A slab continuous caster full-process collaborative breakout prevention method

Abstract

The application discloses a kind of slab continuous casting machine whole-process collaborative breakout prevention and control method, belong to continuous casting production technical field, comprising: based on the automatic casting opening speed control of solidification characteristics, obtain the solidification shrinkage characteristics of target steel grade, set automatic casting opening speed curve;Efficient lubrication mould powder matching, adopt special mould powder for medium carbon steel, control its physicochemical index: viscosity is 0.2Pa·s~0.4Pa·s, melting rate is 35s~45s, basicity is 1.1~1.3, melting point is 1080℃~1120℃;Submerged entry nozzle and flow field stability control, submerged entry nozzle insertion depth is controlled at 160mm~190mm, and before each casting opening, measure tundish car levelness, inhibit slag entrapment;Hydrogen embrittlement and environmental humidity linkage control, real-time monitoring hydrogen content and environmental humidity, and take whole-process moisture-proof measures to raw and auxiliary materials.The application reduces the breakout overflow rate to 0.001% or less.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting production technology, specifically relating to a method for preventing steel leakage in a slab continuous casting machine through a coordinated process. Background Technology

[0002] Slab continuous casting is a core process in modern steelmaking. Slab leakage accidents directly lead to continuous casting machine shutdowns, equipment damage, and production disruptions, while also reducing metal yield and causing significant economic losses. With the development of high-efficiency slab continuous casting technology, the range of steel grades that can be cast has expanded, and casting speeds have continuously increased. This has led to deterioration in heat transfer, friction, and lubrication conditions in the crystallizer, uneven cooling of the initial slab shell, and decreased stability of the protective slag inflow. Adhesive leakage has become the most prevalent form of leakage. Current technologies mostly rely on single leakage prediction or local parameter adjustments, lacking an integrated control scheme encompassing the casting schedule, protective slag, nozzle, hydrogen content, and equipment alignment. This makes it difficult to fundamentally prevent leakage from occurring. Summary of the Invention

[0003] This invention addresses the problems of frequent steel leakage accidents, high overflow rate, large equipment wear and tear, and low metal recovery rate in existing slab continuous casting. It provides a collaborative steel leakage prevention and control method for the entire process of slab continuous casting machine, which reduces the overflow rate and improves the continuous casting machine's operating rate.

[0004] A method for preventing steel leakage in a slab continuous casting machine through a coordinated process includes:

[0005] Based on the solidification characteristics, the automatic start-up speed control is used to obtain the solidification shrinkage characteristics of the target steel grade and set the automatic start-up speed curve: the casting speed is increased to 0.4 m / min within 1.5 min after start-up, and this casting speed is maintained for 2 min to ensure uniform growth of the initial billet shell. Then, the speed is increased to 0.7 m / min within 1.5 min, and then the manual speed increase stage is entered. The matching of high-efficiency lubricating protective slag is to use special protective slag for medium carbon steel, and control its physical and chemical properties as follows: viscosity of 0.2 Pa●s~0.4 Pa●s, melting rate of 35s~45s, basicity of 1.1~1.3, and melting point of 1080℃~1120℃, so as to form a uniform liquid slag film in the crystallizer. Submerged sprue and flow field stability control: control the insertion depth of the submerged sprue to 160mm-190mm, and measure the level of the tundish before each pouring, and use shims to level and ensure the verticality of the sprue to suppress slag entrapment. Hydrogen embrittlement is controlled in conjunction with ambient humidity. The hydrogen content (H) in molten steel and ambient humidity are monitored in real time: when H > 5 ppm, the drawing speed is reduced by 0.2 m / min; when H > 8 ppm, the drawing speed is reduced to the safe drawing speed; and moisture-proof measures are taken for raw and auxiliary materials throughout the process.

[0006] Preferably, the acceleration curve is specifically controlled by a piecewise function: t∈[0,1.5]: The pulling speed V(t) increases linearly from 0 to 0.4 m / min, and the acceleration a1=2.40 m / min 2 ; t∈(1.5,3.5]: The pulling speed V(t) is kept at 0.4 m / min, and the acceleration a2=0; t∈(3.5,5.0]: The pulling speed V(t) increases linearly from 0.4 m / min to 0.7 m / min, and the acceleration a3 = 0.27 m / min 2 .

[0007] Preferably, the protective slag further includes controlling the fluorine content to ≤5%.

[0008] Preferably, the immersion nozzle and flow field stability control further include dynamically matching the argon flow rate according to the pulling speed to control the fluctuation range of the liquid level in the crystallizer to ≤±3mm.

[0009] Preferably, the safe pulling speed is 0.2m / min to 0.3m / min.

[0010] Preferably, the measures to prevent moisture damage to raw and auxiliary materials throughout the process include: taking constant temperature and moisture-proof measures for protective slag and covering agent during the rainy season or in high humidity environments, and drying treatment for quicklime, fluorite and alloy.

[0011] Preferably, during the production of medium carbon steel using a slab continuous casting machine, when H=6.2ppm, the casting speed is reduced by 0.2m / min; when H=8.5ppm, it is reduced to a safe casting speed.

[0012] Preferably, in the process of producing medium carbon steel using a slab continuous casting machine, the physicochemical properties of the protective slag are: viscosity of 0.3 Pa. It has a melting rate of 40s, an alkalinity of 1.2, and a melting point of 1100℃.

[0013] Preferably, materials should be covered with tarpaulins during the rainy season.

[0014] Preferably, the covering agent is stored at a constant temperature.

[0015] Beneficial effects This invention reduces the steel leakage rate from 0.06% to below 0.001% through a strategy of "optimized working conditions, precise matching, and environmental linkage".

[0016] This invention adopts a "slow start-steady hold-gradual increase" casting acceleration curve, which solves the problem of uneven shell growth in the initial stage.

[0017] This invention employs a special protective slag with low viscosity and moderate melting point design to ensure lubrication requirements at high pulling speeds.

[0018] This invention employs a speed-reduction mechanism that links hydrogen content with ambient humidity.

[0019] This invention can reduce the repair costs of copper plates and sector sections in crystallizers, and significantly reduce losses from a single accident.

[0020] This invention can improve the continuous casting machine's operating rate, output, and metal yield. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] A method for preventing steel leakage in a slab continuous casting machine through a coordinated process includes: Based on the solidification characteristics, the automatic start-up speed control is used to obtain the solidification shrinkage characteristics of the target steel grade and set the automatic start-up speed curve: the casting speed is increased to 0.4 m / min within 1.5 min after start-up, and this casting speed is maintained for 2 min to ensure uniform growth of the initial billet shell. Then, the speed is increased to 0.7 m / min within 1.5 min, and then the manual speed increase stage is entered. The matching of high-efficiency lubricating protective slag is to use special protective slag for medium carbon steel, and control its physical and chemical properties as follows: viscosity of 0.2 Pa●s~0.4 Pa●s, melting rate of 35s~45s, basicity of 1.1~1.3, and melting point of 1080℃~1120℃, so as to form a uniform liquid slag film in the crystallizer. Submerged sprue and flow field stability control: control the insertion depth of the submerged sprue to 160mm-190mm, and measure the level of the tundish before each pouring, and use shims to level and ensure the verticality of the sprue to suppress slag entrapment. Hydrogen embrittlement is controlled in conjunction with ambient humidity. The hydrogen content (H) in molten steel and ambient humidity are monitored in real time: when H > 5 ppm, the drawing speed is reduced by 0.2 m / min; when H > 8 ppm, the drawing speed is reduced to the safe drawing speed; and moisture-proof measures are taken for raw and auxiliary materials throughout the process.

[0023] To better understand the technical solution of this invention, it will be described in detail below: The automatic start-up speed-up curve is optimized based on the solidification characteristics of the steel grade and the crystallizer expert system. The start-up speed-up curve is set as follows: 0–1.5 min: the casting speed increases from 0 to 0.4 m / min, and the acceleration is 2.40 m / min²; 1.5 min to 3.5 min: the speed is kept constant at 0.4 m / min; 3.5 min to 5.0 min: the casting speed increases from 0.4 m / min to 0.7 m / min, and the acceleration is 0.27 m / min²; then the manual speed-up stage is entered to ensure uniform growth of the billet shell and avoid steel leakage at the start.

[0024] A special protective slag for medium carbon steel has been optimized and developed. Its physical and chemical properties are as follows: viscosity: 0.2 Pa●s~0.4 Pa●s; melting rate: 35s~45s; basicity: 1.1~1.3; melting point: about 1100℃. It improves the lubrication and heat transfer uniformity in the crystallizer and reduces billet shell adhesion.

[0025] The parameters of the immersion nozzle are precisely controlled, with the insertion depth controlled between 160mm and 190mm; after each pouring, the level of the ladle is measured and adjusted using shims to ensure the verticality of the nozzle; the argon flow rate is reasonably matched according to the steel grade, cross-section, and pouring speed to stabilize the liquid level in the crystallizer.

[0026] Hydrogen content in molten steel and moisture control of materials: When the hydrogen content in molten steel is >5ppm, the casting speed is reduced by 0.2m / min; when the hydrogen content is >8ppm, the casting speed is reduced to the safe casting speed; during the rainy season, materials entering the plant should be covered with tarpaulins; protective slag and covering agents should be stored at constant temperature and opened only when needed; quicklime, fluorite, and alloys should be kept dry.

[0027] Regular maintenance of the equipment status ensures the alignment of the crystallizer and the condition of the copper plates, reducing billet shell tearing and steel leakage caused by equipment deviation.

[0028] Example 1: Steel leakage control under standard operating conditions A slab continuous casting machine produces Q345B medium carbon steel.

[0029] Speed ​​control: The curve of this invention is used. Speed ​​up to 0.4 m / min from 0 to 1.5 min; maintain 0.4 m / min from 1.5 min to 3.5 min (observe whether the thermocouple temperature curve is stable during this stage); speed up to 0.7 m / min from 3.5 min to 5.0 min.

[0030] Protective slag control: Add a special protective slag and monitor its viscosity to be 0.3 Pa●s and melting rate to be 40 s.

[0031] Equipment control: The sprue insertion depth is set to 175mm. Before pouring, check the level of the intermediate drum truck to ensure that the sprue is vertical.

[0032] Results: The crystallizer friction fluctuation was small, there was no adhesion alarm, and the start-up success rate was 100%.

[0033] Example 2: Prevention and control of hydrogen-induced steel leakage in high humidity environments (rainy season) Coastal areas experience frequent rainfall and high humidity during the summer.

[0034] Environmental monitoring: The ambient humidity was detected to be >80%, and the H content of the molten steel was 6.5 ppm.

[0035] Linkage response: The control system automatically triggers a speed reduction command, reducing the current pulling speed by 0.2 m / min.

[0036] Material management: Preheat the protective slag (30℃ constant temperature) before use, and turn on the dryer in the alloy silo.

[0037] Results: Although the hydrogen content of the molten steel was high, the billet shell growth cycle was extended by reducing the casting speed, thus avoiding crack propagation and steel leakage caused by hydrogen embrittlement.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A method for preventing steel leakage in a slab continuous casting machine through a coordinated process, characterized in that, include: Based on the solidification characteristics, the automatic start-up speed control is used to obtain the solidification shrinkage characteristics of the target steel grade and set the automatic start-up speed curve: the casting speed is increased to 0.4 m / min within 1.5 min after start-up, and this casting speed is maintained for 2 min to ensure uniform growth of the initial billet shell. Then, the speed is increased to 0.7 m / min within 1.5 min, and then the manual speed increase stage is entered. The matching of high-efficiency lubricating protective slag is to use special protective slag for medium carbon steel, and control its physical and chemical properties as follows: viscosity of 0.2 Pa●s~0.4 Pa●s, melting rate of 35s~45s, basicity of 1.1~1.3, and melting point of 1080℃~1120℃, so as to form a uniform liquid slag film in the crystallizer. Submerged sprue and flow field stability control: control the insertion depth of the submerged sprue to 160mm-190mm, and measure the level of the tundish before each pouring, and use shims to level and ensure the verticality of the sprue to suppress slag entrapment. Hydrogen embrittlement is controlled in conjunction with ambient humidity. The hydrogen content (H) in molten steel and ambient humidity are monitored in real time: when H > 5 ppm, the drawing speed is reduced by 0.2 m / min; when H > 8 ppm, the drawing speed is reduced to the safe drawing speed; and moisture-proof measures are taken for raw and auxiliary materials throughout the process.

2. The method for preventing steel leakage in a slab continuous casting machine throughout the entire process according to claim 1, characterized in that, The acceleration curve is specifically controlled by a piecewise function: t∈[0,1.5]: The pulling speed V(t) increases linearly from 0 to 0.4 m / min, and the acceleration a1=2.40 m / min 2 ; t∈(1.5,3.5]: The pulling speed V(t) is kept at 0.4 m / min, and the acceleration a2=0; t∈(3.5,5.0]: The pulling speed V(t) increases linearly from 0.4 m / min to 0.7 m / min, and the acceleration a3 = 0.27 m / min 2 .

3. The method for preventing steel leakage throughout the entire process of slab continuous casting machine according to claim 1, characterized in that, The protective slag also includes controlling the fluorine content to ≤5%.

4. The method for preventing steel leakage in a slab continuous casting machine throughout the entire process according to claim 1, characterized in that, The immersion nozzle and flow field stability control also include dynamically matching the argon flow rate according to the pulling speed to control the fluctuation range of the liquid level in the crystallizer to ≤±3mm.

5. The method for preventing steel leakage in a slab continuous casting machine throughout the entire process according to claim 1, characterized in that, The safe pulling speed is 0.2m / min to 0.3m / min.

6. The method for preventing steel leakage throughout the entire process of a slab continuous casting machine according to claim 1, characterized in that, The measures to prevent moisture damage to raw and auxiliary materials throughout the process include: taking constant temperature and moisture-proof measures for protective slag and covering agents during the rainy season or in high humidity environments, and drying lime, fluorite and alloys.

7. The method for preventing steel leakage in a slab continuous casting machine throughout the entire process according to claim 1, characterized in that, In the process of producing medium carbon steel using a slab continuous casting machine, when H=6.2ppm, the casting speed decreases by 0.2m / min; when H=8.5ppm, it decreases to a safe casting speed.

8. The method for preventing steel leakage in a slab continuous casting machine throughout the entire process according to claim 1, characterized in that, In the process of producing medium carbon steel using a slab continuous casting machine, the physicochemical properties of the protective slag are: viscosity of 0.3 Pa. It has a melting rate of 40s, an alkalinity of 1.2, and a melting point of 1100℃.

9. The method for preventing steel leakage in a slab continuous casting machine throughout the entire process according to claim 1, characterized in that, During the rainy season, materials should be covered with tarpaulins.

10. The method for preventing steel leakage in a slab continuous casting machine throughout the entire process according to claim 1, characterized in that, The covering agent should be stored at a constant temperature.