Steel plate for torsion beam and manufacturing method therefor, and torsion beam and manufacturing method therefor

A manufacturing method of a steel plate for a torsion beam, wherein the steel plate comprises the following chemical components in percentage by mass:

• 0.04-0.085% of C, 0.02-0.5% of Si, 1.3-1.8% of Mn, 0.15-0.5% of Cr, 0.12-0.30% of Mo, 0.058% or less of Nb, 0.15% or less of V, 0.02% or less of Ti, 0.02-0.1 % of Al, 0.02% or less of P, 0.005% or less of S, and 0.005% or less of N, and the balance being Fe and inevitable impurities, wherein the steel plate comprises one or two of Nb and V, and the amount of Nb and V satisfies the following formula:
• 0.096%≤2Nb+V≤0.17%;
• and
• the manufacturing method comprises smelting, continuous casting, hot rolling and pickling, wherein
• the hot rolling comprises hot rolling heating, rolling, and cooling coiling, wherein in the hot rolling heating, a slab obtained after smelting and continuous casting is heated to 1200-1260° C. and maintained for 1-3 hr.;
• the rolling comprises rough rolling and finish rolling, wherein an outlet temperature of the rough rolling is controlled at 1020-1100° C., an outlet temperature of the final rolling is controlled at 840-920° C., and a total reduction ratio is controlled to be 80% or more;
• and in the cooling coiling, the rolled steel plate is subjected to laminar flow cooling at a rate of 30-70° C./s to 500-620° C., and then coiled.