A method for preparing metal hafnium tubes for neutron absorbing components in a stack

Abstract

The invention discloses a preparation method of a metal hafnium pipe for an in-reactor neutron absorption assembly. The preparation method comprises the following steps: 1, cleaning and drying a hafnium pipe blank, uniformly applying a graphite colloid lubricant to the inner and outer surfaces of the cleaned and dried hafnium pipe blank, and then carrying out drying in the air, so as to obtain a to-be-rolled metal hafnium pipe blank; 2, under the continuous atmosphere heating condition, rolling the to-be-rolled metal hafnium pipe blank by adopting a two-roll ring and groove high-speed pipe rolling mill; 3, carrying out annealing, straightening, inner and outer surface grinding, and polishing treatment in sequence, so as to obtain a semi-finished metal hafnium pipe product; and 4, carryingout finishing treatment and quality inspection, so as to obtain a finished metal hafnium pipe product for the in-reactor neutron absorption assembly. According to the preparation method disclosed by the invention, the hot rolling action of the two-roll ring and groove high-speed pipe rolling mill and the common annealing technology are combined, so that the pipe machining process can be remarkablyshortened, and the metal hafnium pipe being high in size precision, uniform in structure as well as excellent in mechanical property and anti-corrosion property can be obtained.

Description

technical field [0001] The invention belongs to the technical field of metal hafnium pipe material processing, and in particular relates to a preparation method of metal hafnium pipe material for neutron absorbing components in a stack. Background technique [0002] Metal hafnium has good neutron absorption capacity, and its thermal neutron absorption cross section can reach 115×10 -28 m 2 , can manufacture neutron absorbing components in the reactor to control the reactor chain reaction. Although the neutron absorption capacity of hafnium has no obvious advantages compared with boron and cadmium, the irradiation product of hafnium is a hafnium isotope that still has a high neutron absorption cross section, and can last for several generations. There is no need to replace it during the lifetime of 1 year; at the same time, metal hafnium also exhibits excellent mechanical properties and corrosion properties, and the dense oxide film formed in the high-temperature and high-p...

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Problems solved by technology

Among them, the smelting and preparation of ingots is mainly carried out by electron beam smelting, and the pipe billet is usually prepared by extrusion. The pipe preparation process is traditionally carried out by cold rolling with a multi-roll pipe mill, but the existing manufacturing defects are as follows: First, The work-hardening speed of hafnium is fast, and the deformation of the multi-roll cold rolling method is limited to about 10% to 15%, and the intermediate vacuum annealing needs to be carried out when the total processing rate is 30% to 40%, otherwise it will produce A large number of cracks cause the product to be scrapped; second, according to the traditional processing method, the plastic deformation rate of the hafnium pipe structure is insufficient, and the degree of grain fragmentation is not enough. The deformation twins produced will grow back into coarse grains after heat treatment, and there are certain twins. crystal, typical metallographic structure photos are attached figure 1 , it is difficult to obtain products with higher strength and higher elongation, and the performance of products often does not meet the requirements; third, the uneven structure produced by the traditional cold processing method with small deformation is not good for the corrosion performance of hafnium

Corrosion of hafnium in the reactor first occurs on the surface of neutron absorbing components, forming tetragonal HfO 2 Oxide film, the growth rate of the oxide film is different on different crystal arrangement planes, and its density and stability are related to the microstructure and uniformity of the material, while the traditional cold rolling method has no solution for this; fourth, the traditional processing method Because the total processing rate of cold rolling is 30% to 40%, vacuum annealing is required to eliminate the processing stress, resulting in a long process flow, and the use of degreasing agent and acid solution many times, which is not conducive to environmental protection

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