Heat-Resistant Stainless Steels – Production, Alloys, Characteristics
One defines heat-resistant stainless steels as alloys that are used in temperatures between 500 and 1150 degrees Celsius. In technical language, they are also called heat- and creep resistant.
Chemical composition of heat-resistant steels
Viewing the microstructure respectively the chemical analysis the heat-resistant steels can be divided in the group of ferritic and the austenitic steels and nickel-based alloys.
The melting of these alloys differs only marginally compared to the conventional ferritic and austenitic steels and nickel-based alloys.
However, some elements play a significant role when melting heat-resistant stainless steels. For example, a higher carbon (C) content as for the standard grades is applicable. Depending of the particular grades aluminum (AI), silicon (Si), nitrogen (N) but also metals of the rare earth elements like cerium (Ce) belong to these elements. In nickel-based alloys also copper (Cu), cobalt (Co) and boron (B) can be find within the composition.
Chemical analysis of heat-resistant stainless steels
In the following overview, you find some examples:
Ferritic
| EN-No. | ASTM | C max. | Cr | Ni | Ti | N | Al | Si | Ce | Other | Max o.T. (*) |
| 1.4713 | 0.12 | 6.0-8.0 | – | – | – | 0.5-1.0 | 0.5-1.0 | – | – | 800°C | |
| 1.4724 | 0.12 | 12.0-14.0 | – | – | – | 0.7-1.2 | 0.7-1.4 | – | – | 850°C | |
| 1.4742 | 0.12 | 17.0-19.0 | – | – | – | 0.7-1.2 | 0.7-1.4 | – | – | 1000°C |
Austenitic
| EN-No. | ASTM | C max. | Cr | Ni | Ti | N | Al | Si | Ce | Other | Max o.T.(*) |
| 1.4948 | 304H | 0.2 | 17.0-19.0 | 8.0-11.0 | Max. 0.10 | – | Max. 0.50 | – | – | 750°C | |
| 1.4878 | 321H | 0.1 | 17.0-19.0 | 9.0-12.0 | Min 4x (C+N); Max 0.70 | Max. 0.10 | – | Max. 0.75 | – | – | 850°C |
| 1.4828 | – | 0.2 | 19.0-21.0 | 11.0-13.0 | – | Max. 0.11 | – | 1.5-2.5 | – | – | 1000°C |
| 1.4883 | 309S | 0.08 | 22.0-24.0 | 12.0-15.0 | – | Max. 0.11 | – | Max. 0.75 | – | – | 1000°C |
| 1.4845 | 310S | 0.1 | 24.0-26-0 | 19.0-22.0 | – | Max. 0.11 | – | Max. 1.5 | – | – | 1050°C |
| 1.4818 | – | 0.08 | 18.0-20.0 | 9.0-11.0 | – | 0.12-0.20 | – | 1.0-2.0 | 0.03-0.08 | – | 1050°C |
| 1.4835 | – | 0.12 | 20.0-22.0 | 10.0-12.0 | – | 0.12-0.20 | – | 1.4-2.5 | 0.03-0.08 | – | 1150°C |
| 1.4841 | 314 | 0.2 | 24.0-26.0 | 19.0-22.0 | – | – | – | 1.5-2.5 | – | 1150°C |
Nickel Base Alloys
| EN-No. | ASTM | C max. | Cr | Ni | Ti | N | Al | Si | Ce | Other | Max o.T.(*) |
| 2.4816 | Alloy 600 | 0.05-0.10 | 14.0-17.0 | Min, 72 | Max. 0.3 | – | Max. 0.3 | Max. 0.5 | – | Co, Cu, B | 600-900°C |
| 2.4851 | Alloy 600 | 0.03-0.01 | 21.0-25.0 | 58.0-63.0 | Max. 0.5 | – | 1.0-1.7 | Max. 0.5 | – | Cu, B | 550-1200°C |
(*) Maximal suggested operation temperature to air
The requirements for these steels are not only heat-resistance but also high strength and corrosion resistance at different operation temperatures.
Very important is the criteria for fatigue strength/creep resistance at high temperatures.
Likewise, for other sectors, also here the so-called life cycle costs (LCC) play an essential role when choosing the material.
Characteristic of heat-resistant stainless steels
Different to the conventional ferritic, austenitic and nickel-based alloys with these particular steels the focus is doubtless on stresses due to high temperatures, as previously mentioned. The most important criteria are:
High fatigue strength/creep resistance in the wished temperature range
High temperature corrosion resistance
Scaling resistance by creation of an oxide layer
Special characteristic against stress caused by continuously changing temperatures and the resulting risk for embrittlement (depending of the used material)
Stable microstructure
High mechanical load
Wide use of heat-resistant stainless steels
Heat-resistant stainless steels have a wide range of applications. Following some industries:
Ceramic industry
Glass industry
Chemical and petrochemical industry
Hardening plant
Food industry
Incineration plant
Steam boiler
Pulp industry
Various applications in the apparatus engineering
Cement industry (for example for revolving cylindrical furnace)
Industrial furnace construction (hood-type furnace for the heat treatment of coils and wires, glow systems for steel, stainless steel and nonferrous heavy metals), pusher furnace and so on
Heat exchanger for different applications in higher temperature ranges
Exhaust systems, for example in the automotive industry for exhaust elbows
Surfaces of heat-resistant stainless steels
Heat-resistant stainless steels are mainly used as sheets, both as thin sheets and as thick sheets. The most common surfaces are execution 2B (cold rolled, annealed and pickled), 2C (cold rolled, annealed and non-descaled), 2E (mechanical descaled and pickled), 1C (hot rolled, annealed and non-descaled) and 1D (hot rolled, annealed and pickled). Precision sheets are also available in execution 2R (cold rolled and bright annealed).
Surface with or without scale
In this context, it is to mention that not every producer has the possibility to offer non-pickled material. However, many producers use combined equipment for rolling, pickling and heat treatment (e.g. RAP = rolling, pickling, annealing) but also combined production lines for annealing and pickling are worldwide common.
When using pickled or non-pickled surfaces, opinions vary on international markets. Many equipment manufacturers prefer pickled surfaces. According to them, surface defects are visible immediately. Processing of welding edges and the welding process itself is supposed to be easier and the constitution of the equipment is visually impeccable.
In addition, scale debris on the different machines are non-existent, which is important to avoid problems when further processing of standard stainless steels.
On the contrary, there are producers who see significant advantages using non-pickled surfaces as the scale is already existent.
Welding of heat-resistant stainless steels
The weldability of heat-resistant stainless steels differs considerably due to various alloys.
Ferrites can be seen as conditionally weldable.
Austenites are generally weldable with excellent results.
In either case, filler material of similar base materials shall be used and it is recommended to consult the available data sheets of the particular steel and filler material manufacturer. Usually, all common welding procedures as MIG/MAG, TIG or electrode welding can be used.
Laser welding is a standard method for the production of profiles at Montanstahl. As a condition, the surface must be free of any scale to avoid damage of the welding seam quality.
At Montanstahl, mainly beams, T-sections and angle bars for high-temperature application are welded.
Product shapes of heat-resistant stainless steels
Heat-resistant stainless steels do not belong to the every-day application on the steel market. Nevertheless, almost all components and product shapes to produce relevant constructions, e.g. sheets, pipes, long bars, fittings, filler material and so on are available on the stainless steel market; depending on the grade even at short notice from different stockists or via new production.
At Montanstahl, structural’s made of heat-resistant stainless steels can be purchased. These are manufactured project-specific just-in-time. In addition to standardized profiles, there is also the possibility to receive customized profiles inclusive prefabrication.
