JPH01170556A - Cleaning method for molten metal - Google Patents

Abstract

PURPOSE:To efficiently execute the removal of a floated inclusion by trapping a floating inclusion by the fine gas bubble generated by rapidly reducing the pressure after melting the molten metal under pressurization by bubbling it by a soluble gas, exerting a surface magnetostatic field and constraining the tramping of the molten metal level in case of its floating. CONSTITUTION:A molten steel 3 is poured up to the specified height into a pressure container 2 and after replacing the inner part atm. with an Ar gas the mixed gas consisting of 70% Ar gas and 30% H2 gas is blown from the container 2 bottom face and bubbled into the steel bath 3 to increase the pressure up to 10atm. max. Thereafter as shown in the figure a magnetostatic field is impressed on the molten metal level 1a of the steel bath 3 by an electromagnet 4 to generate the force F constraining the tramping of the level 1a. Thereafter, the bubbling of the mixed gas is stopped, the container 2 inside is rapidly subjected to pressure reducing by a pressure adjusting valve 5, fine gas bubbles are generated from the whole steel bath 3 area, the inclusion inside the steel bath 3 is trapped and removed by its floating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for cleaning molten metal by removing inclusions floating in the molten metal.

[Conventional technology]

Inclusions floating in molten metal (for example, alumina inclusions in molten steel) cause product quality defects, and various methods have been proposed to reduce and remove them.

Among these methods, one method that is widely used as it is relatively efficient is to bubble inert gas into the molten metal from the bottom of the container under normal pressure to trap inclusions in the gas bubbles.
There is a way to remove this after surfacing.

[Problem that the invention seeks to solve]

When the purpose is to manufacture high-grade materials, the total amount of oxygen in molten steel must be suppressed to 10 ppm or less.

However, there is a problem in that the above-mentioned methods cannot meet the requirement for ultra-cleaning of molten metal, and there has been a desire to develop a new method.

In other words, in the conventional gas bubbling method, the bubbling region is limited to an area that spreads upward from the gas inlet at the bottom of the container in a forest-like manner, and furthermore, there is a problem in that it is difficult to bubble from the entire area of the container due to restrictions on the bubbling method. there were. Another cause is that the bubbles created by bubbling are large, and when the bubbles float to the surface, the molten metal flows around them, and along with the flow, fine inclusions also avoid the bubbles. There is also the problem that fine inclusions are difficult to be trapped by air bubbles because they move.

Therefore, the present inventors made a proposal to solve the above problem almost at the same time as filing the present application. The proposal involves bubbling pressurized molten metal with a soluble gas to dissolve the gas in the molten metal, and then rapidly reducing the pressure to generate fine gas bubbles in the molten metal. Inclusions floating in the molten metal are trapped in gas bubbles caused by bubbling and fine gas bubbles generated by reduced pressure,
This is removed after levitation.

Normal inclusions in the molten metal will be trapped by the initial bubbling and will not be brought to the surface.

On the other hand, since this bubbling is performed on the pressurized molten metal, a large amount of bubbling gas melts into the molten metal. The subsequent rapid depressurization causes the gas that had entered the molten metal to become fine gas bubbles that are generated from the entire area of the molten metal. At this time, fine inclusions are trapped by the gas bubbles and float up.

Although this is an extremely efficient and excellent method for removing inclusions from molten metal, it is difficult to remove the inclusions from the molten metal when the gas bubbles caused by bubbling and the countless fine gas bubbles generated by reduced pressure rise to the surface of the molten metal. Because the surface flaps up and down, there is another problem that floating inclusions get mixed into the molten metal again, and even though it is excellent in theory, it is still a problem that still needs to be solved in practice. It had

The present invention was made to solve the above problems, and
This method has been improved so that floating inclusions can be efficiently removed by suppressing the fluttering of the hot water surface.

[Means for solving problems]

Therefore, the basic feature of the present invention is to apply a static magnetic field to the interface 1 as shown in FIG. There is.

[For production]

When a magnetic field is applied perpendicular to the flow of a bath such as a steel bath,
A braking force is generated against the flow.

The above mentioned fluttering at the molten metal interface 1 corresponds to the flow of the bath in the vertical direction, so by applying a static magnetic field to the interface 1, a force is generated to suppress the vertical flow, reducing the amplitude of the fluttering. This can prevent ripples on the interface 1.

〔Example〕

Hereinafter, specific examples of the present invention will be described.

As shown in FIG. 2, a steel bath 3 is poured into a pressure vessel 2 with an inner diameter of 2 m and a height of 3 m to a height of 2 m from the bottom, and the internal atmosphere is replaced with Ar gas. Ar
A mixed gas consisting of 0% Gasnia and 30% H2 gas,
The steel bath 3 was heated for 20 minutes at a blowing rate of 300 Q/win.
It bubbled inside. At this time, the maximum pressure is 10at1
Raised it to 1. After that, as shown in FIG. 3, a static magnetic field is applied to the hot water surface 1a of the steel bath 3 by the electromagnet 4,
The force F that suppresses the flapping is generated in a. This suppressing force F
can be calculated using the formula below.

F=σB2υ However, σ: Electrical conductivity of the steel bath B: Magnetic flux density υ: Flow velocity in the vertical direction of the hot water surface After that, bubbling of the mixed gas is stopped, the pressure inside the container 2 is rapidly reduced by the pressure regulating valve 5, and the steel bath is Fine gas bubbles were generated from the entire bath 3 area. In this embodiment, a static magnetic field is also applied to the hot water surface 1a at this time.

FIG. 4 shows the change in the fluttering of the hot water surface 1a due to the application of this static magnetic field, with the magnetic flux density of the static magnetic field plotted on the X-axis. According to this figure, the effect of suppressing the fluttering of the hot water surface la appears when the magnetic flux density reaches 1000 Gauss or more, and this effect becomes saturated when it reaches 500 Gauss or more.

〔Effect of the invention〕

As explained above, according to the method of the present invention, it is possible to stabilize the interface using electromagnetic force and accurately suppress the fluttering of the interface. These inclusions will not be mixed into the molten metal again and will be removed near the interface.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the method of the present invention, FIG. 2 is a schematic diagram showing the configuration of a pressure vessel used in carrying out the method of the present invention, FIG. 3 is an explanatory diagram showing an example of the method of the present invention, and FIG. The figure is a graph diagram showing changes in the fluttering of the hot water level in this example. In the figure, 1 is an interface, 2 is a pressure vessel, 3 is a steel bath, 4 is an electromagnet, and 5 is a pressure regulating valve. Figure 1 Figure 2 Procedure Amendment (October 28, 1988)

Claims (1)

[Claims] Pressurized molten metal is bubbled with a soluble gas to dissolve the gas in the molten metal, and then the pressure is rapidly reduced to generate fine gas bubbles in the molten metal, which are then suspended in the molten metal. In carrying out a molten metal cleaning method in which inclusions are trapped in gas bubbles caused by bubbling and fine gas bubbles generated by depressurization, and then removed after floating, gas bubbles caused by bubbling and fine gas bubbles generated by depressurization are removed. A method for cleaning molten metal characterized by applying a static magnetic field to the interface when inclusions are trapped and float to the surface.