Improving deep drawability of HC300LA sheet metal by warm forming

The formability of high-strength sheet materials is limited at room temperatures. In this study, the first of its kind to be conducted, experimental research was performed on the formability of HC300LA-grade sheet material using the warm deep drawing (WDD) method. Temperature control is among the most important parameters in the WDD method. To in- crease the limiting drawing ratio (LDR) of HC300LA-grade sheet material, a new warm deep drawing method featuring sensitive temperature control was designedand manufactured. Withthisnew method,theformabilityofHC300L-gradesheet material was considerably increased by heating the flange zone of the blanks under blank-holder force (BHF). Before the experimental study, unidirectional tensile tests were ap- plied at room temperature (RT), 150 °C, and 300 °C. At the completion of the test conducted at 300 °C, dynamic strain aging (DSA) was seen in the test specimen. As a result of DSA, the HC300LA-grade sheet material became brittle and its formability decreased. Experimental studies were therefore conducted in the temperature range of 170 and 295 °C. LDR for a 1.2-mm sheet thickness of HC300LA-grade sheet mate- rial, which is 2.14 at RT, increased to 2.61 after applying this method. In experimental studies on LDR involving 1.5-mm sheet thickness, which is 2.15 at RT, the ratio increased to 2.59. The drawing ratio (DR) increased by 21.96 and 20.45 % for 1.2 mm sheet thickness and 1.5 mm sheet thick- ness, respectively. Moreover, the microstructures of the warm cup's punch corner region, and wall and bottom regions were investigated under an optical microscope. The results showed whether any changes occurred in the microstructures.