Pearlite-based high carbon steel rail having excellent ductility and process for production thereof

1. A pearlitic steel rail, consisting of: in terms of percent by mass,

C: more than 0.85% to 1.40%;

Si: 0.10% to 2.00%;

Mn: 0.10% to 2.00%;

Ti: 0.003% to 0.01%;

V: 0.005% to 0.20%;

N: 0.0024 to less than 0.0040%; and

a balance of Fe and inevitable impurities,

wherein contents of Ti and V fulfill the following formula (1), and

a rail head portion of the pearlitic steel rail has a pearlite structure,

5≦[V(% by mass)]/[Ti(% by mass)]≦20  Formula (1).

2. A method for manufacturing a pearlitic rail, the method comprising subjecting a bloom to hot rolling,

wherein the bloom consists of: in terms of percent by mass, C: more than 0.85% to 1.40%; Si: 0.10% to 2.00%; Mn: 0.10% to 2.00%; Ti: 0.003% to 0.01% V: 0.005% to 0.20%; and N: 0.0024 to less than 0.0040%; and a balance of Fe and inevitable impurities, and contents of Ti and V fulfill the following formula (1), and

finishing rolling of the hot rolling is carried out under conditions where a finishing rolling temperature FT in terms of ° C. is set to be in a range represented by the following formula (3), wherein Tc is represented by the following formula (2) in which [C] is the content of C in terms of % by mass, [V] is the content of V in terms of % by mass, and [Ti] is the content of Ti in terms of % by mass of the bloom,

5≦[V(% by mass)]/[Ti(% by mass)]≦20  Formula (1)

Tc =850+35×[C]+1.35×104×[Ti]+180×[V]  Formula (2)

Tc −25 ≦FT≦Tc +25  Formula (3).

3. The method for manufacturing a pearlitic rail according to claim 2 ,

wherein the finishing rolling is carried out under conditions where a sum FR in terms of % of reductions of cross-sectional area in last two passes is set to be in a range represented by the following formula (5), wherein R, is represented by the following formula (4) in which [C] is the content of C in terms of % by mass, [V] is the content of V in terms of % by mass, and [Ti] is the content of Ti in terms of % by mass of the bloom,

R c =35−13×[C]−600×[Ti]−20×[V]  Formula (4)

R c −5 ≦FR≦R c +5  Formula (5).

4. The pearlitic steel rail according to claim 1 ,

wherein an average grain diameter of Ti-based precipitates, V-based precipitates, or Ti—V complex precipitates is in a range of 10 nm to 100 nm.

5. The pearlitic steel rail according to claim 1 ,

wherein a density of Ti-based precipitates, V-based precipitates, or Ti—V complex precipitates is in a range of 50,000 precipitates to 500,000 precipitates per 1 mm 2 .

6. The pearlitic steel rail according to claim 4 ,

wherein a density of Ti-based precipitates, V-based precipitates, or Ti—V complex precipitates is in a range of 50,000 precipitates to 500,000 precipitates per 1 mm 2 .

7. The pearlitic steel rail according to claim 1 ,

wherein N is 0.0024 to 0.0039%.

8. A pearlitic steel rail, consisting of: in terms of percent by mass,

C: more than 0.85% to 1.40%;

Si: 0.10% to 2.00%;

Mn: 0.10% to 2.00%;

Ti: 0.003% to 0.01%;

V: 0.005% to 0.20%;

N: 0.0024 to less than 0.0040%;

one or more selected from the group consisting of Nb: 0.002% to 0.050%, Cr: 0.05% to 2.00%, Mo: 0.01% to 0.50%, Co: 0.10% to 2.00%, Cu: 0.05% to 1.00%, Ni: 0.01% to 1.00%, Mg: 0.0005% to 0.0200%, Ca: 0.0005% to 0.0150%, Al: 0.0050% to 1.00%, Zr: 0.0001% to 0.2000%, P: 0.035% or less, and S: 0.035% or less; and

a balance of Fe and inevitable impurities,

wherein contents of Ti and V fulfill the following formula (1), and

a rail head portion of the pearlitic steel rail has a pearlite structure,

5≦[V(% by mass)]/[Ti(% by mass)]≦20  Formula (1).

9. The method for manufacturing a pearlitic rail according to claim 2 , wherein N is 0.0024 to 0.0039% in the bloom.

10. A method for manufacturing a pearlitic rail, the method comprising subjecting a bloom to hot rolling,

wherein the bloom consists of: in terms of percent by mass,

C: more than 0.85% to 1.40%;

Si: 0.10% to 2.00%;

Mn: 0.10% to 2.00%;

Ti: 0.003% to 0.01%;

V: 0.005% to 0.20%;

N: 0.0024 to less than 0.0040%;

one or more selected from the group consisting of Nb: 0.002% to 0.050%, Cr: 0.05% to 2.00%, Mo: 0.01% to 0.50%, Co: 0.10% to 2.00%, Cu: 0.05% to 1.00%, Ni: 0.01% to 1.00%, Mg: 0.0005% to 0.0200%, Ca: 0.0005% to 0.0150%, Al: 0.0050% to 1.00%, Zr: 0.0001% to 0.2000%, P: 0.035% or less, and S: 0.035% or less; and

a balance of Fe and inevitable impurities,

wherein contents of Ti and V fulfill the following formula (1), and

finishing rolling of the hot rolling is carried out under conditions where a finishing rolling temperature FT in terms of ° C. is set to be in a range represented by the following formula (3), wherein T c is represented by the following formula (2) in which [C] is the content of C in terms of % by mass, [V] is the content of V in terms of % by mass, and [Ti] is the content of Ti in terms of % by mass of the bloom,

5≦[V(% by mass)]/[Ti(% by mass)]≦20  Formula (1)

T c =850+35×[C]+1.35×10 4 ×[Ti]+180×[V]  Formula (2)

T c −25 ≦FT≦T c +25  Formula (3).

11. The pearlitic steel rail according to claim 8 ,

wherein an average grain diameter of Ti-based precipitates, V-based precipitates, or Ti—V complex precipitates is in a range of 10 nm to 100 nm.

12. The pearlitic steel rail according to claim 8 ,

wherein a density of Ti-based precipitates, V-based precipitates, or Ti—V complex precipitates is in a range of 50,000 precipitates to 500,000 precipitates per 1 mm 2 .

13. The pearlitic steel rail according to claim 11 ,

wherein a density of Ti-based precipitates, V-based precipitates, or Ti—V complex precipitates is in a range of 50,000 precipitates to 500,000 precipitates per 1 mm 2 .

14. The pearlitic steel rail according to claim 8 , wherein N is 0.0024 to 0.0039%.

15. The method for manufacturing a pearlitic rail according to claim 10 ,

wherein the finishing rolling is carried out under conditions where a sum FR in terms of % of reductions of cross-sectional area in last two passes is set to be in a range represented by the following formula (5), wherein R c is represented by the following formula (4) in which [C] is the content of C in terms of % by mass, [V] is the content of V in terms of % by mass, and [Ti] is the content of Ti in terms of % by mass of the bloom,

R c =35−13×[C]−600×[Ti]−20×[V]  Formula (4)

R c −5 ≦FR≦R c +5  Formula (5).

16. The method for manufacturing a pearlitic rail according to claim 10 , wherein N is 0.0024 to 0.0039% in the bloom.