JP2006509908A - Composite metal products and methods of manufacturing such products - Google Patents

Abstract

The present invention relates to a 30-90 hard phase substantially in the form of M (C, N) -carbonitride or M (C, N, O) -carbonitride oxide particles, commonly referred to as MX-type hard phases. It relates to composite metal products containing volume%. However, M consists of titanium up to at least 50 atomic%, the particles are distributed substantially homogeneously in a matrix made of hardenable steel, and the ratio of atomic% between C and N is 0.1 <(formula I) Satisfy the condition of <0.7. In the production of the product, the amount of titanium carbide, titanium nitride, and / or titanium carbonitride powder corresponding to at least 50% of the metal atoms in the hard phase of MX-type in the final metal product. Pulverize together at least the main parts of the powder mixture comprising and other components of the final metal product. A green body is formed from the finely pulverized product, and this green body is subjected to liquid phase sintering at a temperature of 1350 to 1600 ° C., followed by cooling to solidify the liquid phase. Thus, during the liquid phase sintering and subsequent cooling, the MX-type hard phase particles obtain the final composition and size.
N / (C + N) (I)

Description

  The present invention is suitable for use as a material for wear parts and structural members when there are high requirements for materials for shearing, cutting, drilling, and forming tools as well as sufficient strength and wear resistance with sufficient strength. It relates to composite metal products. The invention further relates to a method for producing such a product.

  As materials for tools for shearing, cutting, drilling, and forming, as well as materials for wear parts and structural members that have great demands on hardness and wear resistance, cold-worked steel, high-speed steel, Carbonized carbide materials and ceramic materials are used. In this series, it is believed that high speed steel is generally more suitable than cold worked steel, and sintered carbide material is more suitable than high speed steel. The boundary between cold-worked steel and high-speed steel is becoming more or less largely due to the use of powder technology, but there is still a wide gap between high-speed steel and highly qualified sintered carbide materials. . The concept of “cemented carbide materials” means a material with a very high content of carbide (carbide) sintered together in a binder metal, usually made of a cobalt-based alloy. In the past 50 years, many attempts have been made to fill this gap by the development of steel alloys with a high content of titanium carbide. An earlier proposed material belonging to this category is known under the registered name “Ferro-TiC”, but its practical use was very limited. Another material having the registered name “Coronite” disclosed in US Pat. No. 4,145,213 is no longer on the market as far as the applicant knows.

  The material according to said U.S. Pat. No. 4,145,213 contains a very high content of titanium carbide (titanium carbide) in a matrix of hardenable steel. According to this patent, titanium carbide likewise contains a greater amount of nitrogen than carbon. Furthermore, according to this patent, this material can be obtained by liquid phase sintering of cold compacted powder bodies, by pressure, by liquid phase sintering of powder bodies (so-called pressure sintering), by balanced hot pressing, or It can be produced by forging the powder in the presence or absence of a liquid phase. When sintering in the presence of a liquid phase, it is necessary to carry out the sintering operation for a very short time at the sintering temperature in order to avoid unwanted particle growth of the hard phase product. It is. This is a significant limitation as it makes it difficult or impossible to achieve the desired uniform distribution of hard phase particles in the matrix. To the best of Applicant's knowledge, this seems to be the reason why none of the above techniques has been adopted for the commercial production of “coronite-materials”. Instead, this material was manufactured by an extrusion process, which is an expensive process, and could not compete with either high speed steel or sintered carbide material. No other material is known that can claim to fill the gap between high speed steel and sintered carbide material.

  To provide new materials that can compete with currently available materials for tools including shearing, cutting, drilling and / or molding operations, and other products where great demands are made regarding hardness and wear resistance. It is an object of the present invention. In particular, for at least some applications where high-speed steel, cold-worked steel or wear-resistant structural steel is used today, it is not necessary to exclude the fact that this material can be used. The purpose is to provide an alternative to carbonized carbides.

  The aim is to achieve a hard phase substantially in the form of particles of M (C, N) -carbonitride or M (C, N, O) -carbonitride oxide, usually referred to as MX-type hard phase, from 30 to 30 It can be achieved through the present invention by a composite metal product containing 90% by volume. Here, M is made of titanium up to at least 50 atomic%, and the atomic% ratio between C and N is a condition of 0.1 <N / (C + N) <0.7, preferably 0.2 <N / (C + N ) <0.6, preferably 0.3 <N / (C + N) <0.6, most preferably 0.4 <N / (C + N) <0.5, The particles are distributed substantially uniformly in a matrix of hardenable steel.

  During the development studies that led to the present invention, initial experiments were also conducted with metals other than titanium such as V, Nb and Hf in the MX-type hard phase. These initial experiments did not give the desired results because there were too many of the elements. However, subsequent experiments show that good results can be achieved when the MX-phase contains one or more of the above metals, for example niobium, in moderate contents. Other MX-phase forming metals such as Ta and Zr could also be considered. However, in the MX-type hard phase, M of up to 40 atomic%, preferably up to 30 atomic% may be composed of one or more metals belonging to the group consisting of V, Nb, Ta, Hf and Zr. It is guessed. For example, M can consist of 5 and up to 30 atomic percent V and / or 5 and up to 30 atomic percent Nb, but in total consists of up to 40 atomic percent, preferably up to 30 atomic percent. When Ta, Zr and / or Hf are included, the total amount of these metals must not exceed 3 atomic percent of the total metal content of the MX-type hard phase.

  According to one aspect of the present invention, the metal M in the MX-type hard phase comprises at least 70 atomic percent, preferably at least 80 atomic percent, and most preferably at least 90 atomic percent titanium.

  According to one aspect of the invention, the total content of the MX-type hard phase is 30 to 70% by volume, preferably 40 to 60% by volume of the metal product.

As mentioned above, the matrix is made of hardenable steel. In its quenched and tempered state, the steel also contains secondary crystal carbides that are too small to be observed with an optical microscope, such as vanadium carbide, ie MC-carbide. In addition, the steel contains primary carbides, such as M ₆ C-carbide, characteristic of high speed steel. Thus, the matrix containing secondary crystallized MC-carbide that can be present in the matrix, and all other hard phases other than the MX-type that can be present in the matrix have the following chemical composition in weight percent: Wow:
0.3-3.0% C
Si from the trace amount up to 2%
Mn from trace amount up to 2%
S from trace amount up to 0.5%
2-13% Cr
W up to 18% from the trace amount
Mo up to 12% from the trace amount
Co up to 15% from the trace amount
V from trace amount up to 10%
Nb from trace amount up to 2%
Balance: Fe, but 50% or more of Fe, and normally present impurities from steel production.

  The present invention also relates to particles consisting mainly of M (C, N) -carbonitride or M (C, N, O) -carbonitride oxide, usually referred to as MX-type hard phase (particles are hardenable steel matrix). It is an object of the present invention to provide a method for producing a composite metal product containing 30 to 90% by volume of a hard phase having a shape (substantially uniformly distributed therein) with good reproducibility.

  According to the method of the present invention, this is a powder of titanium carbide, titanium nitride, and / or titanium carbonitride, wherein the content of titanium atoms in the powder mixture is the metal in the hard phase of the MX-type in the final metal product. A powder mixture containing more than 50% of the atoms and at least the main part of the other components of the final metal product are pulverized together to form a constant body with the pulverized mixture. Further, this is achieved by liquid-phase sintering the body at a temperature of 1350 to 1600 ° C., followed by cooling to solidify the liquid phase. The MX-type hard phase particles obtain the final composition and size during the liquid phase sintering and subsequent solidification. It is preferable that 90% or more of the number of particles that can be observed in the portion where the material is viewed with an optical microscope has a size of less than 1 μm.

  In addition, according to one aspect of the present invention, the carbon and nitrogen content is adjusted during the overall process including powder selection and grinding, powder mixture grinding, compacted powder compact formation, and liquid phase sintering. The amount of carbon and nitrogen in atomic% in the hard phase of the final product satisfies the ratio N / (C + N) value described above.

  According to another aspect of the invention, the milling of the powder mixture is carried out with a power supply of at least 10 MJ (megajoules) / kg powder, preferably at least 20 MJ / kg powder. A power supply of 25 MJ / kg powder was found to be suitable. Therefore, the power supply should be limited to a maximum of 50 MJ / kg powder, preferably a maximum of 40 MJ / kg powder so as not to unnecessarily costly manufacture according to one aspect of the present invention.

The uniform distribution of MX-type hard phase particles in the matrix is a typical feature of the method for producing the composite metal product. Uniform distribution means that 0.5% or less of the product portion has a length of 8 μm or more in the longest length direction of the region, a width of 8 μm or less in the lateral direction in the longest length direction in all portions of the region, and A region having an area of 50 μm ² or more, this region must be composed of no MX-type hard phase particles, and 10% or less, preferably 5% or less of the product portion is the longest length of the region is the direction of more 6d length, all parts in the maximum length direction transversely of 6d or more of the width of the region, and 9πd region having ^two or more areas, the hard phase particles of this region MX- types It means that it does not exist. Here, d is the average value of the MX-type hard phase particle size in the longest direction of the observed portion of the particles.

  The titanium carbide, titanium nitride and / or titanium carbonitride powder used in the powder mixture may be oxidized. Experiments conducted have shown that highly oxidized powders can be used and that oxidized powders do not need to be reduced before use. This is a significant benefit from a cost standpoint. No means are needed to prevent further oxygen uptake in a continuous process including grinding, compacting and sintering. Oxygen present in the powder mixture and additional oxygen incorporated in the process combine with titanium present in the hard phase, and oxygen partially replaces carbon and / or nitrogen in the crystal lattice of the hard phase. . In this case, the hard phase can be defined as M (C, N, O) -carbonitride oxide. According to one aspect of the invention, the oxygen content in the hard phase is 0.01 to 4 atomic percent of the total (C + N + O) content in the hard phase.

  Further aspects and specific features of the present invention will become apparent from the following description and discussion and from the claims.

  In the following description of the experiments performed, reference is made to the accompanying drawings.

Description of Experiments Performed Experiments used various mixtures of powdered hard phase, base metal powder, and graphite powdered carbon. The hard phase powder consisted of vanadium carbide (VC), niobium carbide (NbC), hafnium carbide (HfC), hafnium-titanium carbide ((Hf, Ti) C), titanium nitride (TiN), and titanium carbide (TiC). . More specifically, a commercially available powder of the hard phase having a powder particle size on the order of 1 μm was used as the hard phase. These powders contained thousands of ppm oxygen. In other words, these powders were highly oxidized. The order of oxygen content was estimated to be about 4000 ppm (0.4%), but it can reach as much as 1% by weight. The base metal powder consisted of commercially available high speed steel obtained from the applicant's own product. This high speed steel is known by its registered trade name ASP2030 (hereinafter referred to as ASP2030 ^{(R) in the} text ^), and its chemical composition is 1.28C, 0.5Si, 0.3Mn, 4.2Cr, 5% by weight. 0.0 Mo, 3.1 V, 6.4 W, 8.5 Co, balance: iron and inevitable impurities. This powder consists of powder sprayed with gas sieved to a maximum particle size of 125 μm. In this experiment, the aim was to achieve a finished composite product matrix having exactly the same composition as the matrix of steel powder added with grade ASP2030 ^(R) after quenching. Therefore, carbon was also added to the powder mixture in various amounts in the form of graphite powder. A variation of ASP2030 ^(R) was also tested, denoted as ASP20xx.

  Various powder mixtures were ground in a ball mill type so-called attritor mill with ball bearing steel grinding balls. However, unlike conventional ball mills, where energy is supplied to the grinding balls by rotation of the mill housing (mill envelope), in an attritor mill, energy is supplied to the balls by a rotating propeller. This gives the grind a very high speed and thus the ability to transfer more energy to the product being ground.

  Therefore, in the attritor mill, the energy supply per unit time is about 15 times larger than that in the conventional ball mill. This is important because it promotes homogenization of the material during grinding. During milling, the milled particles are crushed, deformed and recombined repeatedly. Deformation, an important part of this process, supplies a large amount of dislocation energy to the product to be ground, resulting in a changed high energy state of powdered material. The energy delivered to the milled material in this way reached about 25 MJ / kg powder. During grinding, no grinding liquid was used. This grinding was carried out under atmospheric pressure. It is possible that oxygen pick-up due to oxidation occurred during the handling of the powder.

  The powder mixture thus ground was compressed into the form of green bodies without adding any compression aids.

  The green body was solidified by liquid phase sintering in a vacuum furnace heated by a graphite electric heater. The sintering temperature was varied between 1300-1540 ° C. and held at each sintering temperature for 30 minutes.

  Prior to mechanical testing, the samples were quenched from 1180 ° C. and subsequently annealed at 560 ° C. for 1 hour × 3 times.

Experiment I Series: Samples containing vanadium carbide (VC) and titanium nitride (TiN) In this experimental series, three different alloys were produced: alloys 63, 64 and 65. In addition to VC and TiN, base metal ASP2030 ^(R) and graphite powder carbon, and a small amount of powder chromium carbide, Cr ³ C ² were also added. The components of this powder mixture are shown in Table 1.

  The powder mixture was pulverized in an attritor mill with an energy supply of about 25 MJ / kg powder for 10 hours, compressed into a green body, and sintered by the method described above. The microstructure of the samples sintered at 1300, 1350 and 1400 ° C. was examined. For comparison, a sample of the same powder mixture that was consolidated by hot isostatic pressing (HIP-ing) was also considered. As a result of this study, it was found that these powder mixtures can achieve a high density and small particle size hard phase after sintering. However, it has also been noted that the homogeneity of the alloy is not improved by sintering compared to the hot equilibrium compressed material. In addition, all three alloys 63, 64 and 65 experienced abnormal growth of hard phase particles, especially in some large areas.

Experiment II series: of base alloy ASP2030 ^(R) , niobium carbide, titanium nitride and carbon (graphite) powders having the same physical properties according to the series of sample experiments I including niobium carbide (NbC) and titanium carbide (TiC) Three mixtures were prepared. The composition of the mixture is shown in Table 2.

  After pulverization and green body production according to the method described above, samples hardened by hot equilibrium compression and liquid phase sintering at 1350 ° C. and 1400 ° C. were produced. Sample microstructure studies have demonstrated that hot equilibrium compression gives a relatively homogeneous microstructure. However, the homogeneity after liquid phase sintering was not good. This could possibly be due to poor wetting between the hard phase and the liquid phase. This type of alloy with a high NbC content was therefore considered unsuitable for liquid phase sintering.

Experiment III Series: Samples containing HfC, (Hf, Ti) C and TiN A powder mixture having a composition according to Table III was prepared. These powders also had the same physical properties as the series of experiments I and II.

  Prior to the production of the green body, these powders were also ground in the same way as in the series of experiments I and II, and consolidated by hot equilibrium compression and sintering at 1400 ° C and 1540 ° C, respectively. However, microstructural studies showed that homogeneity was not improved by sintering at 1400 ° C or 1540 ° C.

Experiment IV Series: Samples containing TiC and TiN The powder mix components in this series of experiments are shown in Table 4. Table 5 shows the nominal chemical composition (target value). The typical properties of the powder were equivalent to that of the previous experimental series.

  The components of the powder mixture were selected so that only the carbon and nitrogen content was varied, and the other elements were present in exactly the same amount in the mixture. Therefore, the chemical composition of this powder mixture contained 0.39 Si, 0.18 Mn, 2.66 Cr, 3.34 Mo, 4.18 W, 2.05 V, 5.60 Co and 25.3 Ti by weight. According to information received from the manufacturer of this component, the oxygen content was about 0.27% by weight. The balance was iron, carbon, nitrogen and inevitable impurities. Table 5 shows the contents of carbon and nitrogen in the powder mixture.

  The powder mixture was pulverized for 10 hours in an attritor mill with the method described above, for example, with an energy supply of 25 MJ / kg powder. The green body was made of pulverized powder, which was hardened by hot equilibrium compression and liquid phase sintering, respectively. Liquid phase sintering was performed between 1300 ° C. and 1540 ° C. with a temperature of 30 minutes at each sintering temperature.

Microstructure studies of sintered samples showed that the homogeneity of the microstructure varies with the chemical composition of the sample. Homogeneity in this context means the degree of uniform distribution of hard phase particles in the matrix alloy. 1-5 show the microstructure of samples of alloys 69, 70, 71, 72 and 73 after liquid phase sintering at 1480 ° C. It is clear that alloys 70 and 71 had a relatively homogeneous microstructure and fine hard phase particles with a size much smaller than 1 μm. Alloy 69 had a relatively coarser hard phase structure. Alloy 72 was poor in homogeneity and high in porosity, but alloy 73 was the worst in homogeneity and the highest in porosity. This difference can be attributed to any of the following factors: the chemical composition of the powder mixture, the chemical reaction during liquid phase sintering between the elements present, and the incorporation of light elements during grinding and sintering or Loss. For example, carbon may have been picked up from a graphite heating element in a sintering operation. Oxygen as well as nitrogen can be taken up from the surroundings during the grinding process. Furthermore, during liquid phase sintering, various elements dissolve in the liquid phase incorporated into the MX-phase, so that M is not completely composed of titanium, but to some extent from vanadium and the base alloy ASP2030 ^(R) . It will be made of another metal. Despite the low solubility of titanium, a small amount of titanium seems to dissolve in the melt. Without being bound to any particular theory, it can be assumed that the reaction rate is relatively slow for at least some alloys. This is advantageous because it does not allow the carbide to grow unacceptably and allows liquid phase sintering to be performed at high temperatures for extended periods of time. It can be assumed that carbon promotes wetting between the hard phase and the liquid phase, but on the one hand to stabilize the hard phase, on the other hand it also incorporates oxygen to replace some carbon and / or nitrogen in the crystal lattice of the hard phase. It appears that a certain amount of nitrogen is also required in the hard phase to enable Furthermore, it is assumed that the existing M ₆ C-carbides enter the liquid phase during the sintering operation and that they form a network around the M (C, N, O) -particles during solidification. The effects can be minimized, for example, by choosing a suitable base alloy with a low content of W and Mo.

  First, in order to examine the importance of the chemical composition of the hard phase particles, the chemical composition of the hard phase and the chemical composition of the matrix alloy were investigated by various methods. An EDS-analysis method (Energy Dispersive Spectroscopy) and a Thermo-Calc calculation were used. Tables 6 and 7 show the compositions calculated by the Thermo-Calc method of the hard phase and matrix at a quenching temperature of 1180 ° C for several selected alloys sintered at 1480 ° C. The Thermo-Calc calculation did not take oxygen content into account. Although the oxygen content is considered negligible in the matrix, it may be about 4 atomic% of the total (C + N + O) content in the hard phase.

  In light of the microstructure studies shown in FIGS. 1-5 and in view of the chemical composition of the hard phase shown in Table 6, the present disclosure in the introductory portion of the specification, as well as the claims It can also be concluded that the hard phase should have a balanced carbon and nitrogen content (expressed in atomic%).

  FIG. 1 shows that alloy 69 was sintered at 1480 ° C. to obtain very good homogeneity with hard phase particles having an average size of about 0.8 μm, and only a few particles exceeded 1 μm. It shows that it had a size. However, the higher the nitrogen portion of the hard phase, the more homogeneity is lost and the hard phase particles become smaller. This is illustrated in FIGS. In order to test whether the homogeneity of a sample in which the hard phase is somewhat more carbon than nitrogen can be affected by the sintering temperature, the alloy 71 sample is liquid phase sintered at a temperature varying between 1350-1540 ° C. Later tested. A sample of the same alloy with hot equilibrium compression was also investigated. The resulting microstructure is shown in FIGS. The microstructure after sintering at 1480 ° C. is shown in FIG. FIG. 6 shows that the microstructure after sintering at 1350 ° C. was almost non-uniform as after hot equilibrium compression (FIG. 11), but the microstructure was 1480 as shown in FIGS. Sintering at temperatures in excess of 0 ° C. indicates that good homogeneity has been achieved with very uniformly distributed hard phase particles whose particle size is much smaller than less than 1 μm.

In accordance with what has been disclosed above, good homogeneity is facilitated by the control ratio N / (C + N) according to the present invention. This is also evident from Tables 6 and 8. The latter table also shows that increasing the sintering temperature effectively improves the microstructure homogeneity if the value of the N / (C + N) ratio proposed by the present invention is satisfied. Table 8 shows the total area of the major region, expressed as a percentage of the investigated area of a portion of the material, which has no visible particles of the MX-phase and is located along the longest length of this region. A length of at least 6d; any portion of this region has a width of at least 6d laterally of the longest length; and an area of at least 9πd ² . Here, d is an average value of the sizes of the MX-type hard phase particles in the longest length direction of the particles in the examined area of the portion. The presence of such large "empty" areas, although crushing of the alloy metals consisting of high speed steel ASP2030 ^(R) of Example enters believed to be very important, poorly before sintering to some extent It can be said that there is a cause in the crushing. If milling is insufficient, the conditions regarding the value of the ratio N / (C + N) are met and the homogeneity obtained by the sintering operation is not sufficient even if the sintering temperature is raised to the highest possible level There can be a risk. The results obtained for the hot equilibrium compressed material are also included in Table 8.

  Samples made in Experiment IV series were also subjected to mechanical testing. After quenching at 1180 ° C. by dissolution treatment, cooling to room temperature and annealing at 560 ° C. 3 times for 1 hour each time, the hardness in the Vicker hardness test reached about 1080-1180 HV30 if the sample had a nominal composition . Incorporation of carbon and nitrogen increased the hardness to 1250-1300 HV30 for certain alloys.

Series of Experiment V: Samples containing TiC, TiN and NbC In this series, we report from experiments with two different alloys, referred to as alloy number 110 and alloy number 160, respectively. In addition to TiC, TiN and NbC, the powder mixture contained the base metal alloy ASP2030 ^(R) and its variants and graphite powdered carbon, respectively. This variant has less Mo and W content than ASP2030 ^(R) and will be referred to as ASP20XX hereinafter. The powder mixture of Alloy 110 also contained a small amount of vanadium carbide (VC). This powder had the same physical properties as the powder in the above experimental series. The ingredients are shown in Table 9.

  The powder mixture was ground in the same manner as in the series of Experiment IV. The green body was made of pulverized powder, and this green body was subjected to liquid phase sintering in the temperature range of 1400 to 1540 ° C. at each sintering temperature for a holding time of 30 minutes.

In addition to Ti (C, N) and the matrix, the alloy 110 also contained M ₆ C-carbide (M consists essentially of molybdenum and tungsten) and MC-carbide (substantially consists of vanadium carbide). Despite the presence of vanadium carbide, the V content of the hard phase was 50% less than expected in terms of the total composition of the alloy. The niobium and vanadium content in the hard phase of alloy 110 was about 4 atomic percent and about 5 atomic percent, respectively, of the total content of M in the hard phase. In alloy 160, the niobium content in the hard phase reached about 15 atomic percent of the metal M content. The chemical content of C and N in the hard phase is about 4.6 wt% C and 3.6 wt% N for alloy 110 and about 5.1 wt% C and 3.6 wt% N for alloy 160, respectively. It became. The ratio N / (C + N) for the hard phase of alloy 110 is thus 3.6 / (3.6 + 4.6) = 0.43, and the same value for alloy 160: 3.9 / (3.9 + 5.1) = 0.43 was obtained.

Tool members were made of alloy 110 in the form of a cutter blade for use as an insert in a single tooth cutter. Prior to assembly, the insert was quenched from 1100 ° C. and subsequently annealed at 560 ° C./(1 hour × 3 times). The cutting ability of the insert was compared to that of an equivalent insert made of high capacity high speed steel ASP2030 ^(R) manufactured by powder metallurgy. Relative productivity due to cutting ability was achieved with inserts made of alloys according to the present invention, which was approximately twice (80-100% greater) than the productivity of known high speed steels. In this connection, it must also be mentioned that the material according to the invention has been produced by a method that is very restrictive on the experimental scale, ie the cleanliness and other characteristics of the material produced. Therefore, further improvements should be achievable in full-scale manufacturing. On the other hand, when the tool member (insert) is made of a sintered carbide material, there is also a need to expect a further increase in cutting ability. This is because the composite metal product of the present invention is made of high-speed steel and sintered carbide material. To make sure that the gap can be filled.

  Alloy 160 includes quenching from 1150 ° C. but was otherwise examined for microstructure after heat treatment performed in the same manner as alloy 110 according to the foregoing; substantially evenly in the quenched and tempered matrix. See FIG. 12 which shows the homogeneous microstructure of the distributed round carbide.

  In toughness measurements, toughness was not quantified with respect to absolute magnitude. However, no systematic differences were observed between samples that were hot equilibrium compressed and samples that were subjected to liquid phase sintering according to the present invention as compared to samples made by hot equilibrium compression.

discussion:
As can be concluded from the previous description of the experiments performed, very good results were achieved in the series of experiments IV. In that series, a powder mixture containing titanium carbide and titanium nitride was used as a starting material, and the process was controlled so that the carbon and nitrogen content otherwise satisfied the balance relationship shown previously. The importance of milling and sintering temperatures to achieve the desired microstructure was also discussed. On the other hand, the importance of the composition of the matrix alloy has not been studied in detail. First, ASP2030 ^(R) type high speed steel was used as the base alloy in the powder mixture. This steel alloy provides a matrix that can be hardened to a hardness of > 500 HV30 in the finished product. However, it is not certain that the chemical composition of the high speed steel is most suitable for providing a matrix having an optimal chemical composition in combination with other components of the powder mixture. For example, ASP2030 ^(R) has a relatively high metal content that can form M ₆ C carbide. While it is true that this type of carbide can be dissolved during liquid phase sintering according to the present invention, they can also be dissolved in the matrix and / or M (C, N) -phase particles and / or M (C, N, O). -It is also true that it can be restored on phase particles (this would be disadvantageous). Therefore, higher speed steels with lower W and Mo contents would be more suitable than ASP2030 ^(R) , as previously indicated in connection with the use of alloy ASP20XX in Experiment V series. Other steel alloys such as high speed steels as well as other hardenable steels such as cold worked steels are also conceivable. However, a steel alloy should preferably be used as the base alloy which, after tempering together with the other components, provides a matrix in the final material that can be hardened to a hardness > 500 HV30.

  The hard phase content in the powder mixture can also be varied. In addition to titanium carbide, titanium nitride, and / or titanium carbonitride powder, and thus for at least some applications, MX- such as VC, NbC, TaC, ZrC, HfC and / or (HfTi) C and corresponding nitrides. It may be conservative to add other carbides or nitrides of the mold. However, the amount is not more than 30 mol% of the total content of the MX-type hard phase achieved in the finished product. An advantage of stimulating the formation of mixed carbonitrides, for example in the presence of a significant amount of vanadium and / or niobium, is that the formation of a dense material is promoted even when sintered at relatively low temperatures. Will correct the addition of a certain amount of VC and / or NbC in the powder mixture, or the addition of a high content of vanadium and / or niobium in the base metal alloy. For example niobium carbide in the powder mixture may also stimulate grinding. Mixed carbonitrides may also be considered harder than pure titanium carbonitride or pure titanium carbonitride oxide, which will increase the hardness of the metal product produced. The results obtained in the series of Experiment V show that the presence of small or moderate amounts of NbC (with or without VC together) in the powder mixture can provide the final product with the desired combination of features. Is shown. Therefore, it is considered advantageous that 3 to 40 atomic percent of the hard phase metal atoms consist of (Nb + V), preferably 5 or more and a maximum of 30 atomic percent of Nb and / or V.

It is a figure which shows the microstructure which is an example in the range with N / (C + N) value of a hard phase in the alloy sample made from the powder mixture containing TiC and TiN. It is a figure which shows the microstructure which shows the other example in the range with N / (C + N) value of a hard phase with the alloy sample made from the powder mixture containing TiC and TiN. It is a figure which shows the microstructure which shows the other example in the range with N / (C + N) value of a hard phase with the alloy sample made from the powder mixture containing TiC and TiN. It is a figure which shows the microstructure which shows the other example in the range with N / (C + N) value of a hard phase with the alloy sample made from the powder mixture containing TiC and TiN. It is a figure which shows the microstructure which shows the other example in the range with N / (C + N) value of a hard phase with the alloy sample made from the powder mixture containing TiC and TiN. FIG. 4 shows the microstructure of a composite product having a chemical composition according to the present invention and produced at a temperature between 1350 ° C. and 1540 ° C. in the sintering temperature. FIG. 2 shows the microstructure of a composite product having a chemical composition according to the invention and produced at different temperatures between 1350 ° C. and 1540 ° C. FIG. 2 shows the microstructure of a composite product having a chemical composition according to the invention and produced at different temperatures between 1350 ° C. and 1540 ° C. FIG. 2 shows the microstructure of a composite product having a chemical composition according to the invention and produced at different temperatures between 1350 ° C. and 1540 ° C. FIG. 2 shows the microstructure of a composite product having a chemical composition according to the invention and produced at different temperatures between 1350 ° C. and 1540 ° C. FIG. 3 shows the microstructure of a material produced by hot equilibrium compression and having the same chemical composition. It is a figure which shows the microstructure of the steel which added NbC according to one aspect | mode of this invention.

Claims (41)

  30-90% by volume of substantially hard particulate phase of M (C, N) -carbonitride or M (C, N, O) -carbonitride oxide, usually called MX-type hard phase, Wherein M is at least 50 atomic percent titanium and the particles are essentially homogeneously distributed in a matrix of hardenable steel; and the atomic percent ratio between C and N is 0. 1 <N / (C + N) <0.7 is satisfied.   2. Product according to claim 1, characterized in that the atomic% ratio between C and N satisfies the condition 0.2 <N / (C + N) <0.6.   3. A product according to claim 2, characterized in that the atomic% ratio between C and N satisfies the condition 0.3 <N / (C + N) <0.6.   4. A product according to claim 3, characterized in that the atomic% ratio between C and N satisfies the condition 0.4 <N / (C + N) <0.5.   The product according to any one of claims 1 to 4, wherein 90% of the number of the hard phase particles has a size having a longest length of less than 1 µm in the observation cross section of the product. 10% or less of the cross section of the product consists of a region having a length of 6d or more in the direction of the longest length, a width of 6d or more in the lateral direction in the longest length direction in any cross section, and an area of 9πd ² or more. Here, d is an average value of MX-type hard phase particles in the longest length direction of the particles in the observation cross section, and MX-type hard phase particles are lacking in the region. The product according to any one of claims 1 to 5. From the region where 0.5% or less of the cross section of the product has a length of 8 μm or more in the longest length direction, a width of 8 μm or less in the lateral direction in the longest length direction in any cross section, and an area of 50 μm ² or more The product according to claim 1, wherein MX-type hard phase particles are lacking in the region.   2. Product according to claim 1, characterized in that M in the hard phase consists of titanium up to at least 70 atomic%.   9. Product according to claim 8, characterized in that M in the hard phase consists of titanium up to at least 80 atomic%.   10. Product according to claim 9, characterized in that M in the hard phase consists of titanium up to at least 90 atomic%.   11. Product according to any one of the preceding claims, characterized in that at most 40 atomic% of M in the MX- type hard phase consists of (V + Nb).   12. Product according to claim 11, characterized in that a maximum of 30 atomic% of M in the hard phase consists of metals belonging to the group consisting of V, Nb, Ta, Hf and Zr or more metals.   13. Product according to claim 11 or 12, characterized in that at most 25 atomic% of M in the hard phase consists of Nb.   14. Product according to claim 13, characterized in that a maximum of 15 atomic% of M in the hard phase consists of Nb.   15. Product according to any one of the preceding claims, characterized in that at least 2 atomic% of M in the hard phase consists of V.   16. Product according to claim 15, characterized in that at least 5 atomic% of M in the hard phase consists of V.   17. Product according to claim 15 or 16, characterized in that a maximum of 15 atomic% of M in the hard phase consists of V.   18. Product according to any one of the preceding claims, characterized in that at least 2 atomic% of M in the hard phase consists of Nb.   19. Product according to claim 18, characterized in that at least 5 atomic% of M in the hard phase consists of Nb.   20. A product according to any one of the preceding claims, characterized in that a maximum of 3 atomic percent of M in the hard phase consists of Ta, a maximum of 3 atomic percent of Zr, and a maximum of 3 atomic percent of Hf.   21. Product according to claim 20, characterized in that the MX-type hard phase does not contain Ta, Zr or Hf above the impurity level.   22. Product according to any one of the preceding claims, characterized in that it contains 30-70% by volume of the MX-type hard phase.   23. Product according to claim 22, characterized in that it contains 40-60% by volume of the MX-type hard phase.   24. The MX-1 type hard phase according to any one of claims 1 to 23, characterized in that it contains oxygen in an amount of 0.01 to 4 atomic% of the total (C + N + O) content in the hard phase. Product listed. The matrix containing secondary crystallized MC-carbide that may be present in the matrix and all hard phases of types other than MX-type that may be present in the matrix have the following chemical composition in weight percent: 25. Product according to any one of claims 1 to 24, characterized in that:
0.3-3.0% C,
Si up to 2% from the trace amount,
Mn from the trace amount up to 2%,
S, up to 0.5% from the trace amount
2 to 13% Cr,
W up to 18% from the trace amount,
Mo up to 12% from the trace amount,
Co, up to 15% from the trace amount
V up to 10% from the trace amount,
Nb from the trace amount up to 2%,
Balance: Fe, but above 50% by weight, and impurities normally present from steel production.   26. Product according to claim 25, characterized in that the matrix comprises up to 2% by weight of Nb.   Chemistry in which the matrix containing all secondary crystallized MC-carbide that may be present in the matrix and all hard phases of types other than MX-type contains up to 1 wt% Si and 3-10 wt% Cr 27. Product according to claim 25 or 26, characterized in that it has a composition.   Characterized in that the (W + Mo + V) content in said matrix comprising all hard phases of a type other than all secondary crystallized MC-carbide and MX-types that may be present in the matrix reaches at least 10% by weight. 28. The product of claim 27.   Characterized in that the (W + Mo + V) content in said matrix comprising all hard phases of a type other than all secondary crystallized MC-carbide and MX-types that may be present in the matrix reaches a maximum of 10% by weight 28. The product of claim 27.   The matrix comprising all hard phases of a type other than all secondary crystallized MC-carbide and MX-types that may be present in the matrix contains 3-7% Cr and 10-20% (W + Mo + V) by weight. 29. A product according to claim 28, having a chemical composition comprising.   The matrix comprising all hard phases of a type other than all secondary crystallized MC-carbide and MX-types that may be present in the matrix contains 2-7% Cr and 5-10% (W + Mo + V) by weight. 30. A product according to claim 29, characterized in that it has a chemical composition.   Titanium carbide, titanium nitride, and / or titanium carbonitride powder is included in an amount corresponding to at least 50% of the metal atoms in the MX-type hard phase of the MX-type hard phase in the final metal product. Pulverizing together the powder mixture and at least the main parts of the other components of the final metal product, forming a constant body with the pulverized mixture, and the body at a temperature of 1350-1600 ° C. Usually MX-, characterized in that it is sintered and subsequently cooled to solidify the liquid phase and the hard phase particles of MX-type obtain the final composition and size during the liquid phase sintering and subsequent solidification Particles, particles consisting mainly of M (C, N) -carbonitride or M (C, N, O) -carbonitride oxide, called the hard phase of the mold, are distributed substantially homogeneously in the matrix of the hardenable steel Method for producing a composite metal product comprising a hard phase 30 to 90 volume% with are in the form of a.   Control the content of carbon and nitrogen during the overall process including powder selection and mixing, fine grinding of the powder mixture, formation of the green body of the finely ground powder mixture, and liquid phase sintering of the green body, and the final product 33. The method according to claim 32, characterized in that the carbon and nitrogen content of said hard phase expressed in atomic% satisfies the ratio 0.1 <N / (C + N) <0.7.   Control the content of carbon and nitrogen during the overall process including powder selection and mixing, fine grinding of the powder mixture, formation of the green body of the finely ground powder mixture, and liquid phase sintering of the green body, and the final product 34. The method according to claim 33, characterized in that the carbon and nitrogen content of said hard phase expressed in atomic% satisfies the ratio 0.2 <N / (C + N) <0.6.   Control the content of carbon and nitrogen during the overall process including powder selection and mixing, fine grinding of the powder mixture, formation of the green body of the finely ground powder mixture, and liquid phase sintering of the green body, and the final product 35. The method according to claim 34, characterized in that the carbon and nitrogen content of said hard phase expressed in atomic% satisfies the ratio 0.3 <N / (C + N) <0.6.   Control the content of carbon and nitrogen during the overall process including powder selection and mixing, fine grinding of the powder mixture, formation of the green body of the finely ground powder mixture, and liquid phase sintering of the green body, and the final product 36. The method according to claim 35, characterized in that the hard phase carbon and nitrogen content of the following is expressed in atomic% and satisfies the ratio 0.4 <N / (C + N) <0.5.   37. A method according to any one of claims 32 to 36, characterized in that the milling of the powder mixture is carried out with an energy supply of at least 10 MJ (megajoule) / kg powder.   38. The method according to claim 37, characterized in that the milling of the powder mixture is carried out with an energy supply of at least 20 MJ / kg powder.   39. A process according to claim 37 or 38, characterized in that the milling of the powder mixture is carried out with an energy supply of 10-50 MJ / kg powder.   The oxygen content is controlled during the synthesis step, so that the oxygen content in the final product is 0.01-4 atomic% of the total (C + N + O) content in the hard phase, 40. The method according to any one of 39.   The liquid phase sintering is carried out at a respective sintering temperature between 1450-1510C for a holding time of 10 minutes to 2 hours, preferably 10 to 60 minutes. The method of any one of Claims.

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