This specification covers the standard requirements for porous metallic sleeve, flange, thrust, and spherical iron-base bearings that are produced from mixed metal powder metallurgy technology and then impregnated with oil to supply operating lubrication. Porous iron-base bearings shall be produced by compaction of a mixture of elemental iron powder and copper, tin, pre-alloyed bronze or graphite powders and sintering in a furnace having a protective atmosphere at a specified time and temperature cycle. The interconnected or open porosity in the bearings shall be filled to the required volume either by an extended soaking in hot oil or preferably by a vacuum impregnation operation with lubricating oil which is a high-grade turbine oil with antifoaming additives and containing corrosion and oxidation inhibitors. Each of the iron-base bearing material shall conform to the chemical composition requirements for iron, carbon, graphite, copper, and tin as shall be determined by chemical analysis. The physical properties for each of the bearing material shall be within the prescribed wet density, oil content, and impregnation efficiency limits. The radial crushing strength and bearing breaking load of the oil-impregnated bearing material determined on a plain sleeve bearing or a test specimen prepared from a flange or spherical bearing shall also meet the minimum and maximum mechanical strength values.

1.1 This specification covers porous metallic sleeve, flange, thrust, and spherical iron-base bearings that are produced from mixed metal powder utilizing powder metallurgy (PM) technology and then impregnated with oil to supply operating lubrication.

1.2 Included are the specifications for the chemical, physical, and mechanical requirements of those ferrous PM materials that have been developed and standardized specifically for use in the manufacture of these self-lubricating bearings.

1.3 This specification accompanies Specification B 438/B 438M that covers the requirements for Bronze-Base Powder Metallurgy (PM) Bearings (Oil-Impregnated).

1.4 Typical applications for iron-base bearings are discussed in Appendix X1.

1.5 Commercial bearing dimensional tolerance data are shown in Appendix X2, while engineering information regarding installation and operating parameters of PM bearings is included in Appendix X3. Additional useful information on self-lubricating bearings can be found in MPIF Standard 35 (Bearings) and the technical literature.

1.6 With the exception of density values for which the g/cm³ unit is the industry standard, the values stated in inch-pound units are to be regarded as standard. The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in this standard.

1.7 The following safety hazards caveat pertains only to the test methods described in this specification. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.