Metallographic phase corrosion method displaying austenitic stainless steel grain boundary

An austenitic stainless steel, metallographic corrosion technology, applied in the field of heat treatment, can solve the problems of affecting the grain size rating, inconvenient metallographic structure analysis, and inability to distinguish grains, etc., to achieve simple assembly, low cost, and repeatability. Good results

Inactive Publication Date: 2014-01-08
NANCHANG HANGKONG UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

After forging or heat treatment of austenitic stainless steel, there are a large number of twins inside the grains. When the existing methods are used for corrosion detection, the twin boundaries and grain boundaries inside the grains are often corro

Method used

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  • Metallographic phase corrosion method displaying austenitic stainless steel grain boundary
  • Metallographic phase corrosion method displaying austenitic stainless steel grain boundary
  • Metallographic phase corrosion method displaying austenitic stainless steel grain boundary

Examples

Experimental program
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Example Embodiment

[0034] Example 1

[0035] First add 1g of sodium chloride to 30ml of distilled water, then add 0.1g of potassium thiocyanate to the sodium chloride solution, and finally add 70ml of 65% nitric acid to the above configured solution slowly, and stir Evenly. The 304 austenitic stainless steel heat-treated at 1150°C for 120 minutes is processed into a sample to be corroded, polished and cleaned, and then connected to a DC stabilized power supply. The sample is connected to the positive electrode, the titanium plate is connected to the negative electrode, the voltage is 3.0V, and the time is 60s. The power is cut off, the sample is removed, rinsed with distilled water, and then washed and dried with alcohol, and the grain size is observed with a metallurgical microscope. figure 1 Shown. The grain boundaries are clear, the grains are uniform, and the grain twins are few or not obvious, which is conducive to the evaluation of grain size.

Example Embodiment

[0036] Example 2:

[0037] First add 3g of sodium chloride to 50ml of distilled water, then add 0.5g of potassium thiocyanate to the sodium chloride solution, and finally add 50ml of 65% nitric acid to the above configured solution slowly, and stir Evenly. The 316LN austenitic stainless steel heat-treated at 1100°C for 30 minutes is processed into a sample to be corroded, polished and cleaned, and then connected to a DC stabilized power supply. The sample is connected to the positive electrode, the titanium plate is connected to the negative electrode, the voltage is 0.5V, and the time is 240s. The power is cut off, the sample is rinsed with distilled water, and then rinsed and dried with alcohol, and the grain size is observed with a metallurgical microscope. figure 2 Shown. The grain boundaries are clear, both large and small grains are corroded, and the grain twins are not obvious, which is conducive to the evaluation of grain size.

Example Embodiment

[0038] Example 3:

[0039] First add 2g of sodium chloride to 40ml of distilled water, then add 0.3g of potassium thiocyanate to the sodium chloride solution, and finally add 60ml of 65% nitric acid to the above configured solution slowly, and stir Evenly. The 316LN austenitic stainless steel heat-treated at 1050°C for 10 minutes is processed into a sample to be corroded, polished and cleaned, and then connected to a DC stabilized power supply. The sample is connected to the positive electrode, the titanium plate is connected to the negative electrode, the voltage is 1.5V, the time is 100s, the power is cut off, the sample is removed, rinsed with distilled water, and then rinsed and dried with alcohol, and the grain size is observed with a metallurgical microscope. image 3 Shown. The grain boundaries are clear, the grains are fine and small, and the grains are twin-free, which is conducive to the evaluation of grain size.

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Abstract

The invention relates to a metallographic phase corrosion method displaying austenitic stainless steel grain boundary. The method comprises two steps of preparation of corrodent and metallographic phase corrosion. After coarse grinding, fine grinding, polishing, washing and drying, a metallographic specimen has a bright polished surface without a scratch. The corrodent is characterized by being prepared through mixing 50-70ml of nitric acid with concentration of 65%, 1-3g of sodium chloride, 0.1-0.5g of potassium rhodanide, and 30-50ml of distilled water, the polished surface of the metallographic specimen is taken as an anode and is soaked in a corrosive liquid, a titanium plate is taken as a cathode and is corroded through electrifying, then the metallographic specimen is washed and dried. The metallographic phase corrosion method is simple to operate, has good reproducibility, and can clearly display the grain boundaries of large grains, small grains and large and small mixed grains in the austenitic stainless steel.

Description

technical field [0001] The invention belongs to the technical field of heat treatment, in particular to a metallographic corrosion method for displaying grain boundaries of austenitic stainless steel. Background technique [0002] The size of metal grains has a decisive influence on its mechanical properties and corrosion resistance at room temperature and high temperature. In the analysis of metallographic structure, the accurate evaluation of grain size is of great significance. After forging or heat treatment of austenitic stainless steel, there are a large number of twins inside the grains. When the existing methods are used for corrosion detection, the twin boundaries and grain boundaries inside the grains are often corroded at the same time, which cannot be distinguished. Grain, which strongly affects the rating of grain size. This phenomenon is more prominent in samples with mixed crystals and large grains, which brings a lot of inconvenience to the analysis of meta...

Claims

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Application Information

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IPC IPC(8): G01N1/32C23F1/28
Inventor 彭新元黄晋华周贤良华小珍刘华英
Owner NANCHANG HANGKONG UNIVERSITY
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