Method for producing high-purity iron-nickel alloy and high-purity iron-nickel alloy produced by the method

Abstract

The present invention provides a high-purity Invar alloy that can be used as a material for fine metal masks. One embodiment of the present invention includes the steps of preparing iron-nickel alloy scrap, forming a melting pool by electron beam cold hearth melting the iron-nickel alloy scrap, and preferably, after the melting pool forming step, melting and evaporating non-metallic inclusions in the melt by setting the electron beam power to material weight ratio (kW / kg) at 1.5 to 2.5 to form a melting pool temperature of 1,800°C or higher, vacuum induction melting the alloy from which the non-metallic inclusions have been melted and evaporated to provide a vacuum induction melted alloy, and vacuum arc remelting the vacuum induction melted alloy, wherein the number of inclusions 2 μm or larger in the produced alloy is 5.0 / mm. 2 Less than 4.0 pieces / mm 2 The present invention provides a method for producing a high-purity iron-nickel alloy having a purity of less than 100%.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a highly clean iron-nickel alloy by applying electron beam melting to iron-nickel alloy scrap, and to a highly clean iron-nickel alloy produced thereby. [Background technology]

[0002] Displays using organic light emitting diodes (OLEDs) are a representative high-resolution display, and the OLED market is gradually expanding, rapidly catching up with the market share of liquid crystal displays (LCDs).In recent years, research and development is underway on micro OLEDs, which can achieve ultra-high resolution that goes beyond the level of OLED displays and enables augmented reality (AR) and virtual reality (VR) technologies.

[0003] There are various issues in the research and development of micro OLED, and the main challenge is to improve the fine metal mask (FMM), which is a core component for manufacturing OLED.

[0004] A fine metal mask is a metal plate with tiny holes that is used in the pixel deposition step of the OLED display manufacturing process. The deposition step involves engraving RGB subpixels, which are the components of a pixel, the smallest unit of an image, onto a substrate. Specific materials are deposited onto the substrate in a vacuum, and the fine metal mask acts as a guideline to ensure that the three subpixels are deposited in the correct position without mixing with each other.

[0005] High-quality displays require highly clean fine metal masks with numerous uniform, fine holes. Cleanliness is related to the size and number of non-metallic inclusions contained within the metal plate, and minimizing impurities and non-metallic inclusions in the metal plate itself, which is the raw material for fine metal masks, makes it possible to form numerous uniform, fine holes.

[0006] In the production of high-purity Invar alloys, which are used to make fine metal masks, it is preferable to use raw materials with extremely low contents of Al, Mg, and other elements that cause non-metallic inclusions. However, such materials are expensive and difficult to stably supply.

[0007] Therefore, there is a growing need for a method for producing high-purity Invar alloy (iron-nickel alloy), which can be used as a material for fine metal masks, from low-purity Invar alloy (iron-nickel alloy) scrap that contains certain amounts of elements such as Al and Mg. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a highly clean Invar alloy that can be used as a material for fine metal masks. [Means for solving the problem]

[0009] One embodiment of the present invention includes the steps of: preparing iron-nickel alloy scrap; forming a melting pool by electron beam cold hearth melting the iron-nickel alloy; after the molten pool is formed, melting and evaporating non-metallic inclusions in the molten pool by preferably performing electron beam melting at a power ratio (kW / kg) of 1.5 to 2.5 relative to the weight of the molten pool; vacuum induction melting the alloy from which the non-metallic inclusions have been melted and evaporated to provide a vacuum induction melted alloy; and vacuum arc remelting the vacuum induction melted alloy, wherein the number of inclusions 2 μm or larger in the alloy is 5.0 / mm 2 The present invention provides a method for producing a high-purity iron-nickel alloy having a purity of less than 100%.

[0010] At this time, preferably, the number of inclusions of 2 μm or more is 4.0 pieces / mm 2 The present invention provides a method for producing a high-purity iron-nickel alloy having a purity of less than 100%.

[0011] The electron beam cold hearth melting is performed in 10 -3 The process is carried out under high vacuum conditions below torr, and slabs of vacuum induction melted iron-nickel alloy may be cast.

[0012] The electron beam cold hearth melting may include the steps of: subjecting iron-nickel alloy scrap to electron beam melting to form a melting pool of the iron-nickel alloy by raising the temperature to 1500°C or higher; and preferably setting the ratio of power to the weight of the iron-nickel alloy (kW / kg) to 1.5 to 2.5 and raising the temperature of the melt to 1800°C or higher, thereby melting and evaporating non-metallic inclusions in the melt.

[0013] The vacuum induction melting is performed at 10 -2The vacuum induction melting may be performed at a pressure of up to 400 torr, and the composition of the vacuum induction melted iron-nickel alloy is, by weight, 35 to 37% Ni, 0.05% or less C, 0.6% or less Mn, 0.015% or less P, 0.015% or less S, 0.4% or less Si, 0.25% or less Cr, 0.5% or less Co, and the remainder being iron and impurities.

[0014] The vacuum arc remelting may be carried out at a melting rate of 2 kg / min to 10 kg / min.

[0015] In one embodiment of the present invention, there is provided a high-purity iron-nickel alloy manufactured by the above manufacturing method, in which the number of inclusions of 2 μm or more in the alloy is 5.0 pieces / mm 2 Less than 4.0 pieces / mm 2 In addition, a high purity iron-nickel alloy having a purity of less than 100% may be provided. [Effects of the Invention]

[0016] According to the manufacturing method of the present invention, it is possible to provide a highly clean iron-nickel alloy in which the number of inclusions (2 μm or more) is reduced by utilizing iron-nickel alloy scrap. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a flowchart illustrating a method for manufacturing a high-purity iron-nickel alloy according to an embodiment of the present invention. [Figure 2] Photographs of inclusions in alloys in examples and comparative examples of the present invention are shown. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a method for manufacturing a high-purity iron-nickel alloy according to an embodiment of the present invention will be described in more detail with reference to the accompanying drawings.

[0019] FIG. 1 is a flowchart illustrating a method for producing a high-purity iron-nickel alloy according to an embodiment of the present invention.

[0020] Referring first to FIG. 1, a method for producing a high-purity iron-nickel alloy according to one embodiment of the present invention includes preparing iron-nickel alloy scrap for melting the alloy.

[0021] The iron-nickel alloy scrap is an iron-nickel alloy having the composition shown in the following Table 1. The form of the iron-nickel alloy is not particularly limited.

[0022] [Table 1]

[0023] A method for producing a high-purity iron-nickel alloy according to an embodiment of the present invention includes the step of subjecting an iron-nickel alloy to electron beam cold hearth melting to provide an electron beam melted alloy.

[0024] For better cleanliness, the electron beam cold hearth melting includes the steps of forming a melting pool and melting and evaporating non-metallic inclusions in the melt by setting the ratio of electron beam melting power to weight (kW / kg) to 1.5 to 2.5 and raising the temperature of the melt to 1,800°C or higher.

[0025] The electron beam cold hearth melting is performed in 10 -3 This step is carried out under high vacuum conditions of less than 1000 torr. In this step, the electron beam cold hearth melting is mainly aimed at reducing non-metallic inclusions in the alloy. In the electron beam cold hearth melting step, an electron beam accelerated in a high vacuum is irradiated onto the surface of the material, and melting is carried out by the heat generated at this time. In particular, the degree of vacuum in this step is 10 -3 This step is performed at a high vacuum of less than 1000 torr, which is higher than the other two steps. This high vacuum removes the oxygen content in the inclusions by evaporating them and the dissolved oxygen by removing gases in the alloy. In this step, non-metallic inclusions or elements such as Al and Mg that cause inclusions are removed by evaporation.

[0026] The inclusions are non-metallic inclusions and include oxides such as MgO and Al2O3.

[0027] A method for producing a high-purity iron-nickel alloy according to an embodiment of the present invention includes the step of subjecting an electron-beam melted alloy to vacuum induction melting to provide a vacuum induction melted alloy.

[0028] Vacuum induction melting is carried out in a conventional manner known to those of ordinary skill in the art and is capable of producing a melt having sufficient structural integrity to permit stable remelting operations. -2 This step is performed at a pressure of 400 torr or more, or alternatively, in a partial inert gas atmosphere. This step focuses on controlling the element content through real-time element analysis and impurity control through vacuum control. The vacuum is used to prevent and remove oxygen, which causes inclusion formation, and the oxygen content is additionally controlled through the addition of a deoxidizer. The vacuum induction melted alloy is preferably cylindrical to accommodate the cylindrical mold commonly used in the remelting step described below.

[0029] A method for producing a high-purity iron-nickel alloy according to an embodiment of the present invention includes a step of vacuum arc remelting a vacuum induction melted alloy.

[0030] The vacuum arc remelting step is performed at a melting rate of 2 kg / min to 10 kg / min. The main purpose of this step is to remove inclusions through the convection effect. By setting the VAR melting rate at 2 kg / min or higher and increasing the depth of the molten metal, the resulting convection within the molten metal pushes internal inclusions outward, resulting in an inclusion reduction effect.

[0031] The vacuum arc remelting step is preferably performed in a cylindrical mold, and the ratio D1 / D2 of the diameter D1 of the vacuum induction-melted alloy to the inner diameter D2 of the mold (the inner diameter of the mold used in the vacuum arc remelting step) is preferably adjusted to 0.80 to 0.95. If D1 / D2 is less than 0.80, uneven heating of the alloy by arc discharge can cause inclusions in the alloy to aggregate and coarsen, making them more likely to remain in the alloy. Furthermore, if D1 / D2 exceeds 0.95, the gap between the alloy and the mold wall becomes too narrow, causing arc discharge between the alloy and the mold wall, which can damage the mold.

[0032] The iron-nickel alloy produced by the method for producing a high-purity iron-nickel alloy according to an embodiment of the present invention has excellent cleanliness. The standard of cleanliness is related to the size or number of inclusions in the produced iron-nickel alloy. The inclusions are oxides that are generated or mixed in during the process. The iron-nickel alloy produced according to an embodiment of the present invention has a number of inclusions with a size of 2 μm or more in the alloy of 5.0 pieces / mm 2 Less than 4.0 pieces / mm 2 is less than.

[0033] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0034] Example 1 To melt the alloy, iron-nickel alloy scrap is prepared. The composition of the iron-nickel alloy scrap is the composition shown in Table 1. The vacuum induction melted alloy is melted for 10 minutes. -3Electron beam melted alloys were produced by electron beam cold hearth melting at a high vacuum of less than 100 torr. Specifically, 150 kg of iron-nickel alloy scrap was subjected to electron beam melting to form a melting pool of iron-nickel alloy, and the basic refining process was carried out by electron beam melting at a power of 150 kW. The electron beam melted alloy was subjected to vacuum induction melting at 100 torr to produce a vacuum induction melted alloy. The vacuum induction melted alloy was subjected to vacuum arc remelting at a melting rate of 8 kg / min to produce an iron-nickel alloy.

[0035] Examples 2, 3, and 4 Iron-nickel alloys were produced in the same manner as in Example 1, except that 100 kg of iron-nickel alloy scrap was used as the iron-nickel alloy, and electron beam outputs were used such that the ratios (kW / kg) of the electron beam melting output after molten metal formation to the weight were 1.5, 2.0, and 2.5, respectively.

[0036] Examples 5, 6, and 7 Iron-nickel alloys were produced in the same manner as in Example 1, except that 150 kg of iron-nickel alloy scrap was used as the iron-nickel alloy, and electron beam outputs were used such that the ratios (kW / kg) of the electron beam melting output after molten metal formation to the weight were 1.5, 2.0, and 2.5, respectively.

[0037] Examples 8, 9, and 10 Iron-nickel alloys were produced in the same manner as in Example 1, except that 200 kg of iron-nickel alloy scrap was used as the iron-nickel alloy, and electron beam outputs were used such that the ratios (kW / kg) of the electron beam melting output after molten metal formation to the weight were 1.5, 2.0, and 2.5, respectively.

[0038] Comparative Example 1 An iron-nickel alloy was produced in the same manner as in Example 1, except that the EBCHM process was not performed and raw materials of iron and nickel were used for melting.

[0039] Comparative Example 2 An iron-nickel alloy was produced in the same manner as in Example 1, except that the EBCHM process was not performed.

[0040] Experimental example The number of inclusions present in the iron-nickel alloys produced in the above examples and comparative examples was evaluated, and the results are shown in Tables 2 and 3 below. Photographs of the inclusions in the alloys are shown in Figure 2. The evaluation method involved SEM photographs of 20 randomly selected locations on the alloy, and the number of inclusions photographed per unit area was measured. The photograph shown in Figure 2 is one of 20 randomly selected locations on the alloy, and the number shown in Table 3 below is the average value of the 20 locations.

[0041] [Table 2]

[0042] [Table 3]

[0043] As shown in Table 2, in Comparative Example 1, in which iron and nickel raw materials were used without EBCHM, the number of inclusions increased by approximately 2.3 times in Comparative Example 2, in which iron-nickel alloy scrap was used without EBCHM, whereas in Example 1, in which EBCHM was performed, the difference in the number of inclusions was 0.78 times, indicating a decrease in inclusions. In other words, it can be seen that even when iron-nickel alloy scrap containing elements such as Al and Mg is used, performing EBCHM provides a higher level of cleanliness than when high-cleanliness iron-nickel raw materials are used.

[0044] Furthermore, it has been found that better cleanliness can be achieved by setting the ratio (kW / kg) of the electron beam melting power after forming the molten metal to the weight of the melting material to 1.5 to 2.5. However, if the ratio (kW / kg) of the electron beam melting power after forming the molten metal to the weight exceeds 2.5, it is not preferable because it results in a low yield.

Claims

1. providing iron-nickel alloy scrap; electron beam cold hearth melting iron-nickel alloy scrap to provide an electron beam melted alloy; subjecting the electron beam melted alloy to vacuum induction melting to provide a vacuum induction melted alloy; vacuum arc remelting the vacuum induction melted alloy; The number of inclusions of 2 μm or more in the manufactured alloy was 5.0 pieces / mm ２ A method for producing a high purity iron-nickel alloy having a purity of less than 100%.

2. 2. The method for producing a high-purity iron-nickel alloy according to claim 1, wherein the iron-nickel alloy scrap contains, by weight, 35 to 37% Ni, 0.1% or less Al, 0.1% or less Mg, 0.1% or less C, 0.05% or less Mn, 0.6% or less P, 0.015% or less S, 0.015% or less Si, 0.4% or less Cr, 0.25% or less Co, and the remainder being iron and impurities.

3. The electron beam cold hearth melting process involves melting iron-nickel alloy scrap to form a melting pool of iron-nickel alloy at 1,500°C or higher, and melting and evaporating non-metallic inclusions in the melt by raising the temperature of the melt to 1,800°C or higher. The number of inclusions of 2 μm or larger in the produced alloy is 4.0 / mm. ２ The method for producing a high-purity iron-nickel alloy according to claim 1, wherein the temperature is less than 100°C.

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