Because of its superior friction and abrasion properties, DLC films are anticipated for application to components of various kinds as a sliding mechanism. In the field of plastic working, the currently used lubricant shall be replaced from a high-viscosity one to a lowviscosity one to simplify washing and cleaning of the products. The ultimate goal in plastic working is to establish a lubricant-free or dry processing technique to meet ecological goals. One steel pipe joining technique is slip-joint technique, which can join two pipes by insertion of a pipe end having a smaller diameter into one with a larger diameter. However, this technique requires a high-viscosity lubricant to form the pipe ends, thereby necessitating washing of the ends before joining. This study addresses the possibility of applying a DLC coated die on the dry forming of the ends of zinc plated steel pipe. Heat-treated SKD11 of HRC60-HRC62 hardness was used as the die material. To ascertain the die surface influence on coating, surfaces of two kinds were prepared: one turned and one sandblasted using greencarborundum grains. Then 3-5 um thick DLC films were synthesized on the die surfaces using an RF plasma CVD system with CH4 gas as the precursor. A dry forming experiment was conducted using a zinc-plated steel pipe to increase the 70 mm inner diameter. Results show no defect such as adhesion of zinc on the die or fracture of the DLC film after forming of 200 pipes.
Polyethylene terephthalate （PET） film laminated steel sheets, which have excellent properties of formability, corrosion resistance, and adhesion to steel sheets, have become widely used for beverage cans. To expand their application, we have sought to develop a new PET film laminated steel sheet for use in food cans. For this application, content release properties are necessary to ease removal of can contents. However, PET film laminated steel sheets have extremely poor content release properties. Prior investigations of properties have revealed dependence on the strength of adhesion between films and contents. The surface free energy of PET films has been inferred as the main factor. Using films with widely diverse surface free energy values, we studied the surface free energy effects on the properties of the materials contacting the cans. Results show that the properties are closely related to the surface free energy of the material and that the materials with surface free energy of less than 23 （mN/m） or more than 44（ mN/m） show excellent properties. Content release properties can be expressed as a function of adhesion in water between the material and protein. Reducing adhesion can significantly improve content release properties.