High-carbon steel sheet and method of manufacturing the same

1. A high-carbon steel sheet comprising:

a chemical composition represented by, in mass %:

C: 0.60% to 0.90%;

Si: 0.10% to 0.40%;

Mn: 0.30% to 1.50%;

N: 0.0010% to 0.0100%;

Cr: 0.20% to 1.00%;

P: 0.0200% or less;

S: 0.0060% or less;

Al: 0.050% or less;

Mg: 0.000% to 0.010%;

Ca: 0.000% to 0.010%;

Y: 0.000% to 0.010%;

Zr: 0.000% to 0.010%;

La: 0.000% to 0.010%;

Ce: 0.000% to 0.010%; and

balance: Fe and impurities; and

a structure represented by:

a concentration of Mn contained in cementite: 2% or more and 8% or less,

a concentration of Cr contained in cementite: 2% or more and 8% or less,

an average grain diameter of ferrite: 10 μm or more and 50 μm or less,

an average particle diameter of cementite: 0.3 μm or more and 1.5 μm or less, and

a spheroidized ratio of cementite: 85% or more.

2. The high-carbon steel sheet according to claim 1 , wherein in the chemical composition,

Mg: 0.001% to 0.010%,

Ca: 0.001% to 0.010%,

Y: 0.001% to 0.010%,

Zr: 0.001% to 0.010%,

La: 0.001% to 0.010%, or

Ce: 0.001% to 0.010%, or any combination thereof is satisfied.

3. A method of manufacturing a high-carbon steel sheet according to claim 1 , comprising:

hot-rolling of a slab to obtain a hot-rolled sheet;

pickling of the hot-rolled sheet;

annealing of the hot-rolled sheet after the pickling to obtain a hot-rolled annealed sheet;

cold-rolling of the hot-rolled annealed sheet to obtain a cold-rolled sheet; and

annealing of the cold-rolled sheet, wherein

the slab comprises a chemical composition represented by, in mass %:

C: 0.60% to 0.90%;

Si: 0.10% to 0.40%;

Mn: 0.30% to 1.50%;

P: 0.0200% or less;

S: 0.0060% or less;

Al: 0.050% or less;

N: 0.0010% to 0.0100%;

Cr: 0.20% to 1.00%;

Mg: 0.000% to 0.010%;

Ca: 0.000% to 0.010%;

Y: 0.000% to 0.010%;

Zr: 0.000% to 0.010%;

La: 0.000% to 0.010%;

Ce: 0.000% to 0.010%; and

balance: Fe and impurities, and

in the hot-rolling,

a finishing temperature of finish-rolling is 800° C. or more and less than 950° C., and

a coiling temperature is 450° C. or more and less than 550° C.,

a reduction ratio in the cold-rolling is 5% or more and 35% or less,

the annealing of the hot-rolled sheet comprises:

heating the hot-rolled sheet to a first temperature of 450° C. or more and 550° C. or less, a heating rate from 60° C. to the first temperature being 30° C./hour or more and 150° C./hour or less;

then holding the hot-rolled sheet at the first temperature for one hour or more and less than 10 hours;

then heating the hot-rolled sheet at a heating rate of 5° C./hour or more and 80° C./hour or less from the first temperature to a second temperature of 670° C. or more and 730° C. or less; and

then holding the hot-rolled sheet at the second temperature for 20 hours or more and 200 hours or less,

the annealing of the cold-rolled sheet comprises:

heating the cold-rolled sheet to a third temperature of 450° C. or more and 550° C. or less, a heating rate from 60° C. to the third temperature is 30° C./hour or more and 150° C./hour or less;

then holding the cold-rolled sheet at the third temperature for one hour or more and less than 10 hours;

then heating the cold-rolled sheet at a heating rate of 5° C./hour or more and 80° C./hour or less from the third temperature to a fourth temperature of 670° C. or more and 730° C. or less; and

then holding the cold-rolled sheet at the fourth temperature for 20 hours or more and 200 hours or less.

4. The method of manufacturing the high-carbon steel sheet according to claim 3 ,

wherein in the chemical composition,

Mg: 0.001% to 0.010%,

Ca: 0.001% to 0.010%,

Y: 0.001% to 0.010%,

Zr: 0.001% to 0.010%,

La: 0.001% to 0.010%, or

Ce: 0.001% to 0.010%, or any combination thereof is satisfied.