  We investigate the critical curve of the string tension sigma(T) as a
function of temperature in quenched gauge invariant SU(3) lattice gauge theory.
We extract sigma(T) from the colour averaged free energy of a static
quark-antiquark pair. To compute the free energy, we utilize a pair of gauge
invariant Polyakov loop and antiloop correlations, and apply the multihit
procedure to enhance the signal to noise ratio. We find that the string tension
departs from the zero temperature sigma(0) at T close to 0.5 Tc. We cover the
relevant temperature range from 0.5 Tc up to the confinement temperature Tc
using 57 different sets of pure gauge lattice configurations with four temporal
extensions (4,6,8,12), different beta and a spatial volume of 48^3 in lattice
units.
