A method for treating a peroxidized steel liquid

Abstract

The application relates to a peroxidized steel liquid treatment method, belonging to the technical field of steel production; the method comprises the following steps: carrying out converter tapping and slag washing on the peroxidized steel liquid to obtain a slag-washed steel liquid; mixing the slag-washed steel liquid with pig iron to deoxidize and cool the slag-washed steel liquid, so that the mixed steel liquid is obtained, and the treatment is completed; the melting endothermic property of the pig iron and the reduction property of Si, Mn and C elements and the endothermic property of limestone are fully utilized by adding the pig iron into the peroxidized steel liquid, so that the peroxidized steel liquid is deoxidized and cooled. The generated CaO and SiO2 products can improve the acid-base property and melting property of the ladle slag, the problem of poor peroxidized steel liquid quality is solved, and the cost is greatly saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel production, and in particular to a method for treating over-oxidized molten steel. BACKGROUND

[0002] The bottom blowing basic converter steelmaking uses molten iron, scrap steel and ferroalloy as main raw materials, and the physical heat of the molten iron and the heat generated by the chemical reaction between the molten iron and oxygen are used to complete the steelmaking process in the converter. At the end of blowing, a large amount of oxygen is continuously blown into the molten steel, part of the oxygen is dissolved in the molten steel to form free oxygen, and the other part of the oxygen reacts with pig iron to generate a large amount of FeO into the converter slag, causing the phenomenon of over-oxidized molten steel. The over-oxidized molten steel has low carbon content, high oxygen content, high phosphorus content and high temperature, which brings great difficulty to the subsequent refining process, and over-oxidation is also not conducive to the protection of the converter, affecting the quality of the cast slab, increasing the consumption of steel and iron materials and the cost of smelting.

[0003] The traditional method for treating over-oxidized molten steel is to add a deoxidizer or carbon powder to the molten steel to reduce the oxidizing property of the molten steel. However, the addition of a large amount of deoxidizer or carbon powder will cause the deoxidizer / carbon powder to react violently with the molten steel and the steel slag, generating a large amount of heat, which will further increase the temperature of the molten steel and slow down the pace of post-converter and refining treatment. The traditional method does not fundamentally solve the problem of over-oxidized molten steel. SUMMARY

[0004] The present application provides a method for treating over-oxidized molten steel to improve the problem of molten steel oxidation.

[0005] The present application provides a method for treating over-oxidized molten steel, which comprises:

[0006] The over-oxidized molten steel is subjected to converter tapping and slag washing to obtain a slag-washed molten steel;

[0007] The slag-washed molten steel is mixed with pig iron to deoxidize and cool the slag-washed molten steel, and a mixed molten steel is obtained, and the treatment is completed.

[0008] As an optional embodiment, the amount of pig iron added is <40 kg / t of steel.

[0009] As an optional embodiment, limestone and fluorite are added during the slag washing process.

[0010] As an optional embodiment, the amount of limestone added is 3-8 kg / t of steel; and / or

[0011] The amount of fluorite added is 0.5-2.0 kg / t of steel.

[0012] As an optional embodiment, the mass content of CaO in the limestone is >40%.

[0013] As an optional implementation, the volume particle size of the limestone ranges from 5mm to 30mm.

[0014] As an optional implementation, the amount of converter slag in the converter tapping process is less than 15kg / t of steel.

[0015] As an optional implementation, when the refining is performed, the ladle slag is modified so that the mass content of FeO in the ladle slag is less than 8%.

[0016] As an optional implementation, the method comprises: refining the mixed molten steel to obtain a target steel grade.

[0017] As an optional implementation, if the upper limit of the mass content of phosphorus in the target steel grade is less than 0.012%, the method further comprises: performing a slag skimming treatment on the mixed molten steel.

[0018] Optionally, the slag skimming rate of the slag skimming treatment is greater than 60%.

[0019] As an optional implementation, the free oxygen content in the over-oxidized molten steel is greater than 800ppm, the temperature of the over-oxidized molten steel is greater than 1660℃, and the mass content of FeO in the ladle slag of the over-oxidized molten steel is greater than 25%.

[0020] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages:

[0021] The method provided by the embodiments of the present application fully utilizes the melting endothermic property of pig iron and the reducing property of Si, Mn and C elements and the endothermic property of limestone to deoxidize and cool the over-oxidized molten steel. The generated CaO and SiO2 products can improve the acid-base property and melting property of the ladle slag, solve the problem of poor quality of the over-oxidized molten steel, and greatly save the cost. BRIEF DESCRIPTION OF DRAWINGS

[0022] The drawings incorporated into the specification and forming a part thereof, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0024] Figure 1 The flowchart of the method provided by the embodiments of the present application. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of the present application.

[0026] Unless otherwise specifically indicated, all the various raw materials, reagents, instruments and equipment and the like used in the present application can be purchased from the market or can be prepared by the existing methods.

[0027] As shown in the following table, the embodiments of the present application provide a method for treating peroxidized steel liquid, which comprises: Figure 1

[0028] S1. The peroxidized steel liquid is subjected to converter tapping and slag washing to obtain a slag-washed steel liquid; the free oxygen content in the peroxidized steel liquid is above 800 ppm, the temperature of the peroxidized steel liquid is above 1660℃, and the mass content of FeO in the ladle slag of the peroxidized steel liquid is greater than 25%.

[0029] In some embodiments, limestone and fluorite are added during the slag washing process. Further, the addition amount of limestone is 3-8 kg / t of steel; and the addition amount of fluorite is 0.5-2.0 kg / t of steel. Still further, the mass content of CaO in the limestone is >40%, and the volume particle size range of the limestone is 5-30 mm.

[0030] The preheated decomposition of limestone absorbs a large amount of heat, which is conducive to the reduction of the temperature of the peroxidized steel liquid; at the same time, the calcium oxide generated after the decomposition of limestone can be used as a desulfurizing agent, a dephosphorizing agent and a ladle slag modifier. If the amount of limestone added is too small, the amount of produced lime is small, and the basicity of the ladle slag is small, which is not conducive to dephosphorization and inclusion adsorption. If the amount of limestone added is too large, the limestone is wasted. Controlling the mass content of CaO in the limestone to be >40% is conducive to the slag washing of the peroxidized steel liquid and the ladle slag making. Controlling the volume particle size range of the limestone to be 5-30 mm, if the particle size is too large, the melting speed of the ladle limestone is affected; and if the particle size is too small, the limestone is sucked by the dust removal equipment during the feeding process, resulting in poor cooling and modification effect.

[0031] The fluorite can promote the rapid melting of the lime after decomposition, which is conducive to dephosphorization and desulfurization. If the amount of fluorite added is too small, the rapid melting of the lime is not conducive; and if the amount of fluorite added is too large, the viscosity of the ladle slag after stirring is low, which is not conducive to slagging.

[0032] In some embodiments, the amount of converter slag during the converter tapping process is <15 kg / t of steel.​

[0033] The reason for controlling the slag amount of the converter slag during the converter tapping process to be < 15 kg / t of steel is to reduce the increase in the oxidizing property of the ladle slag caused by the entry of the oxidizing converter slag into the ladle, and to reduce the rephosphorization of the molten steel caused by excessive converter slag.

[0034] S2. The molten steel and pig iron are mixed to deoxidize and cool the molten steel, and a mixed molten steel is obtained, and the treatment is completed. Usually, stirring is performed during or after the mixing of the molten steel and the pig iron. After the stirring is completed, if the upper limit of the phosphorus content of the target steel is less than 0.012%, the molten steel after the stirring needs to be subjected to a slag skimming treatment. The reason for the slag skimming treatment of the molten steel after the stirring is that the phosphorus element enters the ladle slag after the stirring dephosphorization, and if the slag skimming is not performed, the phosphorus in the ladle slag will be reduced and enter the molten steel during the deoxidization and slag modification of the stirred molten steel. The slag skimming rate is greater than 60% in order to reduce the rephosphorization of the molten steel from the ladle slag. If the upper limit of the phosphorus content of the target steel is greater than 0.012%, the molten steel after the stirring does not need to be subjected to the slag skimming treatment.

[0035] In some embodiments, the amount of pig iron added is < 40 kg / t of steel.

[0036] The amount of pig iron added is controlled to be < 40 kg / t of steel in order to prevent the excessive pig iron from adversely affecting the composition of the molten steel.

[0037] S3. The mixed molten steel is refined to obtain a target steel

[0038] Since a large amount of oxidizing converter slag is brought into the ladle during the tapping process, in some embodiments, the ladle slag is modified during the refining in order to control the mass content of FeO in the ladle slag to be < 8%. The modification can reduce the secondary oxidation of the molten steel and improve the ability of the ladle slag to absorb inclusions, and controlling the mass content of FeO in the ladle slag to be < 8% is beneficial to reducing the secondary oxidation of the molten steel.

[0039] The method takes full advantage of the melting endothermic property of pig iron and the reducing property of Si, Mn, and C elements and the endothermic property of limestone to deoxidize and cool the over-oxidized molten steel. The generated CaO and SiO2 products can improve the acid-base property and melting characteristics of the ladle slag, solve the problem of poor quality of the over-oxidized molten steel, and greatly save the cost.

[0040] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and are not used to limit the scope of the present application. The experimental methods in the following examples are not specified, and the methods are generally determined according to the national standards. If there is no corresponding national standard, the methods are determined according to the general international standards, conventional conditions, or the conditions recommended by the manufacturers.

[0041] Examples 1-3 and Comparative Examples 1-5

[0042] A method for treating peroxidized molten steel, the method comprising:

[0043] Step S1, tapping the peroxidized molten steel, and slag washing to obtain a slag-washed molten steel;

[0044] Step S2, adding pig iron into the slag-washed molten steel to obtain a mixed molten steel;

[0045] Step S3, stirring and treating the mixed molten steel to obtain a stirred molten steel;

[0046] Step S4, transferring the stirred molten steel to a refining station, and refining to obtain a target steel grade.

[0047] The specific parameter controls in each example and comparative example are shown in the following two tables:

[0048]

[0049]

[0050] From the above two tables, it can be seen that, by using the method provided in the present application, by adding pig iron into the peroxidized molten steel, the melting endothermic of pig iron and the reducing property of Si, Mn and C elements and the endothermic property of limestone are fully utilized to deoxidize and cool the peroxidized molten steel. The generated CaO and SiO2 products can improve the acid-base property and melting property of the ladle slag, and solve the problem of poor quality of the peroxidized molten steel, thereby greatly saving the cost.

[0051] From the data of the comparative examples, it can be seen that: in Comparative Example 1, the temperature control effect is poor by using lime for slag washing, resulting in high temperature of the molten steel entering the refining station, increasing the difficulty of the refining process; in Comparative Example 2, the amount of slag added in the slag washing process is insufficient, causing incomplete removal of phosphorus in the slag, and high phosphorus in the finished product; in Comparative Example 3, the particle size of the slag in the slag washing process is too large, causing poor dephosphorization effect in the slag washing process, and high phosphorus in the finished product; in Comparative Example 4, the amount of slag discharged from the converter is too large, the phosphorus content in the ladle slag is high, and there is phosphorus reversion in the refining process, resulting in high phosphorus in the finished product; in Comparative Example 5, the amount of pig iron added is too much, resulting in high phosphorus in the finished product and low temperature of the molten steel entering the station; in Comparative Example 6, the low-phosphorus steel grade is not slagged, causing phosphorus reversion in the refining process, resulting in high phosphorus in the finished product; in Comparative Example 7, the low-phosphorus steel grade has a low slagging rate, causing phosphorus reversion in the refining process, resulting in high phosphorus in the finished product; and in Comparative Example 8, the ladle slag is not modified, and the ladle slag has strong oxidizing property, affecting the cleanliness of the molten steel.

[0052] Various embodiments of the application can exist in a variety of forms; it should be understood that the description of the embodiments as being in a specific form is merely for convenience and brevity and should not be construed to limit the scope of the application; therefore, the description of a specific form should be considered to have specifically disclosed all possible sub-forms and individual numbers within the range. For example, it should be considered that the description of a range from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0053] In this document, the positional words such as "upper" and "lower" are specifically the directions of the drawing surface in the drawings unless otherwise stated. In addition, in the description of the specification, the terms "include", "contain", and the like mean "include but are not limited to". In this document, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this document, "and / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent the cases where A exists alone, A and B exist together, and B exists alone. Where A and B can be singular or plural. In this document, "one or more" means one or more, and "a plurality of" means two or more. "At least one", "at least one of the following", or the like means any combination of the items, including single items or any combination of multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0054] The above description is only a specific embodiment of the application, which enables those skilled in the art to understand or implement the application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application should not be limited to the embodiments shown herein, but should be consistent with the widest range of principles and novel features applied herein.

Claims

1. A method for treating a peroxidized steel liquid, characterized by, The method comprises: carrying out converter tapping and slag washing on the over-oxidized molten steel to obtain a slag-washed molten steel; mixing the slag-washed molten steel with pig iron to deoxidize and cool the slag-washed molten steel, and obtaining a mixed molten steel, and completing the treatment; the free oxygen content in the over-oxidized molten steel is above 800 ppm, the temperature of the over-oxidized molten steel is above 1660 DEG C, and the mass content of FeO in the ladle slag of the over-oxidized molten steel is greater than 25%; limestone and fluorite are added in the slag washing process, the adding amount of limestone is 3-8 kg / t steel, and the adding amount of fluorite is 0.5-2.0 kg / t steel.

2. The method for treating peroxidic steel liquid according to claim 1, characterized in that, The adding amount of the pig iron is less than 40 kg / t steel.

3. The method of treating peroxidic steel solution according to claim 1, wherein The amount of converter slag in the converter tapping process is less than 15 kg / t steel.

4. The method of treating peroxidic steel solution according to claim 1, wherein The volume particle size range of the limestone is 5-30 mm.

5. The method of treating peroxidic steel solution according to claim 1, wherein The method comprises: refining the mixed molten steel to obtain a target steel grade.

6. The method of treating peroxidic steel solution according to claim 5, wherein If the upper limit of the mass content of phosphorus in the target steel grade is less than 0.012%, the method further comprises: performing slag skimming treatment on the mixed molten steel.

7. The method of treating peroxidic steel solution according to claim 6, characterized in that, The slag skimming rate of the slag skimming treatment is greater than 60%.

8. The method of treating peroxidic steel solution according to claim 5, wherein When the refining is performed, the ladle slag is modified, and the mass content of FeO in the modified ladle slag is less than 8%.

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