Method for efficiently removing inclusions through hydrogen blowing in continuous casting production

Abstract

The invention belongs to the technical field of continuous casting, and particularly relates to a method for efficiently removing inclusions through hydrogen blowing in continuous casting production, during continuous casting production, high-flow hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas is blown to molten steel at an argon sealing position of a submerged nozzle sliding plate, a stopper and an upper nozzle of the sliding plate, and blockage of the continuous casting nozzle and accumulation of the inclusions at a stopper head and the upper nozzle are inhibited; the liquid level fluctuation of a crystallizer is inhibited, slag entrapment is reduced, the number of inclusions is increased, a large number of dispersed and tiny hydrogen bubbles, hydrogen-argon mixed bubbles or hydrogen-nitrogen mixed bubbles can be generated, the inclusions are captured in molten steel, floating removal of the inclusions is promoted, aggregation and growth of the inclusions on the surfaces of the bubbles are promoted, and the number of harmful inclusions in steel is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous casting, specifically to a method for removing inclusions in molten steel, and more specifically, to a method for efficiently removing inclusions by blowing hydrogen during continuous casting production. Background Art

[0002] Cold-rolled thin plates of steel such as automotive sheets, electrical steel, stainless steel, and some deep-drawing thin hot-rolled sheets have strict requirements for inclusions in steel. The problem of efficient and deep removal of inclusions in steel has always been a bottleneck in the production of high-quality steel. During continuous casting production, argon is often blown at the submerged entry nozzle slide plate, the stopper rod, and the upper nozzle for protective casting, which can inhibit problems such as clogging of the continuous casting nozzle and accumulation of inclusions at the head of the stopper rod. However, blowing argon easily generates argon bubbles that enter the molten steel in the mold and are finally captured by the solidified shell, forming various product defects; it can also cause large fluctuations in the mold liquid level, resulting in an excessive amount of slag-entrained inclusions. Currently, in production, the above problems are mainly controlled by controlling the argon flow rate of blowing argon at these three locations. The argon sealing flow rate at the submerged entry nozzle slide plate is generally controlled at 5 - 10 L / min, the argon blowing flow rate of the stopper rod is generally controlled at 2 - 10 L / min, the argon blowing flow rate of the upper nozzle is generally controlled at 2 - 10 L / min, and the total blowing argon flow rate at the three locations is generally controlled at 10 - 30 L / min; however, using such a small flow rate of blowing argon cannot well control problems such as clogging of the continuous casting nozzle and accumulation of inclusions at the head of the stopper rod. Summary of the Invention

[0003] To solve the problems existing in this technology, the main object of the present invention is to propose a method for efficiently removing inclusions by blowing hydrogen during continuous casting production.

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

[0005] A method for efficiently removing inclusions by blowing hydrogen during continuous casting production, during continuous casting production, a large flow rate of hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas is blown into the molten steel at the argon seal of the submerged entry nozzle slide plate, the stopper rod, and the upper nozzle of the slide plate, inhibiting clogging of the continuous casting nozzle, accumulation of inclusions at the head of the stopper rod and the upper nozzle of the slide plate, inhibiting fluctuations in the mold liquid level, reducing the increase in the number of inclusions caused by slag entrainment, and generating a large number of dispersed micro-bubbles, capturing inclusions in the molten steel, promoting the floating and removal of inclusions or promoting the aggregation and growth of inclusions on the surface of the bubbles, reducing the number of harmful inclusions in the steel; at the same time, in the mold, some bubbles are captured by the solidified shell and remain in the continuous casting billet, but due to the small size of the bubbles, they are easily pressed together during rolling and are not likely to cause product defects.

[0006] The beneficial effects of the present invention are as follows:

[0007] The present invention provides a method for efficiently removing inclusions by blowing hydrogen during continuous casting production. During continuous casting production, a large flow of hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas is introduced into the molten steel at the argon seal of the submerged entry nozzle slide plate, the stopper rod and the slide plate nozzle, which can improve the cleanliness of the steel and significantly enhance the cleanliness and quality of some hydrogen-insensitive steels. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0009] Figure 1 It is a schematic diagram of the method for efficiently removing inclusions by blowing hydrogen during continuous casting production of the present invention.

[0010] In the figure, 1 - blowing hydrogen through the stopper rod; 2 - blowing hydrogen through the nozzle on the slide plate; 3 - blowing hydrogen at the argon seal of the slide plate.

[0011] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] The following will clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0013] According to one aspect of the present invention, the present invention provides the following technical solutions:

[0014] As Figure 1As shown, a method for efficiently removing inclusions by blowing hydrogen in continuous casting production. During continuous casting production, hydrogen is blown at the argon seal of the submerged entry nozzle slide plate 3, at the stopper rod 1, and at the nozzle on the slide plate 2. Specifically, during continuous casting production, a large flow of hydrogen gas, hydrogen-argon mixed gas, or hydrogen-nitrogen mixed gas is blown into the molten steel at the argon seal of the submerged entry nozzle slide plate, the stopper rod, and the nozzle on the slide plate, inhibiting the clogging of the continuous casting nozzle, the accumulation of inclusions at the stopper rod tip and the nozzle on the slide plate, inhibiting the fluctuation of the mold liquid level, reducing the increase in the number of inclusions caused by slag entrainment, and generating a large number of dispersed and tiny hydrogen bubbles, hydrogen-argon mixed bubbles, or hydrogen-nitrogen mixed bubbles. Since the hydrogen in the bubbles rapidly dissolves into the molten steel, the generated bubbles gradually become smaller, and the small bubbles capture inclusions in the molten steel; some small bubbles float up into the upper protective slag in the mold, promoting the removal of inclusions; some small bubbles promote the enrichment of inclusions on the surface of the bubbles and are finally captured by the solidified shell. However, due to the small size of the bubbles, they are pressed together during the rolling of the billet and do not produce linear defects that cause the downgrading of cold-rolled sheets; some small bubbles disappear in the molten steel, and the inclusions captured in these small bubbles remain in the steel, but due to the small size of the inclusions, they also do not produce linear defects that cause the downgrading of cold-rolled sheets. On the other hand, due to the small size of the bubbles, a large number of small bubbles capture fine inclusions in the molten steel, promoting the aggregation and growth of inclusions, reducing the fine inclusions less than 2 microns in the billet, and significantly improving the control level of fine inclusions in steel grades such as electrical steel.

[0015] Preferably, the volume ratio of hydrogen in the hydrogen-argon mixed gas and the hydrogen-nitrogen mixed gas is both 30 - 100%. Specifically, the volume ratio of hydrogen in the hydrogen-argon mixed gas and the hydrogen-nitrogen mixed gas can be, for example, any one of 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% or the range between any two of them.

[0016] Preferably, the blowing pressure of hydrogen gas, hydrogen-argon mixed gas, or hydrogen-nitrogen mixed gas is 0.2 - 1.0 MPa. Specifically, the blowing pressure of hydrogen gas, hydrogen-argon mixed gas, or hydrogen-nitrogen mixed gas can be, for example, any one of 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa or the range between any two of them.

[0017] Preferably, hydrogen gas, a hydrogen-argon mixture gas, or a hydrogen-nitrogen mixture gas is blown into the molten steel through the original argon-sealing argon-blowing system at the argon seal of the submerged entry nozzle slide plate. The blowing flow rate is 1 to 10 times the original argon-blowing flow rate. Specifically, the blowing flow rate of hydrogen gas, a hydrogen-argon mixture gas, or a hydrogen-nitrogen mixture gas at the argon seal of the submerged entry nozzle slide plate is 5 to 100 L / min; more specifically, the blowing flow rate of hydrogen gas, a hydrogen-argon mixture gas, or a hydrogen-nitrogen mixture gas at the argon seal of the submerged entry nozzle slide plate can be any one of, for example, 5 L / min, 10 L / min, 20 L / min, 30 L / min, 40 L / min, 50 L / min, 60 L / min, 70 L / min, 80 L / min, 90 L / min, 100 L / min or the range between any two of them.

[0018] Preferably, the stopper rod gas blowing is that gas blows into the molten steel from the top of the stopper rod through the original stopper rod argon-blowing system. The stopper rod gas blowing flow rate is 2 to 30 times the original argon-blowing flow rate. Specifically, the blowing flow rate of hydrogen gas, a hydrogen-argon mixture gas, or a hydrogen-nitrogen mixture gas of the stopper rod is 5 to 300 L / min; more specifically, the blowing flow rate of hydrogen gas, a hydrogen-argon mixture gas, or a hydrogen-nitrogen mixture gas of the stopper rod can be any one of, for example, 5 L / min, 10 L / min, 20 L / min, 50 L / min, 100 L / min, 150 L / min, 200 L / min, 250 L / min, 300 L / min or the range between any two of them.

[0019] Preferably, the nozzle gas blowing on the slide plate is that gas blows into the molten steel through the nozzle on the slide plate from the original nozzle argon-blowing system on the slide plate. The nozzle gas blowing flow rate on the slide plate is 2 to 30 times the original argon-blowing flow rate. Specifically, the blowing flow rate of hydrogen gas, a hydrogen-argon mixture gas, or a hydrogen-nitrogen mixture gas of the nozzle on the slide plate is 5 to 300 L / min. More specifically, the blowing flow rate of hydrogen gas, a hydrogen-argon mixture gas, or a hydrogen-nitrogen mixture gas of the nozzle on the slide plate can be any one of, for example, 5 L / min, 10 L / min, 20 L / min, 50 L / min, 100 L / min, 150 L / min, 200 L / min, 250 L / min, 300 L / min or the range between any two of them.

[0020] Further preferably, the total blowing flow rate of hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas at the argon seal of the submerged entry nozzle slide plate, the stopper rod and the upper nozzle of the slide plate is 15 - 400 L / min. Specifically, the total blowing flow rate of hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas at the argon seal of the submerged entry nozzle slide plate, the stopper rod and the upper nozzle of the slide plate can be, for example, any one of 15 L / min, 30 L / min, 50 L / min, 100 L / min, 150 L / min, 200 L / min, 250 L / min, 300 L / min, 350 L / min, 400 L / min or the range between any two of them. Even further preferably, the blowing flow rate of the stopper rod or the blowing flow rate of the upper nozzle of the slide plate is higher than the blowing flow rate at the argon seal of the slide plate.

[0021] Preferably, the higher the hydrogen content in the hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas, the greater the total blowing flow rate of the hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas at the argon seal of the submerged entry nozzle slide plate, the stopper rod and the upper nozzle of the slide plate, and the smaller the bubble size generated.

[0022] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0023] Example 1

[0024] A certain domestic steel plant produces automotive sheet DC06. During continuous casting, argon is blown through the stopper rod with a blowing flow rate of 6 L / min, argon is blown through the upper nozzle of the slide plate with a blowing flow rate of 4 L / min, and argon is blown through the argon seal of the slide plate with a blowing flow rate of 6 L / min, and the blowing pressure is 0.5 MPa. During the second heat of continuous casting, the position of the stopper rod rose significantly, indicating that there was clogging of inclusions between the stopper rod and the upper nozzle; during the third heat of continuous casting, the liquid level in the mold fluctuated severely, with a fluctuation range of ±5 mm; after the third heat of production was completed, the nozzle was replaced and production continued; during the fifth heat of continuous casting, the position of the stopper rod was relatively high, and it was difficult to control the steel flow with the stopper rod. At the same time, the liquid level in the mold fluctuated severely, with a fluctuation range of ±7 mm, and continuous casting production was stopped. The average number of inclusions larger than 50 microns at 3 mm below the surface of the cast slab for this casting heat was 0.0035 per mm 2 , and the downgrading rate due to inclusions during the production of cold-rolled sheets was 15.88%.

[0025] When producing automotive sheet DC06 by the method of the present invention, hydrogen is blown through the stopper rod with a hydrogen flow rate of 300 L / min, hydrogen is blown through the upper nozzle of the slide plate with a hydrogen flow rate of 50 L / min, and hydrogen is blown through the argon seal of the slide plate with a hydrogen flow rate of 15 L / min. The hydrogen blowing pressure at the three places is 0.5 MPa. Six heats of steel were continuously cast. The position of the stopper rod did not rise significantly, and the liquid level fluctuation in the mold was well controlled, with a fluctuation range of ±3 mm. The average number of inclusions larger than 50 microns at 3 mm below the surface of the cast slab produced in this casting heat was 0.0010 per mm 2When producing cold-rolled sheets, the downgrading rate due to inclusions is 5.88%.

[0026] Example 2

[0027] A domestic steel mill produces high-grade non-oriented electrical steel L25WV1300 with a thickness of 0.25 mm. During continuous casting, argon is blown through the stopper rod with a flow rate of 4 L / min, through the upper nozzle with a flow rate of 4 L / min, and through the argon seal of the slide plate with a flow rate of 6.5 L / min and a blowing pressure of 0.6 MPa. The average content of inclusions larger than 80 microns in the produced continuous casting billets is 6.32 mg / 10 kg of steel; the number of inclusions with a size of 0.1 - 1.0 microns in the hot-rolled sheets produced by rolling is 51256 per mm 2 ; the medium-frequency low iron loss P1.0 / 400 of the produced product is 12.75 W / kg.

[0028] Using the method of the present invention to produce high-grade non-oriented electrical steel L25WV1300 with a thickness of 0.25 mm, a hydrogen-argon mixed gas is blown through the stopper rod during continuous casting with a flow rate of 350 L / min, through the upper nozzle of the slide plate with a flow rate of 60 L / min, and through the argon seal of the slide plate with a flow rate of 15 L / min. The volume ratio of hydrogen in the hydrogen-argon mixed gas is 90%, and the blowing pressure of the hydrogen-argon mixed gas is 0.6 MPa. The average content of inclusions larger than 80 microns in the produced continuous casting billets is 1.32 mg / 10 kg of steel; the number of inclusions with a size of 0.1 - 1.0 microns in the hot-rolled sheets produced by rolling is 42215 per mm 2 ; the medium-frequency low iron loss P1.0 / 400 of the produced product is 12.40 W / kg.

[0029] Example 3

[0030] A domestic steel mill produces stainless steel 430 with a thickness of 1.0 mm. During continuous casting, argon is blown through the stopper rod with a flow rate of 5 L / min, through the upper nozzle with a flow rate of 4 L / min, and through the argon seal of the slide plate with a flow rate of 6.5 L / min and a blowing pressure of 0.6 MPa. The average oxygen content of the produced continuous casting billets is 45 ppm, and the average content of inclusions larger than 80 microns in the billets is 8.52 mg / 10 kg of steel; the average number of inclusions with a size of 1 - 50 microns in the hot-rolled sheets produced by rolling is 25.45 per mm 2 , and the incidence rate of metallurgical defects in the production of cold-rolled sheets is 2.2%.

[0031] When producing 1.0 mm thick stainless steel 430 by the method of the present invention, a hydrogen-nitrogen mixed gas is blown through the stopper during continuous casting, with a flow rate of 250 L / min, a hydrogen-nitrogen mixed gas is blown through the nozzle on the slide plate, with a flow rate of 100 L / min, and a hydrogen-nitrogen mixed gas is blown at the argon seal of the slide plate, with a flow rate of 15 L / min. The volume ratio of hydrogen in the hydrogen-nitrogen mixed gas is 80%, and the blowing pressure of the hydrogen-nitrogen mixed gas is 0.65 MPa. The average oxygen content of the produced slab is 35 ppm, and the average content of inclusions larger than 80 microns in the slab is 3.26 mg / 10 kg of steel; the average number of inclusions of 1 - 50 microns in the hot-rolled sheet produced by rolling is 16.34 per mm 2 , and the incidence rate of metallurgical defects in the production of cold-rolled sheets by rolling is 0.5%.

[0032] During continuous casting production of the present invention, a large flow of hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas is blown into the molten steel at the argon seal of the submerged nozzle slide plate, the stopper and the nozzle on the slide plate, which can inhibit the blockage of the continuous casting nozzle, the accumulation of inclusions at the stopper head and the nozzle on the slide plate, inhibit the fluctuation of the mold liquid level, reduce the increase in the number of inclusions caused by slag entrainment, and can generate a large number of dispersed and tiny hydrogen bubbles, hydrogen-argon mixed bubbles or hydrogen-nitrogen mixed bubbles, capture inclusions in the molten steel, promote the floating and removal of inclusions or promote the aggregation and growth of inclusions on the surface of the bubbles, and reduce the number of harmful inclusions in the steel.

[0033] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made by using the content of the specification of the present invention under the inventive concept of the present invention, or any direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A method for efficiently removing inclusions by blowing hydrogen in continuous casting production, characterized in that: During continuous casting, hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas is blown into the molten steel at the argon seal of the immersed nozzle slide, the stopper rod and the upper nozzle of the slide, so as to inhibit nozzle blockage, accumulation of inclusions at the stopper rod head and the upper nozzle of the slide, inhibit the fluctuation of the liquid level of the crystallizer, and reduce the increase in the number of inclusions caused by slag rolling; and a large number of dispersed tiny bubbles can be generated to capture inclusions in the molten steel, promote the floating removal of inclusions or promote the aggregation and growth of inclusions on the surface of the bubble, so as to reduce the number of harmful inclusions in the steel.

2. The method for efficiently removing inclusions by blowing hydrogen in continuous casting production according to claim 1, characterized in that: The volume ratio of hydrogen in the hydrogen-argon mixed gas and the hydrogen-nitrogen mixed gas is 30-100%.

3. The method for efficiently removing inclusions by blowing hydrogen in continuous casting production according to claim 1, characterized in that: The blowing pressure of hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas is 0.2 to 1.0 MPa.

4. The method for efficiently removing inclusions by blowing hydrogen in continuous casting production according to claim 1, characterized in that: The blowing flow rate of hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas at the argon seal of the submerged nozzle slide is 5 to 100 L / min.

5. The method for efficiently removing inclusions by blowing hydrogen in continuous casting production according to claim 1, characterized in that: The flow rate of hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas blown into the stopper rod is 5 to 300 L / min.

6. The method for efficiently removing inclusions by using hydrogen in continuous casting production according to claim 1, characterized in that: The blowing flow rate of hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas at the water inlet of the slide plate is 5 to 300 L / min.

7. The method for efficiently removing inclusions by blowing hydrogen in continuous casting production according to claim 1, characterized in that: The total flow rate of hydrogen, hydrogen-argon mixed gas or hydrogen-nitrogen mixed gas blown into the argon seal of the submerged nozzle slide, the stopper rod and the nozzle on the slide is 15 to 400 L / min.

8. The method for efficiently removing inclusions by blowing hydrogen in continuous casting production according to claim 1, characterized in that: The blowing flow rate of the stopper rod or the blowing flow rate of the water inlet on the slide is higher than the blowing flow rate at the argon seal of the slide.

9. The method for efficiently removing inclusions by blowing hydrogen in continuous casting production according to claim 1, characterized in that: The higher the hydrogen content in the hydrogen-argon mixed gas or the hydrogen-nitrogen mixed gas, the greater the total blowing flow of the hydrogen-argon mixed gas or the hydrogen-nitrogen mixed gas at the argon seal of the submerged nozzle slide, the stopper rod and the upper nozzle of the slide.

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