DE102011011886B4 - Method for compacting the surface of sintered metal components - Google Patents

Abstract

Method for compacting the surface of sintered metal components (2), on the peripheral surface (2.1) of which at least one drivably mounted rolling tool (1) engages and performs abruptly executed single rolling operations, wherein the single rolling operations are carried out either by means of
a. a cylindrical rolling tool (1) having a smooth rolling surface (1.1) with a drive for generating a translatory shock or vibration movement acting in the direction of the sintered metal component (2) or
b. a cylindrical rolling tool (1) with at least partially profiled rolling surface (1.1), wherein the profile (1.3) in cross-section substantially undulating elevations (1.4), which during rotation of the rolling tool (1) periodically on the peripheral surface (2.1) of the sintered metal component (2) attack.
be performed.

Description

The invention relates to a method for compacting the surface of sintered metal components, in particular for compacting cylindrical sintered metal components.

When sintering mostly granular or powdery substances are mixed and then joined together by heating. In contrast to the pure melt, however, no or at least not all starting materials are melted. The main advantages of sintering are the combination of starting materials, which can be combined in other ways only with great difficulty or not at all to a new material, the ability to be able to produce even complex shapes and to call the cheaper compared to the melting manufacturing process.

The main disadvantage of sintered materials, such as metals, is that, mechanically speaking, they still partially consist of macroscopic particles of the starting materials, ie they are not as homogeneous as metal alloys and therefore usually have a porosity as well. For certain applications, however, this (surface) porosity is undesirable because it is accompanied by a reduction in the strength characteristics. Therefore, the porosity must be reduced by subsequent densification processes to a required level.

Various methods for compacting, in particular surface compacting, of sintered metal components are previously known from the prior art. First, this is the conventional compression rolls of cylindrical workpieces to name but which can only be used with sintered metal components with sufficient wall thickness. Also to be mentioned are sinter forging and the DPDS process (double pressing, double sintering). All of the aforementioned compression method adheres to the significant disadvantage that they are either too costly or allow only a limited freedom of design of major and minor forms. Apart from the undesired changes in geometry occurring during the compression process, the state of the art in the prior art methods adds to the fact that a marginal or surface density required for heavy-duty workpieces can not or only insufficiently be achieved.

Of the DE 10 2006 028 184 A1 For this purpose, a method for producing at least partially surface-compacted workpieces having a convex and / or concave surface, wherein a compacted sintered metal or a cast and / or forged material - wherein a deformation of the workpiece with a locally selective allowance based on a final dimension of Workpiece is made - is rolled by means of at least one rolling tool to the final dimension. Essential to this invention is that a gear rolling of sintered metal is performed.

Further, the DE 10 16 222 B a method for generating straight or oblique to the workpiece axis, parallel profiles, for. B. of gears by a rolling process. This rolling process takes place using ring-like profiled rollers in individual abruptly and substantially in the profile longitudinal direction with constant sense of direction performed, rapidly successive and overlapping their attack on the workpiece Teilwalzvorgängen through which the material gradually within each small workpiece longitudinal sections, ie profile sections, from the profile base Workpiece surface is displaced out. Characteristic of this invention is that the individual Teilwalzvorgänge in a conventional manner in a regular change to adjacent, ie approximately in a perpendicular to the feed axis of the workpiece extending zone workpiece longitudinal sections are exercised.

The object of the invention is now to propose a method for compacting the surface of sintered metal components, with which a greater compaction depth can be achieved while maintaining the macrogeometry. Another object of the invention is the cost-effective implementation of the method.

According to the invention, in the method for compacting the surface of sintered metal components, at least one drivably mounted rolling tool acts on the circumferential surface thereof and executes single rolling operations carried out abruptly, wherein the single rolling operations are carried out either by means of a smooth rolling surface having a cylindrical rolling tool with a drive for generating in the direction of Sintered metal component acting translational impact or vibration movement or a cylindrical rolling tool with at least partially profiled rolling surface, wherein the profile has in cross-section substantially wave-shaped elevations, which periodically engage in a rotation of the rolling tool on the peripheral surface of the sintered metal component, are performed.

From a manufacturing point of view, the person skilled in the art would indeed select a profile with several evenly spaced elevations; However, the inventive method can also be with a profile, which only a single Survey or realize by non-periodic surveys.

A significant advantage of this invention is that the sudden single rolling operations lead to a densification of the surface of the sintered metal component without significant deformation, or without relevant change in geometry.

It is also essential to the invention that the abrupt single rolling operations of the rolling tool on the sintered metal component are carried out periodically or not periodically.

It has been found that by rolling with a profiled rolling tool whose pitch of the profile of its rolling surface does not share the diameter of the sintered metal component to be rolled, the surface of the sintered metal component can be compacted significantly deeper than in conventional rolling with the same geometry.

By means of the method according to the invention, sintered metal components can now also be established in the market segment of the mechanically highly loadable metal components, since the component properties can be significantly improved and components previously required, for example bearing rings, can be saved.

It has been successfully proven that the formation of undulating elevations with preferably small radii, the so-called contact radii, can positively influence the compaction depth of the sintered metal component.

In spite of the fact that no significant change in geometry of the sintered metal component to be rolled occurs during rolling, a second method step for achieving optimum roundness-calibrating-can be added to the first method step-compacting the surface. According to the invention, it is provided that the rolling surface of the rolling tool in the direction of its circumferential line comprises a first, profiled area for the purpose of surface compacting and an adjoining second, non-profiled, respectively smooth area for the purpose of calibrating the sintered metal component following the surface compaction. That is, in a first rotation angle range of the rolling tool, the sintered metal component is only compressed, and in the second rotation angle range, the sintered metal component is calibrated. The transition of the profile of the rolling surface of the rolling tool can accordingly proceed continuously in the second, non-profiled, respectively smooth area. Such a design of the rolling surface of the rolling tool can advantageously be used to carry out two method steps directly after one another, without the rolling tools having to be converted or the workpiece having to be moved.

During the compaction process, the rolling tool is usually rotationally driven when using rollers. By contrast, in the case of rolling tools designed as beam bars, at least one of the beams is acted upon by an axially acting force which generates a translatory movement of the beam. The sintered metal component to be machined can additionally be driven rotationally or with feed in the direction of its longitudinal axis, wherein the two rotational movements or the rotational movement and the advancing movement are matched to one another.

Elaborate field tests have shown that during the compaction and / or calibration process, the axis (s) of the rolling tool and the axis of the sintered metal component can be aligned not only parallel but also not parallel to each other. The latter case is realized when the sintered metal component to be machined is to perform an advancing movement in addition to the rotational movement. By the opposite inclined axes of two rollers or rollers relative to the axis of the sintered metal component, the force is generated to feed in the direction of its longitudinal axis by the rollers or rollers themselves. This has the advantage that the compaction process and the optionally subsequent calibration process can be transferred to theoretically infinitely long sintered metal components.

It has been found to provide a large surface compacting depth of the sintered metal component when the rotational speed of the rotating rolling tool is between 5 and 200 rpm.

The rolling tool according to the invention, in addition to the pairing roller-roller, or beam bar also be designed as a roller segment, wherein the arrangement of the two complementary rolling tools each other causes a balance of forces with respect to the diametrically acting rolling forces on the sintered metal component.

For the purposes of the invention, preferably hollow-cylindrical but also fully cylindrical sintered metal components are provided as sintered metal components. In the case of a rolling tool designed as a roller-roller, the sintered metal components to be machined are supported on a mandrel or on tips which can or may be driven rotationally as required.

• • an der Umfangsfläche des zu bearbeitenden Sintermetallbauteils greift zumindest ein antreibbar gelagertes Walzwerkzeug an und führt schlagartig Einzelwalzvorgänge periodisch oder nicht periodisch aus, was zur Verdichtung der Oberfläche ohne signifikante mikroskopische Verformung, respektive ohne relevante Geometrieveränderung, des Sintermetallbauteils führt,
• • die schlagartigen Einzelwalzvorgänge können hierbei zum einen mittels einem eine glatte Walzfläche aufweisenden, zylinderförmigen Walzwerkzeug mit einem Antrieb zur Erzeugung einer in Richtung des Sintermetallbauteils wirkenden translatorischen Stoß- oder Schwingungsbewegung oder zum anderen mittels einem zylinderförmigen Walzwerkzeug mit zumindest partiell profilierter Walzfläche, wobei das Profil im Querschnitt im Wesentlichen wellenförmige Erhebungen aufweist, welche bei einer Rotation des Walzwerkzeugs (periodisch) an der Umfangsfläche des Sintermetallbauteils angreifen, realisiert werden,
• • durch Ausbildung kleiner Kontaktradien der Erhebungen kann die Verdichtungstiefe der Sintermetallbauteile positiv beeinflusst werden,
• • die Walzfläche des Walzwerkzeugs kann in Richtung ihrer Umfangslinie einen ersten, profilierten Bereich zum Zwecke des Oberflächenverdichtens und einen sich daran anschließenden zweiten, nichtprofilierten, respektive glatten Bereich zum Zwecke des an die Oberflächenverdichtung sich anschließende Kalibrierens des Sintermetallbauteils umfassen,
• • während des Verdichtungs- und/oder Kalibrierungsprozesses können die Achse(n) des Walzwerkzeugs und die Achse des Sintermetallbauteils in Abhängigkeit des verwendeten Walzwerkzeugs parallel oder nicht parallel zueinander ausgerichtet sein und
• • als bearbeitbare Sintermetallbauteile eignen sich sowohl hohlzylinderförmige als auch vollzylinderförmige Sintermetallbauteile mit und ohne Rand- und Zusatzgeometrien.

The significant advantages and features of the invention over the prior art are essentially:

• On the peripheral surface of the sintered metal component to be machined, at least one drivably mounted rolling tool engages and abruptly performs single rolling operations periodically or not periodically, resulting in densification of the surface without significant microscopic deformation, or without relevant change in geometry, of the sintered metal component.
• • The sudden single rolling operations can hereby on the one hand by means of a smooth rolling surface, cylindrical rolling tool with a drive for generating a force acting in the direction of the sintered metal component translational shock or vibration or on the other hand by means of a cylindrical rolling tool with at least partially profiled rolling surface, wherein the profile in Cross-section has substantially wave-shaped elevations, which in a rotation of the rolling tool (periodically) attack on the peripheral surface of the sintered metal component can be realized,
• • by forming small contact radii of the elevations, the compaction depth of the sintered metal components can be positively influenced,
• The rolling surface of the rolling tool can comprise, in the direction of its peripheral line, a first, profiled area for the purpose of surface compacting and a subsequent second, non-profiled or smooth area for the purpose of calibrating the sintered metal component subsequent to the surface compaction,
• • During the compaction and / or calibration process, the axis (s) of the rolling tool and the axis of the sintered metal component may be parallel or not aligned parallel to each other depending on the rolling tool used, and
• • Both hollow cylindrical and fully cylindrical sintered metal components with and without marginal and additional geometries are suitable as machinable sintered metal components.

The objectives and advantages of this invention will become better understood and appreciated after a careful study of the following detailed description of the preferred non-limiting example embodiments of the invention herein, together with the accompanying drawings, in which:

1 FIG. 2: an illustration of a roll-shaped rolling tool with a profiled surface, FIG.

2 FIG. 2: a detailed representation of the profiled surface of the rolling tool in cooperation with the peripheral surface of the sintered metal component according to FIG 1 .

3 FIG. 4 is a sectional view of a further rolling tool in which the rolling surface comprises a profiled rolling area and a cylindrical calibrating area, FIG.

4 : A sectional view of a cylindrical rolling tool without rolling surface profile with vibration superposition and

5 : A perspective view of a profiled trained roller-roller-rolling tool with opposite inclined longitudinal axes.

The 1 shows a sectional view of a trained as a roller-roller roller 1 with profiled rolling surface 1.1 , Between the two, the rolling tool 1 forming rollers is a hollow cylindrical sintered metal component 2 placed on a thorn 3 is held. This thorn 3 is driven in the example shown as well as the two rollers rotationally, the associated drives are not shown. The axis (s) of the rolling tool 1.2 and the axis 2.2 of the sintered metal component to be processed 2 are aligned parallel. The profiled trained rolling surface 1.1 is in direct contact with the peripheral surface 2.1 of the sintered metal component 2 , Upon rotation of the rolling tool 1 be abrupt single rolling operations periodically on the peripheral surface 2.1 of the sintered metal component 2 executed, which lead to the densification of the surface without relevant deformation, or without significant change in geometry.

From the 2 is a detailed representation of the profiled rolling surface 1.1 of the rolling tool 1 in cooperation with the peripheral surface 2.1 of the sintered metal component 2 according to 1 refer to. As can be seen, the profile has 1.3 in cross-section substantially undulating elevations 1.4 which, upon rotation of the rolling tool 1 periodically on the peripheral surface 2.1 of the sintered metal component 2 attack. Depending on the selected contact radii of the surveys 1.4 , the rotational frequency of the rolling tool 1 and the rotational frequency of the sintered metal component 2 the compaction depth can be purposefully influenced. It is also essential to the invention that the division 1.5 of the profile 1.3 the rolling surface 1.1 of the rolling tool 1 not on the diameter of the hollow cylindrical sintered metal component 2 Splits. The user of the method according to the invention is left to the rolling tool 1 calibrate so that the sintered metal component 2 diametrically simultaneously rolling forces act, that is, the elevations 1.4 always directly opposite the two complementary rollers or rollers.

The 3 illustrates a sectional view of another rolling tool 1 in which the rolling surface 1.1 a profiled rolling zone and a cylindrical calibration area with a smooth rolling surface 1.1 includes. The rolling surface 1.1 of the rolling tool 1 points towards its perimeter 1.6 a first, profiled area for the purpose of surface compacting and an adjoining second, non-profiled, respectively smooth area for the purpose of calibrating the sintered metal component following the surface compaction 2 on. That is, with only a single revolution of the rolling tool 1 According to the invention, two process steps, which would have to be carried out successively in the prior art by retooling or moving the workpiece, can be realized in a single operation. The ratio between the profiled area of the rolling surface 1.1 and the smooth area of the rolling surface 1.1 may be pronounced depending on various needs. For fully cylindrical sintered metal components 2 is in contrast to hollow cylindrical sintered metal components 2 the profiled area opposite the smooth area of the rolling surface 1.1 smaller to choose, since fully cylindrical sintered metal components 2 tend more to geometry changes in the compression process.

A sectional view of a cylindrical rolling tool 1 without rolling surface profile with vibration superposition is the 4 refer to. To achieve the sudden single rolling operations of the rolling tool 1 on the sintered metal component 2 It is envisaged that this will be a smooth rolling surface 1.1 having, cylindrical rolling tool 1 with a drive, not shown, for producing a direction in the direction of the sintered metal component 2 acting translational shock or vibration movement is equipped. The oscillation superimposition achieved thereby leads to partial compression of the surface or edge surface of the hollow cylindrical sintered metal component 2 , By the simultaneous rotation of the sintered metal component 2 becomes its entire peripheral surface after several passes 2.1 compacted. By subsequent rolling without oscillation superimposition, a calibration process can be imaged in order to further improve the component quality.

The 5 shows a perspective view of a profiled trained roller-roller rolling tool 1 with opposite inclined longitudinal axes 1.2 , As can be seen, the axis 2.2 the locked sintered metal component 2 and the axis (s) 1.2 of the rolling tool 1 skewed aligned. The opposite inclined axes 1.2 of the rolling tool 1 cause the rolling surface 1.1 not parallel to the peripheral surface to be compacted 2.1 of the sintered metal component 2 engages, whereby an axial feed of the sintered metal component 2 is reached. This axial feed movement is preferably used for workpieces with long lengths.

LIST OF REFERENCE NUMBERS

1

rolling tool

1.1

roll face

1.2

longitudinal axis

1.3

profile

1.4

surveys

1.5

division

1.6

peripheral line

2

Sintered metal component

2.1

peripheral surface

2.2

longitudinal axis

3

Thorn or tip

Claims (10)

Method for compacting the surface of sintered metal components ( 2 ), on the peripheral surface ( 2.1 ) at least one drivably mounted rolling tool ( 1 ) attacks and performs abruptly executed single rolling operations, wherein the single rolling operations either by means of a. a smooth rolling surface ( 1.1 ), cylindrical rolling tool ( 1 ) with a drive for generating a in the direction of the sintered metal component ( 2 ) acting translational shock or vibration movement or b. a cylindrical rolling tool ( 1 ) with at least partially profiled rolling surface ( 1.1 ), where the profile ( 1.3 ) in cross-section substantially undulating elevations ( 1.4 ), which during a rotation of the rolling tool ( 1 ) periodically on the peripheral surface ( 2.1 ) of the sintered metal component ( 2 attack). be performed. A method according to claim 1, characterized in that the sudden single rolling operations of the rolling tool ( 1 ) on the sintered metal component ( 2 ) be carried out periodically or not periodically. Method according to claim 1 or 2, characterized in that the division ( 1.5 ) of the profile ( 1.3 ) of the rolling surface ( 1.1 ) of the rolling tool ( 1 ) not on the diameter of the sintered metal component ( 2 ) Splits. Method according to one of claims 1 to 3, characterized in that the rolling surface ( 1.1 ) of the rolling tool ( 1 ) in the direction of its peripheral line ( 1.6 ) a first, profiled area for the purpose of surface compacting and an adjoining second, non-profiled, respectively smooth area for the purpose of subsequent to the surface densification calibration of the sintered metal component ( 2 ). Method according to claim 4, characterized in that the profile of the rolling surface ( 1.1 ) of the rolling tool ( 1 ) steadily merges into a second, non-profiled, respectively smooth area. Method according to one of claims 1 to 5, characterized in that during the compression process, the rolling tool ( 1 ) rotationally driven and the sintered metal component ( 2 ) rotationally or with feed in the direction of its longitudinal axis ( 2.2 ) is driven, wherein the two rotational movements or the rotational movement and the feed movement are coordinated. Method according to one of claims 1 to 6, characterized in that during the compression and / or calibration process, the axis (s) ( 1.2 ) of the rolling tool ( 1 ) and the axis ( 2.2 ) of the sintered metal component ( 2 ) are aligned parallel or not parallel to each other. Method according to one of claims 1 to 7, characterized in that the rotational speed of the rotating rolling tool ( 1 ) is between 5 and 200 rpm. Method according to one of claims 1 to 8, characterized in that the rolling tool ( 1 ) is designed as a pairing roller-roller, roller segment or beam bar whose arrangement is an equilibrium of forces with respect to the diametrically acting rolling forces on the sintered metal component ( 2 ) cause. Method according to one of claims 1 to 9, characterized in that as sintered metal components ( 2 ) hollow cylindrical fully cylindrical sintered metal components ( 2 ) are provided on a drivable mandrel or on tips ( 3 ) are held.

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