High carbon steel wire coil and production method therefor

Abstract

A high carbon steel wire coil and a production method includes: smelting to obtain molten steel; continuously casting the molten steel to obtain a continuous casting bloom, and performing a reduction with reduction rate that is first high, then low, and then high applied to the continuous casting bloom during continuous casting; heating the continuous casting bloom and then performing blooming to obtain a billet; heating the billet and then performing rolling and air cooling to obtain the wire coil. By finely controlling the dynamic soft reduction parameters during continuous casting, and a reduction with reduction rate that is first high, then low, and then high applied to the continuous casting bloom, the present invention significantly improves the segregation and porosity issues in the central region of the bloom from the source.

1 . A method for producing high carbon steel wire coil, wherein the carbon content of the wire coil is 0.8% and above by mass percentage, the method comprising:
 smelting to obtain molten steel;   continuously casting the molten steel to obtain a continuous casting bloom, wherein soft reduction is performed on the continuous casting bloom during continuous casting, the soft reduction comprising: when the central solid fraction fs of the continuous casting bloom is 0.3≤fs<0.5, performing a reduction on the continuous casting bloom with a reduction rate of 3˜5 mm/m, to form negative segregation in the center of the continuous casting bloom; when the central solid fraction fs of the continuous casting bloom is 0.5≤fs<0.8, reducing the reduction rate and performing a reduction on the continuous casting bloom with a reduction rate of 2˜ 4 mm/m; when the central solid fraction fs of the continuous casting bloom is 0.8≤fs<1, increasing the reduction rate and performing a reduction on the continuous casting bloom with a reduction rate of 4˜6 mm/m;   heating the continuous casting bloom and then performing blooming to obtain a billet;   heating the billet and then performing rolling and air cooling to obtain the wire coil.   
     
     
         2 . The method for producing high carbon steel wire coil according to  claim 1 , wherein when the central solid fraction fs of the continuous casting bloom is 0.3≤fs<0.5, performing a reduction on the continuous casting bloom with a reduction rate of 3˜5 mm/m to form negative segregation in the center of the continuous casting bloom, specifically comprising:
 when the central solid fraction fs of the continuous casting bloom is 0.3≤fs<0.5, performing a multi-stage reduction on the continuous casting bloom within the range of a reduction rate of 3˜5 mm/m, with the reduction rate gradually decreasing, to form negative segregation in the center of the continuous casting bloom. 
 
     
     
         3 . The method for producing high carbon steel wire coil according to  claim 2 , wherein the soft reduction on the continuous casting bloom during continuous casting specifically comprises:
 performing soft reduction on the continuous casting bloom in the horizontal section of the continuous casting machine by sequentially passing the continuous casting bloom through eight withdrawal straighteners, wherein the eight withdrawal straighteners are numbered from one to eight, and when the central solid fraction fs of the continuous casting bloom is 0.3≤fs<0.5, performing reduction on the continuous casting bloom through the first to the third withdrawal straighteners, with the reduction rate of the first to the third withdrawal straighteners controlled to decrease sequentially; when the central solid fraction fs of the continuous casting bloom is 0.5≤fs<0.8, performing reduction on the continuous casting bloom through the fourth to the sixth withdrawal straighteners; when the central solid fraction fs of the continuous casting bloom is 0.8≤fs≤1, performing reduction on the continuous casting bloom through the seventh and the eighth withdrawal straighteners.   
     
     
         4 . The method for producing high carbon steel wire coil according to  claim 3 , wherein the reduction rate of the first withdrawal straightener is controlled to be 4˜5 mm/m, the reduction rate of the second withdrawal straightener is controlled to be 3˜5 mm/m, the reduction rate of the third withdrawal straightener is controlled to be 3˜4 mm/m, the reduction rate of the fourth to the sixth withdrawal straighteners is controlled to be 2˜4 mm/m, and the reduction rate of the seventh and the eighth withdrawal straighteners is controlled to be 4˜6 mm/m. 
     
     
         5 . The method for producing high carbon steel wire coil according to  claim 1 , wherein the step of continuously casting the molten steel to obtain a continuous casting bloom further comprises:
 performing electromagnetic induction heating on the molten steel in the tundish, with the superheat controlled to be 10˜20° C., and after the molten steel enters the mould through the tundish, performing electromagnetic stirring with a stirring current controlled to be 400˜600 A and a frequency of 3˜5 Hz.   
     
     
         6 . The method for producing high carbon steel wire coil according to  claim 1 , wherein the step of continuously casting the molten steel to obtain a continuous casting bloom further comprises:
 performing continuous casting using a continuous casting machine with a cross-sectional size of 300 mm×400 mm, with the casting speed controlled to be 0.65˜0.75 m/min, and the specific water ratio in the secondary cooling zone of the continuous casting machine controlled to be 0.15˜0.25 L/kg.   
     
     
         7 . The method for producing high carbon steel wire coil according to  claim 1 , further comprising, after continuously casting the molten steel to obtain a continuous casting bloom:
 after obtaining the continuous casting bloom by continuous casting, loading the continuous casting bloom with a surface temperature greater than 800° C. into a holding pit and holding for more than 72 hours.   
     
     
         8 . The method for producing high carbon steel wire coil according to  claim 1 , wherein the step of heating the continuous casting bloom and then performing blooming to obtain a billet specifically comprises:
 heating the continuous casting bloom in a heating furnace, with the soaking zone temperature in the heating furnace controlled to be 1130˜1180° C., and the time in the furnace of the continuous casting bloom controlled to be 240˜300 min.   
     
     
         9 . The method for producing high carbon steel wire coil according to  claim 1 , wherein the step of heating the billet and then performing rolling and air cooling treatment to obtain the wire coil specifically comprises:
 heating the billet in a heating furnace before rolling, with the soaking zone temperature in the heating furnace controlled to be 1080˜1120° C., controlling the temperature of the billet at the entry of the finishing mill to be 860˜890° C., controlling the water box pressure in the finishing mill to be 3˜4 bar, controlling the water flow rate to be 1100˜1200 m 3 /h, controlling the winding temperature to be 840˜850° C., and rolling the billet to obtain a wire coil with a diameter of 5.0˜5.5 mm.   
     
     
         10 . The method for producing high carbon steel wire coil according to  claim 9 , wherein the step of heating the billet and then performing rolling and air cooling to obtain the wire coil further comprises:
 after rolling, turning on the first to the third fans to cool the wire coil, with the air volume of the fans controlled to be 30˜100%.   
     
     
         11 . The method for producing high carbon steel wire coil according to  claim 1 , wherein the step of smelting to obtain molten steel specifically comprises:
 sequentially performing hot metal pre-desulfuration, BOF smelting or electric furnace smelting, and LF furnace refining to obtain molten steel.   
     
     
         12 . (canceled) 
     
     
         13 . The method for producing high carbon steel wire coil according to  claim 1 , wherein when the carbon content of the wire coil is 0.8˜0.9% by mass percentage, the network cementite rating within the wire coil is 0 under the YB/T 4412 standard, and when the carbon content of the wire coil is more than 0.9% by mass percentage, the network cementite rating within the wire coil is 1 under the YB/T 4412 standard.