KR101175646B1 - Simulating method for evaluating quality of scarfing in continuous casting - Google Patents

Simulating method for evaluating quality of scarfing in continuous casting Download PDF

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KR101175646B1
KR101175646B1 KR1020100040440A KR20100040440A KR101175646B1 KR 101175646 B1 KR101175646 B1 KR 101175646B1 KR 1020100040440 A KR1020100040440 A KR 1020100040440A KR 20100040440 A KR20100040440 A KR 20100040440A KR 101175646 B1 KR101175646 B1 KR 101175646B1
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simulated
slab
radioactive
mold
defect
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KR1020100040440A
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KR20110121036A (en
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장진수
도영주
유석현
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현대제철 주식회사
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Abstract

The present invention comprises the steps of providing a simulated slab; Forming an artificial defect for simulating on the simulated slab; Applying a radioactive material to at least one surface of the artificial defect; Performing a rolling process on a simulated slab having an artificial defect coated with the radioactive material; And analyzing the defect for the rolled simulated slab through an electron microscope using the radioactive material to determine the quality of the scarfing in the continuous casting.

Description

SIMULATION METHOD FOR EVALUATING QUALITY OF SCARFING IN CONTINUOUS CASTING}

The present invention relates to a simulation method for evaluating the quality of scarfing in continuous casting.

In general, a continuous casting machine is a facility for producing slabs of a constant size by receiving a molten steel produced in a steelmaking furnace and transferred to a ladle in a tundish and then supplying it as a mold for a continuous casting machine.

The continuous casting machine includes a ladle for storing molten steel, a continuous casting machine mold for cooling the tundish and the molten steel discharged from the tundish to form a casting having a predetermined shape, and a casting formed in the mold connected to the mold. It includes a plurality of pinch roller to move.

In other words, the molten steel tapping out of the ladle and tundish is formed of a slab (Slab) or bloom (Bloom), billet (Billet) having a predetermined width and thickness in the mold and is transferred through the pinch roller.

The present invention is to determine whether the uncut in the scarping process in the simulation process (simulating experiment) serves as a defect in the rolling process.

In order to solve the above problems, a simulation method for evaluating the quality of the scarfing in the continuous casting of one embodiment of the present invention, preparing a simulated slab; Forming an artificial defect for simulating on the simulated slab; Applying a radioactive material to at least one surface of the artificial defect; Performing a rolling process on the simulated slabs having artificial defects coated with the radioactive material; And analyzing the radioactive material and analyzing whether the rolled woolen yarn is defective.

The simulated slab and the artificial defect portion may be made of a soft metal as compared with iron.

Here, the simulated slabs and artificial defects may be made of one of aluminum and aluminum alloy.

In addition, the radioactive material may be boron nitride.

Here, applying the radioactive material to at least one surface of the artificial defect may include applying boron nitride to the side of the artificial defect by spraying.

Here, the step of grasping the radioactive material and analyzing the defects of the rolled simulated slabs may include determining whether the defects are formed in the simulated slabs by inserting the artificial defects into the simulated slabs by the rolling process. It may include a step.

Here, identifying the radioactive material and analyzing the defects of the rolled simulated slabs may include analyzing the defects of the rolled simulated slabs using the radioactive material through an electron microscope. .

According to the embodiment of the present invention described above, it can be seen whether the internal material defects occur after the rolling process according to the side shape of the side cutting part scarping using a soft material and boron nitride scarping part.

1 is a side view showing a continuous casting machine according to an embodiment of the present invention.
Figure 2 is a conceptual diagram for explaining the continuous caster of Figure 1 centered on the flow of molten steel (M).
Figure 3 is a flow chart for explaining a simulation method for evaluating the quality of the scarfing in continuous casting, an embodiment of the present invention.
4A-4D are schematic diagrams for explaining a simulating method for evaluating the quality of the scarfing in a continuous casting of one embodiment of the present invention.

Hereinafter, a simulating method for evaluating the quality of the scarfing in continuous casting according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the present specification, different embodiments are given the same or similar reference numerals for the same or similar configurations, and the description is replaced with the first description.

Continuous casting is a casting method in which a casting or steel ingot is continuously extracted while solidifying molten metal in a mold without a bottom. Continuous casting is used to manufacture simple products such as squares, rectangles, circles, and other simple cross-sections, and slab, bloom and billets, which are mainly for rolling.

The type of continuous casting machine is classified into vertical type, vertical bending type, vertical axis difference bending type, curved type and horizontal type. 1 and 2 illustrate a curved shape.

1 is a side view showing a continuous casting machine related to an embodiment of the present invention.

Referring to this drawing, the continuous casting machine may include a tundish 20, a mold 30, secondary cooling tables 60 and 65, a pinch roll 70, and a cutter 90.

The tundish 20 is a container that receives molten metal from the ladle 10 and supplies molten metal to the mold 30. Ladle 10 is provided in a pair, alternately receives molten steel to supply to the tundish 20. In the tundish 20, the molten metal supply rate is adjusted to the mold 30, the molten metal is distributed to each mold 30, the molten metal is stored, and the slag and the non-metallic inclusions are separated.

The mold 30 is typically made of water-cooled copper and allows the molten steel to be primary cooled. The mold 30 forms a hollow portion in which molten steel is accommodated as a pair of structurally facing faces are opened. In manufacturing the slab, the mold 30 comprises a pair of barriers and a pair of end walls connecting the barriers. Here, the short wall has a smaller area than the barrier. The walls of the mold 30, mainly short walls, may be rotated to move away from or close to each other to have a certain level of taper. This taper is set to compensate for shrinkage caused by solidification of the molten steel M in the mold 30. The degree of solidification of the molten steel (M) will vary depending on the carbon content, the type of powder (steel cold Vs slow cooling), casting speed and the like depending on the steel type.

The mold 30 has a strong solidification angle or solidifying shell 81 (see FIG. 2) so that the casting extracted from the mold 30 maintains its shape and does not leak molten metal which is still less solidified. It serves to form. The water cooling structure includes a method of using a copper pipe, a method of drilling a water cooling groove in the copper block, and a method of assembling a copper pipe having a water cooling groove.

The mold 30 is oscillated by the oscillator 40 to prevent the molten steel from sticking to the wall of the mold. Lubricants are used to reduce friction between the mold 30 and the casting during oscillation and to prevent burning. Lubricants include splattered flat oil and powder added to the molten metal surface in the mold 30. The powder is added to the molten metal in the mold 30 to become slag, as well as the lubrication of the mold 30 and the casting, as well as the oxidation and nitriding prevention and thermal insulation of the molten metal in the mold 30, and the non-metal inclusions on the surface of the molten metal. It also performs the function of absorption. In order to inject the powder into the mold 30, a powder feeder 50 is installed. The part for discharging the powder of the powder feeder 50 faces the inlet of the mold 30.

The secondary cooling zones 60 and 65 further cool the molten steel that has been primarily cooled in the mold 30. The primary cooled molten steel is directly cooled by the spray 65 spraying water while maintaining the solidification angle by the support roll 60 so as not to deform. Casting solidification is mostly achieved by the secondary cooling.

The drawing device adopts a multidrive method using a plurality of sets of pinch rolls 70 and the like so that the casting can be taken out without slipping. The pinch roll 70 pulls the solidified tip of the molten steel in the casting direction, thereby allowing the molten steel passing through the mold 30 to continuously move in the casting direction.

The cutter 90 is formed to cut continuously produced castings to a constant size. As the cutter 90, a gas torch, a hydraulic shear, or the like can be employed.

FIG. 2 is a conceptual view illustrating the continuous casting machine of FIG. 1 based on the flow of molten steel M. Referring to FIG.

Referring to this figure, the molten steel (M) is to flow to the tundish 20 in the state accommodated in the ladle (10). For this flow, the ladle 10 is provided with a shroud nozzle 15 extending toward the tundish 20. The shroud nozzle 15 extends to be immersed in the molten steel in the tundish 20 so that the molten steel M is not exposed to air and oxidized and nitrided. The case where molten steel M is exposed to air due to breakage of shroud nozzle 15 is called open casting.

The molten steel M in the tundish 20 flows into the mold 30 by a submerged entry nozzle 25 extending into the mold 30. The immersion nozzle 25 is disposed in the center of the mold 30 so that the flow of molten steel M discharged from both discharge ports of the immersion nozzle 25 can be symmetrical. The start, discharge speed, and stop of the discharge of the molten steel M through the immersion nozzle 25 are determined by a stopper 21 installed in the tundish 20 corresponding to the immersion nozzle 25. Specifically, the stopper 21 may be vertically moved along the same line as the immersion nozzle 25 to open and close the inlet of the immersion nozzle 25. Control of the flow of the molten steel M through the immersion nozzle 25 may use a slide gate method, which is different from the stopper method. The slide gate controls the discharge flow rate of the molten steel M through the immersion nozzle 25 while the sheet material slides in the horizontal direction in the tundish 20.

The molten steel M in the mold 30 starts to solidify from the part in contact with the wall surface of the mold 30. This is because heat is more likely to be lost by the mold 30 in which the periphery is cooled rather than the center of the molten steel M. The rear portion along the casting direction of the strand 80 is formed by the non-solidified molten steel 82 being wrapped around the solidified shell 81 in which the molten steel M is solidified by the method in which the peripheral portion first solidifies.

As the pinch roll 70 (FIG. 1) pulls the tip portion 83 of the fully solidified strand 80, the unsolidified molten steel 82 moves together with the solidified shell 81 in the casting direction. The uncondensed molten steel 82 is cooled by the spray 65 for spraying cooling water in the course of the above movement. This causes the thickness of the unsolidified molten steel 82 to occupy the strand 80 gradually decreases. When the strand 80 reaches a point 85, the strand 80 is filled with the solidification shell 81 in its entire thickness. The solidified strand 80 is cut to a certain size at the cutting point 91 and divided into a product P such as a slab.

The product P may have defects on its surface due to inadequate process conditions. Therefore, linear defects are created on the surface during coiling in the rolling process. In order to prevent the generation of defects in such a post process, the casting process is followed by a scarfing process in which the slab surface portion is finished. In the scarfing process, the surface part is dissolved and removed using an oxygen torch to cut the surface of the slab. Such uncut parts may cause linear defects in the rolling process or may not cause defects. If the uncut part causes a linear defect in the rolling process, it is necessary to remove the uncut part.

Of these beauty cutting parts, it is necessary to evaluate in advance the quality of the beauty cutting part of the type that causes a linear defect.

Hereinafter, with reference to Figures 3 and 4, it will be described in detail with respect to the simulation method for evaluating the quality of the scarfing in the continuous casting of one embodiment of the present invention.

3 is a flowchart illustrating a simulating method for evaluating the quality of the scarfing in continuous casting, which is one embodiment of the present invention. First, as shown, a product (simulating slab) is provided (S1). Here, the simulated slabs are not slabs produced by actual operations, but artificially made slabs for experimentation. And an artificial defect part for simulating is formed on this simulation slab (S3). Imitation Slabs and Artificial Defects It is formed of a material (aluminum or aluminum alloy). The reason why the aluminum material is used as a simulated slab and artificial defects is that due to the characteristics of aluminum, a strong oxide film called alumina is formed on the part exposed to the atmosphere, so that there is no scale in which the surface part is rusted even during the air contact. In addition, since aluminum is very ductile and has low strength compared to iron, aluminum can be rolled at a much lower temperature than rolling iron (Fe), thereby simulating simulation process conditions. Then, at least one side of the artificial defect portion is coated with boron nitride (BN) (formation of boron nitride layer) (S5). The reason for applying the boron nitride is that the boron, which is a radioactive material, is present in the defect portion generated by the unscaping portion after the test rolling, and an electron microscope capable of detecting an element using a secondary electron image (EPMA: Electron Probe Micro Analyzer) When boron can be detected, boron can be detected and defects can be accurately analyzed. The description thereof will be described in detail with reference to Table 1 attached later. In addition, since boron nitride generally comes out in the form of a spray, boron can be easily sprayed on the side of the specimen so that boron can be applied to the side of the artificial defect. Therefore, boron nitride plays a good role as a tracer to increase economic and experimental accuracy. In this case, boron nitride is a radioactive material and is easily detected through an electron microscope. Although boron nitride is used in this embodiment, a radioactive material other than boron nitride may be applied to one side of the artificial defect.

The rolling process is performed on the simulated slab having an artificial defect coated with the radioactive material (boron nitride) (S7). Then, when the electron microscope is scanned on the rolled simulated slab (S9), it is possible to confirm whether the side coated with the radioactive material is inserted into the simulated slab. This will be described later in detail with reference to FIGS. 4 and 1. In short, if it is detected that the radioactive material is inserted into the simulated slab, it is determined that a defect of this kind causes a defect in the simulated slab by a rolling process. In addition, if it is detected that the radioactive material is not inserted into the simulated slab, it is determined that the defect part of this kind will not cause a defect in the simulated slab by the rolling process (S11).

4A to 4D are schematic diagrams for explaining a simulating method for evaluating the quality of the scarfing in continuous casting, which is one embodiment of the present invention.

4A illustrates a state in which an artificial defect 110 is formed in the simulated slab 100. As shown, the artificial defect portion 110 having the shape of the non-scarping portion that may occur after the scarfing process is formed on the simulated slab 100. As described above, the woolen yarn slab 100 and the artificial defect part 110 may be made of aluminum or an aluminum alloy material as described above. In this state, as shown in FIG. 4B, boron nitride may be applied to one side of the artificial defect part 110 (boron nitride application layer) 111 by a spray method. In the illustrated example, boron nitride is applied to the side, but in addition to the top or other side may be applied to boron nitride. When boron nitride is applied to one side 111 of the artificial defect part 110 as described above, as shown in FIGS. 4C and 4D, at least a part of the artificial defect part 110 is simulated. It may be inserted into the slab (100). At this time, since the one side 111 is coated with boron nitride, boron can be detected by the E PMA analysis of the simulated slab after the rolling process, and the presence and absence of defects caused by the artificial defects 110 are observed. Can be analyzed accurately.

Table 1 shows an embodiment of the defect generation and the shape of the simulated slab according to the shape of the artificial defect portion (110).

First embodiment Second Embodiment Third Embodiment Fourth embodiment Artificial defect shape

Figure 112010028022256-pat00001
Figure 112010028022256-pat00002
Figure 112010028022256-pat00003
Figure 112010028022256-pat00004
EPMA Results
Figure 112010028022256-pat00005
Figure 112010028022256-pat00006
Figure 112010028022256-pat00007
Figure 112010028022256-pat00008
Fault presence O O X X

When the artificial defect part was formed using the aluminum material, and then rolled and evaluated the presence or absence of the defect, the above result was obtained. If the angle of the side of the artificial defect (that is, the boron nitride-coated portion) is 90 degrees or less, the side portion may be folded during rolling and defects may be generated therein (see the first and second embodiments). However, when the angle of the side portion exceeds 90 °, the phenomenon that the unfolding occurs during the rolling process does not cause a defect inside the material (third and fourth embodiments).

The simulating method for evaluating the quality of the scarfing in such continuous casting is not limited to the construction and manner of operation of the embodiments described above. The above embodiments may be configured such that various modifications may be made by selectively combining all or part of the embodiments.

10: ladle 15: shroud nozzle
20: tundish 25: immersion nozzle
30: mold 40: mold oscillator
50: powder feeder 60: support roll
65: spray 70: pinch roll
80: strand 85: solidification completion point
100: product 110: artificial defect
111: Boron nitride coating layer

Claims (7)

Preparing a woolen slab;
Forming an artificial defect for simulating on the simulated slab;
Applying a radioactive material to at least one surface of the artificial defect;
Performing a rolling process on a simulated slab having an artificial defect coated with the radioactive material; And
Identifying the radioactive material and analyzing for defects in the rolled simulated slabs.
delete The method of claim 1,
And the simulated slab and the artificial defect portion are made of one of aluminum and an aluminum alloy.
The method of claim 1,
And wherein said radioactive material is boron nitride.
The method of claim 1,
The step of applying a radioactive material on at least one surface of the artificial defect,
Applying boron nitride to the side of the artificial defect in a spray manner.
The method of claim 1,
Identifying the radioactive material and analyzing the defects of the rolled simulated slab,
And checking whether the artificial defect portion is formed in the simulated slab by the rolling process as a result of the insertion of the artificial defect portion into the simulated slab.
The method of claim 1,
Identifying the radioactive material and analyzing the defects of the rolled simulated slab,
And analyzing the defect for the rolled simulated slabs using the radioactive material through an electron microscope to evaluate the scarfing quality in continuous casting.
KR1020100040440A 2010-04-30 2010-04-30 Simulating method for evaluating quality of scarfing in continuous casting KR101175646B1 (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006198649A (en) 2005-01-19 2006-08-03 Kobe Steel Ltd Method for determining whether or not hot charge rolling (hcr) is applicable
JP2008151545A (en) 2006-12-14 2008-07-03 Sanyo Special Steel Co Ltd Method of determining presence or absence of a subsurface defect in a bloom

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006198649A (en) 2005-01-19 2006-08-03 Kobe Steel Ltd Method for determining whether or not hot charge rolling (hcr) is applicable
JP2008151545A (en) 2006-12-14 2008-07-03 Sanyo Special Steel Co Ltd Method of determining presence or absence of a subsurface defect in a bloom

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