DE102016112807A1 - Method for producing an annular sintered component - Google Patents

Abstract

The invention relates to a method for producing an annular sintered component (1), in particular a ring gear, comprising the steps in the stated order providing a sintering powder, pressing the sintered powder into a green compact, sintering the green compact and plasma nitriding or plasma nitrocarburizing the sintered component (1) in the sintered component (1) before the plasma nitriding or plasma nitrocarburizing in discrete surface areas zones (6) with a higher plasticization of the material, based on the present in addition to these zones (6) regions of the sintered component (1) are generated.

Description

The invention relates to a method for producing an annular sintered component, in particular a ring gear, comprising the steps in the stated order providing a sintering powder, pressing the sintering powder into a green compact, sintering the green compact and plasma nitriding or plasma nitrocarburizing the sintered component. Furthermore, the invention relates to an annular sintered component.

From the prior art, such as the JP 2003-313649 A , of the DE 10 2005 027 055 A1 , of the JP 32-78262 B2 or the KR 2001-0038555 A , It is known that components made of a sintered material for surface hardening of a plasma nitriding can be subjected. This type of surface hardening has the advantage that the sintered components can be produced in net-shape quality, since virtually no or a very small component distortion occurs during plasma nitriding. Thus, the production steps preceding plasma nitriding are of particular importance, since the at least approximate net-shape quality of the sintered components should also already be present in these production steps.

It is the object of the invention to provide an improved process for the production of sintered components in net-shape quality.

The object of the invention is achieved in the method mentioned above in that in the sintered component before the plasma nitriding or plasma nitrocarburizing in discrete surface areas zones with a higher plasticization of the material, based on the existing addition to these zones areas of the sintered component generated. Further, the object of the invention with the above-mentioned sintered component is achieved in which distributed over its outer and / or inner circumference zones with a higher plasticization of the material, based on the existing addition to these zones areas of the sintered component are formed.

The advantage here is that the effect of the springback of the sintered component during forming, in particular when calibrating the sintered component can be reduced or avoided by the formation of the higher plasticized areas or zones in the sintered component. The term "spring back" is understood to mean that sintered components are normally subjected to permanent plastic and non-elastic elastic deformation during forming. After the discharge of the sintered component, the elastic deformation degrades again, so that the sintered component thus partially returns to its original shape. This effect thus counteracts the shaping of the sintered component before plasma nitriding or plasma nitrocarburizing, as a result of which the net-shape quality can only be achieved with greater effort by mechanical processing. With the method according to the invention can be counteracted by the annular sintered component with a locally non-round, i. is made of the circular geometry deviating shape, however, which, viewed in the entirety of the sintered component, leads to a better accuracy of the circular geometry. Thus, the net-shape quality of the sintered component before plasma nitriding or plasma nitrocarburizing can be significantly improved.

Preferably, the sintered component is calibrated prior to plasma nitriding or plasma nitrocarburizing and thereby the zones with the higher plasticization of the material are produced during the calibration. It can thus be achieved that during the calibration, the sintered component can be calibrated under a remaining system, whereby the net-shape quality can be easily achieved by the aforementioned avoidance or reduction of the springback.

The zones with the higher plasticization can be produced extending in the axial direction and / or in the circumferential direction of the sintered component. It can thus be better taken to the concrete component geometry, especially if it has a toothing, as is the case with a ring gear. In addition, such oriented higher plasticized zones are easier to represent in a sintering process.

According to a particular embodiment variant, the zones with the higher plasticization of the material can be produced as grooves extending in the axial direction, whereby the resiliency of the sintered component can be better avoided. In particular, so that the remaining investment of the sintered component can be made possible during the calibration over the entire component thickness and the net-shape quality of the sintered component in the calibration stage and then can be achieved more easily.

It is advantageous if, for the formation of the zones with the higher plasticization, in particular during the calibration of the sintered component, the sintered component is given a polygonal shape, in particular this is calibrated in the calibration stage of the process to a polygonal outer contour, since this locally from deviates from the ideal geometry, but in its entirety, the rounding itself of the annular sintered component has a higher accuracy.

In addition to the execution of the sintered component with recesses in the higher plasticized zones but there is also the possibility that the green compact is produced in the zones with the higher plasticization of the material with an elevation. It can thus be reduced, the deviation from the circular geometry in local areas of the sintered component.

However, the latter embodiment of the method can also be carried out in combination with the recessed higher plasticized zones.

The method is used particularly advantageously if a sintered powder containing chromium is used as the sintering powder or if the sintered component consists of a chromium-containing sintered material. Chromium-containing sintered components naturally have a relatively high hardness. As a result, these sintered components can only be calibrated to a limited extent since they tend to be more prone to the above-mentioned effect of springback and thus do not hold the shape which they are given when calibrating. By using the method or the formation of the higher plasticized zones, springback can be counteracted so that chromium-containing sintered components of a net-shape production are more accessible.

For a better understanding of the invention, this will be explained in more detail with reference to the following figures.

Each shows in a simplified, schematic representation:

1 a sintered member in the form of a ring gear;

2 a section of the sintered component after 1 ;

3 the sintered component after 1 in cross-section;

4 a detail of a green compact for producing a sintered component;

5 the clipping after 4 after calibration.

By way of introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component names, the disclosures contained in the entire description can be mutatis mutandis to the same parts with the same reference numerals or component names. Also, the location information chosen in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and these position information in a change in position mutatis mutandis to transfer to the new location.

In 1 is a sintered component 1 shown in the form of a ring gear. This is known to be annular and has an internal toothing 2 on. Such sintered components 1 Needless to say, there is no need for further discussion.

It should be noted at this point that the method described below can be applied not only for the production of ring gears. Rather, according to the method annular sintered components 1 can be prepared per se, which optionally instead of or in addition to the internal teeth 2 have an outer toothing.

Particularly preferred is the process for producing thin-walled sintered components 1 applied. The term "thin-walled" is thereby a thickness 3 of the sintered component 1 in the radial direction perpendicular to an axial direction 4 runs, understood, which is much smaller than half the difference between the outer diameter and the inner diameter of the sintered component 1 , The fat 3 is doing between the root circle of the internal teeth 2 and a maximum outer diameter 5 of the sintered component 1 measured, like this in 1 is shown. If the sintered component 1 having only external teeth, is the thickness 3 Accordingly, to measure between the root circle of the toothing and the inner diameter. Should the sintered component 1 both an internal toothing 2 as well as external teeth, is the thickness 3 between the two foot circles of the gears to measure. In particular, a thin-walled sintered component 1 a sintered component 1 the condition da / thickness 3 = 10 to 100, where there is the outer diameter 5 is. The maximum outside diameter 5 of the sintered component 1 is the largest outside diameter 5 , this sintered component 1 having.

The sintered component 1 is produced by a sintering process. For this purpose, a sintered powder, which is prepared from the individual (metallic) powders by mixing, wherein the powder can optionally be used pre-alloyed, produced a green compact in a corresponding mold. The green compact is dewaxed in the sequence at ordinary temperatures and sintered in one or two stages or multi-stage and then preferably cooled to room temperature. The sintering can take place, for example, at a temperature between 1100 ° C and 1350 ° C.

Since these procedures and the process parameters used therein are known from the prior art, reference is made to avoid repetition to the relevant prior art.

As a sintered powder from which the sintered component 1 is prepared, a chromium-containing powder is preferably used. For example, this powder may contain 0.1 wt% to 5 wt% chromium, 0.1 wt% to 0.8 wt% carbon, 0 wt% to 2 wt% molybdenum, and 0 Wt .-% to 2 wt .-% nickel, with the remainder iron forms.

If appropriate, customary processing auxiliaries, such as pressing aids and / or binders, may also be added to the sintering powder in the usual proportions. These proportions relate to the entire powder mixture. By contrast, the abovementioned proportions of the metallic powders are based on the totality of the metallic fractions.

After sintering, the sintered component becomes 1 Hardened to improve wear resistance. Hardening is carried out by plasma nitriding or plasma nitrocarburizing, including in the treatment chamber for the sintered components 1 at least one nitrogen source and optionally at least one carbon source is present. The sintered components 1 are preferably cleaned in the plasma before the heat treatment, optionally after the previous removal of oils and fats in a cleaning plant. The cleaning preferably takes place by means of sputtering. Plasma nitriding or plasma nitrocarburizing of the sintered component 1 can be carried out at a temperature of 350 ° C and 600 ° C in the period of 1 hour to 60 hours at a voltage between 300 V to 800 V and a pressure of 0.1 mbar to 10 mbar.

Before the sintered green compact is plasma nitrided or plasmanitrocarburized, it is envisaged that it will be calibrated. By calibrating the dimensional accuracy of a sintered component is known to be improved, so that the sintered component 1 after calibration has its nominal dimensions. It can thus, among other things, distortions of the sintered component 1 be compensated from previous procedural steps. However, it may happen that the sintered component 1 becomes slightly larger during plasma nitriding or plasma nitrocarburizing. This can be during the shaping or during calibration of the sintered component 1 are taken into account by calibrating it to a dimension that is smaller than the nominal dimension.

Calibrating the sintered component 1 is done with the help of a calibration matrix. During the calibration, it may be provided that in discrete surface areas zones 6 (or areas) with a higher plasticization of the material, based on the present in addition to these areas areas of the sintered component 1 , are generated as in 2 is indicated by dashed lines.

By the term "plasticization" is meant a plastic deformation in the sense of the present description. In the higher plasticized areas of the sintered component 1 So this is subjected to a higher plastic deformation.

According to a first embodiment of the method, the partially higher plasticization of the material of the sintered component 1 be achieved by using a Kalibriermatrize at the points where the zones 6 of the higher plasticized material to arise, tool webs. These tool bars are pressed during calibration, ie during the depression of the sintered component 1 into the calibration die, into the surface of the sintered component 1 a, whereby on the surface of permanent depressions 7 arise in 2 are shown by way of example. To these depressions 7 around it become the higher plasticized zones 6 educated.

A depth 8th the wells 7 is preferably selected from a range of 1 % to 50%, in particular from 1% to 10%, of the thickness 3 (Wall thickness) of the sintered component 1 ..

The recesses are preferred 7 and thus the higher plasticized zones 6 at regular intervals over the entire outer circumference of the sintered component 1 formed so that the sintered component 1 receives a polygonal outer contour. For example, the depressions 7 in radial extension of tooth feet 9 the internal toothing 2 of the sintered component 1 be trained as in 2 is shown, wherein according to a further preferred embodiment in radial extension of each tooth root 9 the internal toothing 2 such a depression 7 and the associated higher plasticized zone 6 is trained. At these points occur during calibration or when pressing round higher voltages than in the remaining areas, so for example in the middle of the tooth, so that the effect of higher plasticization is greater because during plasticizing these stresses are at least partially degraded.

It can with this embodiment, for example, the wells 7 be carried out with a smaller one.

Alternatively or additionally, such depressions 7 and the associated higher plasticized zones 6 also in the area of internal toothing 2 be formed, in particular in the tooth roots 9 as is also in 2 is shown, and here again the effect can be increased for the reasons mentioned.

The wells 7 and thus the higher plasticized zones 6 but can also be formed in other places, for example in tooth flanks 10 and / or the teeth heads 11 the internal toothing 2 and / or other locations than those on the outer periphery of the sintered component 1 ,

The wells 7 For example, they may have an at least approximately triangular, trapezoidal, square, round, etc., cross-section (in the axial direction 4 considered), wherein the corners or edges are preferably made rounded, as shown in 2 is shown.

The zones 6 with the higher plasticization may be in the axial direction 4 and / or in the circumferential direction of the sintered component 1 be made extending. The zones are preferred 6 with the higher plasticization of the material than in the axial direction 4 running grooves 12 produced, this according to a further preferred embodiment over the entire width 13 of the sintered component 1 to be made extending, as is apparent 3 is apparent.

But it is also possible, although not preferred, that the depressions 7 or the grooves 12 only over a partial area of the width 13 of the sintered component 1 be formed extending.

In the 4 and 5 another embodiment of the invention is shown. It is also possible that the higher plasticized zones 6 not via the aforementioned tool bars and the recesses produced thereby 7 in the sintered component 1 but that the green compact in the zones 6 , in which a higher plasticization of the material is formed, with an elevation 14 is made, as shown schematically in 4 is shown. This overshoot will be in the calibration matrix 14 then at least approximately completely, in particular completely, leveled, ie that the material of the elevation 14 in the sintered component 1 forming the higher plasticized zone 6 is pressed in, so that the outer periphery of the sintered component 1 is made with the desired round, in particular circular, geometry, as shown in 5 is shown.

Of course, this embodiment of the invention is also on the inner circumference of the annular sintered component 1 applicable.

It is further possible that the variant with the elevations 14 is combined with the embodiment with the tool webs in the die, so so so at the points where the tool webs to form the wells 7 for contact with the sintered component 1 arrive, the elevations 14 are formed or formed in the green compact.

Although not mentioned above, there is also the possibility in the context of the method that the sintered component 1 before calibrating and after sintering, a single or multistage re-compaction of the surface in a corresponding compaction die is performed.

It is further possible that as an alternative or in addition to the depressions 7 in the area of the tooth feet 9 and / or in the radial direction of these opposite to the end face of the sintered component such depressions 7 in at least one of the two axial end faces 15 , in particular in both axial end faces 15 be formed, for example by knurling, as in the left part of the 1 is indicated. It can thus the flatness of the sintered component 1 be improved in the sense of the foregoing.

The embodiments show possible embodiments of the sintered component 1 , It should be noted at this point that also various combinations of the individual variants are possible with each other.

For the sake of order, it should finally be pointed out that for a better understanding of the structure of the sintered component 1 this or its components have been shown partially uneven and / or enlarged and / or reduced.

LIST OF REFERENCE NUMBERS

1

sintered component

2

internal gearing

3

thickness

4

direction

5

outer diameter

6

Zone

7

deepening

8th

depth

9

tooth root

10

tooth flank

11

addendum

12

groove

13

width

14

camber

15

face

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2003-313649 A [0002]
• DE 102005027055 A1 [0002]
• JP 32-78262 B2 [0002]
• KR 2001-0038555 A [0002]

Claims (9)

Method for producing an annular sintered component ( 1 ), in particular a ring gear, comprising the steps in the stated order providing a sintering powder, pressing the sintering powder into a green compact, sintering the green compact and plasma nitriding or plasmonitrocarburizing the sintered component ( 1 ), characterized in that in the sintered component ( 1 ) prior to plasma nitriding or plasmanitrocarburizing in discrete surface areas zones ( 6 ) with a higher plasticization of the material relative to those adjacent to these zones ( 6 ) existing areas of the sintered component ( 1 ), be generated. Method according to claim 1, characterized in that the sintered component ( 1 ) is calibrated prior to plasma nitriding or plasmanitrocarburizing and that the zones of higher plasticization of the material are produced during calibration. Method according to claim 1 or 2, characterized in that the zones ( 6 ) with the higher plasticization in the axial direction ( 4 ) and / or in the circumferential direction of the sintered component ( 1 ) are made to extend. Method according to one of claims 1 to 3, characterized in that the zones ( 6 ) with the higher plasticization of the material than in the axial direction ( 4 ) running grooves ( 12 ) be generated. Method according to one of claims 1 to 4, characterized in that the sintered component ( 1 ) is calibrated to a polygonal outer contour. Method according to one of claims 1 to 5, characterized in that the green compact in the zones ( 6 ) with the higher plasticization of the material with an elevation ( 14 ) will be produced. Method according to one of claims 1 to 6, characterized in that a chromium-containing sintered powder is used as the sintering powder. Ring-shaped sintered component ( 1 ), characterized in that distributed over its outer and / or inner circumference zones ( 6 ) with a higher plasticization of the material relative to those adjacent to these zones ( 6 ) existing areas of the sintered component ( 1 ), are formed. Sintered component ( 1 ) according to claim 8, characterized in that it consists of a chromium-containing sintered material.

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