JPH0353363B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electromagnetic desulfurization device that effectively obtains a desulfurization effect while preventing a drop in the temperature of the molten metal to be desulfurized.
The present invention also relates to an electromagnetic induction stirring device suitable for use as a device for adjusting the composition of a molten metal by electromagnetically stirring the molten metal and additives.

For example, cupolas are widely used in iron casting factories as a means of obtaining molten metal. On the other hand, in order to obtain high-quality cast iron, it has been considered to add a spheroidizing agent to the molten metal before pouring it into a mold to obtain spheroidal graphite cast iron.

Although the production volume of this spheroidal graphite cast iron is increasing more and more, the molten metal produced using the above-mentioned Cupora contains a high concentration of sulfur derived from coke as a fuel, so the addition of a spheroidizing agent The progress of graphite spheroidization is insufficient and it cannot be put to practical use. For this reason, in the production of spheroidal graphite cast iron using molten metal produced by cupola, it is common to provide a desulfurization step before adding the spheroidizing agent. This desulfurization requires adding a desulfurizing agent to the molten metal and stirring to promote the reaction, and there are several methods available in the prior art. The first method is called the porous plug method, in which _N2 gas that does not react with the molten metal is blown up from the bottom of the molten metal container through _a porous plug installed at the bottom of the container. The second method is called the gas injection method, in which a refractory tube is immersed in the molten metal, and _N2 gas is injected as a carrier gas along with powdered carbide through the tube to obtain stirring and reaction. It is.

By the way, when these two methods are introduced into an actual desulfurization process, temperature reduction is seen as an important problem. Typical examples of the porous plug method are as follows. In other words, "1550°C when tapping the cupola → Temperature inside the porous plug desulfurization equipment 1450°C → 1400°C when tapping after adding the desulfurizing agent → Casting."

However, if the cast product is a small or thin item, the temperature during casting must be 1400°C to 1430°C, and the temperature during casting after adding a desulfurizing agent to the mold, and during the sequential casting time in multiple molds. Considering the temperature drop, it can be seen that the above temperature conditions are not practical. Because of this problem, when producing spheroidal graphite cast iron using a cupola as melting equipment (usually a cupola is used in most cases from the point of view of cost), it is common to provide means for raising the temperature of the molten metal after desulfurization treatment. As a means for this purpose, there is a general tendency to use a trench type induction furnace, but it is difficult to introduce it in relatively small-scale production plants because of its high expense ratio.

An object of the present invention is to provide an electromagnetic induction stirring device equipped with electromagnetic means that has both stirring power and temperature raising ability for uniformly distributing additives such as a desulfurizing agent in molten metal.

The illustrated embodiment will be specifically described below. FIG. 1 is a sectional view of a desulfurization device according to the present invention;
FIG. 2 is a plan view excluding the means for adding molten metal and desulfurizing agent. In each figure, 1 is an induction coil, which is formed by winding a water-cooled pipe into a cylindrical shape, and is sandwiched between circular supports 2 and 3 placed above and below the induction coil.
It is assumed that it is supported by bolts not shown.
Reference numeral 4 denotes a furnace body, which is formed by solidifying furnace materials, and forms a molten metal container 4a in an area surrounded by the coil, and this container 4a and the induction coil 1 constitute a so-called crucible-shaped induction furnace. 4b is a communicating pipe,
For example, it is formed from a pipe made of the same type of material as the molten metal to be treated, and is formed based on melting with the molten metal. The communication pipe 4b is connected to the pouring spout 4c from the bottom of the container 4a. By the way, the level of the melt coming out of the pouring port 4e is adjusted when the level of the molten metal supplied into the molten metal container 4a reaches the upper end of the induction coil 1. Reference numeral 5 denotes iron cores, which are arranged at appropriate intervals around the induction coil 1, facing vertically. A molten metal inlet trough 6 supplies molten metal produced from a cupola (not shown) to the molten metal container 4a of the desulfurization apparatus. Reference numeral 7 denotes a desulfurizing agent addition pipe, which cuts out an appropriate amount of desulfurizing agent into the molten metal container according to the amount of molten metal R supplied to the molten metal container 4a per unit time.

In the above configuration, first, the molten metal R obtained from a cupola (not shown) is poured into the molten metal container 4a formed in the furnace body 4 through the molten metal inlet trough 6, and the level of the molten metal gradually rises. At the same time as the molten metal level in the container 4a rises, the molten metal level in the communication pipe 4b also rises, and the molten metal level in the pouring port 4c rises.
After the point in time when molten metal starts to be supplied, the level of molten metal in the container 4a stops rising, and an equal amount of molten metal that has flowed from the molten metal inflow trough is supplied from the pouring port 4c to a mold (not shown) or the like.

On the other hand, the molten metal flowing into the molten metal container 4a from the molten metal inlet trough 6 receives a desulfurizing agent from the desulfurizing agent addition pipe 7 in the container 4a and undergoes a desulfurizing action. To explain the operation in more detail, first, by applying a single-phase AC voltage to the induction coil 1, an alternating magnetic flux is generated surrounding the vertical cross section of each part of the induction coil 1. The magnetic flux passes through the molten metal R accumulated in the container 4a, and an eddy current is generated by the magnetic flux passing through the molten metal. This eddy current not only compensates for the temperature drop within the container, but also serves to raise the temperature. Simultaneously with this temperature raising action, a current flows in the molten metal in a bundle in the opposite direction to the current flowing through the induction coil 1 due to the magnetic flux passing through the molten metal container 4a. Since these bundled currents are in the same direction, a repulsive force is generated on the molten metal R, which causes the molten metal R to move from the periphery to the center, and when the phase of the voltage supplied to the induction coil 1 is reversed, the current By reversing the flow direction, a constricting action is obtained, and a molten metal flow in the direction of the arrow shown in the figure is obtained, and a stirring action is obtained. As the molten metal R in the container 4a is stirred, the added desulfurizing agent is uniformly distributed and the desulfurizing action is promoted. The molten metal that has completed the desulfurization action in this manner continuously flows out from the pouring port 4c. The magnetic flux surrounding the induction coil 1 is concentrated on the iron core 5 externally to prevent induction heating of the outer frame (made of iron), not shown, but this is not necessarily required if the material of the outer frame and its arrangement are taken into consideration. .

The temperature change of the molten metal in the apparatus of the present invention can be as follows. In other words, the temperature inside the desulfurization equipment is 1500°C.
→ Temperature at tapping after desulfurization: 1450℃ → Casting.”

In other words, it can be seen that the temperature inside the desulfurization apparatus is normally increased by substantially 50° compared to the above temperature state.

In addition, in order to clarify the specific concept of the electromagnetic desulfurization equipment according to the present invention, the specifications are shown using a typical example: Kupora... 2 on/Hr Temperature during tapping 1550℃ This desulfurization equipment... Molten metal amount 400Kg Coil power...100KW Molten metal residence time 400/2000 x 60 = 12 minutes Temperature rising capacity...approximately 50℃.

In addition, in the above explanation, by the time the molten metal level in the desulfurization equipment rises, the molten metal that has already entered the communication pipe has not been subjected to the desulfurization action, or this amount is very small compared to the total amount of molten metal. The molten metal initially discharged from the pouring port 4c may be discarded as necessary with almost no effect. In addition, the connecting position of the communication pipe 4b from the container 4a which is responsible for heating and stirring is the container 4a.
However, due to the shape of the furnace body 4, the bottom of the container 4a
It may also be placed on the lower side of the . However, in this case, it may be necessary to bend a portion of the lower part of the induction coil 1 downward and connect a communication pipe from the side of the coil 1. On the other hand, a part or all of the communication pipe is connected to the induction coil 1
It may be placed inside. Furthermore, the induction coil 1 is not limited to a cylindrical shape, and may be any shape as long as it is cylindrical.

Note that it is of course possible to use the present invention not only for the above-mentioned applications but also as a device for adjusting the composition of molten metal, such as a device for producing a molten alloy by adding an alloy material such as titanium metal to molten aluminum.

As described above, the electromagnetic desulfurization apparatus according to the present invention includes a cylindrical induction coil and a molten metal container made of a refractory material inside the cylindrical induction coil. The external pouring port is on the same level as the upper part of the container, and receives molten metal, desulfurization agent, and other additives simultaneously from the molten metal container as a continuous flow, and desulfurization treatment or addition that overflows from the communication path. It is designed to obtain a molten metal that has been given a chemical agent. Based on this configuration, it is possible to effectively combine both the stirring power and the temperature raising power by electromagnetic induction with the desulfurization effect or the uniform distribution of additives, and in particular, it is possible to separately increase the adverse effects associated with the temperature drop in the desulfurization equipment. The practical advantage of being able to remove it without installing a heating device is great. In addition, the same amount of molten metal introduced into the electromagnetic induction stirring device is obtained regardless of the size of the hole in the communication pipe, and the amount of molten metal discharged is controlled by controlling the amount of molten metal discharged from the cupola. Furthermore, since the head difference between the receiving and tapping hot water is small, it can be easily introduced into existing factory processes.

[Brief explanation of drawings]

FIG. 1 is a sectional view, and FIG. 2 is a partially omitted plan view. 1... Induction coil, 4... Furnace body, 4a... Molten metal container, 4b... Communication pipe, 4c... Pouring port, 6...
Molten metal inflow gutter, 7... desulfurization agent addition pipe.

Claims (1)

[Claims] 1. A molten metal container is formed from a refractory material in a space surrounded by a cylindrical induction coil, and a molten metal pouring port is placed at an appropriate place outside the induction coil at a level corresponding to the upper end of the induction coil in the molten metal container, and An electromagnetic induction stirring device, characterized in that it is provided with a communication pipe connected to the pouring port from the lower part, and is provided with means for supplying molten metal and additives to the molten metal container.