Molten iron desulfurizing agent and molten iron desulfurizing method after adding scrap steel into ladle

Abstract

The invention provides a molten iron desulfurizing agent after steel scrap is added into a ladle. The molten iron desulfurizing agent is used for carrying out pretreatment desulfurization after the steel scrap is added into the ladle; the molten iron desulfurizing agent comprises lime, fluorite and carbon particles, wherein the mass percent of the lime is 30-35%, the mass percent of the fluorite is 20-25%, and the mass percent of the carbon particles is 40-50%. The problems that in the prior art, under the high scrap steel ratio, scrap steel of a ladle is not molten, the molten iron fluidity is poor, the desulfurization efficiency is low, and the consumption of important components (lime and fluorite) of a desulfurizing agent is large can be solved. The invention further provides a molten iron desulfurization method after the scrap steel is added into the ladle, pretreatment desulfurization is carried out after the scrap steel is added into the ladle, and the molten iron desulfurization agent after the scrap steel is added into the ladle is adopted for desulfurization.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting, and specifically to a desulfurizing agent and method for molten iron after adding scrap steel to the ladle. Background Technology

[0002] In modern steel production, hot metal pretreatment desulfurization is a crucial step in ensuring the quality of high-quality steel. Traditional hot metal pretreatment desulfurization processes are mainly designed for pure hot metal. However, with the increasing proportion of scrap steel used in steelmaking, more and more companies are trying to add scrap steel to the molten iron ladle before pretreatment desulfurization. However, in this case, the addition of more scrap steel leads to problems such as the scrap steel not melting, poor hot metal fluidity, reduced desulfurization efficiency, and increased consumption of lime and fluorite. Currently, there is no mature process in the industry that can effectively solve this problem.

[0003] In summary, the existing technology has the following problems: adding scrap steel to the molten iron ladle before pretreatment for desulfurization will result in the scrap steel not melting and the molten iron having poor fluidity, which will lead to reduced desulfurization efficiency and increased consumption of lime and fluorite. Summary of the Invention

[0004] This invention provides a desulfurizing agent for molten iron after adding scrap steel to the ladle, in order to solve the problems that occur when adding scrap steel to the ladle and then performing pretreatment desulfurization, such as the scrap steel not melting, poor molten iron fluidity, resulting in reduced desulfurization efficiency and increased consumption of lime and fluorite.

[0005] Therefore, this invention proposes a desulfurizing agent for molten iron after adding scrap steel to the ladle.

[0006] The desulfurizing agent for molten iron is pretreated by adding scrap steel to the molten iron ladle for desulfurization.

[0007] The molten iron desulfurizing agent includes: lime, fluorite, and carbon particles;

[0008] The lime comprises 30-35% by mass, the fluorite comprises 20-25% by mass, and the carbon particles comprise 40-50% by mass.

[0009] The special desulfurizing agent for molten iron of this invention, expressed as a percentage by mass:

[0010] Its main raw materials are lime, fluorite, and carbon particles. The mass percentage of lime is 30-35%, that of fluorite is 20-25%, and that of carbon particles is 40-50%.

[0011] Specifically, the raw material lime used in the desulfurization reaction is active lime, and its CaO content is required to be ≥80%, with the remainder being unavoidable impurities.

[0012] Specifically, the raw material fluorite is used to lower the melting point of the slag and improve its fluidity. Its CaF2 content is required to be ≥78%, and the remainder is unavoidable impurity components.

[0013] Specifically, the raw material carbon particles are used to promote the melting of scrap steel on the slag surface and improve the fluidity of molten iron. The carbon content is required to be ≥98%, with the remainder being unavoidable impurities.

[0014] The above-mentioned desulfurizing agent raw materials are weighed according to the specified proportions, crushed to a particle size of 1-3 mm, and then loaded into a mixer for thorough mixing. This ensures the desulfurizing agent reacts fully during use, resulting in stable desulfurization efficiency. If the particle size is too large, the desulfurization time will be long; if the particle size is too small, it will be easily carried away by air waves or dust removal flue gas during addition, affecting the yield.

[0015] The aforementioned desulfurizing agent is mainly applicable to the desulfurization process after adding scrap steel to the molten iron ladle. Its usage is primarily related to the total metal charge M in the ladle and the percentage of scrap steel N%. The formula for calculating the desulfurizing agent usage is: M * N% / 10.

[0016] The present invention also provides a method for desulfurizing molten iron after adding scrap steel to the ladle. Scrap steel is added to the molten iron ladle before pretreatment for desulfurization. The desulfurization uses the aforementioned molten iron desulfurizing agent obtained after adding scrap steel to the molten iron ladle.

[0017] This invention solves the problems existing in the prior art, such as the non-melting of scrap steel in molten iron ladles under high scrap steel ratios, poor molten iron fluidity, low desulfurization efficiency, and high consumption of key components of desulfurizing agents (lime and fluorite). The desulfurized molten iron produced by this desulfurizing agent has a low sulfur content, good fluidity, and high latent heat of chemical reaction. It can consume more scrap steel in the subsequent converter blowing process, achieving the requirements of large scrap steel production and green, low-carbon emission steelmaking. Compared with traditional desulfurizing agents, it significantly promotes the melting of scrap steel in the ladle and improves the fluidity of the molten metal, thereby increasing desulfurization efficiency and reducing the amount of lime and fluorite used in the desulfurizing agent, thus reducing environmental pollution. Detailed Implementation

[0018] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the invention is now described.

[0019] This invention provides a desulfurizing agent and desulfurization process for molten iron pretreatment with low manufacturing cost and applicable to high scrap steel ratios. The main raw materials of the desulfurizing agent are lime, fluorite, and carbon particles. The mass percentage of lime is 30-35%, the mass percentage of fluorite is 20-25%, and the mass percentage of carbon particles is 40-50%. The preparation method involves weighing the above raw materials according to the proportions in Table 1, crushing them to a particle size of 1-3 mm, and then mixing them thoroughly in a mixer.

[0020] Table 1. Proportions of Desulfurizing Agent for Molten Iron

[0021]

[0022]

[0023] Experimental Method: At the Liuzhou Iron and Steel Group steelmaking plant, 100 tons of molten iron and 20 tons of scrap steel were added to the ladle, for a total metal loading of M = 120 tons, of which the scrap steel accounted for N = 20 / 120 = 16.7%. Two sets of desulfurizing agents with the proportions in Table 1 were added at a dosage of 120 * 16.7% / 10 = 2 tons. After the desulfurization reaction was complete, conventional slag removal was performed, and the bright surface of the molten iron ladle was controlled at approximately 90%. In the two experimental examples, the initial sulfur content of the molten iron averaged 0.028%, and the slag content was less than 0.5% of the molten iron volume, both within the normal control range. After adding 2 tons of desulfurizing agent according to the method of this invention, the unmelted scrap steel on the slag surface of the molten iron ladle melted rapidly, and the sulfur content of the molten iron after desulfurization was less than 0.002%. Compared with the use of conventional desulfurizing agents, under the same molten iron temperature, this significantly improved the fluidity of the molten iron and enabled rapid steelmaking, avoiding the impact of unmelted scrap steel on the desulfurization of the molten iron. Under the same desulfurization target, the desulfurization time is shortened by 5 to 8 minutes, and the consumption of lime and fluorite in the desulfurizing agent is reduced by 25 to 30% year-on-year, thus reducing the impact on the environment.

[0024] The carbon particles used in this invention are required to be highly reactive lime that can decompose into nano-sized carbon particles. After being added to molten iron, these particles can quickly adsorb onto the surface and crevices of the scrap steel, breaking down the oxide layer and allowing heat to penetrate rapidly. Simultaneously, the carbon particles quickly dissolve in the semi-molten layer between the molten iron and the scrap steel, increasing the carbon content of this layer and rapidly lowering its melting point, thus achieving rapid melting. Normal molten iron has a carbon content of around 4.3%, which, according to the iron-carbon phase diagram, results in a low melting point. Therefore, based on the relationship between the amount of desulfurizing agent used, the total metal loading (M) of the molten iron ladle, and the percentage of scrap steel (N%), the mass percentage of carbon particles in this invention is 40-50% to maintain a high carbon content and low melting point in the molten iron during the melting process.

[0025] The desulfurizing agent of this invention is a desulfurizing agent with the function of a scrap steel flux. Scrap steel melts rapidly, reducing melting time by 20%, and decreasing the consumption of lime and fluorite in traditional desulfurizing agents by 25% to 40%. Simultaneously, the desulfurization time is shortened by 5-8 minutes, a reduction of 15% to 25%. The scrap steel added in steelmaking generally has a very low carbon content. If a large amount is added, the carbon content of the molten iron will definitely decrease significantly, increasing the overall melting point and affecting the melting of the scrap steel. By supplementing with carbon powder, the molten iron can maintain a high carbon content and low melting point during the melting process, thus solving the problem of scrap steel not melting after a large amount is added to the ladle.

[0026] Table 2 compares the embodiments of the present invention with conventional desulfurizers without added carbon.

[0027]

[0028] As can be seen from Table 2, the present invention uses a carbon-added desulfurizing agent, which results in a lower temperature drop during the desulfurization process and can solve the problem of the scrap steel not melting after a large amount of scrap steel is added to the ladle.

[0029] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A desulfurizing agent for molten iron after adding scrap steel to the ladle, characterized in that, The desulfurizing agent for molten iron is pretreated by adding scrap steel to the molten iron ladle for desulfurization. The molten iron desulfurizing agent includes: lime, fluorite, and carbon particles; The lime comprises 30-35% by mass, the fluorite comprises 20-25% by mass, and the carbon particles comprise 40-50% by mass.

2. The desulfurizing agent for molten iron after adding scrap steel to the ladle as described in claim 1, characterized in that, The raw material lime is active lime, and its CaO content is required to be ≥80%.

3. The desulfurizing agent for molten iron after adding scrap steel to the ladle as described in claim 1, characterized in that, The raw material fluorite is used to lower the melting point of the slag and improve its fluidity, and its CaF2 content is required to be ≥78%.

4. The desulfurizing agent for molten iron after adding scrap steel to the ladle as described in claim 1, characterized in that, The raw material carbon particles are used to promote the melting of scrap steel on the slag surface and improve the fluidity of molten iron, and their C content is required to be ≥98%.

5. The desulfurizing agent for molten iron after adding scrap steel to the ladle as described in claim 1, characterized in that, Weigh the above raw materials according to the proportion, crush them to a particle size of 1-3 mm, and put them into a mixer for mixing.

6. The desulfurizing agent for molten iron after adding scrap steel to the ladle as described in claim 1, characterized in that, The desulfurizing agent is applicable to the desulfurization process after adding scrap steel to the molten iron ladle. The amount of desulfurizing agent used is mainly related to the total metal loading amount M of the molten iron ladle and the proportion of scrap steel N%. The formula for calculating the amount of desulfurizing agent used is = M*N% / 10, where M is in tons.

7. The desulfurizing agent for molten iron after adding scrap steel to the ladle as described in claim 1, characterized in that, The mass percentage of lime is 30%, the mass percentage of fluorite is 20%, and the mass percentage of carbon particles is 50%.

8. The desulfurizing agent for molten iron after adding scrap steel to the ladle as described in claim 1, characterized in that, The mass percentage of lime is 35%, the mass percentage of fluorite is 25%, and the mass percentage of carbon particles is 40%.

9. A method for desulfurizing molten iron after adding scrap steel to the ladle, characterized in that, After adding scrap steel to the molten iron ladle, pretreatment and desulfurization are carried out. The desulfurization is carried out using the molten iron desulfurizing agent after adding scrap steel to the molten iron ladle as described in any one of claims 1 to 8.

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