Chain element

Abstract

Disclosed is a chain element (2), in particular for a power transmission chain of a chain drive, made of a carbon-containing material, especially steel, characterized by a core layer (5) that has a ferritic matrix structure including at least one hard phase that is distributed therein, and a hardened peripheral layer (6) that has a martensitic structure.

Claims

1. A chain element made of a carbon-containing material, the chain element comprising: a core layer having a structure made of a ferritic matrix with at least one hard phase distributed therein; and a hardened peripheral layer having a martensitic structure.

2. The chain element as recited in claim 1 wherein the martensitic structure of the hardened peripheral layer includes martensite.

3. The chain element as recited in claim 1 wherein the martensitic structure of the hardened peripheral layer consists of martensite.

4. The chain element as recited in claim 1 wherein the hardened peripheral layer is formed with the aid of a martensitic transformation of at least the areas of the chain element near the surface.

5. The chain element as recited in claim 1 wherein the hard phase distributed in the core layer includes martensite.

6. The chain element as recited in claim 1 wherein the hard phase distributed in the core layer consists of martensite.

7. The chain element as recited in claim 1 wherein the hardened peripheral layer has a hardness of 600 HV to 1,800 HV.

8. The chain element as recited in claim 7 wherein the hardened peripheral layer has a hardness of more than 1,000 HV.

9. The chain element as recited in claim 1 wherein the chain element is a chain link or a chain sleeve or a chain stud.

10. The chain element as recited in claim 1 wherein the carbon-containing material is steel.

11. A transmission chain of a chain drive comprising the chain element as recited in claim 1.

12. The chain element as recited in claim 1 wherein the hard phase is no more than 20% of the core layer.

13. The chain element as recited in claim 2 wherein the martensitic structure is no more than 20% of the core layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) One exemplary embodiment of the invention is illustrated in the drawing and explained in greater detail below.

(2) FIG. 1 shows a characteristic detail of a chain, which includes multiple chain elements according to one exemplary embodiment of the present invention;

(3) FIG. 2 shows a chain element in the form of a chain plate according to one exemplary embodiment of the present invention; and

(4) FIGS. 3 through 5 show the method steps for manufacturing a chain element according to one exemplary embodiment of the present invention.

DETAILED DESCRIPTION

(5) FIG. 1 shows a characteristic detail of a chain 1. Chain 1 is formed from multiple interconnected chain elements 2. It is apparent that chain 1 therefore includes multiple chain elements 2 in the form of consecutively situated, in particular link-shaped, chain plates 3, which are interconnected with the aid of chain studs 4. Chain 1 may be designed as a tooth chain and thus be used, for example, to transmit power in the powertrain or as part of the powertrain of a motor vehicle.

(6) FIG. 2 shows a separate representation of a chain element 2 in the form of a chain plate 3, which, mounted in a chain 1, is interspersed with chain studs 4 via bores provided therein, and is connected in this way to another chain plate 3. The representation illustrated in FIG. 2 is a longitudinal sectional view of chain element 2.

(7) Chain element 2 is originally made of a metallic material based on carbon and iron, i.e., a steel such as CK75. It is apparent that finished chain element 2 illustrated in FIG. 2 includes a core layer 5 as well as a peripheral layer 6 surrounding the core layer.

(8) Core layer 5 and peripheral layer 6 are distinguished from each other by their structural conditions and their mechanical properties resulting therefrom, in particular the hardness, ductility and toughness. Core layer 5 has a structure made of a ferritic matrix and a martensitic hard phase distributed therein, so that the structure of core layer 5 corresponds to the structure of a dual-phase steel. Core layer 5 thus lends chain element 2, in particular, a certain ductility, strength and toughness.

(9) In contrast, peripheral layer 6 only has a martensitic structure. Peripheral layer 6 is thus formed from martensite, which lends it and chain element 2 a great hardness. The hardness of peripheral layer 6 is approximately 1,200 HV (Vickers hardness). The layer thickness of peripheral layer 6 is, for example, approximately 15 μm.

(10) FIGS. 3 through 5 show the essential method steps during the course of manufacturing a chain element 2, as illustrated, for example, in FIGS. 1 and 2, according to one exemplary embodiment of the present invention.

(11) In the method step illustrated in FIG. 3, a previously provided chain element 2, which is made of a steel, is heated to a temperature above the austenitization temperature of the material forming chain element 2, i.e., typically to more than 830° C., and held there for a certain period of time, e.g., half an hour. Both the temperature and the holding period may vary, in particular as a function of the specific chemical composition of provided chain element 2 or the desired properties of chain element 2 to be manufactured.

(12) Heating chain element 2 to a temperature above the austenitization temperature and holding chain element 2 at this temperature induces the formation of a uniform austenitic structure (γ phase, as indicated by the letter γ in FIG. 3).

(13) In the method step illustrated in FIG. 4, at least one measure is carried out for introducing at least carbon into areas of chain element 2 near the surface. The carbon is introduced, in particular, diffusively or thermochemically. The carbon may be introduced, e.g., with the aid of carburization or carbonitriding. It is essential for an enrichment of carbon to take place in the surface or in the areas of chain element 2 near the surface, which represents the basis for the subsequent formation of hardened peripheral layer 6 of chain element 2. As indicated by designations C1 and C2, the carbon content is higher (C1) in the areas of chain element 2 near the surface, which are indicated by the dashed lines, than in inner areas of chain element 2 (C2).

(14) In the method step illustrated in FIG. 5, chain element 2 is quenched in an oil bath or a salt bath to a temperature in the range between 25° C. and 300° C. The abrupt cooling of chain element 2 results in the fact that a core layer 5 is formed, which has a structure made of a ferritic matrix (α phase, as indicated by the letter α in FIG. 5) and includes at least one martensitic hard phase distributed therein in the manner of islands (as indicated by the letters (MS) in FIG. 5) as well as a hardened peripheral layer 6, which has a martensitic structure MS.

(15) The formation of different structures between core layer 5 and peripheral layer 6, due to the quenching, is caused, as mentioned, by the prior enrichment with carbon of the areas of chain element 2 near the surface which form peripheral layer 6, so that a martensitic transformation takes place particularly favorably, due to the high carbon content.

(16) The quenching may take place, for example, by introducing the chain element into an oil bath or a salt bath. Depending on the selection of the quenching medium the quenching may take place down to different temperatures. The chain element is typically quenched to a temperature in the range between 0° C. and 400° C., in particular between 25° C. and 300° C.

LIST OF REFERENCE NUMERALS

(17) 1 chain 2 chain element 3 chain plate 4 chain stud 5 core layer 6 peripheral layer