Metal treatment – Stock – Ferrous
Reexamination Certificate
2001-08-27
2003-08-12
Yee, Deborah (Department: 1742)
Metal treatment
Stock
Ferrous
C148S621000, C148S652000, C148S675000
Reexamination Certificate
active
06605163
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the manufacture of a strip made of an Fe—Ni alloy of the “&ggr;′ and/or &ggr;″ structural hardening” type and to the strip obtained.
To manufacture articles such as tensioned shadow mask support frames for colour television tubes, strips made of an Fe—Ni alloy of the “&ggr;′ and/or &ggr;″ structural hardening” type, having a low expansion coefficient and a high yield strength after hardening, are used.
The process for manufacturing these frames comprises many operations. First of all, parts are cut from a softened strip, which parts are bent and then assembled by welding so as to obtain a frame. A series of operations are carried out on this frame, intended to blacken it, by forming a layer of oxides, and to harden it and to fasten the shadow mask. During these operations, the frame is subjected to forces at high temperature which may cause creep, possibly resulting in unacceptable deformation or even fracture.
SUMMARY OF THE INVENTION.
It is the object of the present invention to provide a process which makes it possible to obtain a strip made of an Fe—Ni alloy of the “&ggr;′ and/or &ggr;″ structural hardening” type which exhibits good creep strength and which, preferably, has good blackenability.
For this purpose, the subject of the invention is a process for manufacturing a strip made of an Fe—Ni alloy of the “&ggr;′ and/or &ggr;″ structural hardening” type, the thermal expansion coefficient between 20° C. and 150° C. of which is less than 7×10
−6
/K, in which:
a hot strip is manufactured either by hot rolling a semi-finished product or by direct casting of a thin strip which is optionally lightly hot-rolled, and the hot strip is subjected to a softening annealing operation consisting of a soak between 950° C. and 1200° C. followed by rapid cooling and optionally a pickling operation, in order to obtain a softened strip;
a cold-worked strip is manufactured by cold rolling the said softened strip, with a reduction ratio of greater than 5%; and
the cold-worked strip is subjected to a recrystallization annealing operation in an inert or reducing atmosphere, carried out either on the run with a residence time between 900° C. and 1200° C. of between 30 s and 5 min, or statically with a soak at a temperature of between 900° C. and 1050° C. for a time of between 15 min to 5 h, followed by cooling down to a temperature below 500° C. at a cooling rate sufficient to prevent the formation of hardening precipitates.
The invention also relates to an unhardened strip made of an Fe—Ni alloy of the “&ggr;′ and/or &ggr;″ structural hardening” type, the thermal expansion coefficient between 20° C. and 150° C. of which is less than 7×10
−6
/K, which after hardening by the precipitation of &ggr;′ and/or &ggr;″ phases has a yield strength greater than 600 MPa and a creep resistance at 600° C. for 1 hour at 350 MPa characterized by a creep strain of less than 0.2%, and at least one side of which optionally includes a uniform gold-coloured layer.
REFERENCES:
patent: 5520755 (1996-05-01), Inoue et al.
patent: 5688471 (1997-11-01), Smith et al.
Cozar Ricardo
Reyal Jean-Pierre
Reydet Pierre Louis
Imphy Ugine Precision
Yee Deborah
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