Recycling method for hot-state steel ladle casting residues

Abstract

The invention discloses a recycling method for hot-state steel ladle casting residues. The recycling method comprises the steps that a recycling mode of the hot-state steel ladle casting residues is selected; the hot-state steel ladle casting residues are recycled; wherein the recycling mode of the hot-state steel ladle casting residues comprises the steps that the hot-state steel ladle casting residues are directly recycled to the steel ladle and are recycled to the steel ladle after being transferred through a transfer tank, and the transfer tank has a heating function. According to the recycling method for the hot-state steel ladle casting residues, the casting residue transfer tank with the heating function is arranged, so that the recycling rhythm of the hot-state steel ladle casting residues can be effectively adjusted, and the recycling proportion of the hot-state steel ladle casting residues is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for recovering hot ladle casting residue. Background Art

[0002] After continuous casting is completed, a portion of ladle residue remains within the ladle. This residue generally consists of slag, residual molten steel, and a small amount of covering agent. For steel grades requiring high cleanliness, a steel retention operation is often required to prevent slag release at the end of ladle casting from affecting the cleanliness of the molten steel. This involves closing the ladle slide before ladle casting is complete. In this case, a relatively large amount of molten steel remains in the ladle. The remaining liquid slag and molten steel in the ladle are referred to as hot ladle residue. Recycling ladle residue increases metal yield, utilizes effective steelmaking slag components, reduces slag consumption, and lowers production costs. Because hot ladle residue is hot and the molten steel and slag are at high temperatures, recycling them effectively utilizes their heat, helping to reduce energy consumption and carbon emissions. Methods for recycling hot ladle residue include returning it to the converter process or the refining process.

[0003] The recovery of hot ladle slag requires identifying appropriate recycling nodes, which, to a certain extent, influence the recycling efficiency of the ladle slag. However, because the steelmaking process involves multiple production nodes, the recovery of the slag requires relatively unimpeded logistics channels and a stable production rhythm. The recovery rate of the ladle slag should be maximized without affecting the normal production rhythm and steelmaking quality. In actual production, due to factors such as production rhythm, return nodes, logistics channels, and recovery volume, efficient recovery and recycling of hot ladle slag is difficult to achieve.

[0004] Chinese patent application number 202310756351.4 discloses a smelting method for recycling and reusing low-basicity hot casting slag. This method uses the hot casting slag after continuous casting as slag-forming material in the refining process and directly adds it to the ladle. By controlling process conditions such as deoxidation and slag adjustment during the refining process, the method achieves a low-basicity target slag system at the end of refining, adsorbs inclusion deformation, reduces operating pressure in subsequent VD / RH and continuous casting processes, and reduces production costs. This technical solution returns the ladle casting slag to the refining process, which is beneficial for improving the alloying element recovery rate of the casting slag molten steel. However, it does not provide a corresponding technical solution for how to solve the problem of matching recycling nodes.

[0005] Chinese patent application number 202211602374.1 discloses a method for recycling casting residue, the method comprising: classifying the casting residue to obtain oxidizing casting residue and reducing casting residue, the oxidizing casting residue being the casting residue produced without undergoing deoxidation, and the reducing casting residue being the casting residue produced after LF treatment; recycling the oxidizing casting residue into the smelting of non-deoxidized aluminum steel; recycling the reducing casting residue into the smelting of silicon-containing steel; and pre-analyzing and classifying the casting residue, and recycling it into different steel smelting according to the type of casting residue. The technical solution of this patent, which reuses the oxidizing and reducing casting residues into different steel smelting according to their types, can effectively avoid the problem of phosphorus and silicon return and carbon decontrol in molten steel after recycling the casting residue, which is beneficial to ensuring the stability of the molten steel composition. However, it does not provide a corresponding technical solution for how to solve the problem of matching recycling nodes.

[0006] Chinese patent application number 202011303819.7 discloses a method for recycling liquid casting slag from continuous casting of stainless steel. The method includes two methods: method 1: directly adding the liquid casting slag into an AOD furnace for double slag smelting, the AOD furnace has been added with hot molten iron, and the liquid casting slag is added between 0 and 25 minutes of smelting, and the amount of liquid casting slag added is 20 to 40 kg / t of steel; or, method 2: after the liquid casting slag is received by a molten iron tank, the hot molten iron and the liquid casting slag are added together into an AOD furnace for double slag smelting, and the amount of liquid casting slag added is 35 to 45 kg / t of steel. However, this technical solution is related to the specific process flow of stainless steel production and has certain limitations on its scope of application.

[0007] Chinese patent application number 201810207217.8 discloses a method for recovering molten steel by returning hot casting slag to a ladle. The method utilizes a holding furnace installed in the molten steel receiving span to receive and circulate multiple ladles of casting slag. The holding furnace is used to supplement the heat of the casting slag to keep it molten. The slag is processed using sophisticated and advanced roller technology. The remaining molten steel is received by a baked ladle and transported by a span trolley to the molten iron receiving span, where it is filled with molten iron. After desulfurization, it is added to the converter, achieving the hot recovery of the remaining molten steel in the casting slag. This patented technical solution allows all casting slag to be returned to production, but for the casting slag of high-quality steel, the effective recovery and utilization of alloying elements in the casting slag molten steel must be comprehensively considered. If all of the casting slag is added to the primary refining furnace, the easily oxidizable alloying elements in the casting slag molten steel will be oxidized, which is not conducive to reducing production costs.

[0008] Chinese patent application number 201310229162.8 discloses a method for recycling refined slag by pouring it into a ladle. The method includes the following steps: molten iron in a torpedo tank → adding iron to the ladle → pre-treating and slagging the KR hot metal → smelting in a converter → refining in a LF furnace → feeding the refining into a casting machine → pouring the refined slag into a ladle → adding molten iron to the ladle, and repeating the above process. This patent also fails to consider the recovery rate of alloying elements in cast steel, particularly high-alloy steel grades.

[0009] It is hoped to provide an improved method for recovering hot ladle waste, particularly with respect to solving the problems of effective matching of recovery nodes and effective utilization of alloy elements in molten steel from ladle waste. Summary of the Invention

[0010] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for recovering hot ladle casting waste, the purpose of which is to effectively adjust the recovery rhythm and increase the recovery ratio of hot ladle casting waste.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is: a method for recovering hot ladle casting residue, comprising:

[0012] Select the recycling method of hot ladle casting residue;

[0013] Recycling of hot ladle casting residue;

[0014] Among them, the recovery methods of the hot ladle casting residue include directly recovering the hot ladle casting residue to the ladle and recovering the hot ladle casting residue to the ladle after circulation in a transfer tank, and the transfer tank has a heating function.

[0015] The transfer tank has a gas baking function.

[0016] The transfer tank should have a dumping device and be able to control the amount of molten steel or slag dumped.

[0017] The transfer tank is provided with a bottom blowing device, which is used to provide argon or nitrogen into the transfer tank.

[0018] The transfer tank has a capacity of more than 10t.

[0019] When the transfer tank is used to recover the hot ladle residue, the molten steel in the transfer tank should be heated to above 1500°C.

[0020] When the transfer tank recovers the hot ladle casting residue, scrap steel materials are added to the transfer tank.

[0021] When the transfer tank recovers the hot ladle casting residue, alloy material is added to the transfer tank.

[0022] The method for recovering the hot ladle casting residue is to directly recover the hot ladle casting residue to the ladle. For the ladle casting residue after LF refining, the slag is turned after the ladle is tapped.

[0023] The hot ladle casting waste recovery method of the present invention can effectively adjust the hot ladle casting waste recovery rhythm and improve the hot ladle casting waste recovery ratio by providing a casting waste transfer tank with a heating function. DETAILED DESCRIPTION

[0024] The following is a further detailed description of the specific implementation methods of the present invention through the description of embodiments, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention and to facilitate their implementation.

[0025] The present invention provides a method for recovering hot ladle casting residue, comprising the following steps:

[0026] S1. Select a method for recovering hot ladle residue;

[0027] S2. Recover the hot ladle casting residue.

[0028] Specifically, the transfer tank is set at a suitable position near the primary refining furnace (converter or electric furnace) and the ladle lifting channel. The transfer tank has induction heating, and is also equipped with a gas baking function and can be covered.

[0029] In the above step S1, the hot ladle casting residue is recovered in two ways: directly recovering the hot ladle casting residue to the ladle and recycling the hot ladle casting residue to the ladle after circulation in a transfer tank, and the transfer tank has a heating function.

[0030] Preferably, the transfer tank should have a dumping device and be able to control the amount of molten steel or slag dumped.

[0031] Preferably, the transfer tank is provided with a ladle slag measuring silo and a feeding device, including lime, refined slag, ladle top slag modifier, etc., and also includes a feeding trolley, etc.

[0032] Preferably, the transfer tank has a bottom blowing device, which is used to provide argon or nitrogen into the transfer tank for stirring in the transfer tank.

[0033] The number and capacity of hot ladle casting transfer tanks can be economically and reasonably configured according to the needs of the production line. Generally, the capacity of the transfer tank is more than 10t.

[0034] During the normal smelting process, based on the characteristics of the steel type and casting slag, production nodes, production scheduling, etc., and on the premise of ensuring smooth production and the quality of smelted molten steel, the optimal recovery plan for hot casting slag is determined to increase the proportion of recovered furnaces and the recovery rate of molten steel and alloy elements, thereby achieving more economical recovery of hot ladle casting slag.

[0035] In the above step S1, the recycling method of hot ladle casting residue can be selected as directly recycling the hot ladle casting residue to the ladle. The preferred recycling scheme for hot casting residue slag, for the same steel type or steel types with similar slag systems and similar residual element control requirements, is to give priority to directly returning to the ladle for recycling before or after tapping according to the production node and the recycling node, so as to increase the casting residue recovery temperature as much as possible; for ladle casting residue after LF refining, especially for steel types that require steel to be retained for casting and have a large amount of alloying elements added, it is preferred to turn the slag after the ladle is tapped to increase the recovery rate of alloying elements in the casting residue molten steel. When scheduling production, steel types with similar slag system requirements and similar composition control should be concentrated as much as possible to increase the proportion of direct recycling to the ladle and reduce production costs as much as possible. Due to the increase in the proportion of recycled furnaces, for steel types with steel retention requirements, the amount of retained steel can be appropriately increased to improve the quality of the corresponding ingots at the end of casting. For the corresponding heats after recycling ladle casting residue, slag-making materials should be added reasonably according to the target slag system of steel grade, the composition and slag amount of ladle casting residue to obtain the final target slag system that meets the refining requirements.

[0036] It should be noted that for multiple recycling cycles, the slag volume, desulfurization capacity and phosphorus recovery should be considered. It is also necessary to avoid the situation where carbon matching is difficult due to too much slag or the difficulty in inserting the immersion tube during RH treatment, which affects the vacuum treatment. The reasonable number of cycles should be determined, generally not more than 4 times.

[0037] In step S1 above, hot ladle slag can be recycled by circulating it through a transfer tank before being returned to the ladle. Ladle slag that cannot be directly recycled due to production mismatches, the need for slag modification, or other reasons can be transferred to a transfer tank first. The molten steel in the transfer tank should be heated to above 1500°C. While waiting, the transfer tank can be heated at a low temperature to minimize the temperature drop of the ladle slag. This can be achieved by controlling the tapping rate of subsequent heats and optimally selecting the timing for recycling within the transfer tank.

[0038] Preferably, when the transfer tank recycles the hot ladle casting waste, since the transfer tank has a heating function, according to production needs and economic principles, when the amount of casting waste steel is large, high-quality scrap steel materials of the same steel grade or steel grades with similar composition control requirements can be appropriately added to the transfer tank. The type of scrap steel material is the same as the steel grade in the ladle or has similar composition control requirements, so as to improve the metal recovery rate of the scrap steel.

[0039] Preferably, during the production of high alloy steel, when the transfer tank is recovering the hot ladle residue, alloy materials can be added to the transfer tank to improve the refining efficiency.

[0040] Preferably, when the transfer tank recycles the hot ladle casting residue, if the amount of molten steel and slag in the transfer tank is large (such as greater than 10t), the ladle casting residue can be poured into the ladle in multiple times, and the steel output of the primary refining furnace can be adjusted to match the amount of molten steel in the transfer tank to meet the requirement of molten steel amount in the ladle during refining.

[0041] As a preferred method, when the hot ladle casting residue is directly recycled into the ladle, the ladle casting residue after LF refining is slag-turned after the ladle is tapped.

[0042] The recovery methods of hot ladle casting residue can be divided into: returning to the primary refining furnace and conventional slag treatment.

[0043] Hot ladle slag should be returned to the primary melting furnace. If, due to unusual circumstances, the slag cannot be recycled before or after tapping, or circulated in a transfer tank, it can be placed on the bottom of a baked hot metal ladle and then returned to the primary melting furnace after receiving water. The sulfur and phosphorus content of the slag should be carefully considered. After returning to the primary melting furnace, the sulfur and phosphorus contents of the tapped steel should meet the required levels.

[0044] Conventional slag treatment is selected as the recycling method for hot ladle casting waste. Ladle casting waste that cannot be returned to primary refining and ladle casting waste that is prohibited from being recycled will not be recycled and will be treated according to conventional methods.

[0045] Due to the adoption of the above technical solution, the present invention has the following positive effects compared with the prior art:

[0046] (1) By adopting the above-mentioned technical solution of the invention, a transfer tank with a heating function for recovering the hot ladle casting residue is set up, which can effectively adjust the recovery rhythm, facilitate the smooth production under the conditions of ladle casting residue recovery, and at the same time increase the recovery ratio of the hot ladle casting residue as much as possible.

[0047] (2) By adopting the technical solution of the invention, the residual molten steel can be completely recovered when the ladle casting residue is recovered, thereby improving the metal recovery rate and billet forming rate, and having significant economic benefits.

[0048] (3) Since the hot ladle casting waste recovery transfer tank with heating function is set up, conditions are provided for recovering the ladle casting waste as much as possible. Therefore, for steel types with steel retention requirements, the amount of retained steel can be appropriately increased to improve the cleanliness of the corresponding ingot at the end of casting.

[0049] (4) Since the transfer tank has a heating function, high-quality scrap steel can be added appropriately according to the production rhythm to improve the scrap metal recovery rate.

[0050] (5) For high alloy steel, alloy can be added in advance in the transfer tank to reduce the LF alloy adjustment pressure and promote smooth production.

[0051] (6) The proportion of ladle casting waste recovery heats increased, which effectively shortened the LF refining cycle and was conducive to improving production efficiency.

[0052] (7) The proportion of ladle casting waste recovery furnaces increased, which effectively utilized heat, reduced energy consumption, and further reduced carbon emissions.

[0053] Example

[0054] The technical solution of the present invention is described in detail below with reference to specific embodiments, which does not limit the scope of protection thereof.

[0055] The technical solution of the present invention is further illustrated by taking the hot ladle casting waste recovery carried out in a special steel plant adopting the process flow of "150t converter → LF furnace → RH furnace → round billet / square billet" as an example.

[0056] Using the technical solution of the present invention, a hot ladle casting waste transfer tank is installed at a suitable location near the converter and ladle lifting channel. The transfer tank is equipped with induction heating, a gas baking function, and a cover. The transfer tank should have a dumping device that can control the amount of molten steel or slag dumped. The transfer tank should be equipped with a ladle slag hopper and a charging device containing lime, refined slag, ladle top slag modifier, etc., as well as a charging trolley. The transfer tank should be equipped with a bottom blowing device and argon stirring. Based on the production line requirements, the hot ladle casting waste transfer tank is configured with a capacity of 20 tons. During the normal smelting process, based on the production steel type, the characteristics of the casting waste, production nodes, production scheduling, etc., while ensuring smooth production and molten steel quality, an optimal recovery plan for the hot casting waste is determined to increase the recovery furnace ratio and the recovery rate of molten steel and alloying elements, thereby achieving more economical recovery of hot ladle casting waste.

[0057] The recycling methods of hot ladle casting residue can be divided into: direct recycling to the ladle, recycling to the ladle after turnover in the transfer tank, returning to the primary refining furnace and conventional slag treatment.

[0058] (1) Directly recovered to the ladle;

[0059] The optimal recovery plan for hot casting slag is to return it directly to the ladle before or after tapping for recycling, based on production and recovery nodes, for the same steel grade or steel grades with similar slag systems and similar residual element control requirements, to maximize the recovery temperature of the casting slag. For ladle casting slag after LF refining, especially for steel grades that require retained steel for casting and require large amounts of alloying elements, it is preferred to turn the slag after tapping to improve the recovery rate of alloying elements in the casting molten steel. When scheduling production, steel grades with similar slag system requirements and similar composition control should be concentrated to increase the proportion of direct recycling to the ladle and minimize production costs.

[0060] As the proportion of recycled heats increases, for steel grades with steel retention requirements, the amount of retained steel can be appropriately increased to improve the quality of the corresponding ingots at the end of the casting. For the corresponding heats after recycling ladle casting residues, slag-making materials should be added according to the target slag system of the steel grade, the composition and slag amount of the ladle casting residue, to obtain the target slag system at the end of refining.

[0061] It should be noted that for multiple recycling cycles, the slag volume, desulfurization capacity and phosphorus recovery should be considered. It is also necessary to avoid the situation where carbon matching is difficult due to too much slag or the difficulty in inserting the immersion tube during RH treatment, which affects the vacuum treatment. The reasonable number of cycles should be determined, generally not more than 4 times.

[0062] (2) After circulation in the transfer tank, it is recycled to the ladle;

[0063] Ladle slag that cannot be directly recycled due to production rhythm mismatches or the need for slag modification can be transferred to a transfer tank first. The molten steel in the transfer tank should be heated to above 1500°C, and a low heat can be used for drying while waiting to reduce the temperature drop. This allows for the controlled tapping rate of subsequent heats and the optimal timing of recycling within the transfer tank. Because the transfer tank has a heating function, high-quality scrap steel of the same steel grade or a similar grade with similar composition control requirements can be added to large volumes of molten steel, based on production needs and economic principles, to increase the scrap metal yield. In the production of high-alloy steel, some alloys can also be added to improve refining efficiency.

[0064] When the amount of molten steel and slag in the transfer tank is large, they can be poured into the ladle in multiple times, or the steel output of the primary refining furnace can be adjusted to match the amount of molten steel in the transfer tank to meet the requirements of the molten steel volume in the ladle during refining.

[0065] Attention should also be paid to the issues that need to be considered in “(1) Direct recovery to ladle”.

[0066] (3) Return to the primary refining furnace;

[0067] If, due to unusual circumstances, ladle remnants cannot be transferred to the transfer tank before or after tapping, they can be placed in a baked hot metal ladle as a base, then returned to the primary melting furnace after receiving the hot metal. However, due to logistical reasons, placing the ladle in the primary melting furnace seriously disrupts smooth production, so returning the ladle to the primary melting furnace is not an option until the logistics channels are modified.

[0068] (4) Conventional slag treatment;

[0069] When the ladle casting residue cannot be recycled before or after tapping, nor can it be circulated in the transfer tank due to abnormal reasons, or the ladle casting residue is prohibited from being recycled, it will not be recycled and will be handled according to the conventional method.

[0070] Comparative Example: The technical solution of the embodiment was not adopted. According to the production rhythm, the heats in which hot ladle casting residues could be recovered were recycled, and the ladle casting residues that could not be recovered were subjected to conventional slag treatment.

[0071] The results of the one-year comparison of the technical solutions for recycling hot ladle casting residues according to the embodiment and the comparative example are shown in Table 1.

[0072] Table 1 Cold steeling conditions of the embodiment and comparative example

[0073] project Ratio of hot slag recovery Annual billet yield Example 38.5 97.3 Comparative Example 24.3 96.5

[0074] In addition, the technical solution of the present invention has the following beneficial effects in addition to the above-mentioned improvement:

[0075] (1) Since the hot ladle casting waste recovery transfer tank with heating function is set up, conditions are provided for recovering the ladle casting waste as much as possible. Therefore, for steel types with steel retention requirements, the amount of retained steel can be appropriately increased to improve the cleanliness of the corresponding ingot at the end of casting.

[0076] (2) Since the transfer tank has a heating function, high-quality scrap steel can be appropriately added according to the production rhythm to improve the scrap metal recovery rate.

[0077] (3) For high alloy steel, alloy can be added in advance in the transfer tank to reduce the LF alloy adjustment pressure and promote smooth production.

[0078] (4) The proportion of ladle casting waste recovery heats increased, which effectively shortened the LF refining cycle and was conducive to improving production efficiency.

[0079] (5) The proportion of ladle casting waste recovery heats increased, which effectively utilized heat, reduced energy consumption, and further reduced carbon emissions.

[0080] The above description of the present invention is illustrative. Obviously, the specific implementation of the present invention is not limited to the above-described method. Any non-substantial improvements made using the method concepts and technical solutions of the present invention, or any direct application of the above-described concepts and technical solutions to other situations without modification, fall within the scope of protection of the present invention.

Claims

1. A method for recovering hot ladle casting waste, characterized in that: include: Select the recycling method for hot ladle waste; Recycling of hot ladle casting residue; Among them, the recovery methods of the hot ladle casting residue include directly recovering the hot ladle casting residue to the ladle and recovering the hot ladle casting residue to the ladle after circulation in a transfer tank, and the transfer tank has a heating function.

2. The method for recovering hot ladle casting residue according to claim 1, characterized in that: The transfer tank has a gas baking function.

3. The method for recovering hot ladle casting residue according to claim 1, characterized in that: The transfer tank should have a dumping device and be able to control the amount of molten steel or slag dumped.

4. The method for recovering hot ladle waste according to any one of claims 1 to 3, characterized in that: The transfer tank is provided with a bottom blowing device, which is used to provide argon or nitrogen into the transfer tank.

5. The method for recovering hot ladle waste according to any one of claims 1 to 3, characterized in that: The transfer tank has a capacity of more than 10t.

6. The method for recovering hot ladle waste according to any one of claims 1 to 5, characterized in that: When the transfer tank is used to recover the hot ladle residue, the molten steel in the transfer tank should be heated to above 1500°C.

7. The method for recovering hot ladle waste according to any one of claims 1 to 6, characterized in that: When the transfer tank recovers the hot ladle casting residue, scrap steel materials are added to the transfer tank.

8. The method for recovering hot ladle waste according to any one of claims 1 to 6, characterized in that: When the transfer tank recovers the hot ladle casting residue, alloy material is added to the transfer tank.

9. The method for recovering hot ladle waste according to any one of claims 1 to 6, characterized in that: The method for recovering the hot ladle casting residue is to directly recover the hot ladle casting residue to the ladle. For the ladle casting residue after LF refining, the slag is turned after the ladle is tapped.