A slag washing desulfurization calcium treatment process

Abstract

The application discloses a slag washing desulfurization calcium treatment process, which comprises the following steps: (1) detecting calcium wire for calcium treatment: the method comprises sample preparation, dissection and analysis; the filling of reduced iron powder and the bonding state of calcium particles, the pressure pit of internal iron sheet, the particle size of iron powder and the observation and data information comparison of the weight of the two kinds of powder should be observed from the cross section and the section; the metallurgical effect of calcium treatment is preliminarily judged according to the influencing factors; (2) strictly controlling the particle size of reduced iron powder and the suitable ratio of calcium particles and reduced iron powder, and selecting calcium wire meeting the requirements to be put into the slag washing desulfurization process; the calcium wire selected by the above detection method can make the wire feeding speed stable at 4-4.5 m / s, so that the wire feeding speed is not reduced due to flash explosion and spatter, and the stability of production is ensured.

Description

Technical Field

[0001] This invention relates to a slag washing desulfurization and calcium treatment process, belonging to the field of steelmaking technology. Background Technology

[0002] To reduce costs, increase efficiency, and enhance competitiveness, more and more companies are adopting ladle refining processes involving slag washing, desulfurization, and calcium treatment for aluminum-containing steel, replacing the high-cost, long-cycle LF refining process. While the wire feeding process is widely used due to its advantages such as fast metallurgical reaction speed, low operational difficulty, high accuracy in composition control, and high alloy yield, the quality of the calcium wire can easily lead to flash explosions and splashing during actual calcium treatment. This not only causes significant temperature drops in molten steel, unstable calcium yield, and affects the calcium treatment effect in both the upper and lower molten steel sections, thus reducing its metallurgical efficiency, but also impacts the safety of ladle car cables, car operation, and ladle hoisting. Therefore, to ensure production rhythm and reduce safety hazards, a detection method different from the traditional method that only measures the chemical composition of the calcium wire is needed to preliminarily assess flash explosions and splashing, clarifying the initial effectiveness of the calcium wire while reducing safety hazards during use. Summary of the Invention

[0003] This invention aims to provide a calcium treatment process for slag washing and desulfurization. By conducting physical testing of calcium wires, calcium wires with excellent manufacturing processes are selected, thereby reducing phenomena such as splashing and flash explosions caused by feeding calcium wires during actual production, resulting in a more stable calcium yield and less temperature drop.

[0004] This invention introduces calcium wire into the ladle during the slag washing desulfurization process. After reaching a certain feeding depth, the iron sheet encasing the calcium particles melts. At this point, the calcium particles react with the molten steel. If the calcium particles are unevenly distributed, severe adhesion occurs, leading to a violent reaction. This causes the molten steel to splash out of the ladle, posing a safety hazard and increasing the temperature drop of the molten steel. Furthermore, it affects the steel's degradation and the floating of inclusions, increasing the risk of re-oxidation. To address this problem, this invention provides a method for detecting calcium wire. This method screens out calcium wire that meets the requirements, adjusts process parameters, and avoids splashing and flash explosions during the calcium wire feeding process.

[0005] This invention provides a slag washing desulfurization and calcium treatment process, comprising the following steps:

[0006] (1) Testing calcium wire for calcium treatment: This method includes sample preparation, dissection and analysis; observation and data comparison should be made on the filling and bonding state of iron powder and calcium particles in the cross section and profile, the pitting of the internal iron sheet, the particle size of iron powder and the weighing of the two powders, etc., and the preliminary judgment of the metallurgical effect of calcium treatment can be made based on these influencing factors.

[0007] The sample preparation process is as follows: Use an angle grinder to cut the sample at a gauge length of 20cm. Calcium lines of the same length should be cut, and appropriate protective measures should be taken to ensure that most of the iron powder and calcium particles can be collected.

[0008] Dissection: Cut along the length of the outer metal sheet to expose the true filling shape of the internal drug core;

[0009] Analysis: By observing and comparing data on the filling state of reduced iron powder and the bonding state of calcium particles in cross-section (transverse) and profile (longitudinal), as well as the pitting of the internal iron sheet, the metallic calcium particles and reduced iron powder filling the cored wire were sieved and weighed to determine the particle size of the reduced iron powder and the weight ratio of the two powders.

[0010] (2) Strictly control the particle size of reduced iron powder and the appropriate ratio of metallic calcium particles 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 feeding speed of 4-4.5 m / s. On the one hand, the feeding depth is guaranteed, making the calcium recovery rate more stable. On the other hand, the surface of the molten steel basically does not splash, which helps the inclusions float and the production stability.

[0011] Specifically, the process flow of step (1) is further defined as follows:

[0012] 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 throughout the process.

[0013] The analysis process specifically includes the following: ① Preliminary analysis of the cross section: observe whether there is reduced iron powder filling between the calcium particles. Generally, it is advisable to observe that the calcium particles are uniformly filled with reduced iron powder; ② Preliminary analysis of the cross section: the reduced iron powder should be uniformly filled in the gaps between the calcium particles. There should be no sticking between the calcium particles or pits in the internal iron scale.

[0014] Iron powder and calcium particles present during the dissection and inside the sheet metal were collected and weighed.

[0015] The iron powder is sieved through a 0.25mm sieve to obtain iron powder particles smaller than 0.25mm. Simultaneously, the calcium particles are collected and weighed; generally, the mass ratio of iron powder to calcium particles should be 1:1-1.3. Calcium powder meeting these requirements can be used in the slag washing process.

[0016] Furthermore, to determine the metallurgical effect of calcium treatment on the calcium wire, the iron sheet after cleaning the internal filling agent can be sent to the finished product inspection laboratory for testing of weld metallographic structure, annealed structure, and iron sheet hardness. The reduced iron powder and remaining iron sheet are sent to the laboratory for chemical composition analysis, and the results are used for further analysis.

[0017] The requirements for the use of calcium threads in this invention (i.e., the calcium threads selected in step (2)) are as follows:

[0018] (1) Cross section and longitudinal section: ① The calcium particles are uniformly covered and embedded with reduced iron powder; ② The calcium particles are distinct, arranged in an orderly manner without sticking together; ③ The reduced iron powder is scattered and concentrated in patches; ④ The calcium particles and iron powder are fully filled as a whole.

[0019] (2) Condition of the inner surface of the iron sheet: ① Most of the reduced iron powder fell off normally, which indicates that the reduced iron powder has played a role in separating calcium particles; ② There are pits caused by iron powder and shallow outline marks pressed out by calcium particles on the inner surface of the iron sheet. This phenomenon indicates that the calcium wire is fully filled and will not break during the wire feeding process due to insufficient material filling.

[0020] In step (2), the selected calcium wire meets the following requirements: the calcium particle size is 3-5mm, the calcium particle size is obvious, there is almost no problem of calcium particle consolidation and adhesion, the proportion of reduced iron powder particles with a particle size of ≤0.25mm is >90%, and the color of reduced iron powder is black.

[0021] In step (2), during the slag washing process, the feeding speed of the calcium wire is 4~4.5m / s, the amount of calcium wire fed is 150-200m, and the temperature drop is 5-6℃. Compared with flash explosion and splashing calcium wire, the temperature drop is 5-15℃ less and the temperature drop is stable, which can avoid the low temperature steel caused by excessive temperature drop and make it easier to determine the tapping temperature.

[0022] The beneficial effects of this invention are:

[0023] (1) The calcium wire detection method provided by the present invention can not only make a preliminary judgment on the metallurgical effect of calcium wire, but also provide a general direction for manufacturers to make subsequent improvements to calcium wire.

[0024] (2) The calcium wire selected by the above detection method can keep the wire feeding speed stable at 4~4.5m / s, and will not reduce the wire feeding speed due to flash explosion or splashing, thus ensuring the stability of the production rhythm.

[0025] (3) The calcium line screened by the above detection methods can make the calcium recovery rate about 10% higher than that of splashing and flash explosion furnaces, avoiding the risk of continuous casting interruption due to low calcium content caused by inadequate calcium treatment.

[0026] (4) Stable control of calcium yield reduces the amount of calcium wire feed, reduces process temperature drop, and after the molten steel is treated by slag washing calcium, there is no flocculation stoppage accident in continuous casting, which improves the hot charging rate of billet, shortens the time in the furnace, saves energy and reduces carbon emissions.

[0027] (5) This invention reduces slag washing costs, shortens the production cycle, and improves the stability of continuous casting production while ensuring quality. It also avoids the impact of flash explosions and splashes on the safety of steel ladle car cables, steel car operation, and steel ladle hoisting, resulting in significant economic and social benefits. Detailed Implementation

[0028] The present invention will be further illustrated by the following embodiments, but is not limited to the following embodiments. Example

[0029] A slag washing desulfurization and calcium treatment process includes the following steps:

[0030] (1) Detection using calcium wire during slag washing process:

[0031] The calcium wire sample was cut at a gauge length of 20 cm using an angle grinder. The outer iron sheet was longitudinally cut along the length to expose the true filling shape of the internal core.

[0032] 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 throughout the process.

[0033] The analysis and testing process specifically includes the following: ① Preliminary analysis of the cross section: observe whether there is reduced iron powder filling between the calcium particles. Generally, it is advisable to observe that the calcium particles are uniformly filled with reduced iron powder; ② Preliminary analysis of the cross section: the reduced iron powder should be uniformly filled in the gaps between the calcium particles. There should be no sticking between the calcium particles or pits in the internal iron scale.

[0034] Iron powder and calcium particles present during the dissection and inside the sheet metal were collected and weighed.

[0035] (2) Through physical testing of calcium threads, calcium threads with excellent manufacturing processes were selected:

[0036] ① Appearance of the internal core filling: The calcium particles are all visiblely coated and embedded with reduced iron powder. The calcium particles are distinct, orderly arranged, and not adhered to each other. No scattered or concentrated patches of reduced iron powder are observed. The calcium particles and iron powder are fully filled. ② Core particle size and inner surface condition of the iron sheet: Most of the reduced iron powder has been sieved off. Not all of the reduced iron powder is bonded to the calcium particles, but a small amount of reduced iron powder remains embedded on the surface of the calcium particles. There are no pits caused by iron powder on the inner surface of the iron sheet; only shallow outlines pressed out by the calcium particles are visible.

[0037] Specific parameter requirements are shown in Table 2.

[0038] ② The calcium metal particles and reduced iron powder filling the cored wire are sieved and weighed to determine the particle size of the reduced iron powder and the weight ratio of the two powders.

[0039] The iron powder is sieved through a 0.25mm sieve to obtain iron powder particles with a size <0.25mm. Simultaneously, the calcium particles are collected and weighed; generally, the mass ratio of iron powder to calcium particles should be 1:1-1.3. Calcium powder meeting these requirements can be used in the slag washing process.

[0040] (3) Calcium wire that meets the requirements of (2) above is considered as qualified calcium wire; other calcium wires are considered as unqualified calcium wires (as a comparative experiment) and are used in the slag washing process. The process parameters and experimental results data during the experiment are shown in Table 1 and Table 3.

[0041] Table 1. Correspondence between the usage of qualified and unqualified calcium wires

[0042]

[0043] Table 2 Requirements for Detection Indicators During Anatomy

[0044]

[0045] Table 3 Detection Indicators for Iron Powder and Calcium Granules

[0046]

[0047] The experimental data in Table 1 above further illustrate that by selecting calcium wire that meets the requirements for particle size of reduced iron powder and appropriate ratio of metallic calcium particles to reduced iron powder, the calcium wire can be fed into the slag washing desulfurization process at a feeding speed of 4-4.5 m / s. This ensures the feeding depth, making the calcium recovery rate more stable, and also prevents splashing on the surface of the molten steel, which helps the inclusions float and the production stability.

[0048] Table 3 shows that using qualified calcium wire generally does not cause flash explosions or splashes.

[0049] The above embodiments are merely best examples and are not intended to limit the implementation of the present invention.

Claims

1. A slag washing desulfurization and calcium treatment process, characterized in that... Includes the following steps: (1) Testing calcium wire for calcium treatment: This method includes sample preparation, dissection and analysis; the metallurgical effect of calcium treatment should be preliminarily judged based on the observation of the filling of iron powder and the bonding state between calcium particles in the cross section and profile, the pitting of the internal iron scale, the particle size of iron powder and the weighing of iron powder and calcium particles. (2) Strictly control the particle size of reduced iron powder and the ratio of metallic calcium particles 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 feeding speed of 4-4.5 m / s. On the one hand, this ensures the feeding depth and makes the calcium recovery rate more stable. On the other hand, the surface of the molten steel basically does not splash, which helps the inclusions float and the production stability. The requirements for metallic calcium particles and reduced iron powder in step (2) are as follows: the iron powder is sieved with a 0.25mm sieve to obtain iron powder particle size <0.25mm; at the same time, the calcium particles are collected and weighed, and the mass ratio of iron powder to calcium particles is 1:1-1.

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

2. The slag washing desulfurization and 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 an angle grinder to cut the sample at a gauge length of 20cm. Calcium lines of the same length should be cut, and appropriate protective measures should be taken to ensure that most of the iron powder and calcium particles can be collected. Dissection: Cut along the length of the outer metal sheet to expose the true filling shape of the internal drug core; Analysis: By observing the filling of reduced iron powder and the bonding state between calcium particles in the transverse and longitudinal cross sections, as well as the pitting of the internal iron sheet, the metallic calcium particles and reduced iron powder filling the cored wire were sieved and weighed to determine the particle size of the reduced iron powder and the weight ratio of iron powder and calcium particles.

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

4. The slag washing desulfurization and calcium treatment process according to claim 2, characterized in that: The analysis 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, and observe that the calcium particles are uniformly filled with reduced iron powder; ② Conduct a preliminary analysis of the cross section: the reduced iron powder should be uniformly filled in the gaps between the calcium particles, and there should be no adhesion between the calcium particles or pitting of the internal iron scale.

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 line meet the following requirements: ① The calcium particles are uniformly covered and embedded with reduced iron powder; ② The calcium particles are clearly separated, arranged in an orderly manner, and without adhesion; ③ The reduced iron powder is scattered and concentrated in patches; ④ The calcium particles and iron powder are fully filled. The inner surface of the iron sheet of the calcium wire should meet the following requirements: ① Most of the reduced iron powder should fall off normally; ② The inner surface of the iron sheet should have pits caused by iron powder and shallow outline marks pressed out by calcium particles.

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

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