Austenitic casting materials and iron castings

Abstract

This austenitic casting material contains 0.1 to 3.5 mass% C, 0.01 to 4.5 mass% Si, 0.01 to 4.5 mass% Mn, 10.0 to 50.0 mass% Ni, 0.001 to1.0 mass% N, 0 to10.0 mass% Co, and 0.0001 to 0.050 mass% Mg, the balance being Fe and unavoidable elements.

Description

Technical Field

[0001] The present invention relates to an austenitic casting material and an iron casting.

Background Art

[0002] The abstract of Patent Document 1 describes that it provides a spheroidal graphite cast iron which has excellent gas defect resistance with few gas defects such as pinholes caused by free N, and has mechanical properties and machinability equal to or higher than conventional ones. It also describes that the spheroidal graphite cast iron having excellent gas defect resistance comprises, by mass ratio: C: 3.3 to 4%, Si: 2 to 3%, P: 0.05% or less, S: 0.02% or less, Mn: 0.8% or less, Cu: 0.8% or less (excluding 0), Mg: 0.02 to 0.06%, Ti: 0.01 to 0.04%, V: 0.001 to 0.01%, Nb: 0.001 to 0.01%, N: 0.004 to 0.008%, with the balance substantially being Fe and unavoidable impurities.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] To provide an austenitic casting material capable of suppressing the occurrence of gas defects and exhibiting good damping characteristics.

Means for Solving the Problem

[0005] One aspect of the present invention is an austenitic casting material comprising 0.10% to 3.50% by mass of C, 0.01% to 4.50% by mass of Si, 0.01% to 4.50% by mass of Mn, 10.0% to 50.0% by mass of Ni, 0.001% to 1.000% by mass of N, 0% to 10.00% by mass of Co, and 0.0001% to 0.0500% by mass of Mg, with the remainder being Fe and unavoidable elements.

[0006] In the above embodiment, by setting the lower limit of the Mg content to 0.0001% by mass, magnesium nitride can be formed by compounding with nitrogen (N) that is mixed into the molten metal for casting (hereinafter referred to as "the molten metal") from, for example, the atmosphere. This allows the nitrogen mixed into the molten metal to be fixed as magnesium nitride. Therefore, the probability of gas defects occurring due to nitrogen mixed into the molten metal during solidification can be reduced. Furthermore, by setting the upper limit of the Mg content to 0.0500% by mass, the graphite crystals that crystallize during the solidification of the molten metal are more likely to become flaky, and the caterpillar-like or spheroidal shape of the graphite can be suppressed. Therefore, the decrease in the damping ratio of the iron casting obtained by solidifying the molten metal can be suppressed. Thus, it is possible to provide a casting material that can suppress the occurrence of gas defects and exhibit good damping characteristics.

[0007] The Mg content is preferably 0.0005% by mass or more and 0.0500% by mass or less. By setting the lower limit of the Mg content to 0.0005% by mass, the probability of gas defects occurring can be further reduced. Furthermore, even if gas defects occur inside the iron casting, the area where the gas defects occur can be reduced to an area close to the casting surface. As a result, the amount of machining required to remove gas defects scattered just below the casting surface can be reduced.

[0008] The Mg content is preferably between 0.0005% by mass and 0.0350% by mass. By setting the upper limit of the Mg content to 0.0350% by mass, the decrease in the damping ratio of the cast iron can be further suppressed.

[0009] The Mg content is more preferably 0.0050% by mass or more and 0.0500% by mass or less. The Mg content is more preferably 0.0050% by mass or more and 0.0350% by mass or less. The Ni content is preferably 20.0% by mass or more and 45.0% by mass or less. The C content is preferably 1.00% by mass or more and 3.50% by mass or less. The Si content is preferably 0.10% by mass or more and 4.00% by mass or less. The Mn content is preferably 0.10% by mass or more and 3.50% by mass or less. The Co content is preferably 0.10% by mass or more and 8.50% by mass or less.

[0010] Another aspect of the present invention is an iron casting cast using the above-mentioned casting material. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows the composition, gas defect depth, and damping ratio of reference examples, examples, and comparative examples of iron castings cast using austenitic casting materials. [Figure 2] Figure 2 shows the depth of gas defects in the Y-shaped cross-section specimen of Comparative Example 1. [Modes for carrying out the invention]

[0012] Embodiments of austenitic casting materials and iron castings according to this disclosure will be described below with reference to the attached drawings. The present invention is not limited to the following embodiments, but includes those defined in the claims. In the following description, unless otherwise specified, terms such as "first" and "second" are used only to distinguish components from one another and do not represent a specific order or sequence.

[0013] An iron casting according to an embodiment of the present invention is obtained by casting using an austenitic casting material. "Austenitic casting material" means a material in which the main structure of the matrix phase (iron matrix structure excluding graphite) of the iron casting at room temperature is the austenite phase. For example, the proportion of the austenite phase in the matrix phase of the iron casting is 50% or more. Preferably, the proportion of the austenite phase in the matrix phase of the iron casting is 70% or more, more preferably 80% or more, more preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more.

[0014] In this disclosure, "casting" includes casting by various casting methods such as sand casting, mold casting, die casting, and lost-wax casting. Furthermore, "mass%" of an element means the percentage of the element's mass relative to the mass of the austenitic casting material. For example, the notation "elements between A mass% and B mass%" means that the mass% of the element is between A% and B%. For example, the notation "elements between 0 mass% and B mass%" means that the element is not included or that the mass% of the element is B% or less. "Remainder" means the components of the austenitic casting material other than the listed elements.

[0015] <First form of casting material> The first form of the austenitic casting material (hereinafter referred to as "this material") contains 10.0% to 50.0% by mass of Ni, 0.001% to 1.000% by mass of N, and 0.0001% to 0.0500% by mass of Mg, with the remainder being Fe and unavoidable elements.

[0016] (Ni: Nickel) The first form of this material contains 10.0% by mass or more and 50.0% by mass or less of Ni. In this first form of the material, the Ni content is set to 10.0% by mass or more and 50.0% by mass or less, causing Ni to segregate around the graphite. That is, the austenite is stabilized by concentrating Ni in the region surrounding the graphite. By setting the lower limit of the Ni content to 10.0% by mass, the austenite can be stabilized and the formation of martensite can be suppressed. Therefore, the decrease in ductility of the iron casting can be suppressed and the machinability of the iron casting can be improved. Furthermore, by setting the upper limit of the Ni content to 50.0% by mass, the increase in the coefficient of thermal expansion can be suppressed. The same applies to the following forms of this material.

[0017] In the first embodiment of this material, the lower limit of the Ni content is preferably 11.0% by mass, more preferably 12.0% by mass, more preferably 13.0% by mass, more preferably 14.0% by mass, more preferably 15.0% by mass, more preferably 16.0% by mass, more preferably 17.0% by mass, more preferably 18.0% by mass, more preferably 19.0% by mass, more preferably 20.0% by mass, more preferably 21.0% by mass, more preferably 22.0% by mass, more preferably 23.0% by mass, and more preferably 24.0% by mass. It is more preferable to have it, more preferably 25.0% by mass, more preferably 25.5% by mass, more preferably 26.0% by mass, more preferably 27.0% by mass, more preferably 28.0% by mass, more preferably 28.5% by mass, more preferably 29.0% by mass, more preferably 30.0% by mass, more preferably 30.5% by mass, more preferably 31.0% by mass, more preferably 31.5% by mass, more preferably 32.0% by mass, more preferably 32.5% by mass, and even more preferably 33.0% by mass. The same applies to the following embodiments of the material.

[0018] In the first embodiment of the present material, the upper limit of the Ni content relative to each of the above lower limits is preferably 49.0% by mass, more preferably 48.0% by mass, still more preferably 47.0% by mass, still more preferably 46.0% by mass, still more preferably 45.0% by mass, still more preferably 44.0% by mass, still more preferably 43.0% by mass, still more preferably 42.0% by mass, still more preferably 41.5% by mass, still more preferably 41.0% by mass, still more preferably 40.5% by mass, and even more preferably 40.0% by mass. The same applies to the following embodiments of the present material.

[0019] (N: Nitrogen) The first embodiment of the present material contains N in an amount of 0.001% by mass or more and 1.000% by mass or less. In the first embodiment of the present material, by setting the lower limit of the N content to 0.001% by mass, the mechanical properties of the iron casting can be improved through solid solution strengthening of the iron base structure. Furthermore, by setting the upper limit of the N content to 1.000% by mass, the probability of occurrence of gas defects such as pinholes and blowholes during casting of the present material can be reduced. The same applies to the following embodiments of the present material.

[0020] In the first embodiment of the present material, the lower limit of the N content is preferably 0.004% by mass, more preferably 0.007% by mass, still more preferably 0.010% by mass, and even more preferably 0.011% by mass. The same applies to the following embodiments of the present material.

[0021] In the first embodiment of the present material, the upper limit of the N content relative to each of the above lower limits is preferably 0.800% by mass, more preferably 0.600% by mass, still more preferably 0.400% by mass, still more preferably 0.200% by mass, still more preferably 0.100% by mass, still more preferably 0.070% by mass, and even more preferably 0.040% by mass. The same applies to the following embodiments of the present material.

[0022] (Mg: Magnesium) The first form of this material contains 0.0001% by mass or more and 0.0500% by mass or less of Mg. In the first form of this material, for example, N dissolved in the molten metal is prone to gas defects as its solubility decreases as the temperature decreases and solidification progresses. In particular, gas defects are prone to occur near the cast surface where the growth rate of solidified crystals is fast. In the first form of this material, by setting the lower limit of the Mg content to 0.0001% by mass, magnesium nitride can be formed by compounding with N mixed into the molten metal from, for example, the atmosphere. This allows the N mixed into the molten metal to be fixed as magnesium nitride. Therefore, the probability of gas defects occurring due to N mixed into the molten metal during solidification can be reduced. Furthermore, by setting the upper limit of the Mg content to 0.0500% by mass, the graphite crystallized during the solidification of the molten metal is more likely to become flaky, and the caterpillar-like or spheroidal shape of the graphite can be suppressed. Therefore, the decrease in the decay ratio of the iron casting obtained by solidifying this molten metal can be suppressed. Therefore, it is possible to provide a casting material that can suppress the occurrence of gas defects and exhibit good damping characteristics. The same applies to the following forms of this material.

[0023] In the first embodiment of the present material, the lower limit of the Mg content is preferably 0.0004 mass%, more preferably 0.0007 mass%, still more preferably 0.0010 mass%, yet more preferably 0.0014 mass%, further more preferably 0.0018 mass%, still further more preferably 0.0022 mass%, yet further more preferably 0.0026 mass%, even more preferably 0.0030 mass%, still even more preferably 0.0034 mass%, yet even more preferably 0.0038 mass%, still more preferably 0.0045 mass%, yet more preferably 0.0050 mass%, further more preferably 0.0055 mass%, still further more preferably 0.0060 mass%, yet further more preferably 0.0065 mass%, even more preferably 0.0070 mass%, still even more preferably 0.0073 mass%, yet even more preferably 0.0078 mass%, still more preferably 0.0083 mass%, yet more preferably 0.0088 mass%, further more preferably 0.0095 mass%, still further more preferably 0.0100 mass%, yet further more preferably 0.0120 mass%, even more preferably 0.0150 mass%, and most preferably 0.0175 mass%. The same applies to the following embodiments of the present material.

[0024] In the first embodiment of the present material, the upper limit of the Mg content is preferably 0.0475 mass%, more preferably 0.0450 mass%, still more preferably 0.0425 mass%, yet more preferably 0.0400 mass%, further more preferably 0.0375 mass%, still further more preferably 0.0350 mass%, yet further more preferably 0.0325 mass%, even more preferably 0.0300 mass%, still even more preferably 0.0275 mass%, yet even more preferably 0.0250 mass%, still more preferably 0.0225 mass%, and further more preferably 0.0200 mass%, with respect to each of the above lower limits. The same applies to the following embodiments of the present material.

[0025] (Fe: Iron, an unavoidable element) The remainder of the first embodiment of this material is Fe and unavoidable elements. Examples of unavoidable elements included in the remainder are P (phosphorus), Cu (copper), Cr (chromium), Mo (molybdenum), V (vanadium), As (arsenic), Sn (tin), Ca (calcium), Nb (niobium), B (boron), Pb (lead), Sb (antimony), W (tungsten), Te (tellurium), Bi (bismuth), and Zn (zinc). The content of unavoidable elements is preferably 10.0% by mass or less in total, more preferably 5.0% by mass or less in total, more preferably 3.0% by mass or less in total, and even more preferably 1.0% by mass or less in total. The same applies to the following embodiments of this material.

[0026] <Second form of casting material> The second form of this material contains 0.10% to 3.50% by mass of carbon, 10.0% to 50.0% by mass of nickel, 0.001% to 1.000% by mass of nitrogen, and 0.0001% to 0.0500% by mass of magnesium, with the remainder being Fe and unavoidable elements.

[0027] (C: carbon) The second form of this material contains 0.10% by mass or more and 3.50% by mass of carbon. In this second form of the material, setting the lower limit of the carbon content to 0.10% by mass lowers the liquidus temperature of the material. This improves the fluidity of the material. Also, setting the lower limit of the carbon content to 0.10% by mass increases the amount of graphite crystallized or precipitated. This improves the machinability of the iron casting. Also, setting the upper limit of the carbon content to 3.50% by mass suppresses graphite flotation. This suppresses a decrease in the strength and ductility of the iron casting. Furthermore, setting the upper limit of the carbon content to 3.50% by mass, along with the upper limit of the Ni content, which acts as a graphitization-promoting element, to 50.0% by mass, suppresses excessive graphitization of carbon. This suppresses the formation of coarse graphite. Therefore, it improves the elongation of the iron casting. Also, setting the upper limit of the carbon content to 3.50% by mass suppresses the occurrence of gas defects caused by CO gas. Furthermore, by setting the carbon content to between 0.10% by mass and 3.50% by mass, the damping ratio of the cast iron can be improved due to frictional heat generation between the crystalline graphite and the iron matrix interface, as well as internal frictional losses within the graphite itself. The same applies to the following forms of this material.

[0028] In the second embodiment of this material, the lower limit of the C content is preferably 0.15 mass%, more preferably 0.20 mass%, more preferably 0.40 mass%, more preferably 0.70 mass%, more preferably 1.00 mass%, more preferably 1.25 mass%, more preferably 1.50 mass%, and even more preferably 1.75 mass%. By setting the lower limit of the C content to 0.70 mass%, the tendency of the graphite crystallized during solidification to form a eutectic structure is increased, thereby increasing the amount of graphite expansion and suppressing the occurrence of shrinkage cavities. The same applies to the following embodiments of this material.

[0029] In the second embodiment of this material, the upper limit of the C content is preferably 3.30% by mass, more preferably 3.20% by mass, more preferably 3.15% by mass, more preferably 3.10% by mass, more preferably 3.00% by mass, more preferably 2.95% by mass, more preferably 2.90% by mass, more preferably 2.85% by mass, more preferably 2.80% by mass, more preferably 2.75% by mass, more preferably 2.70% by mass, more preferably 2.65% by mass, more preferably 2.60% by mass, more preferably 2.55% by mass, more preferably 2.50% by mass, more preferably 2.45% by mass, and even more preferably 2.40% by mass. The same applies to the following embodiments of this material.

[0030] <Third form of casting material> The third form of this material contains 0.10% to 3.50% by mass of carbon, 0.01% to 4.50% by mass of silicon, 10.0% to 50.0% by mass of nickel, 0.001% to 1.000% by mass of nitrogen, and 0.0001% to 0.0500% by mass of magnesium, with the remainder being Fe and unavoidable elements.

[0031] (Si: Silicon) The third form of this material contains Si in an amount of 0.01% to 4.50% by mass. In this third form of the material, the Ni content is set to 10.0% to 50.0% by mass, and the Si content is set to 0.01% to 4.50% by mass, causing Ni to segregate around the graphite, and as a result, Si to segregate in the final solidification region. That is, the austenite is stabilized by concentrating Ni in the region surrounding the graphite, and Si is concentrated in the final solidification region, which is the residual liquid side. Setting the lower limit of the Si content to 0.01% by mass makes it easier to lower the liquidus temperature of this material. Therefore, it is easier to improve the flowability of this material. In addition, setting the lower limit of the Si content to 0.01% by mass makes it possible to increase the ratio of Si content to C content. Therefore, the formation of CO gas can be suppressed. Consequently, gas defects occurring on the surface of iron castings can be reduced. Furthermore, by setting the lower limit of the Si content to 0.01 mass%, the N mixed into the molten metal can be fixed as silicon nitride (Si3N4). This reduces the probability of gas defects occurring due to the N mixed into the molten metal during solidification. Also, by setting the upper limit of the Si content to 4.50 mass%, the amount of Si dissolved in the Fe (iron matrix) can be reduced. This suppresses the increase in the coefficient of linear expansion. In addition, by setting the upper limit of the Si content, which acts as a graphitization promoting element, to 4.50 mass%, excessive graphitization of C can be suppressed. This suppresses the formation of coarse graphite. Consequently, the elongation of the iron casting can be improved. Furthermore, by setting the Si content, which has a graphitization effect similar to C, to between 0.01 mass% and 4.50 mass%, the damping ratio of the iron casting can be improved due to frictional heat generation between the interface between the crystallized graphite and the iron matrix, and internal friction losses of the graphite itself. The same applies to the following forms of this material.

[0032] In the third embodiment of this material, the lower limit of the Si content is preferably 0.05 mass%, more preferably 0.10 mass%, more preferably 0.15 mass%, more preferably 0.18 mass%, more preferably 0.20 mass%, more preferably 0.25 mass%, more preferably 0.50 mass%, more preferably 0.75 mass%, more preferably 1.00 mass%, more preferably 1.20 mass%, more preferably 1.30 mass%, and even more preferably 1.40 mass%. The same applies to the following embodiments of this material.

[0033] In the third embodiment of this material, the upper limit of the Si content is preferably 4.30% by mass, more preferably 4.10% by mass, more preferably 3.90% by mass, more preferably 3.70% by mass, more preferably 3.50% by mass, more preferably 3.30% by mass, more preferably 3.10% by mass, more preferably 2.90% by mass, more preferably 2.70% by mass, more preferably 2.50% by mass, more preferably 2.30% by mass, and even more preferably 2.10% by mass. The same applies to the following embodiments of this material.

[0034] <Fourth form of casting material> The fourth form of this material contains 0.10% to 3.50% by mass of C, 0.01% to 4.50% by mass of Si, 0.01% to 4.50% by mass of Mn, 10.0% to 50.0% by mass of Ni, 0.001% to 1.000% by mass of N, and 0.0001% to 0.0500% by mass of Mg, with the remainder being Fe and unavoidable elements.

[0035] (Mn: Manganese) The fourth form of this material contains Mn in an amount of 0.01% to 4.50% by mass. In this fourth form of the material, by setting the Mn content to 0.01% to 4.50% by mass, the austenite can be stabilized through a synergistic effect with Ni, thereby suppressing the formation of martensite. Therefore, the machinability of iron castings can be improved. By setting the lower limit of the Mn content to 0.01% by mass, the austenite can be stabilized even at room temperature. Furthermore, by setting the upper limit of the Mn content to 4.50% by mass, the amount of Mn dissolved in Fe (iron matrix) can be reduced. Therefore, the increase in the coefficient of linear expansion can be suppressed. In addition, by setting the upper limit of the Mn content to 4.50% by mass, the reaction of MnO suspended in the molten metal with C in the molten metal to generate CO gas can be suppressed. Therefore, the occurrence of gas defects caused by CO gas can be suppressed. The same applies to the following forms of this material.

[0036] In the fourth embodiment of this material, the lower limit of the Mn content is preferably 0.05 mass%, more preferably 0.07 mass%, more preferably 0.08 mass%, more preferably 0.09 mass%, more preferably 0.10 mass%, and even more preferably 0.13 mass%. The same applies to the following embodiments of this material.

[0037] In the fourth embodiment of this material, the upper limit of the Mn content is preferably 4.00% by mass, more preferably 3.50% by mass, more preferably 3.20% by mass, more preferably 3.00% by mass, more preferably 2.50% by mass, more preferably 2.00% by mass, more preferably 1.50% by mass, more preferably 1.00% by mass, more preferably 0.75% by mass, more preferably 0.50% by mass, and even more preferably 0.25% by mass, relative to each of the lower limits. The same applies to the following embodiments of this material.

[0038] <Fifth form of casting material> The fifth form of this material contains 0.10% to 3.50% by mass of C, 0.01% to 4.50% by mass of Si, 0.01% to 4.50% by mass of Mn, 10.0% to 50.0% by mass of Ni, 0.001% to 1.000% by mass of N, 0.10% to 10.00% by mass of Co, and 0.0001% to 0.0500% by mass of Mg, with the remainder being Fe and unavoidable elements.

[0039] (Co: Cobalt) The fifth form of this material contains 0.10% by mass or more and 10.00% by mass or less of Co. In the fifth form of this material, by setting the Co content to 0.10% by mass or more and 10.00% by mass or less, the coefficient of thermal expansion can be further reduced through a synergistic effect with Ni. By setting the lower limit of the Co content to 0.10% by mass, the minimum value of the coefficient of thermal expansion can be reduced through a synergistic effect with Ni. Furthermore, by setting the upper limit of the Co content to 10.00% by mass, it is possible to suppress the increase in the coefficient of thermal expansion after it has reached a minimum value due to the addition of excessive Co.

[0040] In the fifth embodiment of this material, the lower limit of the Co content is preferably 0.50% by mass, more preferably 1.00% by mass, more preferably 1.50% by mass, more preferably 2.00% by mass, more preferably 2.50% by mass, more preferably 3.00% by mass, more preferably 3.50% by mass, more preferably 3.80% by mass, and even more preferably 4.00% by mass.

[0041] In the fifth embodiment of this material, the upper limit of the Co content is preferably 9.50% by mass, more preferably 9.00% by mass, more preferably 8.50% by mass, more preferably 8.00% by mass, more preferably 7.50% by mass, more preferably 7.00% by mass, more preferably 6.50% by mass, more preferably 6.25% by mass, more preferably 6.00% by mass, and even more preferably 5.50% by mass. Furthermore, it is preferable that the Co content be 4.00% by mass or more and 5.50% by mass or less, relative to a Ni content of 31.0% by mass or more and 34.0% by mass or less. Also, when the lower limit of the Ni content is 28.5% by mass, it is preferable that the Co content be 5.00% by mass or more and 8.00% by mass or less. By setting the lower and upper limits of the Co content in this way, the coefficient of linear expansion can be further reduced due to the synergistic effect with Ni.

[0042] By casting using the above-described form of this material, it is possible to provide iron castings that suppress the occurrence of gas defects and exhibit good damping characteristics. An example of a casting method using this material is as follows: First, raw materials (iron scrap, return material, etc.) are melted in a melting furnace (high-frequency induction electric furnace, etc.), and molten metal of the desired composition is produced by adjusting the composition. Next, this molten metal is poured into a predetermined mold (sand mold, metal mold, etc.) and solidified by cooling to room temperature within the mold. Finally, the iron casting can be obtained by dismantling the mold (or demolding from the mold). Iron castings cast using this material are suitable for a wide variety of applications requiring high vibration absorption. Examples of applications for this iron casting include beds, columns and spindle peripheral members of machine tools, bases of semiconductor manufacturing equipment, surface plates of precision measuring instruments, and other components and parts of various machines, devices, and equipment that require high damping performance.

[0043] <Examples and Comparative Examples> Figure 1 shows an iron casting made using this material. Reference example,Figure 1 shows the composition, gas defect depth, and decay ratio of the examples and comparative examples. Figure 2 shows the gas defect depth in the Y-shaped cross-sectional test specimen of Comparative Example 1. In Figure 1, the carbon (C) content (mass%) was measured by combustion-infrared absorption spectroscopy using the EMIA-Expert carbon-sulfur analyzer manufactured by Horiba, Ltd. The silicon (Si), nickel (Ni), cobalt (Co), and magnesium (Mg) content (mass%) was measured by inductively coupled plasma emission spectroscopy using the SPS3520UV emission spectrometer manufactured by Hitachi High-Tech Science Corporation. The content (mass%) of other elements was measured by emission spectroscopy using the PDA-8000 emission spectrometer manufactured by Shimadzu Corporation. Furthermore, the gas defect depth (mm) is the maximum distance measured from the surface (cast surface) of the iron casting to the deepest gas defect among multiple gas defects scattered in the depth direction (perpendicular to the cast surface) when gas defects are present inside the iron casting. Specifically, it represents the maximum distance measured from the surface to the deepest gas defect among multiple gas defects scattered in the depth direction, using a Y-shaped cross-sectional test piece taken from a Y-type B test material according to JIS G 5502 (spheroidal graphite cast iron). For example, the gas defect depth in Comparative Example 1 is 6.35 mm, which is the value measured at the distance indicated by symbol D in the Y-shaped cross-sectional test piece shown in Figure 2. Note that in Figure 1, a gas defect depth of 0 mm indicates that no gas defect formation was confirmed in the Y-shaped cross-sectional test piece. Furthermore, the damping ratio (%) was determined by analyzing the natural frequency component of the mode with the lowest natural frequency (mode 1) among the multiple vibration modes obtained by the hammering test using a 20 × 20 × 100 mm rectangular parallelepiped test piece taken from the above-mentioned Y-type B test material. In the hammering test, an acceleration sensor (Ono Sokki Co., Ltd. / NP-3211) was attached to the test piece, and the test piece was struck using an impulse hammer (Ono Sokki Co., Ltd. / GK-3100). The signals obtained from the acceleration sensor and impulse hammer at that time were acquired by an FFT analyzer (Ono Sokki Co., Ltd. / DS3100) and analyzed using analysis software (Ono Sokki Co., Ltd. / DS-0320).

[0044] ( Reference Examples 1 to 3 and From Example 1 Example 14 (Comparison with Comparative Example 1) As shown in Figure 1, Reference Examples 1 to 3 and From Example 1 Example 14 The Mg content of [comparison] is 0.0001% by mass or more, whereas the Mg content of Comparative Example 1 is 0% by mass (less than 0.0001% by mass). As shown in Figure 1, Reference Examples 1 to 3 and From Example 1 Example 14 Compared to Comparative Example 1, the depth of the gas defect is smaller. Specifically, while the depth of the gas defect in Comparative Example 1 was 6.35 mm, Reference Examples 1 to 3 and From Example 1 Example 14 The depth of the gas defect in this area is 4.97 mm or less. Reference Examples 1 to 3 and From Example 1 Example 14 By increasing the Mg content to 0.0001% by mass or more, the area where gas defects occur can be reduced to an area close to the casting surface. Therefore, the amount of machining required to remove gas defects scattered directly beneath the casting surface can be reduced.

[0045] ( Reference Examples 1 to 3 and From Example 1 Example 14 (and comparison with Comparative Example 2) As shown in Figure 1, Reference Examples 1 to 3 and From Example 1 Example 14 The Mg content of comparative example 1 is 0.0500% by mass or less, whereas the Mg content of comparative example 2 is 0.0590% by mass (exceeding 0.0500% by mass). As shown in Figure 1, Reference Examples 1 to 3 and From Example 1 Example 14 In comparison with Comparative Example 2, the damping ratio is higher. Specifically, while the damping ratio in Comparative Example 2 is 0.085%, Reference Examples 1 to 3 and From Example 1 Example 14 The damping ratio in this case is 0.114% or higher. Reference Examples 1 to 3 and From Example 1 Example 14 Therefore, by reducing the Mg content to 0.0500 mass% or less, the decrease in the damping ratio can be suppressed.

[0046] ( Example 2 from Example 13 and, Reference Example 1, Reference Example 2, and Example 1 (Comparison with) As shown in Figure 1, Example 2 from Example 13 While the Mg content of is 0.0050% by mass or more, Reference Example 1, Reference Example 2, and Example 1 The Mg content is 0.0038% by mass or less (less than 0.0050% by mass). As shown in Figure 1, Example 2 from Example 13 Therefore, the formation of gas defects has not been confirmed. Example 2 from Example 13 Therefore, by increasing the Mg content to 0.0050 mass% or more, the occurrence of gas defects can be suppressed. As a result, it is possible to provide iron castings that are close to the finished product, so-called near-net-shape iron castings. Consequently, the material costs used in casting and the processing costs after casting can be reduced.

[0047] ( Example 2 from Example 13 and, Reference example 3 (Comparison with) As shown in Figure 1, Example 2 from Example 13 While the C content of is 3.15% by mass or less, Reference example 3 The C content is 3.19% by mass (exceeding 3.15% by mass). Also, Example 2 from Example 13 The Si content of is 0.18% by mass or more, Reference example 3 The Si content is 0.15% by mass (less than 0.18% by mass). As shown in Figure 1, Example 2 from Example 13 Therefore, the formation of gas defects has not been confirmed. Example 2 from Example 13 Therefore, by setting the Mg content to 0.0050 mass% or more, the C content to 3.15 mass% or less, and the Si content to 0.18 mass% or more, the occurrence of gas defects can be suppressed. As a result, it is possible to provide iron castings that are close to the finished product, so-called near-net-shape iron castings. Consequently, the material costs used in casting and the processing costs after casting can be reduced.

[0048] ( Example 2 from Example 13 and, Example 14 (Comparison with) As shown in Figure 1, Example 2 from Example 13 The Ni content of is 41.0% by mass or less, Example 14 The Ni content is 41.4% by mass (exceeding 41.0% by mass). Also, Example 2 from Example 13 The Co content of is 0.10% by mass or more, Example 14 The Co content is 0% by mass (less than 0.10% by mass). As shown in Figure 1, Example 2 from Example 13 Therefore, the formation of gas defects has not been confirmed. Example 2 from Example 13 Therefore, by setting the Mg content to 0.0050 mass% or more, the Ni content to 41.0 mass% or less, and the Co content to 0.10 mass% or more, the occurrence of gas defects can be suppressed. As a result, it is possible to provide iron castings that are close to the finished product, so-called near-net-shape iron castings. Consequently, the material costs used in casting and the processing costs after casting can be reduced.

Claims

1. An austenitic casting material comprising 1.50% to 3.20% by mass of carbon, 1.40% to 4.50% by mass of silicon, 0.01% to 4.50% by mass of manganese, 10.0% to 50.0% by mass of nickel, 0.004% to 0.040% by mass of nitrogen, 0% to 10.00% by mass of cocoa, and 0.0022% to 0.0375% by mass of magnesium, with the remainder being Fe and unavoidable elements.

2. The casting material according to claim 1, wherein the Mg content is 0.0022% by mass or more and 0.0350% by mass or less.

3. The casting material according to claim 1, wherein the Mg content is 0.0050% by mass or more and 0.0375% by mass or less.

4. The casting material according to claim 3, wherein the Mg content is 0.0050% by mass or more and 0.0350% by mass or less.

5. The casting material according to any one of claims 1 to 4, wherein the Ni content is 20.0% by mass or more and 45.0% by mass or less.

6. The casting material according to claim 5, wherein the Si content is 1.40% by mass or more and 4.00% by mass or less.

7. The casting material according to claim 6, wherein the Mn content is 0.10% by mass or more and 3.50% by mass or less.

8. The casting material according to claim 7, wherein the Co content is 0.10% by mass or more and 8.50% by mass or less.

9. An iron casting made using the casting material described in any one of claims 1 to 4.

10. An iron casting made using the casting material described in claim 5.

11. An iron casting made using the casting material described in claim 6.

12. An iron casting made using the casting material described in claim 7.

13. An iron casting made using the casting material described in claim 8.

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