Structural steel having excellent brittle fracture resistance and method for manufacturing same
A technology of brittle fracture and structural steel, applied in the field of structural steel, can solve problems such as unapplicable and difficult to control the rolling process, and achieve the effect of high strength characteristics and excellent brittle fracture resistance
Active Publication Date: 2021-08-06
浦项股份有限公司
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Problems solved by technology
[0006] Patent Document 1 proposes a technique for grain refinement of the surface layer portion of steel, but the surface layer portion is mainly formed of equiaxed ferrite grains and elongated ferrite grains, therefore, this technique cannot be applied For high-strength steel with a tensile strength of 800MPa or higher
Furthermore, in Patent Document 1, in order to refine the grains of the surface layer portion, the rolling process basically has to be performed in the middle of recovery heat in the surface layer portion, which makes it difficult to control the rolling process
Method used
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Experimental program
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Embodiment approach
[0105] Hereinafter, the present disclosure will be described in more detail through specific examples.
[0106] (Example)
[0107] Slabs having the steel compositions of Table 1 were prepared, and transformation temperatures were calculated based on the steel compositions of Table 1 and shown in Table 2. In Table 1 below, the contents of boron (B), nitrogen (N) and calcium (Ca) are based on ppm.
[0108] [Table 1]
[0109]
[0110] [Table 2]
[0111]
[0112] The slabs having the composition of Table 1 were subjected to rough rolling, primary cooling, and heat recovery treatment under the conditions of Table 3 below, and were subjected to finish rolling and secondary cooling under the conditions of Table 4. The evaluation results for the steels produced under the conditions of Table 3 and Table 4 are shown in Table 5 below.
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Abstract
A structural steel having excellent brittle fracture resistance according to an aspect of the present invention comprises, by weight%, 0.02-0.12% of C, 0.01-0.8% of Si, 1.5-2.5% of Mn, 0.005-0.5% of Al, 0.02% or less of P, 0.01% or less of S, 0.0015-0.015% of N, and the remainder of Fe and unavoidable impurities, wherein an outer surface layer portion and an inner central portion are microstructurally divided along the thickness direction, the surface layer portion comprises tempered bainite as a matrix structure, the central portion comprises bainitic ferrite as a matrix structure, and the NDT temperature by the NRL drop-weight test may be -70 DEG C or lower.
Description
technical field [0001] The present disclosure relates to structural steel and a method for manufacturing the same, and more particularly, to a structural steel effectively improving brittle fracture resistance by optimizing steel composition, microstructure, and manufacturing process and a method for manufacturing the same. Background technique [0002] With the recent tendency to increase the size of building structures, steel pipes for transportation, bridges, etc., there is an increased demand for the development of structural steels having high strength characteristics. In the past, steel was produced by applying heat treatment such as quenching-tempering to satisfy such high-strength characteristics, but recently, steel produced by cooling after rolling has replaced existing Some heat-treated steels. In the case of steel produced by cooling after rolling, impact toughness is improved due to a refined microstructure, but a microstructure with high strength may be formed...
Claims
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IPC IPC(8): C22C38/04C22C38/02C22C38/06C22C38/00C22C38/08C22C38/16C22C38/18C22C38/12C22C38/14B21B3/00
CPCC22C38/02C22C38/04C22C38/06C22C38/08C22C38/12C22C38/14C22C38/16C22C38/18C22C38/00C21D1/19C21D8/0226C21D8/0263C21D2211/002C21D2211/005C21D9/46C21D1/20C21D1/22C21D1/02Y02P10/20C22C38/001B21B3/00B21B37/74C21D2211/008C21D8/0247C21D2211/001C22C38/002
Inventor 李一彻曹财荣姜相德
Owner 浦项股份有限公司