A control method to prevent continuous casting secondary cooling nozzle from clogging

Abstract

The invention relates to a control method for preventing a continuous casting secondary cooling nozzle from being blocked, and belongs to the technical field of continuous casting. The method controls the water volume of each secondary cooling zone by a target surface temperature control method of a dynamic secondary cooling water distribution model; according to current real-time casting process parameters, a valve of a secondary cooling zone 1 is opened to the maximum, and the duration is until the maximum cooling rate of the surface of the casting blank in the secondary cooling control zone reaches δ, and the water volume of other secondary cooling zones is controlled by a target surface temperature control method; after the valve of the secondary cooling zone 1 is opened to the maximum duration, the secondary cooling water volume of the zone is immediately controlled by the target surface temperature control method, and the position of the casting blank with the maximum cooling rate on the surface of the casting blank in the secondary cooling zone is recorded at the same time, until the casting blank leaves all the secondary cooling zones of the continuous casting machine; and then the other valves of the secondary cooling zone are opened in sequence by the same method; the purpose of preventing the accumulation of residual scale in the nozzle by strong flushing of secondary cooling water is achieved, and the uniformity of secondary cooling can be guaranteed, which is of great significance.

Description

Technical Field

[0001] The invention belongs to the technical field of continuous casting and relates to a control method for preventing a continuous casting secondary cooling nozzle from being blocked. Background Art

[0002] The internal quality, surface quality and shape defects of the continuous casting billet are closely related to the secondary cooling. The continuous casting secondary cooling is mainly achieved by water spray cooling of the nozzle. Since the continuous casting secondary cooling water system is a non-closed system for recycling, the secondary cooling water will inevitably come into direct contact with various equipment in the casting machine during the process of cooling the billet and equipment. During this period, various harmful impurities including industrial oil, iron oxide scale and metal particles will enter the secondary cooling water circulation system. Such harmful impurities are very easy to adhere and accumulate on water circulation equipment such as filters and inner walls of pipes due to their high viscosity. As the water system circulates, it usually causes the secondary cooling nozzle to be blocked. In addition, the various external environments along the way of the water circulation system can easily aggravate the formation of scale and cause it to enter the water circulation system, increasing the risk of blockage of the secondary cooling nozzle.

[0003] The working state of the secondary cooling nozzle of continuous casting has an important influence on the quality of the ingot. If the secondary cooling nozzle is blocked, it will change the distribution state of the secondary cooling water on the surface of the ingot, affect the heat transfer process of the ingot, cause uneven cooling of the ingot, and ultimately lead to quality problems such as cracks, bulging, center segregation and increased porosity of the ingot.

[0004] However, at present, most of the continuous casting machines judge the working condition of the nozzle by manual observation or regular inspection. These methods are subject to great human interference and have many shortcomings such as untimely and inadequate detection. Moreover, they are post-remedial measures, which will inevitably have a significant impact on actual production.

[0005] Therefore, seeking a preventive measure to prevent the blockage of the secondary cooling nozzle during continuous casting is of great significance for maximizing the service life of the secondary cooling nozzle, reducing the downtime and maintenance time of the continuous casting machine, and avoiding the quality problems of the casting caused by nozzle blockage. Summary of the invention

[0006] In view of this, an object of the present invention is to provide a control method for preventing the continuous casting secondary cooling nozzle from being blocked, so as to solve the problem that the continuous casting secondary cooling nozzle is easily blocked.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A control method for preventing a continuous casting secondary cooling nozzle from being blocked comprises the following steps:

[0009] S1 controls the water volume of each secondary cooling zone through the target surface temperature control method of the dynamic secondary cooling water distribution model. According to the current real-time casting process parameters, the valve of the secondary cooling zone 1 is opened to the maximum, and the duration is until the maximum cooling rate of the billet surface in the secondary cooling control zone reaches the maximum cooling rate δ of the billet surface allowed by the dynamic secondary cooling water distribution model. The water volume of other secondary cooling zones of the casting machine is controlled by the target surface temperature control method; after the valve of the secondary cooling zone 1 is opened to the maximum duration, the secondary cooling water volume of the zone is immediately controlled by the target surface temperature control method, and the billet position with the maximum cooling rate of the billet surface in the secondary cooling zone is recorded at the same time, until the billet leaves all the secondary cooling zones of the continuous casting machine;

[0010] S2 opens the valve of the secondary cooling zone 2 to the maximum. The rest of the operations in this zone are the same as those in the secondary cooling zone 1. The operations of the rest of the secondary cooling zones are completed in the same way.

[0011] S3: When all the secondary cooling zones in the casting machine have achieved the maximum valve opening, repeat step S1.

[0012] Optionally, the real-time temperature of the ingot is provided for the target surface temperature control method by an online simulation temperature field model.

[0013] Optionally, in step S1, δ is related to the high temperature performance of the casting steel and the calculation parameters of the simulated temperature field.

[0014] Optionally, in step S1, the calculation method of δ is: obtaining the temperature of all discrete grid nodes on the surface of the second cooling zone of the billet through the real-time temperature field information of the billet; obtaining the temperature of all discrete grid nodes on the surface of the second cooling zone of the billet in the next control cycle according to the real-time process control parameters including the casting speed; and calculating the maximum value of the temperature change of all billet surface nodes in the second cooling zone in real time. Where T i、τ is the temperature of the grid node i on the surface of the same slice unit in the secondary cooling zone at time τ, T i、τ+1 is the temperature of grid node i on the surface of the ingot of the same slice unit in the second cooling zone in the next control cycle, and D is the slice unit spacing.

[0015] Optionally, in step S1, when the target surface temperature method control is performed, the minimum water volume of the secondary cooling zone is the product of the minimum value within the optimal flow range of the secondary cooling nozzle and the number of nozzles in the secondary cooling zone.

[0016] Optionally, in step S1, step S2 is performed only when the surface temperature of the cast strand at all target control points in the secondary cooling zones of the continuous casting machine and the target surface temperature are within an allowable error range.

[0017] The beneficial effects of the present invention are: taking preventive measures in advance and utilizing strong flushing of secondary cooling water can effectively prevent the accumulation of residual scale in the nozzle, ensure the uniformity of secondary cooling, maximize the service life of the secondary cooling nozzle, reduce the downtime and maintenance time of the continuous casting machine, and avoid the quality problems of the casting caused by nozzle blockage, which is of great significance.

[0018] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0020] Figure 1 This is a schematic diagram of the heat transfer principle of the secondary cooling nozzle spray cooling in the continuous casting process;

[0021] Figure 2 Schematic diagram of the secondary cooling zone of the slab continuous casting machine.

[0022] Figure 3 This is a schematic diagram of the secondary cooling zones of the billet continuous casting machine. DETAILED DESCRIPTION

[0023] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0024] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0025] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0026] See also Figure 1 to Figure 3 A control method for preventing a continuous casting secondary cooling nozzle from being blocked comprises the following steps:

[0027] S1 controls the water volume of each secondary cooling zone through the target surface temperature control method of the dynamic secondary cooling water distribution model. According to the current real-time casting process parameters, the valve of the secondary cooling zone 1 is first opened to the maximum, and the duration is until the maximum cooling rate of the billet surface in the secondary cooling control zone reaches the maximum cooling rate δ of the billet surface allowed by the dynamic secondary cooling water distribution model; the water volume of other secondary cooling zones of the casting machine is controlled by the target surface temperature control method; after the valve of the secondary cooling zone 1 is opened to the maximum duration, the secondary cooling water volume of this zone is immediately controlled by the target surface temperature control method; at the same time, the billet position with the maximum cooling rate of the billet surface in the secondary cooling zone is recorded until the billet leaves all the secondary cooling zones of the continuous casting machine;

[0028] S2 opens the valve of the secondary cooling zone 2 to the maximum, and the rest is the same as step S1; the steps of other secondary cooling zones are the same;

[0029] S3: When all the secondary cooling zones in the casting machine have achieved the maximum valve opening, repeat step S1.

[0030] Optionally, in step S1, the real-time temperature of the ingot is provided for the target surface temperature control method through an online simulation temperature field model; in step S1, the maximum cooling rate δ of the ingot surface (in units of ℃ / (m / s)) is related to the high temperature performance of the casting steel type and the calculation parameters of the simulation temperature field; in step S1, the calculation method of the maximum cooling rate δ of the ingot surface is: through the real-time temperature field information of the ingot, the temperature of all discrete grid nodes on the surface of the ingot in the second cooling zone is obtained; according to the real-time process control parameters including the casting speed, the temperature of all discrete grid nodes on the surface of the ingot in the second cooling zone in the next control cycle is obtained; the maximum value of the temperature change of all ingot surface nodes in the second cooling zone is calculated in real time Where T i、τ is the temperature of the grid node i on the surface of the same slice unit in the secondary cooling zone at time τ, T i、τ+1is the temperature of grid node i on the billet surface of the same slice unit in the secondary cooling zone in the next control cycle, and D is the spacing between the slice units; in step S1, when the target surface temperature method is used for control, the minimum water volume in the secondary cooling zone is the product of the minimum value within the optimal flow range of the secondary cooling nozzle and the number of nozzles in the secondary cooling zone; in step S1, step S2 is performed only when the billet surface temperature of all target control points in the secondary cooling zone of the continuous casting machine and the target surface temperature are within the allowable error range.

[0031] The heat transfer principle of secondary cooling nozzle spray cooling in continuous casting process is as follows Figure 1 As shown, the casting heats up by conduction, radiation, water heating and evaporative cooling through the clamping rollers. The present invention takes preventive measures in advance and utilizes the strong flushing of secondary cooling water to effectively prevent the accumulation of residual scale in the nozzle, ensure the uniformity of secondary cooling, maximize the service life of the secondary cooling nozzle, reduce the downtime and maintenance time of the continuous casting machine, and avoid the casting quality problems caused by nozzle blockage, which is of great significance.

[0032] Example 1

[0033] A steel plant uses a straight arc continuous casting machine to produce ingots with a cross-section of 250mm×1870mm, the steel type is X, the casting speed is 0.95m / min, and the casting temperature is 1539℃. The control parameters of the secondary cooling zone are shown in Table 1. Figure 2 As shown, zones 5 to 9 are the width-cutting areas.

[0034] Table 1 Second cooling zone control parameters

[0035]

[0036] The specific steps are as follows:

[0037] 1) During the casting process, the target surface temperature method of the dynamic secondary cooling water distribution model is used to control the water volume in each secondary cooling zone. Among them, the surface temperature of the ingot at the target control point of each secondary cooling zone has been controlled within the allowable deviation range.

[0038] 2) First, the valve of the secondary cooling zone 1 is opened to 100%; according to the current real-time casting process parameters, the dynamic secondary cooling water distribution model is used to calculate that after 6 seconds, the maximum cooling rate of the billet surface at the position 1.12m away from the meniscus in the secondary cooling control zone (hereinafter referred to as the A position billet) reaches 300℃ / (m / s) (for this casting steel type, the maximum cooling rate of the billet surface allowed under the conditions of the dynamic secondary cooling water distribution model is 300℃ / (m / s)); After the valve of the secondary cooling zone 1 is opened to 100% for 6 seconds, the secondary cooling water volume in this zone is immediately controlled by the target surface temperature control method, and the secondary cooling water volume in this zone is first gradually reduced to 289L / min, and after 10 seconds, it is gradually increased to 413L / min At this time, the surface temperature of the ingot at the target control point in zone 1 has been controlled within the allowable deviation range; the water volume in other secondary cooling zones of the casting machine is also controlled by the target surface temperature control method; as the casting proceeds, the ingot at position A leaves zone 1 and enters secondary cooling zone 2, and the cooling water volume in zone 2 gradually decreases to 378L / min, and after 14 seconds, it gradually increases to 456L / min. During this period, the surface temperature of the ingot at the target control point in zone 2 is within the allowable deviation range; the conditions in other secondary cooling zones are similar to that in zone 2; finally, as the casting proceeds, the ingot at position A leaves zone 10 and enters the air cooling zone. At the same time, the surface temperature of the ingot at the target control points in each secondary cooling zone has been controlled within the allowable deviation range.

[0039] 3) Open the valve of secondary cooling zone 2 to 100%, and the rest is the same as step 2); the steps of other secondary cooling zones are the same.

[0040] 4) When all the secondary cooling zones in the casting machine have achieved 100% valve opening, repeat step 1).

[0041] In the actual production process, the improvement effects after one year of using this method are compared with those before one year of not using this method are as follows: 1) The blockage rate of the secondary cooling nozzle is reduced from the original 3.5% to 1.8%; 2) The lateral temperature difference of the billet surface at the outlet of the casting machine under the same process conditions is reduced from the original 50°C to 26°C; 3) The incidence rate of cracks on the billet surface is reduced from the original 2.3% to 1.5%; 4) The qualified rate of center segregation of the billet is increased from the original 98.3% to 99.5%.

[0042] Example 2

[0043] A steel plant uses an arc continuous casting machine to produce ingots with a cross-section of 160mm×160mm, the steel type is X, the casting speed is 3.4m / min, and the casting temperature is 1541℃. The control parameters of the secondary cooling zone are shown in Table 2. Figure 3 shown.

[0044] Table 2 Second cooling zone control parameters

[0045]

[0046] The specific steps are as follows:

[0047] 1) During the production process of the casting machine, the target surface temperature of the dynamic secondary cooling water distribution model is used to control the water volume in each secondary cooling zone. The ingot formed by the crystallizer enters the secondary cooling spray section, where the surface temperature of the ingot at the target control point of each secondary cooling zone has been controlled within the allowable deviation range.

[0048] 2) First, open the valve of the secondary cooling zone 1 (crystallizer foot roll zone) to 100%; according to the current real-time casting process parameters, the dynamic secondary cooling water distribution model is used to calculate that after 5 seconds, the maximum cooling rate of the billet surface at the position 1.33m away from the meniscus in the secondary cooling control zone (hereinafter referred to as the A position billet) reaches 350℃ / (m / s) (for this casting steel type, the maximum cooling rate of the billet surface allowed under the conditions of the dynamic secondary cooling water distribution model is 350℃ / (m / s)); After the valve of the secondary cooling zone 1 is opened to 100% for 5 seconds, the secondary cooling water volume in this zone is immediately controlled by the target surface temperature control method. The secondary cooling water volume in this zone is first gradually reduced to 189L / min, and after 7 seconds, it is gradually increased to 273L / m in, at this time, the surface temperature of the ingot at the target control point in zone 1 has been controlled within the allowable deviation range; the water volume in other secondary cooling zones of the casting machine is also controlled by the target surface temperature control method; as the casting proceeds, the ingot at position A leaves zone 1 and enters secondary cooling zone 2, and the cooling water volume in zone 2 gradually decreases to 198L / min, and after 9 seconds, it gradually increases to 375L / min. During this period, the surface temperature of the ingot at the target control point in zone 2 is within the allowable deviation range; the conditions in other secondary cooling zones are similar to that in zone 2; finally, as the casting proceeds, the ingot at position A leaves zone 5 and enters the air cooling zone and the straightening machine. At the same time, the surface temperature of the ingot at the target control point in each secondary cooling zone has been controlled within the allowable deviation range.

[0049] 3) Open the valve of secondary cooling zone 2 to 100%, and the rest is the same as step 2); the steps of other secondary cooling zones are the same.

[0050] 4) When all the secondary cooling zones in the casting machine have achieved 100% valve opening, repeat step 1).

[0051] In the actual production process, the improvement effects after one year of using this method are compared with those before one year of not using this method are as follows: 1) The blockage rate of the secondary cooling nozzle has dropped from the original 4.2% to 2.3%; 2) The average service life of the secondary cooling nozzle has been extended from the original 2 months to 3 months; 3) The downtime of the continuous casting machine for maintenance has been reduced by 1.05%, and 4) The casting machine capacity has increased by 1.3%.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A control method for preventing blockage of continuous casting secondary cooling nozzle, characterized in that: The following steps are involved: S1 Control the water volume of each secondary cooling sub-area through the target surface temperature control method of the dynamic secondary cooling water distribution model; according to the current real-time casting process parameters, open the valve of the secondary cooling zone 1 to the maximum, and the duration is such that the maximum cooling rate of the billet surface in the secondary cooling zone 1 reaches the maximum cooling rate of the billet surface allowed by the dynamic secondary cooling water distribution model. δ The water volume in other secondary cooling sub-areas of the casting machine is controlled by the target surface temperature control method; after the valve of the secondary cooling zone 1 is opened to the maximum duration, the secondary cooling water volume of the zone is immediately controlled by the target surface temperature control method, and the position of the billet with the maximum cooling rate on the billet surface in the secondary cooling zone 1 is recorded at the same time; until the billet leaves all the secondary cooling sub-areas of the continuous casting machine; The online simulation temperature field model provides the real-time temperature of the ingot for the target surface temperature control method; δ It is related to the high temperature performance of the cast steel and the calculation parameters of the simulated temperature field; δ The calculation method is as follows: the temperature of all discrete grid nodes on the surface of the second cooling sub-region is obtained through the real-time temperature field information of the casting; the temperature of all discrete grid nodes on the surface of the casting sub-region in the next control cycle is obtained according to the real-time process control parameters including the casting speed; Real-time calculation of the maximum value of the temperature change of all the nodes on the surface of the casting billet in the secondary cooling area max{ T }=max{ },in T i、τ The mesh nodes on the surface of the ingot in the same slice unit in the secondary cooling area i exist τ The temperature of the moment, T i、τ+1 The mesh nodes on the surface of the ingot in the same slice unit in the secondary cooling sub-region i In the next control cycle, the temperature D is the slice unit spacing; When the target surface temperature method is used for control, the minimum water volume of the secondary cooling sub-area is the product of the minimum value within the optimal flow range of the secondary cooling nozzle and the number of nozzles in the secondary cooling sub-area; Step S2 is performed only when the surface temperature of the cast strand at the target control points of all secondary cooling sub-areas in the continuous casting machine and the target surface temperature are within the allowable error range; S2 Open the valve of the secondary cooling zone 2 to the maximum. The rest of the operations in this zone are the same as those in the secondary cooling zone 1. Complete the operations of the remaining secondary cooling sub-zones in the same way. S3 When all the secondary cooling sub-areas in the casting machine have achieved the maximum valve opening, repeat step S1.

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