Method for reducing surface scaling amount of low-carbon steel casting blank

Abstract

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a method for reducing the surface scaling amount of a low-carbon steel casting blank, which controls the outlet angle of a submersed nozzle in the continuous casting process, increases the impact depth of molten steel in a crystallizer after flowing out of the outlet of the submersed nozzle, and controls large-size inclusions in the molten steel to float upwards and be captured by a casting blank shell. Near-surface large-size inclusions are formed; the wide surface of the casting blank is divided into a casting blank wide surface center scaling area and a casting blank wide surface edge scaling area, and different scaling areas adopt a differentiated scaling process. The method can effectively reduce the scaling depth of the casting blank, and ensures the surface quality and yield of a low-carbon steel product at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, in particular to a method for reducing the amount of surface peeling of low-carbon steel ingots. Background Art

[0002] Low-carbon production is an important direction for the transformation and development of steel production. Low-carbon steel is often used to produce deep-drawn cold-rolled plates with high surface quality requirements such as automobile panels. Low-carbon steel continuous casting billets are important intermediate products for the production of low-carbon deep-drawn steel cold-rolled plates. Due to the effect of the internal flow field of the continuous casting production crystallizer in the continuous casting production, large-sized inclusions are easily enriched near the surface of the billet. These large-sized inclusions are one of the important reasons for the surface defects of low-carbon deep-drawn steel. In production, it is often necessary to peel the continuous casting billet to control the large-sized inclusions near the surface of the billet from appearing on the surface of the cold-rolled plate in subsequent hot rolling and cold rolling production to form surface defects. However, the continuous casting billet will suffer serious steel loss during the peeling process, which will affect the increase in carbon emissions from steel production. Therefore, controlling the large-sized inclusions in the near-surface layer of the billet and accurately peeling according to the distribution of inclusions near the surface of the billet can improve the yield rate of steel production and reduce carbon emissions from steel production. Summary of the invention

[0003] Aiming at the formation mechanism of surface defects of low-carbon steel cold-rolled plates and the formation and control mechanism of inclusions near the surface of continuous casting billets, the present invention proposes a method for controlling large-sized inclusions near the surface of casting billets in the low-carbon steel continuous casting production process and accurately stripping the billets according to the distribution characteristics of large-sized inclusions near the surface of continuous casting billets, which can significantly reduce the amount of surface stripping of low-carbon steel casting billets.

[0004] According to one aspect of the present invention, the present invention provides the following technical solution:

[0005] A method for reducing the amount of peeling on the surface of a low-carbon steel ingot comprises the following steps:

[0006] S1. Control the outlet angle of the submerged nozzle during continuous casting (i.e., the angle at which the outlet direction is offset downward relative to the nozzle cross section), increase the impact depth of the molten steel in the crystallizer after it flows out of the outlet of the submerged nozzle, control the large-sized inclusions in the molten steel to float up and be captured by the shell of the ingot, and form large-sized inclusions near the surface. It can also control the fluctuation of the crystallizer liquid level, suppress slag curling near the crystallizer liquid level, and avoid the formation of large-sized slag curling inclusions;

[0007] S2. Divide the wide surface of the ingot (i.e., the inner and outer arc surfaces of the ingot) into a central peeling area of ​​the wide surface of the ingot and an edge peeling area of ​​the wide surface of the ingot, and adopt differentiated peeling processes for different peeling areas.

[0008] As a preferred embodiment of the method for reducing the amount of peeling on the surface of low-carbon steel ingots described in the present invention, in step S1, the outlet angle of the submerged nozzle can be calculated, and the outlet angle θ of the submerged nozzle is:

[0009] θ=25·w α ·v β

[0010] In the formula, θ is the outlet angle of the immersion nozzle, °; w is the crystal width, m; v is the pulling speed, m / min; α and β are coefficients, with values ​​ranging from 0.5 to 1.0;

[0011] As a preferred embodiment of the method for reducing the amount of surface peeling of low-carbon steel ingots described in the present invention, in step S1, the large-sized inclusions are Al2O3 inclusions larger than 50 μm.

[0012] As a preferred embodiment of the method for reducing the amount of surface peeling of low-carbon steel ingots described in the present invention, in said step S2, the total width of the peeling area in the center of the wide surface of the ingot is 1 / 2-3 / 4 of the width of the ingot, and the total width of the peeling areas on both sides of the wide surface of the ingot is 1 / 4-1 / 2 of the width of the ingot.

[0013] As a preferred embodiment of the method for reducing the amount of surface peeling of low-carbon steel ingots described in the present invention, wherein: in the step S2, the wide surface of the ingot is peeled by a slab grinder; the peeling depth of the central peeling area of ​​the wide surface of the ingot is 1.5-2.5 mm, and the peeling depth of the edge peeling area of ​​the wide surface of the ingot is 2-3.5 mm; the peeling depth of the central peeling area of ​​the wide surface of the ingot is less than the peeling depth of the edge area of ​​the wide surface of the ingot, and the difference is 0.5-1.0 mm.

[0014] As a preferred embodiment of the method for reducing the amount of surface peeling of low-carbon steel ingots described in the present invention, in step S2, the narrow surface area of ​​the ingot is peeled by flame cleaning, and the peeling depth is 1.0-2.0 mm.

[0015] As a preferred embodiment of the method for reducing the amount of surface peeling of low-carbon steel ingots described in the present invention, in step S2, the corners of the ingots are peeled off by flame cleaning to form chamfers, the angle between the chamfered surface and the wide surface of the ingot is 110-160°, and the cleaning distance on the wide surface of the ingot is 1.5-3.0 mm.

[0016] The beneficial effects of the present invention are as follows:

[0017] The present invention proposes a method for reducing the amount of peeling on the surface of a low-carbon steel ingot, controlling the outlet angle of an immersion nozzle during continuous casting, increasing the impact depth of the molten steel in the crystallizer after it flows out from the outlet of the immersion nozzle, controlling the large-sized inclusions in the molten steel to float up and be captured by the shell of the ingot, and forming large-sized inclusions near the surface; and dividing the wide surface of the ingot into a peeling area at the center of the wide surface of the ingot and a peeling area at the edge of the wide surface of the ingot, and using differentiated peeling processes for different peeling areas. The present invention can effectively reduce the peeling depth of the ingot, and at the same time ensure the surface quality and yield rate of low-carbon steel products. DETAILED DESCRIPTION

[0018] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. 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 creative work are within the scope of protection of the present invention.

[0019] The present invention proposes a method for controlling large-sized inclusions near the surface of the ingot during the low-carbon steel continuous casting production process and accurately stripping the ingot according to the distribution characteristics of large-sized inclusions near the surface of the ingot, which can significantly reduce the amount of surface stripping of the low-carbon steel ingot.

[0020] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0021] Example 1

[0022] A domestic steel plant produces a casting of ultra-low carbon steel. The original outlet angle of the crystallizer immersion nozzle is 15°, the crystallizer thickness is 230mm, the width is 1500mm, and the casting speed is 1.0m / min. The stripping depth of the ingot is 4mm according to the surface quality requirements of the cold-rolled product, and the stripping method is flame grinding.

[0023] According to the method of the present invention, α=0.5, β=0.5, and the outlet angle of the submerged nozzle is calculated to be 30°. When the nozzle is produced at this angle, the liquid level fluctuation of the crystallizer in the casting is less than or equal to ±6mm. The stripping method of the wide surface of the billet is unified as the stripping of the grinding machine, and the stripping depth is changed to 2.5mm for the stripping depth of the central stripping area of ​​the wide surface of the billet (this area is the 3 / 4 area of ​​the center of the wide surface of the billet), and the stripping depth of the edge area of ​​the wide surface of the billet (this area is the 1 / 8 area on both sides of the wide surface of the billet) is 3.5mm; the narrow surface and corner area of ​​the billet are uniformly cleaned by flame, wherein the stripping depth of the narrow surface of the billet is 1mm, and the corner is cleaned into a chamfer, the angle between the chamfer surface and the wide surface of the billet is 120°, and the cleaning distance of the chamfer in the direction of the wide surface of the billet is 2mm.

[0024] The inclusion degradation rate of the cold-rolled sheet prepared by the cast billet after peeling in this embodiment is reduced by 3%.

[0025] Example 2

[0026] A domestic steel plant produces low-carbon steel for a casting. The original outlet angle of the crystallizer immersion nozzle is 20°, the crystallizer thickness is 230mm, the width is 1900mm, and the casting speed is 1.3m / min. The stripping depth of the ingot is 5mm according to the surface quality requirements of the cold-rolled product, and the stripping method is grinding with a grinding machine.

[0027] According to the method of the present invention, α=0.5, β=0.5, and the calculated outlet angle of the submerged nozzle should be 40°. When the nozzle at this angle is used for production, the liquid level fluctuation of the crystallizer in the casting is less than or equal to ±6mm. The peeling method of the wide surface of the billet is unified as peeling by a grinding machine, and the peeling depth is changed to 2mm for the peeling depth of the peeling area in the center of the wide surface of the billet (this area is the 3 / 4 area in the center of the wide surface of the billet), and the peeling depth of the edge area of ​​the wide surface of the billet (this area is the 1 / 8 area on both sides of the wide surface of the billet) is 2.7mm; the narrow surface and corner area of ​​the billet are uniformly cleaned by flame, wherein the peeling depth of the narrow surface of the billet is 1.5mm, and the corner is cleaned into a chamfer, the angle between the chamfer surface and the wide surface of the billet is 120°, and the cleaning distance of the chamfer in the direction of the wide surface of the billet is 2mm.

[0028] The inclusion degradation rate of the cold-rolled sheet prepared by the cast billet after peeling in this embodiment is reduced by 4%.

[0029] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for reducing the amount of surface peeling of low-carbon steel ingots, characterized in that: The steps include: S1. Control the outlet angle of the submerged nozzle during continuous casting, increase the impact depth of the molten steel in the crystallizer after it flows out from the outlet of the submerged nozzle, control the large-sized inclusions in the molten steel to float up and be captured by the shell of the ingot, and form large-sized inclusions near the surface; S2. Divide the wide surface of the ingot into a central peeling area and an edge peeling area of ​​the wide surface of the ingot, and adopt differentiated peeling processes for different peeling areas.

2. The method for reducing the amount of peeling on the surface of low-carbon steel ingot according to claim 1, characterized in that: In step S1, the outlet angle θ of the submerged nozzle is: θ=25·w α ·v β Wherein, θ is the outlet angle of the submerged nozzle, °; w is the width of the crystallizer, m; v is the pulling speed, m / min; α and β are coefficients, with values ​​ranging from 0.5 to 1.

0.

3. The method for reducing the amount of peeling on the surface of low-carbon steel ingot according to claim 1, characterized in that: In the step S1, the large-sized inclusions are Al2O3 inclusions larger than 50 μm.

4. The method for reducing the amount of peeling on the surface of low-carbon steel ingot according to claim 1, characterized in that: In step S2, the total width of the peeling area in the center of the wide surface of the ingot is 1 / 2-3 / 4 of the width w of the ingot, and the total width of the peeling areas on both sides of the wide surface of the ingot is 1 / 4-1 / 2 of the width w of the ingot.

5. The method for reducing the amount of peeling on the surface of low-carbon steel ingot according to claim 1, characterized in that: In the step S2, the wide surface of the ingot is peeled by a slab grinding machine; the peeling depth of the peeling area in the center of the wide surface of the ingot is 1.5-2.5mm, and the peeling depth of the peeling area at the edge of the wide surface of the ingot is 2-3.5mm; the peeling depth of the peeling area in the center of the wide surface of the ingot is less than the peeling depth of the edge of the wide surface of the ingot, and the difference is 0.5-1.0mm.

6. The method for reducing the amount of peeling on the surface of low-carbon steel ingot according to claim 1, characterized in that: In the step S2, the narrow surface area of ​​the ingot is flame cleaned and peeled, and the peeling depth is 1.0-2.0 mm.

7. The method for reducing the amount of peeling on the surface of low-carbon steel ingot according to claim 1, characterized in that: In the step S2, the corners of the ingot are cleaned and peeled by flame to form chamfers, the angle between the chamfered surface and the wide surface of the ingot is 110-160°, and the cleaning distance on the wide surface of the ingot is 1.5-3.0 mm.