A cold etching solution for low-magnification corrosion detection of steel materials and a detection method thereof

Abstract

The application discloses a kind of cold etching liquid for steel material low multiple corrosion detection, it is two liquid systems, including first cold etching liquid and second cold etching liquid;With mass percentage, the first cold etching liquid is as follows: the content of sodium chloride is 2~8%, the content of stannous chloride is 3~9%, hydrochloric acid 10~30%, ethanol 20~50%, and the rest is water;Second cold etching liquid is as follows: the content of magnesium chloride is 3~9%, the content of boric acid is 3~8%, hydrochloric acid 10~30%, ethanol 20~50%, and the rest is water.The advantages of the present application are to quickly and clearly show the internal low multiple organization of steel material at room temperature, safe and environmentally friendly, improve detection efficiency and detection effect, improve the quality control of steel products.

Description

Technical Field

[0001] This invention belongs to the field of metal material testing reagent technology, and particularly relates to a cold etching solution for low-magnification corrosion detection of steel materials and its detection method. Background Technology

[0002] In the steel production process, inspecting the internal structure of products such as continuously cast billets and steel plates is a key step in ensuring product quality.

[0003] Traditional detection methods, such as the sulfur print test, typically use a diluted solution of concentrated sulfuric acid as an etching agent to reveal the sulfur distribution and segregation within the steel. However, this method has significant drawbacks: firstly, concentrated sulfuric acid is a strictly regulated hazardous chemical, and its preparation and use pose a high safety threat to operators; secondly, the waste liquid generated after etching contains strong acid, and improper handling can cause serious environmental pollution; thirdly, for certain materials or structures, the etching effect of concentrated sulfuric acid is not ideal, potentially leading to unclear microstructure and difficulty in identifying defects, thus affecting the accuracy and reliability of the test. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of high safety risks, significant environmental pollution, poor corrosion effect, and low detection accuracy of existing corrosive agents. It provides a cold etching solution for low-magnification corrosion detection of steel materials, which can quickly and clearly display the internal low-magnification structure of steel materials at room temperature. It is safe and environmentally friendly, improves detection efficiency and effect, and enhances the quality control of steel products.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A cold etching solution for low-magnification corrosion detection of steel materials, which is a two-liquid system, including a first cold etching solution and a second cold etching solution; The first etching solution, by mass percentage, consists of: 2-8% sodium chloride, 3-9% stannous chloride, 10-30% hydrochloric acid, 20-50% ethanol, and the remainder is water. The second cold etching solution consists of: 3-9% magnesium chloride, 3-8% boric acid, 10-30% hydrochloric acid, 20-50% ethanol, and the remainder is water.

[0006] This invention also provides a method for low-magnification corrosion detection of steel materials using the above-mentioned cold etching solution. This method is performed at room temperature and includes the following steps: S1, Sample preparation: Cut the billet or steel plate sample to be tested, grind it flat with a grinding machine, and polish it until the surface roughness of the polished sample reaches 0.5 to 0.8 µm. S2, Sample cleaning: Rinse the polished sample with clean water to remove surface impurities and polishing residue, and then use a cold air blower to dry the sample surface. S3, First Etching: Apply the first cold etching solution evenly to the dry sample surface, let it stand for 5-8 minutes, then rinse the sample with clean water and dry it again. S4, Second Etching: Apply the second cold etching solution evenly to the sample surface that has been etched and dried after the first etching, let it stand for 5-8 minutes again, then rinse the sample with clean water and dry it. S5, Microstructure Rating: The specimens that have undergone two etching processes and are finally dried are observed, and their low-magnification microstructure is analyzed and rated.

[0007] Compared with the prior art, the advantages of the technical solution of the present invention are as follows: (1) Safe and environmentally friendly, green detection: This invention uses green substances such as sodium chloride, stannous chloride, magnesium chloride, boric acid, hydrochloric acid, and ethanol for low-magnification detection, replacing concentrated sulfuric acid in the traditional process, which significantly reduces the safety risks in the operation process and avoids physical harm to the operators. At the same time, since the waste liquid is relatively mild and easy to treat, it reduces the pollution to the environment in the heavy industrial production process and realizes the green and sustainable ecological development strategy. (2) High efficiency, clear and accurate: The present invention adopts a unique dual-liquid composition formula, which can quickly and selectively dissolve the solidified structure of steel under normal temperature conditions, forming a relief image with clear outline and distinct layers. In a short time, it can more clearly reveal the internal structure, segregation, porosity, cracks and other defects of steel, which significantly improves the detection efficiency and accuracy. (3) Simple operation and energy saving: The entire detection process of this invention is carried out at room temperature without the need for heating equipment, which saves energy. At the same time, since each component can be quickly dissolved in water at room temperature and can be analyzed in water as a conventional substance, it is easy to dissolve and prepare. Therefore, the operation process is simple and reduces the skill requirements of the operators. Attached Figure Description

[0008] Figure 1 This is a diagram showing the corrosion effect of the etchant in Embodiment 2 of the present invention. Detailed Implementation Example 1

[0009] To make the present invention clearer, the following description, in conjunction with the accompanying drawings, further illustrates a cold etching solution for low-magnification corrosion detection of steel materials. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0010] In this embodiment, taking a continuously cast slab of 370*2570mm and steel grade A as an example, a low-magnification metallographic cold corrosion test of the slab is performed, specifically as follows: The composition and mass percentage of the first etchant used include: 5% sodium chloride, 6% stannous chloride, 20% hydrochloric acid, 30% ethanol, and the remainder is water.

[0011] The composition and mass percentage of the second etchant used include: 6% magnesium chloride, 5% boric acid, 20% hydrochloric acid, 40% ethanol, and the remainder is water.

[0012] The testing steps for low-magnification corrosion detection of steel materials using the above-mentioned cold etching solution include: S1: After the billet and steel plate samples are cut, they are ground flat by a grinding machine and polished. The roughness of the polished sample is 0.6µm. S2: The polished sample is placed flat on the sample bed for pre-test preparation. S3: Rinse the sample with clean water to remove impurities from the sample surface. After rinsing, dry the sample with a cold air blower and apply the first cold etching solution. After applying, let it stand for 6 minutes, rinse it with water and dry it. S4: After the sample is dried, apply the second cold etching solution, let it stand for 6 minutes, rinse it with water and dry it. S5: After the sample is dried, the microstructure of the billet or steel plate sample is evaluated at low magnification. Example 2

[0013] In this embodiment, taking steel plate B (30*4342mm) as an example, a low-magnification metallographic cold corrosion test of the slab is performed, specifically as follows: The composition and mass percentage of the first etchant used include: 4% sodium chloride, 5% stannous chloride, 15% hydrochloric acid, 20% ethanol, and the remainder is water.

[0014] The composition and mass percentage of the second cold etching solution used include: 5% magnesium chloride, 6% boric acid, 30% hydrochloric acid, 30% ethanol, and the balance being water.

[0015] The testing steps for low-magnification corrosion detection of steel materials using the above-mentioned cold etching solution include: S1: After the billet and steel plate samples are cut, they are ground flat by a grinding machine and polished. The roughness of the polished sample is 0.5µm. S2: The polished sample is placed flat on the sample bed for pre-test preparation. S3: Rinse the sample with clean water to remove impurities from the sample surface. After rinsing, dry the sample with a cold air blower and apply the first cold etching solution. After applying, let it stand for 5 minutes, rinse it with water and dry it. S4: After the sample is dried, apply the second cold etching solution, let it stand for 5 minutes, rinse it with water and dry it. S5: After the sample is dried, the microstructure of the billet or steel plate sample is evaluated at low magnification.

[0016] The corrosion effect of the cold etchant is as follows Figure 1 As shown, the process is quick and efficient, creating a clear relief image on the steel plate surface that accurately reflects its internal structure. Example 3

[0017] In this embodiment, the boundary conditions were verified using the following formulations: 2% sodium chloride, 3% stannous chloride, 10% hydrochloric acid, 20% ethanol, with the remainder being water; and 9% magnesium chloride, 8% boric acid, 30% hydrochloric acid, 50% ethanol, with the remainder being water.

[0018] Testing Procedure: The steel sample to be tested shall be processed according to steps S1 to S5 as described in the technical solution. Specifically, the roughness of the sample after polishing in step S1 shall be 0.8 µm; the settling time for steps S3 and S4 shall both be 8 min.

[0019] Working process: Initial etching is performed using a first cold etching solution with component concentrations at the lower limit of the range for 8 minutes; followed by fine etching using a second cold etching solution with component concentrations at the upper limit of the range, also for 8 minutes. The extended etching time compensates for the lower etching rate of the first solution, and the high concentration of the second solution enhances the development effect.

[0020] The results of testing using the cold etching solution of this embodiment show that even under boundary conditions of component concentration, by adjusting the etching time, it is still possible to effectively etch steel samples and obtain clear low-magnification microstructure images that can be used for rating. Example 4

[0021] In this embodiment, the boundary conditions are verified again. The first cold etching solution formula is: 8% sodium chloride, 9% stannous chloride, 30% hydrochloric acid, 50% ethanol, and the remainder is water; the second cold etching solution formula is: 3% magnesium chloride, 3% boric acid, 10% hydrochloric acid, 20% ethanol, and the remainder is water.

[0022] Testing Procedure: The steel sample to be tested shall be processed according to steps S1 to S5 as described in the technical solution. Specifically, the sample roughness after polishing in step S1 shall be 0.5 µm; the settling time for steps S3 and S4 shall both be 5 min.

[0023] Working process: A high-concentration first cold etching solution is used for rapid and powerful initial etching, which takes 5 minutes; then a low-concentration second cold etching solution is used for gentle development, also taking 5 minutes. The effectiveness of the first solution is utilized to shorten the overall detection time.

[0024] This embodiment demonstrates that, with a combination of a high-concentration first solution and a low-concentration second solution, and a shorter etching time, rapid and effective low-magnification tissue detection can still be achieved. In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A cold etching solution for low-magnification corrosion detection of steel materials, characterized in that: The etching solution is a two-component system, consisting of a first etching solution and a second etching solution; The first etching solution, by mass percentage, consists of: 2-8% sodium chloride, 3-9% stannous chloride, 10-30% hydrochloric acid, 20-50% ethanol, and the remainder is water. The second cold etching solution consists of: 3-9% magnesium chloride, 3-8% boric acid, 10-30% hydrochloric acid, 20-50% ethanol, and the remainder is water.

2. The etchant for low-magnification corrosion detection of steel materials according to claim 1, characterized in that: The first cold etching solution comprises, by weight percentage: 5% sodium chloride, 6% stannous chloride, 20% hydrochloric acid, 30% ethanol, with the balance being water; the second cold etching solution comprises, by weight percentage: 6% magnesium chloride, 5% boric acid, 20% hydrochloric acid, 40% ethanol, with the balance being water.

3. The etchant for low-magnification corrosion detection of steel materials according to claim 1, characterized in that: The first cold etching solution comprises, by weight percentage: 4% sodium chloride, 5% stannous chloride, 15% hydrochloric acid, 20% ethanol, with the remainder being water; the second cold etching solution comprises, by weight percentage: 5% magnesium chloride, 6% boric acid, 30% hydrochloric acid, 30% ethanol, with the remainder being water.

4. The etchant for low-magnification corrosion detection of steel materials according to claim 1, characterized in that: The first cold etching solution comprises, by weight percentage: 2% sodium chloride, 3% stannous chloride, 10% hydrochloric acid, 20% ethanol, with the balance being water; the second cold etching solution comprises, by weight percentage: 9% magnesium chloride, 8% boric acid, 30% hydrochloric acid, 50% ethanol, with the balance being water.

5. The etchant for low-magnification corrosion detection of steel materials according to claim 1, characterized in that: The first cold etching solution comprises, by weight percentage: 8% sodium chloride, 9% stannous chloride, 30% hydrochloric acid, 50% ethanol, with the remainder being water; the second cold etching solution comprises, by weight percentage: 3% magnesium chloride, 3% boric acid, 10% hydrochloric acid, 20% ethanol, with the remainder being water.

6. A method for low-magnification corrosion detection of steel materials using the etchant as described in claim 1, characterized in that: Performed at room temperature, including the following steps: S1, Sample preparation: Cut the billet or steel plate sample to be tested, grind it flat with a grinding machine, and polish it until the surface roughness of the polished sample reaches 0.5 to 0.8 µm. S2, Sample cleaning: Rinse the polished sample with clean water to remove surface impurities and polishing residue, and then use a cold air blower to dry the sample surface. S3, First Etching: Apply the first cold etching solution evenly to the dry sample surface, let it stand for 5-8 minutes, then rinse the sample with clean water and dry it again. S4, Second Etching: Apply the second cold etching solution evenly to the sample surface that has been etched and dried after the first etching, let it stand for 5-8 minutes again, then rinse the sample with clean water and dry it. S5, Microstructure Rating: The specimens that have undergone two etching processes and are finally dried are observed, and their low-magnification microstructure is analyzed and rated.

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