A method for removing tundish inclusion clean steel liquid

Abstract

The present application belongs to the technical field of metallurgical continuous casting, and particularly relates to a method for removing inclusions in tundish clean steel liquid. The method for removing inclusions in tundish clean steel liquid is mainly aimed at solving the problem that many inclusions in the tundish steel liquid will lead to clogging of the submerged entry nozzle, and finally improving the quality of the casting blank. The key is to install a steel liquid rotating flow dam in the tundish, and cooperate with a bottom blowing gas device at the rotating flow dam. While increasing the rotating flow of the steel liquid to make the inclusions contact and grow multiple times, the inclusions are captured by the rising bubbles of the bottom blowing gas, so that the inclusions in the tundish steel liquid are removed to the maximum extent. The present application can effectively remove the inclusions in the tundish steel liquid, improve the degree of clogging of the stopper and the submerged entry nozzle, and further optimize the qualified rate of the crystallizer liquid level fluctuation, so as to finally reduce the number of large-size inclusions in the casting blank and improve the quality of the casting blank.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical continuous casting technology, specifically relating to a method for removing inclusions from tundish to clean molten steel. Background Technology

[0002] Steel is the most important basic raw material for the national economy, and its development direction is towards high-end, green, and intelligent manufacturing. With the technological progress and rapid development of my country's energy, transportation, and engineering machinery industries, higher technical requirements have been placed on the performance and quality of high-quality steels such as automotive sheet steel and bearing steel. Since non-metallic inclusions, especially large inclusions, can reduce the plasticity, toughness, and fatigue life of steel, their control has become more stringent.

[0003] Continuous casting is a crucial process in the efficient production of steel, significantly impacting both production efficiency and quality. In continuous casting, molten steel flows from the ladle through a long nozzle into the tundish, then through a submerged entry nozzle into the crystallizer, and finally to the billet. The steelmaking process involves blast furnace ironmaking, converter steelmaking, ladle refining, and continuous casting, requiring the introduction of deoxidizers for deoxidation, inevitably resulting in inclusions. The tundish serves as the final treatment vessel for the molten steel; the effectiveness of inclusion removal directly affects the degree of blockage on the stopper rod and nozzle, consequently impacting the crystallizer level fluctuation compliance rate, and ultimately affecting billet quality. Therefore, a method for removing inclusions and cleaning the molten steel in the tundish is needed. Summary of the Invention

[0004] The purpose of this invention is to propose a method for removing inclusions from tundish to clean molten steel, aiming to remove inclusions from tundish to the maximum extent, improve the nodule layer of stopper rod and nozzle, thereby optimizing the liquid level fluctuation qualification rate of the crystallizer, and ultimately reducing the number of large-sized inclusions in the billet and improving the billet quality.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for removing inclusions from molten steel in an tundish and cleaning it, wherein a long nozzle is inserted into the middle of the tundish; one end of the long nozzle extends out of the tundish, and the other end is located inside the tundish, with the other end of the long nozzle positioned directly above a turbulence controller; characterized in that: a long strip-shaped baffle is provided inside the tundish; the long strip-shaped baffle is symmetrically arranged along the long nozzle, and the upper end of the long strip-shaped baffle is fixed to the top wall of the tundish; an arc-shaped dam is provided on the outer side of each of the two long strip-shaped baffles, the arc-shaped dam curving towards the long strip-shaped baffle with an angle of 45-90°, its height being at least 50mm higher than the lower edge of the long strip-shaped baffle, and its horizontal distance from the long strip-shaped baffle being 50-100mm, so that a vortex is formed between the long strip-shaped baffle and the arc-shaped dam; each Each of the aforementioned arc-shaped retaining dams is equipped with a bottom-blowing air device. This device is fixed to the tundish and has two overflow ports, one of which is located between the elongated retaining dam and the arc-shaped retaining dam. During continuous casting, the molten steel flows out from the turbulence controller, forming a vortex at the arc-shaped retaining dam. This vortex then rebounds after contacting the elongated retaining dam, creating an eddy. Under the combined action of the arc-shaped and elongated retaining dams, the molten steel possesses upward potential energy, causing inclusions in the steel to float upwards and dissolve into the covering agent. Inert gas is then introduced, causing bubbles to break up under the impact of the steel flow, forming smaller bubbles that disperse upwards, increasing the probability of contact with inclusions. These smaller bubbles carry the inclusions to the surface and dissolve into the covering agent. The combined effect of these two processes improves the efficiency of removing inclusions from the intermediate molten steel.

[0007] The bottom blowing device consists of an overflow port and a blowing pipe. The gas used is an inert gas. The gas enters the molten steel through the blowing pipe and the overflow port. The argon gas flow rate is <15L / min.

[0008] The bottom blowing device is 20-30mm away from the dam at a horizontal distance.

[0009] The purpose of this invention is to propose a method for removing inclusions from molten steel in the tundish. This method involves installing elongated weirs and arc-shaped dams within the tundish, and using a bottom-blowing air device at the swirling dam. This increases the swirling flow of the molten steel, causing inclusions to repeatedly contact and grow. Simultaneously, the bottom-blown air bubbles rise and capture the inclusions, maximizing the removal of inclusions from the molten steel in the tundish. This invention effectively removes inclusions from the molten steel in the tundish, improves the thickness of the nodule layer on the stopper rod and nozzle, optimizes the acceptable rate of liquid level fluctuations in the crystallizer, and ultimately reduces the number of large-sized inclusions in the cast billet, improving the quality of the cast billet. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a method for cleaning molten steel by removing inclusions from an tundish.

[0011] Figure 2 for Figure 1 Enlarged view of Part A in the middle.

[0012] Wherein: 1-intermediate drum; 2-stopper rod; 3-conventional dam; 4-arc dam; 5-bottom blowing device; 6-rectangular weir; 7-long nozzle; 8-turbulence controller; 9-bubble. Detailed Implementation

[0013] The present invention will be described in detail with reference to the accompanying drawings and specific embodiments:

[0014] A method for removing inclusions from molten steel in an tundish and cleaning it, the specific operation method is as follows:

[0015] Step 1: As required by the invention, the arc-shaped retaining dam needs to be prefabricated and installed according to the actual dimensions of the dam on site; the dam needs to be processed and the bottom blowing device installed.

[0016] Step 2: After baking in the ladle, continuous casting is carried out;

[0017] Step 3: After continuous casting is completed, observe the degree of nodule formation at the submerged entry nozzle and characterize and analyze the morphology and size of inclusions in the billet.

[0018] The angular radius, height, horizontal distance from the weir, and inert gas injection rate of the arc-shaped retaining dam need to be determined based on the specifications of the tundish and the billet pulling speed. Example 1:

[0019] The arc-shaped retaining dam has an angular radius of 45°, a height 50 mm higher than the lower edge of the retaining dam, a horizontal distance of 50 mm from the retaining dam, an inert gas flow rate of 7 L / min, a tundish capacity of 40 t, and a billet pulling speed of 0.9 m / min.

[0020] Compared to the unmodified tundish continuous casting process, the addition of an arc-shaped dam and bottom blowing device reduces the thickness of the immersion nozzle nodules by 20% and the large-sized inclusions in the billet by 25%. Example 2:

[0021] The arc-shaped retaining dam has an angular radius of 60°, a height 60mm higher than the lower edge of the retaining dam, a horizontal distance of 60mm from the retaining dam, an inert gas flow rate of 7L / min, a tundish capacity of 40t, and a billet pulling speed of 0.9m / min.

[0022] Compared to the unmodified continuous casting process, the addition of an arc-shaped dam and a bottom blowing device reduces the thickness of the immersion nozzle nodules by 32% and the large-sized inclusions in the billet by 35%. Example 3:

[0023] The arc-shaped retaining dam has an angular radius of 80°, a height 80mm higher than the lower edge of the retaining dam, a horizontal distance of 75mm from the retaining dam, an inert gas flow rate of 7L / min, a tundish capacity of 40t, and a billet pulling speed of 0.9m / min.

[0024] Compared to the unmodified tundish continuous casting process, the addition of an arc-shaped dam and bottom blowing device reduced the thickness of the immersion nozzle nodules after continuous casting by 49% and reduced large-sized inclusions in the billet by 51%.

Claims

1. A method for removing inclusions from molten steel in an tundish to clean it, wherein a long nozzle is inserted into the middle of the tundish; one end of the long nozzle extends out of the tundish, and the other end is located inside the tundish, with the other end of the long nozzle positioned directly above a turbulence controller; characterized in that: A long, narrow weir is provided inside the tundish; the long, narrow weirs are symmetrically arranged along the long inlet, and the upper ends of the long, narrow weirs are fixed to the top wall of the tundish; an arc-shaped dam is provided on the outer side of each of the two long, narrow weirs, the arc-shaped dam curving towards the long, narrow weirs with an angle of 45-90°, its height being at least 50mm higher than the lower edge of the long, narrow weirs, and its horizontal distance from the long, narrow weirs being 50-100mm, so that a vortex pit is formed between the long, narrow weirs and the arc-shaped dams; each The bottom of each of the arc-shaped retaining dams is equipped with a bottom blowing device; the bottom blowing device is fixed on the tundish and has two overflow ports, one of which is located between the elongated retaining dam and the arc-shaped retaining dam; during continuous casting, the molten steel flows out from the turbulence controller and forms a vortex at the arc-shaped retaining dam. After the vortex contacts the elongated retaining dam upwards, it continues to rebound and generate eddies. Under the action of the arc-shaped retaining dam and the elongated retaining dam, the molten steel has the potential energy to flow upwards. Inclusions in the molten steel will float upwards under the drive of this potential energy and be incorporated into the covering agent; When an inert gas is introduced, the bubbles are broken up by the impact of the steel flow, forming small bubbles that diffuse upwards, increasing the chance of contact with inclusions. The small bubbles carry the inclusions to the surface of the liquid and dissolve into the covering agent. The two work together to improve the efficiency of removing inclusions from the intermediate molten steel.

2. The method for removing inclusions from molten steel in an tundish as described in claim 1, characterized in that: The bottom blowing device consists of an overflow port and a blowing pipe. The gas used is an inert gas. The gas enters the molten steel through the overflow port via the blowing pipe. The argon gas flow rate is <15L / min.

3. The method for removing inclusions from molten steel in an tundish as described in claim 1, characterized in that: The bottom blowing device is 20-30mm away from the dam at a horizontal distance.

Images