Wire rod for ultrahigh-strength steel cord and manufacturing method thereof

A manufacturing method for a wire rod for an ultrahigh-strength steel cord, wherein the wire rod comprises the following chemical components in percentage by mass:

• 0.78%-0.96% of C, 0.15%-0.30% of Si, 0.30%-0.60% of Mn, ≤0.02% of P, ≤0.02% of S, ≤0.004% of Al, ≤0.001% of Ti, ≤0.005% of N, ≤0.50% of Cr, ≤0.05% of Ni, ≤0.05% of Cu, ≤0.01% of Mo, ≤0.10% of Nb, ≤0.10% of V, ≤0.01% of Sn, ≤0.02% of Pb, and the balance of Fe and other inevitable impurities,
• the manufacturing method sequentially comprising the following steps:
• a steel smelting stage:
• smelting molten steel where inclusions in sizes ≥5 μm are at a number density ≤0.5/mm2 and sizes of inclusions are ≤30 μm;
• a blank casting stage:
• casting tapped molten steel from the steel smelting stage into an ingot blank with a center carbon segregation value of 0.92-1.08;
• a cogging stage:
• cogging the ingot blank into an intermediate blank with a center carbon segregation value of 0.95-1.05;
• a rolling stage:
• rolling the intermediate blank into a wire rod;
• the rolling stage sequentially comprises:
• a second heating procedure:
• heating the intermediate blank in a second heating furnace for 90-150 minutes, and the intermediate blank is kept in a soaking section at a temperature ≥1,050° C. for 30-60 minutes;
• and
• a high-speed rolling procedure:
• high-pressure water dephosphorization is performed under dephosphorization pressure of 9-14 MPa after the intermediate blank leaves the second heating furnace, then the intermediate blank is rolled into the wire rod by a high-speed mill, an initial rolling temperature is controlled to be 950-1,050° C., a finish rolling temperature is controlled to be 900-940° C., a silking temperature is controlled to be 900-940° C., and a maximum rolling speed is controlled to be 110 m/s;
• and
• a controlled cooling stage:
• performing temperature control cooling on the wire rod to obtain a wire rod with tensile strength ≤1,150 MPa.