Method for recovering high-quality automotive sheet casting residual steel

Abstract

The application discloses a method for recovering residual steel of high-quality automobile plate pouring, which comprises the following steps: step 1, in the pouring process, when the residual molten steel in the tundish reaches 8-10 tons, the pouring is terminated, at this time, the ladle bottom comprises residual molten steel and top slag after RH refining treatment, according to the TFe content in the top slag, a modifier is added for modification treatment, and then the weight content of TFe in the top slag is controlled to be less than or equal to 5.0 %; step 2, steel folding operation is performed, and the vertical distance between the liquid surface in the ladle and the ladle opening in the steel folding process is controlled; step 3, the ladle after the steel folding is moved to a refining station to perform slag dipping operation, the top slag state in the ladle is observed, if the dipped slag sample is black and foamy, oxygenation treatment is performed; after the oxygenation, primary slagging refining is performed; step 4, after the treatment, slag dipping operation is performed again, the top slag state in the ladle is observed, if the dipped slag sample is black, secondary slagging refining is performed, and the operation is repeated until the slag state presents a glassy state.

Description

Technical Field

[0001] This invention relates to the field of steel smelting and resource recycling technology, and more specifically, to a method for recycling surplus steel from high-quality automotive sheet casting. Background Technology

[0002] In the automotive steel sheet production process, production quality and cost control are of paramount importance. According to the integrated manufacturing process requirements for automotive steel sheets, to ensure high-quality steel sheet parameters and effectively control secondary oxidation of molten steel during casting to avoid inclusions, slag addition is strictly prohibited in the later stages of casting. When the remaining steel in the casting machine is between 8 and 10 tons, the slide gate must be closed to terminate casting, thus ensuring that no steel slag enters the tundish and contaminates the molten steel. Traditionally, this remaining molten steel is poured into a slag ladle for cooling, followed by separation and cold material recovery. However, this method is inefficient in terms of timeliness and recovery rate, significantly impacting production costs and consequently affecting the company's economic benefits. In the traditional production model, due to the low efficiency of traditional recovery methods, annual steel material losses exceed 4,500 tons, increasing costs by approximately 8 million yuan.

[0003] Currently, the industry lacks an efficient and mature technological system for recycling surplus steel from automotive steel casting. Existing technologies have attempted simple recycling methods, but due to insufficient consideration of factors such as steel grade characteristics, production rhythm, and molten steel quality, the recycling results have been unsatisfactory. This not only fails to effectively reduce costs but may also negatively impact the quality of subsequent steel billets. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned deficiencies in existing technologies and provide a method for recovering residual steel from high-quality automotive steel casting. This method addresses the problem of increased costs due to waste of residual steel in the later stages of high-quality automotive steel casting. By developing a scientific and effective residual steel recovery technology, the invention aims to reduce production cost losses and improve enterprise economic efficiency. Simultaneously, it standardizes the residual steel recovery operation process, ensures production safety, reduces the workload of personnel handling slag ladle ladles, ensures stable molten steel quality, avoids adverse effects on molten steel quality due to improper recovery, improves the steel recovery rate, and promotes the efficient utilization of steel resources.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for recycling surplus steel from high-quality automotive steel casting includes the following steps: Step 1: During the casting process, when the remaining molten steel in the tundish reaches 8-10 tons, casting is terminated. At this time, the bottom of the ladle includes residual molten steel and top slag after RH refining. Based on the TFe content in the top slag, a modifier is added for modification treatment, and the weight content of TFe in the top slag is controlled to be ≤5.0%. Step 2: The ladle containing the top slag and residual molten steel processed in Step 1 is hoisted to the steel bending operation area by an overhead crane. The top slag and residual molten steel in the ladle are then hoisted and bent into the ladle to be used for tapping steel. The vertical distance between the liquid level in the ladle and the ladle opening is controlled during the steel bending process. Step 3: Move the steel ladle after steel bending to the refining station, then perform slag dipping operation and observe the state of the top slag in the ladle. If the slag sample is black and foamy, then perform oxygen determination treatment on the molten steel until the oxygen value of the molten steel is controlled at 250~600ppm. After oxygen determination, add slag-forming agent into the ladle for one slag-forming refining. Step 4: After the first slag-forming refining process, perform the slag-dipping operation again and observe the state of the top slag in the ladle. If the slag sample taken is black, add slag-forming agent for a second slag-forming refining process until the slag becomes glassy.

[0006] Optionally, in step 1, if the weight content of TFe in the top slag is ≤5.0%, no modifier is added; if the weight content of TFe in the top slag is >5.0%, a modifier of 3.79~5.98 kg / ton of steel is added.

[0007] Optionally, in step 2, before folding the steel, the vertical distance from the liquid surface inside the ladle to the ladle opening is >600mm; at the end of folding the steel, the vertical distance from the liquid surface inside the ladle to the ladle opening is ≥400mm.

[0008] Optionally, in step 3: the slag-forming agent is active lime and aluminum balls, wherein the amount of active lime added is 600~800kg and the amount of aluminum balls added is 60~100kg.

[0009] Optionally, in step 4: the slag-forming agent is aluminum balls, and the amount of aluminum balls added is 15~100kg.

[0010] Optionally, in step 3: the temperature is raised to 1610~1630℃ during the slag-making process.

[0011] Optionally, in step 4: the temperature is raised to 1610~1630℃ during the slag-making process.

[0012] Optionally, the weight content of Ti in the automotive sheet is >0.02%, and the weight content of P is >0.015%.

[0013] Implementing the embodiments of the present invention will have the following beneficial effects: 1. Significant economic benefits: By recycling surplus steel, production cost losses are significantly reduced. Based on actual data calculations, it is estimated that approximately 9.864 million yuan in steel material costs can be saved annually.

[0014] 2. Safety and Quality Assurance: Standardized operating procedures effectively ensure production safety and reduce the risk of accidents such as splashing. Simultaneously, this invention effectively controls the quality of molten steel through strict operations such as slag dipping, oxygen determination, and slag refining, ensuring stable steel quality, improving the finished billet yield, and reducing the defect rate.

[0015] 3. Environmental protection and sustainable development: It reduces the use of slag pots, reduces the workload of the dry slag room, reduces energy consumption and environmental pollution, which is in line with the trend of green development in the steel industry and lays the foundation for the sustainable development of enterprises. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0017] This invention discloses a method for recycling surplus steel from high-quality automotive steel sheet casting, comprising the following steps: Step 1: Termination of Casting and Confirmation of Residual Steel Status: During the casting process, to avoid secondary oxidation and contamination of molten steel caused by slag discharge, when the amount of molten steel remaining in the tundish reaches 8-10 tons, the slide gate is closed to terminate casting. At this time, the bottom of the ladle includes residual molten steel and top slag after RH refining treatment. Subsequently, the composition of the top slag is tested and its compliance is judged: The top slag in the ladle is sampled and analyzed to determine its total iron (TFe) content. Based on the TFe content in the top slag, a modifier is added for modification treatment to control the weight content of TFe in the top slag to ≤5.0%.

[0018] In one specific embodiment, in step 1, when the weight content of TFe in the top slag is ≤5.0%, the top slag is considered to have low oxidizability and meets the conditions for recycling and reuse, so no modifier is added and no modification treatment is required; when the weight content of TFe in the top slag is >5.0%, a modifier of 3.79~5.98 kg / ton of steel is added for modification treatment. After modification treatment, it is necessary to resample and test to confirm that the weight content of TFe is ≤5.0%.

[0019] Step 2: Steel Folding Operation: The ladle containing the top slag and residual molten steel treated in Step 1 is hoisted to the steel folding operation area by an overhead crane. The top slag and residual molten steel in the ladle are hoisted and folded into the ladle to be used for tapping steel. The vertical distance between the liquid level in the ladle and the ladle opening is controlled during the steel folding process.

[0020] In one specific embodiment, in step 2, before folding the steel, the vertical distance from the liquid surface inside the ladle to the ladle opening is >600mm; at the end of folding, the vertical distance from the liquid surface inside the ladle to the ladle opening is ≥400mm. During the folding process, the change in the vertical distance from the liquid surface inside the ladle to the ladle opening needs to be monitored in real time to ensure safety while "folding as much as possible".

[0021] In one specific embodiment, during operation, it is necessary to control the crane to operate smoothly and with a slow lifting and lowering speed to minimize molten steel splashing.

[0022] Step 3: Refining treatment: Move the ladle after steel folding to the refining station (such as the LF station). After the ladle is in place, immediately perform slag dipping and observe the state of the top slag inside the ladle. If the slag sample is black and foamy, it indicates that the oxidizing power of the slag may be too high. Then, perform oxygen determination treatment on the molten steel until the oxygen value of the molten steel is controlled at 250~600ppm. After oxygen determination, according to the steel grade requirements and the state of the molten steel, add slag-forming agent into the ladle for a first slag-forming refining.

[0023] In one specific embodiment, in step 3: the slag-forming agent is active lime and aluminum balls, the amount of active lime added is 600~800kg, the amount of aluminum balls added is 60~100kg, and the temperature is raised to 1610~1630℃ during the slag-forming process, and the heating time is 10~25min.

[0024] Step 4: Verification of Top Slag Condition and Secondary Slag Modification: After the first slag-forming refining process, perform the slag dipping operation again and observe the condition of the top slag in the ladle. If the slag sample taken is black, it indicates that the oxidation is not completely controlled. Then, add slag-forming agent for secondary slag-forming refining until the slag is glassy (glassy green), indicating that the properties of the top slag meet the refining requirements. Subsequent refining operations shall be carried out according to the standard process flow for this steel grade.

[0025] In one specific embodiment, in step 4: the slag-forming agent is aluminum balls, the amount of aluminum balls added is 15~100kg, and the temperature is raised to 1610~1630℃ during the slag-forming process, and the heating time is 10~25min.

[0026] In one specific embodiment, the method for recycling high-quality automotive sheet casting waste steel of the present invention is applicable to automotive sheets with a Ti weight content > 0.02% and a P weight content > 0.015%.

[0027] The following are specific embodiments. Example 1 Taking the production of O5 grade IF steel in an LF furnace as an example, the method for recycling high-quality automotive sheet casting waste steel in this embodiment includes the following steps: Step 1: Termination of Casting and Confirmation of Residual Steel State: During the casting process, to avoid secondary oxidation and contamination of molten steel caused by slag discharge, the slide gate is closed to terminate casting when the remaining molten steel in the tundish reaches 8 tons. At this time, the bottom of the ladle includes residual molten steel and top slag after RH refining treatment. Subsequently, the composition of the top slag is tested and its compliance is judged: The top slag in the ladle is sampled and analyzed to determine its total iron (TFe) content. Based on the TFe content of 6% in the top slag, a modifier of 3.79~5.98 kg / ton of steel is added for modification treatment. After modification treatment, the sample needs to be resampled and tested to confirm that the TFe weight content is ≤5.0%.

[0028] Step 2: Steel Folding Operation: The ladle containing the top slag and residual molten steel treated in Step 1 is hoisted to the steel folding operation area by an overhead crane. The top slag and residual molten steel in the ladle are folded into the ladle prepared for tapping. Before folding, the vertical distance from the molten steel surface in the ladle to the ladle opening must be >600mm; at the end of folding, the vertical distance must be ≥400mm. During the folding process, the change in the vertical distance from the molten steel surface in the ladle to the ladle opening must be monitored in real time to ensure safety while folding as much as possible. Furthermore, during the operation, the overhead crane should be operated smoothly with a slow lifting and lowering speed to minimize molten steel splashing.

[0029] Step 3: Refining treatment: Move the folded steel ladle to the refining station. After the ladle is in place, immediately perform slag dipping and observe the top slag condition inside the ladle. If the slag sample is found to be black and foamy, perform oxygen determination treatment on the molten steel until the oxygen value of the molten steel is controlled at 410ppm. After oxygen determination, according to the steel grade requirements and the state of the molten steel, add 600kg of active lime and 70kg of aluminum balls to the ladle for a first slag-forming refining. During the slag-forming process, heating is carried out at a temperature of 1615℃ and the slag-forming time is 11min.

[0030] Step 4: Verification of Top Slag Condition and Secondary Slag Modification: After the first slag-making and refining process, the slag dipping operation is performed again, and the condition of the top slag in the ladle is observed. It is found that the slag sample taken is black, indicating that the oxidation is not completely controlled. Therefore, 15 kg of aluminum balls are added for secondary slag-making and refining. During the slag-making process, the temperature is increased to 1627℃, and the slag modification time is 3 minutes, until the slag state is glassy (glassy green), indicating that the properties of the top slag meet the refining requirements. Subsequent refining operations are carried out according to the standard process flow for this steel grade.

[0031] Example 2 Taking the production of O5 grade IF steel in an LF furnace as an example, the method for recycling high-quality automotive sheet casting waste steel in this embodiment includes the following steps: Step 1: Termination of Casting and Confirmation of Remaining Steel Status: During the casting process, to avoid secondary oxidation and contamination of molten steel caused by slag discharge, the slide gate is closed to terminate casting when the remaining molten steel in the tundish reaches 9 tons. At this time, the bottom of the ladle includes residual molten steel and top slag after RH refining treatment. Subsequently, the composition of the top slag is tested and its compliance is judged: The top slag in the ladle is sampled and analyzed to determine its total iron (TFe) content. Based on the TFe content of 7% in the top slag, a modifier of 3.79~5.98 kg / ton of steel is added for modification treatment. After modification treatment, the sample needs to be resampled and tested to confirm that the TFe weight content is ≤5.0%.

[0032] Step 2: Steel Folding Operation: The ladle containing the top slag and residual molten steel treated in Step 1 is hoisted to the steel folding operation area by an overhead crane. The top slag and residual molten steel in the ladle are folded into the ladle prepared for tapping. Before folding, the vertical distance from the molten steel surface in the ladle to the ladle opening must be >600mm; at the end of folding, the vertical distance must be ≥400mm. During the folding process, the change in the vertical distance from the molten steel surface in the ladle to the ladle opening must be monitored in real time to ensure safety while folding as much as possible. Furthermore, during the operation, the overhead crane should be operated smoothly with a slow lifting and lowering speed to minimize molten steel splashing.

[0033] Step 3: Refining treatment: Move the folded steel ladle to the refining station. After the ladle is in place, immediately perform slag dipping and observe the state of the top slag inside the ladle. If the slag sample is found to be black and foamy, perform oxygen determination treatment on the molten steel until the oxygen value of the molten steel is controlled at 395ppm. After oxygen determination, according to the steel grade requirements and the state of the molten steel, add 660kg of active lime and 65kg of aluminum balls to the ladle for a first slag-forming refining. During the slag-forming process, heating is carried out at a temperature of 1612℃ and the slag-forming time is 8min.

[0034] Step 4: Verification of Top Slag Condition and Secondary Slag Modification: After the first slag-making and refining process, the slag dipping operation is performed again, and the condition of the top slag in the ladle is observed. It is found that the slag sample taken is black, indicating that the oxidation is not completely controlled. Therefore, 15 kg of aluminum balls are added for secondary slag-making and refining. During the slag-making process, the temperature is increased to 1621℃, and the slag modification time is 4 minutes, until the slag state is glassy (glassy green), indicating that the properties of the top slag meet the refining requirements. Subsequent refining operations are carried out according to the standard process flow for this steel grade.

[0035] Example 3 Taking the production of O5 grade IF steel 41 grade O5 plate in an LF furnace as an example, the method for recycling surplus steel from high-quality automotive sheet casting in this embodiment includes the following steps: Step 1: Termination of Casting and Confirmation of Residual Steel State: During the casting process, to avoid secondary oxidation and contamination of molten steel caused by slag discharge, when the remaining molten steel in the tundish reaches 10 tons, the slide gate is closed to terminate casting. At this time, the bottom of the ladle includes residual molten steel and top slag after RH refining treatment. Subsequently, the top slag composition is tested and its compliance is judged: The top slag in the ladle is sampled and analyzed to determine its total iron (TFe) content. Based on the TFe content of 6% in the top slag, a modifier of 3.79~5.98 kg / ton of steel is added for modification treatment. After modification treatment, it is necessary to resample and test to confirm that the TFe weight content is ≤5.0%.

[0036] Step 2: Steel Folding Operation: The ladle containing the top slag and residual molten steel treated in Step 1 is hoisted to the steel folding operation area by an overhead crane. The top slag and residual molten steel in the ladle are folded into the ladle prepared for tapping. Before folding, the vertical distance from the molten steel surface in the ladle to the ladle opening must be >600mm; at the end of folding, the vertical distance must be ≥400mm. During the folding process, the change in the vertical distance from the molten steel surface in the ladle to the ladle opening must be monitored in real time to ensure safety while folding as much as possible. Furthermore, during the operation, the overhead crane should be operated smoothly with a slow lifting and lowering speed to minimize molten steel splashing.

[0037] Step 3: Refining treatment: Move the folded steel ladle to the refining station. After the ladle is in place, immediately perform slag dipping and observe the top slag condition inside the ladle. If the slag sample is found to be black and foamy, perform oxygen determination treatment on the molten steel until the oxygen value of the molten steel is controlled at 420ppm. After oxygen determination, according to the steel grade requirements and the state of the molten steel, add 660kg of active lime and 68kg of aluminum balls to the ladle for a first slag-forming refining. During the slag-forming process, heating is carried out at a temperature of 1611℃ and the slag-forming time is 9min.

[0038] Step 4: Verification of Top Slag Condition and Secondary Slag Modification: After the first slag-making and refining process, the slag dipping operation is performed again, and the condition of the top slag in the ladle is observed. It is found that the slag sample taken is black, indicating that the oxidation is not completely controlled. Therefore, 20 kg of aluminum balls are added for secondary slag-making and refining. During the slag-making process, the temperature is increased to 1625℃, and the slag modification time is 5 minutes, until the slag state is glassy (glassy green), indicating that the properties of the top slag meet the refining requirements. Subsequent refining operations are carried out according to the standard process flow for this steel grade.

[0039] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for recycling surplus steel from high-quality automotive sheet casting, characterized in that, Includes the following steps: Step 1: During the casting process, when the remaining molten steel in the tundish reaches 8-10 tons, casting is terminated. At this time, the bottom of the ladle includes residual molten steel and top slag after RH refining. Based on the TFe content in the top slag, a modifier is added for modification treatment, and the weight content of TFe in the top slag is controlled to be ≤5.0%. Step 2: The ladle containing the top slag and residual molten steel processed in Step 1 is hoisted to the steel bending operation area by an overhead crane. The top slag and residual molten steel in the ladle are then hoisted and bent into the ladle to be used for tapping steel. The vertical distance between the liquid level in the ladle and the ladle opening is controlled during the steel bending process. Step 3: Move the steel ladle after steel bending to the refining station, then perform slag dipping operation and observe the state of the top slag in the ladle. If the slag sample is black and foamy, then perform oxygen determination treatment on the molten steel until the oxygen value of the molten steel is controlled at 250~600ppm. After oxygen determination, add slag-forming agent into the ladle for one slag-forming refining. Step 4: After the first slag refining process, perform the slag dipping operation again and observe the state of the top slag in the ladle. If the slag sample is black, add slag-forming agent for a second slag refining process until the slag is glassy. In step 2, before folding the steel, the vertical distance from the liquid surface inside the ladle to the ladle opening is >600mm; at the end of folding the steel, the vertical distance from the liquid surface inside the ladle to the ladle opening is ≥400mm. In step 3: the temperature is raised to 1610~1630℃ during the slag-making process; In step 4: During the slag-making process, the temperature is raised to 1610~1630℃.

2. The method for recycling surplus steel from high-quality automotive sheet casting according to claim 1, characterized in that, In step 1, when the weight content of TFe in the top slag is ≤5.0%, no modifier is added; when the weight content of TFe in the top slag is >5.0%, a modifier of 3.79~5.98 kg / ton of steel is added.

3. The method for recycling surplus steel from high-quality automotive sheet casting according to claim 1, characterized in that, In step 3: the slag-forming agent is active lime and aluminum balls, and the amount of active lime added is 600~800kg, and the amount of aluminum balls added is 60~100kg.

4. The method for recycling surplus steel from high-quality automotive sheet casting according to claim 1, characterized in that, In step 4: the slag-forming agent is aluminum balls, and the amount of aluminum balls added is 15~100kg.

5. The method for recycling surplus steel from high-quality automotive sheet casting according to claim 1, characterized in that, The automotive sheet contains Ti by weight > 0.02% and P by weight > 0.015%.