JP2006305708A - Sialon throw-away tip, and cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sialon throw-away tip which is excellent in wear resistance even in high-speed machining of a difficult-to-machine material, prevents a cutting edge from being damaged due to fusing thereto of a workpiece material, and has a long service life, and also to provide a cutting tool having the throw-away tip mounted thereon. <P>SOLUTION: The sialon throw-away tip is made of sialon which has a sialon phase consisting of an α sialon phase and a β sialon phase, and a grain boundary phase formed of a glass phase and/or a crystal phase. The β sialon phase is represented by a chemical formula Si<SB>6-Z</SB>Al<SB>Z</SB>O<SB>Z</SB>N<SB>8-Z</SB>, where the Z is in a value of 0.2 to 1, and an α ratio indicating the ratio of the α sialon phase in the sialon phase is in the range of 10 to 40%. The sialon contains at least one or more rare-earth elements selected from the group consisting of Sc, Y, Dy, Yb, and Lu in an amount of 2 to 5 mol% in total in terms of oxide, and the rare-earth elements of 30 to 50 mol% exist in the α sialon phase. The cutting tools is obtained by mounting the sialon throw-away tip on a holder. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sialon throw-away tip and a cutting tool, and more particularly, to a sialon throw-away tip having a long tool life that has a cutting edge that is less likely to wear and a cutting tool equipped with the tip.

  The cutting tool is a throwaway tip (insert, blade tip replacement tip, tool blade tip, etc.) that is a disposable blade tip at the tip of a support called a holder, such as the outer diameter processing holder shown in FIG. 2 or the milling cutter holder shown in FIG. Many structures are also attached. Various materials are used for the throw-away tip depending on the type of work material, the machining process, the cutting speed, and the like. Examples thereof include cemented carbide, cermet, ceramic, CBN, and materials having a coating film on the surface thereof. Among them, throw-away chips made of coated cemented carbide or silicon nitride ceramic are often used for roughing, particularly high-speed machining of ordinary cast iron (referred to as FC material).

  On the other hand, sialon has high hardness, small strength change from room temperature to high temperature, and high chemical stability compared to silicon nitride. Therefore, guide rolls and dies for rolling hot steel that require heat resistance and chemical resistance are required. It is used as a structural material for sleeves of aluminum die casting machines. In addition, since it has good strength and heat resistance, it is also used for cutting tools and bearings. However, sialon cutting tools are often used as rough cutting tools for heat-resistant alloys, which are difficult to cut. In rough machining, the wear resistance of the tool edge was not considered as important. There was not enough improvement.

  In recent years, the weight reduction of automobile parts, mainly FC materials, has become an important issue for the purpose of improving the fuel efficiency of automobiles. The demand for ductile cast iron (FCD) materials that can be made thinner and lighter than FC materials is increasing. Is increasing. Conventionally, a ducted cast iron has been processed using a coated carbide cutting tool under a relatively low cutting speed, for example, 500 m / min or less. However, when cutting is performed at a high speed of, for example, about 1000 m / min for the purpose of improving the cutting efficiency, there has been a problem that the base material of the cemented carbide is plastically deformed and damaged by the heat generated during cutting. In addition, even if a silicon nitride cutting tool with excellent heat resistance is used, the silicon nitride base material and the work material react due to heat generation during high-speed machining, causing welding and damage to the cutting edge. There was a problem of becoming.

  In order to reduce the damage caused by the welding of the work material and the silicon nitride base material, a method of coating the silicon nitride base material with a hard layer made of a titanium compound or an aluminum compound having low reactivity with iron or carbon is known. ing. For example, Patent Literature 1, Patent Literature 2, Patent Literature 3, and the like disclose examples in which a silicon nitride base material is coated with titanium nitride or aluminum oxide and normal cast iron and ductile cast iron are cut. Although the welding damage of the work material and the tool is suppressed by the effect of the coating layer, tensile residual stress tends to occur in the coating layer during coating due to the difference in thermal expansion coefficient between the silicon nitride substrate and titanium nitride or aluminum oxide. The cutting edge of the tool may be lost using the layer as a starting point for destruction. In addition, in order to suppress the chemical reaction between the work material and the silicon nitride base material, a method is known in which titanium nitride or aluminum oxide is added to silicon nitride to improve the chemical reaction resistance of the base material itself. Titanium nitride is present in the structure as dispersed particles and can improve the chemical reactivity resistance of the silicon nitride substrate. Aluminum oxide is dissolved in silicon nitride particles to form sialon particles, which improves the chemical reaction resistance of the silicon nitride particles themselves. Such methods are disclosed in, for example, Patent Literature 4, Patent Literature 5, Patent Literature 6, Patent Literature 7, Patent Literature 8, Patent Literature 9, and the like. However, the addition of titanium nitride or aluminum oxide tends to cause a decrease in high-temperature strength due to the difference in thermal expansion coefficient between titanium nitride and silicon nitride particles, or a decrease in strength of the particles themselves due to sialonization due to the addition of aluminum oxide. It was difficult to control. In particular, there is a difficulty in making a tool that exhibits a sufficient life during high-speed cutting of difficult-to-cut materials such as ductile cast iron.

US Pat. No. 5,525,134 JP 2002-284589 A JP 2002-192403 A JP-A-62-15505 JP 63-35594 A Japanese Patent Laid-Open No. 2-275863 Japanese National Patent Publication No. 8-510965 JP 10-36174 A WO 02/44104 (A2) Publication

  The present invention solves the above-mentioned problems and has sufficient strength, excellent wear resistance, and welded material even in high-speed cutting of difficult-to-cut materials such as ductile cast iron as well as ordinary cast iron. It is an object of the present invention to provide a sialon throw-away tip having a long life that does not cause damage to the cutting edge and a cutting tool equipped with the throw-away tip.

  The present inventors have earnestly studied the mechanism of damage to the tool edge from the above-mentioned welding damage of the cutting tool material, and welded by a chemical reaction between a difficult-to-cut material such as ductile cast iron and the tool material. It has been found that it is important to extend the tool life to suppress to a problem-free level and not cause a decrease in strength of the tool material. The welding reaction between the work material made of ductile cast iron or the like and the cutting tool blade edge is caused by the fact that silicon nitride tends to decompose into silicon and nitrogen when contacting the work material at high temperature and high cutting pressure. It is believed that. Suppressing this silicon nitride decomposition reaction is important in order to reduce cutting edge wear due to welding damage of the silicon nitride-based tool and extend the tool life. For that purpose, it discovered that the production | generation of (beta) sialon phase of a specific composition and control of the composition and abundance ratio of (alpha) sialon phase were important. That is, the means for solving the problems of the present invention are as follows.

(1) and the α-sialon phase and β-sialon phase consisting sialon phase, in sialon having a grain boundary phase composed of a glass phase and / or crystalline phases, represented by _{Si 6-Z Al Z O Z} N 8-Z The β value of β sialon phase is 0.2 to 1, the ratio α ratio of α sialon phase to sialon phase is 10 to 40%, and selected from Sc, Y, Dy, Yb, and Lu in sialon This is a sialon throw-away chip that contains one or more rare earth elements in total in an amount of 2 to 5 mol% in terms of oxide, and 30 to 50 mol% of the rare earth elements are present in the α-sialon phase.
(2) The sialon throwaway tip according to (1), wherein the sialon contains 30 mol% or less of at least one selected from carbide, nitride, and carbonitride of titanium as a hard component.
(3) A cutting tool in which the sialon throwaway tip according to (1) or (2) is mounted on a holder.

The throw-away tip of the present invention is made of a sialon sintered body in which a sialon phase composed of an α sialon phase and a β sialon phase, which is obtained by adding an aluminum compound to silicon nitride and forming a sialon, is bonded with a sintering aid. is there. The β sialon phase in the sintered sialon is a structure in which fine acicular particles similar to silicon nitride are intertwined, and the strength of the particles themselves is higher than that of alumina used in conventional tools. Defects hardly occur and have a long life. However, when the amount of the aluminum compound dissolved is too large, the strength of the sialon phase is lowered, and the tool edge is likely to be damaged. The amount of the aluminum compound added needs to be adjusted to such an extent that the adverse effect of reducing the strength does not occur while suppressing the reactivity with the work material. Even if the aluminum compound is dissolved in silicon nitride and does not become sialon, it exists in the grain boundary phase, and thus has an effect of contributing to suppression of reaction with the work material. Compared to silicon nitride, the sialon phase is chemically stable and does not easily react with iron and carbon, which are the main components of the work material, even at high temperatures. It is important to satisfy both stability requirements. The addition amount of the specific aluminum compound, a range of Z values of β sialon phase represented by _{Si 6-Z Al Z O Z} N 8-Z in sialon sintered body is 0.2 ≦ Z ≦ 1 It is necessary to be. If the Z value is less than 0.2, a welding reaction with the work material is likely to occur, and a sufficient life extension effect cannot be obtained. If the Z value exceeds 1, the aluminum component increases and the strength decreases due to sialonization. Becomes noticeable, the strength of the tool edge decreases, and wear and chipping become noticeable. The method for measuring the Z value is based on the difference between the a-axis lattice constant of the β sialon phase in the sintered sialon body measured by X-ray diffraction and the a-axis lattice constant of β silicon nitride (7.60442 ケ イ 素). Calculated by (For example, refer to page 28 of WO 02/44104 for a detailed calculation method.)

In the present invention, it is important to control the composition of the α sialon phase in the sialon phase and the abundance ratio in the sialon phase. The α sialon phase is represented by a composition formula M _x (Si, Al) ₁₂ (O, N) ₁₆ . M represents an interstitial and solid solution element such as Mg, Ca, Sc, Y, Dy, Er, Yb, and Lu, and X is a value of 0 <X ≦ 2. Since the α sialon phase has an equiaxed particle shape, the α sialon phase has lower toughness than the β sialon phase, but has a feature of high hardness. In this way, a predetermined amount of high-hardness α-sialon phase is produced, and at the same time, the elements to be dissolved in the α-sialon phase and the amount of the solid solution are optimized, so that compared with a sialon sintered body having only the β-sialon phase. It becomes possible to improve the reaction resistance and wear resistance with the cutting material. In the present invention, the α ratio, which is the ratio of the α sialon phase to the total sialon phase, is 10 to 40%, and the total of the rare earth elements Sc, Y, Dy, Yb, and Lu dissolved in the α sialon phase is sialon sintered. By setting it as 30-50 mol% of this rare earth element total amount contained in the whole body, the chemical stability of a sialon sintered compact increases, and reaction with a sialon and a work material can be suppressed. Further, as the sialon sintered body, the sialon sintered body contains at least one kind of the rare earth elements in a total amount of 2 to 5 mol%, and the above-mentioned ratio is solid-solved in the α sialon phase, thereby improving the sinterability of the sialon sintered body. The grain boundary phase can also be reduced while ensuring, and this effectively works to suppress mechanical wear damage caused by the grain boundary phase.

  The ratio α rate of the α sialon phase is defined by β1 for the (101) plane peak intensity of the β sialon phase, β2 for the (210) plane peak intensity in the X-ray diffraction, and α1 for the (102) plane peak intensity of the α sialon phase, (210 ) When the plane peak intensity is α2, (α1 + α2) / (β1 + β2 + α1 + α2) is calculated. When the α ratio is less than 10% and the rare earth element solid-dissolved in the α sialon phase is less than 30 mol% of the whole, the generation of the α sialon phase having excellent reaction resistance with the work material is insufficient, and sialon firing is performed. The reaction resistance as a bonded body is lowered, and welding damage due to a chemical reaction between the work material and the tool edge is likely to occur. When the α ratio exceeds 40%, the equiaxed α sialon phase having low toughness increases, so that the fracture resistance is lowered, which is not preferable. Further, when the solid solution amount of the rare earth element in the α sialon phase exceeds 50 mol% of the entire rare earth element, the reaction resistance of the sialon sintered body to the work material is sufficient, but the α sialon particles themselves This is not preferable because the strength of the resin decreases. Therefore, in the throwaway tip made of sialon of the present invention, the α ratio is 10 to 40%, and the rare earth element to be solid-solved in the α sialon phase is 2 to 5 mol% of the total rare earth element contained in the entire sialon sintered body. Of these, the ratio is 30 to 50 mol%.

  The grain boundary phase between the sialon particles is after the sintering aid, silicon nitride, and silica components contained as impurities in the silicon nitride become liquid phase during sintering, contributing to the generation, rearrangement, and grain growth of the sialon particles. It solidifies upon cooling and is formed as a glass phase or a crystalline phase. Since this grain boundary phase has a low melting point, low toughness and low hardness as compared with sialon particles, it is better to reduce the grain boundary phase in order to improve the heat resistance, toughness and hardness of the sialon sintered body. The grain boundary phase can be reduced, for example, by reducing the sintering aid. However, if the sintering aid is reduced too much, the sialon phase cannot be completely sintered and the strength of the sialon sintered body is reduced. It becomes. In the present invention, the rare earth elements Sc, Y, Dy, Yb, and Lu are used as sintering aids to improve the heat resistance, toughness, hardness, etc. of the sialon sintered body. On the other hand, the total amount of the rare earth elements needs to be 2 to 5 mol% in terms of oxide.

The mol% of the oxide equivalent content of the rare earth element in the sintered body is calculated by the following method.
(A) The amount of each element (excluding nonmetallic elements, the same applies hereinafter) in the sintered body is analyzed by fluorescent X-ray analysis, chemical analysis, or the like, 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 and AlN, Y as Y ₂ O _{3 and the} like.
(C) Further, the weight ratio calculated in (a) is divided by the molecular weight of the compound of each element obtained in (b) to obtain the number of moles of the compound of each element. The total number of these moles is taken as 100 mole%, and the number of moles of each compound is converted to mole%.
As a simple calculation method, it is assumed that the sintered raw material powder will be a sintered body with no excess or deficiency, and it is not the content composition in the sintered body, % Can also be obtained.

  In the sialon throwaway tip 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 It is desirable to contain ~ 20 mol%. 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. Can be suppressed. If the titanium compound content exceeds the upper limit, the titanium compound is a component having a larger coefficient of thermal expansion than sialon, so the tool edge tends to be damaged due to thermal cracks that are generated by the influence of heat during cutting. Therefore, it is not preferable. In addition, it can be confirmed with an optical microscope or an electron microscope whether the titanium compound is dispersed alone. The method for calculating the mol% of the titanium compound is the same as the method for calculating the mol% of the rare earth element oxide content.

  The sialon throw-away tip of the present invention is mounted on a cutting tool holder and used as a high-performance cutting tool. In particular, it is suitable for long-life cutting tools that perform high-speed roughing such as ductile cast iron with high accuracy. 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 sialon throwaway tip of the present invention will be described. Sc ₂ O ₃ powder, Y ₂ O ₃ , which is a rare earth element oxide powder, using a raw material powder containing elements constituting sialon such as Si ₃ N ₄ powder, Al ₂ O ₃ powder, and AlN powder as a sintering aid. Powder, Dy ₂ O ₃ powder, Yb ₂ O ₃ powder, Lu ₂ O ₃ powder, etc. or mixed with several kinds, preferably adding any of hard component TiN powder, TiC powder, TiCN powder and raw material powder And The raw material powder may have an average particle size of 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less. The ratio of these raw material powders may be determined in consideration of the composition of the throw-away tip after sintering. Usually, Si ₃ N ₄ powder is 50 to 90 mol%, Al ₂ O ₃ powder is 0.5 to 15 mol%, AlN powder is 0 to 35 mol%, sintering aid is 2 to 5 mol%, and hard What is necessary is just to make a component into 0-30 mol%. The prepared raw material powder is mixed for 10 to 300 hours by adding a solvent that does not dissolve the powder, such as ethanol, for example, using a Si ₃ N ₄ pot equipped with a ball made of Si ₃ N ₄ such as a ball mill. To produce a slurry. At this time, when the particle size of the raw material powder is large, the pulverization time is lengthened to ensure sufficient 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. In molding, molding is performed in anticipation of the shrinkage of the molded product in the subsequent degreasing process and sintering process. Usually, the degreasing step may 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. The primary sintering may be performed by raising the temperature to 1700 to 1800 ° C. in a nitrogen or Ar atmosphere of 1 to 9 atm in a sheath of carbon, boron nitride, silicon nitride or the like and holding it for 1 to 5 hours. When the sintered body cannot be obtained by sufficiently densifying in the primary sintering, secondary sintering is performed as necessary. 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 is polished into a shape as a throw-away tip as shown in FIGS. 1 and 3 and made from sialon for the cutting tool of the present invention. It can be a chip. Furthermore, as shown in FIG. 2 and FIG. 5, it can be set as the cutting tool for outside diameter processing, or the cutting tool for milling cutter by attaching to the holder for outside diameter processing or the holder for milling cutter.

  The throw-away tip and cutting tool of the present invention are sialon throw-away tips with a controlled composition and sintered structure, and are equipped with defect resistance due to welding damage in addition to high-temperature strength, hardness, and wear resistance. It has a very long life not only for ordinary cutting materials but also for high-speed cutting of difficult-to-cut materials. As a result, difficult-to-cut ductile cast iron and heat-resistant alloys can be processed at high speed, which can contribute to reduction in processing costs and improvement in processing efficiency.

  Preferred embodiments of the sialon throwaway tip of the present invention and a cutting tool equipped with the throwaway tip will be described as an example in comparison with a comparative example.

(1) Production of throw-away tip αSi ₃ N ₄ powder each having an average particle size of 1.0 μm or less, rare earth element oxides Sc ₂ O ₃ , Y ₂ O ₃ , CeO ₂ , Dy ₂ O ₃ as a sintering aid, Er ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ powder, and further Al ₂ O ₃ powder, AlN powder, and TiN powder were blended in the proportions shown in Table 1 to prepare raw material powder. Then, these raw material powders inner wall placed with Si ₃ N ₄ balls to Si ₃ N ₄ made pot was added ethanol and mixed for 24 hours 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 so as to have the shape of a throw-away tip of SNGN120212 according to ISO standards after sintering. The molded body was degreased for 60 minutes at 600 ° C. in a nitrogen atmosphere of 1 atm in a heating apparatus. The primary sintering of the degreased compact was set in a silicon nitride sheath, heated to 1800 ° C. in a nitrogen atmosphere of 6 atm, and held for 120 minutes. In order to remove residual pores in the primary sintered body, secondary sintering was performed by hot isostatic pressing (HIP). In the secondary sintering, heating was performed at 1700 ° C. for 120 minutes in a nitrogen atmosphere at 1000 atmospheres. The obtained sialon sintered body was polished and adjusted to a throw-away tip shape of SNGN120212 according to ISO standards to obtain a throw-away tip for a cutting tool.

(2) Measurement of properties of throw-away tip A method for measuring the characteristics of the throw-away tip will be described. The density of the obtained throw-away tips of Examples and Comparative Examples was measured by the Archimedes method, and the theoretical density ratio was calculated by dividing by the theoretical density. Except for the sample of Comparative Example 1, the theoretical density ratio was sufficiently high, and the micropores did not remain in the sintered body and were densified, so the properties were measured. The measurement and calculation of the Z value and the α rate were performed according to the method described above. The solid solution amount of Sc, Ce, Y, Dy, Er, Yb, and Lu in the α sialon particles was measured by observing the structure with a transmission electron microscope and analyzing the composition of α sialon with the attached EDX analyzer. Then, the ratio (mol) of the amount dissolved in the α-sialon particles with respect to the added auxiliary agent was calculated as the solid solution ratio mol% of the auxiliary agent (microscope observation magnification: 50,000 times). Table 1 shows the compositions and properties of the throw-away tips of the examples of the present invention and the comparative examples prepared by changing the composition.

(3) Evaluation of cutting performance of throw-away tip The following performance test was performed on the throw-away tip of the example and the comparative example prepared in (1) above. The results are shown in Table 1.
The chamfering edge of the throwaway tip of Example and Comparative Example is chamfered with a chamfering width of 0.3 mm and a chamfering angle of 25 °, set in a milling cutter (see FIGS. 4 and 5), and processing shown below Cutting was performed under the conditions. Evaluation was made based on the number of workpieces that could be processed before the wear amount (VB) of the tool edge reached 0.3 mm. Similarly, when the tool edge was lost before VB became 0.3 mm, the tool life was also determined.
(Processing conditions)
Work material: JIS FCD600 (Ductile cast iron with cast skin): Length 130mm x width 700mm x thickness 30mm
Cutting speed: 1000 m / min
Feed rate: 0.15 mm / blade cutting depth: 2.0 mm
Cutting oil: Dry-use cutter: φ100 Processing with one blade.

  As shown in Table 1, the throw-away inserts of Examples A to T of the present invention have a large number of workable materials of 9 or more until the amount of wear (VB) of the tool edge reaches 0.3 mm. In addition, the tool edge was not damaged. However, only five of the throw-away tips of comparative examples that did not satisfy the requirements of the present invention could be cut. In addition, there was a throw-away tip that caused cutting edge failure or poor densification.

  The throw-away tip of the present invention and the cutting tool equipped with the tip-away tip can be used for a wide range of cutting of various materials as a long-life throw-away tip and a cutting tool excellent in wear resistance and fracture resistance.

FIG. 1 is a perspective view of the throw-away tip of the present invention. FIG. 2 is an example of a cutting tool for outside diameter processing in which the throw-away tip of the present invention is mounted on a holder. FIG. 3 is a perspective view of another example of the throw-away tip of the present invention. FIG. 4 is a front view showing chamfering of the throw-away tip of FIG. FIG. 5 is a plan view of a cutting tool in which a throw-away tip is mounted on a milling cutter holder.

Explanation of symbols

1: Throw-away tip 2: Holder for outer diameter processing 3: Presser foot 4: Cutting edge 5: Chamfered portion of throw-away tip 6: Holder for milling cutter 7: Holder for milling cutter 8: Cartridge 9 for throw-away tip mounting : Wedge for throwaway tip mounting

Claims (3)

β sialon represented by Si _6-Z Al _Z O _Z N _8-Z in a sialon having a sialon phase composed of an α sialon phase and a β sialon phase and a grain boundary phase composed of a glass phase and / or a crystal phase. Rare earth element selected from Sc, Y, Dy, Yb, and Lu in the sialon, wherein the Z value of the phase is 0.2 to 1, the ratio α ratio of the α sialon phase in the sialon phase is 10 to 40% A sialon throw-away tip containing one or more kinds in total in an amount of 2 to 5 mol% in terms of oxide, and 30 to 50 mol% of the rare earth element is present in the α sialon phase.   The sialon throwaway tip according to claim 1, wherein the sialon contains at least 30 mol% of one or more selected from carbides, nitrides, and carbonitrides of titanium as a hard component. A cutting tool in which the sialon throwaway tip according to claim 1 or 2 is mounted on a holder.

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