JPS596313A - Removing process for inclusion in molten steel - Google Patents

Abstract

PURPOSE:To clean easily molten steel and to improve the quality of metallic material by means of filtering the floated bubble having collected nonmetallic inclusions during gas blowing in molten steel by a porous inclusion-adsorbing collector dipped into the molten steel. CONSTITUTION:An inclusion-adsorbing collector 9 which in cludes a space 6 and is made of porous fire proof brick is dipped into the upper part of the molten steel in a molten steel holder. Next, gas is blown into the molten steel from the nozzle 13 for blowing gas equipped at the bottom of said molten steel holder, and bubbles 14 are generated. The bubbles 14 having collected nonmetallic inclusions on the interfaces of said bubbles 14 floats and reaches the collector 9. Then, the collector 9 adsorbs the inclusions by making the space 6 of the collector 9 vacuous. Thus the molten steel is cleaned and the quality of the metallic material is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing non-metallic inclusions in molten steel,
In particular, the purpose is to propose a method that can remove even minute inclusions that have been difficult to remove using conventional techniques. Generally, molten steel contains deoxidation products and slag, or the lining of the inner surface of a molten steel holding container. There are many non-metallic inclusions from refractories for use.These non-metallic inclusions not only significantly impair the mechanical strength of the steel but also deteriorate the surface properties of the product, so gas bubbling treatment using a ladle, Efforts are being made to reduce inclusions in steel as much as possible through degassing treatment and the use of stainless steel.

However, in recent years, as the quality requirements for steel materials have become significantly more sophisticated, it is no longer sufficient to remove inclusions using the conventional methods described above, and there is a growing demand for the reduction of microscopic inclusions of 100μ or less than fIOμ. However, the conventional techniques have a limited ability to remove such minute inclusions, and a new, even more powerful removal method is desired. .

The present invention meets the needs of the technical field and provides a new method for directly adsorbing and removing non-metallic inclusions, which overcomes the drawbacks of conventional methods, and the gist thereof is as follows:
Inert gas is fully injected from the bottom of the molten steel holding container, and inclusions in the molten steel are brought to the surface by bubbling. 1. An inclusion adsorption trap made of porous refractory brick is immersed in the molten steel above it, and the adsorption trap is removed. By reducing the pressure on the side that does not come into contact with the molten steel,
The purpose of removing inclusions was achieved by adsorbing all the air bubbles floating in the molten steel, allowing the gas to pass through due to the permeability of the porous bricks, and adsorbing the inclusions to the surface of the bricks.

Next, details of the present invention will be explained. The gas bubbling treatment method, which has traditionally been used to remove non-metallic inclusions in molten steel, involves blowing inert gas from the bottom of the molten steel holding container to float and clean floating inclusions in molten steel. After focusing on a certain point and conducting various studies and studies, we decided to use an inclusion trapping device with a filter function made of porous refractory bricks in the molten steel above the inclusions that floated up during the gas bubbling process under reduced pressure. It has been found that by promoting the floating of air bubbles, it is possible to enhance the effect of trapping and removing inclusions.

The present invention has been made based on this knowledge, and is a molten steel bath of 7 tons, in which an inclusion adsorption trap made of porous refractory bricks with voids provided inside is immersed in the upper layer of the molten steel bath. A gas injection nozzle is installed at the bottom of the container that holds the inclusions, and while inert gas is blown into the molten steel through the nozzle, the void inside the inclusion adsorption trap is depressurized from the outside using a vacuum pump or similar device. state. In this way,
- A method for removing inclusions by adsorbing them to the porous part of the trapping device immersed in molten steel, and the method of this invention removes microscopic inclusions that were previously considered difficult to remove. It was also possible to adsorb and remove substances, clean molten steel, and improve mechanical properties and product surface properties.

Next, specific embodiments of the method of the present invention will be explained in detail.

FIG. 1 shows an example of an inclusion adsorption trap. This inclusion adsorption trap 9 has a filter function and is made of porous refractory bricks 6 having air permeability, and has voids 6 inside. To store. In addition, when this void 6 is depressurized, a 7t mesh 17 that prevents leakage due to the air permeability of the porous refractory bricks that are not in contact with the molten steel, a leak-preventing iron plate 2, a leak-preventing mortar 4, and a wall that protects from the molten steel 8. 8 are provided. Then, pass the exhaust vibrator 1 through the rotary
When the pressure inside the gap 6 is reduced by the evacuation means 7 such as a pump, the air bubbles in the molten steel 8 generate a gas flow 18 that reaches the air gap 6 of the inclusion adsorption trap 9, and the inclusions f' are captured by the air bubbles. is adsorbed to the filter function surface 6 of the porous refractory brick. In Fig. 1, the portion b' of the porous refractory brick other than the filter functional surface 6, which adsorbs air bubbles that have come into contact with molten steel and trapped inclusions, can be made of ordinary refractory brick if necessary. It is.

FIG. 2 shows an example of removing inclusions from molten steel in a tundish, in which the inclusion adsorption trap 9 shown in FIG. 1 is installed between weirs 11 in the tundish. A porous plug brick 18 for stirring molten steel and blowing gas for capturing inclusions is installed at the bottom of the tundish directly below the adsorption trap 9. Molten steel flow 12 passing through weir 11
are mixed and stirred by the air bubbles 14 released from the porous plug brick 18. On the one hand, the air gap 6 in the adsorption trap 9 is depressurized by a vacuum pump 10. The mechanism for trapping and adsorbing inclusions will be explained based on FIG. 9 under the condition that Luga sprinkling is performed from the bottom while reducing the pressure in the cavity 6 in the inclusion adsorption trap. In Fig. 8, 15 bubbles released from the porous Gela brick 1B into the molten steel float to the surface with nonmetallic inclusions trapped at the interface.The bubbles that capture the nonmetallic inclusions float to the surface. The inclusions reach the molten steel contact surface 5 of the porous refractory brick of the inclusion adsorption trap in the state shown in 16. Here, since the void 6 inside the adsorption trap 9 is under reduced pressure, the air bubbles Due to the filter function of the porous refractory brick 5, it passes through as a gas and reaches the void 6, and is exhausted to the outside by the vacuum pump, and the inclusions are adsorbed on the surface of the porous refractory brick 6.
The data is accumulated as shown in the first picture. however,
This accumulated inclusion layer is adsorbed in a state where the inclusions are acicular and have gaps, and there are continuous pores between the inclusions, so the adsorption function does not deteriorate and the tundish It is possible to use more than one series.

Five porous refractory bricks constituting the inclusion adsorption trap of the embodiment shown in FIG. 1, At, 0. -0 system porosity 1
5-10% porous refractory brick, dense refractory brick 8
The dense mortar 4 is a high aluminum refractory material with At, 08 of 90- or more, and porosity of 10% or less, and the degree of vacuum in the void in the adsorption trap is 0.1 to 0.15 Torr. is appropriate.

In Fig. 2, an adsorption trap 9 with a length of 1000 fins is installed at the top of the tandish hedge, and the vacuum level of the gap 6 is 8T.
orr, processing time 41i minutes/oharge.

The results of continuous casting using a bottom-injected Ar gas metering volume of 101/mLn/B plug and a casting speed of 168 ml/ml are as follows: The total (0) of the molten steel used was ao ppm. 18 p when cast
The number of nozzle pluggings (indicated by the number of times the nozzle opening was changed per channel at a constant casting speed), which decreased to 100 pm, was previously about one time per channel.

If gas is not injected using an adsorption trap, it is performed under o and g recovery, and if gas is injected in parallel, it is less than 0.07 times (number #4). Met.

1'J, as explained above, the method of the present invention is extremely effectively applied to the removal of non-metallic inclusions in molten steel, but such effects are not limited to molten steel, but can be applied to general molten metals. It is understood that it is effective when applied to the removal of non-metallic inclusions, and has an extremely large effect in cleaning molten metal, increasing the mechanical strength of the metal material, and improving the surface quality of products. 0 to be done

[Brief explanation of the drawing]

FIG. 1 is a drawing showing an example of the inclusion adsorption trap of the present invention, FIG. 2 is an explanatory drawing of the embodiment, and FIG. 8 is a schematic illustration of removing inclusions from molten steel. l...Exhaust pipe, 2...Leak prevention iron plate, 8.
... Dense refractory brick, 4... Dense refractory mortar,
6.5′...Porous refractory brick, 6...Void, 7.
... Vacuum exhaust means, 8... Molten steel, 9... Inclusion adsorption trap, 10... Vacuum pump, 11... Weir, 12.
... Molten steel flow, 1B... Porous plug brick, 14.
... Bubbles, 15... Floating bubbles, 16... Bubbles on the surface of the porous refractory brick, 17... Inclusions adsorbed and captured on the surface of the porous refractory brick, 18... Gas flow. Figure 2

Claims (1)

[Claims] 1. An inclusion adsorption trap made of porous refractory brick with built-in voids is immersed in the upper layer of the molten steel bath in the molten steel holding container, and a pressure gas blowing nozzle is provided at the bottom of the molten steel holding container. The inclusions in the molten steel are adsorbed and removed by the inclusion adsorption trap by reducing the pressure in the cavity of the inclusion adsorption trap while blowing gas into the molten steel from a nozzle. A method for removing inclusions in molten steel.