Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Takuya Tanahashi

Masaharu Ueda

Teruhisa Miyazaki

Jun Takahashi

Akira Kobayashi

Katsuya Iwano

Yusuke Maeda

Kyohei Sonoyama

According to one aspect of the present invention, what is provided is a rail including, by mass %: C: 0.75% to 1.20%; Si: 0.10% to 2.00%; Mn: 0.10% to 2.00%; Cr: 0.10% to 1.20%; V: 0.010% to 0.200%; N: 0.0030% to 0.0200%; P≤0.0250%; S≤0.0250%; Mo: 0% to 0.50%, Co: 0% to 1.00%; B: 0% to 0.0050%; Cu: 0% to 1.00%; Ni: 0% to 1.00%; Nb: 0% to 0.0500%; Ti: 0% to 0.0500%; Mg: 0% to 0.0200%; Ca: 0% to 0.0200%; REM: 0% to 0.0500%; Zr: 0% to 0.0200%; Al: 0% to 1.00%; and a remainder consisting of Fe and impurities, in which a structure ranging from an outer surface of a head portion as an origin to a depth of 25 mm includes 95% or greater of a pearlite structure by area ratio, the hardness of the structure is in a range of Hv 360 to 500, and in ferrite of the pearlite structure at a position at a depth of 25 mm from the outer surface of the head portion as the origin, the number density of a V nitride having a grain size of 0.5 to 4.0 nm and including Cr is in a range of 1.0×10to 5.0×10cm.

Rail and method of manufacturing rail

A rail including a predetermined chemical composition is provided, in which 90 area % or greater of a metallographic structure in a cross section of a rail web portion is a pearlite structure, a minimum value of a hardness in the cross section of the rail web portion is Hv 300 or greater, and a difference between a maximum value and the minimum value of the hardness in the cross section of the rail web portion is Hv 40 or less.

Rail

A rail provided by the present invention includes: has a predetermined chemical components, wherein, in a region from a head surface constituted of a surface of a top head portion and a surface of a corner head portion to a depth of 10 mm, a total amount of pearlite structures and bainite structures is 95% by area or more, and an amount of the bainite structures is 20% by area or more and less than 50% by area, and an average hardness of the region from the head surface to a depth of 10 mm is in a range of Hv 400 to Hv 500.

Rail and production method therefor

The present invention relates to a rail which has a predetermined chemical composition and satisfies expressions of 1.00&#x3c;Mn/Cr&#x2264;4.00 and 0.30&#x2264;0.25&#xd7;Mn+Cr&#x2264;1.00 and in which a structure to a depth of 25 mm from an outer surface of a head portion as the origin includes 95% or greater of a pearlite structure, the hardness of the structure is in a range of Hv 350 to 480, 50 to 500 V carbonitride having an average grain size of 5 to 20 nm are present per 1.0 &#x3bc;mof an area to be inspected in a transverse cross section at a position having a depth of 25 mm from the outer surface of the head portion, and the value obtained by subtracting the hardness of the position having the depth of 25 mm from the outer surface of the head portion from the hardness of the position having a depth of 2 mm from the outer surface of the head portion is in a range of Hv 0 to Hv 40.

A rail provided by the present invention includes: has a predetermined chemical components, wherein a value of Mn/Cr, which is a ratio of Mn content with respect to Cr content, is within a range of 0.30 to 1.00, structures in a region from a head surface constituted of a surface of a top head portion and a surface of a corner head portion to a depth of 10 mm is 98% by area or more of bainite structures, and an average hardness of the region from the head surface to a depth of 10 mm is in a range of Hv 380 to Hv 500.

A steel rail includes: by mass %, higher than 0.85% to 1.20% of C; 0.05% to 2.00% of Si; 0.05% to 0.50% of Mn; 0.05% to 0.60% of Cr; P&#x2266;0.0150%; and the balance consisting of Fe and inevitable impurities, wherein 97% or more of a head surface portion which is in a range from a surface of a head corner portion and a head top portion as a starting point to a depth of 10 mm has a pearlite structure, a Vickers hardness of the pearlite structure is Hv320 to 500, and a CMn/FMn value which is a value obtained by dividing CMn [at. %] that is a Mn concentration of a cementite phase in the pearlite structure by FMn [at. %] that is a Mn concentration of a ferrite phase is equal to or higher than 1.0 and equal to or less than 5.0.

Steel rail and method of manufacturing the same

A pearlite rail contains, by mass %, 0.65 to 1.20% of C; 0.05 to 2.00% of Si; 0.05 to 2.00% of Mn; and the balance composed of Fe and inevitable impurities, wherein at least part of the head portion and at least part of the bottom portion has a pearlite structure, and the surface hardness of a portion of the pearlite structure is in a range of Hv320 to Hv500 and a maximum surface roughness of a portion of the pearlite structure is less than or equal to 180 &#x3bc;m.

Growing community of inventors

Kitakyushu, Japan

Takuya Tanahashi