Control method for solving ER70S-6 casting furnace shrinkage cavity

Abstract

The invention discloses a control method for solving ER70S-6 casting furnace shrinkage cavity, the method comprises the processes of converter primary smelting, LF furnace refining, continuous casting and casting blank inspection, in the continuous casting process, the residual steel amount of a large ladle is controlled to be larger than or equal to 2 t, protective casting is adopted in the whole process, the baking temperature of a tundish is larger than or equal to 1000 DEG C, a crystallizer is used for electromagnetic stirring, and molten steel component and temperature homogenization is promoted; the casting furnace superheat degree is controlled to be 30-45 DEG C, the casting section is 130 * 130mm-180 * 180mm, the casting pulling speed is 2.0 + / -0.1 m / min, the casting specific water flow is controlled to be 1.6 L / kg-2. 4L / kg, and shrinkage cavities are inhibited. According to the method, key process parameters of a continuous casting procedure are optimized, and the problem that shrinkage cavities are prone to being generated in casting blanks of an ER70S-6 steel casting furnace is solved.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical method technology, and specifically relates to a method for controlling shrinkage cavities in the ER70S-6 casting furnace. Background Technology

[0002] Shrinkage cavities are a critical defect in the production of alloy steel welding wire for ER70S-6. Shrinkage cavities disrupt the continuity of the internal material of the casting, creating fractures. This significantly reduces the mechanical properties of the casting, making it prone to cracks, fractures, and other serious problems during use, thus affecting the overall strength and stability of the casting. Summary of the Invention

[0003] The technical problem this invention aims to solve is to address the shortcomings of existing technologies by providing a reasonably designed and easy-to-use method for controlling shrinkage cavities in the ER70S-6 casting furnace during the first casting run. This invention solves the shrinkage problem in the ER70S-6 casting billet during the first casting run without affecting production output or under continuous casting pressure. The continuous casting machine can maintain a casting speed of 2.0±0.1m / min during the first casting run while ensuring the internal quality of the billet.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for controlling shrinkage cavities in the ER70S-6 casting furnace is disclosed. This method includes converter primary refining, LF furnace refining, continuous casting, and billet inspection processes. The key features are: in the continuous casting process, the ladle residual steel amount is controlled to ≥2t; protective casting is employed throughout; the tundish baking temperature is ≥1000℃; and electromagnetic stirring in the crystallizer is used to promote uniformity of steel composition and temperature. The initial superheat in the casting furnace is controlled at 30℃-45℃; the initial casting cross-section is 130×130mm-180×180mm; the initial casting speed is 2.0±0.1m / min; and the initial casting specific water volume is controlled at 1.6L / kg-2.4L / kg to suppress shrinkage cavities.

[0005] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in the continuous casting process, ER70S-6 special protective slag with an alkalinity range of 1.2 to 1.5 is used, and the amount added is 0.2-0.3 kg / ton. The above-mentioned patented protective slag and ER70S-6 are stirred evenly using a crystallizer.

[0006] The technical problem to be solved by the present invention can also be achieved by the following technical solution: the electromagnetic stirring parameters of the crystallizer are 250-300A current and 3-4Hz frequency, which can improve the surface quality of the billet, refine the grains and reduce the inclusions inside the billet.

[0007] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in the continuous casting process, an integrated submersible nozzle is used, and the insertion depth is controlled at 90-110mm, which can promote the stable melting of the protective slag, form a uniform slag layer, and avoid surface defects of the billet caused by slag entrapment.

[0008] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in the LF furnace refining process, the soft blowing argon time is ≥15min to ensure that the inclusions are fully floated.

[0009] The technical problem to be solved by the present invention can also be achieved through the following technical solution: In the continuous casting process, the chemical composition and mass percentage of ER70S-6 used are as follows: C: 0.06~0.10%, Si: 0.80~0.95%, Mn: 1.40~1.60%, P≤0.025%, S≤0.025%, Al≤0.010%, with the balance being Fe and unavoidable impurities. Through the design of this composition system, the requirements of end customers for the strength, welding performance and toughness of gas-shielded welding wire are met.

[0010] The technical problem to be solved by the present invention can also be achieved by the following technical solution: the opening section is controlled at 165mm*165mm, and the opening water volume is controlled at 1.9L / kg.

[0011] The technical problem to be solved by the present invention can also be achieved through the following technical solution: in the primary refining process of the converter, the carbon content at the end point of the converter is controlled at 0.05-0.07%, the steel is tapped with double slag blocking operation, and the slag discharge is ≤0.5kg / t steel, so as to control the oxygen content at the end point and reduce the total amount of inclusions in the steel.

[0012] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in the LF furnace refining process, 3.0-4.0 kg / t steel of steelmaking lime and 1.0-1.5 kg / t steel of ER70S-6 special fluorite are added to make the refining slag reach the target basicity of 2.0±0.1 and the slag-forming effect is good.

[0013] Compared with existing technologies, the method described in this invention aims to solve the problem of shrinkage cavities in ER70S-6 steel billets during the initial casting process by optimizing key process parameters. Its core control steps include: controlling the ladle steel reserve to ≥2t and the tundish baking temperature to ≥1000℃ during the continuous casting process; using a lower superheat for initial casting, controlling the superheat of the molten steel within the range of 30-45℃; controlling the initial casting water volume to 1.9L / kg, utilizing high water volume and high casting speed to create a temperature gradient between the inside and outside of the billet, thus suppressing shrinkage cavities; employing a higher casting speed for initial casting, 2.0±0.1m / min; strictly controlling the liquid level fluctuation in the crystallizer within ±5mm; and using a special protective slag with high basicity (1.2-1.5), while simultaneously applying electromagnetic stirring in the crystallizer (current 250-300A, frequency 3-4Hz).

[0014] The yield of low-magnification shrinkage cavities in products produced using the control method described in the invention has been increased from 60% to 98%, which effectively improves the solidification conditions of the billet, significantly inhibits the formation of central shrinkage cavities, and improves the internal quality and overall yield of the billet in the casting furnace. Attached Figure Description

[0015] Figure 1 To obtain products using current control methods. Figure 1 ; Figure 2 The product obtained by using the control method described in this invention Figure 2 . Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0017] A method for controlling shrinkage cavities in the ER70S-6 casting furnace during initial casting includes converter primary refining, LF furnace refining, continuous casting, and billet inspection processes. (1) In the primary refining process of the converter, the final carbon content of the converter is controlled at 0.05-0.07%, the steel tapping is carried out with double slag blocking, and the slag discharge is ≤0.5kg / t steel; (2) In the LF furnace refining process, 3.0-4.0 kg / t steel of steelmaking lime and 1.0-1.5 kg / t steel of ER70S-6 special fluorite are added, and the soft blowing argon time is ≥15 min to ensure that the inclusions are fully floated. The chemical composition and mass percentage of the ER70S-6 are as follows: C: 0.06-0.10%, Si: 0.80-0.95%, Mn: 1.40-1.60%, P≤0.025%, S≤0.025%, Al≤0.010%, with the balance being Fe and unavoidable impurities. (3) In the continuous casting process, the amount of steel remaining in the ladle is controlled to be ≥2t, protective casting is adopted throughout the process, the tundish baking temperature is ≥1000℃, and ER70S-6 special protective slag with an alkalinity range of 1.2~1.5 is used. The above-mentioned patented protective slag and ER70S-6 are stirred evenly in a crystallizer to promote the homogenization of steel composition and temperature. The electromagnetic stirring parameters of the crystallizer are current 250~300A and frequency 3~4Hz. The superheat of the first casting furnace is controlled to be 30℃-45℃, the first casting cross section is 130×130mm-180×180mm, and 165mm*165mm is further preferred. The first casting speed is 2.0±0.1m / min, and the first casting specific water volume is controlled to be 1.6L / kg-2.4L / kg, and 1.9L / kg is further preferred to suppress shrinkage cavities. Then, an integrated submerged entry nozzle is adopted, and the insertion depth is controlled to be 90~110mm.

[0018] (4) The billet inspection process includes online infrared detection and low-magnification inspection of the billet, real-time monitoring of shrinkage defects and feedback on process compliance, and production of ER70S-6 product.

[0019] The ER70S-6 product manufactured using the control method described in this invention conforms to the standard references GB / T8110 and AWSA5.18. The product performance testing method standard refers to GB / T222, and the low magnification testing standard for cast billets refers to YB / T2011 and YB / T153.

[0020] This invention optimizes the converter blowing endpoint, employs double slag blocking during steel tapping, and reduces the initial oxygen content in the steel. It utilizes an LF furnace for refining, effectively removing large inclusions and significantly improving the overall inclusion content. The invention employs a 165mm*165mm cross-section and an initial casting speed of 2.0±0.1m / min, effectively ensuring the billet temperature. It uses an initial casting water ratio of 1.9L / kg, effectively maintaining the internal and external temperature gradient of the billet and suppressing shrinkage cavities. This invention provides full-process protective casting to prevent secondary oxidation, and uses electric agitation in the crystallizer to promote inclusion flotation.

[0021] Example 1: A method for controlling shrinkage cavities in the ER70S-6 casting furnace during initial casting. This method includes converter primary refining, LF furnace refining, continuous casting, and billet inspection processes. (1) In the primary refining process of the converter, the final carbon content of the converter is controlled at 0.05%, the steel is tapped with double slag blocking operation, and the slag discharge is 0.5 kg / t steel; (2) In the LF furnace refining process, 3.0 kg / t steel of steelmaking lime and 1.0 kg / t steel of ER70S-6 special fluorite were added, and the soft blowing argon time was 15 min to ensure that the inclusions floated up fully. The chemical composition and mass percentage of the ER70S-6 were obtained as follows: C: 0.06~0.10%, Si: 0.80~0.95%, Mn: 1.40~1.60%, P≤0.025%, S≤0.025%, Al≤0.010%, with the balance being Fe and unavoidable impurities. (3) In the continuous casting process, the amount of steel remaining in the ladle is controlled to be 2t, protective casting is adopted throughout the process, the tundish baking temperature is 1000℃, ER70S-6 special protective slag with an alkalinity range of 1.2 is used, and the amount added is 0.2kg / ton. The above-mentioned patented protective slag and ER70S-6 are stirred evenly in a crystallizer to promote the homogenization of steel composition and temperature. The electromagnetic stirring parameters of the crystallizer are 250A current and 3Hz frequency. The superheat of the first casting furnace is controlled at 30℃, the first casting section is 130×130mm, the first casting speed is 1.9m / min, and the first casting water volume is controlled at 1.6L / kg to suppress shrinkage cavities. Then, an integrated submerged entry nozzle is used, and the insertion depth is controlled at 90mm.

[0022] (4) The billet inspection process includes online infrared detection and low-magnification inspection of the billet, real-time monitoring of shrinkage defects and feedback on process compliance, and production of ER70S-6 product.

[0023] Example 2: A method for controlling shrinkage cavities in the ER70S-6 casting furnace during initial casting. This method includes converter primary refining, LF furnace refining, continuous casting, and billet inspection processes. (1) In the primary refining process of the converter, the final carbon content of the converter is controlled at 0.07%, the steel is tapped with double slag blocking operation, and the slag discharge is 0.1 kg / t steel; (2) In the LF furnace refining process, 4.0 kg / t steel of steelmaking lime and 1.5 kg / t steel of ER70S-6 special fluorite were added, and the soft blowing argon time was 17 min to ensure that the inclusions floated up fully. The chemical composition and mass percentage of the ER70S-6 were obtained as follows: C: 0.06~0.10%, Si: 0.80~0.95%, Mn: 1.40~1.60%, P≤0.025%, S≤0.025%, Al≤0.010%, with the balance being Fe and unavoidable impurities. (3) In the continuous casting process, the amount of steel remaining in the ladle is controlled to be 3t, protective casting is adopted throughout the process, the tundish baking temperature is 1050℃, ER70S-6 special protective slag with an alkalinity range of 1.5 is used, and the amount added is 0.3kg / ton. The above-mentioned patented protective slag and ER70S-6 are stirred evenly in a crystallizer to promote the homogenization of steel composition and temperature. The electromagnetic stirring parameters of the crystallizer are 300A current and 4Hz frequency. The superheat of the first casting furnace is controlled at 45℃, the first casting section is 180×180mm, the first casting speed is 2.1m / min, and the first casting water volume is controlled at 2.4L / kg to suppress shrinkage cavities. Then, an integrated submerged entry nozzle is used, and the insertion depth is controlled at 110mm.

[0024] (4) The billet inspection process includes online infrared detection and low-magnification inspection of the billet, real-time monitoring of shrinkage defects and feedback on process compliance, and production of ER70S-6 product.

[0025] Example 3: A method for controlling shrinkage cavities in the ER70S-6 casting furnace during initial casting. This method includes converter primary refining, LF furnace refining, continuous casting, and billet inspection processes. (1) In the primary refining process of the converter, the final carbon content of the converter is controlled at 0.06%, the steel is tapped with double slag blocking operation, and the slag discharge is 0.3 kg / t steel; (2) In the LF furnace refining process, 3.5 kg / t steel of steelmaking lime and 1.25 kg / t steel of ER70S-6 special fluorite were added, and the soft blowing argon time was 20 min to ensure that the inclusions floated up fully. The chemical composition and mass percentage of the ER70S-6 were obtained as follows: C: 0.06~0.10%, Si: 0.80~0.95%, Mn: 1.40~1.60%, P≤0.025%, S≤0.025%, Al≤0.010%, with the balance being Fe and unavoidable impurities. (3) In the continuous casting process, the amount of steel remaining in the ladle is controlled to be 4t, protective casting is adopted throughout the process, the tundish baking temperature is 1100℃, ER70S-6 special protective slag with an alkalinity range of 1.35 is used, and the amount added is 0.25kg / ton. The above-mentioned patented protective slag and ER70S-6 are stirred evenly in a crystallizer to promote the homogenization of steel composition and temperature. The electromagnetic stirring parameters of the crystallizer are 280A current and 3.5Hz frequency. The superheat of the first casting furnace is controlled at 40℃, the first casting section is 165mm*165mm, the first casting speed is 2.0m / min, and the first casting water volume is controlled at 1.9L / kg to suppress shrinkage cavities. Then, an integrated submerged entry nozzle is used, and the insertion depth is controlled at 100mm.

[0026] (4) The billet inspection process includes online infrared detection and low-magnification inspection of the billet, real-time monitoring of shrinkage defects and feedback on process compliance, and production of ER70S-6 product.

[0027] Comparative Example 1 uses the existing method.

[0028] The ER70S-6 products prepared by the method described in Examples 1-3 and Comparative Example 1 were subjected to an inspection process, and the results are shown in the table below:

[0029] Low-magnification grading was performed using the ingot low-magnification inspection standards YB / T2011 and YB / T153. Shrinkage cavities were all no greater than grade 0.5, and all other low-magnification items met product requirements. Furthermore, the ER70S-6 product prepared using the method described in Example 3... Figure 2 As shown, the ER70S-6 product prepared using a method other than that described in Example 3 is as follows: Figure 1 As shown. Comparison Figure 1 and Figure 2 It can be seen that Figure 1 The diameter of the shrinkage cavity is 3mm. Figure 2 The shrinkage cavity is small, with a diameter of less than 0.1 mm. The product obtained in Example 3 has significant advantages in shrinkage cavity control. The low-magnification shrinkage cavity yield of the product obtained using the control method described in the invention is increased from 60% to 98%.

[0030] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling shrinkage cavities in the ER70S-6 casting furnace, the method comprising converter primary refining, LF furnace refining, continuous casting, and billet inspection processes, characterized in that, In the continuous casting process, the amount of steel remaining in the ladle is controlled to be ≥2t, protective casting is used throughout the process, the tundish baking temperature is ≥1000℃, and electromagnetic stirring is used in the crystallizer to promote the homogenization of steel composition and temperature; the superheat of the first casting furnace is controlled to be 30℃-45℃, the first casting cross section is 130×130mm-180×180mm, the first casting speed is 2.0±0.1m / min, and the first casting specific water volume is controlled to be 1.6L / kg-2.4L / kg to suppress the formation of shrinkage cavities.

2. The method for controlling shrinkage cavities in the ER70S-6 casting furnace according to claim 1, characterized in that, In the continuous casting process, ER70S-6 special protective slag with an alkalinity range of 1.2 to 1.5 is used, and the amount added is 0.2-0.3 kg / ton. The patented protective slag and ER70S-6 are stirred evenly in a crystallizer.

3. The method for controlling shrinkage cavities in the ER70S-6 casting furnace according to claim 1, characterized in that, The electromagnetic stirring parameters of the crystallizer are 250-300A current and 3-4Hz frequency.

4. The method for controlling shrinkage cavities in the ER70S-6 casting furnace according to claim 1, characterized in that, In the continuous casting process, an integrated submersible nozzle is used, and the insertion depth is controlled between 90 and 110 mm.

5. The method for controlling shrinkage cavities in the ER70S-6 casting furnace according to claim 1, characterized in that, In the LF furnace refining process, the soft argon blowing time is ≥15min to ensure that inclusions are fully floated to the surface.

6. The method for controlling shrinkage cavities in the ER70S-6 casting furnace according to claim 1, characterized in that, In the continuous casting process, the chemical composition and mass percentage of ER70S-6 used are as follows: C: 0.06-0.10%, Si: 0.80-0.95%, Mn: 1.40-1.60%, P≤0.025%, S≤0.025%, Al≤0.010%, with the balance being Fe and unavoidable impurities.

7. The method for controlling shrinkage cavities in the ER70S-6 casting furnace according to claim 1, characterized in that, The initial pouring section is controlled at 165mm*165mm, and the initial pouring water volume is controlled at 1.9L / kg.

8. The method for controlling shrinkage cavities in the ER70S-6 casting furnace according to claim 1, characterized in that, In the primary refining process of the converter, the final carbon content of the converter is controlled at 0.05-0.07%, and the steel is tapped with double slag blocking operation, with a slag discharge rate of ≤0.5kg / t steel.

9. The method for controlling shrinkage cavities in the ER70S-6 casting furnace according to claim 1, characterized in that, In the LF furnace refining process, 3.0-4.0 kg / t steel of steelmaking lime and 1.0-1.5 kg / t steel of ER70S-6 special fluorite are added.

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