JPH1177375A - Cobalt base alloy for cladding hot forging die by welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cobalt base alloy for cladding a hot forging die by welding good in cladding properties by welding and damaging resistance after cladding by welding. SOLUTION: This cobalt base alloy for cladding a hot forging die by welding has a compsn. contg., by weight, 0.35 to 1.10% C, <=1.5% Sm, <=1.5% Mn, <=3.0% Ni, 26.0 to 32.0% Cr, 0.5 to 6.0% Mo, 0.5 to 6.0% W, and the balance Co with inevitable impurities. The alloy is clad to a hot forging die by welding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cobalt-based alloy for hot forging type overlay welding.

[0002]

2. Description of the Related Art In hot forging, a metal material (generally steel) heated to a high temperature, for example, 1000 to 1200 ° C., is set in a forging die, and then mechanically or hydraulically. This is a technique for high-pressure molding of a metal material with a forging die by means of pressure means. Hot forging, production efficiency, economy,
Since it is a molding method excellent in high strength, it is widely applied to the production of automobile parts and the like.

[0003] As described above, hot forging is a technique for pressing a metal material heated to a high temperature state and forming the metal material in an extremely short time. Therefore, the hot forging die has severe mechanical stress and thermal stress. And receive. Therefore, the required characteristics for the hot forging die are severe. Generally, the following (1)-
(3) is requested. In particular, there is a strong demand for (3). (1) Excellent strength, particularly high-temperature strength (fatigue strength, hardness) and toughness, to withstand severe mechanical pressure and thermal stress loads. (2) To withstand material flow at high temperature and high pressure,
Excellent heat-softening resistance and excellent wear resistance, especially high-temperature wear resistance. (3) Excellent heat check resistance by thermal cycling. Heat check refers to micro-cracks similar to the turtle shell.

[0004] In general, the main types of damage observed in hot forging dies include die wear damage, die heat check damage, die crack fracture damage, and the like. The above-mentioned mold wear damage is caused by plastic flow of the metal material at the surface of the mold when the metal material heated to high temperature is formed, and a high hardness surface oxide layer formed by heating the metal material. Is generally a phenomenon of damage to the mold surface caused by sliding on the mold surface.

The heat check damage of the mold is said to be caused by a thermal fatigue phenomenon caused by repeated heating and cooling of the mold surface caused by hot forging, and is considered to be a kind of high temperature plastic fatigue phenomenon. It is generally said that the higher the impact strength, the better the toughness, and the higher the strength from the room temperature to the operating temperature (the property that can be substituted by almost hardness), the more the heat check damage is improved.

[0006] There are two types of mold fracture: fracture by the repeated application of mechanical load and thermal stress associated with hot forging, and brittle fracture due to insufficient toughness of the mold material. Due to advances in materials and design techniques, the number of cases where the life of a forged mold is reduced due to crack fracture of the mold has decreased. In consideration of the above-described circumstances, as a material for forming the hot forging die, a material having resistance to the above-described damage form, typically, a JIS-SKD61-based alloy for hot working is used. However, the material that makes up the hot forging die is usually a wrought material, so it has excellent toughness, but it does not always have high high-temperature hardness, and there is a limit to ensuring excellent high-temperature wear resistance. There was a point.

In view of the above, as a countermeasure against the above-mentioned damage form in the hot forging die, it has heretofore been attempted to partially carry out a stellite-based alloy build-up treatment at a site where the wear of the hot forging die is significantly damaged. ing. Here, the stellite-based alloy is an alloy having a main composition of Co-Cr, and has excellent deformation resistance and oxidation resistance at high temperatures. In order to secure particularly excellent abrasion resistance, stellite N
o. 6, Stellite No. 6 20, Stellite No. 21
Is used as a cladding alloy.

Further, as a prior art, Japanese Patent Application Laid-Open No. 62-289
Japanese Patent No. 397 discloses a stellite-based Co-based alloy for cladding. This overlaying Co-based alloy is expressed in weight%
C: 0.7 to 3.0%, Si: ≦ 2%, Mn: ≦ 2%,
Ni: ≦ 3.0%, Cr: 23 to 32%, Mo: over 1 to
7%, W: over 6.5 to 14%, Fe: ≤ 5%, and the balance is specified to have substantially the composition of Co. This overlay C
The o-base alloy has a relatively large amount of W.

Further, Japanese Patent Application Laid-Open No. 55-76036 discloses that
C for overlaying engine valves and valve seats of internal combustion engines
An o-based alloy is disclosed. This Co-based alloy for overlaying is
By weight%, C: 1.0-3.5%, Si: 0.1-2.
0%, Mn: 0.1 to 2.0%, Cr: 20 to 35%,
W: 5 to 20%, Fe 10 to 30%, balance substantially Co
And the content of C, W and Fe is large.

[0010]

As described above, the stellite-based alloy deposited on the hot forging die has excellent deformation resistance and oxidation resistance at a high temperature, but has a hot water flow property and a welded meat. It has been difficult to secure both build-up properties such as build-up properties and weld cracking resistance and high-temperature wear resistance after build-up.

Further, various Co-based alloys have been proposed as an improvement of the stellite-based alloy, but the composition is not determined in consideration of the overlay used in the hot forging die. However, it is not always sufficient to achieve both high heat resistance and high temperature wear resistance. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object of claim 1 is to improve the high-temperature wear resistance while improving the build-up properties such as molten metal flowability, welding build-up properties, and welding crack resistance. It is an object of the present invention to provide a cobalt-based alloy for hot forging die build-up welding which is advantageous for securing the same.

A second object of the present invention is to improve the high-temperature wear resistance while securing the build-up property, and to greatly improve the toughness, thereby obtaining an excellent heat check resistance. It is an object of the present invention to provide a cobalt based alloy for hot forging type overlay welding. A third object of the present invention is to provide a high-temperature abrasion resistance and toughness while securing the build-up property, thereby improving the heat check resistance while maintaining the high-temperature abrasion resistance. An object of the present invention is to provide a cobalt-based alloy for forging die overlay welding.

[0013]

The cobalt-based alloy for hot forging type overlay welding according to the first invention has a C: 0.3% by weight.
5-1.10%, Si: ≦ 1.5%, Mn: ≦ 1.5
%, Ni: ≤3.0%, Cr: 26.0-32.0%,
Mo: 0.5 to 6.0%, W: 0.5 to 6.0%, the balance being Co and unavoidable impurities.

According to the alloy according to the first aspect of the present invention,
C: 0.4 to 0.9%, Si: ≤ 1.5%, Mn: ≤
1.5%, Ni: ≤3.0%, Cr: 26.0 to 32.
0%, Mo: 0.9 to 6.0%, W: 1.0 to 6.0%
The composition may be such that it contains and the balance consists of Co and inevitable impurities. The cobalt-based alloy for hot forging die build-up welding according to the second aspect of the present invention,
C: 0.35 to 0.65%, Mo: 0.5 to 2.0%,
W: 0.5 to 2.0%.

The cobalt-base alloy for hot forging die build-up welding according to the third aspect of the present invention is the composition according to claim 1, wherein C: 0.
80-1.10%, Mo: 0.5-2.0%, W: 2.
0 to 4.0%.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the reasons for limiting the components in the cobalt-based alloy for hot forging type overlay welding according to the present invention will be described in detail. (1) C combines with Cr, Mo, W to form a carbide,
Thereby, high temperature strength (high temperature hardness) and heat softening resistance are improved. 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 was set to 0.35 to 1.10%. For example, it can be set to 0.4 to 0.9%.

Here, in the alloy such as the alloy of the second invention, which further improves the toughness and the heat check resistance, the amount of carbon can be reduced as small as 0.35 to 0.65%. Further, in an alloy that balances high-temperature wear resistance and toughness like the alloy of the second invention, carbon can be increased as much as 0.80 to 1.10%. In this specification,% unless otherwise specified means% by weight. (2) Si is effective as a deoxidizing agent and improves build-up. If the content is large, the toughness is likely to be reduced.
5% or less. Here, the upper limit of Si can be set to 1.4% and the lower limit of Si can be set to 1.1% in accordance with the required characteristics, but the present invention is not necessarily limited to this. (3) Mn stabilizes austenite and is also effective as a deoxidizing agent and improves the build-up property. However, when the content is large, the toughness is easily reduced, so Mn was set to 1.5% or less.
Here, the upper limit of Mn is 1.4% according to the required characteristics, and Mn is Mn.
Can be 1.1%, but is not necessarily limited to this. (4) In the cobalt-based alloy according to the present invention, Ni is considered to be basically an impurity element. If it is 3.0% or less, almost no adverse effect is observed, but if added in excess of 3.0%, the toughness is reduced, so the content was made 3.0% or less. (5) Cr improves heat resistance and corrosion resistance at high temperatures, and also reacts with C to form carbides in the weld overlaying state to form high-temperature strength (can be substituted for high-temperature hardness).
And to improve the heat softening resistance. Therefore, 26.0% or more is necessary. However, even if added in excess of 32.0%, the above-mentioned improvement effect is little increased, but rather, the precipitation of the σ phase is easily promoted at a high temperature, so that the toughness is easily lowered and the heat check resistance is disadvantageously easily ensured. Therefore, Cr was set to 26.0 to 32.0%. In this range, the upper limit of Cr is 30% and the lower limit of Cr is 27% according to the required characteristics.
%, But is not necessarily limited to this. (6) Mo and W each have substantially similar effects, react with C to form carbides, and provide the cobalt-based alloy according to the present invention with high-temperature strength (high-temperature fatigue strength and high-temperature hardness, Fatigue strength) and resistance to heat softening. However, if Mo is less than 0.5% and W is less than 0.5%, a sufficient improvement effect cannot be obtained. However, Mo and W are 6.
If it exceeds 0%, not only the weld build-up tends to occur during welding build-up, but also the build-up property is reduced, as well as the toughness and heat check resistance of the build-up layer.

Therefore, Mo is set to 0.5 to 6.0%, and W is set to 0.5% to 6.0%. Here, according to the required characteristics,
The upper limit of Mo can be 3.0% and 5.0%, the lower limit of Mo can be 0.7% and 1.0%, and the upper limit of W is 5.0% and W
Can be set to 0.7% and 1.0%, but is not necessarily limited thereto. Here, in a preferred embodiment, Mo is 0.5 to 2.0%, and W is 0.5 to 2.0%.
Can be. (7) The sum of the Mo amount and the W amount is not particularly limited in the present invention, but is preferably as follows.

Both (Mo + W) react with C as described above to form carbides and improve the high-temperature strength (high-temperature fatigue strength and high-temperature hardness) of the cobalt-based alloy according to the present invention. If (Mo + W) is less than 1.9%, it is difficult to obtain a sufficient improvement effect. (Mo + W) is 9.0
%, Not only the build-up property is reduced and weld cracking is liable to occur at the time of weld build-up, but also the toughness of the material is easily reduced. Therefore, (Mo + W) is preferably 9.0% or less.

(Mo + W) is preferably 1.0% to 3.0% in an alloy such as the second invention alloy which further improves toughness and heat check resistance. In an alloy that balances high-temperature wear resistance and toughness, such as the third invention alloy,
(Mo + W) is preferably 2.0% to 5.0%. (8) Co improves the high-temperature hardness and oxidation resistance of the build-up alloy. In consideration of usage conditions, cost, and the like, a part of Co can be replaced with Fe. In this case, Fe can be suppressed to 3.0% or less and 2.0% or less,
Depending on the required characteristics, it can be less than 5.0% and less than 10%. (9) The form of the alloy according to the present invention can be rod-like, wire-like, or powder-like. In the case of a rod shape, the molten metal can be cast into a mold and formed into a rod shape. In the case of a powder, the molten metal can be made into a powder by an atomizing method such as gas atomizing.
In this case, it can be used in the powder plasma welding overlay method or the like.

The alloy according to the present invention can be built up by means such as TIG welding, arc welding and gas welding.
In the case of the TIG welding method, it is generally possible to build up under the following conditions. That is, the preheating temperature of the partner material is 250 to 350 °.
C, the flow rate of argon can be 10 to 15 liter / min, and the welding current can be 80 to 180 A. However, it is not limited to these.

The material of the hot forging die on which the alloy according to the present invention is overlaid is generally carbon steel or alloy steel,
An SKD61-based hot working alloy can be used. Representative portions of the hot forging die to be built up include the split surface and the molding cavity die surface. On the split surface, it is possible to build up the portion where the burr flows.

[0023]

The alloy of the present invention and the alloy of the present invention will be described together with the conventional alloy. Using a normal high-frequency melting furnace, molten Co-base alloys having the compositions shown in Table 1 were prepared. Next, each of these melts was poured into the cavity of the shell mold, and a round bar having a diameter of 4 mm was cast.

The conventional alloy is Stellite No. 6 and the conventional alloy was Stellite No. 20 and the conventional alloy was Stellite No. 21. As can be understood from Table 1, the alloys of the present invention are the same as the conventional alloys, that is, Stellite No. Compared to 20, C and W are small and Mo is large. In addition, the alloys of the present invention to the conventional alloy, that is, Stellite No. 21 compared to 21
And W is contained.

As can be understood from Table 1, the alloy of the present invention has a similar composition to that of the alloy of the present invention, but has a larger amount of C than the alloy of the present invention. The round bar manufactured as described above is used as a welding rod for overlaying.
Further, while using a tungsten electrode, FIGS.
The metal layer 2 (material: SKD61) having the long groove 2a shown in FIG. 1 was used to build up the long groove 2a by the TIG welding method in an argon gas atmosphere to form the overlay layer 4. Thereby, the overlay test piece 6 was manufactured. The metal body 2 has a length L of 200 mm, a width D of 60 mm, and a height H of 40 mm.

The basic conditions of the TIG welding method are as follows. That is, the preheating temperature of the metal body 2 is 300 ° C., the flow rate of argon is 12 l / min, and the welding current is 90 to 160.
A. The build-up property in the production of this build-up test piece 6 was evaluated. Specifically, as a build-up property, hot water flowability,
The weld overlay and weld crack resistance were evaluated.

The flowability of the molten metal was determined by visual inspection by both the operator and the inspector at the time of overlaying. The weld overlay was determined by observing poor penetration in the overlay 4 with 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 is slice-cut at a thickness t ₁ and a thickness t ₂ as shown in FIG. Then, samples S3 to S14 were formed. After that, the room temperature hardness (Vickers hardness: load: 20 kgf) of the cladding layer 4 of a predetermined sample among the samples S3 to S14 was evaluated.

With respect to the overlay 4 of another sample, 700
The heat softening property after the heat treatment at 4 ° C. for 4 hours was evaluated. Further, with respect to another sample, the heat softening characteristic after the heat treatment at a temperature of 800 ° C. for 4 hours was also evaluated. This heat softening property was evaluated by the hardness (Vickers hardness: load: 20 kgf) of the cladding layer 4 of the sample which was returned to normal temperature after heating.

Further, with respect to the overlay 4 of another sample, 700
High temperature hardness at ° C (Vickers hardness: 20kg load)
f) was evaluated. 800 for the overlay 4 of another sample
High temperature hardness at ° C (Vickers hardness: 20kg load)
f) was evaluated. From another sample, a Charpy impact test piece 8 (JIS-3) with a notch 8c shown by a virtual line in FIG.
No. test piece), and the impact strength was evaluated using a Charpy impact tester.

(Evaluation) Each evaluation result is shown in Table 2. In Table 2, the symbol ◎ means superior, and △ means inferior. As can be understood from Table 2, regarding the build-up property, a stellite-based alloy (N
o. 6), a stellite-based alloy (No.
In the case of (20), although the molten metal flowability was good, the weld crack resistance was not good. Stellite alloy (No. 21), which is a conventional alloy, has good weld overlayability,
Hot water flow was not good.

In the alloy of the present invention having a similar composition to that of the alloy of the present invention except for the C content, the weld cracking resistance was slightly lowered, but the melt flowability and the weld overlay were good. . On the other hand, the alloys of the present invention ~
Both welding build-up and weld cracking resistance are good with ◎,
Compared to the conventional alloys, the alloy had good melt flowability, weld build-up properties, and weld crack resistance.

Not only that, the alloy of the present invention has a similar flowability and weld build-up property even when compared with the alloy of the present invention having a similar composition to the alloy of the present invention.
The weld cracking resistance was also excellent as ◎. Next, various characteristics when used as a weld overlay member will be compared. As shown in Table 2, the conventional alloy (Stellite No. 20) having a large C content and a large W content has the highest hardness at room temperature, hardness after heat softening, and high-temperature hardness, but has a C content of 2.2%. The impact strength is as low as 3.6 [J / cm ² ] and the toughness is remarkably low. Therefore, the conventional alloy is not suitable as a weld overlay for hot forging die. Not enough.

The conventional alloy has a C content of 0.23%.
It is a low C stellite alloy, so its impact strength is relatively good, but its room temperature hardness, heat softening hardness, and high temperature hardness are considerably lower than those of other stellite-based conventional alloys. Therefore, the conventional alloys are not sufficient in wear resistance, so that the conventional alloys are not sufficient as welding overlay members used for hot forging dies.

The conventional alloy has a C content of 1.0%, which is an intermediate C content between the conventional alloy and the conventional alloy. Despite exhibiting heat softening hardness and high temperature hardness, the impact strength is only 6.1 [J / cm ² ], lower than that of the alloy of the present invention, and is sufficient as a weld overlay material used for a hot forging die. There is a problem that toughness has not reached a certain level.

On the other hand, the alloys of the present invention have a moderate C content.
The evaluation of build-up properties such as melt flowability, weld build-up properties, and weld cracking resistance is ◎, which indicates not only excellent build-up properties but also room-temperature hardness, heat-softening hardness, and high-temperature hardness. Also, it has a moderate level as a cobalt-based alloy for overlay welding.
Further, the alloys of the present invention are also excellent in impact strength. That is, the alloy of the present invention is 14.8 [J / cm ² ], the alloy of the present invention is 12.0 [J / cm ² ], the alloy of the present invention is 10.5 [J / cm ² ], and the alloy of the present invention is 10. 2 [J
/ Cm ² ], and the alloy of the present invention is excellent in toughness (impact strength).

About the alloy of the present invention, hardness at room temperature,
Both the softening hardness under heating and the high-temperature hardness ensure a good level, and since the C content is higher than the alloy of the present invention, that is, C: 0.9% or more, high-temperature hardness can be obtained. It has an improved high-temperature wear resistance and is suitable for use in places where high-temperature wear resistance is strongly required. However, with respect to the alloys of the present invention, the impact strength and toughness are slightly lowered, and the melt flowability and the weld build-up property are 溶, but the welding crack resistance tends to be slightly inferior.

(Second Invention, Third Invention) Now, Alloy B of the present invention
-To-correspond to the second aspect of the invention, in which the build-up property is secured and the high-temperature wear resistance is slightly reduced, but the heat check resistance is further improved. The alloys B- to B- of the present invention correspond to the alloys B- to B- of the present invention.
Have similar compositions, but differ in the amounts of W and Mo. The alloys B- to B- of the present invention were also tested in the same manner as described above.

The alloys C- to C- of the present invention correspond to the third invention, and aim at a balance between high-temperature wear resistance and heat check resistance while ensuring build-up. . Although the alloys C- to C- of the present invention have a similar composition to the alloys C- to C- of the present invention,
The amounts of W and Mo are different. The alloys C- to C- of the present invention were also tested in the same manner as described above.

The alloy B- of the present invention containing the second invention described above.
To B-, alloys C- to C- of the present invention including the third invention.
Is shown in Table 3. Table 4 shows the test results. For the alloys B- to B- of the present invention including the second invention,
It is a low-C system and has an appropriate amount of elements such as Mo and W. As can be understood from Table 4, the evaluations of build-up properties such as melt flowability, weld build-up property, and weld crack resistance are all ◎. It was excellent. Further, the alloys B- to B- of the present invention had good impact strength. In particular, for the alloys B- to B- of the present invention, C, Mo, and W are in appropriate amounts, and the impact strength is 15 J / c.
m ² or more and quite high, toughness was excellent.

The alloys C- to C- of the present invention, including the third invention, have a high C content and an appropriate amount of elements such as Mo and W. The build-up evaluation was ◎, and the weld cracking resistance was ○, but the build-up was good as a whole, and the heat softening hardness and high-temperature hardness were also at appropriate levels, and the impact strength and toughness were high. As a result, the heat check resistance was excellent, and both high temperature wear resistance and heat check resistance could be achieved.

Based on the above test results, the alloys of the present invention having the composition of the second invention and the composition close to the composition of the second invention
Regarding B−, the relationship between the impact strength and the (Mo + W) amount was determined, and this is shown in FIG. Further, after heating at 800 ° C., the temperature is returned to room temperature, and the hardness after heating is softening hardness (Mo +
W) The relationship with the amount is shown in FIG. FIG. 8 shows the relationship between the heat softening hardness and the impact strength.

According to the characteristics shown in FIG. 6, in the alloy having the composition of the second invention and a composition similar thereto, the (Mo + W) amount is not more than 5.0%, especially 3.0, in order to increase the impact strength.
% Is preferred. According to the characteristics shown in FIG. 7, although the heat softening hardness tends to decrease as the (Mo + W) amount increases, the (Mo + W) amount is reduced to 3.0%.
Hv 350 or more (load 20
kgf). As a cobalt forging alloy for hot forging die buildup, if the softening hardness upon heating is Hv350 or more, it is acceptable.

Incidentally, SK which is a typical hot forging die
According to the D61 material, the hardness at room temperature before heating was about Hv400, but the hardness returned to normal temperature after heating at 800 ° C. for 4 hours is about Hv200 to 230, which is higher than that of the above-mentioned overlay alloy. Low. Further, based on the test results described above, the impact strength and (Mo +) of the alloys C- to C- of the present invention having the composition of the third invention and a composition similar thereto were determined.
W) The relationship with the amount was determined and is shown in FIG. Further, 80
FIG. 10 shows the relationship between the heat softening hardness and the (Mo + W) amount when heated at 0 ° C., and FIG. 11 shows the relationship between the heat softening hardness and the impact strength when heated at 800 ° C.

According to the characteristics shown in FIG. 9, in order to increase the impact strength, the (Mo + W) amount is not more than 8.0%, especially 5.0%.
It turns out that the following is preferable. According to the characteristics shown in FIG. 10, the heat softening hardness tends to decrease as the (Mo + W) amount increases, and when the (Mo + W) amount is set to 5.0% or less, the heat softening hardness slightly decreases. Although,
Hv 350 or more (load: 20 kgf) is obtained.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

[Table 4] Each element of the composition according to the present invention alloy can define the content corresponding to the present alloy shown in each table or the content in the vicinity thereof as the upper limit value or the lower limit value.

[0050]

According to the cobalt-based alloy for hot forging type overlay welding according to the first to third aspects of the present invention, good overlay properties such as melt flowability, weld overlay, and weld crack resistance are excellent. . In addition to having good room temperature hardness, heat softening hardness, and high temperature hardness, and excellent toughness (= impact strength) of the build-up layer,
Good damage resistance and heat check resistance after overlaying.
Therefore, when used for overlaying in a hot forging die in which severe mechanical stress and thermal stress act, an effect of contributing to improvement of damage resistance such as wear resistance at high temperatures can be obtained.

According to the cobalt-based alloy for hot forging die overlay welding according to the second aspect of the present invention, the impact build-up is increased while the high-temperature wear resistance is alleviated while ensuring the weld overlayability.
This is advantageous for obtaining excellent heat check resistance. According to the cobalt-based alloy for hot forging die build-up welding according to the third invention, while securing the weld build-up property, the heat softening hardness and the high-temperature hardness are ensured, and the toughness as the build-up alloy ( Impact strength) and good heat check resistance. Therefore, it is advantageous for achieving both high-temperature hardness and heat check resistance.

[Brief description of the drawings]

FIG. 1 is a plan view of a test piece after overlaying.

FIG. 2 is a cross-sectional view of a test piece after overlaying.

FIG. 3 is a plan view showing a form in which a sample for evaluating a material property by cutting a test piece is sampled from the test piece;

FIG. 4 is a cross-sectional view of a slice-cut sample.

FIG. 5 is a configuration diagram showing an embodiment in which an impact test piece is formed from a slice-cut sample.

FIG. 6 shows the impact strength and (M
6 is a graph showing a relationship with (o + W) amount.

FIG. 7 is a graph showing the relationship between the heat softening hardness and the (Mo + W) amount.

FIG. 8 is a graph showing the relationship between heat softening hardness and impact strength.

FIG. 9 shows the impact strength and (M
6 is a graph showing a relationship with (o + W) amount.

FIG. 10 is a graph showing a relationship between heat softening hardness and (Mo + W) amount.

FIG. 11 is a graph showing the relationship between heat softening hardness and impact strength.

[Explanation of symbols]

 In the figure, reference numeral 4 denotes a buildup layer.

Claims (3)

[Claims] C .: 0.35 to 1.10% by weight, S
i: ≦ 1.5%, Mn: ≦ 1.5%, Ni: ≦ 3.0
%, Cr: 26.0-32.0%, Mo: 0.5-6.
Cobalt-based alloy for hot forging die build-up welding, characterized in that it contains 0%, W: 0.5-6.0%, and the balance consists of Co and unavoidable impurities. 2. C .: 0.35 to 0.65% by weight, M
The cobalt-based alloy for hot forging die build-up welding according to claim 1, wherein o: 0.5 to 2.0% and W: 0.5 to 2.0%. 3. C: 0.80 to 1.10% by weight, M
The cobalt-based alloy according to claim 1, wherein o: 0.5 to 2.0% and W: 2.0 to 4.0%.