Pouring stopping method for reducing high-carbon steel small square billet continuous casting tail billet waste quantity

Abstract

The invention relates to the technical field of ferrous metallurgy, and particularly discloses a pouring stopping method for reducing the high-carbon steel small square billet continuous casting tail billet waste product amount. S1, when casting is stopped and a casting blank of a crystallizer passes through a secondary cooling zone 1, the opening degree of a water regulating valve is switched to 100%, and the original pulling speed is maintained; s2, when the casting blank reaches a certain distance of other secondary cooling water areas, the opening degree of a water regulating valve is sequentially switched to 100%, and the original pulling speed is maintained; s3, when the pressure value of the second withdrawal and straightening machine is increased to the overload protection value, the hot blank pressure is switched, and then the hot blank pressure is sequentially switched by other withdrawal and straightening machines applying pressure according to logic; and S4, after the last withdrawal and straightening machine implementing pressing is discharged, the pinch roll applies drive to draw the blank. And then, a 1.5 m tail blank is cut by a flame cutting machine, and the pouring period is ended. On the premise that accidents and casting blank defects are not generated, the pulling speed and the water distribution stability are improved to the maximum extent, the soft reduction logic is optimized, a stable liquid phase cavity is presented, the reduction process is conveniently achieved, the casting blank amount with poor segregation is reduced to the minimum, and therefore tail waste is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a method for stopping casting to reduce the amount of waste products of high-carbon steel billet continuous casting tail billets. Background Art

[0002] When high-carbon steel is continuously cast in small square billets, it is often necessary to reduce the pulling speed and open the secondary cooling water regulating valve to the maximum to prevent steel leakage accidents. However, for continuous casting machines with a light reduction function, changes in the pulling speed and the amount of secondary cooling water will cause changes in the solid phase ratio distribution in the solid-liquid two-phase region at the end of solidification, resulting in inaccurate light reduction positions and worsening the low magnification and segregation quality of the continuous casting billets. In addition, under the conditions of reduced pulling speed and increased secondary cooling water volume, when the billets pulled out of the secondary cooling chamber are pressed down by the straightening machine, the straightening machine will frequently overload and alarm due to the high strength of the billets, reducing the service life of the straightening machine. For the continuous casting machine described in this invention, the amount of scrapped billets at the end of each continuous casting stream reaches more than 12m due to improper stop-casting logic, which wastes production costs and increases equipment maintenance costs.

[0003] In order to reduce the amount of waste high carbon steel billet continuous casting tail pieces and increase the service life of equipment, the present invention provides a method for stopping casting to reduce the amount of waste high carbon steel billet continuous casting tail pieces. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for stopping casting to reduce the amount of waste products produced by continuous casting of high carbon steel billets.

[0005] The present invention provides a method for stopping casting to reduce the amount of waste in the tail billet of continuous casting of high-carbon steel billets, and is used for the production of high-carbon steel in a continuous casting machine with a light reduction function. The secondary cooling area of ​​the continuous casting machine is divided into a first cooling zone, a second cooling zone, a third cooling zone and a fourth cooling zone. The continuous casting machine is equipped with 7 straightening machines with a light reduction function.

[0006] S1. After the last ladle of the continuous casting machine is finished pouring, the molten steel in the tundish pool continues to be poured to the minimum liquid level to ensure the cleanliness of the molten steel. The slide in the tundish pool is closed. At this time, when the billet pulled out from the lower outlet of the crystallizer passes through the secondary cooling zone 1, the opening of the water flow regulating valve is immediately switched to 100%, and the casting speed is maintained at the original casting speed.

[0007] S2. When the billet reaches 2.96m, 2.96m, and 2.24m in secondary cooling zone 2, secondary cooling zone 3, and secondary cooling zone 4, respectively, the opening of the water regulating valve in each zone is immediately switched to 100% in sequence, and the casting speed remains the original casting speed;

[0008] S3. When the pressure value of the second straightening machine suddenly increases from the normal value to the overload protection value of the straightening machine, the pressure value is automatically switched to the hot billet pressure. When the second straightening machine generates overload protection, the billet under the second straightening machine is set to trigger the billet;

[0009] S4. When the triggered billet under the second straightening machine is moved to the third, fourth, and last straightening machine through system tracking, the corresponding straightening machine pressure values ​​are automatically switched to the hot billet pressure by the system;

[0010] S5. When the triggered billet under the second straightening machine moves out of the last straightening machine, the pinch roller applies driving force to continue pulling the billet;

[0011] Subsequently, when each strand of casting is cut into a tail slab of ≤1.5m by the fire cutting machine, the entire casting cycle is completed.

[0012] Furthermore, the cross section of the ingot is 150 square meters;

[0013] The length of the secondary cooling zone 1 is 0.84m, the length of the secondary cooling zone 2 is 3.96m, the length of the secondary cooling zone 3 is 3.96m, and the length of the secondary cooling zone 4 is 3.24m. During normal pouring, the liquid level of the crystallizer is 750mm.

[0014] Furthermore, S1.1, when the depth of the tundish molten pool decreases from 600 mm to 150 mm, the slide of the tundish molten pool is closed.

[0015] Furthermore, the time for the water regulating valve opening in the secondary cooling zone 1 to switch from the normal process water distribution to 100% is ≤ 20s, and the stroke of the cast billet pulled from the lower mouth of the crystallizer in the secondary cooling zone 1 is ≤ 90%.

[0016] Furthermore, the time it takes for the opening of the water regulating valves in secondary cooling zones 2, 3, and 4 to switch from the normal process water distribution to 100% is ≤ 26s.

[0017] Furthermore, the overload protection value of the second tension and straightening machine is 800kN.

[0018] Furthermore, the hot billet pressure of the second and third drawing and straightening machines is 100 kN; the hot billet pressure of the fourth to seventh drawing and straightening machines is 80 kN.

[0019] Furthermore, the pinch rollers apply a driving force of 80 kN to continue pulling the blank until the entire casting cycle is completed.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention maximizes the pulling speed and water distribution stability without causing production accidents and apparent quality defects of the billets, optimizes the soft reduction logic, and presents a stable liquid phase hole length to facilitate the implementation of the soft reduction process, thereby minimizing the amount of billets with deteriorated segregation quality, thereby reducing tail waste. DETAILED DESCRIPTION

[0022] The following will disclose multiple embodiments of the present invention. For the sake of clarity, many physical details will be described in the following description. However, it should be understood that these physical details should not be used to limit the present invention. The technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0023] The present invention provides a method for stopping casting to reduce the amount of waste in the tail billet continuous casting of high carbon steel billets: the secondary cooling area of ​​the continuous casting machine is divided into a first cooling zone, a second cooling zone, a third cooling zone and a fourth cooling zone, and the continuous casting machine is equipped with 7 tensioning and straightening machines with a light reduction function.

[0024] Example 1:

[0025] Taking X55SiCrA steel as an example, the pulling speed is 2.2m / min.

[0026] After the pouring of the last ladle of molten steel in continuous casting is completed, the molten steel in the tundish continues to be poured. When the depth of the molten pool drops from 600mm to 150mm, the slide of the tundish is closed.

[0027] At this time, when the billet pulled out from the lower mouth of the crystallizer passes through the secondary cooling zone 1, the opening of the water regulating valve is immediately switched to 100%. The switching time is 19 seconds. The billet pulled out from the lower mouth of the crystallizer travels 0.70m in the secondary cooling zone 1, and the pulling speed is maintained at 2.2m / min.

[0028] When the ingot pulled out from the bottom of the crystallizer reaches 2.96m, 2.96m, and 2.24m in the secondary cooling zone 2, zone 3, and zone 4, respectively, the water flow regulating valve opening of each zone is immediately switched to 100%. The time for the water flow regulating valve opening of the secondary cooling zone 2, zone 3, and zone 4 to switch from the normal process water supply to 100% is 22s, 24s, and 23s, respectively. The pulling speed is maintained at 2.2m / min.

[0029] Continue to draw the billet. When the pressure value of the second drawing and straightening machine suddenly increases from 250kN to 800kN, the pressure value is automatically switched to 100kN. At this time, the billet under the second drawing and straightening machine is set as the triggered billet; when the triggered billet is moved to the third, fourth... last drawing and straightening machine for pressing down, the hot billet pressure of the third drawing and straightening machine is switched to 100kN, and the hot billet pressure of the fourth and subsequent drawing and straightening machines is switched to 80kN; when the triggered billet moves out of the last drawing and straightening machine for pressing down, the pinch roller applies 80kN driving force to continue drawing the billet.

[0030] Then, a 1.5m tail billet is cut out from each strand by a fire cutting machine, and the entire casting cycle is completed.

[0031] The five-point segregation method was used to continuously take five groups of segregation at the tail of the last qualified billet. After calculation, the segregation indexes were 0.95, 1.03, 1.08, 0.98, and 0.99, all less than 1.10, that is, the remaining billets after 1.5m of the tail billet of each stream was cut into scrap were all of qualified quality.

[0032] Example 2

[0033] Taking 60Si2Mn steel as an example, the pulling speed is 2.2m / min.

[0034] After the pouring of the last ladle of molten steel in continuous casting is completed, the molten steel in the tundish continues to be poured. When the depth of the molten pool drops from 600mm to 150mm, the slide of the tundish is closed.

[0035] At this time, when the billet pulled out from the lower mouth of the crystallizer passes through the secondary cooling zone 1, the opening of the water regulating valve is immediately switched to 100%. The switching time is 17 seconds. The billet pulled out from the lower mouth of the crystallizer travels 0.62m in the secondary cooling zone 1, and the pulling speed is maintained at 2.2m / min.

[0036] When the ingot pulled out from the bottom of the crystallizer reaches 2.96m, 2.96m, and 2.24m in the secondary cooling zone 2, zone 3, and zone 4, respectively, the water flow regulating valve opening of each zone is immediately switched to 100%. The time for the water flow regulating valve opening of the secondary cooling zone 2, zone 3, and zone 4 to switch from the normal process water supply to 100% is 23s, 23s, and 25s, respectively. The pulling speed is maintained at 2.2m / min.

[0037] Continuing with billet drawing, when the pressure value of the second straightening machine suddenly increases from 260kN to 800kN, the pressure value automatically switches to 100kN. At this time, the billet under the second straightening machine is set as the triggered billet. When the triggered billet moves to the third, fourth, and last straightening machine for pressing down, the hot billet pressure of the third straightening machine switches to 100kN, and the hot billet pressure of the fourth and subsequent straightening machines switches to 80kN.

[0038] When the strand is triggered to move out of the last straightening machine, the pinch rolls apply 80kN of driving force to continue strand drawing. A hot shearing machine then cuts off a 1.5m tail strand from each strand, completing the casting cycle. Using the five-point segregation method, five consecutive segregation indices were calculated for the tail of the last qualified strand. The segregation indices were 0.98, 0.99, 1.06, 1.07, and 1.05, respectively—all less than 1.10. This indicates that after the 1.5m tail strand of each strand is scrapped, the remaining strands are of qualified quality.

[0039] Example 3

[0040] Taking XSWRCH82B steel as an example, the pulling speed is 2.1m / min.

[0041] After the pouring of the last ladle of molten steel in continuous casting is completed, the molten steel in the tundish continues to be poured. When the depth of the molten pool drops from 600mm to 150mm, the slide of the tundish is closed.

[0042] At this time, when the billet pulled out from the lower mouth of the crystallizer passes through the secondary cooling zone 1, the opening of the water regulating valve is immediately switched to 100%. The switching time is 20 seconds. The billet pulled out from the lower mouth of the crystallizer travels 0.7 meters in the secondary cooling zone 1, and the pulling speed is maintained at 2.1 meters per minute.

[0043] When the ingot pulled out from the bottom of the crystallizer reaches 2.96m, 2.96m, and 2.24m in the secondary cooling zone 2, zone 3, and zone 4, respectively, the water flow regulating valve opening of each zone is immediately switched to 100%. The time for the water flow regulating valve opening of the secondary cooling zone 2, zone 3, and zone 4 to switch from the normal process water supply to 100% is 23s, 24s, and 20s, respectively. The pulling speed is maintained at 2.1m / min.

[0044] As the billet drawing continues, when the pressure value of the second straightening machine suddenly increases from 275kN to 800kN, the pressure value automatically switches to 100kN. At this time, the billet under the second straightening machine is set as the triggered billet. When the triggered billet moves to the third, fourth, and last straightening machine for pressing down, the hot billet pressure of the third straightening machine switches to 100kN, and the hot billet pressure of the fourth and subsequent straightening machines switches to 80kN.

[0045] When the strand is triggered to move out of the last straightening machine, the pinch rolls apply 80kN of driving force to continue strand drawing. A hot shearing machine then cuts off a 1.5m tail strand from each strand, completing the casting cycle. Using the five-point segregation method, five consecutive segregation indices were calculated for the tail of the last qualified strand, yielding 1.08, 0.95, 1.01, 1.06, and 0.94, respectively—all less than 1.10. This indicates that after the 1.5m tail strand of each strand is scrapped, the remaining strands are of acceptable quality.

[0046] The foregoing is merely an embodiment of the present invention and is not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be included within the scope of the claims of the present invention.

Claims

1. A method for reducing the amount of waste in the tail of a continuous casting of high-carbon steel billets, used in the production of high-carbon steel on a continuous casting machine with a soft-reduction function, wherein the secondary cooling zone of the continuous casting machine is divided into a first cooling zone, a second cooling zone, a third cooling zone, and a fourth cooling zone, and the continuous casting machine is equipped with seven tension levelers with a soft-reduction function, characterized in that: S1. After the last ladle of the continuous casting machine is finished pouring, the molten steel in the tundish pool continues to be poured to the minimum liquid level to ensure the cleanliness of the molten steel. The slide in the tundish pool is closed. At this time, when the billet pulled out from the lower outlet of the crystallizer passes through the secondary cooling zone 1, the opening of the water flow regulating valve is immediately switched to 100%, and the casting speed is maintained at the original casting speed. S2. When the billet reaches 2.96m, 2.96m, and 2.24m in secondary cooling zone 2, secondary cooling zone 3, and secondary cooling zone 4, respectively, the opening of the water regulating valve in each zone is immediately switched to 100% in sequence, and the casting speed remains the original casting speed; S3. When the pressure value of the second straightening machine suddenly increases from the normal value to the overload protection value of the straightening machine, the pressure value is automatically switched to the hot billet pressure. When the second straightening machine generates overload protection, the billet under the second straightening machine is set to trigger the billet; S4. When the triggered billet under the second straightening machine is moved to the third, fourth, and last straightening machine through system tracking, the corresponding straightening machine pressure values ​​are automatically switched to the hot billet pressure by the system; S5. When the triggered billet under the second straightening machine moves out of the last straightening machine, the pinch roller applies driving force to continue pulling the billet; Subsequently, when each strand of casting is cut into a tail slab of ≤1.5m by the fire cutting machine, the entire casting cycle is completed.

2. The method for stopping casting to reduce the amount of waste products of high carbon steel billet continuous casting according to claim 1, characterized in that: The cross section of the ingot is 150 square meters; The length of the secondary cooling zone 1 is 0.84m, the length of the secondary cooling zone 2 is 3.96m, the length of the secondary cooling zone 3 is 3.96m, and the length of the secondary cooling zone 4 is 3.24m. During normal pouring, the liquid level of the crystallizer is 750mm.

3. The method for stopping casting to reduce the amount of waste products of high carbon steel billet continuous casting according to claim 2, characterized in that: S1.

1. When the depth of the tundish molten pool drops from 600mm to 150mm, close the slide of the tundish molten pool.

4. The method for stopping casting to reduce the amount of waste products of high carbon steel billet continuous casting according to claim 1, characterized in that: The time for the water regulating valve opening in the secondary cooling zone 1 to switch from the normal process water distribution to 100% is ≤ 20s, and the stroke of the cast billet drawn from the lower mouth of the crystallizer in the secondary cooling zone 1 is ≤ 90%.

5. The method for stopping casting to reduce the amount of waste products of high carbon steel billet continuous casting according to claim 1, characterized in that: The time for the opening of the water regulating valve in secondary cooling zone 2, zone 3 and zone 4 to switch from normal process water distribution to 100% is ≤ 26s.

6. The method for stopping casting to reduce the amount of waste products of high carbon steel billet continuous casting according to claim 1, characterized in that: The overload protection value of the second tensioning and straightening machine is 800kN.

7. The method for stopping casting to reduce the amount of waste products from the tail billet continuous casting of high carbon steel billets according to claim 1, characterized in that: The hot billet pressure of the second and third straightening machines is 100kN; the hot billet pressure of the fourth to seventh straightening machines is 80kN.

8. The method for stopping casting to reduce the amount of waste products of high carbon steel billet continuous casting according to claim 1, characterized in that: The pinch rollers apply a driving force of 80 kN to continue pulling the blank until the entire casting cycle is completed.