RU2498892C2 - Cutting wheel - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to grinding and may be used for production of abrasive tools, for example, grinding wheels. Cutting wheel comprises multiple abrasive grains, organic binder and active filler. Active filler material comprises active endothermic file in amount of 12-50% of binder volume.

EFFECT: longer life.

12 cl, 3 dwg, 2 ex

Description

The present invention relates, in general, to abrasive products and, in particular, to an abrasive product with improved grain retention and improved characteristics.

Abrasive products are usually used in various industries for the machining of workpieces by cutting, grinding, grinding or polishing. The use of abrasive products for machining covers a wide variety of industries - from the industry for the production of optics, the factory for the repair of automobiles to the industry for the production of metal. In each of these examples, abrasive materials are used in the production equipment to remove bulk material in order to obtain the intended dimensions, shape and surface characteristics of the products (for example, flatness, surface roughness).

Manufacturers of abrasive products for rough grinding are constantly tasked with manufacturing abrasive products that meet the high performance requirements, as well as the high performance requirements put forward by their customers. One of the specific reasons why manufacturers are tasked with manufacturing abrasive products for rough grinding that meet increased performance and performance requirements is that abrasive products are not only subject to mechanical damage due to fracture or abrasion or destruction of adhesion of abrasive grains, but also to thermal damage on the mating surface of the abrasive grains and the surrounding organic binder (i.e., grain removal). In particular, the high energy associated with abrasive products for rough grinding when removing material without using any cutting fluid to remove heat makes these products more susceptible to the latter type of damage (i.e., thermal degradation on the mating surface of abrasive grains and binder). This thermal degradation is even more obvious when using abrasive grains, which are highly resistant to mechanical damage. Ultimately, thermal degradation weakens abrasive products for rough grinding, worsening their performance and ultimately leading to a shorter service life. Thermal degradation can be especially problematic in the case of ultra-thin dry cutting wheels, which usually very quickly reach thermal degradation temperatures on the grain / binder interface.

SUMMARY OF THE INVENTION

In one embodiment of the invention, an ultra-thin, small-diameter cutting wheel is provided comprising: a plurality of abrasive grains, an organic binder material and an active filler material. The material of the active filler contains an effective amount of material of the active endothermic filler, providing an endothermic reaction in the usual cutting mode without coolant.

In a second embodiment, an ultra-thin, small-diameter cutting wheel is provided comprising a plurality of abrasive grains and an organic binder material containing an active endothermic filler material added thereto, providing an endothermic reaction. The amount of material of the active endothermic filler is about 12-50 volume percent of the binder.

In a third embodiment, an ultra-thin, small-diameter cutting wheel is provided comprising a plurality of abrasive grains and an organic binder material with added active endothermic filler material to provide an endothermic reaction that improves grain retention. A plurality of abrasive grains are selected from the group consisting of seeded or ungraded alumina grains of gel gel, Al ₂ O ₃ —ZrO ₂ grains, and combinations thereof. The material of the active endothermic filler is selected from the group consisting of sulfides, oxides with a low melting point and their combinations.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a depiction of an abrasive article in accordance with one embodiment of the present invention;

Figure 2 is a micrograph of a conventional abrasive product, which shows a large amount of removed grain in a known technical solution; and

Figure 3 is a micrograph image of an abrasive article made in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Turning to the drawings, FIG. 1 is an image of an abrasive article 100 in accordance with one embodiment of the present invention. In particular, FIG. 1 shows that the abrasive article 100 is an abrasive wheel product. As is known from the prior art, products of abrasive wheels are available in different sizes, such as, for example, products of abrasive cutting wheels of large diameter, products of abrasive cutting wheels of medium diameter and products of abrasive cutting wheels of small diameter. Typically, large diameter abrasive cutting wheels have a diameter of more than about 1000 mm, medium diameter abrasive cutting wheels have a diameter of more than about 400 mm and less than about 1000 mm, and small diameter abrasive cutting wheels have a diameter of less than about 400 mm. Although the following description of the abrasive mixture used to make the abrasive product 100 preferably relates to products of small diameter abrasive cutting wheels and, especially, ultra-thin products of small diameter abrasive cutting wheels having diameters less than about 250 mm, it will be apparent to those skilled in the art that the abrasive mixture used for manufacturing abrasive products 100, can find application for products of abrasive cutting wheels of large diameter and products of abrasive cutting wheels of medium diameter.

In one embodiment, the abrasive article 100 is an ultra-thin, small-diameter abrasive article with a binder made from an abrasive mixture that contains abrasive grains and an organic binder with active filler materials added thereto, such as active endothermic filler material (s). This (these) material (materials) of the active endothermic filler provides an endothermic reaction in the “normal cutting mode without coolant” to reduce the temperature on the interface of the grains and the surrounding organic binder. Typically, active fillers can be used in binder abrasives to improve grinding performance. Active excipients, also known as reactive excipients, are intended to be physically and / or chemically active. They usually provide longer, longer cutting speeds and a colder cutting condition. Depending on various parameters, such as the size and geometry of the abrasive tool, the type of grain and binder used, as well as the operating conditions encountered, active fillers can fulfill one or more of the following:

1) reduce friction between abrasive grains and the part processed by an abrasive tool;

2) to prevent "capping" of abrasive grains, that is, to prevent the welding of metal particles to the tops of abrasive grains.

3) reduce the temperature at the interface between the abrasive grains and the workpiece;

4) reduce the required grinding force.

These actions may fall under the following different schemes:

1) grease to reduce friction between abrasive grain and the workpiece;

2) chemical corrosion of the metal surface to prevent adhesion of the metal to the tops of abrasive grains or to weld particles of grinding sludge with the workpiece, or by changing the integrity of the metal surface to promote chip formation;

3) prevention of binder ablation by inhibiting the free radical process of oxidation of the binder used to firmly hold abrasive grain in place;

4) controlled binder erosion allows new grains to act and discard old worn abrasive particles;

5) heat dissipation due to the highly endothermic reaction, which helps to dissipate heat from the mating surface during grinding between abrasive grains and the workpiece.

As described herein, the use of at least one type of active endothermic filler material providing an endothermic reaction to lower the temperature at the mating surface of the abrasive grains and the surrounding organic binder in a “normal cutting without coolant” provides improved grain retention or use. The result of improved grain retention is that the abrasive article 100 will have improved cutting characteristics and a longer service life than other ultra-thin abrasive cutting discs made from conventional abrasive mixtures.

In this embodiment, the abrasive article 100 comprises at least one type of base abrasive grain selected from the group of abrasive material families consisting of etched or unsealed alumina gel gel and Al ₂ O ₃ —ZrO ₂ . A non-exhaustive list of abrasive grains from a seeded or unburnt alumina gel family of alumina that can be used in embodiments of the present invention include SG grain and NQ grain from Saint-Gobain Abrasives, Inc., Worcester, Massachusetts; 3M321 Cubitron grain and 3M324 Cubitron grain, both from 3M Corporation, Sao Paulo, Minnesota, and combinations thereof. A non-exhaustive list of abrasive grains from the Al ₂ O ₃ —ZrO ₂ family that can be used in embodiments of the present invention include NZ Plus grains available from Saint-Gobain Abrasives, Inc., Worcester, Massachusetts; ZF grain and ZS grain, both sold by Saint-Gobain Abrasives, Inc., Worcester, Massachusetts; ZK40 grain manufactured by Treibacher Industry, Inc., Toronto, Ontario, Canada; and ZR25B grain and ZR25R grain, both manufactured by Alcan, Inc., Montreal, Quebec, Canada. In one embodiment, the amount of core abrasive grain is from about 20 to about 100 percent of the total amount of abrasive grain by volume.

In one embodiment, at least one type of auxiliary abrasive grain can be mixed with the main abrasive grain to achieve the fulfillment of cost or technical requirements. Auxiliary abrasive grain can be selected from the group consisting of ceramic oxides (e.g. coated or uncoated fused Al ₂ O ₃ , single crystal Al ₂ O ₃ ), nitrides (e.g. Si ₃ N ₄ , AlN) and carbides (e.g. SiC). In one embodiment, the amount of auxiliary abrasive grain may be in the range of about 80 to about 0 percent of the total abrasive grain by volume or residue.

In one embodiment, the organic binder material is essentially an organic binder material recognized in the art, such as one or more organic resins — for example, epoxy, polyester, phenolic and cyanate ester resins or other suitable thermosetting or thermoplastic resins. Specific, non-limiting examples of resins that can be used include the following: resins sold by Dynea Oy, Finland, under the trade name Prefere and available under catalog / product numbers 8522G, 8528G, 8680G and 8723G; resins sold by Hexion Specialty Chemicals, Ohio, under the trade name Rutaphen.RTM. and available under catalog / product numbers 9507P, 8686SP and SP223; and resins sold by Durez Corporation, Texas, under the following catalog / product numbers: 29344, 29346, and 29722. In one embodiment, the binder material comprises dry resin material.

In various embodiments, the types and amounts of active endothermic fillers are selected in such a way as to provide an endothermic reaction in “normal cutting without coolant”. The expression "normal cutting without coolant" usually refers to those conditions encountered on the interface between the grain and the binder of an ultra-thin cutting wheel of small diameter when cutting without coolant conventional materials for cutting / grinding of which the wheel is intended. An “effective amount” of active endothermic filler provides an endothermic reaction in the normal cutting mode without coolant. This mode usually involves a very rapid rise to thermal degradation temperatures in excess of 450 ° C. Thermal degradation can be especially problematic in the case of ultra-thin dry cutting wheels, which usually transfer heat very quickly and very quickly reach thermal degradation temperatures on the interface between grains and a binder. In the proposed ultra-thin circles, active endothermic fillers induce an endothermic reaction under conditions that usually occur when cutting without cutting fluid, and thus reduce the temperature at the surface of the interface of the grains and binder material, providing much better grain retention and longer service life. In various alternative embodiments, active endothermic excipients provide an endothermic reaction when the temperature at the interface between the grains and the binder is at least about 450 ° C, or at least about 500 ° C, or at least about 527 ° C, or at a temperature that provides an amount of thermal energy greater than the activation energy required to decompose the active endothermic filler. It should be noted that if the heating rate is low, or if the temperature at the interface between the grains and the binder material is too low, exothermic reactions can occur; therefore, the thickness of the abrasive article may play a role in obtaining the desired endothermic reaction.

In one embodiment, the at least one type of active endothermic filler material that provides an endothermic reaction is selected from the group of filler types consisting of low melting point sulfides and oxides. A non-exhaustive list of active endothermic sulfide type excipients that may be used in embodiments of the present invention include pyrite, zinc sulfide, copper sulfide, and combinations thereof. A non-exhaustive list of active endothermic fillers such as low melting point oxides that can be used in embodiments of the present invention include bismuth oxide, lead oxide, tin oxide, and combinations thereof. It should be noted that in one embodiment, the active fillers such as oxides with a low melting point preferably have a melting point below about 1000 degrees Celsius.

It will be apparent to those skilled in the art that various other fillers may be added to the organic binder to increase the ability of the abrasive article 100 to cut, grind, grind, or polish. Fillers may be active and / or inactive fillers. A non-exhaustive list of active excipients may include cryolite, PAF, KBF ₄ , K ₂ SO ₄ , NaCl / KCl, and combinations thereof. A non-exhaustive list of inactive fillers may include CaO, CaCO ₃ , Ca (OH) ₃ , CaSiO ₃ , kyanite (a mixture of Al ₂ O ₃ -SiO ₂ ), saran (polyvinylidene chloride), nephenlin (Na, K.) AlSiO ₄ , wood powder , coconut shell flour, stone (rubble) flour, feldspar, kaolin, quartz, short fiberglass, asbestos fibers, ballotini, fine grain with a processed surface (silicon carbide, corundum, etc.), pumice, cork flour and their combinations. In a preferred embodiment, an active filler material, such as PAF, which is a mixture of K ₃ AlF ₆ and KAlF ₄ , can be added to the organic binder material to corrode metals and reduce friction between the wheel and the workpiece.

In some embodiments, the composition of the abrasive mixture used to make the abrasive article 100 may be as follows. In one embodiment, the abrasive grains present in this mixture may represent from about 35 to about 55 percent by volume of the total mixture (i.e., excluding porosity). In another embodiment, the abrasive grains present in this mixture may represent from about 40 to about 54 percent by volume of the total mixture (i.e., excluding porosity). In one embodiment, the organic binder material (eg, resin) in this mixture may represent from about 25 to about 45 percent by volume of the total mixture. In yet another embodiment, the organic binder material (eg, resin) in this mixture may represent from about 30 to about 40 percent by volume of the total mixture. In one embodiment, the material of the active endothermic filler in this mixture may be in an amount of from about 5 to about 30 percent by volume (amount in the total mixture). In one embodiment, the material of the active endothermic filler in this mixture may be in an amount of from about 5 to about 24 percent by volume (amount in the total mixture). In other embodiments, the implementation of the material of the active endothermic filler in this mixture may be in an amount of from about 12 to about 50 percent by volume (amount in the total binder material). In other embodiments, the active endothermic filler material in this mixture may be in an amount of from about 12 to about 35 percent by volume (amount in total binder material). The rest will be other excipients, including active or inactive excipients. In one embodiment, the volume ratio of the active filler material providing the endothermic reaction to the organic binder material is in the range of from about 0.136 to about 1 (e.g., resin). In yet another embodiment, the volumetric ratio of the active filler material providing the endothermic reaction to the organic binder material is in the range of from about 0.136 to about 0.67 (e.g., resin).

As already noted, in one embodiment, the abrasive article 100 is an ultra-thin, small-diameter abrasive cutting disc. In some embodiments, the abrasive article 100 has a diameter in the range of about 75 mm to about 250 mm and a thickness of at least about 2.5 mm. In other embodiments, the circle thickness is between about 0.8 mm and about 2.2 mm. In various embodiments, the wheel may have a diameter to thickness ratio ranging from about 40 to about 160. These dimensions make the ultra-thin, small-diameter abrasive article 100 well suited for cutting without coolant. To provide a significant improvement in performance, the size and composition of the circle can be selected in accordance with the ideas of the present invention.

As described herein, an abrasive article made from the above composition does not suffer from large numbers of removed grains, like conventional abrasive articles. The characteristics of abrasive products made from conventional compositions are adversely affected by the large quantities of removed grains due to the fact that the bond between the abrasive grains and the binder in these mixtures is not able to withstand thermal degradation due to the heat associated with the action of abrasive cutting products. In accordance with various embodiments of the present invention, it has been found that the temperature at the mating surfaces of the grains and the surrounding organic binder at the surface level of the abrasive article is the highest and can range from about 600 degrees Celsius to about 1000 degrees Celsius. Organic binder material due to its low thermal conductivity (i.e., less than 2 W / (m · K)) can act as an insulation layer, so the heat from the action of cutting does not significantly penetrate deep into the abrasive product, where other layers of abrasive material are located. Therefore, the temperature at the mating surfaces of grains and the surrounding organic binder material at these lower levels, which can be from 250 degrees Celsius to 350 degrees Celsius, is significantly lower than the temperatures at the mating surfaces of the upper surface. Since the temperature at the mating surfaces of the grains and the surrounding organic binder at the surface level is very high, the bond becomes weaker (the typical thermal decomposition temperature of an organic binder, such as resin, is 500 degrees Celsius), and ultimately the grain at this level are removed and fall out of the surface instead of gradual wear through a typical abrasion process. An abrasive product made from the above composition is subject to less grain removal, since it is less susceptible to the adverse effects of thermal degradation on the mating surfaces of the grains and the surrounding binder material due to an endothermic reaction that occurs to lower the temperature on the mating surface.

Compared with the known technical solutions, thermal degradation on the mating surface of grains and the surrounding organic binder material does not adversely affect abrasive products in accordance with embodiments of the present invention due to the size of the circle and composition of specific types of abrasive grains and active endothermic fillers. In particular, it was found that the use of active fillers in the above compositions serves to provide thermal decomposition of the active fillers, which causes a cooling effect that reduces the temperature at the interface between the abrasive grains and the binder. This counteracts the occurrence of severe thermal degradation. In addition to using these active fillers, which provide an endothermic reaction in the aforementioned compositions, it has been found that the selection and selection of the composition of the above abrasive grains gives an abrasive product with significantly less grain removal than conventional abrasive products.

FIG. 2 is a micrograph 200 of a conventional abrasive article showing a large number of grain removal holes 210. It should be noted that only a few grain removal holes 210 are marked for ease of illustration. A closer look at image 200 shows that this is an abrasive product, made in accordance with known technical solutions, has a very large number of grain removal holes 210. An abrasive product with such a large number of grain removal holes will not work well It will therefore have a shorter service life.

Compared to the conventional abrasive article shown in FIG. 2, FIG. 3 is a micrograph 300 of an abrasive article manufactured in accordance with embodiments of the present invention. As shown in FIG. 3, an abrasive article made in accordance with embodiments of the present invention has significantly fewer grain removal holes than a conventional abrasive article shown in FIG. 2. Although not all grain removal holes are marked in FIG. 3, it is obvious that in this figure the grain removal holes are much smaller than in FIG.

Since the abrasive product in FIG. 3 has significantly fewer grain removal holes, this product, as described herein, performs better cutting operations and lasts longer than conventional abrasive products. One of the indicators of the abrasive product is the absolute coefficient of grinding. The absolute grinding coefficient, as described herein, is achieved by installing the abrasive product on a mobile cutting machine without coolant, which can have a maximum operating speed of about 80 m / s. The material of the workpiece with typical dimensions (for example, 600 mm (length) × 100 (width) × 6 (thickness) mm) can be clamped in a vice. Then the number of pieces cut from the material of the workpiece is calculated and recorded in a computer system along with the diameter of the abrasive product. Then, an experienced operator manually performs the test using a grinding machine to perform cutting operations on the material of the workpiece. The data acquisition system connected to the grinding machine controls the power and current of the grinding machine and the cutting time during the test. The test lasts until the abrasive product is fully consumed. Then the diameter of the test product is measured and recorded. In addition, the weight of the remaining workpiece is weighed and recorded. The computer system, using the available commercial software application, determines the material removal rate (CCM) and the circle abrasion rate (CIR). The application calculates the absolute grinding coefficient by dividing the CCM by the LMS. A higher absolute grinding coefficient indicates that the abrasive product has better characteristics.

In the present description, to compare the characteristics of abrasive products, a relative grinding coefficient is used - the ratio of the absolute grinding coefficient of the abrasive article B divided by the absolute grinding coefficient of the abrasive article A (reference). Therefore, the relative grinding coefficient of the abrasive article A is 1. A higher relative grinding coefficient indicates that an improvement has been achieved. Using this approach, it was found that an abrasive product made in accordance with the present invention using the aforementioned compositions has relative grinding ratios that are higher than 1.00. The following examples show that relative grinding ratios of between about 1.4 and about 2.4 can be obtained.

Examples

The following are specific examples of abrasive products manufactured in accordance with the embodiments described herein.

Example 1

In this example, the abrasive product is made with the above composition. About 44 pounds of abrasive grain Al ₂ O ₃ —ZrO ₂ mixed with about 25 pounds of abrasive grains of single crystal Al _-2 O ₃ were added to the mixing container. Then at least one process fluid was added to the grains. In this case, approximately 5 pounds of liquid resin were added to the abrasive grains. About 11 pounds of powder resin, about 6 pounds of PAF, and about 9 pounds of pyrite were prepared in a separate mixing container. A mixture of abrasive grains with liquid resin was poured into this separate container for mixing with a mixture of powder resin, PAF and pyrite. Then, the abrasive article was manufactured by the same method as a conventional abrasive article, such as, for example, the molding methods described in US Pat. No. 6,866,691 B1, the disclosure of which is incorporated herein by reference in its entirety. The size of the abrasive product was 125 mm in diameter and 1 mm thick. The work of the abrasive product with the above composition was tested, and its relative grinding coefficient (compared with a conventional abrasive product of the same size) was 2.2. The improvement in performance was due to the fact that the thermal decomposition of pyrite lowered the temperature at the interface between the abrasive grains and the surrounding organic binder, which gave improved grain retention and a longer service life. Although the present disclosure should not be limited to the proposed theories, it is assumed that at temperatures above 527 degrees Celsius decomposition of pyrite will be the predominant process due to the high activation energy.

Example 2

In this example, the abrasive product is made with the above composition. Approximately 68 pounds of abrasive grain of alumina Al ₂ O ₃ seeded or unsealed sol sols were added to the mixing container. Then at least one process fluid was added to the grains. In this case, approximately 5 pounds of liquid resin were added to the abrasive grains. About 11 pounds of powder resin, about 6 pounds of PAF, and about 10 pounds of pyrite were prepared in a separate mixing container. A mixture of abrasive grains with liquid resin was poured into this separate container for mixing with a mixture of powder resin, PAF and pyrite. Then, the abrasive article was manufactured and tested by the same methods as the conventional abrasive article mentioned above. The size of the abrasive product in this example was 125 mm in diameter and 1 mm thick. Its relative grinding coefficient was 1.6. The resulting improvement in performance was due to the fact that thermal decomposition of pyrite lowered the temperature at the mating surface of the abrasive grains and the surrounding organic binder, which gave improved grain retention and a longer service life.

The following is a comparative example of an abrasive product not manufactured in accordance with the embodiments described herein.

Comparative Example 1

In this example, the abrasive article is made with the above-mentioned abrasive grain, but with other active fillers. In particular, about 44 pounds of abrasive grain Al ₂ O ₃ —ZrO ₂ mixed with about 25 pounds of abrasive grains of single crystal Al ₂ O ₃ were added to the mixing container. In this case, approximately 5 pounds of liquid resin were added to the abrasive grains. The only difference between the composition in this example and the composition above in Example 1 was that there was only one type of active filler in the binder — PAF. That is, pyrite in this composition was not. In particular, approximately 11 pounds of powder resin and approximately 13 pounds of PAF were prepared in a separate mixing container. A mixture of abrasive grains with liquid resin was poured into this separate container for mixing with a mixture of powder resin and PAF. Then the abrasive product was manufactured and tested by the same method as described in example 1. The size of the abrasive product in this example was 125 mm in diameter and 1 mm thick. The resulting relative grinding coefficient (compared to a conventional abrasive product of the same size) was 1.1. The service life of the abrasive product or grain retention did not improve in the same manner as in example 1, due to the fact that during the cutting operation the endothermic reaction did not occur.

The invention is specifically shown and described by way of preferred embodiments, however, it is clear that various changes and modifications will be apparent to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all of these modifications and changes within the spirit of the present invention.

Claims (12)

1. A cutting wheel containing a plurality of abrasive grains, an organic binder material and an active filler material, the active filler material containing an active endothermic filler in an amount of from 12 vol.% To 50 vol.% Of the binder material. 2. The cutting wheel according to claim 1, in which a variety of abrasive grains are selected from the group consisting of grains of alumina etched or uncoated sol of the gel, grains of Al ₂ O ₃ -ZrO ₂ and combinations thereof. 3. The cutting wheel according to claim 1, in which many abrasive grains are selected from the group consisting of SG, NQ, 3M321, 3M324, NZ Plus, ZF, ZS, ZK40, ZR25B, ZR25R, and combinations thereof. 4. The cutting wheel according to claim 1, in which many abrasive grains are present in the range from about 35% to about 55% by volume of the total mixture. 5. The cutting wheel according to claim 1, in which the set of abrasive grains contains the main abrasive grain and auxiliary abrasive grain, the main abrasive grain being selected from the group consisting of grains of alumina seeded or unseated sol, grains Al ₂ O ₃ -ZrO ₂ and combinations thereof, and the main grain is from about 20% to about 100% of the total amount of abrasive grain by volume. 6. The cutting wheel according to claim 1, in which the material of the active endothermic filler is selected from the group of types of fillers, consisting of sulfides and oxides with a low melting point. 7. The cutting wheel according to claim 6, in which the material of the active endothermic filler is selected from the group consisting of pyrite, zinc sulfide, copper sulfide, lead oxide, tin oxide, bismuth oxide, and combinations thereof. 8. The cutting disc according to claim 1, wherein the active material contains cryolite filler, PAF, KBF _4, K ₂ SO _4, NaCl / KCl, and combinations thereof. 9. The cutting wheel according to claim 1, wherein the organic binder material contains dry resin material, wherein the organic binder material is present in the range of about 25% to about 45% by volume of the total mixture. 10. Cutting wheel but claim 1, which has a diameter in the range from about 75 mm to about 250 mm 11. The cutting wheel according to claim 1, which has a diameter to thickness ratio ranging from about 40 to about 160. 12. The cutting wheel according to claim 1, which is an abrasive wheel used for cutting without coolant, in which thermal degradation is the main mechanism of wear of the product.

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