Heat-resistant cast iron-based metal short fiber and its manufacturing method

Abstract

To provide a heat-resistant cast iron-based metal short fiber which allows easier chatter-type cutting in the case of a spheroidal graphite cast iron structure, does not require graphite spheroidizing treatment or post-casting heat treatment, and can enhance heat resistance, seizure resistance, oxidation resistance, high-temperature strength, and wear resistance by compounding with ceramic, resin, or other materials, without requiring much costly alloy components; and also to provide a method for producing the same.SOLUTION: A heat-resistant cast iron-based metal short fiber has a component composition comprising, in mass%, C: 1.0-4.0%, Si: 1.5-7.0%, Mn: 0.1-1.0%, Ti: ≤0.40%, and the balance being Fe, has a flake graphite cast iron structure with flake graphite generated in the structure, and is formed by cutting using a chatter vibration cutting method.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to heat-resistant cast iron-based metal short fibers and a method for producing the same. [Background technology]

[0002] Short metal fibers are conventionally used to reinforce, for example, ceramic, resin and other materials. There are several manufacturing methods for metal short fibers, including the melt squeeze method, which produces short fibers directly from molten metal, and the method of cutting short fibers from long fibers produced by die drawing, long fibers produced by planing thick wire rods, or long fibers produced by bundling metal sheets and cutting them into thin strips. The melt squeeze production method tends to produce metal short fibers having non-uniform diameters and lengths, making it difficult to produce small-sized metal short fibers. The manufacturing method of cutting the long fibers into short fibers generally requires high costs and is premised on the use of a metal material that can be processed into wire or sheet form. Furthermore, since heat-resistant metals generally have poor ductility, few metals can be processed into wire or sheet form, and there is also the problem of very high processing costs.

[0003] As a method for producing short metal fibers, a manufacturing method using a chatter vibration cutting method has been conventionally provided. This method uses an elastic tool and cuts short metal fibers directly from a round bar billet by utilizing the forced vibration of the tool. The manufacturing method using this chatter vibration cutting method generally has the advantage that it is easy to produce fine and uniform short metal fibers, and that short fibers of various sizes can be produced relatively inexpensively from a relatively large variety of metal materials. On the other hand, when producing short fibers using the chatter vibration cutting method, a round bar billet with a relatively large diameter is required. Also, the round bar billet needs to be easy to cut (machinable). Therefore, the metal material for the chatter vibration cutting method is preferably a metal material that can be used to produce a round bar billet and is suitable for cutting.

[0004] International Publication No. WO2011 / 145194 (Patent Document 1) relates to heat-resistant cast iron-based metal short fibers and a manufacturing method thereof, and discloses metal short fibers made of spheroidal graphite cast iron by chatter vibration cutting and a manufacturing method thereof. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. WO2011 / 145194 Summary of the Invention [Problem to be solved by the invention]

[0006] In the invention of the above-mentioned Patent Document 1, when the heat-resistant cast iron-based metal short fibers produced by the chatter vibration cutting method have a spheroidal graphite cast iron structure, the heat resistance is good. However, due to the solidification form of mushy solidification, spheroidal graphite cast iron is prone to crystallization of eutectic cementite when cast by mold casting, which requires additional post-cast heat treatment. Furthermore, performing an additional post-heat treatment creates problems associated with the addition of an additional heat treatment step, which in turn significantly increases time and costs. Furthermore, in the invention of Patent Document 1, a spheroidizing treatment must be carried out to spheroidize the graphite. Furthermore, in the invention of Patent Document 1, in addition to forming a spheroidal graphite cast iron structure, Al is added in order to obtain high heat resistance. However, this tends to increase the hardness, which makes chatter vibration cutting difficult and also causes the problem of rapid wear of the cutting blade.

[0007] Therefore, the present invention aims to provide a new heat-resistant cast iron-based metal short fiber and a method for producing the same, which can be more easily formed by chatter vibration cutting than in the case of a spheroidal graphite cast iron structure, can extend the life of a cutting tool, and, unlike the case where spheroidal graphite is generated in the structure, does not require a spheroidizing treatment of graphite or a post-casting heat treatment, and in addition, can be compounded with ceramics, resins, and other materials to improve heat resistance, seizure resistance, oxidation resistance, high-temperature strength, and wear resistance without using large amounts of expensive alloy components, and can be compounded with ceramics, resins, and other materials. [Means for solving the problem]

[0008] The heat-resistant cast iron-based metal short fiber of the present invention that solves the above problems is as follows: A heat-resistant cast iron-based metal short fiber made of chatter vibration cutting short fiber, The composition is, in mass%, C: 1.0-4.0%, Si: 1.5-7.0%, Mn: 0.1-1.0%, Ti: ≦0.40%, and the balance is Fe. The composition has a flake graphite cast iron structure in which flake graphite is generated in the structure. Things to do The first characteristic is: In addition to the first characteristic, the heat-resistant cast iron-based metal short fiber of the present invention has a composition, by mass%, of C: 1.5 to 3.0%, Si: 3.0 to 7.0%, Mn: 0.1 to 0.7%, Ti: 0.01 to 0.40%, and the remainder Fe, and has a flake graphite cast iron structure in which fine eutectic flake graphite with a length of 0.5 to 20 μm is generated in the structure. Things to do The second characteristic is: In addition to the second characteristic, the heat-resistant cast iron-based metal short fiber of the present invention has a composition, by mass%, of C: 1.5 to 2.5%, Si: 5.0 to 7.0%, Mn: 0.3 to 0.7%, Ti: 0.10 to 0.25%, and the remainder Fe, and has a flake graphite cast iron structure in which fine eutectic flake graphite having a length of 0.5 to 20 μm is generated in the structure. Things to do The third characteristic is as follows. The fourth feature of the method for producing heat-resistant cast iron-based metal short fibers of the present invention is that it at least comprises a casting step of casting molten heat-resistant cast iron having a composition, by mass%, of 1.0 to 4.0% C, 1.5 to 7.0% Si, 0.1 to 1.0% Mn, ≦0.40% Ti, and the balance being Fe, into a round bar material having a flake graphite cast iron structure in which flake graphite is generated in the structure, by a mold casting method or a continuous casting method, and a cutting step of cutting the round bar material obtained in the casting step into a round bar billet of a predetermined dimension, with or without cutting, and cutting the round bar billet into metal short fibers by a chatter vibration cutting method. In addition to the fourth feature, the fifth feature of the method for producing heat-resistant cast iron-based metal short fibers of the present invention is that it at least comprises a casting step of casting molten heat-resistant cast iron having a composition, by mass%, of 1.5 to 3.0% C, 3.0 to 7.0% Si, 0.1 to 0.7% Mn, 0.01 to 0.40% Ti, and the remainder of Fe, into a round bar material having a flake graphite cast iron structure in which fine eutectic flake graphite having lengths of 0.5 to 20 μm is generated in the structure by a mold casting method or a continuous casting method, and a cutting step of cutting the round bar material obtained in the casting step into a round bar billet of a predetermined dimension with or without cutting, and cutting the round bar billet into metal short fibers by a chatter vibration cutting method. In addition to the fifth feature, the method for producing heat-resistant cast iron-based metal short fibers of the present invention has a sixth feature in that it at least comprises a casting step of casting molten heat-resistant cast iron having a composition, by mass%, of 1.5 to 2.5% C, 5.0 to 7.0% Si, 0.1 to 0.7% Mn, 0.01 to 0.25% Ti, and the remainder of Fe into a round bar material having a flake graphite cast iron structure in which fine eutectic flake graphite having lengths of 0.5 to 20 μm is generated in the structure by a mold casting method or a continuous casting method, and a cutting step of cutting the round bar material obtained in the casting step into a round bar billet of a predetermined dimension with or without cutting, and cutting the round bar billet into metal short fibers by a chatter vibration cutting method. Furthermore, in addition to any one of the fourth to sixth features, the method for producing heat-resistant cast iron-based metal short fibers of the present invention has a seventh feature in that, in the continuous casting, the molten metal is poured into a reservoir furnace equipped with a water-cooled continuous casting mold, and is continuously solidified in the water-cooled continuous casting mold while being intermittently pulled out, thereby casting a round bar material. Effect of the Invention

[0009] According to the heat-resistant cast iron-based metal short fibers described in claim 1, the metal short fibers are made of a heat-resistant cast iron matrix having the composition shown therein, and furthermore, are made of a flake graphite cast iron structure in which flake graphite is generated within the structure, so that it is possible to provide metal short fibers produced by vibration cutting that have heat resistance, seizure resistance, oxidation resistance, high-temperature strength, and abrasion resistance without using large amounts of expensive alloy components. In addition, the heat-resistant cast iron-based metal short fiber of claim 1 can be reinforced by compounding it with ceramics, resin, or other materials, thereby improving heat resistance, seizure resistance, oxidation resistance, high-temperature strength, or wear resistance. In addition, the heat-resistant cast iron-based metal short fiber described in claim 1 has a flake graphite cast iron structure in which flake graphite is generated, so that it is suitable for chatter vibration cutting and easy to cut, and even if the hardness is high, chatter vibration cutting is easy to form. Therefore, the life of the cutting tool (tip) used for chatter vibration cutting can be extended. In addition, according to the heat-resistant cast iron-based metal short fibers described in claim 1, the composition is a cast iron composition, so the necessary round bar material can be cast at a lower temperature compared to the case of steel, and therefore the metal short fibers can be provided more inexpensively by the chatter vibration cutting method. In particular, according to the heat-resistant cast iron-based metal short fiber described in claim 1, instead of generating spheroidal graphite in the structure of the heat-resistant cast iron base, a flake graphite cast iron structure is generated in which flake graphite is generated, which has the great advantage that chatter vibration cutting is easier to perform than in the case of a spheroidal graphite cast iron structure, and furthermore, no spheroidizing treatment of the graphite or post-casting heat treatment is required.

[0010] Furthermore, according to the heat-resistant cast iron-based metal short fiber described in claim 2, in addition to the advantageous effects of the configuration of claim 1, the cast iron components are limited to the range of the component composition described therein, the Ti content is required to be 0.01 to 0.40 mass%, and the structure is a flake graphite cast iron structure in which fine eutectic flake graphite of 0.5 to 20 μm is generated, thereby further improving heat resistance and making it possible to further refine the flake graphite by adding Ti, thereby further facilitating chatter vibration cutting. Furthermore, according to the heat-resistant cast iron-based metal short fiber described in claim 3, in addition to the advantageous effects achieved by the configuration of claim 2, the cast iron components are further limited to the range of component composition described therein, the Ti content is further limited to 0.10 to 0.25 mass%, and the structure is a flake graphite cast iron structure consisting of fine eutectic flake graphite of 0.5 to 20 μm, thereby further improving heat resistance and making it possible to refine the flake graphite by adding Ti, thereby further facilitating chatter vibration cutting.

[0011] According to the method for producing heat-resistant cast iron-based metal short fibers as set forth in claim 4, a round bar material having a flake graphite cast iron structure in which flake graphite is generated in a structure made of a heat-resistant cast iron matrix can be cast by using a heat-resistant cast iron molten metal having the composition as set forth therein and subjecting it to die casting or continuous casting. Then, by cutting this round bar material into a round bar billet of a predetermined size, or without cutting, and cutting this round bar billet of the flake graphite cast iron structure by a chatter vibration cutting method, heat-resistant cast iron-based metal short fibers can be produced efficiently without the need for a spheroidizing treatment of the graphite or a post-casting heat treatment. Furthermore, according to the method for producing heat-resistant cast iron-based metal short fibers described in claim 4, heat-resistant cast iron-based metal short fibers excellent in heat resistance, seizure resistance, heat resistance, high-temperature strength, and wear resistance can be produced by a chatter vibration cutting method with better machinability than that of spheroidal graphite cast iron structure. According to the method for producing heat-resistant cast iron-based metal short fibers set forth in claim 4, by using mold casting or continuous casting for cast iron casting, which is usually performed in a sand mold, it is possible to obtain a round bar material in which casting defects such as coarsening of the structure, segregation, shrinkage cavities, etc. are suppressed, and the yield can be improved. Since it is generally necessary to use a round bar material with a large radius for the chatter vibration cutting method, the cooling rate in a sand mold is slow, so that the structure becomes coarse and a segregated structure is generated in the center of the round bar, which makes it easy for casting defects to occur.

[0012] Furthermore, according to the manufacturing method for heat-resistant cast iron-based metal short fibers described in claim 5, in addition to the advantageous effects of the configuration of claim 4, the components of the cast iron are limited to the range of the component composition described therein, and the Ti content is made mandatory to be 0.01 to 0.40 mass %, and the molten metal is cast by mold casting or continuous casting into a round bar material with a flake graphite cast iron structure in which fine eutectic flake graphite with lengths of 0.5 to 20 μm are generated in the structure. This further improves heat resistance, and also makes it possible to refine the flake graphite by adding Ti, thereby further facilitating chatter vibration cutting. Furthermore, according to the manufacturing method for heat-resistant cast iron-based metal short fibers described in claim 6, in addition to the advantageous effects achieved by the configuration of claim 5, the components of the cast iron are further limited to the range of the component composition described therein, the Ti content is set to 0.10 to 0.25 mass%, and the cast iron is cast into a round bar material having a flake graphite cast iron structure in which fine eutectic flake graphite having lengths of 0.5 to 20 μm are generated in the structure by a mold casting method or a continuous casting method. This makes it possible to further stably improve heat resistance and to further stably refine the flake graphite by adding Ti, thereby facilitating chatter vibration cutting.

[0013] According to the method for producing heat-resistant cast iron-based metal short fibers described in claim 7, in addition to the effects of any one of claims 4 to 6, in the continuous casting, the molten metal is poured into a reservoir equipped with a water-cooled continuous casting mold, and the molten metal is continuously solidified in the water-cooled continuous casting mold while being intermittently pulled out to cast a round bar material, so that the round bar material to be used for chatter vibration cutting can be mass-produced efficiently and inexpensively. In addition, the continuous casting equipment for cast iron can be operated at a lower temperature than the continuous casting equipment for steel, and inexpensive equipment can be used. Of course, by using a water-cooled continuous casting mold, segregation of the structure of the obtained round bar material can be suppressed. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram for explaining the steps of the manufacturing method of the present invention, showing a case where continuous casting is selected as the casting step. [Diagram 2] FIG. 1 is a diagram showing an example of a chatter vibration cutting machine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Regarding the heat-resistant cast iron-based metal short fiber and its manufacturing method of the present invention, first, the content range of each component element in the component composition of the heat-resistant cast iron-based metal short fiber according to the embodiment and the reasons for limiting the range will be described below.

[0016] The C content is 1.0 to 4.0 mass %. C is an important element that directly affects castability and machinability. If the C content is less than 1.0% by mass, the solidification temperature becomes high like steel, which leads to poor flow of the molten metal and easy occurrence of casting defects. In addition, graphite is difficult to form, and conversely, hard and brittle carbides are easily formed, which significantly impairs machinability. This makes it difficult to manufacture short fibers by chatter vibration cutting. In addition, cutting tools (chips) are easily damaged or their lifespan is significantly shortened. On the other hand, if the C content exceeds 4.0 mass%, the amount of graphite increases, so that the cutting by chatter vibration cutting itself is good, but the graphite is likely to separate and fall off from the short fibers after cutting, and the graphite content in the short fibers changes, resulting in non-uniformity in the physical properties of the short fibers. Furthermore, in order to produce eutectic graphite, which is fine flake graphite with good workability, a hypoeutectic composition is suitable, so from the viewpoint of carbon equivalent, the upper limit of the C content is 4.0 mass %. Taking into consideration castability, machinability, chatter vibration machinability, fiber reinforcement, etc., and also the matrix structure of the heat-resistant cast iron, the generation of flake graphite, and the refinement of flake graphite, the C content is preferably 1.5 to 3.0 mass%, and more preferably 1.5 to 2.5 mass%.

[0017] The Si content is set to 1.5 to 7.0 mass %. Silicon is contained to crystallize carbon as graphite instead of carbide, and to dissolve itself in the cast iron matrix to greatly improve the heat resistance of the matrix structure, and further to improve the seizure resistance and wear resistance of the heat-resistant cast iron-based metal short fiber according to the present invention. If the Si content is less than 1.5 mass %, carbides are likely to be generated in the structure, which may lead to casting defects during the casting process such as continuous casting, etc. Also, the heat resistance is reduced to the same level as that of ordinary cast iron materials. On the other hand, if the Si content exceeds 7.0 mass %, the heat resistance is very good, but a hard and brittle intermetallic compound called silicoferrite is likely to be formed in the metal structure, and the vibration cutting ability is reduced. The Si content is preferably 3.0 to 7.0 mass %, and more preferably 5.0 to 7.0 mass %, taking into consideration the above-mentioned graphite crystallization, heat resistance, seizure resistance, wear resistance, carbide formation, and the like of the matrix structure.

[0018] The Mn content is 0.1 to 1.0 mass %. Mn is added to deoxidize and desulfurize the molten metal. If the Mn content is less than 0.1 mass %, the effects of deoxidizing and desulfurizing the cast iron cannot be sufficiently obtained. On the other hand, if the Mn content exceeds 1.0 mass %, it dissolves in the matrix structure, reducing the amount of Si in solid solution and impairing the heat resistance effect due to the Si in solid solution. The Mn content is preferably 0.1 to 0.7 mass %, and more preferably 0.3 to 0.7 mass %, taking into consideration the effects of deoxidizing and desulfurizing cast iron, a decrease in the amount of solid solution of Si, and the like.

[0019] The Ti content is set to 0.40 mass% or less. Although it is not essential to contain Ti, it is desirable to contain it. Ti is added to promote the refinement of flake graphite. The addition of Ti makes it easier to obtain eutectic graphite, which is fine flake graphite. It can be said that adding Ti is not necessary if the solidification rate during casting is sufficiently fast, but when considering the casting of thick-walled round bar material, it can be said that adding Ti is actually preferable. If the Ti content exceeds 0.40 mass%, the effect of refining the flake graphite will not be any better, and a large amount of carbide will be generated, which is undesirable in that the workability will deteriorate and the cutting tool (chip) will be easily damaged or its life will be significantly shortened. Considering the refinement of flake graphite cast iron, the Ti content is preferably 0.01 to 0.40 mass %, and more preferably 0.10 to 0.25 mass %.

[0020] Regarding the content of Al, if it is added to the extent that it improves heat resistance, it promotes the formation of carbides and shrinkage cavities, which tends to increase hardness, making chatter cutting difficult and causing rapid wear of the cutting blade. It is also undesirable in that the shrinkage cavities generated inside the material tend to damage the cutting tool (tip) or significantly shorten its lifespan. Furthermore, it is easily oxidized during melting, which may cause slag bites, which is undesirable in that it significantly shortens the lifespan of the cutting tool (tip). Therefore, it can be said that it is rather better not to include Al.

[0021] The balance is Fe. Of course, this does not exclude the inclusion of other components as necessary. Inevitably mixed impurities are excluded from the calculation.

[0022] Next, an embodiment of the method for producing the heat-resistant cast iron-based metal short fibers of the present invention will be described. First, the casting process will be described. The molten heat-resistant cast iron having the above-mentioned component composition relating to the heat-resistant cast iron-based metal short fibers can be obtained by melting predetermined raw materials using an electromagnetic induction melting furnace 11 as shown in FIG. The obtained molten metal is poured into a metal mold to obtain a round bar material as a casting, or as shown in FIG. 1, it is poured from a ladle 12 into a distillation furnace 13 and continuously cast through a horizontal jacketed continuous casting mold 14, and then cut to obtain a round bar material 15.

[0023] Usually, cast iron castings are often cast into sand molds. However, the cooling rate in sand molds is slow, so the structure becomes coarse and a segregation structure is generated in the center of the round bar material, which tends to result in a non-homogeneous round bar material. In addition, the center of the round bar becomes the final solidification part, which tends to result in casting defects such as large shrinkage cavities. For this reason, in this embodiment, the round bar material is continuously poured through a metal mold or a water-cooled graphite continuous casting mold, and is rapidly cooled and solidified. The dimensions of the round bar material can be, for example, a cylindrical shape with a length of 500 mm and a radius of 100 mm. Taking into consideration the run-out of the round bar material due to vibration during processing, it is preferable that the length of the round bar material is 250 to 500 mm and the radius is about 75 to 100 mm. The shorter the length, the less the impact of run-out, but the worse the productivity.

[0024] Next, the cutting process will be described. First, the round bar material obtained through the above-mentioned casting process is processed into a round bar billet 22. Round bar material is cut to the specified length of 500 mm to produce a round bar billet. The cut surface must be straight (perpendicular to the ground) so that it can be fixed (chucked) to the vibration cutting machine. However, when mold casting is used, there is a taper, so the taper must be removed. When continuous casting is used, there is no taper, so taper removal is not necessary.

[0025] As shown in FIG. 2, a round bar billet 22 is chatter cut by a chatter vibration cutter to produce short metal fibers. Thus, the heat-resistant cast iron round bar billet 22 having the above-mentioned component composition can be said to be a heat-resistant cast iron-based composition whose exclusive use is the production of short metal fibers by chatter vibration cutting. In FIG. 2, one end of the round bar billet 22 is fixed by four chucks provided on the headstock 21, and the center of the other end is fixed by the tailstock 23. On the other hand, one or more elastic tools are attached to the tool rest 24 arranged on the bed 25, and a cutting tool (tip) is attached to the tip of the elastic tool. In this state, the round bar billet 22 is rotated at high speed, and the rotating round bar billet 22 is cut from its outer periphery toward the center by the cutting tool (tip). When the cutting tool comes into contact with the rotating round bar billet 22, the elastic tool is elastically displaced in reaction, and vibration occurs due to repetition of this. Each time the cutting tool (tip) comes into contact with the round bar billet 22 due to this vibration, the surface of the round bar billet 22 is scraped off, and short metal fibers are obtained. The diameter of the short metal fibers is controlled by the amplitude of the cutting tool (tip) at the tip of the elastic tool. The length of the short metal fibers is controlled by the length of the cutting edge of the cutting tool (tip).

[0026] The dimensions of the short metal fibers cut by the chatter vibration cutting machine are largely dependent on the amplitude of the forced vibration generated in the elastic tool and the length of the cutting edge of the cutting tool (tip). The average minimum diameter of the short metal fibers that can be processed by slowing down the rotation speed of the round bar billet 22 and reducing the amplitude of the forced vibration of the elastic tool is set to 10 μm. If the diameter is less than this, production efficiency is poor, product yield is significantly reduced, and costs are high. On the other hand, increasing the diameter improves productivity, but if it exceeds 100 μm, damage to the cutting tool (tip) becomes significant. On the other hand, regarding the length of the metal short fibers, if the fiber length is less than 1 mm, the productivity is poor, and if the fiber length exceeds 10 mm, the cutting tool (chip) is significantly damaged and the cost is high. Therefore, taking into consideration the productivity, the size of the heat-resistant cast iron-based metal short fibers according to this embodiment is preferably 10 to 90 μm in diameter and 1 to 9 mm in length. EXAMPLES

[0027] Examples will be described below together with comparative examples. As examples of the heat-resistant cast iron-based metal short fibers, Examples 1 to 5 were produced, and as comparative examples, Comparative Examples 1 to 6 were produced. In producing Examples 1 to 5, ductile pig iron, steel scrap, graphite powder, ferrosilicon, and ferrotitanium were used as raw materials, and the raw materials were melted at 1450 to 1500°C in a 150 kg capacity electromagnetic induction melting furnace to prepare 80 kg of molten metal so as to obtain the specified component compositions shown in Table 1. The molten metal was poured into a ladle, then cast into a mold with an inner diameter of 180 mm and a depth of 250 mm at 1350 to 1450°C, and solidified at 0.5 to 5°C / sec to obtain a round bar material. In the preparation of Comparative Examples 1 to 6, ductile pig iron, steel scrap, graphite powder, ferrosilicon, and aluminum particles were used as raw materials, and melted at 1600°C in a 150 kg capacity electromagnetic induction melting furnace to prepare 100 kg of molten metal so as to have the predetermined composition shown in Table 2. After pouring this molten metal into a ladle, Fe-Si-Mg alloy was immediately added and spheroidized, and the molten metal was cast into a mold with an inner diameter of 160 mmφ and a depth of 550 mm at 1500°C to obtain a round bar material. These round bar materials were held at 950°C for 3 hours as a heat treatment, and then cooled to room temperature. Then, they were cut and processed to a predetermined size to prepare round bar billets.

[0028] The round bar material was processed to have a length of 240 mm and a diameter of 175 mm to obtain a round bar billet 22. The round bar billet was cut using a vibration cutting machine as shown in Figure 2 to produce short metal fibers with a diameter of 40 μm and a length of 1 mm.

[0029] The test method is as follows. The hardness was measured in the as-cast state for Examples 1 to 5 and Comparative Examples 1 to 6. The hardness was measured using a Brinell hardness tester (unit: HB). For Examples 1 to 5 and Comparative Examples 1 to 6, the castability was evaluated based on the presence or absence of casting defects in a round bar material cast into a die having an inner diameter of 180 mmφ and a depth of 250 mm. The cutting workability of Examples 1 to 5 and Comparative Examples 1 to 6 was evaluated based on the wear of the cutting tool (tip) when cutting a round bar billet into short metal fibers using the chatter vibration cutting machine shown in Figure 2, and the deviation of the short fibers from the target size distribution.

[0030] The test results are shown in Tables 1 and 2.

[0031] [Table 1]

[0032] [Table 2]

[0033] Evaluate the test results. <About the casting structure> In Examples 1 to 5, all of the samples had a flake graphite structure. In Examples 1 and 2, the cooling rate was fast near the surface, resulting in fine flake graphite, but as the cooling rate approached the center of the wall thickness, the cooling rate slowed down, resulting in coarsening of the flake graphite. In Examples 3 to 5, the flake graphite was refined from the surface to the center of the wall thickness, which is the effect of adding Ti. On the other hand, in Comparative Examples 1 to 6, all of the samples had a spheroidal graphite structure, which was due to the spheroidizing treatment. <Castability (center defects)> In all of Examples 1 to 5, there were no defects even at the center. On the other hand, in the comparative examples, Comparative Examples 1, 2, 5, and 6 had no defects, but Comparative Examples 3 and 4 had shrinkage cavities and slag. <About as-cast hardness> Compared with Examples 1-5, Comparative Examples 1-6 tended to have relatively higher as-cast hardness. <Post-heat treatment> In Examples 1 to 5, no post-heat treatment was performed, so the hardness remained the same as in the as-cast state. On the other hand, in Comparative Examples 1 to 6, the as-cast steel tends to have too high hardness due to the presence of carbides, etc. Therefore, a post-heat treatment is carried out to reduce the hardness. <Machining workability by chatter vibration cutting> In all of Examples 1 to 5, chatter vibration cutting was possible. In Examples 3 to 5, the flake graphite was refined, and therefore the chatter vibration cutting performance was improved compared to Examples 1 and 2, and the life of the cutting tool (tip) was also extended. Furthermore, when the target size of the resulting short fibers was 40 μm in diameter, the actual size distribution was in the range of 20 to 50 μm, and the dimensional precision of the short fibers was good. On the other hand, chatter vibration cutting was possible in Comparative Example 1. However, this was probably made possible by lowering the hardness (HB) to about 250 by performing post-heat treatment. Comparative Examples 2 and 6 have hardness (HB) of 280 and 302, which are greater than 250, and the machinability is poor, making chatter vibration cutting somewhat difficult (△). Furthermore, in Comparative Examples 4 and 5, the hardness (HB) was 340 or more, and when chatter vibration cutting was performed, the cutting tool (tip) was damaged, making it impossible to continue cutting. It is particularly noteworthy that in Comparative Examples 1 to 6, even if post-heat treatment is performed, when the hardness (HB) exceeds 250, chatter vibration cutting becomes difficult. In contrast, in Examples 1 to 5, chatter vibration cutting can be performed well even when the hardness (HB) exceeds 300 and reaches approximately 330 (see Examples 4 and 5). This tendency becomes more pronounced as the flake graphite structure becomes finer, and is therefore considered to be the effect of the refinement of the flake graphite structure. [Industrial Applicability]

[0034] The heat-resistant cast iron-based metal short fiber and its manufacturing method of the present invention have industrial applicability as a material such as a filler that is compounded with ceramics, rubber, resins, etc. that are used at high temperatures to improve the properties of the materials, and as a manufacturing method thereof. [Explanation of symbols]

[0035] 11 Electromagnetic induction melting furnace 12 Ladle 13 Tank Furnace 14 Mold with water-cooling jacket 15 Round bar material 21 Main shaft material 22 Round bar billet 23 Tailstock 24 Tool rest 25 Beds

Claims

1. A heat-resistant cast iron-based metal short fiber made of chatter vibration cutting short fiber, In mass percent, C: 1.0-4.0%, Si: 1.5-7.0%, Mn: 0.1-1.0%, Ti: ≦0.40%, A heat-resistant cast iron-based metal short fiber having a composition with the remainder being Fe and having a flake graphite cast iron structure in which flake graphite is generated within the structure.

2. In mass percent, C: 1.5-3.0%, Si: 3.0 to 7.0%, Mn: 0.1 to 0.7%, Ti: 0.01 to 0.40%, The heat-resistant cast iron-based metal short fiber according to claim 1, characterized in that it has a composition with the remainder being Fe, and has a flake graphite cast iron structure in which fine eutectic flake graphite having a length of 0.5 to 20 μm is generated in the structure.

3. In mass percent, C: 1.5-2.5%, Si: 5.0 to 7.0%, Mn: 0.3 to 0.7%, Ti: 0.10-0.25%, The heat-resistant cast iron-based metal short fiber according to claim 2, characterized in that it has a composition with the remainder being Fe, and has a flake graphite cast iron structure in which fine eutectic flake graphite having a length of 0.5 to 20 μm is generated in the structure.

4. In mass percent, C: 1.0-4.0%, Si: 1.5-7.0%, Mn: 0.1-1.0%, Ti: ≦0.40%, A method for producing heat-resistant cast iron-based metal short fibers, comprising at least a casting step of casting molten heat-resistant cast iron having a composition with the remainder being Fe into a round bar material having a flake graphite cast iron structure in which flake graphite is generated in the structure by a mold casting method or a continuous casting method, and a cutting step of cutting the round bar material obtained in the casting step into a round bar billet of a predetermined dimension, with or without cutting, and cutting the round bar billet into short metal fibers by a chatter vibration cutting method.

5. In mass percent, C: 1.5-3.0%, Si: 3.0 to 7.0%, Mn: 0.1 to 0.7%, Ti: 0.01 to 0.40%, 5. The method for producing heat-resistant cast iron-based metal short fibers according to claim 4, characterized in that it comprises at least a casting step of casting a molten heat-resistant cast iron having a composition consisting of the remainder being Fe into a round bar material having a flake graphite cast iron structure in which fine eutectic flake graphite having lengths of 0.5 to 20 μm are generated in the structure by a mold casting method or a continuous casting method, and a cutting step of cutting the round bar material obtained in the casting step into a round bar billet of a predetermined dimension with or without cutting, and cutting the round bar billet into metal short fibers by a chatter vibration cutting method.

6. In mass percent, C: 1.5-2.5%, Si: 5.0 to 7.0%, Mn: 0.3 to 0.7%, Ti: 0.10-0.25%, 6. A method for producing heat-resistant cast iron-based metal short fibers according to claim 5, characterized in that it comprises at least a casting step of casting a round bar material having a flake graphite cast iron structure in which fine eutectic flake graphite having lengths of 0.5 to 20 μm are generated in the structure by a mold casting method or a continuous casting method from molten heat-resistant cast iron having a composition consisting of the remainder being Fe, and a cutting step of cutting the round bar material obtained in the casting step into a round bar billet of a predetermined dimension with or without cutting, and cutting the round bar billet into metal short fibers by a chatter vibration cutting method.

7. The method for producing heat-resistant cast iron-based metal short fibers according to any one of claims 4 to 6, characterized in that in the continuous casting, the molten metal is poured into a reservoir furnace equipped with a water-cooled continuous casting mold, and is continuously solidified in the water-cooled continuous casting mold while being intermittently pulled out, thereby casting a round bar material.

Images