A method for capping the tail billet of ultra-low carbon steel continuous casting

Abstract

The invention discloses a method for capping the tail of an ultra-low carbon steel continuous casting, which relates to the field of metallurgical manufacturing technology. The method comprises the following steps: after the ultra-low carbon molten steel stops pouring, the pulling speed is controlled to 0.06m / min to 0.17m / min, a cooling piece is placed, and after capping, the pulling speed is controlled to 0.35m / min to 0.45m / min, the pulling speed is accelerated to 1.0m / min to 1.4m / min, and when the tail of the tail reaches the sixth sector, the pulling speed is decelerated to 0.81m / min to 1.18m / min; when the tail of the tail reaches the eighth sector, the pulling speed is accelerated to 1.16m / min to 1.2m / min. By controlling the casting speed, the method can improve the surface defects of the tail, reduce the amount of tail waste, and improve the yield rate. The tail capping operation process is simple, and the tail after capping is of good quality.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical manufacturing, and in particular relates to a method for capping an ultra-low carbon steel continuous casting tail slab. Background Art

[0002] Slab capping is a crucial component of the continuous casting process. It is the process of treating the molten steel in the mold at the end of the continuous casting phase. This process can affect the surface quality of the slab. Failure to properly control process parameters can increase the length of the tail cut, resulting in a low yield or surface defects.

[0003] Due to its low carbon content, ultra-low carbon steel has a small solid shell shrinkage coefficient, high oxygen content in the molten steel, and volume expansion, which causes molten steel to surge, making it very easy for the tail billet to be thrown out. The current process mainly operates as follows: When the continuous casting machine casting speed drops to 0.3m / min, the steel caster checks the capping of the tail billet and pumps water into the crystallizer. If the capping is not good, iron filings are thrown into the crystallizer to accelerate the solidification of the tail. After the tail billet shell reaches a certain thickness, the tail billet is pulled out of the fan-shaped section at the typical casting speed. This capping process is simple, but has the following disadvantages: 1. It is time-consuming. 2. An empty shell often remains during the capping process, making it prone to roof bursts. 3. The long low casting speed leads to low surface temperatures at the tail billet, and the incidence of transverse cracks reaches over 20%. 4. The length of the tail billet and scrap is long, reducing the yield rate. Summary of the Invention

[0004] The object of the present invention is to provide a method for capping the tail slab of ultra-low carbon steel continuous casting, so as to solve at least one aspect of the problems and defects raised in the above-mentioned background technology.

[0005] The present invention provides a method for capping the tail billet of ultra-low carbon steel continuous casting, comprising the following steps:

[0006] S1. After the ultra-low carbon molten steel stops pouring, the pulling speed is controlled to 0.06m / min~0.17m / min;

[0007] S2. Put the cooling piece in and seal the top. After sealing, control the pulling speed to 0.35m / min~0.45m / min;

[0008] S3, and then the acceleration is 0.48m / min 2 ~0.53m / min 2 Accelerate the pulling speed to 1.0m / min~1.4m / min;

[0009] S4, when the tail of the tail billet reaches the fan-shaped section 6, the deceleration is 0.48m / min 2 ~0.53m / min 2The pulling speed is reduced to 0.81m / min~1.18m / min; when the tail of the tail billet reaches the 8th fan-shaped section, the acceleration is increased to 0.48m / min. 2 ~0.53m / min 2 Accelerate the pulling speed to 1.16m / min~1.2m / min.

[0010] According to one technical solution of the method for capping the tail billet of ultra-low carbon steel continuous casting of the present invention, at least the following beneficial effects are achieved:

[0011] The present invention controls the casting speed of the ultra-low carbon steel continuous casting tail billet before and after the capping process, and rationally controls the increase and decrease of the casting speed according to the position of the tail billet in the continuous casting machine, cooperates with the cooling part to perform rapid capping, thereby improving the surface defects of the tail billet, reducing the amount of tail billet cutting waste, and improving the yield rate.

[0012] The present invention controls the pulling speed to 0.06m / min to 0.17m / min after stopping casting to keep the liquid level of the crystallizer stable. At this time, if the pulling speed is too low, the casting will cool and solidify, resulting in difficulty in pulling. If the pulling speed is too high, the crystallization liquid level will drop too quickly, affecting the quality of the tail billet.

[0013] The present invention places a cooling part in the crystallizer and controls the pulling speed to 0.35m / min to 0.45m / min after capping. The tail billet after capping can be pulled out of the crystallizer. If the pulling speed is too slow, the billet shell will be too thick, affecting the subsequent billet discharge. If the pulling speed is too fast, the billet shell will be too thin, causing steel leakage.

[0014] The invention effectively controls the pulling speed according to the different positions of the tail of the tail billet reaching the fan-shaped portion, thereby achieving the effect of improving the surface defects of the tail billet, reducing the amount of tail cutting and waste, and improving the economic benefit.

[0015] In some specific embodiments of the present invention, the pulling speed during pouring is 0.95 m / min to 1.21 m / min.

[0016] In some specific embodiments of the present invention, the pulling speed during pouring is 1.05 m / min to 1.15 m / min.

[0017] In some specific embodiments of the present invention, the specifications of the ultra-low carbon steel continuous casting tail billet are: thickness 200mm-250mm, width 1500-1700mm.

[0018] In some specific embodiments of the present invention, the pulling speed in step S2 is maintained for 80s to 100s.

[0019] In some specific embodiments of the present invention, the pulling speed in step S2 is maintained for 85s to 95s.

[0020] According to the present invention, after a cooling piece is placed in the crystallizer and the top is sealed, the pulling speed is controlled to maintain a certain time so that the tail billet in the crystallizer can be pulled out.

[0021] In some specific embodiments of the present invention, the C content in the ultra-low carbon molten steel is 0.0013% to 0.0016%.

[0022] In some specific embodiments of the present invention, the C content in the ultra-low carbon molten steel is 0.0014% to 0.0015%.

[0023] The content of element C in the present invention has a certain influence on the capping of the tail billet. For the continuous casting capping process of ultra-low carbon steel, if the content of element C is too high, the heat flow ratio in the crystallizer will increase, which will easily cause steel leakage. At the same time, if the content of element C is too high, the element C will easily enter the peritectic when the tail billet is in the crystallizer, causing defects on the surface of the tail billet.

[0024] In some specific embodiments of the present invention, the Si content in the ultra-low carbon molten steel is 0.0043% to 0.0051%.

[0025] In some specific embodiments of the present invention, the Si content in the ultra-low carbon molten steel is 0.0045% to 0.0050%.

[0026] The Si element in the present invention is beneficial to improving the fluidity of the continuous casting billet.

[0027] In some specific embodiments of the present invention, the P content in the ultra-low carbon molten steel is less than 0.002%.

[0028] In the present invention, the P element is easy to segregate in the ingot, resulting in increased cracks inside the tail ingot and defects on the surface.

[0029] In some specific embodiments of the present invention, the S content in the ultra-low carbon molten steel is less than 0.005%.

[0030] In the present invention, the S element is also easy to segregate in the ingot, resulting in increased cracks inside the tail ingot and defects on the surface.

[0031] In some specific embodiments of the present invention, the Mn content in the ultra-low carbon molten steel is 0.085% to 0.095%.

[0032] In some specific embodiments of the present invention, the Mn content in the ultra-low carbon molten steel is 0.087% to 0.091%.

[0033] In the present invention, the Mn element can improve the fluidity of the cast billet, which is beneficial to the control of the casting speed during the capping process of the tail billet.

[0034] In some specific embodiments of the present invention, the Al content in the ultra-low carbon molten steel is 0.062% to 0.075%.

[0035] In some specific embodiments of the present invention, the Al content in the ultra-low carbon molten steel is 0.063% to 0.071%.

[0036] In the present invention, if the Al content is too high, too much Al2O3 will be generated, thereby clogging the cooling water inlet. If the Al content is too low, too little Al2O3 will be generated, resulting in insufficient deoxidation ability, causing pores in the ingot, and further affecting the surface quality of the tail ingot.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention controls the casting speed of the ultra-low carbon steel continuous casting tail billet before and after the capping process, and at the same time reasonably controls the increase and decrease of the casting speed according to the position of the tail billet in the continuous casting machine, and cooperates with the cooling part to perform rapid capping, which can improve the surface defects of the tail billet, reduce the amount of tail billet cutting waste, and improve the yield rate. The tail billet capping operation process is simple and the tail billet quality after capping is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0040] Figure 1 This is a physical picture of the continuous casting tail billet prepared in Example 1. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0042] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0043] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0044] Example 1

[0045] This embodiment is a method for capping the tail billet of ultra-low carbon steel continuous casting, which comprises the following steps:

[0046] S1. After the ultra-low carbon molten steel stops pouring, the pulling speed is controlled to 0.1m / min;

[0047] S2. Lift the tundish to the highest liquid level, quickly remove the submerged nozzle, place the cooling element into the mold, and cap the top. After capping, control the pulling speed to 0.4 m / min and draw the billet at this speed for 90 s.

[0048] S3, then the acceleration is 0.5m / min 2 Accelerate the pulling speed to 1.2m / min;

[0049] S4, when the tail of the billet reaches the sector 6, the deceleration is 0.5m / min 2 The pulling speed is reduced to 1.0m / min; when the tail of the tail billet reaches the fan-shaped 8th segment, the acceleration is increased to 0.5m / min. 2 Accelerate the pulling speed to 1.2m / min.

[0050] The ultra-low carbon steel continuous casting tail slab of this embodiment includes the following chemical elements by mass percentage: C: 0.0015%, Si: 0.0046%, Mn: 0.09%, P: 0.0012%, S: 0.0047%, and Al: 0.065%.

[0051] The specifications of the ultra-low carbon steel continuous casting tail billet in this embodiment are: thickness 240 mm, width 1620 mm.

[0052] In this embodiment, the pulling speed during normal pouring of molten steel is 1.1 m / min.

[0053] The continuous casting tail slab obtained in this embodiment has excellent quality, the tail scrap amount is 1m, and the yield rate is high. Figure 1 It can be seen that the surface quality is excellent, with no cracks or defects on the surface.

[0054] Example 2

[0055] This embodiment is a method for capping the tail billet of ultra-low carbon steel continuous casting, which comprises the following steps:

[0056] S1. After the ultra-low carbon molten steel stops pouring, the pulling speed is controlled to 0.15m / min;

[0057] S2. Lift the tundish to the highest liquid level, quickly remove the submerged nozzle, place the cooling element into the mold, and cap the top. After capping, control the pulling speed to 0.4 m / min and draw the billet at this speed for 90 s.

[0058] S3, and then the acceleration is 0.51m / min 2 Accelerate the pulling speed to 1.5m / min;

[0059] S4, when the tail of the tail billet reaches the fan-shaped section 6, the deceleration is 0.51m / min 2 The pulling speed is reduced to 1.2m / min; when the tail of the tail billet reaches the fan-shaped 8th segment, the acceleration is increased to 0.51m / min. 2 Accelerate the pulling speed to 1.4m / min.

[0060] The ultra-low carbon steel continuous casting tail slab of this embodiment includes the following chemical elements by mass percentage: C: 0.0015%, Si: 0.0046%, Mn: 0.09%, P: 0.0012%, S: 0.0047%, and Al: 0.065%.

[0061] The specifications of the ultra-low carbon steel continuous casting tail billet in this embodiment are: thickness 250mm, width 1620mm.

[0062] In this embodiment, the pulling speed during normal pouring of molten steel is 1.1 m / min.

[0063] The continuous casting tail slab obtained in this embodiment has excellent tail slab quality, a tail scrap amount of 1.1m, a high yield rate, excellent surface quality, and no cracks or defects on the surface.

[0064] Example 3

[0065] This embodiment is a method for capping the tail billet of ultra-low carbon steel continuous casting, which comprises the following steps:

[0066] S1. After the ultra-low carbon molten steel stops pouring, the pulling speed is controlled to 0.1m / min;

[0067] S2. Lift the tundish to the highest liquid level, quickly remove the submerged nozzle, place the cooling element into the mold, and cap the top. After capping, control the pulling speed to 0.4 m / min and draw the billet at this speed for 90 s.

[0068] S3, then the acceleration is 0.5m / min 2 Accelerate the pulling speed to 1.2m / min;

[0069] S4, when the tail of the billet reaches the sector 6, the deceleration is 0.5m / min 2The pulling speed is reduced to 1.0m / min; when the tail of the tail billet reaches the fan-shaped 8th segment, the acceleration is increased to 0.5m / min. 2 Accelerate the pulling speed to 1.2m / min.

[0070] The ultra-low carbon steel continuous casting tail slab of this embodiment includes the following chemical elements by mass percentage: C: 0.0016%, Si: 0.0050%, Mn: 0.085%, P: 0.0018%, S: 0.0049%, and Al: 0.062%.

[0071] The specifications of the ultra-low carbon steel continuous casting tail billet in this embodiment are: thickness 240 mm, width 1620 mm.

[0072] In this embodiment, the pulling speed during normal pouring of molten steel is 1.1 m / min.

[0073] The continuous casting tail slab obtained in this embodiment has excellent tail slab quality, a tail scrap amount of 1.1m, a high yield rate, excellent surface quality, and no cracks or defects on the surface.

[0074] Comparative Example 1

[0075] This comparative example is a method for capping the tail billet of ultra-low carbon steel continuous casting, which consists of the following steps:

[0076] S1. After the ultra-low carbon molten steel stops pouring, the pulling speed is controlled to 0.3m / min;

[0077] S2. Lift the tundish to the highest liquid level, quickly remove the submerged nozzle, place the cooling element into the mold, and cap the top. After capping, control the pulling speed to 0.4 m / min and draw the billet at this speed for 90 s.

[0078] S3. Finally, the tail billet is pulled out of the fan-shaped segment at a pulling speed of 1.2m / min.

[0079] The ultra-low carbon steel continuous casting tail slab of this comparative example includes the following chemical elements by mass percentage: C: 0.0015%, Si: 0.0046%, Mn: 0.09, P: 0.0012%, S: 0.0047%, and Al: 0.065%.

[0080] The specifications of the ultra-low carbon steel continuous casting tail billet in this comparative example are: thickness 240 mm, width 1620 mm.

[0081] The pulling speed of this comparative example during normal pouring of molten steel is 1.1 m / min.

[0082] The continuous casting tail slab obtained in this comparative example has poor quality, a tail scrap amount of 2.6m, a low yield rate, poor surface quality, and many cracks and defects on the surface.

[0083] Comparative Example 2

[0084] This comparative example is a method for capping the tail billet of ultra-low carbon steel continuous casting, which consists of the following steps:

[0085] S1. After the ultra-low carbon molten steel stops pouring, the pulling speed is controlled to 0.3m / min;

[0086] S2. Lift the tundish to the highest liquid level, quickly remove the submerged nozzle, place the cooling element into the mold, and cap the top. After capping, control the pulling speed to 0.5 m / min and draw the billet at this speed for 100 s.

[0087] S3, then the acceleration is 0.5m / min 2 Accelerate the pulling speed to 1.4m / min;

[0088] S4, when the tail of the billet reaches the sector 6, the deceleration is 0.5m / min 2 The pulling speed is reduced to 1.0m / min; when the tail of the tail billet reaches the fan-shaped 8th segment, the acceleration is increased to 0.5m / min. 2 Accelerate the pulling speed to 1.2m / min.

[0089] The ultra-low carbon steel continuous casting tail slab of this comparative example includes the following chemical elements by mass percentage: C: 0.0015%, Si: 0.0046%, Mn: 0.09, P: 0.0012%, S: 0.0047%, and Al: 0.065%.

[0090] The specifications of the ultra-low carbon steel continuous casting tail billet in this comparative example are: thickness 260mm, width 1620mm.

[0091] In this comparative example, the pulling speed during normal pouring of molten steel is 1.1 m / min.

[0092] The continuous casting tail slab obtained in this comparative example has a tail scrap amount of 2.0m, a large scrap amount, a low yield rate, a few cracks on the surface, and an average surface quality of the tail slab.

[0093] Comparative Example 3

[0094] This comparative example is a method for capping the tail billet of ultra-low carbon steel continuous casting, which consists of the following steps:

[0095] S1. After the ultra-low carbon molten steel stops pouring, the pulling speed is controlled to 0.1m / min;

[0096] S2. Lift the tundish to the highest liquid level, quickly remove the submerged nozzle, place the cooling element into the mold, and cap the top. After capping, control the pulling speed to 0.4 m / min and draw the billet at this speed for 90 s.

[0097] S3, and then the acceleration is 0.5m / min2 Accelerate the pulling speed to 1.2m / min;

[0098] S4, when the tail of the billet reaches the sector 6, the deceleration is 0.5m / min 2 The pulling speed is reduced to 1.0m / min; when the tail of the tail billet reaches the fan-shaped 8th segment, the acceleration is increased to 0.5m / min. 2 Accelerate the pulling speed to 1.2m / min.

[0099] The ultra-low carbon steel continuous casting tail slab of this comparative example includes the following chemical elements by mass percentage: C: 0.0026%, Si: 0.0036%, Mn: 0.09%, P: 0.0015%, S: 0.005%, and Al: 0.062%.

[0100] The specifications of the ultra-low carbon steel continuous casting tail billet in this comparative example are: thickness 240 mm, width 1620 mm.

[0101] In this comparative example, the pulling speed during normal pouring of molten steel is 1.1 m / min.

[0102] The continuous casting tail slab obtained in this comparative example has a tail scrap amount of 1.6m, a general yield rate, poor surface quality, and cracks and defects on the surface.

[0103] The difference between Comparative Example 1 and Example 1 is that the traditional process is adopted, and the conventional pulling speed is directly used to pull the tail billet out of the fan-shaped area after the cap is sealed. The resulting continuous casting tail billet has poor quality, a large amount of tail cutting waste, a low yield rate, poor surface quality, and many cracks and defects on the surface.

[0104] The difference between Comparative Example 2 and Example 1 is that the pulling speed was increased before and after capping, and the quality of the continuous casting tail billet obtained was average, and the amount of waste cutting was large. This was mainly because the liquid level of the crystallizer could not be stabilized after the pulling speed was increased, and the pulling speed affected the quality of the billet shell of the crystallizer, thereby affecting the yield and surface quality of the tail billet.

[0105] The difference between Comparative Example 3 and Example 1 is that the chemical element composition of the ultra-low carbon steel continuous casting tail billet is changed. The resulting continuous casting tail billet has a general yield rate, poor surface quality, and cracks and defects on the surface. This is mainly due to the change in chemical elements, which changes the organization of the tail billet's solidification and crystallization, thereby changing the tail billet's performance, and resulting in poor tail billet quality.

[0106] In summary, the present invention controls the casting speed of the ultra-low carbon steel continuous casting tail billet before and after the capping process, and at the same time reasonably controls the increase or decrease of the casting speed according to the position of the tail billet in the continuous casting machine, and cooperates with the cooling part to perform rapid capping, which can improve the surface defects of the tail billet, reduce the amount of tail billet cutting waste, and improve the yield rate. The tail billet capping operation process is simple and the quality of the tail billet after capping is good.

[0107] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are 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 in the scope of protection of the present invention.

Claims

1. A method for capping the tail billet of ultra-low carbon steel continuous casting, characterized in that: The following steps are involved: S1. After the ultra-low carbon molten steel stops pouring, the pulling speed is controlled to 0.06m / min~0.17m / min; S2. Put the cooling piece in and seal the top. After sealing, control the pulling speed to 0.35m / min~0.45m / min; S3, and then the acceleration is 0.48m / min 2 ~0.53m / min 2 Accelerate the pulling speed to 1.0m / min~1.4m / min; S4, when the tail of the tail billet reaches the fan-shaped section 6, the deceleration is 0.48m / min 2 ~0.53m / min 2 The pulling speed is reduced to 0.81m / min~1.18m / min; when the tail of the tail billet reaches the 8th fan-shaped section, the acceleration is increased to 0.48m / min. 2 ~0.53m / min 2 Accelerate the pulling speed to 1.16m / min~1.2m / min.

2. The method for capping the tail billet of ultra-low carbon steel continuous casting according to claim 1, characterized in that: The pulling speed during pouring is 0.95m / min~1.21m / min.

3. The method for capping the tail billet of ultra-low carbon steel continuous casting according to claim 1, characterized in that: The specifications of the ultra-low carbon steel continuous casting tail billet are: thickness 200mm-250mm, width 1500-1700mm.

4. The method for capping the tail billet of ultra-low carbon steel continuous casting according to claim 1, characterized in that: The pulling speed in step S2 is maintained for 80s to 100s.

5. The method for capping the tail slab of ultra-low carbon steel continuous casting according to claim 1, characterized in that: The C element content in the ultra-low carbon molten steel is 0.0013% to 0.0016%.

6. The method for capping the tail billet of ultra-low carbon steel continuous casting according to claim 1, characterized in that: The Si element content in the ultra-low carbon molten steel is 0.0043% to 0.0051%.

7. The method for capping the tail billet of ultra-low carbon steel continuous casting according to claim 1, characterized in that: The P element content in the ultra-low carbon molten steel is less than 0.002%.

8. The method for capping the tail slab of ultra-low carbon steel continuous casting according to claim 1, characterized in that: The S element content in the ultra-low carbon molten steel is less than 0.005%.

9. The method for capping the tail billet of ultra-low carbon steel continuous casting according to claim 1, characterized in that: The Mn element content in the ultra-low carbon molten steel is 0.085% to 0.095%.

10. The method for capping the tail slab of ultra-low carbon steel continuous casting according to claim 1, characterized in that: The Al element content in the ultra-low carbon molten steel is 0.062% to 0.075%.

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