Pearlitic rail with excellent wear resistance and toughness
View Patent ↗This pearlitic rail consists of a steel including: in terms of percent by mass, C: 0.65% to 1.20%; Si: 0.05% to 2.00%; Mn: 0.05% to 2.00%; and REM: 0.0005% to 0.0500%, with the balance being Fe and inevitable impurities, wherein, in a head portion of the rail, a head surface portion which ranges from surfaces of head corner portions and a head top portion to a depth of 10 mm has a pearlite structure, and the hardness Hv of the head surface portion is in a range of 320 to 500.
1. A pearlitic rail comprising a steel consisting of: in terms of percent by mass,
C: 0.65% to 1.20%;
Si: 0.05% to 2.00%;
Mn: 0.05% to 2.00%; and
REM: 0.0005% to 0.0500%,
with the balance being Fe and inevitable impurities,
wherein, in 95% or more of a metallographic structure contained in a head surface portion which ranges from surfaces of head corner portions and a head top portion to a depth of 10 mm in a head portion of the rail or in a portion which ranges from the surfaces of the head corner portions and the head top portion to a depth of 20 mm in the head portion is a pearlite structure,
the hardness Hv of the head surface portion is in a range of 320 to 500, and
an average value of ratios (L/D) of long side lengths (L) to short side lengths (D) of Mn sulfide-based inclusions observed in an arbitrary cross-section taken from a portion ranging from the surface of the head top portion to a depth of 3 mm to 10 mm along a longitudinal direction of the pearlite structure is in a range of 5.0 or lower.
2. The pearlitic rail according to claim 1 ,
wherein Mn sulfide-based inclusions having long side lengths (L) in a range of 1 μm to 50 μm are present at an amount per unit area in a range of 10/mm 2 to 100/mm 2 in an arbitrary cross-section taken along the longitudinal direction of the pearlite structure.
3. A pearlitic rail comprising a steel composition consisting of: in terms of percent by mass,
C: 0.65% to 1.20%;
Si: 0.05% to 2.00%;
Mn: 0.05% to 2.00%;
REM: 0.0005% to 0.0500%, and
one or more selected from S: 0.0020% to 0.0200%, Ca: 0.0005% to 0.0150%, Al: 0.0040% to 0.50%, Co: 0.01% to 1.00%, Cr: 0.01% to 2.00%, Mo: 0.01% to 0.50%, Nb: 0.002% to 0.050%, B: 0.0001% to 0.0050%, Ni: 0.01% to 1.00%, Ti: 0.0050% to 0.0500%, Mg: 0.0005% to 0.0200%, Zr: 0.0001% to 0.2000%, and N: 0.0060% to 0.0200%,
with the balance being Fe and inevitable impurities,
wherein in 95% or more of a metallographic structure contained in a head surface portion which ranges from surfaces of head corner portions and a head top portion to a depth of 10 mm in a head portion of the rail or in a portion which ranges from the surfaces of the head corner portions and the head top portion to a depth of 20 mm in the head portion is a pearlite structure,
the hardness Hv of the head surface portion is in a range of 320 to 500, and
an average value of ratios (L/D) of long side lengths (L) to short side lengths (D) of Mn sulfide-based inclusions observed in an arbitrary cross-section taken from a portion ranging from the surface of the head top portion to a depth of 3 mm to 10 mm along a longitudinal direction of the pearlite structure is in a range of 5.0 or lower.
4. The pearlitic rail according to claim 2 ,
wherein
Mn sulfide-based inclusions having long side lengths (L) in a range of 1 μm to 50 μm are present at an amount per unit area in a range of 10/mm 2 to 100/mm 2 in an arbitrary cross-section taken along the longitudinal direction of the pearlite structure.
5. A pearlitic rail comprising a steel comprising: in terms of percent by mass,
C: 0.65% to 1.20%;
Si: 0.05% to 2.00%;
Mn: 0.05% to 2.00%; and
REM: 0.0005% to 0.0500%,
with the balance being Fe and inevitable impurities,
wherein, in a head portion of the rail, a head surface portion which ranges from surfaces of head corner portions and a head top portion to a depth of 10 mm has a pearlite structure, and
the hardness Hv of the head surface portion is in a range of 320 to 500,
wherein an average value of ratios (L/D) of long side lengths (L) to short side lengths (D) of Mn sulfide-based inclusions observed in an arbitrary cross-section taken along a longitudinal direction of the pearlite structure is in a range of 5.0 or lower.
6. The pearlitic rail according to claim 5 ,
wherein the steel further comprises, in terms of percent by mass, S≦0.0100%, and
Mn sulfide-based inclusions having long side lengths (L) in a range of 1 μm to 50 μm are present at an amount per unit area in a range of 10/mm 2 to 100/mm 2 in an arbitrary cross-section taken along the longitudinal direction of the pearlite structure.