what is the HRC fuse and HRC fuse base?

HRC fuse and HRC fuse base

HRC Fuse for protection of semiconductor devices.
In the same way, they are also required to give the minimum acceptable energy in the case of overload. The quality of the parts is very small, and there are some filling materials.

The filling has two purposes: one is in the long-term current stress from the fuse in the heat conduction out, to provide long-term good working reliability; second, in case of a failure when the fuse melting can quickly extinguish the arc. For transient conditions, the thermal conductivity of the filler is rather limited.
This allows the melt to be melted with the minimum input energy to achieve a fast melting temperature. Under the transient current load, the fuse will soon be blown off.