2001 年 19 巻 4 号 p. 717-726
The development of the joining method of titanium with stainless steel is important to major applications in the field of tableware, automobile and sports equipments. Therefore, this study was performed with the objective of producing a nonleak and high strength lap joint between pure titanium and stainless steel. A pulsed Nd:YAG laser was utilized as a heat source because of its low total heat input and easy combination of pulse width and energy. Using flat sheets of titanium and stainless steel, the properties of lap joints were evaluated by shearing strength as well as metallurgical observation and chemical analyses of their cross sections. Vacuum tubes of dissimilar laser lap joints between titanium and stainless steel were manufactured experimentally, and were subjected to the leakage test.
Dissimilar high strength lap joints could be produced, and the shear load of 4200N per 40mm width and shear stress of 190MPa were achieved for the specimens made under optimum conditions. Then melting of the bottom sheet was confined in a small overlap area to lessen the formation amount and zone of intermetallic compounds by controlling the pulse energy and the power density. In addition, in the case of laser shot at the top titanium sheet, high strength joints were produced under more wide irradiation conditions, probably because of the formation of Ti solid solution containing larger contents of alloying elements such as Fe, Cr, Ni, etc. in the bottom sheet. Moreover, the tubes of nonleak joints could be produced only when a pulsed Nd:YAG laser was irradiated on the titanium inner sheet. This is attributed to the difference in the expansion coefficient between titanium and stainless steel in addition to the above-mentioned easier welding.