Ni alloy excellent in surface property and mechanical property

Abstract

An Ni-based alloy and a method for manufacturing the same, the Ni-based alloy being provided with good surface and mechanical properties with defects being absent from the surface, the N-based alloy comprising, in mass %, 0.0010-0.03% of C, 0.01-0.5% of Si, 0.01-0.5% of Mn, 0.01% or less of P, 0.005% or less of S, 0.5% or less of Cr, 0.1% or less of Mo, 0.1% or less of Cu, 0.001-0.2% of Al, 0.05% or less of Ti, 0.01-0.5% of Fe, 0.0001-0.02% of Ca, 0.0001-0.02% of Mg, 0.005% or less of N, 0.005% or less of O, 1% or less of one or more of Co, W, Nb, and B, with the balance being Ni and unavoidable impurities, and the average composition of non-metal inclusions being MgO: 30-70% of MgO, 15-40% Al2O3, 30% or less of SiO2, 10-40% of CaO, and 1% or less of MnO.

Description

Ni alloy with excellent surface quality and mechanical properties

[0001] The present invention relates to a Ni alloy having excellent surface properties and mechanical properties, and a method for producing the same.

[0002] Because pure nickel plate has excellent corrosion resistance, it is used for conductive components of internal wiring in rechargeable lithium ion batteries, lithium polymer batteries, nickel-metal hydride batteries, and the like, which are power sources for portable electronic devices and the like (see, for example, Patent Documents 1 and 2).

[0003] Nickel plates tend to soften more easily than materials such as iron, and techniques have been developed to maintain their strength (see, for example, Patent Document 3).

[0004] Furthermore, nickel rolled sheets for deep drawing applications are used in a wide range of applications, including electrodes for cold cathode fluorescent lamps, and are also used in nickel electrodes for producing caustic soda due to their excellent corrosion resistance, particularly in alkaline environments (see, for example, Patent Documents 4 and 5).

[0005] As described above, since they are used in extremely precise locations, the occurrence of surface defects must be restricted. Furthermore, since corrosion also progresses from the defects, a technology to prevent this has been sought (see, for example, Patent Document 6).

[0006] Since such electronic components require soldering, efforts have been made to improve the wettability of the nickel plate with solder (see, for example, Patent Documents 7 and 8).

[0007] Furthermore, since nickel plates are more expensive than commonly used metals such as iron and aluminum, not only is an increase in cost due to the occurrence of surface defects unacceptable, but they must also maintain a high level of hot workability (see, for example, Patent Documents 9 and 10).

[0008] In this context, nickel alloys with excellent surface properties have been disclosed. However, the morphology of the nonmetallic inclusions is not controlled, and in some cases, surface defects are formed. Furthermore, it is sometimes difficult to maintain the mechanical properties (see, for example, Patent Document 11).

[0009] JP 63-168259 A JP 2014-43623 A JP 2010-90438 A JP 2011-74437 A JP 2003-89835 A WO2010 / 064642 A JP 2005-82886 A JP 2010-132933 A JP 8-143996 A JP 2010-132934 A Japanese Patent No. 7015410

[0010] As mentioned above, the main aim of the present invention is to prevent the clustering of nonmetallic inclusions, which can cause large surface defects, by controlling not only the composition of the nonmetallic inclusions but also their structure. Furthermore, the steel must also have good mechanical properties. At the same time, the steel must also have good mechanical properties. ２ O ３ Inclusions have a tendency to cluster, so their formation must be prevented. ２ O ３ When it comes to inclusions in the system, they are formed in an environment with a high oxygen concentration, so the total number is large and they are prone to clustering, so they must be prevented.

[0011] That is, an object of the present invention is to comprehensively consider the above and to provide a Ni alloy having a defect-free surface and sound surface properties and mechanical properties, and a method for producing the same.

[0012] In order to solve the problems of the above-mentioned conventional technology, the inventors conducted repeated experiments as follows. First, 20 kg of Ni alloy was melted in a magnesia crucible in a laboratory. The melting equipment used was a high-frequency induction furnace, and argon gas was blown into the crucible from above to isolate it from the atmosphere. The raw materials used were pure Ni, electrolytic iron, ferrochrome, Mo, copper wire, Ti, ferrochrome nitride, Co, W, NiNb, and B. Finally, Si and Al were added to deoxidize the alloy, and an artificial slag, CaO-Al, was obtained. ２ O ３ -MgO-SiO ２One kilogram of -F slag was added, and samples were taken to closely observe the composition of the nonmetallic inclusions. In some experiments, deoxidation was performed using only Si, without adding Al. Observations were performed using a SEM. Analysis was performed using EDS. Elemental mapping was performed with particular care, and the structural morphology was carefully observed. It was found that analysis of at least 10 inclusions is necessary to identify compositional characteristics, with 20 being better and 30 or more being sufficient.

[0013] The alloy ingot cast into the mold was forged to a thickness of 20 mm, after which the surface was ground and cold rolled to a final thickness of 0.5 mm. The surface was carefully observed to determine whether there were any defects.

[0014] As a result, the occurrence of defects is strongly related to the morphology of nonmetallic inclusions, and CaO-Al ２ O ３ -MgO-based oxide is MgO or MgO.Al ２ O ３ We found that the structure containing CaO-Al has a high ability to suppress clustering. A schematic diagram of this is shown in Figure 1. Figure 1(a) shows the structure of CaO-Al ２ O ３ -MgO-based oxide has MgO or MgO.Al within its approximately spherical surface. ２ O ３ On the other hand, as shown in Figure 1(b), part of the outer edge is CaO-Al. ２ O ３ -MgO system, with the majority of the interior being high-melting point MgO or MgO.Al ２ O ３ It has been revealed that when the oxides are in the form of protruding from the approximately spherical surface of the inclusions, clustering is promoted. ２ O ３ It is presumed that the -MgO melt acts as a sintering aid at steelmaking temperatures (1400-1550°C), adhering to each other and sintering. Based on experience, it was speculated that the main sintering location in actual equipment is the inner wall of the submerged nozzle of the continuous casting machine.

[0015] On the other hand, MgO·Al ２ O ３It was also confirmed that sintering behavior did not occur when MgO was used alone. ２ O ３ It has become clear that the structural morphology of the MgO-based oxide melt has a significant effect on the final quality.

[0016] Furthermore, to evaluate the mechanical properties, appropriate test pieces were taken and the Vickers hardness was measured on a cross section parallel to the rolling direction, and it was found that in order to maintain a hardness of 90 Hv or more and an elongation of 25% or more, it is necessary to contain appropriate amounts of Cr, Mo, Cu, Ti, and N. It was also found that it is more desirable to partially contain Co, W, and Nb. Furthermore, it was found that the addition of B is desirable to maintain hot workability.

[0017] For some steel grades, the raw materials were melted in a 60-ton electric furnace, vacuum degassed in a VOD, and refined by adding quicklime from above and simultaneously adding FeSi and / or Al to promote deoxidation and desulfurization. Slabs were then produced in a continuous casting machine, and after surface grinding, they were hot rolled, cold rolled, and finally passed through an annealing and pickling line to produce 0.5 mm thick thin plates.

[0018] That is, the present invention was developed by starting from the above laboratory studies and then conducting actual machine tests to confirm the results, as shown below. The chemical components are all in mass % and are as follows: C: 0.001-0.03%, Si: 0.01-0.5%, Mn: 0.01-0.5%, P: 0.01% or less, S: 0.005% or less, Cr: 0.5% or less, Mo: 0.1% or less, Cu: 0.1% or less, Al: 0.001-0.2%, Ti: 0.05% or less, Fe: 0.01-0.5%, Ca: 0.0001-0.02%, Mg: 0.0001-0.02%, N: 0.005% or less, O: 0.005% or less, and 1% or less of one or more of Co, W, Nb, and B, with the balance being Ni and unavoidable impurities. The average composition of non-metallic inclusions is MgO: 30-70%, Al: 0.001-0.2%, Ti: 0.05% or less, Fe: 0.01-0.5%, Ca: 0.0001-0.02%, Mg: 0.0001-0.02%, N: 0.005% or less, O: 0.005% or less, and 1% or less of one or more of Co, W, Nb, and B, with the balance being Ni and unavoidable impurities. ２ O ３ :15-40%, SiO ２ : 30% or less, CaO: 10 to 40%, MnO: 1% or less.

[0019] Furthermore, it is more preferable that the structural form of the nonmetallic inclusions is one or more of the following five types a to e, in which 70% or more of the nonmetallic inclusions in terms of number ratio to the total nonmetallic inclusions are: a: CaO—Al ２ O ３ -MgO-based oxide is MgO.Al within the approximately spherical surface ２ O ３ Form b: CaO-Al ２ O ３ -MgO-based oxide c: CaO-Al ２ O ３ - A form in which MgO-based oxide completely encompasses MgO within a roughly spherical surface d: MgO alone e: MgO·Al ２ O ３ Single unit

[0020] The above-mentioned CaO—Al ２ O ３ -MgO-based oxides are included, and CaO-Al ２ O ３ -MgO-based oxides include CaO: 20 to 60%, Al ２ O ３ :30~60%, MgO:1~30%, SiO ２ It is more preferable that the content of S is 20% or less and the content of TiO2 is 0.5% or less.

[0021] The Ni alloy described above is MgO.Al ２ O ３ It contains MgO.Al ２ O ３ It is desirable that the content of MnO is 0.5% or less.

[0022] The above-described simple MgO is contained, and the simple MgO is Al ２ O ３ : 3% or less, SiO ２ It is desirable that the content of the SiO2 is 1% or less, CaO is 10% or less, and MnO is 1% or less.

[0023] The Ni alloy preferably has a Vickers hardness of 90 Hv or more and an elongation of 25% or more.

[0024] The present invention also provides a manufacturing method. The raw materials are melted in an electric furnace, and then vacuum degassed in a VOD. After that, quicklime, fluorite, and a magnesia source are added to form a CaO-Al alloy. ２ O ３ -MgO-SiO ２ In this manufacturing method, a ferrosilicon alloy and / or Al is added to form a slag containing fluorine (F), and deoxidized and desulfurized, and then a slab is produced in a continuous casting machine. The surface is ground, and the slab is then subjected to a hot rolling process and then cold rolling.

[0025] 1 is a comparative diagram of the structural morphology of non-metallic inclusions of the present invention and those of other non-metallic inclusions, and FIG. 2 is a schematic diagram showing the classification of the structural morphology of non-metallic inclusions of the present invention and those of other non-metallic inclusions.

[0026] The reasons for the numerical limitations of the present invention and the scientific viewpoint are also explained below. The units below are mass %. C: 0.001-0.03% C is an important element for maintaining the strength of Ni alloys. Therefore, 0.001% is necessary. On the other hand, adding more than 0.03% also has the disadvantage of forming carbides of Ti and the like, which causes embrittlement. Therefore, the addition specified as 0.001-0.03% is controlled by adding a carbon source after desulfurization in VOD. Preferably, it is 0.002-0.025%, more preferably 0.005-0.022%.

[0027] Si: 0.01 to 0.5% Si is an element effective in deoxidation and is very important in the present invention. Deoxidation can be carried out according to the following formula. That is, in VOD, deoxidation is carried out by adding FeSi alloy or pure Si. Si + 2O = (SiO ２ ) ... (1) Here, the underlined parts are the components in the molten steel, and the parentheses are the components in the slag. As will be described later, SiO in the slag ２ By lowering the activity coefficient of , deoxidation can be effectively promoted and the oxygen concentration can be controlled to the level specified in the present invention. Furthermore, desulfurization can also be achieved at the same time. To achieve this effect, 0.01% is necessary, and if it exceeds 0.5%, not only will corrosion resistance decrease but the steel will also become embrittled. Therefore, the range is specified as 0.01 to 0.5%. Preferably, it is 0.03 to 0.3%, and more preferably, it is 0.05 to 0.28%.

[0028] Mn: 0.01 to 0.5% Mn is an extremely effective element because it is useful for deoxidation. Therefore, the content is specified to be 0.01 to 0.5%. The content is preferably 0.03 to 0.47%, and more preferably 0.03 to 0.4%.

[0029] P: 0.01% or less P is a harmful element that not only segregates at grain boundaries and reduces corrosion resistance, but also causes red brittleness during welding, leading to cracks. P is removed by oxygen blowing in an electric furnace. ２ O ５ Therefore, the content is set to 0.01% or less, preferably 0.008% or less, and more preferably 0.002% or less.

[0030] S: 0.005% or less S is a harmful element because it segregates at grain boundaries and forms MnS, which becomes the starting point for pitting corrosion. It also reduces hot workability and causes edge cracking. Therefore, the content is set to 0.005% or less. As will be described in detail later, desulfurization can be promoted by the following reaction formula: 3(CaO) + 2Al + 3S = (Al ２ O ３ )+3(CaS)...(2) 2(CaO)+Si+2S=(SiO ２ ) + 2(CaS) ... (3) Reducing the activity coefficients of alumina and silica in the slag allows the desulfurization reaction to proceed efficiently. If the content is 0.005% or less, the above problems can be avoided, so this range is specified. Preferably, it is 0.003% or less, more preferably, it is 0.0015% or less, and even more preferably, it is 0.0008% or less.

[0031] Ni: 99% or more Ni is a major element in the present invention and is an important element for maintaining mechanical properties, corrosion resistance, and workability. In the present invention, it is treated as the balance. If it is less than 99%, not only will the required corrosion resistance be exceeded, but the mechanical properties will also not be satisfied. Properties required for electronic components, such as electrical conductivity, will also be impaired. Therefore, it is specified to be 99% or more. Preferably, it is 99.2% or more, more preferably 99.3% or more, and even more preferably 99.4% or more.

[0032] Cr: 0.5% or less Cr is an important element in the present invention for maintaining strength through solid solution strengthening. However, if the content is too high, MnO-Cr ２ O ３ There is a risk of forming system inclusions. Therefore, the content is specified to be 0.5% or less. Preferably, it is 0.4% or less, and more preferably, it is 0.3% or less. Although there is no limitation, a content of 0.01% or more is desirable.

[0033] Mo: 0.1% or less Like Cr, Mo is an important element for maintaining strength through solid solution strengthening. However, if the content is too high, it can cause abnormal oxidation during heating in the manufacturing process. Therefore, the content is specified as 0.1% or less. Preferably, it is 0.08% or less. Although not limited, a content of 0.01% or more is desirable.

[0034] Cu: 0.1% or less Like Cr, Cu is an important element for maintaining strength through solid solution strengthening. However, if the Cu content is too high, it can cause softening of the Ni alloy sheet. Therefore, the Cu content is specified to be 0.1% or less. Preferably, it is 0.05% or less, and more preferably, it is 0.03% or less.

[0035] Al: 0.001-0.2% Al is a useful element for deoxidation. It also improves high-temperature oxidation resistance. On the other hand, if the content is too high, AlN is formed, impairing hot workability, and the Ca and Mg concentrations become too high, exceeding the upper limit of the range of the present invention. As a result, harmful CaO-based inclusions are formed, and NiMg ２ The deoxidation reaction proceeds as follows: 2Al + 3O = (Al ２ O ３ ) ... (4) As will be described in detail later, reducing the alumina activity in the slag promotes efficient deoxidation. Furthermore, desulfurization also becomes possible at the same time. Therefore, the range of 0.001 to 0.2% is specified. The range is preferably 0.002 to 0.18%, more preferably 0.005 to 0.15%, and even more preferably 0.008 to 0.13%.

[0036] Ti: 0.05% or less Ti fixes N to form TiN, which prevents the formation of blowholes due to the nitrogen solubility being exceeded during solidification. Therefore, the Ti content is specified to be 0.05% or less. Preferably, it is 0.02% or less. More preferably, it is 0.01% or less.

[0037] Fe: 0.01 to 0.5% In the present invention, Fe is an important element for maintaining strength through solid solution strengthening. However, if the content is too high, the purity of the Ni alloy decreases, impairing corrosion resistance. Therefore, the Fe content is specified as 0.01 to 0.5%. Preferably, it is 0.03 to 0.4%, and more preferably, it is 0.04 to 0.3%.

[0038] Ca: 0.0001 to 0.02% Ca favorably regulates the structure of nonmetallic inclusions to CaO-Al ２ O ３ Ca is an important element for controlling the alloy to MgO-based oxides. By controlling the alloy to this form, it is possible to manufacture a sound product without forming clusters or surface defects. Ca is effectively added by utilizing the following reaction: 3(CaO) + 2Al = (Al ２ O ３ )+3Ca...(5) 2(CaO)+Si=(SiO ２ ) + 2Ca ... (6) To control this reaction, the activity of alumina and silica in the slag can be controlled within an appropriate range. This will be explained in detail in the manufacturing method section. Conversely, if the Ca content is too high, harmful CaO inclusions are formed, which promotes clustering and creates defects. Therefore, the Ca content is specified to be 0.0001 to 0.02%. Preferably, it is 0.0005 to 0.015%, and more preferably, it is 0.001 to 0.01%.

[0039] Mg: 0.0001 to 0.02% Mg is a component that favors the structure of nonmetallic inclusions. ２ O ３ - MgO-based oxides, MgO, MgO.Al ２ O ３ By controlling the morphology in this way, it is possible to produce a sound product without clustering or forming surface defects. Mg is effectively added by utilizing the following reaction: 3(MgO) + 2Al = (Al ２O ３ )+3Mg...(7) 2(MgO)+Si=(SiO ２ ) + 2Mg ... (8) To control this reaction, the activity of alumina and silica in the slag should be controlled within an appropriate range. This will be explained in detail in the manufacturing method section. On the other hand, if the content is too high, Mg will vaporize during solidification and form blowholes, which will cause surface defects. Therefore, the content is specified to be 0.0001 to 0.02%. Preferably, it is 0.0005 to 0.015%, and more preferably, it is 0.001 to 0.01%.

[0040] N: 0.005% or less N is an important element for maintaining strength through solid solution strengthening. However, if the N content is too high, TiN clusters are formed, causing surface defects. Therefore, the N content is specified to be 0.005% or less. Preferably, it is 0.003% or less, and more preferably, it is 0.002% or less.

[0041] O: 0.005% or less The oxygen content must be reduced because it increases the number of nonmetallic inclusions and forms surface defects. Therefore, the oxygen content is set to 0.005% or less. Preferably, the oxygen content is 0.003% or less, more preferably, 0.001% or less, and even more preferably, 0.0008% or less.

[0042] One or more of Co, W, Nb, and B, 1% or less. Co is an effective element because it behaves similarly to Ni. It is also sometimes contained in pure Ni raw materials, and plays an important role in utilizing inexpensive raw materials. W is a beneficial element for maintaining mechanical properties. Nb is useful for maintaining strength through solid solution strengthening. B improves hot workability. It is more preferable to contain one or more of these elements at 1% or less. In other words, they may be added as needed.

[0043] The balance of the Ni alloy of the present invention is Ni. In addition, it may contain trace amounts of unavoidable impurities, such as Pb, Sn, Ta, Ag, Na, K, and Zr. All of these are mixed in from the raw materials, pure Ni and ferroalloys.

[0044] Next, the average composition of the nonmetallic inclusions will be explained. The average composition of the nonmetallic inclusions is as follows: MgO: 30-70% MgO is a harmless CaO-Al ２ O ３ - MgO alone and MgO.Al, which are effective in forming MgO-based oxides and are also harmless. ２ O ３ It is extremely effective for forming a monomer. Therefore, the range is specified as 30 to 70%, and preferably 35 to 65%.

[0045] Al ２ O ３ : 15 to 40% Al ２ O ３ is a harmless CaO-Al ２ O ３ - MgO.Al, which is effective in forming MgO-based oxides and is also harmless. ２ O ３ However, if it is higher than 40%, it can cause harmful Al ２ O ３ Since it forms a single element, it causes defects. Therefore, the content is specified to be 15 to 40%, and preferably 18 to 39%.

[0046] SiO ２ :30% or less SiO ２ is CaO-Al ２ O ３ - It is a compound present in MgO-based oxides, and is effective in lowering the melting point. However, if it exceeds 30%, it acts in the direction of increasing the oxygen concentration, which increases the number of non-metallic inclusions and also increases the number of harmful MnO-Cr ２ O ３ The formation of a base oxide results in the formation of defects. Therefore, the content is specified to be 30% or less, and preferably 28% or less.

[0047] CaO: 10-40% CaO is harmless CaO-Al ２ O ３ Although it is effective for forming MgO-based oxides, if it is too high, harmful CaO inclusions are formed, causing defects. Therefore, the range is specified as 10 to 40%. Preferably, it is 12 to 39%. More preferably, it is 13 to 38%.

[0048] MnO: 1% or less MnO is MgO alone, MgO.Al ２ O ３ It is harmless because it dissolves in the MgO site of the simple inclusion. However, if it is too high, it can become harmful. ２ O ３ The formation of a base oxide results in the formation of defects. Therefore, the content is specified to be 1% or less. Preferably, it is 0.9% or less. More preferably, it is 0.8% or less.

[0049] Cr ２ O ３ : 1.5% or less Although not particularly limited, Cr ２ O ３ When the value is high, MnO-Cr ２ O ３ This makes it easier for non-metallic inclusions to form. Furthermore, the oxygen concentration in the molten steel increases, which increases the number of non-metallic inclusions and causes defects. Therefore, the content is preferably 1.5% or less, more preferably 1.3% or less, and even more preferably 0.6% or less.

[0050] There are several methods for determining the average composition. This can be determined by randomly analyzing 10 points using SEM / EDS. In this case, it is necessary to analyze two points on the periphery of the center, and the average can be determined by taking a mapping image and measuring the area ratio using image analysis. Preferably, 20 or more points are analyzed, and more preferably, 30 or more points are analyzed. The other method is the so-called electrolytic method, widely known as the Speed ​​method. In other words, an appropriate potential is applied in an appropriate solution to dissolve the metal parts. The non-metallic inclusions that remain as residue are then collected by filtration. This can be subjected to chemical analysis to determine the average composition all at once. There are no limitations on the analytical method.

[0051] Furthermore, we will explain the structural form of nonmetallic inclusions. It is more preferable that nonmetallic inclusions account for 70% or more of the total number of nonmetallic inclusions and are one or more of the following five types a to e. The structural forms corresponding to a to e are also shown in Figures 2(a) to (e). a: CaO-Al ２ O ３ -MgO-based oxide is MgO.Al within the approximately spherical surface ２ O ３Form b: CaO-Al ２ O ３ -MgO-based oxide c: CaO-Al ２ O ３ - A form in which MgO-based oxide completely encompasses MgO within a roughly spherical surface d: MgO alone e: MgO·Al ２ O ３ Here, "completely enclosed within a substantially spherical surface" refers to a state in which the inner material is completely enclosed within the outer peripheral material as shown in FIG. 1(a), and does not include a state in which the inner material partially protrudes to the outside as shown in FIG. 1(b).

[0052] As explained in the Summary of the Invention section, the structure shown in Figure 1(b) does not appear with the following procedure. To achieve these structural morphologies, it is sufficient to control the chemical components of Si, Al, Ca, Mg, O, and Mn within the ranges of the present invention, but this is not the only option. A and c are also characteristic of the present invention. To achieve these structural morphologies, the vacuum stirring process in the VOD is crucial. Dolomite is preferred for VOD bricks. During the deoxidation period, quicklime is first added, followed by fluorite and waste bricks containing MgO. The waste MgO bricks can be added as needed. Subsequently, ferrosilicon alloy or pure Si and Al are added, which adds Si and Al to the already formed molten slag. Deoxidation is possible with Si alone. This reacts directly with CaO and MgO in the slag, effectively adding Ca and Mg.

[0053] Mg is supplied to the molten steel in advance according to the reactions of formulas (7) and (8). The reason for this is largely unknown, but the reaction of Ca is delayed. This dissolved Mg reacts first with the original non-metallic inclusions, silica and alumina, as follows: 2Mg + SiO ２ (Inclusions) = 2MgO (Inclusions) + 2Si...(9) 3Mg+Al ２ O ３ (Inclusions) = 3MgO (Inclusions) + 2Al ... (10) 2Mg + 4Al + 4SiO ２ (Inclusions) = 2MgO・Al ２ O ３ (Inclusions) + 4Si ... (11) 3Mg + 4Al ２ O ３(Inclusions)=MgO・Al ２ O ３ (inclusions) + 2Al ... (12) As shown in the above formulas (9) to (12), MgO alone, MgO·Al ２ O ３ Then, Ca is supplied from the slag, and the Ca in the molten steel reacts with the above inclusions, forming CaO-Al on the surface. ２ O ３ -MgO-based oxides are formed vigorously. Then, the molten oxides are MgO alone, MgO.Al ２ O ３ In other words, the harmless CaO-Al melt is covered with the element. ２ O ３ - They behave as MgO-based inclusions. Therefore, if the non-metallic inclusions are spherical, they behave as described above and are harmless.

[0054] Furthermore, the above CaO—Al ２ O ３ The composition range of MgO-based oxides is explained below: CaO: 20-60%, Al ２ O ３ :30~60%, MgO:1~30%, SiO ２ :20% or less, TiO ２ : 0.5% or less The above range was set because the molten state can be maintained at the steelmaking temperature, i.e., around 1500°C. In particular, if the CaO content is too high, harmful simple CaO inclusions are formed, so CaO: 20-60% was specified. ２ O ３ If too high, Al ２ O ３ Al to form a single unit ２ O ３ : 30 to 60%. SiO ２ If the value is too high, harmful MnO-Cr ２ O ３ The content was set to 20% or less to prevent the formation of inclusions.

[0055] MgO.Al ２ O ３ MnO concentration in: 0.5% or less MgO.Al ２ O ３ Since MnO dissolves in the MgO site, MgO can be made harmless. Therefore, the content is specified to be 0.5% or less.

[0056] Al in MgO simple inclusions ２ O ３ : 3% or less, SiO ２ : 1% or less, CaO: 10% or less, MnO: 1% or less. MgO inclusions are harmless, so it is desirable for some solid solution to occur in these inclusions. Taking into account the solid solubility limit, Al ２ O ３ : 3% or less, SiO ２ : 1% or less, CaO: 10% or less, MnO: 1% or less.

[0057] The present invention also provides a manufacturing method. Specifically, raw materials are melted in an electric furnace and then vacuum degassed in a VOD. The raw materials can be blended according to the desired composition, such as pure Ni, ferrosilicon alloy, ferrochromium alloy, iron scrap, Mo, Mo trioxide, ferromolybdenum alloy, ferroniobium alloy, copper wire, etc.

[0058] After the decarburization and dephosphorization processes in the electric furnace are completed, the slag is removed. Then, ferrosilicon alloy and / or Al are added to form a CaO-Al alloy. ２ O ３ -MgO-SiO ２ After forming the -F slag and deoxidizing and desulfurizing it, a slab is produced in a continuous casting machine, the surface is ground, and then the slab is subjected to a hot rolling process and then cold rolling. At this time, in order to control the structural form of the nonmetallic inclusions to a desirable form, it is necessary to control the slag composition within an appropriate range.

[0059] CaO-Al ２ O ３ -MgO-SiO ２ The following range is desirable for -F-based slag: CaO: 35-70%. The CaO concentration can be adjusted by adding quicklime. CaO is extremely effective in deoxidation and desulfurization. In other words, as shown in equations (2) and (3), desulfurization is possible by stably preserving CaS in the slag. However, if the content exceeds 70%, CaO inclusions will form. Therefore, 35-70% is best. 40-65% is preferable. 50-63% is even more preferable.

[0060] Al ２ O３ :35% or less Al ２ O ３ is CaO-Al ２ O ３ -MgO-SiO ２ On the other hand, if it exceeds 35%, the Al content will be too high. ２ O ３ This creates simple inclusions and promotes clustering. Therefore, it is desirable that the content be 35% or less. Preferably, it is 30% or less. More preferably, it is 25% or less.

[0061] MgO: 3 to 25% MgO is CaO-Al ２ O ３ -MgO-SiO ２ It is effective for keeping -F-based slag in a molten state. On the other hand, if the MgO concentration is high, the Mg concentration in the molten steel will increase, which will release Mg gas during solidification and form blowholes. Therefore, a content of 3 to 25% is desirable. A content of 5 to 20% is more desirable, and a content of 7 to 15% is even more desirable.

[0062] SiO ２ :32% or less SiO ２ is CaO-Al ２ O ３ -MgO-SiO ２ -F-based slag is effective in molten state. ２ When the concentration is high, the oxygen concentration in the molten steel becomes high, and the composition of the nonmetallic inclusions becomes MnO-Cr. ２ O ３ As a result, surface defects occur. Therefore, it is desirable that the porosity be 32% or less, more desirably 30% or less, and even more desirably 25% or less.

[0063] F: 1-10% F is added as fluorite. F is CaO-Al ２ O ３ -MgO-SiO ２ -F is effective in molten F-based slag. On the other hand, if the F concentration is high, it will corrode the VOD bricks and ladle bricks, shortening their lifespan. Therefore, a concentration of 1 to 10% is preferable. A concentration of 2 to 9% is more preferable.

[0064] Furthermore, Cr ２It is desirable that the O3 and FeO concentrations are low. ２ O ３ :1% or less Cr ２ O ３ When the concentration is high, the oxygen concentration becomes high and MnO-Cr ２ O ３ This causes the formation of system inclusions. Therefore, it is best to keep it at 1% or less. It is preferably 0.7% or less, and more preferably 0.6% or less.

[0065] FeO: 1% or less If the FeO concentration is high, the oxygen concentration will increase and MnO-Cr ２ O ３ This causes the formation of system inclusions. Therefore, it is best to keep it at 1% or less. It is preferably 0.9% or less, and more preferably 0.8% or less.

[0066] Furthermore, a high S concentration is desirable because it indicates that desulfurization has progressed normally. A concentration of 0.01% or more is desirable, and a concentration of 0.02% or more is more desirable.

[0067] In the present invention, it is also necessary to adjust the mechanical properties. That is, the Vickers hardness is specified as 90 Hv or more, preferably 250 Hv or less. The elongation must be 25% or more, preferably 35% or more.

[0068] The following examples are presented to clarify the effectiveness of the present invention. A 60-70 ton electric furnace was used to melt raw materials, which were then decarburized and refined using a VOD. The raw materials consisted primarily of pure Ni, with stainless steel scrap, ferrosilicon alloy, iron scrap, Mo, Mo trioxide, ferromolybdenum alloy, ferroniobium alloy, ferrochrome alloy, copper wire, and other materials blended according to the target steel type.

[0069] After the decarburization and dephosphorization processes in the electric furnace were completed, the slag was removed in a slag pot. Then, gas components were removed by vacuum degassing in the VOD. Then, quicklime and magnesia-containing waste bricks, as well as fluorite, were added, followed by pure silicon or ferrosilicon alloy. Finally, aluminum was added, resulting in a CaO-Al alloy. ２ O ３ -MgO-SiO ２Even when Al was not added, the Al impurity in the FeSi alloy was oxidized to provide alumina.

[0070] For some Ni alloys, alloying elements such as Nb, Mo, C, Co, Cr, B, and Ni were added to precisely adjust the chemical composition. After deoxidation and desulfurization in this manner, slabs measuring 200 mm thick x 1200 mm wide x 7 m long were produced using a continuous casting machine. After the surface oscillation marks were ground, the slabs were heated to 1000 to 1250°C depending on the steel type, and then subjected to a hot rolling process. Finally, cold rolling was performed and the slabs were passed through an annealing and pickling line. In this way, 1 mm cold-rolled coils were produced for all steel types.

[0071] The evaluation was performed using the following methods. 1) Chemical composition: The surface of a 30 mm diameter x 10 mm high suction sample collected from the tundish of a continuous casting machine was ground with a grinder. Major elements were analyzed by X-ray fluorescence analysis. C and S were partially analyzed by combustion analysis. N and O were analyzed by infrared absorption analysis. 2) Slag composition: Slag was collected with an iron rod and crushed. This was then compressed into a cylindrical powder sample. The values ​​of this sample were determined using X-ray fluorescence analysis. F was determined by chemical analysis. 3) Average composition of nonmetallic inclusions: The above suction sample was cut out, embedded in resin, and mirror-polished. This was then placed in a SEM for observation and quantitative analysis. Thirty inclusions 5 μm or larger were randomly selected, and the center and periphery were analyzed. The element distribution of each inclusion was determined by mapping, and the ratio of each phase was calculated by image analysis. Taking into account the weighted average, a representative analytical value for each inclusion particle was obtained. This was determined by calculating the average value of 30 points. 4) Morphology of non-metallic inclusions: Morphologies were classified when observed and analyzed as described above. Note that no morphology corresponding to Figure 1(b) was confirmed. 5) Composition of each oxide: Determined from the composition of each oxide phase described above. 6) Mechanical properties: Vickers hardness was measured using a micro Vickers hardness tester after embedding and polishing a cross section parallel to the rolling direction. A Vickers hardness of 90Hv or more was considered pass and marked with ◯, and anything less was considered fail and marked with ×. Tensile test pieces were taken and measured with an extensometer. An elongation of 25% or more was considered pass and marked with ◯, and anything less was considered fail and marked with ×. 7) Overall evaluation: An inspector visually evaluated a 1mmt Ni alloy plate when it was threaded. The evaluation results were determined as follows. In the following, the allowable range without cutting refers to the range within 10m of the steel plate surface. ２ This means that there are up to three linear defects of 1 mm or more in length per coil. Pass: ◎ No surface defects (100% good product rate at time of shipping) Pass: 〇 Surface defects occurred in some areas but within the acceptable range of required quality (95% good product rate) Pass: △ Surface defects occurred in some areas but can be shipped by cutting partially (80% good product rate) Fail: × Surface defects occurred along the entire length of the coil and scrapped (0% good product rate) Furthermore, mechanical properties were also taken into consideration, but the evaluation of surface defects was given priority.

[0072]

[0073]

[0074] The structural morphologies of the examples are shown in Figures 2(a) to (e), and those of the comparative examples are shown in Figures 2(f) to (h). The reason the chemical components do not add up to 100% is due to unavoidable impurities. Inventive examples Nos. 1 to 14 had chemical analysis results within the range, and the slag composition also met the desired range. As a result, the structural morphology of the non-metallic inclusions also met the ranges a to e. Ultimately, all products were judged to be acceptable.

[0075] However, in No. 5, there was one alumina inclusion and MnO-Cr ２ O ３ In No. 8, one CaO inclusion was observed. Therefore, the evaluation was ◯. In No. 10, one Al ２ O ３ Simple inclusions and MnO-Cr ２ O ３ One MgO / Al inclusion was observed in each sample. Therefore, the evaluation was rated as good. Furthermore, in No. 11, MgO / Al ２ O ３ The MnO concentration is high in the MgO inclusions, and the SiO ２ At the same time, the content of MnO increased, and simple CaO inclusions and Al ２ O ３ Simple inclusions and MnO-Cr ２ O ３ Inclusions were confirmed. As a result, the evaluation was △.

[0076] Next, we will explain the comparative examples. In No. 15, the Si content was low. Conversely, the Al content was high and the CaO concentration in the slag exceeded the desired range, resulting in high Ca and Mg concentrations. As a result, MgO and CaO were not included in the average composition of the inclusions. The structure also contained more f-CaO alone, resulting in a CaO-Al ２ O ３ - CaO in the MgO-based oxides was high. In other words, the CaO simple substance inclusion became the center, causing defects and resulting in scrap.

[0077] No. 16 was out of the range because the Si concentration was high, and so the Ca and Mg concentrations were also high. The high Si concentration resulted in the SiO ２ The concentration also became too high. In addition, the F concentration was low, and the slag lacked fluidity. The Ti and N concentrations were both too high, and TiN clusters were formed. In the average composition of the inclusions, MgO and CaO were out of range, and the CaO-Al ２ O ３ -Alumina, MgO, SiO in MgO-based oxides ２ The thickness was outside the range, and many f-CaO simple inclusions were formed in the structure. The formation of many TiN and CaO simple inclusions caused many surface defects, and the coil became scrap.

[0078] No. 17 had a low Si content, did not contain Mn, and did not contain Al, which resulted in low Ca and Mg concentrations, and a high oxygen concentration, which increased the number of non-metallic inclusions. In addition, the slag composition was also out of range, with high silica and low CaO, which adversely affected the inclusion composition. The average composition of the inclusions was out of range for all oxides, and the structure was h.MnO-Cr. ２ O ３ Many CaO-Al inclusions were formed. ２ O ３ -Alumina and silica are also removed from MgO-based oxides, and MnO-Cr ２ O ３ As a result, surface defects occurred along the entire length of the coil, and the coil was eventually scrapped.

[0079] No. 18 had a high Al concentration, resulting in a high alumina concentration in the slag, while the CaO concentration was low. The average composition of non-metallic inclusions was 100% alumina, and the structure was also g.Al. ２ O ３ Only simple inclusions remained. Elements that maintain strength, such as Cr, were low, and both hardness and elongation were outside the range. As a result, surface defects occurred along the entire length, causing scrapping.

[0080] No. 19 had a low Al concentration, which resulted in low Ca and Mg concentrations, and a high oxygen concentration, which was out of the range. ２ O ３ The morphology of the MnO-Cr alloy was also high, and three types of structure were formed: f, g, and h. ２ O ３ Many MgO and Al inclusions were observed. ２ O ３ The elements that form a solid solution in the simple inclusions and MgO simple inclusions were also removed. Furthermore, the Ti and N concentrations were high, and TiN clusters were also observed. Furthermore, the contents of elements that maintain strength, such as Cr, were low, and both the hardness and elongation were outside the range. As a result, surface defects occurred along the entire length, resulting in scrapping.

[0081] No. 20 had high Ti and N contents, which were outside the normal range, and TiN clusters formed severe surface defects. In Table 2, all of the inclusion types are listed as a and b, which at first glance seems good, but this is because TiN is not counted as an inclusion. Furthermore, the contents of elements that maintain strength, such as C and Cr, were low, and both the hardness and elongation were outside the range. As a result, the product could not be shipped and was scrapped.

Claims

1. The average composition of non-metallic inclusions is as follows: C: 0.001-0.03%, Si: 0.01-0.5%, Mn: 0.01-0.5%, P: 0.01% or less, S: 0.005% or less, Cr: 0.5% or less, Mo: 0.1% or less, Cu: 0.1% or less, Al: 0.001-0.2%, Ti: 0.05% or less, Fe: 0.01-0.5%, Ca: 0.0001-0.02%, Mg: 0.0001-0.02%, N: 0.005% or less, O: 0.005% or less, and one or more of Co, W, Nb, and B is 1% or less, with the balance being Ni and unavoidable impurities. ２ O ３ :15~40%, SiO ２ : 30% or less, CaO: 10 to 40%, MnO: 1% or less, and having excellent surface properties and mechanical properties.

2. The Ni alloy with excellent surface properties and mechanical properties according to claim 1, characterized in that the structural form of the nonmetallic inclusions is such that 70% or more of the nonmetallic inclusions in terms of number ratio to the total nonmetallic inclusions are one or more of the following five types a to e. a: CaO-Al ２ O ３ -MgO-based oxide is MgO.Al within the approximately spherical surface ２ O ３ Completely containing CaO-Al ２ O ３ -MgO-based oxide c: CaO-Al ２ O ３ - MgO-based oxide completely contains MgO within the approximately spherical surface. d: MgO alone e: MgO.Al ２ O ３ Single 3. The CaO-Al ２ O ３ -MgO-based oxide is included, and the CaO-Al ２ O ３ -MgO-based oxides are CaO: 20-60%, Al ２ O ３ :30~60%, MgO:1~30%, SiO ２ 3. The Ni alloy having excellent surface properties and mechanical properties according to claim 2, characterized in that: Mn: 20% or less, TiO2: 0.5% or less.

4. The MgO.Al ２ O ３ The MgO.Al ２ O ３ 3. The Ni alloy having excellent surface properties and mechanical properties according to claim 2, characterized in that it contains 0.5% or less of MnO.

5. The MgO element is contained, and the MgO element is Al ２ O ３ : 3% or less, SiO ２ 3. The Ni alloy having excellent surface properties and mechanical properties according to claim 2, characterized in that it contains: 1% or less of Mo, 10% or less of CaO, and 1% or less of MnO.

6. The Ni alloy having excellent surface properties and mechanical properties as described in claim 1, characterized in that it has a Vickers hardness of 90 Hv or more and an elongation of 25% or more.

7. A method for producing a Ni alloy according to any one of claims 1 to 6, comprising melting raw materials such as pure Ni in an electric furnace, then subjecting the raw materials to vacuum degassing in a VOD, and then adding quicklime, fluorite and a magnesia source to produce a CaO-Al alloy. ２ O ３ -MgO-SiO ２ A method for producing a Ni alloy having excellent surface properties and mechanical properties, characterized in that a -F-based slag is formed and at the same time a ferrosilicon alloy and / or Al is added to perform deoxidation and desulfurization, then a slab is produced using a continuous casting machine, the surface is ground, and then a hot rolling process is performed, followed by cold rolling.

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