Slag washing desulfurization calcium treatment process

Abstract

The invention discloses a slag washing desulfurization calcium treatment process. The process comprises the following steps: (1) detecting a calcium line for calcium treatment, wherein the method comprises the steps of sample preparation, dissection and analysis; the calcium treatment metallurgical effect is preliminarily judged according to the influence factors by observing and comparing data information in the aspects of filling of cross section and section reduced iron powder, the bonding state of calcium particles, indentation of internal iron sheets, the size fraction of iron powder and weighing of the two kinds of powder; (2) strictly controlling the size fraction of the reduced iron powder and the proper ratio of metal calcium particles to the reduced iron powder, and selecting a calcium line meeting the requirement to be put into a slag washing desulfurization process; according to the calcium wire screened through the detection method, the wire feeding speed can be stabilized at 4-4.5 m / s, the wire feeding speed cannot be reduced due to flash explosion and splashing, and the production stability is guaranteed.

Description

Technical Field

[0001] The present invention relates to a slag washing desulfurization and calcium treatment process, belonging to the technical field of steelmaking. Background Art

[0002] To reduce costs and increase efficiency and enhance the competitiveness of enterprises, more and more enterprises adopt an out-of-furnace refining process of slag washing desulfurization and calcium treatment for aluminum-containing steel to replace the high-cost and long-cycle LF refining process. Due to the advantages such as fast metallurgical reaction rate, low operation difficulty, high accuracy of composition control, and high alloy recovery rate during the wire feeding process, it is widely used. However, in the actual production process of calcium treatment, it is prone to flash explosion and splashing phenomena affected by the quality of the calcium wire, which not only easily leads to large steel water temperature drop, unstable calcium recovery rate, affects the calcium treatment effect of the upper and lower molten steel and reduces its metallurgical effect, but also affects the safety of the ladle car cable, ladle car operation and ladle lifting. Therefore, to ensure the production rhythm and reduce potential safety hazards, a detection method different from the traditional method that can only measure the chemical components of the calcium wire is needed to preliminarily judge its flash explosion and splashing, etc., while clarifying the preliminary use effect of the calcium wire and reducing potential safety hazards during the use process. Summary of the Invention

[0003] The present invention aims to provide a slag washing desulfurization and calcium treatment process. By physically detecting the calcium wire, calcium wires with excellent manufacturing processes are selected, thereby reducing phenomena such as splashing and flash explosion generated during the feeding of the calcium wire in the actual production process, making the calcium recovery rate more stable and the temperature drop less.

[0004] In the slag washing desulfurization process of the present invention, when the calcium wire fed into the ladle reaches a certain feeding depth, the iron sheet wrapping the calcium grains melts, and at this time, the calcium grains come into contact with the molten steel and react. If the calcium grains are unevenly distributed, serious adhesion will occur, resulting in a violent reaction. On the one hand, the molten steel will splash out of the ladle, causing potential safety hazards and increasing the temperature drop of the molten steel; on the other hand, it affects the modification of the molten steel and the floating of inclusions, increasing the risk of re-oxidation of the molten steel. The present invention provides a method for detecting the calcium wire. According to this method, calcium wires meeting the requirements are selected and the process parameters are adjusted, avoiding phenomena such as splashing and flash explosion generated during the feeding of the calcium wire.

[0005] The present invention provides a slag washing desulfurization and calcium treatment process, including the following steps: (1) Detect the calcium wire used for calcium treatment: This method includes sample preparation, dissection, and analysis; the filling of reduced iron powder and the bonding state of calcium grains, the indentation of the internal iron sheet, the particle size of iron powder, and the weighing of two kinds of powders should be observed and the data information compared from aspects such as the cross-section and profile, and the metallurgical effect of calcium treatment is preliminarily judged based on these influencing factors.

[0006] The sample preparation process is as follows: Use a grinding machine to cut the sample into specimens with a gauge length of 20 cm. Calcium wires of the same length should be cut, and relevant protective measures should be taken to ensure that most of the iron powder and calcium particles can be collected.

[0007] Dissection: Cut the outer iron sheet wrapping along the length direction to expose the true filling form of the inner flux core. Analysis: Through the observation of the cross-section (transverse) and profile (longitudinal) to restore the filling of iron powder and the bonding state of calcium particles, the dents on the inner iron sheet, etc., and the comparison of data information, screen and weigh the metallic calcium particles and reduced iron powder filled inside the cored wire to determine the particle size of the reduced iron powder and the weight ratio of the two powders.

[0008] (2) Strictly control the particle size of the reduced iron powder and the appropriate ratio of metallic calcium particles and reduced iron powder. Select the cored wire that meets the requirements and put it into the slag washing and desulfurization process. Ensure that the cored wire enters the molten steel at a wire feeding speed of 4 - 4.5 m / s. On the one hand, it ensures the wire feeding depth and makes the calcium recovery rate more stable. On the other hand, there is basically no splashing on the surface of the molten steel, which helps the floating of inclusions and the stability of production.

[0009] Specifically, the process flow of step (1) is further defined as follows: The entire sample preparation and dissection process should be carried out in a windless environment, and a mat should be laid below to ensure that all the iron powder and calcium particles can be collected as much as possible during the whole process.

[0010] The analysis process specifically includes the following contents: ① Conduct a preliminary analysis of the cross-section: Observe whether there is reduced iron powder filled between the calcium particles. Generally, it is appropriate to observe that the space between the calcium particles is evenly filled with reduced iron powder. ② Conduct a preliminary analysis of the profile: The reduced iron powder should be evenly filled in the gaps between the calcium particles, and there should be no bonding state or dents on the inner iron sheet between the calcium particles.

[0011] Collect and weigh the iron powder and calcium particles existing in the dissection process and inside the iron sheet.

[0012] Screen the iron powder with a 0.25 mm sieve to obtain the iron powder particle size of <0.25 mm. At the same time, collect and weigh the calcium particles. Generally, the mass ratio of iron powder to calcium particles is preferably 1:1 - 1.3. The cored wire that meets this requirement can be used in the slag washing process.

[0013] Furthermore, in order to determine the metallurgical effect of calcium treatment of the cored wire, the iron sheet after cleaning the internal filling agent can also be sent to the finished product inspection room for detection of items such as weld microstructure, annealing microstructure, and iron sheet hardness. Send the reduced iron powder and the remaining iron sheet to the laboratory for detection and analysis of chemical components, and conduct the next step of analysis in combination with the detection results.

[0014] The usage requirements of the cored wire in the present invention (i.e., the cored wire screened in step (2)) are as follows: (1) Cross-section and longitudinal section conditions: ① The surface of the calcium particles is evenly visible with reduced iron powder wrapped and embedded; ② The calcium particles are distinct from each other, arranged orderly without adhesion; ③ The reduced iron powder is scattered and concentrated in patches; ④ The overall filling of the calcium particles and iron powder is full. (2) Inner surface conditions of the iron sheet: ① Most of the reduced iron powder falls off normally, and the normal falling off of the reduced iron powder indicates that it plays a role in separating the calcium particles; ② There are pits on the inner surface of the iron sheet caused by the reduced iron powder and shallow contour marks pressed by the calcium particles. This phenomenon indicates that the inside of the calcium wire is filled solidly, and wire breakage and other phenomena will not occur during the wire feeding process due to insufficient material filling.

[0015] In step (2), the selected calcium wire meets the following requirements: the calcium particle size is 3 - 5 mm, the calcium particle granularity: the particle distribution is obvious, and there is almost no problem of calcium particle consolidation and adhesion. The proportion of particles with a reduced iron powder particle size ≤ 0.25 mm is > 90%, and the color of the reduced iron powder is dark black.

[0016] In step (2), during the slag washing process, the wire feeding speed of the calcium wire is 4 - 4.5 m / s, the amount of calcium wire fed is 150 - 200 m, and the temperature drop is 5 - 6 °C. Compared with the calcium wire for flash explosion and splashing, the temperature drop is 5 - 15 °C less and the temperature drop is stable, which can avoid the occurrence of low-temperature steel caused by excessive temperature drop and is more conducive to determining the tapping temperature.

[0017] The beneficial effects of the present invention: (1) The calcium wire detection method provided by the present invention can not only make a preliminary judgment on the metallurgical effect of the calcium wire, but also provide a general direction for the manufacturer to improve the calcium wire subsequently.

[0018] (2) The calcium wire screened by the above detection method can keep the wire feeding speed stable at 4 - 4.5 m / s, and will not reduce the wire feeding speed due to flash explosion and splashing, ensuring the stability of the production rhythm.

[0019] (3) The calcium wire screened by the above detection method can make the calcium recovery rate about 10% higher than that of the splash and flash explosion furnace charges, avoiding the risk of continuous casting strand breakage due to insufficient calcium treatment and low calcium content.

[0020] (4) The stable control of the calcium recovery rate reduces the feeding amount of the calcium wire, reduces the process temperature drop. After the molten steel is treated by slag washing with calcium, there is no continuous casting strand breakage and pouring stop accident, improving the hot charging rate of the billet, shortening the in-furnace time, saving energy, and reducing carbon emissions.

[0021] (5) While ensuring the quality, the present invention reduces the slag washing cost, shortens the production cycle, improves the stability of continuous casting production, and avoids affecting the safety of the ladle car cable, ladle car operation and ladle lifting due to flash explosion and splashing, with significant economic and social benefits. Specific implementation mode

[0022] The present invention is further illustrated by the following examples, but is not limited to the following examples. Example

[0023] A slag washing desulfurization calcium treatment process comprises the following steps: (1) Detection of slag washing process using calcium wire: Use an angle grinder to cut samples of the calcium wire at a gauge length of 20 cm, and cut the outer iron sheet longitudinally along the length direction to reveal the true filling shape of the internal core.

[0024] Specifically, the entire sample preparation and dissection process should be carried out in a windless environment, with a mat laid underneath to ensure that as much iron powder and calcium particles as possible are collected during the entire process.

[0025] The analysis and testing process specifically includes the following: ① Conduct a preliminary analysis of the cross section: observe whether there is reduced iron powder filling between the calcium particles. It is generally advisable to observe that the calcium particles are evenly filled with reduced iron powder; ② Conduct a preliminary analysis of the cross section: the reduced iron powder should be evenly filled in the gaps between the calcium particles, and there should be no sticky state between the calcium particles, or pressure pits on the internal iron sheet.

[0026] The iron powder and calcium particles present during the dissection process and in the iron sheet were collected and weighed.

[0027] (2) Calcium wires with excellent manufacturing technology can be selected through physical testing of calcium wires: ① The appearance of the internal core filling: the surface of the calcium particles is covered and embedded with visible reduced iron powder, the calcium particles are distinct, arranged in an orderly manner without adhesion, and the reduced iron powder is not scattered and concentrated in pieces. The calcium particles and iron powder are fully filled as a whole; the core particle size and the inner surface of the iron sheet: most of the reduced iron powder is sieved off, and the reduced iron powder is not completely bonded to the calcium particles, but there is still a small amount of reduced iron powder embedded on the surface of the calcium particles. There are no pits on the inner surface of the iron sheet caused by iron powder, and only shallow outlines of calcium particles can be seen.

[0028] Specific parameter requirements are shown in Table 2.

[0029] ② Screen and weigh the metallic calcium particles and reduced iron powder filled inside the cored wire to determine the particle size of the reduced iron powder and the weight ratio of the two powders.

[0030] The iron powder is sieved with a 0.25mm sieve to obtain an iron powder particle size of <0.25mm. At the same time, the calcium particles are collected and weighed. Generally, the mass ratio of iron powder to calcium particles is 1:1-1.3. The calcium wire that meets this requirement can be used in the slag washing process.

[0031] (3) The calcium wire meeting the requirements in the above part (2) is regarded as qualified calcium wire; other calcium wires are regarded as unqualified calcium wires (for comparative experiments), and they are simultaneously used in the slag washing process. The process parameters and experimental effect data during the experiment are shown in Table 1 and Table 3.

[0032] Table 1 Corresponding Table of the Usage of Qualified Calcium Wire and Unqualified Calcium Wire

[0033] Table 2 Requirements for Detection Indexes during the Dissection Process

[0034] Table 3 Detection Indexes of Iron Powder and Calcium Granules

[0035] Further illustrated by the experimental data in Table 1 above, from the particle size of reduced iron powder and the appropriate ratio of metallic calcium granules and reduced iron powder, selecting the calcium wire that meets the requirements and putting it into the slag washing desulfurization process can ensure that the calcium wire enters the molten steel at a wire feeding speed of 4 - 4.5 m / s. On the one hand, it ensures the wire feeding depth, making the calcium recovery rate more stable. On the other hand, there is basically no splashing on the surface of the molten steel, which helps the floating of inclusions and the stability of production.

[0036] It can be seen from Table 3 that the qualified calcium wire after detection basically does not flash or splash.

[0037] The above embodiments are only the best examples and are not intended to limit the implementation manners of the present invention.

Claims

1. A slag washing desulfurization and calcium treatment process, characterized in that It includes the following steps: (1) Detect the calcium wire for calcium treatment: This method includes sample preparation, dissection, and analysis. Observation and data information comparison should be carried out on the filling and calcium granule bonding state of reduced iron powder, the dents of the internal iron sheet, the iron powder particle size, and the weighing of the two powders from the cross-section and profile. Based on these influencing factors, the metallurgical effect of calcium treatment can be preliminarily judged; (2) Strictly control the particle size of reduced iron powder and the appropriate ratio of metallic calcium granules and reduced iron powder. Select calcium wire that meets the requirements and put it into the slag washing desulfurization process. Ensure that the calcium wire enters the molten steel at a wire feeding speed of 4 - 4.5 m / s. On the one hand, it ensures the wire feeding depth, making the calcium recovery rate more stable. On the other hand, there is basically no splashing on the surface of the molten steel, which helps the floating of inclusions and the stability of production.

2. The slag washing desulfurization calcium treatment process according to claim 1, characterized in that: The specific process of step (1) is as follows: The sample preparation process is as follows: Use a grinding wheel to cut the sample at a 20 cm gauge length. Calcium wires of the same length should be cut, and relevant protective measures should be taken to ensure that most of the iron powder and calcium granules can be collected; Dissection: Cut the externally wrapped iron sheet along the length direction to expose the true filling form of the internal core; Analysis: Through observation and data information comparison of the filling and calcium granule bonding state of reduced iron powder, and the dents of the internal iron sheet from the transverse cross-section and longitudinal profile, screen and weigh the metallic calcium granules and reduced iron powder filled inside the cored wire to determine the particle size of the reduced iron powder and the weight ratio of the two powders.

3. The slag washing desulfurization and calcium treatment process according to claim 2, characterized in that: The entire sample preparation and dissection process of step (1) should be carried out in a windless environment, and a mat should be laid below to ensure that all the iron powder and calcium granules are collected during the whole process.

4. The slag washing desulfurization and calcium treatment process according to claim 2, characterized in that: The analysis process specifically includes the following content: ① Conduct a preliminary analysis of the cross-section: Observe whether there is reduced iron powder filling between calcium granules. Generally, it is appropriate to observe that the space between calcium granules is evenly filled with reduced iron powder; ② Conduct a preliminary analysis of the profile: The reduced iron powder should be evenly filled in the gaps between calcium granules, and there should be no bonding state or dents on the internal iron sheet between calcium granules.

5. The slag washing desulfurization and calcium treatment process according to claim 4, characterized in that: The cross-section and longitudinal section of the calcium wire meet the following requirements: ① The surface of calcium granules is evenly visible with reduced iron powder wrapped and embedded; ② The calcium granules are distinct from each other, arranged orderly without adhesion; ③ The reduced iron powder is scattered and concentrated in patches; ④ The overall filling of calcium granules and iron powder is full; The inner surface of the iron sheet of the calcium wire meets the following requirements: ① Most of the reduced iron powder normally falls off; ② There are pits on the inner surface of the iron sheet caused by the iron powder and shallow contour marks pressed by the calcium granules.

6. The slag washing desulfurization and calcium treatment process according to claim 1, characterized in that: In step (2), the requirements for metallic calcium granules and reduced iron powder are as follows: Screen the iron powder with a 0.25 mm sieve to obtain iron powder particles with a particle size of < 0.25 mm. At the same time, collect and weigh the calcium granules. The mass ratio of iron powder to calcium granules is 1:1 - 1.

3.

7. The slag washing desulfurization calcium treatment process according to claim 1, characterized in that: In step (2), the selected calcium wire meets the following requirements: The calcium granule size is 3 - 5 mm, and the calcium granule particle size: The particle distribution is obvious, and there is almost no problem of calcium granule consolidation and adhesion. The proportion of particles with a reduced iron powder particle size of ≤ 0.25 mm is > 90%, and the color of the reduced iron powder is dark black.

8. The slag washing desulfurization calcium treatment process according to claim 1, characterized in that: During the slag washing process, the wire feeding speed of the calcium wire is 4 - 4.5 m / s, the amount of calcium wire fed is 150 - 200 m, and the temperature drop is 5 - 6 °C.

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