Dry Lubricant Films for Aluminum Forming

Abstract

During metal forming, lubricants are necessary to prevent direct contact, adhesion, transfer, and scuffing of workpiece materials and tools. Boric acid films, which can be firmly adhered to clean aluminum surfaces by spraying their methanol solutions, provide extremely low friction coefficients (≈0.04). The adhesion strengths of the bonded films vary with the type of aluminum alloy (6061, 6111, and 5754). Sheet metal forming tests indicate that boric acid films and combined films of boric acid and mineral oil can enable larger strains than commercial liquid and solid lubricants, showing that their lubricities are excellent for aluminum forming. Scanning electron microscopy analyses indicate that the dry boric acid films effectively separate the workpiece and die materials and, thus, prevent direct contact and preserve the surface qualities. Because boric acid is nontoxic and easily removed by water, the authors can expect these films to be environmentally friendly, cost-effective, and very efficient lubricants for sheet aluminum cold forming. Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in Orlando, Florida, October 11–13, 1999