Control method for deoxidation of ferrosilicon alloy for converter

Abstract

The invention discloses a control method for deoxidation of a ferrosilicon alloy for a converter, which belongs to the technical field of converters and comprises the following steps: optimizing chemical components of plain carbon steel; when the content of dissolved oxygen in the molten steel in the converter is smaller than 700 ppm, the molten steel serves as the end point of the converter, the adding amount of the ferrosilicon is determined, and specifically, when the content of dissolved oxygen in the molten steel is smaller than 450 ppm, 350 kg of ferrosilicon is added into the converter; when the dissolved oxygen content of the molten steel is not less than 450ppm and less than 550ppm, adding 450kg / furnace; when the dissolved oxygen content of the molten steel is not less than 550ppm and less than 700ppm, adding 550kg / furnace; when the dissolved oxygen content of the molten steel is 700-1000 ppm, 550 kg of the molten steel is added into a furnace, and 50-100 kg of pure aluminum is added into the furnace; and when the tapping amount is 1 / 4 of the total amount of the steel ladle, alloy is added, and all alloy needs to be added after tapping is completed.

Description

Technical Field

[0001] The invention belongs to the technical field of converters, and in particular relates to a control method for deoxidation of ferrosilicon alloy for converters. Background Art

[0002] As the competition in the steel market becomes increasingly fierce, enterprises are facing severe challenges. In the current market economy environment, how to survive has become a core issue that enterprises urgently need to solve. The key to solving this problem is to ensure the quality stability of the production process, improve key performance indicators and reduce production costs, so as to effectively reduce expenses in the manufacturing process. Among the many cost factors, alloy costs account for one-fifth of the total cost of a steel plant, which is a part that cannot be ignored. In particular, the production proportion of plain carbon steel exceeds 60%, so reducing the alloy cost of plain carbon steel has become the key task of enterprises to reduce costs.

[0003] In the process of smelting plain carbon steel in the converter, the molten steel must be deoxidized and alloyed to ensure that the mass percentages of various chemical components in the molten steel meet the following standards: the carbon (C) content is between 0.14% and 0.18%, the silicon (Si) content is between 0.15% and 0.18%, the manganese (Mn) content is between 0.25% and 0.30%, the phosphorus (P) content is less than 0.040%, and the sulfur (S) content is less than 0.025% (in order to meet the mechanical properties of steel, titanium iron and pure aluminum are added to the traditional chemical composition of plain carbon steel). From these requirements, we can see that under the premise of ensuring that the mechanical and chemical properties of the coil meet the standards, a particularly high aluminum content is not actually required. Therefore, under the existing technical conditions, by changing the deoxidation method and using lower-priced alloys to replace higher-priced alloys, the alloy cost of plain carbon steel can be effectively reduced. Summary of the invention

[0004] The purpose of the present invention is to meet the actual mechanical and chemical performance requirements of plain carbon steel, and to provide a control method for deoxidation of ferrosilicon alloy for converter, by changing the deoxidation mode, using ferrosilicon alloy to replace other alloys; optimizing the chemical composition of plain carbon steel: removing ALs and Ti elements in the chemical composition of the original steel grade (Q235B); optimizing the order of adding alloys to the converter; and determining the amount of ferrosilicon added according to the dissolved oxygen content of molten steel at the converter end point. Through the above method, the cleanliness of molten steel can be effectively improved, and the foundation for enterprises to reduce costs and increase efficiency is laid, so as to achieve a turnaround from loss to profit.

[0005] To achieve the above technical objectives, the present invention aims to provide a control method for deoxidation of ferrosilicon alloy for converter, comprising:

[0006] Optimize the chemical composition of ordinary carbon steel: remove Als and Ti elements in ordinary carbon steel;

[0007] Deoxidation with ferrosilicon alloy: First, detect the dissolved oxygen content of molten steel in the converter. When the dissolved oxygen content of molten steel in the converter is less than 700ppm, it is taken as the converter endpoint. Determine the amount of ferrosilicon alloy to be added. The specific amount of ferrosilicon alloy to be added is:

[0008] When the dissolved oxygen content of molten steel is less than 450ppm, ferrosilicon alloy is added at 350kg / furnace;

[0009] When the dissolved oxygen content of molten steel is not less than 450ppm and less than 550ppm, ferrosilicon alloy is added at 450kg / furnace;

[0010] When the dissolved oxygen content of molten steel is not less than 550ppm and less than 700ppm, ferrosilicon alloy is added at 550kg / furnace;

[0011] When the dissolved oxygen content of molten steel is 700ppm-1000ppm, ferrosilicon alloy is added at 550kg / furnace, and pure aluminum is added at 50kg / furnace-100kg / furnace;

[0012] When the steel output is 1 / 4 of the total steel ladle volume, start adding ferrosilicon alloy. When the steel output is completed, all ferrosilicon alloy needs to be added.

[0013] Preferably, the ferrosilicon alloy comprises the following chemical components in mass percentage: silicon 72% to 80%, iron 20% to 30%, phosphorus ≯ 0.040%, sulfur ≯ 0.020%, and carbon ≯ 0.2%.

[0014] Preferably, in the plain carbon steel, Als: 0.010% to 0.025%, Ti: 0.010% to 0.020%.

[0015] Preferably, the order of adding the ferrosilicon alloy is silicon manganese, ferrosilicon and top slag lime.

[0016] Preferably, the plain carbon steel is Q235B.

[0017] Compared with the prior art, the advantages and positive effects of this application are:

[0018] The present invention proposes an innovative medium and large converter deoxidation technology, which abandons the traditional method of using aluminum alloy as a deoxidizer and instead uses ferrosilicon alloy for deoxidation. In this way, we optimize and adjust the chemical composition of plain carbon steel. Specifically, the Als and Ti elements are removed from the original steel composition, and the content of silicon (Si) is correspondingly increased. In addition, the present invention also specifies in detail the order of adding alloys when the converter is tapped, and determines the dissolved oxygen content in the converter terminal molten steel. Based on this terminal dissolved oxygen content, we can accurately calculate the amount of ferrosilicon alloy to be added. The core of this method is to utilize the strong affinity between silicon and oxygen. In the high temperature environment of steelmaking, ferrosilicon alloy can quickly react chemically with oxygen in molten steel to generate deoxidation products such as silicon dioxide. This chemical reaction effectively reduces the oxygen content in molten steel to a very low level, greatly improving the purity of molten steel. Since the price of ferrosilicon alloy is much lower than that of aluminum alloy, the use of this deoxidation alloying method can significantly reduce the cost of smelting plain carbon steel, thereby bringing economic benefits to steel production companies.

[0019] The core of the present invention is to make innovative improvements to the deoxidation process of plain carbon steel. Specifically, the traditional converter steel deoxidation method is changed from using aluminum alloy to using ferrosilicon alloy for deoxidation. This change significantly improves the yield of the alloy, thereby effectively reducing the cost of using the alloy material. At the same time, through this improvement, the quality of molten steel has been significantly improved, and the amount of inclusions generated has been greatly reduced, which not only improves the overall purity of the steel, but also further improves the processing performance of the steel. In addition, the hardness of the steel has been reduced and the machinability has been enhanced, which makes the steel easier to handle in subsequent processing. Finally, through this improved deoxidation process, the stability of the steelmaking process has been enhanced, and the reaction rate has been effectively controlled, so that the entire steelmaking process is more adaptable to the production needs of different types of steel. DETAILED DESCRIPTION

[0020] In order to further understand the content, features and effects of the present invention, the following embodiments are given and described in detail as follows.

[0021] The invention is applicable to the production process of ordinary carbon steel in medium and large converters, has a wide range of applications, has good technical radiation capabilities, and provides important technical support for reducing the alloy cost of ordinary carbon steel.

[0022] The present invention provides a control method for deoxidation of ferrosilicon alloy for converter, comprising:

[0023] Change the deoxidation method: change the deoxidation method of converter steelmaking to ferrosilicon alloy deoxidation; for example, in the production process of medium and large converters with slab continuous casting machines, when smelting ordinary carbon steel Q235B, the converter deoxidation method used in the past was aluminum alloy deoxidation. Now, this inherent alloy deoxidation method is changed to replace the higher-cost alloy with the lower-cost alloy. The specific method is to use ferrosilicon alloy for deoxidation.

[0024] Optimize the chemical composition of plain carbon steel: After silicon deoxidation, remove Als and Ti elements in the chemical composition of the original steel (Q235B), and the chemical composition of the steel is C: 0.14-0.18%, Si: 0.15-0.18%, Mn: 0.25-0.30%, P: <0.040%, S: <0.025%. For example, the chemical composition of the original plain carbon steel Q235B is: C: 0.14-0.18%, Si: ≯0.10%, Mn: 0.26-0.32%, P: <0.040%, S: <0.025%, ALs: 0.010-0.025%, Ti: 0.010-0.020%; after silicon deoxidation, while ensuring the mechanical properties requirements (yield strength ≮235MPa, tensile strength 375-500MPa, elongation ≮26%, impact energy ≮27J), the precious alloy elements are removed, and the chemical composition of the steel is C: 0.14-0.18%, Si: 0.15-0.18%, Mn: 0.25-0.30%, P: <0.040%, S: <0.025%.

[0025] During the process of tapping steel from the converter, the order of adding ferrosilicon alloy follows a specific rule, that is, adding silicon-manganese alloy first, followed by ferrosilicon alloy, and finally top slag lime. To illustrate with a specific example, if the original deoxidation method is to first use a higher strength deoxidation alloy and then switch to a weaker strength deoxidation alloy, the operation steps are usually as follows: first add the aluminum product deoxidation alloy to achieve a preliminary deoxidation effect, then add silicon-manganese alloy and ferrosilicon alloy for further deoxidation, and finally add titanium-ferrosilicon alloy to complete the entire deoxidation process. However, when ferrosilicon alloy is used as a deoxidizer, the deoxidation method will change, and it will become a weaker deoxidizer first, and then gradually increase. Therefore, the order of addition is adjusted to: first add silicon-manganese alloy, followed by ferrosilicon alloy, and finally add top slag lime to ensure the smooth progress of the deoxidation process.

[0026] In the process of deoxidation and alloying with ferrosilicon alloy, the dissolved oxygen content of the molten steel in the converter must first be accurately detected. When the test results show that the dissolved oxygen content in the converter is less than 700ppm, this moment can be regarded as the end of the converter smelting process. Subsequently, the operator will add ferrosilicon alloy to the ladle while tapping the steel from the converter to ensure that the amount of ferrosilicon per furnace is controlled between 350 and 550 kg. However, if the dissolved oxygen content in the converter is found to be greater than 700ppm during the test process, it is necessary to add aluminum blocks in an appropriate amount, ranging from 50 kg to 100 kg, to make up for the possible deficiencies of using ferrosilicon deoxidation alone, and ensure that the oxygen content in the molten steel can be maintained within the range of 50 to 100 ppm before argon treatment. After the steel tapping process is completed, all alloy materials that need to be added should have been fully added. Taking the smelting of plain carbon steel Q235B as an example, the dissolved oxygen content of the molten steel in the converter is first detected. When the content is less than 700ppm, it is determined as the end point of the converter smelting, and the amount of ferrosilicon added is determined accordingly. Specifically, if the dissolved oxygen content of the molten steel is less than 450ppm, the amount of ferrosilicon added is 350kg / furnace; if the dissolved oxygen content is less than 550ppm, the amount of ferrosilicon added is 450kg / furnace; if the dissolved oxygen content is less than 700ppm, the amount of ferrosilicon added is 550kg / furnace. When the dissolved oxygen content of the molten steel is between 700 and 1000ppm, in addition to adding 550kg / furnace of ferrosilicon, an additional 50 to 100kg / furnace of pure aluminum is required. When the amount of steel tapping reaches 1 / 4 of the total amount of the ladle, start adding ferrosilicon alloy to the ladle until the steel tapping process is completed to ensure that all ferrosilicon alloy has been completely added.

[0027] Ferrosilicon alloy includes the following chemical composition by mass percentage: silicon 72% to 80%, iron 20% to 30%, phosphorus ≯ 0.040%, sulfur ≯ 0.020%, carbon ≯ 0.2%. For example, a ferrosilicon alloy with a chemical composition not lower than the above requirements is used to meet the deoxidation and alloy recovery requirements.

[0028] The specific technical operation plan for steelmaking is:

[0029] 1. Converter process path: blast furnace → backfill station → desulfurization → converter → LF refining furnace → continuous casting;

[0030] 2. Applicable specifications:

[0031] Table 1 is the specification table

[0032] Production Mode Production steel grades All production modes Mainly plain carbon steel Q235B

[0033] III. Measures:

[0034] In order to ensure that the oxygen content in the molten steel can accurately reach the predetermined target range during the deoxidation process, the amount of ferrosilicon added must be accurately controlled. This involves the comprehensive application of theoretical calculations and experience-based adjustments, as well as dynamic monitoring and feedback adjustments. Through these methods, it can be ensured that the oxygen content in the molten steel after deoxidation reaches the target range. In addition, it is also crucial to optimize the order and time of alloy addition, which helps to improve the full contact and reaction between the ferrosilicon alloy and the oxygen in the molten steel, thereby improving the deoxidation efficiency. At the same time, such optimization is also conducive to controlling the temperature and uniformity of the composition of the molten steel. Strengthening stirring and promoting the floating of deoxidation products are also important measures to improve the deoxidation efficiency. Finally, strict control of the temperature during steelmaking, especially the tapping temperature and refining temperature, is crucial to ensure the quality of the molten steel and subsequent processing performance.

[0035] By improving the alloy yield, the present invention effectively reduces the alloy cost. The improvement in alloy yield means that more alloys are effectively utilized during the steelmaking process, reducing waste. This not only reduces production costs, but also improves the quality of molten steel and reduces the generation of inclusions. The reduction of inclusions is crucial to improving the overall quality of steel because it can reduce defects in the steel during subsequent processing. In addition, improving the processing properties of steel, reducing the hardness of steel, and improving the machinability of steel make steel easier to process, which has a positive effect on improving production efficiency and product quality. Stabilizing the steelmaking process and controlling the reaction rate enable the present invention to adapt to the production needs of different grades of steel, providing the possibility for diversified steel production.

[0036] The core of the present invention is to achieve a series of improvements by changing the deoxidation process of plain carbon steel. These improvements include increasing alloy yield, effectively reducing alloy cost; improving molten steel quality, reducing inclusion generation; improving steel processing performance, reducing steel hardness, and improving steel machinability; and stabilizing the steelmaking process, controlling the reaction speed, and adapting to the production of different steel grades. These changes not only improve production efficiency and product quality, but also bring economic and environmental benefits to the steelmaking industry.

[0037] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A control method for deoxidation of ferrosilicon alloy for converter, characterized in that: include: Optimize the chemical composition of ordinary carbon steel: remove Als and Ti elements in ordinary carbon steel; Deoxidation with ferrosilicon alloy: First, detect the dissolved oxygen content of molten steel in the converter. When the dissolved oxygen content of molten steel in the converter is less than 700ppm, it is taken as the converter endpoint. Determine the amount of ferrosilicon alloy to be added. The specific amount of ferrosilicon alloy to be added is: When the dissolved oxygen content of molten steel is less than 450ppm, ferrosilicon alloy is added at 350kg / furnace; When the dissolved oxygen content of molten steel is not less than 450ppm and less than 550ppm, ferrosilicon alloy is added at 450kg / furnace; When the dissolved oxygen content of molten steel is not less than 550ppm and less than 700ppm, ferrosilicon alloy is added at 550kg / furnace; When the dissolved oxygen content of molten steel is 700ppm-1000ppm, ferrosilicon alloy is added at 550kg / furnace, and pure aluminum is added at 50kg / furnace-100kg / furnace; When the steel output is 1 / 4 of the total steel ladle volume, start adding ferrosilicon alloy. When the steel output is completed, all ferrosilicon alloy needs to be added.

2. The control method for deoxidation of ferrosilicon alloy for converter according to claim 1, characterized in that: The ferrosilicon alloy comprises the following chemical components in mass percentage: silicon 72% to 80%, iron 20% to 30%, phosphorus≯0.040%, sulfur≯0.020%, and carbon≯0.2%.

3. The control method for deoxidation of ferrosilicon alloy for converter according to claim 1, characterized in that: In the plain carbon steel, Als: 0.010%-0.025%, Ti: 0.010%-0.020%.

4. The control method for deoxidation of ferrosilicon alloy for converter according to claim 1, characterized in that: The order of adding ferrosilicon alloy is silicon manganese, ferrosilicon and top slag lime.

5. The control method for deoxidation of ferrosilicon alloy for converter according to claim 1, characterized in that: The plain carbon steel is Q235B.