Method for preparing pure iron metallographic sample
Through a multi-step method, including grinding, polishing, black spot removal, mirroring and corrosion, the small scratches, black spots and scratches that occur during polishing and corrosion in metallographic tests of pure iron samples are solved, and the high-quality preparation of the samples is achieved.
Patent Information
- Application Number
- CN202411922985.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-25
- Publication Date
- 2025-03-25
AI Technical Summary
In metallographic tests, pure iron samples are prone to small scratches, black spots and scratches during polishing and corrosion, which are difficult to effectively remove.
A multi-step method is employed, including grinding, polishing, black spot removal, mirroring and corrosion. Specific steps include grinding on sandpaper, using polishing paste and water to produce foam on the polishing cloth for polishing, removing black spots by foam, using foam to remove residues on the polishing cloth during mirror formation, and corrosion in combination with wiping and dripping methods.
Effectively removes fine scratches, black spots and scratches on the surface of pure iron samples, improving the smoothness and quality of the samples, and avoiding the common oxidation and electrochemical corrosion problems in traditional methods.
Smart Images
Figure CN119688422A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of metallographic testing, and in particular to a method for preparing a pure iron metallographic sample. Background Art
[0002] With the development of science and technology and the improvement of product quality requirements in production, the requirements for metallographic preparation are getting higher and higher. The current metallographic preparation methods in engineering are too old-fashioned. An innovative, convenient and fast method is needed to complete metallographic preparation in order to meet the requirements of metallographic preparation.
[0003] Pure iron has low hardness and soft texture, so wear marks are easily caused if uneven force is applied or the abrasive particles are not cleaned properly during the grinding process. Small scratches and a large number of small black spots will appear during the polishing process. In addition, during the corrosion process, electrochemical corrosion will occur if only the drip etching method is used, and scratches will easily appear if the abrasion method is used. Summary of the invention
[0004] In order to overcome the deficiencies of the prior art, the technical problem to be solved by the present invention is: how to improve the problem of fine scratches and small black spots appearing during the polishing process and the problem of scratches appearing during the corrosion process.
[0005] The technical solution adopted by the present invention to solve its technical problem is:
[0006] The method for preparing a pure iron metallographic sample comprises the following steps:
[0007] S1: grinding, chamfering the edge of the test surface of the pure iron sample, and grinding the chamfered pure iron sample on sandpaper with a mesh number of 180-1200 mesh;
[0008] S2: Polishing: polish the ground pure iron sample on a polishing cloth until there is no scratch on the test surface of the pure iron sample;
[0009] S3: In order to remove black spots, a preset amount of water is added to the center of the polishing cloth, and the detection surface of the pure iron sample is brought into contact with a position close to the center of the polishing cloth for 1-10 seconds to form a foaming cycle. After repeating multiple foaming cycles, foam appears on the surface of the polishing cloth, so that the detection surface of the polished pure iron sample is brought into contact with the foam, and at the same time, the pure iron sample is moved radially from the inside to the outside to a preset position along the polishing cloth, and the detection surface of the pure iron sample is rotated 90° every 2-12 seconds, and the position of the pure iron sample remains unchanged, for 1-10 minutes;
[0010] S4: Mirroring, place the test surface of the pure iron sample in contact with the foamy position of the polishing cloth, lift the sample every 1-10 seconds, turn it 90 degrees and place it in the same position, continue to squeeze water with a washing bottle towards the test surface of the pure iron sample, and observe every 30 seconds whether there is any residual polishing paste on the surface of the sample. If there is polishing paste, continue with the above steps; if there is no polishing paste, proceed to the next step;
[0011] S5: Corrosion. First rinse the detection surface with alcohol. After drying, wipe the detection surface of the pure iron sample with a cotton ball added with corrosion liquid. After observing that the detection surface changes to a preset color, rinse the detection surface of the pure iron sample with alcohol and dry it. Drop a preset amount of corrosion liquid on the detection surface of the dried pure iron sample, and immediately rinse it with alcohol and dry it.
[0012] Furthermore, step S1 also includes grinding the pure iron sample from one side of the sandpaper to the other side during the grinding process, repeating 5-10 times, rotating the detection surface of the pure iron sample by 90°, and repeating the above operation.
[0013] Furthermore, in step S2, before entering the polishing procedure, the polishing paste is evenly applied to the surface of the polishing cloth, and the polishing machine is started, a preset amount of water is added to the center of the polishing cloth, and wait for 2-20 seconds.
[0014] Furthermore, in step S2, the test surface of the ground pure iron sample is placed at a preset position on the outside of the polishing cloth, and the test surface of the pure iron sample is driven to circle the surface of the polishing cloth alternately counterclockwise and clockwise. If the sample is overheated in the middle, it is cooled by flushing, and then it continues to circle, and it is observed whether there are wear marks on the surface of the sample every 5-10 seconds. If there are still wear marks, it continues to circle until there are no scratches on the surface of the sample.
[0015] Further, after waiting for 2-20 seconds, the test surface of the pure iron sample is placed against a preset position on the surface of the polishing cloth away from the center, and polishing is performed alternately in clockwise and counterclockwise directions to observe whether there are scratches on the test surface of the pure iron sample. If there are scratches, continue to perform the above steps; if there are no scratches, proceed to the next stage.
[0016] Furthermore, a positioning step is included between step S2 and step S3, and the positioning step includes placing the test surface of the pure iron sample on a polishing cloth coated with polishing paste at a preset position on the outside and fixing it, rotating the sample 90° every 3-15 seconds, and then placing it on the same position on the polishing cloth and fixing it, and repeating this step for 1-10 minutes.
[0017] Furthermore, in step S5, when the cotton ball with the corrosive liquid is used to wipe the detection surface of the pure iron sample, the method is to wipe in a circular motion.
[0018] Furthermore, when a preset amount of corrosive liquid is dripped onto the detection surface of the dried pure iron sample, the detection surface of the pure iron sample is rotated.
[0019] The beneficial effects of the present invention are:
[0020] The sample surface is brought into contact with a polishing cloth with a proper amount of water and polishing paste to generate white foam, and then the foam is used to remove the fine scratches on the sample surface, and the small black spots are taken away from the sample test surface during the mirror forming process. At the same time, the pitting method and the abrasion method are combined to corrode the fine scratches generated by the abrasion method. By adding a foaming process to the polishing process, the fine scratches on the sample surface that are invisible to the naked eye and a large number of small black spots are removed. In addition, by adopting the method of wiping first and then dripping, wiping first can avoid electrochemical corrosion during dripping, and dripping can corrode the fine scratches caused by the first wiping. The entire preparation process can overcome the problems of fine wear marks, black spots, sample surface oxidation, etc. in traditional methods, and improve the sample quality. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 is a flow chart of the method of the present invention;
[0022] Figure 2 is a microstructure morphology diagram of the detection surface of the metallographic sample completed in the embodiment of the present invention; DETAILED DESCRIPTION
[0023] The present invention is further described below in conjunction with the accompanying drawings.
[0024] The present application embodiment proposes a method for preparing a pure iron metallographic sample, comprising the following steps:
[0025] S1: Grinding, chamfer the edge of the pure iron sample detection surface, and grind the chamfered pure iron sample on sandpaper with a mesh size of 180-1200; first, chamfer the pure iron sample at 45° on 180﹟ sandpaper, grind and press the pure iron sample on the sandpaper with greater and uniform force, grind from one side of the sandpaper to the other side after the sample contacts the sandpaper horizontally, repeat 5-10 times, and then turn the pure iron 90° to continue grinding, and repeat this process until the turning marks and deformation layer are ground off and the wear marks on the pure iron surface are uniformly directed. The grinding process mainly grinds the detection surface of the pure iron sample to expose the structural organization, and grinds in sequence with sandpaper of different mesh sizes to ensure the process from coarse grinding to fine grinding, and gradually reduce the scratches on the detection surface caused by grinding.
[0026] S2: Polishing, polish the ground pure iron sample on the polishing cloth until there is no scratch on the test surface of the pure iron sample; before general polishing, evenly apply the polishing paste on the polishing cloth, squeeze water 1-10 times from the washing bottle towards the center of the polishing cloth coated with the polishing paste, wait 2-20 seconds, ensure that the polishing paste is evenly spread on the polishing cloth, and then select the designated position for polishing. After waiting for 2-20 seconds, contact the bottom of the test surface of the pure iron sample with the preset position on the surface of the polishing cloth away from the center, and polish alternately in clockwise and counterclockwise directions to observe whether there are scratches on the test surface of the pure iron sample. If there are scratches, continue to perform the above steps, if there are no scratches, proceed to the next stage.
[0027] The polishing process specifically includes placing the ground pure iron sample test surface on the preset position on the outside of the polishing cloth, and driving the pure iron sample test surface to circle counterclockwise and clockwise alternately on the surface of the polishing cloth. If the sample overheats in the middle, flush it with water to cool it, and then continue to circle. Every 5-10 seconds, observe whether there are wear marks on the sample surface. If there are still wear marks, continue to circle until there are no scratches on the sample surface.
[0028] In addition, in order to eliminate the fine polishing marks that may appear during the polishing process, the sample is fixed on a special position on the outside of the polishing cloth coated with polishing paste. Use light force, rotate the sample 90° every 3-15 seconds, and then fix it in the same position on the polishing cloth. Repeat this step for 1-10 minutes.
[0029] S3: In order to remove black spots, a preset amount of water is added to the center of the polishing cloth, and the detection surface of the pure iron sample is brought into contact with a position close to the center of the polishing cloth for 1-10 seconds to form a foaming cycle. After repeating multiple foaming cycles, foam appears on the surface of the polishing cloth, so that the detection surface of the polished pure iron sample contacts the foam with a light force, and at the same time, the pure iron sample is moved radially from the inside to the outside to a preset position along the polishing cloth. The detection surface of the pure iron sample is rotated 90° every 2-12 seconds, and the position of the pure iron sample remains unchanged for 1-10 minutes. The above process is to remove tiny scratches and a large number of small black spots on the sample surface that are invisible to the naked eye. Due to the presence of impurities on the polishing cloth, if too much force is applied during the polishing process, the impurities will cause scratches on the sample surface. If too little force is applied, the impurities will not be cleaned cleanly, resulting in small black spots. In this process, the foam will mix with the impurities, and the foam can take the impurities away from the sample surface during the mirror forming process.
[0030] The specific principle of foaming is: since the polishing paste is a kind of fine sand particles, when it comes into contact with water and rubs against the test surface of the pure iron sample, it will gather together in large quantities, thus producing white foam.
[0031] S4: Mirror, contact the detection surface of the pure iron sample with the foam position of the polishing cloth, use a washing bottle to squeeze water at the detection surface position of the pure iron sample, lift the sample every 1-10 seconds, turn it 90° and put it in the same position, continue to use the washing bottle to squeeze water at the detection surface position of the pure iron sample, and observe whether there is residual polishing paste on the surface of the sample every 30 seconds. If there is polishing paste, continue with the above steps; if there is no polishing paste, go to the next step; in conventional operation, the polishing cloth is washed and then polished with water, and wrinkles will appear on the polishing cloth, resulting in scratches and small black spots on the detection surface of the pure iron sample. This method does not clean the polishing cloth, and the surface of the polishing cloth is smooth and wrinkle-free, avoiding the above problems
[0032] S5: Corrosion. First rinse the detection surface with alcohol. After drying, wipe the detection surface of the pure iron sample with a cotton ball added with corrosion liquid. After observing that the detection surface changes to the preset color, rinse the detection surface of the pure iron sample with alcohol and then dry it. After dropping a preset amount of corrosion liquid on the detection surface of the dried pure iron sample, rotate the detection surface for a few turns and immediately rinse it with alcohol and then dry it.
[0033] Common corrosion methods include drip etching, wiping and immersion etching. The metallographic preparation method is generally one of the two methods, drip etching and wiping. However, using only the drip etching method may cause electrochemical corrosion, and using only the wiping method may easily cause scratches.
[0034] The corrosion process specifically includes the following steps: rinse the sample surface, rinse the polished sample with alcohol, specifically, use a dropper to drop alcohol onto the sample surface, drop 1-8 droppers of alcohol, then fluff the cotton ball, clamp the cotton ball with the corrosive liquid and gently circle the sample surface, while circling, use a little force to clamp the cotton ball, so that the corrosive liquid is fully in contact with the sample, observe the changes on the sample surface, and when the surface changes from bright to light gray, the corrosion is terminated; after corrosion, immediately use a dropper to drop 1-8 tubes of alcohol onto the sample surface, then use an alcohol cotton ball to gently wipe the sample surface, and finally rinse the sample surface with alcohol; after rinsing, immediately use a hair dryer to quickly dry. When drying, use cold air and the blowing distance should not be less than 1-5cm, nor more than 10-20cm, drop the corrosive liquid on the surface of the dried sample, hold the clamp and turn it 1-8 times, and then quickly rinse the sample surface with alcohol; after rinsing, immediately use a hair dryer to quickly dry, and the prepared metallographic sample is placed under a microscope for observation and analysis. The corrosion method proposed in this embodiment first adopts the method of wiping first and then dripping. Wiping first can avoid electrochemical corrosion during dripping, and dripping can corrode the small scratches caused by wiping first, thereby avoiding corrosion scratches and improving the corrosion effect. Figure 2 The figure shows a metallographic microscopic view of the test surface of the pure iron sample after being processed in this embodiment. It can be clearly seen that the structure is clear, without tiny scratches or black spots.
Claims
1. A method for preparing a pure iron metallographic sample, characterized in that: The following steps are included: S1: grinding, chamfering the edge of the polished surface of the pure iron sample, and grinding the chamfered pure iron sample on sandpaper with a mesh number of 180-1200 mesh; S2: Polishing: polish the ground pure iron sample on a polishing cloth until there is no scratch on the test surface of the pure iron sample; S3: In order to remove black spots, a preset amount of water is added to the center of the polishing cloth, and the detection surface of the pure iron sample is brought into contact with a position close to the center of the polishing cloth for 1-10 seconds to form a foaming cycle. After repeating multiple foaming cycles, foam appears on the surface of the polishing cloth, so that the detection surface of the polished pure iron sample is brought into contact with the foam, and at the same time, the pure iron sample is moved radially from the inside to the outside to a preset position along the polishing cloth, and the detection surface of the pure iron sample is rotated 90° every 2-12 seconds, and the position of the pure iron sample remains unchanged, for 1-10 minutes; S4: Mirroring, place the test surface of the pure iron sample in contact with the foamy position of the polishing cloth, lift the sample every 1-10 seconds, turn it 90 degrees and place it in the same position, continue to squeeze water with a washing bottle towards the test surface of the pure iron sample, and observe every 30 seconds whether there is any residual polishing paste on the surface of the sample. If there is polishing paste, continue with the above steps; if there is no polishing paste, proceed to the next step; S5: Corrosion. First rinse the detection surface with alcohol. After drying, wipe the detection surface of the pure iron sample with a cotton ball added with corrosion liquid. After observing that the detection surface changes to a preset color, rinse the detection surface of the pure iron sample with alcohol and dry it. Drop a preset amount of corrosion liquid on the detection surface of the dried pure iron sample, and immediately rinse it with alcohol and dry it.
2. The method for preparing a pure iron metallographic sample according to claim 1, characterized in that: Step S1 also includes grinding the pure iron sample from one side of the sandpaper to the other side during the grinding process, repeating 5-10 times, rotating the detection surface of the pure iron sample by 90°, and repeating the above operation.
3. The method for preparing a pure iron metallographic sample according to claim 1, characterized in that: In step S2, before entering the polishing procedure, the polishing paste is evenly applied to the surface of the polishing cloth, and the polishing machine is started, a preset amount of water is added to the center of the polishing cloth, and wait for 2-20 seconds.
4. The method for preparing a pure iron metallographic sample according to claim 1, characterized in that: In step S2, the test surface of the ground pure iron sample is placed at a preset position on the outside of the polishing cloth, and the test surface of the pure iron sample is driven to circle counterclockwise and clockwise alternately on the surface of the polishing cloth. If the sample is overheated in the middle, it is cooled by flushing with water, and then continues to circle. Every 5-10 seconds, observe whether there are wear marks on the surface of the sample. If there are still wear marks, continue to circle until there are no scratches on the surface of the sample.
5. The method for preparing a pure iron metallographic sample according to claim 4, characterized in that: After waiting for 2-20 seconds, place the test surface of the pure iron sample against the preset position on the surface of the polishing cloth away from the center, and polish alternately in clockwise and counterclockwise directions to observe whether there are scratches on the test surface of the pure iron sample. If there are scratches, continue to perform the above steps. If there are no scratches, proceed to the next stage.
6. The method for preparing a pure iron metallographic sample according to claim 1, characterized in that: A positioning step is also included between step S2 and step S3, and the positioning step includes placing the test surface of the pure iron sample on a preset position on the outside of the polishing cloth coated with polishing paste and fixing it, rotating the sample 90° every 3-15 seconds, and then placing it on the same position of the polishing cloth and fixing it, and repeating this step for 1-10 minutes.
7. The method for preparing a pure iron metallographic sample according to claim 1, characterized in that: In step S5, the cotton ball with the corrosive liquid added thereto wipes the detection surface of the pure iron sample in a circular motion.
8. The method for preparing a pure iron metallographic sample according to claim 1, characterized in that: When a preset amount of corrosive liquid is dripped onto the detection surface of the dried pure iron sample, the detection surface of the pure iron sample is rotated.