Method for producing low-carbon steel and improving converter metal yield

Abstract

The invention relates to a method for producing low-carbon steel and improving the metal yield of a converter, which comprises the following steps of: 1) smelting by adopting molten iron and scrap steel, and controlling the unit consumption of the scrap steel to be 100-200kg per ton of steel; (2) when blowing is started, lime is added into the furnace at a time, 60-67 wt% of light-burned dolomite is added, the rest light-burned dolomite is added in batches, and the adding amount of the light-burned dolomite in each batch is smaller than or equal to 0.5 ton; (3) an oxygen lance adopts variable flow blowing; the lance position of an oxygen lance is controlled to be 2.2-2.8 m, and the lance position of a carbon pulling lance is 1.8-2.0 m; 4) measuring the oxygen content of the molten steel after measuring the temperature and determining the oxygen of the smelted molten steel in the converter through a sublance, determining the oxidability of the slag according to the oxygen content of the molten steel, and calculating the adding amount of the carbon-containing material; 5) adding a carbon-containing material into the converter, and adjusting a secondary fan of the converter to a high speed in the adding process; and (6) converter bottom argon blowing. The method has the advantages that the total iron content of the slag can reach 15% or below, and the metal yield is increased by 0.05-1%.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for producing low-carbon steel and improving the metal yield of a converter. Background Art

[0002] Oxygen top-blown converter steelmaking mainly uses molten iron as raw material, and molten iron is smelted into molten steel through oxygen supply and slag-making operation system. During the blowing process, impurities such as carbon, sulfur, and phosphorus must be removed, and part of the iron is oxidized. Part of the iron oxide generated by the oxidation of iron is discharged with the furnace gas. The other part remains in the slag. The splashing of metal and slag during the blowing process also loses some metal. The converter slag contains a high total iron content and metallic iron content. The total iron content of the final slag is normally 13% to 20%, and the metallic iron content is normally 2% to 8%. Excessive total iron content in the slag causes an increase in metallic iron loss, increases smelting costs, and aggravates erosion of the furnace lining, posing a great safety challenge to the maintenance of the furnace lining. Summary of the invention

[0003] To overcome the deficiencies of the prior art, the present invention aims to provide a method for producing low-carbon steel to improve the metal yield of a converter, reduce the consumption of steel material indicators, improve the quality of molten steel, and slow down the erosion of the furnace lining.

[0004] To achieve the above object, the present invention is implemented through the following technical solutions:

[0005] A method for producing low-carbon steel and improving the metal recovery rate of a converter, comprising the following contents:

[0006] 1) Adopt molten iron + scrap steel smelting, and the scrap steel consumption is controlled at 100-200kg / ton of steel;

[0007] 2) The consumption of lime is 25-35kg / ton of steel, and the consumption of light-burned dolomite is controlled at 10-25kg / ton of steel. At the beginning of blowing, lime is added into the furnace at one time, and 60wt%-67wt% of the total amount of light-burned dolomite is added. The remaining light-burned dolomite is added in batches, and the amount added in each batch is ≤0.5 ton;

[0008] 3) The oxygen lance adopts variable flow blowing:

[0009] The first step is to supply oxygen at an intensity of 3.1 to 3.3 Nm. 3 / min.t, oxygen blowing time 1~5min;

[0010] The second step is to supply oxygen at an intensity of 2.8 to 3.0 Nm. 3 / min.t, oxygen blowing time 6~10min;

[0011] Step 3: Oxygen supply intensity 3.4~3.6Nm 3 / min.t, oxygen blowing time 10~18min;

[0012] The oxygen lance position is controlled at 2.2-2.8m, the carbon pulling time is ≥2min, and the carbon pulling lance position is 1.8-2.0m;

[0013] 4) After measuring the temperature and oxygen of the molten steel in the converter through the auxiliary gun, measure the oxygen content of the molten steel, determine the oxidizability of the slag based on the oxygen content of the molten steel, and calculate the amount of carbon-containing material to be added:

[0014] Amount of carbon-containing material added = (-0.5 + 0.005 × oxygen content of molten steel) × amount of molten steel

[0015] In the formula, the unit of carbon-containing material addition is kg; the unit of oxygen content in molten steel is ppm, and the unit of molten steel volume is ton;

[0016] 5) Add carbon-containing materials to the converter according to the calculated amount. During the adding process, adjust the converter secondary fan to high speed, and open the nitrogen seal for unloading, oxygen lance, and auxiliary lance;

[0017] 6) The argon gas is blown at the bottom of the converter, and the control is carried out in steps:

[0018] In the first step, the argon supply intensity is 0.10~0.15Nm 3 / min.t, argon blowing time is 10~15s;

[0019] The second step is to supply argon with an intensity of 0.05 to 0.10 Nm 3 / min.t, argon blowing time is 15 to 20 seconds;

[0020] The third step is to supply argon with an intensity of 0.01 to 0.05 Nm 3 / min.t, argon blowing time is 20 to 30s.

[0021] The carbon-containing materials are stored in the converter high-level silo according to the calculated amount.

[0022] The particle size of the carbon-containing material is 10 to 30 mm.

[0023] The carbon-containing material comprises, by mass percentage: 30% to 60% fixed carbon; 30% to 50% MgO; 5% to 10% CaO; and 5% to 15% SiO2.

[0024] The number of revolutions of the converter secondary fan described in step 5) is ≥1300 revolutions.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The total iron content of the slag can reach below 15% by adopting the method of the present invention, and the metal recovery rate can be increased by 0.05% to 1% compared with the conventional process, which can improve the quality of molten steel, slow down the erosion of the furnace lining, and reduce the steel material digestion index of the steel plant. The present invention makes full use of the on-site conditions, is simple to operate, and has obvious effects. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0028] A method for producing low carbon steel (finished product carbon ≤ 0.08%) to improve the metal recovery rate of the converter comprises the following steps:

[0029] 1) Adopt molten iron + scrap steel smelting, and the scrap steel consumption is controlled at 100-200kg / ton of steel;

[0030] 2) The consumption of lime is 25-35kg / ton of steel, and the consumption of light-burned dolomite is controlled at 10-25kg / ton of steel. At the beginning of blowing, lime is added into the furnace at one time, and light-burned dolomite is added in an amount of 60%-67% of the total amount by weight. The remaining light-burned dolomite is added in batches, with the amount added in each batch being ≤0.5 ton. Adding light-burned dolomite in batches can achieve a good slag-making effect, improve the dephosphorization efficiency of the converter, and create conditions for reducing the oxidizability of the final slag in the later stage.

[0031] 3) The oxygen lance adopts variable flow blowing, and the oxygen supply intensity of the oxygen lance is 3.2~3.8Nm 3 / min.t;

[0032] The first step is to supply oxygen at an intensity of 3.1 to 3.3 Nm. 3 / min.t, oxygen blowing time 1~5min;

[0033] The second step is to supply oxygen at an intensity of 2.8 to 3.0 Nm. 3 / min.t, oxygen blowing time 6~10min;

[0034] Step 3: Oxygen supply intensity 3.4~3.6Nm 3 / min.t, oxygen blowing time 10~18min;

[0035] The oxygen lance position is controlled at 2.2-2.8m, the carbon pulling time is ≥2min, and the carbon pulling lance position is 1.8-2.0m; the purpose is to make the temperature of the molten steel composition uniform and reduce the oxidizability of the final slag.

[0036] 4) After measuring the temperature and oxygen of the molten steel in the converter through the auxiliary gun, measure the oxygen content of the molten steel, determine the oxidizability of the slag based on the oxygen content of the molten steel, and calculate the amount of carbon-containing material to be added:

[0037] Amount of carbon-containing material added = (-0.5 + 0.005 × oxygen content of molten steel) × amount of molten steel

[0038] In the formula, the unit of carbon-containing material addition is kg; the unit of oxygen content in molten steel is ppm, and the unit of molten steel volume is ton;

[0039] The particle size of the carbon-containing material is 10-30 mm, and the carbon-containing material includes, by mass percentage: 30%-60% fixed carbon; 30%-50% MgO; 5%-10% CaO; and 5%-15% SiO2.

[0040] 5) Put the carbon-containing material into the high-level silo of the converter, vibrate the carbon-containing material to the collection silo according to the oxygen value tested by the auxiliary gun and the amount added according to the formula, and then add it to the converter through the discharge chute. During the addition process, adjust the converter secondary fan to high speed (fan speed ≥ 1300 revolutions), open the discharge nitrogen seal and oxygen gun and auxiliary gun nitrogen seal;

[0041] 6) Bottom blowing of argon in converter, the bottom blowing intensity is 0.01~0.15Nm 3 / min.t;

[0042] Adopt step-by-step control:

[0043] In the first step, the argon supply intensity is 0.10~0.15Nm 3 / min.t, argon blowing time is 10~15s;

[0044] The second step is to supply argon with an intensity of 0.05 to 0.10 Nm 3 / min.t, argon blowing time is 15 to 20 seconds;

[0045] The third step is to supply argon with an intensity of 0.01 to 0.05 Nm 3 / min.t, argon blowing time is 20 to 30s.

[0046] The step-by-step control can make full use of the favorable kinetic conditions of bottom blowing, strengthen the stirring of the molten pool, promote the carbon-oxygen reaction at the slag interface, further reduce the total iron content and metallic iron content of the slag, and at the same time facilitate the removal of the reaction product CO, thereby preventing the high slag surface from affecting the steelmaking process of the converter.

[0047] Example 1

[0048] Using 260-ton converter to smelt Q235B steel:

[0049] 1) Adopt molten iron + scrap steel smelting, the amount of molten iron is 245 tons and the amount of scrap steel is 40 tons.

[0050] 2) Add 7.5 tons of lime into the furnace, add 2.5 tons of light-burned dolomite, and then add light-burned dolomite in batches, 0.5 tons per batch, once every 1 minute, and the total amount of light-burned dolomite added is 5 tons.

[0051] 3) The initial oxygen supply intensity of the oxygen gun is 3.2Nm 3 / min.t, oxygen supply intensity in the middle of blowing 2.8Nm 3 / min, the oxygen supply intensity in the later stage is 3.5Nm 3 / min oxygen lance position is controlled at 2.2~2.5m, carbon pulling time is 2min, and carbon pulling lance position is 2.0m.

[0052] 4) End point test: the end point temperature is 1680°C, the end point oxygen value is 550ppm, and the final slag TFe content is controlled below 16.5%.

[0053] 5) After the endpoint test, add carbon-containing materials through the converter high-level silo:

[0054] The amount of carbon-containing material added = (-0.5 + 0.005 × 550) × 260 = 585 kg.

[0055] The carbon-containing materials include, by mass percentage: fixed carbon 50±3%; MgO 40±2%; CaO 7±2%; SiO2 10±3%.

[0056] 6) Select argon as the bottom blowing method of the converter: Step 1, bottom blowing flow rate 16Nm 3 / min, argon blowing time is 15s; second step, bottom blowing argon flow rate is 13Nm 3 / min; argon blowing time is 20s; the third step, bottom blowing flow rate, bottom blowing argon flow rate is 5Nm 3 / min; argon blowing time is 20s.

[0057] The total iron content of the slag is 13.5%, and the metallic iron recovery rate of the converter is increased by 0.5%.

[0058] Example 2

[0059] Using 200-ton converter to smelt SPHC steel:

[0060] 1) Use molten iron + scrap steel for smelting, with 200 tons of molten iron and 20 tons of scrap steel.

[0061] 2) Add 5.5 tons of lime into the furnace, add 2 tons of light-burned dolomite, and then add light-burned dolomite in batches, 0.5 tons per batch, once every 1 minute, and the total amount of light-burned dolomite added is 3.5 tons.

[0062] 3) The initial oxygen supply intensity of the oxygen gun is 3.1Nm 3 / min.t, oxygen supply intensity in the middle of blowing 2.8Nm 3 / min, the oxygen supply intensity in the later stage is 3.4Nm 3 / min oxygen lance position is controlled at 2.0~2.4m, carbon pulling time is 2min, and carbon pulling lance position is 1.7m.

[0063] 4) End point test: the end point temperature is 1660°C, the end point oxygen value is 500ppm, and the final slag TFe content is controlled below 17%.

[0064] 5) After the endpoint test, add carbon-containing materials through the converter high-level silo:

[0065] The amount of carbon-containing material added = (-0.5 + 0.005 × 500) × 220 = 440 kg.

[0066] 6) Select argon as the bottom blowing method of the converter: Step 1, bottom blowing flow rate 16Nm 3 / min, argon blowing time is 15s; second step, bottom blowing argon flow rate is 13Nm 3 / min; argon blowing time is 20s; the third step, bottom blowing flow rate, bottom blowing argon flow rate is 5Nm 3 / min; argon blowing time is 20s.

[0067] The total iron content of the slag is 12.5%, and the recovery rate of metallic iron in the converter is increased by 0.8%.

[0068] Example 3

[0069] Use 100-ton converter to smelt B plate steel:

[0070] 1) Adopt molten iron + scrap steel smelting, the amount of molten iron is 95 tons and the amount of scrap steel is 15 tons.

[0071] 2) Add 3 tons of lime into the furnace, add 1 ton of light-burned dolomite, and then add light-burned dolomite in batches, 0.5 tons per batch, add once every 1 minute, and the total amount of light-burned dolomite added is 2 tons.

[0072] 3) The initial oxygen supply intensity of the oxygen gun is 3.2Nm 3 / min.t, oxygen supply intensity in the middle of blowing 2.9Nm 3 / min, the oxygen supply intensity in the later stage is 3.5Nm 3 / min oxygen lance position is controlled at 1.8.0~2.2m, carbon pulling time is 2min, and carbon pulling lance position is 1.5m.

[0073] 4) End point test: the end point temperature is 1665°C, the end point oxygen value is 480ppm, and the final slag TFe content is controlled below 17%.

[0074] 5) After the endpoint test, add carbon-containing materials through the converter high-level silo:

[0075] The amount of carbon-containing material added = (-0.5 + 0.005 × 480) × 100 = 190 kg.

[0076] 6) Select argon as the bottom blowing method of the converter: Step 1, bottom blowing flow rate 16Nm 3 / min, argon blowing time is 15s; second step, bottom blowing argon flow rate is 13Nm 3 / min; argon blowing time is 20s; the third step, bottom blowing flow rate, bottom blowing argon flow rate is 5Nm 3 / min; argon blowing time is 20s.

[0077] The total iron content of the slag is 13%, and the metallic iron recovery rate of the converter is increased by 0.7%.

Claims

1. A method for producing low carbon steel and improving the metal yield of a converter, characterized in that: Includes the following: 1) Adopt molten iron + scrap steel smelting, and the scrap steel consumption is controlled at 100-200kg / ton of steel; 2) The consumption of lime is 25-35kg / ton of steel, and the consumption of light-burned dolomite is controlled at 10-25kg / ton of steel. At the beginning of blowing, lime is added into the furnace at one time, and 60wt%-67wt% of the total amount of light-burned dolomite is added. The remaining light-burned dolomite is added in batches, and the amount added in each batch is ≤0.5 ton; 3) The oxygen lance adopts variable flow blowing: The first step is to supply oxygen at an intensity of 3.1 to 3.3 Nm. 3 / min.t, oxygen blowing time 1~5min; Step 2: Oxygen supply intensity 2.8~3.0Nm 3 / min.t, oxygen blowing time 6~10min; Step 3: Oxygen supply intensity 3.4~3.6Nm 3 / min.t, oxygen blowing time 10~18min; The oxygen lance position is controlled at 2.2-2.8m, the carbon pulling time is ≥2min, and the carbon pulling lance position is 1.8-2.0m; 4) After measuring the temperature and oxygen of the molten steel in the converter through the auxiliary gun, measure the oxygen content of the molten steel, determine the oxidizability of the slag based on the oxygen content of the molten steel, and calculate the amount of carbon-containing material to be added: Amount of carbon-containing material added = (-0.5 + 0.005 × oxygen content of molten steel) × amount of molten steel In the formula, the unit of carbon-containing material addition is kg; the unit of oxygen content in molten steel is ppm, and the unit of molten steel volume is ton; 5) Add carbon-containing materials to the converter according to the calculated amount. During the adding process, adjust the converter secondary fan to high speed, and open the nitrogen seal for unloading, oxygen lance, and auxiliary lance; 6) The argon gas is blown at the bottom of the converter, and the control is carried out in steps: In the first step, the argon supply intensity is 0.10~0.15Nm 3 / min.t, argon blowing time is 10~15s; The second step is to supply argon with an intensity of 0.05 to 0.10 Nm 3 / min.t, argon blowing time is 15 to 20 seconds; The third step is to supply argon with an intensity of 0.01 to 0.05 Nm 3 / min.t, argon blowing time is 20 to 30s.

2. A method for increasing converter metal yield in producing low carbon steel according to claim 1, characterized in that: The carbon-containing materials are stored in the converter high-level silo according to the calculated amount.

3. The method for increasing the metal yield of a converter in producing low carbon steel according to claim 1, characterized in that: The particle size of the carbon-containing material is 10 to 30 mm.

4. The method for increasing the metal yield of a converter in producing low carbon steel according to claim 1, characterized in that: The carbon-containing material comprises, by mass percentage: 30% to 60% fixed carbon; 30% to 50% MgO; 5% to 10% CaO; and 5% to 15% SiO2.

5. The method for increasing the metal yield of a converter in producing low carbon steel according to claim 1, characterized in that: The number of revolutions of the converter secondary fan described in step 5) is ≥1300 revolutions.