Small square billet sulfur-containing titanium-containing welding wire steel and preparation method thereof

Abstract

The invention relates to small square billet sulfur-containing titanium-containing welding wire steel and a preparation method thereof, and belongs to the technical field of steelmaking. Which comprises a converter smelting procedure, a refining procedure and a continuous casting procedure, and specifically comprises the following steps: in the converter smelting procedure, deoxidizing and alloying aluminum blocks, silicon iron and silicon manganese for tapping, adding lime for pre-slagging, and controlling the total mass content of FeO and MnO in slag to be less than or equal to 2.5% after tapping is finished; in the refining process, lime, calcium carbide and aluminum particles are added for slagging and diffusion deoxidation, after slagging is finished, the basicity of slag is controlled to be 2.5-3.0, the total mass content of FeO and MnO in the slag is smaller than or equal to 0.5%, the total oxygen content of molten steel is smaller than or equal to 10 ppm, and a sulfur line and a titanium line are accurately fed; in the continuous casting process, a stopper shaking method is adopted to control gathering of inclusions at the head of a stopper and the bowl of a water gap, and the alkalinity of casting powder is controlled to be 0.85-0.95. The invention also discloses the sulfur-containing titanium-containing welding wire steel prepared by the method. The problems of slag inclusion, middle cracks, nozzle nodulation and the like on the surface of the small square billet sulfur-containing titanium-containing welding wire steel are solved.

Description

Technical Field

[0001] The present invention relates to a small billet sulfur - containing and titanium - containing welding wire steel and a preparation method thereof, belonging to the technical field of steelmaking. Background Art

[0002] Titanium - containing welding wire steel has good cladding property and low spatter property, and has been widely applied and popularized in the field of gas shielded welding. However, due to the high Ti content in this steel grade, a large amount of TiOx is easily generated during the smelting process and accumulates at the head of the stopper rod and the bowl of the tundish nozzle. When using small billet casting, the problem of nozzle caking is relatively prominent, seriously affecting the smooth progress of continuous casting.

[0003] The patent application with the publication number CN104259414A provides a production method of titanium - containing welding wire steel for reducing continuous casting nozzle caking. By establishing the thermodynamic boundary conditions of aluminum - titanium competitive oxidation, controlling the oxygen activity in the steel, controlling the aluminum and titanium contents, determining the titanium - nitrogen product, selecting the nozzle refractories and tundish covering flux, and controlling the continuous casting process parameters, the nozzle caking of titanium - containing welding wire steel is reduced. However, this method does not fundamentally solve the problem that small - sized inclusions are easy to accumulate at the head of the small billet stopper rod and the bowl of the tundish nozzle, and the control measures for the oxygen content, nitrogen content, aluminum content and calcium content in the steel are not clear.

[0004] The patent with the publication number CN115351458B provides a steel for submerged arc welding wire, wire rod, submerged arc welding wire and a preparation method thereof. By calcium treatment, the oxygen content in the steel is reduced, and then the content of aluminum and titanium oxides in the molten steel is reduced, thereby improving the nozzle caking of Al2O3 and TiOx types. However, this method ignores the secondary oxidation of the molten steel caused during the calcium treatment process and the problem of calcium sulfide and calcium titanate caking generated by the calcium treatment of sulfur - containing and titanium - containing welding wire steel.

[0005] In the existing public technologies, there is no relatively good method to solve the problem of nozzle caking during the casting process of small billet sulfur - containing and titanium - containing welding wire steel, and the surface quality and internal quality of the cast billet are often ignored. To solve the above problems, the present invention provides a small billet sulfur - containing and titanium - containing welding wire steel and a preparation method thereof, providing technical support for the production of small billet sulfur - containing and titanium - containing welding wire steel. Summary of the Invention

[0006] In order to solve the above - mentioned existing problems, the present invention discloses a small billet sulfur - containing and titanium - containing welding wire steel and a preparation method thereof. The specific technical solutions are as follows: A preparation method of a small billet sulfur - containing and titanium - containing welding wire steel, including a converter smelting process, a refining process and a continuous casting process, specifically: In the converter smelting process, during tapping, aluminum blocks, ferrosilicon and silicomanganese are used for deoxidation alloying, lime is added for pre - slagging, the bottom - blowing flow rate is controlled at 1000 - 1500 NL / min, and after tapping, the total mass content of FeO and MnO in the slag is controlled ≤2.5%; In the refining process, lime, calcium carbide and aluminum pellets are added for slag formation and diffusion deoxidation. After the slag formation is completed, the basicity of the slag is controlled at 2.5 - 3.0, the total mass content of FeO and MnO in the slag is ≤ 0.5%, and the total oxygen content of the molten steel is ≤ 10 ppm. When refining for 23 - 27 minutes, above the argon blowing point, 1100 - 1300 m of titanium wire is fed. After an interval of 8 - 10 minutes, sulfur wire is fed. When [S] ≤ 30 ppm, 80 - 100 m of sulfur wire is fed. When 30 ppm < [S] ≤ 60 ppm, 40 - 80 m of sulfur wire is fed. The feeding speeds of the titanium wire and sulfur wire are controlled at 200 - 300 m / min, and the bottom blowing flow rate during wire feeding is 100 - 200 NL; In the continuous casting process, the stopper jitter method is used to control the accumulation of inclusions at the head of the stopper and the nozzle bowl of the tundish. The basicity of the mold powder is controlled between 0.85 - 0.95, TiO2 is controlled between 3% - 4%, and the viscosity is controlled between 1.0 - 1.1 Pa·S. The distance between the inner and outer arc nozzles and the left and right side arc nozzles at the same height in the secondary cooling zones 1 and 2 is controlled between 386 ± 0.2 mm, and the distance between the inner and outer arc nozzles and the left and right side arc nozzles at the same height in the secondary cooling zones 3 and 4 is controlled between 364 ± 0.2 mm.

[0007] Furthermore, in the converter smelting process, the tapping volume of the converter is 130 - 140 t. When 30 t of steel is tapped, aluminum blocks, ferrosilicon and silicomanganese are added in sequence for deoxidation alloying. Among them, the aluminum blocks are 60 - 80 kg, the ferrosilicon is 900 - 1000 kg, and the silicomanganese is 800 - 900 kg. When 80 t of steel is tapped, 300 - 400 kg of lime is added for pre - slag formation, and the molten steel is mixed and the bottom blowing flow rate is increased simultaneously for slag - metal stirring.

[0008] Furthermore, in the refining process, the slag composition by mass percentage includes CaO: 59 - 62%, SiO2: 19 - 24%, Al2O3: 5 - 14%, MgO: 4 - 6%, (FeO + MnO) ≤ 0.5%, and the rest are inevitable impurities.

[0009] Furthermore, in the refining process, soft stirring starts 15 - 18 minutes after the titanium wire is fed, and the soft stirring time is 10 - 12 minutes.

[0010] Furthermore, in the continuous casting process, the cross - section of the continuous casting billet is 140 mm × 140 mm, the continuous casting pulling speed is controlled between 2.5 - 2.6 m / min, and the superheat of the tundish is 45 - 55 °C.

[0011] Further, in the continuous casting process, a pre-melted high-alkalinity covering flux with an alkalinity of 6-8 is used in the tundish, and the stopper rod is vibrated. When the loss of [Ti] in the molten steel is ≤200 ppm, the increased amplitude of the stopper rod vibration is 0.2 mm, and the vibration frequency is 3 times per second. When the loss of [Ti] in the molten steel is >200 ppm, the increased amplitude of the stopper rod vibration is 0.3 mm, and the vibration frequency is 5 times per second.

[0012] Further, in the continuous casting process, the composition of the mold powder includes, by mass percentage, SiO2: 34-35%, CaO: 29-33%, MgO: 0.9-1.0%, TiO2: 3-4%, Fe2O3: 1.0-1.1%, Al2O3: 7-8%, F ~ : 3-4%, C: 13-14, moisture content ≤0.5%, and the balance is inevitable impurities.

[0013] A sulfur- and titanium-containing welding wire steel obtained by the preparation method of the above-mentioned small billet sulfur- and titanium-containing welding wire steel.

[0014] Further, the finished product composition of the sulfur- and titanium-containing welding wire steel includes, by mass percentage, C: 0.055-0.085%, Si: 0.75-0.85%, Mn: 1.44-1.54%, Ti: 0.16-0.21%, Al: 0.008-0.01%, P≤0.015%, S: 0.006-0.017%, Ca≤0.0012%, and the rest is Fe and other inevitable impurities.

[0015] The technical principle of the present invention is: During the tapping process of the converter, aluminum blocks, ferrosilicon, silicomanganese, and lime are added for deoxidation alloying and slag formation, which can not only control the total oxygen content of the molten steel but also reduce the oxidability of the slag. When tapping, the mixing of the molten steel is used to increase the bottom blowing flow rate at the same time, enhancing the mixing and stirring between the slag and the metal, which is beneficial to removing a large amount of non-metallic inclusions through slag washing.

[0016] In the refining process, the total oxygen content in the steel is controlled by increasing the slag alkalinity, and calcium carbide and aluminum particles are spread on the slag surface for diffusion deoxidation. During the process, it is inevitable to reduce the sulfur in the steel to a relatively low level. Therefore, it is necessary to feed the sulfur wire in the middle and later stages of refining to meet the composition requirements. Precise control of the wire feeding speed and wire feeding timing can not only reduce the secondary oxidation of the molten steel but also ensure sufficient floating time for inclusions.

[0017] In the continuous casting process, the stopper shaking technology is adopted to control the accumulation of inclusions at the nozzle bowl and the stopper head, and the viscosity of the mold powder is increased to reduce the influence of stopper shaking on the liquid level fluctuation. By increasing the basicity and TiO₂ content of the mold powder, the reaction between SiO₂ in the mold powder and Ti element in the molten steel is inhibited. Increasing the superheat of the tundish is beneficial to the melting of the mold powder and the reduction of TiN precipitation. Increasing the distance between the nozzle in the secondary cooling zone and the billet surface can avoid strong cooling on the surface and in the center, which is beneficial to reducing the generation of intermediate cracks.

[0018] The beneficial effects of the present invention are as follows: By optimizing the deoxidizer and deoxidizing slag-making method, the total oxygen content in the steel is controlled, and the number of inclusions is reduced.

[0019] The present invention accurately controls the wire feeding speed and wire feeding timing, reduces the secondary oxidation of the molten steel, and ensures sufficient floating time for inclusions.

[0020] The present invention adopts the stopper shaking technology to control the accumulation of inclusions at the stopper head and the nozzle bowl, and avoid nozzle clogging.

[0021] The present invention optimizes the composition of the mold powder, reduces the influence of stopper shaking on the liquid level fluctuation, and inhibits the slag-metal reaction.

[0022] The present invention optimizes the position of the secondary cooling nozzle, which is beneficial to the uniform cooling of the billet, thereby controlling intermediate cracks.

[0023] In summary, the present invention solves the problems of surface slag inclusion, intermediate cracks and nozzle clogging in small billet sulfur-containing and titanium-containing welding wire steel. Specific Embodiments

[0024] The following combines specific embodiments to further clarify the present invention. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0025] Four specific embodiments of the present invention are given below. The production method includes converter smelting, LF refining and continuous casting processes. The specific process steps are as follows: In the converter process, during tapping, aluminum blocks, ferrosilicon and silicomanganese are used for deoxidizing alloying, lime is added for pre-slag making, the bottom blowing flow rate is controlled at 1000 - 1500 NL / min, and after tapping, (FeO + MnO) in the slag is controlled ≤ 2.5%; the tapping amount of the converter is 130 - 140 t. When 30 t of steel is tapped, aluminum blocks, ferrosilicon and silicomanganese are added in sequence for deoxidizing alloying, where the aluminum blocks are 60 - 80 kg, the ferrosilicon is 900 - 1000 kg, and the silicomanganese is 800 - 900 kg. When 80 t of steel is tapped, 300 - 400 kg of lime is added for pre-slag making, and the molten steel is mixed and flushed while increasing the bottom blowing flow rate for slag-metal stirring. The data of specific embodiments 1 - 4 are shown in Table 1 below.

[0026] The tapping volume of the converter is 130t. When 30t of steel is tapped, 60kg of aluminum ingots, 900kg of ferrosilicon, and 800kg of silicomanganese are added for deoxidation alloying. When 80t of steel is tapped, 300kg of lime is added for pre-slag making, and the molten steel is mixed and the bottom blowing flow rate is increased simultaneously for slag-metal stirring. During the tapping of the converter, the bottom blowing flow rate is controlled at 1000 - 1500NL / min, and the content of (FeO + MnO) in the slag after tapping is 2.5%.

[0027] Table 1

[0028] In the refining process, lime, calcium carbide, and aluminum pellets are added for slag making and diffusion deoxidation. After the slag making is completed, the slag basicity is controlled at 2.5 - 3.0, the content of (FeO + MnO) in the slag ≤ 0.5%, and the total oxygen content of the molten steel ≤ 10ppm. According to the sulfur and titanium contents of the second refining sample, sulfur wire and titanium wire are accurately fed, and the wire feeding speed is controlled at 200 - 300m / min. The bottom blowing flow rate during wire feeding is 100 - 200NL; the slag composition by mass percentage includes CaO: 59 - 62%, SiO2: 19 - 24%, Al2O3: 5 - 14%, MgO: 4 - 6%, (FeO + MnO) ≤ 0.5%, and the rest are other inevitable impurities. Soft stirring starts 15 - 18 minutes after feeding the titanium wire, and the soft stirring time is 10 - 12 minutes. The data of Specific Examples 1 - 4 are as shown in Table 2 below.

[0029] Table 2

[0030] In the continuous casting process, the stopper shaking technology is adopted to control the aggregation of inclusions at the head of the stopper and the nozzle bowl of the tundish. The increase in the shaking amplitude is 0.2mm, and the shaking frequency is 3 times per second. The basicity of the mold powder is controlled at 0.85, TiO2 is controlled at 3%, and the viscosity is controlled at 1.0Pa·S. The mold powder composition by mass percentage includes SiO2: 34%, CaO: 29%, MgO: 1.0%, TiO2: 4%, Fe2O3: 1.1%, Al2O3: 8%, F ~ : 4%, C: 14, moisture content: 0.5%, and the rest are inevitable impurities. The inner and outer arc nozzle spacing and the left and right arc nozzle spacing at the same height in the first and second cooling zones are controlled at 385.8mm, and the inner and outer arc nozzle spacing and the left and right arc nozzle spacing at the same height in the third and fourth cooling zones are controlled at 363.8mm.

[0031] In the continuous casting process, the stopper shaking method is adopted to control the accumulation of inclusions at the head of the stopper and the nozzle bowl. The basicity of the powder is controlled at 0.85 - 0.95, TiO₂ is controlled at 3% - 4%, and the viscosity is controlled at 1.0 - 1.1 Pa·S. The distance between the inner and outer arc nozzles and the left and right side arc nozzles at the same height in the first and second secondary cooling zones is controlled at 386 ± 0.2 mm, and the distance between the inner and outer arc nozzles and the left and right side arc nozzles at the same height in the third and fourth secondary cooling zones is controlled at 364 ± 0.2 mm. The cross-section of the continuous casting billet is 140 mm × 140 mm, the continuous casting speed is controlled at 2.5 - 2.6 m / min, and the tundish superheat is 45 - 55 °C.

[0032] A tundish covering flux with high basicity is used, and the stopper adopts the shaking method. When the [Ti] loss in the molten steel ≤ 200 ppm, the increased amplitude of the stopper shaking is 0.2 mm, and the shaking frequency is 3 times per second. When the [Ti] loss in the molten steel > 200 ppm, the increased amplitude of the stopper shaking is 0.3 mm, and the shaking frequency is 5 times per second. The composition of the powder includes, by mass percentage: SiO₂: 34 - 35%, CaO: 29 - 33%, MgO: 0.9 - 1.0%, TiO₂: 3 - 4%, Fe₂O₃: 1.0 - 1.1%, Al₂O₃: 7 - 8%, F⁻: 3 - 4%, C: 13 - 14, moisture ≤ 0.5%, and the balance is unavoidable impurities. The data of Specific Examples 1 - 4 are shown in Table 3 below.

[0033] Table 3

[0034] The properties of the molten steel during the preparation process of the methods of Examples 1 - 4 are specifically described below. For details, please refer to Table 4.

[0035] Table 4

[0036] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the field to which this application belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as such here.

[0037] Based on the above ideal embodiments of the present invention as inspiration, through the above description, relevant staff can make various changes and modifications completely within the scope without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A preparation method of small billet sulfur-containing and titanium-containing welding wire steel, characterized in that, It includes a converter smelting process, a refining process, and a continuous casting process, specifically as follows: In the converter smelting process, during tapping, aluminum blocks, ferrosilicon, and silicomanganese are used for deoxidation alloying, lime is added for pre-slagging, the bottom blowing flow rate is controlled at 1000 - 1500 NL / min, and after tapping, the total mass content of FeO and MnO in the slag is controlled to be ≤ 2.5%; In the refining process, lime, calcium carbide, and aluminum pellets are added for slagging and diffusion deoxidation. After slagging, the slag basicity is controlled at 2.5 - 3.0, the total mass content of FeO and MnO in the slag is ≤ 0.5%, and the total oxygen content of the molten steel is ≤ 10 ppm. When refining for 23 - 27 min, above the argon blowing point, 1100 - 1300 m of titanium wire is fed. After an interval of 8 - 10 min, sulfur wire is fed. When [S] ≤ 30 ppm, 80 - 100 m of sulfur wire is fed. When 30 ppm < [S] ≤ 60 ppm, 40 - 80 m of sulfur wire is fed. The feeding speeds of the titanium wire and sulfur wire are controlled at 200 - 300 m / min, and the bottom blowing flow rate during wire feeding is 100 - 200 NL; In the continuous casting process, the stopper jitter method is used to control the accumulation of inclusions at the head of the stopper and the nozzle bowl of the tundish. The basicity of the mold powder is controlled between 0.85 - 0.95, TiO2 is controlled between 3% - 4%, and the viscosity is controlled between 1.0 - 1.1 Pa·S. The distance between the inner and outer arc nozzles and the left and right side arc nozzles at the same height in the secondary cooling zones 1 and 2 is controlled between 386 ± 0.2 mm, and the distance between the inner and outer arc nozzles and the left and right side arc nozzles at the same height in the secondary cooling zones 3 and 4 is controlled between 364 ± 0.2 mm.

2. The preparation method of the small billet sulfur- and titanium-containing welding wire steel according to claim 1, characterized in that, In the converter smelting process described above, the converter tapping volume is 130 - 140 t. When 30 t of steel is tapped, aluminum blocks, ferrosilicon, and silicomanganese are added in sequence for deoxidation alloying, where the aluminum blocks are 60 - 80 kg, the ferrosilicon is 900 - 1000 kg, and the silicomanganese is 800 - 900 kg. When 80 t of steel is tapped, 300 - 400 kg of lime is added for pre-slagging, and the molten steel is mixed and the bottom blowing flow rate is increased simultaneously for slag-metal stirring.

3. The preparation method of the small billet sulfur- and titanium-containing welding wire steel according to claim 1, characterized in that, In the refining process described above, the slag composition by mass percentage includes CaO: 59 - 62%, SiO2: 19 - 24%, Al2O3: 5 - 14%, MgO: 4 - 6%, (FeO + MnO) ≤ 0.5%, and the rest are inevitable impurities.

4. The preparation method of the small billet sulfur-containing and titanium-containing welding wire steel according to claim 1, characterized in that, In the refining process described above, soft stirring starts 15 - 18 min after feeding the titanium wire, and the soft stirring time is 10 - 12 min.

5. The preparation method of the small billet sulfur-containing and titanium-containing welding wire steel according to claim 1, characterized in that, In the continuous casting process described above, the continuous casting billet section is 140 mm × 140 mm, the continuous casting drawing speed is controlled between 2.5 - 2.6 m / min, and the superheat of the tundish is 45 - 55 °C.

6. The preparation method of the small billet sulfur-containing and titanium-containing welding wire steel according to claim 1, characterized in that, In the continuous casting process described above, a pre-melted high-basicity covering agent with a basicity of 6 - 8 is used in the tundish, and the stopper uses the rod shaking method. When the loss of [Ti] in the molten steel ≤ 200 ppm, the increase in the shaking amplitude of the stopper is 0.2 mm, and the shaking frequency is 3 times per second. When the loss of [Ti] in the molten steel > 200 ppm, the increase in the shaking amplitude of the stopper is 0.3 mm, and the shaking frequency is 5 times per second.

7. The preparation method of the small billet sulfur-containing and titanium-containing welding wire steel according to claim 1, characterized in that, In the continuous casting process, the composition of the mold powder includes, by mass percentage, SiO2: 34 - 35%, CaO: 29 - 33%, MgO: 0.9 - 1.0%, TiO2: 3 - 4%, Fe2O3: 1.0 - 1.1%, Al2O3: 7 - 8%, F ~ : 3 - 4%, C: 13 - 14, moisture content ≤ 0.5%, and the balance is inevitable impurities.

8. A sulfur- and titanium-containing welding wire steel obtained by the preparation method of the small billet sulfur- and titanium-containing welding wire steel according to any one of claims 1 to 7.

9. The sulfur- and titanium-containing welding wire steel according to claim 8, characterized in that, The finished product composition of the sulfur- and titanium-containing welding wire steel includes, by mass percentage: C: 0.055 - 0.085%, Si: 0.75 - 0.85%, Mn: 1.44 - 1.54%, Ti: 0.16 - 0.21%, Al: 0.008 - 0.01%, P ≤ 0.015%, S: 0.006 - 0.017%, Ca ≤ 0.0012%, and the balance is Fe and other inevitable impurities.

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