Abstract: A method for manufacturing an ?+? titanium alloy bar comprising hot rolling an ?+? titanium alloy consisting essentially of 4 to 5% Al, 2.5 to 3.5% V, 1.5 to 2.5% Fe, 1.5 to 2.5% Mo, by mass, and a balance of Ti, while keeping the surface temperature thereof to a temperature of ? transus or below.

Abstract: The invention provides a titanium alloy having a narrow distribution of material properties in the thickness direction, allowing easy to finish the surface of the forged material after forging, during working the product to the final shape. The forged titanium alloy has a low sensitivity for cracking, excellent workability, and favorable ductility and fatigue properties, and provides a method for forging the titanium alloy. In order to attain the forged titanium alloy and the method for forging thereof, forging the titanium alloy, which has T&bgr; ° C. of the &bgr;-transus, is conducted, while keeping the relation of 400° C.≦Td and (T&bgr;−400)° C.≦Tm≦T&bgr; at a strain rate of a range from 2×10−4 s−1 to 1 s−1, further limiting the chemical composition of the titanium alloy, keeping the relation of [(Tm−Td)≦250° C.] during forging, where T&bgr; (° C.) is the &bgr;-transus of the titanium alloy, Tm(° C.

Abstract: The invention relates to an &agr;+&bgr; type titanium alloy bar consisting essentially of 4 to 5% Al, 2.5 to 3.5% V, 1.5 to 2.5% Fe, 1.5 to 2.5% Mo, by mass, and balance of Ti, and having 10 to 90% of volume fraction of primary &agr; phase, 10 &mgr;m or less of average grain size of the primary &agr; phase, and 4 or less of aspect ratio of the grain of the primary &agr; phase on the cross sectional plane parallel in the rolling direction of the bar. The &agr;+&bgr; type titanium alloy bar has excellent ductility, fatigue characteristics and formability.

Abstract: A steel pipe is provided which is excellent in resistance to outer surface stress corrosion cracking (SCC) when used for a pipeline without impairing the fundamental requirement for the steel as a pipeline. The steel pipe has a surface adjusted to have a mean line roughness Ra of up to 7 &mgr;m and a maximum height Rmax of up to 50 &mgr;m. The surface is adjusted by sand blasting to have this roughness.

Abstract: A titanium alloy sheet having a surface roughness satisfying the relationship Ra≦2 &mgr;m in all directions and a surface waviness satisfying the relationship WCA≦10 &mgr;m shows excellent workability because of the small anisotropy with respect to mechanical properties such as bending properties, and also excellent appearance after it is formed into a component. Such surface conditions of titanium alloy sheet can be obtained by acid pickling or grinding and acid pickling after rolling. Pack rolling, especially in which a titanium alloy slab is packed with carbon steels in vacuum by electron beam welding method and then rolled, is preferable. Application of cross rolling to the rolling makes it possible to obtain smaller anisotropy with respect to mechanical properties.

Abstract: A method for manufacturing a titanium alloy sheet, which comprises the steps of: covering at least one titanium alloy slab with carbon steel plates, welding together the carbon steel plates by means of a high-energy-density welding under a vacuum atmosphere to prepare a carbon steel envelope, thereby preparing an assembled slab, containing the titanium alloy slab therein, with an interior thereof kept at a degree of vacuum of up to 10.sup.-2 ; applying, prior to preparation of the assembled slab, a release agent comprising a solid content having a particle size of up to 325 mesh, onto the surfaces of the titanium alloy slab or onto the inner surfaces of the carbon steel envelope facing thereto, adjusting the total applying quantity of the release agent so as to satisfy the following formula: 5,000.ltoreq.X.multidot.Y/(1-.sqroot. Z).ltoreq.25,000, where X: weight percentage (wt. %) of the solid content in the release agent, Y: total applying quantity (ml/m.sup.

Abstract: A method for manufacturing an .alpha.+.beta. type titanium alloy plate having a small anisotropy in strength by subjecting an .alpha.+.beta. type titanium alloy slab to a hot-rolling, which comprises: the hot-rolling comprising a cross-rolling which comprises a hot-rolling in a L-direction and a hot-rolling in a C-direction, the L-direction being a final rolling direction in the hot-rolling and the C-direction being a direction at right angles to the L-direction; and controlling the cross-rolling so that a value of an overall cross ratio of rolling (CR.sub.total) determined by means of the following formula is kept within a range of from 0.5 to 2.0:CR.sub.total =(CR.sub.1).sup.0.6 .times.(CR.sub.2).sup.0.8 .times.(CR.sub.3).sup.1.0where, CR.sub.1 is a cross ratio of rolling within a rolling temperature region of from under T.beta. .degree.C. to T.beta. .degree.C.-50.degree. C., CR.sub.2 is a cross ratio of rolling within a rolling temperature region of from under T.beta. .degree.C.-50.degree. C. to T.beta. .

Abstract: A magnetic disk substrate having a composition wherein (V/13)+(Fe/20)+(Cr/17)+(Ni/31)+(Co/23) are no greater than 0.010%, Rem+Si+B+W are no greater than 0.015% (where Rem denotes rare earth metals), 0+2N+0.75C are no less than 0.03% and no greater than 0.5%, and the remainder consists substantially of Ti, all % being weight %.

Abstract: A method of manufacturing a titanium alloy magnetic disk substrate comprising (a) cold-rolling an alloy plate at a rolling ratio of no less than 30%, the alloy plate comprising 0.5 wt. % to 1.0 wt. % of Mo and containing oxygen, nitrogen and carbon in amounts such that O+2N+0.75C is from 0.03 wt. % to 0.5 wt. % of the titanium alloy, and the balance being Ti, wherein O is the wt. % of oxygen, N is the wt. % of nitrogen and C is the wt. % of C to form a magnetic disk substrate material and then (b) thermal-flattening the magnetic substrate material from step (a) under a condition defined as follows:500.ltoreq.T.ltoreq.-(150/11).multidot.t+7,850/11 1.ltoreq.twhere T represents a thermal-flattening temperature in .degree.C., and t represents a thermal-flattening time in hours.

Abstract: A method for lapping two surfaces of a titanium disk comprises inserting loosely a titanium disk to be lapped into an opening in a disk-type carrier, the carrier rotating and revolving between an upper surface plate and a lower surface plate which are held in parallel with each other and which applies lapping pressure to the titanium disk, feeding abrasives between the surface plates and the titanium disk and satisfying the following relationship between thickness t (mm) of the titanium disk and thickness T (mm) of the carrier:0.025 exp (t+1.5).ltoreq.T.ltoreq.0.

Abstract: According to a mirror surface polishing process of the present invention, it is possible to produce Ti-made magnetic disc substrate which have the excellent flatness degree and surface roughness in that the average roughness is not more than 0.05 .mu.m and the flatness degree of the outer periphery is not more than 0.15 .mu.m.

Abstract: After the surface roughness of a titanium substrate is set to be R.sub.max .ltoreq.0.08 .mu.m, a hardened layer having a hardness of H.sub.v .gtoreq.250 is formed thereon to have a thickness of 50 to 250 .mu.m by sputtering, thereby manufacturing a titanium magnetic disk substrate.

Abstract: A magnetic disk substrate composition 0.5 wt % to 1.0 wt % of Mo, 0.03 wt % to 0.5 wt % of O+2N+0.75C, and a balance of Ti. The alloy sheet having a composition of above range is cold-rolled at a rolling ratio of 30% or more to form a magnetic disk substrate material, and the material is thermal-flattened under the following condition:500.ltoreq.T.ltoreq.-(150/11).multidot.t+7850/111.ltoreq.twhere T represents a thermal-flattening temperature (.degree.C.), and t represents a thermal-flattening time (houre), thereby obtaining a magnetic disk substrate having the average grain size of 30 .mu.m or less.

Abstract: Titanium magnetic disk substrates are manufactured by preparing a base by stripping not less than 5 .mu.m from the surface layer of a titanium cold-rolled plate, and then forming a film of not less than 5 .mu.m consisting of 1 or more non-magnetic transition metal elements belonging to Groups IVA, VA, VIA, VIIA and VIIIA of the Periodic Table, on the surface of this base.