JP3869620B2 - Alloy steel powder molding material, alloy steel powder processed body, and manufacturing method of alloy steel powder molding material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an alloy steel powder molding material suitable as a molding material for mechanical parts such as structural parts and sliding parts, and an alloy steel powder processed body obtained by further processing the material.And method for producing alloy steel powder molding materialAbout.
[0002]
[Prior art]
Conventionally, iron-based sintered alloys have been used as various structural parts and sliding parts of automobiles. This technique is disclosed in, for example, Japanese Patent Publication No. 60-6587, Japanese Patent Application Laid-Open Nos. 8-144026, and 8-1444027. No. 7, 224361, No. 7-224362, No. 7-224363, and the like.
[0003]
The technology described in Japanese Patent Publication No. 60-6587 includes 15 to 25% by mass of Cr, 1 to 5% by mass of Cu, 3% by mass or less of Mo, 0.3 to 0.8% by mass of P, 2. By sintering metal powder having a composition of 0 to 4.0% by mass of C and the balance of Fe and inevitable impurities under a predetermined condition, a wear-resistant firing having a structure in which fine carbides are uniformly dispersed is obtained. Bonded gold is obtained, and the sintered alloy obtained by this technique is considered to be used for rock-resistant arm pads, valve lifters and other wear-resistant materials.
[0004]
In addition, the technique described in JP-A-8-144026 and JP-A-8-144027 discloses that a green compact obtained by press-molding a metallic powder having a predetermined composition is sintered under predetermined conditions, thereby reducing C to 0. 5 to 2.0% by mass, containing Ni, Mo, Cu and B (or BN and S) in a predetermined amount, the balance being Fe and inevitable impurities, and having a structure in which free graphite is precipitated The tough iron-based sintered alloy can be obtained, and the sintered alloy obtained by this technology is considered to be used for sliding parts such as automobile oil pump gears and rotary compressor bearings. Yes.
[0005]
Further, the techniques described in JP-A-7-224361, 7-224362, and 7-224363 disclose two or more kinds of alloy element components having different compositions such as Cr, Mo, W, and V. A green compact was formed by press-molding a mixed powder containing a predetermined amount of C into a mixed powder of alloy powder containing a fixed amount and the balance consisting of Fe and inevitable impurities, and the green compact was pre-sintered. Later 12-15ton / cm²By re-pressurizing with, and then heat-treating, a high-strength iron-based sintered alloy having a structure in which alloy grain regions having different compositions are bonded through a diffusion phase can be obtained. The sintered alloy obtained by the technique is considered to be used for a structural member that requires high strength such as a cam piece, a cam shaft, and a compressor rotor.
[0006]
[Problems to be solved by the invention]
However, mechanical properties such as strength and wear resistance required for structural parts and sliding parts such as automobile engine parts are increasing, and the conventional iron-based sintered alloy described above has these mechanical characteristics. I was not satisfied with the aspect.
[0007]
The reason for this is that in the above-mentioned Japanese Patent Publication No. 60-6687, P is added to improve the sinterability, thereby obtaining a high-density sintered body. Since it is based on phase sintering, the dimensional accuracy is greatly lowered, and it is necessary to increase the amount of alloy such as Cr in order to increase the strength.
[0008]
In addition, in the above-mentioned JP-A-8-144026 and 8-144027, B or BN is added in order to precipitate free graphite. In order to reduce the mechanical properties of the steel, the strength obtained is limited.
[0009]
Furthermore, in the above-mentioned JP-A-7-224361, JP-A-7-224362, and JP-A-7-224363, an alloy element such as Cr or V is added in a certain amount or more in order to obtain an alloy grain region. The added alloying element increases the hardness of the molding material before re-pressurization, resulting in a problem that re-pressurization becomes difficult (deformability decreases). Moreover, since the structure obtained by this technique is not a macroscopically uniform structure, there is a limit to the fatigue strength.
[0010]
[Means for Solving the Problems]
  Therefore, the invention according to claim 1 is molybdenum (Mo), nickel (Ni), manganese (Mn), copper (Cu), chromium (Cr), tungsten (W), vanadium (V).andCobalt (Co)Contains at least one alloy element selected fromThe density is 7.3 g / cm, which is obtained by compacting a metallic powder obtained by mixing 0.1 mass% or more of graphite with an alloy steel powder having a part of iron and inevitable impurities.^ThreeThe above preformsAt 800-1000 ° CPre-sintered and graphite remains at the grain boundaries of the metal powder., Having a structure of ferrite or austenite, pearlite or bainite was deposited in the vicinity of the graphite.An alloy steel powder molding material having a structure was used.
[0011]
  The invention according to claim 2 is molybdenum (Mo), nickel (Ni), manganese (Mn), copper (Cu), chromium (Cr), tungsten (W), vanadium (V).andCobalt (Co)At least one kind selected fromA metal powder formed by mixing 0.1% by mass or more of graphite with a metal powder formed by diffusing and adhering a powder containing an alloy element as a main component to a metal powder composed of iron and inevitable impurities is compacted. The resulting density is 7.3 g / cm.^ThreeThe above preforms800-1000 ° CPre-sintered, and graphite remains at the grain boundaries of the metal powder., Ferrite, austenite, or a structure in which one or more of undiffused alloy components are mixed, and pearlite or bainite is precipitated in the vicinity of the graphite.An alloy steel powder molding material having a structure was used.
[0012]
  Invention of Claim 3 is nickel (Ni), manganese (Mn), chromium (Cr), tungsten (W), vanadium (V)and0.1% by mass or more of graphite is mixed with a metal powder obtained by mixing a powder mainly composed of at least one alloy element selected from cobalt (Co) with a metal powder composed of iron and inevitable impurities. Density of 7.3 g / cm, obtained by compacting metal powder^ThreeThe above preformsAt 800-1000 ° CPre-sintered and graphite remains at the grain boundaries of the metal powder., Ferrite, austenite, or a structure in which one or more of undiffused alloy components are mixed, and pearlite or bainite is precipitated in the vicinity of the graphite.An alloy steel powder molding material having a structure was used.
[0013]
The metallic powder used here is a mixture of metal powder containing alloying elements such as alloy steel powder with 0.1% by mass or more of graphite, so when pre-sintering the preform or when the obtained alloy steel powder is used. When the molding material (hereinafter referred to as “molding material”) is re-sintered later, substantially all of the carbon is not decarburized. Therefore, the mechanical strength of a member obtained by recompression molding or re-sintering of the molding material can be sufficiently increased.
[0014]
The density of the preform obtained by compacting is 7.3 g / cm.^ThreeTherefore, in the molding material obtained by pre-sintering this preform, the graphite remains reliably at the grain boundary of the metal powder. As a result, the hardness is low, the elongation is increased, and the metal powder grain The lubricity of the field is increased, and the molding ability is improved as a whole.
[0015]
That is, 7.3 g / cm^ThreeIn the preform formed with the above high density, the voids between the particles of the metal powder are not continuous and are in an isolated state. It is difficult to enter the interior, and the gas generated from the interior graphite is less likely to diffuse around, which greatly contributes to the suppression of carbon diffusion (remaining graphite). For this reason, the structure of the obtained molding material is in a state in which graphite remains at the grain boundary of the metal powder and precipitates such as iron and carbides of alloy elements are hardly generated.
[0016]
  Specifically, in the case of the molding material according to claim 1, the structure has a structure in which pearlite or bainite is slightly precipitated in the vicinity of ferrite, austenite, or graphite. , Ferrite, austenite, or undiffused alloy components such as nickel (Ni)oneSeed ortwoIt is a structure in which more than seeds are mixed, or a structure in which pearlite or bainite is slightly precipitated in the vicinity of graphite. Therefore, the molding material before recompression molding is hardly affected by the diffusion of carbon. As a result, the hardness is low, the elongation increases, and the residual graphite lubricates the grain boundaries of the metal powder. by doing,DeformationThe ability is further enhanced.
[0017]
  Moreover, since sintering by diffusion or melting at the contact surface between the particles of the metal powder occurs over a wide range by pre-sintering, the molding material can obtain a large elongation also from this point.
  Further, since the pre-sintering temperature is 800 ° C. or higher, the bonding of the metal powder by the sintering surely proceeds, and since it does not exceed 1000 ° C., the excess of the molding material due to excessive diffusion of graphite. No increase in hardness occurs.
[0018]
  Claim 4And 5The described invention is an alloy steel powder molding material in which one or more alloy elements selected from molybdenum (Mo), chromium (Cr), manganese (Mn), and vanadium (V) are contained in 0.1% by mass. ≦ Mo ≦ 3.0, 0.1 ≦ Cr ≦ 3.5, 0.1 ≦ Mn ≦ 1.0, 0.01 ≦ V ≦ 1.0.
[0019]
When each additive concentration of molybdenum (Mo), chromium (Cr), manganese (Mn), and vanadium (V) exceeds Mo = 3.0, Cr = 3.5, Mn = 1.0, and V = 1.0 by mass percent, The hardness of the formed molding material increases, and at the same time, forgeability (deformability during recompression molding) decreases. Further, when the respective additive concentrations of the alloy elements are less than Mo = 0.1, Cr = 0.1, Mn = 0.1, and V = 0.01 in terms of mass percent, the surface hardness after the heat treatment is lowered and the effect of improving the mechanical strength is reduced. . Therefore, it is desirable to set the additive concentration of these alloy elements in the above range.
[0022]
  The invention described in claim 6Claim 1 or 4Re-compression molding of the alloy steel powder molding material described inGraphite remains in the grain boundary of the metal powder, and has a structure of ferrite and austenite, and has a structure in which pearlite or bainite is precipitated in the vicinity of the graphite.It was set as the structure of the alloy steel powder plastic processing body.
  Further, the invention according to claim 7 is formed by recompressing the alloy steel powder forming material according to any one of claims 2, 3, and 5, and graphite remains at the grain boundary of the metal powder, and ferrite, austenite Alternatively, an alloy steel powder plastic working body having a structure in which one or two or more kinds of undiffused alloy components are mixed and having a structure in which pearlite or bainite is precipitated in the vicinity of the graphite is used.
[0023]
An alloy steel powder plastic processed body (hereinafter referred to as “plastic processed body”) re-compressed by cold forging or the like is compacted with the graphite remaining in the grain boundary of the metal powder. It becomes a dense structure with almost no voids.
[0024]
In addition, since the molding material used here has almost no carbon diffusion, it can be easily recompressed into a predetermined shape with a small molding load (deformation resistance). In other words, in the case of a molding material (conventional molding material) with a large amount of carbon diffusion in the molding material, it is very difficult to recompress because the hardness is high, the elongation is small, and there is little slip between the metal particles. In the case of the molding material used here, since there is almost no carbon diffusion, the hardness is low and the elongation is large, and the graphite remaining at the grain boundaries ensures slip between the metal particles, resulting in recompression molding. Can be easily performed. Since the recompression molding can be performed at room temperature, the dimensional accuracy of the plastic processed body does not deteriorate due to the generation of scale or transformation, and the plastic processed body that has been processed becomes extremely accurate. .
[0025]
Furthermore, the alloy component added to the metal powder increases the degree of work hardening in the re-compression molding, so that the plastic processed body can obtain a higher hardness than when no alloy element is added, while the residual graphite is In order to lubricate the metal grain boundaries, recompression molding can be performed with a small deformation resistance. In particular, in the case of the forming material according to claims 2 and 3, diffusion of the alloy element appears near the surface of the metal powder and hardly progresses to the inside, so that it is possible to obtain a plastic work body that is work-hardened with a lower deformation resistance. it can.
[0026]
Therefore, this plastic workpiece can be applied to sliding parts that require high strength and high accuracy.
[0027]
  Claim8 and 9The described invention includes a molding die having a molding space filled with metallic powder, an upper punch and a lower punch that are inserted into the molding die and pressurize the metallic powder, and the molding die has a molding space. Is formed with a large-diameter portion into which the upper punch is inserted, a small-diameter portion into which the lower punch is inserted, and a tapered portion connecting the large-diameter portion and the small-diameter portion, and one of the upper punch and the lower punch. Alternatively, a preform is formed by an apparatus in which notches for increasing the volume of the molding space are formed on the end faces facing both of the molding spaces, and the preform thus formed is800-1000 ° CClaimed after pre-sintering with1 and claims 2 and 3The alloy steel powder molding raw material described above was formed, and the alloy steel powder molding raw material was recompressed and formed into an alloy steel powder plastic working body.
[0028]
The overall preform for molding the molding material is 7.3 g / cm^ThreeSince it is necessary to make the density higher than the above, it is considered that the friction for extracting is increased when the preform is released, but the apparatus used here is provided in one or both of the upper punch and the lower punch. At the notched portion, the density of the preform can be locally reduced to reduce the mold release friction. For this reason, the preform is easily released from the molding die in combination with the action of the taper portion formed in the molding space of the molding die, and the density is 7.3 g / cm.^ThreeThus, a preform can be easily obtained.
[0029]
Then, the molding material obtained by pre-sintering the preformed body surely increases the density of the preformed body, so that the carbon material can be diffused while sufficiently containing graphite remaining in the grain boundary of the metal powder. Molding is almost complete, and subsequent recompression molding is easily performed. Therefore, the re-compressed plastic workpiece has a dense structure with almost no voids, and can be re-compressed easily at room temperature, so that it is formed with high accuracy.
[0030]
  ClaimThe invention according to claim 10 is obtained by re-sintering the alloy steel powder plastic working body according to claim 6 at 800 to 1300 ° C., comprising a structure of ferrite, pearlite, bainite, and austenite. An alloy steel powder re-sintered body having a structure in which graphite is scattered in the boundary is used.
  The invention according to claim 11 is obtained by re-sintering the alloy steel powder plastic working body according to claim 7 at 800 to 1300 ° C., and is made of ferrite, pearlite, bainite, austenite, or an undiffused alloy component. An alloy steel powder re-sintered body having a structure in which one type or two or more types are mixed, and has a structure in which graphite is scattered inside or at the grain boundary of the metal powder.
[0031]
  In the plastic workpiece, re-sintering causes surface diffusion at the contact surface of the metal powder or sintering by melting, and at the same time, graphite existing at the grain boundaries of the metal powder is diffused into the ferrite ground (solid solution or carbide is formed). The metal powder is composed of undiffused alloy components such as ferrite, pearlite, austenite, or nickel (Ni).oneSeed ortwoWhen it consists of the structure | tissue with which the seed | species or more was mixed and graphite remains, it becomes a structure | tissue where graphite is scattered inside a metal powder.
[0032]
Furthermore, in re-sintering, alloy elements that dissolve in the substrate are more homogeneously dissolved in the substrate, and alloy elements that generate precipitates such as carbides are produced by the precipitates. The effect of improving the physical characteristics is reflected in the macroscopic organization.
[0033]
As a result, the re-sintered processed body has higher strength than the plastic processed body, and a mechanical strength equal to or higher than that of a cast forged material that does not particularly require a hardened layer can be obtained.
[0034]
In addition, since this re-sintered body was re-sintered after re-compression molding, the crystal grain size became a recrystallized structure having a crystal grain size of about 20 μm or less, which not only increased strength, but also increased elongation and impact. The value increases and the fatigue strength increases.
[0036]
  Also,The re-sintering temperature is800Since the temperature is higher than or equal to ° C., the graphite diffuses reliably in the plastic workpiece, and further does not exceed 1300 ° C., so that the amount of decarburization and the coarsening of crystal grains do not occur.
[0037]
  The inventions described in claims 12 and 13 are described in claim 10 or 11.The alloy steel powder re-sintered processed body described above was heat-treated to form a heat-treated alloy steel powder processed body having a hardened structure.
[0038]
  The re-sintered body that has been heat-treated by quenching or the like forms a hardened layer by solid-dissolving graphite in supersaturation, or by precipitating fine carbides or by precipitating nitrides. For this reason, this alloy steel powder heat-treated body (hereinafter referred to as “heat-treated body”) has less carbon diffusion due to heat treatment, and the inside is still tough and has high hardness only by heat treatment near the surface. It is said.
  The invention described in claims 14 to 16 relates to a method for producing an alloy steel powder molding material, and the invention described in claim 14 includes molybdenum (Mo), nickel (Ni), manganese (Mn), copper (Cu), Alloy steel powder containing at least one alloy element selected from chromium (Cr), tungsten (W), vanadium (V) and cobalt (Co), with the balance being iron and unavoidable impurities. . A metal powder obtained by mixing 1% by mass or more of graphite is compacted to a density of 7 . 3g / cm ^Three A preforming step for obtaining the above preform, and pre-sintering the preform at 800 to 1000 ° C. to obtain an alloy steel powder molding material having a structure in which pearlite or bainite is precipitated in the vicinity of the graphite. And a preliminary sintering step.
  The invention according to claim 15 is selected from molybdenum (Mo), nickel (Ni), manganese (Mn), copper (Cu), chromium (Cr), tungsten (W), vanadium (V) and cobalt (Co). A powder containing at least one alloy element as a main component is diffused and adhered to a metal powder composed of iron and inevitable impurities. . A density of 7 obtained by compacting a metallic powder obtained by mixing 1% by mass or more of graphite. . 3g / cm ^Three Preliminary forming step for obtaining the above preformed body, and preliminarily sintering the preformed body at 800 to 1000 ° C. so that graphite remains in the grain boundary of the metal powder, and ferrite, austenite, or undiffused alloy component And a pre-sintering step of obtaining an alloy steel powder forming material having a structure in which pearlite or bainite is precipitated in the vicinity of the graphite.
  According to a sixteenth aspect of the present invention, the preforming step includes a molding die having a molding space filled with metallic powder, and an upper punch and a lower punch that are inserted into the molding die and pressurize the metallic powder. In the molding space of the molding die, a large diameter portion into which the upper punch is inserted, a small diameter portion into which the lower punch is inserted, and a tapered portion connecting the large diameter portion and the small diameter portion are formed. In addition, a preform is formed by an apparatus in which a notch for increasing the volume of the molding space is formed on an end face facing the molding space of one or both of the upper punch and the lower punch.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0040]
FIG. 1 is an explanatory view of a manufacturing process of an alloy steel powder processed body showing an embodiment of the present invention, and FIG. 2 shows a manufacturing process of a preform, in which a metallic powder is filled in a forming space of a forming die. (A), state in which metal powder is pressed with upper punch and lower punch (b), state in which molding die starts to be lowered for removal of preform after completion of pressurization (c), preform It is explanatory drawing which shows the state (d) taken out sequentially.
[0041]
In FIG. 1, 101 is a pre-forming process, 102 is a pre-sintering process, 103 is a re-compression process, 104 is a re-sintering process, and 105 is a heat treatment process. 102. The molding material is converted into a plastic processed body through a recompression process 103, and the plastic processed body is converted into a re-sintered processed body through a re-sintering process 104 and a heat-treated processed body through a heat treatment process 105.
[0042]
In the molding step 101, as shown in FIGS. 2A to 2D in this embodiment, the metal powder 3 described later is filled in the molding space 5 of the molding die 4, and the upper punch 6 and the lower punch 7 are filled. Pressurized with a density of 7.3 g / cm^ThreeThe above preform 8 is obtained. In this case, the metallic powder 3 and the forming die 4 are in a normal temperature state.
[0043]
The molding space 5 of the molding die 4 includes a large diameter portion 9 into which the upper punch 6 is inserted, a small diameter portion 10 into which the lower punch 7 is inserted, and a tapered portion 11 that connects the large diameter portion 9 and the small diameter portion 10. It has.
[0044]
One or both of the upper punch 6 and the lower punch 7 inserted into the molding space 5 of the molding die 4, in this embodiment, the upper punch 6 has an outer periphery of the end face 12 facing the molding space 5 of the molding die 4. A notch 13 for increasing the volume of the molding space 5 is formed at the end. In this embodiment, the notch 13 is formed in an annular shape with a cross section.
[0045]
Reference numeral 14 denotes a core inserted into the molding space 5 of the molding die 4, and the preform 14 formed in the molding space 5 is shaped into a substantially cylindrical shape by the core 14.
[0046]
In the molding step 101, first, as shown in FIG. 2A, the metal powder 3 is filled into the molding space 5 of the molding die 4. The metallic powder 3 filled here is obtained by mixing the following metal powder with 0.1% by mass or more of graphite.
[0047]
That is, the metal powder used here is molybdenum (Mo), nickel (Ni), manganese (Mn), copper (Cu), chromium (Cr), tungsten (W), vanadium (V), cobalt (Co), etc. A powder containing one or more of the above alloy elements, the balance being composed of iron and a small amount of inevitable impurities (metal powder corresponding to claim 1), or a powder mainly composed of the alloy elements What is diffused and adhered to metal powder containing iron as a main component (metal powder corresponding to claim 2) or mixed (metal powder corresponding to claim 3) is used.
[0048]
Next, the upper punch 6 and the lower punch 7 are inserted into the molding space 5 of the molding die 4 to pressurize the metallic powder 3. Specifically, the upper punch 6 is inserted into the large-diameter portion 9 of the molding space 5, and the lower punch 7 is inserted into the small-diameter portion 10 of the molding space 5 and pressed. At this time, the upper punch 6 in which the notch 13 is formed is stopped in the large diameter portion 9 (see FIG. 2B).
[0049]
After the metallic powder 3 is pressed and compacted, the upper punch 6 is retracted (raised) and the molding die 4 is lowered (see FIG. 2 (c)), and the compacted preformed preform is formed. The body 8 is taken out from the molding space 5 (see FIG. 2D).
[0050]
By the way, in general, when compacting metallic powder, as the density of the compacted product increases, the friction between the compacted product and the mold increases. Due to the spring back or the like, it becomes difficult to take out the green compact from the mold. For this reason, it is said that it is difficult to obtain a high-density compacted product, but this is advantageously solved in the molding step 101.
[0051]
That is, since the molding space 5 of the molding die 4 is provided with the taper portion 11, the taper portion 11 has a so-called draft, and the compacted preform 8 can be easily taken out. Further, the upper punch 6 is formed with a notch 13 for increasing the volume of the molding space 5 at the outer peripheral end of the end surface 12 facing the molding space 5 of the molding die 4. Thus, the density of the preformed body 8 is locally reduced, the friction between the preformed body 8 and the molding die 4 and the spring back of the preformed body 8 are kept low, and the preformed body 8 can be easily taken out. become.
[0052]
Thereby, the density is 7.3 g / cm.^ThreeThe above preform 8 can be easily obtained.
[0053]
Next, the preform 8 obtained in the molding step 101 is temporarily sintered in the preliminary sintering step 102. As a result, as shown in FIG. 3, a molding material having a structure in which graphite 3b remains at the grain boundaries of the metal powder 3a and precipitates such as carbides of iron and alloy elements hardly occur is obtained.
[0054]
That is, when the metal powder 3a corresponding to claim 1 is used, if all of the graphite 3b remains at the grain boundary of the metal powder 3a (there is no diffusion of the graphite 3b), the structure of the metal powder 3a is If the whole becomes a structure of ferrite (F) or austenite (A) and a part of graphite 3b is diffused, the structure of the metal powder 3a is pearlite (P) or bainite (B ) Becomes a slightly precipitated structure. Further, when the metal powder 3a corresponding to claim 2 or 3 is used, when all of the graphite 3b remains at the grain boundary of the metal powder 3a, the whole is made of ferrite (F) or austenite (A). A structure or a structure having an undiffused alloy component such as nickel (Ni), and a structure in which pearlite (P) or bainite (B) is slightly precipitated in the vicinity of the graphite 3b when a part of the graphite 3b is diffused. It becomes. That is, at least the entire metal powder 3a does not have a pearlite (P) or bainite (B) structure. For this reason, the said molding material has the property that hardness is low and elongation is large, and it has the outstanding deformability.
[0055]
More specifically, the preform 8 has a density of 7.3 g / cm.^ThreeBecause of the above, the voids between the particles of the metal powder 3a are not continuous and are in an isolated state. This is largely due to a molding material having low hardness and high elongation after pre-sintering. Will be. That is, when the gaps between the particles of the metal powder 3a are continuous, the atmosphere gas in the furnace during pre-sintering and the gas generated from the graphite penetrates deeply into the preform 8 through the gaps. Although the carburization is promoted, since the voids are isolated, these are advantageously prevented, the hardness is kept low, and a large elongation is obtained. Therefore, the hardness and elongation of the molding material are hardly affected by the amount of graphite 3b.
[0056]
Further, since the pre-sintering step 102 causes surface diffusion or melting of the metal powder 3a at the contact surface between the particles to occur over a wide range, a larger elongation can be obtained.
[0057]
  The sintering temperature in the preliminary sintering step 102 is8If it is less than 00 ° C, the bonding of the metal powder by sintering does not proceed, and if it exceeds 1000 ° C, the graphite 3b is excessively diffused and the hardness becomes too high.8The range of 00-1000 ° C is selectedThe stillThe atmosphere at this time may be any of inert, reducing, and vacuum.
[0058]
Here, FIG. 4 is a test data and graph in which the relationship between the pre-sintering temperature and the elongation of the molding material in the case of Example 1 described later is examined, and FIG. 5 is a diagram of FIG. 4 in the case of Example 2 described later. It is the same test data and graph. 6 is a test data and graph in which the relationship between the pre-sintering temperature and the hardness of the molding material in the case of Example 1 is examined, and FIG. 7 is the same data as FIG. 6 in the case of Example 2. And a graph.
[0059]
  As is clear from these data and graphs, the preliminary sintering temperature is8If it selects in the range of 00-1000 degreeC, the elongation of a comparatively big shaping | molding raw material will be obtained, and hardness can be maintained around HRB60. Incidentally, the value of this HRB60 is comparable to the hardness when annealed to a high-strength cold-forged steel material, but in this molding material according to the present invention, before and after the HRB60 without annealing. A value can be obtained.
[0060]
Further, the molding material obtained in the preliminary sintering step 102 is subjected to recompression molding (cold forging or the like) in the next recompression step 103. The plastic working body obtained here has a structure having almost no voids because the voids of the structure are crushed and densified with respect to the molding material in which the graphite 3b remains at the grain boundaries of the metal powder 3a.
[0061]
In the plastic processed body, graphite 3b remains at the grain boundary of the metal powder 3a of the molding material, and almost no carbon is diffused. Therefore, as shown in FIGS. 8 and 9, the molding load (deformation resistance) is extremely high. Can be made smaller. In other words, since the molding material has almost no carbon diffusion, it has the characteristics of low hardness and high elongation, and further, the graphite existing in the metal grain boundary functions to promote the sliding between the metal powders. The molding load at the time of recompression molding becomes small, and the plastic workpiece is easily formed into a predetermined shape. FIG. 8 shows the molding load in the case of Example 1, and FIG. 9 shows the molding load in the case of Example 2.
[0062]
  Moreover, about the temperature at the time of temporary sintering,8If a range of 00 to 1000 ° C. is selected, the plastic working body can secure a sufficient tensile strength as shown in FIGS. 10 and 11, and further, as shown in FIGS. Hardness can also be secured. However, FIGS. 10 and 12 are for the first embodiment, and FIGS. 11 and 13 are for the second embodiment. Accordingly, the plastic processed body has a tensile strength and hardness comparable to that of the cast forged material, and the mechanical strength is sufficiently high.
[0063]
In the case of re-compression molding with relatively small deformation, re-deformation, that is, re-plastic forming can be easily performed. In the case of re-compression molding with large deformation, high hardness is obtained by work hardening. can get.
[0064]
FIG. 14 and FIG. 15 show the structures of plastic processed bodies when formed by recompression molding with relatively small deformation and when formed by recompression molding with large deformation. Any of these is a structure in which graphite 3b remains at the grain boundary of the metal powder 3a, and the structure of the metal powder 3a is ferrite (F), austenite (A), or graphite as long as it corresponds to claim 1. The structure in which pearlite (P) or bainite (B) is slightly precipitated in the vicinity of 3b, if it corresponds to claims 2 and 3, ferrite (F), austenite (A), nickel (Ni), etc. FIG. 14 shows a structure in which one or two or more of the undiffused alloy components are mixed, or a structure in which pearlite (P) or bainite (B) is slightly precipitated in the vicinity of the graphite 3b. The metal powder 3a has a slightly deformed shape with almost no voids, and the one shown in FIG. 15 is almost completely free of voids, and the metal powder 3a is greatly deformed and has a flat shape. And it has a.
[0065]
In addition, since re-compression molding is performed at room temperature, there is no reduction in dimensional accuracy due to scale generation or transformation, and the molding material can be molded with a low molding load. The re-compression molding makes the entire plastic workpiece substantially the true density. For this reason, the variation in density is smaller than that of a conventional sintered body, and the variation in dimensional change is also small. Therefore, the plastic workpiece obtained by recompressing the molding material has high dimensional accuracy.
[0066]
Therefore, the plastic workpiece obtained in this way can be applied to sliding parts that require high strength and high accuracy.
[0067]
Further, the plastic workpiece is re-sintered in the next re-sintering step 104. Here, the obtained re-sintered body diffuses the graphite 3b existing at the grain boundary of the metal powder 3a into the ferrite ground (solid solution or carbide) simultaneously with surface diffusion or melting by melting on the contact surface of the metal powder. If the metal powder 3a corresponds to claim 1, the ferrite (F), pearlite (P), bainite (B), austenite (A) as shown in FIG. If it corresponds to claims 2 and 3, it is not diffused such as ferrite (F), pearlite (P), bainite (B), austenite (A), or nickel (Ni). It consists of a structure in which one or more alloy components are mixed. And when the graphite 3b remains, it becomes a structure where the graphite 3b is scattered inside the metal powder 3a or at the grain boundary.
[0068]
Further, in the case corresponding to any one of claims 1 to 3, as shown in FIG. 17, the residual ratio of the added graphite 3b (ratio of the amount of undiffused graphite in the total carbon) is determined by the re-sintering temperature. The smaller the size, the smaller the structure in which the graphite 3b is diffused and the structure in which the graphite 3b remains, at a predetermined ratio according to the re-sintering temperature. When the re-sintering temperature is high, the residual ratio of graphite is 0 as shown in the figure, and the structure in which the graphite 3b remains is eliminated.
[0069]
In addition, in the case of alloy elements that are solid-dissolved in the base material during re-sintering, in the case of alloy elements that are more homogeneously dissolved in the base material and generate precipitates such as carbides, they are added by forming precipitates. The effect of improving the mechanical properties by the alloy elements is reflected in the macroscopic structure, and the mechanical properties of the entire re-sintered body are improved.
[0070]
Therefore, the strength is sufficiently higher than that of the plastic workpiece, and a re-sintered workpiece corresponding to strength, lubricity, and other required mechanical properties is obtained by changing the diffusion amount of the graphite 3b. Will be able to. The re-sintered body that has been re-sintered at a predetermined temperature has high tensile strength, high hardness, and mechanical strength equal to or higher than that of a cast forged material that does not particularly require a hardened layer.
[0071]
In addition, the re-sintered body is re-sintered after re-compression molding, thereby forming a recrystallized structure having a crystal grain size of about 20 μm or less, and the crystal grain size of the conventional sintered body is 40 to 50 μm. Than the crystal grain size. For this reason, the strength is further increased, the elongation is large, the fatigue strength is high, the impact value is high, and the mechanical properties are excellent.
[0072]
  By the way, the re-sintering temperature is8If the temperature is lower than 00 ° C, the diffusion of the graphite 3b does not proceed, and if it exceeds 1300 ° C, carburization, decarburization, coarsening of crystal grains, and the like occur.8Set in the range of 00-1300 ° C. The atmosphere at this time may be any of inert, reducing, or vacuum.
[0073]
  Also, as shown in FIGS.8In the case of a relatively low temperature of 00 to 1000 ° C., on the one hand, it is softened by recovery of work hardening, while on the other hand, the diffusion of graphite 3b starts to progress and a fine structure of crystal grains is obtained by mild recrystallization. Therefore, the strength is increased and the hardness is increased. However, there is a case where the degree of recovery of work hardening is large depending on the shape, and after gradually softening, the tendency to harden again at around 1000 ° C.
[0074]
Furthermore, at a high temperature of 1000 to 1300 ° C., the residual rate of the graphite 3b is small, that is, the graphite 3b diffuses into the substrate, so that the strength is further increased and the hardness becomes high. However, when the temperature exceeds 1100 ° C, there is a tendency for the total carbon content to decrease with the increase in the amount of decarburization and the strength and hardness to decrease due to the regrowth of crystal grains. To do. Therefore, the re-sintering temperature is desirably in the temperature range of 900 to 1300 ° C.
[0075]
Further, the re-sintered body is finally subjected to heat treatment such as induction hardening, carburizing and quenching, nitriding and other combinations in the heat treatment step 105. Thereby, the graphite 3b is dissolved in supersaturation, or fine carbides are precipitated to form a hardened layer.
[0076]
As shown in FIGS. 22 and 23, by forming a hardened layer, a greater tensile strength than that of the re-sintered body is obtained, and as can be seen from the relationship between the distance from the surface and the hardness shown in FIG. In this case, since the density is substantially true, the diffusion of carbon due to the heat treatment is less toward the inside, so that only the vicinity of the surface becomes high hardness by the heat treatment while the inside remains tough. Therefore, it has excellent mechanical properties as a whole. On the other hand, in the heat-treated body by the conventional method, the diffusion of carbon proceeds to the inside and the whole has a high hardness, but since it has voids, it is brittle and has low toughness and rigidity.
[0077]
That is, in the conventional heat-treated processed body having voids, the whole was heat-treated, and it was difficult to obtain high strength and high toughness, but the heat-treated processed body according to the present invention was higher than a general sintered product. In addition to strength and high toughness, it is highly rigid and can be subjected to heat treatment according to the required mechanical properties like cast and forged materials. In addition, when an alloying element that improves the heat treatment properties such as hardenability by adding a solid solution to the base such as chromium (Cr), molybdenum (Mo), manganese (Mn) is added, even better mechanical properties Is obtained.
[0078]
Therefore, the heat-treated body obtained in this way is an automobile engine part such as a camshaft and a rotor part, a propeller shaft joint part part, a drive shaft part, a clutch part, a drive part such as a transmission part, a power steering gear part, and an anti-lock brake. When applied to the manufacture of mechanical parts that require high strength, high toughness, and slidability, such as steering parts such as parts, suspension parts, and other various bearings and pump components, these can be obtained at low cost. .
[0079]
Although one embodiment has been described above, the present invention is not limited to this. For example, the preform 8 is obtained by heating the metallic powder 3 and the molding die to a predetermined temperature to obtain the metallic powder 3. You may make it form by what is called warm forming performed in the state which lowered the yield point.
[0080]
Further, the embodiment has been described in which the notch 13 for expanding the volume of the molding space 5 is formed in the upper punch 6. However, the notch 13 may be provided in the lower punch 7, and the upper punch 6 and It may be provided on both of the lower punches 7.
[0081]
【Example】
Example 1:
It contains 0.2% by mass of molybdenum (Mo), the balance is iron (Fe) and a small amount of inevitable impurities alloy steel powder mixed with 0.3% by mass of graphite to form metallic powder. The metal powder is compacted to a density of 7.4 g / cm.^ThreeThe preform was then pre-sintered at 800 ° C. for 60 minutes in a nitrogen gas furnace to produce a molding material. The molding material had an elongation of 11.2% and a hardness of HRB 53.3 (see FIGS. 4 and 6).
[0082]
After that, the molding material was recompressed into a cup shape (cold forging) by backward extrusion at a cross-sectional reduction rate (deformation amount) of 60% to obtain a plastic workpiece.
[0083]
As a result, the molding load (deformation resistance) when the plastic workpiece was obtained was 2078 MPa (see FIG. 8), the tensile strength (converted value from the crushing strength) of the plastic workpiece was 692 MPa, and the hardness was HRB75 (see FIGS. 10 and 12). The density of the plastic workpiece is 7.71 g / cm.^ThreeMet.
[0084]
Thereafter, the plastic processed body was re-sintered at 1150 ° C. in a furnace having a mixed atmosphere of nitrogen gas and hydrogen gas to obtain a re-sintered processed body. The re-sintered body had a tensile strength (converted from the crushing strength) of 676 MPa and a hardness of HRB71 (see FIGS. 18 and 20). The density of the re-sintered processed body is 7.71 g / cm.^ThreeMet.
[0085]
Thereafter, the re-sintered body was carburized at a maximum of 860 ° C. in a furnace having a carbon potential of 1.0%, quenched at 90 ° C., and tempered at 150 ° C. to obtain a heat-treated body. As a result, the tensile strength (converted value from the crushing strength) of the heat-treated body is 1185 MPa (see FIG. 22), the hardness of the surface is HRC59, and the hardness inside (2 mm from the surface) is HRC33 (HV330) Met.
[0086]
Example 2:
0.3% by mass is applied to the alloy steel powder in which 2.0% by mass of nickel (Ni) and 1.0% by mass of molybdenum (Mo) are diffused and adhered to the surface of iron (Fe) and a small amount of inevitable impurities. % Graphite is mixed to form a metallic powder, and this metallic powder is compacted to a density of 7.4 g / cm^ThreeThe preform was then pre-sintered at 800 ° C. for 60 minutes in a nitrogen gas furnace to produce a molding material. The molding material had an elongation of 11.8% and a hardness of HRB52 (see FIGS. 5 and 7).
[0087]
Thereafter, the molding material was re-compressed into a cup shape (cold forging) by backward extrusion at a cross-section reduction rate (deformation amount) of 60% to obtain a plastic workpiece.
[0088]
The molding load (deformation resistance) when the plastic workpiece was obtained was 2428 MPa (see FIG. 9), the tensile strength (converted value from the crushing strength) of the plastic workpiece was 706 MPa, and the hardness was HRB96. (See FIGS. 11 and 13). The density of the plastic workpiece is 7.70 g / cm.^ThreeMet.
[0089]
Thereafter, the plastic workpiece was re-sintered at 1150 ° C. in a furnace in a mixed atmosphere of nitrogen gas and hydrogen gas. At this time, the tensile strength (converted value from the crushing strength) of the re-sintered body is 784 MPa, the hardness is HRB100 (see FIGS. 19 and 21), and the density is 7.70 g / cm.^ThreeMet.
[0090]
Thereafter, the re-sintered body was carburized at a maximum of 860 ° C. in a furnace having a carbon potential of 1.0%, quenched at 90 ° C., and tempered at 150 ° C. to obtain a heat-treated body. As a result, the tensile strength (converted value from the crushing strength) of the heat-treated body was 1678 MPa, the surface hardness was HRC62, and the internal hardness (part 2 mm from the surface) was HRC41 (HV400) (Fig. 23, FIG. 24).
[0091]
Example 3:
Iron powder that is iron (Fe) and a small amount of inevitable impurities is mixed with 2.0 mass% copper (Cu) and 0.3 mass% graphite to form a metallic powder. Powder molded, density is 7.4g / cm^ThreeThe preform was then pre-sintered at 800 ° C. for 60 minutes in a nitrogen gas furnace to produce a molding material. The elongation of the molding material was 12.0% and the hardness was HRB47.
[0092]
Next, the molding material was recompressed into a cup shape (cold forging) by backward extrusion at a cross-section reduction rate of 60%, to obtain a plastic workpiece.
[0093]
The molding load (deformation resistance) when the plastic processed body was obtained was 1960 MPa, the tensile strength (converted value from the crushing strength) of the plastic processed body was 510 MPa, and the hardness was HRB75. The density of the plastic workpiece is 7.70 g / cm.^ThreeMet.
[0094]
Thereafter, the plastic workpiece was re-sintered at 1150 ° C. in a furnace in a mixed atmosphere of nitrogen gas and hydrogen gas. At this time, the tensile strength (converted value from the crushing strength) of the re-sintered body is 735 MPa, the hardness is HRB80, and the density is 7.75 g / cm.^ThreeMet.
[0095]
Thereafter, the re-sintered body was carburized at a maximum of 860 ° C. in a furnace having a carbon potential of 1.0%, quenched at 90 ° C., and tempered at 150 ° C. to obtain a heat-treated body. As a result, the tensile strength (converted value from the crushing strength) of the heat-treated body was 980 MPa, the surface hardness was HRC50, and the internal hardness (part 2 mm from the surface) was HRB91.
[0096]
Hereinafter, Examples 4 to 19 will be described. These examples differ from Example 1 only in the configuration of the alloy steel powder, and the amount of graphite mixed in the alloy steel powder (0.3 mass) %), Density of the preform (7.4 g / cm^Three), Pre-sintering conditions (800 ° C. for 60 minutes in a nitrogen gas furnace), re-compression molding conditions (cross-sectional reduction rate of 60%), re-sintering conditions (nitrogen gas and hydrogen gas) 1150 ° C in a furnace with a mixed atmosphere), conditions for heat treatment (carburization at maximum 860 ° C in a furnace with a carbon potential of 1.0%, oil quenching at 90 ° C, tempering at 150 ° C), etc. The same is said. Therefore, only the composition of the alloy and the test results are described for the following examples.
[0097]
Example 4:
Alloy steel powder contains nickel (Ni) 1.0 mass%, molybdenum (Mo) 0.3 mass%, copper (Cu) 0.3 mass%, the remainder from iron (Fe) and inevitable impurities It became the composition which becomes.
(A) Molding load at the time of recompression molding 2195 MPa
(B) Tensile strength of plastic workpiece: 725 MPa
(C) Hardness of the plastic workpiece ... HRB82
(D) Density of the plastic workpiece ... 7.74 g / cm^Three
(E) Tensile strength of re-sintered body: 755 MPa
(F) Hardness of re-sintered body ... HRB85
(G) Density of re-sintered body: 7.74 g / cm^Three
(H) Tensile strength of heat-treated body ... 1235 MPa
(I) Surface hardness of heat-treated workpiece: HRC60
(Nu) Hardness inside heat-treated body ... HRC41 (HV400)
Example 5:
The alloy steel powder contains components of chromium (Cr) 1.0 mass%, manganese (Mn) 0.7 mass%, molybdenum (Mo) 0.3 mass%, and the balance from iron (Fe) and inevitable impurities. It became the composition which becomes.
(A) Molding load at the time of recompression molding ... 2333 MPa
(B) Tensile strength of plastic workpiece: 706 MPa
(C) Hardness of the plastic workpiece: HRB80
(D) Density of the plastic workpiece ... 7.66 g / cm^Three
(E) Tensile strength of the re-sintered body: 794 MPa
(F) Hardness of re-sintered body: HRB90
(G) Density of re-sintered processed body: 7.66 g / cm^Three
(H) Tensile strength of heat-treated body ... 1323 MPa
(I) Surface hardness of heat-treated workpiece: HRC60
(Nu) Hardness inside heat-treated body ... HRC42 (HV418)
Example 6:
The alloy steel powder contains components of chromium (Cr) 1.0 mass%, molybdenum (Mo) 0.3 mass%, vanadium (V) 0.3 mass%, and the balance from iron (Fe) and inevitable impurities. It became the composition which becomes.
(A) Molding load at the time of recompression molding ... 2362 MPa
(B) Tensile strength of plastic workpiece: 725 MPa
(C) Hardness of the plastic workpiece ... 82HRB
(D) Density of the plastic workpiece ... 7.65 g / cm^Three
(E) Tensile strength of re-sintered processed body: 804 MPa
(F) Hardness of re-sintered body ... HRB88
(G) Density of re-sintered body: 7.65 g / cm^Three
(H) Tensile strength of heat-treated body ... 1333 MPa
(I) Surface hardness of heat-treated workpiece: HRC63
(Nu) Hardness inside heat-treated body ... HRC43 (HV421)
Example 7:
Alloy steel powder contains components of cobalt (Co) 6.5% by mass, chromium (Cr) 8.0% by mass, tungsten (W) 2.0% by mass, molybdenum (Mo) 0.5% by mass, The balance is composed of iron (Fe) and inevitable impurities.
(A) Molding load at the time of re-compression molding ... 2550 MPa
(B) Tensile strength of plastic workpiece: 696 MPa
(C) Hardness of the plastic workpiece ... HRB95
(D) Density of the plastic workpiece ... 7.60 g / cm^Three
(E) Tensile strength of re-sintered body: 784 MPa
(F) Hardness of re-sintered body: HRB100
(G) Density of re-sintered processed body: 7.60 g / cm^Three
(H) Tensile strength of heat-treated body ... 1176 MPa
(I) Surface hardness of heat-treated workpiece: HRC66
(Nu) Hardness inside heat-treated body ... HRC45 (HV450)
Examples 8-19:
The alloy steel powders employed in Examples 8 to 19 each contained an alloy element having the composition shown in FIG. 25, and the balance was composed of iron (Fe) and inevitable impurities. FIG. 25 shows the recompression molding load and the surface hardness of the heat treated body in each of the examples including Examples 1 to 7 described above.
[0098]
As is apparent from the data in FIG. 25, good cold forgeability (formability during recompression) was obtained in any of the examples having different compositions.
[0099]
However, Example 19 in which molybdenum (Mo) exceeds 3.0 mass%, Examples 7 and 14 in which chromium (Cr) exceeds 3.0 mass%, and Examples in which manganese (Mn) exceeds 1.0 mass% 16. In Example 12 where vanadium (V) exceeds 1.0 mass%, the load during cold forging (recompression molding load) shows a high value exceeding 2500 MPa, and the deformation resistance is compared with other examples. A little expensive. In Example 17 in which molybdenum (Mo), chromium (Cr), and manganese (Mn) are less than 0.1% by mass and vanadium (V) is less than 0.01% by mass, the surface hardness after heat treatment is other than It is slightly lower than the example.
[0100]
【The invention's effect】
As described above in detail, the alloy steel powder molding material according to the present invention includes a predetermined amount of graphite suitable for obtaining a member having high mechanical strength, and has a low hardness advantageous for recompression molding. , Has a property of large elongation (deformability).
[0101]
Moreover, the alloy steel powder processed body according to the present invention can surely improve hardness, fatigue strength, and other mechanical characteristics, and can also improve dimensional accuracy.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram of a manufacturing process of an alloy steel powder forming material and an alloy steel powder processed body according to an embodiment of the present invention.
FIG. 2 shows a manufacturing process of a preform, in a state where metal powder is filled in a molding space of a forming die (a), a state where metal powder is pressed with an upper punch and a lower punch (b), pressurization It is explanatory drawing which shows the state (c) which started lowering | hanging the shaping | molding die for taking out a preforming body after completion, and the state (d) which takes out a preforming body.
3 is a drawing showing the structure of a molding material formed by pre-sintering a preform corresponding to Example 1 or 2. FIG.
4 is a drawing showing data and graphs of changes in elongation when the pre-sintering temperature and the amount of graphite are changed for a molding material corresponding to Example 1. FIG.
FIG. 5 is a drawing showing data and graphs of changes in elongation when the pre-sintering temperature and the amount of graphite are changed for a molding material corresponding to Example 2.
FIG. 6 is a drawing showing data and graphs of changes in hardness when the pre-sintering temperature and the amount of graphite are changed for a molding material corresponding to Example 1.
7 is a drawing showing data and graphs of changes in hardness when changing the pre-sintering temperature and the amount of graphite for the molding material corresponding to Example 2. FIG.
8 is a drawing showing data and graphs of molding load (deformation resistance) per unit time when a molding material corresponding to Example 1 is recompression molded (cold forging). FIG.
9 is a drawing showing data and graphs of molding load (deformation resistance) per unit time when a molding material corresponding to Example 2 is recompressed (cold forging). FIG.
FIG. 10 is a drawing showing, in data and graphs, changes in tensile strength when the pre-sintering temperature and the amount of graphite are changed for a plastic workpiece corresponding to Example 1.
11 is a drawing showing data and graphs of changes in tensile strength when the pre-sintering temperature and the amount of graphite are changed for a plastic workpiece corresponding to Example 2. FIG.
12 is a drawing showing data and graphs of the change in hardness when the pre-sintering temperature and the amount of graphite are changed for the plastic workpiece corresponding to Example 1. FIG.
FIG. 13 is a drawing showing data and graphs of the change in hardness when the pre-sintering temperature and the amount of graphite are changed for a plastic workpiece corresponding to Example 2.
14 is a drawing showing the structure of a composition processed body obtained by recompression molding (cold forging) of a molding material corresponding to Example 1 or 2 with a relatively small cross-sectional reduction rate (deformation amount).
15 is a drawing showing the structure of a composition processed body obtained by recompression molding (cold forging) of a molding material corresponding to Example 1 or 2 with a relatively large cross-section reduction rate. FIG.
16 is a drawing showing the structure of a re-sintered body corresponding to Example 1 or 2. FIG.
17 is a drawing showing data and graphs of changes in the residual ratio of graphite when the re-sintering temperature and the re-sintering time are changed for the re-sintered body corresponding to Example 1. FIG.
18 is a drawing showing data and graphs of changes in tensile strength when the re-sintering temperature is changed for the re-sintered body corresponding to Example 1. FIG.
19 is a drawing showing data and a graph of changes in tensile strength when the re-sintering temperature is changed for the re-sintered body corresponding to Example 2. FIG.
20 is a drawing showing data and graphs of changes in hardness when the re-sintering temperature is changed for the re-sintered body corresponding to Example 1. FIG.
21 is a drawing showing data and graphs of changes in hardness when the re-sintering temperature is changed for the re-sintered body corresponding to Example 2. FIG.
22 is a drawing showing data and graphs showing changes in tensile strength when the re-sintering temperature is changed for the heat-treated body corresponding to Example 1. FIG.
FIG. 23 is a drawing showing, in data and graphs, changes in tensile strength when the re-sintering temperature is changed for the heat-treated body corresponding to Example 2.
FIG. 24 shows the internal hardness distribution of the heat-treated product corresponding to Example 2 and the same metallic powder having a density of 7.0 g / cm.^Three1 is a drawing showing data and graphs of the internal hardness distribution of a heat-treated body (conventional method) obtained by temporary compression molding and then processed under the same conditions as in Example 2. FIG.
FIG. 25 is a drawing showing alloy elements contained in the respective plastic workpieces of Examples 1 to 19, and data of recompression molding load and heat treatment workpiece surface hardness in each Example.
[Explanation of symbols]
3a ... metal powder
3b Graphite
4 ... Molding dies
5 ... Molding space
6 ... Upper punch
7 ... Bottom punch
9. Large diameter part
10 ... Small diameter part
11 ... Tapered part

Claims (16)

Contains at least one alloy element selected from molybdenum (Mo), nickel (Ni), manganese (Mn), copper (Cu), chromium (Cr), tungsten (W), vanadium (V) and cobalt (Co). , the alloy steel powder for the remaining part of iron and unavoidable impurities, the metallic powder obtained by mixing 0.1 mass% or more graphite obtained by compacting, density 7.3 g / cm ³ The above preform was pre-sintered at 800 to 1000 ° C., graphite remained at the grain boundaries of the metal powder, had a ferrite or austenite structure, and pearlite or bainite was deposited in the vicinity of the graphite. Alloy steel powder molding material characterized by having a structure . Main component of at least one alloy element selected from molybdenum (Mo), nickel (Ni), manganese (Mn), copper (Cu), chromium (Cr), tungsten (W), vanadium (V) and cobalt (Co) The density obtained by compacting a metal powder obtained by mixing 0.1% by mass or more of graphite with a metal powder obtained by diffusing and adhering the powder to be a metal powder composed of iron and inevitable impurities. There will be presintered the 7.3 g / cm ³ or more preforms at 800 to 1000 ° C., the graphite remains in the grain boundary of the metal powder, ferrite, austenite, or an alloy component of the non-diffusion type or An alloy steel powder forming material characterized by having a structure in which two or more kinds are mixed and having a structure in which pearlite or bainite is precipitated in the vicinity of the graphite . Powders mainly composed of at least one alloy element selected from nickel (Ni), manganese (Mn), chromium (Cr), tungsten (W), vanadium (V) and cobalt (Co) are made of iron and inevitable impurities. A preform having a density of 7.3 g / cm ³ or more obtained by compacting a metal powder obtained by mixing 0.1% by mass or more of graphite with a metal powder obtained by mixing with a metal powder. The body is pre-sintered at 800 to 1000 ° C., graphite remains in the grain boundary of the metal powder, and has a structure in which ferrite, austenite, or one or more of non-diffused alloy components are mixed, An alloy steel powder molding material characterized by having a structure in which pearlite or bainite is precipitated in the vicinity of the graphite . One or more alloy elements selected from molybdenum (Mo), chromium (Cr), manganese (Mn), and vanadium (V) are 0.1% Mo≤3.0, 0.1≤Cr≤3.5, 0.1% by mass%. The alloy steel powder forming material according to claim 1, wherein the alloy steel powder forming material is contained in a range satisfying the conditions of ≦ Mn ≦ 1.0 and 0.01 ≦ V ≦ 1.0. One or more alloy elements selected from molybdenum (Mo), chromium (Cr), manganese (Mn), and vanadium (V) are contained in 0.1 % by weight, 0.1 ≦ Mo ≦ 3.0 , 0.1 ≦ Cr ≦ 3.5 , 0.1 The alloy steel powder forming material according to claim 2, wherein the alloy steel powder forming material is contained in a range satisfying the conditions of ≦ Mn ≦ 1.0 and 0.01 ≦ V ≦ 1.0 . The alloy steel powder molding material according to claim 1 or 4 is re-compressed and formed , wherein graphite remains at the grain boundaries of the metal powder, and has a structure of ferrite and austenite, and pearlite or bainite is adjacent to the graphite. An alloy steel powder plastic working body characterized in that it has a structure in which is precipitated . The alloy steel powder molding material according to any one of claims 2, 3, and 5 is formed by recompression molding, wherein graphite remains at the grain boundary of the metal powder, and is a kind of ferrite, austenite, or undiffused alloy component. Or it has the structure | tissue which 2 or more types mixed, and has the structure | tissue which the pearlite or bainite precipitated in the vicinity of the said graphite, The alloy steel powder plastic processed body characterized by the above-mentioned. A molding die having a molding space filled with a metallic powder, and an upper punch and a lower punch that are inserted into the molding die and pressurize the metallic powder, and the molding punch is provided with the upper punch in the molding space. Are formed, a small-diameter portion into which the lower punch is inserted, a tapered portion connecting the large-diameter portion and the small-diameter portion, and formation of one or both of the upper punch and the lower punch. A preform is formed by an apparatus in which a notch for increasing the volume of the molding space is formed on an end surface facing the space, and the preform thus formed is pre-sintered at 800 to 1000 ° C. 7. The alloy steel powder plastic working body according to claim 6, wherein the alloy steel powder molding material is formed, and the alloy steel powder molding material is recompressed . Molding die having a molding space filled with metallic powder, and the molding die An upper punch and a lower punch that pressurize the metal powder, and a molding space of the molding die includes a large-diameter portion into which the upper punch is inserted and a small-diameter portion into which the lower punch is inserted. In addition, a taper portion connecting the large diameter portion and the small diameter portion is formed, and a notch for increasing the volume of the molding space is formed on the end face facing the molding space of one or both of the upper punch and the lower punch. A preformed body is formed by an apparatus, and the preformed body formed thereby is pre-sintered at 800 to 1000 ° C to form the alloy steel powder molding material according to claim 2 or 3, and the alloy steel powder molding. 8. The alloy steel powder plastic working body according to claim 7, wherein the material is recompressed. The alloy steel powder plastic working body according to claim 6 is re-sintered at 800 to 1300 ° C, and is composed of a structure of ferrite, pearlite, bainite, and austenite, and graphite is scattered inside or at a grain boundary of the metal powder. An alloy steel powder re-sintered body characterized by having a structure . The alloy steel powder plastic working body according to claim 7 is re-sintered at 800 to 1300 ° C, and has a structure in which one or more of ferrite, pearlite, bainite, austenite or undiffused alloy components are mixed. An alloy steel powder re-sintered body having a structure in which graphite is scattered inside or at a grain boundary of metal powder. An alloy steel powder re-sintered body obtained by heat-treating the alloy steel powder re-sintered body according to claim 10 and having a hardened structure. An alloy steel powder heat-treated product obtained by heat-treating the alloy steel powder re-sintered product according to claim 11 and having a hardened structure. Contains at least one alloy element selected from molybdenum (Mo), nickel (Ni), manganese (Mn), copper (Cu), chromium (Cr), tungsten (W), vanadium (V) and cobalt (Co). , 0 to alloy steel powder with the balance being iron and inevitable impurities . A metal powder obtained by mixing 1% by mass or more of graphite is compacted to a density of 7 . 3g / cm ^Three A preforming step for obtaining the above preform,
Pre-sintering the preform at 800-1000 ° C. to obtain an alloy steel powder forming material having a structure in which pearlite or bainite is precipitated in the vicinity of the graphite; and
A method for producing an alloy steel powder molding material characterized by comprising: Main component of at least one alloy element selected from molybdenum (Mo), nickel (Ni), manganese (Mn), copper (Cu), chromium (Cr), tungsten (W), vanadium (V) and cobalt (Co) To a metal powder formed by diffusing and adhering to a metal powder composed of iron and inevitable impurities, . A density of 7 obtained by compacting a metallic powder obtained by mixing 1% by mass or more of graphite. . 3g / cm ^Three A preforming step for obtaining the above preform,
The preform is pre-sintered at 800 to 1000 ° C., and graphite remains at the grain boundary of the metal powder, and has a structure in which one or more of ferrite, austenite, or undiffused alloy components are mixed. And a preliminary sintering step of obtaining an alloy steel powder forming material having a structure in which pearlite or bainite is precipitated in the vicinity of the graphite,
A method for producing an alloy steel powder molding material characterized by comprising: The preforming step includes a molding die having a molding space filled with metallic powder, and an upper punch and a lower punch that are inserted into the molding die and pressurize the metallic powder, and the molding die has a molding space. Are formed with a large-diameter portion into which the upper punch is inserted, a small-diameter portion into which the lower punch is inserted, and a tapered portion connecting the large-diameter portion and the small-diameter portion. The alloy steel according to any one of claims 14 and 15, wherein the preform is formed by an apparatus in which a notch for increasing the volume of the forming space is formed on one or both end faces facing the forming space. Manufacturing method of powder molding material.

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