A control method for high-quality steel deoxidation technology

Abstract

A control method for high-quality steel deoxidation technology includes the following steps: converter blowing, and by adjusting the converter blowing process, achieving the converter medium and high carbon steel endpoint C ≥ 0.10%; converter slag, and using the converter flame analysis system and the converter sonar slag system to control the converter slag and process parameters; converter tapping pre-deoxidation, and by adjusting the converter tapping pre-deoxidation process, the effect of initial molten steel deoxidation is improved; converter tapping slag, and by adjusting the converter tapping slag process, the melting point of the refining slag system is controlled; refining furnace arrival deoxidation, and by adjusting the refining furnace arrival deoxidation process, the inclusions exceed the standard and the aluminum loss is reduced; refining furnace process deoxidation, and by adjusting the refining furnace process deoxidation process, the proportion of Class B fine inclusions exceeding the standard is reduced. The present invention ensures the deoxidation effect of molten steel and reduces the aluminum deoxidation products remaining in the steel.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking, and in particular to a control method for high-quality steel deoxidation technology. Background Art

[0002] With the sudden rise of China's industrial process and the vigorous development of the manufacturing industry, it has brought good development opportunities to steel enterprises, making the prospects of special steel enterprises broader, especially in special fields such as special performance, special environment, petrochemical, automobile, high-speed train, aerospace, military industry, and machinery manufacturing. Therefore, in many special steel enterprises, the purity and performance of steel are increasingly valued. The basic principle of converter steelmaking is based on the chemical exothermic reaction between carbon and oxygen in molten iron, and the various oxides produced by the oxidation reaction are reduced and deoxidized by the molten steel. Some composite inclusions remain in the steel, which have a certain impact on the quality of the steel to varying degrees.

[0003] At present, the deoxidation process of high-quality and special steel is mainly based on silicon-based deoxidation and aluminum-based deoxidation. When silicon-based deoxidation is the main method, the deoxidation capacity is slightly insufficient, and the generated compounds are mostly in the form of silicate complexes, which has a great impact on the performance of the steel. Special steel varieties are mostly based on aluminum-based deoxidation processes. Although the deoxidation capacity is strong and the dispersed small aluminum oxide particles have improved the strength of the steel to a certain extent, it is very easy for composite inclusions to remain in the steel due to insufficient removal, which reduces the performance of the steel under the condition of rolling without deformation, and also increases the destructive power, reducing the fatigue life of the steel. In view of the quality problems such as excessive Class B inclusions and high oxygen and nitrogen gas content in steel in the aluminum-based deoxidation process commonly used by high-quality and special steel steelmaking enterprises, expanding the application technology of molten steel deoxidation, strengthening the deoxidation control ability of molten steel, and improving the purity of molten steel are new ways for high-quality development of high-quality and special steel enterprises. During the smelting process of special steel, reducing the oxygen content in the molten steel, promoting the full floating of inclusions, and further improving the purity of the steel to meet the requirements of downstream customers for the performance and indicators of the steel are the core of quality control for all special steel companies.

[0004] At present, the basic process of deoxidation technology of many domestic high-quality steel enterprises is: first, steel is tapped from the primary furnace (arc furnace, converter) → aluminum block (or aluminum-manganese or silicon-aluminum alloy) → ferroalloy → carburizer → slag; second, diffusion deoxidation + wire feeding deoxidation after the refining furnace arrives at the station and is powered on. Among them, the deoxidation operation of the refining furnace is mainly based on carbon powder + ferrosilicon powder slag surface diffusion deoxidation or aluminum particles + silicon carbide combined diffusion deoxidation. Finally, the composition is adjusted according to demand by feeding aluminum wire, silicon-calcium cored wire, etc. to achieve the purpose of deep deoxidation.

[0005] However, with the rapid promotion of efficient production models in steel enterprises, increasing production and efficiency has become normalized, and a series of problems have followed, such as overoxidation of primary molten steel, slag discharge during steelmaking, low aluminum recovery during pre-deoxidation, low aluminum recovery during alloying, unreasonable refining slag system, and poor castability of continuous casting tundish. The root cause of the above series of quality problems is mainly related to the unstable deoxidation effect of molten steel and the insufficient removal of aluminum-based deoxidation products remaining in the steel.

[0006] Therefore, on the premise of improving the quality of the initial molten steel in the converter, it is imperative to explore a new deoxidation process for high-quality steel, effectively utilize composite slag-forming materials, give full play to the potential of deep deoxidation of the initial molten steel, and improve the purity of the molten steel. Summary of the invention

[0007] In order to overcome the above-mentioned defects of the prior art, the inventors conducted in-depth research and completed the present invention after paying a lot of creative work.

[0008] Specifically, the technical problem to be solved by the present invention is to provide a control method for high-quality steel deoxidation technology to solve the technical problem of quality problems caused by the current conventional slag making system and deoxidation process to high-quality steel.

[0009] In order to solve the above technical problems, the technical solution of the present invention is: a control method for high-quality steel deoxidation technology, comprising the steps of:

[0010] Converter blowing, and by adjusting the converter blowing process, the converter medium and high carbon steel end point C ≥ 0.10% is achieved;

[0011] Converter slagging, and use converter flame analysis system and converter sonar slagging system to control converter slagging and process parameters;

[0012] Pre-deoxidation of converter steel, and by adjusting the process of pre-deoxidation of converter steel, the effect of initial molten steel deoxidation is improved;

[0013] 2. slag making during converter steel tapping, and the melting point of refined slag system can be controlled by adjusting the process of converter steel tapping and slag making;

[0014] Deoxidation at the refining furnace, and by adjusting the deoxidation process at the refining furnace, the inclusions are controlled and the aluminum loss is reduced;

[0015] Deoxidation is carried out in the refining furnace process, and the excessive proportion of B fine inclusions is reduced by adjusting the deoxidation process in the refining furnace process.

[0016] As an improvement, the converter blowing adopts the following adjustment method: through the variable-lance variable-pressure oxygen lance blowing control curve, the position of the overall converter oxygen lance is designed, and the converter oxygen supply intensity is adjusted, thereby increasing the converter medium and high carbon steel end point C ≥ 0.10%.

[0017] As a further improvement, the integral converter oxygen lance positions include a blowing lance position, a desiliconization lance position, a slag removal lance position, a heating lance position, and a decarburization lance position, and the lance position heights are adjusted as follows: high-low-flat-high-low.

[0018] As a further improvement, the converter oxygen supply intensity is adjusted to 15500Nm 3 / h.

[0019] As an improvement, the process of pre-deoxidation of converter steel is adjusted as follows: a carburizer is added into the ladle.

[0020] As a further improvement, the carburizer index is:

[0021]

[0022] As an improvement, the converter slag making process is adjusted as follows: pre-melted aluminum calcium slag and other composite materials are used in combination with conventional lime slag making materials to achieve a refined slag close to 7Al 2 O 3. ·12CaO refined slag system.

[0023] As a further improvement, the pre-melted aluminum calcium slag index is:

[0024]

[0025] As an improvement, the deoxidation process of the refining furnace at the station is adjusted as follows: after the refining furnace arrives at the station, aluminum wire is fed according to the type of steel to achieve deep deoxidation.

[0026] As a further improvement, the specific aluminum wire deep deoxidation process is as follows: after refining at the station, 100 to 200 m of aluminum wire is fed per furnace.

[0027] More specific basis is:

[0028] For 20, 35, 45, 40Cr steel, aluminum wire is fed at the refining station at a rate of 120±20m / furnace;

[0029] For GCr15 steel, 140±20m / furnace of aluminum wire is fed after refining.

[0030] For CM490 and CM690 steel, aluminum wire is fed at 140-180±20m / furnace when arriving at the refining station.

[0031] As an improvement, the deoxidation process of the refining furnace is adjusted as follows: the deoxidation of the refining furnace is adjusted to adopt the method of independent deoxidation of silicon carbide.

[0032] Specifically, the detailed steps of the present invention include:

[0033] S1. Adjust the converter blowing process model. The original control mode was a constant-lance constant-pressure oxygen lance blowing control process model. The highest lance position of the original converter blowing was about 160cm, the process lance position was controlled at about 150cm, and the carbon pulling lance position was about 120cm; the oxygen flow rate was basically stable at 14000Nm 3 The present invention designs the position of the oxygen lance of the entire converter through the variable-lance variable-pressure oxygen lance blowing control curve, wherein the heights of the opening lance, desiliconization lance, slag removal lance, heating lance and decarburization lance are respectively: high-low-flat-high-low, thereby adjusting the oxygen supply intensity of the converter to 15500Nm 3 / h, improve the hit rate of the converter medium and high carbon steel end point C ≥ 0.10%;

[0034] In the present invention, the control of the overoxidation problem at the converter end is strengthened. According to the steelmaking principle, during the converter steelmaking process, the thermal effect of the carbon-oxygen reaction during blowing in the converter furnace is:

[0035] Converter steelmaking is mainly a carbon-oxygen chemical reaction. According to the law of mass action, we can get:

[0036]

[0037] Where K is the equilibrium constant;

[0038] P CO - partial pressure of CO in the gas phase in equilibrium with carbon in the molten pool;

[0039] fC - carbon activity factor;

[0040] fO - oxygen activity factor;

[0041] If Pco=0.1MPa, and when the carbon and oxygen contents are very low, fC and fo can be approximated to 1. It can be concluded that:

[0042]

[0043] set up but

[0044] m=[%C][%O]

[0045] m is called the carbon-oxygen concentration product. The properties of molten steel differ significantly from those of extremely dilute solutions, which changes the value of m. Therefore, the value of m is not conserved.

[0046] The above formula shows the equilibrium relationship between carbon and oxygen in molten steel. The lower the carbon content in the molten steel, the higher the oxygen content in equilibrium, or the equilibrium concentration of oxygen in the molten steel is inversely proportional to the equilibrium concentration of carbon. And when PCO≈100kPa, and the carbon content in the molten steel is less than 0.10%, the oxygen in equilibrium with carbon increases sharply.

[0047] In order to better control the carbon content at the converter end point, according to the carbon-oxygen balance law and the proportional relationship between carbon and oxygen, some data are measured by on-site oxygen determination in the converter to achieve control of the C content and oxygen content at the end point of the molten steel.

[0048] Combining the above principles and current situation, changing the original converter blowing process gun position constant gun constant pressure control method and implementing a variable gun variable pressure blowing mode is beneficial to solving the terminal overoxidation problem.

[0049] S2. Use converter flame analysis and converter sonar slag removal system to control converter slag removal and process parameters. The converter sonar slag removal system includes an audio signal acquisition unit, an audio signal processing and display unit, a splashing video detection unit, a nitrogen solenoid valve and filter, and an industrial computer.

[0050] The audio signal acquisition unit is installed on the converter to collect noise signals, process the signals by the audio signal processing and display unit, obtain a signal corresponding to the slag plane, and transmit it to the industrial computer for display;

[0051] The audio signal acquisition unit has an inert gas protection device, and the nitrogen solenoid valve and the filter are connected to the inert gas protection device;

[0052] The splashing video detection unit is used to obtain the splashing image signal of the converter and transmit the signal to the industrial computer.

[0053] S3. In the early stage of converter steel tapping, the original pre-deoxidation process of the steel ladle is to add aluminum ingots (or aluminum-containing deoxidizing materials). In the present invention, it is changed to: in the early stage of medium and high carbon steel tapping, according to the finished product C: standard lower limit -0.03% (excluding alloy carbon increase), add part of the carburizer in the steel ladle to give full play to the function and advantage of carbon deoxidation.

[0054] To achieve the best deoxidation effect during smelting, the deoxidation steps of steel are as follows:

[0055] The order of addition is: carburizer (standard lower limit of finished product composition - 0.03%), ferrosilicon (standard lower limit of finished product composition - 0.02%), alloy (standard lower limit of finished product composition), and slag.

[0056] In the present invention, the carbon deoxidation principle in steelmaking is fully utilized to reduce the free oxygen in the early stage of converter steelmaking to weaken the dependence on aluminum deoxidation in the middle and late stages of refining, thereby reducing the risk of Class B inclusions in steel being generated or exceeding the standard. Since carbon is a strong deoxidizer, the deoxidation reaction is carried out as follows:

[0057] [C]+[O]={CO}

[0058] When the pressure of CO is 0.1 MPa, the equilibrium constant is:

[0059]

[0060] The relationship between the deoxidation constant KC and the absolute temperature T is:

[0061]

[0062] At 1600℃, K C =2.31×10 -3 .

[0063] The product of carbon deoxidation is CO gas, which is very easy to be removed from the molten steel. Therefore, using carbon as a deoxidizer will prevent the molten steel from being contaminated, which is very beneficial for high-quality special steel. Therefore, using carbon as the initial molten steel pre-deoxidation has the best deoxidation effect. 2 If harmful gases remain in the steel, they will destroy the continuity of the steel, so it can only be used as a single deoxidizer in the early stage of steel smelting. In order to ensure the purity of the steel at the end of smelting, it is necessary to use elements with strong deoxidizing ability such as Al and Si, and use them together with carbon deoxidizers. Therefore, ferrosilicon is added in the later stage to ensure better deoxidation effect.

[0064] S4, adjusting the slag making process of the converter steel tapping. In this step, the slag making system of the converter steel tapping ladle is changed (the original slag making process of the converter steel tapping ladle is the slag making system of lime + refined pre-melted slag), and is adjusted to: using composite materials such as pre-melted aluminum calcium slag, with conventional lime slag making materials, controlling the melting point of the refined slag system, and reaching the refined slag close to 7Al 2 O 3. ·12CaO refined slag system.

[0065] In the present invention, the core is to adjust the slag making system of the converter steel ladle, so as to create necessary conditions for the rapid slag forming of the refining furnace and the smelting of crystallized steel. In modern steelmaking, more composite slag making materials are widely used in practice. 2 O 3 The compounds of CaO and calcium silicate are not as stable as calcium silicate. 2 O 3 In the slag system, when Al 2 O 3 The melting point is lowest (1350-1400℃) when the content of calcium aluminate is 48-56% and the content of CaO is 44-52%. 2 O 3. ·12CaO). But when CaO or Al 2 O 3 When the content is greater than 60%, it becomes a solid phase and is difficult to participate in the reaction. 2 -Al 2 O3 The ternary phase diagram theory uses composite materials such as pre-melted aluminum calcium slag and conventional lime slag making materials to achieve a refined slag close to 7Al 2 O 3. ·12CaO refined slag system.

[0066] S5. Adjust the deoxidation process of the refining furnace at the station, reasonably utilize the carbon deoxidation of steel, and adopt the aluminum wire feeding process according to the steel grade after the refining furnace arrives at the station. The specific aluminum wire deep deoxidation process is as follows:

[0067] For 20, 35, 45, 40Cr steel, aluminum wire is fed at the refining station at a rate of 120±20m / furnace;

[0068] For GCr15 steel, 140±20m / furnace of aluminum wire is fed after refining.

[0069] For CM490 and CM690 steel, aluminum wire is fed at 140-180±20m / furnace upon refining to control the excessive inclusions and reduce aluminum loss.

[0070] In this step, according to the requirements of steel type and performance, the original converter steel-making process of some steel types is changed to directly connect to the pre-deoxidation process of aluminum ingot deoxidation. According to the deoxidation capacity of aluminum in the steelmaking process. Aluminum is a strong deoxidizer and is usually used for pre-deoxidation and final deoxidation of molten steel. The specific reaction is as follows:

[0071] 2[AL]+3[O]=(Al 2 O 3 ) [固]

[0072] [Fe] + 4 [O] + 2 [Al] = (FeO·Al 2 O 3 )

[0073] The equilibrium constant of the above formula is:

[0074]

[0075] When the residual [Al] in the steel is greater than 0.026%, the deoxidation product can be Al 2 O 3 , the activity at this time α Al 2 O 3 ≈1, so the deoxygenation constant K' Al The relationship with absolute temperature T is:

[0076]

[0077] At 1600℃, K'Al=2.09×10 -13 .

[0078] The equilibrium concentration table of oxygen and aluminum is obtained from the above formula, as shown in the following table:

[0079] [Al]％ 0.1 0.05 0.01 0.005 0.002 0.001 [0]％ 0.0003 0.0004 0.0013 0.002 0.0037 0.0059

[0080] S6. Change the diffusion deoxidation process in the refining furnace process, and use the method of independent deoxidation of silicon carbide in the refining furnace process. In the present invention, the original method of using aluminum particles + silicon carbide as the material for deoxidation in the refining furnace process of some steel grades is changed.

[0081] After adopting the above technical solution, the beneficial effects of the present invention are:

[0082] The high-quality and special steel deoxidation method provided by the present invention is a process method for the whole process of associated molten steel deoxidation operation; a converter blowing gun position control curve suitable for the structural requirements of high-quality and special steel varieties is established; the converter newly added sonar slag automatic detection system is easy to operate, has fast results, and requires little investment, and is suitable for the element adjustment of the present invention; the present invention reduces the initial free oxygen in the molten steel during the molten steel deoxidation stage, thereby expanding the technical space for crystalline steel smelting; the present invention overcomes long-term technical prejudices, adopts composite materials such as pre-melted aluminum-calcium slag, and matches conventional lime slag-making materials to reduce the content of aluminum inclusions in special steel products, thereby opening up a new way to improve the cleanliness of molten steel; the present invention expands the carbon deoxidation technology of molten steel by adopting the method of independent deoxidation of silicon carbide, thereby improving the recovery rate of aluminum alloy and reducing the production cost of steelmaking;

[0083] In summary, the present invention creates a high-quality and special steel enterprise from the initial molten steel endpoint control to the innovation of the molten steel deoxidation technology and materials used, ensuring the deoxidation effect of the molten steel and reducing the aluminum-based deoxidation products remaining in the steel, thus realizing a new idea of ​​high-quality and low-consumption control for high-quality and special steelmaking enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 Schematic diagram of the control results of the C content and oxygen content of the molten steel endpoint in an embodiment of the present invention;

[0085] Figure 2 The figure is a converter blowing process parameter diagram after adjustment in the embodiment;

[0086] Figure 3 This is the original blowing process parameter diagram of the converter;

[0087] Figure 4 This is a schematic diagram of the interface of the sonar slag automatic detection system;

[0088] Figure 5 This is a schematic diagram of the target range of final slag refining control;

[0089] Figure 6 It is a structural schematic diagram of the aluminum wire feeding device;

[0090] Figure 7 This is a trend diagram of the converter blowing lance height control in Example 1;

[0091] Figure 8 This is the trend chart of oxygen flow control in converter blowing. DETAILED DESCRIPTION

[0092] The present invention is further described below in conjunction with specific examples. However, the use and purpose of these exemplary embodiments are only used to illustrate the present invention, and do not constitute any form of limitation on the actual protection scope of the present invention, nor do they limit the protection scope of the present invention to them.

[0093] Example

[0094] A control method for high-quality steel deoxidation technology, comprising the steps of:

[0095] S1, converter blowing, and by adjusting the converter blowing process, the converter medium and high carbon steel end point C ≥ 0.10%. In this embodiment, the position of the overall converter oxygen lance is designed by changing the lance and pressure oxygen lance blowing control curve, wherein the lance heights of the opening lance position, the desiliconization lance position, the slag lance position, the heating lance position, and the decarburization lance position are respectively: high-low-flat-high-low, so that the converter oxygen supply intensity is adjusted to 15500Nm 3 / h, improving the hit rate of the converter medium and high carbon steel end point C ≥ 0.10%.

[0096] The lower the carbon content in the molten steel, the higher the oxygen content in equilibrium, or the equilibrium concentration of oxygen in the molten steel is inversely proportional to the equilibrium concentration of carbon. And when PCO≈100kPa, and the carbon content in the molten steel is less than 0.10%, the oxygen in equilibrium with carbon increases sharply. According to the carbon-oxygen balance law in molten steel, its carbon-oxygen balance is shown in the following table:

[0097]

[0098] In this embodiment, in order to better control the carbon content at the converter endpoint, according to the carbon-oxygen balance law and the proportional relationship between carbon and oxygen, the converter on-site oxygen determination measured some data, thereby achieving control of the C content and oxygen content at the end of the molten steel. The end point control result is as follows: Figure 1 shown.

[0099] In this embodiment, the converter blowing gun position control curve is used to control the carbon content and phosphorus content of the converter end point through the blowing process. The specific blowing process parameters are as follows: Figure 2 As shown. When smelting high-quality special steel varieties, there are constraints on composition and performance. Especially when the composition or temperature of molten iron is abnormal, the converter usually adopts a constant gun position and constant oxygen flow blowing process model, which leads to a particularly prominent problem of overoxidation at the converter end point, causing a greater impact on the deoxidation operation of the refining furnace.

[0100] In this embodiment, the inventor has repeatedly explored and compared the five-step method of the converter oxygen lance blowing position, desiliconization lance position, slag removal lance position, heating lance position, and decarburization lance position. The lance position heights of the five-step method are: high-low-flat-high-low. The new converter cooling lance position: the highest point is 2.0m, which is 0.4m higher than the original highest lance position of 1.6m; the lowest lance position is 1.2m, which is 0.3-0.7m lower than the original lowest lance position of 1.5m. The overall lance position is adjusted, and the oxygen lance position activity space is expanded to 0.8m; at the same time, the converter oxygen supply intensity is increased from the original process parameter of 14000Nm 3 / h, adjusted to 15500Nm 3 / h, so that the carbon-oxygen reaction in the converter furnace, the heating rate is accelerated, and the final carbon and phosphorus content control is increasingly stable. The specific converter blowing gun height and oxygen flow control are as follows Figure 7 and Figure 8 shown.

[0101] Compared with the original control mode, the original control mode is a constant-lance constant-pressure oxygen lance blowing control process model. The highest lance position of the original converter blowing is about 160cm, the process lance position is controlled at about 150cm, and the carbon pulling lance position is about 120cm; the oxygen flow rate is basically stable at 14000Nm 3 / h. The original blowing process parameters of the converter are as follows: Figure 3 shown.

[0102] It can be clearly seen that the steps of this embodiment are to adjust the oxygen lance position control range during converter blowing, and the lance height floating space (the difference between the lowest lance position and the highest lance position in the middle of blowing) is expanded from 10cm to 80cm; the oxygen flow rate is increased to 15500Nm 3 / h.

[0103] Since the adoption of the new converter blowing control curve (converter blowing gun height + blowing oxygen flow), the converter end point overoxidation problem has been greatly improved, and the hit rate of the end point carbon content of key steel varieties greater than 0.1% has become increasingly stable, which is conducive to solving the end point overoxidation problem. According to statistics, the proportion of the end point C ≥ 0.10% of the converter medium and high carbon steel is 87.1%, which is 14.5% higher than the original converter blowing gun position control end point C hit rate of 72.6%.

[0104] S2. Converter slagging. In this embodiment, the converter flame analysis system and the converter sonar slagging system are used to control the converter slagging and process parameters.

[0105] The converter sonar slag removal system includes an audio signal acquisition unit, an audio signal processing and display unit, a splashing video detection unit, a nitrogen solenoid valve and a filter, and an industrial computer, wherein the audio signal acquisition unit is installed on the converter to collect noise signals, and the audio signal processing and display unit processes the signals to obtain a signal corresponding to the slag plane, and transmits it to the industrial computer for display; the audio signal acquisition unit has an inert gas protection device, and the nitrogen solenoid valve and the filter are connected to the inert gas protection device; the splashing video detection unit is used to obtain the splashing image signal of the converter and transmit the signal to the industrial computer. More specifically, the sonar slag removal automatic detection system of Hunan Raymo Company can be used in this embodiment. During the blowing process of the converter, the supersonic oxygen flow and solid phase particles (unmelted slag and high melting point silicate) emit very strong noise. This noise reaches its maximum intensity when there is no liquid slag covering, such as when blowing and severe back drying. When the foam slag is formed, the foam slag above the oxygen gun nozzle absorbs the noise emitted by the oxygen stream. The thicker the slag layer, the greater the height of the sound-absorbing foam slag, and the lower the noise intensity from the furnace. By effectively eliminating environmental noise and collecting specific blowing noise intensity in the furnace, the thickness of the foam slag in the furnace can be indirectly reflected, and the trend curve of the slag layer thickness can be drawn to improve the converter slagging effect and the hit rate of the terminal P element and reduce the FeO content of the converter slag, assist and stabilize the converter smelting process control, and improve the stable control of the residual P element in high-quality special steel. Figure 4 The following is a schematic diagram of the interface of the sonar slagging automatic detection system. In actual work, based on the converter flame monitoring and converter sonar slagging system, the converter oxygen lance operator can use the system to: when the sonar slagging computer screen shows a warning of splashing, the oxygen lance control needs to appropriately lower the lance position; when the sonar slagging computer screen shows a warning of drying, the oxygen lance control needs to appropriately raise the lance position, so as to achieve auxiliary functions such as timely adjustment of the blowing lance position, addition of slag, and ensuring good melting of the slag during the process, which plays a huge role in reducing slag splashing and promoting efficient smelting and precise control of the converter.

[0106] Compared with the original converter automated steelmaking, the converter's newly added sonar slagging automatic detection system is more suitable for the element adjustment of the present invention, which can improve the converter's slagging effect and the hit rate of the endpoint P element and reduce the FeO content in the converter slag.

[0107] S3. Pre-deoxidation of converter steel, and by adjusting the process of pre-deoxidation of converter steel, the effect of initial steel liquid deoxidation is improved. Specifically: in the early stage of medium and high carbon steel tapping, according to the finished product C: standard lower limit -0.03% (excluding alloy carbon increase), some carburizer is added into the ladle to give full play to the function and advantage of carbon deoxidation.

[0108] To achieve the best deoxidation effect during smelting, the deoxidation steps of steel are as follows:

[0109] The order of addition is: carburizer (standard lower limit of finished product composition - 0.03%), ferrosilicon (standard lower limit of finished product composition - 0.02%), alloy (equal to the standard lower limit of finished product composition), and slag.

[0110] In this embodiment, taking the output of 40Cr steel of 85 tons as an example, according to the final carbon content, 30-120 kg of recarburizer (added when the amount of molten steel in the ladle reaches 10-15 tons), 500-550 kg of silicon manganese (added when the amount of molten steel in the ladle reaches 15-20 tons), alloy (standard lower limit of finished product composition), and slag are preferentially added to the converter ladle.

[0111] Among them, the carbon raiser index used is:

[0112]

[0113]

[0114] Compared with the original ladle pre-deoxidation process, aluminum ingots (or aluminum-containing deoxidizing materials) are directly added. When the free oxygen in the molten steel is high during the converter tapping, under the premise of not exceeding the C content specification range of the finished product, this embodiment adds a proper amount of carburizer with the steel flow during the converter tapping, so that carbon reacts with oxygen in the molten steel in advance to generate CO or a small amount of CO. 2, The gas can effectively remove part of the oxygen in the molten steel without contaminating the molten steel, which is beneficial to alleviate the subsequent deoxidation pressure of the refining furnace and reduce the probability of the formation of complex inclusions.

[0115] S4, tapping the converter and slagging, and by adjusting the process of tapping the converter and slagging, the melting point of the refined slag system is controlled. In the steps of this embodiment, a pre-melted aluminum-calcium slag composite material is used in combination with conventional lime slagging materials to control the melting point of the refined slag system, so that the refined slag is close to 7Al 2 O 3. ·12CaO refined slag system.

[0116] Among them, the composition of the pre-melted aluminum calcium slag is:

[0117]

[0118] The inventor found that during the steelmaking process, Al 2 O 3 The compounds of CaO and calcium silicate are not as stable as calcium silicate. 2 O 3 In the slag system, when Al 2 O 3 The melting point is lowest (1350-1400℃) when the content of calcium aluminate is 48-56% and the content of CaO is 44-52%. 2 O3. ·12CaO). But when CaO or Al 2 O 3 When the content is greater than 60%, it becomes a solid phase and is difficult to participate in the reaction. 2 -Al 2 O 3 The ternary phase diagram theory uses composite materials such as pre-melted aluminum calcium slag and conventional lime slag making materials to achieve a refined slag close to 7Al 2 O 3. ·12CaO refining slag system, the refining final slag control target range is as follows Figure 5 shown.

[0119] The converter steel ladle adopts a new slag making process: lime + pre-melted aluminum calcium slag, the final slag composition of the refining furnace is shown in the following table:

[0120]

[0121]

[0122] Compared with the original slag making system for converter steel ladle (the original slag making process for converter steel ladle is lime + refined pre-melted slag), the composition and melting point of the new refined slag system are completely close to the low melting point 7Al steelmaking 2 O 3. The index of 12CaO lays the foundation for pure molten steel.

[0123] S5. Deoxidation at the refining furnace. Adjust the deoxidation process at the refining furnace, rationally utilize the carbon deoxidation at the steel tapping point, and use a specially designed aluminum wire feeding device at the working position of the refining furnace to feed aluminum wire. The ￠9mm aluminum wire used has a unit weight of 234g / m.

[0124] like Figure 6 As shown, the device comprises: a ladle 4 and a wire feeder 1 located in a refining furnace, wherein a feeding port 2 is provided at the top of the ladle, and an argon inlet 5 is provided at the bottom for blowing argon into the ladle; the wire feeder is arranged on a mounting platform on one side of the refining furnace, and the wire feeder feeds aluminum wire 6 into the ladle through a wire feeding port provided on the ladle, wherein the wire feeding port is located below the ladle feed port and above the liquid level of the material in the ladle, and a refining furnace cover 3 is provided above the refining furnace.

[0125] In addition, the inventors have found out the standard basis for feeding aluminum wire after the refining furnace arrives at the station according to the steel type. The standard basis for feeding aluminum wire is as follows: for 20, 35, 45, 40Cr steel, 120±20m / furnace of aluminum wire is fed after refining at the station; for GCr15 steel, 140±20m / furnace of aluminum wire is fed after refining at the station; for CM490 and CM690 steel, 140-180±20m / furnace of aluminum wire is fed after refining at the station; according to this standard, the inclusions can be controlled to exceed the standard and the aluminum loss can be reduced. In this embodiment, the aluminum wire is fed at a rate of 120-180m / furnace, i.e. 35-38kg / furnace, for the produced CM690 high-quality steel.

[0126] Compared with the original method, the process of pre-deoxidation of aluminum ingots for some steel grades in the converter, the adjustment of this step and the special device in this embodiment realizes the function of refining and feeding wire in a closed state of the refining furnace, avoids air intake during the refining process of molten steel, truly realizes the deep deoxidation operation under the slight positive pressure of the refining furnace, and greatly reduces the probability of aluminum loss and the production of secondary inclusions.

[0127] S6. Deoxidation in the refining furnace process. By adjusting the deoxidation process in the refining furnace process, the excessive proportion of Class B fine inclusions is reduced. In this embodiment, specifically: the slag-making deoxidation material in the deoxidation in the refining furnace process is adjusted to silicon carbide material.

[0128] Comparative Example 1

[0129] The other steps are basically the same as those in Example 1, except that in the actual converter blowing process, the control mode used in this comparative example is a constant-lance constant-pressure oxygen lance blowing control process model. The highest lance position of the original converter blowing is about 160cm, the process lance position is controlled at about 150cm, and the carbon pulling lance position is about 120cm; the oxygen flow rate is basically stable at 14000Nm 3 / h. The original blowing process parameters of the converter are as follows: Figure 3 shown.

[0130] According to statistics, the endpoint C ≥ 0.10% of the medium and high carbon steel in the converter of Example 1 accounts for 87.1%, while the hit rate of the endpoint C of the original converter blowing gun position control of the comparative example is 72.6%, and Example 1 is 14.5% higher than that of Comparative Example 1.

[0131] Comparative Example 2

[0132] The other steps are basically the same as those in Example 1, except that there is no auxiliary monitoring means for controlling the converter blowing process in the steel plant in this comparative example. The timing of feeding, slag removal effect, slag overflow risk warning, molten pool temperature prediction, etc. are completely determined by visual inspection and experience of the converter oxygen gun operator.

[0133] The results show that the final control result has a certain deviation from the actual value, which has a certain impact on the stability control of product quality. In particular, the hit rate of the end point P element decreased by 12.4%, and the FeO content of the converter slag increased by 5.7%.

[0134] Comparative Example 3

[0135] The other steps are basically the same as those in Example 1, except that in the ladle pre-deoxidation process of this comparative example, a proper amount of aluminum ingots (or aluminum-containing deoxidizing materials) is directly added for precipitation deoxidation.

[0136] This is a long-term technical understanding of technicians in this field. Because in the actual production process, when the converter produces medium-high carbon steel, the probability of C 0.05-0.10% when tapping steel is about 8%. In the actual production process, when the converter produces medium-high carbon steel, the probability of C 0.05-0.10% when tapping steel is about 8%. Because according to the steelmaking theory (carbon-oxygen balance law list) and the converter on-site oxygen determination ( Figure 1 Schematic diagram of the control results of the C content and oxygen content of the steel liquid at the end point) According to the data, to reduce the oxygen in the steel liquid, it is necessary to rely on the deoxidation ability of aluminum during the steelmaking process. This is indeed the case in the original process. Aluminum is a strong deoxidizer and is usually used for pre-deoxidation and final deoxidation of steel liquid. The reaction formula is as follows:

[0137] 2[Al]+3[O]=(Al 2 O 3 ) [固]

[0138] [Fe] + 4 [O] + 2 [Al] = (FeO·Al 2 O 3 )

[0139] The equilibrium constant of the above formula is:

[0140]

[0142] When the residual [Al] in the steel is greater than 0.026%, the deoxidation product can be Al 2 O 3 , the activity at this time α Al 2 O 3 ≈1, so the deoxygenation constant K' Al The relationship with absolute temperature T is:

[0143]

[0144] At 1600℃, K'Al=2.09×10 -13 .

[0145] The equilibrium concentration table of oxygen and aluminum is obtained from the above formula, as shown in the following table:

[0146] [Al]％ 0.1 0.05 0.01 0.005 0.002 0.001 [0]％ 0.0003 0.0004 0.0013 0.002 0.0037 0.0059

[0147] According to the result data, the direct addition of aluminum for pre-deoxidation in Example 3 will produce a large amount of aluminum oxides, which increases the probability of generating type B inclusions by 9.7% compared with Example 1.

[0148] The reason is that the steel-preferential carbon deoxidation process adopted in Example 1 will reduce the generation of the above oxides, and the generated CO promotes the inclusions to float to the slag during the floating process, which truly reduces aluminum deoxidation and reduces the probability of Class B inclusions. Example 1 When the free oxygen in the molten steel is high during the converter tapping, under the premise of not exceeding the C content specification range of the finished product, this embodiment adds a proper amount of carburizer with the steel flow during the converter tapping, so that the carbon reacts with the oxygen in the molten steel in advance to generate CO or a small amount of CO. 2 , gas, without contaminating the molten steel, effectively removes part of the oxygen in the molten steel, which is beneficial to alleviate the subsequent deoxidation pressure of the refining furnace and reduce the probability of the formation of complex inclusions.

[0149] Comparative Example 4

[0150] The other steps are basically the same as those in Example 1, except that the slag making system for the converter steel-tapping ladle in this comparative example adopts the original slag making system: lime+refined pre-melted slag+fluorite.

[0151] Among them, the indicators of refined pre-melted slag are:

[0152]

[0153] The final refining furnace slag composition is shown in the following table:

[0154]

[0155]

[0156] In Example 1, the converter steel ladle adopts a new slag making process: lime + pre-melted aluminum calcium slag, and the final slag composition of the refining furnace is shown in the following table:

[0157] Ingredients CaO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> FeO MnO R content% 45～55 11～15 22～29 0.4～0.6 0.5 3.7～4.3

[0158] By comparison, the melting point of the final slag of the comparative example 4 is in the range of 1510-1590°C; while the melting point of the slag made by the new pre-melted aluminum calcium slag in the embodiment 1 is in the range of 1350-1500°C. The composition and melting point of the new refined slag are completely close to the low melting point 7Al 2 O 3. The index of 12CaO lays the foundation for pure molten steel.

[0159] Comparative Example 5

[0160] In this comparative example, pre-deoxidation is performed before the refining furnace is deoxidized at the station. This point is also a long-term technical understanding of those skilled in the art.

[0161] Because in the steelmaking process, good deoxidation of molten steel is the main task to improve the purity of steel.

[0162] According to the steelmaking principle

[0163] W[C] / % ＜0.05 0.05～0.10 0.11～0.20 0.21～0.30 0.31～0.40 ＞0.41 W[O](×10-6) 700 500 400 250 150 100 Deoxidized Al / kg.t-1 0.84 0.6 0.48 0.30 0.18 0.12

[0164] Based on this, the standard of pre-deoxidized molten steel for converter steelmaking is formulated according to the requirements of molten steel. The specific amount of aluminum added for pre-deoxidation of converter steelmaking is shown in the following table:

[0165] End point C content C≤0.05 C≤0.10 C≤0.15 C≤0.20 Added Al amount (kg) 2.5 2.0 1.5 1.0

[0166] The initial oxygen content of the molten steel is high, and the reduction of 100×10 -6 Oxygen, 0.1125kg / t of metallic aluminum is consumed, and 0.213kg / t of deoxidized product Al is produced. 2 O 3， Inclusions: For every 1kg / t increase in slag at tapping, the (FeO) in the reducing slag must consume 0.05kg / t of metallic aluminum, and produce 0.1kg / t of deoxidation product Al 2 O 3， Inclusions. For aluminum-deoxidized steel, the amount of aluminum used for one deoxidation is 0.5-1.0 kg / t, and the amount of deoxidation product produced is 0.6-1.6 kg / t.

[0167] The results show that: according to the aluminum content of the initial deoxidation of the ladle, when the end point C is 0.15%, the oxides produced by aluminum deoxidation are as follows: 80t*1.5kg / t*1.6kg=192kg oxides. Such a large number of aluminum inclusions bring huge potential risks to the quality of special steel products.

[0168] In Example 1, pre-deoxidation using a carburizer is used in the early stage, which avoids the situation where part of the lime and pre-melted slag previously added during the converter tapping covers the surface of the molten steel, causing part of the added aluminum ingots to float on the surface of the slag steel, thereby reducing the recovered aluminum of the aluminum ingots added to the ladle to varying degrees.

[0169] Comparative Example 6

[0170] The other steps are basically the same as those in Example 1, except that aluminum ingots are directly added for deoxidation during the deoxidation process at the refining furnace.

[0171] The results show that: in the comparative example, taking the same steel grade as an example, under the same steel output statistics, the steel liquid pre-deoxidation process: the original ladle pre-deoxidation process is to add ingots in the ladle 88-114kg / furnace (the carbon content of the converter end is 0.10%), and the Al composition of the refining furnace sample 1 is analyzed, and the aluminum recovery of the ladle plus aluminum ingots is 32.53%. In Example 1, the deoxidation process after the refining furnace arrives at the station is to feed aluminum wire 120-180m / furnace and 35-38kg / furnace according to different steel grades (the single weight of ￠9mm aluminum wire is 234g / m), and the Al composition of the refining furnace sample 1 is analyzed, and the aluminum recovery of the refining furnace feeding aluminum wire is 66.21%. Compared with the comparative example 6, the aluminum recovery rate of Example 1 is increased by 33.83%. Due to the reduction of the amount of aluminum used for steel deoxidation, the total amount of aluminum and composite inclusions generated by steelmaking aluminum deoxidation is reduced year-on-year, which is also conducive to the control of Class B inclusions in steel.

[0172] Comparative Example 7

[0173] The other steps are basically the same as those in Example 1, except that the material used for deoxidation in the refining furnace process is aluminum particles + silicon carbide.

[0174] The results show that during the refining production process, after the silicon carbide is independently deoxidized by the new slag-making deoxidation system in Example 1, the addition is relatively dispersed and uniform, and the carbon-oxygen reaction can better produce CO gas, which improves the foaming effect of the refining slag, increases the permeability of the refining slag, and improves the ability of the refining slag to adsorb inclusions.

[0175] In summary, after using the adjusted molten steel deoxidation process in Example 1, the oxygen content in the steel is reduced, and the probability of producing Class B inclusions by deoxidation of aluminum materials is greatly reduced. After incorporating pre-melted aluminum-calcium slag into the slag making system, the refined slag system is more reasonable and easy to absorb inclusions, the purity of the steel is improved, and the physical properties of the steel are stabilized, meeting the requirements of customers.

[0176] It should be understood that the purpose of these embodiments is only to illustrate the present invention and is not intended to limit the protection scope of the present invention. In addition, it should also be understood that after reading the technical content of the present invention, those skilled in the art can make various changes, modifications and / or variations to the present invention, and all of these equivalent forms also fall within the protection scope defined by the appended claims of this application.

Claims

1. A control method for high-quality steel deoxidation technology, characterized in that: Includes steps: Converter blowing, and by adjusting the converter blowing process, the converter medium and high carbon steel end point C ≥ 0.10% is achieved; Converter slagging, and use converter flame analysis system and converter sonar slagging system to control converter slagging and process parameters; Pre-deoxidation of converter steel, and by adjusting the process of pre-deoxidation of converter steel, the effect of initial molten steel deoxidation is improved; 2. slag making during converter steel tapping, and the melting point of refined slag system can be controlled by adjusting the process of converter steel tapping and slag making; Deoxidation at the refining furnace, and by adjusting the deoxidation process at the refining furnace, the inclusions are controlled and the aluminum loss is reduced; Deoxidation is carried out in the refining furnace process, and the excessive proportion of Class B fine inclusions is reduced by adjusting the deoxidation process in the refining furnace process.

2. The control method of a high-quality steel deoxidation technology as claimed in claim 1, characterized in that: The converter blowing adopts the following adjustment method: through the variable-lance variable-pressure oxygen lance blowing control curve, the position of the overall converter oxygen lance is designed, and the converter oxygen supply intensity is adjusted, thereby increasing the converter medium and high carbon steel end point C≥0.10%.

3. A control method for high-quality steel deoxidation technology as claimed in claim 2, characterized in that: The integral converter oxygen lance positions include a blowing lance position, a desiliconization lance position, a slag removal lance position, a heating lance position, and a decarburization lance position, and the lance position heights are adjusted as follows: high-low-flat-high-low.

4. A control method for high-quality steel deoxidation technology as claimed in claim 3, characterized in that: The converter oxygen supply intensity is adjusted to 15500Nm 3 / h.

5. The control method of a high-quality steel deoxidation technology as claimed in claim 1, characterized in that: The process of pre-deoxidation of converter steel is adjusted as follows: a carburizer is added into the ladle.

6. The control method of a high-quality steel deoxidation technology as claimed in claim 1, characterized in that: The converter slag making process is adjusted as follows: pre-melted aluminum calcium slag and other composite materials are used in combination with conventional lime slag making materials to achieve a refined slag close to 7Al2O 3. ·12CaO refined slag system.

7. A control method for high-quality steel deoxidation technology as claimed in claim 6, characterized in that: The composition indexes of the pre-melted aluminum calcium slag are: CaO≤15w%; SiO2≤10w%; Al2O365-75w%; FeO≤2w%; MgO≤8w%; moisture≤0.5w%; The rest are inevitable impurities.

8. The control method of a high-quality steel deoxidation technology as claimed in claim 1, characterized in that: The deoxidation process of the refining furnace at the station is adjusted as follows: after the refining furnace arrives at the station, aluminum wire is fed according to the type of steel to achieve deep deoxidation.

9. The control method of a high-quality steel deoxidation technology as claimed in claim 1, characterized in that: The deoxidation process of the refining furnace is adjusted as follows: the deoxidation process of the refining furnace is adjusted to adopt the method of independent deoxidation of silicon carbide.

10. A control method for high-quality steel deoxidation technology as claimed in claim 1, characterized in that: include: S1. Adjust the converter blowing process model; The position of the oxygen lance of the entire converter is designed through the variable-lance variable-pressure oxygen lance blowing control curve. The heights of the opening lance, desiliconization lance, slag lance, heating lance, and decarburization lance are high-low-flat-high-low, respectively, so that the oxygen supply intensity of the converter is adjusted to 15500Nm 3 / h, improve the hit rate of the converter medium and high carbon steel end point C ≥ 0.10%; S2, using converter flame analysis and converter sonar slagging system to control converter slagging and process parameters; wherein, the converter sonar slagging system includes an audio signal acquisition unit, an audio signal processing and display unit, a splashing video detection unit, a nitrogen solenoid valve and filter and an industrial computer, wherein the audio signal acquisition unit is installed on the converter to collect noise signals, and the audio signal processing and display unit processes the signal to obtain a signal corresponding to the slag plane, and transmits it to the industrial computer for display; the audio signal acquisition unit has an inert gas protection device, and the nitrogen solenoid valve and filter are connected to the inert gas protection device; the splashing video detection unit is used to obtain the splashing image signal of the converter and transmit the signal to the industrial computer; S3. In the early stage of converter steel tapping, for medium and high carbon steel, some carburizer is added into the ladle according to the standard lower limit of finished product C -0.03% (excluding the carbon increase of alloy); the order of addition is: carburizer (standard lower limit of finished product composition -0.03%), ferrosilicon (standard lower limit of finished product composition -0.02%), alloy (standard lower limit of finished product composition), slag; S4. Adjust the converter tapping and slag making process, use pre-melted aluminum-calcium slag composite material, match with conventional lime slag making material, control the melting point of refined slag system, and reach the refined slag close to 7Al2O 3. ·12CaO refined slag system; S5. Adjust the deoxidation process of the refining furnace at the station, reasonably utilize the carbon deoxidation of the steel, and adopt the process of feeding aluminum wire according to the steel type after the refining furnace arrives at the station. The ￠9mm aluminum wire used has a unit weight of 234g / m; the length of the feeding aluminum wire is 100-200m; S6. Change the diffusion deoxidation process in the refining furnace and adopt the method of independent deoxidation of silicon carbide.

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