A steel rebar and a production method thereof

Abstract

The present invention relates to a steel rebar comprising the following ingredients: 0.005%-0.030% of C, 0.3%-0.6% of Si, 1.2%-2.5% of Mn, 0.01% or less of P, 0.01% or less of S, 8.0%-10.0% of Cr, 1.0%-3.0% of Mo, 0.2%-0.4% of Sn, 0.01%-0.05% of Rare Earth element, and the remainder being Fe and unavoidable impurities. The present invention also provides a production method of steel rebar. The steel rebar of the present invention has excellent comprehensive mechanical properties and corrosion resistance performance, while meeting the requirements of anti-knock, the service life in sea water of the steel rebar is increased, thus it can be widely used in reinforced concrete structures in ocean environment.

1 . A steel rebar, wherein, comprising the following ingredients calculated in weight percentage:
 0.005%-0.030% of C,   0.3%-0.6% of Si,   1.2%-2.5% of Mn,   0.01% or less of P,   0.01% or less of S,   8.0%-10.0% of Cr,   1.0%-3.0% of Mo,   0.2%-0.4% of Sn,   0.01%-0.05% of Rare Earth element, and   the remainder being Fe and unavoidable impurities.   
     
     
         2 . The steel rebar in accordance with  claim 1 , wherein, comprising the following ingredients calculated in weight percentage:
 0.005%-0.030% of C,   0.3%-0.6% of Si,   1.2%-1.8% of Mn,   0.01% or less of P,   0.01% or less of S,   8.0%-10.0% of Cr,   1.0%-1.6% of Mo,   0.2%-0.4% of Sn,   0.01%-0.05% of Rare Earth element, and   the remainder being Fe and unavoidable impurities.   
     
     
         3 . A steel rebar, wherein, comprising the following ingredients calculated in weight percentage:
 0.005%-0.030% of C,   0.3%-0.6% of Si,   1.2%-2.5% of Mn,   0.01% or less of P,   0.01% or less of S,   8.0%-10.0% of Cr,   1.0%-3.0% of Mo,   0.2%-0.4% of Sn,   0.01%-0.05% of Rare Earth element,   0.04%-0.18% of V and/or 0.010%-0.030% of Ti,   and the remainder being Fe and unavoidable impurities.   
     
     
         4 . The steel rebar in accordance with  claim 3 , wherein, comprising the following ingredients calculated in weight percentage:
 0.005%-0.030% of C,   0.3%-0.6% of Si,   1.7%-2.5% of Mn,   0.01% or less of P,   0.01% or less of S,   8.0%-10.0% of Cr,   1.5%-2.0% of Mo,   0.2%-0.4% of Sn,   0.01%-0.05% of Rare Earth element,   0.04%-0.08% of V, and   the remainder being Fe and unavoidable impurities.   
     
     
         5 . The steel rebar in accordance with  claim 3 , wherein, comprising the following ingredients calculated in weight percentage:
 0.005%-0.030% of C,   0.3%-0.6% of Si,   1.7%-2.5% of Mn,   0.01% or less of P,   0.01% or less of S,   8.0%-10.0% of Cr,   1.8%-3.0% of Mo,   0.2%-0.4% of Sn,   0.01%-0.05% of Rare Earth element,   0.10%-0.18% of V,   0.010%-0.030% of Ti, and   the remainder being Fe and unavoidable impurities.   
     
     
         6 . The steel rebar in accordance with  claim 5 , wherein, the steel rebar has a microscopic structure composed of ferrite and bainite, with the ferrite accounting for a percentage of 50%-70%. 
     
     
         7 . The steel rebar in accordance with  claim 5 , wherein, the steel rebar has a ratio of tensile strength to yield strength at greater than 1.25, a maximum stress total elongation percentage greater than 9%, an after-fracture elongation percentage greater than 18%, a corrosion rate by cyclic immersion corrosion test at less than 0.45 m 2 h, and a corrosion rate by salt spray corrosion test at less than 0.45 m 2 h. 
     
     
         8 . A production method of steel rebar, wherein, comprising the following steps:
 S1: performing preliminary desulfurization of molten iron to control the sulfur content at no more than 0.01%;   S2: performing smelting in a convertor, by feeding the molten iron processed by Step S1 together with steel scrap and/or pig iron into a convertor to be smelted, thus obtaining steel with a carbon content less than 0.05% and a phosphorus content less than 0.01% for steel tapping;   S3: performing steel tapping, during the process of which, alloying elements of Si and Mn are added for deoxygenation and carbon powder and slag former are also added;   S4: performing refining outside the convertor, by adding Cr element and meanwhile performing decarburization by blowing oxygen in an RH vacuum refining furnace so as to control the Cr and C contents within the range in accordance with  claim 1 ; carrying out deoxygenation with an LF furnace, adding the required alloying elements of Mn, Mo, Sn and Rare Earth into the steel after deoxygenation, and then adding calcium-ferrum alloy under soft stirring by blowing inert gas, so as to control contents of these elements within the range in accordance with  claim 1 ; raising the temperature of the molten steel and adding a cover agent;   S5: performing continuous casting, by casting the molten steel under protective casting with a continuous casting machine to form a continuous casting slab;   S6: performing rolling, by heating the continuous casting slab to a temperature higher than its austenitization temperature in a heating furnace, rough rolling, moderate rolling, precision rolling, and placing the rolled steel after precision rolling onto a cooling bed for air cooling, so as to produce a finished product of steel rebar with ingredients in accordance with  claim 1 .   
     
     
         9 . A production method of steel rebar, wherein, comprising the following steps:
 S1: performing preliminary desulfurization of molten iron to control the sulfur content at no more than 0.01%;   S2: performing smelting in a convertor, by feeding the molten iron processed by Step S1 together with steel scrap and/or pig iron into a convertor to be smelted, thus obtaining steel with a carbon content less than 0.05% and a phosphorus content less than 0.01% for steel tapping;   S3: performing steel tapping, during the process of which, alloying elements of Si and Mn are added for deoxygenation and carbon powder and slag former are also added;   S4: performing refining outside the convertor, by adding Cr element and meanwhile performing decarburization by blowing oxygen in an RH vacuum refining furnace so as to control the Cr and C contents within the range in accordance with  claim 5 ; carrying out deoxygenation with an LF furnace, adding the required alloying elements of Mn, Mo, Sn, Rare Earth, as well as V and/or Ti, into the steel after deoxygenation, and then adding calcium-ferrum alloy under soft stirring by blowing inert gas, so as to control contents of these elements within the range in accordance with  claim 5 ; raising the temperature of the molten steel and adding a cover agent;   S5: performing continuous casting, by casting the molten steel under protective casting with a continuous casting machine to form a continuous casting slab;   S6: performing rolling, by heating the continuous casting slab to a temperature higher than its austenitization temperature in a heating furnace, rough rolling, moderate rolling, precision rolling, and placing the rolled steel after precision rolling onto a cooling bed for air cooling, so as to produce a finished product of steel rebar with ingredients in accordance with  claim 5 .   
     
     
         10 . The production method in accordance with  claim 9 , wherein, in Step S2, the steel for steel tapping has a temperature no higher than 1690° C. 
     
     
         11 . The production method in accordance with  claim 9 , wherein, in Step S3, a protective gas is blown into the molten steel for stirring during the process of steel tapping. 
     
     
         12 . The production method in accordance with  claim 9 , wherein, in Step S4, the decarburization by blowing oxygen is performed at a temperature no lower than 1605° C. during refining in the RH vacuum refining furnace, the deoxygenation is performed at a temperature no lower than 1575° C. during refining in the LF furnace to control the oxygen content at no more than 50 ppm, the soft stirring is performed for a duration no less than 5 min, and the temperature of the molten steel is raised to 1570-1600° C. 
     
     
         13 . The production method in accordance with  claim 9 , wherein, in Step S6, the continuous casting slab is heated to 1100-1200° C. in the heating furnace, the start rolling temperature before the rough rolling is 1030-1100° C., the temperature during the precision rolling is 950-1050° C., and the temperature when the rolled steel is initially placed onto the cooling bed is 900-960° C. 
     
     
         14 . The steel rebar in accordance with  claim 1 , wherein, the steel rebar has a microscopic structure composed of ferrite and bainite, with the ferrite accounting for a percentage of 50%-70%. 
     
     
         15 . The steel rebar in accordance with  claim 1 , wherein, the steel rebar has a ratio of tensile strength to yield strength at greater than 1.25, a maximum stress total elongation percentage greater than 9%, an after-fracture elongation percentage greater than 18%, a corrosion rate by cyclic immersion corrosion test at less than 0.45 m 2 h, and a corrosion rate by salt spray corrosion test at less than 0.45 m 2 h. 
     
     
         16 . The production method in accordance with  claim 8 , wherein, in Step S2, the steel for steel tapping has a temperature no higher than 1690° C. 
     
     
         17 . The production method in accordance with  claim 8 , wherein, in Step S3, a protective gas is blown into the molten steel for stirring during the process of steel tapping. 
     
     
         18 . The production method in accordance with  claim 8 , wherein, in Step S4, the decarburization by blowing oxygen is performed at a temperature no lower than 1605° C. during refining in the RH vacuum refining furnace, the deoxygenation is performed at a temperature no lower than 1575° C. during refining in the LF furnace to control the oxygen content at no more than 50 ppm, the soft stirring is performed for a duration no less than 5 min, and the temperature of the molten steel is raised to 1570-1600° C. 
     
     
         19 . The production method in accordance with  claim 8 , wherein, in Step S6, the continuous casting slab is heated to 1100-1200° C. in the heating furnace, the start rolling temperature before the rough rolling is 1030-1100° C., the temperature during the precision rolling is 950-1050° C., and the temperature when the rolled steel is initially placed onto the cooling bed is 900-960° C.