Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Teruhisa Miyazaki

Masaharu Ueda

Takuya Tanahashi

Takeshi Yamamoto

Suguru Yoshida

Jun Takahashi

Takashi Morohoshi

Katsuya Iwano

Kyohei Sonoyama

Yusuke Maeda

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 according to an aspect of the present invention is manufactured by melting steel using an electric furnace, satisfies a predetermined range as a chemical composition and particularly includes Pb: 0.0003% to 0.0020%, 95 area % or more of a region from an outer surface of a head portion to a depth of 20 mm is a pearlite structure, and a hardness in the region from the outer surface of the head portion to the depth of 20 mm is in a range of Hv 300 to Hv 500.

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.

The present invention relates to a rail which has a predetermined chemical composition and in which at least 90% of a metallographic structure from an outer surface of the rail bottom portion, as the origin, to a depth of 5 mm is a pearlite structure, a surface hardness HC of a foot-bottom central portion is in a range of Hv 360 to 500, a surface hardness HE of a foot-edge portion is in a range of Hv 260 to 315, and HC, HE, and a surface hardness HM of a middle portion positioned between the foot-bottom central portion and the foot-edge portion satisfy HC&#x2265;HM&#x2265;HE.

A rail is provided in which in a range from a surface of a head of the rail to a depth of 30 mm, 95% or more of a structure is composed of a pearlite structure by area %, and in a range with a depth of 20 mm to 30 mm from the surface of the head of the rail, an average grain size of a pearlite block in a transverse section is 120 &#x3bc;m to 200 &#x3bc;m.

In the rail, 95% or more of a structure in a head surface section, which is a range from surfaces of head corner sections and a head top section of the rail as a starting point to a depth of 20 mm, is a pearlite or bainite structure and the structure contains 20 to 200 MnS-based sulfides formed around an Al-based oxide as a nucleus and having a grain size in a range of 1 &#x3bc;m to 10 &#x3bc;m per square millimeter of an area to be inspected on a horizontal cross section of the rail.

This high-carbon pearlitic steel rail having excellent ductility, includes: 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: 0.001% to 0.01%; V: 0.005% to 0.20%; and N: less than 0.0040%, with the balance being Fe and inevitable impurities, wherein contents of Ti and V fulfill the following formula (1), and a rail head portion has a pearlite structure.5&#x2266;[V(% by mass)]/[Ti(% by mass)]&#x2266;20&#x2003;&#x2003;Formula (1)

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

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

Tokyo, Japan

Teruhisa Miyazaki