JPS61159245A - Production of casting pig - Google Patents

Abstract

PURPOSE:To improve the grade and yield of a pig iron by subjecting the surface of a casting mold to air cooling or spray cooling to form a solidified surface layer in the stage of casting a molten pig for casting then spraying a large amt. of water to the mold to cool forcibly the mold thereby preventing the decarburization of the surface layer and the intrusion of the generated gas therein. CONSTITUTION:The surface of the molten pig in the casting mold is subjected to the air cooling or spray cooling in the stage of casting the molten foundry pig iron to prevent the decarburization of C+H2O CO+H2 reaction and the intrusion of the solidified surface layer owing to the insufficient release of the generated gas. The surface thereof is thereafter forcibly cooled by a large amt. of the water sprayed thereto. The deterioration in the quality of the casting product owing to heredity of the pig iron is prevented and the decrease in the yield owing to the defective surface of the pig iron is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing mold pig iron for foundry by casting hot metal tapped from a blast furnace or other pig iron making furnace.

(Prior Art) When pouring bath pig iron tapped from a blast furnace or other tapping furnace, in order to simplify the iron casting machine equipment and shorten the strand length, or increase the total strand speed, It is well known that large amounts of water cooling are used to increase productivity. However, there is little known about the method of casting pig iron to improve the external shape of the finished product, and the invention related to the shape of the product is disclosed in Japanese Patent Application Laid-Open No. 54-1431.9.
There is only a method for producing high-purity pig iron for casting with an excellent external shape, and although this method is effective within a certain range of ingredients, it is not versatile.

(Problems to be Solved by the Invention) It has been found that in casting pig iron produced by the conventional technology of cooling by large amounts of water spraying, shortening the strand length, or increasing the strand speed, the surface shape often deteriorates. There were some problems, such as a decrease in the yield of good pig iron and an increase in manufacturing costs. In particular, Fe in hot metal
When an 81 adjusting material such as -8i is added to adjust Sl, there is a problem that the shape of the product is more frequently deteriorated.

When using these poorly shaped casting pigs as new products,
As the quality of cast iron products continues to deteriorate due to genetic phenomena, those skilled in the art have been eagerly awaiting the emergence of a practical technology that can improve the shape of finished products.

(Means for Solving Problems) The present invention is a method for manufacturing a foundry pig iron developed in view of the above situation, and was developed by focusing on the state of the surface layer during solidification due to the cause of the deterioration of the surface shape. It is something.

In other words, when casting hot metal for foundry metals tapped from a blast furnace or other pig iron making furnace, after forming a solidified layer on the surface layer of the mold pig iron by air cooling or spray cooling, forced cooling is performed by spraying a large amount of water. This is a method for producing foundry pig iron.

(Function) The process of producing cast iron by casting hot metal for casting is shown in FIG. 1. By tilting the hot metal pot 2, the molten metal*1 is injected into the casting pot 3, where it is separated from the graphite, and then only the hot metal is poured into the mold 5 installed on the strand 4. The hot metal poured into the mold 5 is cooled and solidified by a water sprinkler 6 to form mold pig iron.

The present inventors focused on this cooling solidification process and investigated the surface shape of the pig iron when changing the cooling solidification process.

Table 1 shows an example of the survey, and the quality of hot metal at the time of the survey was the second highest.
As shown in the table. Moreover, the shape of the mold used is as shown in FIG.

Table 1 The number of experiments was 10 for each experiment.

From Table 2 and Table 1, it can be seen that defective pig iron was generated in the iron that had been cooled and solidified by sprinkling a large amount of water. This is because the water layer, water vapor, H2, C
It is thought that three forms are created: a gas layer of o gas and the mold pig iron, and the gas layer sandwiched between the water layer and the mold pig iron deteriorates the surface of the mold pig iron, which has not yet formed a surface solidified layer. it seems to do.

In particular, since carbon exists in supersaturated form in hot metal, carbon precipitates during the cooling process and vaporizes in a reaction of C+ H20→CO+H2. This removal of water turns into gases such as Co and H2, which causes volumetric expansion, and the gases, which have no place to escape due to the layer of water, create cavities or waves on the surface of the hot metal, which shatter and solidify. When Fe-8i is added and the components are adjusted, the degree of carbon supersaturation further increases (FIG. 4), and this phenomenon becomes even more remarkable. On the other hand, when the water is cooled and solidified by spraying water, the spray water is thought to evaporate before reaching the surface of the mold pig iron, and the generated water vapor does not cause defects on the surface of the hot metal because there is no layer of water on top. Instead, the hot metal solidifies. Without watering, there is no water, so there is no problem.

That is, the present invention is characterized in that, in the water spray cooling process, the large water spray region is set after the surface solidified layer is formed after slow cooling such as air cooling or spray cooling.

(Example) The bath iron shown in Table 2 was used with a maneuvering length (strand length) of 57 m.
, casting capacity]. An example is shown in which pig iron was cast using a 75 t/h iron casting machine. 30711 from a position 15m from the injection position
Install 30 water sprinklers up to the location]Ot/min
22% (daily average) when heavy watering was performed.
Pig iron with poor surface shape was generated, but 15
The 10 water sprinklers at 5 m from the 771 position were replaced with water spray devices capable of spraying water, and water was sprinkled at a rate of 2 t/min.
15 A/min from 0m position than conventional water sprinkler
On the other hand, when pig iron was cast without changing the strand speed of 23 m/min, there was no generation of pig iron with poor surface shape.

Table 3: In addition, as shown in Figure 5, the surface shape of a typical foundry pig iron manufactured by adding Fe-8i and having the components shown in Table 3 deteriorated when the carbon supersaturation degree Sc value was around 125. . Therefore, the strand speed was set to 20 m/min.
As shown in Figure 6, the time required to reach the 20m point where a large amount of water is sprayed was increased, and as shown in Figure 6, the solidification time was increased to correspond to the increased amount of carbon precipitation, which eliminated the occurrence of surface defects. Ta.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the pig iron process for producing foundry pig iron, Figure 2 is a sketch of the mold used during the test, and Figure 3 is a schematic diagram showing the state between the water spray nozzle and the pig iron during heavy watering. , 4th
The figure shows hot metal as it has been tapped and S after adding Fe-8i etc.
Figure 5 is a graph showing the relationship between C and Sl in hot metal subjected to S1 adjustment, and shows the relationship between C and 81 in hot metal subjected to S1 adjustment, stratified by those with good product shape and those with poor product shape.
FIG. 6 is a graph showing the relationship between the strands and the strands, which are stratified into good and poor product shapes when changing the strand speed. 1... Hot metal 2... Hot metal pot 3... Cast iron trace 4... Strand 5... Mold 6... Water sprinkler device 7... Water flow
8...Water vapor, COgas. 9... Mold pig iron) T2 gas gas phase 1
0...Casting pig iron made from hot metal that has been tapped]■・
・・Casting pig iron made from hot metal added with Fe-8i etc. and subjected to Si adjustment

Claims (1)

[Claims] When casting hot metal for foundry metals tapped from a blast furnace or other pig iron making furnace, air cooling or spray cooling is performed to form a solidified layer on the surface layer of the mold pig iron, and then forced cooling is performed by spraying a large amount of water. Characteristic casting pig manufacturing method