A smelting method for improving the bottom blowing air permeability of a newly launched ladle

Abstract

The present invention discloses a smelting method for improving the bottom blowing air permeability of a newly launched ladle, comprising the following steps: Step 1, heating the bottom of the moving ladle; Step 2, before tapping, blowing argon at the bottom of the moving ladle; during tapping, blowing argon at the bottom of the moving ladle throughout the process. When tapping from the converter, the temperature is ≥1635°C, and only 0.4 - 0.5 Kg / t of metallic aluminum is added during tapping. The metallic aluminum is used as a deoxidizer and a heating agent; Step 3, after tapping is completed, adjust the argon flow rate to 300 - 500 L / min and perform strong argon blowing for 2 - 3 min. Stir through strong argon blowing to avoid cold steel condensation at the bottom of the ladle. After stirring, perform soft argon blowing for 30 - 60 s, then close the argon and connect the moving ladle to the moving small steam drum; Transfer the moving ladle to LF. During the transfer of the moving ladle to LF, maintain bottom blowing argon of the moving ladle through the moving small steam drum; Step 4, after the moving ladle enters LF, connect the ladle argon gas source, perform strong stirring to avoid cold steel condensation at the bottom of the ladle, and then perform normal refining; The present invention has the advantages of high molten steel refining air permeability, reducing the amount of cold steel formation, and preventing blockage of the porous plug.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking, and particularly relates to a smelting method for improving the bottom blowing air permeability of a newly launched ladle. Background Art

[0002] The ladle is the main equipment in the steel mill, mainly used to hold molten steel, with a steel plate shell and refractory lining inside. The bottom of the ladle is designed with a porous plug. After connecting the gas source at the bottom, the ladle has the function of blowing gas. The conventional smelting process is "converter tapping - ladle receiving molten steel - ladle performing bottom blowing argon to uniform temperature and composition - ladle entering the LF furnace and bottom blowing argon and completing refining - ladle going to continuous casting for pouring". The ladle has good argon blowing, temperature adjustment and refining functions. The bottom blowing argon of the ladle runs through the key processes from tapping to the end of refining, and it is a very important smelting and refining tool in the steel mill. However, when using the "converter - LF - continuous casting" process flow, when a newly launched moving ladle is put into use, it often occurs that the bottom blowing air permeability of the converter is normal, but after the converter closes the gas, when the moving ladle is lifted into the LF and the bottom blowing gas is turned on again, there is no air permeability at the bottom blowing (i.e., the porous plug is blocked). If there is no air permeability at the bottom blowing of the ladle, the molten steel needs to be poured into another ladle (i.e., poured into another ladle) or sent back to the furnace for treatment, which will cause the interruption of continuous casting and have a greater impact on steelmaking production.

[0003] In the prior art, there is a lack of a highly operable solution for how to improve the bottom blowing air permeability of newly launched ladles in the converter - LF process flow. In order to solve the problem of no air permeability or low air permeability at the bottom blowing of the moving ladle in the "converter - LF - continuous casting" process, a new technical solution needs to be developed. Summary of the Invention

[0004] The purpose of the present invention is to provide a smelting method for improving the bottom blowing air permeability of newly launched ladles in view of the problems existing in the prior art. This solution has the advantages of high air permeability for molten steel refining, reducing the amount of cold - solidified steel, and preventing blockage of the porous plug.

[0005] To achieve the above - mentioned purpose, the technical solution adopted by the present invention is: a smelting method for improving the bottom blowing air permeability of newly launched ladles, including the following steps:

[0006] Step 1: Heat the bottom of the moving ladle to a temperature ≥ 800 °C, the interval time from the end of heating the moving ladle to tapping ≤ 15 min, and the interval time from uncovering the ladle cover of the moving ladle to tapping ≤ 7 min;

[0007] Step 2: Before tapping, turn on the bottom blowing argon gas of the moving ladle, with a flow rate of 100 - 200 L / min; during the tapping process, the moving ladle performs bottom blowing argon throughout the process. When the converter taps, the temperature ≥ 1635 °C, and only 0.4 - 0.5 Kg / t of metallic aluminum is added during tapping. The metallic aluminum is used as a deoxidizer and heat - generating agent.

[0008] Step 3: After tapping is completed, adjust the argon flow rate to 300 - 500 L / min for strong argon blowing for 2 - 3 min. Stir through strong argon blowing to avoid cold steel condensation at the bottom of the ladle. After stirring, adjust the argon to 80 - 150 L / min, perform soft blowing for 30 - 60 s, then close the argon and connect the moving ladle to the moving small steam drum; Transfer the moving ladle to the LF. During the transfer of the moving ladle to the LF, maintain the bottom argon blowing of the moving ladle through the moving small steam drum, with an argon flow rate of 50 - 80 L / min;

[0009] Step 4: After the moving ladle enters the LF, connect the argon gas source of the ladle. Blow argon strongly at an argon flow rate of 400 - 500 L / min for 1 - 2 min, and perform strong stirring to avoid cold steel condensation at the bottom of the ladle. Then adjust the argon flow rate to the normal state and carry out refining treatment.

[0010] In the above solution, in Step 1, the main reason for the lack of bottom blowing air permeability in the moving ladle is that when the bottom of the ladle contacts the molten steel, due to the large temperature difference between the molten steel and the bottom of the moving ladle, cold steel is easily formed at the bottom of the ladle. Therefore, before starting to tap, first perform bottom heating on the moving ladle. When the temperature reaches above 800 °C, cold steel formation can be effectively avoided. At the same time, strictly control the interval time between the end of heat dissipation and the time of uncovering the ladle cover and tapping to prevent the temperature at the bottom of the moving ladle from dropping significantly before tapping; In Step 2, start blowing argon before tapping to avoid blockage of the air holes in the porous plug. Control the tapping temperature to prevent the temperature from being too low when the molten steel contacts the moving ladle. To reduce the temperature drop during tapping, no alloys such as ferrosilicon manganese are added during tapping, and only metallic aluminum is added during tapping as a deoxidizer and heating agent to maintain the temperature of the molten steel; The moving ladle completes the silicomanganese alloying in the process after LF. The charging sequence adopts the operation of adding molten iron first and then scrap steel; In Step 3, after tapping is completed, first perform strong argon blowing and stirring on the molten steel in the moving ladle to avoid cold steel formation at the bottom of the ladle. After closing the argon, convert the converter argon gas source of the moving ladle to the moving small steam drum, and provide argon for bottom blowing through the moving small steam drum during the transfer of the moving ladle. The main purpose of ventilation is to prevent the molten steel from backflowing into the porous plug and avoid cold steel condensation at the bottom of the ladle where the porous plug is located, maintaining the bottom blowing passage state; In Step 4, immediately connect the argon gas source of the ladle at the LF after the moving ladle enters the LF, blow argon strongly for 1 - 2 min, and perform strong stirring to avoid cold steel condensation at the bottom of the ladle. At this time, the charging operation has been completed, and at the same time, the ventilation rate during bottom blowing is ensured, and normal refining treatment can be carried out.

[0011] Through research, it is found that in the long process flow, that is, the converter - LF - continuous casting process, when the newly launched ladle enters the LF, there is a lack of bottom blowing air permeability. The main reason is that the temperature difference between the bottom of the moving ladle and the molten steel is large, and cold steel is easily formed at the bottom of the ladle. Moreover, the thicker the thickness of the cold steel formed at the bottom of the ladle, the more difficult it is to blow through the bottom blowing air permeability. Through the analysis of the steel receiving process of the ladle, the lower the tapping temperature, the lower the bottom temperature of the ladle, the greater the temperature drop during tapping, and the longer the time interval from the converter closing the argon to the LF reopening the argon, the more likely it is to cause the bottom blowing air permeability to be blocked.

[0012] Furthermore, the tapping time of the converter is ≤ 3 min, and the temperature drop of the molten steel during tapping is ≤ 30 °C.

[0013] By controlling the tapping time and ensuring that the temperature drop of the molten steel does not exceed the range, the cold solidification of the molten steel in the ladle due to too low temperature is avoided.

[0014] Furthermore, in step three, the movable small steam drum is detachably installed on the movable ladle, and the movable small steam drum and the movable ladle are transported synchronously.

[0015] By detachably installing the movable small steam drum on the movable ladle, it is convenient to transport with the movable ladle and ensure the argon gas supply during the process.

[0016] Furthermore, the time from the start of tapping in the converter to the end of argon blowing is controlled to be ≤ 8 min.

[0017] The treatment time of the ladle in the converter argon station is controlled. To reduce the temperature drop during the process after tapping, it is required that the time from the start of tapping in the converter to the end of argon blowing is controlled to be ≤ 8 min, and the ladle should be transferred to the LF furnace as soon as possible. The LF furnace has a temperature-raising function, and temperature compensation can be carried out immediately when it enters the LF furnace.

[0018] Furthermore, in step one, the movable ladle is heated by means of bottom baking of the ladle.

[0019] The operation is convenient and the heating effect is good.

[0020] Furthermore, in step one, the cover of the movable ladle is removed at least 8 min after the start of blowing in the smelting heat.

[0021] Ensure sufficient blowing time in the converter to avoid the ladle temperature drop or insufficient blowing caused by removing the cover too early.

[0022] Furthermore, in step three, after stirring, the argon gas is adjusted to 80 - 150 L / min and soft blown for 30 - 60 s.

[0023] Soft blowing removes non-metallic inclusions in the molten steel, improves the cleanliness of the molten steel, and avoids the reverse osmosis of molten steel into the gas bricks.

[0024] Furthermore, the movable ladle and the movable small steam drum are transported synchronously by means of hoisting.

[0025] Transportation by means of hoisting is convenient.

[0026] Furthermore, in step three, when connecting the movable small steam drum, a cover is added to the movable ladle.

[0027] By adding a cover to the movable ladle, the temperature drop rate of the molten steel is reduced.

[0028] Furthermore, the cover is provided with air vents.

[0029] Vent holes are provided for gas outflow to maintain the pressure balance inside and outside the ladle.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. Through the smelting design of the process from tapping in the converter to charging into the LF furnace, the tapping temperature standard is reasonably designed, the tapping time is shortened, alloying only adds aluminum to reduce the tapping temperature drop, the calming time of the molten steel after tapping is shortened, bottom blowing of the ladle is maintained before and during tapping, a steam drum is installed during the transfer of the molten steel and gas is introduced to prevent backflow of the molten steel through the porous plug, key process designs such as staged bottom argon blowing flow control, etc. are carried out to prevent the molten steel from blocking the passage of the porous plug, effectively improving the bottom blowing air permeability rate of the transfer refined ladle;

[0032] 2. By controlling the heating and cover opening time of the moving ladle and the tapping temperature and transfer time of the converter, and by adjusting the alloy process sequence and insulating the temperature of the molten steel during the transfer process, cold steel formation at the bottom of the ladle caused by the temperature difference between the molten steel and the ladle and insufficient molten steel temperature is avoided, the amount of cold steel formation is reduced, which is beneficial to the smooth progress of molten steel refining;

[0033] 3. The process flow of the present invention is simple and clear, highly operable and easy to control. Detailed implementation manners

[0034] The technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. In the description of the present invention, it should be noted that the terms such as front, back, left, and right indicating the orientation or positional relationship are the orientation or positional relationship when the product of the invention is usually placed, which is only for the convenience of describing the present invention or simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed or operated in a specific orientation, and therefore cannot be construed as a limitation of the present invention.

[0035] Embodiment 1

[0036] A smelting method for improving the bottom blowing air permeability rate of a newly launched ladle, comprising the following steps:

[0037] Step 1: Heat the bottom of the moving ladle to a temperature ≥ 800 °C, the interval time from the end of heating the moving ladle to tapping ≤ 15 min, and the interval time from the cover opening time of the moving ladle to tapping ≤ 7 min;

[0038] Step 2: Before tapping, move the ladle and blow argon from the bottom, with a flow rate of 100 - 200 L / min; during tapping, blow argon from the bottom of the moving ladle throughout the process. When tapping from the converter, the temperature ≥ 1635 °C. Only add 0.4 - 0.5 Kg / t of metallic aluminum during tapping. Metallic aluminum is used as a deoxidizer and heating agent.

[0039] Step 3: After tapping is completed, adjust the argon flow rate to 300 - 500 L / min and blow strongly for 2 - 3 min to avoid cold steel coagulating at the bottom of the ladle by strong argon blowing. After stirring, adjust the argon to 80 - 150 L / min and soft blow for 30 - 60 s, then close the argon and connect the moving ladle to the moving small steam drum; transfer the moving ladle to LF. During the transfer of the moving ladle to LF, maintain bottom blowing of argon in the moving ladle through the moving small steam drum, with an argon flow rate of 50 - 80 L / min.

[0040] Step 4: After the moving ladle enters LF, connect the argon gas source of the ladle, blow argon strongly at a flow rate of 400 - 500 L / min for 1 - 2 min, and strongly stir to avoid cold steel coagulating at the bottom of the ladle. Then adjust the argon flow rate to the normal state and carry out refining treatment.

[0041] In the above solution, in Step 1, when the moving ladle is first put into use, the internal temperature is low. The main reason for the lack of bottom blowing air permeability of the moving ladle is that when the bottom of the ladle contacts the molten steel, due to the large temperature difference between the molten steel and the bottom of the moving ladle, cold steel is likely to form at the bottom of the ladle. Therefore, before starting to tap, first heat the bottom of the moving ladle. When the temperature reaches above 800 °C, cold steel formation can be effectively avoided. At the same time, strictly control the interval time between the end of heat dissipation and the time of uncovering the ladle cover and tapping to avoid a large drop in the temperature at the bottom of the moving ladle before tapping. Limit the bottom temperature of the moving ladle, the end time of heating, and the time of uncovering the moving ladle cover; the moving ladle finishes baking when blowing starts in the smelting heat, so as to ensure the heating effect of the ladle and adapt to the ladle blowing steps; in Step 2, start blowing argon before tapping to avoid blockage of the pores of the porous plug, control the tapping temperature, avoid too low temperature when the molten steel contacts the moving ladle, and to reduce the temperature drop during tapping, do not add alloys such as silicomanganese during tapping, and only add metallic aluminum during tapping as a deoxidizer and heating agent to maintain the temperature of the molten steel; the moving ladle completes the silicomanganese alloying in the process after LF, and the charging sequence adopts the operation of adding scrap steel after charging molten iron first; in Step 3, after tapping is completed, first strongly blow and stir the molten steel in the moving ladle to avoid cold steel coagulating at the bottom of the ladle. After closing the argon, convert the converter argon gas source of the moving ladle to the moving small steam drum, and provide argon for bottom blowing during the transfer of the moving ladle through the moving small steam drum. The main purpose of ventilation is to prevent the molten steel from backflowing into the porous plug and avoid cold steel coagulating at the bottom of the ladle where the porous plug is located, and maintain the bottom blowing passage state; in Step 4, immediately connect the argon gas source of the ladle at LF after the moving ladle enters LF, strongly blow argon for 1 - 2 min, and strongly stir to avoid cold steel coagulating at the bottom of the ladle. At this time, the charging operation has been completed, and at the same time, the ventilation rate during bottom blowing is ensured, and normal refining treatment can be carried out.

[0042] It is found through research that when the long-process technology (i.e., converter - LF - continuous casting process) moves the ladle into LF, there is no bottom blowing air permeability. The main reason is that the temperature difference between the bottom of the moving ladle and the molten steel is relatively large, and cold steel is likely to form at the bottom of the ladle. Moreover, the thicker the thickness of the cold steel at the bottom of the ladle, the more difficult it is to blow through the bottom blowing air permeability. Through the analysis of the ladle steel receiving process, the lower the tapping temperature, the lower the bottom temperature of the ladle, the greater the temperature drop during tapping, and the longer the time interval from the converter closing the argon gas to the LF reopening the gas, the more likely it is to cause the bottom blowing air permeability to be blocked. Therefore, corresponding improvements have been made to this discovery in this solution.

[0043] Furthermore, the tapping time of the converter ≤ 3 min, and the temperature drop of the molten steel during tapping ≤ 30 °C.

[0044] By controlling the tapping time and ensuring that the temperature drop of the molten steel does not exceed the range, it is avoided that the molten steel in the ladle is too cold and freezes.

[0045] Furthermore, in step three, the movable small steam drum is detachably installed on the movable ladle, and the movable small steam drum and the movable ladle are transported synchronously.

[0046] By detachably installing the movable small steam drum on the movable ladle, it is convenient to transport with the movable ladle and ensure the argon gas supply during the process.

[0047] Mounting brackets are respectively arranged on the movable ladle and the movable small steam drum, and the corresponding brackets are fixedly connected by bolts.

[0048] Furthermore, the time from the converter starting to tap to the end of argon blowing is controlled ≤ 8 min.

[0049] The processing time of the ladle in the converter argon station is controlled. To reduce the temperature drop during the process after tapping, it is required that the time from the converter starting to tap to the end of argon blowing is controlled ≤ 8 min, and the ladle should be transferred to the LF furnace as soon as possible. The LF has a temperature-raising function, and temperature compensation can be carried out immediately when it enters the LF.

[0050] Furthermore, in step one, the movable ladle is heated by the way of bottom baking.

[0051] It is convenient to operate and has a good heating effect.

[0052] After the movable ladle is manufactured, it is only allowed to be put into use after being baked by gas until the temperature of the ladle lining reaches the baking temperature standard.

[0053] Furthermore, in step one, the ladle cover of the movable ladle is removed at least 8 min after the start of blowing in the smelting heat.

[0054] Ensure sufficient blowing time of the converter and avoid premature removal of the ladle cover, which may cause the ladle to cool down or insufficient blowing.

[0055] Further, in step three, after stirring, the argon gas is adjusted to 80 - 150 L / min and soft blown for 30 - 60 s.

[0056] Soft blowing removes non-metallic inclusions in the molten steel, improves the cleanliness of the molten steel, and avoids reverse osmosis of molten steel into the gas bricks.

[0057] Further, the moving ladle and the moving small steam drum are synchronously transported by hoisting.

[0058] Transportation by hoisting is convenient.

[0059] Use a crane for lifting.

[0060] In the embodiment, 1) There are restrictions on the bottom temperature of the moving ladle, the end time of baking, and the time to remove the ladle cover of the moving ladle. The bottom baking temperature of the moving ladle is 850 °C. The ladle baking of the moving ladle ends when the blowing of the smelting furnace starts. The interval time from the end of baking to tapping is 15 min. The ladle cover is removed 8 min after the blowing of the smelting furnace starts, and the interval time from uncovering to tapping is 7 min.

[0061] 2) Requirements for the tapping temperature of the converter and alloying. The tapping temperature is 1635 °C. Only 0.4 Kg / t of metallic aluminum is added during tapping; The tapping is carried out through a tapping hole with a large inner diameter, and the tapping time is 3 min. The temperature drop during tapping is 30 °C, and the temperature after tapping is 1605 °C.

[0062] 3) Requirements for bottom argon blowing: Argon gas is turned on before tapping, with a flow rate of 150 L / min. Bottom argon blowing is carried out throughout the tapping process. After tapping, the argon gas flow rate is adjusted to 400 L / min for strong argon blowing for 2 min. After strong stirring, the argon gas flow rate is adjusted to 80 L / min and soft blown for 30 s before closing the argon gas.

[0063] 4) Treatment time of the ladle at the converter argon station. The time from the start of tapping to the end of argon blowing in the converter is 8 min.

[0064] 5) During the transfer of the ladle to the LF, a small steam drum is used to maintain bottom argon blowing in the ladle, with an argon gas flow rate of 50 L / min.

[0065] 6) Immediately after entering the LF, connect the argon gas source of the ladle, and carry out strong argon blowing at a flow rate of 400 L / min for 1 min.

[0066] Comparison table of the technical content of the prior art and the embodiment:

[0067]

[0068] Referring to the above table, it can be seen that for the newly launched ladle entering the LF in the comparative example, the bottom blowing air permeability is 60 - 75%, while in the existing conventional mode in the industry, the argon blowing flow rate is not restricted, and the bottom blowing air permeability is only 50 - 65% close to that of the comparative example. In the embodiment of the present invention, the bottom blowing air permeability of the newly launched ladle entering the LF is ≥90%, and the air permeability is effectively improved.

[0069] Example 2

[0070] Furthermore, in step three, when connecting the movable tundish, a ladle cover is added to the movable ladle.

[0071] By adding a ladle cover to the movable ladle, the cooling rate of the molten steel is reduced.

[0072] Furthermore, ventilation holes are provided on the ladle cover.

[0073] Ventilation holes are provided for gas to flow out to maintain the pressure balance inside and outside the ladle.

[0074] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A smelting method for improving the bottom blowing air permeability of a newly launched ladle, characterized in that, It includes the following steps: Step 1: Heat the bottom of the moving ladle to a temperature ≥ 800°C. The interval time from the end of heating of the moving ladle to tapping is ≤ 15 min, and the interval time from uncovering the ladle cover of the moving ladle to tapping is ≤ 7 min. And the time for uncovering the ladle cover of the moving ladle is at least 8 min after the start of blowing in the smelting heat; Step 2: Before tapping, start bottom blowing argon in the moving ladle with a flow rate of 100 - 200 L / min. During tapping, the moving ladle is bottom blown with argon throughout the process. Control the tapping time of the converter ≤ 3 min, the temperature during tapping of the converter ≥ 1635°C. Only add 0.4 - 0.5 Kg / t of metallic aluminum during tapping. The metallic aluminum is used as a deoxidizer and heat - generating agent. The temperature drop of the molten steel during tapping is ≤ 30°C; Step 3: After tapping is completed, adjust the argon flow rate to 300 - 500 L / min for strong argon blowing for 2 - 3 min. Stir through strong argon blowing to avoid cold steel condensation at the bottom of the ladle. Then adjust the argon to 80 - 150 L / min for soft blowing for 30 - 60 s. Then close the argon and connect the moving ladle to the moving small steam drum. Transfer the moving ladle to LF. During the transfer of the moving ladle to LF, maintain bottom blowing argon in the moving ladle through the moving small steam drum, with an argon flow rate of 50 - 80 L / min. The moving small steam drum is detachably installed on the moving ladle, and the moving small steam drum and the moving ladle are synchronously transferred by hoisting; Step 4: After the moving ladle enters LF, connect the argon gas source of the ladle. Blow argon strongly at a flow rate of 400 - 500 L / min for 1 - 2 min for strong stirring to avoid cold steel condensation at the bottom of the ladle. Then adjust the argon flow rate to the normal state and carry out refining treatment. And the time from the start of tapping of the converter to the end of argon blowing is controlled ≤ 8 min.

2. The smelting method for improving the bottom blowing air permeability of a newly launched ladle according to claim 1, characterized in that, In Step 1, the bottom of the moving ladle is heated by means of bottom baking.

3. The smelting method for improving the bottom blowing air permeability of a newly launched ladle according to claim 1, characterized in that, In Step 3, when connecting the moving small steam drum, put a ladle cover on the moving ladle.

4. The smelting method for improving the bottom blowing air permeability of a newly launched ladle according to claim 3, characterized in that, The ladle cover is provided with vent holes.

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