EP2140953A1 - Method for stamping metal parts - Google Patents

Abstract

Process of stamping of a metal or metal alloy component using matrix of a press, comprises: (a)preparing a lubricating composition comprising at least one anionic surfactant compound and at least one amphoteric or non-ionic surfactant compound, in an aqueous solution; (b) bubbling a gas in the composition; applying the obtained composition on the component; and (c) stamping the component by applying a pressure on a patch, volume and dimensions for obtaining the component, through the matrix.

Description

Technical area

The present invention relates to a method of stamping metal parts.

State of the art

The implementation of stamping processes, cold or hot, is common to achieve high quality metal parts, including having precise dimensions and a good surface. In these processes, a piece of metal or metal alloy is subjected to high pressure exerted by counter-matrices, possibly after having been preheated. The dies are machined with great precision to guarantee the reliability of the result of stamping.

Given the harsh conditions for carrying out these methods, the surfaces of forgings or dies may be damaged. In the case of parts, the damage may be a change in the surface condition and a change in appearance of the parts, which are no longer usable. In the case of dies, damage requires at least a correction that takes time and can lead to high costs due to the cessation of production.

Various technical solutions have been proposed in the prior art to limit or even avoid such complications.

For example, the patent US5,743,121 , issued on 28 April 1998 in the name of General Electric Company, proposes a stamping process in which a billet, on the one hand, is covered with a glass-based protective layer, and the dies, on the other hand , are lubricated with graphite.

More specifically, the graphite generally used in stamping processes is in the form of a colloidal suspension of very fine graphite particles, in aqueous phase or in concentrated ammonia. The solution is sprayed on the dies of the press before the stamping operation to avoid the aforementioned damage.

In addition, the use of a lubricant on the dies facilitates extraction of the forging out of the dies. Indeed, if a piece remains stuck in one of the matrices, the damage can be much larger and require, for example, the completion of a new matrix, or both.

However, graphite suspensions available on the market all contain traces of crystalline silica, found in natural graphite and which has the major disadvantage of being carcinogenic. In addition, the stamped pieces tend to integrate iron, present in the graphite in the form of traces, during the application of the pressure, because of the crystalline phase changes involved in this operation, which gives them a depreciated aspect related to the appearance of a black coloring. This last disadvantage is particularly noticeable when the stamped parts are made of a metal or light metal alloy, such as for example titanium.

It may be noted that, in an attempt to solve the above problem, boron nitride, sometimes called "white graphite", has been used as a lubricant to replace graphite. However, the very high price of this product, which is also toxic, makes it unsuitable for regular use.

Disclosure of the invention

The main object of the present invention is to propose an alternative to the stamping methods currently used, by proposing a method that does not present a danger for the health of its users, and that is ecological.

Another object of the present invention is to provide a stamping process which ensures an immaculate appearance on the surface of the stamped metal or metal alloy.

1. a) préparer une composition lubrifiante comprenant, en solution aqueuse, au moins un composé tensioactif de type anionique et, au moins un composé tensioactif de type amphotère ou non ionique;
2. b) faire barboter un gaz dans ladite composition;
3. c) appliquer sur ladite pièce la composition issue de l'étape b);
4. d) étamper ladite pièce par application d'une pression sur un lopin, de volume et dimensions adaptés à l'obtention de ladite pièce, par l'intermédiaire desdites matrices

For this purpose, the present invention relates more particularly to a method of stamping a piece of metal or metal alloy by means of dies of a press comprising the following steps:

1. a) preparing a lubricating composition comprising, in aqueous solution, at least one anionic surfactant compound and at least one amphoteric or nonionic surfactant compound;
2. b) bubbling a gas in said composition;
3. c) applying to said part the composition resulting from step b);
4. d) stamping said workpiece by applying a pressure on a billet, of volume and dimensions adapted to obtain said workpiece, by means of said dies

Thanks to these particular characteristics, the application of the lubricant composition obtained according to the invention to the parts before carrying out a stamping operation guarantees a good quality of the part obtained as well as its extraction from the dies.

Indeed, while anionic surfactants are commonly used in the field of soaps and nonionic surfactants in the fields of cosmetics and pharmaceuticals, the Applicant has unexpectedly found that injection of a gas in the lubricating composition in which the parts before stamping are quenched, provides a lubrication quality superior to that obtained with the methods of the state of the art. In addition, the process according to the invention is distinguished by its absence of toxicity.

It has even emerged from these experiments that, particularly in the case of stainless steels, the surface finish of the stamped pieces is better than with the processes of the state of the art.

Other features and advantages of the present invention will become more apparent upon reading the detailed description of a preferred embodiment which follows.

Mode (s) of realization of the invention

1. a) préparer une composition lubrifiante comprenant, en solution aqueuse, au moins un composé tensioactif de type anionique et, au moins un composé tensioactif de type amphotère ou non ionique;
2. b) faire barboter un gaz dans ladite composition;
3. c) appliquer sur ladite pièce la composition issue de l'étape b);
4. d) étamper ladite pièce par application d'une pression sur un lopin, de volume et dimensions adaptés à l'obtention de ladite pièce, par l'intermédiaire desdites matrices.

According to the present invention, the method of stamping a piece of metal or metal alloy by means of dies of a press comprises the following steps:

1. a) preparing a lubricating composition comprising, in aqueous solution, at least one anionic surfactant compound and at least one amphoteric or nonionic surfactant compound;
2. b) bubbling a gas in said composition;
3. c) applying to said part the composition resulting from step b);
4. d) stamping said workpiece by applying a pressure on a billet, of volume and dimensions adapted to obtain said workpiece, by means of said dies.

Preferably, the lubricating composition comprises between 1 and 20%, preferably between 2 and 15%, and more preferably between 4 and 9%, by weight, of an anionic surfactant compound relative to its total mass, and less of 10%, preferably less than 5% and more preferably less than 2%, by weight, of an amphoteric or nonionic surfactant compound, based on its total mass.

With regard to surfactants, any known surfactant meeting the criteria required for the practice of the present invention may be used. Those skilled in the art will not encounter any particular difficulty in selecting surfactants that meet their specific needs. Preferably, the surfactants retained will not be toxic to the users of the lubricant composition used according to the present invention and will have a high biodegradability.

By way of non-limiting example, one or more of the following compounds may be used as surfactant of the anionic type: alkyl sulphates, alkylarylsulphates, soaps (R-CH ₂ -COO-Na, with R = C ₁₀ to C ₁₆ ) or alkylbenzenesulfonates (or ABS, RC ₆ H ₄ -SO ₃ -Na, with R = C ₁₀ to C ₁₃ ). Such compounds are 90% biodegradable.

Similarly, by way of non-limiting example, one or more of the following compounds may be used as a nonionic surfactant: polyethylene glycol ether alcohols (R-CH ₂ -O- (CH ₂ -CH ₂ -O) _n -H, with R = C ₁₀ -C ₁₈ ) or alkylphenolethoxylates (RC ₆ H ₄ -O- (CH ₂ -CH ₂ -O) _n -H, with R = C ₈ -C ₁₂ ). These compounds are also 90% biodegradable.

It is important to note that the composition just described is clean, from an environmental point of view, odorless and non-toxic.

It may advantageously be used mainly demineralized water to produce the lubricant composition to optimize the qualities of the latter.

The gas bubbling into the lubricating composition can be injected into the lubricant composition at a pressure of between 2 and 15 bar, preferably between 5 and 10 bar.

The gas used may preferably be carbon dioxide, but any other suitable gas may be used.

Advantageously, the lubricating composition can be prepared according to step a) in a bath, into which said gas is injected according to step b), the workpiece to be stamped then being dipped in said bath according to step c ).

Thus, for example, a bath containing demineralised water, about 6% by weight of an anionic surfactant soap, and less than 2% by weight of a nonionic surfactant can be made. Carbon dioxide is injected into the bath with a pressure of 5 bar. The pieces placed in a basket are soaked in the bath and then stamped.

The parts obtained according to the process of the invention have a beautiful appearance and the stamping process does not present a danger to the health of its users.

For comparison, the parts were soaked in an identical bath but in which no gas is injected. Stamping could not be achieved due to seizing of the die.

The method according to the invention is more particularly applicable, by way of non-limiting indication, to the stamping of precious metal parts, of steel, of any type, stainless steel, brass, titanium or titanium alloy, of zirconium or zirconium alloy, tantalum or tantalum alloy, these components being commonly used for example in the manufacture of watch cases and other timepieces. Of course, the skilled person can adapt the teaching of the present invention to the stamping of metals or alloys other than those mentioned without departing from the scope of the invention.

In addition, the process according to the invention mainly concerns cold processes.

However, the method according to the invention can also be advantageously used in a hot stamping process without departing from the scope of the present invention. In this case, the part can be heated between 700 ° C and 1000 ° C. By way of non-limiting example, the stamping of titanium alloy parts is usually carried out at a temperature between about 800 ° C and 920 ° C.

Moreover, thanks to its particular characteristics giving it a high efficiency, the first steps of the stamping method according to the present invention can be implemented in a simple manner, before stamping a part by applying a pressure on a piece, of volume and dimensions adapted to obtain this piece, through antagonistic matrices of a press.

The Applicant has found that the application of a lubricating composition on the dies, in combination with the application of the lubricant composition on the billet before proceeding to stamping, as described in the prior art, was not necessary to ensure a good quality surface finish.

Advantageously, the original color of the stamped part, which is a function of its composition, is not affected by the stamping process in which the lubricant composition according to the present invention is applied to the parts. In addition, as already mentioned, it should be emphasized that parts stamped in this way have a better surface condition than those obtained by the processes of the prior art, insofar as the microcracks visible on the latter do not appear.

The foregoing description corresponds to a preferred embodiment of the invention described in a non-limiting manner. In particular, the nature of the reagents described to achieve the composition that have been described are not limiting.

Claims (6)

A method of stamping a piece of metal or metal alloy by means of dies of a press comprising the steps of: a) preparing a lubricating composition comprising, in aqueous solution, at least one anionic surfactant compound and at least one amphoteric or nonionic surfactant compound; b) bubbling a gas in said composition; c) applying to said part the composition resulting from step b); d) stamping said workpiece by applying a pressure on a billet, of volume and dimensions adapted to obtain said workpiece, by means of said dies. Process according to claim 1, characterized in that the lubricating composition comprises between 1 and 20%, preferably between 2 and 15%, and more preferably between 4 and 9%, by weight, of a surfactant compound of anionic type relative to to its total mass, and less than 10%, preferably less than 5% and more preferably less than 2%, by weight, of an amphoteric or nonionic surfactant compound, based on its total mass. Process according to either of Claims 1 and 2, characterized in that the lubricating composition contains at least predominantly deionized water. Process according to any one of Claims 1 to 3, characterized in that the gas bubbling into the lubricating composition is injected into said composition at a pressure of between 2 and 15 bar, preferably between 5 and 10 bar. Process according to any one of the preceding claims, characterized in that said gas is carbon dioxide. Process according to any one of the preceding claims, characterized in that said lubricating composition is prepared according to step a) in a bath in which said gas is injected according to step b), the workpiece to be stamped being soaked in said bath according to step c).