JP5437669B2 - Hot and hot forging die - Google Patents

Description

  The present invention relates to a hot forging die.

  Conventionally, for example, various automobile parts and the like are formed by hot forging using a mold. Until now, tool steels such as matrix high speed have been widely used as mold materials. In addition to various tool steels, Ni-base heat-resistant superalloys such as Inconel 718 and Inconel X-750 may be applied as the mold material.

  In addition, for example, Patent Document 1 discloses an alloy having a composition in which Cr is 25 to 50% by weight, Al is 1.5 to 9% by weight, and the balance is substantially Ni, although it is not a hot forging die. A hot pressing mold in which is used as a mold material is disclosed. According to the document, the hot pressing method is a method in which metal powder filled in the mold is pressed while being heated to a predetermined temperature.

  In Patent Document 2, as a Ni-based alloy, by weight, C: 0.1% or less, Si: 2.0% or less, Mn: 2.0% or less, P: 0.03% or less, S : 0.01% or less, Cr: 30-45%, and Al: 1.5-5.0%, the balance having a Ni-based alloy composition consisting of inevitable impurities and Ni, A non-magnetic high-hardness alloy that has been subjected to warm plastic working and then aging treatment is disclosed.

JP-A 63-18031 JP 2006-274443 A

  However, conventionally known hot forging dies have the following problems. That is, the hot forging die is often used in a situation where a large mechanical and thermal load is applied. Particularly in the molding of automobile parts and the like, the molding load is very high, and the temperature difference between heating and cooling during molding is severe.

  When tool steel such as matrix high-speed steel is applied as the mold material, the mold forming surface is remarkably softened by the above-described heat load, and damage such as wear and heat check occurs. In addition, depending on the forging conditions, the mold forming surface may become a high temperature of 800 ° C. or higher, which may exceed the transformation point of the tool steel. Thus, when the temperature of the molding surface exceeds the transformation point, a re-quenched layer with low toughness is generated on the surface layer of the molding surface.

  For these reasons, the conventional hot forging die made of tool steel has a problem that the die life is short. When the die life is shortened, the die cost increases and the productivity decreases due to die replacement, thereby deteriorating the manufacturing cost of the forged product.

  In order to extend the mold life as much as possible, a cooling hole is formed in a hot forging mold made of conventional tool steel, and the mold is cooled through this hole to suppress the temperature rise of the mold. Things are also done. However, according to such a method, it is necessary to separately perform mold processing for forming a hole in the mold, and the mold cost is increased accordingly.

  As described above, the mold material made of iron having a transformation point near 800 ° C. has a limit to the correspondence. Therefore, it is considered effective to apply a Ni-base heat-resistant superalloy (Inconel 718 etc.) having no transformation point in this temperature range to the mold material.

  However, a mold made of a Ni-based heat-resistant superalloy such as Inconel 718 has low hardness in the cold. Therefore, buckling may occur during hot forging due to insufficient compression strength of the mold body. Therefore, there was a limit to the applicable range.

  In addition, diverting the hot press metal mold | die of patent document 1 to the metal mold | die for warm hot forging is also considered. However, this hot press die is optimized for the molding application of a powder material having a relatively small molding load. Specifically, there is a description that an alloy lump composed of 38% by weight of Cr and 3.8% by weight of remaining Ni was subjected to a solid solution treatment (agreement with a solution treatment) at 1200 ° C. for 60 minutes. However, as will be described later, since the solution treatment conditions are not appropriate, the crystal grain size becomes 0 or less and the toughness is lowered. Therefore, if it is diverted to a hot forging die that is often used in a situation where a large mechanical and thermal load is applied, the die may be greatly cracked, and it is difficult to divert as it is.

  This invention is made | formed in view of the said situation, The subject which this invention tends to solve is providing the metal mold | die for hot forging which can improve a die life compared with the past.

In order to solve the above problems, the hot forging die according to the present invention is in mass%, C: 0.1% or less, Si: 2.0% or less, Mn: 2.0% or less, Cr: 35 -40%, Al: 3.0 to 4.5%, the balance being formed from Ni and an inevitable impurity Ni-based alloy, and a solution temperature T ± 20 represented by the following formula (1) After the solution treatment is performed in the range of 1000 to 1250 ° C., the aging treatment is performed in the range of 700 to 820 ° C., and the hardness is 45 to 55 HRC.
Formula (1): T = -348.06 + 32.04Cr + 71.53Al
(T: Solution temperature (° C.), Cr, Al: Content (mass%))

  Here, the hot forging die according to the present invention preferably has a crystal grain size of 2 or more as defined in JIS G0551.

  In the hot forging die according to the present invention, the work material is preferably a billet.

Further, in the hot forging die according to the present invention, the Ni-based alloy may contain, by mass%, Fe: 5% or less (except when Fe is 1.0% or less). good.

Further, in the hot forging die according to the present invention, the Ni-based alloy is in mass%, Co: 2% or less (except when Co is 0.1% or less) , Mo: 2.5 % Or less (except when Mo is 0.1% or less) and W: 2.5% or less (except when W is 0.1% or less) or 1 or 2 It contains more than seed elements and may be Mo + 0.5W: 2.5% or less (except when Mo + 0.5W is 0.15% or less) .

Further, in the hot forging die according to the present invention, the Ni-based alloy is, in mass%, B: 0.0005% to 0.015%, Mg: 0.0005% to 0.01%, And Ca: You may contain 1 type, or 2 or more types of elements selected from 0.0005% or more and 0.01% or less.

Further, in the hot forging die according to the present invention, the Ni-based alloy contains one or more elements selected from Ti, Zr and Hf in an amount of 0.05% to 2.0% by mass. % Or less may be contained.

Further, in the hot forging die according to the present invention, the Ni-based alloy contains one or more elements selected from V, Nb and Ta in an amount of 0.2% to 2.0% by mass. % Or less may be contained.

Further, in the hot forging die according to the present invention, the Ni-based alloy is, by mass%, Cu: 2.0% or less (except in the case of 0.1% or less) , and REM: 0 One or two or more elements selected from 0.005% or more and 0.1% or less may be contained.

On the other hand, another hot forging die according to the present invention comprises a forging part having a forging surface at one end, a body part constituting the die body, and a joining part including a joining interface, , C: 0.1% or less, Si: 2.0% or less, Mn: 2.0% or less, Cr: 35-40%, Al: 3.0-4.5% , The gist is that the balance is formed of Ni and an inevitable impurity Ni-based alloy, the forged part has a hardness of 50 HRC or more, the body part has a hardness of 45 HRC or more, and the joint part has a hardness of 350 Hv or more.

  Here, the other hot forging die according to the present invention is preferably a reclaimed die regenerated using the above-described hot forging die according to the present invention.

  At this time, the body portion is preferably formed of a Ni-based alloy or matrix high-speed steel similar to the forged portion.

  Moreover, it is preferable that the presence rate of the oxide type and / or nitride type foreign matter in the bonded interface is 35% or less in the bonded portion.

  Further, when the body portion is a Ni-based alloy, heat treatment is performed within a range of 550 to 800 ° C., and when the body portion is matrix high-speed steel, heat treatment is performed within a range of 550 to 625 ° C. Is preferably applied.

  The hot forging die according to the present invention is formed from a Ni-base alloy containing a specific component in a specific ratio, and is tempered to a hardness of 45 to 55 HRC that cannot be obtained by a conventional general-purpose Ni-base alloy. Therefore, it has higher softening resistance, wear resistance, and strength than conventional hot forging dies. Moreover, the balance between hardness and toughness is improved by setting the solution treatment temperature to a condition suitable for the alloy component. Therefore, according to the hot forging die according to the present invention, the die life can be improved as compared with the conventional die. Further, in order to improve the mold life, it is not necessary to bother to form a cooling hole in the mold as in the prior art. Therefore, the mold cost can be easily reduced accordingly.

  Here, when the crystal grain size specified in JIS G0551 after the solution treatment is 2 or more, the hardness and the crystal grain size are optimized, and thereby high toughness with respect to the similar alloy shown in the prior patent. Can be demonstrated.

  Further, when the work material is a billet, the temperature of the mold is remarkably increased, and the molding load applied to the work material increases. This increases the thermal and mechanical load on the mold. When the hot forging die according to the present invention is used for such applications, it is advantageous because the above-mentioned effects are easily exhibited.

  Moreover, when the Ni-based alloy contains a specific ratio of Fe, the high temperature strength of the mold is easily maintained.

  Further, when the Ni-based alloy contains a specific ratio of one or more elements selected from Co, Mo and W and the value of Mo + 0.5W is within a specific range, the mold strength is improved. It becomes easy to let you.

  Further, when the Ni-based alloy contains one or more elements selected from B, Mg and Ca in a specific ratio, the hot workability of the mold material can be improved. . Therefore, it is excellent in mold manufacturability.

  Further, when the Ni-based alloy contains one or more elements selected from Ti, Zr and Hf in a specific ratio, the mold strength is easily improved.

  Further, when the Ni-based alloy contains one or more elements selected from V, Nb, and Ta in a specific ratio, the mold strength is easily improved.

  Further, when the Ni-based alloy contains a specific ratio of one or more elements selected from Cu and REM, the cold workability of the mold material can be improved. Therefore, it is excellent in mold manufacturability.

  On the other hand, another hot forging die according to the present invention comprises a forging part having a forging surface at one end, a body part constituting the die body, and a joining part including a joining interface, The forged part is tempered to a hardness of 50 HRC or more, the body part is 45 HRC or more, and the joint part is 350 Hv or more. Therefore, it has both plastic deformation resistance, wear resistance, and strength sufficient for practical use as a mold. Therefore, the other hot forging die according to the present invention can improve the die life.

  Here, when the other hot forging mold according to the present invention is a recycled mold regenerated using the above-described hot forging mold according to the present invention, the mold life is further improved. Can contribute.

  In addition, when the body portion is formed of a Ni-based alloy similar to the forged portion, since the softening resistance is high, it is easy to perform repetitive reproduction, and the die manufacturing cost can be easily reduced. In addition, since the mixing of components at the joint is reduced, the loss of material properties at the joint is reduced. Furthermore, compared to remelting the waste mold, it can be regenerated repeatedly with energy saving, so it is also environmentally friendly. On the other hand, when it is formed from the body part or the matrix high-speed steel, it is less softened by the heat treatment, and the strength is easily maintained. In addition, the use of matrix high-speed steel, which is less expensive than Ni-based alloys, makes it easier to reduce mold manufacturing costs.

  Further, when the abundance of oxide-based and / or nitride-based foreign matter at the joint interface of the joint is 35% or less, the joint strength is excellent, so that it can be applied to applications with a large mechanical load. It is advantageous.

  Further, when the body portion is a Ni-based alloy, heat treatment is performed within a range of 550 to 800 ° C., and when the body portion is matrix high-speed steel, heat treatment is performed within a range of 550 to 625 ° C. When it is, it is excellent in the hardness balance of each site | part of the said forge part, a trunk | drum part, and a junction part.

It is the figure which showed the relationship between Cr content and the hardness after solution treatment. It is the figure which showed the relationship between Al content and the maximum age hardness in 700 degreeC and 800 degreeC. It is the figure which showed the relationship between the hardness of an aging treatment material, and an aging treatment condition. It is the figure which showed the solution temperature T calculated from Formula (1) on the calculation state figure of a Ni-Cr-Al ternary system. It is the figure which showed the relationship between solution treatment conditions and crystal grain size. It is the figure which showed the relationship between an impact value, crystal grain size, and hardness. 2 is an SEM photograph showing a solution structure of the alloy of Example 1. 2 is an SEM photograph showing an aging structure of the alloy of Example 1. It is the figure which showed the softening resistance when performing the softening process at each temperature and each time about the test piece using the alloy of Example 1, and each test piece using the alloy of each comparative example. It is a figure for demonstrating the measuring method of the amount of punch wear in an abrasion resistance test. It is the figure which showed the hardness distribution of the depth direction from the forge surface of the small punch which concerns on Example 1 and each comparative example after an abrasion test. It is the figure which showed typically the punch shape used for shaping | molding of automotive components. It is the figure which showed typically the metal mold | die for other warm forging which concerns on one Embodiment of this invention.

  Hereinafter, a hot forging die according to an embodiment of the present invention (sometimes referred to as “main die”) and a manufacturing method thereof (also referred to as “main manufacturing method”), an embodiment of the present invention. Another hot forging die (sometimes referred to as “the second die”) according to the embodiment will be described in detail.

1. This metal mold | die The content rate of a specific component shall be in the range prescribed | regulated below, and the remainder is formed using Ni base alloy which consists of Ni and an unavoidable impurity. In the Ni-based alloy, the reason why the type and content of the specific component are specified is as follows. In addition, the unit of the following content rate is the mass%.

C: 0.1% or less C acts as a deoxidizing agent when dissolved. Further, when Ti, Zr, Hf, V, Nb, and Ta are present, carbides are formed with these elements, which suppresses crystal grain coarsening during solution heat treatment and contributes to strengthening of grain boundaries. When the C content exceeds 0.1%, the strength and toughness of the mold are reduced. Therefore, the upper limit of the C content is set to 0.01% or less. The upper limit of the C content is preferably 0.08% or less.

Si: 2.0% or less Si acts as a deoxidizer when dissolved. In order to obtain the effect, the lower limit of the Si content is preferably 0.05% or more, and more preferably 0.2% or more.

  However, the addition of a large amount of Si causes a reduction in the strength and toughness of the mold. Therefore, the upper limit of the Si content is set to 2.0% or less. The upper limit of the Si content is preferably 1.0% or less.

-Mn: 2.0% or less Mn is an element useful as a deoxidizer like Si. In order to obtain the effect, the lower limit of the Mn content is preferably 0.05% or more, and more preferably 0.2% or more.

  However, the addition of a large amount of Mn also causes a decrease in mold strength and toughness. Therefore, the upper limit of the Mn content is set to 2.0% or less. The upper limit of the Mn content is preferably 1.0% or less.

・ Cr: 35-40%
Cr is a main element that forms an α phase. High strength and high hardness can be obtained by precipitating the α phase with the γ phase in a lamellar form. Of course, Cr contributes to the improvement of corrosion resistance. In order to obtain the effect, the lower limit of the Cr content is set to 35% or more. The lower limit of the Cr content is preferably 37% or more.

  However, the addition of a large amount of Cr causes a decrease in workability. FIG. 1 shows the relationship between the Cr content of the Ni—Cr alloy and the solution treatment material. The solution hardness decreases as the Cr content decreases, and a hardness of Hv 200 or less can be obtained with a content of 40% or less. Therefore, the upper limit of the Cr content is set to 40% or less. The upper limit of the Cr content is preferably 39% or less.

-Al: 3.0-4.5%
Al is an important element for forming the γ ′ phase, and further contributes to improvement of high-temperature corrosion resistance. FIG. 2 shows the relationship between the Al content and the maximum hardness of the aging treatment material. The maximum hardness peak is shown when the Al content is 3.8%. Therefore, in order to obtain the hardness necessary for the mold, the lower limit of the Al content is set to 3.0% or more. The lower limit of the Al content is preferably 3.4% or more.

  However, the addition of a large amount of Al causes a decrease in workability. Therefore, the upper limit of the Al content is set to 4.5% or less. The upper limit of the Al content is preferably 4.2% or less.

  The Ni-based alloy constituting the mold may optionally contain the following elements in addition to the above constituent elements.

Fe: 5% or less Fe is an element that has a high possibility of being mixed as an impurity. Since Fe tends to lower the high temperature strength of the mold, it is preferable to keep the mixing amount as low as possible by examining the raw materials. However, if the Fe content is excessively reduced, the cost of the mold is increased. The upper limit of the allowable Fe content is 5% or less. The upper limit of the Fe content is preferably 3.0% or less. In addition, if Fe is 1.0% or less, it can be contained as an unavoidable impurity.

Co: 2.0% or less, Mo: 2.5% or less, and W: One or more elements selected from 2.5% or less, Mo + 0.5W: 2.5% or less Co Enhance the strength of the alloy by solid solution strengthening. Further, Co is that contribute to increase the amount of precipitation of gamma 'phase.

  However, the addition of a large amount of Co leads to an increase in cost of the mold. Therefore, the upper limit of the Co content is set to 2.0% or less. The upper limit of the Co content is preferably 1.0% or less. Note that Co can be included as an inevitable impurity if it is 0.1% or less.

  Mo increases the strength of the alloy by solid solution strengthening. Mo also contributes to the improvement of the corrosion resistance of the mold. In order to obtain the effect, the lower limit of the Mo content is preferably 0.2% or more.

  However, the addition of a large amount of Mo leads to an increase in cost of the mold. Therefore, the upper limit of the Mo content is set to 2.5% or less. The upper limit of the Mo content is preferably 1% or less. Mo can be included as an inevitable impurity if it is 0.1% or less.

  W increases the strength of the alloy by solid solution strengthening. In order to obtain the effect, the lower limit of the W content is preferably 0.2% or more.

  However, the addition of a large amount of W causes an increase in cost of the mold. Therefore, the upper limit of the W content is set to 2.5% or less. The upper limit of the W content is preferably 1% or less. If W is 0.1% or less, it can be included as an inevitable impurity.

  The value of Mo + 0.5W represents the rate at which the effects of adding Mo and W are added. When the value of Mo + 0.5 W is excessive, workability and high temperature corrosion resistance are impaired. Therefore, the upper limit of the value of Mo + 0.5W is set to 2.5% or less. The upper limit of the value of Mo + 0.5W is preferably 1% or less.

  The lower limit of the value of Mo + 0.5W is not particularly limited, but is preferably 0.2% or more from the viewpoint of improving the strength by solid solution hardening. Mo + 0.5W can be included as an inevitable impurity if it is 0.15% or less.

One or more elements selected from B: 0.015% or less, Mg: 0.01% or less, and Ca: 0.01% or less B, Mg, and Ca are all hot-worked Helps improve sex. Further, B is segregated at the grain boundaries to strengthen the grain boundaries, and also serves to increase the creep strength. Mg and Ca can also be added in consideration of deoxidation and desulfurization during dissolution. In order to obtain the effect, the lower limit of the B content is preferably 0.0005% or more, and more preferably 0.001% or more. The lower limit of the Mg content is preferably 0.0005% or more, and more preferably 0.001% or more. The lower limit of the Ca content is preferably 0.0005% or more, and more preferably 0.001% or more.

  However, the addition of a large amount of these elements decreases the hot workability. Therefore, the upper limit of the B content is set to 0.015% or less. The upper limit of the B content is preferably 0.01% or less, and more preferably 0.008% or less. Further, the upper limit of the Mg content is set to 0.01% or less. The upper limit of the Mg content is preferably 0.008% or less, and more preferably 0.005% or less. Further, the upper limit of the Ca content is set to 0.01% or less. The upper limit of the Ca content is preferably 0.008% or less, and more preferably 0.005% or less.

One or more elements selected from Ti, Zr, and Hf: 2.0% or less Ti, Zr, and Hf are dissolved in the γ ′ phase by substituting Al to form the γ ′ phase. It contributes to strengthening and has the effect of further increasing the strength of the alloy. Therefore, it is preferable to add in combination with Al. In order to obtain the effect, the lower limit of the content of these elements is preferably 0.05% or more, and more preferably 0.2% or more.

  However, when the total amount with Al becomes excessive, workability will deteriorate. Therefore, the upper limit of the content of these elements is set to 2.0% or less. The total content with Al is preferably 5% or less.

  Of these elements, Ti is the most effective element for improving the strength. The upper limit of the Ti content is preferably 2.0% or less, and more preferably 1% or less.

  Zr and Hf also have the effect of segregating at the grain boundaries and strengthening the grain boundaries. From the viewpoint of efficiently obtaining this effect, the upper limit of the content ratio of Zr and Hf is preferably 0.1% or less, and more preferably 0.05% or less.

One or more elements selected from V, Nb and Ta: 2.0% or less V, Nb and Ta are dissolved in the γ ′ phase by substituting Al for forming the γ ′ phase. It contributes to strengthening and has the effect of further increasing the strength of the alloy. Therefore, it is preferable to add in combination with Al. In order to obtain the effect, the lower limit of the content of V, Nb, and Ta is preferably 0.2% or more.

  However, when the total amount with Al becomes excessive, workability will deteriorate. Therefore, the upper limit of the V content is set to 2.0% or less. The upper limit of the content of V is preferably 1% or less, and more preferably 0.5% or less. Moreover, the upper limit of the content rate of Nb and Ta shall be 2.0% or less. The upper limit of the Nb and Ta content is preferably 1% or less, and more preferably 0.5% or less. If V is 0.1% or less, it can be included as an inevitable impurity.

-One or more elements selected from Cu: 2% or less and REM: 0.1% or less Cu improves cold workability. Furthermore, there is an effect of remarkably improving the sulfuric acid corrosion resistance. However, the addition of a large amount of Cu causes deterioration of hot workability. Therefore, the upper limit of the Cu content is set to 2% or less. The upper limit of the Cu content is preferably 1% or less. In addition, if Cu is 0.1% or less, it can be contained as an inevitable impurity.

  REM contributes to increasing the oxidation resistance at high temperatures. This effect is obtained mainly through a mechanism that suppresses peeling of the adhered scale. In order to obtain the effect, the lower limit of the REM content is preferably 0.005% or more, and more preferably 0.02% or more.

  However, addition of a large amount of REM leads to deterioration of hot workability. Therefore, the upper limit of the REM content is set to 0.1% or less. The upper limit of the REM content is preferably 0.08% or less.

This mold uses the Ni-based alloy as described above as a mold material. And this metal mold | die has the hardness of 45-55HRC. In addition, this mold has a crystal grain size of 2 or more by being subjected to a solution treatment within a range of a solution temperature T ± 20 ° C. represented by the following formula (1) within a range of 1000 to 1250 ° C. Yes.
Formula (1): T = -348.06 + 32.04Cr + 71.53Al
(T: Solution temperature (° C.), Cr, Al: Content (mass%))

  Here, the “hardness” is the Rockwell hardness of the mold material itself measured in the cold. The hardness is not affected by work hardening by cold working or various surface treatments, for example, the mold surface exposed by removing parts affected by work hardening or various surface treatments, It can be measured from inside the mold.

  The lower limit of the hardness of the die is preferably 47 HRC or more, more preferably 49 HRC or more, and even more preferably 51 HRC or more from the viewpoint of preventing plastic deformation during forging.

  The upper limit of the hardness of the present mold is preferably 54 HRC or less, more preferably 53 HRC or less, from the viewpoint of preventing cracking of the mold due to a decrease in toughness.

  The aging conditions for refining to the above-mentioned hardness can be determined from the relationship between the hardness and the aging treatment temperature shown in FIG. It can be seen that in order to obtain a hardness of 45 to 55 HRC, the treatment should be performed at an aging temperature of 820 to 700 ° C.

  The above equation (1) was determined as follows. In the calculation state diagram shown in FIG. 4, a region 10 ° C. lower than the boundary line between the γ phase and the γ + α phase is a point indicated by T in Equation (1). Based on this point, the following phenomenon was assumed. When solution treatment is performed at T ° C., spherical α-Cr dispersed and precipitated in the structure acts as a pinning effect and prevents coarsening of crystal grains. When the solution treatment is performed at a temperature exceeding T + 20 ° C., α-Cr is completely dissolved in the γ phase, no pinning effect appears, and the crystal grains become extremely coarse. Moreover, when solution treatment is performed at a temperature lower than T-20 ° C., the amount of α-Cr deposited becomes excessive, and the hardness during solution treatment increases. And the point shown in the calculation state diagram of FIG. 4 was plotted, and Formula (1) was calculated by the multiple regression equation.

  In order to verify the above assumption, after performing a solution treatment at 1000 to 1200 ° C. using an alloy of Cr: 38%, Al: x%, and Cr: y%, Al: 3.8%, The crystal grain size was confirmed. As an example, a photograph of a solution structure of an alloy having Cr: 38%, Al: 3.8% and Cr: 38%, Al: 4.2% is shown in FIG. T of these alloys is 1141 ° C. and 1170 ° C., respectively, from the formula (1). The solution treatment temperature is T-20 ° C. or lower in FIGS. 5 (a) and 5 (e), within T ± 20 ° C. in (b) (f) (g), and in (c) (d) (h). T + 20 ° C. or higher. In (a) and (e), the crystal grain size is No. 6, indicating a fine grain structure, but the hardness is 300 Hv or more, and the workability is reduced. In (b), (f), and (g), the crystal grain size is 2 to 6, and it can be said that the solution treatment conditions are appropriate. In (c) and (d), the crystal grain size is No. 1 or less, which will be described later, but this greatly deteriorates the toughness. Therefore, the optimum value of the solution treatment conditions of this mold was defined as the range of T ± 20 ° C.

  In addition, the above-mentioned “crystal grain size” test method conforms to JIS G0551. Specifically, by electrolytic solution corrosion with a 10% oxalic acid solution using a solution heat treatment method, the particle size is measured with a microscope.

  The material to be trained in the mold is not particularly limited, but preferably a billet or the like can be exemplified. When the work material is a billet, the temperature of the mold is remarkably increased, and the molding load applied to the work material increases. This increases the thermal and mechanical load on the mold. This is because the use of this mold for such a purpose is advantageous because it is easy to exert the effect of improving the mold life.

  In the present invention, the “billette” is a massive material having a substantially circular cross section or a substantially square cross section, and is used as a concept including a plate-like material.

  Examples of forged products formed using billets as the work material include automobile parts, electrical home appliance parts, and industrial machine parts. Among these, the present mold can be suitably used for forging of automobile parts and the like, in which the temperature of the mold is remarkably increased and the molding load applied to the work material is large.

  The mold shape of the present mold can be selected in consideration of the shape of the forged product to be molded. Examples of the mold shape of the present mold include punches, pins, dies, and the like. Preferably, in general, when a shape such as a punch or a pin, which tends to increase the temperature when it is struck against the work material and tends to shorten the die life, is selected, the effect of the present invention is particularly easily exhibited.

  The present mold is preferably a solid body in which a cooling hole is not formed in the mold. This is because if the hole for cooling is not formed in the mold in order to improve the mold life, the extra mold processing is reduced correspondingly and the mold cost is easily reduced.

In addition, since the softening resistance of conventional molds is small, a large amount of lubricant coating or mold cooling by water cooling or air cooling is necessary. However, since this mold has excellent softening resistance, a large amount of lubricant is required. There is no need to cool the mold by coating, water cooling or air cooling. In other words, it can be said that the present mold is a mold that does not require mold cooling or requires only a minimum.
More specifically, as a forging condition in the case of using the present mold, a minimum necessary amount of lubricant can be applied in a molding and mold portion where a lubricant is required. That is, the lubricant coating amount of the mold can be reduced by about 30 to 40% compared to the conventional lubricant coating amount. On the other hand, in molding and mold parts that do not require a lubricant, there is an effect that it is not necessary to perform water cooling and air cooling for mold cooling.

  From the viewpoints of improving toughness, improving heat check resistance, etc., the Ni-based alloy constituting the mold has a grain size number of preferably 2 or more, more preferably 4 or more, and still more preferably. , 6 or better.

2. Next, an example of the manufacturing method of this metal mold | die is demonstrated. First, a Ni-based alloy having the above-described chemical composition is prepared as a material for the mold.

  Specifically, each raw material is weighed so as to have the above-described chemical composition, and a Ni-based alloy ingot is melted using, for example, a melting furnace such as a vacuum induction furnace. After that, the obtained Ni-based alloy ingot is soaked as necessary, then hot forged, hot rolled, etc., and suitable for the production of dies such as bar materials, plate materials, block materials, coil materials, etc. What is necessary is just to form in a raw material shape.

  Next, a solution treatment is performed on the prepared material having a predetermined shape. This is because the material is softened to a hardness (about 20 HRC) that allows easy roughing of the mold. A large amount of processing strain is introduced into the material by plastic processing such as forging and rolling. When solution treatment is performed from this state, recrystallization occurs with strain as a nucleus. The larger the strain, the finer the crystal grain size after recrystallization.

The solution treatment needs to be performed within the range where the solution temperature T ± 20 ° C. represented by the following formula (1) is 1000 to 1250 ° C.
Formula (1): T = -348.06 + 32.04Cr + 71.53Al
(T: Solution temperature (° C.), Cr, Al: Content (mass%))

  The holding time is preferably 0.1 to 10 hours, more preferably 0.2 to 5 hours, and still more preferably 0.5 to 1 hour.

  Next, the material subjected to the solution treatment is roughly processed into a die shape such as a punch shape. The rough machining can be performed by mechanical cutting, electric discharge machining, or the like.

  Next, the obtained rough processed body is tempered to a hardness of 45 to 55 HRC. Specifically, the roughened body may be tempered by aging treatment. Specifically, for example, the temperature is preferably 700 to 820 ° C., more preferably 720 to 780 ° C., and still more preferably 740 to 760 ° C. Preferably, the time can be illustrated in the range of 1 to 40 hours, more preferably 5 to 30 hours, and still more preferably 10 to 20 hours.

  Next, the rough processed body having the tempered hardness is finely processed into a predetermined mold shape. The precision machining can be performed by mechanical cutting or the like.

  Basically, the present mold can be obtained through the above steps.

3. Second Mold FIG. 13 schematically shows the second mold. The second mold RP has a forged part A, a body part B, and a joint part C. The forging part A has a forging surface A1 at one end. The body part B constitutes a part of the mold body. The joint C includes a joint interface C1.

  FIG. 13A illustrates a case where a joint C is provided between the forged part A and the body part B. FIG. 13B illustrates the case where the joint portion C is provided between the forged portion A and the body portion B and between the body portions B. As described above, in the second mold RP, the joint portion C may exist between the forged portion A and the body portion B, or may exist between the body portion B. In the second mold RP, one or two or more body parts B and joints C may exist.

Here, as for this 2nd metal mold | die RP, the forging part A is the mass%, C: 0.1% or less, Si: 2.0% or less, Mn: 2.0% or less, Cr: 35-40% , Al: formed from a Ni-based alloy containing 3.0 to 4.5%. In the Ni-based alloy forming the forged part A, the remaining part may be Ni and inevitable impurities other than the above components, and contain one or more of the following component elements (mass%). Also good.
Fe: 5% or less,
Co: 2.0% or less,
Mo: 2.5% or less,
W: 2.5% or less,
B: 0.015% or less,
Mg: 0.01% or less,
Ca: 0.01% or less,
At least one selected from Ti, Zr and Hf: 2.0% or less,
At least one selected from V, Nb and Ta: 2.0% or less,
Cu: 2% or less,
REM: 0.1% or less,
However, Mo + 0.5W: 2.5% or less

  In addition, since the prescription | regulation reason of each component element, the suitable range of content rate, etc. are based on "1. this metal mold | die", detailed description here is abbreviate | omitted.

  Further, in the second mold RP, it is preferable that the body part B is formed of a Ni-based alloy (co-material) similar to the forged part A or matrix high-speed steel. When the body part B is formed of a Ni-based alloy similar to the forged part A, the softening resistance is high, so that it is easy to repeatedly reproduce, and the die manufacturing cost is easily reduced. This is because there is an advantage that the loss of material characteristics of the joint C is reduced because the component mixing is reduced. On the other hand, when the body part B is made of matrix high-speed steel, softening due to heat treatment is less and it becomes easier to maintain strength. By using matrix high-speed steel that is less expensive than Ni-based alloys, This is because there is an advantage that the mold manufacturing cost can be easily reduced.

  The shape of the second mold RP illustrated in FIG. 13 can be obtained, for example, as follows. First, the material of the forging part A is prepared (preparation process). At this time, it is preferable to prepare a used metal mold (as described in “1. Metal mold”) as a material of the forged part A. In this case, the mold life can be further improved by the above-described regeneration of the mold. Note that “used main mold” is a main mold used for forging, and a deteriorated portion such as wear or cracking is generated on the forged surface.

  Next, the deteriorated portion existing on the forged surface of the prepared mold is removed, and the surface is lowered so as to have the original forged surface shape (surface lowering step). A new forging surface A1 is exposed by this lowering. Examples of the surface lowering method include electric discharge machining, cutting, polishing, and the like, and these may be combined with one or more.

  Next, a die material such as a Ni-based alloy or matrix high-speed steel is joined to the rear end portion of the prepared die (joining step). As said joining method, friction welding, arc welding (TIG welding, PPW welding, etc.) etc. can be applied suitably, for example.

  At this time, it is preferable that the bonding portion C has an oxide-based and / or nitride-based foreign matter content of 35% or less at the bonding interface C1. This is because the bonding strength is excellent, which is advantageous for forging with a large mechanical load. The presence rate of the foreign matter is more preferably 20% or less, and further preferably 5% or less, from the viewpoint of reducing the starting point of fracture and improving the bonding strength.

  The foreign matter existence ratio is the total length M of foreign matters existing over the entire joining line observed by observing the cross section with an optical microscope after cutting in a plane direction substantially perpendicular to the joining interface C1. It can be calculated by dividing by the length L of the entire joining line (existence rate of foreign matter (%) = M / L × 100).

  Next, the excess portion of the bonded mold material is removed and shaped into the original mold shape (shaping step). Thereby, the shape of this 2nd metal mold | die RP shown to Fig.13 (a) is obtained.

  Moreover, in preparing the material of the forging part A, the second mold RP of FIG. 13 (a) that has been used is prepared, and after the above procedure, the metal shown in FIG. 13 (b) is obtained. A mold shape is obtained.

  In addition, although it demonstrated in order of the used mold preparation process-> surface lowering process-> joining process-> shaping process in the above, in addition, the used metal mold preparing process-> joining process-> surface lowering process-> shaping process It is also possible to follow this order. The former is preferred. This is because the mold materials are joined after the surface is lowered first, so that there is an advantage that the alignment at the time of the surface lowering is easy to perform, and the accuracy at the time of surface reduction is easily improved. However, it is also possible to prepare a die material made of the Ni-base alloy having the above-described chemical composition as the material of the forged part A. In this case, a die material such as a Ni-base alloy or matrix high-speed steel that becomes the body portion B may be joined to the prepared die material that becomes the forged portion A, and the entire shape may be shaped into a die shape. .

  In the second mold RP, the hardness of each part is tempered so that the forged part A is 50 HRC or more, the body part B is 45 HRC or more, and the joint C is 350 Hv.

  The “hardness” is the Rockwell hardness (forged part A, body part B) or Vickers hardness (joined part C) of the mold material itself measured in the cold. The hardness is not affected by work hardening by cold working or various surface treatments, for example, the mold surface exposed by removing parts affected by work hardening or various surface treatments, It can be measured from inside the mold.

  The lower limit of the hardness of the forged part A is preferably 50 HRC or more, more preferably 52 HRC or more, from the viewpoint of obtaining high wear resistance and making it difficult to plastically deform the forged surface.

  The upper limit of the hardness of the forged part A is not particularly limited, but is preferably 56 HRC or less, more preferably from the viewpoint of easily suppressing a sudden large crack by obtaining sufficient toughness. 54 HRC or less.

  The lower limit of the hardness of the body part B is preferably 45 HRC or more, more preferably 47 HRC or more, and further preferably 49 HRC or more, from the viewpoint of improving the effect of preventing plastic deformation due to forging load.

  The upper limit of the hardness of the body part B is not particularly limited, but is preferably 56 HRC or less, more preferably from the viewpoint of easily suppressing a sudden large crack by obtaining sufficient toughness. 54 HRC or less.

  The lower limit of the hardness of the joint C is preferably 350 Hv or more, more preferably 400 Hv or more, from the viewpoint that it is easy to suppress a change in the mold dimensions within the clearance range of the forged product even if the joint C is distorted. More preferably, it should be 450 Hv or more.

  The upper limit of the hardness of the joint C is not particularly limited, but is preferably 650 Hv or less, more preferably from the viewpoint of easily suppressing sudden large cracks by obtaining sufficient toughness. It is good that it is 550 Hv or less.

  In order to adjust the hardness to the above-described hardness, a predetermined heat treatment may be performed in accordance with the material of the body part B after the above-described shaping process. That is, when the body part B is a Ni-based alloy, the aging treatment is preferably performed within a range of 550 to 800 ° C, more preferably 600 to 770 ° C, and still more preferably 650 to 750 ° C. . On the other hand, when the body part B is matrix high-speed steel, the tempering treatment is preferably performed within a range of 550 to 625 ° C, more preferably 565 to 615 ° C, and still more preferably 585 to 605 ° C. .

Hereinafter, the present invention will be described more specifically with reference to examples.
1. Experiment 1
An alloy ingot having a chemical composition (mass%) shown in Table 1 was melted by vacuum melting. Next, the obtained alloy ingot was soaked and forged to obtain a bar having a diameter of 32 mm.

(Shock value)
In order to confirm the effect of the refinement of grain size on toughness, a Charpy impact test was conducted as follows. The test material used the alloy of the component shown by Example 1, 2, and 6 of Table 1, and gave the solution treatment of 2 levels with respect to said 32 mm rod. That is, the grain size was changed at two levels, a temperature within T ± 20 ° C. and a temperature exceeding T + 20 ° C. calculated by the above formula (1). After the solution-treated material was roughly processed, it was tempered to a hardness of 40 to 59 HRC by an aging treatment at 550 to 900 ° C. Thereafter, a 10R notch impact test piece having a shape of 10 mm × 10 mm × 55 mm in length was precisely processed and subjected to a Charpy impact test.
Table 2 shows the calculated value T, the applied solution treatment temperature, and the crystal grain size after solution treatment. From Table 2, it was confirmed that the crystal grain size of each test material was No. 2 or more for newly added symbols A1, B1, and C1, and less than No. 1 for A2, B2, and C2.
The result of the impact test is shown in FIG. The impact value required for a warm hot forging die is at least 40 J / cm ² . This value is cleared when the crystal grain size is 2 or more and the hardness satisfies the condition of 55 HRC or less. The fracture surface of the test material having a crystal grain size of less than No. 1 exhibits an aspect of grain boundary fracture, which is considered to be a cause of a low impact value. Further, at 56HRC or more, almost no dimples are observed on the fracture surface fractured in the grains, and it is considered that the impact value is low due to insufficient ductility.

(Softening resistance)
The softening resistance of each alloy was measured as follows. That is, solution treatment was performed on each of the forged bars described above under the conditions of a temperature T ° C. given by the above-described formula (1) and a holding time of 1 hour. From this, a 15 mm square cubic test piece was cut out. Next, the test piece using the example alloy applied to the mold of the present invention was subjected to an aging treatment at a temperature of 750 ° C. and a holding time of 16 hours, and tempered so that the hardness became HRC54. On the other hand, the test piece using the comparative alloy applied to the conventional mold was tempered to have the highest hardness. And about each of these test pieces, the Rockwell hardness (cold) before a softening process was measured previously using the Rockwell hardness meter.

  FIG. 7 shows the solution structure of the alloy of Example 1, and FIG. 8 shows the aging structure of the alloy of Example 1. As shown in FIG. 7, in the solution structure, the matrix phase was a γ phase, and precipitation of spheroidized α-Cr for pinning of crystal grains was observed. Further, as shown in FIG. 8, in the aging structure, a lamellar structure composed of two phases of α + γ on the entire surface, and fine γ ′ phase dispersion and precipitation were confirmed, though not clear in the structure photograph.

  Next, each test piece was softened by heating under the conditions of a temperature of 550 to 750 ° C. and a holding time of 1 to 100 hours. Next, the Rockwell hardness (cold) was measured for each test piece after the softening treatment using a Rockwell hardness meter. Table 3 shows the results when the softening treatment was performed at a temperature of 700 ° C. and a holding time of 1 hour. FIG. 9 shows the softening resistance when the softening treatment is performed at each temperature and each time for each test piece using the alloy of Example 1 and each test piece using the alloy of each comparative example.

  According to the results of Experiment 1, the following can be understood. That is, it can be seen that the conventional tool steel (the alloys of Comparative Examples 1 to 3) is significantly softened when heated to a temperature of 700 ° C. or higher. From this result, if the conventional tool steel is applied to the material for the hot forging die, the die forming surface is softened by the thermal load during molding, and the die life is shortened due to damage such as wear and heat check. I can easily imagine that.

  In addition, in a hot forging die using conventional tool steel, in order to suppress softening due to thermal load, if a hole for cooling is formed in the die, and the heating of the die is not suppressed as much as possible, It can be said that it is difficult to improve the mold life.

  On the other hand, it can be seen that general-purpose Ni-based alloys such as Inconel 718 (Comparative Examples 4 and 5) are not easily softened even when heated to a temperature of 700 ° C. or higher. However, these Ni-based alloys have a relatively low hardness in the cold. Therefore, if these Ni-based alloys are applied to the material for the hot forging die, it is expected that the die body will buckle during the hot forging due to insufficient compression strength of the die body. In particular, Ni-based alloys that have been widely used in the past are used for applications such as warm forging of automobile parts, etc., where a high forming load is applied and a billet that is a material to be formed is formed. It can be said that it is no longer difficult.

  On the other hand, the Ni-based alloy defined in the present invention hardly keeps softening even when heated to a temperature of 700 ° C. or higher, and can maintain a relatively high hardness in the cold. Therefore, if a hot forging die is formed using the Ni-based alloy defined in the present invention, an improvement in die life is expected. Therefore, in the following, a small hot forging die (small punch) was produced using each alloy, and a punch wear test was performed using this, and the die performance was actually confirmed.

(Abrasion resistance test)
Each bar having a diameter of 32 mm was subjected to a solution treatment under the conditions of a temperature T ° C. given by the above-described formula (1) and a holding time of 1 hour by the forging described above. The solution treated material was roughly processed, and then subjected to an aging treatment at 750 ° C., followed by precision processing, thereby producing each small punch according to the example and the comparative example. The produced small punch has a length of 104 mm and a body diameter of 16.2 mm, and the evaluation portion at the tip of the punch is tapered by 15 °. Prior to forging, the material hardness of each small punch was measured in advance using a Rockwell hardness meter.

  Next, each obtained small punch was attached to a 140 ton part former (manufactured by Daido Machine Co., Ltd., “NS5-10PL”), and warm forging was performed. The work material is a billet made of JIS S53C (a cylindrical shape having a diameter of 13.3 mm and a length of 28.3 mm). A cup-shaped forged product was produced from this billet in two steps.

  The first step is upsetting with a compression ratio of 54%, and the second step is backward extrusion. The forging speed was 85 spm, and the amount of cooling water from the outside of the punch was 60 m / s. The temperature of the work material was set to 930 ° C. at the end of the high-frequency heating and about 820 ° C. at the start of the first step.

  The wear amount of the rear extrusion punch was calculated from the shape change of the first shot and the 5000th shot. That is, as shown in FIG. 10, the amount of decrease in the punch radius at a position 0.2 mm from the tip of the punch P was defined as the wear amount R.

  In addition, for the small punch according to Example 1, in order to measure the softening amount of the molding surface of the punch after the above test, the punch was cut vertically, and the hardness distribution in the depth direction from the forged surface was measured by the Vickers hardness tester. (Load: 100 g) was used for measurement.

  Table 4 shows the measurement results of the material hardness and punch wear amount of each small punch according to the example and the comparative example. In FIG. 11, the hardness distribution of the depth direction from the forge surface of the small punch which concerns on Example 1 and each comparative example after an abrasion test is shown.

  These results show the following. That is, it can be seen that the small punches according to Comparative Examples 1 to 3 using conventional tool steel have relatively poor wear resistance and a short mold life due to softening of the punch surface.

  In addition, although the small punch which concerns on the comparative examples 4 and 5 using a general purpose Ni alloy tempered the alloy to the maximum hardness vicinity, alloy strength was not enough and buckling generate | occur | produced at the time of forging.

  On the other hand, it can be seen that the small punches according to the respective examples do not soften the punch surface and have relatively little die wear. From this, it was confirmed that the small punch according to the example can improve the mold life.

(Forming automotive parts)
In this example, a large punch capable of forming an automobile part (constant velocity joint part) was produced, and actual production hot forging was performed as follows.

  That is, an alloy ingot 1.3 ton having the chemical composition (mass%) of Example 1 shown in Table 1 was melted by vacuum melting. Next, the obtained alloy ingot was soaked and forged to obtain a bar having a diameter of 98 mm. Next, the obtained bar is subjected to a solution treatment to form a punch die having a roughly processed shape, and after being subjected to an aging treatment so that the hardness becomes HRC53, it is subjected to precision processing to obtain Example 1. Such a large punch was produced. As shown in FIG. 12, the produced large punch is a solid body having a length of 300 mm and a body portion diameter of 90 mm, and is not subjected to a nitriding treatment described later.

  On the other hand, a solid punch of the same shape made of SKH51 material (Comparative Example 1) tempered to HCR57 and nitrided on the surface was used for comparison. In actual production, a hollow body in which a cooling hole for suppressing high-temperature softening is formed from the punch rear end surface to the vicinity of the punch tip portion along the punch axis with respect to the conventional large punch according to Comparative Example 1 in actual production. This is referred to as Comparative Example 1 ′.

  Each of the prepared large punches was used for hot forging of automobile parts. At this time, with respect to the forging conditions of Example 1, from the viewpoint of suppressing the heat check, the application amount of the lubricant that also serves as cooling was set to the minimum necessary so as to suppress the thermal amplitude. The same conditions were applied to Comparative Example 1. In Comparative Example 1 ', for the purpose of suppressing the softening wear, the cooling condition that was generally performed conventionally was set to be enhanced. Specifically, the amount of lubricant applied was 1.5 times that of Example 1, and air was blown into the cooling holes of the punch for air cooling.

  As a result, it was confirmed that the large punch according to Example 1 had a mold life about 100 times that of Comparative Example 1. In addition, a mold life approximately three times as long as that of Comparative Example 1 'under the conventional conditions was obtained, and a dramatic improvement in mold life could be confirmed.

2. Experiment 2
As illustrated in FIG. 13A, each small punch according to an example and a comparative example having a forged part A, a joint part C, and a body part B in order was produced. The produced small punch has a total length of 104 mm, a diameter of 16.2 mm, a length of the forged part A of 30 mm, a length of the joint part C of 3 mm, and a length of the body part B of 71 mm. ° taper processing. The alloy composition of the forged part A and the body part B, the joining method of the forged part A and the body part B, the hardness of the forged part A, the joined part C and the body part B, and the heat treatment conditions after the small punch shaping will be described later. Are shown in Tables 5 to 8.

(Abrasion resistance test of forged part A)
The wear resistance test of the forged part A was performed in the same manner as in (1. Experiment 1) (Abrasion resistance test). When the wear amount R was less than 0.15 mm, “A” was evaluated as “Abrasion resistance was good”, and when the wear amount R was 0.15 mm or more, “B” was evaluated as “Inferior wear resistance” (Table below). 9).

(Tensile test)
A round bar having a diameter of 25 mm and a length of 120 mm according to an example having a forged part A, a joint part C, and a body part B in this order and a comparative example is manufactured under the same conditions as the small punch, and the joint part C is a test part from there. Thus, a tensile test piece having a test part diameter of 8 mm and a gauge distance of 34 mm was processed. The tensile test was performed according to JIS4. The case where the tensile strength is 1750 MPa or more is “A +” as “excellent bonding strength”, and the case where the tensile strength is within the range of 1150 MPa or more and less than 1750 MPa is “A” indicating that the bonding strength is good. When the tensile strength is in the range of 1000 MPa or more and less than 1150 MPa, “B” is assumed that the bonding strength is somewhat good, and “Bad strength is insufficient” when the tensile strength is in the range of less than 1000 MPa. As “C” (Table 9 described later).

(Compressive deformation test)
A body part B having a hardness of 45 HRC or more is “A” with excellent resistance to compression deformation, and a body part B having a hardness of less than 45 HRC is “B” with an inferior compression resistance. Evaluation was made (Table 9 described later).

  According to the results of Experiment 2, the following can be understood. That is, Comparative Examples 1 and 2 are inferior in wear resistance since the hardness of the forged part A is less than 50 HRC. This is because a high-hardness Ni-base heat-resistant alloy of less than 50 HRC was used for the forged part A.

  Since the hardness of the trunk | drum B is less than 45HRC, the comparative examples 3 and 4 are inferior to compression deformation resistance. This is because a high hardness Ni-base heat-resistant alloy and Fe-base alloy (hot die steel) of less than 45 HRC were used for the body part B.

  Since the hardness of the junction part C is less than 350 Hv, the comparative examples 5 and 6 are inferior in joining strength. This is thought to be due to the excessive thermal effect during friction welding.

  Comparative Examples 7 and 8 are inferior in wear resistance because the material of the forged part A is an Fe-based alloy (hot die steel).

  In Comparative Examples 9 and 10, since the material of the forged part A is a general-purpose Ni-based alloy (Inconel 718), a hardness of 45 HRC or higher cannot be obtained. Therefore, it is inferior to abrasion resistance. Moreover, it is also inferior to compression deformation resistance.

  In Comparative Example 11, the material of the body part B is hot die steel (SKD61). Since this hot die steel has low softening resistance, it is softened at the time of age hardening heat treatment, and a hardness of 45 HRC or more cannot be obtained. Therefore, it is inferior to compression deformation resistance.

  In Comparative Example 12, since the material of the body part B is a general-purpose Ni-based alloy (Inconel 718), a hardness of 45 HRC or higher cannot be obtained. Therefore, it is inferior to compression deformation resistance.

  Comparative Examples 13 and 14 are inferior in wear resistance because the forged part A has a hardness of less than 50 HRC. This is probably because the aging treatment temperature was too high.

  Since the hardness of the trunk | drum B is less than 45HRC, the comparative example 15 is inferior to compression deformation resistance. This is because a high-hardness Ni-base heat-resistant alloy of less than 45 HRC was used for the body part B. Moreover, the hardness of the junction part C is less than 350 Hv, and it is inferior also to joint strength.

  Since the hardness of the trunk | drum B is less than 45HRC, the comparative example 16 is inferior to compression deformation resistance and joint strength. This is because a high-hardness Ni-base heat-resistant alloy of less than 45 HRC was used for the body part B.

  Since the hardness of the junction part C is less than 350 Hv, the comparative example 17 is inferior to joining strength. This is thought to be because the thermal effect during arc welding was excessive.

  In Comparative Examples 18 and 19, since the welding material of the forged part A is an Fe-based alloy (hot die steel), high hardness cannot be obtained and the wear resistance is inferior. Moreover, the hardness of the junction part C is less than 350 Hv, and it is inferior also to joint strength.

  In Comparative Examples 20 and 21, since the welding material of the forged part A is a general-purpose Ni-based alloy (Inconel 718), a hardness of 45 HRC or higher cannot be obtained. Therefore, it is inferior to abrasion resistance. Moreover, it is also inferior to compression deformation resistance.

  In Comparative Example 22, the material of the body part B is hot die steel (SKD61). Since this hot die steel has low softening resistance, it is softened at the time of age hardening heat treatment, and a hardness of 45 HRC or more cannot be obtained. Therefore, it is inferior to compression deformation resistance. Moreover, the hardness of the junction part C is less than 350 Hv, and it is inferior also to joint strength.

  In Comparative Example 23, since the material of the body part B is a general-purpose Ni-based alloy (Inconel 718), a hardness of 45 HRC or more cannot be obtained. Therefore, it is inferior to compression deformation resistance.

  On the other hand, Examples 1-6 all have wear resistance, compression deformation resistance, and joint strength. That is, even if it has the forging part A, the joint part C, and the body part B, the material of the forging part is formed from a specific Ni-based alloy, and the hardness of each part is set to an appropriate range. It can be set as the metal mold | die which can be provided. Therefore, when a deteriorated part is generated in the so-called solid mold produced in Experiment 1, the deteriorated part is removed, and a mold having the structure, material, and hardness shown in Experiment 2 is newly regenerated. It was confirmed that the life could be further improved.

  Moreover, the following can be understood by comparing Examples of Experiment 2. That is, it can be seen that by forming the forged part A and the body part B from a common material, the loss of the material properties of the joint part is reduced, and a high joint strength can be obtained. Further, when the forged part A and the body part B are a co-material, when the forged part A disappears by repeatedly regenerating the die, the body part B in contact with the forged part A is processed into a new forged part A. Thus, a new regeneration mold can be constructed. Therefore, it can be said that it is easy to contribute to the improvement of the mold life.

  It was also confirmed that the bonding strength was excellent when the abundance of oxide-based and / or nitride-based foreign matter at the bonding interface of the bonding portion C was 35% or less.

  As mentioned above, although the hot forging die according to the present invention and the other hot forging die according to the present invention have been described, the present invention is not limited to the above-described embodiments and examples, and the purpose thereof Various modifications can be made without departing from the scope of the invention.

  For example, in the above embodiment, the hot forging die has a punch shape, but the hot forging die according to the present invention and the other hot forging die according to the present invention have a die shape or the like. The mold shape is not particularly limited.

Claims (10)

% By mass
C: 0.1% or less,
Si: 2.0% or less,
Mn: 2.0% or less,
Cr: 35-40%,
Al: containing 3.0 to 4.5%, the balance being formed from Ni and an inevitable impurity Ni-based alloy,
The solution treatment temperature T ± 20 ° C. represented by the following formula (1) is subjected to the solution treatment within the range of 1000 to 1250 ° C., and then the aging treatment is performed within the range of 700 to 820 ° C.,
A hot forging die having a hardness of 45 to 55 HRC.
Formula (1): T = -348.06 + 32.04Cr + 71.53Al
(T: Solution temperature (° C.), Cr, Al: Content (mass%))   2. The hot forging die according to claim 1, wherein the crystal grain size defined by JIS G0551 after the solution treatment is 2 or more.   The hot forging die according to claim 1 or 2, wherein the work material is a billet. 4. The Ni-based alloy according to claim 1, wherein the Ni-based alloy contains, by mass%, Fe: 5% or less (except when Fe is 1.0% or less). Mold for warm forging. The Ni-based alloy is, by mass%, Co: 2.0% or less (except when Co is 0.1% or less) , Mo: 2.5% or less (however, Mo is 0.1% or less) And W: 2.5% or less (excluding the case where W is 0.1% or less) , containing one or more elements selected from Mo + 0.5W: The hot forging die according to any one of claims 1 to 4, wherein the die is 2.5% or less (except when Mo + 0.5W is 0.15% or less) . The Ni-based alloy is, by mass%, B: 0.0005% to 0.015%, Mg: 0.0005% to 0.01%, and Ca: 0.0005% to 0.01%. The hot forging die according to any one of claims 1 to 5, comprising one or more elements selected from the group consisting of: The Ni-based alloy contains 0.05% or more and 2.0% or less by mass% of one or more elements selected from Ti, Zr and Hf. The hot forging die according to any one of the above. The Ni-based alloy contains one or more elements selected from V, Nb, and Ta in an amount of 0.2% to 2.0% by mass. The hot forging die according to any one of the above. The Ni-based alloy is, by mass%, Cu: 2% or less (except in the case of 0.1% or less) and REM: one selected from 0.005% or more and 0.1% or less The hot forging die according to any one of claims 1 to 8, comprising two or more elements. A forging part having a forging surface at one end, a body part constituting a mold body, and a joining part including a joining interface;
% By mass
C: 0.1% or less,
Si: 2.0% or less,
Mn: 2.0% or less,
Cr: 35-40%,
Al: containing 3.0 to 4.5% , the balance being formed from Ni and an inevitable impurity Ni-based alloy,
The hot forging die, wherein the forged part has a hardness of 50 HRC or more, the body part has a hardness of 45 HRC or more, and the joint part has a hardness of 350 Hv or more.