sandpaper in order.
7. A display method according to claim 1, wherein the polishing in step (2) is specifically polishing with a diamond polish of 1-2.5 μm.
8. The display method according to claim 1, wherein the concentration of the nitrate alcohol solution in the step (3) is 2 to 5%.
9. The display method according to claim 1, wherein the etching time in the step (3) is 10 to 30 seconds.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311194864.7A CN117309537A (en) | 2023-09-15 | 2023-09-15 | Display method of austenite grain boundary of low-carbon quasi-bainitic steel |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311194864.7A CN117309537A (en) | 2023-09-15 | 2023-09-15 | Display method of austenite grain boundary of low-carbon quasi-bainitic steel |
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| CN117309537A true CN117309537A (en) | 2023-12-29 |
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