EP3875626A1 - Packaging sheet product - Google Patents

Abstract

The invention relates to a sheet-metal packaging product made from a cold-rolled steel sheet with a thickness of less than 0.6 mm, which has the following composition in relation to weight: C: 0.001-0.06%, Si: <0.03%, preferred 0.002 to 0.03%, - Mn: 0.17-0.5%, - P: <0.03%, preferably 0.005 to 0.03%, - S: 0.001-0.03%, - Al: 0.001 - 0.1%, - N: 0.002-0.12%, preferably 0.004 to 0.07%, - optional Cr: <0.1%, preferably 0.01-0.1%, - optional Ni: <0 , 1%, preferably 0.01-0.05%, - optional Cu: <0.1%, preferably 0.002-0.05%, - optional Ti: <0.01%, - optional B: <0.005%, - optional Nb: <0.01%, - optional Mo: <0.02%, - optional Sn: <0.03%, - remainder iron and unavoidable impurities, whereby the packaging sheet product is a biaxial deformation in a bulge test lower yield point (Sb _eL) of more than 300 MPa and an associated elongation at break (Ab) of more than 10% and in the plastic range between the Lüders elongation (Abe) and an upper one (plastic) limit strain of ε _max = 0.5 · Ab · (Sb _eL / Sb _m) a biaxial stress / strain diagram σ _B (ε), which can be represented with a function σ _B = b · ε ⁿ, where- σ <sub> B < / sub> the true, biaxial stress in MPa, - ε the amount of true elongation in the direction of the thickness in%, - Sb _eL the lower yield point, - Sb _m the absolute strength - If the Lüders expansion, - b is a proportionality factor and - n is a hardening exponent, and a hardening of the sheet metal packaging product in the thickness direction is characterized by a hardening exponent of n≥0.353−5.1⋅SbeL / 104MPa.

Description

The invention relates to a sheet packaging product made from a cold-rolled steel sheet with a thickness of less than 0.6 mm.

Sheet metal packaging products are cold-rolled steel sheets with a thickness of up to 0.6 mm, which are used for the production of packaging such as beverage, tin or aerosol cans. Since the sheet-metal packaging products are exposed to severe deformations during the production of packaging, for example in deep-drawing or ironing processes, sheet-metal packaging products must, on the one hand, have a high degree of deformability. In order to reduce the weight of the packaging, on the other hand, the thinnest possible high-strength steel sheets are used as packaging sheet products, which are brought to the desired final thickness from a hot-rolled steel sheet in a single or a double cold-rolling step. The total degree of cold rolling (degree of reduction in the thickness reduction in cold rolling) is usually at least 80%, with the hot-rolled steel sheet (hot strip) being cold-rolled once or twice to reduce the thickness. Simply cold-rolled steel sheets (single-reduced: SR) are annealed in a recrystallizing manner after cold rolling to restore the formability and then, if necessary, re-rolled or skin-passivated with a low degree of re-rolling of less than 5%. In the case of double cold-rolled steel sheets (double-reduced: DR), after the recrystallizing annealing, a second cold rolling step with re-rolling degrees between 5% and 45% takes place in order to bring the steel sheet to a desired final thickness of often less than 0.3 mm.

Since the total degree of cold rolling, i.e. the reduction of the thickness of a hot-rolled steel sheet by single or double cold rolling to a desired final thickness, is limited for technological and material-specific reasons, a low thickness of the hot-rolled steel sheet (hot strip) is desirable in order to achieve the lowest possible final thicknesses for the cold-rolled steel sheet achieve. However, small thicknesses of the hot strip are disadvantageous on the one hand for economic reasons and on the other hand because of material defects that occur in the hot strip. In order to be able to produce steel sheets with the smallest possible final thickness of less than 0.6 mm, preferably less than 0.5 mm and particularly preferably less than 0.35 mm by cold rolling once or twice from hot strips with the usual thicknesses, total degrees of cold rolling are required of more than 85% required. However the total degree of cold rolling of a steel sheet with a given composition, both for technological reasons and because of the deformation behavior of the steel sheets required for the production of packaging, cannot be increased to arbitrarily high values. If the total degree of cold rolling is too high, for example, the lobing of the cold-rolled steel sheets deteriorates. A steel sheet with a given composition of the steel has a tail which is dependent on the total degree of cold rolling and which, at a certain, optimal degree of cold rolling, has a minimum of the ear height at the upper edge of a cup formed from the cold rolled steel sheet.

The optimal total degree of cold rolling (total degree of cold rolling optimum) of cold-rolled steel sheets, in which these have the least possible lobing, depends in turn on the composition of the steel. Steels with a relatively low carbon and nitrogen content have a high total degree of cold rolling. However, carbon and nitrogen contribute to increasing the strength of steels, which is why steels with a very low carbon and nitrogen content have only moderate strength. However, from steels with only moderate strength, packaging of small thickness cannot be produced which has sufficient final stability.
Proceeding from this, the invention is based on the object of showing a cold-rolled steel sheet for the production of packaging, which has a sufficiently high biaxial strength with the smallest possible thickness and at the same time good deformation behavior with multi-axis deformation for the production of packaging. The cold-rolled steel sheet should be able to be produced from a hot-rolled steel sheet (hot strip) by simple cold rolling with skin pass after recrystallization annealing or by double cold rolling with a second cold rolling step after recrystallization annealing with the highest possible total degree of cold rolling, so that it can be produced despite the desired low final thickness of less than 0.6 mm and a preferred final thickness in the range of 0.10 mm to 0.50 mm hot strips in the usual thickness range can be used. The cold-rolled steel sheets of the invention are intended to meet the high requirements in multi-axial forming processes in the production of packaging, such as deep-drawing or ironing processes, as packaging sheet products, with the packaging sheet products in particular multi-axis deformations and thinning in the direction of thickness without material failure and without loss of strength the three-dimensional packaging body produced from it should withstand.

These objects are achieved with a sheet metal packaging product according to claim 1. Preferred features and properties of the sheet metal packaging products of the invention and processes for their production can be found in the dependent claims. A method for characterizing sheet metal packaging products according to the invention is defined in claim 15.

The invention is based on the following considerations:
In forming processes for the production of packaging from sheet packaging products, such as deep-drawing and ironing processes for the production of beverage cans, the packaging sheet is deformed in several axes (cold-rolled steel sheet) and locally a considerable thinning of the original thickness of the packaging sheet of less than 0.6 mm. For example, when deep-drawing and ironing a beverage can, the thickness of a packaging sheet is reduced to approx. 30% of the original thickness by reshaping the packaging sheet using reshaping tools in the middle section of the can body. The material stress that occurs is insufficiently characterized by the mechanical properties such as tensile strength and elongation at break, which are determined in uniaxial tensile tests using stress / strain diagrams. For this reason, optimization of the mechanical properties of packaging sheets based on the characteristic values determined in uniaxial tensile tests is not preferable.

The invention therefore assumes that the characterization of the mechanical properties of packaging sheets and in particular their deformation behavior can be better characterized by multi-axis tensile tests in order to be able to optimize the material properties based thereon. The mechanical properties and the deformability of the sheet metal packaging products according to the invention are therefore advantageously determined using the hydraulic cupping test with optical measuring systems (hereinafter also referred to as "bulge test" or "bulge test") as defined in the standard DIN EN ISO 16808 (corresponding to EN ISO 16808). designated). In the hydraulic cupping test in accordance with the DIN EN ISO 16808 standard, a biaxial stress / strain curve is determined on a sample of a steel sheet by means of an optical measuring system in the direction of thickness) taking into account the reduction in thickness. For this purpose, a sample of the steel sheet, which is in particular in the form of a round, clamped at its edge between a die and a hold-down device and then a liquid is pressed against the clamped steel sheet, whereby a curvature is formed until a crack occurs in the steel sheet. During the hydraulic cupping test, the pressure of the liquid is measured and the development of the deformation of the sheet is recorded with an optical measuring device. Based on the recorded sheet deformation, the local curvature, the degree of deformation on the surface and the thickness of the deformed sheet can be recorded. The (true) biaxial stress and the true strain in the direction of the thickness can also be calculated from the liquid pressure, the thickness and the radius of curvature of the deformed sheet metal. The biaxial stress / strain curve (flow curve in the biaxial stress state) is determined from this data. The curve shape of the biaxial stress / strain curve from a bulge test has a similar curve shape compared to a uniaxial tensile test (as defined, for example, in the standard DIN EN ISO 6892-1). In the hydraulic cupping test of the bulge test, however, higher deformation values and in particular higher elongations as well as more pronounced strain hardening after overcoming the elastic range are achieved on the same material.
It is assumed that due to the similar curves of the stress / strain curves of a uniaxial tensile test and a bulge test on the same sample in the biaxial stress / strain curve of the hydraulic cupping test (bulge test or bulge test) the Mechanical parameters usually determined in the uniaxial tensile test, such as the absolute strength, the lower and the upper yield point, the elongation at break and the Lüders elongation can be assigned accordingly. Table 1 shows the assignment of the mechanical parameters from a uniaxial tensile test and the hydraulic cupping test according to the bulge test. In Figure 1 an example of the biaxial stress / strain curve of an aged steel sheet sample determined from a bulge test is shown, with the true biaxial stress σB in [MPa] versus the amount of true strain in the thickness direction | ε | in [%] and the recorded mechanical parameters according to Table 1 are given and drawn in. The true elongation in the direction of thickness is negative due to the reduction in thickness in the biaxial tensile test of the bulge test. The (true) elongation ε is therefore always understood to be the amount of negative elongation in the thickness direction of the sheet, with the reduction in thickness being taken into account when determining the true elongation. The areas of elastic and plastic deformation are in the inserts of the Figure 1 shown enlarged.

1. (1) Elastischer Bereich mit linearem Anstieg der Spannung über der Dehnung:
   Im lokalen Maximum dieser Geraden, bevor der erste deutliche Spannungsabfall erfolgt, wird die obere Streckgrenze Sb_eH abgelesen;
2. (2) Unstetiger Kurvenverlauf, der den Übergang zum bzw. Beginn des plastischen Bereichs markiert und in dem die Spannung etwa konstant ist über der Dehnung:
   Die niedrigste Spannung innerhalb dieses unstetigen Bereichs entspricht der unteren Streckgrenze Sb_eL, wobei Einschwingerscheinungen keine Berücksichtigung finden. Am Ende des unstetigen Bereichs (2) und somit im Übergang zum sich anschließenden, wieder stetig ansteigenden Kurvenzug des Bereichs (3) wird die Lüdersdehnung Abe ermittelt. Hierzu wird eine Parallele zu der anfänglichen Gerade des elastischen Bereichs gezogen und in deren Schnittpunkt mit der Abszisse die Lüdersdehnung abgelesen. Die elastische Rückfederung des Werkstoffs findet somit keine Berücksichtigung.
3. (3) Plastischer Bereich stetiger Kaltverfestigung, in dem die Spannung kontinuierlich über der Dehnung ansteigt bis zum Bruch:
   Am Ende des Kurvenzugs wird einerseits die absolute Festigkeit Sb_m ermittelt, welche die maximale Spannung bei Bruch darstellt. Andererseits wird die Bruchdehnung Ab abgelesen, wobei das Vorgehen analog zur Ermittlung der Lüdersdehnung ist. Es wird eine Parallele zu der anfänglichen Gerade des elastischen Bereichs gezogen und in deren Schnittpunkt mit der Abszisse die Bruchdehnung abgelesen. Die elastische Rückfederung des Werkstoffs findet somit auch hier keine Berücksichtigung.

The mechanical parameters of a steel sheet sample listed in Table 1 are shown in a biaxial stress / strain diagram, as exemplified in Figure 1 is determined as follows:
The curve of the stress / strain diagram shows three characteristic areas one after the other on the abscissa:

1. (1) Elastic area with a linear increase in stress over elongation:
   At the local maximum of this straight line, before the first significant drop in tension occurs, the upper yield point Sb _{eH is} read off;
2. (2) Discontinuous curve, which marks the transition to or start of the plastic area and in which the stress is roughly constant over the elongation:
   The lowest stress within this discontinuous range corresponds to the lower yield point Sb _eL , with transient effects not being taken into account. At the end of the discontinuous area (2) and thus in the transition to the subsequent, again steadily increasing curve of the area (3), the Lüders expansion Abe is determined. For this purpose, a parallel is drawn to the initial straight line of the elastic area and the Lüders strain is read off at its intersection with the abscissa. The elastic springback of the material is therefore not taken into account.
3. (3) Plastic area of continuous work hardening, in which the stress increases continuously over the elongation until it breaks:
   At the end of the curve, on the one hand, the absolute strength Sb _{m is} determined, which represents the maximum stress at break. On the other hand, the elongation at break Ab is read, the procedure being analogous to the determination of the Lüders elongation. A parallel is drawn to the initial straight line of the elastic region and the elongation at break is read off at its intersection with the abscissa. The elastic springback of the material is therefore not taken into account here either.

In Figure 2 is the plastic range of the stress / strain curve of Figure 1 in the range between the Lüders elongation Abe and an upper (plastic) limit elongation of ε _max = 0.5 • Ab · (Sb _eL / Sb _m ), where Ab is the elongation at break, Sb _{eL is} the lower yield point and Sb _{m is} the absolute strength. The in Figure 2 The plastic range of the stress / strain curve shown can be described by a function σ _B = b ε ⁿ , where σ _{B is} the true, biaxial stress (in MPa), ε the amount of true strain in the direction of the thickness (in%), b is a proportionality factor and n is a hardening exponent. In the example of the Figure 2 the elastic-plastic range of the stress / strain curve between the Lüders strain Abe and the upper (plastic) limit strain ε _{max can be represented} by the function σ _B = b · ε ⁿ with b = 402 MPa and n = 0.132. A corresponding fit curve is shown in the stress / strain diagram of FIG Figure 2 drawn.

• C: 0,001 - 0,06 %,
• Si: < 0,03 %, bevorzugt 0,002 bis 0,03 %,
• Mn: 0,17 - 0,5 %,
• P: < 0,03 %, bevorzugt 0,005 bis 0,03 %,
• S: 0,001 - 0,03 %,
• Al: 0,001 - 0,1 %,
• N: 0,002 - 0,12 %, bevorzugt 0,004 bis 0,07 %,
• optional Cr: < 0,1 %, bevorzugt 0,01 - 0,08 %,
• optional Ni: < 0,1 %, bevorzugt 0,01 - 0,05 %,
• optional Cu: < 0,1 %, bevorzugt 0,002 - 0,05 %,
• optional Ti: < 0,01 %,
• optional B: < 0,005 %,
• optional Nb: < 0,01 %,
• optional Mo: < 0,02 %,
• optional Sn: < 0,03 %,
• Rest Eisen und unvermeidbare Verunreinigungen,

wobei das Verpackungsblecherzeugnis bei einer biaxialen Verformung in einem BulgeVersuch eine untere Streckgrenze (Sb_eL) von mehr als 300 MPa und eine zugehörige Bruchdehnung (Ab) von mehr als 10 % und im plastischen Bereich zwischen der Lüdersdehnung (Ab_e) und einer oberen (plastischen) Grenzdehnung von ε_max = 0,5·Ab·(Sb_eL/Sb_m) ein biaxiales Spanungs-Dehnungs-Diagramm σ_B(ε) aufweist, das mit einer Funktion σ_B = b·εⁿ darstellbar ist, wobei

• σ_B die wahre, biaxiale Spannung (in MPa),
• ε der Betrag der wahren Dehnung in Dickenrichtung (in %),
• Sb_eL die untere Streckgrenze,
• Sb_m die absolute Festigkeit,
• Ab_e die Lüdersdehnung,
• Ab die Bruchdehnung,
• b ein Proportionalitätsfaktor und
• n ein Verfestigungsexponent ist,

und eine Verfestigung des Verpackungsblecherzeugnisses in Dickenrichtung durch einen Verfestigungsexponenten von $$\mathrm{n}\ge 0,353-5,1\cdot {\mathrm{Sb}}_{\mathrm{eL}}/{10}^4\mathrm{MPa}$$

charakterisiert ist.Based on these preliminary considerations, the invention relates to:
Sheet packaging product made from a cold-rolled steel sheet with a thickness of less than 0.6 mm, which has the following composition in relation to weight:

• C: 0.001-0.06%,
• Si: <0.03%, preferably 0.002 to 0.03%,
• Mn: 0.17-0.5%,
• P: <0.03%, preferably 0.005 to 0.03%,
• S: 0.001-0.03%,
• Al: 0.001 - 0.1%,
• N: 0.002-0.12%, preferably 0.004-0.07%,
• optional Cr: <0.1%, preferably 0.01-0.08%,
• optional Ni: <0.1%, preferably 0.01-0.05%,
• optional Cu: <0.1%, preferably 0.002-0.05%,
• optional Ti: <0.01%,
• optional B: <0.005%,
• optional Nb: <0.01%,
• optional Mo: <0.02%,
• optional Sn: <0.03%,
• Remainder iron and unavoidable impurities,

The sheet metal packaging product has a lower yield point (Sb _eL ) of more than 300 MPa and an associated elongation at break (Ab) of more than 10% and in the plastic range between the Lüders elongation (Ab _e ) and an upper (plastic) in the case of a biaxial deformation in a bulge test ) Limit strain of ε _max = 0.5 · Ab · (Sb _eL / Sb _m ) has a biaxial stress-strain diagram σ _B (ε), which can be represented with a function σ _B = b · ε ⁿ , where

• σ _B the true, biaxial stress (in MPa),
• ε is the amount of true elongation in the thickness direction (in%),
• Sb _{eL is} the lower yield point,
• Sb _m the absolute strength,
• From _e the Lüders expansion,
• From the elongation at break,
• b a proportionality factor and
• n is a hardening exponent,

and a consolidation of the packaging sheet product in the thickness direction by a consolidation exponent of $$\mathrm{n}\ge 0,353-5,1\cdot {\mathrm{Sb}}_{\mathrm{eL}}/{10}^{\mathrm{4th}}\mathrm{MPa}$$

is characterized.

Sheet metal packaging products with corresponding properties of a biaxial stress / strain curve determined in the bulge test can be produced by reducing the thickness of the steel sheet by cold-rolling a hot strip with a preferred thickness of 2 mm to 4 mm to final thicknesses of less than 0, 6 mm and are characterized on the one hand by a sufficiently high biaxial strength for the production of packaging, and on the other hand they have a sufficiently high multi-axial deformability, which enables the production of packaging in demanding deep-drawing processes with multi-axis deformation even with a considerable thinning of the material in the direction of the thickness without cracking. Due to the high biaxial strength and the high multiaxial deformability, thinner sheet metal packaging products can be used for the production of packaging without having to fear losses in the stability of the packaging produced. By using thinner sheet metal packaging products, the weight of the packaging made from them can be reduced.

It has been shown that these advantageous mechanical properties of the packaging sheet products according to the invention, which can be determined by the hydraulic cupping test of the bulge test by recording a biaxial stress / strain curve, on the one hand by the composition of the steel of the cold-rolled steel sheets with a low Carbon content in the range from 0.001 to 0.06% by weight and, on the other hand, can be achieved by a high nitrogen content of 0.002 to 0.12% by weight. The nitrogen is preferred and is introduced into the cold-rolled steel sheet at least essentially by embroidering the cold-rolled steel sheet in an annealing furnace with a nitriding gas atmosphere, in particular an ammonia atmosphere. By embroidering the steel sheet in the annealing furnace, the nitrogen introduced can be interstitially embedded in the (ferrite) grid of the steel over the cross-section of the steel sheet. As a result, the positive properties of the hot-rolled steel sheet (hot strip) can be retained in order to maintain a high overall degree of cold rolling and a high solid solution strengthening. In particular, the nitrogen content in the hot strip can be kept low and in particular be less than 0.016% by weight. This ensures that during the production of a slab from the molten steel there are no cracks or pores in the slab and that the hot strip produced from the slab by hot rolling does not have too high strengths double cold rolling) of more than 80% can be cold rolled.

The nitrogen introduced in the annealing furnace when the cold-rolled steel sheet is embroidered can be distributed homogeneously over the thickness of the steel sheet without the formation of hard and brittle nitride layers on the surfaces of the steel sheet. This can be achieved in particular by the fact that the cold-rolled steel sheet is nitrogenized in a continuous annealing furnace, through which the steel sheet is carried out in strip form (i.e. as a cold-rolled steel strip) with a predetermined belt speed of preferably more than 200 m / min, and a nitriding gas , in particular ammonia gas, is introduced into the annealing furnace on the one hand to form a nitrogen-containing gas atmosphere and on the other hand is uniformly sprayed onto at least one or both surfaces of the steel strip by means of nozzles.

The hot strip preferably already has an initial nitrogen content N ₀ in the range from 0.001% by weight to 0.016% by weight in order to maximize the total nitrogen content in the cold-rolled steel sheet and thereby the solid solution strengthening brought about by the embroidery of the cold strip. The initial nitrogen content of the hot strip is preferably increased by at least 0.002% by weight when embroidering in the annealing furnace. The total nitrogen content, which is made up of the sum of the initial nitrogen content N ₀ in the hot strip and the nitrogen content ΔN introduced when the cold-rolled steel sheet is embroidered in the annealing furnace, is set during the annealing of the cold-rolled steel sheet by the presence of the nitrogen donor in the annealing furnace by taking at the annealing temperatures Dissociated, atomic nitrogen from the nitrogen donor diffuses into the cold-rolled steel sheet, thereby increasing the nitrogen content by ΔN. The nitrogen content .DELTA.N introduced in the annealing furnace during embroidery is preferably at least 0.002% by weight. Weight%

Dabei wird davon ausgegangen, dass der beim Aufsticken im Durchlaufglühofen eingebrachte Stickstoffanteil ΔN zumindest im Wesentlichen interstitiell in Zwischengitterplätze eingelagert wird. Die Obergrenze für den Gewichtsanteil des freien Stickstoffs im kaltgewalzten Stahlblech wird dabei durch die Löslichkeitsgrenze von Stickstoff im Ferritgitter des Stahls bestimmt, die bei ca. 0,1 Gew. % liegt.The total weight fraction of the free nitrogen in the cold-rolled steel sheet results from the sum of the free nitrogen content in the hot strip N _free (hot strip) and the nitrogen ΔN added by the nitrogenization in the continuous annealing furnace: $${\mathrm{N}}_{\mathrm{free}}={\mathrm{N}}_{\mathrm{free}}\left(\mathrm{Hot\; strip}\right)+\mathrm{\Delta N}$$

It is assumed here that the nitrogen component .DELTA.N introduced during embroidery in the continuous annealing furnace is at least essentially stored interstitially in interstitial spaces. The upper limit for the weight fraction of the free nitrogen in the cold-rolled steel sheet is determined by the solubility limit of nitrogen in the ferrite lattice of the steel, which is approx. 0.1% by weight.

The nitrogen donor used to embroider the cold-rolled steel sheet in the annealing furnace can be, for example, a nitrogen-containing gas atmosphere in the annealing furnace, in particular an ammonia-containing atmosphere, or a nitrogen-containing liquid that is applied to the surface of the cold-rolled steel sheet before it is in the Annealing furnace is heated. The nitrogen donor should be designed in such a way that atomic nitrogen is provided in the annealing furnace by dissociation, which nitrogen can diffuse into the steel sheet. In particular, the nitrogen donor can be ammonia gas Act. In order for this to dissociate in the annealing furnace to form atomic nitrogen, furnace temperatures of more than 400 ° C. are preferably set in the annealing furnace when the cold-rolled steel sheet is embroidered.

The cold-rolled steel sheet can be embroidered in the continuous annealing furnace before, during or after the recrystallizing annealing. For example, it is possible to embroider in the continuous annealing furnace in an upstream first zone of the continuous annealing furnace at a first temperature below the recrystallization temperature in the presence of a nitrogen donor and then the steel sheet in a downstream second zone of the continuous annealing furnace for recrystallizing annealing to a second temperature above to heat the recrystallization temperature. This sequence of embroidery and recrystallizing annealing can also be reversed. Such a decoupling of the embroidery and the recrystallizing annealing in different zones of the continuous annealing furnace has the advantage that the optimal temperature can be set for the respective process, the optimal temperature for the embroidery being lower than for the recrystallizing annealing. For economic reasons, however, simultaneous embroidery and annealing of the steel sheet in a continuous annealing furnace at a temperature above the recrystallization temperature in the presence of a nitrogen donor is preferable.

By embroidering the cold-rolled steel sheet in the annealing furnace, it can be achieved that the nitrogen introduced in the process is introduced into the steel sheet essentially in unbound form, i.e. in dissolved form in the ferrite lattice of the steel, since the nitrogen introduced during embroidery in the annealing furnace does not interact with strong Binds nitride formers such as aluminum or chromium to form nitrides. This in turn achieves high strength because the unbound nitrogen dissolved in the steel contributes to an increase in strength due to solid solution strengthening. A weight fraction of more than 0.003%, preferably of at least 0.01%, of the nitrogen in unbound form is preferably incorporated interstitially in the steel. The nitrogen introduced into the cold-rolled steel sheet by embroidering in the annealing furnace can therefore (almost) completely contribute to solid solution strengthening and thus to an increase in the strength parameters of the sheet metal packaging product, which in the hydraulic cupping test under a biaxial deformation (bulge test) results in a lower limit strain Sb _eL of more than 300 MPa can be achieved.

• Al: < 0,1 %, bevorzugt weniger als 0,05 %;
• Ti: < 0,01 %, bevorzugt weniger als 0,002 %;
• B: < 0,005 %, bevorzugt weniger als 0,001 %;
• Nb: < 0,01 %, bevorzugt weniger als 0,002 %;
• Cr: < 0,1 %, bevorzugt weniger als 0,08 %,
• Mo: < 0,001 %.

Since the solid solution strengthening generated by embroidering the steel sheet is most efficient when the nitrogen introduced is interstitially stored in unbound form in interstitial spaces of the steel (especially the ferrite lattice), it is useful if the alloy composition of the steel has as few (strong) nitride formers as Al , Ti, B, Cr, Mo and / or Nb in order to prevent the nitrogen from being bound in the form of nitrides. The alloy composition of the steel therefore preferably has the following upper limits for the weight fraction of the following, nitride-forming alloy components:

• Al: <0.1%, preferably less than 0.05%;
• Ti: <0.01%, preferably less than 0.002%;
• B: <0.005%, preferably less than 0.001%;
• Nb: <0.01%, preferably less than 0.002%;
• Cr: <0.1%, preferably less than 0.08%,
• Mo: <0.001%.

The total proportion by weight of the nitride formers is preferably less than 0.1%. In this way, in particular, a weight fraction of unbound nitrogen of more than 0.003% can be guaranteed.

Furthermore, by comparing sheet-metal packaging products according to the invention with comparison samples not according to the invention, it has been shown that by embroidering the cold-rolled steel sheet in the annealing furnace, higher values for the solidification exponent n can be achieved for the sheet-metal packaging products according to the invention. The solidification exponent n is a measure of the strain hardening of the sheet metal packaging product in the direction of the thickness. The sheet-metal packaging products according to the invention are therefore distinguished from comparison samples not according to the invention due to the higher nitrogen content caused by the embroidery in the annealing furnace due to an increased work hardening in the plastic range between the Lüders elongation Abe and the upper (plastic) limit elongation of ε _max = 0.5 Ab · (Sb _eL / Sb _m ).

The mechanical properties of the sheet packaging products according to the invention, which can be determined with the bulge test by determining a biaxial stress / strain curve, are achieved after an (artificial or natural) aging of the material. Natural aging can be caused by long storage of the material or by painting with subsequent drying of the paint. To characterize the material, however, artificial aging can also be carried out by thermal treatment of the sheet metal packaging products over a treatment period of 20 to 30 minutes at an aging temperature of 200 ° C to 210 ° C.

• C: 0,001 - 0,06 %,
• Si: < 0,03 %, bevorzugt 0,002 bis 0,03 %,
• Mn: 0,17 - 0,5 %,
• P: < 0,03 %, bevorzugt 0,005 bis 0,03 %,
• S: 0,001 - 0,03 %,
• Al: 0,001 - 0,1 %,
• N: < 0,016%, bevorzugt 0,001 bis 0,010 %,
• optional Cr: < 0,1 %, bevorzugt 0,01 - 0,08%,
• optional Ni: < 0,1 %, bevorzugt 0,01 - 0,05 %,
• optional Cu: < 0,1 %, bevorzugt 0,002 - 0,05 %,
• optional Ti: < 0,01 %,
• optional B: < 0,005 %,
• optional Nb: < 0,01 %,
• optional Mo: < 0,02 %,
• optional Sn: < 0,03 %,
• Rest Eisen und unvermeidbare Verunreinigungen

For the production of sheet metal packaging products according to the invention, a slab is first cast from a steel with the following composition in relation to the weight proportions of the alloy components listed:

• C: 0.001-0.06%,
• Si: <0.03%, preferably 0.002 to 0.03%,
• Mn: 0.17-0.5%,
• P: <0.03%, preferably 0.005 to 0.03%,
• S: 0.001-0.03%,
• Al: 0.001 - 0.1%,
• N: <0.016%, preferably 0.001 to 0.010%,
• optional Cr: <0.1%, preferably 0.01-0.08%,
• optional Ni: <0.1%, preferably 0.01-0.05%,
• optional Cu: <0.1%, preferably 0.002-0.05%,
• optional Ti: <0.01%,
• optional B: <0.005%,
• optional Nb: <0.01%,
• optional Mo: <0.02%,
• optional Sn: <0.03%,
• Remainder iron and unavoidable impurities

The slab is hot rolled to form a hot strip, the final rolling temperature during hot rolling of the slab preferably being above the Ar3 temperature of the steel and in particular in the range from 800 to 920.degree. The hot strip preferably has a thickness in the range from 2 mm to 4 mm. For economic and qualitative reasons, the greatest possible hot strip thicknesses, preferably more than 2 mm, should be aimed for. However, in order to achieve lower final thicknesses of the cold-rolled steel sheet, higher hot-rolled strip thicknesses are required required if the hot strip is to be cold-rolled with conventional rolling stands without increasing the total degree of cold rolling to values that are no longer technologically achievable. The thickness of the hot strip should therefore not exceed 4 mm. A range of 2 to 4 mm of the hot strip thickness on the one hand prevents the formation of defects in the hot strip due to an excessively high degree of reduction during hot rolling as well as maintaining the preferred final rolling temperature and on the other hand enables the production of thin steel sheets by cold rolling the hot strip once or twice with conventional roll stands with one high total degree of cold rolling in the range of 80% to 98%.

The hot strip is then preferably wound into a roll (coil) at a winding temperature below the Arl temperature and in particular in the range from 500 ° C. to 750 ° C. The rolled-up roll of hot strip is then preferably cooled to room temperature by natural cooling and is expediently freed from scale by pickling. This is followed by (primary) cold rolling of the hot strip with a reduction ratio (degree of cold rolling) of at least 80% to a cold rolled steel strip. The cold-rolled steel strip is then placed in an annealing furnace. The annealing furnace is preferably a continuous annealing furnace through which the cold-rolled steel strip is passed at a predetermined strip speed of preferably more than 200 m / min. In the annealing furnace, on the one hand, recrystallization annealing and, on the other hand, embroidering takes place, wherein the embroidery and recrystallization annealing can take place both simultaneously and in the same sections of the annealing furnace or also one after the other and in particular in different sections of the continuous annealing furnace. The recrystallization annealing takes place at an annealing temperature of the steel strip of at least 630 ° C. The steel band is embroidered in the annealing furnace in the presence of a nitrogen donor, which provides a nitriding gas atmosphere in the annealing furnace. The nitrogen donor, which is a nitriding gas and in particular ammonia gas, is preferably additionally sprayed by means of nozzles onto at least one surface and preferably onto both surfaces of the steel strip in order to achieve a uniform distribution of the nitrogen introduced over the thickness of the steel strip.

The dwell time of the steel strip in the annealing furnace is preferably between 10 seconds and 400 seconds and, when using a continuous annealing furnace, can be adjusted by the strip speed at which the steel strip is guided through the continuous annealing furnace. This annealing time is sufficient for complete recrystallization on the one hand of the steel sheet and, on the other hand, to achieve as homogeneous a distribution as possible of the nitrogen introduced into the steel strip during embroidery in the annealing furnace over the thickness of the steel strip.

In the annealing furnace or in the area of the annealing furnace in which the steel strip is embroidered, a temperature is expediently set to maintain a nitriding gas atmosphere at which the nitrogen donor, which is preferably ammonia gas, is at least partially set dissociated to atomic nitrogen. This ensures the most complete, rapid and uniform diffusion of nitrogen in atomic form on interstitial spaces of the steel lattice and leads to a homogeneous distribution of unbound nitrogen in the steel strip and thus to a high solid solution strengthening.

After embroidering and recrystallization annealing, the steel strip is cooled to room temperature. The cooling can take place passively by emitting heat or actively by means of a cooling fluid, such as cooling gas or water. After the steel strip has cooled to room temperature, the steel strip is tempered or re-rolled with a re-rolling degree of 0.2% to 45%. The degree of re-rolling is preferably <20% and is in particular in the range from 1 to 18%.

The total degree of cold rolling of GKWG = 1 - d / D resulting from the thickness d of the sheet metal packaging product and the thickness D of the hot strip after skin passing or re-rolling is preferably at least 80%, particularly preferably 85% or more. Particularly preferably, the total degree of cold rolling approaches the optimum total degree of cold rolling, which is dependent on the composition of the steel, and is expediently within a tolerance of ± 5% of the optimum degree of total cold rolling. The total degree of cold rolling correlates with the geometric formation of lobes that are formed in a cup pulling test on a sheet metal sample and is characterized by a minimum in the ear height and a number of six lobes. The preferred final thicknesses of the sheet metal packaging products according to the invention are in the range from 0.10 mm to 0.50 mm and particularly preferably in the thickness range from 0.12 mm to 0.35 mm.

Due to the increase in strength brought about by solid solution strengthening by embroidering the steel sheet during annealing in the (continuous) annealing furnace in In the presence of the nitrogen donor, the sheet metal packaging products according to the invention do not require re-rolling with a high degree of re-rolling in order to additionally increase the strength by means of work hardening. The degree of re-rolling can therefore preferably be limited to a maximum of 20% and preferably in the range of in particular in the range from 1 to 18%, whereby a deterioration in the isotropy of the material properties by a second cold rolling with high degrees of re-rolling can be avoided.

After the second cold rolling or skin pass, a coating can be applied to the surface of the flat steel product to improve the corrosion resistance, for example by electrolytic deposition of a tin or chromium / chromium oxide coating and / or by painting with a varnish or by laminating a polymer film made of a thermoplastic material, in particular a film made of a polyester such as PET or a polyolefin such as PP or PE.

The sheet metal packaging products according to the invention are distinguished, despite the low carbon content, by a high basic strength, which is achieved in particular by solid solution strengthening due to the introduction of unbound nitrogen when the sheet steel is embroidered in the annealing furnace. On the other hand, the sheet metal packaging products according to the invention have a higher strain hardening during multi-axis plastic deformation in the production of packaging, which is particularly advantageous in the case of highly demanding deformations (such as the ironing process known as the DWI process) in order to be able to guarantee sufficient component safety. The strength of the sheet metal packaging products according to the invention can additionally be increased by natural or artificial aging of the sheet steel or of the end product (packaging) made from it.

The advantageous material properties and further features of the sheet metal packaging products according to the invention as well as the manufacturing process and the characterization of the sheet metal packaging products according to the invention by hydraulic bulge tests result from the examples described below with reference to the associated tables and drawings. The examples shown serve only to explain the invention and to illustrate the advantageous material properties of the sheet metal packaging products according to the invention compared with those not according to the invention Comparative examples and do not limit the scope of protection of the invention, which is determined by the finally defined patent claims.

Fig. 1:

Beispiel für eine aus einem Bulge-Test ermittelte biaxiale Spannung-/Dehnung-Kurve σ_B (ε) einer gealterten Stahlblech-Probe, wobei die dabei erfassten mechanischen Kenngrößen gem. Tabelle 1 eingezeichnet sind und der Bereich der elastisch-plastischen Verformung in dem Einschub vergrößert dargestellt ist;

Fig. 2:

Detaildarstellung des plastischen Bereichs der biaxialen Spannung-/Dehnung-Kurve von Figur 1 oberhalb der Lüders-Dehnung (Ab_e) mit einem zugehörigen Fit der Funktion σ_B = b·εⁿ ;

Fig. 3:

aus einem Bulge-Test ermittelte biaxiale Spannung-/Dehnung-Kurven von erfindungsgemäßen und nicht-erfindungsgemäßen Stahlblech-Proben mit jeweils vergleichbarer Komposition des Warmbands und unterschiedlichem Stickstoffgehalt und jeweils gleichem Nachwalzgrad, wobei in Figur 3a die Spannung-/Dehnung-Kurve von erfindungsgemäßen und nichterfindungsgemäßen Stahlblech-Proben mit niedrigem Kohlenstoffgehalt (C< 0,03 Gew.%) und in Figur 3b die Spannung-/Dehnung-Kurven von erfindungsgemäßen und nicht-erfindungsgemäßen Stahlblech-Proben mit höherem Kohlenstoffgehalt (C> 0,03 Gew.%) gezeigt sind;

Fig. 4:

Darstellung des Verlaufs der aus der biaxialen Spannung-/Dehnung-Kurve ermittelten unteren Streckgrenze (Sb_eL in MPa) von erfindungsgemäßen und nicht-erfindungsgemäßen Stahlblech-Proben in Abhängigkeit des Nachwalzgrads (NWG in %), wobei in Figur 4a die Werte von Proben mit niedrigem Kohlenstoffgehalt (C< 0,03 Gew.%) und in Figur 4b die Werte von Proben mit höherem Kohlenstoffgehalt (C> 0,03 Gew.%) gezeigt sind;

Fig. 5:

Darstellung des Verlaufs der aus der biaxialen Spannung-/Dehnung-Kurve ermittelten Bruchdehnung (Ab in MPa) von erfindungsgemäßen und nichterfindungsgemäßen Stahlblech-Proben in Abhängigkeit des Nachwalzgrads (NWG in %), wobei in Figur 5a die Werte von Proben mit niedrigem Kohlenstoffgehalt (C< 0,03 Gew.%) und in Figur 5b die Werte von Proben mit höherem Kohlenstoffgehalt (C> 0,03 Gew.%) gezeigt sind;

Fig. 6:

Darstellung des Verlaufs der aus dem plastischen Bereich der biaxialen Spannung-/Dehnung-Kurve σ_B = b·εⁿ ermittelten Verfestigungsexponenten n von erfindungsgemäßen und nicht-erfindungsgemäßen Stahlblech-Proben in Abhängigkeit des Nachwalzgrads (NWG in %), wobei in Figur 6a die Werte von Proben mit niedrigem Kohlenstoffgehalt (C< 0,03 Gew.%) und in Figur 6b die Werte von Proben mit höherem Kohlenstoffgehalt (C> 0,03 Gew.%) gezeigt sind;

Fig. 7:

Darstellung des Verlaufs der aus dem elastisch-plastischen Bereich der biaxialen Spannung-/Dehnung-Kurve σ_B = b·εⁿ ermittelten Verfestigungsexponenten aus Figur 6 von erfindungsgemäßen und nicht-erfindungsgemäßen Stahlblech-Proben in Abhängigkeit ihrer unteren Streckgrenze (Sb_eL in MPa) gemäß Figur 4;

The drawings show:

Fig. 1:

Example of a biaxial stress / strain curve σ _B (ε) of an aged sheet steel sample determined from a bulge test, with the recorded mechanical parameters according to Table 1 and the range of elastic-plastic deformation in the insert is shown enlarged;

Fig. 2:

Detailed representation of the plastic range of the biaxial stress / strain curve of Figure 1 above the Lüders strain (Ab _e ) with an associated fit of the function σ _B = b · ε ⁿ ;

Fig. 3:

Biaxial stress / strain curves of steel sheet samples according to the invention and not according to the invention, each with a comparable composition of the hot strip and different nitrogen content and the same degree of post-rolling, determined from a bulge test, wherein in Figure 3a the stress / strain curve of steel sheet samples according to the invention and not according to the invention with a low carbon content (C <0.03 wt.%) and in Figure 3b the stress / strain curves of inventive and non-inventive steel sheet samples with a higher carbon content (C> 0.03% by weight) are shown;

Fig. 4:

Representation of the course of the lower yield point (Sb _eL in MPa) determined from the biaxial stress / strain curve of steel sheet samples according to the invention and non-according to the invention as a function of the degree of rerolling (NWG in%), with in Figure 4a the values of samples with low carbon content (C <0.03 wt.%) and in Figure 4b the values of samples with higher carbon content (C> 0.03 wt.%) are shown;

Fig. 5:

Representation of the course of the elongation at break determined from the biaxial stress / strain curve (Ab in MPa) of steel sheet samples according to the invention and not according to the invention as a function of the degree of rerolling (NWG in%), with in Figure 5a the values of samples with low carbon content (C <0.03 wt.%) and in Figure 5b the values of samples with higher carbon content (C> 0.03 wt.%) are shown;

Fig. 6:

Representation of the course of the hardening exponents n determined from the plastic range of the biaxial stress / strain curve σ _B = b · ε ^{n of} steel sheet samples according to the invention and non-according to the invention as a function of the degree of re-rolling (NWG in%), where in Figure 6a the values of samples with low carbon content (C <0.03 wt.%) and in Figure 6b the values of samples with higher carbon content (C> 0.03 wt.%) are shown;

Fig. 7:

Representation of the course of the hardening exponents determined from the elastic-plastic range of the biaxial stress / strain curve σ _B = b · ε ⁿ Figure 6 of inventive and non-inventive steel sheet samples as a function of their lower yield point (Sb _eL in MPa) according to Figure 4 ;

For the production of sheet metal packaging products according to the invention, a slab is cast from a steel melt and hot-rolled to form a hot strip. In the following, the constituents of the steel from which sheet metal packaging products according to the invention can be produced are explained in detail, with the percentages relating to the weight percentages of the components of the steel:

Composition of the steel: • Carbon, C: at least 0.001% and at most 0.06%;

Carbon increases hardness and strength. The steel therefore contains at least 0.001% by weight of carbon. Steels with a low carbon content have a higher overall degree of cold rolling, which is why thinner steel sheets can be produced from hot strips with a low carbon content and conventional hot strip thicknesses in the range of 2 to 4 mm by cold rolling while maintaining the same lobing. The carbon content should therefore not be higher than 0.06% in order to ensure the rollability of the steel sheet during primary cold rolling and, if necessary, in a second cold rolling step (re-rolling or skin pass) and, at the same time, to ensure low lobing and not to reduce the elongation at break. A low carbon content also prevents pronounced anisotropy in the form of rows during the production and processing of the steel sheets, since the carbon is largely in the form of cementite due to the low solubility in the ferrite lattice of the steel. In addition, as the carbon content increases, the surface quality deteriorates and the risk of slab cracks increases as the peritectic point is approached.

• Manganese, Mn: at least 0.17% and at most 0.5%;

Manganese also increases hardness and strength. Manganese also improves the weldability and wear resistance of steel. Furthermore, by adding manganese, the tendency towards red breakage during hot rolling is reduced, as sulfur is bound to form less harmful MnS. Furthermore, manganese leads to grain refinement and manganese can increase the solubility of nitrogen in the iron lattice and prevent diffusion of carbon onto the surface of the slab. Therefore, a manganese content of at least 0.17% by weight is preferable. To achieve high strengths, a manganese content of more than 0.2% by weight, in particular 0.30% by weight or more, is preferred. However, if the manganese content becomes too high, the corrosion resistance of the steel is at the expense and food compatibility is no longer guaranteed. In addition, if the manganese content is too high, the strength of the hot strip becomes too high, which means that the hot strip can no longer be cold-rolled economically. Therefore, the upper limit for the manganese content is 0.5% by weight.

• Phosphorus, P: less than 0.03%

Phosphorus is an undesirable accompanying element in steels. A high phosphorus content leads in particular to embrittlement of the steel and therefore worsens the formability of steel sheets, which is why the upper limit for the phosphorus content is 0.03% by weight.

• sulfur. S: more than 0.001% and not more than 0.03%

Sulfur is an undesirable accompanying element that deteriorates ductility and corrosion resistance. The steel should therefore not contain more than 0.03% by weight of sulfur. On the other hand, elaborate and cost-intensive measures have to be taken to desulphurize steel, which is why, from an economic point of view, a sulfur content of less than 0.001% by weight is no longer justifiable. The sulfur content is therefore in the range from 0.001% by weight to 0.03% by weight, particularly preferably between 0.005% by weight and 0.01% by weight.

• Aluminum, Al: more than 0.001% and less than 0.1%

In steel production, aluminum is required as a deoxidizer to calm the steel. Aluminum also increases the scaling resistance and formability. The aluminum content is therefore more than 0.001% by weight. However, aluminum forms with nitrogen Aluminum nitrides, which are disadvantageous in the steel sheets according to the invention, since they reduce the proportion of free nitrogen. In addition, too high aluminum concentrations can lead to surface defects in the form of aluminum clusters. For this reason, aluminum is used in a maximum concentration of 0.1% by weight.

• silicon, Si: less than 0.03%;

Silicon increases the scaling resistance in steel and is a solid solution hardener. Silicon is used as a deoxidizer in steel production. Another positive influence of silicon on steel is that it increases the tensile strength and the yield point. Therefore, a silicon content of 0.002% by weight or more is preferable. However, if the silicon content becomes too high, and in particular exceeds 0.03% by weight, the corrosion resistance of the steel can be deteriorated and surface treatments, particularly by means of electrolytic coatings, can be made difficult.

• optional nitrogen, N ₀ : less than 0.007%, and preferably more than 0.001%

Nitrogen is an optional component in the steel melt from which the steel for the steel sheets according to the invention is produced. Nitrogen acts as a solid solution strengthener and increases hardness and strength. However, if the nitrogen content in the steel melt is too high, the hot strip produced from the steel melt is more difficult to cold-roll. Furthermore, a high nitrogen content in the steel melt increases the risk of defects in the hot strip, since the hot formability is lower at nitrogen concentrations of 0.007% by weight or more. In the manufacture of sheet metal packaging products according to the invention, provision is made for the nitrogen content of the steel sheet to be subsequently increased by embroidering the cold-rolled steel sheet in an annealing furnace. Therefore, the introduction of nitrogen into the steel melt can be dispensed with entirely. In order to achieve a high solid solution strengthening, however, it is preferable if the steel melt already contains an initial nitrogen content of more than 0.001% by weight.

To introduce an initial nitrogen content N ₀ into the steel sheet before embroidering in the annealing furnace, nitrogen can be added to the molten steel in the appropriate amount, for example by blowing in nitrogen gas and / or by adding a solid nitrogen compound such as lime nitrogen (calcium cyanamide) or manganese nitride.

• optional: nitride formers, especially niobium, titanium, boron, molybdenum, chromium:

• Titan, Ti: bevorzugt mehr als 0,0005 %, aber aus Kostengründen weniger als 0,01 %,
• Bor, B: bevorzugt mehr als 0,0005 %, aber aus Kostengründen weniger als 0,005 %, und/oder
• Niob, Nb: bevorzugt mehr als 0,001 %, aber aus Kostengründen weniger als 0,01 %, und/oder
• Chrom, Cr: bevorzugt mehr als 0,01 % um den Einsatz von Schrott bei der Herstellung der Stahlschmelze zu ermöglichen und die Diffusion von Kohlenstoff an der Oberfläche der Bramme zu erschweren, aber zur Vermeidung von Karbiden und Nitriden höchstens 0,1 %, und/oder
• Molybdän, Mo: weniger als 0,02 %, um eine zu starke Erhöhung der Rekristallisationstemperatur zu vermeiden;

Nitride-forming elements such as aluminum, titanium, niobium, boron, molybdenum and chromium are disadvantageous in the steel of the steel sheets according to the invention because they reduce the proportion of free nitrogen through nitride formation. In addition, these elements are expensive and therefore increase manufacturing costs. On the other hand, the elements niobium, titanium and boron, for example, act as micro-alloy constituents through grain refinement to increase strength without reducing toughness. Therefore, the mentioned nitride formers can advantageously be added to the molten steel as alloy components within certain limits. The steel can therefore (optionally) contain the following nitride-forming alloy components based on weight:

• Titanium, Ti: preferably more than 0.0005%, but less than 0.01% for cost reasons,
• Boron, B: preferably more than 0.0005%, but less than 0.005% for reasons of cost, and / or
• Niobium, Nb: preferably more than 0.001%, but less than 0.01% for reasons of cost, and / or
• Chromium, Cr: preferably more than 0.01% to enable the use of scrap in the production of the steel melt and to make the diffusion of carbon on the surface of the slab more difficult, but at most 0.1% to avoid carbides and nitrides, and /or
• Molybdenum, Mo: less than 0.02% in order to avoid an excessive increase in the recrystallization temperature;

To avoid a reduction in the proportion of free, unbound nitrogen N _free due to nitride formation, the total weight proportion of the nitride formers mentioned in the molten steel is preferably less than 0.1%.

Further optional components:

• optional Kupfer, Cu: mehr als 0,002 %, um den Einsatz von Schrott bei der Herstellung der Stahlschmelze zu ermöglichen , aber weniger als 0,1 % um die Lebensmittelverträglichkeit zu gewährleisten;
• optional Nickel, Ni: mehr als 0,01 %, um den Einsatz von Schrott bei der Herstellung der Stahlschmelze zu ermöglichen und die Zähigkeit zu verbessern, aber weniger als 0,1 % um die Lebensmittelverträglichkeit zu gewährleisten;
• optional Zinn, Sn: bevorzugt weniger als 0,03 %;

In addition to the residual iron (Fe) and unavoidable impurities, the molten steel can also contain other optional components, such as

• optional copper, Cu: more than 0.002% to enable the use of scrap in the production of the steel melt, but less than 0.1% to ensure food compatibility;
• optional nickel, Ni: more than 0.01% to enable the use of scrap in the production of the steel melt and to improve the toughness, but less than 0.1% to ensure food compatibility;
• optionally tin, Sn: preferably less than 0.03%;

Production method:

For the production of sheet metal packaging products according to the invention, a steel melt is first produced using the steel composition described, which is continuously cast and, after cooling, is divided into slabs. The slabs are then reheated to preheating temperatures of more than 1100 ° C., in particular 1200 ° C., and hot-rolled to produce a hot strip with a thickness in the range from 2 to 4 mm.

The final rolling temperature in hot rolling is preferably above the Ar3 temperature in order to remain austenitic, and is in particular between 800.degree. C. and 920.degree.

The hot strip is wound into a roll (coil) at a predetermined and expediently constant winding temperature (reel temperature, HT). The winding temperature is preferably below Arl in order to remain in the ferritic region, preferably in the range from 500 ° C. to 750 ° C., and particularly preferably less than 640 ° C. in order to avoid the precipitation of A1N. For economic reasons, the winding temperature should be more than 500 ° C. After being wound up, the roll of hot strip cools down naturally. The formation of iron nitrides on the surface of the hot strip can be avoided by actively cooling the hot strip after the end of hot rolling until it is wound up at higher cooling rates.

To produce a packaging steel in the form of a thin steel sheet in a thickness range of less than 0.6 mm (ultra-fine sheet thickness) and preferably with a final thickness of less than 0.35 mm, the hot strip is first pickled and then cold-rolled. Degree of cold rolling) of at least 80% and preferably in the range from 85% to 98%. To restore the crystal structure of the steel that was destroyed during cold rolling, the cold-rolled steel strip is then annealed to recrystallize in an annealing furnace. This is done, for example, by passing the in the form a cold-rolled steel strip, preferably at a strip speed of at least 200 m / min, through a continuous annealing furnace in which the steel strip is heated to temperatures above the recrystallization temperature of the steel. Before or preferably simultaneously with the recrystallization annealing, the cold-rolled steel sheet is stitched on by heating the steel sheet in the annealing furnace in the presence of a nitrogen donor. The embroidery is preferably carried out simultaneously with the recrystallization annealing by introducing a nitrogen donor, in particular in the form of a nitrogen-containing gas, into the annealing furnace and heating the steel sheet to an annealing temperature above the recrystallization temperature of the steel and for an annealing time (holding time) of preferably 10 to 150 seconds is kept at the annealing temperature. The annealing temperature is preferably above 630.degree. C. and in particular in the range from 640.degree. C. to 750.degree. The nitrogen donor is selected in such a way that at the temperatures in the annealing furnace, atomic nitrogen is formed by dissociation of the nitrogen donor, which can diffuse into the steel sheet. Ammonia has proven to be a suitable nitrogen donor for this. In order to avoid oxidation of the surface of the steel sheet during annealing, a protective gas atmosphere is expediently used in the annealing furnace. The atmosphere in the annealing furnace preferably consists of a mixture of the nitrogen-containing gas acting as a nitrogen donor and a protective gas such as forming gas or nitrogen gas (N ₂ gas), the volume fraction of the protective gas at the feed preferably being between 95% and 99.98% and the The remainder of the volume fraction of the gas fed in is formed by the nitrogen-containing gas, in particular ammonia gas (NH ₃ gas). An equilibrium concentration of 0.02 to 2% by volume of ammonia is preferably maintained during the sticking in the annealing furnace and at the same time ammonia gas is sprayed onto the surfaces of the steel sheet by means of nozzles. This prevents the formation of a hard and brittle nitride layer on the surface of the steel sheet and ensures that the nitrogen diffuses in high concentration into the interior of the steel sheet and is evenly interstitial there in the (ferrite) lattice of the steel. The stitching on preferably increases the initial nitrogen _{concentration N 0} by ΔN 0.002% by weight. The weight fraction of the total nitrogen in the recrystallized and embroidered steel sheet produced by the embroidery in the annealing furnace is preferably between 0.002 and 0.12%, particularly preferably between 0.004 and 0.07%.

Embodiments:

Embodiments of the invention and comparative examples are explained below. The steel sheets of the exemplary embodiments of the invention and the comparative examples were produced from molten steel with the alloy compositions listed in Table 2 by hot rolling and subsequent cold rolling. The cold-rolled steel sheets were then annealed for recrystallization in a continuous annealing furnace by keeping the steel sheets at annealing temperatures of 630 ° C. or more for a predetermined annealing time in the range from 10 to 120 seconds.

The steel sheets according to the invention, which are marked "according to the invention" in Table 2, were embroidered before or during the recrystallization annealing in the annealing furnace by setting an ammonia atmosphere in the annealing furnace with an equilibrium concentration of ammonia of 0.02 to preferably 2% by volume and at the same time Ammonia gas has been directed onto the surfaces of the steel sheets by means of nozzles. The nitrogen content was thereby embroidered in the steel sheets according to the invention from the initial nitrogen content N _{0 of} the hot strip to a higher nitrogen content N. In Table 2, both the initial nitrogen content N _{0 and the nitrogen content N = N 0} + ΔN achieved after embroidery in the annealing furnace are given for the steel sheets according to the invention, with ΔN being the nitrogen content introduced into the steel sheet during embroidery in the annealing furnace.

During the recrystallization annealing of the steel sheets not according to the invention, which are marked in Table 2 as "not according to the invention", an inert gas atmosphere without nitrogen donor (i.e. without nitriding constituents) was present in the annealing furnace, so that the steel sheets not according to the invention were not embroidered in the annealing furnace and the weight percentage of the nitrogen before and after the thermal treatment in the annealing furnace is the same (ie N = N ₀ ).

After the thermal treatment in the annealing furnace, both the steel sheets according to the invention and the steel sheets not embroidered in the annealing furnace of the comparative examples not according to the invention, which are labeled "not according to the invention" in Table 2, were re-rolled or dressed in a second cold-rolling step.

• Dicke die Enddicke der nachgewalzten Stahlbleche (in mm),
• NWG der Nachwalzgrad beim sekundären Kaltwalzen (in %),
• Sb_eH die obere Streckgrenze (in MPa),
• Sb_eL die untere Streckgrenze (in MPa),
• Sb_m die absolute Festigkeit (in MPa),
• Ab die Bruchdehnung (in %),
• Ab_e die Lüdersdehnung (in %),
• b ein Proportionalitätsfaktor in MPa und n ein Verfestigungsexponent ist, die sich aus der Beschreibung der im Bulge-Test ermittelten biaxialen Spanung-Dehnung-Kurve σ_B(ε) im plastischen Bereich oberhalb der Lüdersdehnung (Ab_e) durch die Funktion σ_B = b·εⁿ ergeben wenn σ_B die im Bulge-Test ermittelte (wahre) biaxiale Spannung in MPa und ε der Betrag der wahren Dehnung (in %) in Dickenrichtung ist (Die wahre Dehnung in Dickenrichtung ist aufgrund der Dickenreduktion im biaxialen Zugversuch des Bulge-Tests negativ; unter der Dehnung ε wird daher immer der Betrag der negativen Dehnung in Dickenrichtung des Blechs verstanden).

Finally, ie after the second cold rolling (rerolling or skin pass), the steel sheets were artificially aged by heating the sample to 200 ° C. for 20 minutes. The mechanical properties of the samples artificially aged in this way Steel sheets according to the invention and the comparative examples not according to the invention are listed in Table 3 , where

• Thickness is the final thickness of the re-rolled steel sheets (in mm),
• NWG the degree of re-rolling in secondary cold rolling (in%),
• Sb _{eH is} the upper yield point (in MPa),
• Sb _{eL is} the lower yield point (in MPa),
• Sb _{m is} the absolute strength (in MPa),
• From the elongation at break (in%),
• From _e the Lüders strain (in%),
• b is a proportionality factor in MPa and n is a hardening exponent resulting from the description of the biaxial stress-strain curve σ _B (ε) determined in the bulge test in the plastic range above the Lüders strain (Ab _e ) by the function σ _B = b Ε ⁿ result if σ _{B is} the (true) biaxial stress in MPa determined in the bulge test and ε is the amount of true elongation (in%) in the thickness direction (the true elongation in the thickness direction is due to the thickness reduction in the biaxial tensile test of the bulge Tests negative; the elongation ε is therefore always understood to be the amount of negative elongation in the thickness direction of the sheet).

The mechanical parameters of the samples, such as the upper yield point (Sb _eH in MPa), the lower yield point (Sb _eL in MPa), the absolute strength (Sb _m in MPa), the elongation at break (Ab in%) and the Lüders elongation (Ab _e in%) were determined from the biaxial stress / strain diagram as in the example of Figure 1 explained by way of example.

In Figure 3 biaxial stress / strain curves are shown by way of example, which have been determined from a bulge test on samples of steel sheets according to the invention and not according to the invention, wherein in Figure 3a Low carbon samples (C <0.03%) and in Figure 3b Samples with higher carbon content (C> 0.03%) are shown. In this case, samples according to the invention and samples not according to the invention, each with an identical composition and the same degree of post-rolling (NWG), are compared. The comparison of the biaxial stress / strain curves of inventive and non-inventive samples shows that the biaxial stress in the plastic range above the Lüders strain (ε> Ab _e ) is regularly greater in the inventive samples than in the non-inventive samples -in accordance with the invention Rehearse. This indicates a higher work hardening of the samples according to the invention in the bulk test. The difference in work hardening between the samples according to the invention and the samples not according to the invention is particularly noticeable at higher carbon concentrations (C> 0.03%) in the composition of the steel (see Figure 3b ).

Another measure of the hardening of a steel sheet sample is the (biaxial) lower yield point Sb _eL determined in the bulge test. This depends, among other things, on the degree of re-rolling (NWG). For the graphical representation of the solidification of samples according to the invention and samples not according to the invention are therefore in Figure 4 the lower yield strengths Sb _eL determined from the bulge test as a function of the degree of re-rolling NWG (in%) are shown, again in Figure 4a Steel sheet samples with low carbon content (C <0.03%) and in Figure 4b Samples with higher carbon content (C> 0.03%) are shown.

From a comparison of the samples according to the invention and the samples not according to the invention, the representations of FIG Figure 4 recognize that the samples according to the invention have a higher lower yield point (Sb eL) _{compared to the samples not according to the invention with the same degree of re-rolling.}

In Figure 5 the course of the elongation at break (Ab in%) from the bulge test of samples according to the invention and samples not according to the invention is shown as a function of the degree of re-rolling (NWG in%), with in Figure 5a Samples with lower carbon content (C <0.03%) and in Figure 5b Samples with higher carbon content (C> 0.03%) are shown. From a comparison of the elongation at break of the samples according to the invention and the samples not according to the invention, from the Figures 5a and 5b it can be seen that the elongation at break of the samples according to the invention is higher for the same degree of re-rolling (NWG).

From the biaxial stress / strain curves of the samples according to the invention and the samples not according to the invention determined in the bulge test, a determination was made in the plastic range between the Lüders strain Abe and an upper (plastic) limit strain of ε _max = 0.5 * Ab * (Sb _eL / Sb _m ), where Ab is the elongation at break, SbeL is the lower yield point and Sb _{m is} the absolute strength _{, using fit functions σ B} = b · ε ^{n to determine} the proportionality factor b and the hardening exponent n. The values determined for the samples examined for the The proportionality factor b and the hardening exponent n are given in Table 3. The hardening exponent n is a measure of the strain hardening of a steel sheet sample in the bulge test. Since the hardening exponent n is also dependent on the degree of post-rolling, in Figure 6 the hardening exponents n determined from the bulge test of samples according to the invention and samples not according to the invention as a function of the degree of post-rolling (NWG in%), where in Figure 6a Low carbon samples (C <0.03%) and in Figure 6b Samples with higher carbon content (C> 0.03%) are shown. From a comparison of the samples according to the invention and the samples not according to the invention it can be seen that the hardening exponent n of the samples according to the invention is higher than for the samples not according to the invention with the same degree of re-rolling (NWG).

A quantification of the work hardening of steel sheet samples in the bulge test, independent of the degree of post-rolling, can be achieved with a representation of the hardening _exponent n determined in the bulge test as a function of the lower yield point Sb eL. In Figure 7 _{The solidification exponents} n determined in the bulge test are therefore shown as a function of the lower yield point Sb eL. the end Figure 7 _{it can be seen that the solidification exponents n of the samples according to the invention are} higher than in the samples not according to the invention with the same lower yield point Sb eL. For lower yield strengths of Sb eL> 300 MPa and a minimum elongation at break of Ab> 10%, a differentiation of the samples _{according to the invention from the samples not according to the invention} can be specified by the following curve of the hardening exponent n as a function of the lower yield strength Sb eL (in MPa) : $$\mathrm{n}\ge \mathrm{0},\mathrm{353}-\mathrm{5},\mathrm{1}\cdot {\mathrm{Sb}}_{\mathrm{eL}}/{\mathrm{10}}^{\mathrm{4th}}\mathrm{MPa}\mathrm{.}$$

The samples according to the invention that satisfy the above equation are distinguished in comparison to the samples not according to the invention by a higher yield point and higher work hardening and are therefore better suited for multi-axial deformations, as they are, for example, in comparison to the samples not according to the invention Manufacture of three-dimensional can bodies from sheet packaging products. The samples according to the invention are characterized in particular by a higher work hardening after aging (ie after natural or artificial aging of the sample). The higher work hardening can be seen in the samples according to the invention achieve the introduction of unbound nitrogen when embroidering the samples in the annealing furnace and the resulting solid solution strengthening. <b> Table 1 </b> size Upper yield point Lower yield point Absolute strength Lüder's stretching Elongation at break Upper limit elongation Solidification exponent Proportionality factor Tensile test R _eH R _eL R _m approx. A _e A. - - - Bulge attempt Sb _eH Sb _eL Sb _m From _e away ε _max n b Description of the bulge experiment Highest biaxial true stress before the first significant voltage drop towards the discontinuous area Smallest biaxial true stress in the discontinuous area during plastic flow Highest biaxial true tension after the discontinuous area and shortly before breakage Permanent true elongation in the direction of the thickness in the transition between the discontinuous and the subsequent continuous area Maximum permanent true elongation in the direction of thickness shortly before breakage Amount of true elongation in the direction of the thickness, which results as a function of elongation at break, absolute strength and lower yield point Exponent of a power function that describes the curve between the Lüders' strain and the upper limit strain Multiplicative factor of a power function that describes the curve between the Lüders' strain and the upper limit strain No. category C [%] N [%] Mn [%] P [%] S [%] Si [%] Ni [%] Cr [%] Al [%] Cu [%] Mo [%] Ti [%] Nb [%] N ₀ [%] 1 not according to the invention 0.0016 0.0016 0.1900 0.0080 0.0070 0.0070 0.0130 0.0140 0.0020 0.0290 0.0090 0.0008 0.0007 0.0016 2 not according to the invention 0.0017 0.0020 0.2300 0.0100 0.0040 0.0130 0.0150 0.0230 0.0020 0.0060 0.0020 0.0004 0.0007 0.0020 3 not according to the invention 0.0017 0.0020 0.2300 0.0100 0.0040 0.0130 0.0150 0.0230 0.0020 0.0060 0.0020 0.0004 0.0009 0.0020 4th not according to the invention 0.0017 0.0020 0.2300 0.0100 0.0040 0.0130 0.0150 0.0230 0.0020 0.0060 0.0020 0.0004 0.0004 0.0020 5 not according to the invention 0.0017 0.0020 0.2300 0.0100 0.0040 0.0130 0.0150 0.0230 0.0020 0.0060 0.0020 0.0004 0.0008 0.0020 6th not according to the invention 0.0017 0.0020 0.2300 0.0100 0.0040 0.0130 0.0150 0.0230 0.0020 0.0060 0.0020 0.0004 0.0007 0.0020 7th not according to the invention 0.0017 0.0018 0.2200 0.0120 0.0040 0.0100 0.0260 0.0210 0.0270 0.0090 0.0040 0.0004 0.0008 0.0018 8th according to the invention 0.0018 0.0430 0.2000 0.0070 0.0263 0.0070 0.0290 0.0180 0.0020 0.0100 0.0110 0.0006 0.0009 0.0022 9 according to the invention 0.0019 0.0041 0.2200 0.0090 0.0040 0.0160 0.0160 0.0190 0.0010 0.0070 0.0020 0.0010 0.0010 0.0017 10 according to the invention 0.0019 0.0041 0.2200 0.0090 0.0040 0.0160 0.0160 0.0190 0.0010 0.0070 0.0020 0.0010 0.0008 0.0017 11 according to the invention 0.0019 0.0041 0.2200 0.0090 0.0040 0.0160 0.0160 0.0190 0.0010 0.0070 0.0020 0.0010 0.0010 0.0017 12th not according to the invention 0.0019 0.0041 0.2200 0.0090 0.0040 0.0160 0.0160 0.0190 0.0010 0.0070 0.0020 0.0010 0.0010 0.0017 13th not according to the invention 0.0021 0.0016 0.2400 0.0110 0.0050 0.0230 0.0180 0.0350 0.0020 0.0070 0.0040 0.0004 0.0010 0.0016 14th not according to the invention 0.0022 0.0031 0.2200 0.0090 0.0050 0.0170 0.0380 0.0280 0.0010 0.0120 0.0070 0.0010 0.0010 0.0031 15th not according to the invention 0.0022 0.0031 0.2200 0.0090 0.0050 0.0170 0.0380 0.0280 0.0010 0.0120 0.0070 0.0010 0.0010 0.0031 16 not according to the invention 0.0022 0.0031 0.2200 0.0090 0.0050 0.0170 0.0380 0.0280 0.0010 0.0120 0.0070 0.0010 0.0010 0.0031 17th not according to the invention 0.0022 0.0031 0.2200 0.0090 0.0050 0.0170 0.0380 0.0280 0.0010 0.0120 0.0070 0.0010 0.0010 0.0031 18th according to the invention 0.0024 0.0052 0.2300 0.0110 0.0050 0.0190 0.0160 0.0210 0.0010 0.0070 0.0030 0.0010 0.0007 0.0022 19th according to the invention 0.0024 0.0136 0.2300 0.0100 0.0050 0.0250 0.0150 0.0210 0.0010 0.0120 0.0040 0.0005 0.0005 0.0022 20th according to the invention 0.0024 0.0052 0.2300 0.0110 0.0050 0.0190 0.0160 0.0210 0.0010 0.0070 0.0030 0.0010 0.0010 0.0022 21 according to the invention 0.0024 0.0052 0.2300 0.0110 0.0050 0.0190 0.0160 0.0210 0.0010 0.0070 0.0030 0.0010 0.0011 0.0022 22nd not according to the invention 0.0027 0.0020 0.2300 0.0110 0.0050 0.0250 0.0130 0.0240 0.0020 0.0070 0.0020 0.0004 0.0013 0.0020 23 not according to the invention 0.0029 0.0021 0.2300 0.0100 0.0050 0.0270 0.0150 0.0210 0.0020 0.0120 0.0040 0.0005 0.0005 0.0021 24 according to the invention 0.0030 0.0119 0.2400 0.0080 0.0040 0.0210 0.0180 0.0220 0.0020 0.0060 0.0020 0.0004 0.0005 0.0017 25th according to the invention 0.0041 0.0050 0.1800 0.0110 0.0194 0.0140 0.0540 0.0120 0.0260 0.0220 0.0140 0.0005 0.0008 0.0020 26th not according to the invention 0.0064 0.0025 0.1900 0.0100 0.0250 0.0280 0.0320 0.0180 0.0010 0.0090 0.0010 0.0005 0.0008 0.0025 27 according to the invention 0.0080 0.0050 0.1700 0.0110 0.0250 0.0060 0.0180 0.0140 0.0280 0.0210 0.0180 0.0006 0.0005 0.0018 28 according to the invention 0.0120 0.0090 0.1900 0.0140 0.0210 0.0160 0.0170 0.0190 0.0340 0.0290 0.0090 0.0028 0.0016 0.0024 29 not according to the invention 0.0120 0.0022 0.2300 0.0150 0.0060 0.0090 0.0130 0.0230 0.0370 0.0080 0.0140 0.0004 0.0023 0.0022 30th according to the invention 0.0130 0.0210 0.1800 0.0070 0.0220 0.0150 0.0140 0.0150 0.0410 0.0160 0.0030 0.0006 0.0005 0.0045 31 according to the invention 0.0140 0.0080 0.2100 0.0090 0.0028 0.0160 0.0150 0.0230 0.0270 0.0080 0.0030 0.0060 0.0010 0.0034 32 according to the invention 0.0140 0.0080 0.2100 0.0090 0.0016 0.0024 0.0150 0.0230 0.0270 0.0080 0.0030 0.0060 0.0010 0.0034 33 not according to the invention 0.0140 0.0080 0.2100 0.0090 0.0430 0.0160 0.0150 0.0230 0.0270 0.0080 0.0030 0.0060 0.0010 0.0034 34 according to the invention 0.0170 0.0420 0.2000 0.0080 0.0280 0.0190 0.0230 0.0200 0.0140 0.0220 0.0180 0.0004 0.0008 0.0043 35 according to the invention 0.0210 0.0120 0.2200 0.0100 0.0290 0.0230 0.0350 0.0130 0.0170 0.0120 0.0180 0.0007 0.0007 0.0037 36 not according to the invention 0.0210 0.0021 0.2500 0.0140 0.0260 0.0060 0.0170 0.0230 0.0450 0.0090 0.0040 0.0007 0.0009 0.0021 37 according to the invention 0.0240 0.0170 0.2300 0.0200 0.0260 0.0260 0.0160 0.0170 0.0450 0.0250 0.0180 0.0007 0.0008 0.0028 38 not according to the invention 0.0280 0.0026 0.2100 0.0200 0.0120 0.0280 0.0120 0.0210 0.0460 0.0150 0.0070 0.0008 0.0010 0.0026 39 according to the invention 0.0290 0.0230 0.2200 0.0080 0.0250 0.0240 0.0450 0.0210 0.0470 0.0240 0.0060 0.0007 0.0023 0.0027 40 according to the invention 0.0320 0.0140 0.2800 0.0110 0.0090 0.0290 0.0330 0.0340 0.0380 0.0160 0.0040 0.0006 0.0006 0.0047 41 according to the invention 0.0330 0.0180 0.2300 0.0120 0.0060 0.0090 0.0160 0.0260 0.0330 0.0080 0.0030 0.0010 0.0009 0.0039 42 not according to the invention 0.0340 0.0041 0.2500 0.0090 0.0130 0.0130 0.0180 0.0260 0.0360 0.0100 0.0030 0.0007 0.0010 0.0041 43 not according to the invention 0.0350 0.0046 0.2300 0.0140 0.0070 0.0130 0.0190 0.0320 0.0370 0.0090 0.0030 0.0008 0.0009 0.0046 44 according to the invention 0.0360 0.0180 0.2200 0.0140 0.0070 0.0100 0.0150 0.0240 0.0350 0.0070 0.0020 0.0007 0.0010 0.0048 45 not according to the invention 0.0360 0.0028 0.2300 0.0150 0.0100 0.0060 0.0150 0.0260 0.0460 0.0090 0.0020 0.0007 0.0007 0.0028 46 not according to the invention 0.0360 0.0028 0.2300 0.0150 0.0100 0.0060 0.0150 0.0260 0.0460 0.0090 0.0020 0.0007 0.0010 0.0028 47 not according to the invention 0.0360 0.0028 0.2300 0.0150 0.0100 0.0060 0.0150 0.0260 0.0460 0.0090 0.0020 0.0007 0.0010 0.0028 48 not according to the invention 0.0360 0.0028 0.2300 0.0150 0.0100 0.0060 0.0150 0.0260 0.0460 0.0090 0.0020 0.0007 0.0002 0.0028 No. category C [%] N [%] Mn [%] P [%] S [%] Si [%] Ni [%] Cr [%] Al [%] Cu [%] Mo [%] Ti [%] Nb [%] N ₀ [%] 49 according to the invention 0.0370 0.0200 0.2400 0.0180 0.0070 0.0170 0.0190 0.0290 0.0280 0.0110 0.0030 0.0009 0.0005 0.0043 50 according to the invention 0.0380 0.0176 0.2300 0.0130 0.0060 0.0130 0.0170 0.0260 0.0330 0.0090 0.0030 0.0007 0.0008 0.0039 51 according to the invention 0.0380 0.0215 0.2400 0.0100 0.0060 0.0100 0.0150 0.0220 0.0260 0.0080 0.0010 0.0007 0.0008 0.0041 52 not according to the invention 0.0380 0.0037 0.2500 0.0110 0.0060 0.0070 0.0160 0.0290 0.0390 0.0090 0.0030 0.0004 0.0011 0.0037 53 according to the invention 0.0410 0.0139 0.2300 0.0100 0.0060 0.0110 0.0150 0.0210 0.0390 0.0160 0.0010 0.0008 0.0010 0.0032 54 according to the invention 0.0410 0.0139 0.2300 0.0100 0.0060 0.0110 0.0150 0.0210 0.0390 0.0160 0.0010 0.0008 0.0010 0.0032 55 according to the invention 0.0430 0.0133 0.2800 0.0080 0.0060 0.0110 0.0180 0.0250 0.0290 0.0080 0.0010 0.0007 0.0010 0.0035 56 according to the invention 0.0440 0.0180 0.2300 0.0130 0.0040 0.0130 0.0180 0.0270 0.0320 0.0140 0.0020 0.0010 0.0006 0.0045 57 not according to the invention 0.0440 0.0043 0.2400 0.0080 0.0120 0.0090 0.0150 0.0180 0.0450 0.0150 0.0010 0.0005 0.0005 0.0043 58 not according to the invention 0.0470 0.0038 0.2300 0.0090 0.0110 0.0210 0.0190 0.0310 0.0270 0.0180 0.0140 0.0008 0.0014 0.0038 59 not according to the invention 0.0480 0.0046 0.2400 0.0370 0.0140 0.0300 0.0570 0.0270 0.0360 0.0060 0.0040 0.0043 0.0013 0.0046 60 according to the invention 0.0490 0.0142 0.2500 0.0070 0.0060 0.0090 0.0180 0.0220 0.0440 0.0070 0.0010 0.0023 0.0010 0.0037 61 according to the invention 0.0490 0.0280 0.2100 0.0240 0.0020 0.0090 0.0200 0.0410 0.0270 0.0110 0.0030 0.0015 0.0007 0.0029 62 not according to the invention 0.0520 0.0052 0.1600 0.0140 0.0220 0.0023 0.0130 0.0230 0.0470 0.0130 0.0130 0.0009 0.0006 0.0052 63 according to the invention 0.0530 0.0490 0.4300 0.0100 0.0280 0.0270 0.0120 0.0260 0.0490 0.0030 0.0070 0.0005 0.0008 0.0057 64 according to the invention 0.0530 0.0540 0.4800 0.0150 0.0180 0.0270 0.0280 0.0330 0.0390 0.0300 0.0080 0.0005 0.0013 0.0063 65 according to the invention 0.0540 0.0570 0.5000 0.0280 0.0090 0.0220 0.0420 0.0430 0.0180 0.0130 0.0010 0.0004 0.0009 0.0023 66 not according to the invention 0.0560 0.0057 0.1600 0.0130 0.0260 0.0140 0.0200 0.0280 0.0430 0.0230 0.0150 0.0010 0.0010 0.0057 67 according to the invention 0.0570 0.0310 0.3400 0.0270 0.0130 0.0090 0.0110 0.0310 0.0260 0.0190 0.0010 0.0031 0.0009 0.0067 68 not according to the invention 0.0580 0.0037 0.3500 0.0110 0.0090 0.0080 0.0236 0.0240 0.0290 0.0180 0.0050 0.0005 0.0005 0.0037 69 according to the invention 0.0590 0.0101 0.3700 0.0230 0.0280 0.0120 0.0180 0.0480 0.0210 0.0200 0.0050 0.0007 0.0005 0.0048 70 not according to the invention 0.0710 0.0087 0.2500 0.0180 0.0030 0.0270 0.0150 0.0280 0.0460 0.0200 0.0180 0.0027 0.0007 0.0087 No. category Thickness [mm] NWG [%] Sb _eH [MPa] Sb _eL [MPa] Sb _m [MPa] From _e [%] Away [%] b [MPa] n [1] 1 not according to the invention 0.48 0.4 351 276 494 1.7 42.3 264 0,201 2 not according to the invention 0.30 1 331 286 493 1.9 38.0 243 0.199 3 not according to the invention 0.22 7.5 390 350 536 0.7 39.0 371 0.095 4th not according to the invention 0.27 10 413 372 465 1.1 31.4 371 0.114 5 not according to the invention 0.25 15th 464 435 487 0.8 27.3 443 0.061 6th not according to the invention 0.24 20th 486 465 494 0.8 17.3 470 0.045 7th not according to the invention 0.20 0.4 364 291 501 1.8 39.4 279 0.183 8th according to the invention 0.17 0.6 387 315 541 4.1 42.7 264 0,201 9 according to the invention 0.22 1 409 317 557 2.7 41.8 257 0.215 10 according to the invention 0.19 10 486 454 587 2.1 28.7 404 0.128 11 according to the invention 0.18 15th 537 486 594 1.6 21.6 471 0.114 12th not according to the invention 0.13 40 693 662 675 1.6 9.3 657 0.022 13th not according to the invention 0.22 6th 417 367 566 1.3 42.8 356 0.130 14th not according to the invention 0.23 1 402 313 551 1.6 46.0 272 0.179 15th not according to the invention 0.21 10 490 425 581 1.8 33.5 409 0.108 16 not according to the invention 0.20 15th 545 477 588 1.7 26.8 478 0.068 17th not according to the invention 0.14 40 685 640 645 1.4 10.5 650 0.013 18th according to the invention 0.22 1 405 341 591 2.5 41.1 283 0.207 19th according to the invention 0.21 4.5 463 421 656 1.3 32.9 395 0.163 20th according to the invention 0.20 8th 548 496 663 2.0 26.0 455 0.126 21 according to the invention 0.18 16 551 502 629 1.4 21.8 481 0.100 22nd not according to the invention 0.17 40 673 651 692 1.0 10.8 670 0.011 23 not according to the invention 0.21 4.5 424 405 580 1.5 42.6 351 0.141 24 according to the invention 0.18 5 472 428 645 1.9 36.4 376 0.163 25th according to the invention 0.28 0.6 444 354 514 3.4 43.1 375 0.177 26th not according to the invention 0.18 2 402 329 532 1.8 36.6 308 0.153 27 according to the invention 0.32 0.4 441 347 578 2.5 36.5 309 0.183 28 according to the invention 0.29 0.4 459 393 604 2.3 35.8 337 0.170 29 not according to the invention 0.29 1 410 337 534 1.9 36.9 307 0.163 30th according to the invention 0.14 4.5 501 472 682 1.3 32.1 438 0.160 31 according to the invention 0.48 0.6 451 375 597 2.1 36.7 337 0.174 32 according to the invention 0.23 20th 611 561 658 1.9 17.9 546 0.075 33 not according to the invention 0.45 33 717 683 698 0.8 5.4 694 0.031 34 according to the invention 0.16 1 461 447 692 1.3 37.4 432 0.183 35 according to the invention 0.15 11 567 514 661 2.1 25.8 478 0.118 36 not according to the invention 0.19 0.8 435 347 542 2.2 37.4 321 0.157 37 according to the invention 0.26 20th 643 614 715 1.5 17.1 602 0.079 38 not according to the invention 0.14 4.5 483 407 562 1.6 32.3 376 0.109 39 according to the invention 0.34 7th 567 538 717 1.6 28.4 504 0.133 40 according to the invention 0.29 0.6 523 459 653 2.5 34.1 401 0.149 41 according to the invention 0.17 5 541 498 667 2.1 27.0 447 0.134 42 not according to the invention 0.16 22nd 606 588 615 1.2 24.6 596 0.010 43 not according to the invention 0.22 0.8 470 395 588 3.2 41.6 349 0.129 44 according to the invention 0.18 17th 657 638 741 1.3 20.6 623 0.072 45 not according to the invention 0.21 0.4 498 370 591 3.5 45.4 293 0.157 46 not according to the invention 0.21 1 509 401 580 3.0 40.4 344 0.132 47 not according to the invention 0.20 5 543 486 588 2.7 26.5 454 0.066 48 not according to the invention 0.18 15th 665 571 608 2.4 8.6 546 0.048 49 according to the invention 0.17 10 645 602 762 1.5 26.6 575 0.103 50 according to the invention 0.21 1.2 538 483 654 3.3 29.4 403 0.149 51 according to the invention 0.15 8th 584 540 631 2.3 17.8 497 0.096 52 not according to the invention 0.17 10 532 477 601 1.2 30.9 470 0.077 53 according to the invention 0.22 0.4 559 430 667 3.0 40.5 343 0.168 54 according to the invention 0.19 15th 720 649 703 3.3 13.3 632 0.039 55 according to the invention 0.21 7.5 571 531 668 2.2 27.2 482 0.108 56 according to the invention 0.13 8th 626 578 677 3.0 16.6 524 0.100 57 not according to the invention 0.17 10 565 507 597 1.7 20.0 488 0.081 58 not according to the invention 0.14 11 589 518 615 2.4 25.2 492 0.054 59 not according to the invention 0.28 2.2 525 454 588 2.6 32.1 401 0.104 60 according to the invention 0.21 6th 573 522 655 2.3 24.1 481 0.096 61 according to the invention 0.14 0.6 581 546 747 1.9 31.9 498 0.137 62 not according to the invention 0.23 12th 601 549 614 1.2 23.7 499 0.060 63 according to the invention 0.24 14th 694 682 757 0.9 14.8 652 0.064 64 according to the invention 0.20 1.4 601 576 770 1.8 31.1 537 0.154 65 according to the invention 0.23 5 630 608 781 1.7 27.4 570 0.117 66 not according to the invention 0.35 18th 667 607 647 0.8 18.1 586 0.036 67 according to the invention 0.15 8th 661 641 793 1.6 24.4 607 0.101 68 not according to the invention 0.23 15th 649 572 630 1.3 10.5 548 0.031 69 according to the invention 0.25 12th 682 605 692 3.1 21.4 553 0.068 70 not according to the invention 0.22 6th 624 545 646 2.7 27.3 503 0.054

Claims (15)

Sheet packaging product made from a cold-rolled steel sheet with a thickness of less than 0.6 mm, which has the following composition in relation to weight: - C: 0.001-0.06%, - Si: <0.03%, preferably 0.002 to 0.03%, - Mn: 0.17-0.5%, - P: <0.03%, preferably 0.005 to 0.03%, - S: 0.001-0.03%, - Al: 0.001-0.1%, - N: 0.002-0.12%, preferably 0.004-0.07%, - optional Cr: <0.1%, preferably 0.01-0.1%, - optional Ni: <0.1%, preferably 0.01-0.05%, - optional Cu: <0.1%, preferably 0.002-0.05%, - optional Ti: <0.01%, - optional B: <0.005%, - optional Nb: <0.01%, - optional Mo: <0.02%, - optional Sn: <0.03%, - remainder iron and unavoidable impurities, _{The sheet metal packaging product has} a lower yield point (Sb eL) of more than 300 MPa and an associated elongation at break (Ab) of more than 10% and in the plastic range between the Lüders elongation (Ab _e ) and an upper one in the case of biaxial deformation in a bulge test (Plastic) limit strain of ε _max = 0.5 Ab (Sb _eL / Sb _m ) has a biaxial stress / strain diagram σ _B (ε), which can be represented with a function σ _B = b ε ⁿ , whereby - σ _{B is} the true, biaxial stress in MPa, - ε is the amount of true elongation in the thickness direction in%, - Sb _{eL is} the lower yield point, - Sb _m the absolute strength, - Abe the stretching of the Lüders, - b a proportionality factor and - n is a hardening exponent, and a consolidation of the packaging sheet product in the thickness direction by a consolidation exponent of
n ≥ 0.353 - 5.1 Sb _eL / 10 ⁴ MPa
is characterized. Sheet metal packaging product according to Claim 1, characterized in that a proportion by weight of at least 0.002%, preferably more than 0.004% of the nitrogen, is interstitially incorporated in the steel in unbound form. Sheet packaging product according to one of the preceding claims, wherein the sheet packaging product is obtainable by Hot rolling of a slab made of the steel to form a hot strip, the hot strip preferably having a thickness in the range from 2 mm to 4 mm, - Coiling of the hot strip at a coiling temperature below the Arl temperature and in particular in the range from 500 ° C to 750 ° C, - cold rolling of the hot strip with a reduction ratio of at least 80% to a cold rolled steel strip, - Embroidery of the cold-rolled steel strip in an annealing furnace, in particular a continuous annealing furnace, in the presence of a nitrogen donor at a temperature of at least 550 ° C and recrystallization annealing of the cold-rolled steel strip in an annealing furnace at an annealing temperature of at least 630 ° C, - cooling the recrystallizing annealed steel strip to room temperature, - Rerolling the recrystallized steel strip at a rerolling degree of 0.2% to 45%. Sheet metal packaging product according to Claim 3, characterized in that the final rolling temperature during hot rolling of the slab is greater than the Ar3 temperature and is in particular in the range from 800 ° C to 920 ° C. Sheet metal packaging product according to one of Claims 3 or 4, characterized in that the length of time the steel strip remains in the annealing furnace is between 10 seconds and 400 seconds. Sheet packaging product according to one of Claims 3 to 5, characterized in that the degree of post-rolling is 20% or less and in particular is in the range from 1 to 18%. Sheet packaging product according to one of Claims 3 to 6, the nitrogen donor being at least partially dissociated to atomic nitrogen at the temperatures in the annealing furnace. The sheet packaging product according to any one of claims 3 to 7, wherein the nitrogen donor is ammonia gas. Sheet metal packaging product according to one of claims 3 to 8, characterized in that the hot strip has an initial nitrogen content No in the range from 0.001% by weight to 0.016% by weight, preferably from 0.001% by weight to 0.008% by weight, and that the weight fraction of the Nitrogen in the flat steel product during annealing is increased by ΔN ≥ 0.002% by weight due to the presence of the nitrogen donor. Sheet metal packaging product according to one of the preceding claims, characterized in that it has a surface coating on at least a surface of the cold-rolled steel sheet, in particular an electrolytically applied tin and / or chromium / chromium oxide coating and / or an organic coating, in particular in the form of a lacquer or a polymer film. Packaging sheet product according to one of the preceding claims, wherein the properties of the packaging sheet product are obtained after aging of the packaging sheet product, in particular after artificial aging by a thermal treatment for 20 to 30 minutes at an aging temperature in the range of 200 ° C to 210 ° C or after a Storage and / or by painting with subsequent drying. Sheet packaging product according to one of Claims 3 to 11, the total degree of cold rolling of GKWG = 1 - d / D resulting from the thickness (d) of the sheet packaging product and the thickness (D) of the hot strip is at least 0.90. Sheet metal packaging product according to one of the preceding claims, which is a single or double reduced fine sheet with a thickness (d) in the range from 0.10 mm to 0.50 mm, preferably from 0.12 mm to 0.35 mm. Use of a sheet metal packaging product according to one of the preceding claims for the production of can bodies. A method for the production and characterization of a packaging sheet product from a cold-rolled steel sheet with a thickness of less than 0.6 mm, the packaging sheet product being produced from a hot strip by cold-rolling the hot strip once or twice at a reduction ratio of at least 80% and the hot strip having the following composition in terms of weight: - C: 0.001-0.06%, - Si: <0.03%, preferably 0.002 to 0.03%, - Mn: 0.17-0.5%, - P: <0.03%, preferably 0.005 to 0.03%, - S: 0.001-0.03%, - Al: 0.001-0.1%, - N: <0.016%, preferably 0.001 to 0.008%, - optional Cr: <0.1%, preferably 0.01-0.08%, - optional Ni: <0.1%, preferably 0.01-0.05%, - optional Cu: <0.1%, preferably 0.002-0.05%, - optional Ti: <0.01%, - optional B: <0.005%, - optional Nb: <0.01%, - optional Mo: <0.02%, - optional Sn: <0.03%, - remainder iron and unavoidable impurities, wherein the cold-rolled steel strip is embroidered in an annealing furnace, in particular a continuous annealing furnace, in the presence of a nitrogen donor at a temperature of at least 550 ° C to a nitrogen content based on weight of ΔN ≥ 0.002% and annealed recrystallizing at an annealing temperature of at least 630 ° C, then cooled to room temperature and re-rolled cold at a re-rolling degree of 0.2% to 45% and then subjected to biaxial deformation in the bulk test in the plastic range in order to characterize the deformability, in which the _sheet-metal packaging product has a lower yield point (Sb eL) of more than 300 MPa and an associated elongation at break (Ab) of more than 10% as well as biaxial stress _{in the area between the Lüders elongation (Ab e} ) and an upper (plastic) limit elongation of ε _max = 0.5 Ab (Sb _eL / Sb _m) - Strain diagram σ _B (ε) shows that can be represented with a function σ _B = b · ε ⁿ , where - σ _{B is} the true, biaxial stress in MPa, - ε is the amount of true elongation in the thickness direction in%, - Sb _{eL is} the lower yield point, - Sb _m the absolute strength, - Abe the stretching of the Lüders, - b a proportionality factor and - n is a hardening exponent that
n ≥ 0.353 - 5.1 Sb _eL / 10 ⁴ MPa fulfilled.

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