US 2020/0347480 A1Published application

Steel reinforcing bar and production method therefor

AssigneeHyundai Steel Company

InventorsJun Ho Chung, Tae Hyung Kim, Ju Sang Lee, Se Jin Kim, Kyoung Rok Lim

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Abstract

A steel reinforcing bar contains 0.06 wt % to 0.11 wt % carbon, more than 0 and not more than 0.25 wt % silicon, 0.8 wt % or more and less than 2.0 wt % manganese, more than 0 and not more than 0.01 wt % phosphorus, more than 0 and not more than 0.01 wt % sulfur, 0.01 to 0.03 wt % aluminum, 0.50 to 1.00 wt % nickel, 0.027 to 0.125 wt % molybdenum, more than 0 and not more than 0.25 wt % chromium, more than 0 and not more than 0.28 wt % copper, more than 0 and not more than 0.01 wt % nitrogen, and the remainder being iron and unavoidable impurities. The reinforcing bar has a surface layer and a core. The surface layer has a hardened layer of tempered martensite, and the core has a mixed structure of bainite, ferrite and pearlite.

Claims9

Dependent claims

A steel reinforcing bar comprising 0.06 wt % to 0.11 wt % of carbon (C), more than 0 and not more than 0.25 wt % of silicon (Si), 0.8 wt % or more and less than 2.0 wt % of manganese (Mn), more than 0 and not more than 0.01 wt % of phosphorus (P), more than 0 and not more than 0.01 wt % of sulfur (S), 0.01 to 0.03 wt % of aluminum (Al), 0.50 to 1.00 wt % of nickel (Ni), 0.027 to 0.125 wt % of molybdenum (Mo), more than 0 and not more than 0.25 wt % of chromium (Cr), more than 0 and not more than 0.28 wt % of copper (Cu), more than 0 and not more than 0.01 wt % of nitrogen (N), and the remainder being iron (Fe) and unavoidable impurities,

wherein the steel reinforcing bar has a surface layer and a core excluding the surface layer,
wherein the steel reinforcing bar has, in the surface layer, a hardened layer consisting essentially of tempered martensite, and
wherein the steel reinforcing bar has, in the core, a mixed structure of bainite, ferrite and pearlite.

A method for producing a steel reinforcing bar, the method comprising steps of:

reheating a slab, comprising 0.06 wt % to 0.11 wt % of carbon (C), more than 0 and not more than 0.25 wt % of silicon (Si), 0.8 wt % or more and less than 2.0 wt % of manganese (Mn), more than 0 and not more than 0.01 wt % of phosphorus (P), more than 0 and not more than 0.01 wt % of sulfur (S), 0.01 to 0.03 wt % of aluminum (Al), 0.50 to 1.00 wt % of nickel (Ni), 0.027 to 0.125 wt % of molybdenum (Mo), more than 0 and not more than 0.25 wt % of chromium (Cr), more than 0 and not more than 0.28 wt % of copper (Cu), more than 0 and not more than 0.01 wt % of nitrogen (N), and the remainder being iron (Fe) and unavoidable impurities, at a temperature of 1,030° C. to 1,250° C.;
hot-rolling the reheated slab at a finishing delivery temperature of 920° C. to 1,030° C. to form a steel reinforcing bar;
and
cooling the surface of the hot-rolled steel reinforcing bar to a martensite transformation starting temperature (Ms temperature) or lower through a TEMPCORE process,
wherein the TEMPCORE process comprises a step of subjecting the steel reinforcing bar to recuperation at 520° C. to 600° C.

2 more elements

Dependencies are inferred from the claim text.