Heat-resistant steels with good stability properties under short- and long-term stress are particularly resistant to effects from hot gases and combustion products at temperatures above 550°C.
Material selection:
The selection of a heat-resistant steel will depend on environmental conditions and mechanical properties. A high-alloyed and heat-resistant material may also have some disadvantages, e.g. brittleness.
Ferritic steels:
The main alloy element of these steels is chrome, supplemented by silicium and aluminium. These steels feature a non-deformed ferritic pattern. Its toughness when subjected to impulsive stress is relatively low. At temperatures above approx. 900°C, these steels develop coarse grits, which are associated with brittleness.
- Cold forming is difficult
- Only shielded arc welding (where possible TIG, MAGM and laser) is recommended
- Not sensitive to sulphur-containing gases
Austenitic steels:
The additional alloying of more than 9% nickel creates steels with a non-deformed austenitic pattern. They are very tough and not sensitive to impulsive stress and sudden temperature changes. Other properties include:
- Not susceptible to coarse grit formation at high temperatures
- Much better hot and creep strength
- Good formability with all methods
- Sensitive to sulphur-containing gases
- Metal-cutting machining is more difficult