Title of Invention

A PROCESS FOR THE PREPARATION OF CASTING MATERIAL FOR MACHINE PARTS UNDER SLIDING LOAD

Abstract

This invention relates to a process for the preparation of casting material for machine parts under sliding load, especially for fluid-lubricated friction bearings, comprising preparing by known steps a composition in percentage by weight of; 1.5-14.0 Cr <5.0 Ni < 2.0 Mo < 3.0 Si <1.0 Mn 3.0-6.0 C, 3.0-7.0 rest being Fe and smeltlng-caused impurities, the structural composition being with ferritic, ferrtic-pearlltic or bainrtic matiix with simultaneous presence of chromium carbides and free carbon.

Full Text

2(3) - 1A- DascriPtion Material for machine parts under sliding load The Invention pertains to a casting material for machine parts under sliding load, especially a material for fluid-lubricated friction bearings. For fluid-lubricated friction bearings, like for example friction bearings used in centrifugal pumps which are lubricated by the flow medium, various kinds of metallic and non-metallic materials are used. Thus, in friction bearings where the flow medium of pure water serves as lubricating agent, one uses as material metallic alloys, ceramics, elastomers and hard rubber, or even electographited carbon with and without synthetic resin impregnation or hard carbon with synthetic resin- or antimony impregnation. Among the metallic materials one preferably uses non-iron-base-alloys like aluminium- or copper alloys or white metals on lead- and tin base, as well as to a limited extent also iron-base-alloys. Typical examples of bearing materials of Fe-base are martensitic chrome steel like X 13 CrMoS 13 with sulphur addition or chill-cast alloys like the materiel G-X 120 CrMo 29 2(1.4318). These alloys are excellent due to a relatively good wear resistance; however, they have a scuffing tendency under mixed friction. As against this, materials like grey cast Iron and spheroidal graphite Iron have very good properties of emergency run on account of the embedded graphite which acts as lubricating agent. The permissible specific surface pressure of these materials is however very low, just like the wear resistance, so that the areas of application of such bearing gets very much reduced. It is the task of this Invention to create a mettallc alloy on iron base which would have a high permissible specific pressure, which at the same time Is highly wear resistant and whose scuffing tendency is low. Thus according to this Invention Is provided a process for the preparation of casting material for machine parts under sliding load, especially for fluid- -2- lubricated friction bearings, comprising preparing by known steps a composition in percentage by weight of: 1.5-13.0 Cr 3.0-6.0 C, rest being Fe and smelting-caused impurities, the structural composition being with ferrttic, ferrltic-pearlltlc or bafnlflc matrix with simultaneous presence of chromium carbides and free carbon. A globular formation of the free carbon is of particular advantage.. Use of this material can be recommended particularly for fluid-lubricated friction bearings, especially for friction bearings used in centrifugal pumps where the lubrication is effected by the flow fluid. Surface hardening of a machine part manufactured with a casting material according to the invention, e.g. nitration, has a favourable effect on its life. In fluid-lubricated friction bearings, natural pairing with this alloy fs possible; as sliding partner one could however also consider hard materials like metals and ceramics and soft materials like carbon and CFC. The casting material as per the invention, with separated chromium carbides and free carbon, shows a favourable frictional behaviour, especially under mixed and dry friction. The chromium carbides embedded in the structure increase the wear resistance on account of their high hardness, whereby one attains a higher stability than In case of hard-phase-free materials or carbon-deficient, martensitic steels. One should ensure a balanced carbide content, because a too low carbide content -3- would reduce the wear resistance and the life of the machine part, whereas a too high carbide content and the high briiffeness resulting therefrom - especially in case of a cohesive carbide network - the energy generation under mixed and dry friction could lead to thermal stress cracks. The effect of carbon as dry lubricant for improving the emergency run properties of friction bearings is known. Therefore, contrary to hard case types, in the material as per the invention the content of chromium and carbon is regulated in such a way that, after formation of the carbides a not bound portion of free carbon Is available in the structure which is sufficient for lubrication purposes If this free carbon is globuiarly structured, i.e. if it is there in the form of spherulites, then after they are consumed on the surface of the machine part, pores get formed which take up fluid and act as lubrication pockets. Due to avoiding of the cohesive graphite network which is characteristic of grey cast irons, the alloy is resistant to graphitic corrosion. - 4- WE CLAIM 1. A process for the preparation of casting material for machine parts under sliding load, especially for fluid-lubricated friction bearings, comprising preparing by known steps, a composition in percentage by weight of: 1.5-13.0 Cr =. 5.0 Ni =1.0 Mn 3.0-6.0 C, rest being Fe and smelting-caused impurities, the structural composition being with ferritic, ferritic-pearlftic or bainitic matrix with simultaneous presence of chromium carbides and free carbon. 2. The process as claimed in claim 1, having a globular formation of the free carbon. Dated this 24th day of October 1997. This invention relates to a process for the preparation of casting material for machine parts under sliding load, especially for fluid-lubricated friction bearings, comprising preparing by known steps a composition in percentage by weight of; 1.5-14.0 Cr 3.0-6.0 C, 3.0-7.0 rest being Fe and smeltlng-caused impurities, the structural composition being with ferritic, ferrtic-pearlltic or bainrtic matiix with simultaneous presence of chromium carbides and free carbon.

Documents:

02007-cal-1997- abstract.pdf

02007-cal-1997- claims.pdf

02007-cal-1997- correspondence-1.1.pdf

02007-cal-1997- correspondence-1.2.pdf

02007-cal-1997- correspondence.pdf

02007-cal-1997- description (complete).pdf

02007-cal-1997- form-1.pdf

02007-cal-1997- form-2.pdf

02007-cal-1997- form-26.pdf

02007-cal-1997- form-3.pdf

02007-cal-1997- form-5.pdf

02007-cal-1997- priority document.pdf