JP3872665B2 - Manufacturing method of inclined composite material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention provides a gradient composite in which the composition ratio of ceramics increases and the composition ratio of metals decreases from the surface toward the inside.MaterialIt relates to a manufacturing method.
[0002]
[Prior art]
  Processing tools used in various processing fields, such as cutting tools and rolling rolls, are required to be excellent in hardness, wear resistance, heat resistance, oxidation resistance, compressive strength, and the like. From this point of view, in recent years, machining tools have been used for WC-Co cemented carbides obtained by sintering cobalt (Co) powder and tungsten carbide (WC) powder, and molybdenum (Mo) powder and titanium carbide (TiC). ) It has been attempted to form a composite material containing metal and ceramics, such as TiC cermet obtained by sintering powder. If a rolling roll is described as an example, a rolling roll made of this type of composite material has the above-mentioned characteristics to some extent, so that the rolling reduction in one rolling process can be increased. is there.
[0003]
  In addition, in order to further improve the hardness and wear resistance of the surface of the blade and the rolling roll, the surface is made of TiN or TiC by a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method. A film may be formed.
[0004]
  When the rolling roll is significantly worn, it becomes difficult to spread the work on a plate material having a predetermined thickness, and thus replacement is necessary.
[0005]
  By the way, the dimensions of the rolling roll are about 1 cm to 1 m in diameter and about 50 cm to 1.5 m in length even if they are general ones. On the other hand, the composite material as described above is expensive even if it has a small size, and inevitably, the composite material rolling roll having the above size is quite expensive. For this reason, if the exchange frequency increases, the purchase cost of the composite material-made rolling rolls rises, resulting in a problem that the rolling cost increases. Therefore, the composite material rolling roll is required to have excellent wear resistance as compared with a normal rolling roll.
[0006]
  In order to improve the wear resistance of the composite-made rolling roll, the hardness of the roll may be improved by increasing the composition ratio of ceramics. However, in this case, the strength and toughness of the roll are lowered, and as a result, a problem that brittle fracture is likely to occur in the roll is caused. For these reasons, a composite material-made rolling roll that has sufficient wear resistance but hardly causes brittle fracture has not been obtained so far.
[0007]
  Further, when a film is formed by the PVD method or the CVD method, there is a disadvantage that the size and shape of the film formation target are restricted, and thus the film cannot be formed efficiently. For this reason, the manufacturing cost of a composite material-made rolling roll is raised, and the price of a composite material-made roll is eventually raised further. Moreover, this coating easily peels off under high stress.
[0008]
  In view of this, the present applicant proposed in JP-A-2000-301216 a rolling roll made of a gradient composite material in which the ceramic composition ratio decreases from the surface to the inside and the metal composition ratio increases. ing. In this case, it is possible to form a rolling roll that has a high hardness on the surface and is excellent in wear resistance and has a high toughness inside, and is less likely to be cracked or chipped.
[0009]
[Problems to be solved by the invention]
  The rolling roll proposed in Japanese Patent Application Laid-Open No. 2000-301216 has a problem that finishing is not easy because the surface has high hardness. In order to eliminate this problem, it is considered that the metal composition ratio on the surface should be increased. This is because, as is well known, workability increases as the composition ratio of the metal increases.
[0010]
  This type of gradient composite material is, for example, 100 volume% metal particles, 80 volume% metal particles and 20 volume% ceramic particle mixed powder, 60 volume% metal particles and 40 volume% ceramic particle mixed powder. , 40 volume% metal particles and 60 volume% ceramic particles mixed powder, 20 volume% metal particles and 80 volume% ceramic particles mixed powder, 100 volume% ceramic particles, 20 volume% metal particles and 80 Mixed powder of volume% ceramic particles, mixed powder of 40 volume% metal particles and 60 volume% ceramic particles, mixed powder of 60 volume% metal particles and 40 volume% ceramic particles, 80 volume% metal particles, Manufactured by laminating 20 vol% ceramic powder mixed powder and 100 vol% metal particles in this order and then sintering the laminate. Rukoto can.
[0011]
  However, the sinterable temperature of the metal particles and the sinterable temperature of the ceramic particles are greatly different as is well known, and the latter is higher. Therefore, when the laminated body is sintered at a temperature at which the metal particles can be sintered, the ceramic particles are not densified, so that a low-strength gradient composite material is obtained. On the other hand, when the laminated body is sintered at a temperature at which the ceramic particles can be sintered, the metal is melted, so that a gradient composite material having a desired shape cannot be manufactured. In addition, when the laminates having different composition ratios are sintered stepwise as described above, the sintered body (gradient composite material) is deformed because the densification rate and the degree of shrinkage associated with the sintering are different in each layer. To do. Furthermore, cracks may occur in the sintered body during sintering.
[0012]
  That is, the manufacturing method of the gradient composite material according to the prior art has a problem that it is extremely difficult to manufacture a gradient composite material having a hardness and toughness that can be put to practical use in a desired shape.
[0013]
  The present invention has been made to solve the above-described problems. The metal composition ratio decreases from the surface toward the inside, and the ceramic composition ratio increases. For this reason, the surface is highly tough and the interior is Inclined composite that has high hardness and can be easily processedMaterialAn object is to provide a manufacturing method.
[0014]
[Means for Solving the Problems]
  To achieve the above objective,In the present invention, the composition ratio of ceramics increases from the surface toward the inside and the composition ratio of metals decreases.In addition, the ceramic particles present inside grew larger than the ceramic particles present on the surface.A method of manufacturing an inclined composite material, comprising:
  At least one selected from the group of W, Cr, Mo, Ti, V, Zr, Hf, lanthanoid carbides, nitrides or carbonitridesWith ceramic particlesFe, Ni, Co or at least one selected from the group of alloys composed of two or more thereofMetal particles60:40 to 97: 3 by weightA molding step of forming a mixed powder obtained by mixing the mixture powder; and
  A primary sintering step of sintering the molded body to form a porous body;
  Inside the porous body, Fe, Ni, Co, Mn, Cr, Mo, Ti or grain growth promoter containing lanthanoidAn impregnation step of impregnating the containing solution;
  SaidGrain growth promoterNitrogen the porous body impregnated with the containing solutionElementaryA secondary sintering step of re-sintering in a gas atmosphere to form a dense sintered body;
  Have
  The primary sintering step is terminated when the metal particles are fused to form a neck, and the ceramic particles are not fused to each other,
  In the secondary sintering step, nitrogen is added from the start of temperature rise.ElementaryIt is characterized by introducing gas.
[0015]
  In this case, in the secondary sintering step, the metal particles existing near the surface of the porous body start grain growth earlier than the ceramic particles. Further, the ceramic particles existing in the vicinity of the surface of the porous body are suppressed from growing by a nitriding gas such as nitrogen. This is because the nitriding gas generally inhibits the grain growth of ceramic particles. On the other hand, since the nitriding gas hardly reaches the ceramic particles existing inside the porous body, the grain growth is not suppressed. Moreover,Grain growth promoterThis promotes grain growth. For this reason, rearrangement occurs such that metal particles concentrate on the surface, and as a result, a gradient composite material is obtained in which the metal composition ratio decreases from the surface to the inside and the ceramic composition ratio increases. It is done.
[0016]
  As the nitriding gas, nitrogen is used because it is easy to handle and the reaction rate can be easily controlled.
[0017]
  The gradient composite material thus obtained has both toughness derived from metal and hardness and strength derived from ceramics. For this reason, it is possible to constitute various processing tools that are less likely to be cracked or chipped, and that have improved wear resistance and are less likely to be deformed.
[0018]
  Moreover, the composition ratio of the metal in this gradient composite material is the highest on the surface. In other words, processing The site that is easiest to apply is the surface. For this reason, various kinds of machining such as grinding can be easily performed, and eventually a product having a desired dimensional accuracy can be obtained.
[0019]
  In order to obtain a machining tool having sufficient hardness, strength and toughness when various kinds of machining are performed on the workpiece, the ceramic particles are made of W, Cr, Mo, Ti, V, Zr, Hf, lanthanoid carbide, nitride or And at least one selected from the group of carbonitrides, and the metal particles are at least one selected from the group of Fe, Ni, Co, or an alloy composed of two or more of these.TheFurthermore, you may make it add at least 1 sort (s) of Cr, Mn, V, and Ti to a metal particle. In this case, the composition ratio between the ceramic particles and the metal particles is set to 60:40 to 97: 3 by weight.. MoneyThis is because if the genus is less than 3 parts by weight, the toughness becomes poor and cracks and chips are likely to occur. On the other hand, when the amount exceeds 40 parts by weight, the hardness and strength are lowered, so that the wear resistance is poor and deformation is likely to occur during processing of the workpiece.
[0020]
  Also,Grain growth promoterContained in contained solutionGrain growth promoterAs suitable examples, Fe, Ni, Co, Mn, Cr, Mo, Ti, or a lanthanoid can be cited.
[0021]
  A suitable example of the inclined composite material is a rolling roll.When a rolling roll is manufactured, a molded body having a shape corresponding to the rolling roll may be produced in the forming step. In this case, in order to obtain a rolling roll having excellent dimensional accuracy, it is preferable to perform a finishing process for grinding the surface of the obtained dense sintered body to obtain a rolling roll.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the inclined composite according to the present inventionMaterialPreferred embodiments of the manufacturing method will be described and described in detail with reference to the accompanying drawings. In the present embodiment, a description will be given by exemplifying a rolling roll as the inclined composite material.
[0023]
  A schematic overall perspective view of the rolling roll according to the present embodiment is shown in FIG. 1, and a longitudinal sectional view thereof is shown in FIG. The rolling roll 10 is a cold rolling tool, and includes a roll portion 12 and small-diameter support shafts 14 a and 14 b provided at both ends of the roll portion 12.
[0024]
  The rolling roll 10 is composed of a composite material including ceramics and metal. And when the inside and the surface are compared, the composition ratio of the metal is larger on the surface. That is, the rolling roll 10 is provided with a metal-rich portion 20 having a relatively large metal composition ratio on the surface, whereas the metal-rich portion 20 has a smaller metal composition ratio and a ceramic composition ratio larger than the metal-rich portion 20. The portion 22 is provided inside, and the inclined portion 24 is further provided between the metal rich portion 20 and the ceramic rich portion 22. In the inclined portion 24, the ratio of the metal gradually decreases from the metal rich portion 20 side toward the ceramic rich portion 22 side.
[0025]
  That is, in the rolling roll 10, the metal composition ratio is highest at the inner peripheral wall portion and the outer peripheral wall portion, which are the surfaces, and decreases toward the inside. On the contrary, the composition ratio of ceramics is lowest at the inner peripheral wall portion and the outer peripheral wall portion which are the surfaces, and increases toward the inside.
[0026]
  As the ceramic as the constituent material of the rolling roll 10, at least one selected from the group of W, Cr, Mo, Ti, V, Zr, Hf, a lanthanoid carbide, nitride, or carbonitride is preferable, The metal is preferably at least one selected from the group of Fe, Ni, Co, or an alloy composed of two or more of these. In addition to these, the metal may further contain at least one of Cr, Mn, V, and Ti. By using the above ceramics and metal as constituent materials, it is possible to obtain the roll 10 having practically necessary strength, hardness and toughness.
[0027]
  When the above-described ceramics and metal are used as the constituent material of the rolling roll 10, the composition ratio of ceramics and metal is set to 60:40 to 97: 3 (weight ratio, the same applies hereinafter). If the metal content is less than 3 parts by weight, the toughness becomes poor, and cracks and chips are likely to occur. On the other hand, when the amount exceeds 40 parts by weight, the amount of ceramics is reduced, so that the hardness and strength are lowered. As a result, the wear resistance is poor and deformation is easily caused when the workpiece is rolled.
[0028]
  In order to balance the wear resistance and toughness sufficient for the rolling roll 10, the composition ratio of ceramics to metal is preferably 85:15 to 95: 5.
[0029]
  The metal composition ratio in the rolling roll 10 is the highest on the surface. For this reason, the surface can be easily processed. Therefore, the dimensional accuracy of the rolling roll 10 can be made desired.
[0030]
  The rolling roll 10 can be manufactured by the manufacturing method shown in FIG. As shown in FIG. 3, this manufacturing method includes a forming step S1 for obtaining a rolled roll-shaped formed body, a primary sintering step S2 for sintering the formed body to form a porous body, and the porous body. InsideGrain growth promoterImpregnation step S3 for impregnating the contained solution, secondary sintering step S4 for re-sintering the porous body to form a dense sintered body, and finishing step S5 for grinding the dense sintered body And have.
[0031]
  First, in the forming step S1, a mixed powder of ceramic particles and metal particles is prepared.
[0032]
  For the reasons described above, the ceramic particles are preferably at least one selected from the group of W, Cr, Mo, Ti, V, Zr, Hf, lanthanoid carbides, nitrides or carbonitrides, and metal particles. Is preferably at least one selected from the group consisting of Fe, Ni, Co, or an alloy composed of two or more thereof. Furthermore, you may make it add at least 1 sort (s) of Cr, Mn, V, and Ti. And the composition ratio of the ceramic particle and metal particle in mixed powder is adjusted so that the composition ratio of the ceramic and metal in the finally obtained rolling roll 10 may be 60: 40-97: 3.
[0033]
  Then, a compact is manufactured by applying a molding load to the mixed powder. At this time, the molding load is set to such an extent that the metal particles do not undergo plastic deformation in order to obtain a porous body in the primary sintering step S2 described later. Specifically, the molding load is preferably about 100 to 300 MPa. In this case, since the metal particles can be prevented from causing plastic deformation, the open pores of the molded body are not blocked.
[0034]
  In this case, since the rolling roll 10 is manufactured, a molded product having a shape corresponding to the shape of the rolling roll 10 is produced.
[0035]
  Next, in the primary sintering step S2, the molded body is sintered to form a porous body so that open pores remain. If it is a dense sintered body at this point, in the impregnation step S3Grain growth promoterThis is because it becomes difficult to impregnate the containing solution.
[0036]
  Therefore, the sintering temperature and time in the primary sintering step S2 are set such that the metal particles are fused and the necking is completed between the metal particles. That is, the ceramic particles are not fused in the primary sintering step S2. For this reason, in the process in which a molded object becomes a porous body, the volume hardly changes.
[0037]
  Next, in the impregnation step S3,Grain growth promoterContainsGrain growth promoterThe containing solution is impregnated inside the porous body. In particular,Grain growth promoterThe porous body is immersed in the containing solution. This immersionGrain growth promoterThe contained solution permeates into the porous body through the open pores.
[0038]
  In addition,Grain growth promoterIs not particularly limited as long as it is a substance that promotes the grain growth of ceramic particles in the secondary sintering step S4. Fe, Ni, Co, Mn, Cr, Mo, Ti, lanthanoids, and the like are preferable examples. Can be cited asGrain growth promoterWhat is necessary is just to use what melt | dissolved the metal salt containing the above-mentioned metal in the solvent, and an organometallic solution as a containing solution.
[0039]
  in this case,Grain growth promoterIs dissociated into single molecules or ions by being dispersed or dissolved in a solvent. Therefore, in the impregnation step S3, it was dissociated into single molecules or ions.Grain growth promoterAre uniformly dispersed inside the porous body. For this reason, the grain growth of the ceramic particles in the secondary sintering step S4 is promoted from the surface to the inside of the porous body.
[0040]
  After performing the impregnation step S3, by natural standingGrain growth promoterThe containing solution is dried. Or, heat the porous bodyGrain growth promoterThe contained solution may be dried.
[0041]
  Next, in the secondary sintering step S4, the porous body is re-sintered in a nitrogen gas atmosphere such as nitrogen to obtain a dense sintered body. Note that the nitriding gas as the atmosphere is introduced from the start of the temperature increase in the secondary sintering step S4. Thereby, a dense sintered body (gradient composite material) is obtained.
[0042]
  In the secondary sintering step S4, the growth of ceramic particles existing in the vicinity of the surface of the porous body is inhibited by the nitriding gas as the atmosphere. On the other hand, the nitriding gas hardly reaches the inside of the porous body. For this reason, the degree to which the grain growth of ceramic particles existing inside is inhibited by the nitriding gas is smaller than that of the surface. Moreover, the grain growth of the ceramic particles present inside isGrain growth promoterPromoted by.
[0043]
  Eventually, in the secondary sintering step S4, the grain growth of the ceramic particles is suppressed on the surface of the porous body and promoted inside. As a result, rearrangement occurs in which the metal particles are concentrated near the surface. That is, a gradient composite material having a high metal composition ratio on the surface and a high ceramic composition ratio on the inside can be obtained.
[0044]
  Thus, by introducing the nitriding gas atmosphere from the start of the temperature rise and performing the secondary sintering step S4,Grain growth promoterThe degree of grain growth of the ceramic particles existing inside the porous body impregnated with the containing solution can be increased as compared with the vicinity of the surface. Along with this, the metal particles are rearranged, whereby a gradient composite material in which the metal composition ratio decreases from the surface toward the inside and the ceramic composition ratio increases can be obtained.
[0045]
  Finally, in finishing S5, by grinding the surface of the inclined composite material, the composition ratio of ceramics to metal is 60:40 to 97: 3, preferably 85:15 to 95: 5 and the product As a result, a roll 10 having dimensional accuracy is obtained. In general, it is sufficient that the grinding width in grinding is about 0.5 to several mm.
[0046]
  In this finishing process, since the metal composition ratio on the surface of the gradient composite material is relatively high, the surface can be easily ground. That is, in the rolling roll 10 after being subjected to grinding, the thickness of the ceramic rich portion 24 having high hardness and high strength is remarkably increased. On the other hand, the metal rich portion 20 remains on the surface of the rolling roll 10. Therefore, the rolling roll 10 which has toughness, hardness, and intensity | strength can be obtained.
[0047]
  In the present embodiment, the forming step S1 and the primary sintering step S2 are performed separately. However, both steps S1 and S2 are performed simultaneously as in hot isostatic pressing (HIP) or the like. May be.
[0048]
  In the above-described embodiment, the rolling roll 10 is illustrated as an example of the inclined composite material. However, the present invention is not particularly limited thereto, and other processing tools, structural materials, and the like may be used. Not too long.
[0049]
【Example】
  90 parts by weight of tungsten carbide (WC) particles having an average particle diameter of 1 μm and 10 parts by weight of cobalt (Co) particles having an average particle diameter of 1 μm were wet mixed using hexane to obtain a mixed powder. Next, while this mixed powder is molded at a pressure of 100 MPa by a hydrostatic pressure molding method, nitrogen is circulated at 30 liters / minute and held at 900 ° C. for 30 minutes to have a diameter of 15 mm and a length of 25 mm. A cylindrical porous body was obtained. Molding was performed while discharging hexane from the cavity through the clearance of the mold.
[0050]
  Next, this porous body was immersed in a 10% concentration Ni ion solution for 3 minutes to disperse Ni ions inside the porous body. Furthermore, the porous body was dried by holding at 90 ° C. for 1 hour.
[0051]
  Next, the porous body was re-sintered in a nitrogen atmosphere in the pattern shown in FIG. 4 to obtain a dense sintered body (gradient composite material). When the obtained tilted composite material was cut and observed with an electron microscope, the ceramic particles present on the surface were rounded and fine, while the ceramic particles present inside were greatly grown. Was recognized.
[0052]
  In addition, as a result of instrumental analysis, it was found that the metal composition ratio decreased from the surface toward the inside, and the ceramic composition ratio increased. Furthermore, it was confirmed that WC near the surface was nitrided and tungsten carbonitride was generated. This is considered to be the reason why the surface ceramic particles are rounded.
[0053]
  Vickers hardness and A-scale Rockwell hardness were measured from the surface to the inside of the cross section of the inclined composite material. The results are shown in FIG. From FIG. 5, it is apparent that the obtained gradient composite material has increased hardness from the surface toward the inside.
[0054]
  Further, WC particles having an average particle diameter of 3 μm were weighed to 93% by weight and Co particles having an average particle diameter of 0.8 μm to 7% by weight, and both particles were wet mixed using hexane to obtain a mixed powder. And after drying until hexane became 9 weight%, this mixed powder was shape | molded by the hydrostatic pressure method in a metal mold | die with the pressure of 100 Mpa in the cylindrical body shape of diameter 80mm x length 320mm. Molding was performed while discharging hexane from the cavity through the clearance of the mold.
[0055]
  Next, this cylindrical molded body was held at 900 ° C. for 30 minutes in a nitrogen atmosphere to obtain a porous body.
[0056]
  Further, the porous body was immersed in an aqueous nickel nitrate solution having a concentration of 10% to disperse Ni ions inside the porous body, and then dried by holding at 130 ° C. for 2 hours.
[0057]
  And this WC particle | grain growth was carried out by hold | maintaining this porous body in nitrogen atmosphere at 1400 degreeC for 2 hours. That is, a composite cylinder made of a sintered body of WC and Co was obtained. This is Example 1. Nitrogen was introduced from the start of the temperature increase.
[0058]
  In addition, except that WC particles were 90% by weight, Co particles were 3% by weight, Ni particles having an average particle diameter of 0.4 μm were 5% by weight, and Cr particles having an average particle diameter of 5 μm were 2% by weight to obtain a mixed powder. In accordance with Example 1, a composite cylinder made of a sintered body of WC, Co, Ni, and Cr was prepared. This is Example 2.
[0059]
  Regarding the composite cylinders of Examples 1 and 2, the relationship between the distance from the surface and the Vickers hardness was examined. The results are shown in FIG. From FIG. 6, it is clear that in the composite material cylinders of Examples 1 and 2, the hardness increases from the surface toward the inside. This is because the composition ratio of ceramics increases from the surface toward the inside.
[0060]
  Furthermore, for comparison, the ratio of WC particles, Co particles, Ni particles, and Cr particles was changed as shown in FIG. And after making it the cylindrical molded object of the same dimension based on Example 1, 2, this cylindrical molded object was made into the cylinder body made from a composite material by hold | maintaining at 1400 degreeC for 2 hours in nitrogen atmosphere. These are referred to as Comparative Examples 1 to 4, respectively. FIG. 7 also shows the composition of the mixed powder in Examples 1 and 2. The compositions of Example 1 and Comparative Examples 3 and 4 correspond to the composition of the cemented carbide adopted as the raw material of the composite material roll.
[0061]
  With respect to the side peripheral wall portion of each of the above composite material cylinders, the entire surface was cut and removed from the surface to a depth of 0.2 mm. The relationship between the temperature and the A-scale Rockwell hardness was investigated for the exposed surface after this removal. The higher the hardness, the more excellent the wear resistance. The results are shown in FIG. From FIG. 8, the composite material cylinders of Examples 1 and 2 exhibit significantly higher hardness than the composite material cylinders of Comparative Examples 1 to 4 over the entire temperature range, that is, the wear resistance is high. It is clear that it is excellent.
[0062]
  In addition, each composite cylinder of Example 1 and Comparative Example 1 was subjected to a wear test using a low carbon steel as a counterpart material with an Ogoshi type wear tester. FIG. 9 is a graph showing the relationship between the sliding distance and the wear amount. From FIG. 9, it can be seen that the composite cylindrical body of Example 1 has significantly superior wear resistance despite the same metal ratio.
[0063]
  Furthermore, the bending strength was measured for each of the composite material cylinders of Examples 1 and 2 and Comparative Examples 1 and 2. For Example 1 and Comparative Example 1, Young's modulus was also measured. The results are also shown in FIG. From this measurement result,Grain growth promoterBy impregnating the contained solution and then sintering in a nitriding gas atmosphere, the composition ratio of the metal and the ceramic can be changed in an inclined manner. As a result, the strength and Young's modulus can be improved as compared with a general composite material. It can be said that it can be improved.
[0064]
  From the above results,Grain growth promoterIt is understood that an inclined composite material having excellent wear resistance, high strength and high Young's modulus can be obtained by impregnating the containing solution and then sintering in a nitriding gas atmosphere. And the wear resistance, strength, Young's modulus, etc. of the inclined composite material are sufficient values when the inclined composite material is used as a rolling roll. That is, by using this inclined composite material, it is possible to obtain a rolling roll that is less likely to be exchanged and is less likely to cause brittle fracture, and that can efficiently perform a rolling process on a workpiece.
[0065]
【The invention's effect】
  As explained above,According to the manufacturing method of the inclined composite material according to the present invention,Grain growth promoterThe porous body impregnated with the contained solution is re-sintered in a nitrogen gas atmosphere such as nitrogen to obtain a dense sintered body (gradient composite material). In this case, the growth of ceramic particles near the surface of the porous body is suppressed by nitrogen, while the ceramic particles existing inside areGrain growth promoterThis promotes grain growth. For this reason, rearrangement occurs in which metal particles concentrate on the surface, and as a result, the gradient composite material in which the metal composition ratio decreases from the surface to the inside and the ceramic composition ratio increases, that is, the surface is increased. The effect is achieved that a gradient composite material having high toughness and high hardness inside can be obtained.
[0066]
  The gradient composite material thus obtained is excellent in various properties such as toughness, strength and hardness. For this reason, for example, it is possible to easily configure a rolling roll that has excellent wear resistance and is less likely to crack or chip. In addition, since the composition ratio of the metal in the inclined composite material is the highest on the surface, machining such as grinding can be easily performed, and a product with good dimensional accuracy can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic overall perspective view of a rolling roll (gradient composite material) according to the present embodiment.
FIG. 2 is a longitudinal sectional view of the rolling roll of FIG.
FIG. 3 is a flowchart of a method for manufacturing a tilted composite material according to the present embodiment.
FIG. 4 is a graph showing a temperature pattern when performing a secondary sintering step.
FIG. 5 is a graph showing the change in hardness of the obtained gradient composite material directed from the surface to the inside.
6 is a graph showing the relationship between the distance from the surface and the Vickers hardness in the composite cylinders of Examples 1 and 2. FIG.
7 is a chart showing composition ratios of raw material particles, bending strength, and Young's modulus in sintered bodies (composite cylinders) of Examples 1 and 2 and Comparative Examples 1 to 4. FIG.
FIG. 8 is a graph showing the relationship between the temperature and the A-scale Rockwell hardness in the composite cylinders of Examples 1 and 2 and Comparative Examples 1 to 4.
9 is a graph showing the relationship between the sliding distance and the amount of wear in the composite cylinders of Example 1 and Comparative Example 1. FIG.
[Explanation of symbols]
  10 ... rolling roll 12 ... roll part
  14a, 14b ... support shaft 20 ... metal rich part
  22 ... Ceramics rich part 24 ... Inclined part

Claims (4)

Manufacture of a graded composite material in which the ceramic composition ratio increases from the surface to the interior, the metal composition ratio decreases , and the ceramic particles present inside grow larger than the ceramic particles present on the surface. A method,
W, Cr, Mo, Ti, V, Zr, Hf, at least one ceramic particle selected from the group of carbides, nitrides or carbonitrides of lanthanoids, and Fe, Ni, Co, or two of them A molding step of molding a mixed powder obtained by mixing at least one metal particle selected from the group of alloys configured as described above at a weight ratio of 60:40 to 97: 3 ;
A primary sintering step of sintering the molded body to form a porous body;
Impregnation step of impregnating the inside of the porous body with a grain growth promoter- containing solution containing Fe, Ni, Co, Mn, Cr, Mo, Ti or a lanthanoid ;
A secondary sintering step of a dense sintered body by re-sintering the grain growth promoting agent containing solution wherein the porous body impregnated with nitrogen gas atmosphere,
Have
The primary sintering step is terminated when the metal particles are fused to form a neck, and the ceramic particles are not fused to each other,
The secondary The primary sintering step, the manufacturing method of the gradient composite material and introducing a nitrogen gas from the start heating. The manufacturing method according to claim 1 , wherein at least one of Cr, Mn, V, and Ti is further mixed with the metal. The manufacturing method according to claim 1 or 2 , wherein a molded body having a shape corresponding to a rolling roll is produced in the forming step. The manufacturing method according to claim 3 , further comprising a finishing step of grinding the surface of the obtained dense sintered body to form a rolling roll.

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