Stainless steel: characteristics, popular grades

Stainless steel is a complex alloyed compound of ordinary steel and various metals with high resistance to atmospheric corrosion and other types of destruction. Stainless steel does not rust under the influence of atmospheric precipitation, in solutions of salts, alkalis, acids and some gas environments.

Main advantages of stainless steel:

High melting temperature.
Variety of brands.
Plastic.
High quality welded joints.
Ease of processing.
Durability.

The main component that ensures the unique qualities of steel is chromium - chromium oxides form a protective passivating film on the metal surface. The minimum mass fraction of chromium in the alloy is 10.5%, and the maximum mass fraction of carbon is 1.2%.

The introduction of various alloying elements into the alloy adds certain properties of stainless steel:

chromium increases the strength and hardness of the alloy, reduces the coefficient of linear expansion, increases corrosion resistance;
nickel increases plasticity, toughness, reduces the coefficient of thermal expansion;
titanium increases the strength and density of the alloy;
manganese contributes to an increase in hardness and wear resistance;
niobium provides low corrosion in welded products;
molybdenum increases tensile strength, elasticity, anti-corrosion properties and resistance to high temperatures;
tungsten reduces brittleness during heat treatment;
copper gives resistance to atmospheric corrosion;
silicon increases elasticity, heat resistance, electrical resistance, scale resistance and acidity;
cobalt improves heat-resistant properties;
aluminum reduces aging of the metal.

Classification of stainless steel

Steel is classified according to various criteria, and one of the main types of stainless steel classification is the chemical classification.

There are three main types of stainless steel:

ferritic (chromium) steels - these alloys contain more than 20% chromium and up to 0.15% carbon, due to which they are plastic and have high resistance to aggressive environments;
austenitic (austenitic-ferritic and austenitic-martensitic), which up to 33% consist of nickel and chromium;
martensitic and ferritic-martensitic - these alloys contain up to 17% chromium and up to 0.5% carbon, and they have maximum resistance to aggressive environments.

Popular steel grades

Steel marking	Steel type	Application	Chemical composition
12Х18Н10Т	austenitic chromium-nickel steels	for the manufacture of equipment to be welded in various industries	Cr 17-19 C up to 0,12 Si up to 0,8 Mn up to 2 Ni 9-11 S up to 0,02 Р up to 0,0,5 Ti 5C-0,8
08Х18Н10Т	austenitic chromium-nickel steels	for the manufacture of welded products operating in environments with a higher aggressiveness than steel grades 12X18H10T and 12X18H9T	Cr 17-19 C up to 0,08 Si up to 1 Mn up to 2 Ni 9-12 S up to 0,02 Р up to 0,0,4
08Х18Г8Н2Т	chromium-manganese-nickel steels of the austenite-ferritic class	for the manufacture of welded equipment operating in aggressive environments, in the chemical, food and other industries	Cr 17-19 C up to 0,08 Si up to 0,8 Mn 7-9 Ni 1,8-2,8 S up to 0,025 Р up to 0,0,35 Ti 0,2-0,5
08Х22Н6Т	chromium-nickel-molybdenum steels of austenitic-ferritic class	for the manufacture of welded equipment in the chemical, food and other industries, operating at a temperature not exceeding 300ºС	Cr 21-23 C up to 0,08 Si up to 0,8 Mn up to 0,8 Ni 5,3-6,3 S up to 0,025 Р up to 0,0,35 Ti 5C-0,65
08Х18Н10	austenitic chromium-nickel steels	for products subjected to heat treatment (hardening)	Cr 17-19 C up to 0,08 Si up to 0,8 Mn up to 2 Ni 9-11 S up to 0,02 Р up to 0,0,04 Ti 5C-0,7
08Х17Н13М2, 08Х17Н13М2Т	chromium-nickel molybdenum steels of the austenitic class	for technological equipment of the chemical industry	Cr 16-18 C up to 0,08 Si up to 0,8 Mn up to 2 Ni 12-14 S up to 0,02 Р up to 0,035 Ti 5C-0,70 Mo 2-3
03Х17Н13М2	austenitic chromium-nickel-molybdenum stainless steels	for chemical equipment, instruments that come into contact with sea water and the atmosphere, for food processing plants, containers for waste oils	Cr 16,5-18,0 C до 0,03 Si до 1,0 Mn до 2,0 Ni 11,0-13,5 S до 0,03 Р до 0,04 Mo 2,0 - 2,5 Fe Остальное
08Х17T	corrosion-resistant heat-resistant steels of ferritic class	for oxidizing environments, as well as atmospheric conditions, except for the marine atmosphere, where pitting corrosion is possible	Cr 16-18 C до 0,08 Si до 0,8 Mn до 0,8 Ni до 0,6 S до 0,025 Р до 0,035 Ti до 0,08 Cu до 0,03
03X18H10	corrosion-resistant and heat-resistant steels of the austenitic class	for the manufacture of cold-rolled sheet steel; expansion bellows; parts and welded structures; cold rolled strip	Cr 17-19 C до 0,08 Si до 0,8 Mn до 2 Ni 9-11 S до 0,02 Р до 0,035 Ti до 0,5 V до 0,2 Cu до 0,3 W до 0,2 Mo до 0,3 Fe остальное
07X16H6	corrosion-resistant ordinary steels	for products operating in atmospheric conditions, acetic acid and other saline environments and for elastic elements; for cryogenic equipment; austenitic - martensitic steel	Cr 15,5-17,5 C 0,05-0,09 Si до 0,8 Mn до 0,8 Ni 5-8 S до 0,02 Р до 0,035 Ti до 0,2 V до 0,2 Cu до 0,3 W до 0,2 Mo до 0,3 Fe остальное

Analogues of stainless steel grades

In Russia, the marking of stainless steel is adopted in accordance with GOST 5632-2014, but other countries use other standardization systems. So, in Europe, steel is marked in accordance with the European Committee for Standardization EN, in the USA, AISI standards are used, in Germany - the European Institute for Standardization DIN. Below is a table of correspondences of the main types of stainless steel:

GOST marking	AISI marking	EN marking	DIN marking
12Х18Н10Т	AISI 321	1.4878	X12CrNiTi18-9
08Х18Н10	AISI 304	1.4301	X5CrNi18-10
08Х17Н13М2	AISI 316	1.4436	X5CrNiMo17-13-3
08Х17Н13М2Т	AISI 316Ti	1.4571	Х6CrNiMoTi17-12-2
03Х17Н13М2	AISI 316L / 316	1.4404 / 1.4401	X2CrNiMo17-12-2
08Х17T	AISI 430Ti / 439	1.4510	Х6СrTi17
03X18H10	AISI 304 L	1.4307
07X16H6	AISI 301	1.4310	X10CrNi18-8
02Х18М2 БТ	AISI 444	1.4521	X2CrMoTi18-2