JP2007007726A - Method for reinforcing die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for reinforcing a die which can obtain the strong and sure reinforcement and can contribute to the improvement of the durability of the die, the productivity of a product and economical efficiency. <P>SOLUTION: A mixed powder layer 14 composed of a first element powder having the property, in which the hardness of the die 10 for forging composed of Fe-base alloy by making into the carbide, is raised, and a second element powder having lower melting point than that of the first element powder, is coated on at least the reinforcing prepared zone (carbide) 11a, 12a in the forging die 10 and thus, the heat treatment to the forging die 10 coated with the mixed powder layer 14 is performed by utilizing the working heat at the working time of a work with the forging die 10. In this way, a reflow of the mixed powder layer 14 is generated and the carbide is diffused into the forging die 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mold reinforcing method for reinforcing various molds including a forging mold.

  In general, in a die such as a forging die, a pressing die, and a casting die, stress acts on a contact portion between the dies and a portion where molten metal hot water collides at high speed, and cracks, wear, etc. Arise.

  Damaged parts such as cracks and wear in the mold cause burrs and distortions in the product, increasing the deburring and shaping operations of the product in the subsequent process. Therefore, in order to prevent such product defects from occurring, it has been attempted to reinforce the mold before use to make it difficult to generate a damaged portion.

  Conventionally, as a method for reinforcing a mold of this type, there is known a method of depositing on a part where the mold is easily damaged by using a discharge coating. In this overlaying method, electrode materials such as metals, carbide ceramics, and cermets are deposited on the surface of the mold where damage is likely to occur using the high temperature associated with spark discharge, and surface treatment is performed to obtain hardness and corrosion resistance. In addition, a discharge coating process that improves durability and the like is performed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 1-210133

  However, the above-mentioned reinforcing method has a drawback in that the bonding strength between the build-up portion and the mold is fragile and its durability is limited, so that repairs need to be performed frequently, leading to a decrease in product productivity. There is.

  In particular, forging dies have high stress during use, thermal fatigue is added, and the built-up part is easy to peel off, so it is difficult to maintain reinforcement for a long time even if it is reinforced by building up. is there. Therefore, if the forging die is damaged, it is forced to be disposed of, which is uneconomical.

  The present invention has been made to solve the above-described problems, and enables a strong and reliable reinforcement, and a mold reinforcement method capable of contributing to improvement of mold durability, product productivity and economy. The purpose is to provide.

In order to achieve the above object, a mold reinforcing method according to the present invention includes a first element powder having a property of increasing the hardness of a mold made of an Fe-based alloy by being carbideized, and the first element powder. Coating the mixed powder having the second element powder having a low melting point on at least the region to be reinforced of the mold;
The first element powder in the mixed powder is carbonized by heat-treating at least a region to be reinforced of the mold covered with the mixed powder using processing heat when processing a workpiece with the mold. And diffusing into the mold,
It is characterized by including. That is, this reinforcing method is performed before a damaged part is generated in the mold.

  According to the present invention, since the hardness and strength of the mold can be reliably improved, for example, a highly durable forging mold that is difficult to wear even if the forging process is repeatedly performed and that is not easily damaged. Can be obtained, and can contribute to the improvement of product productivity and economy. Of course, the same applies to dies such as press dies and casting dies.

  And since heat processing of a metal mold | die is performed using the process heat of a workpiece | work, a man-hour and a labor can be reduced and manufacturing cost can be reduced.

  Suitable examples of the Fe-based alloy include tool steel, high-speed tool steel, die steel, powder steel alloy steel, SCM, SNC, SNCM, SCr structural alloy steel, or carbon steel, low carbon steel structure. For example.

  In addition, it is preferable that the first element powder is at least one of a group of Fe, Ni, and Co. This is because the hardness of the mold made of the Fe-based alloy is improved satisfactorily by being carbideized.

  Further, as the second element powder, Al or an Al—Mn eutectic alloy is preferable. Al has a lower melting point than the first element powder, and the eutectic point of the Al—Mn eutectic alloy is lower than the melting point of Al. Such Al and Al-Mn eutectic alloys act as attractants for the first element powder.

  Furthermore, it is preferable to add a reducing agent for reducing the oxide film present on the surface of the Fe-based alloy to the mixed powder. In this case, since the oxide film is removed when the atoms of the first element powder diffuse, atomic diffusion occurs with low energy.

  In addition, when Al is used as the second element powder, the reducing agent captures oxygen to prevent oxidation of Al. Therefore, the characteristic deterioration of Al is prevented and the adhesion of the first element powder to the Fe-based alloy is improved.

  Preferable examples of the reducing agent include carbon powder, resin or Si.

  Moreover, it is more preferable to add W, Ti, V, Mo, or Nb to the mixed powder. This is because the strength of the mold is further improved in this case.

  Here, when the workpiece is processed by the mold, the contact between the mixed powder and the workpiece may be prevented by a release agent applied to the inner surface of the mold. Thereby, it is avoided that mixed powder acts on a workpiece | work.

  According to the method of reinforcing a mold according to the present invention, the hardness and strength of the mold can be reliably improved, so that it is difficult to wear even if the forging process is repeated, and a highly durable metal that is not easily damaged. A mold is obtained. Eventually, product productivity and economy can be improved.

  Hereinafter, preferred embodiments of the mold reinforcing method according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic overall perspective view of a forging die 10 in which the die reinforcing method according to the present embodiment is implemented. This forging die 10 is a die for forging a spider that constitutes a constant velocity joint for smoothly and uniformly transmitting the engine power of an automobile to a wheel. An Fe-based alloy, for example, tool steel, It consists of alloy steels such as high speed tool steel, die steel and powdered high speed steel.

  The forging die 10 includes a lower die 11 and an upper die 12 that can be displaced relative to the lower die 11, and the lower die 11 and the upper die 12 are matched to the shape of the spider, Cavities 11a and 12a into which materials (workpieces) such as heat-softened steel materials are press-fitted are formed.

  A method for reinforcing the forging die 10 will be described with reference to FIGS. 2A to 2C. First, a first element powder having the property of increasing the hardness of a forging die 10 made of alloy steel which is an Fe-based alloy by being carbideized, and a lower melting point than the first element powder, for example, a melting point of 600 ° C. to A mixed powder with the second element powder at 750 ° C. is prepared.

  Preferable examples of the first element powder include at least one selected from the group consisting of Fe, Ni, and Co. In the subsequent step, if the metal species of the carbide to be diffused is Fe, a mixed powder containing Fe powder may be prepared. If the metal species to be diffused is Ni, a mixed powder containing Ni powder is prepared, and if it is Co, a mixed powder containing Co powder may be prepared. Of course, for example, when both Fe and Co are diffused, a mixed powder containing both Fe powder and Co powder may be prepared.

  On the other hand, a suitable example of the second element powder is Al or an Al—Mn eutectic alloy.

  Here, a spontaneously formed oxide film usually exists on the surface of the forging die 10 (alloy steel) to be reinforced. In order to diffuse the metal atoms contained in the first element powder in this state, a large amount of heat energy must be supplied so that the metal atoms can pass through the oxide film. In order to avoid this, the mixed powder is preferably mixed with a reducing agent capable of reducing the oxide film, for example, carbon.

  Alternatively, a mixed powder of the first element powder and the second element powder is added to a solvent, and a substance that acts as a reducing agent on the oxide film and does not react with the alloy steel is dispersed or dissolved in the solvent. An agent may be prepared. Preferable examples of such a reducing agent include nitrocellulose, polyvinyl, acrylic, melamine, styrene, and epoxy resins, but are not particularly limited thereto. Note that the concentration of the reducing agent may be about 5%.

  Furthermore, you may make it add the substance which has the property to raise the reinforcement intensity | strength of the metal mold | die 10 for forging to mixed powder. As a suitable example of such a substance, at least one member of the group of W, Ti, V, Mo, and Nb can be mentioned.

  Then, as shown in FIG. 2A, the mixed powder is applied to the surface of the cavity 11 a (12 a), which is a region scheduled for reinforcement of the forging die 10, to form a mixed powder layer 14.

  The mixed powder may be applied by applying a coating agent prepared by dispersing the mixed powder in a solvent as described above. As the solvent, it is preferable to select an organic solvent that easily evaporates, such as acetone or alcohol. When the coating agent is prepared, powders such as Ni and Co may be dispersed in a solvent, and powders such as C and Si as a reducing agent may be dispersed.

  Moreover, as a coating method, a brush coating method using the brush 13 may be employed. Of course, a known coating technique other than the brush coating method, for example, spray coating may be employed.

  Next, as shown in FIG. 2B, a release agent 15 is applied on the mixed powder layer 14 in the cavity 11a (12a).

  Next, a heated material (not shown) is pressed into the cavity 11a (12a). At this time, since the release agent 15 exists, the mixed powder layer 14 does not come into contact with the material.

  Next, so-called mold closing is performed. As a result, the forging process for the material is started, and finally, a constant velocity joint having a predetermined shape is formed.

  At this time, the heat treatment for the cavity 11a (12a) of the forging die 10 proceeds. This is because heat is transferred from the material to the lower mold 11 and the upper mold 12 as the mold is closed.

  Thus, in the present embodiment, the forging die 10 is heat-treated using the processing heat of the material. For this reason, man-hours and labor can be reduced, and the cost required for reinforcement is reduced.

  During the heat treatment, the mixed powder layer 14 is reflowed, and the inner surface of the cavity 11a (12a) of the forging die 10 is uniformly coated with the mixed powder. At this time, the second element powder having a melting point lower than that of the first element powder is first melted so that the second element powder is attracted to the first element powder, and further, W, Ti, V, Mo , At least one of the Nb groups is evenly coated.

  This phenomenon is more likely to occur as the melting point of the second element powder is lower. Therefore, as described above, among metals, it is preferable to use Al having a relatively low melting point or an Al—Mn eutectic alloy whose eutectic point is lower than the melting point of Al. Al moves to the surface layer while being replaced by the first element powder, and finally combines with oxygen such as a solvent to be sludged on the surface layer. For this reason, it is avoided that the forging die 10 is embrittled or broken due to the presence of Al inside.

In addition, when reducing agents, such as carbon powder and resin, exist in mixed powder, this reducing agent captures O. For example, carbon powder or C generated by decomposition of resin combines with O to become CO and CO ₂ . For this reason, it can prevent that various metals including Al are oxidized.

  Furthermore, in the cavity 11a (12a) of the forging die 10, C, which is a constituent element of alloy steel, C generated by decomposition of the reducing agent, and the first element powder react to generate carbide. The When at least one member selected from the group consisting of W, Ti, V, Mo, and Nb is added, these also form carbides.

  The generated carbide diffuses deep inside the cavity 11a (12a) of the forging die 10 while repeating decomposition and generation. That is, the generated carbide is immediately decomposed and returned to the first element powder, and in this state, the carbide moves relatively to the surface layer side.

  In this way, the carbide diffuses inside the cavity 11a (12a) of the forging die 10, and as a result, a diffusion layer 16 is formed as shown in FIG. 2C. The thickness of the diffusion layer, i.e., the diffusion distance of carbides, extends up to a depth of about 15 mm from the surface.

  Note that the carbide concentration gradually decreases, and a clear interface does not occur between the carbide diffusion reaching end portion and the forging die 10. Therefore, it is possible to avoid the occurrence of brittle fracture due to stress concentration at this portion, and thus the toughness of the cavity 11a (12a) of the forging die 10 in which the diffusion layer 16 is formed is ensured.

  In other words, in this case, it is possible to avoid an increase in brittleness due to the diffusion of the metal element. Therefore, even if the forging process is repeatedly performed, the forging die 10 is hardly damaged such as a crack. That is, the life of the forging die 10 can be extended.

  In addition, the hardness of the forging die 10 is improved in the region where carbide is present. As described above, according to the mold reinforcement method according to the present embodiment, since carbide exists deep inside the forging mold 10, the hardness and strength of the forging mold 10 are increased to the inside, As a result, the internal wear resistance is improved and deformation is difficult.

  Furthermore, when TiC, TiN, or the like is generated, the heat resistance of the metal is improved by a so-called carbide effect, and the strength of the metal is improved by a so-called carbide dispersion effect.

  The spider is continuously manufactured using a forging die 10 reinforced during the previous forging process. That is, warm forging or hot forging is repeatedly performed. However, as described above, since the forging die 10 is reinforced, the forging die 10 is prevented from being cracked or worn. Eventually, it becomes possible to produce a spider with excellent dimensional accuracy over a long period of time.

  The mold reinforcing method according to the present embodiment has been described in detail above. However, the present invention is not particularly limited to this embodiment, and the spirit of the invention described in the claims of the present invention. Various modifications can be made without departing from the scope.

  For example, the Fe-based alloy may be a structural alloy steel of SCM, SNC, SNCM, or SCr, or a structural steel of carbon steel or low carbon steel, in addition to the alloy steel.

  The die is not limited to the forging die 10 and may be a die provided for other than forging, such as a pressing die and a casting die.

It is a schematic perspective view of the die for forging in which the metal mold | die reinforcement method which concerns on this Embodiment is implemented. 2A to 2C are process explanatory views showing a reinforcing process of the forging die in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Forging die 11 ... Lower die 11a, 12a ... Cavity 12 ... Upper die 13 ... Brush 14 ... Mixed powder layer 15 ... Mold release agent 16 ... Diffusion layer

Claims (8)

A mixed powder having a first element powder having a property of increasing the hardness of a mold made of an Fe-based alloy by being carbideized and a second element powder having a melting point lower than that of the first element powder is at least reinforced to the mold. Covering the planned area;
The first element powder in the mixed powder is carbonized by heat-treating at least a region to be reinforced of the mold covered with the mixed powder using processing heat when processing a workpiece with the mold. And diffusing into the mold,
A mold reinforcement method comprising:   2. The mold reinforcing method according to claim 1, wherein the Fe-based alloy is a tool steel, a high-speed tool steel, a die steel, a powder steel alloy steel, a structural alloy steel of SCM, SNC, SNCM, or SCr, or a carbon steel. A method for reinforcing a mold, characterized by being a structural steel of low carbon steel.   3. The mold reinforcing method according to claim 1, wherein the first element powder is at least one of a group of Fe, Ni, and Co. 4.   4. The mold reinforcing method according to claim 1, wherein the second element powder is Al or an Al—Mn eutectic alloy. 5.   5. The mold reinforcing method according to claim 1, wherein a reducing agent for reducing an oxide film present on the surface of the Fe-based alloy is blended in the mixed powder. Mold reinforcement method.   6. The mold reinforcing method according to claim 5, wherein the reducing agent is carbon powder, resin, or Si.   The mold reinforcement method according to any one of claims 1 to 6, wherein at least one member selected from the group consisting of W, Ti, V, Mo, and Nb is added to the mixed powder. Reinforcement method.   The mold reinforcing method according to claim 1, wherein contact between the mixed powder and the workpiece is prevented by a mold release agent applied to an inner surface of the mold. Mold reinforcement method.

Images