Method for manufacturing rail, and rail
Proposed are the welding conditions under which welds are always stably formed such that the difference in hardness between flash-butt welds and rail base metal and the deflection in a bending test are in better ranges. A plurality of pieces of rail base metal are joined via welds formed by flash-butt welding, where the rail base metal has a chemical composition containing C: 0.60 to 1.20 mass %, Si: 0.10 to 1.50 mass %, Mn: 0.10 to 1.50 mass %, and Cr: 0.10 to 1.50 mass %, with the balance being Fe and inevitable impurities, and the flash-butt welding is performed with an amount of welding heat input of 1.50×10 5 kA 2 ×sec or more and 4.50×10 5 kA 2 ×sec or less.
1. A method of manufacturing a rail, comprising joining a plurality of pieces of rail base metal via welds formed by flash-butt welding, wherein
the rail base metal comprises a chemical composition containing
C: 0.60 mass % to 1.20 mass %,
Si: 0.10 mass % to 1.50 mass %,
Mn: 0.10 mass % to 1.50 mass %, and
Cr: 0.10 mass % to 1.50 mass %,
with the balance being Fe and inevitable impurities,
the flash-butt welding is performed with an amount of welding heat input of 1.50×10 5 kA 2 ×sec or more and 4.50×10 5 kA 2 ×sec or less,
an absolute value of difference in hardness between the rail base metal and the welds in a surface layer from a surface of a rail head to a depth of 2.5 mm after the welding is 20 or less in Vickers hardness, and
deflection of the welds is 20 mm or more.
2. The method of manufacturing a rail according to claim 1 , wherein the chemical composition further contains at least one selected from the group consisting of
V: 0.30 mass % or less,
Cu: 1.0 mass % or less,
Ni: 1.0 mass % or less,
Nb: 0.2 mass % or less,
Mo: 0.5 mass % or less,
Al: 0.07 mass % or less,
W: 1.0 mass % or less,
B: 0.005 mass % or less, and
Ti: 0.05 mass % or less.
3. A rail in which a plurality of pieces of rail base metal are joined via welds, wherein
the rail base metal comprises a chemical composition containing
C: 0.60 mass % to 1.20 mass %,
Si: 0.10 mass % to 1.50 mass %,
Mn: 0.10 mass % to 1.50 mass %, and
Cr: 0.10 mass % to 1.50 mass %,
with the balance being Fe and inevitable impurities, and
an absolute value of difference in hardness between the rail base metal and the welds in a surface layer from a surface of a head of the rail to a depth of 2.5 mm is 20 or less in Vickers hardness, and deflection of the welds is 20 mm or more.
4. The rail according to claim 3 , wherein the chemical composition further contains at least one selected from the group consisting of
V: 0.30 mass % or less,
Cu: 1.0 mass % or less,
Ni: 1.0 mass % or less,
Nb: 0.2 mass % or less,
Mo: 0.5 mass % or less,
Al: 0.07 mass % or less,
W: 1.0 mass % or less,
B: 0.005 mass % or less, and
Ti: 0.05 mass % or less.