EP2699373A1

EP2699373A1 - Ceramic drill for high-performance drilling of cast-iron materials

Info

Publication number: EP2699373A1
Application number: EP12720072.3A
Authority: EP
Inventors: Oswald SCHEIBENBAUER
Original assignee: TCM International Tool Consulting&Management GmbH
Current assignee: TCM International Tool Consulting&Management GmbH
Priority date: 2011-04-19
Filing date: 2012-04-10
Publication date: 2014-02-26
Also published as: AT511377B1; AT511377A1; JP2014511776A; WO2012142641A1

Abstract

The invention relates to a tool (1) for machining workpieces, in particular for drilling cast-iron materials, comprising a main body (2) of a first material and a cutting insert (3) of a second material, which has a greater hardness than the first material, wherein the cutting insert (3) is attached to the main body (2) by a material bond. In order to achieve high cutting speeds and long service lives, it is provided according to the invention that the cutting insert (3) has a v-shaped end (4) and the main body (2) has a region (5) corresponding thereto and that the cutting insert (3) is attached by the end (4) to the corresponding region (5) of the main body (2) by a material bond.

Description

Ceramic drills for high-performance drilling of cast iron materials

The invention relates to a tool for machining workpieces, in particular for drilling cast iron materials, comprising a base body of a first material and a cutting insert of a second material having a higher hardness than the first material, wherein the cutting insert on

Basic body is attached cohesively.

Ceramic inserts are today used in the machining industry

Processing of workpieces used only in a few areas, for example in a dry machining of cast materials. As cutting material for corresponding inserts usually a ceramic based on silicon nitride is used to achieve a high wear resistance. With such a ceramic machining is currently possible in an economical manner and with a positive cost-benefit ratio, while at the same time limiting to geometrically simple tools or inserts and special applications is given.

In the specific applications mentioned above, practical advantages can be achieved in milling or turning with ceramic indexable inserts through shorter throughput and machining times compared with milling or turning with carbide indexable inserts, but the ceramic cutting materials used for this purpose are significantly more expensive than carbides. Although by a suitable

Regrinding of cutting an indexable insert the cutting costs per

Cutting edge can still be lowered, so still remain the high cost of the ceramic cutting material, which partially compensate for the practical advantages.

In addition to ceramic indexable inserts, in recent years more and more experiments have been made with all-ceramic milling and drilling tools. However, these tools have never been mass-produced due to very high cost and high failure rates, especially tool breakage, except in niche applications. The reason for this is a high brittleness of the ceramic cutting materials and for the

High performance drilling unsuitable tip geometries of the drilling tools that cause too high cutting forces. From DE 101 14 882 A1 a drilling tool has become known, which has a shank made of a hard metal and a cutting insert made of a ceramic made of silicon nitride. The cutting insert is in the region of a slot of the base body made of hard metal materially joined to the body, wherein the cohesive connection soldering or gluing comes into question. Mentioned is also a dull cohesive

Connection of a mostly cylindrical cutting insert with one end of a shaft-shaped base body. In such a tool is advantageous that the shaft is tough and has a high strength, whereas the attached

Cutting insert can have a high wear resistance. However, such tools have not prevailed in practice, since they have neither sufficient quality in terms of high cutting speeds nor long tool life.

The object of the invention is to provide a tool of the type mentioned, in particular a drill, with the high cutting speeds can be achieved in a machining of workpieces and at the same time provides long life.

This object is achieved according to the invention when, in the case of a tool of the type mentioned above, the cutting insert has a V-shaped projection and the base body has a corresponding area and the cutting insert is cohesively attached to the corresponding area of the base body.

In the context of the invention, it has been found in extensive simulations and experiments that when connecting a composite tool comprising a base body made of a hard metal and a cutting insert made of a ceramic, a connection region is of essential importance. First simulations and experiments in which the base body with a projecting pin and the ceramic cutting insert were formed with a corresponding recess for encompassing the pin in a soldering, resulting in the same processing of a blank in massive damage, especially cracks, but sometimes also fractures. Further simulations showed that for this purpose high tensile stresses are responsible for different thermal expansion coefficients of ceramic, solder and

Return carbide. A blunt soldering brought improvements in terms of punctual tensile stresses in the sense of a reduction of the same, revealed but also not completely satisfactory results. Only that

inventive provision of a V-shaped projection at one end of the

Cutting insert and a training of the body with a to

Corresponding area and a connection of the cutting insert with the approach to the corresponding region of the body by soldering or other type of material connection leads to a (cutting) tool of sufficient quality or a tool that not only high

Cutting speeds allowed, but also provides long service life in use. The corresponding V-shaped design also allows maximizing a boundary or connecting surface, which is favorable for a good grip of the cutting insert on the body. In addition, those acting on a deployment can also

Torsional forces are controlled efficiently.

Although any type of cohesive bonding is possible, it is preferred because of the action of heat on the tool during the drilling process that the cutting insert is soldered to the base body.

The V-shaped projection is preferably formed with an opening angle of 120 ° to 160 °, preferably 130 ° to 150 °. In this case, the v-shaped projection is advantageously formed on the cutting insert projecting. It then results for the main body a corresponding groove or recess for the corresponding area. But it is also possible a reverse situation, wherein the groove is formed in the cutting insert as a negative v-shaped approach and the body has a corresponding projecting portion. Regardless of the chosen variant, it is important in both cases with respect to durability of the tool that there are no edges in the connection region, which can be the starting point for high tensile stresses through the material sequence of ceramic-solder-cemented carbide, and at the same time a connection surface is maximized. Incidentally, both the v-shaped projection in the cutting insert and the corresponding region in the base body can be created in a simple manner by Einschieifen.

According to the above statements, the basic body consists of

Solid carbide. The cutting insert may consist of a ceramic or a ceramic whisker composite material. The main body preferably extends to the cutting insert or vice versa.

As a result, neither the base body surrounds the cutting insert nor the cutting insert the base body, so that no edges are present in the region of a connecting surface, which otherwise to the mentioned tensile stresses and thus in a row

Material failure could result.

The general concept of the invention can be transferred to any tools for machining, but is preferably used when the tool is designed as a drill, in particular twist drill. An inventively designed drill basically has several main cutting edges, preferably two main cutting edges are provided, which extend at the end of the drill. In connection therewith, a residual cross-section may be provided at the end, which has a length of 1% to 5%, in particular 2% to 3%, of one

Drill nominal diameter is formed. The main cutting edges close to the

Residual cross-section on. The formation of the residual cross-section with the mentioned length on the one hand leads to a good centering behavior in a cutting and

on the other hand ensures a low axial cutting pressure of the drill.

Basically, even smaller values for drilling a workpiece would be even more favorable, but this could lead to breakouts in the drill center due to high hardness and associated brittleness of a ceramic cutting material, where extremely low cutting speeds generally occur during drilling. The major cutting edges extend from the residual cross-section to an outer diameter of the drill. It is preferred that at a transition to

Rest cross cutting a radius is provided. By such a radius-shaped

Shaping the main cutting edge also shows that a high abrasive wear, which occurs in particular when machining cast iron materials, fewer attack points and thus lower acting forces and, as a result, longer tool life are given. It is particularly favorable if the main cutting edges are rounded, preferably at least along rectilinear regions thereof. If the main cutting edges are provided with a defined rounding starting from the cross cutting edge to an outer side of the drill, it is possible despite a high hardness of the ceramic

Cutting material and an associated brittleness a crumbling of the ceramic cutting material in use as well as subsequently a complete breakage of the drill are basically avoided. The corresponding rounding is expediently carried out by a Schleppentgrat method, which is an optimal

Cutting rounding along the main cutting edges allows. An extent of

Rounding can be controlled by a process duration and is thus very easy to reproduce, which is essential for high process reliability in the production of drills. For example, a radius of edge rounding may range from 0.5% to 2%, preferably 0.8% to 1.2%, of an outer diameter of the drill.

Furthermore, a plurality of, preferably two, flutes may be provided, wherein a spacing of the flutes in plan view of one end of the drill is at least 20%, preferably 25% to 35%, of the outer diameter of the drill. By a corresponding spacing of the flutes a core diameter is reinforced, so that even at high speeds sufficient rigidity of the drill is given. Incidentally, by this measure, high axial cutting forces can be better excluded from the shank of the drill.

Furthermore, in a drill according to the invention, a plurality, preferably four, guide bevels may be provided, which extend along the outer side or an outer surface of the drill. Compared with the usual two guide bevels along flutes, four chamfers allow a better guidance of the drill in a borehole and thus lead to a higher stability of the tool in the drilling process. A smoother running of the drill by a better support results in a better circular accuracy and a much better bore surface and incidentally leads to less vibration, which for ceramic cutting a special

Pose a threat. In this case, it can also be provided, in particular, that the guide bevels, viewed from the main cutting edges, are designed to taper in the axial direction in order to reduce frictional forces and to prevent the drill from jamming in the borehole, which is usually caused by incipient abrasive wear on the outer diameter of the drill is. In this

Connection can also be provided that the drill in the field of

Base body has a smaller diameter than in the region of the main cutting or the cutting insert, with a transition to smaller diameter preferred lies in the area of the guide chamfers. In this case, only the ceramic cutting head takes over a guide of the tool or drill in a bore. Jamming of the drill can then be at least largely avoided. Further features, advantages and benefits of the invention will become apparent from the embodiment illustrated below. In the drawings, to which reference is made, show:

1 shows a blank of a tool according to the invention;

2 shows an inventive tool in the form of a drill in a side view.

Fig. 3 is a plan view of a drill of Fig. 2;

Fig. 4 is a section along the line III-III in Fig. 3;

Fig. 5 is an enlarged view of an area at the transition of a main cutting edge to a secondary cutting edge.

In Fig. 1, a blank of a tool 1 according to the invention is shown in a highly schematic representation. The blank of the tool 1 comprises a base body 2, which is only partially shown, and a cutting insert 3, which is arranged on the base body 2. The basic body 2, which is shown only partially, usually consists of a hard metal which has a high toughness and a high strength. The cutting insert 3, however, is formed of a ceramic, for example

Silicon nitride or other highly wear-resistant ceramic, which may optionally be reinforced with particles and / or fibers, such as whiskers. Of the

Cutting insert 3 is formed by grinding at one end with a projecting V-shaped projection 4, which may have an opening angle α of 120 ° to 160 °. One end of the V-shaped projection 4 is made flat or truncated. A corresponding region 5 is also created in the main body 2 by grinding, but with a central edge, so that when joining a distance between the truncated end of the v-shaped projection 4 and the central edge is given. Subsequently, the cutting insert 3 is connected to the base body 2 by soldering, wherein a commercial active solder is used. In principle, it is favorable if the opening angle α has a value of 130 ° to 150 °, for example 140 °, as in the exemplary embodiment. After joining the cutting insert 3 with the main body. 2 is made of the blank of the tool 1, a drill, which is shown in Fig. 2 in a side view. Both the main body 2, as well as a

subsequent holding part 2a are made of solid carbide. The cutting insert 3 is cohesively connected to the base body 2 by a solder along the projecting V-shaped projection 4. In the end region of the cutting insert 3, two main cutting edges 7 are arranged, which, as is apparent from Fig. 3, from an outer diameter or Bohrernenndurchmesser D to a center or a

Tool axis X, which is arranged along the longitudinal axis of the substantially cylindrically shaped drill run. The main cutting edges 7 extend substantially straight from an outer edge of the drill first and then pass over a radius into a residual cross cutting edge 6 arranged in the center. The residual cross-section 6 is rectilinear and preferably has a length of about 2.5% of the drill nominal diameter D, which at the same time ensures a good centering behavior when cutting at a low axial cutting pressure of the drill. Due to the curved transition of the main cutting edges 7 into the residual cross cutting edge 6 or the intended radius, possibly also a plurality of adjoining curved regions with different radii, an abrasive wear in the use of the drill can be reduced. The main cutting edges 7 may be rounded at least in the region of the rectilinear portions in order to prevent the chips from breaking away

To prevent cutting edges as much as possible. The main cutting edges 7 are arranged as shown in Fig. 2 with a tip angle ß of 140 °, although the tip angle ß may also have other values in the range of 130 ° to 150 °. To everyone

Main cutting edge 7 connect two open spaces 11, 12. The first free surface 1 1 connects to the second free surface 12 such that a common connecting edge extends through the center of the drill. The first flank 1 1 has a sloping angle of about 8 ° to 13 °, while the second flank 12 may have a larger sloping angle, for example 17 ° to 25 °. In the specific embodiment, the corresponding angles are 9 ° for the first free surface 11 and 20 ° for the second free surface 12, as shown in Fig. 4.

At the outer diameter or at the outer end of the main cutting edges 7 close to these minor cutting edges 13. At the transition from the main cutting 7 to the

Side cutting 13 occur in use, the highest cutting speeds and therefore the largest thermal loads. To the corresponding corners in front To protect premature wear and chipping, a protective chamfer 14 is provided, which has approximately an angle of 30 ° to 40 ° to the tool axis X. Following the protective chamfer 14, the secondary cutting edges 13, which are chamfered, run. The secondary cutting edges 13, as well as the four guide chamfers 8, which each define in pairs a recess 9, a spiral-shaped course, wherein a spiral angle is about 5 °. A defined by the minor cutting edges 13 surface 15 eventually goes into flutes 10 on. The deviating from 0 ° spiral angle of about 5 ° simultaneously leads to an axial rake angle with the same value at the main cutting edge 7, whereby cutting forces and also a torsional moment on the drill are significantly reduced. Incidentally, the small spiral angle, which deviates from 0 °, makes it easier to transport resulting shavings from a borehole.

As can be seen from FIG. 4, the flutes 10 are spaced from each other in cross-section at a distance A. The distance A is about 30% of

Drill nominal diameter D, which gives the drill a correspondingly strong center or high rigidity.

As can be seen in particular from FIG. 5, the cutting insert 3 is provided with a

slight recession 16 is formed or tapered an outer diameter of the cutting insert abruptly at a predetermined location before. By a

appropriate deduction of a diameter, a good clearance of the drill is achieved in use. At the same time, only the cutting insert 3 takes over

Guide the drill. With a tool 1 or drill according to the invention, sufficiently long service life or travel distances were achieved for an economical application when machining cast workpieces at cutting speeds v _c of 600 m / min and more.

Claims

claims

1. tool (1) for machining workpieces, in particular for drilling iron cast materials, comprising a base body (2) made of a first material and a cutting insert (3) made of a second material having a higher hardness than the first material , wherein the cutting insert (3) is materially attached to the base body (2), characterized in that the cutting insert (3) has a V-shaped projection (4) and the base body (2) has a corresponding area (5) and the cutting insert (3) is cohesively attached to the projection (4) on the corresponding region (5) of the base body (2).

2. Tool (1) according to claim 1, characterized in that the cutting insert (3) on the main body (2) is soldered.

3. Tool (1) according to claim 1 or 2, characterized in that the V-shaped projection (4) with an opening angle (a) of 120 ° to 160 °, preferably 130 ° to 150 °, is formed.

4. Tool (1) according to claim 3, characterized in that the V-shaped projection (4) on the cutting insert (3) is formed protruding.

5. Tool (1) according to claim 3 or 4, characterized in that the V-shaped projection (4) in the cutting insert (3) and / or the corresponding region (5) in the base body (2) are ground.

6. Tool (1) according to any one of claims 1 to 5, characterized in that the base body (2) consists of a hard metal.

7. Tool (1) according to one of claims 1 to 6, characterized in that the cutting insert (3) consists of a ceramic or a ceramic whisker composite material.

8. Tool (1) according to any one of claims 1 to 7, characterized in that the base body (2) extends only to the cutting insert (3).

9. Tool (1) according to one of claims 1 to 8, characterized in that the tool (1) as a drill, in particular twist drill, is formed.

10. Tool (1) according to claim 9, characterized in that the drill has two main cutting edges (7).

1 1. Tool (1) according to claim 9 or 10, characterized in that an end-side residual cross-section (6) with a length of 1% to 5%, in particular 2% to 3%, of a drill nominal diameter (D) is provided.

12. Tool (1) according to claim 10 or 1 1, characterized in that the main cutting edges (7) connect to the residual cross-cutting edge (6).

13. Tool (1) according to claim 12, characterized in that the

Main cutting edge (7) from the residual cross-cutting edge (6) extend to an outer diameter of the drill.

14. Tool (1) according to claim 12 or 13, characterized in that at a transition of the main cutting edges (7) to the residual cross-cutting edge (6), a radius is provided.

15. Tool (1) according to any one of claims 12 to 14, characterized in that the main cutting edges (7) are rounded, preferably at least along rectilinear portions thereof.

16. Tool (1) according to any one of claims 9 to 15, characterized in that a plurality, preferably two, flutes (10) are provided and a distance of the flutes (10) in plan view of one end of the drill at least 20%, preferably 25 % to 35% of the outside diameter of the drill.

17. Tool (1) according to any one of claims 9 to 16, characterized in that a plurality, preferably four, guide chamfers (8) are provided, which extend along an outer surface of the drill.

18. Tool (1) according to claim 17, characterized in that the

Guide chamfers (8) viewed from the main cutting edges (7) tapered in the axial direction are formed running.

19. Tool (1) according to any one of claims 9 to 18, characterized in that the drill in the region of the base body (2) has a smaller diameter than in the region of the main cutting edges (7) and the cutting insert (3).

20. Tool (1) according to claim 19, characterized in that a transition to the smaller diameter in the region of the guide chamfers (8).