JPS62158814A - Composite refining agent and refining method - Google Patents

Abstract

PURPOSE:To manufacture a composite refining agent for secondary steel refining excellent in meltability and reactivity by blending uniformly specific percentage of respectively powdered or granular materials of quick lime, fluorite, calcium carbide, deoxidizers, and carbon and by compacting the resulting mixture. CONSTITUTION:The mixture containing, by weight, >=50% quick lime, 5-20% fluorite, and <=10% calcium carbide and also containing deoxidizers and carbon in the amounts specfied by inequalities [C]<6, (CaO)/(SiO2)> 2.3, and 0.4[Ca]+1.4[Si]+1.33[C]>9 is prepared. In the above inequalities, [C] means the sum of raw-material carbon quantities ]wt%]; (CaO) and (SiO2) mean, severally, the total amounts of Ca and Si expressed in terms of CaO and SiO2, respectively [wt%]; [Ca] means the sum of Ca content in CaC2 and calcium silicon [wt%]; and [Si] means the sum of Si content in silicon carbide, calcium silicon, and ferrosilicon [wt%]. The above components (about 10-20mm grain size) are crushed to <= about 5mm and mixed uniformly, and the resulting mixture is compacted into spherical shape of about 10-20mm so as to be formed into acomposite refining agent.

Description

[Detailed Description of the Invention] [Industrial Application Field] In recent years, in steel refining, molten steel that has been melted or roughly refined is separated from the oxidizing slag of the rough refining, and transferred to a separate outside furnace refining equipment to be deoxidized. Refining methods that involve adding additives and slag-forming agents to perform reduction and desulfurization are widely practiced. In this case, it is necessary not to bring the slag from the previous process into the external refining process, but it is also important to select and use an appropriate deoxidizer or slag forming agent. The present invention relates to the above-mentioned out-of-furnace refining (hereinafter defined as secondary refining) of the molten steel.
This invention relates to a composite refining agent that has the properties of both a deoxidizing agent and a slag-forming agent, and is added to molten steel during processing.

[Conventional technology]

The materials added to molten steel in secondary refining are quicklime, flux, and deoxidizer, and conventionally these have been used singly or in combination. In other words, the mixed usage methods were classified as follows.

(a) A slag forming agent with a quicklime + flux system; a slag conditioner as an auxiliary slag forming agent that improves the fluidity and slag formation of slag; (c) an auxiliary deoxidizing agent (CaCZ) as a slag conditioner.

SiC, Fe-5i, etc.) was added as a reducing deoxidizing slag agent, but its form was a powder mixture and granules, and it also had all the capabilities necessary for reduction refining (hereinafter referred to as one-touch slag). Since it is not a one-touch refining agent (defined as a formula), it has the following drawbacks. In other words, the types of refining agents become complicated, the hopper and charging equipment become complicated, and the handling load becomes large.In addition, in the case of powdery mixtures, the raw material components are separated due to vibrations during handling, which impairs homogeneity. Compared to the one-touch refining agent, it required more skill in furnace operation.

Also, when using quicklime, flux, or deoxidizing agent alone, it is desirable to add it in powder form to speed up melting and improve reactivity, but blowing with carrier gas requires large-scale equipment. Moreover, adding powder directly to molten steel requires a separate dust collector, so it is not universally used. No effort was made to do so.

[Problem that the invention seeks to solve]

The present invention is an additive for secondary refining molten steel, which melts quickly and has good reactivity, generates little dust when added, and is a one-touch type that combines all alternating additives in an appropriate ratio. The purpose is to produce a refining agent for secondary refining, and to perform secondary refining efficiently using this refining agent.

[Means for solving problems]

The present invention provides a deoxidizing agent containing 50% by weight or more of quicklime, 5-20% by weight of fluorite, 10% by weight or less of calcium carbide, and an amount specified by the following formulas (1) to (3). It is a composite refining agent that is a mixture containing carbon, in which each component is made into powder and granules, mixed uniformly and then pressure molded or granulated using a binder. A mixture containing one or more of stone, nacre, obsidian, pinestone, and expanded shale in an amount of 5% by weight or less, in which each component raw material is made into powder and granules, mixed uniformly, and then pressure-molded. It is a heat-collapse type composite refining agent that is granulated by processing or using a binder, and the above-mentioned composite refining agent or heat-collapse type composite refining agent is placed in advance in a steel receiving tank for out-of-furnace refining. A secondary refining method for molten steel, which is characterized in that molten steel from which slag has been separated is fed into the molten steel, and deoxidized, slag-formed, and deflowed in a short time by the strong stirring force of the molten steel flow during steel receiving. It is.

(C) < 6 −−−−−−−−−−−−−・・・・
−・・−・−−−−−−−−(1) However, C) is the total amount of carbon in the raw materials (wt%) (CaO) / (S
iOz) > 2.3-------- (2) However, CaO) is the total amount of Ca in the raw material, and (S
iO□) is the weight% of the total amount of St converted to 5i02 0.4 (Ca) + 1.14 (St) + 1
．． 33 (C) > 9 - (3) However, [Ca] is the total calcium content (weight%) in calcium carbide and calcium silicon, and C3i) is the total silicon content (weight %) in silicon carbide, calcium silicon, and ferrosilicon. %).

[For production]

The operation of the present invention will be explained below. First, the ingredients will be explained. It was decided to contain quicklime in an amount of 50% by weight or more in order to create a slag with good reactivity for desulfurization and the like. In addition, although this refining agent is a refining agent that has been molded, as will be described later (if the quicklime content is less than 50% by weight, the strength of the pressure-molded molded product will be low.Furthermore, in the present invention, granular quicklime is used as the raw material). Because it is a fine particle, it melts quickly to form a homogeneous slag, and there are no unreacted quicklime particles in the slag that are found when conventional lump quicklime is used.

It was decided to contain 5 to 20% by weight of fluorite in order to promote slag formation of the refining agent and increase reactivity. It was decided to contain calcium carbide in an amount of 10% by weight or less because calcium carbide has strong desulfurization and dephosphorization power. However, like fluorite, if it is included in excess, it will cause greater damage to refractories. Next, as for the content of the deoxidizing agent, it was decided that the deoxidizing power specified by the third formula % formula % (C) should be 9 or more. Contains the equivalent amount of deoxidizing agent required to remove oxygen from 100 kg or more of molten steel,
suitable amount (usually several kg per ton of molten steel)
This is to sufficiently deoxidize the molten steel by adding . The total amount of carbon contained in this refining agent is (C
)<6 or less, in order to keep the carbon content of molten steel within a range that does not cause any problem when the above-mentioned appropriate amount of the present refining agent is used. Furthermore, in this refining agent, < (Cab)/(S i 02 )> was set to 2.3 as shown in the second equation, in order to form a slag with excellent reactivity.

Next, the reason why this refining agent is made into a molded product after uniformly mixing the powders and granules of each component will be explained. Table 1 shows the melting properties and reactivity of both refining agents, when the refining agent is a simple mixture of grains or lumps, and when the refining agent is a mixture of particles or lumps, and when all the components are uniformly mixed as powder and granules as in the present invention. This is a comparison. Ingredients for both are CaO: 65% by weight, CaF2
: 20% by weight, Ca Ct: 5% by weight, SiC
: 5% by weight, ferrosilicon: 5% by weight, and the molded product is made by pulverizing each component to 5% by weight or less, mixing uniformly, and 10 to 2% by weight.
It is a molded article pressure-molded into a spherical shape of 0 fl, and the mixture is simply a mixture in which each component has a particle size of 10 to 20 mm. Comparative tests of meltability and reactivity were conducted using a molybdenum silicide resistance photothermal furnace, melting and heating 1500 duram of blast furnace pig to 1630℃, and placing 3 molded products or mixtures on top of the molten blast furnace pig.
0 grams added.

After addition, both the molded product and the mixture were allowed to stand in the furnace for 7 minutes, and then the hot metal and slag were stirred to investigate desulfurization properties.

Table 1 As is clear from Table 1, conventional additives take a long time to melt and have a low desulfurization rate. Although it is unsatisfactory as an additive for deoxidizing, slag-forming, and desulfurization in a short time due to stirring power, this refining agent, which is made by mixing and molding each crushed component, melts quickly and is highly reactive. Therefore, it is a refining agent that can deoxidize, create slag, and desulfurize by stirring the molten steel for a short time during steel receiving. Next, a method for molding the refining agent will be explained. In the present invention, the term "powder and granule" refers to a size of 5 mm or less, preferably LU+ or less; if the size of the powder or granule is larger than this, pressure molding becomes difficult.

If the proportion of quicklime is lower than 50%, the strength of the molded product will be low and powder will easily be generated during transportation and handling. Table 2 is an example of pressure molding, CaF: 2 parts by weight, CuCz: 1
The powder and granules of the heavy foot part, SiC: 1 overlap part, and ferrosilicon Go 1 overlap part were mixed, and the powder and granule of CaO was mixed with this in the proportions shown in Table 2, and the mixture was heated using the 21' + - rule method. 1 with Brigette molding machine
30mm x 20 with roll pressure of 70kg/crl
An almond-shaped brigette of mmXIQ+am was molded.

Table 2 As shown in Table 2, when the CaO mixing ratio is 60%, the crushing strength is sufficiently large and is 15 kg or more, and in this case, the molded product is dropped from an anvil from a height of about 2 m. However, almost no powder is generated. In addition to pressure molding, granulation molding using a binder can also be used as a molding method, but pitch, asphalt,
Examples include paraffin, wax, clay, starch, latex, etc. As mentioned above, the refining agent of the present invention has better meltability and reactivity than conventional additives, but if you want to melt and react the refining agent in a shorter time, add 50% of the heat disintegrating agent powder.
It is preferable to mix and mold in an amount of less than % by weight. Suitable thermal disintegrants include vermiculite, perlite, obsidian, pinestone, and expanded shale. The thermal disintegrant has a large volumetric expansion at 700° to 1500°C, and therefore, the refining agent becomes powder when it is drawn into the receiving steel stream, so it is rapidly melted and has good reactivity.

The refining agent of the present invention does not particularly limit the constituent raw materials other than those mentioned above, but aluminum oxide, river sand, and the like are also desirable constituent raw materials in order to improve meltability and reactivity.

〔Example〕

1. Using the energy of stirring molten steel during tapping in a bottom-tapping type electric furnace, this refining agent was placed in advance in a ladle refining furnace for receiving wire to promote melting and slag formation. Examples are shown below.

B. Electric furnace used: Bottom tap type 120 ton electric furnace mouth,
Secondary refining process = 120 tons ladle smelting furnace C, Refining agent amount: 500 kg/l charge, Shortened slaging time: 5 minutes instead of about 15 minutes E, Reduction in power consumption: Approximately 20%
The desulfurization rate improved by about 25% or more (the slag time in the secondary smelting process was shortened and the power consumption was reduced. Also, secondary smelting such as desulfurization became easier). This is an example of the combined benefits of a bottom tap system that prevents electric furnace oxide slag from being carried into the secondary refining process.

2. With bottom-tap type electric furnaces, it is now possible to operate the electric furnace without bringing oxidized slag into the secondary refining process.
Examples in which the four refining agents of the present invention were used in the secondary refining step are shown below.

B. Electric furnace used: bottom tap 2 120 ton electric furnace mouth,
Secondary refining process: 120) Ladle smelting furnace C, Refining agent amount: 1000 kg/l charge, Reduction of slag time: 11 minutes instead of 15 minutes E, Reduction in power consumption: Approximately 1
0% reduction in desulfurization rate: As shown by the approximately 10% improvement, it was possible to shorten the slag formation time in the secondary refining process and reduce power consumption. Also, secondary refining such as desulfurization has become easier.

〔effect〕

Although we mainly explained the case where this refining agent is used for out-of-furnace refining,
This refining agent has good melting properties and reactivity, so it is highly effective when used during in-furnace reduction. That is, by using the present refining agent in the refining of molten steel after the oxidation period in the steelmaking process, both inside and outside the reduction furnace, the problems listed in the description of the prior art were solved at once.

With the advancement of split refining technology based on the trend toward higher-grade products, the conventional three functions of melting, oxidation refining, and reduction refining have been separated, and reduction refining has come to be performed in equipment outside the furnace. It is necessary not to carry slag into the next process, and a composite additive that quickly turns into slag has become necessary, and the present invention satisfies this need. Although the refining method itself has become simpler through division, it is desired that the refining agent be unified to streamline handling, and that it has high refining performance and less power loss.However, the present invention is a one-touch refining agent. It satisfies that demand.

As a refining agent, it can be thrown into the tapping stream or placed in a ladle to receive molten steel from above and use the stirring energy to accelerate the reaction and reduce the load on secondary refining. The present invention is a refining agent suitable for such a method of use.

Conventional additives could not be added during the limited time of tapping due to dust and other work environment issues, so they were added after tapping and turned into slag using electrical energy.However, the present invention eliminates dust. There was no occurrence, and there was no need to apply electricity for slag formation.

Patent! ! I Applicant Topie Industry Co., Ltd. Yabashi Kogyo Co., Ltd.

Claims (1)

[Claims] 1. Quicklime is 50% by weight or more, fluorite is 5-20% by weight,
Calcium carbide is 10% by weight or less and the following item (1)
~A mixture containing an amount of a deoxidizing agent and carbon specified by formula (3), in which each component is made into powder and granules, mixed uniformly, and then pressure molded or granulated using a binder. Composite refining agent. [C]<6………………………………(1) However, [C] is the total amount of carbon in the raw materials (weight%) (CaO)
/(SiO_2)>2.3……(2) However (CaO)
(SiO_2) is S
Weight% of total amount of i converted to SiO_2 0.4 [Ca] + 1.14 [Si] + 1.33 [C]>
9...(3) However, [Ca] is the total calcium content (weight%) in calcium carbide and calcium silicon, [Si
] is the total silicon content (% by weight) in silicon carbide, calcium silicon, and ferrosilicon. 2. Quicklime is 50% by weight or more, fluorite is 5-20% by weight,
A raw material containing 10% by weight or less of calcium carbide and a predetermined amount of deoxidizing agent and carbon, as a heat disintegrating agent, vermiculite,
A mixture containing one or more of pearlite, obsidian, pinestone, and expanded shale in an amount of 5% by weight or less, each component being made into powder and granules, mixed uniformly, and then pressure molded or a binder is added. A heat-decomposable composite refining agent granulated using 3. Quicklime is 50% by weight or more, fluorite is 5-20% by weight,
A composite refining agent or heat-decomposable composite refining agent containing 10% by weight or less of calcium carbide and a predetermined amount of deoxidizing agent and carbon is placed in a steel receiving tank in advance, and the molten steel from which the slag has been separated is received. A molten steel refining method characterized by deoxidizing, slag forming, and deflowing in a short time using the strong stirring force of the molten steel flow during receiving.