FR2657624A1 - Process for the manufacture of plates made of ductile metal and its applications - Google Patents

Abstract

The process makes it possible to manufacture plates made of ductile metal such as nickel and copper, whose purity is higher than 99.95 % and which has grains of substantially homogeneous size. …<??>A plate (1) is employed, obtained by electrolytic deposition of the said ductile metal from a master sheet (3) of the same ductile metal. The said plate (1) is subjected to at least one compression or rolling stage followed by an annealing stage, the temperature and the duration of the said annealing and the degree of compression or of rolling being adapted to obtain a substantially uniform size of the grains of metal throughout the thickness of the plate. …<??>Application especially to the manufacture of coatings for hollow charges. … …

Description

The present invention relates to a process for the manufacture of plates

made of ductile metal, such as nickel and copper, whose purity is greater than 99.95% and

having grains of substantially homogeneous dimensions.

The invention also relates to the application of the above process to the production of ductile metal coatings for shaped charges in which the plates obtained are deformed into conical-shaped coatings by flow-forming. It is known that shaped charge coatings, generally made of ductile metal such as nickel and copper, must be made of extremely pure metal (purity

greater than 99.95%).

Furthermore, the dimension of the metal grains of these coatings must be small (less than 50 gm) and this dimension must be as homogeneous as possible in

the entire thickness of the coating.

In addition, the roughness of the surface of these plates

should be low (less than 1 µm).

If these conditions are not met, the jet or dart formed by the metal of these coatings after firing the shaped charge, risks fragmenting more quickly, which would considerably affect

the effectiveness of said jet vis-à-vis a shielding.

It is also known that nickel is obtained by a hydrometallurgical treatment process from mattes with a high nickel content In the final purification operation, an electrolytic deposition of nickel is obtained on a thin nickel substrate produced separately.

and referred to as the "mother" sheet.

Nickel plates are then obtained, also called cathodes, with a thickness of between 10 and 20 mm (depending on the duration of the deposit) These cathodes are made of a high purity nickel (generally greater than 99.97%) with a extremely trace element level

low and very low gas contents.

These plates, the surface of which can reach 1 m 2, have a fairly irregular surface state and a heterogeneous structure in their thickness.In particular, the mother sheet on which the deposit was made has a very heterogeneous structure with grains of large dimensions (up to 'to about 0.5 mm) and a separation surface with the deposited nickel. In addition, the deposition by electrolysis causes, when the cathode reaches a certain thickness, a preferential orientation of the grains perpendicular to the mother sheet. 'accentuates around the surface

outside of the cathode.

For the manufacture of semi-finished and finished products, these pure nickel cathodes undergo annealing operations to facilitate cutting into small squares.

allowing packaging in barrels.

These blocks of material are then melted to produce cast products which will then be transformed.

by various operations of wrought in semi-finished products

finished (bars, tubes, sheets or plates for example).

To avoid the oxidation of nickel during the melting of nickel, it is necessary to add certain elements such as iron, silicon, magnesium or titanium.But the addition of these elements leads to contamination of the nickel, these elements found in the final product in the form of impurities in solution or most often in the form of precipitates In certain applications, these impurities can be particularly troublesome Obtaining nickel of purity equivalent to the starting material can only be achieved by mergers and rejections under vacuum or in a neutral atmosphere of a

significantly higher cost than air casting.

Obtaining a semi-finished product in plates made of high purity nickel with very fine grains

is not only expensive but also difficult to obtain.

Increasing the purity of a metal generally results in difficulty in grain refinement thus, while grains of to 30 µm can be readily obtained in common 99.2% nickel products. metal with a purity greater than 99.9% is most often offered with grains with an average diameter greater than 60 μm

and often even 100 lim.

The above explanations also apply to the case of copper which can also be obtained in the form of plates formed by an electrolytic deposit of copper.

very pure on a mother sheet also in pure copper.

Thus, the nickel or copper plates obtained by electrolytic deposition have the high purity

desired to achieve coatings of shaped charges.

However, the inhomogeneity of the grain size of these plates, as well as the roughness of their surface, does not make them usable as such in the aforementioned application, or in any other application involving the same requirements. The aim of the present invention is to provide a process making it possible to produce ductile metal plates (copper or nickel) having both a purity greater than 99.95, grains of substantially regular dimensions throughout the thickness of the plates, as well as a

low surface roughness.

According to the invention, this method is characterized in that a plate obtained by electrolytic deposition of said ductile metal on a mother sheet of the same ductile metal is used, and in that said plate is subjected to at least one compression step and successive rolling in several passes, followed by an annealing step, the temperature and duration of said annealing and the compression or rolling ratio being adapted to obtain a substantially uniform dimension of the metal grains

throughout the thickness of the plate.

These annealing and compression or rolling operations have the effect of refining the size of the grains and considerably reducing the difference between the size of the grains of the mother sheet of the plates and that of the grains corresponding to the electrolytic deposit applied on

both sides of this mother sheet.

Besides, rolling or compressing

decreases the roughness of the plate surface.

The method according to the invention thus makes it possible to obtain at low cost, starting from semi-finished plates a very pure ductile metal, plates having the properties required in particular for the manufacture of

shaped charge coatings.

Other peculiarities and advantages of

the invention will appear further in the description below.

after. In the accompanying drawings given by way of non-limiting examples: FIG. 1 is a view in section of a nickel or copper plate obtained by electrolytic deposition on a mother sheet, FIG. 2 is a view in partial section and to scale enlarged of this plate after annealing, figure 3 shows schematically the rolling of a plate, figure 4 is a plan view of a plate showing the eight directions of the successive rolling passes, figure 5 is a view similar to FIG. 2, showing the fineness and the homogeneity of the grains of the plate obtained according to the method according to the invention, FIG. 6 shows in longitudinal section, a conical coating for shaped charge obtained from a ductile metal plate produced according to the method of the invention. In the process for the manufacture of ductile metal plates, such as nickel and copper, the purity of which is greater than 99.95% and having grains of substantially homogeneous dimensions, a plate 1 as shown in the figure is used. 1 obtained by electrolytic deposition 2 of said ductile metal on both sides

of a mother sheet 3 of the same ductile metal.

As shown in figure 2, the mother leaf 3 consists essentially of grains 4 of large

dimension (some reach 0.5 mm).

The electrolytic deposits 2 applied on either side of the mother sheet 3 consist of grains 5 more or less elongated in a direction perpendicular to the mother sheet 3 Such a plate 1 is not directly usable in the applications envisaged by the present

invention.

The method according to the invention essentially consists in subjecting the plate 1 to at least one step of compressions and successive rolling in several passes, followed by an annealing step The temperature and duration of said annealing and the compression ratio or rolling are adapted to obtain a substantially uniform dimension of the metal grains in

the entire thickness of the plate 1.

According to a preferred version, the method according to the invention, applied to the production of substantially pure nickel plates comprises the following steps: the initial plate 1 is annealed at a temperature above 6000 ° C. under a neutral atmosphere or under vacuum, the plate is cut. plate 1, in plates of smaller dimensions according to the desired final format, said cut plates are subjected to a succession of crossed rolling or uniaxial compression to reduce their thickness by 25 to 30%, the plates are annealed at a temperature above 4500 C for approximately 2 hours, the plates are again subjected to a succession of cross-rollings in order to reduce their thickness by approximately 50% and a final annealing of the plates is carried out.

between 3500 C and 4500 C for about 2 hours.

The rolling step is illustrated by the figures

3 and 4.

After implementation of the aforementioned method, the dimension of the grains of the plates obtained is substantially homogeneous throughout their thickness, their average dimension being less than 30 μm. This result is shown on

figure 5.

Moreover, in particular thanks to rolling, the roughness of the surface of the plates obtained is lower

at 1 pm.

In an alternative embodiment of the process according to the invention, also applied to the production of substantially pure nickel plates, the following steps are carried out: the initial plate 1 is annealed at a temperature above 6000 ° C. under a neutral atmosphere or under vacuum, the plate 1 is cut into smaller size plates according to the desired final format, said plates are subjected to a succession of cross-rolling in several passes to reduce their thickness by more than 50%, and they are subjected to a final annealing at a temperature between 350 and 5000 C for

a duration of approximately 1 to 2 hours.

In this case, the grain size of the plates obtained is less than about 35 μm in the central zone 3 and less than approximately 25 μm in the outer zones corresponding to the electrolytic deposition of nickel 2. Preferably, the lamination of the plates is carried out in at least eight successive passes, the rolling direction undergoing a rotation of 450 after each pass, as shown by the directions A, B, C, D, E, F, G,

H in figure 4.

This way of proceeding makes it possible to laminate the plates in all directions thereof, which is favorable to obtaining a perfect homogeneity of the dimensions of the grains, and makes it possible to avoid detachment.

possible between the different nickel layers.

The method according to the invention can also be applied to the production of substantially pure copper plates, constituted as above by electrolytic deposits of copper on a mother sheet.

also made of pure copper.

According to this process, the initial plate is annealed at a temperature between 300 and 5500 C under a neutral atmosphere or under vacuum, the plate is cut into smaller-sized plates according to the desired final format, said plates are subjected to a succession of cross-rolling, in several passes to reduce their thickness by more than 50% and, they are subjected to annealing at a temperature between 200 and 4000 C for a period of

duration of about 1 to 2 hours.

Two numerical examples are given below which illustrate the process for manufacturing nickel plates.

having a degree of purity greater than 99.95%.

Example 1:

We start with raw plates of electrolytically deposited nickel and having an initial thickness of

16 mm.

These plates are first annealed at 6500 C for 4 hours, then cut into square plates or

circulars of 120 mm side or diameter.

The cut plates are then rolled with an overall hardening rate of 30% in three times four cross passes at 900 in the directions A, C, E and G of

figure 4.

The thickness reduction is 0.5 mm for the first four passes, 0.4 mm for the four passes

following steps and 0.3 mm for the last four passes.

The plates thus have, after this rolling

a thickness equal to 11.2 mm.

The plates are then annealed at 5500 C for 2 hours, then they are again subjected to a rolling three times eight cross passes at 450 C according to the directions ABCDEFGH of Figure 4 This rolling reduced by 50%

the thickness of the plates.

The thickness reduction is 0.4 mm for the first eight passes, 0.2 mm for the eight passes

following steps and 0.1 mm for the last eight passes.

The final thickness of the plates is 5.6 mm.

These plates undergo a final annealing at 3500 C

during 2 hours.

Example 2

The initial plates of Example 1 undergo after an initial annealing at 6500 C and cutting, a first rolling achieving a thickness reduction rate equal to% The rolling is carried out by cross passes at 450

as shown in figure 4.

The thickness reduction is 0.5 mm for the first 16 passes, 0.3 mm for the next 8 passes, and

0.1 mm for the last 8 passes.

The plates thus rolled undergo annealing

final at 390 WC for 2 hours.

The plates thus obtained have grains of substantially uniform size equal to approximately 10 Vm. Thanks to the high purity of the metal of these plates, the fineness and uniformity of the grains thereof and the low roughness of their surface, these plates can be

used to make coatings of shaped charges.

For this purpose, it suffices to deform these plates into conical shaped coatings, according to the known technique of

flow-forming.

Another application of the method according to the invention

is the manufacture from the plates treated as below

above, coin by stamping or forging.

Claims (4)

1 Process for the manufacture of ductile metal plates, such as nickel and copper, the purity of which is greater than 99.95% and having grains of substantially homogeneous dimensions, characterized in that a plate (1) is used obtained by electrolytic deposition of said ductile metal on a mother sheet (3) of the same ductile metal, and in that said plate is subjected to at least one step of compressions and successive rolling in several passes, followed by an annealing step , the temperature and the duration of said annealing and the compression or rolling ratio being adapted to obtain a substantially uniform dimension of the metal grains throughout the thickness of the plate. 2 A method according to claim 1, applied to the production of substantially pure nickel plates, characterized by the following steps: the initial plate (1) is annealed at a temperature above 6000 C under a neutral atmosphere or under vacuum, the cut is cut. plate (1), in plates of smaller dimensions according to the desired final format, said plates are subjected to a succession of cross-rolling or uniaxial compression to reduce their thickness by 25 to 30%, the plates are annealed at a temperature above 4500 C for approximately 2 hours, the plates are again subjected to a succession of cross-rollings in order to reduce their thickness by approximately 50% and a final annealing of the plates is carried out. between 3500 C and 4500 C for about 2 hours. 3 A method according to claim 2, characterized in that the grain size of the plates obtained is substantially homogeneous throughout their thickness, their average dimension being less than 30 μm. 4 A method according to claim 2, characterized in that the roughness of the surface of the plates obtained is less than 1 aum. Process according to Claim 1, applied to the production of substantially pure nickel plates, characterized by the following steps: the initial plate is annealed at a temperature above 6000 C under a neutral atmosphere or under vacuum, the plate is cut into plates of smaller dimensions depending on the desired final format, said plates are subjected to a succession of cross-rolling, in several passes, to reduce their thickness by more than 50% and, they are subjected to a final annealing at a temperature between 350 and 5000 C for a duration of approximately 1 to 2 hours. 6 A method according to claim 5, characterized in that the grain size of the plates obtained is less than approximately 35 pn in the central zone (3) and less than approximately 25 μm in the outer zones corresponding to the electrolytic deposition of nickel (2 ). 7 Method according to one of claims 2 to 6, characterized in that the rolling of the plates is carried out in at least eight successive passes, the rolling direction undergoing a rotation of 450 after each pass. 8 A method according to claim 1, applied to the production of substantially pure copper plates, characterized by the following steps: the initial plate is annealed at a temperature between 300 and 5500 C under a neutral atmosphere or under vacuum, the plate is cut. , in plates of smaller dimensions according to the desired final format, said plates are subjected to a succession of cross-rolling, in several passes, to reduce their thickness by more than 50%, and they are subjected to annealing at a temperature between 200 and 4000 C for a period of approximately 1 to 2 hours. 9 Application of the process in accordance with one of the claims 1 to 8 to the production of coatings in ductile metal for shaped charges in which the resulting plates are deformed into shaped coatings conical by flow-forming.