Smelting method for controlling Ds inclusions below 1.0 level
By adding appropriate amount of slag and argon stirring during the steel discharge and LF refining of the converter, combined with VD treatment and pure calcium line feeding, the problem of controlling Ds inclusions is solved, and the smelting method of Ds inclusions in the molten steel is realized below level 1.0, and the castability and quality of the molten steel are improved.
Patent Information
- Application Number
- CN202510486389.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-17
- Publication Date
- 2025-07-08
AI Technical Summary
The prior art is difficult to effectively control and remove Ds-type inclusions, especially large Ds-type inclusions in steel, which affects the water-water inability of molten steel, and small Ds-type inclusions are prone to grow and form large inclusions.
By adding appropriate aluminum blocks and slag materials when the converter is discharged, slag washing and argon stirring are performed during the LF refining process, the fluidity of the refining slag is adjusted, and pure calcium wire is fed after VD treatment. Combined with soft blowing and protective casting, the Ds inclusions in the molten steel are controlled below level 1.0.
Effective control of Ds-type inclusions is achieved, ensuring that the molten steel is good and there are few inclusions, especially the Ds-type inclusions are controlled below level 1.0, which improves the quality of molten steel.
Smart Images
Figure CN120272807A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of steel manufacturing, and relates to a process control technology for slag making, deoxidation, and inclusion control during the smelting process of strongly deoxidized steel grades. Background Art
[0002] After the economic society enters the high-quality development stage, the application requirements for steel materials in all walks of life are getting higher and higher, especially the requirements for controlling non-metallic inclusions in steel are getting higher and higher. For some aluminum-deoxidized steel grades, it is required that class B inclusions ≤ grade 1.5, class C inclusions ≤ grade 1.0, and class Ds inclusions ≤ grade 1.5; while for some steel grades with extremely high requirements, it is even required that class Ds inclusions ≤ grade 1.0.
[0003] Formation mechanism of class Ds inclusions: According to the classification in national standard GB / T 10561, class Ds inclusions are spherical inclusions. The reason why inclusions are spherical in steel is that such inclusions have a low melting point and are liquid in molten steel, and according to the principle of surface tension, they are spherical in molten steel. The liquid inclusions are low-melting calcium aluminate inclusions formed by the reaction of high-melting-point Al2O3 inclusions generated during aluminum deoxidation with the calcium content in steel. Such inclusions continuously float up during the soft blowing process and will collide and grow, making the diameter of class Ds inclusions continuously increase. Part of them enter the refining top slag through the steel-slag interface, and the other part remains in the steel, which can improve the castability of molten steel. This is the current consensus in metallurgical production and also a widely used method by steel enterprises to improve the castability of molten steel. However, this is also the main culprit for the generation of large class Ds inclusions. To control large class Ds inclusions, they must be removed from the process. In addition, the growth of fine class Ds inclusions should be suppressed as much as possible.
[0004] In order to improve the castability of molten steel in aluminum-deoxidized steel, steel enterprises generally use a large amount of calcium wire to perform calcium treatment on molten steel to increase the calcium content in molten steel, realize the transformation of high-melting-point Al2O3 inclusions into low-melting-point calcium aluminate, and generate a large number of class Ds inclusions, that is, low-melting-point calcium aluminate, in molten steel. These class Ds inclusions continuously grow, and the inclusions that are not removed remain in the steel to form large class Ds inclusions (see Figure 1 ) Summary of the Invention
[0005] The present invention aims to provide a smelting method for controlling class Ds inclusions below grade 1.0, which can realize the transformation of strong deoxidation products in molten steel into low-melting-point inclusions. This is not only conducive to the removal of large-size class Ds inclusions through the kinetic conditions of the steel-slag interface, but also conducive to controlling the size of class Ds inclusions in molten steel, and obtaining molten steel with class Ds inclusions below grade 1.0.
[0006] Technical solution of the present invention: A smelting method for controlling Ds inclusions below level 1. During tapping from the converter, appropriate deoxidizing alloys such as aluminum blocks are added according to the oxygen content of the molten steel. When one-third of the tapping is completed, the prepared slag materials are added to wash the molten steel. After tapping is completed, the molten steel is vigorously stirred with argon. During the LF refining process, strict control is exerted over the refining slag materials, deoxidizing alloys, and heating time, and the slag is adjusted according to the fluidity of the refining slag to ensure that the refining slag has good fluidity. After the LF refining is completed, the molten steel is directly sent to the VD for vacuum treatment. After breaking the vacuum, an appropriate amount of pure calcium wire is fed in, and then the molten steel is softly blown. Protective casting is carried out during continuous casting; it includes the following technological steps: (1) During the tapping process of the converter, 250 kg of lime, 200 kg of calcium carbide, and 150 kg of bauxite are added to wash the molten steel. At the same time, the weight of alloys such as ferrotitanium or aluminum blocks required for deoxidizing the molten steel is calculated based on the oxygen content at the end of the converter tapping to ensure that the aluminum content in the molten steel entering the LF station meets the finished product aluminum content of the molten steel + 0.010%; (2) After the molten steel enters the LF station, bottom blowing argon is carried out throughout the process, and the molten steel is temperature measured and sampled. Then, power is supplied to make slag. The first batch of slag materials includes 400 kg of lime and 400 kg of sintered slag. At the same time, 50 kg of aluminum pellets are added during the slag-making process for deoxidation; (3) After 5 minutes of power supply, the second batch of slag materials, 350 kg of lime and 250 kg of sintered slag, are continuously added. At the same time, 15 kg of aluminum pellets are added during the slag-making process for deoxidation; (4) After the second batch of slag materials is added and power is supplied for 5 minutes, the third batch of slag materials, 150 kg of lime and 100 kg of sintered slag, are added. At the same time, 15 kg of aluminum pellets are added during the slag-making process for deoxidation; (5) Rapid slag formation. After the refining slag is made, the composition of the molten steel is finely adjusted and the power is supplied to increase the temperature. After both the composition and temperature meet the requirements, the power supply is stopped, the bottom blowing argon is switched to soft blowing, and at the same time, 6 kg of aluminum pellets are added to the slag every 8 minutes to prevent the oxidation of the refining top slag; (6) After the LF refining is completed, the molten steel enters the VD for vacuum treatment operation. The vacuum holding time is 12 minutes. After breaking the vacuum, pure calcium wire ≤ 30 meters is fed in according to the calcium content in the molten steel, and then soft blowing is carried out for 20 minutes, and then it is left standing until continuous casting; (7) During continuous casting, protective casting is adopted. At the same time, a layer of tundish covering agent is first added to the molten steel surface in the tundish, and then a layer of carbonized rice husk is added on top of the covering agent to obtain molten steel with good castability and few various inclusions, especially with Ds inclusions controlled below level 1.0.
[0007] Advantages of the present invention: Based on the formation mechanism of Ds-type large inclusions and the basic principles of the steel-slag interface reaction during the smelting process, the present invention selects appropriate refining slag systems and slag-making methods, and obtains the appropriate composition of the refining top slag through thermodynamic calculations. Such a top slag not only facilitates the steel-slag interface reaction, but also can achieve the modification and removal of aluminum deoxidation products, reducing the Ds-type large inclusions remaining in the steel. Through the above process control, molten steel with good castability and few inclusions of various types can be stably obtained, especially the Ds-type inclusions can be controlled below grade 1.0. Description of the Drawings
[0008] Figure 1 Fig. is the metallographic photo and energy spectrum diagram of Ds-type inclusions in molten steel before continuous casting by the traditional process.
[0009] Figure 2 Fig. is the metallographic photo and energy spectrum diagram of Ds-type inclusions in molten steel before continuous casting in Example 1.
[0010] Figure 3 Fig. is the metallographic photo and energy spectrum diagram of Ds-type inclusions in molten steel before continuous casting in Example 2. Detailed Embodiments Example 1
[0011] A smelting method for controlling Ds-type inclusions below grade 1.0. In the converter smelting, 112 tons of hot metal and 37 tons of scrap steel are added. The carbon content [C] in the hot metal is 4.03%, the silicon content [Si] is 0.42%, the phosphorus content [P] is 0.135%, the sulfur content [S] is 0.036%, and the temperature is 1362°C. The converter is smelted according to the normal process, and overoxidation at the converter end is avoided. It includes the following process steps: (1) During the tapping process of the converter, 250 kg of lime, 200 kg of calcium carbide, and 150 kg of bauxite are added for slag washing of the molten steel. At the same time, 210 kg of aluminum blocks are added for deoxidizing the molten steel, and the aluminum content in the molten steel entering the LF station is 0.058%; (2) After the LF refining station is entered, bottom blowing argon is carried out throughout the process, and the molten steel is temperature measured and sampled, and then power is supplied for slag making. The first batch of slag materials added are 400 kg of lime and 400 kg of sintered slag. At the same time, 50 kg of aluminum pellets are added for deoxidation during the slag-making process; (3) After 5 minutes of power supply, the second batch of slag materials, 350 kg of lime and 250 kg of sintered slag, are continuously added. At the same time, 15 kg of aluminum pellets are added for deoxidation during the slag-making process; (4) After the second batch of slag materials are added and power is supplied for 5 minutes, the third batch of slag materials, 150 kg of lime and 100 kg of sintered slag, are added. At the same time, 15 kg of aluminum pellets are added for deoxidation during the slag-making process; (5) Rapid slag formation is required. After the refining slag is made, the composition of the molten steel is finely adjusted and the power is supplied to raise the temperature. After the composition and temperature meet the requirements, the power supply is stopped, the bottom blowing argon is switched to soft blowing, and at the same time, 6 kg of aluminum pellets are added to the slag every 8 minutes to prevent the oxidation of the refining top slag; (6) After the LF refining is completed, the molten steel enters the VD for vacuum treatment operation. The vacuum holding time is 12 minutes. After breaking the vacuum, a sample is taken. The calcium content in the molten steel is 0.0006%. A 28-meter pure calcium wire is fed, and then soft blowing is carried out for 20 minutes, and then it is left standing until continuous casting; (7) Protective casting is adopted for continuous casting. At the same time, a layer of tundish covering agent is first added to the molten steel surface in the tundish, and then a layer of carbonized rice husk is added on top of the covering agent.
[0012] Through the above process control, the inclusion control situation in the steel is shown in Table 1, and typical Ds-type inclusions are shown in Figure 2 . Example 2
[0013] A smelting method for controlling Ds-type inclusions below grade 1. During converter smelting, 107 tons of hot metal and 35 tons of scrap steel are added. The carbon content [C] in the hot metal is 4.21%, the silicon content [Si] is 0.45%, the phosphorus content [P] is 0.137%, the sulfur content [S] is 0.031%, and the temperature is 1352 °C. The converter is smelted according to the normal process, and overoxidation at the converter end is avoided. It includes the following process steps: (1) During the converter tapping process, 250 kg of lime, 200 kg of calcium carbide, and 150 kg of bauxite are added to wash the molten steel slag. At the same time, 150 kg of aluminum blocks are added to deoxidize the molten steel, and the aluminum content in the molten steel when entering the LF is 0.026%; (2) After entering the LF refining station, bottom blowing argon is carried out throughout the process, and the molten steel is temperature measured and sampled, and then power is supplied to make slag. The first batch of slag materials added are 400 kg of lime and 400 kg of sintered slag. At the same time, 50 kg of aluminum pellets are added for deoxidation during the slag-making process; (3) After 5 minutes of power supply, the second batch of slag materials, 350 kg of lime and 250 kg of sintered slag, are added continuously. At the same time, 15 kg of aluminum pellets are added for deoxidation during the slag-making process; (4) After the second batch of slag materials are added and power is supplied for 5 minutes, the third batch of slag materials, 150 kg of lime and 100 kg of sintered slag, are added. At the same time, 15 kg of aluminum pellets are added for deoxidation during the slag-making process; (5) Rapid slag formation is required. After the refining slag is made, the composition of the molten steel is finely adjusted and the power is supplied to raise the temperature. After the composition and temperature meet the requirements, the power supply is stopped, the bottom blowing argon is switched to soft blowing, and at the same time, 6 kg of aluminum pellets are added to the slag every 8 minutes to prevent the oxidation of the refining top slag; After the LF refining is completed, the molten steel enters the VD for vacuum treatment. The vacuum holding time is 12 minutes. After breaking the vacuum, a sample is taken. The calcium content in the molten steel is 0.0012%. A 0-meter pure calcium wire is fed in, and then soft blowing is carried out for 20 minutes. Then it is left standing until continuous casting; (7)Continuous casting adopts protected casting. At the same time, a layer of tundish covering agent is first added to the molten steel surface in the tundish, and then a layer of carbonized rice husk is added on top of the covering agent.
[0014] Through the above process control, the inclusion control situation in the steel is shown in Table 2. Typical Ds-type inclusions are shown in Figure 3 .
[0015] Table 1 Inclusion types and rating situations of the test heats in Example 1 .
[0016] Table 2 Inclusion types and rating situations of the test heats in Example 2 .
Claims
1. A smelting method for controlling Ds inclusions below level 1.0, characterized in that: During the tapping of the converter, appropriate deoxidizing alloys such as aluminum blocks are added according to the oxygen content of the molten steel. When the tapping reaches one-third, the prepared slag materials are added to carry out slag washing on the molten steel. After the tapping is completed, the molten steel is vigorously stirred with argon. During the LF refining process, strict control is carried out on the refining slag materials, deoxidizing alloys, and heating time, and the slag is adjusted according to the fluidity of the refining slag to ensure that the refining slag has good fluidity. After the LF refining is completed, the molten steel is directly sent to the VD for vacuum treatment. After breaking the vacuum, an appropriate amount of pure calcium wire is fed in, and then the molten steel is softly blown. Protective casting is carried out during continuous casting. It includes the following technological steps: (1) During the converter tapping process, 250 kg of lime, 200 kg of calcium carbide, and 150 kg of bauxite are added to carry out slag washing on the molten steel. At the same time, the weight of alloys such as ferrotitanium or aluminum blocks required for deoxidizing the molten steel is calculated according to the oxygen content at the end of the converter, ensuring that the aluminum content in the molten steel entering the LF station meets the finished product aluminum content of the molten steel + 0.010%. (2) After the LF refining enters the station, bottom blowing argon is carried out throughout the process, and the molten steel is temperature measured and sampled. Then, power is supplied to make slag. The first batch of slag materials added is 400 kg of lime and 400 kg of sintered slag. At the same time, 50 kg of aluminum pellets are added during the slag-making process for deoxidation. (3) After 5 minutes of power supply, the second batch of slag materials, 350 kg of lime and 250 kg of sintered slag, are continuously added. At the same time, 15 kg of aluminum pellets are added during the slag-making process for deoxidation. (4) After the second batch of slag materials is added and power is supplied for 5 minutes, the third batch of slag materials, 150 kg of lime and 100 kg of sintered slag, are added. At the same time, 15 kg of aluminum pellets are added during the slag-making process for deoxidation. (5) Rapid slag formation. After the refining slag is made, the composition of the molten steel is finely adjusted and the power is supplied to increase the temperature. After both the composition and temperature meet the requirements, the power supply is stopped, the bottom blowing argon is switched to soft blowing, and at the same time, 6 kg of aluminum pellets are added to the slag every 8 minutes to prevent the refining top slag from oxidizing. (6) After the LF refining is completed, the molten steel enters the VD for vacuum treatment operation. The vacuum holding time is 12 minutes. After breaking the vacuum, pure calcium wire ≤ 30 meters is fed in according to the calcium content in the molten steel, and then soft blowing is carried out for 20 minutes, and then it is left to stand until continuous casting. (7) During continuous casting, protective casting is adopted. At the same time, a layer of tundish covering agent is first added to the molten steel surface in the tundish, and then a layer of carbonized rice husk is added on top of the covering agent to obtain molten steel with good castability and few various inclusions, especially capable of controlling Ds-type inclusions below grade 1.0.