Method for judging steelmaking decarburization end point by using converter gas

Abstract

The invention relates to a method for judging a steelmaking decarburization end point by using converter gas, which comprises the following steps: S1, mounting a flue gas analysis system at a converter flue and the tail section of a boiler, and collecting flue gas; s2, transmitting CO and CO2 numerical values obtained by analysis of the flue gas analysis system into a data acquisition system; s3, calculating the obtained numerical values in a data acquisition system, and adding the numerical values of CO and CO2 to obtain a mole sum x; and S4, a threshold value is set at the position where the mole sum x is reduced to 70% of the peak value in the middle stage at the blowing last stage, a linear function relation between the mole sum x and the molten steel carbon content value is set according to the change of the mole sum x in the steelmaking process, a dynamic molten steel carbon content value of end point decarburization is obtained, and when the target value is reached, gun lifting blowing is ended. According to the method, the furnace gas components of CO and CO2 can be accurately analyzed in time, the decarburization end point is judged in time in the oxygen blowing decarburization steelmaking process of the converter, alloy waste caused by over-blowing during deoxidation alloying is avoided, the molten steel quality is stabilized, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of converter steelmaking technology, and in particular to a method for judging the end point of steelmaking decarburization by using converter gas. Background Art

[0002] The main task of converter steelmaking is to blow oxygen to decarbonize, raise the temperature and remove impurities. Confirming the decarbonization end point is a key step in the steelmaking process. The accuracy of the end point judgment will directly affect the quality of the steel and production efficiency.

[0003] At present, the commonly used method for judging the decarburization endpoint is mainly based on parameters such as the weight and chemical composition of the molten iron entering the furnace, statically calculating the total amount of oxygen blown, and relying on the test results of the auxiliary gun process near the endpoint and manual observation of the furnace mouth flame to judge the blowing endpoint.

[0004] However, the above judgment methods all have certain limitations in actual operation, such as high dependence on equipment, high dependence on operator experience, low accuracy, etc. Therefore, it is of great practical significance to develop a new method for judging the decarburization endpoint in steelmaking. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a method for judging the end point of steelmaking decarburization by using converter gas, timely and accurately analyzing the gas composition of CO and CO2, and timely judging the decarburization end point during the converter oxygen decarburization steelmaking process to avoid waste of alloy during deoxidation and alloying due to overblowing, which is beneficial to high carbon drawing, stabilizing the quality of molten steel, and improving production efficiency.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The present invention proposes a method for determining the end point of steelmaking decarburization by using converter gas, comprising the following steps:

[0008] S1. Install a flue gas analysis system in the converter flue and the end of the boiler to collect flue gas;

[0009] S2, transferring the CO and CO2 values ​​obtained by the flue gas analysis system into the data acquisition system;

[0010] S3, calculating the obtained value in the data acquisition system, adding the values ​​of CO and CO2 to obtain a molar sum x;

[0011] S4. At the end of blowing, a molar sum threshold is set when the molar sum x drops to 70% of the mid-term peak value, and a linear function relationship between the molar sum x and the carbon content of the molten steel is set according to the change of the molar sum x during the steelmaking process to obtain a dynamic terminal decarburization carbon content value of the molten steel. When the target value is reached, the gun is lifted and the blowing is ended.

[0012] Furthermore, in step S4, the setting of the linear function includes: setting f(x)=ax+b, where f(x) is the predicted endpoint carbon value, b is the lowest value of carbon in the converter molten steel, which defaults to 0.02, and a value a is obtained based on the corresponding values ​​of the endpoint sample and the furnace gas, which defaults to 0.0015.

[0013] Furthermore, the flue gas analysis system is a furnace gas analyzer.

[0014] Furthermore, the data acquisition system is a PLC control system.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention determines the decarburization speed by real-time monitoring of the volume fraction mole sum of CO2+CO in the steelmaking converter gas, and can intuitively, quickly and accurately determine the decarburization endpoint of steelmaking at the end of steelmaking, avoiding the problem of unstable product quality caused by over-decarburization or under-decarburization, and has a certain effect on the determination of the end point of high carbon drawing, saving carburizer and deoxidizer. In addition, the method can also flexibly adjust the preset threshold according to the actual production demand and the lag time of the furnace gas system to adapt to the decarburization endpoint judgment under different process conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic flow chart of a method for determining the end point of steelmaking decarburization using converter gas proposed by the present invention;

[0018] Figure 2 This is the converter blowing furnace gas trend chart. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] See attached Figure 1 The method for determining the end point of steelmaking decarburization by using converter gas proposed by the present invention specifically comprises the following steps:

[0021] S1. Install a flue gas analysis system, such as a furnace gas analyzer, in the converter flue and the end of the boiler to collect gas in the flue;

[0022] S2, the CO, CO2 and other values ​​obtained by the furnace gas analyzer are transmitted to the data acquisition system, such as the PLC system;

[0023] S3. Calculate the obtained values, add the values ​​of CO and CO2, and obtain a molar sum x;

[0024] The molar sum x is equivalent to the decarbonization rate under a fixed flue gas flow rate;

[0025] When steelmaking begins, this molar value and x will rise to a fixed value. At this time, as the oxygen supply intensity is fixed, the decarburization rate is basically fixed, and it fluctuates up and down with the changes in the gun position, material feeding, and TFe, but it does not exceed a certain threshold.

[0026] Near the end of blowing, the values ​​of mole and x will have a sudden decline inflection point and exceed this threshold, which means the decarburization end point is reached.

[0027] S4. According to the end of blowing, when the molar sum x drops to 70% of the mid-term peak, a molar sum threshold value, such as 60%, is set, and according to the change of the molar sum x during the steelmaking process, a linear function relationship f(x) between the molar sum x and the carbon content of the molten steel is set, and f(x) = ax + b, f(x) is the predicted end point carbon value, b is the lowest value of carbon in the converter molten steel, generally defaulted to 0.02, and a value a is obtained according to the corresponding value of the end point sample and furnace gas, which is about 0.0015. The coefficient of this linear function can be adjusted with different converters. When x = 60, i.e. 60%, f(x) = 0.11; then when f(x) is equal to 0.11, it is considered to be the starting value of the end point of blowing decarburization. With the continuous change of the molar sum x, f(x) also changes continuously, and a dynamic end point decarburization carbon content of the molten steel is obtained. When the set end point, such as 0.6, is reached, the gun is lifted and the blowing is ended.

[0028] The specific working principle of the present invention is: steelmaking is mainly a decarburization reaction, and the CO and CO2 contents in the furnace gas directly reflect the speed of the decarburization reaction. Steelmaking is mainly divided into three stages: the first stage is the initial silicon-manganese reaction period of decarburization, at which time the decarburization speed rises slowly and the furnace gas; the second stage is the middle stage of decarburization, reaching equilibrium, and fluctuating in a small range around a fixed value; the third stage is the final stage of decarburization, as the carbon in the molten steel decreases, the decarburization speed decreases significantly, at which time the furnace gas will suddenly drop and reach the end point of decarburization. By monitoring the values ​​of CO and CO2, the carbon content in the molten steel at the end point can be indirectly detected.

[0029] Matters not described in detail in the present invention are all known technologies.

[0030] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for determining the end point of steelmaking decarburization using converter gas, characterized in that: The method comprises the following steps: S1. Install a flue gas analysis system in the converter flue and the end of the boiler to collect flue gas; S2, transferring the CO and CO2 values ​​obtained by the flue gas analysis system into the data acquisition system; S3, calculating the obtained value in the data acquisition system, adding the values ​​of CO and CO2 to obtain a molar sum x; S4. At the end of blowing, a molar sum threshold is set when the molar sum x drops to 70% of the mid-term peak value, and a linear function relationship between the molar sum x and the carbon content of the molten steel is set according to the change of the molar sum x during the steelmaking process to obtain a dynamic terminal decarburization carbon content value of the molten steel. When the target value is reached, the gun is lifted and the blowing is ended.

2. The method for determining the end point of steelmaking decarburization by using converter gas according to claim 1, characterized in that: In step S4, the setting of the linear function includes: setting f(x)=ax+b, where f(x) is the predicted endpoint carbon value, b is the lowest carbon value in the converter molten steel, which defaults to 0.02, and a value a is obtained based on the corresponding values ​​of the endpoint sample and the furnace gas, which defaults to 0.0015.

3. The method for determining the end point of steelmaking decarburization by using converter gas according to claim 1, characterized in that: The flue gas analysis system is a furnace gas analyzer.

4. The method for determining the end point of steelmaking decarburization by using converter gas according to claim 1, characterized in that: The data acquisition system is a PLC control system.

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