A dephosphorized steel block and a molten steel dephosphorization method

Abstract

This invention discloses a dephosphorized steel block and a method for dephosphorizing molten steel, relating to the field of steel dephosphorization technology. The dephosphorized steel block and method employ a circumferentially arranged spray structure. When magnesium gas is sprayed, the steel block rotates, allowing the magnesium gas to uniformly diffuse the impurity removal agent, such as the dephosphorizing agent, from the spray structure into the molten steel. By placing the spray structure at the top of the steel block, this method eliminates the requirement for steel block density (the ratio of magnesium to dephosphorizing agent). The magnesium gas sprayed from the top spray structure propels the steel block towards the bottom of the molten steel.

Description

Technical Field

[0001] This invention relates to the field of steel dephosphorization technology, specifically to a dephosphorized steel block and a method for dephosphorizing molten steel. Background Technology

[0002] Dephosphorization in steelmaking refers to the physicochemical process of removing harmful phosphorus impurities from molten steel. During continuous casting in a blast furnace, almost all the phosphorus in the raw materials is reduced to pig iron. Depending on the phosphorus content of the iron ore, the phosphorus content in pig iron can range from 0.1% to 1.0%, and in some special cases, it can reach over 2.0%. Ferroalloys also contain a considerable amount of phosphorus. Phosphorus causes steel to become brittle at low temperatures, a phenomenon known as "cold brittleness."

[0003] Experimental studies have shown that phosphorus segregates and accumulates at grain boundaries during steel solidification. Even small amounts of phosphorus, such as 0.01% (100 ppm), can cause steel to exhibit low-temperature brittleness. Smelting ordinary steel requires phosphorus levels to be reduced to 0.030%–0.040%, while steels used in low-temperature applications, such as those for drilling platforms in cold regions and for liquefied gas storage and transportation, require phosphorus content as low as 0.002%–0.003% (i.e., 20–30 ppm). Therefore, dephosphorization is one of the main tasks in the steelmaking process.

[0004] The invention with application number CN202110943119.2 discloses a method for dephosphorizing molten steel in the LF refining process, in which the dephosphorizing agent is added by feeding wire. However, the wire feeding method requires a large investment in equipment and is not conducive to the diffusion of the dephosphorizing agent in the molten steel, which can easily cause local overheating of the molten steel.

[0005] The invention with application number CN201410273795.3 discloses a method for dephosphorization outside the furnace in medium frequency furnace smelting, wherein a preheated dephosphorizing agent is added during the process of molten metal being tapped out of the furnace, and the addition rate and height of the dephosphorizing agent need to be strictly controlled. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a dephosphorized steel block and a method for dephosphorizing molten steel, solving the following technical problems:

[0008] 1. The existing method of adding dephosphorizing agent to molten steel using wire feeding requires significant equipment investment, and the wire feeding method is not conducive to the diffusion of dephosphorizing agent in molten steel;

[0009] 2. In the existing technology, the method of adding dephosphorizing agent during the process of molten metal tapping requires preheating the dephosphorizing agent in advance. In order to ensure the dephosphorizing effect, the timing and speed of adding the dephosphorizing agent need to be strictly controlled.

[0010] 3. When using steel blocks for dephosphorization, the density of the steel blocks is less than that of the molten steel, thus preventing them from sinking into the molten steel.

[0011] (II) Technical Solution

[0012] To achieve the above objectives, the present invention provides the following technical solution: a steel block for removing impurities from molten steel, wherein the steel block is provided with a spraying structure, and the spraying structure contains magnesium and an impurity removal agent;

[0013] The magnesium, after being heated and vaporized, can push the steel block;

[0014] The vaporized magnesium can carry out the impurity removal agent in the spraying structure and enter the molten steel.

[0015] The magnesium is ejected from the injection structure after being heated and vaporized.

[0016] Preferably, the outer edge of the steel block is provided with multiple spraying structures, and the spraying direction of the spraying structures does not intersect with the center of gravity of the steel block;

[0017] When the magnesium in the spray structure is heated to vaporization, it can drive the steel block to rotate.

[0018] Preferably, the spraying structure is a nozzle, and the end of the nozzle is provided with a plug, which can be broken by the vaporized magnesium after being heated and melted by the molten steel.

[0019] Preferably, the spraying direction of the spraying structure is parallel to the plane where the steel block is located.

[0020] Preferably, the spraying direction of the spraying structure is not parallel to the plane where the steel block is located, and both are inclined upwards.

[0021] Preferably, the top of the steel block is provided with an upward spraying structure, the spraying direction of the upward spraying structure is vertically upward, and magnesium is disposed inside the upward spraying structure.

[0022] Preferably, the bottom of the steel block is provided with a spiral structure, which can drive the steel block to rotate when it sinks in molten steel.

[0023] A method for dephosphorizing molten steel includes a steel block and the following steps:

[0024] For example, the density of a steel block is greater than the density of molten steel:

[0025] S1A: When a steel block is placed on the surface of molten steel, the steel block can descend under its own weight and absorb the heat of the molten steel to heat up.

[0026] S2A: When the magnesium inside the spraying structure of the steel block is heated and vaporized, it will be sprayed out from the spraying structure. The sprayed magnesium will undergo a desulfurization reaction in the molten steel. At the same time, since the spraying of magnesium can push the steel block to change position in the molten steel, it will also change the spraying direction of the spraying structure.

[0027] If the density of the steel block is less than the density of the molten steel:

[0028] S1B: When a steel block is placed on the surface of molten steel, the steel block will absorb the temperature of the molten steel and rise in temperature.

[0029] S2B: When the magnesium inside the spraying structure of the steel block is heated and vaporized, it will be sprayed out from the spraying structure. The sprayed magnesium will undergo a desulfurization reaction in the molten steel. At the same time, since the spraying of magnesium can push the steel block to change position in the molten steel, it will also change the spraying direction of the spraying structure.

[0030] If the top of the steel block is equipped with an upward spraying structure: the vaporized magnesium in the upward spraying structure will provide a reaction force to move the steel block towards the bottom of the molten steel after it is sprayed out.

[0031] If the spraying direction of the steel block spraying structure is not parallel to the plane where the steel block is located, and both are inclined upwards: the vertical upward component force provided by the spraying structure after spraying magnesium vapor will provide a reaction force to move the steel block towards the bottom of the molten steel.

[0032] Preferably, the steel dephosphorizing agent contains at least one of ferrous oxide and calcium oxide.

[0033] (III) Beneficial Effects

[0034] This invention provides a dephosphorized steel block and a method for dephosphorizing molten steel. It has the following beneficial effects:

[0035] (1) The dephosphorized steel block and dephosphorization method of the steel adopts a circumferentially arranged spray structure, which can rotate the steel block when magnesium gas is sprayed out, so that the magnesium gas can evenly diffuse the impurity removal agent such as dephosphorizing agent in the spray structure into the steel.

[0036] (2) The dephosphorized steel block and molten steel dephosphorization method can eliminate the requirement for steel block density (the ratio of magnesium to impurity removal agent) by setting a spray structure on the top of the steel block. The magnesium gas sprayed by the top spray structure can push the steel block to the bottom of the molten steel. Attached Figure Description

[0037] Figure 1 This is a top view of the steel block of the present invention;

[0038] Figure 2 This is a plan view of the steel block structure of the present invention;

[0039] Figure 3This is a side view of the steel block structure of the present invention (the spraying direction of the spraying structure is parallel to the plane of the steel block);

[0040] Figure 4 This is a longitudinal sectional view of the steel block structure of the present invention;

[0041] Figure 5 This is a side view of the steel block structure of the present invention (the spraying direction of the spraying structure is not parallel to the plane of the steel block);

[0042] Figure 6 This is a side view of the steel block structure of the present invention (with a spiral structure connected to the bottom);

[0043] Figure 7 This is a schematic diagram of the rotating state of the steel block according to the present invention.

[0044] In the diagram: 1. Steel block; 2. Spraying structure; 3. Upward spraying structure; 4. Blocking; 5. Spiral structure. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1: The density of steel block 1 is greater than the density of molten steel.

[0047] When the density of steel block 1 is greater than that of molten steel, the following dephosphorization method can be selected for the molten steel:

[0048] Option 1: Let steel block 1 sink in the molten steel under its own weight.

[0049] The steel block 1 can be disc-shaped (or other uniformly shaped, conducive to rotation). During manufacturing, multiple nozzle structures are formed on a cross-section of the steel block 1. Ideally, the spray direction of the nozzle structure should form a tangential circle, so that the magnesium gas can drive the steel block 1 to rotate uniformly when sprayed. An equal amount of magnesium is placed in the nozzle structure. Since the density difference between the steel block 1 and the molten steel is not significant at this point, the descent of the steel block 1 is relatively slow. It is best to seal the nozzle outlet to a certain extent after placing the magnesium to prevent the magnesium from being heated into gas prematurely (before sinking to the bottom of the molten steel) during the descent of the steel block 1, causing the steel block 1 to rotate too early and release all the magnesium gas. Sealing can delay the release time of the magnesium gas, because after the magnesium is heated into gas, it cannot be sprayed directly from the nozzle due to the presence of the seal. It is necessary to wait for the seal to be heated to the point where it can no longer withstand the pressure of the magnesium gas before breaking the seal, allowing the magnesium gas to spray out and drive the steel block 1 to rotate. This waiting time allows the steel block 1 to sink fully. The specific sinking depth at the injection point can be determined by those skilled in the art through a limited number of experiments, and the thickness of the seal 4 should be appropriate. When magnesium vapor is ejected, it also carries out impurity removal agents, such as dephosphorizing agents, placed inside the nozzle structure and disperses them in the molten steel.

[0050] In this embodiment, the main function of magnesium is to carry impurity removal agents, such as dephosphorizing agents, out of the nozzle structure and disperse them in the molten steel. However, it is also possible that magnesium will participate in the deoxidation and desulfurization reactions.

[0051] In addition, the sealing device can also prevent magnesium from flowing directly into the molten steel from the nozzle after melting, thus preventing magnesium vapor from forming in the nozzle.

[0052] Option 2: Accelerate the sinking of steel block 1 in molten steel.

[0053] Based on Scheme 1, an upward spraying structure 3 is set on the top of the steel block 1, and magnesium is added to the upward spraying structure. During processing, multiple nozzles can be opened on the top of the steel block 1. When in use, several nozzles are selected to add magnesium according to the required sinking speed. After adding magnesium, the nozzles on the top of the steel block 1 need to be sealed to prevent the magnesium from flowing directly into the molten steel.

[0054] During the descent of steel block 1, the magnesium vapor in the top nozzle breaks through the blockage and provides the power to accelerate the sinking of steel block 1.

[0055] Alternatively, based on scheme 1, the spraying direction of spraying structure 2 can be made non-parallel to the plane where steel block 1 is located, and both are inclined upwards (e.g., Figure 5 This allows the magnesium gas to provide a downward force to the steel block 1 when it is ejected, thereby increasing the sinking speed of the steel block 1.

[0056] In this embodiment 1, in order to improve the stability of the steel block 1 and the uniformity of heat transfer around the circumference of the steel block 1, both Scheme 1 and Scheme 2 can set a spiral structure 5 at the bottom of the steel block 1 so that the steel block 1 can rotate to a certain extent during the sinking process. In addition, setting the spiral structure 5 can shift the center of gravity of the steel block 1 downward, making the sinking of the steel block 1 in the molten steel more stable.

[0057] Example 2: The density of steel block 1 is less than the density of molten steel.

[0058] At this point, the density of steel block 1 is less than the density of molten steel, so it cannot rely on its own weight to sink in the molten steel.

[0059] Therefore, in Example 2, only an upward spraying structure 3 can be set on the top of the steel block 1, and magnesium can be added to the upward spraying structure. During processing, multiple nozzles can be opened on the top of the steel block 1. When in use, several nozzles can be selected to add magnesium according to the required sinking speed. After adding magnesium, the nozzles on the top of the steel block 1 need to be sealed to prevent the magnesium from flowing directly into the molten steel after melting.

[0060] During the descent of steel block 1, the magnesium vapor in the top nozzle breaks through the blockage and provides the power to accelerate the sinking of steel block 1.

[0061] Alternatively, the spraying direction of spraying structure 2 can be non-parallel to the plane of steel block 1, and both can be inclined upwards (e.g., Figure 5 This allows the magnesium gas to provide a downward force to the steel block 1 when it is ejected, thereby increasing the sinking speed of the steel block 1.

[0062] The density of steel block 1 is equal to the total mass of steel block 1 (including the mass of steel block 1 itself + the mass of magnesium + the mass of impurity removal agent) divided by the total volume enclosed by the outer surface of steel block 1 after sealing. Since the spray structure 3 is not completely filled with magnesium and impurity removal agent (there may be cavities), and the total amount of magnesium and impurity removal agent required by different processes varies, the density of steel block 1 will be affected.

[0063] In addition to considering the different density comparisons between the steel block 1 and molten steel, this invention also provides a method for controlling the rotational position and height of the steel block 1. The thickness of the seal can control the start time of magnesium ejection, and the amount of magnesium placed in the nozzle structure can control the duration of magnesium ejection. Therefore, through a limited number of experiments, those skilled in the art can determine the thickness of the seal and the total amount of magnesium, thereby controlling the position to which the steel block 1 sinks before ejecting magnesium, as well as the duration and total amount of magnesium ejection. However, the thickness of the seal structure cannot be increased indefinitely. During use, this invention carries the risk of molten steel splashing. An excessively thick seal can cause excessive pressure on the nozzle structure, potentially leading to an explosion. Therefore, this aspect should be fully considered during application, and the seal thickness should be rationally selected to avoid explosions.

[0064] It should be noted that in the description of the invention, the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the description of the structure of the invention shown in the accompanying drawings. They are only for the convenience of describing the invention and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0065] The terms "first" and "second" in this technical solution are merely designations for corresponding structures that are identical or similar, or that perform similar functions. They do not represent an arrangement of the importance of these structures, nor do they imply any ranking, comparison of size, or other meaning.

[0066] Furthermore, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two structures. Those skilled in the art can understand the specific meaning of the above terms in this invention by considering the overall concept of the invention and the specific context of the solution.

Claims

1. A steel block for removing impurities from molten steel, characterized in that: The steel block (1) has multiple spray structures (2) arranged around its outer edge. The spray structures (2) contain magnesium and impurity removal agent. The spray direction of the spray structures (2) does not intersect with the center of gravity of the steel block (1). The spray structure (2) is a nozzle, and a plug (4) is provided at the end of the nozzle. The blockage (4) can be broken by the vaporized magnesium after being heated and melted by the molten steel, so that the magnesium is sprayed out from the spray structure (2) after being heated and vaporized, pushing the steel block to rotate. The vaporized magnesium can carry out the impurity removal agent in the spray structure (2) and enter the molten steel. The impurity is phosphorus, and the impurity removal agent is a dephosphorizing agent.

2. The steel block according to claim 1, characterized in that: The spraying direction of the spraying structure (2) is parallel to the plane where the steel block (1) is located.

3. The steel block according to claim 1, characterized in that: The spraying direction of the spraying structure (2) is not parallel to the plane where the steel block (1) is located and is inclined upward.

4. A steel block according to claim 1, characterized in that: The top of the steel block (1) is provided with an upward spraying structure (3), the spraying direction of the upward spraying structure (3) is vertically upward, and magnesium is provided inside the upward spraying structure (3).

5. A steel block according to claim 1, characterized in that: The bottom of the steel block (1) is provided with a spiral structure (5), which can drive the steel block (1) to rotate when the steel block (1) sinks in the molten steel.

6. A method for dephosphorizing molten steel, characterized in that: Includes a steel block as described in any one of claims 1 to 5 and the following steps: When the density of the steel block (1) is greater than the density of the molten steel: S1A: Place the steel block (1) on the surface of the molten steel. The steel block (1) can descend under its own weight and absorb the heat of the molten steel to heat up. S2A: When the magnesium in the spraying structure (2) of the steel block (1) is heated and vaporized, it is sprayed out from the spraying structure (2). The sprayed magnesium undergoes a desulfurization reaction in the molten steel. At the same time, the spraying of magnesium can push the steel block (1) to change its position in the molten steel and also change the spraying direction of the spraying structure (2). When the density of the steel block (1) is less than the density of the molten steel: S1B: Place the steel block (1) on the surface of the molten steel. The steel block (1) absorbs the heat of the molten steel and heats up. S2B: When the magnesium inside the spraying structure (2) of the steel block (1) is heated and vaporized, it is sprayed out from the spraying structure (2). The sprayed magnesium undergoes a desulfurization reaction in the molten steel. At the same time, the spraying of magnesium can push the steel block (1) to change its position in the molten steel and also change the spraying direction of the spraying structure (2). In order to push the steel block (1) to move towards the bottom of the molten steel, any of the following methods can be used: The top of the steel block (1) is provided with an upward spraying structure (3): the gasified magnesium in the upward spraying structure (3) on the top of the steel block (1) will provide a reaction force to make the steel block (1) move towards the bottom of the molten steel after being sprayed out. The spraying direction of the spraying structure (2) is not parallel to the plane where the steel block (1) is located and both are inclined upward: the vertical upward component force provided by the spraying structure (2) after spraying magnesium vapor will provide a reaction force to move the steel block (1) towards the bottom of the molten steel.

7. A method for dephosphorizing molten steel according to claim 6, characterized in that: The impurity removal agent contains at least one of ferrous oxide and calcium oxide.

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