Method for removing phosphorus by blowing nitrogen through oxygen lance in converter

Abstract

The invention provides a method for nitrogen blowing and dephosphorization of a converter through an oxygen lance, and belongs to the technical field of ferrous metallurgy. On the basis of a low-temperature dephosphorization principle, oxygen supplied by an oxygen lance is converted into supplied nitrogen in the early stage of converter steelmaking smelting, and the supplied nitrogen does not oxidize heating elements and a stirring molten pool loses physical heat, so that the temperature of the molten pool is reduced, the time period when the temperature of molten steel is smaller than 1400 DEG C is prolonged, dephosphorization dynamic conditions are improved, and the dephosphorization rate is increased; the purpose of saving the lime consumption is achieved, and the processing cost of steelmaking is reduced. The dephosphorization thermodynamic conditions are improved through oxygen lance nitrogen blowing, the dephosphorization rate can be increased in the converter steelmaking process, lime consumption is saved, the billet machining cost is reduced, and therefore economic benefits and social benefits are remarkably improved.

Description

Technical Field

[0001] The invention relates to a method for dephosphorizing a converter by blowing nitrogen through an oxygen lance, and belongs to the technical field of steel metallurgy. Background Art

[0002] In the prior art, the phosphorus content of molten iron, the raw material for converter steelmaking in the metallurgical industry, is 0.012%. The phosphorus content is reduced by supplying oxygen and adding lime, and steel with a phosphorus content of about 0.030% is smelted. During the smelting process, oxygen, lime and alloy materials are consumed. The processing cost of smelting molten iron into 1 ton of steel is 360 yuan.

[0003] The invention improves converter smelting in the steelmaking process and further provides a method for dephosphorizing the converter by blowing nitrogen through an oxygen lance. The dephosphorization thermodynamic conditions are improved by blowing nitrogen through the oxygen lance, thereby increasing the dephosphorization rate and reducing ash consumption, thereby saving the processing cost of steelmaking. Summary of the invention

[0004] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art and further provide a method for dephosphorizing a converter by blowing nitrogen through an oxygen lance.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A method for dephosphorizing a converter by blowing nitrogen through an oxygen lance, comprising the following steps:

[0007] Step 1: After adding molten iron and scrap steel into the steelmaking converter, oxygen is supplied through the oxygen lance for blowing;

[0008] Step 2: After blowing for 20 seconds, start adding slag-making materials: lime and magnesium balls, and add all of them after 240 seconds;

[0009] Step 3: After blowing for 180 seconds, the oxygen lance switches from supplying oxygen to supplying nitrogen, and the blowing time is 30 seconds;

[0010] Step 4: After blowing for 210 seconds, the oxygen lance switches from supplying nitrogen to supplying oxygen, and the smelting end point is determined based on the change in the furnace mouth flame and bomb detection;

[0011] Step 5: When the blowing end is reached, close the oxygen lance;

[0012] Step 6: Take samples and measure the temperature of the converter. When the temperature of the molten steel reaches 1640℃~1660℃ and the phosphorus content is less than 0.030%, the smelting and steelmaking can be completed.

[0013] Furthermore, the blowing conditions in step 1 are: oxygen pressure 0.8 MPa, oxygen flow rate 20000m 3 / h, oxygen lance position 1.5m.

[0014] Furthermore, in the step 2, the amount of lime and magnesium balls added is 3 / 4 of that in a normal furnace.

[0015] Furthermore, in step 3, the nitrogen pressure is 0.7 MPa and the flow rate is 17000 m 3 / h.

[0016] The beneficial effects of the present invention are:

[0017] The invention improves the thermodynamic conditions of dephosphorization by blowing nitrogen through an oxygen lance, can increase the dephosphorization rate in the converter steelmaking process, save lime consumption, reduce the processing cost of steel billets, and thus significantly improve economic and social benefits.

[0018] The invention is based on the principle of low-temperature dephosphorization. In the early stage of converter steelmaking, oxygen supplied by an oxygen lance is converted into nitrogen supply. Since nitrogen supply does not oxidize heat-generating elements and physical heat is lost by stirring the molten pool, the temperature of the molten pool is reduced, the time period of the molten steel temperature being less than 1400°C is extended, the dephosphorization kinetic conditions are improved, the dephosphorization rate is increased, the purpose of saving lime consumption is achieved, and the processing cost of steelmaking is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a process flow chart of converter steelmaking through oxygen lance nitrogen blowing and dephosphorization. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below in conjunction with the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method is given, but the protection scope of the present invention is not limited to the following embodiments.

[0021] like Figure 1 As shown, a method for dephosphorizing a converter by blowing nitrogen through an oxygen lance according to this embodiment comprises the following steps:

[0022] Step 1: After adding molten iron and scrap steel into the steelmaking converter, oxygen is supplied through the oxygen lance for blowing, with an oxygen pressure of 0.8MPa and an oxygen flow rate of 20000m 3 / h, oxygen lance position 1.5m;

[0023] Step 2: After blowing for 20 seconds, start adding slag-making materials: lime and magnesium balls. After 240 seconds, all the addition is completed. The amount of lime and magnesium balls added is 3 / 4 of the normal furnace;

[0024] Step 3: After 180 seconds of blowing, the oxygen lance switches from supplying oxygen to supplying nitrogen. The blowing time is 30 seconds, the nitrogen pressure is 0.7MPa, and the flow rate is 17000m 3 / h;

[0025] Step 4: After blowing for 210 seconds, the oxygen lance switches from supplying nitrogen to supplying oxygen, and the smelting end point is determined based on the change in the furnace mouth flame and bomb detection;

[0026] Step 5: When the blowing end is reached, close the oxygen lance;

[0027] Step 6: Take samples and measure the temperature of the converter. When the temperature of the molten steel reaches 1640℃~1660℃ and the phosphorus content is less than 0.030%, the smelting and steelmaking can be completed.

[0028] Example 1

[0029] In this embodiment, the chemical composition of molten steel produced by smelting molten iron raw materials for steelmaking is shown in the following table:

[0030] chemical composition

[0031] chemical composition C(％) Si(%) Mn(%) P(％) S(％) molten iron 4.0 0.38 0.25 0.120 0.020 Molten Steel 0.24 0.42 1.35 0.030 0.030

[0032] Step 1: Add molten iron and scrap steel into the steelmaking converter. The chemical composition of the molten iron is as follows: C is 4.0%, Si is 0.38%, Mn is 0.25%, P is 0.120%, and S is 0.020%. Then, oxygen is supplied through an oxygen lance for blowing, with an oxygen pressure of 0.8 MPa and an oxygen flow rate of 20,000 m 3 / h, oxygen lance position 1.5m;

[0033] Step 2: After blowing for 20 seconds, start adding slag-making materials: lime and magnesium balls. After 240 seconds, all the addition is completed. The amount of lime and magnesium balls added is 3 / 4 of the normal furnace;

[0034] Step 3: After 180 seconds of blowing, the oxygen lance switches from supplying oxygen to supplying nitrogen. The blowing time is 30 seconds, the nitrogen pressure is 0.7MPa, and the flow rate is 17000m 3 / h;

[0035] Step 4: After blowing for 210 seconds, the oxygen lance switches from supplying nitrogen to supplying oxygen, and the smelting end point is determined based on the change in the furnace mouth flame and bomb detection;

[0036] Step 5: When the blowing end is reached, close the oxygen lance;

[0037] Step six: Take samples and measure the temperature of the converter. When the temperature of the molten steel reaches 1640℃~1660℃ and the phosphorus content is less than 0.030%, the smelting and steelmaking can be completed. The chemical composition of the molten steel is as follows: C is 0.24%, Si is 0.42%, Mn is 1.35%, P is 0.030%, and S is 0.030%.

[0038] In the steelmaking process of this embodiment, the converter converts oxygen supply from the oxygen lance to nitrogen supply in the early stage of smelting, reduces the temperature of the molten pool, improves the dephosphorization rate, and changes the proportion of P from 0.120% to 0.030%. This implementation is based on the principle of low-temperature dephosphorization. In the early stage of smelting, the converter converts oxygen supply from the oxygen lance to nitrogen supply. Because nitrogen supply does not oxidize the heat-generating elements and physical heat is lost by stirring the molten pool, the molten pool temperature is reduced, the time period of the molten steel temperature being less than 1400°C is extended, the dephosphorization kinetic conditions are improved, the dephosphorization rate is improved, the purpose of saving lime usage is achieved, and the processing cost of steelmaking is reduced.

[0039] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for dephosphorizing a converter by blowing nitrogen through an oxygen lance, characterized in that: The steps include: Step 1: After adding molten iron and scrap steel into the steelmaking converter, oxygen is supplied through the oxygen lance for blowing; Step 2: After blowing for 20 seconds, start adding slag-making materials: lime and magnesium balls, and add all of them after 240 seconds; Step 3: After blowing for 180 seconds, the oxygen lance switches from supplying oxygen to supplying nitrogen, and the blowing time is 30 seconds; Step 4: After blowing for 210 seconds, the oxygen lance switches from supplying nitrogen to supplying oxygen, and the smelting end point is determined based on the change in the furnace mouth flame and bomb detection; Step 5: When the blowing end is reached, close the oxygen lance; Step 6: Take samples and measure the temperature of the converter. When the temperature of the molten steel reaches 1640℃~1660℃ and the phosphorus content is less than 0.030%, the smelting and steelmaking can be completed.

2. The method for dephosphorizing a converter by blowing nitrogen through an oxygen lance according to claim 1, characterized in that: The blowing conditions in step 1 are: oxygen pressure 0.8 MPa, oxygen flow rate 20000m 3 / h, oxygen lance position 1.5m.

3. The method for dephosphorizing a converter by blowing nitrogen through an oxygen lance according to claim 1, characterized in that: In the step 2, the amount of lime and magnesium balls added is 3 / 4 of the normal furnace.

4. The method for dephosphorizing a converter by blowing nitrogen through an oxygen lance according to claim 1, characterized in that: In step 3, the nitrogen pressure is 0.7MPa and the flow rate is 17000m 3 / h.

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