DE2535618A1 - TIN CONTAINER AND METHOD FOR MANUFACTURING IT - Google Patents

Description

Sponsorship

Dr. O. Iea θϊ-beck

Dipl.-! π · trek

Dipl.-Ing. L> s: .nbock

Hi Bitfeld, Herford Street 17

METAL BOX LIMITED, Queens House, Forbury Road, Reading RGl 3JH ,

Berkshire, UK

Sheet metal container and process for its manufacture

The invention relates to containers which are made from sheet iron or sheet steel by first drawing a bowl which is then drawn to the final shape.

It is known to make beverage cans either made of aluminum or of tin-coated steel, such as tinplate, to be produced by first drawing a cup from the sheet metal material, which is then reshaped by drawing tools that contain a punch and one or more dies and flattening tools. Have such doses a bottom wall that is essentially the same thickness as the material fed to the tools, and side walls, that are thinner than the ground. Such cans are usually coated on the inside to prevent corrosion and provided with a decoration on the outside. However, the tin coating is very expensive.

The present invention provides a method for drawing a can from mild steel sheet or black sheet metal, that is that the mild steel sheet surface is first chemically treated to create a surface that the ability of controlled lubricant retention to

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has, in which case a lubricant is then applied to the treated surface, a cup is drawn from the piece of sheet metal is, the cup is then provided again with lubricant and then subsequent redrawing and / or flattening processes are carried out will.

According to a preferred embodiment of the invention Process consists of the chemical treatment that the sheet is provided with a solid coating that contains a phosphate radical. The coating is preferably selected from the group consisting of iron phosphate, zinc phosphate, Calcium phosphate and magnesium phosphate are formed. However, it can also be a mixed coating.

A press tool lubricant, which is preferably an emulsion of oil in water, is used as the lubricant.

The invention also relates to one according to the invention Process made can. A can that is drawn from mild steel sheet is affected, at least that is is provided on the outside with a surface that has a lubricant.retaining properties. According to a preferred .. embodiment, the can has a thicker bottom wall as a side wall, the bottom wall extending downward and inward from the side wall and forming a standing bead and from it upwards inwards to form a wall section which is particularly resistant to internal pressure is directed.

Embodiments of the subject matter of the invention are described below with reference to the accompanying drawing *
Show it

Fig. 1 shows a section of a soft steel sheet with a Lubricant-retaining coating on it,

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FIG. 2 shows a diagrammatic sectional illustration through the sheet metal piece according to FIG. 1, with added lubricant,

3 shows a schematic representation of parts of a press with associated tools for illustration of the successive manufacturing stages of a can according to the invention.

According to one embodiment of the invention, FIG. 1 shows a piece of sheet metal 1 made of mild steel sheet in the form of black sheet metal shown with a degree of hardness and a surface finish suitable for drawing. Such a degree of hardness is known as Temper 1, Temper 2, or Temper 3. A suitable surface roughness is on the order of 890 micromillimeters medium surface roughness. The piece of sheet metal is subjected to chemical treatments that include a solid coating 2 on its surface. Suitable coatings include:

Iron phosphate in a coating of 215-2150

(preferably 645) mg / m

Zinc phosphate in a coating of 1075 - 21500 "

(preferably 10750) mg / m

Zinc or calcium phosphate <■

in a coating of 540-10750

(preferably 2700) mg / m

Magnesium phosphate in a coating of 1075-10750 _?

(preferably 3250) mg / m

Other coatings that include a phosphate radical may also be suitable, and the coating thickness on one side of the sheet metal plate can be different from that on the other side of the sheet metal. The reason

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this is explained in more detail below.

The coated piece of sheet metal is then coated with a lubricant lubricated. Examples of this are mineral and vegetable metalworking oils. A suitable example is one Emulsion consisting of 10% mineral oil and 2 to 5% fatty acid in water. Such an emulsion acts both as a lubricant as well as a coolant for the tools. Other emulsions can also be used.

In Fig. 2 it is shown how the lubricant 4 on the surface of the coating 2 and how it enters between the gaps 3 of the crystallites of the coating. The lubricant can be applied on both sides. However, it can be beneficial to only apply it to one side, such as is explained in more detail below.

The coated and lubricated sheet metal piece is then processed on a press which has a tool that punches out a disc which is then drawn into a cup 11 which has a larger diameter than the finished container to be produced. The cup 11 is then brought to a further press 13 of known type which is provided with tools which are shown schematically in FIG. These tools include a hold-down device 5, a drawing punch 6, a drawing die 7, a first flat ring 8 and a second flat ring 9 and a bottom mold block 10. If necessary, more than two flat rings can be provided. A line 12 brings lubricant to the pressing tools and has three outlets. The outlet 12A directs the lubricant to the first washer 8, the outlet 12B directs the lubricant to the second washer 9 and the outlet 12C directs the lubricant to the cup 11 and the die 7. The lubricant is continuously passed over the line and the tools on the way

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promoted through a memory 14 in the return process through the system.

The hold-down device 5 is lowered and enters the cup 11 and is thereby caught by the surface of the die 7, whereupon the drawing or redrawing begins when the punch 6 drives the cup 11 through the redrawing die 7, thereby reducing the diameter of the cup and increasing its height. During this process, the wall thickness of the cup is maintained substantially constant to that of the bottom of the cup by known means such as a controlled hold-down pressure or a corresponding flattening and smoothing process in the Drawing opening 7A of the die 7. In this way, a cup is produced which is essentially free from wrinkles and from There is fluctuations in wall thickness. When the cup emerges from the redrawing die 7, it encounters a jet of lubricant from outlet 12A and is lubricated again so that afterwards the cup is then prepared for flattening when the punch 6 brings the cup to the first plate ring 8. The wall thickness of the redrawn cup is reduced when the The punch drives it through the first plate ring 8, namely by means of the gap between the punch 6 and the ring 8, which is kept smaller than the material thickness, and a further reduction takes place in the same way when passing through drive through the second bearing ring 9. There is a further application of lubricant between the bearing rings 8 and 9 by means of a jet of lubricant emerging from outlet 12B.

During the flattening process, wall material is pulled up on the punch in such a way that there is a certain amount of rubbing contact on the inside of the bowl with the punch is present, which facilitates the transmission of force to the bottom of the can. This is the reason, why it is beneficial to have any lubrication on the inside

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of the bowl as small as possible and also the surface roughness of the mild steel sheet in contact with the punch. The working surface of the Die and the rings, however, benefit from the lubrication that results from the combination of the solid coating produced with the lubricant results.

After the flattening, the can is transported on to interact with the bottom mold block 10. During the return stroke the can is stripped from the punch 6 in a known manner such as external mechanical scrapers 15, which are from an ejection device in the stamp (not shown) can be supported. The cans are then degreased and washed. The boxes can be decorated and are then provided with constrictions on the top in the usual way.

Cans made by the method described above can be used for a wide variety of products, including with heat processed foods and beverages are used. The can 111 shown on block 10 in Fig. 3 is particularly suitable for beverages as it has a bottom wall that is particularly resistant to pressure. This includes a thick concave dome portion 112 and circumferential beads 113 which then merge into the thin side wall 114. There are but also.Cans for hot food, the end wall of which expands and contracts the product during processing must allow within the scope of the invention. Such cans usually have a bottom wall that is thick corresponds to the side wall, the bottom wall being designed so that it can enable the corresponding movements.

While the solid coating described above Forms a suitable surface onto which protective coatings and decorations can be applied, can also use a similar result can be achieved with an etching treatment.

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However, such an etching treatment must be very carefully controlled in order to prevent breakage of grain boundaries during processing to prevent by the pressing tools.

In the tool arrangement described, each workpiece leaves each die or each ring before entering the next tool takes place, so that the load on the press is limited to that which results from a machining step results. Machining closely spaced dies and rings is known, but is used here not used because there is little possibility of dissipating heat there.

The invention has been described above with reference to chemically created coatings containing a phosphate radical. However, coatings deposited electrophoretically on the sheet, for example made of aluminum, can also be used. bring about the desired retention of lubricant.

The invention shows a method for producing seamless can bodies, wherein a cup is formed from black sheet metal, which has a phosphated surface and which is then drawn or redrawn and flattened, with a lubricant is used, either in form

a) an emulsion containing a high pressure additive, or in the form

b) a hydrocarbon, containing boundary layer lubricants and / or extreme pressure additives.

The invention also includes a method of making seamless can bodies with the formation of a cup from black plate without a phosphated surface and a pulling or redrawing and flattening of the bowl using a liquid, which is a hydrocarbon, the boundary layer lubricants and / or extreme pressure additives.

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The essence of the present invention is therefore based on the knowledge that black plate is drawn and flattened can, if the liquid to be used has the desired lubricating and cooling properties. Phosphating the Black plate supports the lubrication considerably, enables a wider range of lubricants to be used, but these must in any case be of a higher quality than those used when drawing and flattening tinplate to be used.

The metal can, for example, by immersion in an aqueous phosphating solution at 50 to 90 C for a period of 10 to 150 seconds. It can either the piece of sheet metal from which the bowl is to be formed or the bowl itself is phosphated. Preferably will the former is phosphated. Both the inside and the outside of the bowl are preferably phosphated, with however, it can sometimes be useful to phosphate only the outside. Suitable cations for the phosphate are iron, zinc or a combination of zinc and calcium, especially the latter. Preferably the metal is with

2
540 to 10750 mg of phosphate per m of surface, especially with

2
1075 to 6450 mg / m phosphated. Excessive phosphating is unnecessary and could even be harmful.

Emulsion means an aqueous emulsion of a hydrocarbon oil. The oil can be two to thirty percent by weight make up the emulsion, and emulsifiers and additives can be added to ensure a stable emulsion. The hydrocarbon oil can be paraffinic or naphthenic lubricating oil fraction based on petroleum, with a viscosity of 15 to 700 centistokes, preferably from 20 to 300 centistokes, at a temperature of 37.8 ° C.

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253561B

A high pressure additive is conveniently used when making an emulsion is used. The term "high pressure additive" means an additive that works by working with the metal surface reacts, for example by sulfiding or chlorinating. Suitable additives are therefore sulphurized fatty oils and acids, chlorinated paraffins and other corresponding reactive halogens, sulphated vegetable oils and alkylic and arylic ones Poly sulfides. The amount of high pressure additives can be from 0.5 to 50 percent by weight, but is preferably 5 to 40 percent by weight of the undiluted concentrate.

An alternative and preferred fluid related with phosphated black plate is a hydrocarbon oil. The superior lubricating properties of hydrocarbon oils in relation to emulsions make the question of additives appear much less critical or, alternatively, improved results associated with the use of a high pressure additive.

The hydrocarbon can be paraffinic or raphthenic Be lubricating oil fraction based on petroleum, preferably with a viscosity of 100 to 500 centistokes at 100 ° C, in particular between 200 and 300 centistokes.

High-pressure additives can be used, as described above in connection with lubricant emulsions, especially on the order of 5 to 40 percent by weight of the oil.

Additionally or alternatively, a boundary layer lubricant can be used, which means a composition especially a polar composition that has a greater affinity for the metal than the rest of the lubricant and consequently is able to act as an antiwear additive. Examples of additives in this sense are organophosphorus

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Salts, for example alkyl or aryl phosphates or phosphites, organo-thiophosphates, for example zinc dialkyldithiophosphates, Fatty acids or esters, for example oleic acid, soaps, for example soda stearate, amines, for example Oleylamines and long-chain alcohols, for example cetyl alcohol. The antiwear additive can be in a On the order of 0.1 to 30 percent by weight of the oil, especially in the range of 1 to 10 percent by weight.

In the exemplary embodiment which starts from a non-phosphated black plate plate, it is necessary, as indicated above, to use a hydrogen oil which contains a high-pressure additive. The oil and the additive can be configured as described above, the amount of additive preferably being between 5 and 40 percent by weight of the oil, but the use of 100 % high-pressure additives from natural fats is possible.

One of the functions of the lubricant is to Pull arising to a considerable extent. To absorb heat. Hydrocarbon oils have a lower heat absorption capacity than lubricant emulsions, and it may be necessary to take additional measures to prevent overheating to avoid, such as the introduction of known improvement aids for heat transfer, for example Aluminum alkoxides.

Each of the following lubricant combinations has been used used to manufacture cans in continuous operations using conventional drawing and flattening equipment.

Example 1: Mild steel sheet with a coating of 2690 mg / m * of zinc-calcium phosphate was lubricated with a 25% emulsion of soluble oil containing 20% sulphurized fat.

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Example 2: A mild steel sheet with a coating of

2
2690 mg / m zinc-calcium phosphate is lubricated with clear hydrocarbon oil containing 5% oleic acid and having a viscosity of 264 centistokes at 100 ° C.

Example 3: A mild steel sheet with a coating of

2
2690 mg / m zinc-calcium phosphate is lubricated with clear hydrocarbon oil containing 10 % sulphurized fat and having a viscosity of 253 centistokes at 100 ° C.

Example 4: A mild steel sheet is lubricated with a clear hydrocarbon oil containing 40 % sulphurized fat and having a viscosity of 254 centistokes at 100 ° C.

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Claims (10)

Claims f 1.! A method for drawing a can from mild steel sheet or black sheet, characterized by the steps of a chemical treatment of the sheet metal surface to form a surface with controlled lubricant retention properties, the application of a lubricant to the treated surface, the drawing of a cup from the sheet metal piece and the relubricating the cup prior to any subsequent redrawing and / or wall flattening operation. 2. The method according to claim 1, characterized in that at least a wall plating takes place after the drawing process. 3. The method according to claim 1 or 2, characterized in that the chemical treatment consists in the sheet metal piece to be provided with a solid coating that contains a phosphate radical. 4. The method according to claim 3, characterized in that a phosphate coating is applied from the group of Iron phosphate, zinc phosphate, calcium phosphate and magnesium phosphate is selected. 5. The method according to one or more of the preceding claims, characterized in that a press tool lubricant is used as the lubricant. 6. The method according to claim 5, characterized in that an emulsion of oil in water is used as the lubricant. 7. The method according to claim 6, characterized in that the emulsion contains 10 % of a mineral oil and between 2 to 5 % fatty acid. 609810/0621 8. tin can, characterized in that it is made of mild steel sheet is sucked, which at least on the outside with a lubricant in a controlled manner receiving surface is provided. 9. Can according to claim 8, characterized in that the mild steel sheet has a surface coating (2) which contains a phosphate radical. 10. Can according to claim S or 9, characterized in that it has a bottom wall thicker than the side wall and extends the bottom wall downward inward from the side wall to one Standing bead extends and runs from there upwards inward to form a pressure-resistant section. 6098 1 0/0621 Blank page