JPH0539503A - Production of punch for marking - Google Patents

Abstract

PURPOSE:To produce a punch for marking hardly causing chipping at the time of marking and having a long service life in a small number of processes. CONSTITUTION:Metal powder 3-20mum average particle diameter is kneaded with a binder to obtain a kneaded body and this kneaded body is injected into a metal mold to form a molded body similar in shape to a desired punch for marking. The binder is then removed and sintering is carried out to obtain a punch for marking having >=99.5% relative density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a punch for stamping, which is used when stamping on a metal material or the like.

[0002]

2. Description of the Related Art In order to display specific characters, numbers, figures, etc. on a material, in addition to the usual display with paint, a punch for marking having a convex portion or a concave portion corresponding to the specific character on a metal material is used. , There is a method of displaying a specific character or the like by stamping. In particular, metal materials are often subjected to heat treatment, surface treatment, etc. in the manufacturing process of materials, and ordinary paints cannot withstand these treatments. Therefore, a marking method using a punch for marking is used. .. The conventional method of manufacturing punches for stamping is to cut out a material from a molten metal material and apply letters, numbers or symbols to the stamped surface by machining, and then heat-treat or heat-treat the material and then discharge the stamped surface. The shape is given by processing.

[0003]

In the method of manufacturing the stamp for stamping described above, the problem is the method of processing the stamped surface. In the case of machining, it is a single product production one by one, which is not suitable for mass production, and further there is a problem that tool marks remain on the marking surface. There is also a problem that the life of the drill is short when processing fine characters. Further, in the case of electrical discharge machining, a plurality of electrodes for electrical discharge machining are used to process a plurality of marking surfaces at one time to increase the number of products produced, but the number of products produced is still limited. Also, when a melted material is used as the material for the punch for marking, the melted material has an average carbide grain size of 10μ.
Since it is as large as m or more, it may cause chipping. In view of the above problems, an object of the present invention is to provide a method for manufacturing a punch for stamping, which significantly improves the production efficiency, and which does not perform machining or electric discharge machining on the stamped surface, and which has improved toughness. is there.

[0004]

Means for Solving the Problems The present invention is a method of manufacturing a punch for stamping, in which a metal powder having an average particle size of 3 to 20 μm is kneaded with a binder to obtain a kneaded body, and then the kneaded body is injected into a mold. Then, a molding having a shape similar to the desired punch for stamping is formed, after removing the binder, it is sintered and the relative density is 99.5%.
A method for manufacturing a stamping punch, which is characterized in that the above-mentioned solid body is used. The most characteristic feature of the present invention is that an injection molding method is used as a method for molding the raw material powder and a near net shape is formed. As a near net shape method, a precision casting method can be considered, but it cannot be said that the toughness value is particularly sufficient in terms of mechanical properties. As a forming method of metal powder, a press forming method and a cold isostatic pressing (hereinafter referred to as CIP) forming method are widely known. However, since the press forming method is limited to a shape that can be formed in a uniaxial direction, other than a stamped surface. It is not possible to simultaneously perform the machining required for the marking punch such as displaying the marking shape on the. The CIP molding method can mold a three-dimensional shape, but since it is molded in a rubber mold, there are problems that dimensional accuracy cannot be ensured and mass productivity is not achieved.

The average particle size of the metal powder is preferably fine with respect to the microstructure of the sintered body and miniaturization of the carbide particle size. However, if it is too fine, the specific surface area of the powder increases, the amount of binder required for kneading increases, and the gap through which the decomposed binder passes at the time of debinding decreases, resulting in defective debinding, so the average particle size is 3 μm.
m or more. Also, if the average particle size becomes too large,
The sinterability of the powder itself deteriorates, making it difficult to achieve true density by sintering, or sintering at high temperature is necessary, and this causes the microstructure and carbide grain size to become coarse, so the particle size was set to 20 μm or less. High-speed tool steel is particularly preferable as the composition of the metal powder. This is because, due to the diversification of the materials to be engraved, the number of cases with particularly high hardness is increased, and the wear resistance of punch materials is required.In the alloy tool steel class, depending on the materials to be engraved,
Wear may occur earlier than with high speed tool steel.
Further, when a cemented carbide is used, chipping may occur during stamping, which may cause a problem of life.

[0006]

In the method of manufacturing a stamping punch according to the present invention, even if a cubic shaped article is targeted, it is possible to mold the details with high accuracy and use an injection molding method that is excellent in mass productivity.
It has the final shape in the state of a sintered body, and almost no post-processing is required. Also, as a metal powder, the average particle size is 3 to 20 μm.
If the high-speed tool steel powder is used as a raw material, a stamping punch having an extremely fine and uniform microstructure, higher toughness than the ingot, and good wear resistance can be obtained.

[0007]

EXAMPLES Examples of the present invention will be described in detail below. (Example 1) C 1.45 in a weight ratio equivalent to AISI T15
%, Si 0.40%, Mn 0.37%, Cr 4.2%, W 12.10%, Mo
A preliminary alloy powder consisting of 0.9%, V 4.72%, Co 4.40%, the balance Fe and unavoidable impurities was prepared. Average particle size is 39μ
The O ₂ content in m was 4500 ppm. This powder was dry pulverized with an attritor and then classified with 350 mesh to have an average particle size of 11 μm. Add 0.3% of graphite powder to this powder, and add V
After mixing with a mold blender, 1.5 parts by weight of polybutyl metaacrylate, 3.3 parts of ethylene vinyl acetate copolymer, 2.0 parts of paraffin wax and 1.2 parts of dibutyl phthalate were added and kneaded with a Henschel mixer to obtain a kneaded product.
This kneaded body is injection-molded by an injection molding machine and the convex portion 1 for marking shown in FIG.
And a molded body was obtained by injecting into a mold so as to have a shape having the engraved character display concave portion 2. This molded body in a nitrogen atmosphere
After removing the binder at 450 ° C for a holding time of 30 minutes,
Sintering was carried out in vacuum at 1233 ° C. and a holding time of 45 minutes. The C content of the sintered body was 1.53 wt% and the specific gravity was 8.20 g / cm ³ ,
No residual pores were observed on the microstructure, and it was judged that the true density was substantially achieved. Further, as a result of X-ray inspection, no internal defect was found. Quench the above stamp for engraving at 1200 ° C in a vacuum furnace of 1 × 10 -4 torr and then at 560 ° C 3
It was tempered and tempered to a hardness of HRC63.0. When this was attached to an engraving machine and an engraving test was conducted on a flat plate of SUS304, no chipping was observed even after the engraving test of 100,000 times.

(Example 2) A metal powder having a composition substantially similar to that of Example 1 is shown in Table 1 as an example.
The same kind of binder as in Example 1 was added to the powder having an average particle diameter of 3 to 20 μm and kneaded until kneading was possible. Each kneaded body was injection-molded in the same manner as in Example 1 to remove the binder and sinter, and then heat-treated to obtain the stamping punch shown in FIG. Further, as comparative examples, powders having average particle diameters of 2 μm and 21 μm were obtained in the same manner. Similarly, as a comparative example, the ingot was formed by electric discharge machining to form a convex portion for marking, and the shape shown in FIG. 1 was obtained. In the case of the fine cast material, the shape shown in FIG. 1 was directly obtained by casting. Table 1 shows the results of mounting these on a stamping machine and performing a stamping test on a flat plate of SUS304.

[0009]

[Table 1]

In Table 1, the defects of the sintered body indicate the presence or absence of cracks which are defects in appearance. The density is a relative value of the theoretical density calculated from the composition. Durability is the number of stamps in which chipping was confirmed. From Table 1, it can be seen that if the particle size of the metal powder as the raw material is smaller than 3 μm, cracks are generated, which is not preferable.
On the other hand, if the particle size is larger than 20 μm, the density decreases, chipping during stamping occurs early, and the life is shortened, which is not preferable. Further, in the comparative example, it was confirmed in the stamping test that the ingots and refined castings had more chipping and were inferior in toughness than the materials of the present invention.

(Example 3) C 3.10% by weight, Si 0.44
%, Mn 0.37%, Cr 4.08%, W 9.00%, Mo 7.8%, V 8.0
A water atomized prealloy powder consisting of 9%, Co 8.4%, balance Fe and unavoidable impurities was prepared. Average particle size is 15μ
The O ₂ content in m was 4500 ppm. 10% Ti on this powder
After adding N powder, it was dry-ground with an attritor to obtain an average particle size of 8 μm. Graphite powder was added to this powder in a weight ratio of 0.21% and mixed with a V-type blender for 12 hours to obtain a raw powder of ultra-hard high-speed tool steel. To this mixed powder, 1.6 parts of polybutyl metaacrylate, 3.4 parts of ethylene vinyl acetate copolymer,
Paraffin wax (2.0 parts) and dibutyl phthalate (1.2 parts) were added, and the mixture was kneaded with a Henschel mixer at 160 ° C. and coarsely pulverized to obtain a kneaded body for injection molding. This kneaded body was injected into a mold in the same manner as in Example 1 to obtain a stamped punch compact shown in FIG. Obtained compacts in hydrogen atmosphere at 500 ℃
After that, the binder was removed by holding for 1 hour. Then 1x
Sintering was performed by holding at 1240 ° C. for 1 hour in a reduced pressure atmosphere of 10 −4 torr. The density of the obtained sintered body was 100% true density. This sintered body was hardened at 1230 ° C. in a vacuum furnace of 1 × 10 -4 torr and then tempered 3 times at 560 ° C. to obtain a punch for hardness HRC71. When this punch for marking was attached to a stamping machine and a stamping test was conducted on a flat plate of SUS304, no chipping was observed even after the stamping test of 100,000 times.

[0012]

According to the present invention, it is possible to remarkably reduce the manufacturing process of the punch for stamping, which has been time-consuming.
Further, the stamping punch obtained by the present invention is a stamping punch with less chipping at the time of stamping, high durability, and long life, and is extremely useful in maintaining the quality of stamped characters and the like. ..

[Brief description of drawings]

FIG. 1 is an external view of a marking punch manufactured according to the present invention.

[Explanation of symbols]

 1 Convex part for engraving 2 Recessed part for engraved character display

Claims (2)

[Claims] 1. A metal powder having an average particle diameter of 3 to 20 μm is kneaded with a binder to obtain a kneaded body, and the kneaded body is injected into a mold to have a molding similar in shape to a desired punch for marking. The method for producing a stamp for stamping is characterized in that after the binder is removed, it is sintered to obtain a solid body having a relative density of 99.5% or more. 2. The method for manufacturing a stamping punch according to claim 1, wherein the composition of the metal powder is high speed tool steel.