To provide a force-connection-type self-locking nut for screw tightening so as to guarantee highly reliable screw fixation with the external measurements of the nut maintained, in a simple method, especially when securing a brake disk of rail wheels.

The nut (6) has at least one tightening curve (9) formed by two almost parallel adjacent slits (10a, 10b), and the tightening curve is placed in the radial direction in the area of a screw crest (11) of the nut (6), and consequently a screw crest section (11a) placed in the tightening curve (9) in the internal radial direction is plastically deformed against the remaining crest section (11b) of the screw crest so that it can be secured that the nut (6) is not loosened or lost against the bolt elements to which the nut (6) corresponds.