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

Austenitic

Nickel Base Alloys

(*) 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