Bars and forgings of as-annealed corrosion resistant steel serve as parts working in aggressive medium.
Employing of annealed and corrosion resistant steel in machine building allows reducing power consumption and labour content during part production.
Recently increase in application of low-carbon, corrosion resistant steel and alloys in chemical, cryogenic, food and light industries has been observed that results from high resistance of this steel to aggressive medium.
Low-carbon corrosion resistant steel grades are used in welding equipment production, as well as for pipelines working in contact with nitric acid and ammonium nitrate. The steel is intended for production of main units of equipment for carbamide and caprolactone synthesis working in boiling phosphoric or 10%-acetic acid, or sulphate medium.
Ropes of stainless steel are used in conditions where corrosion is not permitted, as well as in high temperature conditions, e.g. yacht sport, aviation, chemical and food industry.
Regardless of a relatively small manufacturing value, stainless steel is practically an industry-forming material in a number of cases. For instance, development of such industries as airspace, petrol and chemical, food, medical industries depends on stainless steel market directly.
Stainless steel is used in agricultural machine building, railway car building, motor industry, airspace, petrol and chemical, medical food, industries (as well as in wine industry for pumping of wine, juice etc). It is also used in complex-shaped tool production (for example, knives for leather), atomic machine building, power machine building, designing and styling, shipbuilding, at overhaul plants.
Corrosion resistant steel is the steel that does not oxidize in aggressive medium (vapour, acid, salt or other chemical substances).
Steel corrosion resistance results from formation of thin film of compound oxides that are snug against the metal surface and protect it from penetration of aggressive substance into metal. Such films are known as passive films and the process of their development is called passivation.
Corrosion resistant steels are capable of self-passivation. Passivation film breakdowns are easily restored. All corrosion resistant steels are divided into 2 groups that are chromium and chromium-nickel steels. Chromium steels with low carbon content (less than 1%) and high chromium content (over 15%) are ferrous steels; they are not amenable to quenching.
Other chromium steels are subjected to quenching with low-temperature tempering to obtain anticorrosion properties. Chromium-nickel steels have austenitic structure. These steels are high resistant to different acids.
The main disadvantage of these steels is susceptibility to intercrystalline corrosion. Resistance to intercrystalline corrosion is obtained by solution annealing at 900-1000°C with further cooling in water or air. Sensibility to intercrystalline corrosion can be significantly decreased by adding 0.6-0.8% of titanium.
Carbon content reducing results in decreasing of a tendency to intercrystalline corrosion. To fix carbon in stable carbides small amount of niobium is added to the steel, however it may result in ferrite phase forming. Silicon adding makes austenitic steel more strengthened and elastic.