Method for preventing molten iron tank from being frozen by remelted molten steel

Abstract

The invention discloses a method for preventing molten steel from freezing a molten iron tank, and relates to the technical field of steelmaking metallurgy. The method comprises the following specific steps: preparing coke; packaging the coke; hot-metal bottle inspection; putting coke; and adding molten steel. The method has the beneficial effects that the treatment thought of the tank freezing problem is converted into beforehand active prevention from post passive remedy, specific coke is added into the molten iron tank, mixing is achieved through impact generated when molten steel is added, and therefore the solidification temperature of the molten steel is scientifically reduced, the tank freezing accident is effectively avoided from the source, and the production cost is reduced. The method is reliable in principle and remarkable in effect, the needed raw materials are easy to obtain, the operation process is simple and convenient, the existing production rhythm can be rapidly fused, response is rapid, production interruption and high disposal cost caused by tank freezing are thoroughly avoided with extremely low preventive cost, and the method is suitable for large-scale production. And a powerful guarantee is provided for stable, efficient and low-cost operation of steel production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steelmaking metallurgy, and particularly relates to a method for preventing molten steel freezing in a ladle. BACKGROUND

[0002] In the continuous production process of a steel-iron joint enterprise, due to the failure of a continuous casting machine, unqualified molten steel temperature, or production plan adjustment, etc., part of the molten steel needs to be returned to the converter for re-smelting, which is referred to as "returning to the furnace". The conventional returning to the furnace operation is to pour the molten steel from a ladle into a ladle, and then transport it to the converter charging cross by a cross car, and finally hoist it by a crane and pour it into the converter. However, the solidification temperature of the molten steel is usually as high as about 1500℃. When the returning to the furnace molten steel with a low temperature enters the ladle at room temperature or low temperature, the heat will be quickly absorbed by the ladle, causing the temperature to drop sharply, and the molten steel in the ladle is prone to solidification. If the molten steel stays in the ladle for a long time, it will cause the "frozen ladle" accident, which not only causes the equipment to be difficult to turn over, but also seriously disrupts the production rhythm, causing significant economic losses.

[0003] To deal with the frozen ladle accident, the existing technology focuses on post-treatment solutions. For example, Chinese patent CN120023325A discloses a frozen ladle treatment method, the core of which is to ablate several pits on the surface of the frozen molten steel by burning oxygen pipes to increase the contact area between the high-temperature molten steel and the frozen block, and promote melting. Another Chinese patent CN119747631A discloses a comprehensive treatment method combining oxygen burning, baking, and ladle preheating to resolve the frozen ladle. Although these methods can treat the frozen ladle under certain conditions, they are essentially passive remedial measures.

[0004] Such post-treatment methods have obvious limitations in practical application. First, the treatment process usually takes a long time, requires a large amount of manpower and energy (such as oxygen and fuel), and has high economic costs. Second, the treatment operation itself will cause great disturbance to the originally tense production logistics and equipment scheduling, affecting the overall production efficiency. More importantly, for the completely frozen ladle, the treatment difficulty is extremely great, and sometimes it may even cause damage to the refractory material of the ladle, shortening the service life of the equipment. Therefore, the steel industry has long needed a preventive technology that can avoid the occurrence of frozen ladles from the source, moving the treatment point forward to ensure stable, efficient and low-cost operation of production. SUMMARY

[0005] The present application aims at the deficiencies and defects in the prior art, and provides a method for preventing frozen ladle of molten steel, which changes the processing idea of frozen ladle from passive remedy to active prevention, adds specific coke into the molten steel ladle, mixes by using the impact when the molten steel is poured in, and scientifically reduces the solidification temperature of the molten steel, thereby effectively avoiding the occurrence of frozen ladle accident from the source.

[0006] To achieve the above object, the present application adopts the following technical scheme: a method for preventing frozen ladle of molten steel, which comprises the following specific steps: coke preparation: selecting coke with fixed carbon content ≥ 86%, sulfur content ≤ 0.6%, and ash content ≤ 12.5%; coke packaging: packaging the selected coke into polyethylene woven bags with a thickness ≥ 0.08 mm for standardized packaging, and storing the packaged coke; molten steel ladle inspection: before receiving the molten steel, checking and ensuring that the inner wall of the molten steel ladle is clean and no obvious large frozen slag residues are left; coke feeding: 3-5 minutes before pouring the molten steel into the molten steel ladle, feeding the packaged coke into the molten steel ladle, and the feeding amount of the coke is 1% to 2% of the weight of the molten steel; molten steel pouring: pouring the molten steel into the molten steel ladle where the coke has been fed, and using the impact force of the molten steel to melt the coke and mix it with the molten steel.

[0007] Further, the particle size of the coke in the coke preparation is 5-30 mm.

[0008] Further, the weight of each bag of coke in the coke packaging is controlled at 20±0.5 kg.

[0009] Further, the feeding amount of the coke is adjusted according to the temperature of the molten steel and the inner wall temperature of the molten steel ladle, specifically: when the temperature of the molten steel is > 1540℃ and the inner wall temperature of the molten steel ladle is > 800℃, the feeding amount of the coke is 1.0% of the weight of the molten steel; when the temperature of the molten steel is > 1540℃ and the inner wall temperature of the molten steel ladle is ≤ 800℃, the feeding amount of the coke is 1.2% of the weight of the molten steel; when the temperature of the molten steel is ≤ 1540℃ and the inner wall temperature of the molten steel ladle is > 800℃, the feeding amount of the coke is 1.5% of the weight of the molten steel; and when the temperature of the molten steel is ≤ 1540℃ and the inner wall temperature of the molten steel ladle is ≤ 800℃, the feeding amount of the coke is 2.0% of the weight of the molten steel.

[0010] Further, the feeding method in the coke feeding can be manual throwing or mechanical conveying, and the coke is uniformly distributed at the bottom of the molten steel ladle.

[0011] After the technical scheme is applied, the application has the beneficial effects that the application changes the processing idea of the frozen ladle problem from passive remedy after the event to active prevention beforehand, the specific coke is added into the hot metal ladle, mixing is realized by using the impact when the molten steel is poured in, the solidification temperature of the molten steel is scientifically reduced, the frozen ladle accident is effectively avoided from the source, the method not only has reliable principle and remarkable effect, but also has easy-to-obtain raw materials and simple operation process, can quickly integrate into the existing production rhythm, responds quickly, and at a very low preventive cost, the production interruption and high disposal cost caused by the frozen ladle are completely avoided, and a powerful guarantee is provided for realizing stable, efficient and low-cost operation of the steel production. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0013] Figure 1 is a flowchart of the application. DETAILED DESCRIPTION

[0014] The application fundamentally solves the problem of frozen ladle accident when the molten steel is poured into the hot metal ladle by increasing the carbon content of the molten steel and then reducing the liquidus temperature of the molten steel, wherein the solidification temperature of the molten steel is affected by the content of multiple elements, and the calculation formula is: Tn=1536-(78ω[C]+7.6ω[Si]+4.9ω[Mn]+34ω[P]+30ω[S]+5.0ω[Cu]+3.1ω[Ni]+2.0ω[Mo]+2.0ω[V]+1.3ω[Cr]+18ω[Ti]+3.6ω[Al]+80ω[B]+80ω[O]+90ω[N]+1300ω[H]).

[0015] From the formula, it can be clearly seen that the solidification temperature of the molten steel will be reduced by 78℃ when the carbon content of the molten steel is increased by 1%. Based on this principle, the application adds coke into the hot metal ladle to mix the coke with the molten steel to increase the carbon content and reduce the solidification temperature, thereby effectively preventing the frozen ladle.

[0016] Referring to Figure 1 The technical scheme adopted in the specific embodiment is as follows: S1, coke preparation: select coke with fixed carbon content ≥ 86%, sulfur content ≤ 0.6%, ash content ≤ 12.5%; ensure that while increasing the carbon content of molten steel, reduce the adverse effects of other impurity elements on the quality of molten steel, and the particle size of the coke is 5mm-30mm.

[0017] S2, coke packaging: the selected coke is packaged in a polyethylene woven bag with a thickness of ≥0.08mm, and the packaged coke is stored; wherein the weight of each bag of coke is controlled at 20±0.5kg to ensure the accuracy of the amount of coke.

[0018] S3, molten iron tank inspection: before receiving the molten steel, check and ensure that the inner wall of the molten iron tank is clean and no obvious large frozen slag residues are left to create good conditions for subsequent operations.

[0019] S4, coke feeding: 3-5 minutes before pouring the molten steel into the molten iron tank, the packaged coke is fed into the molten iron tank, (the feeding method can be manual throwing or mechanical conveying to ensure uniform distribution of the coke at the bottom of the molten iron tank) the amount of coke is 1% to 2% of the weight of the molten steel, wherein the amount of coke is adjusted according to the temperature of the molten steel and the inner wall temperature of the molten iron tank, specifically: 1) when the temperature of the molten steel >1540℃ and the inner wall temperature of the molten iron tank >800℃, the amount of coke is 1.0% of the weight of the molten steel; 2) when the temperature of the molten steel >1540℃ and the inner wall temperature of the molten iron tank ≤800℃, the amount of coke is 1.2% of the weight of the molten steel; 3) when the temperature of the molten steel ≤1540℃ and the inner wall temperature of the molten iron tank >800℃, the amount of coke is 1.5% of the weight of the molten steel; 4) when the temperature of the molten steel ≤1540℃ and the inner wall temperature of the molten iron tank ≤800℃, the amount of coke is 2.0% of the weight of the molten steel.

[0020] S5, molten steel pouring: pour the molten steel into the molten iron tank with the coke, and use the impact force of the molten steel to melt the coke and mix it with the molten steel. For example, 1000kg of coke is fed into 100t of molten steel, which can increase the carbon content of the molten steel by about 0.8% through this mixing method, and according to the formula for calculating the solidification temperature of the molten steel, the solidification temperature of the molten steel can be reduced by 62.4℃. Reducing the solidification temperature of the molten steel effectively avoids the occurrence of frozen tank accidents and ensures the smooth progress of the steel production process The following are related embodiments of the present application Example 1 A certain furnace smelting 45# steel, after 10 minutes of pouring, because of the need for continuous casting through the tundish, the remaining molten steel was treated by re-melting, the estimated weight of molten steel was 83t, the temperature of molten steel for re-melting was 1550℃, the solidification temperature of molten steel was 1490℃, and the inner wall temperature of the ladle was 850℃.

[0021] 1. According to the temperature of molten steel for re-melting and the inner wall temperature of the ladle, because the temperature of molten steel for re-melting was >1540℃ and the inner wall temperature of the ladle was >800℃, it was determined that the amount of coke to be put was 83t*1.0%=830kg.

[0022] 2. Four minutes before the molten steel for re-melting was poured into the ladle, the coke was evenly distributed at the bottom of the ladle by mechanical conveying. During the mechanical conveying process, the conveying speed and direction were controlled to ensure that the coke was evenly distributed at the bottom of the ladle.

[0023] 3. After the coke was put, 83t of molten steel for re-melting was slowly poured into the ladle by a metallurgical special crane. During the pouring process, the powerful impact of the molten steel caused the coke to fully melt and rapidly mix with the molten steel. It was detected that the 830kg of coke increased the carbon content of the molten steel by about 0.8%, and according to the formula for calculating the solidification temperature of molten steel, the solidification temperature of the molten steel decreased by 62.4℃ (78x0.8=62.4℃) from 1490℃ to 1427.6℃, effectively avoiding the occurrence of ladle freezing accidents and ensuring the smooth progress of production.

[0024] Case Two A certain furnace smelting ML08Al needed to be re-melted due to low temperature of molten steel, the estimated weight of molten steel for re-melting was 132t, the temperature of molten steel for re-melting was 1530℃, the solidification temperature of molten steel was 1515℃, and the inner wall temperature of the ladle was 750℃.

[0025] 1. According to the temperature of molten steel for re-melting 1530℃ (≤1540℃) and the inner wall temperature of the ladle 750℃ (≤800℃), the estimated weight of molten steel for re-melting was 132t, and the amount of coke to be put was determined to be 132t*2.0%=2640kg according to the table.

[0026] 2. Three minutes before the molten steel for re-melting was poured into the ladle, a number of workers were arranged to evenly throw the coke onto the bottom of the ladle by manual throwing, ensuring that the coke was evenly distributed at the bottom of the ladle.

[0027] 3. After the coke was put, 132t of molten steel for re-melting was poured into the ladle. The impact force generated during the pouring of the molten steel caused the coke to rapidly melt and fully mix with the molten steel. It was detected that the 2640kg of coke increased the carbon content of the molten steel by about 1.4%, and according to the formula for calculating the solidification temperature of molten steel, the solidification temperature of the molten steel decreased by 109.2℃ (78x1.4=109.2℃) from 1515℃ to 1405.8℃, successfully avoiding the occurrence of ladle freezing accidents and ensuring the normal progress of production.

[0028] The above description is only to illustrate the technical solutions of the present application but not to limit the present application. Other modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art should be covered in the scope of claims of the present application as long as they are not deviated from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preventing molten steel from freezing in a ladle during remelting, characterized in that: It includes the following specific steps: S1, Coke preparation: Select coke with a fixed carbon content ≥86%, sulfur content ≤0.6%, and ash content ≤12.5%; S2, Coke Packaging: The selected coke is packaged in standardized manner in polyethylene woven bags with a thickness of ≥0.08mm, and the packaged coke is stored. S3, Ladle Inspection: Before receiving molten steel for recycling, inspect and ensure that the inner wall of the ladle is clean and free of large pieces of frozen slag. S4, Coke addition: 3-5 minutes before the molten steel is poured into the ladle, add packaged coke to the ladle section. The amount of coke added is 1% to 2% of the weight of the molten steel. S5, molten steel addition: Pour the recycled molten steel into the molten iron ladle that has been filled with coke, and use the impact force of the molten steel to melt the coke and mix it with the molten steel.

2. The method for preventing molten steel from freezing in a ladle according to claim 1, characterized in that: The particle size of the coke in S1 is 5mm-30mm.

3. The method for preventing molten steel from freezing in a ladle according to claim 1, characterized in that: The weight of each bag of coke in S2 is controlled at 20±0.5kg.

4. The method for preventing molten steel from freezing in a ladle according to claim 1, characterized in that: The amount of coke added in S4 is adjusted according to the temperature of the molten steel and the inner wall temperature of the ladle, specifically as follows: 1) When the temperature of the molten steel to be recycled is >1540℃ and the temperature of the inner wall of the ladle is >800℃, the amount of coke added is 1.0% of the weight of the molten steel to be recycled; 2) When the temperature of the molten steel to be recycled is >1540℃ and the temperature of the inner wall of the ladle is ≤800℃, the amount of coke added is 1.2% of the weight of the molten steel to be recycled; 3) When the temperature of the molten steel to be recycled is ≤1540℃ and the temperature of the inner wall of the ladle is >800℃, the amount of coke added is 1.5% of the weight of the recycled steel; 4) When the temperature of the molten steel to be recycled is ≤1540℃ and the temperature of the inner wall of the molten iron ladle is ≤800℃, the amount of coke added is 2.0% of the weight of the molten steel to be recycled.

5. The method for preventing molten steel from freezing in a ladle according to claim 1, characterized in that: The feeding method in S4 can be manual throwing or mechanical conveying to feed coke, and ensure that the coke is evenly distributed at the bottom of the molten iron ladle.

Images