Smelting process for recycling oxide skin

Abstract

The invention discloses a smelting process for reusing oxide skin, relates to the technical field of metallurgy, is reasonable in design, and can effectively solve the problems of resource waste, pollution and difficult recovery of traditional oxide skin treatment. Low-benefit recovery is avoided by screening high-alloy oxide skin meeting the alloy content requirement, such as high-speed tool steel; the smelting efficiency is improved through ball pressing and drying pretreatment; intermediate frequency furnace smelting is combined with furnace rocking and slagging reduction technologies, so that the problems of many oxide skin impurities and difficulty in reduction are solved, and the service life of a furnace lining is prolonged; in the LF and VD refining, the purity of molten steel is improved through precise slag control, deoxidation and vacuum degassing; the whole-course quality control ensures that the recycled molten steel reaches the standard. The resource recycling is realized, and the pollution is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, in particular to a smelting process for recycling oxide scale. Background Art

[0002] The steel processing process typically includes core steps such as heat treatment, forging, rolling, and grinding. During the heat treatment phase, as the steel is heated at high temperatures, a large amount of oxide scale inevitably forms on the surface, directly causing hidden material loss.

[0003] In terms of composition, oxide scale is primarily composed of iron oxides (such as FeO, Fe2O3, and Fe3O4), along with alloying elements such as W, Mo, Cr, and V. However, due to its high proportion of impurities and oxygen content, the recycling and reuse process is relatively complex and technically challenging. Traditional smelters typically sell this type of oxide scale at low prices or simply discard it, which not only wastes valuable metal resources but can also pollute the surrounding environment through dust and leaching if not properly handled. Summary of the Invention

[0004] In response to the problems disclosed in the background technology, the present invention provides a smelting process for recycling oxide scale.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A smelting process for recycling oxide scale, characterized by comprising the following specific process steps:

[0007] Step S1, classification and collection: Classify and recycle the oxide scales of different steel grades, and select the oxide scales of high-alloy steels as the recycled materials for reuse;

[0008] Step S2, pressing the oxide skin into balls: pressing the oxide skin into balls;

[0009] Step S3, drying: baking and drying the spherical oxide skin sphere;

[0010] Step S4, smelting in an intermediate frequency furnace: adding 20% ​​of the rated capacity of the oxidized spheres into the intermediate frequency furnace and smelting them. After they are completely melted, a mixture of the oxidized spheres and the reducing agent is added in batches;

[0011] Step S5, accelerating smelting: adopting the shaking furnace method to accelerate the reaction interface. When shaking the furnace, control the intermediate frequency furnace body to tilt 45°-60°, and repeat 3-5 times so that the molten steel does not flow out of the furnace nozzle to increase the contact interface between the molten steel and the slag;

[0012] Step S6, slag reduction in the intermediate frequency furnace: When the intermediate frequency furnace is charged with more than half of the material and enters the oxidation period, the slag is mostly oxidized slag. At this time, lime is added into the furnace to slag;

[0013] Step S7, refining, stirring and reducing: after the smelting in the medium frequency furnace is completed, a small amount of slag is removed and the molten steel is sampled to detect the element ratio of the molten steel, and alloy is added according to the element ratio for adjustment; after the alloy addition is completed, the molten steel and slag are all poured into the ladle and transferred to the LF furnace for refining and reduction; during the refining and reduction period, argon is continuously stirred, and an appropriate amount of slag is added to balance the slag alkalinity. The slag is replaced after the alkalinity is controlled to be ≥3;

[0014] Step S8, secondary refining and slag reduction: after pouring the slag, re-add slag material and add reducing agent for full deoxidation to ensure the purity of the molten steel;

[0015] Step S9, LF refining thin slag tapping: before tapping after the LF furnace refining is completed, the slag needs to be adjusted to a thin slag state before tapping;

[0016] Step S10, VD vacuum refining: After the ladle is transferred to the VD station after tapping the LF furnace, it is first subjected to a slag skimming process to remove surface slag, and then the vacuum system is activated to evacuate the steel to reduce the N and H contents in the molten steel;

[0017] Step S11, VD soft blowing calming: After the VD vacuuming is completed, the argon flow rate is adjusted to a relatively low state, and the weak stirring effect of the argon gas is used to form a stable convection circulation of the molten steel. At this time, the argon pressure is 0.1-0.2 MPa, and the calming time should be ≥20 min;

[0018] Step S12, quality control: After the VD soft blowing calming process is completed and before LF refining and tapping, the molten steel needs to be tested online to detect the gas content and trace elements therein.

[0019] In the above-mentioned smelting process for recycling oxide scale, the high-alloy oxide scale used as the recycled material is one or more groups of high-speed tool steel oxide scale, powder tool steel oxide scale and high-alloy mold steel oxide scale, and must meet the alloy element content requirements: Mo ≥ 1.0% and Cr ≥ 3.0% and V ≥ 1.0%, or meet any one of the conditions of Mo > 2.0% and V > 2.0%.

[0020] In the above-mentioned smelting process for recycling oxide scale, in step S2, the oxide scale pressed into a spherical shape is spherical and has a diameter of φ≤60mm.

[0021] In the above-mentioned smelting process for recycling oxide scale, in step S3, when the spherical oxide scale spheres are baked and dried, the baking temperature is controlled at 120° C.-150° C. until the moisture content thereof is ≤1%.

[0022] In the above-mentioned smelting process for recycling oxide scale, in step S4 and step S8, the mixture is formed by mixing oxide scale spheres and a reducing agent in proportion, and the reducing agent is added and mixed at a ratio of 100 kg of reducing agent per ton of oxide scale spheres.

[0023] In the above-mentioned smelting process for recycling oxide scale, in step S6, the amount of lime added needs to be adjusted according to the rated capacity of the medium frequency furnace, and is performed in a ratio of (100-150) / 15Kg of lime per ton of rated capacity.

[0024] In the above-mentioned smelting process for recycling oxide scale, the slag material in step S7 and step S8 is a mixture of one or more of lime, fluorite and quartz sand, and in step S7, the argon pressure is controlled at 0.2-0.4 MPa.

[0025] The above-mentioned smelting process for recycling oxide scale, wherein in step S8, the slag material added again after slag pouring is a mixture of lime, fluorite and quartz sand, with a ratio of 35-40:15-20:3-4, and the addition amount is carried out according to the ratio of adding 350-400 kg of lime, 150-200 kg of fluorite and 30-40 kg of quartz sand for every 15 tons of rated capacity; in addition, the reducing agent is added by the following method: Al wire is fed into the molten steel through a wire feeder for deep deoxidation, and the residual Al content is detected to be controlled at 0.08-0.12%, and according to the C and Si contents of the molten steel, C powder and Si powder are added in small amounts and multiple times for diffusion deoxidation.

[0026] In the above-mentioned smelting process for recycling oxide scale, in step S10, when slag removal is performed, the amount of slag removed should be ≥ 2 / 3 of the total slag amount, until the molten steel leaks out of the mirror surface; when vacuuming, the vacuum degree needs to be controlled to be ≤ 30Pa, and the pressure holding time should be ≥ 15min.

[0027] Technical effects and advantages of the present invention:

[0028] The present invention discloses a smelting process for recycling oxide scale, which relates to the field of metallurgy. The present invention has a reasonable design and can effectively solve the resource waste, pollution and recycling difficulties of traditional oxide scale treatment. By screening high-alloy oxide scales that meet the alloy content requirements of high-speed tool steel, such as high-speed tool steel, low-efficiency recycling is avoided; smelting efficiency is improved through ball pressing and drying pretreatment; medium-frequency furnace smelting is combined with furnace shaking and slag reduction technology to solve the problems of excessive oxide scale impurities and difficulty in reduction, while extending the life of the furnace lining; LF and VD refining improve the purity of molten steel through precise slag control, deoxidation and vacuum degassing; full-process quality control ensures that the recycled molten steel meets the standards. This achieves both resource recycling and pollution avoidance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] This embodiment discloses a smelting process for recycling oxide scale, which is characterized by comprising the following specific process steps:

[0032] Step S1, Classification and Collection: The oxide scale of different steel grades is classified and recycled. The oxide scale reduction period requires investment of electricity costs, processing costs and reducing agents. In order to ensure economic benefits, only high-alloy oxide scale is selected as the recycled material for reuse. Low-alloy steel grades are not used due to their low alloy content and negative benefits.

[0033] Step S2, sizing the oxide scale: Since the oxide scale is in granular / powdered form, which is not conducive to melting, in order to improve the energy efficiency of the medium frequency furnace and speed up smelting, the oxide scale is sizing and pressed into a spherical shape;

[0034] Step S3, drying: In order to ensure production safety and accelerate the reaction, the oxide skin balls need to be baked after pressing to ensure dryness, and the spherical oxide skin balls are baked and dried;

[0035] Step S4, smelting in an intermediate frequency furnace: adding 20% ​​of the rated capacity of the oxidized spheres into the intermediate frequency furnace and smelting them. After they are completely melted, a mixture of the oxidized spheres and the reducing agent is added in batches;

[0036] Step S5, accelerating smelting: adopting the shaking furnace method to accelerate the reaction interface. When shaking the furnace, control the intermediate frequency furnace body to tilt 45°-60°, and repeat 3-5 times so that the molten steel does not flow out of the furnace nozzle to increase the contact interface between the molten steel and the slag, thereby improving the smelting efficiency and shortening the smelting cycle;

[0037] Step S6, slag reduction in the intermediate frequency furnace: When the intermediate frequency furnace is charged with more than half of the materials and enters the oxidation period, the slag is mostly oxidized slag. At this time, lime is added to the furnace for slag formation. Lime, as an alkaline slag-forming agent, can react with the acidic components in the oxidized slag, effectively reducing the oxidizability of the slag and thereby improving the reduction effect. In addition, the slag adjusted with lime can reduce the chemical erosion of the refractory materials of the furnace lining, prevent the oxidized slag from continuously reacting with the furnace lining, thereby extending the service life of the furnace lining;

[0038] Step S7, refining, stirring and reducing: in order to ensure the full reduction of alloy elements in the molten steel in the slag, after the intermediate frequency furnace smelting is completed, a small amount of slag is removed and the molten steel is sampled to detect the element ratio of the molten steel, and alloy is added according to the element ratio; after the alloy addition is completed, the molten steel and slag are all poured into the ladle and transferred to the LF furnace for refining and reduction; during the refining and reduction period, argon is continuously stirred, and an appropriate amount of slag is added to balance the slag alkalinity. The slag is replaced after the alkalinity is controlled to be ≥3;

[0039] Step S8, secondary refining and slag reduction: after pouring the slag, re-add slag material and add reducing agent for full deoxidation to ensure the purity of the molten steel;

[0040] Step S9, LF Refining Thin Slag Tapping: After the LF furnace refining is completed and before tapping, the slag needs to be adjusted to a thin slag state before tapping. Thin slag treatment helps reduce the basicity of the slag and ensures the permeability, fluidity, and adsorption properties of the slag, thereby enhancing the adsorption capacity of inclusions in the steel and preventing slag agglomeration from blocking the air permeability channel. At the same time, it also ensures the vacuum chamber evacuation and molten steel degassing effect during subsequent VD vacuum refining.

[0041] Step S10, VD vacuum refining: After the ladle from the LF furnace is transferred to the VD station, it is first skimmed to remove surface scum, and then the vacuum system is activated to evacuate the molten steel to reduce the nitrogen and hydrogen contents in the molten steel. By continuously reducing the pressure in the vacuum tank, gases such as nitrogen and hydrogen dissolved in the molten steel escape due to reduced solubility, driving the molten steel to produce boiling agitation, ultimately achieving an effective reduction in nitrogen and hydrogen contents in the molten steel.

[0042] Step S11, VD soft blowing calming: After the VD vacuuming is completed, the argon flow rate is adjusted to a low state. Through the weak stirring effect of the argon gas, the molten steel forms a stable convection circulation. At this time, the argon pressure is 0.1-0.2 MPa, and the calming time should be ≥ 20 minutes. During this process, the molten steel fluctuates slightly without breaking the slag surface. The fine inclusions in the molten steel are pushed, gradually gathered and floated into the slag, which can effectively avoid the residue of inclusions and further improve the purity of the molten steel.

[0043] Step S12, quality control: After the VD soft blowing calming process is completed and before LF refining and tapping, the molten steel needs to be tested online to detect the gas content and trace elements therein.

[0044] Among them, the high-alloy oxide scale used as the recycled material is one or more groups of high-speed tool steel oxide scale, powder tool steel oxide scale and high-alloy mold steel oxide scale, and must meet the alloy element content requirements: Mo ≥ 1.0% and Cr ≥ 3.0% and V ≥ 1.0%, or meet any of the conditions of Mo > 2.0% and V > 2.0%.

[0045] In step S2, the oxide skin pressed into a spherical shape is spherical and has a diameter of 60 mm or less. In step S3, the spherical oxide skin sphere is baked and dried at a temperature of 120° C. to 150° C. until its moisture content is ≤1%.

[0046] Among them, in step S4 and step S8, the mixture is formed by mixing the oxidized spheres and the reducing agent in proportion. The reducing agent is added and mixed at a ratio of 100 kg of reducing agent per ton of oxidized spheres. The type of reducing agent is formulated according to the element content of the oxidized scale of the selected high-alloy and is formed by mixing powder / wire materials of one or more of C, Si, and Al in proportion.

[0047] Among them, in step S6, the amount of lime added needs to be adjusted according to the rated capacity of the medium frequency furnace, and is performed in a ratio of (100-150) / 15Kg of lime per ton of rated capacity.

[0048] The slag material in step S7 and step S8 is a mixture of one or more of lime, fluorite and quartz sand. In step S7, the argon pressure is controlled at 0.2-0.4 MPa so that the molten steel slightly breaks the slag surface. In addition, the added alloy is adaptively adjusted according to the type of steel to be produced.

[0049] Among them, in step S8, the slag material added again after slag pouring is a mixture of lime, fluorite and quartz sand in a ratio of 35-40:15-20:3-4, and the added amount is based on the ratio of 350-400 kg of lime, 150-200 kg of fluorite and 30-40 kg of quartz sand for every 15 tons of rated capacity; in addition, the reducing agent is added by the following method: Al wire is fed into the molten steel through a wire feeder for deep deoxidation, and the residual Al content is detected to be controlled at 0.08-0.12%, and C powder and Si powder are added in small amounts and multiple times according to the C and Si contents of the molten steel for diffusion deoxidation; in step S10, when performing slag skimming treatment, the skimming amount should be ≥ 2 / 3 of the total slag amount, until the molten steel leaks out of the mirror surface; when vacuuming, the vacuum degree should be controlled to ≤ 30 Pa, and the pressure holding time should be ≥ 15 minutes.

[0050] In the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed or detachable connections, or integration; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific contexts.

[0051] The standard parts used in the present invention can all be purchased from the market, and special-shaped parts can all be customized according to the description and the drawings.

[0052] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A smelting process for recycling oxide scale, characterized in that: The specific process steps include: Step S1, classification and collection: Classify and recycle the oxide scales of different steel grades, and select the oxide scales of high-alloy steels as the recycled materials for reuse; Step S2, pressing the oxide skin into balls: pressing the oxide skin into balls; Step S3, drying: baking and drying the spherical oxide skin sphere; Step S4, smelting in an intermediate frequency furnace: adding 20% ​​of the rated capacity of the oxidized spheres into the intermediate frequency furnace and smelting them. After they are completely melted, a mixture of the oxidized spheres and the reducing agent is added in batches; Step S5, accelerating smelting: adopting the shaking furnace method to accelerate the reaction interface. When shaking the furnace, control the intermediate frequency furnace body to tilt 45°-60°, and repeat 3-5 times so that the molten steel does not flow out of the furnace nozzle to increase the contact interface between the molten steel and the slag; Step S6, slag reduction in the intermediate frequency furnace: When the intermediate frequency furnace is charged with more than half of the material and enters the oxidation period, the slag is mostly oxidized slag. At this time, lime is added into the furnace to slag; Step S7, refining, stirring and reducing: after the smelting in the medium frequency furnace is completed, a small amount of slag is removed and the molten steel is sampled to detect the element ratio of the molten steel, and alloy is added according to the element ratio for adjustment; after the alloy addition is completed, the molten steel and slag are all poured into the ladle and transferred to the LF furnace for refining and reduction; during the refining and reduction period, argon is continuously stirred, and an appropriate amount of slag is added to balance the slag alkalinity. The slag is replaced after the alkalinity is controlled to be ≥3; Step S8, secondary refining and slag reduction: after pouring the slag, re-add slag material and add reducing agent for full deoxidation to ensure the purity of the molten steel; Step S9, LF refining thin slag tapping: before tapping after the LF furnace refining is completed, the slag needs to be adjusted to a thin slag state before tapping; Step S10, VD vacuum refining: After the ladle is transferred to the VD station after tapping the LF furnace, it is first subjected to a slag skimming process to remove surface slag, and then the vacuum system is activated to evacuate the steel to reduce the N and H contents in the molten steel; Step S11, VD soft blowing calming: After the VD vacuuming is completed, the argon flow rate is adjusted to a relatively low state, and the weak stirring effect of the argon gas is used to form a stable convection circulation of the molten steel. At this time, the argon pressure is 0.1-0.2 MPa, and the calming time should be ≥20 min; Step S12, quality control: After the VD soft blowing calming process is completed and before LF refining and tapping, the molten steel needs to be tested online to detect the gas content and trace elements therein.

2. The smelting process for recycling oxide scale according to claim 1, characterized in that: The high-alloy oxide scale used as the recycled material is one or more groups of high-speed tool steel oxide scale, powder tool steel oxide scale and high-alloy mold steel oxide scale, and must meet the alloy element content requirements: Mo ≥ 1.0% and Cr ≥ 3.0% and V ≥ 1.0%, or meet any of the conditions of Mo > 2.0% and V > 2.0%.

3. The smelting process for recycling oxide scale according to claim 1, characterized in that: In step S2, the oxide scale is pressed into a spherical shape, which has a φ≤60 mm.

4. The smelting process for recycling oxide scale according to claim 1, characterized in that: In step S3, the spherical oxide skin spheres are baked and dried at a temperature of 120° C. to 150° C. until the moisture content is ≤1%.

5. The smelting process for recycling oxide scale according to claim 1, characterized in that: In step S4 and step S8, the mixture is formed by mixing the oxidized skin spheres and the reducing agent in proportion, and the reducing agent is added and mixed at a ratio of 100 kg of reducing agent per ton of oxidized skin spheres.

6. The smelting process for recycling oxide scale according to claim 1, characterized in that: In step S6, the amount of lime added needs to be adjusted according to the rated capacity of the medium frequency furnace, and is performed in a ratio of (100-150) / 15 kg of lime per ton of rated capacity.

7. The smelting process for recycling oxide scale according to claim 1, characterized in that: The slag material in step S7 and step S8 is a mixture of one or more of lime, fluorite and quartz sand. In step S7, the argon pressure is controlled at 0.2-0.4 MPa.

8. The smelting process for recycling oxide scale according to claim 1, characterized in that: In step S8, the slag material added again after slag pouring is a mixture of lime, fluorite and quartz sand in a ratio of 35-40:15-20:3-4, and the added amount is carried out according to the ratio of 350-400 kg of lime, 150-200 kg of fluorite and 30-40 kg of quartz sand for every 15 tons of rated capacity. In addition, the reducing agent is added by the following method: Al wire is fed into the molten steel through a wire feeder for deep deoxidation. The residual Al content needs to be controlled at 0.08-0.12%. According to the C and Si contents of the molten steel, C powder and Si powder are added in small amounts and multiple times for diffusion deoxidation.

9. The smelting process for recycling oxide scale according to claim 1, characterized in that: In step S10, when performing slag removal, the amount of slag removed should be ≥ 2 / 3 of the total slag amount, until the molten steel leaks out of the mirror surface; when performing vacuuming, the vacuum degree should be controlled to be ≤ 30 Pa, and the pressure holding time should be ≥ 15 minutes.

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