DE19806888A1 - Increasing wear resistance of workpiece - Google Patents

Abstract

A non-deformable wear resistant element (2) and a workpiece (1) are joined to one another by a cold or hot forming process.

Description

The invention relates to a method for increasing the wear resistance of a Workpiece according to the preamble of claim 1.

To increase the wear resistance of a workpiece, it is known to be burdened surface of the workpiece by a material of greater hardness than the work to protect piece material. Non-formable materials are particularly suitable for this fe such as hard metal or ceramic, hereinafter referred to as core materials.

Connections between ceramic materials or hard metals and a me tall or non-ferrous metal as a workpiece are currently at the basic joining techniques form locking, friction locking and material locking are generated.

Non-detachable connections are currently mainly made by the process Soldering, welding, shrinking and various bending processes, e.g. B. Bör deln or rotary pressure forming, realized.

Processes are predominantly used for mechanically highly stressed connections soldering (e.g. high temperature or active soldering) and welding in Fra ge.

The disadvantage of the processes of soldering and welding are the high manufacturing cost, as well as mostly the need adapted to the expansion behavior To use additives and / or intermediates, or constructive measures take, which compensate for the different coefficients of thermal expansion to reduce tension.

The invention has for its object a method for increasing the Ver Wear resistance of a workpiece according to the preamble of claim 1 to improve that with simple means cheaper an extremely durable Ver bond of the core material with the workpiece is reached. The still should Dimensions of the workpiece are retained.

According to the invention this object is achieved in that the core material Cold extrusion or hot extrusion of the workpiece material with the workpiece is positively connected.

The process according to the invention is a forming process in which pressure or Push-pull made a plastic change in the shape of a solid body becomes. The material properties and the dimensions of the body are retained Cold extrusion is an extrusion without additional heat input into the building parts or tools before or during forming. By reshaping however, heat can / will be generated. Hot extrusion takes place during the A heat supply.

A fundamentally new idea of the process is the plastic change of the work piece material, advantageously steel or non-ferrous metal, in extrusion and the non-formability of the ceramic sintered materials with high grain boundary strength based on dense, high-melting metal oxides, carbides and nitrides or of hard metals and hardened metals to make a non-releasable connection manufacture. The sintered materials, the hard metal or the hardened metal of the Core materials is extrusion designed so that the plastic deformation of the Metals / non-ferrous metals are not hindered, rather promoted, and the sintered material fe or the hard metal with regard to their material properties, in particular the Strength properties, not to be overloaded. Outside and inside contours of the Workpieces are based on the manufacturability of the tools.  

The connection is through the use of this new technology (time and material savings) significantly cheaper.

To the ceramic sintering plant particularly suitable for the present invention substances include oxide ceramics, such as. B. aluminum oxide, zirconium oxide, magnesium oxide Mixtures of aluminum oxide and zirconium oxide, silicon nitride, such as B. sintered Silicon nitride (SSN), hot pressed (HPSN) or gas pressure sintered (GPSN) silicon umnitrid, silicon carbide, such as. B. densely sintered silicon carbide (SSiC), silicon infil silicon carbide (SiSiC), dispersion ceramics, silicate ceramics as well as a mixture of titanium carbide and alumina. In the context of the present invention who those materials - magnesium oxide Calcium oxide and yttrium oxide and other sintering aids in small amounts contain, which usually z. B. added as grain growth inhibitor.

The particularly suitable hard metals in this invention include all hard metals which have strength values of σ _B <350 N / mm ² .

The particularly suitable hardenable metals include, for example, all of the metals Material group 1.2379.

To achieve a security against rotation or higher strength of the connection, who the secondary form elements suitable in the core materials, such as B. rounded ker ben and / or surfaces or cavities and / or undercuts incorporated or creates special surface qualities.

In a particularly advantageous embodiment, the secondary form elements are one on the Knurling on the outside. Advantageously, the Core material to the outside of the workpiece. This is an even better ver the core material is anchored in the workpiece.  

According to the invention, a press sleeve with egg is advantageously used as the press tool ner bore used, in which a movable punch the workpiece with the Core material connected by cold extrusion or hot extrusion. Here will the core material in the workpiece or vice versa the workpiece in the core plant pressed material until the workpiece material becomes flowable under pressure and the Core material flows around. Favored by the cold ver Fixing the workpiece material creates a permanent, extremely strong connection of the core material with the workpiece.

Advantageously, in the bore in the press sleeve as a counter bearing for the Workpiece or the core material provided a sliding ejector. This Ejector is used to eject after extrusion, i.e. H. to push out of the finished workpiece from the press sleeve.

As a counter bearing for the workpiece can also be in a special advantageous embodiment form a constriction in the bore in the press sleeve. With the The ejector described above can be used to extrude the workpiece be pushed out of the press rifle.

Depending on the required application, it is also appropriate to use the stamp as Form hollow punches. In this case, the pressurization only occurs an annular outer region of the hollow punch. It also makes sense in special Cases when the stamp on its face towards the workpiece or core material End has a distance from the hole in the press sleeve.

In a special embodiment, there is a further displaceable and force-transmitting in the stamp openable stamp arranged. With this further stamp the order can be Controlling the shaping of the workpiece material.

This method is advantageously used for workpieces of valve systems, in particular special valve trains of internal combustion engines used. This includes e.g. B. one of  the camshaft driven tappet or the adjusting screw of the Kipphe bels.

Further features of the invention emerge from the figures, which are below are written. It shows:

Fig. 1 the valve train of an internal combustion engine having advantageous Anwendungsfäl len of the invention,

FIG. 2a, b a core material such. B. as an insert for a plunger in plan view ( Fig. 2a) and as a section ( Fig. 2b),

Fig. 3 is a set screw of a valve drive of an internal combustion engine,

Fig. 4a, b schematically illustrates the well-forward extrusion,

Fig. 5a, b schematically illustrates the well-backward extrusion,

Fig. 6a, b schematically the hollow-forward extrusion,

Fig. 7a, b schematically the hollow backward extrusion,

Fig. 8a, b schematically illustrates the full-forward extrusion or reduction,

Fig. 9a, b schematically the full backward extrusion and

Fig. 10a, b schematically the lateral extrusion or swaging.

In Fig. 1, the valve train of an internal combustion engine is shown schematically. It consists essentially of a camshaft 11 , a tappet 12 , a bumper 13 , egg nem rocker arm 14 with a rocker arm axis 15 , an adjusting screw 16 , a valve 17 with spring plate 18 , valve guide 19 and valve spring 20th Some of these parts are very susceptible to wear. It is known to increase the wear resistance on the tread of the camshaft 11 on the plunger 12 to attach a core material 2 with a greater hardness than the material of the plunger 12 , for. B. by soldering welding, shrinking or the like. As the material of the core material z. B. hard metals, hardened metals or ceramics are used.

According to the method of the invention, a non-deformable core material 2 is made by cold extrusion or hot extrusion with the workpiece, here, for. B. the plunger 12 , positively connected.

In FIGS. 2a, 2b, a core material 2 is z. B. as an insert in a plunger in plan view ( Fig. 2a) and as a section ( Fig. 2b) shown. The core material 2 is designed here as a disk and has knurling 3 on its circumferential edge to prevent rotation. The outside 21 of the core material 2 tapers to the outside of the workpiece. In this case, the core material 2 consists of a sintered ceramic, namely of silicon nitride Si ₃ N ₄ .

Fig. 3 shows, as another example, a 16 adjusting a valve drive of an internal combustion engine (see also Fig. 1). At the end facing towards the valve end of the adjusting screw 16, a workpiece 1 is fixed by means of extrusion, said ses workpiece 1 is positively connected with a ceramic 23 by extrusion.

In the following FIGS. 4 to 10 each schematically shows a tool for performing the method according to the invention. FIGS. 4a, 5a, 6a, 7a, 8a, 9a, 10a respectively show the workpiece in the tool prior to bonding, and Fig. 4b, 5b, 6b, 7b, 8b, 9b, 10b after bonding.

Fig. 4a, b, the well-forward extrusion schematically. Here, a bore 5 is made in a press sleeve 4 , in which a plunger 6 and an ejector 7 are slidably arranged. The ejector 7 serves as a counterbearing for the punch 6 and after the connection for pressing out the workpiece 1 during the pressing process. The workpiece 1 and the core material 2 are located between the ejector 7 and the punch 6 . The core material 2 is a sintered ceramic and the workpiece 1 is steel or non-ferrous metal. The core material 2 rests on the ejector 7 and has an elevation 23 facing the workpiece 1 . During the pressing process, the punch 6 presses the workpiece 1 onto the core material 2 so that the material of the workpiece 1 begins to flow and flows around the elevation 23 of the core material 2 . The result is shown in FIG. 4b, namely the positive connection. After the cold extrusion process, the punch 6 is retracted and the workpiece 1 is pushed out with the ejector 7 . Hot extrusion is similar, except that additional heat is added here.

Fig. 5a, b shows schematically the cup back extrusion. This is very similar to the cup forward extrusion according to FIGS. 4a, b, only here the core material 2 is pressed into the workpiece 1 .

Fig. 6a, b schematically shows the hollow-forward extrusion. As a special feature, the bore 5 in the press sleeve 4 has a constriction 8 . This constriction 8 serves as an abutment for the workpiece 1 during cold extrusion. The work piece 1 additionally has a recess 24 and the core material 2 has an adapted pin 25 , wherein the pin 25 is inserted into the recess 24 before the connec. During the connection, the workpiece is pressed beyond the constriction 8 in the direction of the ejector 7 . The ejector 7 is pushed back and only serves to push out the workpiece 1 after the connection. After the connection, a cavity 26 is created in the recess 24 present before the connection.

Fig. 7a, b schematically shows the hollow backward extrusion. The core material 2 rests on the ejector 7 , which in turn has a pin 25 facing the material, which is inserted in a recess 24 of the workpiece 1 . As a special unit, however, the stamp 6 is designed as a hollow stamp. Therefore, only the outer area of the workpiece 1 is subjected to cold extrusion. After the connection, as already shown in FIG. 6 b, a cavity 26 in the workpiece 1 is created.

Fig. 8a, b, the full-forward extrusion shows or reduction. Here in the drilling 5 again a constriction 8 is formed as a slope on which the workpiece 1 is seated. After connecting, the ejector 7 only serves to push out the workpiece 1 . A recess 24 is made in the workpiece 1 , into which the core material 2 is inserted. In this embodiment, the punch 6 is at a distance 9 from the bore 5 in the press sleeve 4 . The diameter of the punch 6 resting on the core material 2 corresponds exactly to the diameter of the core material 2 . In cold extrusion, the workpiece 1 is reduced in diameter by the constriction 8 , whereby a firm connection is achieved.

Fig. 9a, b shows the full-backward extrusion. Here, the workpiece 1 is arranged on the ejector 7 , which is disc-shaped before the connection. On the workpiece 1 is set in a ring on the outer region of the core material 2 . During cold extrusion, the core material 2 is pressed down by the punch 6 , as a result of which the workpiece material flows into the cavity 10 .

Fig. 10a, b shows the lateral extrusion or swaging. Here, the workpiece 1 is T-shaped in cross section before the cold extrusion and the core material 2 is placed in a ring shape. In cold extrusion, the workpiece material flows around the core material 2 , so that the core material is surrounded on three sides by the workpiece 1 . Accordingly, the pin created by the backward extrusion is reshaped by a subsequent upsetting or transverse flow operation in such a way that the connection is tightened in the axial direction.

Combinations of the individual processes are in succession or in one operation possible. As an example, there is always talk of advantageous cold extrusion, it  However, the method of hot extrusion may also be useful be applied.

Claims (14)

1. A method for increasing the wear resistance of a workpiece, wherein the workpiece ( 1 ) with a non-deformable core material ( 2 ) is connected with a greater hardness than the workpiece material, characterized in that the core material ( 2 ) by cold extrusion or hot extrusion Workpiece material is positively connected to the workpiece ( 1 ). 2. The method according to claim 1, characterized in that the workpiece ma material is steel or non-ferrous metal. 3. The method according to claim 1 or 2, characterized in that the core material ( 2 ) is a hard metal or a hardened metal. 4. The method according to claim 1 or 2, characterized in that the core material ( 2 ) is a ceramic sintered material. 5. The method according to any one of claims 1 to 4, characterized in that the core material ( 2 ) secondary form elements such. B. has rounded notches and / or surfaces or cavities and / or undercuts. 6. The method according to claim 5, characterized in that the secondary formulas are a knurling attached to the outside ( 3 ). 7. The method according to any one of claims 1 to 5, characterized in that the core material ( 2 ) tapers to the outside of the workpiece. 8. The method according to any one of claims 1 to 7, characterized in that a bore ( 5 ) is arranged in a press sleeve ( 4 ) in which a displaceable punch ( 6 ) connects the workpiece ( 1 ) with the core material ( 2 ). 9. The method according to claim 8, characterized in that a sliding ejector ( 7 ) is provided as a counter bearing for the workpiece ( 1 ) or the core material ( 2 ) in the bore. 10. The method according to claim 8, characterized in that a constriction ( 8 ) is provided in the bore ( 5 ) as a counter bearing for the workpiece ( 1 ) or the core material ( 2 ). 11. The method according to any one of claims 8 to 10, characterized in that the stamp ( 6 ) is a hollow stamp. 12. The method according to any one of claims 8 to 11, characterized in that the punch ( 6 ) at its end facing the workpiece ( 1 ) or core material ( 2 ) a distance ( 9 ) to the bore ( 5 ) in the press sleeve ( 4 ) having. 13. The method according to any one of claims 8 to 12, characterized in that a further displaceable and loadable stamp is arranged in the stamp ( 6 ). 14. The method according to any one of claims 1 to 13, characterized in that this method for workpieces of valve systems, especially valve train ben of internal combustion engines is used.