Abstract: A sheet, a plate, a bar or wire is made of Ti and has high ductility and low material anistropy in a plane of a sheet or plate, or in a sectional plane of a bar or a wire and contains Fe, in mass, at 0.15-0.5%, N at 0.015-0.041 and 0, with the balance Ti and unavoidable impurities. When the Fe content is defined as [Fe], the N content as [N] and the 0 content as [0], the oxygen equivalent value Q=[0]+2.77[N]+0.1 [Fe] is 0.11-0.28.

Abstract: The present invention provides a sheet, a plate, a bar or a wire which is made of titanium and has a strength equal to, and a ductility higher than, those of a titanium material of JIS class 2 or 3 and, moreover, a low material anisotropy in a plate plane of a sheet or a plate, or in a sectional plane of a bar or a wire, and a method of producing the same.

Abstract: A method of straightening a wire rod of titanium or titanium alloy wherein the rod is hot-straightened to a straight rod at the straightening temperature T and elongation .epsilon. satisfying the expression (1) or (2). The method includes hot rolling a titanium billet of .beta. titanium alloy, (.alpha.+.beta.) titanium alloy or a near .alpha. titanium alloy into a wire rod, winding the hot rolled wire rod into a coil, cold drawing the wire rod, cutting the wire rod to obtain a bent wire rod, heating the bent wire rod to a straightening temperature T while both end portions of the bent wire rod are fixed, applying a predetermined elongation .epsilon. to the wire rod, maintaining a straightening temperature T, hot-straightening the wire in accordance with the expression (2).epsilon.(T-400).gtoreq.400 (1).epsilon.(T-500).gtoreq.200 (2)and cooling the wire rod while applying tension. The method is suitable for preparing a straight rod for use in an engine valve.

Abstract: Bars of titanium alloys suited for the manufacture of at least the stems (2), (3) of engine valves are mass-producible while maintaining good configurational and dimensional accuracies throughout the valve fabricating process and the wear-resistance imparting processes to at least the stems (2), (3), by surface oxidizing and nitriding. The alloys are of the .alpha.+.beta. type whose microstructure consists of any of an acicular .alpha.-phase consisting of acicular .alpha. crystals having a width of not smaller than 1 .mu.m, an acicular .alpha.-phase consisting of acicular .alpha. crystals having a width of not smaller than 1 .mu.m and dispersed with equiaxed .alpha. crystals, and an equiaxed .alpha.-phase consisting of .alpha. crystals whose diameter is not smaller than 6 .mu.m. Their microstructure may also include one in which the diameter of the pre-.beta. crystals in the acicular .alpha.-phase is not larger than 300 .mu.m and the width of the acicular .alpha. crystals is not smaller than 1 .mu.