Ultra-thick steel excellent in brittle crack arrestability and manufacturing method therefor
AssigneePosco
InventorHak-Cheol Lee
Life of this patent
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Abstract
An ultra-thick steel excellent in brittle crack arrestability according to an aspect of the present invention comprises, by weight, C: 0.02-0.07%, Mn: 1.8-2.2%, Ni: 0.7-1.2%, Nb: 0.005-0.02%, Ti: 0.005-0.02%, Cu: 0.1-0.4%, P: 0.01% or less, S: 0.004% or less, and the balance of Fe and inevitable impurities, wherein crystal grains that have a high angle grain boundary of 15 degrees or more, as measured by EBSD, may have an average grain size of 15 μm or less in the t/4−(3*t)/8 region (wherein t represents a thickness of the steel, the same below).
Claims11
An ultra-thick steel excellent in brittle crack arrestability, comprising:
- by wt %, 0.02 to 0.07% of C, 1.8 to 2.2% of Mn, 0.7 to 1.2% of Ni, 0.005 to 0.02% of Nb, 0.005 to 0.02% of Ti, 0.1 to 0.4% of Cu, 0.01% or less of P, 0.004% or less of S, and a balance of Fe and inevitable impurities, wherein grains that have a high angle grain boundary of 15° or more, as measured by EBSD, have an average grain size of 15 μm or less in the t/4−(3*t)/8 region, where t represents a thickness of the steel, and the same below.
A manufacturing method of an ultra-thick steel excellent in brittle crack arrestability, comprising:
- reheating a slab including, by wt %, 0.02 to 0.07% of C, 1.8 to 2.2% of Mn, 0.7 to 1.2% of Ni, 0.005 to 0.02% of Nb, 0.005 to 0.02% of Ti, 0.1 to 0.4% of Cu, 0.01% or less of P, 0.004% or less of S, and the balance of Fe and inevitable impurities;
- rough rolling the reheated slab;
- finishing rolling the roughly rolled slab at a cumulative reduction rate of 50% or more;
- cooling the finishing-rolled steel material;
- and
- initiating the finishing rolling in a temperature range of 700 to 850° C.
Dependencies are inferred from the claim text.