KR101798863B1 - Manufacturing method of additive for steel making - Google Patents

Abstract

The present invention relates to a method of manufacturing an additive for steelmaking. The present invention comprises: a process of dissolving a first raw material containing silicon, a second raw material containing iron (Fe), and a reductant to produce molten steel; a process of injecting molten steel to a mold; a process of solidifying the molten steel to manufacture a casted product; a process of crushing the casted product; and a process of selecting a particle size of the crushed casted product. The present invention is able to easily remove carbon in ferrosilicon while restraining a loss of silicon.

Description

Technical Field [0001] The present invention relates to a manufacturing method of additive for steel making,

The present invention relates to a method for manufacturing additive for steelmaking, and more particularly, to a method for manufacturing additive for steelmaking which can improve the purity of ferro silicon.

As the demand for cold-rolled directional electrical steel sheets increases, demand for ferro-silicon alloys is increasing, and interest in high-purity ferrosilicon, which is a core additive, is increasing.

Ferrosilicon is a ferroalloy used for the purpose of deoxidation and addition of silicon (Si) in steel during the production of electrical steel sheets. Due to the characteristics of the electrical steel sheet, the more impurities in the additives, the more obstacles in the metal structure are obstructed and the current flow is impeded, which causes the quality nonconformity.

In addition, as the electric steel sheet becomes more sophisticated, there is a demand for ferrosilicon having a low impurity, that is, high purity, and the demand for minimizing the carbon component in the ferrosilicon is also maximized. Therefore, a refining process for removing carbon in the molten metal by using oxygen after the ferro silicon molten metal is produced is being carried out.

However, in the process of removing carbon in the molten metal by using oxygen, silicon having good reactivity with oxygen is oxidized together to lower the yield of silicon in ferrosilicon. In addition, ferrosilicon having a silicon content higher than the target silicon content is produced by the reduction of the silicon yield due to refining, thereby increasing the amount of raw materials used and increasing the production cost.

KR 2015-0076424A KR 0035624 B

The present invention provides a method for manufacturing additive for steelmaking which can improve the purity of ferrosilicon.

The present invention provides a method for manufacturing additive for steelmaking which can reduce the production cost.

A process for producing an additive for steelmaking according to an embodiment of the present invention comprises the steps of: melting a first raw material containing silicon, a second raw material containing iron (Fe) and a reducing material to prepare a molten metal; Injecting the molten metal into the mold; A step of solidifying the molten metal to produce a casting; Crushing the casting; And a process of sorting the crushed castings.

The molten metal may include molten ferrosilicone.

In the process of injecting the molten metal, the molten metal may be injected into the mold as it is produced in the melting furnace.

In the course of manufacturing the casting, the casting may be manufactured to have a thickness of 160 to 200 mm.

In the process of manufacturing the casting, the carbon component in the molten metal may be moved to the center of the casting to form a center segregation containing a carbon component in the casting.

In the process of crushing the casting, the casting can be crushed to a size of 50 mm or less.

In the process of selecting the size of the crushed castings, castings in the range of 10 to 50 mm can be selected with additives.

A casting of more than 0 mm and less than 10 mm out of the crushed castings can be used as the reducing material.

According to the embodiments of the present invention, carbon in the ferrosilicon can be easily removed while suppressing the loss of silicon in the production of ferrosilicon. Carbon contained in ferro silicon is usually removed using oxygen. In this case, the loss of silicon is inevitable. However, in the process of producing the cast iron by solidifying the ferro silicon melt, the solidification time is delayed so that the carbon in the ferrosilicon is moved to the inside of the casting to form segregation, and the casting is crushed and the particle size is sorted to easily remove carbon in the ferrosilicon . Therefore, the purity of the ferrosilicon can be improved while suppressing the loss of silicon in the ferrosilicon.

In addition, since the refining process for removing carbon in the ferrosilicon can be omitted, it is not necessary to compensate for the silicon that is lost during refining, thereby reducing the resources and cost required for manufacturing ferrosilicon.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a casting facility for producing steelmaking additives according to an embodiment of the present invention; FIG.
FIG. 2 is a flowchart sequentially showing a method of manufacturing additive for steelmaking according to an embodiment of the present invention; FIG.
Fig. 3 is a graph showing changes in state of silicon with carbon content and temperature. Fig.
4 is a graph showing the cross-sectional shape of the casting and the carbon content change in the thickness direction of the casting.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of other various forms of implementation, and that these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know completely.

FIG. 1 is a schematic view of a casting facility for producing steelmaking additive according to an embodiment of the present invention, and FIG. 2 is a flowchart sequentially showing a method of manufacturing steelmaking additive according to an embodiment of the present invention.

Referring to FIG. 1, the casting equipment may include a main table 100 and a main table 200 provided on the main table 100. And a ladle 300 for receiving the molten metal M manufactured in the melting furnace (not shown).

The juncture table 100 may include a cast and may be used as the bottom surface of the mold 200. The protection material P may be provided on the upper surface of the jigging table 100 to prevent the loss of the molten metal during the production of the casting.

The juncture 200 is installed on the juncture table 100 and can be formed into a frame shape having upper and lower openings, for example, a rectangular frame. The mandrel 200 may be formed to have a size capable of producing a casting having a length and a width of 1000 mm or more, respectively. The mandrel 200 may be formed to have a thickness capable of forming a thickness of the casting 100 mm or more. For example, the casting 200 may have a length and width of 1900 mm and a casting of 160 to 200 mm. For reference, conventionally, castings were manufactured to have a thickness of less than 100 mm.

Hereinafter, a method for producing a steelmaking additive using the casting equipment shown in FIG. 1 will be described.

Referring to Fig. 2, a first raw material containing silicon, a second raw material containing iron and a reducing material are charged into a melting furnace to produce a molten ferro silicon. At this time, the first raw material may include silica and the second raw material may include scrap or molten steel. The reducing material is for reducing the first raw material and the second raw material, and a material containing carbon (C) may be used. For example, the reducing material may include coke, SiC, and the like. Each raw material may be put into the furnace so that the molten ferrosilicon has a target silicon content, for example, a silicon content of about 74 wt%. This is because the refining process for removing the carbon (C) component in the molten metal after the production of the ferrosilicone molten metal is not performed separately in the present invention. In other words, according to the present invention, since the refining process for removing oxygen from the ferrosilicone molten metal by blowing oxygen into the molten ferrosilicone is not performed, silicon loss due to the refining process is not generated.

When the molten ferro silicon is produced in the melting furnace, it is transferred to the casting equipment in the ladle 300.

When the ferrosilicone molten metal is transferred, molten ferrosilicone is injected into the mandrel 200. The protective material P may be injected into the juncture 200 to prevent the melting of the juncture table 100 before the molten ferro silicon is injected. The protective material (P) may be ferrosilicon powder. Some of the protective materials P are dissolved by the heat of the molten ferrosilicone, and then solidified together with the molten ferrosolicon to form the casting.

The ferro silicon melt can be injected into the juncture 200 so that the casting can have a thickness of 160 to 200 mm. At this time, when the thickness of the casting is smaller than 160 mm, the solidification of the casting rapidly occurs in the subsequent solidification process, so that the center segregation is hardly formed inside the casting. When the thickness of the casting is larger than 200 mm, the coagulation time of the casting is excessively delayed, so that core segregation is formed inside the casting and then the casting is loosened again. Therefore, it is possible to manufacture the casting so as to have a thickness in the range shown, so that center segregation can be smoothly formed inside the casting.

The molten ferrosilicone injected into the mold 200 can be directly injected into the mold in the state of being manufactured in the melting furnace, that is, without refining to remove the carbon component. This is because the carbon component is segregated inside the casting and removed in the subsequent crushing and sorting process.

When the molten ferro silicon is injected into the mandrel 200, the molten ferro silicon is allowed to stand for a predetermined time, for example, about 50 to 60 minutes to cool and solidify the molten ferro silicon. During the solidification of the molten ferrosilicon, segregation containing carbon components may be formed in the casting.

Fig. 3 shows the change in the state of silicon in the ferrosilicon with changes in carbon content and temperature.

Referring to Fig. 3, the silicon component in the molten ferro silicon is converted from Si (l) to SiC (s) and Si (l). At this time, when the carbon content is high, this phase transformation takes place at a relatively high temperature. In the ferrosilicon, carbon bonds with Si to form SiC, and dendrite is grown from the surface of the casting material toward the central portion to form segregation in the casting. At this time, in the casting, SiC is formed concentrating on the grain boundary of Si (s), and acts as an impurity in the Si (s) bond, so that the bonding force with Si (s) is weaker than other structures.

When such a property is used to fracture the casting, SiC can be fractured to a smaller size than other structures, such as Si. Accordingly, in the present invention, it is possible to effectively remove the carbon component in the casting after crushing the casting to a predetermined size and sorting the granules.

When the molten ferro silicon melt is solidified to produce the casting, the casting is put into a crusher and crushed to have a particle size of a certain size, for example, about 10 to 50 mm. In this case, when the casting is crushed to a size smaller than the specified range, it is difficult to select Si and SiC, and when crushed to a larger extent than the specified range, Si and SiC are not properly separated and the carbon removal efficiency may be lowered.

After the casting is broken, the SiC component and the Si component can be separated from the crushed casting by using a separator. At this time, the SiC structure may have a particle size of more than 0 mm but less than 10 mm. Particle size determination of the crushed castings, such as crushed materials, can be performed using a sorter capable of selecting particle sizes on the order of 10 to 50 mm, and the SiC structure can be crushed to a smaller size than the Si structure. This is because the bonding force is weaker than that of the Si structure as described above and is easily broken.

The Si structure selected by particle size selection can be used as an additive in the production of electrical steel, and the SiC structure can be used as an additive in other operations or as a reducing material in the production of ferrosilicon.

Hereinafter, an experimental result of measuring the carbon content in the casting produced by the method for producing steel additive according to the present invention will be described.

Molten silicon, scrap and coke were dissolved in a melting furnace to prepare a ferro silicon melt, and the ferrosilicon additive was prepared by casting, crushing and screening without refining. At this time, a casting having a thickness of about 160 to 200 mm was manufactured by using the molten ferrosilicone. The carbon content in the molten ferro silicon was measured at the casting time, and the carbon content in the finally prepared ferro silicon additive was measured and compared. The results are shown in Table 1 below.

Casting number (US refinement)
Carbon content (wt%) Boil Crushing and screening Difference One 0.7880 0.0309 -0.7571 2 0.1720 0.0122 -0.1598 3 0.1410 0.0178 -0.1232 4 0.1610 0.0279 -0.1331 5 0.0749 0.0124 0.0625 6 0.0699 0.0577 0.0122 7 0.1180 0.0186 0.0994 8 0.2242 0.0415 0.1825

Referring to Table 1, it can be seen that the carbon content in the ferrosilicone molten metal produced in the melting furnace for each casting number is higher than the carbon content in the ferrosilicon additive obtained through crushing and sorting.

The reason why the carbon content in the molten ferro silicon is high is that the refining process using oxygen before casting is omitted. The low content of carbon in the ferrosilicon additive is due to the fact that carbon segregates in the casting during the casting process by solidifying the ferrosilicon melt, and the casting material is crushed and the particle size is selected to remove the carbon component.

In order to measure the position of the segregation in the casting, the casting was cut and the components at various points in the thickness direction of the casting were measured.

Referring to FIG. 4 (a), the point P3 of the casting is substantially middle in the thickness direction of the casting, P1 and P2 are the upper side at the intermediate point in the thickness direction of the casting, .

The tissues were taken at each site to measure the carbon content in the tissues, and the results are shown in Fig. 4 (b).

Referring to FIG. 4 (b), it can be seen that the carbon content is the highest at the intermediate point, that is, at the point P3 in the thickness direction of the casting, and the carbon content decreases toward the surface side of the casting. This is because carbon in the molten metal moves toward the center of the casting while the molten ferrosilicone solidifies and segregation is formed.

Although not shown, when the casting is manufactured to a thickness of 100 mm or less, the carbon content is measured very similar over the entire region in the thickness direction of the casting.

As a result, the casting is formed to be as thick as about 160 to 200 mm, so that the solidification of the molten ferro silicon is delayed and the segregation in the casting is smoothly formed.

Although the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Therefore, the scope of the present invention should not be limited by the described embodiments, but should be defined by the appended claims and equivalents thereof.

100: mold table 200: mold
300: Ladle

Claims (8)

A step of dissolving a first raw material containing silicon, a second raw material containing iron (Fe) and a reducing material to prepare a molten metal;
Injecting the molten metal into the mold;
A step of solidifying the molten metal to produce a casting;
Crushing the casting; And
A process of sorting crushed castings;
/ RTI >
Wherein the casting is manufactured to have a thickness of 160 to 200 mm to move a carbon component in the molten metal to a center portion of the casting to form a center segregation containing a carbon component in the casting. The method according to claim 1,
Wherein the molten metal comprises a molten ferrosilicone. The method of claim 2,
In the process of injecting the molten metal,
Wherein the molten metal is injected into the mold as it is produced in the melting furnace. delete delete The method of claim 3,
In the process of crushing the casting,
Wherein the casting is crushed to a size of 50 mm or less. The method of claim 6,
The process for selecting the particle size of the crushed castings is characterized by selecting castings ranging from 10 to 50 mm as additives. The method of claim 7,
Wherein the cast material having a size of more than 0 mm and less than 10 mm is used as the reducing material.

Images