JPS6363603B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for producing spheroidal graphite cast iron and an operating method thereof.

As is well known, spheroidal graphite cast iron is widely used in various mechanical parts, pipes, etc. because of its high toughness, ductility, and excellent heat resistance. Spheroidal graphite cast iron is cast by adding a graphite spheroidizing agent (for example, magnesium-iron-silicon alloy) to molten cast iron to promote spheroidization of graphite. It is manufactured by performing spheroidization treatment using two methods.

A method in which a spheroidizing agent is added to molten cast iron in advance, and then the molten metal is poured into a mold using a pouring device.

A method of mixing molten cast iron and a spheroidizing agent inside a mold.

First, method (1) is a conventionally conventional method, in which molten metal is received in a special ladle for spheroidization → conveyed → spheroidization treatment by adding a spheroidizing agent → slag removal → transportation → transferred to a pouring ladle The metal is cast through the following steps: receiving the metal and pouring it into the mold. However, this method requires a long time to pour the molten metal into the mold due to the multiple steps described above, and therefore the temperature of the molten metal decreases significantly, which may cause defects in the cast product. There was a problem. Furthermore, in this method, since the spheroidizing agent added to the molten metal is in a supersaturated state in the atmospheric atmosphere, volatilization of the spheroidizing agent progresses over time after the spheroidizing process and until it is poured into the mold. However, as the concentration decreases, the so-called fading phenomenon occurs in which the spheroidizing ability decreases.
Therefore, the spheronizing agent is added at a sufficiently high concentration in consideration of the decrease in the spheronizing ability after the spheroidizing process until the final pouring and solidification. This method has a problem in that it requires a large amount of spheronizing agent and is uneconomical.

In addition, method 2 is a method devised to solve the problems of method 2 described above, in which a spheroidizing chamber is formed inside the mold, and a spheronizing agent is placed inside this chamber. This is a method in which the molten metal being poured is subjected to a spheroidizing process inside the mold. According to this method, the molten metal is poured in a short time without requiring a large number of steps, so that the temperature of the molten metal does not drop and the fading phenomenon does not occur.

However, in this method, the spheroidizing chamber is provided inside the mold, which makes the shape of the mold complicated, and the remaining metal in the spheroidizing chamber lowers the yield of the cast product relative to the amount poured. This has led to the problem of increasing the cost of the product. Furthermore, since the efficiency of mixing the molten metal and the spheronizing agent is low, unreacted spheronizing agent tends to remain in the product, resulting in the problem that the quality of the product is unstable.

The present invention was made in view of the above circumstances, and
A mold with a simple structure can be used, and at the same time, after adding a spheroidizing agent to molten cast iron, the molten metal can be poured into the mold in a short time, and the spheroidizing process can be performed reliably. The purpose of this invention is to provide an apparatus for producing spheroidal graphite cast iron and a method for operating the apparatus.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention.
A manufacturing apparatus 1 for spheroidal graphite cast iron shown in this figure schematically includes a mold 2, a stirring device 3 installed above the mold 2, a control device 4 for controlling the operation of the stirring device 3, and a pouring device. It consists of a device 5 and a spheroidizing agent addition device 6.

The mold 2 has a structure similar to that of molds commonly used in the past, and is provided with a sprue 2a for pouring molten metal at its upper part.

The stirring device 3 includes a refractory crucible 7 formed into a bottomed cylindrical shape having an opening 7a at the top, and an electromagnetic induction coil unit (electromagnetic induction stirring mechanism) 8 provided around the outer periphery of the refractory crucible 7. It is made up of The refractory crucible 7 has a pouring nozzle 9 formed at its bottom with a predetermined inner diameter. Further, the coil unit 8 applies horizontal rotational force to the molten metal introduced into the refractory crucible 7 to stir it.

Further, the control device 4 includes a power supply circuit 10 for supplying power to the coil unit 8 of the stirring device 3, and a control section 11 for controlling the power supplied by the power supply circuit 10. In this case, the power supply circuit 10 includes a transformer 13 for output conversion connected to a power source (not shown) via a circuit breaker 12, a first terminal 13a (supplying large power) of the transformer 13, and a Switching contacts 14a and 14b each connected to a second terminal (supplying small power) 13b, and these switching contacts 14
a, 14b, and a power factor improvement capacitor 16 inserted between the switching contacts 14a, 14b and the output matching transformer 15. Electric power is supplied to the coil unit 8 from the coil unit 8. Further, the control unit 11
Detectors 17 and 18 are arranged near the opening 7a of the refractory crucible 7 and the pouring nozzle 9 to detect the presence or absence of molten metal flow, and a circuit is supplied with outputs from these detectors 17 and 18. It consists of part 19.
This circuit section 19 connects the first and second switching contacts 14 based on the detection outputs of the detectors 17 and 18.
a, 14b are controlled to open and close. Furthermore, in this case, the circuit section 19 has a timer (not shown), and the switching of the switching contacts 14a and 14b can be controlled by the operation of this timer.

Based on the above configuration, the control device 3 includes the circuit section 19
When the first switching contact 14a is closed by the output of It's summery.

Further, the spheroidizing agent addition device 6 is installed above the stirring device 3 so that its discharge nozzle 6a faces inside the opening 7a of the refractory crucible 7. This spheronizing agent addition device 6 is capable of delivering a predetermined amount of spheronizing agent into the refractory crucible 7 per unit time.

Further, the pouring device 5 is a normal pouring ladle, and is adapted to receive molten cast iron and transport it above the stirring device 3, and in this case pours the molten metal into the refractory crucible 7.

The spheroidal graphite cast iron manufacturing apparatus 1 configured as described above is installed at a pouring site so that the pouring nozzle 9 of the refractory crucible 7 is located directly above the sprue 2a of the mold 2. In a mold transport system that sequentially transports and pours a plurality of molds, the molds are moved in a tact manner so that the sprue of the mold stops directly below the pouring nozzle 9.

Next, a method for manufacturing spheroidal graphite cast iron using the manufacturing apparatus 1 described above will be explained with reference to FIGS. 1 and 2.

First, the pouring of molten metal from the pouring device 5 into the refractory crucible 7 is started, and at the same time, the delivery of the spheroidizing agent into the refractory crucible 7 is started from the spheroidizing agent adding device 6. When the resulting molten metal flow is detected by the detector 17,
The circuit section 19 is configured to perform a first detection based on the output of the detector 17.
Close the switching contact 14a. That is, as shown in FIG. 2, at time _t1 when the detection output of the detector 17 (indicated by the curve in FIG. 2a) rises, the supply of high power _W1 to the coil unit 8 is started.
Accordingly, the molten metal introduced into the refractory crucible 7 at the initial stage of pouring is given a large stirring force in the magnetic field generated by the coil unit ₈ supplied with a large electric power W1. Then, after a predetermined time T ₁ set in the timer of the circuit section 19 has elapsed from the start of pouring t ₁ , the circuit section 19
The output signal causes the first switching contact 14a to open and the second switching contact 14b to close at the same time. And the coil unit 8 has a small power W ₂
will be supplied. In this case, the circuit section 19
The set time T ₁ of the timer is set in anticipation of a sufficient amount of horizontal rotation stirring movement to the molten metal inside the refractory crucible 7 at the initial stage of pouring.

During the spheroidization process inside the refractory crucible 7 as described above, the fluid slag produced by the reaction of the spheroidizing agent, oxygen in the air, etc. with the molten metal is classified as floating because it has a lower specific gravity than the molten metal. Ru. Then, slag-free molten metal is poured into the mold 2 from the pouring nozzle 9 of the refractory crucible 7.

The molten metal continuously injected from the pouring device 5 is continuously spheroidized inside the refractory crucible 7 while being continuously added with an appropriate amount of spheroidizing agent by the spheroidizing agent addition device 4, and then poured. The hot water is poured into the mold 2 from the hot water nozzle 9.

When all the molten metal inside the refractory crucible 7 has flowed out, the output of the detector 18 falls as shown by the curve in _FIG . 14b to stop power supply to the coil unit 8.

The slag floated and classified inside the refractory crucible 7 flows into the mold 2 at the end of pouring, and is applied to fill the sprue 2a of the mold 2, and is used to fill the feeder part to compensate for solidification shrinkage of the casting. It will be attached to the obidome. Therefore, slag does not mix into the parts that become products.

The ingot of spheroidal graphite cast iron produced as described above is manufactured into a product through normal steps such as demolding and casting treatment.

As mentioned above, according to the above-mentioned apparatus for manufacturing spheroidal graphite cast iron, the molten metal is immediately cast into the mold after the spheroidizing agent is added, so that almost no fading phenomenon occurs, and therefore the necessary minimum amount of spheroidization is achieved. Just add the agent. Further, since there is no need to form a spheroidizing chamber inside the mold, a mold with a simple shape can be used. Further, the fluid slag produced in the molten metal is floated and classified in the refractory crucible 7 based on the difference in specific gravity and flows into the mold 2 at the end of pouring, so that the slag does not get mixed into the part that will become the product. Further, since the molten metal and the spheroidizing agent are thoroughly mixed in the refractory crucible 7 and then cast into the mold 2, no unreacted spheroidizing agent remains in the product.

In addition, the above-mentioned spheroidal graphite cast iron manufacturing apparatus 1 is easy to automate by providing a detector for detecting the flow of molten metal in the stirring device as described above, so that the spheroidal graphite cast iron manufacturing apparatus 1 includes a spheroidizing treatment process. It is possible to simplify the manufacturing process and save labor.

Further, according to the method of operating the spheroidal graphite cast iron production apparatus of the present invention, it is possible to apply sufficient stirring force to the molten metal immediately after the start of pouring, which requires a large stirring force during the acceleration stage, and to After the molten metal has obtained sufficient rotational kinetic energy, the molten metal can be stirred with a sufficiently small stirring force, which saves the energy required for stirring, and at the same time allows sufficient spheroidization of the entire molten metal. can be administered.

As explained above, the apparatus for manufacturing spheroidal graphite cast iron according to the first aspect of the present invention can use a mold with a simple shape and at the same time avoid the fading phenomenon, so Only a limited amount of spheroidizing agent can be used, which is economical, and furthermore, since the molten metal and the spheroidizing agent can be sufficiently mixed before being poured into a mold, unreacted spheroidizing can be avoided. This method has the advantage that the agent does not remain in the product, and therefore, high quality products can be manufactured.

Furthermore, in the second aspect of the present invention, the method for operating the apparatus for producing spheroidal graphite cast iron is capable of applying sufficient stirring power to the entire molten metal, including the initial stage of pouring, to perform spheroidizing treatment. Therefore, it has the advantage of being able to manufacture excellent products with uniform quality.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the spheroidal graphite cast iron manufacturing apparatus of the present invention, and FIGS. 2 a to 2 c show the detection output of the detector and the coil unit in the manufacturing apparatus shown in FIG. FIG. 2a is a graph showing an example of the relationship between power supply and the power supplied to the coil unit. FIG. The graph shown in FIG. 2c is a graph showing the detection output of the detector installed in the pouring nozzle of the refractory crucible. 1... Apparatus for producing spheroidal graphite cast iron, 2... Mold, 2a
... Mold sprue, 3... Stirring device, 4... Control device, 5
...Pouring device, 6. Spheroidizing agent addition device, 7. Fireproof crucible, 8. Electromagnetic induction coil unit (electromagnetic induction stirring mechanism), 9. Pouring nozzle.

Claims (1)

[Scope of Claims] 1. A stirring device comprising a mold, a refractory crucible having a pouring nozzle, and an electromagnetic induction stirring mechanism, with the pouring nozzle facing the sprue of the mold;
A pouring device that introduces molten cast iron into the stirring device,
An apparatus for producing spheroidal graphite cast iron, comprising: a spheroidizing agent addition device for adding a spheroidizing agent to molten cast iron introduced into the stirring device. 2. A stirring device comprising a mold and a refractory crucible having a pouring nozzle and an electromagnetic induction stirring mechanism, with the pouring nozzle facing the sprue of the mold;
A pouring device that introduces molten cast iron into the stirring device,
In the apparatus for producing spheroidal graphite cast iron, which includes a spheroidizing agent addition device for adding a spheroidizing agent to molten cast iron introduced into the stirring device, the stirring force of the stirring device is variable, _At least the introduction start time t ₁ within the time period from the time t 1 when the introduction of the molten metal starts to the time t ₂ when the outflow of the molten cast iron from the stirring device ends.
1. A method for operating an apparatus for manufacturing spheroidal graphite cast iron, characterized in that the stirring apparatus is operated with a high stirring force for a predetermined time _T1 set from .