A method for improving center segregation of a bloom continuous casting slab

Abstract

The application discloses a method for improving center segregation of square billet continuous casting billet, and controls the pouring temperature of molten steel to be 25-35 DEG C higher than the liquidus point, sets an elliptical electromagnetic stirrer at the solidification end of the square billet continuous casting billet, the electromagnetic stirrer is at a certain angle alpha with the pulling direction of the continuous casting billet, generates electromagnetic force at a certain angle alpha with the pulling direction of the continuous casting billet, and makes the not completely solidified molten steel move not only vertically to the pulling direction, but also along the pulling direction, thereby improving the center segregation of the square billet continuous casting billet. The application can improve the center segregation of the square billet continuous casting billet, and can also improve the center shrinkage hole, center porosity and center crack.

Description

Technical Field

[0001] The invention relates to the field of continuous casting of square billets, and in particular to a method for improving the center segregation of continuous casting square billets. Background Art

[0002] Centerline segregation in continuous casting billets refers to the uneven distribution of components during the solidification process. This is primarily caused by the concentration of certain solutes in the molten steel during the solidification process due to varying solubility. Due to the solidification characteristics of steel products and the limitations of product variety, it is difficult to fundamentally eliminate centerline segregation in continuous casting billets during metallurgical production. The only approach is to minimize and improve centerline segregation within acceptable limits for billet quality.

[0003] The center segregation of continuous casting billet is due to the large accumulation of certain solute elements (such as P, S and some micro-alloying components such as V, Ti, Nb, etc., which are prone to cracking. These elements can also be called trace elements or partially called residual elements) which will be accompanied by the generation of center cracks and center shrinkage cavities, which will have a serious impact on the internal quality of the steel.

[0004] Center segregation of continuous casting billets is a common quality defect in continuous casting production and a challenging issue in billet quality that the continuous casting industry is currently working on. Researching and developing new methods to control and improve center segregation of continuous casting billets is of great significance for improving continuous casting quality and increasing continuous casting productivity. In addition to controlling the composition, temperature, and pouring conditions of the molten steel, electromagnetic stirring technology at the end of solidification is an effective method for controlling and improving center segregation of square billets. Through electromagnetic stirring at the end of solidification, the flow of molten steel in the liquid phase of the continuous casting billet can be enhanced, prompting the reflux and redistribution of the enriched segregated solutes, which can improve the center segregation of the continuous casting billet to a certain extent. However, whether electromagnetic stirring can accurately act at the end of solidification of the continuous casting billet has become a technical limitation and difficulty in actual operation.

[0005] Currently, there are three common types of electromagnetic stirrers used for stirring liquid metal in the metallurgical and foundry industries: a rotating magnetic field stirrer, a traveling wave magnetic field stirrer, and a spiral magnetic field stirrer. Currently, rotating magnetic field and traveling wave magnetic field electromagnetic stirrers are relatively mature in structure and process, and have been applied in metal smelting and continuous steel casting. However, due to the fixed direction of the magnetic field, they can only produce a stirring effect parallel or perpendicular to the casting direction. Spiral magnetic field electromagnetic stirrers are still under development, have a complex structure, require special power supply equipment, and are not used in on-site production. Therefore, it is necessary to develop new methods to improve the center segregation of continuous casting billets to overcome the above problems. Summary of the Invention

[0006] Purpose of the invention: In view of the shortcomings and defects of the existing technology, the present invention provides a method for improving the center segregation of square billet continuous casting, which can improve the center segregation of square billet continuous casting and improve the center shrinkage cavity, center porosity and center crack.

[0007] Technical solution: A method for improving the center segregation of square billet continuous casting according to the present invention is characterized in that: the pouring temperature of molten steel is controlled at 25°C to 35°C above the liquidus point, an elliptical electromagnetic stirrer is arranged at a certain angle to the billet drawing direction near the end of the billet continuous casting solidification, and an electromagnetic force is generated at a certain angle α to the billet drawing direction, so that the incompletely solidified molten steel can move both perpendicular to the billet drawing direction and along the billet drawing direction, thereby improving the center segregation of the square billet continuous casting.

[0008] Wherein, the elliptical electromagnetic stirrer is installed within a range of 0.5 m before and after the liquidus point of the billet continuous casting machine.

[0009] Wherein, the angle α between the center line of the elliptical electromagnetic stirrer and the casting direction of the continuous casting machine is -45° to 45°.

[0010] The elliptical electromagnetic stirrer generates a clockwise and counterclockwise rotating magnetic field, driving the incompletely solidified molten steel to produce corresponding movement.

[0011] The elliptical electromagnetic stirrer generates continuous and intermittent magnetic fields, driving the incompletely solidified molten steel to produce corresponding movements.

[0012] Wherein, the frequency of the elliptical electromagnetic stirrer is 4 Hz to 9 Hz.

[0013] Wherein, the current intensity of the elliptical electromagnetic stirrer is 0-1200A.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the present invention controls the pouring temperature of molten steel at 25°C to 35°C above the liquidus point, and arranges an elliptical electromagnetic stirrer at a certain angle to the drawing direction of the continuous casting billet at the end attachment of the continuous casting solidification of the square billet, thereby generating an electromagnetic force at a certain angle to the drawing direction of the continuous casting billet, driving the incompletely solidified molten steel to move at a certain angle to the drawing direction of the continuous casting billet, so that the incompletely solidified molten steel can move both vertically and along the drawing direction, thereby improving the center segregation of the square billet continuous casting billet, and at the same time improving the center shrinkage cavity, center porosity and center cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the present invention;

[0016] In the figure, 1 is an elliptical electromagnetic stirrer and 2 is a continuous casting billet. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0018] The present invention controls the pouring temperature of molten steel at 25°C to 35°C above the liquidus point, and arranges an elliptical electromagnetic stirrer 1 at a certain angle to the drawing direction of the continuous casting billet 2 at the end attachment of the continuous casting solidification of the square billet, thereby generating an electromagnetic force at a certain angle to the drawing direction of the continuous casting billet 2, so that the incompletely solidified molten steel can move both perpendicular to the drawing direction and along the drawing direction, thereby improving the center segregation of the square billet continuous casting billet, and at the same time can improve the center shrinkage cavity, center looseness and center cracks.

[0019] The pouring temperature of the molten steel is controlled at 25 to 35°C above the liquidus point, and the elliptical electromagnetic stirrer 1 is installed within 0.5m before and after the liquidus point of the billet continuous casting machine. The angle α between the center line of the elliptical electromagnetic stirrer 1 and the casting direction of the continuous casting machine is -45° to 45°. The elliptical electromagnetic stirrer 1 can generate clockwise and counterclockwise rotating magnetic fields, driving the incompletely solidified molten steel to produce corresponding movement. The elliptical electromagnetic stirrer 1 can generate continuous and intermittent magnetic fields, driving the incompletely solidified molten steel to produce corresponding movement. The frequency of the elliptical electromagnetic stirrer 1 is 4Hz to 9Hz, and the current intensity is 0 to 1200A.

[0020] Example 1:

[0021] In the continuous casting process of a certain steel billet, the steel grade used is a low-alloy steel with a carbon content of 0.20%. The pouring temperature of the molten steel is controlled at 35°C above the liquidus point. An elliptical electromagnetic stirrer is installed 0.5 m in front of the liquidus point of the billet continuous caster. The angle α between the centerline of the elliptical stirrer and the casting direction of the continuous caster is 45°. The elliptical electromagnetic stirrer generates a clockwise rotating magnetic field, which generates an intermittent magnetic field, causing the partially solidified molten steel to move accordingly. The frequency of the electromagnetic stirrer is 4 Hz, and the current intensity is 600 A. The low-magnification center segregation of the continuous cast billet is 0.5, the center shrinkage cavity is 0.5, and the center porosity is 0.5. No center cracks are observed.

[0022] Example 2:

[0023] The continuous casting process for a certain steel billet involved a low-alloy steel with a carbon content of 0.45%. The pouring temperature of the molten steel was controlled at 30°C above the liquidus point. An elliptical electromagnetic stirrer was installed at the liquidus point of the billet continuous caster. The angle α between the centerline of the elliptical stirrer and the casting direction of the continuous caster was -25°. The elliptical electromagnetic stirrer generates a counterclockwise rotating magnetic field, which generates an intermittent magnetic field and causes the partially solidified molten steel to move accordingly. The frequency of the electromagnetic stirrer was 9 Hz, and the current intensity was 900 A. The low-magnification center segregation of the continuous cast billet was level 0.5, the center shrinkage cavity was level 0.5, and the center porosity was level 1.0. No center cracks were observed.

[0024] Example 3:

[0025] The continuous casting process for a certain steel billet involved a low-alloy steel with a carbon content of 0.45%. The pouring temperature of the molten steel was controlled at 30°C above the liquidus point. An elliptical electromagnetic stirrer was installed at the liquidus point of the billet continuous casting machine. The angle α between the centerline of the elliptical stirrer and the casting direction of the continuous casting machine was -45°. The elliptical electromagnetic stirrer generates a counterclockwise rotating magnetic field, which continuously generates a magnetic field and causes the partially solidified molten steel to move accordingly. The frequency of the electromagnetic stirrer was 6 Hz, and the current intensity was 900 A. The low-magnification center segregation of the continuous casting billet was 0.5, the center shrinkage cavity was 0.5, and the center porosity was 0.5. No center cracks were observed.

[0026] Example 4:

[0027] The continuous casting process for a certain steel billet involved a low-alloy steel with a carbon content of 0.9%. The pouring temperature of the molten steel was controlled at 25°C above the liquidus point. An elliptical electromagnetic stirrer was installed 0.5 m behind the liquidus point of the billet continuous caster. The angle α between the centerline of the elliptical stirrer and the casting direction of the continuous caster was -45°. The elliptical electromagnetic stirrer generates a clockwise rotating magnetic field, which generates an intermittent magnetic field and causes the partially solidified molten steel to move accordingly. The frequency of the electromagnetic stirrer was 6 Hz, and the current intensity was 1200 A. The low-magnification center segregation of the continuous cast billet was 0.5, the center shrinkage cavity was 0.5, and the center porosity was 0.5. No center cracks were observed.

Claims

1. A method for improving the center segregation of a continuous casting billet, characterized by: The pouring temperature of the molten steel is controlled at 25°C to 35°C above the liquidus point, and an elliptical electromagnetic stirrer (1) is arranged near the solidification end of the continuous casting of the square billet, which is at a certain angle to the casting direction of the continuous casting billet (2) to generate an electromagnetic force at a certain angle α to the casting direction of the continuous casting billet (2), so that the incompletely solidified molten steel can move both perpendicular to the casting direction and along the casting direction, thereby improving the center segregation of the square billet continuous casting billet; the elliptical electromagnetic stirrer (1) is installed within a range of 0.5m before and after the liquidus point of the square billet continuous casting machine; the angle α between the center line of the elliptical electromagnetic stirrer (1) and the casting direction of the continuous casting machine is -45° to 45°.

2. The method for improving center segregation of a continuous casting billet according to claim 1, characterized in that: The elliptical electromagnetic stirrer (1) generates a clockwise and counterclockwise rotating magnetic field, driving the incompletely solidified molten steel to produce corresponding movement.

3. The method for improving center segregation of a continuous casting billet according to claim 1, characterized in that: The elliptical electromagnetic stirrer (1) generates continuous and intermittent magnetic fields, driving the incompletely solidified molten steel to produce corresponding movements.

4. The method for improving center segregation of a continuous casting billet according to claim 1, characterized in that: The frequency of the elliptical electromagnetic stirrer (1) is 4 Hz to 9 Hz.

5. The method for improving center segregation of a continuous casting billet according to claim 1, characterized in that: The current intensity of the elliptical electromagnetic stirrer (1) is 0~1200A.

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