JPH08209217A - Production of spherical graphite cast iron - Google Patents

Abstract

PURPOSE: To provide a process for producing a spherical graphite cast iron capable of preventing the chilling of the cast iron by sufficiently exhibiting its effect even near the surface of a casting mold without the generation of the inoculant remaining without melting. CONSTITUTION: This inoculant has the melting temp. lower than the melting temp. of the spherical graphite cast iron and is basically obtd. by using, for example, an Ni-Si alloy as the inoculant. The inoculant melts easily and rapidly in a casting process. While it takes time for the inoculation effect to be exhibited in the case where inoculant does not easily and rapidly melt, the inoculation effect is exhibited rapidly and, therefore, the generation of the inoculant remaining without melting does not arise even if the inoculant is added in the state of large size grains into the cast iron. The inoculant remaining without melting is lessened even if the inoculant is added into the casting mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing spheroidal graphite cast iron.

[0002]

2. Description of the Related Art As is well known, when casting spheroidal graphite cast iron, inoculation is carried out to improve the material quality of the casting obtained by adding a substance that forms crystal nuclei to the molten metal. It is possible to suppress the tendency of chilling and improve the graphite structure of the casting by adding, and ferrosilicon, calcium silicon, etc. are used in spheroidal graphite cast iron as the inoculant.

[0003]

However, the above-mentioned conventional method for producing spheroidal graphite cast iron has the following problems. Since the melting temperature of the inoculant used in the conventional method for producing spheroidal graphite cast iron is higher than the melting temperature of the spheroidal graphite cast iron, undissolved residue is inevitable, and when the undissolved residue is generated, particles of the inoculant are formed. Since it remains in the casting as it is, and the hardness of the portion increases significantly, there arises a problem that the portion cannot be processed. Further, particularly in the mold surface portion, since the cast iron molten metal is rapidly cooled, in the conventional inoculant having a melting temperature higher than that of the spheroidal graphite cast iron, the inoculant does not sufficiently function near the mold, There is a problem that chilling easily occurs on the surface portion.

Therefore, the present invention has been made in view of the above problems in the prior art, in which unmelted residue does not occur,
It is an object of the present invention to provide a method for producing spheroidal graphite cast iron, which is capable of sufficiently exerting the effect even in the vicinity of the surface of the mold and preventing the spheroidal graphite cast iron from being chilled.

[0005]

The method for producing spheroidal graphite cast iron of the present invention which achieves the above object is obtained by using an inoculant containing a graphitization promoting element and having a melting temperature lower than the melting temperature of spheroidal graphite cast iron. It is characterized in that graphite cast iron is cast. According to the method for producing a spheroidal graphite cast iron of the present invention as described above, since the inoculant having a melting temperature lower than the melting temperature of the spheroidal graphite cast iron is used, when an inoculant having a melting temperature higher than the melting temperature of the spheroidal graphite cast iron is used. Since it begins to dissolve at a lower temperature than that, the inoculation effect develops faster, and the inoculant dissolves at a lower temperature, so that the effect of preventing undissolved residue can be obtained.

Further, the method for producing spheroidal graphite cast iron of the present invention which achieves the above-mentioned object, is a spheroidal graphite in a mold coated with an inoculant containing a graphitization-promoting element and having a melting temperature lower than the melting temperature of spheroidal graphite cast iron. It is characterized by pouring molten cast iron. That is, as an aspect of adding the inoculant to the spheroidal graphite cast iron molten metal in the present invention, for example, if the spheroidal graphite cast iron molten metal is poured into a mold in which the inoculant is applied to the mold surface, the molten metal temperature becomes lower. However, since the inoculant melts at a low temperature, it is possible to prevent the undissolved residue from occurring, and it is possible to accelerate the onset of the inoculation effect.

The method for producing spheroidal graphite cast iron of the present invention is
Spheroidal graphite using an inoculant mixed or alloyed with an inoculant containing a graphitization-promoting element and having a melting temperature lower than that of spheroidal graphite cast iron and an inoculant having a melting temperature higher than that of spheroidal graphite cast iron. It is characterized in that cast iron is cast. Further, the method for producing the spheroidal graphite cast iron of the present invention, an inoculant having a melting temperature lower than the melting temperature of the spheroidal graphite cast iron containing the graphitization promoting element and an inoculant having a melting temperature higher than the melting temperature of the spheroidal graphite cast iron. It is characterized in that the spheroidal graphite cast iron melt is poured into a mold having a mixed or alloyed inoculant applied on the surface. An inoculant whose melting temperature is higher than that of spheroidal graphite cast iron usually causes unmelted residue, and when inoculated in a mold with a normal casting, it often melts when the casting becomes smaller. If such unmelted residue occurs, the particles of the inoculant remain as they are inside the casting, and the hardness increases extremely at that portion, which causes a problem that processing cannot be performed at that portion. On the other hand, with an inoculant having a melting temperature lower than that of spheroidal graphite cast iron, undissolved residue does not occur even when applied to a mold for use. However, on the other hand, inoculants whose melting temperature is lower than the melting temperature of spheroidal graphite cast iron do not cause undissolved residue, but it dissolves early, so it may be difficult to maintain the inoculation effect, and the inoculation as a whole may occur. The effect may be insufficient. Therefore, as in the present invention, by using an inoculant having a melting temperature lower than the melting temperature of the spheroidal graphite cast iron and an inoculant having a high temperature mixed or alloyed with each other, an inoculating effect while preventing undissolved inoculant is obtained. It can be continued to obtain a high inoculation effect as a whole.

Further, in the method for producing spheroidal graphite cast iron of the present invention, an inoculant containing a graphitization-promoting element and having a melting temperature lower than the melting temperature of spheroidal graphite cast iron is applied to the mold surface, and the melting temperature of spheroidal graphite cast iron is An inoculant having a temperature higher than the melting temperature is added to the molten metal. By doing so, the inoculant whose melting temperature is lower than the melting temperature of the spheroidal graphite cast iron does not cause unmelted residue when applied to the mold, while the melting temperature is higher than the melting temperature of the spheroidal graphite cast iron. By adding the inoculant as described above to the molten metal and using it, it is possible to prevent the undissolved part of the inoculant from remaining and to maintain the inoculating effect and obtain a high inoculating effect as a whole.

Further, the method for producing spheroidal graphite cast iron of the present invention is characterized in that the spheroidal graphite cast iron is cast using an inoculant containing a graphitization promoting element and containing Si and Ni as main components. In addition, the method for producing spheroidal graphite cast iron of the present invention is characterized in that the spheroidal graphite cast iron molten metal is poured into a mold having a surface coated with an inoculant containing graphitization-promoting elements and whose main components are Si and Ni. The eutectic temperature of the Ni-Si inoculant whose main components are Si and Ni is 993 ° C, and that of Fe-Si is 1270 ° C.
Lower. Therefore, when added to the melt, Fe-S
Since it begins to dissolve at a temperature lower than that of i, the inoculation effect develops quickly, and since it dissolves at a low temperature, undissolved residue can be prevented.

In addition, the method for producing spheroidal graphite cast iron of the present invention comprises a graphitization promoting element and the main components are Si and Ni.
It is characterized in that spheroidal graphite cast iron is cast using an inoculant containing less than wt% of Ba. In addition to the above, the method for producing spheroidal graphite cast iron of the present invention comprises the step of applying the spheroidal graphite cast iron molten metal to a mold coated with an inoculant containing graphitization-promoting elements as main components of Si and Ni and containing 3 wt% or less of Ba. It is characterized by pouring hot water. The reason why Ba is added in an amount of 3 wt% or less is that it is effective for maintaining the inoculation effect. In particular, the inoculation in which the melting temperature used in the method for producing spheroidal graphite cast iron of the present invention is lower than the melting temperature of spheroidal graphite cast iron. Agents such as Ni-
The Si-based inoculant is effective because the synergistic effect of the early dissolution of the inoculant and the sustained inoculation effect due to the addition of Ba is recognized.
Here, the addition amount of Ba is 3 wt% because the addition amount is 3 wt%.
This is because the effect of addition is not increased even if it exceeds.

The method for producing spheroidal graphite cast iron according to the present invention comprises an inoculant containing a graphitization-promoting element and having Si and Ni as main components, and an inoculant obtained by mixing or alloying an inoculant having Si and Fe as main components. It is characterized in that it is used to cast spheroidal graphite cast iron. Further, the method for producing spheroidal graphite cast iron of the present invention comprises applying an inoculant, which is a mixture or alloy of an inoculant containing graphitization-promoting elements and whose main components are Si and Ni, and an inoculant whose main components are Si and Fe, to the surface. It is characterized in that the spheroidal graphite cast iron molten metal is poured into the formed mold. That is, the main components are Fe and S
The inoculant i is usually unmelted, and when in-mold inoculation is performed with a normal casting, the casting often becomes smaller as the casting becomes smaller. If such unmelted residue occurs, the particles of the inoculant remain as they are inside the casting, and the hardness increases extremely at that portion, which causes a problem that processing cannot be performed at that portion. On the other hand, with the inoculants whose main components are Si and Ni, for example, even if they are applied to a mold and used, undissolved residue does not occur. On the other hand, on the other hand, the inoculants whose main components are Si and Ni do not cause undissolved residue, but they dissolve early so that it may be difficult to maintain the inoculation effect, resulting in insufficient inoculation effect as a whole. In some cases Therefore, as in the present invention, an inoculant whose main components are Si and Ni and a main component F
By mixing or alloying e and Si inoculants to produce spheroidal graphite cast iron, the inoculant is prevented from being undissolved and the inoculant effect is sustained to obtain a high inoculant effect as a whole. You can

In the above, the mixing or alloying ratio of the inoculants whose main components are Si and Ni and the inoculants whose main components are Si and Fe is preferably 1/3 to 3/1. Inoculants whose main components are Si and Ni and whose main components are Si and F
When the mixing ratio or alloying ratio with the inoculant which is e is less than 1/3, the undissolved residue of the inoculant becomes strong, which is not preferable. On the contrary, if the mixing or alloying ratio of the inoculants whose main components are Si and Ni and the inoculants whose main components are Si and Fe exceeds 3/1, the overall inoculation effect becomes insufficient. . When the inoculants having Si and Ni as the main components and the inoculants having Si and Fe as the main components are mixed and used in the above, it is possible to adopt a mode in which both powders are mixed.

Further, in the method for producing spheroidal graphite cast iron of the present invention, an inoculant containing graphitization-promoting elements and whose main components are Si and Ni is applied to the mold surface, and an inoculant whose main components are Si and Fe are melted. It is characterized by being added in. By doing so, the main component containing the graphitization promoting element is Si
With the inoculants of Ni and Ni, undissolved residue does not occur even when applied to a mold and used. On the other hand, by using the inoculants of which the main components are Si and Fe in the molten metal, the undissolved residue of the inoculants is It is possible to maintain the inoculation effect while preventing it and obtain a high inoculation effect as a whole.

In the above cases, the main components are Si and N.
It is preferable that the inoculant i is 3 wt% or less of Ba. Further, in each of the above cases, in the present invention, it is preferable that the Si content of the inoculants whose main components are Si and Ni is 50 to 80 wt%. That is, when Si is less than 50 wt%, the liquidus temperature in the phase diagram of the inoculant is lower than the melting temperature of the spheroidal graphite cast iron, the inoculation effect disappears very quickly, and the inoculation effect as a whole becomes low, which is preferable. Absent. Further, when Si exceeds 80 wt%, it becomes difficult to industrially manufacture.

[0015]

At present, Fe-Si is generally used as an inoculant in the production of spheroidal graphite cast iron. The method for producing spheroidal graphite cast iron of the present invention is based on the use of an inoculant having a melting temperature lower than the melting temperature of spheroidal graphite cast iron, such as a Ni-Si alloy, as an inoculant instead of Fe-Si. Thus, by the method for producing spheroidal graphite cast iron of the present invention, spheroidal graphite cast iron without chilling and having a uniform graphite spheroidization rate can be obtained. Looking at the phase diagrams of the Ni-Si alloy and the Fe-Si alloy, the eutectic temperature of the Fe-Si alloy is 1210.
˜1220 ° C., whereas the eutectic temperature of Ni—Si alloy is 950 to 990 ° C.
It can be seen that it melts more easily at a lower temperature than e-Si. At the same time, the Ni-Si alloy can contain the same amount of Si as compared with the Fe-Si alloy. Here, it is Si that exerts the inoculation effect in the inoculant, and if the amount of Si is the same, Fe-Si and Ni-Si exhibit the same inoculation effect. Moreover, as described above, Ni-Si
Since the alloy has a lower melting point than Fe-Si, it starts to work early. On the other hand, when the Ni-Si alloy and the Fe-Si are completely melted, the temperatures of both Fe-Si and Ni-Si are about the same, as shown by the liquidus lines in those phase diagrams.

From the above, Ni-Si begins to work from an early stage, and continues to work until the same period as Fe-Si. In the above, the melting temperature of spheroidal graphite cast iron is 11
When the temperature is 50 ° C. and 30Si—Ni is added, 30
The melting temperature of Si—Ni is 950 ° C., and it melts immediately and cannot be used as an inoculant. So Ni-S
It is added as an i alloy. As described above, the inoculant used in the method for producing the spheroidal graphite cast iron of the present invention is at a temperature lower than the melting temperature of the spheroidal graphite cast iron, so that the inoculant easily and quickly melts in the casting process, and the inoculant easily and quickly melts. If it is not present, it takes time for the inoculation effect to appear, but the inoculation effect appears in a short time. Therefore, even if the inoculant is put in large grains, the inoculant remains undissolved in the method for producing spheroidal graphite cast iron of the present invention. Does not occur. Even when it is placed in a mold, there is little undissolved residue.

Further, in the present invention, an inoculant having a melting temperature lower than that of spheroidal graphite cast iron, such as Ni-Si alloy, and an inoculant having a melting temperature lower than that of spheroidal graphite cast iron, such as Fe-Si. It is used as an inoculant by mixing with the inoculant of 1., but it is possible to reduce the cost by mixing the two in this way. It is also particularly effective when it is necessary to use an inoculant having an intermediate property between those of the Ni-Si alloy inoculant and the Fe-Si inoculant. That is, this is a case where the effect appears too quickly only with the Ni-Si alloy inoculant, and conversely the undissolved residue occurs only with the Fe-Si inoculant. Further, in the method for producing spheroidal graphite cast iron of the present invention, it is recognized that the number of graphite particles increases. That is, since the surface of the spheroidal graphite cast iron melt has a low temperature, for example, the surface of the mold has a low temperature, it cannot be melted by the Fe-Si inoculant. On the other hand, the inoculant used in the method for producing spheroidal graphite cast iron of the present invention, for example, the Ni-Si alloy inoculant, is Fe.
-Begin to melt from a very low temperature compared to inoculants such as Si. Therefore, to prevent chilling of the surface of the casting, an inoculant such as Ni used in the method for producing spheroidal graphite cast iron of the present invention is used.
-Si alloy inoculants are much more advantageous.

That is, the inoculant such as Fe-Si cannot sufficiently prevent chilling of the casting surface, whereas
In the method for producing spheroidal graphite cast iron of the present invention, an inoculant having a temperature lower than the melting temperature of spheroidal graphite cast iron, for example, an inoculant of Ni-Si alloy is used, so that surface chilling can be prevented. Along with that, in the method for producing spheroidal graphite cast iron of the present invention, an inoculant having a temperature lower than the melting temperature of spheroidal graphite cast iron, for example, an inoculant of Ni-Si alloy is used, so that the spheroidal graphite is used. The number of graphite particles increases when added to the cast iron melt.

[0019]

EXAMPLES Examples of the method for producing spheroidal graphite cast iron of the present invention will be described below. Example 1 Using the Ni-Si type inoculant of the components shown in Table 1, Ni-
The method for producing spheroidal graphite cast iron according to the present invention was carried out by inoculating a mold by making use of the characteristics of low temperature dissolution in a Si-based inoculant.
As shown in FIG. 1, the particle size is 0.1 in a partial region A of the mold 1.
A test piece obtained by pouring spheroidal graphite cast iron molten metal into the mold 1 without applying the inoculant to the other region B as a comparative example by applying a Ni-Si inoculant 2 of about 0.3 mm. The metallographic structure near the casting surface was investigated. As a result, Ni-S
In the area corresponding to the area A to which the i-type inoculant 2 was applied, the surface of the test piece was sufficiently spheroidized and no chill was observed, whereas the area B to which the inoculant was not applied was observed.
It was recognized that the region corresponding to was chilled. Further, in the area corresponding to the area A coated with the Ni-Si inoculant 2, not only the chill near the casting surface in the obtained cast iron has been eliminated, but also the case where the Fe-Si inoculant is used. Almost no unmelted residue was observed.

[0020]

[Table 1]

In the composition of the inoculant used in the above-mentioned examples, Al and Ca are generally contained in the inoculant in this amount, and they come from silica sand in the manufacturing process. On the other hand, Ba is intentionally added.

Example 2 A spheroidal graphite cast iron molten metal was cast using the mold of the casting method shown in FIG. In the casting method shown in FIG. 2, t1 is a 1 mm thick test piece mold, t2 is a 2 mm thick test piece mold, t3 is a 3 mm thick test piece mold, and t4 is a 4 mm thick test piece. It is a mold of. Upon casting, Ni-S having the composition shown in Table 1 above
The method for producing spheroidal graphite cast iron of the present invention was carried out by inoculation with a coating type using an i-type inoculant. As a comparative example, the conventional F
Mold casting was performed using an e-Si inoculant and casting was performed in the same manner. As another comparative example, casting was performed in the same manner without using the inoculant. The relationship between the distance from the casting surface and the number of graphite particles was investigated for each of the obtained test pieces. The results are shown in FIGS. In FIGS. 3 to 5, ◯ indicates the results of the investigation using the 1 mm-thick test piece obtained by the t1 mold in FIG. 2, and ⋄ indicates the 2 mm-thick test piece obtained by the t2 mold in FIG. The results of the investigation were shown, and □ indicates 3 obtained by the template of t3 in FIG.
2 shows the result of the investigation using the test piece having a thickness of mm, and Δ shows the result of the investigation using the test piece having a thickness of 4 mm obtained by the mold of t4 in FIG.

As shown in FIG. 3, when casting was carried out without adding an inoculant, the number of graphite particles in the vicinity of the casting surface was extremely low, and the possibility of chilling was recognized. On the other hand, as shown in FIG. 4, when casting was performed by inoculation with the Fe-Si type inoculant, when casting was performed without adding the inoculant shown in FIG. Compared with, the number of graphite particles is increasing. However, as shown in FIG.
F in the case of an example in which a coating type inoculation was carried out using a system inoculant
The number of graphite particles is further increased as compared with the case of the example of FIG. 4 in which the inoculation with the coating type is performed using the e-Si inoculant, and the number of graphite particles is remarkably large.

Therefore, as shown in the results of the example of FIG. 5 and the comparative examples of FIGS. 3 and 4, in the method for producing spheroidal graphite cast iron of the present invention, the temperature is lower than the melting temperature of the spheroidal graphite cast iron, so that the inoculation is performed. In the case of the comparative example in which the agent dissolves easily and quickly and the inoculum does not dissolve quickly, the inoculation effect takes time to appear, whereas the inoculation effect appears in a short time and the number of graphite particles increases. In particular, since the temperature of the molten spheroidal graphite cast iron on the surface of the mold is low, the spheroidal graphite cast iron is not melted by the Fe-Si inoculant, whereas Ni used in the method for producing spheroidal graphite cast iron of the present invention.
The -Si alloy inoculant begins to melt at a temperature extremely lower than that of Fe-Si and the like, and the number of graphite particles increases. Therefore, in order to prevent chilling of the casting surface, conventional inoculants such as Fe-Si are used. Compared with the method for producing spheroidal graphite cast iron used, the method for producing spheroidal graphite cast iron using the Ni—Si alloy inoculant of the present invention is much more advantageous.

Example 3 Using the Ni-Si type inoculant having the components shown in Table 1, Ni-
Using the characteristic of the low temperature dissolution in the Si-based inoculant, a mold-type inoculation was performed to carry out the method for producing spheroidal graphite cast iron of the present invention.
A 0 mmφ test piece was cast. On the other hand, as a comparative example, coating inoculation was performed using a conventional inoculant to produce spheroidal graphite cast iron by a conventional method, and a test piece similar to that of the example was obtained. The test shown in FIG. 6 was conducted using the test pieces of the obtained Examples and Comparative Examples. That is, as shown in FIG. 6, the test piece 4 is placed on the supports 3 which are arranged at intervals of 300 mm, the weight 5 is placed on the test piece 4, and the displacement x of the test piece 4 caused by the test piece 4 is set. It was measured. The measurement result is shown in FIG. 8 and 9 are photographs of the metallographic structures of the cross-sections of the surface layers of the test pieces 4 of Examples and Comparative Examples, respectively. As shown in FIG. 7, the test piece 4 of the embodiment shown by the solid line in the figure does not break even when the load exceeds 1000 kg, and finally breaks when the load exceeds 1500 kg, whereas the comparative example shown by the broken line in the figure. Test piece 4
In fact, it is recognized that if the load exceeds 1000 kg before the load reaches 1500 kg, it breaks. Since the test piece of the example is a test piece obtained by carrying out the present invention, the surface layer part is ferritic as shown in FIG. 8 and has high toughness, whereas the test piece of the comparative example is conventional. Since it was manufactured by the method, the surface layer was not sufficiently spheroidized and the surface layer portion was pearlite as shown in FIG.

In each of the above examples, the coating type inoculation was mainly used as a method of adding the Ni-Si inoculant to the spheroidal graphite cast iron melt, but the Ni-Si inoculant of the present invention was added to the spheroidal graphite cast iron melt. The addition method is not limited to this, and the addition method in each of the following modes (1) to (4) can be adopted. (1) Primary inoculation (charged into the ladle at the same time as Fe-Si-Mg) (2) Secondary inoculation (charged into the ladle after the spheroidizing reaction) (3) Charged with the original hot water (4) Pouring flow Inoculate.

[0027]

As described above, according to the method for producing spheroidal graphite cast iron of the present invention, the spheroidal graphite cast iron molten metal is prepared by using the inoculant containing the graphitization promoting element and having the melting temperature lower than the melting temperature of the spheroidal graphite cast iron. Since the inoculation agent is easily and quickly melted, it takes time for the inoculation effect to appear when the inoculation agent does not dissolve easily and quickly. Spheroidal graphite cast iron with little unmelted residue can be obtained. Further, the inoculant used in the method for producing spheroidal graphite cast iron of the present invention, for example, the Ni-Si alloy inoculant, starts to melt at a temperature extremely lower than that of the conventional inoculants such as Fe-Si, and therefore, the spheroidal graphite of the present invention. According to the method for producing cast iron, the number of graphite particles at the time of adding the inoculant to the surface of the molten spheroidal graphite cast iron is increased, and chilling of the surface can be prevented.

Further, in the method for producing spheroidal graphite cast iron of the present invention, an inoculant having a melting temperature lower than that of spheroidal graphite cast iron, for example, an inoculant of Ni-Si alloy and a melting temperature lower than that of spheroidal graphite cast iron are used. Some inoculants such as Fe-S
Since the inoculant i is mixed and used as the inoculant, the production cost of the spheroidal graphite cast iron can be reduced by mixing the both. The method for producing spheroidal graphite cast iron of the present invention is particularly effective when it is necessary to use an inoculant having an intermediate property between the inoculant of Ni-Si alloy and the inoculant of Fe-Si.

[Brief description of drawings]

FIG. 1 is a photograph of a metal structure near a casting surface in a test piece obtained by carrying out the present invention and a test piece of a comparative example.

FIG. 2 is a front view of a casting method used in an example of the present invention.

FIG. 3 is a diagram showing the results of an investigation of the relationship between the distance from the casting surface and the number of graphite particles in the test piece of the comparative example with respect to the example of the present invention.

FIG. 4 is a diagram showing the results of an investigation of the relationship between the distance from the casting surface and the number of graphite particles in the test piece of another comparative example with respect to the example of the present invention.

FIG. 5 is a diagram showing the results of an examination of the relationship between the distance from the casting surface and the number of graphite particles in the test piece of the example of the present invention.

FIG. 6 is an explanatory diagram showing a test method of a strength test performed in Example 3 of the present invention.

FIG. 7 is a diagram showing the results of a strength test conducted in Example 3 of the present invention.

FIG. 8 is a photograph of a metallographic structure of a surface layer section of a test piece obtained in Example 3 of the present invention.

FIG. 9 is a photograph of a metal structure of a cross section of a surface layer of a test piece obtained in a comparative example.

[Explanation of symbols]

1 ... Template, 2 ... Inoculant, 3 ... Support, 4 ...
..Test pieces, 5 ... Weight, A ... Inoculant-added portion, B ... Inoculant-free portion, t1 ... 1 mm thick test piece, t2 ... 2 mm thick test piece, t3・ ・
・ 3 mm thick test piece, t4 ... 4 mm thick test piece, ◯ ... Investigation result using 1 mm thick test piece obtained by t1 mold, ◇ ... 2 mm thick test piece obtained by t2 mold Survey results used, □ ・ ・ ・
Investigation result using 3 mm thick test piece obtained by t3 mold, Δ ... Investigation result using 4 mm thick test piece obtained by t4 mold.

Claims (14)

[Claims] 1. A method for producing spheroidal graphite cast iron, which comprises casting the spheroidal graphite cast iron using an inoculant containing a graphitization promoting element and having a melting temperature lower than the melting temperature of the spheroidal graphite cast iron. 2. A spheroidal graphite cast iron characterized in that a spheroidal graphite cast iron melt is poured into a mold having a surface coated with an inoculant containing a graphitization promoting element and having a melting temperature lower than that of spheroidal graphite cast iron. Production method. 3. An inoculant comprising a graphitization-promoting element and having a melting temperature lower than that of spheroidal graphite cast iron and an inoculant having a melting temperature higher than that of spheroidal graphite cast iron. A method for producing spheroidal graphite cast iron, characterized in that spheroidal graphite cast iron is cast by using. 4. An inoculant containing a graphitization-promoting element and having a melting temperature lower than that of spheroidal graphite cast iron, and an inoculant having a melting temperature higher than that of spheroidal graphite cast iron. A method for producing spheroidal graphite cast iron, which comprises pouring molten spheroidal graphite cast iron into a mold having a surface coated with slag. 5. An inoculant containing a graphitization-promoting element and having a melting temperature lower than that of spheroidal graphite cast iron is applied to a mold surface, and an inoculant having a melting temperature higher than that of spheroidal graphite cast iron is melted. A method for producing spheroidal graphite cast iron, characterized by being added to the inside. 6. A method for producing spheroidal graphite cast iron, which comprises casting spheroidal graphite cast iron using an inoculant containing a graphitization promoting element and having Si and Ni as main components. 7. A method for producing spheroidal graphite cast iron, which comprises pouring the spheroidal graphite cast iron molten metal into a mold having a surface coated with an inoculant containing graphitization-promoting elements and whose main components are Si and Ni. 8. Production of spheroidal graphite cast iron, characterized in that spheroidal graphite cast iron is cast using an inoculant containing graphitization promoting elements as main components of Si and Ni and containing 3 wt% or less of Ba. Method. 9. A spheroidal graphite cast iron molten metal is poured into a mold having Si and Ni as main components containing a graphitization promoting element and having an inoculant containing 3 wt% or less of Ba applied on the surface thereof. Manufacturing method of spheroidal graphite cast iron. 10. Casting of spheroidal graphite cast iron is carried out using an inoculant which is a mixture or alloy of an inoculant containing graphitization-promoting elements and whose main components are Si and Ni and an inoculant whose main components are Si and Fe. A method for producing spheroidal graphite cast iron, comprising: 11. A spheroidal graphite cast iron in a mold having a surface coated with an inoculant which is a mixture or alloy of an inoculant containing graphitization-promoting elements and whose main components are Si and Ni and an inoculant whose main components are Si and Fe. A method for producing spheroidal graphite cast iron, which comprises pouring molten metal. 12. The mixing or alloying ratio of an inoculant having Si and Ni as main components and an inoculant having Si and Fe as main components is set to 1/3 to 3/1.
A method for producing the spheroidal graphite cast iron described. 13. An inoculum containing a graphitization-promoting element, the main components of which are Si and Ni, is applied to the surface of the mold, and the main component is Si.
A method for producing spheroidal graphite cast iron, characterized in that an inoculant of Fe and Fe is added to the molten metal. 14. The method for producing spheroidal graphite cast iron according to claim 13, wherein the inoculant whose main components are Si and Ni contains 3 wt% or less of Ba.