Claims
- 1. A method for producing a cold rolled steel sheet having press formability, which comprises:
- hot rolling, at a temperature of at least 850.degree. C., and Al-killed, boron-free steel consisting of, by weight, not more than 0.07% C, 0.10-0.40%Mn, 0.010-0.050% Al, not more than 0.0020%N, not more than 0.010%P, and not more than 0.02%Si, wherein the relation between P and N is such that P+5N.ltoreq.0.0175%, the remainder of the steel being Fe and unavoidable impurities,
- cold rolling the hot rolled steel at a reduction of at least 50%, and
- subjecting the cold rolled steel to recrystallization continuous annealing at a temperature between the recrystallization temperature and the A.sub.3 point for not longer than five minutes.
- 2. A cold rolled, continuously annealed boron-free steel sheet having press formability, consisting of, by weight, not more than 0.07%C, 0.10-0.40%Mn, 0.10-0.50%Al, not more than 0.0020%N, not more than 0.010%P, and not more than 0.02%Si, wherein the relation between P and N is such that P+5N.ltoreq.0.0175%, the remainder of the steel being Fe and unavoidable impurities.
- 3. A method for producing a cold rolled steel sheet having press formability, which comprises:
- hot rolling, at a temperature of at least 850.degree. C., an Al-killed, boron-free steel consisting of, by weight, not more than 0.05%C, 0.10-0.40%Mn, 0.010-0.050% Al, not more than 0.0020%N, not more than 0.010%P, not more than 0.02%Si, and Cr in an amount of not more than 0.10%, wherein the relation between P and N is such that P+5N.ltoreq.0.0175%, the remainder of the steel being Fe and unavoidable impurities,
- cold rolling the hot rolled steel at a reduction of at least 50%, and
- subjecting the cold rolled steel to recrystallization continuous annealing at a temperature between the recrystallization temperature and the A.sub.3 point for not longer than five minutes.
- 4. A method for producing a cold rolled steel sheet having press formability, which comprises:
- hot rolling, at a temperature of at least 850.degree. C., an Al-killed, boron-free steel consisting of, by weight, not more than 0.005%C, 0.10-0.40%Mn, 0.010-0.050%Al, not more than 0.0020%N, not more than 0.010%P, not more than 0.02%Si, and at least one element selected from not more than 0.10% Ti and not more than 0.10% Nb, wherein the relation between P and N is such that P+5N.ltoreq.0.175%, and the relation between P and C is such that P.ltoreq.4C, the remainder of the steel being Fe and unavoidable impurities,
- coiling the hot rolled steel at a temperature of 550.degree.-650.degree. C.,
- cold rolling the hot rolled steel at a reduction of at least 50%, and
- subjecting the cold rolled steel to recrystallization continuous annealing at a temperature between the recrystallization temperature and the A.sub.3 point for not longer than five minutes.
- 5. A cold rolled, continuously annealed boron-free steel sheet having press formability, consisting of, by weight, not more than 0.005%C, 0.10-0.40%Mn, 0.010-0.050%Al, not more than 0.020%N, not more than 0.010%P, not more than 0.02%Si, and at least one element selected from not more than 0.10%Ti and not more than 0.10%Nb, wherein the relation between P and N is such that P+5N.ltoreq.0.0175%, and the relation between P and C is such that P.ltoreq.4C, the remainder of the steel being Fe and unavoidable impurities.
- 6. A method as claimed in claim 1 in which said C is not more than 0.05% by weight.
- 7. A method as claimed in claim 1 in which said C is not more than 0.005% by weight and the relation between said P and said C is P.ltoreq.4C.
- 8. A steel sheet as claimed in claim 2 in which said C is not more than 0.005% by weight and the relation between P and C is P.ltoreq.4C.
Priority Claims (2)
Number |
Date |
Country |
Kind |
56-146348 |
Sep 1981 |
JPX |
|
56-146349 |
Sep 1981 |
JPX |
|
Parent Case Info
This application is a continuation of now abandoned application Ser. No. 591,902 filed Mar. 21, 1984, which is a continuation of now abandoned application Ser. No. 419,055 filed Sept. 16, 1982.
US Referenced Citations (6)
Foreign Referenced Citations (8)
Number |
Date |
Country |
137021 |
Nov 1978 |
JPX |
58633 |
May 1979 |
JPX |
135616 |
Oct 1979 |
JPX |
97431 |
Jul 1980 |
JPX |
94446 |
Jul 1980 |
JPX |
145123 |
Nov 1980 |
JPX |
141555 |
Nov 1980 |
JPX |
38449 |
Apr 1981 |
JPX |
Continuations (2)
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Number |
Date |
Country |
Parent |
591902 |
Mar 1984 |
|
Parent |
419055 |
Sep 1982 |
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