Vanadium extraction and deep dephosphorization converter steelmaking process

Abstract

According to the method, vanadium-containing molten iron with the P content ranging from 0.15% to 0.20% is used for vanadium extraction smelting according to the molten iron, the semisteel is obtained after vanadium extraction is finished, ferrosilicon is added, and the semisteel smelting deep dephosphorization technology is used for steelmaking. The silicon iron is added to adjust the components of the semi-steel, increase the content of Si in the furnace, compensate the heat of the semi-steel and help the primary slag to be rapidly melted, so that the effects of rapid dephosphorization and deep dephosphorization are achieved; meanwhile, by optimizing the process and adopting a new lance position and oxygen supply flow method, the phosphorus content of the molten steel after vanadium extraction and dephosphorization is 0.012% or below, and the dephosphorization rate reaches 91% or above.

Description

Technical Field

[0001] The invention relates to the technical field of converter smelting, and in particular to a vanadium extraction and deep dephosphorization converter steelmaking process. Background Art

[0002] With the increasingly fierce competitiveness of the steel market and the continuous improvement of customers' requirements for steel quality, the smelting process requirements are constantly optimized. Most high-quality steels require the phosphorus content (mass fraction) of the molten steel at the end of the converter to be less than 0.015%; dephosphorization is one of the key reactions that need to be effectively monitored in the converter steelmaking process, and has corresponding requirements for converter operation and slag control. Its control effect directly affects the converter smelting efficiency, cost and the stability and smoothness of the production process.

[0003] Semi-steel generally refers to hypereutectoid cast steel with a carbon content of 1.4% to 2.4%. This type of high-carbon cast steel has actually extended into the category of cast iron, so it is commonly known as semi-steel. The vanadium extraction process is a physical and chemical reaction process that utilizes the principle of selective oxidation and uses a high-speed oxygen jet to stir the vanadium-containing molten iron in the converter to oxidize the vanadium in the molten iron into stable vanadium oxide V2O5 to produce vanadium slag. The molten iron after vanadium extraction is called semi-steel. In the process of vanadium extraction, elements such as C, Si, Mn, Ti, Cr, and V are all greatly oxidized, resulting in a serious lack of chemical heat for semi-steel, making slag extremely difficult, poor converter dephosphorization effect, and frequent accidents such as oxygen lance sticking to steel and flue, which seriously affects efficient steelmaking.

[0004] Chinese patent CN103525979B discloses a dephosphorizing agent suitable for semi-steel obtained after vanadium extraction in a converter, a method for dephosphorizing the semi-steel obtained after vanadium extraction in a converter using the dephosphorizing agent, and a steelmaking method using the dephosphorizing agent. Although the method can reduce the dephosphorization cost, the P content of the semi-steel obtained after dephosphorization is in the range of 0.034% to 0.046%, and the dephosphorization effect is relatively poor.

[0005] In order to solve the above problems, technical researchers tracked the semi-steel smelting process, analyzed the semi-steel dephosphorization mechanism and optimized the process measures, effectively improved the converter dephosphorization rate, ensured that the phosphorus content of the molten steel met the requirements, ensured the stability and smoothness of the smelting process, and improved the economic benefits of converter smelting. Summary of the invention

[0006] The purpose of the present invention is to provide a vanadium extraction and deep dephosphorization converter steelmaking process, which utilizes molten iron with a phosphorus content of about 0.15% to 0.20% to extract vanadium and then produce finished low-phosphorus steel with a phosphorus content of ≤0.012%.

[0007] A vanadium extraction and deep dephosphorization converter steelmaking process, characterized by comprising the following steps: S1 molten iron vanadium extraction smelting; S2 after vanadium extraction, semi-steel is produced and ferrosilicon is added; S3 semi-steel smelting deep dephosphorization.

[0008] The step S1 of the steelmaking process of the present invention is to extract vanadium from molten iron, specifically: the scrap steel ratio in the furnace is 10% to 13%, a four-hole nozzle oxygen lance is used, and the top blowing oxygen flow rate is 11500 to 16000 Nm 3 / h to start smelting, add 500-2100kg of cooling material cold solid balls, oxygen supply time is 3.5-6min, the gun position is controlled from high 1.5-1.6m to low 1.1-1.2m and then to low 0.8-0.9m, the molten pool temperature in the furnace is 1340-1440℃ at the end of vanadium extraction, and the smelting is ended when the C content in the molten pool is 3.0%-3.8%.

[0009] Preferably, in the step S1 of the steelmaking process of the present invention, the vanadium extraction from molten iron is carried out, and the top blowing oxygen flow rate is 15000 Nm 3 / h and start blowing, with oxygen supply time of 5min.

[0010] In the step S1 of the steelmaking process of the present invention, vanadium is extracted from molten iron for smelting, and the molten iron has a Si content of 0.05% to 0.50%, a V content of ≥0.15%, and a P content of 0.15% to 0.20%.

[0011] In the step S2 of the steelmaking process of the present invention, ferrosilicon is added after the vanadium extraction is finished and the semi-steel is produced. Specifically, ferrosilicon is added during the process of finishing the vanadium extraction and producing the semi-steel, and the added amount is 3-4 kg / t 铁 , take half of the ladle sample for composition testing.

[0012] Preferably, in the step S2 of the steelmaking process of the present invention, ferrosilicon is added after the vanadium extraction is completed and the semi-steel is produced. Specifically, ferrosilicon is added during the process of the semi-steel production after the vanadium extraction is completed, and the added amount is 3.5 kg / t 铁 , take half of the ladle sample for composition testing.

[0013] The ferrosilicon of the present invention has a Si content of 40% to 55%, an S content of 0.002% to 0.010%, and a P content of 0.04% to 0.07%.

[0014] The step S3 of semi-steel smelting deep dephosphorization in the steelmaking process of the present invention is specifically as follows: the top blowing gun position is 1.2-1.8m, and the top blowing flow rate is 18000-21000Nm 3 / h, during the blowing process, 1800-3000kg of lime, 1000-1500kg of light-burned dolomite, and 20-40kg / t of sintered ore are added. 钢 , the C content of molten steel is 0.10% ~ 0.25%, the molten steel temperature is 1560 ~ 1620 ℃ when carbon is pulled into the furnace, the molten steel P ≤ 0.015%, the lance is lowered and oxygen blowing is continued for 40 ~ 80s, no slag is added during supplementary blowing, the final steel C content is 0.06% ~ 0.18%, P ≤ 0.012%, and the temperature is 1590 ~ 1620 ℃.

[0015] In the step S3 of the steelmaking process of the present invention, the semi-steel smelting deep dephosphorization, the gun position control is specifically as follows:

[0016] In the first 1 minute of semi-steel, the gun position is 1.8m;

[0017] 2-4min early stage of semi-steel, gun position 1.4m;

[0018] 5-8min mid-semi-steel period, gun position 1.6m;

[0019] 8-10min dry-back period, gun position 1.8m;

[0020] At the final carbon pulling stage, the gun position is 1.1m.

[0021] In the step S3 of the steelmaking process of the present invention, the oxygen supply system for semi-steel smelting deep dephosphorization is as follows: the blowing flow rate is 18000Nm 3 / h control, and the oxygen flow rate is adjusted to 21000Nm after two minutes 3 / h, mid-blowing period 18000Nm 3 / h, final carbon pulling flow rate 21000Nm 3 / h.

[0022] The beneficial effects of the present invention are:

[0023] 1. The present invention uses ferrosilicon to adjust the semi-steel composition, increase the Si content in the furnace, compensate for the converter heat, and help the primary slag to melt quickly, thereby achieving the effect of rapid and deep dephosphorization.

[0024] 2. The present invention optimizes the process, and the specific operation is: firstly, vanadium is extracted from molten iron for smelting, then ferrosilicon is added to semi-steel after vanadium extraction, and finally, semi-steel is smelted for deep dephosphorization, so that the phosphorus content of molten steel after vanadium extraction and dephosphorization is controlled below 0.012%, and the dephosphorization rate can reach more than 93%, so that low-phosphorus steel can be produced on a large scale. DETAILED DESCRIPTION

[0025] The present invention is described in detail below using general instructions, specific implementation methods and experiments. However, some modifications or improvements may be made on the basis of the present invention, which is obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

[0026] Example 1

[0027] S1 vanadium extraction from hot metal: In this case, the furnace is charged with 82t hot metal and 9.2t pig iron. The hot metal composition is: C4.05%, Si0.31%, Mn0.44%, P0.172%, Ti0.150%, Cr0.153%, V0.185%, S0.0038%. A four-hole nozzle is used, and the top blowing oxygen flow rate is 15000Nm 3 / h to start smelting, add 1491kg of cold solid balls when oxygen supply starts, oxygen supply time is 5min, specifically, 0 to 120 seconds from the start of blowing, top blowing oxygen flow rate is 15000m 3 / h, oxygen lance position 1.6m; 121 to 260 seconds after blowing, top blowing oxygen flow rate 15000m 3 / h, oxygen lance position 1.2m; 261-300 seconds after blowing, top blowing oxygen flow rate 15000m 3 / h, oxygen lance position 0.8m, vanadium extraction end furnace molten pool temperature 1393 ℃, vanadium extraction smelting ended when the C content in the molten pool was 3.44%.

[0028] S2 adds ferrosilicon when vanadium extraction is finished and semi-steel is produced: 3.5kg / t of ferrosilicon is added during the semi-steel production process after vanadium extraction is finished. 铁 ,

[0029] Take half of the ladle sample for composition testing.

[0030] Steel composition: C3.44%, Si0.007%, Mn0.08%, P0.168%, Ti0.0029%, Cr0.0986%, V0.0382%, S0.0091%.

[0031] The composition after adding ferrosilicon is adjusted as follows: C3.42%, Si0.33%, Mn0.09%, P0.171%, Ti0.0025%, Cr0.104%, V0.040%, S0.011%.

[0032] S3 semi-steel smelting deep dephosphorization: 91.3t semi-steel liquid steel was charged into the furnace, 2720kg lime, 1371kg light-burned dolomite and 30kg / t sintered ore were added during blowing process 钢 , the C content of molten steel is 0.25%, the carbon content of molten steel is pulled into the furnace when the temperature is 1580℃, the P content of molten steel is 0.011%, the lance is lowered and oxygen blowing is continued for 40s, no slag is added during supplementary blowing, the final C content of steel is 0.17%, the P content is 0.009%, and the temperature is 1604℃.

[0033] The specific gun position control is as follows: in the first 1 minute of semi-steel initial stage, the gun position is 1.8m; in the 2-4 minutes of semi-steel early stage, the gun position is 1.4m; in the 5-8 minutes of semi-steel middle stage, the gun position is 1.6m; in the 8-10 minutes of drying period, the gun position is 1.8m; in the final carbon pulling period, the gun position is 1.1m.

[0034] The specific oxygen supply system is: the blowing flow rate is 18000Nm 3 / h control, and the oxygen flow rate is adjusted to 21000Nm after two minutes 3 / h, mid-blowing period 18000Nm 3 / h, final carbon pulling flow rate 21000Nm 3 / h.

[0035] Example 2

[0036] S1 vanadium extraction from hot metal: In this case, the hot metal is 84.9t and the pig iron is 10.7t. The hot metal composition is: C4.1%, Si0.33%, Mn0.48%, P0.176%, Ti0.153%, Cr0.143%, V0.191%, S0.0036%. A four-hole nozzle is used, and the top blowing oxygen flow rate is 11500Nm 3 / h to start smelting, add cooling material cold solid ball 1666kg when oxygen supply starts, oxygen supply time 3.5min, specifically, 0 to 90 seconds from the start of blowing, top blowing oxygen flow rate 11500m 3 / h, oxygen lance position 1.7m; 91-200 seconds after blowing, top blowing oxygen flow rate 11500m 3 / h, oxygen lance position 1.2m; 201-210 seconds after blowing, top blowing oxygen flow rate 11500Nm 3 / h, oxygen lance position 0.8m, vanadium extraction end furnace molten pool temperature 1403 ℃, vanadium extraction smelting ends when the C content in the molten pool is 3.55%.

[0037] S2 Add ferrosilicon when semi-steel is produced after vanadium extraction: Add ferrosilicon 4kg / t during semi-steel production after vanadium extraction 铁 , take half of the ladle sample for composition testing.

[0038] Steel composition: C3.55%, Si0.000%, Mn0.09%, P0.170%, Ti0.003%, Cr0.098%, V0.040%, S0.010%.

[0039] The composition after adding ferrosilicon is adjusted as follows: C3.50%, Si0.40%, Mn0.09%, P0.168%, Ti0.025%, Cr0.095%, V0.043%, S0.011%.

[0040] S3 semi-steel smelting deep dephosphorization: 89.5t semi-steel liquid steel was charged, 2711kg lime, 1168kg light-burned dolomite and 40kg / t sintered ore were added during blowing process 钢 , the C content of molten steel is 0.21%, the carbon content of molten steel is pulled into the furnace when the temperature is 1615℃, the P content of molten steel is 0.015%, the lance is lowered and oxygen blowing is continued for 60s, no slag is added during supplementary blowing, the final C content of steel is 0.13%, the P content is 0.013%, and the temperature is 1612℃.

[0041] The specific gun position control is as follows: in the first 1 minute of semi-steel initial stage, the gun position is 1.8m; in the 2-4 minutes of semi-steel early stage, the gun position is 1.4m; in the 5-8 minutes of semi-steel middle stage, the gun position is 1.6m; in the 8-10 minutes of drying period, the gun position is 1.8m; in the final carbon pulling period, the gun position is 1.1m.

[0042] The specific oxygen supply system is: the blowing flow rate is 18000Nm 3 / h control, and the oxygen flow rate is adjusted to 21000Nm after two minutes 3 / h, mid-blowing period 18000Nm 3 / h, final carbon pulling flow rate 21000Nm 3 / h.

[0043] Example 3

[0044] S1 vanadium extraction from hot metal: In this case, the hot metal is 85.1t, pig iron is 9.5t, the hot metal composition is: C4.57%, Si0.35%, Mn0.46%, P0.175%, Ti0.170%, Cr0.143%, V0.185%, S0.0032%, four-hole nozzle is used, oxygen supply time is 6min, top blowing oxygen flow rate is 16000Nm 3 / h, add 2082kg of cooling material cold solid balls when starting to supply oxygen, oxygen supply time 5min, specifically, 0 to 140 seconds from the beginning of blowing, top blowing oxygen flow rate 16000m 3 / h, oxygen lance position 1.6m; 141-300 seconds after blowing, top blowing oxygen flow rate 16000m 3 / h, oxygen lance position 1.3m; 301-360 seconds from the start of blowing, top blowing oxygen flow rate 16000m 3 / h, oxygen lance position 0.9m, vanadium extraction end furnace molten pool temperature 1431 ℃, vanadium extraction smelting ends when the C content in the molten pool is 3.65%.

[0045] S2 Add ferrosilicon when semi-steel is produced after vanadium extraction: Add ferrosilicon 3kg / t during semi-steel production after vanadium extraction 铁 , take half of the ladle sample for composition testing.

[0046] Steel composition: C3.65%, Si0.003%, Mn0.08%, P0.170%, Ti0.005%, Cr0.075%, V0.02%, S0.019%.

[0047] The composition after adding ferrosilicon is adjusted as follows: C3.61%, Si0.215%, Mn0.08%, P0.171%, Ti0.006%, Cr0.071%, V0.0016%, S0.018%.

[0048] S3 semi-steel smelting deep dephosphorization: 92.3t semi-steel liquid steel was charged into the furnace, 2938kg lime, 1354kg light-burned dolomite and 20kg / t sintering ore were added during blowing process 钢, the C content of molten steel is 0.11%, the carbon content of molten steel is pulled into the furnace when the temperature is 1590℃, the P content of molten steel is 0.020%, the lance is lowered and oxygen blowing is continued for 80s, no slag is added during supplementary blowing, the final C content of steel is 0.10%, the P content is 0.015%, and the temperature is 1601℃.

[0049] The specific gun position control is as follows: in the first 1 minute of semi-steel initial stage, the gun position is 1.8m; in the 2-4 minutes of semi-steel early stage, the gun position is 1.4m; in the 5-8 minutes of semi-steel middle stage, the gun position is 1.6m; in the 8-10 minutes of drying period, the gun position is 1.8m; in the final carbon pulling period, the gun position is 1.1m.

[0050] The specific oxygen supply system is: the blowing flow rate is 18000Nm 3 / h control, and the oxygen flow rate is adjusted to 21000Nm after two minutes 3 / h, mid-blowing period 18000Nm 3 / h, final carbon pulling flow rate 21000Nm 3 / h.

[0051] In order to further verify the effectiveness of the present invention, the inventor conducted a series of verification experiments, the excerpts of which are as follows:

[0052] 1. Ferrosilicon addition test

[0053] Schemes 1 to 3 are the same as Examples 1 to 3; Schemes 4 to 6 add 4 kg / t of ferrosilicon 铁 , the rest are the same as the corresponding smelting processes of Examples 1 to 3; the amount of ferrosilicon added in Schemes 7 to 9 is 3kg / t 铁 , the rest are the same as the corresponding smelting processes of Examples 1 to 3, and the dephosphorization effects are compared. The dephosphorization rate is calculated according to the following formula:

[0054]

[0055] Where X is the dephosphorization rate, A is the phosphorus content of molten iron before vanadium extraction, and B is the phosphorus content of molten steel after deep dephosphorization.

[0056] The smelting results are shown in Table 1.

[0057] Table 1 Comparison of smelting results with different ferrosilicon addition amounts

[0058]

[0059] Results: 9 schemes were used to verify the effect of different ferrosilicon additions on smelting results. The results showed that the ferrosilicon addition amount was 3.0kg / t 铁 ~4.0kg / t 铁 The dephosphorization rate is high in all the above ranges, reaching more than 91%; among them, the semi-steel dephosphorization rate of Schemes 1 to 3 is the highest, reaching more than 93%, so the ferrosilicon addition amount is 3.5kg / t铁 It is the preferred amount of ferrosilicon added to help semi-steel to quickly slag and efficiently dephosphorize.

[0060] 2 Ferrosilicon effectiveness test

[0061] Scheme 1 is the same as Example 1; Scheme 2 does not add ferrosilicon when producing semi-steel, and the rest of the smelting process is the same as Example 1. The smelting results are shown in Table 2.

[0062] Table 2 Comparison of smelting results with and without ferrosilicon addition

[0063]

[0064] Results: The influence of ferrosilicon addition on the dephosphorization smelting effect was compared through two schemes. The results showed that the semi-steel smelted by the present invention (Scheme 1) had a high dephosphorization rate, normal slag formation during the smelting process, and no splashing and drying phenomenon. Therefore, ferrosilicon is an effective additive to help semi-steel quickly slag formation and efficiently dephosphorize.

[0065] 3. Ferrosilicon addition time test

[0066] Scheme 1 is the same as Example 1; Scheme 2 adds ferrosilicon at the end of S1 molten iron vanadium extraction smelting; Scheme 3 adds ferrosilicon when S3 semi-steel smelting deep dephosphorization starts blowing. The smelting results are shown in Table 3.

[0067] Table 3 Comparison of smelting results of ferrosilicon at different addition times

[0068]

[0069] Results: The effects of different ferrosilicon addition times on the dephosphorization smelting effect were compared through three schemes. The results showed that in the present invention (Scheme 1), ferrosilicon was added during the tapping of semi-steel, the dephosphorization rate of the smelted semi-steel was high, the slag formation was normal during the smelting process, and there was no splashing and drying phenomenon. Therefore, adding ferrosilicon during the tapping stage of semi-steel is an effective process step to help the semi-steel to quickly slag and efficiently dephosphorize.

[0070] Although the present invention has been described in detail above using general descriptions, specific implementation methods and experiments, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A vanadium extraction semi-steel deep dephosphorization converter steelmaking process, characterized in that: The steps include: S1 vanadium extraction from hot metal; S2 vanadium extraction is completed and semi-steel is added with ferrosilicon; S3 semi-steel smelting deep dephosphorization.

2. The vanadium extraction semi-steel deep dephosphorization converter steelmaking process according to claim 1 is characterized in that: The step S1 of vanadium extraction from molten iron is specifically as follows: the scrap steel ratio in the furnace is 10% to 13%, a four-hole nozzle oxygen lance is used, and the top blowing oxygen flow rate is 11500 to 16000 Nm 3 / h to start smelting, oxygen supply time is 3.5-6min, the gun position is controlled from high 1.5-1.6m to low 1.1-1.2m and then to low 0.8-0.9m. 500-2100kg of cooling material cold solid balls are added during the smelting process. The molten pool temperature in the furnace is 1340-1440℃ at the end of vanadium extraction, and the smelting is ended when the C content in the molten pool is 3.0%-3.8%.

3. The vanadium extraction semi-steel deep dephosphorization converter steelmaking process according to claim 2 is characterized in that: In step S1, vanadium extraction from molten iron is carried out, and the oxygen flow rate of the top blowing of the vanadium extraction furnace is 15000Nm 3 / h and start blowing, with oxygen supply time of 5min.

4. The vanadium extraction semi-steel deep dephosphorization converter steelmaking process according to claim 1 is characterized in that: In the step S1, vanadium is extracted from molten iron and smelted, wherein the molten iron has a Si content of 0.05% to 0.50%, a V content of ≥0.15%, and a P content of 0.15% to 0.20%.

5. The vanadium extraction semi-steel deep dephosphorization converter steelmaking process according to claim 1 is characterized in that: The step S2 of adding ferrosilicon after the vanadium extraction is completed and the semi-steel is produced is specifically: during the process of the semi-steel being produced after the vanadium extraction is completed, ferrosilicon is added in an amount of 3-4 kg / t 铁 , take half of the ladle sample for composition testing.

6. The vanadium extraction semi-steel deep dephosphorization converter steelmaking process according to claim 5 is characterized in that: The step S2 of adding ferrosilicon after the vanadium extraction is completed and the semi-steel is produced is specifically as follows: when the vanadium extraction is completed and the semi-steel is produced, ferrosilicon is added in an amount of 3.5 kg / t 铁 , take half of the ladle sample for composition testing.

7. The vanadium extraction semi-steel deep dephosphorization converter steelmaking process according to claim 1 is characterized in that: The ferrosilicon has a Si content of 40% to 55%, an S content of 0.002% to 0.010%, and a P content of 0.04% to 0.07%.

8. The vanadium extraction semi-steel deep dephosphorization converter steelmaking process according to claim 1 is characterized in that: The step S3 of semi-steel smelting deep dephosphorization is specifically as follows: the top blowing gun position is 1.2-1.8m, and the top blowing flow rate is 18000-21000Nm 3 / h, during the blowing process, 1800-3000kg of lime, 1000-1500kg of light-burned dolomite, and 20-40kg / t of sintered ore are added. 钢 , the C content of molten steel is 0.10% ~ 0.25%, the molten steel temperature is 1560 ~ 1620 ℃ when carbon is pulled into the furnace, the molten steel P ≤ 0.015%, the lance is lowered and oxygen blowing is continued for 40 ~ 80s, no slag is added during supplementary blowing, the final steel C content is 0.06% ~ 0.18%, P ≤ 0.012%, and the temperature is 1590 ~ 1620 ℃.

9. The vanadium extraction semi-steel deep dephosphorization converter steelmaking process according to claim 8, characterized in that: In step S3, semi-steel smelting deep dephosphorization, the gun position control is specifically as follows: In the first 1 minute of semi-steel, the gun position is 1.8m; 2-4min early stage of semi-steel, gun position 1.4m; 5-8min mid-semi-steel period, gun position 1.6m; 8-10min dry-back period, gun position 1.8m; At the final carbon pulling stage, the gun position is 1.1m.

10. The vanadium extraction semi-steel deep dephosphorization converter steelmaking process according to claim 8, characterized in that: In step S3, the semi-steel smelting deep dephosphorization, the oxygen supply system is specifically as follows: the blowing flow rate is 18000Nm 3 / h control, and the oxygen flow rate is adjusted to 21000Nm after two minutes 3 / h, mid-blowing period 18000Nm 3 / h, final carbon pulling flow rate 21000Nm 3 / h.

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