# US 10,246,764 B2 · Method of manufacturing a cold-rolled steel plate

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- Number: US 10,246,764 B2
- Document ID: US10246764B2
- Status: Granted
- Kind: B2
- Application number: 15/496,192
- Filed: 2017-04-25
- Published: 2017-08-10
- Granted: 2019-04-02
- Earliest claimed: 2013-01-31
- Assignees: Nisshin Steel Co., Ltd.
- Applicants: Nisshin Steel Co., Ltd.
- Inventors: Satoshi Tagashira; Masahito Suzuki; Tomohiro Imanaka
- Web page: https://patentgrep.com/patent/US10246764B2

## CPC

- C22C 38/28: with titanium or zirconium
- B21B 1/22: for rolling {plates, strips,} bands or sheets of indefinite length (B21B1/42 takes precedence)
- B21B 45/004: {Heating the product}
- C21D 8/02: during manufacturing of plates or strips (C21D8/12 takes precedence)
- C21D 8/0226: {Hot rolling}
- C21D 8/0236: {Cold rolling}
- C21D 8/0273: {Final recrystallisation annealing}
- C21D 9/46: for sheet metals
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/08: containing nickel {(C22C38/105 takes precedence)}
- C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium
- C22C 38/14: containing titanium or zirconium
- C22C 38/26: with niobium or tantalum
- C21D 2211/004: Dispersions; Precipitations
- C21D 2211/005: Ferrite
- Y02P 10/20: Recycling
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- B21B: ROLLING OF METAL (auxiliary operations used in connection with metal-working operations covered in B21, see B21C; bending by rolling B21D; manufacture of particular objects, e.g. screws, wheels, rings, barrels, balls, by rolling B21H; pressure welding by means of a rolling mill B23K20/04)
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

Manufacturing a cold-rolled steel plate, having a steel slab having the chemical composition containing, on the basis of percent by mass, C from 0.03 to 0.08%, Si from 0 to 1.0%, Mn from 0.2 to 0.8%, P at 0.03% or less, S at 0.01% or less, and Al at 0.05% or less so as to satisfy the following: formula (1) and at least one of Nb from 0.03 to 0.4%, V from 0.01 to 0.3%, and Ti from 0.01 to 0.3% so as to satisfy the following formula (2), with a residue being formed of Fe and unavoidable impurities. The steel slab is heated to 1200° C. or more and hot rolled to form a hot-rolled steel plate, which is wound from 550 to 700° C. to form a hot-rolled coil, and the hot-rolled coil is cold rolled or annealed and cold rolled, obtaining cross-sectional hardness from 200 to 350 HV.

## Claims

### Claim 1

A method of manufacturing a cold-rolled steel plate, wherein
a steel slab having a chemical composition containing, on the basis of percent by mass, C from 0.03 to 0.08%, Si from 0 to 1.0%, Mn from 0.2 to 0.8%, P at 0.03% or less, S at 0.01% or less, and Al at 0.05% or less so as to satisfy the following formula (1) and at least one of Nb from 0.03 to 0.4%, V from 0.01 to 0.3%, and Ti from 0.01 to 0.3% so as to satisfy the following formula (2), with a residue being formed of Fe and unavoidable impurities, wherein
5*C %−Si %+Mn %−1.5*Al %<1; and formula (1):
0.04<(Nb %/1.4)+(V %/1.1)+Ti %<0.3, is smelted, formula (2):
the steel slab is heated to 1200° C. or more and hot rolled at a finishing temperature of 850° C. or more and 950° C. or less to form a hot-rolled steel plate,
the hot-rolled steel plate is cooled at an average cooling rate of 20° C. per second or more from the finishing temperature to the winding temperature,
the cooled hot-rolled steel plate is wound from 550 to 700° C. to form a hot-rolled coil, and
as a final step or steps, the hot-rolled coil is cold rolled or the hot-rolled coil is annealed and cold rolled, forming a product, thereby obtaining cross-sectional hardness from 200 to 350 HV an average diameter of particles of a carbide as a precipitate containing any of Nb, V, and Ti from 20 to 100 nm, and a second phase structure having a longitudinal diameter of 5 μm or more has an area fraction of 5% or less in a cross-sectional structure.

### Claim 2

A method of manufacturing a cold-rolled steel plate, wherein
a steel slab having a chemical composition containing, on the basis of percent by mass, C from 0.03 to 0.08%, Si from 0 to 1.0%, Mn from 0.2 to 0.8%, P at 0.03% or less, S at 0.01% or less, and Al at 0.05% or less so as to satisfy the following formula (1) and at least one of Nb from 0.03 to 0.4%, V from 0.01 to 0.3%, and Ti from 0.01 to 0.3% so as to satisfy the following formula (2), the chemical composition further containing at least one of Cr from 0.10 to 2.0%, Ni from 0.05 to 0.5%, Mo from 0.05 to 0.5%, and B from 0.0002 to 0.002% so as to satisfy the following formula (3), wherein
5*C %−Si %+Mn %−1.5*Al %<1; formula (1)
0.04<(Nb %/1.4)+(V %/1.1)+Ti %<0.3; and formula (2):
5*C %−Si %+Mn %+1.6*Cr %+0.8*Ni %−1.5*Al %<1 is smelted, formula (3):
the steel slab is heated to 1200° C. or more and hot rolled at a finishing temperature of 850° C. or more and 950° C. or less to form a hot-rolled steel plate,
the hot-rolled steel plate is cooled at an average cooling rate of 20° C. per second or more from the finishing temperature to the winding temperature,
the cooled hot-rolled steel plate is wound from 550 to 700° C. to form a hot-rolled coil, and
as a final step or steps, the hot-rolled coil is cold rolled or the hot-rolled coil is annealed and cold rolled, forming a product, thereby obtaining cross-sectional hardness from 200 to 350 HV, an average diameter of particles of a carbide as a precipitate containing any of Nb, V, and Ti is from 20 to 100 nm, and a second phase structure having a longitudinal diameter of 5 μm or more has an area fraction of 5% or less in a cross-sectional structure.