Marking of steels and alloys, how to understand it

The presence of a wide range of steels and alloys produced in different countries has necessitated their identification, but to date there is no unified system for marking steels and alloys, which creates certain difficulties for the metal trade.

Thus, in Russia and the CIS countries (Ukraine, Kazakhstan, Belarus, etc.), an alphanumeric system for designating steel and alloy grades, developed early in the USSR, has been adopted, where, according to GOST, letters conventionally indicate the names of elements and methods of steel smelting, and numbers indicate the content elements.

The European steel designation system is regulated by standard EN 100 27. The first part of this standard determines the order of naming steels, and the second part regulates the assignment of serial numbers to steels.

In Japan, the names of steel grades usually consist of several letters and numbers. The letter designation determines the group to which the steel belongs, and the numbers indicate its serial number in the group and its property.

In the United States, there are several systems for naming metals and their alloys. This is due to the presence of several standardization organizations, these include AMS, ASME, ASTM, AWS, SAE, ACJ, ANSI, AJS. It is quite clear that such marking requires additional clarification and knowledge when trading metal, placing orders, etc.

To date, international standardization organizations have not developed a unified steel marking system. In this regard, there are discrepancies that lead to errors in orders and, as a result, poor quality of products.

In Russia and the CIS countries, an alphanumeric system has been adopted, according to which numbers indicate the content of steel elements, and letters indicate the name of the elements. Letter designations are also used to indicate the method of steel deoxidation “KP - boiling steel, PS - semi-quiet steel, SP - calm steel”. There are certain designation features for different groups of steels: structural, construction, tool, stainless steel, etc. The designations common to all are the letter designations of alloying elements: N - nickel, X - chromium, K - cobalt, M - molybdenum, B - tungsten, T - titanium, D - copper, G - manganese, C - silicon.

Structural steels of ordinary quality, unalloyed (GOST 380-94) are designated by the letters ST., for example ST. 3. The number after the letters conventionally indicates the percentage of carbon in the steel.

Structural unalloyed quality steels (GOST 1050-88) are designated by a two-digit number indicating the average carbon content in the steel (for example, ST. 10).

High-quality steels for the production of boilers and high-pressure vessels according to (GOST 5520-79) are designated as structural non-alloy steels, but with the addition of the letter K (for example, 20K).

Structural alloy steels, according to GOST 4543-71, are designated by letters and numbers. The numbers after each letter indicate the approximate content of the corresponding element, however, if the content of the alloying element is less than 1.5%, the number after the corresponding letter is not placed. Qualitative additional indicators, a reduced content of impurities such as sulfur and phosphate, are designated by the letter - A or Ш, at the end of the designation, for example (12 X NZA, 18ХГ-Ш), etc.

Cast structural steels, according to GOST 977-88, are designated as high-quality and alloyed, but the letter L is placed at the end of the name.

Construction steels, according to GOST 27772-88, are designated by the letter C and numbers corresponding to the minimum yield strength of the steel. Additionally, the following designations are used: T - heat-strengthened rolled steel, K - increased corrosion resistance (for example, C 345 T, C 390 K, etc.). Similarly, the letter D denotes high copper content.

Bearing steels, according to GOST 801-78, are designated in the same way as alloy steels, but with the letter Ш at the end of the name. It should be noted that for electroslag remelted steels, the letter Ш is denoted by a dash (for example, ШХ 15, ШХ4-Ш).

Unalloyed tool steels, according to GOST 1435-90, are divided into high-quality, denoted by the letter U and a number indicating the average carbon content (for example, U7, U8, U10) and high-quality, denoted by an additional letter A at the end of the name (for example, U8A) or an additional letter G, indicating an additional increase in manganese content (for example, U8GA).

Alloyed tool steels, according to GOST 5950-73, are designated in the same way as structural alloyed steels (for example, 4Х2В5МФ, etc.).

High-speed steels have the letter P in their designation (the designation of steel begins with this), followed by a number indicating the average tungsten content, and then letters and numbers determining the mass content of elements. They do not indicate the chromium content, since it is consistently about 4% in all high-speed steels, and carbon, since the latter is always proportional to the vanadium content. It should be noted that if the vanadium content exceeds 2.5%, the letter F and number are indicated (for example, steel R6M5 and R6 M5F3).

Standard stainless steels, according to GOST 5632-72, are marked with letters and numbers according to the principle adopted for structural alloy steels (for example, 08Х18Н10Т or 16Х18Н12С4ТУЛ).

Stainless steel, non-standard experimental batches are designated by letters - indices of the manufacturer's plant and serial numbers. The letters EI, EP, or EK are assigned to steels first smelted by the Elektrostal plant, ChS - to steels smelted by the Chelyabinsk Mechel plant, DI - to steels smelted by the Dneprospetsstal plant, for example, EI-435, ChS-43, etc. For designation method of smelting and finishing, the names of a number of steels are supplemented with letters (for example, 13Х18Н10-VI), which means vacuum induction smelting.

International analogues of corrosion-resistant and heat-resistant steels

Heat-resistant steels

Approximate purpose of corrosion-resistant steel grades

GOST 5632-72

Depending on the basic properties, steels and alloys are divided into groups:

• Corrosion-resistant (stainless) steels and alloys that are resistant to electrochemical and chemical corrosion (atmospheric, soil, alkaline, acid, salt), intergranular corrosion, stress corrosion, etc.;
• Heat-resistant (scale-resistant) steels and alloys that are resistant to chemical destruction of the surface in gas environments at temperatures above 550°C, operating in an unloaded or lightly loaded state;
• Heat-resistant steels and alloys that are capable of operating under load at high temperatures for a certain time and at the same time possessing sufficient heat resistance.

             Approximate purpose of grades of corrosion-resistant steels and alloys of group I

                      Approximate purpose of heat-resistant steels and alloys of group II