WO2023188837A1 - Submerged entry nozzle for continuous casting, and continuous casting method for steel - Google Patents
Submerged entry nozzle for continuous casting, and continuous casting method for steel Download PDFInfo
- Publication number
- WO2023188837A1 WO2023188837A1 PCT/JP2023/003993 JP2023003993W WO2023188837A1 WO 2023188837 A1 WO2023188837 A1 WO 2023188837A1 JP 2023003993 W JP2023003993 W JP 2023003993W WO 2023188837 A1 WO2023188837 A1 WO 2023188837A1
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- WIPO (PCT)
- Prior art keywords
- discharge hole
- mold
- discharge
- molten steel
- immersion nozzle
- Prior art date
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 100
- 239000010959 steel Substances 0.000 title claims abstract description 100
- 238000009749 continuous casting Methods 0.000 title claims abstract description 59
- 238000000034 method Methods 0.000 title claims description 15
- 238000005266 casting Methods 0.000 claims abstract description 12
- 238000007654 immersion Methods 0.000 claims description 92
- 239000000843 powder Substances 0.000 claims description 21
- 239000011261 inert gas Substances 0.000 claims description 20
- 230000002829 reductive effect Effects 0.000 claims description 10
- 230000003068 static effect Effects 0.000 claims description 3
- 238000007664 blowing Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 230000005499 meniscus Effects 0.000 description 23
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 16
- 239000007789 gas Substances 0.000 description 10
- 229910052786 argon Inorganic materials 0.000 description 8
- 230000007547 defect Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 3
- 230000035515 penetration Effects 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 230000036961 partial effect Effects 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/114—Treating the molten metal by using agitating or vibrating means
- B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
- B22D41/50—Pouring-nozzles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
- B22D41/50—Pouring-nozzles
- B22D41/58—Pouring-nozzles with gas injecting means
Definitions
- the present invention relates to a immersion nozzle for injecting molten steel into a mold during continuous casting of molten steel, and a continuous steel casting method using the immersion nozzle.
- the present invention relates to an immersion nozzle for continuous casting and a method for continuous casting of steel, which can suppress both the capture of inert gas bubbles blown into the immersion nozzle into the solidified shell and the entrainment of mold powder into the solidified shell. .
- the following two criteria are used to judge the quality of steel slabs manufactured with a continuous casting machine.
- the first is that the amount of inert gas bubbles such as argon gas blown into the molten steel flowing down the immersion nozzle is trapped in the slab.
- the second problem is that the amount of mold powder added to the meniscus (molten steel surface in the mold) that is captured in the slab is small. Inert gas bubbles and mold powder trapped in the slab cause surface defects on steel products, so it is important to reduce them.
- the immersion nozzle used is generally a immersion nozzle that has discharge holes facing the short sides of the left and right molds. Therefore, the discharge flow of molten steel discharged from the discharge hole of the immersion nozzle collides with the solidified shell on the short side of the mold (short side solidified shell of the slab), and after the collision, branches upward and downward.
- One of the branched flows becomes a flow heading downwards from the mold (hereinafter referred to as “branched downward flow”), and the other becomes a flow directed toward the upper meniscus (hereinafter referred to as "branched upward flow").
- the branched upward flow toward the meniscus forms an upward flow along the short side solidified shell of the slab slab (hereinafter referred to as "short side upward flow”).
- This upward flow on the short side has a large effect on the flow velocity of molten steel at the meniscus.
- the faster the branched upward flow the faster the short side upward flow, and as the flow velocity of the short side upward flow increases, the flow rate of molten steel at the meniscus increases.
- the frequency of the mold powder present on the meniscus being rolled into the solidified shell is increased.
- the problem is how to slow down the branching upward flow after the solidified shell collides with the short side of the slab.
- short side downward flow the branched downward flow heading below the mold forms a downward flow along the short side solidified shell of the slab slab (hereinafter referred to as "short side downward flow").
- This downward flow on the short side reaches deep into the unsolidified layer.
- the faster the branched downward flow becomes the faster the short side downward flow becomes, and the penetration depth of the short side downward flow into the unsolidified layer increases.
- Inert gas such as argon gas is blown into the molten steel flowing down inside the immersion nozzle to prevent alumina adhesion on the inner wall of the immersion nozzle, and is discharged as bubbles from the discharge hole of the immersion nozzle to the molten steel in the mold. .
- a part of the inert gas bubbles discharged into the molten steel in the mold enters the lower part of the mold along with the branched downward flow.
- Patent Document 1 discloses that the immersed part of the immersion nozzle into molten steel is formed such that the opening area of the discharge hole provided on the lower side is smaller than the opening area of the discharge hole provided on the upper side.
- an immersion nozzle for continuous casting that has a plurality of upper and lower discharge holes, and in which the inner diameter of the molten steel flow path inside the immersion nozzle is smaller in the area where the discharge hole is installed than in the upper part where the discharge hole is not installed. is disclosed.
- the discharge flow from the discharge hole can be made to be a slow and uniform flow, thereby making it possible to weaken the downward flow on the short side, and to prevent inert gas bubbles and non-metallic inclusions from flowing into the slab. It is said that the amount of trapped water can be reduced.
- Patent Document 2 discloses that the immersion nozzle has four discharge holes in the molten steel immersion portion: an upper left row, a lower left row, an upper right row, and a lower right row, and the opening area of the lower discharge hole is as follows. is smaller than the opening area of the upper discharge hole, and the ratio of the opening area of the lower discharge hole to the sum of the opening areas of the upper and lower discharge holes is 0.2 or more and 0.4 or less;
- a submerged nozzle for continuous casting is disclosed that has a discharge hole formed such that the discharge angle of the discharge hole is downward by 10 degrees or more with respect to the discharge angle of the upper discharge hole.
- the flow rate of molten steel near the inner wall on the solidified shell side of the short side of the slab can be sufficiently controlled, thereby preventing inert gas bubbles and nonmetallic inclusions from flowing downward on the short side. It is possible to suppress the intrusion into the deep part of the slab and obtain slabs with fewer internal defects.
- Patent Document 3 discloses that a part of the mold that is immersed in molten steel has two or more pairs of discharge holes that are symmetrical with respect to the axis of the immersion nozzle, and two discharge holes that are vertically positioned above and below.
- the opening area of the discharge hole located on the lower side is equal to or larger than the opening area of the discharge hole located on the upper side, and the discharge angle of each discharge hole is an upward limit of 15° with respect to the horizontal. and the downward limit is 50° with respect to the horizontal, and with two discharge holes located vertically above and below, the discharge angle of the discharge hole located on the lower side is the discharge angle of the discharge hole located on the upper side.
- a submerged nozzle is disclosed in which the downward angle is larger than that of the immersion nozzle, and the difference between the discharge angle of the discharge hole located on the lower side and the discharge angle of the discharge hole located on the upper side is 20 degrees or more and 55 degrees or less.
- the above conventional technology has the following problems.
- the preferred range of the discharge angle of the discharge hole is from 10 degrees upward to 45 degrees downward.
- the discharge angle of the discharge hole provided on the lower side and the discharge angle of the discharge hole provided on the upper side are the same. In other words, there is no difference between the discharge angle of the discharge holes provided on the lower side and the discharge angle of the discharge holes provided on the upper side. Therefore, the discharge streams discharged from the upper and lower discharge holes merge with each other, making it difficult to obtain the ideal discharge flow damping effect.
- Patent Document 2 has a structure in which the opening area of the lower discharge hole is smaller than the opening area of the upper discharge hole, and the difference between the discharge angle of the lower discharge hole and the discharge angle of the upper discharge hole. Since this is small, the flow rate of molten steel at the meniscus increases, and there is a high risk that mold powder will be involved.
- Patent Document 3 describes the angle of the discharge hole, there is no specific description of the relationship between the internal cross-sectional area of the straight body of the submerged nozzle and the area of the discharge hole, and the detailed conditions are unknown. However, it is difficult to imagine that any improvement will actually be achieved.
- the present invention has been made in view of the above circumstances, and its purpose is to provide an immersion nozzle for continuous casting that improves slab quality when pouring molten steel into a continuous casting mold during continuous steel casting. It is to provide.
- inert gas bubbles such as argon gas blown into the molten steel flowing down the immersion nozzle are stably prevented from being captured in the slab, and mold powder added to the meniscus is captured in the slab.
- a continuous casting immersion nozzle according to the present invention for solving the above problems is a bottomed cylindrical immersion nozzle for continuous casting that injects molten steel into a continuous casting mold.
- the part immersed in the molten steel has two or more pairs of discharge holes that are axially symmetrical with respect to the axis of the immersion nozzle, and the molten steel flow path in the straight body of the immersion nozzle extends from the upper end of the upper discharge hole.
- the inner diameter of the immersion nozzle is the same as that of other parts or reduced in the range up to the bottom of the immersion nozzle, and the opening area on one side of the upper discharge hole is S3, and the opening area on one side of the lower discharge hole is S4.
- the ratio of the internal cross-sectional area (S1) of the straight body in the range from the upper end to the upper end of the upper discharge hole to the total opening area of one side of the discharge hole (S3+S4) is in the range of 0.30 to 0.50, and the upper
- the ratio of the internal cross-sectional area (S2) of the straight body in the range from the upper end of the discharge hole to the bottom of the immersion nozzle to the total opening area (S3+S4) on one side of the discharge hole is in the range of 0.10 to 0.40
- the inner cross-sectional area of the immersion nozzle straight body (S1, S2) and the opening area of one side of the discharge hole (S3, S4) have a relationship of 0.20 ⁇ (S2/S4) ⁇ (S1/S3) ⁇ 1.0.
- the discharge angle of each discharge hole is in the range of +20° to -50° with the upward direction being positive based on the horizontal plane, and the discharge angle of the vertically lower discharge hole is equal to that of the vertically upper discharge hole. It is characterized by being vertically downward in the range of 20° to 55° based on the discharge angle.
- the two discharge holes located vertically in a vertical position are oriented in different directions in a horizontal plane, and at least one pair of the discharge holes are arranged in the mold. Orientation parallel to the long sides may be a more preferred solution.
- the continuous casting method of steel according to the present invention uses the above-mentioned immersion nozzle, adds mold powder to the surface of the molten steel in the continuous casting mold, and inert gas is added to the molten steel flowing down the molten steel flow path of the immersion nozzle.
- the molten steel in the tundish is injected into the mold through the immersion nozzle while blowing.
- the method for continuous casting of steel according to the present invention is as follows: (a) Direct current flows from a DC magnetic field generator installed on the back side of the continuous casting mold to the molten steel in the mold above the vertically uppermost discharge hole of the immersion nozzle and below the vertically lowermost discharge hole. Injecting molten steel in the tundish into the mold through the immersion nozzle while applying a static magnetic field; (b) While applying an AC moving magnetic field to the molten steel in the mold from an AC magnetic field generator installed on the back side of the continuous casting mold, the molten steel in the tundish is injected into the mold through the immersion nozzle. to do, etc. may be a more preferable solution.
- the discharge flow rate of molten steel discharged from the upper and lower discharge holes of the immersion nozzle can be maintained appropriately, and the discharge streams discharged from the upper and lower discharge holes can join together.
- the short side of the slab collides with the solidified shell.
- the discharge flow from the discharge hole located on the upper side branches down after colliding with the solidified shell on the short side of the slab, and the discharge flow from the discharge hole located on the lower side branches after colliding with the solidified shell on the short side of the slab.
- the rising flow collides with the rising flow, and the respective flow velocities are attenuated.
- the downward flow on the short side that affects the trapping of inert gas bubbles in the slab is the branched downward flow after the discharge flow discharged from the vertically lowest discharge hole collides with the solidified shell on the short side of the slab. becomes the main subject.
- the upward flow on the short side that affects the flow velocity of molten steel at the meniscus, which controls the entrainment of mold powder is mainly the upward flow branching off after the discharge flow discharged from the uppermost discharge hole collides with the solidified shell on the short side of the slab. becomes.
- (a) is a longitudinal cross-sectional view of a submerged nozzle according to an embodiment of the present invention
- (b) is a perspective view seen from above in the discharge direction. It is a figure which shows typically the investigation result of the flow in a mold in the water model experiment which simulated the flow of molten steel in a mold using the immersion nozzle concerning the said embodiment.
- the width of the slab is much larger than the thickness of the slab, and slab slabs of various widths are required.
- the slab width/slab thickness is often in the range of about 4 to 12. Therefore, continuous casting machines that manufacture slab slabs use continuous casting molds that correspond to the cross-sectional dimensions of the slab slabs to be cast.
- the continuous casting mold has a pair of opposing mold long sides and a pair of opposing mold short sides in order to adjust the rectangular mold internal space, and the mold short sides can move inside the mold long sides. It is composed of
- a immersion nozzle having one or more pairs of discharge holes facing each other on a pair of opposing short sides of the mold is used as the immersion nozzle for injecting molten steel into this continuous casting mold.
- Molten steel is injected from each discharge hole toward the short side of each mold. Therefore, the discharge flow of molten steel discharged from the discharge hole collides with the solidified shell on the short side of the mold, that is, the solidified shell on the short side of the slab, and after the collision, branches upward and downward.
- One of them is a flow directed downwards from the mold, that is, a branched downward flow.
- the other flow is a flow toward the upper meniscus, that is, a branched upward flow.
- the branched upward flow toward the meniscus forms an upward flow along the short side solidified shell of the slab slab, that is, a short side upward flow.
- the branched downward flow toward the lower part of the mold forms a downward flow along the short side solidified shell of the slab slab, that is, a short side downward flow.
- the immersion nozzle according to this embodiment is a bottomed cylindrical refractory that injects molten steel into a continuous casting mold.
- the continuous casting mold has two or more pairs of discharge holes that are symmetrical with respect to the axis of the immersion nozzle in a portion that is immersed in molten steel.
- the molten steel flow path in the straight body of the immersed nozzle has the same inner diameter as other parts or has a reduced diameter in a range from the upper end of the upper discharge hole to the bottom of the immersed nozzle.
- the discharge angle of each discharge hole is in the range of +20° to ⁇ 50° for the discharge holes arranged above and below.
- the discharge angle of the discharge hole on the lower side in the vertical direction is downward in the vertical direction within a range of 20° to 55° based on the discharge angle of the discharge hole on the upper side in the vertical direction.
- the discharge angle of the discharge hole refers to the angle formed between the central axis of the discharge hole and the horizontal plane, and the upward direction is positive.
- the immersion nozzle according to this embodiment has two or more pairs of discharge holes that are axially symmetrical with respect to the axis of the immersion nozzle in a portion of the continuous casting mold that is immersed in molten steel. This is because by having two or more pairs of discharge holes that are axially symmetrical, the discharge flow discharged from the discharge holes is dispersed and the flow velocity of the discharge flow is reduced. As a result, both the branched downward flow and the branched upward flow that are formed after the discharge flow collides with the short side solidified shell of the slab are decelerated.
- the molten steel flow path in the straight body of the immersed nozzle has the same inner diameter as other parts or has a reduced diameter in the range from the upper end of the upper discharge hole to the bottom of the immersed nozzle.
- the discharge angle of each discharge hole is in the range of +20° to ⁇ 50° for the discharge holes arranged above and below. This is because if the discharge angle of each discharge hole is set upwards from 20 degrees upwards with respect to the horizontal, the discharge flow from the discharge hole provided at the uppermost side in the vertical direction will not collide with the solidified shell on the short side of the slab. This is because there is a risk that the vehicle will head directly toward the meniscus without being decelerated. On the other hand, if the discharge angle of each discharge hole is set downward from 50 degrees with respect to the horizontal, the position where the discharge flow from the discharge hole provided at the lowest vertical side collides with the solidified shell on the short side of the slab will be in the mold. This is because the position is deeper than the lower end, and the downward flow on the short side may not be decelerated. Therefore, the discharge angle of the discharge hole is set in the range of +20° to -50°.
- the discharge angle of the discharge hole located on the lower side is larger than the discharge angle of the discharge hole located on the upper side, and the discharge hole located on the lower side
- the difference between the discharge angle of the hole and the discharge angle of the discharge hole located on the upper side is 20° or more and 55° or less. The reason for doing this is to prevent the discharge flow from the discharge hole located on the upper side and the discharge flow from the discharge hole located on the lower side from merging before colliding with the solidified shell on the short side of the slab. be. If the difference in discharge angle is less than 20°, there is a possibility that the discharge flows from the two discharge holes will merge.
- the difference in discharge angle exceeds 55°
- the discharge flow from the discharge hole located on the lower side collides with the solidified shell on the short side of the slab below the lower end of the mold, and the penetration depth of the downward flow on the short side increases. may become deeper.
- the discharge flow from the discharge hole located on the upper side collides with the short side solidified shell of the slab directly below the meniscus, and the upward flow on the short side becomes faster.
- the two discharge holes located vertically in a vertical position are oriented in different directions in a horizontal plane, and at least one pair of the discharge holes is parallel to the long side surface of the mold. It is preferable to face the direction. It is preferable if the discharge flow from the upper discharge hole and the discharge flow from the lower discharge hole are directed in different directions within the horizontal plane, since this reduces the risk of the discharge flows interfering with each other and merging, and increasing the dispersion effect of the discharge flow. .
- the directions that differ in the horizontal plane are at most less than 90°.
- the flow of molten steel in the mold can be appropriately controlled by orienting the discharge hole with a large discharge flow rate in a direction parallel to the long side surface of the mold among the two discharge holes located vertically above and below.
- FIG. 1 shows an immersion nozzle for continuous casting according to an embodiment of the present invention.
- FIG. 1(a) is a vertical cross-sectional view taken along a plane including the central axis C of the immersion nozzle 1 and the central axis of the discharge hole 2, and FIG. It is a perspective view seen from the direction.
- the immersed nozzle 1 according to the embodiment shown in FIG. 1 has two pairs of discharge holes 2 that are axially symmetrical with respect to the axis C of the immersed nozzle 1 above and below the portion immersed in molten steel in the vertical direction. It is 1.
- reference numeral 1 is an immersion nozzle
- 2 is a discharge hole
- 3 is a discharge hole located on the vertically upper side (hereinafter referred to as “upper discharge hole")
- 4 is a discharge hole located on the vertically lower side (hereinafter referred to as “upper discharge hole”).
- 5 is the molten steel flow path provided inside the immersion nozzle
- 6 is the bottom of the immersion nozzle
- 7 is the upper end position of the immersion nozzle 1
- 8 is the upper discharge hole 3.
- the upper end position, ⁇ is the discharge angle of the upper discharge hole 3
- ⁇ is the discharge angle of the lower discharge hole 4
- S1 is the molten steel flow path in the range from the upper end position 7 of the immersion nozzle 1 to the upper end position 8 of the upper discharge hole 3.
- S2 is the area of the molten steel flow path in the range from the upper end position 8 of the upper discharge hole 3 to the bottom 6 of the immersion nozzle 1 (the inner cross-sectional area of the straight body)
- S3 is the upper discharge hole
- S4 is the opening area of one side of the lower discharge hole 4.
- the upper discharge hole 3 corresponds to the discharge hole 2 provided on the uppermost side in the vertical direction
- the lower discharge hole 4 corresponds to the discharge hole 2 provided at the lowest side in the vertical direction.
- the upper discharge hole 3 and the lower discharge hole 4 are in the same direction within a horizontal plane.
- the immersion nozzle 1 of this embodiment is configured as described above.
- a continuous steel casting method using the immersion nozzle 1 according to the present embodiment configured as described above will be explained.
- the immersion nozzle 1 is installed at the bottom of the tundish, and the tundish is installed above the continuous casting mold so that the immersion nozzle 1 is located approximately at the center of the mold space.
- Molten steel is injected into a tundish from a ladle containing molten steel produced in a refining furnace such as a converter, and is injected from the tundish into a continuous casting mold through an immersion nozzle 1.
- Mold powder is added to the meniscus, that is, the surface of the molten steel in the mold, to coat the surface of the molten steel in the mold.
- An inert gas such as argon gas or nitrogen gas is blown into the molten steel flowing down the molten steel channel 5 of the immersion nozzle 1 through a sliding nozzle or an upper nozzle.
- FIG. 2 shows the results of an investigation of the flow in the mold in a water model experiment simulating the flow of molten steel in the mold, which was conducted using the immersion nozzle 1 of this embodiment in which two pairs of discharge holes 2 are provided vertically above and below. It is a figure shown typically. The flow of molten steel in the mold will be explained below based on FIG. 2.
- FIG. 2 shows only one half of the continuous casting mold, the other half also shows a similar configuration with the central axis C as the axis of symmetry.
- 9 is the short side of the mold
- 10 is the bath surface in the mold (corresponding to the meniscus)
- 11 is the discharge flow from the upper discharge hole 3
- 12 is the discharge flow from the lower discharge hole 4
- 13 is the upper side.
- 14 is a branched upward flow formed by branching the discharge flow 11 from the upper discharge hole 3;
- 14 is a branch downward flow formed by branching the discharge flow 11 from the upper discharge hole 3;
- 15 is a branched downward flow formed by branching the discharge flow 11 from the lower discharge hole 4;
- 16 is a branched upward flow formed by branching the discharge flow 12, 16 is a branched downward flow formed by branching the discharge flow 12 from the lower discharge hole 4, and 17 is a short side flowing along the short side 9 of the slab.
- FIG. 18 is a short side downward flow flowing along the short side 9 of the slab, and 19 is a meniscus flow.
- reference numeral 20 is a current meter sensor that measures the flow velocity of the meniscus flow 19 in a water model experiment
- 21 is a current meter sensor that measures the flow velocity of the short side downward flow 18.
- the discharge flow 11 discharged from the upper discharge hole 3 and the discharge flow 12 discharged from the lower discharge hole 4 do not merge until they collide with the short side 9 of the mold. Collisions with side 9. After colliding with the mold short side 9, the discharge flow 11 branches into a branched upward flow 13 and a branched downward flow 14, and the discharge flow 12 branches into a branched upward flow 15 and a branched downward flow 16.
- the discharge flow is dispersed into two, a discharge flow 11 and a discharge flow 12.
- the branched upward flow and branched downward flow when there is a pair of discharge holes 2 (only one on one side) In comparison, in this embodiment, the flow speeds of the branched upward flow 13, the branched downward flow 14, the branched upward flow 15, and the branched downward flow 16 are reduced. Further, the branched downward flow 14 and the branched upward flow 15 are flows directed to opposite sides, and the branched downward flow 14 and the branched upward flow 15 collide and interfere with each other to decelerate each other.
- the short-side upward flow 17 that influences the meniscus flow 19 that controls the entrainment of mold powder is hardly affected by the branched upward flow 15 and is mainly determined by the flow velocity of the branched upward flow 13. Since the branched upward flow 13 is slower than the speed of the branched upward flow when there is a pair of discharge holes 2, the short side upward flow 17 is decelerated, and thereby the flow velocity of the meniscus flow 19 is reduced.
- the short-side downward flow 18, which affects the capture of gas bubbles in the slab, is hardly affected by the branched downward flow 14 and is mainly determined by the flow velocity of the branched downward flow 16. Since the branched downward flow 16 is slower than the velocity of the branched downward flow when there is a pair of discharge holes 2, the flow velocity of the short side downward flow 18 is reduced.
- a meniscus flow 19 that affects the entrainment of mold powder and a downward flow on the short side side 18 that affects the capture of gas bubbles in the slab are created. Both are slowed down. As a result, it is possible to stably suppress both the entrainment of mold powder and the capture of inert gas bubbles in the slab.
- one pair of discharge holes 2 is used on the upper side and one pair on the lower side.
- two or more pairs of discharge holes 2 on either the upper or lower sides, which discharge fluid at the same position in the vertical direction and in different directions horizontally.
- the opening cross-sectional area of the discharge hole 2 is the total opening area on one side with respect to the central axis.
- the short side upward flow 17 affects the molten steel flow velocity at the meniscus which controls the entrainment of mold powder
- the short side side upward flow 17 affects the capture of inert gas bubbles into the slab.
- Both of the side downward flows 18 can be decelerated, and both the entrainment of mold powder and the capture of inert gas bubbles in the slab can be stably suppressed.
- the present invention is configured as described above, and the feasibility and effects of the present invention will be further explained below using Examples.
- a continuous casting operation was carried out using the immersion nozzle 1 according to the present embodiment (invention example).
- the cross-sectional dimensions of the continuously cast slab slab are 220 to 260 mm thick and 1000 to 2200 mm wide.
- Argon gas is used as the inert gas blown into the immersion nozzle 1, and the molten steel surface in the mold is The optimum molding powder was added according to the drawing speed and steel type.
- the immersion nozzle has a pair of discharge holes on the left and right sides of the immersion nozzle and the two pairs of discharge holes on the left and right sides of the immersion nozzle, the installation conditions of the two pairs of discharge holes are within the scope of the present invention.
- An external immersion nozzle was also used.
- the continuous casting mold used was a mold without a magnetic field generator, a DC magnetic field generator was installed on the back of the continuous casting mold, one stage above the upper discharge hole, and one stage below the lower discharge hole.
- Three types of continuous casting molds 2 stages in total, molds placed facing each other across the long sides of the mold, and molds with an AC magnetic field generator placed opposite to each other across the long sides of the mold on the back of the continuous casting mold. It is a mold.
- a slab slab produced using a continuous slab casting machine was hot rolled into a hot rolled steel plate, and the hot rolled steel plate was investigated for surface defects caused by argon gas bubbles and mold powder. Based on these surface defects, argon gas bubbles and mold powder remaining in the slab were evaluated. In other words, it was evaluated that the lower the defect index of the steel product, the fewer argon gas bubbles and mold powder remained in the slab.
- Table 1 shows the conditions of the immersion nozzle
- Table 2 shows the operating conditions and operating results.
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- Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
Abstract
The present invention provides a submerged entry nozzle for improving intermediate casting quality, and also provides a steel production method. This bottomed, cylindrical submerged entry nozzle for continuous casting has at least two pairs of discharge holes at sites submerged in molten steel inside a continuous casting mold, said discharge hole pairs being axisymmetric with respect to the axial center of the nozzle. In a molten steel flow passage inside a trunk section of said nozzle, the inner diameter of the lower section thereof is the same as or smaller than the inner diameter of the upper section thereof. With S3 defined as the opening area of the upper-side discharge holes and S4 defined as the opening area of the lower-side discharge holes, the ratio of a cross-sectional area S1 inside the upper trunk section to the total opening area of the discharge holes on one side is in the range of 0.30 to 0.50, the ratio of a cross-sectional area S2 inside the lower trunk section to the total opening area of the discharge holes on one side is in the range of 0.10 to 0.40, and the relationship 0.20≤(S2/S4)≤(S1/S3)≤1.0 is satisfied. The discharge angle of each discharge hole is in the range of +20° to -50° with upward from the horizontal being positive, and the discharge angle of the lower-side discharge holes is downward in the range of 20° to 55° using the discharge angle of the upper-side discharge holes as a reference.
Description
本発明は、溶鋼を連続鋳造する際に、溶鋼を鋳型内に注入する浸漬ノズルおよびその浸漬ノズルを用いた鋼の連続鋳造方法に関する。詳しくは、浸漬ノズル内に吹き込まれる不活性ガス気泡の凝固シェルへの捕捉およびモールドパウダーの凝固シェルへの巻き込みの双方を抑制することのできる、連続鋳造用の浸漬ノズルおよび鋼の連続鋳造方法に関する。
The present invention relates to a immersion nozzle for injecting molten steel into a mold during continuous casting of molten steel, and a continuous steel casting method using the immersion nozzle. Specifically, the present invention relates to an immersion nozzle for continuous casting and a method for continuous casting of steel, which can suppress both the capture of inert gas bubbles blown into the immersion nozzle into the solidified shell and the entrainment of mold powder into the solidified shell. .
連続鋳造機で製造される鋼鋳片の品質を判定する基準として、以下の2つが挙げられる。1つめは浸漬ノズル内を流下する溶鋼中に吹き込まれたアルゴンガスなどの不活性ガス気泡の鋳片への捕捉量が少ないことである。2つめは、メニスカス(鋳型内溶鋼湯面)に添加されたモールドパウダーの鋳片への捕捉量が少ないことである。鋳片に捕捉された不活性ガス気泡およびモールドパウダーは鋼製品の表面欠陥になるので、低減することが重要である。
The following two criteria are used to judge the quality of steel slabs manufactured with a continuous casting machine. The first is that the amount of inert gas bubbles such as argon gas blown into the molten steel flowing down the immersion nozzle is trapped in the slab. The second problem is that the amount of mold powder added to the meniscus (molten steel surface in the mold) that is captured in the slab is small. Inert gas bubbles and mold powder trapped in the slab cause surface defects on steel products, so it is important to reduce them.
連続鋳造機でスラブ鋳片を鋳造する場合、一般的に、使用する浸漬ノズルは、左右の鋳型短辺に相対する吐出孔を有する浸漬ノズルである。したがって、浸漬ノズルの吐出孔から吐出された溶鋼の吐出流は、鋳型短辺側の凝固シェル(鋳片短辺凝固シェル)に衝突し、衝突した後に上下に分岐する。分岐した流れの一方は鋳型下方に向かう流れ(以下、「分岐下降流」と記す)となり、他方は上部のメニスカスに向かう流れ(以下、「分岐上昇流」と記す)となる。
When casting slab slabs with a continuous casting machine, the immersion nozzle used is generally a immersion nozzle that has discharge holes facing the short sides of the left and right molds. Therefore, the discharge flow of molten steel discharged from the discharge hole of the immersion nozzle collides with the solidified shell on the short side of the mold (short side solidified shell of the slab), and after the collision, branches upward and downward. One of the branched flows becomes a flow heading downwards from the mold (hereinafter referred to as "branched downward flow"), and the other becomes a flow directed toward the upper meniscus (hereinafter referred to as "branched upward flow").
このうち、メニスカスに向う分岐上昇流は、スラブ鋳片の短辺凝固シェルに沿った上昇流(以下、「短辺側上昇流」と記す)を形成する。そして、この短辺側上昇流はメニスカスでの溶鋼流速に大きな影響を与える。つまり、分岐上昇流が速いほど短辺側上昇流が速くなり、短辺側上昇流の流速増加に伴って、メニスカスでの溶鋼流速が速くなる。その結果としてメニスカス上に存在するモールドパウダーの凝固シェルへの巻き込み頻度を増大させる。つまり、モールドパウダー性の欠陥を低減するためには、鋳片短辺凝固シェル衝突後の分岐上昇流を如何に減速するかが課題となる。
Of these, the branched upward flow toward the meniscus forms an upward flow along the short side solidified shell of the slab slab (hereinafter referred to as "short side upward flow"). This upward flow on the short side has a large effect on the flow velocity of molten steel at the meniscus. In other words, the faster the branched upward flow, the faster the short side upward flow, and as the flow velocity of the short side upward flow increases, the flow rate of molten steel at the meniscus increases. As a result, the frequency of the mold powder present on the meniscus being rolled into the solidified shell is increased. In other words, in order to reduce mold powder defects, the problem is how to slow down the branching upward flow after the solidified shell collides with the short side of the slab.
一方、鋳型下方に向かう分岐下降流は、スラブ鋳片の短辺凝固シェルに沿った下降流(以下、「短辺側下降流」と記す)を形成する。そして、この短辺側下降流は未凝固層の深くまで到達する。この場合、分岐下降流が速いほど短辺側下降流が速くなり、短辺側下降流の未凝固層への侵入深さが増大する。
On the other hand, the branched downward flow heading below the mold forms a downward flow along the short side solidified shell of the slab slab (hereinafter referred to as "short side downward flow"). This downward flow on the short side reaches deep into the unsolidified layer. In this case, the faster the branched downward flow becomes, the faster the short side downward flow becomes, and the penetration depth of the short side downward flow into the unsolidified layer increases.
浸漬ノズル内壁でのアルミナ付着を防止するために浸漬ノズル内を流下する溶鋼中に吹き込まれたアルゴンガスなどの不活性ガスは、気泡となって浸漬ノズルの吐出孔から鋳型内溶鋼に排出される。鋳型内溶鋼に排出された不活性ガス気泡の一部は、分岐下降流とともに鋳型下方に侵入する。分岐下降流が速いほど短辺側下降流が速くなり、結果として不活性ガス気泡の未凝固層内部への侵入深さが深くなり、不活性ガス気泡の鋳片への捕捉量が増大する。つまり、不活性ガス気泡の鋳片への捕捉量を低減するためには、鋳片短辺凝固シェル衝突後の分岐下降流を如何に減速するかが課題となる。
Inert gas such as argon gas is blown into the molten steel flowing down inside the immersion nozzle to prevent alumina adhesion on the inner wall of the immersion nozzle, and is discharged as bubbles from the discharge hole of the immersion nozzle to the molten steel in the mold. . A part of the inert gas bubbles discharged into the molten steel in the mold enters the lower part of the mold along with the branched downward flow. The faster the branched downward flow is, the faster the short side downward flow is, and as a result, the penetration depth of inert gas bubbles into the unsolidified layer becomes deeper, and the amount of inert gas bubbles trapped in the slab increases. That is, in order to reduce the amount of inert gas bubbles trapped in the slab, the problem is how to slow down the branched downward flow after colliding with the solidified shell on the short side of the slab.
これらの課題に対して、いくつかの対策が提案されており、そのうちの一つとして、浸漬ノズルの溶鋼への浸漬部の左右の上下に、複数の吐出孔を有する浸漬ノズルを使用して連続鋳造する技術が提案されている。
Several countermeasures have been proposed to address these issues, one of which is to use an immersion nozzle with multiple discharge holes above and below the left and right of the immersion part of the molten steel. A casting technique has been proposed.
例えば、特許文献1には、浸漬ノズルの溶鋼への浸漬部に、下側に設けられた吐出孔の開口部面積が上側に設けられた吐出孔の開口部面積よりも小さくなるように形成された、上下複数の吐出孔を有し、かつ、浸漬ノズル内部の溶鋼流路の内径が、吐出孔の設置されていない上部よりも吐出孔の設置された範囲の方が小さい連続鋳造用浸漬ノズルが開示されている。
For example, Patent Document 1 discloses that the immersed part of the immersion nozzle into molten steel is formed such that the opening area of the discharge hole provided on the lower side is smaller than the opening area of the discharge hole provided on the upper side. In addition, an immersion nozzle for continuous casting that has a plurality of upper and lower discharge holes, and in which the inner diameter of the molten steel flow path inside the immersion nozzle is smaller in the area where the discharge hole is installed than in the upper part where the discharge hole is not installed. is disclosed.
特許文献1によれば、吐出孔からの吐出流を緩慢かつ均一な流れにでき、これにより、短辺側下降流を弱くすることができ、不活性ガス気泡や非金属介在物の鋳片への捕捉量を減少させることができるとしている。
According to Patent Document 1, the discharge flow from the discharge hole can be made to be a slow and uniform flow, thereby making it possible to weaken the downward flow on the short side, and to prevent inert gas bubbles and non-metallic inclusions from flowing into the slab. It is said that the amount of trapped water can be reduced.
特許文献2には、浸漬ノズルの溶鋼への浸漬部に、左列上段、左列下段、右列上段、右列下段の4つの吐出孔を有し、下段の吐出孔の開口部面積は、上段の吐出孔の開口部面積より小さく、かつ、上段および下段の吐出孔の開口部面積の合計に対する下段の吐出孔の開口部面積の比が0.2以上0.4以下であり、下段の吐出孔の吐出角度が上段の吐出孔の吐出角度を基準として10°以上下向きになるように形成された吐出孔を有する連続鋳造用浸漬ノズルが開示されている。
Patent Document 2 discloses that the immersion nozzle has four discharge holes in the molten steel immersion portion: an upper left row, a lower left row, an upper right row, and a lower right row, and the opening area of the lower discharge hole is as follows. is smaller than the opening area of the upper discharge hole, and the ratio of the opening area of the lower discharge hole to the sum of the opening areas of the upper and lower discharge holes is 0.2 or more and 0.4 or less; A submerged nozzle for continuous casting is disclosed that has a discharge hole formed such that the discharge angle of the discharge hole is downward by 10 degrees or more with respect to the discharge angle of the upper discharge hole.
特許文献2によれば、鋳片短辺凝固シェル側の内壁近傍での溶鋼流速を十分に制御することができ、これにより、不活性ガス気泡や非金属介在物が短辺側下降流を介して鋳片の深部に侵入することを抑制して、内部欠陥の少ない鋳片を得ることができるとしている。
According to Patent Document 2, the flow rate of molten steel near the inner wall on the solidified shell side of the short side of the slab can be sufficiently controlled, thereby preventing inert gas bubbles and nonmetallic inclusions from flowing downward on the short side. It is possible to suppress the intrusion into the deep part of the slab and obtain slabs with fewer internal defects.
特許文献3には、、鋳型内の溶鋼に浸漬される部位に、浸漬ノズルの軸心に対して左右対称である二対以上の吐出孔を有し、鉛直方向上下の位置関係の2つの吐出孔で、下側に位置する吐出孔の開口部面積が上側に位置する吐出孔の開口部面積と等しいかまたは大きく、各吐出孔の吐出角度は、水平に対して上向き15°を上向きの限度とし、かつ、水平に対して下向き50°を下向きの限度とし、鉛直方向上下の位置関係の2つの吐出孔で、下側に位置する吐出孔の吐出角度が上側に位置する吐出孔の吐出角度よりも下向き角度が大きく、かつ、下側に位置する吐出孔の吐出角度と上側に位置する吐出孔の吐出角度との差が20°以上55°以下である浸漬ノズルが開示されている。
Patent Document 3 discloses that a part of the mold that is immersed in molten steel has two or more pairs of discharge holes that are symmetrical with respect to the axis of the immersion nozzle, and two discharge holes that are vertically positioned above and below. The opening area of the discharge hole located on the lower side is equal to or larger than the opening area of the discharge hole located on the upper side, and the discharge angle of each discharge hole is an upward limit of 15° with respect to the horizontal. and the downward limit is 50° with respect to the horizontal, and with two discharge holes located vertically above and below, the discharge angle of the discharge hole located on the lower side is the discharge angle of the discharge hole located on the upper side. A submerged nozzle is disclosed in which the downward angle is larger than that of the immersion nozzle, and the difference between the discharge angle of the discharge hole located on the lower side and the discharge angle of the discharge hole located on the upper side is 20 degrees or more and 55 degrees or less.
しかしながら、上記従来技術には以下の問題があった。
特許文献1に記載の技術は、吐出孔の吐出角度の好適範囲を上向き10°から下向き45°の範囲としている。ところが、特許文献1の実施例では、下側に設けられた吐出孔の吐出角度と上側に設けられた吐出孔の吐出角度が同じである。つまり、下側に設けられた吐出孔の吐出角度と上側に設けられた吐出孔の吐出角度に差を設けていない。したがって、上下の吐出孔から吐出された吐出流同士が合流してしまい、理想とする吐出流の減衰効果が得られにくい。 However, the above conventional technology has the following problems.
In the technique described inPatent Document 1, the preferred range of the discharge angle of the discharge hole is from 10 degrees upward to 45 degrees downward. However, in the embodiment of Patent Document 1, the discharge angle of the discharge hole provided on the lower side and the discharge angle of the discharge hole provided on the upper side are the same. In other words, there is no difference between the discharge angle of the discharge holes provided on the lower side and the discharge angle of the discharge holes provided on the upper side. Therefore, the discharge streams discharged from the upper and lower discharge holes merge with each other, making it difficult to obtain the ideal discharge flow damping effect.
特許文献1に記載の技術は、吐出孔の吐出角度の好適範囲を上向き10°から下向き45°の範囲としている。ところが、特許文献1の実施例では、下側に設けられた吐出孔の吐出角度と上側に設けられた吐出孔の吐出角度が同じである。つまり、下側に設けられた吐出孔の吐出角度と上側に設けられた吐出孔の吐出角度に差を設けていない。したがって、上下の吐出孔から吐出された吐出流同士が合流してしまい、理想とする吐出流の減衰効果が得られにくい。 However, the above conventional technology has the following problems.
In the technique described in
特許文献2に記載の技術は、下段の吐出孔の開口部面積が上段の吐出孔の開口部面積よりも小さく、また、下段の吐出孔の吐出角度と上段の吐出孔の吐出角度との差が小さいので、メニスカスでの溶鋼流速が速くなり、モールドパウダーの巻き込みの起こる危険性が高い。
The technology described in Patent Document 2 has a structure in which the opening area of the lower discharge hole is smaller than the opening area of the upper discharge hole, and the difference between the discharge angle of the lower discharge hole and the discharge angle of the upper discharge hole. Since this is small, the flow rate of molten steel at the meniscus increases, and there is a high risk that mold powder will be involved.
特許文献3に記載の技術は、吐出孔の角度は記載してあるものの、浸漬ノズルの直胴部内断面積と吐出孔の面積との関係に関する具体的な記載がなく、詳細な条件が不明であり、実際に改善効果が得られるとは考えにくい。
Although the technique described in Patent Document 3 describes the angle of the discharge hole, there is no specific description of the relationship between the internal cross-sectional area of the straight body of the submerged nozzle and the area of the discharge hole, and the detailed conditions are unknown. However, it is difficult to imagine that any improvement will actually be achieved.
本発明は上記事情に鑑みてなされたもので、その目的とするところは、鋼の連続鋳造で溶鋼を連続鋳造用鋳型に注入する際に、鋳片品質を向上させる連続鋳造用の浸漬ノズルを提供することである。つまり、浸漬ノズル内を流下する溶鋼中に吹き込まれたアルゴンガスなどの不活性ガス気泡の鋳片への捕捉を安定して抑制し、かつ、メニスカスに添加されたモールドパウダーの鋳片への捕捉を安定して抑制することである。また、この浸漬ノズルを用いた鋼の連続鋳造方法を提案することである。
The present invention has been made in view of the above circumstances, and its purpose is to provide an immersion nozzle for continuous casting that improves slab quality when pouring molten steel into a continuous casting mold during continuous steel casting. It is to provide. In other words, inert gas bubbles such as argon gas blown into the molten steel flowing down the immersion nozzle are stably prevented from being captured in the slab, and mold powder added to the meniscus is captured in the slab. The aim is to stably suppress the Another object of the present invention is to propose a method for continuous casting of steel using this immersion nozzle.
上記課題を解決するための本発明にかかる連続鋳造用の浸漬ノズルは、連続鋳造用鋳型内に溶鋼を注入する有底筒状の連続鋳造用の浸漬ノズルであって、前記連続鋳造用鋳型内の溶鋼に浸漬される部位に、前記浸漬ノズルの軸心に対して軸対称である二対以上の吐出孔を有し、前記浸漬ノズルの直胴部内溶鋼流路は、上側吐出孔の上端から前記浸漬ノズルの底までの範囲で他の部位と同じ内径または縮径されており、上側吐出孔の片側開口部面積をS3、下側吐出孔の片側開口部面積をS4として、前記浸漬ノズルの上端から前記上側吐出孔の上端までの範囲の直胴部内断面積(S1)の前記吐出孔の片側合計開口部面積(S3+S4)に対する比が0.30~0.50の範囲にあり、前記上側吐出孔の上端から前記浸漬ノズルの底までの範囲の直胴部内断面積(S2)の前記吐出孔の片側合計開口部面積(S3+S4)に対する比が0.10~0.40の範囲にあり、前記浸漬ノズル直胴部内断面積(S1、S2)と吐出孔の片側開口面積(S3、S4)とが、0.20≦(S2/S4)≦(S1/S3)≦1.0の関係を満たし、それぞれの吐出孔の吐出角度は、水平面を基準に上向きを正として、+20°~-50°の範囲にあり、鉛直方向下側の吐出孔の吐出角度が、鉛直方向上側の吐出孔の吐出角度を基準として20°~55°の範囲で鉛直方向下向きであることを特徴とする。
A continuous casting immersion nozzle according to the present invention for solving the above problems is a bottomed cylindrical immersion nozzle for continuous casting that injects molten steel into a continuous casting mold. The part immersed in the molten steel has two or more pairs of discharge holes that are axially symmetrical with respect to the axis of the immersion nozzle, and the molten steel flow path in the straight body of the immersion nozzle extends from the upper end of the upper discharge hole. The inner diameter of the immersion nozzle is the same as that of other parts or reduced in the range up to the bottom of the immersion nozzle, and the opening area on one side of the upper discharge hole is S3, and the opening area on one side of the lower discharge hole is S4. The ratio of the internal cross-sectional area (S1) of the straight body in the range from the upper end to the upper end of the upper discharge hole to the total opening area of one side of the discharge hole (S3+S4) is in the range of 0.30 to 0.50, and the upper The ratio of the internal cross-sectional area (S2) of the straight body in the range from the upper end of the discharge hole to the bottom of the immersion nozzle to the total opening area (S3+S4) on one side of the discharge hole is in the range of 0.10 to 0.40, The inner cross-sectional area of the immersion nozzle straight body (S1, S2) and the opening area of one side of the discharge hole (S3, S4) have a relationship of 0.20≦(S2/S4)≦(S1/S3)≦1.0. The discharge angle of each discharge hole is in the range of +20° to -50° with the upward direction being positive based on the horizontal plane, and the discharge angle of the vertically lower discharge hole is equal to that of the vertically upper discharge hole. It is characterized by being vertically downward in the range of 20° to 55° based on the discharge angle.
なお、本発明にかかる連続鋳造用の浸漬ノズルは、鉛直方向上下の位置関係にある2つの前記吐出孔が、水平面内で異なる方向に向いており、少なくとも1対の前記吐出孔が前記鋳型の長辺面に平行な方向に向いていることが、より好ましい解決手段になり得る。
In addition, in the immersion nozzle for continuous casting according to the present invention, the two discharge holes located vertically in a vertical position are oriented in different directions in a horizontal plane, and at least one pair of the discharge holes are arranged in the mold. Orientation parallel to the long sides may be a more preferred solution.
また、本発明にかかる鋼の連続鋳造方法は、上記浸漬ノズルを使用し、連続鋳造用鋳型内溶鋼表面にモールドパウダーを添加し、前記浸漬ノズルの溶鋼流路を流下する溶鋼中に不活性ガスを吹き込みながら、前記浸漬ノズルを介してタンディッシュ内の溶鋼を前記鋳型内に注入することを特徴とする。
Further, the continuous casting method of steel according to the present invention uses the above-mentioned immersion nozzle, adds mold powder to the surface of the molten steel in the continuous casting mold, and inert gas is added to the molten steel flowing down the molten steel flow path of the immersion nozzle. The molten steel in the tundish is injected into the mold through the immersion nozzle while blowing.
なお、本発明にかかる鋼の連続鋳造方法は、
(a)前記連続鋳造用鋳型の背面に設置された直流磁場発生装置から前記浸漬ノズルの鉛直方向最上部の吐出孔の上側および鉛直方向最下部の吐出孔の下側で鋳型内の溶鋼に直流静磁場を印加しながら、前記浸漬ノズルを介してタンディッシュ内の溶鋼を前記鋳型内に注入すること、
(b)前記連続鋳造用鋳型の背面に設置された交流磁場発生装置から前記鋳型内の溶鋼に交流移動磁場を印加しながら、前記浸漬ノズルを介してタンディッシュ内の溶鋼を前記鋳型内に注入すること、
などが、より好ましい解決手段になり得る。 The method for continuous casting of steel according to the present invention is as follows:
(a) Direct current flows from a DC magnetic field generator installed on the back side of the continuous casting mold to the molten steel in the mold above the vertically uppermost discharge hole of the immersion nozzle and below the vertically lowermost discharge hole. Injecting molten steel in the tundish into the mold through the immersion nozzle while applying a static magnetic field;
(b) While applying an AC moving magnetic field to the molten steel in the mold from an AC magnetic field generator installed on the back side of the continuous casting mold, the molten steel in the tundish is injected into the mold through the immersion nozzle. to do,
etc. may be a more preferable solution.
(a)前記連続鋳造用鋳型の背面に設置された直流磁場発生装置から前記浸漬ノズルの鉛直方向最上部の吐出孔の上側および鉛直方向最下部の吐出孔の下側で鋳型内の溶鋼に直流静磁場を印加しながら、前記浸漬ノズルを介してタンディッシュ内の溶鋼を前記鋳型内に注入すること、
(b)前記連続鋳造用鋳型の背面に設置された交流磁場発生装置から前記鋳型内の溶鋼に交流移動磁場を印加しながら、前記浸漬ノズルを介してタンディッシュ内の溶鋼を前記鋳型内に注入すること、
などが、より好ましい解決手段になり得る。 The method for continuous casting of steel according to the present invention is as follows:
(a) Direct current flows from a DC magnetic field generator installed on the back side of the continuous casting mold to the molten steel in the mold above the vertically uppermost discharge hole of the immersion nozzle and below the vertically lowermost discharge hole. Injecting molten steel in the tundish into the mold through the immersion nozzle while applying a static magnetic field;
(b) While applying an AC moving magnetic field to the molten steel in the mold from an AC magnetic field generator installed on the back side of the continuous casting mold, the molten steel in the tundish is injected into the mold through the immersion nozzle. to do,
etc. may be a more preferable solution.
本発明にかかる浸漬ノズルを使用することで、浸漬ノズルの上下の吐出孔から吐出される溶鋼の吐出流量が適正に保たれ、かつ、上下の吐出孔から吐出された吐出流同士が合流することなく鋳片短辺凝固シェルに衝突する。それにより、上側に位置する吐出孔からの吐出流の鋳片短辺凝固シェル衝突後の分岐下降流と、下側に位置する吐出孔からの吐出流の鋳片短辺凝固シェル衝突後の分岐上昇流とが衝突して、それぞれの流速が減衰する。その結果、不活性ガス気泡の鋳片への捕捉に影響する短辺側下降流は、鉛直方向最下側の吐出孔から吐出された吐出流の鋳片短辺凝固シェル衝突後の分岐下降流が主体となる。一方、モールドパウダーの巻き込みを左右するメニスカスでの溶鋼流速に影響する短辺側上昇流は、最上側の吐出孔から吐出された吐出流の鋳片短辺凝固シェル衝突後の分岐上昇流が主体となる。これにより、短辺側上昇流および短辺側下降流の双方を減速させることができ、モールドパウダーの巻き込みおよび不活性ガス気泡の鋳片への捕捉の双方を安定して抑制することが実現される。したがって、鋼の連続鋳造で本発明にかかる浸漬ノズルを用いて溶鋼を連続鋳造用鋳型に注入する際に、鋳片品質を向上させることが可能となる。
By using the immersion nozzle according to the present invention, the discharge flow rate of molten steel discharged from the upper and lower discharge holes of the immersion nozzle can be maintained appropriately, and the discharge streams discharged from the upper and lower discharge holes can join together. The short side of the slab collides with the solidified shell. As a result, the discharge flow from the discharge hole located on the upper side branches down after colliding with the solidified shell on the short side of the slab, and the discharge flow from the discharge hole located on the lower side branches after colliding with the solidified shell on the short side of the slab. The rising flow collides with the rising flow, and the respective flow velocities are attenuated. As a result, the downward flow on the short side that affects the trapping of inert gas bubbles in the slab is the branched downward flow after the discharge flow discharged from the vertically lowest discharge hole collides with the solidified shell on the short side of the slab. becomes the main subject. On the other hand, the upward flow on the short side that affects the flow velocity of molten steel at the meniscus, which controls the entrainment of mold powder, is mainly the upward flow branching off after the discharge flow discharged from the uppermost discharge hole collides with the solidified shell on the short side of the slab. becomes. This makes it possible to decelerate both the upward flow on the short side and the downward flow on the short side, making it possible to stably suppress both the entrainment of mold powder and the capture of inert gas bubbles in the slab. Ru. Therefore, when pouring molten steel into a continuous casting mold using the immersion nozzle according to the present invention in continuous casting of steel, it is possible to improve the quality of the slab.
以下、本発明の実施の形態について具体的に説明する。なお、各図面は模式的なものであって、現実のものとは異なる場合がある。また、以下の実施形態は、本発明の技術的思想を具体化するための装置や方法を例示するものであり、構成を下記のものに特定するものでない。すなわち、本発明の技術的思想は、特許請求の範囲に記載された技術的範囲内において、種々の変更を加えることができる。
Hereinafter, embodiments of the present invention will be specifically described. Note that each drawing is schematic and may differ from the actual drawing. Furthermore, the following embodiments are intended to exemplify devices and methods for embodying the technical idea of the present invention, and the configuration is not limited to the following. That is, the technical idea of the present invention can be modified in various ways within the technical scope described in the claims.
以下、本発明を具体的に説明する。
スラブ鋳片の横断面は鋳片厚みに対して鋳片幅が格段に大きく、かつ、種々の鋳片幅のスラブ鋳片が必要である。一般に鋳片幅/鋳片厚みが約4~12の範囲にあることが多い。したがって、スラブ鋳片を製造する連続鋳造機では、鋳造対象のスラブ鋳片の横断面寸法に応じた連続鋳造用鋳型が使用されている。その連続鋳造用鋳型は、矩形の鋳型内部空間を調整するために、相対する一対の鋳型長辺と相対する一対の鋳型短辺とを有し、鋳型短辺が鋳型長辺の内側を移動可能に構成されている。 The present invention will be explained in detail below.
In the cross section of a slab slab, the width of the slab is much larger than the thickness of the slab, and slab slabs of various widths are required. Generally, the slab width/slab thickness is often in the range of about 4 to 12. Therefore, continuous casting machines that manufacture slab slabs use continuous casting molds that correspond to the cross-sectional dimensions of the slab slabs to be cast. The continuous casting mold has a pair of opposing mold long sides and a pair of opposing mold short sides in order to adjust the rectangular mold internal space, and the mold short sides can move inside the mold long sides. It is composed of
スラブ鋳片の横断面は鋳片厚みに対して鋳片幅が格段に大きく、かつ、種々の鋳片幅のスラブ鋳片が必要である。一般に鋳片幅/鋳片厚みが約4~12の範囲にあることが多い。したがって、スラブ鋳片を製造する連続鋳造機では、鋳造対象のスラブ鋳片の横断面寸法に応じた連続鋳造用鋳型が使用されている。その連続鋳造用鋳型は、矩形の鋳型内部空間を調整するために、相対する一対の鋳型長辺と相対する一対の鋳型短辺とを有し、鋳型短辺が鋳型長辺の内側を移動可能に構成されている。 The present invention will be explained in detail below.
In the cross section of a slab slab, the width of the slab is much larger than the thickness of the slab, and slab slabs of various widths are required. Generally, the slab width/slab thickness is often in the range of about 4 to 12. Therefore, continuous casting machines that manufacture slab slabs use continuous casting molds that correspond to the cross-sectional dimensions of the slab slabs to be cast. The continuous casting mold has a pair of opposing mold long sides and a pair of opposing mold short sides in order to adjust the rectangular mold internal space, and the mold short sides can move inside the mold long sides. It is composed of
この連続鋳造用鋳型に溶鋼を注入する浸漬ノズルとしては、相対する一対の鋳型短辺に相対する一対以上の吐出孔を有する浸漬ノズルが使用される。それぞれの鋳型短辺に向けてそれぞれの吐出孔から溶鋼を注入している。したがって、吐出孔から吐出された溶鋼の吐出流は、鋳型短辺側の凝固シェル、つまり鋳片短辺凝固シェルに衝突し、衝突した後に上下に分岐する。その一方は鋳型下方に向かう流れ、つまり、分岐下降流となる。また、他方は上部のメニスカスに向かう流れ、つまり、分岐上昇流となる。メニスカスに向う分岐上昇流は、スラブ鋳片の短辺凝固シェルに沿った上昇流、つまり、短辺側上昇流を形成する。鋳型下方に向かう分岐下降流は、スラブ鋳片の短辺凝固シェルに沿った下降流、つまり、短辺側下降流を形成する。
As the immersion nozzle for injecting molten steel into this continuous casting mold, a immersion nozzle having one or more pairs of discharge holes facing each other on a pair of opposing short sides of the mold is used. Molten steel is injected from each discharge hole toward the short side of each mold. Therefore, the discharge flow of molten steel discharged from the discharge hole collides with the solidified shell on the short side of the mold, that is, the solidified shell on the short side of the slab, and after the collision, branches upward and downward. One of them is a flow directed downwards from the mold, that is, a branched downward flow. The other flow is a flow toward the upper meniscus, that is, a branched upward flow. The branched upward flow toward the meniscus forms an upward flow along the short side solidified shell of the slab slab, that is, a short side upward flow. The branched downward flow toward the lower part of the mold forms a downward flow along the short side solidified shell of the slab slab, that is, a short side downward flow.
発明者らは、このようなスラブ連続鋳造機において、短辺側下降流および短辺側上昇流の双方を減速することのできる浸漬ノズルについて検討した。その結果、以下の形状の浸漬ノズルが最適であることがわかった。
すなわち、本実施形態にかかる浸漬ノズルは連続鋳造用鋳型内に溶鋼を注入する有底筒状の耐火物である。そして、連続鋳造用鋳型内の溶鋼に浸漬される部位に、浸漬ノズルの軸心に対して左右対称である二対以上の吐出孔を有する。その浸漬ノズルの直胴部内溶鋼流路は、前記上側吐出孔の上端から前記浸漬ノズルの底までの範囲で他の部位と同じ内径または縮径されている。また、浸漬ノズル内径上部直胴部の断面積S1と吐出孔が配置された直胴部の断面積S2と上に配置された吐出孔の開口部面積S3と下に配置された吐出孔の開口部面積S4とが、S1/(S3+S4)=0.30~0.50、S2/(S3+S4)=0.10~0.40の関係を満たす。加えて、0.20≦(S2/S4)≦(S1/S3)≦1.0の関係を満たす。さらに、各吐出孔の吐出角度は、上下に配置された吐出孔が、+20°から-50°までの範囲にある。そして、鉛直方向下側の吐出孔の吐出角度が、鉛直方向上側の吐出孔の吐出角度を基準として20°~55°の範囲で鉛直方向下向きである。ここで、「吐出孔の吐出角度」とは、吐出孔の中心軸と水平面とのなす角度をいい、上向きを正とする。 The inventors studied a submerged nozzle that can reduce the speed of both the downward flow on the short side and the upward flow on the short side in such a continuous slab casting machine. As a result, it was found that a submerged nozzle with the following shape was optimal.
That is, the immersion nozzle according to this embodiment is a bottomed cylindrical refractory that injects molten steel into a continuous casting mold. The continuous casting mold has two or more pairs of discharge holes that are symmetrical with respect to the axis of the immersion nozzle in a portion that is immersed in molten steel. The molten steel flow path in the straight body of the immersed nozzle has the same inner diameter as other parts or has a reduced diameter in a range from the upper end of the upper discharge hole to the bottom of the immersed nozzle. In addition, the cross-sectional area S1 of the inner diameter upper straight body part of the immersion nozzle, the cross-sectional area S2 of the straight body part where the discharge hole is arranged, the opening area S3 of the discharge hole arranged above, and the opening of the discharge hole arranged below. The partial area S4 satisfies the relationships of S1/(S3+S4)=0.30 to 0.50 and S2/(S3+S4)=0.10 to 0.40. In addition, the relationship 0.20≦(S2/S4)≦(S1/S3)≦1.0 is satisfied. Furthermore, the discharge angle of each discharge hole is in the range of +20° to −50° for the discharge holes arranged above and below. The discharge angle of the discharge hole on the lower side in the vertical direction is downward in the vertical direction within a range of 20° to 55° based on the discharge angle of the discharge hole on the upper side in the vertical direction. Here, "the discharge angle of the discharge hole" refers to the angle formed between the central axis of the discharge hole and the horizontal plane, and the upward direction is positive.
すなわち、本実施形態にかかる浸漬ノズルは連続鋳造用鋳型内に溶鋼を注入する有底筒状の耐火物である。そして、連続鋳造用鋳型内の溶鋼に浸漬される部位に、浸漬ノズルの軸心に対して左右対称である二対以上の吐出孔を有する。その浸漬ノズルの直胴部内溶鋼流路は、前記上側吐出孔の上端から前記浸漬ノズルの底までの範囲で他の部位と同じ内径または縮径されている。また、浸漬ノズル内径上部直胴部の断面積S1と吐出孔が配置された直胴部の断面積S2と上に配置された吐出孔の開口部面積S3と下に配置された吐出孔の開口部面積S4とが、S1/(S3+S4)=0.30~0.50、S2/(S3+S4)=0.10~0.40の関係を満たす。加えて、0.20≦(S2/S4)≦(S1/S3)≦1.0の関係を満たす。さらに、各吐出孔の吐出角度は、上下に配置された吐出孔が、+20°から-50°までの範囲にある。そして、鉛直方向下側の吐出孔の吐出角度が、鉛直方向上側の吐出孔の吐出角度を基準として20°~55°の範囲で鉛直方向下向きである。ここで、「吐出孔の吐出角度」とは、吐出孔の中心軸と水平面とのなす角度をいい、上向きを正とする。 The inventors studied a submerged nozzle that can reduce the speed of both the downward flow on the short side and the upward flow on the short side in such a continuous slab casting machine. As a result, it was found that a submerged nozzle with the following shape was optimal.
That is, the immersion nozzle according to this embodiment is a bottomed cylindrical refractory that injects molten steel into a continuous casting mold. The continuous casting mold has two or more pairs of discharge holes that are symmetrical with respect to the axis of the immersion nozzle in a portion that is immersed in molten steel. The molten steel flow path in the straight body of the immersed nozzle has the same inner diameter as other parts or has a reduced diameter in a range from the upper end of the upper discharge hole to the bottom of the immersed nozzle. In addition, the cross-sectional area S1 of the inner diameter upper straight body part of the immersion nozzle, the cross-sectional area S2 of the straight body part where the discharge hole is arranged, the opening area S3 of the discharge hole arranged above, and the opening of the discharge hole arranged below. The partial area S4 satisfies the relationships of S1/(S3+S4)=0.30 to 0.50 and S2/(S3+S4)=0.10 to 0.40. In addition, the relationship 0.20≦(S2/S4)≦(S1/S3)≦1.0 is satisfied. Furthermore, the discharge angle of each discharge hole is in the range of +20° to −50° for the discharge holes arranged above and below. The discharge angle of the discharge hole on the lower side in the vertical direction is downward in the vertical direction within a range of 20° to 55° based on the discharge angle of the discharge hole on the upper side in the vertical direction. Here, "the discharge angle of the discharge hole" refers to the angle formed between the central axis of the discharge hole and the horizontal plane, and the upward direction is positive.
本実施形態にかかる浸漬ノズルは、連続鋳造用鋳型内の溶鋼に浸漬される部位に、浸漬ノズルの軸心に対して軸対称である二対以上の吐出孔を有している。これは、軸対称である二対以上の吐出孔を有することで、吐出孔から吐出される吐出流が分散されて、吐出流の流速が減速することによる。これにより、吐出流が鋳片短辺凝固シェルに衝突した後に形成される分岐下降流および分岐上昇流の双方が減速することになる。
The immersion nozzle according to this embodiment has two or more pairs of discharge holes that are axially symmetrical with respect to the axis of the immersion nozzle in a portion of the continuous casting mold that is immersed in molten steel. This is because by having two or more pairs of discharge holes that are axially symmetrical, the discharge flow discharged from the discharge holes is dispersed and the flow velocity of the discharge flow is reduced. As a result, both the branched downward flow and the branched upward flow that are formed after the discharge flow collides with the short side solidified shell of the slab are decelerated.
そして、浸漬ノズルの直胴部内溶鋼流路は、前記上側吐出孔の上端から前記浸漬ノズルの底までの範囲で他の部位と同じ内径または縮径されている。また、浸漬ノズル内径上部直胴部の断面積S1と吐出孔が配置された直胴部の断面積S2と上に配置された吐出孔の開口部面積S3と下に配置された吐出孔の開口部面積S4とが、S1/(S3+S4)=0.30~0.50、S2/(S3+S4)=0.10~0.40の関係を満たす。加えて、0.20≦(S2/S4)≦(S1/S3)≦1.0の関係を満たす。このことにより、圧力差によって鉛直方向下側の吐出孔から吐出される吐出流の流量が多くなる現象を緩和することが可能である。加えて、上下に設置された吐出孔から分配された吐出流により、短辺側下降流の更なる抑制が可能となる。この条件を外れた場合には、吐出孔間の流量バランスが変化することにより、浸漬ノズル内壁などへのアルミナなどの付着物によって溶鋼流路が塞がるおそれがある。
The molten steel flow path in the straight body of the immersed nozzle has the same inner diameter as other parts or has a reduced diameter in the range from the upper end of the upper discharge hole to the bottom of the immersed nozzle. In addition, the cross-sectional area S1 of the inner diameter upper straight body part of the immersion nozzle, the cross-sectional area S2 of the straight body part where the discharge hole is arranged, the opening area S3 of the discharge hole arranged above, and the opening of the discharge hole arranged below. The partial area S4 satisfies the relationships of S1/(S3+S4)=0.30 to 0.50 and S2/(S3+S4)=0.10 to 0.40. In addition, the relationship 0.20≦(S2/S4)≦(S1/S3)≦1.0 is satisfied. This makes it possible to alleviate the phenomenon in which the flow rate of the discharge flow discharged from the discharge hole on the lower side in the vertical direction increases due to the pressure difference. In addition, the discharge flow distributed from the discharge holes installed above and below makes it possible to further suppress the downward flow on the short side. If this condition is not met, the flow rate balance between the discharge holes changes, and there is a risk that the molten steel flow path will be blocked by deposits such as alumina on the inner wall of the immersion nozzle.
また、各吐出孔の吐出角度は、上下に配置された吐出孔が、+20°から-50°までの範囲にある。これは、各吐出孔の吐出角度を水平に対して上向き20°よりも上向きにすると、鉛直方向で最も上側に設けられた吐出孔からの吐出流が鋳片短辺凝固シェルに衝突せず、かつ減速されないまま直接メニスカスに向かうおそれがあるからである。一方、各吐出孔の吐出角度を水平に対して下向き50°よりも下向きにすると、鉛直方向最下側に設けられた吐出孔からの吐出流が鋳片短辺凝固シェルに衝突する位置が鋳型下端よりも深い位置となり、短辺側下降流が減速されないおそれがあるからである。そこで、吐出孔の吐出角度は、+20°~-50°の範囲とする。
Further, the discharge angle of each discharge hole is in the range of +20° to −50° for the discharge holes arranged above and below. This is because if the discharge angle of each discharge hole is set upwards from 20 degrees upwards with respect to the horizontal, the discharge flow from the discharge hole provided at the uppermost side in the vertical direction will not collide with the solidified shell on the short side of the slab. This is because there is a risk that the vehicle will head directly toward the meniscus without being decelerated. On the other hand, if the discharge angle of each discharge hole is set downward from 50 degrees with respect to the horizontal, the position where the discharge flow from the discharge hole provided at the lowest vertical side collides with the solidified shell on the short side of the slab will be in the mold. This is because the position is deeper than the lower end, and the downward flow on the short side may not be decelerated. Therefore, the discharge angle of the discharge hole is set in the range of +20° to -50°.
また、鉛直方向上下の位置関係の2つの吐出孔では、下側に位置する吐出孔の吐出角度が上側に位置する吐出孔の吐出角度よりも下向き角度が大きく、かつ、下側に位置する吐出孔の吐出角度と上側に位置する吐出孔の吐出角度との差を20°以上55°以下とする。このようにする理由は、上側に位置する吐出孔からの吐出流と、下側に位置する吐出孔からの吐出流とが鋳片短辺凝固シェルに衝突する以前では合流しないようにするためである。吐出角度の差が20°未満では、2つの吐出孔からの吐出流が合流するおそれがある。一方、吐出角度の差が55°を超えると、下側に位置する吐出孔からの吐出流が鋳型下端よりも下方の鋳片短辺凝固シェルに衝突して短辺側下降流の侵入深さが深くなるおそれがある。あるいは、上側に位置する吐出孔からの吐出流がメニスカス直下の鋳片短辺凝固シェルに衝突して短辺側上昇流が速くなるおそれがある。
In addition, for two discharge holes located vertically in a vertical position, the discharge angle of the discharge hole located on the lower side is larger than the discharge angle of the discharge hole located on the upper side, and the discharge hole located on the lower side The difference between the discharge angle of the hole and the discharge angle of the discharge hole located on the upper side is 20° or more and 55° or less. The reason for doing this is to prevent the discharge flow from the discharge hole located on the upper side and the discharge flow from the discharge hole located on the lower side from merging before colliding with the solidified shell on the short side of the slab. be. If the difference in discharge angle is less than 20°, there is a possibility that the discharge flows from the two discharge holes will merge. On the other hand, when the difference in discharge angle exceeds 55°, the discharge flow from the discharge hole located on the lower side collides with the solidified shell on the short side of the slab below the lower end of the mold, and the penetration depth of the downward flow on the short side increases. may become deeper. Alternatively, there is a possibility that the discharge flow from the discharge hole located on the upper side collides with the short side solidified shell of the slab directly below the meniscus, and the upward flow on the short side becomes faster.
さらに、本実施形態にかかる浸漬ノズルは、鉛直方向上下の位置関係にある2つの吐出孔は、水平面内で異なる方向に向いており、少なくとも1対の前記吐出孔が鋳型の長辺面に平行な方向に向いていることが好ましい。上側吐出孔からの吐出流と下側吐出孔からの吐出流とを水平面内で異なる方向とすれば、吐出流どうしが干渉して合流するおそれが小さくなり、吐出流の分散効果が高まるので好ましい。水平面内で異なる方向は最大で90°未満である。吐出流が鋳型長辺面側の凝固シェルに衝突すると、凝固シェルの厚みバランスが崩れ、鋳片品質に悪影響を及ぼす恐れがあるからである。特に、鉛直方向上下の位置関係にある2つの吐出孔のうち、吐出流量の多い吐出孔を、鋳型の長辺面に平行な方向に向けることで、鋳型内溶鋼流動を適切に制御できる。
Further, in the immersion nozzle according to the present embodiment, the two discharge holes located vertically in a vertical position are oriented in different directions in a horizontal plane, and at least one pair of the discharge holes is parallel to the long side surface of the mold. It is preferable to face the direction. It is preferable if the discharge flow from the upper discharge hole and the discharge flow from the lower discharge hole are directed in different directions within the horizontal plane, since this reduces the risk of the discharge flows interfering with each other and merging, and increasing the dispersion effect of the discharge flow. . The directions that differ in the horizontal plane are at most less than 90°. This is because if the discharge flow collides with the solidified shell on the long side of the mold, the thickness balance of the solidified shell will be lost, which may adversely affect the quality of the slab. In particular, the flow of molten steel in the mold can be appropriately controlled by orienting the discharge hole with a large discharge flow rate in a direction parallel to the long side surface of the mold among the two discharge holes located vertically above and below.
図1に、本発明の一実施形態にかかる連続鋳造用の浸漬ノズルを示す。図1(a)は、浸漬ノズル1の中心軸Cおよび吐出孔2の中心軸を含む面で切断したときの縦断面図であり、図1(b)は、吐出孔2と相対する斜め上方向から見た斜視図である。なお、図1に示す実施形態の浸漬ノズル1は、溶鋼に浸漬される部位の鉛直方向上下に、浸漬ノズル1の軸心Cに対して軸対称である二対の吐出孔2を有する浸漬ノズル1である。
FIG. 1 shows an immersion nozzle for continuous casting according to an embodiment of the present invention. FIG. 1(a) is a vertical cross-sectional view taken along a plane including the central axis C of the immersion nozzle 1 and the central axis of the discharge hole 2, and FIG. It is a perspective view seen from the direction. The immersed nozzle 1 according to the embodiment shown in FIG. 1 has two pairs of discharge holes 2 that are axially symmetrical with respect to the axis C of the immersed nozzle 1 above and below the portion immersed in molten steel in the vertical direction. It is 1.
図1中の、符号1は浸漬ノズル、2は吐出孔、3は鉛直方向上側に位置する吐出孔(以下「上側吐出孔」と記す)、4は鉛直方向下側に位置する吐出孔(以下「下側吐出孔」と記す)、5は、浸漬ノズル1の内部に設けられた溶鋼流路、6は浸漬ノズル1の底、7は浸漬ノズル1の上端位置、8は上側吐出孔3の上端位置、αは上側吐出孔3の吐出角度、βは下側吐出孔4の吐出角度、S1は、浸漬ノズル1の上端位置7から上側吐出孔3の上端位置8までの範囲の溶鋼流路の面積(直胴部内断面積)、S2は、上側吐出孔3の上端位置8から浸漬ノズル1の底6までの範囲の溶鋼流路の面積(直胴部内断面積)、S3は上側吐出孔3の片側開口部面積、S4は下側吐出孔4の片側開口部面積である。図1に示す浸漬ノズル1では、吐出孔2が鉛直方向上下に二対設けられていることから、上側吐出孔3が鉛直方向最上側に設けられた吐出孔2に該当し、下側吐出孔4が鉛直方向最下側に設けられた吐出孔2に該当する。図1の例では、上側吐出孔3と下側吐出孔4とは水平面内で同じ方向としている。
In FIG. 1, reference numeral 1 is an immersion nozzle, 2 is a discharge hole, 3 is a discharge hole located on the vertically upper side (hereinafter referred to as "upper discharge hole"), and 4 is a discharge hole located on the vertically lower side (hereinafter referred to as "upper discharge hole"). 5 is the molten steel flow path provided inside the immersion nozzle 1, 6 is the bottom of the immersion nozzle 1, 7 is the upper end position of the immersion nozzle 1, and 8 is the upper discharge hole 3. The upper end position, α is the discharge angle of the upper discharge hole 3, β is the discharge angle of the lower discharge hole 4, and S1 is the molten steel flow path in the range from the upper end position 7 of the immersion nozzle 1 to the upper end position 8 of the upper discharge hole 3. area (inner cross-sectional area of the straight body), S2 is the area of the molten steel flow path in the range from the upper end position 8 of the upper discharge hole 3 to the bottom 6 of the immersion nozzle 1 (the inner cross-sectional area of the straight body), S3 is the upper discharge hole S4 is the opening area of one side of the lower discharge hole 4. In the immersion nozzle 1 shown in FIG. 1, since two pairs of discharge holes 2 are provided vertically above and below, the upper discharge hole 3 corresponds to the discharge hole 2 provided on the uppermost side in the vertical direction, and the lower discharge hole 4 corresponds to the discharge hole 2 provided at the lowest side in the vertical direction. In the example of FIG. 1, the upper discharge hole 3 and the lower discharge hole 4 are in the same direction within a horizontal plane.
本実施形態の浸漬ノズル1は、上記のように構成されている。以下、このように構成される本実施形態にかかる浸漬ノズル1を用いた鋼の連続鋳造方法を説明する。
The immersion nozzle 1 of this embodiment is configured as described above. Hereinafter, a continuous steel casting method using the immersion nozzle 1 according to the present embodiment configured as described above will be explained.
タンディッシュの底部に浸漬ノズル1を設置し、浸漬ノズル1が鋳型空間のほぼ中心に位置するようにタンディッシュを連続鋳造用鋳型の上方に設置する。転炉などの精錬炉で溶製された溶鋼を収容する取鍋からタンディッシュに溶鋼を注入しながら、浸漬ノズル1を介してタンディッシュから連続鋳造用鋳型に溶鋼を注入する。メニスカス、つまり、鋳型内溶鋼湯面には、モールドパウダーを添加し、鋳型内溶鋼表面を被覆する。浸漬ノズル1の溶鋼流路5を流下する溶鋼中に、スライディングノズルや上ノズルを介して、アルゴンガスや窒素ガスなどの不活性ガスを吹き込む。
The immersion nozzle 1 is installed at the bottom of the tundish, and the tundish is installed above the continuous casting mold so that the immersion nozzle 1 is located approximately at the center of the mold space. Molten steel is injected into a tundish from a ladle containing molten steel produced in a refining furnace such as a converter, and is injected from the tundish into a continuous casting mold through an immersion nozzle 1. Mold powder is added to the meniscus, that is, the surface of the molten steel in the mold, to coat the surface of the molten steel in the mold. An inert gas such as argon gas or nitrogen gas is blown into the molten steel flowing down the molten steel channel 5 of the immersion nozzle 1 through a sliding nozzle or an upper nozzle.
図2は、吐出孔2が鉛直方向上下に二対設けられている本実施形態の浸漬ノズル1を使用して行った、鋳型内溶鋼流動を模擬した水モデル実験における鋳型内流動の調査結果を模式的に示す図である。以下、図2に基づいて、鋳型内の溶鋼流動を説明する。なお、図2は、連続鋳造用鋳型の片側の半分のみを表示しているが、他方の側の半分も中心軸Cを対称軸として、同様の形態を示す。
FIG. 2 shows the results of an investigation of the flow in the mold in a water model experiment simulating the flow of molten steel in the mold, which was conducted using the immersion nozzle 1 of this embodiment in which two pairs of discharge holes 2 are provided vertically above and below. It is a figure shown typically. The flow of molten steel in the mold will be explained below based on FIG. 2. Although FIG. 2 shows only one half of the continuous casting mold, the other half also shows a similar configuration with the central axis C as the axis of symmetry.
図2中の、符号9は鋳型短辺、10は鋳型内浴面(メニスカスに相当)、11は上側吐出孔3からの吐出流、12は下側吐出孔4からの吐出流、13は上側吐出孔3からの吐出流11が分岐して形成される分岐上昇流、14は上側吐出孔3からの吐出流11が分岐して形成される分岐下降流、15は下側吐出孔4からの吐出流12が分岐して形成される分岐上昇流、16は下側吐出孔4からの吐出流12が分岐して形成される分岐下降流、17は鋳片短辺9に沿って流れる短辺側上昇流、18は鋳片短辺9に沿って流れる短辺側下降流、19はメニスカス流である。図2において、図1と同一の部分は同一符号で示し、その説明は省略する。また、図2中の、符号20は水モデル実験において、メニスカス流19の流速を測定する流速計センサー、21は短辺側下降流18の流速を測定する流速計センサーである。図2では、吐出流11および吐出流12を直線で表示しているが、吐出流11および吐出流12は、実際には、時間の経過に伴って上下に変動しながら鋳型短辺9に向かって流れる。
In FIG. 2, 9 is the short side of the mold, 10 is the bath surface in the mold (corresponding to the meniscus), 11 is the discharge flow from the upper discharge hole 3, 12 is the discharge flow from the lower discharge hole 4, and 13 is the upper side. 14 is a branched upward flow formed by branching the discharge flow 11 from the upper discharge hole 3; 14 is a branch downward flow formed by branching the discharge flow 11 from the upper discharge hole 3; 15 is a branched downward flow formed by branching the discharge flow 11 from the lower discharge hole 4; 16 is a branched upward flow formed by branching the discharge flow 12, 16 is a branched downward flow formed by branching the discharge flow 12 from the lower discharge hole 4, and 17 is a short side flowing along the short side 9 of the slab. 18 is a short side downward flow flowing along the short side 9 of the slab, and 19 is a meniscus flow. In FIG. 2, the same parts as in FIG. 1 are indicated by the same reference numerals, and the explanation thereof will be omitted. Further, in FIG. 2, reference numeral 20 is a current meter sensor that measures the flow velocity of the meniscus flow 19 in a water model experiment, and 21 is a current meter sensor that measures the flow velocity of the short side downward flow 18. Although the discharge flow 11 and the discharge flow 12 are shown as straight lines in FIG. 2, the discharge flow 11 and the discharge flow 12 actually move toward the short side 9 of the mold while fluctuating up and down with the passage of time. It flows.
図2に示すように、上側吐出孔3から吐出された吐出流11および下側吐出孔4から吐出された吐出流12は、鋳型短辺9に衝突するまでの範囲で合流することなく鋳型短辺9に衝突する。鋳型短辺9に衝突した後、吐出流11は、分岐上昇流13と分岐下降流14とに分岐し、吐出流12は、分岐上昇流15と分岐下降流16とに分岐する。本実施形態の浸漬ノズル1では、吐出流が吐出流11と吐出流12との2つに分散される。鋳型内に注入する溶鋼量が同一の場合には、つまり、鋳片引き抜き速度が同一の場合には、吐出孔2が一対の場合(片側に1個のみ)における分岐上昇流および分岐下降流に比較して、本実施形態では、分岐上昇流13、分岐下降流14、分岐上昇流15、分岐下降流16の各流速は減速する。更に、分岐下降流14と分岐上昇流15とは、反対側に向いた流れであり、分岐下降流14と分岐上昇流15とが衝突・干渉して互いに減速する。
As shown in FIG. 2, the discharge flow 11 discharged from the upper discharge hole 3 and the discharge flow 12 discharged from the lower discharge hole 4 do not merge until they collide with the short side 9 of the mold. Collisions with side 9. After colliding with the mold short side 9, the discharge flow 11 branches into a branched upward flow 13 and a branched downward flow 14, and the discharge flow 12 branches into a branched upward flow 15 and a branched downward flow 16. In the immersion nozzle 1 of this embodiment, the discharge flow is dispersed into two, a discharge flow 11 and a discharge flow 12. When the amount of molten steel injected into the mold is the same, that is, when the slab withdrawal speed is the same, the branched upward flow and branched downward flow when there is a pair of discharge holes 2 (only one on one side) In comparison, in this embodiment, the flow speeds of the branched upward flow 13, the branched downward flow 14, the branched upward flow 15, and the branched downward flow 16 are reduced. Further, the branched downward flow 14 and the branched upward flow 15 are flows directed to opposite sides, and the branched downward flow 14 and the branched upward flow 15 collide and interfere with each other to decelerate each other.
その結果、モールドパウダーの巻き込みを左右するメニスカス流19に影響する短辺側上昇流17は、分岐上昇流15の影響をほとんど受けることはなく、主に分岐上昇流13の流速によって決定される。分岐上昇流13は、吐出孔2が一対の場合の分岐上昇流の速度よりも減速していることから、短辺側上昇流17が減速し、これによってメニスカス流19の流速が低下する。
As a result, the short-side upward flow 17 that influences the meniscus flow 19 that controls the entrainment of mold powder is hardly affected by the branched upward flow 15 and is mainly determined by the flow velocity of the branched upward flow 13. Since the branched upward flow 13 is slower than the speed of the branched upward flow when there is a pair of discharge holes 2, the short side upward flow 17 is decelerated, and thereby the flow velocity of the meniscus flow 19 is reduced.
同様に、ガス気泡の鋳片への捕捉に影響する短辺側下降流18は、分岐下降流14の影響をほとんど受けることはなく、主に分岐下降流16の流速によって決定される。分岐下降流16は、吐出孔2が一対の場合の分岐下降流の速度よりも減速していることから、短辺側下降流18の流速が低下する。
Similarly, the short-side downward flow 18, which affects the capture of gas bubbles in the slab, is hardly affected by the branched downward flow 14 and is mainly determined by the flow velocity of the branched downward flow 16. Since the branched downward flow 16 is slower than the velocity of the branched downward flow when there is a pair of discharge holes 2, the flow velocity of the short side downward flow 18 is reduced.
すなわち、本実施形態にかかる浸漬ノズル1を使用して溶鋼を連続鋳造することで、モールドパウダーの巻き込みに影響するメニスカス流19およびガス気泡の鋳片への捕捉に影響する短辺側下降流18がともに減速される。その結果、モールドパウダーの巻き込みおよび不活性ガス気泡の鋳片への捕捉の双方を安定して抑制することができる。
That is, by continuously casting molten steel using the immersion nozzle 1 according to this embodiment, a meniscus flow 19 that affects the entrainment of mold powder and a downward flow on the short side side 18 that affects the capture of gas bubbles in the slab are created. Both are slowed down. As a result, it is possible to stably suppress both the entrainment of mold powder and the capture of inert gas bubbles in the slab.
上記実施形態では、上側に一対、下側に一対の吐出孔2を用いた。これに変えて、上下いずれかの側に、鉛直方向で同じ位置に、水平方向で異なる方向に吐出する二対以上の吐出孔2を用いることもできる。その場合、吐出孔2の開口断面積は、中心軸に対し片側の合計開口面積とする。
In the above embodiment, one pair of discharge holes 2 is used on the upper side and one pair on the lower side. Instead, it is also possible to use two or more pairs of discharge holes 2 on either the upper or lower sides, which discharge fluid at the same position in the vertical direction and in different directions horizontally. In that case, the opening cross-sectional area of the discharge hole 2 is the total opening area on one side with respect to the central axis.
以上説明したように、本実施形態によれば、モールドパウダーの巻き込みを左右するメニスカスでの溶鋼流速に影響する短辺側上昇流17および不活性ガス気泡の鋳片への捕捉に影響する短辺側下降流18の双方を減速させることができ、モールドパウダーの巻き込みおよび不活性ガス気泡の鋳片への捕捉の双方を安定して抑制することが実現される。
As explained above, according to the present embodiment, the short side upward flow 17 affects the molten steel flow velocity at the meniscus which controls the entrainment of mold powder, and the short side side upward flow 17 affects the capture of inert gas bubbles into the slab. Both of the side downward flows 18 can be decelerated, and both the entrainment of mold powder and the capture of inert gas bubbles in the slab can be stably suppressed.
本発明は以上のように構成されたものであり、以下、実施例により、本発明の実施可能性および効果についてさらに説明する。
実機スラブ連続鋳造機において、本実施形態にかかる浸漬ノズル1を使用して連続鋳造操業を実施した(発明例)。連続鋳造したスラブ鋳片の横断面寸法は、厚みが220~260mm、幅が1000~2200mmであり、浸漬ノズル1に吹き込む不活性ガスとしてアルゴンガスを使用し、鋳型内溶鋼表面には、鋳片引き抜き速度および鋼種に応じて最適なモールドパウダーを添加した。また、比較のために、浸漬ノズルの左右に一対の吐出孔を有する浸漬ノズル、および、浸漬ノズルの左右に二対の吐出孔を有するものの、二対の吐出孔の設置条件が本発明の範囲外である浸漬ノズルも使用した。 The present invention is configured as described above, and the feasibility and effects of the present invention will be further explained below using Examples.
In an actual continuous slab casting machine, a continuous casting operation was carried out using theimmersion nozzle 1 according to the present embodiment (invention example). The cross-sectional dimensions of the continuously cast slab slab are 220 to 260 mm thick and 1000 to 2200 mm wide. Argon gas is used as the inert gas blown into the immersion nozzle 1, and the molten steel surface in the mold is The optimum molding powder was added according to the drawing speed and steel type. In addition, for comparison, although the immersion nozzle has a pair of discharge holes on the left and right sides of the immersion nozzle and the two pairs of discharge holes on the left and right sides of the immersion nozzle, the installation conditions of the two pairs of discharge holes are within the scope of the present invention. An external immersion nozzle was also used.
実機スラブ連続鋳造機において、本実施形態にかかる浸漬ノズル1を使用して連続鋳造操業を実施した(発明例)。連続鋳造したスラブ鋳片の横断面寸法は、厚みが220~260mm、幅が1000~2200mmであり、浸漬ノズル1に吹き込む不活性ガスとしてアルゴンガスを使用し、鋳型内溶鋼表面には、鋳片引き抜き速度および鋼種に応じて最適なモールドパウダーを添加した。また、比較のために、浸漬ノズルの左右に一対の吐出孔を有する浸漬ノズル、および、浸漬ノズルの左右に二対の吐出孔を有するものの、二対の吐出孔の設置条件が本発明の範囲外である浸漬ノズルも使用した。 The present invention is configured as described above, and the feasibility and effects of the present invention will be further explained below using Examples.
In an actual continuous slab casting machine, a continuous casting operation was carried out using the
使用した連続鋳造用鋳型は、磁場発生装置が設置されていない鋳型、直流磁場発生装置が、連続鋳造用鋳型の背面に、上側吐出孔の上側および下側吐出孔の下側にそれぞれ1段、合計2段、鋳型長辺を挟んで相対して設置された鋳型、交流磁場発生装置が連続鋳造用鋳型の背面に鋳型長辺を挟んで相対して設置された鋳型の3種類の連続鋳造用鋳型である。
The continuous casting mold used was a mold without a magnetic field generator, a DC magnetic field generator was installed on the back of the continuous casting mold, one stage above the upper discharge hole, and one stage below the lower discharge hole. Three types of continuous casting molds: 2 stages in total, molds placed facing each other across the long sides of the mold, and molds with an AC magnetic field generator placed opposite to each other across the long sides of the mold on the back of the continuous casting mold. It is a mold.
直流磁場発生装置が設置された連続鋳造用鋳型を使用した連続鋳造操業では、上下2段の直流磁場発生装置から、それぞれ、上側吐出孔の上側、および、下側吐出孔の下側で、鋳型内の溶鋼に直流静磁場を印加した。また、交流磁場発生装置を設置した連続鋳造用鋳型を使用した連続鋳造操業では、交流磁場発生装置から連続鋳造用鋳型内の溶鋼に交流移動磁場を印加し、メニスカスにおいて鋳型内溶鋼を水平方向に旋回させながら、連続鋳造した。
In a continuous casting operation using a continuous casting mold equipped with a DC magnetic field generator, the DC magnetic field generators in two stages, upper and lower, cast the mold above the upper discharge hole and below the lower discharge hole, respectively. A direct current static magnetic field was applied to the molten steel inside. In addition, in continuous casting operations using a continuous casting mold equipped with an AC magnetic field generator, an AC moving magnetic field is applied from the AC magnetic field generator to the molten steel in the continuous casting mold, and the molten steel in the mold is horizontally moved at the meniscus. Continuous casting was performed while swirling.
スラブ連続鋳造機で製造したスラブ鋳片を熱間圧延して熱延鋼板とし、この熱延鋼板でアルゴンガス気泡およびモールドパウダーに起因する表面欠陥を調査した。この表面欠陥から、鋳片に残留したアルゴンガス気泡およびモールドパウダーを評価した。つまり、鋼製品の欠陥指数が低いほど、鋳片に残留したアルゴンガス気泡およびモールドパウダーが少ないと評価した。
A slab slab produced using a continuous slab casting machine was hot rolled into a hot rolled steel plate, and the hot rolled steel plate was investigated for surface defects caused by argon gas bubbles and mold powder. Based on these surface defects, argon gas bubbles and mold powder remaining in the slab were evaluated. In other words, it was evaluated that the lower the defect index of the steel product, the fewer argon gas bubbles and mold powder remained in the slab.
表1に浸漬ノズルの条件を、表2に操業条件および操業結果を示す。本発明範囲内にて浸漬ノズルを設計することにより、鋼製品の欠陥混入率は低下した。
Table 1 shows the conditions of the immersion nozzle, and Table 2 shows the operating conditions and operating results. By designing the submerged nozzle within the scope of the present invention, the defect inclusion rate of steel products was reduced.
1 浸漬ノズル
2 吐出孔
3 上側吐出孔
4 下側吐出孔
5 溶鋼流路
6 浸漬ノズルの底
7 浸漬ノズルの上端位置
8 上側吐出孔の上端位置
9 鋳型短辺
10 鋳型内浴面
11 上側吐出孔からの吐出流
12 下側吐出孔からの吐出流
13 分岐上昇流
14 分岐下降流
15 分岐上昇流
16 分岐下降流
17 短辺側上昇流
18 短辺側下降流
19 メニスカス流
20 流速計センサー
21 流速計センサー
α、β 吐出角度
S1 (浸漬ノズルの上端位置から上側吐出孔の上端位置までの範囲の)直胴部内断面積
S2 (上側吐出孔の上端位置から浸漬ノズルの底までの範囲の)直胴部内断面積
S3 (上側吐出孔の片側)開口部面積
S4 (下側吐出孔の片側)開口部面積
C 中心軸(軸心) 1Immersed nozzle 2 Discharge hole 3 Upper discharge hole 4 Lower discharge hole 5 Molten steel channel 6 Bottom of the immersed nozzle 7 Upper end position of the immersed nozzle 8 Upper end position of the upper discharge hole 9 Short side of the mold 10 Bath surface in the mold 11 Upper discharge hole 12 Discharge flow from the lower discharge hole 13 Branched upward flow 14 Branched downward flow 15 Branched upward flow 16 Branched downward flow 17 Short side upward flow 18 Short side downward flow 19 Meniscus flow 20 Velocity meter sensor 21 Flow velocity Meter sensor α, β Discharge angle S1 (range from the upper end of the immersed nozzle to the upper end of the upper discharge hole) Internal cross-sectional area of the straight body S2 (range from the upper end of the upper discharge hole to the bottom of the immersed nozzle) Body internal cross-sectional area S3 (One side of the upper discharge hole) Opening area S4 (One side of the lower discharge hole) Opening area C Central axis (axis)
2 吐出孔
3 上側吐出孔
4 下側吐出孔
5 溶鋼流路
6 浸漬ノズルの底
7 浸漬ノズルの上端位置
8 上側吐出孔の上端位置
9 鋳型短辺
10 鋳型内浴面
11 上側吐出孔からの吐出流
12 下側吐出孔からの吐出流
13 分岐上昇流
14 分岐下降流
15 分岐上昇流
16 分岐下降流
17 短辺側上昇流
18 短辺側下降流
19 メニスカス流
20 流速計センサー
21 流速計センサー
α、β 吐出角度
S1 (浸漬ノズルの上端位置から上側吐出孔の上端位置までの範囲の)直胴部内断面積
S2 (上側吐出孔の上端位置から浸漬ノズルの底までの範囲の)直胴部内断面積
S3 (上側吐出孔の片側)開口部面積
S4 (下側吐出孔の片側)開口部面積
C 中心軸(軸心) 1
Claims (6)
- 連続鋳造用鋳型内に溶鋼を注入する有底筒状の連続鋳造用の浸漬ノズルであって、
前記連続鋳造用鋳型内の溶鋼に浸漬される部位に、前記浸漬ノズルの軸心に対して軸対称である二対以上の吐出孔を有し、
前記浸漬ノズルの直胴部内溶鋼流路は、上側吐出孔の上端から前記浸漬ノズルの底までの範囲で他の部位と同じ内径または縮径されており、
上側吐出孔の片側開口部面積をS3、下側吐出孔の片側開口部面積をS4として、
前記浸漬ノズルの上端から前記上側吐出孔の上端までの範囲の直胴部内断面積(S1)の前記吐出孔の片側合計開口部面積(S3+S4)に対する比が0.30~0.50の範囲にあり、
前記上側吐出孔の上端から前記浸漬ノズルの底までの範囲の直胴部内断面積(S2)の前記吐出孔の片側合計開口部面積(S3+S4)に対する比が0.10~0.40の範囲にあり、
前記浸漬ノズル直胴部内断面積(S1、S2)と吐出孔の片側開口面積(S3、S4)とが、0.20≦(S2/S4)≦(S1/S3)≦1.0の関係を満たし、
それぞれの吐出孔の吐出角度は、水平面を基準に上向きを正として、+20°~-50°の範囲にあり、
鉛直方向下側の吐出孔の吐出角度が、鉛直方向上側の吐出孔の吐出角度を基準として20°~55°の範囲で鉛直方向下向きである、連続鋳造用の浸漬ノズル。 A bottomed cylindrical immersion nozzle for continuous casting that injects molten steel into a continuous casting mold,
having two or more pairs of discharge holes that are axially symmetrical with respect to the axis of the immersion nozzle in a portion of the continuous casting mold that is immersed in molten steel;
The molten steel flow path in the straight body of the immersion nozzle has the same inner diameter as other parts or has a reduced diameter in the range from the upper end of the upper discharge hole to the bottom of the immersion nozzle,
The opening area of one side of the upper discharge hole is S3, and the opening area of one side of the lower discharge hole is S4,
The ratio of the straight body internal cross-sectional area (S1) in the range from the upper end of the immersion nozzle to the upper end of the upper discharge hole to the total opening area on one side of the discharge hole (S3+S4) is in the range of 0.30 to 0.50. can be,
The ratio of the internal cross-sectional area (S2) of the straight body in the range from the upper end of the upper discharge hole to the bottom of the immersion nozzle to the total opening area (S3+S4) on one side of the discharge hole is in the range of 0.10 to 0.40. can be,
The inner cross-sectional area of the immersion nozzle straight body (S1, S2) and the opening area of one side of the discharge hole (S3, S4) have a relationship of 0.20≦(S2/S4)≦(S1/S3)≦1.0. meet,
The discharge angle of each discharge hole is in the range of +20° to -50° with the upward direction being positive with respect to the horizontal plane,
A submerged nozzle for continuous casting, wherein the discharge angle of the vertically lower discharge hole is vertically downward in the range of 20° to 55° based on the discharge angle of the vertically upper discharge hole. - 鉛直方向上下の位置関係にある2つの前記吐出孔が、水平面内で異なる方向に向いており、少なくとも1対の前記吐出孔が前記鋳型の長辺面に平行な方向に向いている、請求項1に記載の連続鋳造用の浸漬ノズル。 The two discharge holes located vertically in a vertical position are oriented in different directions in a horizontal plane, and at least one pair of the discharge holes are oriented in a direction parallel to a long side surface of the mold. 1. The immersion nozzle for continuous casting according to 1.
- 請求項1または2に記載の連続鋳造用の浸漬ノズルを使用し、連続鋳造用鋳型内溶鋼表面にモールドパウダーを添加し、前記浸漬ノズルの溶鋼流路を流下する溶鋼中に不活性ガスを吹き込みながら、前記浸漬ノズルを介してタンディッシュ内の溶鋼を前記鋳型内に注入する、鋼の連続鋳造方法。 Using the immersion nozzle for continuous casting according to claim 1 or 2, adding mold powder to the surface of the molten steel in the mold for continuous casting, and blowing an inert gas into the molten steel flowing down the molten steel flow path of the immersion nozzle. A continuous steel casting method, wherein molten steel in a tundish is injected into the mold through the immersion nozzle.
- 前記連続鋳造用鋳型の背面に設置された直流磁場発生装置から前記浸漬ノズルの鉛直方向最上部の吐出孔の上側および鉛直方向最下部の吐出孔の下側で鋳型内の溶鋼に直流静磁場を印加しながら、前記浸漬ノズルを介してタンディッシュ内の溶鋼を前記鋳型内に注入する、請求項3に記載の鋼の連続鋳造方法。 A direct current static magnetic field is applied to the molten steel in the mold above the vertically uppermost discharge hole and below the vertically lowest discharge hole of the immersion nozzle from a DC magnetic field generator installed on the back side of the continuous casting mold. 4. The continuous steel casting method according to claim 3, wherein the molten steel in the tundish is injected into the mold through the immersion nozzle while applying the molten steel.
- 前記連続鋳造用鋳型の背面に設置された交流磁場発生装置から前記鋳型内の溶鋼に交流移動磁場を印加しながら、前記浸漬ノズルを介してタンディッシュ内の溶鋼を前記鋳型内に注入する、請求項3に記載の鋼の連続鋳造方法。 The molten steel in the tundish is injected into the mold through the immersion nozzle while applying an AC moving magnetic field to the molten steel in the mold from an AC magnetic field generator installed on the back side of the continuous casting mold. The continuous casting method of steel according to item 3.
- 前記連続鋳造用鋳型の背面に設置された交流磁場発生装置から前記鋳型内の溶鋼に交流移動磁場を印加しながら、前記浸漬ノズルを介してタンディッシュ内の溶鋼を前記鋳型内に注入する、請求項4に記載の鋼の連続鋳造方法。 The molten steel in the tundish is injected into the mold through the immersion nozzle while applying an AC moving magnetic field to the molten steel in the mold from an AC magnetic field generator installed on the back side of the continuous casting mold. The continuous casting method of steel according to item 4.
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Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
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JP2001001115A (en) * | 1999-04-20 | 2001-01-09 | Nippon Steel Corp | Continuous casting method of steel |
JP2007319923A (en) * | 2006-06-05 | 2007-12-13 | Nippon Steel Corp | Continuous casting method for molten steel |
WO2010109887A1 (en) * | 2009-03-25 | 2010-09-30 | 新日本製鐵株式会社 | Immersion nozzle for continuous casting |
JP2015085370A (en) * | 2013-10-31 | 2015-05-07 | Jfeスチール株式会社 | Continuous casting method of steel |
JP2019063851A (en) * | 2017-10-05 | 2019-04-25 | Jfeスチール株式会社 | Immersion nozzle for continuous casting and method for steel continuous casting |
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JP2001001115A (en) * | 1999-04-20 | 2001-01-09 | Nippon Steel Corp | Continuous casting method of steel |
JP2007319923A (en) * | 2006-06-05 | 2007-12-13 | Nippon Steel Corp | Continuous casting method for molten steel |
WO2010109887A1 (en) * | 2009-03-25 | 2010-09-30 | 新日本製鐵株式会社 | Immersion nozzle for continuous casting |
JP2015085370A (en) * | 2013-10-31 | 2015-05-07 | Jfeスチール株式会社 | Continuous casting method of steel |
JP2019063851A (en) * | 2017-10-05 | 2019-04-25 | Jfeスチール株式会社 | Immersion nozzle for continuous casting and method for steel continuous casting |
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