Does coil break marks formed in hot rolled steel, had their origin in in yield point phenomenon / discontinuous yielding?

1) How do they depend on chemistry of steel?

2) Does grain size play any important role in their occurrence, or are fine grained steels more prone to coil breaks?

3) How Coiling and un-coiling operations after re-opening of hot rolled coils plays a role in their formation?

4) Coil break marks are not formed in high strength hot rolled steel ?  (Say YS> 300 MPa)