STEEL CORD WITH REDUCED RESIDUAL TORSIONS

摘要

A steel cord (132) adapted to reinforce a breaker or belt ply in a rubber tire comprises a core group and a sheath group. The core group consists of two to four core steel filaments (102) with a first diameter dcand the sheath group consists of one to six sheath steel filaments (116) with a second diameter ds. The ratio dc/ds of the first diameter dcto the second diameter dsranges from 1.10 to 1.70. The two core steel filaments (102) are untwisted or have a twisting step greater than 300 mm. The sheath group is twisted around the core group with a cord twisting step in a cord twisting direction. The ratio of the difference in residual torsions of the core group and the sheath group to the difference in saturation level between the core group and the sheath group ranges from 0.10 to 0.65, preferably from 0.10 to 0.60. The steel cord (132) has no flare and plastic deformation of the steel filaments (102, 116) can be reduced while still obtaining a steel cord (132) without flare. A twisting equipment (100) comprising a buncher (106) and a method of manufacturing said steel cord (132) is disclosed, too.