Low-iron-consumption low-silicon duplex few-slag smelting method

Abstract

The invention relates to a low-iron-consumption low-silicon duplex few-slag smelting method, and belongs to the technical field of smelting. The smelting method comprises the following steps: (1) feeding; (2) blowing; (3) terminal point control; (4) tapping; (5) splashing slag; in the step (1), 70%-73% of molten iron and the balance of scrap steel are put into a converter, and the converter is adopted for smelting; in the molten iron, w [P] is not more than 0.18%, and w [Si] is not more than 0.40%. According to the method, the dephosphorization efficiency of the converter is improved while the smelting slag amount is reduced, w [P] in chemical components of molten steel at the end point of the converter is smaller than or equal to 0.015%, the step of waiting for component detection after blowing is completed is omitted, and the smelting period is shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of smelting, and in particular relates to a smelting method with low iron loss, low silicon and low slag. Background Art

[0002] As an energy-carrying resource, the increase in the use of scrap steel will help reduce the production pressure of high-energy-consuming processes such as coking, sintering, and ironmaking. This can not only save a lot of coke and raw coal, but also help reduce carbon emissions and wastewater emissions in the steel production process, and promote the steel industry to develop towards low-carbon and green development. In order to reduce costs and increase efficiency, and increase profits per ton of steel, steel companies generally adopt the method of increasing the scrap steel ratio. With the continuous increase in the scrap steel ratio, the heat in the furnace is insufficient, the original thermal balance is broken, and sludge and terminal overoxidation are prone to occur, which brings problems to production and quality, and indirectly increases the cost per ton of steel.

[0003] In order to solve these problems, various steel enterprises have proposed many methods. For example, patent CN112981039A discloses a scrap steel preheating system and working method. The scrap steel preheating method adopted by the patent requires preheating the scrap steel in the ladle, and the on-site equipment needs to be modified. The combustible gas used is CO, which is prone to carbon monoxide poisoning or explosion accidents, posing a threat to the life and health of employees. For another example, patent CN114196798A discloses a single-flow channel secondary combustion oxygen gun and its use method, which can improve the combustion rate of CO and supply heat to the furnace. However, it needs to modify the oxygen gun, the service life of the modified oxygen gun is short, and the secondary combustion is carried out above the molten pool, the heat is easily drawn away, the thermal efficiency is low, and it will also affect the converter gas value, which has an adverse effect on the lime kiln; adding a warming agent to the converter will not only prolong the blowing time, but also its main heat-generating element Si will form SiO2 after oxidation, which reduces the slag basicity, and it is necessary to add additional lime to increase the slag basicity, which increases the slag amount. Summary of the invention

[0004] In view of the problem of high residue content caused by the increase of scrap steel ratio in the prior art, the present invention provides a low iron consumption, low silicon, double-linked and low slag smelting method to solve the above problem. The method of the present invention improves the dephosphorization efficiency of the converter while reducing the amount of smelting slag. The chemical composition of the molten steel at the converter end point is w[P]≤0.015%, which reduces the steps of waiting for component detection after the blowing is completed and reduces the smelting cycle.

[0005] The technical solution of the present invention is as follows: A low iron consumption, low silicon, double-linked and low slag smelting method comprises the following steps: (1) Feeding; (2) Blowing; (3) End point control; (4) Steel tapping; (5) Slag splashing; Step (1) is: adding molten iron and scrap steel into a converter, wherein the molten iron accounts for 70% to 73% and the rest is scrap steel, and smelting is performed in a converter; w[P]≤0.18% and w[Si]≤0.40% in the molten iron.

[0006] Furthermore, in step (1), the amount of molten iron entering the furnace is less than 185 tons.

[0007] Furthermore, step (2) is: during the blowing process, slag-making materials and cold materials such as lime, raw dolomite, magnesium balls, sintered ore, etc. are added, the reaction conditions in the furnace are judged by the flame, the gun position and flow rate are controlled, and decarburization and dephosphorization reactions are carried out.

[0008] Furthermore, step (3) is: using a secondary gun to measure the temperature and composition of the blowing process and the end point, and in order to avoid the high process temperature causing the molten steel P to be out of control, lime or sinter is added to the furnace according to the process temperature to reduce the molten steel temperature. The cooling effect of lime is 10~12℃ / ton, and the cooling effect of sinter is 15~20℃ / ton; w[C] in the molten steel at the end point of converter blowing is 0.04~0.10%, and the end point temperature is 1600~1640℃, the blowing is completed, and steel tapping begins.

[0009] Furthermore, in step (4), a slag sample is taken at the end point for testing when the steel is tapped, and the basicity is 2.6-3.3.

[0010] Furthermore, in step (5), an appropriate amount of magnesium balls or raw dolomite (mainly composed of CaCO3 and MgCO3) is added according to the final slag conditions to adjust the slag basicity and fluidity; the slag splashing operation time is 3 to 5 minutes.

[0011] Furthermore, the slag composition after slag splashing includes: SiO2: 12%~16%, CaO: 35%~43%, MgO: 3%~7%, TFe: 13%~20%.

[0012] Furthermore, after step (5) is completed, slag is retained according to the conditions of the molten iron and the type of steel. After the slag is poured, the amount of slag remaining in the furnace is 1 to 2 tons.

[0013] The beneficial effects of the present invention are: (1) The present invention increases the heat in the converter by reducing the amount of slag-making material added and the total slag amount, increases the amount of scrap steel charged, and improves the scrap steel ratio. By reducing the total slag amount, the iron content in the slag is reduced, and the consumption of steel materials is reduced.

[0014] (2) The present invention utilizes the characteristics of the final slag basicity and high fluidity of iron oxide to accelerate the dephosphorization reaction rate at the slag interface. By reducing the amount of slag added to accelerate the early slag, the dephosphorization efficiency of the converter desiliconization period is improved; the amount of slag added during the process is small, ensuring that the slag is thoroughly slag, and improving the dephosphorization efficiency during the blowing process. The converter end point w[P] ≤ 0.015%, reducing the dynamic dephosphorization and late phosphorus regeneration pressure, and avoiding the loss caused by high phosphorus in molten steel.

[0015] (3) In the whole blowing process, the present invention only needs to discharge the slag once after slag splashing. After carbon pulling is completed, there is no need to wait for the detection of the end point composition, and steel can be directly tapped, thereby shortening the smelting cycle, improving the converter rhythm, and reducing the smelting cost. DETAILED DESCRIPTION

[0016] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0017] In Examples 1 to 3, a 210-ton top and bottom blown converter was used to smelt AH36 steel.

[0018] Example 1 A low iron consumption, low silicon, double-linked and low slag smelting method comprises the following steps: (1) Feeding 181 tons of molten iron and 66 tons of scrap steel were put into the converter, with w[P]: 0.12% and w[Si]: 0.15% in the molten iron.

[0019] (2) Blowing During the blowing process, 7134kg of lime, 632kg of magnesium balls, and 299kg of ferrosilicon were added. The blowing gun position was 2600mm and the flow rate was 28500m 3 / h; process gun position 2300mm, flow rate 48500m 3 / h, after the slag in the furnace is fully melted, the gun position is adjusted appropriately according to the reaction in the furnace; the carbon pulling gun position is 2000mm, and the flow rate is 51800m 3 / h, to carry out decarburization and dephosphorization reactions.

[0020] (3) End point control The blowing process, final temperature and composition were measured by auxiliary gun. In the final stage of converter blowing, w[C] in the molten steel was 0.063%, the final temperature was 1615℃, and w[P] was 0.011%.

[0021] (4) Steel tapping After blowing, steel tapping begins. When tapping, a terminal slag sample is taken for testing, and the basicity is 2.9.

[0022] (5) Slag splashing According to the final slag conditions, 1033kg of raw dolomite was added to adjust the slag basicity and fluidity; the slag splashing operation time was 3-5 minutes. The slag composition after slag splashing included: SiO2 14.7%, CaO 43.8%, MgO 7.4%, TFe 17.2%.

[0023] (6) After the slag splashing is completed, the slag is retained according to the conditions of the molten iron and the type of steel. The amount of slag left in the furnace after the slag pouring is completed is 1.5 tons.

[0024] Example 2 A low iron consumption, low silicon, double-linked and low slag smelting method comprises the following steps: (1) Feeding 179 tons of molten iron and 66 tons of scrap steel were put into the converter, with w[P]: 0.106% and w[Si]: 0.2% in the molten iron.

[0025] (2) Blowing During the blowing process, 6999kg of lime, 625kg of magnesium balls, and 308kg of ferrosilicon were added. The blowing gun position was 2600mm and the flow rate was 28500m 3 / h; process gun position 2300mm, flow rate 48500m 3 / h, after the slag in the furnace is fully melted, the gun position is adjusted appropriately according to the reaction in the furnace; the carbon pulling gun position is 2000mm, and the flow rate is 51800m 3 / h, to carry out decarburization and dephosphorization reactions.

[0026] (3) End point control The auxiliary gun was used to measure the blowing process, final temperature and composition; in the final molten steel of the converter blowing, w[C] was 0.045%, the final temperature was 1629℃, and w[P] was 0.012%.

[0027] (4) Steel tapping After blowing, steel tapping began. When tapping, a terminal slag sample was taken for testing, and the basicity was 2.76.

[0028] (5) Slag splashing According to the final slag conditions, 1003kg of raw dolomite is added to adjust the slag basicity and fluidity; the slag splashing operation time is 3-5 minutes. The slag composition after slag splashing includes: SiO215.4%, CaO 45.5%, MgO 5.59%, TFe14.7%.

[0029] (6) After the slag splashing is completed, the slag is retained according to the conditions of the molten iron and the type of steel. The amount of slag left in the furnace after the slag pouring is 1.8 tons.

[0030] Example 3 A low iron consumption, low silicon, double-linked and low slag smelting method comprises the following steps: (1) Feeding 181 tons of molten iron and 67 tons of scrap steel were put into the converter, with w[P]: 0.126% and w[Si]: 0.24% in the molten iron.

[0031] (2) Blowing During the blowing process, 7386kg of lime, 623kg of magnesium balls, 227kg of ferrosilicon and 678kg of raw dolomite were added. The blowing gun position was 2600mm and the flow rate was 28500m 3 / h; process gun position 2300mm, flow rate 48500m 3 / h, after the slag in the furnace is fully melted, the gun position is adjusted appropriately according to the reaction in the furnace; the carbon pulling gun position is 2000mm, and the flow rate is 51800m 3 / h for decarburization and dephosphorization reactions.

[0032] (3) End point control The blowing process and final temperature and composition were measured by auxiliary gun; in the final molten steel of converter blowing, w[C] was 0.065%, the final temperature was 1630℃, and w[P] was 0.009%.

[0033] (4) Steel tapping After blowing, steel tapping begins. When tapping, a terminal slag sample is taken for testing, and the basicity is 3.0.

[0034] (5) Slag splashing According to the final slag conditions, 665kg of raw dolomite was added to adjust the slag basicity and fluidity; the slag splashing operation time was 3-5 minutes. The slag composition after slag splashing included: SiO2 14.6%, CaO 45.3%, MgO 4.8%, TFe 13.2%.

[0035] (6) After the slag splashing is completed, the slag is retained according to the conditions of the molten iron and the type of steel. The amount of slag left in the furnace after the slag pouring is completed is 1.3 tons.

[0036] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily conceive of changes or substitutions within the technical scope disclosed by the present invention, and such changes or substitutions shall be within the scope of protection of the present invention.

Claims

1. A low iron loss, low silicon, duplex and low slag smelting method, characterized in that: The following steps are involved: (1) Feeding; (2) Blowing; (3) End point control; (4) Steel tapping; (5) Slag splashing; Step (1) is: adding molten iron and scrap steel into a converter, wherein the molten iron accounts for 70% to 73% and the rest is scrap steel, and smelting is performed in a converter; w[P]≤0.18% and w[Si]≤0.40% in the molten iron.

2. The low iron loss, low silicon duplex and low slag smelting method according to claim 1, characterized in that: In step (1), the amount of molten iron entering the furnace is less than 185 tons.

3. The low iron loss, low silicon duplex and low slag smelting method according to claim 1, characterized in that: Step (2) is: during the blowing process, lime, raw dolomite, magnesium balls or sintered ore slag material and cold material are added, the reaction situation in the furnace is judged by the flame, the gun position and flow rate are controlled, and decarburization and dephosphorization reactions are carried out.

4. The low iron loss, low silicon duplex and low slag smelting method according to claim 1, characterized in that: Step (3) is: using the auxiliary gun to measure the blowing process and terminal temperature and composition, and adding lime or sintered ore into the furnace according to the process temperature to reduce the temperature of the molten steel. The cooling effect of lime is 10-12°C / ton, and the cooling effect of sintered ore is 15-20°C / ton. The w[C] in the molten steel at the end of converter blowing is 0.04-0.10%, and the terminal temperature is 1600-1640°C. The blowing is completed and steel tapping begins.

5. The low iron loss, low silicon duplex and low slag smelting method according to claim 1, characterized in that: In step (4), when steel is tapped, a slag sample is taken at the end point for testing, and the basicity is 2.6-3.

3.

6. The low iron loss, low silicon duplex and low slag smelting method according to claim 1, characterized in that: In step (5), magnesium balls or raw dolomite are added to adjust the slag basicity and fluidity according to the final slag conditions; the slag splashing operation time is 3 to 5 minutes.

7. The low iron loss, low silicon duplex and low slag smelting method according to claim 1, characterized in that: The slag composition after slag splashing includes: SiO2: 12%~16%, CaO: 35%~43%, MgO: 3%~7%, TFe: 13%~20%.

8. The low iron loss, low silicon duplex and low slag smelting method according to claim 1, characterized in that: After step (5) is completed, slag is retained according to the conditions of the molten iron and the type of steel. After the slag is poured, the amount of slag remaining in the furnace is 1 to 2 tons.