400 MPa CORROSION-RESISTANT STEEL BAR AND PRODUCTION METHOD THEREOF

Abstract

The present invention discloses a 400 MPa corrosion-resistant steel bar and a production method thereof. The steel bar includes the following chemical ingredients: 9.5-10.4% of Cr, 1.0-1.2% of Mo, 0.3-0.6% of Mn, 0.01-1% of Ni, 0.01-0.5% of Cu, at most 0.014% of C, at most 0.004% of N, 0.01-0.05% of Nb, 0.2-0.6% of Si, and the balance of Fe, where Cr+Mo+0.5Mn+0.35Ni+0.25Cu is 11.1-12.2%, and C+N+0.3Si+Mn+1.8Nb is 0.4-0.8%.

1 . A 400 MPa corrosion-resistant steel bar, comprising the following chemical ingredients in percentage by mass: 9.5-10.4% of Cr, 1.0-1.2% of Mo, 0.3-0.6% of Mn, 0.01-1.00% of Ni, 0.01-0.5% of Cu, at most 0.014% of C, at most 0.004% of N, 0.01-0.05% of Nb, 0.2-0.6% of Si, at most 0.004% of S, at most 0.003% of O, at most 0.01% of As, 0.01-0.03% of P, and the balance of Fe and unavoidable impurities, wherein Cr+Mo+0.5Mn+0.35Ni+0.25Cu is 11.1-12.2%, and C+N+0.3Si+Mn+1.8Nb is 0.4-0.8%. 
     
     
         2 . The 400 MPa corrosion-resistant steel bar according to  claim 1 , further comprising the following chemical ingredients in percentage by mass: any one or more of 0.1-0.15% of V, 0.01-0.05% of Ti, 0.01-0.03% of Al and 0.0005-0.0020% of B. 
     
     
         3 . The 400 MPa corrosion-resistant steel bar according to  claim 1 , wherein a micro-structure of the steel bar is ferrite and bainite, and the ferrite accounts for 28%-40%. 
     
     
         4 . The 400 MPa corrosion-resistant steel bar according to  claim 1 , wherein an A-type inclusion, B-type inclusion, C-type inclusion and D-type inclusion of the steel bar at the standard of GB/T10561 are all less than or equal to 1.0 level. 
     
     
         5 . The 400 MPa corrosion-resistant steel bar according to  claim 1 , wherein a yield strength of the steel bar is greater than or equal to 420 MPa, a tensile strength is greater than or equal to 540 MPa, a percentage elongation after fracture is greater than or equal to 18%, and a maximum force total elongation percentage is greater than or equal to 7.5%. 
     
     
         6 . The 400 MPa corrosion-resistant steel bar according to  claim 1 , wherein a nominal diameter of the steel bar is 6-32 mm. 
     
     
         7 . The 400 MPa corrosion-resistant steel bar according to  claim 6 , wherein when the nominal diameter of the steel bar is 6-10 mm, the steel bar is made into a coiled steel bar; and when the nominal diameter of the steel bar is 12-32 mm, the steel bar is made into a straight steel bar. 
     
     
         8 . The 400 MPa corrosion-resistant steel bar according to  claim 1 , wherein in a periodic infiltration corrosion test, an average weight loss corrosion rate of the steel bar is 0.05-0.1 g/(m 2 ·h); in a salt mist corrosion test, an average weight loss corrosion rate of the steel bar is 0.01-0.04 g/(m 2 ·h);
 and in simulated concrete pore fluid with the chloride ion concentration greater than or equal to 3 mol/L, a self-corrosion potential of the steel bar is −0.1 V to −0.15 V, a polarization resistance is 2500-3000 kΩ/cm 2 , and a self-corrosion current density is less than or equal to 0.13 μA/cm 2 . 
 
     
     
         9 . The 400 MPa corrosion-resistant steel bar according to  claim 1 , wherein the steel bar is able to be prepared by a process route I and a process route II,
 wherein the process route I comprises a molten iron pre-desulfuration working procedure, a converter smelting working procedure, an AOD furnace refining working procedure, an LF furnace refining working procedure, a square billet continuous casting working procedure, a hot continuous rolling working procedure and a temperature-controlled cooling working procedure which are performed in sequence; and   the process route II comprises a molten iron pre-desulfuration working procedure, a converter smelting working procedure, an LF furnace refining working procedure, an RH furnace refining working procedure, a square billet continuous casting working procedure, a hot continuous rolling working procedure and a temperature-controlled cooling working procedure which are performed in sequence.   
     
     
         10 . The 400 MPa corrosion-resistant steel bar according to  claim 9 , wherein in the process route I:
 a tapping temperature of the converter smelting working procedure is 1600-1660° C.;   in the AOD furnace refining working procedure, high-carbon ferro-chrome alloy and ferro-molybdenum alloy are added into molten steel to realize preliminary alloying on the molten steel, slagging-off is performed after reduction, then, manganese alloy is added, before tapping, a steel ladle for tapping is purged by argon gas for 5 min or a longer time, 20 kg of aluminum ingots are added into the molten steel in the tapping process, a tapping temperature is 1630-1670° C., and a tapping C content is less than or equal to 0.010%;   in the LF furnace refining working procedure, after the molten steel reaches the steel ladle of an LF furnace, slag regulation is performed according to a scheme of adding 13-15 kg of lime and 4.0-6.5 kg of fluorite into per ton of molten steel, a white slag maintaining time is greater than or equal to 8 min, a soft stirring time is 8-15 min, and a tapping temperature is 1600-1620° C.; and   in the square billet continuous casting working procedure, carbon-free protection slag or ultra-low-carbon protection slag is used, a continuous casting temperature is 1520-1560° C., and a drawing speed in the continuous casting process is 1.2-1.6 m/min.   
     
     
         11 . The 400 MPa corrosion-resistant steel bar according to  claim 9 , wherein in the process route II:
 in the converter smelting working procedure, micro-carbon ferro-chrome alloy is added into molten steel in the tapping process to realize preliminary alloying on the molten steel, and a tapping temperature is 1700-1750° C.;   in the LF furnace refining working procedure, a steel ladle in an LF furnace is subjected to whole-process bottom blowing at an argon gas flow rate of 80-160 L/min, and a tapping temperature is 1560-1600° C.;   in the RH furnace refining working procedure, after vacuum pumping on an RH furnace for 3 min, oxygen is started to be blown into the RH furnace, a total oxygen blowing amount is 500-700 Nm 3 , then, micro-carbon ferro-chrome alloy is added into molten steel to realize alloying on the molten steel, clean circulation treatment is performed for 5 min or a longer time when a vacuum degree is less than 2 mbar, a tapping temperature is 1560-1600° C., and a tapping C content is less than or equal to 0.015%; and   in the square billet continuous casting working procedure, carbon-free protection slag or ultra-low-carbon protection slag is used, a continuous casting temperature is 1520-1560° C., and a drawing speed in the continuous casting process is 2.2-2.6 m/min.   
     
     
         12 . The 400 MPa corrosion-resistant steel bar according to  claim 9 , wherein according to the process route I and the process route II:
 in the hot continuous rolling working procedure, continuous-casting billets are heated in heating furnaces, a heating temperature is 1100-1200° C., an in-furnace time is 60-120 min, then, the billets are rolled into straight thread steel bars with a diameter of 12-32 mm, an initial rolling temperature is 1000-1100° C., and a finish rolling temperature is 850-950° C.; and   in the temperature-controlled cooling working procedure, the rolled straight thread steel bars are naturally cooled on a cooling bed, and a temperature on the cooling bed is 860-920° C.   
     
     
         13 . The 400 MPa corrosion-resistant steel bar according to  claim 9 , wherein according to the process route I and the process route II:
 in the hot continuous rolling working procedure, continuous-casting billets are heated in heating furnaces, a heating temperature is 1080-1130° C., an in-furnace time is 60-120 min, then, the billets are rolled into coiled thread steel bars with a diameter of 6-10 mm, an initial rolling temperature is 980-1030° C., a finish rolling temperature is 850-950° C., and a spinning temperature is 830-920° C.   
     
     
         14 . The 400 MPa corrosion-resistant steel bar according to  claim 9 , wherein both the process route I and the process route II comprise an on-line acid pickling working procedure and a packing working procedure which are performed in sequence after the temperature-controlled cooling working procedure; and
 in the on-line acid pickling working procedure, the steel bars sequentially pass through an acid pickling tank, a passivation tank and a drying device, and gas jet holes of the acid pickling tank are distributed around a center line of the acid pickling tank.   
     
     
         15 . The 400 MPa corrosion-resistant steel bar according to  claim 1 , wherein when the two steel bars are connected into a welded sample through electric slag pressure welding, a breaking point of the obtained welded sample in a tensile test is formed in a base material position of the two steel bars. 
     
     
         16 . A production method of a 400 MPa corrosion-resistant steel bar, comprising the following steps:
 (1) steel making:   sequentially using a molten iron pre-desulfuration working procedure, a converter smelting working procedure, an AOD furnace refining working procedure and an LF furnace refining working procedure for molten steel melting, or sequentially using a molten iron pre-desulfuration working procedure, a converter smelting working procedure, an LF furnace refining working procedure and an RH furnace refining working procedure for molten steel melting, and making the molten steel into steel billets through continuous casting, wherein the steel billets comprise the following chemical ingredients in percentage by mass: 9.5-10.4% of Cr, 1.0-1.2% of Mo, 0.3-0.6% of Mn, 0.01-1.00% of Ni, 0.01-0.5% of Cu, at most 0.014% of C, at most 0.004% of N, 0.01-0.05% of Nb, 0.2-0.6% of Si, at most 0.004% of S, at most 0.003% of O, at most 0.01% of As, 0.01-0.03% of P, and the balance of Fe and unavoidable impurities, wherein Cr+Mo+0.5Mn+0.35Ni+0.25Cu is 11.1-12.2%, and C+N+0.3Si+Mn+1.8Nb is 0.4-0.8%; and   (2) controlled rolling and controlled cooling:   heating the steel billets obtained in Step (1) in a heating furnace at a heating temperature of 1100-1200° C. for an in-furnace time of 60-120 min, then, rolling the steel billets into straight thread steel bars with a diameter of 12-32 mm at an initial rolling temperature of 1000-1100° C. and a finish rolling temperature of 850-950° C.; then, naturally cooling the rolled straight thread steel bars on a cooling bed at a temperature on the cooling bed of 860-920° C.;   or heating the steel billets obtained in Step (1) in a heating furnace at a heating temperature of 1080-1130° C. for an in-furnace time of 60-120 min, then, rolling the steel billets into coiled thread steel bars with a diameter of 6-10 mm at an initial rolling temperature of 980-1030° C., a finish rolling temperature of 850-950° C., and a spinning temperature of 830-920° C., then, cooling the rolled coiled thread steel bars in a Stelmor cooling manner while all fans under a roller bed are turned off.   
     
     
         17 . The production method of a 400 MPa corrosion-resistant steel bar according to  claim 16 , wherein in Step (1), the steel billets further comprise the following chemical ingredients in percentage by mass: any one or more of 0.1-0.15% of V, 0.01-0.05% of Ti, 0.01-0.03% of Al and 0.0005-0.0020% of B. 
     
     
         18 . The production method of a 400 MPa corrosion-resistant steel bar according to  claim 16 , wherein in Step (1), if a molten iron pre-desulfuration working procedure, a converter smelting working procedure, an AOD furnace refining working procedure and an LF furnace refining working procedure are sequentially used for molten steel melting, a tapping temperature of the converter smelting working procedure is 1600-1660° C.; in the AOD furnace refining working procedure, high-carbon ferro-chrome alloy and ferro-molybdenum alloy are added into molten steel to realize preliminary alloying on the molten steel, slagging-off is performed after reduction, then, manganese alloy is added, before tapping, a steel ladle for tapping is purged by argon gas for 5 min or a longer time, 20 kg of aluminum ingots are added into the molten steel in the tapping process, a tapping temperature is 1630-1670° C., and a tapping C content is less than or equal to 0.01%; in the LF furnace refining working procedure, after the molten steel reaches the steel ladle of an LF furnace, slag regulation is performed according to a scheme of adding 13-15 kg of lime and 4.0-6.5 kg of fluorite into per ton of molten steel, a white slag maintaining time is greater than or equal to 8 min, a soft stirring time is 8-15 min, and a tapping temperature is 1600-1620° C.; and in the square billet continuous casting working procedure, carbon-free protection slag or ultra-low-carbon protection slag is used, a continuous casting temperature is 1520-1560° C., and a drawing speed in the continuous casting process is 1.2-1.6 m/min; and
 if a molten iron pre-desulfuration working procedure, a converter smelting working procedure, an LF furnace refining working procedure and an RH furnace refining working procedure are sequentially used for molten steel melting, in the converter smelting working procedure, micro-carbon ferro-chrome alloy is added into molten steel in the tapping process to realize preliminary alloying on the molten steel, and a tapping temperature is 1700-1750° C.; in the LF furnace refining working procedure, a steel ladle in an LF furnace is subjected to whole-process bottom blowing at an argon gas flow rate of 80-160 L/min, and a tapping temperature is 1560-1600° C.; in the RH furnace refining working procedure, after vacuum pumping on an RH furnace for 3 min, oxygen is started to be blown into the RH furnace, a total oxygen blowing amount is 500-700 Nm 3 , then, micro-carbon ferro-chrome alloy is added into molten steel to realize alloying on the molten steel, clean circulation treatment is performed for 5 min or a longer time when a vacuum degree is less than 2 mbar, a tapping temperature is 1560-1600° C., and a tapping C content is less than or equal to 0.015%; and in the square billet continuous casting working procedure, carbon-free protection slag or ultra-low-carbon protection slag is used, a continuous casting temperature is 1520-1560° C., and a drawing speed in the continuous casting process is 2.2-2.6 m/min. 
 
     
     
         19 . The production method of a 400 MPa corrosion-resistant steel bar according to  claim 16 , further comprising following steps:
 (3) on-line acid pickling:   sequentially passing the steel bars obtained in Step (2) through an acid pickling tank, a passivation tank and a drying device for on-line acid pickling, wherein gas jet holes of the acid pickling tank are distributed around a center line of the acid pickling tank; and packing the steel bars after the steel bars leave away from the drying device.   
     
     
         20 . The production method of a 400 MPa corrosion-resistant steel bar according to  claim 16 , wherein when the two steel bars prepared by the production method are connected into a welded sample through electric slag pressure welding, a breaking point of the obtained welded sample in a tensile test is formed in a base material position of the two steel bars.