JPS6033881B2 - Sintering method - Google Patents

Description

[Detailed description of the invention] Conventional powder sintering involves inserting and filling sintered powder into a required die,
This is punch-pressed and heat-sintered, but the surface of the powder has oxides and oil stains, which reduces the sintering result, and usually requires extremely long heat treatment, which reduces the strength of the finished product. etc. also have low disadvantages.

In order to eliminate this drawback, the present invention sinters the powder while activating it during feeding, and is characterized in that the activation is performed by causing an electric discharge between the powders.

The discharge competitive mackerel method invented by the present inventor is already well known.

This is done by filling a sintering mold made of heat-resistant and electrically conductive graphite with scorching powder, and pressing the powder with a pressing body (usually made of graphite) that also serves as a roaring pole to approx. 0.5 to 10 k9/carp. By applying a large current while applying a light compression pressure, a discharge is generated between the powders, and along with this, Joule heat is generated to sinter the powder. The powder is initially activated by electrical discharge, heated in the activated state, and compacted by compressive pressure.The powder follows the pressure during this electrical discharge treatment, that is, the activation treatment of the powder is best carried out. It is not easy to optimally control the state in which the powders approach each other, and furthermore, the sintering time is usually performed in a noisy short time of several to several hundred seconds, so the powder control is extremely difficult. The present invention also utilizes this principle of interpowder discharge, but before sintering, the powders are bonded and molded with an adhesive resin, etc. In this case, unlike conventional furnace heating sintering, If the powders are brought into contact with each other by high pressure press molding of several tons/ground and the specific resistance (of the molded body) is large and is less than lmQ, no discharge between the powders can be expected, and adhesive bonding of the powders cannot be expected. It is characterized in that they are combined so that the specific resistance of is equal to or higher than lmQ. An embodiment of the present invention will be explained below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a screw device for kneading and extruding powder to be sintered with adhesive resin, etc., and raw materials are mixed and supplied from hoppers 2 and 3. Hopper 2 is filled with sintered powder, and the other hopper 3 is filled with adhesive. Adhesives include gum arabic, trigant rubber, natural rubber, EP rubber, SBR, NBR, CR.
, 11R, P1, PB, etc., various synthetic rubbers, vinyl acetate type, polyvinyl type, vinyl chloride type, asphalt type,
Various resins such as acrylic, cellulose, polyurethane, polyester, polystyrene, butyral, ethylcellulose, styrene, phenol, urea, and melamine, as well as alginic acid, dextrin, glycerin, gelatin, casein, and water glass. , and various other substances are used, and usually several types are used in combination, and other adjuvants and solvents are required. Each hopper 2 and 3 is equipped with a screw for adjusting the supply amount, and the adhesive supplied from hopper 3 is usually adjusted by volume to the powder of metal, alloy, non-metal, etc., which is the sintered powder supplied from hopper 2. Supply and blend in a range of about 10 to 80%. The mixture thus supplied to the rice bran device 1 is mixed with a small amount of solvent and kneaded by rotating the screw, and is mixed into rice bran while being heated if necessary, and extruded from the tip nozzle in a well-kneaded state.

4 is a rolling device that rolls the injected material into a desired shape;
Although not shown, heating drying, blowing drying, etc. are also carried out as appropriate during molding.

5 is cut and formed into blocks, plate pieces, etc. of required dimensions by a cutting device.

Of course, the forming is not limited to the above-mentioned roller rolling, but other suitable methods such as die extrusion and die press forming can be used, but the key is to make an ingot with resin bonded sintered powder, or to create a sintered raw material with the desired shape. to make.

By controlling the amount of resin and compressive force, the specific resistance can be reduced to l.
They are coupled to have a resistance equal to or higher than mQc. FIG. 2 shows an example for explaining the competitive bonding process, in which 7 is a vacuum-resistant container constituting a sintering device, 8 is a base, and these two are airtightly connected via a vacuum packing.

Reference numeral 9 denotes a rotatable turntable, on which the bonded body 6 obtained by adhesive bonding in the previous step is placed in a layer.

1 is a nine-rotation table motor; 11 is a magnetron for irradiating a high-frequency electric field; 12 is a waveguide; and 13 is a loss fan.

14 is an exhaust port suitable for a vacuum pump device (not shown).

During firing, the inside of the container 7 is evacuated.

The degree of vacuum is controlled according to the type of sintered metal. Usually 1
It is applied to various metals in the range of 0-1 to 10-3 tons. After vacuum control is performed in this manner, the magnetron 11 is operated to irradiate high frequency waves. The high-frequency waves are irradiated through the waveguide 12, and the combined body 6 is rotated by the Azusa fan and the turntable 9, so that the high-frequency waves are evenly irradiated to the entire unbroken body 6. Due to this high frequency irradiation, an electromotive force is generated in the bonded body and an eddy current flows, but the adhesive resin is interposed between the metal powder particles of the bonded body 6, and the resistivity as a whole is higher than lmQ skin level. It is configured to have high resistance, and eddy current flows between powders accompanied by interpowder discharge, and this discharge occurs,
The eddy current is applied uniformly throughout. Oxides and oil films are usually attached to the powder surface, but the micro-discharge generated between the powders decomposes these impurities, and the decomposed products become gaseous and are expelled to the outside, thus forming powder particles. is cleaned and further ionized, etc., to bring it into a highly activated state. The powder in this state is simultaneously heated by Joule heat caused by the eddy current, and becomes diffusely bonded to each other. During the setting, the adhesive resin and the like present in the bonded body are decomposed and scattered, resulting in a good setting process with no impurities in the bran body. Practical high-frequency electric fields are used with frequencies of about 10 KHZ to 1 MHZ, but
Furthermore, even at frequencies lower than this, for example, when a sintered body is inserted into an induction coil and sintered, a frequency of about HZ to 10 KHZ can be used.

Note that a changing magnetic field can be applied to the sintering power, and in addition to these changing electric and magnetic fields, direct energization can also be superimposed by bringing the poles into contact with each other.

Also, various configurations of bidding devices are available. In addition, if vacuum sintering is used as the marriage atmosphere, the gases generated due to powder purification by electric discharge, decomposition of the binder, gas deoxidation, degassing effect will be enhanced, the sintering will become more compact, and good results will be achieved. However, the present invention is not limited to these, and it is also possible to carry out the process in air. If the process is carried out in a reducing atmosphere of an inert gas, the atmospheric pressure can be controlled arbitrarily. Dawning time is sand with a bullet constant of 1.
It can be sintered in a very short time, within one minute at most. For example, styrene resin 10%, triol 6
%, methyl ethyl chelone 3%, glycerol phthalate 1
．． 2% and the rest of #150 A〆 powder to make an outer shape of 2mm? , inner diameter 1 x ◇, length 15 side cylinder and molded together,
The specific resistance is 0.010c, which is 2.469 M.
HZ, 1. When an electric field of arc W was applied and sintering was performed in 250q0 air, 19 sand could be sintered.

Also, when 1 to 2 pieces of WC was sintered, it was possible to sinter with about 3 pieces of sand. Sintering is completed as described above, but in the present invention, the sintered powder is first hardened with an adhesive, and it may have a desired shape or may be an ingot. are combined so that they have a high resistance equal to or higher than lm○ skin, and this is sintered, so conventional press equipment, etc.
Unlike secondary discharge sintering, there is no need to perform difficult pressure control during sintering, making it easy to sinter silk.

Sintering is performed by inducing an electromotive force by applying a changing electric field or changing magnetic field to the bonded powders having high resistance, so that the induced electromotive force generates a discharge between the powders and an eddy current is generated. Flowing, the surface of the powder is purified and activated, and at the same time, diffusion bonding is performed by Joule heating, and the electromotive force is applied to the entire bonded powder, resulting in rapid sintering in a short time. . This is conventionally several tons
When high-pressure press-molded powder with a size larger than a whisker is subjected to current resistance sintering and high-frequency sintering, the powders in the compact are closely bonded to each other, and the specific resistance is sufficiently lower than that of m○ skin, making it susceptible to lightning strikes. Due to the flow, only inefficient Joule heating could be performed, and interpowder discharge could not be expected at all.
As mentioned above, the present invention can perform sufficient treatment by electric discharge,
This enables activated sintering, which enables sintering with high bond strength in an extremely short period of time due to ion diffusion and thermal diffusion effects. After sintering, the corded product can be subjected to forging, sizing, or coining to increase its density, or can be processed in various ways to obtain a predetermined shape by cutting.

In addition, sintering is effective when a powder composite is placed on a base and welding is performed at the same time as sintering.In this case, for example, it is effective when welding a wear-resistant material to the wear-resistant part of the base. It is preferable to bond and mold them into a tape or sheet shape with an adhesive and sinter them while affixing them to a base.

[Brief explanation of drawings]

The drawings are folded configuration diagrams of an embodiment of the present invention, in which FIG. 1 shows an apparatus for performing powder bonding, and FIG. 2 shows a sintering apparatus. 1... Moat kneading screw, 2, 3... Competitive powder and binder supply hopper, 4... Rolling device, 5
. . . Cutter, 6 . . . Unsintered bonded powder, 9 . . . Turntable, 11 . . . Magnetron, 14 . Saifu spear 2i seal

Claims (1)

[Claims] 1. Powder particles to be sintered are bonded using an adhesive resin or the like so that the resistivity becomes 1 mΩcm or more, and a changing magnetic field or a changing electric field is applied to the bonded body to generate an interpowder discharge. A sintering method characterized by sintering while sintering. 2. The sintering method according to claim 1, wherein the sintering is performed in controlled air, vacuum, or reducing atmosphere. 3. The sintering method according to claim 1 or 2, wherein the entire bonded body is sintered while being moved during sintering.