JP2002210525A - Carbide tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service life of a carbide tool. SOLUTION: The carbide tool (e.g. a punch for press die) is made of cemented carbide in which a WC powder is sintered with Co, and the product is put through a surface treatment by nitriding or soft nitriding. When the cemented carbide is subjected to nitriding (or soft nitriding), N atoms for example diffuse and penetrate through the surface of the alloy, thereby nitriding the composition of impurities to provide a hardening effect. As a result, the surface hardness is enhanced through the reinforcement of WC-Co bonding strength, while wear resistance and fatigue strength are also improved through the increase in compressive stress. However, the effect of the surface treatment for hardness varies depending on the Co content in the cemented carbide; to obtain an expected effect, a proper range for the Co content seems to exist.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cemented carbide tool manufactured from a cemented carbide.

[0002]

2. Description of the Related Art Heretofore, as a means for improving the life of a punch used in a press die, for example, a nitriding treatment (or abrasion resistance, surface hardness, etc.) of a metal material used for the punch has been carried out (or a nitriding treatment). Nitrocarburizing treatment). In the nitriding treatment, metal elements such as Fe, Cr, Al, and Mo react with nitrogen to generate nitrides. However, there is no record of application to cemented carbides without these elements. Therefore, for tools manufactured from cemented carbide (for example, cutting tools, punches, etc.), select materials with excellent hardness and toughness in consideration of processing conditions, and further, surface treatments such as TiC, TiN, TiCN, DLC (coating etc.) ) Is used to improve the service life.

[0003]

However, if the hardness increases, the material has poor resistance to rejection and impact resistance, and causes problems such as chipping. In consideration of the above, a material having a slightly lower hardness has been selected. Also, when adding the effect of increasing the surface hardness or lowering the friction coefficient by surface treatment, etc., sufficient adhesion to the base material cannot be obtained especially with a hard metal having high hardness, and the surface treatment peels off during processing. However, the intended effect of improving the life is not obtained. From the above, a tool using a cemented carbide has been hitherto utilized, but there has been no known means for sufficiently improving the life of the tool. The present invention has been made based on the above circumstances, and an object of the present invention is to realize an improvement in the life of a carbide tool.

[0004]

According to the present invention, there is provided a cemented carbide tool comprising a WC
(Tungsten carbide) is manufactured from a cemented carbide obtained by sintering and forming a powder with Co (cobalt), and the manufactured product is subjected to a surface treatment by nitriding or nitrocarburizing. The cemented carbide obtained by sintering WC and Co contains impurities in small amounts in addition to WC and Co. When a nitriding treatment or a soft nitriding treatment is applied to the cemented carbide, N atoms and the like diffuse and infiltrate from the surface of the alloy, and the components of the impurities are nitrided to develop a hardening action,
As a result, it can be estimated that the bonding force between WC and Co is strengthened. Thereby, the surface hardness of the cemented carbide tool is improved, and the wear resistance and the fatigue strength can be improved by increasing the compressive stress.

[0005] However, the effect of the surface treatment on the hardness depends on the content of Co contained in the cemented carbide, and it is considered that an appropriate range exists for the Co content in order to obtain the expected effect. . According to the measurement results of the present inventor, Co
The highest effect (improvement of surface hardness) could be obtained with a content of 8% by weight. Further, when the Co content of the cemented carbide exceeds a predetermined amount (for example, 8% by weight), the surface treatment (nitriding treatment,
Since the surface roughness is increased (the surface is roughened) by the nitrocarburizing treatment, the effect of significantly improving the adhesion to the coating layer can be obtained when a necessary coating is applied thereon.

[0006]

Next, embodiments of the present invention will be described with reference to the drawings. The cemented carbide tool of this embodiment uses WC powder.
It is manufactured from a cemented carbide sintered and formed of Co, and is, for example, a cutting tool or a press-type component (punch, die) or the like, and has been subjected to nitriding (or nitrocarburizing). In nitriding, nitrogen is diffused and permeated into the material (hard alloy) in a gas atmosphere, and combined with the elements contained in the material (trace components other than WC and Co: Fe, Mo, etc.) to form nitrides. Is formed to form a cured layer on the surface of the material.

The effect of this surface treatment will be described. 1) Surface hardness of cemented carbide material Three kinds of cemented carbide materials with different Co contents are prepared, and before and after the surface treatment, the internal hardness is measured every 0.01 mm from the surface of each material. did. The three types of cemented carbide materials used for the hardness measurement were V with a Co content of 6% by weight.
10 kinds, 30 kinds of V with 8% by weight of Co, and 50 kinds of V with 13% by weight of Co (see FIG. 1). As a result of the hardness measurement, as shown in FIG. 1, the V30 super hard material exhibited the most effect, and the hardness near the surface increased to the same level as the V10 super hard material. In addition, the effect was obtained at a depth of 0.06 mm from the treated surface of the V50 type super-hard material. On the other hand, the expected effect was not obtained with the V10 superhard material.

2) Surface Roughness / Wear a) The surface roughness of each of the above three types of carbide materials was measured before and after the surface treatment. As a result of measuring the surface roughness, as shown in FIG.
In the ten types, the surface roughness is improved after the surface treatment (the numerical value indicating the surface roughness is small).
In the 50 types, the surface roughness is worse after the surface treatment (the numerical value indicating the surface roughness is larger).

B) A pin-disk abrasion test was performed on each of the three types of carbide materials before and after the surface treatment. As shown in FIG. 2 (a), the test method is as follows: a pin 2 (SK material) with a load applied to the surface of the disc 1 (carbide material) is rotated at a constant speed for a predetermined time, and the disc surface and the pin 2 are worn. Check the situation. As a result of the wear test, as shown in FIG. 2 (c), the wear amount of the pin 2 increased after the surface treatment for the V10 type (about 2.5% before the treatment).
However, in the V30 and V50 types, the abrasion amount of the pin 2 is reduced after the surface treatment (about 1/3 of that before the treatment).

In the case of V30, wear occurred on the disk surface before the surface treatment, but no wear was observed on the disk surface after the surface treatment. As a result of the above, V30
In the case of V50 and V50, although the surface roughness of the disk surface was deteriorated (increased in numerical value) due to the surface treatment, the amount of wear of the pin 2 was reduced, and the lubricity of the disk surface was improved. It is estimated that This is considered to be a result of the Co component on the material surface being liberated into the gas, since the numerical value indicating the surface roughness increases as the Co content increases.

Subsequently, the effect of surface treatment was investigated using a carbide tool (press-type punch) manufactured from the above-mentioned V30 type carbide material. The cemented carbide tool used is used for a press die (see FIG. 3) for molding the lamination core 3 used for the armature core of the starter. As shown in FIG. 4 (a), the slot of the lamination core 3 is used. A punch 4 for punching 3a. Note that the armature core is formed by laminating a plurality of lamination cores 3 that are press-formed in the same shape.

[Investigation result 1] Evaluation method: Of 21 punches 4 used for a press die, one of which had been subjected to surface treatment was incorporated, and the difference depending on the presence or absence of the surface treatment was compared. However, 100
Re-polishing (re-polishing amount: 0.2 mm) is performed with 10,000 shots as the number of interval shots. Number of interval shots: The number of shots at which burrs that cause problems in product quality occur. Evaluation items: Abrasion of tip of punch and amount of chipping at every interval shot are measured. The measurement site of the punch 4 is
As shown in FIG. 4 (a), two places (,) where wear easily occurs were selected.

As a result of the measurement, as shown in FIG. 4 (b), in the punch not subjected to the surface treatment, the amount of wear increased at every interval shot, and sag occurred on the side surface of the punch (measurement site). As a result, at the time of 7 million shots, the amount of sag (0.58 mm) on the side surface of the punch is large, and a polishing amount of about 0.6 mm is required for complete removal. On the other hand, in the punch 4 subjected to the surface treatment, no dripping occurs on the side surface of the punch, and the wear amount is substantially stable without increasing at every interval shot (average wear amount: 0.16).
mm), and the worn portion can be completely removed with a polishing amount of 0.2 mm. As described above, there is a great difference in the amount of wear at the tip of the punch depending on the presence or absence of the surface treatment.
An excellent effect of reducing the amount of wear was obtained.

[Investigation Result 2] Evaluation method: punches subjected to surface treatment for all 21 pieces,
The change in the amount of sag on the side surface of the punch with and without the surface treatment was investigated for all 21 punches that had not been subjected to the surface treatment. It is assumed that the number of interval shots is 2,000,000 shots. Evaluation items: The wear amount of the punch tip and the amount of sag on the side surface of the punch are measured for each interval shot.

As a result of the measurement, as shown in FIG. 5, in the case of a punch that has not been subjected to a surface treatment, the amount of re-polishing for each interval shot is large because the amount of wear is large.
It becomes necessary to remove the sag on the side surface of the punch every 100,000 shots. As a result, the total polishing amount reaches the effective blade length (8 mm) of the punch 4 in 3 million shots. On the other hand, in the punch 4 which has been subjected to the surface treatment, as shown in the above [Investigation result 1], the sagging of the side surface of the punch does not occur. It can be maintained in the best condition. as a result,
The service life of the punch can be extended up to 80 million shots, and the service life can be extended by about 2.7 times compared to a punch without surface treatment.

As described above, the results of the investigation that the properties (surface hardness, wear resistance, etc.) of the material are improved by nitriding the cemented carbide have been obtained. There is a high possibility that the expectation and demand for the nitridation treatment of the steel will increase. Here, as a result of studying that the effect of the nitriding treatment was obtained even with a cemented carbide that does not contain Fe, Cr, Al, and Mo, it can be considered as follows, though inferred. Cemented carbide is a sintered body of WC and Co, but Co contains impurities (Fe, Mo, etc.) in a small amount. When this cemented carbide is subjected to nitriding treatment, it can be estimated that the impurity components (Fe, Mo, etc.) are nitrided as shown in FIG. As a result, it is considered that the bonding force between WC and Co is strengthened, the wear resistance is improved, and the nitrided component also has lubrication performance.

The reason why the numerical value indicating the surface roughness increases as the Co content increases is considered that the Co component on the material surface is released into the gas. Therefore, V with low Co content
As shown in FIG. 6 (b), the ten kinds of carbide materials expose a large amount of hard WC due to liberation of the Co component, so that the workpiece (pin 2 in the example) is easily worn. On the other hand, as shown in FIG. 6 (c), in the V50 type carbide material having a large Co content, a lubricating component tends to remain together with Co, so that the surface treatment increases the numerical value indicating the surface roughness. Nevertheless, it is considered that lubricating properties are improved by the effect of the nitrided components. However, regarding the hardness, the influence of the ductility of Co is greater than the hardening action by the trace component, and the hardness does not improve so much.

(Effects of the present embodiment) By subjecting a cemented carbide tool made of cemented carbide to nitriding treatment (or nitrocarburizing treatment), wear resistance and fatigue strength can be improved, and the life of the cemented carbide tool can be extended. Can be extended significantly. Particularly, in the case of a press-formed product such as the lamination core 3 described in the embodiment, the mold cost accounts for about 50% of the cost. Therefore, the mold cost can be reduced by improving the life of the tool (punch 4). Also,
If the Co content of the cemented carbide exceeds a predetermined amount (for example, 8% by weight), the surface roughness increases due to nitriding, and when applying the necessary coating thereon, the adhesion with the coating layer is greatly increased. The effect that can be improved is obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of a surface treatment on hardness.

FIG. 2 is a graph showing the effect of surface treatment on surface roughness and abrasion loss.

FIG. 3 is a side view of a press die and a plan view of a lamination core.

FIG. 4 is a perspective view of a punch (a) and a graph (b) showing a measurement result of a wear amount.

FIG. 5 is a graph showing a difference in punch life depending on the presence or absence of a surface treatment.

FIG. 6 is a view for explaining the operation of the surface treatment.

[Explanation of symbols]

 4 Punch (carbide tool)

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Ryoji Nishikori 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Co., Ltd. (72) Inventor Yasuhiro Horikoshi 6-13-5 Kutsuya, Shizuoka-shi, Shizuoka Pref. F term in Kanak (reference) 3C046 FF03 FF09 FF32 FF39 FF52 4E050 JA03 JB07 JB09 JD03

Claims (2)

[Claims] (1) It is manufactured from a cemented carbide obtained by sintering WC (tungsten carbide) powder with Co (cobalt), and the manufactured product is subjected to a surface treatment by nitriding or nitrocarburizing. Carbide tool. 2. The cemented carbide tool according to claim 1, wherein the Co content is 8% by weight.