34CrMo round pipe billet with diameter being 350 mm and smelting method of 34CrMo round pipe billet

The invention discloses a 34CrMo round pipe billet with the diameter being 350 mm and a smelting method of the 34CrMo round pipe billet and belongs to the field of steel pipe smelting and rolling. The 34CrMo round pipe billet with the reasonable alloy component content and low in center segregation in an inner crystal structure and the smelting method of the 34CrMo round pipe billet are provided. The 34CrMo round pipe billet comprises C, Si, Mn, P, S, Cr, Mo, Cu, Ni and residual elements of Nb, Ti, B, V+Nb+Ti+B+Zr, As, Sn, As+Sn+Pb+Sb+Bi and Fe, wherein the porosity of the finished 34CrMo round pipe billet ranges from 0.5 level to 1.0 level, the loose region area proportion ranges from 24.8% to 25.0%, and a central zone of metal in situ analysis density ranges from 0.81 to 0.82. The smelting method includes the steps of converter smelting, LF furnace refining, RH refining and continuous casting of the 34CrMo round pipe billet with the diameter phi of the section being 350 mm.