KR100992925B1 - Mold flux used in continuos casting of isotropic electromagnetic steel slab - Google Patents

Abstract

The present invention is a continuous casting mold for non-oriented electrical steel sheet in which the SiO ₂ component of the component is suppressed as much as possible to minimize the aluminum oxidation reaction in molten steel when continuously casting the steel for producing a non-oriented electrical steel sheet having a high aluminum content It's about flux.

To this end, the present invention in the mold flux for continuous casting of non-oriented electrical steel sheet containing silicon (Si) and aluminum (Si), by weight%, Al ₂ O ₃ 10-30%, SiO ₂ 3% or less, 1.0% or less of flux (Na ₂ O + Li ₂ O + K ₂ O), 5 to 15% of fluorine (F), 2 to 6% of MgO, 5 to 10% of MnO, and the balance includes CaO and unavoidable impurities Provided is a mold flux for continuous casting of non-oriented electrical steel sheet, characterized in that.

As described above, the mold flux of the present invention is obtained by comparing the Al component in molten steel with SiO ₂ in the mold flux during continuous slab production for producing a high aluminum-containing non-oriented electrical steel sheet containing 1.0-1.5% Al component by weight in molten steel. It has a very useful effect that significantly reduces the explosion and flame outbreaks caused by the reaction.

Mold Flux, Electrical Steel, Continuous Casting, Non-Oriented, Aluminum, Oxidation Reaction

Description

Mold flux for continuous casting of non-oriented electrical steel sheet {MOLD FLUX USED IN CONTINUOS CASTING OF ISOTROPIC ELECTROMAGNETIC STEEL SLAB}

1 is a graph showing the iron loss of electrical steel sheet according to the addition of aluminum;

2 is a schematic diagram showing the role of the mold flux in the continuous casting mold;

3 is an elling feeling diagram showing oxygen affinity for each alloy component;

4 is a graph showing the relationship between the flux and the viscosity contained in the mold flux according to the present invention.

♣ Explanation of symbols for main part of drawing ♣

1: tundish 2: molten steel 3: immersion nozzle 4: performance mold 5: mold flux

6: mold slag 7: solidified cell 8: molten steel in the mold

The present invention relates to a mold flux for continuous casting of non-oriented electrical steel sheet, and more particularly, to minimize aluminum oxidation in molten steel when continuously casting steel for manufacturing non-oriented electrical steel sheet having a high aluminum content. The present invention relates to a mold flux for continuous casting of non-oriented electrical steel sheet in which SiO _{2 component} in the mold is suppressed as much as possible.

In general, an electrical steel sheet is a soft magnetic material that is made of silicon (Si) to add a reduction effect of iron loss in the plate and excellent electromagnetic properties compared to other steel materials. In this case, in order to increase the electromagnetic characteristics such as iron loss and magnetic flux density of the material, a method of increasing the content of silicon (Si) and aluminum (Al) is mainly used.

In particular, the special non-oriented electrical steel sheet used for the motor core for the electric vehicle should secure the magnetic properties requiring iron loss and magnetic flux density of 2.30W / kg or less and 1.63 Tesla or more, respectively. To this end, the magnetic properties should be secured by adding more than 4.0% of silicon (Si) than conventional non-oriented electrical steel sheet.However, continuous casting of molten steel with excessive addition of silicon (Si) results in continuous operation stability due to the delay in solidification. Casting is impossible.

Therefore, in recent years, the addition of aluminum (Al), which plays a role similar to that of silicon (Si), increases the specific resistance of steel materials and lowers iron loss. At this time, the iron loss effect of the electrical steel sheet according to the addition of aluminum (Al) is as shown in FIG. Based on this fact, we developed a special non-oriented electrical steel sheet containing 3.0 to 3.4% of Si and 1.0 to 1.5% of Al to satisfy the iron loss and magnetic flux density requirements of the steel sheet. , Si: 3.0 to 3.4%, Mn: 0.5% or less, S: 0.01% or less, P: 0.01% or less, Al: 1.0 to 1.5% and the balance is composed of Fe and other unavoidable impurities.

In the continuous casting process, as shown in FIG. 2, when molten steel 2 in the tundish 1 is introduced into the playing mold 4 through the immersion nozzle 3, the water is cooled. Solidification of the molten steel 2 is started in the mold 4, and an intermediate product slab (slab) is obtained. At this time, during continuous casting, a mold flux 5 is injected onto the molten steel 8 in the mold 4 to form an unmelted layer, a semi-melted layer, and a molten slag layer, and the molten slag vibrates up and down ( 4) flows into the gap between the coagulation cell (7) to form a thin film (slag film) and lubrication action, the slag film (slag film) along with the cast steel is drawn downward down the continuous casting machine It is consumed as it is washed by the water sprayed to cool it.

The mold flux 5 is a synthetic synthetic slag in the form of powder or granules put on the molten steel 8 in the above-described playing process, and the thin cast slag on which only the surface in contact with the water-cooled mold 4 solidifies is broken. Lubricate to prevent. In addition to the lubrication action that reduces the friction between the cast and the mold, the mold flux 5 absorbs and dissolves non-metallic inclusions separated from the molten steel 8, and applies molten steel to prevent reoxidation with the atmosphere. It suppresses heat release and keeps the molten steel 8 warm, as well as acts as a heat transfer medium from the cast steel to the mold 4.

On the other hand, the general mold flux used during the electrical steel casting in the above-described playing process is shown in Table 1.

As shown in Table 1, a large amount of SiO ₂ was selected to 35-45% in the conventional mold flux, and the flux is a mixed component of Na ₂ O + Li ₂ O + K ₂ O.

However, continuous casting using a conventional mold flux on high-quality non-oriented electrical steel sheet (aluminum 1.0-1.5%) for applying the mold flux of the present invention has the following problems.

In the continuous casting using the existing mold flux, a violent exothermic oxidation reaction occurs between the aluminum component present in the molten steel and the oxygen (O 2) generated by decomposition of the silica (SiO ₂ ) component of the mold flux. Continuous casting was virtually impossible due to the explosive flames generated during this reaction.

In detail, as can be seen in the elling feeling diagram of each metal component shown in FIG. 3, the dissociated oxygen (O 2) in the SiO ₂ component in the mold flux and the aluminum having a relatively high affinity with oxygen may react. The energy generated at 780 Kilo-Joule at 1500 ℃ is the highest when the oxidizing power is after Ca. The background of the reaction temperature set at 1500 占 폚 is that the molten steel in the mold is about 1500 占 폚 at which temperature the molten steel contacts the mold flux.

In short, when using the existing mold flux containing a large amount of SiO ₂ component during continuous casting of high quality non-oriented electrical steel sheet containing 1.0 ~ 1.5% of aluminum, explosion and flame are caused by the intense reaction between aluminum and SiO ₂ component in molten steel. There is a manufacturing problem that can not be continuous casting operation.

In order to solve the above problems, the present invention does not contain or minimize the amount of SiO ₂ component in the mold flux used in the reflowing process of the electrical steel sheet having a high aluminum content to minimize the oxidation reaction with aluminum in the molten steel in the mold. An object of the present invention is to provide a mold flux for continuous casting of non-oriented electrical steel sheet.

In order to achieve the above object, the present invention is a mold flux used in the continuous casting of non-oriented electrical steel sheet containing silicon (Si) and aluminum (Si), as a weight%, Al ₂ O ₃ 10-30% , SiO ₂ 3% or less, flux (Na ₂ O + Li ₂ O + K ₂ O) 1.0% or less, fluorine (F) 5-15%, MgO 2-6%, MnO 5-10%, and the balance is CaO And it provides a mold flux for continuous casting non-oriented electrical steel sheet containing an inevitable impurity component.

In addition, the mold flux uses a viscosity of 1.0 ~ 2.0 poise at a temperature of 1300 ℃ or more.

Hereinafter, the reason for limiting the component adjustment of the mold flux according to the present invention will be described in detail.

First, unlike the conventional mold flux, the mold flux according to the present invention is characterized by containing almost no SiO ₂ component, or limiting the maximum content to 3.0% by weight or less.

In the present invention, the amount of SiO ₂ contained in the mold flux is limited to 3.0% or less. The reason for this is that when more than 3% of SiO ₂ is contained, the intense oxidation reaction with Al in the molten steel proceeds in the mold. This was because continuous casting was not possible due to the accompanying explosion and flame.

In general, when the amount of the SiO ₂ component is reduced, the basicity (CaO / SiO ₂ ) of the mold flux is very high, in which case the viscosity of the mold flux may be excessively low. When the viscosity is excessively low, the consumption of mold flux (mold flux used weight per molten molten steel weight) becomes excessively high, and also an oscillation mark is generated deeply on the surface of the cast steel to be cast. Can be lowered.

Therefore, in the present invention, in order to maintain the viscosity of the mold flux of which the amount of SiO ₂ component is lowered to an appropriate level, a flux is introduced, which serves to adjust the viscosity of the powder.

As the flux in the present invention, a liquid flux in which a conventional Na ₂ O component and a Li ₂ O and K ₂ O component were mixed was used. When the amount is more than 1% by weight, the viscosity of the mold flux becomes very low and the mold The consumption of flux (the weight of mold flux per molten molten steel weight) becomes excessively high, and very deep oscillation marks are generated on the surface of the cast slab, which deteriorates the quality of the cast. Because you can.

The CaO component of the mold flux of the present invention is a main component which limits each of the components, and then occupies the rest of the mold flux. The CaO component may be more than 50% by weight, but preferably 30 to 50% by weight. . That is, when the CaO component is more than 50%, the viscosity of the slag is very low, the amount of slag flowing into the mold wall surface is increased, on the contrary, when the CaO component is less than 30%, the viscosity of the slag is excessively As a result, the lubricating ability of the mold and the slab decreases, which increases the possibility of slab bursting (hereinafter referred to as 'binding slab bursting') due to slab restraint.

In addition, when the Al ₂ O ₃ component formed in the present invention is more than 30%, the viscosity of the mold flux increases and the absorption capacity of non-metallic inclusions in the molten steel is lowered. When the Al ₂ O ₃ component is less than 10%, it is added to the Al ₂ O ₃ component of the slag. Due to the excessive absorption capacity, the slag viscosity is excessively increased, which reduces the lubrication ability of the mold and the cast steel.

Other components constituting the mold flux of the present invention, fluorine (F), magnesium oxide (MgO) and manganese oxide (MnO) are 5 to 15% of fluorine (F), MgO 2 to 6%, MnO 5-10%.

On the other hand, it is preferable that the mold flux according to the present invention to have a viscosity in the range of 1.0 ~ 2.0 poise at a temperature of 1300 ℃ or more, because the consumption of the mold flux is excessive when the viscosity is less than 1.0 poise, accordingly There is a risk of lowering the surface quality of the cast steel, and if the viscosity exceeds 2.0 poise, the lubricating ability of the mold and the cast steel is reduced, thereby increasing the possibility of constrained cast steel burst.

Hereinafter, the present invention will be described in detail through preferred embodiments.                     

By weight% C: 0.01% or less, Si: 3.0 ~ 3.4%, Mn: 0.5% or less, S: 0.01% or less, P: 0.01% or less, Al: 1.0-1.5% and the balance is Fe and other unavoidable impurities The slab, which is a high-aluminum-containing non-oriented electrical steel sheet, was continuously cast under the same casting conditions in a continuous casting machine, and the size was cast at a thickness of 200 to 250 mm and a width of 900 to 2000 mm.

At this time, as the mold flux applied, a product having the composition shown in Table 2 was added, and the comparative mold flux and the mold flux of the present invention were applied to the actual slab player while the explosion and flame generation and the restraint cast slab generation occurred in the mold. 2 is shown together.

As a result of repeated tests in the actual slab continuous casting machine, it was confirmed that the explosion and restraint cast slab generation during casting are greatly improved when using the other mold flux in the present invention. Table 2 is based on the preferred CaO component range of 30 to 50% in the mold flux of the present invention, but even if the CaO component is formed in excess of this range, explosion and flame hardly occurred at the top of the mold. The restraint cast rupture phenomenon did not occur.

As described above, the mold flux of the present invention is SiO in the molten steel and the mold flux during slab continuous casting for the production of high aluminum-containing non-oriented electrical steel sheet in which the Al component is added 1.0-1.5% by weight in molten steel. There is a very useful effect that significantly reduces the explosion and the flame generated by the reaction with ₂ . Therefore, this effect can produce a good quality slab can be produced a good electrical steel sheet in the post-process.

Claims (2)

In the continuous casting mold flux of non-oriented electrical steel sheet containing silicon (Si) and aluminum (Si), As a _{weight%, Al 2 O 3 10 ~} 30%, SiO 2 3% or less, the flux _{(Na 2 O + Li 2 O} + K 2 O) 1.0% or less, a fluorine (F) 5 ~ 15%, MgO 2 ~ 6 %, MnO 5 ~ 10%, the remainder of the mold flux for continuous casting of non-oriented electrical steel sheet, characterized in that the balance contains CaO and inevitable impurities. The mold flux for continuous casting of non-oriented electrical steel sheet according to claim 1, wherein the mold flux has a viscosity of 1.0 to 2.0 poise at a temperature of 1300 ° C or higher.

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