JPH09316524A - Calcium-packed wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the pickup of nitrogen content in each heat at the time of adding a wire into molten steel by specifying the grain size of metallic calcium or calcium compound in a calcium-packed wire. SOLUTION: In the calcium-packed wire formed by coating the metallic calcium or the calcium compound for adding the calcium into molten steel with a steel hoop, the metallic calcium or the calcium compound is used in the range of 150μm-1mm grain size. The calcium compound is desirable to use the calcium-silicon alloy. By this constitution, vigorous reaction between the molten steel and the calcium can be restrained and chance, in which new molten steel surface becomes in contact with the air, is reduced and the pickup of the nitrogen content in the molten steel can be reduced. Further, the development of dust at the feeding position of the wire is reduced and the good operational circumference can be kept.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calcium-filled wire, and particularly to prevent operational inconvenience such as nitrogen pickup which occurs when the wire is fed into molten steel held in a refining vessel such as a ladle and a tundish. Related to technology.

[0002]

2. Description of the Related Art In recent years, in order to meet the demands for higher quality steel products and rationalization of manufacturing processes, in steelmaking, the process flow of hot metal pretreatment-converter-ladle refining-continuous casting has become common and the refining function Is being divided. Among these processes, especially in ladle refining, equipment and operation improvement are added according to the purpose of low carbon of steel, phosphorus, sulfurization and reduction of inclusions, and recently, [C] ≤ 20 ppm, [ S] ≦
Steel materials with 10 ppm and [O] ≦ 10 ppm are manufactured. Further, when the molten steel [N] is high, the amount of nitride-based inclusions increases, which affects the cracking of the steel material. However, even if the so-called RH vacuum degassing method is used for ladle refining, denitrification is not sufficiently performed by itself. for that reason,
To produce ultra-low nitrogen steel, dephosphorization hot metal pretreatment is used as a starting material, and so-called slagless refining and top-bottom blowing are carried out in a converter to reduce the blow stop [N] as much as possible. In the process (1), a method of thoroughly preventing nitrogen absorption (pickup) from the atmosphere was adopted, and now, steel materials with [N] ≦ 25 ppm can also be obtained.

On the other hand, high-quality steel materials include, for example, so-called calcium-added steel such as HIC-resistant steel used for transporting petroleum and natural gas, as disclosed in Japanese Patent Laid-Open No. 54-12162. These steel materials are manufactured by removing sulfur in molten steel at the stage of steelmaking by the addition of calcium to float and separate it as calcium-based inclusions for cleaning. At that time, calcium was added by various methods.
The wire feeder method as shown in (a) is often used. As this calcium-containing wire, Japanese Patent Laid-Open No. 54-72
There is one disclosed in Japanese Patent Publication No. 750, but as shown in FIG. 4 (b), a wire 1 having a structure in which a metallic calcium simple substance or a powder of a calcium compound is covered with an Fe tape (also called an iron hoop) It is fed into the molten steel at a predetermined speed through the wire feeder 3 provided with.
By this method, it became possible to stably supply calcium, which has a high vapor pressure and is difficult to put in molten steel.

However, when this wire feeder method was adopted and the calcium-silicon alloy was actually added in the tundish of the continuous casting machine, the following problems occurred. First, depending on the brand of the wire 1 used, the nitrogen pickup amount may not be constant, and the pickup amount may be 10 ppm or more. In the case of HIC resistant steels, this exceeds the allowable nitrogen content in the steel of 10 ppm. The dust generation also differs depending on the brand of the wire 1, and when it is significant, the working environment deteriorates, and further, the base metal that adheres to the vicinity of the opening of the nozzle for pouring the molten metal into the mold grows, causing nozzle clogging, which is what is called continuous casting. There was a restriction on the number of times.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has a stable nitrogen pickup amount for each charge when adding molten steel to a calcium filling wire, prevents dust generation at the addition position, and improves the working environment. The present invention aims to provide a calcium-filled wire.

[0006]

In order to achieve the above-mentioned object, the inventor has focused on the particle size distribution of the powder itself of the calcium-containing wire to be filled in the calcium-filled wire (hereinafter sometimes referred to simply as the wire). That is, when the fillers of different brands were extracted and the particle size distribution was investigated, the maximum particle size was suppressed to 1 mm, but the lower limit particle size was different for each brand. Since calcium has a high vapor pressure and causes a violent reaction with the components in the molten steel, the inventor thought that it was necessary to limit the fine grain side, and earnestly conducted research to complete the present invention. That is, the present invention relates to a calcium-filled wire which is fed into molten steel and is coated with metallic calcium or a calcium compound for adding calcium to the molten steel with an iron hoop, wherein the particle size of the metallic calcium or calcium compound is 150 μm or more and 1 mm or less. It is a calcium-filled wire characterized in that The present invention also provides a calcium-filled wire, characterized in that the calcium compound is a calcium-silicon alloy.

In the present invention, since the so-called calcium-filled wire for adding calcium to molten steel has the above-mentioned structure, it is possible to suppress the radical reaction between molten steel and calcium, and to reduce the chance that a new steel bath surface comes into contact with air. , It becomes possible to reduce the amount of nitrogen picked up in molten steel. In addition, the generation of dust at the wire feeding position is reduced, and a good working environment can be maintained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is an example of a particle size distribution of a wire filling that has been conventionally existing. Since this particle size distribution had the above problem, the selection of an appropriate particle size distribution was examined, and the best results were obtained when fine particles of 150 μm or smaller as shown in FIG. 1 were cut. That is, 15
If there are many fine particles having a size of 0 μm or less, the reaction is too fast and the stirring action of the molten steel becomes large, so that a new molten metal often appears on the bath surface. Therefore, in the present invention, the fine grain side is limited by the grain size. On the other hand, when the particle size is large, the reaction is too slow, which slows the formation of inclusions of calcium and sulfur. In addition, since the wire diameter of the wire 1 is 7 mm or less, the filling rate is also taken into consideration.
m.

[0009]

EXAMPLES Calcium having the particle size distribution shown in FIG.
Powder of silicon alloy (filler 6) having a thickness of 0.2 to
A large number of calcium-filled wires 1 according to the present invention were manufactured by filling a 0.6 mm iron hoop 7 wound into a wire having a diameter of 13 mm. The calcium-silicon alloy has a Ca concentration of 25 to 35% by weight and a filling amount of 150 to 250 g / m. The manufactured wire 1 is wound around the bobbin 2 in a coil shape.

Next, these wires 1 are fed at a maximum feed rate of 200 using the wire feeder 3 shown in FIG.
It was fed into the molten steel for HIC resistant steel as m / min to add calcium. The addition place was provided by disposing the wire feeder 3 and the ladle 4 holding the degassed molten steel in a passage on the way from the RH vacuum degassing apparatus to the continuous casting. The wire 1 according to the present invention is not limited to the addition place, and may be a tundish of a continuous casting machine or the like in addition to the above place.

Finally, the effect of the present invention is shown in FIG. 3 with a nitrogen pickup. From FIG. 3, when the calcium-filled wire 1 according to the present invention is used, the increase in nitrogen in the steel during its use is 5 ppm on average as compared with the conventional wire use.
You can see that it is small. This 5 ppm is important for the production of HIC-resistant steel, and it has succeeded in staying within its component allowable range. In addition, the state of dust generation when these wires 1 were fed was also greatly improved compared to the previous time, and a good working environment could be secured by using ordinary dust collecting equipment.

[0012]

As described above, according to the present invention, it is possible to suppress the pickup of nitrogen in the steel when it is fed into the molten steel, so that the so-called calcium-added steel can be stably manufactured. At the same time, a secondary work environment improvement effect was also obtained.

[Brief description of drawings]

FIG. 1 is an example of particle size distribution of a filler used for a calcium-filled wire according to the present invention.

FIG. 2 is an example of particle size distribution of a filler used in a conventional calcium-filled wire.

FIG. 3 is a diagram showing changes in the nitrogen content in steel when a calcium-filled wire according to the present invention and a conventional wire are used.

FIG. 4 is a diagram illustrating a wire feeder method,
(A) is a longitudinal sectional view showing an apparatus for feeding a calcium-filled wire into molten steel, and (b) is a cross-sectional view of the calcium-filled wire.

[Explanation of symbols]

 1 Calcium-filled wire (wire) 2 Bobbin 3 Wire feeder 4 Ladle (smelting vessel) 5 Dust collection duct 6 Filling material (metal calcium or compound) 7 Iron hoop 8 Truck 9 Dust collection hood

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshio Fujimura 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi (no street address) Inside the Mizushima Steel Works, Kawasaki Steel Works (72) Kenji Oshima 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi (no street number) ) Kawasaki Steel Works Mizushima Steel Works

Claims (2)

[Claims] 1. A calcium-filled wire which is fed into molten steel and coated with iron hoops of metallic calcium or calcium compound for adding calcium to the molten steel, wherein the particle size of the metallic calcium or calcium compound is 150 μm or more and 1 mm or less. The calcium-filled wire is characterized in that 2. The calcium-filled wire according to claim 1, wherein the calcium compound is a calcium-silicon alloy.