JP7300351B2 - Polishing surface plate using spheroidal graphite cast iron - Google Patents

Description

The present invention relates to a polishing surface plate using spheroidal graphite cast iron.

A polishing surface plate using spheroidal graphite cast iron is used for polishing an object to be polished such as a silicon wafer, and thus is required to have properties suitable for polishing the object to be polished. Properties suitable for polishing an object to be polished include, for example, resistance to deformation of the polishing surface plate during polishing and resistance to damage to the object to be polished.

A polishing surface plate using spheroidal graphite cast iron is preferable not only for the above properties but also for cost reduction because it can be easily manufactured. For example, if the polishing surface plate is not heat-treated after being cast, the time, equipment, and processes for heat treatment are not required, which greatly contributes to cost reduction.

Conventionally, there have been proposed products using spheroidal graphite cast iron that has sufficient hardness without heat treatment after casting (see, for example, Patent Document 1). This product has portions with different hardness, and the content of components as spheroidal graphite cast iron is appropriately adjusted.

JP-A-2000-345279

By the way, the spheroidal graphite cast iron described in Patent Document 1 is assumed to be used for wheel hubs of construction machinery vehicles, as described in paragraph [0016] of Patent Document 1. It is not intended to be used as a board. In general, cast iron, which is easy to deform, is preferable to cast iron, which is hard to deform, in order to absorb the impact caused by the running of the vehicle. For this reason, the spheroidal graphite cast iron described in Patent Document 1 is considered to have a low proof stress ratio, which is an index of resistance to deformation.

On the other hand, as described above, the polishing surface plate is required to be difficult to deform as a property suitable for polishing the object to be polished. This is because the easily deformable polishing surface plate makes it difficult to polish the object to be polished with high accuracy, and the nonconformity rate of the object to be polished after polishing increases. For this reason, the spheroidal graphite cast iron described in Patent Document 1 has a problem that even if it is used for a polishing platen, it cannot properly polish the object to be polished due to its low proof stress ratio.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a polishing surface plate using spheroidal graphite cast iron, which can be easily manufactured and can improve properties suitable for polishing an object to be polished.

In order to solve the above problems, the polishing surface plate using spheroidal graphite cast iron according to the first invention contains 3.5 to 4.0% by mass of C, 2.2 to 2.5% by mass of Si, and 2.2 to 2.5% by mass of Mn. 0.60 to 0.75% by mass, 0.025% by mass or less of P, 0.02% by mass or less of S, 0.03 to 0.07% by mass of Mg, Cr, Cu, a graphite nucleating element, and , and other unavoidable impurities, and a polishing surface plate using spheroidal graphite cast iron with the balance being Fe,
The spheroidal graphite cast iron is
Cr contained is 0.18 to 0.23% by mass,
Cu content is 1.5 to 2.0% by mass.

In order to solve the above problems, a polishing surface plate using spheroidal graphite cast iron according to the second invention contains 3.5 to 4.0% by mass of C, 2.2 to 2.5% by mass of Si, and Mn. 0.60 to 0.75% by mass, 0.025% by mass or less of P, 0.02% by mass or less of S, 0.03 to 0.07% by mass of Mg, Cr, Cu, a graphite nucleating element, and , and other unavoidable impurities, and a polishing surface plate using spheroidal graphite cast iron with the balance being Fe,
The spheroidal graphite cast iron is
Cr contained is 0.21 to 0.23% by mass,
Cu content is 1.5 to 2.0% by mass.

The polishing surface plate using the spheroidal graphite cast iron has a high yield strength ratio and does not contain carbides that may damage the object to be polished. can.

4 shows a microphotograph of spheroidal graphite cast iron according to Comparative Example 5. FIG. 1 shows a microphotograph of spheroidal graphite cast iron according to Example 2 of the present invention.

A polishing surface plate using spheroidal graphite cast iron according to an embodiment of the present invention will be described below. First, the components of the spheroidal graphite cast iron used for the polishing platen will be described.

This spheroidal graphite cast iron contains 3.5 to 4.0% by mass of C (carbon), 2.2 to 2.5% by mass of Si (silicon), and 0.60 to 0.75% by mass of Mn (manganese). , P (phosphorus) 0.025% by mass or less, S (sulfur) 0.02% by mass or less, Mg (magnesium) 0.03 to 0.07% by mass, Cr (chromium) and Cu (copper) contains. The spheroidal graphite cast iron also contains graphite nucleation elements and other unavoidable impurities, and the balance consists of Fe (iron) and the like. Here, the graphite nucleating element is, for example, Ca (calcium), RE (rare earth), and/or Al (aluminum). In addition, when Si functions as a graphite nucleation element, a separate graphite nucleation element is not required. Graphite nucleation elements include not only elements for generating graphite nuclei, but also elements related to the generation of graphite nuclei, such as promoting the generation of graphite nuclei.

In particular, the spheroidal graphite cast iron is characterized by containing 0.18 to 0.23 mass % of Cr and containing 1.5 to 2.0 mass % of Cu. Further, the spheroidal graphite cast iron is preferably an as-cast material.

Next, the reason why the spheroidal graphite cast iron is set to the above composition range will be explained.

The respective ranges of C and Si contents were determined so that the CE value (C+Si/3) was 4.23 to 4.83. This is because there is a strong correlation between the CE value and the mechanical strength, and high mechanical strength is ensured while ensuring the graphite spheroidization ratio (90% or more) necessary for a polishing surface plate.

Regarding the content of Mn, the lower limit is set to 0.60% by mass in order to fix S to render it harmless, to stabilize the presence of pearlite, and to improve the strength of pearlite. On the other hand, if the Mn content is too high, massive carbides are formed that may damage the object to be polished during polishing, so the upper limit was made 0.75% by mass.

The content of P and S is not particularly limited because P and S are each one of inevitable impurities, but as an example, P is 0.025% by mass or less and S is 0.02 % by mass or less.

Regarding the content of Mg, the lower limit was set to 0.03% by mass in order to prevent poor spheroidization of graphite. On the other hand, if the Mg content is too high, the amount of inclusions produced increases as the Mg content increases, and the mechanical properties deteriorate, so the upper limit was made 0.07% by mass. As a method for adding Mg to the spheroidal graphite cast iron, there is, for example, addition using a spheroidizing agent, which will be described later.

Regarding the Cr content, in order to improve the yield strength ratio (the value obtained by dividing the 0.2% yield strength by the tensile strength), which is an index of the resistance to deformation, the 0.2% yield strength is specifically improved. The lower limit was made 0.18% by mass. On the other hand, if the Cr content is too high, massive carbides are formed that may damage the object to be polished during polishing, so the upper limit was made 0.23% by mass. In particular, when the Cr content is 0.21% by mass or more, the proof stress ratio is 0.65 or more, as shown in Table 1 below by comparing Examples 1 to 3 with Comparative Examples 1 to 6. Therefore, it is more preferable. That is, a more preferable Cr content is 0.21% by mass to 0.23% by mass.

Regarding the Cu content, in order to improve the yield strength ratio (the value obtained by dividing the 0.2% yield strength by the tensile strength), which is an index of the resistance to deformation, the 0.2% yield strength is specifically improved. The lower limit was set to 1.5% by mass. On the other hand, even if the content of Cu is increased, the tensile strength does not increase, and from the viewpoint of cost effectiveness for improving the yield strength ratio, the upper limit was set to 2.0% by mass.

The polishing surface plate using the spheroidal graphite cast iron according to the present embodiment may be a polishing surface plate made of the spheroidal graphite cast iron, or may be a polishing surface plate obtained by adding other members to the spheroidal graphite cast iron. When the polishing surface plate using spheroidal graphite cast iron according to the present embodiment is a polishing surface plate in which other members are added to the spheroidal graphite cast iron, at least the surface for polishing the object to be polished is made of the spheroidal graphite cast iron.

A method of manufacturing a polishing surface plate using the spheroidal graphite cast iron will be described below.

First, after the molten metal is transferred from the melting furnace to a ladle, a spheroidizing agent containing a graphite nucleation element and an inoculant are added to the molten metal in the ladle by, for example, a sandwich method. Among the elements contained in the spheroidizing agent and/or the inoculant, elements other than elements related to spheroidization (spheroidizing elements), elements related to the generation of graphite nuclei (graphite nucleation elements), and Fe are unavoidable impurities.

In this way, the molten metal adjusted to the above range of components is poured from the ladle into the mold of the polishing platen. After casting, no heat treatment is performed, that is, the cast iron is left as cast to manufacture a polishing surface plate using the spheroidal graphite cast iron. In addition, you may heat-process after casting.

Examples 1 to 3 specifically showing the components of the spheroidal graphite cast iron and Comparative Examples 1 to 6 thereof will be described below based on Table 1 below.

The spheroidal graphite cast irons according to Examples 1 to 3 contain elements that satisfy the component range according to the present invention, and the spheroidal graphite cast irons according to Comparative Examples 1 to 6 contain elements that correspond to the present invention. It does not satisfy the component range. These spheroidal graphite cast irons were all manufactured by the manufacturing method described in the above embodiment. The mechanical properties of the manufactured spheroidal graphite cast iron were investigated using a Y-shaped specimen (corresponding to JIS G 5502B). Also, a cylindrical block (φ300×100 mm) of spheroidal graphite cast iron with a chill installed was produced, and the microstructure of the cylindrical block near the chill was observed.

As is clear from Table 1, the yield strength ratio, which is the value obtained by dividing the 0.2% yield strength by the tensile strength, was greater in Examples 1-3 than in Comparative Examples 1-4. In particular, in Examples 1 to 3 in which the Cr content was 0.21% by mass or more, the yield strength ratio was 0.65 or more.

In Comparative Examples 5 and 6, a yield strength ratio of 0.65 or more was also obtained, but since the Cr content exceeded the composition range according to the present invention, massive carbides were generated in the spheroidal graphite cast iron. In FIG. 1, which is a photograph of the microstructure of the spheroidal graphite cast iron according to Comparative Example 5, massive carbides C1 to C9 can be clearly seen at nine locations. In contrast, no massive carbide is observed in FIG. 2, which is a photograph of the microstructure of the spheroidal graphite cast iron according to Example 2.

As described above, according to the polishing surface plate using the spheroidal graphite cast iron according to the above-described embodiments and examples, since the proof stress ratio is high and there is no carbide that may damage the object to be polished, it can be easily manufactured and can be polished. Properties suitable for polishing objects can be improved.

In addition, since the Cr content in the spheroidal graphite cast iron is 0.21% by mass to 0.23% by mass, the proof stress ratio is as high as 0.65 or more, so it can be easily manufactured and can be used for polishing objects to be polished. It is possible to further improve the properties suitable for

Furthermore, since the tensile strength of the spheroidal graphite cast irons according to Examples 1 to 3 is all 800 MPa or more, both the yield strength ratio (value obtained by dividing the 0.2% yield strength by the tensile strength) and the tensile strength can be higher.

By the way, the above embodiment is an example in all respects and is not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. Of the configurations described in the above embodiments, the configuration other than the configuration described as the first or second invention in "Means for Solving the Problems" is an arbitrary configuration, and can be deleted and changed as appropriate. is.

C1-C9 massive carbide

Claims (2)

3.5 to 4.0% by mass of C, 2.2 to 2.5% by mass of Si, 0.60 to 0.75% by mass of Mn, 0.025% by mass or less of P, and 0.02% of S A polishing surface plate using spheroidal graphite cast iron containing 0.03 to 0.07% by mass of Mg, Cr, Cu, graphite nucleation elements, and other unavoidable impurities, and the balance being Fe. There is
The spheroidal graphite cast iron is
Cr contained is 0.18 to 0.23% by mass,
A polishing surface plate using spheroidal graphite cast iron containing 1.5 to 2.0% by mass of Cu. 3.5 to 4.0% by mass of C, 2.2 to 2.5% by mass of Si, 0.60 to 0.75% by mass of Mn, 0.025% by mass or less of P, and 0.02% of S A polishing surface plate using spheroidal graphite cast iron containing 0.03 to 0.07% by mass of Mg, Cr, Cu, graphite nucleation elements, and other unavoidable impurities, and the balance being Fe. There is
The spheroidal graphite cast iron is
Cr contained is 0.21 to 0.23% by mass,
A polishing surface plate using spheroidal graphite cast iron containing 1.5 to 2.0% by mass of Cu.

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