Heat-resistant Sheets
High temperatures are unforgiving when it comes to random material selection. When a component is intended to operate in a furnace, boiler, industrial installation, or in contact with hot exhaust gases, ordinary steel loses its properties very quickly. Scaling, deformations, structural weakening, and the risk of costly downtime occur. That is exactly why heat-resistant sheets are used in such conditions — materials designed to operate where resistance to temperature, oxidation, and aggressive gaseous environments is crucial.
Heat-resistant sheets for high-temperature applications
| Grade PN | EN | AISI | Thickness [mm] |
|---|---|---|---|
| H25T | 1.4439 | – | 1,0 – 20 |
| – | 1.4713 | – | 1,0 – 25 |
| H13JS | 1.4724 | – | 2,0 – 20 |
| H18JS | 1.4742 | – | 1,0 – 20 |
| H24JS | 1.4762 | (446) | 1,0 – 20 |
| H20N12S2 | 1.4828 | 309 | 1,0 – 30 |
| H25N20S2 | 1.4841 | 314 | 1,0 – 50 |
| – | 1.4845 | 310S | 2,0 – 25 |
Heat-resistant sheets are designed for applications where the material is exposed to prolonged or cyclic high temperatures,most commonly above 550°C. In such conditions, standard carbon steel oxidizes very quickly. Scale, a layer of iron oxides, forms on its surface, which can flake off and gradually expose subsequent layers of the metal. The result is the thinning of the component, a loss of strength, and an increasing risk of failure.
Heat-resistant sheet metal acts differently. Thanks to its appropriate chemical composition, it forms a stable, adhering layer of protective oxides on the surface. This layer is exactly what restricts the access of oxygen and hot gases to the deeper layers of the material. In practice, this means greater durability of components, slower degradation, and better predictability of the installation’s operation.
These properties are of great importance wherever steel operates in contact with:
- hot gases and exhaust fumes,
- open flames or thermal radiation,
- cyclic heating and cooling,
- oxidizing, reducing, carburizing, or sulfidizing atmospheres,
- mechanical loads occurring at high temperatures.
Well-chosen heat-resistant sheets help maintain structural stability, reduce thermal deformations, and extend the safe operation time of equipment.
What distinguishes heat-resistant sheet metal?
Heat-resistant sheet metal is primarily distinguished by its alloy composition. The key element is chromium, which is responsible for forming a protective oxide layer. In many grades, its content is high, often exceeding 18%, and in selected steels, it can reach even higher levels. It is chromium that forms the basis of oxidation resistance at high temperatures.
In austenitic steels, nickel also plays an important role. It improves the material’s plasticity, stabilizes the steel’s structure, and supports resistance to specific types of industrial atmospheres, including carburizing environments. As a result, the sheet better withstands harsh working conditions, including temperature spikes and mechanical loads.
Silicon and aluminum may also appear in the composition of heat-resistant sheets. Their task is to additionally strengthen the oxide layer, especially in environments where the steel is exposed to the intense action of hot gases. It is precisely this synergy of elements that makes heat-resistant sheets significantly better suited for high-temperature operation than standard steel grades.
It is worth distinguishing heat resistance from high-temperature strength. Heat resistance refers to resistance to gas corrosion and oxidation at high temperatures. High-temperature strength, on the other hand, relates to the material’s ability to carry mechanical loads at high temperatures, including resistance to creep. For structural components, both parameters can be equally important.
Heat-resistant sheets for furnaces, boilers, and industrial installations
Heat-resistant sheets are used in places where ordinary steel would not be able to operate for long without sustaining damage. In the smelting, foundry, and metallurgical industries, they are used, among other things, for the construction of furnace chambers, muffles, retorts, charging baskets, thermal shields, and components of heat treatment equipment.
In the power sector, heat-resistant sheets are used in boilers, burners, superheaters, flue gas exhaust systems, and installation components exposed to high temperatures and aggressive combustion products. In the chemical and petrochemical industries, they are utilized wherever steel comes into contact with hot process gases, reactors, or installations operating in demanding thermo-chemical conditions.
The cement, ceramics, machinery, and manufacturing industries also utilize heat-resistant sheets. In such applications, not only temperature resistance but also the predictability of the material’s performance is crucial. A failure of a furnace, boiler, or technological installation component can result in a production stoppage, costly repairs, and the risk of damaging subsequent parts of the system.
Therefore, when selecting a material, it is worth considering not only the purchase price of the sheet but its entire operational life cycle. A well-chosen heat-resistant sheet can reduce the risk of downtime, decrease the frequency of replacements, and improve the operational safety of the installation.
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Resistance of heat-resistant sheets to temperature, oxidation, and corrosion
High temperatures change the way steel degrades. At ambient temperatures, we most often speak of wet corrosion, associated with water, moisture, salts, or aggressive solutions. At very high temperatures, dry, or gaseous, corrosion becomes more significant. The material is then damaged by oxygen, exhaust gases, sulfur compounds, carbon, hydrogen, carbon monoxide, and other components of the working atmosphere.
Heat-resistant sheets are designed to limit the effects of these types of interactions. In an oxidizing atmosphere, their task is to form a stable protective layer that slows down further oxidation. In carburizing environments, resistance to carbon penetration into the steel’s structure is important, because excessive carburization can lead to brittleness and the deterioration of mechanical properties.
Atmospheres containing sulfur compounds require special attention. Not every heat-resistant steel grade will perform well in such an environment. In many cases, grades with an appropriate chromium content and limited nickel content are needed, because under certain conditions sulfur can accelerate material degradation.
That is why, when selecting a heat-resistant sheet, one cannot rely solely on the question: “how many degrees can the steel withstand?”. A comprehensive understanding of the working environment is much more important. The same sheet may behave differently in clean air, differently in exhaust gases, differently in a reducing atmosphere, and yet differently in an installation where sulfur compounds are present.
How to choose heat-resistant sheet metal for working conditions?
The selection of heat-resistant sheet metal should begin with determining the maximum and constant operating temperature. A component operating continuously at a stable temperature will have different requirements than a part exposed to frequent heating and cooling. Thermal shocks can cause cracking or spalling of the scale layer, which is why grade selection is particularly important in cyclic operation.
The second step is to analyze the working atmosphere. It must be determined whether the environment is oxidizing, reducing, carburizing, sulfidizing, or perhaps a mixture of different factors is present. In industrial practice, it is very often the composition of the atmosphere that determines which steel grade will be appropriate.
Mechanical loads are also significant. If the sheet is used to create a load-bearing element, a charging basket, a furnace part, or a component exposed to stress at high temperatures, the material’s high-temperature strength must be considered. In such cases, creep resistance, i.e., slow deformation under the influence of temperature and load, is what counts.
When making a choice, it is worth analyzing:
- continuous operating temperature and maximum temperature spikes,
- composition of the working atmosphere,
- the presence of exhaust gases, sulfur, carbon, water vapor, or reducing gases,
- mechanical loads acting on the component,
- frequency of heating and cooling,
- required thickness, format, and method of further processing,
- planned method of cutting, bending, rolling, or welding.
At GammaSteel, we take a practical approach to selecting heat-resistant sheets. Instead of proposing the “strongest” material without context, we help tailor the grade to a specific application. This is important because the most highly alloyed sheet is not always the best or most cost-effective solution.
Heat-resistant sheet metal in various thicknesses, formats, and steel grades
Heat-resistant sheet metal comes in various grades, thicknesses, and formats, which allows the material to be selected for both lightweight thermal shields and massive structural elements. In practice, austenitic grades from the 1.48xx group, such as 1.4828, 1.4841, or 1.4845, are often used. They are valued for their good resistance to high temperatures, plasticity, and suitability for many processing methods.
In selected applications, ferritic grades are also used, for example, 1.4742 or 1.4749. They can be a good choice for specific working atmospheres, especially where resistance to sulfurous environments is important, but they usually require greater caution when welding and designing components exposed to mechanical loads.
Heat-resistant sheets can be supplied as cold-rolled or hot-rolled material. Cold-rolled sheets are typically thinner and have a better surface quality, which is why they work well for precise components, covers, and details requiring an aesthetic finish. Hot-rolled sheets are used more often for thicker structures and industrial components, where durability and adequate load-bearing capacity are the priority.
The availability of a specific format depends on the grade and thickness, but in practice, it is possible to work with both standard sheets and materials prepared for further cutting. For many companies, this is of great importance, as it reduces the amount of waste and facilitates production planning.
Application of heat-resistant sheets in production and further processing
Heat-resistant sheets are a technical material that can be subjected to further processing, but this requires appropriate experience and the maintenance of correct technological parameters. Laser, plasma, and waterjet cutting are possible. The choice of the method depends on the material’s thickness, the required accuracy, edge quality, and the subsequent application of the component.
Cold forming, such as bending or rolling, is also possible, especially in the case of austenitic grades. However, it must be remembered that steels of this type can significantly work-harden during deformation. This means greater demands on machines, tools, and process parameters than with ordinary structural steel.
Heat-resistant sheets are also suitable for welding, but they should not be treated the same as standard steel sheets. The key is to select the right filler metal, control the heat input, and properly prepare the joint. In the case of certain ferritic grades, preheating may be necessary to reduce the risk of cracking and adverse structural changes.
In industrial production, heat-resistant sheets are used to manufacture, among other things:
- components of industrial furnaces and heating chambers,
- retorts, muffles, charging baskets, and thermal shields,
- parts of boilers, burners, and flue gas ducts,
- components of power, chemical, and petrochemical installations,
- components of machinery operating at high temperatures,
- parts intended for further cutting, bending, rolling, and welding.
If the material is intended to operate in harsh conditions, it is worth discussing not only the grade and thickness but also the processing method already at the ordering stage. This allows avoiding problems during production and better tailoring the sheet to its final application.
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