Converter smelting method using direct reduced iron

Abstract

The invention discloses a converter smelting method using direct reduced iron, which comprises the following steps of: (1) adding the direct reduced iron into a converter along with scrap steel according to the adding amount of 10-150kg / t; (2) carrying out blowing operation; the lance position of an oxygen lance for blowing for 0-5 min is 1500-2200 mm, the added coolant is less than or equal to 15 kg / t, and the slag former is less than or equal to 60 kg / t; the lance position of an oxygen lance for blowing for 5-10 minutes is 1700-2500mm, the added coolant is less than or equal to 30kg / t, and the slag former is less than or equal to 20kg / t; the lance position of an oxygen lance after blowing for 10 minutes is 1300-2000 mm, the added coolant is less than or equal to 10 kg / t, and the slag former is less than or equal to 10 kg / t. According to the method, the direct reduction iron is added into the converter along with the waste steel, and by controlling the adding amount and the smelting process, it is guaranteed that decarburization and temperature rising reactions in the converter are normally carried out, and the abnormal conditions such as dry returning and waste steel non-melting are avoided. After the method is adopted, the converter blowing process is stable, the dry returning and splashing conditions are avoided, the scrap steel is completely molten, and smooth converter smelting is effectively guaranteed while the carbon emission of the whole process is reduced.

Description

Technical Field

[0001] The invention relates to a steelmaking method, in particular to a converter smelting method using direct reduced iron. Background Art

[0002] Direct Reduced Iron (DRI) is a low-carbon porous material formed by low-temperature reduction of refined iron powder or iron oxide in a furnace. It has a stable chemical composition and low impurity content. It is mainly used as a raw material for electric furnace steelmaking and can also be used as a coolant for converter steelmaking. If it undergoes secondary reduction, it can also be used for powder metallurgy.

[0003] At present, in the steel industry, each steel mill is based on accelerating the high-quality development stage of greening and low-carbonization. The use of direct reduced iron in the converter process can reduce carbon emissions in the entire process. Adding direct reduced iron to the converter can reduce carbon emissions in the entire process, but after adding direct reduced iron to the converter, it is easy to cause the converter to dry out and the scrap steel to not be completely melted. The operation method of adding direct reduced iron to the converter has not yet been developed. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a converter smelting method using direct reduced iron which can ensure smooth converter smelting.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention comprises the following steps: (1) the direct reduced iron is added into the converter along with the scrap steel, and the added amount is 10-150 kg / t; (2) Carry out blowing operation; the oxygen lance position during blowing for 0 to 5 minutes is 1500 to 2200 mm, and the added coolant is ≤15 kg / t, and the slag-forming agent is ≤60 kg / t; the oxygen lance position during blowing for 5 to 10 minutes is 1700 to 2500 mm, and the added coolant is ≤30 kg / t, and the slag-forming agent is ≤20 kg / t; the oxygen lance position after blowing for 10 minutes is 1300 to 2000 mm, and the added coolant is ≤10 kg / t, and the slag-forming agent is ≤10 kg / t.

[0006] Furthermore, in step (2), during the blowing process for 0 to 5 minutes, 5 to 15 kg / t of coolant and 25 to 60 kg / t of slag-forming agent are added; during the blowing process for 5 to 10 minutes, 10 to 30 kg / t of coolant and 5 to 20 kg / t of slag-forming agent are added.

[0007] Furthermore, in step (2), the coolant is mainly iron ore, sintered ore, pelletized ore, iron balls, red mud balls or iron slag balls.

[0008] Furthermore, in step (2), the slag-making agent is mainly lime, limestone, light-burned dolomite, raw dolomite or magnesium balls.

[0009] Furthermore, in step (2), argon is blown from the bottom of the converter throughout the entire process, and the bottom blowing flow rate is 0.05 to 0.15 Nm 3 / (t·min).

[0010] The beneficial effect of adopting the above technical solution is that the present invention adds direct reduced iron into the converter together with scrap steel, and by controlling the addition amount and smelting process, ensures that the decarburization and temperature rise reaction in the furnace proceed normally, and avoids abnormal situations such as back drying and scrap steel not melting. After adopting the present invention, the converter blowing process is stable, without back drying and splashing, and the scrap steel is completely melted, which effectively ensures the smooth progress of converter smelting while reducing the carbon emission of the whole process. DETAILED DESCRIPTION

[0011] The present invention is further described in detail below in conjunction with specific implementation modes.

[0012] The converter smelting method using direct reduced iron comprises the following steps: (1) adding molten iron, scrap steel and direct reduced iron into the converter, wherein the direct reduced iron is added into the converter along with the scrap steel, and the amount of the direct reduced iron added is 10 to 150 kg / t.

[0013] The chemical composition and weight percentage of the direct reduced iron are: TFe 85% to 92%, C 2.11% to 4.5%, Mn≤0.5%, S≤0.020%, P≤0.030%, SiO2≤5.0%, Al2O3≤1.0%, MgO≤1.0%, CaO≤1.0%, and the rest are iron and inevitable impurity elements; the weight percentage of impurity elements in the direct reduced iron is ≤0.10%, so as to minimize the impurity elements brought into the steel and reduce the pollution to the molten steel. The direct reduced iron is pressed into balls with a diameter of ≤40mm to ensure that the direct reduced iron can be completely melted in the molten steel as soon as possible.

[0014] (2) Smelting: Carry out blowing operation; the oxygen lance position during blowing for 0 to 5 minutes, i.e. the distance between the lance tip and the calm metal liquid surface is 1500 to 2200 mm, the amount of coolant added is ≤15 kg / t, preferably 5 to 15 kg / t, and the amount of slag-forming agent is ≤60 kg / t, preferably 25 to 60 kg / t; the oxygen lance position during blowing for 5 to 10 minutes is 1700 to 2500 mm, the amount of coolant added is ≤30 kg / t, preferably 10 to 30 kg / t, and the amount of slag-forming agent is ≤20 kg / t, preferably 5 to 20 kg / t; the oxygen lance position after blowing for 10 minutes until the end of blowing is 1300 to 2000 mm, the amount of coolant added is ≤10 kg / t, and the amount of slag-forming agent is ≤10 kg / t. The temperature of the molten steel at the end of smelting is ≥1580℃, preferably 1580~1680℃, to ensure that the direct reduced iron can be completely melted as soon as possible; the dissolved oxygen content in the molten steel at the end of smelting is ≥200ppm, preferably 200~800ppm. The bottom of the converter is blown with argon gas throughout the whole process, and the bottom blowing flow rate is 0.05~0.15Nm 3 / (t·min); The purpose of blowing argon gas at the bottom of the whole process is to stir the molten pool, ensure that the direct reduced iron can be completely melted as soon as possible, and prevent the increase of nitrogen in the molten steel. After the carbon content is qualified, the steelmaking operation is carried out.

[0015] (3) The coolant is an iron-containing material, mainly iron ore, sintered ore, pelletized ore, iron balls, red mud balls or iron slag balls. The slag-forming agent is a slag-forming material, mainly lime, limestone, light-burned dolomite, raw dolomite or magnesium balls.

[0016] Embodiment 1-6: The converter smelting method using direct reduced iron is specifically described as follows.

[0017] Example 1-6 Direct reduced iron was added to the converter. The weight percentage of the direct reduced iron is shown in Table 1. The content of each impurity element in the direct reduced iron did not exceed 0.10wt%. The diameter of the direct reduced iron is shown in Table 1.

[0018] Table 1: Direct reduced iron composition ratio

[0019] The oxygen lance position, coolant addition amount, and slag forming agent addition amount of the converter stage blowing process of Example 1-6 are shown in Table 2.

[0020] Table 2: Blowing parameters

[0021] Examples 1-6 The amount of direct reduced iron added to the converter, the end point temperature of smelting, the end point oxygen content of smelting, the bottom blowing conditions and flow rate, whether to return to dry, and whether the scrap steel is completely melted are shown in Table 3.

[0022] Table 3: Smelting results .

Claims

1. A converter smelting method using direct reduced iron, characterized in that: The method comprises the following steps: (1) adding the direct reduced iron into a converter along with scrap steel in an amount of 10 to 150 kg / t; (2) Carry out blowing operation; the oxygen lance position during blowing for 0 to 5 minutes is 1500 to 2200 mm, and the added coolant is ≤15 kg / t, and the slag-forming agent is ≤60 kg / t; the oxygen lance position during blowing for 5 to 10 minutes is 1700 to 2500 mm, and the added coolant is ≤30 kg / t, and the slag-forming agent is ≤20 kg / t; the oxygen lance position after blowing for 10 minutes is 1300 to 2000 mm, and the added coolant is ≤10 kg / t, and the slag-forming agent is ≤10 kg / t.

2. A converter smelting method using direct reduced iron according to claim 1, characterized in that: In the step (2), during the blowing process for 0 to 5 minutes, 5 to 15 kg / t of coolant and 25 to 60 kg / t of slag-forming agent are added; during the blowing process for 5 to 10 minutes, 10 to 30 kg / t of coolant and 5 to 20 kg / t of slag-forming agent are added.

3. A converter smelting method using direct reduced iron according to claim 1, characterized in that: In the step (2), the coolant is mainly iron ore, sintered ore, pelletized ore, iron balls, red mud balls or iron slag balls.

4. A converter smelting method using direct reduced iron according to claim 1, characterized in that: In the step (2), the slag-making agent is mainly lime, limestone, light-burned dolomite, raw dolomite or magnesium balls.

5. A converter smelting method using direct reduced iron according to any one of claims 1 to 4, characterized in that: In step (2), argon is blown from the bottom of the converter throughout the entire process, and the bottom blowing flow rate is 0.05 to 0.15 Nm 3 / (t·min).

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