PRODUCTION OF LOW YIELD RATIO HIGH TOUGHNESS SEAMLESS PIPE

Japanese Patent JP2556643

B2

PURPOSE: To manufacture a low yield ratio, high toughness seamless pipe by heating a slab having a specified compsn. contg. Ti, Nb or the like to a specified temp. and thereafter executing specified heat treatment in combination with hot piercing continuous rolling and specified hot rolling.
CONSTITUTION: The slab contg., by weight, 0.05 to 0.35% C, 0.01 to 2.5% Si, 0.15 to 2.5% Mn, 0.01% or lower S, 0.02% or lower P, 0.005 to 0.1% Al, 0.005 to 0.1% Ti, 0.005 to 0.1% Nb and ≤0.01% N and furthermore contg., at need, prescribed amounts of one or more kinds among Cr, Mo, Ni, V and B or one more kinds among rare earth elements, Ca, Co and Cu, and the balance substantial Fe is heated to ≥ 1200°C or a higher temp and is thereafter subjected to hot piercing continuous rolling, and in this process, it is subjected to forced cooling to 1100 to 900°C. Successively, the steel pipe is subjected to hot rolling at 15% or a higher reduction rate of area in thickness. Next, the hollow pipe stock whose temp. is reduced to 850°C to the Ar1 point is heated to 900 to 1000°C higher than the same, is thereafter subjected to hot finish rolling at the finishing temp. of the Ar3 point + 50°C or above is subsequently subjected to air cooling treatment.

YAGI AKIRA
ASAHI HITOSHI
UENO MASAKATSU
SATO HISAMI

JP10708692A

November 20, 1996

April 24, 1992

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SHINNIPPON SEITETSU KK

C21D8/10; C22C38/00; C22C38/14; C22C38/54; (IPC1-7): C21D8/10

JP421721A
JP3162524A
JP364415A

Hiroaki Tamura (1 outside)

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