Metallurgical analysis of seamless tube

Metallographic analysis of the seamless tube includes high magnification test and low magnification test.

High magnification test

A high magnification test is a method of evaluating the internal structure and defects of a material through a microscope. The high-power test items that are usually performed on seamless tubes include: microscopic evaluation of non-metallic inclusions in steel; determination of average grain size; determination of decarburized layer depth; micro-structure inspection.

Seamless tubes Currently, the assessment of non-metallic inclusions in steel is generally performed at a magnification of 100 times the field of view. The seamless steel tube compares the most serious field of inclusions in the sample with the standard level map to evaluate inclusions in the steel. The level of things.

Non-metallic inclusions are graded according to the A method in GBIP 10561, which can be classified as: Type A monosulfide type; Type B-aluminum oxide type: Type 17 monosilicate type; Type n-spherical oxide type and DS Inclusions. Seamless tubes Similarly, the grain size, depth of decarburized layer, and evaluation of microstructure are all compared with the corresponding standard rating charts.

Low magnification test

The low magnification test, also known as macroscopic analysis, refers to a method of assessing low-degree tissue defects in a material by visual observation or observation under a magnification of 10 times or less. Commonly used low magnification test methods include acid etching test, sulfur test, and tower hairline test. The acid etching test and the sulfuric acid test method are mainly used for tube blank inspection to show the low magnification structure and defects of the tube blank. The common tube blanks of the seamless tube have loose microstructure, segregation, subcutaneous bubbles, peeling, white spots, and inclusions.

In the direct rolling of tubes using steel ingots, the acid etching test and the sulfur test are also often used for the inspection of finished steel tubes. When the sulfur content of steel in the seamless tube is relatively low, because the sulfur-indicated test method can not reflect the low-order microstructure defects in the steel, it has gradually been replaced by the acid etching test method. The tower-shaped hairline test method uses artificial eyes to observe and verify the number, length and distribution of hair lines on each turning surface of each step of the sample. If necessary, observe under a magnifying glass no larger than 10 times.

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