A corrosion agent for metal stream line detection, a preparation method and a corrosion method

Abstract

This invention relates to the field of bearing testing technology, specifically to a corrosive agent, its preparation method, and the etching method for detecting metal flow lines. The corrosive agent comprises water, concentrated hydrochloric acid, ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate; the volume ratio of water to concentrated hydrochloric acid is (12-20):(1-3); the mass ratio of ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate is (5-10):(5-10):(2-6):(5-15); and the mass ratio of ferric chloride to water is (1-2):(12-20). By controlling the etching rate through the synergistic effect of the raw materials, compared to existing hydrochloric acid aqueous solution etching methods, the corrosive agent of this application has a fixed heating temperature and holding time, and the display of metal flow lines is not affected by the bearing size. It can clearly and completely display the flow lines of the bearing rings, and the effect is stable; it solves the problem that the degree of corrosion is difficult to control and the flow lines of the bearing rings are not clearly displayed during the metal flow line etching process.

Description

Technical Field

[0001] This invention relates to the field of bearing testing technology, specifically to a corrosive agent, its preparation method, and its corrosion method for detecting metal flow lines. Background Technology

[0002] Bearings are essential basic mechanical components, used in a wide range of fields including automobiles, ships, chemical equipment, and aerospace. Their quality directly determines the reliability and precision of mechanical equipment. Currently, there are various forming methods for bearing rings, such as cold extrusion of bar stock, turning of tube stock, hot forging of bar stock, and cold rolling and expanding of bar stock. The cross-section of bearing rings formed by different methods will produce metal flow lines with certain directions. The metal flow lines generated by different processing methods have a crucial impact on the contact fatigue strength of the bearing. After the machined bearing is polished by metallography and chemically etched, the forming method and fatigue performance of the bearing rings can be determined by observing the flow lines. Therefore, the metal flow line detection of bearing rings can serve as a means of bearing quality monitoring.

[0003] Patent application CN115728062A discloses a method for detecting the influence of metal flow lines on the fatigue life of M50 / 8Cr4Mo4V steel bearing rings. This method involves cutting multiple contact fatigue test specimens along the circumference of the bearing ring forging using wire cutting. The precision-machined specimens are then placed on a contact fatigue testing device, and accelerated contact fatigue testing is performed by rotating the specimens using a double-roller until fatigue spalling occurs. Finally, the spalled specimens are axially cut and placed in an etchant for corrosion. By analyzing the relationship between the fatigue spalling location and the direction of the metal flow line exposure, it is determined whether the contact fatigue life is reduced in the direction of the exposed metal flow lines compared to the non-exposed direction. Although this method can obtain the influence of metal flow lines on the contact fatigue performance of bearing parts in a relatively short time, the etchant used is a 1:1 volume ratio of 35% hydrochloric acid aqueous solution and water. While this etchant is widely used and simple to operate... However, during use, the etching time and temperature of bearing rings formed by different methods are not exactly the same, making it difficult to control the degree of corrosion. Secondly, the streamlines of some bearing rings with smaller cross-sectional dimensions cannot be displayed, resulting in long testing time and inaccurate test results for bearing fatigue performance. Summary of the Invention

[0004] To address the problems in existing technologies where the degree of corrosion is difficult to control and the flow lines of bearing rings are not clearly displayed during metal flow line corrosion, this invention provides a corrosive agent, its preparation method, and the corrosion method for metal flow line detection.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a corrosive agent for metal flowline detection, comprising water, concentrated hydrochloric acid, ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate; wherein the volume ratio of water to concentrated hydrochloric acid is (12-20):(1-3); the mass ratio of ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate is (5-10):(5-10):(2-6):(5-15), and the mass ratio of ferric chloride to water is (1-2):(12-20).

[0007] The preparation method of the etchant for metal flowline detection, as described above, includes the following steps:

[0008] A corrosive agent is prepared by mixing water, concentrated hydrochloric acid, ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate in a specific ratio.

[0009] Preferably, the etchant is prepared at room temperature.

[0010] The etching method using the above-mentioned etchant for metal flowline detection includes the following steps:

[0011] Take a sample of the bearing ring to be inspected to obtain the bearing ring sample;

[0012] The bearing ring sample to be inspected is pretreated to prepare a test specimen.

[0013] The sample is immersed in an etchant and heated to etch it.

[0014] After corrosion, the sample was removed and cleaned to obtain the metal streamline morphology of the bearing ring to be inspected.

[0015] Furthermore, the specific operation for sampling the bearing ring to be tested is as follows: the bearing ring to be tested is cut along the axial direction to obtain a sample of the bearing ring to be tested with a width of 8mm to 12mm.

[0016] Furthermore, the specific steps for pre-treating the bearing ring sample to be inspected and preparing it into a test specimen are as follows:

[0017] The cut surface of the bearing ring sample to be inspected is roughly ground;

[0018] The bearing ring samples to be inspected after rough grinding are then finely ground.

[0019] The bearing ring samples to be inspected after fine grinding are polished.

[0020] The polished bearing ring sample to be inspected is cleaned and dried to obtain the test sample.

[0021] Preferably, the bearing ring sample to be inspected after coarse grinding is finely ground by sequentially using 400-mesh aqueous phase sandpaper, 600-mesh aqueous phase sandpaper, and 800-mesh metallographic sandpaper.

[0022] Preferably, the finely ground bearing ring sample is polished using canvas and velvet.

[0023] Furthermore, the heating temperature is 85℃~95℃, and the heating time is 18~22min.

[0024] Furthermore, the method for cleaning the sample is as follows: immerse the corroded sample in anhydrous ethanol, shake it to clean off the corrosion products adhering to the sample surface, then take out the sample, wipe the sample surface with degreased cotton soaked in anhydrous ethanol, and blow it dry.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention discloses an etchant for detecting metal flow lines, comprising water, concentrated hydrochloric acid, ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate; the volume ratio of water to concentrated hydrochloric acid is (12-20):(1-3); the mass ratio of ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate is (5-10):(5-10):(2-6):(5-15); and the mass ratio of ferric chloride to water is (1-2):(12-20). By creatively adding ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate to the hydrochloric acid solution and utilizing the synergistic effect of these raw materials, the corrosion rate is controlled. While clearly displaying metal flow lines, the sodium dodecylbenzenesulfonate delays the corrosion of the substrate by the etchant, thereby reducing the problem of blackened and unidentifiable corrosion sections due to prolonged corrosion by concentrated hydrochloric acid. Testing revealed that, compared to existing hydrochloric acid aqueous etching methods, the etchant heating temperature and holding time of this application are fixed, and the display of metal flow lines is not affected by the bearing size. The flow lines of the bearing rings can be clearly and completely displayed, and the effect is stable. At the same time, the etchant reagents of this invention are all readily available and inexpensive, which can greatly reduce the cost of bearing ring forming methods and fatigue testing.

[0027] The present invention also provides a method for preparing the etchant for metal flow line detection as described above. In the process of preparing the etchant, it is only necessary to mix the raw materials evenly at room temperature according to the volume ratio or mass ratio. It can be prepared as needed, the preparation method is simple, the reaction conditions are mild, and the operation is convenient and safe.

[0028] The etching method using the aforementioned etchant for metal flowline detection involves cutting and sampling the bearing to be inspected. The sample is prepared by a single process of coarse grinding, fine grinding, polishing, and cleaning. The sample is then immersed in the etchant and heated for etching. After etching, the sample is removed and cleaned to obtain the metal flowline morphology of the bearing race. This method provides a fixed etching time and temperature for the bearing race, is unaffected by bearing size, and clearly displays the metal flowlines of the bearing race. The operation is simple and helps improve the accuracy of bearing race forming methods and fatigue testing. Attached Figure Description

[0029] Figure 1 This is a flowchart of a corrosion method for detecting metal flow lines according to the present invention.

[0030] Figure 2 This is a flowchart illustrating the pretreatment process for bearing ring samples in a corrosion method for detecting metal flow lines according to the present invention.

[0031] Figure 3 The image shows the metal streamline pattern after corrosion using the corrosion method for metal streamline detection according to the present invention, where a is the hot forging streamline pattern and b is the rolling and expanding streamline pattern.

[0032] Figure 4 The diagram shows the streamlines of a metal after etching with hydrochloric acid aqueous solution using existing technology. In the diagram, a is the streamline diagram after etching with hydrochloric acid aqueous solution, and b is the streamline diagram after etching with hydrochloric acid aqueous solution without visible streamlines. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0038] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0039] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0040] This invention discloses a corrosive agent for metal flowline detection, comprising water, concentrated hydrochloric acid, ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate; wherein the volume ratio of water to concentrated hydrochloric acid is (12-20):(1-3); the mass ratio of ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate is (5-10):(5-10):(2-6):(5-15), and the mass ratio of ferric chloride to water is (1-2):(12-20).

[0041] This invention discloses a method for preparing the etchant for metal flowline detection as described above, comprising the following steps:

[0042] A corrosive agent is prepared by mixing water, concentrated hydrochloric acid, ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate in a specific ratio at room temperature.

[0043] The present invention also provides a corrosion method using the above-mentioned etchant for metal flowline detection, comprising the following steps:

[0044] S1: Take a sample of the bearing ring to be inspected to obtain a sample of the bearing ring to be inspected. Specifically, cut the bearing ring to be inspected along the axial direction of the bearing ring to be inspected to obtain a sample of the bearing ring to be inspected with a width of 8mm to 12mm.

[0045] S2: Pre-treatment of the bearing ring sample to be inspected to prepare a test specimen, specifically:

[0046] S2.1: Roughly grind the cut surface of the bearing ring sample to be inspected. Preferably, a surface grinder is used to rough grind the cut surface.

[0047] S2.2: The bearing ring sample to be inspected after coarse grinding is finely ground. Preferably, 400-mesh water phase sandpaper, 600-mesh water phase sandpaper and 800-mesh metal phase sandpaper are used in sequence to finely grind the bearing ring sample to be inspected after coarse grinding.

[0048] S2.3: Polish the bearing ring sample to be inspected after fine grinding. Preferably, coarse polishing is performed with canvas, followed by fine polishing with 1μm cloth.

[0049] S2.4: Clean and dry the polished bearing ring sample to be inspected to obtain the sample. Preferably, the sample is washed with water, then washed with ethanol, and then dried.

[0050] S3: Immerse the sample in the corrosive agent and heat it to corrode the sample, wherein the heating temperature is 85℃~95℃ and the heating time is 18~22min;

[0051] S4: After corrosion is complete, the sample is removed and cleaned to obtain the metal streamline morphology of the bearing ring to be inspected. Specifically, the corroded sample is immersed in anhydrous ethanol, shaken, and the corrosion products attached to the sample surface are cleaned off. Then the sample is removed, the sample surface is wiped with degreased cotton soaked in anhydrous ethanol, and then dried.

[0052] Example 1

[0053] A corrosive agent for detecting the metal flow lines of bearing rings is prepared by weighing 5g of ferric chloride and 8g of copper chloride and dissolving them in 100mL of water, stirring until fully dissolved, and then adding 10mL of concentrated hydrochloric acid and stirring until homogeneous; weighing 2g of citric acid and adding it to the above solution, stirring until completely dissolved; and weighing 7g of sodium dodecylbenzenesulfonate and adding it to the above solution, stirring until completely dissolved.

[0054] The method for using this etchant to inspect the metal flow lines of bearing rings is as follows:

[0055] First, a sample is cut from the bearing race to be inspected using an abrasive wheel cutter. The sample width is approximately 10 mm, and the cut surface is axial and basically perpendicular to the race surface. Sufficient cooling is ensured during the cutting process to prevent the cut surface from overheating.

[0056] Then, each cut surface was first coarsely ground using a flat grinder, then finely ground using 400-mesh aqueous phase sandpaper, 600-mesh aqueous phase sandpaper and 800-mesh metallographic sandpaper in sequence, and polished with canvas and 1μm cloth in sequence. After cleaning with water and ethanol, it was dried to prepare the sample.

[0057] Finally, place the sample in a beaker, ensuring the cut surface does not touch the beaker wall; add the above-mentioned etchant, ensuring the etchant completely covers the sample; heat the etchant to 90℃ and hold for 20 minutes; stir once or twice during the holding process.

[0058] Pour out the corrosive agent, add anhydrous ethanol, and gently shake the beaker to wash away the corrosion products adhering to the test surface; remove the sample, wipe the test surface with degreased cotton soaked in anhydrous ethanol, and then dry it with a hair dryer; see below. Figure 3 a. Observe the metal flow lines on the cut surface under a stereomicroscope. Based on the flow line morphology, it can be determined that the bearing ring was formed by hot forging and then machining.

[0059] Example 2

[0060] A corrosive agent for detecting the metal flow lines of bearing rings is prepared by weighing 7g of ferric chloride and 5g of copper chloride and dissolving them in 100mL of water, stirring until fully dissolved, and then adding 8mL of concentrated hydrochloric acid and stirring until homogeneous. 5g of citric acid and 10g of sodium dodecylbenzenesulfonate are weighed and added to the above solution, and stirred until completely dissolved to obtain the corrosive agent.

[0061] The method for using this etchant to inspect the metal flow lines of bearing rings is as follows:

[0062] First, a sample is cut from the bearing race to be inspected using an abrasive wheel cutter. The sample width is approximately 10 mm, and the cut surface is axial and basically perpendicular to the race surface. Sufficient cooling is ensured during the cutting process to prevent the cut surface from overheating.

[0063] Then, each cut surface was first coarsely ground using a flat grinder, then finely ground using 400-mesh aqueous phase sandpaper, 600-mesh aqueous phase sandpaper and 800-mesh metallographic sandpaper in sequence, and polished with canvas and 1μm cloth in sequence. After cleaning with water and ethanol, it was dried to prepare the sample.

[0064] Finally, place the sample in a beaker, ensuring the cut surface does not touch the beaker wall; add the above-mentioned etchant, ensuring the etchant completely covers the sample; heat the etchant to 90℃ and hold for 20 minutes; stir once or twice during the holding process.

[0065] Pour out the corrosive agent, add anhydrous ethanol, and gently shake the beaker to wash away the corrosion products adhering to the test surface; remove the sample, wipe the test surface with degreased cotton soaked in anhydrous ethanol, and then dry it with a hair dryer; see below. Figure 3b. Observe the metal flow lines on the cut surface under a stereomicroscope. Based on the flow line morphology, the bearing ring is determined to be formed by rolling and expanding.

[0066] Example 3

[0067] The etching solution was prepared by mixing 35% hydrochloric acid and water in a 1:1 volume ratio. First, a sample was cut from the bearing race under inspection using an abrasive wheel cutter. The sample width was approximately 10 mm, and the cut surface was axial, essentially perpendicular to the race surface. Sufficient cooling was ensured during the cutting process to prevent overheating of the cut surface.

[0068] Then, each cut surface was first coarsely ground using a flat grinder, then finely ground using 400-mesh aqueous phase sandpaper, 600-mesh aqueous phase sandpaper and 800-mesh metallographic sandpaper in sequence, and polished with canvas and 1μm cloth in sequence. After cleaning with water and ethanol, it was dried to prepare the sample.

[0069] Finally, place the sample in a beaker, ensuring the cut surface does not touch the beaker wall; add the above-mentioned etchant, ensuring the etchant completely covers the sample; heat the etchant to 90℃ and hold for 20 minutes; stir once or twice during the holding process.

[0070] Pour out the corrosive agent, add anhydrous ethanol, and gently shake the beaker to wash away the corrosion products adhering to the test surface; remove the sample, wipe the test surface with degreased cotton soaked in anhydrous ethanol, and then dry it with a hair dryer; see below. Figure 4 a. When observing the metal flow lines on the cut surface under a stereomicroscope, excessive corrosion makes the flow lines unclear, making it impossible to determine the forming method. See also Figure 4 b. Using a different bearing ring sample, the bearing ring etched with the same etchant did not show metal flow lines due to the short etching time, making it impossible to determine the forming method. This demonstrates that using existing etchants to etch different bearing rings requires adjusting the etching temperature and time according to the specific bearing ring type to control the degree of corrosion, making it difficult to control the corrosion level during operation.

[0071] In summary, this invention provides an etchant, its preparation method, and an etching method for detecting metal flow lines. This etchant provides a fixed etching time and temperature for bearing rings, unaffected by bearing size or model, and can clearly display the metal flow lines of the bearing rings. The operation method is simple, providing support for improving the accuracy of bearing ring forming methods and fatigue testing.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A corrosive agent for metal flowline detection, characterized in that, The mixture includes water, concentrated hydrochloric acid, ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate; wherein the volume ratio of water to concentrated hydrochloric acid is (12-20):(1-3); the mass ratio of ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate is (5-10):(5-10):(2-6):(5-15), and the mass ratio of ferric chloride to water is (1-2):(12-20).

2. The method for preparing the etchant for metal flowline detection as described in claim 1, characterized in that, Includes the following steps: A corrosive agent is prepared by mixing water, concentrated hydrochloric acid, ferric chloride, copper chloride, citric acid, and sodium dodecylbenzenesulfonate in a specific ratio.

3. The method for preparing an etchant for metal flowline detection according to claim 2, characterized in that, The etchant was prepared at room temperature.

4. The etching method using the etchant for metal flowline detection as described in claim 1, characterized in that, Includes the following steps: Take a sample of the bearing ring to be inspected to obtain the bearing ring sample; The bearing ring sample to be inspected is pretreated to prepare a test specimen. The sample is immersed in a corrosive agent and heated to etch it; the heating temperature is 85℃~95℃ and the heating time is 18~22min. After corrosion, the sample was removed and cleaned to obtain the metal streamline morphology of the bearing ring to be inspected.

5. The corrosion method for detecting metal flow lines according to claim 4, characterized in that, The specific procedure for sampling the bearing ring to be tested is as follows: cut the bearing ring to be tested along the axial direction to obtain a sample of the bearing ring to be tested with a width of 8mm to 12mm.

6. The corrosion method for detecting metal flow lines according to claim 5, characterized in that, The specific steps for pre-treating the bearing ring sample to be inspected and preparing the specimen are as follows: The cut surface of the bearing ring sample to be inspected is roughly ground; The bearing ring samples to be inspected after rough grinding are then finely ground. The bearing ring samples to be inspected after fine grinding are polished. The polished bearing ring sample to be inspected is cleaned and dried to obtain the test sample.

7. The corrosion method for detecting metal flow lines according to claim 6, characterized in that, The bearing ring samples to be inspected after coarse grinding were then finely ground using 400-mesh aqueous phase sandpaper, 600-mesh aqueous phase sandpaper, and 800-mesh metallographic sandpaper in sequence.

8. The corrosion method for detecting metal flow lines according to claim 6, characterized in that, The finely ground bearing ring samples were polished using canvas and velvet.

9. The corrosion method for detecting metal flow lines according to claim 4, characterized in that, The method for cleaning the sample is as follows: Immerse the corroded sample in anhydrous ethanol, shake it to clean off the corrosion products attached to the sample surface, then take out the sample, wipe the sample surface with degreased cotton soaked in anhydrous ethanol, and blow it dry.

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