GB/T 38222-2019Metallographic examination method of medium and high strength stainless steel castings for general engineering applications (English PDF)

3.1 Delta ferrite

Crystallization occurs when liquid iron is cooled to 1538 ° C, and liquid iron is converted into high-temperature ferrite of delta-Fe.

Note. delta ferrite is used as high-temperature ferrite. In medium and high-strength stainless steel, since a small amount of carbon and a large amount of alloying elements have a great influence on the high temperature equilibrium, the room temperature is obtained.

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4.1

The metallographic specimens are taken on the casting test block of the casting or casting, and can also be inspected directly on the casting.

4.2

The preparation method of the metallographic sample shall be carried out in accordance with the provisions of GB/T 13298. During the process of intercepting and preparing the sample, the tissue shall be prevented from changing.

Before the sample surface is etched, the surface should be clean and free from scratches and polishing defects.

4.3

The area of the test surface of the sample shall be not less than 100mm2. When the inspection area of a single sample is less than 100mm2, the number of samples shall be increased.

When the sample size is large, it is allowed to be divided into several pieces, but it is still regarded as a piece of sample.

4.4

The martensite grade, delta ferrite content and non-metallic inclusion content in the metallographic structure of the casting can be carried out separately on the same sample.

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4.5 Etch

It is recommended to use picric acid 1g hydrochloric acid 5mL absolute ethanol 95mL, ferric chloride (FeCl3·6H2O) 2g~5g

Hydrochloric acid 5 mL of absolute ethanol 100 mL and ferric chloride (FeCl3·6H2O) 5 g hydrochloric acid 50 mL of water 100 mL.