In metallurgy, the main application of products made of ceramic materials is the ceramic refractories used predominantly in the iron and steel industry.
For special applications in non-ferrous metals, products made of these materials, however, are no longer adequate if, primarily on account of their chemical composition, they do not reach the required level of purity and temperature, contamination-free processing is necessary or special measurement and analysis technology is to be used.
For such applications, dense-sintered, high-purity materials made of oxide or non-oxide ceramics are suitable, for example, for crucibles, as these materials have frequently been developed to meet a specific requirements profile. To increase their thermal shock resistance, such crucibles are used in porous form, insofar they are not wetted by the respective molten metal.
In metal foundries, machine and plant components made of ceramic materials are used predominantly in positions exposed to highly abrasive and corrosive attack. In addition to the mostly dense-sintered materials, for several decades components made of high-grade foamed ceramics have been used for metal filtration in order to ensure the high purity of the molten metals.
The range of requirements that must be met by the ceramic materials is extensive in line with the wide variety of applications, as the following examples show, although no claim to completeness is made:
- Purity above 99.5 % with minimized content of Si compounds
- Thermal stability up to 2000 °C, even in reducing conditions
- No contamination of the molten metal by the ceramic components
- Resistance to corrosion from the molten metals and vapours, especially metals with high oxygen affinity
- Usability in metal coating processes
- Oxygen ion conductivity for measurement and analysis purposes
In the processing and machining of metals, tool components made of ceramic materials or metal-ceramic composites such as carbides have now been introduced as standard for cost-efficient production. The advantages of these materials are therefore used for extrusion, wire-drawing, belt und deep-drawing tools as well as for stamping/punching tools or for machining of steel and also for manual tooling purposes.
Typical requirements that must be met in this context can be summarized as follows:
- Reliably long service lifetime in operating conditions
- High local mechanical and thermomechanical strength
- High toughness
- High wear resistance
- Low friction coefficient
- No corrosion as a result of contact reactions between ceramic and metal
In the field of forming technology, even today high potential for improving process efficiency can be identified as the ceramic materials used often have dry-running properties, which in some cases already enable elimination of the need for lubrication in areas of contact between ceramic and metal.