Low-relaxation high-strength prestressed steel and production method thereof

The invention discloses low-relaxation high-strength prestressed steel which comprises the following components in percentage by weight: 0.29 to 0.36 percent of C, 0.80 to 1.20 percent of Si, 0.60 to 0.80 percent of Mn, 0.10 to 0.15 percent of Cr, 0.010 to 0.020 percent of V, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S and the balance of iron and inevitable impurities. The production method comprises the following steps: pre-desulfurizing blast furnace molten iron by adopting a magnesium spraying desulfurization method, smelting in a top-bottom combined blown converter, and deoxidizing and alloying in a tapping process after smelting is completed; refining in an LF furnace, wherein the LF furnace adopts a whole-course argon bottom blowing mode; active lime and fluorite are added in the refining process to prepare refining slag; the LF refining time is not less than 40 minutes; carrying out soft argon blowing on the molten steel after LF; argon sealing protection pouring