Warm forming is a technique aimed at enhancing the formability of aluminum, gaining interest since the 1970s. An aluminum alloy with 6 percent magnesium content was discovered to provide a remarkable 300 percent total elongation at approximately 250 degrees Celsius.
In warm aluminum bending, the die and blank holder are typically heated to a temperature ranging from 200 to 300 degrees Celsius. Numerous studies indicate a significant increase in formability, especially for 5XXX and 6XXX series, when warm forming is employed.
Electric heating rods heat the dies and blank holder, with a focus on heating the critical corners of the dies, as they play a key role in controlling metal flow. It’s not necessary to heat the entire die in most cases, and straight sides can be cooled using water or oil to reduce material flow, similar to the effect of a draw bead.
Research on warm forming of aluminum alloys, such as an experimental analysis of rectangular conical cups from aluminum alloy (5754-O), has been conducted. Cup heights obtained without fracture were compared at different temperatures (20°C, 100°C, 175°C, and 250°C). The study revealed that while cup height increases moderately from 20°C to 175°C, a significant increase occurs at 250°C.
In warm forming of rectangular conical cups, the flange softens due to heating, allowing more material to be drawn into the die cavity without defects. A major challenge in warm forming is the absence of a satisfactory lubricant. Evaluation of various lubricants and encouragement for the development of lubricants specifically for this process is essential. A satisfactory lubricant must exhibit good lubrication, stability at operating temperatures, non-toxicity, good adhesion, ease of application and removal, and cost-effectiveness.