Deoxidation treatment method for steelmaking converter

Abstract

The invention belongs to the technical field of steelmaking deoxidation, and particularly discloses a steelmaking converter deoxidation treatment method which comprises the following steps: S1, according to the carbon content in molten steel, putting a deoxidizing agent into a converter for the first time, and introducing inert gas into the molten steel to stir the molten steel to assist in deoxidation; s2, during tapping of the molten steel, secondary deoxidizing agent feeding is carried out, feeding is started when 25%-30% of the molten steel flows out, secondary feeding is completed when 75%-80% of the molten steel flows out, and the oxygen content of the molten steel is monitored; if the unqualified molten steel is detected, the unqualified molten steel is placed into the furnace again, and vacuumizing is conducted till the internal pressure of the unqualified molten steel is 98-114 pa; s3, a deoxidizing agent is put into the converter for the third time, and meanwhile inert gas is continuously introduced; and S4, tapping, and monitoring the oxygen content of the molten steel. The method provided by the invention can greatly ensure the final deoxidation effect, and has a good practical application effect.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking deoxidation, and in particular relates to a deoxidation treatment method for a steelmaking converter. Background Art

[0002] Converter steelmaking is a common steelmaking process that mainly relies on the physical heat of molten iron itself and the heat generated by the chemical reaction between the components of the molten iron to complete the steelmaking process without the help of additional energy. In order to produce clean steel and ultra-clean steel to improve the quality of steel and improve the mechanical properties of steel, it is necessary to carry out deoxidation, desulfurization, dephosphorization and removal of non-metallic inclusions in the steel during the steelmaking process, and a steelmaking converter deoxidation treatment method needs to be applied.

[0003] The Chinese patent application with publication number CN107779549A discloses a steelmaking converter deoxidation process, which includes the following steps: smelting in a converter to obtain molten steel; tapping, so that the molten steel in the converter enters the ladle; at the same time, adding a deoxidizer to the ladle during tapping to partially deoxidize the molten steel, the deoxidizer includes carbon powder, steel sand aluminum, bauxite, lime, silicon manganese and ferrosilicon alloy; the order of adding the deoxidizer is: first add carbon powder, then add steel sand aluminum, bauxite and lime, and finally add silicon manganese and ferrosilicon alloy; the amount of the carbon powder, steel sand aluminum, bauxite, lime, silicon manganese and ferrosilicon alloy is determined according to the data of the carbon oxygen product of the converter molten steel end point; the ladle enters a vacuum environment for deoxidation and alloying. This process changes the previous deoxidation mode, and gradually cancels the use of silicon, aluminum and iron, so that the qualified rate of oxygen content in molten steel is significantly improved, and the consumption of deoxidizers and alloys is significantly reduced. Although the current steelmaking converter deoxidation process can complete the deoxidation of molten steel, the overall deoxidation effect is not good. Summary of the invention

[0004] The object of the present invention is to provide a steelmaking converter deoxidation treatment method, which divides the deoxidation into multiple different steps and introduces inert gas treatment during the deoxidation process, thereby greatly ensuring the final deoxidation effect.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A deoxidation treatment method for a steelmaking converter comprises the following steps: S1. According to the carbon content in the molten steel, a deoxidizer is added to the converter for the first time, and an inert gas is introduced into the molten steel to stir the molten steel and assist deoxidation; S2. When the molten steel is being tapped, the second deoxidizer is added; the addition starts when 25%-30% of the molten steel flows out, and the second addition is completed when 75%-80% of the molten steel flows out, and the oxygen content of the molten steel is monitored; for the unqualified molten steel, it is placed back into the furnace and evacuated to an internal pressure of 98-114pa; S3, adding deoxidizer to the converter for the third time, while continuously introducing inert gas; S4. Steel is tapped and the oxygen content of the molten steel is monitored.

[0006] Furthermore, the deoxidizer of the present invention is one or more of ferrosilicon deoxidizer, ferromanganese deoxidizer and ferroaluminum deoxidizer. Ferrosilicon deoxidizer has a stable effect and is suitable for low-carbon steel. Ferromanganese deoxidizer has a slightly weaker ability but can improve the strength and toughness of steel. Ferroaluminum deoxidizer has a strong ability but is prone to produce impurities in molten steel.

[0007] Furthermore, the deoxidizer of the present invention is added by a spraying method.

[0008] Furthermore, the amount of the deoxidizer added in step S1 of the present invention is calculated as follows: if the carbon content of the molten steel is ≤0.25%, the amount of the deoxidizer added is 0.1-0.15% of the total amount of the molten steel; if the carbon content of the molten steel is >0.25%, the amount of the deoxidizer added is 0.2-0.25% of the total amount of the molten steel.

[0009] Furthermore, the inert gas in step S1 of the present invention is argon gas with a flow rate of 0.7-0.9 m / s. 3 / min.

[0010] Furthermore, in step S2 of the present invention, the oxygen content of the molten steel is monitored. For killed steel, the oxygen content needs to be controlled between 0.004% and 0.009%; for rimmed steel, the oxygen content needs to be controlled between 0.025% and 0.045%; for semi-killed steel, the oxygen content needs to be controlled between 0.015% and 0.024%.

[0011] Furthermore, the inert gas in step S3 of the present invention is argon gas with a flow rate of 0.2-0.3 m 3 / min, holding time is 20-30s.

[0012] The method of the present invention can control the oxygen content between 0.004% and 0.045%.

[0013] The beneficial effects of the technical solution of the present invention are: The present invention greatly improves the deoxidation effect on the molten steel by setting multiple molten steel deoxidation treatment processes and optimizing the type and addition method of the deoxidizer, and the deoxidation effect on the molten steel is increased step by step. In addition, the present invention strictly controls the amount of deoxidizer added, which can effectively avoid the waste of deoxidizer and will not affect the quality of the final molten steel due to excessive or insufficient addition. The present invention is also provided with a strict oxygen content monitoring process, which can monitor the oxygen content in the molten steel every time the steel is tapped. When the monitoring is unqualified, the molten steel circuit can be deoxidized again until the requirements are met, which can greatly ensure the final deoxidation effect and has better practical application effects. DETAILED DESCRIPTION

[0014] The following will be combined with embodiments to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0015] The steel in this embodiment is semi-killed steel, and the deoxidation treatment method of the steelmaking converter comprises the following steps: S1, the carbon content of molten steel is 0.23%, and ferrosilicon deoxidizer of about 0.1% of the total amount of molten steel is added into the converter by injection method, and 0.7m 3 Inert gas argon is introduced at a flow rate of / min to stir the molten steel and assist deoxidation; S2. When the molten steel is tapped, the carbon content is 0.21%. About 0.1% of the total amount of the remaining molten steel is injected into the converter by the injection method again. The injection begins when about 30% of the molten steel flows out, and the injection is completed when about 80% of the molten steel flows out. The oxygen content of the molten steel is monitored and the oxygen content is 0.18%. The molten steel is put back into the furnace and the furnace is evacuated to an internal pressure of 98 Pa. S3, using the injection method to add about 0.12% of the total amount of remaining molten steel into the converter for the third time, and at the same time 3 Inert gas argon was continuously introduced at a flow rate of / min, and the argon introduction time was maintained for 20s; S4. Steel is tapped and the oxygen content of the molten steel is monitored, and the oxygen content is 0.042%. Example 2

[0016] The steel in this embodiment is semi-killed steel, and the deoxidation treatment method of the steelmaking converter comprises the following steps: S1, the carbon content of molten steel is 0.27%, and ferromanganese deoxidizer of about 0.25% of the total amount of molten steel is added into the converter by injection method, and 0.8m3 Inert gas argon is introduced at a flow rate of / min to stir the molten steel and assist deoxidation; S2. When the molten steel was tapped, the carbon content was 0.26%. The ferromanganese deoxidizer, which accounted for about 0.23% of the total amount of the remaining molten steel, was injected into the converter again by the injection method. The injection started when about 27% of the molten steel flowed out, and was completed when about 78% of the molten steel flowed out. The oxygen content of the molten steel was monitored and the oxygen content was 0.021%. S3, using the injection method to add about 0.21% of the total amount of remaining molten steel into the converter for the third time, and at the same time, 0.3m 3 Inert gas argon was continuously introduced at a flow rate of / min, and the argon introduction time was maintained for 25s; S4. Steel is tapped and the oxygen content of the molten steel is monitored, and the oxygen content is 0.041%. Example 3

[0017] The steel in this embodiment is killed steel, and the deoxidation treatment method of the steelmaking converter comprises the following steps: S1, the carbon content of molten steel is 0.26%, and the aluminum iron deoxidizer of about 0.22% of the total amount of molten steel is added into the converter by the injection method, and 0.9m 3 Inert gas argon is introduced at a flow rate of / min to stir the molten steel and assist deoxidation; S2. When the molten steel is tapped, the carbon content is 0.23%. The aluminum-iron deoxidizer, which accounts for about 0.14% of the total amount of the remaining molten steel, is injected into the converter again by the injection method. The injection begins when about 30% of the molten steel flows out, and the injection is completed when about 80% of the molten steel flows out. The oxygen content of the molten steel is monitored and the oxygen content is 0.007%. S3, using the injection method to add about 0.13% of the total amount of remaining molten steel into the converter for the third time, and at the same time, 0.25m 3 Inert gas argon was continuously introduced at a flow rate of / min, and the argon introduction time was maintained for 30s; S4. Steel is tapped and the oxygen content of the molten steel is monitored, and the oxygen content is 0.004%. Example 4

[0018] The steel in this embodiment is killed steel, and the deoxidation treatment method of the steelmaking converter comprises the following steps: S1, the carbon content of molten steel is 0.23%, and ferromanganese deoxidizer of about 0.13% of the total amount of molten steel is added into the converter by injection method, and 0.7m 3 Inert gas argon is introduced at a flow rate of / min to stir the molten steel and assist deoxidation; S2. When the molten steel is tapped, the carbon content is 0.22%. The ferromanganese deoxidizer of about 0.11% of the total amount of the remaining molten steel is injected into the converter again by the injection method. The injection begins when about 30% of the molten steel flows out, and the injection is completed when about 80% of the molten steel flows out. The oxygen content of the molten steel is monitored and the oxygen content is 0.011%. The molten steel is put back into the furnace and evacuated to an internal pressure of 102 Pa. S3, using the injection method to add about 0.12% of the total amount of remaining molten steel into the converter for the third time, and at the same time, 0.3m 3 Inert gas argon was continuously introduced at a flow rate of / min, and the argon introduction time was maintained for 30s; S4. Steel is tapped and the oxygen content of the molten steel is monitored, and the oxygen content is 0.006%. Example 5

[0019] The steel in this embodiment is rimmed steel, and the deoxidation treatment method of the steelmaking converter comprises the following steps: S1, the carbon content of molten steel is 0.33%, and ferrosilicon deoxidizer of about 0.25% of the total amount of molten steel is added into the converter by injection method, and 0.9m 3 Inert gas argon is introduced at a flow rate of / min to stir the molten steel and assist deoxidation; S2. When the molten steel is tapped, the carbon content is 0.29%. The ferrosilicon deoxidizer of about 0.23% of the total amount of the remaining molten steel is injected into the converter again by the injection method. The injection starts when about 25% of the molten steel flows out, and the injection is completed when about 80% of the molten steel flows out. The oxygen content of the molten steel is monitored and the oxygen content is 0.057%. The molten steel is put back into the furnace and evacuated to an internal pressure of 114 Pa. S3, use the injection method to add about 0.25% of the total amount of remaining molten steel into the converter for the third time, and at the same time, 0.2m 3 Inert gas argon was continuously introduced at a flow rate of / min, and the argon introduction time was maintained for 30s; S4. Steel is tapped and the oxygen content of the molten steel is monitored, and the oxygen content is 0.019%. Example 6

[0020] The steel in this embodiment is rimmed steel, and the deoxidation treatment method of the steelmaking converter comprises the following steps: S1, the carbon content of molten steel is 0.17%, and ferrosilicon deoxidizer of about 0.11% of the total amount of molten steel is added into the converter by injection method, and 0.8m 3 Inert gas argon is introduced at a flow rate of / min to stir the molten steel and assist deoxidation; S2. When the molten steel is tapped, the carbon content is 0.15%. The ferrosilicon deoxidizer, which accounts for about 0.14% of the total amount of the remaining molten steel, is injected into the converter again by the injection method. The injection starts when about 25% of the molten steel flows out, and the injection is completed when about 75% of the molten steel flows out. The oxygen content of the molten steel is monitored and the oxygen content is 0.035%. S3, use the injection method to add about 0.15% of the total amount of remaining molten steel into the converter for the third time, and at the same time, 0.3m 3 Inert gas argon was continuously introduced at a flow rate of / min, and the argon introduction time was maintained for 25s; S4. Steel is tapped and the oxygen content of the molten steel is monitored, and the oxygen content is 0.014%.

[0021] The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A deoxidation treatment method for a steelmaking converter, characterized in that: The steps include: S1. According to the carbon content in the molten steel, a deoxidizer is added to the converter for the first time, and an inert gas is introduced into the molten steel to stir the molten steel and assist deoxidation; S2. When the molten steel is being tapped, the second deoxidizer is added. The addition starts when 25%-30% of the molten steel flows out, and the second addition is completed when 75%-80% of the molten steel flows out. The oxygen content of the molten steel is monitored. For the unqualified molten steel, it is put back into the furnace and evacuated to an internal pressure of 98-114pa. S3, adding deoxidizer to the converter for the third time, while continuously introducing inert gas; S4. Steel is tapped and the oxygen content of the molten steel is monitored.

2. A steelmaking converter deoxidation treatment method according to claim 1, characterized in that: The deoxidizer is one or more of ferrosilicon deoxidizer, ferromanganese deoxidizer and ferroaluminum deoxidizer.

3. A steelmaking converter deoxidation treatment method according to claim 1, characterized in that: The deoxidizer is added by a spraying method.

4. A steelmaking converter deoxidation treatment method according to claim 1, characterized in that: The amount of the deoxidizer added in step S1 is calculated as follows: if the carbon content of the molten steel is ≤0.25%, the amount of the deoxidizer added is 0.1-0.15% of the total amount of the molten steel; if the carbon content of the molten steel is >0.25%, the amount of the deoxidizer added is 0.2-0.25% of the total amount of the molten steel.

5. A steelmaking converter deoxidation treatment method according to claim 1, characterized in that: The inert gas in step S1 is argon with a flow rate of 0.7-0.9m 3 / min.

6. A steelmaking converter deoxidation treatment method according to claim 1, characterized in that: In step S2, the oxygen content of the molten steel is monitored. For killed steel, the oxygen content needs to be controlled between 0.004% and 0.009%; for rimmed steel, the oxygen content needs to be controlled between 0.025% and 0.045%; for semi-killed steel, the oxygen content needs to be controlled between 0.015% and 0.024%.

7. A steelmaking converter deoxidation treatment method according to claim 1, characterized in that: The inert gas in step S3 is argon with a flow rate of 0.2-0.3 m 3 / min, holding time is 20-30s.