| 摘要 |
The hot rolled steel sheet for parts of wheel, automotive floor materials, panel and reinforcing materials provides a combination of lower yield ratio (yield strength/tensile strength=G100%), high strength and good corrosion resistance. The steel slab is composed of, in weight percent, 0.05 to 0.09% carbon, 0.4 to 1.5% manganese, 0.02 to 0.1% aluminum, 0.2 to 0.6% copper, 0.04 to 0.08% phosphorus, up to 0.3% titanium and/or up to 0.1% niobium, X/C>0.9 [X=12(Ti/48+Nb/93) , and the balance of iron as the remainder and inevitable impurities. The disclosed steel sheet is produced by the processes of heating of the steel slab having the same chemical composition as mentioned above as a starting material at 1150 to 1250deg.C, final hot rolling of the heated steel slab at 850 to 920deg.C, hot reeling of the hot rolled sheet at the temperature below 600deg.C. The yield ratio at X/C of over 0.9 is lower than that at X/C of below 0.9.
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