WO2008102006A1

WO2008102006A1 - Packaging steel, method of producing said packaging steel and its use

Info

Publication number: WO2008102006A1
Application number: PCT/EP2008/052189
Authority: WO
Inventors: Nigel David Jenks; Maarten Arie De Haas
Original assignee: Corus Staal Bv
Priority date: 2007-02-23
Filing date: 2008-02-22
Publication date: 2008-08-28

Abstract

This invention relates to the use of a high strength, cold rolled packaging steel with good deformation capability comprising o C : 0.0005 - 0.004 wt.% o Mn : 0.050 - 0.300 wt.% o AlSOι : 0.010 - 0.100 wt.% o N : 0.0005 - 0.0050 wt.% o S : 0- 0.020 wt.% o P: 0 - 0.020 wt.% o Cr: 0 - 0.050 wt.% o Cu: 0 - 0.050 wt.% o Si : 0 - 0.020 wt.% o Ni : 0 - 0.050 wt.% o Ti : 0.01 - 0.085 wt.% Further optionally comprising one or more of the micro-alloying elements selected from the group of: o B : 0.0005 - 0.0030 wt.% o V: 0.01 - 0.150 wt.% o Zr: 0.01 - 0.150 wt.% the remainder being iron and unavoidable impurities, the steel having a full hard microstructure, to produce packagings such as containers or can ends, and to a method for producing said packagings and said packagings.

Description

PACKAGING STEEL, METHOD OF PRODUCING SAID PACKAGING STEEL AND ITS USE

The present invention relates to the use of a high strength, cold rolled steel with good deformation capability to produce steel packagings, a method for producing said packaging and use of said packaging.

Most packaging steels used nowadays are aluminium killed low carbon steels (AK-LC). In some cases when good formability is required, such as for a DWI- application, an ultra low carbon steel is used. As a result of the cost-driven desire for thinner gauges in the finished packaging, the demand for high strength packaging steels has increased over the years. Several methods are available to produce this increased strength. A common method used to produce high strength packaging steel is by subjecting the material to a secondary reduction after recrystallisation annealing. These high strength steels are commonly referred to as double-reduced (DR) grades. US 3,095,361 discloses a method for producing tinplate having a high hardness by cold reducing the strip in a conventional cold rolling mill, followed by annealing, and reduced again for 30 to 60% in a second cold rolling step followed by a tinning operation.

A major disadvantage of DR-grades is that the increased strength is accompanied with a substantial loss in ductility. This loss in ductility significantly restricts the use of these steels in many packaging applications. For example for welded can bodies often a shaping step is desired where the ductility of the material is critical. In can ends terracing is often necessary for enhancement of stiffness. In easy- open-ends riveting is needed for fixing the tab with which the packaging can be opened. Both terracing and riveting put a high demand on ductility. In the DR-process it is necessary to repeatedly handle, transfer and process the thin strip which increases the risk of damaging the strip and the chance of rejects.

The object of the present invention is to provide a high strength packaging with good deformation capability. Another object of the invention is to provide a high strength packaging in a more economical way.

Another object of the invention is to provide a high strength packaging with a reduced risk damaging the strip and the chance of rejects.

One or more of these objects is achieved by the use of a cold-rolled steel comprising

C : 0.0005 - 0.004 wt.% Mn : 0.050 - 0.300 wt.% Al_soi : 0.010 - 0.100 wt.%

N : 0.0005 - 0.0050 wt.%

S : 0- 0.020 wt.%

P: 0 - 0.020 wt.% - Cr: 0 - 0.050 wt.%

Cu: 0 - 0.050 wt.%

Si : 0 - 0.020 wt.%

Ni : 0 - 0.050 wt.%

Ti : 0.01 - 0.085 wt.% further optionally comprising one or more of the micro-alloying elements from the group of:

B : 0.0005 - 0.0030 wt.%

V: 0.01 - 0.150 wt.%

Zr: 0.01 - 0.150 wt.% the remainder being iron and unavoidable impurities, the steel having a full hard microstructure, to produce high strength packagings such as cans or can ends.

The strip according to the invention has a substantially or completely full-hard structure. In other words, the steel has a substantially or completely unrecrystallised microstructure or in other words, the work-hardened structure as a result of the cold- rolling has been fully retained. No recovery or recrystallisation of the work-hardened microstructure has occurred. This structure provides a very high strength, a fairly low yield strength and a significantly higher total strain and uniform strain when compared to recrystallisation annealed and subsequently work-hardened LC or ELC-steels (double reduced). The use of this full hard steel strip, which has been subjected to a single cold deformation during production only, to produce a packaging for which conventionally DR LC or DR ELC steels would be used results in significant cost reduction because of the omission of the annealing step and the second cold rolling step. This reduction outweighs the slightly more expensive steel base. Moreover, the omission of the annealing step and the second cold-rolling step reduces the risk of damaging the strip. Packaging in the context of this invention include, but is not limited to, food cans, pet-food cans, non-food cans, beverage cans, can ends, plates and bowls (optionally microwaveable), bakeware, lids for sealing a 2-piece or 3-piece can, or a lid for an easy open end to which a rivet must be provided. Consequently, the inventors surprisingly found that the high strength packagings could be produced from a single reduced dedicated steel grade for which conventionally a double reduced ELC- or LC-steel was required. The production of the packaging from the full hard steel strip is similar to producing the packaging from a DR-LC or DR-ELC steel. It is preferable that the dedicated steel grade comprises at least titanium between 0.01 and 0.085% and vanadium and zirconium, if present, are unavoidable impurities. This steel provides good and stable mechanical properties in its full-hard state. It is noted that the titanium has a strong affinity to carbon and nitrogen. As the aluminium in the steel has already bound the oxygen during the killing operation during steelmaking, substantially all titanium is available to bind carbon and/or nitrogen, thereby rendering the steel substrate interstitial free. In a preferable embodiment, the titanium content is at most 0.065%.

In an embodiment of the invention a steel is used to produce high strength packagings wherein the full-hard microstructure is subjected to a heat treatment resulting in a recovered microstructure prior to producing the high strength packaging.

The term 'recovered microstructure' is understood to mean a heat treated cold rolled microstructure which shows minimal recrystallisation, with such recrystallisation being confined to localised areas such as at the edges of the strip. Preferably the microstructure is completely unrecrystallised. The microstructure of the packaging steel is therefore substantially or completely unrecrystallised. This recovered microstructure provides the steel with a significantly increased deformation capability at the expense of a limited decrease in strength. Recrystallisation is a process by which deformed grains are replaced by a new grain structure by the formation and migration of high angle grain boundaries driven by the stored energy of deformation. High angle boundaries are those with greater than a 10-15° misorientation. New grains nucleate and grow until the original grains have been entirely consumed. Recovery is a process by which deformed grains can reduce their stored energy by the removal or rearrangement of defects in their crystal structure. These defects, primarily dislocations, are introduced by plastic deformation of the material and act to increase the yield strength of a material. Since recovery reduces the dislocation density, the process is normally accompanied by a reduction in a materials strength and a simultaneous increase in the ductility. Recovery can be defined as all annealing processes occurring in deformed materials that occur without the migration of a high- angle grain boundary. No new, undeformed grains are formed during recovery. Thus recrystallisation can be differentiated from recovery (where high angle grain boundaries do not migrate, and no new ones are formed) and grain growth (where the driving force is only due to the reduction in boundary area).

The continuously annealed steel is preferably provided in the form of a coiled strip. Unlike annealing processes wherein the strip is annealed in a coiled form, such as a batch annealing process or a continuous coil annealing process, the continuous strip annealing process provides a strip with a homogeneous distribution of the properties over the length and width of the strip. After continuous strip annealing the strip may be coiled. It was found that the steel according to the invention can be produced, using adapted process parameters, in a conventional continuous annealing line for continuously annealing steel strip material. The addition of the micro-alloying elements serve a dual purpose. Firstly, the elements show a strong affinity to the interstitial elements in the steel, nitrogen and carbon. The elements therefore perform a scavenging function. Moreover, the micro- alloying elements, and titanium in particular, suppress the recrystallisation of the cold rolled steel, thereby opening the parameter window for the recovery annealing step. Within the optimal window the recrystallisation tendency is effectively suppressed. This is an advantage in industrial practice because normal scatter in the annealing conditions will not cause scatter in the properties of the recovery annealed strip. Consequently, in a preferable embodiment of the invention titanium is a mandatory element. Since titanium has a strong affinity to carbon and nitrogen, in a preferable embodiment titanium is between 0.01 and 0.085%, and vanadium and zirconium, if present, are unavoidable impurities. In a preferable embodiment, the titanium content is at most 0.065%.

On the other hand, the increase in rolling force during hot rolling is limited, particularly when compared to the other much used micro-alloying element niobium. The suppression of the recrystallisation during hot-rolling causes a strong increase of the rolling forces during hot rolling, thereby causing shape problems and causing difficulty to attain the desired low thickness of the hot rolled strip. Since the steel according to the invention is not a DR-steel, the steel will not be subjected to a second cold-rolling step. In order to attain the required cold-rolled thickness in one cold-rolling passage the initial thickness with which the hot-rolled strip enters the cold-rolling mill has to be reduced in comparison to the hot-rolled strip which will be subjected to a double reduction, i.e. two cold rolling-passages. Consequently, niobium is not a suitable element to be used in producing full-hard or recovery annealed packaging steels. In an embodiment of the invention, the full hard steel used to produce high strength packagings has a yield strength of at least 600 MPa, and an A50 of at least 0.5%. In an embodiment of the invention, the recovery annealed steel used to produce high strength packagings has a yield strength of at least 500 MPa, and an A50 of at least 4%. The A50-value is measured according to EN 10002/1 on a gauge length of 50 mm.

According to a second aspect of the invention, a process for producing a steel packaging is provided comprising the steps of: a) providing input stock with a chemical composition comprising

C : 0.0005 - 0.004 wt.% Mn : 0.050 - 0.300 wt.% Al_soi : 0.010 - 0.100 wt.% - N : 0.0005 - 0.0050 wt.%

S : 0- 0.020 wt.% P: 0 - 0.020 wt.% Cr: 0 - 0.050 wt.% Cu: 0 - 0.050 wt.% - Si : 0 - 0.020 wt.%

Ni : 0 - 0.050 wt.% Ti : 0.01 - 0.085 wt.% further optionally comprising one or more of the micro-alloying elements from the group of: - B : 0.0005 - 0.0030 wt.%

V: 0.01 - 0.150 wt.% Zr: 0.01 - 0.150 wt.% the remainder being iron and unavoidable impurities b) cold rolling the input stock with a cold rolling reduction to a cold-rolled full-hard strip to a cold rolled thickness; in a single cold rolling operation c) producing a packaging from said cold-rolled strip.

The strip according to the invention has a substantially or completely full-hard structure prior to producing a packaging therefrom. This structure, which is the result of the combination of the process and the chemical composition provides a very high strength, a fairly low yield strength and a significantly higher total strain and uniform strain when compared to recrystallisation annealed and subsequently work-hardened LC or ELC-steels (double reduced). The steel according to the invention is subjected to only one cold-rolling step, albeit that this single cold-rolling step may be performed in a multi-stand cold rolling mill, or by two or more passes through a reversible mill, but no recrystallisation annealing takes place between any of these rolling steps. Moreover, although the steel basis is somewhat more expensive than the LC or ELC- steels, the omission of the process step is ample compensation from a financial and logistical point of view. In an embodiment of the invention, the zirconium content, the boron content and the vanadium content are at impurity level, i.e. the elements are not added to the steel for alloying purposes. In a preferable embodiment, the titanium content is at most 0.065%.

Preferably the titanium content is at least 0.025%, more preferably at least 0.035%. A suitable maximum titanium content is 0.060%. In an embodiment of the invention the full-hard strip is subjected to a continuous recovery strip annealing process after the single cold rolling operation and prior to producing a packaging from the strip wherein the process parameters of the annealing process, and the annealing temperatures and times in particular, are selected so as to prevent recrystallisation and to promote recovery of the full-hard strip resulting in a strip having a recovered microstructure and wherein the packaging is produced from the recovery annealed strip. A continuous recovery strip annealing process is preferably performed in a conventional continuous annealing line. These devices allow each part of the strip to be subjected to the same thermal treatment, thereby achieving homogeneous properties all through the length and width of the strip. After the annealing and cooling to ambient temperature the strip may be coiled. Continuous coil annealing devices are not suitable for the annealing because in the coiled form not each part of the strip is be subjected to the same thermal treatment. The middle wraps of the coil heat up and cool down much more slowly then the outer or inner wraps.

During recovery annealing the dislocation density in the full-hard microstructure decreases as a result of annihilation of dislocation pairs. Each dislocation is associated with a strain field which contributes some small but finite amount to the materials stored energy. At increased temperature dislocations become mobile and are able to glide, cross-slip and climb. If two dislocations of opposite sign meet then they effectively cancel out and their contribution to the stored energy is removed. Alternatively, recovery can be defined as all annealing processes occurring in deformed materials that occur without the migration or formation of high-angle grain boundaries. Temper rolling may be used for shape correction of the recovery annealed strip or for the suppression of Lϋders-lines, with temper rolling reductions below 2%, preferably below 1.0%, and preferably at least 0.5%. When the temper rolling reductions are below 3% they are not considered to be a second cold rolling reduction in the sense of the double reduced steels. The second cold rolling reduction in double reduced steels is in the order of 30% or more.

It is noted that the cold-rolling process and the continuous annealing process may be linked so as to have a fully continuous rolling and annealing operation. Alternatively, the strip may be coiled after cold-rolling, and uncoiled prior to annealing. In between the cold rolling and the annealing step a cleaning step may be provided, for instance to remove rolling oil from the strip prior to the annealing step. The strip may be tinned or supplied as ECCS (TFS).

The input stock may be provided in the form of continuously cast slabs, continuously cast thin slabs, or cast strip. In case the input stock is too thick to be cold- rolled, such as a conventional slab of 220 mm thickness or a thin slab of 70 mm, or too thick to achieve the required cold-rolled thickness after cold rolling at a preselected percentage of cold reduction, the input stock is first subjected to a hot-rolling step to produce a strip having a suitable entry thickness for the cold-rolling step. This hot rolling starts from a hot rolling starting temperature and finishes at the finish rolling temperature. The hot-rolling step may be performed while the microstructure of the steel is austenitic. It is preferable that the hot rolling step is performed austenitically because this ensures that the starting material for the cold rolling step has a random crystallographic texture, or as random as possible. The crystallographic texture influences the formability of the final product as the hot-rolling texture is inherited by the cold rolled and optionally annealed product. Alternatively, the hot-rolling step may be performed while the microstructure of the steel is predominantly or completely ferritic, or wherein at least the final deformation step or steps in the hot rolling process are performed while the microstructure of the steel is predominantly or completely ferritic. The latter is sometimes also referred to as ferritic rolling or warm rolling, and within the context of this description this should be understood to be a hot-rolling process. Ferritic rolling is particularly relevant if the hot strip is to be provided with the crystallographic starting structure associated with ferritic rolling. Although during cold rolling the strip also heats up due to deformation heat, or the strip may still be warm from the preceding pickling and/or cleaning step, this is still considered to be cold- rolling within the context of this description.

In case of the input stock being thick slabs, the slab reheating temperature is chosen such that the microalloying elements are essentially dissolved and the hot- rolled strip is preferably coiled at a coiling temperature which is high enough to benefit from the scavenging effect of the microalloying elements. Preferably the coiling temperature is at least 610⁰C, more preferably at least 640°. The maximum coiling temperature is determined by the grain growth which occurs when the strip is coiled at a high coiling temperature. A suitable maximum coiling temperature is 740⁰C, preferably the coiling temperature is at most 710⁰C. It is noted that these temperature windows are normally used for achieving full recrystallisation in low carbon or extra low carbon steel. In order to compensate for the more rapid cooling of the head and tail end of the hot-rolled strip, the aforementioned temperatures may be offset at the head and tail through the use of a so-called u-type cooling whereby the coiling temperature of the head and tail is chosen higher than that of the middle part of the strip. Usually, the temperature is offset by 20 to 30⁰C. The higher local coiling temperature compensates for the faster cooling rate of the coiled strip, thereby achieving a more homogeneous scavenging effect over the entire strip. It is therefore important that the coiling temperature is chosen so as to maximise the precipitation of the micro-alloying elements after cooling the hot-rolled coil to ambient temperature.

With the process according to the invention a recovery annealed steel strip is provided, wherein microstructure of the strip shows minimal, if any, recrystallisation, with such recrystallisation being confined to localised areas such as at the edges of the strip. Preferably, the microstructure shows no recrystallisation.

The microstructure of the packaging steel is therefore substantially unrecrystallised. This recovered microstructure provides the steel with a significantly increased deformation capability at the expense of a limited decrease in strength.

In an embodiment of the invention the soaking temperature during the recovery annealing process is not higher than 650⁰C. Preferably the soaking temperature is not higher than 640°C.

The low soaking temperature according to the invention ensures that recovery is promoted, but recrystallisation does not occur. The scavenging effect of the microalloying element or elements ensures that the yield point remains suppressed. In an embodiment of the invention the cold rolling reduction, which is the only cold rolling reduction, is at least 70%, preferably the cold rolling reduction is at least 75%. The cold rolling reduction proved to be a very effective and reliable way to influence the mechanical properties not only of the full-hard structure, but also of the recovery annealed microstructure. In an embodiment of the invention, the manganese content of the steel is at most 0.2%. This means the strength of the cold deformed steel decreases. To compensate, it is preferable that a combination of cold rolling reduction of at least 82% and a manganese content of at most 0.2% is chosen in order to guarantee an Rp₀₂ value of at least 500 MPa in the recovered condition or at least 650 MPa in the full-hard condition. In an embodiment of the invention the soaking temperature during the recovery annealing process is between 600⁰C and 640⁰C. Preferably the soaking temperature is between 615 and 635°C.

In an embodiment of the invention the final thickness after the recovery annealing process is between 0.10 and 0.35mm. The final thickness is the result of the incoming product in the cold rolling step and the cold rolling reduction.

According to a third aspect, use of the packaging steel according to the invention or the packaging steel produced according to the invention is provided for producing packagings such as containers or can ends. The invention therefore also relates to a container or a can end produced by cold-rolling a packaging steel comprising

C : 0.0005 - 0.004 wt.%

Mn : 0.050 - 0.300 wt.% - Al_SOι : 0.010 - 0.100 wt.%

N : 0.0005 - 0.0050 wt.%

S : 0- 0.020 wt.%

P: 0 - 0.020 wt.%

Cr: 0 - 0.050 wt.% - Cu: 0 - 0.050 wt.%

Si : 0 - 0.020 wt.%

Ni : 0 - 0.050 wt.%

B : 0.0005 - 0.0030 wt.%

V: 0.01 - 0.150 wt.%

Zr: 0.01 - 0.150 wt.% the remainder being iron and unavoidable impurities, the steel prior to forming the packaging such as the container or the can end having a full hard microstructure. In a preferable embodiment, the titanium content is at most 0.065%.

The invention further relates to a packaging, such as a container or a can end, produced by the process according to the invention, the steel prior to forming the packaging such as the container or the can end having a full-hard microstructure, or a recovered microstructure and substantially or completely unrecrystallised microstructure.

The much increased deformation capability of the steel according to the invention makes it well suited for application in packagings where a high strength and adequate formability are needed, such as for producing can ends, easy-open-end can ends, or can bodies and the like.

The invention will now be further explained by the following, non limiting examples. The table provides four continuously cast steel grades, austenitically hot rolled to 2.5 mm and coiled at 650⁰C.

Table 1 : Chemical composition of four continuously cast and hot-rolled steels subjected to the process according to the invention (all elements, except C and N (ppm), are in 10^"3wt%, Cold Rolling reduction (CR) in %).

After pickling, the strips were cold rolled 77, 84, 86 and 88% respectively, and recovery annealed in a continuous annealing line, using a soaking temperature of 630⁰C. There appeared to be little or no effect of an overaging at temperatures between 350 and 450⁰C after the soaking at 630°C. This is believed to be caused by the fact that recovery is a thermally activated process. The lower temperature of the overageing in comparison to the higher soaking temperature therefore has little effect. The effect on the A50-value (in %, on the vertical axis) is illustrated by Fig. 1. The value for Rp₀₂ (in MPa) is given on the horizontal axis of Fig. 1. The improvement of the strain of the full-hard structure (closed circles, triangles and diamonds) in respect to LC-DR reference material (full squares) is clearly demonstrated. The further increase of the strain of the recovery annealed material in (open circles, triangles and diamonds) is demonstrated by comparing these values to the full-hard material (closed circles, triangles and diamonds) and to the LC-DR reference material (full squares). The uniform strain values (in %, Fig. 2) show similar tendencies with a much improved Au at the same yield strength for recovery annealed material (open circles) when compared to in comparison to LC-DR reference material of the same strength. Uniform strains of full-hard materials (closed circles) according to the invention were already higher and much stronger than the strongest LC-DR (closed squares). Fig. 3 shows three production processes. In Fig 3a the production of a double reduced low carbon steel is schematically indicated starting from a hot rolled coil (left) showing a first cold rolling treatment of said hot rolled coil (CR1 ), a continuous recrystallisation annealing treatment (rex. CA) followed by the second cold rolling step (CR2). The reduction in the second cold rolling step is between 10 and 40%. In Fig. 3b the process according to the main claim of the invention is indicated wherein the hot rolled coil is subjected to a cold rolling treatment of said hot rolled coil (CR) whereafter a full-hard final product according to the invention is obtained. In Fig. 3c the process according to a preferred embodiment of the invention is indicated wherein the hot rolled coil is subjected to a cold rolling treatment of said hot rolled coil (CR) followed by a continuous recovery annealing treatment (rec. CA). This recovery annealed final product may be subjected to a temper rolling treatment to correct the shape of the coil.

Claims

1. Use of a high strength cold rolled packaging steel comprising o C : 0.0005 - 0.004 wt.% o Mn : 0.050 - 0.300 wt.% o Al_soi : 0.010 - 0.100 wt.% o N : 0.0005 - 0.0050 wt.% o S : 0- 0.020 wt.% o P: 0 - 0.020 wt.% o Cr: 0 - 0.050 wt.% o Cu: 0 - 0.050 wt.% o Si : 0 - 0.020 wt.% o Ni : 0 - 0.050 wt.% o Ti : 0.01 - 0.085 wt.% further optionally comprising one or more of the micro-alloying elements selected from the group of: o B : 0.0005 - 0.0030 wt.% o V: 0.01 - 0.150 wt.% o Zr: 0.01 - 0.150 wt.% the remainder being iron and unavoidable impurities, wherein the microstructure of the packaging steel is a full hard microstructure, to produce packagings such as containers or can ends.

2. Use of a steel according to claim 1 , wherein boron, vanadium and zirconium, if present, are unavoidable impurities.

3. Use of a steel according to claim 1 or 2, wherein titanium is at most 0.065%.

4. Use of a steel according to claim 1 , 2 or 3, wherein titanium is between 0.025 and 0.060%.

5. Use of the steel according to any one of the preceding claims wherein the microstructure of the packaging steel is a recovered microstructure.

6. Use of the steel according to any one of the preceding claims having a yield strength of at least 600 MPa, and an A50 of at least 0.50%.

7. Use of the steel according to claim 5 having a yield strength of at least 500 MPa, and an A50 of at least 4%.

8. Process for producing a steel packaging comprising the steps of: o providing input stock with a chemical composition comprising

C : 0.0005 - 0.004 wt.%

Mn : 0.050 - 0.300 wt.%

Al_soi : 0.010 - 0.100 wt.%

N : 0.0005 - 0.0050 wt.% ■ S : 0- 0.020 wt.%

P: 0 - 0.020 wt.%

Cr: 0 - 0.050 wt.%

Cu: 0 - 0.050 wt.%

Si : 0 - 0.020 wt.%

Ni : 0 - 0.050 wt.%

B : 0.0005 - 0.0030 wt.%

V: 0.01 - 0.150 wt.%

Zr: 0.01 - 0.150 wt.% the remainder being iron and unavoidable impurities o cold rolling the input stock with a cold rolling reduction to a cold-rolled full hard strip to a cold rolled thickness in a single cold rolling operation o producing a packaging from said cold-rolled strip

9. Process according to claim 8, wherein boron, vanadium and zirconium, if present, are unavoidable impurities.

10. Process according to claim 8 or 9, wherein titanium is at most 0.065%, preferably wherein titanium is between 0.025 and 0.060%.

1 1. Process according to any one of claims 8 to 10, wherein the cold rolling reduction is between 75 and 90%, preferably wherein the cold rolling reduction is at least 77% and/or at most 88%.

12. Process for producing a steel packaging according to any one of claims 8 to 11 further comprising the step of subjecting the full hard strip to a continuous recovery strip annealing process wherein the process parameters of the annealing process, and the annealing temperatures and times in particular, are selected so as to prevent recrystallisation and to promote recovery of the full- hard strip and wherein the packaging is produced from the recovery annealed strip;

13. Process for producing a steel packaging according to any one of claims 8 to 1 1 , wherein the cold rolling reduction is at least 70%, preferably at least 75%.

14. Process for producing a steel packaging according to claim 12 or 13, wherein the soaking temperature during the recovery annealing process is not higher than 650⁰C, preferably not higher than 640⁰C.

15. Process for producing a steel packaging according to claim 12 or 13, wherein the soaking temperature during the recovery annealing process is between 600°C and 640⁰C, preferably between 615 and 635°C.

16 Process for producing a steel packaging according to any one of claim 8 to 15, wherein the final thickness after the cold rolling step is between 0.10 and 0.35mm.

17. Steel packaging produced according to any one of claims 8 to 16.