JP4477897B2 - Rolled cast iron and method for producing the same - Google Patents

Description

  The present invention relates to rolled cast iron and a method for producing rolled cast iron. The rolled cast iron of the present invention is suitably used as a vibration damping material.

  For the purpose of preventing vibration and noise, various damping materials are used in various usage environments. For example, materials for industrial machinery used in railway bridges that run close to residential areas and places close to residential areas are required to have high vibration damping properties in addition to strength, which is a basic characteristic of structural materials. That is, it is preferable to use an iron product that is capable of suppressing vibration and noise when the vehicle is running or when using an industrial machine and that is excellent in vibration damping.

  As a vibration damping material, Patent Document 1 proposes a cast iron plate formed by rolling spheroidal graphite cast iron and depositing graphite in layers. Patent Document 2 proposes an austenitic flake graphite cast iron containing graphite having a length of 400 μm or more. Patent Document 3 discloses a damping alloy that has a predetermined composition and is systematically a ferrite single phase.

However, rolling of the spheroidal graphite cast iron disclosed in Patent Document 1 is difficult, and the workability of the rolled cast iron is also low. The flake graphite cast iron disclosed in Patent Document 2 is also difficult to roll and has low workability. When the damping alloy disclosed in Patent Document 3 is welded, the damping property is lost.
Japanese Patent Laid-Open No. 2-80514 JP-A-4-147940 Japanese Patent Application Laid-Open No. 6-220583

  Then, the objective of this invention is providing the cast iron which is excellent in both workability and vibration suppression property.

The present invention
(1) extending the graphite particles is a rolled iron you are dispersed, the average width of the distracted graphite particles is 0.05-0.4 mm, average length of the distracted graphite particles 1. Rolled cast iron, characterized in that it is 25 to 50 mm, and the average interval between the elongated graphite particles is 30 μm or less,
(2) The rolling according to (1), wherein the concentration [C] (mass%) of carbon atoms and the concentration [Si] (mass%) of silicon atoms in the rolled cast iron satisfy the following formula: cast iron,

(3) The rolled cast iron according to (1) or (2), which is a damping material,
(4) The carbon atom concentration [C] (mass%) and the silicon atom concentration [Si] (mass%) satisfy the following formula, and the spheroidizing agent oxide, sulfide, nitride, or these Obtaining molten iron in which the composite compound is dispersed;

Casting the molten iron to obtain a cast slab having a white cast iron structure, and rolling the cast slab at a temperature of 900 ° C. or more at a reduction ratio of 25 or more to obtain rolled cast iron. A method for producing rolled cast iron in which elongated graphite particles are dispersed ,
It is.

  The rolled cast iron of the present invention is excellent in both workability and vibration damping properties. For this reason, application to various parts is possible.

  A first aspect of the present invention is a rolled cast iron having a white cast iron structure in which elongated graphite particles are dispersed, wherein the average width of the elongated graphite particles is 0.05 to 0.4 mm, and the elongated The rolled cast iron is characterized in that an average length of graphite particles is 1.25 to 50 mm, and an average interval between the elongated graphite particles is 30 μm or less.

  Rolled cast iron is formed by rolling a slab. The slab means a material molded using a mold, such as billet, bloom, or slab. The composition of the rolled cast iron of the present invention is not particularly limited as long as the rolled cast iron has a white cast iron structure. There are various types of cast iron such as white cast iron, gray cast iron, and mottled cast iron. White cast iron is cast iron that does not contain graphite. White cast iron is preferably composed of hypoeutectic components. Gray cast iron is cast iron that exists in the state of graphite with C liberated. The mottled cast iron is cast iron mixed with gray cast iron or white cast iron. The rolled cast iron of the present invention has a white cast iron structure. “Having a white cast iron structure” means that at least a part of the rolled cast iron is white cast iron. Preferably, the rolled cast iron of the present invention is white cast iron entirely or substantially entirely. Here, “substantially the whole” is a concept including a state in which a non-white cast iron structure based on impurities inevitably mixed is present in a part of the rolled cast iron. As will be described later, when adopting the process of rolling a cast slab in which graphite nuclei are dispersed in a white cast iron structure to produce a rolled cast iron, a rolled cast iron excellent in both vibration damping and workability can be obtained. It is done.

  In order to become white cast iron, the content of carbon atoms and silicon atoms is important. Carbon atoms are preferably contained in an amount of 1.7% by mass or more with respect to the mass of the rolled cast iron. The upper limit of the carbon atom content is usually 4.3% by mass or less. The preferred content of silicon atoms depends on the content of carbon atoms. Specifically, the carbon atom concentration [C] (mass%) and the silicon atom concentration [Si] (mass%) in the white cast iron structure preferably satisfy the following formula. The carbon concentration in the rolled slab is measured using, for example, an infrared absorption method, and the silicon concentration in the slab is measured using, for example, an absorptiometry.

  More preferably, the concentration [C] (mass%) of carbon atoms and the concentration [Si] (mass%) of silicon atoms in the white cast iron structure present in the rolled cast iron satisfy the following formula.

  There are no particular limitations on the components other than carbon atoms and silicon atoms. For example, the concentration of iron, the concentration of phosphorus, the concentration of sulfur, etc. are usually in the general range for cast iron. However, rolled cast iron whose concentration of sulfur, phosphorus, etc. is not in the general concentration range is not excluded from the technical scope of the present invention.

  Since cast iron can be manufactured without performing a refining process such as a decarburization process, it can be manufactured at a low cost. However, if necessary, a refining process such as a desulfurization process may be performed. Cast iron produced through a refining process is not excluded from the technical scope of the present invention.

  In the rolled cast iron of the present invention, elongated graphite particles are dispersed. High vibration damping is ensured by the elongated graphite particles. Moreover, the rolled cast iron of the present invention having a white cast iron structure is excellent in workability. In the prior art, the elongated graphite particles could not be dispersed inside the rolled cast iron having a white cast iron structure. However, the present inventors have developed such an excellent rolled cast iron.

  Although the manufacturing method of the rolled cast iron of this invention is demonstrated in detail later, here, a manufacturing process is demonstrated easily. FIG. 1 is a flow diagram showing a process for producing rolled cast iron for each of spheroidal graphite cast iron (ductile cast iron), white cast iron in which no graphite nuclei are dispersed, and white cast iron in which graphite nuclei are dispersed. .

  FIG. 1A is a flow diagram showing a rolled cast iron manufacturing process for spheroidal graphite cast iron (ductile cast iron). Ductile cast iron is cast iron made of a hypereutectic component. In the melting process, spherical graphite 120 formed around graphite production nuclei 110 such as a magnesium compound is dispersed in molten iron 10. Also in the slab 20 manufactured in the casting process, the spherical graphite 120 formed around the graphite generation nucleus 110 is dispersed. The slab 20 that is ductile cast iron has a certain degree of workability because the spherical graphite 120 is dispersed inside the slab. However, when the cast slab in which the spheroidal graphite is dispersed is rolled, coarse flaky graphite 121 derived from the spheroidal graphite is generated in the rolled cast iron 30 and becomes a rolled cast iron having a problem in the surface shape.

  In order to enable the slab to be rolled, it is preferable to produce a slab in which graphite particles are not dispersed. FIG. 1B is a flowchart showing a rolled cast iron manufacturing process for black core malleable cast iron that is white cast iron. Black core malleable cast iron is cast iron composed of hypoeutectic components, and the spheroidizing agent element is not blended in molten iron 11 in the melting process. Therefore, the graphite particles are not dispersed even in the slab 21 made of the white cast iron component manufactured in the casting process, and can be rolled. However, it is difficult to continuously cast a slab that is black core malleable cast iron. Rolled cast iron 31 obtained in the rolling process is superior in surface shape compared to ductile cast iron. However, since the cast cast iron 31 is hard and brittle, it is preferable that post-treatment such as annealing described above is performed. First, rolled cast iron 41 in which free cementite is decomposed is obtained by a short-time heat treatment. The rolled cast iron 41 is subjected to a long-time heat treatment to obtain a rolled cast iron 51 in which the graphite particles 122 are dispersed. The graphite particles 122 are usually massive graphite. By generating the graphite particles 122 inside the rolled cast iron 51, the workability of the rolled cast iron 51 is improved. Normal annealing conditions are short-time heat treatment at a temperature of 900 to 980 ° C. and 10 to 20 hours. The long-time heat treatment combines slow cooling at a temperature of 700 to 760 ° C. with long-time treatment in the range of 700 to 730 ° C. The time required for the total annealing process is usually about 20 to 100 hours.

  By the process shown in FIG. 1B, it is possible to obtain rolled cast iron having excellent workability and vibration damping properties. However, since graphitization by annealing requires a long time, it is preferable to use a simpler manufacturing method from the viewpoint of improving the productivity of rolled cast iron. The inventors of the present invention have a rolling process that is excellent in workability by adopting a production method in which graphite forming nuclei that promote graphite formation are mixed in molten iron composed of components that become white cast iron, and graphite is generated after the rolling step. It has been found that cast iron can be produced efficiently in a short time.

  FIG. 1C is a flowchart showing a rolled cast iron manufacturing process for white cast iron in which graphite nuclei are dispersed. White cast iron is cast iron made of hypoeutectic components, and graphite forming nuclei 130 are dispersed in the molten iron 12 in the melting process. Also in the slab 22 made of white cast iron component produced in the casting process, the generation of graphite particles does not proceed, and the graphite nuclei 130 are dispersed. Since the graphite particles are not dispersed in the slab like the slab 10 in FIG. 1A, the slab 12 can be rolled.

  The internal structure of the rolled cast iron obtained in the rolling process varies depending on the rolling conditions. When the rolling conditions are high, in the rolling process, graphitization proceeds rapidly with the graphite forming nuclei 130 as nuclei, and the rolled cast iron 32 in which the graphite particles 123 are dispersed is obtained. Graphite particles 123 that have been graphitized during rolling have an elongated shape due to pressure during rolling. The rolled cast iron 32 of the present invention is a cast iron having excellent vibration damping properties in which elongated graphite particles 123 formed by such a manufacturing method are dispersed. Moreover, since it has a white cast iron structure, it is excellent also in workability. In the rolled cast iron 32 of the present invention, graphite particles other than the elongated graphite particles may be dispersed. For example, spherical graphite particles may be dispersed. In the present invention, “elongated graphite particles” mean graphite particles deformed in the rolling direction of the rolled cast iron due to the pressure during rolling. For example, elliptical spherical graphite particles, acicular graphite particles, and the like correspond to elongated graphite particles.

  Thus, when the cast slab which disperse | distributed the graphite production nucleus is produced, the rolled cast iron excellent in workability is obtained very simply. When it is desired to improve the workability of the rolled cast iron 32, the rolled cast iron 32 may be heat-treated for a short time to produce the rolled cast iron 42 in which more graphite particles 123 are dispersed. Graphite particles 123 ′ that have been graphitized by heat treatment after rolling become spherical graphite. By dispersing more graphite particles 123, workability of the rolled cast iron 42 is improved. Even when heat treatment is performed after rolling to generate graphite particles, graphitization proceeds with a short heat treatment when the graphitization proceeds with the graphite generation nuclei 130 as nuclei. For this reason, productivity of the rolled cast iron which is excellent in workability improves.

  By such a production method, rolled cast iron in which the elongated graphite particles are dispersed is produced. When rolled cast iron in which the elongated graphite particles are dispersed can be produced by other methods, the above-described production method is used. Different manufacturing methods may be employed.

  In addition, when rolling conditions are low temperature, graphitization does not advance in a rolling process and the rolled cast iron 33 in which the graphite production | generation nucleus 130 was disperse | distributed is obtained. When the rolled cast iron 33 in which the graphitization has not progressed is obtained, the rolled cast iron 33 may be subjected to heat treatment for a short time to generate the graphite particles 124 formed with the graphite forming nuclei 130 as nuclei. In this case, the vibration damping property can be improved by cold rolling and extending the dispersed graphite.

  In the present invention, the shape of the elongated graphite particles dispersed in the rolled cast iron is defined. Specifically, the average width of the elongated graphite particles is 0.05 to 0.4 mm, the average length of the elongated graphite particles is 1.25 to 50 mm, and the average interval between the elongated graphite particles is 30 μm or less. It is. The lower limit value of the average interval between the graphite particles is not particularly limited, but is actually 5 μm or more.

  Here, the concepts of “width of elongated graphite particles”, “length of elongated graphite particles”, and “interval between elongated graphite particles” will be described with reference to the drawings. FIG. 2 is a schematic cross-sectional view in the thickness direction of rolled cast iron for explaining the concepts of “width of elongated graphite particles”, “length of elongated graphite particles”, and “interval between elongated graphite particles”. FIG. 3 is a schematic sectional view in the width direction of rolled cast iron. 2 and 3 are exaggerated for convenience of explanation, and the technical scope of the rolled cast iron of the present invention is limited by the shape and size described in FIGS. 2 and 3. It is not something. The “width of the elongated graphite particles” means the width (W) in the minor axis direction of the elongated graphite particles in FIG. W tends to be shorter as the graphite particles are elongated by the pressure during rolling. The “length of the elongated graphite particles” means the width (L) in the major axis direction of the elongated graphite particles in FIGS. 2 and 3. L tends to be longer as the graphite particles are elongated by the pressure during rolling. “Width of elongated graphite particles” and “length of elongated graphite particles” are defined as average values. The calculation method of the average value of width and length is not particularly limited as long as it is a method that is statistically measured with a certain degree of accuracy. For example, an arbitrary 10 cm × 10 cm cross section of the rolled cast iron is observed, the width and length of the elongated graphite particles to be confirmed are measured, and the average is calculated. It is convenient to measure the width and length using a cross-sectional photograph. As shown in FIG. 2, the “interval between the elongated graphite particles” means the shortest distance (S) in the thickness direction from the closest elongated graphite particle when the cross section is observed. The average value of the interval can be calculated in the same manner as the width and length. For example, using a cross-sectional photograph, the interval between all graphite particles existing in a range of 10 cm × 10 cm is measured, and the average value is calculated.

  Rolled cast iron that satisfies the above-mentioned specifications for width, length, and interval is cast iron that has excellent vibration damping properties and excellent workability, and can be applied to various applications by taking advantage of its characteristics. . Since the rolled cast iron of the present invention is excellent in vibration damping properties, it is particularly suitable for use as a vibration damping material.

  Preferably, the graphite particles dispersed in the rolled cast iron are partially or entirely covered with ferrite. Rolled cast iron in which graphite particles in which ferrite is formed on the outer periphery is dispersed has good workability. Preferably, the proportion of ferrite in cast iron is 70% by volume or more. When the proportion of ferrite is 70% by volume or more, rolled cast iron with good workability can be obtained. The ratio of ferrite is calculated by measuring the area of ferrite in the cross section of the slab.

The amount of graphite particles dispersed in the rolled cast iron is not particularly limited, but if the amount of dispersion is too small, the workability may be lowered. For this reason, Preferably, the number density of the graphite particles in rolled cast iron is 50 particles / mm ² or more.

  Next, the second of the present invention will be described. The second of the present invention relates to a method for producing rolled cast iron in which elongated graphite particles are dispersed. That is, the second aspect of the present invention is that the carbon atom concentration [C] (mass%) and the silicon atom concentration [Si] (mass%) satisfy the following formula, and the spheroidizing agent oxide or sulfide: Obtaining molten iron in which nitride or a composite compound thereof is dispersed;

  Casting the molten iron to obtain a cast slab having a white cast iron structure, and rolling the cast slab at a temperature of 900 ° C. or higher at a reduction ratio of 25 or more to obtain rolled cast iron. Is a method for producing rolled cast iron in which elongated graphite particles are dispersed.

  First, molten iron having a carbon atom concentration [C] (mass%) and a silicon atom concentration [Si] (mass%) satisfying the above formula is obtained. Various materials such as iron ore, sintered ore, limestone, coke, and pellets can be used as the iron source. In some cases, resources may be effectively used by using iron scrap or the like as an iron source. About the usage-amount of raw materials, such as an iron ore, a sintered ore, limestone, coke, and a pellet, and a ironmaking process, if a carbon content and a silicon content are the above-mentioned ranges, it will not specifically limit.

  In the molten iron, an oxide, sulfide, nitride or complex compound of the spheroidizing element is dispersed. The spheroidizing agent element means an element that combines with oxygen, sulfur, and nitrogen contained in cast iron and forms a compound that promotes the formation of graphite particles as a nucleus when heat is applied. In other words, when a spheronizing element is blended in molten iron, the spheronizing element combines with oxygen, sulfur or nitrogen contained in the iron to form an oxide, sulfide, nitride or a composite compound thereof. To form particles. These particles act as nuclei for generating graphite particles, and when the slab or rolled cast iron is heated, the generation of graphite particles is promoted. By dispersing such spheroidizing element oxides, sulfides, nitrides, or composite compounds thereof, it is possible to perform heat treatment for a relatively short time without performing heat treatment for a long time, or rolling. Due to the heat of the time, graphite particles are generated inside the rolled cast iron. This graphite particle improves the workability of the rolled cast iron.

  As a spheroidizing agent element, it is preferable that at least one of Mg or Ca is contained, and it is more preferable that Mg having a great effect of promoting spheroidization is contained. Rare earth elements (REM) may be included as a spheronizing agent element. The spheronizing agent element may be a single element or a mixture of a plurality of elements. Specific examples of spheroidizing agent elements include Fe-Si-Mg, Ca-Si, Fe-REM, Fe-Mg, Fe-Si-Ca-Mg, Fe-Si-Mg-REM, Misch metal, Ni-Mg Etc.

The dispersion amount of the graphite nuclei is not particularly limited. However, if the dispersion amount is too small, the production of graphite particles during the heat treatment is delayed, and the productivity may be reduced. Moreover, since the density of the produced spherical graphite is slightly reduced and the graphite particles are coarse, there is a possibility that the workability is lowered. Therefore, the number density of graphite forming nuclei in the slab is preferably 50 pieces / mm ² or more.

  The size of the graphite-forming nuclei is not particularly limited as long as it can act as a nucleus for forming graphite particles, but the average particle diameter of the graphite-forming nuclei is preferably 0.05 μm to 5 μm. If the graphite formation nuclei are too small, it may be difficult to act as nuclei for the formation of graphite particles. On the other hand, if the graphite nuclei are too large, the generated graphite particles become coarse and the workability may be reduced. Here, the particle diameter means the equivalent circle diameter of the particle. The diameter of the particles can be obtained, for example, by observing a cross section, measuring the equivalent circle diameter of all particles in a predetermined region, and calculating the average. Other measurement methods may be employed.

  When a spheroidizing agent element is added and graphite formation nuclei are dispersed inside the slab, it is preferable that the slab before rolling is dispersed as graphite formation nuclei without causing graphitization. . However, it is not intended to exclude an aspect in which graphite particles are present as much as possible, but graphite particles having graphite-forming nuclei as a center may be generated within a range where rolling is possible. That is, a slab in which only graphite-forming nuclei are dispersed and graphite particles are not dispersed is preferable, but a slab in which some graphite particles are dispersed together with graphite-forming nuclei may be used.

  The spheronizing agent element is added to a ladle or tundish. Thereby, the spheroidizing agent oxide, sulfide, nitride or a composite compound thereof can be dispersed in the molten iron. The addition amount of the spheroidizing agent element may be determined according to how much graphite particles are desired to be dispersed in the rolled cast iron. When a large amount of graphite particles is dispersed in rolled cast iron, the amount of spheroidizing agent element added may be increased. Usually, the spheroidizing agent element is added so as to have a concentration of about 0.02% by mass with respect to the molten iron.

  If necessary, other components such as chromium and nickel may be added to the molten iron. However, since expensive materials such as nickel increase the manufacturing cost, it is preferable to reduce the addition amount.

  Next, molten iron is cast to obtain a slab having a white cast iron structure. In the production of the slab, a batch casting method using a large number of molds may be used, or a continuous casting method using tundish and a hollow mold may be used. In consideration of the productivity of the slab, the slab is preferably manufactured using a continuous casting method. The apparatus used for casting may be determined by appropriately referring to the knowledge already obtained. For example, in the continuous casting method, a continuous casting apparatus including a ladle, a tundish, a mold, a support roll, a spray nozzle, and the like is used. Preferably, a water-cooled copper mold is used as the mold. By using a water-cooled copper mold, it is possible to increase the cooling rate of the slab. In addition, it is possible to suppress the generation of graphite due to the mold as compared with the case of using with a graphite mold.

  The casting conditions are preferably controlled so as to obtain a cooling rate at which white cast iron is obtained. Although the specific cooling rate is unambiguously defined because it is affected by the casting conditions, it may be appropriately determined by using the obtained knowledge or preliminary investigation. In general, white cast iron is easily obtained when the cooling rate is high.

  If the slab obtained by continuous casting is too thick, the cooling rate at the center portion may decrease, and graphitization may proceed. For this reason, the thickness of the slab which is a slab or bloom obtained by continuous casting is preferably 1 to 120 mm. In order to manufacture a slab of this thickness, for example, when it is manufactured using a thin slab continuous casting machine, a slab having a thickness of about 30 to 120 mm is obtained. Furthermore, when casting is performed by a twin belt, a short belt, a twin drum, or a short drum casting machine using a moving mold such as a belt or a roll, a slab having a thickness of about 1 to 30 mm is obtained. In the case of manufacturing a rod-shaped product, a billet continuous casting machine having a square or circular cross section may be used. As for the cross section of the slab which is a billet, the length of a square side or the diameter of a circle is usually about 75 to 250 mm.

  The slab is rolled into rolled cast iron. As the rolling treatment, hot rolling is preferably used. In order to obtain rolled cast iron in which elongated graphite particles are dispersed, graphitization is performed with a focus on the graphite nuclei in the rolling treatment step. In that case, it is important to control the temperature condition of the hot rolling process. When the hot rolling treatment temperature is high, the generation of graphite proceeds during rolling, and the elongated graphite particles are dispersed inside the obtained rolled cast iron (see the rolled cast iron 32 in FIG. 1).

  Specifically, when the rolling temperature exceeds 900 ° C., the generation of graphite tends to proceed. Therefore, the rolling temperature is set to a temperature exceeding 900 ° C. The heating temperature before rolling may be controlled from the same viewpoint. The upper limit of the heating temperature and rolling temperature before rolling is not particularly limited, but is usually set to 1150 ° C. or lower which is the melting point of iron. When the production of graphite particles is advanced in the rolling process, a rolled cast iron having excellent workability in which the graphite particles are dispersed inside can be obtained without using the heat treatment process. However, in order to improve workability, heat treatment may be applied to the rolled cast iron.

  The rolling ratio in the rolling process is 25 or more. The “reduction ratio” is the ratio of the thickness of the cast slab before rolling to the thickness of the rolled cast iron after rolling. For example, when the thickness of the slab before rolling is 30 mm and the thickness of the rolled cast iron after rolling is 1 mm, the reduction ratio is 30. By rolling at such a reduction ratio, elongated graphite particles are formed, and vibration damping properties of the rolled cast iron are ensured. The upper limit of the reduction ratio is not particularly limited, but if the reduction ratio is increased more than necessary, the shape of the rolled cast iron may be deteriorated. Therefore, in practice, the reduction ratio is preferably 300 or less.

  In the cooling step after hot rolling, it is preferable to control the cooling step so that the ratio of ferrite is increased and the workability of the rolled cast iron is improved. Specifically, it is desirable to hold at 730 to 650 ° C. in the cooling process after hot rolling or to gradually cool between 730 ° C. and 300 ° C., and the cooling rate is 10 ° C./min or less. It is preferable to set the speed. Outside this temperature range, ferrite formation may not proceed well.

  The hot-rolled cast iron may be wound into a coil shape. In that case, in order to increase the amount of ferrite, it is preferable to wind the coil at a temperature of 750 to 550 ° C. By winding the rolled cast iron at a temperature in this range, the formation of ferrite proceeds well. Moreover, you may cold-roll the hot-rolled cast iron further as needed.

  By such a process, rolled cast iron in which elongated graphite particles are dispersed is obtained. The rolled cast iron preferably satisfies the provisions described in the first aspect of the present invention. That is, the rolled cast iron has a white cast iron structure, the average width of the elongated graphite particles is 0.05 to 0.4 mm, the average length of the elongated graphite particles is 1.25 to 50 mm, and is elongated. The average interval between the graphite particles is 30 μm or less. Since the meaning of these rules and the average value measuring method are the same as those described in the first embodiment of the present invention, the description thereof is omitted here.

<Example 1>
After the hot metal discharged from the blast furnace was transferred to a converter-type refining vessel, steel scrap was added and adjusted to the components shown in Table 1. Then, it moved to the pan and Fe-Si-Mg was added as a spheroidizing agent. The molten iron to which the spheroidizing agent was added was poured into a vertical continuous casting machine equipped with a water-cooled copper mold, and a slab having a width of 800 mm and a thickness of 100 mm was continuously cast at a casting speed of 1.0 m / min. The obtained slab having the white cast iron structure was heated at 1100 ° C. in a heating furnace, and then rolled at 1000 to 850 ° C. with a hot rolling mill to obtain a rolled plate. In the obtained rolled sheet, the elongated graphite was dispersed, and it was excellent in vibration damping properties and workability.

<Examples 2-5, Comparative Examples 1-4>
The components of the slab and the spheroidizing agent were changed as shown in Table 1 to produce rolled sheets. In Comparative Example 3, the temperature in the heating furnace was set to 900 ° C., the rolling temperature was set to 850 to 700 ° C., and the obtained rolled plate was further subjected to heat treatment at 950 ° C. A rolled sheet in which graphite was dispersed was obtained. Except for Comparative Example 3, as in Example 1, the temperature in the heating furnace was set to 1100 ° C. and the rolling temperature was set to 1000 to 850 ° C. to obtain rolled sheets. The evaluation of the obtained rolled sheet is as shown in Table 1.

  The vibration damping property was evaluated by measuring the vibration loss coefficient by the vibration damping method and comparing with ordinary steel materials. In Table 1, ◎ indicates extremely excellent, ◯ indicates excellent, and x indicates the same as ordinary steel. For workability, a bending test was performed to evaluate the presence or absence of cracks in the test piece.

  As shown in Table 1, a slab having a white cast iron structure and dispersed graphite particles satisfying a predetermined condition is excellent in both vibration damping properties and workability.

It is a flowchart which shows the process of manufacturing rolled cast iron about each of spheroidal graphite cast iron (ductile cast iron), white cast iron in which the graphite formation nucleus is not dispersed, and white cast iron in which the graphite formation nucleus is dispersed. FIG. 3 is a schematic cross-sectional view of rolled cast iron for explaining the concepts of “width of elongated graphite particles”, “length of elongated graphite particles”, and “interval between elongated graphite particles”. It is a cross-sectional schematic diagram of the width direction of rolled cast iron explaining the concept of "width of the elongated graphite particle", "length of the elongated graphite particle", and "interval of the elongated graphite particle".

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Molten iron, 11 ... Molten iron, 12 ... Molten iron, 20 ... Cast slab, 21 ... Cast slab, 22 ... Cast slab, 30 ... Rolled cast iron, 31 ... Rolled cast iron, 32 ... Rolled cast iron, 33 ... Rolled cast iron, 41 ... Rolled Cast iron, 42 ... Rolled cast iron, 43 ... Rolled cast iron, 51 ... Rolled cast iron, 110 ... Graphite-forming nuclei, 120 ... Spheroidal graphite, 121 ... Flaky graphite, 122 ... Graphite particles, 123 ... Graphite particles, 123 '... Graphite particles, 124 ... graphite particles, 130 ... graphite formation nuclei.

Claims (4)

Distracted graphite particles a rolled cast iron that has been dispersed, the average width of the distracted graphite particles are 0.05-0.4 mm, average length of the distracted graphite particles 1.25~50mm A rolled cast iron, wherein an average interval between the elongated graphite particles is 30 μm or less. 2. The rolled cast iron according to claim 1, wherein a concentration [C] (mass%) of carbon atoms and a concentration [Si] (mass%) of silicon atoms in the rolled cast iron satisfy the following formula.

  The rolled cast iron according to claim 1, wherein the rolled cast iron is a damping material. The carbon atom concentration [C] (mass%) and the silicon atom concentration [Si] (mass%) satisfy the following formula, and the oxide, sulfide, nitride or composite compound of the spheroidizing agent element is Obtaining dispersed molten iron;

Casting the molten iron to obtain a slab having a white cast iron structure;
Rolling the cast slab at a temperature of 900 ° C. or higher and a reduction ratio of 25 or more to obtain rolled cast iron;
A method for producing rolled cast iron in which elongated graphite particles are dispersed.

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