Name of the invention: the cast continuous casting method

Art

[1]

The present invention relates to a state as convenience continuous casting method, and more particularly, to a cast continuous casting method for controlling the position of the segregation and the shrinkage cavity that is generated in the cast steel.

BACKGROUND

[2]

In general, a steel plant by the production of molten steel through the iron making process and a steel making process to produce semi-finished product is cast in the continuous casting process, and produce a cast steel is produced by a coil having a thickness of consumers want in the rolling process.

[3]

1 is a schematic representation showing a typical casting facilities, Figure 2 is a schematic diagram showing the solidification structure is produced in a typical casting facilities.

[4]

FIG placed on top of the next tundish 20 is moved in a continuous casting plant can package the cost of the molten steel (1) in the steel refining process, as shown in Figure 1 in the ladle (10). Further, accommodated in the ladle 10, molten steel (1) is a molten steel (1) implanted in the tundish tundish 20 is introduced into (20), and through the shroud nozzle 11, through the immersion nozzle (21) then continuously injected into the mold (30). Supplied to the mold 30, the molten steel (1) is mainly cooled by the cooling water spray in between passes through the mold 30, the first is cooled and then drawn multiple segments rolls at the same time roll and the roll that is pressed down by the 40 as is made according to the slab (2).

[5]

The thus continuously cast slab (2) is cut to a predetermined length by the cutter 50 is transported to the next step of the rolling process by the conveying rollers 60. The

[6]

In particular, a case of slab (2) is caused by a defect is a defect remaining after rolling of the cast slab (2) when rolled to heavy plate steel occurs. FIG. Examples of such defects can seat solidification shrinkage ball and the center piece for generating a main central convenience thickness direction as in the second.

[7]

When the solidification solute concentration remaining molten steel in the constriction in the vicinity of the solidification completion point of the continuous casting step to assemble this segregation (4) are, nameumyeon the same space without being solidification shrinkage added filled solidification shrinkage cavity (3) that is central pore (center and the porosity), these defects are to remain in the center of the cast plates after rolling.

[8]

In addition, while passing through the steel plate rolling / cooling process, the center of the cast thickness becomes a tensile stress is generated. The cast surface in the cooling stage after rolling is rapidly dropping the temperature below the center of the center of the cast thickness by such a temperature difference is able under tensile stress. In particular, the thicker the cast thickness size of a tensile stress due to this temperature difference is large becomes and when these tensile stresses the aforementioned segregation 4 and the coagulation to focus on the shrinkage cavity (3) easy to cast steel (2) extended defects in the heart will be presented causes a malfunction.

[9]

An exemplary technique for reducing defects such as center segregation 4 and the coagulation shrinkage cavity (3) for generating a defective product is a soft reduction (soft reduction). The soft reduction technique by pressing a slab (2), by the solidification contraction in the solidification end of slab (2) Solidification shrinkage cavity (3) by pushing down to as to impart push-down force by the segment rolls 40 of the continuous casting physically , to minimize the pore due to solidification shrinkage and at the same time that the center segregation (4) occurs in the slab (2) a solute, which is present between the main phase defined by the solidification contraction concentrated molten steel to inhibit the inflow to the top center of the cast steel thickness It is inhibited. However, this soft reduction technology, it is impossible to have to install a large-scale reduction in the caster equipment, sufficiently remove segregation 4 and the coagulation shrinkage cavity 3 due to conduct the reduction in clotting end.

[10]

Moreover, center segregation 4 and the coagulation shrinkage cavity (3) Even if the suppression of generating a tensile stress generated when the thickness center of the product / products and the portion remaining rolling / cooling since the maximum from the center of the thickness of the slab (2) the center of the thickness, thereby generating a defect. In particular, the thicker the thickness of the slab (2) or to an accelerated cooling from the rolling process has been further increased, the temperature difference between the central thickness and the surface is the product defects increases further.

[11]

Then, the center segregation 4 and the coagulation shrinkage cavity (3) a technique for reducing defects such as the submerged nozzle 21, in particular cooling water spray control on the discharge port structure improvement and the secondary cooling zone of the immersion nozzle 21 and the like. However, these methods have had a problem that can not be the center segregation (4) and solidified what the purpose of suppressing the formation of shrinkage cavity (3), but center segregation (4) and solidified completely eliminate shrinkage (3).

Detailed Description of the Invention

SUMMARY

[12]

The present invention provides a cast continuous casting method by changing the position of the immersion nozzle for supplying molten steel into a mold to control the position of segregation and the shrinkage cavity that is generated in the cast steel.

Problem solving means

[13]

One embodiment the cast of continuous casting process according to the present invention includes the steps of injection, while the eccentric region in the cast thickness direction from the center of the molten steel inside the mold by the mold and the primary cooling; While drawing a cast slab is first cooled by the mold spray coolant on the surface by a step of cooling the secondary.

[14]

Wherein in the step of primary cooling is the incoming immersion nozzle to the inside of a mold composed of a pair of long sides and short sides of the pair being disposed to each other opposite in any one doedoe molten steel is injected into the immersion nozzle is a choice of a long side of the pair characterized in that the eccentric direction of the long side.

[15]

In the step of the secondary cooling of the direction of the cast slab it is drawn downward from the mold and pulled out while bending forward, in the step of the primary cooling direction to which the immersion nozzle the eccentricity is to be the primary side pull-out of the long side of the pair based it characterized in that the long side direction are arranged on the front.

[16]

The difference between the distance (d1) to the distance (d2) between the immersion nozzle and a pair of long side of the other long side between the long side in the step of cooling said first selected among long side of the immersion nozzle and the pair is not less than 20mm It shall be.

[17]

In the step of cooling the primary to not less than each of the distance (d2) between the immersion nozzle and the distance between the long side being pair of long side selection of the (d1) and the immersion nozzle and a pair of long side of the other long side 10mm do.

[18]

The first step of cooling in length between the distance (d1) to the distance (d2) between the immersion nozzle and a pair of long side of the other long side between the long side is selected from a long side of the immersion nozzle and the pair ratio (d1: d2 ) is from 1: characterized in that the three.

[19]

The two are drawn in the step of primary cooling to the lower side at the slab is molded and pulled out while bending forward, that is to be pulled out state shift spray on the cast upper until a point before it is completely solidified coolant cooling which the water spray on the cast lower quantity lot more maintenance, and that is pulled out state shift is characterized in that for holding the completely solidified after this cooling water spray on the cast be lower than the cooling water spray on the cast be greater or equal to the upper starting point.

Effects of the Invention

[20]

According to an embodiment of the invention, the location of occurrence of segregation and solidification shrinkage of a change the position of the immersion nozzle to inject the molten steel in an eccentric area, the cast thickness direction than the central portion of the mold disposed in the mold the cast there is an effect that can be moved in the surface direction in the center.

[21]

In this way prevent segregation and solidification, and so that solidification shrinkage cavity more easily squeezed from the cast-rolling process, in accordance with moving the location of the shrinkage cavity in the surface direction, not present segregation in the position where the maximum tensile stress generated in the subsequent rolling, the cooling stage cracking by preventing the propagation of the effect of reducing the internal defects in the final product.

Brief Description of the Drawings

[22]

1 is a schematic representation showing a typical casting facilities,

[23]

2 is a schematic diagram showing the solidification structure is manufactured in general play equipment,

[24]

Figure 3a is a view showing an immersion nozzle position within the mold in a typical casting facilities,

[25]

Figure 3b is a view showing that the inner mold that is applied to the cast continuous casting method is immersion nozzle position change according to an embodiment of the present invention,

[26]

4 is a result of the flow analysis, and the temperature of the molten steel in the mold yi cast continuous casting method according to one embodiment of the present invention is applied,

[27]

Figure 5 is a picture produced according to cast the cast of continuous casting method according to one embodiment of the present invention,

[28]

6 is a simulation result of the compression during rolling coagulation shrinkage position,

[29]

Figure 7 is a schematic diagram showing the center segregation and the stress distribution left in the product.

Mode for the Invention

[30]

With reference to the accompanying drawings, the present will be described in more detail in an embodiment of the invention. However, the present invention is not limited to the embodiments set forth herein will be embodied in many different forms, but the embodiment are also the teachings of the present invention to complete, and will fully convey the concept of the invention to those of ordinary skill It will be provided to make known. Same numerals in the drawings refers to the same element.

[31]

[32]

Figure 3a is a view showing an immersion nozzle position within the mold in a typical casting facilities, Figure 3b is a view showing that the inner mold that is applied to the cast continuous casting method is immersion nozzle position change according to an embodiment of the present invention , Figure 4 is produced according to the cast of continuous casting method according to an embodiment of a steel analysis flow and temperature results for the mold yi cast continuous casting method according to one embodiment of the present invention is applied, Figure 5 is the invention and the main picture convenience, FIG. 6 is a simulation result of the compression solidification shrinkage during rolling position, Figure 7 is a schematic diagram showing the center segregation and the stress distribution left in the product.

[33]

The cast of continuous casting method according to one embodiment of the present invention as shown in the drawing is carried out by using a common casting facilities illustrated in Figure 1. However, it is achieved by changing the position where the molten steel 1 to be injected into the mold 30 by changing the position of the immersion nozzle 21 that contained in the tundish 20 is injected into the molten steel 1 in the mold 30.

[34]

A gritty words, while the cast of continuous casting method according to one embodiment of the present invention is significantly injecting the molten steel (1) in an eccentric area, in the center of the mold 30 in the thickness direction of the slab (2) a mold (30) by the step of cooling the first and; And drawing the slab (2) is cooled by the first mold 30, a cooling water spray on the surface comprises the step of cooling the secondary.

[35]

First the molten steel (1) in the step of cooling the mold 30, the mold (30 as shown in Figure 3a the positions of the immersion nozzle (21a) for injecting an eccentric region in the width direction of the slab (2) than the center of the inner ) is disposed in an eccentric area, the position of the immersion nozzle (21b) as shown in Figure 3b, not the central part of the inside in the width direction of the slab (2). Specifically, the mold 30 is makin composed of a long side (30a, 30b) and short sides (30c, 30d) of the pair of the pair being disposed opposite to each other are disposed opposite to each other, wherein the immersion nozzle (21b) is a long side of the pair ( 30a, 30b) of any one long side (30a) direction of the selected one it is arranged to be eccentric.

[36]

Thus, to induce the flow strength (velocity) of the molten steel (1) in an eccentric zone so that a larger effect than the other areas. Then it is possible to obtain the results shown in (a) of FIG. As Figure 4 (a) red region represented by the (relatively dark portion) is the flow intensity is greater than the area at the, in the, but the difference in flow rate by the area of ​​the bath surface size, 2m below the area from the bath surface is eccentric implanted region the can than determine that the strong flow field is formed. And (b) in that one calculates the temperature field in the region 4, it can be confirmed that similar to the flow field is the temperature difference in the thickness direction. That also in the 4 (b) red color zone appear as (relatively dark portion) relative to a region of high temperature and the temperature difference occurs is solidified complete seen that occurs unevenly in the eccentric direction it does not occur in the center thickness It can allow.

[37]

On the other hand, even there is 1 and the casting facilities as are disposed a number of segments rolls 40 for drawing while pressing the slab (2) towards the lower side of the mold (30) is bent in the forward direction, wherein the immersion nozzle direction (21) which is eccentric to a pair of long sides (30a, 30b) of the slab (2) the long side (30a) that is disposed in front relative to the direction that the pull-out direction is preferred. So, so that the upper surface direction of the slab (2) the direction of the immersion nozzle (21) being eccentric to be drawn. The lower surface of the slab (2) is drawn along by the eccentric to the point at which solidification is completed, the upper region direction from the area thus eccentric to the point at which the segregation 4 and the coagulation shrinkage cavity (3) occurs in the upper surface direction of the product (2) .

[38]

Next will be explained about the immersion nozzle (21) is eccentric.

[39]

In general, the immersion nozzle 21, which is located in the center of the mold 30 as shown in Figure 3b was a casting going to move in the direction of the arrow. The immersion nozzle 21, and a pair of long sides (30a, 30b) the long side (30a) defining the distance 'd1', and the immersion nozzle 21 and a long side (30a, 30b) of the pair between a selected one of It defines the distance between the other long side (30b) to a 'd2'.

[40]

Thus, the length of d1 and d2 ratio (d2 / d1) is respectively 1, 3, 4, place the submerged nozzle (21) such that the following seven performance was carried out. At this time there was d1 and the length where the larger the difference between the solidification is complete, the d2 can check the movement in the surface direction than the center thickness of the slab (2). That is, it was confirmed that the solidification shrinkage cavity 3 and the segregation 4 is moving in the surface direction than the center thickness. However, the difference between d1 and d2 are in need of more than 20mm, otherwise, the segregation 4 and the coagulation generated position of the shrinkage cavity (3) do not leave much from the center of slab (2) thickness to improve the quality of the rolled product for it was not effective. And, by the year d1 and d2 which length of one side of the re-dissolving the solidified layer while molten steel and the solidified layer strongly collision coagulation to be discharged if the less than 10mm can lead to operational accidents.

[41]

Thus while the difference between d1 and d2 is larger than 20mm the difference is larger glass to move the solidification completion position, however, d1 and d2 are preferably both being the immersion nozzle 21 disposed above 10mm. Preferably, the length ratio of d1 and d2 (d1: d2) is from 1: that the optimal conditions 3.

[42]

Figure 5 is the length ratio of d1 and d2 (d1: d2) is from 1: indicates that as a result, when casting with 3, red color is the relatively high temperature region showing a (solidification completion peripheral line), the location is cast it can be seen (2) that the image is shifted upward than the center thickness. That is, due to sikimeuro moving the position of the immersion nozzle 21 changes sheets flow and temperature, it can be seen that this is where the solidification is completed, can be biased to either side rather than the center thickness over. So that segregation is a 4 and the coagulation shrinkage cavity (3) formed by the eccentric direction of the upper surface a predetermined distance than the center of the thickness direction of the slab (2). However, where d2 is too larger than d1, the segregation 4 and the coagulation shrinkage cavity (3), since too eccentrically formed in the surface of the slab (2) is the defect is exposed to the surface in the rolling process may result in surface defects the length of d1 and d2 ratio because (d1: d2) is from 1: it is desirable to keep to 3.

[43]

Thereby offset the point at which the solidification is completed by giving a difference in the sheet flow and the temperature of the molten steel (1) As to the eccentric position of the immersion nozzle 21 as described above, injected into the molten steel 1 in the upper surface direction of the product (2) there is, in these cases difficulty in transferring the slab (2) to the transfer roller 60 to the slab (2) deflection caused by the residual stress due to cooling differences generated during solidification between upper and lower surfaces of the slab (2) occurs a problem that may occur.

[44]

The lower portion of this embodiment, up to a point before the slab (2) is drawn in the step of secondary cooling is fully solidified slab (2) cooling water slab (2) which spray the upper part of the in order to prevent this occurs, maintain more than the amount of cooling water is spray on, and the starting point after the completely solidified is drawn slab (2) many lower cooling water is spray on of the product (2) than the amount of cooling water is spray on top of the slab (2) or equal to It can be maintained.

[45]

[46]

Next will be described the segregation 4 and the coagulation shrinkage cavity 3 which is generated at the time of manufacture of the product (2) to the effect that can be expected by the upper surface direction offset from the center of the thickness direction of the slab (2).

[47]

First, the internal defects of steel plate products is confirmed by ultrasonic test. For most products during ultrasonic plate there is to be a defect is detected in the center thickness which is caused by the solidification shrinkage cavity 3 and the segregation 4 to be generated in the center of the thickness at the time of continuous casting. Even if the same solidification shrinkage cavity 3 and segregation (4) inside the slab (2) occurs the more the product is a high strength going geukhu materialization, easily there is a defect is detected during ultrasonic inspection, which is due to the following reasons:

[48]

First, it becomes The more the product is thickened is reduced the amount of rolling of the slab (2) difficult to crimp the solidification shrinkage cavity (3). In particular, the thickness center of the cast steel during rolling (2) is more difficult to squeeze the solidification shrinkage cavity (3) is smaller than the surface deformation. It can be seen that also, even if the rolling with the same rolling reduction as shown at 6, and the solidification shrinkage cavity (well squeezed than 3b is present in the position to 1 / 4t thickness than solidification shrinkage cavity (3a) of the center thickness. Slab ( 2) If the to produce geukhu muljae while the determined amount by which the thickness of the rolling not bound to be relatively small solidification shrinkage cavity 3 is that the more difficult to crimp.

[49]

However, when solidification shrinkage cavity 3 is eccentric in the top surface direction than the center thickness of the slab (2) it is present in the pores more easily squeezed thereby reducing defects by ultrasonic flaw detection.

[50]

In addition to the slab (2) rolling the product is produced from the surface to cool. That is, the surface of the product, the low temperature state, there is the state of the interior is relatively high temperatures thereby to a tensile stress, the thickness of the center of the product. In particular, the central slab (2) thickness be segregated 4 is present it is to propagate the crack is easy to occur due to stress concentration causes a defect during ultrasonic inspection. In particular, this tensile stress greater the increase in strength geukhu materialization of the plate product is further increased is defective rate raised.

[51]

Therefore, as in the embodiment segregation 4 and the coagulation shrinkage cavity 3 as a in FIG. 7, even if not completely eliminate segregation 4 and by solidification moves the location of occurrence of the shrinkage cavity (3), easily pressed than when the rolling process and it is not present are segregated 4 to the position where the maximum tensile stress generated in the subsequent cooling process, by preventing the propagation of cracks will to obtain the effect of reducing the defects in the end product.

[52]

[53]

Although described with reference to the foregoing preferred embodiment and the accompanying drawings of the present invention, the present invention is not only limited to this, and is only limited by the claims below. Thus, those skilled in the art can vary the invention within the without departing from the technical spirit of the claims described below and modified strain range.

[54]

[55]

[56]

1: steel 2 cast

[57]

3: solidification shrinkage 4: Segregation

[58]

10: Ladle 11: shroud nozzle

[59]

20: tundish 21: immersion nozzle

[60]

30: mold 30a, 30b: longitudinal

[61]

30c, 30d: the short side 40 Segment roll

[62]

50: cutter 60: transport roller

[63]

Claims

[Claim 1]

A method for casting a cast steel continuously, while injecting from the center of the inside of the molten steel mold in an eccentric area, the cast thickness direction phase and of the primary cooling by the mold; while drawing a cast slab is first cooled by the mold surface thereof to spray the cooling water to secondary cooling step the cast of continuous casting method which includes a.

[Claim 2]

The method according to claim 1, the step of cooling the primary to each other opposite the nozzle inlet is immersed into the interior of the mold consisting of long sides and short sides of the pair of the pair disposed doedoe molten steel is injected, of the immersion nozzle is a long side of the pair selection main convenience continuous casting method characterized in that the eccentric in which one long side direction.

[Claim 3]

The method according to claim 2, of the step of the secondary cooling the cast slab is drawn downward from the mold and pulled out while bending forward, the long side of the pair in the step of the primary cooling direction to which the immersion nozzle the eccentricity of the main shifting the cast of continuous casting method which is characterized in that the long side direction are disposed in front relative to the direction in which the pull-out.

[Claim 4]

The method according to claim 2, the difference between the distance (d1) to the distance (d2) between the immersion nozzle and a pair of long side of the other long side between the long side at the step of the primary cooling is selected of the long side of the immersion nozzle and the pair how to cast a continuous casting comprising not less than 20mm.

[Claim 5]

The method according to claim 2, the distance (d2) between the step of the primary cooling the immersion nozzle and the distance between the long side being pair of long side selection of the (d1) and the immersion nozzle and a pair of long side of the other long side are each 10mm cast continuous casting characterized in that at least.

[Claim 6]

The method according to claim 2, in the step of the primary cooling length with the distance (d1) to the distance (d2) between the immersion nozzle and a pair of long side of the other long side between the long side is selected from a long side of the immersion nozzle and the pair ratio (d1: d2) is from 1: continuously cast, characterized in that three cast method.

[Claim 7]

The method according to claim 2, in the step of the secondary cooling the cast slab is drawn downward from the mold and pulled out while bending forward, that is up to prior to being drawn the main shift completely solidifying point watering in the cast upper cooling quantity is cast lower maintain more than the amount of cooling water is spray on, cast continuously, characterized in that the pull-out state shift to maintain a fully solidified after cooling to be spray on the cast upper cast lower than the amount of cooling water which spray the starting point number is greater or equal to how to cast.