Simply put I don't think the fuse knows the difference between AC & DC it has to do with the point of has it been tested under those conditions.The voltage rating value is the level that can still be safely(and been tested for) applied when the fuse is blown and not arc across the gap thus still conducting a current.
If AC or DC is different in this regard would someone explain that or post a link.
dick
AC VERSUS DC OPERATION
It is true that some AC fuses are also suitable for DC circuit
operation; however, testing is the only sure way to
determine the DC voltage capability of a particular AC fuse.
There is no ?rule of thumb? that safely converts an AC
voltage rating on a fuse to a DC voltage rating. To ensure a
fuse will safely interrupt a DC circuit, the fuse must have
been tested using circuit parameters representing the specific
application. The key question is how much DC capability
does an AC rated fuse have?
On a 60 Hertz, AC system, the current crosses zero 120
times per second. This natural zero crossing helps the fuse
extinguish any residual arcing that occurs after the element
melts. There is no natural zero crossing on DC circuits;
therefore, the fuse must be capable of absorbing and
extinguishing all of the energy in the DC arc
see this for complete paper:
http://www.arcadvisor.com/pdf/Fuse-Protection-of-DC-Systems.pdf