JPH0481246A - Production of casting pig iron - Google Patents

Abstract

PURPOSE:To prevent the generation of bad shaped appearance of a mold pig iron by using steam having the specific value or lower of droplet diameter, cooling with atomized water spreading and making the specific temp. or lower of super heat at near surface layer of molten pig iron in the mold before cooling with much water spraying. CONSTITUTION:In this invention, the super heat at near the surface layer of molten pig iron in the mold before cooling with water spreading is made to be >=50 deg.C. In the case of the general casting pig iron, this can apply the well- known cooling method, but in the case of high Si pig iron having >=2.0% Si, as this solidifying temp. is low, the case, which can not cool to the prescribed temp., is developed. In this case, in this invention, by colliding atomized water particles having very fine, such as <=20mum particle size, to a material to be cooled with the air force, sensible heat according to the vaporization of water particles, is utilized. By this method, as the surface of molding pig iron is scarcely wetted and cooling capacity as the same degree as the ordinary water spraying, is obtd., cooling water is not invaded into inner part of the molded pig iron and the bad appearance is not developed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing foundry pig iron with an excellent external shape by casting hot metal tapped from a blast furnace or other pig iron making furnace. It is something.

[Prior Art] When producing mold pig iron by casting hot metal tapped from a blast furnace or other pig iron making furnace, the strand length of the iron casting machine is shortened due to equipment cost and installation space issues. Therefore, a large amount of water is applied to cool the mold to the temperature required for demolding. On the other hand, it is also known that if the vicinity of the surface layer of the hot metal in the mold is cooled with water before it is completely solidified, the appearance of the hot metal will be impaired, and an invention related to this problem is disclosed in JP-A No. 159245/1988 entitled ``Method for Producing Casting Pig''. In this method, watering is divided into spray water and water sprinkling. However, although the above method is effective for low-t pig iron, productivity decreases for high-Si pig iron.

[Problem to be solved by the invention] When producing mold pig iron for foundry in a casting machine, in order to cool it down to a temperature at which it can be demolded in the demolding section, the hot metal poured into the mold is cooled by air during the movement process. , spray water cooling, water spray cooling. At that time, if the surface layer of the mold pig iron is cooled by water spraying before it has completely solidified, the cooling water that has accumulated on the thin skin surface of the mold pig iron will enter the interior through the cracks on the surface of the thin skin, come into contact with the molten pig iron, and vaporize, causing the thin skin to surface. The thin skin and part of the molten pig iron in that area are scattered, and the appearance of the solidified pig iron is significantly deteriorated. Figure 3 schematically represents the situation. In the figure, 10 is the mold, 11 is the cooling water, 12 is the solidification part, 13
indicates an unsolidified area.

It has also been found that this phenomenon is particularly noticeable in high-Si pig iron. The only way to avoid this is to perform air cooling until the vicinity of the surface layer of the hot metal in the mold is completely solidified, and then perform water cooling. That is, in order to secure the time necessary for air cooling, a decrease in productivity due to a decrease in mold conveyor speed becomes a problem.

[Means for Solving the Problems] The present invention provides a method for performing air cooling, spray water cooling, and water spray cooling during casting of foundry pig iron tapped from a blast furnace or other pig iron making furnace. This is a casting pig iron production method characterized by reducing the superheat near the surface layer of hot metal in the mold to 50°C or less, and by cooling the hot metal temperature before pouring it into the mold, the surface layer of hot metal in the mold before cooling by water spraying. This is a casting pig iron manufacturing method characterized by reducing the nearby superheat to 50°C or less, and the droplet diameter is 20°C.
Superheat near the surface layer of hot metal in the mold to 50°C before cooling by spraying water using air water with a particle size of less than μm.
This is a method for producing foundry pig iron characterized by the following steps.

[Made for production] Hereinafter, the present invention will be specifically explained based on the drawings.

Figure 1 shows an overview of the cast iron machine equipment. Hot metal tapped from a blast furnace or other pig iron making furnace is transported to a casting machine in a pig iron mixing car or a hot metal ladle 2.

The hot metal that has arrived at the casting machine and is cast from the hot metal mixer car or the hot metal ladle 2 passes through the movable gutter 3, fixed bridge, and branch gutter 4, and is poured into the mold 5 that is continuously arranged on the mold conveyor 1. . After being poured, the hot metal is cooled and solidified, forming a molded pig iron into a product. The hot metal and die pig iron in the mold 5 are first air cooled as the mold conveyor moves, and then soft cooled by spray water cooling 6 to solidify the vicinity of the surface layer of the hot metal in the mold 5. Next, the mold is forced to a temperature at which it can be demolded by spraying a large amount of water 7.

After cooling, the mold pig iron falls naturally under its own weight during the process in which the upper surface of the mold 5 changes from upward to downward in the demolding section 8, is demolded, and is transferred by the apron conveyor 9. At that time, if the solidification of the mold pig iron is incomplete due to insufficient cooling, if the mold pig iron breaks or cracks, the unsolidified hot metal inside the mold pig iron will be released to the outside, causing equipment trouble and product defects. , cooling of mold pig iron, and solidification control are very important.

However, as described above, if the molten pig iron in the mold 5 is cooled with water spray in a state where the surface layer and its vicinity are not completely solidified, the external appearance of the manufactured pig pig iron will deteriorate.

The present inventors measured the difference between the solidification temperature of the hot metal poured into the mold 5 and the surface temperature of the hot metal in the mold 5 immediately before cooling with water spraying, the so-called superheat, and found that the cast iron temperature in Figure 2 and the temperature at the start of water spraying were As shown in the relationship between the quality of appearance and shape depending on the difference in super heat, casting iron with a similar composition to
It was confirmed that in the cast iron temperature range of 1,350 to 1,450°C, no defective appearance of the pig iron shape occurred when the superheat I was 50°C or less. Table 1 shows typical test conditions shown in Figure 2.

Table 1 Typical Test Conditions Therefore, the present invention provides a method for cooling foundry pig iron tapped from a blast furnace or other pig iron making furnace during the process of performing air cooling, spray water cooling, and water sprinkling cooling. The superheat near the surface layer of the hot metal in the mold before cooling is reduced to 50°C or less.

As mentioned above, as a specific means to reduce the superheat near the surface layer of the hot metal in the mold to 50°C or less before cooling with water, for example, a coolant such as mold pig iron is poured into the hot metal in the mixer car or the hot metal ladle 2. A method for controlling the temperature of hot metal within a set temperature range in consideration of transportation time, and a casing that collects dust and air-cools the movable gutter 3, fixed bridge, and branch gutter 4 through which the hot metal passes before being poured into the mold 5. (not shown), a method of forcibly cooling the hot metal to be injected, and a combination thereof can be adopted.

The above-mentioned method of cooling the hot metal temperature to a predetermined temperature before injection can be effectively applied to, for example, low-Si pig iron with St: 2.0% or less.
With high SI pig iron, which is 0% or more, since its solidification temperature is low, there are cases where it cannot be cooled to a predetermined temperature.

However, in the present invention, water is atomized with gas so that the droplet diameter is 20 μm.
The surface of the molten pig iron in the mold 5 before being cooled by water spraying is solidified by spraying cooling using air water of less than 1000 ml. This air-water cooling uses very fine spray particles of 20 μm or less to collide with the object to be cooled using air force, and utilizes the sensible heat that accompanies the evaporation of the water particles. Since the cooling performance is comparable to that of spray water, there is no possibility of cooling water entering the pig iron mold.

[Example] Table 2 shows the results of a cooling test using a conventional type spray nozzle and an air-water nozzle of the present invention type. Table 3 shows the hot metal components and operating conditions at that time. Cooling started at a position 7.6 m from the injection position, and the cooling length was 9.5 m. The external shape of the molded pig iron was sampled and visually evaluated before the strong cold water spraying.

As a result, the spray type had a phenomenon in which cooling water accumulated on the surface of the pig iron, and the appearance was poor. When the spray particle size of the air-water type was 20 μm or less, there was no phenomenon in which cooling water accumulated on the surface of the mold pig iron, and the appearance shape was good.

Table 4 shows the results when an air-water nozzle was applied to a conventional spray watering zone. The cooling start position was 18 m from the injection position, and the nozzle used was the same as the test product in Table 2, and the water pressure was set at 0.5 and the air pressure was set at 2.5 kg/cm2. As a result, the production volume was the same as before the measures were implemented, and the incidence of defective products was completely eliminated.

[Effects of the Invention] By controlling the superheat of the surface of the molten pig iron (shaped pig iron) in the mold to 50° C. or less before cooling with water in a cast iron casting machine, there is a remarkable effect that there is no defect in the external appearance of the shaped pig iron.

[Brief explanation of the drawing]

Figure 1 is an overview diagram of the pig iron casting machine equipment, and Figure 2 is an illustration of the relationship between cast iron temperature and the quality of the external appearance due to the difference in superheat at the start of water spraying. Fig. 3 is a model diagram of the occurrence of a shape defect. 1...Mold conveyor 2...Pig iron mixer car or hot metal pot 3...Movement line 4...Fixed bridge and nuclide 5
...Mold 6...Ladder for spraying water 7...Header for watering 8...Mold removing section 9...Apron conveyor 10...Mold 11...Ning water 12
...Coagulated section 13...Uncoagulated section and 4 others

Claims (1)

[Scope of Claims] 1. During the casting of foundry pig iron tapped from a blast furnace or other pig iron making furnace, in the process of performing air cooling, spray water cooling, or water spray cooling, near the surface layer of hot metal in the mold before water spray cooling. A method for producing foundry pig iron, characterized by reducing superheat to 50°C or less. 2. By pre-cooling the hot metal temperature before pouring it into the mold in the process of performing air cooling, spray water cooling, and water spray cooling during casting of foundry pig iron tapped from a blast furnace or other pig iron making furnace, A method for producing foundry pig iron, characterized by reducing superheat near the surface layer of hot metal in a mold to 50°C or less before cooling with water spray. 3 During the process of air cooling, spray water cooling, and water spray cooling during casting of foundry pig iron tapped from a blast furnace or other pig iron making furnace, spray cooling using air water with a droplet diameter of 20 μm or less is performed. A method for producing foundry pig iron, characterized by reducing superheat near the surface layer of hot metal in a mold to 50°C or less before cooling with water spray.