JPH0362762B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a composite material of iron-based metal and ceramic (including metal carbide, metal nitride, and metal oxide; the same shall apply hereinafter). [Prior art and its problems] Materials with high strength and high wear resistance are required in a wide range of fields including tools and structural materials. In recent years, ceramics, which have excellent wear resistance, have attracted attention as one such material, and their use is progressing in various fields. However, this ceramic has a basic drawback of being unreliable in terms of toughness, and this point has prevented its use in a general and wide range of fields. Therefore, composite materials of iron-based metals and ceramics, which have high toughness, are attracting attention as materials that take advantage of the excellent properties of ceramics, and various manufacturing techniques are being researched. non-uniform dispersion, poor adhesion, presence of vacancy defects,
There are various problems such as the complexity of the manufacturing process, and the technology has not yet been established enough to be put into practical use. For example, in liquid casting methods (melt infiltration method, pressure casting method, vacuum casting method) using ceramic fibers,
There are few pore defects and the adhesion between the ceramic and the base metal is good, but if there is a difference in specific gravity between the ceramic and the molten metal, the ceramic floats or sinks, making it difficult to uniformly disperse the ceramic. Another drawback is that during production, work is required at relatively high temperatures in order to melt the base metal. In addition, in the solid diffusion method (sintering method) using powder, hot pressing, extrusion, etc.
A reducing atmosphere is essential to enable diffusion bonding, and long-term heating is required to achieve sufficient diffusion bonding, and large-capacity hot press equipment is required to eliminate void defects. The disadvantage is that the production is extremely complex and, especially when producing composites containing large amounts of ceramic, diffusion bonding of the parent metal is very difficult. As described above, all conventional methods have fundamental problems in terms of the material quality and manufacturing process of the composite materials obtained.Therefore, it is possible to easily produce composite materials of appropriate materials without causing these problems. It has been desired to develop a method that can be obtained through a simple process. [Means and Examples for Solving Problems] The present invention has been researched and developed in view of the current situation. The present inventors have found that contact between the molten matrix metal and the ceramic is effective in improving the adhesion strength in order to solve the conventional problems of non-uniform dispersion and insufficient adhesion strength in this type of composite material. From the viewpoint that the presence of a solid phase of the parent metal is effective for uniform dispersion, it has been found that the above problems can be solved at once by utilizing the semi-molten state in which the solid and liquid of the parent metal coexists. That is, as schematically shown in Fig. 1, the parent metal is made into a semi-molten state to form a liquid phase, and this is pressure molded to strengthen the adhesion with the ceramic and eliminate pores. Since floating and settling of the ceramic is suppressed by the solid phase portion of the semi-molten base metal, it becomes possible to uniformly disperse the ceramic. In addition, the pressure required to eliminate pores is relatively small due to the presence of a liquid phase (molten phase), and the heating temperature is also lower than that of conventional casting methods since the parent metal is only brought into a semi-molten state. It has the advantage of being low in production, and further has the advantage that a reducing atmosphere is not particularly required and a composite material with sufficient strength can be produced even in the atmosphere. However, this manufacturing method also has a drawback in that the composition and temperature range of the parent metal, which is in a semi-molten state, is not very wide. For example, iron
The amount of C that exhibits a semi-molten state at 1150 to 1400℃, which is a practical temperature range from the carbon phase diagram, is 1.3.
It is about ~3wt%, and if this continues, only composite materials having a limited composition of the matrix metal can be obtained. Therefore, the present inventors have succeeded in developing a manufacturing method that further advances such a basic manufacturing method and allows a wide range of selection of the composition of the matrix metal. That is, the basic structure of the present invention is to heat a mixture of metal powder to be a matrix and ceramic powder or fiber, and press-mold the matrix metal in a semi-molten state.
In particular, there are two different types of metal powders: metal powders that can easily obtain a semi-molten state as the metal powders to form the matrix iron-based metal, and metal powders that are used to adjust the overall composition of the matrix metal in relation to the metal powders. Based on the functions of these different types of metals,
This allows the parent phase iron-based metal to have a wide range of compositions, and also enables the production of high-density composite materials. That is, the first feature of the present invention is that the metal powder to form the parent phase iron-based metal is mixed with the parent phase iron-based metal in the relationship between the high carbon steel powder, which becomes molten at a relatively low temperature, and the powder. Iron-based metal powder for adjusting the overall composition toward mild steel, including Ti, Nb,
one or more metal powders selected from the group of iron alloys V, Ta, W, Mo, Cr or Mn, heating a mixture of these metal powders and ceramic powder or fibers, Pressure molding is carried out with the matrix metal in a semi-molten state, and the heated state is maintained during the heating and pressure molding to homogenize the dissimilar metals constituting the matrix metal and to precipitate carbides. The reason is that diffusion processing is performed. The second feature of the present invention is that a mixture similar to the above is heated and pressure molded in a state in which the matrix metal is semi-molten, and after the pressure molding, the matrix metal is homogenized. and diffusion heat treatment for the purpose of carbide precipitation. The details of the present invention will be explained below. A major feature of the present invention is that it makes it possible to ensure uniform dispersion and increase the density of the material when there is a difference in specific gravity between the matrix iron-based metal and ceramic, which was previously considered extremely difficult, in a relatively easy way. Moreover, the composition of the iron-based metal can be selected from a wide range. In general, there are very few ceramics that have a specific gravity that is almost the same as that of iron-based metals, and currently commonly used ceramics such as alumina (Al ₂ O ₃ ) and metal carbides such as chromium carbide have a specific gravity difference with carbon steel (reinforcing material/iron). The difference in specific gravity causes the ceramic to float or settle, resulting in its non-uniform dispersion. As mentioned above, conventional sintering methods do not melt iron-based metals, so it is possible to uniformly disperse ceramics, but in order to eliminate pores, extremely high pressures, e.g. It requires tens of thousands of atmospheres of pressure and requires post-processing such as casting after sintering. On the other hand, in the present invention, the liquid phase of the base metal, which is basically in a semi-molten state, fills the pores at a relatively low pressure, and the floating or settling of the ceramic is restrained by the solid phase. A high-density composite material with uniformly dispersed particles is obtained. In addition, in the present invention, the metal powder to form the matrix iron-based metal is a metal powder that has the function of bringing the entire matrix metal into a semi-molten state at a relatively low temperature, that is, a high carbon steel that itself melts at a relatively low temperature. The high density of the composite material and the uniform dispersion of ceramics are achieved by using a metal powder that has the function of adjusting the composition of the entire matrix metal to the mild steel side from the viewpoint of preventing toughness deterioration in relation to the metal. The composition of the parent phase iron-based metal can be selected from a wide range while ensuring the following, and a composite material made of the parent phase iron-based metal with an arbitrary composition can be obtained. Among the different types of metals mentioned above, the former, that is, high carbon steel powder that melts at a relatively low temperature, has a carbon content of, for example, 0.5 to 4.3 wt%, and the latter, that is, the composition adjustment of the entire matrix metal. Target metals include Ti, Nb, V, Ta, W, Mo,
Cr, Mn (elements with greater carbide forming ability than Fe)
iron alloys (FeTi, FeNb, FeTa, FeV, FeW,
FeMo, FeCr, FeMn). These metal powders can be used alone or in combination. In addition, since different types of metals are used in the present invention, the carbon content is different between the region that becomes a solid phase and the region that becomes a liquid phase when it becomes a semi-molten state. Upon cooling, micro-segregation of carbon will occur in the matrix metal. Therefore, primarily to promote uniform diffusion of these dissimilar metals throughout the matrix, and incidentally to promote carbon absorption by the metals, that is, carbide precipitation, for the purpose of adjusting the composition of the matrix metal. For,
During or after manufacture, diffusion heat treatment is performed to maintain a predetermined heating state for a certain period of time. That is, the second
As shown in the figure, during manufacturing, the parent metal is kept at a temperature in a semi-molten state for a certain period of time to uniformly diffuse the dissimilar metals that make up the parent metal, or the cooled composite material is By reheating and holding for a certain period of time, the matrix metal itself undergoes a diffusion heat treatment, and the metal powder is used to adjust the composition of the matrix metal to promote carbide precipitation. Furthermore, in concretely implementing the present invention,
There is a preferable range of the liquid phase ratio (volume ratio of the molten phase to the entire matrix metal and reinforcing material mixture, hereinafter the same) in a semi-molten state of the matrix metal. In other words, if the liquid phase ratio exceeds 50%, the ceramic is less constrained by the solid phase, and the ceramic tends to be unevenly distributed due to sedimentation or flotation, making it impossible to ensure uniform dispersion of the ceramic. Furthermore, if the liquid phase ratio is less than 5%, it becomes difficult to obtain the necessary adhesion. Therefore, the liquid phase ratio of this matrix metal is 5
The range is preferably 50%. The major advantages of carrying out the present invention compared to conventional sintering methods are: (1) A reducing atmosphere is not particularly required. (2) Heating time can be significantly shortened. Points such as: These advantages are due to the density improvement mechanism of the method of the present invention being different from that of the sintering method. In other words, in sintering, the number of vacancies is reduced due to the promotion of chemical bonds, so it is necessary to avoid contact with oxygen in the atmosphere, which inhibits this, as much as possible. Pressing (or forging after sintering)
In contrast, in the method of the present invention, if the matrix metal is heated to a semi-melting temperature, a composite material with true density can be obtained with a low pressure due to the presence of a liquid phase, and it can be maintained at a semi-melting temperature for a long time. do not have to. In other words, if a desired composite material can be obtained by diffusion heat treatment after pressurization, a high-density composite material can be obtained by applying pressure at the moment when the temperature reaches half-melting temperature. Furthermore, when performing advanced quality control of ferrous metals that are the base material of composite materials (i.e., when it is necessary to extremely prevent reactions between ferrous metals and atmospheric components), the following canning method - isostatic press is used. The law is valid. As shown in Figure 16, this method first mixes iron-based metal powder and ceramic powder or fibers, cans the mixture, pulls it under vacuum (<10 ^-1 torr), heats it, and pressurizes it using hydrostatic pressure. It is something to do. Example 1 Ferrotungsten powder (80W,
0.32), Al ₂ O ₃ powder is used as the ceramic.
The mixture was added in the proportions shown in the table and thoroughly mixed, and this mixture was filled into a graphite mold, and pressure molded by heating at 1130°C for 15 minutes while pressurizing to 1500 kg/cm ² to produce a composite material. After cooling in the furnace, some samples were subjected to oil quenching at 1000°C for 1 hour and tempering at 600°C for 2 hours for the purpose of diffusion heat treatment. For comparison, composite materials were produced with and without heat treatment using 3% C cast iron powder: 80% and Al ₂ O ₃ powder: 20%.
Figure 3 shows the results of the abrasion resistance test of these composite materials using an Amsler abrasion tester, and Figures 4 and 5 show the results.
The figure shows the hardness and Charpy impact test results. According to the above-mentioned FIG. 3, it can be seen that WC precipitates in the case where the diffusion heat treatment was particularly performed in the present invention, and exhibits excellent wear resistance.

[Table] Example 2 FeX powder (X is W, V, Nb and
Cr) and Al ₂ O ₃ as ceramics are added and mixed in the proportions shown in Table 2, and this mixture is
Pressure molded by heating at 1130℃ for 15 minutes while pressurizing to 1500Kg/ ^cm2 , and after cooling in the furnace, for the purpose of diffusion heat treatment.
A composite material was produced by quenching at 1000°C for 1 hour and tempering at 600°C for 2 hours. The proportion of FeX powder was calculated to be 2% when the matrix C was completely diffused. In addition, as a comparative material, 3% C cast iron powder 80%,
A composite material consisting of 20% Al ₂ O ₃ powder was produced under similar conditions. Figures 6, 7, and 8 show the wear test results, hardness, and Shapey impact test results of the composite materials obtained, and they are the materials of the present invention in which the parent metal composition is adjusted with FeX powder. It can be seen that both abrasion resistance and hardness are higher than that of the comparative material.

[Table] Example 3 3% C cast iron powder, FeV powder as metal powder for adjusting the matrix metal component, and Al ₂ O ₃ as ceramic
The powders were mixed in the proportions shown in Table 3 to prepare composite samples with different FeV powder particle sizes. Note that the pressure molding and heat treatment conditions are the same as in Example 2.
In addition, as comparison materials, 3% C cast iron powder 80%, Al ₂ O ₃ powder
A composite consisting of 20% was made under similar conditions. Figures 9 and 10 show the relationship between the FeV particle size, hardness, and Charpy impact test value from the obtained composite material. In particular, the smaller the average FeV particle size, the larger the impact value. There is.

[Table] Example 4 Composite materials were manufactured using the materials shown in Table 4 by the conventional sintering method and the method of the present invention. In the conventional method, after primary sintering at 1120°C, sintering was performed in a reducing atmosphere under the conditions of the heating pattern shown in Fig. 11 and a pressing force of 13 kg/mm ² , and in the method of the present invention, sintering was performed in the atmosphere.
Each was manufactured under the conditions of the heating pattern shown in the figure and the pressing force of 8 Kg/mm ² .

〔Effect of the invention〕

According to the present invention described above, by making the matrix metal into a semi-molten state and press-molding it, it is possible to eliminate pores and obtain a high degree of adhesion, and also to make the matrix metal in a semi-molten state. Uniform dispersibility of the ceramic can be appropriately ensured by the solid phase portion. In addition, the pressure required to eliminate pores is relatively small due to the presence of a liquid phase, and since the parent metal is only brought into a semi-molten state, the heating temperature is also lower than in conventional casting methods. This has manufacturing advantages. In addition to these advantages, metal powders that have the function of bringing the entire matrix metal into a semi-molten state at relatively low temperatures, particularly as metal powders to form matrix iron-based metals, that is, metal powders that themselves melt at relatively low temperatures. In order to prevent toughness deterioration in relation to this metal, high carbon steel powder is used, and metal powder has the function of adjusting the overall composition of the matrix metal to a mild steel side. While ensuring the uniform dispersibility of ceramics, the composition of the matrix iron-based metal can be selected from a wide range, making it possible to easily obtain a composite material consisting of the matrix iron-based metal of any composition, and also to ensure uniform diffusion of the metal. Since diffusion heat treatment is performed on the material, it is possible to create a matrix iron-based metal composite material with a uniform composition while using different types of iron-based metals. Furthermore, composite materials can be manufactured using simple processes and equipment without requiring a non-oxidizing atmosphere or long-term heating, and the workability in manufacturing composite materials is improved, especially compared to conventional sintering methods. , which has the advantage of greatly reducing efficiency and the complexity of equipment for heating and pressurizing, and when manufacturing large quantities of products, it does not require long heating, so the energy required for heating can be reduced. Compared to the sintering method, it is possible to reduce the amount significantly, and it is also possible to manufacture a large amount of products in a short time. In addition, since there is no need for equipment necessary for atmosphere control, heating and
The pressurizing device can also be made relatively compact, and there is an advantage that a large-capacity pressurizing device is not required.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing the basic principle adopted by the present invention. FIG. 2 schematically shows the steps of the method of the present invention. FIG. 3 shows the influence of the amount of FeW added on the wear resistance properties in Example 1. Figure 4 is also in Example 1.
This shows the influence of the amount of FeW added on hardness. FIG. 5 also shows the influence of the amount of FeW added on the Charpy impact test value in Example 1. FIG. 6 shows the wear resistance of each sample in Example 2. FIG. 7 similarly shows the hardness of each sample in Example 2. 8th
The figure also shows the Charpy impact test values of each sample in Example 2. Figure 9 shows Example 3
This figure shows the influence of FeV particle size on hardness. FIG. 10 shows the influence of the FeV particle size on the Charpy impact test value in Example 3. 11 and 12 show heating patterns taken in Example 4, with FIG. 11 showing the conventional sintering method and FIG. 12 showing the heating patterns of the present invention. 13 and 14 are microscopically enlarged photographs of the ceramic-metal composite structure of the composite material obtained in Example 4, in which FIG. 13 shows the composite material obtained by the method of the present invention, and FIG. 14 shows the composite material obtained by the conventional sintering method. This shows a composite material made by Figure 15 shows Example 5
1 is an enlarged microscopic photograph of the ceramic-metal composite structure of the composite material obtained in . FIG. 16 is an explanatory diagram showing the canning-isostatic press method used in the method of the present invention in the order of steps.

Claims (1)

[Scope of Claims] 1. The metal powder that is to form the parent phase iron-based metal is a high carbon steel powder that becomes molten at a relatively low temperature, and the composition of the entire parent phase iron-based metal is made to be on the side of mild steel in relation to the powder. Metal powder for adjusting Ti, Nb, V,
It is composed of one or more metal powders selected from the group of iron alloys Ta, W, Mo, Cr, or Mn, and a mixture of these metal powders and ceramic powder or fibers is heated to form a matrix. Diffusion treatment for the purpose of homogenizing the dissimilar metals constituting the matrix metal and precipitating carbides by press-molding the metal in a semi-molten state and maintaining the heated state during the heating-press molding. A method for manufacturing a composite material made of iron-based metal and ceramic, characterized by performing the following steps. 2. A method for producing a composite material made of iron-based metal and ceramic according to claim 1, characterized in that heating and pressure molding is carried out in the atmosphere. 3. The method according to claim 1, characterized in that a mixture of iron-based metal powder and ceramic powder or fiber is canned, evacuated, and then molded by hydrostatic pressure after heating or while heating. A method for manufacturing a composite material made of iron-based metals and ceramics. 4. A material made of iron-based metal and ceramic according to claim 1, 2 or 3, characterized in that the matrix metal is semi-molten and heated so that the liquid phase volume fraction with respect to the entire mixture becomes 5 to 50%. Method of manufacturing composite materials. 5. Claim 1, characterized in that, in the metal powder to form the matrix iron-based metal, a high carbon steel powder having a carbon content of 0.5 to 4.3 wt% is used as the powder that becomes molten at a relatively low temperature. A method for producing a composite material comprising an iron-based metal and ceramic according to 2, 3 or 4. 6 A metal powder for adjusting the overall composition of the parent phase ferrous metal to a mild steel side in relation to a high carbon steel powder that becomes molten at a relatively low temperature and the powder to form the parent phase ferrous metal. and Ti, Nb, V,
It is composed of one or more metal powders selected from the group of iron alloys Ta, W, Mo, Cr, or Mn, and a mixture of these metal powders and ceramic powder or fibers is heated to form a matrix. An iron-based metal characterized in that the metal is pressure molded in a semi-molten state, and after the pressure molding, a diffusion treatment is performed for the purpose of homogenizing the dissimilar metals constituting the matrix metal and precipitating carbides. A method for manufacturing a composite material consisting of and ceramic. 7. A method for producing a composite material made of iron-based metal and ceramic according to claim 6, characterized in that heating and pressure molding is carried out in the atmosphere. 8. The method according to claim 6, characterized in that a mixture of iron-based metal powder and ceramic powder or fiber is canned, evacuated, and then molded by hydrostatic pressure after heating or while heating. A method for manufacturing a composite material made of iron-based metals and ceramics. 9. A material made of iron-based metal and ceramic according to claim 6, 7 or 8, characterized in that the matrix metal is semi-molten and heated so that the liquid phase volume ratio to the entire mixture becomes 5 to 50%. Method of manufacturing composite materials. 10 Claim 6, characterized in that, in the metal powder to form the matrix iron-based metal, a high carbon steel powder having a carbon content of 0.5 to 4.3 wt% is used as the powder that becomes molten at a relatively low temperature. A method for producing a composite material comprising an iron-based metal and ceramic according to 7, 8 or 9.