Method for improving casting blank quality and reducing steel wire rod rolling scabs

Abstract

The invention discloses a method for improving the quality of a casting blank and reducing rolling scabs of a wire rod, belongs to a steelmaking metallurgy technology, and provides a scheme aiming at the problem of high rejection rate in the prior art. Factors of rolled metal scabbing caused by casting blank quality defects are systematically controlled, and casting blank skin bubbles, casting blank center cracks, casting blank surface vibration mark depth at a high pulling speed and cleaning difficulty of casting blank residual cutting slag are reduced. And in combination with a field production process, a process route and parameter design conforming to actual production are formulated, the casting blank quality is effectively controlled, and the rolled metal surface scabbing defect is greatly reduced.

Description

Technical Field

[0001] The invention belongs to steelmaking metallurgical technology and relates to a method for improving the quality of ingots and reducing scarring during wire rod rolling. Background Art

[0002] At present, the domestic steel mills producing low-carbon and low-silicon wire rods have a large output. Different steel mills implement different production processes. When producing low-carbon square billets, when the continuous casting billet drawing speed is ≥4m / min, it is necessary to solve the scarring defect of the billet rolling at high drawing speed.

[0003] Due to the fast drawing speed of continuous casting billet and liquid core straightening, the billet has subcutaneous bubbles, deep vibration marks on the surface, and cracks on the surface corners. At the same time, the billet is flame cut, which has a certain amount of cutting slag. During the rolling process, due to the presence of multiple types of billet quality defects, there is no systematic solution to improve the quality, resulting in scar defects on the surface quality of the rolled material, and the finished product is scrapped. Summary of the invention

[0004] The object of the present invention is to provide a method for improving the quality of ingots and reducing scarring during wire rod rolling, so as to solve the problems existing in the above-mentioned prior art.

[0005] The method for improving the quality of ingot casting and reducing wire rod rolling scarring described in the present invention comprises the following steps:

[0006] The final carbon content is controlled at 0.04-0.06%, 240 kg / furnace of high aluminum aluminum-manganese iron alloy is added for deoxidation and alloying, slag is blocked for tapping, and 200 kg / furnace of synthetic slag is added after tapping, and the oxygen content entering the station is ≤120 ppm;

[0007] The tapping temperature of the converter is controlled at 1620-1630℃, the inlet temperature is 1580-1595℃, the S content of the molten steel is ≤0.03%, and the Mn / S is adjusted to ≥13 according to the S content in the molten steel, and the Mn content of the molten steel is 0.31-0.34%; the aluminum wire is fed for deoxidation operation, the oxygen content of the molten steel at the outlet is 28-34ppm, and the outlet temperature is adjusted to 1565-1575℃ by adding scrap steel, and the superheat of the molten steel is 15-30℃;

[0008] Molten steel soft blowing argon flow rate 10~25m 3 / h, the argon blowing time is 14-17min, and the argon blowing time after feeding the calcium silicon wire is ≥5min;

[0009] During the transportation of molten steel, the ladle is covered, and the long nozzle and the lower nozzle are argon sealed for continuous casting to ensure that there is no oxygen absorption in the nozzle during the pouring process;

[0010] The baking time of the pouring tundish is 2 to 2.5 hours, and the baking temperature is ≥ 1100°C;

[0011] The crystallizer cooling water flow rate is 12m / S, and the water volume is controlled at 165m 3 / h;

[0012] Continuous casting casting speed ≥ 4m / min, negative slip time of crystallizer is controlled at 0.09~0.1s, negative slip rate ≥ 16%, negative sliding amount is controlled at 3~5mm, and crystallizer liquid level fluctuation is stable within ±5mm;

[0013] Secondary cooling intensity control parameter ≤1.6L / kg, secondary cooling water pressure 1.8MPa., secondary cooling chamber first to fourth zone cooling intensity gradually decreases, nozzle is full water pressure nozzle, billet straightening machine temperature 950~1050℃;

[0014] After the flame cutting of the ingot is completed, an automatic cutting slag cleaning device is installed at the bottom of the ingot in the conveying section to clean the cutting slag at the head and tail of the ingot.

[0015] The method for improving the quality of ingots and reducing scarring during wire rod rolling described in the present invention has the advantages of systematically controlling the factors causing scarring of rolled materials due to ingot quality defects, reducing the difficulty of cleaning subcutaneous bubbles of ingots, central cracks of ingots, depth of vibration marks on the surface of ingots at high pulling speeds, and residual cutting slag of ingots. Combined with the on-site production process, a process route and parameter design that conform to actual production are formulated, the quality of ingots is effectively controlled, and the scarring defects on the surface of rolled materials are greatly reduced. DETAILED DESCRIPTION

[0016] The present invention is aimed at analyzing the causes of rolling scarring caused by defects in continuous casting square billets, clarifying the relationship between the quality defects of billets and the surface quality of rolled materials during the rolling process, systematically improving the quality of billets, and reducing the scarring defects of rolled materials. The main measures for controlling related defects are: controlling the free oxygen content in steel and promoting the floating of inclusions, designing the optimal molten steel composition, using a low superheat casting mode for molten steel casting, protecting the casting throughout the process, controlling the cooling water volume of the crystallizer, modifying the copper tube of the crystallizer, using full water cooling for the secondary cooling system, designing the parameters of the vibration table of the R9 meter arc continuous casting machine, applying electromagnetic stirring technology, and improving the support system of the secondary cooling chamber, etc., to achieve the improvement of the billet quality at high drawing speed, significantly reduce the rolling scarring defects, and improve the product qualification rate.

[0017] Embodiment 1

[0018] Furnace No. 1, the final carbon content is 0.04%, 240kg / furnace of high aluminum aluminum-manganese iron alloy is added for deoxidation and alloying, slag is blocked for tapping, and 200kg / furnace of synthetic slag is added after tapping, and the oxygen content entering the station is 120ppm.

[0019] The converter tapping temperature is controlled at 1620°C, the station inlet temperature is 1580°C, the S content of the molten steel is 0.03%, and Mn / S is adjusted to 13 according to the S content in the molten steel, and the Mn content of the molten steel is 0.31%. Aluminum wire is fed for deoxidation operation, the oxygen content of the molten steel at the station outlet is 28ppm, and scrap steel is added to adjust the station outlet temperature to 1565°C, and the superheat of the molten steel is 15°C.

[0020] Molten steel soft blowing argon flow rate 10m 3 / h, argon blowing station time is 14min, argon blowing is 5min after feeding the silicon-calcium wire, the continuous casting casting speed is stable, and there is no problem of poor fluidity of molten steel.

[0021] During the transportation of molten steel, the ladle is covered and the long shroud and lower shroud are argon sealed for continuous casting to ensure that there is no oxygen absorption at the shroud during the pouring process.

[0022] The baking time of the pouring tundish is 2h, and the baking temperature is ≥1100℃.

[0023] The crystallizer cooling water flow rate is 12m / S, and the water volume is controlled at 165m 3 / h.

[0024] The continuous casting casting speed is 4m / min, the negative slip time of the crystallizer is controlled at 0.09s, the negative slip rate is 16%, the negative sliding amount is controlled at 3mm, and the crystallizer liquid level fluctuation is stable within ±5mm.

[0025] The secondary cooling intensity control parameter is 1.6L / kg, the secondary cooling water pressure is 1.8MPa. The cooling intensity of the secondary cooling chamber from the first to the fourth zone is gradually reduced, the nozzle is a full water pressure nozzle, and the temperature of the billet through the straightening machine is 950℃.

[0026] After the flame cutting of the ingot is completed, an automatic cutting slag cleaning device is installed at the bottom of the ingot in the conveying section to clean the cutting slag at the head and tail of the ingot.

[0027] After the hot rolling in this furnace is completed, the surface quality of the rolled material is good and no scar defects are produced.

[0028] Embodiment 2

[0029] Furnace No. 2, the final carbon content is 0.052%, 240kg / furnace of high aluminum aluminum-manganese iron alloy is added for deoxidation and alloying, slag is blocked for tapping, and 200kg / furnace of synthetic slag is added after tapping, and the oxygen content entering the station is 96ppm.

[0030] The converter tapping temperature is controlled at 1622°C, the station inlet temperature is 1589°C, the S content of the molten steel is 0.025%, and Mn / S is adjusted to 14 according to the S content in the molten steel, and the Mn content of the molten steel is 0.32%. Aluminum wire is fed for deoxidation operation, the oxygen content of the molten steel out of the station is 30ppm, and scrap steel is added to adjust the station outlet temperature to 1568°C, and the superheat of the molten steel is 24°C.

[0031] Molten steel soft blowing argon flow rate 15m 3 / h, argon blowing station time is 15min, argon blowing is 5.5min after feeding the silicon-calcium wire, the continuous casting casting speed is stable, and there is no problem of poor fluidity of molten steel.

[0032] During the transportation of molten steel, the ladle is covered and the long shroud and lower shroud are argon sealed for continuous casting to ensure that there is no oxygen absorption at the shroud during the pouring process.

[0033] The baking time of the pouring tundish is 2.15h, and the baking temperature is ≥1100℃.

[0034] The crystallizer cooling water flow rate is 12m / S. The water volume is controlled at 165m 3 / h.

[0035] The continuous casting casting speed is 4.1m / min, the negative slip time of the crystallizer is controlled at 0.093s, the negative slip rate is 18%, the negative sliding amount is controlled at 4.73mm, and the crystallizer liquid level fluctuation is stable within ±5mm.

[0036] The secondary cooling intensity control parameter is 1.58L / kg, the secondary cooling water pressure is 1.8MPa. The cooling intensity of the secondary cooling chamber from the first to the fourth zone gradually decreases, the nozzle is a full water pressure nozzle, and the temperature of the billet through the straightening machine is 980℃.

[0037] After the flame cutting of the ingot is completed, an automatic cutting slag cleaning device is installed at the bottom of the ingot in the conveying section to clean the cutting slag at the head and tail of the ingot.

[0038] After the hot rolling in this furnace is completed, the surface quality of the rolled material is good and no scar defects are produced.

[0039] Embodiment 3

[0040] Furnace No. 3, the final carbon content is 0.058%, 240kg / furnace of high aluminum aluminum-manganese iron alloy is added for deoxidation and alloying, slag is blocked for tapping, and 200kg / furnace of synthetic slag is added after tapping, and the oxygen content entering the station is 84ppm.

[0041] The converter tapping temperature is controlled at 1626°C, the inlet temperature is 1594°C, the S content of the molten steel is 0.020%, and the Mn / S-15 is adjusted according to the S content in the molten steel. The Mn content of the molten steel is 0.33%. Aluminum wire is fed for deoxidation operation, the oxygen content of the molten steel out of the station is 32ppm, and scrap steel is added to adjust the outlet temperature to 1571°C, and the superheat of the molten steel is 27°C.

[0042] Molten steel soft blowing argon flow rate 20m 3 / h, argon blowing station time is 16min, argon blowing is 6min after feeding the silicon-calcium wire, the continuous casting casting speed is stable, and there is no problem of poor fluidity of molten steel.

[0043] During the transportation of molten steel, the ladle is covered and the long shroud and lower shroud are argon sealed for continuous casting to ensure that there is no oxygen absorption at the shroud during the pouring process.

[0044] The baking time of the pouring tundish is 2.35h, and the baking temperature is ≥1100℃.

[0045] The crystallizer cooling water flow rate is 12m / S. The water volume is controlled at 165m 3 / h.

[0046] The continuous casting casting speed is 4.2m / min, the negative slip time of the crystallizer is controlled at 0.097s, the negative slip rate is 20%, the negative sliding amount is controlled at 4.80mm, and the crystallizer liquid level fluctuation is stable within ±5mm.

[0047] The secondary cooling intensity control parameter is 1.56L / kg, the secondary cooling water pressure is 1.8MPa. The cooling intensity of the secondary cooling chamber from the first to the fourth zone gradually decreases, the nozzle is a full water pressure nozzle, and the temperature of the billet through the straightening machine is 985℃.

[0048] After the flame cutting of the ingot is completed, an automatic cutting slag cleaning device is installed at the bottom of the ingot in the conveying section to clean the cutting slag at the head and tail of the ingot.

[0049] After the hot rolling in this furnace is completed, the surface quality of the rolled material is good and no scar defects are produced.

[0050] Embodiment 4

[0051] Furnace No. 4, the final carbon content is 0.06%, 240kg / furnace of high aluminum aluminum-manganese iron alloy is added for deoxidation and alloying, slag is blocked for tapping, and 200kg / furnace of synthetic slag is added after tapping, and the oxygen content entering the station is 78ppm.

[0052] The converter tapping temperature is controlled at 1630°C, the station inlet temperature is 1595°C, the S content of the molten steel is 0.015%, and Mn / S is adjusted to 16 according to the S content in the molten steel, and the Mn content of the molten steel is 0.34%. Aluminum wire is fed for deoxidation operation, the oxygen content of the molten steel out of the station is 34ppm, and scrap steel is added to adjust the station outlet temperature to 1575°C, and the superheat of the molten steel is 30°C.

[0053] Molten steel soft blowing argon flow rate 25m 3 / h, the argon blowing station time is 17min, and the argon blowing is 6.5min after feeding the silicon-calcium wire. The continuous casting casting speed is stable, and there is no problem of poor fluidity of molten steel.

[0054] During the transportation of molten steel, the ladle is covered and the long shroud and lower shroud are argon sealed for continuous casting to ensure that there is no oxygen absorption at the shroud during the pouring process.

[0055] The baking time of the pouring tundish is 2.5h, and the baking temperature is ≥1100℃.

[0056] The crystallizer cooling water flow rate is 12m / S. The water volume is controlled at 165m 3 / h.

[0057] The continuous casting casting speed is 4.3m / min, the negative slip time of the crystallizer is controlled at 0.01s, the negative slip rate is 22%, the negative sliding amount is controlled at 5mm, and the crystallizer liquid level fluctuation is stable within ±5mm.

[0058] The secondary cooling intensity control parameter is 1.5L / kg, the secondary cooling water pressure is 1.8MPa. The cooling intensity of the secondary cooling chamber from the first to the fourth zone gradually decreases, the nozzle is a full water pressure nozzle, and the temperature of the billet through the straightening machine is 1050℃.

[0059] After the flame cutting of the ingot is completed, an automatic cutting slag cleaning device is installed at the bottom of the ingot in the conveying section to clean the cutting slag at the head and tail of the ingot.

[0060] After the hot rolling in this furnace is completed, the surface quality of the rolled material is good and no scar defects are produced.

[0061] By comparing the embodiments with the prior art, the scarring ratios shown in the following table are obtained:

[0062] Production volume / 10,000 tons Scarring amount / 10,000 tons Scar ratio Before improvement 24.2 0.132 0.545％ Embodiment 1 24.2 0.015 0.062％ Embodiment 2 24.2 0.013 0.054％ Embodiment 3 24.2 0.010 0.041％ Embodiment 4 24.2 0.012 0.050％

[0063] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for improving the quality of ingot casting and reducing wire rod rolling scarring, characterized in that: The following steps are involved: The final carbon content is controlled at 0.04-0.06%, 240 kg / furnace of high aluminum aluminum-manganese iron alloy is added for deoxidation and alloying, slag is blocked for tapping, and 200 kg / furnace of synthetic slag is added after tapping, and the oxygen content entering the station is ≤120 ppm; The tapping temperature of the converter is controlled at 1620-1630℃, the inlet temperature is 1580-1595℃, the S content of the molten steel is ≤0.03%, and the Mn / S is adjusted to ≥13 according to the S content in the molten steel, and the Mn content of the molten steel is 0.31-0.34%; the aluminum wire is fed for deoxidation operation, the oxygen content of the molten steel at the outlet is 28-34ppm, and the outlet temperature is adjusted to 1565-1575℃ by adding scrap steel, and the superheat of the molten steel is 15-30℃; Molten steel soft blowing argon flow rate 10~25m 3 / h, the argon blowing time is 14-17min, and the argon blowing time after feeding the calcium silicon wire is ≥5min; During the transportation of molten steel, the ladle is covered, and the long nozzle and the lower nozzle are argon sealed for continuous casting to ensure that there is no oxygen absorption in the nozzle during the pouring process; The baking time of the pouring tundish is 2 to 2.5 hours, and the baking temperature is ≥ 1100°C; The crystallizer cooling water flow rate is 12m / S, and the water volume is controlled at 165m 3 / h; Continuous casting casting speed ≥ 4m / min, negative slip time of crystallizer is controlled at 0.09~0.1s, negative slip rate ≥ 16%, negative sliding amount is controlled at 3~5mm, and crystallizer liquid level fluctuation is stable within ±5mm; Secondary cooling intensity control parameter ≤1.6L / kg, secondary cooling water pressure 1.8MPa., cooling intensity of secondary cooling chamber 1 to 4 zones gradually decreases, nozzle is full water pressure nozzle, temperature of billet through straightening machine 950~1050℃; After the flame cutting of the ingot is completed, an automatic cutting slag cleaning device is installed at the bottom of the ingot in the conveying section to clean the cutting slag at the head and tail of the ingot.

2. A method for improving the quality of ingot casting and reducing wire rod rolling scarring according to claim 1, characterized in that: The endpoint carbon content is 0.52% or 0.58%; The incoming oxygen content was 96ppm, 84ppm or 78ppm.

3. A method for improving the quality of ingot casting and reducing wire rod rolling scarring according to claim 1, characterized in that: The tapping temperature is controlled at 1622°C or 1626°C; The entry temperature is 1589℃ or 1594℃; Molten steel composition S content 0.15% or 0.20% or 0.25%; Mn / S is 14 or 15 or 16; The Mn content of molten steel is 0.32% or 0.33%; The oxygen content of molten steel out of the station is 30ppm or 32ppm; The outgoing temperature is 1568℃ or 1571℃; The superheat of molten steel is 24℃ or 27℃.

4. A method for improving the quality of ingot casting and reducing wire rod rolling scarring according to claim 1, characterized in that: The soft blowing argon flow rate of molten steel is 10m 3 / h or 20m 3 / h; The argon blowing station time is 15min or 16min; After feeding the calcium silicon wire, the argon blowing time is 5.5min, 6.0min or 6.5min.

5. A method for improving the quality of ingot casting and reducing wire rod rolling scarring according to claim 1, characterized in that: The baking time of the pouring tundish is 2.15h or 2.25h.

6. A method for improving the quality of ingot casting and reducing wire rod rolling scarring according to claim 1, characterized in that: The continuous casting speed is 4.1m / min, 4.2m / min or 4.3m / min; The negative slip time of the crystallizer is controlled at 0.093s or 0.97s Negative slip rate is 18% or 20% or 22%; The negative sliding amount is controlled at 4.73mm or 4.80mm.

7. A method for improving the quality of ingot casting and reducing wire rod rolling scarring according to claim 1, characterized in that: The secondary cooling intensity control parameter is 1.5L / kg or 1.56L / kg or 1.58L / kg; The temperature of the casting through the straightening machine is 980℃ or 985℃.