CN110646424A - Rapid quantitative evaluation method for metallographic structure anisotropy - Google Patents
Rapid quantitative evaluation method for metallographic structure anisotropy Download PDFInfo
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Abstract
The invention relates to a rapid quantitative evaluation method of metallographic structure anisotropy, which realizes rapid quantitative evaluation of metallographic structure anisotropy through metallographic sample preparation, picture acquisition, characteristic phase selection, measurement linear grid setting, intercept point counting, evaluation parameter input, automatic calculation of evaluation results and the like; the working efficiency can be improved, and the labor intensity can be reduced; and a simple and easy-to-use relative accuracy Ra calculation method is established, and when the accuracy does not meet the requirement, the rating view field can be timely increased to improve the detection accuracy.
Description
Technical Field
The invention belongs to the technical field of metallographic analysis and test, and relates to a rapid quantitative evaluation method for metallographic structure anisotropy.
Background
The banded structure in the steel represents the uneven distribution of chemical components of the material, and the grade of the banded structure represents the segregation degree of the components of the material. The band-like structure in the steel material is a structure in which a band mainly composed of pro-eutectoid ferrite and a band mainly composed of pearlite are stacked in the rolling direction, and the presence of the band-like structure makes the steel material structure uneven, easily causes stress concentration, and deteriorates the properties of the steel material such as strength and toughness.
American standard ASTM E1268 adopts a stereology method to determine strip-shaped tissue and direction degree in steel, namely anisotropy of the tissue, the test principle is similar to that of a grid intercept method in grain size determination to carry out quantitative analysis, calculation methods such as statistics and the like are utilized to realize quantitative evaluation of anisotropy of microscopic tissue in steel, relative measurement precision Ra is introduced to evaluate and measure accuracy, and the evaluation result is more detailed, more scientific and more representative. However, the American standard requires a large number of test fields, so that test photos need to be processed, data statistics is large, and data processing is complex, so that the detection speed is low, and the labor intensity of detection personnel is high. At present, the evaluation of the anisotropy of American standard organization takes more than 30min for detecting one sample, the detection efficiency is low, and the popularization and application of the standard are restricted to a great extent.
The national standard GB/T13299 'Steel microstructure assessment method' uses the comparison of the most severe visual field and a standard map for grading. The method has high detection speed, can finish the detection of a sample within 2 to 3 minutes generally, and is suitable for the rapid detection of mass production. However, in the method, the worst view field represents the whole situation by one view field, system deviation exists between different view fields, and meanwhile, due to the fact that the inspection personnel rate the standard map, the rate recurrence is poor for different inspection personnel due to different work experiences and different comprehensions of the evaluation standards.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a rapid quantitative evaluation method for the anisotropy of a metallographic structure, which can improve the working efficiency and reduce the labor intensity; and a simple and easy-to-use relative accuracy Ra calculation method is established, and when the accuracy does not meet the requirement, the rating view field can be timely increased to improve the detection accuracy.
The technical scheme adopted by the invention for solving the technical problems is as follows: a metallographic structure anisotropy rapid quantitative evaluation method is characterized in that metallographic structure anisotropy rapid quantitative rating is achieved through metallographic sample preparation, picture collection, characteristic phase selection, measurement linear grid setting, intercept point counting, evaluation parameter input, automatic evaluation result calculation and the like; the method comprises the following specific steps:
step (1): preparing a metallographic sample, and sampling according to the requirements of ASTM E1268 standard, wherein if a full-section sample is taken, the longitudinal length of the sample is not less than 10 mm; non-full cross section, sample area greater than 100mm2The longitudinal length is not less than 10mm, the metallographic sample is ground into a metallographic sample through the steps of coarse grinding by a coarse grinding machine, fine grinding by abrasive paper and polishing by a polishing machine, and the polished sample is etched by a nitric acid-alcohol corrosive agent;
step (2): collecting pictures, namely placing a sample subjected to polishing and etching on a metallographic microscope stage, adjusting the magnification of the microscope to be 50-200 times, and selecting a proper magnification capable of displaying a microstructure; adjusting the focal length of the microscope until a clear microstructure appears; observing the morphology of the tissue, adjusting the position direction of the sample and ensuring that the deformation direction of the tissue is horizontal; moving an object stage, randomly selecting a field of view, and then taking a micrograph;
and (3): selecting characteristic phases, judging which phase in the tissue is in a strip shape on a taken photomicrograph, and if both phases have directionality, calculating according to the phase with small content;
and (4): and (3) setting a measuring straight line grid, and randomly drawing a plurality of line segments with known lengths on the obtained photomicrograph by taking the calibrated ruler as a reference, wherein the line is parallel to the deformation direction and penetrates through the banded tissue phase, and the sum of the lengths of the line segments is not less than 500 mm. Then drawing several line segments with known length, the line is perpendicular to the deformation direction and passes through the banded tissue phase to be judged, the sum of the length of the line segments is not less than 500mm, and all the line segment positions can not have the subjective deviation of an operator;
and (5): counting the number of the intercept points intersected with the grain boundaries of the banded structure phase by the marked measuring lines in the parallel deformation direction and the vertical deformation direction respectively, wherein the counting rule is according to ASTM E1268;
and (6): evaluation parameter input, namely respectively inputting the total lengths of the measuring lines in the parallel deformation direction and the vertical deformation direction, the total number of corresponding intercept points and the like into an Excel function table which is designed in advance according to the calculation rule of ASTM E1268, and recommending that not less than 5 measuring view fields are selected to improve the detection accuracy;
and (7): automatically calculating an evaluation result, namely automatically calculating the anisotropy coefficient AI of the tissue, and the relative accuracy Ra of the respective intercept point measurement of the parallel deformation direction and the vertical deformation direction in a pre-designed Excel function table according to the input evaluation parameters; if Ra exceeds 30%, the measurement field of view is increased, the Ra value is corrected, and the AI is recalculated.
The invention has the positive effects that: the rapid quantitative evaluation of the anisotropy of the metallographic structure is realized through the steps of metallographic phase sample preparation, picture collection, characteristic phase selection, measurement linear grid setting, intercept point counting, evaluation parameter input, automatic evaluation result calculation and the like. The working strength is greatly reduced, and the detection efficiency is improved; meanwhile, a simple and easy-to-use relative accuracy Ra calculation method is established, and the detection accuracy is improved.
Drawings
FIG. 1 is a metallographic original picture;
FIG. 2 shows a metallographic image after the grid treatment;
FIG. 3 is an original picture of a 20CrMo alloy steel band-shaped structure;
FIG. 4 is a metallographic picture of alloy steel 20CrMo strip structure after being processed by a test grid;
FIG. 5 is an original photograph of a low alloy plate Q345B with a ribbon structure;
fig. 6 is a metallographic picture of a low alloy plate Q345B after a strip structure test grid treatment.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
Referring to fig. 1 and 2, a rapid quantitative evaluation method for metallographic structure anisotropy is used for realizing rapid quantitative evaluation of metallographic structure anisotropy through metallographic sample preparation, picture collection, feature phase selection, measurement linear grid setting, intercept counting, evaluation parameter input, automatic evaluation result calculation and the like; the method comprises the following specific steps:
step (1): preparing a metallographic sample, and sampling according to the requirements of ASTM E1268 standard, wherein if a full-section sample is taken, the longitudinal length of the sample is not less than 10 mm; non-full cross section, sample area greater than 100mm2The longitudinal length is not less than 10mm, the metallographic sample is ground into a metallographic sample through the steps of coarse grinding by a coarse grinding machine, fine grinding by abrasive paper and polishing by a polishing machine, and the polished sample is etched by a nitric acid-alcohol corrosive agent;
step (2): collecting pictures, namely placing a sample subjected to polishing and etching on a metallographic microscope stage, adjusting the magnification of the microscope to be 50-200 times, and selecting a proper magnification capable of displaying a microstructure; adjusting the focal length of the microscope until a clear microstructure appears; observing the morphology of the tissue, adjusting the position direction of the sample and ensuring that the deformation direction of the tissue is horizontal; moving an object stage, randomly selecting a field of view, and then taking a micrograph;
and (3): selecting characteristic phases, judging which phase in the tissue is in a strip shape on a taken photomicrograph, and if both phases have directionality, calculating according to the phase with small content;
and (4): measuring a linear grid, and randomly drawing a plurality of line segments with known lengths on the obtained photomicrograph by taking a calibrated scale as a reference, wherein the line is parallel to the deformation direction and penetrates through a banded tissue phase, and the sum of the lengths of the line segments is not less than 500 mm; then drawing several line segments with known length, the line is perpendicular to the deformation direction and passes through the banded tissue phase to be judged, the sum of the length of the line segments is not less than 500mm, and all the line segment positions can not have the subjective deviation of an operator;
and (5): counting the number of the intercept points intersected with the grain boundaries of the banded structure phase by the marked measuring lines in the parallel deformation direction and the vertical deformation direction respectively, wherein the counting rule is according to ASTM E1268;
and (6): evaluation parameter input, namely respectively inputting the total lengths of the measuring lines in the parallel deformation direction and the vertical deformation direction, the total number of corresponding intercept points and the like into an Excel function table which is designed in advance according to the calculation rule of ASTM E1268, and recommending that not less than 5 measuring view fields are selected to improve the detection accuracy;
and (7): automatically calculating an evaluation result, namely automatically calculating the anisotropy coefficient AI of the tissue, and the relative accuracy Ra of the respective intercept point measurement of the parallel deformation direction and the vertical deformation direction in a pre-designed Excel function table according to the input evaluation parameters; if Ra exceeds 30%, the measurement field of view is increased, the Ra value is corrected, and the AI is recalculated.
The table for rapidly calculating Excel function for evaluating tissue anisotropy is as follows
Example 1
The method is used for quantitatively evaluating the anisotropy of the 20CrMo structure of the alloy structural steel. The test sample is a phi 20mm hot rolled wire rod, and is cut along a longitudinal symmetrical line, and the test sample is inlaid, roughly ground, finely ground, polished and corroded according to the test sample, and then analyzed by a metallographic microscope and self-contained picture processing software. The metallographic photograph is shown in fig. 3, and it can be seen from the metallographic structure that the microstructure is a ferrite and pearlite two-phase structure, both the two-phase structure have obvious directionality, wherein the pearlite content is lower than the ferrite content, so the anisotropy of the pearlite structure is evaluated, 6 photographs are randomly taken to perform measurement grid processing, the total length of the line segment measured in the direction parallel to the structure deformation direction and in the direction perpendicular to the structure deformation direction of each photograph is respectively recorded, the processed photographs are shown in fig. 4, and the number of the intercept points of the intersection of the drawn parallel deformation direction and perpendicular deformation direction measurement lines and the grain boundary of the banded structure phase is respectively counted. The total length of the measuring lines and the number of the intercept points of the 6 photographs are respectively recorded into a preset Excel function table, and the relative accuracy Ra of the intercept point measurement in the parallel tissue deformation direction is 11.48 percent, the relative accuracy Ra of the intercept point measurement in the vertical tissue deformation direction is 5.98 percent, the anisotropy coefficient AI of the tissue is calculated as follows: 1.95, the relative accuracy of the measurement of the intercept points in the vertical and parallel tissue deformation directions is less than 30 percent, the measurement accuracy requirement is met, and the calculated tissue anisotropy coefficient AI meets the requirement.
The Excel function table for evaluating the anisotropy of the alloy steel 20CrMo structure is as follows:
example 2
The method is used for quantitatively evaluating the structural anisotropy of the low alloy plate Q345B. The sample is a hot-rolled low-alloy steel plate with the thickness of 20mm, longitudinal samples are taken for sample coarse grinding, fine grinding, polishing and corrosion, and then a metallographic microscope and self-contained picture processing software are adopted for analysis. As shown in fig. 5, the metallographic structure shows that the microstructure is a ferrite-pearlite two-phase structure, both of which have a significant orientation, and the pearlite content is lower than the ferrite content, and therefore, the pearlite structure anisotropy is evaluated. And randomly taking 6 pictures for grid measurement processing, and respectively recording the total length of the measurement line segment of each picture parallel to the tissue deformation direction and perpendicular to the tissue deformation direction, wherein the processed pictures are shown in figure 6. And respectively counting the number of intercept points of the intersection of the measuring lines and the grain boundaries of the banded structure phase through the marked parallel deformation direction and the marked vertical deformation direction. The total length of the measuring lines and the number of the intercept points of the 6 photographs are respectively recorded into a preset Excel function table, the relative accuracy Ra of the intercept point measurement in the parallel tissue deformation direction is 11.48 percent, the relative accuracy Ra of the intercept point measurement in the vertical tissue deformation direction is 5.98 percent, the anisotropy coefficient AI of the tissue is 1.95 percent, the relative accuracy of the intercept point measurement in the vertical and parallel tissue deformation directions is less than 30 percent, the measuring accuracy requirement is met, and the calculated tissue anisotropy coefficient AI meets the requirement.
The Excel function and the calculation process are shown in the following table:
the two embodiments show that the invention can rapidly carry out quantitative evaluation on the tissue anisotropy of the material microstructure according to American standard ASTM E1268 and output the tissue anisotropy coefficient AI. And calculating the relative accuracy Ra of the intercept point measurement in the parallel and vertical tissue deformation directions, correcting the measurement result with Ra greater than 30% by supplementing the measurement view field, recalculating the tissue anisotropy coefficient AI, and improving the detection accuracy. The total time consumption of the two implementation cases from metallographic analysis to calculation of the anisotropy coefficient AI is about 5min, the detection efficiency is obviously improved, the analysis time consumption of each sample is reduced by more than 25min, and the efficiency is improved by more than 80%.
Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still optimize the technical solutions described in the foregoing embodiments, but any modifications, equivalents, improvements, etc. within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (1)
1. A metallographic structure anisotropy rapid quantitative evaluation method is characterized in that metallographic structure anisotropy rapid quantitative rating is achieved through metallographic phase sample preparation, picture collection, characteristic phase selection, measurement straight line grid setting, intercept point counting, evaluation parameter input, automatic evaluation result calculation and the like; the method comprises the following specific steps:
step (1): preparing a metallographic sample, and sampling according to the requirements of ASTM E1268 standard, wherein if a full-section sample is taken, the longitudinal length of the sample is not less than 10 mm; non-full cross section, sample area greater than 100mm2The longitudinal length is not less than 10mm, the metallographic sample is ground into a metallographic sample through the steps of coarse grinding by a coarse grinding machine, fine grinding by abrasive paper and polishing by a polishing machine, and the polished sample is etched by a nitric acid-alcohol corrosive agent;
step (2): collecting pictures, namely placing a sample subjected to polishing and etching on a metallographic microscope stage, adjusting the magnification of the microscope to be 50-200 times, and selecting a proper magnification capable of displaying a microstructure; adjusting the focal length of the microscope until a clear microstructure appears; observing the morphology of the tissue, adjusting the position direction of the sample and ensuring that the deformation direction of the tissue is horizontal; moving an object stage, randomly selecting a field of view, and then taking a micrograph;
and (3): selecting characteristic phases, judging which phase in the tissue is in a strip shape on a taken photomicrograph, and if both phases have directionality, calculating according to the phase with small content;
and (4): measuring a linear grid, and randomly drawing a plurality of line segments with known lengths on the obtained photomicrograph by taking a calibrated scale as a reference, wherein the line is parallel to the deformation direction and penetrates through a banded tissue phase, and the sum of the lengths of the line segments is not less than 500 mm; then drawing several line segments with known length, the line is perpendicular to the deformation direction and passes through the banded tissue phase to be judged, the sum of the length of the line segments is not less than 500mm, and all the line segment positions can not have the subjective deviation of an operator;
and (5): counting the number of the intercept points intersected with the grain boundaries of the banded structure phase by the marked measuring lines in the parallel deformation direction and the vertical deformation direction respectively, wherein the counting rule is according to ASTM E1268;
and (6): evaluation parameter input, namely respectively inputting the total lengths of the measuring lines in the parallel deformation direction and the vertical deformation direction, the total number of corresponding intercept points and the like into an Excel function table which is designed in advance according to the calculation rule of ASTM E1268, and recommending that not less than 5 measuring view fields are selected to improve the detection accuracy;
and (7): automatically calculating an evaluation result, namely automatically calculating the anisotropy coefficient AI of the tissue, and the relative accuracy Ra of the respective intercept point measurement of the parallel deformation direction and the vertical deformation direction in a pre-designed Excel function table according to the input evaluation parameters; if Ra exceeds 30%, the measurement field of view is increased, the Ra value is corrected, and the AI is recalculated.
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| CN112634200A (en) * | 2020-12-01 | 2021-04-09 | 宝钢特钢韶关有限公司 | Method for evaluating strip structure in steel |
| CN113740336A (en) * | 2021-09-03 | 2021-12-03 | 广东韶钢松山股份有限公司 | Evaluation method for directly obtaining edge recarburization of continuous casting billet |
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Cited By (4)
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| CN112634200A (en) * | 2020-12-01 | 2021-04-09 | 宝钢特钢韶关有限公司 | Method for evaluating strip structure in steel |
| CN112634200B (en) * | 2020-12-01 | 2024-06-11 | 宝武杰富意特殊钢有限公司 | Method for evaluating strip-shaped structure in steel |
| CN113740336A (en) * | 2021-09-03 | 2021-12-03 | 广东韶钢松山股份有限公司 | Evaluation method for directly obtaining edge recarburization of continuous casting billet |
| CN113740336B (en) * | 2021-09-03 | 2024-03-12 | 广东韶钢松山股份有限公司 | Evaluation method for directly obtaining carburetion of continuous casting blank edge |
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