A smelting method for reducing dry dusting and explosion relief by high-carbon steel converter phosphorus control point blowing

Abstract

A smelting method of high-carbon steel converter control phosphorus point blowing for reducing dry dusting and explosion, the smelting method at least includes the following steps: mixing scrap steel with molten iron, adjusting the oxygen lance position after adding iron, blowing I by inputting oxygen, after the molten iron is ignited, adding slagging material to control the alkalinity, adjusting the oxygen lance position again, blowing II by constant oxygen flow, until the smelting endpoint is reached, obtaining P content >= 0.013% of the molten steel liquid to be tapped; adjusting the position of the converter skirt, starting the fan to ensure the micro-positive pressure in the furnace, adjusting the oxygen lance position again, inputting nitrogen to dilute the gas in the pipeline, adding dephosphorizing agent, inputting oxygen to carry out "point blowing", lifting the oxygen lance, stopping blowing oxygen, tilting the converter for tapping, restoring the converter to the original position, adjusting the oxygen lance position, inputting nitrogen to carry out slag splashing for protecting the furnace, tilting the converter for slagging after slag splashing, reserving part of the slag for the next furnace smelting. The method can effectively reduce the "explosion" accident rate, shorten the oxygen lance blowing-off time, and improve the dephosphorization rate.

Description

Technical Field

[0001] This invention relates to the field of high-carbon steel smelting technology, and in particular to a smelting method for controlling phosphorus blowing in a high-carbon steel converter to reduce dry dust removal and explosion venting. Background Technology

[0002] Dephosphorization requires strong oxidizing properties (high FeO slag, mainly obtained from the reaction of oxygen and iron) and low temperature (≤1600℃). However, under high carbon conditions, carbon will preferentially react with oxygen (C+O→CO). High carbon steel requires a higher final carbon content (e.g., ≥0.6%) to inhibit the formation of FeO in the slag and weaken the dephosphorization ability. However, low phosphorus must be achieved at the same time. This leads to the following contradiction in the smelting process: high temperature (≥1650℃) is conducive to decarburization, but it will worsen the dephosphorization reaction (the dephosphorization reaction proceeds in reverse at high temperature). High-carbon steel is produced at high tapping temperatures and has high carbon content. If the endpoint control is not properly implemented, P2O5 in the slag may be reduced by carbon (P2O5 + 5C → 2P + 5CO), leading to phosphorus reversion. Therefore, during the endpoint of high-carbon steel production, oxygen blowing is stopped at the lance and the sampling results are awaited to determine whether to tap the steel. If the endpoint composition is not in line with the requirements, mainly due to excessive phosphorus content, it is necessary to stop oxygen blowing again. This process is called "point blowing" and is used to balance the endpoint hit rate of carbon and phosphorus.

[0003] Many steelmaking enterprises use dry dust removal systems. During the smelting process, when the gas analyzer detects that the carbon monoxide concentration in the pipeline is greater than 9% and the oxygen concentration is greater than 6%, the converter dry dust removal system will interlock and force the converter to stop oxygen blowing (i.e., raise the lance) to ensure the safe operation of the equipment, thereby reducing the probability of system "explosion" and avoiding affecting the normal steelmaking process. However, when the lance is lowered for "point blowing," the high temperature of the molten steel will cause a violent reaction between carbon and oxygen, generating carbon monoxide. At this time, the instantaneous gas composition in the pipeline is air, with an oxygen concentration greater than 6% and a carbon monoxide concentration greater than 9%, resulting in an "explosion" accident.

[0004] Currently, the high phosphorus content in high-carbon steel smelting technology leads to a high probability of explosion accidents due to the "point blowing" of phosphorus-controlled lances in converters. To address this issue, a smelting method for reducing explosion accidents caused by point blowing of phosphorus-controlled lances in high-carbon steel converters using dry dust removal is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a smelting method for controlling phosphorus levels in high-carbon steel converters by point blowing to reduce dry dust and explosion venting. Because high-carbon steel has high tapping temperatures and high carbon content, improper endpoint control can lead to the reduction of P2O5 in the slag by carbon (P2O5 + 5C → 2P + 5CO), resulting in phosphorus reversion. Therefore, at the endpoint of high-carbon steel production, oxygen blowing is stopped by raising the lance and awaiting sampling results to determine whether to tap the steel. If the phosphorus level is too high, oxygen blowing needs to be resumed, but at this time, a large amount of air remains in the pipeline, with an oxygen concentration far exceeding 9 mg / L. 3 / h, under these carbon conditions, a large amount of carbon monoxide is generated the instantaneously upon starting the blowing process, with the concentration exceeding 6m³. 3 The explosion occurred at a rate of / h, forcing a production halt while awaiting the restoration of the dry dust collection equipment. This impacted equipment utilization and increased production costs.

[0006] To prevent explosion accidents caused by "point blowing" of high-carbon steel, this invention provides a method for preventing explosions, which specifically includes the following scheme:

[0007] 1. Adjust the position and flow rate of the oxygen lance (to reduce the oxygen concentration at the moment of starting the blowing);

[0008] 2. Add dephosphorization residue for dephosphorization (cooling down and increasing oxidizing properties are beneficial for dephosphorization, and inhibit the instantaneous generation of carbon monoxide);

[0009] 3. Before the bottom blower is applied, the converter hood is lowered and the blower is turned on to ensure a slight positive pressure inside the furnace and prevent outside air from entering the furnace.

[0010] 4. Raise the oxygen lance to the oxygen lance inlet and blow nitrogen into the converter to eliminate and dilute the air in the pipeline and reduce the oxygen concentration in the pipeline.

[0011] According to one aspect of the present invention, a smelting method for controlling phosphorus blowing and reducing dry dust removal and explosion venting in a high-carbon steel converter is provided, the smelting method comprising the following steps:

[0012] Step 1, Iron mixing and slag blowing: Mix scrap steel with molten iron, adjust the oxygen lance position after mixing with iron, and introduce oxygen for blowing I. After the molten iron ignites, add slag material to control the basicity to 2.8-3.0 and the magnesium oxide content in the slag to 6%-8%. Adjust the oxygen lance position again and maintain a constant oxygen flow rate for blowing II until the smelting endpoint. Test if the P content in the molten steel to be tapped is ≥0.013%, then "spot blowing" is required, i.e., the molten steel to be "spot blown".

[0013] Step 2, "Ignition Blowing": Before ignition blowing, adjust the position of the converter skirt, turn on the blower to ensure a slight positive pressure inside the furnace, and adjust the oxygen lance position to the oxygen lance inlet, with an incoming flow rate of 22,000–28,000 Nm³. 3 Nitrogen gas is used to dilute the gas in the pipeline at a rate of / h. A dephosphorizing agent is added, the oxygen lance position is readjusted, and oxygen is introduced to "spot blow" the molten steel described in step 1 to obtain the molten steel after "spot blowing".

[0014] Step 3, tapping: The tilting converter taps the molten steel obtained in Step 2 after "point blowing". After tapping, the converter is returned to its original position, the oxygen lance position is adjusted, and nitrogen is introduced for slag splashing and furnace protection. After slag splashing and furnace protection, the tilting converter is used to dump the slag, and some slag is retained for the next heat of smelting.

[0015] Optionally, the mass ratio of scrap steel to molten iron in step 1 is 1:6 to 8.

[0016] Optionally, after adding iron in step 1, adjust the oxygen lance position to be 1.8–2.2 m above the molten iron surface;

[0017] In step 1, the oxygen flow rate during blowing I is 28000–35000 Nm³. 3 / h;

[0018] The blowing time in step 1 is 10-20 seconds.

[0019] Optionally, the slag-forming material in step 1 is CaO and CaMg(CO3)2;

[0020] The amount of slag-forming material added in step 1 is 4-6% of the molten iron;

[0021] In step 1, the oxygen lance position was readjusted to be 2.2m to 2.4m above the molten iron surface.

[0022] The blowing time in step 1 is 12.8–13.5 min;

[0023] The constant oxygen flow rate of the blowing process II described in step 1 is 28000–32000 Nm³. 3 / h.

[0024] Furthermore, at the end of the smelting process described in step 1, oxygen blowing is stopped, and the oxygen lance is raised to a distance of 10m from the surface of the molten steel. At this time, the instantaneous oxygen concentration in the pipeline is 1-4%, and the temperature of the molten steel is 1600-1670℃.

[0025] When the smelting endpoint is reached as described in step 1, stop blowing oxygen and raise the oxygen lance to the waiting position, that is, the oxygen lance nozzle is 10m away from the surface of the molten steel. At this time, the oxygen concentration in the pipeline is 22-26%.

[0026] The carbon monoxide concentration in the pipeline at the end of the smelting process described in step 1 is 0-9%.

[0027] Optionally, the distance between the converter shroud and the furnace opening in step 2 is ≤20mm;

[0028] The nitrogen flow rate in step 2 is 22000–28000 Nm³. 3 / h;

[0029] After nitrogen gas is introduced to dilute the oxygen in the pipeline in step 2, the oxygen concentration is 0-3%.

[0030] After nitrogen gas is introduced in step 2 for dilution, the carbon monoxide concentration in the pipeline is 0-3%.

[0031] Optionally, the dephosphorizing agent in step 2 is iron oxide scale.

[0032] Optionally, the amount of dephosphorizing agent added in step 2 is 0.3-0.6% of the molten iron;

[0033] In step 2, the oxygen lance position is adjusted again to be 2.4 to 2.5 meters away from the molten steel surface.

[0034] Optionally, the oxygen flow rate during the "point blowing" in step 2 is 26000–28000 Nm³. 3 / h;

[0035] The "point blowing" time mentioned in step 2 is 10-12 seconds.

[0036] Optionally, when tapping steel from the tilted converter described in step 3, the tilt angle of the converter is 90 to 100°.

[0037] The tapping time in step 3 is 5 to 7 minutes;

[0038] The nitrogen flow rate during slag splashing for furnace protection in step 3 is 22000–26000 Nm³. 3 / h;

[0039] In step 3, the oxygen lance position is adjusted to be 2.5–3 m above the steel slag.

[0040] The slag splashing and furnace protection time mentioned in step 3 is 2 to 4 minutes.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] (1) The technical solution of the present invention reduces the concentration of oxygen and carbon monoxide by adjusting the oxygen lance position and flow rate, improving the slag formation mode, and optimizing the temperature system. The number of "explosion leakage" accidents has been reduced from 77 per 100 furnaces to 35 after optimization, effectively reducing the "explosion leakage" accident rate.

[0043] (2) Through the technical solution of the present invention, the oxygen lance stop blowing time after the "explosion" accident is reduced from 8.11 min to 3.62 min, the waiting time is significantly reduced, and the effective operation rate of the converter is guaranteed.

[0044] (3) Through the technical solution of the present invention, the converter blowing time is not significantly changed, but the dephosphorization rate of the slag in the converter is increased by 0.45% compared with the previous one, which ensures the final component qualification rate of the molten steel. Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0046] Unless otherwise specified, the raw materials and reagents used in the examples and comparative examples were all obtained through purchase;

[0047] In this embodiment of the invention, the molten iron is obtained by self-production through blast furnace steelmaking;

[0048] The basicity calculation formula in the examples is CaO / SiO2. The CaO content mainly comes from the decomposition of lime and dolomite; the SiO2 content is mainly produced by the oxidation of silicon in molten iron. The main component of lime is CaO; the main component of dolomite is CaCO3·MgCO3 (i.e., CaMg(CO3)2, which decomposes into CaO and MgO after high-temperature calcination). Adding dolomite can increase the MgO content in the slag, effectively reducing the erosion of the furnace lining by the slag.

[0049] This invention provides a smelting method for controlling phosphorus blowing and reducing dry dust removal and explosion venting in a high-carbon steel converter, as detailed in the specific embodiments section. The smelting method includes at least the following steps:

[0050] Step 1, Iron mixing and slag blowing: Mix scrap steel with molten iron, adjust the oxygen lance position after mixing with iron, and introduce oxygen for blowing I. After the molten iron ignites, add slag material to control the basicity to 2.8-3.0 and the magnesium oxide content in the slag to 6%-8%. Adjust the oxygen lance position again and maintain a constant oxygen flow rate for blowing II until the smelting endpoint. Test if the P content of the molten steel to be tapped is ≥0.013%, then "spot blowing" is required, i.e., the molten steel to be "spot blown".

[0051] Step 2, "Ignition Blowing": Before ignition blowing, adjust the position of the converter skirt, turn on the blower to ensure a slight positive pressure inside the furnace, and adjust the oxygen lance position to the oxygen lance inlet, with an incoming flow rate of 22,000–28,000 Nm³. 3 Nitrogen gas is used to dilute the gas in the pipeline at a rate of / h. A dephosphorizing agent is added, the oxygen lance position is readjusted, and oxygen is introduced to "spot blow" the molten steel described in step 1 to obtain the molten steel after "spot blowing".

[0052] Step 3, tapping: The tilting converter taps the molten steel obtained in Step 2 after "point blowing". After tapping, the converter is returned to its original position, the oxygen lance position is adjusted, and nitrogen is introduced for slag splashing and furnace protection. After slag splashing and furnace protection, the tilting converter is used to dump the slag, and some slag is retained for the next heat of smelting.

[0053] Based on the above technical solution, the mixing mass ratio of scrap steel to molten iron in step 1 is 1:6 to 8.

[0054] Based on the above technical solution, in step 1, after adding iron, adjust the oxygen lance position to be 1.8 to 2.2 m away from the molten iron surface;

[0055] In step 1, the oxygen flow rate during blowing I is 28000–35000 Nm³. 3 / h;

[0056] The blowing time in step 1 is 10-20 seconds.

[0057] Based on the above technical solution, the slag-forming material mentioned in step 1 is CaO and CaMg(CO3)2;

[0058] The amount of slag-forming material added in step 1 is 4-6% of the molten iron;

[0059] In step 1, the oxygen lance position was readjusted to be 2.2m to 2.4m above the molten iron surface.

[0060] The blowing time in step 1 is 12.8–13.5 min;

[0061] The constant oxygen flow rate of the blowing process II described in step 1 is 28000–32000 Nm³. 3 / h.

[0062] Based on the above technical solution, when the smelting endpoint is reached in step 1, oxygen blowing is stopped, and the oxygen lance is raised to a distance of 10m from the surface of the molten steel. At this time, the instantaneous oxygen concentration in the pipeline is 1-4%, and the temperature of the molten steel is 1600-1670℃.

[0063] When the smelting endpoint is reached as described in step 1, stop blowing oxygen and raise the oxygen lance to the waiting position, that is, the oxygen lance nozzle is 10m away from the surface of the molten steel. At this time, the oxygen concentration in the pipeline is 22-26%.

[0064] The carbon monoxide concentration in the pipeline at the end of the smelting process described in step 1 is 0-9%.

[0065] Based on the above technical solution, the distance between the converter shroud and the furnace opening in step 2 is ≤20mm;

[0066] The nitrogen flow rate in step 2 is 22000–28000 Nm³. 3 / h;

[0067] After nitrogen gas is introduced to dilute the oxygen in the pipeline in step 2, the oxygen concentration is 0-3%.

[0068] After nitrogen gas is introduced in step 2 for dilution, the carbon monoxide concentration in the pipeline is 0-3%.

[0069] Based on the above technical solution, the dephosphorizing agent in step 2 is iron oxide scale;

[0070] The amount of dephosphorizing agent added in step 2 is 0.3-0.6% of the molten iron;

[0071] In step 2, the oxygen lance position is adjusted again to be 2.4 to 2.5 meters away from the molten steel surface.

[0072] Based on the above technical solution, the oxygen flow rate during the "point blowing" in step 2 is 26000~28000 Nm³. 3 / h;

[0073] The "point blowing" time mentioned in step 2 is 10-12 seconds.

[0074] Based on the above technical solution, when the tilted converter is tapping steel in step 3, the tilt angle of the converter is 90-100°.

[0075] The tapping time in step 3 is 5 to 7 minutes;

[0076] The nitrogen flow rate during slag splashing for furnace protection in step 3 is 22000–26000 Nm³. 3 / h;

[0077] In step 3, the oxygen lance position is adjusted to be 2.5–3 m above the steel slag.

[0078] The slag splashing and furnace protection time mentioned in step 3 is 2 to 4 minutes.

[0079] Example 1

[0080] Step 1, Iron Mixing and Slag Formation: Mix 18 tons of scrap steel with 153 tons of molten iron (molten iron with a C mass concentration of 4.22%, Si mass concentration of 0.41%, Mn mass concentration of 0.15%, P mass concentration of 0.087%, S mass concentration of 0.016%, and molten iron temperature of 1325℃). Adjust the oxygen lance position to 1.8m above the molten iron, and set the oxygen flow rate to 30000 Nm³. 3 / h, blowing for 18s; after the molten iron ignites, add 4900kg CaO and 1600kg CaMg(CO3)2 to control the basicity at 3.0, and the magnesium oxide content in the slag is 8%; adjust the oxygen lance position to 2.2m away from the molten iron, and keep the oxygen flow rate constant at 32000Nm 3 The oxygen blowing time is 13.2 minutes per hour, continuing until the smelting endpoint. At the endpoint, oxygen blowing is stopped, and the oxygen lance is raised to the waiting position (i.e., the oxygen lance nozzle is 10 meters away from the molten steel surface). The instantaneous oxygen concentration in the pipeline is 4%, and after a short while, the oxygen concentration in the pipeline is 26.2%, the carbon monoxide concentration is 4.8%, the P mass concentration in the molten steel is 0.015%, and the temperature of the molten steel is 1662℃. The resulting molten steel has a P content ≥ 0.013%, which does not meet the steel grade requirement of P ≤ 0.013%, so a spot blowing operation is required.

[0081] Step 2, "Instantaneous Blowing": Before instantaneous blowing, place the converter hood skirt 20mm from the furnace opening, turn on the blower to ensure a slight positive pressure inside the furnace (i.e., the flue gas in the furnace escapes from the furnace opening), and prevent outside air from entering the furnace; adjust the oxygen lance position to the oxygen lance inlet (i.e., the oxygen lance nozzle is 10mm from the molten steel surface), with a flow rate of 26000 Nm³. 3Nitrogen gas is introduced at a rate of 26000 Nm³ / h to dilute the air in the pipeline and reduce the gas concentration (after dilution, the oxygen concentration in the pipeline is 3.0% and the carbon monoxide concentration is 2.6%). 500 kg of iron oxide scale is added to the furnace, and the oxygen lance is raised to a position 2.4 m above the molten steel surface. 3 / h "spot blow" the molten steel with P content ≥0.013% obtained in step 1 for 12s to obtain the molten steel to be tapped, and no leakage or explosion accident occurred.

[0082] Step 3, tapping: The converter is tilted 96° to tap the molten steel obtained in Step 2 after "point blowing". After tapping for 6 minutes, the converter is returned to its original position (i.e., 0°). The oxygen lance position is adjusted to 2.5m above the slag. Oxygen blowing is stopped, the gas is switched, and nitrogen is introduced for slag splashing protection for 2 minutes. After the slag splashing protection is completed, the converter is tilted 97° to remove 1 / 2 of the slag (4200kg), and 1 / 2 of the slag (4300kg) is retained for the next heat. The blowing and explosion relief conditions in this embodiment are shown in Table 1. As can be seen from Table 1, the dephosphorization rate is 86.13% through blowing in this embodiment, the average stop blowing time is 3.21 minutes per 100 heats, and the number of explosion reliefs is 36.

[0083] Example 2

[0084] Step 1, Iron Mixing and Slag Formation: Mix 20 tons of scrap steel with 151 tons of molten iron (molten iron with a C mass concentration of 4.15%, Si mass concentration of 0.38%, Mn mass concentration of 0.15%, P mass concentration of 0.091%, S mass concentration of 0.015%, and molten iron temperature of 1322℃). Adjust the oxygen lance position to 1.8m above the molten iron, and set the oxygen flow rate to 30000 Nm³. 3 / h, blowing for 18s; after the molten iron ignites, add 5100kg CaO and 2100kg CaMg(CO3)2 to control the basicity at 3.0, and the magnesium oxide content in the slag is 8%; adjust the oxygen lance position to 2.2m away from the molten iron, and keep the oxygen flow rate constant at 32000Nm 3 The oxygen blowing time is 13.4 minutes per hour, continuing until the smelting endpoint is reached. At the endpoint, oxygen blowing is stopped, and the oxygen lance is raised to the waiting position, i.e., the oxygen lance nozzle is 10 meters from the molten steel surface. The instantaneous oxygen concentration in the pipeline is 2.5%, and after a short while, the oxygen concentration in the pipeline is 25.2%, the carbon monoxide concentration is 5%, the P mass concentration in the molten steel is 0.016%, and the temperature of the molten steel is 1660℃. The resulting molten steel has a P content ≥ 0.013%, which does not meet the steel grade requirement of P ≤ 0.013%, necessitating a periodic blowing operation.

[0085] Step 2, "Instantaneous Blowing": Before instantaneous blowing, place the converter hood skirt 20mm from the furnace opening, turn on the blower to ensure a slight positive pressure inside the furnace (i.e., the flue gas in the furnace is escaping from the furnace opening), and prevent outside air from entering the furnace; adjust the oxygen lance position to the oxygen lance inlet (i.e., the oxygen lance nozzle is 10mm from the molten steel surface), with a flow rate of 28000 Nm³. 3 Nitrogen gas is introduced at a rate of 200 Nm³ / h to dilute the air in the pipeline and reduce the gas concentration (after dilution, the oxygen concentration in the pipeline is 2% and the carbon monoxide concentration is 3%). 600 kg of iron oxide scale is added to the furnace, and the oxygen lance is raised to a distance of 2.4 m from the molten steel, with an oxygen flow rate of 26000 Nm³ / h. 3 / h "spot blow" the molten steel with P content ≥0.013% obtained in step 1 for 11s to obtain the molten steel to be tapped, and no leakage or explosion accident occurred.

[0086] Step 3, tapping: Tilting the converter at 97°, tap the molten steel obtained in Step 2 after "point blowing" for 5 minutes. After tapping, return the converter to its original position (0°), and place the oxygen lance 2.4m above the slag, with a nitrogen flow rate of 24000 Nm³. 3 The slag splashing protection process is carried out for 2 minutes per hour. After the slag splashing protection is completed, the converter is tilted at 98° to remove 1 / 2 of the slag (4250 kg), and 1 / 2 of the slag (4500 kg) is retained for the next furnace smelting. The blowing and explosion relief conditions in this embodiment are shown in Table 1. As can be seen from Table 1, the dephosphorization rate is 85.27% through blowing in this embodiment, the average shutdown time per 100 furnaces is 4.14 minutes, and the number of explosion reliefs is 29.

[0087] Example 3

[0088] Step 1, Iron Mixing and Slag Formation: Mix 20 tons of scrap steel with 151 tons of molten iron (molten iron with a C mass concentration of 4.02%, Si mass concentration of 0.33%, Mn mass concentration of 0.175%, P mass concentration of 0.094%, S mass concentration of 0.015%, and molten iron temperature of 1318℃). Adjust the oxygen lance position to 1.8m above the molten iron, and set the oxygen flow rate to 33000 Nm³. 3 / h, blowing for 12s; after the molten iron ignites, add 4100kg CaO and 1800kg CaMg(CO3)2 to control the basicity at 2.9, and the magnesium oxide content in the slag is 8%; adjust the oxygen lance position to 2.2m away from the molten iron, and keep the oxygen flow rate constant at 32000Nm 3 / h, the total oxygen blowing time is 12.8min until the end of smelting. When the end of smelting is reached, oxygen blowing is stopped and the oxygen lance is raised to the waiting position, that is, the oxygen lance nozzle is 10m away from the surface of the molten steel. The instantaneous oxygen concentration in the pipeline is 1%, and after a while the oxygen concentration in the pipeline is 26%, the carbon monoxide concentration is 4.7%, the mass concentration of P in the molten steel is 0.015%, and the temperature of the molten steel is 1650℃. The molten steel with P content ≥0.013% is obtained.

[0089] Step 2, "Instantaneous Blowing": Before instantaneous blowing, place the converter hood skirt 20mm from the furnace opening, turn on the blower to ensure a slight positive pressure inside the furnace (the flue gas in the furnace escapes from the furnace opening), and prevent outside air from entering the furnace; adjust the oxygen lance position to the oxygen lance inlet (i.e., the oxygen lance nozzle is 10mm from the molten steel surface), with a flow rate of 35000 Nm³. 3 Nitrogen gas is introduced at a rate of 28000 Nm³ / h to dilute the air in the pipeline and reduce the oxygen concentration (after dilution, the oxygen concentration in the pipeline is 2.3% and the carbon monoxide concentration is 2%). 750 kg of iron oxide scale is added, and the oxygen lance is raised to a position 2.5 m above the molten steel. 3 / h "spot blow" the molten steel with P content ≥0.013% obtained in step 1 for 10s to obtain the molten steel to be tapped, and no leakage or explosion accident occurred.

[0090] Step 3, tapping: The converter is tilted at 95° to tap the molten steel obtained in Step 2 after "point blowing". After tapping for 6 minutes, the converter is returned to its original position (tilt angle is 0°). The oxygen lance is placed 2.4m above the slag, oxygen blowing is stopped, and nitrogen is introduced for slag splashing protection for 3 minutes. After the slag splashing protection is completed, the converter is tilted at 94° to remove 1 / 2 of the slag (4700kg), and 1 / 2 of the slag (4500kg) is retained for the next heat. The blowing and explosion relief conditions in this embodiment are shown in Table 1. As can be seen from Table 1, the dephosphorization rate is 86.78% through blowing in this embodiment, the average stop blowing time is 3.51 minutes per 100 heats, and the number of explosion reliefs is 40.

[0091] Comparative Example

[0092] The difference from Example 1 is that step 2 involves "point blowing," during which a venting explosion occurs, forcing a production halt. This is equivalent to step 1, iron mixing and slag formation: 18 tons of scrap steel are mixed with 153 tons of molten iron (the molten iron has a C concentration of 4.22%, Si concentration of 0.41%, Mn concentration of 0.15%, P concentration of 0.087%, S concentration of 0.016%, and a temperature of 1325°C). The oxygen lance is positioned 1.8 meters from the molten iron, and the oxygen flow rate is 35000 Nm. 3 / h, blowing for 18s; after the molten iron ignites, add 5000kg CaO and 1600kg CaMg(CO3)2 to control the basicity at 3.0, and the magnesium oxide content in the slag is 8%; adjust the oxygen lance position to 2.2m away from the molten iron, and keep the oxygen flow rate constant at 32000Nm 3 / h, the total oxygen blowing time is 13.3min, until the smelting end point, to obtain molten steel with P content ≥0.013% to be tapped.

[0093] Step 2, Pre-tapping preparation: Upon reaching the smelting endpoint, adjust the oxygen lance position to the oxygen lance inlet (i.e., 9.8m from the molten steel surface). At this point, the oxygen concentration in the pipeline is 26.2%, the carbon monoxide concentration is 4.8%, the phosphorus concentration in the molten steel is 0.015%, and the steel temperature is 1662℃. The converter shroud is positioned 40mm from the furnace opening, as in Step 1. The blower is turned on at a flow rate of 32000 Nm³. 3 Oxygen was introduced into the molten steel with a P content ≥ 0.013% obtained in step 1. An explosion occurred after 5 seconds, and blowing was stopped for 8.11 minutes. At this time, the oxygen concentration in the pipeline was 22.4%, and the carbon monoxide concentration was 12.3%. Production resumed after 9.16 minutes of stopping. The P content in the furnace was tested and found to be 0.013%, meeting the tapping conditions. The converter was tilted 95° to tap the molten steel. Tapping took 6 minutes. After tapping, the converter was returned to its original position (0°) and waited for 8.11 minutes. After the dry dust removal equipment was restored, the oxygen lance was placed 2.4m above the steel slag, and nitrogen gas was introduced for slag splashing protection for 2 minutes. After the slag splashing protection was completed, the converter was tilted at 97° to remove 1 / 2 of the slag (5000kg), and 1 / 2 of the slag (5000kg) was retained for the next heat of smelting. The blowing and explosion relief conditions of this comparative example are shown in Table 1. As can be seen from Table 1, the dephosphorization rate was 85.61% through blowing in this comparative example, the average shutdown time per 100 heats was 8.11 minutes, and the number of explosion reliefs was 77.

[0094] Table 1 shows the blowing conditions and explosion venting conditions of Examples 1-3 and the comparative examples.

[0095]

[0096] The above description is merely a few embodiments of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the technical solution of the present invention using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A smelting method for controlling phosphorus levels and reducing dry dust and explosion hazards in a high-carbon steel converter, characterized in that, The smelting method includes at least the following steps: Step 1, Iron mixing and slag blowing: Mix scrap steel with molten iron, adjust the oxygen lance position after mixing with iron, and introduce oxygen for blowing I. After the molten iron ignites, add slag material to control the basicity to 2.8 ~ 3.0 and the magnesium oxide content in the slag to 6% ~ 8%. Adjust the oxygen lance position again and maintain a constant oxygen flow rate for blowing II until the smelting endpoint. Test if the P content in the molten steel to be tapped is ≥0.013%, then "spot blowing" is required, i.e., the molten steel to be "spot blown". Step 2, "Spot blowing": Before "spot blowing", adjust the position of the converter skirt, turn on the blower to ensure a slight positive pressure inside the furnace, adjust the oxygen lance position to the oxygen lance inlet, and introduce nitrogen gas with a flow rate of 22000~28000 Nm³ / h to dilute the gas in the pipeline. Add dephosphorizing agent, adjust the oxygen lance position again, and introduce oxygen to "spot blow" the molten steel to be "spot blown" in Step 1 to obtain the molten steel after "spot blowing". Step 3, tapping: The tilting converter taps the molten steel obtained in Step 2 after "point blowing". After tapping, the converter is returned to its original position, the oxygen lance position is adjusted, and nitrogen is introduced to splash slag and protect the furnace. After splashing slag and protecting the furnace, the tilting converter is used to dump the slag, and some slag is retained for the next heat of smelting. The slag-forming materials mentioned in step 1 are CaO and CaMg(CO3)2; The amount of slag-forming material added in step 1 is 4-6% of the molten iron; In step 1, the oxygen lance position was readjusted to be 2.2m~2.4m away from the molten iron surface; The blowing time in step 1 (II) is 12.8~13.5 min; The constant oxygen flow rate of the blowing process II described in step 1 is 28,000~32,000 Nm³ / h; When the smelting endpoint is reached as described in step 1, stop blowing oxygen and raise the oxygen lance to a distance of 10m from the surface of the molten steel. At this time, the instantaneous oxygen concentration in the pipeline is 1~4% and the temperature of the molten steel is 1600~1670℃. When the smelting reaches its endpoint as described in step 1, stop blowing oxygen and raise the oxygen lance to the waiting position, that is, the oxygen lance nozzle is 10m away from the surface of the molten steel. At this time, the oxygen concentration in the pipeline is 22~26%. The carbon monoxide concentration in the pipeline at the end of the smelting process described in step 1 is 0-9%; In step 2, the distance between the converter shroud and the furnace opening is ≤20mm; In step 2, the oxygen concentration in the pipeline after dilution with nitrogen is 0-3%. In step 2, after diluting with nitrogen, the carbon monoxide concentration in the pipeline is 0-3%. The dephosphorizing agent mentioned in step 2 is iron oxide scale; The amount of dephosphorizing agent added in step 2 is 0.3~0.6% of the molten iron; In step 2, the oxygen lance position is readjusted to be 2.4~2.5m away from the molten steel surface; The oxygen flow rate during the "point blowing" described in step 2 is 26,000~28,000 Nm³ / h; The "point blowing" time mentioned in step 2 is 10~12 seconds.

2. The smelting method according to claim 1, characterized in that, In step 1, the mass ratio of scrap steel to molten iron is 1:6~8.

3. The smelting method according to claim 1, characterized in that, In step 1, after adding iron, adjust the oxygen lance position to be 1.8~2.2m away from the molten iron surface; In step 1, the oxygen flow rate during blowing I is 28000~35000 Nm³ / h; The blowing time in step 1 is 10~20s.

4. The smelting method according to claim 1, characterized in that, When tapping steel in the tilted converter described in step 3, the tilt angle of the converter is 90~100°; The tapping time in step 3 is 5-7 minutes; The nitrogen flow rate during slag splashing for furnace protection in step 3 is 22000~26000 Nm³ / h; In step 3, the oxygen lance position is adjusted to be 2.5~3m above the steel slag; The slag splashing and furnace protection time mentioned in step 3 is 2~4 minutes.

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