JPH11347678A - Composite die for hot forging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite die for hot forging advantageous to make a service life further longer. SOLUTION: In this hot forging, a flush fluid promoting zone K1 for promoting a flush fluid from a blank becoming a forging product and a flush fluid restraining zone K2 for restraining the flush fluid from the blank, are provided. A padding layer is properly used for the flush fluid promoting zone K1 and the flush fluid restraining zone K2. That is, in at least a part of the flush fluid promoting zone K1, a first padding layer which attaches importance to the security of hardness at a high temp., is built up and in at least a part of the flush fluid restraining zone K2, a second padding layer which attachs importance to the security of strength at a high temp., is built up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite forging for hot forging of a type in which a cladding layer is coated on a die body, and a composite for hot forging in which a flash as a flash is generated. Regarding the mold.

[0002]

2. Description of the Related Art Hot forging is performed at a high temperature, for example, from 1000 to 12 hours.
This is a method of forming a metal material that is plastically processed into a shape close to the finished product by pressing a rough material heated to 00 ° C by pressing means such as mechanical or hydraulic pressure, and has excellent production efficiency and economic efficiency. It is widely applied to the production of automobile parts and the like because of its molding method. A hot forging die is used for hot forging. Since hot forging dies are subjected to severe mechanical and thermal stresses in order to perform plastic deformation at high temperature and pressure in a short time, the characteristics required for mold materials from the viewpoint of durability are strict. 1) to (3) are required. (1) High temperature strength and toughness to withstand loads such as high mechanical pressure and thermal stress. (2) It has excellent high-temperature wear resistance to withstand sliding abrasion caused by flashing from coarse materials at high temperature and high pressure. (3) Excellent heat check resistance by thermal cycling. Heat check refers to micro-cracks similar to the turtle shell.

[0003] are required. In particular, it is required that the mold has excellent resistance to high-temperature wear, which is a major factor in determining the life of the hot forging die. by the way,
Conventionally, JIS-SK has been used as a standard hot forging die material.
D61-based hot working alloys (hereinafter, also simply referred to as "SKD61-based alloys") are widely used. SKD61
The main types of damage observed in hot forging dies using a base alloy include die wear damage due to flash friction sliding, die heat check damage, and die crack damage.

[0004] Abrasion damage of the hot forging die at a high temperature is caused by plastic flow on the surface of the die during molding of the heated rough material, and sliding of the oxidized layer having high hardness generated by heating. It is said to be a surface damage phenomenon. In addition, heat check damage of hot forging dies is said to be a thermal fatigue phenomenon due to repeated heating and cooling of the die surface,
Since it is a kind of high-temperature plastic fatigue phenomenon, it is said that if there is toughness within a predetermined limit, it will be improved.

For this reason, conventionally, the following measures have been devised as a general method to extend the life of the hot forging die. For example, in a hot forging die requiring high temperature wear resistance, a forged material of an SKD61-based hot working alloy is used for the die body, and the surface hardness of the die is increased by quenching and tempering, or For example, a nitride layer is formed. Further, as a countermeasure against the above-mentioned damage in the hot forging die, in recent years, formation of a build-up layer partially at a damaged portion of the hot forging die has been performed.

As a mold technology in which a buildup layer is partially formed, conventionally, a cobalt-based buildup is provided on the cutting edge of a steel-based punch die for hot-punching a flash which is a flash of a forged product. A technique in which a layer is partially coated to form a composite is also known (JP-A-62-28997). Furthermore, there is also known a technique in which a cutting edge of a punch die for punching a forged product is partially covered with a hardfacing layer for improving abrasion resistance to form a composite (see Japanese Utility Model Application Laid-Open No. Hei 4-4-2). 1733
No. 6).

Further, as a form in which the build-up layer is used entirely, conventionally, when the molding cavity mold surface and the flash flow surface of a forging die are damaged, the damaged mold cavity mold surface and the flash flow surface are completely covered. There is known a technique called an Eureka method in which a build-up layer is laminated, and the build-up layer is engraved to newly form a molding cavity mold surface and a flash flow surface.

[0008]

SUMMARY OF THE INVENTION The present invention is a further development of the above-mentioned build-up of the build-up layer, in which a flash flow promoting region where flash considerably flows and a surface pressure at the time of forging tend to increase. An object of the present invention is to provide a composite die for hot forging, which is advantageous for prolonging the service life by using different materials for the build-up layer in the flash flow suppression region.

[0009]

SUMMARY OF THE INVENTION A composite mold for hot forging according to the present invention comprises: a flash flow promoting region for promoting the flow of flash from a rough material to be a forged product; In the composite mold for hot forging, which has a flash flow suppression area that suppresses and covers the mold body with a build-up layer, the build-up layer is selectively used for the flash flow promotion area and the flash flow suppression area. And at least a portion of the flush flow promotion region
The build-up layer is built-up, a second build-up layer is built-up in at least a part of the flash flow suppression area, and the alloy forming the first build-up layer is made of high-temperature wear resistance, and the second build-up layer is used. The alloy constituting the layer is characterized by emphasizing high-temperature strength.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The flash flow promoting region means a region for promoting the flow of flash which is a burr from a coarse material during forging. The flush flow promotion area is
Since the flow of the flash from the coarse material is promoted, it can effectively contribute to suppressing an excessive pressure load acting on the die-sinking surface of the hot forging die. The flash flow suppression region means a region that suppresses the flow of flash from the coarse material as much as possible during forging. The flash flow suppressing region suppresses the flow of the flash, so that it can effectively contribute to the filling of the coarse material in the product cavity and the suppression of the underfill. According to the present invention, the first buildup layer is built up on at least a part of the flash flow promoting region. A second build-up layer is built up on at least a part of the flash flow suppression region.

The alloy constituting the first build-up layer places an emphasis on ensuring high-temperature wear resistance in order to cope with the sliding friction of the flash. Generally, the alloy forming the second build-up layer is more important than the alloy forming the second build-up layer. Excellent high temperature wear resistance. The alloy forming the second build-up layer emphasizes high-temperature strength to cope with a large pressure load, and generally has higher high-temperature strength than the alloy forming the first build-up layer. It is preferable that the alloy forming the second build-up layer has better impact strength than the alloy forming the first build-up layer.

Therefore, according to one embodiment of the present invention, the first
As the alloy constituting the build-up layer, an alloy having excellent high-temperature wear resistance, for example, a Co-based stellite alloy can be used.
As a Co-based stellite-based alloy, C:
0.35 to 1.10%, Si: ≦ 1.5%, Mn: ≦
1.5%, Ni: ≤3.0%, Cr: 26.0 to 32.
0%, Mo: 0.5 to 6.0%, W: 0.5 to 6.0%
It is possible to adopt an alloy containing and having a prescribed composition such as Co and inevitable impurities.

Here, the composition limitation of the stellite alloy will be described. That is, C combines with Cr, Mo, and W to form carbides, thereby improving high-temperature hardness and heat softening resistance. However, when the amount of carbon is too small, the build-up property is reduced, and when the amount is excessively large, the build-up property is improved but the toughness tends to be reduced. Therefore, C is preferably in the above range. In the case of stellite cladding alloys which further improve toughness and further improve heat check resistance, 0.35-0.
Carbon can be reduced to as low as 65%. Further, in a stellite-based cladding alloy that balances high-temperature wear resistance and toughness, carbon can be increased as much as 0.80 to 1.10%. In this specification,% unless otherwise specified is% by weight.
Means

Although Si is effective as a deoxidizing agent and improves the build-up property. Since the toughness is likely to be reduced when the content is large, the above range is preferable. Mn stabilizes austenite, is also effective as a deoxidizing agent, and improves the build-up property. However, the higher the content, the easier the toughness is to be lowered, so the above range is preferable. In the cobalt-based alloy according to the present invention, Ni is considered to be basically an impurity element.

[0015] Cr improves heat resistance and corrosion resistance at high temperatures and also reacts with C in the weld overlay to form carbides to improve high temperature hardness and heat softening resistance.
However, if the content is excessive, the toughness is easily reduced, for example, the precipitation of the σ phase is easily promoted at a high temperature, and the heat check resistance is liable to be disadvantageous. Therefore, the above range of Cr is preferable.

Mo and W each have substantially similar effects, react with C to form carbides, and improve the high-temperature hardness, fatigue strength, and heat softening resistance of the Co-based stellite system. However, if Mo or W is excessive, not only the weld build-up tends to occur at the time of weld build-up, but also the build-up property is lowered, as well as the toughness and heat check resistance of the build-up layer. Therefore, Mo and W are set in the above range.

Further, as the alloy constituting the second build-up layer provided in the flash flow suppression region, an alloy excellent in high-temperature strength, for example, a Ni-based superalloy (superalloy) can be adopted. As the composition of the Ni-based superalloy, a composition containing at least 40 to 70% of Ni, 12 to 30% of Cr, and 2 to 5% of Mo can be adopted. Here, the amount of Ni was defined in consideration of solid solution strengthening in the matrix. The amount of Cr was specified in consideration of oxidation resistance and weld crack resistance. The amount of Mo was defined in consideration of securing high temperature strength and ductility (toughness). Creep strength at high temperatures and harmful phases (eg σ
It is preferable that an appropriate amount of Nb is contained in consideration of prevention of precipitation of the phase).

According to another embodiment of the present invention, the first
Both the alloy forming the build-up layer and the alloy forming the second build-up layer may be a Co-based stellite alloy, and the composition thereof may be changed according to the required characteristics. In this case, the following can be performed. That is, the composition of the stellite-based alloy constituting the first build-up layer, which is required to have higher-temperature wear resistance than the second build-up layer, is as follows:
C: 0.80 to 1.10%, Mo: 0.5 to 5.0%, particularly 0.5 to 2.0%, W: 2.0 to 4.0%.
In this case, the amount of carbon and the amount of W are high, and the softening hardness under heating and the high-temperature hardness can be ensured while ensuring the weld overlaying property, and the toughness is relatively high. Therefore, high-temperature wear resistance can be improved while ensuring heat check resistance. In the stellite-based alloy constituting the first build-up layer, (Mo + W) is 2.0 to 5.0% or 5.0 to 5.0 in order to obtain good high-temperature wear resistance.
8.0%.

[0019] A second device provided in the flash flow suppression region
When the build-up layer is made of a stellite-based alloy, its composition is as follows:
0.35 to 0.65%, Mo: 0.5 to 2.0%, W:
0.5% to 2.0%. In this case, the carbon content, W
The amount is relatively low, and while securing the weld overlay, the high-temperature strength, toughness, and impact strength can be increased while reducing the high-temperature wear resistance. Further improvement can be achieved. In the stellite alloy constituting the second build-up layer, (Mo + W) is 1.0 to 3.0 in order to give priority to ensuring high-temperature strength over high-temperature wear resistance.
0%.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Structure of Embodiment) An embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a high temperature (for example, 800 to 1)
In this method, a rough ground forging is hot-formed from a carbon steel-based rough material heated to 200 ° C.). Wasteland forgings are wasteland forgings of crankshafts.

FIG. 1 shows a first die 10 as an upper die constituting a forging die which is a composite die according to the present embodiment. FIG.
2 shows a cross section along the line AA in FIG. 1. FIG. 3 shows a second die 30 serving as a lower die constituting the forging die. FIG. 4 shows B in FIG.
4 shows a cross section taken along line -B. FIG. 5 shows a section taken along line CC of FIG. FIG. 6 shows a cross section along the line DD in FIG.

As shown in FIG. 1, the first mold 10 has a product cavity 11, a first flush surface 13 provided around the product cavity 11 for flowing a flash from a coarse material, and a product cavity 11. And a first inclined surface 15 provided in the vicinity of the periphery. As shown in FIG. 1, the product cavity 11 has a long shaft end journal cavity portion 11.
a, a short shaft end journal cavity 11b, an intermediate journal cavity 11c, a counterweight cavity 11d, and a pin cavity 11e.

When the rough material is forged in rough terrain, the first inclined surface 15 functions as a wall for suppressing the flow of flashes, which are burrs from the coarse material, together with the second inclined surface 35 in a clamped state. is there. As shown in FIG.
The inclined surface 15 approaches the counterweight cavity 11d via the distance L1. Therefore, on the first flash surface 13, the periphery of each counter weight cavity portion 11d is a flash flow suppression region K2 that restricts the flow of the flash from the coarse material to the outside.

As shown in FIG. 1, the first inclined surface 15 is not formed in front of the long shaft end journal cavity portion 11a. The distance L2 between the lateral side of the shaft end journal cavity 11a and the first inclined surface 15 is relatively large (L
2> L1). Therefore, the periphery of the long shaft end journal cavity portion 11a is a flash flow promoting region K1 for promoting the flow of the flash. The first inclined surface 15 is not formed in front of the short shaft end journal cavity portion 11b. Short shaft end journal cavity 11
The distance L3 between the side of b and the first inclined surface 15 is relatively large (L3> L1). Therefore, a portion around the short shaft end journal cavity portion 11b of the first flush surface 11 is a flush flow promoting region K1 for promoting flush flow.
It has been.

FIG. 3 shows a second die 30 as a lower die constituting a forging die which is a composite die according to the present embodiment. As shown in FIG. 3, the second mold 30 is provided with a product cavity 31, a second flash surface 33 provided near and around the product cavity 31 for flowing a flash, and provided near the product cavity 31. And a second inclined surface 35.
The product cavity 31 has a long shaft end journal cavity 31a and a short shaft end journal cavity 31b.
, An intermediate journal cavity 31c, a counterweight cavity 31d, and a pin cavity 31e.
With

When the coarse material is forged, the second inclined surface 35, together with the first inclined surface 15, suppresses the flow of the flash. As shown in FIG. 3, the second inclined surface 35 is disposed close to each counter weight cavity 31d via a distance M1. Therefore, the second flash surface 3
3, the periphery of the counterweight cavity 31d is a flash flow suppression region K2 for suppressing the flow of flash from the coarse material.

As shown in FIG. 3, the second inclined surface 35 is not formed in front of the long shaft end journal cavity portion 31b. The distance M2 between the lateral side of the shaft end journal cavity portion 31b and the second inclined surface 35 is relatively large (M2
> M1). Therefore, the periphery of the long shaft end journal cavity portion 31a in the second flush surface 33 is a flush flow promoting region K1 for promoting the flow of the flush. The distance M3 between the lateral side of the short shaft end journal cavity portion 31b and the second inclined surface 35 is relatively large (M3>
M1). Therefore, a portion of the second flush surface 33 around the short shaft end journal cavity portion 31b is a flush flow promoting region K1 for promoting the flow of the flush.

According to the present embodiment, as shown in FIG. 1, in the first die 10, around the long shaft end journal cavity portion 11a constituting the flush flow promoting region K1,
First overlay layers 51 (regions indicated by hatching) are stacked. Similarly, of the first mold 10, the short shaft end journal cavity portion 1 constituting the flush flow promoting region K1
A first buildup layer 51 (a region indicated by hatching) is stacked around 1b. As shown in FIG.
Among them, the second build-up layer 52 (the filled area) is stacked around the long counterweight cavity 11d constituting the flash flow suppression area K2.

As shown in FIG. 3, in the second mold 30, around the long shaft end journal cavity portion 31a constituting the flash flow promoting region K1, the first buildup layer 5 is formed.
1 (areas indicated by hatching) are stacked. Similarly, in the second mold 30, around the short shaft end journal cavity portion 31b constituting the flow promoting region K1, the first
Overlay layers 51 (areas indicated by hatching) are stacked. As shown in FIG. 3, in the second die 30, a second buildup layer 52 (solid area) is stacked around the counterweight cavity 31 d that forms the flash flow suppression area K2.

The first build-up layer 51 emphasizes ensuring high-temperature wear resistance, and is a stellite-based Co-based alloy that is more excellent in high-temperature wear resistance than the alloy constituting the second build-up layer 52. That is, it is formed by building up a stellite-based Co-based alloy having a good balance between high-temperature hardness and toughness while increasing high-temperature hardness. In addition, the second build-up layer 52 places importance on high-temperature strength and deformation resistance at high temperatures, has higher high-temperature strength than the alloy constituting the first build-up layer 51, and has high resistance to thermal deformation. Further, it is formed by building up a Ni-based superalloy having a high impact strength.

According to this embodiment, as shown in FIG. 2, the first built-up layer 51 was laminated as follows. That is, after forming a groove with a minimum depth in a corresponding portion by cutting, the underlaying material 50 of the austenitic stainless steel is formed in the groove.
(18Cr-8Ni-based, JIS-Y308 equivalent) 1
Add layers. Then, on the underlaying material 50, the first overlay 51
Was coated. The bondability of the first build-up layer 51 made of a stellite-based alloy whose build-up property is not always good is
Reserved by 0. The same procedure is performed for the second buildup layer 52 using the lower buildup material 50.
Was secured.

In this embodiment, as can be understood from FIG. 2, the build-up layer 51 is provided at the boundary between the flash surfaces 13, 33 and the engraved surfaces of the journal cavities 11a, 31a (11b, 31b). ing. As can be understood from FIG. 6, the second cladding layer 52 is formed on the flash surfaces 13, 33.
A shoulder radius portion 42 is provided at the boundary between the counterweight cavity portions 11d and 31d and the engraved surfaces.

Further explanation will be given. FIG. 6 shows the vicinity of the counterweight cavities 11d and 31d. Since the counterweight cavities 11d and 31d are deeply carved, it is required that the filling material of the coarse material W be high in filling and that the underfilling hardly occurs. In consideration of these factors, the flow of flash from the coarse material W is considerably suppressed in the vicinity of the counterweight cavities 11d and 31d. As described above, since the flow of the flash from the rough material W is suppressed, it can be said that the sliding wear caused by the flash is relatively small in the flash surfaces 13 and 33 in the vicinity of the counter weight cavities 11d and 31d.

However, since the counter weight cavities 11d and 31d have deep depths H1 and H2 and a small thickness DA (see FIG. 6) between the counter weights,
Poor surface pressure balance during forging. Further, the flow of the flash from the coarse material on the flash surfaces 13 and 33 is suppressed by the first inclined surface 15 and the second inclined surface 35. Therefore, at the time of forging, the counterweight cavity portion 11d,
The surface pressure related to the 31d shoulder round portion 42 is considerably high. Further, the counterweight cavities 11d and 31 are narrow and deep.
Since d is a portion that has little heat radiation in terms of shape, the mold surfaces of the counterweight cavities 11d and 31d are likely to become hot, and a lubricant is also fixed to the mold surface of the narrow and deep counterweight cavities 11d and 31d. Hateful. For this reason, in the counterweight cavities 11d and 31d where the surface pressure tends to increase, especially in the shoulder radius portion 42, the strength of the mold surface tends to decrease due to the softening of the mold surface, and plastic flow of the coarse material occurs. As a result, the surface of the mold tends to cause plastic flow relatively. According to the present embodiment, of the flash surfaces 13 and 33, in the vicinity of the counterweight cavities 11d and 31d having such circumstances, particularly in the vicinity of the shoulder radius portion 42,
As can be understood from FIG. 6, a Ni-based superalloy having higher high-temperature strength than the alloy forming the first overlay layer 51 and having high resistance to deformation at high temperatures is used as the second overlay layer 52 as described above.
Is overlaid on the undercoat material 50.

In this embodiment, the shaft end journal cavities 11a, 11b and 31
a, 31b, the flash F from the coarse material W
Since the flow of L is promoted, as can be understood from FIG. 4, the flash FL slides along the arrow direction S1. Further, as the mold temperature rises, it is affected by the hard oxide film FO formed on the surface of the rough material, and the sliding wear caused by the flash FL becomes severe, and the abrasion along the sliding direction of the flash FL occurs. It easily appears as a mark α (see FIG. 5).

However, according to the present embodiment, a stellite alloy having a higher temperature hardness and a higher resistance to softening by heating than the second build-up layer 52 is used as the first build-up layer 51 beforehand. Prevention of progress of wear marks α,
It is advantageous for delay. By experience, the life of a hot forging die for a crankshaft is determined mainly by the vicinity of the counterweight cavities 11d, 31d, the shaft end journal cavities 11a, 11b and 31a, 31.
Damage near b. Therefore, in the present embodiment, in consideration of the cost and the like, neither the first build-up layer nor the second build-up layer is formed around the pin cavities 11e and 31e in the flash surfaces 13 and 33.

In the present embodiment, the alloy constituting the first buildup layer 51 for which high-temperature wear resistance is required is expressed in terms of% by weight.
C: 0.35 to 1.10%, Si: ≦ 1.5%, Mn:
≦ 1.5%, Ni: ≦ 3.0%, Cr: 26.0-3
2.0%, Mo: 0.5-6.0%, W: 0.5-6.
It is a Co-based stellite alloy containing 0% and having a specified composition such as the balance of Co and unavoidable impurities.

As the Ni-based superalloy constituting the second build-up layer 52, Ni is 40 to 70%, Cr is 12 to 30%,
Mo is 2 to 5%, C is 0.01 to 0.1%, Nb is 1 to
7%, and a composition containing Ti, Al, and Fe as appropriate. (Effects of Embodiment) As described above, according to the present embodiment, the overlay layer is selectively used in the flash flow promotion region K1 and the flash flow suppression region K2. That is,
Co is contained in at least a part of the flash flow promoting region K1.
The first buildup layer 51 made of a base stellite-based alloy is built up, and at least a part of the flash flow suppression region K2 is made of a second buildup layer made of a Ni-based superalloy.
The cladding layer 52 is clad, and the alloy forming the first cladding layer 51 places importance on high-temperature wear resistance, and the second cladding layer 5
2 is superior to the high-temperature wear resistance of the alloy composing No. 2. The alloy forming the second build-up layer 52 emphasizes high-temperature strength and deformation resistance at high temperatures, and is superior to the alloy forming the first build-up layer 51 in high-temperature strength and deformation resistance at high temperatures. .

According to the present embodiment, the flash flow promoting region K1 in which the sliding friction due to the flow of the flash is intense is protected by the first overlaying layer 51 having good high-temperature wear resistance. Further, the flash flow suppression region K2 in which the surface pressure tends to be excessively large during forging is protected by the second overlay layer 52 having good high-temperature strength and high deformation resistance at high temperatures. That is, since the buildup layer is formed of an alloy having characteristics according to the damage form for the damage form that differs depending on the portion of the hot forging die, the hot forging according to the hot forging die, This is advantageous for improving the life of the composite mold for use.

In a hot forging die for forging a crankshaft, one of the causes of the die life is as follows.
A crack at the bottom of e, 31e may also be mentioned. As can be understood from FIG. 7, at the time of forging, the mechanical load P due to the forging load is applied to the pin cavity portions 11e and 31e.
e is loaded almost perpendicularly to the engraving surface. Assuming that the friction coefficient is μ, a frictional force (P × μ) acts along the tangential direction of the engraved surface due to the frictional force between the rough material and the engraved surface, and as a result, the pin cavities 11e and 31e It is presumed that a crack CA is generated and grows at the bottom of the die-cut surface. In the present embodiment, in order to prevent such mold cracking of the engraved surfaces of the pin cavities 11e and 31e, in the present embodiment, the base material constituting the mold body constituting the first mold 10 and the second mold 30 is tough. Since a material having high fracture toughness (e.g., a material equivalent to JIS SKT-4) is used, it is advantageous for extending the life of the mold body.

(Test Examples) Mold materials of the present invention shown in Table 1
Were prepared and tested. Further, the comparative mold materials conventionally used were similarly tested. The comparative mold material is a material equivalent to JIS SKT-4.
The comparative mold material is a DAC10 equivalent material. The comparative mold material is a material equivalent to SKD61. The comparative mold material is DAC10
This is a material which has been subjected to hardness increasing treatment, that is, quenching and tempering. The comparative mold material is obtained by subjecting a material equivalent to SKD61 to a hardness increasing process, that is, quenching and tempering.

[0042]

[Table 1]

[0043]

[Table 2]

As shown in Table 1, the build-up welding material of the mold material of the present invention is a Co-based stellite-based alloy and has a C content of 0.1%.
5%, Mo is contained 1.0%, and W is contained 1.0%. The build-up welding material of the mold material of the present invention is a Co-based stellite-based alloy, in which C is 0.6%, Mo is 4.2%, and W is 3.0%.
Contains 3%. The cladding layer of the mold material of the present invention is a Co-based stellite-based alloy, in which C is 1.0% and Mo is 1.1.
% And W are contained in 3.4%.

In this test example, a test piece was formed as follows. In the mold material of the present invention, a round bar formed of each overlay welding material is used as a welding rod for overlay. Further, while using a tungsten electrode, the long groove 2a shown in FIGS.
Using a metal body 2 having
By TIG welding, overlay welding is performed on the long groove 2a and the overlay 4
Was formed. Thereby, the overlay test piece 6 was manufactured. As build-up properties in the production of the build-up test piece 6, welding build-up properties and welding crack resistance were evaluated. Welding overlay is 4
Was determined by observing the poor penetration in an optical microscope. The weld cracking resistance is determined by determining the presence or absence of cracks in the build-up layer 4 by a color check test in which a penetrating liquid is brought into contact with the build-up layer 4 before cutting the slice. The boundary between the buildup layer 4 and the metal body 2 was determined by observation with an optical microscope.

Further, after removing the excess build-up portion of the build-up layer 4 of the build-up test piece 6, the build-up test piece 6 was slice-cut to form a large number of samples. Thereafter, for the overlay 4 of a certain sample, the room temperature hardness (Vickers hardness: load 2)
0 kgf) was evaluated. Further, with respect to the cladding layer 4 of another sample, the heat softening characteristic after the heat treatment at a temperature of 700 ° C. for 4 hours was evaluated. For yet another sample, 800
The heat softening properties after the heat treatment at 4 ° C. for 4 hours were also evaluated. This heating softening characteristic is determined by the hardness of the cladding layer 4 (Vickers hardness: load of 20 k) of the sample returned to normal temperature after heating.
gf). In addition, for the overlay 4 of another sample,
High temperature hardness at 700 ° C (Vickers hardness: load 2)
0 kgf) was evaluated. For the overlay 4 of another sample,
High temperature hardness at 800 ° C (Vickers hardness: load 2)
0 kgf) was evaluated.

From another sample, a Charpy impact test piece 8 (JIS-3 test piece) with a notch 8c shown by a virtual line in FIG. 10 was formed, and the impact strength of the overlay 4 itself was measured by a Charpy impact tester. Was evaluated. Table 2 shows the test results. As shown in Table 2, although the comparative mold material using the forged mold material has excellent impact strength, its high-temperature hardness at 800 ° C. is as low as Hv 150 to 227, and its high-temperature wear resistance is not sufficient. It is considered that the wear is large.

A comparative die material obtained by subjecting a conventional forged die material to a hardness increasing treatment (quenching / tempering) has improved high-temperature wear resistance. This comparative mold material,
Since the room temperature hardness (= initial hardness) is quite high as Hv520, the high-temperature wear resistance to flash is good, but the impact strength is 15 J / cm ² , 20 J /
The eyes become as low as cm ^2, and mold cracks easily occur.

On the other hand, the mold material of the present invention ~ (= a stellite alloy build-up) has good room temperature hardness, heat softening hardness, and high temperature hardness, and particularly high temperature hardness (1800). C) is as high as about Hv 246 to 270, so that it is considered to be excellent in high-temperature wear resistance during hot forging and, therefore, to have little wear due to flash. Accordingly, the mold material of the present invention is suitable for the flash flow promoting region K1.
In addition, the high-temperature strength of the overlay welding material of the mold material of the present invention is 84.
It is considerably large at 2 MPa and has good deformation resistance at high temperatures. Therefore, the mold of the present invention is suitable for the flash flow suppression region K2.

Based on the above test results, FIGS.
2 was created. FIG. 11 shows the relationship between the heat softening hardness (800 ° C.) and the impact strength. FIG. 12 shows the high temperature hardness (800
C) and the impact strength. In FIG. 11 and FIG. 12, △ * ● marks respectively correspond to the mold material of the present invention. As can be understood from the above description, the mold material of the present invention ~
FIG. 11 and FIG. 1 show a structure in which each of the stellite-based overlay layers is overlaid on a mold body material equivalent to SKT-4.
In Example 2, as the impact strength of the mold material of the present invention indicated by the mark △ ***, the impact strength data of the SKT-4 equivalent material (comparative mold material) is adopted instead of the impact strength data of the overlay layer itself. Is appropriate.

As can be understood from FIG. 11, SKT-4
According to the mold material of the present invention in which the stellite-based cladding layers are overlaid on the equivalent mold body material, the heat softening hardness (800 ° C.) is high while ensuring the impact strength. As can be understood from FIG. 12, according to the mold material of the present invention, the high-temperature hardness (800 ° C.) is high while ensuring the impact strength. From this, it can be said that the mold material of the present invention has good resistance to friction by flash.

(Other Embodiments) Table 3
It is also possible to use the forms A to C shown in FIG. That is, when the heat check damage is large on the flash surfaces 13 and 33, the form A in which the build-up welding material having the composition shown in Table 1 (Mo and W are small) is used as the first build-up layer 51. it can. When the abrasion on the flash surfaces 13 and 33 is large, a form B in which a build-up welding material having a composition shown in Table 1 (Mo and W are large) can be adopted as the first build-up layer 51. In the case where the flash surfaces 13 and 33 have a large amount of wear and a large amount of heat check damage, a form C in which a build-up welding material having the composition shown in Table 1 is used as the first build-up layer 51 can be used. Form A ~
In C, the counterweight cavities 11d, 31d
As the second overlay layer 52 covering the shoulder radius portion 42, an overlay weld material having a composition shown in Table 1 is employed.

[0053]

[Table 3] As described above, the pin cavities 11e and 31e
As a countermeasure against die cracking on the die-sculpted surface, it is possible to use a high-toughness die material. When the forging pressure is excessive, as a countermeasure against die cracking in the die-sculpted surfaces of the pin cavities 11e and 31e, a build-up welding material having excellent high-temperature strength and high resistance to deformation at high temperatures (see Table 1). (Ni-base superalloy) shown in FIG.
It is also preferable to directly build up on the engraved surfaces of e and 31e.

Although the above embodiment is applied to a forging die for hot forging a crankshaft, the invention is not limited to this. For example, a knuckle arm. The present invention can be applied to a forging die for hot forging a lower arm or the like.

[0055]

According to the composite die for hot forging according to the present invention, the build-up layer is selectively used in the flash flow promoting region and the flash flow suppressing region, and the abrasion due to the flash tends to increase during forging. In at least a part of the flash flow promoting region, a first build-up layer made of an alloy that emphasizes high-temperature wear resistance is built up, and surface pressure tends to increase during forging because of the suppression of flash flow. In at least a part of the flash flow suppression region, a second build-up layer made of an alloy that emphasizes high-temperature strength is built up.
Therefore, it is advantageous for extending the life of the composite die for hot forging according to the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first type.

FIG. 2 is a cross-sectional view of the composite die for hot forging taken along the line AA shown in FIG.

FIG. 3 is a configuration diagram of a second type.

FIG. 4 is a configuration diagram showing a flow form of a flash on a flash surface.

FIG. 5 is a sectional view taken along the line CC shown in FIG.

FIG. 6 is a cross-sectional view taken along line DD shown in FIG.

FIG. 7 is a configuration diagram illustrating a crack at the bottom of the pin cavity portion.

FIG. 8 is a plan view of a test piece coated with a build-up layer.

FIG. 9 is a side view of a test piece coated with a build-up layer.

FIG. 10 is a configuration diagram showing a form of producing an impact test piece.

FIG. 11 is a graph showing the relationship between the heat softening hardness and the impact strength of the mold material of the present invention and the comparative mold material.

FIG. 12 is a graph showing the relationship between high-temperature hardness and impact strength of the mold material of the present invention and the comparative mold material.

[Explanation of symbols]

In the figure, 10 is the first mold, 11 is the product cavity, 15 is the first inclined surface, 11d is the counterweight cavity, 3
0 is a second mold, 31 is a product cavity, 35 is a second inclined surface, 31d is a counterweight cavity portion, 51 is a first buildup layer, 52 is a second buildup layer, K1 is a flash flow promoting area, and K2 is 3 illustrates a flush flow suppression region.

 ──────────────────────────────────────────────────の Continued from the front page (72) Inventor Tomoyuki Nishi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (1)

[Claims] A flash flow promoting region for promoting the flow of flash from a rough material to be a forged product, and a flash flow suppressing region for suppressing the flow of flash from a rough material, and a build-up on a mold body. In the composite die for hot forging, which is formed by coating a layer, a buildup layer is selectively used in the flash flow promotion region and the flash flow suppression region, and at least a part of the flash flow promotion region is a first layer.
A build-up layer is built-up, and at least a part of the flash flow suppression area is
The build-up layer is built-up, the alloy forming the first build-up layer emphasizes high-temperature wear resistance, and the alloy forming the second build-up layer emphasizes high-temperature strength. Composite mold for hot forging.