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A Metallographic Corrosion Method for Revealing Grain Boundary of Austenitic Stainless Steel

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

Inactive Publication Date: 2016-03-30
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 corroded at the same time, which cannot be distinguished. Grain, heavily influences 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 metallographic analysis.

Method used

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  • A Metallographic Corrosion Method for Revealing Grain Boundary of Austenitic Stainless Steel
  • A Metallographic Corrosion Method for Revealing Grain Boundary of Austenitic Stainless Steel
  • A Metallographic Corrosion Method for Revealing Grain Boundary of Austenitic Stainless Steel

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0034] 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 nitric acid with a concentration of 65% to the above-mentioned prepared solution slowly, and stir uniform. The 304 austenitic stainless steel that has been heat-treated at 1150°C for 120 minutes is processed into a sample to be corroded. After polishing and cleaning, it is connected to a DC stabilized voltage power supply. The sample is connected to the positive electrode, the titanium plate is connected to the negative electrode, the voltage is 3.0V, the time is 60s, the power is cut off, the sample is removed, rinsed with distilled water, then washed with alcohol and dried, and the grain size is observed with a metallographic microscope. figure 1 shown. The grain boundaries are clear, the grains are uniform, and the grain twins are less or not obvious, which is conducive to the evaluation of grain size.

Embodiment 2

[0036] First add 3g of sodium chloride into 50ml of distilled water, then add 0.5g of potassium thiocyanate into the sodium chloride solution, and finally add 50ml of nitric acid with a concentration of 65% into the above-mentioned prepared solution slowly, and stir uniform. The 316LN austenitic stainless steel that has been heat-treated at 1100°C for 30 minutes is processed into a sample to be corroded. After polishing and cleaning, it is connected to a DC stabilized voltage power supply. The sample is connected to the positive electrode, the titanium plate is connected to the negative electrode, the voltage is 0.5V, the time is 240s, the power is cut off, the sample is removed, rinsed with distilled water, then washed with alcohol and dried, and the grain size is observed with a metallographic microscope. figure 2 shown. The grain boundaries are clear, both large grains and small grains are corroded, and grain twins are not obvious, which is conducive to the evaluation of ...

Embodiment 3

[0038] First add 2g of sodium chloride into 40ml of distilled water, then add 0.3g of potassium thiocyanate into the sodium chloride solution, and finally add 60ml of nitric acid with a concentration of 65% into the above-mentioned prepared solution slowly, and stir uniform. The 316LN austenitic stainless steel that has been heat-treated at 1050°C for 10 minutes is processed into a sample to be corroded. After polishing and cleaning, it is connected to a DC stabilized voltage 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, then washed with alcohol and dried, and the grain size is observed with a metallographic microscope. image 3 shown. The grain boundaries are clear, the grains are fine and uniform, and the grains have no twins, 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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Patent Type & Authority Patents(China)
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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