Device and method for preventing oxide scale fusion in heating furnace

Abstract

The present invention provides: a heating furnace device for heating a material to be heated while supporting same by a skid beam and transferring same; and a method for preventing oxide scale fusion in a heating furnace using same. The heating furnace device comprises a skid rider disposed on one side of a skid beam so as to be in contact with the lower surface of a material to be heated, wherein the height of the skid rider is 75 mm to 100 mm, and the area of the upper surface of the skid rider is 7,500 mm2 to 10,000 mm2.

Description

Device and method for preventing oxidation scale deposition in a heating furnace

[0001] The present invention relates to a device and method for preventing oxide scale fusion in a heating furnace, and more particularly, to a device and method capable of suppressing oxide scale fusion on the upper part of a skid rider.

[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, the configuration of a conventional furnace is briefly described. The inside of a typical furnace is composed of a skid beam (2) supporting a square-shaped heated material (1), a skid rider (8), and a burner for increasing the temperature, and the heated material (1) inside the furnace comes into direct contact with the skid rider (8). During this process, as shown in Fig. 3, the heated material (1) comes into contact with the fused oxide scale (a) on the upper part of the skid rider (8), causing surface flaws (b) to occur on the lower surface.

[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, there have been attempts to manufacture the skid rider with a Cr-based heat-resistant alloy to improve its corrosion resistance. However, Cr-based alloys have the problem of promoting fusion after the formation of oxide scale by reacting with iron oxide (FeO), the main component of scale, at high temperatures for a long time, thereby forming FeO-Cr2O3 oxide on the surface of the skid rider. In addition, when the shape of the skid rider is implemented as an inclined shape to prevent oxide scale from accumulating on the upper surface of the rider member, there is a limit to dispersing the stress caused by the load of the heated material, so it is not effective in preventing the fusion of oxide scale.

[0006] The present invention aims to solve these conventional problems by preventing the deposition of oxide scale on the upper surface of a skid rig and reducing surface flaws that occur on the underside of a heated material. 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 heating device is provided.

[0008] The above heating device is a heating device that heats the material to be heated while supporting and transporting it with a skid beam, and includes a skid rider that is arranged on one side of the skid beam and is formed to contact the lower surface of the material to be heated, and the height of the skid rider is 75 mm to 100 mm, and the upper surface area is 7,500 mm. 2 10,000 mm 2 It could be.

[0009] In one embodiment, the temperature of the upper surface of the skid rider can be controlled to a temperature below the melting point of Fe2SiO4.

[0010] In one embodiment, scale that falls off from the lower surface of the heated material and is deposited on the upper surface of the skid rider can be suppressed.

[0011] In one embodiment, the skid riders may be arranged in multiple numbers along the centerline of the skid beam. The centerline may refer to a centerline in a direction parallel to the direction of movement of the heated material, or may refer to a centerline in the longitudinal direction of the skid beam.

[0012] According to another aspect of the present invention, a method for preventing oxidation scale fusion using the heating device is provided.

[0013] The above method may be to control the lower atmosphere temperature of the heated material to be 25°C to 50°C lower than the upper atmosphere temperature.

[0014] In one embodiment, as the lower ambient temperature of the heated material decreases, the upper surface temperature of the heated material can be controlled to be lower.

[0015] In one embodiment, the lower atmosphere temperature of the heated material can be controlled to 1230°C or lower.

[0016] In one embodiment, the lower ambient temperature of the heated material can be controlled by adjusting the gas flow rate of the burner.

[0017] According to the embodiment of the present invention as described above, quality defects can be reduced due to reduction of surface flaws of the heated material, and cost can be reduced due to reduction of the replacement cycle of the skid rider.

[0018] Of course, the scope of the present invention is not limited by these effects.

[0019] Figure 1 is a schematic diagram showing a skid beam and skid rider in a typical furnace.

[0020] Figure 2 is an enlarged perspective view of Figure 1.

[0021] Figure 3 is a photograph showing the oxidation scale (a) on the upper part of a skid rider and the surface flaws (b) of the heated material observed in a conventional heating furnace.

[0022] Figure 4 is a schematic diagram showing the scale generation pattern on the upper surface of a skid rider in a conventional heating furnace.

[0023] Figure 5 shows the change in upper surface temperature according to the change in height of the ski rider according to an embodiment of the present invention.

[0024] Figure 6 shows changes in the shape of a ski rider according to a conventional and an embodiment of the present invention.

[0025] Figures 7a and 7b are the results of stress distribution analysis according to the reduction in the upper area of ​​a skid rider according to an embodiment of the present invention.

[0026] Figure 8 is a result of analyzing the temperature of a heated material according to the control of the lower atmosphere temperature of a heating zone in a heating furnace according to an embodiment of the present invention.

[0027] Fig. 9 is a photograph comparing the upper surface of a skid rider according to a conventional embodiment and an embodiment of the present invention.

[0028] 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.

[0029] Hereinafter, a continuous heating furnace including a skid rider according to an embodiment of the present invention will be described.

[0030] Figure 2 shows the appearance of a typical continuous heating furnace. Referring to Figure 2, the continuous heating furnace is equipped with a walking beam-type skid beam (2) so that the heated material is transported in the transport direction by being raised, advanced, and lowered. The skid beam (2) is equipped with a skid pipe (3) through which cooling water (7) circulates internally, and a skid rider (8) made of insulating material is fixedly supported on the upper side of the skid pipe (3).

[0031] The pattern of scale fusion on the upper surface of a skid rider in a conventional heating furnace is shown in Fig. 4.

[0032] Referring to Fig. 4, (a) shows the scale formation process according to physical bonding, and (b) shows the scale formation process according to chemical bonding. A Cr2O3 oxide layer (9) is formed on the surface of the skid rider (8), and an oxide scale (10) is formed on the upper portion of the oxide layer. In the case of Fig. 4(a), the primary oxide scale is deposited on the upper surface of the skid rider, and the scale is plastically deformed under the load of the heated material at high temperature and high pressure, and additionally, secondary and tertiary oxide scales are deposited, thereby forming physical fusion by diffusion. In the case of Fig. 4(b), the primary oxide scale is deposited on the upper surface of the skid rider, and chemical fusion is formed due to the binding effect of a low-melting-point element under high temperature and high pressure. Typically, fusion occurs at a temperature exceeding the melting point of 1173℃ of Fe2SiO4, a low-melting-point oxide.

[0033] As a method for removing and reducing the above-described oxide scale, the present invention proposes a device and method for (1) controlling the temperature of the upper surface of the skid rider by changing the height of the skid rider, (2) minimizing the area of ​​the skid rider where the oxide scale can be deposited, and (3) controlling the ambient temperature of the lower part of the heating zone in the heating furnace.

[0034] Specifically, according to one aspect of the present invention, the height of the ski rider is 75 mm to 100 mm, and the upper surface area is 7,500 mm 2 10,000 mm 2 A heating device is provided. This is to control the temperature of the upper surface of the skid rider to a temperature below the melting point of Fe2SiO4, a low-melting-point oxide, and to minimize the area of ​​the skid rider on which oxide scale can be deposited.

[0035] Figure 5 shows the change in upper surface temperature according to the change in height of the ski rider according to an embodiment of the present invention.

[0036] Figure 5 (a) shows the temperature change according to the skid rider height, showing the temperatures when (a-1) 50 mm, (a-2) 100 mm, (a-3) 150 mm, and (a-4) 200 mm. It can be seen that as the skid rider height decreases, the temperature on the upper surface of the skid rider decreases due to skid beam cooling. When the height is 200 mm, the scale is elongated and fused, whereas when the height is 50 mm, the scale is destroyed, thereby preventing the fusion of the oxide scale.

[0037] Figure 5 (b) is a graph showing the results according to (a). When the skid rider height is maintained at 100 mm or less, the upper surface temperature can be designed to be 1173℃ or less, which is lower than the melting point of low-melting-point oxides, thereby reducing oxide scale fusion. Basically, if scale fusion is reduced, the bonding strength of the scale itself is reduced, making removal easier. Preferably, the skid rider height is maintained at 75 mm or more. If the height is less than 75 mm, the upper surface temperature of the skid rider may become too low to sufficiently heat the material to be heated.

[0038] Figure 6 is a schematic diagram showing changes in the shape of a ski rider according to (a) a conventional method and (b) an embodiment of the present invention.

[0039] Referring to Fig. 6, (b) the skid rider according to the embodiment of the present invention is designed to have a lower height and a reduced upper surface area compared to a conventional skid rider. In addition, the lower surface of the body may be designed in an arch shape to distribute the stress applied from the upper surface to both ends of the lower surface by the reduced upper surface area. In Fig. 6, for example, the upper surface area is (a) 12,000 mm 2 Contrast (b)7,500 mm 2 10,000 mm 2 Accordingly, the probability and extent of oxide scale deposition on the upper surface of the skid rider can be reduced.

[0040] Figures 7a and 7b are the results of rider stress distribution analysis according to the reduction in the upper area of ​​the ski rider according to Figure 6.

[0041] As a result of the stress analysis of Figs. 7a and 7b, in the case of Fig. 7a, the stress is concentrated overall at the center connecting the upper and lower parts of the skid rider, whereas in the case of Fig. 7b, the stress may be distributed to both lower ends due to the reduced cross-sectional area of ​​the upper surface of the skid rider and the arched body structure. The average stress slightly increased from 1.54 MPa (Fig. 7a) to 2.24 MPa (Fig. 7b), but the effect on the function of the skid rider to support and move the material and the quality of the heated material was determined to be minimal.

[0042] In this way, the upper area of ​​the ski rider is 7,500 mm 2 10,000 mm 2 By reducing the scale, the scale that falls off from the underside of the heated material and is deposited on the upper surface of the skid rider can be suppressed.

[0043] According to another aspect of the present invention, a method for preventing oxidation scale fusion using the heating device is provided.

[0044] Specifically, the lower atmosphere temperature of the heated material can be controlled to be 25°C to 50°C lower than the upper atmosphere temperature of the heated material, thereby preventing the fusion of oxide scale. As the lower atmosphere temperature of the heated material is lowered, the temperature of the upper surface of the heated material can be controlled lower.

[0045] Figure 8 illustrates the results of temperature analysis of a heated material according to the control of the lower ambient temperature of a heating zone within a heating furnace according to an embodiment of the present invention. For example, in Figure 8(a), by controlling the lower ambient temperature to 1230°C or lower compared to the upper ambient temperature, the temperatures of the lower portion of the skid rider (8) and the heated material (1) can be reduced, thereby lowering the temperature of oxide scale deposited on the upper surface of the skid rider (8). This can prevent the fusion of oxide scale.

[0046] In Fig. 8, (b-1) shows the temperature of the heated material (1) when the upper and lower atmosphere temperatures of the heating zone are controlled to be the same at 1250°C, and it can be confirmed that the temperature is symmetrically distributed in the y-axis direction and that the temperatures of the upper and lower surfaces are the same. (b-2) shows the case when the upper atmosphere temperature of the heating zone is controlled to 1250°C and the lower atmosphere temperature is controlled to 1200°C, and it can be confirmed that the temperature of the lower surface of the heated material (1) is lowered to close to 1200°C, and the temperature of the upper surface of the heated material (1) is also lowered to 1240°C to 1245°C compared to (b-1).

[0047] The lower ambient temperature of the heated material can be appropriately controlled by adjusting the gas flow rate supplied to the burner, which provides a heat source to the furnace. There may be a plurality of burners, and a first burner may be arranged at the upper portion of the furnace, and a second burner may be arranged at the lower portion of the furnace. The lower ambient temperature can be controlled by supplying a second gas flow rate, which is less than the first gas flow rate supplied to the first burner, to the second burner.

[0048] Experimental example

[0049] 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.

[0050] Table 1 below shows the skid rider shape and heating furnace operating conditions according to comparative examples and examples.

[0051] Classification Comparison Example Example Comparison Example Comparison Skid rider material Heat-resistant alloy Heat-resistant alloy Same Skid rider height 120 mm 75 mm 25.0% reduction Skid rider top surface area 80 x 150 ㎟ 50 x 150 ㎟ 37.5% reduction Heating furnace upper temperature (heating zone) 1250 ℃ 1265 ℃ 15 ℃ increase Heating furnace lower temperature (heating zone) 1250 ℃ 1230 ℃ 20 ℃ reduction

[0052] Using comparative and exemplary examples, 10 skid riders were randomly selected after heating the material, and the maximum thickness of the fused scale was measured. This is because the thicker the scale, the higher the probability of the material surface becoming dented and causing surface flaws. The results are shown in Table 2.

[0053] Skid Rider No. Comparative Example Example 12.10.420.50.232.31.144.20.356.50.562.70.273.40.385.40.192.40.6100.20.7Average 2.530.24

[0054] In the comparative example, the average fusion scale thickness was 2.53 mm, and in the example, a result of 0.24 mm was confirmed.

[0055] Figure 9 is a photograph comparing the upper surface of a skid rider according to a comparative example and an embodiment of the present invention. Through this, it was confirmed that the embodiment showed almost no scale fusion, and that only a small amount of deposited oxide scale was present as it was compressed by the material, resulting in the presence of only a thin deposited scale.

[0056] According to the embodiment of the present invention as described above, there is an effect of reducing quality defects due to reduction of surface flaws of the heated material, and reducing costs due to reduction of the replacement cycle of the skid rider.

[0057] 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. In a heating device that heats while transporting the heated material by supporting it with a skid beam, It includes a skid rider arranged on one side of the skid beam and formed to contact the lower surface of the heated material, The height of the above skid rider is 75 mm to 100 mm and the top surface area is 7,500 mm 2 Within 10,000 mm 2 person, Heating device.

2. In paragraph 1, The upper surface temperature of the above skid rider is Fe 2 SiO 4 Controlled at a temperature below the melting point of Heating device.

3. In paragraph 1, The scale that falls off from the lower surface of the above-mentioned heating material and is deposited on the upper surface of the above-mentioned skid rider is suppressed. Heating device.

4. In paragraph 1, The above skid riders are arranged in multiple numbers along the center line of the skid beam. Heating device.

5. Using a heating device according to any one of clauses 1 to 4, Controlling the lower atmosphere temperature of the above-mentioned heated material to be 25℃ to 50℃ lower than the upper atmosphere temperature, Method for preventing oxidation scale deposition in a heating furnace.

6. In paragraph 5, As the lower ambient temperature of the above-mentioned heated material decreases, the upper surface temperature of the above-mentioned heated material is controlled to be lower. Method for preventing oxidation scale deposition in a heating furnace.

7. In paragraph 5, The lower atmosphere temperature of the above-mentioned heating material is controlled to 1230℃ or lower. Method for preventing oxidation scale deposition in a heating furnace.

8. In paragraph 5, The lower atmosphere temperature of the above-mentioned heating material is Controlled by adjusting the gas flow rate of the burner in the heater. Method for preventing oxidation scale deposition in a heating furnace.

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