Fire Resistant High Strength Rolled Steel Material and Method of Production of The Same
OwnerTeruhisa Okumura, Hiroshi Kita +2inventors
InventorsTeruhisa Okumura, Hiroshi Kita, Kohichi Yamamoto, Suguru Yoshida
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Abstract
A fire resistant high strength rolled steel material superior in fire resistance and toughness used for a structural member of a building etc. containing, by mass %, C: 0.005% to less than 0.04%, Mn: 0.8 to 1.7%, Si: 0.05 to less than 0.4%, Nb: 0.02 to 1%, Ti: 0.005 to 0.02%, N: 0.005% or less, B: 0.0003 to 0.003%, and Al: 0.005% to 0.03%, and a balance of Fe and unavoidable impurities, and having the ratio Ti/N of 2 to 8, the value C-Nb/7.74 of 0.02% or less, and having the ratio of the 0.2% yield strength at 600° C. to the yield strength at room temperature of 0.50 or more.
Claims6
A fire resistant high strength rolled steel material containing, by mass %,
- C:
- 0.005% to less than 0.04%,
- Mn:
- 0.8 to 1.7%,
- Si:
- 0.05 to less than 0.4%,
- Nb:
- 0.02 to 1%,
- Ti:
- 0.005 to 0.02%,
- N:
- 0.005% or less,
- B:
- 0.0003 to 0.003%,
- Al:
- 0.005% to 0.03%,
- and the balance of Fe and unavoidable impurities, and having the ratio Ti/N of 2 to 8, the value C—Nb/7.74 of 0.02% or less by mass %, and having the ratio of the 0.2% yield strength at 600° C. to the yield point strength (when the yield point is unclear, 0.2% yield strength) at room temperature of 0.50 or more.
A method of production of a fire resistant high strength rolled steel material comprising preparing a cast slab containing, by mass %,
- C:
- 0.005% to less than 0.04%,
- Mn:
- 0.8 to 1.7%,
- Si:
- 0.05 to less than 0.4%,
- Nb:
- 0.02 to 1%,
- Ti:
- 0.005 to 0.02%,
- N:
- 0.005% or less,
- B:
- 0.0003 to 0.003%, and
- Al:
- 0.005% to 0.03%,
- and the balance of Fe and unavoidable impurities, and having the ratio Ti/N of 2 to 8, the value C—Nb/7.74 of 0.02% or less by mass %, heating this to a temperature region of 1250 to 1350° C., then starting rolling and rolling to give a cumulative reduction rate at 1000° C. or less of 30% or more to thereby give the ratio of a 0.2% yield strength at 600° C. and a yield point strength (when yield point is unclear, a 0.2% yield strength) at room temperature of 0.50 or more.
A method of production of a fire resistant high strength rolled steel material comprising preparing a cast slab containing, by mass %,
- C:
- 0.005% to less than 0.04%,
- Mn:
- 0.8 to 1.7%,
- Si:
- 0.05 to less than 0.4%,
- Nb:
- 0.02 to 1%,
- Ti:
- 0.005 to 0.02%,
- N:
- 0.005% or less,
- B:
- 0.0003 to 0.003%, and
- Al:
- 0.005% to 0.03%,
- and a balance of Fe and unavoidable impurities, and having the Ti/N of 2 to 8, the value C—Nb/7.74 of 0.02% or less by mass %, heating this to a temperature region of 1250 to 1350° C., then starting rolling, and cooling, after the end of said rolling, at 800 to 500° C. in temperature range by a 0.1 to 10° C./sec average cooling rate to thereby give a ratio of 0.2% yield strength at 600° C. and yield point strength (when yield point is unclear, 0.2% yield strength) at room temperature of 0.50 or more.
Dependencies are inferred from the claim text.