High temperature alloy continuous casting starting method

Abstract

The application discloses a high-temperature alloy continuous casting starting method, before starting of a continuous casting ladle, a tracer material is first put into a tundish, then inert gas is filled into the tundish, the tracer material has a density greater than that of air and less than that of the inert gas, the tracer material can withstand the environmental temperature in the tundish, the tracer material floats on the upper edge of the inert gas and rises with continuous filling of the inert gas, when it is observed that the tracer material is higher than the whole ladle nozzle, it is judged that the inert gas filled into the tundish is sufficient, then the ladle nozzle is opened, the molten steel enters the tundish from the ladle nozzle, and the inert gas isolates the high-temperature molten steel from air. The method avoids the problem of unstable molten steel quality caused by exposure of high-temperature molten steel during starting.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting, and specifically relates to a method for the initial casting of high-temperature alloys. Background Technology

[0002] High-temperature alloys are special steels with extremely high value, requiring very high purity and as-cast microstructure. Therefore, they are primarily produced using a medium-frequency furnace / electric furnace-in-mold casting-electroslag process. The resulting electroslag ingots are virtually free of shrinkage cavities and segregation defects. Although this process is costly and inefficient, no successful and mature continuous casting process has yet replaced it. This is because continuous casting of high-temperature alloys presents numerous challenges that can lead to inconsistent quality, such as:

[0003] During the start of continuous casting, the ladle nozzle is opened after it arrives at the casting platform, and molten steel continuously enters the tundish from the ladle nozzle. At this time, the high-temperature molten steel is completely exposed to the air. Only when the molten steel level in the tundish rises to the production level is a covering agent added to isolate the high-temperature molten steel from the air. Simultaneously, the tundish begins casting, and the molten steel enters the casting runner through the submerged entry nozzle. During the start of continuous casting, the high-temperature molten steel in the tundish is exposed to the air, which leads to instability in the steel composition and an increase in inclusions. In existing continuous casting, due to the large number of heats cast and the wide range of steel grade requirements, this can be downgraded or ignored. However, for high-temperature alloys, the number of heats cast in each run is small, and the requirements for quality stability are higher. The impact of the high-temperature molten steel being exposed to the air during the start of continuous casting cannot be ignored. Currently, there is no experience in the stable production of high-temperature alloys through continuous casting, and the problem of unstable steel quality caused by the exposure of high-temperature molten steel during the start of casting has not been addressed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the initial casting of high-temperature alloys, which avoids the problem of unstable steel quality caused by the exposure of high-temperature molten steel during the initial casting process.

[0005] The technical solution adopted in this invention is:

[0006] A method for starting casting of high-temperature alloys involves placing tracer material into the tundish before starting casting in the ladle, followed by filling the tundish with inert gas. The tracer material has a density greater than that of air but less than that of the inert gas. The tracer material can withstand the ambient temperature inside the tundish. The tracer material floats on the upper edge of the inert gas and rises as the inert gas is continuously filled. When the tracer material is observed to be higher than the ladle nozzle, it is determined that the amount of inert gas filled in the tundish is sufficient. Then, the ladle nozzle is opened, and molten steel enters the tundish from the ladle nozzle. The inert gas isolates the high-temperature molten steel from the air.

[0007] Preferably, the tracer material degrades automatically upon contact with molten steel at high temperatures.

[0008] Preferably, the tracer material is a material with a composition similar to that of a high-temperature alloy, or a material with a composition similar to that of the protective slag used in molten steel, or a material with a composition similar to that of the tundish covering agent.

[0009] Preferably, the tracer material can withstand temperatures above 500°C.

[0010] Preferably, the tracer material is silica aerogel, alumina aerogel, silicon carbide aerogel, or aluminosilicate aerogel.

[0011] Preferably, the tracer material is in the form of granules or irregular flakes.

[0012] Preferably, the inert gas is argon.

[0013] Preferably, the density of the tracer material is greater than 1.3 kg / m³. 3 Less than 1.7 kg / m 3 .

[0014] Preferably, when placing the tracer material into the intermediate package, the tracer material should be distributed evenly on the bottom surface of the intermediate package as much as possible; when filling with inert gas, the outlet of the gas storage container should be as close as possible to the center of the bottom surface of the intermediate package and the filling should be carried out at a uniform speed.

[0015] Preferably, the capacity of the bulk pack is V, ensuring that the inert gas storage container can release at least 1.1V of inert gas.

[0016] The beneficial effects of this invention are:

[0017] This method utilizes inert gas to seal high-temperature alloys during the continuous casting process, isolating the high-temperature molten steel from air and avoiding the problem of unstable steel quality caused by the exposure of high-temperature molten steel during the casting process. By observing the tracer material, the filling status of the inert gas can be determined, ensuring that the filling amount of inert gas exceeds the ladle nozzle while avoiding excessive filling and waste. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the continuous casting process of high-temperature alloys in this invention.

[0019] In the diagram: 1-intermediate package; 2-inert gas; 3-tracer material; 4-main package nozzle. Detailed Implementation

[0020] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0021] This embodiment discloses a method for the initial casting of high-temperature alloys, such as... Figure 1As shown: Before pouring from the tundish, tracer material 3 is placed into the tundish 1, followed by inert gas 2. The density of tracer material 3 is greater than that of air but less than that of inert gas 2. Tracer material 3 can withstand the ambient temperature inside the tundish 1. It floats on the upper edge of the inert gas 2 and rises as more inert gas is added. When the tracer material 3 is observed to be higher than the ladle nozzle 4, it is determined that the amount of inert gas 2 in the tundish 1 is sufficient. Then, the ladle nozzle 4 is opened, and molten steel enters the tundish 1 from the nozzle. The inert gas 2 isolates the high-temperature molten steel from the air. This method utilizes inert gas 2 to achieve sealing of the high-temperature alloy during the pouring process, isolating the high-temperature molten steel from air and avoiding the problem of unstable steel quality caused by exposure of the high-temperature molten steel during pouring. By observing the tracer material 3, the filling status of inert gas 2 can be determined, ensuring that the amount of inert gas 3 exceeds the ladle nozzle 4 while avoiding overfilling and waste.

[0022] The selection of tracer material 3 is crucial to this application. In this embodiment, preferably: tracer material 3 automatically degrades upon contact with high-temperature molten steel, avoiding impact on subsequent processes; tracer material 3 can be a material with a composition similar to that of the high-temperature alloy, a material with a composition similar to that of the protective slag used in the molten steel, or a material with a composition similar to that of the covering agent in the tundish 1. Although the amount of tracer material added is small and will hardly affect the high-temperature alloy, using materials with similar compositions can further reduce the impact; tracer material 3 can withstand temperatures above 500°C, preventing premature degradation and failure to perform its tracer function; tracer material 3 is granular or irregularly shaped, which can be easily identified and distinguished.

[0023] The tracer material 3 is preferably silica aerogel, alumina aerogel, silicon carbide aerogel, or aluminosilicate aerogel.

[0024] In this embodiment, the inert gas 2 is preferably argon, and the density of the tracer material 3 is greater than 1.3 kg / m³. 3 Less than 1.7 kg / m 3 .

[0025] In order to ensure that the tracer material 3 can fully display the filling degree inside the intermediate package 1, when putting the tracer material 3 into the intermediate package 1, try to make the tracer material 3 evenly distributed on the bottom surface of the intermediate package 1. In order to make the inert gas 2 fully carry the tracer material 3 to float, when filling the inert gas 2, make the outlet of the gas storage container as close as possible to the center of the bottom surface of the intermediate package 1 and keep the filling at a uniform speed.

[0026] To avoid insufficient inert gas 2 during filling, the filling amount of inert gas 2 is calculated during the preparation stage. Let the capacity of the bulk bag be V. Based on V, when the filling amount of inert gas 2 reaches V, the inert gas 2 basically reaches the bulk bag nozzle 4. Furthermore, for reliability requirements, a safety redundancy of 1.1 times is set to ensure that the gas storage container of inert gas 2 can release at least 1.1V of inert gas 2.

[0027] Taking a φ300 vertical round billet casting machine of a steel plant in China as an example, which mainly produces iron-nickel-based and nickel-based high-temperature alloys, during continuous casting: first, irregularly shaped aluminosilicate aerogel is used as tracer material 3 and placed into the tundish 1 (the tracer material 3 is dispersed in the tundish 1). Then, argon is used as inert gas 2 and is filled into the tundish 1. Since the density of tracer material 3 is greater than the density of air and less than the density of inert gas 2, tracer material 3 floats on the upper edge of inert gas 2 and rises as inert gas 2 is continuously filled. When it is observed that the tracer material 3 is higher than the ladle nozzle 4, it is judged that the inert gas 2 filled into the tundish 1 is sufficient (the tracer material 3 is slightly higher than the lower end of the ladle nozzle 4, and the filling amount of inert gas 2 is 8m3). Then the ladle nozzle 4 is opened, and molten steel enters the tundish 1 from the ladle nozzle 4. The inert gas 2 isolates the high-temperature molten steel from the air.

[0028] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for continuous casting of high-temperature alloys, characterized in that: Before pouring from the tundish, tracer material is placed into the tundish, followed by inert gas. The tracer material has a density greater than that of air but less than that of the inert gas. It can withstand the ambient temperature inside the tundish. The tracer material floats on the upper edge of the inert gas and rises as the inert gas is continuously poured in. When the tracer material is observed to be higher than the ladle nozzle, it is determined that there is enough inert gas in the tundish. Then the ladle nozzle is opened, and the molten steel enters the tundish from the ladle nozzle. The inert gas isolates the high-temperature molten steel from the air.

2. The high-temperature alloy continuous casting start-up method as described in claim 1, characterized in that: The tracer material degrades automatically upon contact with molten steel at high temperatures.

3. The high-temperature alloy continuous casting start-up method as described in claim 1, characterized in that: The tracer material is made of a material similar to that of high-temperature alloys, or a material similar to that of protective slag used in molten steel, or a material similar to that of the tundish covering agent.

4. The high-temperature alloy continuous casting start-up method as described in claim 1, characterized in that: The tracer material can withstand temperatures above 500°C.

5. The high-temperature alloy continuous casting start-up method as described in claim 1, characterized in that: The tracer material is silica aerogel, alumina aerogel, silicon carbide aerogel, or aluminosilicate aerogel.

6. The high-temperature alloy continuous casting start-up method as described in claim 1, characterized in that: The tracer material is in the form of granules or irregular flakes.

7. The high-temperature alloy continuous casting start-up method as described in claim 1, characterized in that: Argon is used as the inert gas.

8. The high-temperature alloy continuous casting start-up method as described in claim 7, characterized in that: The density of the tracer material is greater than 1.3 kg / m³. 3 Less than 1.7 kg / m 3 .

9. The high-temperature alloy continuous casting start-up method as described in claim 1, characterized in that: When placing tracer material into the intermediate package, try to distribute the tracer material evenly on the bottom surface of the intermediate package; when filling inert gas, make the outlet of the gas storage container as close as possible to the center of the bottom surface of the intermediate package and keep the filling at a uniform speed.

10. The high-temperature alloy continuous casting start-up method as described in claim 1, characterized in that: Let the capacity of the large package be V, and ensure that the inert gas storage container can release at least 1.1V of inert gas.

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