JP2000256732A - PRODUCTION OF Fe-Ni BASE ALLOY COLD-ROLLED SHEET BLANK FOR SHADOW MASK EXCELLENT IN ETCHING PERFORATION - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce the blank for Fe-Ni base alloy cold-rolled sheet which can be used for shadow mask in high visibility and high brightness TV excellent in etching perforation. SOLUTION: It is a producing method where molten steel obtd. by refining in a converter 3 and molten Ni-containing crude metal obtd. by melting in a melting furnace 4 are combined to obtain the molten alloy containing 30-45 wt.% Ni. After heating the molten alloy, decarburization is executed under reduced pressure in an RH vacuum degassing apparatus 6, and after decarburizing, deoxidation is executed with Al, and successively casting is executed, and Al adding quantity in the Al deoxidation after decarburizing is regulated to <=3.0 kg/ton of molten alloy. Also, at least after Al deoxidation, CaO-Al2O3-MgO base slag containing >=57 wt.% CaO+Al2O3, <=25 wt.% MgO, <=15 wt.% SiO2 and <=3 wt.% the total oxide quantity of metals having the affinity with oxygen at the level weaker than that of Si and >=0.45 that is a ratio of CaO/(CaO+Al2 O3) is brought into contact with the molten alloy in the ladle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a material for a cold rolled Fe-Ni alloy for a shadow mask of a high definition TV which is excellent in etching piercing property and which does not cause a defective hole shape at the time of etching piercing. It is about.

[0002]

2. Description of the Related Art Fe-N for shadow mask of high definition TV
The i-type alloy cold-rolled sheet is required to be free from a defect of a hole shape at the time of etching perforation. As a means for solving this problem, a method for producing a material for a cold rolled Fe—Ni alloy for a shadow mask is disclosed in JP-A-4-218644. In the present invention, the Fe-Ni-based alloy cold rolled material is an ingot and a slab of the Fe-Ni-based alloy.

[0003] The method disclosed in the above publication is disclosed in Japanese Patent Application Publication No.
In a ladle made of MgO-CaO-based refractory containing wt% CaO, F containing 30-45 wt% Ni
While adding Al to the e-Ni molten alloy to deoxidize it,
CaO + Al ₂ O ₃ : 57 wt% or more, MgO: 25 w
t% or less, SiO ₂ : 15 wt% or less, total amount of metal oxides having an affinity for oxygen weaker than Si: 3 wt% or less, and a ratio of CaO / (CaO + Al ₂ O ₃ ) of 0. 45 more than is reacted with CaO-Al ₂ O ₃ -MgO slag performs deoxidation by slag, then
This is a method of manufacturing a material for a cold rolled sheet of an Fe-Ni alloy by casting into an ingot.

According to the publication, CaO-A having the above composition is used.
The slag deoxidation by l ₂ O ₃ -MgO slag, F
The oxygen content in the e-Ni-based alloy is reduced to 0.002 wt% or less, and the size of oxide-based nonmetallic inclusions (hereinafter, referred to as “inclusions”) is reduced to 6 μm or less. It is stated that an excellent Fe-Ni alloy cold rolled sheet can be manufactured.

[0005]

However, the method disclosed in Japanese Patent Application Laid-Open No. 4-218644 has the following problems. That is, even if deoxidation is performed together with Al using a slag having the disclosed composition, when the amount of Al added is large, Al ₂ O ₃ generated during deoxidation increases, and the particle size of each inclusion is 6 μm. Even when the following occurs, they are aggregated and coalesced into clusters. As a result, when manufacturing a shadow mask for a high-brightness CRT in which the area ratio of the etching hole on the large diameter side exceeds 55%, clustered Al ₂ O ₃ -based inclusions are applied to the etching hole, resulting in poor etching hole shape. Become.

As described above, a method for producing a material for a cold rolled Fe-Ni alloy which does not generate defects during etching and can be stably used as a shadow mask material for a high definition and high brightness TV. Has not yet been established.

[0007] The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a method for stably producing a material for a cold rolled Fe-Ni alloy which is excellent in etching piercing property and can be used as a shadow mask material of a high definition and high brightness TV. That is.

[0008]

According to the first aspect of the present invention, there is provided a method for producing a material for a cold rolled sheet of an Fe—Ni alloy for a shadow mask having excellent etching piercing properties, comprising: a molten steel obtained by refining in a converter; A molten Ni-containing molten metal obtained by melting in a melting furnace was combined with a ladle in a ladle to obtain a molten alloy containing 30 to 45 wt% of Ni, and after heating the molten alloy, RH vacuum degassing was performed. Decarburized at the facility and deoxidized with Al after decarburization,
Next, a method for producing a material for a cold-rolled Fe-Ni-based alloy, which is performed by casting, wherein the amount of Al added during Al deoxidation after decarburization is set to 3.0 kg or less per ton of molten alloy, At least after Al deoxidation, CaO + Al
₂ O ₃ : 57 wt% or more, MgO: 25 wt% or less, S
iO ₂ : 15 wt% or less, total amount of oxides of metals having a lower affinity for oxygen than Si: 3 wt% or less, and the ratio of CaO / (CaO + Al ₂ O ₃ ) is 0.45 or more. the and the molten alloy CaO-Al ₂ O ₃ -MgO based slag is characterized in that the contacting in the ladle.

According to a second aspect of the present invention, there is provided a method of manufacturing a material for a cold rolled sheet of an Fe-Ni alloy for a shadow mask having excellent etching piercing properties, wherein molten steel obtained by refining in a converter is melted in a melting furnace. The molten Ni-containing molten metal obtained in
Is obtained by heating the molten alloy, decarburizing it with a RH vacuum degassing facility under reduced pressure, decarburizing it and then deoxidizing with Al. An inert gas is blown into the molten alloy to stir the molten alloy, and then refining is performed again in an RH vacuum degassing facility, and then casting is performed. The amount of Al added at the time of Al deoxidation after decarburization is set to 3.0 kg or less per ton of molten alloy,
At least after Al deoxidation, CaO + Al ₂ O ₃ : 57
wt% or more, MgO: 25 wt% or less, SiO ₂ : 15
wt% or less, the total amount of oxides of metals having a lower affinity for oxygen than Si: 3 wt% or less, and CaO /
Ca having a (CaO + Al ₂ O ₃ ) ratio of 0.45 or more
And O-Al ₂ O ₃ -MgO slag and molten alloy is characterized in that the contacting in the ladle.

The inventor of the present invention has found that even when used as a shadow mask material for a high-definition and high-brightness TV in which the area ratio on the wide-diameter side of the etching hole exceeds 55%, an etching hole without defective hole shape is produced. Intensive research was conducted to develop a method for manufacturing a material for a cold rolled Fe-Ni alloy having excellent heat resistance. As a result, the following was found.

As shown in FIG. 1, the etching hole shape defect of the shadow mask material is such that inclusions each having a size of several μm are clustered and expanded in the rolling direction. The occurrence was found from the results of electron microscopic observation. That is, even if the amount of inclusions in the alloy is reduced to about 0.002 wt% in terms of oxygen in the cold-rolled sheet stage, if the remaining inclusions are clustered together, the clustered inclusions will It expands during the rolling process and is applied to the etching hole, which causes a defective hole shape.
FIG. 1 is a view schematically showing the state of occurrence of an etching hole shape defect.

Therefore, when melting a Fe-Ni-based molten alloy containing 30 to 45 wt% of Ni, the A
A test was performed in which the amount added, the refining equipment for performing Al deoxidation, and the treatment process after Al deoxidation were performed, and the effects on the incidence of hole-shaped defect defects during etching perforation were investigated. The test conditions are as follows.

First, two refining facilities, an RH vacuum degassing facility and a VOD facility, are used for adjusting the Ni content and heating the molten alloy using an LF facility, and thereafter performing Al deoxidation. After vacuum decarburization in these refining facilities, Al was added to deoxidize the molten alloy.
At this time, the amount of Al added should be 0.8 to 1 ton of molten alloy.
It was changed to 5.4 kg (hereinafter, referred to as “kg / ton”). Then, after deoxidation was reacted with CaO-Al ₂ O ₃ -MgO based slag composition disclosed in the aforementioned JP-A-4-218644 discloses that were previously added to the ladle and the molten alloy. In some tests, after refining by RH vacuum degassing equipment, an inert gas was blown into the molten alloy by gas injection equipment, and the CaO-Al ₂ O
After accelerating the reaction between the _3- MgO-based slag and the molten alloy, refining was again performed using an RH vacuum degassing facility.
Note that the LF facility is a ladle refining facility without a vacuum processing facility, and the VOD facility is a refining facility that accommodates a ladle in a vacuum tank and processes the ladle under reduced pressure.

FIG. 3 is a graph showing the results of an examination of the relationship between the amount of Al added per ton of molten alloy during deoxidation and the rate of occurrence of hole shape defects during etching drilling in this test operation. In FIG. 3, the molten alloy is classified according to the processing step, and in FIG.
Represents RH vacuum degassing equipment, GI represents gas injection equipment, and VOD represents VOD equipment. FIG. 3 will be described in detail in an embodiment.

As shown in FIG. 3, when the amount of Al added at the time of deoxidation exceeds 3.0 kg / ton, the occurrence rate of hole shape defects at the time of etching drilling increases. This is because when the amount of Al added exceeds 3.0 kg / ton, the amount of Al ₂ O ₃ generated by the reaction of the added Al not only with the dissolved oxygen in the molten alloy but also with the lower oxide in the slag is large. A generated
During the floating and separation process of l ₂ O ₃ , the clustering proceeds by agglomeration and coalescence, and among these, the clustered Al ₂ O ₃ that could not be separated and removed becomes a cause of defects during etching perforation. By setting the amount of Al added to 3.0 kg / ton or less, the amount of generated Al ₂ O ₃ is reduced, the amount of remaining clustered Al ₂ O ₃ is reduced, and the occurrence rate of defective hole diameter during etching is reduced. I do.

However, as shown in FIG. 3, even if the amount of Al added is 3.0 kg / ton or less, the deoxidizing treatment equipment is
In the case of the OD equipment, the hole shape defect occurrence rate does not decrease to the target value, and therefore, it is necessary to limit the deoxidizing equipment to the RH vacuum degassing equipment. This is the RH vacuum degassing equipment,
And stirred in a vacuum chamber by circulating a gas, by stirring with molten alloy to reflux between the vacuum tank and the ladle, a large stirring force to the molten alloy is applied, clustered Al ₂ O
_{This is because} the floating / separation of ₃ is promoted.

Further, at least after Al deoxidation, CaO +
Al ₂ O ₃ : 57 wt% or more, MgO: 25 wt% or less, SiO ₂ : 15 wt% or less, and affinity for oxygen is Si
Total amount of oxides of weaker metals: 3 wt% or less, and the ratio of CaO / (CaO + Al ₂ O ₃ ) is 0.
The a CaO-Al ₂ O ₃ -MgO based slag and molten alloy is 45 or more is required to be contacted with the ladle. In CaO-Al ₂ O ₃ -MgO slag of this composition, the activity of activity of and SiO ₂ to Al ₂ O ₃ in the slag is lowered. Therefore, when the slag is brought into contact with the molten alloy, the dissolved oxygen in the molten alloy is reduced by the activity of Al ₂ O _{3 in} the slag and the activity of Si.
At or near equilibrium with the activity of O ₂ ,
Stable when the amount of dissolved oxygen in the molten alloy is low. In addition, since the low activity of of Al ₂ O ₃ in the slag, resulting Al ₂
O ₃ is quickly absorbed by the slag. That is, C of the above composition
By contacting the aO-Al ₂ O ₃ -MgO-based slag and the molten alloy at least after Al deoxidation, the dissolved oxygen in the molten alloy is reduced, and the generated Al ₂ O ₃ is quickly separated and removed. Therefore, the cleanliness of the molten alloy can be improved.

The reason why the composition of the CaO-Al ₂ O ₃ -MgO slag is limited to the above range will be described below.

(1) CaO / (CaO + Al ₂ O ₃ ):
When the ratio of CaO / (CaO + Al ₂ O ₃ ) is less than 0.45, the activity of Al ₂ O _{3 in} the slag exceeds 0.5, and when the Al content in the molten alloy is kept constant, The deoxidizing power of is decreased. Therefore, CaO / (CaO + Al ₂
The ratio of O ₃ ) must be at least 0.45.

(2) MgO content: MgO content is 25
If it exceeds wt%, the melting point of the slag increases and the reactivity with the molten alloy decreases, so the MgO content must be limited to 25 wt% or less.

(3) SiO ₂ content: When the SiO ₂ content exceeds 15 wt%, the activity of SiO _{2 in} the slag increases, and accordingly, the dissolved oxygen in the Fe—Ni-based molten alloy is increased. The amount increases. As a result, the amount of oxygen in the Fe—Ni-based alloy increases, so that the SiO ₂ content is 15 wt%.
It must be:

(4) Total content of oxides of metals whose affinity for oxygen is weaker than Si: If the total amount of oxides of metals whose affinity for oxygen is weaker than Si exceeds 3 wt%, Fe
-The dissolved oxygen amount in the Ni-based molten alloy increases. Therefore,
The total content of oxides of metals whose affinity with oxygen is weaker than that of Si needs to be 3 wt% or less.

By limiting the MgO content, SiO ₂ content, and the total content of oxides of metals having a lower affinity for oxygen than Si as described above, the CaO content and Al The sum with the ₂ O ₃ content is limited to 57 wt% or more.

Further, in the RH vacuum degassing equipment, Al deoxidation is performed.
After carrying out, the gas injection equipment
Inert gas is blown into the molten alloy to form the molten alloy and slag.
Are stirred and mixed, and then again in the RH vacuum degassing facility.
Refining the Al in the molten alloy _TwoO_ThreeTo promote the emergence of
With RH vacuum degassing equipment, cast as it is after deoxidizing Al
Rather than remaining in the cold rolled Fe-Ni alloy sheet
Clustered Al_TwoO_ThreeTo reduce the amount of
And further reduces the rate of defective hole diameter during etching.
Can be

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a diagram showing a manufacturing process of an Fe—Ni alloy cold rolled sheet material for a shadow mask according to the present invention.
It is an example. Hereinafter, the present invention will be described with reference to FIG.

The hot metal discharged from the blast furnace 1 is subjected to desulfurization treatment and dephosphorization treatment in a hot metal pretreatment facility 2 such as a mechanical stirring method or a gas injection stirring method which is generally performed. In the Fe—Ni-based alloy for shadow mask, the material properties are improved as both the S content and the P content are smaller. Therefore, both desulfurization treatment and dephosphorization treatment are usually performed. Thereafter, the hot metal is charged into the converter 3 and oxygen gas is blown by an upper blowing oxygen lance to decarburize and refine the hot metal to obtain molten steel.

In this converter 3, as in the case of ordinary carbon steel refining, iron scraps, including scraps of Fe—Ni alloys for shadow masks, can be charged together with hot metal. At that time, in terms of heat balance, the mixing ratio of iron scrap to the total weight of hot metal and iron scrap is set to a maximum of 20 watts.
It can be up to about t%. In the converter 3, decarburization refining is preferably performed until the C content becomes 0.05 wt% or less. After refining, steel is produced in a ladle.
It is preferable that the molten steel is discharged to a ladle in a non-deoxidized state without adding a strong deoxidizing agent such as i or Zr. This is because, by tapping in a non-deoxidized state, pickup of nitrogen in the air can be suppressed. The type of the converter 3 may be either a top-blowing converter or a vertical-blowing converter using a gas for stirring at the bottom of the converter, and lime used as a slag-making agent in the converter may be mixed with S. It is preferable to use low-sulfur lime in order to prevent the occurrence of lime.

On the other hand, alloy raw material or alloy raw material and Fe—N
The i-based alloy scrap is melted in a melting furnace 4 such as an electric furnace to obtain a Ni-containing crude molten metal. The molten steel obtained by refining in the converter 3 does not contain the Ni component, or even if it contains the Ni component, the amount is small.
It is necessary to determine the Ni content in the Ni-containing molten metal. Including N
i If the Ni content in the crude molten metal is a content that secures 80% or more of the Ni content of the final target Fe-Ni-based alloy, the Fe-Ni molten alloy obtained by adding the alloy raw material after the combined metal is used. This is preferable because heat loss due to a decrease in temperature is reduced and manufacturing cost is reduced. Then, the Ni-containing crude molten metal melted in the melting furnace 4 is poured into a ladle. In addition, at the time of tapping, from the viewpoint of preventing nitrogen pickup, Al, C
It is preferable that tapping be performed in a non-deoxidized state without adding a strong deoxidizing agent such as a, Ti, and Zr.

The molten Ni-containing molten metal thus obtained is poured into a ladle for storing molten steel, and the molten steel is mixed with the molten Ni-containing molten metal. When a ladle for storing molten steel can be disposed in the melting furnace 4, the ladle for storing molten steel can directly receive the Ni-containing molten metal from the melting furnace 4.

The molten alloy obtained from the combined bath is refined in the LF equipment 5. The LF equipment 5 heats the molten alloy whose temperature has been lowered by the mixing bath and adjusts the components until the Ni content reaches a predetermined value. Fe-Ni for shadow mask
In a system alloy, since the material properties are more excellent as the S content is smaller, desulfurization treatment is preferably performed by the LF facility 5.
The desulfurization method in the LF equipment 5 is to add a strong deoxidizer such as Al to the molten alloy to deoxidize the molten alloy and add a desulfurizing agent into the ladle, and then blow an inert gas into the molten alloy, It can be performed by stirring and mixing the molten alloy and the desulfurizing agent. It is not necessary to use a desulfurizing agent that is particularly limited, and a desulfurizing agent that is usually used in the steelmaking industry, such as a CaO-based desulfurizing flux or a metal Mg-based desulfurizing agent, may be used.

After refining in the LF facility 5, the molten alloy is transferred to the RH vacuum degassing facility 6. Fe-N for shadow mask
In the i-based alloy, if the C content exceeds 0.005 wt%, carbides are formed to cause drilling defects, and press formability is impaired.
t% or less. Therefore, in the RH vacuum degassing facility 6, first, decarburization of the molten alloy is performed. In this decarburization method, oxygen gas is blown to a molten alloy in a vacuum chamber, or iron ore, mill scale, or the like is added, and the molten alloy is reacted with these oxygen sources (decarburization method ( This decarburization method is referred to as “acid-feeding decarburization”) and a decarburization method in which the molten alloy is placed in a non-deoxidized state and the pressure in the vacuum chamber is reduced (this decarburization method is referred to as “vacuum decarburization”). There are two ways.
If the molten alloy is in an undeoxidized state and the C content in the molten alloy is about 0.05 wt%, the decarburization of the molten alloy can be performed only by reducing the pressure in the vacuum chamber.
In the case of deoxidizing for desulfurization treatment, it is necessary to completely remove deoxidizing elements such as Al using oxygen gas, iron ore, or mill scale before decarburizing. That is,
It is necessary to carry out acid decarburization. This is because the decarburization reaction does not proceed even if the pressure is reduced in a state where the strongly deoxidized element such as Al remains in the molten alloy.

When the C content of the molten alloy has decreased to a predetermined value, Al is added to the molten alloy to deoxidize the molten alloy.
At this time, the amount of Al added is set to 3.0 kg / ton or less.
That is, by setting the amount of Al added to 3.0 kg / ton or less, 0.003 to 0.03 wt% of Al in the molten alloy after deoxidation.
It is necessary to control the amount of dissolved oxygen in the molten alloy before deoxidation so as to remain. This is achieved by appropriately adjusting the amount of oxygen gas used during the decarburization process in the converter 3 and the RH vacuum degassing facility 6.

After Al deoxidation, CaO + Al ₂ O ₃ : 57w
t% or more, MgO: 25 wt% or less, SiO ₂ : 15 w
t% or less, the total amount of metal oxides having an affinity for oxygen weaker than Si: 3 wt% or less, and CaO /
Ca having a (CaO + Al ₂ O ₃ ) ratio of 0.45 or more
O-Al ₂ O ₃ -MgO slag (hereinafter, simply "CaO
Ternary slag ") and the molten alloy.

The following methods are available for bringing the molten alloy into contact with the CaO-based ternary slag. In the RH vacuum degassing equipment 6, a method of adding a CaO-based ternary slag to the molten alloy surface in the ladle to cover the molten alloy surface before or after the Al deoxidation, A method of adding Ca-based ternary slag to a ladle and a vacuum chamber and transporting the CaO-based ternary slag into the ladle to cover the surface of the molten alloy, or immersing the molten alloy in the molten alloy. There is a method of blowing into a molten alloy through an injection lance. LF equipment 5
In addition, there is also a method of adding in advance to the surface of the molten alloy.

Although any method may be used, when desulfurization treatment is performed in an LF facility, the composition of the desulfurizing agent is CaO.
Similar to the composition range of the system ternary slag, it is preferable to remove the slag after desulfurization unless the desulfurizing agent can be used to adjust the composition of the desired CaO-based ternary slag. Also, the composition of the CaO-based ternary slag to be added needs to be determined in consideration of the amount of Al ₂ O ₃ generated by Al deoxidation. The CaO-based ternary slag may be added as a synthetic slag synthesized in advance to have a predetermined composition, or raw materials such as lime, dolomite, and bauxite may be added directly to the molten alloy so as to have a predetermined composition. But it doesn't matter.

In the first invention, after Al deoxidation, the other components are adjusted to finish the refining in the RH vacuum degassing equipment 6, and then the molten alloy is cast by a continuous casting method or a normal ingot casting method. The material is conveyed to the facility 8 and cast, and is used as an ingot or slab as a material for a cold-rolled Fe—Ni alloy sheet for a shadow mask.

In the second invention, after the refining in the RH vacuum degassing facility 6 is completed, the molten alloy is transferred to the gas injection facility 7. In the gas injection equipment 7,
An inert gas is blown into the molten alloy in the ladle to stir and mix the molten alloy and the CaO-based ternary slag. The gas injection equipment 7 may be any equipment as long as it has an inert gas blowing mechanism. For example, the gas injection equipment 7 may also serve as the LF equipment 5 or may be an independent equipment.

After the refining in the gas injection equipment 7 is completed, the gas is conveyed again to the RH vacuum degassing equipment 8 for refining. In this refining, the final components of the molten alloy are adjusted, and the floating and separation of Al ₂ O ₃ is promoted. After the second refining in the RH vacuum degassing facility 6, the molten alloy is conveyed to a casting facility 8 such as a continuous casting method or an ordinary ingot casting method to be cast, and is cast as an ingot or a slab for Fe-Ni for a shadow mask.
Based alloy cold rolled material.

As described above, the Fe--N for shadow mask
By producing a material for an i-based alloy cold rolled sheet, the amount of clustered Al ₂ O ₃ -based inclusions remaining in the material can be reduced, and the occurrence rate of hole diameter defects during etching can be reduced.

In the above description, the heat treatment, the Ni adjustment treatment, and the desulfurization treatment of the molten alloy after the mixing bath are performed using the LF equipment 5, but the present invention is not limited to this. Since the heat treatment, the component adjusting function, and the desulfurization treatment of the alloy can also be performed in the RH vacuum degassing facility 6, if the operation rate of the RH vacuum degassing facility 6 has a margin, immediately after the mixing bath, It is also possible to transport the molten alloy to the RH vacuum degassing facility 6 and perform a heating process, a Ni adjustment process, and a desulfurization process. V instead of LF equipment 5
AD equipment may be used.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In melting a molten alloy of Fe-Ni alloy for a shadow mask containing 30 to 45 wt% of Ni,
l Amount of Al added during deoxidation, refining equipment for performing Al deoxidation,
And a total of 3 test runs with different treatment steps after Al deoxidation
The test was performed six times to investigate the influence on the incidence of defective hole-shaped defects during etching. Test No. 1-36
The test conditions for a total of 36 test runs are as follows.

In all the test operations, about 110 tons of hot metal from a blast furnace was desulfurized and dephosphorized in a hot metal pretreatment facility, and then decarburized and refined in a converter. After refining, the tapping temperature was set to 1665 to 1675 ° C, and tapping was performed on a ladle.

On the other hand, about 60 tons of electrolytic Ni was melted in a 60-ton electric furnace to obtain a Ni-containing coarse molten metal, which was heated to 1650 ° C. and then poured into a ladle. Next, the molten steel refined in the converter and the NI-containing crude molten metal were combined to obtain a 170-ton molten alloy.

After that, the ladle was moved to the LF facility,
The r flow rate is 0.5 to 2.0 Nl / min · ton, and calcined lime: 22 kg / ton, fluorite: 5.5 k as a slag-making agent
g / ton, bauxite: 2.8 kg / ton was immediately added immediately after refining was started, the temperature was raised to 1650 ° C. by a three-phase electrode heating device, and the Ni component was 36.0 w.
Electrolytic Ni was added to adjust to t%. After the addition of the slag-making agent, the molten alloy was deoxidized with Al, an inert gas was blown into the molten alloy, and desulfurization was performed using the added slag-making agent as a desulfurizing agent. After the desulfurization treatment, the residue was removed, and a CaO-based ternary slag was added to the ladle at a fixed amount of 20 kg / ton.

Test No. In 1 to 30, after that, the molten alloy is conveyed to the RH vacuum degassing equipment, and refining is started with the reflux Ar flow rate of 5.5 to 12.0 Nl / min · ton. First, the pressure in the vacuum chamber is reduced to 50 torr. Oxygen gas is blown onto the molten alloy at a flow rate of 3.0 to 7.0 Nm ³ / Hr · ton to carry out acid decarburization while maintaining the pressure in the vacuum chamber, and then the pressure in the vacuum chamber is maintained at 1 torr or less. Vacuum decarburization was performed. The total treatment time of the deacidification and vacuum decarburization was 35 minutes. In this way, the C content is reduced to 0.0
The content was set to 05 wt% or less. Next, while the recirculation Ar flow rate was set to 5.5 to 12.0 Nl / min · ton and the pressure in the vacuum chamber was maintained at 1 torr or less, the molten alloy was deoxidized by adding Al to the molten alloy. did. At that time, the amount of Al added was changed in the range of 0.8 to 5.4 kg / ton. Refining was continued while keeping the ring flow rate and the pressure in the vacuum chamber the same even after the introduction of Al.

Test No. In 1 to 15, when the temperature of the molten alloy becomes 1540 ° C., the RH vacuum degassing refining is finished, and then, using a 7 ton or 12 ton upper mold, casting is performed by the downward pouring ingot casting method. To obtain an ingot. that time,
Injection flow temperature 1490-1525 ° C, pouring speed 15
At a pressure of 0 to 190 mm / min, the space between the ladle nozzle and the injection pipe is surrounded by a cover, and Ar is set to 130 Nm ³ / H in the cover.
The molten alloy was cast at a flow rate of r to prevent air oxidation of the molten alloy. After deoxidation of Al, C reacted with molten alloy
Table 1 shows composition examples of the aO-based ternary slag. Table 1
In the CaO-based ternary slag shown in Fig. 5, CaO / (CaO + A
l ₂ O ₃ ) is 0.71, and MnO, Cr ₂ is an oxide of a metal having a lower affinity for oxygen than Si.
O ₃ , and T.I. Fe was contained, and the total amount thereof was 1.19 wt%. In addition, T. Fe is FeO or F
It is the total amount of iron oxides such as e ₂ O ₃ .

[0047]

[Table 1]

Test No. In 16 to 30, when the temperature of the molten alloy reaches 1615 ° C., the RH vacuum degassing refining is once terminated, and then the molten alloy is transported to a gas injection facility, and the Ar blowing amount is set to 8.8 to 12. 0Nl
Ar was blown for 7 to 15 minutes at / min · ton, and the molten alloy and the CaO-based ternary slag were stirred and mixed. After that, the molten alloy was transported to the RH vacuum degassing facility again, and the Ar flow rate for reflux was set to 5.5 to 12.0 Nl / min.
-Ton, RH vacuum degassing and refining is performed until the temperature of the molten alloy becomes 1540 ° C. with the pressure in the vacuum chamber set to 1 torr or less (this is also referred to as “secondary RH vacuum degassing and refining”).
did. Thereafter, Test No. Casting was performed under the same conditions as in Nos. 1 to 15 to obtain an ingot. Table 2 shows transition examples of the chemical composition of the molten alloy in each step.

[0049]

[Table 2]

Test No. In 31 to 36, after refining by the LF facility, the molten alloy was transported to the VOD facility. And
In the VOD equipment, adjust the bottom blow Ar flow rate to 1.0 to 2.5 Nl.
/ Min · ton, first, the pressure in the vacuum chamber is set to 100
While maintaining the pressure at not more than torr, oxygen degassing by blowing oxygen gas was performed, and then the pressure in the vacuum chamber was reduced to 1 torr or less to perform vacuum decarburization. After the decarburization treatment, Al was added to deoxidize the molten alloy. The addition amount of Al was changed in the range of 1.2 to 5.2. Test No. In 31 to 36, the molten alloy and the CaO-based ternary slag were stirred and mixed by the bottom blow gas. The molten alloy thus obtained was subjected to Test No. 1 to 1
Casting was performed under the same conditions as in Example 5 to obtain an ingot.

The thus obtained ingot is subjected to a series of production steps including slab rolling, slab surface treatment, hot rolling, cold rolling, annealing, cold rolling, and strain removing heat treatment to produce a cold rolled sheet for a shadow mask. did. Then, in each test operation, 200 shadow mask plates were extracted and etched under the condition that the area ratio on the wide side of the etching hole was 60%, and the occurrence rate of the etching hole shape defect was investigated. In Table 3,
The production rate of the hole shape defect is shown together with the production conditions of each test operation.
FIG. 3 shows the relationship between the amount of Al added per ton of the molten alloy at the time of deoxidation and the rate of occurrence of hole shape defects at the time of etching perforation. The present inventors set the target level of the hole shape defect occurrence rate to 1.
The evaluation was made as less than 0%. In Table 3, a mark 極 indicates an extremely excellent failure rate of less than 0.5%, a mark ○ indicates an excellent failure rate of less than 1%, and a mark X. Indicates that the defect rate is 1% or more.

[0052]

[Table 3]

As shown in Table 3 and FIG.
When the deoxidation was performed in an RH vacuum degassing facility and the amount of Al added during deoxidation was 3.0 kg / ton or less, the rate of occurrence of etching hole shape defects satisfied the target level. Then, after Al deoxidation, gas injection is further performed, and R
In a test operation in which H vacuum degassing refining was performed, it was found that the occurrence rate of etching hole shape defects was particularly low. In the remarks column of Table 3, test runs within the scope of the present invention were shown as examples, and other test runs were shown as comparative examples. In a test run within the scope of the present invention, the oxygen content in the ingot was 0.002 watts.
t% or less, and the ingot was extremely clean.

[0054]

As described in detail above, according to the present invention,
Cluster-like Al ₂ O ₃ contained in the material for cold rolled Fe—Ni alloys for shadow masks can be extremely reduced. It is possible to stably produce a material for a cold rolled Fe-NI alloy for a shadow mask which is free from defects and has excellent etching piercing properties.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a state of occurrence of an etching hole shape defect.

FIG. 2 is an example of a manufacturing process diagram of a material for a cold rolled Fe—Ni alloy for a shadow mask according to the present invention.

FIG. 3 is a view showing a result of an examination in an example, and is a view showing a relationship between the amount of Al added at the time of deoxidation and the incidence rate of defective etching hole shape.

[Explanation of symbols]

 Reference Signs List 1 blast furnace 2 molten iron pretreatment equipment 3 converter 4 melting furnace 5 LF equipment 6 RH vacuum degassing equipment 7 gas injection equipment 8 casting equipment

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C21C 7/00 C21C 7/00 H J7 / 04 7/04 B 7/06 7/06 7/068 7 / 068 7/076 7/076 A C22B 9/04 C22B 9/04 C22C 33/04 C22C 33/04 H // H01J 9/14 H01J 9/14 G (72) Inventor Hiroki Asada Marunouchi, Chiyoda-ku, Tokyo No. 1-2, Nippon Steel Pipe Co., Ltd. F-term (reference) 4K001 AA10 BA22 DA05 EA02 EA04 FA10 GA13 GA18 KA01 KA02 KA06 KA13 4K013 AA01 BA02 BA08 CB09 CE01 CE04 CE07 CF13 DA01 DA10 DA12 DA14 EA01 EA03 EA04 EA05 H05

Claims (2)

[Claims] 1. A molten steel obtained by refining in a converter and a Ni-containing molten metal obtained by melting in a melting furnace are combined in a ladle,
Obtaining a molten alloy containing 30 to 45 wt% of Ni, heating the molten alloy, decarburizing under reduced pressure in an RH vacuum degassing facility, decarburizing, deoxidizing with Al, and then casting. A method for producing a material for cold-rolled Fe—Ni-based alloys comprising: reducing the amount of Al added during Al deoxidization after decarburization to 3.0 kg or less per ton of molten alloy;
At least after Al deoxidation, CaO + Al ₂ O ₃ : 57
wt% or more, MgO: 25 wt% or less, SiO ₂ : 15
wt% or less, the total amount of oxides of metals having a lower affinity for oxygen than Si: 3 wt% or less, and CaO /
Ca having a (CaO + Al ₂ O ₃ ) ratio of 0.45 or more
O-Al ₂ O ₃ -MgO slag molten alloy and the manufacturing method of etching perforation excellent in Fe-Ni-based alloy cold-rolled sheet for the material for a shadow mask which comprises contacting in a ladle. 2. A molten steel obtained by refining in a converter and a Ni-containing crude molten metal obtained by melting in a melting furnace are combined in a ladle,
A molten alloy containing 30 to 45 wt% of Ni was obtained, and after heating the molten alloy, decarburization was performed under reduced pressure using an RH vacuum degassing facility, and after decarburization, deoxidized with Al. After injecting an inert gas into the molten alloy and stirring the molten alloy, refining is again performed in the RH vacuum degassing facility,
A method for producing a material for cold-rolled Fe—Ni alloys, comprising casting, wherein the amount of Al added at the time of deoxidation of Al after decarburization is 3.0 kg or less per ton of molten alloy, and at least Al is added. After deoxidation, CaO + Al ₂ O ₃ :
57 wt% or more, MgO: 25 wt% or less, SiO ₂ :
15 wt% or less, the total amount of oxides of metals whose affinity with oxygen is weaker than that of Si: 3 wt% or less, and Ca
_{O / (CaO + Al 2 O} 3) ratio is excellent in etching perforated, which comprises causing the the CaO-Al ₂ O ₃ -MgO based slag and molten alloy is 0.45 or more into contact with the ladle shadow A method for producing a material for a cold rolled Fe-Ni alloy for a mask.