A method for controlling the nitrogen content of molten steel of fully desulfurized, dephosphorized and deoxidized low-nitrogen steel grades

Abstract

The present application relates to the field of steel smelting, and in particular to a method for controlling the nitrogen content of low-nitrogen steel melt produced by full three-step desulfurization; the method comprises: obtaining smelted steel melt; subjecting the molten steel to full three-step desulfurization to obtain steel melt with low nitrogen content; wherein, in the full three-step desulfurization process, process charging, process gun position, converter bottom blowing and tapping charging are controlled respectively; by controlling the process charging in view of the fact that the amount of slag in full three-step desulfurization is small, the steel melt coverage effect during the slagging process can be enhanced, and then by controlling the process gun position and converter bottom blowing, sufficient nitrogen absorption by the steel melt is ensured, and the situation that the nitrogen absorption is insufficient due to the poor steel melt coverage effect caused by the small amount of slag is compensated, and then the tapping charging is controlled, thereby standardizing the alloying use process of the tapping charging, and then controlling the amount of the alloy with high nitrogen addition, thereby comprehensively ensuring the stable control of the nitrogen content of the converter steel melt produced by full three-step desulfurization.

Description

Technical Field

[0001] The present application relates to the field of steel smelting, and in particular to a method for controlling the nitrogen content of molten steel with a low nitrogen content through full three-step desulfurization. Background Art

[0002] Full three-desulfurization smelting has great advantages for efficient and low-cost steelmaking due to the small amount of slag added such as lime and the fast production pace. However, due to the small amount of slag in the smelting process, the coverage of the molten steel is poor, resulting in serious nitrogen absorption by the molten steel during the blowing process. When smelting low-nitrogen varieties such as automotive plates and tinplate, as well as crack-sensitive steels such as wheel steel with stricter nitrogen requirements, the control of nitrogen in the converter molten steel becomes a restrictive link. The converter process can easily cause the nitrogen in the molten steel to exceed the standard, which in turn affects the quality of steel products and the fulfillment of varieties.

[0003] Therefore, how to ensure the stable control of nitrogen content in converter steel with full three-step denitrification is a technical problem that needs to be solved urgently. Summary of the Invention

[0004] The present application provides a method for controlling the nitrogen content of low-nitrogen steel molten steel produced by full triple desulfurization, so as to solve the technical problem in the prior art that the nitrogen content of converter steel molten steel produced by full triple desulfurization is difficult to stably control.

[0005] In a first aspect, the present application provides a method for controlling the nitrogen content of low-nitrogen steel molten steel produced by full three-way desulfurization, the method comprising:

[0006] Obtain molten steel after smelting;

[0007] The molten steel is subjected to full three-step desulfurization to obtain molten steel with low nitrogen content;

[0008] In the full three-demetallization smelting process, process charging, process gun position, converter bottom blowing and steel tapping charging are controlled respectively.

[0009] Optionally, the control of the process feeding includes controlling the total amount of decarbonization smelting lime added, controlling the amount of lime added in the dynamic process, controlling the amount of ore added in the dynamic process and controlling the feeding in the blowing and drying period.

[0010] Optionally, the total amount of decarbonization smelting lime added is 5t to 6t;

[0011] The amount of lime added in the dynamic process is ≥0.5t;

[0012] The ore dosage in the dynamic process is 0.5t to 1.0t.

[0013] Optionally, the adding of materials during the blowing and drying period includes: adding slag agent or fluorite in batches, and the amount of the batch addition is 280kg to 320kg each time.

[0014] Optionally, the control of the process gun position includes controlling the height adjustment of the blowing gun during the blowing period and controlling the height adjustment of the gun position during the back-drying period.

[0015] Optionally, the blowing gun during the blowing period is adjusted to a height of 1.6m to 1.7m from the molten steel surface;

[0016] The gun position is adjusted during the re-drying period to a height of 2.6m to 3.0m from the molten steel surface.

[0017] Optionally, the converter bottom blowing includes performing converter bottom blowing with argon or a mixed gas, and the mixed gas includes a mixture of carbon dioxide and argon.

[0018] Optionally, the flow rate of the converter bottom blowing is ≤800Nm 3 / h.

[0019] Optionally, the control of the steel tapping and charging includes controlling the bottom blowing time before steel tapping, controlling the timing of adding alloy during steel tapping, and controlling the manganese element adjustment process.

[0020] Optionally, the bottom blowing time before tapping is 20s to 30s; the time for adding alloy to the tapping is when the steel is tapped to 150t; the manganese element adjustment process includes: adjusting the manganese element by using only low-carbon ferromanganese and medium-carbon ferromanganese as regulators.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] The embodiment of the present application provides a method for controlling the nitrogen content of low-nitrogen molten steel produced by full three-step desulfurization. By controlling the process charging in view of the characteristic of small amount of slag in full three-step desulfurization, the coverage effect of molten steel in the slagging process can be enhanced to prevent the molten steel from absorbing too much nitrogen. The process gun position and the bottom blowing of the converter are controlled to control the position and gas flow of the gas entering the molten steel, thereby ensuring sufficient nitrogen absorption by the molten steel and compensating for the poor coverage effect of the molten steel caused by the small amount of slag, which leads to insufficient nitrogen absorption. The steel-tapping charging is then controlled to standardize the alloying use process of the steel-tapping charging, and then the amount of alloy with high nitrogen increase is controlled, thereby comprehensively ensuring the stable control of the nitrogen content of the full three-step desulfurization converter steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 A flowchart of the method provided in the embodiment of the present application. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0027] In one embodiment of the present application, Figure 1 As shown, a method for controlling the nitrogen content of low-nitrogen steel molten steel produced by full three-way desulfurization is provided, the method comprising:

[0028] S1. Obtain molten steel after smelting;

[0029] S2. The molten steel is subjected to full three-stage smelting to obtain a molten steel with a low nitrogen content;

[0030] In the full three-demetallization smelting process, process charging, process gun position, converter bottom blowing and steel tapping charging are controlled respectively.

[0031] In some optional embodiments, the control of process feeding includes controlling the total amount of decarbonization smelting lime added, controlling the amount of lime added in the dynamic process, controlling the amount of ore added in the dynamic process, and controlling the feeding during the blowing and drying period.

[0032] In the embodiment of the present application, by controlling the different charging stages of the full three-desulfurization process, the total amount of lime added is first controlled to ensure that the lime slag-making effect is sufficient and the slag volume is guaranteed, thereby enhancing the steel liquid coverage effect and reducing the nitrogen absorption. Then, by controlling the amount of lime added in the dynamic process, it is possible to ensure that the slag is properly foamed in the dynamic process, thereby achieving a good steel liquid coverage effect and reducing nitrogen absorption in the later stage of blowing. Then, the charging in the blowing and drying period is controlled to ensure that the slag process is carried out uniformly, thereby further reducing the nitrogen absorption of the molten steel.

[0033] In some optional embodiments, the total amount of decarbonization smelting lime added is 5t to 6t;

[0034] The amount of lime added in the dynamic process is ≥0.5t;

[0035] The ore dosage in the dynamic process is 0.5t to 1.0t.

[0036] In the embodiment of the present application, the positive effect of the total amount of decarbonization smelting lime added being 5t to 6t is that within the range of the amount added, the amount of slag produced by the lime slag formation can be sufficient, thereby completely covering the molten steel and reducing the possibility of nitrogen absorption by the molten steel; when the value of the total amount added is greater than the maximum value of the endpoint of the range, the adverse effect that will result is that too much lime will increase the difficulty of subsequent slag formation, thereby being detrimental to the control of the final phosphorus and nitrogen content; when the value of the total amount added is less than the minimum value of the endpoint of the range, the adverse effect that will result is that too little lime will not produce enough slag, thereby failing to completely cover the molten steel.

[0037] The positive effect of the lime addition amount ≥0.5t in the dynamic process is that within the range of this addition amount, it can ensure that the lime slag can produce sufficient slag in the dynamic process, thereby completely covering the molten steel in the dynamic process; when the lime addition amount is too low, it will lead to insufficient slag, and the molten steel cannot be completely covered in the dynamic process, thereby affecting the control of nitrogen absorption by the molten steel.

[0038] The positive effect of the ore addition amount in the dynamic process being 0.5t to 1.0t is that within the range of this addition amount, by adding the ore-based oxidizing slag-reducing agent, it is possible to ensure that the slag foams appropriately in the dynamic process, further promote the complete coverage of the slag on the molten steel, improve the coverage effect of the molten steel, and thus reduce the nitrogen absorption in the later stage of blowing; when the addition amount is greater than or less than the end point value of this range, the foaming effect will be affected, resulting in the coverage effect of the molten steel being affected.

[0039] In some optional embodiments, the adding of materials during the blowing and drying period includes adding slag agent or fluorite in batches, and the amount of the batch addition is 280 kg to 320 kg each time.

[0040] In the embodiment of the present application, the positive effect of adding materials in batches with an addition amount of 280kg to 320kg each time is that within the range of the addition amount, the slag agent or fluorite can be fully slaged, so that the slag covering the molten steel is decomposed and floated, thereby ensuring the purity of the molten steel; when the value of the addition amount is greater than or less than the endpoint value of the range, the slag removal effect of the molten steel will be incomplete, thereby affecting the quality of the molten steel.

[0041] In some optional embodiments, the control of the process gun position includes controlling the height adjustment of the blowing gun during the blowing period and controlling the height adjustment of the gun position during the back-drying period.

[0042] In the embodiment of the present application, by controlling the process gun position including controlling the height adjustment of the blowing gun during the blowing period and controlling the height adjustment of the gun position during the drying period, it is ensured that the position and height of the gun are suitable during the blowing process, thereby ensuring that the slag is fully melted, and then obtaining a uniform low-nitrogen content molten steel.

[0043] In some optional embodiments, the blowing lance during the blowing period is adjusted to a height of 1.3m to 1.7m from the molten steel surface;

[0044] The gun position is adjusted during the re-drying period to a height of 2.6m to 3.0m from the molten steel surface.

[0045] In the embodiment of the present application, the positive effect of adjusting the blowing lance during the blowing period to a height of 1.3m to 1.7m from the molten steel surface is that within this height range, the height of the blowing lance during the blowing period can be ensured to be appropriate, thereby ensuring that the slag is brought out and evenly distributed; when the height value is greater than or less than the endpoint value of the range, the height of the blowing lance will be unsuitable for promoting the generation of slag, thereby failing to ensure sufficient melting of the slag.

[0046] The positive effect of adjusting the gun position during the dry-down period to a height of 2.6m to 3.0m from the molten steel surface is that within this height range, the slag can be fully melted during the dry-down period; when the height value is greater than or less than the end point value of this range, the height of the blowing gun will be unsuitable for melting the slag, thereby failing to ensure sufficient melting of the slag.

[0047] In some optional embodiments, the converter bottom blowing includes performing converter bottom blowing with argon or a mixed gas, and the mixed gas includes carbon dioxide and argon.

[0048] In the embodiment of the present application, by limiting the gas used for bottom blowing, the bottom blowing of molten steel can be controlled in combination with actual conditions, thereby preventing the molten steel from absorbing nitrogen, and fully stirring the molten steel to improve the quality of the molten steel.

[0049] In some optional embodiments, the flow rate of the converter bottom blowing is ≤800Nm 3 / h.

[0050] In the embodiment of the present application, the flow rate of the converter bottom blowing is ≤800Nm 3 The positive effect of / h is that within this flow rate range, it can ensure sufficient bottom blowing of the molten steel, thereby avoiding nitrogen absorption by the molten steel, and can fully stir the molten steel to improve the quality of the molten steel.

[0051] In some optional embodiments, the control of the steel tapping and charging includes controlling the bottom blowing time before steel tapping, controlling the timing of adding alloy during steel tapping, and controlling the manganese element adjustment process.

[0052] In the embodiment of the present application, the control of the steel feeding is formed by controlling the bottom blowing time before steel tapping, controlling the timing of adding alloys during steel tapping, and controlling the manganese element adjustment process, so as to further prevent the molten steel from absorbing nitrogen by bottom blowing before steel tapping, and then controlling the timing of adding alloys during steel tapping and the manganese element adjustment process, thereby controlling the amount of alloys with high nitrogen content, thereby creating conditions for controlling the stability of the nitrogen content in the molten steel.

[0053] In some optional embodiments, the bottom blowing time before tapping is 20s to 30s; the tapping and alloying time is when the steel is tapped to 150t; the manganese element adjustment process includes: adjusting the manganese element by using only low-carbon ferromanganese and medium-carbon ferromanganese as regulators.

[0054] In the embodiment of the present application, the positive effect of the bottom blowing time before steel tapping being 20s to 30s is that within this time range, it can ensure that the molten steel is stirred more evenly after bottom blowing, while preventing the molten steel from absorbing nitrogen; when the time value is greater than or less than the endpoint value of this range, it will lead to uneven stirring distribution of the molten steel during the bottom blowing process.

[0055] By limiting the time of adding alloy to the tapping process to when 150t of steel is tapped, it can be ensured that the tapping quality is not affected during the alloy addition process during the tapping stage, and at the same time, the alloying of the molten steel can proceed smoothly.

[0056] By limiting the use of only low-carbon ferromanganese and medium-carbon ferromanganese as regulators for the manganese element regulation process, it is avoided that excessive or insufficient addition of carbon affects the quality of the molten steel.

[0057] Example 1

[0058] like Figure 1 As shown, a method for controlling the nitrogen content of low-nitrogen steel molten steel after full three-way desulfurization, comprising:

[0059] S1. Obtain molten steel after smelting;

[0060] S2. The molten steel is subjected to full three-stage smelting to obtain a molten steel with a low nitrogen content;

[0061] Among them, in the whole three-demetallization smelting process, the process charging, process gun position, converter bottom blowing and steel-tapping charging are controlled respectively.

[0062] The control of process charging includes the control of the total amount of decarbonization smelting lime added, the control of the lime addition amount in the dynamic process, the control of the ore addition amount in the dynamic process and the control of charging during the blowing and drying period. At the same time, coke temperature increase is not used during the process charging stage.

[0063] The total amount of decarbonization smelting lime added is 5.5t;

[0064] The lime dosage in the dynamic process is 1.5t;

[0065] The ore dosage in the dynamic process is 0.7t.

[0066] The feeding during the blowing and drying period includes: adding slag agent or fluorite in batches, and the amount of feeding in batches is 300kg each time.

[0067] The control of process gun position includes the control of adjusting the height of the blowing gun during the blowing period and the control of adjusting the height of the gun position during the drying period.

[0068] During the blowing period, the blowing gun is adjusted to a height of 1.6m from the molten steel surface;

[0069] During the re-drying period, the gun position is adjusted to a height of 2.8m from the molten steel surface.

[0070] The converter bottom blowing includes performing converter bottom blowing with argon or a mixed gas, and the mixed gas includes a mixture of carbon dioxide and argon.

[0071] The flow rate of converter bottom blowing is 600Nm 3 / h.

[0072] The control of steel-tapping charging includes the control of bottom blowing time before steel-tapping, the control of alloying time during steel-tapping and the control of manganese element adjustment process.

[0073] The bottom blowing time before tapping is 25s; the time for adding alloy to the tapping is when the steel reaches 150t; the manganese element adjustment process includes: adjusting the manganese element by using only low-carbon ferromanganese and medium-carbon ferromanganese as regulators.

[0074] Example 2

[0075] Comparing Example 2 with Example 1, the difference between Example 2 and Example 1 is:

[0076] The total amount of decarbonization smelting lime added is 5t;

[0077] The lime dosage in the dynamic process is 0.5t;

[0078] The ore dosage in the dynamic process is 0.5t.

[0079] The amount of material added in batches is 280 kg each time.

[0080] During the blowing period, the blowing gun is adjusted to a height of 1.3m from the molten steel surface;

[0081] During the re-drying period, the gun position is adjusted to a height of 2.6m from the molten steel surface.

[0082] The bottom blowing time before tapping is 20s.

[0083] Example 3

[0084] Comparing Example 3 with Example 1, the difference between Example 3 and Example 1 is:

[0085] The total amount of decarbonization smelting lime added is 6t;

[0086] The ore dosage in the dynamic process is 1.0t.

[0087] The amount of material added in batches is 320 kg each time.

[0088] During the blowing period, the blowing gun is adjusted to a height of 1.7m from the molten steel surface;

[0089] During the re-drying period, the gun position is adjusted to a height of 3.0m from the molten steel surface.

[0090] The bottom blowing time before tapping is 30s.

[0091] Comparative Example 1

[0092] Comparing Comparative Example 1 with Example 1, the difference between Comparative Example 1 and Example 1 is:

[0093] Process charging, process gun position, converter bottom blowing and steel-tapping charging are not controlled separately.

[0094] Comparative Example 2

[0095] Comparing Comparative Example 2 with Example 1, the difference between Comparative Example 2 and Example 1 is:

[0096] The total amount of decarbonization smelting lime added is 4t;

[0097] The lime dosage in the dynamic process is 0.2t;

[0098] The ore dosage in the dynamic process is 0.4t.

[0099] The amount of material added in batches is 250 kg each time.

[0100] During the blowing period, the blowing gun is adjusted to a height of 1.6m from the molten steel surface;

[0101] During the re-drying period, the gun position is adjusted to a height of 2.5m from the molten steel surface.

[0102] The bottom blowing time before tapping is 10s.

[0103] Comparative Example 3

[0104] Comparing Comparative Example 3 with Example 1, the difference between Comparative Example 3 and Example 1 is:

[0105] The total amount of decarbonization smelting lime added is 8t;

[0106] The ore dosage for the dynamic process is 1.5t.

[0107] The amount of material added in batches is 350 kg each time.

[0108] During the blowing period, the blowing gun is adjusted to a height of 1.7m from the molten steel surface;

[0109] During the re-drying period, the gun position is adjusted to a height of 3.5m from the molten steel surface.

[0110] The bottom blowing time before tapping is 40s.

[0111] Related experiments:

[0112] The nitrogen contents in the molten steels obtained in Examples 1-3 and Comparative Examples 1-3 were statistically analyzed, and the results are shown in Table 1.

[0113] Test methods for related experiments:

[0114] Nitrogen content: Measured using HORIBA EMGA-620W oxygen and nitrogen analyzer.

[0115] Table 1

[0116] Group Nitrogen content (ppm) Example 1 13 Example 2 15 Example 3 14 Comparative Example 1 20 Comparative Example 2 19 Comparative Example 3 16

[0117] Table 1 Detailed analysis:

[0118] Nitrogen content refers to the nitrogen content in the resulting molten steel. The more the nitrogen content meets the standard, the more accurately the nitrogen content of the molten steel product is controlled.

[0119] From the data of Examples 1-3, it can be seen that by adopting the method of the present application, by controlling the process charging, process gun position, converter bottom blowing and steel-tapping charging respectively during the full three-demetallization smelting process, it is possible to ensure the stable control of the nitrogen content of the converter steel liquid in the full three-demetallization smelting process.

[0120] From the data of Comparative Examples 1-3, we can see that:

[0121] If the method of the present application is not adopted, or if the process parameters are not controlled within the corresponding range, the nitrogen content of the steel after the final full three-step desulfurization will be affected.

[0122] One or more technical solutions in the embodiments of the present application may have at least the following technical effects or advantages:

[0123] (1) The method provided in the embodiment of the present application controls the process charging, process gun position, converter bottom blowing and steel-tapping charging respectively. By controlling the process charging, the steel liquid coverage effect during the slagging process can be enhanced to prevent the steel liquid from absorbing too much nitrogen. Then, by controlling the process gun position and converter bottom blowing, the position of the gas entering the steel liquid and the gas flow rate can be controlled to ensure that the steel liquid absorbs nitrogen fully, making up for the poor steel liquid coverage effect caused by the small amount of slag, which leads to insufficient nitrogen absorption. Then, the steel-tapping charging is controlled to standardize the alloying process of the steel-tapping charging, and then the amount of the alloy with high nitrogen content can be controlled, so as to ensure the stable control of the nitrogen content of the converter steel liquid after the full three-desulfurization process.

[0124] (2) The method provided in the embodiments of the present application provides a set of effective operating instructions for the full three-desulfurization smelting process, creating favorable conditions for stable production and stable quality.

[0125] (3) The method provided in the embodiment of the present application can also effectively control the content of manganese element, while avoiding carbon increase of molten steel during the alloying process, thereby ensuring the quality of molten steel.

[0126] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0127] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but is intended to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for controlling the nitrogen content of low-nitrogen steel molten steel after full three-way desulfurization, characterized in that: The method comprises: Obtain smelted molten steel; The molten steel is subjected to full three-step desulfurization to obtain molten steel with low nitrogen content; Wherein, in the said full three-demetallization smelting process, process charging, process gun position, converter bottom blowing and tapping charging are controlled respectively; The control of the process charging includes controlling the total amount of decarbonization smelting lime added to 5t~6t, the lime addition amount of the dynamic process to be ≥0.5t, the ore addition amount of the dynamic process to be 0.5t~1.0t, and adding molten slag agent or fluorite in batches, with the addition amount of batches being 280kg~320kg each time. At the same time, coke is not used to increase the temperature during the process charging stage; The control of the process gun position includes controlling the blowing gun to adjust the height from the molten steel level to 1.6m~1.7m during the blowing period and adjusting the gun position to 2.6m~3.0m during the back-drying period; The control of the steel tapping and charging includes controlling the bottom blowing time before steel tapping to be 20s~30s.

2. The method according to claim 1, characterized in that The converter bottom blowing includes performing converter bottom blowing with argon or a mixed gas, and the mixed gas includes carbon dioxide and argon.

3. The method according to claim 2, characterized in that The flow rate of the converter bottom blowing is ≤800Nm 3 / h.

4. The method according to claim 1, wherein The control of the steel tapping and charging includes the control of the steel tapping and alloying timing and the control of the manganese element adjustment process.

5. The method according to claim 4, characterized in that The time for adding alloy to the steel is when the steel is tapped to 150t; the manganese element adjustment process includes: adjusting the manganese element by using only low-carbon ferromanganese and medium-carbon ferromanganese as regulators.

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