JP2016132783A - Manufacturing method of spheroidal graphite cast iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a spheroidal graphite cast iron capable of producing a fine spheroidal graphite particle in a cast iron structure from carbon contained in molten iron.SOLUTION: In a manufacturing method of a spheroidal graphite cast iron, granular graphite spheroidizing agent 6, powdery bismuth 7 and granular copper 8 are arranged in a layered state in a ladle 20 in this order from a bottom side of the ladle 20 so that Cu of 2.2 to 2.7 mass% and Bi of 0.005 to 0.05 mass% are added to molten iron. A spheroidal graphite cast particle is produced from carbon of molten iron M by injecting the molten iron M from upper of the ladle 20 into the ladle 20 and contacting the molten iron M with the granular graphite spheroidizing agent 6, the powdery bismuth 7 and he granular copper 8 in the ladle 20.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing spheroidal graphite cast iron in which spheroidal graphite particles are produced from carbon in a molten cast iron by bringing a graphite spheroidizing agent into contact with the molten cast iron.

  Conventionally, spheroidal graphite cast iron may be employed for automobile engines, undercarriage parts, drive parts, and the like. Since spheroidal graphite cast iron contains spheroidal graphite particles in the iron base, it can be expected to have higher strength than other cast irons. Such spheroidal graphite cast iron is produced by contacting and reacting a cast iron melt with a graphite spheroidizing agent containing Mg, Ca, Ce or the like.

  For example, Patent Document 1 proposes a method for producing spheroidal graphite cast iron in which cast iron contains 1.8 to 4.0 mass% Cu and 0.0005 to 0.01 mass% Bi. In this technique, first, Cu having the above content is added to molten cast iron (JIS standard: FCD450 equivalent). Next, Bi and Sn are added to the cast iron melt to which Cu is added during the graphite spheroidization treatment by the sandwich method in which an Fe-Si-Mg-Ca-REM alloy (graphite spheroidizing agent) is added.

JP 2009-197311 A (see paragraph [0063] of the specification)

  However, in the technique shown in Patent Document 1, since Cu is added to the cast iron melt in advance, a long time elapses from Cu addition to Bi addition, and the effect of refining graphite by Bi can be sufficiently exhibited. There were cases where it was not possible. Also, depending on the amount of Cu added, all of the Cu was dissolved in Fe and the fineness of the graphite was inhibited, or irregularly shaped graphite was generated, and the graphite did not spheroidize.

  The present invention has been made in view of these points, and an object of the present invention is to provide a method for producing spheroidal graphite cast iron capable of generating fine spheroidal graphite particles from carbon of the cast iron melt. It is in.

  In view of the said subject, the manufacturing method of the spheroidal graphite cast iron which concerns on this invention is such that Cu is added to a cast iron melt 2.2-2.7 mass%, Bi is added 0.005-0.05 mass%. A granular graphite spheroidizing agent, powdered Bi, and granular Cu are arranged in layers in the container in order from the bottom side of the container, and the cast iron melt is poured into the container from above the container, In the container, spherical graphite particles are generated from carbon of the cast iron melt by bringing the granular graphite spheroidizing agent, the powdered Bi, and the granular Cu into contact with the cast iron melt. And

  According to the present invention, fine spherical graphite particles can be generated from the carbon of the cast iron melt.

The schematic diagram for demonstrating the manufacturing method of the spheroidal graphite cast iron which concerns on embodiment of this invention. The typical sectional view of the ladle shown in FIG. (A) Schematic diagram for explaining the mechanism by which spherical graphite particles are produced by the production method according to the present embodiment, (b) To explain the mechanism by which spherical graphite particles are produced by the method according to the prior art. FIG. (A) Structure photograph of spheroidal graphite cast iron according to Example 1, (b) Structure photograph of spheroidal graphite cast iron according to Comparative Example 1. The structure photograph of the spheroidal graphite cast iron according to Example 1 and Comparative Examples 2 and 3.

Embodiments of the present invention will be described below with reference to the drawings.
The spheroidal graphite cast iron according to the present embodiment is a spheroidal graphite cast iron product (JIS standard: FCD700), Cu is 2.2 to 2.7 mass%, Bi is 0.005 to 0.05 mass%, and further inoculated and added Which satisfies the component ranges shown in Table 1 below. The balance other than the components shown in Table 1 is composed of iron and inevitable impurities. In the spheroidal graphite cast iron according to the present embodiment, many fine spheroidal graphite particles are dispersed in the iron base as compared with the conventional (for example, FCD700).

  Below, the manufacturing method of the spheroidal graphite cast iron which concerns on this embodiment is demonstrated. FIG. 1 is a schematic view for explaining a method for producing spheroidal graphite cast iron according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of the ladle shown in FIG.

  First, as shown in FIG. 1, the components of the cast iron melt M are adjusted in the melting furnace 10 within a range not exceeding the content of elements shown in Table 1. The total amount of the elemental content of the cast iron melt M, the components of which are adjusted here, and the addition amount of each additive element of the granular / powder material placed in the ladle 20 to be described later is finally obtained. The components of the molten cast iron M are adjusted in the melting furnace 10 so that the contents shown in Table 1 are obtained. In the present embodiment, at the time of adjusting the components of the cast iron melt M, at least Mg and Bi are not added.

  Next, when pouring the molten cast iron M from the melting furnace 10 to the ladle (container) 20, Cu is 2.2 to 2.7 mass% and Bi is added to the molten cast iron M using the sandwich method shown below. Cu, Bi, and a graphite spheroidizing agent (Fe—Si—Mg powder) are inoculated and added to the cast iron melt M so as to contain 0.005 to 0.05 mass%.

  Here, in the ladle 20 used in the present embodiment, an accommodating portion 22 that accommodates the cast iron melt M to be poured is formed, and by providing a partition wall portion 22b at the bottom of the accommodating portion 22, An accommodation recess 22a for accommodating a granular / powder-like material described later is formed.

  In this embodiment, as shown in FIG.1 and FIG.2, in the accommodation recessed part 22a of the ladle 20, granular graphite spheroidizing agent (Fe-Si-Mg) 6, powdered Bi (bismuth) 7, Granular Cu (copper) 8 is charged. More specifically, the granular graphite spheroidizing agent 6, the powdery bismuth 7, and the granular copper 8 are arranged in layers in the accommodating recess 22a in order from the bottom side of the ladle 20. Here, the granular copper 8 is disposed in layers so as to cover the granular graphite spheroidizing agent 6 and the powdered bismuth 7 disposed in layers in the accommodating recess 22a.

  Further, the amount of granular copper 8 is larger than the amount of powdered bismuth 7, and the granular copper 8 functions as a covering agent for powdered bismuth 7. Here, “granular” in the present specification means a state in which the particle size is larger than “powder”.

  Next, the cast iron melt M whose components are adjusted is discharged from the melting furnace 10, and the cast iron melt M is poured into the ladle 20 from the top of the ladle 20 (pouring). Thereby, the cast iron molten metal M comes into contact with the granular copper 8, the powdered bismuth 7, and the granular graphite spheroidizing agent 6 in this order, and the elements made of these granular and powdered materials are contained in the cast iron molten metal M. It reacts with the carbon (graphite spheroidizing treatment reaction). Thereby, spherical graphite particles are generated in the cast iron melt M. Thus, the accommodation recess 22a of the ladle 20 functions as a reaction chamber in which the powder element and the element of the cast iron melt M react.

  After spheroidal graphite particles are generated in the cast iron melt M in the ladle 20, unnecessary substances such as silica generated on the surface of the cast iron melt M are removed, and the cast iron melt M is discharged from the ladle 20. The cast iron melt M is poured into the pouring port 51 of the mold 50 arranged in the metal frame 40. Thereafter, the cast iron melt M is cooled in the mold 50. Thereby, the spheroidal graphite cast iron in which spheroidal graphite particles are formed in the cast iron structure (iron base) in which the molten cast iron M is cooled can be obtained.

  Here, the spheroidizing reaction described above will be described in detail with reference to FIGS. 3 (a) and 3 (b). FIG. 3A is a schematic diagram for explaining a mechanism by which spherical graphite particles are generated in the manufacturing method according to the present embodiment, and FIG. It is a schematic diagram for demonstrating the mechanism in which particle | grains are produced | generated.

  In the case where spherical graphite particles are produced using a graphite spheroidizing agent without adding Bi and Cu as in the prior art, as shown in FIG. C) may diffuse, and spherical graphite particles may grow, producing coarse spherical graphite particles.

  However, in the present embodiment, by adding the powdered bismuth component of bismuth 7 to the molten cast iron M, more spherical graphite particles are dispersed than in the past with bismuth dispersed in the iron matrix as a core. Thereby, compared with the case shown in FIG.3 (b), the number of the spherical graphite particles in an iron base can be increased (refer Fig.3 (a)). Furthermore, by adding the copper component of the granular copper 8 to the cast iron melt M, the diffusion of carbon into the spherical graphite particles can be suppressed, and the coarsening of the spherical graphite particles can be suppressed. Thereby, compared with the past, fine spherical graphite particles can be formed in the cast iron structure.

  In particular, in this embodiment, the cast iron melt M can be brought into contact with these powders without leaving time in the order of the granular copper 8, the powdered bismuth 7, and the granular graphite spheroidizing agent 6. It is thought that such an effect can be expressed further.

  Here, when Bi added to the cast iron melt M is less than 0.005% by mass, the effect of dispersing graphite particles by bismuth in the iron base cannot be sufficiently expected, and Bi added. If it exceeds 0.05 mass%, there is a concern that the granulation of graphite particles may be hindered and the cost of cast iron products may increase.

  On the other hand, when the Cu added to the cast iron melt M is less than 2.2% by mass, the refinement of the graphite particles by copper is inhibited, and the Cu added to the cast iron melt M exceeds 2.7% by mass. In this case, the spheroidization of the graphite particles is inhibited.

Hereinafter, the present invention will be described by way of examples.
<Example 1>
Spheroidal graphite cast iron added with elements in the content range shown in Table 1 was manufactured by the method shown in FIG. First, spheroidal graphite cast iron (JIS standard: FCD700) having the components shown in Table 2 was prepared, and this was heated and melted to a temperature of 1510 ° C. in a melting furnace to prepare a cast iron melt M.

  Next, granular graphite spheroidizing agent (Fe-Si-Mg), powdered Bi so that the components of Table 2 contain 2.5 mass% Cu and 0.03 mass% Bi finally. And granular Cu was arrange | positioned in the ladle in order from the bottom face side of the ladle. In addition, as shown in Table 2, copper may be added in the melting furnace. Next, the cast iron melt M is poured into the ladle from the melting furnace, and the cast iron melt M is brought into contact with the granular graphite spheroidizing agent, powdered Bi, and granular Cu, and the spheroidizing treatment reaction is carried out. Spherical graphite particles were produced. The cast iron melt M in which spheroidal graphite particles were generated was poured into a mold, and then cooled, to produce spheroidal graphite cast iron in which spheroidal graphite particles were formed in the cast iron structure.

<Comparative Example 1>
As in Example 1, nodular graphite cast iron was produced. The difference from Example 1 is that powdered Bi and granular Cu are not placed in the pan (that is, Bi and Cu are not added to the cast iron melt M), and a granular graphite spheroidizing agent (Fe- Spherical graphite particles were produced in the cast iron melt M by the spheroidizing treatment reaction using only the Si-Mg powder.

<Comparative example 2>
As in Example 1, nodular graphite cast iron was produced. The difference from Example 1 is that the amount of granular Cu placed in the ladle is reduced so that the Cu added to the cast iron melt is 2.0 mass%.

<Comparative Example 3>
As in Example 1, nodular graphite cast iron was produced. The difference from Example 1 is that the amount of granular Cu placed in the ladle is increased so that the Cu added to the cast iron melt is 3.0 mass%.

(Microscopic observation)
The structure photograph of the spheroidal graphite cast iron according to Example 1 and Comparative Examples 1 to 3 was magnified 400 times with an optical microscope and observed. The results are shown in FIGS. 4A is a structural photograph of the spheroidal graphite cast iron according to Example 1, and FIG. 4B is a structural photograph of the spheroidal graphite cast iron according to Comparative Example 1. FIG. 5 is a structure photograph of the spheroidal graphite cast iron according to Example 1 and Comparative Examples 2 and 3.

(result)
As shown in FIGS. 4 (a) and 4 (b), the spheroidal graphite cast iron of Example 1 has a smaller particle diameter of the spheroidal graphite particles and a larger number of spheroidal graphite particles than the spheroidal graphite cast iron of Comparative Example 1. It was. Specifically, within the same area, the average particle size of the spherical graphite particles of Example 1 was 12 μm, and the average particle size of the spherical graphite particles of Comparative Example 1 was 24 μm. Further, the number of spherical graphite particles in Example 1 was 708, and the number of spherical graphite particles in Comparative Example 1 was 175. That is, as in Example 1, by adding specific amounts of Cu and Bi, the average particle size of the spherical graphite particles is reduced to about 50% (reduced), and the refined spherical graphite particles The number is considered to increase about four times.

  Furthermore, as shown in FIG. 5, the spheroidal graphite particles of the spheroidal graphite cast iron according to Comparative Example 2 were coarser than those of Example 1. This is probably because the amount of Cu added in Comparative Example 2 is smaller than that in Example 1. From this, it is presumed that if the amount of Cu added is 2.2% by mass or more, the refinement of the graphite particles is not hindered.

  On the other hand, as shown in FIG. 5, the spheroidization of the graphite particles of the spheroidal graphite cast iron according to Comparative Example 3 was inhibited. This is considered to be because the amount of Cu added in Comparative Example 2 is larger than that in Example 1. From this, it is presumed that if the amount of Cu added is 2.7% by mass or less, the spheroidization of the graphite particles is not inhibited.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to the said embodiment, In the range which does not deviate from the mind of this invention described in the specification and the claim, Various design changes can be made.

6: granular graphite spheroidizing agent, 7: powdered Bi powder, 8: granular Cu, 10: melting furnace, 20: ladle, 22: storage part, 22a: storage recess, 22b: partition wall, 40: Gold frame, 50: mold, 51; pouring gate

Claims (1)

A granular graphite spheroidizing agent, powdered Bi, and granular Cu are added so that Cu is added to the cast iron melt in an amount of 2.2 to 2.7% by mass and Bi is added in an amount of 0.005 to 0.05% by mass. In order from the bottom side of the container, arrange in layers in the container,
The molten cast iron is poured into the container from above the container, and the granular graphite spheroidizing agent, the powdered Bi, and the granular Cu are brought into contact with the molten cast iron in the container. A method for producing spheroidal graphite cast iron, comprising producing spheroidal graphite particles from carbon of the molten cast iron.

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