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How to Identify Steel?
Sep 08, 2018

How to Identify Steel?



Color identification

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In order to indicate the grades and specifications of metal materials, we often make certain marks, such as coloring, printing, and listing. The coloring mark of the metal material is the end face or end portion of the steel material and the steel type applied to one end of the material. The specific coloring methods are specified in the relevant standards. The examples are as follows:


Carbon structural steel Q235 steel is red;

High quality carbon structural steel 20 steel is brown plus green, 45 steel is white plus brown;

Alloy structural steel 20CrMnTi steel is yellow plus black, 40CrMo steel is green plus purple;

Chromium bearing steel GCr15 steel is blue;

High speed steel W18Cr4V steel is brown and blue;

Stainless steel 1Cr18Ni9Ti steel is green country blue;

Hot work die steel 5CrMnMo steel is purple plus white.



 Fracture macro identification


The material or component is broken by some physical, chemical or mechanical action, and the natural surface formed at this time is called a fracture. At the production site, the toughness and brittleness of the material is determined according to the natural shape of the fracture, thereby inferring the carbon content of the material. If the fracture is fibrous, no metallic luster, the color is dark, there is no crystal grain, and the edge of the fracture has obvious plastic deformation characteristics, indicating that the steel has good plasticity and toughness, and the carbon content is low. If the fracture is flush, silver-gray, and has obvious metallic luster and crystalline particles, it indicates a brittle material. After the hypereutectoid steel or alloy is quenched, the fracture is bright gray with a satin luster, similar to the fracture characteristics of fine porcelain. The fracture characteristics of commonly used steel materials are as follows:


Low carbon steel is not easy to break, and the edge of the fracture has obvious plastic deformation characteristics, and there are trace particles;


The plastic deformation characteristics of the fracture edge of medium carbon steel are not obvious in low carbon steel, and the fracture particles are finer and more;


The fracture edge of high carbon steel has no obvious plastic deformation characteristics, and the fracture particles are very fine;


The cast iron is easily broken, the fracture is not plastically deformed, and the grains are coarse and dark gray.


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Tone Discrimination


The method of distinguishing between steel and cast iron is called sound color discrimination, depending on the sound produced when the steel is struck.


When struck, the material that emits a relatively crisp sound is steel, and the material that emits a lower sound is cast iron.


In order to accurately identify the materials, on the basis of the above-mentioned on-site identification, chemical analysis, metallographic examination and hardness test can also be used for identification.


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