Smelting method for increasing number of continuous casting furnaces of sulfur-containing and aluminum-containing steel

Abstract

The invention discloses a smelting method for increasing the number of continuous casting furnaces of sulfur-containing and aluminum-containing steel, and relates to the technical field of steel production, and the smelting method comprises the following steps: adopting a slag stopping mode of combining a sliding plate slag stopping mode and a slag stopping cone slag stopping mode during converter tapping, and adding an aluminum block for final deoxidation; the target aluminum content of LF refining is controlled to be 0.020%-0.050%; in the early stage of electrified slagging, aluminum wires and high-purity silicon carbide are adopted for slag surface deoxidation, then a diffusion deoxidizing agent is added, and white slag is kept in the process; desulfurization treatment is carried out in the LF refining process, the target sulfur content is controlled to be smaller than or equal to 0.005%, a sulfur line is additionally fed before RH vacuum treatment, and a calcium line is fed for calcium treatment after vacuum breaking. According to the method, the number of continuous casting furnaces is increased by improving the purity of the molten steel, the deoxidation process, the slagging process, the calcium treatment process and the sulfurizing process are mainly optimized, the number of high-melting-point inclusions such as CaO-Al2O3 and CaS is reduced, tundish can be saved, head and tail blanks and tundish casting residues can be reduced, and cost reduction is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel production, in particular to a smelting method for increasing continuous casting furnace number of sulfur and aluminum containing steel. BACKGROUND

[0002] High-end automobile gear steel, non-adjustable steel contains certain S and Al content, which belongs to sulfur and aluminum controlled steel. Because the molten steel contains S and Al elements, the reactions of oxygen, sulfur and calcium are competitive. When S and Al are both greater than or equal to 0.020%, the inclusion "liquid window" range of the molten steel after calcium treatment is sharply reduced, even disappears, so that the sulfur and aluminum controlled steel is more likely to occur the following reaction: 2[Al]+3(CaO)+3[S]=3(CaS)+(Al2O3), thereby generating high melting point CaS or Al2O3 inclusions, which are extremely easy to adhere to the inner wall of the nozzle to form nodules during pouring process, causing continuous casting nozzle blockage, and further leading to reduction of continuous casting furnace number, which seriously affects production rhythm and product quality. SUMMARY

[0003] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a smelting method for increasing continuous casting furnace number of sulfur and aluminum containing steel.

[0004] In order to solve the above technical problems, the technical scheme of the present application is as follows: A smelting method for increasing continuous casting furnace number of sulfur and aluminum containing steel, comprising: A sliding plate slag stopping and slag stopping cone slag stopping combined slag stopping mode is used when the converter is tapped, and aluminum blocks are added for final deoxidization; The target aluminum content of LF refining is controlled to be 0.020-0.050%; Aluminum wire and high-purity silicon carbide are used for slag surface deoxidization in the early stage of electric slagging, then diffusion deoxidizer is added, and white slag is maintained; Desulfurization treatment is carried out in the LF refining process, the target sulfur content is controlled to be less than or equal to 0.005%, and sulfur line is supplemented before RH vacuum treatment, and calcium line is fed after breaking the vacuum for calcium treatment.

[0005] As a preferred scheme of the smelting method for increasing continuous casting furnace number of sulfur and aluminum containing steel, the method further comprises: adding lime and refining slag when the converter is tapped, and adding lime and refining slag after LF refining and aluminum deoxidization, and the target slag system is controlled to be: basicity R: 4-6, Al2O3: 25-32%, TFe≤0.5%.

[0006] As a preferred scheme of the smelting method for increasing continuous casting furnace number of sulfur and aluminum containing steel, the addition amount of the aluminum block is 120 kg.

[0007] As a preferred scheme of the smelting method for increasing continuous casting furnace number of sulfur-containing and aluminum-containing steel of the present application, wherein: after the target aluminum content of the LF refining is controlled to be 0.020-0.050%, further comprising: LF to post-sampling analysis, determine whether the aluminum content is lower than 0.035%, and when the aluminum content is lower than 0.035%, supplement feeding of aluminum wire to the aluminum content of 0.035%, and controlling the aluminum content before RH vacuum treatment to be 0.020-0.040%.

[0008] As a preferred scheme of the smelting method for increasing continuous casting furnace number of sulfur-containing and aluminum-containing steel of the present application, wherein: the addition amount of the aluminum wire is 10-20 kg, and the addition amount of the high-purity silicon carbide is 60-80 kg.

[0009] As a preferred scheme of the smelting method for increasing continuous casting furnace number of sulfur-containing and aluminum-containing steel of the present application, wherein: the time interval between the supplement feeding of sulfur wire and the feeding of calcium wire is greater than 10 min.

[0010] As a preferred scheme of the smelting method for increasing continuous casting furnace number of sulfur-containing and aluminum-containing steel of the present application, wherein: the addition amount of lime at the converter tapping is 550 kg, the addition amount of refining slag is 500 kg, the supplement addition amount of lime after the LF refining and aluminum deoxidization is 100-200 kg of lime, and the supplement addition amount of refining slag is 50-100 kg.

[0011] As a preferred scheme of the smelting method for increasing continuous casting furnace number of sulfur-containing and aluminum-containing steel of the present application, wherein: soft blowing is carried out after calcium treatment, and the soft blowing time is controlled to be greater than or equal to 15 min.

[0012] The beneficial effects of the present application are: (1) The present application improves the continuous casting furnace number by improving the purity of the molten steel, mainly optimizes the deoxidization process, slag making process, calcium treatment process and sulfur increasing process, reduces the number of CaO-A l2 O3 and CaS type inclusions with high melting point, saves the tundish and reduces the head and tail billets, and realizes cost reduction.

[0013] (2) The present application has wide applicability, and the deoxidization process, slag making process and precise calcium treatment process are also applicable to the production of other aluminum-containing steels, etc., and the special sulfur and aluminum control slag system can well control the Ca content in the molten steel, so that the inclusion composition before LF departure is mainly MgO-Al2O3 type and Al2O3 type inclusions, fully plays the effect of RH in removing inclusions, and improves the purity of the molten steel.

[0014] (3) The smelting method provided by the present application has simple and clear process flow, strong operability and easy control. DETAILED DESCRIPTION

[0015] For the purpose of making the content of the present application more easily understood, the present application is further explained in detail below according to the specific embodiments.

[0016] The present application provides a smelting method for improving the continuous casting furnace number of sulfur-containing and aluminum-containing steel, which specifically comprises the following steps: Step S101: The combined slag blocking mode of the sliding plate slag blocking and the slag blocking cone is used during the converter tapping, and aluminum blocks are added for final deoxidization.

[0017] Specifically, the converter tapping adopts the sliding plate slag blocking + slag blocking cone mode to improve the slag blocking effect and avoid slagging during tapping. Aluminum blocks of 120 kg are added during the converter tapping to improve the post-furnace deoxidization strength and achieve the purpose of deep deoxidization.

[0018] Step S102: The target aluminum content of LF refining is controlled to be 0.020-0.050%.

[0019] Specifically, the aluminum content during the LF refining process is controlled to be 0.020-0.050%, the electrode is sent after the LF arrives at the station, and the composition is analyzed by sampling. If the aluminum content is lower than 0.035%, the aluminum wire is supplemented according to 0.035%. The aluminum content is controlled to be 0.020-0.040% before the RH vacuum treatment.

[0020] It can be understood that the aluminum is supplemented as soon as possible, and if the aluminum is supplemented at the end, the deoxidization is continued, and the ladle is allowed to be lifted 10 minutes after the aluminum wire is fed.

[0021] Step S103: Aluminum wire and high-purity silicon carbide are used for slag surface deoxidization before power-on slagging, and then diffusion deoxidizers are added to maintain white slag during the process.

[0022] Specifically, 10-20 kg of aluminum wire and 60-80 kg of high-purity silicon carbide (which can be adjusted according to the post-furnace sample C) are used for slag surface deoxidization before power-on slagging, and then small batches and multiple batches of diffusion deoxidizers such as silicon carbide and silicon iron powder are added to maintain white slag during the process.

[0023] Step S104: Desulfurization treatment is performed during the LF refining process, the target sulfur content is controlled to be less than or equal to 0.005%, and sulfur wire is supplemented before the RH vacuum treatment, 30-40 m of calcium wire is fed for calcium treatment after the vacuum is broken, and the soft blowing time after calcium treatment is greater than or equal to 15 min.

[0024] Specifically, deep desulfurization operation is performed during the refining process, and no sulfur is added. The S of the LF is less than or equal to 0.008% when it leaves the station, and the target is less than or equal to 0.005%. After the RH seat bag is fed, the sulfur wire is supplemented before the vacuum is extracted. 180 m of sulfur wire is fed, and the sulfur content is adjusted by further supplementing after the vacuum is broken.

[0025] It should be noted that the time interval between the supplementation of the sulfur wire and the calcium wire is greater than 10 min.

[0026] Step S105: Add lime and refining slag at the converter tapping, and add lime and refining slag after LF refining and aluminum deoxidation, and control the target slag system as follows: basicity R: 4-6, Al2O3: 25-32%, TFe≤0.5%.

[0027] Specifically, the slag composition is optimized and controlled, so that the inclusion composition before LF leaving is mainly MgO-Al2O3 type and Al2O3 type inclusions, 550 kg of lime and 500 kg of refining slag are added at the converter tapping, 100-200 kg of lime and 50-100 kg of refining slag are added after LF refining and aluminum deoxidation according to the slag condition, and the target slag system is as follows: basicity R: 4-6, Al2O3: 25-32%, TFe≤0.5%.

[0028] The above scheme will be further described through specific examples.

[0029] Example 1: The smelting method for improving the continuous casting furnace number of steel containing sulfur and aluminum in this example comprises the following steps: Step S101: The converter tapping adopts the slide plate slag blocking + slag blocking cone mode, and no slag is added at the tapping; 120 kg of Al block is added at the converter tapping for final deoxidation.

[0030] Step S102: After the LF arrives, the electrode is lowered to supply power to the slag, and the composition is sampled and analyzed after 8 minutes of power supply. The Al content is 0.022%, 130 m of aluminum wire is supplemented, the Al content is 0.0236% before entering the vacuum, and no aluminum is supplemented in the later period.

[0031] Step S103: 20 kg of aluminum wire and 60 kg of high-purity silicon carbide are added before power-on slagging for slag surface deoxidation, and then 6 batches of silicon carbide are added, each batch of 30 kg, for diffusion deoxidation. The white slag is obtained after 13 minutes of refining, and then the white slag is maintained.

[0032] Step S104: Deep desulfurization operation is performed during the refining process, and no sulfur is added. The S content is 0.0063% at the LF leaving. After entering the RH seat package, 180 m of sulfur line is supplemented before vacuumizing, and the sampling S content is 0.0361%. Calcium treatment is performed after 27 minutes.

[0033] Step S105: 550 kg of lime and 500 kg of refining slag are added at the converter tapping, 100 kg of lime and 50 kg of refining slag are added after LF refining and aluminum deoxidation, and the final slag basicity R is 4.3, Al2O3 is 29.52%, and TFe≤0.44%.

[0034] Step S106: After the RH breaks the vacuum, 30 m of calcium wire is fed through the wire feeder, and the soft blowing time is 22 minutes after calcium treatment.

[0035] The continuous casting furnace number in this example is 11.

[0036] Embodiment 2: The present embodiment is a smelting method for improving the continuous casting furnace number of sulfur-containing and aluminum-containing steel, comprising the following steps: Step S101: The converter tapping adopts the way of slide plate slag stopping + slag stopping cone, and no slag is discharged during tapping; Al block 120kg is added for final deoxidization during converter tapping.

[0037] Step S102: After the LF arrives at the station, the electrode is lowered to send power to the slag, and the power is supplied for 9 minutes to analyze the composition of the sample. The Al content is 0.028%, 100m of aluminum wire is supplemented, the Al content before entering the vacuum is 0.0252%, and no aluminum is supplemented in the later period.

[0038] Step S103: Before power-on slagging, 20kg of aluminum wire and 60kg of high-purity silicon carbide are added for slag surface deoxidization, and then 5 batches of silicon carbide are added, each batch of 30kg, for diffusion deoxidization, and the refining time is 11min to change the white slag, and then the white slag is maintained.

[0039] Step S104: Deep desulfurization operation is performed during the refining process, and no sulfur is added. The S content is 0.0048% when the LF leaves the station. After entering the RH seat package, 180m of sulfur line is supplemented before vacuumizing, and the sampling S content is 0.0331%. Calcium treatment is performed after 23 minutes.

[0040] Step S105: 550kg of lime is added during converter tapping, 500kg of refining slag is added, 100kg of lime and 70kg of refining slag are supplemented after LF refining and aluminum deoxidization, the final slag basicity R is 4.1, Al2O3 is 28.87%, and TFe is ≤0.49%.

[0041] Step S106: After the RH breaks the vacuum, 30m of calcium wire is fed through the wire feeder, and the soft blowing time is 25min after calcium treatment.

[0042] The continuous casting furnace number in the present embodiment is 11.

[0043] Therefore, the technical scheme of the present application improves the continuous casting furnace number by improving the purity of the molten steel, mainly optimizes the deoxidization process, the slag making process, the calcium treatment process and the sulfur increasing process, reduces the number of high melting point inclusions such as CaO-Al2O3 and CaS, can save the tundish and reduce the head and tail billets, and realize cost reduction.

[0044] In addition to the above embodiments, the present application can also have other embodiments; any technical scheme formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present application.

Claims

1. A smelting method for increasing the number of continuous casting furnaces for sulfur-containing and aluminum-containing steel, characterized by: include: When tapping the converter, a slag blocking method combining slide plates and slag cones is used, and aluminum blocks are added for final deoxidation. The target aluminum content in LF refining is controlled at 0.020~0.050%; In the early stage of electrified slag treatment, aluminum wire and high-purity silicon carbide are used to deoxidize the slag surface, and then a diffusion deoxidizer is added to maintain white slag during the process. Desulfurization treatment is carried out in the LF refining process, and the target sulfur content is controlled to be less than or equal to 0.005%. The sulfur line is fed before the RH vacuum treatment, and the calcium line is fed for calcium treatment after breaking the vacuum.

2. The smelting method for increasing the number of continuous casting furnaces for sulfur-containing and aluminum-containing steel according to claim 1, characterized in that: Also includes: Lime and refined slag are added during converter tapping, and additional lime and refined slag are added after LF refining and aluminum deoxidation. The target slag system is controlled to be: basicity R: 4-6, Al2O3: 25-32%, TFe≤0.5%.

3. The smelting method for increasing the number of continuous casting furnaces for sulfur-containing and aluminum-containing steel according to claim 1, characterized in that: The amount of the aluminum block added was 120 kg.

4. The smelting method for increasing the number of continuous casting furnaces for sulfur-containing and aluminum-containing steel according to claim 1, characterized in that: After controlling the target aluminum content of LF refining to be 0.020-0.050%, the method further comprises: After LF arrives at the station, samples are taken for analysis to determine whether the aluminum content is lower than 0.035%. If the aluminum content is lower than 0.035%, aluminum wire is fed until the aluminum content reaches 0.035%, and the aluminum content before RH vacuum treatment is controlled at 0.020~0.040%.

5. The smelting method for increasing the number of continuous casting furnaces for sulfur-containing and aluminum-containing steel according to claim 1, characterized in that: The amount of the aluminum wire added is 10-20 kg, and the amount of the high-purity silicon carbide added is 60-80 kg.

6. The smelting method for increasing the number of continuous casting furnaces for sulfur-containing and aluminum-containing steel according to claim 1, characterized in that: The time interval between the sulfur feeding line and the calcium feeding line is greater than 10 minutes.

7. The smelting method for increasing the number of continuous casting furnaces for sulfur-containing and aluminum-containing steel according to claim 2, characterized in that: The amount of lime added when tapping the converter is 550kg, and the amount of refined slag added is 500kg. The amount of lime added after LF refining and aluminum deoxidation is 100~200kg, and the amount of refined slag added is 50~100kg.

8. The smelting method for increasing the number of continuous casting furnaces for sulfur-containing and aluminum-containing steel according to claim 1, characterized in that: After the calcium treatment, soft blowing is performed, and the soft blowing time is controlled to be greater than or equal to 15 minutes.