Titanium slab for surface melting treatment and titanium material for hot rolling using same

Abstract

Provided is a titanium slab for surface melting treatment which is used in production of a titanium material by forming a re-melted/solidified layer having a depth of d1, through surface melting treatment, on a surface of a titanium slab in an as-cast state obtained by DC slab casting in a vacuum or in an inert gas atmosphere, and performing hot rolling using the surface as a rolling surface, wherein an increase C1 in average oxygen concentration in a first region (a region between the surface and a position at d1/2) is 0.20 mass% or less, and an increase C2 in average oxygen concentration ina second region (a region between the position at d1/2 and a position at d1) is 0.05 mass% or less, with respect to the average oxygen concentration of a base material for the titanium slab, in the thickness direction of the titanium slab, and Cd (=C1-C2) is more than 0 and not more than 0.15 mass%. The titanium slab for surface melting treatment has excellent workability in cold rolling or cold molding after hot rolling.

Description

technical field [0001] The present invention relates to a titanium slab for surface fusion treatment made of industrially pure titanium and a titanium blank for hot rolling obtained by subjecting the slab to surface fusion treatment. Background technique [0002] Generally speaking, as pure titanium for industrial use, sponge titanium and titanium chips obtained by the Kroll method are usually used as smelting raw materials, and vacuum arc melting (VAR), electron beam melting (EBR) or plasma arc melting is used. The smelting method of a high-density heat energy source performs smelting to form a large slab (ingot). Here, the shape of the slab is limited to a cylindrical slab (round ingot) in the case of vacuum arc melting, while in the case of electron beam melting and plasma arc melting, it can be Cast into rectangular billets, ie slabs. [0003] Furthermore, when such a large cast slab is used as a raw material to manufacture a titanium thin plate, in general, after the ...

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Problems solved by technology

Therefore, the yield of the material is lowered, and cutting work and cost are required, so there is still a strong demand for improvement.

[0008] Furthermore, even when the DC slab is subjected to surface machining and then subjected to hot rolling, there is a problem that the surface properties of the hot-rolled sheet after hot rolling are not necessarily good.

That is, there is a problem that a large number of cap-shaped (Japanese: 袁さり-shaped) flaws with a length of sev

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