JP2003113404A - Sintering method for hard alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintering method for a hard alloy, which reduces adverse effects to operators, air and soil and which prevents the contact reaction of the sintering tray. SOLUTION: The sintering method for the hard alloy comprises mounting pressed bodies 3 of the hard alloy on a sintering tray 2 to sinter it, and applying a coating material 1 which contains; at least one of carbon, graphite, aluminum oxide and zirconium oxide; a material containing (C6 H10 O5 )n ; and water; onto the surface of the sintering tray 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention suppresses the diffusion of the constituent elements of the sintering tray on which the pressed body is placed into the inside of the pressed body when the pressed body of the hard alloy material powder is sintered. The present invention relates to a sintering method for a hard alloy, which is optimal for reducing adverse effects on the atmosphere and the atmosphere.

[0002]

BACKGROUND OF THE INVENTION Hard alloys usually mix their materials,
The pressed compact is placed on a sintering tray and sintered.
The sintering tray is made of carbon or graphite, which has a high heat resistant temperature and good workability. During sintering, depending on the type of hard alloy, the sintering tray causes a contact reaction with the press body and partially welds, making it difficult to peel the hard alloy after sintering, or damaging the hard alloy during peeling. There is a risk of doing it.

FIG. 4 is an explanatory view schematically showing a sintered state of a press body placed on a sintering tray. As shown in FIG. 4 (A), for example, a hard phase 42 made of WC and a binder phase 43 made of Co.
A hard alloy press body 41 composed of is placed on a sintering tray 40 made of carbon and sintered.
When the sintering starts, as shown in FIG. 4 (B), it liquefies as a eutectic phase of the hard phase 42 and the binder phase 43 at around 1300 ° C., and part of it oozes out to the surface of the sintered body 44. . Also, sintering tray 40
, A part of carbon escapes as carbon, and a void 45 is generated. As the sintering progresses further, the hard phase 42
The liquefaction part 46 liquefied as a eutectic phase of the binder phase 43 and the binder phase 43 flows to the surface of the sintering tray 40. The active carbon that has escaped from the sintering tray 40 through the liquefaction part 46 diffuses inside the sintered body 44 or exists as solid carbon as a solid solution, and an abnormal phase (in this case, in the sintered body 44). WC + Co + C). The hard alloy having such characteristic abnormality is a defective product.

Therefore, conventionally, on the surface of the sintering tray,
It is known to apply a coating material that suppresses contact reaction with a sintered body of a hard alloy. As this coating material, a mixture of carbon powder that suppresses a contact reaction and vinyl acetate resin that functions as an adhesive that fixes the carbon powder on the surface of the sintering tray is used. Since vinyl acetate resin alone has a high viscosity at room temperature and is difficult to apply to the sintering tray, an organic solvent such as dichloromethane having a high dissolving ability is used to facilitate the application. Such a conventional coating material is applied to the surface of the sintering tray by using a spray or a brush.

[0005]

However, organic solvents such as dichloromethane may adversely affect workers. Further, since it has high volatility, it may be diffused or scattered in the air or soil during the coating work to contaminate the air or soil.
In particular, application by spraying tends to further increase the above diffusion and scattering. This spray application causes a relatively large loss of the coating material due to the rebound from the sintering tray, and is not economical. Further, after the covering material is scattered, it takes time to clean the equipment and floor surface, and the workability is poor. Then, in order to apply the coating material to the sintering tray evenly and uniformly using a spray or a brush, the skilled skill of the operator is required, and it is often necessary for any operator to rework, and the workability and The economy is poor.

[0006] Therefore, an object of the present invention is to provide a method for sintering a hard alloy which can suppress the contact reaction of the sintering tray and reduce the adverse effects on the operator, the atmosphere, the soil and the like. .

[0007]

SUMMARY OF THE INVENTION The present invention is a method for sintering a hard alloy, in which a pressed body of a hard alloy material is placed on a sintering tray and sintered, which comprises at least carbon, graphite, aluminum oxide and zirconium oxide. One kind, (C ₆ H
A coating material containing ₁₀ O ₅ ) n and water is applied to the surface of the sintering tray. That is, in the coating material applied to the surface of the sintering tray, the present invention plays a role of an adhesive agent for fixing the material that suppresses the contact reaction with the sintered body of the hard alloy material (C ₆ H ₁₀ A material containing O ₅ ) n is used, and water is used as a solvent.

The present invention provides a coating material for a sintering tray (C₆H
_TenO_Five) n, by using materials and water,
Extremely less adverse effect on soil compared to conventional
can do. In addition, carbon, graphite, acid
Contact inhibitors such as aluminum oxide and zirconium oxide
Active carbon that has come out of the sintering tray because it contains
Are diffused inside the hard alloy to form an abnormal phase, which may cause abnormal characteristics.
It never happens. Furthermore, (C₆H_TenO_Five) n containing materials and water
By using it, it can be applied by spraying and the coating material can be scattered.
However, it is easy to clean the equipment, floor, etc.
Good. In addition, (C₆H _TenO_Five) n-containing materials and water are easily
Because it is cheap and affordable, it is also economical. And
(C₆H_TenO_Five) n-containing material is thermally decomposed by high temperature
Some of the carbon remains in the coating and remains
A covering material used in the present invention, which is considered to have a similar function.
Have superior properties to conventional dressings.

The present invention will be described in detail below. (C ₆ H
₁₀ O ₅ ) n is a hydrophilic linear polymer compound composed of amylopectin and amylose, and the ratio of both depends on the raw material. (C ₆ H ₁₀ O ₅ ) n becomes a viscous state by dissolving it in water or heating this aqueous solution to a certain temperature, and functions as an adhesive. When heated at high temperature during sintering, (C ₆ H ₁₀ O ₅ ) n is decomposed into carbon dioxide, carbon, water, etc., diffused into the sintering furnace, and exhausted outside the furnace by an exhaust pump. .

Examples of the material containing (C ₆ H ₁₀ O ₅ ) n include grains and potato powders, processed products using them, and chemically synthesized products. In the present invention, in particular, Preferred is starch paste, starch starch, or wheat flour. More preferably,
It is a starch paste that is highly viscous at room temperature. As these materials, commercially available materials may be used. In the present invention, the material comprising _{(C 6 H 10 O 5)} n , in a state excluding the water _{(C 6 H 10 O 5)} n ratio of (weight) is assumed to occupy 50% or more. More preferably, it is 80% or more.

As the starch raw material, the starch paste includes, for example, a mixture of wheat flour, corn flour and starch starch. Among these flours, especially wheat flour, in addition to the viscosity of (C ₆ H ₁₀ O ₅ ) n, produces gluten rich in viscosity when it absorbs water. Therefore, the coating material mixed with wheat flour was superior in viscosity. It becomes a thing.

(C ₆ H ₁₀ O ₅ ) n of potato starch (many of which are commercially available is made of potato) has a preferable viscosity as an adhesive unless it is kept at a constant temperature (gelatinization temperature range of 56 to 66 ° C.). Not. Therefore, when starch starch is used, it is preferable to apply it while maintaining the gelatinization temperature.

[0013] Wheat flour is preferable as a material for the adhesive because it has the viscosity of gluten in addition to the viscosity of (C ₆ H ₁₀ O ₅ ) n as described above.

Carbon powder, graphite powder, aluminum oxide powder and zirconium oxide powder which are stable compounds are liquefied in the pressed body by being interposed between the pressed body of the hard alloy material and the sintering tray. Prevents the binder phase from contacting the sintering tray. Such a powder preferably has a particle size of several μm to several tens of μm. More preferably, a mesh (Taylor formula, the same applies below) of 100 to 60 is 10% by volume or less, a mesh of 300 to 200 is 15 to 90% by volume, and particularly a mesh of 80 or more is 5% by volume or less, a mesh. A mixture of 20 to 80% by volume of 250 or less is suitable. Further, any one of these powders exerts a sufficient function as a contact inhibitor, but, of course, a plurality of types may be mixed and used.

With respect to the above-mentioned mixing ratio, the amount of water may be appropriately adjusted depending on the water content of the material containing (C ₆ H ₁₀ O ₅ ) n. For example, when using only starch paste, the contact inhibitor in weight (kg):
Starch glue: water = 1: 1.5: 5 to 1.5: 3: 5 is preferred. In particular,
1: 2: 4 is preferred. Since potato starch and wheat flour have a lower water content than starch paste, it is better to increase the water content than the above ratio. Further, the viscosity required as a coating material can be realized by the above-mentioned composition.

In the present invention, the coating material is preferably applied uniformly. When the pressed body of the hard alloy material powder is sintered, the volume shrinks to about half. Therefore, if the coating material is not applied uniformly and there are irregularities (unevenness of coating), when the sintered body shrinks, there is a large frictional resistance such as catching on the irregularities, and the shrinkage cannot be performed well and distortion occurs. It becomes a defective product. Therefore, in the present invention, in particular,
The coating material is applied uniformly to improve the slipperiness at the boundary between the sintering tray and the sintered body. To apply the coating material uniformly, a brush or the like may be used, but a commercially available known flow coater type automatic application device (for example,
The use of JP-A Nos. 7-168015 and 6-154686) is preferable because it can be applied easily and uniformly and the workability can be improved without the need for rework.

A flow coater means that the coating material is not discharged like a curtain from the tip of the lip portion of the funnel-shaped mouthpiece, that is, the coating material is not dropped but dropped into a liquid state without interruption, and the tip of the lip portion is dropped. This is a method of coating without contacting the material to be coated. In this method, since the supply path of the coating material until it is discharged is closed, there is almost no foreign matter mixed in, and since there is little change in the viscosity of the coating material, the coating film thickness can be made uniform. This flow coater type automatic coating device has a tank for storing the coating material, a head portion having a die for discharging the coating material supplied from the tank in a curtain shape, a belt conveyor or a roller for transporting the coating material. It is known to have a carrying part made up of, for example. The lip portion of the die has a size suitable for the size of the sintering tray.

When using the above automatic coating device, the coating material is
It is necessary to have a flow rate that is enough to expel in a curtain shape. Specifically, the flow rate of the coating material before coating is preferably 3.5 to 8.0 sec / 40 ml. Particularly, 5.0 to 7.0 sec / 40 ml is preferable. Such flow rate can be realized with the above-mentioned mixing ratio. When using a brush or spray, 3.0 to 10 s
ec / 40 ml is preferred.

In the present invention, the flow rate means a funnel having a maximum inner diameter of the conical portion of 75 mm, a height of the conical portion of 60 mm, a length of the cylindrical portion of 10 mm, and an inner diameter of the cylindrical portion of 5 mm, and the opening of the cylindrical portion is closed. In the state, 40 ml (40 cm ³ ) of the coating material was put, and the time (seconds) from the opening of the cylindrical portion to the disappearance of the coating material in the funnel is shown.

The coating thickness of the coating material is 0 before drying.
01 to 1.0 mm, particularly 0.03 to 0.2 mm is preferable. If the thickness is too thicker than the above stipulation, it is difficult to obtain flatness and uniformity, which is not preferable. On the contrary, if the thickness is less than the above range, the effect of suppressing the contact reaction becomes uneven, which is not preferable. The thickness after drying is preferably 0.01 to 0.1 mm, particularly preferably 0.02 to 0.05 mm. The drying after coating is preferably performed to such an extent that the press body does not get wet with the coating material when the press body is placed.

In the present invention, the sintering tray may be a known one formed of any one of carbon, graphite, aluminum oxide and spinel. Hard alloy, for example, periodic table IVa, Va, VIa group metal elements, one or more elements selected from the group consisting of Si and Al, and one selected from the group consisting of carbon, nitrogen, boron and oxygen. Hard phase consisting of compounds with the above elements, Fe, N
Examples thereof include those made of iron group metals such as i and Co, Al ₂ O ₃ and spinel ceramics. The sintering conditions may be the same as conventional ones.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic diagram showing a state in which a coating material is applied to a sintering tray and a pressed body of a hard alloy material is placed in the sintering method of the present invention. The sintering method of the present invention comprises a coating material 1 containing at least one powder of carbon, graphite, aluminum oxide and zirconium oxide, water, and a material containing (C ₆ H ₁₀ O ₅ ) n of a hard alloy material powder. This is performed by coating the surface of the sintering tray 2 on which the press body 3 is placed.

FIG. 2 is an explanatory view schematically showing the sintered state of the hard alloy material powder press body 3 placed on the sintering tray 2 in the present invention. As shown in FIG. 2 (A), for example, on the surface of the sintering tray 2 formed of carbon, the coating material 1
Is applied, and a press body 3 composed of a hard phase 4 made of WC and a binder phase 5 made of Co is placed and sintered thereon. When sintering starts, as shown in Fig. 2 (B), 1300
The eutectic of the hard phase 4 and the binder phase 5 is liquefied at around 0 ° C, and a part thereof oozes out on the surface of the sintered body 6. However, even if the sintering progresses further, as shown in FIG. 2 (C), the hard phase 4 in which the contact suppressor 7 of the coating material 1 existing between the sintering tray 2 and the sintered body 6 is liquefied
The lower part 8 of the eutectic of the binding phase 5 and the binding phase 5 is received to prevent the liquefaction part 8 from directly contacting the tray 2. Therefore, sintering tray 2
Even if the carbon is released, the carbon does not diffuse into the sintered body 6 through the liquefaction part 8.

The sintering method of the present invention may be carried out by the following steps. (1) Remove stains on the surface of the sintering tray 2 and
Apply. The coating material 1 may be applied using a brush or a spray, but a flow coater type automatic application device described later may be used. When an automatic coating device is used, it is possible to coat efficiently and uniformly. (2) Dry the coating material. The coating material used in the present invention is
Since water of low volatility is used as a solvent, it is preferable to dry the coating material after application so that the press body placed on it is not wet with water. The drying may be natural drying, but it is efficient to use a dryer such as a warm air dryer. (3) A hard alloy material powder press body is placed on a sintering tray coated with a coating material and sintered. The sintering conditions may be appropriately changed according to the material and shape of the hard alloy, and may be the same as conventional ones.

FIG. 3 is a schematic diagram for explaining a state in which a coating material is applied using an automatic application device. Automatic coating device 10
The tank includes a tank 11 for storing the coating material 1, a die 12 for discharging the coating material 1 supplied from the tank 11 in a curtain shape, and a plurality of rollers 13 for carrying the sintering tray 2. The mouthpiece 12 is composed of a pair of mouthpiece members each having a trapezoidal vertical cross section having a size suitable for the width (or length) of the sintering tray 2, and the lower sides of the die are opposed to each other in the cross section to form a gap between both members. And the covering material 1 is discharged from the gap. That is, the gap has a rectangular cross section, and when the covering material 1 is supplied, it spreads along the shape of the gap, and the covering material 1 is discharged in a curtain shape. For example, when the size of the sintering tray is 300 mm wide × 300 mm long × 5 mm thick, the tip of the die 12 may be over 300 mm wide × 10 mm long. At this time, the covering material 1 has a width of more than 300 mm in the cross section.
× It is discharged in the shape of a curtain with a length of 10 mm, and covers the sintering tray 2. It should be noted that the horizontal means a direction from the surface of the paper to the back in FIG. 3, and the vertical means a size in the left-right direction. The width means the size in the horizontal direction, and the length means the size in the vertical direction.

The coating material 1 is supplied from the tank 11 to the base 12 through a pipe 14 equipped with a pump 15. In the case where the coating material 1 is continuously discharged, if the sintering trays 2 are applied side by side without a gap, the coating material 1 does not drop between the sintering trays 2 and is wasted. On the other hand, when the sintering tray 2 is automatically supplied to the die 12 side or when the trays 2 are automatically loaded and collected after coating, it is preferable to apply them side by side with a gap between the trays 2. At this time, the coating material 1
When is discharged, a part of it will fall between the sintering trays 2. Therefore, it is preferable to collect the dropped coating material 1 and reuse it. At this time, the funnel 16 is placed below the roller 13.
Is arranged, the collection efficiency is good. Where the dressing 1
If (C ₆ H ₁₀ O ₅ ) n is stored in the tank 11 for a long time, it will precipitate. Therefore, it is preferable that the tank 11 includes a stirring screw (not shown) and the like. roller
13 is rotated by a drive source such as a motor, and is a sintering tray.
Carry 2 in order.

When such a coating device 10 is used, the coating material 1 has a flow rate of 3.5 to 8.0 sec / 40 ml, particularly 5.0 to 7.0 sec / 4.
It is preferably set to 0 ml.

In the present invention, by using a material containing water and (C ₆ H ₁₀ O ₅ ) n as the solvent of the coating material 1 and the adhesive respectively, the coating material 1 is prevented from adversely affecting workers, the atmosphere, and soil. It can be significantly reduced compared to the conventional case. Also, sintering tray 2
Since the tray 2 and the sintered body 6 do not come into direct contact with each other by applying the coating material 1 on the surface of the sintered body 6, the elements contained in the tray 2 are liquefied parts 8 of the sintered body 6. Through the sintered body 6
It does not diffuse inside and the abnormal phase does not occur. Furthermore, by uniformly coating the coating material 1 on the surface of the sintering tray 2 using an automatic coating device or the like, the sintered body 6 can be shrunk without resistance.

(Test Example) The sintered state of the hard alloy obtained by the sintering method of the present invention and the hard alloy obtained by the conventional sintering method was examined. The hard alloy material powder, the sintering tray, and the sintering conditions used in the test were the same for both.
Further, the number of hard alloy press bodies placed on one sintering tray was 100, and the press bodies for 10 trays were sintered.

Coating material in the example of the present invention   Carbon powder: Starch paste: Water = 1: 2: 4   Aluminum oxide powder: starch paste: water = 1: 2: 4   (Carbon powder + zirconium oxide): Starch paste: Water
= 1: 2: 4   Graphite: Flour: Water = 1: 2: 10   Carbon powder: potato starch: water = 1: 2: 14

The above ratios are by weight. All the starch pastes used are trade name "Nishiki glue", manufactured by Nishiki Paste Industry Co., Ltd., wheat flour is trade name "Nisshin Flower", manufactured by Nisshin Seifun Co., Ltd. ", Manufactured by Nakao Bussan Co., Ltd. Also, the particle size of carbon powder, graphite powder, aluminum oxide powder,
Zirconium oxide has a mesh of 1 to 5% by volume,
The mesh 250 was used at 40 to 80% by volume and the mixing ratio was changed. The flow rate of the coating material before coating is 3.0 to 5.0 sec /
It is 40 ml. Further, the coating material had a required viscosity.

In the example of the present invention, the coating material was transported by an FL-S3G automatic coating device manufactured by Anest Iwata Co.
Sintered trays 2 are lined up at an interval of about 1 m at 85 m / min, and the thickness is 0.
It was applied to 2 mm and then dried with a warm air dryer before use. At this time, the thickness was 0.03 to 0.05 mm. In the case of using starch starch, the coating material was applied while being kept at 60 ° C.

Coating Material in Conventional Example Dichloromethane: Vinyl Acetate Resin: Carbon Powder =
5: 1: 2 All the above ratios are by weight. In this test, coating materials of 2.5 kg, 0.5 kg, and 1.0 kg were prepared. The vinyl acetate-based resin used in this test was a conventionally used one. The coating material was applied to a thickness of 1.0 mm by a conventionally used spray.

[0034]   Hard alloy material: 93% by weight WC-6% by weight Co-1% by weight TaC               Shape: Tip for tip replacement               Model: DNMG150408N   Sintering tray Material: Carbon               Size: width 300 mm x length 300 mm x thickness 5 mm   Sintering conditions Temperature: 1450 ℃

As a result, in the examples of the present invention, all the hard alloys were sintered well, and no defective products were found. On the other hand, in the conventional example, on average, three defective products were detected due to an abnormal phase per sintered tray, and two defective products were detected due to distortion of the shape due to frictional resistance.
From this, it is understood that the inventive examples have good slipperiness and the chemical reaction between the hard alloy and the sintering tray is suppressed.

In the above-mentioned invention example, when a similar test is conducted using a sample in which only the composition of the coating material is changed, the compounding ratio is a material containing starch paste: water: (C ₆ H ₁₀ O ₅ ) n by weight. = 1: 2: 1 to 1.
It turns out that 5: 5: 3 is preferred. Further, in the present invention example, the scattering loss weight is extremely small, about 2% of the conventional example,
It was economical. Furthermore, the cleaning time after application was less than half the time of the conventional example, and workability was also good.

[0037]

As described above, according to the sintering method of the present invention, the adverse effect of the coating material applied to the surface of the sintering tray on the worker, the atmosphere, the soil, etc. is markedly increased as compared with the conventional case. The excellent effect that it can be reduced can be achieved.
In addition, the sintering method of the present invention can easily remove stains on the equipment and floor surface due to the covering material of the sintering tray, facilitates cleaning, and has good workability. Further, the sintering method of the present invention, by applying a coating material containing a contact inhibitor to the sintering tray,
Since the tray does not come into direct contact with the pressed body, the elements that have escaped from the tray do not diffuse inside the sintered body and cause an abnormal phase.

On the other hand, in the sintering method of the present invention, by regulating the flow rate of the coating material, it is possible to easily apply the coating material uniformly to the sintering tray. And, because the coating material is applied uniformly, the sintered body of hard alloy has less frictional resistance and can move smoothly on the sintering tray when shrinking during sintering, thus reducing defective products. can do.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a state in which a coating material is applied to a sintering tray and a pressed body of hard alloy material powder is placed in the sintering method of the present invention.

FIG. 2 is an explanatory view schematically showing a sintered state of a pressed body of hard alloy material powder placed on a sintering tray in the present invention.

FIG. 3 is a schematic diagram illustrating a state in which a coating material is applied to the surface of a sintering tray using an automatic application device in the present invention.

FIG. 4 is a conventional explanatory view schematically showing a sintered state of a pressed body of hard alloy material powder placed on a sintering tray.

[Explanation of symbols]

1 Cover material 2, 40 Sintering tray 3, 41 Press body 4,
42 Hard phase 5,43 Binder phase 6,44 Sintered body 7 Contact suppressor 8,46
Liquefaction part 10 Automatic coating device 11 Tank 12 Base 13 Roller
14 Piping 15 Pump 16 Funnel 45 Void

Claims (3)

[Claims] 1. A method for sintering a hard alloy, comprising placing a pressed body of a hard alloy material on a sintering tray and sintering it, wherein at least the surface of the sintering tray contains at least carbon, graphite, aluminum oxide and zirconium oxide. A method of sintering a hard alloy, characterized in that a coating material containing one type of material, (C ₆ H ₁₀ O ₅ ) n-containing material, and water is applied. 2. The material containing (C ₆ H ₁₀ O ₅ ) n is any one of starch paste, starch starch and wheat flour.
The method for sintering a hard alloy according to claim 1. 3. The flow rate of the coating material before coating is 5.0 to 7.0 sec / 40.
The method for sintering a hard alloy according to claim 1, wherein the hard alloy is ml.