Abstract: GPa-grade bainite steel having an ultra-high yield ratio, containing, in addition to Fe, the following chemical elements in mass percentages: 0.12-0.24% of C; 0.2-0.5% of Si; 1.3-2.0% of Mn; 0.001-0.004% of B; 0.01-0.05% of Al; and at least one of Cr, Nb, Ti, and Mo, wherein Cr?0.4%, Nb?0.06%, Ti?0.1%, and Mo?0.4%. Also disclosed are a manufacturing method and annealing process for the steel.

Abstract: Disclosed are a steel plate for a torsion beam and a manufacturing method therefor, and a torsion beam and a manufacturing method therefor. The steel plate for the torsion beam has the following chemical components in percentages 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, 0.005% or less of N, and the balance being Fe and inevitable impurities. The steel plate has one or two of Nb and V, and the amount of Nb and V satisfies 0.096%<2Nb+V<0.17%. The steel plate for the torsion beam of the present invention has an excellent elongation and excellent cold bending properties while ensuring high strength, and meets the requirement for producing lightweight torsion beams.

Abstract: Disclosed in the present invention is complex-phase steel having high hole expansibility. The complex-phase steel has a microstructure of ferrite and bainite. The complex-phase steel having high hole expansibility comprises the following chemical elements in percentage by mass: C: 0.06-0.09%, Si: 0.05-0.5%, Al: 0.02-0.1%, Mn: 1.5-1.8%, Cr: 0.3-0.6%, Nb?0.03%, Ti: 0.05-0.12%, and the balance of Fe and inevitable impurities. In addition, also disclosed in the present invention is a manufacturing method for the foregoing complex-phase steel having high hole expansibility. The method comprises the following steps: (1) smelting and casting; (2) heating; (3) hot-rolling; (4) phosphorous removal; (5) laminar cooling: a relaxation time period is controlled to be 0-8 s, and a laminar cooling rate is 40-70° C./s; (6) coiling; (7) leveling; and (8) pickling. The complex-phase steel having high hole expansibility can simultaneously satisfy the requirements for hole expansibility and good plasticity.

Abstract: The present invention provides a martensitic stainless steel and manufacturing process therefor, the mass ratio of chemical elements of the stainless steel is C: 0.01˜0.18 wt %, Si: 0.4˜1.5 wt %; Mn: 0.4˜3.0 wt %, P: ?0.04 wt %, S: 0.002˜0.01 wt %, Cr: 11.0˜15.0 wt %, N: 0.01˜0.15 wt %, Nb: 0.001˜0.01 wt %, V: 0.05˜0.25 wt %, Ti: 0.001˜0.01 wt %, Mo: 0.01˜1.50 wt %, B: 0.0005˜0.001 wt %, and balance being Fe and other unavoidable impurities. Further, the present invention provides a method for producing a martensitic stainless steel. The martensitic stainless steel of this present patent has a high hardness and high toughness and has excellent high-temperature oxidation resistance.