Method for recycling heat of heavy rail steel continuous casting residual steel

Abstract

The invention discloses a heavy rail steel continuous casting residual steel heat cyclic utilization method which comprises the following steps: S1, recovering the casting residual heat, and reducing the total loading amount of a converter to ensure that the clearance of a steel ladle after tapping reaches 400-500mm; s2, in the continuous casting steel ladle molten steel pouring process, part of molten steel and steel slag are reserved in pouring residues of a steel ladle after pouring is stopped; s3, the steel ladle with the pouring residues is hoisted to the position above the pouring residue tank, part of the pouring residues are poured out, and pouring residues are stopped when steel flowers appear; s4, molten steel in steel ladle remaining pouring residues is poured into a steel ladle obtained after continuous casting furnace converter tapping or poured into a steel ladle in the earlier stage of LF refining; and S5, pouring the residual pouring slag of the steel ladle into a slag ladle. According to the invention, recycling is realized from converter tapping to the earlier stage of LF refining, so that the purity of molten steel is improved, and steel ladle roughing slag is avoided; the heat of the residual steel of the continuous casting ladle can be recycled, the influence of the residual steel on the steelmaking cost is reduced, and meanwhile, the quality of molten steel is improved.

Description

Technical Field

[0001] The invention relates to a continuous casting method, in particular to a method for heat recycling of excess steel from continuous casting of heavy rail steel. Background Art

[0002] In the process of steelmaking, when molten steel is poured from the ladle to the tundish, as the molten steel level in the ladle drops in the later stage of pouring, a converging vortex will be generated, and it will become more and more intense, promoting the emulsification of slag and steel, so that the molten slag enters the tundish with the steel flow. It has become a consensus that the slag under the ladle should be avoided in the process of high-quality steel smelting to deteriorate the purity of molten steel. Heavy rail steel is used to produce rails, and it has strict requirements for inclusions and flaw detection. Therefore, the ladle residual steel operation is adopted in the continuous casting production of heavy rail steel.

[0003] The current conventional processing technology is to pour the steel slag into a slag pot, transport it to a slag workshop for processing, separate the slag and steel after processing, and then utilize them.

[0004] The current conventional casting slag treatment technology has the following disadvantages: ① The hot slag from the continuous casting ladle is poured into the slag pot, which not only causes iron loss, but also has a low recycling rate and increases the labor processing cost; ② The residual steel and slag left over from ladle casting have a temperature as high as over 1480℃, and their heat is not fully utilized. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for thermal recycling of excess steel from continuous casting of heavy rail steel.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention includes the following steps: S1, recovering the remaining heats and reducing the total amount of converter loading to ensure that the clearance of the ladle after steel tapping reaches 400-500mm; S2. During the pouring process of molten steel in the continuous casting ladle, some molten steel and slag remain in the ladle after the pouring is stopped; S3, lift the ladle with remaining pouring to the top of the pouring tank, pour out some of the remaining slag, and stop pouring when steel flowers are seen; S4, pouring the remaining molten steel in the ladle into the ladle after the continuous casting furnace converter steel is tapped, or pouring into the ladle in the early stage of LF refining; S5. Pour the remaining slag from the ladle into the slag pot.

[0007] Furthermore, in step S2, the remaining amount of the ladle after stopping pouring is 5±0.2 tons.

[0008] Furthermore, in step S4, after the remaining molten steel is poured into the ladle after the continuous casting furnace converter has tapped steel, the clearance of the ladle reaches 300 to 400 mm.

[0009] Furthermore, in step S4, the early stage of LF refining refers to one third of the total refining time and earlier.

[0010] The beneficial effect of adopting the above technical scheme is that: after the pouring is completed, the present invention will first pour out part of the liquid slag from the hot molten steel and slag left in the ladle, and then recover the remaining molten steel into the subsequent continuous casting furnace ladle, so as to realize circular recycling between the tapping of the converter and the early stage of LF refining, thereby improving the purity of the molten steel and avoiding slag in the ladle; in short, the present invention can heat the surplus steel left over from the continuous casting ladle casting, reduce the influence of surplus steel on the steelmaking cost, and improve the quality of the molten steel.

[0011] The present invention discharges most of the LF refining slag in each cycle, effectively recovers molten steel, and can avoid the problem of multiple cycles of increasing the refining slag affecting the ladle clearance and weakening the LF refining function. The present invention realizes the recycling of hot casting surplus steel, effectively recovers the casting surplus molten steel, reduces production costs, and has greater economic and social benefits in the steelmaking production process. DETAILED DESCRIPTION

[0012] The present invention is further described in detail below in conjunction with specific implementation modes.

[0013] The method for heat recycling of excess steel from continuous casting of heavy rail steel is carried out during continuous production of the same type of steel and adopts the following steps: S1. For the heats that recycle the excess molten steel, the total amount of converter loading is reduced by 2 to 4 tons to ensure that the ladle clearance after steel tapping reaches 400 to 500 mm; in this way, enough ladle clearance is left to ensure the full recovery of the excess molten steel.

[0014] S2. During the pouring process of the continuous casting ladle, do not pour all the molten steel. After stopping the pouring, some molten steel and slag remain in the ladle; the remaining amount, i.e. the total amount of the molten steel and slag left, is 5±0.2 tons; S3, lifting the ladle with the remaining pouring residue in step S2 to the top of the pouring residue tank, pouring out part of the remaining slag, and stopping pouring the remaining residue when steel flowers are seen; the remaining slag in the ladle after pouring contains molten steel and the remaining slag that has not been poured out; S4, pouring the remaining molten steel in the ladle after pouring the remaining molten steel in step S3 into the ladle after the converter is tapped, or into the ladle in the early stage of LF refining; after the remaining molten steel is poured into the ladle after the converter is tapped, ensure that the ladle clearance reaches 300-400mm to meet the requirements of LF refining and RH refining for the ladle clearance; the early stage of LF refining refers to one third of the total refining time and before; after pouring out the remaining molten steel, only the remaining slag is left in the ladle; S5, pouring the remaining slag in the ladle after pouring out the molten steel in step S4 into the slag pot.

[0015] In the following embodiments, the heavy rail steel production process is as follows: molten iron discharging from a tank dump station - molten iron pre-desulfurization - converter smelting - LF refining - RH refining - bloom continuous casting.

[0016] The total normal converter loading capacity is 154 tons. Five turnover ladles are used for heavy rail steel production. These five ladles are hot-packed after producing other silicon-deoxidized steel grades, and the empty ladles are weighed on the turntable of the large square billet continuous casting machine (the continuous casting machine for heavy rail steel production). The order of ladles put into production and the weight of the ladles are shown in Table 1. Table 1: Order of ladle use and ladle tare weight in heavy rail steel production

[0017] According to the production rhythm, the fourth furnace of each pouring starts the thermal cycle operation of pouring the remaining steel in the continuous casting ladle. Example 1

[0018] S1, the fourth furnace in the casting sequence, the total converter loading is 152 tons; the ladle clearance after tapping is 400mm; S2. In the continuous casting of large square billets, the pouring of the first furnace is completed. The ladle weighing shows 72.4 tons, and the total amount of remaining slag in the ladle casting is 4.8 tons; S3, the overhead crane hoists the ladle of the first furnace (15# ladle) that has just finished pouring to the top of the pouring tank, pours out some of the pouring slag, and stops pouring when steel flowers are seen; S4, the 4th furnace molten steel has been refined in the LF furnace for 15 minutes. The ladle car is driven from the refining position to the receiving span. The overhead crane lifts the 1st furnace ladle (15# ladle) to the top of the 4th furnace ladle and pours the remaining steel into the 4th furnace molten steel. The ladle clearance is 300mm. The 4th furnace molten steel is refined in the LF furnace for 45 minutes and then leaves the station and is lifted to the RH for refining. S5. The overhead crane pours the remaining slag in the 4th furnace ladle (15# ladle) into the slag pot. Example 2

[0019] S1, casting sequence 10, total converter loading 150 tons; ladle clearance 500mm after tapping; S2. After the pouring of the 7th furnace was completed in the continuous casting of large square billets, the ladle weighing showed 73.1 tons, and the total amount of slag remaining in the ladle pouring was 5 tons; S3, the crane hoists the ladle of the seventh furnace (19# ladle) that has just finished pouring to the top of the pouring tank, pours out some of the pouring slag, and stops pouring when steel flowers are seen; S4, the 10th furnace molten steel has been refined in the LF furnace for 10 minutes. The ladle car is driven from the refining position to the receiving span. The overhead crane lifts the 7th furnace ladle (19# ladle) to the top of the 10th furnace ladle, and pours the remaining steel into the 10th furnace molten steel. The ladle clearance is 350mm. The 10th furnace molten steel leaves the station after 53 minutes of refining in the LF furnace and is lifted to enter the RH refining; S5. The overhead crane pours the remaining slag in the 7th furnace ladle (19# ladle) into the slag pot. Example 3

[0020] S1, casting sequence 12, total converter loading 151 tons; steel ladle clearance 450mm; S2, bloom continuous casting, the 9th furnace pouring is finished, the ladle weighing shows 72.8 tons, and the total amount of remaining slag in the ladle pouring is 5.2 tons; S3, the overhead crane hoists the ladle of the 9th furnace (11# ladle) that has just finished pouring to the top of the pouring tank, pours out some of the pouring slag, and stops pouring when steel flowers are seen; S4, the 12th furnace steel, the converter steel tapping is completed, the ladle car is driven from the back of the converter to the receiving span, the crane lifts the 9th furnace steel ladle (11# steel ladle) to the top of the 12th furnace steel ladle, and the remaining steel is poured into the 12th furnace steel, the ladle clearance is 320mm. The 12th furnace steel is refined in the LF furnace for 41 minutes and then discharged from the station and lifted to the RH for refining; S5. The overhead crane pours the remaining slag in the 9th furnace ladle (11# ladle) into the slag pot.

Claims

1. A method for thermal recycling of excess steel from continuous casting of heavy rail steel, characterized in that: The method comprises the following steps: S1, recovering the remaining heats and reducing the total amount of converter loading to ensure that the clearance of the ladle after steel tapping reaches 400-500 mm; S2. During the pouring process of molten steel in the continuous casting ladle, some molten steel and slag remain in the ladle after the pouring is stopped; S3, lift the ladle with remaining pouring to the top of the pouring tank, pour out some of the remaining slag, and stop pouring when steel flowers are seen; S4, pouring the remaining molten steel in the ladle into the ladle after the continuous casting furnace converter steel is tapped, or pouring into the ladle in the early stage of LF refining; S5. Pour the remaining slag from the ladle into the slag pot.

2. The method for thermal recycling of excess steel from continuous casting of heavy rail steel according to claim 1, characterized in that: In step S2, the remaining amount of the ladle after stopping pouring is 5±0.2 tons.

3. The method for thermal recycling of excess steel from continuous casting of heavy rail steel according to claim 1 or 2, characterized in that: In step S4, after the remaining molten steel is poured into the ladle after the continuous casting furnace converter has tapped steel, the clearance of the ladle reaches 300 to 400 mm.

4. The method for thermal recycling of excess steel from continuous casting of heavy rail steel according to claim 1 or 2, characterized in that: In step S4, the early stage of LF refining refers to one third of the total refining time and before.

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