EP1133374B1 - Method for producing a sintered part with a subsequent shaping of the green compact - Google Patents

Abstract

The invention relates to a method for producing a sintered part comprised of a powdery material, especially comprised of a sintered metallurgical powder. According to the inventive method, a green compact which forms an elementary shape of the part is firstly compression molded from the powder. The desired final shape of the part is produced by subjecting partial areas of the elementary shape on the green compact to a successive non-cutting shaping. Afterwards, said final shape is finished by sintering.

Description

The invention relates to a method for producing a sintered component made of powdery material, in particular made of sintered metallurgical powder, the component being a Has external and / or internal teeth.

The production of sintered components by pressing one metallurgical powder and subsequent sintering is essential known. When pressing the powder into a so-called Greenery depends on the one hand, one if possible to achieve uniform compaction of the powder, and secondly to design the geometry of the component so that the Shaping carried out with the simplest possible pressing tools can be, in addition, the requirement there is that the pressed green body from the mold can also be shaped is. In many cases, however, the functional No requirements for the geometry of the finished component by a pressing process if, for example Undercuts, grooves running transverse to the pressing direction or external contours are present that ensure even compaction not allow. Some of the problems can be solved solve in that the finished component of two or more for pressed and sintered elements becomes a raw part or by pressing and sintering is generated, which is then in a chip-forming process still has to be finished. A structure a component made up of several sub-elements cannot be created always realize. Machining a finished sintered component is particularly in a series production expensive.

DE-A-196 36 524 describes a process for the production of Prototype known, in which with the help of a press tool an at least one-step basic molding process from binder metal powder containing a green compact as a basic component shape is formed under the influence of pressure and / or heat, which only approximates the final shape of the component. In at least another, material-removing or material-forming The molding process then gives the green compact a first component shape given and then sintered. The so created The prototype is examined with regard to the necessary ones Changes in shape to take into account the influences of the sintering process with regard to its suitability for the intended mechanical use. Here is the reduction in particular the amount of material, d. H. a slimmer form of Interest. As a rule, the first prototype created in this way another does not meet all requirements In turn, a green body from the existing pressing tool created according to those obtained from the investigation Knowledge revised, sintered and again is examined. This makes it possible to use just one mold to gradually develop the necessary final component shape and based on the final sample obtained in this way, then for series production to produce the necessary pressing tools.

A molding process for the production of a sintered component already with the basic molding process to connect, a method is described in EP 826 449 in the case of several separate, one after the other Press stamping a green body in a press tool its final shape is formed from powder material, whereby Cross-sectional contours with different degrees already during pressing Material thicknesses, such as wheel hubs and wheel rims can be molded on. Requirement is, that the component has no undercuts in its geometry has, so that it comes out of the press tool after pressing is removable.

Basically, this method can be used for any geometry insert without undercuts when the press tool is adapted to the contours accordingly. Indeed it has been shown that only with bodies with surfaces that are in the essentially perpendicular to the direction of movement of the pressing tools are aligned, achieved a uniform compression can be. As soon as the component to be manufactured by this Basic condition has different geometries, the described described bumps Process to its technical limits.

In particular on the edges or protrusions of what is to be produced Component can due to the low flowability of the Powder, areas with lower material density arise that in the subsequent sintering to material defects such as cracks or breaks. In the same way it can too Overuse and breakage in such exposed areas Place the press tool.

In the case of components, their contours or geometries, such partial areas have that not with an axially guided pressing tool are producible, is either a complicated, divided pressing tool, for example with so-called Sideshift required, or it is after the basic molding process separate processing is necessary. In the material-removing processing will be the corresponding Geometries or undercuts on the component to achieve the desired final component shape.

GB-A-2 051 639 describes a process for the production of Threaded spindles are known, first of all from a sintered metal powder a green compact is pressed in the form of a cylinder body and then sintered. After that, by reshaping the cylinder outer surface of the sintered cylinder body with Using a form roller, the thread is applied, being in the area of the threads significantly densifies the surface becomes. Then the threaded rod or Bolts are sintered.

From CH-A-335 196 is a process for the manufacture of bullet rings known from iron powder, in which the ring is pre-pressed and is pre-sintered and subsequently for adjustment pressed to a defined density and sintered again becomes. Because bullet rings made out of cylindrical smooth rings are formed, the re-pressing only causes calibration, in order to avoid excessive structural compaction as far as possible.

The object of the invention is to provide a method avoids the disadvantages described above.

The object is achieved by that specified in claim 1 Process for producing a component from a sintered metallurgical Powder. This procedure caters for a variety of geometries the advantage that the green body for the Basic component shape in a correspondingly simplified, on a uniform compression designed press tool manufactured can be. It is useful if the basic component shape in their geometry the geometry of the final component shape as possible comes close. The special final shape is then by at least one further separate forming the relevant sections of the green body with the help of a generated another forming tool.

The fact that the sub-areas to be reshaped in separate Forming tools can be pressurized Areas that were less densely compressed in the first pressing step become clogged. Here - without removing material - special ones that are difficult or impossible to form in the first pressing step Geometries in the sub-areas of the basic component shape be shaped. The forming tools are with pressure and counter pressure media fitted. With these procedures can an isostatic pressure component on the to be reshaped Partial areas are transferred that even with very brittle material deformability is still possible. By reshaping the relevant part of the green compact becomes the final component shape manufactured, which are then sintered can.

With the appropriate geometry of the component, it is even possible in the sub-areas through the subsequent forming to increase the material density and thus an additional one Strength in these areas on the finished sintered component to achieve.

In an embodiment of the method according to the invention, this can Forming by pressing and / or rolling. Forming can in particular be carried out in stages, whereby individual contours, such as undercuts on the final component shape, each generated at least by one forming step become.

According to the invention it is also provided that the forming depth is gradual is increased. It is achieved that without destruction the material structure has done more forming can be.

In a further advantageous embodiment of the method it is provided that the green body before at least one forming is pre-sintered to increase the green strength. This called pre-sintering joining of the powdered and pressed Powder material is preferably at a lower Temperature made than that leading to the final component shape High Intern. The pre-sintering is carried out in such a way that further forming work on the component is still possible is. Pre-sintering ensures that the inner structure of the molding in the areas that have already been finally formed largely retained when reshaping parts and a higher pressure on these sections for forming can be applied.

According to the invention, the component can be a green body before sintering and / or calibrated as a solidified part after sintering become. In particular, it is also provided, at least part of the forming work by calibrating Afford. By calibrating the surface, however also the structure of the component can be qualitatively improved. It is particularly possible to have burrs and / or points eliminate sharp edges.

Fig. 1

als Fertigbauteil ein Ritzel mit bogenförmigen Zähnen,

Fig. 2

das Füllen der Preßform zur Herstellung des Ritzels gemäß Fig. 1,

Fig. 3

eine Stirnansicht eines Formstempels zur Herstellung des Bauteils gemäß Fig. 1,

Fig. 4

den ersten Preßschritt,

Fig. 5

die Form des im Preßschritt gemäß Fig. 4 geformten Grünlings,

Fig. 6

den Grünling gemäß Fig. 5 im Preßwerkzeug durch Durchführung der Umformung,

Fig. 7

das Preßwerkzeug gemäß Fig. 6 in Umformposition,

Fig. 8

perspektivisch einen Zahnring,

Fig. 9

eine Ausschnittvergrößerung für einen Zahn des Zahnrings gemäß Fig. 8,

Fig. 10

eine Aufsicht auf den Ausschnitt gemäß Fig. 9,

Fig. 11

einen Grünling für einen Zahnring mit hinterschnittener Innenverzahnung nach dem ersten Preßschritt,

Fig. 12

eine Abwicklung der Innenverzahnung am Grünling gemäß Fig. 1,

Fig. 13

die Innenverzahnung in der Ansicht gemäß Fig. 12 nach der Umformung,

Fig. 14

den Umformungspreßvorgang zu Fig. 13.

The invention is explained in more detail with reference to schematic drawings. Show it:

Fig. 1

as a finished component, a pinion with curved teeth,

Fig. 2

the filling of the mold for the production of the pinion according to FIG. 1,

Fig. 3

2 shows an end view of a die for producing the component according to FIG. 1,

Fig. 4

the first pressing step,

Fig. 5

the shape of the green body formed in the pressing step according to FIG. 4,

Fig. 6

5 in the press tool by performing the forming,

Fig. 7

6 in the forming position,

Fig. 8

perspective a gear ring,

Fig. 9

8 shows an enlarged section for a tooth of the toothed ring according to FIG. 8,

Fig. 10

9 shows a top view of the detail according to FIG. 9,

Fig. 11

a green compact for a toothed ring with undercut internal teeth after the first pressing step,

Fig. 12

a development of the internal toothing on the green compact according to FIG. 1,

Fig. 13

the internal toothing in the view according to FIG. 12 after the forming,

Fig. 14

the forming press operation to Fig. 13th

In Fig. 1 pinion 1 is shown in longitudinal section, the one has cylindrical base body 2 with at one end an external toothing 3 is provided. As can be seen in FIG. 1 lets, the teeth 4 of the external teeth 3 are so-called Arch teeth formed. The component is in the sintering process made from a sintered metallurgical powder. FIG. 1 shows the component in the final sintered state.

3, 4, 6 and 7 is the method of manufacture 1 based on the workflow in the press tool shown in more detail.

As can be seen from Fig. 3, the pressing tool consists essentially from an essentially encompassing the outer contour Die 5, a lower stamp 6 and an upper form stamp 7. The lower stamp 6 is initially filled by a predetermined dimension lowered and the mold space thus formed with sintered metallurgical powder 8 filled. Then the Form stamp 7 lowered, the outer contour 9 substantially corresponds to the inner contour 10 of the upper region of the die 5. 3 shows an end view of the die 7.

As can be seen from Fig. 4, the next step the die 7 inserted into the die 5 and simultaneously the lower stamp 6 moves upward, so that the stamp and lower stamps are guided against each other and the only poured powder filling into a solid green compact 1.1 compacted. The cylindrical base body 2 already receives its final shape, while the teeth 4 of the external toothing 3 in its lower area 4.1 due to the corresponding Shape of the die 5 already have the curved tooth course, while the upper area 4.2 the contour of a normal one Has straight teeth.

The intermediate shape of the green compact thus produced is from FIG. 5 seen. Here you can also see that after lifting of the stamp 7 of the green compact 1.1 by the lower stamp 6 can be ejected from the die 5 since there is no undercut is available.

6, the green compact 1.1 is in one second work step used in a die 5.1, the has a lower stamp 6.1, and its shape space essentially is formed by a tooth mold space 11.1 which in its geometry corresponds to the area 4.1 on the green compact (FIG. 2).

An upper die-shaped pressing tool 5.2 is with a Tooth form space 11.2 provided, which is identical to area 4.1 on Green compact (Fig. 5) is formed and which serves the area 4.2 on the green compact, which is also designed as a straight toothing to be reshaped so that this tooth area is the one shown in FIG Receives final contour. The upper matrix-shaped - Tool 5.2 is assigned an inner punch 12 so that the Lower stamp 6.1 and the inner stamp 12 when moving together the entire tool assembly can be performed so that apart from the reshaping of the external teeth, no relative displacements of the green body between the two tools 5.1 and 5.2. This pressing situation is shown in Fig. 7.

Comparing the geometry of the die 7, as it is 2 and 3 results, it can be easily seen that the tooth areas 4.2 in the specified manner not at all to be shaped with a simple form stamp, as this is in tongue-like tips would leak, so that neither the required Pressures still the required stability of the Tool is given. Surprisingly, it has now been shown that due to this multi-stage pressing process the intrinsically complicated Tooth geometry, as can be seen from FIG. 1, with high precision and even compaction of the powder can be carried out if by a die-like molding tool the green compact is partially reshaped so that the only preformed one Gearing in this area 4.2 encompasses and the application of high pressing forces and possibly also a densification of the green compact in the area of the external teeth allows.

Surprisingly, it has been shown that such forming of partial areas of a green compact that is actually pressed is possible and in terms of material density and shape accuracy leads to very good results.

Below are other examples of components which are advantageously produced by the method according to the invention can be. 8 shows a perspective view of one Ring 13 with an external toothing 14, as it is for example used as a clutch body in a manual transmission place. Like Fig. 8, but even more the enlarged, perspective view in Fig. 9 and the top view in Fig. 10, can be seen, the individual teeth 15 of the external toothing 14 not designed as normal straight teeth, but have a complicated geometric shape. The Tooth flanks 15.1 are shaped as involute surfaces however - as FIG. 10 shows - at an angle to one another. The end face 16 is straight, while the End face 17 by two inclined to each other, however flat surface areas 17.1 is formed.

Because the level of the necessary to manufacture this component Press tool aligned perpendicular to the axis A of the component is, d. H. the required ram is in the direction the axis A is guided, in particular Fig. 10 can be seen, that such interlocking due to the given undercut not molded with a simple die can be. This can also be done in the manufacture of this component be moved that in a first molding step the ring body and the external toothing is shaped with the end faces 17.1 is, so that the subsequent side surfaces 15.1 are designed as "straight teeth". In the second forming step is then shaped again with a matrix Tool on the already pressed green compact the final Forming the tooth flanks 15.1 causes, not only the mutual Inclination in the axial direction, but also the Involute surfaces are formed.

11 is a green compact as a further design example 18 shown for a ring with internal teeth. The Green body shown in Fig. 11 is analogous to that based on 2 and 4 described method as the basic component shape manufactured. 11 is on a ring body 18.1 only one tooth 19 of the internal toothing in a side view and in Fig. 12 are a plurality of teeth 19 in a processing of the internal toothing shown in a supervision. Such a contoured green body can be in one first pressing step analogous to the representation according to FIGS. 2 and 4 produce as basic component shape including the special one Contouring the teeth 19.

The application case shown here, for example, is required however, a tooth shape with undercuts, as shown in Fig. 13 is shown. This tooth shape can be made by a pure one Pressing process because of the undercuts on both sides 20 no longer generate on the tooth flank. However, this is after the inventive method by a forming process possible, which - as indicated in Fig. 14 - by rolling or rolling is possible. For this, the green compact 18 is opened held a rotatable counter element 21, for example on a roller or in a support ring. The undercuts 20 are then with an appropriately shaped rolling tool 22 as a pressure element that occurs when the counter element rotates 21 rolls on the inner surface of the toothing, by Forming manufactured. For technical reasons the undercuts 20 are shown coarsened in FIG. 13. In practical application it is by only slight depressions compared to the adjacent ones Areas of the tooth flanks.

Others can also be used in the process according to the invention Form undercuts and designs through reshaping, which cannot be produced in the "classic" pressing process. It these are practically all shapes for which pressing forces are required are essentially transverse to the pressing direction run to produce the basic component shape, for example 3 and 4 are necessary.

Claims (5)

1. A process for the manufacture of a sintered toothed wheel or toothed ring by forming a green compact from a sinter-metallurgical powder which is subsequently sintered, wherein in a first step the green compact is shaped by pressing from the sinter-metallurgical powder by means of axially guided pressing tools, with a basic component form, the geometry of which substantially corresponds to the final component form, except for partial regions of the teeth which have geometries which are not formable or formable only with difficulty in the pressing tools of the first step, and in at least one further step the partial regions of the teeth which have not had their geometry finally formed in the first pressing tool are deformed under pressure into their final form by non-cutting deformation on the green compact by means of separate deformation tools, so that the final component form is imparted to the unsintered green compact, and that then the green compact is sintered in its final component form to form the finished component.
2. A process according to Claim 1, characterised in that the deformation of the partial regions is effected by pressing and/or rolling.
3. A process according to Claims 1 or 2, characterised in that the deformation takes place in steps, wherein individual contours, in particular undercuts on the final component form, are produced in each case at least by one deformation stage.
4. A process according to one or more of Claims 1 to 3, characterised in that the green compact is pre-sintered before at least one deformation operation to increase the green strength.
5. A process according to one or more of Claims 1 to 4, characterised in that the component is sized as a green compact prior to a sintering operation and/or as a consolidated part after a sintering operation.

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