To improve the metallic running properties, some deva.metal® materials were manufactured in the past with the addition of lead powder. The uniform and very fine distribution of the lead powder supports the self-lubricating effect of the solid lubricant. The lead remains unchanged hygroscopically effective in the metal skeleton. DEVA offers only a few alloys with lead.
Since lead is practically insoluble in copper (chemical neutrality), it is freely present in the metallic matrix and is deposited at the grain boundaries. During powder metallurgical processing, the necessary compaction and deformation in the metal matrix places it under pre-stress. By means of a specially controlled annealing process, a large part of these stresses is relieved. However, remaining residual stresses cannot be completely eliminated - as is the case with cast materials - and are recognized in materials science. Further diffusion processes may follow. These are only relieved over very long periods, which may be days or weeks. This relaxation occurs on the plain bearings in the uninstalled state.
Depending on the diameter, the changes range from a few thousandths of a millimeter to a maximum of a few hundredths of a millimeter. These changes have no influence on the function and assembly if they remain within the range described below.
The permissible variation with constant wall thickness
0.0004 to 0.0005 x outside diameter should not exceed
Within this slight range of change, perfect mounting of the plain bearings is possible and the desired tolerance range of the plain bearing inner diameter is then established.
If the outer diameter of the plain bearing is 20 mm, a max. increase of the inner and outer diameter of (0.0005 x 20 mm) 0.01 mm above the upper tolerance limit is permissible.
We request that you pass this information sheet to your incoming inspection and processing plant for guidance and information.
Lead is considered toxic and harmful to health. For some years now, it has been listed in the "candidate list" under the REACH Regulation, which has led in particular to information obligations in the supply chain and, since the beginning of 2021, to reporting obligations in the SCIP database.
All our materials that exceed the limits according to the candidate list are entered in the database. In the meantime, however, there are equivalent substitute materials for all lead-containing alloys. DEVA also aims to stop processing lead powder by the end of the year.