Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Reexamination Certificate
1999-05-03
2001-07-31
King, Roy (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
C148S671000
Reexamination Certificate
active
06267831
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the continuous manufacturer of a titanium or titanium alloy strip in a continuous processing line wherein annealing and pickling, or pickling alone is carried out, and more particularly, to a useful method for making a titanium or titanium alloy strip wherein gloss or glossiness is rendered homogeneous or uniform between different titanium strips or throughout the same titanium strip.
2. Description of the Prior Art
As the development of water front is now in progress and acidic rain is generated, an environment on buildings is beginning to turn severe in recent years. Moreover, a rise in maintenance cost has been experienced. Hence, attention has now been paid to maintenance-free building materials, which are excellent in corrosion resistance and long in lifetime. Under these circumstances, building materials consisting of titanium strips and titanium alloy strips (which may be sometimes referred generically as “titanium strip or strips”) are recently used in steadily increasing amounts.
The main reason for this is that titanium has very good corrosion resistance and undergoes little corrosion in an atmospheric environment. Besides, one of factors, with which titanium is favored, is that it assumes a peculiar silver white color and various kinds of design properties can be imparted thereto by surface treatments. As titanium is increasing in its applications to buildings, diverse demands are created for surface design properties, and particularly, it is frequently required to appropriately control a surface gloss.
It is known that the surface finishing method of a pure titanium strip for building material is broadly classified into vacuum annealing finish and pickling finish. The titanium strip obtained by the vacuum annealing finish has an as-rolled surface texture and has a glittering feel, with a loss of a decorative appearance. In addition, gloss control is difficult, which often leads to the problem that a difference in gloss appears between the sites of an actual titanium strip article. In contrast to the vacuum annealing finish, the pickling finish is sometimes favored due to the fact that a surface gloss can be at a relatively low level, and thus, reflection of light can be suppressed as desired.
Where a titanium strip used as a pickling finish material is industrially obtained, usual practice is to use a continuous annealing and pickling line having such an arrangement as shown in FIG.
1
. In this line, an atmospheric annealing furnace, a salt bath and a pickling bath are arranged in series, and a titanium strip is passed successively through these devices. As a result, a cold rolled titanium strip for building material can be continuously annealed and de-scaled. Among these steps, the atmospheric annealing is carried out for the purpose of removing the strain caused in the course of cold rolling and controlling the structure in order to obtain desired mechanical properties.
The immersion in the salt bath is for the purpose that the scale formed during the atmospheric annealing is more likely to be removed by pickling. The titanium strip obtained after the atmospheric annealing is immersed in a salt bath containing sodium hydroxide and sodium nitrate as main components at high temperatures of about 500° C., whereupon part of the scale is dissolved in the bath, and simultaneously, the scale is cracked due to thermal shock exerted thereon. Subsequently, pickling using hydrofluoric acid and nitric acid is performed, under which a pickling solution is impregnated in to the base metal through the cracks thereby causing the boundary between the scale and the base metal to be dissolved out. Eventually, the scale can be completely removed to provide metallic luster. Since the continuous annealing and pickling line has such multiple steps as set out above, the relationship between the treating conditions in the respective steps and the gloss has not been always fully made clear. Accordingly, it has been difficult to make a uniform gloss between titanium strips and also on or throughout the same titanium strip although not so difficult as in the case of the vacuum annealing finish. Thus, it is believed that any reliable technique of obtaining such a gloss as required by users has never been established.
For instance, Japanese Laid-open Patent Application No. Hei 8-296071 discloses a method of making a titanium material having a reduced gloss and a good anti-glazing property. However, this method has the problem that gloss cannot be made uniform between different titanium strips or throughout the same titanium strip. Further, in Japanese Laid-open Patent No. Hei 9-3573, there is disclosed a titanium material having good anti-glazing property and its manufacture. However, a uniform gloss cannot be obtained between different titanium strips or throughout the same titanium strip.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for making a titanium strip in a continuous annealing and pickling line or in a pickling line alone, which overcomes the problems of the prior art counterparts.
It is another object of the invention to provide a method for making a titanium strip that has a homogeneous or uniform gloss between different titanium strips or throughout the same titanium strip.
The above objects can be achieved, according to one embodiment of the invention, by a method for making a titanium or titanium alloy strip, which comprises subjecting a titanium or titanium alloy strip to pickling finish according to a continuous annealing and pickling line or a pickling line wherein the titanium or titanium alloy strip is passed through a pickling vessel having a pickling roll plural times while inverting the strip in the vessel at least once during the plural time. The term “inverting” used herein is intended to mean that the upside of the strip is turned down in the vessel.
The above objects can also be achieved according to further embodiments of the invention which are summarized below as (1) to (3).
(1) When titanium or titanium alloy strips having different widths are subjected to pickling finish in a continuous annealing and pickling line or in a pickling line, the pickling finish is carried out in such a way that a difference in width between the preceding and succeeding strips is within a range of not more than 50% of the width of the preceding strip.
(2) When a titanium or titanium alloy strip is subjected to pickling finish in a continuous annealing and pickling line or a pickling line, the pickling finish is carried out in such a way that a titanium ion concentration in a pickling solution is within a range of not less than 0.1 g/liter.
(3) When a titanium or titanium alloy strip is subjected to pickling finish in a continuous annealing and pickling line or a pickling line, the pickling finish is carried out in such a way that an oxygen content in a furnace atmosphere in an annealing furnace is within a range of not lsee than 0.1 vol %.
The embodiments (1) to (3) may be used singly or, if necessary, in combination. For instance, the first-mentioned method of the invention may be carried out in combination with the embodiment (1). Likewise, the first-mentioned method of the invention may be carried out while satisfying the requirements of the embodiments (1) and (3). Moreover, the first-mentioned method of the invention may be performed while satisfying the requirements of the embodiments (2) and (3). As a matter of course, it is very effective to carry out the method of the invention while satisfying the requirements of all of the further embodiments (1) to (3).
REFERENCES:
patent: 4643939 (1987-02-01), Sugiyama et al.
patent: 5759307 (1998-06-01), Berger et al.
patent: 5-222558 (1993-08-01), None
patent: 6-10329 (1994-02-01), None
patent: 8-291397 (1996-11-01), None
patent: 8-296071 (1996-11-01), None
patent: 9-3573 (1997-01-01), None
patent: 9-143769 (1997-06-01), None
patent: 9-157871 (1997-06-01), None
patent: 9-157872 (1997-06-01), None
Takashi Yas
Coy Nicole
Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel Ltd).
King Roy
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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