A method for preventing and controlling cutting cracks in continuous casting billets

Abstract

The present invention provides a method for preventing and controlling cutting cracks generated in continuous casting billets, which is applied to crack-sensitive steel types, including: S1, cutting the billet by flame cutting through a cutting gun; S2, after cutting the billet, the cutting gun closes the valve and turns off the flame, while continuing to move forward without stopping, and after a certain period of movement, the cutting gun stops moving again and returns to its original position. The present invention prevents the gas from being turned off by closing the valve and turning off the flame through the cutting gun, and continues to move along the way to discharge the residual high-pressure gas in the pipeline, so as to prevent the gas from being turned off at a point on the billet, and to concentrate on flushing the high-temperature billet that has just been cut, thereby preventing the shallow grooves and slag from being generated, reducing the thickness of the heat-affected zone at the cutting part, and reducing the segregation of crack-inducing elements when recrystallizing the cutting molten zone, avoiding the billet from generating cutting cracks after cutting, and reducing the burrs caused by slag, so as to avoid scar defects that are easily formed during the rolling process, reduce billet quality accidents, and improve the yield rate of billet products, with timeliness and effectiveness.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous casting machine slab cutting in the steel field, and in particular to a method for preventing and controlling cutting cracks generated in continuous casting slabs. Background Art

[0002] Continuous casting technology is widely used in the iron and steel metallurgical industry. Since some types of continuous casting billets will produce crack defects on the flame cutting end face during the cutting process, cracks will occur at the head or tail of the continuous casting billet during the subsequent rolling process. In severe cases, the head or tail web will tear in a "V" shape along the longitudinal direction, resulting in an increase in the cutting of the head and tail of the rolled plate, or even the scrapping of the entire plate. Crack defects not only affect product quality, but also waste steel and increase production costs. At present, the measures taken by the industry to suppress crack defects in continuous casting billets include: improving billet segregation, controlling rolling compression ratio, normalizing heat treatment, steel plate warm cutting and steel plate insulation, but the above measures are complicated to handle and have little effect.

[0003] According to the relevant Chinese patent document CN110814309B, in this scheme, the thickness of the heat affected zone at the cutting part is reduced by steadily and quickly cutting and reducing the flame cutting time, and the segregation of crack-inducing elements during recrystallization of the cutting molten zone is reduced; then, during the cutting stage, the cutting gun is first turned off and then stopped to avoid cutting cracks in the ingot after cutting.

[0004] As the relevant patent literature does not point out specific quantitative operation instructions, when the flameout and then stop operation are used in actual production, for crack-sensitive steel types, a shallow groove will be generated at the middle stop position of the ingot cutting, and a small amount of high-temperature slag will accumulate below the groove. This is due to the discharge and scouring of the high-pressure residual gas in the pipe behind the valve when the cutting gun is closed and the flameout is turned off. It will also increase the segregation of crack-inducing elements during recrystallization in the cutting molten zone, causing cracks in the head or tail of the subsequent rolled continuous casting ingot. The high-temperature slag below the groove will form burrs, which are prone to form scar defects during the rolling process, affecting product quality.

[0005] In order to solve the problem of high-pressure residual gas flushing in the pipeline when the cutting gun is closed and the valve is turned off, some equipment manufacturers have designed imported coaxial solenoid valves to replace the original two-position two-way solenoid valves to solve the problem. Although the coaxial solenoid valve responds quickly and closes in time, the two-position three-way structure of the valve body is equivalent to adding a residual gas exhaust hole, which has some effect, the coaxial solenoid valve is expensive, and the annual equipment consumption and replacement labor costs increase, which is not conducive to production cost reduction and efficiency improvement. In view of the above shortcomings, combined with the experience of field use, a simple, fast and effective method for preventing and controlling continuous casting billet cutting cracks has been invented, thereby effectively avoiding the flame cutting cracks generated by continuous casting billets. Summary of the invention

[0006] In response to the technical problems raised above, a method for preventing and controlling cutting cracks in a continuous casting billet is provided.

[0007] The technical means adopted by the present invention are as follows:

[0008] A method for preventing and controlling cutting cracks in a continuous casting billet, which is applied to crack-sensitive steel grades, comprises:

[0009] S1. Cutting the ingot by flame cutting with a cutting gun;

[0010] S2. After cutting the ingot, the cutting gun turns off the valve and extinguishes the flame, while continuing to move forward. After moving for a certain period of time, the cutting gun stops moving and returns to its original position.

[0011] Furthermore, the cutting gun is a double gun, including a main gun and a secondary gun.

[0012] Furthermore, the main gun and the auxiliary gun cut the ingot from both sides synchronously. After the main and auxiliary guns meet, the auxiliary gun turns off and returns, and the main gun continues to cut until the ingot is cut off. At this time, the main gun closes the valve and turns off, and the main gun body continues to move for a certain period of time.

[0013] Furthermore, the travel time of the cutting gun after the valve is closed and the flame is extinguished is determined according to the effect of residual gas discharge and the travel track length of the cutting gun, and can be long or short.

[0014] Furthermore, after the valve is closed and the flame is extinguished, the cutting gun moves for 2s to 3s before stopping and returning to its original position.

[0015] Furthermore, after the cutting gun is turned off by closing the valve, it stops moving after running for 2 seconds.

[0016] Furthermore, the cutting gun is connected to a PLC controller, and the running time is controlled by the PLC controller.

[0017] Furthermore, the ingot is a crack-sensitive steel grade, and has a niobium content of ≥0.03% and a carbon content of between 0.06% and 0.14%.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The present invention shuts off the flame of the cutting gun without stopping the gun, and continues to discharge the residual high-pressure gas in the pipeline along the way, so as to prevent the gas flameout position from corresponding to a point on the billet, and concentrates on flushing the high-temperature billet that has just been cut, thereby preventing the shallow grooves and slag from being generated, reducing the thickness of the heat-affected zone of the cut-off part, and reducing the segregation of crack-inducing elements during recrystallization in the cutting molten zone, avoiding the billet from generating cutting cracks after cutting, reducing the burrs caused by slag, avoiding the scar defects that are easily formed during the rolling process, reducing billet quality accidents, and improving the yield rate of billet products, with timeliness and effectiveness. After the system-related parameters of the present invention are set, they do not need to be adjusted frequently, the operation workload is small, the labor intensity is low, and the economic benefits are significant.

[0020] Based on the above reasons, the present invention can be widely promoted in the fields of continuous casting machine casting cutting and the like in the steel field. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 A schematic diagram of a method for preventing and controlling cutting cracks in a continuous casting slab provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps described in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0027] The technical problem to be solved by the present invention is to provide a method for preventing and controlling cutting cracks in continuous casting billets. After the billet is cut, the flame cutting gun first closes the valve and extinguishes the flame, while the cutting gun body continues to move, discharging high-pressure residual gas in the gas pipeline behind the valve along the way to prevent concentrated flushing at one point. After running for a period of time, the cutting gun stops moving to reduce the thickness of the heat-affected zone at the cutting position, and at the same time reduce the segregation of crack-inducing elements during recrystallization of the cutting molten zone, so as to avoid cutting cracks in the continuous casting billet after cutting.

[0028] Another object of the present invention is to provide a method for preventing and controlling cutting cracks in the above-mentioned continuous casting billet.

[0029] To achieve the above object, the present invention provides the following technical solutions:

[0030] The present invention provides a method for preventing and controlling cutting cracks generated in a continuous casting billet, which is applied to crack-sensitive steel grades, comprising:

[0031] S1. Cutting the ingot by flame cutting with a cutting gun;

[0032] S2. After cutting the ingot, the cutting gun turns off the valve and extinguishes the flame, while continuing to move forward. After moving for a certain period of time, the cutting gun stops moving and returns to its original position.

[0033] As a preferred embodiment, the cutting gun of the present invention is a double gun, including a main gun and a sub-gun. The ingot is cut by flame cutting, and the main and sub-guns cut the ingot synchronously from both sides of the ingot. After the two guns meet, the sub-gun turns off and returns, and the main gun continues to cut until the ingot is cut off. At this time, the main gun turns off the valve and the gun body keeps moving. After the main gun turns off the valve and moves for 2s to 3s, it stops moving forward and returns to its original position. The main gun continues to move after it turns off, so as to discharge the residual gas in the high-pressure pipeline along the way, prevent the scouring caused by the concentrated discharge of high-pressure gas, and produce shallow grooves and slag at the flameout position of the high-temperature ingot that has just been cut off, so as to reduce the thickness of the heat-affected zone of the cutting part, and reduce the segregation of crack-inducing elements when the molten zone of the ingot is recrystallized; reduce burrs caused by slag, and avoid the formation of scar defects during rolling.

[0034] As a preferred embodiment, the cutting gun body travels for 2s, which can be longer or shorter depending on the effect of residual gas discharge and the travel track length of the cutting gun.

[0035] As a preferred embodiment, the ingot is a crack-sensitive steel, and the niobium content is ≥ 0.03%, and the carbon content is between 0.06% and 0.14%.

[0036] Example 1

[0037] The purpose of the present invention is to provide a method for preventing and controlling cutting cracks in continuous casting billets, which is applied to crack-sensitive steel types. After the billet is cut, the main flame cutting gun first turns off the valve to extinguish the flame, while the cutting gun body continues to move. After running for a period of time, the residual high-pressure gas in the pipeline is discharged along the way, and then the cutting gun stops moving to prevent the concentrated point from scouring the high-temperature billet that has just been cut. This reduces the thickness of the heat-affected zone at the cutting site, and at the same time reduces the segregation of crack-inducing elements during recrystallization in the cutting molten zone, so as to avoid the billet from producing cutting cracks after cutting, and reduce the burrs caused by slag hanging at the billet extinguishing point, so as to avoid the formation of scar defects during the rolling process, so that the billet quality is significantly improved, and at the same time, the product yield rate is improved, which is timely and effective. After the system-related parameters of the present invention are set, they do not need to be adjusted frequently.

[0038] Another object of the present invention is to provide a method for preventing and controlling cutting cracks in the above-mentioned continuous casting billet.

[0039] See also Figure 1 The present invention provides a method for preventing and controlling cutting cracks in continuous casting billets, which is applied to crack-sensitive steel grades, comprising:

[0040] S1. Cut the ingot by flame cutting using the main gun and the auxiliary gun;

[0041] S2, the main and auxiliary guns cut the billet synchronously from both sides of the billet. When the main and auxiliary guns meet, the auxiliary gun turns off and returns, and the main gun continues to cut until the billet is cut off. At this time, the main gun turns off the valve and turns off the flame without stopping;

[0042] S3, the main gun body moves for about 2 seconds and stops, then returns to the home position. The cutting gun body moves for 2 seconds, which can be longer or shorter depending on the effect of residual gas discharge and the travel track length of the cutting gun. The travel time can be added and set in the program of the PLC controller of the cutting gun (the existing controller can be used in this embodiment).

[0043] Preferably, in order to achieve stable and efficient cutting, the flame cutting method is double-gun cutting, using a main gun and a secondary gun. The main and secondary guns cut the ingot synchronously from both sides of the ingot. After the two guns meet, the secondary gun turns off and returns, and the main gun continues cutting until the ingot is cut off.

[0044] Preferably, the ingot is a crack-sensitive steel, and has a niobium content of ≥0.03% and a carbon content of between 0.06% and 0.14%.

[0045] There are two main reasons for the generation of cutting cracks. One is that the temperature of the ingot rises during flame cutting, resulting in local phase change, and phase change stress is generated at this position; the other is the characteristics of the steel type, or the segregation is more serious, resulting in uneven mechanical properties of the ingot, or the composition is highly sensitive to cracks. A method for preventing and controlling cutting cracks in a continuous casting ingot according to the present invention closes the valve of the cutting gun and turns off the flame without stopping the gun, and continues to discharge the residual gas in the high-pressure pipeline along the way, so as to prevent the residual gas from concentrating on flushing the high-temperature ingot that has just been cut at the point corresponding to the ingot when the flame is turned off, and prevent the shallow grooves and slag caused thereby. Reduce the thickness of the heat-affected zone at the cutting part, reduce the burrs caused by slag, so as to avoid scar defects formed during the rolling process, eliminate poor cutting, and at the same time reduce the segregation of crack-inducing elements during recrystallization in the cutting molten zone, so as to avoid cutting cracks in the ingot after cutting.

[0046] In order to prevent cutting crack defects, the existing technology mainly takes measures on steel plates, while the present invention mainly improves the method of cutting the ingot. After use, there is no cutting crack on the end face of the ingot, which is timely and effective. The present invention mainly aims at the problem that niobium-containing steel is prone to cutting crack defects when cutting the ingot. It optimizes and controls the cutting method, and specifically suppresses the crack sensitivity of the steel, thereby achieving a good cutting effect, effectively reducing the generation of crack defects, reducing ingot quality accidents, and improving the yield rate of ingot products. At the same time, it does not use expensive imported coaxial solenoid valves, reduces equipment consumption and labor replacement costs, and is conducive to reducing production costs and increasing efficiency.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preventing and controlling cutting cracks in continuous casting billets, applied to crack-sensitive steel grades, characterized in that: include: S1. Cutting the ingot by flame cutting with a cutting gun; S2. After cutting the ingot, the cutting gun turns off the valve and extinguishes the flame, while continuing to move forward. After moving for 2s to 3s, the cutting gun stops moving and returns to its original position.

2. The method for preventing and controlling cutting cracks in continuous casting slabs according to claim 1, characterized in that: The cutting gun is a double gun, including a main gun and a secondary gun.

3. The method for preventing and controlling cutting cracks in continuous casting slabs according to claim 2, characterized in that: The main gun and the auxiliary gun cut the ingot synchronously from both sides of the ingot. After the main gun and the auxiliary gun meet, the auxiliary gun turns off and returns, and the main gun continues to cut until the ingot is cut off. At this time, the main gun closes the valve and turns off, and the main gun body continues to move for a certain period of time.

4. The method for preventing and controlling cutting cracks in continuous casting slabs according to claim 1, characterized in that: The travel time of the cutting gun after the valve is closed and the flame is extinguished is determined according to the effect of residual gas discharge and the travel track length of the cutting gun, and can be long or short.

5. The method for preventing and controlling cutting cracks in continuous casting slabs according to claim 1, characterized in that: The cutting gun stops moving after the valve is closed and the flame is extinguished after running for 2 seconds.

6. The method for preventing and controlling cutting cracks in continuous casting slabs according to claim 1, characterized in that: The cutting gun is connected to a PLC controller, and the running time is controlled by the PLC controller.

7. The method for preventing and controlling cutting cracks in continuous casting slabs according to claim 1, characterized in that: The ingot is a crack-sensitive steel grade, and has a niobium content of ≥0.03% and a carbon content of between 0.06% and 0.14%.

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