JP2806620B2 - Cast pig iron and method for producing casting pig iron - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a casting pig iron having a clean surface shape and a pig iron casting.

[Prior Art] Raw material pig iron for casting is mainly cast as a long pyramid truncated pyramid called a shape pig (namako pig) 1 as shown in FIG. 5 and supplied to the market. There are various cross-sectional shapes from a trapezoidal shape to a semicircular shape, but the basic shape is a shape connected by a notch 2 for the purpose of breaking when used, that is, a double mountain shape.

As shown schematically in FIG. 6, the pig iron 1 is manufactured by connecting a cast iron mold 5 in an endless track shape, and rotating and connecting the cast iron to the mold and cooling it. The equipment for continuously casting the pig iron 1 is referred to as a cast iron machine 9. In general, it is used not only for the production of cast iron, but also for converting hot metal into cold iron when the production of the blast furnace and the converter becomes inconsistent due to an accident at an ironworks. The feature of this mold is that it is a top-open mold unlike a general casting.

The shape of the pig iron is not determined for any particular reason, and is determined mainly by the ease of casting during casting and the ease of removal from the mold because it is cast by the casting machine 9 as described above. ing. The unit weight is determined by transportation convenience and productivity. Therefore, the casting pig iron as the iron source for casting has the following problems during casting.

[Problems to be Solved by the Invention] In the conventional cross section of a fish-shaped pig iron, shrinkage cavities are likely to occur on the open surface at the uppermost surface of the pig iron. Further, depending on the conditions of the cast iron, that is, when the temperature of the cast iron is high or when the speed of the cast iron is large, a larger honeycomb-like shrinkage cavity is generated on the open surface at the top of the pig iron. This defect is called perforated pig iron at the manufacturing site. Therefore, in order to prevent these defects from occurring, measures have been taken to reduce the speed of the cast iron or to lower the temperature of the cast iron, such as leaving the molten iron until the proper temperature of the cast iron. In any case, these pig iron defects were a major productivity impediment for casting iron operations.

In addition, this defect is susceptible to rust, and furthermore, sediment and the like easily accumulate during slag or yard storage, which increases the amount of slag generated when using pig iron and wears out useful elements such as C and Si in the molten metal. Furthermore, since it causes a casting defect of a product casting, not only a problem that the commercial value is reduced from the appearance and appearance of the pig iron, but also a countermeasure is desired from the viewpoint of the quality of the pig iron.

As described above, according to the present invention, the sectional shape of the conventional pig iron for casting tends to cause defects in the open surface of the pig iron during production, which is not only a problem in the appearance of the pig pig, but also the use of the pig iron. In order to solve the problems, it has been found that the casting iron speed could not be increased because it causes casting defects in the product casting.

That is, an object of the present invention is to provide a pig iron shape excellent in productivity, in which defects do not occur in the pig iron at the time of casting iron, and a method for producing the same.

[Means for Solving the Problems] The present invention provides: (1) In a one-piece iron casting pig cast by a metal mold, the shape of the pig iron is a truncated pyramid, and the long side and the short side of the open surface are formed. The relationship and the area and the wall thickness are as follows: L ₁ (short side): L ₂ (long side) = 1: 1 to 2 H (wall thickness) ≦ 0.4 S (area of open surface) ^1/2; and (2) in the method of manufacturing a pig iron for casting, forming a plurality of concave portions corresponding to the pig iron described in (1) above in a metal mold; A small-section runner is formed on the metal mold corresponding to the short side of the pig iron to connect between adjacent recesses, cast iron is cast on the metal mold, and the cast iron is cast from the metal mold at the end of the casting machine. A method for producing a casting pig iron, characterized in that the runner portion is broken at the time of demolding and subsequent impact to form a single casting casting pig iron.

It is.

As the shape characteristics of the Operation] The present invention is pig iron, the relationship between the long side L ₂ and a short side L ₁ of the release surface and the relationship of its release surface area S and thickness H,
Since L ₁ : L ₂ = 1: 1 to 2 and H ≦ 0.4 · S ^1/2 , the solidification from the lower surface and the surrounding surface and the solidification from the release surface are balanced, and the release surface is In addition, since the coagulation shrinkage is dispersed throughout, there is almost no drawback in the cross section.

Also, a plurality of recesses corresponding to the pig iron are formed in the metal mold by aligning them, and a small-section runner is formed in the metal mold at a portion corresponding to the short side of the pig iron to connect adjacent recesses, The cast iron is cast into the metal mold, and after the cast iron, the runner is broken at the time of demolding from the metal mold at the end of the casting machine and by subsequent impact to form a single-piece cast iron, so that the conventional mold is used. The cast iron has no portion corresponding to the notch portion of the iron, and defects occurring in the portion are prevented.

 Hereinafter, the present invention will be described specifically.

In order to solve the above-mentioned problems, we first investigated why the open face is likely to have defects in the conventional pig shape. As a result, it was found that the thick part of the conventional pig had the shape of the cross section of the hot metal just cast, so that the release surface was likely to be the final solidified part. In addition, it was found that the projections in the mold for providing the notch in the pig iron became heat retaining portions, delaying the solidification, and this also became the final solidification portion, which contributed to the generation of defects.

Furthermore, depending on the casting iron conditions, that is, when the casting iron temperature is high or the casting iron speed is high, the unsolidified molten metal in the large drawhole generated in this final solidification part and the cooling water react, and a larger honeycomb-like It turned out to be a so-called hole in the shrinking nest. Therefore, in order to eliminate the heat stagnant portion of the mold pig notch 2, the inventor invented the cast iron by removing the notch from the seashell-shaped pig iron shape and taking one piece in a single block shape. Thus, it is possible to prevent a defect occurring in the notch portion. However, in the conventional pig iron shape, the notch is entangled and it is easy to form a bridge in the hopper, and it is almost impossible to automatically cut and charge the pig iron into the melting furnace, but this single-piece pig iron makes it possible to some extent A side effect was also created.

The second problem is a defect that occurs in the upper open portion of the thick part of the die.
As a result of examining this problem from the perspective of mold pig solidification,
I found the relationship shown in the figure. That is, it was found that when the thickness of the pig iron was set to 40% or less of the square root of the area of the open surface, no shrinkage cavity was generated on the open surface. With such a relationship, the solidification from the lower surface and the surrounding surface and the solidification from the release surface are balanced, and the release surface does not become the final solidified portion. It was found that almost no shrinkage cavities occurred. In addition, such a relationship is such that the relationship between the short side and the long side of the release surface is as shown in FIG.
It is found that it is established by about 1: 1 to 2, and when the longer side is larger than this, the progress of solidification from the side is large, and it is understood that a shrinkage cavity occurs in the center of the release surface in the longitudinal direction as in the past, as in the past .

From the above, the thickness of the pig iron and the shape of the release surface were defined as follows, and the defect of the release surface of the pig iron could be solved.

L ₁ (short side): L ₂ (long side) = 1: 1 to 2 H (thickness) ≦ 0.4 · S (area of open surface) ^1/2 Of course, the shape is basically a truncated pyramid. For example, a shape that satisfies the above condition, such as a truncated cone, can also be used.

However, such small block-shaped pig iron is cast iron,
If multiple cast irons are placed in one mold due to productivity,
Single weight variation occurs between the pig irons. This is a major problem for many foundries that omit weighing during melting and control the number of pig irons. This problem was solved by the following casting method.

First, as shown in FIGS. 1 (a) and 1 (b), first, all the pigs 1 in the mold 5 are connected and cast.
That is, a plurality of concave portions corresponding to the pig iron 1 are aligned and formed,
A small-section hot runner is added to the mold 5 at a position corresponding to the short side of the pig iron 1.
Construct 10 to connect between adjacent recesses. Thereby, the mold 5
When cast iron is used, the hot metal passes through the runner 10 and reaches each recess, so that the unit weight of the pig iron 1 can be made substantially uniform.

Next, it is necessary to separate the connected pig irons 1 individually. The notch 2 of the conventional pig iron 1 requires one process for breaking, which increases the manufacturing cost. This was solved by using the energy of the pig iron 1 separating from the mold 5 at the end of the cast iron machine 9 and falling into the hopper 6 and the energy of unloading for transportation. That is, the relationship between the unit weight of the pig iron 1 and the cross-sectional area of the runner 10 is taken as shown in FIG. 4 and is preferably formed in a flat plate shape.
It was found that it broke. As a result, the cast pig iron 1 is broken by the energy of the drop from the end of the nine pig iron machines, and further broken completely by loading and unloading to the yard for storage, and becomes individual pig pig 1. .

Of course, the cross section of the runner 10 may be not only a flat plate but also a semicircular shape, a wedge shape, or the like, and a plurality of runners 10 may be provided by being divided.

[Examples] The present invention will be described in detail below using specific examples.

FIG. 6 shows one embodiment of a pig iron casting apparatus. Reference numeral 3 is a hot metal receiving bowl, 4 is a pool, 5 is a mold, 6 is a hopper, and 7 is a sprinkler.

When the hot metal is supplied to the upper pool 4, a certain amount of hot metal is supplied to the casting machine 5 from the holes of the skinmer 8. The casting machine 5 adjusts the speed in conjunction with the supply amount of the molten metal so that the supply amount of the molten iron to the mold 5 becomes constant. Using this cast iron machine, the present invention was used to cast cast iron equivalent to FIC pig under the following conditions. As the pig iron, the size of the pig iron which does not decrease the charging density even in a melting furnace having a small furnace diameter, such as a high-frequency melting furnace which has been widely used in recent years, is used. Cast iron was also used when the runner of the present invention was not used, and the effect was compared with that of a conventional sea cucumber pig cast with the same casting machine 9.

Hot metal temperature: 139 ° C Type pig size: 7.5 × 15.0 × 4cm Number of type pigs per mold: 12 Mold weight: 175 kg (mold ratio: about 5.8) Weir cross section: 7 cm Type ² single pig iron weight: 3 kg Cast iron amount: 200 t Result Is as shown in Table 1. Conventionally 5 kg of pig iron weight
Was cast at 30 kg under almost the same conditions. Compared with the single-piece pig iron of the present invention, the casting iron speed was improved by about 37%, and the defect generation rate on the pig iron upper surface was also reduced by about 37%.
It has dropped to 1/7. In order to increase the casting iron speed, the draft angle was required to be 60 ° in the conventional pig, but in the present invention, since the thickness of the pig iron was reduced, it was possible to reduce the draft angle to 70 °. Effects are also included.

In addition, a single amount of variation, which is a problem when casting single-piece pig iron, is improved by about 20% by providing the weir of the present invention.

[Effects of the present invention] According to the present invention, it is possible to cast a sound single-piece pig iron having no defects on its upper surface with no change in unit weight and high productivity. In addition, this pig iron can be automatically charged into the melting furnace, and the charging density in small-diameter melting furnaces such as the high-frequency induction melting furnace, which has recently become widespread, increases the melting efficiency. There is an effect of doing. Therefore, the practical value of the present invention is great.

[Brief description of the drawings]

1 (a), 1 (b) and 1 (c) are explanatory diagrams of the shape of the pig iron of the present invention, and FIG. 2 is a graph showing the relationship between the wall thickness / surface area of the pig iron upper surface releasing portion and the amount of defects generated. FIG. 3 is a graph showing the relationship between the long side / short side of the open part of the die pig upper surface and the defect generation amount, and FIG.
Diagram showing the relationship between the cross section of a weir that can be broken at a drop distance of 1 m and the single weight of pig iron,
5 (a) and 5 (b) are explanatory views of the shape of a conventional pig, and FIG.
The figure is a schematic explanatory diagram of a cast iron machine. DESCRIPTION OF SYMBOLS 1 ... Shaped pig, 2 ... Notch part 3 ... Hot metal receiving pot 4, ... Hot water pool 5 ... Mold, 6 ... Hopper 7 ... Sprinkling device, 8 ... Skinmer 9 ... Cast iron machine, 10 …… runner

Claims (2)

(57) [Claims] 1. A pig iron for one-piece casting, which is cast by a metal mold, wherein the pig iron has a truncated pyramid shape, and the relationship between the long side and short side of the open surface and the area and wall thickness are as follows. L ₁ (short side): L ₂ (long side) = 1: 1 to 2 H (wall thickness) ≦ 0.4 · S (area of open surface) ^1/2 2. A method of manufacturing a pig iron for casting, wherein a plurality of recesses corresponding to the pig iron according to claim 1 are formed in the metal mold by aligning them, and the metal mold at a portion corresponding to the short side of the pig iron is formed. A runner having a small cross section is formed to connect between adjacent recesses, cast iron is cast into the metal mold, and the runner is cast by the impact after the casting from the metal mold at the end of the cast iron machine and the subsequent impact. A method for producing a casting pig iron, which is broken to form a single casting casting pig iron.