CN117890187A - Step-by-step corrosion method for cast structure of vanadium-containing bearing steel - Google Patents
Step-by-step corrosion method for cast structure of vanadium-containing bearing steel Download PDFInfo
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- 238000005260 corrosion Methods 0.000 title claims abstract description 85
- 230000007797 corrosion Effects 0.000 title claims abstract description 85
- 229910052720 vanadium Inorganic materials 0.000 title claims abstract description 68
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 title claims abstract description 68
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 65
- 239000010959 steel Substances 0.000 title claims abstract description 65
- 238000000034 method Methods 0.000 title claims abstract description 38
- 238000005530 etching Methods 0.000 claims abstract description 67
- 239000007788 liquid Substances 0.000 claims abstract description 35
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 68
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 45
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 39
- 229910017604 nitric acid Inorganic materials 0.000 claims description 39
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 30
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims description 27
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 27
- 238000005266 casting Methods 0.000 claims description 15
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 13
- 239000003945 anionic surfactant Substances 0.000 claims description 13
- 238000001035 drying Methods 0.000 claims description 13
- 238000005498 polishing Methods 0.000 claims description 12
- 238000000227 grinding Methods 0.000 claims description 8
- 230000003287 optical effect Effects 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 7
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 4
- 244000137852 Petrea volubilis Species 0.000 claims description 3
- 230000000007 visual effect Effects 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 21
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract description 21
- 230000000694 effects Effects 0.000 abstract description 18
- 210000001787 dendrite Anatomy 0.000 abstract description 11
- 229910000859 α-Fe Inorganic materials 0.000 abstract description 9
- 238000009826 distribution Methods 0.000 abstract description 4
- 238000011156 evaluation Methods 0.000 abstract description 3
- 238000005259 measurement Methods 0.000 abstract description 3
- 238000011160 research Methods 0.000 abstract description 3
- 239000000243 solution Substances 0.000 description 11
- 239000008367 deionised water Substances 0.000 description 9
- 229910021641 deionized water Inorganic materials 0.000 description 9
- 238000003756 stirring Methods 0.000 description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- 239000003518 caustics Substances 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 4
- 238000004090 dissolution Methods 0.000 description 3
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 3
- 238000001878 scanning electron micrograph Methods 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 2
- 239000003599 detergent Substances 0.000 description 2
- 238000011010 flushing procedure Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- OXNIZHLAWKMVMX-UHFFFAOYSA-N picric acid Chemical class OC1=C([N+]([O-])=O)C=C([N+]([O-])=O)C=C1[N+]([O-])=O OXNIZHLAWKMVMX-UHFFFAOYSA-N 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 238000013441 quality evaluation Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 230000002000 scavenging effect 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- ing And Chemical Polishing (AREA)
- Investigating And Analyzing Materials By Characteristic Methods (AREA)
Abstract
The invention provides a step-by-step corrosion method for a cast structure of vanadium-containing bearing steel, and relates to the technical field of metallographic analysis. According to the invention, the sample is corroded by using the rough etching corrosive liquid, so that the basic outline of dendrite, ferrite and precipitated phases in the as-cast structure of the vanadium-containing high-nitrogen bearing steel can be displayed, and then the fine etching corrosive liquid is adopted to corrode the rough etching sample, so that the morphology, the size, the distribution and the number of dendrite, ferrite and precipitated phases in the as-cast structure of the vanadium-containing high-nitrogen bearing steel can be clearly and completely displayed; the invention adopts step-by-step corrosion, so that the corrosion quality is high, the effect is easy to control, and the method can be used for observation and research of as-cast structure and measurement and evaluation of macrosegregation. The invention provides a step-by-step corrosion method which is applicable to vanadium-containing high-nitrogen bearing steel.
Description
Technical Field
The invention relates to the technical field of metallographic analysis, in particular to a step-by-step corrosion method for a cast structure of vanadium-containing bearing steel.
Background
Aeroengines are open beads on manufacturing crowns, where high nitrogen bearing steels are of great interest as third generation raw materials for aeroengine bearings, with high temperature, corrosion, hardness, fracture toughness, rolling contact fatigue life and dimensional stability. As a key microalloying element of the high-nitrogen bearing steel, vanadium not only can refine grains, improve the toughness of the steel and obtain good formability and weldability, but also can ensure excellent mechanical property and corrosion resistance. Therefore, the corrosion method which can be used for evaluating the quality of the cast structure of the vanadium-containing bearing steel is found, and has great significance for improving the quality control of the vanadium-containing high-nitrogen bearing steel.
At present, dendrite corrosion methods for bearing steel have been reported, but the effect for vanadium-containing bearing steel is poor, and the corrosion time is difficult to control. For example, the patent application with the application number of 202111020989.9 discloses a corrosive agent of bearing steel cast dendrite structure and a display method, wherein the corrosive agent is prepared from supersaturated picric acid aqueous solution and detergent according to the proportion of 100mL:0.6 g-1.2 g; etching for 2-5 min; the supersaturated picric acid solution requires complex operation steps, and has low production efficiency; as the detergent is added in the corrosion of the corrosive agent, generated bubbles are easily adsorbed to the surface of the sample, so that the corrosion is uneven, and the corrosive agent is not suitable for vanadium-containing high-nitrogen bearing steel.
Therefore, it is highly desirable to provide a corrosion method capable of clearly displaying the as-cast structure of vanadium-containing bearing steel, which is used for quality evaluation of the as-cast structure of the vanadium-containing bearing steel and provides a basis for producing high-quality vanadium-containing high-nitrogen bearing steel.
Disclosure of Invention
The invention aims to provide a step-by-step corrosion method for a cast structure of vanadium-containing bearing steel, which can clearly display the cast structure of the vanadium-containing high-nitrogen bearing steel and solve the problems that the vanadium-containing bearing steel is difficult to corrode and the corrosion effect is difficult to control.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a step-by-step corrosion method of a vanadium-containing bearing steel cast structure, which comprises the following steps:
carrying out first corrosion on the vanadium-containing bearing steel ingot casting sample by using the rough etching corrosive liquid to obtain a rough etching sample; the time of the first corrosion is 2.5-3.5 s; the rough etching corrosive liquid comprises first nitric acid, first water, first ferric chloride, first hydrochloric acid and an anionic surfactant; the mass ratio of the first hydrochloric acid to the first water to the first ferric chloride to the anionic surfactant is (14-18) mL: (48-52) mL: (4.3-5.2) g: (0.8-1.3) g;
the volume of the first nitric acid is calculated according to formula 1:
formula 1;
in the formula 1, V is the volume of the first nitric acid and mL; m is the mass percentage of vanadium in the vanadium-containing bearing steel ingot casting sample;
counting the area ratio of carbide in the rough engraving sample by using an optical microscope;
performing second corrosion on the rough carving sample by using the fine carving corrosive liquid;
the etching solution comprises second hydrochloric acid, second nitric acid, second water, acetic acid and second ferric chloride; the mass ratio of the volume of the second hydrochloric acid to the volume of the second nitric acid to the volume of the second water to the volume of the acetic acid to the second ferric chloride is (7-10) mL: (2-3) mL: (48-52) mL: (3-4) mL: (2.1-2.5) g;
the mass concentration of the first nitric acid and the second nitric acid is 65-68% independently; the mass concentration of the first hydrochloric acid and the second hydrochloric acid is 70-75% independently; the mass concentration of the acetic acid is 28-33%;
when the area ratio of the carbide is less than 6%, the second corrosion time is 4.5-5.5 s;
when the area ratio of the carbide is 6-10%, the second corrosion time is 4.9-5.9 s;
and when the area ratio of the carbide is more than 10%, the second corrosion time is 5.5-6.5 s.
Preferably, the vanadium-containing bearing steel ingot sample comprises, in mass percent: 0.32+/-0.03% of C, 0.30+/-0.15% of N, 0.50+/-0.03% of Si, 0.40+/-0.03% of Mn, 15.3+/-0.3% of Cr, 1.00+/-0.03% of Mo, more than 0 and less than or equal to 1.00% of V, and the balance of Fe.
Preferably, the anionic surfactant comprises sodium dodecyl sulfate.
Preferably, the first and second etches independently comprise an etch or a pour.
Preferably, the rough engraving sample remains rotated during the second etching.
Preferably, the rotation speed is 50-80 r/min.
Preferably, before the first corrosion, the method further comprises pretreating the vanadium-containing bearing steel ingot casting sample, wherein the pretreatment comprises: and sequentially carrying out sand paper grinding, polishing and surface cleaning on the vanadium-containing bearing steel ingot casting sample.
Preferably, the area ratio of carbide in the rough engraving sample counted by using an optical microscope is not less than 30 visual fields, and the observation multiple is not higher than 200.
Preferably, after the first etching is completed, the method further comprises immediately washing the obtained etched sample with absolute ethyl alcohol and drying.
Preferably, after the second etching is completed, the method further comprises immediately washing the obtained etched sample with absolute ethanol and drying.
The invention provides a step-by-step corrosion method of a cast structure of vanadium-containing bearing steel, which comprises the steps of firstly corroding a sample by using a rough etching corrosive liquid to show basic outlines of dendrites, ferrite and precipitated phases in the cast structure of the vanadium-containing high-nitrogen bearing steel, and then corroding the rough etching sample by adopting a fine etching corrosive liquid to clearly and completely show the morphology, the size, the distribution and the quantity of the dendrites, the ferrite and the precipitated phases in the cast structure of the vanadium-containing high-nitrogen bearing steel; the invention adopts step-by-step corrosion, so that the corrosion quality is high, the effect is easy to control, and the method can be used for observation and research of as-cast structure and measurement and evaluation of macrosegregation. The invention provides a step-by-step corrosion method which is applicable to vanadium-containing high-nitrogen bearing steel.
The rough etching corrosive liquid and the fine etching corrosive liquid take nitric acid, hydrochloric acid and ferric chloride as main components, wherein chloride ions in the ferric chloride and the hydrochloric acid can lead elements such as Cr, fe and the like in the high-nitrogen bearing steel to be desolventized preferentially, and the corrosion effect of the chloride ions on metals is obvious; the use of anionic surfactants can slow the corrosion rate, making the corrosion effect easy to control; the use amount of nitric acid in the rough etching corrosive liquid is inversely related to the mass percent of vanadium in the corroded sample, so that the first corrosion (namely, rough etching) can be better controlled; when the finely cut corrosive liquid is adopted for the second corrosion, the corrosion time is determined according to the area ratio of carbide in the rough carving sample, and the corrosion effect can be well controlled. The step-by-step corrosion method provided by the invention is applicable to both the edge part (fine grain area) and the central part (equiaxed grain area) of the cast ingot. The invention solves the problem that the corrosion effect of other corrosive agents on cast ingots in different areas of vanadium-containing high-nitrogen bearing steel is difficult to control, and has the advantages of simple ratio of the corrosive agents, good corrosion effect and high efficiency.
Further, during the second corrosion, the rough engraving sample keeps rotating, so that bubbles can be prevented from being gathered on the surface of the sample, and the corrosion uniformity is prevented from being influenced.
Drawings
FIG. 1 is an as-cast structure chart showing the rough engraving of example 1;
FIG. 2 is a metallographic photograph of an as-cast structure shown after the finish of example 1;
FIG. 3 is an as-cast tissue scanning electron micrograph taken after being polished in example 1;
FIG. 4 is an as-cast structure chart showing the rough engraving of example 2;
FIG. 5 is a metallographic photograph of an as-cast structure shown after the finish of example 2;
FIG. 6 is an as-cast tissue scanning electron micrograph taken after being polished in example 2;
FIG. 7 is a scanning electron micrograph of the as-cast structure of the corrosion coupon of comparative example 1.
Detailed Description
The invention provides a step-by-step corrosion method of a vanadium-containing bearing steel cast structure, which comprises the following steps:
carrying out first corrosion on the vanadium-containing bearing steel ingot casting sample by using the rough etching corrosive liquid to obtain a rough etching sample; the time of the first corrosion is 2.5-3.5 s; the rough etching corrosive liquid comprises first nitric acid, first water, first ferric chloride, first hydrochloric acid and an anionic surfactant; the mass ratio of the first hydrochloric acid to the first water to the first ferric chloride to the anionic surfactant is (14-18) mL: (48-52) mL: (4.3-5.2) g: (0.8-1.3) g;
the volume of the first nitric acid is calculated according to formula 1:
formula 1;
in the formula 1, V is the volume of the first nitric acid and mL; m is the mass percentage of vanadium in the vanadium-containing bearing steel ingot casting sample;
counting the area ratio of carbide in the rough engraving sample by using an optical microscope;
performing second corrosion on the rough carving sample by using the fine carving corrosive liquid;
the etching solution comprises second hydrochloric acid, second nitric acid, second water, acetic acid and second ferric chloride; the mass ratio of the volume of the second hydrochloric acid to the volume of the second nitric acid to the volume of the second water to the volume of the acetic acid to the second ferric chloride is (7-10) mL: (2-3) mL: (48-52) mL: (3-4) mL: (2.1-2.5) g;
the mass concentration of the first nitric acid and the second nitric acid is 65-68% independently; the mass concentration of the first hydrochloric acid and the second hydrochloric acid is 70-75% independently; the mass concentration of the acetic acid is 28-33%;
when the area ratio of the carbide is less than 6%, the second corrosion time is 4.5-5.5 s;
when the area ratio of the carbide is 6-10%, the second corrosion time is 4.9-5.9 s;
and when the area ratio of the carbide is more than 10%, the second corrosion time is 5.5-6.5 s.
In the present invention, the raw materials used are commercially available products well known in the art, unless specifically described otherwise.
The method comprises the step of carrying out first corrosion on a vanadium-containing bearing steel ingot casting sample by using a rough engraving corrosive liquid to obtain a rough engraving sample.
In the present invention, the vanadium-containing bearing steel ingot sample preferably comprises, in mass percent: 0.32+/-0.03% of C, 0.30+/-0.15% of N, 0.50+/-0.03% of Si, 0.40+/-0.03% of Mn, 15.3+/-0.3% of Cr, 1.00+/-0.03% of Mo, more than 0 and less than or equal to 1.00% of V, and the balance of Fe.
The invention preferably further comprises pre-treating the vanadium-containing bearing steel ingot sample prior to the first corrosion, the pre-treating preferably comprising: and sequentially carrying out sand paper grinding, polishing and surface cleaning on the vanadium-containing bearing steel ingot casting sample. In the present invention, the sandpaper grinding is preferably: firstly, adopting 200# abrasive paper to grind and remove oxide skin, and then adopting 400# abrasive paper, 800# abrasive paper, 1200# abrasive paper, 1500# abrasive paper and 2000# abrasive paper to grind; the polishing is preferably performed by sequentially polishing with polishing pastes with the granularity of 3.5 mu m, 2.5 mu m and 1.5 mu m; the surface cleaning preferably comprises: and washing the surface of the polished sample by deionized water and absolute ethyl alcohol in sequence, and putting the sample into a drying box to ensure the surface to be smooth and free of water stains.
In the invention, the rough etching corrosive liquid comprises first nitric acid, first water, first ferric chloride, first hydrochloric acid and an anionic surfactant; the mass concentration of the first nitric acid is preferably 65-68%, more preferably 66-67%; the first water is preferably deionized water; the mass concentration of the first hydrochloric acid is preferably 70 to 75%, more preferably 71 to 74%, and even more preferably 72 to 73%. In the present invention, the anionic surfactant preferably includes sodium dodecyl sulfate. In the invention, in the rough engraving corrosive liquid, the first nitric acid mainly plays a role of displaying carbide details to the greatest extent; the first hydrochloric acid mainly dissolves the oxide layer on the metal surface, so that dissolution and corrosion rate are accelerated; the first ferric chloride is capable of forming complexes with the iron on the metal surface, which complexes can accelerate dissolution of the metal surface, thereby scavenging oxides and other impurities from the metallographic specimen. The components are matched to obtain a clearer and more accurate tissue structure during metallographic analysis.
In the invention, the mass ratio of the first hydrochloric acid to the first water to the first ferric chloride to the anionic surfactant is (14-18) mL: (48-52) mL: (4.3-5.2) g: (0.8-1.3) g, preferably (15-17) mL: (49-51) mL: (4.5-5.0) g: (0.9 to 1.2) g. In the present invention, the volume of the first nitric acid is calculated according to formula 1:
formula 1;
in the formula 1, V is the volume of the first nitric acid and mL; m is the mass percentage of vanadium in the vanadium-containing bearing steel ingot casting sample. According to the method, the dosage of the first nitric acid is determined according to the mass percentage of vanadium in the vanadium-containing bearing steel ingot sample, so that the corrosion effect is easy to control.
The invention has no special requirement on the preparation process of the coarse engraving corrosive liquid, and the components are directly and uniformly mixed. In the embodiment of the invention, the components are mixed, stirred continuously for 2min, the stirring speed is 60-70 r/min, and then the mixture is kept stand for 4-5 min.
In the present invention, the first etching preferably includes etching or pouring; the etching is carried out by completely immersing the surface to be detected in corrosive liquid; and the etching is to directly pour the corrosive liquid to the surface to be tested.
In the present invention, the time of the first etching is preferably 2.5 to 3.5s, more preferably 2.7 to 3.3s, and still more preferably 2.9 to 3.1s.
The rough engraving corrosive liquid takes nitric acid, hydrochloric acid and ferric chloride as main components, wherein chloride ions in the ferric chloride and the hydrochloric acid can lead elements such as Cr, fe and the like in the high-nitrogen bearing steel to be desolventized preferentially, and the corrosion effect of the chloride ions on metals is obvious; the use of anionic surfactants can slow the corrosion rate, making the corrosion effect easy to control; the use amount of nitric acid in the rough etching corrosive liquid is inversely related to the mass percentage of vanadium in the corroded sample, so that the first corrosion can be better controlled. After being corroded by the rough etching corrosive liquid, the basic outlines of dendrites, ferrite and precipitated phases in the cast structure of the vanadium-containing high-nitrogen bearing steel can be shown.
After the first corrosion is completed, the method preferably washes the obtained corrosion sample with absolute ethyl alcohol immediately, and dries the corrosion sample to obtain a rough engraving sample.
After the rough engraving sample is obtained, the invention utilizes an optical microscope to count the area ratio of carbide in the rough engraving sample.
In the present invention, the number of fields of view used for the statistics is preferably not less than 30, and the observation magnification is preferably not more than 200. Because carbide distribution is uneven, excessive observation times can possibly lead to the accidental phenomenon that carbide is not generated in the field of view or a large amount of carbide is gathered, the observation times are controlled to be not higher than 200, and the statistical result error is prevented from becoming larger due to the fact that the observation times are too high. The invention controls at least 30 visual fields and ensures high reliability of results.
After the area ratio of carbide in the rough engraving sample is obtained, the invention uses the fine etching liquid to carry out second etching on the rough engraving sample.
In the present invention, the etching solution includes a second hydrochloric acid, a second nitric acid, a second water, acetic acid, and a second ferric chloride; the mass concentration of the second hydrochloric acid is preferably 70-75%, more preferably 71-74%, and even more preferably 72-73%; the mass concentration of the second nitric acid is preferably 65-68%, more preferably 66-67%; the mass concentration of the acetic acid is 28-33%, preferably 29-31%; the second water is preferably deionized water. In the present invention, the primary function of the second hydrochloric acid is to show dendrite structure; the second nitric acid is mainly used for displaying ferrite conveniently; the acetic acid has the functions of regulating the pH value, enhancing the corrosion effect and controlling the corrosion rate; the second ferric chloride acts so that the ferric chloride can form complexes with the iron on the metal surface, and the complexes can accelerate the dissolution of the metal surface, so that oxides and other impurities on the metallographic sample can be removed. The coordination effect of the components can obtain clearer and more accurate tissue structure during metallographic analysis.
In the invention, the mass ratio of the volume of the second hydrochloric acid, the volume of the second nitric acid, the volume of the second water, the volume of the acetic acid and the second ferric chloride is (7-10) mL: (2-3) mL: (48-52) mL: (3-4) mL: (2.1-2.5) g, preferably (8-9) mL: (2.3-2.8) mL: (49-51) mL: (3.2-3.8) mL: (2.2-2.4) g.
The invention has no special requirement on the preparation process of the fine etching liquid, and the components are directly and uniformly mixed. In the embodiment of the invention, the components are mixed, stirred continuously for 2min, the stirring speed is 60-70 r/min, and then the mixture is kept stand for 4-5 min.
In the present invention, the second etching preferably includes etching or pouring.
In the invention, the second corrosion time is determined according to the area ratio of carbide in the rough engraving sample, specifically, when the area ratio of carbide is less than 6%, the second corrosion time is 4.5-5.5 s, preferably 4.7-5.3 s, more preferably 5s; when the area ratio of the carbide is 6-10%, the second etching time is 4.9-5.9 s, preferably 5.1-5.7 s, and more preferably 5.4s; when the area ratio of the carbide is more than 10%, the second etching time is 5.5-6.5 s, more preferably 5.8-6.2 s, and still more preferably 6s. The second corrosion time is determined according to the area ratio of carbide in the rough engraving sample, so that the corrosion effect can be well controlled.
In the present invention, the rough engraving sample is preferably kept rotating at the time of the second etching; the rotation speed is preferably 50-80 r/min. According to the invention, the rough engraving sample is kept rotating during the second corrosion, so that bubbles can be prevented from being gathered on the surface of the sample, and the corrosion uniformity is prevented from being influenced.
According to the invention, the finely etched corrosive liquid is adopted to corrode the rough engraving sample, so that the morphology, the size, the distribution and the number of dendrites, ferrite and precipitated phases in an as-cast structure of the vanadium-containing high-nitrogen bearing steel can be clearly and completely displayed.
After completion of the second etching, the present invention preferably washes the resulting etched sample immediately with absolute ethanol and dries.
The invention adopts step-by-step corrosion, so that the corrosion quality is high, the effect is easy to control, and the method can be used for observation and research of as-cast structure and measurement and evaluation of macrosegregation. The invention provides a step-by-step corrosion method which is applicable to vanadium-containing high-nitrogen bearing steel.
The following is a detailed description of the method of step-wise corrosion of the as-cast structure of vanadium-containing bearing steel provided by the present invention, but is not to be construed as limiting the scope of the invention.
Example 1
The vanadium-containing bearing steel casting ingot sample composition is as follows: 0.4% of N, 0.5% of Si, 0.4% of Mn, 15.5% of Cr, 1% of Mo, 0.3% of C, 0.2% of V and the balance of Fe, wherein the mass fraction of vanadium is 0.2%, namely the mass fraction is 0.2; the etching steps are as follows:
(1) And (3) grinding the oxide skin on the surface of the vanadium-containing bearing steel casting ingot sample by using 200# abrasive paper, and grinding by using 400# abrasive paper, 800# abrasive paper, 1200# abrasive paper, 1500# abrasive paper and 2000# abrasive paper in sequence.
(2) Polishing was performed with 3.5 μm, 2.5 μm, and 1.5 μm polishing pastes in this order.
(3) After polishing, the sample is washed clean by deionized water, finally sprayed with absolute ethyl alcohol for washing, and put into a drying box for drying (the temperature is 70 ℃ and the drying time is 1 min) to ensure that the surface of the sample is smooth and free from water stains.
(4) Preparing a rough etching corrosive liquid: 6.6mL of nitric acid (with the mass concentration of 65%), 14.3mL of hydrochloric acid (with the mass concentration of 72%), 50mL of deionized water, 4.8g of ferric chloride and 0.8g of sodium dodecyl sulfate are mixed, the stirring speed is 60-70 r/min, the stirring lasts for 2min, and then the mixture is kept stand for 5min.
(5) Rough engraving: and (3) immersing the sample in a rough engraving corrosive liquid for 3.2s, immediately flushing the surface with absolute ethyl alcohol after the sample is finished, and drying to obtain a rough engraving sample.
(6) Carbide statistics; and taking an as-cast structure picture of the rough engraving sample by using an optical microscope, obtaining an as-cast structure picture as shown in figure 1, and then carrying out carbide duty ratio statistics to obtain the area of the carbide as 11.049%.
(7) Preparing a fine etching solution: 2.5mL of nitric acid (with the mass concentration of 65%), 7.5mL of hydrochloric acid (with the mass concentration of 72%), 50mL of deionized water, 3.5mL of acetic acid solution (with the mass concentration of 30%) and 2.2g of ferric chloride are mixed, the stirring speed is 60-70 r/min, the stirring lasts for 2min, and then the mixture is kept stand for 5min.
(8) Finely cut: the sample is soaked in the refined etching liquid and slowly moves clockwise at a constant speed, the rotating speed is 80r/min, the etching time is 6s, and the surface is immediately washed by absolute ethyl alcohol and dried after the etching is finished.
And (3) observing the surface of the sample corroded in the step (8) by using a metallographic microscope OLympus DSX510, and obtaining an as-cast structure chart shown in figure 2. And (3) observing the surface of the sample after the corrosion in the step (8) by using a scanning electron microscope Hitachi SU8000, and obtaining an as-cast structure chart shown in figure 3. Fig. 2 and 3 clearly show the as-cast structure of the vanadium-containing high nitrogen bearing steel, and as can be seen from fig. 2 and 3, the as-cast structure of the vanadium-containing bearing steel of this embodiment is dendrite, ferrite and precipitated phase in the as-cast structure.
Example 2
The composition of the vanadium-containing bearing steel cast ingot sample is as follows: 0.4% of N, 0.5% of Si, 0.4% of Mn, 15.6% of Cr, 1% of Mo, 0.3% of C, 0.4% of V and the balance of Fe; wherein the mass fraction of vanadium is 0.4%, namely, the mass percentage is 0.4; the etching steps are as follows:
(1) And (3) grinding the surface oxide skin of the vanadium-containing bearing steel casting ingot sample by using 200# abrasive paper, and grinding by using 400# abrasive paper, 800# abrasive paper, 1200# abrasive paper, 1500# abrasive paper and 2000# abrasive paper in sequence.
(2) Polishing was performed with 3.5 μm, 2.5 μm, and 1.5 μm polishing pastes in this order.
(3) After polishing, the sample is washed clean by deionized water, finally sprayed with absolute ethyl alcohol for washing, and put into a drying box for drying (the temperature is 70 ℃ and the drying time is 1 min) to ensure that the surface of the sample is smooth and free from water stains.
(4) Preparing a rough etching corrosive liquid: 6.1mL of nitric acid (with the mass concentration of 65%), 14.3mL of hydrochloric acid (with the mass concentration of 72%), 48mL of deionized water, 4.5g of ferric chloride and 1g of sodium dodecyl sulfate are mixed, the stirring speed is 60-70 r/min, the stirring lasts for 2min, and then the mixture is kept stand for 4.5min.
(5) Rough engraving: and (3) immersing the sample in a rough engraving corrosive liquid for 3s, immediately flushing the surface with absolute ethyl alcohol after the sample is completed, and drying to obtain a rough engraving sample.
(6) Carbide statistics; and taking an as-cast structure picture of the rough engraving sample by using an optical microscope, obtaining an as-cast structure picture as shown in fig. 4, and then carrying out carbide duty ratio statistics to obtain the area of the carbide of the sample as 7.931%.
(7) Preparing a fine etching solution: 3mL of nitric acid (with the mass concentration of 65%), 8mL of hydrochloric acid (with the mass concentration of 72%), 49mL of deionized water, 2.3g of ferric chloride and 3.4mL of acetic acid solution (with the mass concentration of 30%) are mixed, the stirring speed is 60-70 r/min, the duration is 2min, and the subsequent standing time is 4.5min.
(8) Finely cut: the sample is soaked in the refined etching liquid and slowly moves anticlockwise at a constant speed, the rotating speed is 80r/min, the etching time is 5.5s, and the surface is immediately washed by absolute ethyl alcohol and dried after the etching is finished.
And (3) observing the surface of the sample after the corrosion in the step (8) by using a metallographic microscope OLympus DSX510, and obtaining an as-cast structure chart as shown in figure 5. And (3) observing the surface of the sample after the corrosion in the step (8) by using a scanning electron microscope Hitachi SU8000, and obtaining an as-cast structure chart as shown in figure 6. Fig. 5 and 6 clearly show the as-cast structure of the vanadium-containing high nitrogen bearing steel, and as can be seen from fig. 5 and 6, the as-cast structure of the vanadium-containing bearing steel of this embodiment is dendrite, ferrite and precipitated phase in the as-cast structure.
Comparative example 1
The samples used were those used in example 2, the mixture ratio of the rough etching solution was also that in example 2, and the difference from example 2 was that the fine etching process was omitted, namely steps (6) to (8) were omitted, and the rough etching solution was used only for one-time etching for 9.2s, and as a result, the etching effect was poor and uneven, as shown in fig. 7.
According to the embodiment, the invention provides a step-by-step corrosion method for the cast structure of the vanadium-containing bearing steel, which can clearly display the cast structure of the vanadium-containing high-nitrogen bearing steel and solve the problems that the vanadium-containing bearing steel is not easy to corrode and the corrosion effect is not easy to control.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A step-by-step corrosion method for a cast structure of vanadium-containing bearing steel comprises the following steps:
carrying out first corrosion on the vanadium-containing bearing steel ingot casting sample by using the rough etching corrosive liquid to obtain a rough etching sample; the time of the first corrosion is 2.5-3.5 s; the rough etching corrosive liquid comprises first nitric acid, first water, first ferric chloride, first hydrochloric acid and an anionic surfactant; the mass ratio of the first hydrochloric acid to the first water to the first ferric chloride to the anionic surfactant is (14-18) mL: (48-52) mL: (4.3-5.2) g: (0.8-1.3) g;
the volume of the first nitric acid is calculated according to formula 1:
formula 1;
in the formula 1, V is the volume of the first nitric acid and mL; m is the mass percentage of vanadium in the vanadium-containing bearing steel ingot casting sample;
counting the area ratio of carbide in the rough engraving sample by using an optical microscope;
performing second corrosion on the rough carving sample by using the fine carving corrosive liquid;
the etching solution comprises second hydrochloric acid, second nitric acid, second water, acetic acid and second ferric chloride; the mass ratio of the volume of the second hydrochloric acid to the volume of the second nitric acid to the volume of the second water to the volume of the acetic acid to the second ferric chloride is (7-10) mL: (2-3) mL: (48-52) mL: (3-4) mL: (2.1-2.5) g;
the mass concentration of the first nitric acid and the second nitric acid is 65-68% independently; the mass concentration of the first hydrochloric acid and the second hydrochloric acid is 70-75% independently; the mass concentration of the acetic acid is 28-33%;
when the area ratio of the carbide is less than 6%, the second corrosion time is 4.5-5.5 s;
when the area ratio of the carbide is 6-10%, the second corrosion time is 4.9-5.9 s;
and when the area ratio of the carbide is more than 10%, the second corrosion time is 5.5-6.5 s.
2. The step-and-etch method of claim 1, wherein the vanadium-containing bearing steel ingot sample comprises, in mass percent: 0.32+/-0.03% of C, 0.30+/-0.15% of N, 0.50+/-0.03% of Si, 0.40+/-0.03% of Mn, 15.3+/-0.3% of Cr, 1.00+/-0.03% of Mo, more than 0 and less than or equal to 1.00% of V, and the balance of Fe.
3. The step-wise corrosion method according to claim 1, wherein the anionic surfactant comprises sodium dodecyl sulfate.
4. The step-etch method of claim 1, wherein the first etch and the second etch independently comprise an etch or a pour.
5. The step-and-etch method of claim 1, wherein the rough etched sample remains rotated during the second etch.
6. The step-wise etching method according to claim 5, wherein the rotation speed is 50 to 80r/min.
7. The step-and-etch method of claim 1 or 2, further comprising pre-treating the vanadium-bearing steel ingot sample prior to the first etch, the pre-treating comprising: and sequentially carrying out sand paper grinding, polishing and surface cleaning on the vanadium-containing bearing steel ingot casting sample.
8. The step-by-step etching method according to claim 1, wherein the area ratio of carbide in the rough engraving sample is counted by using an optical microscope to be not less than 30 visual fields, and the observation magnification is not higher than 200.
9. The step-etching method according to claim 1 or 4, wherein after the completion of the first etching, further comprising washing the resulting etched sample with absolute ethanol immediately, and drying.
10. The step-etching method according to claim 1 or 4, wherein after completion of the second etching, further comprising washing the resulting etched sample with absolute ethanol immediately, and drying.
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