JPH09241706A - Production of sintered compact for cutting tool with hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a sintered compact for a cutting tool with holes obtd. by imparting the holes for outflow of cooling fluid to the cutting tool by a slip casting method. SOLUTION: Molds 1 templated from pattern mold, cores 2 for forming the holes and a slurry-like mixture prepd. by allowing a viscosity control agent for maintaining a prescribed viscosity to coexist in a raw material consisting of metallic powder and/or alloy powder and ceramic power and/or whiskers are used. The cores 2 are disposed in the molds 1 and the mixture is injected into the molds. The molds 1 are removed and the cores 2 are removed. The molding formed after the solidification of the mixture is sintered by heating, by which the molding is made into the sintered alloy with the holes. In the process described above, the viscosity control agent consists of a self-curing agent and the slurry-like mixture has a viscosity of 1000 to 5000cps at ordinary temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sintered body for a cutting tool having a hole by a slip casting method for producing a cutting tool having a hole for allowing a cooling liquid to flow out during cutting. The present invention relates to a method for producing a sintered body for a cutting tool having holes, in which a cutting tool typified by a drill, an end mill, and a gun drill is provided with holes for cooling liquid outflow by a slip casting method.

[0002]

2. Description of the Related Art Conventionally, in a powder metallurgical process, there is a process of molding a mixed powder into a desired molded body. A typical example of the molding method in this process is a mold molding method, an injection molding method,
There are doctor blade method, extrusion molding method and slip casting method. In the case of forming a molded body from the mixed powder by the slip casting method among these, when roughly classified, firstly, the slurry-like mixture is directly slipped onto a liquid-absorbent mold such as gypsum molded into a desired molded body. Method, secondly, insert a core molded into a desired molded body into the mold,
There is a method of slipping the slurry mixture. Representative examples of these slip cast methods are disclosed in Japanese Patent Laid-Open No. 7-237959 and Japanese Patent Laid-Open No. 3-237959.
There are Japanese Patent No. 120005 and Japanese Patent Laid-Open No. 5-138448.

[0003]

Among the conventional slip casting methods, Japanese Patent Laid-Open No. 7-237959 discloses a slurry containing a ceramic raw material powder and a viscosity adjusting agent containing a solvent in a solvent-absorbing mold. A manufacturing method is disclosed in which the ceramic raw material powder is injected to have a predetermined wall thickness, the solvent is absorbed in a mold to solidify, and then the mold is removed to mold a ceramic molded body having a predetermined shape.

[0004]

[Patent Document 1] Japanese Patent Laid-Open No. 3-120
No. 005, a molding die is formed by using a core of a low melting point alloy and an outer die of a water-absorbing material, and a mixture of raw material powder suspended in a dispersion liquid is injected into the molding die to form an outer die. A slip cast molding method is disclosed in which a dispersion liquid is absorbed, an outer mold is removed, and a core and a molded body are heated at least at a melting temperature of a low melting point alloy to melt and remove the core.

Further, in Japanese Unexamined Patent Publication (Kokai) No. 5-138448, a removable core produced in a shape with oil holes is inserted in a casting mold, and a mixture of material powder and binder is placed in the casting mold. Disclosed is a method for manufacturing a drill with an oil hole, in which the core is removed from the molded product after injection by molding, and the materials of the binder and the core are different, specifically, when one is a water-soluble synthetic resin. Discloses that the other is a water-insoluble synthetic resin.

Of these three publications, the former two publications use an absorptive mold or an outer mold to absorb the solvent contained in the mixture into the mold or the outer mold. A method of solidifying the mixture is disclosed. According to the method disclosed in these two publications in which the mold or the outer mold absorbs the solvent, it takes a long time from the injection to the mold release, and the mold is obtained by the mold release. Since the solvent remains in the molded product itself, it takes a long time to dry the molded product, and distortion and cracks easily occur in the molded product during the demolding and drying processes. There is a problem that it is difficult to obtain a shaped body.

Of these three publications, the latter two publications disclose a method of molding a molded body using a core and a mold, and removing the core and the core from the molded body after molding. Has been done. The method of using the core disclosed in these two publications is not likely to cause chipping or damage of the molded body at the time of demolding, and is capable of molding a relatively complicated shape. However, when the water-soluble synthetic resin disclosed in JP-A-5-138448 is used to sprinkle water and cure, a raw material for forming a cemented carbide or cermet, particularly an iron group metal, is used. When the binder phase forming powder is included, the surface of the raw material is oxidized, and the molded body or the sintered alloy obtained by sintering the same is apt to be distorted or cracked. In the case of bonding gold, there is a problem in that deformation near the holes frequently occurs, resulting in defective products, resulting in a high defective rate.

The present invention solves the above-mentioned problems. Specifically, a self-curing viscosity modifier is used to control the viscosity of a slurry mixture for slip casting. PROBLEM TO BE SOLVED: To provide a method for manufacturing a sintered body for a cutting tool with a hole, capable of producing a powder metallurgical sintered body part having fine holes for a cooling liquid with a low defect rate and molding the product while shortening the manufacturing process time. It is intended.

[0009]

Means for Solving the Problems The inventors of the present invention have studied a method of providing a cooling liquid hole in a central shaft portion of a cemented carbide having a cylindrical shape represented by a drill tool. Among the various methods of forming the molded body of, the slip casting method is preferable, but in the conventional slip casting method, most of the products are defective due to bubbles or deformation, especially in the sintered alloy after sintering, the cooling liquid is used. A large amount of defective products are generated due to deformation and cracks caused by the use holes. To solve this cause, the material of the viscosity modifier and the viscosity of the slip obtained by it are very important factors. The present invention has been completed with the knowledge that

The method for producing a sintered body for a cutting tool with holes according to the present invention comprises a mold for molding from a template, a core for forming holes, a metal powder and / or an alloy powder, and a ceramic powder. And / or whiskers are used as a raw material and a slurry-like mixture in which a viscosity adjusting agent for maintaining a predetermined viscosity is mixed, and the core is disposed in the molding die, In the first step of injecting the mixture, the second step of removing the mold from the core and the mixture and the mold, the third step of removing the core from the core and the mixture,
A fourth step of heat-sintering a compact formed by solidifying the mixture to form a sintered alloy with holes, wherein the viscosity modifier is self-curing. The slurry-like mixture has a viscosity of 1000 to 5000 cP at room temperature.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The molding die used in the method for producing a sintered body of the present invention is a material that can be cast from a template produced in consideration of shrinkage and in accordance with the appearance of the desired sintered alloy. There is no particular restriction on the material if there is, for example, various resins,
Rubber, metal, alloys including steel, etc. can be used. Silicone resins and silicone rubbers are particularly preferable for this mold because of ease of molding at room temperature and releasability from a molded product formed by curing a slurry-like mixture described below. It is also preferable that the molding die is a split mold that can be divided into a plurality of pieces so that the molded body can be easily released from the mold, if necessary.

The core fixed in the mold is specifically made of, for example, Ni, Co, W, Mo metal wires, brass, stainless steel, steel wires of iron-based alloys, various fibers, or resins. can do. The shape of this core matches the shape of the target sintered alloy, such as a drill, gun drill, end mill, or its length, and has a hole diameter for cooling liquid suitable for letting out the cooling liquid in consideration of shrinkage. It has a length or a shape in which a spiral curve is added if necessary. It is important that this core is easy to remove in the third step and avoids the influence that the molded body becomes a defective product when removing the core. As a specific method for this purpose, for example, wax, paraffin (stone wax), paraffin hydrocarbon, which is solid at room temperature, is formed on the surface of the core so that the core can be easily removed from the molded body. Organic-based waxes as solid esters consisting of fatty acids and higher monohydric alcohols,
It is also preferable to coat with a thin film removing agent such as various plastics.

The slurry-like mixture injected into the molding die has a raw material for forming a sintered alloy and an optimum viscosity capable of being transferred and formed into a template shape which is a basic die of the molding die. And a viscosity modifier for controlling the viscosity. This slurry-like mixture has a moldability such that the ratio of the composition component and particle size of the raw material and the composition component of the viscosity modifier is the shape of the mold in the above-described first step to fourth step,
In addition, it becomes the most important factor for suppressing air bubbles around the core that becomes the hole for the cooling liquid, and therefore 1000 to 5
The viscosity is 000 cP. This viscosity is 100
If it is less than 0 cP, the molding time will be long, the shape retention will be poor, and deformation will easily occur.
If it exceeds the range, the effect of suppressing bubbles will be poor and molding will be difficult. Particularly, in the case of a raw material made of a composition component of cemented carbide, it is preferable that the raw material has a viscosity of 1500 to 4500 cP. If this viscosity tends to be high,
It is also preferable to apply hydrostatic pressure (CIP method) at room temperature after the first step. The viscosity can be adjusted mainly by the material, particle size and content of the raw material, and the material and content of the solvent and binder described later.

Of the substances constituting this slurry-like mixture, the raw materials are various substances conventionally used in powder metallurgy, specifically, Co and N, for example.
i, Fe, Cr, V metal, Co-Ni, Co-Cr,
One or more of Ni-Cr alloys and 4a of the periodic table,
Carbides, nitrides, carbonitrides, carbon oxides, oxynitrides, oxycarbonitrides, Al ₂ O ₃ , AlN, ZrO of 5a and 6a group metals
₂ , Si ₃ N ₄ , SiC, and ceramic powder composed of mutual solid solutions thereof, SiC, Si ₃ N ₄ , TiC, Al
It is composed of at least one of ₂ O ₃ and carbon whiskers, and more specifically, is a substance capable of forming various cemented carbides or cermet sintered alloys.

In addition to this raw material, the viscosity modifier which is another substance constituting the slurry-like mixture is a binder for molding the raw material, specifically, for example, epoxy resin or poly Vinyl alcohol, phenol resin, melamine resin, urea resin or urethane resin and a solvent for dissolving this binder to form a slurry, specifically, for example, toluene, benzene, xylene, hexane or butanol, in a mixture In order to prevent the agglomeration of fine raw materials in the above, and to improve the fluidity and dispersibility, specifically, for example, polycarboxylic acid ammonium, acrylic acid oligomer, polyester or triethanolamine, and a mold After injecting the mixture into the mixture, a curing agent as an accelerator for curing the mixture, specifically, for example, Triethylenetetramine, iso Roman diamine is that containing the xylylenediamine or formaldehyde. This viscosity modifier
Having a self-curing property at room temperature is particularly preferable in terms of shortening the manufacturing process and speed of workability. Among these, in the case of producing the above-mentioned cemented carbide, the viscosity modifier contains a binder of epoxy resin, a solvent of butanol, a peptizer of ammonium polycarboxylic acid, and a curing agent of triethylenetetramine. It is preferable because the excellent effect of suppressing pores when the slurry-like mixture is solidified is obtained.

Among these slurry-like mixtures, a binder phase forming powder containing cobalt as a main component, the balance being tungsten carbide, or a main component of tungsten carbide containing carbides of elements 4a, 5a and 6a of the periodic table, When the raw material is a hard phase forming powder to which a cubic crystal compound forming substance consisting of a nitride, a carbonitride and a mutual solid solution thereof is added, the viscosity is 1000 to 4500 at room temperature.
cP is preferable, and the binder phase forming powder containing cobalt and / or nickel as a main component and the balance consisting of a hard phase forming powder containing titanium carbide, titanium nitride or titanium carbonitride as a main component. If it is a raw material,
It is preferable that the viscosity is 1500 to 5000 cP at room temperature.

In the method for manufacturing a sintered body for a cutting tool with holes of the present invention, the shrinkage rate is first roughly estimated in advance by using the above-mentioned materials, and a shape similar to the shape of the target sintered alloy is obtained. A first step of injecting this slurry-like mixture into a molding die transfer-molded by using the template prepared and formed
Second, removing the mold to make the injected mixture and core
The step, the third step of removing the core in the state where the mixture is semi-solidified or solidified, and the molded body formed by solidifying the mixture is heated under a heating condition, specifically, a non-oxidizing atmosphere. At that time, the pressure can be atmospheric pressure, pressurization or depressurization, and heating and sintering can be performed at a temperature of 1300 to 1500 ° C.

Of these manufacturing steps, the removal of the core in the third step is an important factor for reducing the defective rate, and as a method therefor, a method of heating at room temperature or heating depending on the material of the core is used. There is also a method of dissolving with a solvent or a method of scattering by heating, but it is also preferable to coat the surface of the core with a thin film removing agent and withdraw it at room temperature from the degree of influence on the molded body. In the method of pulling out the core at room temperature, it is necessary to consider the solidified state of the mixture. Regarding the solidified state of the mixture, the core may be removed in a state where the mixture is a semi-solidified or a solidified mixture, but a semi-solidified state from the relationship between the stress during contraction of the mixture and the stress of the core. It is preferable to remove the core in the state of the mixture. The semi-solidification here means that the shrinkage of the mixture has not been completed and is solidified in a state that it does not deform during handling.

[0019]

EXAMPLE 1 First, as a manufacturing method 1 of the present invention, a tungsten carbide powder (WC) having an average particle size of 0.5 μm was added to 89.
5% by weight and 0.5% by weight of chromium carbide powder (Cr ₃ C ₂ )
And a cobalt powder (Co) in an amount of 10% by weight as a raw material (125 g), a solvent of n-butanol (15 cc), a deflocculant of ammonium polycarboxylate (1 cc) and a binder of an epoxy resin (5.5 g) And a viscosity modifier composed of a curing agent of triethylenetetramine (1.5 cc) were mixed to prepare a slurry mixture. The viscosity of the slurry mixture thus obtained was measured and found to be 3000 cP.

Next, a thin film of solid fats and oils is formed on the surface by using a mold made of silicone resin, which is in the state shown in FIG. After arranging the core of the steel wire coated in a spiral shape and fixed in the upper and lower central portions of the mold, the above-mentioned slurry mixture was injected into the mold. The mold and the core into which this mixture is injected are left at room temperature for about 1 day, then the mold is removed, and the core is rotated while rotating the molded body from the semi-solidified molded body in which the mixture is not completely solidified. Was removed. The molded body obtained by solidifying the mixture thus obtained is further dried at 50 ° C., and
After primary heating at 00 ° C, heating and sintering was performed at 1350 ° C to obtain the solid drill with spiral holes made of cemented carbide shown in Fig. 2. Ten solid drills with spiral holes made of cemented carbide obtained by the method of the present invention were manufactured, and the defective rate was zero.

As a comparative production method 1, a slurry mixture having a viscosity of 5500 cP was prepared by mixing the above-mentioned raw material with a water-curable acrylic resin and toluene. Using this mixture, a solid drill with a spiral hole made of cemented carbide similar to that described above was obtained in the same manner as in Production Method 1 of the present invention described above. Cemented carbide solid drills with spiral holes manufactured by this comparative manufacturing method 1 all manufactured 10 and had defects due to deformation or cracks.

[0022]

Example 2 Table 1 shows substantially the same as in Production Method 1 of Example 1 of the present invention except that the contents of the solvent, binder and curing agent were slightly changed to change the viscosity modifier. A slurry-like mixture having different viscosities was obtained. With these mixtures,
The production method 2 of the present invention shown in Table 1 in the same manner as in Example 1.
7 to 7 and comparative manufacturing methods 2 to 5 that deviate from the present invention, 10 solid drills made of cemented carbide each with a spiral hole are formed.
Each piece was produced one by one, and the number of these non-defective products and the solidification time are also shown in Table 1.

[0023]

[Table 1]

[0024]

EFFECTS OF THE INVENTION The manufacturing method of the present invention is easier to mold as compared with the conventional manufacturing method by the slip casting method, and the oxidation in the molding process such as cemented carbide molding material and cermet molding material is minimized. In the case of molded products that need to be avoided and those that need to be machined with a coolant cutting tool such as a drill or end mill, defects due to processing distortion, deformation, chipping, etc. are significantly reduced. effective.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a slip cast model provided with a core for forming a hole for a coolant, which is shown as an example of a manufacturing method of the present invention.

FIG. 2 is a schematic vertical external view of a solid drill with holes for cooling liquid obtained as an example of the manufacturing method of the present invention.

[Explanation of symbols]

1 Mold: 1a: Lower part of the mold, 1b: Upper part of the mold, 2
Core, 2a: Coolant hole 3, Cavity into which slurry mixture is injected, 4 Drill blade groove portion, 4a: Blade portion 5 Shank portion

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C22C 1/05 B22F 3/02 M

Claims (8)

[Claims] 1. A predetermined viscosity is maintained in a raw material consisting of a molding die taken from a template, a core for forming holes, a metal powder and / or an alloy powder, a ceramic powder and / or whiskers. A first step of arranging the core in the molding die and injecting the mixture in the molding die using a mixture in the form of a slurry in which a viscosity adjusting agent is mixed, A second step of removing the molding die from the mixture and the molding die, a third step of removing the core from the core and the mixture, and heat-sintering a compact formed by solidifying the mixture. And a fourth step of forming the shaped body into a sintered alloy having holes, wherein the viscosity modifier is self-hardening, and the slurry-like mixture is 1000 to 500 at room temperature.
A method for producing a sintered body for a cutting tool with a hole, which has a viscosity of 0 cP. 2. The method for producing a sintered body for a cutting tool with a hole according to claim 1, wherein the molding die is made of silicone resin or silicone rubber. 3. The method for producing a sintered body for a cutting tool with holes according to claim 1, wherein the core is made of metal, alloy, resin or fiber. 4. The raw material is composed of a binder phase forming powder containing cobalt as a main component and the balance of tungsten carbide, or tungsten carbide containing the main component of 4a, 5a, 6 of the periodic table.
a hard phase forming powder to which a cubic compound forming material consisting of a carbide, a nitride, a carbonitride of a group a element and a mutual solid solution thereof is added, and the viscosity is 100 at room temperature.
0 to 4500 cP, and the sintered alloy has a binder phase containing cobalt as a main component in an amount of 4 to 15 wt% and a balance of tungsten carbide as a hard phase, or tungsten carbide as a 4a, 5a, or 6a group element of the periodic table. Is a cubic compound composed of carbides, nitrides, carbonitrides and their mutual solid solutions.
The method for producing a sintered body for a cutting tool with a hole according to claim 1, wherein the cemented carbide is a hard phase alloy containing a hard phase containing less than or equal to wt%. 5. The viscosity modifier contains, in addition to a solvent, a deflocculant, and a binder, a curing agent for accelerating the solidification of the mixture. Or 4
A method for producing a sintered body for a cutting tool having a hole as described above. 6. The method for producing a sintered body for a perforated cutting tool according to claim 5, wherein the curing agent is one or more of triethylenetetramine, isophorodiamine, xylenediamine, and formaldehyde. Method. 7. The method for producing a sintered body for a cutting tool with holes according to claim 1, 2, 3, 4, 5 or 6, wherein the sintered alloy is a drill or an end mill. 8. The removal of the core in the third step is performed in a state where the mixture is in a semi-solidified state, 1, 2, 3, 4, 5, 6 or 7. A method for producing a sintered body for a cutting tool having a hole as described above.