High-temperature and creep-resistant steels are used at temperatures up to 650 °C [1202.0°F], are mainly alloyed with Chromium, Molybdenum, Vanadium, Tungsten and Niobium and exhibit high resistance to high-temperature corrosion. Stable precipitations of the alloying elements results in high creep-resistance. The use application of this steel group is closely linked to the development of energy technology.
Heat-resistant and high-temperature steels are metallic materials that can be used at higher temperatures and have high stability against temperature-related plastic creep and changes in material properties. The maximum operating temperature is approx. 400 to approx. 620 °C; in the upper temperature range, these are referred to as high-temperature steels. Heat-resistant and high-temperature steels should be able to withstand the highest possible mechanical loads at elevated temperatures and have sufficient resistance to high-temperature corrosion. The evaluation criterion for strength at high temperatures is, for example, the 1% time strain limit Rp1/1000. The 1% time strain limit Rp1/1000 indicates the stress at which a permanent strain of 1% is present after 1000 hours.
While the mechanical strengths of conventional unalloyed steels drop significantly with increasing operating temperature, the strength properties of heat-resistant steels are significantly improved at higher temperatures through alloying measures. The steels are mainly alloyed with chromium, molybdenum, vanadium and tungsten, which gives these steels good creep resistance and sufficient structural stability.
The choice of steels depends on their operating temperature, the mechanical stresses, the area of application and the intended use. The group of heat-resistant and high-temperature steels includes numerous different types of steel.
Low-alloy, heat-resistant steels for application temperatures in the lower temperature range are used in normalised or martensitic-bainitic quenched and tempered condition. These steels are strengthened by carbides and carbonitrides of the elements Cr, Mo,W,V and Nb.
High-temperature steels for use in the upper temperature range contain 9 to 12 % Cr and are quenched and tempered. These steels are also strengthened by carbides and carbonitrides of Cr,Mo,W,W and Nb. However, through special alloying and heat treatment, more thermally stable precipitates are achieved, primarily Nb carbonitrides and improved scaling resistance.
As the precipitates gradually coarsen or dissolve again due to creep stress, the strengthening mechanism looses its effectiveness and there is an upper limit temperature for the application of normalised or quenched and tempered steels. Austenitic steels based on Cr-Ni show a significantly higher creep resistance at temperatures above 600°C and are sometimes used semi-hardened or precipitation-hardened.
The application of heat-resistant and high-temperature steels is closely related to the development of energy technology and is in the field of steam and gas turbines, petrochemicals and e.g. valves in combustion engines. The steels are selected according to the thermal design, taking economic efficiency into account. For the highest thermal loads, it is sometimes necessary to use Ni-based alloys.
“This specification covers a corrosion and heat resistant steel in the form of bars, wire, forgings and forging stock. It is an austenitic, precipitation hardenable, iron-nickel-chromium-molydenum-titanium steel of ESR quality. Alloying elements of aluminium and titanium allow this material to undergo precipitation hardening (ageing) through the formation of intermetallic phases. The addition of molybdenum increases the mechanical properties and resistance to creep at high temperatures. These products have been typically used for parts in power generation engineering i.e. gas turbines requiring moderate strength up to 704 °C (1300 °F) and oxidation resistance up to 816 °C (1500 °F), but their use is not limited to such applications.”
Read MoreComponents for steam and gas turbines, such as blades, discs, bolts and pins.
Read MoreComponents for boiler plants and thermal engines, as turbine discs and blades, components for the chemical and petrochemical industries.
Read MoreComponents featuring elevated high-temperature strength for use in thermal engines and power plants, such as turbine blades, turbine discs, screws, bolts, pins and shafts.
Read MoreBÖHLER T552 is a premium aircraft-quality corrosion-resistant chromium-nickel-molydenum steel in the form of bars, wire, forgings and stock for forging. These products have been used typically for parts such as compressor wheels and structural members requiring corrosion resistance and high strength up to 800°F (427 °C), but usage is not limited to such applications.
Read MoreHighly stressed turbine blades and turbine discs , screws, shafts, bolts, pins and rings.
Read MoreComponents featuring elevated high temperature strength for use in thermal engines, such as turbine blades and turbine discs.
Read MoreBÖHLER T670 is a corrosion-resistant steel for aerospace applications in the form of bars, wire, and forgings with diameters/thicknesses up to 305 mm in the solution-annealed condition, as well as pre-forging material of any size. It is a martensitic, precipitation-hardenable chromium-nickel-copper-molybdenum steel with high strength and toughness. BÖHLER T670 is primarily suitable for parts requiring corrosion resistance close to that of Cr-Ni 18-8 steels and exceeding the strength of martensitic 12% Cr steels. This steel can be processed in the solution-annealed condition and, through precipitation treatment, achieves tensile strengths of up to 1080 MPa with good ductility and strength in the transverse directions, even in large cross-sections. Certain processing methods and operating conditions can cause stress corrosion cracking in these products.
Read MoreBÖHLER T671SB is a corrosion-resistant steel for aerospace applications in the form of bars, wire, and forgings with diameters/thicknesses up to 305 mm in the solution-annealed condition, as well as pre-forging stock of any size. It is a martensitic, precipitation-hardenable chromium-nickel-copper-molybdenum steel with high strength and toughness. BÖHLER T671 SB is primarily suitable for parts requiring corrosion resistance close to that of Cr-Ni 18-8 steels, exceeding the strength of martensitic 12% Cr steels, and can be used up to a service temperature of 371 °C. This steel can be processed in the solution-annealed condition and, through precipitation treatment, achieves tensile strengths of up to 1241 MPa with good transverse ductility and transverse strength at large cross-sectional dimensions. Certain processing methods and operating conditions can cause stress corrosion cracking in these products.
Read MorePlease fill out this contact form for further information
Fields marked with * are mandatory.