Converter endpoint differential control method for grading steel grades based on phosphorus content

Abstract

The invention belongs to the technical field of iron and steel smelting, and discloses a converter endpoint differential control method for grading steel grades based on phosphorus content, which comprises the following steps: grading steel grades based on endpoint phosphorus requirements, and carrying out process temperature and process carbon control on each grade of steel grade, and setting a differentiated target range of the phosphorus content at the end point of the converter according to the steel grade of each grade, and matching a corresponding slagging system, a temperature system and end point carbon control. By utilizing the method disclosed by the invention, the terminal point of the converter can be controlled by accurately matching the actual requirements of different steel types, and differentiated and refined economic control on the phosphorus content of the terminal point is realized, so that accurate control on the dephosphorization cost is realized, and the production cost is reduced and the economic benefit is improved on the premise of ensuring the quality of molten steel.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel smelting technology, specifically relating to a converter steelmaking endpoint control method, and in particular a converter endpoint differential control method based on phosphorus content-graded steel grades. This method classifies steel grades according to their different requirements for endpoint phosphorus content and implements differentiated slag formation, temperature, and endpoint control systems for economical converter control. Background Technology

[0002] The endpoint control in converter steelmaking mainly includes the control of carbon content, temperature, and phosphorus content. Among these, dephosphorization is one of the core tasks of the converter. Currently, the commonly used method is to pursue deep dephosphorization, that is, to reduce the phosphorus content of the molten steel to a very low level at the end of the blowing process to ensure the quality of most steel grades. This "excessive dephosphorization" results in serious "quality overcapacity" and "cost waste" for ordinary steel grades. Deep dephosphorization requires slag conditions with high basicity, large slag volume, low endpoint carbon, and high oxidizing properties. High basicity and large slag volume lead to higher consumption of slag-forming agents such as lime and dolomite; low endpoint carbon and high oxidizing slag conditions exacerbate the erosion rate of the furnace lining, causing a decline in economic indicators such as metal yield and alloy recovery rate.

[0003] Therefore, there is an urgent need for a method that can accurately match the actual needs of different steel grades to control the endpoint of converter steelmaking, so as to achieve differentiated and refined economic control of the endpoint phosphorus content. Summary of the Invention

[0004] To address the aforementioned technical problems in the existing technology, this invention provides a converter endpoint differentiation control method based on phosphorus content-graded steel grades, comprising: (1) Steel grade classification based on final phosphorus requirements Based on the final phosphorus content specifications of the steel grades, the steel grades are divided into the following four control levels: P0 grade, or ultra-low phosphorus controlled grade, requires the finished product to have a phosphorus content of ≤0.012% by mass. P1 grade, also known as the lower phosphorus control grade, requires a phosphorus content of ≤0.018% by mass in the finished product; P2 grade, also known as low phosphorus control grade, requires the finished product to have a phosphorus content of ≤0.025% by mass. P3 grade, also known as ordinary phosphorus control grade, requires a phosphorus content of ≤0.035% by mass in the finished product; (2) Differentiated process control and endpoint target control (2.1) When the oxygen blowing rate reaches 80%~85% of the total oxygen supply, process control shall be implemented, and the process temperature and process carbon shall be controlled to meet the following objectives for each grade of steel: For P0 grade steel: the process temperature is controlled at 1550~1570℃, and the process carbon [C] is controlled at 0.20%~0.30%; For P1 grade steel: the process temperature is controlled at 1570~1590℃, and the process carbon [C] is controlled at 0.25%~0.35%; For P2 grade steel: the process temperature is controlled at 1580~1590℃, and the process carbon [C] is controlled at 0.40%~0.50%; For P3 grade steel: the process temperature is controlled at 1580~1600℃, and the process carbon [C] is controlled at 0.45%~0.55%; (2.2) Set differentiated target ranges for converter final phosphorus content for each grade of steel, and match them with corresponding slag-forming regimes, temperature regimes, and final carbon control: For P0 grade steel: the target phosphorus content at the end point is controlled at ≤0.010%, the slag basicity R is controlled at 3.0~3.5, the carbon [C] at the end point is controlled at ≤0.06%, and the end point temperature T is controlled at 1610~1630℃; For P1 grade steel: the target phosphorus content at the end point is controlled at ≤0.015%, the slag basicity R is controlled at 2.8~3.0, the carbon [C] at the end point is controlled at 0.04~0.07%, and the temperature at the end point is controlled at 1620~1635℃; For P2 grade steel: the target phosphorus content at the end point is controlled at ≤0.022%, the slag basicity R is controlled at 2.5~2.8, the carbon [C] at the end point is controlled at 0.07~0.10%, and the end point temperature T is controlled at 1630~1645℃; For P3 grade steel: the target phosphorus content at the end point is controlled at ≤0.030%, the slag basicity R is controlled at 2.2~2.5, the carbon [C] at the end point is controlled at 0.08~0.12%, and the temperature at the end point is controlled at 1635~1655℃.

[0005] Furthermore, the converter endpoint differential control method based on phosphorus content graded steel grades of the present invention also includes: in process control, if the detected value of process temperature or process carbon deviates from the target range, correction is made by dynamically adjusting the subsequent coolant addition amount and oxygen supply amount, so as to control the process temperature or process carbon to the target range.

[0006] Furthermore, the converter endpoint differentiation control method based on phosphorus content graded steel grades of the present invention also includes the use of a single slag retention process: after the previous heat of steel is tapped, 1 / 3 to 2 / 3 of the final slag is left in the furnace for smelting in the next heat.

[0007] Furthermore, in the converter endpoint differentiation control method based on phosphorus content graded steel grades of the present invention, the silicon content of the molten iron fed into the furnace is controlled to be 0.20%~0.60%.

[0008] The converter endpoint differentiation control method based on phosphorus content-graded steel grades of the present invention has the following advantages and beneficial effects: (1) By adopting differentiated process control and endpoint control for steel grades with different endpoint phosphorus content requirements, it is possible to accurately match the actual needs of different steel grades, realize differentiated and refined economic control of endpoint phosphorus content, reduce the consumption of slag-forming agents such as lime and dolomite, and reduce production costs.

[0009] (2) The number of peroxidation furnaces and the blowing rate were reduced, and the total amount of slag was reduced, thereby improving the metal recovery rate and alloy recovery rate and reducing resource waste.

[0010] (3) This method is simple to operate and facilitates low-cost steady-state operation of the converter, thereby improving economic benefits while ensuring the quality of molten steel. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0012] To address the shortcomings of existing technologies, this invention aims to provide a differentiated control method for converter endpoints based on phosphorus content grading of steel grades. This method categorizes steel grades according to their different requirements for endpoint phosphorus content and implements differentiated slag-forming, temperature, and endpoint control regimes. This allows for precise matching of the actual needs of different steel grades to control converter endpoints, achieving differentiated and refined economic control of endpoint phosphorus content. This results in precise control of dephosphorization costs, reducing production costs and improving economic efficiency while ensuring steel quality.

[0013] The converter endpoint differentiation control method based on phosphorus content graded steel grades of the present invention includes: (1) Steel grade classification based on final phosphorus requirements Based on the final phosphorus content specifications of the steel grades, the steel grades are divided into the following four control levels: P0 grade, or ultra-low phosphorus controlled grade, requires the finished product to have a phosphorus content of ≤0.012% by mass. P1 grade, also known as the lower phosphorus control grade, requires a phosphorus content of ≤0.018% by mass in the finished product; P2 grade, also known as low phosphorus control grade, requires the finished product to have a phosphorus content of ≤0.025% by mass. P3 grade, also known as ordinary phosphorus control grade, requires a phosphorus content of ≤0.035% by mass in the finished product.

[0014] (2) Differentiated process control and endpoint target control (2.1) When the oxygen blowing rate reaches 80%~85% of the total oxygen supply, process control is implemented. For each grade of steel, the process temperature and process carbon are controlled to meet the following targets to ensure the endpoint is reached: For P0 grade steel: the process temperature is controlled at 1550~1570℃, and the process carbon [C] is controlled at 0.20%~0.30%; For P1 grade steel: the process temperature is controlled at 1570~1590℃, and the process carbon [C] is controlled at 0.25%~0.35%; For P2 grade steel: the process temperature is controlled at 1580~1590℃, and the process carbon [C] is controlled at 0.40%~0.50%; For P3 grade steel: process temperature is controlled at 1580~1600℃, and process carbon [C] is controlled at 0.45%~0.55%.

[0015] (2.2) Set differentiated target ranges for converter final phosphorus content for each grade of steel, and match them with corresponding slag-forming regimes, temperature regimes, and final carbon control: For P0 grade steel: the target phosphorus content at the end point is controlled at ≤0.010%, the slag basicity R is controlled at 3.0~3.5, the carbon [C] at the end point is controlled at ≤0.06%, and the end point temperature T is controlled at 1610~1630℃; For P1 grade steel: the target phosphorus content at the end point is controlled at ≤0.015%, the slag basicity R is controlled at 2.8~3.0, the carbon [C] at the end point is controlled at 0.04~0.07%, and the temperature at the end point is controlled at 1620~1635℃; For P2 grade steel: the target phosphorus content at the end point is controlled at ≤0.022%, the slag basicity R is controlled at 2.5~2.8, the carbon [C] at the end point is controlled at 0.07~0.10%, and the end point temperature T is controlled at 1630~1645℃; For P3 grade steel: the target phosphorus content at the end point is controlled at ≤0.030%, the slag basicity R is controlled at 2.2~2.5, the carbon [C] at the end point is controlled at 0.08~0.12%, and the temperature at the end point is controlled at 1635~1655℃.

[0016] Furthermore, the converter endpoint differential control method based on phosphorus content graded steel grades of the present invention also includes: in process control, if the detected value of process temperature or process carbon deviates from the target range, correction is made by dynamically adjusting the subsequent coolant addition amount and oxygen supply amount, so as to control the process temperature or process carbon to the target range.

[0017] Furthermore, the converter endpoint differentiation control method based on phosphorus content-graded steel grades of the present invention also includes a single-slag retention process: after the previous heat of steel is tapped, 1 / 3 to 2 / 3 of the final slag is retained in the furnace for use in the next heat. This single-slag retention process utilizes the rich iron oxide and effective basicity in the retained slag, which facilitates rapid slag formation in the early stage of smelting, improves the early dephosphorization efficiency, and lays the foundation for subsequent differentiation control.

[0018] Furthermore, in the converter endpoint differentiation control method based on phosphorus content graded steel grades of the present invention, the silicon content of the molten iron fed into the furnace is controlled to be 0.20%~0.60%.

[0019] The following specific embodiments further illustrate the converter endpoint differentiation control method of the present invention based on phosphorus content graded steel grades. Example 1

[0020] Example 1 of this invention involves smelting Q355B steel in a 120-ton converter. The finished product phosphorus content of this steel is required to be ≤0.035%. Based on the final phosphorus requirement, the steel is classified as P3 grade. A single slag retention process is used for converter smelting, with the amount of slag retained being about 1 / 2. The silicon content of the molten iron entering the furnace is 0.43%.

[0021] The specific implementation process of Example 1 is as follows: Process control: When the total oxygen content is 83% during blowing, process monitoring is carried out through the auxiliary lance to control the process temperature at 1590℃ and the process carbon [C] at 0.52%, which meets the process control target requirements of P3 grade steel. Endpoint control: The final phosphorus content is controlled at 0.023%, the final carbon content is controlled at 0.09%, the slag basicity R is controlled at 2.32, and the final temperature is controlled at 1645℃, which meets the endpoint control target requirements of P3 grade steel.

[0022] Actual testing and analysis showed that the phosphorus content of the finished Q355B steel in Example 1 was 0.025%. Example 2

[0023] Example 2 of the present invention involves smelting Q355ND steel in a 120-ton converter. The finished product phosphorus content of this steel is required to be ≤0.018%. Based on the final phosphorus requirement, the steel is classified as P1 grade. A single slag retention process is used for converter smelting, with the amount of slag retained being about 1 / 2. The silicon content of the molten iron entering the furnace is 0.36%.

[0024] The specific implementation process of Example 1 is as follows: Process control: When the total oxygen content is 81% during blowing, process monitoring is carried out through the auxiliary lance to control the process temperature at 1582℃ and the process carbon [C] at 0.31%, which meets the process control target requirements of P1 grade steel. Endpoint control: The final phosphorus content is controlled at 0.014%, the final carbon content is controlled at 0.052%, the slag basicity R is controlled at 2.92, and the final temperature is controlled at 1632℃, which meets the endpoint control target requirements of P1 grade steel.

[0025] Actual testing and analysis showed that the phosphorus content of the finished Q355ND steel in Example 2 was 0.017%.

[0026] In summary, compared with the prior art, the converter endpoint differentiation control method based on phosphorus content-graded steel grades of the present invention has the following advantages and beneficial effects: (1) By adopting differentiated process control and endpoint control for steel grades with different endpoint phosphorus content requirements, it is possible to accurately match the actual needs of different steel grades, realize differentiated and refined economic control of endpoint phosphorus content, reduce the consumption of slag-forming agents such as lime and dolomite, and reduce production costs.

[0027] (2) The number of peroxidation furnaces and the blowing rate were reduced, and the total amount of slag was reduced, thereby improving the metal recovery rate and alloy recovery rate and reducing resource waste.

[0028] (3) This method is simple to operate and facilitates low-cost steady-state operation of the converter, thereby improving economic benefits while ensuring the quality of molten steel.

[0029] It should be noted that, unless otherwise specified, the terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, when a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum. Further, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Moreover, when multiple ranges are provided to describe features, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0030] It should also be noted that, in this document, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A converter endpoint differentiation control method based on phosphorus content-graded steel, characterized in that, include: (1) Steel grade classification based on final phosphorus requirements Based on the final phosphorus content specifications of the steel grades, the steel grades are divided into the following four control levels: P0 grade, or ultra-low phosphorus controlled grade, requires a phosphorus content of ≤0.012% by mass in the finished product; P1 grade, also known as the lower phosphorus control grade, requires the finished product to have a phosphorus content of ≤0.018% by mass. P2 grade, also known as low phosphorus control grade, requires the finished product to have a phosphorus content of ≤0.025% by mass. P3 grade, also known as ordinary phosphorus control grade, requires a phosphorus content of ≤0.035% by mass in the finished product; (2) Differentiated process control and endpoint target control (2.1) When the oxygen blowing rate reaches 80%~85% of the total oxygen supply, process control shall be implemented, and the process temperature and process carbon shall be controlled to meet the following objectives for each grade of steel: For P0 grade steel: the process temperature is controlled at 1550~1570℃, and the process carbon [C] is controlled at 0.20%~0.30%; For P1 grade steel: the process temperature is controlled at 1570~1590℃, and the process carbon [C] is controlled at 0.25%~0.35%; For P2 grade steel: the process temperature is controlled at 1580~1590℃, and the process carbon [C] is controlled at 0.40%~0.50%; For P3 grade steel: the process temperature is controlled at 1580~1600℃, and the process carbon [C] is controlled at 0.45%~0.55%; (2.2) Set differentiated target ranges for converter final phosphorus content for each grade of steel, and match them with corresponding slag-forming regimes, temperature regimes, and final carbon control: For P0 grade steel: the target phosphorus content at the end point is controlled at ≤0.010%, the slag basicity R is controlled at 3.0~3.5, the carbon [C] at the end point is controlled at ≤0.06%, and the end point temperature T is controlled at 1610~1630℃; For P1 grade steel: the target phosphorus content at the end point is controlled at ≤0.015%, the slag basicity R is controlled at 2.8~3.0, the carbon [C] at the end point is controlled at 0.04~0.07%, and the temperature at the end point is controlled at 1620~1635℃; For P2 grade steel: the target phosphorus content at the end point is controlled at ≤0.022%, the slag basicity R is controlled at 2.5~2.8, the carbon [C] at the end point is controlled at 0.07~0.10%, and the end point temperature T is controlled at 1630~1645℃; For P3 grade steel: the target phosphorus content at the end point is controlled at ≤0.030%, the slag basicity R is controlled at 2.2~2.5, the carbon [C] at the end point is controlled at 0.08~0.12%, and the temperature at the end point is controlled at 1635~1655℃.

2. The converter endpoint differentiation control method based on phosphorus content-graded steel as described in claim 1, characterized in that, Also includes: In process control, if the detected values ​​of process temperature or process carbon deviate from the target range, the subsequent coolant addition and oxygen supply are dynamically adjusted to correct the deviation and bring the process temperature or process carbon back to the target range.

3. The converter endpoint differentiation control method based on phosphorus content-graded steel as described in claim 1, characterized in that, It also includes the use of single-slag retention process: after the previous heat of steel is tapped, 1 / 3 to 2 / 3 of the final slag is left in the furnace for the next heat of smelting.

4. The converter endpoint differentiation control method based on phosphorus content-graded steel as described in claim 3, characterized in that, The silicon content of the molten iron fed into the furnace should be controlled at 0.20%~0.60%.