Steel for high-strength petroleum casing pipe used in heavy oil thermal recovery well and manufacturing method thereof

The invention relates to steel for a high-strength petroleum casing pipe used in a heavy oil thermal recovery well and a manufacturing method thereof. The steel comprises the following chemical components in percentage by weight: 0.20-0.35% of C, 0.15-0.35% of Si, 1.10-2.50% of Mn, not more than 0.018% of P, not more than 0.003% of S, 0-0.40% of Cr, 0.005-0.10% of Ti, 0.005-0.10% of Nb, 0.005-0.05% of V, 0.10-0.30% of Ni, 0.05-0.60% of Mo and the balance of Fe and unavoidable trace impurities. The manufacturing method comprises the following steps: pre-treating molten iron; carrying out converter steelmaking; refining in a ladle furnace (LF); casting a plate blank; finishing a steel billet; warehousing and inspecting; heating in a heating furnace; carrying out controlled rolling; carrying out controlled cooling; coiling; and inspecting and warehousing. The high-strength petroleum casing pipe made of the hot rolled steel coils has the advantages of stable mechanical properties and excellent welding performance