JP6204091B2 - Metal fiber composite - Google Patents

Description

  The present invention relates to a metal fiber composite suitably applied to refractories and concrete.

  Improves brittleness common to refractories such as concrete of building structures, civil engineering structures, linings of molten metal containers, structural members, and wall materials of industrial kiln furnaces, especially indefinite refractories, and reduces their breaking energy. In order to improve, materials obtained by mixing organic fibers and metal fibers alone or in combination are widely used, and are known as fiber reinforced concrete and fiber reinforced refractories.

  Conventionally, the mechanism by which the fracture energy is improved by adding fibers to concrete or refractory is generally described by the fiber drawing effect.

  That is, when a brittle body such as concrete or refractory is subjected to a tensile force exceeding the material strength, a crack is generated, and the fibers present on the crack surface bear the tensile force. When the tensile load loaded on the fiber reaches the maximum fiber strength and the fiber breaks and further cracks progress or exceeds a certain limit before the fiber breaks, the fiber and the matrix peel off. When the peeling reaches the entire length of the embedded fiber, the fiber starts to be pulled out, resists the tensile force by frictional adhesion with the matrix, and the tensile load decreases while the fiber is pulled out.

  In non-patent literature 1, for example, even in Non-Patent Document 1, a fiber pulls out and resists an external force, and requires a large amount of work to break the fiber. The mechanism is considered to be a fiber pulling effect.

  Furthermore, in the concrete field, a high toughness cement composite material was developed in the 1990s by adding high-strength organic fibers having a fiber diameter of 100 μm or less in addition to metal fibers. This is designed to maximize the fracture energy by increasing the strength of the organic fiber and optimizing its pull-out resistance, and to have multiple crack properties in which countless fine cracks are dispersed. The most important factors to consider are the fiber tensile strength and bond strength. For example, it is described in detail in Non-Patent Document 2, and as the fiber strength and adhesion strength are higher, the crosslinking performance is improved. However, even if the strength of the fibers is high, if the adhesion strength is weak, the fibers are pulled out before exhibiting the strength, and the contribution of the fiber strength to the crosslinking performance is not important. On the other hand, if the fiber strength is weak even if the adhesion strength is high, the crosslinking performance is low, and the balance between the fiber strength and the adhesion strength is important.

  Against the background of the above theory, in the development of conventional fiber reinforced refractories and fiber reinforced concrete, the focus has been on fiber types, shapes, and combinations thereof, mainly to maximize the pulling effect (e.g. Patent Documents 1 to 6, Non-Patent Document 3). Among them, since refractory materials are required to have fire resistance, heat-resistant metal fibers have been mainly used as metal fibers. Further, since fiber strength is required, hardened stainless steel metal fibers have been used.

  However, there is a limit to improving the fracture energy only by the type, shape, and combination of fibers.

JP-A 49-120907 Japanese Patent Laid-Open No. 62-143880 JP-A-8-268767 Japanese Patent Laid-Open No. 11-157948 JP 2005-179150 A JP 2008-222510 A

Takeshi Hayashi, Yoshihisa Hamasaki, “Effect of Steel Fiber on the Properties of Castable Refractories”, Refractories 30, 1978, p. 334-337 Hirohisa Mitsuhashi, Keisetsu Rokugo, Satoshi Kunieda, “Cracking and fracture mechanics of concrete”, Gihodo Publishing, 2010, p. 192-204 Satoshi Kunieda, “Example of application to civil engineering structures: Based on the transition of short fibers”, Concrete Engineering, 2012, Vol. 50, No. 5, p. 451-456

  The problem to be solved by the present invention is to increase the fracture energy based on a mechanism different from the above-described increase mechanism of the fracture energy, and provide a metal fiber composite such as concrete or refractory having a greater fracture energy than the pulling effect. There is to do.

According to one aspect of the present invention , a metal fiber composite that is a refractory or concrete containing metal fibers, and the metal fibers have an elongation of 10% at the maximum load in an evaluation by a uniaxial tensile test. As described above, a material made of stainless steel having a maximum tensile strength of 350 MPa or more which is “maximum load / fiber cross-sectional area” is added, the surface roughness Ra of the metal fiber is 0.1 μm or more, and the maximum height A metal fiber composite having a thickness Rz of 1.3 μm or more is provided.

  Thus, the present invention is characterized in that the elongation and the maximum tensile strength of the metal fiber added as a raw material to the metal fiber composite are not less than a specific value, whereby the ductility (elongation) possessed by the metal fiber is increased. ) And work hardening (strain hardening) to the maximum, and a metal fiber composite such as concrete or refractory having high fracture energy is provided.

  That is, the mechanism for increasing the fracture energy according to the present invention is as follows.

  When a crack is generated in a metal fiber composite containing metal fibers, the metal fiber existing on the crack surface bears a tensile force as described above, and the crack surface is crosslinked. In the prior art, this fiber cross-linking effect is fiber strength and pull-out force, and until the fiber strength is reached, the metal fiber stretches due to elastic elongation and then ductility, and spreads between the generated crack surfaces as the crack progresses. Although it can follow, if the elongation is less than 10%, the displacement of the generated crack surface spacing that can follow is small. When displacement exceeding the limit of elongation of the metal fiber occurs, the fiber breaks or fiber drawing starts, and the crosslinking effect is small.

  On the other hand, in the present invention, a crack is generated, and a load is loaded on the metal fiber on the crack surface as described above, and a crosslinking effect is generated. As the load is loaded on the fiber and the crack progresses and the displacement between the generated crack surfaces spreads, the metal fiber having an elongation of 10% or more endures the loading while the elongation due to ductility continues to occur without breaking, Follows the spread between crack faces. Even if the space between the cracks further spreads, it can continue to grow without breaking because of the elongation. This effect is higher for metal fibers with higher elongation. Further, while the elongation occurs, not only the external force is cross-linked, but also the work hardening mechanism due to ductility acts to increase the strength of the fiber itself, increasing the fiber cross-linking stress and preventing the development of cracks. If the stress increase due to this work hardening becomes higher than the initial crack strength of the material, cracks will occur in areas where the base material (matrix) is not cracked, and where the strength is weak, and the metal fibers in the vicinity of the cracks In some cases, cracks are cross-linked and multiple cracks are generated.

  Due to such a mechanism, the effect of crosslinking of the tensile force until the metal fiber breaks, or the conventional mechanism based on the fiber pulling fracture energy by the sum of the adhesion peeling force and pulling force of the metal fiber without breaking the metal fiber. However, even greater destruction energy can be obtained.

  In the present invention, the elongation of the metal fiber is preferably 30% or more. A metal fiber having an elongation of 30% or more may have a slightly lower maximum tensile strength than that having an elongation of 10% or less, but the breaking energy until the metal fiber breaks becomes very large. If the metal fiber is firmly attached without being pulled out, the breaking energy until the metal fiber breaks depends on the amount of fiber added, but substantially contributes to the breaking energy of the metal fiber composite. Therefore, by adding metal fibers having an elongation of 30% or more, the above-mentioned work hardening mechanism can be sufficiently exhibited, and a metal fiber composite having a large fracture energy that cannot be achieved by the conventional mechanism can be obtained.

  In addition, even metal fibers that have been used in the past and whose elongation and maximum tensile strength are not controlled in advance are, for example, metal fibers that are composited in a refractory material are annealed by receiving a thermal history during use, The elongation and maximum tensile strength specified in the present invention may be obtained. However, the thermal history that makes the metal fibers have the desired properties is not of course controllable, and the thermal history varies depending on the environment and location where the refractory is used, and the temperature history varies, making it ideal. A thermal history that is an annealing condition is not necessarily obtained. Until the state where the annealing effect is obtained by the thermal history during use of the metal fiber, the fracture energy due to the conventional drawing effect is mainly used. Therefore, in such a case, it is obvious that the mechanism according to the present invention is not always expressed.

  On the other hand, in the present invention, the elongation and the maximum tensile strength are already controlled at the time of addition of the metal fiber. Therefore, the effect of increasing the fracture energy due to the above-described ductility and work hardening mechanism is effective in the heat resistance of the metal fiber. Obtained stably over the entire temperature range. In particular, in non-fired refractories and amorphous refractories using cement as a binder, maintaining strength at 110 ° C. to 800 ° C. or increasing fracture energy is an important issue. Even in the temperature region, ductility and fracture energy increase due to work hardening are ensured, and the thermal shock resistance can be greatly improved compared to conventional products.

  As described above, in order to maximize the effect of increasing the fracture energy due to the ductility and work hardening mechanism of the metal fiber, it is important to control the elongation and the maximum tensile strength of the metal fiber to a specific value or more in advance. is there. As specific numerical values, it has been found from the verification by the examples described later that the elongation is 10% or more, preferably 30% or more, and the maximum tensile strength is 350 MPa or more.

  In this way, by adding metal fibers whose elongation and maximum tensile strength are controlled in advance, the metal fibers can withstand the maximum temperature of 1100 ° C. to 1200 ° C., particularly fire resistance, due to the ductility and work hardening mechanism of the metal fibers. The effect of increasing the fracture energy can be reliably exhibited in a temperature range of 800 ° C. or lower where it is difficult to obtain an annealing effect on the metal fibers in the object.

  Here, since the present invention increases the fracture energy by the ductility of the metal fiber and the mechanism of work hardening, if the surface of the metal fiber is smooth and easy to pull out, the effect of the ductility and work hardening is sufficient. It may not be obtained. In this respect, the metal fiber preferably has a surface roughness Ra of 0.1 μm or more and a maximum height Rz of 1.3 μm or more. The surface roughness Ra of the metal fiber is more preferably 0.2 μm or more. If the surface roughness Ra is 3 μm, the adhesion becomes strong, and the breaking energy until the metal fiber breaks is used as the breaking energy of the metal fiber composite. I can pass on. As described above, in the present invention, in order to make it difficult to pull out the metal fiber, it is preferable to specify the surface roughness Ra and the maximum height Rz of the metal fiber. For example, the metal fiber is pulled by changing the shape of the metal fiber. Since it can be made difficult to come off, the specification of the surface roughness Ra and the maximum height Rz of the metal fiber is not an essential requirement in the present invention.

  The inventor has also obtained new knowledge through a metal fiber pull-out test described below. That is, the surface roughness Ra of the metal fiber is 0.2 to 3 μm, preferably 0.5 to 3 μm, and the maximum height Rz is 1.5 μm or more and 14 μm or less, so that the above-described ductility and work hardening metal fiber is achieved. It was found that not only the breaking energy of itself but also the effect of pulling out metal fibers can be added.

  Here, in the metal fiber according to the present invention in which the elongation and the maximum tensile strength are controlled in advance, unlike the conventional simple pulling effect, a load is loaded on the metal fiber existing in the generated crack surface, and elongation due to ductility occurs. To do. The work hardening phenomenon occurs due to the elongation, and the strength of the metal fiber between the crack surfaces increases and the fiber diameter (cross-sectional area) decreases due to the elongation. At the same time, in the minute region where the metal fiber near the crack surface is embedded, the work hardening of the metal fiber existing between the crack surfaces propagates, and similarly the strength increases and the fiber diameter decreases. At this time, unlike the conventional mechanism in which separation occurs over the entire length in which fibers are embedded and the fibers are pulled out, separation of the matrix and fibers is likely to occur in the minute region where the embedded fiber diameter is reduced near the crack surface. In addition, the peeled site is replaced by resistance due to friction, and the strength increase due to work hardening and the cross-sectional area reduction proceed simultaneously. This action propagates and acts further from the micro area near the crack generation surface to the micro area where the matrix and fibers are still attached to the crack generation surface. Decrease in area and accompanying peeling, resistance of frictional force occurs, the action propagates from the crack generation surface to the back direction where the metal fibers are embedded, and finally pulls out, but with simple pulling The phenomenon described above is different, and it is considered that in addition to ductility and work hardening, a frictional force after adhesion is added, and an effect higher than that of the conventional mechanism can be obtained.

  As described above, according to the present invention, it is possible to provide a metal fiber composite such as concrete or refractory having a large breaking energy that has not been conventionally obtained.

An example of the stress (MPa) -elongation (%) diagram obtained by the uniaxial tension test of the metal fiber is shown. An example of the load-displacement curve obtained by the three-point bending test is shown. No. in Table 1 The stress (MPa) -displacement curve obtained by the 27, 29, 31-33 pull-out test is shown. The load-displacement curve obtained by the three-point bending test of the sample shown in FIG. 3 is shown.

  The metal fiber composite of the present invention can be obtained by adding and mixing in advance a metal fiber whose elongation, maximum tensile strength, surface roughness and the like are controlled to a raw material such as a refractory or concrete.

  The elongation and maximum tensile strength of the metal fiber can be controlled by selecting an appropriate material and applying an appropriate heat treatment as necessary. In addition, the surface roughness of the metal fiber is determined in advance in the case of metal fibers by the thin plate shearing method, the surface roughness and shape of the thin plate used as the fiber material, the surface roughness and shape of the shear jig, and the wire cutting method in the wire cutting method. The surface roughness can be controlled by controlling the surface roughness using a die or the like, or by introducing a coiled wire or a cut wire into a fluidized bed of abrasive powder such as fused alumina fine powder.

  In the present invention, the material of the metal fiber is preferably stainless steel in consideration of the requirement of the present invention that the elongation is 10% or more and the maximum tensile strength is 350 MPa or more, and particularly in the case of refractories, stainless steel is preferable. Among these, austenitic stainless steel such as SUS304, which is rich in ductility and work hardening, is optimal.

  The method for adding and mixing the metal fibers is the same as the conventional method. The addition amount of the metal fiber is also equivalent to the conventional one, and generally the addition amount is about 0.2 to 10% by mass. If the added amount of the metal fiber exceeds 10% by mass, fiber balls are likely to be formed, the metal fiber is not uniformly dispersed, the fracture energy tends to decrease, and the strength tends to decrease.

  Conventional techniques can also be applied to the length and shape of metal fibers and combinations thereof. By applying these conventional techniques, not only the same effects as the conventional techniques can be obtained, but also greater effects can be obtained in combination with the features of the present invention.

  The metal fiber composite of the present invention is preferably applied to a refractory or concrete, and particularly preferably applied to an amorphous refractory or an unfired fixed refractory.

Example 1
For various metal fibers shown in Table 1, elongation, maximum tensile strength, breaking energy, surface roughness Ra, and maximum height Rz were evaluated. In addition, a metal fiber pull-out test was performed on a metal fiber composite (unshaped refractory) to which these metal fibers were added, and fracture energy and thermal shock resistance were evaluated. These evaluation results are shown together in Table 1.

  First, an evaluation method for the evaluation items shown in Table 1 will be described.

1. Elongation, maximum tensile strength and breaking energy of metal fiber The elongation, maximum tensile strength and breaking energy of the metal fiber were evaluated by a uniaxial tensile test. A Shimadzu micro autograph was used for the uniaxial tensile test. The effective test length was 10 mm, and both ends were held by sandwiching metal fibers with a chuck jig. The tensile speed was 1 mm / min, data was collected at 100 msec, and the point at which the load became maximum was taken as the maximum load. The elongation of the metal fiber was evaluated as the elongation at the maximum load (hereinafter also simply referred to as “elongation”). This elongation was converted to% by the following formula.
Elongation = Crosshead movement during measurement (mm) / Test effective length (10mm) x 100%

Moreover, the maximum tensile strength (MPa) was calculated | required by dividing the maximum load by the fiber cross-sectional area before a test. The fiber cross-sectional area before the test was obtained by calculation from the theoretical values of fiber weight, length and density. The breaking energy of the metal fiber was determined from the area surrounded by the stress (MPa) -elongation (mm) curve obtained in the uniaxial tensile test. That is, the breaking energy is obtained by dividing the area (N · mm) by the pre-test fiber cross-sectional area (mm ² ), and the unit is N / mm.

  In the uniaxial tensile test, those that broke at the base of the chuck were regarded as abnormal and were excluded, and those that broke within the test effective length range were considered normal, and the average values of 9 measurements that could be measured normally are shown in Table 1. It was shown to.

2. Metal fiber surface roughness Ra and maximum height Rz
The surface roughness Ra and the maximum height Rz of the metal fiber were evaluated according to “JIS B 0601: 2001”.

3. Fracture energy The fracture energy of the metal fiber composite (amorphous refractory) was evaluated by a three-point bending test. In the three-point bending test, each metal fiber in Table 1 was added in an amount of 2.4% by mass to the alumina-magnesia amorphous refractory shown in Table 2 assuming a block per ladle hot water, and moisture was applied. After adding 4.85% by mass and kneading, casting into a 40 × 40 × 160 mm mold, drying at 110 ° C. overnight, heating at a predetermined temperature and time, once returning to normal temperature, a three-point bending test It was used for. The predetermined temperature and time are shown in Table 1 as heating temperature (° C.) × holding time (h). The test conditions were such that the distance between the lower fulcrums was 140 mm, the loading speed was 1 mm / min, the crosshead displacement was the displacement, and the load and displacement were measured. The area surrounded by the obtained load-displacement curve was regarded as energy required for fracture, and a value obtained by dividing this value by sample cross-sectional area × 2 (40 × 40 mm × 2) was defined as fracture energy. The calculation of the area surrounded by the load-displacement curve was made up to a displacement of 7 mm, and the region of displacement exceeding 7 mm was not included in the calculation. This is because when the displacement exceeds 7 mm, the bending test jig interferes with the sample and accurate data cannot be obtained.

4). Thermal shock resistance The thermal shock resistance (spalling resistance) of the metal fiber composite (amorphous refractory) was evaluated by an immersion spalling test. In the immersion spalling test, a 40 × 40 × 160 mm sample was immersed in hot metal held at 1650 ° C. by melting pig iron in a high-frequency furnace, taken out after being held for 5 minutes, and cooled with air to quench quickly. The leaving time was 60 minutes or more. This was repeated until the refractory broke.

5. Metal fiber pull-out test No. 26 to No. 26 in Table 1 were applied to the alumina-magnesia amorphous refractory shown in Table 2. 33 metal fibers were added by 2.4% by weight, and 4.85% by weight of water was added and kneaded, and then a 40 mm cubic mold was used, and a 10 mm thick was formed at the bottom of the mold. Styrofoam was laid, one piece of metal fiber cut to 20 mm in the center was inserted at a right angle, cast in that state, and a metal fiber drawing test sample was obtained. Accordingly, the metal fiber is embedded in a 10 mm cast body. These samples were heated at 1000 ° C. for 3 hours, and a pull-out test was performed on those returned to room temperature. Specifically, the metal fiber jumping out from the sample in which the metal fiber is embedded in a 40 mm cubic mold is the same as the chuck jig used in the uniaxial tensile test of the metal fiber, and 1 to The upper part of 1.2 mm was chucked. With the upper part chucked, the vertical direction of the fiber and the load direction of the uniaxial tensile test were matched, and then the 40 mm square casting was chucked and the same micro-autograph used for the uniaxial tensile test of the metal fiber was used. The tensile test was performed at a tensile speed of 1 mm / min.

  In addition, the 0.5 mm square in the cross section (mm) × length (mm) in Table 1 represents a regular square or a parallelogram with a side of 0.5 mm, but a square with slightly rounded corners. Including non-linear shapes and non-straight lines. Further, φ0.5 mm indicates that the cross section is round.

  Hereinafter, the evaluation results shown in Table 1 will be described.

  First, the relationship between “elongation and maximum tensile strength of metal fiber” and “fracture energy and thermal shock resistance of metal fiber composite (unshaped refractory)” will be described.

  From Table 1, all of the examples satisfying the requirements of the present invention (elongation: 10% or more, maximum tensile strength: 350 MPa or more) with respect to elongation and maximum tensile strength of the metal fiber have higher fracture energy than the comparative example, and thermal shock resistance. The property was also good.

  Regarding the elongation of the metal fiber, in the SUS304 series, the elongation is 5.5% (maximum tensile strength: 806 MPa). No. 1 having an elongation of 10.1% (maximum tensile strength: 823 MPa) compared to No. 1 (typical conventional product). No. 2 has a fracture energy increased by about 28% and an elongation of 13.2% (maximum tensile strength: 844 MPa). No. 3 has a fracture energy increased by about 43% and an elongation of 35.1% (maximum tensile strength: 752 MPa). No. 4 further increased the breaking energy. In the SUS430 system, No. having an elongation of 7% (maximum tensile strength: 480 MPa). No. 10 having an elongation of 10% (maximum tensile strength: 480 MPa). No. 11 and elongation of 14.5% (maximum tensile strength: 470 MPa). 12 increased the fracture energy by about 28%.

  As described above, when the evaluation results of the fracture energy when the elongation is changed for the metal fibers having the same shape and the approximate maximum tensile strength and the evaluation results of the thermal shock resistance are comprehensively considered, the fracture energy increase of the present invention described above is increased. In order to express the mechanism effectively, it was determined that the elongation of the metal fiber needs to be 10% or more, and preferably 30% or more.

  For the maximum tensile strength of metal fibers, see No.1. When the maximum tensile strength is as low as 25, the effect of increasing the breaking energy by the breaking energy increasing mechanism of the present invention cannot be obtained. No. with a maximum tensile strength of 360 MPa. 24, considering that the effect of increasing the fracture energy according to the present invention is obtained, it is determined that the maximum tensile strength of the metal fiber needs to be 350 MPa or more in order to effectively develop the mechanism for increasing the fracture energy of the present invention. It was done.

  In addition, as shown in Table 1, when “the elongation and maximum tensile strength of metal fibers” increases, “the breaking energy of metal fibers” and “the breaking energy of metal fiber composites (indefinite refractories)” increase proportionally. I understand. This is visually shown in FIG. 1 and FIG.

  That is, FIG. 1 shows an example of a stress-elongation curve obtained by a uniaxial tensile test of a metal fiber, and FIG. 2 shows an example of a load-displacement curve obtained by a three-point bending test. “No.” in FIGS. 1 and 2 corresponds to “No.” in Table 1. Further, as described above, the area surrounded by the curve in FIG. 1 represents the breaking energy, and the area surrounded by the curve in FIG. 2 represents the breaking energy.

  As can be seen from FIGS. 1 and 2, as “elongation and maximum tensile strength of metal fiber” increase, “breakage energy of metal fiber” and “breakage energy of metal fiber composite (unshaped refractory)” increase proportionally. I understand that This shows the effect of increasing the breaking energy according to the present invention, that is, the effect of increasing the breaking energy due to the ductility and work hardening mechanism of the metal fiber.

  Next, the relationship between “surface roughness Ra, Rz of metal fiber” and “fracture energy and thermal shock resistance of metal fiber composite (unshaped refractory)” will be described.

  As described above, the present invention increases the fracture energy by the ductility of the metal fiber and the mechanism of work hardening. Therefore, if the surface of the metal fiber is smooth and easily pulled out, the effect of the ductility and work hardening is sufficient. May not be obtained. Looking at the evaluation results in Table 1 from this point, 14 is No.14. Compared to 1, the maximum tensile strength of the metal fiber was large and the breaking energy was large, but the surface roughness was small, and no increase in breaking energy as a refractory was observed. No. Considering the evaluation results of 18 and the like, it was determined that the surface roughness Ra of the metal fiber is preferably 0.1 μm or more and the maximum height Rz is preferably 1.3 μm or more.

  Next, the results of the metal fiber pull-out test will be described. FIG. The stress-displacement curve obtained by the pull-out test of 27, 29, 31-33 is shown. FIG. 4 shows a load-displacement curve obtained by a three-point bending test of these samples. Moreover, the area surrounded by the stress-displacement curve obtained by the pull-out test is defined as “pull-out energy”, and the fiber break energy and the three-point bending break energy of the fibers used in Table 1 are listed again. The obtained drawing energy is shown together in Table 3.

  As shown in FIG. As for 27 (Ra: 4 μm, Rz: 15.6 μm), it can be seen that the metal fiber is broken without being pulled out. On the other hand, no. 33 (Ra: 0.14 μm, Rz: 1.2 μm) shows that the metal fibers are easily pulled out. And, the surface roughness of the metal fiber is an intermediate level. About 29, 31, 32, it turns out that the metal fiber is extended while pulling out.

  That is, from FIG. 3, FIG. 4 and Table 3, by controlling the surface roughness of the metal fiber within an appropriate range, not only the breaking energy of the metal fiber itself due to the above-described ductility and work hardening, but also the effect of pulling out the metal fiber (Extraction energy) was also added, and it was newly found that the total destruction energy can be increased. As for the specific range of the specific surface roughness, it was determined that the surface roughness Ra was 0.2 μm to 3 μm and the maximum height Rz was 1.5 μm to 14 μm.

  As described above, according to the present invention, the fracture energy of the metal fiber composite can be increased by a new mechanism that has not existed before. In other words, a sufficient breaking energy can be realized by adding a smaller amount of metal fiber than in the prior art. That is, conventionally, when a large amount of metal fiber is added to increase the breaking energy, a fiber ball is formed, and the metal fiber is not uniformly dispersed. However, according to the present invention, such a problem is avoided. However, the destruction energy can be increased.

(Example 2)
In order to confirm the effect of the present invention, the fracture energy of the refractory was evaluated in the same manner as in Example 1 for the mullite amorphous refractory shown in Table 4 assuming lance use. The results are shown in Table 5. Similarly, the fracture energy of the refractory was evaluated in the alumina-spinel amorphous refractory shown in Table 6 assuming RH dip tube use. The results are shown in Table 7. The “No.” of the metal fiber shown in Table 5 and Table 7 corresponds to the “No.” of the metal fiber in Table 1.

  In the evaluation of fracture energy, in the mullite amorphous refractories shown in Table 4, each metal fiber was added to the composition shown in the same table by 5% by mass and water was added by 4.85% by mass. After kneading, the sample which was heat-treated at 350 ° C. for 12 hours and returned to room temperature was subjected to a three-point bending test. In addition, in the mullite amorphous refractory shown in Table 6, each metal fiber was added to the composition shown in the same table by 5.2% by mass, and 4% by mass of water was added and kneaded. A sample that was heat-treated at 350 ° C. and returned to room temperature was subjected to a three-point bending test.

  From Tables 5 and 7, it can be seen that in the examples of the present invention, the effect of increasing the breaking energy is obtained as in Example 1.

Claims (3)

A metal fiber composite which is a refractory or concrete containing metal fibers,
As the metal fiber, in the evaluation by a uniaxial tensile test, a metal fiber made of stainless steel having an elongation of 10% or more at the maximum load and a maximum tensile strength of 350 MPa or more which is “maximum load / fiber cross-sectional area” is added. A metal fiber composite having a surface roughness Ra of 0.1 μm or more and a maximum height Rz of 1.3 μm or more .   The metal fiber composite according to claim 1, wherein the elongation of the metal fiber is 30% or more.   3. The metal fiber composite according to claim 1, wherein the metal fiber has a surface roughness Ra of 0.2 μm to 3 μm and a maximum height Rz of 1.5 μm to 14 μm.