JPH0323010A - Die for wire drawing and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture an excellent die in wear resistance at low cost by forming the film of hard carbon on the inside surface of the hole of die of sintered hard alloy for wire drawing. CONSTITUTION:Under reduction of pressure, hydrocarbon gas, which is raw materials for hard carbonic film, is introduced and ionized by glow discharge and a red heated filament 33 and that ion is drawn out under spreading magnetic field of the magnet 34. The ion which is drawn out is accelerated toward a base material 31 which is applied with negative bias voltage and is brought into collision and vapor deposition with the base material. It is enough to use hydrocarbon of methane, etc., as material gas and also hydrogen gas may be used as dilute gas. Pressure in a vessel is taken as a prescribed vacuum to produce plasma and to accelerate ion. As the temperature of the base material, a good film is formed in a prescribed range of temp. from room temperature. A prescribed bias voltage is applied between the base material and ion source which is taken as a prescribed magnetic flux density. Thereby, the hard carbonic film 11 is formed and the excellent die in wear resistance can be manufactured at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wire drawing die used for drawing metal wire and a method for manufacturing the same.

(Prior art) The processing of cotton material made of metal materials such as steel and copper usually involves a drawing process in which the material is passed through a die with a hole in the center and pulled out to reduce its cross-section to a round or irregularly shaped cross-sectional shape. is being carried out. The equipment used for this is called a wire drawing machine, and the part with the hole for wire drawing is called a wire drawing die, and conventionally steel dies, cemented carbide dies, and diamond dies have been used. Steel dies have been used for the longest time, and high carbon steel and high chromium steel have been used, but due to their poor wear resistance, they are now rarely used.

Cemented carbide dies are sintered alloys that contain 80 to 95% of the main precept, tungsten carbide, as well as several percent of cobalt and carbon, and are superior in hardness to steel.
Due to its good abrasion resistance, it is currently widely used for drawing various metal materials.

For wire drawing of metal materials, it has high hardness and excellent wear resistance.
It is necessary to use a die with good surface smoothness. That is, in wire drawing of metal materials, a very large shear stress acts on the wire drawing die as well as the wire rod, so a die with high hardness, excellent wear resistance, and durability is desirable. If the durability of the die is poor, wear will be severe and the inner diameter of the die will expand during wire drawing, making it impossible to draw the wire to the correct wire diameter. At the same time, since the surface smoothness of the die is lost, the surface of the metal wire to be drawn also becomes uneven.

If the die deteriorates, it will be necessary to replace it even during the wire drawing process, so a die with excellent durability is desirable from the perspective of improving the operation rate of the wire drawing process. For wire drawing dies to have high durability, it is important that they have high hardness, excellent wear resistance, and a smooth surface with a low coefficient of friction. Wire drawing of metals such as steel and copper is often carried out cold because it is difficult to maintain a constant high temperature due to the nature of the processing, but recently the drawing speed has been increased to 800 m.p.m. to improve productivity. High-speed machining performed at speeds of 1/min or more has become mainstream. As wire drawing dies are used under extremely harsh conditions, there has been a demand for further improvement in their durability. Due to its excellent hardness, diamond dies are used for thin wires that are difficult to machine with cemented carbide, but they require large diamonds and are very expensive (for example, ``Mechanical Engineering Handbook'') (Published by the Japan Society of Mechanical Engineers, 1981).

(Problems to be Solved by the Invention) The present invention provides a wire drawing die that has better wear resistance than cemented carbide dies and has a manufacturing cost equivalent to that of cemented carbide dies, and a method for manufacturing the same. be. In the wire drawing process of metal materials, if the life of the wire drawing die can be extended and the cost reduced, the wire drawing cost can be significantly reduced, and the present invention makes this possible.

(Means and effects for solving the problems) In order to solve the above problems, the present invention forms a hard carbon film with excellent hardness and wear resistance on the inner surface of the hole of a wire drawing die made of cemented carbide. The hard carbon film is deposited using a vapor phase method.

The hard carbon film referred to in the present invention is as follows. The main element in the structure is carbon, which has a hardness similar to that of natural diamond, and is amorphous, with an electron diffraction pattern showing a halo pattern. The Ramanth vector shows broad peaks characteristic of amorphous materials near 1580 cm-' and 1360C11-'. A thin film of hard carbon was examined using a scanning electron microscope.
When observed under magnification, the film is uniform and smooth with no crystal grains. Hard carbon films are generally produced by a gas phase process using hydrocarbon compounds as raw materials, and have a thickness of approximately 4Qa.
Contains less than toa+% hydrogen. It is thought that hydrogen enters the dangling pond portion of the carbon atom, stabilizing the amorphous state and creating a highly hard structure. It is presumed that in the presence of an appropriate amount of hydrogen, hard carbon exhibits high hardness comparable to natural diamond.

If there is too much hydrogen in the hard carbon film, it becomes a soft organic film. Therefore, in the hard carbon film of the present invention, the proportion of hydrogen in the film is 35 atom% or less, preferably 5 to 3 Qa.
A tor of 6% is suitable. Such a hard carbon film has a vinyl hardness of 4,000 to 7,000 and a friction coefficient of 0.
1 to 0.2, it is known to exhibit physical properties second only to natural diamond.

The base material targeted by the present invention is a cemented carbide, which, as explained earlier, contains 88% of the main strength of tungsten carbide.
It is a sintered alloy containing 0 to 95% of cobalt and several percent of carbon. The hard carbon film can be a coating with excellent film adhesion when a material such as tungsten that forms a highly covalent bond with carbon is used as the base material. Unless the adhesion between the base material and the film is strong, even if the film itself is extremely hard, the film will peel off at the interface between the base material and the film, making it unsuitable for practical use.

In particular, in the present invention, as explained in the examples, in order to maintain the temperature of the die at a high temperature and irradiate the die with high-speed ions, it is necessary to make the adhesion between the tungsten carbide cemented carbide and the hard carbon film extremely good. I can do it.

Generally, the shape of a wire drawing die has a conical hole 21 as shown in FIG. The drawn wire rod and bar material come out. FIG. 1 shows a cross-sectional view of a hard carbon film 11 formed on the inner surface of the hole of this wire drawing die using a vapor phase method.

The method of the present invention will be explained below. As already mentioned, conventional wire drawing dies use cemented carbide containing 80 to 95% tungsten carbide as a main ingredient and several percent cobalt and carbon as sintering agents. However, in the present invention, a hard carbon film is deposited on this cemented carbide wire drawing die by a vapor phase method. The vapor phase deposition method of the hard carbon film used in the present invention includes the plasma CVD method (for example, "Fundamentals of Plasma and Command Film", published by Nikkan Kogyo Shimbun, 1985) and ionization vapor deposition method, which have been commonly used in the past. However, the adhesion of the film to the substrate.
From the viewpoint of uniformity of film quality, smoothness of film surface, and productivity,
JP-A-59-174507, JP-A-59-174
An ionized vapor deposition method such as that disclosed in Japanese Patent No. 508 is preferred.

FIG. 3 shows a diagram of the principle of the ionization vapor deposition apparatus. A hydrocarbon gas, which is a raw material for a hard carbon film, is introduced under reduced pressure, and is ionized by a glow discharge and a red-hot filament 33.
'The expanding magnetic field of the g1 magnet 34 pulls out these ions.
This part covered with electromagnets is called the ion source. The extracted ions are accelerated toward the base material 3l to which a negative bias voltage is applied, collide with the base material, and are deposited. Methane and ethane are used as raw material gases. Hydrocarbons that can be easily introduced as a gas such as acetylene and benzene may be used, but methane is particularly preferred. Hydrogen gas may be used as a diluent gas for the above-mentioned raw material gas. Since it is necessary to generate plasma and accelerate ions, the pressure inside the container is I
to 1 Torr may be sufficient, but the film quality may vary. From the point of view of film growth rate IX 10'''Torr to lX10-'
orr is desirable. The temperature of the base material is set to room temperature (25℃
A good thin film is produced when the temperature is set from 100°C to 600°C. Within this range, a particularly preferred range is from room temperature (about 25°C) to 300°C. If the substrate temperature is higher than 600°C, the film created tends to become graphite-like, and even if a hard carbon film is formed, if it is left to cool to room temperature, the bond between the substrate and the film will deteriorate. Residual thermal stress increases, and the film becomes more likely to peel off during subsequent use.

The bias voltage between the substrate and the ion source is from -50V to -
The voltage is set at 1500V, with a preferable range of -500V to -IOOOV. When hydrocarbon ions are accelerated by a bias voltage and collide with a substrate, the C-H bonds of the colliding ions are broken due to the collision energy, and the hydrogen atoms are ejected. The amount of hydrogen atoms ejected depends on the kinetic energy of the colliding ions, that is, the bias voltage; if the bias voltage is too low, a soft, organic film with a large amount of hydrogen tends to form, whereas if the bias voltage is too high, a graphite-like film tends to form. Furthermore, self-sputtering of the membrane occurs and the membrane speed decreases.

The appropriate range of magnetic flux density in the ion source is from IOOG to IOOOG, and more preferably from 300G to 500G. The detailed manufacturing conditions vary depending on the arrangement of the gas inlet in the apparatus, the size of the ion source, the position of the substrate, etc., and therefore it is desirable to set optimal conditions as appropriate.

By the above method, a die on which a hard carbon film is deposited is produced as shown in FIG. The die made by this method has a hardness of 4000 to 7000 on the Vickers scale,
Compared to conventional cemented carbide dies, the durability is significantly improved and the lifespan of the dies is greatly extended.

In addition, the hard carbon film has a friction coefficient of 0. 1 to 0.2, and the surface smoothness is good, so that the wire rod or bar material slides easily, and the surface smoothness and gloss of the wire-drawn material are excellent.

This will be explained in more detail in Examples below. [Example] Example 1 As shown in Figure 2, the hole diameter is 4f with a mirror finish on the surface.
Made of fIII1 cemented carbide (tungsten carbide 9
The wire drawing die (containing 2% cobalt, 5% cobalt, and 3% carbon) was washed with hydrochloric acid as a pre-evaporation treatment to remove cobalt on the surface. Next, using the ionization vapor deposition apparatus shown in FIG.
X 1 0-”Torr, base material bias voltage-8 0
0 V, base material temperature 300°C, ion current 2 ta
It was deposited for 60 minutes under the conditions of A/cn.

The prepared die had a smooth surface and was uniformly coated with a hard carbon film about 2n thick that did not peel off.

The hydrogen content of this film was 13 atom%, and the electron beam diffraction image showed a halo pattern.

In the Lamans vector, 158 leaves are around 1 and 1360 cm.
A broad peak was observed near +-'. Areas where vapor deposition was not required were masked to prevent the hard carbon film from being vapor deposited.

When a steel wire with a diameter of 4III1 was drawn using this cotton drawing die, 3500 kg of steel wire could be drawn. For comparison, when wire was drawn using a conventional cemented carbide die, the wire deteriorated after 600 kg of wire was drawn and had to be replaced.

Furthermore, the surface of the wire drawn using the die of the present invention was more glossy than that drawn using a conventional cemented carbide die.

Example 2 A wire drawing die made of cemented carbide (containing 95% tungsten carbide, 3% cobalt, and 2% carbon) with a three-shaped hole was subjected to the same pretreatment as in Example 1. Thereafter, a hard carbon film was deposited using the apparatus shown in FIG.

The conditions for vapor deposition were to use pure methane as the source gas and a pressure of 10.
-'Torr, acceleration voltage 600V, base material temperature 300'C
, and an ionic current of 2.3 mA/cffl. A mask was placed on areas where vapor deposition was not required to prevent the hard carbon film from adhering.

When a copper wire with a diameter of 3 m was drawn using the wire drawing die made in this manner, it was possible to draw 6,000 kg of wire. For comparison, when wire was drawn using a conventional cemented carbide die, the wire deteriorated at 800 kg.

Furthermore, the surface of the wire drawn using a die was more glossy than that drawn using a conventional cemented carbide die.

(Effects of the Invention) As explained above, according to the present invention, by applying a hard carbon film to a wire drawing die made of cemented carbide, it is possible to manufacture a die with excellent wear resistance at low cost. the result,
The cost of drawing metal materials is greatly reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a wire drawing die provided with a hard carbon film 11. FIG. 2 is a cross-sectional view of a normal wire drawing die on which a hard carbon film is not deposited. FIG. 3 is a schematic diagram of the ionization vapor deposition apparatus. 3l: base wire drawing die, 32: grid, 33: filament, 34: electromagnet, 35: gas introduction tube. Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A wire drawing die made of cemented carbide with a hard carbon film provided on the inner surface of the hole. (2) A method for manufacturing a wire drawing die, which comprises depositing a hard carbon film on the inner surface of a hole of a wire drawing die made of cemented carbide by a vapor phase method.