JPH06220575A - Article packing steel unpackable by tearing least resistible line - Google Patents

Abstract

The packaging according to the invention is of the type in which the lid is to be opened by breaking a line of lowest strength arranged in a part of the wall made of steel sheet. The steel of which the sheet consists has a carbon content of between 0.02 and 0.08 % by weight and a boron content of between 0.002 and 0.004 % by weight, the steel also containing nitrogen, the ratio of the boron content to the nitrogen content being higher than 0.8 and the remainder being chiefly iron and residual elements.

Description

Detailed Description of the Invention

The present invention relates to a packaging article which is opened by breaking a line having the least resistance, a so-called easy open can.

[0002] For example, packaging articles intended to contain beverages, preserves and other products are known.

The packaging article has a lid formed with lines of least resistance, such as cuts, so as to define the boundaries of the open panels.

The drive ring is fixed to the aperture panel by rivets.

The opening is created by a pulling force applied to the drive ring so as to break the metal in the cut area, and the opening panel optionally includes a portion that articulates to the lid so that it does not completely disengage from the lid. be able to.

The packaging article may be made of aluminum, which would be relatively expensive.

When the packaging articles are made of steel to reduce costs, it is common to use sheet metal of standard low carbon steel that is continuously annealed at about 680 ° C. and tin plated. .

The mechanical properties of the tin-plated steel are as follows: transverse yield stress (Re) of about -415 MPa, transverse breaking load (Rm) of about -430 MPa.

The steel used to make the packaging articles must be able to form rivets which secure the opening ring on the one hand and, on the other hand, the line of least resistance without the need to apply excessive force. It must be easy to destroy.

In order to do this, otherwise the breaking force Rm must not be too great, as the opening force applied must be large in order to break the line of least resistance.

Similarly, the ratio of the yield stress Re to the load at break Rm must approach 1 so that the steel becomes more fragile as the openings become easier.

On the other hand, if the ratio Re / Rm must not be too large, ie too close to 1, in this case the steel becomes very brittle, so that the steel depth of the lid of the packaging article is This makes this rivet forming operation, which requires drawing, virtually impossible.

By the way, in the standard steel generally used, the yield stress Re is almost equal to 415 MPa and the load at break is about 430 MPa, so the ratio Re / Rm is 0.96.
It will be about.

Easy made by using such steel
The open lid has a large opening force due to the Rm value and the relatively large residual thickness of the cut area.

Furthermore, the plateau of the yield stress is high, which leads to the formation of a visible Luders band when drawing the packaging article, which is unfavorable for its aesthetic appearance.

To overcome these drawbacks, it is an object of the present invention to provide a packaging article which opens by breaking the line of least resistance, while reducing the overall force required for opening, while Another object of the present invention is to provide a packaging article which has an excellent appearance after drawing of the packaging article and has good rivet formability.

For this reason, the subject of the present invention is that, in a metal packaging article in which the line of least resistance formed in the wall of the steel sheet is opened, the steel constituting the metal sheet is less than 0. Having a carbon content of 02-0.08% by weight and a boron content of 0.002-0.004% by weight, the steel also contains nitrogen and the ratio of boron content to nitrogen content is greater than 0.8. A metal packaging article characterized in that the balance is mainly iron and the remaining elements.

According to other characteristics: -The weight composition of the steel constituting the sheet metal is preferably (expressed in thousands per cent):-Carbon: 50-Manganese: 200-Phosphorus: 10-Nitrogen: 3.5-aluminum: 30-silicon: 5-boron: 3-the balance is iron and the balance metal.

The subject of the invention is also a thin steel sheet intended for the production of packaging articles, the ratio of the yield stress to the load at break of which is 0.87 to 0.96, preferably 0.91 to 0.
92 is a thin steel plate.

The subject of the invention is also a process for the production of sheet metal suitable for making packaging articles according to the invention, the process wherein the sheet metal is obtained by continuous rolling and, after this continuous rolling, the metal sheet. About 550 annealing on a thin plate
It is carried out at a temperature of ˜650 ° C. for 8 to 10 hours, a temperature rise from room temperature is carried out for about 20 hours, and a thin metal plate is cold rerolled to have an elongation of 5 to 10%. Is the way.

The invention will be better understood by reading the following detailed description, given by way of example.

To reduce the force required to open the lid, it is necessary to use steels having a relatively low yield stress, which in addition rolls up the apertured panel after a break fracture. And has a large Re / Rm ratio.

On the other hand, for good rivet formability, Re / R
It is necessary to use steel with a small m ratio.

The appearance of the packaging article and its corrosion resistance are improved by using a sheet metal having a texture of equiaxed grains and having no yield stress plateau.

The desired mechanical properties and equiaxed grain structure are obtained as a result of: -adoption of a metal sheet made of steel with a defined composition, -including annealing on the base and cold rerolling. Application of metal sheet manufacturing method.

More precisely, the packaging article according to the invention is made of sheet steel, which has a carbon content of 0.02 to 0.
08% by weight, with a boron content of 0.002 to 0.004% by weight, the steel also contains nitrogen in an amount of less than 0.005% by weight and the ratio of boron content to nitrogen content is greater than 0.8. .

A carbon content of less than 0.02% by weight is difficult to obtain by conventional refining processes and may produce lids of insufficient mechanical strength.

Above a carbon content of 0.08% by weight, the breaking load Rm of the sheet metal intended for making packaging articles will be too great.

In order to obtain a metal sheet which makes it possible to produce packaging articles according to the invention, the structure of the metal sheet must be equiaxed and the ratio of boron content to nitrogen content must be greater than 0.8. And, if the boron content is more than 0.004%, the improvement of mechanical properties and preferential oxidation of the metal sheet appear to appear at the edge of the product, which is aesthetically unfavorable, so that the boron content is 0%. It is recognized that it is limited to 0.004%.

The weight composition of the steel constituting the metal sheet intended for the packaging article according to the present invention is preferably the following (1000
In units of one-percent):-Carbon: 50-Manganese: 200-Phosphorus: 10-Nitrogen: 3.5-Aluminum: 30-Silicon: 5-Boron: 3-The balance is iron and the remaining elements.

The method used to make a metal sheet suitable for packaging articles according to the present invention is that after continuous rolling of the steel, the metal sheet is annealed on a base at a temperature of about 550 to 650 ° C. for 8 to 10 hours. , The temperature rise from room temperature is about 20
It takes time to do it. Next, the thin metal plate is cold rerolled to have an elongation of 5 to 10%.

The following mechanical properties can be obtained by combining the steel composition and a suitable manufacturing method.

Re = about 310 MPa Rm = about 340 MPa The ratio of yield stress to load at break is 0.91 to 0.92.

A packaging article which is quite easy to open and has good rivet formability is thus obtained.

On the other hand, such steels are able to withstand deep incisions, ie deeper incisions, before opening undesired damage, thereby reducing opening forces.

As a practical matter, in the case of standard low carbon steel the residual thickness at the bottom of the cut should not be less than 70 microns in order to avoid undesired damage, but in the case of the steel according to the invention Can have a residual thickness at the bottom of the cut as thin as 50 microns.

This packaging article made of a thin metal sheet of equiaxed grain structure prevents the appearance of undesired yields and the appearance of deformation wrinkles due to the integrity of the varnish, which is not desirable in the appearance of the packaging article during rivet forming.

The presence of boron can also delay the cementite coalescence as evidenced by the excellent uniformity of the force exerted when opening the packaging article.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Patrick Zime France 57365 Enpais Marechal Ferran 2 Enneri, (72) Inventor Michelle Estonje France 57330 Methange Grande, Are du Grand Cell 1

Claims (5)

[Claims] 1. In a metal packaging article which is opened by breaking a line of least resistance formed on a wall portion of a thin steel plate, the steel constituting the thin metal plate is 0.02 to 0.
With a carbon content of 08% by weight and a boron content of 0.002-0.004% by weight, the steel also contains nitrogen,
A packaging article, characterized in that the ratio of the boron content to the nitrogen content is greater than 0.8, the balance being mainly iron and the remaining elements. 2. The weight composition of steel constituting the thin metal plate is as follows (in units of one-thousandth percent):-Carbon: 50-Manganese: 200-Phosphorus: 10-Nitrogen: 3.5-Aluminum: 30- The packaging article according to claim 1, characterized in that silicon: 5-boron: 3-residue is preferably iron and the remaining elements. 3. The ratio of yield stress to load at break is 0.87-
It is 0.96, The thin steel plate for packaging articles of Claim 1 or Claim 2 characterized by the above-mentioned. 4. The ratio of the yield stress to the load at break is 0.91 to
It is 0.92, The thin steel plate of Claim 3 characterized by the above-mentioned. 5. Including continuous rolling, after this continuous rolling, a thin metal plate is annealed on a base at a temperature of about 550 to 650 ° C. for 8 to 10 hours, and a temperature rise from room temperature requires about 20 hours. 5. The method for producing a metal sheet according to claim 3 or 4, wherein the elongation is 5 to 10% by cold rerolling the metal sheet.