A method for preventing corner cracks in a peritectic steel slab

Abstract

The embodiment of the application provides a method for preventing cracks in the corner of a peritectic steel slab, comprising using a right-angle crystallizer to produce a peritectic steel slab; wherein the depth of the water tank on the copper plate of the right-angle crystallizer is 11 mm; different water flow rates are distributed in the wide face and narrow face directions of the peritectic steel slab during primary cooling, and different water flow rates are distributed in the wide face and narrow face directions of the peritectic steel slab; during secondary cooling, nine cooling zones are divided, and different water distribution ratios are set for the corresponding cooling zones. In the technical scheme of the application, by means of the design of the wide face and narrow face cooling water tanks of the right-angle crystallizer, the design of the foot roller spraying, the optimization of the wide face and narrow face flow rate ratio of the primary cooling water, the optimization of the secondary cooling water, the optimization of the protective slag, the optimization of the drawing speed and temperature system and other measures, the problem that cracks are prone to occur in the corner of the peritectic steel slab when the right-angle crystallizer is used to produce the peritectic steel slab is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel production, and particularly relates to a method for preventing cracks in the corner of a peritectic steel slab. BACKGROUND

[0002] At present, the corner of a large slab is prone to cracks in the production of peritectic steel with a C content of 0.10-0.15%, mainly because the peritectic steel has a large shrinkage of the slab shell, and the cracks in the corner of the slab are difficult to control. When a continuous casting machine produces peritectic steel, the peritectic reaction occurs in the crystallizer, the shrinkage of the slab shell is large, the heat flow in the crystallizer is uneven, and thus the solidification thickness of the slab shell is uneven, and the slab is prone to cracks, especially the corner of the slab, which is two-dimensional heat transfer, and is more prone to cracks. The cracks are further expanded under the action of secondary cooling after the slab is discharged from the crystallizer. In order to solve the problem of cracks in the corner of the peritectic steel with a carbon content of 0.10-0.15%, two methods are generally used to solve the above problem: 1. The weak cooling method is used to avoid the expansion of the cracks in the corner; and 2. The chamfered crystallizer is used to solve the cracks in the corner of the slab.

[0003] In the implementation of the present application, the inventors have found that at least the following problems exist in the prior art:

[0004] The above two measures cannot effectively solve the above problem: when the weak cooling method is used, the effect is not good, and the problem of cracks in the corner cannot be fundamentally solved, and the corner of the slab needs to be cleaned after production; and when the chamfered crystallizer is used, the chamfered crystallizer is difficult to cool at the chamfered corner, and thus the service life of the crystallizer is generally low, which affects the operation rate of the continuous casting machine and the service life of the crystallizer. Therefore, how to avoid the cracks in the corner of the slab in the process of continuous casting of the peritectic steel slab by using the right-angle crystallizer is a problem to be solved. SUMMARY

[0005] The embodiment of the present application provides a method for preventing cracks in the corner of a peritectic steel slab, so as to solve the problem that the corner is prone to cracks when the right-angle crystallizer is used to produce the peritectic steel slab in the prior art.

[0006] In order to achieve the above purpose, the embodiment of the present application provides a method for preventing cracks in the corner of a peritectic steel slab, comprising: using a right-angle crystallizer to produce a peritectic steel slab; wherein the depth of the water groove on the copper plate of the right-angle crystallizer is 11 mm; different water flow rates are distributed in the wide face and narrow face directions of the peritectic steel slab when primary cooling is performed, and different water flow rates are distributed in the wide face and narrow face directions of the peritectic steel slab; in the secondary cooling process, nine cooling zones are divided, and different water distribution ratios are set for the corresponding cooling zones.

[0007] Further, the method further comprises: controlling the water flow rate in the wide face direction of the peritectic steel slab to be 7.7-8.2 m / s, and controlling the water flow rate in the narrow face direction of the peritectic steel slab to be 8.1-8.6 m / s.

[0008] Further, the method further comprises: setting different water distribution ratios for the respective cooling zones, specifically: the first cooling zone accounts for 11.5%, the second cooling zone accounts for 14.5%, the third cooling zone accounts for 16.5%, the fourth cooling zone accounts for 13.5%, the fifth cooling zone accounts for 10.5%, the sixth cooling zone accounts for 7%, the seventh cooling zone accounts for 11.2%, and the eighth cooling zone accounts for 7.8%, and the ninth cooling zone accounts for 7.5%.

[0009] Further, the method further comprises: for the cooling zones other than the first cooling zone, the ratio of the water amount distributed to the edge of the peritectic steel slab to the total distribution water amount of the corresponding cooling zone is determined according to the following formula:

[0010]

[0011] wherein q is the ratio of the water amount distributed to the edge of the peritectic steel slab to the total distribution water amount of the corresponding cooling zone, W max is the maximum width of the peritectic steel slab, in mm, W min is the minimum width of the peritectic steel slab, in mm, and K is a preset width variation coefficient, and K ranges from 0.5 to 1.0.

[0012] Further, the method further comprises: using a protective slag when producing the peritectic steel slab; wherein the weight percentage of each chemical component in the protective slag is: SiO2: 26-28 Wt%, CaO: 32.5-34.5 Wt%, Al2O3: 2-3 Wt%, Na2O: 9-11 Wt%, and F: 6-8 Wt%; the melting point of the protective slag is 1020-1080℃; and the viscosity of the protective slag is 1.0-1.5 poise.

[0013] Further, the method further comprises: controlling the withdrawal speed to be 1.0-1.2 m / min.

[0014] Further, the method further comprises: controlling the superheat of the molten steel to be 20-30℃.

[0015] Further, the method further comprises: in the range of the first cooling zone, arranging 7 rows of cooling nozzles in the narrow face direction of the peritectic steel slab.

[0016] Further, the method further comprises that nine cooling zones adopt different nozzle forms.

[0017] The above technical solution has the following beneficial effects:

[0018] In the technical solution of the present application, the commonly used right-angle crystallizer is used, and the problem of reduced service life caused by replacing the chamfered crystallizer is avoided; meanwhile, through the improved design of the wide surface and narrow surface cooling water tank of the right-angle crystallizer, the foot roller spraying design, the optimization of the water flow rate ratio of the wide surface and narrow surface in the primary cooling process, the water optimization in the secondary cooling process, the optimization of the protective slag, the optimization of the drawing speed and temperature, the problem of corner cracks of the peritectic steel cast slab produced by using the right-angle crystallizer is solved. According to actual tests, after the measures of the present application are adopted, when the peritectic steel cast slab with carbon content of 0.10-0.15% is produced, the cast slab corner has no cracks, and the cleaning-free level can be reached, and the product quality and production efficiency are effectively improved. In addition, the service life of the crystallizer copper plate and the operation rate of the casting machine can also be improved after the technical solution is adopted. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0020] The embodiments of the present application provide a method for preventing cracks in the corner of a peritectic steel slab, which comprises:

[0021] S100, producing a peritectic steel slab by using a right-angle crystallizer; wherein the water tank depth on the crystallizer copper plate in the right-angle crystallizer is 11mm;

[0022] S200, when primary cooling is performed, different water flow rates are distributed in the wide surface and narrow surface directions of the peritectic steel slab, and different water flow rates are distributed in the wide surface and narrow surface directions of the peritectic steel slab;

[0023] S300, in the secondary cooling process, nine cooling zones are divided, and different water distribution ratios are set for the corresponding cooling zones.

[0024] At present, in the right-angle crystallizer, the copper plate of the crystallizer is generally designed with a 15mm deep water groove, and it is considered through analysis that the depth is too large, thereby causing the shell shrinkage temperature gradient to be too large, which is directly related to the occurrence of the corner crack of the cast slab, therefore, the application adopts a 11mm shallow water groove design: the width of the water groove on the wide surface of the copper plate of the crystallizer is 10.84mm, and the depth is 11mm; the width of the water groove on the narrow surface of the copper plate of the crystallizer is 6mm, and the depth is 11mm. At the same time, the distance between the adjacent water grooves on the wide surface of the crystallizer is different according to the heat transfer, so as to maximize the problem of the too large shell shrinkage temperature gradient. In addition, when the peritectic steel is cast, if the water distribution of the crystallizer does not match the casting speed of the continuous casting slab, the cooling intensity of the crystallizer will be too large or too small, the former will increase the solidification shrinkage of the primary shell of the continuous casting slab in the meniscus region of the crystallizer, intensify the uneven cooling of the continuous casting slab in the crystallizer, thereby being not conducive to the uniform growth of the solidified shell, and increasing the probability of surface crack; the latter will cause the shell thickness of the continuous casting slab at the outlet of the crystallizer to fail to meet the requirement of the safe shell thickness (≥15mm), and increase the risk of leakage; therefore, in order to alleviate the stress unevenness caused by the uneven cooling of the wide surface and the narrow surface and lead to the corner crack, the water amount and flow rate ratio between the wide surface and the narrow surface are designed.

[0025] Further, the step S200 specifically comprises:

[0026] The water flow in the wide surface direction of the peritectic steel slab is controlled to be 3200-3400L / min, and the water flow rate is controlled to be 7.7-8.2m / s; the water flow in the narrow surface direction of the peritectic steel slab is controlled to be 430-460L / min, and the water flow rate is controlled to be 8.1-8.6m / s.

[0027] Through stress simulation analysis and multiple field tests, when the flow rate ratio and water amount distribution of the wide surface and the narrow surface in the primary cooling process are optimized to the above numerical range, the crack occurrence probability can be effectively reduced.

[0028] Further, the step S300 specifically comprises:

[0029] The water amount distribution ratio of the nine cooling zones is as follows: the first cooling zone accounts for 11.5%, the second cooling zone accounts for 14.5%, the third cooling zone accounts for 16.5%, the fourth cooling zone accounts for 13.5%, the fifth cooling zone accounts for 10.5%, the sixth cooling zone accounts for 7%, the seventh cooling zone accounts for 11.2%, the eighth cooling zone accounts for 7.8%, and the ninth cooling zone accounts for 7.5%. It is proved through multiple tests that the distribution ratio is reasonable, the surface temperature of the continuous casting slab is uniform, the quality is good, and good effects can be achieved.

[0030] Further, the step S300 further comprises:

[0031] For the rest of the cooling zones except the first cooling zone, the proportion of the water amount allocated to the edge of the peritectic steel slab to the total allocated water amount of the corresponding cooling zone is determined according to the following formula:

[0032]

[0033] wherein q is the proportion of the water amount allocated to the edge of the peritectic steel slab to the total allocated water amount of the corresponding cooling zone, W max is the maximum width of the peritectic steel slab, W min is the minimum width of the peritectic steel slab, unit: mm, K is a preset width variation coefficient, unit: mm, and the range of K is 0.5-1.0.

[0034] During the secondary cooling, except the first zone, the water amount of the edge of the other zones is controlled according to different regression coefficients of the slab width, so as to solve the problem of overcooling of the edge and corner of the slab. Generally, the water amount of the edge is controlled according to (the maximum width of the slab-the minimum width of the slab) / the maximum width of the slab, and the water amount of the edge is adjusted according to the width variation coefficient, which is generally controlled between 0.4-1.0. For example, the width range of the slab produced by the caster is 1000-1600mm, the maximum width is 1600mm, and the minimum width is 1000mm. The width variation coefficient is gradually increased with the increase of the width of the slab. If the width of the produced peritectic steel slab is 1000mm, the width variation coefficient is 0.5. When the width of the slab reaches the maximum section of 1600mm, the width variation coefficient reaches the maximum of 1.0. When the peritectic steel slab with the width of 1000mm is produced, the width variation coefficient is 0.5, and according to the above formula, q=0.1875, that is, the water amount allocated to the edge and corner of the slab accounts for 18.75% of the total water amount in the corresponding cooling zone.

[0035] Further, the method for preventing cracks from occurring at the corner of the peritectic steel slab further comprises:

[0036] S400, using a protective slag in the production of the peritectic steel slab; wherein,

[0037] The weight percentage of each chemical component in the protective slag is:

[0038] SiO2: 26-28wt%, CaO: 32.5-34.5wt%, Al2O3: 2-3wt%, Na2O: 9-11wt%, F: 6-8wt%; the melting point of the protective slag is 1020-1080℃; and the viscosity of the protective slag is 1.0-1.5 poise.

[0039] Peritectic steel is easy to produce cracks due to its carbon content in the peritectic zone, the design of the mold powder mainly prevents cracks, so the high basicity of the mold powder is beneficial to prevent the slab cracks, but the high basicity mold powder is easy to cause the slab sticking, therefore, for the peritectic steel production, both the slab surface quality and the sticking prevention should be considered. The mold powder design in the application adopts high basicity, and the low viscosity and melting point design is adopted to reduce the sticking.

[0040] Further, the step S100 further comprises:

[0041] The drawing speed is controlled to 1.0-1.2 m / min, and the overheating degree of the molten steel is controlled to 20-30 DEG C.

[0042] In the peritectic steel slab continuous casting production process, the applicant believes that the temperature and the drawing speed must be matched. The peritectic steel must control the appropriate overheating degree and the drawing speed matching, otherwise the corner cracks are easy to produce. It is proved by the actual measurement that the overheating degree of the molten steel is controlled to 20-30 DEG C, and the drawing speed is controlled to 1.0-1.2 m / min. The overheating degree is too low to cause the low temperature in the later pouring stage, which is easy to cause the machine stop, the pouring temperature is too high to be not conducive to the control of the corner cracks of the slab, and the drawing speed is too low to be not conducive to the pouring smooth, and the drawing speed is too high to cause the large liquid level fluctuation of the mold, which is also easy to produce the corner cracks.

[0043] Further, the step S300 further comprises:

[0044] In the first cooling zone range, 7 rows of cooling nozzles are arranged in the narrow surface direction of the peritectic steel slab.

[0045] In the technical solution, special foot roller (first zone) spraying design is also carried out. At present, the narrow surface nozzle of the ordinary continuous casting machine is 5 rows, the nozzle is increased to 7 rows in the application, the design not only can prevent the slab bulging under the high drawing speed, thereby causing the corner cracks, but also can avoid the corner cracks through the water quantity control.

[0046] Further, the step S300 further comprises that the nine cooling zones adopt different nozzle forms.

[0047] In order to obtain better cooling effect, different nozzles can be arranged in each cooling zone. For example, the first cooling zone adopts a round nozzle, and the other zones adopt a flat nozzle, and the opening angle of the flat nozzle can be 90-120 DEG. At the same time, the water quantity of each nozzle can be different, but the total water quantity distribution ratio of each zone still needs to meet the set ratio that the first cooling zone accounts for 11.5%, the second cooling zone accounts for 14.5%, the third cooling zone accounts for 16.5%, the fourth cooling zone accounts for 13.5%, the fifth cooling zone accounts for 10.5%, the sixth cooling zone accounts for 7%, the seventh cooling zone accounts for 11.2%, the eighth cooling zone accounts for 7.8%, and the ninth cooling zone accounts for 7.5%.

[0048] In the detailed description above, various features are grouped together in single embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than the claims do. Rather, inventive embodiments can lie in fewer than all features of a single disclosed embodiment. Thus, the following claims are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate preferred embodiment. By way of example, an element in one claim can be a

[0049] The disclosed embodiments are to be considered as illustrative of the principles of the application. Numerous modifications and adaptations will be readily apparent to those skilled in the art in view of this description. This application is therefore to be considered as including all such modifications and adaptations insofar as they come within the scope of the principles of the application. Accordingly, the disclosure is not to be limited to the specific embodiments disclosed herein, but only to the specific embodiments of the application as defined in the appended claims.

[0050] The above detailed description merely describes preferred embodiments of the application, and is not intended to limit the scope of the application. Various modifications of the embodiments described herein will be apparent to those skilled in the art, and it is intended that the scope of the application be limited solely by the claims appended hereto.

Claims

1. A method for preventing cracks at the corners of peritectic steel slabs, characterized in that, include: A right-angle crystallizer is used to produce peritectic steel slabs; wherein, in the right-angle crystallizer, the depth of the water tank on the copper plate of the crystallizer is 11 mm; During a single cooling process, different water flow rates and different water flow velocities are distributed in the wide and narrow directions of the peritectic steel slab. During the secondary cooling process, nine cooling zones are divided, and different water distribution ratios are set for each cooling zone. The specific method for setting different water distribution ratios for each cooling zone is as follows: The water distribution ratio of the nine cooling zones is as follows: 11.5% for the first cooling zone, 14.5% for the second cooling zone, 16.5% for the third cooling zone, 13.5% for the fourth cooling zone, 10.5% for the fifth cooling zone, 7% for the sixth cooling zone, 11.2% for the seventh cooling zone, 7.8% for the eighth cooling zone, and 7.5% for the ninth cooling zone. For the remaining cooling zones other than the first cooling zone, the proportion of water allocated to the edge of the peritectic steel slab relative to the total allocated water volume of the corresponding cooling zone is determined by the following formula: Where q is the proportion of water allocated to the edge of the peritectic steel slab to the total water allocated to the corresponding cooling zone, and W max W represents the maximum width of the peritectic steel slab in mm. min The minimum width of the peritectic steel slab is in mm, and K is a preset width variation coefficient, ranging from 0.5 to 1.

0.

2. The method for preventing cracks at the corners of peritectic steel slabs as described in claim 1, characterized in that, The method of distributing different water flow rates and different water flow velocities in the wide and narrow directions of the peritectic steel slab specifically includes: The water flow rate in the wide direction of the peritectic steel slab is controlled at 3200-3400 L / min, and the water velocity is controlled at 7.7-8.2 m / s; the water flow rate in the narrow direction of the peritectic steel slab is controlled at 430-460 L / min, and the water velocity is controlled at 8.1-8.6 m / s.

3. The method for preventing cracks at the corners of peritectic steel slabs as described in claim 1, characterized in that, Also includes: Protective slag is used in the production of peritectic steel slabs; among which... The weight percentages of each chemical component in the protective slag are as follows: SiO2: 26~28Wt%, CaO: 32.5~34.5Wt%, Al2O3: 2~3Wt%, Na2O: 9~11Wt%, F: 6~8Wt%; The melting point of the protective slag is 1020℃~1080℃; The viscosity of the protective slag is 1.0 poise to 1.5 poise.

4. The method for preventing cracks at the corners of peritectic steel slabs as described in claim 1, characterized in that, Also includes: Control the pulling speed between 1.0 and 1.2 m / min.

5. The method for preventing cracks at the corners of peritectic steel slabs as described in claim 1, characterized in that, Also includes: The superheat of the molten steel should be controlled at 20-30℃.

6. The method for preventing corner cracks in peritectic steel slabs as described in claim 1, characterized in that, Within the first cooling zone, seven rows of cooling nozzles are arranged in the narrow face direction of the peritectic steel slab.

7. The method for preventing cracks at the corners of peritectic steel slabs as described in claim 1, characterized in that, The nine cooling zones employ different nozzle designs.

Images