WO2003083143A1 - Method for removing manganese in molten cast iron and method for producing spheroidal graphite cast iron - Google Patents

Abstract

A method for removing manganese in molten cast iron, characterized in that it comprises adding sodium sulfate while mixing into a molten cast iron as an additive. The method can be employed in the production of cast iron for decreasing the Mn content thereof, and thus allows the production of a cast iron of high ductility which is improved in elongation characteristics without detriment to tensile strength, even when a steel scrap being cheap and having a high Mn content is used as a raw material. Further, the method can be practiced with labor-saving in operation control, with reduced generation of wastes, and with reduced consumption of an additive and the like, and thus allows the production of cast iron at a suppressed cost.

Description

 Specification

 マ ン ガ ン Method of removing manganese in molten iron and method of producing spheroidal graphite iron

 The present invention relates to a method for removing manganese in the production of iron. Background art

 Among iron, spheroidal graphite and iron are used for various applications because they have particularly excellent mechanical properties and are relatively inexpensive. Applications include, for example, automobile parts, and are particularly suitably used for underbody parts such as lower arms, upper arms, knuckle housings, suspensions, and the like. Spheroidal graphite iron is also referred to as ductile iron, and is generally iron in which graphite is crystallized in a spherical state in an undisturbed state.

 Of the mechanical properties of this spheroidal graphite-iron, the tensile strength is usually in the range of 400 to 500 MPa, but can be increased to about 80 OMPa by alloy components. The elongation is related to a decrease with an increase in the strength. Usually, the FCD 450 (Japanese Industrial Standard) has a tensile strength of 45 OMPa or more and the elongation is about 20%, which is a high level. Further improvement is required for the above applications, for example, which are exposed to severe use environments. If the elongation is to be increased by heat treatment such as ferritizing annealing, the tensile strength tends to decrease, and it is not easy to achieve both tensile strength and elongation.

 As a method of improving the elongation characteristics of spheroidal graphite and iron while maintaining at least the tensile strength, it has been conventionally known to reduce the manganese (Mn) content in the component composition. Mn is a means of increasing the elongation of spheroidal graphite and iron by reducing the content of Mn, because Mn increases strength but decreases elongation as a pearlite stabilizing element.

However, contrary to such a measure, the raw material for spheroidal graphite-iron has an increasing Mn content, and it is not uncommon for the raw material to have an Mn content of 1% by mass or more. The main raw material of spheroidal graphite iron was pig iron for animals before the 1970s, but it is now steel scrap. Because it ’s been You.

 As a raw material for spheroidal graphite and iron, the price of pig iron for animals has soared, and due to the growth of the automobile industry, a large amount of punching debris has been generated mainly from car bodies due to the growth of the car body, so that it can be supplied at low cost. As a result, steel scrap was used more often. In recent years, the ratio of high-tensile steel sheets (high-tensile steel sheets) containing a large amount of Mn has been increasing in steel materials used in automobiles, which are the main source of steel scrap.

 This is because there is a strong global need to reduce the fuel consumption of automobiles, which is said to have a significant impact on global warming, and car manufacturers need to develop technology to improve fuel efficiency. In order to reduce the weight that can be applied in combination with other fuel-consumption reduction technologies, thin high-strength steel sheets, which are less expensive than lightweight alloys made mainly of aluminum, are being mass-produced as main materials for automobiles. This is because it has come to be used.

 However, high-tensile steel contains a large amount of Mn. According to the inventors' analysis of the composition of steel scrap mainly composed of thin high-strength steel sheets for vehicle bodies, it has been confirmed that Mn is contained in an amount of about 1.3 to 2.0% by mass. If such steel scrap is used as a raw material, it becomes an obstacle for improving the elongation characteristics of the spheroidal graphite-iron as described above. Therefore, it is conceivable to remove Mn from the molten iron. However, there is no effective and practical method for removing MnP from the molten iron, and no method has been actually implemented. On the other hand, low-Mn iron raw materials such as high-purity pig iron and base metal are expensive and not economical, even if they are to be diluted with materials with low Mn content.

 Conventionally known methods for removing Mn include an oxygen treatment method, a sulfide treatment method, a chlorination treatment method, and a vacuum treatment method. However, the vacuum processing method requires vacuum equipment and increases equipment costs, and the chlorination method is not suitable for practical use because harmful chlorine gas is generated.

 It is known that the oxygen treatment method can remove Mn as MnO, as typified by the refining process by blowing oxygen in the steelmaking process. However, in iron, carbon (C), the main component element, is removed. However, it is not economical because the amount of carburized material and siliconized material must be increased due to oxidation and depletion of silicon (Si).

Therefore, the present inventors have tried to remove Mn by sulfide treatment ("Petroleum" No. 62). Vol. (1990) No. 8, pp. 643-647, herein referred to as Non-Patent Document 1). When a carbon-saturated alloy containing 5% by mass of Mn was melted and potassium sulfide (K ₂ S) was added as a sulfide, a high Mn removal rate was obtained, and the Mn content after treatment was reduced to 0.3%. It was confirmed that the content could be reduced to not more than mass%. However, in this method, K ₂ S is expensive, which leads to an increase in the cost of spheroidal graphite-iron that MnP is removed, and also generates a large amount of slag as a product of removing Mn, which is an environmental problem. There has been a problem to be solved that raises the cost of spheroidal graphite and iron, such as incurring the processing costs.

Regarding the sulfide treatment method, there is a description in Japanese Patent Application Laid-Open No. Sho 61-266515 (herein referred to as Patent Document 1) as published information on the Mn removal method. Its publication, a dehydrated sulfide source one Da (Na ₂ S) and sodium sulfate (Na ₂ S_〇 _4), a weight ratio of 100: 10 to 100: with 300 mixture was added, the low from copper-bearing molten iron It discloses a method for producing copper steel, but it states that Mn was reduced as well as copper (Cu).

However, since it aims to remove C and Si together with Cu, it is aimed at molten steel, and does not take into account the reduction of C and Si, which are the main components, unlike iron. In addition, the Mn content in the copper-containing molten iron as a raw material is a relatively low level of 0.53 to 0.61% by weight. with Mn removal effect is unknown, the two additives _{(Na 2 S, Na 2 S0} 4) and that leads to the production cost including the complexity and additives consumption operation management because it is necessary to use mixed- Had a problem. Disclosure of the invention

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to increase the elongation without lowering the tensile strength even when using inexpensive steel chips with a high Mn content as a raw material. Highly ductile iron with improved properties can be obtained, and furthermore, labor can be saved in operation management, and the amount of waste generated is smaller, the consumption of additives etc. is smaller, and production costs are lower. (2) To provide a method for removing manganese in molten iron, in which the amount of manganese in the molten iron is reduced. The present inventors have demanded that the elongation as well as the tensile strength be improved as a property, but on the other hand, there is a demand for lower cost. As a result of repeated research on Mn removal methods to cope with the reality of increasing the concentration of Mn contained in steel, it was found that the above objectives could be achieved by the following means.

 That is, according to the present invention, there are provided the following four methods for removing manganese in molten iron.

First manganese removal method is a method of reducing the manganese content in the production of铸鉄, characterized by mixing adding sodium sulfate (N a ₂ S 0 ₄₎ as an additive铸鉄meltマ ン ガ ン This is a method for removing manganese from molten iron. The second method removed by manganese removal is a method of reducing the manganese content in the production of铸鉄, characterized by mixing addition of sodium sulfide (N a ₂ S) as an additive in铸鉄melt铸This is a method for removing manganese in molten iron. The third manganese removal method is a method of reducing the manganese content in the production of iron, and is characterized by adding sodium hydrosulfide (NaHS) as an additive to the molten iron and mixing. This is a method for removing manganese from the molten metal.

 When the molten iron iron as a raw material contains at least 2.1% by mass of carbon and at least 1.8% by mass of silicon and has a manganese content of 0.4 to 1.5% by mass, The manganese content of the molten iron after the manganese removal method 3 is performed can be 0.4% by mass or less.

 In the first to third manganese removal methods, it is preferable that the temperature of the molten iron be approximately 130 to 150.

 In the first to third manganese removal methods, it is possible to suitably use a steel scrap material of a high-tensile steel sheet having a high Mn content as a raw material of the molten iron.

 The fourth method for removing manganese is a method for reducing the manganese content in the production of iron, which comprises removing a sulfur compound containing an element having a boiling point lower than the temperature of the molten iron and containing no manganese. (2) A method for removing manganese in molten iron, which is characterized by adding to and mixing with molten iron.

Further, according to the present invention, there is provided the following method for producing spherical graphite and iron. Departure The method for producing spheroidal graphite iron according to the present invention comprises the steps of preparing a molten iron as a raw material, and using any one of the above-described methods of removing manganese from the molten iron. A graphite spheroidizing process to add a graphite spheroidizing agent to the molten iron with reduced manganese content and react it to spheroidize the graphite in the molten iron; and A step of pouring the treated molten iron into a desired mold.

 In the method for producing spheroidal graphite iron according to the present invention, the graphite spheroidizing agent is preferably a magnesium to magnesium alloy. Further, the method for producing spheroidal graphite iron according to the present invention can be applied to the case where molten iron as a raw material is mainly produced by melting a high-tensile steel sheet. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a graph showing the relationship between the amount of additive and the MnP removal rate in Examples.

 FIG. 2 is another graph showing the relationship between the amount of additive and the Mn removal rate in the examples.

 FIG. 3 is still another graph showing the relationship between the additive amount of the additive and the MnP removal rate in the example.

 FIG. 4 is a graph showing the relationship between the additive amount of the additive and the Si content in Examples.

 FIG. 5 is a graph showing the relationship between the additive amount of additives and the C content in Examples.

 FIG. 6 is a graph showing the relationship between the additive amount of additives and the S content in Examples.

 FIG. 7 is another graph showing the relationship between the additive amount of additives and the S content in Examples.

FIG. 8 is still another graph showing the relationship between the additive amount of the additive and the S content in the example. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, embodiments of the present invention will be described in detail. The first to fourth methods for removing manganese from ferrous iron provided by the present invention are methods for reducing the Mn content in the production of ferrous iron, respectively, and are preferably used in the process of producing spherical graphite and iron. The spheroidal graphite iron having a low Mn content obtained by implementing the present invention becomes a highly ductile spheroidal graphite iron having unprecedented high elongation characteristics even when released, which can be said to be a drawback of iron. Since the elongation value and the impact value are improved, they are extremely useful in the technical fields of, for example, automobile parts, electric parts, and building materials. Mn content is low, and in particular, the heat-treated spheroidal graphite-iron has an elongation of around 30% while maintaining the tensile strength at about 350 to 40 OMPa. It is suitably used as undercarriage parts for severe automobile parts.

 In spheroidal graphite iron, Mn is preferably contained in an amount of about 0.4% by mass or less, and more preferably in an amount of about 0.05 to 0.15% by mass. Therefore, by implementing the present invention and reducing the Mn content to this range, it becomes possible to obtain spheroidal graphite-iron having high elongation characteristics while maintaining the tensile strength preferably. If the content of Mn exceeds 0.4% by mass, elongation properties begin to decrease, which is not preferable.

 銬 The mechanical properties of iron such as tensile strength and elongation are in accordance with the test method specified in JIS Z2201.

In the first Mn removing method according to the present invention, characterized in that the mixing added pressure only N a ₂ S_〇 ₄铸鉄melt. By Na ₂ S_〇 ₄ is added, Mn present in铸鉄melt reacts with N a ₂ S 0 ₄ to form a Mn S, N a is铸鉄melt the formed M nS From the surface. As a result, the Mn content in the molten iron is reduced as a result of being discharged out of the molten metal as slag.

As described in Patent Document 1, it is not necessary to suppress the volatilization of Na using Na ₂ S in the first Mn removal method according to the present invention. Rather, as described later, it is preferable to use the volatilization of Na with the temperature of the molten iron in an appropriate range. This is because Mn S is easily separated from the molten iron.

Further, in the first Mn removal method according to the present invention, as described in Patent Document 1, To, but not being over Na ₂ S_〇 ₄ as an oxidizing agent for Mn.

 In these respects, the present invention clearly differs from the information described in Patent Document 1 in its technical idea.

Na ₂ S_〇 ₄ is very inexpensive as compared with K ₂ S. Although not particularly limited, it is more desirable to use products sold as industrial products in terms of cost. This is because those containing some impurities can be used.

When using Na ₂ S ₄ , the required amount of Na ₂ S ₄ can be simply introduced into the molten iron, and there is no need to control the mixing ratio with other additives, so the operation management is simpler. Further, N a ₂ S_〇 ₄ may be dissolved in advance, Na ₂ S_〇 ₄ l 00% charged method if the amount is only to be ensured in accordance with the manganese removal level in terms is not limited.

 In the first Mn removal method according to the present invention, C in the molten iron does not deplete. CIf C, the main element of iron, is depleted, it must be compensated by adding a carburizing agent such as graphite.However, if C in the molten iron does not deplete, a carburizing agent is added. Production costs are reduced because there is no need to do so.

 The first method for removing MnP according to the present invention is a method for producing a spheroidal graphite, which is a component suitable for producing iron, that is, a raw material containing iron of 2.1 mass% or more and silicon of 1.8 mass% or more. In this case, even if the raw material contains 0.4 to 1.5 mass% of manganese, the manganese content of the molten iron can be reduced to 0.4 mass% or less after the method is performed.

The first of MnP excess removed by a method according to the present invention, depending on the amount of N a ₂ S_〇 ₄ to be added, even Mn content錶鉄melt 0.4 mass% or more, and further However, even if the Mn content of the molten iron is 1.5% by mass or more, the Mn removal rate can be 70% or more. Mn removal rate, until the addition amount is about 10 wt% of Na ₂ S_〇 _4, in order to improve in accordance with the amount of Na ₂ S 〇 _4, and Mn content of the feed serving铸鉄melt, after Mn removal the spheroidal graphite in view of the desired Mn content in铸鉄, Na ₂ S_〇 ₄ of addition amount can be determine. Therefore, there is no wasteful consumption of additives, and production costs are reduced.

The addition amount of the additive of Na ₂ S_〇 _4, etc. In the present invention, represented by the mass ratio of the additive serving铸鉄melt amount. In the first method for removing Mn according to the present invention, it is preferable that the temperature of the molten iron as a raw material is approximately 1300 to 1500, and that only Na ₂ SO ₄ is added and mixed into the molten metal. More preferably, it is 1400-1450.

When the temperature of铸鉄melt is less than 1300, S i 0 ₂ generation is vigorous, depletion is largely undesirable in S i is a major component of铸鉄. In the case where the temperature of铸鉄melt exceeds 1500, C_〇, C_〇 ₂ generation is vigorous, C depletion is largely undesirable for a major component of铸鉄.

MWhen Mn and S coexist in the molten iron, MnS is formed or Mn and S are free depending on the content and the temperature of the molten metal. As shown in FIG. 4 in “Peace”, Vol. 38, No. 12, pp. 808-814 (hereinafter referred to as Non-Patent Document 2), in the molten iron above 1300, Mn or S It can be seen that MnS is not formed unless the content (%) of is very high. Since this, the addition of N a ₂ S_〇 ₄ in铸鉄melt, Na, S, is believed to O and S_〇 solution to ₂ binary, S is locally high concentration in铸鉄melt Therefore, it is considered that MnS is formed temporarily, and the volatilized Na becomes bubbles to capture MnS in the molten iron and float and separate.

Next, a second Mn removal method according to the present invention will be described. The second Mn removal method is characterized in that only Na ₂ S is added to and mixed with the molten iron. When Na ₂ S is added, Mn present in the molten iron reacts with S in Na ₂ S to form MnS, and Na floats and separates the formed MnS from the molten iron Let it. As a result, the Mn content in the molten iron is reduced as a result of being discharged out of the molten metal as slag.

 In the second Mn removal method according to the present invention, similarly to the first Mn removal method, the technical description clearly differs from the information described in Patent Document 1 in that the volatilization of Na is not suppressed. Are different.

Na ₂ S is much cheaper than K ₂ S. Although not particularly limited, it is more desirable to use those sold as industrial products in terms of cost. This is because those containing some impurities can be used.

In use, Na ₂ S, like the Na ₂ S0 ₄ in the first Mn removal method,錄 Operation management is simpler because it is only necessary to put the required amount into the molten iron and there is no need to control the mixing ratio with other additives. Further, Na ₂ S may be dissolved in advance, turned methods if the added amount is secured by N a ₂ S 100% conversion is not limited. In the second Mn removal method according to the present invention, C in the molten iron is not depleted. CIf C, the main element of iron, is depleted, it must be compensated by adding a carburizing agent such as graphite.However, if C in the molten iron does not deplete, a carburizing agent is added. Since there is no need to perform this, manufacturing costs can be reduced.

Further, in the second Mn removal method according to the present invention, the Si in the molten iron is less depleted. SIf Si, the main element of iron, is depleted, it must be compensated by adding a silicate additive such as an Fe-Si alloy. S If the depletion of Si in the molten iron is small, since it is possible to reduce the generation amount of slag containing S i 〇 ₂ produced by depletion of S i it is possible to reduce the pressure珪剤to pressure, manufacturing costs i Ru suppressed.

 The second method for removing Mn according to the present invention is a method for producing spheroidal graphite, which is a component suitable for producing iron, that is, a molten iron having carbon of 2.1% by mass or more and silicon of 1.8% by mass or more. In this case, the manganese content of the molten iron can be reduced to 0.4% by mass or less after the method is performed, even if the raw material contains 0.4 to 1.5% by mass of manganese.

Further, the second method for removing MnP according to the present invention is characterized in that, according to the amount of added Na ₂ S, even if the Mn content of the molten iron is 0.4% by mass or more, Even if the Mn content of the molten iron is 1.5% by mass or more, the Mn removal rate can be increased to 35% or more. Mn removal rate, until the addition amount is generally 5 mass% of Na ₂ S, in order to improve in accordance with the amount of Na ₂ S, and Mn content of the feed serving铸鉄melt, spherical black lead after Mn removal铸 The amount of Na ₂ S to be added can be determined in view of the desired Mn content in iron. Therefore, as in the case of the first Mn removal method, wasteful consumption of additives cannot occur, and production costs can be reduced.

In the second method for removing Mn according to the present invention, it is preferable that the temperature of the molten iron as a raw material is approximately 1300 to 1500 ° C, and that only Na ₂ S is added and mixed into the molten metal. More preferably, the temperature is from 1400 to: I 450 ° C. When the temperature of铸鉄melt is less than 1300, S i 0 ₂ generation is vigorous, depletion is largely undesirable in S i is a major component of鎵鉄. In the case where the temperature of铸鉄melt exceeds 1500, C_〇, C0 ₂ generation is vigorous, C depletion is largely undesirable for a major component of铸鉄.

As described in FIG. 4 in Non-Patent Document 2, in the molten iron of 1300 or more, Mn S is not formed unless the Mn or S content (%) is in a very high region. I understand. From this, it is considered that when Na ₂ S is added to molten iron, Na and S are decomposed into Na and S. Since S locally increases in concentration in molten iron, MnS is formed temporarily. However, it is considered that the volatilized Na becomes bubbles and captures MnS in the molten iron and floats and separates.

 Next, a third Mn removal method according to the present invention will be described. The third Mn removal method is characterized in that only NaHS is added to and mixed with the molten iron. With the addition of NaHS, Mn present in the molten iron reacts with S in NaHS to form MnS, and Na floats and separates the formed MnS from the molten iron. As a result, the Mn content in the molten iron is reduced as a result of being discharged out of the molten metal as slag.

 Also in the third Mn removal method according to the present invention, similar to the first and second Mn removal methods, the information described in Patent Document 1 refers to the fact that the volatilization of Na is not suppressed. Clearly different technical ideas.

NaHS is much cheaper than K ₂ S. Although not particularly limited, it is more desirable to use products sold as industrial products in terms of cost. This is because those containing some impurities can be used.

In use, NaHS, like Na ₂ S in Na ₂ S_〇 ₄ and the second M n removal method in the first Mn removal method, it is sufficient simply put the required amount in铸鉄melt, other Operation management is simpler since it is not necessary to control the mixing ratio with additives. In addition, NaHS may be dissolved in advance, and the method of introduction is not limited as long as the addition amount is secured in 100% NaHS conversion.

In the third Mn removal method according to the present invention, C in the molten iron is not depleted. CWhen C, the main element of iron, is depleted, it can be supplemented by adding a carburizing agent such as graphite. However, if C in the molten iron is not depleted, there is no need to add a carburizing agent, and production costs can be reduced.

Further, in the third Mn removal method according to the present invention, the Si in the molten iron is less depleted. SIf Si, the main element of iron, is depleted, it must be compensated by adding a silicate additive such as an Fe-Si alloy. S If the depletion of Si in the molten iron is small, since it is possible to reduce the pressure珪剤to pressure it is possible to reduce the generation amount of slag containing S i 0 ₂ produced by depletion of S i, Ru is suppressed manufacturing cost.

 The third method for removing Mn according to the present invention is a method for producing a spheroidal graphite, a component suitable for producing iron, that is, a molten iron having a carbon content of 2.1% by mass or more and a silicon content of 1.8% by mass or more. In this case, the manganese content of the molten iron can be reduced to 0.4% by mass or less after the method is performed, even if the raw material contains 0.4 to 1.5% by mass of manganese.

 Further, it is considered that the third Mn removal method according to the present invention can increase the Mn removal rate according to the amount of NaHS to be added. Since the Mn removal rate increases with NaHS addition up to about 5% by mass of NaHS, the Mn content of the raw material iron melt and the spheroidal graphite after removal of MnP and iron In view of the Mn content, the amount of NaHS to be added can be determined. Therefore, as in the case of the first and second Mn removal methods, wasteful consumption of additives cannot be caused, and production costs can be reduced. In the third Mn removal method according to the present invention, it is preferable that the temperature of the molten iron as a raw material is approximately 1300 to 1500 ° C., and that only NaHS is added and mixed into the molten metal. More preferably, it is 1400-1450.

When the temperature of銬鉄melt is less than in 1300, S i 0 ₂ generation is vigorous, depletion is largely undesirable in S i is a major component of铸鉄. In the case where the temperature of铸鉄melt exceeds in 1500, CO, C0 ₂ generation is vigorous, C depletion is largely undesirable for a major component of铸鉄.

As shown in Fig. 4 in Non-Patent Document 2, in molten iron of 1300 or more, Mn S may not be formed unless the Mn or S content (%) is in a very high region. Understand. From this, when NaHS is added to molten iron, Na, H And S is thought to decompose into S. Since S locally increases in concentration in the molten iron, MnS is formed temporarily, and the volatile Na becomes bubbles, and MnS in the molten iron It is thought that it will catch and float.

In the first to third Mn removal methods according to the present invention, a steel scrap material having a high Mn content can be used as a raw material for iron. That is, Na ₂ SO ₄ , Na ₂ S or NaHS is added to the molten metal in which steel scrap is melted to remove Mn, and the spheroidal graphite-iron can be obtained by the molten metal treatment with a graphite spheroidizing agent. As the raw material to be dissolved, return materials such as feeders and runners generated in the pig iron and steel manufacturing industry, press scrap materials for automobiles, and the like can be used for each S source, and any of them can be used.

 In addition, high-strength steel sheets, surface-treated (plated) steel sheets, other carbon steels for general structures, and the like are listed as the steel sheet types, and any of them can be used. In particular, high-tensile steel sheets, which are frequently used for automobiles, have a high Mn content, which has been an obstacle in improving the mechanical properties of spheroidal graphite and iron, but the present invention has eliminated the obstacle. It is.

 Furthermore, in the second Mn removal method according to the present invention, the increase in S in the molten iron is small. In the case of spheroidal graphite and iron, S is an element that inhibits the spheroidization of graphite, so it is necessary to keep the S content to 0.02% by mass or less, but the increase in S in the molten iron is small. If this is the case, the desulfurizing agent to be added can be reduced, and the production cost can be reduced.

 Subsequently, a fourth Mn removal method according to the present invention will be described. The fourth Mn removal method is characterized in that a sulfur compound containing an element whose boiling point is lower than the temperature of the molten iron and not containing manganese is added to and mixed with the molten iron.

 硫黄 Sulfur (S) generated by the decomposition of sulfur compounds in the molten iron easily reacts with Mn in the molten iron and forms MnS by reaction. The compound Mn S immediately after its formation is present in the molten iron.

 On the other hand, a substance contained in a sulfur compound and having an element whose boiling point is lower than the temperature of the molten iron is volatilized because the ambient temperature is higher than its own boiling point in the molten iron, and is diffused into the molten iron to form bubbles. And 铸 rise in the molten iron.

Since the generation of Mn S and the generation of air bubbles occur almost simultaneously, the air bubbles separate Mn S from the molten iron and become slag. As a result, the Mn content in the molten iron is reduced. Since it is a method to remove Mn, the sulfur compound to be added It is not preferable that n is included.

Examples of the substance contained in the sulfur compound include K, Na, and the like. Further, examples of sulfur compounds containing the same include K ₂ SO ₄ , and the like.

 铸 Regarding the steps other than the processing for performing the Mn removal method of the present invention in the production of iron, the production can be performed by a known method. Hereinafter, an example of spheroidal graphite and iron will be described.

 After the raw material including the steel scrap from the material yard and blended in consideration of the blended component amount is melted as molten iron using an electric furnace (induction heating melting furnace or arc furnace) or a gas furnace, the present invention An Mn removal method is performed. The molten metal produced according to the target composition is then taken out to a ladle and subjected to inoculation with the addition of Fe-Si alloy, etc., and melt treatment such as spheroidization of graphite with addition of magnesium or magnesium alloy. .

 After the molten metal treatment, the molten metal is poured into the mold and poured, and then solidified and cooled in the mold.物品 After the articles in the mold are cooled, the mold is separated and cooled by a shakeout machine or a drum cooler, and the sand adhered to the surface of the articles is removed by shot blasting. Can be hung. Finishing such as weirs and deburring is performed in this finishing process, and the iron product is obtained.

 Hereinafter, the present invention will be described more specifically based on examples.

 (Examples 1 to 6)

 Using high-purity pig iron, electrolytic iron, and Fe-Mn alloy, a master alloy prepared to contain 0.35% by mass of Mn was melted using a high-frequency electric furnace. Then, the Mn content (mass%) in the alloy was examined by chemical analysis (this Mn content was defined as Mn 1). Table 1 shows Mn and other chemical components (% by mass) of this master alloy.

 (table 1)

 [% By mass]

次いで、 母合金 600 gを内径 75mm(f)X高さ 95mmの黒鉛坩堝にとり、 高周波電気炉中で溶解した。 そして、 140 Ot:に保持しながら添加剤として N a₂S〇₄を投入し混合し、 5分後にスラグを除去し分析用試料を採取し、 Na₂S 〇₄添加後の Mn含有量 （質量％) を化学分析して調べた （この Mn含有量を Mn 2とする） 。 又、 Mn含有量 （質量％) の化学分析に加えて、 同様な方法により 、 Na₂S〇₄添加後の C含有量 （質量％) を調べた。 更に、 その分析用試料につい て EPMA (電子線マイクロアナライザ） により観察を行ったところ、 反応生成 物として多数の Mn Sが確認された。 尚、 Na₂S〇₄は、 Na₂S〇₄* 10H₂〇を 電気炉にて 350 で過熱脱水したものを用いた。

Next, 600 g of the mother alloy was placed in a graphite crucible having an inner diameter of 75 mm (f) x a height of 95 mm, Melted in a high frequency electric furnace. Then, 140 Ot: the N a ₂ S_〇 ₄ was charged and mixed as an additive while maintaining, removing slag samples for analysis were taken after 5 minutes, Na ₂ S 〇 ₄ Mn content after the addition ( Mass%) was analyzed by chemical analysis (this Mn content is referred to as Mn 2). In addition to the chemical analysis of the Mn content (mass%), in the same manner, was tested C content after the addition Na ₂ S_〇 ₄ (mass%). Further, when the sample for analysis was observed by an electron beam microanalyzer (EPMA), a large number of MnS were confirmed as reaction products. Incidentally, Na ₂ S_〇 ₄ was used as the superheated dehydrated at 350 the Na ₂ S_〇 ₄ * 10H ₂ 〇 in an electric furnace.

Amount of Na ₂ S_〇 _4, 0.5 wt% (Example 1), 1 wt% (Example 2), 3 wt% (Example 3), 5 wt% (Example 4), 7 mass % (Example 5) and 10% by mass (Example 6). The C content (% by mass) was investigated in Examples 2, 4, and 6 only.

Then, we calculated Mn removal rate by the addition of Na ₂ S_〇 ₄ (%) by the following equation.

Mn removal rate = the (Mn 1 -Mn 2) / Mn 1 X 100 Examples 1-6, shown in Figure 1 the relationship between the addition amount of Mn removal rate of Na ₂ S_〇 _4. Also shows the relationship between the added amount and the C content of Na ₂ S_〇 ₄ according to Example 2, 4, 6 in FIG. 5

(Examples 7 to 12)

The Mn removal rate (%) was determined in the same manner as in Examples 1 to 6, except that a master alloy prepared so as to contain 0.7% by mass of Mn was used. Table 1 shows the Mn and other chemical components (% by mass) of the master alloy. Amount of Na ₂ S_〇 _4, 0.5 wt% (Example 7), 1 wt% (Example 8), 3 wt% (Example 9), 5 mass% (Example 10), 7 mass % (Example 11) and 10% by mass (Example 12). The relationship between the addition amount and the M n removal rate of Na ₂ S_〇 ₄ according to example 7-12 shown in FIG.

 (Examples 13 to 18)

The Mn removal rate (%) was determined in the same manner as in Examples 1 to 6, except that a master alloy prepared to contain 1.5% by mass of Mn was used. Table 1 shows the Mn And other chemical components (% by mass). Amount of Na ₂ S0 _4, the 0.5 wt% (Example 13), 1 mass% (Example 14), 3 wt% (Example 15), 5 mass% (Example 16), 7 wt% (Example 17) and 10% by mass (Example 18). The relationship between the addition amount of Mn removal rate of Na ₂ S0 ₄ by actual施例13-18 shown in FIG.

 (Examples 19 to 22)

Except that Na ₂ S was used as an additive, the Mn removal rate was the same as in Examples 1 to 4.

(%). In addition to the chemical analysis of the Mn content (mass%), more similar manner, S i content after Na ₂ S added (wt%), C content (mass%) and the S content

(% By mass). Incidentally, Na ₂ S was used as the overheated dehydrated at 350 the Na ₂ S · 9 H ₂ 0 in an electric furnace. The addition amounts of Na ₂ S are 0.5% by mass (Example 19), 1% by mass (Example 20), 3% by mass (Example 21), and 5% by mass (Example 22). The C content (% by mass) was investigated only in Examples 20 to 22. FIG. 1 shows the relationship between the added amount of Na ₂ S and the Mn removal rate in Examples 19 to 22. FIG. 4 shows the relationship between the added amount of Na ₂ S and the Si content according to Examples 19 to 22, and FIG. 5 shows the relationship between the added amount of Na ₂ S and the C content according to Examples 20 to 22. FIG. 6 shows the relationship between the added amount of Na ₂ S and the S content according to Examples 19 to 22, respectively.

 (Examples 23 to 26)

The Mn removal rate (%) was determined in the same manner as in Examples 7 to 10, except that Na ₂ S was used as an additive. In addition to the chemical analysis of the Mn content (% by mass), the S content (% by mass) after the addition of Na ₂ S was examined by the same method. The addition amounts of Na ₂ S are 0.5% by mass (Example 23), 1% by mass (Example 24), 3% by mass (Example 25), and 5% by mass (Example 26). FIG. 2 shows the relationship between the amount of added Na ₂ S and the Mn removal rate according to Examples 23 to 26. FIG. 7 shows the relationship between the added amount of Na ₂ S and the S content according to Examples 23 to 26.

 (Examples 27 to 30)

The Mn removal rate (%) was determined in the same manner as in Examples 13 to 16, except that Na ₂ S was used as an additive. In addition to the chemical analysis of the Mn content (% by mass), the S content (% by mass) after the addition of Na ₂ S was examined by the same method. The addition amount of Na ₂ S is 0.5% by mass (Example 27), 1% by mass (Example 28), 3% by mass (Example 29). And 5% by mass (Example 30). FIG. 3 shows the relationship between the added amount of Na ₂ S and the Mn removal rate according to Examples 27 to 30. FIG. 8 shows the relationship between the added amount of Na ₂ S and the S content according to Examples 27 to 30.

 (Examples 31, 32)

The Mn removal rate (%) was determined in the same manner as in Examples 21 and 22, except that NaHS was used as an additive. In addition to the chemical analysis of the Mn content (% by mass), the Si content (% by mass) and the C content (% by mass) after the addition of NaHS were examined by the same method. Incidentally, NaHS is used was overheated dehydrated at 350 NaHS · 2 H ₂ 〇 in an electric furnace. The addition amount of NaHS is 3% by mass (Example 31) and 5% by mass (Example 32). Figure 1 shows the relationship between the amount of NaHS added and the Mn removal rate in Examples 31 and 32. FIG. 4 shows the relationship between the amount of NaHS added and the Si content according to Examples 31 and 32. FIG. 5 shows the relationship between the amount of NaHS added and the C content according to Examples 31 and 32.

 (Comparative Examples 1 to 6)

The Si content (% by mass) after the addition of K ₂ S was examined in the same manner as in Examples 19 to 22, except that K ₂ S was used as an additive. In the same manner, the addition amount was increased to 10% by mass, and the S content (% by mass) after the addition of K ₂ S was examined. The addition amounts of K ₂ S are 0.5% by mass (Comparative Example 1), 1% by mass (Comparative Example 2), 3% by mass (Comparative Example 3), 5% by mass (Comparative Example 4), 7% by mass ( Comparative Example 5) and 10% by mass (Comparative Example 6). FIG. 4 shows the relationship between the added amount of K ₂ S and the Si content according to Comparative Examples 1 to 4. FIG. 6 shows the relationship between the added amount of K ₂ S and the S content according to Comparative Examples 1 to 6.

 (Comparative Examples 7 to 12)

Except that as an additive with K ₂ S, in the same manner as in Example 23 to 26, the amount was increased to 10 wt%, was examined S content after K ₂ S added (mass%). The addition amounts of K ₂ S are 0.5% by mass (Comparative Example 7), 1% by mass (Comparative Example 8), 3% by mass (Comparative Example 9), 5% by mass (Comparative Example 10), 7% by mass ( Comparative Example 11 1) and 10% by mass (Comparative Example 12). FIG. 7 shows the relationship between the added amount of K ₂ S and the S content according to Comparative Examples 7 to 12.

(Comparative Example 13: L 8) Except that as an additive with K ₂ S, in the same manner as in Example 27 to 30, the amount was increased to 10 wt%, was examined S content after K ₂ S added (mass%). The addition amounts of K ₂ S are 0.5% by mass (Comparative Example 13), 1% by mass (Comparative Example 14), 3% by mass (Comparative Example 15), 5% by mass (Comparative Example 16), 7% by mass ( Comparative Example 17), 10% by mass

(Comparative Example 18). FIG. 8 shows the relationship between the added amount of K ₂ S and the S content according to Comparative Examples 13 to 18.

 (Discussion)

From the results of Examples 1 to 32, generation of MnS was confirmed by adding and mixing the additive to a molten metal in which an alloy having a high Mn content was melted at a predetermined temperature, and FIGS. 1 to 3 and FIG. As shown in Fig. 5, it was confirmed that the Mn content can be reduced from the master alloy having a high Mn content according to the additive amount without depleting C. Also, as shown in FIG. 4, it was confirmed that when the additive was Na ₂ S or NaHS, Si was hardly depleted. Furthermore, as shown in FIGS. 6 to 8, it was confirmed that when the additive was Na ₂ S, the increase in S was small. Industrial applicability

 As described above, according to the present invention, one type of additive is mixed with a raw material molten iron, preferably at a desired molten temperature, so that C is not depleted, and the amount of additive added is reduced. Accordingly, the Mn content can be reduced. Also, by selecting the additive, the depletion of Si and the increase of S can be suppressed. Therefore, it is possible to actively accept high-tensile steel sheets with a high Mn content, which are increasing as raw materials, and it is not necessary to use expensive pig iron or the like. The spheroidal graphitized iron obtained by the present invention can reduce the Mn content without sacrificing the tensile strength even when using inexpensive steel scrap with a high Mn content as a raw material. Elongation properties can be improved. That is, the present invention has an excellent effect that iron can be obtained at low cost and with high mechanical properties.

Claims

The scope of the claims  1. A method for reducing the manganese content in the production of iron, which comprises adding sodium sulfate as an additive to the molten iron and mixing it.  2. A method for reducing manganese content in the production of iron, which comprises adding and mixing sodium sulfide as an additive to the molten iron, and removing manganese from the molten iron.  3. A method for reducing manganese content in the production of iron, which comprises adding sodium hydrogen sulfide as an additive to the molten iron and mixing it.  4. The molten iron contains 2.1% by mass or more of carbon, 1.8% by mass or more of silicon, and 0.4 to 1.5% by mass of manganese. 4. The method for removing manganese in molten iron according to any one of claims 1 to 3, wherein the molten iron has a manganese content of 0.4% by mass or less.  5. The method for removing manganese in a molten iron melt according to any one of claims 1 to 4, wherein the temperature of the molten iron melt is approximately 130 to 150.  6. The method for removing manganese in molten iron according to any one of claims 1 to 5, wherein the molten iron is made of a steel scrap material of a high-tensile steel sheet.  7. A method for reducing the manganese content in the production of iron, characterized by adding and mixing a sulfur compound containing an element having a boiling point lower than the temperature of the molten iron and containing no manganese to the molten iron.铸 Method for removing manganese from molten iron.  8. A step of preparing molten iron as a raw material, and reducing the manganese content of the molten iron by using the method for removing manganese in molten iron according to any one of claims 1 to 7. The manganese content is reduced. A graphite spheroidizing agent is added to the molten iron to cause a reaction. The graphite spheroidizing process for spheroidizing the graphite in the molten iron, and the graphite spheroidizing treatment are performed. A step of pouring the molten iron into a desired mold, and a method for producing spheroidal graphite and iron, comprising: 9. The method for producing spheroidal graphite and iron according to claim 8, wherein the graphite spheroidizing agent is magnesium or a magnesium alloy. 10. The method for producing spheroidal graphite iron according to claim 8, wherein the molten iron as the raw material is mainly produced by melting a high-tensile steel sheet.