Method for smelting ultra-low phosphorus steel from medium-low silicon molten iron

Abstract

The invention provides a method for smelting ultra-low phosphorus steel from medium-low silicon molten iron, which comprises the following steps: firstly, selecting molten iron with the silicon content of 0.20-0.40 wt% and the phosphorus content of 0-0.16%, and jointly adding molten steel and waste steel into a converter by utilizing the characteristic that Al2O3 in LF (ladle furnace) refining slag is beneficial to slugging, so as to be beneficial to making high-alkalinity slag by the converter; meanwhile, after all the raw materials for steelmaking are added into the converter, the oxygen supply system is selected as the lance position system of high-low-low-low; meanwhile, in order to improve the fluidity of the slag, no magnesium material is added in the slagging process, and conditions are created for smelting low-phosphorus steel. In conclusion, a proper slag system and a proper smelting process condition are selected, the purpose of efficient single-slag dephosphorization is achieved, molten steel with the phosphorus content lower than 0.005% can be produced, and meanwhile the TFe content of final slag is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of converter steelmaking in the iron and steel metallurgical industry, and specifically relates to a method for smelting ultra-low phosphorus steel with medium-low silicon molten iron. Background Art

[0002] With the development of science and technology, some fields have higher and higher requirements on the performance and quality of steel, especially the phosphorus content in steel, which has lower and lower numerical requirements. In order to meet customer requirements, various steel companies continue to develop high-quality steel grades such as low-phosphorus or ultra-low-phosphorus.

[0003] At present, the main methods for converter smelting low-phosphorus and ultra-low-phosphorus steel are the double-link method, double-slag method and double-slag slag retention method. Among them, the double-link method is a method that uses a dephosphorization furnace and a decarburization furnace separately for smelting. Since the entire smelting process requires two converters, it has high requirements for the production site, high production costs, and low production efficiency; when using double slag or double slag slag retention method to smelt low-phosphorus and ultra-low-phosphorus steel, due to the influence of multiple factors such as smelting process temperature, slag conditions, and molten iron conditions, although many steel companies and research institutes have conducted certain research on the use of double slag dephosphorization for different steel mills, it is still difficult to control the entire double slag dephosphorization process, especially the timing of slag dumping, to achieve stable smelting of low-phosphorus and ultra-low-phosphorus steel according to different raw material quality and molten iron conditions. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for smelting ultra-low phosphorus steel from medium-low silicon molten iron. The method can obtain molten steel with a phosphorus content of ≤0.005%, which can not only achieve efficient dephosphorization, but also has relatively high production efficiency.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for smelting ultra-low phosphorus steel with medium-low silicon molten iron, which comprises the following steps:

[0007] After the mixture of molten iron, molten steel, LF refined slag and scrap steel is smelted by oxygen blowing through oxygen supply and slag making, steel is tapped from the converter according to the requirements of endpoint control;

[0008] The silicon content in the molten iron is 0.20-0.40 wt%, and the phosphorus content is 0-0.16 wt%; the Al content in the LF refined slag is 0.20-0.40 wt%. 2 O 3 The content is 28~37 wt%;

[0009] Auxiliary materials are added during the slag making process; the auxiliary materials include ore and lime;

[0010] The process of oxygen supply is as follows:

[0011] Early gun position: blowing 0~4 min, gun position 1800~1900 mm, oxygen supply intensity 2.95~3.20 (m 3 / min·t); blowing for 4~6 min, using a gun position of 1700~1800 mm, and an oxygen supply intensity of 3.30~3.50 (m 3 / min·t);

[0012] Mid-late gun position: blowing 6~14 min, gun position 1600~1650 mm, oxygen supply intensity 3.30~3.50 (m 3 / min·t);

[0013] End gun position: blowing for 14 min~stop blowing, gun position 1100~1200 mm, oxygen supply intensity 3.60~3.70 (m 3 / min·t).

[0014] Preferably, the mass ratio of the molten iron, molten steel, LF refined slag and scrap steel is (8~13):(0~0.25):(0.10~0.40):1.

[0015] Preferably, the amount of ore added is 35-55 kg / t molten steel, which refers to the ore consumption per ton of molten steel.

[0016] Preferably, the amount of lime added is 40-60 kg / t molten steel, which refers to the lime consumption per ton of molten steel.

[0017] Preferably, the slag making process is as follows:

[0018] Supply oxygen for 1-2 minutes, add 30-40% of the total ore; add 60-70% of the total lime;

[0019] Supply oxygen for 3-6 min, then add the remaining 30-40% lime in 3-6 batches, with the interval between adding lime in each batch being 20-60 s;

[0020] Supply oxygen for 5 to 12 minutes, and add the remaining 60 to 70% of the ore in 4 to 8 batches, with the interval between adding each batch of ore being 20 to 60 seconds.

[0021] Preferably, the mass of lime added in each batch is 2.5-5.0 kg / t of scrap steel.

[0022] Preferably, the mass of ore added in each batch is 3.0-5.5 kg / t of scrap steel.

[0023] Preferably, the temperature of the molten iron is 1280-1360°C.

[0024] Preferably, the LF refined slag comprises SiO2 4~7%, CaO 50~60%, MgO 4~6% and Al 2 O 3 28~37%.

[0025] Preferably, the basicity of the LF refined slag is 8-14.

[0026] Preferably, the parameters of the endpoint control are as follows:

[0027] The endpoint carbon content is 0.04~0.06 wt%; the endpoint temperature is 1600~1620℃.

[0028] Preferably, after the slag making is completed, the basicity of the final slag obtained is 5.5-8.0.

[0029] Preferably, the phosphorus content in the molten steel obtained by tapping the converter is less than 0.005%.

[0030] Preferably, after the slag making is completed, the content of TFe in the final slag obtained is less than 18%.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention provides a method for smelting ultra-low phosphorus steel with medium-low silicon molten iron. The method first selects molten iron with a silicon content of 0.20-0.40 wt% and a phosphorus content of 0-0.16 wt%. The present invention uses low-silicon molten iron to facilitate process control. The amount of high-basicity slag is large, and it is difficult to smelt with single slag using medium-high silicon molten iron. This method avoids the disadvantages of double slag smelting, does not dump slag during the process, and can achieve steady-state smelting process by grasping the smelting cycle. The Al in the LF refined slag is used to control the smelting process. 2 O 3 The characteristic of being conducive to slag formation is that molten steel and scrap steel are added to the converter together, which is conducive to making high-basicity slag in the converter and realizing rapid slag formation. At the same time, after the raw materials for steelmaking are added to the converter, the oxygen supply system is selected as a high-low-low-low gun position system, which is conducive to rapid slag formation in the early stage and stable control of the process. At the same time, in order to improve the fluidity of the slag, magnesium material is no longer added in the slag formation process, creating conditions for smelting low-phosphorus steel.

[0033] In summary, the present invention selects a suitable slag system and smelting process conditions to achieve the purpose of efficient dephosphorization of single slag, and can produce molten steel with a phosphorus content of less than 0.005%, while reducing the TFe content of the final slag. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. 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 are within the scope of protection of the present invention.

[0035] Since it is still difficult to stably smelt low-phosphorus and ultra-low-phosphorus steel in the prior art, the present invention provides a method for smelting ultra-low-phosphorus steel from medium-low silicon molten iron, comprising the following steps:

[0036] After the mixture of molten iron, molten steel, LF refined slag and scrap steel is smelted by oxygen blowing through oxygen supply and slag making, steel is tapped from the converter according to the requirements of endpoint control.

[0037] In the present invention, the silicon content in the molten iron is 0.20-0.40 wt%, preferably 0.25-0.35 wt%; the phosphorus content is ≤0.160 wt%, such as 0-0.160 wt%, preferably ≤0.150 wt%. The present invention can achieve stabilization of the smelting process by controlling the silicon content and phosphorus content in the molten iron. The temperature of the molten iron is 1280-1360°C, preferably 1290-1350°C. By controlling the temperature of the molten iron, the intake of cold material in the process can be stabilized to avoid adding too much or too little, which is conducive to stable control of the smelting process.

[0038] In the present invention, the LF refined slag comprises SiO 2 4~7 wt%, CaO 50~60 wt%, MgO4~6 wt% and Al 2 O 3 28~37 wt%, preferably including SiO 2 4.5~6.5 wt%, CaO 52~55 wt%, MgO 4~5 wt% and Al 2 O 3 30~32 wt%. Among them, Al in LF refined slag 2 O 3 It is beneficial to slag formation, thereby facilitating the production of high-basicity slag in a converter. The basicity of the LF refined slag is 8-14, preferably 10-11.5.

[0039] In the present invention, the molten steel is the remaining molten steel after the ladle pouring is completed, which is usually called "large ladle pouring surplus" in the art.

[0040] In the present invention, the scrap steel is a commonly used raw material for steelmaking.

[0041] In some embodiments of the present invention, after the slag splashing furnace protection operation is completed, the scrap steel and the molten iron poured into the LF refined slag and the excess ladle are added to the converter, and oxygen blowing smelting is performed by oxygen supply and slag making. The mass ratio of the molten iron, molten steel, LF refined slag and scrap steel is (8-13):(0-0.25):(0.10-0.40):1, preferably (9-12):(0.05-0.20):(0.15-0.30):1.

[0042] In the present invention, the process of oxygen supply is as follows:

[0043] Early gun position: blowing 0~4 min, gun position 1800~1900 mm, oxygen supply intensity 2.95~3.20 (m 3 / min·t); blowing for 4~6 min, using a gun position of 1700~1800 mm, and an oxygen supply intensity of 3.30~3.50 (m 3 / min·t);

[0044] Mid-late gun position: blowing 6~14 min, gun position 1600~1650 mm, oxygen supply intensity 3.30~3.50 (m 3 / min·t);

[0045] End gun position: blowing for 14 min~stop blowing, gun position 1100~1200 mm, oxygen supply intensity 3.60~3.70 (m 3 / min·t).

[0046] As a preferred technical solution, the process of oxygen supply is as follows:

[0047] Early gun position: blowing 0~4 min, gun position 1820~1880 mm, oxygen supply intensity 2.98~3.18 (m 3 / min·t); blowing for 4~6 min, using a gun position of 1720~1780 mm, and an oxygen supply intensity of 3.35~3.45 (m 3 / min·t);

[0048] Lance position in the middle and late stages: blowing for 6 to 14 minutes, lance position 1620 to 1640 mm, oxygen supply intensity 3.35 to 3.45 (m 3 / min·t);

[0049] End gun position: blowing for 14 min~stop blowing, gun position 1120~1180 mm, oxygen supply intensity 3.62~3.68 (m 3 / min·t)

[0050] In some embodiments of the present invention, the process of supplying oxygen is as follows:

[0051] Early gun position: blowing 0~4 min, gun position 1860 mm, oxygen supply intensity 3.00 (m 3 / min·t); blowing for 4~6min, using a gun position of 1760 mm and an oxygen supply intensity of 3.33 (m3 / min·t).

[0052] Mid-late gun position: blowing 6~14 min, gun position 1600 mm, oxygen supply intensity 3.40 (m 3 / min·t);

[0053] Final gun position: blowing for 14 min~stop blowing, gun position 1150 mm, oxygen supply intensity 3.65 (m 3 / min·t);

[0054] or

[0055] Early gun position: blowing 0~4 min, gun position 1880 mm, oxygen supply intensity 2.96 (m 3 / min·t); blowing for 4~6min, using a gun position of 1780mm and an oxygen supply intensity of 3.36 (m 3 / min·t).

[0056] Lance position in the middle and late stages: blowing for 6 to 14 minutes, lance position 1620 mm, oxygen supply intensity 3.35 (m 3 / min·t);

[0057] Final gun position: blowing for 14 min~stop blowing, gun position 1180 mm, oxygen supply intensity 3.60 (m 3 / min·t);

[0058] or

[0059] Early gun position: blowing 0~4 min, gun position 1830 mm, oxygen supply intensity 3.12 (m 3 / min·t); blowing for 4~6min, using a gun position of 1770 mm and an oxygen supply intensity of 3.42 (m 3 / min·t).

[0060] Mid-late gun position: blowing 6~14 min, gun position 1620 mm, oxygen supply intensity 3.45 (m 3 / min·t);

[0061] Final gun position: blowing for 14 min~stop blowing, gun position 1100 mm, oxygen supply intensity 3.68 (m 3 / min·t).

[0062] The present invention selects the high-low-low-low lance oxygen supply system and controls the oxygen supply intensity within a suitable range, which is beneficial to rapid slagging in the early stage and stable control of the process.

[0063] In the present invention, auxiliary materials need to be added in the slag making process; the auxiliary materials include ore and lime. Compared with the prior art, there is no need to add magnesia materials such as dolomite and carbon magnesium balls, which can create better conditions for smelting low-phosphorus steel.

[0064] In the present invention, the amount of ore added is 35-55 kg / t molten steel, preferably 40-50 kg / t molten steel, which refers to the ore consumption per ton of molten steel.

[0065] In the present invention, the amount of lime added is 40-60 kg / t molten steel, preferably 45-55 kg / t molten steel, which refers to the lime consumption per ton of molten steel.

[0066] In the present invention, the slag making process is as follows:

[0067] Supply oxygen for 1-2 minutes, add 30-40% of the total ore; add 60-70% of the total lime;

[0068] Supply oxygen for 3-6 min, add the remaining 30-40% lime in 3-6 batches, the mass of lime added in each batch is 2.5-5.0 kg / t scrap steel, preferably 2.7-4.0 kg / t scrap steel; the interval time for adding lime in each batch is 20-60 s, preferably 40-60 s;

[0069] Supply oxygen for 5 to 12 minutes, and add the remaining 60 to 70% of the ore in 4 to 8 batches, with the mass of the ore added in each batch being 3.0 to 5.5 kg / t of scrap steel, preferably 3.5 to 5.0 kg / t of scrap steel; the interval time for adding the ore in each batch is 20 to 60 seconds, preferably 30 to 60 seconds.

[0070] In some embodiments of the present invention, the slag making process is as follows:

[0071] Supply oxygen for 1-2 min, add 35% of the total ore at one time, and add 65% of the total lime at one time; supply oxygen for 3-6 min, add the remaining 35% lime in 5 batches, the amount of lime added in each batch is 3.96 kg / t, 3.90 kg / t, 4.0 kg / t, 4.20 kg / t and 3.75 kg / t respectively, and the interval time of each batch of lime is controlled at 40-60 s; supply oxygen for 5-10 min, add the remaining 65% ore (32.5 kg / t) in 7 batches, the amount of ore added in each batch is controlled at 4.0-5.0 kg / t, and the interval time of each batch of ore is controlled at 40-60 s;

[0072] or

[0073] Supply oxygen for 1-2 min, add 38% of the total ore at one time; add 62% of the total lime at one time; supply oxygen for 3-6 min, add the remaining 38% lime in 6 batches, the amount of lime added in each batch is 3.00 kg / t, 2.90 kg / t, 2.80 kg / t, 3.12 kg / t, 2.70 kg / t and 2.87 kg / t respectively, and the interval time of each batch of lime is controlled at 40-60 s; supply oxygen for 5-12 min, add the remaining 62% ore in 8 batches, 28.55 kg / t, the amount of ore added in each batch is controlled at 3.0-4.0 kg / t, and the interval time of each batch of ore is controlled at 40-60 s;

[0074] or

[0075] Supply oxygen for 1-2 min, add 36% of the total ore at one time; add 68% of the total lime at one time; supply oxygen for 4-6 min, add the remaining 32% lime in 5 batches, the amount of lime added in each batch is 4.00 kg / t, 3.98 kg / t, 4.12 kg / t, 3.80 kg / t and 4.17 kg / t respectively, and the interval time of each batch of lime is controlled at 40-60 s; supply oxygen for 5-12 min, add the remaining 64% ore in 8 batches, 34.45 kg / t, the amount of ore added in each batch is controlled at 4.0-4.5 kg / t, and the interval time of each batch of ore is controlled at 40-60 s.

[0076] The above-mentioned slag making process adopted by the present invention can realize rapid slag making in the early stage and stable process control by adding different amounts of ore and lime in batches in different three oxygen supply time periods. Among them, dephosphorization is mainly carried out in the early stage. The purpose of adding a large amount of lime in the early stage of the present invention is to make slag, and the ore is added in the middle and late stages, on the one hand, to adjust the temperature, and on the other hand, to supplement FeO in the process.

[0077] It should be noted that after the slag making is completed, the basicity of the final slag is controlled to be 5.5-8.0, preferably 6.0-8.0, in order to achieve efficient dephosphorization.

[0078] End point control of smelting is one of the key technologies in the converter steelmaking production process. Accurate judgment of the end point is of great significance for improving the quality of molten steel and shortening the smelting cycle. Generally, the basic requirement for the end point of converter smelting is that when oxygen blowing is completed, the composition and temperature of the molten steel can simultaneously meet the requirements for steel tapping. In the present invention, the parameters of the end point control are as follows: the end point carbon content is 0.04~0.06 wt%, preferably 0.05 wt%; the end point temperature is 1600~1620℃, preferably 1605~1610℃. By setting the above parameters, efficient dephosphorization can be guaranteed.

[0079] The present invention performs a spectroscopic analysis of phosphorus on the steel tapped by the above method, and the results show that the phosphorus content in the molten steel obtained by the converter tapping is less than 0.005%. After testing, the TFe content in the final slag obtained after the slag making is less than 18%.

[0080] It can be seen that the present invention selects a suitable slag system and smelting process conditions to achieve the purpose of efficient dephosphorization of single slag, and can produce molten steel with a phosphorus content of less than 0.005%, while reducing the TFe content of the final slag.

[0081] In order to further illustrate the present invention, the following examples are provided for detailed description.

[0082] Embodiment 1:

[0083] (1) Prepare steelmaking raw materials: 125 t of molten iron, with a Si content of 0.34 wt%, a P content of 0.158 wt%, a molten iron temperature of 1348°C, 3.5 t of ladle remnant and LF refined slag, and 15 t of scrap steel.

[0084] The composition and basicity of LF refined slag of low carbon and low silicon SPHC series steel are shown in Table 1:

[0085] Table 1

[0086]

[0087] (2) After slag splashing is completed, pour out all the slag.

[0088] (3) The scrap steel in step (1), the LF refined slag and the excess molten iron from the ladle are added into the converter for smelting.

[0089] (4) Blowing process in the smelting process:

[0090] 4.1 Oxygen supply

[0091] Early gun position: blowing 0~4 min, gun position 1860 mm, oxygen supply intensity 3.00 (m 3 / min·t); blowing for 4~6min, using a gun position of 1760 mm and an oxygen supply intensity of 3.33 (m 3 / min·t).

[0092] Mid-late gun position: blowing 6~14 min, gun position 1600 mm, oxygen supply intensity 3.40 (m 3 / min·t);

[0093] Final gun position: blowing for 14 min~stop blowing, gun position 1150 mm, oxygen supply intensity 3.65 (m 3 / min·t).

[0094] 4.2 Slag making

[0095] Supply oxygen for 1min30s, and add 35% of the total amount of ore at one time, the amount added is 2275 kg; supply oxygen for 1min32s, and add 65% of the total amount of lime at one time, the amount added is 4784 kg; supply oxygen for 3-6 min, and add the remaining 35% lime in 5 batches, the adding time and amount of each batch are: 515 kg in 3min40s, 507 kg in 4min12s, 520 kg in 4min38s, 546 kg in 5min10s and 488 kg in 5min43s; supply oxygen for 5-10 min, and add the remaining 65% ore (4225 kg) in 7 batches, the adding time and amount of each batch are: 572 kg in 5min15s, 637 kg in 6min, 560 kg in 6min42s, 599 kg in 7min20s, 645 kg in 8min2s, 570 kg in 8min45s and 642 kg in 9min30s.

[0096] 4.3 End point control:

[0097] End point carbon: 0.046%, end point temperature: 1615℃.

[0098] The phosphorus content of the endpoint sample was 0.005% by spectral analysis; the basicity of the final slag after sampling and testing was: 6.36.

[0099] Embodiment 2:

[0100] (1) Prepare steelmaking raw materials: 130 t of molten iron, with a Si content of 0.23 wt%, a P content of 0.158 wt%, a molten iron temperature of 1358°C, 4.0 t of ladle remnant and LF refined slag, and 10 t of scrap steel.

[0101] The composition of low carbon and low silicon SPHC series steel LF refined slag is shown in Table 2:

[0102] Table 2

[0103]

[0104] (2) After slag splashing is completed, pour out all the slag.

[0105] (3) Add the scrap steel in step (1) and the LF refined slag and the excess molten iron from the ladle into the converter for smelting. Calculate the amount of lime and ore added. The basicity is calculated as 8.0, the steel output is calculated as 130 t, and the amount of lime added is calculated as 5952 kg.

[0106] (4) Process blowing process:

[0107] 4.1 Oxygen supply

[0108] Early gun position: blowing 0~4 min, gun position 1880 mm, oxygen supply intensity 2.96 (m 3 / min·t); blowing for 4~6min, using a gun position of 1780mm and an oxygen supply intensity of 3.36 (m 3 / min·t).

[0109] Lance position in the middle and late stages: blowing for 6 to 14 minutes, lance position 1620 mm, oxygen supply intensity 3.35 (m 3 / min·t);

[0110] Final gun position: blowing for 14 min~stop blowing, gun position 1180 mm, oxygen supply intensity 3.60 (m 3 / min·t).

[0111] 4.2 Slag making

[0112] Supply oxygen for 1min26s, add 38% of the total amount of ore at one time, the amount added is 2275 kg; supply oxygen for 1min28s, add 62% of the total amount of lime at one time, the amount added is 3689 kg; supply oxygen for 3-6 min, add the remaining 38% lime in 6 batches, the addition time and amount of each batch are: 3min30s to add 390 kg, 4min6s to add 377 kg, 4min33s to add 364 kg, 5min1s to add 406 kg, 5min30s to add 351 kg and 5min56s to add 373 kg; supply oxygen for 5-12 min, add the remaining 62% ore (3712 kg) in 8 batches kg), the adding time and amount of each batch are as follows: 471kg in 5min5s, 436kg in 5min48s, 460kg in 6min22s, 499kg in 7min5s, 425kg in 7min52s, 456kg in 8min35s, 462kg in 9min15s and 503kg in 9min58s.

[0113] No magnesium materials such as dolomite and carbon magnesium balls were added during the feeding process.

[0114] 4.3 End point control:

[0115] End point carbon: 0.052%, end point temperature: 1620℃.

[0116] The phosphorus content of the endpoint sample was 0.004% by spectral analysis; the basicity of the final slag after sampling and testing was: 7.68.

[0117] Embodiment 3:

[0118] (1) Prepare steelmaking raw materials: 125 t of molten iron, with a Si content of 0.40 wt%, a P content of 0.146 wt%, a molten iron temperature of 1300°C, 3.8 t of ladle remnant and LF refined slag, and 15 t of scrap steel.

[0119] The composition of low carbon and low silicon SPHC series steel LF refined slag is shown in Table 3:

[0120] Table 3

[0121]

[0122] (2) After slag splashing is completed, pour out all the slag.

[0123] (3) Add the scrap steel in step (1) and the LF refined slag and the excess molten iron from the ladle into the converter for smelting. Calculate the amount of lime and ore added. The basicity is calculated as 6.0, the steel output is calculated as 130t, and the lime added is calculated as 8151 kg.

[0124] (4) Process blowing process:

[0125] 4.1 Oxygen supply

[0126] Early gun position: blowing 0~4 min, gun position 1830 mm, oxygen supply intensity 3.12 (m 3 / min·t); blowing for 4~6min, using a gun position of 1770 mm and an oxygen supply intensity of 3.42 (m 3 / min·t).

[0127] Mid-late gun position: blowing 6~14 min, gun position 1620 mm, oxygen supply intensity 3.45 (m 3 / min·t);

[0128] Final gun position: blowing for 14 min~stop blowing, gun position 1100 mm, oxygen supply intensity 3.68 (m 3 / min·t).

[0129] 4.2 Slag making

[0130] Supply oxygen for 1min22s, add 36% of the total amount of ore at one time, the amount added is 2519 kg; supply oxygen for 1min23s, add 68% of the total amount of lime at one time, the amount added is 5543 kg; supply oxygen for 4-6 min, add the remaining 32% lime in 5 batches, the addition time and amount of each batch are: 3min58s to add 520 kg, 4min36s to add 517 kg, 4min50s to add 536 kg, 5min28s to add 494 kg and 5min45s to add 542 kg; supply oxygen for 5-12 min, add the remaining 64% ore (4479 kg), the adding time and amount of each batch are as follows: 5min1s to add 578kg, 5min42s to add 556kg, 6min25s to add 555kg, 7min11s to add 572kg, 7min42s to add 543kg, 8min23s to add 556kg, 9min6s to add 576kg, 9min50s to add 543kg.

[0131] No magnesium materials such as dolomite and carbon magnesium balls were added during the feeding process.

[0132] 4.3 End point control:

[0133] End point carbon: 0.058%, end point temperature: 1616℃.

[0134] The phosphorus content of the endpoint sample was 0.004% by spectral analysis; the basicity of the final slag after sampling and testing was 5.88.

[0135] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for smelting ultra-low phosphorus steel from medium-low silicon molten iron, characterized in that: The following steps are involved: After the mixture of molten iron, molten steel, LF refined slag and scrap steel is smelted by oxygen blowing through oxygen supply and slag making, steel is tapped from the converter according to the requirements of endpoint control; The silicon content in the molten iron is 0.20-0.40 wt%, and the phosphorus content is 0-0.16 wt%; the Al2O3 content in the LF refined slag is 28-37 wt%; Auxiliary materials are added during the slag making process; the auxiliary materials include ore and lime; The process of oxygen supply is as follows: Early gun position: blowing 0~4 min, gun position 1800~1900 mm, oxygen supply intensity 2.95~3.20 (m 3 / min·t); blowing for 4~6 min, using a gun position of 1700~1800 mm, and an oxygen supply intensity of 3.30~3.50 (m 3 / min·t); Mid-late gun position: blowing 6~14 min, gun position 1600~1650 mm, oxygen supply intensity 3.30~3.50 (m 3 / min·t); End gun position: blowing for 14 min~stop blowing, gun position 1100~1200 mm, oxygen supply intensity 3.60~3.70 (m 3 / min·t).

2. The method according to claim 1, characterized in that The mass ratio of the molten iron, molten steel, LF refined slag and scrap steel is (8~13):(0~0.25):(0.10~0.40):

1.

3. The method according to claim 1 or 2, characterized in that: The amount of the ore added is 35-55 kg / t of molten steel, and the amount of the lime added is 40-60 kg / t of molten steel.

4. The method according to any one of claims 1 to 3, characterized in that The slag making process is as follows: Supply oxygen for 1-2 minutes, add 30-40% of the total ore; add 60-70% of the total lime; Supply oxygen for 3-6 minutes, and add the remaining 30-40% lime in 3-6 batches, with an interval of 20-60 seconds between each batch. Supply oxygen for 5 to 12 minutes, and add the remaining 60 to 70% of the ore in 4 to 8 batches, with the interval between adding each batch of ore being 20 to 60 seconds.

5. The method according to claim 4, characterized in that The mass of lime added in each batch is 2.5~5.0 kg / t of scrap steel; The mass of ore added in each batch is 3.0~5.5 kg / t scrap steel.

6. The method according to any one of claims 1 to 5, characterized in that The temperature of the molten iron is 1280-1360°C.

7. The method according to any one of claims 1 to 6, characterized in that The LF refined slag comprises SiO2 4-7%, CaO 50-60%, MgO 4-6% and Al2O3 28-37% by mass fraction; The basicity of the LF refined slag is 8-14.

8. The method according to any one of claims 1 to 7, characterized in that The parameters of the endpoint control are as follows: The endpoint carbon content is 0.04~0.06 wt%; the endpoint temperature is 1600~1620℃.

9. The method according to any one of claims 1 to 8, characterized in that After the slag making is completed, the basicity of the final slag obtained is 5.5-8.

0.

10. The method according to any one of claims 1 to 8, characterized in that: The phosphorus content in the molten steel obtained by tapping the converter is less than 0.005%.

Images