Stainless Steel - Types of Marking And Traceability Of Their Decoding

At present, it is difficult to underestimate the demand for stainless steel in various spheres of human activity. The most popular types of stainless steel are stainless sheet and stainless pipe. Stainless pipes can be round and profile. Stainless steel pipes with square and rectangular cross-section are used for the profile.

The main consumers of stainless steel are the food, chemical, oil refining and energy industries, as well as engineering and construction. Stainless steel is popular because of its excellent qualities, the main of which is high resistance to aggressive media. In addition, stainless steel products have aesthetic qualities that cause their use for finishing various elements of the interior and exterior.

In addition to geometric differences (length, width, thickness of sheet or pipe wall) and differences in the form of polishing, stainless steel is distinguished by the chemical composition inherent in a particular grade of steel. In order for the consumer to see the steel grade of a certain type of stainless steel, there is a certain marking of stainless steels, which is a combination of letters and numbers.

Currently, three main markings are used: Russian marking according to GOST, EN / DIN and AISI, which are used in the USA and Europe. The principle of Russian marking will be considered on this example: 12Х18Н10Т. The first two digits (12) represent the average carbon content in tenths of a percent (in this case, 0.12%). If there are no figures ahead, then this steel grade contains one or more percent of carbon. Next comes a letter corresponding to one or another chemical element (symbols that can be easily found on the Internet or special literature). For example, the nitrogen (N) is designated by the letter A, the aluminum (Ai) is denoted by the letter Ю, the beryllium (Be) is denoted by the letter A, the boron (B) by the letter P, vanadium (V) is denoted by the letter Ф, tungsten (W) is denoted by the letters Ba, gallium (Ga) is denoted by the letter B, iridium (Ir) is denoted by the letter I, cadmium (Cd) is denoted by the letters Kd, cobalt (Co) is denoted by the letter K, silicon (Si) is denoted by the letter C., magnesium (Mg) Lead (Pb) is denoted by the letters AC, copper (Cu) is denoted by the letter D.

The numbers following this letter indicate the average content of this element in percent. In our case, X18 means that this steel contains 18% chromium. Absence of a letter after the letter means the content of the element in steel in the amount of 1 - 1.5%. The following (in our case) H10 speak of a ten percent nickel content. Well, the last letter T without numbers shows the presence of this brand in stainless steel 1.5% titanium.

In the EN / DIN marking system, unlike the Russian one, all the chemical elements included in the composition are listed first, and then their mass contents are indicated. The first figure can be used to judge the average mass fraction of carbon. If we have a stainless steel pipe (for example) with a marking of the type X5CrNi18-10, this indicates that the pipe is made of steel, which contains 0.05% carbon, 18% chromium and 10% nickel.

In the marking of the American Institute of Steel and Alloys AISI there are three figures and in some cases one - three letters that follow them. The first figure indicates the class of steel (2 or 3 - austenitic, 4 - ferritic or martin), the second and third digits indicate the serial number of stainless steel in the group. Numerous letters can denote the following: L - low carbon content, S - normal carbon content, N - nitrogen content, F - high sulfur and phosphorus content, B - silicon additive, Cu - copper presence.