Dephosphorization method for reducing converter steelmaking cost

Abstract

The invention discloses a dephosphorization method for reducing converter steelmaking cost, and belongs to the technical field of steelmaking. The method comprises the following steps: S1, pretreating blast furnace molten iron; s2, the preheated scrap steel is added into a converter, and then the pretreated molten iron is added; s3, magnetic separation materials and auxiliary materials are added into the furnace; s4, bottom blowing and stirring are conducted in the whole process, the process is detected, and the temperature, slag alkalinity and phosphorus content are adjusted; and S5, after converter dephosphorization smelting is completed, molten steel tapping and deslagging are conducted. According to the method, the smelting parameters are adjusted, the slag components and the dephosphorization time are optimized, and the dephosphorization cost is remarkably reduced on the premise that the dephosphorization effect is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking, and in particular to a dephosphorization method for reducing converter steelmaking costs. Background Art

[0002] Phosphorus is a harmful impurity in steel materials. High phosphorus content will increase the brittleness of steel and reduce its toughness and ductility, seriously affecting the performance and quality of steel. In the converter steelmaking process, dephosphorization is a key step, and its efficiency and cost are directly related to the production benefits and market competitiveness of steel companies. Although the traditional double-slag method can achieve effective dephosphorization to a certain extent, it often has high costs, low efficiency, and complex and time-consuming operations. The single-slag method is popular because of its simple process and easy operation, but how to reduce costs while ensuring the dephosphorization effect has always been a hot topic in the steelmaking field. The reaction formula for converter dephosphorization is as follows:

[0003] 2[P]+5(FeO)+3CaO=(3CaO·P2O5)+5[Fe]

[0004] Donghua Iron & Steel (Tangshan Donghua Iron & Steel Enterprise Group Co., Ltd.) adopts the single-slag method for converter steelmaking. The single-slag method only produces slag once during the blowing process, without dumping or removing slag in the middle. For most types of steel, phosphorus in steel is a very harmful element, and the lower the better. However, when the phosphorus content in molten iron is high, the dephosphorization effect of the single-slag method is difficult to meet the strict requirements of the steel type.

[0005] Therefore, it is necessary to provide a dephosphorization method for reducing the cost of converter steelmaking. Summary of the invention

[0006] The purpose of the present invention is to provide a dephosphorization method for reducing the cost of converter steelmaking, so as to solve the problems of high dephosphorization cost, low efficiency, complex operation and long time consumption in the prior art.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A dephosphorization method for reducing converter steelmaking costs comprises the following steps:

[0009] S1, pre-treating blast furnace molten iron;

[0010] S2, adding the preheated scrap steel into the converter, and then adding the pretreated molten iron;

[0011] S3, adding magnetic separation material and auxiliary materials into the furnace;

[0012] Among them, according to the amount of molten iron added, the amount of lime added is 15.15kg / t~24.24kg / t, the amount of dolomite is 12.12kg / t~18.18kg / t, and the amount of secondary magnetic separation material selection is 1000kg~3000kg, and they are added to the converter at one time after preparation;

[0013] S4, bottom blowing and stirring throughout the whole process; process detection and adjustment of temperature, slag basicity and phosphorus content;

[0014] S5, after the converter dephosphorization smelting is completed, the molten steel is tapped and the slag is poured.

[0015] Furthermore, after pretreatment in step S1, the temperature of the molten iron is 1300-1450°C; the mass content of C is 4.3%-5.14%; the mass content of Si is 0.12%-0.44%; the mass content of Mn is 0.20%-0.51%; the mass content of P is 0.132%-0.166%; and the mass content of S is 0.012%-0.054%.

[0016] Furthermore, in step S2, the amount of scrap steel added is based on a mass ratio of molten iron to scrap steel of 4.29 to 5.78:1.

[0017] Furthermore, during the bottom blowing process in step S4, the oxygen flow rate is 35000-45000 Nm 3 / h, oxygen supply time is 12 minutes and 30 seconds.

[0018] Furthermore, the component contents in the slag are controlled in the later stage of smelting as follows: the final slag basicity is 2.4-4; FeO is 10%-29%; P2O5 is 2.8%-4.4%; MgO is 7%-12%; CaO is 30%-42%; SiO2 is 8%-14%; and Al2O3 is 1.2%-5.7%.

[0019] Furthermore, the temperature of the molten steel is regulated to be 1600° C. to 1680° C. during steel tapping; the component contents in the molten steel are: C content is 0.034% to 0.09%; Si content is 0.001%; ​​and Mn content is 0.035% to 0.09%.

[0020] Furthermore, after the dephosphorization smelting in the converter is completed in step S5, a certain amount of slag is retained in the converter for slag splashing to protect the furnace.

[0021] The present invention has the following beneficial effects:

[0022] The present invention adopts single slag converter steelmaking, first pre-treats molten iron, then adds scrap steel in proportion, then adds auxiliary materials for further smelting, and reasonably adjusts the amount of auxiliary materials added, and then adjusts the content of terminal slag components and controls the components of terminal molten steel. The method significantly reduces the dephosphorization cost while ensuring the dephosphorization effect by adjusting smelting parameters, optimizing slag components and dephosphorization timing, and solves the problems of high dephosphorization cost, low efficiency, complex operation and long time consumption in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The process flow chart provided by the present invention. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0025] This embodiment provides a dephosphorization method for reducing the cost of converter steelmaking, which optimizes the feed ratio and smelting process in the converter steelmaking dephosphorization industrial process to achieve efficient and low-cost dephosphorization effects, including the following steps:

[0026] S1, pre-treat the blast furnace molten iron; before converter steelmaking, pre-treat the molten iron to remove some impurities, mainly to regulate the C, Si, Mn, P, S and molten iron temperature in the molten iron, to create favorable conditions for subsequent dephosphorization. After pre-treatment, the molten iron temperature is 1300-1450℃; the C mass content is 4.3%-5.14%; the Si mass content is 0.12%-0.44%; the Mn mass content is 0.20%-0.51%; the P mass content is 0.132%-0.166%; the S mass content is 0.012%-0.054%.

[0027] S2, adding the preheated scrap steel into the converter, and then adding the pretreated molten iron; wherein the amount of scrap steel added is based on a mass ratio of molten iron to scrap steel of 4.29 to 5.78:1.

[0028] S3, adding magnetic separation material and auxiliary materials into the furnace;

[0029] Among them, according to the amount of molten iron added, the amount of lime added is 15.15kg / t~24.24kg / t, the amount of dolomite is 12.12kg / t~18.18kg / t, and the amount of secondary magnetic separation material selection is 1000kg~3000kg, and they are added to the converter at one time after preparation.

[0030] S4, full bottom blowing, stirring; process detection and adjustment of temperature, slag basicity, phosphorus content. During the bottom blowing process, the oxygen flow rate is 35000-45000Nm 3 / h, oxygen supply time is 12 minutes and 30 seconds. The content of components in the slag in the later stage of smelting is controlled as follows: the basicity of the final slag is 2.4-4; FeO is 10%-29%; P2O5 is 2.8%-4.4%; MgO is 7%-12%; CaO is 30%-42%; SiO2 is 8%-14%; Al2O3 is 1.2%-5.7%.

[0031] S5, after the dephosphorization smelting in the converter is completed, the molten steel is tapped, the slag is poured, and a certain amount of slag is left in the converter for slag splashing and furnace protection; the temperature of the molten steel is regulated to be 1600℃~1680℃ during tapping; the composition content in the molten steel: C content is 0.034%~0.09%; Si content is 0.001%; ​​Mn content is 0.035%~0.09%.

[0032] The present embodiment provides a dephosphorization method for reducing the cost of converter steelmaking. The single-slag method converter steelmaking is adopted. The molten iron is first pretreated, and then scrap steel is added in proportion, and then auxiliary materials are added for further smelting, and the amount of auxiliary materials added is reasonably regulated, and then the content of the final slag component is regulated and the final molten steel component is controlled. The process operation is simple and the dephosphorization cost is reduced while ensuring a good dephosphorization effect, thereby solving the problems of high dephosphorization cost, low efficiency, complex operation and long time consumption in the prior art.

[0033] In this embodiment, Donghua Iron and Steel produced 40 furnaces of products according to the dephosphorization method for reducing the cost of converter steelmaking provided in this embodiment, and the process is adding scrap steel - adding molten iron - adding auxiliary materials - blowing oxygen - tapping. Table 1 shows some cases.

[0034] Table 1

[0035]

[0036] The single-slag converter steelmaking process in this embodiment includes adding scrap steel - adding molten iron - adding auxiliary materials - blowing oxygen - tapping - pouring slag - splashing slag to protect the furnace, achieving a phosphorus content of ≤0.02% at the end of converter steel tapping and a dephosphorization rate of ≥90%. This method significantly reduces the dephosphorization cost while ensuring the dephosphorization effect by adjusting smelting parameters, optimizing slag composition and dephosphorization timing.

[0037] The raw materials listed in the present invention, as well as the upper and lower limits and interval values ​​of the raw materials of the present invention, and the upper and lower limits and interval values ​​of process parameters (such as temperature, time, etc.) can all realize the present invention, and the embodiments are not listed one by one here.

[0038] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A dephosphorization method for reducing converter steelmaking costs, characterized in that: The following steps are involved: S1, pre-treating blast furnace molten iron; S2, adding the preheated scrap steel into the converter, and then adding the pretreated molten iron; S3, adding magnetic separation material and auxiliary materials into the furnace; Among them, according to the amount of molten iron added, the amount of lime added is 15.15kg / t~24.24kg / t, the amount of dolomite is 12.12kg / t~18.18kg / t, and the amount of secondary magnetic separation material selection is 1000kg~3000kg, and they are added to the converter at one time after preparation; S4, bottom blowing and stirring throughout the whole process; process detection and adjustment of temperature, slag basicity and phosphorus content; S5, after the converter dephosphorization smelting is completed, the molten steel is tapped and the slag is poured.

2. The dephosphorization method for reducing converter steelmaking costs according to claim 1, characterized in that: After pretreatment in step S1, the temperature of the molten iron is 1300-1450°C; the mass content of C is 4.3%-5.14%; the mass content of Si is 0.12%-0.44%; the mass content of Mn is 0.20%-0.51%; the mass content of P is 0.132%-0.166%; and the mass content of S is 0.012%-0.054%.

3. The dephosphorization method for reducing converter steelmaking cost according to claim 1, characterized in that: In step S2, the amount of scrap steel added is based on a mass ratio of molten iron to scrap steel of 4.29 to 5.78:

1.

4. The dephosphorization method for reducing converter steelmaking cost according to claim 1, characterized in that: During the bottom blowing process in step S4, the oxygen flow rate is 35000-45000Nm 3 / h, oxygen supply time is 12 minutes and 30 seconds.

5. The dephosphorization method for reducing converter steelmaking cost according to claim 1, characterized in that: In step S4, the component contents in the slag in the later stage of smelting are controlled as follows: the final slag basicity is 2.4-4; FeO is 10%-29%; P2O5 is 2.8%-4.4%; MgO is 7%-12%; CaO is 30%-42%; SiO2 is 8%-14%; and Al2O3 is 1.2%-5.7%.

6. The dephosphorization method for reducing converter steelmaking cost according to claim 1, characterized in that: In step S5, the temperature of the molten steel is regulated to be 1600° C. to 1680° C. during steel tapping; the component contents in the molten steel are: C content is 0.034% to 0.09%; Si content is 0.001%; ​​and Mn content is 0.035% to 0.09%.

7. The dephosphorization method for reducing converter steelmaking cost according to claim 1, characterized in that: After the dephosphorization smelting in the converter is completed in step S5, a certain amount of slag is retained in the converter for slag splashing to protect the furnace.

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