Method and device for increasing continuous casting straightening temperature of oversized round billets

Abstract

The invention relates to a method and device for increasing the continuous casting straightening temperature of an oversized round billet, a nozzle is arranged in a continuous casting withdrawal and straightening area and used for heating the casting billet, the temperature of the casting billet is not lower than the brittleness temperature of the casting billet, and the device comprises a fan unit, a natural gas supply system, a nozzle unit, a nozzle control system and a smoke exhaust and heat dissipation device. Each burner unit comprises two burners which are symmetrically arranged relative to the casting flow, the four withdrawal and straightening machines are respectively provided with the burner units in the withdrawal and straightening direction, and the burner units are arranged in gaps between the front withdrawal and straightening machine and the rear withdrawal and straightening machine; the burner control system is composed of four burner control boxes, each burner control box controls natural gas of each burner of each burner unit to be opened and closed, and an ignition transformer and an ignition controller are arranged in the burner control box and control ignition of each burner respectively. Aiming at round billets with ultra-large specifications and various sizes, the burner units can be adjusted to different heights so as to meet a proper baking angle; and accurate control of the heating temperature is met by adjusting the air volume and the fuel gas.

Description

Technical Field

[0001] The invention relates to a continuous casting process, in particular to heating of a continuous casting billet during straightening. Background Art

[0002] In existing continuous casting machines, the billet is mainly straightened at multiple points by a straightening machine. However, as the billet enters the straightening zone, the temperature continues to drop. Generally, the straightening temperature of large round billet continuous casting drops by about 100°C from the first straightening machine (about 850°C) to the last straightening straightening machine (about 750°C). When the billet temperature is less than 800°C for straightening, cracks are inevitable for many steel grades, which leads to batch quality problems of continuous casting billets. In severe cases, the billet batches are scrapped. The multi-point straightening temperature of the continuous casting machine plays a vital role in the high-quality production of modern large round billet continuous casting machines. Summary of the invention

[0003] The purpose of the present invention is to heat the ingot in the straightening zone without changing the temperature of the molten steel, the drawing speed and the cooling parameters, thereby increasing the straightening temperature of the continuous casting ingot, making the straightening temperature of the ingot not lower than the brittle temperature of the ingot, reducing the cracks caused by straightening, and improving the quality of the ingot. In addition, the present invention is further designed to discharge the heat between the upper and lower rollers of the straightening machine and between the front and rear straightening machines in time to prevent the damage of the electrical components of the straightening machine by high temperature, ensure the stability of the straightening machine equipment, and improve the continuous casting operation rate.

[0004] The technical solution adopted by the present invention to solve the above-mentioned problem is: a method for increasing the continuous casting and straightening temperature of super-large round billets, characterized in that: a burner is arranged in the continuous casting and straightening zone to heat the billet so that the billet temperature is not lower than the billet brittle temperature, and the burner is arranged before and after the straightening machine.

[0005] A device for increasing the straightening temperature of super-large round billets during continuous casting, comprising a fan unit, a natural gas supply system, a burner unit, a burner control system, and a smoke exhaust and heat dissipation device. Each group of burner units can be controlled to work independently through local or HMI control; for billets of different sizes, the burner unit can adjust different heights to meet the appropriate baking angle; the heating temperature can be precisely controlled by adjusting the air volume and the size of the gas; a smoke exhaust and heat dissipation device is added to exhaust smoke and hot air to reduce the damage to electrical components caused by heat. The equipment stability is ensured and the continuous casting operation rate is improved.

[0006] The fan unit contains a damper regulating proportional valve. The fan is preferably a fixed frequency fan. Its main function is to provide combustion air for each group of burners and to adjust the size of the burner flame by controlling the damper.

[0007] The natural gas supply system provides natural gas for combustion, and controls the opening and closing of the natural gas of each burner through the cut-off valves on the pipeline. The control valves include main cut-off valves, pressure reducing valves and pressure relief valves, and are equipped with corresponding pressure sensors. To ensure safety, the main cut-off valve will automatically close in the event of abnormal pressure.

[0008] Burner unit: Each burner unit contains two burners. Along the straightening direction, each flow is divided into four straightening machines, totaling four burner units. The burner is made of stainless steel. The burner can adjust the height according to different billet diameters to meet the production requirements of three round billet sections of φ1200mm, φ1000mm, and φ800mm. Each burner unit is connected to 2 natural gas supply pipelines and combustion air pipelines. In addition, it includes a heat insulation protection plate, an ignition line, and a signal feedback line. The heat insulation protection plate of the burner is preferably a combination of stainless steel plate and refractory ceramic fiber wool, which can be well insulated and corrosion-resistant; prolong the life of the burner. Each burner unit has two burners, and the gas control of each burner can be controlled separately. The baking power of the burner can be adjusted according to the actual billet temperature, so as to accurately control the straightening temperature of the billet (about 850-950℃).

[0009] Burner control system: The burner control system consists of four burner control boxes per flow. Each burner control box controls the opening and closing of the natural gas of each burner in each burner unit. Each burner control box has two natural gas inlet pipes and two natural gas outlet pipes. The burner control box has a built-in ignition transformer and an ignition controller to control the ignition of each burner respectively. To ensure safety, the opening condition of the solenoid valve in the burner control box must meet the normal operation of the fan and detect that the pipeline air pressure meets the operating conditions. Ignition can be achieved after the conditions are met. If the ignition fails, the solenoid valve controlling the natural gas will be closed immediately.

[0010] Smoke exhaust and heat dissipation device: a smoke exhaust and heat dissipation device is arranged on the top of each group of burners, including a special-shaped collection hood (conical smoke collection hood), two convection chimneys and a heat insulation protection layer, etc.; according to the installation position of the burner and the space size between the straightening machines, based on the large temperature difference between the upper and lower parts of the straightening machines, and using the principle of hot air rising, the smoke, heat and heat radiated by the ingot during the combustion process can be quickly discharged to form an area with suitable temperature, thereby preventing the adjacent equipment from being burned by the high-temperature smoke. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the structure of the device in the embodiment of the present invention; Figure 2 It is a cross-sectional view of the straightening part along the straightening direction in the embodiment of the present invention; Figure 3 for Figure 2 Middle CC section view; Figure 4A schematic structural diagram of a burner in an embodiment of the present invention; Figure 5 Figure 4 A view of the structure shown; Figure 6 Figure 4 A B-direction view of the structure shown; Figure 7 Figure 4 A perspective view of the burner shown; Figure 8 Figure 4 A perspective view of the burner from another perspective; Fig. 9 Schematic diagram of angle adjustment of the burner body in an embodiment of the present invention; Fig.10 Schematic diagram of axial depth adjustment of the burner body in the embodiment of the invention; In the figure, fan unit 1, natural gas supply system 2, burner unit 3, burner control system 4, smoke exhaust and heat dissipation device 5, damper adjustment proportional valve 6, straightening machine 7, 301 burner body, 302 natural gas pipeline, 303 air pipeline, 304 air hose connection, 305 natural gas hose connection, 306 stroke adjustment point, 307 adjustment screw, 308 U-bolt. DETAILED DESCRIPTION

[0012] The present invention is further described in detail below in conjunction with the accompanying drawings. The embodiments are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0013] The present application relates to a novel method and device for increasing the straightening temperature of super-large round billets in continuous casting, including a fan unit, a natural gas supply system, a burner unit, a burner control system, and a smoke exhaust and heat dissipation device. The fan unit includes a damper adjustment proportional valve for each group. The fan is a fixed-frequency fan, and its main function is to provide combustion air for each group of burners. By controlling the damper, the size of the burner flame is adjusted. The natural gas supply system mainly provides natural gas for combustion. The opening and closing of each group of natural gas is controlled by a cut-off valve. The control valve includes a main cut-off valve, a pressure reducing valve, and a pressure relief discharge valve, and is equipped with a corresponding pressure sensor. To ensure safety, the main cut-off valve is automatically closed when the pressure is abnormal. The burner unit, each burner unit contains two upper and lower burners, and each flow is divided into 1-4 straightening machines, totaling 8 burner units; the burner can be made of stainless steel, and the burner unit can adjust the height according to different billet diameters to meet the production requirements of various sections of super-large round billets; each burner unit is connected to 2 natural gas supply pipelines and combustion air pipelines, and also includes a heat insulation protection plate, an ignition line, and a signal feedback line. Burner control system, the burner control system consists of four burner control boxes per flow, each burner control box controls the opening and closing of natural gas for each group of four burners, each burner control box has two natural gas inlet pipes and four natural gas outlet pipes, the burner control box has built-in ignition transformers and ignition controllers, respectively controlling the ignition of each burner in each group; to ensure safety, the opening conditions of the solenoid valve of the burner control box must meet the normal operation of the fan and detect that the pipeline wind pressure meets the operating conditions; ignition can be performed after the conditions are met, if the ignition fails, the solenoid valve controlling the natural gas will be closed immediately. Smoke exhaust and heat dissipation device, a smoke exhaust and heat dissipation device is set on the upper part of each group of burners, including a special-shaped collection hood, two convection chimneys and a heat insulation protective layer, etc.; according to the installation position of the burner and the space size between the straightening machine, based on the large temperature difference between the upper and lower parts of the straightening machine, the principle of hot air rise can be used to quickly discharge the smoke, heat and heat radiated by the ingot during the combustion process, forming an area with suitable temperature to prevent the adjacent equipment from being burned by high-temperature smoke. For extra-large round billets, the burner unit can adjust different heights to meet the appropriate baking angle; the heating temperature can be accurately controlled by adjusting the air volume and gas size; the method and device for increasing the continuous casting straightening temperature are applied to the extra-large round billet continuous casting machine to increase and maintain the straightening point temperature of large round billets and reduce the risk of cracks caused by low-temperature straightening of the billets.

[0014] The above method and device are suitable for the continuous casting process of round billets with super-large specifications of φ800mm or more.

[0015] One fan unit controls four burner units with four pipelines. Each pipeline uses a regulating valve to control the air volume separately. The valve opening is adjusted according to the temperature of the ingot, and the natural gas is adjusted at the same time to control the intensity of the burner flame to meet the requirements of the ingot baking temperature. After the main pipe regulating valve and pressure reducing valve are adjusted, the natural gas with appropriate pressure is delivered to each burner control system, and it works synchronously with the pressure of the fan unit. When the pressure of the fan air duct is abnormal, the cut-off valve in the natural gas supply system will be closed immediately.

[0016] The burner unit is located at each straightening point of the straightening machine. The burner directly bakes the billet. The straightening temperature of the billet will not change due to the change of the straightening position of the continuous casting billet. The billet temperature at the straightening point can be maintained at about 850-950℃. Each burner unit has two burners, and the gas control of each burner can be controlled separately. The baking power of the burner can be adjusted according to the actual billet temperature, so as to accurately control the straightening temperature of the billet.

[0017] The baking angle and height of each burner unit can be adjusted at any time as the size of the ingot changes, ensuring that the baking position is at the point where the straightening stress is concentrated.

[0018] The burner's protective heat insulation device is made of stainless steel plate and refractory ceramic fiber wool, which can provide good heat insulation and corrosion resistance, and extend the life of the burner. The burner's protective heat insulation device adopts a special-shaped design and is installed in the gap position before and after the straightening machine, which can eliminate the gap between the straightening machines, prevent the entry of cold air to affect the surface of the billet, and also play the role of a billet insulation cover.

[0019] The burner control system consists of four burner control boxes for each flow. Each burner control box is divided into 4-way control. Each control includes a flow regulating valve, a solenoid valve, an ignition transformer and an ignition controller, which respectively control the ignition, shutdown and burner flame size of each burner in each group. The natural gas size can be adjusted according to the change of the billet temperature, or several burners can be used for baking.

[0020] A special-shaped collection hood and two convection chimneys are set in the upper space of the burner, and the height of the chimney is about 2 meters; according to the installation position of the burner and the space size between the straightening machine, based on the large temperature difference between the upper and lower straightening machines, the principle of hot air rise is used to quickly discharge the flue gas, heat in the combustion process and the heat radiated by the ingot. The heat dissipation device can be made of galvanized steel plate or stainless steel plate, and a layer of heat-resistant cotton is fixed inside to reduce the influence of heat radiation on its deformation and increase its service life. In order to better collect high-temperature flue gas, its shape is a bell mouth. In order to ensure the sealing performance, its size is made according to the installation gap size of the front and rear straightening machines, and the error cannot be greater than 3 mm.

[0021] Example 1: A novel method and device for increasing the straightening temperature of ultra-large round billets during continuous casting. Figure 1As shown, it includes a fan unit, a natural gas supply system, a burner unit using 4 groups, a height adjustment of 800, a burner control system, and a smoke exhaust and heat dissipation device.

[0022] The ingot type 1 was straightened at a speed of 0.2m / min. The temperature before entering the straightening machine was measured at about 840℃. The air door of the fan unit was adjusted to 40%, and the air flow rate was 60Nm 3 / h; natural gas pressure is adjusted to 1.5bar; the height of 4 burner units in 1 stream is all adjusted to 800; the burner control box adjusts the natural gas pressure to 1.5KPa, the burner controls all 4 burner units to ignite and bake, the exhaust and heat dissipation device operates normally, and the temperature of the billet entering the straightening point is measured to be about 855 degrees; it meets the process requirements. When the casting speed remains unchanged, there is no need to adjust the above control systems, and it can work continuously until the end of production.

[0023] Example 2: A novel method and device for increasing the straightening temperature of ultra-large round billets during continuous casting. Figure 1 As shown, it includes a fan unit, a natural gas supply system, 2 sets of burner units, a height adjustment of 800, a burner control system, and a smoke exhaust and heat dissipation device.

[0024] The ingot type 1 was straightened at a speed of 0.22m / min. The temperature was measured at 860℃ before entering the straightening machine. The air door of the fan unit was adjusted to 30% and the air flow rate was 45Nm 3 / h; natural gas pressure is adjusted to 1.0bar; the height of 4 burner units in 1 stream is all adjusted to 800; the burner control box adjusts the natural gas pressure to 1.0KPa, and the burner control box controls the ignition and baking of 2 burner units at the rear of the straightening machine, and the exhaust and heat dissipation device operates normally. The temperature of the ingot entering the straightening point is measured to be about 855 degrees; the process requirements are met. Others are the same as Example 1.

[0025] Example 3: A novel method and device for increasing the straightening temperature of ultra-large round billets during continuous casting. Figure 1 As shown, it includes a fan unit, a natural gas supply system, 2 sets of burner units, a height adjustment of 1000, a burner control system, and a smoke exhaust and heat dissipation device.

[0026] The second type of ingot was straightened at a speed of 0.15m / min. The temperature was measured at 870℃ before entering the straightening machine. The air door of the fan unit was adjusted to 20%, and the air flow rate was 30Nm 3 / h; natural gas pressure is adjusted to 1 bar; the height of 4 burner units in 1 stream is all adjusted to 1000; the burner control box adjusts the natural gas pressure to 1.0 KPa, the burner control box controls the ignition and baking of 2 burner units at the rear of the straightening machine, the exhaust and heat dissipation device operates normally, and the temperature of the ingot entering the straightening point is measured to be about 860 degrees; it meets the process requirements. Others are the same as Example 1.

[0027] Example 4: A novel method and device for increasing the straightening temperature of ultra-large round billets during continuous casting. Figure 1 As shown, it includes a fan unit, a natural gas supply system, a burner unit using 4 groups, a height adjustment of 1000, a burner control system, and a smoke exhaust and heat dissipation device.

[0028] The second type of ingot was straightened at a speed of 0.13m / min. The temperature was measured at 830℃ before entering the straightening machine. The air door of the fan unit was adjusted to 60% and the air flow rate was 90Nm 3 / h; natural gas pressure is adjusted to 2bar; the height of 1 stream 4 groups of burner units are all adjusted to 1000 position; the burner control box adjusts the natural gas pressure to 2.0KPa, the burner control box controls the ignition and baking of 4 groups of burner units, the exhaust and heat dissipation device operates normally, and the temperature of the ingot entering the straightening point is measured to be about 855 degrees; it meets the process requirements. Others are the same as Example 1.

[0029] Example 5: A novel method and device for increasing the straightening temperature of ultra-large round billets during continuous casting. Figure 1 As shown, it includes a fan unit, a natural gas supply system, 2 sets of burner units, a height adjustment of 1200, a burner control system, and a smoke exhaust and heat dissipation device.

[0030] The slab type 3 was straightened at a speed of 0.12m / min. The temperature was measured at 860℃ before entering the straightening machine. The air door of the fan unit was adjusted to 40% and the air flow rate was 60Nm 3 / h; natural gas pressure is adjusted to 1.5bar; the height of 4 burner units in 1 stream is all adjusted to 1200; the burner control box adjusts the natural gas pressure to 1.5KPa, the burner control box controls the ignition and baking of 2 burner units at the rear of the straightening machine, the exhaust and heat dissipation device operates normally, and the temperature of the ingot entering the straightening point is measured to be about 850 degrees; the process requirements are met. Others are the same as Example 1.

Claims

1. A method for increasing the straightening temperature of ultra-large round billets during continuous casting, characterized in that: A burner is arranged in the continuous casting straightening zone to heat the ingot so that the temperature of the ingot is not lower than the brittle temperature of the ingot. The burner is arranged before and after the straightening machine.

2. A device for implementing the method of claim 1, characterized in that: Including fan unit, natural gas supply system, burner unit, burner control system, smoke exhaust and heat dissipation device, The fan unit provides combustion air for each burner of the burner unit, and is provided with a damper regulating proportional valve to control the damper to adjust the size of the burner flame; The natural gas supply system provides natural gas for combustion to each burner of the burner unit, and controls the opening and closing of the natural gas of each burner through the control valves on the connecting pipelines. The control valves include main shut-off valves, pressure reducing valves and pressure relief valves, and are equipped with corresponding pressure sensors. In the case of abnormal pressure, the main shut-off valves will automatically close; The burner unit: each burner unit comprises two burners symmetrically arranged relative to the casting strand. Along the straightening direction, four straightening machines are respectively equipped with a burner unit, and the burner unit is arranged at the interval between the front and rear straightening machines; The burner control system is composed of four burner control boxes, each of which controls the opening and closing of the natural gas of each burner of each burner unit. Each burner control box is provided with a natural gas inlet pipeline and a natural gas outlet pipeline, which are independently connected to each burner. The burner control box has a built-in ignition transformer and an ignition controller to control the ignition of each burner respectively. The opening condition of the solenoid valve of the burner control box satisfies the normal operation of the fan, and ignition is performed after the air pressure of the pipeline meets the operating conditions. In the case of unsuccessful ignition, the solenoid valve controlling the natural gas will be closed immediately. The smoke exhaust and heat dissipation device is arranged on the upper part of each burner, including a collecting hood, two convection chimneys and a heat insulation protective layer. According to the installation position of the burner and the space size between the straightening machines, and the large temperature difference between the upper and lower parts of the straightening machines, the smoke and heat of the combustion process and the heat radiated by the casting are discharged by utilizing the principle of rising hot air.

3. The device according to claim 2, characterized in that: The burner control box controls the burner unit individually through local or HMI control.

4. The device according to claim 2, characterized in that: The burner is made of stainless steel, and the heating height and angle of the burner are adjustable.

5. The device according to claim 4, characterized in that: The burner body can be adjusted in two ways: angle adjustment and axial depth adjustment. The burner is installed on the waist hole of the bracket through an adjusting screw, and the installation angle is adjusted by adjusting the position of the screw in the waist hole to achieve heating angle adjustment. The burner is installed through a U-bolt, and the axial depth adjustment is achieved by adjusting the U-bolt.

6. The device according to claim 2, characterized in that: The heat-insulating protective layer of the burner is made of a combination of stainless steel plate and refractory ceramic fiber wool. It adopts a special-shaped design that is adapted to the front and rear gaps of the straightening machine. It is installed in the gap position before and after the straightening machine to eliminate the gap between the straightening machines and serve as a heat-insulating cover for the ingot.

7. The device according to claim 2, characterized in that: The collecting hood is a bell-shaped mouth, and its size is adapted to the installation gap size of the front and rear straightening machines.

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