Heat-resistant and heat-resistant a> steels are characterized by the ability to resist oxidation, change in the original shape, destruction in an aggressive environment at significant temperatures.
By purpose, they are divided into categories:
The stability of iron compounds with carbon and other products is determined by the technology of the production process.
Resistance to corrosion changes depends on many factors leading to the destruction of the product due to chemical or electrochemical interaction with the environment.
Highly alloyed compounds contain more than 10% alloying additives and are divided into classes:
x austenitic. They form a stable single-phase austenitic structure, contain 18 – 25% Cr, up to 35% nickel. They are used in the production of non-magnetic structures – radio-technical parts, stainless pipes, protective covers against electromagnetic fields. They are used in almost all sectors of the national economy. They account for about 65% of world consumption;
x ferritic Fe-Cr. They belong to the cheapest segment, they are used for the production of equipment for the food, light, machine-building industries. They include 18.5 – 20.5% chromium, aluminum, magnesium, yttrium, titanium carbonitrides, zirconium, which enhances strength, elasticity and resistance to corrosion. Phosphorus and sulfur degrade the quality of the product, but it is impossible to remove them completely;
x martensitic. Thanks to martensite with a needle-like non-equilibrium structure and internal tension, the metal acquires strength and hardness. Contain 11-17% Cr, nickel, molybdenum, tungsten, vanadium. They are used for the manufacture of rotors, compressor parts, cutting tools.
Heat resistance is determined by the work of the alloy under stress at significant temperatures in a given time period, it is estimated:
Heat-resistant stainless steel are characterized by:
According to World steel data as of November 2018, in the world ranking Ukraine ranks 13th among the producers of long products. The leading position in the segment of supply of heat-resistant steel in Ukraine belongs to the company A-Synthesis.
High temperature resistance
Heat resistance allows you to resist corrosive processes at rates exceeding 500 ° C. With a chromium content of more than 13%, the metal is considered stainless. The best result of corrosion-resistant and heat-resistant steel is obtained with the simultaneous use of silicon and chromium additives (for example, alloy 15X28). When steel is heated, the oxides of chemical elements form a protective scale that protects the metal from corrosion at temperatures up to 1100°C.
Heat-resistant alloys are used for lightly loaded parts of heating devices, resistance elements and power plants.