EFFECT OF PARTICULATE ADDITIVES TO DEEP DRAWING DIES LUBRICANTS IN FORMING ALUMINUM SHEETS

The executed work as a whole has shown an urgency and favorable prospects of practical use of firm powder additives on the basis of (graphite) and soft metal (Copper) powders at a range of concentration (2–5) %wt and (1–3) %wt respectively. Improving the characteristics of liquid lubricants was experimentally revealed at friction contact surfaces by using the composite additive powders of the graphite – copper (mixing) in comparison with a case of separately introduction of the same of graphite and copper powders, entered separately. The given effect took place in deep drawing process of aluminum alloy type AA2024-T4 by using two types of lubricants, die and castor oils. The antifriction ability of powder lubrication and the state of powder layer are strongly related to the service conditions. Therefore, the effects of sliding velocity and normal load under powder lubrication were studied using a pin on disc contact apparatus according to ASTM G-99 specification.

The theoretical concept according to which introduction in the base lubricant environment of graphite and copper in quality thin layer covering the surface of contact should lead to increase anti-frictional and anti-wear efficiency of the lubricants in comparison with a case when metal and nonmetallic additives are entered separately was put forward. The tribotechnical characteristics of investigated graphite and copper additives to lubricants were received during wide range of experiments. Optimum lubricating effect concluded at concentration of the graphite and copper additive powders are (3) %wt and (2) %wt respectively, by the formation of

protective boundary layer between the sliding tribo-surfaces that prevents wear.

Tribological characteristics significantly improved i.e. the wear rate

dropped about (89%) for die oil and about (99.7%) for castor oil compared

with the case of using the lubricant oils without additives. The effect of applied load vs. wear rate for all wear tests with and without lubricant and at all %wt of particulate additives submitted to second order polynomial equation model with high correlation coefficient more than 97% and lowest standard deviation ≤0.1.The hybrid optimum percentage of powder

additives (2% Cu + 3% Gr) with castor oil gives lowest wear rate compared with that added to die oil.

The investigated lubricant was used in deep drawing process of aluminum alloy type AA2024-T4. A circular blanks with 1.2mm thickness were drawn to cup with flange, using reverse circular drawing die in cold and dry conditions with punch nose radius and blank holder angle of (12mm) and (0º) respectively.

Results had revealed that deep drawing parameters of aluminum alloy type AA2024-T4 were significantly improved the drawing force, cup height, surface roughness and thickness distribution of the produced cups. The effect of hybrid particulate lubricants is clearly had the best deep drawing parameters with ( 7.2 %, ,70.5 %, and 6%) for drawing force, surface roughness and thickness distribution respectively compared with pure lubricant deep drawing process.