EP2406037A1

EP2406037A1 - Method for fine processing of boreholes, processing tool and processing machine for same and work piece

Info

Publication number: EP2406037A1
Application number: EP10708506A
Authority: EP
Inventors: Josef Schmid
Original assignee: Elgan Diamantwerkzeuge GmbH and Co KG
Current assignee: Elgan Diamantwerkzeuge GmbH and Co KG
Priority date: 2009-03-11
Filing date: 2010-03-11
Publication date: 2012-01-18
Also published as: DE102009013625A1; WO2010102805A1

Abstract

In a method for fine processing of an internal surface of a borehole in a work piece, which is composed at least in the region of the borehole substantially of a light metal material, a processing tool performs during at least one processing operation a working motion within the borehole to be processed. The method comprises a friction strengthening operation, wherein a processing tool is used which has at least one friction element, which has at least one contact surface provisioned for friction contact with the internal surface. The friction element is moved over the internal surface at a relative speed with respect to the internal surface and at a friction-inducing pressure so that under the influence of dynamic friction and pressure in the region of the internal surface, a friction strengthened layer is produced which is induced essentially by friction and pressure. The method can be used in particular for processing cylinder running surfaces in the production of light-metal engine blocks.

Description

description

Process for fine machining bores. Machining tool and machining machine for this and workpiece

BACKGROUND OF THE INVENTION

Field of the invention

The invention relates to a method for fine machining an inner surface of a bore in a workpiece, which consists essentially of a light metal material at least in the region of the bore, in particular for machining a cylinder surface in the manufacture of engine blocks for internal combustion engines, a processing tool that can be used to carry out the method for the implementation of the method suitable processing machine as well as a producible by the process workpiece.

Description of the Related Art

The cylinder surfaces in engine blocks of internal combustion engines are subjected to strong tribological stress during operation of the internal combustion engine. Therefore, it is important in the manufacture of engine blocks to process these and other tribologically stressable surfaces, such as sliding bearings in connecting rod bores, so that later under all operating conditions sufficient lubrication is ensured by an oil film and that the frictional resistance of relatively moving parts and the wear during operation are kept as low as possible.

The finishing of tribologically stressable internal bore surfaces in engine construction is generally carried out with a suitable refining A method of operation in which, during at least one machining operation, a machining tool executes a working movement within the bore to be machined, and at least one machining element attached to the machining tool mechanically acts on the inner surface. As processing elements of a honing tool honing stones or honing stones, for example, are provided which enable a machining with geometrically indefinite cutting edge. When honing is created by a simultaneous rotational movement and lifting movement of the honing tool a typical for this process cross-cutting pattern on the inner surface to be machined, which is important for the carrying and lubricating properties of the machined workpiece. In addition, the macro shape of the bore is approximated to the desired desired shape by honing usually.

With regard to the reduction of fuel consumption and to the increase of the performance weight of motor vehicles many possibilities of mass reduction on all components have been pursued for years. Since the engines have a relatively high proportion of the total vehicle weight, motors offer a particularly high potential for saving weight-reducing measures. The use of light metal materials in components for vehicle propulsion is of particular importance. Thus, for example, monolithic engine blocks for high-performance gasoline engines have been produced for years from a hypereutectic aluminum-silicon casting alloy, ie from its aluminum alloy with a silicon content of more than 12.5% by weight, for example from the Al-Si alloy AISiI 7Cu4Mg , which is offered under the brand name ALUSIL ^® . Overutilized aluminum-silicon casting alloys form hard primary silicon precipitates upon solidification, which are exposed during machining of the cylinder liners, resetting the softer metallic matrix so that the piston rings can slide on the primary silicon crystals. Cylinder surfaces manufactured in this way have a high wear resistance and provide sufficient holding volume for oil. Finishing methods for machining such cylinder surfaces in the manufacture of engine blocks and crankcases are given, for example, in EP 0 818 271 B1 and the documents cited therein.

Hypereutectic Al-Si alloys are also used to make cylinder liners which are inserted into a crankcase made of another light metal material and then finish machined. The patent application DE 10 2006 005 193 A1 describes crankcase of a hypoeutectic aluminum alloy with an inserted cylinder liner of a hypereutectic aluminum alloy. In such a heterogeneous design, the crankcase material does not have to have the required properties for a cylinder tread material but can be selected for its suitability as a crankcase material. When using a hypoeutectic aluminum alloy for the crankcase, the mechanical strength increases and the casting process is simplified compared to over-eutectic alloys. However, sub-eutectic Al-Si alloys, i.a. because of an increased tendency to seize, considered not suitable for the formation of cylinder surfaces.

As an alternative to the installation of separate cylinder liners in a cast crankcase and the production of crankcases from a hypoeutectic Al-Si alloy in combination with a coating of the cylinder bore is known. Such designs are sometimes referred to as quasi-monolithic forms. In known quasi-monolithic crankcases, a nickel dispersion layer is galvanically applied to the cylinder bore. The nickel dispersion layer contains nickel-bonded silicon carbide particles which are embedded uniformly distributed. Such coated cylinder liners have good running properties and low wear and tear can be combined with pistons and piston rings made of commercially available materials. However, the manufacturing process is relatively expensive due to the coating and problematic from an environmental point of view.

Magnesium alloys are also used as lightweight materials in engine construction, e.g. in combination with aluminum alloys for the production of magnesium-aluminum composite crankcases (see EP 1 433 552 A1).

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method, which can be used in particular for the machining of cylinder running surfaces for light metal engine blocks, for machining an inner surface of a bore in a workpiece, with which tribologically optimized inner surfaces can be produced. In particular, an improved wear resistance of the machined inner surfaces is to be achieved in the intended use.

This object is achieved by a method having the features of claim 1, and by a machining tool having the features of claim 19 or a machining machine having the features of claim 27.

Advantageous developments are specified in the dependent claims. The wording of all claims is incorporated herein by reference.

In the method, the inner surface of a bore is finished in a workpiece, wherein the workpiece, at least in the region of the bore adjacent to the inner surface, essentially consists of a There is a light metal material. The method includes a friction consolidation operation. To carry out the friction hardening operation, a machining tool having at least one friction element is used which has a contact surface or effective surface provided for rubbing contact with the inner surface. The friction element is moved over the inner surface at a relative speed with respect to the inner surface and under a friction-promoting pressure in such a way that under the influence of sliding friction and pressure in the area of the inner surface a friction-strengthening layer essentially induced by sliding friction and pressure is produced.

In the Reibverfestigungsoperation a more or less thick near-surface layer is generated in the near-surface zone of influence due to structural transformation or structural change of the light metal material, which has greater strength and possibly greater hardness than the underlying bulk material and thus the desired inner surface, compared to unprocessed surfaces gives improved tribological properties. It is thus produced a surface material with improved tribological properties. The layer produced is also referred to in this application as a "friction hardening layer".

A peculiarity of the Reibverfestigungsschicht produced is that they - in contrast to subsequently applied coatings (coatings) - chemically, ie in terms of their composition, may be substantially identical to the underlying bulk material. The layer structure can be transformed into the structure of the bulk material in a more or less sharply defined transition zone. The bond between the light metal material in the layer and the underlying light metal material is usually not weaker than the internal binding forces in the bulk material, as the Layer is produced from the light-metal material of the workpiece by structural transformation.

Typical sheath thicknesses of the surface layer produced in the rubbing consolidation operation may be in the range of one or more micrometers, or even greater, for example in the range of one to several tens of millimeters. Optionally, layer thicknesses in the order of up to one millimeter or more are possible.

In the Reibverfestigungsoperation preferably takes place virtually no material removal on the inner surface. Rather, the near-surface layer is preferably produced by non-cutting sliding of the at least one friction element on the surface. As a result, an influence zone is heated and / or deformed in the region near the surface in such a way that a microstructure transformation occurs in a near-surface layer of the light metal material, which gives the surfaces processed by the rubbing consolidation operation an improved hardness and strength compared to the unprocessed surface. The rubbing consolidation operation can result in surface hardening and solidification of a near-surface layer without significantly changing the dimension of the bore (particularly diameter and shape).

In the friction strengthening operation, different working mechanisms can be initiated in the near-surface region of the light metal material.

In some embodiments, the processing parameters of the friction consolidation operation are adjusted to induce strain hardening of the light metal material in a layer adjacent the inner surface of the bore. The term "strain hardening" Here, an increase in strength of the light metal material, which occurs in a plastic deformation of the light metal material in the largely cold state. The temperatures present in the vicinity of the inner surface of the lightweight material are typically far below the material-specific melting temperature T _s . The temperatures may, for example, be in the range of less than 150 ^° C. or less than 100 ^° C.

The polycrystalline light metal material has within its crystallites (grains) sliding possibilities as well as construction errors, which cause dislocations within the crystal structure. The shear stresses which occur due to the external action of force on the crystal lattice can lead to the sliding of entire crystal areas onto slip planes and to the movement of dislocations. The dislocations can migrate to the grain boundaries of the crystals, accumulating and multiplying there, and depending on their arrangement and density, can block further deformations of the crystal material. This effect then leads to the desired increase in strength, whereby normally at the same time the ductility (ductility) decreases. If cold compaction is to be induced by the friction hardening operation, the forces and movements necessary for inducing these processes must thus be applied with the aid of the friction element.

Preferably, the work hardening working tool is rotationally rotated during the rubbing operation so that the rotation direction of the work tool is changed several times during the period of the rubbing operation, so that the work tool is reciprocated in the bore. A working movement involving such an oscillating left-right rotation leads particularly quickly to a strong surface hardening. It can be superimposed on a possibly oscillating stroke movement, but what is often not necessary. A mechanical friction mediated by sliding friction appears favorable.

In other variants of the Reibverfestigungsoperatäon the machining parameters are adjusted so that a considerable amount of frictional heat is generated and under the action of frictional heat in the region of the inner surface is generated substantially by sliding friction heat induced surface hardening. In this case, therefore, a substantially thermally induced microstructure transformation is produced, which can also lead to a near-surface layer whose strength is significantly greater than the strength of the underlying, not thermally converted or influenced volume material.

As a rule, one of the processes mentioned in the friction consolidation operation (work hardening or thermally induced microstructure transformation) is dominant, which can be adjusted by suitable machining parameters (for example speed profile of the working movement, contact pressure, friction element selection).

In order to achieve a predominantly thermally induced structural change, in the friction hardening operation in the near-surface heat-affected zone temperatures T can be generated which are significantly higher than the temperatures occurring during operation of the workpiece. For example, the temperature may reach at least 50% of the material specific melting temperature Ts of the light metal material, ie T> 0.5 Ts, in phases (typically one or more seconds). Frequently, T> 0.6 Ts or T> 0.8 Ts or T> 0 , 9 Ts Preferably, at least temporarily generates temperatures of more than 300 ⁰ C or more than 500 ⁰ C or more than 600 ° C or more than 700 ° C in the Reibverfestigungsoperation in the region near the machined inner surface. With such strong friction-induced heating of near-surface regions of the light metal material, changes in the light metal material can occur in this area in the manner of solution annealing, which increase the strength of the layer close to the surface. In a subsequent cooling, which may optionally be supported by active cooling, residual compressive stresses in the near-surface layer may increase, whereby the mechanical strength increases.

In a further development of the method with thermally induced structural transformation, the light metal material is at least partially melted during the friction consolidation operation in the region of the inner surface under the influence of the generated frictional heat and subsequently solidifies. The Reibverfestigungsoperation is performed for this purpose that the light metal material is heated by the frictional heat over a certain period of time to temperatures above the material-specific melting temperature T _s . The temporal temperature profile, ie the temperature-time profile during Reibverfestigungsoperation, can be controlled, for example so that increase by the melting following solidification compressive stresses in the Oberflächennahtschicht and thereby increases the mechanical strength, eg the fatigue strength of the bore. In addition, a hardening can be produced, resulting in an increased wear resistance of the machined inner surface.

The extent of the heating can be influenced by influencing the process parameters, in particular by selecting suitable friction elements, the setting of the movement speed or the speed profile for the movement of the friction elements and the duration of the engagement time. For example, it may range from eutectic aluminum-silicon alloy (eutectic temperature at approx. 577 ° C) for superficial melting when If the near-surface temperature is increased to 580 ° to 600 ° C. or above, significantly higher near-surface temperatures or longer intervention times may be required for the melting of larger volumes of supereutectic aluminum alloys, for example about 850 ° or above for complete melting of hypereutectic Al-Si. Alloys with approx. 30 wt.% Silicon. For the partial melting of hypoeutectic aluminum alloys in turn lower temperatures, which may be just above the eutectic temperature, for example in the range between 600 ⁰ C and 650 ⁰ C. Pure aluminum (melting point at about 660 ⁰ C) can be processed with appropriate process guidance and thereby melted superficially. In the processing of light metal materials based on magnesium, in particular in magnesium-aluminum alloys, usually lower temperatures, for example, about 460 ⁰ C for a eutectic magnesium-aluminum alloy with about 33 wt.% Aluminum range.

A particularly great increase in the strength and wear resistance can result in some developments of the method in that the inner surface is actively quenched by an at least partial melting of the light metal material in the region of the inner surface by supplying a liquid or gaseous cooling fluid. As a result, a particularly rapid solidification can be achieved, whereby possibly the resulting compressive compressive stresses during solidification are even higher than in process variants without the active deterrent. In addition, finer solidification structures with different strength properties can result.

Suitable cooling fluids may be suitable liquids, for example water, water-based solutions, oils, for example hardening oils, or emulsions, which may optionally be sprayed, sprayed or rinsed under suitable pressure. In some embodiments, prior to and / or during the friction consolidation operation, solid particles and / or solid fibers are introduced into the bore and incorporated into the light metal material by the surface bonding operation in a near-surface layer on the inner surface of the bore. The introduction can be made directly into the bore and / or via the equipped with corresponding feed channels machining tool. The solid material introduced may be, for example, powders and / or fibers of ceramic material such as silicon, glass, mullite, zirconium oxide, magnesium oxide and / or sufficiently hard metallic materials, for example tungsten, molybdenum or the like, or mixtures of these materials. When selecting the material, it should be noted that the materials should not wear too much on the friction elements and do not release any gases, eg H ₂ O or the like, during installation.

The added solids may optionally be superficially pressed into the unfused light metal material by means of the friction elements. A particularly firm installation in the light metal matrix results when the Leichmetallwerkstoff is melted superficially during the Reibverfestigungsoperation so that the added solids in the near-surface melt layer can be well distributed and tightly integrated. Due to the incorporated solids, a particle reinforcement occurs at the near-surface layer, which on the one hand increases the strength of the material in the region of the inner surface and also improves the wear resistance.

The solid state material may be added throughout the rubbing operation. It is also possible that the material addition takes place only during certain periods of Reibverfestig ungsprozesses, eg at the beginning or at the end of the Reibverfestigungsoperation. Although it is possible to add an optional friction enhancing liquid processing aid in the friction consolidation operation, in preferred variants the friction bonding operation is performed dry. Normally, it is desired that the inner surface to be machined is already substantially dry, ie free of liquids, at the beginning of the rubbing operation. By thus possible dry sliding friction between the friction element and the workpiece surface, a particularly rapid heating or a particularly effective work hardening of the near-surface layer is possible.

In some variants of the method it is provided that, before the friction consolidation operation, a material-removing preparation of the bore is carried out using a liquid processing aid. In these cases, it may be provided that the inner surface is actively dried before the start of the rubbing operation or in the initial stage of the rubbing-solidifying operation in a liquid residue removing drying step. For the drying step, for example, compressed air or another compressed gas can be inflated onto the inner surface by means of a fluid channel system integrated into the tool with outlet nozzles directed towards the inner surface.

The working movement of the machining tool during the Reibverfestigungsoperation usually includes a rotation of the machining tool within the bore, this rotation, as in honing, an axial reciprocating stroke movement may be superimposed. An exclusively axially oscillating working movement or a movement with reversal of the direction of rotation, if necessary without axial movement, is likewise possible. Furthermore, it is possible that the machining tool is excited so that the tool is periodically expanded and contracted. For fast oscillating working For example, the tool can be excited by means of ultrasound.

In order to achieve a particularly rapid heating and friction-induced temperatures of several hundred degrees Celsius, the machining tool in preferred process variants during the Reibverfestigungsoperation is at least phased rotated at a speed of more than 1000 min ^'1 , the speed preferably at least in phases at more than 5000 min ^'1 and can be, for example, in the range of 8000 to 10,000 min ^-1 or above, especially at such high rotational speeds, the working movement may be a pure rotational movement without superimposed lifting movement.

If in a pure rotary friction elements are used, which are significantly shorter than the bore lengths, axially narrow zones can be generated with Reibverfestig ungsschicht whose axial extent is short compared to the bore length, for example, less than 50% or less than 30% or less than 20% of the bore length. For example, in the region of the upper reversal point and / or in the region of the lower reversal point of a piston movement, intensification zones can be introduced on a cylinder surface. When the friction elements are about as long as the bore length or longer, a friction hardening layer may be created that extends substantially the entire length of the bore.

In general, the friction consolidation operation may be performed so that the entire usable length of the bore is machined by friction bonding. For this purpose, machining tools can be used, the friction elements are about the same length as the bore or longer than the bore. Processing can be done without a stroke or only with zem stroke, wherein the stroke length in a short stroke is much shorter than the axial bore length, for example, less than 50% or less than 30% or less than 10% of the axial longitudinal bore.

If only part of the bore inner surface is to be machined, shorter machining times and less drive power are generally required; in the case of process variants with material addition, less additional material is required. This results in both technical and economic advantages.

It is also possible that machining tools are used in which the friction elements are much shorter than the bore. When operated with a suitable axial stroke, frictional consolidation can be achieved substantially over the entire bore length. However, the use of machining tools with friction elements that are significantly shorter than the bore length may also be used to modify the surface by friction bonding only in selected axial portions of the bore. For example, on cylinder surfaces in internal combustion engines, the local solidification can be introduced only at locations with particularly high load, for example in the form of a strip near or at the upper Umsteuerpunkt the piston movement and / or in the vicinity or at the lower Umsteuerpunkt the piston movement. The axial extent of such circumferentially extending strips may be less than half the bore length, e.g. 40% or less or 30% or less or 20% or less of the axial bore length.

In this way, on the machined workpiece at least two adjacent in the axial direction of the bore bore sections can be produced with different surface properties, wherein At least one of the bore portions is provided a Reibverfestigungsschicht generated by friction hardening. Another bore portion may remain recessed in the friction consolidation operation and thus be free of a friction hardening layer.

The rubbing operation may be the last processing operation of a single-stage or multi-stage finishing process. The rubbing consolidation operation may be performed immediately after pre-processing, e.g. is designed, on the inner surface, e.g. by means of honing or laser structuring or by means of a combination of these methods to produce a functional surface structure. This structure is then possibly slightly modified by the Reibverfestigungsoperation.

In some variants of the method, a material-removing post-processing operation is performed after the friction-strengthening operation. The post-processing operation may be for shaping the bore and / or creating a functional surface structure. For example, a post-processing of the provided with the Reibverfestigungsschicht inner surface by honing, laser exposure or laser structuring or by a combination of these methods is possible.

The invention further relates to a suitable and suitable for performing the method processing tool for machining an inner surface of a bore in a workpiece, in particular for machining a cylinder surface in the production of engine blocks for internal combustion engines. The machining tool has at least one friction element which has at least one non-abrasive contact surface provided for frictional contact with the inner surface. A friction element is significantly smoother in the region of the preferably non-compliant (rigid) contact surface than an abrasive machining element, such as a honing stone. The friction element can, for example in the area of the contact surface a Oberflächεnrauheit R μrn of less than 20 or less than 10 microns and an average surface roughness or _Ra of less than 1 micron, or less than 0.1 microns _z. The contact surface can be smoothed by polishing.

If the friction element, at least in the area of the contact surface provided for the contact with the inner surface, consists of a material which is non-adhesive relative to the light metal material, a particularly trouble-free heating or effective work hardening of the workpiece is possible without appreciable removal of material. A friction element, for example a friction strip or friction shell, can consist of a ceramic material, such as silicon nitride, cubic boron nitride, boron carbide, silicon carbide, aluminum oxide, zirconium oxide or the like, at least in the region of the contact surface. In particular silicon nitride (SiaN-O has proved to be very favorable for the processing of light metal based materials, because it is largely inert to this group of materials and is not or hardly wetted by aluminum-containing melts Molybdenum or Inconel can be used for the friction elements or the area of the contact surface coming into contact with the light metal material, and friction elements consisting essentially of cobalt or a cobalt alloy are also possible, and this material has proven to be less adhesive to aluminum materials At temperatures below the graphitization temperature of diamond, it is also possible to use diamond-like materials such as PCD (polycrystalline diamond) or MKD (monocrystalline diamond material), which are particularly wear-resistant really smooth DLC (Diamond Like Carbon) Layer on a ceramic or metallic support member, for example, are usable. Above the graphitization temperature of diamond, for example, cubic boron nitride can be used for the friction elements, especially when working under particularly wear-resistant conditions.

Preferably, a possibility for internal cooling of the machining tool is provided in order to support the friction elements and / or the friction-bearing supporting elements, e.g. Support bars to cool during the Reibverfesti- gungsoperation. For this purpose, the machining tool may not have fluid channels, which belong to an expansion system, for guiding cooling fluid (normally a cooling fluid) from a coolant reservoir into the machining tool.

The machining tool should be actively or passively expandable or expandable in order to be able to apply an all-round friction-promoting contact pressure in rotationally symmetrical bores after the introduction. An active expansion can be achieved by a suitable delivery system. A passive expandability may e.g. be achieved in that the friction elements in the radial direction of the machining tool are movable and possibly spring-mounted, so that upon rapid rotation of the machining tool by centrifugal forces radially outward forces that determine the contact pressure of the friction elements on the bore inner surface.

The invention also relates to a processing machine suitable for carrying out the method and correspondingly adapted for processing an inner surface of a bore in a workpiece. It can be, for example, a specially configured honing machine or a specially configured machining center or a specially configured drilling spindle. The invention further relates to a workpiece, which consists essentially of a light metal material, at least in the region of a bore, wherein the bore has a claimed in the proper use of the workpiece träbologäsch inner surface. The workpiece has a Reibungsverfestigungsschicht after processing the inner surface and before the intended use in one of the inner surface near the edge zone of the workpiece. The workpiece may be, for example, an engine block or a cylinder liner for an internal combustion engine having at least one bore with an inner surface serving as a cylinder surface.

Preferably, the workpiece consists at least in the region of the bore, possibly even completely, substantially of aluminum or of an aluminum alloy, in particular of an aluminum-silicon alloy, e.g. a hypoeutectic or eutectic Al-Si alloy.

The above and other features will become apparent from the claims and from the description and from the drawings, wherein the individual features each alone or more in the form of sub-combination in an embodiment of the invention and in other fields be realized and advantageous and for can represent protectable embodiments. Embodiments of the invention are illustrated in the drawings and explained in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a schematic overall view of a honing machine, which can be used as a processing machine for carrying out embodiments of inventive processing method; FIG. 2 is a schematic illustration of components of the expansion system of the honing machine shown in FIG. 1, along with a modified honing tool that may be used for a friction-hardening operation in a honed workpiece; FIG.

3 shows various phases of an embodiment of a machining method which comprises a friction hardening operation in which a region of the bore inner surface which is near the surface is partially melted; and

4 shows an embodiment of a machining method which comprises a friction hardening operation in which a work hardening layer is produced in the area of the workpiece surface (4a), wherein subsequently in a honing operation the solidified surface is still patterned by grooves (FIG. 4B).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In Fig. 1, the front view of a honing machine 100 is shown schematically, which can be used in various embodiments of inventive method for processing of inner surfaces of holes in workpieces as a processing machine to perform on the one hand in a conventional manner, one or more honing operations on the workpiece and on the other also to produce on the same workpiece a friction strengthening operation for producing a near-surface strengthening layer in an edge zone of the workpiece near the inner surface. On the machine bed 102 of the honing machine a clamping plate 104 is fixed, which carries a workpiece 106 clamped thereon, which in the example is an engine block of a multi-cylinder internal combustion engine. The engine block consists practically completely of a light metal material, such as a hypoeutectic aluminum-silicon alloy with an Si content of about 9% by weight. In the monolithic engine block produced by a pressure, sand or low pressure casting process, a plurality of cylinder bores are formed with generally vertical orientation of their cylinder axes. The cylinder surfaces formed by the inner surfaces of the cylinder bores are subjected to a quality-determining finishing on the honing machine, in which both the macro-shape of the cylinder surfaces, as well as their surface topography is produced by suitable honing processes. In addition, the cylinder surfaces are hardened by friction-induced microstructure transformation in a near-surface layer (friction hardening layer).

In the two-spindle honing machine 100, two essentially identical honing units 110, 112 are mounted on a portal-like support structure 108 and can be used alternately or simultaneously during workpiece machining. Their structure is explained in more detail with reference to the honing unit 110. The honing unit comprises a spindle box 114 fastened on the support structure, which carries the honing spindle 116 serving as the tool spindle of the processing machine. The honing spindle can be rotated around its longitudinal axis by means of a spindle motor 118 attached to the spindle box.

The rotary drive equipped with the spindle motor is designed to produce speeds of the tool spindle within the range of 10000 min ^-1 or above, for this purpose a special motor with a suitable transmission gear is provided. At the lower end of the honing spindle, a joint rod 120 is attached, at the lower, free end of the honing tool 130 serving as a machining tool is limited mechanically coupled mechanically movable. A lifting drive 124 mounted on the lock box 114 causes the vertical movement of the honing spindle upon insertion of the tool into the workpiece or withdrawal from the workpiece and is controlled during the honing process so that the honing tool performs a vertical reciprocating motion within the bore of the workpiece ,

The honing machine is equipped with a feed system 140 shown schematically in FIG. 2, which comprises two feed devices which can be actuated independently of one another and which are assigned to different sets of processing elements on the honing tool. A hydraulically actuated first feed device 150 comprises a hydraulic cylinder 151 in which a piston which can be acted upon by hydraulic pressure on both sides is seated, which is fastened to one end of a push rod 152. Accordingly, it can be controlled in both directions by controlling the hydraulic pressure within the hydraulic cylinder parallel to its longitudinal axis. The massive push rod 152 is disposed within a hollow push rod 162 coaxial therewith and movable relative thereto. The hollow push rod belongs to an electromechanical second feed system 160, the drive of which is formed by an electric stepper motor 161 which acts on the outer, hollow push rod 162 via a suitable gear 163 to move it up and down parallel to the common axis of the push rods to move.

The at the lower, free end of the connecting rod 120 coupled honing tool 130 has a substantially rotationally symmetrical to its tool axis 131 tool body 132 having not shown in detail at its upper end coupling structures for releasably securing the honing tool to the articulated rod. The coupling For example, support structures can be designed in such a way that the tool can be fastened to the articulated rod in the manner of a bayonet connection.

On the tool body two independently operable sets of processing elements are mounted radially movable. The first set of processing elements comprises three or more evenly distributed around the circumference of the honing tool honing stones 170, which are fixed to the outside of radially within the body guided radially honing carriers 171. The support brackets 171 have on their inner side at the upper and lower end oblique surfaces 173, which cooperate in the manner of a wedge drive with conical surfaces 174 of the first feed system such that an axial movement of the inner push rod 152 of the first feed device a radial parallel displacement of the honing stones 170 perpendicular to the tool axis 131st caused against the radially inward tensile force of return springs.

The second set of machining elements circumferentially disposed between the honing stones 170 includes friction elements 180 mounted on the radially outer side of carrier bars 181 which are radially movably guided within the tool body against the inward force of return springs. Normally, between two and six offset in the circumferential direction friction elements are provided, if necessary, more or less. The carrier strips have in the upper and lower end portion inwardly directed inclined surfaces 183 which form a wedge drive with corresponding conical surfaces 184 of the second feed device, so that an axial movement of the hollow push rod 162 leads to a radial movement of the second processing elements 180 on the tool body. The friction elements are non-cutting friction strips made of silicon nitride with a relatively smooth, cutting edge-free, provided for frictional contact with the cylinder surface contact surface. The contact surface is cylindrically curved, with a curvature of the inner surface adapted curvature. The polished contact surface has a surface roughness Rz of less than 5 to 10 μm. The silicon nitride is single phase (essentially no binders of other material) to form a non-abrasive contact surface. The strip-shaped friction elements are relatively wide in the circumferential direction (more than 5 mm, for example 6 to 8 mm) to allow a large-area Gleitreibkontakt with the bore inner surface. The support strips and possibly the Aufweitkonus may consist of the same material, whereby a comparison with conventional honing tools improved temperature resistance is achieved.

The honing machine further comprises a not shown in detail first fluid channel system, which serves towards the end of Reibverfestigungs- operation a cooling liquid on the heated by frictional heat and possibly partially melted inner surface of the bore. The fluid channels extend from a coolant reservoir 190 to exhaust nozzles which open radially outward in the circumferential direction between them and / or in the region of the friction strips on the machining tool in the vicinity of the friction strips. The cooling system also cools the support strips of the friction elements from the inside.

Another unillustrated second fluid channel system leads from a source of compressed air to a plurality of nozzles attached to the circumference of the machining tool. This pneumatic system is for drying the workpiece surface immediately before the friction bonding operation. In the following, a first embodiment of a method for machining cylinder running surfaces in the production of light metal engine blocks from a hypoeutectic aluminum-silicon alloy will be described in connection with FIG. This embodiment comprises a friction strengthening operation with friction heat induced microstructure transformation.

The subfigures of Fig. 3 each show perpendicular to the cylinder bore axis extending cuts through the workpiece 306 in the region of the inner cylindrical inner surface 310, which serves as a cylinder surface in the finished engine block and thus as a friction partner for the piston rings worn on the piston.

Before clamping the engine block on the chuck plate of the honing machine, ie, provided in the subsequent processing steps processing position, the cylinder bores are prepared by fine turning or comparable machining so far that the desired final shape and surface structure in the subsequent steps of the finishing process by machining the honing machine can be achieved. The fine boring operation can be used to precisely set the desired position and angular position of the bore. The fine boring operation is carried out with a precision boring tool with a geometrically determined cutting edge, which gives the inner surface a characteristic structure with spirally encircling grooves. As an alternative to fine boring, it is also possible to use other cutting methods with heavy material removal, for example roughing or high-performance machining in accordance with EP 1 932 620 A1. If the hole already has the desired position and angular position, this first operation of the method can also be omitted. Typically, a honing operation, commonly referred to as "pre-honing," is followed by relatively coarse-grained cutting grains and high chip removal to substantially define the desired macro-shape of the bore and reduce the molding errors and potential diameter spreads resulting from pre-machining The resultant pre-honed inner surface typically has roughnesses R _z in the range of 10 μm and 30 μm The structure of the inner surface 310 on the workpiece 306 resulting from the pre-honing is shown schematically in FIG.

In order to support these coarse machining processes, water-containing cooling lubricants or honing oils are normally used to remove the machining residues produced during machining and to cool the machining tool and the workpiece machined to moderate temperatures, which are generally not substantially above 40 ^° C.

To prepare the subsequent Reibverfestigungsoperation, which is explained in more detail with reference to FIG. 3B, the pre-honed surface wetted with residues of cooling lubricant is first dried in a drying step, ie freed from liquid coolant lubricant residues. For this purpose, compressed air is blown onto the pre-honed surface 310 with the aid of one or more compressed-air nozzles 320. The Vorhon- tool may for this purpose contain a fluid channel system, the channels open in compressed-air nozzles, which are directed to the inner surface of the machined bore. The fluid channels are connected to the pneumatic system of the honing machine. After the drying step, the pre-honed inner surface is largely dry and free from processing residues of previous processing stages. The next machining operation, namely, the friction bonding operation, is performed by means of a modified double-widening honing tool 130, on the circumference of which are a plurality of friction members 180 mounted on the radially outer side of carrier bars which are radially displaceable within the tool body of the honing tool are (see Fig. 2). The friction elements are made in the region of the inner surfaces 310 facing contact surface 181 made of silicon nitride and form a substantially smooth, non-machined acting, ie non-abrasive contact surface to the surface of the light metal material. After the friction elements have been brought into contact with the inner surface by expanding (increasing the diameter) of the machining tool, the rotary drive of the honing machine is accelerated to speeds well above 500 min ^'1 , wherein the speeds often in the range between 5000 min ^"1 and 10000 min ^{' 1} or As a result, the friction elements are moved at a very high relative speed with respect to the inner surface of the bore and slide therefrom under a predetermined contact pressure. The simultaneous heating of the tool body is counteracted by the internal cooling of the carrier bars The frictional heat in the near-surface zone via the associated melting temperature T _s (eg 600 ⁰ C to 650 ⁰ C) heated so that the material in a near-surface zone partially melts and forms a melt layer 312. Due to the very high rotational speeds and the relatively small volume to be melted, the friction consolidation operation requires only very short processing times, which are typically in the range of less than 5 s. The thickness of the melt layer is highly dependent on the process control and is typically at a few microns (eg between 10 .mu.m and 100 .mu.m), if necessary, above.

As soon as the near-surface region of the workpiece has exceeded the melting temperature, which may optionally be monitored by a temperature sensor, the friction elements are depressurized and retracted. At the same time, the rotational speed of the work spindle is reduced again. As a result, the "heat source" for the near-surface melting virtually "turned off", so that the partially melted near-surface layer solidifies again. The solidification can be supported by an active cooling of the entire workpiece, in which case the heat dissipation takes place predominantly in the interior of the workpiece.

If more rapid cooling is desired, this can be achieved by spraying or irradiating the inner surface of the heated bore with the aid of a cooling fluid during the final stage of the friction consolidation operation. In the exemplary embodiment explained with reference to FIG. 3C, the machining tool has a fluid channel system whose fluid channels on the outside of the machining tool open into cooling nozzles 330 which are directed onto the workpiece surface. On the machine side, the fluid channel system is connected to a coolant tank 190.

By Reibverfestigungsoperation a near-surface layer 350 is generated in the region of the inner surface of the bore, the structure of which differs significantly from the structure of the underlying casting material. Depending on the temperature-time profile generated during the friction consolidation operation, for example, substantially higher compressive residual stresses may be present in the near-surface layer. lie as in the underlying, produced by a casting process material. As a result, the near-surface layer has an increased mechanical strength compared to the bulk material. In addition, by the Reibverfestigungsoperation an increase in the hardness of the material and thus an increased wear resistance is achieved. The surface materials produced with the help of friction hardening are ideally suited for strong tribological loads. In addition, by varying process sedimentation in the friction consolidation operation, different properties of the near-surface layer 350 with respect to residual compressive stresses, hardness, microstructure, etc. can be achieved.

The friction strengthening operation may be the final machining operation of the finishing process such that the unprocessed workpiece surface created by the friction hardening operation acts directly as a friction partner for piston rings in the intended use of the engine. Often, however, it is favorable if the friction consolidation operation is followed by further processing to produce a functional surface structure and / or processing to modify the shape. In the embodiment explained with reference to FIG. 3, a honing operation is performed subsequent to the friction strengthening operation to impart a cross-cut structure to the free surface of the surface hardened material for improving the oil resistance (FIG. 3B). For this purpose, in the tool 130 after retraction of the friction elements 180, the honing stones 170 are delivered radially outward in order to finish the inner surface by honing. In the solidified layer, honing marks 311 with typical mean depths of a few micrometers are formed.

4, a second embodiment of a method with Reibverfestigungsoperation is described, with which a workpiece 406 is processed from a eutectic aluminum-silicon alloy (about 12.5 wt .-% Si) in the region of a cylindrical bore. The pre-machining of the bore incl. Fine turning and pre-honing and drying can be carried out as described in connection with FIG. 3A.

In this variant of the method, the processing parameters of the friction hardening operation are selected such that plastic deformation of the structure of the light metal material occurs in the surface-near layer 450 adjoining the inner surface 410 at relatively low temperatures, which leads to an increase in strength by means of work hardening. For this purpose, the friction elements 180 are pressed from binder-free (single-phase) silicon nitride with a relatively strong contact pressure against the inner surface. The smooth polished unyielding (rigid) contact surface 181 provided for contact with the inner surface has a convex-cylindrical curvature adapted to the cylindrical curvature of the bore to ensure a large-area contact with the inner surface. A working movement is generated with multiple reversals of movement direction. For this purpose, the rotary drive can be controlled so that the direction of rotation of the machining tool during the period of Reibverfestigungsoperation changes several times, so that the machining tool is rotated in the bore back and forth. Alternatively or additionally, an axially oscillating working movement can be provided. Favorable for the production of a work hardening layer is the mechanical alternating stress of the near-surface layer by the friction elements pressed on over large areas. As a result, dislocation movements are induced in the polycrystalline light metal material directly below the inner surface 410 and entire crystal regions can slide on slip planes. At the grain boundaries of the relatively soft material, there may be an accumulation of dislocations and mutual blocking of further dislocation movements, whereby a solidification of the light metal material while reducing the ductility is achieved. In Fig. 4A _1B some induced by the mechanical cycling of crystal defects 451 are shown schematically, whose density is significantly higher in the hardening layer 450 as in darunterüegenden, chemically identical Volumenrnateriai 452. In this manner, a monolithic workpiece are produced that in the region Bore inner surface 410 has a much higher strength than deeper in the volume of the material.

In this process variant, the honing operation is followed by a honing operation, by means of which honing marks 411 are produced on the surface by mechanically machining with geometrically indeterminate cutting edges whose average depth in the example corresponds approximately to the layer thickness of the work hardening layer 450 (a few μm depth).

In another variant of the method, the order of rubbing operation and structuring operation is reversed. First, a patterning operation (e.g., honing or laser patterning) is performed to produce a defined surface pattern with recessed machining marks on the inner surface of the workpiece. Thereafter, the structured surface is work hardened in a rubbing-solidifying operation. In this case, some of the existing on the surface profile tips of the workpiece are flattened or bent, but the deeper grooves remain and are at most slightly compressed. This results in a superficially solidified material with a particularly high load-bearing ratio of the structured surface.

Depending on the depth of effect of the Reibverfestigungsoperation and material removal during subsequent or previous structuring, the average depth of the processing tracks may be smaller or larger than the layer thickness of Reibungsverfestigungsschicht or about this layer thickness correspond. Particularly in the case of workpieces made of a hypoeutectic or eutectic Al-Si alloy, it has proven to be favorable when honing processes produce honing marks on the cylindrical inner surface, which only have relatively small angles, for example max., To the axial direction. 30 ° or max. 40 °. It can thereby be achieved that the honing marks introduced into the still relatively soft base material are not compressed during use as a sliding surface for piston rings and are partially smeared. In order to produce the predominantly extending in the axial direction honing traces, for example, during machining by honing a ratio between the axial velocity component and peripheral speed component of the machining tool between 2: 1 and 10: 1 are set, so that the for the "Spiralgleithonen" In particular, honing traces include relatively large honing angles of, for example, more than 120 ° and less than 170 ° (corresponding to angles to the axial direction between 30 ° and 5 °.) Spiral gliding method are described, for example, in DE 196 07 774 B4 described.

The schematic round insert figure in Fig. 4B shows a plan view of the inner surface 411, which has a cross-cut structure, in which the honing marks 411 include a honing angle HW of about 140 °, which is an angle WA to the axial direction AX of the bore of about 20 ° equivalent.

Processing marks in the manner of honing marks can also be achieved by laser structuring by means of a focused and suitably controlled laser beam.

Both variants of the method, ie both the thermal microstructure transformation explained by way of example with reference to FIG. 3 (possibly with melting) as well as the exemplified by reference to FIG. 4 near-surface strain hardening lead to workpieces that are much harder and harder in the machined surface than in the underlying Voiumenwerkstoff, without the need for a coating or a separate element of a different material must be applied. As a result, it is particularly possible to use hypoeutectic aluminum-silicon alloys, ie Al-Si alloys having a Si content of less than 12.5% by weight, or eutectic or near-eutectic aluminum-silicon alloys, to use in monolithic workpieces without the specific disadvantages of these bulk materials adversely affect the tribological properties of the inner surface.

For motor blocks made of a hypoeutectic Al-Si alloy, e.g. by a Reibverfestigungsoperation, which leads to an inner surface near strain hardening layer, the tendency to seize with the friction partner piston ring can be significantly reduced. As a result, the cold start properties of these engines can be improved and the risk of piston eaters in the run-in phase is significantly reduced.

If a near-surface particle reinforcement for the machined workpiece is desired, the process variants described above can be modified by the fact that before and / or during the Reibverfestigungsoperation fine fibrous and / or granular solid particles in the form of a suitable powder or the like. be incorporated into the processing zone and incorporated in the Reibverfestigungsoperation in the near-surface layer. Typical mean particle sizes may be below 100 μm, for example. In the friction-strengthening layers produced by local melting, the reinforcing particles are typically distributed relatively uniformly throughout the layer, while the reinforcing particles are found in work-hardened surface layers only in the immediate vicinity of the inner surface. are and are partially open, because they are pressed by the friction elements only mechanically into the relatively soft light metal matrix.

The processing machine may be a conventionally constructed honing machine whose rotary drive may possibly be modified in order to be able to produce the high rotational speeds favorable for the melting process. Separate fluid channel fluid cooling system for cooling or quenching the workpiece surface and for pneumatically drying the inner surface prior to the friction consolidation operation may be provided. Even conventional or possibly modified machining centers can be used as processing machines, in particular if they are designed to work with expandable processing tools.

Instead of the classical honing, another finishing operation for producing defined surface properties of the workpiece can be carried out after the friction consolidation operation, for example a surface structuring of the surface with the aid of laser radiation, for example the structure of the briefly melted and then solidified surface layer 350 at least in the region the free surface to change.

Some advantageous variants of the invention have been explained with reference to exemplary embodiments which originate from the field of fine machining of inner surfaces on engine blocks (cylinder crankcases) made of aluminum-based light metal materials. However, the invention is not limited to the fine machining of such workpieces. Thus, not only parts for internal combustion engines or compressors have been processed by the process, but also the inner surfaces of pipes, which can be used for example for extrusion. Bearing surfaces in connecting rods, piston bores or the like can also be machined.

A Reibverfestigungsoperation may also be provided in the machining of workpiece outer surfaces with a suitable modification of conventional external machining processes, for. To consolidate convex-cylindrical bearing surfaces on piston pins or other workpieces on the surface.

The processable light metal materials mainly include magnesium and aluminum and alloys based on aluminum or based on magnesium, wherein the composition of the alloy components may each be such that an alloy is hypoeutectic, eutectic or hypereutectic. It is also possible to machine the inner surfaces of workpieces made of spray-compacted hypereutectic Al-Si materials. These extremely fine-grained and relatively strong materials are e.g. used for the production of cylinder liners.

The light metal materials may be free of hard material phases, but they may also be reinforced by enclosed hard material phases, wherein the hard material phases may be particulate and / or fibrous.

Claims

claims

1. A method for fine machining an inner surface of a bore in a workpiece, which consists essentially of a light metal material, at least in the region of the bore, in particular for machining a cylinder surface in the manufacture of engine blocks for internal combustion engines, wherein during at least one machining operation, a machining tool within the machining boring performs a working movement and at least one machining element attached to the machining tool mechanically acts on the inner surface, characterized in that the method comprises a Reibverfestigungsoperation in which a machining tool with at least one friction element (180) is used, the one for frictional contact with the inner surface (310, 410) provided contact surface (181), wherein the friction element with a relative speed to the inner surface and with a friction-promoting pressure so over the inner surface is moved, that under the action of sliding friction and pressure in the region of the inner surface a substantially by sliding friction and pressure induced Reibverfestigungsschicht (350, 450) is generated.

2. The method of claim 1, wherein a layer thickness of the Reibverfestig ungsschicht (350, 450) is in the range of one micron to one millimeter.

3. The method of claim 1 or 2, wherein the Reibverfestigungs- layer (350, 450) is produced essentially by non-cutting sliding of the friction element on the inner surface.

4. Method according to one of the preceding claims, wherein machining parameters of the friction hardening operation are set in this way in that one of the light metal material is induced in the friction bonding layer (450) adjacent the inner surface of the bore.

5. The method of claim 4, wherein Bearbeitungspararneter the Reibverfestigungsoperation be adjusted so that in the region near the inner surface of the light metal material temperatures of at most 150 ⁰ C _1, in particular less than 100 ⁰ C are generated.

6. A method according to claim 4 or 5, wherein the machining tool is rotated in phase during the friction strengthening operation such that the rotational direction of the machining tool changes several times during the period of the friction strengthening operation, so that the machining tool is reciprocated in the bore.

A method according to any one of claims 1 to 3, wherein machining parameters of the friction strengthening operation are adjusted to generate a considerable amount of frictional heat and to generate a frictional heat-induced frictional strengthening layer (350) under the influence of frictional heat in the area of the inner surface.

8. The method of claim 7, wherein in the Reibverfestigungsoperation in a near-surface heat affected zone temperatures are generated, the phases amount to at least 50% of the material-specific melting temperature Ts of the light metal material.

9. The method of claim 8, wherein the light metal material is at least partially melted during the Reibverfestigungsoperation in the region of the inner surface under the influence of frictional heat generated and then solidified to form a Reibverfestigungsschicht (350).

10. The method according to any one of claims 7 to 9, wherein the machining tool during the Reibverfestigungsoperation is rotated in phases at a speed of more than 500 min ^"1 , wherein the speed is preferably at least in phases at more than 5000 min ^{" 1} , in particular in the range of 8000 min ^"1 to 10000 min ^{" 1} .

11. The method according to any one of claims 7 to 10, wherein the inner surface is quenched by a cooling fluid after a friction-induced heating, in particular after an at least partial melting of the light metal material in the region of the inner surface.

A method according to any one of the preceding claims, wherein the rubbing consolidation operation is performed dry.

13. A method according to any one of the preceding claims, wherein prior to the rubbing operation, boring is carried out using a liquid processing aid, and wherein the inside surface is actively dried in a drying step for removing liquid residues prior to the start of the rubbing operation or in an initial stage of the rubbing operation, wherein preferably in the drying step compressed air or another compressed gas is inflated onto the inner surface.

14. A method according to any one of the preceding claims, wherein solid particles and / or solid fibers are introduced into the bore prior to and / or during the friction consolidation operation and incorporated into the light metal material by the friction hardening operation in a near-surface layer on the inner surface of the bore, solid particles and / or Preferably solid fibers from a ceramic material, in particular silicon, glass, MuMt, Zirconia, magnesium oxide or of a hard metallic material, in particular of tungsten or molybdenum, exist.

15. A method according to any one of the preceding claims, wherein after the rubbing consolidation operation, a material-removing or material-converting post-processing operation is performed on the inner surface solidified by the rub-hardening layer, in particular a post-machining operation by means of honing, laser-irradiating and / or laser-structuring.

16. The method according to any one of the preceding claims, wherein before the Reibverfestigungsoperation a material-removing structuring operation is performed on the inner surface, in particular a structuring operation by means of honing or laser structuring.

17. The method according to claim 15 or 16, wherein in the post-machining operation or during the structuring operation on the cylindrical inner surface machining tracks are generated, which are compared to an axial direction of the bore only relatively small angle to max. 30 °, wherein preferably angles are generated to the axial direction between 30 ° and 5 °.

18. The method according to any one of the preceding claims, wherein the light metal material consists essentially of aluminum or an aluminum alloy, in particular of an aluminum-silicon alloy, wherein the light metal material is preferably a hypoeutectic or eutectic Al-Si alloy.

19. Machining tool for machining an inner surface of a bore in a workpiece consisting of a light metal material, at least in the region of the bore, in particular for machining a cylinder surface in the manufacture of engine blocks for combustion engines. Power machines, characterized in that the machining tool (130) has at least one friction element (180) having at least one provided for frictional contact with the inner surface non-abrasive Kontaktfiäche (181).

20. Processing tool according to claim 19, wherein the friction element (180) in the region of the contact surface (181) has a surface roughness R _z of less than 20 microns, in particular less than 10 microns, wherein the contact surface is preferably smoothed by polishing.

21. Machining tool according to claim 19 or 20, wherein the friction element (180) at least in the region of the intended for contact with the inner surface contact surface (181) consists of a material which is non-adhesive relative to the light metal material.

22. Processing tool according to claim 19, 20 or 21, wherein the friction element at least in the region of the contact surface (181) consists of a preferably single-phase ceramic material, in particular of silicon nitride, or of a hard metallic material.

23. Machining tool according to one of claims 19 to 22, wherein the friction element is a friction strip (180) or Reibschale.

24. A machining tool according to any one of claims 19 to 23, wherein the machining tool comprises means for internally cooling the machining tool to cool the friction member and / or the friction member carrying support members during the Reibverfestigungsoperation, the machining tool preferably not belonging to an expansion system fluid channels for guiding Contains cooling fluid.

25. Processing tool according to one of claims 19 to 24, wherein the machining tool (130) is actively or passively expandable.

A machining tool according to any one of claims 19 to 25, wherein the machining tool (130) is adapted for use in a honing machine (100) and has a coupling structure for releasably securing the machining tool to a honing spindle (116).

27. Processing machine for fine machining an inner surface of a bore in a workpiece, in particular for fine machining a cylinder surface in the manufacture of engine blocks for internal combustion engines, with at least one tool spindle for moving a coupled to the tool spindle machining tool within the bore such that at least one of the machining tool attached processing element, an inner surface treatment is performed, characterized in that the processing machine is configured to perform a method according to any one of claims 1 to 18 on the workpiece using a machining tool according to any one of claims 19 to 26.

28. Processing machine according to claim 27, wherein the processing machine for fast rotation of the tool spindle has a spindle drive, which is designed for maximum speeds of more than 500 min ^"1 , preferably for maximum speeds of more than 5000 min ^'1 , in particular for maximum speeds in Range of 8000 min ^"1 to 10000 min ^{" 1} .

29. Processing machine according to claim 27 or 28, wherein the processing machine is a honing machine (100) or a machining center.

30. workpiece, which consists at least in the region of a bore substantially of a light metal material, wherein the bore has a designated use of the workpiece tribologically stressed inner surface, in particular engine block for an internal combustion engine having at least one bore with a cylinder surface serving as an inner surface, wherein the workpiece (106, 306, 406) has, after machining the inner surface and before intended use in a near the inner surface (310, 410) edge zone of the workpiece under the influence of sliding friction and pressure Reibungsverfestigungsschicht (350, 450).

31. The workpiece of claim 30, wherein the friction strengthening layer (350, 450) is chemically substantially identical to the underlying bulk material of the light metal material.

32. A workpiece according to claim 30 or 31, wherein a layer thickness of the friction strengthening layer (350, 450) is in the range of one micron to one millimeter.

33. A workpiece according to claim 30, 31 or 32, wherein the friction strengthening layer (450) is a work hardening layer.

34. The workpiece of claim 30, 31 or 32, wherein the friction strengthening layer (350) has the texture of a solidified melt layer.

35. A workpiece according to any one of claims 30 to 34, wherein on the inner surface of machining marks (411) are present, the only relatively small angle to an axial direction of the bore to max. Enclose 30 °, preferably with angles to the axial direction between 30 ° and 5 °.

36. A workpiece according to any one of claims 30 to 35, wherein the workpiece has at least two bore portions adjacent to each other in the axial direction of the bore having different surface properties, wherein at least one of the bore portions has a friction strengthening layer formed by friction strengthening.

37. A workpiece according to any one of claims 30 to 36, wherein the light metal material consists essentially of aluminum or of an aluminum alloy, in particular of an aluminum-silicon alloy, wherein the light metal material is preferably a hypoeutectic or eutectic Al-Si alloy.

38. A workpiece according to any one of claims 30 to 37, wherein the workpiece (106, 306, 406) consists substantially entirely of the light metal material.

39. A workpiece according to any one of claims 30 to 38, wherein the workpiece is an engine block (106, 306, 406) or a cylinder liner and the inner surface (310, 410) is a cylinder liner.