Creep-resistant Ferritic Steel

Simple SummaryContent extracted from patent full text and abstract with AI.

This patent describes a ferritic steel alloy that is highly creep-resistant at high temperatures (600–1000°C). The steel contains specific intermetallic phases (Fe2(M,Si) and/or Fe7(M,Si)6, where M is a metal such as niobium, molybdenum, tungsten, or tantalum, partially substituted by silicon) that can precipitate during production, heat treatment, or use. These unique phases allow for greater creep-resistance without sacrificing oxidation resistance. Chromium can be included to form a protective chromium-oxide layer, making the steel especially suitable for use in fuel cell components like bipolar plates, which require high mechanical stability, chemical resistance, and electrical conductivity under harsh conditions.

Use CasesContent extracted from patent full text and abstract with AI.

• Bipolar plates in high-temperature solid oxide fuel cell (SOFC) stacks, providing improved durability and performance.
• Structural components subjected to high temperature and mechanical stress, such as steam pipes or superheaters in power plants.
• Electrodes or electrode holders used in molten metal or glass production processes where high creep and oxidation resistance are needed.
• Heating elements or current collectors for ceramic heaters (e.g., MoSi2 or SiC-based heaters).
• Construction of electrostatic or catalytic filters for flue gas cleaning systems, where exposure to elevated temperatures and corrosive gases occurs.
• Oxygen sensors (like lambda probes) working in high-temperature environments.

BenefitsContent extracted from patent full text and abstract with AI.

• Significantly enhanced creep resistance at high temperatures compared to conventional ferritic steels, greatly improving component longevity.
• Maintains high oxidation resistance, minimizing degradation and corrosion during prolonged exposure to reactive atmospheres.
• Allows for higher concentrations of strengthening precipitates without compromising the steel’s protective oxide layers.
• Chromium oxide surface layers provide both corrosion protection and good electrical conductivity, critical for fuel cell applications.
• Reduced evaporation of volatile chromium compounds, decreasing contamination and extending device life in fuel cells.
• Thermal expansion can be tailored to match ceramic components, reducing mechanical stress and risk of failure in composite assemblies.
• Can be produced and processed using standard metallurgical techniques, keeping manufacturing costs reasonable compared to exotic alternatives.

Technical Classifications (CPCs)

Inventors & Applicants

Patent Abstract

The invention relates to a ferritic steel that is particularly creep-resistant at temperatures from 600 to 1000°C and contains precipitations of an intermetallic phase Fe2 (M, Si) and/or Fe7 (M, Si), where M is a metal, in particular niobium, molybdenum, tungsten and/or tantalum. The precipitations may be formed during its production, during a heat treatment or during use at high temperature. The metal is partially substituted by silicon. As a result, it is possible to introduce considerably more creep-resistance enhancing precipitations into the steel than on the basis of the prior art, without thereby impairing the oxidation resistance of the material. If the alloy additionally contains chromium, the steel can be made into a chromium-oxide forming steel, which can be used inter alia for the bipolar plate in a stack of high-temperature fuel cells. The bipolar plate can be designed in such a way that its oxidic surface layer has good electrical conductivity and low chromium evaporation.