A metal strip is stretched as it is moved longitudinally generally continuously between an upstream traction-roll set and a downstream traction-roll set. The roll sets are differentially driven—with the downstream set moving at a slightly higher peripheral speed than the upstream set—so as to apply to the strip in a region between the sets a tension generally equal to a stretch limit of the strip. The strip is locally heated or cooled at an upstream location in the region between the roll sets so as to set in the strip in the region a temperature distribution that is nonhomogeneous transversely across the strip at least immediately downstream of the upstream location.