CN110441201B - Method for detecting austenite grain size of steel by oxidation method - Google Patents
Method for detecting austenite grain size of steel by oxidation method Download PDFInfo
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- 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
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- G—PHYSICS
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- 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
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- 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
- G01N2001/2866—Grinding or homogeneising
Abstract
The invention discloses a method for detecting austenite grain size of steel by an oxidation method, which comprises the following steps: taking a sample, polishing a detection surface and carrying out heat treatment; vertically cutting the heat-treated sample along the detection surface to prepare two heat-treated samples; taking a heat treatment sample, grinding and polishing a section of the heat treatment sample, and then eroding the section by nitric acid and alcohol with the volume percentage of 4%; observing the oxide layer structure of the section of the heat treatment sample, wherein the oxide layer structure is a full martensite structure and is a qualified sample, and otherwise, the oxide layer structure is a non-qualified sample; when the test sample is qualified, grinding and polishing the detection surface of another heat treatment test sample to obtain austenite grains of an oxide layer, and corroding the test sample by using a hydrochloric acid alcohol solution with the volume percentage of 15% to observe the austenite grains of the test sample; when the sample is a non-qualified sample, the sample is taken again, the detection surface is polished, then a layer of carbon powder particles for carburizing is covered on the detection surface, and then heat treatment is carried out; the heat treated samples were tested as described above. The method has simple process and accurate detection.
Description
Technical Field
The invention relates to a method for detecting austenite grain size of steel, in particular to a method for detecting austenite grain size of steel by an oxidation method.
Background
The direct hardening method has the best detection effect of the austenite grain size of the steel and the simplest and simplest operation, and is the most accurate austenite grain size detection method recognized at home and abroad. The direct hardening method uses supersaturated picric acid solution to erode and display austenite grain size, but picric acid belongs to one type of explosive, and the picric acid cannot be purchased along with the more and more strict national control on toxic explosive products; this results in a limitation in the use of the method in which the hardening method shows austenite grain size. The detection of the austenite grain size of the steel material urgently needs other methods.
The oxidation method specified in GB/T6394-2017 "method for measuring average grain size of metals" is also a widely used method for detecting austenite grains of steel materials, and may become a trend of future methods for detecting austenite grain size. However, the oxidation method for detecting the austenite grain size has many problems in practical use, the data obtained by different laboratories have large difference, the detection result is inaccurate, and misjudgment is easily caused to material acceptance.
The prior operation steps for detecting the austenite grain size according to an oxidation method comprise:
i, a sample heating system: the oxidation method is suitable for carbon steel and alloy steel with carbon content of 0.25-0.60%. The test surface of the sample is polished (preferably with an abrasive of about 400 grit or 15 μm) and the polished surface of the sample is placed in the oven facing upward. Unless otherwise specified, the carbon content (mass fraction) is not more than 0.35%, and the sample is heated at 890 ℃. + -. 10 ℃; the carbon content (mass fraction) is more than 0.35 percent, the sample is heated at 860 +/-10 ℃, the temperature is kept for 1h, and the sample is quenched in cold water or brine.
II, sample preparation: the sample processed according to the heating system is inclined at an angle of 10-15 degrees according to the oxidation condition, lightly ground and polished to remove the iron scale on the polished surface, and ground and polished to ensure that the prior austenite grain boundary is completely displayed as much as possible due to the existence of the oxide.
III, selecting an aggressive agent: the display method of the prior austenite grain size and the erosion agent aim to clearly display the prior austenite grain size according to the specific situation of a sample; for the purpose of clarity, the etching can be performed with a 15% ethanol hydrochloride solution, and in practice, 4% nital is often used for clarity.
The current operating procedures have the following problems:
i, a sample heating system: since the standard only specifies the heating temperature and the holding time of the sample heat treatment, the influence of the heating speed on the size of the austenite grains is ignored. The faster the heating speed, the higher the superheat degree, the higher the actual forming temperature of austenite, the higher the nucleation rate and the growth speed, the increased phase-change driving force, the reduced activation energy required for growth, the reduced bonding force between interstitial atoms in the crystal lattice and surrounding atoms, and the easier the atoms are moved. Therefore, the initial austenite grain size can be obtained by rapid heating and short-time heat preservation; the rapid heating and the long-time heat preservation have larger tendency of growing austenite grains. There are differences in austenite grain size obtained with different heating rates.
II, sample preparation: the principle of the oxidation method is that the surface of a sample is oxidized when being heated and insulated at high temperature; because the oxidation resistance of the grain boundary is poorer than that of the grain boundary, the austenite grain boundary is preferentially oxidized to form an oxide network at high temperature; along with the prolonging of the heating and heat preservation time, fine austenite grains grow gradually, and an oxide layer on the surface of the sample is thickened continuously to reflect that an oxide network of the austenite grains forms iron scales at the previous moment; the oxide network reflecting the austenite grains at the present moment is a brand new grain boundary which is equivalent to the size of the grown austenite grains in the sample.
The oxidation method has the problems that various steels have different high-temperature oxidation resistance and poorer high-temperature oxidation resistance, the thickening speed of an oxidation layer is basically synchronous with the growth speed of austenite grains, and the size of the austenite grains displayed by the oxidation method is equivalent to that of the grains displayed by a direct hardening method; in the steel with strong high-temperature oxidation resistance, the thickening speed of an oxidation layer lags behind the growth speed of austenite grains, and the austenite grains displayed by an oxidation method are smaller than those displayed by a direct hardening method.
Simultaneously in sample heating heat preservation process, the surface carbon content also constantly reduces when the surface is oxidized, and sample surface texture can form three kinds of states: in the first state, the carbon content of the surface of a test sample is slightly reduced and kept in a single-phase austenite region of an iron-carbon ternary phase diagram in the heat preservation process of the test sample at a specified temperature, and after the test sample is quickly cooled after heat preservation for a certain time, the surface oxidation layer structure is a martensite structure with reduced carbon content and an oxide network along crystals; in the second state, the carbon content of the surface of the sample is reduced to a two-phase region of an iron-carbon ternary phase diagram in the heat preservation process of the sample at a specified temperature, partial ferrite can be separated out in the high-temperature heat preservation stage of the sample, and after the sample is quickly cooled after heat preservation for a certain time, the surface oxidation layer structure is a martensite structure with the reduced carbon content, an oxide network along crystals and a ferrite structure; in the third state, when the carbon content on the surface of the sample is reduced to a single-phase ferrite region of an iron-carbon ternary phase diagram in the heat preservation process of the sample at the specified temperature, ferrite is completely precipitated in the high-temperature heat preservation stage of the sample, and after the sample is quickly cooled after heat preservation for a certain time, the surface oxidation layer structure is a full ferrite structure. The three states of the structure exhibited the first grain boundary as an austenite grain boundary with a reduced carbon content, the second grain boundary as a mixed grain boundary of ferrite and austenite grain with a reduced carbon content, and the third grain boundary as a full ferrite grain boundary.
The oxidation method cannot detect the decarburized steel at present, and a method is needed to be found, so that the surface of the metallographic sample treated by the oxidation method is fully oxidized, and the carbon content of the surface of the metallographic sample in a high-temperature heat preservation stage is not reduced to a two-phase region or a ferrite single-phase region. The grain size obtained by the oxidation method is guaranteed to be austenite grain size instead of ferrite or full ferrite grain, so that the material is judged wrongly.
III, selecting an aggressive agent: the selection of the etching agent has problems in practical use, grain boundaries cannot be displayed sometimes due to the etching by using a 15% hydrochloric acid alcohol solution, and the grain boundaries can be displayed by using 4% nitric acid alcohol in some laboratories; however, the oxidation process should be able to observe the grain boundaries of the oxide network without erosion, which is more clear after erosion with 15% alcohol nicotinate, and if 4% alcohol nitrate is used, which shows mixed ferrite and austenite grains or fully ferrite grains, a wrong conclusion can be drawn.
Disclosure of Invention
The invention aims to provide a method for detecting the austenite grain size of steel by an oxidation method with good accuracy.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: (1) taking a sample, polishing the detection surface of the sample, and then carrying out heat treatment;
(2) vertically cutting the heat-treated sample along the detection surface to prepare two heat-treated samples;
(3) taking a heat treatment sample, grinding and polishing the section of the heat treatment sample, and then eroding the heat treatment sample by using 4% nitric acid alcohol; observing the oxide layer structure of the section of the heat treatment sample, wherein the oxide layer structure is a full martensite structure and is a qualified sample, and otherwise, the oxide layer structure is a non-qualified sample;
(4) when the test sample is qualified, grinding and polishing the detection surface of another heat treatment test sample to obtain austenite grains showing an oxide layer, and corroding the austenite grains by using 15% hydrochloric acid alcohol solution to observe the austenite grains of the test sample;
(5) when the sample is a non-qualified sample, the sample is taken again, the detection surface is polished, then a layer of carbon powder particles for carburizing is covered on the detection surface, and then heat treatment is carried out;
(6) the heat-treated samples were examined according to steps (2), (3), (4) and (5).
In the heat treatment process of the steps (1) and (5), the sample is heated along with the furnace to raise the temperature.
The method is suitable for carbon steel and alloy steel with the carbon content of 0.25-0.60%.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: according to the method, a section of a vertical detection surface is detected for each metallographic sample treated by an oxidation method, whether the sample treated at this time obtains a real austenite crystal boundary is firstly judged, and if the sample treated at this time is the austenite crystal boundary, the oxidation surface normally detects the grade of austenite crystal grains; if not pure austenite grain boundaries, must be discarded, avoiding the formation of false results at the source.
The surface decarburization phenomenon of the sample treated by the oxidation method inevitably occurs, so that ferrite is precipitated from many samples in the high-temperature heat preservation stage, and a pure austenite crystal boundary cannot be obtained, namely, the easy decarburization material cannot be used for detecting the austenite grain size by the oxidation method. According to the invention, the polished surface of the sample easy to decarbonize is covered with carbon powder particles for carburization, so that the surface of the sample is oxidized, the decarburization tendency is greatly reduced, partial or all ferrite is not precipitated in a high-temperature heat preservation stage, the accurate austenite crystal boundary obtained by using an oxidation method for the material easy to decarbonize is realized, and the operation is convenient and feasible.
Because the size of the austenite grain heat treatment sample is smaller, if the sample enters a furnace after reaching the temperature, the sample is quickly sintered to reach the austenitizing temperature, and the heating speed is far higher than 100 ℃/Min; the sample is heated along with the furnace, so that the abnormal growth of the material in the subsequent heat preservation process due to the abnormally high heating speed can be avoided, and the austenite grain size obtained by heat treatment is the most accurate austenite grain representing the material.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a graph of austenite grains shown by heating to warm temperature;
FIG. 2 is a graph of austenite grains shown as furnace heat;
FIG. 3 is a metallographic structure diagram of an oxidation method section oxide layer;
FIG. 4 is a graph showing austenite grains by an oxidation method;
FIG. 5 is a graph showing austenite grains by direct quench hardening;
FIG. 6 is a sectional oxide layer structure of the oxidation method;
FIG. 7 is a graph of uneroded structure of the test surface of the oxidation method;
FIG. 8 is a 15% hydrochloric acid alcohol attack detection surface austenite grain diagram;
FIG. 9 is a diagram of martensite structure of 4% nitric acid alcohol attack detection surface.
Detailed Description
The method for detecting the austenite grain size of the steel by the oxidation method adopts the following process steps:
(1) sampling: according to the regulation of an oxidation method in GB/T6394-2017 'Metal average grain size determination method', the method is suitable for carbon steel and alloy steel with the carbon content of 0.25-0.60% (mass fraction). Samples were taken from the above carbon or alloy steels.
(2) And (3) heat treatment: the test surface of the sample was polished using an abrasive of 400 grit or 15 μm. Placing the sample in a heating furnace with the detection surface facing upwards, heating the sample along with the furnace to a temperature required by a standard, and placing the sample in the furnace at the furnace temperature of less than or equal to 600 ℃; unless otherwise specified, the carbon content (mass fraction) is not more than 0.35%, and the sample is heated at 890 ℃. + -. 10 ℃; the carbon content (mass fraction) is more than 0.35 percent, and the sample is heated at 860 +/-10 ℃; keeping the temperature for 1h after the temperature is reached, and quenching in cold water or saline water.
(3) Preparing a sample: the heat-treated samples were cut vertically along the middle of the test surface to produce two heat-treated samples.
(4) A heat treatment sample is taken to grind a section vertical to the detection surface, 4% (volume content) nitric acid alcohol is used for erosion after polishing, and the oxide layer tissue at the section position is observed. If the section oxidation layer structure is an all-martensite structure, the test sample is qualified; the section oxidation layer structure is ferrite + martensite or full ferrite structure, and is a non-qualified sample, and the sample is used as a waste and cannot be used for detecting the austenite grain size by an oxidation method.
The grinding and polishing of the cut surface are due to the following:
firstly, only a thin oxide layer is detected on a surface, and an oxide network for displaying austenite grain boundaries is needed to be ground and corroded and cannot be damaged in advance; and the oxidation layer structure can be compared with the internal structure by observing the section structure, and whether ferrite exists in the oxidation layer structure or not can be judged better.
Secondly, after the detection surface is polished according to the specification, 15 percent (volume content) hydrochloric acid alcohol is used for corrosion, if an oxide layer is an oxide network of an austenite crystal boundary, no problem is shown; if the oxide layer is a part of ferrite and austenite crystal boundaries, the crystal boundaries can be displayed after the etching by using 15% hydrochloric acid alcohol, only the ferrite part can not be displayed, but an experimenter can not distinguish that the crystal boundaries can not be displayed due to the existence of ferrite or a part of the area caused by poor etching effect can not be displayed, even if the subsequent etching by using 4% nitric acid alcohol is used, an incorrect conclusion can be obtained and the experimenter cannot know the result. If the oxidized layer forms a full ferrite structure, the grain boundary cannot be observed by using 15% hydrochloric acid alcohol for corrosion, and an experimenter cannot accurately judge whether the corrosion effect is poor or a decarburized layer exists, so when the conventional high-purity decarburized material is used for detecting the austenite grain size by an oxidation method, because the grain boundary cannot be displayed by using 15% hydrochloric acid alcohol for corrosion, 4% nitric acid alcohol for corrosion is used instead, the grain is found to be very clear, and the grain is regarded as the austenite grain, and an error result is also formed (most laboratories operate like the same).
If the detection surface is ground and polished according to the specification, 4% nitric acid alcohol is directly used for erosion, because the detection surface generates oxidation and decarburization phenomena in the heat treatment process, the surface structure of the detection surface is low-carbon martensite with large decarburization degree or low-carbon martensite with a small amount of ferrite, the color of the eroded detection surface after grinding and polishing is observed by a metallographic microscope is light, and whether the ferrite structure exists is not easy to distinguish. If a section perpendicular to the polishing surface is used for grinding the erosion, the entire transition from the oxidized decarburized layer of the surface to the matrix structure is observed, and the difference in the structure of the oxidized layer is clearly observed due to the reference with the matrix structure.
From the above, the purpose of grinding and polishing the section is to observe whether the oxide layer of the detection surface has a ferrite structure, so as to judge whether the grain boundary of the oxide layer of the detection surface is an oxide network along the austenite grain boundary or a non-austenite grain boundary doped with ferrite; because the detection surface oxidation layer is a very thin layer, when the tangent plane is ground, one side of the edge of the detection surface is required to be ensured not to generate chamfering and rounding, so that the phenomenon that the oxidation layer tissue of the detection surface cannot be observed at the edge of the ground and polished tangent plane is avoided.
(5) When the step (4) is qualified sample: taking another heat treatment sample; and (3) lightly grinding the detection surface by using fine sand paper until a small amount of iron scale remains, and tilting the test sample by 10-15 degrees according to the oxidation condition to grind and polish, so that austenite grains of the oxide layer are completely displayed as far as possible. Then, the austenite grains of the sample were observed by etching with a 15% hydrochloric acid alcohol solution.
(6) When the step (4) is a non-qualified sample: taking one sample again to polish the detection surface of the sample, and using an abrasive with the granularity of 400 or 15 mu m; covering a layer of carbon powder particles for carburizing on the detection surface of the polished sample; carrying out heat treatment according to the process in the step (2), and preparing two heat treatment samples according to the step (3); taking a heat treatment sample for erosion according to the step (4); if the sample is qualified, carrying out austenite grain size detection in the step (5); if the sample is a non-qualified sample, the sample is re-sampled according to the step.
And (3) process design test: cutting out a sample, carrying out heat treatment on the sample, preparing the sample, corroding and grading the austenite grain size to execute GB/T6394-2017, and comparing each case by using a direct hardening method in order to verify the accuracy of the austenite grain size obtained by an oxidation method because the direct hardening method is internationally accepted as the most accurate austenite grain size detection method.
(1) Influence of heating rate on austenite grain size:
taking a section of 55Cr3 material, and cutting 2 metallographic samples according to GB/T6394-2017. When the temperature of a sample in the high-temperature furnace reaches 860 ℃, the sample is put into the furnace, the temperature is kept for 1 hour, water cooling is carried out, the oxide layer of the sample is removed, the sample is ground and polished, the supersaturated picric acid is corroded, and the austenite grain size is 5.5 grades, which is shown in figure 1. And the other sample is put into the furnace at room temperature, the temperature is increased to 860 ℃ along with the furnace, the temperature is kept for 1 hour, the water cooling is carried out, the oxide layer of the sample is removed, the sample is ground and polished, the supersaturated picric acid is corroded, and the austenite grain size is 7.0 grade, which is shown in figure 2.
As can be seen from the graphs 1 and 2, the heating speed has influence on the austenite grain size, the metallographic sample is small in the actual operation of austenite grain size detection, the sample is heated to the heating temperature quickly for a short time when entering the furnace at the temperature, and the obtained grain size cannot represent the real austenite grain size of the material in later use, so that the heat treatment of the sample is required to be carried out along with the furnace.
(2) Influence of decarburization and erosion agent on austenite grain size detection by an oxidation method:
A. taking a section of 60Si2Mn material, and cutting 2 metallographic samples according to GB/T6394-2017. Detecting one sample by an oxidation method: polishing the detection surface of the sample → placing the detection surface of the sample upwards into a furnace and heating to 860 ℃ along with the furnace → preserving heat for 1 hour → discharging from the furnace and cooling by water → cutting along the detection surface → grinding and polishing the cut surface of a half sample → polishing and detecting the surface of the other half sample, and slightly grinding and polishing by fine sand paper with the inclination of 10-15 degrees till a small amount of iron scale is left → 15 percent of hydrochloric acid alcohol solution is corroded.
And another sample is detected by a hardening method: putting the sample into a furnace, heating the sample to 860 ℃ along with the furnace for 1 hour → preserving the heat, discharging the sample from the furnace, cooling the sample by water → corroding with supersaturated picric acid.
The sample is detected by an oxidation method, and the oxidation layer structure of the detection surface of the sample is observed from a section to be full ferrite, which is shown in figure 3; after the other half of the test sample is polished, coarse grains can be directly observed without erosion, coarse grains can be observed by erosion of 15% hydrochloric acid alcohol solution, coarse grains can be observed by erosion of 4% nitric acid alcohol, and the grade of the grains is 3.0, as shown in fig. 4. The sample is detected by a hardening method, the austenite grain size is 8.0 grade, and the figure 5 shows.
The sample with ferrite in the oxide layer structure of the sample has large grain size difference with the austenite obtained by the hardening method, and the sample treated by the oxidation method is discarded without being used for detecting the austenite grain size so as to avoid misjudgment on the material.
B. And (3) taking a gold phase sample again, polishing a detection surface, covering the detection surface with carbon powder particles for carburization, putting the sample in a furnace with the detection surface upward, heating the sample to 860 ℃ along with the furnace, keeping the temperature for 1 hour, taking out of the furnace, cooling by water, splitting from the center of the detection surface, grinding and polishing a half sample, grinding and polishing the other half sample to the detection surface, slightly grinding and polishing by fine sand paper inclined at 10-15 ℃ until a small amount of iron oxide scales are left, and corroding by 15% hydrochloric acid alcohol solution.
At this time, the sample is detected by an oxidation method, and the structure of an oxide layer on the detection surface of the sample is observed from a section and is a martensite structure, as shown in figure 6; after the other half of the test surface of the sample is polished, the invisible crystal grain network is not corroded, as shown in figure 7; clear austenite grain boundary networks can be seen after the 15% hydrochloric acid alcohol is corroded, and the graph is shown in FIG. 8; the austenite grain size rating is 8.0 according to GB/T6394-2017, and the microstructure is seen as martensite + intergranular oxide network by etching with 4% nitre alcohol, as shown in FIG. 9.
(3) Taking a section of 40 steel material, and cutting 2 metallographic samples according to GB/T6394-2017. Detecting one sample by an oxidation method: polishing the test sample surface → placing the test sample polishing surface upwards into a furnace, heating to 860 ℃ along with the furnace → preserving heat for 1 hour → discharging from the furnace and cooling by water → cutting along the test surface → grinding and polishing the cut surface of a half of the test sample → grinding and polishing the test surface of the other half of the test sample, and slightly grinding and polishing by using fine sand paper inclined at 10-15 degrees until a small amount of iron scale is left → 15% hydrochloric acid alcohol solution is corroded.
And another sample is detected by a hardening method: putting the sample into a furnace, heating the sample to 860 ℃ along with the furnace for 1 hour → preserving the heat, discharging the sample from the furnace, cooling the sample by water → corroding with supersaturated picric acid.
Detecting the sample by an oxidation method, and observing that the oxidation layer structure of the sample is a martensite structure with reduced carbon content and a black oxide network from a section; after the other half of the test sample is ground and polished, grains can not be observed by direct observation without erosion, the grain size of 15% hydrochloric acid alcohol can not be observed clearly when the 15% nitric acid alcohol solution erodes austenite grain size of 8.0 grade, and grains can not be shown clearly when the 4% nitric acid alcohol erodes. The sample is detected by a hardening method, and the austenite grain size is 8.0 grade.
The sample with no ferrite in the oxide layer structure is equivalent to the grain size shown by the hardening method in the grain size shown by the oxidation method, and the sample treated by the oxidation method can be used for austenite grain size detection.
Example 1: the method for detecting the austenite grain size of the steel by the oxidation method is specifically described as follows.
(1) Sampling from a steel material with SAE8620 as a steel grade, wherein the carbon content in the steel is less than or equal to 0.35 wt%; the test surface of the sample was polished with a 400 grit abrasive. Placing the sample in a furnace with the detection surface facing upwards at the furnace temperature of 600 ℃, heating the sample to 890 ℃ along with the furnace, preserving the heat for 1h, and finally quenching the sample in cold water.
(2) The heat-treated samples were cut vertically along the middle of the test surface to produce two heat-treated samples. And grinding a heat treatment sample into a section vertical to the detection surface, polishing, corroding by using 4% nitric acid alcohol, and observing that the oxidation layer structure of the section of the sample is a full martensite structure, so that the sample is qualified.
(3) And (3) lightly grinding the detection surface of the other heat-treated sample by using fine sand paper until a small amount of iron scale is remained, and properly inclining the sample by 10-15 degrees according to the oxidation condition for grinding and polishing. Then, the sample is corroded by 15% hydrochloric acid alcohol solution, and the austenite grain size of the sample can be observed to be 7.5-8.0 grade.
(4) The steel is sampled and detected by a hardening method, and the austenite grain size is detected to be 7.5 grade.
Example 2: the method for detecting the austenite grain size of the steel by the oxidation method is specifically described as follows.
(1) Sampling from a steel material with the steel grade of 20Mn2, wherein the carbon content in the steel is less than or equal to 0.35 wt%; the test surface of the sample was polished with a 400 grit abrasive. Placing the sample in a furnace with the detection surface facing upwards at the furnace temperature of 400 ℃, heating the sample to 880 ℃ along with the furnace, preserving the heat for 1h, and finally quenching the sample in cold water.
(2) The heat-treated samples were cut vertically along the middle of the test surface to produce two heat-treated samples. Grinding a heat treatment sample into a section vertical to the detection surface, polishing, then using 4% nitric acid alcohol to erode, observing that the oxidation layer structure of the section of the sample is ferrite and martensite, and then the sample is a non-qualified sample.
(3) Taking one sample again to polish the detection surface of the sample, and covering a layer of carbon powder particles for carburizing on the polished detection surface of the sample; placing the sample in a furnace with the detection surface facing upwards, heating the sample to 880 ℃ along with the furnace, preserving the heat for 1h, and finally quenching the sample in cold water. The heat-treated samples were cut vertically along the middle of the test surface to produce two heat-treated samples. Grinding a heat treatment sample into a section vertical to the detection surface, polishing, then using 4% nitric acid alcohol to erode, observing that the oxidation layer structure of the detection surface of the sample is a full martensite structure from the section, and then the sample is qualified.
(4) And (3) lightly grinding the detection surface of the other heat-treated sample of the qualified sample by using fine sand paper until a small amount of scale is remained, and properly inclining the sample by 10-15 degrees according to the oxidation condition for grinding and polishing. Then, the sample is corroded by 15% hydrochloric acid alcohol solution, and the austenite grain size of the sample can be observed to be 7.0 grade.
(5) The steel is sampled and detected by a hardening method, and the austenite grain size is detected to be 7.0 grade.
Example 3: the method for detecting the austenite grain size of the steel by the oxidation method is specifically described as follows.
(1) Sampling from a steel material with the steel grade of 27SiMn, wherein the carbon content in the steel is less than or equal to 0.35 wt%; the test surface of the sample was polished with a 400 grit abrasive. Placing the sample in a furnace at room temperature with the detection surface facing upwards, heating to 900 ℃ along with the furnace, preserving heat for 1h, and finally quenching in saline water.
(2) The heat-treated samples were cut vertically along the middle of the test surface to produce two heat-treated samples. And grinding a heat treatment sample into a section vertical to the detection surface, polishing, corroding by using 4% nitric acid alcohol, and observing that the oxidation layer structure of the section of the sample is a full ferrite structure, so that the sample is a non-qualified sample.
(3) Taking one sample again to polish the detection surface of the sample, and covering a layer of carbon powder particles for carburizing on the polished detection surface of the sample; placing the sample in a furnace with the detection surface facing upwards, heating the sample to 900 ℃ along with the furnace, preserving the heat for 1h, and finally quenching the sample in saline water. The heat-treated samples were cut vertically along the middle of the test surface to produce two heat-treated samples. And grinding a heat treatment sample into a tangent plane vertical to the detection surface, polishing, corroding by using 4% nitric acid alcohol, and observing the oxidation layer structure full martensite structure of the detection surface of the sample, wherein the sample is qualified.
(4) And (3) lightly grinding the detection surface of the other heat-treated sample of the qualified sample by using fine sand paper until a small amount of scale is remained, and properly inclining the sample by 10-15 degrees according to the oxidation condition for grinding and polishing. Then, the sample is corroded by 15% hydrochloric acid alcohol solution, and the austenite grain size of the sample can be observed to be 7.0 grade.
(5) The steel is sampled and detected by a hardening method, and the austenite grain size is detected to be 7.0 grade.
Example 4: the method for detecting the austenite grain size of the steel by the oxidation method is specifically described as follows.
(1) Sampling from a steel material with the steel grade of SAE1055, wherein the carbon content in the steel is more than 0.35 wt%; the test surface of the sample was polished with a 400 grit abrasive. Placing the sample in a furnace with the detection surface facing upwards at the furnace temperature of 100 ℃, heating the sample to 870 ℃ along with the furnace, preserving the heat for 1h, and finally quenching the sample in cold water.
(2) The heat-treated samples were cut vertically along the middle of the test surface to produce two heat-treated samples. And grinding a heat treatment sample into a section vertical to the detection surface, polishing, corroding by using 4% nitric acid alcohol, and observing that the oxidation layer structure of the section of the sample is a full martensite structure, so that the sample is qualified.
(3) And (3) lightly grinding the detection surface of the other heat-treated sample by using fine sand paper until a small amount of iron scale is remained, and properly inclining the sample by 10-15 degrees according to the oxidation condition for grinding and polishing. Then, the sample is corroded by 15% hydrochloric acid alcohol solution, and the austenite grain size of the sample can be observed to be 7.5-8.0 grade.
(4) The steel is sampled and detected by a hardening method, and the austenite grain size is detected to be 7.5 grade.
Example 5: the method for detecting the austenite grain size of the steel by the oxidation method is specifically described as follows.
(1) Sampling from a steel material with the steel grade of 60Si2MnA, wherein the carbon content in the steel is more than 0.35 wt%; the test surface of the sample was polished with a 400 grit abrasive. Placing the sample in a furnace with the detection surface facing upwards at the furnace temperature of 200 ℃, heating the sample to 860 ℃ along with the furnace, preserving the heat for 1h, and finally quenching the sample in cold water.
(2) The heat-treated samples were cut vertically along the middle of the test surface to produce two heat-treated samples. And grinding a heat treatment sample into a section vertical to the detection surface, polishing, corroding by using 4% nitric acid alcohol, and observing that the oxidation layer structure of the section of the sample is a full ferrite structure, so that the sample is a non-qualified sample.
(3) Taking one sample again to polish the detection surface of the sample, and covering a layer of carbon powder particles for carburizing on the polished detection surface of the sample; placing the sample in a furnace with the detection surface facing upwards, heating the sample to 860 ℃ along with the furnace, preserving the temperature for 1h, and finally quenching the sample in cold water. The heat-treated samples were cut vertically along the middle of the polished surface to make two heat-treated samples. And grinding a heat treatment sample into a section vertical to the polished surface, using 4% nitric acid alcohol for corrosion after polishing, and observing the oxide layer structure full martensite structure of the detected surface of the sample, wherein the sample is qualified.
(4) And (3) lightly grinding the detection surface of the other heat-treated sample of the qualified sample by using fine sand paper until a small amount of scale is remained, and properly inclining the sample by 10-15 degrees according to the oxidation condition for grinding and polishing. Then, the sample is corroded by 15% hydrochloric acid alcohol solution, and the austenite grain size of the sample can be observed to be 8.0 grade.
(5) The steel is sampled and detected by a hardening method, and the austenite grain size is detected to be 8.0 grade.
Example 6: the method for detecting the austenite grain size of the steel by the oxidation method is specifically described as follows.
(1) Sampling from a steel material with the steel grade of 55Cr3, wherein the carbon content in the steel is more than 0.35 wt%; the test surface of the sample was polished with a 400 grit abrasive. Placing the sample in a furnace with the detection surface facing upwards at the furnace temperature of 300 ℃, heating the sample to 850 ℃ along with the furnace, preserving the heat for 1h, and finally quenching the sample in saline water.
(2) The heat-treated samples were cut vertically along the middle of the test surface to produce two heat-treated samples. Grinding a heat treatment sample into a section vertical to the detection surface, polishing, then using 4% nitric acid alcohol to erode, observing that the oxidation layer structure of the section of the sample is ferrite and martensite, and then the sample is a non-qualified sample.
(3) Taking one sample again to polish the detection surface of the sample, and covering a layer of carbon powder particles for carburizing on the polished detection surface of the sample; placing the sample in a furnace with the detection surface facing upwards, heating the sample to 850 ℃ along with the furnace, preserving the heat for 1h, and finally quenching the sample in saline water. The heat-treated samples were cut vertically along the middle of the test surface to produce two heat-treated samples. Grinding a heat treatment sample into a section vertical to the detection surface, polishing, corroding by using 4% nitric acid alcohol, and observing the oxide layer structure full-martensite structure of the detection surface of the sample from the section, so that the sample is qualified.
(4) And (3) lightly grinding the detection surface of the other heat-treated sample of the qualified sample by using fine sand paper until a small amount of scale is remained, and properly inclining the sample by 10-15 degrees according to the oxidation condition for grinding and polishing. Then, the sample was corroded with 15% hydrochloric acid alcohol solution, and the austenite grain size of the sample was observed to be 7.5 grade.
(5) The steel is sampled and detected by a hardening method, and the austenite grain size is detected to be 7.5 grade.
Case counting: and randomly extracting 50 batches of steel, and detecting by adopting the method and the hardening method, wherein the austenite grain size grades detected by the two methods are basically the same.
Claims (3)
1. A method for detecting the austenite grain size of steel by an oxidation method is characterized by comprising the following steps:
(1) taking a sample, polishing the detection surface of the sample, and then carrying out heat treatment;
(2) vertically cutting the heat-treated sample along the detection surface to prepare two heat-treated samples;
(3) taking a heat treatment sample, grinding and polishing a section of the heat treatment sample, and then eroding the section by nitric acid and alcohol with the volume percentage of 4%; observing the oxide layer structure of the section of the heat treatment sample, wherein the oxide layer structure is a full martensite structure and is a qualified sample, and otherwise, the oxide layer structure is a non-qualified sample;
(4) when the test sample is qualified, grinding and polishing the detection surface of another heat treatment test sample to obtain austenite grains of an oxide layer, and corroding the test sample by using a hydrochloric acid alcohol solution with the volume percentage of 15% to observe the austenite grains of the test sample;
(5) when the sample is a non-qualified sample, the sample is taken again, the detection surface is polished, then a layer of carbon powder particles for carburizing is covered on the detection surface, and then heat treatment is carried out;
(6) the heat-treated samples were examined according to steps (2), (3), (4) and (5).
2. The method of claim 1 for the oxidation testing of the austenite grain size of a steel material, wherein: and (3) in the heat treatment process of the steps (1) and (5), heating the sample along with the furnace to raise the temperature.
3. A method of checking the austenite grain size of a steel product by oxidation according to claim 1 or 2, characterized in that: the method is suitable for carbon steel and alloy steel with the carbon content of 0.25-0.60%.
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| CN111850563B (en) * | 2020-07-30 | 2022-04-12 | 北京钢研高纳科技股份有限公司 | Rapid detection method for surface structure of nickel-based superalloy forging and high-power structure corrosion liquid |
| CN112198037B (en) * | 2020-09-29 | 2023-12-01 | 宝武杰富意特殊钢有限公司 | Method for displaying precipitation condition of ferrite along prior austenite |
| CN112304993B (en) * | 2020-10-28 | 2022-07-26 | 湖南华菱湘潭钢铁有限公司 | Spring steel austenite grain size detection method |
| CN113640183B (en) * | 2021-08-05 | 2024-01-12 | 常州天山重工机械有限公司 | Method for inspecting carburizing steel austenite grains by oxidation method |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103257098A (en) * | 2013-05-16 | 2013-08-21 | 江苏省沙钢钢铁研究院有限公司 | High-carbon steel wire rod austenite crystal grain size measuring method |
| CN103454188A (en) * | 2013-09-06 | 2013-12-18 | 鞍钢股份有限公司 | Quenching test method of austenite grain size of high-strength ship plate steel |
| CN105092437A (en) * | 2015-09-22 | 2015-11-25 | 中国第一重型机械股份公司 | Ultra-supercritical martensite heat resisting cast steel original austenite grain size display method |
| CN105203438A (en) * | 2015-10-14 | 2015-12-30 | 武汉钢铁(集团)公司 | Determination method for austenitic grain size of pearlite type wire rod |
| CN106596234A (en) * | 2016-12-02 | 2017-04-26 | 昆明理工大学 | Method for displaying original austenite grain boundary of low-carbon microalloyed steel |
| CN106967946A (en) * | 2017-05-22 | 2017-07-21 | 上海电气核电设备有限公司 | The annealing device and its application method tested for autstenitic grain size acieration |
| CN109187152A (en) * | 2018-09-05 | 2019-01-11 | 天津重型装备工程研究有限公司 | It is a kind of for showing the corrosive agent and display methods of heat resisting steel original austenite crystal boundary |
| CN109536881A (en) * | 2018-11-14 | 2019-03-29 | 中国大唐集团科学技术研究院有限公司火力发电技术研究院 | A kind of method of laboratory testing autstenitic grain size case-carbonizing |
| CN109916787A (en) * | 2019-04-02 | 2019-06-21 | 鞍钢股份有限公司 | A method of spring steel wire rod autstenitic grain size is measured with oxidizing process |
-
2019
- 2019-07-30 CN CN201910695033.5A patent/CN110441201B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103257098A (en) * | 2013-05-16 | 2013-08-21 | 江苏省沙钢钢铁研究院有限公司 | High-carbon steel wire rod austenite crystal grain size measuring method |
| CN103454188A (en) * | 2013-09-06 | 2013-12-18 | 鞍钢股份有限公司 | Quenching test method of austenite grain size of high-strength ship plate steel |
| CN105092437A (en) * | 2015-09-22 | 2015-11-25 | 中国第一重型机械股份公司 | Ultra-supercritical martensite heat resisting cast steel original austenite grain size display method |
| CN105203438A (en) * | 2015-10-14 | 2015-12-30 | 武汉钢铁(集团)公司 | Determination method for austenitic grain size of pearlite type wire rod |
| CN106596234A (en) * | 2016-12-02 | 2017-04-26 | 昆明理工大学 | Method for displaying original austenite grain boundary of low-carbon microalloyed steel |
| CN106967946A (en) * | 2017-05-22 | 2017-07-21 | 上海电气核电设备有限公司 | The annealing device and its application method tested for autstenitic grain size acieration |
| CN109187152A (en) * | 2018-09-05 | 2019-01-11 | 天津重型装备工程研究有限公司 | It is a kind of for showing the corrosive agent and display methods of heat resisting steel original austenite crystal boundary |
| CN109536881A (en) * | 2018-11-14 | 2019-03-29 | 中国大唐集团科学技术研究院有限公司火力发电技术研究院 | A kind of method of laboratory testing autstenitic grain size case-carbonizing |
| CN109916787A (en) * | 2019-04-02 | 2019-06-21 | 鞍钢股份有限公司 | A method of spring steel wire rod autstenitic grain size is measured with oxidizing process |
Non-Patent Citations (2)
| Title |
|---|
| 氧化法显示钢的奥氏体晶粒度的准确性;刘铁山等;《理化检验-物理分册》;20131231;第49卷(第12期);第808-812页 * |
| 氧化法检验钢的奥氏体晶粒度的研究;刘天佑;《理化检验－物理分册》;20001130;第36卷(第11期);第501-504页 * |
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