Use of heat-resistant steel in industry

Heat-resistant steel is a material with exceptional properties that plays a crucial role in many branches of industry. Thanks to its resistance to high temperatures and corrosion, it is widely used in environments where other common industrial materials may quickly fail.

Properties of Heat-Resistant Steel

Heat-resistant steel stands out for several key characteristics:

• Resistance to oxidation and corrosion: Due to its high content of chromium, nickel, and other alloying elements, this steel forms a protective surface layer that prevents oxidation and corrosion at high temperatures.
• Creep resistance: Heat-resistant steel retains its mechanical properties even under long-term exposure to high temperatures, which is critical in many industrial applications.
• Structural stability: Thanks to its chemical composition, heat-resistant steel maintains its structural integrity under extreme working conditions.

Classification of Heat-Resistant Steels

Heat-resistant steels are divided into several groups depending on their chemical composition and structure:

• Austenitic steels: Characterized by high chromium and nickel content, offering excellent resistance to corrosion and high temperatures. Example: 1.4841 steel.
• Ferritic steels: Contain less nickel but more chromium, making them more resistant to oxidation at high temperatures. Example: 1.4724 steel.
• Martensitic steels: Have a high carbon content, providing great hardness and strength, but are less resistant to corrosion. Example: 1.4762 steel.

Industrial Applications of Heat-Resistant Steel

Energy Industry

In energy production, heat-resistant steel is essential for manufacturing components exposed to high temperatures and pressure. It is used in:

• Steam boilers and combustion chambers: In addition to withstanding temperature, resistance to flue gas components – such as halogens or hydrogen sulfide – is critical. Heat-resistant steel not only protects the structure but also improves combustion efficiency and boiler performance.
• Turbine components: Rotors, blades, and turbine housings operate under extreme mechanical and thermal stress. Thanks to its creep and oxidation resistance, heat-resistant steel helps maintain precise alignment and dynamic balance – directly influencing performance and safety.

Chemical and Petrochemical Industry

In the chemical industry, heat-resistant steel is used for manufacturing:

• Chemical reactors: Devices used in chemical processes requiring high temperatures and resistance to aggressive chemicals.
• Furnaces and combustion chambers: Components such as burners or linings in industrial furnaces, where extreme temperatures and aggressive gases occur.
• Pipelines and tanks: For transporting and storing chemicals at high temperatures.

Metallurgical Industry

In metallurgy, heat-resistant steel is used for:

• Furnace components: Used in linings and casings of furnaces for heat treatment of steel and non-ferrous metals. Resistance to process gases like sulfur or carbon oxides is essential to maintain integrity and avoid contamination.
• Pipes and transport systems for molten materials: Ducts or channels that transport hot gases or molten metals must withstand rapid temperature changes and thermal stress. Heat-resistant steels resist deformation under these conditions, ensuring process safety.
• Support structures and equipment frames: In furnaces and production lines, structural frames exposed to long-term heating would creep if made from standard steel. Heat-resistant steel prevents deformation, extending machinery lifespan and reducing downtime.

Automotive and Aerospace Industry

In automotive and aerospace applications, heat-resistant steel is used for:

• Exhaust systems: Components that must withstand high exhaust gas temperatures.
• Combustion engines: Engine components operating under extreme temperature conditions require heat-resistant steels.
• Turbines: Turbine parts must resist sudden pressure and temperature spikes – heat-resistant steels prevent failure during demanding turbocharger operations (e.g., in motorsports).
• Aero-engine components: Jet engines and gas turbines must remain stable during sudden temperature and pressure changes. Creep and oxidation resistance ensures safety while optimizing the strength-to-weight ratio – key in aviation.

Food Industry

In the food industry, heat-resistant steel is used in:

• Evaporators and industrial dryers: Thermal processes such as milk powder drying or concentrate evaporation require materials resistant to repeated heating cycles and cleaning agents. Heat-resistant steels ensure hygiene and resistance to fatigue cracking.
• Conveyors in tunnel ovens: Belts and guides in bakery or processing ovens must withstand frequent contact with food, moisture, and high temperature. Heat-resistant steels retain surface cleanliness and do not react with food.

Heat-Resistant vs. Creep-Resistant Steel – Key Differences

In engineering practice, two terms are often encountered: heat-resistant steel and creep-resistant steel. Although both materials are designed to operate at high temperatures, they differ in application range and operating mechanism.

Heat-Resistant Steel

Heat-resistant steel is resistant to high temperatures and oxidation, but its main feature is chemical resistance to oxidation and gas corrosion above 500°C. It does not always maintain high mechanical strength under long-term thermal loads.

Creep-Resistant Steel

Creep-resistant steel, on the other hand, maintains its mechanical properties at high temperatures—especially resistance to creep. Some creep-resistant steels do not have good oxidation resistance and require surface protection or are used in controlled atmospheres.

Types of Heat-Resistant Steel from StainlessEurope

Steel 1.4841 | Type: austenitic heat-resistant | AISI: 314 / DIN: X15CrNiSi25-21 / PN: H25N20S2

Grade 1.4841 is an austenitic heat-resistant steel. It can be successfully used for glass-blowing pipe ends, porcelain firing baskets, or heavily loaded conveyor parts. Heat-resistant up to 1150°C, and in environments with exhaust gases and sulfur compounds up to 1000°C depending on concentration.

Steel 1.4845 | Type: austenitic heat-resistant | AISI: 310S / DIN: X8CrNi25-21 / PN: H23N18

Grade 1.4845 is an austenitic chromium-nickel stainless steel (25/20 type) suitable for high-temperature applications. It offers good resistance to carburization, sulfidation, and oxidation, with moderate creep resistance and structural stability.

1.4845 offers very good oxidation and sulfidation resistance. It can be used in:

• Air: up to 1100°C (2010°F)
• Sulfur-containing atmospheres: up to 650–1050°C (1200–1920°F), depending on operating conditions. Important factors include whether the atmosphere is oxidizing or reducing, and if contaminants such as sodium and vanadium are present.

Steel 15X25T | Type: ferritic heat-resistant | AISI: – / DIN: 15Cr25Ti / PN: H25T

This grade of steel is characterized by the following properties:

• exceptional resistance to reducing sulfurous gases,
• very good oxidation resistance in air,
• good resistance to ash/oil-type corrosion,
• good resistance to molten copper, lead, and tin.

Steel H25T can be used at temperatures up to 1150 °C (2102 °F). However, in the highest temperature range, this material shows low creep strength, which can result in deformation due to its own weight.

Due to its very high elongation under creep (often exceeding 100%) and low resistance to this process, when designing elements made from this steel, it is necessary to consider significant creep deformations before cracking occurs. Even under typical operating conditions, i.e. above 700 °C (1290 °F), the self-weight of pipes may generate stresses leading to major deformation.

For this reason, the proper support method for pipes is crucial. Steel H25T, like other ferritic chromium steels, has lower initial strength than austenitic stainless steels. Its transition temperature is around 100–150 °C (210–300 °F). Over time, its room-temperature strength may decrease further, so during repairs, high-impact stresses and similar loads should be avoided.