A rail-manufacturing method according to the present invention performs forced cooling on at least a head of a hot rail hot-rolled at or heated to the austenite region temperature or higher. The forced cooling is performed for 10 seconds from start of the forced cooling so that the cooling rate at the head surface becomes 1 C./s or higher to 20 C./s or lower, the forced cooling is performed after a lapse of 10 seconds from the start of the forced cooling until heat generation during transformation begins in the head surface so that the cooling rate at the head surface becomes 1 C./s or higher to 5 C./s or lower, the forced cooling is performed during transformation from beginning to end of the heat generation during transformation so that the cooling rate at the head surface becomes lower than 1 C./s or the temperature-rising rate becomes 5 C./s or lower, and the forced cooling is performed after the end of the heat generation during transformation until the rail-head surface temperature becomes 450 C. or lower so that the cooling rate at the head surface becomes 1 C./s or higher to 20 C./s or lower.

A rail-manufacturing method according to the present invention performs forced cooling on at least a head of a hot rail hot-rolled at or heated to the austenite region temperature or higher. The forced cooling is performed for 10 seconds from start of the forced cooling so that the cooling rate at the head surface becomes 1 C./s or higher to 20 C./s or lower, the forced cooling is performed after a lapse of 10 seconds from the start of the forced cooling until heat generation during transformation begins in the head surface so that the cooling rate at the head surface becomes 1 C./s or higher to 5 C./s or lower, the forced cooling is performed during transformation from beginning to end of the heat generation during transformation so that the cooling rate at the head surface becomes lower than 1 C./s or the temperature-rising rate becomes 5 C./s or lower, and the forced cooling is performed after the end of the heat generation during transformation until the rail-head surface temperature becomes 450 C. or lower so that the cooling rate at the head surface becomes 1 C./s or higher to 20 C./s or lower.

Provided is a continuous hot-dip galvanizing apparatus comprising: a vertical annealing furnace having heating, soaking zone, and cooling zones therein; and a hot-dip galvanizing line downstream of the cooling zone. The heating, soaking, and cooling zones each have, in its upper portion, at least one upper hearth roll and, in its lower portion, at least one lower hearth roll. The soaking zone has a first and second humidified gas supply ports to supply a humidified gas having a dew point of 10? C. to 30? C. to the soaking zone. The first and second humidified gas supply ports are 1.0 m to 5.0 m lower than the center of the lower and upper hearth rolls, respectively, and overlap the steel sheet. The first humidified gas supply port is provided only for an ascending pass and the second humidified gas supply port is provided only for a descending pass.

The invention discloses a drill pipe having ultra-high toughness and high strength and comprising the following chemical elements in mass percentage: C: 0.24-0.30%, Si: 0.1-0.5%, Mn: 0.7-1.5%, Cr: 0.7-1.5%, Mo: 0.5-0.75%, V: 0.01-0.10%, Nb: 0.01-0.05%, P0.015%, S0.005%, and the balance of Fe and unavoidable impurities; and a process of manufacturing the drill pipe having ultra-high toughness and high strength, comprising: heating the drill pipe as a whole to 900-950 C.; subjecting the inner surface of the drill pipe to axial-flow water-spray cooling and the outer surface of the drill pipe to laminar-flow water-spray cooling while controlling the amount of the water sprayed at thickened ends of the drill pipe and that along the pipe body to be different from each other; and controlling the tempering temperature to be 650-675 C. The inventive drill pipe having ultra-high toughness and high strength has a longitudinal full-size impact toughness at 20 C. of at least 100 J and has a strength of 135 ksi.

The invention discloses a drill pipe having ultra-high toughness and high strength and comprising the following chemical elements in mass percentage: C: 0.24-0.30%, Si: 0.1-0.5%, Mn: 0.7-1.5%, Cr: 0.7-1.5%, Mo: 0.5-0.75%, V: 0.01-0.10%, Nb: 0.01-0.05%, P0.015%, S0.005%, and the balance of Fe and unavoidable impurities; and a process of manufacturing the drill pipe having ultra-high toughness and high strength, comprising: heating the drill pipe as a whole to 900-950 C.; subjecting the inner surface of the drill pipe to axial-flow water-spray cooling and the outer surface of the drill pipe to laminar-flow water-spray cooling while controlling the amount of the water sprayed at thickened ends of the drill pipe and that along the pipe body to be different from each other; and controlling the tempering temperature to be 650-675 C. The inventive drill pipe having ultra-high toughness and high strength has a longitudinal full-size impact toughness at 20 C. of at least 100 J and has a strength of 135 ksi.

Rail manufacturing method performs, on at least a head of the rail that is hot after hot-rolled at an austenite region temperature or higher or after heated to the austenite region temperature or higher, forced cooling: for 10 seconds from start of the forced cooling so that a cooling rate at a surface of the head becomes 1 C./s to 20 C./s; during a period after a lapse of 10 seconds from the start until heat generation during transformation begins at the surface so that the cooling rate becomes 1 C./s to 5 C./s; during transformation from beginning to end of the heat generation during transformation so that the cooling rate becomes lower than 1 C./s or a temperature-rising rate becomes 5 C./s or lower; and during a period after the end of the heat generation during transformation until temperature at the surface becomes 450 C. or lower so that the cooling rate becomes 1 C./s to 20 C./s.

Rail manufacturing method performs, on at least a head of the rail that is hot after hot-rolled at an austenite region temperature or higher or after heated to the austenite region temperature or higher, forced cooling: for 10 seconds from start of the forced cooling so that a cooling rate at a surface of the head becomes 1 C./s to 20 C./s; during a period after a lapse of 10 seconds from the start until heat generation during transformation begins at the surface so that the cooling rate becomes 1 C./s to 5 C./s; during transformation from beginning to end of the heat generation during transformation so that the cooling rate becomes lower than 1 C./s or a temperature-rising rate becomes 5 C./s or lower; and during a period after the end of the heat generation during transformation until temperature at the surface becomes 450 C. or lower so that the cooling rate becomes 1 C./s to 20 C./s.

Provided is a large crankshaft comprising a pin fillet portion, wherein: an average initial compression stress in a surface layer region from a surface of the pin fillet portion to a depth of 500 m is 500 Mpa or more; an average Vickers hardness of the surface of the pin fillet portion is 600 or more; an arithmetic average roughness Ra of the surface of the pin fillet portion is 1.0 m or less; and an average prior austenite grain size of a metallographic structure is 100 m or less. The large crankshaft has composition comprising C: 0.2% by mass to 0.4% by mass, Si: 0% by mass to 1.0% by mass, Mn: 0.2% by mass to 2.0% by mass, Al: 0.005% by mass to 0.1% by mass, N: 0.001% by mass to 0.02% by mass, and a balance being Fe and inevitable impurities.

A method of heat transfer between a metallic or non-metallic item and a heat transfer fluid including a fluid medium, hydrophobic nanoparticles having a lateral size between 26 and 50 m and a dispersing agent is provided. The nanoparticles concentration/dispersing agent concentration ratio in weight is between 3 and 18 and the nanoparticles do not include carbon nanotubes. A heat transfer fluid is also provided.

A method of heat transfer between a metallic or non-metallic item and a heat transfer fluid is provided. The method includes a fluid medium and nanoparticles. A thickness/lateral size ratio of the nanoparticles is below 0.00044. The nanoparticles do not include carbon nanotubes.