Gas cutting method and gas cutting machine for continuously cast materials

Abstract

To provide a gas cutting method and gas cutting machine for continuously cast materials that can perform gas cutting at high speed even when the cutting oxygen pressure is less than 1.0 MPa. [Solution] A gas cutting method for a continuously cast material 11 cast by a continuous casting equipment 1, comprising: a preheating step of injecting preheating gas and preheating oxygen from a nozzle provided at the tip of a torch 62 to heat the widthwise end of the continuously cast material 11; and a cutting step of injecting cutting oxygen from the nozzle after the preheating step and moving the torch 62 in the widthwise direction of the continuously cast material to cut the continuously cast material 11, wherein in the cutting step the torch 62 is moved at a cutting speed of 100 mm / min or more, and then moved at a cutting speed of 500 mm / min or more, the pressure of the cutting oxygen is set to a gauge pressure of 0.90 MPa or more and 0.99 MPa or less, and the cutting oxygen flow velocity on the surface of the continuously cast material is set to 700 m / s or more and 1160 m / s or less.

Description

[Technical Field]

[0001] This invention relates to a gas cutting method and a gas cutting machine for continuously cast materials. [Background technology]

[0002] In a continuous steel casting facility, refined molten steel is continuously cast to obtain a continuously cast material, which is a solidified slab of molten steel with a predetermined cross-sectional shape. Then, by gas cutting this continuously cast material, castings such as slabs of a predetermined length can be obtained.

[0003] Continuous casting equipment is required to increase the production volume of castings. However, when the slab to be cut is short (when the cutting pitch of the continuously cast material is short), the cutter carriage cannot return to its original cutting origin after cutting the slab, making it impossible to perform the next cut. To solve this problem, it is necessary to either reduce the casting speed of the continuous casting equipment or increase the cutting speed of the continuously cast material by the torch.

[0004] Reducing the casting speed of a continuous casting machine lowers the production volume of castings. Therefore, in order to maintain production volume while also accommodating short cutting pitches of the continuous casting material, it is necessary to increase the cutting speed of the continuous casting material.

[0005] For example, Patent Document 1 discloses a method for increasing the cutting speed of continuously cast materials by adjusting the cutting oxygen pressure to a gauge pressure of 1.0 MPa to 1.2 MPa and performing gas cutting. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-241144 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the method described in Patent Document 1 requires setting the cutting oxygen pressure to 1.0 MPa or higher, which necessitates permission and notification under the High-Pressure Gas Safety Act. For this reason, it has been difficult to easily introduce such gas cutting machines, which use high-pressure cutting oxygen.

[0008] Therefore, the present invention has been made in view of the above-mentioned problems, and aims to provide a gas cutting method and gas cutting machine for continuously cast materials that can perform gas cutting at high speed even when the cutting oxygen pressure is less than 1.0 MPa. [Means for solving the problem]

[0009] (1) According to one aspect of the present invention, a gas cutting method for a continuously cast material cast by a continuous casting equipment is provided, comprising: a preheating step of injecting preheating gas and preheating oxygen from a nozzle provided at the tip of a torch to form a preheating flame and heat the widthwise end of the continuously cast material; and a cutting step of injecting cutting oxygen from the nozzle after the preheating step and moving the torch in the widthwise direction of the continuously cast material to cut the continuously cast material, wherein in the cutting step the torch is moved at a cutting speed of 100 mm / min or more, and then moved at a cutting speed of 500 mm / min or more, and the cutting oxygen flow velocity on the surface of the continuously cast material is set to 700 m / s or more and 1160 m / s or less.

[0010] (2) In the gas cutting method for continuously cast materials described in (1) above, the pressure of the cutting oxygen shall be 0.90 MPa or more and 0.99 MPa or less in gauge pressure, the pressure of the preheating gas shall be 0.09 MPa or more and 0.12 MPa or less in gauge pressure, and the pressure of the preheating oxygen shall be 0.10 MPa or more and 0.15 MPa or less in gauge pressure.

[0011] (3) According to one aspect of the present invention, a gas cutting machine for continuous castings, which gas cuts a continuously cast material cast by a continuous casting equipment, is provided, comprising: a torch configured to be movable in the width direction of the continuously cast material and which injects preheating gas, preheating oxygen and cutting oxygen from a nozzle provided at its tip, wherein when cutting the continuously cast material, the torch is moved at a cutting speed of 100 mm / min or more, and then moved at a cutting speed of 500 mm / min or more, and the cutting oxygen flow velocity on the surface of the continuously cast material is set to 700 m / s or more and 1160 m / s or less.

[0012] (4) The gas cutting machine for continuous casting materials described in (3) above further comprises: a cutting oxygen supply means for supplying the cutting oxygen at a gauge pressure of 0.90 MPa to 0.99 MPa to the torch; a preheating gas supply means for supplying the preheating gas at a gauge pressure of 0.09 MPa to 0.12 MPa to the torch; and a preheating oxygen supply means for supplying the preheating oxygen at a gauge pressure of 0.10 MPa to 0.15 MPa to the torch. [Effects of the Invention]

[0013] According to one aspect of the present invention, a gas cutting method and gas cutting machine for continuously cast materials are provided that can perform gas cutting at high speed even when the cutting oxygen pressure is less than 1.0 MPa. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing a continuous casting apparatus in one embodiment of the present invention. [Figure 2] This is a cross-sectional view showing the nozzle of a gas cutting machine for continuous casting materials according to one embodiment of the present invention. [Modes for carrying out the invention]

[0015] In the following detailed description, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals, and redundant descriptions are omitted. Each drawing is schematic and may include cases where it is different from the actual one. Further, the embodiments shown below illustrate devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the materials, structures, arrangements, etc. of the components as follows. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

[0016] <Device Configuration> The continuous casting facility 1 manufactures a slab 12, which is a semi-finished product of steel, by continuously casting molten steel 10. In the continuous casting facility 1, the molten steel 10 accommodated in the casting ladle 2 is poured into the mold 4 via the tundish 3. Next, the molten steel 10 is cooled by the mold 4 and the subsequent secondary cooling spray 5, thereby casting a continuous casting material 11 having a predetermined cross-sectional shape. Further, the continuous casting material 11 is cut to a predetermined length by the gas cutting machine 6, thereby manufacturing a slab 12 having a desired shape.

[0017] The gas cutting machine 6 includes a cutter carriage 61, two torches 62, a cutting oxygen supply means 63, a preheating gas supply means 64, and a preheating oxygen supply means 65.

[0018] The cutter carriage 61 is configured to be movable in the casting direction of the continuous casting material 11 (the extending direction of the continuous casting material 11 and the conveying direction of the slab 12, which is the left-right direction in FIG. 1 at the installation position of the gas cutting machine 6) above the continuous casting material 11. The moving means of the cutter carriage 61 is not particularly limited, and conventional moving means in the technical field can be used.

[0019] The two torches 62 are positioned opposite each other in the width direction (front-to-back direction in Figure 1) of the continuous casting material 11 and are movable in the width direction. The means of moving the torches 62 are not particularly limited, and conventional means of moving in this art can be used. The tip of the body of the torch 62 is provided with a nozzle 66 as shown in Figure 2.

[0020] When cutting the continuous casting material 11, first, a preheating process is performed by forming a preliminary flame with two torches 62 and heating both ends of the continuous casting material 11 in the width direction (preheating process). Then, cutting oxygen is sprayed from the two torches 62, and the continuous casting material 11 is cut by moving the two torches 62 from both ends of the continuous casting material 11 in the width direction toward the center in the width direction (cutting process). During the cutting process, the movement speed of the two torches 62 is changed from the cutting speed to the cutting speed. Details of the preheating process and the cutting process will be described later.

[0021] In the center of the nozzle 66, a cutting oxygen passage 661 is formed for ejecting cutting oxygen, which is oxygen gas used for cutting. Around the cutting oxygen passage 661, a preheating gas passage 662 is formed for ejecting preheating gas to form a preheating flame, and a preheating oxygen passage 663 is formed for ejecting preheating oxygen.

[0022] Cutting oxygen is supplied to the cutting oxygen passage 661 from the cutting oxygen supply means 63 via the body of the torch 62. The cutting oxygen passage 661 has a throat diameter d t and outlet diameter d e It has a Laval-shaped nozzle consisting of [the specified components]. Cutting oxygen is supplied to the cutting oxygen passage 661 at a pressure of less than 1.0 MPa, preferably between 0.9 MPa and 0.99 MPa, in gauge pressure.

[0023] Preheating gas, which is a fuel gas for preheating, is supplied to the preheating gas passage 662 from the preheating gas supply means 64 via the body of the torch 62. The preheating gas is a flammable gas, and in this embodiment, it is propane gas. It is preferable that the preheating gas supplied to the preheating gas passage 662 is adjusted to a gauge pressure of 0.09 MPa or more and 0.12 MPa or less. In addition, other fuel gases, such as coke oven gas generated in a coke oven, may be used as the preheating gas.

[0024] Preheating oxygen, which is oxygen gas for preheating, is supplied to the preheating oxygen passage 663 from the preheating oxygen supply means 65 via the body of the torch 62. Preferably, the oxygen gas supplied to the preheating oxygen passage 663 is adjusted to a gauge pressure of 0.10 MPa or more and 0.15 MPa or less.

[0025] The cutting oxygen supply means 63, the preheating gas supply means 64, and the preheating oxygen supply means 65 are not particularly limited as long as they are capable of supplying various gases to the torch 62. For example, the cutting oxygen supply means 63, the preheating gas supply means 64, and the preheating oxygen supply means 65 are pipes connected to cylinders or other supply equipment. In this embodiment, since the oxygen gas pressure is less than 1.0 MPa, it is not necessary for the cutting oxygen supply means 63 to be a high-pressure device.

[0026] The preheating gas passage 662 and the preheating oxygen passage 663 may be connected just before the outlet of the nozzle 66. In this way, the preheating gas and preheating oxygen are ejected from the nozzle 66 in a mixed state. The nozzle 66 may also be configured so that the preheating gas and preheating oxygen are mixed at the outlet.

[0027] Furthermore, the cutting oxygen flow rate of the gas cutting machine 6, which is the flow rate of the cutting gas ejected from the nozzle 66 when it reaches the surface of the continuously cast material 11, is set to 700 m / s or more and 1160 m / s or less. Details on adjusting the cutting oxygen flow rate will be described later.

[0028] <Method for cutting continuously cast materials> Next, a method for cutting the continuous cast material 11 according to this embodiment will be described. The cross-sectional shape of the slab 12 cast in this embodiment is a width of 700 mm to 1700 mm and a thickness of 200 mm to 300 mm.

[0029] In this embodiment, first, when the planned cutting position of the continuous casting material 11 reaches the gas cutting machine 6 which is waiting in the standby position, the preheating process described above is performed. In the preheating process, a mixed gas of preheated oxygen and preheated gas is injected from the nozzle 66, and both ends in the width direction of the continuous casting material 11 are heated by the preheating flame formed by the combustion of the injected mixed gas. During the cutting process (between the preheating and cutting processes), the cutter carriage 61 moves downstream in the casting direction at the same speed as the casting speed of the continuous casting material 11.

[0030] The preheating conditions, such as the flow rates of various gases and the height of the torch 66, are not particularly limited as long as the continuous casting material 11 is heated to a degree that it can be cut (melted) by the cutting oxygen. However, if the height of the torch 66 in the preheating process is too low, there is a possibility that the heat will be insufficient and the cutting process in the subsequent cutting process will be slower, and if it is too high, the preheating flame may bounce back and blow up. For this reason, it is preferable to set the height of the torch 66 to an appropriate and optimal height according to the shape of the torch 66 and the flow rates of various gases. The preheating process is completed when both ends of the continuous casting material 11 reach an ignition temperature or higher by heating with the preheating flame, or when a predetermined time has elapsed that is set so that both ends reach an ignition temperature or higher.

[0031] After the preheating process, the cutting process described above is performed. In the cutting process, cutting oxygen is sprayed from the nozzle 66, and when the cutting oxygen hits the continuously cast material 11, which has reached a temperature above the ignition temperature, the continuously cast material 11 is melted and cut. In the cutting process, the two torches 62 start cutting with the moving speed as the cutting speed, and then the moving speed is changed to the cutting speed to continue cutting. The switching of the moving speed of the torches 62 is performed according to the cutting position of the slab 12 by the torches 62 (the distance the torches 62 have traveled from the start of cutting), and cutting is performed at the cutting speed up to a predetermined distance from the widthwise end of the slab 12, and cutting thereafter is performed at the cutting speed. In other words, the switching of the moving speed of the torches 62 is performed at the timing when the cutting position of the torches 62 reaches a predetermined position. For example, the position for switching the moving speed may be 50 mm from the widthwise end of the slab 12. The cutting speed is 100 mm / min or more, and the cutting speed is higher than the cutting speed, and is 500 mm / min or more. By setting the cutting speed and the entry speed within these ranges, high-speed gas cutting can be performed even when the cutting oxygen pressure is less than 1.0 MPa. Furthermore, it is preferable that the entry speed be 170 mm / min or less, and the cutting speed be 560 mm / min or less. The upper limits of the entry speed and cutting speed are determined within a range that maintains the integrity of the cut surface. If the entry speed or cutting speed is too high, insufficient heat input will occur, making it easier for steps or sagging to occur on the cut surface.

[0032] Furthermore, in the cutting process, the cutting oxygen flow velocity, which is the central flow velocity (maximum flow velocity) of the cutting oxygen ejected from the torch 66 on the surface of the continuously cast material 11, is set to be between 700 m / s and 1160 m / s. The flow velocity of the cutting oxygen is calculated using equations (1) to (3) and is a value that can be calculated in advance from the thickness of the continuously cast material 11 to be cut. Note that the ejection flow velocity V0 is the flow velocity of the cutting oxygen at the exit side of the torch 66. Torch height L h L is the height from the top surface of the continuous casting material 11 to the bottom surface of the torch 66. In this embodiment, the cutting oxygen flow rate is adjusted by adjusting the adjustable parameters of equations (1) to (3). For example, the torch height L h The cutting oxygen flow rate may be adjusted by adjusting the throat diameter d.t and the outlet diameter d e The cutting oxygen flow rate may be adjusted by adjusting the nozzle shape of the nozzle 66 such as this. In the equations (2) and (3), the nozzle back pressure may be the gauge pressure at a position close to the nozzle 66. When the pressure gauge (gauge) can be installed only at a position far from the nozzle 66, the pressure corresponding to the position near the nozzle 66 corrected for the pressure loss (pressure drop) from the nozzle 66 to the gauge position may be used as the nozzle back pressure.

[0033]

Number

[0034] Here, V [m / s]: central flow velocity, V0 [m / s]: ejection flow velocity, L h [mm]: nozzle height, d e [mm]: outlet diameter, C [-]: correction coefficient, P e [kgf / cm 2 : atmospheric pressure, P0 [kgf / cm 2 : nozzle back pressure, F [Nm 3 / h]: oxygen supply rate, K p [-]: coefficient according to gas type (O2: 0.456), d t [mm]: throat diameter, provided that 1 kgf / cm 2 = 0.0981 MPa.

[0035] When the cutting oxygen flow rate is less than 700 m / s, especially when the thickness of the continuous casting material 11 is thick, there is a possibility of residue remaining under the continuous casting material 11. On the other hand, when the cutting oxygen flow rate exceeds 1160 m / s, the flame becomes thin. Therefore, when cutting is performed with two torches 62 as in this embodiment, the cutting regions of the two torches 62 do not overlap at the center in the width direction, and there is a possibility of cutting failure. For this reason, by setting the cutting oxygen flow rate to 700 m / s or more and 1160 m / s or less, the continuous casting material 11 can be stably cut in the cutting speed and cutting speed regions of this embodiment.

[0036] Furthermore, the preheating and cutting processes are performed entirely automatically. After the cutting process is completed, the gas cutting machine 6 moves to the standby position, and the same preheating and cutting processes are repeated, allowing for continuous gas cutting of subsequent materials from the continuous casting material 11.

[0037] In this embodiment, during the cutting process, the pressure of the cutting oxygen is set to less than 1.0 MPa in gauge pressure, and the cutting oxygen flow velocity on the surface of the continuously cast material 11 is set to 700 m / s or more and 1160 m / s or less. This makes it possible to gas-cut the continuously cast material 11 at high speed with a cutting speed of 100 mm / min or more and a cutting speed of 500 mm / min or more, without the need for high-pressure gas equipment. Furthermore, by setting the cutting speed to 100 mm / min or more and the cutting speed to 500 mm / min or more, gas cutting can be performed in a typical continuous casting equipment 1 without reducing the casting speed, even when the cutting pitch is short.

[0038] <Variation> Although the present invention has been described above with reference to specific embodiments, this description is not intended to limit the invention. By referring to the description of the present invention, those skilled in the art will also see other embodiments of the invention, including various modifications, in addition to the disclosed embodiments. Accordingly, the embodiments of the invention described in the claims should be understood to include embodiments that include these modifications described herein, either individually or in combination.

[0039] For example, in the above embodiment, the outlet of the cutting oxygen passage 661 is a Laval-shaped nozzle, but the present invention is not limited to such examples. For example, the outlet of the cutting oxygen passage 661 may be a straight-shaped nozzle with a constant inner diameter. When the nozzle is straight, in equations (1) to (3), the throat diameter d t and outlet diameter d e These two values ​​are the same.

[0040] Furthermore, although the above embodiment shows that the gas cutting machine 6 has two torches 62, the present invention is not limited to this example. For example, the gas cutting machine 6 may have only one torch 62. In this case, during the preheating process, the widthwise end of the continuous casting material 11 is heated, and during the cutting process, the torch 62 moves from the heated end of the continuous casting material 11 across its entire width to perform gas cutting. [Examples]

[0041] The present inventors will now describe an embodiment they performed. In the embodiment, a gas cutting machine 6 similar to that in the above embodiment was used to perform gas cutting on a continuously cast material 11. The cutting conditions in the embodiment and the evaluation of the cut surface as a result of the cutting test are shown in Table 1. As shown in Table 1, in the embodiment, gas cutting was performed under multiple conditions in which the cutting oxygen, preheating oxygen and preheating gas pressure, cutting oxygen flow rate, cutting oxygen, and cutting speed were varied. The thickness of the slab used in the embodiment was 260 mm.

[0042] Furthermore, in Table 1, the evaluation of the cut surface is as follows: "◎" means there are no noticeable scratches on the cut surface and no unevenness causing drag delay; "〇" means there are dents on the cut surface but no noticeable scratches and no unevenness causing drag delay; "△" means that cutting was possible but scratches and unevenness on the cut surface are noticeable; and "×" means that there was a cutting defect or a cut-off occurred. In this example, among the above evaluations, cases of ◎ and 〇 were considered to have no quality problems.

[0043] As shown in Examples 1 to 24 of the present invention in Table 1, it was confirmed that gas cutting could be performed without problems by setting the cutting oxygen flow rate, cutting speed, and cutting speed within the range of the above embodiments. In Examples 1 to 24, the pressure of the cutting oxygen, preheating oxygen, and preheating gas were also set within the preferred range in the above embodiments. On the other hand, in Comparative Examples 1 to 4, where the cutting oxygen flow rate was less than 700 m / s or greater than 1160 m / s, it was confirmed that gas cutting could not be performed satisfactorily. In Comparative Examples 1 to 4, it was also confirmed that the cutting speed improved when the pressure of the preheating gas and preheating oxygen was set higher. In the results in Table 1, the evaluation of the cut surface in Example 9 of the present invention was the best.

[0044] [Table 1]

[0045] Furthermore, Table 2 shows the cutting conditions and results when the pressures of the preheating oxygen and preheating gas are within the preferred range of the above embodiments (Examples 25, 27, 29) and when the pressures of the preheating oxygen and preheating gas are outside the preferred range of the above embodiments (Examples 26, 28, 30). For Examples 25 to 30, the cutting oxygen flow rate, cutting oxygen pressure, cutting speed, and cutting speed are within the range of the above embodiments. As shown in Table 2, it was confirmed that gas cutting could be performed without problems in all cases. It was also confirmed that a better cut surface could be obtained by setting the pressures of the preheating oxygen and preheating gas within the preferred range of the above embodiments, as in Examples 25, 27, and 29.

[0046] [Table 2] [Explanation of Symbols]

[0047] 1. Continuous casting equipment 2 Cast iron pot 3 Tan Dish 4 molds 5. Secondary cooling spray 6. Gas cutting machine 61 Cutter Cart 62 Torches 63 Cutting oxygen supply means 64 Preheating gas supply means 65 Preheating oxygen supply means 66 Craters 661 Cutting oxygen passage 662 Preheating gas passage 663 Preheating oxygen passage 10 Molten steel 11 Continuous casting material 12 Slabs

Claims

1. A gas cutting method for continuously cast materials, wherein the continuously cast material is gas cut by a continuous casting equipment, A preheating step is performed in which preheating gas and preheating oxygen are injected from a nozzle provided at the tip of the torch to form a preheating flame, thereby heating the widthwise end of the continuous casting material. After the preheating step, a cutting step is performed in which cutting oxygen is injected from the nozzle and the torch is moved in the width direction of the continuous casting material to cut the continuous casting material, Equipped with, In the cutting process, the torch is moved at a cutting speed of 100 mm / min or more, and then moved at a cutting speed of 500 mm / min or more. A gas cutting method for a continuously cast material, wherein the cutting oxygen flow rate on the surface of the continuously cast material is set to 700 m / s or more and 1160 m / s or less.

2. The pressure of the cutting oxygen is set to a gauge pressure of 0.90 MPa or more and 0.99 MPa or less. The pressure of the preheating gas is set to a gauge pressure of 0.09 MPa or more and 0.12 MPa or less. The gas cutting method for a continuously cast material according to claim 1, wherein the pressure of the preheated oxygen is set to 0.10 MPa or more and 0.15 MPa or less in gauge pressure.

3. A gas cutting machine for continuously cast materials, which gas-cuts continuously cast materials cast by a continuous casting facility, A torch is configured to be movable in the width direction of the continuous casting material and sprays preheating gas, preheating oxygen, and cutting oxygen from a nozzle provided at its tip. Equipped with, When cutting the aforementioned continuously cast material, the torch is moved at a cutting speed of 100 mm / min or more, and then moved at a cutting speed of 500 mm / min or more. A gas cutting machine for continuous cast materials, wherein the cutting oxygen flow rate on the surface of the continuous cast material is set to 700 m / s or more and 1160 m / s or less.

4. A cutting oxygen supply means for supplying the cutting oxygen to the torch at a gauge pressure of 0.90 MPa or more and 0.99 MPa or less, A preheating gas supply means for supplying the preheating gas, at a gauge pressure of 0.09 MPa or more and 0.12 MPa or less, to the torch, A preheated oxygen supply means for supplying the preheated oxygen to the torch at a gauge pressure of 0.10 MPa or more and 0.15 MPa or less, The gas cutting machine for continuously cast materials according to claim 3 is further provided.

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