Converter final slag magnesium oxide dynamic control method

Abstract

The application discloses a kind of converter final slag magnesium oxide dynamic control method, in the process of secondary converter smelting, MgO target content in final slag is calculated using the following formula to control;y={[(1.8x 3 -3.96x 2 +3.4x+7.5)+a]×b×(1 / c)×(1 / d)×e×(1 / f) / 100;Wherein: y is the target content of MgO in slag;X is the Si content of hot metal;A is the end temperature correction value;B is the end carbon correction value;C is the end phosphorus correction value;D is the dephosphorization efficiency correction value;E is the FeO correction value in final slag;F is the correction value of converter slag amount.This method comprehensively considers the influence of slag amount, slag basicity, end point phosphorus content requirement, end point temperature and end point carbon content and other factors on dephosphorization effect, so as to carry out dynamic linear adjustment to MgO in slag, through the adjustment, the effect of reducing the loss of furnace lining, stabilizing dephosphorization rate, complex blowing synchronous furnace age promotion can be realized, and dephosphorization is realized at the lowest cost.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for dynamic control of magnesium oxide in converter final slag. Background Technology

[0002] Converter steelmaking is a steelmaking method that primarily uses molten iron and scrap steel as raw materials. Its core principle is to remove impurities (such as carbon, silicon, phosphorus, and sulfur) from the molten iron through oxidation reactions, while simultaneously controlling the composition and temperature of the molten steel. Magnesium oxide (MgO), as an indispensable raw material, regulates the melting point, viscosity, and fluidity of the smelting slag. An appropriate amount of MgO can form a "magnesia protective layer" with the furnace lining (mainly composed of MgO-C bricks), reducing slag erosion and thus extending the furnace life. Furthermore, an appropriate amount of MgO in the slag can regulate slag fluidity, maintain a balanced proportion of components in the slag, and protect and enhance the auxiliary blowing effect. This facilitates the full chemical reaction between the molten steel and the slag, thereby improving the efficiency of dephosphorization and desulfurization reactions. The combined effect of these two factors increases the service life of the furnace lining and stabilizes the dephosphorization effect.

[0003] Traditional converter smelting of final slag magnesium oxide (MgO) mostly adopts a static control method with a target value range of 6-14. The target content is set in stages according to experience and furnace conditions. This method is difficult to adapt to complex and ever-changing process conditions in real time, such as the effects of fluctuations in molten iron composition, changes in final slag composition, changes in final slag FeO, and changes in final slag quantity. The following problems are likely to occur: (1) When the amount of magnesium-containing material added is too large, the melting point of the slag increases and the viscosity increases, resulting in poor fluidity, serious adhesion to the furnace bottom and furnace chamber, and the bottom blowing hole is covered by high melting point slag, affecting the bottom blowing effect. The direct impact is poor dephosphorization effect in the process, and the indirect impact is that it is easy to fall into a vicious cycle of "adding a large amount of MgO - poor dephosphorization effect - increasing the oxidation of the final slag and increasing the dephosphorization rate - further erosion of the refractory by the oxidized slag - increasing the addition of MgO"; (2) When too little magnesium-containing material is added, the slag formation stability in the process is poor and the slag volume is small, which increases the difficulty of dephosphorization. Moreover, the slag with high oxidation and low MgO content continuously washes the magnesia-carbon refractory bricks, which leads to the aggravation of MgO mass transfer loss and thus worsens the furnace life. Therefore, too high or too low MgO will affect the furnace lining life, resulting in increased production costs and low smelting efficiency. Low MgO slag has a low melting point and poor adhesion. The protective slag layer cannot be effectively attached to the furnace lining and the surface of the auxiliary blowing element. As a result, in subsequent furnace smelting, the auxiliary blowing element will continue to be eroded by high-temperature slag and molten steel, and its service life will be greatly shortened. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for dynamic control of magnesium oxide in converter final slag.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: during the converter smelting process, the target MgO content in the final slag is controlled by the result calculated by the following formula (1); y={[(1.8x 3 -3.96x 2 +3.4x+7.5)+a]×b×(1 / c) ×(1 / d) ×e×(1 / f) / 100 (1); Where: y is the target MgO content in the slag, %; x is the Si content in the molten iron, % × 100; a is the final temperature correction value; b is the final carbon correction value; c is the final phosphorus correction value; d is the dephosphorization efficiency correction value; e is the FeO correction value in the final slag; f is the converter slag quantity correction value. The endpoint temperature correction value a = 0.013 × (T) 目标 -T 参考 The endpoint temperature range is set to 1620℃~1700℃; The endpoint carbon correction value b = [1 - 60 × (C)] 目标 -C 参考 The endpoint carbon range was set at 0.02% to 0.075%. The endpoint phosphorus correction value c = [1 - 140 × (P)] 目标 -P 参考 The endpoint phosphorus range was set at 0.008%–0.020%. The phosphorus removal efficiency correction value d = [1 + 0.6 × (TP)] 目标 -TP 参考 )]; The final FeO correction value e = [1 + 0.4 × (FeO)] 目标 -FeO 参考 )]; The converter slag amount correction value f = [1 + 0.0004 × (m)] 目标 -m 参考 )).

[0006] Furthermore, the following parameters were controlled in the molten iron: Si 0.15%–0.75%, P < 0.130%.

[0007] Furthermore, the magnesium oxide content in the slag is controlled by adding lightly calcined dolomite.

[0008] The beneficial effects of adopting the above technical solution are as follows: This invention comprehensively considers the influence of various factors such as slag quantity, slag basicity, final phosphorus content requirements, final temperature, and final carbon content on the dephosphorization effect, thereby dynamically and linearly adjusting the MgO in the slag. Through this adjustment, the effects of reducing furnace lining wear, stabilizing the dephosphorization rate, and simultaneously increasing the furnace life of the reblowing process can be achieved, thus realizing dephosphorization at the lowest cost. Due to its low cost and high efficiency, it has high promotion and application value in steelmaking plants, meeting the production needs of modern converter steelmaking for high efficiency, energy saving, environmental protection, and low cost. Detailed Implementation

[0009] The present invention will now be described in further detail with reference to specific embodiments.

[0010] This converter final slag MgO dynamic control method controls the following in the converter smelting process: Si 0.15%~0.75%, P<0.130% in the molten iron fed into the furnace; single slag operation is carried out, and MgO is corrected by setting adjustment parameters for endpoint temperature, endpoint carbon, endpoint phosphorus, dephosphorization efficiency, and converter slag amount. The target MgO content in the final slag is dynamically controlled according to the results calculated by formula (1). y=[(1.8x 3 -3.96x 2 +3.4x+7.5)+a]×b×(1 / c) ×(1 / d) ×e×(1 / f) / 100 (1); Where: y is the target MgO content in the slag, wt%; x is the Si content in the molten iron (wt%) × 100; a is the endpoint temperature correction value; b is the endpoint carbon correction value; c is the endpoint phosphorus correction value; d is the dephosphorization efficiency correction value; e is the FeO correction value in the final slag; and f is the converter slag quantity correction value.

[0011] The correction factor for the endpoint temperature is 0.013, and the endpoint temperature correction value a = 0.013 × (T) 目标 -T 参考 ), where T 目标 The target temperature for the converter's final stage is set before smelting begins, with a range of 1620℃ to 1700℃; T 参考 This is the reference temperature for recent historical heats of the same steel grade, i.e., the actual final temperature of the most recent historical heat, in °C.

[0012] The correction factor for the endpoint carbon is -60, and the endpoint carbon correction value b = [1 - 60 × (C)]. 目标 -C 参考 )], where C 目标 The target carbon content at the converter endpoint ranges from 0.02% to 0.075 wt%; C 参考 The reference endpoint carbon for recent historical heats of the same steel grade is the actual endpoint carbon for recent historical heats, expressed in wt%.

[0013] The correction factor for the endpoint phosphorus is -140, and the endpoint phosphorus correction value c = [1 - 140 × (P)]. 目标 -P 参考 )], where P 目标 The target phosphorus content at the converter endpoint is defined as 0.008%–0.020 wt%; P 参考 The reference endpoint phosphorus content for recent historical heats of the same steel grade is the actual endpoint phosphorus content for recent historical heats, expressed in wt%.

[0014] The correction factor for dephosphorization efficiency is 0.6, and the dephosphorization efficiency correction value d = [1 + 0.6 × (TP)]. 目标 -TP 参考 )]; where TP 目标 The target dephosphorization efficiency is determined according to the following formula: (Phosphorus content in molten iron % - Target phosphorus content %) / Phosphorus content in molten iron % TP 参考 This is derived from recent historical heats of the same steel grade, i.e.: (recent historical molten iron phosphorus content % - corresponding endpoint phosphorus content %) / recent historical molten iron phosphorus content.

[0015] The correction factor for the final FeO slag is 0.4, and the correction value for the final FeO slag is e = [1 + 0.4 × (FeO)]. 目标 -FeO 参考 )]; where FeO 目标 The target endpoint slag FeO content for this furnace run is expressed in wt%; FeO 参考 The FeO content (wt%) is the result of the final slag test for the same steel grade in recent historical heats. It can be obtained based on the actual content of the final slag composition in the converter.

[0016] The correction factor for converter slag quantity is 0.0004, and the correction value for converter slag quantity is f = [1 + 0.0004 × (m 目标 -m 参考 )]; where m 目标 This refers to the actual converter slag quantity for this heat, expressed in kg / t, obtained based on the actual slag weight measured at the converter's final stage; m 参考 The actual slag volume at the end of the converter for the same steel grade in recent historical heats is expressed in kg / t.

[0017] The aforementioned recent historical heats of the same steel grade refer to recent qualified heats that meet the conditions, excluding those with process changes or abnormalities. Process abnormalities include hot metal composition exceeding the range and final phosphorus content exceeding the standard.

[0018] In the process of controlling the MgO content in the final slag, it is adjusted by adding lightly calcined dolomite. The main components of the lightly calcined dolomite used are MgO≥34%, CaO≥45%, SiO2≤2.5% by mass percentage, with a particle size of 10mm~60mm of ≥90%, a particle size of less than 10mm of ≤5%, and a particle size of more than 50mm of ≤5%.

[0019] Example 1: The following process steps are used in the dynamic control method of magnesium oxide in the final slag of this converter.

[0020] (1) For conventional smelting in a 260-ton converter, based on recent historical information for the same steel grade, the molten iron has a phosphorus content of 0.12%, a silicon content of 0.25%, a final temperature of 1650℃, a final carbon content of 0.045%, a final phosphorus content of 0.014%, a final FeO content of 16.3%, a dephosphorization efficiency of 87.5%, a converter slag content of 92 kg / t, and a final slag MgO value of 8.55. The information for this smelting furnace is as follows: single slag operation with a silicon content of 0.15% and a phosphorus content of 0.119 wt%, a target final temperature of 1640℃, a target carbon content of 0.04%, a target final phosphorus [P] requirement of ≤0.015%, a target final slag FeO content of 16%, and a target converter slag content of 90 kg / t; (2) Based on the smelting furnace, the correction values ​​for the final temperature are a=-0.13, the correction values ​​for the final carbon are b=1.003, the correction values ​​for the final phosphorus are c=0.999, the correction values ​​for the dephosphorization efficiency are d=0.999, the correction values ​​for the final FeO slag in the converter are e=0.999, and the correction values ​​for the amount of slag in the converter are f=0.999. (3) Substitute the final slag magnesium oxide (MgO) calculation formula y={[(1.8x 3 -3.96x 2 +3.4x+7.5)+a]×b×(1 / c) ×(1 / d) ×e×(1 / f) / 100=7.83%; (4) During the converter smelting process, the target MgO content in the slag is controlled at 7.83%. Actual test results of the converter endpoint: final phosphorus [P] = 0.015%, final temperature T = 1643℃, final carbon [C] = 0.038%, final slag MgO value = 8.01%.

[0021] Example 2: The following process steps are used for the dynamic control method of magnesium oxide in the final slag of this converter.

[0022] (1) For conventional smelting in a 260-ton converter, based on recent historical information for the same steel grade, the molten iron has a phosphorus content of 0.105%, a silicon content of 0.40%, a final temperature of 1630℃, a final carbon content of 0.028%, a final phosphorus content of 0.010%, a final FeO content of 17%, a dephosphorization efficiency of 90.5%, a converter slag content of 95 kg / t, and a final MgO value of 7.64. The information for this smelting furnace is as follows: single slag operation with a silicon content of 0.50% and a phosphorus content of 0.110 wt%, a target final temperature of 1620℃, a target carbon content of 0.03%, a target final phosphorus [P] requirement of ≤0.008%, a target final slag FeO content of 17.5%, and a target converter slag content of 100 kg / t; (2) Based on the smelting furnace, the correction values ​​for the final temperature are a=-0.13, the correction values ​​for the final carbon are b=0.999, the correction values ​​for the final phosphorus are c=1.003, the correction values ​​for the dephosphorization efficiency are d=1.013, the correction values ​​for the final FeO slag in the converter are e=1.002, and the correction values ​​for the amount of slag in the converter are f=1.002. (3) Substitute the final slag magnesium oxide (MgO) calculation formula y={[(1.8x 3 -3.96x 2 +3.4x+7.5)+a]×b×(1 / c) ×(1 / d) ×e×(1 / f) / 100=8.16%; (4) During the converter smelting process, the target MgO content in the slag is controlled at 8.16%. Actual test results of the converter endpoint: final phosphorus [P] = 0.008%, final temperature T = 1615℃, final carbon [C] = 0.034%, final slag MgO value = 8.01%.

[0023] Example 3: The following process steps are used in the dynamic control method of magnesium oxide in the final slag of the converter.

[0024] (1) 260-ton converter conventional smelting, based on recent historical information of the same steel grade furnace, the molten iron phosphorus content is 0.125%, the molten iron silicon content is 0.55%, the final temperature is 1670℃, the final carbon content is 0.053%, the final phosphorus content is 0.022%, the final FeO content is 16.5%, the dephosphorization efficiency is 84%, the converter slag content is 105kg / t, and the final MgO value is 9.53. The information of this smelting furnace is that the molten iron silicon content is 0.75%, the phosphorus content is 0.130wt%, the target final temperature is 1700℃, the target carbon content is 0.045%, the target final phosphorus [P] requirement is ≤0.020%, the target final slag FeO content is 17%, and the target converter slag content is 100kg / t; (2) Based on the smelting furnace, the correction values ​​for the final temperature are a=0.39, the correction values ​​for the final carbon are b=1.005, the correction values ​​for the final phosphorus are c=1.003, the correction values ​​for the dephosphorization efficiency are d=1.004, the correction values ​​for the final FeO slag in the converter are e=1.002, and the correction values ​​for the amount of converter slag are f=0.998. (3) Substitute the final slag magnesium oxide (MgO) calculation formula y={[(1.8x 3 -3.96x 2 +3.4x+7.5)+a]×b×(1 / c) ×(1 / d) ×e×(1 / f) / 100=8.99%; (4) During the converter smelting process, the target MgO content in the slag is controlled at 8.99%. Actual test results of the converter endpoint: final phosphorus [P] = 0.017%, final temperature T = 1699℃, final carbon [C] = 0.047%, final slag MgO value = 9.16%.

[0025] Example 4: The following process steps are used for the dynamic control method of magnesium oxide in the final slag of this converter.

[0026] (1) For conventional smelting in a 260-ton converter, based on recent historical information for the same steel grade, the molten iron has a phosphorus content of 0.110%, a silicon content of 0.40%, a final temperature of 1641℃, a final carbon content of 0.066%, a final phosphorus content of 0.020%, a final FeO content of 15.5%, a dephosphorization efficiency of 83.6%, a converter slag content of 89 kg / t, and a final MgO value of 8.83. The information for this smelting furnace is as follows: single slag operation with a silicon content of 0.35% and a phosphorus content of 0.120 wt%, a target final temperature of 1650℃, a target carbon content of 0.07%, a target final phosphorus [P] requirement of ≤0.018%, a target final slag FeO content of 16%, and a target converter slag content of 95 kg / t; (2) Based on the smelting furnace, the correction values ​​for the final temperature are a=0.117, the correction values ​​for the final carbon are b=0.998, the correction values ​​for the final phosphorus are c=1.003, the correction values ​​for the dephosphorization efficiency are d=1.008, the correction values ​​for the final FeO slag in the converter are e=1.002, and the correction values ​​for the amount of slag in the converter are f=1.002. (3) Substitute the final slag magnesium oxide (MgO) calculation formula y={[(1.8x 3 -3.96x 2 +3.4x+7.5)+a]×b×(1 / c) ×(1 / d) ×e×(1 / f) / 100=8.28%; (4) During the converter smelting process, the target MgO content in the slag was controlled at 8.28%. Actual test results of the converter endpoint: final phosphorus [P] = 0.017%, endpoint temperature T = 1655℃, endpoint carbon [C] = 0.071%, final slag MgO value = 8.11%.

Claims

1. A method for dynamic control of magnesium oxide in converter final slag, characterized in that: During the converter smelting process, the target MgO content in the final slag is controlled according to the result calculated by the following formula (1); y={[(1.8x 3 -3.96x 2 +3.4x+7.5)+a]×b×(1 / c) ×(1 / d) ×e×(1 / f) / 100 (1); Where: y is the target MgO content in the slag, %; x is the Si content in the molten iron, % × 100; a is the final temperature correction value; b is the final carbon correction value; c is the final phosphorus correction value; d is the dephosphorization efficiency correction value; e is the FeO correction value in the final slag; f is the converter slag quantity correction value. The endpoint temperature correction value a = 0.013 × (T) 目标 -T 参考 The endpoint temperature range is set to 1620℃~1700℃; The endpoint carbon correction value b = [1 - 60 × (C)] 目标 -C 参考 The endpoint carbon range was set at 0.02% to 0.075%. The endpoint phosphorus correction value c = [1 - 140 × (P)] 目标 -P 参考 The endpoint phosphorus range was set at 0.008%–0.020%. The phosphorus removal efficiency correction value d = [1 + 0.6 × (TP)] 目标 -TP 参考 )]; The final FeO correction value e = [1 + 0.4 × (FeO)] 目标 -FeO 参考 )]; The converter slag amount correction value f = [1 + 0.0004 × (m)] 目标 -m 参考 )).

2. The method for dynamic control of magnesium oxide in converter final slag according to claim 1, characterized in that, Control the following concentrations in molten iron: Si 0.15%–0.75%, P < 0.130%.

3. A method for dynamic control of magnesium oxide in converter final slag according to claim 1 or 2, characterized in that: The magnesium oxide content in the slag is controlled by adding lightly calcined dolomite.