Sintering is a calcination process conducted at a temperature below the melting point of a powdered material (metals, metal alloys, metal compounds, ceramics). Granules of the material compacted in a shaped body are hardened either by grain surface melting of the material or by means of binder smelts. Surface melting is promoted by sintering agents (e. g. boron, beryllium or aluminium in the case of pressureless sintered silicon carbide). Grain surface melting makes the microstructure denser and involves shrinkage. With grain bonding by way of a low-melting material (e. g. tungsten carbide with nickel binder) there is no significant shrinkage.