Original paper(Vol.49 No.6 pp.661)

Improvement of the Mechanical Properties of Pure Titanium Sheet by Surface Oxidation and Laminated

Jun Nakahigashi and Hirofumi Yoshimura

Abstract: This paper describes the mechanical properties of clad plate produced by pure titanium and oxidized titanium with hot rolling. The purpose of this investigation is to make a new recyclable clad plate having mechanical properties equal to those of commercially pure titanium of JIS grades 3 or 4.
The specimen is commercially pure titanium of JIS grade 2, two experiments were conducted. One is oxidizing treatment, the other is a process in which a clad plate was made experimentally from a combination of both non-oxidized and oxidized titanium. Oxidizing treatment were conducted by subjecting the specimen to a heating oxidizing treatment in air（oxidizing temperature:873～1273K, holding time:3.6～36ks）, and then a tensile test, a hardness test, and observation of the tensile fracture surface using a scanning electron microscope（SEM）were carried out in order to ascertain the mechanical properties of the oxidized material. To make a clad plate, the specimen was produced by sandwiching oxidized material between two sheets of non-oxidized materials. Next, the circumference of the specimen was subjected to TIG welding, and then it was hot rolled. Then, a tensile test, and an element analysis using an electron probe micro analysis （EPMA）were carried out. The experimental results obtained were as follows.
The tensile strength of the oxidized material increases with increases in oxidizing temperature and holding time. However, when the oxidizing temperature is more than about 1000 K, the elongation decreases rapidly in spite of a short holding time. The clad plate produced using pure titanium and oxidized titanium shows tensile properties roughly equal to those commercially pure titanium of JIS grades 3 or 4.

Key Words:Recycling, Oxidazing, Mechanical property, Hot-rolling, Clad plate