CN107755679B - Argon blowing sealing and molten steel cleaning long nozzle device and argon blowing method - Google Patents

Abstract

The invention discloses an argon blowing sealing and molten steel cleaning long nozzle device and an argon blowing method, and belongs to the technical field of ferrous metallurgy. The long nozzle is characterized in that the shape of the middle part is changed, a flow storage area is formed in the middle of the long nozzle, and meanwhile, an argon blowing hole is formed in the flow storage area.

Description

A long nozzle device and argon blowing method for sealing and cleaning molten steel with argon

Technical field

The invention relates to the technical field of iron and steel metallurgy, and more specifically, to a long nozzle device and an argon blowing method for sealing and cleaning molten steel with argon.

Background technique

With the development of social economy and science and technology, the performance requirements for steel are increasing day by day. How to effectively prevent and remove inclusions to the greatest extent to improve the cleanliness of molten steel is the main direction of current research. The cleanliness of the cast slab can be controlled from two aspects. On the one hand, it is to remove inclusions in the molten steel through various methods as much as possible; on the other hand, it is to reduce the entry and generation of inclusions during the smelting and pouring process, especially the molten steel. Suction problem: The suction of molten steel can bring about two hazards. One hazard is the secondary oxidation of molten steel, that is, the acid-soluble aluminum and other elements in the molten steel are oxidized into oxides. The other hazard is the increase in nitrogen content in the molten steel. With the improvement of refining technology, the removal of inclusions in molten steel has reached a high level. At present, it is becoming more and more important to prevent the molten steel from absorbing air during the pouring process.

Nitrogen is a solid solution strengthening element in steel, which can cause aging and blue brittleness. It can also form sharp inclusions with titanium, aluminum, etc. Nitrogen in steel can reduce the toughness, plasticity, welding performance, etc. of the steel. . The nitrogen content in molten steel is the lowest at the end of steelmaking. The increase in nitrogen in molten steel is mainly caused by the inhalation of air during the subsequent refining and pouring processes. Therefore, in order to prevent air absorption during the pouring process, protective pouring is required to prevent the molten steel from absorbing nitrogen.

Aluminum is often used for deoxidation in molten steel. In order to obtain lower dissolved oxygen, the acid-soluble aluminum content is generally controlled between 0.025-0.045%, and the acid-soluble aluminum content of some high-aluminum steels such as 38CrMoAl is as high as 0.7-1.1%. If the molten steel absorbs air during the pouring process, the acid-soluble aluminum in the molten steel will combine with the oxygen in the air to form alumina inclusions, which will cause a series of problems such as nozzle blockage and flow accumulation during pouring.

In order to prevent air inhalation during ladle transfer and pouring and improve the purity of molten steel, in the current continuous casting production process, argon blowing seals of the ladle nozzle and ladle long nozzle are commonly used to achieve ladle protection pouring. However, the joint between the two is prone to inhaling air due to the negative pressure caused by the pouring steel flow, resulting in an increase in the nitrogen and oxygen content in the molten steel. The use of breathable ring-type argon blowing sealing method mainly has shortcomings such as poor later effects and easy clogging when steel overflows, while the sealing gasket has shortcomings such as easy damage and unstable sealing effect.

At present, there are some patents that use the shroud to blow argon to utilize the potential energy of the large package, such as the invention patent CN102864283A, the patent name is: an argon blowing shroud for clean steel; the application is set between the inner wall and the outer wall of the shroud An annular air chamber connected with the argon blowing conduit; the annular air chamber extends in the radial direction of the inner wall of the nozzle, and a plurality of ventilation holes connecting the inside of the nozzle and the annular air chamber are also provided on the inner wall of the nozzle. In this application, argon gas is blown into the air chamber through the argon blowing pipe, and the argon gas is blown into the molten steel through each ventilation hole in the air chamber. A larger number of small bubbles can be generated on the inner wall of the nozzle. At the same time, the velocity gradient of the flow of the molten steel generates Shear force can break small bubbles into smaller bubbles. Small bubbles capture inclusions and quickly float up after entering the tundish, and are adsorbed by the tundish covering agent to improve the cleanliness of the slab. The invention patent CN104139179A, the patent name is: a multifunctional argon blowing nozzle, the application also proposes to improve the argon blowing nozzle to better seal the argon gas and use the potential energy of the large bag to generate small bubbles. However, the above-mentioned applications are all technical improvements to the argon blowing part of the long nozzle, and do not improve or innovate the long nozzle. The invention patent CN102864283A sets a stepped funnel at the upper end of the shroud, mainly so that the shroud can better connect with the ladle, wrap the ladle better, and achieve a better sealing effect, but it cannot effectively dissipate the potential energy of molten steel. role.

Chinese patent number ZL201621488358.4, the date of authorization announcement is July 14, 2017, the name of the invention is: an immersed ladle spout for pouring; the top of the spout body in this application is provided with a bowl mouth, and the bowl The mouth is connected with the inner cavity, the diameter of the inner cavity at the lower end of the shroud body is larger than the inner cavity diameter at the upper end of the shroud body, and the inner cavity is in the shape of a bell mouth. This application expands the volume of the inner cavity at the lower end of the ladle shroud body. Even if there is residual air when pouring is started, the thermal expansion pressure is very small, which will not impact the seal between the shroud and the ladle outlet, and avoids the sealing between the shroud and the ladle outlet. leakage, improving the pouring quality. However, this application mainly relies on the bell mouth structure installed at the lower end of the shroud body to avoid impact. The molten steel can further spread out at the last moment after passing through the shroud. The potential energy of the molten steel is dissipated relatively passively and the effect is not ideal; and in order not to produce a larger impact Due to the impact depth, the cross-sectional area of the bell mouth structure at the lower end will be designed to be larger, and the long nozzle has structural design flaws.

Contents of the invention

1. The technical problem to be solved by the invention

In view of the problems raised by the background technology, the present invention provides a shroud device and an argon blowing method for blowing argon to seal and clean molten steel. The present invention mainly dissipates the potential energy of molten steel by setting a storage area in the middle of the shroud, and in the Argon gas is blown into the sealing area, and the argon gas rises to the sealing area to form a slightly positive pressure argon atmosphere, which effectively prevents the molten steel from inhaling; the kinetic energy dissipated by the molten steel in the storage area is used to break the argon gas into small bubbles, which are carried in by the molten steel. The tundish is used to further remove inclusions; the long nozzle outlet is in the shape of a bell mouth to further dissipate the potential energy of the molten steel and reduce the impact on the molten steel in the tundish.

2.Technical solutions

In order to achieve the above objects, the technical solutions provided by the present invention are:

The present invention provides a shroud device for blowing argon to seal and clean molten steel. It includes a shroud body. The shroud body is provided with a hollow inner cavity. The diameter of the inner cavity in the middle of the shroud body is larger than the diameter of the inner cavities at both ends, forming a flow reservoir. district.

As a further improvement of the present invention, one end of the long nozzle body is provided with a bowl mouth, which is connected to the ladle water outlet, and a sealing gasket is provided between the bowl mouth and the ladle water outlet.

As a further improvement of the present invention, an argon blowing hole is provided on the side wall of the end of the flow storage area close to the bowl mouth. The argon blowing conduit is connected to the argon blowing hole, and argon gas is blown into the long nozzle flow storage area through the argon blowing conduit.

As a further improvement of the present invention, 4-6 argon blowing conduits are arranged at circumferential intervals along the side wall of the flow storage area.

As a further improvement of the present invention, on the side wall of the flow storage area, there is at least one row of argon blowing conduits evenly distributed along the circumferential direction 30cm away from the intersection between the flow storage area and the upper long nozzle body, and each row is provided with 4 -6 argon blowing tubes.

As a further improvement of the present invention, the diameter of the inner cavity of the flow storage area is 1.3-1.8 times the diameter of the inner cavity of the long nozzle body at both ends.

As a further improvement of the present invention, the flow storage area is arranged at a distance of 140-170cm from the lower part of the bowl mouth.

As a further improvement of the present invention, the 10cm section of the outlet of the shroud body is provided with a bell mouth, and the diameter of the inner cavity of the bell mouth is 1.4-1.6 times the diameter of the inner cavity of the shroud body.

A method of blowing argon using the shroud device of the present invention first opens the ladle water outlet. After confirming that the ladle water outlet can be opened, the ladle water outlet is closed, and then the bowl mouth of the shroud body is connected to the ladle outlet. The nozzles are connected, argon is blown into the flow storage area through the argon blowing duct, and then the ladle outlet is opened for the second time to pour molten steel.

As a further improvement of the present invention, after the ladle water outlet is opened for the second time, the flow rate of argon gas blown is 30-60L/h, and the argon blowing pressure is 0.1-2Mpa.

3. Beneficial effects

The technical solution provided by the present invention has the following significant effects compared with the existing known technology:

(1) A shroud device of the present invention for blowing argon to seal and clean molten steel. By improving the traditional shroud structure, a flow storage area with an inner cavity diameter larger than the inner cavity diameter at both ends of the shroud is provided in the middle of the shroud body, making the ladle The molten steel inside enters the tundish below in a stepped manner, and the potential energy of the molten steel is fully dissipated in the long nozzle storage area, effectively reducing the impact of the molten steel on the tundish;

(2) A shroud device for blowing argon to seal and clean molten steel according to the invention uses the flow storage area in the middle of the shroud to blow in argon gas and form a storage of argon gas in the flow storage area, and the flow storage area forms an argon gas atmosphere seal The long nozzle prevents the molten steel from absorbing nitrogen. At the same time, due to the storage area in the middle, the impact of the molten steel impacts part of the argon gas into small argon bubbles, which are then rolled into the tundish by the molten steel, thus ensuring the purity of the molten steel. At the same time, the ability of the tundish to remove inclusions is improved;

(3) The shroud device of the present invention for blowing argon seal and clean molten steel has made certain shape improvements at the outlet end of the shroud, that is, the outlet of the shroud is designed to be in the shape of a bell mouth, and the diameter of the inner cavity of the bell mouth is only the diameter of the shroud. 1.4-1.6 times the diameter of the inner cavity of the body. Compared with the traditional large bell mouth design, on the one hand, the present invention can further dissipate the potential energy of the molten steel at the outlet end of the long nozzle to reduce the impact on the tundish on the premise that there is a flow storage area at the front end. The impact of molten steel; on the other hand, the bell mouth area is smaller, making the long nozzle structure more optimized;

(4) The long nozzle device for blowing argon to seal and clean molten steel according to the present invention not only directly sets the argon blowing conduit in the flow storage area, but also distributes multiple argon blowing conduits evenly along the circumferential direction of the side wall of the flow storage area. Multiple ducts are designed in a symmetrical and radial shape, which is easy to form a uniform atmosphere of argon gas and facilitate sealing; and the inner cavity of the flow storage area becomes thicker, which also gives more space for argon gas. When molten steel enters the flow storage area, the argon gas can timely and evenly When the molten steel is protected, when the potential energy of the molten steel is dissipated in the storage area, it is easier to inhale and break up the nearby argon gas to form small bubbles and enter the tundish along with the molten steel;

(5) A method of blowing argon using the long nozzle device according to the present invention. In conjunction with the structural improvement of the long nozzle, it is designed that the flow rate of argon gas blown in is 30-60L/h during the normal pouring of molten steel. The argon pressure is 0.1-2Mpa. Under this condition, the argon gas rises to the sealing area to form a slightly positive pressure argon atmosphere, which can effectively prevent the molten steel from absorbing air, and the kinetic energy dissipated by the molten steel in the storage area can fully break up the argon gas, forming Small bubbles enter the tundish to further remove inclusions and ensure the cleanliness of molten steel.

Description of drawings

Figure 1 is a schematic structural diagram of the argon blowing seal and the long nozzle for clean molten steel according to the present invention.

Label description in the schematic diagram:

1. Ladle outlet; 2. Sealing gasket; 3. Long nozzle body; 4. Argon blowing conduit; 5. Flow storage area; 6. Bell mouth.

Detailed ways

In order to further understand the content of the present invention, the present invention will be described in detail with reference to the accompanying drawings and embodiments.

Example 1

With reference to Figure 1, a long nozzle device for blowing argon to seal and clean molten steel in this embodiment is provided at the connection between the ladle and the tundish. The shroud body 3 is a reducer with a protruding middle and a trumpet-shaped outlet at the lower end. Specifically, the upper end of the shroud body 3 is a funnel-shaped bowl mouth. The bowl mouth is connected to the ladle water outlet 1, and the bowl mouth and the ladle water outlet 1 are connected. Set sealing gasket 2 between them. The shroud body 3 is provided with a hollow inner cavity. In this embodiment, a flow storage area 5 is provided at a distance of 150 cm from the lower part of the bowl mouth. The inner cavity diameter of the flow storage area 5 is larger than the inner cavity diameter of the shroud body 3 at both ends. The main function of the flow storage area 5 is to allow the molten steel in the ladle to enter the tundish below in a stepped manner. The potential energy of the molten steel is fully dissipated in the flow storage area 5 to reduce the impact of the molten steel on the tundish. At the same time, argon gas is stored in the flow storage area, forming an argon atmosphere to seal the long nozzle to prevent the molten steel from absorbing nitrogen. After long-term theoretical research and practical summary in steel plants, the inventor believes that it is more appropriate to set the inner cavity diameter of the flow storage area 5 to be 1.3-1.8 times the inner cavity diameter of the long nozzle body 3 at both ends. Specifically, the flow storage in this embodiment The diameter of the inner cavity of zone 5 is 1.5 times the diameter of the inner cavity of main body 3 of the long nozzle at both ends.

In this embodiment, an argon blowing hole is provided on the side wall of the flow storage area 5, 30cm away from the junction between the flow storage area 5 and the upper long nozzle body 3. The argon blowing conduit 4 is directly connected to the argon blowing hole, and the argon blowing conduit 4 is along the flow storage area. There are four circumferentially spaced side walls of zone 5, and argon gas is blown into the long nozzle flow storage zone 5 through the argon blowing conduit 4. Four argon blowing conduits are designed in a symmetrical and radial shape, which is easy to form a uniform atmosphere of argon gas and facilitate sealing.

It is worth mentioning that to improve the purity of molten steel, in addition to preventing external gases from entering and forming oxides, it is also necessary to remove deoxidation products after tapping. According to the existing theory, capturing inclusions through bubbles and removing them by floating is a simple and effective method. At the same time, relevant research shows that the bubbles that can effectively remove inclusions should be small bubbles, with the optimal range being 2-15mm. The invention patent CN102864283A mentioned in the background art, the patent name is: a long nozzle for blowing argon for clean steel; that is, the shear force generated by the potential energy of the large package of molten steel is used to break large bubbles into small bubbles, forming more fine bubbles. Good for removing inclusions.

Although this embodiment also uses the above theory, this embodiment directly places the argon blowing conduit 4 in the flow storage area 5. Since the inner cavity of the flow storage area 5 becomes thicker, more space is provided for the argon gas. First, it is easy to form an argon atmosphere, which is convenient for sealing; secondly, when the molten steel enters the flow storage area 5, the argon gas can protect the molten steel in a timely and uniform manner. Furthermore, when the potential energy of the molten steel is dissipated in the flow storage area 5, it is easier to remove the nearby argon gas. The air is inhaled, fully dispersed to form fine bubbles, and then enter the tundish along with the molten steel, which improves the ability of the tundish to remove inclusions. In terms of argon blowing sealing, traditional argon blowing is to set the argon blowing port at the upper end of the long nozzle and blow argon towards the outlet of the wrapped ladle. This leaves less space for argon blowing, resulting in poor sealing effect at the interface. Very good, it does not effectively prevent molten steel from absorbing nitrogen. In this embodiment, the flow storage area 5 holds more argon gas, and the argon gas can be pushed to the ladle outlet 1 with a small pressure, which can achieve the same or even better sealing effect as the traditional argon blowing method.

The 10cm section of the outlet of the shroud body 3 is provided with a bell mouth 6. The inner cavity diameter of the uppermost end of the bell mouth 6 is 1.4 times the inner cavity diameter of the shroud body 3, and the inner cavity diameter of the lowermost end is the diameter of the inner cavity of the shroud body 3. 1.6 times. This embodiment improves the traditional shroud structure and sets a flow storage area 5 in the middle of the shroud body, so that the molten steel in the ladle enters the lower tundish in a stepped manner, and the potential energy of the molten steel is fully dissipated in the shroud storage area, effectively The impact of molten steel on the tundish is reduced, and the buffer distance in the middle can also be adjusted according to the actual situation, making the dissipation of potential energy more flexible and proactive. Compared with the traditional method of separately setting a large bell mouth at the lower end of the shroud, on the one hand, on the premise that there is a flow storage area 5 at the front end, the potential energy of the molten steel can be further dissipated at the outlet end of the shroud to reduce the impact on the molten steel in the tundish; On the other hand, the bell mouth area of this embodiment is small and the impact depth is small. When the depth of the molten steel is relatively shallow in the early stage, the refractory material will not be hit, and the slag layer will not be easily involved in the molten steel.

In order to cooperate with the structural improvement of the shroud, this embodiment also designs a method of blowing argon using the shroud device. The specific process is: first open the ladle outlet 1, and after confirming that the ladle outlet 1 can be opened, Close the ladle outlet 1, then connect the bowl mouth of the long nozzle body 3 with the ladle outlet 1, blow argon through the argon blowing conduit 4 to the flow storage area 5, and then open the ladle outlet 1 for the second time to pour molten steel. At this time, control the flow rate of argon blown into the range of 30-40L/h, and the pressure of blown argon gas within the range of 0.1-1Mpa. Under this condition, the argon gas rises to the sealing area to form a slightly positive pressure argon atmosphere, which can effectively prevent the molten steel from absorbing air, and the kinetic energy dissipated by the molten steel in the storage area can fully break up the argon gas to form small bubbles, which enter the tundish. Further remove inclusions to ensure the cleanliness of molten steel.

Example 2

A shroud device for blowing argon to seal and clean molten steel in this embodiment is basically the same as Embodiment 1. The difference is that in this embodiment, a flow storage area 5 is provided at a distance of 140 cm from the lower part of the nozzle bowl. 5. The inner cavity diameter is 1.3 times the inner cavity diameter of the long nozzle body 3 at both ends. On the side wall of the flow storage area 5, there are two rows of argon blowing ducts evenly distributed in the circumferential direction at a distance of 30cm from the junction between the flow storage area 5 and the upper long nozzle body 3, with 6 argon blowing ducts in each row. In order to cooperate with the structural improvement of the long nozzle, in this embodiment, after the ladle outlet is opened for the second time, the flow rate of argon gas blown in is controlled to be in the range of 50-60L/h, and the argon blowing pressure is controlled to be in the range of 0.5-1.5Mpa.

Example 3

A shroud device for blowing argon to seal and clean molten steel in this embodiment is basically the same as Embodiment 1. The difference is that in this embodiment, a flow storage area 5 is set 170cm away from the lower part of the nozzle bowl. 5 The inner cavity diameter is 1.8 times the inner cavity diameter of the long nozzle body 3 at both ends. On the side wall of the flow storage area 5, there are two rows of argon blowing ducts evenly distributed in the circumferential direction at a distance of 30cm from the junction between the flow storage area 5 and the upper long nozzle body 3, with 5 argon blowing ducts in each row. In order to cooperate with the structural improvement of the long nozzle, in this embodiment, after the ladle outlet is opened for the second time, the flow rate of argon gas blown in is controlled to be in the range of 40-50L/h, and the argon blowing pressure is controlled to be in the range of 1-2Mpa.

The present invention and its embodiments are schematically described above. This description is not limiting. What is shown in the drawings is only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person of ordinary skill in the art is inspired by the invention and without departing from the spirit of the invention, can devise structural methods and embodiments similar to the technical solution without inventiveness, they shall all fall within the protection scope of the invention. .

Claims (4)

1. The utility model provides a long mouth of a river device of sealed and clean molten steel of argon blowing, includes long mouth of a river body (3), long mouth of a river body (3) inside is equipped with cavity inner chamber, its characterized in that: the diameter of the inner cavity in the middle of the long nozzle body (3) is larger than that of the inner cavities at the two ends, so as to form a flow storage area (5); one end of the long water gap body (3) is provided with a bowl opening, the bowl opening is in butt joint with the ladle water outlet (1), and a sealing gasket (2) is arranged between the bowl opening and the ladle water outlet (1); an argon blowing hole is formed in the side wall of one end, close to the bowl mouth, of the flow storage area (5), an argon blowing pipe (4) is connected with the argon blowing hole, and argon is blown into the long water gap flow storage area (5) through the argon blowing pipe (4); at least one row of argon blowing guide pipes (4) which are uniformly distributed along the circumferential direction are arranged on the side wall of the flow storage area (5) at a position which is 30cm away from the junction position of the flow storage area (5) and the upper end long nozzle body (3), and 4-6 argon blowing guide pipes (4) are arranged in each row;

the diameter of the inner cavity of the flow storage area (5) is 1.3-1.8 times of the diameter of the inner cavity of the long water gap body (3) at the two ends;

the flow storage area (5) is arranged at a position 140-170cm away from the lower part of the bowl mouth.

2. The long nozzle apparatus for argon blowing sealing and cleaning molten steel as claimed in claim 1, wherein: the 10cm section of the outlet of the long water gap body (3) is provided with a horn mouth (6), and the diameter of the inner cavity of the horn mouth (6) is 1.4-1.6 times of the diameter of the inner cavity of the long water gap body (3).

3. A method of argon blowing using the long nozzle apparatus of claim 1 or 2, characterized in that: firstly, a ladle water outlet (1) is opened, after the ladle water outlet (1) is confirmed to be opened, the ladle water outlet (1) is closed, then a bowl mouth of a long water gap body (3) is butted with the ladle water outlet (1), argon is blown to a flow storage area (5) through an argon blowing conduit (4), and then the ladle water outlet (1) is opened for the second time to open molten steel.

4. A method of argon blowing according to claim 3, wherein: after the ladle water outlet (1) is opened for the second time, the flow rate of the blown argon is 30-60L/h, and the pressure of the blown argon is 0.1-2Mpa.