DE102010008654A1 - Method for producing a sintered or forged component - Google Patents

Abstract

A method for producing a component (10), in particular a connecting rod, with a bore (16) and an at least partially tempered bore surface (18) comprises the following steps: providing a sintered green body; - Providing a bore (16) in the green compact; - sintering the green compact; and - tempering at least part (18a) of the bore surface (18) without prior machining of the bore surface (18) to be tempered. As an alternative to a sintered green compact, a forged blank can also be provided. In this case, the blank is forged and a bore (16) is provided in the forged component (10) before at least part of the bore surface (18) is tempered without prior machining.

Description

The invention relates to a method for producing a component, in particular a connecting rod, with a bore and an at least partially annealed bore surface.

Connecting rods for motor vehicle internal combustion engines are usually produced in a forging, sintering or sintering / forging process. For connecting rods without separate sliding or roller bearings (so-called integral connecting rods), the inner surfaces of the connecting rod eyes (bore surfaces) represent the bearing surfaces which are tempered or coated due to the high stress.

In the DE 10 2006 015 888 A1 describes how in a connecting rod forged from a steel material, the small connecting rod eye can be tempered by inductive heat treatment or laser radiation. To reduce the heat distortion, only the bore of the connecting rod is heat treated, in such a way that a heat-treated zone does not reach to the axial edge of the hole.

However, the known method is limited to connecting rods, which are drop-forged from a steel material. In particular powder-metallurgically produced connecting rods of iron-based, carbon-containing powder are not included. When drop-forged Stahlpleueln for motor vehicle internal combustion engines (passenger car, commercial vehicle and motorcycle engines) pre-processing is required before tempering (full drilling), which leads to an increased effort in the production of the connecting rod. In addition, there is the risk of overheating of the near-surface material region during induction hardening with an HF generator. Further disadvantages are the narrow process parameter limits and the technical difficulties in the subsequent inductive tempering.

The object of the invention is to provide a cost effective and efficient method for producing a component, in particular a connecting rod, with an at least partially annealed bore surface, with which the above limitations and disadvantages are avoided.

This object is achieved by a method having the features of claim 1 and by a method having the features of claim 4. Advantageous and expedient embodiments of the method according to the invention are specified in the subclaims.

• – Bereitstellen eines Sintergrünlings;
• – Vorsehen einer Bohrung im Grünling;
• – Sintern des Grünlings; und
• – Vergüten wenigstens eines Teils der Bohrungsoberfläche ohne vorherige Bearbeitung der zu vergütenden Bohrungsoberfläche.

The inventive method for producing a component, in particular a connecting rod, having a bore and an at least partially annealed bore surface, according to a first aspect comprises the following steps:

• - providing a sintered green compact;
• - Provide a hole in the green body;
• - sintering of the green body; and
• - Tempering at least a portion of the bore surface without prior processing of the bore surface to be annealed.

The invention is based on the recognition that in a component with a bore to be annealed, in particular a connecting rod, in which the bore is not first incorporated after sintering, but is already present in the green, no further processing of the bore surface is required before this is remunerated. The method according to the invention therefore provides a preformed green compact which is sintered and the bore surface of which is directly subjected to a tempering process.

Overall, this results in a robust process in which the process parameter limits for tempering are wider than would be possible with components having a machined bore surface. In particular, the danger of overheating at the bore surface and at the bore edges is reduced. The method according to the invention makes it possible to produce reliably a hardening zone which runs off or does not leak towards the axial bore edges.

By the method according to the invention, the process chain is shortened in the powder metallurgical production of the component, since the hole is not formed after sintering and then still has to be processed; Thus, labor and costs can be reduced. Due to the shortened process chain, the area required for the processing machines is also reduced; Less cooling lubricant (KSS) tools are needed, and overall the energy required to manufacture the component is reduced. Disposal is also simplified, since less chips are produced during production.

• – Bereitstellen eines Schmiederohlings;
• – Schmieden des Rohlings;
• – Vorsehen einer Bohrung im geschmiedeten Bauteil; und
• – Vergüten wenigstens eines Teils der Bohrungsoberfläche ohne vorherige Bearbeitung der zu vergütenden Bohrungsoberfläche.

According to a second aspect, the method according to the invention comprises the following steps:

• - providing a forging blank;
• - forging the blank;
• - Provide a hole in the forged component; and
• - Tempering at least a portion of the bore surface without prior processing of the bore surface to be annealed.

In this case, the annealing of the bore surface follows a forging process, that is, it is assumed that a forged connecting rod, as it is used in particular in commercial vehicles. Here, too, arise due to the unnecessary previous processing to annealing bore surface substantially the same advantages as previously described in connection with a sintered component.

Details of the invention will be described below with reference to the accompanying drawings. In the drawings show:

1 a connecting rod in plan view;

2 the connecting rod 1 in longitudinal section; and

3 a sectional view of a Pleueldetails.

That in the 1 and 2 illustrated component 10 has a shaft 12 , a larger hole 14 and a smaller hole 16 on. The component 10 is designed as a connecting rod for a motor vehicle internal combustion engine, wherein the larger bore 14 a big eye for bearing a crankshaft and the smaller hole 16 a small connecting rod eye for supporting a piston pin corresponds. The following only applies to the in 3 shown in detail smaller hole 16 received.

The surface 18 the bore 16 is, as will be described in more detail later, depending on the requirement wholly or partially remunerated. In 3 is an example of a tempered sub-surface 18a shown. It can be seen that the remunerated part 18a the bore surface 18 extends only about 180 ° around the bore circumference here. The axial extent of the remuneration may vary; For example, a certain axial distance from the axial bore edge may be provided, which also depends on the outer shape of the bore 16 surrounding component section (here: the small connecting rod eye) can depend.

To the production of such a component 10 Efficient, measures are taken so that no (mechanical) processing of the surface to be annealed bore 18a must be carried out immediately before tempering.

In the case of a powder metallurgically produced component 10 For example, a sintered green compact made of an iron-based carbonaceous powder having a carbon content of 0.3 to 0.8% is provided. In the pre-pressed green body is at least the bore before the sintering process 16 , preferably also the outer shape of the bore 16 surrounding component portion (eg trapezoidal shape, bow shape, stepped shape) provided. The hole 16 can be formed by the pressing tool, with which the green compact is produced, or by a mechanical processing of the pre-pressed green compact.

In the subsequent sintering process, the thus pre-pressed and preformed green compact is compacted and cured by heat treatment below the melting temperature. It is assumed that the component 10 is edge-decarburized after sintering, at least in the area of the bore surface 18 although this is not necessarily so.

Without special machining of the bore surface 18 this is tempered after sintering. In this case, as already indicated above, the complete bore surface 18 , a ring cutout and / or a peripheral portion (segment) of the bore surface 18 be provided for compensation. A tempering of other sections of the component 10 is not scheduled.

The tempering of the bore surface 18 includes a heat treatment and is preferably done by induction or laser hardening. The parameters of the heat treatment are chosen so that a hardening depth of 0.2-1.5 mm based on the finished component is achieved. The machining allowance for equalizing the shape and position inaccuracies of the green body and / or the thickness of the edge-decarburized zone is maintained.

Subsequently, a tempering of at least the bore surface to be tempered takes place 18a , Annealing may be performed inductively in an RF generator, thermally in a continuous furnace, or with the aid of another suitable thermal process.

In the case of a component made of a steel material and produced by forging, a forging blank is provided instead of the sintered green compact. The steel material of the blank in turn has a carbon content of 0.3 to 0.8%.

When forging the blank, among other things, a contour of the later bore 16 preformed. The outer shape of the hole 16 surrounding component portion may be present on the blank before forging. Again, it is assumed that the component 10 after the forging is randentkohlt.

After forging becomes the hole 16 in the forged component 10 perforated. The punching of the hole 16 is done by means of a device integrated into a trimming tool, so that after trimming no separate working step is required in an additional processing machine.

The subsequent tempering of the bore surface 18 or part 18a this is done as described above - ie in particular without previous special machining of the bore surface 18 - By means of a heat treatment by induction or laser hardening and subsequent tempering. The process parameters are in turn chosen so that a hardening depth of 0.2-1.5 mm based on the finished component is achieved.

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

• DE 102006015888 A1 [0003]

Claims (11)

Method for producing a component ( 10 ), in particular a connecting rod, with a bore ( 16 ) and an at least partially annealed bore surface ( 18 ), the method comprising the steps of: - providing a sintered green compact; - providing a bore ( 16 ) in the green; - sintering of the green body; and - at least one part ( 18a ) of the bore surface ( 18 ) without prior processing of the surface to be tempered ( 18 ). Method according to claim 1, characterized in that the bore ( 16 ) is formed in the green compact before sintering using a pressing tool. Method according to claim 1, characterized in that the bore ( 16 ) is formed in the green compact before sintering by mechanical processing of the green compact. Method for producing a component ( 10 ), in particular a connecting rod, with a bore ( 16 ) and an at least partially annealed bore surface ( 18 ), the method comprising the steps of: - providing a forging blank; - forging the blank; - providing a bore ( 16 ) in the forged component ( 10 ); and - tempering at least a portion of the bore surface without prior machining of the bore surface to be annealed ( 18 ). A method according to claim 4, characterized in that during the forging of the blank, the contour of the later bore ( 16 ) is preformed. Method according to claim 5, characterized in that the bore ( 16 ) in the forged component ( 10 ) is punched. Method according to claim 6, characterized in that the bore ( 16 ) is punched using a device integrated into a deburring tool. Method according to one of the preceding claims, characterized in that the tempering involves induction or laser hardening, preferably with a hardening depth of 0.2 to 1.5 mm. Method according to claim 8, characterized by a subsequent tempering of at least the hardened bore surface ( 18 ). Method according to one of the preceding claims, characterized in that the material of the green body or of the blank has a carbon content of 0.3 to 0.8%. Method according to one of the preceding claims, characterized in that the outer shape of the bore ( 16 ) is formed on the green body before sintering or on the blank prior to forging.

Images