Currently, cold working cannot reduce thickness of works as much as hot working from only single molding and its distinct disadvantages include the fact that steel rolling in solid condition causes stress-strain and the metals are fragile and easily broken. Furthermore, it requires high investment in installing large and expensive machines resulting in higher production cost. Therefore, this research aimed to study behaviors of permanent transformation in lead and tin hollow pipe rolling and thickness of led and tin was specified to be 4, 3.5, 3, 2.5 and 2 millimeter respectively. Pipes with 12-millimeter diameter would be rolled and tested for tension. The test result for both lead and tin was likely to be unidirectional that when reducing size in each time, pressure would increase and stress would decline accordingly. The test result was found that force for molding tin would become less powerful while strain value of lead was higher than tin and it was suitable for molding.
Keyword: permanent transformation, hollow pipe rolling process, stress-strain