Metallographic corrosive agent for austenitic stainless steel welded joint and corrosion method of metallographic corrosive agent

Abstract

The invention discloses an austenitic stainless steel welded joint metallographic corrosive agent and a corrosion method thereof, and belongs to the technical field of metal material detection. Dissolving picric acid in deionized water until the solution is saturated to obtain a saturated picric acid aqueous solution; dissolving ferric chloride and hydrochloric acid in a solvent to obtain a ferric chloride hydrochloric acid solution; and after the saturated picric acid aqueous solution and the ferric chloride hydrochloric acid solution are evenly mixed, a hand sanitizer containing a surfactant is added and evenly mixed, and the austenitic stainless steel welding metallographic corrosive agent is obtained. After the metallographic structure of the austenitic stainless steel welded joint is corroded, the metallographic structure is clear, dendrites and sizes of the austenitic stainless steel welded joint can be accurately distinguished, and then the metallographic structure, grain size and other data of the austenitic stainless steel welded joint can be accurately obtained, so that the welding process can be adjusted in time; the method is very important for improving the performance of the austenitic stainless steel welded joint.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material detection, and in particular relates to a novel metallographic corrosive agent for austenitic stainless steel welding joints. Background Art

[0002] Austenitic stainless steel is a special steel with high alloy content, which is often used for important parts. The quality of its welded joints is extremely important to the life and safety of the equipment. In the welding process of austenitic stainless steel, different metallographic structures are often obtained due to differences in welding processes, so the performance of austenitic stainless steel welded joints is also different. In order to obtain austenitic stainless steel welded joints with the required performance, metallographic corrosive agents are usually used to corrode them and then observe the metallographic structure, and combined with performance test data, the welding process is adjusted in time to ensure high-quality welded joints.

[0003] The patent application with publication number CN 109628933 A discloses a stainless steel metallographic etchant and its application method. The metallographic etchant comprises the following components: concentrated nitric acid solution, anhydrous ethanol solution and ferric chloride solution. Through the synergistic effect between different solutions, the phase boundary of deformed stainless steel and the grain boundary of powder metallurgy stainless steel can be quickly and clearly revealed. Compared with the existing dilute aqua regia or ferric chloride etchants, the application claims that the prepared etchant has a steady and slow corrosion process, and will not cause over-corrosion to the grain boundary of powder metallurgy stainless steel when corroding the phase boundary of deformed stainless steel, which provides great convenience for the subsequent detection of welding quality.

[0004] However, it is difficult to obtain good corrosion effect when corroding austenitic stainless steel welded joint samples with common metallographic corrosive agents. Specifically, it will confuse the grain boundary or grain characteristics of the metallographic structure of the austenitic stainless steel welded joint, which will have an adverse effect on the observation of the metallographic structure, thereby affecting the improvement of the welding process. In view of this, it is necessary to develop a metallographic corrosive agent and a corrosion method for austenitic stainless steel welded joints to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a novel metallographic etchant for austenitic stainless steel welded joints and a method for etching the same, which can clearly display the grain boundaries of the metallographic structure and improve the performance of austenitic stainless steel welded joints.

[0006] The first object of the present invention is to provide a metallographic etching agent for austenitic stainless steel welded joints.

[0007] The invention discloses a metallographic etching agent for an austenitic stainless steel welding joint, comprising a picric acid aqueous solution, a ferric chloride hydrochloric acid solution and a hand washing liquid containing a surfactant.

[0008] Furthermore, the picric acid aqueous solution is prepared by dissolving picric acid in deionized water until a saturated picric acid aqueous solution is obtained.

[0009] Furthermore, the dosage ratio of ferric chloride, hydrochloric acid and solvent in the ferric chloride hydrochloric acid solution is (6-10) g: (12-18) mL: (120-150) mL.

[0010] Furthermore, the solvent is deionized water or anhydrous ethanol.

[0011] Furthermore, the hand sanitizer containing a surfactant is a hand sanitizer containing a surfactant APG.

[0012] Furthermore, the usage ratio of the picric acid aqueous solution, the ferric chloride hydrochloric acid solution and the hand sanitizer containing a surfactant is (80-120) mL: (130-180) mL: (20-40) g.

[0013] The second object of the present invention is to provide a method for preparing a metallographic etching agent for austenitic stainless steel welded joints.

[0014] A method for preparing a metallographic etching agent for austenitic stainless steel welding joints comprises the following steps:

[0015] After the picric acid aqueous solution and the ferric chloride hydrochloric acid solution are mixed evenly, a hand washing liquid containing a surfactant is added and mixed evenly to obtain a metallographic etching agent for austenitic stainless steel welding joints.

[0016] The third object of the present invention is to provide a method for metallographic corrosion of austenitic stainless steel welded joints.

[0017] A method for metallographic corrosion of austenitic stainless steel welded joints, the specific steps are as follows:

[0018] Performing metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain the austenitic stainless steel weld joint to be corroded;

[0019] The austenitic stainless steel weld joint to be corroded is immersed in a metallographic corrosive agent for the austenitic stainless steel weld joint, cleaned and dried to obtain a corroded austenitic stainless steel weld joint.

[0020] Furthermore, the soaking time is 60s to 180s.

[0021] Furthermore, the method for metallographic corrosion of austenitic stainless steel welded joints comprises the following steps:

[0022] Performing metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain the austenitic stainless steel weld joint to be corroded;

[0023] The surface of the austenitic stainless steel weld joint to be corroded is wiped with a liquid-absorbing cloth dipped in a metallographic corrosive agent for the austenitic stainless steel weld joint, and then cleaned and dried to obtain the corroded austenitic stainless steel weld joint.

[0024] Furthermore, the number of wiping is 20-100 times.

[0025] Furthermore, the cleaning is one of ultrasonic cleaning or alcohol rinsing; the ultrasonic cleaning time is 1 min to 10 min, and the alcohol rinsing time is 5 s to 20 s.

[0026] Furthermore, the drying is drying by oven drying, blow drying with a hair dryer or natural air drying.

[0027] Beneficial effects of the present invention:

[0028] (1) The present invention provides a metallographic etchant and a corrosion method for an austenitic stainless steel weld joint. After the metallographic structure of the austenitic stainless steel weld joint is corroded by a mixed etchant prepared by a picric acid aqueous solution, a ferric chloride hydrochloric acid solution and a hand soap containing a surfactant, the metallographic structure is clear, and the dendrites and their sizes of the austenitic stainless steel weld joint can be accurately distinguished, thereby accurately obtaining data such as the metallographic structure and grain size of the austenitic stainless steel weld joint, based on which the welding process can be adjusted in time, which is extremely important for improving the performance of the austenitic stainless steel weld joint.

[0029] (2) The surfactant APG contained in the hand sanitizer used in the present invention can effectively reduce the surface tension of the liquid, weaken the adhesion between impurities and the surface of the austenitic stainless steel weld joint, so that the metallographic corrosive agent is more easily penetrated, making the corrosion more thorough; on the other hand, the surfactant APG can increase the solubility of ferric chloride, make it evenly distributed, further reduce the surface tension of the liquid, and improve the corrosion effect; in addition, the surfactant APG also has good biodegradability and can be decomposed by microorganisms more quickly in the natural environment, reducing pollution to the environment and meeting environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below in conjunction with the accompanying drawings.

[0031] Figure 1 The metallographic structure of the austenitic stainless steel weld joint after corrosion obtained by the method of Example 1 of the present invention under a microscope. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides a metallographic etchant for an austenitic stainless steel weld joint and a method for etching the same, comprising the following steps:

[0035] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid aqueous solution; dissolve 8 g of analytical pure ferric chloride and 15 mL of hydrochloric acid in 130 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid aqueous solution and 150 mL of the ferric chloride hydrochloric acid solution, add 30 g of hand sanitizer containing a surfactant APG and mix well to obtain an austenitic stainless steel welding metallographic etchant;

[0036] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 120 seconds, perform ultrasonic cleaning for 5 minutes, and blow dry with a hair dryer to obtain a corroded austenitic stainless steel weld joint.

[0037] Observe the metallographic structure under a microscope. Figure 1 shown.

[0038] Example 2

[0039] Compared with Example 1, the difference between this example and Example 1 is that "8 g of analytically pure ferric chloride and 15 mL of hydrochloric acid are dissolved in 130 mL of anhydrous ethanol" in S1 is changed to "6 g of analytically pure ferric chloride and 18 mL of hydrochloric acid are dissolved in 120 mL of anhydrous ethanol", and the specific implementation steps are as follows:

[0040] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid aqueous solution; dissolve 6 g of analytical pure ferric chloride and 18 mL of hydrochloric acid in 120 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid aqueous solution and 150 mL of the ferric chloride hydrochloric acid solution, add 30 g of hand sanitizer containing a surfactant APG and mix well to obtain an austenitic stainless steel welding metallographic etchant;

[0041] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 120 seconds, perform ultrasonic cleaning for 5 minutes, and blow dry with a hair dryer to obtain a corroded austenitic stainless steel weld joint.

[0042] The remaining raw materials and preparation process remain the same as in Example 1.

[0043] Example 3

[0044] Compared with Example 1, the difference between this example and Example 1 is that "8 g of analytically pure ferric chloride and 15 mL of hydrochloric acid are dissolved in 130 mL of anhydrous ethanol" in S1 is changed to "10 g of analytically pure ferric chloride and 12 mL of hydrochloric acid are dissolved in 150 mL of anhydrous ethanol", and the specific implementation steps are as follows:

[0045] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid aqueous solution; dissolve 10 g of analytical pure ferric chloride and 12 mL of hydrochloric acid in 150 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid aqueous solution and 150 mL of the ferric chloride hydrochloric acid solution, add 30 g of hand sanitizer containing a surfactant APG and mix well to obtain an austenitic stainless steel welding metallographic etchant;

[0046] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 120 seconds, perform ultrasonic cleaning for 5 minutes, and blow dry with a hair dryer to obtain a corroded austenitic stainless steel weld joint.

[0047] The remaining raw materials and preparation process remain the same as in Example 1.

[0048] Example 4

[0049] Compared with Example 1, the difference between this embodiment and Example 1 is that the "100 mL saturated picric acid aqueous solution and 150 mL ferric chloride hydrochloric acid solution, 30 g of hand sanitizer containing surfactant APG" in S1 is changed to "80 mL saturated picric acid aqueous solution and 130 mL ferric chloride hydrochloric acid solution, 40 g of hand sanitizer containing surfactant APG", and the specific implementation steps are as follows:

[0050] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid aqueous solution; dissolve 8 g of analytical pure ferric chloride and 15 mL of hydrochloric acid in 130 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 80 mL of the saturated picric acid aqueous solution and 130 mL of the ferric chloride hydrochloric acid solution, add 40 g of hand sanitizer containing a surfactant APG and mix well to obtain an austenitic stainless steel welding metallographic etchant;

[0051] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 120 seconds, perform ultrasonic cleaning for 5 minutes, and blow dry with a hair dryer to obtain a corroded austenitic stainless steel weld joint.

[0052] Example 5

[0053] Compared with Example 1, the difference between this embodiment and Example 1 is that the "100 mL saturated picric acid aqueous solution and 150 mL ferric chloride hydrochloric acid solution, 30 g of hand sanitizer containing surfactant APG" in S1 is changed to "120 mL saturated picric acid aqueous solution and 180 mL ferric chloride hydrochloric acid solution, 20 g of hand sanitizer containing surfactant APG", and the specific implementation steps are as follows:

[0054] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid aqueous solution; dissolve 8 g of analytical pure ferric chloride and 15 mL of hydrochloric acid in 130 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 120 mL of the saturated picric acid aqueous solution and 180 mL of the ferric chloride hydrochloric acid solution, add 20 g of hand sanitizer containing a surfactant APG and mix well to obtain an austenitic stainless steel welding metallographic etchant;

[0055] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 120 seconds, perform ultrasonic cleaning for 5 minutes, and blow dry with a hair dryer to obtain a corroded austenitic stainless steel weld joint.

[0056] Example 6

[0057] Compared with Example 1, the difference between this embodiment and Example 1 is that the "anhydrous ethanol" in S1 is changed to "deionized water". The specific implementation steps are as follows:

[0058] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid aqueous solution; dissolve 8 g of analytical pure ferric chloride and 15 mL of hydrochloric acid in 130 mL of deionized water to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid aqueous solution and 150 mL of the ferric chloride hydrochloric acid solution, add 30 g of hand sanitizer containing a surfactant APG and mix well to obtain an austenitic stainless steel welding metallographic etchant;

[0059] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 120 seconds, perform ultrasonic cleaning for 5 minutes, and blow dry with a hair dryer to obtain a corroded austenitic stainless steel weld joint.

[0060] The remaining raw materials and preparation process remain the same as in Example 1.

[0061] Example 7

[0062] Compared with Example 1, the difference between this embodiment and Example 1 is that the treatment method "immersing" in S2 is changed to "wiping with liquid-absorbing cloth", and the specific implementation steps are as follows:

[0063] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid aqueous solution; dissolve 8 g of analytical pure ferric chloride and 15 mL of hydrochloric acid in 130 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid aqueous solution and 150 mL of the ferric chloride hydrochloric acid solution, add 30 g of hand sanitizer containing a surfactant APG and mix well to obtain an austenitic stainless steel welding metallographic etchant;

[0064] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; wipe the surface of the austenitic stainless steel weld joint to be corroded with an absorbent cloth dipped in a metallographic corrosive agent for the austenitic stainless steel weld joint, wipe 50 times, ultrasonically clean for 5 minutes, and blow dry with a hair dryer to obtain a corroded austenitic stainless steel weld joint.

[0065] The remaining raw materials and preparation process remain the same as in Example 1.

[0066] Comparative Example 1

[0067] Compared with Example 1, this comparative example differs in that the hand sanitizer containing the surfactant APG is not added, and the specific implementation steps are as follows:

[0068] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid aqueous solution; dissolve 8 g of analytical pure ferric chloride and 15 mL of hydrochloric acid in 130 mL of anhydrous ethanol to obtain a ferric chloride hydrochloric acid solution; mix 100 mL of the saturated picric acid aqueous solution and 150 mL of the ferric chloride hydrochloric acid solution to obtain an austenitic stainless steel welding metallographic etchant;

[0069] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 120 seconds, perform ultrasonic cleaning for 5 minutes, and blow dry with a hair dryer to obtain a corroded austenitic stainless steel weld joint.

[0070] The remaining raw materials and preparation process remain the same as in Example 1.

[0071] Comparative Example 2

[0072] This comparative example is compared with Example 1, except that no ferric chloride is added, and the specific implementation steps are as follows:

[0073] S1. Dissolve picric acid in deionized water until saturated to obtain a saturated picric acid aqueous solution; dissolve 12 mL of hydrochloric acid in 150 mL of anhydrous ethanol to obtain a hydrochloric acid solution; mix 100 mL of the saturated picric acid aqueous solution and 150 mL of the hydrochloric acid solution, add 30 g of hand sanitizer containing a surfactant APG and mix well to obtain an austenitic stainless steel welding metallographic etchant;

[0074] S2. Perform metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain an austenitic stainless steel weld joint to be corroded; immerse the austenitic stainless steel weld joint to be corroded in an austenitic stainless steel weld joint metallographic corrosive for 120 seconds, perform ultrasonic cleaning for 5 minutes, and blow dry with a hair dryer to obtain a corroded austenitic stainless steel weld joint.

[0075] The remaining raw materials and preparation process remain the same as in Example 1.

[0076] Performance Test:

[0077] The corroded austenitic stainless steel welded joints obtained in Example 1-7 and Comparative Example 1-2 were observed under a microscope. Figure 1 The metallographic structure of the corroded austenitic stainless steel weld joint under a microscope is obtained in Example 1.

[0078] After the metallographic structure of the austenitic stainless steel weld joint is corroded by a mixed corrosive agent prepared by picric acid aqueous solution, ferric chloride hydrochloric acid solution and surfactant, the metallographic structure is clear, and the dendrites and their sizes of the austenitic stainless steel weld joint can be accurately distinguished, and then the metallographic structure, grain size and other data of the austenitic stainless steel weld joint can be accurately obtained. Based on this, the welding process can be adjusted in time, which is extremely important for improving the performance of austenitic stainless steel weld joints.

[0079] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0080] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A metallographic etchant for austenitic stainless steel welded joints, characterized in that: These include picric acid aqueous solution, ferric chloride hydrochloric acid solution, and hand sanitizer containing surfactant; The dosage ratio of the picric acid aqueous solution, the ferric chloride hydrochloric acid solution and the hand washing liquid containing a surfactant is (80-120) mL: (130-180) mL: (20-40) g.

2. The metallographic etching agent for austenitic stainless steel welded joints according to claim 1, characterized in that: The picric acid aqueous solution is prepared by dissolving picric acid in deionized water until a saturated picric acid aqueous solution is obtained.

3. The metallographic etching agent for austenitic stainless steel welded joints according to claim 1, characterized in that: The hand washing liquid containing a surfactant is a hand washing liquid containing a surfactant APG.

4. The metallographic etching agent for austenitic stainless steel welded joints according to claim 1, characterized in that: The dosage ratio of ferric chloride, hydrochloric acid and solvent in the ferric chloride hydrochloric acid solution is (6-10) g: (12-18) mL: (120-150) mL.

5. The metallographic etching agent for austenitic stainless steel welded joints according to claim 4, characterized in that: The solvent is deionized water or anhydrous ethanol.

6. A method for preparing a metallographic etching agent for austenitic stainless steel welded joints according to any one of claims 1 to 5, characterized in that: The following steps are involved: After the picric acid aqueous solution and the ferric chloride hydrochloric acid solution are mixed evenly, a hand washing liquid containing a surfactant is added and mixed evenly to obtain a metallographic etching agent for austenitic stainless steel welding joints.

7. A method for metallographic corrosion of an austenitic stainless steel weld joint according to any one of claims 1 to 6, characterized in that: The following steps are involved: Performing metallographic sample preparation and cleaning on the surface of the austenitic stainless steel weld joint to obtain the austenitic stainless steel weld joint to be corroded; The austenitic stainless steel weld joint to be corroded is treated with an austenitic stainless steel weld joint metallographic corrosive agent, cleaned and dried to obtain a corroded austenitic stainless steel weld joint.

8. The method for metallographic corrosion of austenitic stainless steel welded joints according to claim 7, characterized in that: The treatment includes soaking or wiping; the soaking time is 60s to 180s; the wiping times are 20-100 times.

9. The method for metallographic corrosion of austenitic stainless steel welded joints according to claim 7, characterized in that: The cleaning is one of ultrasonic cleaning or alcohol rinsing; the ultrasonic cleaning time is 1min to 10min, and the alcohol rinsing time is 5s to 20s.

10. The method for metallographic corrosion of austenitic stainless steel welded joints according to claim 7, characterized in that: The drying may be drying by oven drying, blow drying with a hair dryer or natural air drying.

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