LU86831A1 - Appts. for continuous electrodeposition of thin metallic strip - has endless titanium belt cathode and perforated graphite sheet anodes - Google Patents

Abstract

A machine for the continuous production by electro-deposition of very thin metallic strip. The main feature is the use of a continuously moving metallic belt as the cathode. A horizontal metallic belt, preferably made from titanium, and with a highly polished surface, is stretched between two driven rollers. Anodes made from perforated graphite sheets are fixed along the outer faces of the upper and lower strands of the belt. These sections are contained in a sealed enclosure. Electrolyte is pumped from a reservoir into the narrow voids between the anodes and the cathode belt, draining to the reservoir directly or via a duct. The negative terminal of an electrical supply is connected to the belt by bruches submerged in the electrolyte, and the positive terminal is connected to the graphite anodes via copper bars running the length of the submerged part of the machine. After leaving the enclosure, the deposit on the belt is washed by jets of hot water and dried by an air blast. The deposited sheet is separated from the belt by a roller mounted at the level of the pulley centre-line. Subsequent treatments on the product strip can include flash heating to form a protective oxide coating, gas carburisation to adjust the carbon content of an iron deposit, tinning, and the application of protective finishes such as lacquer, varnish and resin.

Description

C 2396 - 2.5482

- * 6-8-5-1 GRAND-DUCHY OF LUXEMBOURG

N® patent ........................................

March 27, 1987 Minister * ... Rwp§> j of the Economy and the Middle Classes

Title issued ......................................... çgLjg Intellectual Property Service ' SM LUXEMBOURG! 27.1.82 w • jo Invention Patent Application yt ο, ** ..

I. Request

The METALLURGICAL RESEARCH CENTER-CENTRUM VOOR RESEARCH (1) IN DE METALLURGIE.association non-profit-vereniging zonder winstoogmerk.47.rue Montover.1040 Brussels, Belgium.represented by Me Alain RUKAVINA from Luxembourg, acting as mandata deposit (s) this .....: v: ing ± .- .. s.ep ± .... March ..... l.9.QQ .... q.untr.e-.y : irig ± -.sept _______________ (3) at. 15 ..,. 00 ..... hours, at the Ministry of the Economy and the Middle Classes, in Luxembourg: 1. this request for obtaining a patent of invention concerning: ----- ---------------------------------------------------------- ---------------------------------------------------------- ----------------------- (4) "Extra-thin metallic foil and manufacturing process .............. ........

of a. such sheet "________________________________________________________________________________________________________________________________________________________________________________ 2. 2. the delegation of power, dated ........ Brussels______________________ on ..... 2.5 · ... mar-S — lâ & 7 .....- 3. the description in language________ . £ .r. & N.Ç.ais.g ._________________________ of the invention in two copies; 4 .................... drawing boards, in two copies; 5. the receipt of the taxes paid to the Luxembourg Registration Office, ........... 2.7 ..... March ..... 19.82 ......... .................................................. .................................................. .................................................. .................................................. .....

declares (s) assuming responsibility for this declaration, that the inventor (s) is (are): dd.Qnsieur ..... Mar.ios ... £ C.QN.OMQÈO.U.LO .S., ...... Quai ..... Marcal-lis ·., ...... 6./.144., -4020 ------------- (5)

Liège., ...... Be.lgi.Quej .................................... .................................................. .................................................. .................................................. ...........................

Mademo.isel.le ..... Nicole ...... LAMBERT .., ....... aY.enue ...... Guillaume ..... J..aac.h .im., ...... 42., __________________________

Br.437.Q..Waremm Belgium ......................................... .................................................. .................................................. ..................

claims (s) for the above patent application the priority of one (s) application (s) of (6) ................... LL .... .................................................. ............... filed in (7) ........... L1 ............... .................................................. ..............................................

on .................... LL ............................ .................................................. .................................................. .................................................. .................................................. ............ (8) on behalf of .............. LJ ................. .................................................. .................................................. .................................................. .................................................. ....... (9) elect (elect) for him / her and, if appointed, for his / her proxy, in Luxembourg .................... .............

IDA., ...... bouley.ar.d ..... de .... la .... Eoire .................. .................................................. .................................................. ................................. (10) seeks (s) the grant of a patent for invention for the object described and represented in the abovementioned appendices, - with postponement of this issue to ....... eighteen ^ eighteen months ... (11)

The manda # ai v .....................................

I J / s Q, Procès-verbal de Dépôt / / The aforementioned patent application has been filed with the Ministry of the Economy and Classes / Medium-sized, Intellectual Property Service in Luxembourg, on:

A * 'V \ I

(i "··. * t \ Pr. lé Minister at 15.00 hours J |. \ é Se l'Economie et ^ las Classes Moyennes, à / A 68007 f" s i.stii "C 2396/8703.

DESCRIPTIVE MEMORY

filed in support of an INVENTION PATENT application

in the Grand Duchy of LUXEMBOURG

on behalf of: METALLURGICAL RESEARCH CENTER - CENTRUM VOOR RESEARCH IN DE METALLURGIE,

Non-profit association -Vereniging zonder winstoogmerk in Brussels, (Belgium) for: "Extra-thin metallic foil and process for manufacturing such a foil".

i.

"- i -

Extra-thin metal sheet and method of manufacturing such a sheet.

The present invention relates to an extra-thin metal sheet, in particular an iron-based sheet, as well as to a method for manufacturing such an extra-thin sheet.

5 Thin metal sheets are currently used in many fields, in particular in the packaging industry, or for the manufacture of composite insulating panels intended for the construction industry.

For essentially economic reasons, it is sought to use sheets having a thickness as small as possible, so as to minimize the weight of the articles thus produced.

The thin sheets used industrially today are almost exclusively produced by cold rolling. They therefore have several limitations and drawbacks, which do not affect the extra-thin sheets according to the present invention.

The thinnest sheets commonly used at present are tin sheets made by the well known double reduction process. These are cold rolled mild steel sheets with thickness reduction rates from 20% to 40%. This cold rolling causes significant hardening of the steel, which gives the sheets thus produced a hardness leading to a breaking load of 550 MPa to 650 MPa. Such an increase in the breaking load however causes a loss of ductility of the steel, in particular a reduction in its elongation, which limits the ability to stamp these sheets. In addition, it is known that rolling introduces a clear anisotropy in the properties of steel; it follows that the properties of these sheets, in particular their elastic limit and their elongation, are not equal in the directions respectively parallel and perpendicular to the direction of rolling. The drawing ability is also adversely affected. Finally, cold rolling does not produce, economically, sheets whose thickness is less than about 140 μιτι. It is in fact not possible to laminate to such a small thickness in a train with several cages, because the thin sheet cannot withstand without tearing the traction which it is necessary to exert between the successive cages. On the one hand, rolling with a single cage leads to a significant increase in costs as the thickness decreases, and it also has very low productivity, which removes this technique from any possibility of economic implementation.

15

Already known, from patent BE-A-905,476, a flexible metal sheet comprising an iron film with a thickness of between 5 μπι and 100 μπι, produced by electrolysis and covered with a metal protective film Such a film is in fact made of an extremely mild steel, which has a hardness and a breaking load clearly insufficient to allow its use as a replacement for high-strength tinplate. In particular, the breaking load of such a flexible sheet does not exceed about 200 MPa, while the high-strength tin achieves a rup-25 ture load of 550 to 650 MPa, as indicated more high.

The present invention provides an extra-thin metal sheet, which does not have the disadvantages of anisotropy and work hardening affecting cold-rolled thin sheets while having a breaking load of at least 500 MPa.

The iron-based extra-thin metal sheet, of a thickness of between 5 μπι and 100 μπι approximately, which is the subject of the present invention, is characterized in that it contains carbon in an amount between 35 0.6% and 0.9% by weight, and in that it has a microstructure composed essentially of fine perlite.

- 3 -

According to a particular variant, said metal sheet is covered with a protective metallic layer, which can be at least partially, alloyed with said sheet. This protective layer advantageously consists of tin, which can form with said sheet 3 an intermediate layer of Fe-Sn.

According to other variants of the invention, which can moreover be carried out individually or in combination, said metal layer can also be coated with a protective film consisting of an oxide such as chromium oxide or an organic substance such as a lacquer, a resin or a varnish.

The present invention also relates to a process for manufacturing an extra-thin metal sheet of the type which has just been described. 15

This process is based on the manufacture of an extra-thin sheet by electrolytic deposition by means of an installation described in patent LU-A-86,773 and it aims to specify the conditions for processing such a sheet with a view to it. confer the desired properties.

20

The process for manufacturing an extra-thin metal sheet with a thickness of between 5 μιη and 100 pm approximately, said metal sheet containing carbon in an amount between 0.6% and 0.9% by weight, and preferably between 0.7% and 0.8% by weight, and having a microstructure composed essentially of fine perlite, in which an initial iron-based sheet is formed continuously by electrolytic deposition on a mobile cathode, is characterized in that after separation of said initial iron-based sheet and the movable cathode, said initial iron-based sheet is subjected to a treatment causing an increase in its carbon content.

According to the invention, this treatment is advantageously constituted by a gas carburizing operation.

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Such a treatment by gas cementation has proved to be particularly advantageous for increasing the carbon content of an initial iron-based sheet produced by electrolytic deposition. In fact, the tests carried out by the Applicant have shown, in an absolutely unexpected manner, that the rate of cementation of such a sheet was particularly high, provided that the conditions of the treatment were judiciously chosen. This high cementation speed, which could in particular be due to the purity of the initial sheet, makes it possible to achieve the desired degree of cementation in a very short time, perfectly compatible with a continuous manufacturing process.

According to the invention, said initial iron-based sheet is heated to a temperature between 900 ° C. and 1050 ° C., under a fuel atmosphere, it is kept within this temperature range and under this atmosphere for a period of time. which does not exceed 5 min., it is then cooled with a speed of 5 ° C / s to 20 ° C / s in the temperature range from 800 ° C to 600 ° C, then it is cooled to Room temperature.

20

The final cooling can be carried out according to any known technique, for example with air or water, since it no longer exerts any influence on the structure or on the properties of the metal sheet.

25

For this treatment, any fuel atmosphere known per se, such as CH 2 or a gas mixture rich in CH 2 and / or CO and W 2, can be used.

Also in the context of the process of the invention, said sheet is then covered with a protective metallic layer, with a flash heating step to cause the formation of an intermediate layer of intermetallic alloy between said sheet and the layer. protection.

► - 5 -

This protective metallic layer advantageously consists of tin deposited electrolytically, with a thickness corresponding to approximately 1 to 3 g of tin per m2, per face of the sheet.

The sheet thus protected can then be subjected to a finishing operation such as a chromating treatment, possibly followed by an application of a varnish, a lacquer or a paint.

Additional characteristics as well as advantages of the present invention will emerge from the implementation example which is described below; this example relates, without any limiting character however, to the production of an extra-thin sheet intended for the manufacture of tinplate, from an initial sheet based on iron formed by electrolytic means.

15

The initial iron-based sheet was formed electrolytically in an installation of the type described in the aforementioned patent LU-A-86,773. The electrolyte used contained 400 g / l of FeCl2, 80 g / l of CaCl2 and 2 ml / 1 of a wetting agent; the temperature of the electrolyte 20 was 100 ° C and the current density was 17.5 A / dm2. The sheet obtained under these conditions had a thickness of 40 μm and had the following average composition: C: 0.006%, Si: 0.001%, Cu: 0.364? Ί; Ni: 0.13% by weight; in the recrystallized state at 750 ° C, this initial sheet had a breaking load of 227 MPa.

25

In accordance with the invention, it was then subjected to gas cementation. This treatment was carried out in an experimental tubular oven, electrically heated. The iron-based sheet was wound into loosely wound turns and then introduced into a cold area of the oven. After sweeping with CH 4, the sheet was transferred to the hot zone of the oven, which was preheated to 1030 ° C to provide carburetion. The gas was introduced at room temperature.

After a stay of about 150 s beyond 900 ° C, various samples of the iron-based sheet were cooled at different rates, according to techniques known per se, to examine the influence of the cooling rate in the transformation range, namely between 800 ° C and 600 ° C. A first sample of the sheet was cooled slowly (5.8 ° C / s), while a second sample was cooled more quickly (17.4 ° C / s). The final cooling, without any particular influence, was carried out by immersion in an aqueous bath.

The extra-thin cemented sheet thus obtained had a composition close to the eutectoid composition, that is to say a carbon content substantially equal to 0.75% by weight, distributed uniformly throughout the volume of the sheet. The breaking load of the various samples was between 610 MPa and 685 MPa, and the elongations at break varied from 8.3% to 8.8%. The hardness, measured on the edge (20 gr), varied between 234 HV and 318 HV.

15

This sheet also has remarkable ductility despite its high strength; it thus underwent 60.5 folding-unfolding, according to the Jenkins test, before starting to crack.

The microstructure of the extra-thin sheet depends in particular on the rate of cooling.

For slow cooling from the cementation temperature, perlite colonies are observed, between which cementite lamellae surrounded by ferrite are formed.

When the cooling is faster, the cementite lamellae between the perlite colonies disappear, and on the contrary, the formation of a very fine and homogeneous perlitic structure is observed.

This structure is both hard, without being hardened, and ductile. It gives the extra-thin sheet the properties desired for the manufacture of very thin tinplate.

In this regard, it would not be departing from the scope of the present invention to interrupt the cooling slightly below 600 ° C., to reheat the cemented sheet beyond its point Aj, then to cool it again. , with this same speed from 5 ° C / s to 20 ° C / s between 5800 ° C and 60D ° C. Such a double heating-cooling cycle makes it possible to homogenize the microstructure of the cemented sheet without, however, causing additional refinement of the perlite.

Owing to its method of production by electrolytic deposition, the extra-thin sheet according to the invention, as well as the products derived therefrom, such as tinplate, exhibit practically total isotropy and therefore pose no problem. deformation, especially in stamping.

Claims (11)

4 * - 8 - 1. An extra-thin metal sheet based on iron, with a thickness of between 5 μιτι and 100 μm, characterized in that it contains carbon in an amount between 0.6% and 0.9% by weight and in that it has a microstructure composed essentially of 5 fine perlite. 2. Metallic sheet according to claim 1, characterized in that it is covered with a protective metallic layer. 3. Metal sheet according to claim 2, characterized in that it is, at least in part, alloyed with said protective metal layer. 4. Metal sheet according to either of claims 1 to 15 3, characterized in that it is coated with a non-metallic protective film, consisting of a metal oxide and / or a organic substance. 3. Method for manufacturing an iron-based extra-thin metal sheet with a thickness of between 5 μm and 100 μm approximately, said metal sheet containing carbon in an amount between 0, ~ 6% and 0, 9% by weight and having a microstructure composed essentially of fine perlite, in which an initial iron-based sheet is formed continuously by electrolytic deposition on a mobile cathode, characterized in that after separation of said initial sheet based on iron and the movable cathode, said initial iron-based sheet is subjected to a treatment causing an increase in its carbon content. 6. Method according to claim 5, characterized in that an initial iron-based sheet having a carbon content of less than 0.05% by weight is formed by electrolytic deposition. "- 9 - 7. Method according to either of Claims 5 and 6, characterized in that said treatment consists of a gas carburizing operation. 8. Method according to claim 7, characterized in that said initial iron-based sheet is heated to a temperature between 900 ° C and 1050 ° C under a fuel atmosphere, in that said said is maintained sheet in this temperature range and under this atmosphere for a period which does not exceed 5 min., in that it is then cooled with a speed of 5 ° C / s to 20 ° C / s in the meantime from 800 ° C to 600 ° C, and in that it is finally cooled to room temperature. 9. Method according to one of claims 7 and 8, characterized in that a fuel atmosphere consisting essentially of CH 2 or of a gas mixture rich in CH 2 is used for gas carburization. 10. Method according to one of claims 5 to 9, characterized in that said sheet, after cementation, is coated with at least one protective metallic layer and optionally with a finishing layer. Drawings: ........ boards M .pages including ......... A- PsGe §arcle .......... 'Â' .. description pages φ - key claims; j description Luxemb ^ rs b v mmj Le lïîc v »> c; Alain Lu avina