EP3765223A1

EP3765223A1 - Method for producing a sinter-joined composite body

Info

Publication number: EP3765223A1
Application number: EP19712673.3A
Authority: EP
Inventors: Johannes Mayr; Jonathan SCHÄFER; Peter PÖLL; Alexander AMBOSS; Thomas SCHENNACH; Josef Friedl
Original assignee: Ceratizit Austria GmbH
Current assignee: Ceratizit Austria GmbH
Priority date: 2018-03-12
Filing date: 2019-03-08
Publication date: 2021-01-20
Also published as: AT16369U1; WO2019173855A1; CN112118927A; CN112118927B

Abstract

The invention relates to a method for producing a sinter-joined composite body (3) made of hard metal: at least two hard-metal blanks (1, 2), which differ from one another with regard to a binder content and/or a grain size of the hard-material phase, being sinter-joined to form a composite body (3); the at least two hard-metal blanks (1, 2) being arranged with respect to one another, prior to the sinter-joining process, such that at least portions of a first hard metal blank (1) of the at least two hard-metal blanks (1, 2), which has a lower binder content and/or a smaller grain size, is located inside an opening (9) or a cavity (10) of the second hard-metal blank (2) of the at least two hard-metal blanks (1, 2); the at least two hard-metal blanks (1, 2) being arranged so as to have clearance with respect to one another prior to the sinter-joining process and such that, during the sinter-joining process, a liquid phase of the binder of the at least two hard-metal blanks (1, 2) is produced and maintained until, owing to diffusion of binders, the first hard-metal blank (1) of the at least two hard-metal blanks (1, 2) increases in volume, owing to the diffusion of binders, to such an extent and the second hard-metal blank (2) of the at least two hard-metal blanks (1, 2) shrinks, owing to loss of volume because of the diffused binder, to such an extent that, after the sinter-joining process, the at least two hard-metal blanks (1, 2) are materially bonded without clearance.

Description

Process for producing a sintered composite body

The invention relates to a method for producing a sintered composite body made of hard metal with the features of the preamble of claim 1 and a sintered cutting tool blank or a sintered cutting tool of at least two carbide blanks having the features of the preamble of claim 10.

A cemented carbide in the present disclosure is understood as meaning a powder-metallurgically produced particle composite consisting of a hard material phase (eg tungsten carbide, "WC" for short) and a binder metal (eg cobalt, Co, sometimes also referred to as "binder") , The binder metal may optionally be doped, for. B. to limit the grain growth of the hard material phase.

Sintering in the present disclosure is understood as meaning a joining of at least two hard metal blanks by liquid phase sintering. Of the at least two carbide blanks, with respect to at least one hard metal blank, it may be in the form of a green compact, pre-sintered (not sintered to complete theoretical density), or, more preferably, sintered (sintered to complete theoretical density).

Carbide blanks (which are blanks with a carbide body) are used to make a variety of components or tools:

Carbide blanks for the production of cutting tools are produced on a large scale, including with internal cooling channels (IK). The positioning of these channels is done with geometrically limited freedoms. In addition, due to the production route, a single carbide grade is usually used, from which all areas of the carbide body are formed. However, the increasing demands on the tools in use and their service life require locally different material properties, such as hardness or toughness. For example, a higher wear resistance (high hardness) in the area of the later-shaped cutting edges and a high degree of toughness in the area of the later-shaped shank. Cemented carbide components sintered together in a sinter joining process are now state of the art. Here different carbide types can be combined to bring in individual areas of the body formed hard metals with different properties used and / or realized by combining several body geometric features that can not be represented with conventional manufacturing methods.

Sintering is already used on some carbide tools, cutting tool blanks or cutting tools. This is done for the sake of:

• Material efficiency

• geometric freedoms (for example when cooling the tool)

A generic method is shown in US 6,908,688 B1.

In the prior art, the surface contact of the two bodies to be joined along the entire joining surface for the entire duration of the thermal treatment is critical for a secure and mechanically highly reliable joining connection during sintering. In the generic state of the art, therefore, the surfaces of the carbide blanks in the region of the joining surface are to be prepared in such a way that play-free contact is achieved. This preparation is labor intensive and costly.

The object of the invention is to provide a generic method and a generic Zerspanungswerkzeugrohlings or Zerspanungswerkzeugs, in which the problems discussed above are avoided.

This object is achieved by a method having the features of claim 1 and a sintered cutting tool blank or a sintered cutting tool having the features of claim 10. Advantageous embodiments of the invention are defined in the dependent claims. Due to the lower binder content and / or due to the smaller grain size of the first hard metal blank relative to the second hard metal blank, binder migration takes place from the second hard metal blank to the first hard metal blank. This leads to a volume reduction of the second hard metal blank and an increase in volume of the first hard metal blank.

Because it is provided that the at least two carbide blanks are arranged with each other before Sinterfügen with play and that during sintering a liquid phase of the binder of at least two carbide blanks is produced and maintained until the first hard metal blank of the at least two carbide blanks by diffusion of binder Binder migration increases so much in volume and the second hard metal blank of the at least two carbide blanks is shrunk so much by the decrease in volume because of the diffused binder, that the at least two carbide blanks are connected material-tight with each other after sintering, the joining surfaces must not be present with a high geometric precision , Moreover, the placement of the first carbide blank in the opening or in the cavity of the second carbide blank is simplified because the first carbide blank can be introduced substantially free of force. A particular advantage of the method according to the invention is that due to the swelling of the first hard metal blank and the shrinkage of the second hard metal blank, the clearance remaining during insertion disappears anyway, and it therefore does not depend on a positionally correct introduction. Preferably, a cohesive connection is present over the entire surface of the former joining surfaces.

If the first hard metal blank of the at least two carbide blanks has a lower binder content (irrespective of the grain size), this has a smaller thermal expansion coefficient than the second hard metal blank due to the lower binder content. When heated, consequently, the first hard metal blank expands to a lesser extent than the second hard metal blank.

The coefficient of thermal expansion of conventional hard metals is in the range of 5 - 7 · 10 ⁶ K ^{· 1} . The coefficient of thermal expansion of tungsten carbide is much lower than that of cobalt (12.4 to 10 ^-6 K ¹⁾ with from 5.2 to 10 ⁶ K. ¹ The thermal expansion coefficient of the cemented carbide scales with the content of binder metal (for example cobalt) approximately according to the mixing rule,

according to which hard metals with a low content of binder metal have a smaller thermal expansion coefficient than carbide with a higher content of binder metal (cf Hartmetall for the Praktiker, Wolfgang Schedler, VDI Verlag 1988).

Due to the lower binder content and / or due to the smaller grain size of the first hard metal blank relative to the second hard metal blank, binder migration takes place from the second hard metal blank to the first hard metal blank. Where the two carbide blanks already touch each other at the beginning of sintering despite the existing play, the binder migration first sets in. The binder migration causes a swelling of the first hard metal blank and a shrinkage of the second hard metal blank. It forms preferably over the entire surface of the former joining surfaces a cohesive connection. Due to the presence of a liquid phase, the joining process is stress-free. Any defects in the joint zone (ie, where no complete wetting or bridging of the gap has occurred, for example due to a curvature of the core and / or cladding) can be closed.

In a cutting tool blank or cutting tool made by the method of the present invention, the first hard metal blank forms the first (inner) portion and the second hard metal blank forms the second (outer) portion.

Because of the lower coefficient of thermal expansion of the first cemented carbide blank having a lower binder content than the second cemented carbide blank having a higher binder content, the second cemented carbide blank has a stronger contraction tendency than the first hard metal blank. This causes in the finished cutting tool blank or cutting tool that tensile stresses remain in the outer region (shell), which exert compressive stresses on the core (the former first carbide blank) and the joining zone due to the prevailing balance of forces. As a result, a particularly stable connection is achieved. The binder migration from the second carbide blank to the first carbide blank begins where the two carbide blanks touch despite the existing game already at the beginning of Sinterfügens.

The arrangement of the at least two carbide blanks with play can be carried out such that, although there is at least one linear or planar contact zone between the at least two carbide blanks, at least in some areas a gap remains between the at least two carbide blanks. The contact in the contact zone can be present directly between the at least two hard metal blanks or indirectly by a film or a film between the at least two carbide blanks (eg to improve wetting or positioning, for example to prevent slipping of the individual components). is arranged.

The linear or area contact zone may, for. B. can be easily prepared by utilizing the weight of the at least two carbide blanks by a horizontal positioning of the at least two carbide blanks. Alternatively, an additional contact force can be applied between the at least two hard metal blanks (eg by weighting or by a clamping device).

If the gap has a gap of about 1 pm to about 200 pm, it is possible for the first and second hard metal blank to be joined to one another or to one another without the influence of force. In other words, it can be provided that the inner, first hard metal blank does not have to be pressed into the fit of the outer second hard metal blank provided for it before the sintering, but can be pushed into it with a certain play.

It is preferably provided that the at least two carbide blanks are finished sintered prior to sintering, d. H. sintered to full density.

It can be provided that the at least two carbide blanks have a different binder doping, ie additives to cobalt such as M02C, TiC, TaC, vanadium carbide. This can influence the grain growth during the production of the at least two carbide blanks before sintering become. The different grain size resulting, inter alia, from the different binder doping influences the degree of diffusion of the binder in the subsequent sintering by the different wettability (the smaller the grain size, the greater the capillary action and thus the binder migration).

In a preferred embodiment, it is provided that the first hard metal blank of the at least two hard metal blanks and the second hard metal blank of the at least two hard metal blanks are arranged along a common longitudinal axis. Thus, it is possible to produce a rotationally symmetrical composite body for a cutting tool or a Zerspanungswerkzeugrohling, which has sections of different material properties and yet a material and positive connection between the two carbide blanks.

It can be provided that the at least two carbide blanks are arranged axially in front of the sintering joining to one another so that one hard metal blank of the at least two carbide blanks is located axially in front of the other carbide blank of the at least two carbide blanks, whereby an axial gap between the two carbide blanks can arise. This arrangement can be carried out both along or parallel in the direction of the longitudinal axis or transversely to the longitudinal axis of at least one carbide blank. Thus, in addition to the radial material bond and an axial material bond can be achieved. In this way, the first hard metal blank can act, for example, as a closure or plug which is not radially but axially attached to at least partially close an opening in the second hard metal blank.

It can also be provided that an axial and a radial material bond takes place between the carbide blanks.

Optionally, it is also necessary that not only a radial gap between the first and second hard metal blank is filled in the sintering, but also an axial spacing in the form of a gap. Thus, high precision even with axial alignment of the carbide blanks to each other or in the production of their axial Joining surfaces not necessarily required, which simplifies the production of the composite body.

Alternatively, it can be provided that the first hard metal blank of the at least two hard metal blanks is located completely within the opening or the hollow space of the second hard metal blank of the at least two hard metal blanks.

It may be provided that the binder contents in the first and in the second hard metal blank move in a proportion of between 3% by weight and 20% by weight. With different binder contents between the first and the second hard metal blank thus a difference in the binder content of up to 17% by weight is achieved. The minimum difference in binder content between the two carbide blanks is 1% by weight, more preferably at least 2% by weight.

It can be provided that the outer diameter of the second hard metal blank and thus the outer diameter of the composite body or cutting tool and its sintered blank is in a range between 2 mm and 30 mm. In the interior of the sintered composite body, at least one cooling channel may be provided which has a diameter of 0.03 mm to 5 mm.

Preferably, the at least one cooling channel is wired, d. H. follows a screw curve. If tools made of concrete carbide blanks, for example drilling tools, have spiral grooves, the internal cooling channels preferably extend along the spiral grooves.

For this purpose, the internal cooling channels should have the same pitch as the spiral grooves, otherwise the cooling channels could be exposed during a grinding process.

The twist angle of an inner cooling channel is usually related to the outer diameter of the carbide blank for practical reasons.

The actual slope of the channels is a function of the radial distance of the channel to the longitudinal axis. The twist is usually introduced by applying a twist during extrusion. This production route sets certain limits with regard to the achievable external diameter distortion. It can For larger outer diameters only lower twisting can be realized than for smaller outer diameters.

The twist angle with which the at least one cooling channel extends with respect to the longitudinal axis of the first hard metal blank is z. B. between 15 ° to 60 °, based on the outer diameter of the first hard metal blank. This is possible with an outer diameter of the first carbide blank of 0.7 mm to 40 mm.

The helix angle can alternatively be described by means of that axial offset over which the at least one cooling channel completes a complete rotation. Such an indication is given, for example, as a gradient in millimeters, meaning the axial extension of a 360 ° revolution of a cooling channel.

The first hard metal blank is produced, for example, in the form of an extrusion process, wherein during extrusion, the at least one cooling channel is mitgeformt.

From the above-mentioned helix angle results in a slope of at least 2.5 mm in extruded carbide blanks for micro drills with an outer diameter of at least 0.7 mm. The diameter of the at least one cooling channel is at least 0.03 mm.

For larger extruded carbide blanks, for example, have a diameter up to 30 mm, the slope is up to 400 mm. The diameter of the cooling channels can be up to 5 mm. For larger (> 15 mm) outside diameters of carbide blanks, the diameters of the cooling channels are typically between 1.5 mm and 3 mm.

A cutting tool blank according to the invention or a cutting tool according to the invention having at least two regions of hard metal which differ from one another with regard to their mechanical properties, preferably hardness and / or bending strength and / or toughness, is characterized in that the at least two regions of hard metal at least are arranged in sections to each other so that the first region of the at least two areas of hard metal at least partially within the the second region of the at least two regions is made of cemented carbide and that between the at least two regions of cemented carbide with respect to the binder content is a transition region with a rising from the first region to the second region course, and that based on the hardness of a transition region with a in the direction of second range decreasing hardness profile is present.

A particularly preferred cutting tool blank or particularly preferred cutting tool is provided which has at least one inner, preferably wired cooling channel.

It is particularly preferred that the first region has a higher hardness than the second region. This can be achieved for example by a lower binder content and / or a smaller grain size. The inner, harder region can be in the finished cutting tool that region which has the cutting edges or a region of the cutting edges. If at least one cooling channel is provided, this should preferably also be arranged in the inner region.

The embodiment according to which the inner, harder region in the finished cutting tool is the region which has the cutting edges or a cutting region is associated with particular advantages:

If the outer region and the joining zone between the inner and the outer region are substantially completely removed, for example by grinding, then the region carrying the cutting edges or a cutting region is essentially free of the joining zone. This is in addition to the higher hardness additionally favorable for the mechanical properties of the cutting or a cutting area bearing area.

In a further preferred case, wherein the inner region in the finished cutting tool has a lower binder content than the outer region, it is additionally achieved that the outer region with higher binder content forming the shank has a high toughness and good damping properties. Furthermore, the compressive stresses introduced by the method according to the invention with different binder contents bring about a particularly secure connection of the outer and inner regions to the joining zone. In one exemplary embodiment of the invention, it may be provided that a tool bevel is formed on the sintered cutting tool such that flutes or cutting edges are formed along a longitudinal section in the first region (hard core) and along an adjacent longitudinal section in the second region (tough shell). In such an embodiment, the front (more stressed) cutting edges are also formed by the harder core; however, the laterally located cutting edges (which form a countersink area) are of the tougher shell.

Especially in the case of cutting tool blanks or cutting tools with a smaller diameter, in order to improve the spatial resolution of the gradient of the binder content and / or the hardness, it may be necessary to provide a measuring path with an enlarged length (eg spiral course) over a linear course, on the one hand to have enough space between the individual measurement points to isolate the compaction effect caused by the measurement, and to have enough measurement points to achieve the desired spatial resolution.

The binder content can be measured, for example, by chemical analysis methods such as X-ray fluorescence analysis or energy dispersive X-ray spectroscopy (EDX).

The hardness can be measured, for example, by hardness measurement according to Vickers according to ISO 3878, for example in the range HV1 to HV30.

A preferred embodiment of the invention relates to a Zerspanungswerkzeugrohling, preferably for a drill or cutter, more preferably for a cutting tool with at least one inner cooling channel, which may be straight or wired. Another preferred embodiment relates to such a cutting tool, ie a further processed blank. The invention is particularly advantageous for the production of cutting tool blanks or cutting tools used, which are provided with at least one inner wired cooling channel. Such wired cooling channels are usually manufactured by means of extrusion molding. A disadvantage of the prior art is that - due to the production by extrusion - the production of strong twisting or, in other words, a large angle of twist was difficult because the Umformvermögen an extruded material is limited. In the invention, that part of the blank (first hard metal blank) which is to have the at least one inner wired cooling channel and a smaller outer diameter than the finished blank may be separately produced. Due to the smaller diameter of the at least one cooling channel having, first carbide blank, the production of the twist or pitch of the carbide blank, Zerspanungswerkzeugrohlings or the finished cutting tool can be simplified. After the separate sintering of the sleeve-shaped part of the blank (second hard metal blank) and the rod-shaped part of the blank (first carbide blank) comprising the at least one cooling channel, both parts can be joined by the method according to the invention to form a composite body in which the first region comprises the at least one Cooling channel and radially considered at least partially located within the second region.

It can preferably be provided that the outside diameter of the first hard metal blank (in relation to the method) or of the first area (with respect to the cutting tool blank or the cutting tool) is greater than or equal to 0.4 mm to 20 mm, preferably 0.7 mm to 10 mm and / or the outer diameter of the first hard metal blank (with respect to the method) or the second portion (with respect to the cutting tool blank or the cutting tool) in a range of 2 mm to 35 mm. More preferably, the application for micro or micro drills having an outer diameter of the first carbide blank between 0.4 mm and 3 mm.

It can be particularly easy Zerspanungswerkzeugrohlinge or cutting tools with a strong twisting of at least one internal cooling channel can be made in combination with a small diameter of the area that carries the cutting geometry.

Embodiments of the invention will be discussed with reference to the figures. Show it:

1 shows the at least two carbide blanks, which are arranged radially with play to each other before sintering,

2, the at least two carbide blanks, after sintering,

Fig. 3a, b, a first embodiment of a sintered according to the invention

Composite,

Fig. 4a, b, a second embodiment of a sintered according to the invention

Composite,

5a, b, a third embodiment of a sintered according to the invention

Composite,

Fig. 6a, b, a fourth embodiment of a sintered according to the invention

Composite,

Fig. 7a, b, a fifth embodiment of a sintered according to the invention

Composite,

8 is a schematic representation of the diffusion process,

Fig. 9 is a schematic representation of the method according to the invention, Fig. 10 resulting from the method of the preceding figure

Composite body

Fig. 11 a is a schematic representation of an embodiment of a

Composite body with schematically arranged measuring points,

11b measured values and measuring points for a composite body according to the invention, FIG. 12a a further schematic representation of an embodiment of a

Composite body with schematically arranged measuring points,

12b measured values for a composite body according to the invention,

13a, b helix angle of at least one cooling channel,

Fig. 14a-c steps in the manufacture of an inventive

Cutting tool and

Fig. 15a, b steps in the preparation of another invention

Cutting tool. 1 relates to an inventive method for producing a composite body 3 made of hard metal, using at least two carbide blanks 1, 2, which differ from each other in relation to a binder content and / or a grain size of the hard material phase.

The at least two carbide blanks 1, 2 are arranged radially to each other before Sinterfügen so that a first hard metal blank 1 of at least two carbide blanks 1, 2, which has a lower binder content and / or a smaller grain size, viewed radially at least in sections within an opening. 9 or a cavity 10 of the second hard metal blank 2 of the at least two carbide blanks 1, 2 is located. It can be seen in Fig. 1 that the at least two carbide blanks 1, 2 were arranged with radial play to each other in such a way that between the at least two carbide blanks 1, 2 Although at least one linear or planar contact zone, but at least partially a gap. 6 between the at least two carbide blanks 1, 2 remains.

In sintering a liquid phase of the binder of at least two carbide blanks 1, 2 is prepared and maintained until by diffusion of binder of the first hard metal blank 1 of at least two carbide blanks 1, 2 swelled so far and the second hard metal blank 2 of the at least two carbide blanks 1, 2 has shrunk so far that the at least two hard metal blanks 1, 2 are connected to one another in a material-tight manner after sintering joining (see FIG. 2).

3a to 7a show in each case exemplary embodiments of composite bodies 3 according to the invention in the form of blanks for a cutting tool 7 (see Fig. 10) in a sectional view through a plane which contains a longitudinal axis LA of the composite body 3. FIGS. 3b to 7b show associated perspective views, wherein for the sake of better recognition, a dashed representation of hidden and thus invisible lines has been dispensed with.

The first embodiment of Fig. 3a, b shows a composite body 3, in which the first hard metal blank 1 of the at least two carbide blanks 1, 2 completely within the opening 9 or the cavity 10 of the second hard metal blank 2 of the at least two carbide blanks 1, 2 is located.

The second to fifth exemplary embodiments of FIGS. 4 a, b to 7 a, b each show a composite body 3, in which the at least two hard metal blanks 1, 2 are arranged axially to each other along the longitudinal axis LA prior to sintering, so that the one carbide blank 1, 2 of the at least two carbide blanks 1, 2 seen axially in sections before the other carbide blank 1, 2 of the at least two carbide blanks 1, 2 is located.

In the second exemplary embodiment of FIGS. 4a, b, a straight cooling channel 8 running along the longitudinal axis LA is provided for a cooling liquid. The first hard metal blank 1 projects in sections out of the second hard metal blank 2. Unlike shown, the first hard metal blank 1 can also be flush with the second hard metal blank 2 (FIG. 3 a) or can also be arranged sunk in it.

In the third embodiment of FIGS. 5a, b, two helical cooling channels 8 extending along the longitudinal axis LA are provided for a cooling liquid. In FIGS. 5a, b, the first hard metal blank 1 projects in sections from the second hard metal blank 2. However, it can also be provided that the first hard metal blank 1 is flush with the second hard metal blank 2.

In the fourth embodiment of Fig. 6a, b is a along the longitudinal axis LA extending, straight cooling channel 8 is provided for a cooling liquid, branch off from which transverse to the longitudinal axis LA two cooling channels 8 and open into outlet openings 1 1 for the cooling liquid. Other than shown, z. B. also the first carbide blank 1 do not extend along the longitudinal axis LA of the second hard metal blank 2, but in an area parallel thereto or at an angle obliquely thereto. Thus, the first hard metal blank 1 could for example also be arranged in at least one of the laterally arranged on the composite body 3 outlet openings 1 1 and thus, for example, act only as a stopper or as an outlet nozzle, throttle or the like. In the fifth exemplary embodiment of FIGS. 7a, b, a step 12 is provided in the second hard metal blank 2 (before sintering joining) or in the second region 4 (after sintering joining) which forms an axial stop for the first hard metal blank 1 (before sintering joining) represents the first area 5 (after sintering). Of course, such a stop could also be provided in the other embodiments.

FIG. 8 is intended to schematically illustrate the diffusion process, which results in binder particles 13 diffusing from a region of higher binder concentration / higher binder content in the first hard metal blank 1 into a region of lower binder concentration in the second hard metal blank 2. This balancing of the binder content (Co content) also results in a volume and / or mass flow during diffusion.

The individual steps of a method according to the invention are shown in FIG. 9:

First, in step 14, the two carbide blanks 1, 2 are prepared, for. B. by a pressing and subsequent sintering process. Subsequently, for reasons of higher precision, optionally in step 15, a grinding process is carried out on one or both carbide blanks 1, 2. It may also be provided that at least one of the two carbide blanks 1, 2 is produced by an eroding process, the precision required for sintering joining is generated directly by the eroding method with respect to the geometry and / or the joint surface. A post-processing step such as grinding or honing can be omitted or only partially done. The two carbide blanks are arranged or aligned with each other in step 16 with radial play and sintered together in this arrangement in step 17. The resulting composite body 3 can be further processed in step 18, for. B. to a Zerspanungswerkzeugrohling or cutting tool 7 (see Fig .. 10), in which a shaft through the second hard metal blank 2 and 1 1 cutting through the first hard metal blank 1 are formed. For sintering, temperatures of, for example, 1 100 ° C to 1600 ° C are used. The sintering in step 17 can take place under pressure, with pressures between 0 bar and 1000 bar are conceivable. The particle sizes of the binder are included between about 0.4 mhh - about 5 pm, the weight-based binder content is between 3% by weight and 20% by weight.

Fig. 1 a shows the two carbide blanks 1, 2 with different binder content. The binder content of the first hard metal blank 1 is about 6% by weight, the binder content of the second hard metal blank 2 is about 10% by weight. Individual measurement points MP represent, for example and schematically, the binder content, the hardness or the toughness of the carbide blanks 1, 2, which is explained in greater detail in FIG.

FIG. 11b shows in a diagram the different measured values of the measuring points MP from FIG. 11a along the abscissa (x-axis). The numbers on the x-axis do not directly indicate a radial distance, but the number of the measuring point. In addition, on the left side of the table along the ordinate (y-axis), the hardness in Vickers (HV) is given in a range between 1560 and 1720. By comparison, the fracture toughness of the material (Ki _c ) is shown on the right along the ordinate (y-axis). The value extends in a range from 9.5 to 11, 0 [MPa ^* m ⁰ ' ⁵ ].

On the right, the first (inner) area 5 with the binder content of 6% by weight can be seen; on the left, the second (outer) area 4 with the binder content of 10% by weight can be seen. The particle size of the binder, in this embodiment tungsten carbide, is less than 1 pm.

The measuring points represented in the form of triangles show the hardness in Vickers (HV), the measuring points shown in the form of circles show the fracture toughness (Ki _c ). It can thus be seen from the diagram and the measurement that differences in hardness and fracture toughness result between the first region 5 and the second region 4, which is due to the different binder content.

FIG. 12a also schematically shows another embodiment with a different binder content in the first region 5. In this case, this is 7.5% by weight. Thus, different hardness and toughness values are achieved, which can be inferred from the diagram of FIG. 12b in comparison to the diagram of FIG. 11b. The first hard metal blank 1 is produced, for example, in the form of an extrusion process, wherein the at least one cooling channel 8 is co-formed during the extrusion.

FIG. 13a shows a first hard metal blank 1, on which the helix angle a is registered. The helix angle a is determined by the slope of the twisting with respect to the longitudinal axis LA at the outer diameter d _{r of} the first hard metal blank 1. The helix angle a is between 15 ° to 60 °. In the present illustration, ribs on the outer circumference of the first hard metal blank 1 can be seen, which result from extrusion, wherein the outer diameter d _{r of} the first hard metal blank 1 is determined at the area between the ribs. The diameter of a cooling channel 8 is indicated by d _k .

FIG. 13 b shows the gradient S, which results from the twist of the at least one cooling channel 8. The slope S thus results from the axial offset of the at least one wired cooling channel 8 along the longitudinal axis LA per completed rotation through 360 ° about the longitudinal axis LA. This results in dependence on the helix angle a, a slope S of at least 2.5 mm in extruded carbide blanks 1 for microdrill with an outer diameter d _r of at least 0.7 mm. The diameter d _{k of} the at least one cooling channel 8 is at least 0.03 mm.

For larger extruded first carbide blanks 1, which for example have a diameter up to about 30 mm, the slope S is up to 353 mm. The diameter d _{k of} the cooling channels is between 2 mm to 5 mm.

14a shows a cutting tool blank produced by the method according to the invention with an inner, first and an outer, second region 5, 4, wherein the first region 5 has a greater hardness (and a lower binder content, and thus a smaller thermal expansion coefficient) than that second area 4.

FIGS. 14b and 14c show the result of a processing step in which, for example by grinding, in the region of an axial end of the Cutting tool blanks according to Fig. 14a, the outer region 4 and the joining zone between the inner and the outer region 5, 4 were substantially completely removed so that the area carrying the cutting or a cutting portion 19 is substantially free of the joining zone. The cutting area 19 is arranged exclusively on the inner area 5 in this embodiment of a cutting tool 7. The tougher shell (outer region 4) with more favorable damping properties forms the shaft section.

The embodiment shown in FIGS. 15a and 15b differs from that of FIGS. 14a-c only insofar as at least one cutting edge extends here on the conical part on the jacket (outer region 4), which can thus serve as countersink.

LIST OF REFERENCE NUMBERS

1 first carbide blank

2 second carbide blank

3 composite body

4 first area

5 second area

6 gap

7 cutting tool blank or cutting tool

8 cooling channel

9 opening

10 cavity

11 outlet opening

12 level

13 binder particles

14 step of a method according to the invention

15 step of a method according to the invention

16 step of a method according to the invention

17 step of a method according to the invention

18 step of a method according to the invention

19 cutting area

LA longitudinal axis

a twist angle

S slope

d _r diameter blank

d _k diameter cooling channel

Claims

claims

1 . Method for producing a sintered composite body (3) made of hard metal, wherein:

- At least two carbide blanks (1, 2), which differ from each other in relation to a binder content and / or a grain size of the hard material phase, are sintered into a composite body (3)

- The at least two carbide blanks (1, 2) are arranged before the sintering joining to each other so that a first hard metal blank (1) of at least two carbide blanks (1, 2), which has a lower binder content and / or a smaller grain size, at least in sections within an opening (9) or a cavity (10) of the second hard metal blank (2) of the at least two hard metal blanks (1, 2),

characterized in that

- The at least two carbide blanks (1, 2) are arranged before the sintering joining with play each other and that

- During sintering a liquid phase of the binder of at least two carbide blanks (1, 2) is produced and maintained until by diffusion of binder of the first hard metal blank (1) of the at least two carbide blanks (1, 2) by the diffusion of binder so increases far in volume and the second hard metal blank (2) of the at least two carbide blanks (1, 2) has shrunk by volume decrease because of the diffused binder so that the at least two carbide blanks (1, 2) are connected without backlash material-locking after sintering.

2. The method of claim 1, wherein the first hard metal blank (1) of the at least two carbide blanks (1, 2) inside the opening (9) or the cavity (10) of the second hard metal blank (2) of the at least two carbide blanks (1, 2 ) is used, that between the at least two carbide blanks (1, 2) Although at least one linear or planar contact zone, but at least partially a gap (6) between the at least two carbide blanks (1, 2) remains.

3. The method according to the preceding claim, wherein the gap (6) has a gap of about 1 pm to about 200 pm.

4. The method according to at least one of the preceding claims, wherein the at least two carbide blanks (1, 2) are finished sintered prior to sintering.

5. The method according to claim 1, wherein the percentage, weight-based binder content in at least one of the two carbide blanks (1, 2) is selected between 3% by weight and 20% by weight, wherein a maximum difference in binder content between the first carbide blank (1 ) and the second hard metal blank (2) of 17% by weight and a minimum difference in binder content of 1% by weight, wherein a difference in binder content between the first and second hard metal blanks (1, 2) is at least 2% by weight and at most 17 Gew% is particularly preferred.

6. The method according to at least one of the preceding claims, wherein the at least two carbide blanks (1, 2) have a different binder doping.

7. The method according to at least one of the preceding claims, wherein the first hard metal blank (1) of the at least two carbide blanks (1, 2) and the second hard metal blank (2) of the at least two carbide blanks (1, 2) arranged along a common longitudinal axis (LA) become.

8. The method according to at least one of the preceding claims, wherein the first hard metal blank (1) of the at least two carbide blanks (1, 2) completely within the opening (9) or the cavity (10) of the second hard metal blank (2) of the at least two carbide blanks (1, 2).

9. The method according to at least one of the preceding claims, wherein prior to sintering the at least two carbide blanks (1, 2), the joining surface of one or a plurality of the at least two carbide blanks (1, 2) is machined by honing or grinding.

10. Sintered cutting tool blank or sintered

Cutting tool (7), in particular produced by a method according to at least one of the preceding claims, comprising at least two sections (4, 5) of cemented carbide differing in their mechanical properties, preferably hardness and / or bending strength and / or toughness differ, characterized in that the at least two areas (4, 5) made of hard metal at least partially arranged to each other so that the first area (5) of the at least two areas (4, 5) of carbide at least partially within the second area ( 4) of the at least two areas (4, 5) is made of hard metal and that between the at least two areas (4, 5) made of hard metal with respect to the binder content

Transition region is present with a rising from the first region (5) to the second region (4) course, and that based on the hardness, there is a transition region with a decreasing in the direction of the second region (4) hardness profile.

11. A cutting tool blank or cutting tool according to the preceding claim, wherein the first region (5) has a greater hardness than the second region (4).

12. Zerspanungswerkzeugrohling or cutting tool according to at least one of the preceding claims, wherein at least one inner, preferably twisted, cooling channel (8) is provided.

13. The cutting tool blank or cutting tool according to at least one of the preceding claims, wherein the pitch in the form of the axial offset along the longitudinal axis (LA) of the at least one wired cooling channel (8) at least 2 mm to a maximum of 250 mm per completed rotation through 360 ° about the longitudinal axis (LA) is.

14. Zerspanungswerkzeugrohling or cutting tool according to at least one of the preceding claims, characterized in that the

Outer diameter of the first region (5) is greater than or equal to 0.4 mm to 20 mm, preferably 0.7 mm to 10 mm and / or the outer diameter of the second region (4) in a range of 2 mm to 35 mm.

15. Cutting tool blank or cutting tool according to at least one of the preceding claims, characterized in that the factor between the inner diameter of the second region (4) and the outer diameter of the second region (4) is at most ten times.

16. Zerspanungswerkzeugrohling or cutting tool according to at least one of the preceding claims, characterized in that the

Outer diameter of the Zerspanungswerkzeugrohlings or cutting tool (7) is not more than 40 mm and the helix angle (a) of the at least one cooling channel (8) is between 15 ° to 60 °.