Dephosphorization method for RH furnace

Abstract

The invention belongs to the field of iron and steel smelting, and particularly relates to an RH furnace dephosphorization method which comprises the following steps: after the bottom of a vacuum chamber of an RH furnace is completely covered with molten steel, a lifting gas pipeline of the RH furnace starts to blow dephosphorization powder into the molten steel; after blowing of the dephosphorization powder is finished, the molten steel is kept circulating for a period of time, and dephosphorized molten steel is obtained; the components of the dephosphorization powder comprise lime, sodium carbonate and iron oxide red. The lifting gas pipeline of the RH furnace is transformed to have the powder injection function, and after the bottom of the vacuum chamber of the RH furnace is completely covered with the molten steel, the lifting gas pipeline starts to inject the dephosphorization powder for dephosphorization. According to the method, phosphorus in the molten steel can be effectively removed in the RH refining process, the dephosphorization pressure of the ultra-low phosphorus steel can be relieved, and the quality of the molten steel can be improved.

Description

Technical Field

[0001] The present invention belongs to the field of steel smelting, and particularly relates to a method for dephosphorizing molten steel in an RH furnace. Background Art

[0002] With the rapid development of the new energy vehicle industry, the demand for ultra-low phosphorus steel with deep-expanded holes is increasing day by day. This type of steel has extremely high requirements for phosphorus, usually requiring less than 0.005%, and even less than 0.003%. The traditional converter deep dephosphorization process can no longer meet the production needs. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for dephosphorizing molten steel in an RH furnace, which can effectively remove phosphorus in molten steel during the RH refining process, is beneficial to reducing the dephosphorization pressure of ultra-low phosphorus steel, and helps to improve the quality of molten steel.

[0004] The present invention provides a method for dephosphorizing molten steel in an RH furnace, comprising the following steps:

[0005] After the bottom of the vacuum chamber of the RH furnace is completely covered with molten steel, the lifting gas pipeline of the RH furnace starts to blow dephosphorization powder into the molten steel; after the blowing of the dephosphorization powder ends, the molten steel is circulated for a period of time to obtain dephosphorized molten steel;

[0006] The components of the dephosphorization powder include lime, soda ash and iron oxide red.

[0007] Preferably, the content of lime in the dephosphorization powder is 45 - 65 wt%, the content of soda ash in the dephosphorization powder is 10 - 20 wt%, and the content of iron oxide red in the dephosphorization powder is 25 - 40 wt%.

[0008] Preferably, the particle size of the dephosphorization powder is ≤ 0.1 mm.

[0009] Preferably, the diameter of the lifting gas pipeline is ≥ 5 mm.

[0010] Preferably, the gas flow rate of the lifting gas pipeline is 1500 - 3000 NL / min.

[0011] Preferably, after starting to blow the dephosphorization powder, the powder-gas ratio of the lifting gas pipeline is ≥ 30 kg / m 3 .

[0012] Preferably, the powder-gas ratio of the lifting gas pipeline is 30 - 50 kg / m 3 .

[0013] Preferably, the blowing amount of the dephosphorization powder is 2 - 5 kg / t of molten steel.

[0014] Preferably, the operating temperature of the RH furnace is 1570 - 1600 °C.

[0015] Preferably, the time of the cycle is 5 to 10 minutes.

[0016] Compared with the prior art, the present invention provides a method for dephosphorizing molten steel in an RH furnace, which comprises the following steps: after the bottom of the vacuum chamber of the RH furnace is completely covered with molten steel, the lifting gas pipeline of the RH furnace starts to blow dephosphorization powder into the molten steel; after the blowing of the dephosphorization powder is completed, the molten steel is circulated for a period of time to obtain dephosphorized molten steel; the components of the dephosphorization powder include lime, soda ash and iron oxide red. The present invention transforms the lifting gas pipeline of the RH furnace into a pipeline with the function of blowing powder. After the bottom of the vacuum chamber of the RH furnace is completely covered with molten steel, the lifting gas pipeline starts to blow dephosphorization powder for dephosphorization. The present invention can effectively remove phosphorus in molten steel during the RH refining process, which is beneficial to reducing the dephosphorization pressure of ultra-low phosphorus steel and contributing to the improvement of the quality of molten steel. Detailed implementation manners

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] The present invention provides a method for dephosphorizing molten steel in an RH furnace, which comprises the following steps:

[0019] After the bottom of the vacuum chamber of the RH furnace is completely covered with molten steel, the lifting gas pipeline of the RH furnace starts to blow dephosphorization powder into the molten steel; after the blowing of the dephosphorization powder is completed, the molten steel is circulated for a period of time to obtain dephosphorized molten steel.

[0020] In the method provided by the present invention, the operating temperature of the RH furnace is preferably 1570 - 1600 °C, specifically, it can be 1570 °C, 1575 °C, 1580 °C, 1585 °C, 1590 °C, 1595 °C or 1600 °C.

[0021] In the method provided by the present invention, the initial phosphorus content of the molten steel is preferably 0.005 - 0.01 wt%, specifically, it can be 0.005 wt%, 0.006 wt%, 0.007 wt%, 0.008 wt%, 0.009 wt% or 0.01 wt%.

[0022] In the method provided by the present invention, the components of the dephosphorization powder include lime, soda ash, and iron oxide red; wherein, the content of lime in the dephosphorization powder is preferably 45-65 wt%, specifically it can be 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, or 65 wt%; the content of soda ash in the dephosphorization powder is preferably 10-20 wt%, specifically it can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%; the content of iron oxide red in the dephosphorization powder is preferably 25-40 wt%, specifically it can be 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, or 40 wt%.

[0023] In the method provided by the present invention, the particle size of the dephosphorization powder is preferably ≤0.1 mm, specifically it can be 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, or 0.1 mm.

[0024] In the method provided by the present invention, the pipe diameter of the lifting gas pipeline is preferably ≥5 mm, specifically it can be 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, or 10 mm.

[0025] In the method provided by the present invention, the gas flow rate of the lifting gas pipeline is preferably 1500-3000 NL / min, specifically it can be 1500 NL / min, 1600 NL / min, 1700 NL / min, 1800 NL / min, 1900 NL / min, 2000 NL / min, 2100 NL / min, 2200 NL / min, 2300 NL / min, 2400 NL / min, 2500 NL / min, 2600 NL / min, 2700 NL / min, 2800 NL / min, 2900 NL / min, or 3000 NL / min.

[0026] In the method provided by the present invention, after starting to blow the dephosphorization powder, the powder-gas ratio of the lifting gas pipeline is preferably ≥30 kg / m 3 , more preferably 30-50 kg / m3 , specifically it can be 30 kg / m 3 , 31 kg / m 3 , 32 kg / m 3 , 33 kg / m 3 , 34 kg / m 3 , 35 kg / m 3 , 36 kg / m 3 , 37 kg / m 3 , 38 kg / m 3 , 39 kg / m 3 , 40 kg / m 3 , 41 kg / m 3 , 42 kg / m 3 , 43 kg / m 3 , 44 kg / m 3 , 45 kg / m 3 , 46 kg / m 3 , 47 kg / m 3 , 48 kg / m 3 , 49 kg / m 3 or 50 kg / m 3 .

[0027] In the method provided by the present invention, the injection amount of the dephosphorization powder is preferably 2 - 5 kg / t molten steel, specifically it can be 2 kg / t molten steel, 2.1 kg / t molten steel, 2.2 kg / t molten steel, 2.3 kg / t molten steel, 2.4 kg / t molten steel, 2.5 kg / t molten steel, 2.6 kg / t molten steel, 2.7 kg / t molten steel, 2.8 kg / t molten steel, 2.9 kg / t molten steel, 3 kg / t molten steel, 3.1 kg / t molten steel, 3.2 kg / t molten steel, 3.3 kg / t molten steel, 3.4 kg / t molten steel, 3.5 kg / t molten steel, 3.7 kg / t molten steel, 3.8 kg / t molten steel, 3.9 kg / t molten steel, 4.1 kg / t molten steel, 4.2 kg / t molten steel, 4.3 kg / t molten steel, 4.4 kg / t molten steel, 4.5 kg / t molten steel, 4.6 kg / t molten steel, 4.7 kg / t molten steel, 4.8 kg / t molten steel, 4.9 kg / t molten steel or 5 kg / t molten steel.

[0028] In the method provided by the present invention, the cycle time is preferably 5 - 10 min, specifically it can be 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min or 10 min.

[0029] In the method provided by the present invention, the phosphorus content of the molten steel after dephosphorization is preferably 0.001 - 0.005 wt%, specifically it can be 0.001 wt%, 0.002 wt%, 0.003 wt%, 0.004 wt% or 0.005 wt%.

[0030] The technical solution provided by the present invention transforms the lifting gas pipeline of the RH furnace into a pipeline with the function of injecting powder agents. After the bottom of the vacuum chamber of the RH furnace is completely covered with molten steel, the lifting gas pipeline starts to inject dephosphorization powder agents for dephosphorization. The technical solution provided by the present invention can effectively remove phosphorus in the molten steel during the RH refining process, which is beneficial to reducing the dephosphorization pressure of ultra-low phosphorus steel and contributing to the improvement of the quality of molten steel.

[0031] For the sake of clarity, the following is a detailed description through the following examples.

[0032] Example 1

[0033] Lime, soda ash and iron oxide red are used as dephosphorization powder agents, and the particle size is all < 0.1 mm. The three are mixed according to the weight ratio of 65%: 10%: 25%; the lifting gas flow rate of the 120t RH treatment furnace is controlled at 2000 NL / min, the pipe diameter of the lifting gas pipeline is ≥ 5 mm, and the powder-gas ratio is 40 kg / m 3 . The starting temperature of the RH treatment is 1600 °C. After the bottom of the vacuum chamber of the RH furnace is completely covered with molten steel, the lifting gas pipeline starts to inject dephosphorization powder agents into the molten steel; the injection of dephosphorization powder agents is calculated according to the amount of molten steel and is controlled at 2 kg / t of molten steel. After the powder agent injection is completed, the molten steel is kept circulating for 10 min. After the treatment, the phosphorus in the molten steel is reduced from 0.007 wt% to 0.003 wt%, and the dephosphorization rate is 57.14%.

[0034] Example 2

[0035] Lime, soda ash and iron oxide red are used as dephosphorization powder agents, and the particle size is all < 0.1 mm. The three are mixed according to the weight ratio of 45%: 20%: 35%; the lifting gas flow rate of the 80t RH treatment furnace is controlled at 1500 NL / min, the pipe diameter of the lifting gas pipeline is ≥ 5 mm, and the powder-gas ratio is 30 kg / m 3 . The starting temperature of the RH treatment is 1590 °C. After the bottom of the vacuum chamber of the RH furnace is completely covered with molten steel, the lifting gas pipeline starts to inject dephosphorization powder agents into the molten steel; the injection of dephosphorization powder agents is calculated according to the amount of molten steel and is controlled at 5 kg / t of molten steel. After the powder agent injection is completed, the molten steel is kept circulating for 8 min. After the treatment, the phosphorus in the molten steel is reduced from 0.008 wt% to 0.004 wt%, and the dephosphorization rate is 50%.

[0036] Example 3

[0037] Lime, soda ash and iron oxide red are used as dephosphorization powder, with particle sizes all < 0.1 mm, and the three are mixed according to a weight ratio of 50%:10%:40%; the lifting gas flow rate of a 200t RH treatment furnace is controlled at 3000 NL / min, the pipe diameter of the lifting gas pipeline ≥ 5 mm, and the powder-gas ratio is 50 kg / m 3 . The starting temperature of the RH treatment is 1570 °C. After the bottom of the vacuum chamber of the RH furnace is completely covered with molten steel, the lifting gas pipeline starts to inject the dephosphorization powder into the molten steel; the injection of the dephosphorization powder is calculated according to the amount of molten steel and is controlled at 3 kg / t of molten steel. After the powder injection is completed, the molten steel is circulated for 5 minutes. After the treatment, the phosphorus in the molten steel is reduced from 0.005 wt% to 0.002 wt%, and the dephosphorization rate is 60%.

[0038] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for dephosphorization in an RH furnace, characterized in that, It includes the following steps: After the bottom of the vacuum chamber of the RH furnace is completely covered with molten steel, the lifting gas pipeline of the RH furnace starts to blow dephosphorization powder into the molten steel; after the blowing of the dephosphorization powder is completed, the molten steel is circulated for a period of time to obtain dephosphorized molten steel; The composition of the dephosphorization powder includes lime, soda ash and iron oxide red.

2. The method according to claim 1, wherein The content of lime in the dephosphorization powder is 45 - 65 wt%, the content of soda ash in the dephosphorization powder is 10 - 20 wt%, and the content of iron oxide red in the dephosphorization powder is 25 - 40 wt%.

3. The method according to claim 1, wherein The particle size of the dephosphorization powder is ≤ 0.1 mm.

4. The method according to claim 1, wherein The pipe diameter of the lifting gas pipeline is ≥ 5 mm.

5. The method according to claim 1, wherein The gas flow rate of the lifting gas pipeline is 1500 - 3000 NL / min.

6. The method according to claim 1, wherein After starting to inject the dephosphorization powder, the powder-gas ratio of the lifting gas pipeline ≥ 30 kg / m 3 .

7. The method according to claim 6, wherein The powder-gas ratio of the lifting gas pipeline is 30 to 50 kg / m 3 .

8. The method according to claim 1, wherein The blowing amount of the dephosphorization powder is 2 - 5 kg / t of molten steel.

9. The method according to claim 1, characterized in that, The operating temperature of the RH furnace is 1570 - 1600 °C.

10. The method according to claim 1, wherein The circulation time is 5 - 10 min.