JP7178086B2 - Graphite spheroidizing agent for cast iron - Google Patents

Description

TECHNICAL FIELD The present invention relates to a spheroidizing agent for increasing the number of graphite grains, which is carbon, in cast iron, which is iron containing predetermined amounts of carbon and silicon.

In general, cast iron contains a large amount of carbon, about 3 to 5% by weight, so that graphite crystallizes in the structure, and the mechanical properties of cast iron vary depending on the shape of the crystallized graphite. do. Cast iron in which graphite crystallizes in flakes is called gray cast iron, and cast iron that is hard but brittle because it does not stretch is called ductile cast iron. It is used in various structures such as automobile parts and water pipes because it improves the toughness of cast iron. Therefore, if the number of spheroidal graphite grains in cast iron increases and they are scattered, the cast iron becomes tougher, and the range of applications expands and high quality can be achieved by meeting high standards. There is a need for spheronizing agents that increase the

Also, various graphitization spheroidizing agents are known to solve various problems associated with the spheroidization of graphite in cast iron.

For example, in Patent Document 1, silicon 40-50%, magnesium 4-5%, calcium 0.5-1.5%, aluminum 1-3%, rare earth 0.5-1.5%, zirconium 0.2% .about.1.0%, 0.5-3% carbon, unavoidable impurities, the balance being a nodular graphite cast iron spheroidizing agent with a composition substantially iron.

JP-A-10-237528

However, the spheroidizing agent disclosed in Patent Document 1 is disclosed as being added to further reduce the chilling of molten metal after spheroidizing treatment, and has the effect of increasing the number of spheroidal graphite grains. is not specified, and is clearly different from the problem to be solved by the present application.

Therefore, in view of the above problems, an object of the present invention is to provide a graphite spheroidizing agent for cast iron that spheroidizes graphite in cast iron and increases the number of spheroidal graphite grains.

[1] That is, the present invention is a spheroidizing agent for increasing the number of spheroidal graphite particles in cast iron, comprising 30 to 60% by weight of silicon, 4 to 30% by weight of magnesium, and 0.0% of zirconium. A graphite spheroidizing agent for cast iron characterized by containing 1 to 10% by weight and a predetermined amount of iron.

[2] The graphite spheroidizing agent for cast iron according to [1], which contains 0.1 to 5% by weight of rare earth.

According to the present invention, graphite in cast iron can be spheroidized and the number of spheroidal graphite grains can be increased.

1 is a micrograph of ductile cast iron immediately after addition of a graphite spheroidizing agent for cast iron according to an example of the present invention. 4 is a micrograph of ductile cast iron 7 minutes after adding the graphite spheroidizing agent for cast iron of the example of the present invention. 4 is a micrograph of ductile cast iron immediately after adding a graphite spheroidizing agent for cast iron of a comparative example. 4 is a micrograph of ductile cast iron 7 minutes after adding a graphite spheroidizing agent for cast iron of a comparative example.

Hereinafter, the graphite spheroidizing agent for cast iron according to the present invention will be described in detail. In addition, the expression representing the range includes the upper limit and the lower limit.

Silicon (Si):
The graphite spheroidizing agent for cast iron of the present invention is a ferrosilicon-based treatment agent, and silicon is added to lower the concentration of magnesium to be blended and to suppress the explosive reaction of magnesium. The mixing ratio of silicon is preferably 30 to 60% by weight, more preferably 40 to 50% by weight. When the blending ratio of silicon is within this range, the graphite spheroidizing agent for cast iron can be stably produced. The graphite spheroidizing agent for cast iron can be easily melted to disperse other components in the molten metal, and the cost of the graphite spheroidizing agent for cast iron can be reduced.

Magnesium (Mg):
Magnesium is an active ingredient for spheroidizing graphite in cast iron. The mixing ratio of magnesium is preferably 4 to 30% by weight, preferably 10 to 30% by weight. When the proportion of magnesium is within this range, the graphite can be reliably spheroidized when the graphite spheroidizing agent for cast iron is added to the molten metal, and the explosive reaction of magnesium is suppressed to prevent the molten metal from scattering. It is possible to suppress a decrease in yield due to

Zirconium (Zr):
Zirconium is an active ingredient for increasing the number of spheroidized graphite grains in cast iron. It is thought that there is a synergistic effect that accelerates the increase in the number of graphite grains. The blending ratio of zirconium is preferably 0.1 to 3% by weight, preferably 0.50 to 2% by weight. When the blending ratio of zirconium is within this range, the graphite is spheroidized to the extent that the toughness of the cast iron obtained when the graphite spheroidizing agent for cast iron is added to the molten metal is not impaired, and the number of spheroidized graphite grains is increased. can be made

Rare earth (RE):
Rare earth is a component that assists in spheroidizing graphite in cast iron, and is a general term for two elements, scandium and yttrium, and 15 elements with atomic numbers from lanthanum to lutetium. The rare earth content is preferably 0.1 to 5% by weight, more preferably 0.5 to 3% by weight. When the blending ratio of the rare earth is within this range, it is possible to promote the spheroidization of graphite when the graphite spheroidizing agent for cast iron is added to the molten metal, and to suppress the amount of shrinkage when the molten metal solidifies.

Calcium (Ca):
Calcium has the effect of suppressing the reaction during the spheroidizing treatment, and also has the function of assisting the spheroidizing action of magnesium. If it is less than 0.5%, the effect cannot be obtained, and if it exceeds 6%, a large amount of Ca oxide will be generated after the treatment, which is not suitable for practical use.

Iron (Fe):
It is the base material of the graphite spheroidizing agent for cast iron of the present invention, and like silicon, it can reduce the concentration of magnesium to be blended and suppress the explosive reaction of magnesium.

In addition, manganese, phosphorus, chromium, titanium, aluminum, tin, and the like may be unavoidably mixed as impurities in the graphite spheroidizing agent for cast iron.

When the graphite spheroidizing agent for cast iron of the present invention is added to the molten metal, it is formed in a linear form as a solid wire made of the above material, or a cored wire in which the above material is closely coated with a thin steel plate or the like. It is preferable that it is formed in a linear shape as. When the cored wire is formed linearly, the coated steel sheet is also included in the total weight, and the ratio of each component is the ratio to the total weight of the compounded amount of each component and the coated steel plate. be.

[Example 1]
A cored wire filled with a FeSiMg alloy containing 47.6% by weight of Si, 23.5% by weight of Mg, 2.8% by weight of Ca, 0.8% by weight of RE, 1.2% by weight of Zr, and an impurity component was produced.

Then, 0.42% (420 g) of the spheroidizing agent was added to 100 kg of molten cast iron. A medal sample for Kantback analysis and a cylindrical test piece by casting were taken from the molten cast iron containing the spheroidizing agent immediately after the treatment and after 7 minutes, respectively.

[Comparative Example 1]
A cored wire filled with a FeSiMg alloy containing 41.2 wt% Si, 24.6 wt% Mg, 2.8 wt% Ca, 0.8 wt% RE and an impurity component as a spheroidizing agent was produced.

Then, 0.42% by weight (420 g) of the spheroidizing agent was added to 100 kg of molten cast iron. A medal sample for Kantback analysis and a cylindrical test piece by casting were taken from the molten cast iron containing the spheroidizing agent immediately after the treatment and after 7 minutes, respectively.

<Number of spherical graphite grains>
Then, after cutting and polishing the cross section of the test piece of the example and the test piece of the comparative example obtained in this manner, the polished portion was observed using a microscope and a tissue image was taken. The number of spheroidized graphite grains per unit area of this image was measured using graphite spheroidization measurement software (manufactured by Nippon Steel & Sumikin Technology) compliant with JIS standards (JIS G5502: spheroidal graphite cast iron). In addition, the graphite spheroidization rate in the image was measured using the same software. These measurements were taken 5 times and they were arithmetically averaged.

<Mg yield>
Furthermore, the component analysis of the sample for cantback analysis of the example and the sample for cantback analysis of the comparative example was performed, and the amount of residual Mg found in the product of the analyzed Mg value and the weight of the molten metal was found in the wire. The ratio of each Mg yield was calculated by dividing by the amount of Mg added to the molten metal to obtain a percentage.

Table 1 shows the composition of the spheroidizing agent in the above examples and comparative examples, and Table 2 shows the results of the number of spheroidized graphite particles, the spheroidization rate, and the Mg yield.

As shown in Table 2, when the spheroidizing agents of the examples are used, the graphite in the cast iron is spheroidized, and the number of spheroidal graphite grains is significantly higher than when the spheroidizing agents of the comparative examples are used. Furthermore, as shown in FIG. 1, it was found that spheroidal graphite was scattered in the cast iron. Regarding the yield of Mg, when the spheroidizing agent of the example was used, it was higher than the case of using the spheroidizing agent of the comparative example even immediately after the addition, and after 7 minutes, it was higher than the case of the comparative example. Although it tends to decrease similarly, there is an effect that the decrease is suppressed.

Claims (2)

A spheroidizing agent for increasing the number of spheroidal graphite grains in cast iron, comprising 30-60% by weight of silicon, 10-30% by weight of magnesium, 0.1-10 % by weight of zirconium and a predetermined amount of iron Graphite spheroidizing agent for cast iron, characterized by containing Graphite spheroidizing agent for cast iron according to claim 1, characterized by containing 0.1 to 5% by weight of rare earth.

Images