Method for producing low-boron steel

Abstract

The invention discloses a method for producing low-boron steel. The method comprises the step of controlling the slag amount of an electric arc furnace / converter, the use frequency of a refractory material, the addition amount of a silicon alloy and the type of a deoxidizing agent. According to the method, the initial boron content of the molten steel can be reduced, and the external boron content in the production process is reduced, so that the boron content of the steel plate is controlled to be less than or equal to 0.0005%, and the problem that the boron content exceeds the standard in the low-boron steel production process is solved.

Description

Technical Field

[0001] The invention belongs to the field of clean steel production, and in particular relates to a method for producing low-boron steel. Background Art

[0002] Bridge steel, platform steel and some hydroelectric steel have very strict requirements for boron, most of which require the boron content to be within 0.0005%. In addition, most of the boron in steel exists in the form of boron nitride. For such steels with high requirements for low-temperature impact performance, the presence of boron nitride will greatly reduce its impact performance and cannot be saved. If the boron element is not controlled, it will not only cause the steel plate composition to exceed the standard, but also seriously affect the impact performance, causing the steel plate to be scrapped and causing huge quality losses. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for producing low-boron steel. By controlling the amount of slag in an electric arc furnace / converter, the number of times refractory materials are used, the type of alloy selected, and the type of deoxidizer selected, the boron content in the steel plate is made ≤0.0005%, which not only meets the composition standard requirements but also improves the low-temperature impact performance.

[0004] In order to solve the above method problems, the method scheme adopted by the present invention is: A method for producing low-boron steel comprises controlling the amount of slag in an electric arc furnace / converter, the number of times refractory materials are used, the amount of silicon alloy added and the type of deoxidizer.

[0005] Furthermore, the amount of slag discharged during steel tapping in the electric arc furnace / converter of the present invention is controlled to be ≤300kg. The boron oxide content in the slag of the electric arc furnace / converter can reach more than 0.1%. If it enters the ladle, it will be reduced in large quantities during the smelting process of the ladle furnace, causing the boron content to exceed the standard. Therefore, the electric arc furnace / converter uses the slag discharge operation before steel tapping and the slag baffle to control the slag during steel tapping, so that the amount of slag discharged is ≤300kg, which can reduce the boron content by 60-65%.

[0006] Furthermore, the ladle of the present invention should be used ≥5 times. The boron content in the commonly used magnesia carbon brick refractory is about 0.005%. After being washed and eroded by molten steel, it enters the molten steel, resulting in an increase in the boron content. Therefore, a ladle that has been loaded with molten steel for more than 5 times is used to produce low-boron steel. At this time, the boron element consumption ratio in the ladle refractory is more than 80%, and only a very small part can be reduced and enter the molten steel.

[0007] Furthermore, the amount of silicon alloy added in the present invention is ≤500kg. In order to improve the hot brittle temperature, oxidation resistance and plasticity of the alloy, a certain amount of boron element is added to the alloy, especially in silicon-containing alloys, boron element is added the most, reaching more than 0.02%, so controlling the amount of silicon alloy added to ≤500kg can reduce the boron content by 20-30%.

[0008] Furthermore, the present invention selects a diffusion deoxidizer with a reducing property weaker than that of boron, such as calcium carbide and carbon powder. Aluminum, magnesium and other deoxidizers have a stronger reducing property than boron, and can reduce the boron oxide in the slag, thereby entering the molten steel. Therefore, during the ladle furnace smelting process, a deoxidizer with a reducing property weaker than that of boron is selected for diffusion deoxidation.

[0009] The boron content of the low-boron steel described in the present invention is ≤0.0005%.

[0010] The inventive principle and beneficial effects of the technical solution of the present invention are: (1) By controlling the slag during steelmaking in an electric arc furnace or converter, the increase of boron in the molten steel can be reduced and slag rolling in the molten steel can be avoided, thereby improving the purity of the molten steel.

[0011] (2) The use of mid- and late-stage packages to produce low-boron steel can not only reduce the amount of boron in the refractory material entering the molten steel, but also ensure that the refractory material is fully dried and reduce the content of gas elements in the molten steel.

[0012] (3) Using deoxidizers such as calcium carbide and carbon powder for ladle furnace smelting can avoid boron addition in slag, ensure continuous diffusion deoxidation, and significantly reduce the production of solid inclusions, thereby improving the cleanliness of molten steel.

[0013] (4) The boron content of the steel plate produced by the method of the present invention is ≤0.0005%, and the component qualification rate is 100%. DETAILED DESCRIPTION Example 1

[0014] In this embodiment, 100 Q345qD steel plates are produced, and the production method is as follows: Before tapping the electric arc furnace, slag discharge is performed. During the tapping process, slag retaining plates are used. According to the weighing display, slag-free tapping is achieved. The ladle used is the late-stage ladle which has been used 13 times; During the ladle furnace smelting process, 350kg of ferrosilicon alloy is used, and other non-silicon alloys are used; During the ladle furnace smelting process, except for the use of 600m aluminum wire for wire feeding deep deoxidation, the rest is diffused deoxidation using calcium carbide and carbon powder, the amount of calcium carbide used is 150kg, and the amount of carbon powder used is 10kg.

[0015] The boron content in the finished steel plate produced in this embodiment is 0.0002-0.0003%. Example 2

[0016] In this embodiment, 100 Q345qC steel plates are produced, and the production method is as follows: Before tapping the electric arc furnace, the slag is discharged. The slag retaining plate is used during the tapping process. The weighing shows that the slag discharge amount is about 200 kg. The ladle is a late-stage ladle that can be used 15 times; In the ladle furnace smelting process, 350kg of ferrosilicon alloy is used, and other non-silicon alloys are selected; During the ladle furnace smelting process, except for the use of 650m aluminum wire for wire feeding deep deoxidation, the rest is diffused deoxidation using calcium carbide and carbon powder, the amount of calcium carbide used is 150kg, and the amount of carbon powder used is 10kg.

[0017] The boron content in the finished steel plate produced in this embodiment is 0.0003-0.0005%. Example 3

[0018] This embodiment produces 50 Q420qE steel plates, and the production method is as follows: (1) Slag discharge is performed before tapping the electric arc furnace. The slag retaining plate is used during the tapping process. The weighing shows that the amount of slag discharged is about 180 kg. (2) The ladle is a medium-term ladle with a usage of 8 times; (3) In the ladle furnace smelting process, 400 kg of ferrosilicon alloy is used, and other non-silicon alloys are used; (4) During the ladle furnace smelting process, except for the use of 650 m aluminum wire for wire feeding deep deoxidation, the rest of the deoxidation was carried out using calcium carbide and carbon powder, with the amount of calcium carbide being 180 kg and the amount of carbon powder being 10 kg.

[0019] The boron content in the finished steel plate produced in this embodiment is 0.0002-0.0004%. Example 4

[0020] This embodiment produces 50 Q420qE steel plates, and the production method is as follows: (1) Slag discharge is performed before tapping the electric arc furnace. The slag retaining plate is used during the tapping process. According to the weighing display, slag-free tapping is achieved. (2) The ladle used is the late-stage ladle which has been used 13 times; (3) In the ladle furnace smelting process, 400 kg of ferrosilicon alloy is used, and other non-silicon alloys are used; (4) During the ladle furnace smelting process, except for the use of 650 m aluminum wire for wire feeding deep deoxidation, the rest of the deoxidation was carried out using calcium carbide and carbon powder. The amount of calcium carbide used was 160 kg and the amount of carbon powder used was 5 kg.

[0021] The boron content in the finished steel plate produced in this embodiment is 0.0002-0.0003%. Example 5

[0022] This embodiment produces 30 S355MLO steel plates, and the production method is as follows: (1) Slag discharge is performed before tapping the electric arc furnace. The slag retaining plate is used during the tapping process. According to the weighing display, slag-free tapping is achieved. (2) The ladle is a medium-term ladle with a usage of 8 times; (3) In the ladle furnace smelting process, 300 kg of ferrosilicon alloy is used, and other alloys are non-silicon alloys; (4) During the ladle furnace smelting process, except for the use of 750 m aluminum wire for wire feeding deep deoxidation, the rest is diffused deoxidation using calcium carbide and carbon powder, the amount of calcium carbide used is 200 kg, and the amount of carbon powder used is 5 kg.

[0023] The boron content in the finished steel plate produced in this embodiment is 0.0001% to 0.0002%. Example 6

[0024] This embodiment produces 35 S355MLO steel plates, and the production method is as follows: (1) Slag discharge is performed before tapping the electric arc furnace. The slag retaining plate is used during the tapping process. According to the weighing display, slag-free tapping is achieved. (2) The ladle used is the late-stage ladle with a usage of 16 times; (3) In the ladle furnace smelting process, 400 kg of ferrosilicon alloy is used, and other non-silicon alloys are used; (4) During the ladle furnace smelting process, except for the use of 600 m aluminum wire for wire feeding deep deoxidation, the rest was carried out by diffusion deoxidation using calcium carbide and carbon powder, wherein the amount of calcium carbide used was 180 kg and the amount of carbon powder used was 10 kg.

[0025] The boron content in the finished steel plate produced in this embodiment is 0.0001% to 0.0003%.

[0026] The above embodiments are only used to illustrate rather than limit the method scheme of the present invention. Although the present invention is described in detail with reference to the above embodiments, ordinary method personnel in the field should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for producing low-boron steel, characterized in that: This includes controlling the amount of slag in the electric arc furnace / converter, the number of times refractory materials are used, the amount of silicon-based alloy added, and the type of deoxidizer.

2. A method for producing low-boron steel according to claim 1, characterized in that: The amount of slag discharged during steel tapping in the electric arc furnace / converter is controlled to be ≤300kg.

3. A method for producing low-boron steel according to claim 1, characterized in that: The ladle should be used ≥5 times.

4. A method for producing low-boron steel according to claim 1, characterized in that: The amount of silicon alloy added is ≤500kg.

5. A method for producing low-boron steel according to claim 1, characterized in that: A deoxidizer with a reducing strength weaker than that of boron is selected for diffusion deoxidation.

6. A method for producing low-boron steel according to claim 1, characterized in that: The deoxidizer includes calcium carbide and carbon powder.

7. A method for producing low-boron steel according to claim 1, characterized in that: The boron content of the low-boron steel is ≤0.0005%.