Immersed argon blowing nozzle structure and application process

Abstract

The submerged argon blowing nozzle structure structurally comprises a protective shell and a nozzle body, the protective shell is arranged on the periphery of the nozzle body, an argon chamber is formed between the protective shell and the nozzle body, the bottom of the argon chamber is arranged in a sealed mode, an argon blowing nozzle is assembled on the outer side of the protective shell, and the argon blowing nozzle is arranged in the protective shell. The argon blowing nozzle extends into the argon chamber, a plurality of argon blowing grooves are distributed in the periphery of the top of the nozzle body in a surrounding mode and communicated with the argon chamber, and the included angle between each argon blowing groove and the tangent line of the outer circle of the nozzle body is smaller than 90 degrees. The argon blowing amount of the crystallizer is optimized, the bowl part of the argon blowing nozzle is designed, flames around the wrist part of the lower nozzle can be completely emitted, argon sealing can be comprehensively achieved between the upper nozzle and the lower nozzle through argon, the effect that molten steel is isolated from air is achieved, secondary oxidation of the molten steel is effectively prevented, and the service life of the molten steel is prolonged. The defects such as slag holes in the surfaces of casting blanks produced by variety steel can be reduced, and the quality of the casting blanks is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of molten steel smelting, and particularly to an immersed argon-blowing nozzle structure and an application process thereof. Background Art

[0002] In recent years, with the booming development of the manufacturing industry, the XGL steel grade has been widely used in many fields due to its unique performance advantages. And users' requirements for the performance of XGL steel are getting higher and higher, expecting the product to have higher yield strength, tensile strength and toughness. As a widely used low-carbon steel, non-metallic inclusions, oxygen and nitrogen contents, and microstructural defects in XGL steel have a great impact on the performance of the continuous casting billet and the final product. In the existing steelmaking continuous casting process, in order to improve the quality of the continuous casting billet and the purity of the molten steel, before the molten steel enters the mold, efforts should be made to minimize the pollution of the molten steel from each process, and to maximize the removal of inclusions from the molten steel and reduce the secondary oxidation of the molten steel.

[0003] At present, there are certain misunderstandings in the setting of the argon-blowing process for the immersed nozzle in continuous casting of small square billets. The non-blockage of the nozzle should be regarded as the ultimate goal of the blowing process setting, and the liquid level fluctuation in the mold caused by argon blowing can be used as an indirect reference basis during actual control. However, the unreasonable design of the argon blowing amount, pressure and the bowl part of the nozzle under argon blowing makes the liquid level in the mold fluctuate violently during argon blowing, which not only easily causes slag entrainment phenomenon, resulting in defects such as slag holes on the surface of the continuous casting billet for the production of special steel grades, affecting the surface quality of the continuous casting billet. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an immersed argon-blowing nozzle structure and an application process thereof, optimize the argon-blowing process parameters and the design of the lower nozzle, reduce defects such as slag holes on the surface of the continuous casting billet for the production of special steel grades, and improve the quality of the continuous casting billet.

[0005] The technical solution adopted by the present invention to solve its technical problems is: an immersed argon-blowing nozzle structure, including a protective shell and a nozzle body. The protective shell is arranged on the outer periphery of the nozzle body, and an argon chamber is formed between the protective shell and the nozzle body. The bottom of the argon chamber is sealed. A blowing nozzle is assembled on the outer side of the protective shell, and the blowing nozzle extends into the argon chamber. A plurality of argon-blowing grooves are distributed around the outer periphery of the top of the nozzle body, and the argon-blowing grooves are communicated with the argon chamber. The included angle between the argon-blowing grooves and the outer circle tangent of the nozzle body is less than 90°.

[0006] As a further improvement of the present invention: a step is provided on the inner circle of the top of the nozzle body near the argon-blowing grooves, and a slope is provided on the outer side of the step. The slope extends from the top of the nozzle body to the lower argon-blowing grooves.

[0007] As a further improvement of the present invention: the top end of the step is higher than the top end face of the protective shell.

[0008] As a further improvement of the present invention: a bowl mouth is provided on the inner ring of the nozzle body close to the step, and there is a gap between the inner flanging of the bowl mouth and the step.

[0009] As a further improvement of the present invention: a sealing portion is formed between adjacent argon blowing grooves, and the outer edge of the outer ring of the sealing portion is close to the inner wall of the protective shell.

[0010] As a further improvement of the present invention: a chamber is left in the middle of the nozzle body, and the chamber is communicated with the argon blowing chamber.

[0011] An application process of an immersion argon blowing nozzle structure, using the above-mentioned immersion argon blowing nozzle structure, includes:

[0012] Setting the critical blowing gas volume q of the slab under different casting speeds 临 , when the casting speed is higher than 3.5 m / min, reducing the argon blowing flow rate;

[0013] q 临 is proportional to the pouring flow rate Q of the molten steel in the mold, q 临 = 0.0841 * Q - 19.97, where q 临 and Q are in the unit of L / min.

[0014] As a further improvement of the present invention: applied to the casting of 155 mm * 155 mm small square billets, setting the argon blowing flow rate lower than the critical blowing gas volume q 临 ; adjusting the argon blowing flow rate according to the mold liquid level detection data, and controlling the fluctuation of the mold liquid level within ±5 mm.

[0015] As a further improvement of the present invention: applied to the casting of 155 mm * 155 mm small square billets, the argon casting speed is less than 3.5 m / min, and the opening argon pressure is lower than 0.3 MPa.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] Through the special design of the immersion argon blowing lower nozzle of the present invention, the argon seal between the upper nozzle and the lower nozzle can be effectively realized, preventing the secondary oxidation of molten steel and improving the quality of molten steel. Reasonably controlling the argon blowing volume and argon blowing pressure can effectively reduce the fluctuation of the liquid level in the mold, reduce the risk of slag entrainment, reduce the generation of defects such as slag holes on the surface of the casting billet, and improve the surface quality of the casting billet. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic structural diagram of an immersion argon blowing nozzle structure of the present invention.

[0019] Figure 2 is a schematic structural diagram of the nozzle body of the present invention.

[0020] Figure 3 Figure a showing the surface quality of the slab when the argon opening of an immersion argon-blowing nozzle structure of the present invention is too large.

[0021] Figure 4 Figure b showing the surface quality of the slab when the argon opening of an immersion argon-blowing nozzle structure of the present invention is < 0.3 MPa.

[0022] Reference numerals: 1, protective shell; 2, nozzle body; 3, argon-blowing groove; 4, argon-blowing nozzle; 5, step; 6, bowl opening. Detailed implementation manners

[0023] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] To solve the technical problems in the prior art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0025] As Figures 1 to 2 shown, an embodiment of the present invention discloses an immersion argon-blowing nozzle structure, including a protective shell 1 and a nozzle body 2. The protective shell 1 is arranged on the outer periphery of the nozzle body 2. An argon chamber is formed between the protective shell 1 and the nozzle body 2. The bottom of the argon chamber is hermetically sealed. An argon-blowing nozzle 4 is assembled on the outer side of the protective shell 1. The argon-blowing nozzle 4 extends into the argon chamber. A plurality of argon-blowing grooves 3 are circumferentially distributed on the outer periphery of the top of the nozzle body 2. The argon-blowing grooves 3 communicate with the argon chamber. The angle between the argon-blowing grooves 3 and the outer circle tangent of the nozzle body 2 is less than 90°.

[0026] This immersion argon-blowing nozzle is mainly composed of two core components: a protective shell 1 and a nozzle body 2. On the outer side of the protective shell 1, an argon-blowing nozzle 4 dedicated to introducing argon is assembled. One end of the argon-blowing nozzle 4 is connected to an external argon gas source, and the other end extends steadily into the argon chamber. The outer periphery of the top of the nozzle body 2 is the distribution area of the argon-blowing grooves 3. The argon-blowing grooves 3 are evenly distributed in a circumferential shape and are in seamless communication with the argon chamber. Argon enters the argon chamber through the argon-blowing nozzle 4. Since the bottom of the argon chamber is sealed, argon gradually accumulates in the chamber and forms a certain pressure. Driven by the pressure difference, argon begins to flow into the argon-blowing grooves 3 communicating with the argon chamber. The argon ejected from the argon-blowing grooves 3 forms a continuous argon protection layer around the nozzle, effectively isolating the molten steel from the outside air, greatly reducing the contact opportunity between the molten steel and oxygen in the air, thereby significantly reducing the risk of secondary oxidation of the molten steel, ensuring the purity of the molten steel, and improving the quality of the steel.

[0027] Furthermore, a step 5 is provided at the top of the nozzle body 2 near the inner circle of the argon blowing groove 3 , and a slope is provided on the outer side of the step 5 , which extends from the top of the nozzle body 2 to the argon blowing groove 3 below.

[0028] Furthermore, a bowl mouth 6 is provided on the inner circle of the nozzle body 2 close to the step 5 , and a distance is left between the inner flange of the bowl mouth 6 and the step 5 .

[0029] Compared with the existing traditional argon blowing nozzle structure, the top of the nozzle body 2 is designed with a bowl mouth 6, and a chamber is left in the middle. After flame detection, the flame only emerges from a local position of the bowl of the lower nozzle. The immersed argon blowing nozzle structure of the present invention passes the flame detection. After the argon gas is connected from the argon blowing nozzle 4, the flame can emerge from all around the bowl of the lower nozzle. The argon gas can fully realize the argon seal between the upper nozzle and the lower nozzle, play the role of isolating the molten steel from the air, and effectively prevent the secondary oxidation of the molten steel.

[0030] The submerged argon blowing nozzle is a key functional refractory material in the continuous casting process. It serves as a receiver for the molten steel between the tundish and the crystallizer, protecting the molten steel from secondary oxidation, preventing nitrogen from dissolving or slag from mixing into the molten steel to affect the quality of the ingot. Especially when casting special steels such as alloy steel, high carbon steel, and aluminum-containing steel that have high requirements for the molten steel environment, the sealing of the upper and lower nozzles is particularly important. The submerged argon blowing nozzle of the present invention is reasonably designed, which can well solve this sealing problem and meet the process requirements of continuous casting production.

[0031] In some embodiments, the top of the step 5 is higher than the top end surface of the protective shell 1. Further, the slope of the step 5 is higher than the top end surface of the protective shell 1.

[0032] In some implementations, a sealing portion is formed between adjacent argon blowing slots 3 , and an outer edge of the sealing portion is close to the inner wall of the protective shell 1 .

[0033] In some embodiments, a cavity is left in the middle of the nozzle body 2 .

[0034] The present invention can effectively realize argon sealing between the upper water inlet and the lower water inlet through the special design of the immersed argon blowing lower water inlet, prevent the secondary oxidation of molten steel, and improve the quality of molten steel.

[0035] During the production process, an argon supply device is also included, which is connected to the argon blowing nozzle of the submerged argon blowing tundish nozzle for supplying argon to the argon chamber and has functions of flow rate regulation and pressure control; a liquid level detection device is installed on the mold for real-time detecting the fluctuation of the molten steel level in the mold and transmitting the detected data to the control system, and the control system controls the flow rate and pressure of the argon supply device according to the liquid level detection data; a mold powder adding device is used for adding mold powder into the mold and has functions of automatic addition and metering, and can adjust the addition amount in real time according to the production demand and the consumption amount of the mold powder; a billet detection device is used for detecting the off-line billets, including detecting the surface quality, internal inclusions and porosity defects of the billets, etc., and feeding back the detected data to the control system, and the control system adjusts the production process parameters according to the detected data, including the argon blowing amount, casting speed, etc.

[0036] The present invention also discloses an application process of an immersion argon blowing tundish nozzle structure. Using the above-mentioned immersion argon blowing tundish nozzle structure, it includes:

[0037] Setting the critical blowing gas volume q of the slab under different casting speed conditions 临 ;

[0038] q 临 is proportional to the pouring flow rate Q of the molten steel in the mold. q 临 = 0.0841 * Q - 19.97, where the units of q 临 and Q are L / min.

[0039] The change of the argon blowing amount has a great influence on the flow pattern in the mold. The amount of blowing not only affects the temperature of the molten steel in the mold, but also has an important influence on the floating of inclusions and the surface slag entrainment behavior in the mold. By reasonably controlling the argon blowing amount and argon blowing pressure, the present invention can effectively reduce the liquid level fluctuation in the mold, reduce the risk of slag entrainment, reduce the generation of defects such as slag holes on the surface of the billet, and improve the surface quality of the billet.

[0040] The impact depth and liquid level fluctuation of the submerged nozzle jet directly determine the flow field state in the mold. Under the conditions of argon blowing through the stopper rod and the submerged nozzle, the impact depth and liquid level fluctuation of the submerged nozzle jet are affected by factors such as casting speed, the inclination angle and shape of the submerged nozzle, and the argon blowing amounts of the stopper rod and the submerged nozzle.

[0041] Through on-site actual tracking, after blowing inert gas into the immersion argon blowing tundish nozzle, the flow field characteristics in the mold were studied. Referring to the slab under different casting speed process parameters, to prevent phenomena such as violent liquid level fluctuation and slag entrainment, there is a corresponding critical blowing gas volume (q 临 ). q 临 is approximately proportional to the pouring flow rate Q of the molten steel in the mold. The regression into a unary equation is q critical = 0.0841 * Q - 19.97 (where q 临The unit of [quantity] and Q is L / min). However, in the casting of 155mm * 155mm billets, this formula is not applicable during the actual casting process. The corresponding critical blowing gas volume should be to minimize the argon blowing volume without the risk of nozzle blockage, preventing the entrainment of slag caused by violent fluctuations in the mold liquid level. The argon blowing flow rate should be adjusted at any time according to the liquid level detection data to control the fluctuation of the mold liquid level within ±5mm. If the argon gas is turned on at ≥0.3MPa, the liquid level in the mold tumbles severely, which has a certain impact on the surface quality of the billet.

[0042] In some embodiments, when applied to the casting of 155mm * 155mm billets, the set argon blowing flow rate is lower than the critical blowing gas volume q 临 ; Adjust the argon blowing flow rate according to the mold liquid level detection data to control the fluctuation of the mold liquid level within ±5mm.

[0043] Furthermore, when applied to the casting of 155mm * 155mm billets, the casting speed is less than 3.5m / min, and the argon gas opening pressure is lower than 0.3MPa.

[0044] After the inert gas is blown into the submerged argon blowing nozzle of the present invention, when the argon gas opening pressure ≥0.3MPa, the consumption of the mold powder in the mold increases significantly, and the consumption of the mold powder increases abnormally at the same casting speed, which may cause the mold powder in the mold not to melt, forming slag pit defects on the surface of the billet. Through the real-time monitoring data of the amount of mold powder added per minute, it is found that under the same conditions, comparing the consumption of the mold powder in the large argon blowing state with that in the small argon blowing state, the average increase is about 30 grams per minute.

[0045] Also, the argon gas blown into the submerged argon blowing nozzle forms bubbles under the action of the molten steel flow, enters the mold with the molten steel flow, and generates a force on the molten steel flow field in the mold. The submerged argon blowing nozzle can effectively reduce the probability of nozzle blockage, and at the same time is conducive to the floating of non-metallic inclusions, reducing inclusions in the billet. However, once the bubbles adsorbed with inclusions are captured by the solidified billet during the floating process, it will also deteriorate the quality of the billet. As the casting speed changes, the argon blowing volume is also constantly adjusted. Generally speaking, the larger the casting speed, the larger the argon blowing flow rate, and the lower the casting speed, the lower the argon blowing flow rate. Also, due to the increase in casting speed, the impact depth of the bubbles at high casting speeds intensifies, and it is more likely to be captured by the solidification of the billet. Therefore, it is necessary to verify the inclusion and porosity defects inside the billet under the critical state where the argon gas causes the mold liquid level to tumble by ±5mm, as shown in Table 1 and Table 2 below.

[0046]

[0047] Table 1: Low magnification non-metallic inclusion grade with argon gas opening pressure < 0.3MPa

[0048]

[0049] Table 2: Macro non-metallic inclusion grade with argon opening pressure ≥ 0.3 MPa

[0050] Select the heats with relatively high total aluminum content, take the macro of the caster billet at the lower limit, and compare the state where the argon opening pressure of the submerged entry nozzle is < 0.3 MPa with large argon opening and small argon opening under the low casting speed of < 3.5 m / min. It is obvious that the grade of non-metallic inclusion defects inside the caster billet taken with the argon opening pressure < 0.3 MPa is lower than that with the argon blowing pressure ≥ 0.3 MPa. At the casting speed > 3.5 m / min, the grades of non-metallic inclusion defects of both increase, and the difference between the two is not obvious (as Figure 3 and Figure 4 shown).

[0051] At high casting speeds, the bubbles generated by argon blowing at the submerged entry nozzle have a greater impact depth, and the bubbles and the non-metallic inclusions adsorbed by them are easily captured by the primary caster billet, resulting in a significant increase in non-metallic inclusions in the caster billet at high casting speeds and an aggravation of the surface structure defects of the caster billet. At high casting speeds, the argon blowing flow rate should be reduced to reduce the slag pits on the surface of the caster billet to improve the surface quality of the caster billet. In actual production, these process parameters should be adjusted to match each other to make the flow field in the mold reach an ideal state. According to the corresponding relationship between the pouring flow rate (mold overflow) and the casting speed section, the critical argon blowing volume under different section and casting speed conditions can be obtained.

[0052] Adjusting the argon blowing volume according to the casting speed can meet the production requirements at different casting speeds, reduce the non-metallic inclusions and surface structure defects in the caster billet at high casting speeds, and improve the overall quality of the caster billet.

[0053] Example

[0054] The structure of the submerged entry nozzle for argon blowing includes a protective shell and a nozzle body. The protective shell is provided with argon blowing nozzles. An argon chamber is formed between the protective shell and the nozzle body. The argon blowing nozzles are located at the argon chamber. The bottom of the argon chamber is sealed. The top of the nozzle body is provided with a number of argon blowing grooves, and the argon blowing grooves are communicated with the argon chamber. There is a step at the inner circle of the top of the nozzle body, a slope is provided outside the step, there is a distance between the step and the inward flange, and the included angle between the argon blowing groove and the tangent of the outer circle of the nozzle body is less than 90°. The design of the bowl part of the lower nozzle plays an important role in the argon seal between the upper nozzle and the lower nozzle, which can effectively prevent the secondary oxidation of molten steel and improve the quality of molten steel.

[0055] The nozzle body is made of refractory materials with high temperature resistance and erosion resistance, and the protective shell is made of materials with certain strength and sealing performance to ensure the sealing performance of the argon chamber. The number of argon blowing nozzles is multiple and they are evenly distributed on the protective shell to ensure that argon can enter the argon chamber evenly. The shape of the argon blowing groove is arc-shaped or linear, and its depth and width are designed according to actual production requirements to ensure that argon can enter the molten steel smoothly and achieve a good argon blowing effect.

[0056] The main functions of the present invention:

[0057] The design of the argon-blowing tundish nozzle bowl part can effectively achieve the argon seal between the upper nozzle and the lower nozzle. By reducing the casting speed, the argon flow rate, and the downward inclination angle of the submerged nozzle, the possibility of slag entrainment can be reduced, the surface quality of the slab can be improved, and the secondary oxidation of the molten steel can be reduced. During the production process, controlling the argon flow rate to be less than the critical argon flow rate is an effective means to prevent slag entrainment.

[0058] In summary, after reading the documents of the present invention, those of ordinary skill in the art can make various corresponding transformation schemes without creative mental labor according to the technical solutions and technical concepts of the present invention, and all of them fall within the scope protected by the present invention.

Claims

1. An immersion type argon blowing nozzle structure, characterized in that, It includes a protective shell and a nozzle body. The protective shell is arranged on the outer periphery of the nozzle body, and an argon chamber is formed between the protective shell and the nozzle body. The bottom of the argon chamber is sealed. A tuyere for blowing argon is assembled on the outer side of the protective shell, and the tuyere for blowing argon extends into the argon chamber. A number of argon-blowing grooves are distributed around the outer periphery of the top of the nozzle body, and the argon-blowing grooves are communicated with the argon chamber. The included angle between the argon-blowing groove and the outer circle tangent of the nozzle body is less than 90°.

2. The immersion argon-blowing nozzle structure according to claim 1 is characterized in that, There is a step on the inner ring of the top of the nozzle body near the argon-blowing groove, and a slope is arranged on the outer side of the step. The slope extends from the top of the nozzle body to the lower argon-blowing groove.

3. The structure of an immersion argon-blowing nozzle according to claim 2, wherein, The top end of the step is higher than the top end face of the protective shell.

4. The structure of an immersion argon-blowing nozzle according to claim 2 or 3, characterized in that, There is a bowl mouth on the inner ring of the nozzle body near the step, and there is a gap between the inner flanging of the bowl mouth and the step.

5. The structure of an immersion argon-blowing nozzle according to claim 1, wherein A sealing part is formed between adjacent argon-blowing grooves, and the outer circle edge of the sealing part is close to the inner wall of the protective shell.

6. The immersion type argon blowing nozzle structure according to claim 4, characterized in that, There is a chamber in the middle of the nozzle body.

7. An application process of an immersion argon-blowing nozzle structure, characterized in that, Using an immersion argon-blowing nozzle structure according to any one of claims 1 to 6, including: Set the critical gas blowing volume q of the slab under different casting speeds 临 , and reduce the argon blowing flow rate when the casting speed is higher than 3.5 m / min; q 临 is directly proportional to the pouring flow rate Q of the molten steel in the mold, q 临 = 0.0841 * Q - 19.97, where q 临 and Q are in the unit of L / min.

8. The application process of an immersion argon-blowing nozzle structure according to claim 7, characterized in that, Applied to the casting of 155mm * 155mm small square billets, the set argon blowing flow rate is lower than the critical blowing gas volume q 临 ; Adjust the argon blowing flow rate according to the mold liquid level detection data, and control the fluctuation of the mold liquid level within ±5mm.

9. The application process of an immersion argon-blowing nozzle structure according to claim 8, characterized in that, The drawing speed is less than 3.5 m / min, and the opening argon pressure is lower than 0.3 MPa.

Images