JP4989146B2 - Layered Fe-based alloy and method for producing the same - Google Patents

Description

  The present invention relates to a layered Fe-based alloy in which a diffusion layer containing carbide and nitride and having a hardness higher than that of the base material is provided on the surface of a base material made of an Fe-based alloy, and a method for manufacturing the same.

  For the purpose of improving various properties such as wear resistance, corrosion resistance, and strength of steel materials that are Fe-based alloys, physical vapor deposition (PVD) method, chemical vapor deposition (CVD) method, plating, anodic oxidation, etc. A film may be provided on the surface of the steel material. However, in this case, there is a problem that it takes a long time to form a film and the film formation cost is high.

Therefore, various surface treatments such as carburizing, sulfiding, nitriding, carbonitriding, etc. are widely performed to improve various characteristics of the surface of the steel material without providing a coating (for example, Patent Document 1). 2). Further, in Patent Document 3, by applying a mechanical treatment such as shot peening or shot blasting and applying a compressive stress of 10 kgf / cm ² (approximately 0.1 MPa) to the surface, the wear resistance of the cutting tool and It has been proposed to improve fracture resistance.

  Further, in Patent Documents 4 and 5, attention is paid to the corrosion resistance of the Fe—Al alloy, and it is attempted to diffuse and infiltrate the steel material by heat treatment. In order to realize this, Patent Document 4 proposes to apply Al powder or Al alloy powder and Ti powder or Ti alloy powder to a steel material and heat-treat, while Patent Document 5 discloses Al powder. Alternatively, it has been proposed to apply a heat treatment by applying a mixed powder of an Al alloy powder and at least one of a metal oxide, a metal nitride, a metal carbide, and a metal boride to a steel material.

JP 2003-129216 A JP 2003-239039 A JP-A-5-171442 Japanese Patent No. 3083292 JP 2004-323891 A

  However, it is limited to the surface of a metal material that various characteristics improve by the conventional techniques as described in Patent Documents 1 to 3. For example, in nitriding or carburizing, the element diffuses from the surface of the metal material only a few μm and at most about 200 μm, and it is difficult to improve various internal characteristics. For this reason, it is difficult to say that the wear resistance and fracture resistance are remarkably improved.

  In addition, in the processing method according to the prior art, an interface exists between the formed nitride layer or the like and the metal material as the base material. For this reason, there is a concern that brittle fracture occurs from the interface under conditions where stress concentration occurs at the interface.

  Also in the techniques described in Patent Documents 4 and 5, since the diffusion and penetration depth of Al is about 100 μm, it is difficult to improve various characteristics deep inside the metal material.

  The present invention has been made in order to solve the above-described problems. The layered Fe which is hard to cause brittle fracture because the hardness and strength are improved deep inside, and the change in physical properties is gentle, so that stress concentration hardly occurs. An object is to provide a base alloy and a method for producing the same.

In order to achieve the above object, a first layered Fe-based alloy according to the present invention includes a base material composed of an Fe-based alloy containing a pearlite structure, and carbides and nitrides diffuse from the surface side of the base material. And a diffusion layer having a hardness higher than that of the base material,
The diffusion layer is characterized in that the concentration of the carbide and the nitride gradually decreases as the depth increases in the depth direction.

In addition, the second layered Fe-based alloy according to the present invention is formed by diffusion of carbide and nitride from a base material made of an Fe-based alloy containing a troostite structure or a sorbite structure, and from the surface side of the base material. And having a diffusion layer having a hardness higher than that of the base material,
The diffusion layer is characterized in that the concentration of the carbide and the nitride gradually decreases as the depth increases in the depth direction.

  That is, the layered Fe-based alloy according to the present invention includes a structure formed as a result of the quenching process and the tempering process. When the tempering temperature is less than 400 ° C., a pearlite structure is formed, and when it is 400 ° C. or more, a troostite structure or a sorbite structure is formed.

  The Fe-based alloy subjected to the quenching treatment exhibits high hardness, and the Fe-based alloy subjected to the tempering treatment is improved in brittleness. Therefore, the first and second Fe-based alloys according to the present invention exhibit high hardness while exhibiting excellent brittleness.

  In addition, in the layered Fe-based alloy according to the present invention, since carbides and nitrides containing AlN are diffused deep inside the Fe-based alloy as a base material, excellent hardness and strength are exhibited up to the inside. In this layered Fe-based alloy, no interface exists between the diffusion layer and the base material. For this reason, stress concentration is unlikely to occur, so that brittle fracture is less likely to occur.

  Here, compressive residual stress is imparted along with the presence of nitride, carbide, etc., but in the present invention, carbide and nitride diffuse to a depth of 0.5 mm or more from the outermost surface as a base point. Yes. Therefore, the compressive residual stress can be increased deep inside. In addition, since the density | concentration of a carbide | carbonized_material and nitride reduces gradually as it goes inside from the outermost surface, a compressive residual stress also reduces gradually. Also from this point, stress concentration is avoided.

  Preferable examples of the metal carbide include carbides of Cr, W, Mo, V, Ni, and Mn. In addition, preferable examples of nitrides other than AlN include nitrides of these metals.

In the carbides in this, when the metal element is represented by M, the composition formula is preferably M ₆ C or M ₂₃ C ₆ . This is because the carbide whose composition formula is expressed in this way is particularly excellent in the effect of improving the hardness of the Fe-based alloy.

  The carbide may be a carbide of a solid solution of at least one of Cr, W, Mo, V, Ni, and Mn and Fe. In this case, since the relative amount of the metal carbide as described above is reduced, it is possible to prevent the metal carbide from being excessively generated and the brittleness from being increased.

A preferred solid solution carbide is one in which the composition formula is represented by (Fe, M) ₆ C or (Fe, M) ₂₃ C ₆ when the metal element is represented by M.

The present invention also includes a base material made of an Fe-based alloy containing a pearlite structure, and a diffusion layer formed by diffusing carbide and nitride from the surface side of the base material and having a higher hardness than the base material. In the diffusion layer, the concentration of the carbide and the nitride gradually decreases as the depth increases in the depth direction,
A step of performing a tempering treatment by heating the Fe-based alloy to 150 ° C. or more and less than 400 ° C. after performing a quenching treatment on the Fe-based alloy;
Applying metal powder to the surface of the Fe-based alloy;
Nitriding the Fe-based alloy; and
It is characterized by having.

Furthermore, the present invention is formed by a base material composed of an Fe-based alloy containing a troostite structure or a sorbite structure, and carbide and nitride are diffused from the surface side of the base material, and compared with the base material. A diffusion layer having a high hardness, and in the diffusion layer, the concentration of the carbide and the nitride gradually decreases as the depth increases in the depth direction,
A step of performing a tempering treatment by heating the Fe-based alloy to 400 ° C. or more and an Ac1 transformation point or less after quenching the Fe-based alloy;
Applying metal powder to the surface of the Fe-based alloy;
Nitriding the Fe-based alloy; and
It is characterized by having.

  That is, according to the present invention, the structure contained in the base material can be made different by changing the tempering temperature. In particular, when an operation (tempering) for precipitating a troostite structure or a sorbite structure by tempering is performed, a layered Fe-based alloy exhibiting high toughness is obtained.

  Here, the manufacturing method of the layered Fe-based alloy in the present invention includes a case where a so-called tempered material is used. The tempered material is commercially available after being tempered at a temperature of less than 400 ° C. and below the Ac1 transformation point, and the metal structure includes a troostite structure or a sorbite structure. In other words, when using a tempered material, it is obtained in a state where the quenching process and the tempering process have been performed in advance, and after that, the remaining steps are performed. become.

  Then, through the steps as described above, a thick diffusion layer can be formed, and a layered Fe-based alloy having no interface between the diffusion layer and the base material can be manufactured. The obtained layered Fe-based alloy has excellent hardness and strength due to the presence of the diffusion layer.

  The carbide contained in the diffusion layer is formed by combining the metal applied as a powder and the carbon constituting the Fe-based alloy during the heat treatment, while the nitride is a metal that remains as an unreacted material during the heat treatment. It is thought that it is formed by nitriding during nitriding.

  As the metal powder to be applied, nitride can be formed by diffusing deep inside the Fe-based alloy, and since it can also be diffused deep inside as a carbide, Cr, W, Mo, V, Ni It is preferable to use a powder of Mn.

  Further, it is preferable to use a mixture of Al. In this case, the thickness of the diffusion layer can be further increased.

  The reason why the thickness of the diffusion layer and thus the diffusion distance of each component becomes large when Al is applied is that, by applying Al and heat treatment, lattice defects are generated in the steel material, and each component is introduced into the steel material via the lattice defect. It is assumed that this is because it easily diffuses deep inside.

  According to the present invention, a pearlite structure, a troostite structure, or a sorbite structure is formed by a quenching process and a tempering process, and carbide and nitride are diffused from the surface of the Fe-based alloy as a base material. A diffusion layer is formed deep inside the base material. For this reason, the layered Fe-based alloy in which the hardness and strength of the Fe-based alloy are improved to the inside and the compressive residual stress is improved to the deep inside can be configured.

  This effect is particularly noticeable when Al is applied. This is presumably because Al causes lattice defects in the steel material, which causes Al and other metals to diffuse deep inside, and then these components are nitrided.

  Furthermore, when a troostite structure or a sorbite structure is formed, there is also an advantage that toughness is improved.

  Hereinafter, preferred embodiments of a layered Fe-based alloy and a manufacturing method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

  A schematic overall perspective view of a hot forging punch made of a layered Fe-based alloy according to the present embodiment is shown in FIG. This hot forging punch 10 is manufactured using SKH51 as a raw material (base material), and has a large diameter portion 12 and a reduced diameter portion 14 connected to the large diameter portion 12 and reduced in a taper shape. And a small-diameter portion 16 and a curved protruding portion 18 that is formed to protrude from one end portion of the small-diameter portion 16 and is curved. Of these, the curved protruding portion 18 and the side wall portion at the tip of the small diameter portion 16 press the work housed in a die cavity (not shown) to form the work into a predetermined shape. That is, the distal end portion of the small-diameter portion 16 and the curved protruding portion 18 are molding portions that press the workpiece.

  Here, when the microstructure of the base material SKH51 is observed with a scanning electron microscope (SEM) or the like, it is recognized that a layered structure containing ferrite and cementite, that is, a pearlite structure exists. This pearlite structure is formed by quenching / tempering described later.

  Further, as can be understood from FIG. 2 in which the cross section in the vicinity of the forming portion is enlarged, the diffusion layer 20 formed by diffusing metal carbide and nitride in the base material SKH51 exists in the surface layer portion of the forming portion. is doing.

  Further, nitrogen diffuses and permeates in the vicinity of the outermost surface of the molded part. That is, in the vicinity of the outermost surface in the diffusion layer 20, in addition to carbide and nitride, nitrogen is contained in the base material as a base in the form of a so-called nitride layer (nitrogen diffusion layer) formed by nitriding.

  Preferable examples of the metal element that forms carbide or nitride include Cr, W, Mo, V, Ni, and Mn. The diffusion layer 20 in which the carbides and nitrides of such metal elements are diffused exhibits high hardness and high strength based on the same mechanism as that of the precipitation hardening type composite material.

  Further, in the vicinity of the outermost surface in the diffusion layer 20, there is a nitride layer formed by diffusion and permeation of nitrogen as described above. For this reason, in the hot forging punch 10, the molded portion where the diffusion layer 20 exists has higher hardness and strength than the large diameter portion 12 and the reduced diameter portion 14 where the diffusion layer 20 does not exist. In other words, the molded part provided with the diffusion layer 20 has higher hardness and higher strength than other parts.

Carbides, when represents a metal element in M, tables in M ₆ C as may be carbide composition formula is represented by M ₇ C _{3 but, Cr 6 C, W 6 C} , Mo 6 C , etc. And a carbide represented by M ₂₃ C ₆ is preferred. In this case, it is because it is most excellent in the effect of improving hardness and strength.

Note that when M ₆ C and M ₂₃ C ₆ are present in an excessively large amount, the hot forging punch 10 becomes brittle. Therefore, it is preferable to generate a solid solution carbide of Fe and the above metal element. That is, the carbide may be represented by (Fe, M) ₆ C, (Fe, M) ₂₃ C ₆ or the like. When such a carbide is generated, the relative amounts of M ₆ C and M ₂₃ C ₆ are reduced, so that the hot forging punch 10 can be reliably prevented from showing brittleness.

For example, when the C amount of the steel material is large, WC, VC, Mo ₂ C, Cr ₃ C _{4 and the} like may be present as carbides in addition to those represented by these composition formulas.

  Moreover, as a suitable example of nitride, the nitride of Cr, W, Mo, V, Ni, Mn mentioned above is mentioned. Among these, Cr is particularly preferable. Further, in the present embodiment, in addition to these nitrides, AlN is also included in the diffusion layer 20. Such a nitride exists so as to be interposed between the fine carbide and the pearlite structure.

  Here, the thickness of the diffusion layer 20, in other words, the diffusion distance of carbide and nitride, the depth from the outermost surface of the hot forging punch 10 reaches at least 0.5 mm (500 μm), Usually, it may reach 3 to 7 mm (3000 to 7000 μm), and 15 mm (15000 μm) at the maximum. This value is remarkably large while the diffusion distance of elements in nitriding, carburizing, etc. is several tens of μm, at most about 200 μm. That is, in the present embodiment, carbides and nitrides can be diffused to a deeper site than the elements introduced by the surface treatment method according to the prior art.

  Further, in the present embodiment, AlN is diffused to a depth substantially equal to the thickness of the diffusion layer 20. In other words, AlN reaches a depth of at least 0.5 mm from the outermost surface, and thus the diffusion layer 20 has a form containing AlN. AlN may be diffused to a deeper position than carbides and other nitrides.

  In the molded part provided with such a diffusion layer 20, the hardness of the base material is improved to the depth at which the carbides are diffused. That is, the hardness and strength increase to the inside of the hot forging punch 10, and as a result, the internal wear resistance is improved and the deformation becomes difficult.

  The diffusion layer 20 may contain carbonitrides such as Cr, W, Mo, V, Ni, Mn, etc. in addition to the above-described carbides and nitrides.

  As will be described later, the diffusion layer 20 is formed by generating carbide and nitride by a metal element diffused from the surface of the base material. For this reason, the concentration of carbide and nitride is highest on the surface and gradually decreases toward the inside of the base material.

  Further, since the concentrations of carbide and nitride gradually decrease in this way, there is no clear interface between the diffusion layer 20 and the base material. For this reason, since it can avoid that stress concentration arises, it can avoid that brittleness increases with diffusing a metallic element. In FIG. 2, a boundary line is provided for convenience between the diffusion layer 20 and the base material in order to clarify that the diffusion layer 20 exists.

  The hot forging punch 10 configured in this manner is used when hot forging is performed on a workpiece. At this time, the forming portion of the hot forging punch 10 is used as a workpiece. Press. As described above, since the diffusion layer 20 is present, the molded portion has high hardness and high strength, and toughness is ensured. Therefore, the molded part is not easily worn even if the forging process is repeatedly performed, and is not easily damaged. That is, a long life can be ensured.

  The hot forging punch 10 can be manufactured as follows.

  First, the cylindrical workpiece W made of SKH 51 shown in FIG. 3A is cut by a cutting tool 30 as shown in FIG. 3B to obtain the shape of the hot forging punch 10. The corresponding preform 32 is formed.

  Next, as shown in FIG. 3C, the preform 32 is subjected to a quenching process and a tempering process.

  As is well known, the quenching treatment is performed by heating to a temperature equal to or higher than the Ac3 transformation point in hypoeutectoid steel, and to a temperature equal to or higher than the Ac1 transformation point in hypereutectoid steel and then cooling with a coolant such as oil. Thereby, austenite in the metal structure of the preformed body 32 is transformed into martensite, and as a result, the hardness and strength of the preformed body 32 are improved.

  However, the preform 32 exhibits brittleness only by performing the quenching process. A tempering treatment is performed to improve this brittleness.

  As the tempering process is performed, martensite changes to thermodynamically stable ferrite and cementite. A pearlite structure is formed by arranging these in parallel in layers. That is, the preformed body 32 including a pearlite structure is obtained.

  In this case, the temperature during the tempering process is set to 150 ° C. or more and less than 400 ° C. Of course, it is preferable to avoid a temperature at which temper embrittlement occurs. For example, in the present embodiment, since SKH51 is a high-speed tool steel, it may be set to 150 to 250 ° C. or 350 ° C. or more and less than 400 ° C.

  Next, as shown in FIG. 3D, a metal powder to be diffused is applied to the surface of the molding part of the preform 32.

  The metal powder to be diffused is a metal that forms carbides and nitrides and increases the hardness of the steel material, and Al. Suitable examples of metals other than Al are Cr, W, Mo, V, Ni, and Mn as described above. In particular, when Cr is present, the nitride layer becomes deep, which is preferable. In addition, the presence of Mo and Ni provides an advantage that the elongation of the hot forging punch 10 is improved.

  The powder is applied by applying a coating agent 34 prepared by dispersing the powder in a solvent. As the solvent, it is preferable to select an organic solvent that easily evaporates, such as acetone or alcohol. And powder, such as W and Cr, is disperse | distributed to this solvent.

  Here, an oxide film is usually formed on the surface of the base material SKH 51. In order to diffuse Al, Cr, etc. in this state, a great amount of thermal energy must be supplied so that Al, Cr, etc. can pass through the oxide film. In order to avoid this, it is preferable to mix the coating agent 34 with a reducing agent capable of reducing the oxide film.

  Specifically, a substance that acts as a reducing agent on the oxide film and does not react with SKH51 is dispersed or dissolved in a solvent. Preferable examples of the reducing agent include nitrocellulose, polyvinyl, acrylic, melamine, and styrene resins, but are not particularly limited thereto. Note that the concentration of the reducing agent may be about 5%.

  The coating agent 34 in which the above substances are dissolved or dispersed is applied to the surface of the molded part by a brush coating method using a brush 36, as shown in FIG. 3 (d). Of course, you may make it employ | adopt well-known coating techniques other than the brush coating method.

  Next, heat treatment is performed on the preform 32 in which the coating agent 34 is applied to the surface of the molding part. This heat treatment can also be performed by applying a burner flame 38 from one end face side of the preform 32 as shown in FIG. Of course, heat treatment may be performed in an inert atmosphere in a heat treatment furnace.

  In this temperature rising process, the reducing agent begins to decompose at about 250 ° C., and carbon and hydrogen are generated. The oxide film of the preform 32 is reduced and disappears under the action of carbon and hydrogen. For this reason, it is not necessary for Al, Cr, or the like to pass through the oxide film, so that the time required for diffusion can be shortened and thermal energy can be reduced.

When the temperature is further increased, C and Fe, which are constituent elements of SKH51, which is the base material, and C produced by decomposition of the reducing agent react with Cr and the like, and Cr ₆ C, Cr ₂₃ C ₆ And so on. When Fe is involved, (Fe, Cr) ₆ C, (Fe, Cr) ₂₃ C _{6 and the} like are also generated.

A part of the generated carbides such as Cr ₆ C and (Fe, Cr) ₆ C are immediately decomposed and returned to Fe and Cr. Among these, Cr is then combined with C, Fe, which are constituent elements of the base material existing on the inner side of the base material, and C existing in a free state on the inner side of the base material, Newly produced are Cr ₆ C, (Fe, Cr) ₆ C, and the like. This Cr ₆ C, (Fe, Cr) ₆ C also immediately decomposes and returns to Cr, and then C, Fe, which are constituent elements of the base material existing on the inner side of the base material, and the base material It combines with C existing in a free state on the inner layer side, and again produces Cr ₆ C, (Fe, Cr) ₆ C and the like. In this way, the carbide is repeatedly decomposed and produced, so that the carbide diffuses deep inside the base material.

  On the other hand, Al causes lattice defects in the crystal structure of SKH51 and promotes diffusion through the lattice defects. Unreacted metals other than Al also diffuse through these lattice defects. In other words, Al causes lattice defects so that a part of the metal diffuses into the preform 32 before forming carbide.

In this way, Cr ₆ C, Al, Cr, etc. can be diffused inside the base material.

  Next, the preform 32 is subjected to nitriding treatment by a known method such as gas nitriding, ion nitriding, salt bath nitriding, plasma nitriding. Of these, salt bath nitriding is particularly preferred. The molten salt used for the salt bath nitriding has good convection, uniform heat transfer, and high density, so that the preform 32 and the coating agent 34 can be heated quickly. Because it can. Further, since the thermal conductivity is high, the preform 32 is heated deep inside. For this reason, a large amount of N is penetrated deep inside the preform 32 using N that penetrates the surface of the preform 32 as a source. It becomes possible to diffuse. Furthermore, there is an advantage that capital investment can be reduced.

  The nitriding conditions may be, for example, 550 ° C. and 14 hours in the case of salt bath nitriding.

  Of course, ion nitriding may be performed instead of salt bath nitriding. In this case, for example, a DC voltage of a predetermined voltage is applied using the nitriding furnace as an anode and the preformed body 32 as a cathode, while a nitriding gas such as nitrogen is supplied at a predetermined pressure and held at 520 ° C. for 10 hours. In ion nitriding, nitriding proceeds by causing a sputtering phenomenon in which nitriding gas ions are accelerated at high speed and collide with the preform 32.

  Due to the above nitriding treatment, a large amount of nitride is present in the diffusion layer 20, so that the compressive residual stress of the preform 32 increases and the hardness increases. As a result, the hot forging punch 10 with improved resistance to cracks and cracks is obtained.

  The hot forging punch 10 preferably has a large compressive residual stress because a compressive pressure is applied along the pressing direction as it is subjected to pressing from the workpiece during forging. That is, according to the nitriding treatment, the hot forging punch 10 suitable for forging can be provided.

  Before the nitriding treatment, the metal powder and impurities remaining on the surface may be removed, or the surface (diffusion layer 20) may be slightly ground. As a result, the nitriding process proceeds smoothly and efficiently. This is because N easily diffuses from the surface. As a result, the film quality can be easily controlled and the time required for the nitriding treatment can be shortened. This effect is particularly remarkable in the case of ion nitriding.

  Further, the nitriding treatment may be performed a plurality of times.

  By nitriding, Al, Cr or the like diffused inside the preform 32 is nitrided to produce AlN or CrN. Further, part of the carbide is also nitrided to become carbonitride. Thereby, the diffusion layer 20 is formed (see FIG. 2). Further, as nitrogen diffuses and penetrates into the preform 32, a nitride layer is also formed near the outermost surface of the diffusion layer 20.

  Note that the concentrations of carbide, nitride, and carbonitride gradually decrease, and no clear interface is formed between the diffusion reaching termination portion and the base material. For this reason, since compressive residual stress changes gently, it is avoided that stress concentrates on a specific location. As a result, the occurrence of brittle fracture can be avoided, so that the toughness of the molded part in which the diffusion layer 20 is formed can be ensured.

  Here, the depth and compressive residual stress in the steel material that has been subjected to the salt bath nitriding treatment without being coated with the metal powder, and the steel material that has undergone the above procedure after the mixed powder containing Al and Cr is applied as the metal powder. The relationship is shown in a graph in FIG. In addition, the numerical value of Al in FIG. 4 is weight% which Al occupies in mixed powder. From FIG. 4, it is clear that the compressive residual stress can be improved by applying a nitriding treatment after applying a mixed powder containing Al and Cr.

  When the hot forging punch 10 is subjected to pressing from a workpiece when performing hot forging, the hot forging punch 10 is expanded along a direction substantially perpendicular to the pressing direction. In other words, tensile stress acts. According to the present embodiment, since the compressive residual stress can be increased deep inside the hot forging punch 10, resistance to tensile stress during the hot forging can be increased.

  The thickness of the diffusion layer 20, particularly the diffusion distance of AlN, extends up to a depth of about 15 mm from the surface, and the compressive residual stress at the outermost surface may reach 1200 MPa.

  Finally, as shown in FIG. 3F, the preforming body 32 is finished with a cutting tool 30 to obtain a hot forging punch 10.

  In the same manner as described above, Mo, V, and Ni carbides and nitrides can be diffused into the base material.

  The base material may include a troostite structure or a sorbite structure instead of the pearlite structure. In this case, the tempering temperature in FIG.

  In the present invention, the main structure constituting the metal structure of the preform 32 can be made different by making the tempering temperature different. In the present invention, the method for producing a layered Fe-based alloy in which the base material includes a troostite structure or a sorbite structure is performed by using the tempered material and performing the steps shown in FIG. Shall be included. The tempered material is commercially available after being tempered at a temperature below the Ac1 transformation point of less than 400 ° C. after quenching. Because it can be considered. Of course, it is not particularly necessary to perform quenching and tempering after obtaining a tempered material on the market.

  When a troostite structure or a sorbite structure is formed, the hot forging punch 10 exhibits further excellent toughness. That is, by performing so-called tempering, there is an advantage that the hot forging punch 10 showing excellent toughness while having high hardness can be obtained.

  The hot forging punch 10 obtained as described above is cut along the longitudinal direction, and the Vickers hardness measured from the surface side to the inside of the cut surface is nitrided without applying metal powder. This is shown in FIG. In this case, the coated material was mixed in a weight ratio of Group III metal: Group IV metal: Group VI metal: Group VII metal: Group VIII metal: Al = 2: 13: 26: 20: 31: 4. The product was prepared by adding it to an acetone solution of 10% epoxy resin. Moreover, application | coating was performed by brush coating and the thickness of the coated material was 1 mm. Furthermore, before apply | coating a coating material, the quenching process was performed by hold | maintaining at 1000-1180 degreeC for 2 hours, and the tempering process was then hold | maintained at 500-600 degreeC for 2 hours. That is, in this case, the base material includes a sorbite structure.

  From FIG. 5, the normal nitriding treatment increases the hardness only up to about 0.07 mm from the outermost surface, and thereafter shows a substantially constant hardness, whereas in the present embodiment, it exceeds 1.0 mm from the outermost surface. It is clear that it shows high hardness and decreases gradually.

  In the above-described embodiment, the hot forging punch 10 has been described as an example of the layered Fe-based alloy. However, the present invention is not limited to this, and cold or warm including the punch is not limited thereto. Needless to say, it may be a forging die or other members.

Further, the carbide may have a compositional formula represented by M ₇ C ₃ or may be represented by another compositional formula.

It is a schematic whole perspective view of the hot forging punch which is a layered Fe-based alloy. FIG. 2 is an enlarged vertical cross-sectional view of a main part of the hot forging punch in FIG. 1. FIG. 2 is a flow explanatory diagram illustrating a manufacturing process of the hot forging punch of FIG. 1. It is a graph which shows the relationship between the depth and compressive residual stress in each steel material after nitriding was performed. It is a graph which shows the Vickers hardness measured toward the inside from the surface of the cut surface of the obtained punch for hot forging.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Hot forging punch 16 ... Small diameter part 18 ... Curve protrusion 20 ... Diffusion layer 30 ... Bit 32 ... Preliminary molded body 34 ... Coating agent 36 ... Brush

Claims (4)

A base material made of an Fe-based alloy containing a troostite structure or a sorbite structure, and a diffusion layer formed by diffusing carbides and nitrides from the surface side of the base material and having a hardness higher than that of the base material. Have
When the metal element is represented by M (where M is at least one of Cr, W, Mo, V, Ni, and Mn), the composition formula of the carbide is M ₆ C, M ₂₃ C ₆ , (Fe, M) ₆ C or (Fe, M) ₂₃ C ₆
The nitride includes at least one of nitrides of Cr, W, Mo, V, Ni, Mn,
In the diffusion layer, the layered Fe-based alloy is characterized in that the concentrations of the carbide and the nitride gradually decrease as the depth increases in the depth direction.   2. The layered Fe-based alloy according to claim 1, further comprising AlN as the nitride. A base material made of an Fe-based alloy containing a troostite structure or a sorbite structure, and a diffusion layer formed by diffusing carbides and nitrides from the surface side of the base material and having a hardness higher than that of the base material. Having a metal element represented by M (wherein M is at least one of Cr, W, Mo, V, Ni, and Mn), the composition formula of the carbide is M ₆ C, M ₂₃ C ₆ , (Fe, M) ₆ C or (Fe, M) ₂₃ C ₆ , and the nitride includes at least one of nitrides of Cr, W, Mo, V, Ni, and Mn, and the diffusion The layer is a method for producing a layered Fe-based alloy in which the concentrations of the carbide and the nitride gradually decrease as the depth increases in the depth direction,
A step of performing a tempering treatment by heating the Fe-based alloy to 400 ° C. or more and an Ac1 transformation point or less after quenching the Fe-based alloy;
On the surface of the Fe-based alloy, at least one metal powder of Cr, W, Mo, V, Ni, and Mn is added to M ₆ C, M ₂₃ C ₆ , (Fe, M) ₆ C, or (Fe, M) applying in an amount that produces a carbide represented as ₂₃ C ₆ ;
Nitriding the Fe-based alloy; and
A method for producing a layered Fe-based alloy, comprising: The manufacturing method of claim 3 Symbol mounting method of the organic layer Fe-based alloy, characterized by using a mixed powder Al was further mixed as the metal powder.

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