A method to avoid freezing of billets after steel leakage in continuous casting machine

Abstract

The invention relates to a method for avoiding freezing of billets after steel leakage in a continuous casting machine. By adding a steel leakage button, steel leakage control is enforced to prevent steel leakage and freezing of billets caused by untimely steel leakage detection. The steel leakage button is added, and improvements are made to sector position control, drawing speed control, secondary cooling water cooling circuit control, support roller opening control and support roller target force control respectively. By increasing the sector opening value, the volume of the tail slab is increased, the steel overflow problem is effectively solved, and the billet drawing resistance is reduced by 20-40%. By controlling the billet drawing speed and the secondary cooling water flow rate, the cooling intensity of the slab and the steel leakage point is increased by 30-50%. By controlling the automatic opening of the support roller to prevent the excessive support force from squeezing the slab, most of the molten steel overflow can be reduced. By increasing the support roller target force, the friction between the roller and the slab is increased, so as to provide a guarantee for pulling out the slab, reduce the equipment repair time after steel leakage, save costs, and improve the operation rate of the casting machine.

Description

Technical Field

[0001] The invention relates to the technical field of continuous casting, and in particular to a method for preventing billets from freezing after steel leakage from a continuous casting machine. Background Art

[0002] Steel leakage in continuous casting machine refers to the phenomenon that the solidification of ingot shell is not good or the shell breaks or leaks due to other external forces during the casting process, causing the internal molten steel to flow out. Steel leakage is a vicious accident in continuous casting production. Severe steel leakage accidents not only affect the normal production of continuous casting machines, but also cause frozen ingot accidents due to inability to pull, reduce the operating rate of casting machines, and cause major equipment losses. Steel leakage accidents can be divided into many types according to the time and location of occurrence on the casting machine, such as steel leakage at the beginning of casting, steel leakage during casting, steel leakage at the corner of the ingot, steel leakage inside or outside the arc of the ingot, etc. After steel leakage occurs, the casting machine will control the corresponding equipment in the tail billet discharge mode to pull the ingot out of the fan-shaped segment. During this period, the casting machine's supporting rollers, fan-shaped segments, and secondary cooling water will act according to the tail billet tracking control sequence to complete the tail billet discharge.

[0003] In the process of steel leakage and tail discharge of the current continuous casting machine, the fan-shaped segments will be opened in sequence according to the tail billet tracking value to the actual thickness of the crystallizer outlet (the thickness of the crystallizer outlet is different for different casting machine types), the supporting rollers will be opened in sequence according to the tail billet tracking value, and the secondary cooling water will be closed in sequence according to the tail billet tracking value. The tail billet is tracked to the last fan-shaped segment and the tail discharge of the casting machine is completed. According to the summary in recent years, when the casting machine leaks steel, the production operator activates the casting machine for steel leakage. When the amount of steel leakage is not large, the casting machine can pull out the billet. However, in production, due to factors such as untimely discovery, the amount of steel leakage is large, and most of the billets cannot be pulled out, resulting in a vicious continuous casting frozen billet accident. Even if the billet is pulled out, due to the fact that a large amount of liquid steel in the fan-shaped segments 0 to 6 has not been cooled and solidified in time, the liquid steel will overflow onto the fan-shaped segments for the second time under the action of the fan-shaped segment extrusion, causing serious damage to the fan-shaped segments 0 to 6, and will also increase the handling time of the steel leakage accident. It is urgent to solve the above problems.

[0004] A Chinese patent with publication number CN101332499A discloses a slab continuous casting leak prediction control method, comprising the following steps: a. capturing typical temperature characteristics: determining the typical temperature characteristics of each thermocouple according to the mold parameters and the installation position of the thermocouple in the mold; b. determining the leak probability: determining the leak probability of each thermocouple according to the typical temperature characteristics of adjacent thermocouples, while considering the leak temperature transfer and temperature abnormality distribution characteristics; c. controlling the casting speed: stopping casting when the thermocouple leak probability reaches 95%; however, the patent's dynamic monitoring and tracking of temperature changes will cause control lag due to temperature lag, resulting in leak accidents.

[0005] The present invention provides a method for preventing the continuous casting machine from freezing the billet after steel leakage. In order to prevent the steel leakage and freezing billet accident caused by untimely steel leakage detection, a steel leakage button is added to enforce steel leakage control. The opening value of the fan-shaped segment is increased to increase the content volume of the tail slab, effectively solve the problem of steel overflow, and reduce the billet drawing resistance. The billet drawing speed and the secondary cooling water flow rate are controlled to increase the cooling intensity of the slab and the steel leakage point. The automatic opening of the supporting roller is controlled to prevent the slab from being squeezed by excessive supporting force, which can reduce most of the overflow of molten steel. The friction between the roller and the slab is increased by increasing the target force of the supporting roller, so as to provide a guarantee for pulling out the slab, reduce the equipment repair time after steel leakage, save costs, and improve the operation rate of the casting machine.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preventing freezing of billets after steel leakage in a continuous casting machine comprises the following steps:

[0008] 1) Activate the steel leakage button;

[0009] 2) Sector control:

[0010] (1) Segment position control: Segments 1 to 3 are opened to a size 10 to 40 mm greater than the mold thickness, and segments 4 to 15 are opened to the mold thickness;

[0011] (2) Casting speed control: Control the casting speed to 0.8-1.1 m / min;

[0012] (3) Secondary cooling water cooling circuit control: The control valves of the 1st to 6th cooling circuits of the secondary cooling water of the fan-shaped segment are opened by 70-100℅ to supply water;

[0013] (4) Holding roller opening control: When the tail position tracking value of segments 1 to 3 is 0 to 500 mm, holding rollers 1 to 3 are lifted; when the tail position tracking value of segments 4 to 15 is ±500 mm of the actual metallurgical length of the corresponding holding roller from the crystallizer, the corresponding holding roller is automatically opened;

[0014] (5) Holding roller target force control: Control the holding roller target force at 100% to 150%;

[0015] 3) When the tracking value of the tail position of the casting billet is greater than the metallurgical length of the sector 0 entrance from the crystallizer ±500mm, the equipment starts the next action;

[0016] (1) Segment position control: Segments 4 to 15 are opened sequentially to a size 10 to 40 mm greater than the mold thickness;

[0017] (2) Casting speed control: After activating the leakage button for 3 minutes, the casting speed is controlled to increase to 1.1-1.3 m / min;

[0018] (3) Secondary cooling water circuit control: The secondary cooling water circuit of the fan-shaped segment remains open until the tail billet of the casting strand is pulled out of the corresponding fan-shaped segment, and then the secondary cooling water circuit of the previous fan-shaped segment is automatically closed;

[0019] (4) Holding roller opening control: Holding rollers 1 to 3 are kept lifted up. When the position tracking value of the tail billet of the casting strand of segments 4 to 15 is ±500 mm of the actual metallurgical length of the holding roller of the corresponding segment from the crystallizer, the holding roller of the corresponding segment is automatically opened until the tail billet is completely pulled out of the segment, thus ending the entire leakage and tail billet discharge process.

[0020] Furthermore, the cooling positions of the 1st to 2nd cooling circuits of the secondary cooling water of the fan-shaped segment are the foot roll area, the cooling positions of the 3rd to 6th cooling circuits of the secondary cooling water of the fan-shaped segment are the fan-shaped segment 0, and the cooling positions of the 7th to 20th cooling circuits of the secondary cooling water of the fan-shaped segment are the fan-shaped segments 1 to 15.

[0021] Furthermore, the acceleration of the ramp section of the casting speed in step 2) is 4 to 8 m / Min2.

[0022] Furthermore, when the tracking value of the tail position of the casting strand is greater than the metallurgical length of the secondary cooling water circuit corresponding to the fan-shaped segment, the corresponding secondary cooling water circuit of the fan-shaped segment and the secondary cooling water circuit of the previous fan-shaped segment are automatically closed.

[0023] Furthermore, the segment 0 is located at the front end of the sector segment.

[0024] Furthermore, the tracking value of the tail position of the casting strand is the length of the slab pulled out by the straightening machine.

[0025] Furthermore, the steel leakage button is installed in the central control room, and the machine side and the central control room are interlocked for operation.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) Add a steel leakage button to enforce steel leakage control to prevent steel leakage and frozen billet accidents caused by untimely steel leakage detection. Add a steel leakage button;

[0028] 2) By increasing the opening value of the fan-shaped segment, the volume of the tail slab is increased, which effectively solves the problem of steel overflow and reduces the billet drawing resistance by 20-40%;

[0029] 3) By controlling the billet drawing speed and the secondary cooling water flow rate, the cooling intensity of the slab and the leaking point is increased by 30-50%;

[0030] 4) By controlling the automatic opening of the holding roller to prevent excessive holding force from squeezing the slab, most of the molten steel overflow can be reduced. By increasing the target force of the holding roller, the friction between the roller and the slab is increased to provide a guarantee for pulling out the slab;

[0031] 5) Reduce the time for emergency repair of equipment after steel leakage, save costs and improve the operation rate of casting machines. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the process flow of the present invention.

[0033] In the figure: 1. Crystallizer 2. Sector 3. Secondary spray cooling 4. Straightening machine 5.0 section 6. Slab DETAILED DESCRIPTION

[0034] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0035] See Figure 1 , is a process flow chart of the present invention, molten steel flows from a crystallizer 1 into a sector 2, the sector 2 is 0 to 15 segments from top to bottom, the sector 2 is subjected to secondary spray cooling 3, and a drawing and leveling machine 4 is used to pull out the cooled slab 6. The present invention provides a method for preventing frozen slabs after steel leakage in a continuous casting machine, characterized in that it comprises the following steps:

[0036] 1) Activate the steel leakage button. The steel leakage button is installed in the central control room and can be chained operated both at the machine side and in the central control room.

[0037] 2) Segment 2 parameter control, including segment 2 position control, casting speed control, secondary cooling water cooling circuit control, holding roller opening control and holding roller target force control:

[0038] (1) Segment 2 position control: The thickness of the crystallizer 1 is 242.5 mm, and segments 1 to 3 of the segment 2 are opened to 260 mm, and segments 4 to 15 of the segment 2 are opened to 242.5 mm. The billet will bulge under the static pressure of the molten steel, increasing the volume of the slab 6, effectively solving the problem of steel overflow, and preventing the liquid steel from leaking onto the segment 2 under the squeezing of the segment 2 when the billet moves downward, thereby increasing the damage to the equipment. This reduces the amount of steel wrapped around the rollers, and reduces the billet drawing resistance by 20 to 40%;

[0039] (2) Casting speed control: Control the casting speed to 1.0 m / min, and the acceleration of the ramp section of the casting speed is 6 m / min 2 ;

[0040] (3) Secondary cooling water circuit control: Under the condition of no steel leakage, the target flow rate of the secondary cooling water circuit of sector 2 is given according to the billet drawing speed table, see Table 1:

[0041] Table 1

[0042]

[0043]

[0044] Loop1~Loop20 are the 1st~20th cooling loops of the secondary cooling water of sector 2. The control valves of Loop1~Loop6 are opened 100℅ for water supply. The target flow rate of the secondary cooling water of Loop7~Loop20 is still given according to the closest speed of the speed table, which increases the cooling intensity of slab 6 and the leaking point by 30%;

[0045] (4) Holding roller opening control: When the tail position tracking value of segments 1 to 3 of sector 2 is 0 mm, holding rollers 1 to 3 are lifted to prevent excessive holding force from squeezing the slab 6 and reduce most of the overflowing molten steel. When the tail position tracking value of segments 4 to 15 of sector 2 is ±500 mm of the actual metallurgical length of the holding roller of the corresponding segment from the crystallizer 1, the holding roller of the corresponding sector 2 is automatically opened. The holding rollers are opened one by one according to the tail tracking value, as shown in Table 2:

[0046] Table 2

[0047]

[0048] (5) Control of target force of supporting roller: Increase the target force of supporting roller and control the target force of supporting roller at 120% to compensate the torque and improve the drawing torque. Due to the excessive resistance caused by steel leakage, the billet adheres to the main body of the fan-shaped segment 2, resulting in insufficient straightening torque. Increasing the target force of supporting roller increases the friction between the roller and the slab 6, thereby providing a guarantee for pulling out the slab 6.

[0049] 3) The slab 6 is gradually pulled out by the straightening machine 4, and the pulling length is the position tracking value of the tail of the casting strand. When the position tracking value of the tail of the casting strand is greater than the metallurgical length of the entrance of the 0th segment 5 of the sector 2 from the crystallizer 1 by ±500mm, the equipment starts the next step of the sector 2 position control, the pulling speed control, the secondary cooling water cooling circuit control and the holding roller opening control;

[0050] (1) Segment 2 position control: Segments 4 to 15 of segment 2 are opened to 260 mm in sequence. When the position tracking values ​​of the tail billet of the four segments of segment 2 are greater than the actual metallurgical length of segment 0 5 inlet from the crystallizer 1 ±500 mm and the actual metallurgical length of segment 0 5 outlet from the crystallizer 1 ±500 mm, the four segments of segment 2 are opened to 260 mm. Similarly, 5 to 15 correspond to the metallurgical lengths of segments 1 to 11. After the breakout, if the tracking value of the tail billet of the mainstream is greater than the value in Table 3, the segments are opened to 260 mm in sequence.

[0051] Table 3

[0052]

[0053] By increasing the opening value of sector 2, the problem of large billet pulling resistance after steel leakage and the billet being difficult to pull out of sector 2 can be effectively solved;

[0054] (2) Pulling speed control: After activating the steel leakage button for 3 minutes, the pulling speed of the slab 6 is controlled to 1.2 m / min;

[0055] (3) Secondary cooling water circuit control: The secondary cooling water circuit of segment 2 remains open until the tail of the casting strand is pulled out of the corresponding segment 2, then the secondary cooling water circuit of the previous segment 2 is automatically closed. The secondary cooling water circuit corresponding to segment 2 is closed as shown in Table 4.

[0056] Table 4

[0057]

[0058]

[0059] (4) Holding roller opening control: Holding rollers 1 to 3 are kept lifted up. When the position tracking value of the tail billet of segments 4 to 15 of sector 2 is ±500 mm of the metallurgical length of the corresponding holding roller from the actual distance to the crystallizer 1, the holding roller of the corresponding sector 2 is automatically opened until the tail billet is completely pulled out of sector 2, thus ending the entire leakage and tail billet discharge process.

[0060] After applying this improved method, the repair time of equipment after steel leakage is reduced by 8 to 23 hours. Based on the calculation of 50 people each time, 16 hours per person, and 25 yuan per hour, 2 machines and 3 flows occur about 4 times a year, which reduces labor costs by about 80,000 yuan, reduces the number of fan-shaped segments 2 being offline in advance by about 12 units, and increases the service life of fan-shaped segments 2. Based on the annual overflow of molten steel after steel leakage and the burning of fan-shaped segment 2 driven rollers, etc., the maintenance of fan-shaped segments 2 causes an increase in spare parts costs of about 1.2 million yuan and maintenance labor costs of about 60,000 yuan. Improve the operation rate of the casting machine, and based on the calculation of reducing the steel leakage processing time by about 50 hours per year, 50 more furnaces can be produced, each furnace is 180 tons, and the indirect income is about 4.5 million yuan.

[0061] The above embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the above embodiments. The methods used in the above embodiments are conventional methods unless otherwise specified.

Claims

1. A method for preventing freezing of billets after steel leakage in a continuous casting machine, characterized in that: The following steps are involved: 1) Activate the steel leakage button; 2) Sector control: (1) Segment position control: Segments 1 to 3 are opened to a size 10 to 40 mm greater than the mold thickness, and segments 4 to 15 are opened to the mold thickness; (2) Casting speed control: Control the casting speed to 0.8-1.1 m / min; (3) Secondary cooling water cooling circuit control: The control valves of the 1st to 6th cooling circuits of the secondary cooling water of the fan-shaped segment are opened by 70-100℅ to supply water; (4) Holding roller opening control: When the tail position tracking value of segments 1 to 3 is 0 to 500 mm, holding rollers 1 to 3 are lifted; when the tail position tracking value of segments 4 to 15 is ±500 mm of the actual metallurgical length of the corresponding holding roller from the crystallizer, the corresponding holding roller is automatically opened; (5) Holding roller target force control: Control the holding roller target force at 100% to 150%; 3) When the tracking value of the tail position of the casting billet is greater than the metallurgical length of the sector 0 entrance from the crystallizer ±500mm, the equipment starts the next action; (1) Segment position control: Segments 4 to 15 are opened sequentially to a size 10 to 40 mm greater than the mold thickness; (2) Casting speed control: After activating the leakage button for 3 minutes, the casting speed is controlled to increase to 1.1-1.3 m / min; (3) Secondary cooling water circuit control: The secondary cooling water circuit of the fan-shaped segment remains open until the tail billet of the casting strand is pulled out of the corresponding fan-shaped segment, and then the secondary cooling water circuit of the previous fan-shaped segment is automatically closed; (4) Holding roller opening control: Holding rollers 1 to 3 are kept lifted up. When the position tracking value of the tail billet of the casting strand of segments 4 to 15 is ±500 mm of the actual metallurgical length of the holding roller of the corresponding segment from the crystallizer, the holding roller of the corresponding segment is automatically opened until the tail billet is completely pulled out of the segment, thus ending the entire leakage and tail billet discharge process.

2. A method for preventing freezing of billets after steel leakage in a continuous casting machine according to claim 1, characterized in that: The cooling positions of the 1st to 2nd cooling circuits of the secondary cooling water of the fan-shaped segment are the foot roll area, the cooling positions of the 3rd to 6th cooling circuits of the secondary cooling water of the fan-shaped segment are the fan-shaped segment 0, and the cooling positions of the 7th to 20th cooling circuits of the secondary cooling water of the fan-shaped segment are the fan-shaped segments 1 to 15.

3. A method for preventing freezing of billets after steel leakage in a continuous casting machine according to claim 1, characterized in that: The acceleration of the ramp section of the casting speed in the step 2) is 4 to 8 m / min2.

4. A method for preventing freezing of billets after steel leakage in a continuous casting machine according to claim 1, characterized in that: When the tracking value of the tail position of the casting strand is greater than the metallurgical length of the secondary cooling water circuit corresponding to the fan-shaped segment, the corresponding secondary cooling water circuit of the fan-shaped segment and the secondary cooling water circuit of the previous fan-shaped segment are automatically closed.

5. The method for preventing freezing of billets after steel leakage in a continuous casting machine according to claim 1, characterized in that: The steel leakage button is installed in the central control room, and the machine side and the central control room are interlocked for operation.

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