Continuous heating furnace comprising skid riders

Abstract

The present invention provides a skid device for a continuous heating furnace, the skid device comprising: a skid beam for supporting a material to be heated in a heating furnace; and a plurality of skid riders disposed on the upper portion of the skid beam along the longitudinal direction of the skid beam so that the material to be heated can be placed thereon and moved. When a direction parallel to the longitudinal direction of the skid beam is defined as the lengthwise dimension (x) of the upper surface of the skid riders and a direction parallel to the width direction of the skid beam is defined as the widthwise dimension (y) of the upper surface of the skid riders, the lengthwise dimension (x) is equal to or greater than the widthwise dimension (y), and the relative ratio of the widthwise dimension to the lengthwise dimension is 0.7 to 1.0.

Description

Continuous heating furnace equipped with skid rig

[0001] The present invention relates to a continuous heating furnace equipped with a skid rider, and more particularly, to a continuous heating furnace equipped with a skid rider having a square upper surface so as to disperse stress.

[0002] Typically, the hot rolling process involves heating materials such as slabs, blooms, and billets, followed by rough rolling, finishing rolling, cooling, and straightening to produce rolled steel plates, bars, and wires. These materials are heated to temperatures ranging from 1100 to 1300°C in a heating furnace before rolling to reduce the load during rolling and achieve the required mechanical properties during the cooling process. The heating furnace, which heats the material to the rolling temperature, is divided into a preheating zone, a heating zone, and a soaking zone, and a constant amount of fuel is continuously supplied to each zone to maintain the required temperature. The material loaded into the heating furnace moves from the charging point to the extraction point, and upon reaching the extraction point, it is maintained in a heated state so that it has a temperature sufficient for rolling.

[0003] Referring to Fig. 1(a), the configuration of a conventional heating furnace is briefly described. The interior of a typical heating furnace comprises a skid beam (2) that supports a rectangular bar-shaped heating material (1) and a skid rider (8), and the heating material (1) inside the heating furnace comes into direct contact with the skid rider (8). During this process, surface flaws occur at the corners and center of the lower surface of the heating material.

[0004] In the past, the furnace operation was regularly stopped to remove the fused scale formed on the upper surface of the skid rider or to replace the skid rider. After the furnace was stopped, the worker had to manually remove the fused scale or replace the skid rider. This interruption of the furnace operation was a factor in lowering the operating rate and productivity. In particular, when a surface defect problem occurred on the lower side of the material, not only did it have to respond to the quality defect, but it was impossible to immediately take action in the high-temperature furnace to remove the fused scale or replace the skid rider. Instead, it had to wait until the temperature dropped before taking action, resulting in a significant loss in productivity.

[0005] Accordingly, an attempt was made to suppress surface flaws in the material by modifying the shape of the skid rider, but this caused stress to be concentrated in other parts of the material, which in turn caused surface flaws caused by other impressions.

[0006] The present invention aims to address these conventional problems and to reduce surface flaws caused by scratches on the edges of heated materials. However, these tasks are exemplary and do not limit the scope of the present invention.

[0007] According to one aspect of the present invention, a skid device for a continuous heating furnace is provided.

[0008] The skid device of the continuous heating furnace includes a skid beam that supports a heated material to be heated within the furnace; and a plurality of skid drivers arranged along the longitudinal direction of the skid beam on the upper portion of the skid beam so that the heated material is placed and moved, wherein the skid drivers are characterized in that a horizontal length (x) parallel to the longitudinal direction of the skid beam is shorter than or equal to a vertical length (y) parallel to the width direction of the skid beam, the vertical length (y) is shorter than or equal to the width of the skid beam, and a relative ratio of the vertical length (y) to the horizontal length (x) is 0.7 to 1.0.

[0009] In one embodiment, the relative ratio of the vertical length to the horizontal length may be 0.7 to 0.9.

[0010] In one embodiment, the edge of the upper surface of the ski rider may be rounded to a curvature of 5R to 10R.

[0011] In one embodiment, the curvature may be 7.5R to 9R.

[0012] In one embodiment, the heated material may be a slab, bloom or billet, which is a rolling object.

[0013] In one embodiment, the maximum stress applied to the skid ride may be characterized as being less than 29 MPa.

[0014] According to the embodiment of the present invention as described above, the stress concentration phenomenon occurring at the edge of the material can be alleviated, and quality defects can be reduced due to reduction of surface flaws.

[0015] Of course, the scope of the present invention is not limited by these effects.

[0016] Figure 1 is a schematic diagram showing a skid device of a continuous heating furnace according to an embodiment of the present invention.

[0017] Figure 2 is a perspective view showing the shape of a ski rider according to a conventional and an embodiment of the present invention.

[0018] Figure 3 is a schematic diagram showing the pattern of surface flaws occurring in a heated material when a conventional skid rider is applied.

[0019] Figures 4 to 6 are graphs showing the results of analyzing the maximum stress (MPa) according to the change in the aspect ratio of a ski rider according to an embodiment of the present invention, and simulation results thereof.

[0020] Fig. 7 is a perspective view illustrating an example of a ski rider according to an embodiment of the present invention in which the curvature (R) of the upper edge portion is changed.

[0021] FIGS. 8 to 10c are graphs showing the results of analyzing the maximum stress (MPa) according to the change in the curvature (R) of the upper surface edge of the skid rider according to an embodiment of the present invention, and simulation results thereof.

[0022] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings. These embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. The following embodiments may be modified in various different forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to more faithfully and completely explain the present disclosure and to fully convey the spirit of the present invention to those skilled in the art. In addition, the thickness and size of each layer in the drawings are exaggerated for convenience and clarity of explanation.

[0023] Hereinafter, a skid device of a continuous heating furnace according to an embodiment of the present invention will be described.

[0024] Figure 1 is a schematic diagram showing a skid device of a continuous heating furnace according to an embodiment of the present invention.

[0025] In the hot rolling process, a walking beam type heating furnace is used to heat steel. This heating furnace is equipped with multiple rows of skid beams (2) to support and transport the material to be rolled (1), such as a slab, bloom, or billet.

[0026] The skid beam (2) is composed of a moving beam and a fixed beam, and transports the heated material (1) by alternately moving it between the moving beam and the fixed beam by periodically repeating the lifting and horizontal reciprocating movements of the moving beam.

[0027] On the upper part of the skid beam (2), a plurality of skid drivers (8) are arranged at regular intervals in the longitudinal direction. As illustrated in Fig. 1(b), the skid drivers (8) are blocks in the shape of square columns, and their upper surfaces are in direct contact with the heated material (1). As such, the skid drivers (8) are members that come into contact with the heated material (1), and thus have problems such as deformation or surface flaws occurring due to the load of the heated material (1).

[0028] To address the above-described problems, the present invention provides a skid device having a shape capable of effectively dispersing stress applied to a skid rider (8). Specifically, the present invention provides a stress reduction effect through improved structure of the upper surface, which is the interface where the skid rider (8) comes into contact with the heated material (1).

[0029] The skid rider (8) of the present invention controls the stress applied to the skid rider (8) by optimizing the ratio of the upper surface horizontal length (x) and the upper surface vertical length (y). Here, the upper surface length in the longitudinal direction of the skid beam (2), i.e., in the direction parallel to the transport direction of the heated material (1), is defined as the horizontal length (x). In addition, the upper surface length in the direction parallel to the width direction of the skid beam (2) is defined as the vertical length (y).

[0030] In an embodiment of the present invention, the horizontal length (x) is shorter than or equal to the vertical length (y), and the vertical length (y) is shorter than or equal to the width of the skid beam (2).

[0031] If the above vertical length (y) is longer than the width of the skid beam (2), there is a concern that at least a part of the skid rider (8) may not be supported by the skid beam (2), and thus the strength to withstand the load of the heated material (1) may not be secured. Therefore, it is preferable that the above vertical length (y) be formed to be longer than the width of the skid beam (2) or at least the same length.

[0032] The above vertical length (y) is limited to within the width of the skid beam (2), but the horizontal length (x) is equal to or shorter than the vertical length (y). This is to increase the number of skid riders (8) supporting the heated material (1) when compared with a conventional skid rider with the same area, thereby distributing the load of the heated material (1) to multiple skid riders (8).

[0033] Hereinafter, a detailed explanation will be given with reference to Fig. 2.

[0034] Figure 2 is a perspective view exemplarily showing the shape of a ski rider according to a conventional and an embodiment of the present invention.

[0035] Referring to Fig. 2, the existing skid rider (a) is characterized by being arranged lengthwise in the direction in which the heated material advances, and having a rectangular shape in which the upper surface horizontal length (x) is longer than the vertical length (y). On the other hand, the skid rider (b) of the present invention is characterized by having the same height and material as the existing skid rider (a), but having an upper surface that is close to a square shape, so that the area in contact with the heated material is widely expanded in the longitudinal direction of the heated material.

[0036] Specifically, a skid rider according to an embodiment of the present invention may have the same upper surface area as a conventional skid rider, but with a changed horizontal and vertical ratio. In this case, it is preferable that the skid rider be arranged along the longitudinal center line of the skid beam.

[0037] In Fig. 2, in the case of (b) according to the embodiment of the present invention, the horizontal length (x) and the vertical length (y) are almost the same. Preferably, the relative ratio of the vertical length (y) to the horizontal length (x) (hereinafter referred to as the aspect ratio) is 0.7 to 1.0, and more preferably 0.7 to 0.9. On the other hand, in the case of (a), the existing ski rider is formed with a large deviation between the horizontal length (x) and the vertical length (y), and for example, the aspect ratio may be 3 or more.

[0038] In accordance with an embodiment of the present invention, the number of skid riders (8) supporting the heated material (1) in a certain area of ​​the skid beam is increased, so that the load of the heated material (1) can be distributed to multiple skid riders (8).

[0039] Fig. 3 is a schematic diagram showing the pattern of surface flaws occurring in a heated material when a conventional skid rider having a rectangular shape such as Fig. 2(a) is applied.

[0040] Referring to Fig. 3(a), in the process of the skid rider (8) supporting the lower surface of the heated material (1), local stress is concentrated in the area A where the contact area between the skid rider (8) and the heated material (1) is narrow, so there is a high possibility that surface flaws may occur on the lower surface of the heated material (1).

[0041] In addition, during the heating operation of the material to be heated in the furnace, a scale layer, which is a metal oxide that is generated on the surface of the material to be heated, adheres to the skid rider (8) that supports the material to be heated (1), and at this time, the scale layer is peeled off from the material to be heated (1) and remains on the skid rider (8).

[0042] Figure 3(b) shows a tilting phenomenon of a heated material (1) due to foreign matter (B) including oxide scale deposited on the upper part of a skid rider (8), and shows that this causes a stress concentration phenomenon due to line contact in the C area, which is another upper area of ​​a skid rider.

[0043] In this way, in the case of the existing skid rig, the heated material inside the heating furnace develops surface flaws due to the stress concentration of the skid rig and the imprinting of the corners.

[0044] Accordingly, in an embodiment of the present invention, the upper surface of the skid rider was changed to a square shape to alleviate the stress concentration on the lower surface of the heated material and improve the phenomenon of surface flaws. Since the skid rider is an expensive component manufactured from a heat-resistant casting material, the shape of the skid rider was changed under the condition of a constant volume, and the optimal shape necessary for alleviating the concentrated stress was derived by changing the width-to-length ratio of the skid rider.

[0045] As shown in Fig. 2(b), the skid rider according to an embodiment of the present invention has a square upper surface, thereby reducing the possibility of surface flaws. As the upper surface of the skid rider changes to a square shape, the total length of the upper surface edge portion is reduced, and the area where the heated material can be dented during heating can be minimized.

[0046] Figure 4 is a graph showing the results of analyzing the maximum stress (MPa) according to the change in the aspect ratio of a ski rider according to an embodiment of the present invention.

[0047] Referring to Figure 4, it can be seen that the maximum stress (MPa) gradually decreases as the aspect ratio of the ski rider decreases from 3.0 to 1.0. This trend persists until the aspect ratio reaches 0.8, and the maximum stress increases slightly when the aspect ratio reaches 0.7. Therefore, it can be confirmed that the most ideal maximum stress (MPa) value is derived when the aspect ratio is around 0.8.

[0048] Specifically, it was found that the maximum stress applied to the skid rider was less than 29 MPa when the aspect ratio of the skid rider was in the range of 0.7 to 1.0, and more preferably, the maximum stress was found to be less than 28 MPa when the aspect ratio of the skid rider was in the range of 0.7 to 0.9.

[0049] Figures 5 and 6 are simulation results that derived the results shown in Figure 4 above.

[0050] In Fig. 5, the aspect ratios are (a) 3.0, (b) 2.0, and (c) 1.1, respectively, and in Fig. 6, the aspect ratios are (a) 1.0, (b) 0.9, (c) 0.8, and (d) 0.7, respectively.

[0051] For example, different aspect ratios were set by changing the vertical length (y) while keeping the horizontal length (x) fixed.

[0052] In Figures 5 (a) and (b), it was confirmed that scales were deposited due to stress concentration, and as stress concentration increases, there is a high possibility that additional surface flaws will be formed. In comparison to Figure 5, it was confirmed that the stress concentration phenomenon was relatively alleviated in Figure 6.

[0053] According to another aspect of the present invention, by rounding the edge portion of the upper surface of the ski rider, an effect of reducing average stress can be expected.

[0054] In the present invention, the skid rider can be bent to various curvatures (R) according to a desired shape, but if the curvature is too small, stress may be concentrated in the central portion of the skid rider, causing deformation such as twisting. Conversely, if the curvature is too large, it is difficult to control the curvature.

[0055] Accordingly, the edge portion of the upper surface of the ski rider may have a structure forming a curved surface within a curvature (R) range of 5R to 10R. More preferably, it may have a curvature (R) of 7.5R to 9R. A larger curvature means a larger degree of bending, and a smaller curvature means a smaller degree of bending. In the present invention, the unit of the curvature (R) may be millimeters or centimeters.

[0056] Fig. 7 is a perspective view illustrating an example of a ski rider according to an embodiment of the present invention in which the curvature (R) of the upper edge portion is changed.

[0057] Referring to Fig. 7, the curvature of the edge increases in the order of (a) R2, (b) R5, and (c) R10.

[0058] Although the radius of the circle may be slightly different at every point on the curved surface of the above edge portion, this is within the range of error in the manufacturing process, and can be considered to have substantially the same curvature. Specifically, the curvature (R) can be defined as the average of the curvatures on the above curved surface.

[0059] FIGS. 8 to 10c are graphs showing the results of analyzing the maximum stress (MPa) according to the change in the curvature (R) of the upper surface edge of the skid rider according to an embodiment of the present invention, and simulation results thereof.

[0060] Referring to FIGS. 8 to 10c, it can be seen that the maximum stress (MPa) gradually decreases as the curvature (R) of the ski rider increases from 2.0 to 8.0. That is, the maximum stress shows a minimum value when the curvature is 8.0, and the maximum stress slightly increases when the curvature exceeds 8.0. Therefore, when considering the maximum stress, a curvature (R) range of 5R to 10R, or 7.5R to 9R is preferable.

[0061] Experimental example

[0062] Below, preferred experimental examples are presented to aid understanding of the present invention. However, the following experimental examples are provided solely to aid understanding of the present invention, and the present invention is not limited to the following experimental examples.

[0063] A conventional rectangular skid rider with an aspect ratio of 3 and a square skid rider with an aspect ratio of 0.9 according to an embodiment of the present invention were applied, and after bloom heating, 5 blooms were randomly collected from each, and the number of surface flaws at the corners was measured.

[0064] The result of dividing the number of surface flaws at the corners by the total number of surface flaws was derived as the surface flaw occurrence rate, and the result is shown in Table 1. In the conventional case, the average surface flaw occurrence rate at the corners was 0.23, and in the case of the present invention, it was 0.08, confirming that the occurrence of surface flaws in the invention was reduced by 15% compared to the existing material.

[0065] Bloom No.Previous invention 10.250.120.20030.350.240.200.150.150Average 0.230.08

[0066] According to the embodiment of the present invention as described above, the phenomenon of stress concentration occurring at the edge of a material is alleviated, and quality defects are reduced due to the reduction of surface flaws.

[0067] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will appreciate that various modifications and equivalent alternative embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

1. A skid beam supporting a heated material inside a heating furnace; and It includes a plurality of skid riders arranged along the length of the skid beam on the upper part of the skid beam so that the above-mentioned heating material is placed and moved, The above ski rider, The horizontal length (x) parallel to the longitudinal direction of the above skid beam is shorter than or equal to the vertical length (y) parallel to the width direction of the above skid beam, The above vertical length (y) is shorter than or equal to the width of the skid beam, It is characterized in that the relative ratio of the vertical length (y) based on the horizontal length (x) is 0.7 to 1.

0. Skid device for continuous heating furnace.

2. In paragraph 1, Characterized in that the relative ratio of the vertical length to the horizontal length is 0.7 to 0.

9. Skid device for continuous heating furnace.

3. In paragraph 1, The edge of the upper surface of the above ski rider is rounded to a curvature of 5R to 10R. Skid device for continuous heating furnace.

4. In paragraph 3, The above curvature is 7.5R to 9R, Skid device for continuous heating furnace.

5. In paragraph 1, The above-mentioned heating material is a slab, bloom or billet, which is a rolling target. Skid device for continuous heating furnace.

6. In paragraph 1, The maximum stress applied to the above skid ride is characterized in that it is less than 29 MPa. Skid device for continuous heating furnace.

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