Method for reducing pouring flocculation rate of cold-rolled material

Abstract

The invention relates to the technical field of iron and steel smelting, and provides a method for reducing the pouring flocculation flow rate of a cold-rolled material, which comprises the following technical characteristics a-c: a, during converter smelting, the content of C at the end point is controlled to be 0.03-0.05% and the content of O at the end point is controlled to be 350-450ppm in percentage by weight; b, during tapping, the tapping temperature is controlled to be 1610-1630 DEG C; and c, during LF refining, after calcium wires are fed, pulse bottom argon blowing treatment is adopted for soft blowing, the pulse frequency of the pulse bottom argon blowing treatment is 0.5-1 time / min, the pulse duty ratio is 50%-70%, the flow peak value is 140-390 L / min, and the pulse waveform is a square wave. By means of the technical scheme, the problem that in the related technology, the pouring flocculation rate of the cold-rolled material is high is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and in particular to a method for reducing the pouring flocculence rate of cold-rolled material. Background Art

[0002] Pouring flocculence refers to the phenomenon during the steelmaking process whereby large amounts of inclusions and gases in the molten steel form suspended matter or bubbles within the casting process. These bubbles gradually aggregate over time, forming larger flocs that settle to the bottom of the molten steel as it flows. In the production of cold-rolled material, pouring flocculence can lead to surface defects in the ingot and an increase in internal inclusions. These problems increase the difficulty and scrap rate of subsequent cold rolling processes, severely impacting product quality and production efficiency.

[0003] To reduce the pouring flocculation rate, common existing solutions include optimizing the design of the submerged nozzle, changing the nozzle inner wall material, blowing argon into the nozzle, and using induction heating. However, production has proven that these common solutions are still ineffective in reducing the pouring flocculation rate of cold-rolled stock. Therefore, there is an urgent need to develop a method that can effectively reduce the pouring flocculation rate of cold-rolled stock. Summary of the Invention

[0004] The present invention provides a method for reducing the flocculation rate of cold-rolled material casting, which solves the problem of high flocculation rate of cold-rolled material casting in the related art.

[0005] The technical solutions of the present invention are as follows: The present invention proposes a method for reducing the flocculent flow rate of cold-rolled material casting, including the following technical features a to c: a: During converter smelting, the C content at the end point is controlled to be 0.03%~0.05% and the O content is 350~450ppm by weight; b: When tapping steel, control the tapping temperature to 1610~1630℃; c: During LF refining, after the calcium wire is fed, pulse bottom blowing argon is used for soft blowing. The pulse frequency of the pulse bottom blowing argon treatment is 0.5-1 times / min, the pulse duty ratio is 50%-70%, the flow peak is 140-390 L / min, and the pulse waveform is square wave.

[0006] As a further technical solution, during the converter smelting, based on the converter tonnage, when the molten iron temperature is less than 1350°C, the amount of scrap steel added is 7% to 12% of the converter tonnage; When the molten iron temperature is ≥1350℃, the amount of scrap steel added is 15%~30% of the converter tonnage.

[0007] In the present invention, when the molten iron temperature is less than 1350°C, sufficient heat for smelting can be ensured by reducing the amount of scrap steel added; when the molten iron temperature is greater than or equal to 1350°C, excess heat can be absorbed by increasing the amount of scrap steel added, thereby avoiding violent reaction of the molten iron and stabilizing the converter smelting process.

[0008] As a further technical solution, during the converter smelting, gradient oxygen supply is adopted in the blowing process, and the blowing start time is recorded as 0 min. The gradient oxygen supply is specifically: .

[0009] In the present invention, by supplying oxygen in a gradient during the blowing process, oxygen can quickly penetrate the slag layer and react with the molten iron in the early stage of smelting, thereby accelerating the oxidation of impurity elements in the molten iron; the decarburization efficiency can be ensured while reducing splashing in the middle stage of smelting; and the smelting end point can be stably controlled in the late stage of smelting.

[0010] As a further technical solution, during the converter smelting, based on the converter tonnage, the total slag volume during slag making accounts for 8% to 12% of the converter tonnage.

[0011] As a further technical solution, the bottom blowing of argon is carried out throughout the steel tapping process, and the bottom blowing of argon has an intensity of 150-250 L / min.

[0012] As a further technical solution, during the steel tapping, the amount of slag dropped is less than 70 mm.

[0013] As a further technical solution, during the LF refining, the Al content in the molten steel is 0.015% to 0.04% by weight.

[0014] As a further technical solution, during the LF refining, 200-300 m of calcium wire is fed, and the feeding speed is 240-300 m / min.

[0015] As a further technical solution, during the LF refining, the soft blowing time is ≥8 minutes.

[0016] As a further technical solution, the cold-rolled material is composed of the following components in weight percentage: C≤0.09%, Si≤0.06%, Mn 0.15%~0.3%, P≤0.035%, S≤0.035%, Al 0.015%~0.04%, Cr≤0.07%, Ni≤0.055%, and the rest is Fe and other unacceptable impurities.

[0017] The working principle and beneficial effects of the present invention are: Unlike existing methods that reduce the cold-rolled stock pouring flocculence by optimizing the submerged nozzle design, changing the nozzle inner wall material, blowing argon into the nozzle, and induction heating, this invention focuses on the steelmaking process itself. By optimizing the converter smelting process, the tapping process, and the LF refining process, the cold-rolled stock pouring flocculence is synergistically reduced from three aspects: stabilizing the smelting process, reducing the amount of oxide inclusions generated, and improving the inclusion floatation rate, bringing the pouring flocculence rate to less than 2%. Specifically, by controlling the carbon content at the converter smelting endpoint to 0.03%-0.05% and the oxygen content to 350-450ppm, overblowing is avoided and the smelting process is stabilized. The tapping temperature is controlled at 1610-1630°C, effectively reducing the amount of oxide inclusions generated. After the LF refining calcium line is fed, the soft blowing adopts pulsed bottom argon blowing to effectively improve the inclusion floatation removal rate. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0019] Example 1 A method for reducing the flocculent flow rate of cold-rolled material casting comprises the following steps: S1. Converter smelting: adding scrap steel to molten iron, blowing, and slag making; The molten iron is composed of the following components in weight percentage: C 4.5%, Si 0.3%, Mn 0.3%, P 0.16%, S 0.03%, Cr 0.03%, and the rest is Fe and inevitable impurities. The molten iron temperature is 1353°C. The scrap steel consists of the following components in weight percentage: C 0.2%, Si 0.3%, Mn 0.8%, P 0.1%, S 0.08%, Cr 0.5%, and the remainder is Fe and unavoidable impurities. Based on the converter tonnage, the amount of scrap steel added is 7% of the converter tonnage; During blowing, gradient oxygen supply is used. The blowing start time is recorded as 0 min. The specific gradient oxygen supply is:

[0020] When making slag, the total slag volume accounts for 8% of the converter tonnage, and the slag material is composed of lime and dolomite with a mass ratio of 2:1; In terms of weight percentage, the C content at the end point of converter smelting is controlled to be 0.05% and the O content is controlled to be 350ppm; S2, tapping: When 1 / 5 of the steel is tapped, medium carbon ferromanganese (Mn 80%, C 1.5% by weight) accounting for 5% of the converter tonnage is added, and the addition is completed when 2 / 3 of the steel is tapped. During the tapping process, bottom argon blowing is carried out throughout the process, with an argon blowing intensity of 150L / min and a slag discharge of 65mm; S3, LF refining: at the beginning of refining, the molten steel was adjusted to the target composition, calculated as a percentage by weight. During the refining process, the aluminum content of the molten steel was controlled at 0.04%. 200 m of calcium wire (diameter of the calcium wire was 9 mm, and the calcium content of the calcium wire was 70 g / m) was fed at a feed speed of 240 m / min. After the calcium wire was fed, pulsed bottom argon was used for soft blowing. The pulse frequency of the pulsed bottom argon blowing was 0.5 times / min, the pulse duty cycle was 50%, the flow peak was 140 L / min, the pulse waveform was square wave, and the soft blowing time was 8 min. S4 continuous casting: During continuous casting, the casting speed is controlled at 1.3m / min to obtain cold rolled material; The cold rolled material is composed of the following components in weight percentage: C 0.09%, Si 0.06%, Mn 0.15%, P 0.035%, S 0.035%, Al 0.04%, Cr 0.07%, Ni 0.055%, and the rest is Fe and other unacceptable impurities.

[0021] Example 2 A method for reducing the flocculent flow rate of cold-rolled material casting comprises the following steps: S1. Converter smelting: adding scrap steel to molten iron, blowing, and slag making; The molten iron is composed of the following components in weight percentage: C 4.0%, Si 0.3%, Mn 0.3%, P 0.16%, S 0.03%, Cr 0.03%, and the rest is Fe and inevitable impurities. The molten iron temperature is 1347°C; The scrap steel consists of the following components in weight percentage: C 0.2%, Si 0.3%, Mn 0.8%, P 0.1%, S 0.08%, Cr 0.5%, and the remainder is Fe and unavoidable impurities. Based on the converter tonnage, the amount of scrap steel added is 15% of the converter tonnage; During blowing, gradient oxygen supply is used. The blowing start time is recorded as 0 min. The specific gradient oxygen supply is:

[0022] When making slag, the total slag volume accounts for 12% of the converter tonnage, and the slag material is composed of lime and dolomite with a mass ratio of 2:1; In terms of weight percentage, the C content at the end point of converter smelting is controlled to be 0.03% and the O content is controlled to be 450ppm; S2. Steel tapping: When 1 / 5 of the steel is tapped, medium carbon ferromanganese (Mn 80%, C 1.5% by weight) accounting for 7% of the converter tonnage is added, and the addition is completed when 2 / 3 of the steel is tapped. During the tapping process, bottom argon blowing is carried out throughout the process, with an argon blowing intensity of 250L / min and a slag discharge of 65mm; S3, LF refining: at the beginning of refining, the molten steel was adjusted to the target composition, calculated as a percentage by weight. During the refining process, the aluminum content of the molten steel was controlled at 0.015%. 300 m of calcium wire (diameter of the calcium wire was 9 mm, and the calcium content of the calcium wire was 70 g / m) was fed at a feeding speed of 300 m / min. After the calcium wire was fed, pulsed bottom argon was used for soft blowing. The pulse frequency of the pulsed bottom argon blowing was 1 time / min, the pulse duty cycle was 70%, the flow peak was 390 L / min, the pulse waveform was square wave, and the soft blowing time was 10 min. S4 continuous casting: During continuous casting, the casting speed is controlled at 1.3m / min to obtain cold rolled material; The cold rolled material is composed of the following components in weight percentage: C 0.07%, Si 0.05%, Mn 0.3%, P 0.03%, S0.03%, Al 0.015%, Cr 0.05%, Ni 0.05%, and the rest is Fe and other unacceptable impurities.

[0023] Example 3 The only difference between this embodiment and embodiment 1 is that, in this embodiment, the amount of scrap steel added is 12% of the converter tonnage.

[0024] Example 4 The only difference between this embodiment and embodiment 2 is that, in this embodiment, the amount of scrap steel added is 30% of the converter tonnage.

[0025] Comparative Example 1 The only difference between this comparative example and Example 1 is that, in this comparative example, the C content at the end point of the converter smelting is controlled to be 0.02% and the O content is controlled to be 300 ppm, calculated in weight percentage.

[0026] Comparative Example 2 The only difference between this comparative example and Example 1 is that, in this comparative example, the C content at the end point of the converter smelting is controlled to be 0.08% and the O content is controlled to be 500 ppm, calculated in weight percentage.

[0027] Comparative Example 3 The only difference between this comparative example and Example 1 is that in this comparative example, the tapping temperature is controlled to be 1600°C during tapping.

[0028] Comparative Example 4 The only difference between this comparative example and Example 1 is that in this comparative example, the tapping temperature is controlled to be 1650°C during tapping.

[0029] Comparative Example 5 The only difference between this comparative example and Example 1 is that, in this comparative example, after the calcium wire is fed, the soft blowing adopts bottom blowing argon treatment, and the bottom blowing argon intensity is 140 L / min.

[0030] 100 furnaces (3 ton furnaces) were produced according to the methods of Examples 1-4 and Comparative Examples 1-5. The number of flocculation events was recorded, and the flocculation rate was calculated according to the following formula: Flocculation rate = number of flocculation events / 100 × 100%. The results are shown in Table 1 below.

[0031] Table 1 Flocculation rate test results

[0032] Comparison between Example 1 and Comparative Examples 1 to 5 shows that the present invention synergistically reduces the pouring flocculence rate of cold-rolled material by optimizing the converter smelting process, the steel tapping process and the LF refining process, and brings the pouring flocculence rate to within 2%.

[0033] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for reducing the flocculent flow rate of cold rolled material casting, characterized in that: Including the following technical features a~c: a: During converter smelting, the C content at the end point is controlled to be 0.03%~0.05% and the O content is 350~450ppm by weight; b: When tapping steel, control the tapping temperature to 1610~1630℃; c: During LF refining, after the calcium wire is fed, pulse bottom blowing argon is used for soft blowing. The pulse frequency of the pulse bottom blowing argon treatment is 0.5-1 times / min, the pulse duty ratio is 50%-70%, the flow peak is 140-390 L / min, and the pulse waveform is square wave.

2. The method for reducing the flocculent flow rate of cold-rolled material casting according to claim 1, characterized in that: During the converter smelting, based on the converter tonnage, when the molten iron temperature is less than 1350°C, the amount of scrap steel added is 7% to 12% of the converter tonnage; When the molten iron temperature is ≥1350℃, the amount of scrap steel added is 15%~30% of the converter tonnage.

3. The method for reducing the flocculent flow rate of cold-rolled material casting according to claim 1, characterized in that: During the converter smelting, gradient oxygen supply is used in the blowing process, and the blowing start time is recorded as 0 min. The gradient oxygen supply is specifically: 。 4. The method for reducing the flocculent flow rate of cold-rolled material casting according to claim 1, characterized in that: During the converter smelting, based on the converter tonnage, the total slag volume during slag making accounts for 8% to 12% of the converter tonnage.

5. The method for reducing the flocculent flow rate of cold-rolled material casting according to claim 1, characterized in that: During the steel tapping process, argon is blown from the bottom of the steel tapping machine at an intensity of 150-250 L / min.

6. The method for reducing the flocculent flow rate of cold rolled material casting according to claim 1, characterized in that: During the steel tapping, the slag amount is less than 70 mm.

7. The method for reducing the flocculent flow rate of cold-rolled material casting according to claim 1, characterized in that: During the LF refining, the Al content in the molten steel is 0.015% to 0.04% by weight.

8. The method for reducing the flocculent flow rate of cold-rolled material casting according to claim 1, characterized in that: During the LF refining, 200-300 m of calcium wire is fed, and the feeding speed is 240-300 m / min.

9. The method for reducing the flocculent flow rate of cold-rolled material casting according to claim 1, characterized in that: During the LF refining, the soft blowing time is ≥8 min.

10. The method for reducing the flocculation rate of cold-rolled stock casting according to claim 1, characterized in that: The cold-rolled material is composed of the following components in weight percentage: C≤0.09%, Si≤0.06%, Mn 0.15%~0.3%, P≤0.035%, S≤0.035%, Al 0.015%~0.04%, Cr≤0.07%, Ni≤0.055%, and the rest is Fe and other unacceptable impurities.

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