EP4168195A1

EP4168195A1 - Method for producing a sintered component

Info

Publication number: EP4168195A1
Application number: EP20739868.6A
Authority: EP
Inventors: Franz Josef SCHLEIFSTEIN; Martin Joachim GERTLER; Ulla HAUFF
Original assignee: Schunk Sintermetalltechnik GmbH
Current assignee: Schunk Sintermetalltechnik GmbH
Priority date: 2020-06-23
Filing date: 2020-06-23
Publication date: 2023-04-26
Also published as: WO2021259455A1

Abstract

The invention relates to a method for producing a sintered component having a free volume, comprising the method steps of: - filling at least one sinter powder into a mold, - pressing the sinter powder and subsequent sintering, wherein an insert material specifying the free volume is present in the pressed sinter powder, said insert material being removed by a thermal process.

Description

Description Process for the production of a sintered component

The invention relates to a method for producing a sintered component with a free volume of predetermined geometry, such as an opening, channel, cavity, comprising the process steps:

- Filling at least one sintering powder into a mold,

- Pressing the sintering powder and then sintering.

Sintered products are used in a variety of ways, particularly in the automotive industry, e.g. as bearings or bearing shells, components for engines and gears, sieves, filters, friction and brake linings, gear wheels. But sintered products are also used for tools such as indexable inserts made of hard metals.

It is often necessary that channels, e.g. serving as cooling channels, run in the sintered products, which can only be formed during the pressing process if they run in the pressing direction. Otherwise, mechanical processing is required, which makes the product more expensive. Regardless of this, there are limits with regard to the course of the free spaces to be produced, i.e. free volumes. If, for example, channels have sections with differing longitudinal directions, discontinuities occur in the transition, which can lead to disruptions when fluids flow through them.

The object of the present invention is to develop a method of the type mentioned at the outset in such a way that sintered components are made available in which the free volume or volumes have a desired or basically any geometry can have, without there being any mechanical post-processing of the

Sintered component needs.

In order to achieve the object, it is essentially proposed that at least one insert material, which defines the free volume and is removed by a thermal process, is located in the pressed sintering powder.

In particular, the invention provides that the thermal process is carried out before and / or during and / or after the sintering, the thermal process preferably being the sintering itself.

The thermal process can be carried out, for example, by means of laser, infrared radiation and / or induction heating. The inlay material can be a solid body or, for example, pourable material such as powder or granules. Curable foam material that is introduced into a free space previously formed in the sintered material, which can also be referred to as a recess, can be used to produce a volume in the sintered component that has a desired, predetermined geometry that is simple, such as a sphere or cylinders, or highly complex, such as channels with sections deviating from one another longitudinal axes, can be designed with complex geometry preferably insert elements are used, which are at least partially surrounded by the sintered material and specify the geometry of the free volume.

The at least one insert material can be removed by, for example, burning or gasifying the material of which the insert element is made.

The invention therefore provides that an insert element or a material, in particular pourable material such as powder material, introduced into the sinter powder in at least one recess that has or delimits the negative shape of the free volume to be formed is used as the insert material. Hydraulic pistons, gearwheels, chain wheels, bushings, rotors, pistons, camshaft bearings are to be mentioned in particular as sintered components.

The targeted creation of free space allows components such as oil to flow through them. Cavities can be used to reduce weight and reduce noise.

The sintering powder is especially an iron-based one such as Sint-D10 to Sint-D39 according to DIN 30910-4, March 2010. Other sintering powders based on copper or titanium are also possible, just to name other materials by way of example.

According to the invention, a method is made available in which free spaces are formed which show a desired geometric profile that is independent of the pressing direction. For example, channels can be formed which have sections with mutually different longitudinal directions that are not or not all of them in

Must run in the pressing direction. At the same time, the transition between the sections can be formed continuously, a possibility that is basically not given by mechanical processing or can only be done with a complex manufacturing process, which leads to a high cost burden.

There are various options for creating the free volume, such as an opening, channel, or cavity enclosed on all sides. In this way, part of the sintering powder can first be introduced into the pressing tool and then the insert element or elements can be inserted. Pre-pressing can then take place. The remainder of the sintering powder is then introduced and pressed with the possibly previously pre-pressed unit.

There is also the option of first filling the insert element into the mold or die and then the sintering powder in order to finally carry out the pressing process.

It is possible to create free volumes which, viewed in the pressing direction, have cross-sections that differ from one another. For this purpose, it is provided in particular that a tool with two press rams is used, those from opposite one another Pages are adjusted in the direction of the insert element or elements predetermined for the free spaces.

There is the possibility of using the insert element or elements to form one or more possibly unconnected cavities and / or a cavity with sections whose main axis direction enclose an angle other than 180 °.

The insert element or elements can extend up to at least one pressing tool delimitation, such as a wall, which extends transversely to the pressing direction.

The pressing tool used can be one with a dome or slide extending in the pressing direction, from which at least one insert element or a recess for the insert material to be filled extends.

At least one material from the group consisting of plastic, wax or a combination of these is used as the material for the inlay material. It is provided in particular that when the sintering powder contains a wax, the insert material consists of or contains the same wax material.

Amide waxes should be mentioned as waxes to be emphasized.

On the basis of the teaching according to the invention, sintered bodies with desired cavities, which also include through bores or openings, can be made available without the complex mechanical processing required according to the prior art for forming them.

Cavities running completely within the sintered component can be formed, a possibility which is excluded by machining the sintered component.

The inlay material forms a mustard shape that evaporates during sintering.

The insert element is volatilized during the sintering process due to the high temperatures, which are in the range of 1,100 ° C when using iron-based materials, so that the space formed by the insert material such as the insert element or elements when filling the pressing tool is available in the sintering powder after sintering, which is required, for example, when using the sintered component to perform functions such as the flow of fluids and the supply of lubricating oil etc., to enable. The cavity can also have geometries that cannot be achieved in principle with mechanical processing. Cavities can be created with a geometry that cannot be produced with exclusively axial pressing. In general, it should be noted that the materials used for the sintering powder are those based on aluminum, titanium, copper or tungsten, in particular iron-based.

The sintering temperature should in particular be equal to or greater than 70% of the melting temperature of the powder.

The sintering powder is preferably only pressed axially to produce the sintered component. Further details, advantages and features of the invention emerge not only from the claims, the features to be taken from them - individually and / or in combination - but also from the following description of preferred exemplary embodiments that can be taken from the drawing. Show it:

1 shows a basic illustration of a pressing tool,

2 to 7 basic representations of bodies made of pressed sintering powder with insert elements present therein,

8 shows a further embodiment of a pressed body made of sintered powder with an insert element, FIG. 9 is a sectional view of FIG. 8,

10 sectional views of bodies made of pressed sintering powder with insert elements,

11 shows a further longitudinal section of a body made of pressed sintering powder,

FIG. 12 shows a cross section through the body according to FIG. 11 and FIG. 13 shows basic representations of the positioning of insert elements.

The teaching according to the invention is explained purely in principle with the aid of the drawing, based on which sintered components with free volumes, simple or complex geometries such as cylinders, spheres, through channels can be produced without mechanical processing being necessary to form the free volumes, i.e. the free spaces. However, this does not rule out post-processing if necessary.

In the figures, the pressed bodies are shown with one or more insert elements, which are then lost during a thermal process and thus the desired cavities are available. By using the

Insert elements, however, are not restricted to the teaching according to the invention. Rather, instead of insert elements that are formed by inherently rigid bodies, cavities can also be formed by forming depressions, recesses or other geometric indentations in the sintering powder, into which insert material is introduced or filled, which is removed during a thermal process to be carried out , so is lost

The corresponding inlay material is, in particular, a pourable material, such as powder or granulate. However, foam material can also be used if it does not undergo such a change in geometry during the pressing process that the desired free space cannot be formed in the sintered body.

If the removal of the insert element, which is to be understood as a synonym for insert material, is carried out in accordance with the following explanation in the thermal process of sintering removed, this likewise does not result in a restriction. Rather, a thermal process can also be carried out before or after sintering or both before and during sintering or also during sintering or after sintering or before, during and after sintering. In this respect, material-dependent thermal processes have to be carried out in order to remove the insert material and thus to form the desired cavities in the sintered body. Cavity also means that a free volume extends as far as the edge region of the sintered body, that is to say is accessible from the outside in order, for example, to fill a fluid into a corresponding cavity or to allow a fluid to flow through corresponding free volumes.

In the following, sintering powder on an iron base material is also used, which can be materials Sint-D10 to Sint-D39 according to DIN 30910-4 (March 2010). However, this does not restrict the invention. Rather, other suitable sintering powders, e.g. based on copper or titanium, can also be used.

In general, it should be noted that pre-pressing can be carried out at a pressure of up to 500 MPa. A pressure of between 200 and 1,000 MPa can be used to press the green body, i.e. before the sintering process is carried out.

If the sintering powder is iron-based, the inlay material should be used at temperatures below 1,000 ° C. be removable.

In Fig. 1, a pressing tool is shown in principle, by means of which, for example, iron material-based sintering powder, which may contain admixtures of carbon, molybdenum, nickel, copper and especially wax, is pressed into a molded body, which is then sintered at temperatures of e.g. 1,120 ° C. When the powder is pressed, a pressure of the order of magnitude of 800 MPa can act without the invention being restricted by the numerical values given.

The pressing tool consists of a one-part or multi-part die 12 which defines the circumferential shape of the sintered body to be produced. In the exemplary embodiment, two punches 16, 18 act in the axial direction on the sintering powder filled into the interior of the die 12, as is symbolized by the arrows 20, 22. In order to produce a free volume in the sintered component to be produced, which is formed after the sintering process without the need for mechanical processing, an insert element 24 is introduced into the powder 14 before the pressing process, which, according to FIG. 1, can be a rod, for example , which contacts the inner walls 24 of the die 12 so that there is a through-opening in the sintered component.

The insert element 24, which is to be referred to as a loose form, can consist of a suitable plastic material, but in particular of a wax, specifically preferably of the wax that is mixed with the sintering powder.

The advantage of using wax is that pre-damage does not occur.

Amide waxes should be mentioned as the wax material to be emphasized.

Independently of this, the insert element 24 must be press-resistant, that is to say it must retain its shape during pressing.

During sintering, the insert element is volatilized e.g. by burning or gasifying.

Due to the teaching according to the invention, there is the possibility of forming openings not only starting from the edge region of the sintered body, which do not extend in their longitudinal direction in the pressing direction (arrows 20, 22), but transversely and perpendicularly to this. If, for example, according to the state of the art, transverse openings are to be formed perpendicular to the axial pressing direction, radial pressing must also be carried out. Alternatively, mechanical processing can be carried out. All of these measures are complex and make the sintered components more expensive. The teaching according to the invention avoids the disadvantages. The teaching according to the invention also provides the possibility of forming free volumes within a sintered body which cannot be made available according to the prior art. In Fig. 2 an example of an insert element 26 is shown in principle, which is designed as a ring element and rests against the inner wall of the die during pressing. There is the possibility that the insert element - as shown in the drawing - has edges, a possibility which, according to the state of the art, could only be realized with a considerable amount of time-consuming mechanical machining of an annular groove.

From FIG. 3 it can be seen that within the pressed body made of sintered metal powder, in particular iron-based, a cavity is formed in the interior by means of an insert element 28, which is thus completely surrounded by the sintered powder material 14.

FIGS. 4 and 5 are intended to make it clear that channels can be formed in a sintered body to be produced which have mutually offset sections and can run in any direction to the pressing direction 20, 22.

Thus, in FIG. 4, an insert element 30 is introduced into a sintered metal powder 14, which has two outer sections 32, 34 and an inner section 36 connecting these, which continuously merge into one another. The sections 32, 34 run perpendicular to the pressing direction 20, 22. The connecting section 36 can run inclined to the pressing direction.

The insert element 38 according to FIG. 5 likewise has two outer sections 40, 42 and an inner section 44 connecting them. The outer sections 40, 42 run parallel to the pressing direction 20, 22, but offset from the central axis, whereas the connecting section 44 is inclined to the pressing direction 20, 22 and continuously merges into the outer sections 40, 42.

If a dome or slide extending in the pressing direction 20, 22 is not used in the exemplary embodiments of FIGS. 1 to 5, the insert elements 24, 26, 28, 30, 38 can of course also be used to produce sintered bodies Pressing domes and / or slides can be used.

FIGS. 6 and 7 show examples of insert elements 46 and 48 which have a T-geometry in section, with FIG. 6, viewed in the pressing direction Cross section of the outer section 50 is larger than the inner section 52. Conversely, the situation arises from the exemplary embodiment of the insert element, ie the inner section 54 has a larger cross section than the outer section 56. The outer section 50 of the insert element 46 can be designed circumferentially, that is to say ring-shaped, in order to form an annular channel or groove from which protrude sections which run at a distance from one another and have the smaller cross section 52 and form bores.

Conversely, in the case of the insert element 48, the inner section 54 can be designed in the form of a ring as a groove from which individual outer sections 56, 58 extend, which perform the function of bores.

In FIGS. 8 and 9, an insert element 58 is pressed with the sintering powder 14, which starts from the inner wall 25 of the die 12 and is angularly formed lying on the wall.

In FIG. 10, sectional representations of two bodies made of pressed sintering powder 14 are shown, one half each, wherein the insert element 46 shown on the right can correspond to that of FIG. 6. On the left, an insert element 60 is shown, which consists of two sections of differing cross-sections.

Of course, the corresponding insert elements can also be designed and assembled in several parts. Insert elements in the powder can also be positioned at a distance from one another. There are no limits to this. FIGS. 11 and 12 show an exemplary embodiment in which a pressing tool is used which has domes which form free spaces 62, 64. Insert elements 66, 68 extending obliquely to the pressing direction 20, 22 are then positioned in the sintering powder 14, via which a connection to the cavity 62, 64 is established, which is formed by the dome.

The pressing process itself is carried out in particular in such a way that part of the powder is first poured into the mold and then the insert element is introduced. This is followed by pre-pressing, for example with a pressure of 130 MPa. Then the rest of the material is filled in and the pressing process is carried out at a pressure of, for example, 800 MPa.

Alternatively, there is also the possibility of first introducing the insert element into the mold, which is then filled, in order to then carry out the pressing process.

After the body has been removed from the mold, the sintering process is carried out, in particular at a temperature in the region of 1,120 ° C. if the sintering powder is an iron-based material which, as mentioned, can contain additives such as carbon, molybdenum or nickel copper and wax.

The insert element or elements present in the pressed powder body are preferably removed or volatilized during the sintering process, e.g. by melting, burning and / or gasifying.

The required temperature for the thermal process can be generated using e.g. laser, infrared radiation or induction.

With the aid of FIG. 13, various variants are to be shown purely in principle, which illustrate the positioning of the insert elements by way of example. The examples in brackets are intended to make clear that the free volumes in the sintered bodies produced on the basis of the insert elements can also be produced in the classic way, i.e. by mechanical processing or by using domes or slides of the pressing tool or by radial pressing.

In principle, the bodies are produced exclusively by axial pressing.

In particular, it can be seen that when cavities run in the sintered body at a distance from the top and bottom of the body on which the press rams act, the classic methods cannot be used, provided that the pressing is only axially. Cavities running inside the sintered body cannot be formed by pressing and mechanical work either.

Claims

Claims method for producing a sintered component

1. A method for producing a sintered component with free volume, such as an opening, channel, cavity, comprising the process steps: - Filling at least one sintered powder into a mold (12),

- Pressing the sintering powder and then sintering, characterized in that the pressed sintering powder contains at least one insert material which defines the free volume and which is removed by a thermal process.

2. The method according spoke 1, characterized in that the thermal process is carried out before and / or during and / or after sintering.

3. The method according to claim 1 or 2, characterized in that the insert material is burned and / or melted and / which is gasified during the thermal process.

4. The method according to at least one of the preceding claims, characterized in that the thermal process is carried out by sintering.

5. The method according to at least one of the preceding claims, characterized in that an insert element (24, 26, 28, 30, 38, 46, 48, 58, 60) or one having or delimiting at least one negative shape of the free volume is used as the insert material Recess in the sinter powder introduced material, in particular pourable material such as powder material, is used.

6. The method according to at least one of the preceding claims, characterized in that the insert material is completely surrounded by the powder before pressing.

7. The method according to at least one of the preceding claims, characterized in that the insert material extends to at least one pressing tool delimitation, such as a wall, which extends transversely to the pressing direction (20, 22).

8. The method according to at least one of the preceding claims, characterized in that the pressing tool used is one with a dome extending in the pressing direction (20, 22) from which at least one insert material proceeds.

9. The method according to at least one of the preceding claims, characterized in that first the insert material or the insert element (24, 26, 28, 30, 38, 46,

48, 58, 60) into the mold and then the or part of the powder is introduced into the mold.

10. The method according to at least one of the preceding claims, characterized in that part of the powder and the insert material are introduced into the mold and pre-pressed and then the remainder of the powder remaining on the unit thus formed are introduced into the mold and pressed with the unit.

11. The method according to at least one of the preceding claims, characterized in that at least one material from the group of plastic, wax or a combination of these is used as the material for the insert material.

12. The method according to at least one of the preceding claims, characterized in that a wax-containing material based on iron, copper, titanium, aluminum and / or tungsten is used as the material for the sintering powder.

13. The method according to at least one of the preceding claims, characterized in that the powder with the insert material is exposed to a pressure P with 250 MPa <P <1,000 MPa.

14. The method according to at least one of the preceding claims, characterized in that the pressed iron-based sintering powder with the insert material during sintering at a temperature T with 750 ° C <T <1,300 ° C, preferably over a sintering time t with 15 min <t <45 min is suspended.

15. The method according to at least one of the preceding claims, characterized in that a wax is used for the material of the inlay material which corresponds to that which is added to the sintering powder or contains this.

16. The method according to at least one of the preceding claims, characterized in that by means of the insert element or elements (24, 26, 28, 30, 38, 46, 48, 58, 60) or the one or more recesses in the sintered powder, preferably pourable Inlay material, a cavity, in particular a passage opening, such as a channel, is formed with sections that continuously merge into one another and run offset to one another.

17. The method according to at least one of the preceding claims, characterized in that by means of one or more insert elements (24, 26, 28, 30, 38, 46, 48, 58, 60) or one or more recesses filled with the pourable material in the Sintered body, a cavity is formed with cross-sections that differ from one another when viewed in the pressing direction (20, 22).

18. The method according to at least one of the preceding claims, characterized in that by means of the insert element or elements (24, 26, 28, 30, 38, 46, 48, 58, 60) or the recesses formed with the pourable material, one or more optionally unconnected cavities are formed and / or that a cavity is formed as a plurality of sections with at least an angle a with a <180 ° enclosing longitudinal extensions.

19. The method according to at least one of the preceding claims, characterized in that an insert element (24, 26, 28, 30, 38, 46, 48, 58, 60) is used, by means of which a cavity with sections with continuously merging boundary walls is formed will.