CN115418429A - Method for smelting 200-series stainless steel in AOD furnace - Google Patents
Method for smelting 200-series stainless steel in AOD furnace Download PDFInfo
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
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- C21C7/0685—Decarburising of stainless steel
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- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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Abstract
The invention belongs to the field of steelmaking, and particularly relates to a method for smelting 200-series stainless steel in an AOD furnace, which sequentially comprises the following steps: (1) primary slagging-off: adding molten iron, a slagging agent and high-carbon ferrochrome into the AOD furnace, and then slagging off; (2) adding high-carbon ferromanganese: adding a slagging agent after slagging off, and adding more than or equal to 40kg/t of high-carbon ferromanganese at 1600-1630 ℃; (3) decarburization and manganese conservation: controlling the decarburization temperature to be 1630-1685 ℃, reducing the proportion of oxygen in the decarburization gas along with the increase of the decarburization temperature, and finishing decarburization when the content of C in the molten steel is lower than 0.1 wt%; (4) reduction: adding a reducing agent and a slagging agent, converting, deslagging, detecting the temperature and components of molten steel, introducing argon gas, converting and then tapping; the method improves the consumption of the high-carbon ferromanganese to more than 40kg/t, controls the smelting time to be less than or equal to 125min, meets the requirement of mass production, and effectively reduces the unit consumption of electrolytic manganese.
Description
Technical Field
The invention belongs to the field of steelmaking, and particularly relates to a method for smelting 200-series stainless steel in an AOD furnace.
Background
Manganese is one of indispensable elements in steel production, is an important alloy element for steel making, and is mainly used for improving the mechanical property of steel, increasing the strength, hardness, ductility, wear resistance and the like of the steel. Manganese is used in a large amount because of its large proportion in the 200-series stainless steel.
The manganese alloy used for smelting 200 series stainless steel by the AOD furnace comprises high-silicon silicomanganese, ordinary silicon silicomanganese, high-carbon ferromanganese, low-carbon ferromanganese, electrolytic manganese and the like, wherein the unit consumption of the electrolytic manganese is 30 kg/t-50 kg/t according to different tons of steel.
In 2021, the market situation of raw materials is changing rapidly, the price of raw materials is rising continuously, and the production cost of 200 series stainless steel is rising continuously. Among the raw materials, the price rise of electrolytic manganese is particularly serious in the early 2021 year, and the price rise is from 10000 yuan/ton to nearly 40000 yuan/ton, which becomes one of the most main factors influencing the cost in the production of 200 series stainless steel.
The AOD smelting time of a steel plant is matched with the continuous casting and drawing speed, the AOD smelting time control cannot exceed 125 minutes generally according to the production condition of stainless steel, otherwise, the AOD smelting time control cannot be applied to large-scale production. At present, a relatively mature and stable process for increasing the consumption of high-carbon ferromanganese in AOD smelting of 200 series stainless steel does not exist, and when the smelting time is controlled within 125 minutes, the average unit consumption of the high-carbon ferromanganese is only about 13kg/t. If the amount of high-carbon ferromanganese is increased, the manganese content in the molten steel is greatly increased, the decarburization efficiency is reduced, the decarburization time is increased, the smelting period is obviously increased, and the method cannot be implemented in large-scale production.
Therefore, the method improves the dosage of the high-carbon ferromanganese without increasing the smelting time, and has important significance for reducing cost and improving efficiency of the current AOD smelting 200 series stainless steel and finishing the national target of energy consumption double control.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and aims to provide a method for smelting 200 series stainless steel by using an AOD furnace, which can improve the use amount of high-carbon ferromanganese of the 200 series stainless steel smelted by using the AOD furnace to be more than 40kg/t, such as 40-70 kg/t, control the smelting time within 125 minutes, meet the large production requirement, effectively reduce the unit consumption of electrolytic manganese and realize cost reduction and efficiency improvement.
A method for smelting 200 series stainless steel by using an AOD furnace, which sequentially comprises the following steps:
(1) Primary slag skimming: adding molten iron and a slagging agent into an AOD furnace for blowing, heating to 1580-1620 ℃ (1590 ℃, 1600 ℃ and 1610 ℃), adding high-carbon ferrochrome for continuous blowing, and slagging when the temperature of the molten steel reaches 1510-1580 ℃ (1520 ℃, 1530 ℃, 1540 ℃, 1550 ℃, 1560 ℃ and 1570 ℃);
(2) Adding high-carbon ferromanganese: removing slag, adding slag former, heating to 1600-1630 deg.C (such as 1605 deg.C, 1610 deg.C, 1615 deg.C, 1620 deg.C, 1625 deg.C), and adding high-carbon ferromanganese into molten steel at a ratio of 40kg/t or more;
(3) Decarburization and manganese preservation: controlling the decarburization temperature to be 1630-1685 ℃ (such as 1640 ℃, 1650 ℃, 1660 ℃, 1670 ℃ and 1680 ℃), wherein the decarburization gas is oxygen and inert gas, the oxygen content in the decarburization gas is reduced with the increase of the decarburization temperature, the initial oxygen content in the decarburization gas is 60% -100% (such as 65%, 70%, 75%, 80%, 85%, 90% and 95%) by volume percent, when the temperature reaches 1650 ℃, the oxygen content in the decarburization gas starts to be reduced, the final oxygen content is 18-23% (such as 19%, 20%, 21% and 22%) and the decarburization is finished when the C content in the molten steel is lower than 0.1 wt%;
(4) Reduction: adding a reducing agent and a slagging agent, sequentially introducing oxygen and nitrogen for converting, discharging slag, detecting the temperature and components of molten steel, adjusting the components of the molten steel according to the component requirements of a target steel grade, introducing argon for converting, and then discharging steel; if the manganese content in the molten steel is lower than the component requirement of the target steel grade, the manganese content in the molten steel is adjusted by supplementing electrolytic manganese so as to meet the component requirement of the target steel grade;
the smelting time of the method for smelting 200 series stainless steel by using the AOD furnace is less than or equal to 125min.
The invention adopts a double-slag-method AOD furnace smelting process, and realizes the one-time reverse slag skimming amount of more than 80 percent by controlling the one-time reverse slag skimming condition. The primary slag skimming before the addition of the high-carbon ferromanganese has the following advantages: firstly, the purpose of reducing phosphorus can be achieved, and conditions are created for the subsequent charging of high-carbon ferromanganese into the furnace. The high-carbon ferromanganese and the silicon-manganese alloy both have higher phosphorus content, and part of phosphorus in the molten iron is removed through slag removal operation to prevent the phosphorus of terminal components from exceeding the standard; secondly, the silicon in the blast furnace molten iron and the high-carbon ferrochrome is preferentially oxidized and enters the slag in the early stage, and the slag containing a large amount of silicon dioxide can be discharged out of the furnace once the slag is removed, so that the subsequent consumption of slagging agents (lime and fluorite) is saved; thirdly, the addition of the follow-up slagging agent (mainly lime) is reduced after slagging off, the slag layer becomes thin, and the removal of CO gas generated in the furnace is facilitated, so that the decarburization and the manganese preservation are promoted.
In the above method for smelting 200-series stainless steel in an AOD furnace, as a preferred embodiment, in the step (1), the molten iron is blast furnace molten iron, and the charging temperature of the blast furnace molten iron is 1250 to 1350 ℃ (for example, 1260 ℃, 1270 ℃, 1280 ℃, 1290 ℃, 1300 ℃, 1310 ℃, 1320 ℃, 1330 ℃, 1340 ℃); preferably, the blast furnace molten iron comprises the following components in percentage by weight: 4 to 6 percent of C, 0.5 to 1.5 percent of silicon, 3 to 5 percent of chromium, 0.5 to 2.0 percent of manganese, 0.03 to 0.04 percent of copper, 1.3 to 1.8 percent of nickel, less than 0.05 percent of phosphorus, less than 0.2 percent of sulfur, and the balance of Fe and inevitable impurities.
In the above method for smelting 200 series stainless steel in the AOD furnace, as a preferred embodiment, in the step (1), after the high carbon ferrochrome is added, the molten steel composition is adjusted to: 2 to 4 percent of C, 0 to 0.2 percent of silicon, 13.5 to 15 percent of chromium, 0.2 to 1.5 percent of manganese, 0.03 to 0.04 percent of copper, 1.1 to 1.6 percent of nickel, less than 0.05 percent of phosphorus, less than 0.15 percent of sulfur, and the balance of Fe and inevitable impurities.
In the above method for smelting 200 series stainless steel in the AOD furnace, as a preferred embodiment, in the step (1), the gas used for the blowing is a mixed gas of 6:1 in a volume ratio of oxygen to nitrogen, wherein the oxygen pressure is 1.7 to 1.8MPa.
In the above method for smelting 200-series stainless steel in an AOD furnace, as a preferred embodiment, in the step (1), the temperature during slag removal is 1520 to 1580 ℃ (e.g., 1530 ℃, 1540 ℃, 1550 ℃, 1560 ℃ and 1570 ℃); preferably, the fluidity of the slag during slag skimming is 0.1 to 0.4 pas (for example, 0.15 pas, 0.2 pas, 0.25 pas, 0.3 pas, 0.35 pas), and the surface of the slag has no agglomerates; preferably, the slag skimming amount reaches more than 80 percent; preferably, the thickness of the slag layer in the furnace after slagging-off is less than 30mm.
In the above method for smelting 200 series stainless steel in an AOD furnace, as a preferred embodiment, in the step (2), the temperature is raised by feeding oxygen simultaneously to the top lance and the side lance of the AOD furnace; preferably, the time for heating to 1600-1630 ℃ (e.g., 1605 ℃, 1610 ℃, 1615 ℃, 1620 ℃, 1625 ℃) is less than or equal to 8min; preferably, the time for heating to 1600-1630 ℃ is 6-8 min (e.g. 6.5min, 7min, 7.5 min); preferably, the amount of high carbon ferromanganese added is 40 to 70kg/t (e.g., 45kg/t, 50kg/t, 55kg/t, 60kg/t, 65 kg/t).
In the invention, top-bottom combined blowing is carried out by adopting a mode of simultaneously feeding oxygen by a top gun and a side gun of the AOD furnace so as to rapidly heat. The temperature is quickly increased to 1600-1630 ℃, the decarburization rate can be increased, the heat utilization rate can be increased, conditions are created for adding high-carbon ferromanganese or other cold materials, and the smelting time is shortened.
The temperature of adding high-carbon ferromanganese is controlled to be 1600-1630 ℃, manganese and carbon can have the problem of selective oxidation at the steelmaking temperature, the temperature is controlled to be 1600-1630 ℃, and carbon in molten steel can be oxidized in preference to manganese; when the temperature is lower than 1600 ℃, high-carbon ferromanganese is added, manganese is oxidized before carbon, the oxidation of carbon is inhibited, the decarburization time is prolonged, the manganese is vaporized and evaporated due to the oxidation of manganese and long-time decarburization, and the yield of manganese is greatly reduced. The melting of high-carbon ferromanganese in a furnace is a gradual process and needs a certain time. When the adding temperature is higher than 1630 ℃, the decarburization speed of the molten pool is high, part of high-carbon ferromanganese may not be completely melted and enter molten steel when decarburization reaches the end point, and the decarburization is judged to be finished according to the carbon content of the molten steel at the moment and enters the reduction step, so that the carbon content at the end point exceeds the standard, and the molten steel is scrapped.
In the above method for smelting 200 series stainless steel in an AOD furnace, as a preferred embodiment, in the step (3), the inert gas is nitrogen or argon, and more preferably nitrogen for steel making.
In the above method for smelting 200 series stainless steel in the AOD furnace, as a preferred embodiment, in the step (3), oxygen and inert gas are blown into the furnace by using a side lance in the decarburization manganese-keeping step.
In the above method for smelting 200-series stainless steel in an AOD furnace, as a preferred embodiment, in the step (3), after the decarburization temperature has reached 1650 to 1660 ℃ (e.g., 1651 ℃, 1652 ℃, 1653 ℃, 1654 ℃, 1655 ℃, 1656 ℃, 1657 ℃, 1658 ℃ and 1659 ℃), the ratio of oxygen gas to inert gas volume is (0.8 to 1.2): 1 (e.g., 0.9, 1.0; when the decarburization temperature reaches 1670-1675 ℃ (e.g. 1671 ℃, 1672 ℃, 1673 ℃ and 1674 ℃), the volume ratio of oxygen to inert gas is 1 (1.8-2.2) (e.g. 1; after the decarburization temperature reaches 1680-1685 ℃, the volume ratio of oxygen to inert gas is 1 (3.8-4.2) (for example, 1.
In the preferred embodiment of the present invention, after the decarburization temperature reaches 1650 ℃, the partial pressure of CO is reduced by increasing the amount of nitrogen gradually to accelerate the discharge of CO from the molten steel, in order to ensure that the decarburization is carried out smoothly, the temperature is constant and the decarburization is carried out with a constant temperature, in accordance with the "C-chromium-temperature" three-phase equilibrium relationship. If the ratio of nitrogen is not increased, the partial pressure of CO is increased, and decarburization is suppressed.
At a temperature of 1650 ℃ or higher, the carbon content of the molten steel is low, and at this time, if pure oxygen is used for blowing, the proportion of oxygen used for decarburization is small, most of the oxygen oxidizes chromium, iron and the like in the molten steel, so that iron oxide in slag is increased, and manganese in the molten steel is further oxidized or burned. Therefore, when the temperature is higher than 1650 ℃, the pure oxygen blowing can cause the oxidation burning loss of the metal and reduce the metal yield.
In the above method for smelting 200 series stainless steel in the AOD furnace, as a preferred embodiment, in the step (3), the decarburization temperature is 1630 ℃, and the volume ratio of oxygen to inert gas is 2:1; the decarburization temperature reaches 1650 ℃, and the volume ratio of oxygen to inert gas is 1:1; the decarburization temperature reaches 1670 ℃, and the volume ratio of oxygen to inert gas is 1:2; the decarburization temperature reaches 1680 ℃, and the volume ratio of oxygen to inert gas is 1:4; preferably, after the decarburization is finished, the temperature of the molten steel is 1650-1685 ℃ (for example 1655 ℃, 1660 ℃, 1665 ℃, 1670 ℃, 1675 ℃ and 1680 ℃), the slag in the furnace is piled up, and the slag-forming agent is supplemented to the molten steel when the piled up slag does not meet the requirement; preferably, in step (3), the basicity of the slag, i.e. CaO/SiO in the slag 2 The mass fraction ratio is not less than 3.5.
In the invention, after decarburization is finished, the content of terminal carbon can be reduced to below 0.1wt% when the temperature of molten steel is detected to be between 1650 and 1685 ℃. The slag pile meets the requirements, the reaction decarburization is normal, and the metal oxide is less.
In the above method for smelting 200 series stainless steel in the AOD furnace, as a preferred embodiment, the slag former in step (1), step (2) and step (3) is lime; preferably, the amount of the slag former used in the step (1) is 35 to 45kg/t (e.g., 37.5kg/t, 40kg/t, 42.5 kg/t); preferably, the amount of the slag former used in the step (2) is 30 to 40kg/t (e.g., 31kg/t, 32kg/t, 33kg/t, 34kg/t, 35kg/t, 36kg/t, 37kg/t, 38kg/t, 39 kg/t); preferably, the amount of slag former used in step 3 is 25 to 35kg/t (e.g., 26kg/t, 27kg/t, 28kg/t, 29kg/t, 30kg/t, 31kg/t, 32kg/t, 33kg/t, 34 kg/t).
In the invention, manganese and carbon are selectively oxidized in molten steel of the AOD furnace. In order to ensure that carbon is oxidized preferentially to manganese and achieve the effects of decarburization and manganese protection, the temperature of a molten pool after high-carbon ferromanganese is fed into a furnace must be higher than the oxidation conversion temperature of carbon and manganese. In a preferred embodiment of the present invention, the addition conditions and oxygen supply system of the high carbon ferromanganese are further combined: the temperature of the molten pool is raised to 1600-1630 ℃, high-carbon ferromanganese is added, the gas supply proportion is adjusted, the oxidation and burning loss of terminal manganese are reduced, and the decarburization time is shortened.
In the above method for smelting 200 series stainless steel in an AOD furnace, as a preferred embodiment, in the step (4), the reducing agent is a silicomanganese alloy; preferably, the silicon-manganese alloy is at least one of high silicon-manganese, medium silicon-manganese and common silicon-manganese; preferably, the silicon-manganese alloy is used in an amount of 70 to 95kg/t (e.g., 75kg, 80kg, 85kg, 90 kg).
In the preferred embodiment of the invention, the dosage of the silicon-manganese alloy is 70-95 kg, and silicon in the silicon-manganese alloy has three uses, namely, the silicon-manganese alloy is mainly used for reducing oxides such as oxidized chromium, manganese, iron and the like in an oxidation period, so that the metal yield is improved; secondly, according to the temperature control requirement, oxygen is fed to oxidize a part of silicon to increase the temperature of the molten steel; thirdly, the silicon in the silicon-manganese alloy is partially consumed by oxygen feeding and temperature rising, the oxide is partially consumed by reduction, and the rest silicon is left in molten steel for alloying. The silicon content in the molten steel of the 200 series stainless steel is required to be 0.3-0.7%, so that the proper amount of silicon in the silicon-manganese alloy is required to be alloyed after the silicon in the silicon-manganese alloy is heated and reduced. When the amount of the added silicon-manganese alloy is small, the silicon is insufficient, the oxide in the silicon-free slag can not be reduced due to no silicon, the chromium and manganese oxides are wasted, the yield is low, the content of the silicon in the molten steel is lower than 0.3 percent, and the components are unqualified; if the silicon content is excessive, the silicon content in the molten steel exceeds 0.7%, and the components exceed the standard and are not qualified.
In the method for smelting 200 series stainless steel in the AOD furnace, as a preferred embodiment, in the step (4), the time for introducing oxygen to blow is 1-4 min; preferably, the time for blowing the nitrogen is 5-7 min; preferably, the time for blowing the argon is 2-4 min.
In the above method for smelting 200 series stainless steel in AOD furnace, as a preferred embodiment, in step (4), the basicity of slag, i.e., caO/SiO in slag 2 The mass fraction ratio is controlled to be 1.8 to 2.4 (for example, 1.9, 2.0, 2.1, 2.2, 2.3); preferably, the slagging agent is in fluorite pellets, fluorite ore and ferrosiliconAt least one of; preferably, the slagging agent is fluorite balls; preferably, the amount of the fluorite balls is 18-22 kg/t (such as 19kg/t, 20kg/t, 21 kg/t); preferably, the temperature of the reducing agent after all the reducing agent is fed into the furnace is controlled to be 1550-1600 ℃ (such as 1560 ℃, 1570 ℃, 1580 ℃ and 1590 ℃); preferably, all slag in the AOD furnace is liquefied during slag discharging and has fluidity, and the slag is taken out to be observed to be grey white or white; preferably, the tapping temperature is 1530 ℃ or higher.
In the preferred embodiment of the invention, the reduction of the manganese oxide is promoted in the reduction period through alkalinity control, temperature control and feeding control, so that the yield of manganese is improved, and the aim of reducing the consumption of electrolytic manganese by increasing the use amount of high-carbon ferromanganese by AOD is fulfilled. Adopting silicomanganese alloy as a reducing agent, reducing oxides of chromium, manganese and the like in a furnace by silicon in the alloy, removing impurities, feeding oxygen to burn silicon, heating for 1-4 minutes, and controlling the temperature of a molten pool after all reducing materials are fed into the furnace to be 1550-1600 ℃; stopping feeding oxygen, switching nitrogen to reduce for 5-7 min, making the slag in the furnace completely liquid and have fluidity, taking the slag, observing the color ash or white slag, and discharging the slag. Reducing for 2-4 minutes by argon, controlling the temperature to be more than 1530 ℃, and tapping. The yield of manganese reaches more than 93 percent.
Has the advantages that:
the method is suitable for smelting 200 series stainless steel by the AOD furnace, can improve the consumption of the high-carbon ferromanganese to 40-70 kg/t, controls the smelting time to be less than or equal to 125min, and meets the large production requirement of smelting 200 series stainless steel by the AOD furnace by using the high-carbon ferromanganese.
The invention can improve the consumption of high-carbon ferromanganese, effectively realize the aims of reducing the cost and improving the quality of the smelted stainless steel, and has important significance for guiding the large-scale production of 200 series stainless steel.
Detailed Description
The invention is further described with reference to specific embodiments, without limiting its scope.
The silicon-manganese alloy used in the embodiment of the invention comprises the following main components in percentage by weight:
high silicon manganese: 0.20% of C, 61% of Mn, 28% of Si, 0.10% of P, and the balance of Fe and inevitable impurities; medium silicon manganese: 0.90% of C, 65% of Mn, 20% of Si, 0.10% of P, and the balance of Fe and inevitable impurities. Ordinary silicon, silicon and manganese: 1.50% of C, 65% of Mn, 18% of Si, 0.18% of P, and the balance of Fe and inevitable impurities.
The high-carbon ferromanganese used in the embodiment of the invention comprises the following components in percentage by weight: 7% of C, 71% of manganese, 0.16% of phosphorus, 0.01% of sulfur, 0.35% of silicon, and the balance of iron and inevitable impurities.
The high-carbon ferrochrome used in the embodiment of the invention comprises the following components in percentage by weight: 7.4 percent of C, 52 percent of chromium, 3.5 percent of silicon, 0.022 percent of phosphorus, 0.029 percent of sulfur, and the balance of iron and inevitable impurities.
The% not specifically described in the following examples is a mass percentage.
Example 1
The 200 series steel smelted in the embodiment has the following component requirements: 0.11 to 0.16 percent of C, 0.3 to 0.7 percent of silicon, 13.0 to 13.4 percent of chromium, 9.70 to 10.5 percent of manganese, 1.0 to 1.8 percent of nickel, less than 0.05 percent of phosphorus and less than 0.005 percent of sulfur.
(1) 56 tons of blast furnace molten iron is added into the AOD furnace, and the molten iron comprises the following components: 4.5% of C, 0.85% of silicon, 4.32% of chromium, 1.23% of manganese, 1.46% of nickel, 0.04% of phosphorus, 0.13% of sulfur and 0.035% of copper, 40kg/t of lime is added, and the weight ratio of oxygen: the nitrogen is 6: blowing at a ratio of 1 to oxygen consumption of 1300m 3 When the temperature reaches 1603 ℃, 15 tons of high-carbon ferrochrome (with the chromium content of 52 wt%) is added, and the molten steel is regulated to have the following components: 3.02% of C, 0.011% of silicon, 13.76% of chromium, 0.76% of manganese, 0.031% of copper, 1.23% of nickel, 0.039% of phosphorus and 0.076% of sulfur. Continuing the blowing at the same gas ratio until the oxygen consumption reaches 2260m 3 And (4) carrying out slag skimming operation (the temperature reaches 1511 ℃), wherein the fluidity of the slag is 0.2 Pa.S during slag skimming, no conglomeration exists on the surface of the slag, and the thickness of a slag layer is detected to be about 25mm after the slag skimming is finished.
(2) After the slag is reversely removed, 40kg/t of lime is added, top-bottom combined blowing is carried out by adopting a mode that a top gun and a side gun of an AOD furnace simultaneously send oxygen, the temperature is rapidly increased to 1620 ℃, and 56kg/t of high-carbon ferromanganese is added.
(3) Continuously heating to the decarbonization temperature of 1641 ℃, wherein the ratio of oxygen to inert gas is 2:1; the decarburization temperature reaches 1655 ℃, the ratio of oxygen to inert gas is 1:1, and 27kg/t lime is added; the decarburization temperature reaches 1671 ℃, and the ratio of oxygen to inert gas is 1:2; the decarburization temperature reaches 1683 ℃, and the ratio of oxygen to inert gas is 1:4. Detecting the carbon content of the molten steel to be 0.08 percent and the molten steel temperature to be 1681 ℃.
(4) 60kg/t of high-silicon silicomanganese, 13kg/t of ordinary silicon silicomanganese and 22kg/t of fluorite balls are added, oxygen is fed for 2 minutes, nitrogen is fed for 7 minutes, and slag is discharged; measuring the temperature of the molten steel by 1575 ℃, detecting the components of the molten steel, and supplementing 4.12kg/t of electrolytic manganese to obtain the following components: 0.11% of C, 0.46% of silicon, 13.23% of chromium, 9.75% of manganese, 1.10% of nickel, 0.046% of phosphorus and 0.002% of sulfur, argon is fed for 3 minutes for tapping, and the furnace finishes smelting in 116 minutes.
The unit consumption of electrolytic manganese is reduced to 4.12kg/t, the yield of manganese is 94.22 percent, and the smelting is finished within 125 minutes, which shows that the smelting of the furnace steel for improving the consumption of high-carbon ferromanganese is successful.
Example 2
The 200 series steel smelted in the embodiment has the following component requirements: 0.10 to 0.13 percent of C, 0.3 to 0.7 percent of silicon, 13.5 to 14 percent of chromium, 9.50 to 10.2 percent of manganese, 1.0 to 1.8 percent of nickel, less than 0.05 percent of phosphorus and less than 0.005 percent of sulfur.
(1) 56 tons of blast furnace molten iron is added into the AOD furnace, and the molten iron comprises the following components: c4.7%, silicon 0.96%, chromium 4.01%, manganese 1.03%, nickel 1.43%, phosphorus 0.040%, sulfur 0.13%, copper content 0.034%, adding lime 40kg/t, adding oxygen: the nitrogen is 6: blowing at a ratio of 1 until the oxygen consumption reaches 1210m 3 When the temperature reaches 1586 ℃, 15.3 tons of high-carbon ferrochrome (52%) are added, and the molten steel components are adjusted as follows: 2.78% of C, 0.08% of silicon, 13.95% of chromium, 0.69% of manganese, 0.032% of copper, 1.25% of nickel, 0.038% of phosphorus and 0.056% of sulfur. The same gas ratio is continuously blown until the oxygen consumption reaches 2360m 3 (the temperature reaches 1533 ℃), carrying out slag skimming operation, wherein the fluidity of the slag is 0.3 Pa.S during slag skimming, no conglomeration exists on the surface of the slag, and the thickness of a slag layer is detected to be about 16mm after the slag skimming is finished.
(2) After the slag is reversely removed, 40kg/t of lime is added, top-bottom combined blowing is carried out by adopting a mode that a top gun and a side gun of an AOD furnace simultaneously send oxygen, the temperature is quickly raised to 1622 ℃, and 47kg/t of high-carbon ferromanganese is added.
(3) Continuously heating, wherein the decarburization temperature reaches 1635 ℃, and the ratio of oxygen to inert gas is 2:1; the decarburization temperature reaches 1656 ℃, the ratio of oxygen to inert gas is 1:1, and 26kg/t lime is added; after the decarburization temperature reaches 1673 ℃, the ratio of oxygen to inert gas is 1:2; after the decarburization temperature reaches 1685 ℃, the ratio of oxygen to inert gas is 1:4. Detecting the carbon content of the molten steel to be 0.07 percent and the molten steel temperature to be 1679 ℃.
(4) Adding 33kg/t of high-silicon silicomanganese, 60kg/t of ordinary silicon silicomanganese and 20kg/t of fluorite balls, feeding oxygen for 2 minutes and nitrogen for 7 minutes, and discharging residues; the temperature of the molten steel is 1578 ℃, and the detected molten steel comprises the following components: 0.12 percent of C, 0.52 percent of silicon, 13.64 percent of chromium, 9.85 percent of manganese, 1.08 percent of nickel, 0.048 percent of phosphorus and 0.002 percent of sulfur, and argon is fed to stir for 3 minutes without supplementing electrolytic manganese to tap steel, and the furnace finishes smelting in 112 minutes.
The unit consumption of electrolytic manganese is reduced to 0kg/t, the yield of manganese is 94.01 percent, and the smelting is completed within 125 minutes, which shows that the smelting of the furnace steel improves the consumption of high-carbon ferromanganese.
Example 3
The 200 series steel smelted in the embodiment has the following component requirements: 0.11 to 0.16 percent of C, 0.3 to 0.7 percent of silicon, 13.0 to 13.4 percent of chromium, 9.70 to 10.5 percent of manganese, 1.0 to 1.8 percent of nickel, less than 0.05 percent of phosphorus and less than 0.005 percent of sulfur.
(1) 57 tons of blast furnace molten iron is added into the AOD furnace, and the molten iron comprises the following components: 5.1% of C, 0.79% of silicon, 3.96% of chromium, 1.24% of manganese, 1.45% of nickel, 0.038% of phosphorus, 0.09% of sulfur and 0.035% of copper, 43kg/t of lime is added, and the weight ratio of oxygen: the nitrogen is 6: blowing at a ratio of 1 to oxygen consumption of 1169m 3 When the temperature reaches 1598 ℃, 16.1 tons of high-carbon ferrochrome (52 percent) is added, and the molten steel is adjusted to have the following components: 3.31 percent of C, 0.13 percent of silicon, 13.67 percent of chromium, 0.77 percent of manganese, 0.032 percent of copper, 1.26 percent of nickel, 0.037 percent of phosphorus and 0.046 percent of sulfur. Continuing the blowing at the same gas ratio until the oxygen consumption reaches 2280m 3 And (3) (the temperature reaches 1523 ℃), carrying out slag skimming operation, wherein the fluidity of the slag is 0.2 Pa.S during slag skimming, no conglomeration exists on the surface of the slag, and the thickness of a slag layer is detected to be about 15mm after the slag skimming is finished.
(2) After the slag is reversely removed, 40kg/t of lime is added, top-bottom combined blowing is carried out by adopting a mode that a top gun and a side gun of an AOD furnace simultaneously send oxygen, the temperature is quickly raised to 1628 ℃, and 53kg/t of high-carbon ferromanganese is added.
(3) Continuously heating to 1639 ℃, wherein the ratio of oxygen to inert gas is 2:1; the decarburization temperature reaches 1652 ℃, the ratio of oxygen to inert gas is 1:1, and 26kg/t lime is added; after the decarburization temperature reaches 1671 ℃, the ratio of oxygen to inert gas is 1:2; after the decarburization temperature reaches 1681 ℃, the ratio of oxygen to inert gas is 1:4. The carbon content of the molten steel is detected to be 0.08 percent, and the temperature of the molten steel is 1679 ℃.
(4) Adding 91kg/t of medium silicon-manganese silicate and 21kg/t of fluorite balls, feeding oxygen for 2 minutes and nitrogen for 7 minutes, and discharging residues; the temperature of the molten steel is 1578 ℃, and the detected molten steel comprises the following components: 0.12% of C, 0.36% of silicon, 13.16% of chromium, 9.91% of manganese, 1.05% of nickel, 0.044% of phosphorus and 0.001% of sulfur, wherein electrolytic manganese is not supplemented any more, argon is fed and stirring is carried out for 3 minutes to tap, and the furnace finishes smelting in 117 minutes.
The unit consumption of electrolytic manganese is reduced to 0kg/t, the manganese yield is 93.11 percent, and the smelting is finished within 125 minutes, which shows that the smelting of the furnace steel for improving the consumption of the high-carbon ferromanganese is successful.
Comparative example 1
The 200 series steel smelted in the comparative example has the following component requirements: 0.11 to 0.16 percent of C, 0.3 to 0.7 percent of silicon, 13.0 to 13.4 percent of chromium, 9.70 to 10.5 percent of manganese, 1.0 to 1.8 percent of nickel, less than 0.05 percent of phosphorus and less than 0.005 percent of sulfur.
(1) 57 tons of blast furnace molten iron is added into the AOD furnace, and the molten iron comprises the following components: c5%, silicon 0.92%, chromium 4.23%, manganese 1.08%, nickel 1.41%, phosphorus 0.042%, sulfur 0.16%, copper 0.036%, adding lime 40kg/t, adding oxygen: the nitrogen is 6: blowing at a ratio of 1 until oxygen consumption reaches 1600m 3 When the temperature reaches 1615 ℃, 15.3 tons of high-carbon ferrochrome (52%) are added, and the molten steel components are adjusted as follows: 2.35 percent of C, 0.16 percent of silicon, 13.66 percent of chromium, 0.65 percent of manganese, 0.031 percent of copper, 1.22 percent of nickel, 0.040 percent of phosphorus and 0.053 percent of sulfur, and continuously converting the mixture in the same gas proportion until the oxygen consumption is 2560m 3 And (the temperature reaches 1566 ℃) carrying out slag skimming operation, wherein the fluidity of the slag is 0.35 Pa.S during slag skimming, no conglomeration exists on the surface of the slag, and the thickness of a slag layer is detected to be about 50mm after the slag skimming is finished.
(2) And adding 40kg/t of lime after reverse slagging-off, carrying out top-bottom combined blowing by adopting a mode of simultaneously sending oxygen by using an AOD furnace top gun and a side gun, quickly heating to 1613 ℃, and adding 60kg/t of high-carbon ferromanganese.
(3) Continuing to heat up, wherein the ratio of oxygen to inert gas is 2:1 after the decarburization temperature reaches 1630 ℃; after the decarburization temperature reaches 1650 ℃, the proportion of oxygen and inert gas is 1:1, and 26.67kg/t lime is added; after the decarburization temperature reaches 1670 ℃, the ratio of oxygen to inert gas is 1:2; after the decarburization temperature reaches 1680 ℃, the ratio of oxygen to inert gas is 1:4. Detecting the carbon content of the molten steel to be 0.10 percent and the temperature of the molten steel to be 1723 ℃.
(4) Adding 66.67kg/t of high-silicon silicomanganese, 13.33kg/t of ordinary silicon silicomanganese and 20kg/t of fluorite balls, feeding oxygen for 1 minute and nitrogen for 7 minutes, and discharging residues; temperature measurement of molten steel 1618 ℃, components of molten steel: 0.12 percent of C, 0.56 percent of silicon, 13.03 percent of chromium, 9.25 percent of manganese, 1.13 percent of nickel, 0.049 percent of phosphorus and 0.003 percent of sulfur, 400kg of electrolytic manganese is supplemented, argon is fed and stirred for 3 minutes to tap, and the furnace finishes smelting in 135 minutes.
Because the slag removal amount does not reach the standard, the decarburization efficiency is low, the heat release amount is high due to severe metal oxidation, the molten steel temperature is too high after decarburization is finished, the smelting time exceeds 125 minutes, and meanwhile, the manganese yield is 91.3%, which indicates that the smelting of the furnace steel for improving the use amount of high-carbon ferromanganese is unsuccessful.
Comparative example 2
The 200 series steel smelted in the comparative example has the following component requirements: 0.11 to 0.16 percent of C, 0.3 to 0.7 percent of silicon, 13.0 to 13.4 percent of chromium, 9.70 to 10.5 percent of manganese, 1.0 to 1.8 percent of nickel, less than 0.05 percent of phosphorus and less than 0.005 percent of sulfur.
(1) 58 tons of blast furnace molten iron is added into the AOD furnace, and the molten iron comprises the following components: 5.11% of C, 0.66% of silicon, 3.85% of chromium, 0.96% of manganese, 1.41% of nickel, 0.038% of phosphorus, 0.15% of sulfur and 0.034% of copper, 40kg/t of lime is added, and the weight ratio of oxygen: the nitrogen is 6: blowing at a ratio of 1 to 1309m oxygen consumption 3 Adding 15.5 tons of high-carbon ferrochrome (52 percent) when the temperature reaches 1589 ℃, and adjusting the molten steel components as follows: 3.35% of C, 0.09% of silicon, 13.75% of chromium, 0.72% of manganese, 0.032% of copper, 1.22% of nickel, 0.041% of phosphorus and 0.063% of sulfur, and continuously blowing until the oxygen consumption reaches 2360m according to the same gas proportion 3 (the temperature reaches 1522 ℃) and slag skimming is carried out, the fluidity of the slag is 0.25 Pa.S during slag skimming, and no conglomeration exists on the surface of the slagAnd after the slag is completely removed, detecting the thickness of a slag layer to be about 20mm.
(2) After the slag is reversely removed, 40kg/t of lime is added, top-bottom combined blowing is carried out by adopting a mode that a top gun and a side gun of an AOD furnace simultaneously send oxygen, the temperature is rapidly increased to 1613 ℃, and 53.33kg/t of high-carbon ferromanganese is added.
(3) Continuously heating, wherein the decarburization temperature reaches 1639 ℃, and the ratio of oxygen to inert gas is 2:1; after the decarburization temperature reaches 1650 ℃, the proportion of oxygen and inert gas is 1:1, and 26.67kg/t lime is added; after the decarburization temperature reaches 1691 ℃, the ratio of oxygen to inert gas is 1:2; after the decarburization temperature reached 1708 ℃, the ratio of oxygen to inert gas was 1:4. Detecting the carbon content of the molten steel to be 0.09 percent and the temperature of the molten steel to be 1709 ℃.
(4) 26.67kg/t of high-silicon silicomanganese, 66.67kg/t of ordinary silicon silicomanganese and 18.67kg/t of fluorite balls are added, oxygen is fed for 1 minute, nitrogen is fed for 7 minutes, and slag is discharged; measuring the temperature of the molten steel by 1623 ℃, and the components of the molten steel are as follows: 0.14 percent of C, 0.59 percent of silicon, 13.03 percent of chromium, 9.05 percent of manganese, 1.06 percent of nickel, 0.047 percent of phosphorus and 0.002 percent of sulfur, 600kg of electrolytic manganese is added, argon is fed and stirred for 3 minutes to tap, and the furnace finishes smelting in 138 minutes.
Because the temperature of a molten pool reaches 1670 ℃ in the later stage of decarburization, the oxygen supply proportion is adjusted to be larger, excessive oxygen oxidizes the metal in the molten steel, the metal oxidation is serious, the smelting time exceeds 125 minutes, and meanwhile, the manganese yield is 90.2 percent, which indicates that the smelting of the furnace steel for improving the using amount of the high-carbon ferromanganese is unsuccessful.
Comparative example 3
The 200 series steel smelted in the comparative example has the following component requirements: 0.11 to 0.16 percent of C, 0.3 to 0.7 percent of silicon, 13.0 to 13.4 percent of chromium, 9.70 to 10.5 percent of manganese, 1.0 to 1.8 percent of nickel, less than 0.05 percent of phosphorus and less than 0.005 percent of sulfur.
(1) Basically the same as example 1, except that 56kg/t of high carbon ferromanganese in step (2) was added to the furnace together with 40kg/t of lime (bath temperature 1511 ℃) after reverse slagging.
(2) Continuously heating to the decarbonization temperature of 1641 ℃, wherein the ratio of oxygen to inert gas is 2:1; the decarburization temperature reaches 1655 ℃, the ratio of oxygen to inert gas is 1:1, and 27kg/t lime is added; the decarburization temperature reaches 1671 ℃, and the ratio of oxygen to inert gas is 1:2; the decarburization temperature reaches 1683 ℃, and the ratio of oxygen to inert gas is 1:4. At this time, the carbon content of the molten steel is detected to be 0.18%, and the temperature of the molten steel is 1685 ℃. At the moment, the slag pile in the furnace does not meet the requirement, the slag pile is spread flatly, 9kg/t lime is added, after the blowing is carried out for 11 minutes with the oxygen and inert gas ratio of 1:4, the carbon content of the molten steel is detected to be 0.09%, and the temperature of the molten steel is 1675 ℃.
(3) 60kg/t of high-silicon silicomanganese, 13kg/t of ordinary silicon silicomanganese and 22kg/t of fluorite balls are added, oxygen is fed for 2 minutes, nitrogen is fed for 7 minutes, and slag is discharged; measuring the temperature of the molten steel to 1596 ℃, detecting the components of the molten steel, and supplementing 7.30kg/t of electrolytic manganese to obtain the following components: 0.13% of C, 0.42% of silicon, 13.12% of chromium, 9.79% of manganese, 1.09% of nickel, 0.048% of phosphorus and 0.002% of sulfur, argon is fed for 3 minutes for tapping, and the furnace finishes smelting in 133 minutes.
The unit consumption of electrolytic manganese is increased to 7.30kg/t, the manganese yield is 91.02 percent, and the smelting is finished after more than 125 minutes, which indicates that the smelting for increasing the consumption of the high-carbon ferromanganese by the furnace steel is unsuccessful.
Comparative example 4
The 200 series steel smelted in the comparative example has the following component requirements: 0.11 to 0.16 percent of C, 0.3 to 0.7 percent of silicon, 13.0 to 13.4 percent of chromium, 9.70 to 10.5 percent of manganese, 1.0 to 1.8 percent of nickel, less than 0.05 percent of phosphorus and less than 0.005 percent of sulfur.
(1) substantially the same as in example 3 except that 53kg/t of the high-carbon ferromanganese in step (2) was added after the decarburization temperature in step (3) reached 1681 ℃. According to the procedure of example 3, 53kg/t of high-carbon ferromanganese was added after the decarburization temperature reached 1681 ℃ and the ratio of oxygen to inert gas was 1:4. After blowing for 7 minutes, the carbon content of the molten steel is detected to be 0.07 percent, and the temperature of the molten steel is detected to be 1661 ℃.
(2) Adding 91kg/t of medium silicon-manganese silicate and 21kg/t of fluorite balls, feeding oxygen for 2 minutes and nitrogen for 7 minutes, and discharging residues; the temperature of the molten steel is measured to be 1548 ℃, and the detected molten steel comprises the following components: 0.28% of C, 0.62% of silicon, 13.16% of chromium, 9.97% of manganese, 1.05% of nickel, 0.046% of phosphorus and 0.001% of sulfur.
After the high-carbon ferromanganese of the furnace steel is added too late and is not completely melted down in the furnace, the carbon content is detected to be 0.07 percent in the step (3), after a reducing agent is added into the furnace, the high-carbon ferromanganese which is not melted down enters molten steel after furnace slag is melted, the carbon carried in the high-carbon ferromanganese leads the terminal carbon content to exceed 0.12 percent, and the molten steel is scrapped and returned to the furnace for treatment due to unqualified carbon components. The smelting for increasing the dosage of the high-carbon ferromanganese of the furnace steel is not successful.
It should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and the present invention is not limited thereto, and although the present invention has been described in detail with reference to the embodiments, it will be apparent to those skilled in the art that modifications can be made to the technical solutions described in the above-mentioned embodiments, or equivalent substitutions of some technical features, but any modifications, equivalents, improvements and the like within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims (10)
1. A method for smelting 200 series stainless steel by using an AOD furnace is characterized by sequentially comprising the following steps of:
(1) Primary slag skimming: adding molten iron and a slagging agent into an AOD furnace for blowing, heating to 1580-1620 ℃, adding high-carbon ferrochrome for continuous blowing, and slagging off when the temperature of the molten steel reaches 1510-1580 ℃;
(2) Adding high-carbon ferromanganese: adding a slagging agent after slagging off, heating to 1600-1630 ℃, and adding high-carbon ferromanganese into molten steel according to the amount of more than or equal to 40 kg/t;
(3) Decarburization and manganese conservation: controlling the decarburization temperature to be 1630-1685 ℃, wherein the decarburization gas is oxygen and inert gas, the oxygen content in the decarburization gas is reduced with the increase of the decarburization temperature, the initial oxygen content in the decarburization gas is 60-100% by volume percent, when the temperature reaches 1650 ℃, the oxygen content in the decarburization gas is reduced, the final oxygen content is 18-23%, and the decarburization is finished when the C content in the molten steel is lower than 0.1 wt%;
(4) Reduction: adding a reducing agent and a slagging agent, sequentially introducing oxygen and nitrogen for converting, discharging slag, detecting the temperature and components of molten steel, adjusting the components of the molten steel according to the component requirements of a target steel grade, introducing argon for converting, and then discharging steel; if the manganese content in the molten steel is lower than the component requirement of the target steel grade, the manganese content in the molten steel is adjusted by supplementing electrolytic manganese so as to meet the component requirement of the target steel grade;
the smelting time of the method for smelting 200 series stainless steel by using the AOD furnace is less than or equal to 125min.
2. The method for smelting 200 series stainless steel by using the AOD furnace according to claim 1, wherein in the step (1), the molten iron is blast furnace molten iron, and the charging temperature of the blast furnace molten iron is 1250-1350 ℃; preferably, the blast furnace molten iron comprises the following components in percentage by weight: 4 to 6 percent of C, 0.5 to 1.5 percent of silicon, 3 to 5 percent of chromium, 0.5 to 2.0 percent of manganese, 0.03 to 0.04 percent of copper, 1.3 to 1.8 percent of nickel, less than 0.05 percent of phosphorus, less than 0.2 percent of sulfur, and the balance of Fe and inevitable impurities; preferably, in the step (1), after the high carbon ferrochrome is added, the molten steel components are adjusted as follows by weight percentage: 2 to 4 percent of C, 0 to 0.2 percent of silicon, 13.5 to 15 percent of chromium, 0.2 to 1.5 percent of manganese, 0.03 to 0.04 percent of copper, 1.1 to 1.6 percent of nickel, less than 0.05 percent of phosphorus, less than 0.15 percent of sulfur, and the balance of Fe and inevitable impurities.
3. The AOD furnace smelting method of 200 series stainless steel according to claim 1, wherein in the step (1), the gas used for the blowing is a mixed gas of 6:1 in a volume ratio of oxygen to nitrogen, wherein the oxygen pressure is 1.7 to 1.8MPa; preferably, in the step (1), the temperature for slagging-off is 1520-1580 ℃; preferably, the fluidity of the slag is 0.1-0.4 Pa.S during slag skimming, and no conglomeration exists on the surface of the slag; preferably, the slag skimming amount reaches more than 80 percent; preferably, the thickness of the slag layer in the furnace after slagging-off is less than 30mm.
4. The method for smelting 200 series stainless steel by using the AOD furnace according to claim 1, wherein in the step (2), the temperature is increased by simultaneously feeding oxygen to the top lance and the side lance of the AOD furnace; preferably, the time for heating to 1600-1630 ℃ is less than or equal to 8min; preferably, the time for heating to 1600-1630 ℃ is 6-8 min; preferably, the amount of the high-carbon ferromanganese added is 40-70 kg/t.
5. The method of AOD furnace smelting 200 series stainless steel according to claim 1, wherein in step (3), the inert gas is nitrogen or argon, more preferably nitrogen for steel making; preferably, in the step (3), oxygen and inert gas are blown in by a side lance in the decarbonization and manganese protection step; preferably, in the step (3), after the decarburization temperature reaches 1650-1660 ℃, the volume ratio of oxygen to inert gas is (0.8-1.2): 1; after the decarburization temperature reaches 1670-1675 ℃, the volume ratio of oxygen to inert gas is 1 (1.8-2.2); when the decarbonization temperature reaches 1680-1685 ℃, the volume ratio of oxygen to inert gas is 1 (3.8-4.2).
6. The AOD furnace process for smelting 200 series stainless steel according to claim 1, wherein in the step (3), the decarburization temperature is 1630 ℃, and the ratio of the volume of oxygen to the volume of inert gas is 2:1; the decarburization temperature reaches 1650 ℃, and the volume ratio of oxygen to inert gas is 1:1; the decarburization temperature reaches 1670 ℃, and the volume ratio of oxygen to inert gas is 1:2; the decarburization temperature reaches 1680 ℃, and the volume ratio of oxygen to inert gas is 1:4; preferably, when the temperature of the molten steel is 1650-1685 ℃, the slag in the furnace is piled up, and the slag-forming agent is supplemented to the molten steel when the piled slag does not meet the requirement; preferably, the slagging agent is lime, and the using amount is 25-35 kg/t; preferably, in step (3), the basicity of the slag, i.e. CaO/SiO in the slag 2 The mass fraction ratio is more than or equal to 3.5.
7. The method for smelting 200 series stainless steel by using the AOD furnace according to claim 5, wherein the slagging agent in the step (1) and the step (2) is lime; preferably, the dosage of the slag former in the step (1) is 35-45 kg/t; preferably, the dosage of the slag former in the step (2) is 30-40 kg/t.
8. The method of AOD furnace smelting 200-series stainless steel according to claim 1, wherein in step (4), the reducing agent is a silicomanganese alloy; preferably, the silicon-manganese alloy is at least one of high silicon-manganese, medium silicon-manganese and common silicon-manganese; preferably, the dosage of the silicon-manganese alloy is 70-95 kg/t.
9. The AOD furnace smelting method of 200 series stainless steel according to claim 1, wherein in the step (4), the time of introducing oxygen for blowing is 1-4 min; preferably, the time for blowing the nitrogen is 5-7 min; preferably, the time for blowing the argon is 2-4 min.
10. The method of AOD furnace smelting 200 series stainless steel according to claim 1, wherein in the step (4), the basicity of the slag, caO/SiO in the slag 2 The mass fraction ratio is controlled to be 1.8-2.4; preferably, the slagging agent is at least one of fluorite balls, fluorite ores and ferrosilicon; preferably, the slagging agent is fluorite balls; preferably, the dosage of the fluorite balls is 18-22 kg/t; preferably, the temperature of all reducing agents after being fed into the furnace is controlled to be 1550-1600 ℃; preferably, all slag in the AOD furnace is liquefied during slag discharging and has fluidity, and the slag is taken out to be observed to be grey white or white; preferably, the tapping temperature is 1530 ℃ or higher.
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