Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Patent
1997-04-17
1999-03-02
Sheehan, John
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
148519, C22F 118
Patent
active
058765247
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for the manufacture of tubes of zirconium-based alloys for cladding of nuclear core materials and for the manufacture of skeletons of nuclear elements for usage in nuclear reactors including several successive deformation and annealing steps. The invention in particularly useful but not only for the manufacture of cladding tubes and construction of guide tubes and instrumental tubes for fuel elements in pressurized water reactors (PWR), the cladding and construction tubes of which are manufactured of a zirconium-based alloy.
The most frequently used Zirconium alloys "Zircaloys" sofar are Zircaloy-2 and Zircaloy-4 according to ASTM B 811. These alloys have the following composition:
______________________________________ Percentage by weight
Element Zircaloy-2
Zircaloy-4
______________________________________
Sn 1.2-1.7 1.2-1.7
Fe 0.07-0.20
0.18-0.24
Cr 0.05-0.15
0.07-0.23
Ni 0.03-0.08
--
Zr Rest Rest
______________________________________
In addition to the fulfillment of the above analysis these alloys should also contain oxygen at amounts between 900 and 1600 ppm, usually 1200.+-.200 ppm for cladding tubes and construction tubes for fuel element skeletons. Commercial Zircaloy-2 and Zircaloy-4 are also used which contain small and well defined amounts of Si and/or C, preferably in amounts of 50-120 ppm Si and 80-270 ppm C.
These zirconium-based alloys are chosen because of their nuclear properties, primarily their small ability of neutron absorption, mechanical properties and their resistance towards corrosion in water and steam at high temperatures. Nevertheless it is important to improve the mechanical properties and the corrosion resistance in order to achieve a longer service life in the reactor and thereby increasing the degree of burn-up. It is of particular interest to be able to reduce the irradiation induced axial growth in construction tubes. Various types of heat treatments of the tubes during their manufacture have been suggested in order to extend their service lives.
It has been common practice to manufacture cladding and construction tubes of Zircaloy-2 and Zircaloy-4 by a process which includes: hot working of an ingot into a solid billet, heating said billet to the beta phase range followed by quenching, so-called beta-quenching, machining to obtain a hollow extrusion tube billet, extruding said tube billet at high temperature within the alfa phase range to an extruded hollow tube followed by reduction thereof in several steps by cold rolling to substantially final dimension whilst subjecting said tube to a recrystallization annealing in vacuum before each cold rolling step. The cold worked tube which substantially has a final dimension is then subjected to vacuum annealing in the alfa phase range or in case of a construction tube is subjected to an additional cold deformation such as rolling or drawing before the final vacuum annealing. The final annealing in vacuuim is performed consisting of a stress-relief, a partial recrystallization or a complete recrystallization. The kind of final vacuum annealing is selected based upon the specification by the fuel manufacturer regarding the mechanical properties for the cladding tubes and the construction tubes.
By ".alpha. range" should be understood the temperature range in which the crystalline structure of the alloy is hexagonal and close packed (.alpha. phase), and by ".beta. range" the temperature range in which the crystalline structure of the alloy is body centered cubic (.beta. phase). The transition temperature from a phase to .beta. phase of pure zirconium is 862.degree. C.
Zirconium-based alloys have an intermediate range where the two crystalline structures .alpha. and .beta. are present. This range, where the Zircaloy-2 and Zircaloy-4 alloy is in the so-called a .alpha.+.beta. phase, extends in the temperature range between 800.degree. C. and 950.degree. C.
Various types of different manufacturing methods have been suggested for the purpose of improving the corrosion resistan
REFERENCES:
patent: 3847684 (1974-11-01), Amick
patent: 3865635 (1975-02-01), Hofvenstam et al.
patent: 4450016 (1984-05-01), Vesterlund et al.
patent: 4450020 (1984-05-01), Vesterlund
patent: 4908071 (1990-03-01), Anderson et al.
Sandvik AB
Sheehan John
LandOfFree
Method for the manufacture of tubes of a zirconium based alloy f does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the manufacture of tubes of a zirconium based alloy f, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the manufacture of tubes of a zirconium based alloy f will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-418438