Application of wheat flour lubricants to the press-forming process

Lubrication with wheat flour was investigated in an attempt to develop a nonpolluting lubricant for the sheet metal-forming process. A series of wheat flour-based lubricants were prepared by suspending wheat flour in water at varying concentrations, and then a coating of each suspension was applied to sheets of commercially pure titanium (CP Ti-1), stainless steel (SUS304), and common steel (C-steel). The performance of the lubricants was evaluated by the Erichsen cupping test, and the surfaces of the deformed specimens were observed by scanning electron microscopy. The Erichsen values increased with increasing concentrations of wheat flour in the suspension and the microscopic observations suggested that starch particles covered with protein and lipids reduced the friction between the specimens and dies. A deep drawing test (diameter: 150 mm) performed to evaluate the material for practical applications showed that sheet coated with wheat flour had a higher formability than a sheet coated with press oil.