Development of the microbiological population in water miscible metal working fluids

The deterioration of metal working fluids (MWFs) due to the microbial colonization and degradation is a considerable economic factor in the metal working industry. Microorganisms (MO) are able to metabolize almost all components of MWFs and thus lead to a loss of its function by the reduction or depletion of additives. Microbial growth cannot be avoided completely, although various methods exist to reduce the bacterial load in MWFs. This paper presents a study on the colonization of MWFs by bacteria and fungi in an industrial environment. The cooling lubricants have been periodically examined based on biological and chemical methods. The level of the total bacterial load in the lubricant is considered as well as the composition of the species community and its development over the evaluation period. With regard to the increasing relevance of environment friendly processes, a conventional mineral oil based MWF has been compared to a product based on renewable resources

Influence of Additives in Metalworking Fluids on the Wear Resistance of Steels

AbstractTheability of metalworking fluids (MWF) to cool and lubricate the contact zone between tool and workpiece is strongly dependent on the surface-active substances such as extreme pressure additives (EP) and passive extreme pressure additive (PEP) as well as the chemical surface properties of steel.Low alloyed steels and stainless steels were examined with a wear resistance test by applying MWF with defined varied concentrations of additivesfeaturing different properties e.g. regarding activity and molecular structure.The wear resistance was assessed and correlated with the chemical properties of the metals. Synergistic and antagonistic effects were obtained and will be discussed. The results gained from the experiments, clearly indicate, why the amount of the additives is less decisive for wear resistance than the relative ratio of polar and unpolar EP/PEP-additives.The optimal result furthermore depends on the chemical properties of the considered surfaces