Method for manufacturing high-purity iron-nickel alloy and high-purity iron-nickel alloy manufactured by method

Abstract

The purpose of the present invention is to provide a high-purity invar alloy which is a material for a fine metal mask. One embodiment of the present invention provides a method for manufacturing a high-purity iron-nickel alloy, comprising the steps of: preparing an iron-nickel alloy scrap; a step in which the iron-nickel alloy scrap is subjected to electron beam cold bed melting to form a melt pool; preferably, after the molten pool forming step, a step for melting and evaporating non-metallic inclusions in the molten pool by setting the ratio of electron beam power to material weight (kW / kg) to 1.5-2.5 and the molten pool temperature to 1,800 DEG C or more; a step of performing vacuum induction melting on the alloy obtained by melting and evaporating the non-metallic inclusions, so as to provide the alloy after the vacuum induction melting; and a step of vacuum arc remelting the alloy after vacuum induction melting, the number of inclusions of 2 [mu] m or more in the manufactured alloy being less than 5.0 / mm < 2 >, preferably less than 4.0 / mm < 2 >.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a high-purity iron-nickel alloy by electron beam melting of iron-nickel alloy waste, and a high-purity iron-nickel alloy manufactured by this method. Background Art

[0002] Displays using Organic Light Emitting Diodes (OLEDs) are representative high-resolution displays. Currently, the OLED market size is gradually increasing and is rapidly catching up with the market share of Liquid Crystal Displays (LCDs). In recent years, research and development of micro-OLEDs with ultra-high definition resolution required for augmented reality (AR) and virtual reality (VR) technologies that can achieve levels beyond those of OLED displays have been underway.

[0003] There are multiple problems in the research and development of micro-OLEDs. Among them, improvement of a Fine Metal Mask (FMM), which is a core component for manufacturing OLEDs, is a major issue.

[0004] The fine metal mask is a metal plate with tiny holes and is applied to the pixel evaporation step in the OLED display manufacturing process. Here, the evaporation step is a process of etching the constituent elements RGB sub-pixels of a pixel, which is the smallest unit of an image, onto a substrate. This is an operation of coating a specific substance on the substrate in a vacuum state, where the fine metal mask acts as a guiding wire to enable the three sub-pixels to be evaporated at accurate positions without mixing with each other.

[0005] To achieve high image quality of a display, a high-purity fine metal mask with uniform and tiny holes needs to be formed. The purity is related to the size and quantity of non-metallic inclusions contained in the metal plate. The metal plate itself, which is the material of the fine metal mask, needs to contain the least amount of impurities or non-metallic inclusions in order to uniformly form multiple tiny holes.

[0006] In the manufacture of high-purity invar alloy, which is the material of the fine metal mask, raw materials with extremely low contents of elements such as Al and Mg that cause non-metallic inclusions are preferably used. However, such raw materials are expensive and have unstable supplies.

[0007] Therefore, the necessity for a method of manufacturing a high-purity invar alloy (iron-nickel alloy), which is the material of the fine metal mask, from low-purity invar alloy (iron-nickel alloy) waste containing a certain amount of elements such as Al and Mg has become prominent. Summary of the Invention

[0008] Technical Problem

[0009] An object of the present invention is to provide a high-purity Invar alloy as a material for a fine metal mask.

[0010] Technical means

[0011] An implementation example of the present invention provides a method for manufacturing a high-purity iron-nickel alloy, including: a step of preparing iron-nickel alloy waste; a step of performing electron beam cold crucible melting on the iron-nickel alloy waste to form a melting pool; preferably after forming the melting pool, setting the ratio of the electron beam melting power to the weight (kW / kg) to 1.5 to 2.5, and melting and evaporating non-metallic inclusions in the melting pool; a step of performing vacuum induction melting on the alloy after melting and evaporating the non-metallic inclusions to provide an alloy after vacuum induction melting; and a step of performing vacuum arc remelting on the alloy after vacuum induction melting, wherein the number of inclusions larger than 2 μm in the manufactured alloy is less than 5.0 pieces / mm 2 .

[0012] At this time, it is preferable to provide a method for manufacturing a high-purity iron-nickel alloy in which the number of inclusions larger than 2 μm is less than 4.0 pieces / mm 2 .

[0013] The above electron beam cold crucible melting is performed under a high vacuum condition of 10 -3 torr or less, and the iron-nickel alloy after vacuum induction melting can be cast into a plate shape.

[0014] The above electron beam cold crucible melting may include: a step of performing electron beam melting on the iron-nickel alloy waste to form a temperature of 1500 °C or higher and form a melting pool for iron-nickel alloy melting; and preferably performing melting with the ratio of the power to the weight of the iron-nickel alloy (kW / kg) set to 1.5 to 2.5 to raise the temperature of the melting pool to 1800 °C or higher, and melting and evaporating non-metallic inclusions in the melting pool.

[0015] The above vacuum induction melting can be performed at 10 -2 to 400 torr, and the content of the components of the iron-nickel alloy after the above vacuum induction melting in weight % is as follows: Ni: 35 to 37%, 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: 0.5% or less, and the rest is iron and impurities.

[0016] The above vacuum arc remelting can be performed at a melting speed of 2 kg / min to 10 kg / min.

[0017] An implementation example of the present invention provides a high-purity iron-nickel alloy, which is a high-purity iron-nickel alloy manufactured by the above manufacturing method, and the number of inclusions larger than 2 μm in the alloy is less than 5.0 pieces / mm 2 , preferably less than 4.0 pieces / mm 2 .

[0018] Advantages of the Invention

[0019] According to the manufacturing method of the present invention, it is possible to provide a high-purity iron-nickel alloy with a reduced number of inclusions (larger than 2 μm) manufactured from iron-nickel alloy waste. Description of the Drawings

[0020] Figure 1 A flowchart showing a manufacturing method of a high-purity iron-nickel alloy according to an implementation example of the present invention is shown.

[0021] Figure 2 Photographs showing inclusions in the alloys of the examples and comparative examples of the present invention are shown. Detailed Description of the Invention

[0022] Hereinafter, a manufacturing method of a high-purity iron-nickel alloy according to an implementation example of the present invention will be described in more detail with reference to the drawings.

[0023] Figure 1 A flowchart showing a manufacturing method of a high-purity iron-nickel alloy according to an implementation example of the present invention is shown.

[0024] First, with reference to Figure 1 , a manufacturing method of a high-purity iron-nickel alloy according to an implementation example of the present invention includes a step of preparing iron-nickel alloy waste for melting the alloy.

[0025] The above iron-nickel alloy waste is an iron-nickel alloy having the composition shown in Table 1 below. The form of the above iron-nickel alloy is not limited to this.

[0026] [Table 1]

[0027]

[0028] A manufacturing method of a high-purity iron-nickel alloy according to an implementation example of the present invention includes a step of subjecting the iron-nickel alloy to electron beam cold hearth melting to provide an alloy after electron beam melting.

[0029] For a more preferable purity, the above electron beam cold crucible melting includes: a step of forming a melting pool; and a step of performing melting with the ratio of electron beam melting power to weight (kW / kg) set to 1.5 to 2.5 to raise the temperature of the melting pool to 1800 °C or higher, so that non-metallic inclusions in the melting pool are melted and evaporated.

[0030] The above electron beam cold crucible melting is carried out under a high vacuum condition of 10 -3 torr or less. In this step, the main purpose of the electron beam cold crucible melting is to reduce non-metallic inclusions in the alloy. When performing the above electron beam cold crucible melting step, an electron beam accelerated in a high vacuum irradiates the surface of the material, and melting is performed by the heat generated at this time. In particular, the vacuum degree of this step is a high vacuum of 10 -3 torr or less and is carried out in a high vacuum compared with the other two processes. Such a high vacuum enables the removal of the oxygen content in the inclusions by inclusion evaporation and the removal of dissolved oxygen by removing gases in the alloy. In this step, elements such as Al and Mg that become non-metallic inclusions or the cause of inclusions are evaporated and removed.

[0031] The above inclusions, as non-metallic inclusions, include oxides such as MgO and Al2O3.

[0032] The method for manufacturing a high-purity iron-nickel alloy according to an implementation example of the present invention includes a step of performing vacuum induction melting on the alloy after electron beam melting to provide an alloy after vacuum induction melting.

[0033] The vacuum induction melting is carried out in a conventional manner known to those skilled in the art and can generate a melt with sufficient structural integrity to allow stable remelting operations. The above vacuum induction melting is carried out at 10 -2 to 400 torr, or it can also be carried out in a local inert gas environment. This step focuses on composition content control through real-time composition analysis and impurity control through vacuum control. The inflow of oxygen, which is the cause of inclusion formation, is prevented and removed by using a vacuum, and the oxygen content is further controlled by adding a deoxidizer. The alloy after the above vacuum induction melting is preferably cylindrical in shape to correspond to the cylindrical mold commonly used in the subsequent remelting step.

[0034] The method for manufacturing a high-purity iron-nickel alloy according to an implementation example of the present invention includes a step of performing vacuum arc remelting on the alloy after vacuum induction melting.

[0035] The above vacuum arc remelting step is carried out at a melting speed of 2 kg / min to 10 kg / min. The main purpose of this step is to remove inclusions through the convection effect. When the melting speed of VAR is set to be more than 2 kg / min to increase the depth of the molten pool, the resulting convection in the molten pool will push the internal inclusions to the outside of the material, thereby producing an inclusion reduction effect.

[0036] The above vacuum arc remelting step is preferably carried out in a cylindrical mold. Preferably, the ratio D1 / D2 of the diameter D1 of the alloy after vacuum induction melting to the inner diameter D2 of the mold (the inner diameter of the mold used in the vacuum arc remelting step) is adjusted to 0.80 to 0.95. When D1 / D2 is less than 0.80, the heating of the alloy caused by arc discharge becomes uneven, resulting in the aggregation and coarsening of inclusions in the alloy and being liable to remain in the alloy. In addition, when D1 / D2 is greater than 0.95, the gap between the alloy and the mold wall becomes too narrow, resulting in arc discharge between the alloy and the mold wall, which becomes the cause of mold damage.

[0037] The iron-nickel alloy manufactured by the manufacturing method of the iron-nickel alloy according to an embodiment of the present invention has excellent purity. The criterion of purity is related to the size or quantity of inclusions in the manufactured iron-nickel alloy. The above inclusions are oxides generated or mixed in the process. In the iron-nickel alloy manufactured according to an embodiment of the present invention, the number of inclusions with a size of 2 μm or more in the alloy is less than 5.0 pieces / mm 2 , preferably less than 4.0 pieces / mm 2 .

[0038] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

[0039] Example 1

[0040] For the melting of the alloy, iron-nickel alloy scrap is prepared. The composition of the iron-nickel alloy scrap is as described in Table 1 above. At 10 -3The alloy after the above vacuum induction melting is subjected to electron beam cold hearth melting in a high vacuum of less than torr to produce an alloy after electron beam melting. Specifically, 150 kg of iron-nickel alloy scrap is subjected to electron beam melting to form a melting pool of molten iron-nickel alloy, and electron beam melting is carried out at a power of 150 kW to perform a basic refining process. The alloy after electron beam melting is subjected to vacuum induction melting at 100 torr to produce an alloy after vacuum induction melting. The alloy after the above vacuum induction melting is subjected to vacuum arc remelting at a melting speed of 8 kg / min to produce an iron-nickel alloy.

[0041] Examples 2, 3, and 4

[0042] In Example 1, as the iron-nickel alloy, 100 kg of iron-nickel alloy scrap is used, and electron beam powers with ratios of electron beam melting power to weight (kW / kg) of 1.5, 2.0, and 2.5 after the formation of the melting pool are used. Except for this, the iron-nickel alloy is produced in the same manner as in Example 1.

[0043] Examples 5, 6, and 7

[0044] In Example 1, as the iron-nickel alloy, 150 kg of iron-nickel alloy scrap is used, and electron beam powers with ratios of electron beam melting power to weight (kW / kg) of 1.5, 2.0, and 2.5 after the formation of the melting pool are used. Except for this, the iron-nickel alloy is produced in the same manner as in Example 1.

[0045] Examples 8, 9, and 10

[0046] In Example 1, as the iron-nickel alloy, 200 kg of iron-nickel alloy scrap is used, and electron beam powers with ratios of electron beam melting power to weight (kW / kg) of 1.5, 2.0, and 2.5 after the formation of the melting pool are used. Except for this, the iron-nickel alloy is produced in the same manner as in Example 1.

[0047] Comparative Example 1

[0048] Compared with Example 1, the EBCHM process is not carried out, and iron and nickel raw materials are used as the materials for melting. Except for this, the iron-nickel alloy is produced in the same manner as in Example 1.

[0049] Comparative Example 2

[0050] Compared with Example 1, the EBCHM process was not carried out. Except for this, an iron-nickel alloy was manufactured in the same manner as in Example 1.

[0051] Experimental Example

[0052] The number of inclusions present in the iron-nickel alloys manufactured 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 alloy are shown in Figure 2 . The evaluation method was to take SEM photographs at 20 arbitrary locations of the alloy and measure the number of inclusions captured per unit area. Figure 2 The photograph shown is one of the photographs taken at 20 arbitrary locations of the alloy, and the numbers shown in Table 3 below are the averages of the 20 locations.

[0053] [Table 2]

[0054]

[0055] [Table 3]

[0056]

[0057] As shown in Table 2, compared with Comparative Example 1 in which the EBCHM process was not carried out and iron and nickel raw materials were used, in Comparative Example 2 in which the EBCHM process was not carried out and iron-nickel alloy scrap was used, the number of inclusions increased by about 2.3 times. In Example 1 in which the EBCHM process was carried out, the inclusions were reduced to 0.78 times the difference in the number of inclusions. That is, it can be seen that even when using iron-nickel alloy scrap containing elements such as Al and Mg, if the EBCHM process is carried out, it can have a purity more excellent than when using high-purity iron-nickel raw materials.

[0058] In addition, it is known that when the ratio of the electron beam melting power to the weight of the melting material (kW / kg) is 1.5 to 2.5 after the molten pool is formed, it has more excellent purity. However, when the ratio of the electron beam melting power to the weight (kW / kg) is greater than 2.5 after the molten pool is formed, it is not preferred because of the low yield.

Claims

1. A manufacturing method of a high-purity iron-nickel alloy, comprising: A step of preparing iron-nickel alloy scrap; A step of subjecting the iron-nickel alloy scrap to electron beam cold hearth melting to provide an alloy after electron beam melting; A step of subjecting the alloy after electron beam melting to vacuum induction melting to provide an alloy after vacuum induction melting; and A step of subjecting the alloy after vacuum induction melting to vacuum arc remelting, The number of inclusions larger than 2 μm in the produced alloy is less than 5.0 per mm 2 .

2. The manufacturing method of the high-purity iron-nickel alloy according to claim 1, wherein, In the composition of the iron-nickel alloy scrap, by weight %, it contains Ni: 35-37%, Al: below 0.1%, Mg: below 0.1%, C: below 0.05%, Mn: below 0.6%, P: below 0.015%, S: below 0.015%, Si: below 0.4%, Cr: below 0.25%, Co: below 0.5%, and the balance is iron and impurities.

3. The manufacturing method of the high-purity iron-nickel alloy according to claim 1, wherein, The electron beam cold hearth melting includes: A step of melting the iron-nickel alloy scrap to form a molten pool of iron-nickel alloy at a temperature above 1500 °C; and The step of forming a molten pool temperature above 1800 °C to melt and evaporate non-metallic inclusions in the molten pool, such that the number of inclusions larger than 2 μm in the produced alloy is less than 4.0 pieces / mm 2 .

Images