Steel sheet for pipe having excellent hydrogen-induced crack resistance and method for manufacturing same

Abstract

The present disclosure relates to a steel sheet for pipes having excellent hydrogen-induced crack resistance and a method for manufacturing the same. One aspect of the present invention is to provide a steel sheet for a pipe having excellent hydrogen-induced crack resistance and a method for manufacturing same. According to an aspect of the present disclosure, a steel sheet for pipes having excellent hydrogen-induced crack resistance and a method for manufacturing the same may be provided.

1 . A steel sheet for a pipe having excellent hydrogen-induced crack resistance, the steel sheet comprising:
 by weight, C: 0.06 to 0.12%, Si: 0.10 to 0.50%, Mn: 0.8 to 2.2%, P: 0.010% or less, S: 0.001% or less, Nb: more than 0.05% to 0.1% or less, Cr: 0.05% 0.6%, Ti: more than 0.02% to less than 0.05%, Ca: 0.001 to 0.006%, N: 0.008% or less, a balance of Fe and other inevitable impurities,   wherein a microstructure in the entire region of the steel sheet in a thickness direction, includes, by area %, 90% or more of acicular ferrite and lower bainite, and including 10% or less of one or more of pearlite and island-like martensite,   wherein microstructure in a ⅖ to ⅗ region of the steel sheet in the thickness direction includes, by area %, 95% or more of acicular ferrite and lower bainite, and 5% or less of island-like martensite,   wherein the acicular ferrite and lower bainite have an average grain size of 5 μm or less.   
     
     
         2 . The steel sheet of  claim 1 , wherein the steel sheet has a CLR of 15% or less measured under conditions of H 2 S partial pressure: 0.1 bar and pH: 5.0 according to NACE TM0284 standard after pipe forming. 
     
     
         3 . The steel sheet of  claim 1 , wherein the steel sheet has a yield strength of 552 MPa or more and a tensile strength of 655 MPa or more without a heat treatment after pipe forming. 
     
     
         4 . A method for manufacturing a steel sheet for a pipe having excellent hydrogen-induced crack resistance, the method comprising:
 reheating a slab including, by weight, C: 0.06 to 0.12%, Si: 0.10 to 0.50%, Mn: 0.8 to 2.2%, P: 0.010% or less, S: 0.001% or less, Nb: more than 0.05% to 0.1% or less, Cr: 0.05% 0.6%, Ti: more than 0.02% to less than 0.05%, Ca: 0.001 to 0.006%, N: 0.008% or less, a balance of Fe and other inevitable impurities, at 1100° C. to 1300° C.;   rough rolling the reheated slab at 900° C. to 1100° C. to obtain a rough rolled bar;   finish hot-rolling the rough-rolled bar at 800° C. to 900° C. to obtain hot-rolled steel;   cooling the hot-rolled steel at 10° C. to 50° C./s; and   coiling the cooled hot-rolled steel at 450° C. to 550° C.