Recycling method of steel billet block

Abstract

The invention relates to the technical field of metal recovery, in particular to a steel billet block recycling method. The steel billet block recycling method comprises the following steps that S1, a crane and a hoisting tool are used for hoisting steel billet blocks into a steel ladle, and the steel billet blocks obliquely lean against the ladle wall of the steel ladle; s2, preheating the steel ladle until the steel ladle is red; (S3); and high-temperature molten steel with the same steel type as the steel billet is injected into the steel ladle, so that the steel billet is heated and melted in the molten steel. According to the recycling method of the steel billet, the oxidation period is avoided, the steel billet is molten in the steel ladle, oxidation burning loss of precious alloy elements such as manganese is thoroughly avoided, the yield is improved, a large amount of alloy cost is saved, and due to the fact that new MnO is not generated, consumption of silicon iron used for reducing MnO is saved, and the smelting period is shortened.

Description

Technical Field

[0001] This invention relates to the field of metal recycling technology, and more specifically to a method for recycling steel billets. Background Technology

[0002] In the continuous casting process of stainless steel slabs, there are many defects at the head and tail, which usually need to be removed. Specifically, in each casting, a 3-4.5 meter billet head needs to be removed from the head and a 1-1.5 meter long billet tail needs to be removed from the tail. Then the long billet head is cut into short steel billet blocks of 1-1.2 meters.

[0003] Currently, these steel billet blocks (bill tails and short billet blocks cut from billet heads) need to be fed into the AOD furnace for recycling via a hopper. However, this recycling method causes the metallic Mn in the steel billet blocks to be oxidized during the oxidation period, resulting in a low yield (the yield depends on the Mn content of different steel grades; for example, the Mn content of 200 series steel is above 9%, and the Mn content of 304 steel is 0.75%). The reasons for the low yield are as follows: The AOD furnace (argon-oxygen decarburization furnace) mainly includes an oxidation period and a reduction period in the stainless steel smelting process. When the steel billet blocks... When adding steel to an AOD furnace via a hopper, it is usually done during the oxidation period. During this period, oxygen or an oxygen-argon mixture is blown into the furnace to remove carbon and other impurities (such as silicon and phosphorus) from the molten steel. However, this oxidizing atmosphere also causes alloying elements to be oxidized, especially manganese (Mn). Because manganese has high chemical reactivity, it easily reacts with oxygen to form manganese oxide (MnO) and enters the slag. The oxidation loss of Mn directly causes the steel composition to deviate from the target value, requiring the addition of ferromanganese alloy to adjust the composition. This increases the raw material cost and reduces the yield. Summary of the Invention

[0004] (a) The problem to be solved by the present invention is that the yield of existing methods for recycling stainless steel billets in an AOD furnace is low.

[0005] (II) Technical Solution A method for recycling steel billets includes the following steps: S1: Use cranes and hoisting equipment to lift the steel billet into the ladle, and tilt the steel billet against the ladle wall; S2: Preheat the ladle until it turns red; S3; High-temperature molten steel of the same grade as the billet is poured into the ladle, causing the billet to heat up and melt in the molten steel.

[0006] According to one embodiment of the present invention, the method further includes step S4, which is to move the ladle to the LF furnace station and heat and refine the molten steel in the ladle so that the billet is completely integrated into the molten steel.

[0007] According to an embodiment of the present invention, step S1 includes: S101: Weld a U-shaped hook to the middle position on one side of the steel billet, 100mm-300mm from the edge; S102: Press both ends of a 20-25mm diameter steel wire rope into hanging loops and install a lock buckle in the middle of the steel wire rope; S103: Attach the two wire rope loops to the crane lifting hook and attach the lock to the U-shaped hook; S104: The overhead crane lifts the steel billet and moves it above the ladle; S105: Instruct the crane to lower the steel billet so that the billet tilts and leans against the wall of the ladle.

[0008] According to one embodiment of the present invention, step S101 further includes: removing oxide scale from the surface of the steel billet.

[0009] According to one embodiment of the present invention, the temperature of the molten steel in step S3 is 1550℃-1650℃.

[0010] According to one embodiment of the present invention, in step S2, the temperature of the steel-filled red envelope is not lower than 800°C.

[0011] According to one embodiment of the present invention, the heating and refining of the molten steel in the ladle in step S4 includes: S401: The electric arc heating function of the LF furnace is used to raise the temperature of the molten steel in the ladle until the temperature of the molten steel reaches 1580℃ ~ 1620℃; S402; By using the argon blowing and stirring function of the LF furnace, inclusions such as oxides on the surface of the steel billet are floated up and removed, ensuring the purity of the molten steel.

[0012] The beneficial effects of this invention are: The method for recycling steel billets has at least the following advantages compared to the previous method of recycling steel billets in an AOD furnace: First, the atmosphere in the ladle and LF furnace is reducing or neutral with low oxygen partial pressure. The oxidation reaction of manganese will not occur spontaneously under low oxygen partial pressure, thus avoiding the oxidation and burn-off of precious alloying elements such as manganese, making the recovery rate close to 100% and improving the yield.

[0013] Secondly, in the method of recovering steel billets using an AOD furnace, cold material needs to be added to the AOD furnace. During the reduction period in the AOD furnace, ferrosilicon is usually added to reduce the oxidized manganese. However, this recycling method does not require the addition of cold material to the AOD furnace, shortening the smelting time. Since no new MnO is generated, it also saves the consumption of ferrosilicon (Si-Fe) used to reduce MnO.

[0014] Third, the composition of the steel billet is highly consistent with that of the molten steel. Its addition does not affect the stability of the chemical composition of the molten steel. Through the argon blowing and stirring function of the LF furnace, inclusions such as oxides on the surface of the steel billet are floated up and removed, ensuring the purity of the molten steel and making the product quality more stable. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 A flowchart illustrating a method for recycling steel billets provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a crane lowering a steel billet into a ladle, provided in an embodiment of the present invention.

[0017] Icons: 1. Ladle; 2. Crane; 201. Crane lifting hook; 3. Steel billet; 4. Wire rope. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0019] like Figure 1 As shown, one embodiment of the present invention provides a method for recycling steel billets, comprising the following steps: S1: Use the overhead crane 2 and hoisting tools to hoist the steel billet 3 into the ladle 1, and make the steel billet 3 lean against the ladle wall of the ladle 1 at an angle; S2: Preheat ladle 1 until ladle 1 turns red; S3; High-temperature molten steel of the same grade as billet 3 is poured into ladle 1, causing billet 3 to heat up and melt in the molten steel. It should be noted that billet 3 is already a continuously cast product, and its chemical composition is very close to that of molten steel of the same grade. Directly adding it to ladle 1 will not introduce foreign elements or disrupt the composition balance of the molten steel, reducing the need for alloy additives to adjust the composition and lowering costs.

[0020] Secondly, the billet 3 is surrounded by molten steel in all directions, and is rapidly heated and melted through efficient heat conduction and convection. This environment is reducing or neutral, which perfectly avoids the oxidation period of the AOD furnace, thus ensuring that easily oxidized elements such as manganese (Mn) in the billet 3 are not burned off, and the recovery rate is close to 100%.

[0021] S4: Move ladle 1 to the LF furnace station, heat and refine the molten steel in ladle 1, so that billet 3 is completely integrated into the molten steel.

[0022] The recycling method for this steel billet involves directly placing the steel billet 3 into the ladle 1, and then pouring high-temperature molten steel of the same grade as the steel billet 3 into the ladle 1. At this point, the molten steel has already undergone the oxidation period and entered the refining stage in a reducing or neutral atmosphere. The ladle 1 is usually filled with argon gas for stirring (to homogenize the composition and temperature), but argon is an inert gas and will not cause oxidation. Secondly, the steel billet 3 is immersed and melted in the ladle 1 at a high temperature of 1550°C-1650°C. The molten steel itself is a liquid metal, and its surface has a protective slag or inert atmosphere to prevent air contact. Therefore, the steel billet 3 is in a reducing or neutral environment during the melting process, and manganese will not be oxidized. Finally, the ladle 1 containing molten steel is then fed into the LF furnace (Ladle 1 refining furnace). The main function of the LF furnace is to raise the temperature and remove inclusions. The LF furnace usually uses a reducing atmosphere (such as argon protection or the addition of reducing agents) to further ensure that manganese is not oxidized. After the billet 3 is melted, its composition is mixed with the molten steel. Since the composition is similar, it will not cause composition fluctuations.

[0023] That is, by avoiding the oxidation period, the steel billet 3 is melted in the ladle 1, which completely avoids the oxidation and burning loss of precious alloying elements such as manganese, making the recovery rate close to 100%, improving the yield, saving a lot of alloy costs. Since no new MnO is generated, the consumption of ferrosilicon used to reduce MnO is also saved, and the smelting cycle is shortened.

[0024] In this embodiment, step S1 specifically includes: S101: removing oxide scale from the surface of the steel billet 3 to reduce the introduction of inclusions from the source.

[0025] S102: Weld a U-shaped round steel hook with a diameter of 20-25mm to the center of one side of the billet 3, 100mm-300mm from the edge. This step aims to provide a standardized connection point, avoiding potential safety hazards such as slippage and tilting that might occur when directly binding the billet 3 with wire rope 4. It should be noted that the welding point of the U-shaped hook is sufficiently far from the edge of the billet 3 to help maintain its balance and stability during hoisting, laying the foundation for subsequent "tilted" placement within the ladle 1. Furthermore, the U-shaped hook must be welded fully and firmly to ensure it can withstand the weight of the billet 3 and the impact during hoisting.

[0026] S103: Press the two ends of the 20-25mm diameter steel wire rope 4 into hanging loops, and install a spiral lock in the middle of the steel wire rope 4. The steel wire rope 4 can be put in and taken out by turning the bolt on the spiral lock.

[0027] S104: Attach the two wire rope 4 hanging rings to the lifting hook of the crane 2, and attach the lock to the U-shaped hook; the lock design allows the operator to quickly connect and disconnect from the U-shaped hook on the ground, improving operational safety and work efficiency.

[0028] S105: The overhead crane 2 lifts the steel billet 3 and moves it above the ladle 1; S106: The crane 2 lowers the steel billet 3 so that it leans against the ladle wall of the ladle 1 at an angle. It should be noted that the purpose of placing the steel billet 3 at an angle is: the angled position allows the steel billet 3 to contact the high-temperature molten steel with the maximum surface area, resulting in the highest heat transfer efficiency and a rapid acceleration of the melting process; by making it stand stably against the ladle wall, it effectively avoids serious accidents that might occur if it were laid flat at the bottom of the ladle, such as clogging the argon gas permeable bricks or the drain outlet, thus ensuring the smooth operation of subsequent refining and continuous casting processes.

[0029] It should be noted that the amount of steel billet 3 added to ladle 1 should not be too large, generally within 5 tons, otherwise it may cause a significant drop in the temperature of the molten steel, resulting in a longer heating time in the LF furnace and affecting the production rhythm.

[0030] In this method, by controlling the amount added (generally within 5 tons) and using an LF furnace to quickly heat the molten steel to the target temperature, the temperature loss is effectively compensated and the production rhythm is basically not affected.

[0031] In this embodiment, step S2 specifically includes: lowering the burner of the ladle 1 baking device to near the opening of the ladle 1, then igniting it and heating the ladle 1 for a long time and evenly with a specific heating curve, so that the overall temperature of the refractory material lining the ladle 1 is raised to above 800°C, making it a "red envelope" full of heat energy.

[0032] In this step, the inner lining of the ladle 1 is preheated to a high temperature of over 800°C. This way, when the molten steel is poured in, the ladle 1 itself hardly absorbs the heat of the molten steel. This preserves the initial heat energy of the molten steel to the maximum extent, providing sufficient heat margin for melting the cold steel billet 3. It can also avoid the problem of thermal stress damage to the inner lining of the ladle 1 caused by instantaneous contact with high-temperature molten steel, thereby extending the service life of the ladle 1.

[0033] In some embodiments, the temperature of the molten steel in step S3 is 1550°C-1650°C, preferably 1650°C.

[0034] In this embodiment, step S4, which involves heating and refining the molten steel in ladle 1, includes: S401: The electric arc heating function of the LF furnace is used to raise the temperature of the molten steel in the ladle 1 until the temperature of the molten steel reaches 1580℃ ~ 1620℃, preferably 1620℃; that is, the electric arc heating function of the LF furnace is used to accurately and quickly compensate for the temperature drop of the molten steel caused by the addition of cold steel billet 3, so that it reaches the temperature required for continuous casting.

[0035] S402: By using the argon blowing and stirring function of the LF furnace, inclusions such as oxides on the surface of the steel billet 3 are floated up and removed, ensuring the purity of the molten steel.

[0036] It should be noted that the LF furnace (Ladle 1 refining furnace) is an intermediate processing station used after tapping and before continuous casting to perform final temperature and composition "fine-tuning" and "purification" of the molten steel. The top of the LF furnace typically has three large graphite electrodes. When energized, these electrodes generate a strong electric arc, directly heating the molten steel in Ladle 1 to precisely control its temperature. The bottom of Ladle 1 has permeable bricks that allow inert argon gas to be blown into the molten steel. As the argon gas bubbles rise, they maintain a consistent temperature and alloy composition throughout the molten steel and lift tiny, non-metallic impurities (such as oxides and sulfides) to the top slag, thus purifying the steel.

[0037] In summary, the recycling method for this steel billet has the following steps: The first step is to remove the oxide scale from the surface of the steel billet 3 to reduce the introduction of inclusions from the source.

[0038] The second step is to weld a round steel U-shaped hook with a diameter of 20-25mm at the middle position 100mm-300mm away from the edge on one side of the steel billet 3.

[0039] The third step is to press the two ends of the 20-25mm diameter steel wire rope 4 into hanging loops, and install a spiral lock in the middle of the steel wire rope 4.

[0040] The fourth step is to attach the two wire rope loops to the crane lifting hook 201 and attach the lock to the U-shaped hook.

[0041] Fifth step: Use crane 2 to lift the steel billet 3 and move it above the ladle 1.

[0042] Step 6: Direct the crane 2 to lower the steel billet 3 so that the steel billet 3 tilts and leans against the wall of the ladle 1, achieving the desired effect. Figure 2 The state shown.

[0043] Step 7: Lower the burner of the ladle 1 heater to near the ladle 1 opening, then ignite it and heat the ladle 1 evenly with a specific heating curve, so that the overall temperature of the refractory material lining the ladle 1 is raised to above 800°C.

[0044] Step 8: Pour high-temperature molten steel (1650°C) of the same steel grade as billet 3 into ladle 1, so that billet 3 heats up and melts in the molten steel.

[0045] Step 9: Move ladle 1 to the LF furnace station and use the electric arc heating function of the LF furnace to heat the molten steel in ladle 1 until the temperature of the molten steel reaches 1580℃ ~ 1620℃. Through the argon blowing and stirring function of the LF furnace, the inclusions such as oxides on the surface of the billet 3 are floated up and removed to ensure the purity of the molten steel.

[0046] It is evident that this method of recycling steel billets has at least the following advantages compared to the previous method of recycling steel billets in an AOD furnace: First, in the ladle 1 and LF furnace, the atmosphere is reducing or neutral with a low oxygen partial pressure. The oxidation reaction of manganese will not occur spontaneously under low oxygen partial pressure, thus avoiding the oxidation and burn-off of precious alloying elements such as manganese, making the recovery rate close to 100% and improving the yield.

[0047] Secondly, in the method of recovering steel billets using an AOD furnace, cold material needs to be added to the AOD furnace. During the reduction period in the AOD furnace, ferrosilicon is usually added to reduce the oxidized manganese. However, this recycling method does not require the addition of cold material to the AOD furnace, shortening the smelting time. Since no new MnO is generated, it also saves the consumption of ferrosilicon (Si-Fe) used to reduce MnO.

[0048] Third, the composition of billet 3 is highly consistent with that of molten steel. Its addition does not affect the stability of the chemical composition of molten steel. Through the argon blowing and stirring function of the LF furnace, inclusions such as oxides on the surface of billet 3 are floated up and removed, ensuring the purity of molten steel and making the product quality more stable.

[0049] In the description of this invention, it should be noted that the terms "upper" and "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, 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, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0050] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recycling a steel compact, characterized by, It comprises the following steps: S1: using the crane and lifting tools to hoist the steel billet into the ladle, and make the steel billet lean against the ladle wall; S2: preheat the ladle until the ladle is red; S3: inject high-temperature molten steel of the same steel grade as the steel billet into the ladle, so that the steel billet is heated and melted in the molten steel.

2. The method for recycling a steel compact according to claim 1, characterized by, It also comprises S4 step, which is: moving the ladle to the LF furnace station, heating and refining the molten steel in the ladle, so that the steel billet is completely melted into the molten steel.

3. A method of recycling a steel compact according to claim 2, characterized in that, The S1 step comprises: S101: weld a U-shaped hook at the middle position of the steel billet, 100-300 mm away from the edge; S102: press the two ends of the steel wire rope with a diameter of 20-25 mm into a hanging ring, and install a lock at the middle position of the steel wire rope; S103: hang the two steel wire rope hanging rings on the crane lifting hook, and hang the lock on the U-shaped hook; S104: the crane hoists the steel billet and moves it above the ladle; S105: instruct the crane to lower the steel billet so that it leans against the ladle wall.

4. The method for recycling a steel compact according to claim 1, characterized by, The S101 step further comprises: removing the surface scale of the steel billet.

5. The method for recycling a steel compact according to claim 1, wherein The temperature of the high-temperature molten steel in the S3 step is 1550-1650℃.

6. The method for recycling a steel compact according to claim 1, wherein In the S2 step, the temperature of the red ladle is not lower than 800℃.

7. The method for recycling a steel compact according to claim 2, wherein The S4 step of heating and refining the molten steel in the ladle comprises: S401: use the electric arc heating function of the LF furnace to heat the molten steel in the ladle until the temperature of the molten steel reaches 1580-1620℃; S402: use the argon blowing and stirring function of the LF furnace to remove the inclusions brought by the melting of the surface oxides of the steel billet, and ensure the purity of the molten steel.

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