Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Akira Kobayashi

Kazuo Fujita

Masaharu Ueda

Koichi Uchino

Koichiro Matsushita

Katsuya Iwano

Takashi Morohoshi

Kenichi Karimine

Takeshi Yamamoto

Seiji Sugiyama

Teruhisa Miyazaki

Takuya Tanahashi

Kouichi Uchino

Hideo Tottori

Kyohei Sonoyama

A method of reheating a rail weld zone after rails were welded, a distance C between a reheating region P of a rail web portionand a welding center Q is set to more than or equal to 0.2 times and less than or equal to three times a HAZ length Lh of the rail weld zone. A length B of the reheating region P may be more than or equal to 0.5 times and less than or equal to five times the HAZ length Lh of the rail weld zone. A height A of the reheating region P may be more than or equal to 0.2 times a height Hw of the rail web portion. A temperature Th reached in a reheating process at a center of the reheating region P may be higher than or equal to 400&#xb0; C. and lower than or equal to 750&#xb0; C.

Method of reheating rail weld zone

The invention provides a method of cooling a rail weld zone. The method includes a first rail web portion cooling process of cooling a rail web portion cooling region of the rail weld zone in a part of a temperature range until the completion of transformation from austenite to pearlite, a second rail web portion cooling process of cooling the rail web portion cooling region after the entire rail web portion of the rail weld zone is transformed to pearlite, a foot portion cooling process of cooling a foot portion of the rail weld zone, and a head portion cooling process of cooling a head portion of the rail weld zone. When cooling time of the first and second rail web portion cooling processes is t minute, a k value satisfies an expression represented as &#x2212;0.1t+0.63&#x2266;k&#x2266;&#x2212;0.1t+2.33.

Method of cooling rail weld zone, and rail weld joint

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.

Pearlite rail

The present invention is: a pearlitic steel rail excellent in wear resistance and ductility, characterized in that, in a steel rail having pearlite structure containing, in mass, 0.65 to 1.40% C, the number of the pearlite blocks having grain sizes in the range from 1 to 15 &#x3bc;m is 200 or more per 0.2 mmof an observation field at least in a part of the region down to a depth of 10 mm from the surface of the corners and top of the head portion; and a method for producing a pearlitic steel rail excellent in wear resistance and ductility, characterized by, in the hot rolling of said steel rail, applying finish rolling so that the temperature of the rail surface may be in the range from 850&#xb0; C. to 1,000&#xb0; C. and the sectional area reduction ratio at the final pass may be 6% or more, and then applying accelerated cooling to the head portion of said rail at a cooling rate in the range from 1 to 30&#xb0; C./sec. from the austenite temperature range to at least 550&#xb0; C.

Pearlitic steel rail excellent in wear resistance and ductility and method for producing same

High-strength bainitic steel rails have improved resistances to surface fatigue failures and wear required of the head of rails for heavy-load service railroads. The high-strength bainitic steels rails having excellent resistances to surface fatigue failures and wear contain constituents of specific ranges and consisting of bainitic structures at least in part are characterized in that the total area occupied by carbides whose longer axes are 100 to 1000 nm in a given cross section of said bainitic structures accounts for 10 to 50 percent thereof.

Bainitic type rail excellent in surface fatigue damage resistance and wear resistance

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Tokyo, Japan

Katsuya Iwano