JP4434938B2 - Sialon insert manufacturing method - Google Patents

Description

  The present invention relates to a sialon insert and a cutting tool, and more particularly, to a sialon insert and a cutting tool having a long life and excellent wear resistance.

  The cutting tool has a structure in which an insert (a throwaway tip, a blade tip replacement tip, etc.), which is a disposable blade tip, is attached to the tip of a support body called a holder, like an outer diameter processing holder illustrated in FIG. Many. Various materials are used for this insert depending on the type of work material, machining process, cutting speed, and the like. For example, cemented carbide, cermet, ceramic, CBN, and materials having a coating film on the surface thereof are used. Among them, an insert made of silicon nitride ceramic is suitable for rough machining of ordinary cast iron (abbreviated as FC) material, particularly high speed machining.

  In recent years, for the purpose of improving the fuel efficiency of automobiles, weight reduction of automobile members mainly made of FC materials has become a major issue. Against this background, demands for thinner and lighter automobile members are increasing, and high-precision machining is required for roughing and wrinkling. For rough machining of these FC materials, silicon nitride cutting tools have been used in the past, but silicon nitride itself is a covalent material and can be easily decomposed into silicon and nitrogen at high temperatures during high-speed machining. It was a drawback. The decomposition reaction proceeds faster when silicon nitride comes into contact with iron or carbon, which are the main components of the FC material, at high cutting pressure during cutting. The cutting edge is worn and damaged by the decomposition of silicon nitride at the cutting edge of the tool. When the cutting edge wears, the surface roughness and dimensional accuracy of the work material deteriorate, and the tool becomes unusable and the tool life is reached.

  As a method for suppressing the chemical reaction of the insert material by the work material, it is known that the insert surface is coated with a hard layer made of a titanium compound or an aluminum compound that has low reactivity with iron. For example, Patent Document 1 discloses an example in which an FC material is cut by coating a titanium compound such as titanium nitride or titanium carbide and an aluminum compound such as alumina. Furthermore, in order to suppress the chemical reaction between the work material and the insert base material, a method is known in which titanium nitride or alumina is added to suppress the chemical reactivity of the base material itself. This titanium nitride is present in the structure as dispersed particles, and improves the chemical reaction resistance of the substrate. Alumina is considered to be dissolved in silicon nitride particles to improve the chemical resistance of the silicon nitride particles themselves. These methods are reported in Patent Document 2, Patent Document 3, Patent Document 4, and the like.

Japanese Patent No. 3107168 Japanese National Patent Publication No. 8-510965 JP 10-36174 A JP 2004-527434 A

  On the other hand, sialon is known as a material having excellent hardness and high strength from room temperature to high temperature compared with silicon nitride and the like, and having high chemical stability. For this reason, it has been used as a structural material for hot steel rolling guide rolls and dies that require heat resistance and chemical reaction resistance, and sleeves for aluminum die casting machines. In addition, its wear resistance has been good, and its use has been extended to cutting tools and bearings. However, sialon cutting tools are only used for rough cutting of difficult-to-cut heat-resistant alloys, etc., and little consideration is given to the wear resistance of the tool edge that affects the surface roughness and dimensional accuracy of the work material. It was.

  In inserts with a coating layer on the substrate surface as described above, wear due to the chemical reaction between the work material and the cutting tool substrate is suppressed, but the thermal expansion coefficient of the silicon nitride substrate and titanium nitride or alumina during coating Due to this difference, a tensile residual stress is generated in the coating layer, and the tool edge may be lost using the coating layer as a starting point of destruction, and the tool life may be reduced. Recently, when titanium nitride is added to a silicon nitride substrate, thermal shock resistance may be lowered due to the difference in thermal expansion coefficient between titanium nitride and silicon nitride particles. The mere sialonization by adding an aluminum compound to a silicon nitride base material reduces the strength of the particles themselves, and in particular, may reduce the tool life during high-speed cutting. In addition, the aluminum compound does not dissolve in the silicon nitride particles, and the aluminum compound remaining as the grain boundary phase is not significantly different from the aluminum compound dissolved in the wear and damage caused by the decomposition reaction. Wear may increase.

Since the present invention is to solve such problems, without reducing the material strength, wear due to chemical reactions of the workpiece and the insert, and reducing the abrasive mechanical wear, a method of manufacturing a long-sialon-made insert preparative life The purpose is to provide.

  The present inventors diligently studied the mechanism by which the cutting edge wears due to such a decomposition reaction of the cutting tool material, and suppressing the chemical reaction between the FC material and the tool material is important for extending the tool life. I found out. It was also found that specific sialon inserts can reduce tool wear and abrasive wear due to chemical reaction between the work material and the tool edge and reduce tool life without reducing the strength of the substrate. That is, the means for solving the problems of the present invention are as follows.

(1) The grain boundary phase in the sintered body is 5 to 20%,
The α ratio indicating the ratio of α-sialon in the sialon particles is 40% or less,
Z value of β-sialon represented by Si _6-Z Al _Z O _Z N _8-Z is 0.2 to 1.0,
The solid solution ratio A of Al represented by {(actually measured Z value of β-sialon) / (theoretical Z value calculated from sintered body composition)} in the sintered body is 70% to 93%,
In the manufacturing method of the insert made from sialon which contains 3-10 mol% in conversion of oxide with respect to the said sintered compact 1 or more types chosen from each element of Sc, Y, Ce, Er, Dy, Yb, and Lu. There,
A raw material containing 30 to 95 mol% silicon nitride, 0.5 to 20 mol% alumina, less than 20 mol% aluminum nitride, and 3 to 10 mol% of one or more selected from the above elements. the powder, after the primary sintering is set to refractory made in sheath, which is characteristic and be Rusa Iaron manufactured insert manufacturing method of that secondary sintering.

According to the method for producing a sialon insert of the present invention, it is possible to provide an insert that not only has a high cutting blade strength but also can suppress decomposition and wear due to a chemical reaction between the work material and the tool base material. Also, defining the solid solution ratio of aluminum can suppress mechanical damage represented by abrasive wear when using sialon as a cutting tool, and can greatly improve the tool life. In particular, according to the method for manufacturing a sialon insert of the present invention, the cutting edge of the tool blade that is most suitable for cutting FC materials and the like and that affects the surface roughness and dimensional accuracy of the work material even when used as a rough cutting tool. excellent abrasion resistance, can be provided an insert good cutting of surface roughness and dimensional accuracy can be continued for a long time.

The insert according to the present invention is a sintered body obtained by sintering a sialon phase composed of β-sialon and α-sialon or a sialon phase composed of β-sialon as a main phase and adding a sintering aid. And this sialon insert has a grain boundary phase in the sintered body of 5 to 20%, an α ratio indicating the proportion of α-sialon in the sialon particles is 40% or less, and Si _6-Z Al _Z The Z value of β-sialon represented by O _Z N _8-Z is 0.2 to 1.0, and is calculated from the actually measured Z value of β-sialon in the sintered body and the composition of the sintered body. The Al solid solution ratio A (= measured Z value / theoretical Z value × 100) represented by the ratio of the theoretical Z value is 70% or more.

Sialon is obtained by sintering a raw material powder containing constituent elements such as Si, Al, O, and N such as silicon nitride, alumina, aluminum nitride, and silica as a raw material by adding a sintering aid. Usually, sialon includes β-sialon represented by a composition formula Si _6-Z Al _Z O _Z N _8-Z (0 <Z ≦ 4.2), and a composition formula Mx (Si, Al) ₁₂ (O, N ) ₁₆ (0 <X ≦ 2, M represents an interstitial and solid solution element such as Mg, Ca, Sc, Y, Dy, Er, Yb, Lu) In the sintered body, α-sialon represented by Are mixed. Since β-sialon has a structure in which needle-like structures are entangled like silicon nitride, it has high toughness, and α-sialon has an equiaxed particle shape, so it has low toughness, but compared to β-sialon. And has a high hardness.

  The grain boundary phase between the sialon particles is a liquid phase during sintering, such as a sintering aid, silicon nitride and silica components contained as impurities in the silicon nitride, resulting in generation of sialon particles, rearrangement of sialon particles, and grain growth. After contributing, it solidifies upon cooling and forms at the sialon grain boundary as a glass phase or a crystalline phase. Since this grain boundary phase has a low melting point, low toughness, and low hardness compared to sialon particles, it must be controlled to an appropriate amount in order to improve the heat resistance, toughness, and hardness of the sialon sintered body. is there. However, the grain boundary glass phase and the grain boundary crystal phase can be reduced, for example, by reducing the amount of the sintering aid. However, if the grain boundary glass phase and the grain boundary crystal phase are reduced to less than 5%, the strength of the sialon sintered body is reduced. . On the other hand, when the content is increased from 20%, the grain boundary phase is a component inferior in melting point, toughness, and hardness as compared with sialon particles as described above, so that the heat resistance, toughness, and hardness of the sialon sintered body are lowered. It will be. As a result, the life is shortened due to mechanical damage represented by abrasive wear, which is not preferable. That is, the grain boundary phase of the grain boundary crystal phase and the grain boundary glass phase needs to be 5 to 20%. The grain boundary phase ratio (%) was measured with a scanning electron microscope (SEM), and after taking a photograph of a cross section of 1 mm or more from the burned surface of the sialon sintered body at an observation magnification of 5000 times, the photograph was constant. By measuring the area ratio of the grain boundary phase portion in the region with image processing software, it is obtained as the ratio (%) of the area of the grain boundary phase portion to the entire fixed region. In the sintered body containing hard component particles such as titanium carbide, the hard component particles are not the grain boundary layer portion.

  The insert of the present invention has high toughness when the sialon particles are β-sialon, so that good cutting performance can be obtained. However, even if some of them are α-sialon, no reduction in cutting performance is observed. When the (101) plane peak intensity of β-sialon in X-ray diffraction is β1, the (210) plane peak intensity is β2, the (102) plane peak intensity of α-sialon is α1, and the (210) plane peak intensity is α2. , {(Α1 + α2) / (β1 + β2 + α1 + α2)} × 100 A good cutting performance was obtained when the α-sialon ratio α rate was 40%. When the α ratio exceeds 40%, the number of equiaxed α-sialon crystal particles having low toughness increases, so that the fracture resistance is inferior, which is not preferable. That is, as described above, when the α rate is 40% or less, it has a sufficient cutting performance (wear resistance and fracture resistance), which is preferable.

In the insert of the present invention, the Z value of β-sialon represented by the composition formula Si _6-Z Al _Z O _Z N _8-Z is 0.2 to 1.0. Usually, those having a Z value in the range of 0 to 4.2 are regarded as β-sialon. Since the insert of the present invention has a Z value (actually measured Z value) in the range of 0.2 to 1.0, it is less likely to be decomposed by a chemical reaction with the work material than silicon nitride, and the strength is reduced by sialonization. Few. Furthermore, the insert of the present invention has an Al solid solution rate of 70% or more. Thereby, the residual amount of the aluminum component in the grain boundary phase is small, and mechanical damage as typified by abrasive wear with the work material is suppressed. Here, the actually measured Z value is the a-axis lattice constant of β-sialon and the a-axis lattice constant of β-silicon nitride (7.60442Å) 1 mm or more inside the sintered surface of the sialon sintered body measured by X-ray diffraction measurement. ) (See, for example, WO02 / 44104, page 28). The theoretical Z value is calculated by calculating the Si and Al amounts (% by weight) from chemical analysis such as fluorescent X-rays inside 1 mm or more from the sintered skin of the sintered body, and using the following formula from these values. .
Theory Z = 6 × (Al / 26.98) / {(Al / 26.98) + (Si / 28.09)}
In the formula, Al represents Al wt%, and Si represents Si wt%.

  The insert of the present invention has a Al solid solution ratio of 70% or more represented by measured Z value / theoretical Z value, so that the residual amount of aluminum component at the grain boundary is small, and is representative of abrasive wear with the work material. Such mechanical damage is suppressed. The solid solution ratio of Al can be controlled by adjusting the firing temperature, temperature rise time, firing atmosphere during firing of the sintered body, or changing the ratio of nitrogen and oxygen in the sintered body. is there.

  As a sintering aid used for sintering the sialon insert, at least one selected from the rare earth elements Sc, Y, Ce, Er, Dy, Yb, and Lu is converted into an oxide in terms of oxide. It is preferable to use 5 to 10 mol%. By specifying the kind of rare earth element contributing to acicularization of the sialon structure of the insert of the present invention and the content thereof as described above, the sialon structure can be controlled appropriately. If it is less than 0.5 mol%, the sialon structure is not sufficiently needle-like, which causes a decrease in the strength of the sialon substrate. On the other hand, if it exceeds 10 mol%, the heat resistance, toughness, and hardness of the sintered body itself will decrease. As a result, the service life is reached by mechanical damage such as abrasive wear, which is not preferable.

In addition, mol% of oxide equivalent content of the said rare earth element in a sintered compact is computed with the following method.
(A) The amount of each element in the sintered body (excluding nonmetallic elements, hereinafter the same) is analyzed by fluorescent X-rays, chemical analysis, etc., and the weight ratio is calculated.
(B) The molecular weight is determined by regarding each of the above elements as a compound such as an oxide or a nitride. For example, Si is calculated as Si ₃ N ₄ , Al as Al ₂ O ₃ , aluminum nitride, and Y as Y ₂ O ₃ .
(C) Further, the weight ratio calculated in (a) is divided by the molecular weight of the compound of each element obtained in (b) to make this a mole. The total of these moles is taken as 100 and calculated as the mole% of each compound.
As a simple calculation method, assuming that the sintering raw material powder will be a sintered body without excess or deficiency, it is also possible to obtain mol% from the composition at the time of preparing the substrate, not the contained composition in the sintered body. it can.

  In the sialon insert of the present invention, at least one selected from carbide, nitride and carbonitride of titanium as a hard component is 30 mol% or less, preferably 0.1 to 25 mol%, more preferably 1 to 20 mol. % Content is desirable. Usually, such a hard component is dispersed alone in the sintered body. Since the titanium compound is less reactive with iron and carbon, which are the main components of the work material, as compared with silicon nitride, as with alumina, the presence of the titanium compound in the sintered body increases the reactivity with the work material. It is possible to suppress. The titanium compound is not dispersed in the sintered body but is dispersed alone. If the titanium compound content exceeds the above upper limit, no reduction in cutting performance was observed, but it is a component with a larger coefficient of thermal expansion than sialon, so it is affected by heat cracks that occur due to the heat generated during cutting. This is not preferable because the tool edge is missing. In addition, it can be confirmed with an optical microscope or an electron microscope whether the titanium compound is dispersed alone. Moreover, the calculation method of mol% is computed similarly to the calculation method of mol% of the oxide conversion content of the said rare earth element.

  Thus, the insert of the present invention is used as a high-performance cutting tool by being mounted on a holder as a throw-away tip. In particular, it is optimal as a long-life insert that accurately performs high-speed roughing of cast iron and the like. The cutting tool of the present invention is a cutting tool in a broad sense, and refers to all tools that perform roughing and finishing such as turning, milling, and grooving.

A preferred method for producing the insert of the present invention will be described below. SC ₂ O ₃ powder and Y ₂ O ₃ powder which are oxide powders of rare earth elements as sintering aids, including powders containing elements constituting sialon such as Si ₃ N ₄ powder, Al ₂ O ₃ powder and AlN powder , CeO ₂ powder, Dy ₂ O ₃ powder, Er ₂ O ₃ powder, Yb ₂ O ₃ powder, Lu ₂ O ₃ powder, etc., preferably any of hard component TiN powder, TiC powder, TiCN powder To make a raw material powder. As the raw material powder, a powder having an average particle size of 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less is used. The ratio of these raw material powders may be determined in consideration of the composition of the insert after sintering. Usually, the Si ₃ N ₄ powder is 95 to 30 mol%, the Al ₂ O ₃ powder is 0.5 to 20 mol%, the AlN powder is 0 to 20 mol%, and the sintering aid is 0.5 to 10 mol%. The hard component may be 0 to 30 mol%. Prepared raw material powders as a ball mill, such mixing and grinding machine, for example by mixing 10 to 300 hours by adding a solvent which does not dissolve the powder such as ethanol using a Si ₃ N ₄ pot having a Si ₃ N ₄ balls A slurry is produced. At this time, when the particle size of the raw material powder is large, the pulverization time is lengthened for pulverization.

  When coarse particles are present in the slurry, the slurry is passed through a sieve of about 200 to 500 mesh to remove the coarse particles. Then, an organic binder such as a micro wax is added in an amount of 3 to 15% by weight based on the raw material powder, and granulated and dried by spray drying or the like. The obtained granulated powder is press-molded into a desired shape, and then degreased in an inert gas atmosphere such as nitrogen in a heating apparatus. For molding, injection molding, extrusion molding, cast molding, or the like can be applied. Degreasing can be performed at 400 to 800 ° C. for 30 to 120 minutes. The degreased compact is sintered at 1500-1900 ° C, preferably 1700-1800 ° C. Sintering is preferably carried out in two stages, and the primary sintering is carried out in a sheath of carbon, boron nitride, silicon nitride or the like and heated to 1700-1800 ° C. in a nitrogen or Ar atmosphere of 1-9 atm. What is necessary is just to hold | maintain for 5 hours. Secondary sintering may be performed by hot isostatic pressing (HIP). For example, it heats at 1700-1800 degreeC for 1 to 5 hours in 100-2000 atmospheres nitrogen atmosphere. The sintered body thus obtained is a sialon sintered body, which can be polished into a shape as an insert as shown in FIG. 1 to obtain a throw-away tip for a cutting tool of the present invention. Furthermore, it can be set as a cutting tool by attaching to a holder as shown in FIG.

(1) Production of inserts α-Si ₃ N ₄ powder having an average particle size of 1.0 μm or less and Sc ₂ O ₃ powder, Y ₂ O ₃ powder, CeO having an average particle size of 1.0 μm or less as a sintering aid Table 1 shows the powder, Dy ₂ O ₃ powder, Er ₂ O ₃ powder, Yb ₂ O ₃ powder, Lu ₂ O ₃ powder, and further Al ₂ O ₃ powder, AlN powder, TiN powder, TiC powder, and TiCN powder. The raw material powder was prepared by blending at a ratio. Next, the raw material powder of each inner wall with a Si ₃ N ₄ made of pods and Si ₃ N ₄ balls and ethanol and mixed for 96 hours by adding to prepare a slurry. This slurry was passed through a 325 mesh sieve, and 5.0% by weight of a microwax organic binder dissolved in ethanol was added to prepare granules by spray drying. The obtained granule was press-molded into the shape of an SNGN120408 insert according to the ISO standard shown in FIG. 1, and then degreased in a heating apparatus at 600 ° C. for 60 minutes in a nitrogen atmosphere. The primary sintering of the degreased molded body was set in a sheath made of carbon, boron nitride or silicon nitride, heated to 1700-1800 ° C. in a nitrogen atmosphere of 1-9 atm, and held for 120 minutes. Finally, secondary sintering was performed by hot isostatic pressing (HIP). In the secondary sintering, heating was performed at 1700 to 1800 ° C. for 180 minutes in a 1000 atmosphere nitrogen atmosphere. The obtained sialon sintered body was polished and adjusted to the SNGN120408 shape according to ISO standards to obtain an insert for a cutting tool. Table 1 shows the properties and cutting performance of the inserts of Examples and Comparative Examples of the present invention produced by changing the composition or firing temperature. The composition of the components in the sintered body was determined by a method of calculating mol% from the raw material composition.

(2) Method for measuring properties of insert A method for measuring the properties of the insert will be described. The density of the obtained inserts of Examples and Comparative Examples was measured by the Archimedes method, and divided by the theoretical density to calculate the theoretical density ratio. All the samples had a sufficiently high theoretical density ratio, and the micropores did not remain in the sintered body and were densified. Further, area% of grain boundary phase, actual measurement Z value measurement and calculation, calculation of theoretical Z value and solid solution ratio, and measurement and calculation of α ratio were obtained by the above-described methods.

(3) Evaluation method of cutting performance The following performance tests were performed on the inserts of the examples and comparative examples prepared in (1) above. The results are shown in Table 1.
Cutting distance Insert shape: SNGN120408, chamfer 0.2 mm, work material: cast iron (FC200), cutting speed: 500 mm / min, cutting depth: 0.3 mm, feed rate: 0.3 mm / min, and dry conditions After cutting, the cutting distance when the maximum VB wear amount (VBmax) of the front flank reached 0.3 mm was calculated.

Boundary wear amount Insert shape: SNGN120408, chamfer 0.2 mm, work material: cast iron with cast sand remaining on the side (FC200), cutting speed: 300 mm / min, cutting depth: 1.5 mm, feed rate: 0.2 mm Per minute and dry conditions, the maximum flank wear amount was measured and used as the boundary wear amount (unit: mm).

・ Fracture resistance Insert shape: SNGN120408, chamfer 0.085 mm, work material: cast iron (FC200), cutting speed: 150 mm / min, cutting depth: 2.0 mm, feed speed: 0.6 mm / rev The evaluation method was increased by 0.05 mm / rev for each processing pass, and the evaluation was performed based on the feed rate leading to the defect under dry conditions.

  As shown in Table 1, the insert of the embodiment of the present invention has a long cutting distance of the tool blade edge, a small amount of boundary wear, and excellent fracture resistance. On the other hand, the insert of the comparative example is not preferable because any one of the cutting distance, the boundary wear amount and the fracture resistance is inferior.

  The insert of the present invention and a cutting tool provided with the insert can be used for processing various materials as a long-life insert and cutting tool having excellent wear resistance and fracture resistance.

FIG. 1 shows an example of an insert (a throw-away tip). FIG. 2 shows an example of a cutting tool in which an insert is attached to a holder.

Explanation of symbols

1: Insert (throw away tip) 2: Holder 3: Presser foot

Claims (1)

The grain boundary phase in the sintered body is 5 to 20%,
The α ratio indicating the ratio of α-sialon in the sialon particles is 40% or less,
Z value of β-sialon represented by Si _6-Z Al _Z O _Z N _8-Z is 0.2 to 1.0,
The solid solution ratio A of Al represented by {(actually measured Z value of β-sialon) / (theoretical Z value calculated from sintered body composition)} in the sintered body is 70% to 93%,
In the manufacturing method of the insert made from sialon which contains 3-10 mol% in conversion of oxide with respect to the said sintered compact 1 or more types chosen from each element of Sc, Y, Ce, Er, Dy, Yb, and Lu. There,
A raw material containing 30 to 95 mol% silicon nitride, 0.5 to 20 mol% alumina, less than 20 mol% aluminum nitride, and 3 to 10 mol% of one or more selected from the above elements. the powder, after the primary sintering is set to refractory made in sheath, features and be Rusa Iaron made manufacturing method of the insert to secondary sintering.

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