Improvement of seizure resistance by roughening surface of stainless steel drawn cup in ironing using die having lubricant pockets

The seizure resistance in ironing of ferritic stainless steel drawn cups using a die having lubricant pockets was improved by roughening the sidewall of the cups. The effect of the surface roughness of the cup on the seizure resistance in ironing was investigated. The seizure resistance using the die having lubricant pockets was higher than that of a polished die, and was heightened by the surface roughness of the cup in the axial direction. To increase the surface roughness of the cup, deep drawing processes with a large clearance and a two-stage deep drawing process were developed. The ironing limits for the roughened cups by the two deep drawing processes were higher than that of the conventionally drawn cup. The thickness of the remaining lubricant film in the sidewall of the ironed cup increased with increasing surface roughness of the cup. It was found that the seizure resistance in ironing was improved by roughening the sidewall of the cup.