WO2022176237A1

WO2022176237A1 - Flake graphite cast-iron product and method for manufacturing same

Info

Publication number: WO2022176237A1
Application number: PCT/JP2021/030544
Authority: WO
Inventors: 亮輔藤本; 俊明小関
Original assignee: 芝浦機械株式会社
Priority date: 2021-02-16
Filing date: 2021-08-20
Publication date: 2022-08-25
Also published as: CN115516123A; JP2022124625A; JP7278316B2

Abstract

A flake graphite cast-iron product satisfies the inequalities: 2.7 ≤ C ≤ 3.5, 1.2 ≤ Si ≤ 1.7 and CE ≤ -0.33×Si+4.36 wherein C and Si respectively represent the amounts (% by mass) of carbon and silicon contained therein and the carbon equivalent (% by mass) is calculated in accordance with the equation: CE = C+1/3×Si.

Description

Flaky graphite cast iron product and its manufacturing method

The present disclosure relates to flake graphite cast iron products and manufacturing methods thereof. In general, cast iron may refer to castings or may refer to materials for castings. The same applies to the present disclosure. In addition, in the present disclosure, the term cast iron products may be used for castings.

　Flake graphite cast iron products are formed by cooling molten metal (molten cast iron) in a mold and solidifying it. At this time, shrinkage cavities (spaces) may be formed in the casting due to solidification shrinkage. Methods for reducing shrinkage cavities include, for example, increasing the amount of graphite that crystallizes when cast iron is cooled, and placing a chill in places where shrinkage cavities are likely to occur in the mold (e.g., thick parts). There are known methods for uniforming the cooling temperature. Patent Document 1 below discloses a technique for reducing the occurrence of shrinkage cavities while achieving high rigidity by, for example, setting the carbon equivalent (CE) value within a predetermined range in spheroidal graphite cast iron.

JP-A-2000-17372

If a large amount of graphite is crystallized to reduce shrinkage cavities, the mechanical properties (eg tensile strength) of the casting will decrease. Further, when using a chill, for example, if the shape of the casting is complicated, it is difficult to identify the position of the shrinkage cavities. As a result, it is difficult to set the arrangement position of the chill. Larger castings also increase the number of chills and/or increase the volume of the chills. As a result, man-hours, purchase costs, and management costs increase. Therefore, a flake graphite cast iron product capable of improving shrinkage while ensuring certain mechanical properties and a method for producing the same are awaited.

In the flake graphite cast iron product according to the present disclosure, the mass% of carbon and silicon contained is represented by C and Si, respectively, and the carbon equivalent (mass%) is expressed by the following formula CE = C + 1/3 × Si
When calculating with the following inequality,
2.7≦C≦3.5,
1.2≦Si≦1.7, and CE≦−0.33×Si+4.36
meet.

A method for producing a flake graphite cast iron product according to the present disclosure is a method for producing a flake graphite cast iron product by cooling and solidifying molten cast iron that has been melted in a furnace in a mold, wherein the cast iron is The mass% of carbon and silicon contained is represented by C and Si, respectively, and the carbon equivalent is expressed by the following formula CE = C + 1/3 × Si
When calculating with, the molten metal in the furnace is the following inequality,
2.7≦C≦3.5,
1.2≦Si≦1.7, and CE≦−0.33×Si+4.36
meet.

According to the above configuration or procedure, it is possible to improve shrinkage while ensuring certain mechanical properties.

A flow chart showing the procedure of a casting method. Sectional drawing which shows a part of casting_mold|template. 4 is a chart showing characteristics of Examples and Comparative Examples; FIG. 4 is a diagram showing carbon and silicon contents in Examples and Comparative Examples;

(Overview of casting method)
The casting method according to the present embodiment (in other words, the method for producing a flake graphite cast iron product) may take various forms except for the composition of the cast iron and the composition of the inoculant. and/or may be similar to conventional casting methods. An outline of an example of the casting method will be described below.

FIG. 1 is a flow chart showing an example of the procedure of the casting method according to this embodiment.

In step ST1, various raw materials that will become cast iron are melted in a furnace to produce molten metal. In step ST2, the molten metal in the furnace is conveyed by the ladle. In step ST3, molten metal is poured from the ladle into the mold. In step ST4, the molten metal is cooled and solidified within the mold. This forms a flake graphite cast iron product.

Inoculation may be performed for various purposes at an appropriate time in the above series of procedures. The illustrated example shows inoculation performed in a ladle (step ST5) and inoculation performed after pouring (step ST6). In the present disclosure, the former may be referred to as primary inoculation and the latter as secondary inoculation. Of course, one or both of these inoculations may not be performed. Just to make sure, "after pouring" includes not only after pouring but also during pouring.

The equipment configuration and procedure in each step may be known and/or common. For example, furnace configurations, ladle configurations, and mold configurations may be of various known and/or conventional types. In the production of relatively small castings, the furnace and ladle may be replaced by a crucible used for both melting and transport. The temperature of the molten metal in the furnace and the cooling rate of the molten metal in the mold may also be set appropriately. The cooling of the molten metal may be performed only by allowing the heat of the mold to be taken away by the atmosphere, or may be performed by supplying a coolant (for example, normal temperature water) into the mold at appropriate times.

FIG. 2 is a schematic cross-sectional view showing part of an example of the mold 1. FIG.

The mold 1 is a so-called sand mold, and has, for example, a frame (not shown) and a sand part 3 arranged in the frame. Furthermore, in the illustrated example, the mold 1 has

chills

5A and 5B. Inside the mold 1, a casting part 7, which is a space filled with molten metal, is formed by a sand part 3 (

further chills

5A and 5B in the illustrated example). It should be noted that the mold 1 may be any other type of mold such as a metal mold. Also, the chillers 5A and/or 5B may not be provided.

In the mold 1, a frame (not shown) is made of metal or wood, for example. The sand portion 3 is made of, for example, sand and a binder that binds the sand. Sand is, for example, silica sand. Binders are, for example, resins, clays or water glass. The

chills

5A and 5B are made of a material having a higher thermal conductivity than the sand portion 3 (in other words, the main material of the mold 1). Such materials include, for example, steel and carbon. In addition, as understood from the example of carbon, the material of the chill is not limited to metal.

(casting)
The size and shape of the casting part 7 (in other words, casting) are not particularly limited. However, since the cast iron according to the present embodiment improves shrinkage due to its composition (described later), it is particularly useful for castings having thick-walled portions where shrinkage cavities are likely to occur. In addition, for example, the number and / or volume of the chills can be reduced by improving the shrinkage based on the composition, so it is particularly useful for large castings, and it is difficult to set the arrangement of the chills. It is highly useful even for castings with complex shapes.

As a shape having a thick-walled portion, for example, a plate-like portion (see the plate-corresponding portion 7a of the casting portion 7) and a rib rising from one of the front and back surfaces of the plate-like portion (the rib-corresponding portion 7b of the casting portion 7). see). In this shape, since it can be said that the thickness of the plate-like portion becomes thicker at the position of the rib to form a thick portion, shrinkage cavities are likely to occur at that position. A casting having such a shape can be, for example, a machine tool table.

Examples of large castings include those with a maximum length of 1m or more, 3m or more, or 5m or more, and/or those with a mass of 1000kg or more, 3000kg or more, or 5000kg or more. Examples of such large castings include the table of a machine tool.

The susceptibility to shrinkage cavities is expressed by various parameters. Therefore, the cast iron according to the present embodiment is a casting in which the value of a predetermined parameter is within a predetermined range in the cast iron in the mold 1 (more precisely, in the casting part 7) (from another point of view, the casting method ) can be said to be particularly useful for

Niiyama parameter G/R ^1/2 ((° C.×min) ^1/2 /cm) can be mentioned as such a parameter (hereinafter, the unit of G/R ^1/2 is the same). Here, G (°C/cm) is the temperature gradient. R (°C/min) is the cooling rate. The smaller the G/R ^1/2 , the more likely shrinkage cavities are formed. For example, when the cast iron is cooled (step ST4), the cast iron in the casting part 7 may have a portion (position or point from another point of view) where G / R ^1/2 is 0.4 or less. .

In determining whether or not G/R ^1/2 is 0.4 or less, the second decimal place may be rounded off. That is, the range of 0.4 or less includes 0.44 and does not include 0.45. The portion where G/R ^1/2 is 0.4 or less may occur at any time (time point) during the cooling period of the cast iron. The method of calculating G / R ^1/2 (including procedures and condition settings, etc.) may be appropriate. It may be set in various aspects to be less than 0.05 or 0.01 or less.

(Position of chiller)
When a chill is arranged, the arrangement position may be set appropriately. For example, the chill may be in contact with a local portion of the casting where shrinkage cavities are relatively likely to occur, or may be in contact with the casting as a whole. In the example of FIG. 2, the chill 5A contacts substantially the entire surface of the plate-like portion (see the plate corresponding portion 7a) of the casting on the opposite side of the rib (see the rib corresponding portion 7b). Also, the chill 5B abuts on corners (that is, local parts) formed by the plate-shaped part of the casting and the ribs.

As described above, the composition of the cast iron according to the present embodiment improves the shrinkage property, so the number and/or volume of the chills can be reduced compared to the conventional ones. Whether or not the chill has been reduced may be determined, for example, using the Niiyama parameter G/R ^1/2 described above when the cast iron is being cooled in the mold 1 .

Specifically, for example, as described above, when the cast iron in the mold 1 has a portion having a period in which G / R ^1/2 is 0.4 or less, shrinkage cavities are likely to occur. . In such cases, when no chill is provided, it may be determined that the chill is reduced.

Further, in the case where a chill is provided, it may be determined that the chill is reduced when, for example, the following first portion exists. The cast iron inside the mold 1 (strictly speaking, inside the casting part 7) has a first part (the volume and the like can be set arbitrarily). No chill is provided on the part of the inner surface of the mold that is located at the shortest distance from the first part. The first part has a period during which G/R ^1/2 is 1.0 or less or 0.4 or less.

In the case where the first portion as described above exists, the portion provided with the chill may be the second portion as described below. The cast iron inside the mold 1 (strictly speaking, inside the casting part 7) has a second part (the volume and the like can be set arbitrarily). A chill is provided on the part of the inner surface of the mold that is located at the shortest distance from the second part. The second portion has a period of time during which G/R ^1/2 is less than or equal to 0.01 assuming no chill is provided. Note that the first portion may be a portion that does not have a period in which G/R ^1/2 is 0.01 or less.

In determining whether or not G/R ^1/2 is 0.01 or less, the third decimal place may be rounded off. That is, 0.014 is less than or equal to 0.01 and 0.015 is greater than 0.01. Similarly, in determining whether G/R ^1/2 is less than or equal to 1.0 or less than or equal to 0.4, two decimal places may be rounded off. As described above, the method of calculating G/R ^1/2 (including procedures and condition settings, etc.) may be appropriate, for example, when it contributes to the determination of whether or not may have various modes in which the error is less than 0.005 or 0.001 or less.

(Composition of cast iron)
The composition and the like of the flake graphite cast iron according to the present embodiment will be described below. In addition, in the following description, mass % (wt%) of components of cast iron may be indicated by element symbols. For example, the weight percent of carbon may be represented by C and the weight percent of silicon by Si.

Cast iron is generally considered to be a ternary alloy of iron (Fe) containing 2.14% by mass or more and 6.67% by mass or less of carbon (C) and containing approximately 1% by mass or more and 3% by mass or less of silicon (Si). there is Here, the carbon equivalent CE (% by mass) shall be calculated by the following formula (1).
CE = C + 1/3 x Si (1)

At this time, the flake graphite cast iron according to the present embodiment satisfies the following inequality.
2.7≤C≤3.5
1.2≤Si≤1.7
CE≦−0.33×Si+4.36 (2)

By specifying the upper limits of C, Si and CE as described above, the probability of graphite coarsening is reduced, and certain mechanical properties can be secured. On the other hand, by specifying the lower limits of C and Si as described above, the amount of crystallization of graphite can be increased. As a result, shrinkage cavities can be reduced.

In the above, digits smaller than the digits indicated by the value may be rounded off. For example, 2.65 may fall within the range of 2.7 or greater, and 3.54 may fall within the range of 3.5 or less. The value of CE may be rounded to three decimal places. The same applies to other inequalities and the like shown below.

The certain mechanical properties mentioned above may be assumed as appropriate. For example, the mechanical properties of FC300 defined by JIS (Japanese Industrial Standards) and ISO (International Organization for Standardization) or similar mechanical properties may be assumed. FC300 has a tensile strength (hereinafter sometimes abbreviated as TS) greater than 300 MPa. Also, the Brinell hardness (hereinafter sometimes abbreviated as HB) is less than 262HB.

The flake graphite cast iron according to the present embodiment may further contain manganese (Mn) and/or tin (Sn). In this case, the mass % of these components may be within the following ranges.
0.90≦Mn≦1.00
0.02≦Sn≦0.05

Compared to other materials, Mn and Sn have a small effect of inhibiting graphitization during the eutectic reaction where the amount of solidification shrinkage is the largest. On the other hand, Mn and Sn have a greater effect of promoting pearlitization during the eutectoid reaction than other materials. By promoting the pearlitization of Mn and/or Sn, for example, the matrix structure can be entirely pearlitic and the tensile strength can be improved. If the mass % of Mn and/or Sn is at least the above lower limit, for example, a pearlitizing effect can be obtained. Further, when the mass % of Mn and/or Sn is equal to or less than the above upper limit, for example, the embrittlement effect is suppressed, and it is easy to ensure mechanical properties.

In general, Mn and Sn are not added to cast iron because they inhibit graphite crystallization. In particular, since spheroidal graphite cast iron requires ductility, the mass % of Mn is made as low as possible so as not to inhibit the decomposition of compound carbon during annealing.

The mass % mentioned above may be calculated, for example, from the mass of various materials melted in the furnace, or may be calculated by analyzing the casting taken out from the mold. Cast iron is inoculated so that the component ratio in the furnace differs from the component ratio in the mold. However, in general, the weight percent of inoculant is small (eg, 1% or less, or 0.5% or less). Therefore, although it depends on the materials contained in the inoculant, the effect on the range of mass % described above is relatively small.

Cast iron may contain minute amounts of components other than the above. The component may be intentionally added aiming at a predetermined effect, or may be included unavoidably (unwanted). The weight percent of such other components (including inoculant) is, for example, 2% or less, 1% or less, or 0.5% or less in total.

The cast iron according to the present embodiment is flake graphite cast iron in which the shape of the graphite is flake (plate-like). From another point of view, in the method for producing cast iron according to the present embodiment, a specific treatment (for example, addition of Mg) for making graphite spherical is not performed. Specific aspects such as the shape of flake graphite may be appropriately selected. For example, the flake graphite cast iron may be any of A-type to E-type defined by ASTM, and for example, the majority (for example, 80% or more of an arbitrary cross section) is A-type.

(Primary inoculation)
As already mentioned, in this embodiment, primary inoculation, inoculating in a ladle, may be performed. The inoculation method may take various forms. For example, inoculation may be by placing the inoculant in the bottom of the ladle before the molten metal is poured, or by adding the inoculant to the surface of the molten metal in the ladle. Alternatively, a wire on which an inoculant is placed may be brought into contact with the molten metal in the ladle or the molten metal being poured into the ladle.

The material of the inoculant (the purpose from another point of view) is also arbitrary. Examples of materials for the inoculant include Fe--Si, Ca--Si, Si--Zr and Fe--Cr. The amount to be added is, for example, 0.1% by mass or more and 0.5% by mass or less with respect to the mass of the molten metal before addition, depending on the type of inoculant.

For example, when an inoculant is referred to as an Fe—Si system, it means that Fe and Si constitute the main components of the inoculant. The main component may be, for example, 50% by mass or more, 60% by mass or more, or 80% by mass or more of the inoculant. Thus, for example, in an Fe—Si based inoculant, the total weight of Fe and Si accounts for 50% or more, 60% or more, or 80% or more by weight of the inoculant.

As described above, the material and the amount of the inoculant added in the primary inoculation are arbitrary, but for example, 0.4% by mass or more and 0.6% by mass or less of the Fe—Si-based inoculant is inoculated with respect to the mass of the molten metal. may be performed. Specific examples of Fe—Si-based inoculants include 50% by mass of Si, 10% by mass of Ca, 5% by mass of Ba, and the rest of Fe by mass with respect to 100% by mass of the inoculant. can be used.

(secondary inoculation)
As described above, in the present embodiment, secondary inoculation may be performed after the hot water is poured. This method of inoculation may vary. For example, inoculation may be by adding an inoculant to the molten metal being poured into the mould, or by touching a wire with an inoculant placed thereon to the molten metal being poured into the mould. Alternatively, the inoculant may be placed in a pool or mold before the molten metal is poured. The material and addition amount of the inoculant are also arbitrary, and the above description of the primary inoculation may be used for these.

As described above, the material and amount of the inoculant in the secondary inoculation are arbitrary. Inoculation may be performed. As the Fe—Si based inoculant, for example, those exemplified in the explanation of the primary inoculation above may be used.

In this embodiment, the Si content in the molten metal in the furnace is 1.7% by mass or less as described above, which is relatively small. Then, when an Fe—Si based inoculant is used in secondary inoculation (and/or primary inoculation), the amount of crystallized graphite can be increased while ultimately reducing the amount of Si contained in cast iron. On the other hand, in such cast iron with an increased amount of graphite crystallized out, it is possible to refine the structure with an Fe—Si based inoculant to improve shrinkage and strength. The above effect is further improved in a structure that is pearliticized by adding Sn.

(Example)
A flake graphite cast iron having the composition described above was actually produced, and its mechanical properties (TS and HB) were investigated. The results are shown below.

FIG. 3 is a chart showing the composition and mechanical properties of flake graphite cast iron according to Examples and Comparative Examples.

In this figure, the "No." column indicates the serial numbers assigned to the examples and comparative examples. No. 1 to No. 7 and no. 9 is a comparative example. No. 8 and no. 10 to No. 17 is an example.

The columns of "C (wt%)", "Si (wt%)", "Mn (wt%)" and "Sn (wt%)" respectively indicate flake graphite cast iron (100 % by mass) of C, Si, Mn and Sn. Although not shown, Fe essentially (ignoring unintended minor constituents) makes up the remaining weight percent. It should be noted that the mass % here is obtained from the mass ratio of these materials supplied to the furnace, and the effects of inoculation and the like are excluded.

The column "CE (wt%)" is the value of CE (mass%) calculated by substituting the values in the "C (wt%)" and "Si (wt%)" columns into the above formula (1). is shown. The column of "CE_L (wt%)" is CE (mass%) calculated by substituting the values in the "C (wt%)" and "Si (wt%)" columns into the right side of the above formula (2). indicates the upper limit of

The "TS (MPa)" column indicates tensile strength. The "HB" column indicates the Brinell hardness (no units). All values are values obtained by experiments. "Eval." indicates the evaluation results for TS and HB. Here, when the conditions of FC300, TS>300 MPa and HB<262, were satisfied, "A" was given, and otherwise, "B" was given.

In the examples and comparative examples, primary and secondary inoculations are performed. In the primary inoculation, 0.5% of the Fe-50%Si-10%Ca-5%Ba inoculant described above was added in a ladle. In the secondary inoculation, 0.1% of the aforementioned inoculant of Fe-50% Si-10% Ca-5% Ba was added by a weir.

FIG. 4 is a diagram showing mass % of Si and C in the examples and comparative examples shown in FIG.

In this figure, the horizontal axis indicates the mass % of Si. The vertical axis indicates the mass % of C. The minimum and maximum values on each axis generally match the minimum and maximum mass% values of Si and C in general cast iron.

In the upper right of the figure, a legend for the points or lines shown in the figure is shown. The "EX" points correspond to examples. The "REF" point corresponds to the comparative example. The "EQ" line shows the relationship between C and Si when the left side and right side of the above-described equation (2) are the same (when CE is the upper limit). Expression (2) is satisfied in the lower left region of the "EQ" line.

In the figure, there are also lines indicating the lower limit (2.7) and upper limit (3.5) of C (mass%), and lines indicating the lower limit (1.2) and upper limit (1.7) of Si (mass%). It is shown. In addition, hatching indicates a range that satisfies the conditions for C, Si, and CE in this embodiment.

In addition, in FIG. 4, the values of C (mass %) and Si (mass %) shown in FIG. On the other hand, the ranges of C and Si are defined by values up to the first decimal place. As a result, around Si=1.2, No. The points corresponding to 16 (example) are located outside the hatched area (area indicating the example).

As shown in FIG. 3, all examples are rated A. On the other hand, all the comparative examples are rated B. As shown in FIG. 4, the examples and the comparative examples are concentrated near the "EQ" line, and are divided into the lower left and upper right parts of the figure with the "EQ" line as a boundary. ing. From the above, it was confirmed that by setting CE so as to satisfy the formula (2), the CE (% by mass) can be maximized while ensuring the mechanical properties of FC300 or properties close thereto. By maximizing the CE, it is possible to increase the amount of graphite crystallized and improve shrinkage.

In FIG. 3, No. No. 16 is an example with less Sn than other examples. No. No. 14 has C and Si conditions. It is an embodiment close to 16. From the comparison of both TS, it can be confirmed that the addition of Sn improves the tensile strength.

From the examples shown in FIGS. 3 and 4, it is possible to extract a range narrower than the mass % range described in the embodiment as follows.

For example, as the lower limit of C (% by mass), 2.9 (No. 17), which is the lowest C value in the examples, can be extracted. As the upper limit of C (% by mass), 3.4 (No. 8), which is the highest C value in the examples, can be extracted. As the upper limit of Si (% by mass), 1.5 (No. 10), which is the lowest Si value in the examples, can be extracted.

In the embodiment, the lower limit of CE was not directly mentioned, and the lower limit of CE was indirectly defined by the lower limit of C and the lower limit of Si. However, for example, the lower limit of CE may be defined by a line parallel to the "EQ" line and away from the "EQ" line.

More specifically, for example, the lower limit may be a line passing through the example (No. 17) farthest from the "EQ" line among the examples. In this case, the following inequality may be satisfied.
CE≧−0.33×Si+3.83

Also, for example, assuming that the CE is as close to the "EQ" line as possible, the No. No. 13 or CE of 3.83. With the line through 15 as a lower bound, the following inequality may be satisfied.
CE≧−0.33×Si+4.15, or CE≧−0.33×Si+4.27
Note that the former inequality is No. In addition to No. 13, No. 8, No. 10 to No. 12 and no. 15 is filled. The latter inequality is given by No. In addition to No. 15, No. 8 and no. 10 to No. 12 is filled.

(improvement of shrinkage)
A flake graphite cast iron product according to the embodiment was actually produced and evaluated for shrinkage. Specifically, it is as follows.

A machine tool table was produced from flake graphite cast iron according to the embodiment. The shape of the table, as described with reference to FIG. 2, is generally a shape having a plate-like portion and ribs rising from the plate-like portion. The mass of the table was 3800 kg. A cross-section at the intersection of the plate-shaped portion and the rib was imaged, and the area of the shrinkage cavities in the cross-section was measured by image processing. As a result, the area of the shrinkage cavities was 4990 mm ² in the known general composition. On the other hand, in the composition according to this embodiment, the shrinkage cavities were 1500 mm ² . That is, shrinkage cavities were reduced by 70%.

As described above, in the flake graphite cast iron product according to the present embodiment, the mass% of carbon and silicon contained is represented by C and Si, respectively, and the carbon equivalent (mass%) is calculated by the above-described formula (1) ,
The following inequality,
2.7≦C≦3.5,
1.2≦Si≦1.7, and CE≦−0.33×Si+4.36
meet.

From another point of view, the method for manufacturing a flake graphite cast iron product according to the present embodiment is a method for manufacturing a flake graphite cast iron product by cooling and solidifying molten cast iron that has been melted in a furnace in a mold. and the molten metal in the furnace satisfies the above inequality.

As already mentioned, this makes it possible to increase the amount of graphite crystallized and improve shrinkage while ensuring certain mechanical properties.

1...Mold, 3...Sand section, 5A and 5B...Chill, 7...Casting section.

Claims

The mass% of carbon and silicon contained is represented by C and Si, respectively,
The carbon equivalent (mass%) is given by the following formula CE = C + 1/3 x Si
When calculating with
The following inequality,
2.7≦C≦3.5,
1.2≦Si≦1.7, and CE≦−0.33×Si+4.36
satisfy the
Flaky graphite cast iron products.
When the mass% of manganese contained is represented by Mn, the following inequality 0.90 ≤ Mn ≤ 1.00
satisfy the
The flake graphite cast iron product according to claim 1.
When the mass% of tin contained is represented by Sn, the following inequality 0.02 ≤ Sn ≤ 0.05
satisfy the
The flake graphite cast iron product according to claim 1 or 2.
The following inequality,
CE≧−0.33×Si+4.27
satisfy the
The flake graphite cast iron product according to any one of claims 1 to 3.
A method for producing a flake graphite cast iron product by cooling and solidifying molten cast iron that has been melted in a furnace in a mold, comprising:
The mass% of carbon and silicon contained in the cast iron is represented by C and Si, respectively,
The carbon equivalent is given by the following formula CE = C + 1/3 x Si
When calculating with
The molten metal in the furnace is determined by the following inequality:
2.7≦C≦3.5,
1.2≦Si≦1.7, and CE≦−0.33×Si+4.36
satisfy the
A method for producing flake graphite cast iron products.
The method for producing a flake graphite cast iron product according to claim 5, wherein an Fe—Si based inoculant is added to the molten metal in a ladle.
The method for producing a flake graphite cast iron product according to claim 5 or 6, wherein an Fe—Si based inoculant is added to the molten metal after the timing of pouring the molten metal into the mold.
When the temperature gradient and cooling rate when cooling the cast iron in the mold are represented by G (° C./cm) and R (° C./min), respectively, the cast iron in the mold has a Niiyama parameter G / R 1 /2 ((° C.×min) 1/2 /cm) is 0.4 or less.
The method for producing a flake graphite cast iron product according to claim 8, wherein the mold is not provided with a chill.
A chill is provided in the mold,
The cast iron in the mold has a first portion having a period in which G/R 1/2 is 1.0 or less,
9. The method of manufacturing a flake graphite cast iron product according to claim 8, wherein no chill is provided in a portion of the inner surface of the mold that is located at the shortest distance from the first portion.
The method for manufacturing a flake graphite cast iron product according to claim 10, wherein the first portion has a period in which G/R 1/2 is 0.4 or less.
said cast iron in said mold having a second portion;
A chill is provided on the part of the inner surface of the mold that is located at the shortest distance from the second part, and the second part is G / R when it is assumed that the chill is not provided. The method for producing a flake graphite cast iron product according to claim 10 or 11, having a period in which 1/2 is 0.01 or less.