Proceedings of SerbiaTrib '13

additives, that had been, until recently, based onchlorinated paraffins are a group of chemicals thatneeds to be replaced as soon as possible withcomponents that are environmentally acceptable.In this paper, in laboratory conditions areprepared samples of several different formulationof neat oil which are intended for differentmetalworking operations. Among the otherstandard characteristics, are also tested antiwearand EP characteristics of samples containingsynthetic polymeric esters, as one of the possiblereplacement for chlorinated paraffines. The resultsof analysis are compared with the results of thesamples that are formulated with chlorinatedparaffins.2. EXTREME PRESSURE (EP) ADDITIVESPrimary functions of metalworking fluids areheat control, cooling the surfaces of tools and partsprocessed in the cutting zone and lubrication andenduring the extreme pressures and heavy loadingduring processing. It is particularly important inorder to achieve desired size, shape and degree ofsurface processing of workpiece, and longer toollifetime. Removal of cuttings from operating zoneis considered as secondary role, but it is veryimportant and it needs to be done continually.Corrosion protection of tools, machines andworkpieces is also important. Freshly processedmetal have tendency to corrode faster duringmachine operations, than protected metal.For metalworking it isn’t enough to use only onekind of lubricant, but every applicable processrequires specially formulated oil. In order toemphasize differences in characteristics of certainlubricants, in this case, of neat oils, and point outthe complexity of choosing the basestocks forformulations, we start with metalworkingprocesses, which are:- Removal (formation of cuttings), mostlynamed cutting operations- Shaping: pressing, rolling, drawing...- Treating (surface strengthening): quenching- Protection (corrosion protection: temporarywith interprocess, during transport...)Cutting operations can be considered as the mostcommon in metalworking operations. Basicmethods of metalworking cutting are:- Scraping- Planning (during operation it is identical toscraping, but the process is discontinuous- Drilling (beveling, widely considered:drilling, widening, reaming)- Milling (oblique and orthogonal cutting)- Grinding (removal of thin layer of materialduring the finest final processing)Operations of metal forming, such as: pressing,rolling, drawing (wire, profiles) are also veryused and are considered as demanding.2.1. EP additives and their role in metalworkingfluids for heavy operationsTraditional additive packages that are added toneat metalworking oils in the boundary lubricationregime remain on the metal surfaces and theycannot prevent increased friction, wear and thedamage to the tool. EP additives are needed toenable the application in the more difficultconditions of elevated temperatures and pressures.The main groups of EP additives are:1. Chlorine compounds2. Phosphorus additives3. Sulphur additives4. Prebasic sulfonates (calcium and sodium)The first three EP additives are activated inreactions with the metal surfaces in a certaintemperature range. Chlorinated additives areactivated at temperatures between 180 i 420 ⁰C,phosphorus are activated at higher temperatures andsulphur at even higher temperature range whichends at 1000 ⁰C. In the reaction with the metalsurface these three types of additives produce Fechloride,Fe-phosphide and Fe-sulphide, whichserve as a barrier to reduce friction and wear andelimination of welding.The fourth EP additive, prebasic sulfonate, actby other mechanisms, whose process doesn’tdepend on temperature, and operate below 500 o C.In each category of EP additives there areseveral different types. The main used chlorinatedadditives are chlorinated paraffin, or even called achlorparaffine. In case of phosphorus compounds,the most common type is phosphate ester. Withsuphur additives those are: sulphurated fats,sulphurated esters, sulphurated hydrocarbons andpolysulphide, which differ in the concentration offree (active) sulphur.In order to select EP additive in formulations formetalworking fluids, one must be familiar with theapplications itself, machining operations, state ofthe tools and to have defined expectedperformance. One of the most importantinformation is the possibility of early cancellationof tools before the operation has reached the righttemperature for EP additive to become activated.Besides the choice of EP additive, it is necessary toknow the synergism with other additives includedin the formulation, and also to reduce undesirableinteractions which can bring to instability ofproduct using certain combination (foaming,sludge).13 th International Conference on Tribology – Serbiatrib’13 309