350mm-diameter 34CrMo circular tube steel blank and smelting and casting method thereof

The invention discloses a 350mm-diameter 34CrMo circular tube steel blank and a smelting and casting method thereof, belonging to the technical field of steel tube smelting and rolling. The invention provides a 350mm-diameter 34CrMo circular tube steel blank with reasonable alloy component content and higher equiaxed crystal rate content in the interior crystal phase structure, and a smelting and casting method of the circular tube steel blank. The 34CrMo circular tube steel blank comprises the following heavy components: C, Si, Mn, P, S, Cr, Mo, Cu and Ni. The 34CrMo circular tube steel blank also comprises the following residual elements: Nb, Ti, B, V+Nb+Ti+B+Zr, As, Sn, As+Sn+Pb+Sb+Bi and Fe. The length ratio of the zone of equiaxed crystals of the finished product 34CrMo circular tube steel blank is 50.0-52.3%. The smelting and casting method comprises the following steps: converter smelting, LF (ladle furnace) refining, RH refining, and continuous casting of the 34CrMo circular tube steel blank with the phi350mm cross section.