A device (100) for fixing a ring (8), in particular a ring (8) for large-diameter bearings, during the hardening of the ring (8) is proposed, wherein the device (100) comprises a bottom plate (1) having a main extension plane (M), an expanding ring (4) movable in an axial direction (A) orthogonal to the main extension plane (M), and jaws (5) movable in a radial direction (R) orthogonal to the axial direction (A), the device (100) being configured such that movement of the expanding ring (4) in an axial direction (A) towards the bottom plate (1) leads to movement of the jaws (5) in a radial direction (R) away from a center (O) of the bottom plate (1) outwards. Furthermore, a method for fixing a ring (8) for hardening the ring (8) is proposed.