JPH08337838A - Cemented carbide for metal plastic working tool - Google Patents

Abstract

PURPOSE: To improve the chipping resistance, impact resistance and damage resistance of a tool, as for a cemented carbide used for a punch, by reducing the content of a bonding phase, reducing the average particle size of tungsten carbide and reducing the content of chromium carbide compared to those in a cemented carbide used for a die. CONSTITUTION: This cemented carbide has a compsn. in which a bonding phase with chromium carbide is present by 3 to 13% weight ratio to Ni and/or Co contained by 5 to 15wt.% to the whole body of the cemented carbide, and the balance tungsten carbide having <=3.5μm average particle size with inevitable impurities. By the cemented carbide, a punch and a die are produced, and the compsns. of the cemented carbide used for a punch and a die are made to satisfy at least one among three conditions. As for a punch, the compsn. contg. 5 to 10% Ni is preferable. As for a die, the compsn. contg. 8 to 15% Ni is preferable. The service lives of plastic working tools are prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal plastic working tool which mainly uses a material to be machined (metals in this specification include alloys) as a combination of a punch and a die. Regarding cemented carbide, specifically, cemented carbide for metal plastic working tools, which is an optimal combination of punch and die for extrusion, upsetting, drawing including deep drawing or punching. It is about.

[0002]

2. Description of the Related Art Generally, a cemented carbide composed of a hard phase containing tungsten carbide as a main component and a binder phase containing Co as a main component is excellent in hardness, wear resistance, fracture resistance, toughness, strength and the like. It has cutting characteristics, wear resistant tools,
It is used as a tool represented by civil engineering mining tools.
Among these tools, a plastic working tool, which is one type of wear resistant tool, may use a working fluid in order to prevent seizure during working and ease of working.

Recently, CFCs have been abolished due to problems related to ecology, and as a result, the working fluid used during the use of punching tools among plastic working tools has been changed from oil-based to water-soluble. There is a problem of shortening the life of plastic working tools made of the above cemented carbide.

Among the conventional cemented carbides, a representative of the prior art proposed as a cemented carbide for plastic working tools or a cemented carbide suitable therefor is disclosed in Japanese Examined Patent Publication No. Sho 45-1321.
No. 2, JP-A-1-8245, JP-A 1-24
7552, JP-A-2-97640 and Me.
tal Powder Report (1987) page 512.

[0005]

Among the prior art as cemented carbide for plastic working tools or cemented carbide suitable therefor,
JP-B-45-13212, JP-A-1-8245 and JP-A-1-247552 disclose a cemented carbide in which Cr is added to a hard phase made of submicron fine tungsten carbide and a Ni binding phase. Alloys are described, and it is described that these cemented carbides have corrosion resistance and are suitable as a die for ferrite. However, the cemented carbides described in these three publications are extremely difficult to manufacture and have large variations in performance, so that they are not suitable for use as a plastic working tool requiring impact resistance. Therefore, there is a problem that the life becomes short.

Further, Japanese Patent Laid-Open No. 2-97640 discloses that
A hard phase composed of submicron fine tungsten carbide;
Cemented carbide for precision molds containing Co and / or Ni containing chromium carbide is described, and it is described that this cemented carbide is suitable as a mold for molding glass and plastics. In addition, Metal Pow
der Report (1987), page 512, Table 1
Describes a cemented carbide containing a hard phase made of submicron fine tungsten carbide, a binder phase of Co and Ni, and an additive of chromium carbide. The cemented carbides described in both of these prior arts are also excellent in corrosion resistance, hardness, and strength, but when the metal is plastically processed by combining a punch and a die, impact resistance is particularly required. When used as a plastic working tool, there is a problem that chipping or chipping occurs and the life becomes short.

The present invention has solved the above-mentioned problems. Specifically, the punch and the die are combined in an optimum composition, in particular, the corrosion resistance of each is increased, and the corrosion resistance of each is improved. It is an object of the present invention to provide a cemented carbide for a metal plastic working tool, which has a long life by remarkably improving the chipping property and the impact resistance.

[0008]

The inventors of the present invention have been studying, for many years, a cemented carbide for a plastic working tool as a punch or a die, and found that each of the punch and the die has an optimum composition component. It is possible to remarkably improve the fracture resistance and the impact resistance by combining them so as to increase the corrosion resistance of both, and to maintain the optimum hardness, wear resistance and strength for each. We obtained the knowledge that a significantly longer life can be achieved in plastic working of
The present invention has been completed.

The cemented carbide for metal plastic working tools of the present invention is
5 to 15% by weight of Ni and / or Co metal with respect to the entire cemented carbide, and 3 to 13% by weight relative to the metal.
Binder phase consisting of chromium carbide and the rest has an average particle size of 3.5
A cemented carbide composed of tungsten carbide having a size of less than or equal to μm and unavoidable impurities, wherein the cemented carbide is a combination of a punch and a die, and the combination of the punch and the die is (A): a punch. The cemented carbide used has a smaller content of binder phase than the cemented carbide used for the die,
(B): The cemented carbide used for the punch has a smaller average grain size of tungsten carbide than the cemented carbide used for the die, and (C): the cemented carbide used for the punch is the cemented carbide used for the die. Content of chromium carbide is less than
That is, at least one of the conditions (A), (B), and (C) is satisfied.

Specifically, the binder phase in this cemented carbide is a state in which chromium carbide is solid-dissolved in a metal composed of Ni, Co or a Ni--Co alloy. And / or Co is a state in which elements Cr and C are contained in the metal. If the metal content of Ni and / or Co at this time is less than 5% by weight with respect to the entire cemented carbide, the strength, fracture resistance and impact resistance are markedly deteriorated.
Alternatively, when the metal content of Co exceeds 15% by weight with respect to the entire cemented carbide, the hardness and wear resistance are significantly reduced. On the other hand, when the chromium carbide content is less than 3% by weight with respect to the Ni and / or Co metal, the corrosion resistance, particularly the corrosion resistance to the water-soluble lubricating liquid, remarkably deteriorates. And / or Co
When the weight ratio of the metal is more than 13%, the strength, fracture resistance and impact resistance are significantly reduced.

When the condition (A) is satisfied among the conditions (A), (B), and (C) described above, the punch particularly has a metal content of Ni and / or Co with respect to the entire cemented carbide. Is preferably 5 to 10% by weight, and the die preferably has a metal content of Ni and / or Co of 8 to 15% by weight based on the whole cemented carbide.
Further, when the condition (C) is satisfied, the punch is
It is preferable that the content of chromium carbide for the metal of Ni and / or Co is 5 to 13% by weight, and the die has the content of chromium carbide for the metal of Ni and / or Co of 3 to 10 by weight. % Is preferred.

In addition to this binder phase, the hard phase which is another main component has an average grain size of tungsten carbide of 3.5 μm.
If it exceeds the range, the hardness and wear resistance are significantly deteriorated, and the life of the plastic working tool becomes short. When the above condition (B) is satisfied, the punch preferably has an average grain size of tungsten carbide of 3.0 μm or less, particularly 2.0 μm or less. The die has an average particle size of tungsten carbide of 1.
It is preferably 0 μm or more, and particularly preferably 2.0 μm or more.

Any one of the above three conditions (A), (B) and (C) may be satisfied, but it is preferable to satisfy two or three of these conditions. ,
Above all, in the case of plastic working using a working liquid, it is preferable to satisfy (A) and (B) or (B) and (C).

The unavoidable impurities contained in a trace amount in addition to the binder phase and the hard phase include unavoidable impurities mixed in the starting material and unavoidable impurities mixed in from the manufacturing process. It is preferable to suppress the content of these unavoidable impurities as much as possible. Among them, the former inevitable impurities such as Ca, S, Si, Al, and Mg are disclosed in JP-A-2-9764.
It is preferable to make restrictions as described in No. 0, and it is preferable to make the same restrictions for Na, K and Li. In addition, as the latter unavoidable impurities,
There are mainly Co, Fe, W, Mo, and Ti that are mixed from the mixing container and grinding medium in the mixing and grinding process, but these do not form a different phase in the cemented carbide, and have corrosion resistance, fracture resistance, and impact resistance. It is within an allowable range as long as the deterioration of the property does not occur, and specifically, it is 0.5% by volume or less, more preferably 0.2% by volume or less based on the whole cemented carbide.

In order to produce the cemented carbide for a plastic working tool of the present invention, a conventional powder metallurgy method, specifically, for example, a mixing and pulverizing step using a ball mill or an attritor, slip It can be obtained through a powder molding process such as casting, extrusion molding, mold molding, temporary sintering (dewaxing) and sintering process.

[0016]

The cemented carbide for a plastic working tool of the present invention brings out an action of significantly increasing the corrosion resistance, particularly the corrosion resistance to a water-soluble lubricating liquid, in the binder phase containing chromium carbide, and the binder phase in the punch and the die is improved. By optimizing the combination with the hard phase made of tungsten carbide, the action of improving the fracture resistance and the impact resistance without lowering the wear resistance and the strength is brought out.

[0017]

[Example] Four kinds of WCs having different average particle sizes within the average particle size of 1 μm to 5 μm, and Ni and Co of 1 to 2 μm
Each of the powders is used to weigh a predetermined amount of the compounding composition, and is inserted into a stainless steel pot together with an acetone solvent and a cemented carbide ball, and after adjusting the ball content and the crushing time, the mixture is crushed. Then, it was dried to obtain a mixed powder. These mixed powders are pressure-molded into a powder compact, and then the atmospheric pressure 1
Sample Nos. 1 to 13 shown in Table 1 were obtained as cemented carbides that were heated and held at a temperature of 1300 to 1400 ° C. for 1 hour in a vacuum of 0 Pa and sintered. The cemented carbide thus obtained is # 230
Wet-grinding with a diamond whetstone of 4.0 × 8.0
× 25.0 mm in shape, and bending strength (JIS standard B41
No. 04) and hardness were measured and the results are shown in Table 1. Further, one surface of each cemented carbide is lapped with a diamond paste of 1 μm, and then a corrosion resistance test is performed by a method of immersing it in a commercially available water-soluble lubricating liquid used for punching for 50 hours. Corrosion resistance was judged by the presence or absence of discoloration of the surface, and the results are also shown in Table 1. Further, in order to confirm the average grain size and composition of the hard phase in each cemented carbide, investigation was conducted by a metallographic microscope, a scanning electron microscope, etc., and the results are also shown in Table 1.

Then, punches and dies were prepared by selecting from among the cemented carbides shown in Table 1, and combinations 1 to 10 and comparisons made of the present invention consisting of the combinations shown in Table 2 respectively. Punching tests were conducted under the following conditions as combinations 1 to 7 of products. Punching conditions are: punch diameter: 10 mm, work material: nickel white plate (JIS C77
(Corresponding to 01-SH), the thickness of the material to be processed: 0.25 mm, and the number of processing: 250,000 shots. For the evaluation of the test, the damage state of each punch and die was observed with a metallographic microscope and a projector for every 50,000 shots processed, and the results are shown in Table 2.
It was also described in. The punches and dies of combinations 1 to 10 of the present invention all showed normal wear even after 250,000 shots were processed, whereas the combinations 1 to 7 of the comparative product
Is the life when a minute defect occurs on the edge of each punch or when a linear scratch is generated on the nib portion of each die. (In Table 2, the life is assumed to be 1 after 50,000 shots and the ratio is shown as 1.)

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

EFFECTS OF THE INVENTION The cemented carbide for plastic working tools of the present invention has a higher fracture resistance in plastic working, especially in the punching test, as compared with the combination of the conventional cemented carbide and the comparative product made of the conventional combination. It has excellent impact resistance and damage resistance, and has the effect of extending the service life. As described above, the cemented carbide for a plastic working tool of the present invention, which is remarkably excellent in fracture resistance, impact resistance, and damage resistance, is sufficient for extrusion processing, upsetting, and drawing including deep drawing. The effect is exhibited and the life can be extended.

Claims (4)

[Claims] 1. A binder phase composed of 5 to 15% by weight of a metal of Ni and / or Co with respect to the whole cemented carbide and 3 to 13% by weight of chromium carbide with respect to the metal, and the rest. Is a cemented carbide composed of tungsten carbide having an average particle diameter of 3.5 μm or less and unavoidable impurities. The cemented carbide is a combination of a punch and a die, and the combination of the punch and the die is A cemented carbide for metal plastic working tools, which satisfies at least one of the following conditions (A), (B) and (C). (A): The cemented carbide used in the punch has a smaller binder phase content than the cemented carbide used in the die. (B): The cemented carbide used in the punch is the cemented carbide used in the die. The average grain size of tungsten carbide is small in comparison, (C): the cemented carbide used for the punch has a smaller content of chromium carbide than the cemented carbide used for the die, 2. The cemented carbide for metal plastic working tools according to claim 1, wherein said punch is made of 5 to 10% by weight of Ni with respect to the entire cemented carbide. 3. The cemented carbide for metal plastic working tools according to claim 1, wherein the die comprises 8 to 15% by weight of Ni with respect to the entire cemented carbide. 4. The conditions (A), (B) and (C) above are as follows:
The cemented carbide for metal plastic working tools according to claim 1, wherein the condition 2 or 3 is satisfied.