KR20160138830A - Method of manufacturing high carbon steel slab - Google Patents

Method of manufacturing high carbon steel slab Download PDF

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Publication number
KR20160138830A
KR20160138830A KR1020150073211A KR20150073211A KR20160138830A KR 20160138830 A KR20160138830 A KR 20160138830A KR 1020150073211 A KR1020150073211 A KR 1020150073211A KR 20150073211 A KR20150073211 A KR 20150073211A KR 20160138830 A KR20160138830 A KR 20160138830A
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South Korea
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casting
bender
cooling
slab
unbender
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KR1020150073211A
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Korean (ko)
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KR101727803B1 (en
Inventor
박종현
이은규
조원재
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현대제철 주식회사
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Priority to KR1020150073211A priority Critical patent/KR101727803B1/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0637Accessories therefor
    • B22D11/068Accessories therefor for cooling the cast product during its passage through the mould surfaces
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12Accessories for subsequent treating or working cast stock in situ
    • B22D11/124Accessories for subsequent treating or working cast stock in situ for cooling
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24Ferrous alloys, e.g. steel alloys containing chromium with vanadium

Abstract

According to an embodiment of the present invention, the present invention relates to a method of manufacturing a high carbon steel slab. Molten steel comprising 0.50-0.54 wt% of carbon (C), 0.20-0.35% of silicon (Si), 0.95-1.05 wt% of manganese (Mn), 1.0-1.2 wt% of chromium (Cr), 0.10-0.12 wt% of vanadium (V), and the remainder consisitng of iron (Fe) and inevitable impurities is injected into a mold and then firstly cooled. A slab is manufactured from the molten steel as the molten steel sequentially passes through a bender unit and an un-bender unit of a continuous casting apparatus for second cooling. The bender unit has a height of 150-190 mm from the slab, and has a gap of 190-360 mm between the nozzles. The un-bender unit has a height of 260-420 mm from the slab, and has a gap of 650-900 mm between the nozzles. An amount of the second cooling is represented by formula 1 for the bender unit and by formula 2 for the un-bender unit. Qv = 990*Vc-27.1 ------------ (1) Qu = 46.6 + 352*Vc + 0.195*Wc ----------- (2). Qv is an amount of cooling (liter/min) of the bender unit and Qu is an amount of cooling (liter/min) of the un-bender unit; and Vc is a casting speed (meter/min) and Wc is a width of casting (millimeter). The present invention is to provide a method of reducing cracks on the corners generated on the slab.

Description

[0001] METHOD OF MANUFACTURING HIGH CARBON STEEL SLAB [0002]

The present invention relates to a method of manufacturing a slab, and more particularly, to a method of manufacturing a high-carbon steel slab that reduces a corner portion crack of a cast steel during a continuous casting process.

In general, the process of continuously solidifying molten steel treated with a desired component in a certain form is referred to as continuous casting. The continuous casting machine which continuously performs the continuous casting is produced in the steel making furnace, the molten steel transferred to the ladle is received in the turndish, and supplied to the mold for the continuous casting machine to produce the slab of a certain size.

The conventional continuous casting machine includes a casting mold having a desired shape by cooling the molten steel of the tundish primarily in the mold and cooling the casting piece while moving the casting mold connected to the mold and moving the casting mold do.

That is, the molten steel introduced in the tundish is formed into a slab, a slab, a billet, or a billet having a predetermined width and thickness in the mold. The molten steel is first cooled in the mold, And then cooled by the cooling water injected while moving along the stand, and is conveyed while maintaining the shape formed in the mold.

A related prior art is Korean Laid-Open Publication No. 2015-00141031 (published on Feb. 26, 201, entitled "Continuous Casting Method").

It is an object of the present invention to provide a method for reducing a corner crack generated in a slab during a continuous casting process of high carbon steel.

A method for manufacturing high carbon steel slabs according to one aspect of the present invention is disclosed. The method of manufacturing slabs according to claim 1, wherein 0.5 to 0.4% of carbon (C), 0.20 to 0.35% of silicon (Si), 0.95 to 1.05% of manganese (Mn), 1.0 to 1.2% ) 0.10 to 0.12%, and molten steel consisting of the remaining iron (Fe) and unavoidable impurities are injected into the mold, and the molten steel is first cooled. The cast steel is produced from the molten steel through secondary cooling sequentially passing through the bender portion and the unbender portion of the casting machine. The bender portion has a height of 150 to 190 mm from the cast, a nozzle interval is 190 to 360 mm, the unbender portion has a height of 260 to 420 mm from the cast, and a nozzle interval is 650 to 900 mm. The quantity of the secondary cooling is set so as to follow the formula 1 in the case of the above-mentioned bender section and to follow the formula 2 in the case of the above-mentioned unbender section.

Qv = 990 * Vc-27.1 - (1)

Qu = 46.6 + 352 * Vc + 0.195 * Wc - (2)

Qv is the cooling rate (liter / min) of the bender portion, Qu is the cooling rate of the unbender portion (liter / min), Vc is the casting speed (meter / min)

In one embodiment, the casting speed is from 0.8 to 1.1 meters / min, and the casting width is from 900 to 1600 mm.

In another embodiment, the non-yield may be from 0.6 to 1 liter / min.

In still another embodiment, the set secondary cooling water quantity may be monitored in units of slabs, and the step of managing the set secondary cooling water quantity may be controlled to a process error of 5% or less of the set quantity.

According to the embodiment of the present invention, it has been found that, when the secondary cooling water amount injected for solidification of the cast steel during the continuous casting process is excessive, subcooling of the cast steel corner portion is promoted and a corner crack can occur. In the bender part, the cooling water quantity is controlled according to the casting speed regardless of the casting speed. In the unbender part, the cooling water quantity is controlled according to the casting speed and the casting width. It is possible to reduce the surface crack of the billet corner portion.

1 is a schematic view of a continuous casting machine according to an embodiment of the present invention.
FIG. 2A is a schematic view showing a configuration of a cooling device of a bender part of a continuous casting machine according to an embodiment of the present invention, and FIG. 2B is a schematic view showing a configuration of a cooling device of an unbender part of a continuous casting machine according to an embodiment of the present invention. Fig.
FIGS. 3A and 3B are graphs illustrating a regression equation for determining a secondary cooling quantity according to a casting speed and a casting width according to an embodiment of the present invention. FIG.
4 is a graph showing a corner defect crack index of a continuous casting specimen according to an embodiment of the present invention.

Hereinafter, a method for manufacturing a high carbon steel slab according to an embodiment of the present invention will be described in detail. The terms used below are appropriately selected terms in consideration of functions in the present invention, and definitions of these terms should be made based on the contents throughout this specification.

The present invention provides, for example, a method for reducing cracks on the surface of a cast iron portion of a cast steel of a high carbon steel such as an alloy tool steel applied to a passive clutch for an automobile.

If hot rolling continues after the continuous casting process, such as the alloy tool steel, a correction inspection process to inspect the surface after the slab has cooled after the continuous casting process may not be possible. In the continuous casting process, the cracks generated at the corners of the cast steel are detected in the form of edge scab defects in the hot-rolled coil because they are hot-rolled without inspection and correction. The hot-rolled coil in which such a bond is produced causes a cost increase because an additional process is required to cut both edges.

Although it is difficult to explain defects in the continuous casting process by any one cause or theory, it is possible to determine the occurrence of the defects for the following reasons. That is, first, it may be related to the change of the high temperature strength of the steel according to the casting temperature in the vertical curved type machine. In general, the steel has a brittle zone in three zones depending on the temperature, and cracks can easily occur even if the surface temperature of the bracing zone is in the range of 700 to 900 ° C (hereinafter referred to as 'third zone brittle zone' . Second, in a conventional vertical bending machine, stress may be applied to the cast during bending or straightening of the cast steel. If the surface temperature of the cast steel is included in the third zone brittle zone in the section where stress is applied to the cast steel, a corner crack may occur.

Accordingly, as described below, in the embodiment of the present invention, the slab exerciser applied to the production of the high carbon steel slab is divided into the portions of the bender portion and the unbender portion, and different amounts of cooling are set in the respective portions, Thereby suppressing the supercooling of the corner portion, thereby reducing the crack on the surface of the slab corner portion.

1 is a schematic view of a continuous casting machine according to an embodiment of the present invention. As shown, the continuous casting machine may be a vertical curved player.

The continuous casting machine 100 is supplied with molten steel M through a ladle 10 containing molten steel M refined in a steelmaking process and an injection nozzle 15 connected to the ladle 10 A tundish 20 for temporarily storing the molten steel temporarily stored in the tundish 20 and a mold 30 for receiving the molten steel temporarily stored in the tundish 20 through the immersion nozzle 25 to perform initial solidification in a predetermined shape, And a cooling line 40 in which a plurality of segments 50, 52 are continuously arranged to perform a series of molding operations while cooling the unfused cast slab S, At this time, a certain region of the cooling line 40 under the mold 30 is referred to as a secondary cooling zone. On the other hand, the stopper 21 can adjust the amount of the molten steel M moving to the immersion nozzle 25.

In the secondary cooling zone, the casting (30) is primarily cooled in the casting (30) to quickly cool the casting (S) coming out from the casting (30). In the secondary cooling zone, cooling water is injected into the non-solidified slab S, and the region immediately below the mold 30 may be referred to as a bender portion 40a. On the other hand, the rear end portion of the bender portion A can be referred to as an unbender portion 40b, which is connected to the bender portion A. As shown in Figs. 2A and 2B, the bender portion 40a and the unbender portion 40b are different from each other in the configuration of the cooling device.

FIG. 2A is a schematic view showing a configuration of a cooling device of a bender part of a continuous casting machine according to an embodiment of the present invention, and FIG. 2B is a schematic view showing a configuration of a cooling device of an unbender part of a continuous casting machine according to an embodiment of the present invention. Fig.

Referring to FIG. 2A, in the bender section 40a, a plurality of injection nozzles 410a may be disposed in the width direction of the slab S. The height h1 from the cast steel S to the injection nozzle 410a may be about 50 to 190 mm and the distance d1 between the injection nozzles 410a may be 190 to 360 mm. On the other hand, the casting width w of the cast steel may be 900 to 1600 mm.

Referring to FIG. 2B, in the unbender portion 410b, a plurality of injection nozzles 410b may be disposed in the width direction of the slab S. The height h2 from the cast steel S to the injection nozzle 410b may be about 260 to 420 mm and the distance d2 between the injection nozzles 410b may be 650 to 900 mm. On the other hand, the casting width w of the cast steel may be 900 to 1600 mm.

In the embodiment of the present invention, in the continuous casting machine having the above-described structure, 0.50 to 0.54% of carbon (C), 0.20 to 0.35% of silicon (Si), 0.95 to 1.05% of manganese (Mn) When molten steel consisting of 1.0 to 1.2% of vanadium (V) and 0.10 to 0.12% of vanadium (V) and remaining iron (Fe) and unavoidable impurities is continuously cast, if the secondary cooling water amount injected for solidification of the cast steel during the continuous casting step is excessive , It has been found that a supercooling of the corner portion of the cast steel is promoted and a crack can be generated on the surface of the cast steel corner portion.

In order to prevent cracking of the surface of the bending corner portion, the present invention proposes a method of controlling the casting speed by controlling the secondary cooling rate. In the embodiment, first, in the bender portion 40a, the amount of the secondary cold water is changed using the casting speed as an independent variable irrespective of the casting width. Second, in the unbender portion 40b, the secondary cooling quantity is changed using the casting width and the casting speed as independent variables.

FIGS. 3A and 3B are graphs illustrating a regression equation for determining a secondary cooling quantity according to a casting speed and a casting width according to an embodiment of the present invention. FIG.

As shown in FIG. 3A, when the punching width was 900 mm, the secondary cooling water variation value according to the casting speed was calculated as an experimental value, and regression analysis was performed to cover each experimental value. Thus, as shown in FIG. 3A, reliable regression equations were obtained for R 2 of 0.9964 and 2 for the bender portion and the unbender portion, respectively.

As shown in FIG. 3B, in the case of a casting speed of 1.1 m / min, the secondary cooling water variation value according to the casting width was calculated as an experimental value, and regression analysis was performed to cover each experimental value. Thus, as shown in FIG. 3B, a reliable regression equation can be derived for R 2 of 0.9958 for the unbender portion. As described above, the casting width was excluded from the independent variables for the bender part.

Based on the results of the regression analysis shown in FIGS. 3A and 3B, it is possible to derive the cooling water quantity control formula for each position of the compressor as follows.

Qv = 990 * Vc-27.1 - (1)

Qu = 46.6 + 352 * Vc + 0.195 * Wc - (2)

Qv is the cooling rate of the bender portion (liter / min), Qu is the cooling rate of the unbender portion (liter / min), Vc is the casting speed (meter / min), and Wc is the main gauge (milimeter).

The secondary cooling quantity can be set by using the cooling quantity control formula for each position of the performance device. When the actual continuous casting process is performed, the set secondary cooling water quantity may be monitored in units of slabs, and the actual cooling water quantity may be managed with a process error of 5% or less of the set quantity.

Example

Molten steels satisfying the content of the ingot in the examples of the present invention were continuously cast as Comparative Examples and Examples according to the conditions shown in Table 1 below.

In the case of the embodiment, the secondary cooling water quantity was adjusted to follow the quantity control formula of Equation (1) and Equation (2) for each position of the performance equipment.


Main gang
(mm)
Casting speed
(m / min)
Second cooling rate (l / min) Total cooling water (l / min)
Total rain rate
(l / kg)
The vendor department Unbender Department Comparative Example 1120 1.0 1497 667 2165 1.1 Example 1120 1.0 960 581 1540 0.8

Compared to the conventional comparative example conditions, the embodiment has reduced the secondary cooling water quantity in the bender part and the unbender part together. Accordingly, in the case of the embodiment, the total rainfall is reduced.

On the other hand, after continuous casting, the specimens of the comparative example and the example were subjected to defect inspection to calculate the corner portion crack index.

4 is a graph showing a corner defect crack index of a continuous casting specimen according to an embodiment of the present invention. Referring to FIG. 4, the specimens of the examples showed a relatively large reduction in the corner cracking index, as compared with the specimens of the comparative examples.

As described above, according to the embodiment of the present invention, in the continuous casting step, the amount of the secondary cooling water injected for solidification of the cast steel is excessive, so that the surface crack generated in the corner portion of the cast steel can be effectively reduced. In the bender part, the cooling water quantity is controlled according to the casting speed regardless of the casting speed. In the unbender part, the cooling water quantity is controlled according to the casting speed and the casting width. It is possible to reduce the surface crack of the billet corner portion.

It is to be understood that the invention includes various modifications and equivalent embodiments that can be derived from the disclosed embodiments as well as those of ordinary skill in the art to which the present invention pertains. Accordingly, the technical scope of the present invention should be defined by the following claims.

-

Claims (4)

(Si), 0.95 to 1.05% of manganese (Mn), 1.0 to 1.2% of chromium (Cr), 0.10 to 0.12% of vanadium (V), and 0.50 to 0.55% of carbon Injecting molten steel consisting of the remaining iron (Fe) and unavoidable impurities into the mold and performing a primary cooling; And
And producing a cast from the molten steel through secondary cooling sequentially through the bender portion and the unbender portion of the performer,
Wherein the bender portion has a height of 150 to 190 mm from the casting, the nozzle spacing is 190 to 360 mm, the unbender portion has a height of 260 to 420 mm from the cast, the nozzle spacing is 650 to 900 mm,
Wherein the quantity of the secondary cooling is set so as to follow the formula 1 in the case of the bender section and to follow the formula 2 in the case of the unbender section,
Qv = 990 * Vc-27.1 - (1)
Qu = 46.6 + 352 * Vc + 0.195 * Wc - (2)
Qv is the cooling rate of the bender portion (liter / min), Qu is the cooling rate of the unbender portion (liter / min), Vc is the casting speed (meter / min), and Wc is the main gauge (milimeter).
Method of manufacturing high carbon steel slabs.
The method according to claim 1,
The casting speed is from 0.8 to 1.1 meters / min
The casting width is 900 to 1600 mm
Method of manufacturing high carbon steel slabs.
3. The method of claim 2,
The non-yield is from 0.6 to 1 liter / min
Method of manufacturing high carbon steel slabs.
The method according to claim 1,
The above-described secondary cooling water quantity may be monitored in units of slabs, and the step of managing the set secondary water quantity may be controlled to a process error of 5%
Method of manufacturing high carbon steel slabs.
KR1020150073211A 2015-05-26 2015-05-26 Method of manufacturing high carbon steel slab KR101727803B1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108774712A (en) * 2018-06-21 2018-11-09 河南中原特钢装备制造有限公司 Superelevation thermal conductivity hot stamping die steel and its manufacturing method
CN109894593A (en) * 2019-04-08 2019-06-18 山东钢铁股份有限公司 A kind of Spraying Water of Nozzles in Secondary Cooling method based on continuous small-billet casting simulation pulling rate

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5708340B2 (en) 2011-07-21 2015-04-30 新日鐵住金株式会社 Cooling method for continuous cast slab
JP2013202631A (en) 2012-03-27 2013-10-07 Jp Steel Plantech Co Secondary cooling device for continuous casting apparatus

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108774712A (en) * 2018-06-21 2018-11-09 河南中原特钢装备制造有限公司 Superelevation thermal conductivity hot stamping die steel and its manufacturing method
CN109894593A (en) * 2019-04-08 2019-06-18 山东钢铁股份有限公司 A kind of Spraying Water of Nozzles in Secondary Cooling method based on continuous small-billet casting simulation pulling rate

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