Process for obtaining a mechanical component

Abstract

A process for obtaining a mechanical component by joining a first metallic material and a second metallic material. The process comprises: (A) putting the first material and the second material in contact with each other, (B) fixating a sheet metal element onto the first material to at least partly enclosing the second material and so that the sheet metal element is at least partly in contact with the second material. The sheet metal element comprises carbon, joining the first material and the second material by diffusion welding. The carbon activity of the second material Ca.sub.2 and the carbon activity of the sheet metal element Ca.sub.m at the temperature of joining fulfills a relation Ca.sub.2Ca.sub.m.

Claims

1. A process for obtaining a mechanical component by joining a first and a second metallic material, the process comprising steps of: (A) putting the first and the second material in contact with each other; (B) fixating a sheet metal element onto the first material to at least partly enclosing the second material and so that the sheet metal element is at least partly in contact with the second material, wherein the sheet metal element comprises carbon; (C) joining the first and second material by means of diffusion welding; and wherein the carbon activity of the second material Ca.sub.2 and the carbon activity of the sheet metal element Ca.sub.m at the temperature of joining fulfills the relation Ca.sub.2Ca.sub.m.

2. The process according to claim 1, wherein the sheet metal element is enclosing the second material and creates a closed space for the second material.

3. The process according to claim 1, wherein the second material, before it is joined, is in a form of a metallic powder.

4. The process according to claim 1, wherein the carbon activity of the second material Ca.sub.2 and the carbon activity of the sheet metal element Ca.sub.m at the temperature of joining fulfills the relation Ca.sub.2<Ca.sub.m.

5. The process according to claim 1, wherein the sheet metal element further comprises nitrogen.

6. The process according to claim 1, wherein the second material is a high performance bearing steel.

7. The process according to claim 6, wherein the high performance bearing steel is one of: M50, M50 NIL, XD15NW, Bearing steel as shown in ISO 683-17:1999(E) pages 9-10, Stainless tool steel, Stainless steel suitable for martensitic hardening, N-alloyed stainless steel, suitable for martensitic hardening, or Stainless steel suitable for surface enrichment and martensitic hardening.

8. The process according to claim 1, wherein the first material is one of: a cast iron, a cast steel, a hot rolled steel, or a cold rolled steel.

9. The process according to claim 1, wherein the mechanical component is a bearing component.

10. The process according to claim 9, wherein the bearing component is one of: an inner ring of a bearing, an outer ring of a bearing, or a roller of a roller bearing.

11. The process according to claim 1, wherein the diffusion welding is made by hot isostatic pressing (HIP).

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Exemplifying embodiments of the present invention will now be described in more detail, with reference to the accompanying drawings, wherein:

(2) FIG. 1 shows a cross-sectional view of a mechanical component according to an embodiment of the invention; and

(3) FIG. 2 shows a flow diagram of an embodiment of the process according to the invention.

(4) The drawings show diagrammatic exemplifying embodiments of the present invention and are thus not drawn to scale. It shall be understood that the embodiments shown and described are exemplifying and that the invention is not limited to these embodiments. It shall also be noted that some details in the drawings may be exaggerated in order to better describe and illustrate the invention.

DETAILED DESCRIPTION OF DRAWINGS

(5) FIG. 1 shows an illustration of a cross section of a mechanical component, which in this illustration is a bearing component 1. The bearing component 1 comprises a first metallic material 11 and a second metallic material 12 which has been joined by diffusion welding. Diffusion welding will lead to that the first material 11 and the second material 12 will diffuse into each other leading to a tight bond between the two materials 11 and 12. For the diffusion welding process, a sheet metal element 2 has been fixated onto the first material 11, in this embodiment the core or body part of the bearing component 1. The bearing component 1 is in this embodiment an inner ring of a bearing, wherein the second material 12 at least partly is intended to be a raceway on the inner ring onto which rolling elements is intended to roll. Further, the bearing component comprises a through-hole 3 into which a shaft (not shown) may be fitted. The sheet metal element 2 is intended to create a closed space for the second material 12 during the diffusion welding process, which may be made by hot isostatic pressing. Hot isostatic pressing requires that a closed space is created, especially when the second material 12 is in powder form before joining. The sheet metal element 2 is in this embodiment fixated to the first material 11 via two flanges 13 and 14. The two flanges 13 and 14 also create a groove 15 for the second material 12. This is an advantageous design for creating the closed space for the second material 12 and for the hot isostatic pressing process. Further, the design allows the second material 12 to only be present where it is needed, viz. at the rolling contact surface (the raceway). The second material 12 may be a high performance bearing steel, such as M50 or M50 Nil. The steel 12 may be any wear resistant steel, corrosion resistant steel, or any other suitable metallic material depending on the demands of the mechanical component in its intended application. The carbon activity of the second material 12 Ca.sub.2 and the carbon activity of the sheet metal element 2 Ca.sub.m at the temperature of joining fulfills the relation Ca.sub.2Ca.sub.m. This leads to that no or substantially no carbon will be diffused from the second material 12 to the sheet metal element 2. It is as stated above not good for the second material 12 if carbon would be diffused from it to the sheet metal element 2 during the diffusion welding process, for instance by means of hot isostatic pressing. This is especially true when there are high demands for the second material 12 due to wear resistance etc., such as for a rolling bearing component. Further, if the carbon activity in the sheet metal is higher than in the second material at the temperature of joining, carbon will be diffused into the second material 12. This would result in a surface enriched with carbon which would lead to an increased hardness and wear resistance of the outer surface of the second material 12. Other elements, such as nitrogen may also be diffused into the second material 12 during the diffusion welding process from the sheet metal element 2, depending on the properties that are wanted for the final mechanical component 1.

(6) FIG. 2 is an illustration showing a flow diagram representing an embodiment of the present invention. In step A, the first 11 and the second material 12 are put in contact with each other. In step B, a sheet metal element 2 is fixated onto the first material 11 to enclose the second material 12 and so that the sheet metal element 2 is at least partly in contact with the second material 12. The sheet metal element 2 also comprises carbon. In step C, the first 11 and the second 12 material are joined by means of diffusion welding, for instance hot isostatic pressing. Further, the carbon activity of the second material 12 Ca.sub.2 and the carbon activity of the sheet metal element 2 Ca.sub.m at the temperature of joining fulfills the relation Ca.sub.2Ca.sub.m.