JP2000345214A - Tap formed of composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tap formed of composite material which is hard in surface, wear-resistant, and having highly tough inside. SOLUTION: In a screw part 12 to constitute a tap, a metal-rich metal part 20 is provided inside the tap, a ceramic-rich ceramic part 22 is provided on the tap surface, and an inclined part 24 in which the ratio of the metal component is gradually reduced toward the tap surface from the inside the tap is formed therebetween. The thickness of the inclined part 24 in which the ratio of the metal component is gradually reduced is set in the range of 0.3-10 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite tap made of a composite material containing a ceramic component and a metal component.

[0002]

2. Description of the Related Art Generally, in various machining fields,
2. Description of the Related Art Cutting using a tap is performed to tap a prepared hole formed by a drill or the like. During this type of machining operation, various stresses are acting on the tap. For example, there are a compressive stress when applying a pressing force to a work material, a tensile stress acting on a biting portion and a cutting portion, and a tensile stress between a portion to be processed and a portion not used for the processing. These various stresses make the cutting operation by the tap practically unstable, which may cause chipping, chipping, breakage, or reduction in thread cutting accuracy. Therefore, taps having high hardness, high strength, and high toughness are required, and high-speed steel, powdered high-speed steel, carbide, and the like are generally widely used as tap materials.

[0003]

However, while high-speed steel and powdered high-speed steel have high strength and high toughness, they have problems in wear resistance, compressive strength and rigidity.
Carbide has high rigidity, high hardness and high compressive strength, but has a problem in toughness. In other words, toughness and strength deteriorate when trying to improve rigidity and abrasion resistance, while rigidity and hardness decrease when trying to improve strength and toughness, which can withstand particularly high-speed processing and high load Making taps has been extremely difficult in practice.

At this time, various measures have been taken to apply a surface treatment such as hard coating to the superhard material, high-speed steel, or powdered high-speed steel material. In such a case, peeling of the film or the like is caused, and the film cannot be put to practical use.

[0005] Therefore, the development of a tap having high hardness and wear resistance in the vicinity of the tap surface layer where cutting is actually performed and high strength inside the tap was studied.
Japanese Patent No. 2593354 and Japanese Unexamined Patent Application Publication No.
It has been found that a “composite material having a gradient function containing a ceramic powder and a metal component” disclosed in, for example, Japanese Patent No. 27807 is applied.

That is, an object of the present invention is to provide a tap made of a composite material having a tilting function in which the surface has high hardness and physical properties such as toughness and strength are improved as it goes inward.

[0007]

In the composite tap according to the present invention, the tap is composed of a composite material containing a ceramic component and a metal component. The ratio of the metal component is gradually decreasing. Here, there is a correlation between the ratio of the metal component in the composite material and the hardness, strength and toughness, and when the ratio of the metal component decreases and the ratio of the ceramic component increases,
Although hardness, wear resistance, rigidity, etc. are improved, they become brittle. On the other hand, when the proportion of the metal component is increased to improve the brittleness, although the strength and toughness are improved,
Rigidity and wear resistance are reduced.

Therefore, the tap surface to be actually processed is made to have high hardness and wear resistance physical properties, and the inside is made to have high toughness and high strength physical properties. If the composition and the physical properties are changed gradually, a tap having a sharp cutting edge with high dimensional accuracy can be obtained without stress concentration and with desired wear resistance.

For this reason, the ceramic particles in the vicinity of the tap surface promote grain growth as compared with the inside and become coarser and become smaller toward the inside, and the metal component is accumulated inside by the rearrangement of the particle composition accompanying the grain growth. You. Therefore,
The composition of the tap surface that is actually processed is ceramic-rich and has high wear resistance, the inside of the tap is metal-rich and has high strength and toughness, and it is possible to effectively reduce the stress concentration inside the tap become.

In addition, since the vicinity of the tap surface where cutting is actually performed is made ceramic-rich and the particles are coarsened, the transmission and diffusion of heat generated near the tap surface during cutting are improved. Therefore, the generation of micro cracks due to heat, and the resulting chipping and the cutting edge, are improved to greatly improve the cutting performance.

[0011]

FIG. 1 is a side view of a composite tap 10 according to an embodiment of the present invention, and FIG.
It is an II-II sectional view taken in the middle.

The tap 10 has a screw portion 12 and a shank portion 1.
4 are integrally provided. A plurality of, for example, four grooves 16 are formed in the screw portion 12 over a predetermined length in the axial direction (the direction of the arrow A).
8 are provided. The tap 10 is made of a composite material containing a ceramic component and a metal component. A metal-rich metal portion 20 is provided inside the tap, and a ceramic-rich ceramic portion 22 is provided on the tap surface.
Is provided. An inclined portion 24 is provided between the metal portion 20 and the ceramic portion 22 such that the ratio of the metal component gradually decreases from the inside of the tap toward the tap surface.

The metal component is at least one selected from the group consisting of iron (Fe), nickel (Ni) and cobalt (Co) in the group VIII of the periodic table, and if necessary, chromium (Cr) and vanadium. (V) or molybdenum (Mo) is mixed in to improve the strength.
The ratio of the metal component in the composite material is 3 wt% to 15 wt%,
More preferably, it is set in the range of 5 wt% to 10 wt%.

If the metal component is less than 3% by weight, the amount of the metal becomes too small and the tap 10 becomes brittle, so that the tap 10 cannot be practically used. 3w metal component
When the content is not less than t%, the ratio of the metal component on the surface side of the tap 10 can be 1 wt% or less, and the metal component of about 8 wt% can be relatively accumulated inside the tap. Can be provided. In addition, when the tap 10 is manufactured by performing processing such as blade cutting after sintering the material, it is necessary to consider the strength of the cutting edge, and it is desirable that the ratio of the metal component be 5 wt% or more. .

Here, when a powder material of about 2 μm is used as ceramic particles, particles near the tap surface are:
It changes depending on the added particle growth agent, sintering temperature, time, atmosphere, etc., and grows about 3 to 30 times, for example.
In the tap 10, when the strength of the threaded portion 12 is required, the thread is grown up to about 3 to 6 times, while when the wear resistance is mainly required, it is grown up to about 10 to 20 times. . At this time, the ratio of the metal component near the surface of the tap 10 is about 1 wt% to 5 wt%, and the ratio of the metal component inside the tap 10 changes depending on the growth degree, the thickness of the inclined portion 24, and the like. In the case of 5 wt% in the vicinity,
Internally, the content is about 8 wt% to 13 wt% or more.

The upper limit of the ratio of the metal component is set to 15 wt%, more preferably 10 wt%. For example, in deep hole processing, a long tap 10 similar to a gun drill is used, and high rigidity and high strength are required, and particularly, high tensile strength is required. In this case, when trying to avoid breakage or the like by increasing the amount of the contained metal component, if the ratio of the metal component is 15 wt% or more, the abrasion resistance may be deteriorated.

Further, the ratio of the metal component is set to 15 wt%, and the tap 10 having a metal component of about 5 wt% near the surface.
In the case of trying to secure a hardness of about H _R A93, if the diameter of the tap 10 is about 25 mm, the metal component at the center of the tap becomes about 20 wt% or more, which is close to high-speed steel. It is tough and functionally sufficient.

In the tap 10 having a diameter of about 10 mm to 20 mm, in order to make the amount of the metal component at the center of the tap about 20 wt% or more as described above, the ratio of the metal component in the composite material is set to 10 wt%. Just set it to%,
Even if the metal component is added at a ratio higher than this, it does not contribute to the strength and toughness, and the rigidity of the entire tap 10 is reduced.

The thickness of the inclined portion 24 of the tap 10 is given by
It is set to 0 μm, preferably 0.3 mm or more. In the tap 10, since the amount of the metal component and the heat conduction and the size of the particles and the heat conduction are correlated, and the generated thermal stress becomes a gradient of the heat transfer, the thermal stress itself is changed by changing the thickness of the inclined portion 24. Changes. The thickness of the inclined portion 24 is several μm or more.
If the thickness is several tens of μm, the amount of relaxation of the generated thermal stress and the stress at the time of processing is small, and a desired effect cannot be obtained even if the ratio of the metal component is appropriately controlled.

On the other hand, it is conceivable that the thickness of the inclined portion 24 is set large, but the tap 10 becomes large in diameter. Since the diameter of the tap 10 in practical use is about 25 mm or less, the upper limit of the thickness of the inclined portion 24 is set to 10 mm.

The ceramic in the composite material constituting the tap 10
The components are tungsten carbide (WC) and titanium carbide
(TiC), titanium nitride (TiN), 2 molybdenum carbide
(Mo _TwoC), tantalum carbide (TaC), niobium carbide
(NbC), chromium carbide (Cr_ThreeC_Two) Or carbonized banana
At least one selected from the group consisting of zinc (VC)
With nitrides and borides as necessary
Or even if various carbonitrides are added to some of them
Good.

The amount of ceramic is 85 wt% ≦ WC + TiC + TiN + Mo ₂ C + TaC
+ NbC + Cr ₃ C ₂ + VC ≦ 97 wt% These ceramic components are
It forms the surface layer of the threaded portion 12 that actually cuts at the time of cutting by zero, and has properties such as heat resistance, wear resistance, and corrosion resistance. If the amount of the ceramic component exceeds 97 wt%, the amount of the metal component becomes too small and the abrasion resistance is sufficient, but the strength and toughness are reduced and breakage and breakage are liable to occur, making it difficult to put to practical use. If the ceramic component is less than 85 wt%, the slope at which the metal component gradually decreases in the inclined portion 24 becomes steep, and a sufficient tilting function as the composite material tap 10 cannot be secured.

On the other hand, when the ceramic component is 85% by weight or more, preferably 90% by weight to 95% by weight, the thickness of the ceramic part 22 which is a high hard part is secured to about 0.3 mm to 1 mm at the thinnest part, and the inclined part 24 is formed.
Can be configured to a thickness of 0.3 to 10 mm or more,
It is possible to secure the edge strength and the stress relaxation layer.

Of these ceramic components, tungsten carbide is a main component of the composite material ceramic component, and corresponds to titanium carbide, titanium nitride, molybdenum carbide 2, tantalum carbide, niobium carbide, chromium carbide according to the work material. Alternatively, vanadium carbide or the like is appropriately added. For example, when the work material is aluminum or an aluminum alloy, a copper alloy, a magnesium alloy, cast iron, nickel or cobalt-based super gold, etc., the main component is tungsten carbide, and niobium carbide, tantalum carbide, or both are 2 wt% or more. 8w
By adding about t%, the machinability is improved.

When the work material is an iron-based material such as steel or stainless steel, titanium carbide, titanium nitride, chromium carbide, vanadium carbide or vanadium carbide is used to improve abrasion resistance, heat resistance and adhesion resistance. At least one compound selected from molybdenum carbide is added in a range of 15 wt% to 45 wt%.

The surface hardness of the tap 10 becomes the H _R A90~94.5 more than the above composition range, even compared to hard ceramic coating is good value. Moreover, CV
Hard ceramic coatings such as D and PVD make it difficult to secure the cutting edge accuracy and affect the hole accuracy. However, the tap 10 according to the present embodiment can perform finishing with high accuracy. Surface hardness of the tap 10 is H _R A9
If it is less than 0, the cutting accuracy is reduced, the wear resistance is also reduced, and it becomes difficult to effectively maintain the accuracy of the finished hole.

The surface hardness and strength of the tap 10 are related to the ceramic component contained in the composite material. For example, changing from those mainly comprising tungsten carbide those containing titanium carbide or titanium nitride, hardness H _R A91~
96. This phenomenon also occurs by changing the grain growth promoter.

In the tap 10, the ceramic portion 22, which is a high-hardness portion, the inclined portion 24, which is a gradient function portion, and the metal portion 20, which is a high-strength and high-toughness portion, follow the outer peripheral shape of the tap 10. It is formed in a shape. This relates to the growth of ceramic particles contained in the composite material, and is achieved by impregnating a solution with an elemental compound that promotes grain growth in the sintering process. The grain growth promoting material is a solution, for example, is supplied so that water is impregnated into pumice, and thus penetrates inside the tap 10 along the outer peripheral shape thereof.

The tilting is carried out by evaporating a solution component such as water from the impregnated compact. The evaporation of water is performed from the surface of the molded body, and the gradient of the concentration of the accelerator is increased as the temperature difference between the inside of the molded body and the surface of the molded body is set higher by rapidly heating the molded body. It becomes sudden. In addition, the higher the concentration of the grain growth promoter, the larger the grain growth, so that the metal component is accumulated inside.

As a result, the ceramic portion 22, the inclined portion 24, and the metal portion 20 can be formed along the outer peripheral shape (blade shape) of the tap 10. Here, the thickness of the ceramic portion 22 is set in a range of 0.3 mm to 3 mm. If the thickness is less than 0.3 mm, it may be removed by cutting after the crystallization, while if it exceeds 3 mm, the distance to the stress relieving layer becomes too long, the relieving action does not work, and the cutting edge chipping occurs. Easier to do.

As described above, the tap 10 according to the present embodiment
Is advantageous in physical properties as compared with high-speed steel, and the processing accuracy and the processed surface are effectively improved. Moreover,
The frequency of replacement of the tap 10 is reduced, and it is possible to use the tap 10 satisfactorily for a long period of time. Specifically, as compared with taps having the same raw material particle size and the same composition, the resistance strength is 1.
It improved 5 to 2 times, and the toughness increased 1.8 to 3 times in relative comparison. Further, the strength is improved by strengthening the surface hardness.
Up to 7 times. In addition, the conventional cemented carbide is weak to tensile stress and has a flexural strength of about 1/10 to 4/10 even in simple tension without torsional stress. The reinforcement increased the static tensile strength to 3/10 to 6/10 of the transverse rupture strength. Example 1 In Example 1, 89 wt% of tungsten carbide (WC) powder having an average crystal grain size of 2.2 μm, 2 wt% of niobium carbide (NbC) powder having an average grain size of 2 μm, and an average grain size of 2.
4 μm of tantalum carbide (TaC) powder and 1 wt% of cobalt (Co) powder were sufficiently mixed at a ratio of 8 wt% using a ball mill with an organic solvent as a solvent for 72 hours. After preparing this mixture so that the liquid content becomes 9%,
In order to avoid the influence of the molding binder, a molded body having a circumscribed circle of φ25 mm × 150 mm was formed without a binder by a molding pressure of 100 MPa by an in-mold hydrostatic pressure molding method.

After molding, 50 P
After removing the hexane remaining in the molded body in a,
For 30 x 60 seconds to prevent collapse during impregnation of the molded article. Further, in order to improve the homogeneity of the calcined body, a cutting process was performed so as to have a diameter of 15 mm after the burning. Next, the calcined body was immersed in a 10% concentration aqueous solution of Ni salt, and then subjected to a drying treatment in an exhaust-type hot-air drying oven at 130 ° C., thereby steepening the Ni concentration in the calcined body.

On the other hand, in the above basic physical properties, the amount of cobalt is increased or decreased by controlling the amount of tungsten carbide while keeping the Ni concentration the same, and the calcined body is immersed in an aqueous solution of Ni salt and embedded in powder. By drying, a homogeneous composition was obtained.

After these were sufficiently dried, they were maintained at a temperature of 1400 ° C. under a flow of nitrogen at 50 Pa for 1 hour to perform a sintering treatment. FIG. 3 shows the relationship between the distance from the surface of the sintered body, hardness, and toughness as basic physical properties at that time.

Here, the gradient functional area is about 7 mm, the thickness of the high hardness homogeneous layer on the surface is about 0.3 mm, and the hardness is H
Was _R A93. In the equivalent product of the commercial material shown in FIG.
The hardness was about H _{R A} 90.5, and the hardness of Example 1 was very high compared to this commercial material. The toughness was measured under the same test conditions as that of a commercial product at 7 MPa.
The value inside was almost twice as large as that of m ^1/2 .

Further, the cross section of the sintered body obtained in Example 1 was observed using a microscope, and the size of the particles was measured. As a result, the result shown in FIG. 4 was obtained. As a result, it was found that the particles near the surface of the sintered body grew about three to four times as large as the inside.

FIG. 5 is a graph comparing the relationship between the amount of metallic cobalt (%) and the transverse rupture strength (GPa) in the case of a homogeneous composition, with and without impregnation of a Ni grain growth agent. According to this, by performing the impregnation operation, the impregnated material promoted the growth of the ceramic particles, and was closely bonded to cobalt, which plays a role of a binder, and the strength was improved. That is, the ceramic particles and the metal were more closely bonded than before, and the effect of improving the strength was enhanced. As a result, the properties of the sintered body obtained in Example 1 are superior to those of the carbide, and the effect of dramatically improving the performance as a tap can be obtained.

[0038]

In the composite tap according to the present invention, since the ratio of the metal component in the composite gradually decreases from the inside of the tap toward the tap surface, the cutting edge portion to be actually processed has a high hardness and While having abrasion resistance, the inside of the tap has high toughness and high strength, and the composition and physical properties during this change gradually. Thereby, while being suitable for high-speed machining, the durability is greatly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory side view of a composite tap according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a diagram showing a relationship between hardness and toughness from a tap surface.

FIG. 4 is an explanatory diagram of a growth state of tungsten carbide particles by adding nickel.

FIG. 5 is a diagram showing the relationship between the amount of metal, strength, and nickel impregnation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Tap 12 ... Screw part 14 ... Shank part 16 ... Groove 18 ... Land 20 ... Metal part 22 ... Ceramics part 24 ... Inclined part

Claims (5)

[Claims] 1. A composite material comprising a composite material containing a ceramic component and a metal component, wherein the ratio of the metal component in the composite material gradually decreases from the inside of the tap toward the tap surface. Made tap. 2. The composite tap according to claim 1, wherein
The thickness of the inclined portion where the ratio of the metal component gradually decreases is 0.3
A composite tap set in a range of 10 mm to 10 mm. 3. The composite material tap according to claim 1, wherein the metal component in the composite material is VI in a periodic table.
At least one metal component selected from the group II Fe, Ni or Co; and the ceramic component in the composite material is WC, Ti
C, TiN, a _{Mo 2 C, TaC, NbC,} Cr 3 C 2 , or at least one or more ceramic components selected from the VC, and ceramic weight, 85wt% ≦ WC + TiC + TiN + Mo 2 C + TaC
A composite material tap characterized by being set to + NbC + Cr ₃ C ₂ + VC ≦ 97 wt%. 4. A composite material tap according to any one of claims 1 to 3, the hardness of the tap surface H _R A
A composite tap characterized by being 90 or more. 5. The composite material tap according to claim 1, wherein a high hard portion is provided on the surface of the tap along a blade shape, and a thickness of the high hard portion is reduced. , Set in the range of 0.3 mm to 3 mm.