JPH04300048A - Manufacture of small-sized molding pig iron - Google Patents

Abstract

PURPOSE:To manufacture a small-sized molding pig iron by making mold ratio the specific value, air-cooling after casting, successively, cooling surface of the molding pig iron with water-spraying and making shrinking speed of the molding pig iron faster than shrinking speed of the mold. CONSTITUTION:The mold ratio (mold wt./molding pig iron wt.) is set to >=8. Molten pig iron 2 is cast in the mold 1. After casting, the air cooling is executed for one min and then, water spraying cooling is executed for two min. The cast pig iron 2 is cooled and solidifying-shrunk in faster than the mold 1 and gap between the pig iron and the mold 1 is developed, and by turning over the mold 1, the pig iron is easily released and dropped. The small-sized molding pig iron having <=1kg unit wt. can be manufactured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing small-sized pig iron having a unit weight of 1 kg or less.

0002

[Prior Art] As a method of forming molten pig iron produced in a blast furnace or electric furnace into shaped pig iron, it is common to use a pig iron casting machine equipped with a large number of molds that move at variable speeds. 1983. p. 132, p. 1
85 and Iron and Steel Handbook October 15, 1971
Published by Himaruzen Co., Ltd. p. 298-299, p. 398
).

[0003] Conventionally, the size of pig iron molds that can be produced using this iron casting machine is 5 to 40 kg/piece in weight, and it has been said that small pig iron molds with a unit weight of less than 5 kg cannot be manufactured. The reason for this is that ``After the molten pig iron poured into the mold cools and solidifies, the fact that it peels off from the mold depends on the weight of the pig iron itself, so a certain weight or more is required.'' Ta. In the conventional mold pig manufacturing method, even the lightest mold pig iron having a unit weight of 5 kg has a mold ratio (mold weight/mold pig weight) of about 5 as shown in FIG.

[0004] In addition, there are methods for turning molten metal into small particles of about 10 mm in size, such as using water pulverization, oil pulverization, or a turntable.
There are examples in the refining industry.

[0005]

[Problem to be solved by the invention] Pig iron with a unit weight of 5 to 40 kg is only used as raw material for iron in the foundry industry, etc.
For example, when ferroalloys such as FeCr pig iron and FeMn pig iron are added to molten steel to produce ferroalloys, they are too large to be used as raw materials and are difficult to handle using flexible container bags or conveyors.

On the other hand, methods using water fracking (flow iron machine) and oil fracking are accompanied by the generation of steam or oil smoke, which poses the problem of environmental pollution, and methods using a turntable are limited to metals with a small heat capacity (for example, Al). The problem was that pig iron could not be processed and was not suitable for mass production. It is an object of the present invention to eliminate the above-mentioned drawbacks of the prior art and to provide a method for manufacturing small-sized pig iron having a unit weight of 1 kg or less with good releasability.

[0007]

[Means for Solving the Problems] That is, the present invention provides a mold ratio (mold weight/mould weight) of 8 or more when casting blast furnace hot metal or electric furnace hot metal into a small mold pig iron with a unit weight of 1 kg or less. , after casting, the surface of the pig iron is cooled by air cooling, and then by water spraying, and the shrinkage speed of the pig iron is controlled by the expansion of the mold.
This is a method for manufacturing small-sized pig iron characterized by making the shrinkage speed faster.

[0008]

[Function] According to the present invention, when casting a small pig iron with a unit weight of 1 kg or less, the mold ratio is set to 8 or more, air cooling and water spraying are performed, and the contraction speed of the mold pig iron is adjusted from the expansion to contraction speed of the mold. Because it performs controlled cooling that makes it faster than
The mold pig iron contracts before the mold starts shrinking, and a gap is created between the mold and the mold pig iron due to the difference in shrinkage, and even a small mold pig iron can be peeled off from the mold extremely easily, which is difficult to do with conventional technology. It became possible to manufacture small-sized pig iron with a unit weight of 1 kg or less.

Incidentally, FIG. 5 shows an investigation of the influence of the unit weight of the mold pig iron and the mold ratio on the releasability when air-cooled for 1 minute and cooled with 2 dispersion water. According to this, when the unit weight of the die pig iron is large, there is a large dependence on the own weight, and the range of mold ratios that can be adopted is wide, from 5 to 15, but as the unit weight becomes smaller, the influence of the mold ratio becomes greater than that of the own weight. In particular, it can be seen that when the mold pig iron unit weight is 1 kg or less, stable releasability cannot be obtained unless the mold ratio is 8 or more.

Furthermore, FIG. 6 shows the mold ratio and peeling rate when the mold was reversed when a mold piglet weighing 0.5 kg was air cooled for 1 minute and then cooled with 2 dispersion water. It can be seen that a peeling rate of 100% was obtained by setting the above. In addition, the mold pig removal rate is defined as follows. Mold pig peeling rate={(Number of pieces peeled off by mold reversal)/(Number of die pigs per mold)}×100 (%) Next, the present invention will be described in more detail based on Examples.

[0011]

Embodiment FIG. 2 is a sectional view of a mold showing an embodiment of the present invention. In this example, the pig iron 2 has a base size of 65 mm x 65 m.
It was a square pyramid with a height of 36 mm and an apex angle of 60°. In the mold 1, the pig irons 2 were formed at a pitch of 85 mm, and the thickness of the outer peripheral part was 20 mm. According to this example, the weight of the mold piglet 2 is approximately 0.5 kg/month, and the mold ratio (mold weight/mold pig weight) is 8.

[0012] When molten pig iron is cast using this mold 1, and after being air-cooled for 1 minute, it is cooled with water spray from above for 2 minutes.
The cast pig iron cools, solidifies, and shrinks faster than the mold.
A gap was created between the mold and the mold, and it easily peeled off and fell when the mold was turned over. Figure 3 shows the temperature change of the pig iron and mold at this time, and Figure 4 shows the coefficient of thermal expansion and contraction. The cooling contraction of the mold 2 proceeds faster than the thermal expansion and contraction of the molten pig iron of the mold 1, and a gap is created between the mold pig iron 2 and the mold 1.

On the other hand, in the case of the conventionally commonly used 5 kg pig iron with a mold ratio of about 5, as shown by the broken line in Fig. 3, the cooling and shrinkage speed of the mold pig iron is slow, so the mold is removed within about 2 minutes after pouring. Since the pig iron and the mold reach approximately the same temperature and then cool and contract almost as one, it is difficult for gaps to form between the pig iron and the mold. In addition, in the above embodiment, water cooling is performed after air cooling, but cooling of the mold pig iron 2 is accelerated by the water spray cooling, and at the same time, cooling and shrinkage of the mold 1 start slightly, and a gap is formed. As the mold contracts, it has the effect of lifting the mold pig iron.

[0014] As described above, by setting the mold ratio to 8 or more and performing controlled cooling that promotes cooling of the mold pig iron by air cooling and water cooling after casting, even small mold pig iron weighing about 0.5 kg or less can be manufactured. . It has been confirmed that the present invention can produce mold pig iron weighing at least 0.25 kg. As a second embodiment of the present invention, the pig iron weight shown in FIG. 7 is 0.5 kg/month,
For the case of a mold ratio of 10 and the case of a mold piggy weight of 0.5 kg/month and a mold ratio of 7 shown in FIG. 8 as a comparative example,
An experiment similar to that described above was conducted.

When a mold with a mold ratio of 10 was used, the releasability of the pig iron was further improved compared to when a mold with a mold ratio of 7 was used. When a mold with a mold ratio of 7 was used, approximately 5% of the pig iron was not separated from the mold simply by inverting the mold, and countermeasures such as applying vibration to the mold were required.

[0016]

[Effects of the Invention] In the present invention, the mold ratio is set to 8 or more, and controlled cooling is performed such that the cooling contraction speed of the mold pig iron progresses faster than the expansion-contraction speed of the mold by air cooling and water spray cooling. The pig iron can now be easily separated from the mold, making it possible to manufacture small pig pigs with a unit weight of 1 kg or less. Therefore, compared to the conventional limit of 5 kg/month of pig iron, it is easier to handle, and the fields of use of pig iron can be expanded.

[0017] Furthermore, the present invention can be applied to existing pig iron casting machines by simply changing the shape of the mold and improving the cooling system, and has the effect that small-sized pig iron can be manufactured without much investment.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional pig iron and a mold.

FIG. 2 is a sectional view of a pig iron and a mold in the first embodiment of the present invention.

FIG. 3 is a diagram showing temperature changes between the pig iron and the mold.

FIG. 4 is a diagram showing the coefficient of thermal expansion and contraction of pig iron and mold.

FIG. 5 is a diagram showing the releasability of mold pig iron using the mold pig iron unit weight as a parameter.

FIG. 6 is a diagram showing the relationship between mold ratio and peeling rate of 0.5 kg/month of pig iron.

FIG. 7 is a sectional view of a pig iron and a mold according to a second embodiment of the present invention.

FIG. 8 is a sectional view of a pig iron and a mold of a comparative example.

Claims (1)

[Claims] Claim 1: When casting blast furnace hot metal or electric furnace hot metal into small mold pig iron with a unit weight of 1 kg or less, the mold ratio (mold weight / mold pig iron weight) is set to 8 or more, air cooling is performed after casting, and then the mold is A method for manufacturing small-sized pig iron, characterized by cooling the surface of the pig iron and making the contraction speed of the mold piglet faster than the expansion-contraction speed of the mold.