Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Patent
1992-05-28
1993-05-04
Roy, Upendra
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
148669, 420421, C22C 1400
Patent
active
052078450
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for manufacturing rolled articles of titanium material.
BACKGROUND OF THE INVENTION
Titanium reacts with oxygen in the air when the titanium becomes at high temperature (about more than 600.degree. C.) to form an oxide layer or film having several tens of .mu. in depth on and in the surface layer of titanium. Therefore, in case of hot rolling of titanium, the oxide film is formed on the surface of red heated titanium. However, since the titanium oxide is inferior in ductility, it causes a problem that the titanium is easily cracked. Conventionally, rolling speed and rolling temperature must be suitably adjusted or fitted to each kind and quality or property of the material to prevent its cracking.
However, it is very hard to adjust the rolling speed and rolling temperature fitting each kind and quality of the material and it is substantially impossible to exclude the crack and the like.
Accordingly, an object of the present invention is to provide a process for manufacturing rolled articles of titanium material wherein an oxide layer on the surface of titanium material is removed to be able to exclude crack and the like caused in rolling.
SUMMARY OF THE INVENTION
To accomplish the above object, the process for manufacturing rolled articles of titanium material comprises steps of contacting titanium material in a heated condition with fluorine- or fluoride-containing gas to form a fluoride layer on the surface of the titanium material, removing the fluoride layer formed on the surface of the titanium material just before rolling and then rolling the titanium material to give a rolled article.
In detail, in the process for manufacturing rolled articles of titanium material, prior to rolling the titanium material, the titanium material in a heated condition is contacted with a fluorine- or fluoride-containing gas by, for example, passing it through a fluorine- or fluoride-containing gas atmosphere. An oxide layer formed on the surface of the titanium material by its reaction with oxygen in the air is thereby removed with the fluorine- or fluoride-containing gas to clean the surface of the titanium material and simultaneously to form a fluoride layer on the cleaned surface. The fluoride layer is stable, so that re-formation of an oxide layer and adsorption of O.sub.2 on the base material of the titanium material are prevented until the subsequent removal process. Then, the fluoride layer on the surface of the titanium material is decomposed and removed just before rolling to cause the base material of the titanium material to be exposed. When the titanium material is rolled, no oxide layer is left on its surface. The oxide layer is not formed during the rolling because of high rolling speed, so that cracking in the rolling process can be prevented.
Next, the present invention is described in detail.
Fluorine- or fluoride-containing gas to be used for the process in the present invention is an inert gas, such as N.sub.2, containing at least one of the fluorine source components, such as NF.sub.3, BF.sub.3, CF.sub.4, HF, SF.sub.6, and F.sub.2. NF.sub.3 is most preferable and practical in respect of reactivity, easiness of handling and other properties.
As mentioned above, in the process for manufacturing a rolled articles of titanium material according to the present invention, heated titanium material is contacted with a fluorine- or fluoride-containing gas prior to rolling to conduct a surface treatment of the titanium material by, for example, passing the titanium material through a fluorine- or fluoride-containing gas atmosphere. Thereafter, H.sub.2 gas or the like is sprayed on the titanium material just before rolling to remove a fluoride layer from its surface to expose base material thereof. The material is then rolled to obtain a rolled article. Concentration of the fluorine source components, such as NF.sub.3 of the fluorine- or fluoride-containing gas is, for example, 1000 to 100000 ppm, preferably 20000 to 70000 ppm and most preferably
REFERENCES:
patent: 4098623 (1978-07-01), Ibaraki et al.
patent: 4528043 (1985-07-01), Mills
patent: 4634478 (1987-01-01), Shimogori et al.
patent: 4874480 (1989-10-01), Sonoda et al.
Senbokuya Haruo
Tahara Masaaki
Yoshino Akira
Daidousanso Co. Ltd.
Roy Upendra
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