Pass system rolling continuous cast round billet into round steel and rolling method thereof

The invention provides a pass system rolling a continuous cast round billet into round steel and a rolling method thereof. The pass system comprises five passes which are box-type passes, wherein thefive passes are a pass I, a pass II, a pass III, a pass IV and a pass V separately; each of the five passes is composed of a groove opening, a sidewall and a pass groove bottom; the pass groove bottoms of the pass II and the pass III are convex-arc; and the pass groove bottoms of the pass I, the pass IV and the pass V are straight lines. The rolling method provided by the invention comprises the steps of rolling the continuous cast round billet into a square billet by using the pass system, and then rolling the square billet into the round steel. With the adoption of the rolling method provided by the invention, the continuous cast round billet can be rolled into the round steel, so that the symmetry and the uniformity of the macrostructure ingot segregation of the round steel are improved; and according to the ro