阅读说明：本技术 预防板坯连铸机纵裂纹产生及粘结漏钢的方法 (Method for preventing longitudinal crack generation and bonding breakout of slab caster ) 是由 韦耀环 韦军尤 王志国 王利星 程建军 陈秋宇 张德俊 杜国利 杨建� 宋育仕 于 2019-09-02 设计创作，主要内容包括：本发明实施例提供一种预防板坯连铸机纵裂纹产生及粘结漏钢的方法,其特征在于,所述预防板坯连铸机纵裂纹产生及粘结漏钢方法包括：通过计算机自动控制连铸机工作拉速V<Sub>1</Sub>以每10秒下降0.02m/min幅度下降到换水口拉速值V<Sub>2</Sub>,换水口拉速值V<Sub>2</Sub>为0.80～0.85m/min,且维持换水口拉速值V<Sub>2</Sub>三分钟,同时结晶器下水口进行更换,保护渣进行渣条检查；其次,通过计算机自动控制程序将连铸机工作拉速以每40秒提升0.03m/min幅度上升到1m/min；然后,退出计算机自动控制程序,同时连铸机保持在1m/min拉速条件下2-3min；最后,再以每40秒提升0.03m/min幅度将连铸机拉速提升到1.15～1.50m/min。(The embodiment of the invention provides a method for preventing longitudinal cracks of a slab casting machine from generating and bonding breakout, which is characterized by comprising the steps of automatically controlling the working pulling speed V 1 of the slab casting machine to be lowered by 0.02m/min per 10 seconds to a water changing pulling speed value V 2 through a computer, controlling the water changing pulling speed value V 2 to be 0.80-0.85 m/min, maintaining the water changing pulling speed value V 2 for three minutes, replacing a lower water gap of a crystallizer, carrying out slag strip inspection on protective slag, raising the working pulling speed of the slab casting machine to 1m/min by 0.03m/min per 40 seconds through the automatic control program of the computer, withdrawing the automatic control program of the computer, maintaining the pulling speed of the slab casting machine at 1m/min for 2-3min, and raising the pulling speed of the slab casting machine to 1.15-1.50 m/min by 0.03m/min per 40 seconds.)

1. The method for preventing the longitudinal cracks of the slab caster from generating and bonding the breakout is characterized by comprising the following steps of:

Automatically controlling the working pulling speed V ₁ of the continuous casting machine to drop to a water changing port pulling speed value V ₂ by 0.02m/min per 10 seconds through a computer, wherein the water changing port pulling speed value V ₂ is 0.80-0.85 m/min, the water changing port pulling speed value V ₂ is maintained for three minutes, a water discharging port of a crystallizer is replaced at the same time, and the covering slag is subjected to slag strip inspection;

Secondly, the working drawing speed of the continuous casting machine is increased to 1m/min by 0.03m/min per 40 seconds through a computer automatic control program;

Then, quitting the computer automatic control program, and simultaneously keeping the continuous casting machine at the drawing speed of 1m/min for 2-3 min;

and finally, the pulling speed of the continuous casting machine is increased to 1.15-1.50 m/min by increasing the pulling speed by 0.03m/min every 40 seconds.

2. the method for preventing the longitudinal crack generation and the bonding breakout of the slab caster as claimed in claim 1, wherein the method for preventing the longitudinal crack generation and the bonding breakout of the slab caster is suitable for the steel grade with the carbon content of 0.10-0.19 Wt%, the steel section width of 220mm, the length of 1500-1820 mm, the liquidus temperature of the molten steel of 1511-1528 ℃ and the superheat degree of 10-30 ℃.

3. the method for preventing the generation of longitudinal cracks and the bonding of breakout in a slab caster as claimed in claim 2, wherein the carbon content of the steel is 0.07-0.09 Wt%, the liquidus temperature of the molten steel is 1519-1521 ℃, the degree of superheat is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the operating casting speed V ₁ is 1.27-1.36 m/min.

4. The method for preventing the generation of longitudinal cracks and the bonding of breakout in a slab caster as claimed in claim 2, wherein the carbon content of the steel is 0.07-0.09 Wt%, the liquidus temperature of the molten steel is 1519-1521 ℃, the degree of superheat is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the operating casting speed V ₁ is 1.12-1.15 m/min.

5. The method for preventing the generation of longitudinal cracks and the bonding of breakout in a slab caster as claimed in claim 2, wherein the carbon content of the steel is 0.08-0.12 Wt%, the liquidus temperature of the molten steel is 1518-1521 ℃, the degree of superheat is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the operating casting speed V ₁ is 1.27-1.33 m/min.

6. The method for preventing the generation of longitudinal cracks and the bonding of breakout in a slab caster as claimed in claim 2, wherein the carbon content of the steel is 0.08-0.12 Wt%, the liquidus temperature of the molten steel is 1518-1521 ℃, the degree of superheat is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the operating casting speed V ₁ is 1.12-1.15 m/min.

7. The method for preventing the generation of longitudinal cracks and the bonding breakout of a slab caster according to claim 2, wherein the carbon content of the steel is 0.12-0.16 Wt%, the liquidus temperature of the molten steel is 1514-1519 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the operating casting speed V1 is 1.36-1.42 m/min.

8. The method for preventing the generation of longitudinal cracks and the bonding breakout of the slab caster as claimed in claim 2, wherein the carbon content of the steel is 0.12-0.16 Wt%, the liquidus temperature of the molten steel is 1514-1519 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the operating casting speed V1 is 1.18-1.21 m/min.

9. The method for preventing the generation of longitudinal cracks and the bonding breakout of a slab caster according to claim 2, wherein the carbon content of the steel is 0.16-0.19 Wt%, the liquidus temperature of the molten steel is 1514-1517 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the operating casting speed V1 is 1.24-1.27 m/min.

10. The method for preventing the generation of longitudinal cracks and the bonding breakout of the slab caster as claimed in claim 2, wherein the carbon content of the steel is 0.16-0.19 Wt%, the liquidus temperature of the molten steel is 1514-1517 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the operating casting speed V1 is 1.18 m/min.

Technical Field

The invention relates to the field of steel production and manufacturing, in particular to a method for preventing longitudinal cracks of a slab caster from generating and bonding breakout.

Background

the surface longitudinal cracks of the slab continuous casting billet can affect the quality performance of a casting billet rolling product, and even can cause casting billet waste and continuous casting machine leakage when the longitudinal cracks are serious. The study indicated that: longitudinal cracks are caused by the thickness nonuniformity of a primary blank shell of a meniscus of the crystallizer, the tensile stress acting on the blank shell exceeds the allowable strength of steel, stress concentration is generated at the weak part of the blank shell to cause surface fracture, and the fracture is expanded in a secondary cooling area after the blank shell is taken out of the crystallizer.

The water gap changing operation in the slab production process (when changing the water gap, the pulling speed is reduced to a certain value to complete the replacement of the lower water gap of the crystallizer, then the pulling speed is increased to the working pulling speed), along with the large-range fluctuation of the pulling speed, the fluctuation of the liquid level of the steel in the crystallizer and the consumption of the protective slag in the crystallizer have great changes, and the change of the production working conditions in the crystallizers ensures that the occurrence probability of longitudinal cracks and the occurrence probability of bonding of the casting blank in the water gap changing process are particularly sensitive, so the water gap changing operation is used as the unsteady condition mainly occurring in the slab production, and the control of the longitudinal cracks on the surface of the casting blank and the prevention of bonding and steel leakage are always the key and difficult points in.

In the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art: cracks are easy to appear on the surface of the slab continuous casting billet, and bonding breakout is easy to occur.

Disclosure of Invention

The embodiment of the invention provides a method for preventing longitudinal cracks of a slab caster from generating and bonding breakout, which has the advantages of meeting the requirements of production rhythm, reducing the probability of surface cracks and bonding breakout of a casting blank and the like.

The embodiment of the invention provides a method for preventing longitudinal cracks of a slab caster from generating and bonding breakout, which comprises the following steps:

Automatically controlling the working pulling speed V ₁ of the continuous casting machine to drop to a water changing port pulling speed value V ₂ by 0.02m/min per 10 seconds through a computer, wherein the water changing port pulling speed value V ₂ is 0.80-0.85 m/min, the water changing port pulling speed value V ₂ is maintained for three minutes, a water discharging port of a crystallizer is replaced at the same time, and the covering slag is subjected to slag strip inspection;

Secondly, the working drawing speed of the continuous casting machine is increased to 1m/min by 0.03m/min per 40 seconds through a computer automatic control program;

Then, quitting the computer automatic control program, and simultaneously keeping the continuous casting machine at the drawing speed of 1m/min for 2-3 min;

And finally, the pulling speed of the continuous casting machine is increased to 1.15-1.50 m/min by increasing the pulling speed by 0.03m/min every 40 seconds.

Preferably, the method for preventing the longitudinal cracks of the slab caster from generating and the bonding breakout is suitable for the steel with the carbon content of 0.10-0.19 Wt%, the width of the steel section of 220mm, the length of 1500-1820 mm, the liquidus temperature of the molten steel of 1511-1528 ℃ and the superheat degree of 10-30 ℃.

Preferably, the carbon content of the steel is 0.07-0.09 Wt%, the liquidus temperature of the molten steel is 1519-1521 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the work drawing speed V ₁ is 1.27-1.36 m/min.

Preferably, the carbon content of the steel is 0.07-0.09 Wt%, the liquidus temperature of the molten steel is 1519-1521 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the work drawing speed V ₁ is 1.12-1.15 m/min.

preferably, the carbon content of the steel is 0.08-0.12 Wt%, the liquidus temperature of the molten steel is 1518-1521 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the work drawing speed V ₁ is 1.27-1.33 m/min.

Preferably, the carbon content of the steel is 0.08-0.12 Wt%, the liquidus temperature of the molten steel is 1518-1521 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the working pulling speed V ₁ is 1.12-1.15 m/min.

Preferably, the carbon content of the steel is 0.12-0.16 Wt%, the liquidus temperature of the molten steel is 1514-1519 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the work drawing speed V ₁ is 1.36-1.42 m/min.

preferably, the carbon content of the steel is 0.12-0.16 Wt%, the liquidus temperature of the molten steel is 1514-1519 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the working pulling speed V ₁ is 1.18-1.21 m/min.

Preferably, the carbon content of the steel is 0.16-0.19 Wt%, the liquidus temperature of the molten steel is 1514-1517 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the work drawing speed V ₁ is 1.24-1.27 m/min.

Preferably, the carbon content of the steel is 0.16-0.19 Wt%, the liquidus temperature of the molten steel is 1514-1517 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the working pulling speed V ₁ is 1.18 m/min.

Detailed Description

the technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention provides a method for preventing longitudinal cracks of a slab caster from generating and bonding breakout, which comprises the following steps:

the method comprises the steps that a computer automatically controls the working pulling speed V ₁ of the continuous casting machine to be lowered to a water changing port pulling speed value V ₂ in a range of 0.02m/min every 10 seconds, the water changing port pulling speed value V ₂ is 0.80-0.85 m/min, the water changing port pulling speed value V ₂ is maintained for three minutes, meanwhile, a crystallizer water outlet is replaced, and slag strip inspection is carried out on protective slag;

secondly, the working drawing speed of the continuous casting machine is increased to 1m/min by 0.03m/min per 40 seconds through a computer automatic control program; experiments prove that when the working pulling speed of the continuous casting machine is increased to 1m/min by 0.03m/min per 40 seconds, the pulling speed is automatically and slowly increased, so that the reasonable safe pulling speed for ensuring that the covering slag is melted and preventing the bonding steel leakage caused by large liquid level fluctuation of the crystallizer is ensured, and the replacement frequency of a lower nozzle of the crystallizer, the generation of longitudinal cracks and the generation of bonding steel leakage at the water changing nozzle are effectively reduced;

Then, quitting the computer automatic control program, and simultaneously keeping the continuous casting machine at the drawing speed of 1m/min for 2-3 min; the continuous casting machine is kept at the drawing speed of 1m/min for 2-3min to avoid the large-range fluctuation of the drawing speed, further causing the fluctuation of the liquid level of the steel in the crystallizer, generating longitudinal cracks and nozzle replacement bonding bleed-out; on the premise of ensuring the efficiency, the casting powder is kept for 2-3min after the casting powder is pulled up to 1m/min, which is the most critical time for ensuring the optimal balance of the molten covering slag, ensuring the thickness of a liquid slag layer, promoting lubrication, preventing longitudinal cracks from generating and bonding breakout;

finally, the pulling speed of the continuous casting machine is increased to 1.15-1.50 m/min by increasing the pulling speed by 0.03m/min every 40 seconds; the drawing speed is automatically and slowly increased, so that the casting slag is ensured to be melted to keep up, the reasonable safe drawing speed for preventing bonded breakout caused by large liquid level fluctuation of the crystallizer is ensured, and the drawing speed of the continuous casting machine is increased to meet the requirement of a casting blank.

preferably, the method for preventing the longitudinal cracks of the slab caster from generating and bonding the breakout is suitable for the steel with the carbon content of 0.10-0.19 Wt%, the width of the section of the steel is 220mm, the length of the section of the steel is 1500-1820 mm, the liquidus temperature of molten steel is 1511-1528 ℃, and the superheat degree of the molten steel is 10-30 ℃, and experiments prove that when the carbon content of the steel is more than 0.12 Wt%, the faster the working drawing speed V ₁ of the continuous caster is, the higher the probability of the longitudinal cracks and the bonding breakout of a water change port are.

Preferably, the carbon content of the steel is 0.07-0.09 Wt%, the liquidus temperature of the molten steel is 1519-1521 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the work drawing speed V ₁ is 1.27-1.36 m/min.

Preferably, the carbon content of the steel is 0.07-0.09 Wt%, the liquidus temperature of the molten steel is 1519-1521 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the work drawing speed V ₁ is 1.12-1.15 m/min.

Preferably, the carbon content of the steel is 0.08-0.12 Wt%, the liquidus temperature of the molten steel is 1518-1521 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the work drawing speed V ₁ is 1.27-1.33 m/min.

Preferably, the carbon content of the steel is 0.08-0.12 Wt%, the liquidus temperature of the molten steel is 1518-1521 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the working pulling speed V ₁ is 1.12-1.15 m/min.

Preferably, the carbon content of the steel is 0.12-0.16 Wt%, the liquidus temperature of the molten steel is 1514-1519 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the work drawing speed V ₁ is 1.36-1.42 m/min.

Preferably, the carbon content of the steel is 0.12-0.16 Wt%, the liquidus temperature of the molten steel is 1514-1519 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the working pulling speed V ₁ is 1.18-1.21 m/min.

Preferably, the carbon content of the steel is 0.16-0.19 Wt%, the liquidus temperature of the molten steel is 1514-1517 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1500mm, and the work drawing speed V ₁ is 1.24-1.27 m/min.

Preferably, the carbon content of the steel is 0.16-0.19 Wt%, the liquidus temperature of the molten steel is 1514-1517 ℃, the superheat degree is 10-30 ℃, the width of the steel section is 220mm, the length is 1810mm, and the working pulling speed V1 is 1.18 m/min.

The invention is mainly applied to the production of the common carbon steel and the low alloy steel of the slab caster, the series of steel belongs to peritectic steel, the longitudinal crack defect is easy to appear, and the bonding and the pull leakage are easy to appear due to the large working condition fluctuation in the water gap changing process.

The invention improves the pulling speed control method of the water changing port in the slab production process, and reasonably controls the pulling speed under the existing process conditions, thereby not only meeting the requirement of the production rhythm, but also ensuring the consumption of the protective slag in the crystallizer, further maintaining the stable environment of the primary slab shell in the crystallizer in the solidification process, and reducing the probability of casting slab surface cracks and bonding breakout.

Table 1: parameters of steel grades in each example

table 2: specific process parameters of the examples

Table 3: longitudinal crack ratio and times of breakout adhesion for each example

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.