Smelting method for making foaming slag by using direct reduction iron powder and carbon powder

Abstract

The invention discloses a smelting method for making foamed slag by using direct reduction iron powder and carbon powder, the smelting process adopts steel and slag remaining operation, the steel remaining amount is 40-50%, and the slag remaining amount is 7-12%. The method comprises the following steps of: starting an arc, electrifying, adding a metal material, blowing a mixture of direct reduced iron powder and carbon powder into molten steel when the temperature of the molten steel reaches 1520-1580 DEG C, respectively blowing different types of mixtures of direct reduced iron powder and carbon powder in different stages of smelting, simultaneously blowing oxygen into the molten steel, and controlling the blowing amount of the mixture of direct reduced iron powder and carbon powder per ton of steel to be 25-35kg / t of steel, the oxygen injection amount per ton of steel is 25-30 Nm < 3 > / t of steel, lime and light-burned dolomite are added into molten steel in batches in the smelting process, and the slag alkalinity, the MgO content and the FeO content are controlled. The method shortens the smelting period and reduces the steelmaking cost of the electric arc furnace.

Description

Technical Field

[0001] The invention relates to an electric arc furnace metallurgy technology, in particular to a smelting method for making foamed slag by directly reducing iron powder and carbon powder. Background Art

[0002] DRI size is a key performance indicator. A high proportion of small DRI in DRI results in poor performance. Small DRI, when dropped from the furnace roof, has little impact force and cannot penetrate the slag layer, overflowing from the furnace door. Furthermore, dust removal and flue gas blowers during the smelting process remove some of the powdered DRI, reducing DRI metal yield. Using an EAF with a high proportion of small DRI can lead to increased slag overflow, higher FeO content in the slag, reduced slag basicity and lining life, and increased smelting power consumption. Some steel mills screen the DRI before use and briquette the small-sized DRI. However, briquetting increases costs and reduces the iron content of the briquetting DRI, leading to higher smelting costs.

[0003] When carbon powder is injected into an electric arc furnace to create foamed slag, due to its low density, weak impact force, and shallow impact depth, the reaction products of carbon powder and oxygen, CO and CO2, remain in the slag for a short time, resulting in a short retention time of the foamed slag. Especially in the early stages of smelting, the carbon powder is far from the slag surface and cannot easily penetrate the slag layer. Burning on the slag surface and in the shallow slag layer, the carbon powder utilization rate is low, and the foamed slag is unstable. This leads to a deterioration of the submerged arc power supply, a decrease in the power factor, and increased heat loss from the arc radiation to the furnace lining and furnace cover, which shortens the life of the furnace lining, increases smelting power consumption, lengthens the smelting cycle, and increases smelting costs. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a smelting method for making foamed slag using direct reduced iron powder and carbon powder, efficiently utilizing small-sized direct reduced iron after screening, and making foamed slag using a mixture of small-sized direct reduced iron powder and carbon powder after screening, thereby realizing the whole process of foamed slag making and reducing the cost of electric arc furnace steelmaking.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A smelting method for producing foamed slag using direct reduced iron powder and carbon powder comprises the following steps: (1) Adopting steel and slag retention operation; (2) Start the arc and add metal materials. When the temperature of the molten steel reaches 1520-1580℃, spray the mixture of direct reduced iron powder and carbon powder into the molten steel. The spraying amount of the direct reduced iron powder and carbon powder mixture is 25-35kg / ton of steel. (3) While spraying the mixture of direct reduced iron powder and carbon powder, oxygen is sprayed into the molten steel. The oxygen injection rate is 25-30 Nm per ton of steel. 3 / t steel; (4) During the smelting process, lime and light-burned dolomite are added to the molten steel in batches; the slag basicity is controlled to 1.8-2.2, the MgO content is 7-10wt%, and the FeO content is 20-30wt%.

[0006] Preferably, the amount of steel retained in step (1) is 40-50 wt%, and the amount of slag retained is 7-12 wt%.

[0007] Preferably, the direct reduced iron powder in step (2) has a metallization rate of 90-95%, a total iron content of ≥80wt%, a carbon content of 2-6wt%, and a gangue content of ≤8wt%; The carbon content in the carbon powder is ≥80wt%, and the moisture content is ≤1%.

[0008] Preferably, when the amount of metal material added in step (2) is different, the direct reduced iron powder and carbon powder mixture injection rate, oxygen injection rate, carbon powder and direct reduced iron powder ratio, and direct reduced iron powder and carbon powder size are different, and the direct reduced iron powder and carbon powder mixture is divided into type I direct reduced iron powder and carbon powder mixture, type II direct reduced iron powder and carbon powder mixture, and type III direct reduced iron powder and carbon powder mixture.

[0009] Preferably, the amount of metal material added is within 30wt%, and the mixture of type I direct reduced iron powder and carbon powder is sprayed at a rate of 80-120kg / min and an oxygen spray rate of 60-100Nm 3 / min; the proportion of direct reduced iron powder in the mixture of Type I direct reduced iron powder and carbon powder is 30wt% to 50wt%; the size of the direct reduced iron powder in the mixture of Type I direct reduced iron powder and carbon powder is 2 to 4mm, and the size of the carbon powder is 1 to 3mm.

[0010] At this time, the molten steel level is low, the direct reduced iron powder and carbon powder mixture is far away from the molten steel level, and the density of the direct reduced iron powder is large. By spraying larger size and higher proportion of direct reduced iron powder, the density of type I direct reduced iron powder and carbon powder mixture is increased, and its impact depth is increased, so that it passes through the slag layer and enters deep into the molten steel or slag layer. The carbon in the direct reduced iron powder and FeO, the carbon in the carbon powder, and the injected oxygen react to quickly generate CO and CO2 gases, increase the residence time of the reaction products CO and CO2 gases in the slag, achieve rapid foam slag production and increase the foam slag retention time.

[0011] Preferably, the amount of metal material added is 30-70 wt%, the mixture of type II direct reduced iron powder and carbon powder is sprayed, the spraying rate of the mixture of type II direct reduced iron powder and carbon powder is 150-200 kg / min, and the oxygen spraying rate is 150-200 Nm 3 / min; the proportion of direct reduced iron powder in the type II direct reduced iron powder and carbon powder mixture is 20-30wt%; the size of the direct reduced iron powder in the type II direct reduced iron powder and carbon powder mixture is ≤3mm, and the size of the carbon powder is ≤3mm.

[0012] During this stage, the molten steel level rises and the slag layer thickness increases. Using 20-30% direct-reduced iron powder increases the density of the mixture of Type II direct-reduced iron powder and carbon powder, increasing its impact depth, the residence time of the reaction products CO and CO2 gases in the slag, and the retention time of the foamed slag. At the same time, the carbon powder content in the mixture of direct-reduced iron powder and carbon powder is increased to prevent excessive FeO content in the slag, which may deteriorate the foamed slag.

[0013] Preferably, the amount of metal material added exceeds 70wt%, and the mixture of type III direct reduced iron powder and carbon powder is sprayed at a rate of 120-150kg / min and an oxygen spray rate of 100-150Nm 3 / min; the proportion of direct reduced iron powder in the mixture of type III direct reduced iron powder and carbon powder is 10-20wt%; the size of the direct reduced iron powder in the mixture of type III direct reduced iron powder and carbon powder is 2-4mm, and the size of the carbon powder is ≤1mm.

[0014] During this stage, slag is discharged. Larger DRI powder is used to prevent small DRI powder from being unable to penetrate the slag layer and overflowing with the slag, causing iron loss. Smaller carbon powder is used as it reacts quickly in the slag layer, preventing larger carbon particles from incompletely reacting and overflowing with the slag into the slag pot, causing further reaction and splattering in the pot.

[0015] Preferably, in step (4), the amount of lime and light-burned dolomite added in each batch is 500-1000 kg, the total amount of lime added is 20-30 kg / t steel, and the total amount of light-burned dolomite added is 15-25 kg / t steel.

[0016] The beneficial effects of adopting the above technical solution are: The present invention efficiently utilizes small-sized direct reduced iron (DRI) after screening. The DRI contains C and FeO. By spraying a mixture of DRI powder and carbon powder, and also by spraying oxygen, the following reaction occurs: C+(FeO)=[Fe]+CO, 2C+O2=2CO, C+O2=CO2, and C+CO2=2CO, rapidly generating CO and CO2 gases and quickly producing foamed slag. The density of DRI is much higher than that of carbon powder. The impact depth of spraying the mixture of DRI powder and carbon powder is much higher than that of spraying carbon powder alone, which increases the residence time of the reaction product, CO, in the slag, achieving rapid foamed slag production and increasing the retention time of the foamed slag. Furthermore, the sprayed DRI powder has a large impact depth, allowing it to penetrate deep into the slag layer or into the molten steel, preventing it from overflowing from the furnace door and being drawn away by the dust removal fan and the flue gas blower, thereby improving the metal yield of the DRI powder. By spraying a mixture of direct reduced iron powder and carbon powder, the amount of carbon powder used is reduced, the metal recovery rate of direct reduced iron powder is improved, foam slag is produced throughout the entire process, the submerged arc effect of the electric furnace is improved, the power consumption of the electric arc furnace smelting is reduced, the smelting cycle is shortened, and the production cost is reduced.

[0017] Because about 25-35 kg / t of a mixture of direct-reduced iron (DRI) powder and carbon powder is injected into every ton of steel, DRI powder accounts for 10-30% of the total. Approximately 6 kg of DRI powder is injected into every ton of steel, and the DRI powder produced into every ton of molten steel is 6 kg, a proportion too small to calculate the DRI powder yield. In the actual smelting process, DRI is often added continuously from the furnace top. Small DRI falling from the furnace top has little impact force and cannot penetrate the slag layer, flowing out with the furnace door slag overflow. Furthermore, dust removal fans and flue gas blowers remove some of the powdered DRI during the smelting process. Excessive levels of fines in the DRI reduce the DRI metal yield. Therefore, the DRI is screened and the small-sized DRI is briquette-pressed. This increases costs and requires the addition of binders, which reduces the iron content and yield. The present invention uses a carbon gun to blow screened direct-reduced iron powder into molten steel, preventing it from being drawn away by dust removal fans and flue gas blowers. It also prevents it from overflowing from the furnace door with slag, resulting in a higher yield. This also allows for efficient utilization of the screened direct-reduced iron powder, avoiding the increased cost of briquetting. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the power factor diagram of the smelting process of the blank comparative heat (injection of carbon powder); Figure 2 This is the power factor diagram of the furnace smelting process in Example 1. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0020] Taking a 150-ton electric arc furnace as an example, the total amount of molten steel in the electric arc furnace can reach 230-250 tons. 60 tons of steel (about 40% of steel) and 12 tons of slag (about 8% of slag) are retained from the previous furnace. The arc is struck and energized, and metal material is added at a rate of 5-7 tons / min. When the furnace temperature reaches 1520°C, a mixture of Type I direct reduced iron powder and carbon powder and oxygen are sprayed (the metallization rate of the direct reduced iron powder is 94%, the total iron content is 89.3%, the carbon content is 3.2%, and the gangue content is 5.9%; the carbon content of the carbon powder is 81.4% and the moisture content is 0.7%). The injection rate of the Type I direct reduced iron powder and carbon powder mixture is 80 kg / min, and the oxygen injection rate is 60 Nm 3 / min, in the mixture of type I direct reduced iron powder and carbon powder, direct reduced iron powder accounts for 50%, carbon powder accounts for 50%, direct reduced iron powder size is 2-4mm, carbon powder size is 1-3mm. When the amount of metal material added exceeds 50 tons, type II direct reduced iron powder and carbon powder mixture is sprayed, the injection rate of type II direct reduced iron powder and carbon powder mixture is 150kg / min, and the oxygen injection rate is increased to 150Nm 3 / min, in the mixture of type II direct reduced iron powder and carbon powder, direct reduced iron powder accounts for 30%, carbon powder accounts for 70%, direct reduced iron powder size ≤ 3mm, carbon powder size ≤ 3mm. When the amount of metal material added exceeds 110 tons, type III direct reduced iron powder and carbon powder mixture is sprayed, the injection rate of type III direct reduced iron powder and carbon powder mixture is 120kg / min, and the oxygen injection rate is reduced to 100Nm 3 / min, the mixture of Type III direct reduced iron powder and carbon powder accounts for 20% direct reduced iron powder and 80% carbon powder. The direct reduced iron powder size is 2-4mm, and the carbon powder size is ≤1mm. Lime and light-burned dolomite are added in batches during the smelting process, with each batch adding 500kg. The direct reduced iron powder and carbon powder mixture is injected at 27.5kg / t steel throughout the smelting process; oxygen blowing is 26Nm 3 / t steel; total lime addition was 20.3kg / t steel, and total light-burned dolomite addition was 15.5kg / t steel. The slag basicity was 1.82, the MgO content was 7.2wt%, and the FeO content was 25.2wt%. Foamy slag was produced throughout the smelting process, achieving good submerged arc performance. The final smelting temperature was 1624°C, the power consumption was 340kWh / t steel, and the smelting cycle was 35 minutes. Example 2

[0021] Taking a 150-ton electric arc furnace as an example, the total amount of molten steel in the electric arc furnace can reach 230 to 250 tons. 75 tons of steel (about 50% of the steel is retained) and 18 tons of slag (about 12% of the slag is retained) are left in the previous furnace. The arc is struck and the power is turned on. Metal materials are added at a rate of 5-7 tons / min. When the temperature in the furnace reaches 1540°C, type I direct reduced iron powder and carbon powder mixture and oxygen are sprayed (direct reduced iron powder metallization rate 94%, total iron content 89.3%, carbon content 3.2%, gangue content 5.9%; carbon content in carbon powder 81.4%, moisture 0.7%). The injection rate of type I direct reduced iron powder and carbon powder mixture is 120kg / min, and the oxygen injection rate is 100Nm 3 / min, direct reduced iron powder and carbon powder mixture is injected, in which direct reduced iron powder accounts for 30% and carbon powder accounts for 70%. The size of direct reduced iron powder is 2-4mm and the size of carbon powder is 1-3mm. When the amount of metal material added exceeds 50 tons, the injection rate of type II direct reduced iron powder and carbon powder mixture is 200kg / min, and the oxygen injection rate is increased to 200Nm 3 / min, in the mixture of type II direct reduced iron powder and carbon powder, direct reduced iron powder accounts for 20%, carbon powder accounts for 80%, direct reduced iron powder size ≤3mm, carbon powder size ≤3mm. When the amount of metal material added exceeds 110 tons, type III direct reduced iron powder and carbon powder mixture is sprayed, the injection rate of type III direct reduced iron powder and carbon powder mixture is 150kg / min, and the oxygen injection rate is reduced to 150Nm 3 / min, the mixture of Type III direct reduced iron powder and carbon powder accounts for 10% direct reduced iron powder and 90% carbon powder. The direct reduced iron powder size is 2-4mm, and the carbon powder size is ≤1mm. Lime and lightly burned dolomite are added in batches during the smelting process, with each batch adding 1000kg. The direct reduced iron powder and carbon powder mixture is injected at 34.5kg / t steel throughout the smelting process; oxygen blowing is 29.5Nm 3 / t steel; total lime addition was 25.3kg / t steel, and total light-burned dolomite addition was 20.6kg / t steel. The slag basicity was 2.04, the MgO content was 8.1wt%, and the FeO content was 20.3wt%. Foamy slag was produced throughout the smelting process, achieving good submerged arc performance. The final smelting temperature was 1635°C, the power consumption was 347kWh / t steel, and the smelting cycle was 36 minutes. Example 3

[0022] Taking a 150-ton electric arc furnace as an example, the total amount of molten steel in the electric arc furnace can reach 230 to 250 tons. 70 tons of steel (about 48% of the steel is retained) and 15 tons of slag (about 10% of the slag is retained) are left in the previous furnace. The arc is struck and the power is turned on. Metal materials are added at a rate of 5-7 tons / min. When the temperature in the furnace reaches 1530°C, type I direct reduced iron powder and carbon powder mixture and oxygen are sprayed (direct reduced iron powder metallization rate 94%, total iron content 89.3%, carbon content 3.2%, gangue content 5.9%; carbon content in carbon powder 81.4%, moisture 0.7%). The injection rate of type I direct reduced iron powder and carbon powder mixture is 100kg / min, and the oxygen injection rate is 80Nm 3 / min, in the mixture of type I direct reduced iron powder and carbon powder, direct reduced iron powder accounts for 40%, carbon powder 60%, direct reduced iron powder size is 2-4mm, carbon powder size is 1-3mm. When the amount of metal material added exceeds 50 tons, type II direct reduced iron powder and carbon powder mixture is sprayed, the injection rate of type II direct reduced iron powder and carbon powder mixture is 180kg / min, and the oxygen injection rate is increased to 170Nm 3 / min, in the mixture of type II direct reduced iron powder and carbon powder, direct reduced iron powder accounts for 25%, carbon powder accounts for 75%, direct reduced iron powder size ≤ 3mm, carbon powder size ≤ 3mm. When the amount of metal material added exceeds 110 tons, type III direct reduced iron powder and carbon powder mixture is sprayed, the injection rate of type III direct reduced iron powder and carbon powder mixture is 135kg / min, and the oxygen injection rate is reduced to 125Nm 3 / min, the mixture of Type III direct reduced iron powder and carbon powder accounts for 15% direct reduced iron powder and 85% carbon powder. The size of the direct reduced iron powder is 2-4mm, and the size of the carbon powder is ≤1mm. Lime and light-burned dolomite are added in batches during the smelting process, with each batch adding 800kg. The direct reduced iron powder and carbon powder mixture is injected at 30.5kg / t steel throughout the smelting process; oxygen blowing is 29Nm 3 / t steel; total lime addition was 29.5kg / t steel, and total light-burned dolomite addition was 24.3kg / t steel. The slag basicity was 2.18, the MgO content was 9.7wt%, and the FeO content was 25.3wt%. Foamy slag was produced throughout the smelting process, achieving good submerged arc performance. The final smelting temperature was 1614°C, power consumption was 337kWh / t, and the smelting cycle was 35 minutes. Example 4

[0023] Taking a 150-ton electric arc furnace as an example, the total amount of molten steel in the electric arc furnace can reach 230-250 tons. 60 tons of steel (about 40% steel) and 10.5 tons of slag (about 7% slag) are retained from the previous furnace. The arc is struck and energized, and metal material is added at a rate of 5-7 tons / min. When the furnace temperature reaches 1580°C, a mixture of Type I direct reduced iron powder and carbon powder and oxygen are sprayed (the metallization rate of the direct reduced iron powder is 94%, the total iron content is 89.3%, the carbon content is 3.2%, and the gangue content is 5.9%; the carbon content of the carbon powder is 81.4% and the moisture content is 0.7%). The injection rate of the Type I direct reduced iron powder and carbon powder mixture is 80 kg / min, and the oxygen injection rate is 80 Nm 3 / min, in the mixture of type I direct reduced iron powder and carbon powder, direct reduced iron powder accounts for 40%, carbon powder accounts for 60%, direct reduced iron powder size is 2-4mm, carbon powder size is 1-3mm. When the amount of metal material added exceeds 50 tons, type II direct reduced iron powder and carbon powder mixture is sprayed, the injection rate of type II direct reduced iron powder and carbon powder mixture is 150kg / min, and the oxygen injection rate is increased to 180Nm 3 / min, in the mixture of type II direct reduced iron powder and carbon powder, direct reduced iron powder accounts for 20%, carbon powder accounts for 80%, direct reduced iron powder size ≤3mm, carbon powder size ≤3mm. When the amount of metal material added exceeds 110 tons, type III direct reduced iron powder and carbon powder mixture is sprayed, the injection rate of type III direct reduced iron powder and carbon powder mixture is 120kg / min, and the oxygen injection rate is reduced to 130Nm 3 / min, the mixture of Type III direct reduced iron powder and carbon powder accounts for 10% direct reduced iron powder and 90% carbon powder. The size of the direct reduced iron powder is 2-4mm, and the size of the carbon powder is ≤1mm. Lime and light-burned dolomite are added in batches during the smelting process, with each batch adding 800kg. The mixture of direct reduced iron powder and carbon powder is injected at 26.5kg / t steel throughout the smelting process; oxygen blowing is 26Nm 3 / t steel; total lime addition was 23.3kg / t steel, and total light-burned dolomite addition was 22.5kg / t steel. The slag basicity was 1.92, the MgO content was 8.7wt%, and the FeO content was 28.2wt%. Foamy slag was produced throughout the smelting process, achieving good submerged arc performance. The final smelting temperature was 1630°C, the power consumption was 345kWh / t steel, and the smelting cycle was 37 minutes. Example 5

[0024] Taking a 150-ton electric arc furnace as an example, the total amount of molten steel in the electric arc furnace can reach 230 to 250 tons. 68 tons of steel (about 45% of the steel is retained) and 15 tons of slag (about 10% of the slag is retained) are left in the previous furnace. The arc is struck and the power is turned on. Metal materials are added at a rate of 5-7 tons / min. When the temperature in the furnace reaches 1560°C, type I direct reduced iron powder and carbon powder mixture and oxygen are sprayed (direct reduced iron powder metallization rate 94%, total iron content 89.3%, carbon content 3.2%, gangue content 5.9%; carbon content in carbon powder 81.4%, moisture 0.7%). The injection rate of type I direct reduced iron powder and carbon powder mixture is 110kg / min, and the oxygen injection rate is 90Nm 3 / min, direct reduced iron powder and carbon powder mixture is injected, direct reduced iron powder accounts for 35%, carbon powder accounts for 65%, direct reduced iron powder size is 2-4mm, carbon powder size is 1-3mm. When the amount of metal material added exceeds 50 tons, type II direct reduced iron powder and carbon powder mixture is injected, the injection rate of type II direct reduced iron powder and carbon powder mixture is 190kg / min, and the oxygen injection rate is increased to 180Nm 3 / min, in the mixture of type II direct reduced iron powder and carbon powder, direct reduced iron powder accounts for 25%, carbon powder accounts for 75%, direct reduced iron powder size ≤3mm, carbon powder size ≤3mm. When the amount of metal material added exceeds 110 tons, type III direct reduced iron powder and carbon powder mixture is sprayed, the injection rate of type III direct reduced iron powder and carbon powder mixture is 125kg / min, and the oxygen injection rate is reduced to 130Nm 3 / min, the mixture of Type III direct reduced iron powder and carbon powder accounts for 15% direct reduced iron powder and 85% carbon powder. The size of the direct reduced iron powder is 2-4mm, and the size of the carbon powder is ≤1mm. Lime and light-burned dolomite are added in batches during the smelting process, with each batch adding 700kg. The direct reduced iron powder and carbon powder mixture is injected at 32.5kg / t steel throughout the smelting process; oxygen blowing is 27.5Nm 3 / t steel; total lime addition was 28.6kg / t steel, and total light-burned dolomite addition was 17.6kg / t steel. The slag basicity was 2.13, the MgO content was 7.7wt%, and the FeO content was 25.3wt%. Foamy slag was produced throughout the smelting process, achieving good submerged arc performance. The final smelting temperature was 1621°C, the power consumption was 343kWh / t steel, and the smelting cycle was 36 minutes.

[0025] Blank comparison

[0026] Taking a 150-ton electric arc furnace as an example, the total amount of molten steel in the furnace can reach 230-250 tons. 68 tons of steel (about 45% steel) and 15 tons of slag (about 10% slag) are retained from the previous furnace. The arc is struck and energized, and metal is added at a rate of 5-7 tons / min. When the furnace temperature reaches 1560°C, carbon powder and oxygen are injected (the carbon content of the carbon powder is 81.4% and the moisture content is 0.7%). The carbon powder injection rate is 85kg / min, and the oxygen injection rate is 800Nm 3 / min, carbon powder size ≤3mm. When the amount of metal material added exceeds 50 tons, the carbon powder blowing rate is 160kg / min, and the oxygen blowing rate is increased to 180Nm 3 / min, carbon powder size ≤3mm. When the amount of metal material added exceeds 110 tons, the carbon powder blowing rate is 120kg / min, and the oxygen blowing rate is reduced to 120Nm 3 / min, carbon powder size ≤3mm. Lime and light-burned dolomite are added in batches during the smelting process, with each batch adding 800kg. During the entire smelting process, 32.5kg / t steel of carbon powder is injected; 29Nm of oxygen is blown. 3 / t steel; total lime addition was 28kg / t steel, and total calcined dolomite addition was 24kg / t steel. Foamy slag was produced throughout the smelting process, achieving good submerged arc performance. The final smelting temperature was 1617°C, power consumption was 362kWh / t, and the smelting cycle was 40 minutes.

[0027] Figure 1 The power factor of the smelting process of the blank comparison furnace (injection of carbon powder) is: Figure 2 This is the power factor of the smelting process of Example 1. A high power factor and a stable power factor indicate that the slag is well foamed and the arc buried effect of the foamed slag is good. Figure 1 and Figure 2 As shown, it can be seen that the power factor of the blank comparative heat is low and the power factor control is unstable, indicating that the foam slag is unstable during the smelting process and the submerged arc effect is poor. The power factor of the embodiment 1 heat is high and the power factor control is stable. The foam slag is produced throughout the smelting process, the slag foaming is good, and the submerged arc effect is good, which is conducive to reducing smelting power consumption, shortening the smelting cycle, and reducing steelmaking costs.

[0028] The embodiments described above are only used to illustrate the technical ideas and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of the present invention. Equivalent changes and modifications made without departing from the concept and principles of the present invention still fall within the scope of the patent of the present invention.

Claims

1. A smelting method for producing foamed slag using direct reduced iron powder and carbon powder, characterized in that: The method includes the following steps: (1) Adopting steel and slag retention operation; (2) Start the arc and add metal materials. When the temperature of the molten steel reaches 1520-1580℃, spray the mixture of direct reduced iron powder and carbon powder into the molten steel. The spraying amount of the direct reduced iron powder and carbon powder mixture is 25-35kg / ton of steel. (3) While spraying the mixture of direct reduced iron powder and carbon powder, oxygen is sprayed into the molten steel. The oxygen injection rate is 25-30 Nm per ton of steel. 3 / t steel; (4) During the smelting process, lime and light-burned dolomite are added to the molten steel in batches; the slag basicity is controlled to 1.8-2.2, the MgO content is 7-10wt%, and the FeO content is 20-30wt%.

2. The smelting method of making foamed slag using direct reduced iron powder and carbon powder according to claim 1, characterized in that: In step (1), the amount of steel retained is 40-50 wt%, and the amount of slag retained is 7-12 wt%.

3. The smelting method of making foamed slag using direct reduced iron powder and carbon powder according to claim 1, characterized in that: The direct reduced iron powder in step (2) has a metallization rate of 90-95%, a total iron content of ≥80wt%, a carbon content of 2-6wt%, and a gangue content of ≤8wt%; The carbon content in the carbon powder is ≥80wt%, and the moisture content is ≤1%.

4. The smelting method of making foamed slag using direct reduced iron powder and carbon powder according to claim 1, characterized in that: When the amount of metal material added in step (2) is different, the injection rate of the direct reduced iron powder and carbon powder mixture, the oxygen injection rate, the ratio of carbon powder to direct reduced iron powder, and the size of the direct reduced iron powder and carbon powder are different, and the direct reduced iron powder and carbon powder mixture is divided into type I direct reduced iron powder and carbon powder mixture, type II direct reduced iron powder and carbon powder mixture, and type III direct reduced iron powder and carbon powder mixture.

5. The smelting method of making foamed slag using direct reduced iron powder and carbon powder according to claim 4, characterized in that: The amount of metal material added is within 30wt%, and the mixture of type I direct reduced iron powder and carbon powder is sprayed. The spraying rate of type I direct reduced iron powder and carbon powder mixture is 80-120kg / min, and the oxygen spraying rate is 60-100Nm 3 / min; the proportion of direct reduced iron powder in the mixture of Type I direct reduced iron powder and carbon powder is 30wt% to 50wt%; the size of the direct reduced iron powder in the mixture of Type I direct reduced iron powder and carbon powder is 2 to 4mm, and the size of the carbon powder is 1 to 3mm.

6. The smelting method of making foamed slag using direct reduced iron powder and carbon powder according to claim 4, characterized in that: The amount of metal material added is 30-70wt%, and the mixture of type II direct reduced iron powder and carbon powder is sprayed at a rate of 150-200kg / min and an oxygen spray rate of 150-200Nm 3 / min; the proportion of direct reduced iron powder in the type II direct reduced iron powder and carbon powder mixture is 20-30wt%; the size of the direct reduced iron powder in the type II direct reduced iron powder and carbon powder mixture is ≤3mm, and the size of the carbon powder is ≤3mm.

7. The smelting method of making foamed slag using direct reduced iron powder and carbon powder according to claim 4, characterized in that: The amount of metal added exceeds 70wt%, and a mixture of type III direct reduced iron powder and carbon powder is sprayed. The spraying rate of the mixture of type III direct reduced iron powder and carbon powder is 120-150kg / min, and the oxygen spraying rate is 100-150Nm 3 / min; the proportion of direct reduced iron powder in the mixture of type III direct reduced iron powder and carbon powder is 10-20wt%; the size of the direct reduced iron powder in the mixture of type III direct reduced iron powder and carbon powder is 2-4mm, and the size of the carbon powder is ≤1mm.

8. The smelting method for producing foamed slag using direct reduced iron powder and carbon powder according to claim 1, characterized in that: In step (4), the amount of lime and light-burned dolomite added in each batch is 500-1000 kg, the total amount of lime added is 20-30 kg / t steel, and the total amount of light-burned dolomite added is 15-25 kg / t steel.

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