Seams in Seel Rebars

[CCQS2014]

Good day for all,
I want to ask about seam defect in steel rebar , its appearing in higher rolling sizes only more than 25 mm , but its disconitnuous.do you know how its generating from Rolling Mill or Caster.

 

[gerhardl]

Impossible to tell without a lot of details checked:

http://pmpaspeakingofprecision.com/2012/05/24/seams-on-rolled-steel-products/